[advances in food research] advances in food research volume 4 volume 4 || the use of ascorbic acid...

The Use of Ascorbic Acid in Processing Foods

BY J. C. BAUERNFEIND

Eoflmann-La Roohe Inc., Nutley 10, New Jersey

CONTENTS Page

I. His tory . . . . . . . . . . . . . . . . . . . . . . . . 359

II.# Nutritional Value . . . . . . . . . . . . . . . . . . . . 361

111. Chemistry . . . . . . . . . . . . . . . . . . . . . . . 364

IV. Exhaustion of Oxygen in Sealed Aqueous Solutions . . . . . . . . 366

V. Oxidative Browning in Heat-Processed Foods . . . . . . . . . . 367

VI. Flavor and Nutritional Value in Juices . . . . . . . . . . . . 371

VII. Enzyme-Catalyzed Oxidation in Frozen Fruits . . . . . . . . . . 381

VIII . Synergistic Action in Edible Fats . . . . . . . . . . . . . . 388

IX. Rusting and Rancidity in Frozen Fish . . . . . . . . . . . . . 390

X. Discolorations and Rancidity in Meat Products . . . . . . . . . 392

395

XII. Oxidized Flavor in Beverage Products . . . . . . . . . . . . 403

XIV. Nutritional Value in Miscellaneous Products . . . . . . . . . . 407

XV. Needed Research . . . . . . . . . . . . . . . . . . . . 408

References . . . . . . . . . . . . . . . . . . . . . . 409

XI. Oxidized Flavor in Dairy Products . . . . . . . . . . . . . .

XII I . Flour and Dough Improver . . . . . . . . . . . . . . . . 406

I. HISTORY

Twenty-five years ago, the chemistry, nutritional values, and food processing qualities of ascorbic acid (vitamin C) were essentially nature's secrets. Today pure crystalline ascorbic acid is economically produced by several companies in large volumes for medicinal and food enrichment purposes. Crystalline 1-ascorbic acid has been demonstrated to be the specific preventive of scurvy and to be of value in many of the disorders of man, some of which require relatively large doses for therapeutic effects (Abt, 1939 ; Farmer, 1944 ; Kyhos et al., 1945 ; Biclr- nell and Prescott, 1946 ; Markwell, 1947 ; Osol and Farrar , 1947 ; Ruskin, 1947 ; Fletscher and Fletscher, 1951 ; Klassen, 1951 ; Silbert, 1951). Ascorbic acid administered in massive, repeated doses intravenously or intramuscularly has a potent chemotherapeutic action in acute infectious processes and has been declared to be free from toxic or allergic reactions by McCormick (1952). Large intakes of ascorbic acid have been re-

359

360 J. C. BAUERNFEIND

ported to halt the development of acute poliomyelitis (Baur, 1952). The gradual decline in the incidence and case mortality rates of some infectious diseases during the past century have been attributed, in part, to an improved vitamin C intake (McCormick, 1951).

The early history of diets lacking this vitamin are crowded with ac- counts of multimasted sailing vessels carrying scurvy-ridden sailors long without proper foods. One early authentic record of scurvy on ship- board is found in the account of Vasco da Gama’s voyage around the Cape of Good Hope in 1498 (Bicknell and Prescott, 1946). Early therapeutic agents for the disease were the juice of sassafras leaves, pine- needle tea, sour lemons, and lime juice.

Citrus fruits, berries, melons, tomatoes, and green vegetables are good natural sources of ascorbic acid (Anonymous, 1945a ; Watt and Aterrill, 1950). The ascorbic acid content of fruits and vegetables varies, however, with variety, climate, sunlight, maturity, and handling practices (Harding e t al., 1940; Murphy, 1942; Carroll, 1943; Holmes e t al., 1943a ; Holmes et al., 1943b ; Anonymous, 1944 ; Jones e t al., 1944 ; Pep- kowitz e t al., 1944; Anonymous, 1 9 4 5 ~ ; Harding and Fischer, 1945; Somers and Beeson, 1948 ; Paul e t al., 1949 ; Maynard, 1950 ; Zscheile, 1950 ; Miller and Schaal, 1951 ; Peterson et al., 1951 ; Strachan e t al., 1951 ; Mustard, 1952).

This vitamin is also more subject to destruction during processing and storage than most other nutritive essentials. Oser (1952) briefly summarizes the effects of processing and handling on ascorbic acid content as well as on other nutritional components in a recent review for food manufacturers. The factors influencing the vitamin content of canned foods have been reviewed (Clifcorn, 1948) and are currently being studied (Brenner e t al., 1948; Guerrant e t al., 1948; Anonymous, 1949d; Freed e t al., 1949 ; Monroe e t al., 1949 ; Sheft e t al., 1949 ; Feaster e t al., 1950; Lamb e t al., 1951). The behavior of ascorbic acid in processing and storing frozen fruits and vegetables has also been investigated (Fenton, 1946, 1950; Cotton e t al., 1947; Ferguson and Scoular, 1949; Tressler and Pederson, 1951). Extensive information has been gathered on cooking and serving losses when foods containing ascorbic acid are prepared by various methods (Fellers, 1936 ; King and Tressler, 1940 ; Nagel and Harris, 1942 ; Heller et al., 1943 ; Jenkins, 1943 ; Oser et al., 1943; Gleim e t al., 1946; Streightoff e t al., 1946, 1949; Branion e t al., 1947, 1948 ; Sutherland e t al., 1947 ; Thomas e t al., 1947 ; Clifcorn, 1948 ; Hewston e t al., 1948; MunselI e t al., 1949; Krehl and Winters, 1950; Storvick et al., 1950; Nobel, 1951; Van Duyne e t al., 1951; Fisher and Dodds, 1952). The effect of electromagnetic radiation, a new heatless method of processing, on ascorbic acid stability and the role of added as-

USE O F ASCORBIC ACID IN PROCESSING FOODS 361

corbic acid has been observed (Proctor and Goldblith, 1948,1950 ; Brasch c t al., 1949 ; Huber, 1951 ; Proctor and O’Meara, 1951 ; Proctor e t al., 1952).

Ascorbic acid was first isolated from lemons by Waugh and King (1932a,b) and from the adrenal gland by Svirbely and Szent-Gyiirgyi (1932). Synthesis of ascorbic acid followed the next year by Reichstein e t al. (1933). Large-scale synthesis was developed shortly thereafter to manufacture the first crystalline vitamin in commercial quantities (Klein, 1936; Major, 1942). Current production in the United States now approximates 10 tons of ascorbic acid per week (Cardinal, 1950).

11. NUTRITIONAL VALUE

The Food and Nutrition Board of the National Research Council (Anonymous, 1948a) recommends for optimum nutrition a daily intake of 75 mg. of ascorbic acid for adults, 100 to 150 mg. during pregnancy and lactation, and 30 to 75 mg. for children up to 12 years of age. The Food and Drug Administration (Anonymous7 1941) has set the minimum daily requirement to be 30 mg. of ascorbic acid for adults. The minimum requirement according to standards of the Army (Anonymous, 1949e) is 50 mg. daily. Label claims for nutritional value of foods enriched with ascorbic acid are based on Food and Drug Administration minimum requirements. Food products containing added ascorbic acid must display simple label copy showing its addition to conform to the Food and Drug Administration’s rulings, whether ascorbic acid is used in the food for retardation of deteriorative changes, for nutritive value, or for both purposes (Anonymous, 1941, 1950b).

Although scurvy is no longer a major disease, there is good evidence that moderate deficiencies of ascorbic acid impair health (Youmans, 1951). Scurvy is more prevalent in infants not receiving breast milk than has been suspected on the basis of clinically recognized cases (Follis et al., 1950; Anonymous, 1951e). Many recent nutrition surveys in the United States and Canada demonstrate an appreciable incidence of chronic ascorbic acid deficiency. Studies on the diets of children in New York State (Trulson e t al., 1949a; Young e t al., 1951), in Oregon (Storvick e t al., 1951), in Vermont (Pierce e t al., 1947 ; Brown and Pierce, 1950), in Maine (Clayton, 1951), in Florida (Anonymous, 1951 j ; Phipard, 1951), in Alabama and South Dakota (Phipard, 1951), in Louisiana (Dallyn and Moschette, 1952), in West Virginia (Chalmers and Law- less, 1952), in Iowa (Hathaway e t al., 1952), as well as in the West Pacific Coast asea (Anonymous, 1951i) have demonstrated that vitamin C intakes are frequently below the daily allowance recommended by the

362 J. C . BAUERNFEIND

National Research Council or that insufficient f rui t juices and green vegetables are consumed. A reliable intake of ascorbic acid in foodstuffs consumed by people i n the United States as well as all over the world continues to be a subject of interest and practical concern (Jolliffe e t al., 1942 ; Anonymous, 1943a ; Lockhart e t al., 1944 ; Sevringhaus, 1944 ; Koch, 1945 ; Anonymous, 1946b ; Branion and Cameron, 1948 ; Fincke e t al., 1948 ; Trulson e t al., 1949b ; Anonymous, 1950c ; King, 1950, 1951 ; Phipard, 1951).

The biochemical function of ascorbic acid is not yet clear (King, 1951 ; Bacharach, 1952), although its reversible oxidation-reduction capacity is its most striking property. P a r t of its function may be said to be that of transporting hydrogen in cellular respiration. It possesses a detoxifying function and is a factor in amino acid and carbohydrate metabolism. The ascorbic acid tissue level is an important factor in the oxidation of aromatic drugs by the body (Axelrod e t al., 1952). I n vitro studies indicate that the oxidation of aromatic drugs by ascorbic acid and oxygen seems to involve a n organic peroxide intermediate (Udenfriend e t al., 1952). Ascorbic acid plays a role in tyrosine metabolism by acting as a coenzyme in the oxidation of the deaminated amino acids (Sealock and Goodland, 1951).

Recent research has revealed that glucose (Horowitz e t al., 1952) or a condensation product of glucose (Nath e t al., 1952) is the origin of ascorbic acid synthesis in the body. Analogues of ascorbic acid have been studied, with little success, in an attempt to find a compound which would alter the ability of animals to synthesize their own vitamin C and hence hope to gain further knowledge on the site and mechanism for in vivo synthesis (Anonymous, 1951g).

Ascorbic acid is absorbed by the tissue of the intestinal tract, particularly the small intestines, and passes into the blood stream (Lowry e t al., 1946 ; Roe e t al., 1947 ; Putnam e t al., 1949). It is not stored in the body to any appreciable extent (Crandon e t nl., 1940 ; Rosenberg, 1942 ; Farmer, 1944), and excess ingested quantities are excreted primarily in the urine and to a very small extent in sweat (Shields e t al., 1945). I n fact, a physiological test on man has been devised to determine the availability of ascorbic acid in various products based on rapid excretion of excess ascorbic acid in the urine over a 24-hour period (Melniclr e t al., 1945).

Ascorbic acid enhances the conversion of folic acid to citrovorum factor (folinic acid) both in vivo and in v i t r o . This interrelationship explains the favorable effect of the administration of ascorbic acid to folk acid deficient rats (Anonymous, 1949c, 1950f) and to folic acid


deficient infants (Govan and Gordon, 1949 ; Anonymous, 1951c, Anony- mous, 1952a ; Nichol and Heinle, 1952).

Suggestions of an interrelationship between ascorbic acid and vitamin A appears to be evident but not clearly demonstrated from published reports. Decreases in blood levels as well as lowered urinary excretion of ascorbic acid have been reported as accompanying vitamin A depletion (Boyer e t al., 1942; Moore, 1946; Anonymous, 1949f). I n a recent blood study (Getz e t al., 1951) of tubercular patients, markedly sub- standard values for vitamins A and C were reported prior to the development of the disease. Investigations with the ra t have indicated an ascorbic acid blood and tissue decrease in severe vitamin A deficiency (Mayer and Krehl, 1948). Supplements of ascorbic acid seem to decrease the vitamin A requirements of fox pups and mink kits on a low vitamin A diet (Eassett e t al., 1948). The question of the effect of the general plane of nutrition has been injected into this interrelation since Eaton e t al. (1952) found no blood ascorbic acid decrease in calves until the very terminal stages of vitamin A depletion. Ascorbic acid supple- mentation did not alleviate vitamin A cleficiencies, decrease spinal fluid pressure or decrease loss of appetite. Furthermore, ascorbic acid synthesis has been reported in rats deprived of vitamin A (Mapson and Walker, 1947 ; 1948).

The ingestion of large amounts of ascorbic acid can counteract the lack of certain vitamins of the R group. Two per cent ascorbic acid in either a pantothenic acid or riboflavin dcficient dipt prevented o r delayed the deficiency signs in the majority of rats u p to a year in a one year study. In preliminary studies 5% ascorbic acid in thiamin-free diets prevented o r delayed the onset of the deficiency signs (Daf t nncl Schwarz, 1952). On the other hand, increasing the water-soluble G vitamin intake did not greatly affect the development of scurvy in guinea pigs (De Felice, 1950). Dietary ascorbic acid a t a 2% diet level prevented or delayed granulocytopenia on diets containing high levels of ferric citrate. Thera- peutic effects were also observed by IlkDaniel and Daft (1952). Other workers have also demonstrated ascorbic acid to improve the metabolism of iron (Albers, 1951).

It is generally accepted that ascorbic acid is non-toxic when administered in moderate doses to humans (nosenberg, 1942; Osol and Farrar , 1947), Daily divided doses of hundreds of milligrams are recommended in certain disorders (Biclrnell and Prescott, 1946 j Jolliffe e t al., 1950). No toxic signs were observed in human beings who were given doses of from 1 to 6 g. daily, 30 to 200 times the minimum daily requirement (Abt and Farmer, 1938; Abt, 1939; Anonymous, 1945b; Kyhos e t al., 1945 ; Massell e t al., 1950 ; Bauer, 1952 ; Lowry e t al., 1952 ; BlcCormick,


1952). The possibility of overdosage of ascorbic acid through eating excessive quantities of ascorbic acid enriched foods seems very remote.

Experimental evidence has been accumulated since 1934 on the identical biological activity of crystalline ascorbic acid and ascorbic acid as it exists in natural foods for humans and animals (Harris, 1934; Crandon e t al., 1940; Ralli and Sherry, 1941; Dunker e t al., 1942; Hangartner and Gordonoff, 1942 ; Todhunter e t al., 1942 ; Clayton and Borden, 1943 ; Anonymous, 1948b ; Elliott and Schuck, 1949). Recent physiological availability trials on man (Melnick e t al., 1947) as well as a new biological technique on guinea pigs (Crampton and Lloyd, 1950) ha.ve further confirmed the finding that crystalline ascorbic acid is absorbed and utilized by the body as well as ascorbic acid from natural sources.

111. CHEMISTRY

Pure ascorbic acid (vitamin C) occurs as white, odorless crystals or powder, melting at about 190" C. (374" F.). It is freely soluble in water (1 g. in approximately 3 ml.), but i t is almost insoluble in oil (Rosen- berg, 1942). I n structure it strongly resembles a simple sugar but is modified to contain an enediol and acid lactose group. It has a slight acid taste and is the only substance in most plant and animal tissues which displays strong reducing properties in acid solution (Anonymous, 1946b).

The reducing action imparted by the enediol group serves as a basis fo r simple laboratory (Tillmanns, 1927; Bessey and King, 1933; Sharp, 1938; Rubin e t al., 1945) and plant control methods (Bauern- feind and Jahns, 1946; Strachan and Moyls, 1946). More complex methods have also been developed for determining dehydroascorbic acid and interfering reducing substances when these are suspected to be present (Bessey, 1938 ; Nelson and Somers, 1945 ; Robinson and Stotz, 1945; Rubin e t al., 1945; Stewart and Sharp, 1945; Tuba e t al., 1946; Harris and Mapson, 1947; Miller, 1947; Goldblith and Harris, 1948; Mills e t al., 1949; Brown and Adam, 1950; Hewston e t al., 1950; Map- son and Ingram, 1951; Parkinson, 1952). A new colorimetric reaction of ascorbic acid has been recently announced. Due to its di-enol character ascorbic acid can be coupled with diazotized 3 nitro-4-amino-anisol, which in acid medium forms a yellow azo compound. I n alkaline solution this dye is a vivid blue and can be utilized for colorimetric determina- tions at a wave length of 570 mp. The method is highly specific for the determination of ascorbic acid in the presence of dehydroascorbic acid and other vitamins normally found in pharmaceutical preparations. Preliminary results indicate that it is quite promising for foods (Schmall

USE OF ASCORBIC ACID IN PROCESSING FOODS 365

e t al., 1953). Interference of reductones in the 2,4-dinitrophenylhydrazine method (Roe and Oesterling, 1944; Mills et al., 1949) for the determination of ascorbic acid has been eliminated by the inclusion of one of two corrective measures (Schocken and Roe, 1952). An improved tech- nic has been developed for the determination of bound ascorbic acid in tissues (Sumerwell and Sealock, 1952).

The dry crystals of ascorbic acid are stable on exposure to air in daylight a t room temperature for several years. During prolonged storage they tend to become buff-colored without undergoing appreciable decomposition (King, 1939).

I n aqueous solution ascorbic acid deteriorates more easily, especially in the presence of dissolved and headspace oxygen. The rate of destruction is catalyzed by dissolved copper and, to a lesser extent, by iron (Szent-Gyorgyi, 1928 ; Weissberger and LuValle, 1944; Clifcorn, 1948 ; Joslyn and Miller, 1949; Lamden, 1950; Stribley et aE., 1950). I n the presence of riboflavin, light accelerates its destruction (Sharp and Hand, 1940). It can be heated for long periods of time, provided all contact with oxygen is excluded.

co-

Ho-y H-C - I I

CH,OII

I-Ascorbic acid

CO-,

- 2H H-C-

I CH,OH

Dehydro-l- ascorbic acid

Oxidation of ascorbic acid with one atom of oxygen yields dehydroascorbic acid, which in turn can be reversibly reduced to ascorbic acid with two atoms of hydrogen by means of hydrogen sulfide, glutathione, sulfhydryl compounds, and probably other substances (Borsook et al., 1937; Giri, 1942; Rosenberg, 1942). Dehydroascorbic acid is the main product of the autoxidation of ascorbic acid with oxygen in acid solutions (Peterson and Walton, 1943). Dehydroascorbic acid has been prepared in pure form (Kenyon and Munro, 1948; Pecherer, 1951) and shown to possess biological activity equivalent to reduced ascorbic acid in guinea pigs and man (Johnson and Zilva, 1934; Todhunter et al., 1950; De Rit- ter et al., 1951). In neutral and alkaline solution, dehydroascorbic acid


is unstable, even a t room temperature, and further immediate irreversible breakdown products are formed (Ball, 1937; Guild e t al., 1948). Dissolved copper catalyzes the oxidative reaction of ascorbic acid ; u p to two atoms of oxygen are used in the reaction (Peterson and Walton, 1943; Weissberger and LuValle, 1944). The most recent reports have concluded that the reaction involved in the autoxidation of ascorbic acid is a reaction of the first order with respect to the ascorbic acid concentration ; its rate is directly proportional to the square root of the copper concentration and inversely proportional as the sqirare root of the hydrogen ion concentration in acid solutions (Joslyn and Miller, 1949). The oxidation of ascorbic acid is further affected by the presence of inhibitors which act as buffering agents, hydrogen donors, copper scaven- gers, or enzyme inactivators (Giri, 1942 ; Peterson and Walton, 1943 ; Richardson and Mayfield, 1944 ; Weissberger and LuValle, 1944 ; Camp- bell and Tubb, 1950). Ascorbic acid and dehydroascorbic acid heated in concentrated acid solution yield furfural compounds polymerizing to form dark-brown substances due to mutarotation, hydration, decarboxy- lation, and dehydration reactions (von Wolier and Antener, 1937 ; Joslyn, 1941 ; Lamden and Harris, 1950).

d-Isoascorbic acid possesses antioxidant properties for 1-ascorbic acid in pure solutions and in the presence of food products (Esselen e t al., 1945 ; Scliulte and Schillinger, 1952). I n actual practice, however, this observation is primarily of research interest only, since the protection value of the d-form is only equivalent to like quantities of the added 1-form which can satisfactorily and economically act as a protective measure.

IV. EXHAUSTION OF OXYGEN IN SEALED AQUEOUS SOLUTIONS

The effect of oxygen on ascorbic acid in solution under controlled conditions has been observed by Bayes (1950). Aqueous standardized solutions containing 100 mg. of ascorbic acid were prepared with varied but known dissolved and headspace oxygen contents and stored for 6 weeks a t 35" C. (95" F.). Theoretically, 1 ml. of oxygen reacts with 15.7 mg. of ascorbic acid (based on one mole of ascorbic acid combining with one atom of oxygen). This would be equivalent to a reaction of approximately 3.3 mg. with 1 ml. of air. Data secured in this storage trial are presented as Table I. The experimental and theoretical values agree fairly well, indicating that, under the conditions employed, the destruction of ascorbic acid is directly proportional to the amount of available oxygen in the containers.

In a study by Yourga e t al. (1944), aqueous solutions containing added

USE OF ASCORBIC ACID I N PROCESSING FOODS 367

TABLE I

Behavior of Ascorbic Acid in Sealed Aqueous Solutions * t

Available Oxygen ascorbic Ascorbic acid loss Test num- Solution Total acid content Experimental Theoretical ber m1./100 inl. IIcadspace ml. mg./pt. mg. mg.

2 0.53 Nitrogen 2.4 58 42 37.7

4 0.01 Nitrogen 0.0 97 3 0

1 0.53 Air 6.6 0 100 103.6

3 0.01 Air 4.2 38 62 65.9

* Bayes, 1950. f Conditions of tr ial: initial ascorbic acid, 100 mg. per pint; storage period 6 weeks at

35' C . (95" F.).

ascorbic acid at pH 4.0, placed in crown-sealed bottles with a large known volume of headspace, were pasteurized for 30 min., cooled and stored. Samples stored for 8 months at 26" C. (79" F.) had utilized 2.9 mg. of ascorbic acid per milliliter of headspace air ; those stored at 60" C. (140' F . ) utilized 3.3 mg.

V. OXIDATIVE BROWNING IN HEAT-PROCESSED FOODS

Alterations in flavor and appearance brought about by contact of the food with oxygen occupy a prominent position among the causes of food deterioration (Coulter and Jennes, 1946 ; Walker, 1949 ; Tutton and Coonen, 1950). However, it is only in the last 10 to 15 years that many segments of the food industry have come to realize the importance of oxidative changes. The review by Joslyn and Ponting (1950) presents this problem in detail.

Peaches, apples, plums, pears, apricots, and sweet cherries possess, in their normal fresh condition, a relatively low natural ascorbic acid content. When fruits such as apples and peaches are home canned, the preserved product, after a few months of storage, frequently undergoes color and flavor changes brought about by the oxygen in the air trapped in the headspace of the sealed container. Ascorbic acid applied in fine granular form or in aqueous solution to the top surface of the fruit prior to sealing and processing prevents or retards the discoloration and flavor change during storage (Powers and Fellers, 1945 ; Eauernfeind et al., 1947a ; Thiessen, 1949). Experimental data on home-canned sliced apples are shown as Table 11.

Ascorbic acid in amounts recommended for home canning (125 to 200 mg. per ja r ) is not detectable by smell, taste, or appearance. There are two advantages in adding ascorbic acid to home-canned fruits: it


TABLE I1

Effect of Added Ascorbic Acid on Canned Sliced Apples * 1

After 6 months' storage at I

After canning 24" C. (75" F.) Pack Added num- ascorbic Ascorbic Total Ascorbic Total Appearance

~~

ber acid $ acid vitamin C acid $ vitamin C $ of pack

mg./pt. jar

1 0 0.1 3 - 5 Dark throughout 2 67 15 18 5 15 Slightly dark

Normal 3 135 57 59 22 33 4 200 118 118 74 82 Normal

* Bauernfeind el at., 1947a. t MeIntosh apples peeled and sliced, cooked 3 to 4 min. to soften, hot-packed with 50%

t Ascorbic acid added in aqueous solution before sealing jar. 8 As determined by assay of Rubin et al., 1945.

syrup in Ball Ideal pint jars, 956-in. headspace, processed 10 niin. in boiling water.

is a method of retarding undesirable flavor and color changes during storage, and it enables the canned product to serve as a substantial source of vitamin C in the diet. For example, in Wyoming and Mon- tana (Richardson and Mayfield, 1941; Thiessen, 1949) more home- canned fruits are served in place of fresh fruit during the winter months. As a result of their canning trials several workers have suggested the addition of ascorbic acid to tomato juice and snap beans to further improve them as winter sources of vitamin C (Clayton et al., 1948 ; Thies- sen, 1949). Surveys on farm diets in Georgia, Mississippi, Minnesota, and New York indicate that ascorbic acid shortages are not uncommon, particularly in the spring (Phipard, 1951). The extension services of agricultural colleges have issued bulletins recommending the use of ascorbic acid in home canning (Esselen & Fellers, 1950 ; Ellis, 1951).

Special preparations of ascorbic acid mixed with a sugar base in powder form or as a water-soluble tablet may now be secured a t food markets and a t food locker plants for use in home canning. If these are not available, ascorbic acid can be secured from the drugstore. These preparations, when applied according to directions, can also be used in the home for retarding browning in home freezing of fruits and in the preparation of fresh fruit salads. Recommendations regarding the use of ascorbic acid in the home freezing of fruits are included in the agricultural extension bulletins (Clark, 1945 ; Fenton e t al., 1950 ; Masterman and Lee, 1950; Anonymous, 1951a; Van Blaricom et al., 1951 ; Woodroof and Shelor, 1951).

Although modern commercial canning methods have been fairly successful in excluding air from the container and the product as well,

USE OF ASCORBIC ACID IN PROCESSING FOODS, 369

thereby providing better retention of natural ascorbic acid and superior flavor, there are processing plants where these improvements have not been made. Furthermore, some products are more sensitive than others to deteriorative changes during processing. Added ascorbic acid has been beneficial in the canning of certain products, such as mushrooms, sauerkraut, cranberry juice, apple juice, etc.

During the past twenty years the American mushroom industry has expanded continuously until it is now one of the important food indus- tries. I n addition to the fresh market, large quantities of mushrooms are canned as such or in soups. Ascorbic acid is, in small quantities, a natural constituent of fresh mushrooms (Esselen and Fellers, 1946). Until a few years ago all mushrooms were packed in tin cans. The canned products which darkened during processing become lighter in color during storage owing to the reducing action of the tin surface. Mushrooms processed in glass containers without the benefit of exposure to a tin surface do not lighten during storage and hence are judged to be of inferior quality.

A study in which ascorbic acid was added to glass- and tin-packed mushrooms during commercial processing revealed the following general findings (Bauernfeind e t al., 1952).

1. Although 150 to 300 mg. of ascorbic acid added per 6% fl. oz. pack containing approximately 4 oz. of drained mushrooms noticeably delayed the development of the muddy gray color when packed in glass, the effect of the ascorbic acid addition in preventing discoIoration in the glass containers was immediately evident after processing. Further- more, the mushrooms do not darken after months of storage. In mushroom packs processed in tin containers, 150 mg. of ascorbic acid provided a product immediately superior in color to the canned pack without ascorbic acid.

2. Opened containers of processed mushrooms without the ascorbic acid addition darken when exposed to air a t room temperature for 12 hr. or more. The liquid content becomes three to four times darker after standing, as compared to a freshly opened can. When processed mushrooms with ascorbic acid added are opened and stored in the refrigerator or a t room temperature, they will retain their color and flavor for a longer period of time.

3. Taste panel trials have demonstrated that products prepared from mushrooms canned with ascorbic acid and stored in tin or glass possess superior mushroom flavor over packs not so treated. Creamed mushrooms, cream of mushroom soup, and mushroom broth with vegetables prepared with ascorbic acid treated mushrooms have a more bland and


creamy flavor than mushrooms packed without ascorbic acid in both types of containers.

New definitions and standards of identity for hcat-processed mushrooms (Anonymous, 1952b) effective December 1952, amend previous regulations by making ascorbic acid, in amounts not exceeding 37.5 mg. per 1 oz. of drained mushrooms, an optional ingredient. The reaction of ascorbic acid, although not established, indicates that i t combines with oxygen inside the container, and, although there is slight increase in acidity when ascorbic acid is used, its effect on the pII of canned mushrooms is less pronounced than when effective levels of citric acid wcre used. Salt is continued in the new definitions and standards as an optional ingredient, but citric acid, vinegar, spice, sugar and corn sugar have been deleted.

It is known that the color of hcat-processed sauerkraut remains whiter i n tin than in glass, probably owing to the reducing action of the tin. Pederson observed a relation between the natural ascorbic acid content and the quality of kraut as reflected in its flavor, color, and texture. With this earlier observation in mind, Pcderson and Beattie (1946) packed sauerkraut containing 1.5% lactic acid and 2.2570 salt in pint glass jars. J a r s were also packed containing added ascorbic acid a t levels of 75, 100, and 160 mg. per jar. Samples were stored and examined periodically. After 9 months' storage a t temperatures of 7" C . (43" F.) and 20" C. (68" F.) there wcre no differences in color. IIowevcr, a t temperatures of 37" C. (99" F.) and 45" C. (113" F.) the samples to which 160 mg. were added were rated highest in color in the majority of cases. Other studies with ascorbic acid in quart containers are described. The authors therefore find that added ascorbic acid has some effect in inhibiting color changes (Pedcrson and Ecattic, 1946). Others have noted the most desirable color of canned kraut to be associated with high ascorbic acid content (Brown, 1950). More studies arc needed on this subject before the value of ascorbic acid added to glass-packed, heat-processed sauerkraut can be properly evaluated for coinnicrcial practice.

Several commercial packers of non-heat-sterilized sauerkraut are successfully using ascorbic acid to delay darkening of the refrigerated product packaged in plastic bags. One research report has appeared which reveals that the darkening of kraut is essentially an oxidative process. The oxidation of ascorbic acid appears to precede the darkening of color of the kraut. Oxygen and copper accelerate the oxidation. Darkening is less in the presence of ascorbic acid which acts as an antioxidant. The elimination of oxygen should contribute to the efficacy of ascorbic acid in the protection of color (Sedsky et a!., 1952). I n experiments with


fresh kraut and juice packed in one Ib. heat-sealed pliofilm bags, 150 to 250 mg. of ascorbic acid delayed darkening for one month under storage at 4" C. (40" F . )

Experimental packs have indicated that the application of ascorbic acid to brine-packed Spanish olives and artichoke hearts delays the development of undesirable color during shelf life. Discoloration of canned, strained carrots, occurring as a brownish tinge diffused throughout the contents of the ja r and as a localized gray-brown off-color in the top layer is apparently due to oxidation. It can be prevented by high vacuum. Low vacuum plus 0.01 to 0.1% ascorbic acid also prevents discoloration and improves the color of the product throughout the jar (Yourga, 1948).

Ascorbic acid will not prevent heat-induced browning of the non- oxidative type, for example, the browning occurring in dried frui t (Stadtman, 1948) or that caused by a reaction between sugars and nitrogenous compounds (Danehy and Pigman, 1950). I n heated concentrated milk products, the brown discoloration associated with the formation of hydroxymethylfurfural formerly thought to have originated from the ascorbic acid in milk now has been demonstrated to originate from lactose (Patton, 1950).

(Bauernfeind e t al., 1953).

VI. FLAVOR AND NUTRITIONAL VALUE IN JUICES

Commercially canned fruit and vegetable juices have been available as a food group only for the past twenty-five years, yet today they occupy a prominent part of our daily diet. During the past five years frozen fruit juice concentrates have become the largest selling frozen food item and make up an appreciable percentage of the total amount of fruit juice consumed.

A national survey covering 10,000 urban American families was conducted early in 1950, revealing that 92% of the homes serve juice in some form and 77% had served juice the day before the interviewer called. Breakfast loomed as the most significant serving period, with 74% of all servings; lunch, 8 % ; dinner, 11%; and other times, 7% (Anonymous, 1950d). The preponderance of breakfast menus that in- elude juices makes these products important carriers of ascorbic acid. According to a national retail store audit conducted by Market Research Corporation of America for the U. S. Department of Agriculture covering 1,800 food stores (Anonymous, 1 9 5 2 ~ ) ~ canned orange juice was carried by 95% of the stores, canned grapefruit juice by 89%, canned apple juice by 54%, canned pineapple juice by 83%, canned prune juice by 72%, canned tomato juice by 94%, frozen orange juice concentrate by


51%, frozen grape juice concentrate by 38% and frozen grapefruit juice concentrate by 24% during the month of August 1952. Other juices were also carried. United States consumer purchases of juices for the period of April to June 1952 (Anonymous, 1952d) were as follows: frozen orange juice concentrate, 11,797,000 gal. ; frozen grapefruit juice concentrate, 200,000 gal. ; frozen grape juice concentrate, 667,000 gal. ; canned tomato juice (single strength), 5,605,000 cases (approximately 18,900,000 gal.) ; canned prune juice, 1,259,000 cases ; canned pineapple juice, 4,206,000 cases ; canned apple juice, 929,000 cases ; canned grapefruit juice, 3,444,000 cases; and canned orange juice, 5,621,000 cases. The 1950 pack (Anonymous, 1951h) of canned and bottled single-strength, heat-processed juices was 95,700,000 cases ; in 1949 it was 94,500,000 cases. The 1950 pack of frozen juice concentrates, all types, was 30,100,000 gal. ; in 1949 it was 12,500,000 gal.

If the diet is to supply 75 mg. of ascorbic acid daily, fruit, vegetables, and their juices must be included. Fincke e t al. (1948) investigated the amount of ascorbic acid available to students from meals served a t Oregon State College, the University of Washington, and the University of Idaho. The ascorbic acid intakes were below the N.R.C. recommended level on 40% of the days when analyses were conducted. On only 2 of the 48 days when N.R.C. levels were achieved was it accomplished without the use of citrus fruits. Bessey and White (1942) found that the amounts of ascorbic acid in vegetables and fruits available to city children were not sufficiently great to affect the blood plasma values unless fruits or tomatoes were among the foods eaten daily. As further evidence of the importance of tomatoes, tomato juice, and citrus fruits or juices for an adequate intake of ascorbic acid, 230 assays of all food served for a 5-day period in the various R.C.A.F. messes situated across Canada showed an average content of 71.1 mg. of ascorbic acid per day. Of this amount, fruit and juices supplied not less than 47.5 mg. (Branion and Cameron, 1948). I n a 20 day study of school lunches in a Texan school using the National Research Council’s Recommended Dietary Al- lowances as a guide, Scoular and Bryan (1944) report that an adequate quantity of ascorbic acid for any age group was furnished by the school lunch on only one day of the study when 97-99% of the ascorbic acid intake was furnished by an orange. Children at the end of the luncheon period were given foods containing 44 to 100% as much ascorbic acid as those first served.

Richardson and Mayfield (1941) find that little attention has been given to the cost of fruits and vegetables in relation to their vitamin C content. They noted that canned citrus juices are good sources of the vitamin, likewise tomato juice if used in large amounts, but they were


surprised to note how many of the other fruits, including the home- canned and the commercially canned products, which supply less than 10 mg. of vitamin C per serving, are costly relative to their ascorbic acid content. Holmes e t al. (1941) made a study of vitamin C in fresh and commercially canned fruit and vegetable juices as purchased in the Boston market. The cost of supplying 50 mg. of vitamin C in the form of these juices varied from 2.1 to 158.5 cents.

The Council on Foods and Nutrition of the American Medical Associa- tion is vitally interested in the ascorbic acid content of processed juices and the efficiency with which fruit processing can consistently produce juice with a specific natural ascorbic acid content; it grants its seal of acceptance to juice packs which possess the following minimum content of natural ascorbic acid per 100 ml. of juice: orange juice, 40 mg.; grapefruit juice, 35 mg. ; and tomato juice, 20 mg. (Anonymous, 1946a). Later announcements have lowered the required level of natural ascorbic acid to 30 mg. for grapefruit juice (Anonymous, 1950h) and to 17.5 mg. for tomato juice per 100 ml. (Anonymous, 19511). To obtain the seal the packer must make assays and submit records over a prescribed period of time.

As mentioned earlier, nature’s factors (variety, sunlight, climate, maturity, etc.) plus those more nearly subject to control (handling practices, methods and processing, warehouse storing, etc.) all have an effect on the ascorbic acid content of a processed juice. Clifcorn (1948) has reviewed the canning data on citrus juices and, on the basis of 1944- 1946 studies, reports an average ascorbic acid retention of 97% for Texas and Florida grapefruit and an average retention of 98% fo r California orange juice during well-controlled canning operations. As- corbic acid retention as high as 96% has been obtained in the canning of tomato juice where efficient deaerators were operated (Clifcorn, 1948). Lower retention figures, 54%, have been obtained where the chopped fruit was subjected to prolonged heating or where some other important factor was overlooked. Under efficient manufacturing conditions tomato juice should contain a t least 80% of the ascorbic acid content of the trimmed tomatoes, according to Robinson e t al. (1945). Good processing techniques help to obtain a juice with a more uniform vitamin content.

Evidence is recorded that fresh product variables and commercial canning procedures can yield canned products with a wide range of ascorbic acid values. For example, ascorbic acid values of 6.3 to 13.0 mg. per 100 ml. (31/2 fl. oz.) for mixed vegetable juices (Anonymous, 1943b) and average ascorbic acid values of 4.3 to 25.0 mg. per 100 mL

TABLE I11

Ascorbic Acid Content of Juices

Juice

Apple Grape Grapefruit Orange Pineapple Tomato

U. S. Department of Agriculture data *

Number of Average Maximum Minimum samples value value value

mgJ100 g.

23 1.0 3.6 0.2 27 Trace 4.7 0.0

268 35.0 49.0 10.0 134 42.0 70.0 9.7 56 9.0 18.0 5.4

330 16.0 32.0 2.5

National Canners Association data t Number of Average Maximum Minimum

samples value value value

mg./100 g.

- - - - - - - - 54 33.2 44.7 26.3 36 35.0 52.4 11.1 18 8.5 14.2 3.2

140 14.4 30.0 2.5

* Watt and Bierrill, 1950. t Cameron and Esty, 1950.

Note: To convert values in terms of percentage of the daily adult requirement supplied by 4 fl. 02. of the above juices, proceed as follows: (1) ( 2 ) Multiply by 118, Multiply by 118. divide by 30, to obtain percentage in terms of Food and Drug Administration minimum daily requirement.

divide by 75, to obtain percentage in terms of National Research Council recommended daily allowance.


for tomato juice (Somers et al., 1945 ; Sale et. ul., 1946 ; Atkinson and Strachan, 1949) have been reported.

Several compilations have been made on the average, maximum, and minimum ascorbic acid contents of juices. Values on some of the common juices from two of the most recent compilations are presented in Table 111.

Apple, grape, pineapple, prune, and cranberry juices and peach and apricot nectars contain little or no ascorbic acid unless enriched. The enrichment of processed frui t juices naturally low in ascorbic acid is a subject of considerable interest a t the present time. I n many homes frui t juices low in ascorbic acid are used interchangeably with those of high ascorbic acid content. It is the contention of some groups that it would be desirable to enrich the former juices in order to make them more comparable with the latter from a standpoint of nutritive value (Esselen e t at., 1946). A recent release from the U. S. Department of Agriculture advises consumers on the selection of breakfast juices for maximum ascorbic acid content (Anonymous, 195Oi).

The acid-type frui t and vegetable juices are good carriers of ascorbic acid, thus providing a relatively stable environment. Several years ago the Canadian Government established, in its Meat and Canned Foods Act, specifications for ascorbic acid enriched apple juice (Peder- son and Beattie, 1944). During World War 11, the United States Army produced enriched apple juice (Esselen e t al., 1946), and limited enrichment of commercial apple juice continued after the war (Jones and Alexander, 1949; Aitlren, 1950; Wiegand and Yang, 1950). Blends of processed dried prune juice and grapefruit juice have been sng- gested as a breakfast beverage high in vitamin C (Cruess e t al., 1946).

Several investigators have studied the behavior of added ascorbic acid in juices. Esselen e t al. (1946) set up experimental packs of apple, cranberry, and grape juices enriched with ascorbic acid and observed the stability of this vitamin during storage. The value of added ascorbic acid on the color of these juices was measured by its effect on the light transmission values of the juices. Table IV contains data from the Esselen report. The added ascorbic acid in the fortified juices was well retained during processing and storage a t room temperature. The addition of 50 mg. of ascorbic acid per 100 ml., or 190 g. (6.7 oz.) per 100 gal., of juice before pasteurization should be adequate to provide a finished apple, cranberry, or grape juice that should contain a t least 35 mg. of ascorbic acid per 100 ml. after normal distribution to the consumer. Under good plant-operating conditions, the amount of added ascorbic acid might be slightly reduced. The addition of ascorbic acid to bottled apple juice had a marked effect in lightening the color of the


TABLE I V

Stability of Added Ascorbic Acid in Processed Fru i t Juices *

After storage, 21"-27" C. (70"-80" F.) Added

ascorbic After Fruit juice acid processing 6 months 8 months 9 montlis 12 months

mg.t/100 ml. juice

Apple juice - 50

Cranberry juice - 50 -1 50 t

Grape juice - 50

1.10 49.85 0.90

48.27 3.02

44.87

0.95 36.36 0

44.51 0

46.92

- -

0.00 36.00

1.34 32.31 1.40

41.60

* Esselen et d., 1946. t As determined by assay of Bessey, 1938. $ Packed in enameled cans; the other juices were packed in glass.

juice and in retarding darkening during storage. In the opinion of many people the lighter color in apple juice produced by added ascorbic acid improves its appearance. A favorable effect on flavor retention was noted in most cases. I n both bottled and canned cranberry juice, the addition of ascorbic acid was effective in retarding darkening that takes place during storage. The color of bottled grape juice was relatively stable during storage, and there was but little change in its light transmission characteristics o r visual appearance (Esselen e t al., 1946).

The Georgia Experiment Station has developed a method of using muscadine grapes for the production of grape juice. When bottled it is red in color, but when opened i t becomes purplish owing to oxidation. Furthermore, there is a marlred reduction in flavor. Dissolved copper, iron, and aluminum accelerate this change. As a result of experiments designed to prevent these changes, the addition of ascorbic acid was found to be beneficial. By adding 10 oz. of ascorbic acid per ton of grapes, oxidation is delayed and the final juice contains about 30 mg. of ascorbic acid per 100 ml., a desirable standard (White, 1950). A new grape juice developeu at the New York State Agricultural Experiment Station from white grapes utilizes added ascorbic acid before the crush- ing operation to safeguard the original color and prevent darkening, as well as to add to the nutritive value of the juice (Pederson e t al., 1953).

Lee et al. (1950) also prepared juices with added ascorbic acid and processed them by various methods previously found satisfactory for the individual fruit product. Some of the juice was stored raw, and part was pasteurized and stored. Color, ascorbic acid content, and flavor

TOLE V

Ascorbic Acid Content of Enriched and Unenriched Pasteurized Bottled Fruit Juices Stored a t Different Temperatures *

Stored 6 months Stored 11 months Added Immediately Fruit ascorbic after 21" C. 1 ° C . -8O C. -18°C. 21°C. l ° C . -8OC. -18" C.

juice t acid processing (70" F.) (34O F.) (18" F.) ( O o F.) (70" F.) (34" F.) (18" F.) (0" F.)

mg.S/100 ml. juices

Apple Deaerated Not deaerated

Strawberry, Culver

Cherry, Montmorency Fresh Prune, Italian

Rhubarb Raspberry, Red March

Apple-raspberry

40 40

40 40

40 40

40 40

-

-

-

31 31 32 67 39 25 59 41

46 37

8.3

- - - - - - - - - - 25 30 60 64 33 40 33 42 20 20 2 1 20 60 47 65 68 - 38 47 37

46 40 42 45 - 34 26

- -

7.7 8.6 4.9 7.7

-

* Lee et at., 1950. t Strawberv and raspberry, 7% sugar added: cherry, 7 % % sugar added; rhubarb, 10% sugar added. $ As determined by assay of Robinson and Stotz, 1945.

30 32 34 34 34 27 33 32

31 20 26 - 60 - 66 25 36 27 34 13 18 15 17 38 47 46 48 - - 41 42

37 44 42 42 - 36 25 30

-

7.8 7.6 6.5 7.5


studies were made on the juices after various storage periods. Some of the data of Lee appears in Table V. Ascorbic acid was well retained by apple, strawberry, cherry, prune, and rhubarb juices even after storage for 11 months a t 21' C. ('70" F . ) . However, with the exception of apple juice, the added ascorbic acid did not noticeably prevent or defi- nitely retard deterioration in the pasteurized juices a t this temperature. Ascorbic acid added to apple juice retarded development of brown color and slightly improved the flavor. It also retarded the development of brown color in strawberry juice and cherry juice, but i t hastened the destruction of the red color (Lee e t al., 1950). Marshall (1951) has also observed some protective action of ascorbic acid in apple juice.

An experiment station bulletin on the home processing of juices de- scribes the use of added ascorbic acid to retard color and flavor changes in fruit juices. One-half teaspoonful (about 1.6 gm.) of ascorbic acid is added to 2 gallons of pear or apple juice immediately after the pressing operation in the juice preparation (Yang and Wiegand, 1952).

It is now possible to produce an apple juice which retains more of the natural flavor and other characteristics of the apple (Pederson, 1947 ; Holgate e t al., 1948; Atkinson and Strachan, 1949). Juice freshly ex- pressed from an apple is colorless or has a very pale yellowish tan color. The important change in processing has involved the spraying of the fruit with an ascorbic acid solution during or immediately after milling but prior to the pressing operation. Sufficient ascorbic acid is also added to the juice to enable the canned product to retain a fresh flavor during storage at cool temperatures and to serve as a dietary vitamin C source. Such juices are delicately flavored and light colored, and they shonld be accepted readily by the public. Introductory commercial packs as large as 100,000 cases have been prepared (Atkinson and Strachan, 1949). Recently, nitrogen gas was included in the processing of this ascorbic acid treated product for further improvement (Atkinson and Strachan, 1950 ; Chambers, 1950). Frozen and canned natural apple juice concentrates are being developed which can be utilized in the preparation of natural-type apple ices and ice cream (Hening, 1949). Ascorbic acid added to conventional unpasteurized apple juice to be frozen prevents the development of a musty odor and helps to retain more of the original flavor (Lee et al., 1947).

Strachan (1942) made an extensive study of the feasibility of fortify- ing processed apple juice with ascorbic acid. He found that, with certain precautions and depending upon the exact method employed, the retention of added ascorbic acid in processed apple juice after several months of storage may be expected to be at least 50% and possibly as much as 96%.

U S E O F ASCORBIC ACID IN PROCESSING FOODS 379

These data, as shown in Table VI, were obtained during commercial trial runs.

TABLE VI

Enriclimeiit of Commercial Apple Juice with Ascorbic Acid *

Added Coiiteiit t % retained

ascorbic Ascorbic Total Ascorbic Total Juice treatment acid acid vitamin C acid vitamin C

mg./100 ml. juice

Plant 1 $ After processing 24.4 22.6 22.8 92.6 93.4 After 3 months

storage 24.4 23.5 24.0 96.3 98.3

After processing 24.6 13.7 15.5 55.7 63.0 After 2 months

Plant 2 $

storage 24.6 12.1 14.2 49.3 57.7

* Strachan, 1942. t As determined by assay modification of Bessey, 1938. t. Crushed-type juice, deaerated, nitrogen-filled headspace, 12-oa. cans. 0 Clarified filtered juice, not deaerated, 26-02. cans.

The data of Strachan (1942) and others (Clifcorn, 1948) prove that, if juices of high ascorbic acid retention are desired, the following steps should be included: heat juices quickly; eliminate air by deaeration or by use of inert gas and avoid its re-entrance ; avoid unnecessary pump- ing and handling ; eliminate contact with copper ; use short-cycle processing lines ; and seal in vacuum-pack containers with minimum headspace. If processing conditions are not ideal, slightly larger processing losses will require somewhat higher quantities of ascorbic acid to obtain desired levels.

Although it may be said that i t is economically, practically, and nutritionally feasible to add ascorbic acid to f rui t and vegetable juices to standardize their vitamin C potency (Anonymous, 1946c ; Esselen e t al., 1946 ; Siemers, 1946 ; Oser, 1948 ; Atkinson and Strachan, 1949 ; Cowgill, 1950), the level of enrichment also needs to be considered. Standardi- zation of enrichment means that a particular juice can be relied upon by the consumer to provide a definite ascorbic acid content. It does not necessarily mean that all fruit and vegetable juices should be enriched to the same level, but it would be desirable from the viewpoint of the consumer to have a nutritionally significant amount present for each particular juice.

If a juice is to be enriched to a level comparable to a high natural ascorbic acid level in that particular product, should this level be based


on present commercial fruit and vegetable varieties, or on the best variety available regardless of present commercial usage ? A high natural ascorbic acid content has been reported in Florida orange juice, 68 mg. per 100 ml. (Sale et al., 1947) ; in South American orange juice, 80-100 mg. per 100 ml. (Pecci and Ribeiro, 1943 ; Ribeiro, 1944 ; Ugon and Bertullo, 1945) ; in Texan grapefruit, 65 mg. per 100 ml. (Holmes et at., 1941) ; in Abachi pineapple juice, 62 mg. per 100 ml. (Miller and Schaal, 1951) ; in tomato juice, 33 mg. per 100 ml. (Atlrinson and Strachan, 1949) ; in selected strains of tomatoes, 53 to 160 mg. per 100 gm. of tissue (Lincoln e t al., 1949-1950), and in Calville apples, 27 mg. per 100 gm. of tissue (Howe, 1946). The role of genetics in food quality improvement is a t work and may give rise to varieties with higher vitamin content (Anony- mous, 1945c, 1950e; Somers and Beeson, 1948; Strachan e t d., 1951; Anonymous, 1952e) than present varieties. They may still have all the desirable flavor and production attributes, thus offering a future solution to the juice problem.

For the present, one practical level of enrichment for juice is to have i t contain the minimum daily adult requirement in one serving. I n a juice used for breakfast or luncheon this would amount to 30 mg. per 4 fl. oz., a frequently used volume. On the basis of trial runs, i t is usually anticipated that juices to which 45 to 50 mg. of ascorbic acid are added per 4 fl. oz. will contain 30 to 40 mg. after processing and market storage (Johnston, 1943 ; Esselen e t al., 1946 ; Siemers, 1946 ; Marshall, 1947 ; Atkinson and Strachan, 1949 ; Lee e t al., 1950). The cost of this amounts to approximately 3 cents per gallon of juice or I / lo cent per serving. From the viewpoint of the consumers’ desire for a vasied diet and because of the definite problems of intolerance and allergies caused by certain fruits (Feinberg, 1946; Urbach and Gottlieb, 1946; Jeans, 1951), a wide selection of juices rich in ascorbic acid is desirable. The availability and economy of crystalline ascorbic acid permit man to supplement his foods with it, thus enabling certain prodacts to become standardized sources of the vitamin by adjusting the variability found in the natural vitamin content normally resulting from the idiosyncrasies of nature and the habits of and abuses by man.

The development of concentration and freezing techniques has brought a variety of fruit juices to the consumer in a convenient concentrated form which, when properly processed and stored, retain more natural flavor than juices preserved by any other method (Anonymous, 1949a; Hellier and Weingartner, 1950 ; Kaufman and Campbell, 1950 ; Eskew et al., 1951). Frozen orange juice concentrate has led in this development and is the major concentrate on today’s market. Other frozen concentrates, namely, grape juice, grapefruit juice, lemon juice, pine-


apple juice, apple juice, lime juice, tangerine juice, prune juice, cranberry juice, tomato juice, etc., have been developed also.

Ascorbic acid is quite stable in these juice concentrates providing it is present a t the time the juice goes into storage and if approved storage and handling procedures are followed. Frozen concentrated orange juice, properly processed, has recently been declared to be an excellent and dependable source of ascorbic acid, the initial content having been assured by the use of good quality fruit, picked at the proper time. The excellent stability of ascorbic acid in frozen orange juice concentrate during frozen storage is well known (Cotton e t al., 1947; Roy and Russell, 1948; Rakieten e t al., 1951). The Council on Foods and Nu- trition of the American Medical Association has declared frozen concentrated orange juice eligible for acceptance and grants the use of the Council's seal when not less than 40 mg. of ascorbic acid is retained in each 100 ml. of reconstituted juice (Anonymous, 1951f). Apparently all frozen orange juice concentrates do not meet the above standard, since Anderson and Fagerson (1952), reporting on the ascorbic acid content of frozen orange concentrates on the retail market, find a range of values from 28.7 to 51.5 mg. per 100 ml. reconstituted juice.

Frozen grape juice concentrate and apple juice concentrate, which are naturally low in ascorbic acid content yet yield tasty reconstituted beverages, are now commercially enriched with added ascorbic acid by some manufacturers. Commercially enriched concentrates sealed in 6-fl. oz. containers have been stored at -18" C. (0" F.) and assayed for ascorbic acid content by the method of Rubin et al. (1945). For example, a frozen enriched apple juice concentrate assayed 15.2 mg. of vitamin C per ounce of concentrate after manufacturing and 15.5 mg. 6 months later; a frozen enriched grape juice assayed 15.0 mg. of vitamin C per ounce of concentrate initially and 15.1 mg. 9 months later ; and a sample of frozen enriched tomato juice assayed 38.5 mg. per ounce of concentrate initially and 36.6 mg. 12 months later (Bauernfeind e t al., 1953). Frozen enriched concentrated juices require a smaller excess of added ascorbic acid to maintain a claim level in the reconstituted juice owing to lower processing and storage losses in the concentrate as compared to heat- processed single-strength juices.

VII. ENZYME-CATALYZED OXIDATION IN FROZEN FRUITS

Twenty years ago Szent-Gyorgyi (1930) divided fruits and vegetables into two main groups: those that show discoloration on cutting or in- jury, such as the apple and the banana, and those that do not, such as the lemon and the orange. The tissues that discolor have a relatively


low concentration of ascorbic acid and a highly active phenol oxidase. A similar study has been made by Onslow (Joslyn and Ponting, 1950). I n the intact f rui t cell, oxygen tension, enzyme activity, and numerous chemical compounds are organized to carry on normal respiration and ripening practices. When cut f rui t is frozen and thawed, however, the cell walls are broken or their permeability is disturbed, which allows the constituents to mix, thereby accelerating enzymatic browning.

Ascorbic acid is known to be oxidizable by several systems (Joslyn, 1941 ; Ponting and Joslyn, 1948 ; Joslyn and Ponting, 1950) : direct oxidation by ascorbic acid oxidase ; indirect oxidation by quinones aris- ing from activity of peroxidase or by flavones in the presence of peroxidase and peroxide ; and indirect oxidation by orthoquinones formed by catechol plus polyphenolase and by the cytochrome system. It is believed that the rate of oxidation of ascorbic acid by polyphenolase may be extremely rapid. I n the presence of oxygen, for example, the browning of cut apples (containing polyphenolase and peroxidase) and the oxidation of its ascorbic acid seem to correlate well (Ponting and Joslyn, 1948). As long as ascorbic acid is present, the enzyme-oxidized phenolic compounds (oxidizable tannins and polyphenols) oxidize ascorbic acid. When the ascorbic acid content is exhausted, the oxidized phenols no longer serve as an intermediate in this reaction, and browning results probably due to further oxidation and polymerization reactions continued in the presence of oxygen and the enzyme (Joslyn and IIohl, 1948; Ponting and Joslyn, 1948; Reddi e t al., 1950). Ascorbic acid oxidase is absent in some fruit . Human availability studies indicate that ascorbic acid oxidase causes no biological inactivation of either naturally occurring ascorbic acid or added ascorbic acid i n vivo prior to absorption (Hochberg e t al., 1945).

Polyphenol oxidase is largely responsible for ascorbic acid losses and darkening, peroxidase activity being of minor importance (Ponting and Joslyn, 1948). In peaches a fairly good correlation mas establiihed between the oxidation of phenolic compounds and the extent of browning. Howe-cer, the initial rate of oxidation is roitghly proportional to enzyme activity, provided that sufficient substrate is present (Gua- clagni e t ul., 1949). Enzyme-catalyzed oxidative browning in f rui t products has been recently reviewed by Joslyn and Ponting (1930).

Most varieties of peaches, apricots, pears, plums, nectarines, cherries, bananas, and apples readily discolor when the frozen product is thawed. There is a concomitant off-flavor development. The addition of ascorbic acid to delay enzymatic browning was first tested in frozen fruit about 1938 and by fruit processors and experiment stations, but i t was not described in the literature until some years later (Tressler and DuBois,


1944 ; Bauernfeind and Siemers, 1945a, 194513 ; Bauernfeind et al., 1946; Hohl, 1946; Wiegand, 1946; Woodroof et al., 1946; Anony- mous, 1947; Woodroof et at., 1947; Joslyn and Eohl, 1948; Joslyn e t al., 1949-1950; Strachan and Moyls, 1949; Knight and Paul, 1950). The addition of ascorbic acid (150 to 250 mg. per pound of finished pack) : ( a ) does not introduce foreign substances or unnatural flavors; ( b ) is

FIG. 1. Sliced lye-peeled peaches, covered with medium syrup, frozen for 5 months, then thawed for 4 lir. Upper f ru i t had 200 mg. of ascorbic acid added to 4 oz. of syrup covering the 12 oz. of sliced fruit as a prefreezing treatment; lower fruit had no ascorbic acid added (Anonymous, 1947).


not detectable in the pack by appearance, smell, or taste; (c) is easily detected by applying recognized chemical and biological tests ; ( d ) significantly increases the vitamin C value of the pack; and ( e ) has been proved to be practical from the viewpoint of cost and quality (Anony- mous, 1947). Besides serving as an effective inhibitor of darkening, ascorbic acid has a striking effect in the retention of natural fresh flavor and aroma of fresh fruit (Hohl, 1946). The new proposed standards of identity for frozen fruit provide for the use of ascorbic acid singularly or in combination with citric acid (Anonymous, 1950b).

Since the treatment can only extend the retention of quality characteristics of the pack, top-grade, tree-ripened fruit should be used, with proven methods of packaging, transportation, and storage. Figure 1 demonstrates the value of added ascorbic acid in tha,wed frozen sliced peaches. Table VII contains data illustrating the behavior of added ascorbic acid in frozen peaches.

TABLE VII

Vitamin C Content of Thawed Frozen Sliced Peaches Packed with Sugar Syrup * t

Pack number

Assayed after holding 24 hr. a t 22" C .

after thawing (72" I?.) thawed

Added Ascorbic Total Ascorbic Total

Assayed immediately

yo sugar ascorbic acid vitamin C acid vitamin C in syrup acid content t. content t. content $ content t:

mg./lb. of pack

65 0 9 11 2 9 65 150 140 146 76 154 65 200 178 188 88 190 35 0 4 7 1 11 35 150 36 141 79 156

* Bauernfeind e t al., 1946. t Hale Haven, yellow-fleshed, freestone sliced peaches ( 3 parts) packed in sugar syrup (1

$ As determined by assay of Rubin et al., 1915. part by weight).

Frozen cut fruit processed with ascorbic acid has been observed to contain significant quantities of dehydroascorbic acid (Bauernfeind et al., 1946). The exact amount depends on the history of the pack between the time of processing and consumption. The enzyme activity of non-heated frozen fruit is almost inhibited at -18' C. (Oo F.) or lower, but a t higher temperatures and during thawing enzyme activity increases and converts ascorbic acid to dehydroascorbic acid. As this conversion takes place, the antioxidant value or reducing potential of

USE O F ASCORBIC ACID I N PROCESSING FOODS 385

the pack diminishes, for, although dehydroascorbic acid possesses biological activity, it possesses no antioxidant value in retarding the browning action. Before all the ascorbic acid in the package is converted to dehydroascorbic acid, some browning of the fruit may occur a t the surface during thawing where localized conversion is nearly complete. The relative amount of dehydroascorbic acid present in frozen packs not thawed serves as an index of the storage conditions during shipment and storage. Results from experimental and commercial packs of frozen fruit treated with ascorbic acid and held in frozen storage from 8 to 16 months, then thawed and assayed, demonstrated that 80% o r more of the added ascorbic acid is retained as biologically active vitamin C (Bauernfeind et al., 1946; Strachan and Moyls, 1949). Contrary to these data, other investigators working with frozen plant material report very rapid oxidation of ascorbic acid to dehydroascorbic acid a t a temperature of -20" C. (-4" F.) (Gustafson and Cooke, 1952).

Most frozen cut fruit can be treated by merely dissolving ascorbic acid with the sugar syrup in the dessert packs or by mixing it uniformly with the moist fruit and dry sugar in the pie and preserve packs (Hart- man, 1950; Alexander, 1951). Special frozen pie mixes have also been developed using the ascorbic acid treatment (Johnson, 1950). I n either instance the fruit must be completely covered by the solution of ascorbic acid, sugar, and juice.

It is a well-established fact that gases are contained within the intercellular spaces of apple tissue. When untreated frozen apple slices thaw, browning takes place inside the slice as well as on the surface. Cover- ing the conventional slices during freezing with an ascorbic acid-sugar syrup would retard external browning only, since the penetration of ascorbic acid solutions into the slice is limited. Two practical solutions are possible : the size of the slice can be reduced (julienne and flat, home- style cuts) to permit complete penetration of the ascorbic acid solution (Bauernfeind and Siemers, 1946 ; Bauernfeind e t al., 1947b ; Harris, 1951), or the oxygen content of the conventional wedge-shaped slice can be exhausted. I n the latter case ascorbic acid should be included in the solution used for exhaustion or applied to the fruit surface after the exhaustion treatment (Bauernfeind and Siemers, 1946 ; Bauernfeind e t al., 1947b; Grab and IIaynes, 1948; Guadagni, 1949; Knight and Paul, 1950; Rodgers et al., 1950). I n other special cases, such as the freezing of certain fruit purkes, i t is advantageous a t times to use nitrogen gas during the filling operations or to deaerate the ascorbic acid treated fruit before filling (Joslyn and Hohl, 1948).

I n using ascorbic acid successfully in a dry sugar pack for sliced ap-

Certain fruits, such as apples, require special processing.


ples, it is helpful to employ compounds which supplement or assist the action of ascorbic acid without significantly affecting fruit flavor. A large group of compounds including sodium chloride, hydrochloric acid, sulfites, thiourea, citric acid, malic acid, cysteine hydrochloride, glutathione, tyrosine, etc., were tested in the presence of added ascorbic acid in delaying fruit discolorations during thawing. Of the group the chlorides and the snlfites when carefully controlled, are the most promising. Since several states prohibit the use of sulfites without qualification there remains the chlorides, of which sodium chloride is best known, as a useful supplement to the action of ascorbic acid. Another known objection to the use of sulfites is that even though small amounts are used, some people are able to detect a slight foreign and objectionable flavor in baked goods made from apples so treated (Bauernfeind and Siemers, 1946). Johnson and Johnson (1952) have reported on a successful combination of sodium chloride, sodium bisulfite and ascorbic acid which retains natural flavor in frozen uncooked apple pulp.

Pitted cherries freeze well in a sugar syrup containing ascorbic acid, but when a dry sugar pack is prepared, the top portion of the pack easily discolors during the thawing process (Loutfi e t al., 1952). Preliminary trials indicate that the top section of the frui t in the dry-sugar pack can be better protected if the ascorbic acid is applied i n a gum or gum-sugar thickened solution to the top surface after the cherry-sugar mix is leveled and pressed in the can before the sealed pack is placed in the freezing room.

Enzymatic browning is markedly influenced by the pI I of the environment. Low pII values inhibit browning action but do not permanently prevent it (Woodroof, 1940; DuBois, 1949 ; Guadagni e t al., 1949). Early control measures for browning involved dipping the frui t in dilute solutions of hydrochloric, citric, and phosphoric acids ( Woodroof, 1940). On the basis of experiments with frozen products (Woodroof e t al., 1946) and on experiments with freshly cut f rui t (Luther and Cragwell, 1946) low and high levels of citric acid in combinations with ascorbic acid were suggested. It has been reported that citric acid and ascorbic acid (0.1% and 0.05%, respectively, based on the weight of the sliced peaches) stabilizes the ascorbic acid and improves the pack. The use of excess citric acid must be avoided or the frui t may taste too sour (Woodroof e t al., 1947). More recent studies have indicated that citric acid used with ascorbic acid has limited value in the freezing of sweet cherries (Strachan and Moyls, 1949) and in fruit purdes (Joslyn and IIohl, 1948) but little if any value in the freezing of peaches, apricots, and nectarines (Anonymous, 1947 ; Joslyn and IIohl, 1948 ; DuBois, 1949; Joslyn e t al., 1949-1950; Strachan and Moyls, 1949).


Ascorbic acid treated fruit should be thawed in the closed container, whether thawed slowly at room temperature or more quickly by placing the container in running water. After thawing, the container should be opened and the fruit used fairly promptly. If the thawed fruit is to be held longer (up to 24 hr.) it should be held a t refrigerated temperatures, 4' to 7" C. (40" to 45" F.), and the sliced thawed fruit should be covered with the sugar-juice solution. After thawing, ascorbic acid treated frozen fruit will eventually brown when the protective value of the ascorbic acid has been exhausted. Specific thawing directions should be included on all cans or packages of ascorbic acid treated frozen fruit, particularly for large units to be used in the bakery and ice cream trades (Bauernfeind e t al., 1947b).

A thawing indicator has been developed which, when packaged with the product, makes i t easy to determine whether frozen food packages have been subjected to thawing temperatures and to what extent. The indicator developed by Ramstad and Volz (1950) of Cornell University consists of an oxygen-permeable transparent envelope containing a gelatin gel in which is dissolved an enzyme, ascorbic acid, and a colorless phenolic compound capable of being oxidized. As the storage temperature increases, the enzyme catalyzes the oxidation of the phenolic compound, causing a dark coloration. The ascorbic acid delays the oxidation in amounts proportional to its inhibiting power. By using a series of gels containing known amounts of ascorbic acid in a package, i t is possible to get a history of thawing during shipment of the frozen product.

Freshly sliced apples are marketed to bakeries for pie use. Browning must be delayed in this product while the sliced fruit is transported and used by the baker. Ascorbic acid, in combination with salt (NaC1) and in edible acid (phosphoric or citric), has been found to serve as a satisfactory dipping solution for the slices. Darkening in slices so treated was retarded for 1 to 2 weeks at -1" C. (30' F.) or for 24 to 48 hr. at room temperature (Esselen et al., 1948).

Other methods for controlling the oxidative enzyme activity of fruit have been developed and used commercially (Denny, 1942 ; Hohl, 1945 ; Cruess and Seagrave-Smith, 1946 ; Wiegand, 1946 ; Grab and Haynes, 1948 ; Joslyn and Hohl, 1948 ; Esselen e t al., 1949 ; Joslyn e t al., 1949- 1950; Joslyn and Ponting, 1950). Sulfur dioxide is a very effective, low-cost, easily applied chemical inhibitor of browning. However, there are several disadvantages to its use: ( a ) it may cause unpleasant worlr- ing conditions because of its disagreeable odor; ( b ) it may frequently cause a residual sulfite flavor in the fruit or baked goods; ( G ) it may corrode the interior of the baker's oven when sulfited fruits are used


continually; (d) i t destroys fruit aroma and frequently bleaches the red color around the pit cavity of the peach; (e) i t destroys vitamin Br by a chemical cleavage in fruit and in baked goods (pies, cakes) made from enriched flour and sulfited fruit (Eauernfeind e t al., 1953) ; and ( f ) its use in foods is prohibited by several states. The new proposed standards of identity for frozen fruits, which exclude apples, bananas, and pineapples, do not provide for the use of sulfur dioxide. Some investigators have favored the combined use of ascorbic acid and sulfur dioxide (Johnson and Gnadagni, 1949; Lee e t al., 1951).

Heat destroys the oxidative enzymes (Dimiclr e t al., 1951) ; blanching is a time-honored method of applying heat to prevent browning. When this method is applied, the fruit is no longer fresh, as it takes on a stewed or cooked flavor. Steam blanching and water cooling of the fruit cause heavy losses in flavor, sugar, and soluble solids (20 to 40%), and softening of the fruit tissue (Cruess and Seagrave-Smith, 1946 ; Mylene and Seegmiller, 1950).

VIII. SYNERGISTIC ACTION IN EDIBLE FATS

The stabilization of edible fats during storage is a problem of much concern in civilian and particularly in military food operations. Oxida- tive rancidity in animal and vegetable fats is characterized in its very early stages by a sweet taste and an undesirable odor, which become more pungent and penetrating as the deterioration progresses. During these changes, oxygen unites with fat, forming peroxides and hydro- peroxides, which induce further oxidation. Antioxidants or inhibitors retard oxidation by inactivation of pro-oxidants o r by interruption of chain reactions (Lundberg, 1947 ; Riemenschneider, 1947 ; Michaelis, 1948).

Mattill has divided the inhibitors into three classifications : ( a ) substances which have primary antioxygenic action ; ( b ) substances which re-enforce antioxidants, known as synergists ; and (c) substances which do both (Mattill, 1945; Golnmbic, 1946). Ascorbic acid is very slightly soluble in animal fats. Even at a 0.4% level i t offers little or no primary antioxidant value in lard. At a level of 0.1% it re-enforces the activity of 0.04% tocopherol when added to lard. I n vegetable oil ascorbic acid is effective by itself. I n both instances, ascorbic acid acts synergis- tically to tocopherol, either added or naturally present (Golumbic and Mattill, 1941). Other instances of synergism with ascorbic acid compounds have been recorded (Isler, 1938; Olcott, 1941; Mattill and Golum- bie, 1943a, 194313, 1943c, 1943d j Callrins and Mattill, 1944 ; Lundberg e t al., 1944; Norris, 1945a, 1945b, 1945c, 1949; Riemenschneider and


Turer, 1945a, 1945b, 1948a, 1948b, 1952 ; Riemenschneider and Wells, 1945 ; Hall and Gershbein, 1949 ; Spannuth, 1949 ; Hall, 1950a, 1950b, 1950c, 1950d, 1951; Icraybill and Beadle, 1950). In a recent comparative study of synergists, ascorbic acid was found to be most effective with tocopherol and hydroquinone (Schwenk & Henderson, 1945 ; Clau- sen e t d., 1947). One commercial antioxidant formulation contains butylated hydroxyanisole and an alkyl gallate synergized with ascorbic acid and homogenized in an edible vegetable oil.

When ascorbic acid is introduced in aqueous solution in contact with lard, oxidation is accelerated. The presence of tocopherol with ascorbic acid inhibits this oxidation (Scarborough and Watts, 1949 ; Lehmann and Watts, 1951; Watts and Wong, 1951). The transitory formation of hydrogen peroxide during the autoxidation of ascorbic acid has been offered as an explanation of ascorbic acid acting as an oxidizing agent under certain conditions (Calcutt, 1951). I n emulsified foodstuffs, salad dressings, mayonnaise, and so forth, oxidation was retarded by added ascorbic acid (Gray and Stone, 1939a ; 1939b). Ascorbic acid compounds when added to peanut butter have been declared to retard the development of rancidity (Owen, 1950).

An explanation for synergistic action of ascorbic acid in fa t oxidation has been offered (Mattill, 1945; Golumbic, 1946). F a t peroxides readily oxidize phenolic inhibitors. The oxidation potential of ascorbic acid is below that of phenolic inhibitors, but, despite the large potential differences between fat peroxides and ascorbic acid, ascorbic acid is not appreciably oxidized during the induction period. The present explanation is that the oxidation of ascorbic acid is a sluggish two-step process which requires an intermediary. When a phenolic inhibitor donates hydrogen to a fa t peroxide and therefore becomes a phenoxyl radical, the lost hydrogen is restored by ascorbic acid, which thereby becomes dehydroascorbic acid. As long as ascorbic acid or any of its oxidation products remain to restore hydrogen to the phenoxyl group, fa t peroxides do not accumulate. Ascorbic acid is a potential reservoir of hydrogen for the maintenance of the status quo in the fat, but ascorbic acid cannot supply hydrogen directly to the nascent fa t peroxide ; it requires an intermediary.

Fat ty acid monoesters of I-ascorbic acid have been prepared (Mukher- jee e t al., 1950; Swern e t al., 1943), and, although they have been examined for useful properties in the food industry, no large commercial application has been found for them.


IX. RUSTING AND RANCIDITY IN FROZEN FISH

For a decade or two it has been known that frozen fish, particularly of the fatty type, tends to undergo enzymatic oxidation and become rancid (Banks, 1937; Tarr, 1942; Lundborg and Hard, 1946). I n the past, recommended procedures (Tressler and Evers, 1947) to overcome this type of deterioration have usually been to glaze the whole product with ice or to wrap the cut product in moisture-vapor resistant films. With either method the product must be stored at a very low temperature. These two treatments have been effective primarily in retarding dehydration. Low-temperature storage, -29" C. (-20" F.) , is costly to maintain but is effective in slowing the enzymic and chemical changes. About twenty years ago thought was given to retarding this type or deterioration by packing frozen fatty fish in the absence of oxygen. It was essential, however, to use containers impervious to gas since the presence of a small amount of oxygen would lead to an appreciable oxidation of fa t (Tarr, 1946a).

The use of acceptable antioxidants to delay oxidation in frozen fish is a relatively recent development. Because of the nature of fish and the processing followed, the use of water-soluble compounds is to be preferred. These compounds, when applied to the cut-fish surface by dipping, spraying, or brushing techniques, permit their quick diffusion into the water phase of the fish flesh and thus retard the enzyme-catalyzed oxidation and rancidification. Treatment of cut-fish tissue with ascorbic acid has been demonstrated to retard the development of rusting, yellow- ing, and rancidity (Tarr, 1946b, 1947; 1948; Bauernfeind e t al., 1948, 1951; Stoloff et al., 1948; Stoloff, 1951). Although such treatment actually tends to increase the nutritive value of the fish, no added value is claimed for the treatment, since most of the ascorbic acid is destroyed during storage and in the coolring process. The effectiveness of ascorbic acid (an expendable substance) is believed to be due to its entrance into the normal fish oxidase system and to its ability to unite easily with the oxygen of the air. Support for the latter simple conception of the mechanism is gained from the observation that a glaze of R water solution of ascorbic acid on frozen cut fish gives significantly greater protection than plain water glazes. Data on the effect of ascorbic acid on frozen fish are presented in Table VIII.

Commercially, two methods of applying ascorbic acid are practical, the dip and the spray application. I n both cases, aqueous ascorbic acid solutions, with or without thickening agents, may be employed (Anony- mous, 1950g; Lantz, 1950; Tarr et al., 1950, 1951; Bauernfeind et ul., 1951). If aqueous solutions are employed in the dipping method, a


TABLE VIII

Effect of Added Ascorbic Acid on Mackerel Fillets during Frozen Storage * t

After 8 months'

-18" C. (0" F.) Pack treat- num- Dipping ment Peroxide Observations 011 observations on

1 Water 10 6.6 Rancid odor Slightly rancid 2 17. ascorbic

Time of After 2 months' storage storage a t a t -11" C. (12" F.)

ber solution see. value t thawed fish cooked fish

acid in water 10 1.6 Good color Fresh fish flavor

* Banernfeind et nl. , 1948. t Mackerel fillets were secured within a few hours from fish brought into Boston Harbor in

I Milliliters of 0.002 N sodium thiosulfate per gram of fat. 5 Partially thawed fish were individually pIaced in a small pan, covered with hot water, and

early June, promptly dipped a t 4' C. (40' F.), wrapped in cellophane, and quickly frozen.

heated until cooked.

concentration of ascorbic acid of 0.5 to 2% solution is used for a 10- to 2 0 - s ~ ~ . dip. If thickened solutions are used, an ascorbic acid concentration of only 0.25 to 1% is used, since during the dipping operation more of this viscous solution adheres to the fish tissues. In treating large, dressed fish with ascorbic acid, a spraying technique is recommended, using a conventional spray gun (only aluminum or stainless steel to come in contact with the solution) operated under low pressure. Ascorbic acid solutions with or without thickeners are stable during the spraying operation. Commercial trials on dressed salmon, salmon steaks, and salmon fillets as well as on mackerel fillets and other sea fish have demonstrated the effect of ascorbic acid in retarding deteriorative changes previously assumed to be normal. Trials with fresh-water fish such as lake trout, white fish, and lake herring have also given excellent results, thus demonstrating that the ascorbic acid treatment is not limited to ocean fish (Bauernfeind et at., 1951). As in the processing of frozen fruit, the fish must be of top-quality grade, and approved processing, freezing, and storage practices must be used. Banks (1952) did not obtain significantly improved results in cold-storage herrings after treatment with ascorbic acid or other antioxidants.

Some darkening of frozen, freshly shucked oysters occurs during storage, the cause of which is unknown. The use of ascorbic acid, up to the level of 300 mg. per pound, as a prefreezing treatment did not delay darkening in a year storage test (Pottinger, 1952). It is not known whether the development of black spots or bands in frozen uncooked shrimp, an enzymic deteriorative change, can be retarded by the use

'392 J. C. BAUERNFEIND

of ascorbic acid. The sulfites have been found to be effective (Fieger, 1951 ; Alford & Fieger, 1952).

X. DISCOLORATIONS AND RANCIDITY IN MEAT PRODUCTS

Self-service merchandising of meats packaged in weighed quantities and wrapped in transparent films has emphasized the need for desirable meat color in fresh, frozen, and cured products. The natural color of air-exposed fresh meat is a light cherry red. The tissue myoglobin combines with the oxygen of the air, producing oxymyoglobin, a bright red pigment. Myoglobin is a dull or dark red pigment readily noted when meat is first cut. Packaged meat frequently discolors, particularly if frozen, and takes on a brownish red color due to the formation of methemoglobin. Films possessing oxygen-transfer properties are helpful in holding the desirable red color in meat. Exposure to light does not seem to greatly affect fresh meat color. On the other hand, cured, smoked, or table-ready meat possessing the pink color of nitric oxide myoglobin and wrapped in transparent film rapidly discolors under the lights of the display cases to shades of brown and gray, owing to oxidation of nitric oxide myoglobin. The oxidative nature of this color change is revealed by the observation that processed meat under a high vacuum does not discolor upon exposure to light (Lavers, 1948; Allen, 1949; Kraf t and Wanderstock, 1950; Ramsbottom et al., 1951). Frozen ground meats are subject to the development of rancidity, in addition to color problems (DuBois and Tressler, 1943).

The addition of ascorbic acid to meat may result in an improvement of meat color. If it is added to the surface of beefsteak or chopped beef or ground pork shoulder and the meat is refrigerated, the bright red color is better retained than in control samples (Watts and Lehmann, 1952a). Ascorbic acid also aids the fixation of nitric oxide myoglobin and lessens the discoloring effect of light (Chang and Watts, 1949).

Watts and Lehmann (195213) describe the reactions of the hemoglobin pigments with ascorbic acid as follows:

1. Reduced myoglobin or hemoglobin (Hb) does not react with ascorbic acid in the absence of oxygen.

2. Oxyhemoglobin (HbOz) , receiving hydrogen from ascorbic acid, forms the unstable hydrogen peroxide hemoglobin (Hb€IZOz). Par t of this forms the green decomposition product choleglobin, and part oxidizes to methemoglobin.

3. Methemoglobin (metHb) , the ferric hemoglobin, is reduced to hemo-


globin (Gibson, 1943) which, in the presence of oxygen, becomes oxyhemoglobin. The above three reactions may proceed simultaneously.

Ascorbic acid HbO, ___ + HbH,O, t Choleglobin

(plus dehydroascorbic acid)

fog Ascorbic acid J. H b +- metIIb

(plus dehydroascorbic acid)

4. Nitric oxide hemoglobin (NOHb) forms readily in the presence Ascorbic acid tends to stabilize this com- of ascorbic acid and nitrite.

pound.

I n a study of the effect of ascorbic acid on hemoglobin employing washed red cells of hog or beef blood, Watts and Lehmann (1952b) found temperature and concentration of the ascorbic acid solution to be of the greatest importance. At elevated temperatures, 40" C. (104' F.), discolorations of the hemoglobin solutions quickly occur, owing to choleglobin formation. At room temperature low concentrations protected the hemoglobin color ; higher levels brought about discolorations. Under refrigerated storage better protection of red color was noted, but a t the highest level of ascorbic acid concentration (25 times the lowest level) some choleglobin formation occurred. Under frozen storage, all levels of ascorbic acid produced frozen solutions of hemoglobin possessing a dull red color, although lower levels of ascorbic acid returned the hemoglobin color to a brighter red color upon thawing in the presence of oxygen.

These results of Watts and Lehmann help explain practical tests in which fresh meat dipped in aqueous ascorbic acid solution and stored in the refrigerator unwrapped or wrapped in proper films is improved in color through the reduction of methemoglobin and the stabilizing effect on oxyhemoglobin by ascorbic acid (Coleman, Steffen and Hopkins, 1949, 1951 ; Cominsky, 1950 ; Bauernfeind e t al., 1953). For this purpose 100 to 400 mg. of ascorbic acid is added per pound of meat.

Fresh meat to be frozen and marketed in this form probably should not be treated with ascorbic acid, owing to the brownish red discoloration produced in the meat in a frozen state, even though added ascorbic acid delays the development of rancidity in meat held in prolonged storage. With thawing and exposure to oxygen, the discoloration is slowly reversed.

Chang and Watts (1949) concluded that ascorbic acid, owing to its


strong reducing action, appears to be by far the most promising of any synergist tried for preventing both rancidity and color loss in cured meat. The stabilizing effect of ascorbic acid on nitrosohemoglobin prompted these investigators t o suggest the combined use of ascorbic acid and nitrite in the curing brine of meat, and ascorbic acid as an ingredient in canned meat. These suggestions were predicated on the presence of an adequate tocopherol (or other phenolic inhibitor) content from the meat and the smoking process (Watts and Wong, 1951). Ex- periments were carried out by Watts and Lehmann (1952a, 1952b) on ground pork treated with nitrite, ascorbic acid solutions (adjusted to pH 6.0 to 6.4), and salt, singularly and in combination. Samples were held

TABLE I X

Effect of Ascorbic Acid and Salt on Color and Rancidity of Frozen Ground Pork * t

Pack num- Additions to Peroxide Surface ber 1 2 3 4 5 6 7

ground pork 5

Control, no addition Ascorbate, 0.1% Nitrite, 0.02% Ascorbate and nitrite Salt, 2% Salt and ascorbate Salt and nitrite

ralue t 0 0 0 0

11.5 13.3 8.1

8 Salt and ascorhate 9.0 aiid nitrite

appearance Slightly dulled Increased dulling Brownish gray Bright pink $ Gray Gray Pink 11

Very bright pink

Odor and flavor

- Off-flavors and odors Off-flavors and odors Cured meat flavor

and color after cooking

Definite cured meat flavor aid typical cured meat color a f te r cooking

*Watts and Lehmann, 1952a, 1952b. t Stored 2 months at -17' C. ( l o F.). $ Millimoles of peroxide per 1,000 g. of fat. § Present after 4 days of storage. II Developed after 4 to 6 weeks of storage,

under refrigerated and frozen storage (see Table IX). Ascorbic acid was found useful in developing and maintaining cured meat color in ground pork containing nitrite. This was achieved by the incorporation of a mixture of nitrite and ascorbic acid, followed by heating o r freezing to accelerate color fixation. Whereas the use of salt and a low pH medium accelerated color development, nitrates and sugar had no effect on the reaction.


XI. OXIDIZED FLAVOR IN DAIRY PRODUCTS

“Tallowy” or “cardboardy” flavors resulting from oxidative rancidity of the cream fraction of the milk are troublesome off-flavors in many dairy products (Brown and Thurston, 1940 ; Greenbank, 1948). These flavors develop more intensely in certain lots of fluid milk during the winter when the cows are fed dry rations. The development is influenced by oxygen content of the milk, oxidative enzyme activity, oxidation-reduction potential, exposure of the milk to light, presence of dissolved copper, tocopherol, and ascorbic acid content of the milk, etc. It is often associated with high-quality milk. It has been stated that one of the chief reasons consumption of milk is not greater than at present is the off-flavors which occur so often (Chilson, 1935).

The biochemical mechanisms causing these changes are unknown, bnt various theories have been proposed. These theories are based on enzyme action, “ redox” potentials, reducing compounds, ascorbic acid, etc. (Ihnde, 1932 ; Chilson, 1935 ; Brown and Thurston, 1940 ; Greenbank, 1940 ; Krukovsky and Guthrie, 1945 ; Greenbank, 1948 ; Krukovsky, 1952). From reports i t is evident that the development of oxidized flavor in susceptible milk can be controlled either by the complete and rapid oxidization of all ascorbic acid present in the milk by sunlight or hydrogen peroxide (Krukovsky and Guthrie, 1945, 1946; Chilson e t al., 1949 ; Guthrie and Krukovsky, 1949) o r by the addition of more ascorbic acid to the milk (Chilson, 1935 ; Krukovsky and Guthrie, 1946). Chil- son e t al. (1949), after examining both methods, found that the latter method, namely, the addition of ascorbic acid to milk, is of commercial interest a t the present time.

Freshly drawn cows’ milk may contain as much as 30 mg. of ascorbic acid in the reduced form per liter or per quart. The customary handling methods, pasteurization, and the long time interval necessary for shipment and storage between milking and consumption may destroy 70 to 80% of the natural ascorbic acid originally present (Hand, 1943; Law- rence e t al., 1945 ; Stewart and Sharp, 1946 ; Holmes, 1951). Although not all cows’ milk low in natural ascorbic acid will develop the oxidized flavor, milk capable of developing the flavor usually becomes tallowy when 50 to 75% of its natural reduced ascorbic acid is oxidized and significant amounts of dehydroascorbic acid are present (Leeder and Herreid, 1942 ; Krukovsky and Guthrie, 1945). Milk susceptible to the off-flavor development loses its natural ascorbic acid content a t a faster rate than non-susceptible milk (Sharp e t al., 1937; Trout and Gjessing, 1939 ; Weinstein et al., 1948). When milk is taken from the cow it contains no oxygen; however, when it comes in contact with the air it ab-


sorbs oxygen. This oxidizes the natural ascorbic acid content of the milk and also brings about oxidized flavor development. Deaeration of the milk preserves both the natural ascorbic acid content and the original flavor of the milk (Guthrie, 1946).

I n 1935 Chilson (1935) added reducing agents such as ascorbic acid to milk at levels of 50 to 60 mg. per liter. The development of the tallowiness, which, under ordinary conditions, would develop within 3 days, was delayed for 7 days by this treatment. Chilson also noted that the addition of ascorbic acid to milk gave it a pleasing flavor, apparently superior to that of the original milk. Since that time a number of studies have shown a protective influence of ascorbic acid on milk flavor when added in sufficiently large quantities (35 to 100 mg. per quart or liter) (Dahle and Palmer, 1937; Sharp et al., 1937; Kieferle and Seuss, 1939; Greenbank, 1940; Sharp and Hand, 1940; Swanson and Sommer, 1940; Corbett and Tracy, 1941; Krukovsky and Guthrie, 1946; Reed, 1947; Weinstein et al., 1948; Chilson et al., 1949). Some of these reports (Krukovsky and Guthrie, 1946 ; Holmes and Jones, 1948 ; Chilson e t aZ., 1949; Holmes, 1949) contain data on the stability of ascorbic acid in milk during storage.

I n more recent studies the ascorbic acid treatment of fluid milk has been tested on a commercial scale. Two 100-gal. lots of milk were processed in an identical manner a t a dairy plant in a western college, except that 12.9 g. of ascorbic acid was added to one batch just after pasteurization a t 54' C. (130" F.), and prior to cooling (Weinstein e t al., 1948). One hundred and two trials like the one just described were run between December, 1947, and April, 1948. During that period 45% of the control lots of milk developed oxidized flavor, whereas none of the lots treated with ascorbic acid developed this off-flavor. Flavor tests were made on milk samples previously stored for 72 hr. a t 4" C. (40" F.).

Another study, published by Chilson e t al. (1949), also concerns split batches of milk representing ascorbic acid treated milk and control milk. Ascorbic acid was added at the rate of 1.5 g. per 100 lb. of milk (approximately 35 mg. per quart) after pasteurization but before cooling. Storage observations on these sixteen lots of milk are summarized in Table X.

The ascorbic acid content of the treated milk was three times that of the control milk at the start. After 5 days' storage the ascorbic acid content of the treated milk was within the range normally found directly after milking. No oxidized flavors were detected in the treated milk during the 5-day storage period, whereas oxidized flavors began to develop in the control milk on the second day and became more intense with further storage.

TABLE X

Relationship of Ascorbic Acid Destruction and the Development of Oxidized Flavor in Pasteurized Milk *

Control milk (4 lots) Trial num- Days Ascorbic acid Ascorbic acid Flavor ber stored i mg./l. t loss in mg. score $

Winter ration; February and kiaroh

I 0 14.7 - 4- 1 11.6 3.1 4-

3 3.4 11.3 2++ 2+++

5 1.3 13.4 If++ 3++++

Grass ration; April and May

I1 0 17.2 - 4- 1 12.8 4.4 4- 3 4.4 12.8 3-

I+ 5 1.1 16.1 I+

3++

* Chilson et al., 1949. t Refrigerated 2 ' to 4' C. (35' to 40' F.), protected from light. $ As determined on assay of Woessner e t al., 1939. I No oxidized flavor (-) : increasing intensity of oxidized flavor ( + to + + + + ). II Ascorbic acid added at rate of 1.5 g. per 100 Ib. of fluid milk.

Treated milk 11 (4 lots)

Ascorbic acid Ascorbic acid Flavor mg./l.S loss in mg. score

48.6 - 4- 44.0 4.6 4- 33.2 15.4 4-

24.2 24.3 4-

51.2 - 4- 48.6 2.6 4- 34.3 16.9 4-

26.4 24.8 4-

cu W 4

398 J . C. BAUERNFEIND

The Bureau of Dairy Industry has also reported on the protective value of added ascorbic acid and found that, the sooner fresh milk is fortified with ascorbic acid, pasteurized, homogenized, deaerated, and cooled, the better it will keep (Reed, 1947). The Food and Nutrition Board of the National Research Council has issued a statement favoring properly planned and controlled market trials, preferably under the auspices of universities for the purpose of gaining further evidence on the merits of ascorbic acid treated milk (Anonymous, 1949b).

Ascorbic acid treated milk should not be contaminated with copper by the use of copper equipment during processing or unduly exposed to sunlight. As more soluble copper is added to milk, more ascorbic acid is required to retard the oxidized flavor (Weinstein e t ccl., 1948; Stribley e t al., 1950). Exposure of milk to sunlight quiclrly nullifies the protection of added ascorbic acid (Chilson e t al., 1949).

Vitamin C enrichment of fluid milk is practical if contamination with copper is rigidly prevented and if the milk is protected from light (Woessner e t al., 1940). As containers, the ruby glass bottle proved to be the most protective against light, followed by amber glass, paper, and the clear glass bottle. Only 5 and 17% destruction of ascorbic acid was observed in the ruby bottle after 1 hour of sun irradiation during winter and summer respectively (Herreid e t al., 1952). blnltivitamin cnriched milk, some formulas of which contain 30 mg. of added ascorbic acid per quart, has been developed for the immediate interest of those having specific dietaxy problems (Manning e t al., 1945; Grindrod, 1949 ; Weckel, 1951).

Earlier investigators attempted to feed ascorbic acid preparations to cows in order to change characteristics of the milk. Comprehensive in vivo and in v i t r o experiments have shown ascorbic acid to be destroyed in the rumen of the cow (Vavich e t al., 1945). Furthermore, the cow, unlike humans, normally synthesizes ascorbic acid for her own needs.

An abnormal flavor in homogenized milk, known as solar or light-induced “burnt” flavor, seems to be associated with the proteins of milk. The addition of ascorbic acid has no preventive effect on the solar- activated flavor of homogenized milk (Weinstein and Trout, 1951).

Megaloblastic anemia, a macrocytic anemia occurring in infants 5 to 11 months of age, indicates an interruption of normal hematopoiesis. Milk, the chief article of the diet in early infancy, contains both vitamin BI2 and pteroylglutamic acid. Present evidence points to the unlikeliness of a simple o r uncomplicated deficiency of these factors as the cause of this anemia. Clinical reports have frequently recorded a dietary inade- quacy of ascorbic acid in infants with megaloblastic anemia (May et al.,


1950; Anonymous, 1 9 5 1 ~ ) . Scurvy is not uncommon in infants of this age group (Anonymous, 1951e). Indirectly increased ascorbic acid intakes have been found beneficial. During the past two years megaloblastic anemia has declined significantly, an observation coincident with the introduction of a procedure of adding ascorbic acid to two com- monly used proprietary infant foods. Earlier, many infants who developed megaloblastic anemia had been on formulas containing these foods (Anonymous, 1951d). The subject of ascorbic acid in maternal nutrition and child health has been recently reviewed by Toverud et al. (1950).

Although i t is possible to add ascorbic acid to the infant’s formula in the home prior to warming by means of specially compounded tablets (Holmes et al., 1951), many liquid and dry infant milks are already enriched with ascorbic acid.

Hodson (1949) has studied the effect of terminal heating on the ascorbic acid content of an enriched infant formula (evaporated milk base). With a prescribed low-pressure terminal heating, an average ascorbic acid retention of 95% was obtained; with a prescribed high- pressure terminal heating, an average retention of 97% was obtained. McCollum and Grubb (1944) developed and studied a fortified evaporated milk product containing a minimum content of 50 mg. of ascorbic acid per 141/2-oz. can. Data have been collected on the stability of ascorbic acid in the sealed can during storage as well as its characteristics during formula preparation. The nutritional adequacy of a similar product was also reported by Gonce and Lewis (1950).

The ascorbic acid content of evaporated milk is quite low (Josephson and Doan, 1945; Stewart and Sharp, 1946), and although added ascorbic acid has no effect on the flavor improvement of the product, research studies have been completed emphasizing the suitability of evaporated milk as a special dietary product. Enrichment of evaporated milk with 50 to 100 mg. of ascorbic acid or sodium ascorbate per liter of reconstituted milk has been judged to be commercially feasible and economical if the cans are sealed under vacuum. Evaporated milk enrichment a t the 100-mg. level and packed under vacuum retained 71% of the added ascorbic acid after processing and storage for 12 months at room temperature. Infant formulas prepared with ascorbic acid enriched evaporated milk can be depended upon as a source of this vitamin in infant feeding (Josephson and Doan, 1945; Doan and Jo- sephson, 1946).

Dried whole milk is normally gas packed by vacuumizing the cans and filling the headspace with an inert gas (Coulter and Jenness, 1946). The removal of oxygen from the container has proved to be the most


effective method of preventing tallowiness. This method protects as long as the can is kept sealed. However, owing to partial oxidation by minute amounts of oxygen left within the sealed can, the product in a stored container opened at the same time as a recently sealed container has a shorter life than the fresher product. Ascorbic acid is suggested as one of the antioxidants which show promise in prolonging storage (Coulter e t al., 1950). The removal of ascorbic acid from milk in the fluid state as suggested by Krukovslry and Guthrie (1945, 1946) does not constitute an effective method of inhibiting the development of tallowy flavor in dried milk (Coulter e t al., 1950).

In drying milk containing natural ascorbic acid, it was noticed that the milk seemed to vary in the degree of retention of ascorbic acid during processing. Milk that retained the greatest amount of apparent ascorbic acid during processing possessed the best keeping qualities (Wright and Greenbank, 1949). Fluid milk containing added ascorbic acid when dried was found to be superior in keeping quality to control samples (Reed, 1947; Wright and Greenbank, 1949). The addition of 100 mg. of ascorbic acid or 1 g. of sodium citrate per liter of milk did not ma- terially prolong the storage life of dried whole milk packed in air and stored a t 29' C. (85" F . ) . A combined treatment increased storage life by 3 to 5 months. Eventual staleness was noted in the treated packs as compared to tallowiness in the control packs (Decker and Ashworth, 1951).

Ascorbic acid is also currently added to dry milk products especiallg designed for infant feeding. A study has been published on the characteristics of such a dried product in which ascorbic acid was added to the liquid product prior to drying in regular commercial operation. The enriched product packaged in 1-lb. containers hermetically sealed under inert gas lost 2.7% ascorbic acid after 1 year of storage a t room temperature. After the containers were opened and exposed to the air for 4 and 8 days the losses were 3 and 6.5%, respectively. Reconstituted formulas containing 75 mg. of ascorbic acid per quart retained 69 mg. after 24 hr. of refrigerated storage; after terminal heating and 24 hr. of storage, 60 to 64 mg. were retained. Warming the refrigerated formula quickly to body temperature just before feeding did not affect the ascorbic acid content (Keeney e t d., 1949).

Studies are now being continued on the comparative value of oxygen removal and the ascorbic acid method, as well as on the combined treatments in commercial plant trials. More research is desirable on the value of added ascorbic acid plus partial gas treatment (headspace re- placement) as compared to the more involved complete degassing procedures. A current study on the interrelationship of processing treat-


ments and oxidation-reduction systems as factors affecting the keeping quality of dry whole milk revealed that the ascorbic acid content alone as with other individual criterion is not a reliable measure of the resistance of the dried product to oxidation (Harland et al., 1952).

Vitamin C has been recommended for the enrichment of sour milk in order to increase the daily intake of ascorbic acid in Sweden (Bang, 1951).

Frozen homogenized milk and concentrated milks have been considered both for war and peacetime use. After months of frozen storage, however, deteriorative changes take place. The two major problems to be solved are methods for the preservation of flavor quality and the prevention of separation of milk solids (Doan and Leeder, 1944; Babcock et al., 1949 ; Anderson e t al., 1950 j Anonymous, 1950a). Investigations over the past years (Bell, 1948; Babcock e t aZ., 1949; Bell and Mucha, 1949; Randall, 1949; Anderson et al., 1950; Bell & Mucha, 1952) have demonstrated that the development of oxidized flavor can be retarded and the original flavor retained by the addition of ascorbic acid; however, no significant improvement in delaying physical separation of the milk has been noted by this treatment. To demonstrate the behavior of added ascorbic acid in frozen homogenized milk, the 90-day storage results of Anderson e t al. (1950) are presented in Table XI.

TABLE XI

Flavor Evaluation and Ascorbic Acid Stability in Frozen Homogenized Milk *

Sam-

ple number

Ascorbic acid added

g./lOO lb. fluid milk

0 (control) 1.5 3.0 6.0

12.0 t

After 90 days' storage at -18" C. (0" F.)

Ascorbic Total PH Taste and flavor acid vitamin C

g./lOO lb. fluid milk

6.72 Strongly oxidized 0 0.37 6.69 Oxidized slightly 1.06 1.32 6.69 Very slightly oxidized 1.61 2.25 6.68 Normal, no off-flavor 4.4 5.12 6.62 Normal, no off-flavor 11.30 12.10

* Anderson et aZ., 1950. t Initial assays indicated more nearly 13.0 g. were added instead of 12.0.

Babcock and others (1952) haxe reported that added sucrose improves the physical properties of frozen milk. Sucrose plus ascorbic acid (100 mg. per 1.) to homogenized milk frozen a t -23.3' C. (-10' F.) and stored at -18" C. (0" F.) increased the time the milk remained normal in appearance and more than doubled the time it remained normal in flavor.


A study is now in progress on the value of added ascorbic acid as a means of delaying the oxidized flavor development in cream. As a result of ten trials on 40% butterfat pasteurized cream frozen and stored for 6 months a t -23" C. (-10" F.), it was found that the addition of 100 mg. of ascorbic acid per kilogram of cream prevented the flavor defect. Low levels of ascorbic acid addition tend to increase the degree of oxidized flavor development. Quick freezing of the ascorbic acid treated cream and prompt use of the defrosted cream are also necessary to retard the oxidized flavor development. Slow freezing, prolonged holding of the defrosted product, and contamination with copper promote ascorbic acid oxidation (Smith e t al., 1952). A favorable effect of added ascorbic acid in delaying the oxidative changes of butter has also been reported (Rescigno, 1951).

Tallowy or oxidized flavor occurs more often in ice cream than is generally recognized. Strawberry and pineapple ice cream are quite susceptible, whereas chocolate and vanilla ice cream are more stable. It is believed that the tannins and vanillin help to protect the latter products. The addition of Avenex, an oat flour product, has also been helpful. The occurrence of oxidized flavor is not regular in its appearance but depends on manufacturing variables and on the quality of the dairy products which is in turn affected by the feed of the cow, copper contamination of the milk, etc. (Brown and Thurston, 1940; Greenbank, 1948). Normally, ice cream contains little or no ascorbic acid (Holmes e t al., 1946).

Some preliminary experiments were made to determine the effect of adding ascorbic acid to ice cream a t levels of 30 to 60 mg. per pound of mix. I n one study, strawberry ice cream prepared with commercial- type equipment and containing added ascorbic acid was judged to possess better flavor than the control sample, after both products had been stored for 4 months a t -18" C. (0" F.). It was found that, even though the control strawberry ice cream was prepared from frozen berries, the resulting ice cream possessed a low and variable reduced ascorbic acid content. Since ascorbic acid losses during ice cream manufacturing are very small, the low values in the control samples must be attributed to oxidation prior to manufacturing. Frozen strawberries used for commercial ice cream manufacturing are treated with ascorbic acid, according to the specifications of one ice cream manufacturer. Ascorbic acid treated frozen sliced peaches (150 mg. per pound of pack) used in the preparation of peach ice cream produced a product which retained its peach flavor over a 2-month storage period at -18" C. (0" F.), whereas ice cream prepared from non-treated frozen sliced peaches developed an oxidized flavor over the same storage period. Similar findings also


apply to banana ice cream prepared from frozen and fresh fruit (Bauern- feind e t al., 1953).

XII. OXIDIZED FLAVOR IN BEVERAGE PRODUCTS

Over the past fifteen years there has been an increasing amount of beer packaged in cans and bottles. Since beer so packaged may not be consumed for a few months, it is subject to oxidation by oxygen, as demonstrated by the development of an undesirable bitter, stale flavor, loss of aroma, and haze formation. Dark beer possesses greater stability to pasteurization and shelf life than light beers, the difference being attributed to a higher content of reducing substances in the dark beer. The natural reducing substances include reductones, melanoidins, tannins, and the SK groups of nitrogenous compounds. A finished beer of good flavor and clarity ready for bottling should possess high reducing capacity and should be packaged with a minimum amount of dissolved air and headspace air for maximum shelf life (Segard, 1935; Tenny, 1938; Gray, 1948; de Clerck, 1949; Knorr, 1950).

Dissolved oxygen first disappears from beer in a closed container by entering into chemical combination with the beer constituents. Then oxygen from the air in the headspace dissolves in the beer and follows the same pattern (Gray and Stone, 1939c; Roberts et al., 1947). Con- comitant with the disappearance of oxygen and flaxor changes, an oxidation haze may develop, which first is revealed when the product is chilled. Beer with a high concentration of reducing substances is desired in order to provide greater resistance to oxidation, which ruins the flavor and appearance of the product. Contamination of the beer with certain metals accelerates oxidation (Singruen, 1940). An indirect but practical measure of reducing substances in beer can be obtained by noting the decolorizing rate of an oxidation-reduction potential indicator added to beer under defined conditions (de Clerck, 1934; Hartong, 1934; Gray and Stone, 1939~) . One test is known as the indicator time test (I.T.T.). The test is relatively insensitive to dissolved oxygen but reflects the oxidation which has taken place. Correlations have been made between I.T.T. values and beer flavor. The I.T.T..test must be used with discretion, since flavor changes are irreversible in beer, and for maximum value a previous history on the beer is necessary (Gray and Stone, 1939c, 1939d ; Gray, 1948).

Reducing substances have been compared 6y Gray and Stone (loc. ci t . ) , who found that I-ascorbic acid possesses marked reducing properties in beer even in small quantities. Stability tests conducted on beers treated with ascorbic acid show marked increases in oxidation resistance. Fur-


thermore, ascorbic acid may be added to the beer a t any point in the brewing process (Gray and Stone, 1939d, 1939e). Data on the effect of ascorbic acid and sulfites on the I.T.T. test in beer are shown in Table XII.

TABLE XI1

Effect of Some Reducing Agents on the Indicator Time Test *

Amount added Indicator time

test

Control Sodium formate

Sodium hypo- phospite

Sodium phosphite

Potassium metabi- sulfite (KMS)

Ascorbic acid

mg./bottle

0 357

3,570 357

3,570 357

3,570 9

18 36 72

144 288

10 20

p.p.m. 0

1,000 10,000

1,000 10,000 1,000

10,000 25 50

100 200 400 800 28 56

Beer A 900 900 900 900 900 780 600 360

70 35 15

l x

O t

Beer B

390 330

390

300

250 125 50 25

8 2 x O t O f

* Gray and Stone, 1939c, d. t Instantaneous. x Approximate figures.

Urion (1950), Dean of the Facult6 des Sciences at Nancy, France, finds added ascorbic acid a means of extending the shelf life of beer. By accepting oxygen it protects proteins, tannins, and their mutual adsorbates. It is believed that pasteurization combined with oxidation alters the colloidal structure of the proteins, bringing about precipitation. Added ascorbic acid improves its colloidal stability. Urion regards ascorbic acid in small quantities to be naturally present in wort but only in traces from plant sources. Thus, to have ascorbic acid make a significant contribution, it is only neces9ary to increase it (Urion, 1950). Of twelve chemical beer stabilizers mentioned by Knorr, special importance is attributed to ascorbic acid for its ease of application and small amount required. It does not inhibit aroma, flavor, or appearance (Knorr, 1950; 1951; Szasz, 1950).

In general, tests with ascorbic acid on a 1abora.tory scale were not found to be most satisfactory because of the difficulty in simulating commercial conditions. Therefore, a series of triaIs on a commercial basis,


several days or weeks apart, is recommended for test purposes in which a brew can be split into two parts after the fermentation stage, part of which is treated with ascorbic acid, the remainder serving as the control. Ascorbic acid may be safely added in limited amounts to beer a t any stage after fermentation but before it enters the government tanks. While some breweries prefer to add the ascorbic acid to the beer prior to the final clarification in the pulp filters, others, experiencing oxidation difficulties prior to bottling o r canning, add part of the ascorbic acid immediately after fermentation and the remainder prior to pulp filtration (Siemers, 1952).

Thompson (1952) of the Jorgensen Laboratory of Fermentology, Den- mark has recently reviewed the chemical approaches to avoid oxidation in beers and concludes that the addition of commercially prepared reductones from sugar contributes to the haze problem in beer, and the use of sulfites is very objectionable because of its slow reducing action in beer and its disastrous effect on the flavor, particularly of the finer beers. After a consideration of the above substances, the hypophosphites, for- mates, nordihydroguaiaretic acid and ascorbic acid, only ascorbic acid was thoroughly recommended. I n one trial with a Danish export pilsner beer the addition of 2.45 gm. of ascorbic acid per barrel extended the shelf-life of the beer to 248 days as compared to 149 days for the control sample (Thompson, 1952).

The amount of ascorbic acid added to beer is small, approximately 10 mg. or less per 12-oz. container (2 to 4 grams per barrel). Furthermore, practically none of this remains after processing and storage j hence the role of ascorbic acid in beer is purely a chemical one.

Although orange oil which has been carefully processed and properly handled is quite a stable product, i t is subject to oxidative changes ren- dering it unpleasant to the palate. The changes result from the oxidation and polymerization of the terpenes. When orange oil is added to a food product to impart desirable orange flavor, oxidative changes can make the final product inedible. Various studies have been conducted to stabilize the product (Lakritz, 1943 ; Kesterson and McDuE, 1949 ; Kenyon and Proctor, 1951). Added a-tocopherol a t levels of 0.05 to 0.1 % offers particular promise as an inhibitor delaying the autoxidation. Ascorbic acid is ioluble in orange oil to the extent of 10 mg. per 100 g. and offers synergistic value to a-tocopherol in orange oil.

I n orange oil emulsion concentrates composed of gum tragacanth, water, glycerine, benzoate of soda, and orange oil, ascorbic acid alone in concentrations of 0.5% by weight was markedly effective in retarding discoloration and terpenic flavors when the emulsions were exposed to light or heat [40° C., (104' F.)] during storage. Protection is also se-


cured by the addition of small amounts of alpha-tocopherol (unesteri- fied) , butylated hydroxyanisole, nordihydroguaiaretic acid, gentisic acid esters, etc. (0.02-0.1% of the oil) with ascorbic acid at a level of 0.170 of the emulsion. The oil-soluble antioxidant should be added to the oil prior to the preparation of the emulsion. When the orange FD&C food colors are added to the emulsion it is necessary to limit the level of ascorbic acid to approximately 0.1% or less of the emulsion to eliminate or minimize the reducing (decolorizing) effect upon the added color during long storage or prolonged exposure of the emulsion to light.

Ascorbic acid incorporated in finished beverages also retards such changes and helps to retain true fruit flavor (Shillinglaw and Levine, 1943). Notice must be taken of the compatability of the concentration of added ascorbic acid and the FD&C food colors in the finished beverage, lest fading of the colors be encountered upon exposure of the bottled beverage to sunlight, due to the reducing action of ascorbic acid.

Considerable difficulty has been encountered with the tendency of table wines to darken unduly during aging in the u7ood and after bottling. The addition of ascorbic acid to wine before fermentation or after fermentation has been tried with no change in darkening tendency (Cruess, 1948). The darkening is believed to be of the non-enzymic, non-oxidative type.

XIII . FLOUR AND DOUGH IMPROVER

The improving action of minute quantities of an added chemical compound on the baking strength of wheat flour, thus producing a more voluminous loaf, has been a fascinating and practical field of investigation. By improving or strengthening the gluten of the flour, a more porous, lighter and palatable loaf of bread is produced. The flour improving action of potassium persulfate, potassium bromate and others has been observed and studied over the past century.

I n 1935 Jorgensen, a Danish chemist, discovered that ascorbic acid exerts a marked action on the baking strength of flour (Jorgensen, 1935 ; 1939 ; 1945). Its action was noticed in as low a concentration as 0.5 mg. per 560 gm. of flour and a. new means for the improvement of the baking strength was discovered and patented. I n practice, however, 2 to 5 mg. per 100 gm. of flour yield a considerable improvement in the baking strength of most flours. Further experiments on the action of ascorbic acid by Jorgensen proved that i t does not stimulate the fermentation in the dough in any way nor does i t influence the pH value of the dough. Ascorbic acid, like broma.te, inhibits the gelatin splitting ability of pa- pain and bromelin. It has been reported to be approximately equivalent


on a weight basis with bromate (Feaster and Cathcart, 1941 ; Cathcart and Edelmann, 1944).

Jorgensen theorized tha.t ascorbic acid acts as an oxygen carrier, oxidizing itself by atmospheric oxygen to dehydroascorbic acid, which in turn inactivates the proteinases of wheat flour by an oxidizing action. This theory was supported by the work of Melville and Shattock (1938) and Sandstedt and Hites (1945) as these workers reported dehydroascorbic acid to be a. better bread improver than the reduced form. The theoretical aspect of this action is further discussed by Hopkins and Morgan (1936) and Jorgensen (1945). Premixes of ascorbic acid with inert substances have been prepared which possess desirable physical characteristics for the incorporation of ascorbic acid in flour (van der Lee, 1942 ; Maltha, 1946). The behavior of ascorbic acid in baked products has been investigated (Seeder, 1950).

It is interesting to note that while ascorbic acid as a bread improver is more expensive than other improvers such as potassium bromate, it has been a preferred compound in certain countries. The usual flour improvers have been prohibited in France, Italy, Switzerland, Greece, Belgium and South Africa, yet in these first mentioned three countries ascorbic acid has been authorized as a flour improving agent, and substantial quantities are used for this purpose in France and Switzerland.

XIV. NUTRITIONAL VALUE IN MISCELLANEOUS PRODUCTS

I n time of war, great consideration is given to the problem of food acceptance in order to offer a variety of good-flavored, nutritional foods for feeding troops in the field or under combat conditions, If certain foods are to serve as primary sources of added nutrients, they must be foods which are highly acceptable and in frequent use.

A number of foods used in the armed forces are enriched with ascorbic acid. A summary of some of these foods is presented in Table XIII.

Since, in addition to their nutritive role, beverages serve as thirst quenchers and as stimulants, they are excellent products for ascorbic acid enrichment. Hence, fruit beverage bases which are diluted with water and so consumed are required to be manufactured with added ascorbic acid for the armed forces. As a result of the observation early in World War I1 that cold beverage base powders were not always consumed, ascorbic acid is now added to beverage powders which can be used to prepare hot beverages as well, for example, cocoa beverage powder, soluble coffee powder, and soluble tea powder.

The stability of added ascorbic acid has been well tested in the hot beverages. Dry soluble coffee dissolved in hot water 93" C. (200" F.)


TABLE XI11

Use of Added Ascorbic Acid in Foods of the Armed Forces *

No.

1

2

3 4

5 6 7

Product

Beverage bases, natural and imitation (powders and crystals) Lemon and orange juice powder,

Candy, hard (nonsugared) Cocoa beverage powder (fortified)

synthetic

Coffee, soluble pure Coffee, soluble product Tea, soluble product

Ascorbic acid requirement

50 mg. per 7-g. portion of a bever-

60 mg. per 7-g. portion of powder

40 mg. per 0.6-oz. portion of candy 15 mg. per ounce of cocoa powder ;

same as powder, bu t compressed Not less than 20 mg. per 2% g. Not less than 20 mg. per 5 g. 20 mg. per 1.3 g. soluble tea prod-

age-base mix

uct powder

* Government Specifications, 1949-1951. No. JAN-B-772 ; MIL-G-1067A: MIL-0-1026A; MIL-L-10666; MIL-C-3034: MIL-C-3031: MIL-C-lO19B and MIL-T-3527.

and permitted to stand for 5 and 30 min. has been assayed for ascorbic acid and total vitamin C. These studies revealed that no significant vitamin C activity is lost during brewing and standing as described above (Bauernfeind et al., 1953). Under specialized circumstances ascorbic acid has been reported to be a flavor booster for foods (Phillips, 1951).

The stability of added ascorbic acid has been investigated (Marshall et al., 1944; Brenner e t al., 1947; Freed et al., 1949) in many products for war use. It was found to be very stable in synthetic fruit juice powders, bulk cocoa beverage powder, soluble coffee products, coated jelly beans, hard pressed mints, candy wafers, hard candy, coated chew- ing gum, bulk and disk granulated sugar, all types of premixed bulk cereals, and some types of sandwich cookies. Siemers (1945) and Leigh- ton (1951) have found hard candy to be a good vehicle for ascorbic acid because of the presence of fruit acids. Added ascorbic acid can also be handled satisfactorily in caramels, fudges, and chocolates (Leighton, 1951).

XV. NEEDED RESEARCH

Ascorbic acid is an oxygen acceptor, and, through its ability to accept oxygen from the air, the usual oxidation path can be delayed. It can act as a synergist to primary antioxidants in the role of a hydrogen donor. Where enzymic oxidation is involved, i t can serve a t times as an enzyme substrate.

Although past work has demonstrated many practical uses €or this nutritionally acceptable chemical compound in food processing, more


research of an applied nature is necessary to decide its commercial role in, for example, ready-to-serve meats, the development of frozen, raw, boneless fish cakes for ready cooking and serving, glass-packed sauerkraut, frozen raw shrimp and freshly cut vegetables. I n the manufacture of natural-type apple juice, engineering advances are necessary to bring about the design and production of equipment which will quickly process juice temporarily protected by ascorbic acid.

Preliminary evidence already indicates that added ascorbic acid will delay or inhibit some flavor changes brought about by electromagnetic irradiation. The role of ascorbic acid here requires investigation for its practical application. Combined uses of ascorbic acid with other harm- less chemicals in food processing may extend its present usefulness. Although added ascorbic acid can delay certain deteriorative changes, it cannot, however, be considered a panacea for all oxidative off-flavor and discoloration ills in food products.

REFERENCES

Abt, A. F., and Farmer, C. J. Vitamin C, pharmacology and therapeutics.

Abt, A. F. 1939. Pharmacology and therapeutics of vitamin C. The Vitamins.

Aitken, H. C. 1950. Apple juice processing in U. S. Can. Food Ind. 21, No. 7, 32. Albers, H. The relationship between ascorbic acid and blood iron metab-

olism. Zentralbl. f. Gynak. 73, 995. Alexander, W. F. 1951. Quality control of peach and apricot packs. Quick Frozen

Alford, J. A., and Fieger, E. A. 1952. The non-microbial nature of the black

Allen, N. 1949. Meat-film considerations. Modern Packaging 22, No. 5, 134. Anderson, R. B., Betzold, C . W., and Carr, W. J. A use of ascorbic acid in

Anderson, E. E., and Fagerson, I. S. 1952. Ascorbic acid eontent of frozen orange J . Home Economics 44, 276.

Anonymous. 1941. Label statements concerning dietary properties of foods pix- Federal Begister Nov. 22,

Anonymous. 1943a. Inadequate diets and nutritional deficiencies in the United Natl. Research Council ( U . S.) Bull.

1938. J. Am. Med. Assoc. 111, 1555.

American Medical Association, p. 411.

1951.

pooas 13, NO. 11, 59.

spots on ice-packed shrimp. Food Tech. 6, 217.

1950. frozen homogenized milk.

concentrates as purchased on retail markets.

porting to be or represented for special dietary uses. p. 5921.

States. 109.

Anonymous. 1943b. Vegetable juice cocktails. J . Am. Med. Assoc. 121, 258. Anonymous. Factors influencing the contents of provitnmin A and vitamin

Anonymous. 1945a. Tables of food composition in terms of elcveii nutrients. U. S.

Anonymous. 194513. Effect of large doses of ascorbic acid. J. Am. Med. ASSOC.

Food Pechnol. 4, 297.

Their prevalence and significance.

1944. C in plants. Nutr i t ion Revs. 2, 271.

Dept. Agr. Misc. Pub. No. 572.

127, 683.


Anonymous.

Anonymous. 1946a. Plan for acceptance of juices. J . Am. Med. Assoc. 132, 283. Anonymous. Present knowledge of ascorbic acid (vitamin C) in nutrition.

Anonymous. 1946c. Vitamin C (ascorbic acid) enriched apple juice. Vitamin

Anonymous. 1947. Processing frozen fruit with 1-ascorbic acid (vitamin C). Vita-

Anonymous. 1948a. Recommended dietary allowances. NatE. Research Council

Anonymous. 194813. Utilization of ascorbic acid. J. Am. Med. ASSOC. 136, 402. Anonymous. 1949a. Frozen concentrated citrus juice. Food Inds. 21, 67. Anonymous.

1945c. Relation of genetic and environmental factors to the vitamin content of fruits and vegetables. Nutrition Revs. 3, 216.

194613. Nwtrition Revs. 4, 259.

Division Brochure.

min Division Brochure, 3rd ed.

( U . S.) Circ. No. 129.

Hoffmann-La Roche Inc., Nutley, N. J.

Hoffmann-La Roche Inc., Nutley, N. J.

1949b. Statement pertaining to addition of ascorbic acid to milk Food and Nutrition Board,

Anonymous. 1949c. Biochemical aspects of pteroylglutamates. Nutrition Revs. 7,

Anonymous. 194913. Nutritive value of canned foods. Nutrition Revs. 7, 142. Anonymous. 1949e. Nutrition. U . S. Dept. Army, Tech. Manual No. TM8-501. Anonymous. 1949f. Ascorbic acid metabolism in vitamin A deficient rats. Nutri-

tion Revs. 7, 52. Anonymous. 1949g. Food composition tables for international use. Brochure of

Food and Agriculture Organization of the United Nations. Anonymous. 1950a. Is frozen milk concentrate nextf Quick Frozen Foods, 12,

No. 9, 37; 12, No. 10, 51. Anonymous. 1950b. Proposed rule making : frozen fruits. Definitions and stand-

ards of identity and standards of fill of container. Federal Register 15, No. 192, 6674 (Oct. 4).

Anonymous. 1950c. Nutritive content of city diets. 77. S. Dept. Agr. Special Rep. No. 2.

Anonymous. 1950d. Fru i t and vegetable juice consumption in urban American homes. American Can Company.

Anonymous. 1950e. Role of genetics in food quality improvement. Nutrition Revs. 8, 65.

Anonymous. 1950f. A new form of folic acid-the leuconostoc citrovorum factor. Nutrition Revs. 8, 282.

Anonymous. 1950g. Ascorbic acid, how Pacific fish processors are using it to unlock latent opportunities in package frozen fish. Pacific Pisherman 48, No. 13, 33.

Anonymous. 195011. Ascorbic acid content of grapefruit juice. J. Am. Med. Assoc. 143, 439.

Anonymous. Breakfast juices, importance of choosing those rich in vitamin C. U. 8. Dept. Agr. Food and Home Notes, Nov. 8.

Anonymons. 1951a. Home freezing of fruits and vegetables. 77. S. Lfept. Agr. Home and Garden Bull. No. 10.

Anonymous. 1951b. Fruit and juices, availability in retail food stores. U. S. Department of Agriculture, August; 77. 8. Department of Agriculture Produce and Marketing Administration, October, 1951.

Anonymous. 1951~ . Vitamin B, and folic acid in infant nutrition. J . Am. Med. Assoc. 146, 1028.

for the purpose of preventing oxidized flavor. National Research Council, May 6.

49.

1950i.


Anonymous. 1951d. Deficiencies of ascorbic acid and ptcroylglutamic acid in

Anonymous. l95le. Prevalence of scurvy during iiifaney. Nutrition Ilevs. 9, 297. Anonymous. 195lf. Frozen orange juice concentrate. J . Am. Med. Assoc. 146, 35. Anonymous. 1951g. Toxicity of gluco ascorbic acid. Nutrition Revs. 9, 177. Anonymous. 195111. Statistical review and yearbook number. Western Canner and

Packer 43, No. 6 , 145. Anonymous. What children eat and liow eating habits are improved through

education. General Mills, April, Anonymous. 195lj . No oranges for Floridians. Leon County (Florida) Health

Unit release, August 9. Anonymous. 1931k. Consumer fruit and juice purchases. U. S. Dcpartment of

Agriculture, Ju ly Sept.; U. S. Department of Agriculture Produce and Markct- ing Administration, December.

Anonymous. 19511. Ascorbic acid content of tomato juice. J . Am. N e d . Assoc. 147, 951.

Anonymous. Ascorbic acid and the conversion of pferoylglutamic acid t o citrovorum factor.

Anonymous. 1952b. Final order amending dcfinition and standard of identity and establishing standard of fill of container for canned mushrooms. Federal Register 17, No. 178, 8176 (Sept. 11).

Anonymous. 1 9 5 2 ~ . Fru i t and juices availability in retain food stores. U. S. Dept. of Agr., August; U. S. Dept. of Agr. Prod. & Mktg. Admn., November.

Anonymous. 1952d. Consumer f ru i t and juice purchases. U. S. Dept. Agr., April- June ; U. s. Dept. Agr. Prod. & Mktg. Admn., August.

Anonymous. Increasing the ascorbic acid content of vegetables and fruit. Nutr. Rev. 10, 103.

Atkinson, F. E., and Strachan, C. C. 1949. Production of juices, their manufacture, chemical aspects aiid laboratory control. Can. Dept. Agr. Exp. Farm Service Publ. No. 813.

Atkinson, F. E., and Straclian, C. C. 1950. Preservation of color in milling of apples for natural apple juice.

Axelrod, J., Brodie, B. B., and Udcnfriend, S. 1952. Effect of ascorbic acid on oxidation of aromatic drugs in the body.

Babcock, C. J., Stabile, J. N., Windham, E. S., aiid Randall, R. 1949. Frozen homogenized milk. VI. The use of stabilizers in frozen homogenized milk. J. Dairy Sci. 32, 175.

1952. Frozen homogenized milk. Effect of the addition of sucrose and ascorbic acid on the keeping quality of frozen homogenized milk.

anemia. Nulrition Revs. 9, 52.

1951i.

1953a. Nutr. Rev. 10, 40.

1952e.

Food Teehnol. 4, 133.

Federation Proc. 11, 319.

Babcock, C. J., Strobel, D. R., Yager, R. M., and Windham, E. S.

J . Dairy Sci. 35, 195. Bacliarach, A. L. 1952. Biochemical role of vitamin C. Nature 169, 1107. Bail, E. G. 1937. Studies on oxidation-reduetioil, ascorbic acid. J . Biol. Chem.

Bang, Folke. 1951. Vitamin C enrichment of sour milk for consumption. Svenska

Banks, A. 1937. Rancidity in fats. Effect of low temperatures, sodium chIoride J . SOC. Chem. Ind. (London)

Banks, A. 1952. The development of rancidity in cold-stored herrings: the in-

118, 219.

Mejeratidn. 43, 169; C. A., 45, 10419.

and fish muscle on the oxidation of herring oil. 56, 13.

fluence of some antioxidants. J . Sci. Food & Agr. 3, 250.

412 J. C . BAUERNFEIND

Bassett, C. F., Loosli, J. K., and Wilke, F. 1948. The vitamin A requiremellt for d.

Adding ascorbic acid to penclies

1945b. Retardation of discoloration in Quick Frozen Foods 7, NO. 12, 46.

Vitamin Fruit

Methods of freezing sliced apples with I-ascorbic acid.

Estimating ascorbic acid in enriched apple juice.

1947a. Home canning of fruits with 2-ascorbic acid (vitamin C).

1947b. Processing frozen apples with Z-ascorbic acid. Fruit Products J. 27, 68.

1948. Retardation of rancidity in frozen fish by ascorbic acid. Quick Frozen Foods 10, No. 8, 139; No. 9, 68.

1951. Commercial processing of frozen fish with ascorbic acid.

1952. Better color, better flavor in processing mushrooms by adding ascorbic acid. Food Eng. 24, 88 (Dee.)

growth of foxes aud minks as influenced by ascorbic acid and potatoes. Nutrition 35, 629.

before freezing. Food Ind. 17, 79.

frozen sliced peaches by I-ascorbic acid.

C stability in frozen fruit processed with crystalline Z-ascorbic acid.

Bauernfeind, J. C., and Siemers, G. F.

Bauernfeind, J. C., and Siemers, G. F.

Bauernfeind, J. C., Jahns, F. W., Smith, E. G., and Siemers, G. F.

1945a.

1946.

Products J . 25, 324. Bauernfeind, J. C., and Siemers, G. F.

Bauernfeind, J. C., and Jahns, F. W.

Bauernfeind, J. C., Batcher, 0. M., and Shaw, P.

Bauernfeind, J. C., Smith, E. G., and Siemers, G. F.

Bauernfeind, J. C., Smith, E. G., Bateher, O., and Siemers, G. F.

1946. Fruit Products J . 26, 4.

1946. Food Puckei 27, 64 (August).

Glass Packer 26, No. 4, 268; No. 5, 358.

Bauernfeind, J. C., Smith, E. G., and Siemers, G . F.

Bauernfeind, J. C., Smith, E. G., and Siemers, G. F. Food TecF&noZ. 5, 254.

Bauernfeind, J. C., et al. 1953. Unpublislied data. Baur, H. 1952. Poliomyelitis therapy with ascorbic acid. Eetvct. M e d . Beta. 19,

470. Bayes, A. L. 1950. Investigations on the use of nitrogen for the stabilization of

perishable food products. Food TechnoI. 4, 151. Bell, R. W. 1948. Retention of ascorbic acid, changes in oxidation-reduction

potential and the prevention of an oxidized flavor during freezing preservation of milk.

1949. Deferment of a n oxidized flavor in frozen milk by ascorbic acid fortification and by hydrogen peroxide oxidation of the ascorbic acid of the fresh milk. J . Dairy Sci. 32, 833.

Bell, R. W., and Mucha, T. J. 1952. Stability of milk and i ts concentrates in frozen storage a t various temperatures. J. Dairy Sci. 35, 1.

Bessey, O., and King, C. G. The distribution of vitamin C in plant and animal tissues and its determination. J . Biol. Chem. 103, 687.

Bessey, 0. 1938. A method for the determination of ascorbic acid and dehydroascorbic acid in turbid and colored solutions in the prescnce of other reducing substances.

Bessey, 0. A., and White, R. L. The ascorbic acid requirements of children. J . Nutrition 23, 195.

Bicknell, F., and Prescott, F. 1946. Vitamin C (ascorbic acid). The Vitamins in Medicine. 2nd ed. p. 443. William Heinemaiin Ltd., London.

Borsook, H., Davenport, H. W., Jeffreys, C. E. P., and Warner, R. C. 1937. The oxidation of ascorbic acid and its reduction in vitro and in vivo. J. Biol. Chem. 117, 237.

J . Dairy Sci. 31, 951. Bell, R. W., and Mucha, T. J.

1933.

J . BioZ. Chem. 126, 771. 1942.


Boyer, P. D., Phillips, P. H., Pounden, W. D., Jensen, C. W., Rupel, I. W., and Nesbit, M. E. Certain relationships of avitaminosis A to vitamin C in the young bovine.

The loss of ascorbic acid in the preparation of old and freshly harvested potatoes. J . Am. Dietet. Assoc. 23, 414.

Branion, H. D., Roberts, J. S., Cameron, C. R., and McCready, A. M. 1948. The ascorbic acid content of cabbage. J . A m . Dietet. Assoc. 24, 101.

Branion, H. D., and Cameron, C. R. 1948. Ascorbic acid content of food served in a Royal Canadian Air Force mess.

Brasch, A., Huber, W., Friedemann, U., and Traub, F. B. 1949. Action of high intensity electrons on biological objects. Proc. Rudolf Virchow Med. Society 8, 3.

Brenner, S., Wodicka, V. O., and Dunlop, S. G. 1947. Stability of ascorbic acid in various carriers. Food Research 12, 253.

Brenner, S., Wodicka, V. O., and Dunlop, S. G. 1948. Effect of high-temperature storage on the retention of nutrients in canned foods.

Brown, F., and Adam, W. B. 1950. The determination of ascorbic acid in the presence of ferrous salts with particular reference to canned foods. J . Sci. Food Agr . 1, 51.

Brown, H. D. 1950. Effects of soil fertility and storage on kraut quality. Canning Trade 73, No. 4, 8.

Brown, W. C., and Thurston, L. M. 1940. A review of oxidation in milk and milk products as related to flavor. J . Dairy Sci. 23, 629.

Browne, J. H., and Pierce, H. B. A survey of nutritional status among school children and their response to nutrient therapy. Milbank Memoraal Fund Quar- terly 28, 219.

Calcutt, G. 1951. The formation of hydrogen peroxide during the autoxidation of ascorbic acid. Experientia 7, 26.

Calkins, V. P., and Mattill, H. A. Kinetics of the antioxygenic synergism of quinones with ascorbic acid in f a t systems.

Cameron, E . J., and Esty, J. R. 1950. Canned foods in human nutrition. National Canners Association, Washington, D. C.

Campbell, J., and Tubb, T. G. 1950. The stability of ascorbic acid in solution. Can. J . Research 28, 19.

Cardinal, P. J. 1950. Vitamins by the ton. Science Counselor 13, 83. Carroll, G. 11. 1943. The role of ascorbic acid in plant nutrition. Botan . Rev. 9,

41. Cathcart, W. H., and Edelmann, E. C. A note on the comparative efficiency

of 1-ascorbic acid and potassium bromate as dough conditioners. Cereal Chem. 21, 575.

Chalmers, F. W., Lawless, J. J., and Stregevsky, S. 1952. Nutrition survey of West . Pa. Agr . Exppt. Sta. Bull. 352.

Chambers, G. F. Food Inds. 22, 90. Chang, I., and Watts, B. M. Antioxidants in the hemoglobin catalyzed oxi-

Chilsou, W. 11. 1935. What causes most common off-flavor in market milk. Milk

Chilson, W. H., Martin, W. H., and Parrish, D. B. 1949. The relationship of J . Dairy

1942. J. Nutr i t ion 23, 525.

Branion, H. D., Roberts, J. S., Cameron, C. R., and McCready, A. M. 1947.

J. Am. Dietet. Assoc. 24, 417.

Food Technol. 2, 207.

1950.

1944. J . Am. Chem. Soc. 66, 239.

1944.

West Virginia University students. 1950. Juice color is bettered in a gas blanket.

1949. dation of unsaturated fats.

Plant MonthEy 24, No. 11; No. 12, 30.

ascorbic acid t o the development of oxidized flavor in market milk. Sci. 32, 306.

Food Technol. 3, 1.


Clark, J. H. 1945. Frozen foods. New Jersey Agr. Expt. Sta. Circ. No. 500. Clausen, D. F., Lundberg, W. O., and Burr, G. 0. 1947. Some effects of amino

acids and certain other substances on lard containing phenolic antioxidants. J . Am. Oil Chemists’ Soc. 24, 403.

The availability for human nutrition of the vitamin C in raw cabbage and home-canned tomato juice. J . Nutrition 25, 349.

Clayton, M. M., Pressey, E. F., and Lees, K. H. 1948. Vitamin C content of home-canned tomatoes as determined by variety and method of processing. Food Research 13, 36.

Clayton, M. M. 1951. Breakfasts of Maine teen-agers. Maine Agr. Espt . Sta. Bull. 495.

Clerck, J. de. 1934. Relation between the oxidation-reduction potential of beer and i ts stability. Bull. assoc. Btud. &ole. sup&. brass. univ. Louvain, 34, 78; (C. A . 29, 1932).

Clerck, J., de. 1949. The control of oxidation of worts and beers. Brewers Digest 24, No. 9, 47.

Clifcorn, L. E. Factors influencing the vitamin content of canned foods. Advances in Food Research 1, 39.

Coleman, H. M., Steffen, A. H., and Hopkins, E. W. 1949. Treatment of animal materials. U. S. patent 2,491,646.

Coleman, H. M., Steffen, A. H., and Hopkins, E. W. 1951. Process for treating animal materials.

Comiskey, E. M. 1950. Ascorbic way t o keep meat bloom. Food Inds. 22, 1385. Corbett, W. J., and Tracy, P. H.

Cotton, R. H., Roy, W. R., Brokaw, C .H., McDuff, 0. R., and Schroeder, A. L.

Clayton, M. M., and Borden, R. A. 1943.

1948.

U. S. patent 2,541,572.

1941. Experiments on the use of certain antioxi- Food Research 6, 445.

1947. J. Florida State Hort. Sac. 16,

dants for control of oxidized flavor in dairy products.

Storage studies on frozen citrus concentrates. 39.

Coulter, S. T., and Jenness, R. 1946. Gas packing dry whole milk. Food Inds. 18, 352.

Coulter, S. T., Jenness, R., and Geddes, W. F. 1950. Physical and chemical aspects of the production, storage and utility of dry milk products. Advances in Food Research 3, 45.

Cowgill, G. R. 1950. Improving the quality of cheap staple foods. J. Am. Med. Assoc. 142, 721.

Crampton, E. W., and Lloyd, L. E. 1950. A quantitative estimation of the effect of rutin in the biological potency of vitamin C. J . Nutrition 41, 487.

Crandon, J. H., Lund, C. C., and Dill, D. B. Experimental human scurvy. New Engl. J . Med. 223, 353.

Cruess, W. V., Leonard, S., Ponting, J., and Lane, A. 1946. Prune juice experiments. Fruit Products J . 25, 363.

Cruess, W. V., and Seagrave-Smith, €1. C. 1946. Observations on freezing of apples. Fruit Products J . 26, 36.

Cruess, W. V. 1948. The darkening of white wines. Fruit Products J. 28, 4. Daft, F. S., and Schwarz, K.

with ascorbic acid or antibiotics. Dalilc, C. D., and Palmer, L. S.

dividual cow. Dallyn, M. H., and Moschette, D. S.

J . Am. Diet. Assoc. 28, 718.

1940.

1952. Prevention of certain B vitamin deficiencies

1937. The oxidized flavor in milk from the in-

1952. Ascorbic acid nutrition of children.

Federation Proc. 11, 200.

Penn. State Coll. Agr. Exp. Sta. Bull. No. 347.


Danehy, J. P., and Pigman, W. W. 1950. Reactions between sugars and nitrogenous compounds and their relationship to certain food problems. Advances in Food Research 3, 241.

1951. The keeping quality of whole milk powder. J . Dairy SFi. 34, 633.

De Felice, F. 1950. Later studies on correlation between vitamins. Riboflavin and experimental scurvy. Folic acid and experimental scurvy. Synergism between biotin and ascorbic acid. Synergism between meso-inositol and ascorbic acid. Boll. SOC. ital. biol. sper. 26, 585, 586, 1531, 1658 (C.A., 46:11369e).

Denny, F. E. Inactivation of the browning system in frozen-stored fruit tissue.

De Ritter, E., Cohen, N., and Rubin, S. H. 1951. Physiological availability of dehydroascorbic acid and palmitoyl ascorbic acid. Science 113, No. 2944, 628.

Dimick, K. P., Ponting, J. D., and Makower, B. 1951. Heat inactivation of polyphenolase in fruit purees. Food Z'echwl. 5, 237.

Doan, F. J., and Leeder, J. G. 1944. Milk can be frozen for sale to consumers.

Doan, F. J., and Josephson, D. V. Additional observations on the stability of ascorbic acid and sodium l-ascorbate in evaporated milk. J . Dairy Sci. 29, 625.

Du Bois, C. W., and Tressler, D. K. Seasoning, their effect on maintenance of quality of frozen ground pork and beef. Proc. Inst. Food Technol. 4, 202.

Du Bois, C. W. 1949. Ascorbic acid and color in food products. Food Technol. 3, 119.

Dunker, C. F., Fellers, C. R., and Esselen, Jr., W. B. 1942. A comparison of four methods for determining vitamin C with 25-day weight-response bioassay. Food Research 7, 260.

Eaton, H. D., Helmboldt, C. F., Avampato, J. E., Junghers, C. L., Dolge, K. L., and Moore, L. A. Blood levels of ascorbic acid and vitamin A during vitamin A depletion and effect of administration of ascorbic acid during terminal vitamin A depletion in the dairy cow.

Elliott, K. J., and Schuck, C. 1949. Utilization of ascorbic acid. Crystalline supplement versus grapefruit. J . Am. Dietet. Assoc. 25, 845.

Decker, C. W., and Ashworth, U. S. The use of antioxidants-ascorbic acid and sodium citrate.

1942. Contribs. Boyce Thompson Inst . 12, 309.

Food Inas. 16, 532. 1946.

1943.

1952.

J . Dairy Sci. 35, 607.

Ellis, E. E. 1951. Home canning guide. New Hampshire Agr. Expt . Sta. Ex t . Bull. No. 87.

Eppright, E., Roderuck, C., and Hathaway, M. 1952. Nutritional status of Iowa school children. Federation Proc. 11, 442.

Eskew, R. K., Phillips, G. W. M., Homiller, R. P., and Eisenhardt, W. H. 1951. Preparation of full-flavor frozen grape juice concentrate. 27. S. Dept. Agr., Eastern Regional Research Lab. Agr. lnd. Chern. Publ. No. AIC-301.

Esselen, W. B., Jr., and Fellers, C. R. .1946. Mushrooms for food and flavor. Mass. State Coll. Agr. Expt. Sta. Bull. No. 434.

Esselen, W. B. Jr., Powers, J. J., and Woodward, R. 1945. d-Isoascorbic acid as an antioxidant.

Esselen, W. B., Jr., Powers, J. J., and Fellers, C. 12. 1946. The fortification of fruit juices with ascorbic acid. Fruit Products J . 26, 11.

Esselen, W. B., Jr., Rassmussen, C. L., and Fellers, C. R. 1948. Prepared fresh McIntosh apple slices. Pruit Products J . 27, 276.

Esselen, W. B., Jr., Fellcrs, C. R., and McConnell, J. E. W. 1949. Frozen apples and apple products.

Ind. Eng. Chem. 37, 295.



Esselen, W. B. Jr., aiid Fellers, C. R. 1950. Causes and prevention of failures in home canning.

Farmer, C. J. 1944. Some aspects of vitamin C metabolism. Federation Proc. 3, 179.

Feaster, J. F., and Catheart, W. H. 1941. Value of ascorbic acid from various sources in baking.

Feaster, J. F., Braun, 0. G., Riester, D. W., and Alexander, P. E. 1950. Influence of storage conditions 011 ascorbic acid content and quality of canned orallge juices. Food Technol. 4, 190.

Feinberg, S. M. 1946. Allergy in Practice. The Year Book Publishers, Inc., p. 322. Fellers, C. R. 1936. The effect of processing on vitamins in fruits and vegetables.

A review. Fenton, 2'. 1946. Nutritive value of frozen fonds. Refrigeration Applications.

American Society of Refrigerating Engineers, New York p. 86. Fenton, F. 1950. Nutritive value of frozen foods. Refrigeration Applications.

American Society of Refrigerating Engineers, New York p. 99. Fenton, F., Bryant, G., Miller, C. D., and Orr, K. 1950. Home frcczillg in Hawaii.

Hawaii Agr. Expt . Sta. Cir. No. 33. Ferguson, L. B., and Scoular, F. I. 1949. Ascorbic acid content of frozen and

canned fruits before and after preparation for serving. Food Research 14, 298. Fieger, E. A. 1951. Cause and prevention of black spot on shrimp. Ice and Refrig.

120, No. 4, 49. Fincke, M. L., McGregor, M. A., Storvick, C. A., and Woods, E. 1948. Ascorbic

acid content of foods ns served. J . Am. Dictet. Assoc. 24, 957. Fisher, I<. H., and Dodds, M. L. 1952. Ascorbic acid and ash in vegetables

cooked in stainless steel utensils. Variation with cooking at three levels of water. J . Am. Diet. Assoc. 28, 726.

Fletscher, J. M., and Fletscher, I. C. 1951. Vitamin C and the common cold. Brit. Med. J . 1, 887.

Follis, R. H., Jr., Park, E. A. aiid Jackson, D. The prevalence of scurvy a t autopsy during the first two years of age. Bull. Johns Hopkins Hos. 87, 569.

Freed, N., Brenner, S., and Wodickn, V. 0. 1949. Prediction of thiamine and ascorbic acid stability in stored calmed foods. Food Technol. 3, 148.

Getz, H. R., Long, E. R., and Henderson, H. J. 1951. Relation of nutrition to the development of tuberculosis; influence of ascorbic acid and vitamin A. Am. Rev. Tuberc. 64, 381 (C.A. 4633637h).

Gibson, 0. H. 1943. The reduction of methemoglobin by ascorbic acid. Bioclzcm. J . 37, 615.

Giri, K. V. 1942. Oxidation and stabilization of vitamin C. Science and Culture 8 , No. 3, 111.

Gleim, E., Albury, M., Visnyei, K., McCartney, J. R., and Fenton, F. 1946. Effect of quantity prepxration procedures on vitamin retention : canned tomatoes. J . A m . Dietet. Assoc. 22, 29.

Goldblith, S. A., and Harris, R. S. 1948. Estimation of ascorbic acid in food preparations. Anal. Chem. 20, 649.

Golumbic, C., and Mattill, €1. A. 1941. Antioxidants and the autoxidation of fats. The antioxygenic action of ascorbic acid in association with tocopherols, hydro- quinones and related compounds. J. Am. Chcm. Soc 63, 1279.

Kinetic studics on the antioxidant synergism between tocophcral and ascorbic acid. Trans. 1st Conf. Biological Antioxidants, J . Macy, Jr., Toand., p. 42.

Mass. Agr. Expt. Sta. Bull. 461.

Cereal Chem. 18, 201.

Mass. State Coll. Agr . Exp. Sta. Bull. No. 338.

1950.

Golumbic, C. 1946.


Gonce, J. E., and Lewis, W. D. 1950. Use of a supplemented evaporated milk in the routine feeding of infants.

Govan, C. D., Jr., and Gordon, H. W. 1949. The effects of pteroylglutamic acid on the aromatic acid metabolism of premature infants. ' Science 109, 332.

Grab, E. G., Jr., and Haynes, R. D. 1948. Pretreatment of apple slices to prevent browning.

Gray, P. P., and Stone, I. Ar t of producing improved aqueous-oil emulsions. U. S. patent 2,159,986.

Gray, P. P., and Stone, I. 1939b. New method of preventing rancidity. Ascorbic acid (vitamin C) and related compounds as antioxidants in preventing rancidity. Food Inds. 11, 626.

Gray, P. P., and Stone, I. 1939c. Oxidation in beers. A simplified method for measurement.

Gray, P. P., and Stone, I. 1939d. Oxidation in beers. Oxidation stability of the finished beers.

Gray, P. P., and Stone, I. 1939e. Beer and method of preparing same. U. S. patent 2,159,985.

Gray, P. P. 1948. Oxygen and the shelf-life of beer. Modern Brewery Age, 39, No. 2, 45; No. 3, 49.

Greenbank, G. R. Variation in the oxidation-reduction potential as a cause for the oxidized flavor in milk.

Greenbank, G. R. 1948. The oxidized flavor in milk and dairy products. A review. J. Dazry Sci. 31, 913.

Grindrod, C. E. 1949. Stable milk product containing added antianemia factor and process of making same.

Guadagni, D. G., Sorber, D. G., and Wilber, J. S. 1949. Enzymatic oxidation of phenolic compounds in frozen peaches. Food Technol. 3, 359.

Guadagni, D. G. Sirup treatment of apple slices for freezing preservation. Food Technol. 3, 404.

Guerrant, N. B., Fardig, 0. B., Vavich, M. G., and Ellenberger, H. A. 1948. Nutri- tive value of canned food; influence of temperature and time of storage on vitamin content.

1948. Stability of solutions of pure ascorbic acid and of dehydroascorbic acid.

Oxidation of ascorbic acid t o dehydroascorbic acid at low temperatures.

The results of deaeratioii on the oxygen, vitamin C and the oxidized flavors of milk.

Effect of the quick and complete elimination of vitamin C on the development of the oxidized flavors in homogenized milk with special reference t o the action of daylight.

Am. J . Diseases Children 80, 274.

Quick Frozen Foods 10, No. 11, 71. 1939a.

J . Inst. Brewing 45, 253.

J . Inst. Brewing 45, 443.

1940. J . Dairy Sci. 23, 725.

U. S. Patent 2,481,415.

1949.

Ind. Eng. Chem. 40, 2258. Guild, L. P., Lockhart, E. E., and Harris, R. S.

Gustafson, F. G., and Cooke, A. R.

Guthrie, E. S. 1946.

Guthrie, E. S., and Krukovsky, V. N.

Science 107, 226. 1952.

Sci. 116, 234.

J . Dairy Sci. 29, 359. 1949.

J . Dairy Sci. 32, 786. Hall, L. A,, and Gershbein, L. L. 1949. Antioxidant. U. S. Patent 2,464,927. Hall, L. A. 1930a. Antioxidant. U. S. Patent 2,500,543. Hall, L. A. 1950b. Synergistic antioxidant. U. S. Patent 2,511,802. Hall, L. A. 1 9 5 0 ~ . Antioxidant flakes. U. S. Pa ten t 2,511,803. Hall, L. A. 1950d. Antioxidant salt. U. S. Patent 2,511,804. Hall, L. A. 1951. Antioxidant for food products. U. S. Patent reissue 23,329. Hand, D. B. 1943. Reduced and total vitamin C in milk. IIangartner, J., and Gordonoff, T.

J . Dairy Sci. 26, 7. 1942. Excretion of vitamin C in the urine a f te r

ingestion of natural or synthetic vitamin C. 2. Vitaminforsch. 12, 226.


Harding, P. L., Winston, J. K., and Fisher, D. F.

Harding, P. L., and Fisher, D. F.

Harland, H. A., Coulter, S. T., and Jenness, R.

1940. Seasonal changes in

Florida oranges. Seasonal changes in Florida grapefruit.

U. S. Dept. Agr. Tech. Bull. No. 886. The interrelationships of

processing treatments and oxidation-reduction systems as factors affecting the keeping quality of dry whole milk.

Harris, L. J. 1934. Specificity of ascorbic acid as antiscorbutic factor. Ann. Rev. Biochem. 3, 247.

Harris, L. J., and Mapson, L. W. Determination of ascorbic acid in presence of interfering substances by the ‘(continuous flow” method. Brit. J . Nutri- tion 1, 7.

U. 8. Dept. Agr. Tech. Bull. No. 753. 1945.

1952.

J . Dairy Sci. 35, 643.

1947.

Harris, L. J. 1951. Process for preserving fruit. U. S. patent 2,536,176. Hartman, D. 1950. Sugar-ascorbic acid spreader for frozen apricots. Western

Hartong, B. H. Oxidation-reduction potentials during the production of beer.

Heller, C. A., McCay, C. M., and Lyou, C. B. Losses of vitamins in large-

Hellier, E. G., and Weingartner, H. C. 1950. Frozen fruit juice concentrates. American Society of Refrigerating Engineers, p. 137.

Hening, J. C. 1949. Apple ice and apple ice cream. Fruit Prod. J . 28, 365. Herreid, E. O., Ruskin, B., Clark, G . L., and Parks, T. B. Ascorbic acid

and riboflavin destruction and flavor development in milk exposed to the sun in amber, clear, paper and ruby bottles.

Hewston, E. M., Dawson, E. H., Alexander, L. M., and Orent-Keiles, E. 1948. Vitamin and mineral content of certain foods as affected by home preparation. U. S. Dept. Agr. Misc. Publ. No. 628.

1950. Comparison of the 2,6- dichlorophenoliiidophenol and 2,4-dinitrophenylhydrazine methods with the Crampton bio-assay for determining vitamin C values in foods. Federation Proc. 9, 361; also U. S. Dept. Agr. Tech. Bull. No. 1023 (Jan. 1951).

IIochberg, M., Melnick, D., and Oser, B. 1945. Physiological availability of the vitamins. The effect of dietary ascorbic acid oxidase. J . Nutrit ion 30, 193.

IIodson, A. Z. 1949. Terminal heating of infant formula. Retention of lieat- labile nutrients. J . Am. Dietet. Assoc. 25, 119.

Hohl, L. A. 1945. Sulphur vs. steam blanching of fruit. Quick Frozen Foods 1, No. 6, 38.

Hohl, L. A. 1946. Preparation and pre-treatment of fruit for freezing. Food Freezing 1, 287 (June).

Holgate, K. C., Moyer, J. C., and Pederson, C. S. 1948. The use of ascorbic acid in preventing oxidative changes in apple juice. Fruit Prod. J . 28, 100.

Holmes, A. D., Pigott, M. G., and Tripp, F. 1941. Comparative costs of vitamin C in fresh and commercially canned f ru i t and vegetable juices. New Engl. J . Med. 225, 69.

1943a. The ascorbic acid conteiit of late winter tomatoes. New Engl. J . Med. 229, 461.

1943b. The relation of season, weight and price to the vitamin C content of oranges. New Engl. J . Med. 228, 8.

Canner and Packer 41, No. 12, 45.

Wochschr. Brau. 51, 409; C. A . 29, 4892.

scale cookery.

Refrigerating Data Book.

1934.

1943. J . Nutrition 26, No. 4, 377.

1932.

J. Diary Sci. 35, 772.

Hewston, E. M., Fisher, M., and Orent-Keiles, E.

Holmes, A. D., Jones, C. P., and Ritchie, W. S.

Holmes, A. D., Patch, J. A,, and Tripp, F.


Holmes, A. D., Kuzmeski, J. W., Jones, C. P., and Canavan, F. T. 1946. Ice cream as a source of riboflavin, carotene and ascorbic acid. New Engl. J. Med. 234, 47.

Holmes, A. D., and Jones, C. P. 1948. Permanency of synthetic ascorbic acid added to milk. J. Dairy Sci. 31, 99.

Holmes, A. D. 1949. Comparison of the stability of reduced ascorbic acid in raw and pasteurized milk.

Holmes, A. D. 1951. Store vs. delivered milk as a source of reduced ascorbic acid. J. Am. Dietet. Assoc. 27, 578.

Holrnes, A. D., Jones, C. P., and Tripp, F. 1951. Use of ascorbic acid tablets to enrich milk for infant feeding. J. Pediatrics 39, 320.

Hopkins, F. G., and Morgan, E. J. 1936. Some relations between ascorbic acid and glutathione. Biochem. J . 30, 1946.

Horowitz, H. H., Doerschuk, A. P., and King, C. G. 1952. The origin of 1-ascorbic acid in the albino rat. J. BW. Chem. 199, 193.

Howe, G. H. 1946. Calville blanc apple rich in vitamin C. Farm Besearch 12, 5. Huber, W. 1951. Results and analysis of differential radiation mechanisms in

Isler, 0. 1938. Stabilization of dl-alpha-tocopherol. Helv. Chim. Bcta 21, 1756. Jeans, P. C. 1951. Feeding of healthy infants and children. Handbook of Nutri-

Jenkins, G. N. 1943. Ascorbic acid in mashed potatoes. Nature 151, 473. Johnson, S. W., and Zilva, S.S. 1934. The urinary excretion of ascorbic and

dehydroascorbic acids in man. Biochem. J. 28, 1393. Johnson, G., and Guadagni, D. G. 1949. Treatment of fruits to prevent browning.

U. S. patent 2,475,838. Johnson, G. 1950. New frozen fresh fruit pie-mixes. Quick Frozen Foods 13,

No. 1, 50. Johnson, G., and Johnson, D. K. 1952. Natural flavor retained in new frozen

uncooked apple pulp. Johnston, F. B. 1943. Vitamin C fortification of apple juice. Fruit Prod. J. 22,

195. Jolliffe, N., McLester, J. S., and Sherman, H. C. The prevalence of mal-

nutrition. J . Am. Med. Assoc. 118, 944. Jolliffe, N., Tisdall, F. F., and Cannon, P. R. 1950. Vitamin C malnutrition.

Clinical Nutrition. Paul B. Hoeber, Inc., New York, 586. Jones, W. W., Van Horn, C. W., Finch, A. H., Smith, M. C., and Caldwell, E. 1944.

A note on ascorbic acid-nitrogen relationships in grapefruit. Science 99, 103. Jones, R. E., and Alexander, F. A new approach to apple juice processing.

Western Canner and Packer 41, No. 3, 31. Jorgensen, H. Ein Beitrag zur Beleuchtung der hemmenden Wirkung von

Oxydations mitteln auf proteolytische Enzymtatigkeit. Uber die Natur der Einwirkung von Kaliumbromat und analogen Stoff en auf die Backflhigkeit des Weizenmehles. Bioehem. 2. 280, 1.

Jorgensen, H. 1939. Process of Improving the baking strength of flour. U. S. Patent 2,149,682.

Jorgensen, H. 1945. Studies on the nature of the bromate effect. Eiiiar Munks- gaard, Copenhagen, Denmark j Humphrey Milford, Ozford University Press, London.

Josephson, D. V., and Doan, F. J. 1945. Ascorbic acid in evaporated milk. Penn. State Coll. Agr. Expt. Sta. Bull. No. 473.

Am. J . Diseases Children 78, 899.

some biological systems. Naturwissenschaften. 38, 21.

tion. 2nd ed. American Medical Association, p. 275.

Food Tech. 6, 242.

1942.

1949.

1935.


Joslyn, M. A. 1941. Color retention in fruit products. Ind. Eng. Chem. 33, 308. Joslyn, M. A., and Hohl, L. A.

Joslyn, M. A., and Miller, J. 1949.

Joslyn, M. A., Jones, W. L., Lambert, E., Miller, J., and Shaw, R. L.

1948. Commercial freezing of f ru i t products. Univ. Calif. Agr. Expt . Sta. Bull. No. 703.

Effects of sugars on oxidation of ascorbic acid.

1949-1950. Applications of sugar solutions, with and without antioxidants. Quick Frozen Foods 12, No. 5, 49; No. 6, 49; No. 7, 45; No. 8, 49; No. 9, 133; No. 10, 72.

1950. Enzyme-catalyzed oxidative browning of

1950. Some fundamental considerations in the processing of frozen orange juice concentrate. Food Technol. 3, 395.

1949. Effect of terminal disin- fection and other factors on the stability of ascorbic acid in reliquified milk products used in infant feeding. J. Pediat. 34, 745.

Kende, S. 1932. Research on tallowy changes in milk. MiIchw. Forsch. 13, 111. Kenyon, J., and Munro, N. The isolation and some properties of dehydro-l-

ascorbic acid. J. Chem. SOC. Par t 1, 158. Kenyon, E. M., and Proctor, B. E. Effects of antioxidants on orange oil.

Food Research 16, 365. Eesterson, J. W., and McDuff, 0. R. 1949. Antioxidant studies. Am. Perfumer

Essent. Oil Rev. 54, 285 (Oct.). Kieferle, F., and Seuss, A. The problem of the oxidized flavor in milk.

Milchw. Forsch. 20, 23. King, C. G. 1939. Chemistry of vitamin C. The Vitamins. American Medical

Association, p. 223. King, C. G., and Tressler, D. K. 1940. Effect of processing on the vitamin C

content of foods. Proc. Znst. Food Technol. 1, 123. King, C. G. 1950. Vitamin C. J. Am. Med. Assoc. 142, 563. King, C. G. 1951. Vitamin C. Handbook of Nutrition. 2nd ed. American

Klassen, D. D. 1951. Ascorbic acid in the treatment of burns. N . P. State J .

Klein, L. 1936. Development of vitamin C. Am. Druggist 95, 48 (March). Knight, K. G., and Paul, P. C. When freezing apple slices be sure of your

Knorr, F. The influence of I-ascorbic acid on the poise numbers of different

Knorr, F. 1951. Beer stabilization agents. Schweiz. Brau. Rundschau 62, No. 9. Koch, E. 1945. Chicago's nutrition problem. J. Am. Dietet. Assoc. 21, 214. Kraft , A. A., and Wanderstock, J. J. 1950. Meat-color problem is closer to solu-

tion. Food Inds. 22, NO. 1, 65. Kraybill, H. R., and Beadle, B. W. 1950. Antioxidants for stabilizing glyceride

oils against oxidative rancidity. U. S. Pa ten t 2,521,859. Krehl, W. A., and Winters, R. W. Effect of cooking methods on retention

of vitamins and minerals in vegetables. J. Am. Dietet. Assoc. 26, 966. Krukovsky, V. N., and Guthrie, E. S. Ascorbic acid oxidation, a key factor

in the inhibition or promotion of the tallowy flavor in milk. J. Dairy Sci. 28, 365.

Vitamin C, hydrogen peroxide, copper and the tallowy flavor in milk. J. Dairy Sci. 29, 293.

Kinetics of auto-oxidation of ascorbic acid. Food Research 14, 325.

Joslyn, M. A., and Ponting, J. D.

Kaufman, C. W., and Campbell, H. A.

Keeney, D. G., Baur, L. S., and Garrett, 0. F.

fruit products. Advances in Food Research 3, 1.

1948.

1951.

1939.

Medical Association, p. 197.

z e d . 51, 2388.

1950. variety. Food Inds. 22, 836.

worts and beers. Schweiz. Brau. Rundscha-u 61, No. 12, 203. 1950.

1950.

1945.

Krukovsky, V. N., and Guthrie, E. S. 1946.


Krukovsky, V. N. The origin of oxidized flavors and factors responsible for their developnient in milk and milk products.

Kyhos, E. D., Sevringhaus, E. L., and Hagedorn, D. 1945. Large doses of ascorbic acid in treatment of vitamin C deficiencies.

Lakritz, W. 1943. Lemon and orange oil preservation. Mfg. Confectioners 23, No. 9, 18.

Lamb, F. C., Lewis, L. D., and White, D. G. 1951. The nutritive value of canned foods: The effect of storage on the ascorbic acid content of canned tomato juice and tomato paste. Pood Technol. 5, 269.

Lamden, M. D. 1950. Copper contamination and ascorbic acid loss in Wariiig blendor. Anal. Chem. 22, 1139.

Lamden, M. D., and Harris, R. S. Browning of ascorbic acid in pure solution. Pood Research 15, 79.

Laiitz, A. W. 1950. An apparatus for dipping fish fillets or steaks. Fisheries Research Board Can., Progress Bepts. Pacific Coast Stas. No. 82, p. 6.

Lavers, C. G. 1948. Discoloration of packaged red meat. Modern Packaging 21, 125 (Jan.).

Lawrence, J. M., Herrington, B. L., and Maynard, L. A. 1945. Human milk studies. Comparative values of bovine and human milks in infant feeding. Am. J . Diseases Children 70, 173.

Lee, F. A., Beattie, H. G., Robinson, W. R., and Pederson, C. S. The preservation of apple juice by freezing. Pruit Prod. J. 26, 324.

Lee, F. A., Robinson, W. B., Hening, J. C., and Pederson, C. S. 1950. Low temperature preservation of fruit juices and fruit juice concentrates. N . P. State Agr. Expt. Sta. (Geneva) Bull. No. 743.

Lee, F. A., Fenton, F., and Stevens, H. B. The control of browning in frozen sliced apples.

Lee, van der, G. 1942. Stable mixtures containing ascorbic acid or the like. U. S. Pa ten t 2,300,439.

Leeder, J. G., and Herreid, E. 0. Relation of ascorbic acid and of oxygen t o oxidized flavor in milk. Vermont State. Coll. Agr. Expt. Sta. Bull. No. 481.

Lehmann, B. T., and Watts, B. M. 1951. Antioxidants in aqueous f a t systems. J. Am. Oil Chemists’ SOC. 28, 475.

Leighton, A. E. 1951. How to vitaminize candy. Food Inds. 23, 104; Food Eng. 23, No. 4, 169.

Lincoln, R. E., Kohler, G. W., Silver, W., and Porter, J. W. 1949-1950. Breeding for increased ascorbic acid content in tomatoes. Bot. Gag. 111, 343.

Lockhart, E. E., Harris, R. S., Tapia, E. W., Lockhart, H. S., Nutter, M. K., Tiffany, V., and Nagel, A. N. 1944. Study of the nutritional quality of dietary by chemical analysis. J. Am. Dietet. Assoc. 20, 742.

The use of sugar and ascorbic acid in frozen Montmorency cherries. Quick Prozen Foods 14, No. 12, 55.

1946. The interrelationship of dietary, serum, white blood cells and total body ascorbic acid. J. Bid. Chem. 166, 111.

1952. Effects of prolonged high dosage with ascorbic acid.

The antioxidant properties of nordihgdroguaiaretic acid.

1952. J. Dairy Sci. 35, 21.

Arcla. Internal Med. 75, 407.

1950.

1947.

1951. Pood Technol. 5, No. 3, 114.

1942.

Loutfi, S. E., Bedford, C. L. and Robertson, W. F. 1952.

Lowry, 0. H., Bessey, 0. A., Brock, M. J., and Lopez, J. A.

Lowry, 0. H., Bessey, 0. A., and Burch, H. B.

Lundberg, W. O., Halvorson, H. O., and Burr, G. 0. Proc. Soc. Expt. Bio. & Med. 80, 361.

1944. Oil & Soap 21, 33.


Lundberg, W. 0. 1947. A. survey of present knowledge, researches and practices Hormel Institute,

Lundborg, M., and Hard, E. 1946. The iiifluence of sodium chloride content on

Luther, H. G., and Cragwell, G. 0. Ascorbic-citric acids prevent browning

Major, R. T. 1942. Industrial development of synthetic vitamins. Chem. Eng.

Maltha, P. R. A. Process for the manufacture of an improving agent for

Manning, P. D. V., Woods, B., and Trone, E. 1945. Vitamin product and process

Mapson, L. W., and Walker, S. E. The synthesis of ascorbic acid in the Brit. J.

Mapson, L. W., and Walker, S. E. 1947. Synthesis of ascorbic acid in vitamiu A-

Mapson, L. W., and Ingram, M. Observations on the use of Escherichia coli Biochern. J . 48, 551.

Markwell, N. W. 1947. Vitamin C in the prevention of colds. Med. J. Australia

Marshall, C. R. 1951. Oxidation in apple juice. Oxidation turbidities. J. Sci.

Marshall, J. B., Hopkins, J. W., and Young, G. A. 1944. Effects of conditions of storage and stability of ascorbic acid in various carriers. Can. J. Res. 12, 39.

Marshall, R. E. 1947. Apple juice preparation and preservation. Mich. State Coll. Agr. Expt. Sta. Bull. No. 206.

Massell, B. F., Warren, J. E., Patterson, P. R., and Lehmus, H. J. 1950. Anti- rheumatic activity of ascorbic acid in large doses. New Engl. J. Med. 242, 614.

Masterman, N. K., and Lee, F. A. The home freezing of farm products. N. Y . State Agr. Expt. Sta. (Ithaca) Bull. No. 611.

Mattill, H. A., and Golumbic, C. 1943a. Antioxidant for fa ts and oils. U. S. Patent 2,333,655.

Mattill, H. A., and Golumbic, C. 1943b. Antioxidant for fa ts and oils. U. S. Patent 2,333,656.

Mattill, H. A., and Golumbic, C. 1 9 4 3 ~ . Antioxidant for f a t s and oils. U. S. Patent 2,333,657.

Matthill, H. A., and Golumbic, C. 1943d. Antioxidant for fa ts and oils. U. S. Patent 2,333,658.

Mattill, H. A. 1945. Antioxidants and synergists. Oil 4 Soap 22, 1. May, C. D., Nelson, E. N., Lowe, C. V., and Salmon, R. J.

megaloblastic anemia in infancy. Am. J . Diseases Children 80, No. 2, 191. Mayer, J., and Erehl, W. A. 1948.

vitamin C to vitamin A deficiency. Maynard, L. A. 1950. Soils and health. J. Am. Med. Assoc. 143, 807. McCollum, E. V., and Grubb, W.

McCormick, W. J.

in the United States concerning the stabilization of fats. Univ. of Minn. Publ. No. 20.

oxidase action of mackerel musculature. Svensk Kern. Tid. 58, 240.

of cut fruit. Food Inds. 18, 690.

News 20, 517.

the baking quality of flour.

of manufacture.

rat deprived of vitamin A with and without addition of chloretone. Nutr. 2, 1.

deficient rat. Brit. J . Nutr. 1, 8. 1951.

for the reduction and estimation of dehydroascorbic acid.

2, 777.

Food and Agr. 2, 342.

1946.

1946. Canadian Patent 433,979.

U. S. patent 2,379,586. 1948.

1950.

1950. Pathogenesis of

The relation of the diet composition and J. Nutrition 35, 523.

1944. A completely supplemented evaporated

Vitamin C in the prophylaxis and therapy of infectious milk and i ts use as a food for infants. Am. J . Diseases Children 68, 231.

diseases. Arch. Pediat. 68, 1. 1951.


McCormick, W. J. 1952. Ascorbic acid as a chemotherapeutic agent. Arc7~. Pe- diat. 69, 151.

Me. Daniel, E. G., and Daft , F. S. 1952. Effect of large amounts of ascorbic acid on iron salt-induced f o l k acid deficiency. Federation Proc. 11, 450.

Melnick, D., Hochberg, M., and Oser, B. L. 1945. Physiological availability of the vitamins. The human bioassay technique. J. Nutrition 30, 367.

Melnick, D., Hochberg, M., and Oser, B. L. 1947. Physiological availability of the vitamins. Influence of ascorbic acid stabilizers in fruits and vegetables. J . Nutrition 34, 409.

Melville, J., and Shattock, H. T. 1938. The action of ascorbic acid as a bread improver. Cereal Chem. 15, 201.

Michaelis, L. 1948. The mechanism of autooxidation and the action of an antioxidant. Trans. 3rd Conf. Biological Antioxidants, J . Macy, Jr., Found., p. 11.

Miller, M. C. 1947. Reductone interference in estimation of vitamin C. Food Research 12, 343.

Miller, E. V., and Schaal, E. E. 1951. Individual variation of the fruits of the pineapple in regard to certain constituents of the juice. Food Research 16, 252.

Mills, M. B., Damron, C. M., and Roe, J. H. 1949. Ascorbic acid, dehydroascorbic acid and diketogulonic acid in fresh and processed foods. Anal. Chem. 21, 707.

Monroe, K. H., Breighton, K. W., and Bendix, G. H. The nutritive value of canned foods. Some studies of commercial marehouse temperatures with refcr- ence to the stability of vitamins in canned foods.

Moore, L. A. 1946. Vitamin A, ascorbic acid and spinal fluid pressure relatioii- ships in the young bovine. J. Nutrition 31, 229.

Mukherjee, S., Ray, S., and Goswami, M. 1950. Rancidity of butterfat. 2-Ascorbyl ester of f a t ty acids as antioxidants.

Munsell, H. E., Streightoff, F., Bcndor, B., Orr, M. L., Ezekiel, S. R., Leonard, M. H., Richardson, M. E., and Koch, F. J. 1949. Effect of large-scale methods of preparation on the vitamin content of food. Cabbage. J. Am. Dietet. Assoc. 25, 420.

The ascorbic acid content of different varieties of Maine-grown tomatoes and cabbages as influenced by locality, season and stage of maturity. J. Agr. Research 64, 483.

Mustard, M. J. Ascorbic acid content of some miscellaneous tropical and subtropical plants and plant products. Food Research 17, 31.

Mylene, A. M., and Seegmiller, C. G. 1950. Laboratory studies on factors affecting leaching losses during the processing of apples. Food Technol. 4, 43.

Nagel, A. H., and Harris, R. S. Effect of restaurant cooking and service on vitamin content of foods.

Nath, M. C., Chitale, R. P., and Belavady, B. 1952. Biosynthesis of vitamin C and a new precursor.

Nelson, W. L., and Somers, G. F. 1943. Determination of ascorbic acid. Ind. Eng. Chem. Anal. Ed. 17, 754.

Nichol, C. A., and Heinle, R. W. 1952. Enzymatic conversion of folic acid to citrovorum factor.

Noble, I. 1951. Color and ascorbic acid variations in cabbage cooked by various

Norris, F. A. 1945a. Stabilization of f a t products. U. S. Patent 2,377,029. Norris, F. A. 1945b. Stabilization of fa t ty products. U. S. Patent 2,377,030. Norris, F. A. 1945c. Stabilization of f a t products. U. S. Paten t 2,377,031.

1949.


J . Ind. Chem. SOC. 27, 539.

Murphy, E. 1942.

1952.

1942. J . Am. Dietet. Assoc. 19, 23.

Nature 170, 545.

Federation Proe. 11, 452.

methods. Food Research 16, 71.


Norris, F. A. 1949. Stabilization of oleaginous materials. U. S. Patent 2,462,-

Olcott, H. S. 1941. Antioxidants for edible fa t s and oils. Oil $. Soap 18, 77. Oser, B. L., Melnick, D., and Oser, M.

Oser, B. L. 1948. Grocery stores best source of vitamins. Food Inds. 20, 1440. Oser, B. L. 1952. How nutrients are lost in processing and handling foods.

0901, A., and Farrar, G. E. 1947. Ascorbic acid. The Dispensatory of the United

Owen, J. T. 1950. Peanut products. U. S. patent 2,494,717. Parkinson, T. L. 1952. The determination of ascorbic acid in canned foods con-

taining ferrous iron. Chem. $. Indus. 1, 17 (Jan. 5). Patton, S. 1950. Studies of heated milk. Formation of 5-hydroxymethyl-2-

furfural. J. Dairy Sci. 33, 324. Paul, P., Einbecker, B., Kelley, L., Jackson, M., Jackson, L., Marshall, R. E.,

Robertson W. F., and Ohlson, M. A. 1949. The nutritive value of canned foods. Changes in ascorbic acid of vegetables during storage prior to canning. Food TechnoZ. 3, 228.

Pecci, J. D., and Ribeiro, 0. F. 1943. The vitamin content in citrus simensis, L. Rev. faculdade med. vet., Univ. Sao Paul0 2, 103 (C.A. 38:64141).

Pecherer, B. 1951. The preparation of deliydro-Z-ascorbic acid and its methanol complex. Some reactions of dehydro-l-ascorbic acid. J. Am. Chem. Soe. 73, 3827.

Pederson, C. S., and Beattie, H. G. 1944. Problems in fruit processing. Food in Canada 4, No. 4, 11.

Pederson, C. S., and Beattie, H. G. Effect of processing and storage on the quality and ascorbic acid content of sauerkraut.

Pederson, C. S. 1947. Apple juice with original character retained. Fruit Prod. J. 26, 299.

Pederson, C. S., Robinson, W. B., and Sliaulis, N. 1953. Opalescent juice from white grapes. Farm Research 19, 1.

Pepkowitz, L. P., Larson, R. E., Gardner, J., and Owens, G. 1944. Carotene and ascorbic acid concentrations of vegetable varieties.

Peterson, R. W., and Walton, J. H. 1943. Autoxidation of ascorbic acid. J . Am. Chem. Soc. 65, 1212.

Peterson, W. J., Tucker, H. P., Wakeley, J. T., Comstock R. E., and Cochran, F. D. 1951. Variation in moisture and ascorbic acid content from leaf to leaf and plant to plant in turnip greens.

664.

1943. Influence of cooking procedures upon retention of vitamins and minerals in vegetables. Food Research 8, 115.

Food Eng. 24, 62.

States of America. 24th ed. J. P. Lippincott, p. 114.

1946. Food Packer 27, No. 7, 44.

Plant PhysioZ. 19, 615.

Southern Coop. Series Bull. No. 10, p. 13. Phillips, W. 1951. Food flavor intensifiers. U. S. Patent 2,539,160. Phipard, E. F. 1951. How good are fa rm diets? An address, 29th Annual Agri-

cultural Outlook Conference, Washington, D. C., October 30. Pierce, H. B., Krause, R. F., Browne, J. H., and Memos, S. 1947. Nutritional

status of Burlington, Vermont, children. Ponting, J. D., and Joslyn, M. A. Ascorbic acid oxidation and browning

in apple tissue extracts. Arch. Biochem. 19, 47. Pottinger, S. R. 1952. Frozen Atlantic oyster investigations. Food Technol. 6, 28. Powers, J. J., and Fellers, C. R. Preventing surface darkening in certain

Proctor, B. E., and Goldblith, S. Radar energy for rapid food cooking and

Federation Proc. 6, 418. 1948.

1945. home-canned foods. J . Home Econ. 37, 294.

1948. blanching and its effect on vitamin content. Food Technol. 2, 95.


Proctor, B. E., and Goldblith, S. 1950. Electromagnetic radiation fundamentals and their applications in food technology. Advances in Food Research 3, 119.

Proctor, B. E., and O'Meara, J. P. Effect of high-voltage cathode rays on ascorbic acid. Ind. Eng. Chem. 43, 718.

Proctor, B. E., Goldblith, S. A., Bates, C. J., and Hammerle, 0. A. 1952. Bio- chemical prevention of flavor and chemical changes in foods and tissues sterilized by ionizing radiations. Food Tech. 6, 237.

1949. The statistical association between the diet record of ascorbic acid intake and the blood content of the vitamin in surveyed populations. Milbank Mem. Fund Quart. 22, No. 4, p. 355.

1951. Comparison of some constituents in fresh frozen and freshly squeezed orange juice. J. Am. Dietet. Assoc. 27, 864.

Ralli, E. P., and Sherry, S. Adult scurvy and metabolism of vitamin C. Medicine 20, 251.

Ramsbottom, J. M., Goeser, P. A., and Shultz, H. W. 1951. How light discolors meat: what to do about it. Food Inds. 23, No. 2, 120.

Ramstad, P. E., and Volz, F. E. 1950. Did it thaw$ Gel will tell. Food Inds. 22, 84.

Randall, R. 1949. Frozen homogenized milk for Army use. J . Hilk Tech. 12, 101. Reddi, R. R., Esselen, W. B., Jr., and Fellers, C. R. 1950. Peroxidase activity in

apple tissue. Food Technol. 4, 63. Reed, 0. E. 1947. Vitamin C retards development of oxidized flavor in fresh milk.

Rept. Chief of Dairy I d . , Agr. Res. Admin., 77. S. Dept. Agr., p. 23. Reichstein, T., Griissner, A., and Oppenauer, R. 1933. Synthesis of d - and 1-ascorbic

acid. Helv. Chim. Acta 16, 561, 1019. Rescigno, G. 1951. Vitamin C addition to delay oxidative changes of commer-

cial butter. Latte 25, 292 (C.A. 46:6768c). Ribeiro, 0. F. 1944. Vitamin C in Brazilian citrus fruits. Anak (ISSOC. quim.

Brazil. 3, 40 (C.A. 38:64139). Richardson, J. E., and Mayfield, H. L. 1941. Vitamin C content of winter fruits

and vegetables. Mont. State Coll. Agr. Expt. Sta. Bull. No. 390. Richardson, J. E., and Mayfield, H. L. 1944. Influence of sugars, fruit acids and

pectin on the oxidation of ascorbic acid. Mont. State. Coll. Agr. Expt. Sta. Bull. No. 423.

Riemenschneider, R. W., and Turer, J. 1945a. Antioxidant compositions. U. S. Patent 2,375,250.

Riemenschneider, R. W., and Turer, J. 1945b. Ternary synergistic antioxidant compositions. U. S. Patent 2,383,815.

Riemenschneider, R. W., and Wells, P. A. 1945. Antioxidant. U. S. Patent 2,368,435.

Riemenschneider, R. W. Oxidative rancidity and the use of antioxidants. Trans. Am. Assoc. Cereal Chemists 5, 50.

Riemenschneider, R. W., and Turer, J. 1948a. Alkali compounds coiitaining antioxidant compositions.

Riemenschneider, R. W., and Turer, J. 1948b. Synergistic antioxidant composition of the acidic type. Composition and process ascorbic acid ester and lecithin. U. S. Patent 2,440,383.

Riemenschneider, R. W., and Turer, J. 1952. Antioxidant compositions. U. S. Patent 2,375,250.

1951.

Putnam, P., Milam, D. F., Anderson, R. K., Darby, W. J., and Mead, P. A.

Rakieten, M. L., Newman, B., Falk, K. B., and Miller, I.

1941.

1947.

U. S. Patent 2,383,816.


Roberts, M., Laufer, S., and Stewart, E. D. 1947. Air in beer. Determination of air and oxygen in storage and finished beer. Am. Soc. Brewing Chemists, Proc. 87.

1945. An indophenol-xylene extraction method for ascorbic acid and modifications for interfering substances. J. Biol. Chem. 160, 217.

The effect of maiiufacturing methods on the ascorbic acid content and consistency characteristics of tomato juice. J . Nutrition 30, 435.

Rodgers, P. D., Wegener, J. B., and Baer, B. H. 1950. Vacuum treatment curbs browning of apple slices.

Roe, J. H., and Oesterling, M. J. 1944. The determination of dehydroascorbic acid and ascorbic acid in plant tissues by the 2,4-Dinitrophenylhydrazii1e method. J . Biol. Chem. 152, 511.

Roe, J. H., Kuether, C. A., and Zimler, R. G. The distribution of ascorbic acid in the blood. J. Clin. Invest. 26, 355.

Rosenberg, H. R. Vitamin C-Ascorbic Acid, Chemistry and Physiology of the Vitamins.

Roy, W. F., and Russell, H. E. Concentrated and then quick frozen orange juice retains i ts vitamin C.

Rubin, S. H., Jahns, F. W., and Bauernfeind, J. C. 1945. Determination of vitamin C in fruit products.

Ruskin, S. L. 1947. Sodium ascorbate in the treatment of allergic disturbances. The role of the adrenal cortical hormone-sodium-vitamin C. Am. J . Digestive Diseases 14, 302.

Sale, J. W., e t al. 1947. Ascorbic acid in grapefruit juice, orange juice and their blends: 1947. J . Assoc. Oficial Agr. Chem. 30, No. 4, 673.

Sale, J. W., et al. 1946. Ascorbic acid in tomatoes and tomato juice. J . ASSOC. Oficial Agr. Chem. 29, 69.

Sandstedt, R. M., and Hites, B. D. 1945. Ascorbic acid and some related compounds as oxidizing agents in doughs. Cereal Chem. 22, 161.

Scarborough, D. A., and Watts, B. M. 1949. The pro6xidant effect of ascorhic acid in cysteine in aqueous f a t systems.

Schmall, M., Pifer, C. W., and Wollish, E. G. 1953. Determination of ascorbic acid by a new colorimetric reaction. Anal. Chem. (in press) .

Scliocken, V., and Roe, J. H. 1952. Elimination of interference in determination of ascorbic acid by the 2,4-dinitrophenylhydrazine methods. Federation Proc.

Schulte, K. E., and Schillinger, A. 1952. Oxidative decomposition of I-ascorbic acid. Compaiison of the kinetics of iionfermentative oxidation of d-isonscorbic and I-ascorbic acids. Z. Lebensm.-Untersuch. u. Forsch. 94, 77. (C . A. 46 :4134g).

Scliwenk, E., and Henderson, E. E. 1945. Hydroquinone composition. U. S. Patent 2,376,884.

Scoular, F. I., and Bryan, A. R. 1944. Ascorbic acid content of school lunclies. J . Home Economics, 36, 651.

Sealock, R. R., and Goodland, R. L. Ascorbic acid, a co-enzyme in tyrosine oxidation. Sci. 114, 645.

Sedky, A., Stein, J. A., and Weckel, K. G. 1952. Factors affecting color and flavor of sauerkraut packaged in pliofilm bags.

Robinson, W. B., and Stotz, E.

Robinson, W. B., Stotz, E., and Kertesz, Z. I. 1945.

Food Inds. 22, 1527.

1947.

1942. Interscience Publishers, New York, p. 289.

1948. Food In&. 20, 1764.

Fruit Prod. J . 24, 327.


11, 455.

1951.

Food Tech. 6, 377.


Seeder, W. A. 1950. Process of preparing C-vitaminized baking products. Process of baked foods with good C stability. U. S. Patent 2,497,035.

Segard, J. 1935. Effect of the degree of oxidation of bee1 oh pasteurization. Bull. assoc. anciens blBves inst . super. fermentat ions Gand. 36, 243; (C. A., 30, 231).

Sevringliaus, E. L. 1944. Adult necds of vitamins A and C. J . Am. Med. Assoc. 126, 751.

Sharp, P. F., Trout, G. M., and Guthrie, E. S. 1937. Vitamin C, copper and oxidized flavor of milk. Milk Plant Monthly 26, 32 (May).

Sharp, P. F. Rapid method €or the quantitative determination of reduced ascorbic acid in milk.

Sharp, P. F., and Hand, D. B. Riboflavin, vitamin C and flavor of dairy products.

Sheft, B. B., Griswold, R. M., Tarlowsky, E., and HalIiday, E. G. 1949. Nutritive value of canned foods. Effect of time and temperature of storage on vitamin content of commercially caiiiied fruits and f ru i t juices (stored 18 to 24 months). Ind. Eng. Ghem. 41, 144.

1945. Exeretioil of ascorbic acid and dehydroascorbic acid in sweat and urine under different environmental conditions. J . Biol. Chem. 161, 351.

Shillinglaw, C. A., and Levine, M. Control of oxidative flavors in beverages. Food Research 8, 453.

Siemers, G. F. 1945. Adding vitamins to candies. Food Inds. 17, 128. Siemers, G. F. 1946. Processing of vitamin C (ascorbic acid) enriched apple juice.

Glass Packer 25, No. 8, 612. Siemers, G. F. 1952. Recent developments in ascorbic acid as a n antioxidant in

beer. Silbert, N. E. 1951. Vitamin C. Med. T i m e s 79, 370. Singruen, E. 1940. Oxidation turbidities and their causes. Modern Brewer 23,

No. 1, 31. Smith, A. C., Lowenstein, M., Anderson, R. E., and Olson, H. C. 1952. The use

of ascorbic acid and tocopherol in controlling oxidized flavor in frozen storage cream. Milk Plaiat Monthly 41, No. 5, 26.

1945. Field illumination and commercial handling as factors in determining the ascorbic acid content of tomatoes received at the cannery. J . Nutr i t ion 30, 425.

1948. The influence of climate and fertilizer practices upon the vitamin and mineral content of vegetables. Advances i n Food Research 1, 291.

Spannuth, H. T. 1949. Stabilization and antioxidants. J . Am. Oil Chem. SOC. 36, 618.

Stadtman, E. R. 1948. Nonenzyniatic browning in fr-dit products. Advances in Food Research 1, 325.

Stewart, A. P., Jr., and Sharp, P. 1945. Determination of vitamin C in the presence of interfering reducing substances. I n d . E n g . Chem. Anal . Ed., 17, 373.

Stewart, A. P., Jr., and Sharp, P. Vitamin C content of market, evaporated milk and powdered whole milk. J . Nutr i t ion 31, 161.

Stoloff, L. S., Punocher, J. F., and Crowther, 13. C. 1948. Curb mackerel fillet rancidity with new dip-and-coat technique.

Stoloff, L. S. 1951. Preservation of foodstuff. U. S. patent 2,567,085.

1938. J . Dairy Sci. 21, 85.

Proc. Znst. Food Technol. 1, 139. 1940.

Shields, J. B., Johnson, B. C., Hamilton, T. S., and Mitchell, H. H.

1943.

Abs . of American Soc. of Brewing Chem., 1952 convention, Toronto.

Somers, G. F., Hamner, K. C., and Nelson, W. L.

Somers, G. F., and Beeson, K. C.

1946.

Food Znds. 20, 1130.


Storvick, C. A., Davey, B. L., Nitchals, R. M., and Coffey, R. E. 1950. Reduced ascorbic acid content of food served in institutional quantities. Food Research 15, 373.

1951. Nutritional status of selected population groups in Oregon. Food habits of native born and reared school children in two regions. Milbank Mem. Pund Quart. 29, 165.

Strachan, C. C. 1942. Factors influencing ascorbic acid retention in apple juice. Can. Dept. Agr. Pub. No. 732.

Strachan, C. C., aiid Moyls, A. W. A simple method for estimating ascorbic acid in fortified apple juice.

Strachan, C. C., and Moyls, A. W. Ascorbic, citric and dihydroxymaleic acids as antioxidants in frozen pack fruits.

Strachan, C. C., Moyls, A. W., Atkinson, F. E., and Britton, J. E. 1951. Chemical composition and nutritive value of British Columbia tree fruit. Can. Dept. Agr. Pub. No. 862.

Streightoff, F., Munsell, H. E., Bendor, B., Orr, M. L., Cailleau, R., Leonard, M. H., Ezekiel, S. R., Kornblum, R., and Koch, F. G. 1946. Effect of large-scale methods of preparation on vitamin content of food: Potatoes. J . Am. Dietet. Assoc. 22, 117.

Streightoff, F., Bendor, B., Munsell, H. E., Orr, M. L., Ezekiel, S. R., Leonard, M. H., Richardson, M. E., and Koch, F. G. Effect of large-scale methods of preparation on the vitamin content of food: Spinach. J . Am. Dietet. Assoc. 25, 770.

The effect of interrelationship of copper, iron and pasteurizing temperature on the stability of ascorbic acid added to skim milk. J . Dairy Sci. 33, 573.

1952. The determination of bound ascorbic acid in liver tissue. J. Biol. Ghem. 196, 753.

1947. Vitamin retentioil and acceptability of fresh vegetables cooked by four household methods and by an institutional method. Food Research 12, 496.

Svirbely, J. L., and Szent-Gyorgyi, A. 1932. Hexuronic acid as the antiscorbutic factor. Nature 129, 576; Biochem. J . 26, 865.

Swanson, A. M., and Sommer, H. H. 1940. Oxidized flavor in milk. The relation of oxidation-reduction potentials to i ts development. J . Dairy Sci. 23, 597.

Swern, D., Stirton, A. J., Turer, J., and Wells, P. A. 1943. Fa t ty acid monoesters of Z-ascorbic acid and d-isoascorbic acid.

Szasz, R. 1950. Ascorbic acid in the conservation of beer. Echo de Brasserie 6, No. 5, 18.

Szent-Gyorgyi, A. 1928. Observations on the function of peroxidase systems and the chemistry of the adrenal cortex. Description of a new carbohydrate deriva- tive. Baochem. J . 22, 1387.

Szent-Gyorgyi, A. 1930. On the mechanism of biological oxidation. Science 72, 125.

Tarr, H. L. A. Effect of p H and NaCl on swelling and drip in fish muscle. J . Fisheries Research Board Can. 5, 411.

Tarr, H. L. A. 1946a. Control of rancidity in stored fish. Fisheries Research Board Can., Progress Repts. Pacific Coast Stas. No. 66, 17.

T a n , H. L. A. 1946b. Control of rancidity in stored fish. Fisheries Research Board Can., Progress Repts. Pacific Coast Stas. No. 68 , 52.

Storvick, C. A., Schaad, B., Coffey, R. E., and Deardorff, M. B.

1946. Food in Canada 6, No. 8, 13. 1949.

Pood Technol. 3, 327.

1949.

Stribley, R. C., Nelson, C. W., Jr., Clarke, R. E., and Bernhart, F. W. 1950.

Sumerwell, W. N., and Sealock, R. R.

Sutherland, C. K., Halliday, E. G., and Hiiiman, W. F.

Oil & Soap 20, 224.

1942.


Tam, H. L. A. 1947. Control of rancidity in fish flesh. Chemical antioxidants. J . Fisheries Research Board Can. 7, 137.

Tarr, H. L. A. 1948. Control of rancidity in fish flesh. Physical and chemical methods. J . Fisheries Research Board Can. 7, 5.

Tarr, H. L. A., Lantz, A. W., and Carter, N. M. 1950. The preparation and application of brines and dipping solutions for processing certain fish products. Fisheries Research Board Can., Progress Repts. Pacific Coast Stas. No. 84, 51.

1951. Control of rancidity in stored fish. Fisheries Research Board Can., Progress Repts. Pacific Coast Stas. No. 88, 67.

Tenney, R. I. 1938. Beer oxidation. Wahl-Henius Inst. Chicago Bull. No. 5, 14. Thiessen, E. Conserving vitamin C by varying canning procedure in snap-

beans, tomatoes, peaches and pears. Thomas, M. H., Brenner, S., Eaton, A., and Craig, V. 1947. Effect of electronic

cooking on nutritive value of foods. Thomson, R. M. 1952. Practical control of air in beer. Brewers’ Guild Journal.

May. Tillmans, J. 1927. The determination of electrical oxidation-reduction potential

and its application in food chemistry. 2. Untersuch. Lebensm. 54, 33. Todhunter, E. N., Robbiiis, R. C., and McIntosh, J. A. 1942. The rate of increase

of blood plasma ascorbic acid after ingestion of ascorbic acid (vitamin C). J. Nutrition 23, 309.

Todliunter, E. N., McMillan, T., and Ehmke, D. A. 1950. Utilization of dehydroascorbic acid by human subjects.

Toverud, K. V., Stearns, G., and Macy, I. G. 1950. Maternal nutrition and child health, an interpretive review. Bull. National Res. Council (U. S.) No. 123.

Tressler, D. K., and Du Bois, C. No browning of cut fruit when treated by new process. Food Inds. 16, 701.

Tressler, D. K., and Evers, C. F. 1947. The Freezing Preservation of Foods. Avi Publishing Co., p. 552.

Tressler, D. K., and Pederson, C. S. A sound basis for frozen food standards. Food Packer 32, 29.

Trout, G . M., and Gjessing, E. C. 1939. Ascorbic acid and oxidized flavor in milk. Distribution of ascorbic acid and occurrence of oxidized flavor in commercial grade A raw, in pasteurized irradiated and in pasteurized milk throughout the year. J. Dairy Sci. 22, 271.

1949a. New York State nutrition survey. J. Am. Dietet. Aasoc. 25, 595.

Trulson, M., Ogle, J., and Stare, F. J. A study of one week’s food purchases of 135 families. J . Am. Dietet. Assoc. 25, 764.

Tuba, J., Hunter, G., and Steele, H. R. On the specificity of dye titration for ascorbic acid. Can. J . Research 24, 37.

Tutton, W. R., and Coonen, N. H. The war on oxygen in canned foods. Food in Canada 10, No. 11, 42.

Udenfriend, S., Clark, C. T., Axelrod, J., and Brodie, B. B. 1952. Oxidative properties of ascorbic acid. Fed. Proc. 11, 300.

Ugon, N. A., and Bertullo, W. Degree of maturity of citrus fruits compared with their richness in vitamin C. Anales. assoc. quim. farm. Urugwty 47, NO. 1, 5 (C.A. 40:9661).

Tarr, H. L. A., Southcott, B. A., and Bissett, H. M.

1949. Food Research 14, 481.

J . Am. Dietet. ASSOC. 25, 39.

J . Nutrit ion 42, 297.

1944.

1951.

Trulson, M., Hegsted, D. M., and Stare, F. J. A nutrition survey of pub& school children.

194913.

1946.

1950.

1945.


Urbach, E., and Gottlieb, P. M. 1946. Allergy. Grune and Stratton, New York,

Urion, M. 1950. Ascorbic acid and beer. Brasserie 5, No. 43, 115. Van Blaricom, L. D., Cooper, J. B., Wheeler, R. F., Warner, K. F., and Martin, M.

S. Carolina Agr. Expt. Sta. Bull. No. 110. Van Duyne, F. O., Owen, R. F., Wolfe, J. C., and Charles, V. R. 1951. Effect

J. Am. Diet.

1945. Utiliza- J . Daily Sci.

von Woker, G., and Antener, I. 1937. Ascorbic acid reactions. Helv. Chim. Acta

Walker, W. S. 1949. How nitrogen protects the quality of foods. Food Inds. 21,

Watt, B. K., and Merrill, A. L. Composition of foods, raw, processed and

Watts, B. M., and Chang, I. Antioxidants in the hemoglobin catalyzed oxi-

Watts, B. M., and Wong, R. Some factors affecting the antioxidant behavior

Watts, B. M., and Lehmanii, B. T. 1952a. Ascorbic acid and meat color. Food

Watts, B. M., and Lehmann, B. T. 1952b. The effect of ascorbic acid on the Food

Waugh, W. A., and King, C. G. 1932a. The chemical iiature of vitamin C. Science

Waugh, W. A., and King, C. G. The isolation and identification of vitamin

Weckel, I(. G. 1951. Mineral and vitamin fortified milks. Milk Plant Monthly

Weinstein, B., Loewenstein, M., and Olson, H. C. 1948. Tbe use of ascorbic acid

Weinstein, B. R., and Trout, G. M. The solar-activated flavor of homog- The role of oxidation and the effectiveness of certain treatments.

Weissberger, A., and LuValle, J. E. 1944. Oxidation processes. The autosidation

White, D. A. 1950. Reveal new uses for muscadine grapes. Food Inds. 22, 1719. Wiegand, E. H. 1946. Oxidation and its control. Quick Frozen Foods 8, 81

(April). Wiegand, E. H., and Yang, H. Y. Commercial preservation of apple juice.

Oregon Agr. Expt. Sta. Bull. No. 487. Woessner, W. W., Elvehjem, C. A., and Schuette, H. R. 1939. The determination

of ascorbic acid in commercial milk. Woessner, W. W., Weckel, K. G., and Schuette, H. A. 1940. The effect of com-

mercial practices on ascorbic acid and deliydroascorbic acid (vitamin C) in milk.

How to prevent browning of peaches in the freezing in-

p. 310.

1951.

of cooking vegetables in tightly covered and pressure saucepans. Assoc. 27, 1059.

tion and excretion of ingested ascorbic acid by the dairy cow. 28, 759.

20, 732.

1189.

prepared. 77. S. Dept. Agr. Handbook, No. 8. 1949.

dation of uiisaturated fats.

of ascorbic acid with unsaturated fats. Arch. Biochem. 30, 110.

Tech. 6, 194.

oxidation of hemoglobin and the formation of nitric oxide hemoglobin. Research 17, 100.

Freezing foods for home use.

Vavicli, M. G., Dutcher, R. A., Guerrant, N. B., and Bechdel, S. I.

1950.

Food Technol. 3, 332. 1951.

75, 357. 193213.

C. J . Biol. Chem. 97, 325.

40, No. 12, 20.

in controlling oxidized flavor in milk. Milk Plant Monthly 37, No. 10, 116.

enized milk. J . Dairy Sci. 34, 559.

of ascorbic acid in the presence of copper. J . Am. Chem. SOC. 66, 700.

1951.

1950.

J . Nutrition 18, 619.

J . Dairy Sci. 23, 1131. Woodroof, J. G. 1940.

dustry. Food Inds. 12, No. 5, 35; No. 6, 50.


Woodroof, J. G., Cecil, 8. R., Atkinson, I., and Shelor, E.

Woodroof, J. G., Shelor, E., Cecil, 8. R., and Atkinson, I.

1946. Ascorbic acid improved frozen peach packs. Food Freezing 1, No. 2, 123.

1947. Preparation of peaches for freezing. Univ. Georgia Agr. Expt . Sta. & Tenn. Valley Authority Bull. No. 251.

Woodroof, J. G., and Shelor, E. 1951. Home freezers and home freezing. Georgia Agr. Expt . Sta. Bull. No. 266.

Wright, P. A., and Greenbank, G. R. 1949. The effect of ascorbic acid content on fluid milk upon the keeping quality of its dried product. J . Dairy Sci. 32, 644.

Yang, H. Y., and Wiegand, E. H. Home processing of f ru i t and vegetable juices.

Yonmans, J. B. 1951. Deficiencies of the water soluble vitamins. Handbook of Nutrition. 2nd ed. American Medical Association, p. 563.

Young, C. M., Lightbody, V., Smudski, V. L., and Stelle, B. F. 1951. Fall and spring diets of school children in New York State. J. Am. Dietet. Assoc. 27, 289.

Yourga, F. J., Esselen, W. B., Jr., and Fellers, C. R. 1944. Some antioxidant properties of d-isoascorbic acid and its sodium salt. Food Research 9, 188.

Yourga, F. J. 1948. How to prevent off-color in glassed carrots. Food Inds. 20, 47.

Zscheile, F. P. 1950. Role of genetics in food quality improvement. Nutrit ion Rev. 8, 65.

1952. Oregon Agr. Expt. Sta. Bull. 515.

[advances in food research] advances in food research volume 4 volume 4 || the use of ascorbic acid...

Documents