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UTILIZATION OF SYNTHETIC

GUMS IN THE FOOD INDUSTRY

BY MARTIN GLICKSMAN

Techaical Cenler. General Foods Corporation. Tarrytown. N . Y

I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 A . Economic Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 B . Cellulose Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 C . Completely Synthetic Gums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

11 . Microcrystalline Cellulose (Avicel) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 A . Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 B . Food Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

I11 . Sodium Carboxymethylcellulose (CMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 A . Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 B . Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 C . Dairy Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 D . Bakery Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 E . Salad Dressings, Sauces, and Gravies . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 F . Confectionery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 G . Dietetic Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 H . Processed Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 I . Dry Package Mixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 J . Food Preservation Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 I< . Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

IV . Methylcellulose and Hydroxypropylmethylcellulose . . . . . . . . . . . . . . 314 A . Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 B . Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 C . Bakery Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 D . DieteticFoods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 E . Dehydrated Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 F . FroeenFoods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 G . Edible Protective Coatings 327 H . Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

V Other Cellulose Derivatives 325 A Hydroxyethylcellulose (HEC) B . Ethylcellulose (EC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

D . Carboxymethylhydroxyethylcellulose (CMHEC) . . . . . . . . . . . . . . . . . . 331 E . Klucel-Mixed Cellulose Ether . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

A . Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

C . Food Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336

. . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C . Ethylhydroxyethylcellulose (EHEC) . . . . . . . . . . . . . . . . . . . . . . . . . 331

VI . Polyvinylpyrrolidone (PVP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

B . Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

283

284 MARTIN GLICKSMAN

VII. Carbopol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 A. Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 B. Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 C. Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

VIII. Gantrez An . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 A. Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 B. Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 C. Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

IX. Polyox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 A. Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 B. Preparation , . , , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350 C. Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351 D. Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

X. Research Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

1. INTRODUCTION

A. ECONOMIC BACKGROUND

Gums or hydrophilic colloids have been used in foods and in the food industry for hundreds of years to impart various functional properties to food products and thereby enhance over-all palatability and acceptability. The term “gum” has often been used incorrectly and ambiguously and has been applied to various rubbers, resins, etc., in the paint, rubber, and oil industries. I n the food industry, the term “gum” is more specifically defined as any material that can be dissolved or dispersed in a water medium to give viscous or mucilaginous solutions or dispersions.

In the past, most gums were natural materials derived from seaweed extracts, tree and bush exudates, plant seed flours, and similar sources, and were almost all polysaccharides or mixtures of polysaccharides. To- day a new and growing category of gums, which is still in its infancy, is that of the synthetic gums. Although synthetic gums are currently only a small fraction of the total gum market, comprising about 100,000,000 pounds of the total 3,000,000,000 pounds of water-soluble gums sold domestically (Anonymous, 1961a), they are steadily pressing a t the position of the natural gums and enlarging their foothold in the field as newer and better gums become available.

Proponents of synthetic gums point to the giant advances of organic chemistry and feel that, as silk was replaced by nylon, rubber by neoprenc, waxes by plastics, so the natural gum polymers are targets for the synthetic organic chemist. Although exact duplications may not be possible, or even desirable, sufficient of the functional properties can be reproduced synthetically to create marketing opportunities for these new materials.

As starting materials, the synthetic chemist has available two of

UTILIZATION OF SYNTHETIC GUMS IN THE FOOD INDUSTRY 285

nature’s cheapest and most abundant raw materials-starch, a t about $0.06-0.09 per pound, and alpha-cellulose pulp, a t about $0.09-0.14 per pound. Both of these readily available polysaccharides are excellent starting materials for the production of gums. They both undergo chemical modification easiIy by heat, oxidation, or chemical treatment, and proper control of the modification makes possible a great variety of products. As Whistler (1959) pointed out, i t is conceivable that as more is learned about the relationship of structure to the physical properties of polymers, gum properties will probably be custom-tailored into starch and cellulose molecules so that they will more closely match the properties desired in special gum applications. Caution is urged, however, and i t must be re- membered that although synthetic chemical procedures may modify a polysaccharide to the desired end product, the materials and processing costs may be so high that the new gums will not be competitive in price with the natural gums. This is a stimulating challenge for industrial chemists and is a substantial protective barrier for the lower-cost natural gums. It is probable that in the foreseeable future, chemically modified starches and celluloses, as well as the purely synthetic gums, will con- tinually compete with the natural gums for the expanding markets for these materials.

As mentioned before, the traditional market for water-soluble gums was estimated to have been 3 billion pounds in 1961 (Anonymous, 1961a). Of this total, the largest percentage by far was held by the natural gums, including the starches, whereas only about 100 million pounds was composed of the synthetic gums. A conservative projection of the expanding markets for this material suggests that by 1970 the total market will have expanded to 4 billion pounds, with the proportion held by synthetics doubling to 200 million pounds. The author feels that this estimate is much too conservative, and that the market for synthetic gums will increase a t a much faster rate. This seems to be evident from more recent data compiled by Berger (1962), in Table I, which estimate the total consumption of synthetic gums in 1962 a t 127,000,000 pounds, and this compilation is incomplete, not including data on such synthetics as Gantrez An, Polyox, Carbopol, and other newer and less known gums. In addition, estimates of the potential market for water-soluble films alone range up to 20,000,000 lb per year (Anonymous, 1961a).

In the food industry, the synthetic gums at present occupy a minor role. Of the total market of 100,000,000 pounds in 1961, only an estimated 12,000,000 pounds was consumed by the food industry (Anonymous, 1961a), and this was chiefly by well-established gums such as carboxymethylcellulose and methylcellulose. The newer synthetics will have a difficult, up-hill, and expensive battle to develop markets in the food


TABLE I ESTIMATED CONSUMPTION OF WATER-SOLUBLE GUMS"

Millions of pounds

Cellulose derivatives Carboxymethylcellulose

Carboxymethylhydroxyethylcellulose

Ethylcellulose (not water-soluble) Hy droxy ethylcellulose

Ethylhydroxyethy lcell~ilose Methylcelluloc e

Polyacrylic acid salts Pol yacrylamide

Polyvinyl alcohol Polyvin ylpyrollidone

i Acrylates

Miscellaneous

Total

1957 1962

32.7 48.0

27.0 35.5

1.8 2.5 2.5 4.5

20.0 25.0 1 .o 11.5

85.0 127.0

a Berger, 1062.

industry. The reason, of course, is the stringent FDA regulations requiring extensive animal feeding tests and experimental assurance of nontoxicity before allowing their use as food additives. As a result, most companies developing water-soluble gums tend to loolc for industrial applications and strive to develop profitable markets in these nonfood industries before attempting to penetrate the food industry. The ease of penetration or acceptance is, of course, dictated by the novel and unique functional properties offered by the new gum that cannot be matched by the current available ones, or by the simple advantage of a cost reduction or product quality improvement.

In general, the synthetic gums tend to offer some of the following advantages over the natural gums:

1) Uniformity of properties 2) Constancy of price 3) Unlimited availability-not affected by crop failures, labor short-

4) LowB.0.D. I n a previous article, the author (Glicksman, 1962a) reviewed the

properties and applications of the natural polysaccharide gums in the food industry and covered the common seaweed extracts, tree exudates, and plant seed gums. This chapter is a similar review of the use of the synthetic

ages, etc.


gums in foods. It not only includes the well-established cellulose derivatives and modifications but also investigates the potential utility of newly available nontoxic gums that the author feels will eventually find a place on the shelf of the food manufacturer.

B. CELLULOSE DERIVATIVES The most abundant natural material in the world is cellulose, a linear

polymer of P-D-glucopyranose. It constitutes approximately one-third of all vegetable matter, where i t is the main constituent of the cell walls and provides the primary structural support for the plant. Cellulose has probably the largest molecular weight of all the natural polysaccharides and is one of the most resistant to attack by chemicals and microorgan- isms. I ts molecules tend to remain extended but may normally undergo a degree of turning and twisting. Because of its size and strong associative forces, i t can be brought into solution only under certain conditions.

The purest natural cellulose is cotton fibers or linters, which on a dry basis consist of about 98% cellulose. Wood contains about 40-500/0 and, together with cotton linters, is the most important commercial source for raw-material cellulose. Agricultural residues, such as corn stalks, corn cobs, and wheat straw, contain about 30% cellulose and are available as a vast reservoir of potentially available raw material (Whistler and Smart, 1953).

The cellulose derivatives commonly encountered in industry are ethers in which alkyl or hydroxyalkyl groups have been substituted upon one or more of the three available hydroxy groups in each anhydroglucose unit of the cellulose chain.

The effect of the substituent groups is to disorder and spread apart the cellulose chains so that water or other solvents may enter to solvate the chain. By controlling the type and amount (degree) of substitution, it is possible to produce products that have a wide range of functional properties (Battista, 1958).

A typical substituted structure would be represented as follows : ~ o ~ l p - o + i

I H OR !

I I I H -O I

I

L

where R = a substituent group.


The more important water-soluble derivatives are the following, where R is:

HO-CHZ-CHZ- H y droxyethyl- NaO 0 C-CH 2-

CHS- Methyl- CH3-CH2-O-CHZ-CHz-- Ethyl hydroxyethyl-

Sodium carboxymethyl-

Hydroxypropyl- 1 HO-CH-CH2-CH2-

CHa-HOCH- CHt- or

When all three available hydroxyl positions on the ccllulosc iiioleculc are replaced by a substituent group, the derivative is said to have a degree of substitution (D.S.) of three. Actually, this is usually not the case, since partial substitutions are preferred, but i t can readily be seen that varying the degree of substitution as well as the type of chemi-

TABLE I1 IMPORTANT INDUSTRIAL CELLULOSE DERIVATIVES

Trade name Chemical name Manufacturer

DOME STIC Avicel a-Cellulose (microcr ystalline) Methocel, MC Methylcellulose Methocel, HG Hydroxypropylmethylcellulosc

Sodium carboxymethylcellulose

Cellulose Sodium carboxymethylcellulose

Natrosol 250 Hydroxyethylcellulose Cellosice Hydroxyethylcellulose Natrosol E 75 Ethylhydroxyethylcellulose CMKEC Carboxymethylhydroxyethylcellulose Klucel Mixed cellulose ether

FOREIGN Methofas M Methylcellulose Methofm

Cellofas Ethylmethylcellulose Celacol Methylcellulose Celacol Hydroxyethylmethy lcellulose Modocoll Ethylhydroxyethylcellulose

gum I

HPM Hydroxypropylmethylcellulose

Tylose Methylcellulose

Edifas A Methylethylcellulose Edifas B Sodium carboxymethylcellulose i

American Viscose Co. Dow Chemical Co. Dow Chemical Co. Hercules Powder Co.

Du Pont

Hercules Powder Go. Union Carbide Corp. Hercules Powder Co. Hercules Powder Co. Hercules Powder Co.

Imperial Chemical Industries, England

British Celaneuc,

Mo Och Domsjo,

Kalle and Company,

Imperial Chemical

England

Sweden

Germany

Industries, Eiigland


cal substituent makes possible a tremendous range of permutations and combinations offering a wide range of functional properties. However, only a comparatively limited number of these derivatives have been found to have industrial applications, and the more important ones, which are usually sold under appealing trade names, are listed in Table 11.

In addition to chemical derivatives of cellulose, another modification of cellulose has recently been developed that has functional gum properties and has found novel uses in the food industry, primarily in low- calorie foods. This material is an acid-hydrolyzed cellulose product known as Avicel, or microcrystalline cellulose. Although not soluble in water, this material has a great absorptive capacity and functions as an effective thickening and bodying agent.

C. COMPLETELY SYNTHETIC GUMS In addition to the modified natural products, or semisynthetics, a

completely synthetic approach has led to the preparation of many interesting and useful hydrophilic polymers. The main advantage of the completely synthetic products is elimination of a dependence upon an un- certain natural source of raw materials. In addition, synthetic products permit more accurate tailoring of chemical structure to desired product properties for specific applications.

Although many synthetic polymers have been created over the past few decades, only a comparatively few are of interest to the food industry, primarily because of their lack of toxicity. These are reviewed in this article, and, although they have not yet penetrated the food field significantly, the author feels that this will come with time and is essentially dependent upon meeting FDA regulations concerning proof of nontoxicity.

The more important gums in this category are the vinyl polymers: 1) Polyvinylpyrollidone (PVP) 2) Carboxyvinyl polymer (Carbopol) 3) Poly (methyl vinyl ether/maleic anhydride) (Gantrez An) In addition to these, other vinyl polymers of widespread industrial

applications have only limited potential for food use, because of toxicity or other detrimental features. The more important of these are polyvinyl alcohol (Vinol, Elvanol) , which has found a broad application as a water- soluble packaging film ; polyvinylmethyl ether, a heat-sensitive thickening agent; polyacrylic acid (vinyl formic acid) and its salts, which have a wide range of hydrophilic properties, including a suggested use of the alkali metal acrylates as an ice cream stabilizer (Kamlet, 1954) ; and polyacrylamides, which are effective cationic thickening agents and coagu- lants.


Another group of synthetic gums that have great potential for food applications are the recently developed Polyox resins, which are extremely high-molecular-weight polymers of ethylene oxide having very desirable nonionic thickening properties, and are nontoxic.

The properties and potential uses of these synthetic gums in the food industry are discussed in the following sections. The discussion is restricted to those that have or may have important applications in foods-PVP, Polyox, Carbopol, and Gantrez An.

II. MICROCRYSTALLINE CELLULOSE (AVICEL)

A. BACKGROUND Although cellulose is not a gum material and is insoluble in water, a

new type of cellulose has recently been developed that has many of the functional characteristics and applications of typical hydrophilic materials. For this reason, microcrystalline cellulose-or Avicel, as i t is named-is included in this review.

Cellulose, the most abundant organic material known, has been used as a food product as part of plant foods for many years. The normal alpha-cellulose found in nature is a fibrous material that does not absorb water and is comparatively inert under most conditions. Avicel is a new microcrystalline cellulose that is nonfibrous. It is prepared by the acid treatment of alpha-cellulose under special processing conditions, as disclosed by the recent patent of Battista and Smith (1961). Under controlled hydrolysis with hydrochloric acid, alpha-cellulose is reacted to give two components-an acid-soluble fraction and an acid-insoluble fraction. The acid-insoluble material is composed of a crystalline residue that is washed and separated and is referred to as a cellulose crystallite material. Essentially, what has happened is that the amorphous regions of the polymer are hydrolyzed completely, leaving the crystallite regions as isolated microcrystallites, which are defined as the level-off degree of polymerization cellulose, or DP cellulose. In other words, if the hydrolysis reaction were continued, the degree of polymerization would not change, and essentially, the level-off period, or maximum reactivity, has been achieved. The average level-off DP consists of 15 to 375 anhydroglucose units, the constituent chains of each aggregate being separate from those of neighboring aggregates. These aggregates are characterized by sharp X-ray diffraction patterns indicative of a substantially crystalline structure (Battista and Smith, 1962).

The commercially available microcrystalline cellulose comes as a white, fine flour and is low in ash, metals, and soluble organic materials. It is insoluble in water, dilute acid, common organic solvents, and oils.


TABLE I11

PROPERTIES OF MICROCRYSTALLINE CELLULOSE~

Composition Microcrystalline cellulose

Equilibrium moisture, %

Organic extractables, % <0.04 Ash, % <0.06 Calcium, ppm < 60

Molecular weight 30,000-50,000

(58% R.H., 72°F.) 5

Iron, ppm < 20 Copper, PPm <4 Manganese, ppm 0-2 Absolute density 1.55 Bulk density 0.304.80 Average particle size, .LI 10-50

Solubility Water Insoluble, dispersiblc Dilute alkali Partially soluble, swells Ililute acid Insoluble, resistant Organic solvents Insoluble, inert Oils Insoluble, inert

* Herald, 1962.

It is partially soluble, with some swelling, in dilute alkali. Table 111 summarizes the chemical and physical properties of this material (Herald, 1962).

R. FOOD APPLICATIONS The main food applications for this material were described by Trau-

bcrman (1961) : 1) Avicel in dry form or as a gel can be incorporated as a bulking

agent in many food products to effect significant calorie reduction without impairing the palatability or appearance of the food.

2) Avicel dispersed in water produces stable gels containing up to 20% or more of solids. These gels are spreadable, and a t lower concentrations, creamy colloidal suspensions can be obtained.

3) In dry form, Avicel is an effective absorbent and can convert oil-base foods, such as cheese, peanut butter, and also syrups, such as molasses and honey, to free-flowing, granular powders for use in dry package mixes and similar convenience foods.

The primary application proposed for Avicel is as a new ingredient for the control of calories in a wide range of food products. The promotional literature by the manufacturer, American Viscose Corp. (1962), proclaims Avicel to be the noncaloric ingredient and states that i t con-


tributes functional properties, such as stability, body bulk, opacity, texture, and palatability. These applications are disclosed and illustrated by Battista (1962) in a broad spectrum of diversified food uses.

However, these are all basically reduced-calorie food compositions, and the examples covered are methods and formulations for making a wide variety of low-calorie products, such as honey-flavored doughnuts, peanut butter cookie dry mix, bran muffins, layer cake, fibrous breakfast food, chocolate pudding, chocolate dessert topping or sauce, soft pudding, peanut butter streusel-type crumb topping, low-calorie cream salad dressing, imitation butter or margarine, mayonnaise-type salad dressing, Cheddar cheese spreads, dry-mix ice cream, malted milk shake, catsup, caramel candy, and milk chocolate.

I. Dry Powder Uses

In dry form, Avicel powder, which resembles flour, can be easily incorporated into foods to be blended or homogenized. In baked goods, this has been used for the production of low-calorie cookies marketed by Wes- ton Biscuit Company. The cookies, sold as “Sweet 16” cookies, contain only 16 calories per piece and are fortified with vitamins (Anonymous, 1962a).

Microcrystalline cellulose, which has a vast surf ace area because of the many fissures and holes in the submicroscopic surface area, is cx- tremely absorbent, particularly for fatty materials. This function or property makes i t possible to convert oily or syrupy products into dry, free-flowing powders, It has been suggested that butter-fl avored mixes can be formulated that, upon the addition of water and stirring, produce smooth, butter-flavored, bread spreads. By use of other flavors, such as cheese and spices, other flavored spreads may also be prepared (Anony- mous, 1962d).

In a similar manner, natural dyes can be adsorbed by the microcrystalline celluIose aggregates. These may then be used to carry edible dyes into fat-based products, such as butter or margarine, without causing speckling or blooming in the product. Trauberman (1961) suggests that since many of the oil-soluble dyes have been banned for food use, this application may be helpful for coloring fatty foods with water- soluble nontoxic natural vegetable dyes.

Avicel in dry form can also be compressed to form various shapes and sizes that can disintegrate rapidly in water. Thus, i t can be used in the preparation of individual pre-measured or pre-weighed items, such as cubes or tablets, for dispensing accurately messurcd sinounts of ingredients.

A paste of Avicel with water can be extruded into ribbons and other


shapes, and in this way, spaghetti noodles and macaroni products can be formed.

In one novel applicat,ion, the Nestle Company is using Avicel as an additive to its Keen soft drink powder in order to impart greater opacity to the reconstituted beverage (Anonymous, 1962b).

The oil-absorbent characteristics of Avicel offer advantages for use in various meat products. When used on the surface of bacon, i t is claimed to curb curling and prevent sticking of the slice strip during storage. When used as a coating on each side of hamburger patties, it is claimed to prevent loss of some of the juices and to reduce shrinkage. A suggested use for the material is in meat products, to be added by housewives or insti- tutional operators to ground meat in preparing meat-loaf dishes, sauces, etc.

It can also be used as a vehicle for absorbing oily seasonings or flavor components and for incorporating these materials into processed meats (Trauberman, 1961).

8. Gel-Based Products

The use of Avicel with water a t solids levcls of 30 to 36% will give gel- like materials ranging in degrees of thixotropy, viscosity, and opacity. With these gels, i t is possible to prcpare colloidal spreads containing up to 20% solids or more. These colloidal gels are particularly useful in the formulation of smooth food products such as dressings, spreads, dips, sauces, and aerosol-type toppings.

At higher solids contents, the gels have the physical characteristics of animal fats or hydrogenated vegetable oils. Vegetable oils and fats normally used in products similar to mayonnaise or salad dressing can be partially replaced with Avicel, thus reducing the caloric values by more than 50%. By combining the gels with edible oils or fats and using the proper dispersing agent, calorie-control foods that taste like sour cream, hollandaise sauce, and cheese dips can be made readily (Anonymous, 1960a).

One such product, a low-calorie salad topping containing 82% fewer calories, was recently put on the market by Otto Seidner, Inc., of Westerly, Rhode Island. This product, made with Avicel, contains only 33 calories per teaspoon instead of the normal 20 per teaspoon (Anonymous, 1962~) .

Palatable dietary custards and puddings can also be made by controlling the Avicel content of the product, and aerosol (foamable) preparations, such as toppings, containing excellent body, spreadability, and stability are also easily prepared.

The value of Avicel in aerosol or foamed food toppings was illustrated in a patent by Herald et al. (1962). In addition to reduced calorie


content, the toppings made with Avicel also have the desirable properties of foam retention (no sagging), smoothness in appearance and eating quality, and a rich mouthfeel despite the lower content of fatty materials. In addition, i t is claimed that the products after extrusion and foaming do not leak water, collapse, or develop a coarse texture on standing.

I n frozen dessert preparations, such as simulated ice cream, a substantial amount of Avicel can be incorporated to reduce the formation and amount of ice crystals. These frozen desserts can be more readily thawed and frozen, and in addition to being substantially lower in calories than conventional ice cream have superior textural stability and control overrun properties. Advantages claimed for these frozen desserts with Avicel are that they are less chilling in the mouth upon first contact, there is excellent control of ice crystal formation during freezing and thawing (which is especially useful for popsicles), and the calorie content is readily controllable.

Ill. SODIUM CARBOXYMETHYLCELLULOSE (CMC)

A. BACKGROUND One of the most important derivatives of cellulose and one of the

most widely used synthetic gums in the food industry is the sodium salt of carboxymethylcellulose. The modification of cellulose by the introduction into the molecule of a controlled number of sodium carboxymethyl groups (NaOOC-CH2-) introduces the desirable property of water solubility (Baird and Speicher, 1962).

The sodium salt of carboxymethylcellulose is the common product of commerce and is by far the most widely used salt. It is usually sold or referred to as “CMC,” “carboxymethylcellulose,” or, more simply, “cellulose gum.” Some other soluble salts, such as the potassium or ammonium salts, have been made for specific purposes but are not commonly used. A German patent (Sichel-Werke A.-G., 1952) reported the decomposition of the ammonium salt by heating to give a water-insoluble but water- swellable material that is suitabIe as a substitute for natural swelling gums, such as tragacanth or agar. This product is capable of absorbing 50 times its weight of water and finds use in the manufacture of ice cream, jams, and confections. The free acid itself is insoluble, and cannot be used where solubility is required.

Sodium carboxymethylcellulose was first developed in Germany during World War I, and originally used as a substitute for gelatin. Technical difficulties and high production costs delayed commercial development of the material until World War 11, when the shortage of water- soluble gums in Germany promoted large-scale manufacture of the ma-

UTILlZATION OF SYNTHETIC GUMS IN THE FOOD INDUSTRY 295

terial. The discovery that CMC improved the performnncc of detergents also led to its development in the United States, where i t was first produced in 1943. The rate of production has grown rapidly, from a reported 2 million pounds in 1946 t o about 25 million pounds in 1956 (Batdorf, 1959).

The manufacture of CMC is a fairly simple, conventional chemical reaction whereby purified cellulose is first treated with NaOH and then reacted with sodium monochloroacetate according to the following reaction :

R-OH + NaOH + R-ONa + H20 R-ONa + C1-CH2-COONa -+ R-0-CH2-COONa + NaCl

B. PROPERTIES

Each basic anhydroglucose unit (CoHloOs) in the cellulose structure contains only three available hydroxyl (-OH) groups with which the sodium monochloroacetate can react. Theoretically then, a complete reaction would mean the introduction of three carboxymethyl groups per anhydroglucose unit, and the reaction product would have a degree of substitution (D.S.) of 3. The optimum conditions for best solubility and general physical properties can be obtained with a much lower D.S., and most commercial products available are usually in the range of 0.4 to 1.2 D.S. For food use, this is restricted to a maximum D.S. of 0.9.

The water solubility and solution characteristics of CMC depend not only on the D.S. but also on the uniformity of distribution of the substituent carboxymethyl groups on the polymer chain. The more uniform the distribution, the smoother and less thixotropic the solutions will be. In addition, the properties are also affected by the degree of polymerization (D.P.), with cellulose products of high average D.P. having better film-strength properties than those of lower average D.P. Likewise, products of high average D.P. produce solutions of high viscosity, and as the average D.P. decreases so does the solution viscosity.

Thus, combinations and permutations of the three chemical and physical variables-D.S., D.P., and uniformity of substitution-yield a wide variety of types of CMC. In addition, purely physical characteristics, such as particle size, shape, and density, can be varied over a broad range to produce a vast variety of special types and grades of CMC.

As indicated, water solutions of CMC can be prepared in a wide range of viscosities, with the highest being shown by a 2% CMC-7H with a viscosity of about 50,000 cps, as compared to a 2% CMC-7A with 10 cps (Hercules Powder Co., 1960).

With respect to pH, CMC is fairly stable over a wide pH range of 5 to 11, with best stability a t a pH of 7 to 9. Acidification below pH 5 tends

296 MARTIN GLICIiSMAN

to reduce solution viscosity and viscosity stability, and in the pH range of 2-3 the insoluble free carboxymcthylcellulose acid is precipitated.

As with most gums, when the temperature of CMC gum solutions is increased the viscosity decreases, and conversely, when the temperature is decreased the viscosity increases. This change of viscosity with temperature is reversible and has no permanent effect on the viscosity characteristic of the solution. Loss of viscosity during normal processing conditions is not usually a problem, but prolonged heating to high temperatures will depolymerize CMC and permanently reduce its viscosity.

In common with most water-soluble gums and polymers, CMC is subject to biological attack by molds, fungi, bacteria, etc., and a preservn- tive should be added, such as sodium benzoate, sorbic acid, etc.

CMC solutions are compatible with and largely unaffected by cations that yield soluble salts of CMC. In general, monovalent cations form soluble salts of CMC; divalent cations are borderline, with calcium chloride, for example, producing a haze; and trivalent cations, such as ferric or aluminum, produce precipitates or gels.

Water solutions of CMC can be cast and evaporated to form clear films with excellent and useful physical properties. Where greater flexibility and elongation are desired, the incorporation of a good plasticizer,

TABLE I V FOOD APPLICATIONS OF SODIUM CARBOXYMETHYLCELLULOSE

Aerosol toppings Frozen foods Baker’s jellies Gravies and sauces Beer foam stabilizer Cake mixes Ice cream mixes Cake topping Icings, frostings, glazes Canned fruits and preserves Cheese spreads Meat pies Chiffons Meat sauces and gravies

Ice cream, sherbets, water ices

Icing mixes

Citrus concentrates Confectionery Dehydrated foods Dietetic foods Doughnuts Dry mixes (cakes, etc.) Dry shortenings Fish preservation Food emulsions Fountain syrups French dressings

Meringues Milk beverages Pet foods Pie and pastry fillings Preservative coatings Puddings Potato salad Relishes and condiments Salad dressings Soft drinks and concentrates


such as glycerine, is required. CMC films are insoluble in and unaffected by oils, grease, and most common organic solvents.

In general, the optimum conditions for prolonged storage of CMC solutions are :

1) Maintenance a t a pH close to neutrality or on the alkaline side (pH 7.0 to 9.0)

2) Exclusion of oxygen and sunlight 3) Avoidance of high temperatures 4) Protection against microbial attack In the food industry, CMC has found a broad range of applications,

as illustrated by the compilation in Table IV. It is approved for use as “generally recognized as safe” within the meaning of the Food Additives Amendment. The proposed regulation describes i t as the sodium salt of carboxymethylcellulose, not less than 99.570 on a dry-weight basis, with maximum substitution of 0.95 carboxymethyl groups per anhydroglucose unit, with a minimum viscosity of 25 cps for 270 by weight aqueous solution a t 25°C (Hercules Powder Co., 1960).

C. DAIRY APPLICATIONS

1. Ice Cream Stabilizers

Many reviews and articles have been written on the function and application of stabilizers in the manufacture of ice cream and related frozen confections (Frandsen and Arbuckle, 1961 ; Potter and Williams, 1950; Boyle, 1959; MOSS, 1955; Sperry, 1955).

In general, i t is fairly we11 agreed that the basic role of hydrophilic gums in these products is to reduce the amount of free water in the mix by binding i t as water of hydration or by immobilization within a gel structure.

This is theoretically accomplished by an ideal gum or gum combination without reacting or disturbing thc physical-chemical equilibrium of the mix components so as to introduce artificial viscosity characteristics in the mix. It is the ability of small percentages of gums to absorb and hold large amounts of unbound water, which produces good body, smooth texture, slow melt-down, and heat shock resistance in the resultant products.

The primary purposes of stabilizers can therefore be summarized as follows:

1) To produce smoothness in body and texture 2) To retard or reduce ice crystal growth during storngc 3) To provide uniformity of product


4) To provide resistance to melting From their investigation of stabilizers, Potter and Williams (1950)

listed the following important factors to be considered in selecting n stabilizer:

1) Ease of incorporation into the mix 2) Effect on the viscosity and whipping properties of the mix 3) Type of body produced in the ice cream 4) Effect on melt-down characteristics of the ice cream 5 ) Ability of the stabilizer to retard ice-crystal growth 6) Quantity required to produce the desired stabilization 7) cost Until the second World War these stabilizers were selected from the

various natural hydrophilic gums, such as gelatin, pectin, carrageenan, etc.

But, as with many other developments accelerated by the demands and shortages caused by the war, the use of CMC as an ice cream stabilizer was first evaluated (and reported on favorably) by Josephson and Dahle (1945). Because of wartime scarcities, the synthetic materials- the cellulose derivatives whose viscosity and water-binding properties were known and utilized in other fields-were re-examined for use in food applications (Pompa, 1945).

Preliminary trials were made by Josephson and Dahle (1945) on a wartime ice cream mix consisting of 11% fat, 8.8% serum solids, 15% sugar, and stabilizer. These tests confirmed the efficiency of CMC a t concentrations of 0.15-0.276 of the mix. The outstanding characteristic was that of imparting a “chewy” body as well as a good texture to the product. I n addition, CMC had the ability to enhance the whipping properties of the ice cream mix, which was extremely desirable when butter or frozen cream was used in the mix. These desirable whipping properties were also observed by Werbin (1953).

CMC met with immediate acceptance, although i t was found that results were best when CMC was used together with one or more other stabilizers, such as carrageenan, locust bean gum, etc. (Gould, 1949; Julien, 1953). Blihovde (1952) recommended the combination of 1-12 parts of CMC with 1 part of carrageenan, and today the most common combinations in use are CMC-carrageenan, CMC-gelatin, CMC-gelatin- carrageenan, and CMC-carrageenan-locust bean gum (Frandsen and Arbuckle, 1961).

The amount of CMC needed in ice cream and related products will naturally vary with the fat and total solids content and the texture desired, but the working levels usually recommended by the manufacturer of CMC (Hercules Powder Co., 1962a) are the following:


Product

Ice cream Sherbets Variegated ice cream

Fruit purees Chocolate syrups

Dry ice cream mixes Ice milk and soft frozen desserts

Conc. of CMC (based on final

total wt.)

0.1690 0.2%

1.0% 0.75% 0.2% 0.187,

When used in combination with carrageenan, the total stabiliaer concentration of the CMC-carrageenan blend is 0.35% for a typical ice cream mix containing 10.2% milk fat, 12% serum solids, 13% sucrose, and 0.15% mono-diglyceride-type emulsifier (Keeney, 1962).

McKiernan (1957) pointed out a minor drawback in the use of CMC in that consistently standardizing its basic viscosity from batch to batch is difficult, probably because of its sensitivity to the slightly acidic con- dition of ice cream mixes. But this is more than offset by its excellent water-absorptive properties and its excellent ability to hydrate in cold mixes.

This property of cold-water solubility became increasingly more important as the ice cream industry gradually converted to and adopted the more efficient high-temperature short-time (HTST) continuous production systems. In the constant search for better and more efficient production methods, the ice cream industry within the past decade has investigated and looked a t various manufacturing processes, with the result that in many instances the standard batch method was superseded by an HTST continuous process. This also led to complications with respect to the stabilizers used, since stabilizers that always performed satisfactorily in mixes prepared by the batch system did not always work in an HTST system. This necessitated the development of stabilizers having special properties for these uses (Moss, 1955).

One of the important factors elicited by comparison of data from the HTST systems and the batch system is that the HTST systems require approximately 25% more stabilizer to obtain texture and body properties in ice cream equal to those obtained with the batch system (Moss, 1955; Sperry, 1955). This is thought to be due to difference in holding times a t the various pasteurizing temperatures employed by the two systems. In the HTST system the mix is heated to 175°F for about 2 5 3 0 seconds, whereas in the conventional batch system it is heated a t 160°F for 30 minutes.

Because of its cold-water solubility, CMC, preferably in combination


with carrageenan, can be used successfully in HTST systems (Moss, 1965). This was confirmed by Sperry (1955) , who also nicntioncd thc versatility of its application in that it can be incorporated into the mix by either presolution or dry addition, but greater efficiency is to be expected if the stabilizer is added in the form of a presolution.

In some early work, Landers (1947, 1948) improved the dispersi- bility of CMC by coating it with a mono- or diglyceride. This improved the rate of solution in aqueous media and was especially effective for ice cream mixes.

More recent work by Knightly (1962) with improved fluid emulsifiers for ice creain production also used 0.2% CMC as a stabilizer to give a high-quality ice cream with good body, texture, and overrun.

In a similar vein, Steinitz (1958) facilitated the speedy dispersion of ice cream stabilizers by formulating prepared stabilizer mixtures whereby the various gums or gum combinations were suspended in a mixture of propylene glycol and glyceryl monostearate. This was improved in a related patent (American Food Labs., 1960) where the stabilizer was prepared by suspending CMC in an edible organic liquid (alcohol and glycerine). Upon addition to ice cream mixes during processing, these stabilizers dispersed rapidly without clumping and began to function immediately.

The improvement of ice cream stabilizers by the use of CRilC and similar functional vegetable gums has led to an almost unnoticed but marked improvement in the quality of commercial ice cream, particularly with respect to the disappearance of sandiness (lactose crystallization). Nickerson (1962), in a recent paper, sought an explanation for the virtual disappearance of sandiness from commercial ice cream. In an investigation of 36 commercial samples, only 5 became sandy when stored 7 months at 12°F. Nickerson found that neither the partial substitution of corn syrup solids for sugar nor the use of emulsifiers had any ability to prevent sandiness. He concluded that the primary factor responsible for the reduced incidence of sandiness was the use of gum stabilizers that inhibited the formation of nuclei and thereby inhibited the development of undesirable, large lactose crystals.

CMC (or cellulose gum) is permitted as an allowable optional ingredient in ice cream in the Standards of Identity for frozen desserts published by the Federal Food and Drug Administration (1960).

2. Ice Pops and Sherbets

Because of their lower total solids, the use of gums and their proper combination is perhaps of more importance in ice pops and sherbets than in ice cream. The second most important consideration is the proper


balance of cane and corn sugar or corn syrup solids in the mix (Mc- Kiernan, 1957). In selection of a stabilizer, consideration is usually given to its effect on overrun, syrup drainage, body (crumbliness), availability, and convenience of use (Frandsen and Arbuckle, 1961).

Although ices and ice pops are simple systems composed of sugar, acid, flavor, and color, whereas sherbets also include milk solids, stabilizers for these products have an additional function to perform. During freezing of the products, the water tends to crystallize out first, leaving a more and more concentrated solution of sugar, flavor, and color among the ice crystals. And, conversely, upon being eaten, the color and flavor tend to migrate to the outer surfaces that are melted first by sucking. The function of the stabilizer, therefore, is to improve the texture by preventing the growth of ice crystals and, in addition, to keep the color and flavor evenly distributed and prevent its migration both during freezing and during eating (Boyle, 1959).

Burt (1951, 1956) found that flavored ice products could be cffec- tively stabilized with about 0.1-0.276 CMC having a viscosity greater than 100 cps in a 2% aqueous solution at 25°C.

3. Milk Beverages

Chocolate milk drinks and prepared “egg nog” drinks are both processed in a manner similar to ice cream mixes and require a stabilizer for an acceptable product. When prepared by the HTST pasteurization method, the basic recommendations given for stabilizers in ice cream mixes usually hold true, and when high-viscosity CMC is used i t is pref- erable to include carrageenan as a secondary colloid to prevent mix separation (Sperry, 1955).

However, this is not always the case, and ice cream stabilizers may not work to best advantage in chocolate, sherbet, or custard mixes. This has resulted in the development of stabilizers having special properties for these uses (Moss, 1955).

To prevent curdling when CMC is used in stabilizing chocolate milk and similar milk products, the CMC can be mixed with an organic acid, such as citric, tartaric, acetic, or lactic acid, in the preferred ratio of 0.7- 1.2 moles acid for each sodium carboxyl group (-COONa) (Onderzoe- kingsinstituut “Research” N. V., 1953).

In the preparation of products such as condensed whole milk or skiin milk, CMC has been used to prevent the formation of large, undesirable lactose crystals (Cooperatieve Fabriek Van Melkproducten Te Bedum, 1954). This is done by preparing a seed material by intimately grinding together a powder of CMC and crystalline lactose into a small amount of concentrated milk product, such as spray-dried milk powder. This


yields crystals about 1 p in diameter. When added during the cooling cycle in the production of condensed milk, i t will give a final product with about half the lactose crystals 0-5 p in diameter and half above 5 p.

In the preparation of an acid milk beverage, CMC has again been used as a binding agent (Nutricia, 1962). The product is prepared by mixing a milk product, such as whole milk, skim milk, or cream, with a culture of lactic acid bacteria, a t least 10% fruit juice, and sufficient CMC to keep the milk casein dispersed in finely divided form. The mixture is then pasteurized or sterilized.

CMC has been utilized in the manufacture of a cream substitute (Pritchitt, 1954). An aqueous mixture of skim milk, edible fat containing fatty acid mono- or diglycerides, lecithin, and CMC is homogenized and spray-dried to give a dry powder that can be reconstituted with water to form a cream-like product.

D. BAKERY APPLICAT~ONS Carboxyniethylccllulose is widely used in a variety of bakery prod-

ucts. It is used in icings, meringues, bakery glazes, pie fillings, and other specialty items where consistency and textural rigidity are important characteristics of the product. In many of these applications, the function of the CMC is to inhibit syneresis, repress the formation of sugar crystals, improve body, contribute gelling properties, and improve surface glaze (Anonymous, 1952).

1. Pie Fillings

In pie fillings, which depend primarily on starch as a thickening agent, CMC is used to minimize or prevent syneresis or water separation, which is common in these applications. Pie fillings usually contain modified starches or hydrophilic gums in order to prevent an excessively thin or watery consistency. Selection of the proper type and amount of colloid can be varied to obtain a variety of desired textures ranging from a semifluid to a firm consistency.

All starch fruit pie fillings usually have a starchy, firm appearance, which is not always desirable, This starchy appearance can be avoided by using small amounts of CMC, which thicken the fruit juices to the proper consistency for handling and heating and prevent floating or settling of the fruit. I n addition, the fillings will be clearer and brighter and have a desirable gelling texture in addition to an attractive appearance. In a typical cherry pie filling, less than 0.5% CMC based on total weight is sufficient to obtain the characteristics.

In regular lemon pie fillings, a small amount of CMC will give starch fillings that have a firm body, develop very little syneresis, and show


no signs of cracking or pulling away from the sides of the pie crusts. In a typical lemon pie filling, where the pcrcentage of starch would be about 4747, the addition of 0.5% high-viscosity CMC will give the desired additive properties.

In canned or frozen fruit pie fillings, starches are unsatisfactory because they tend to retrograde in a liquid medium. Gums are not as sus- ceptible to breakdown in fruit pie fillings and can be used satisfactorily in many instances as a partial or complete replacement for starches in these applications. In acid or low-pH fillings, there is some loss of viscosity due to acid degradation, but this can be adjusted for in the initial formulation.

In the preparation of canned berry and berry-apple pie fillings and a storage-life study a t accelerated conditions, Moyls e t al. (1955) found CMC to be a satisfactory stabilizer for pie fillings. A more recent study by Kunz and Robinson (1962) obtained similar results with both canned and frozen peach and cherry pie fillings. The addition of CMC alone or in combination with modified waxy maize starch resulted in peach pie fillings with a clearer, “less milky” liquid phase after 10 months of storage. Levels of 0.370 and 0.5% CMC were considered to be most acceptable. With cherry pie fillings, objectionable gummy textures were encountered when gum concentrations rose above 0.2%. In frozen pie fillings, the incorporation of CMC decreased the amount of syneresis upon thawing.

2. Icings

The importance of icings on baked goods cannot be overestimated, since the appearance and type of icing contributes in large measure to the acceptability and appeal of the final product. In much the same manner as CMC retards the growth of ice crystals in ice cream, CMC retards sugar crystal growth in icings, frostings, glazings, and related toppings that contain high proportions of sugars. CMC is a particularly useful stabilizer for products of this type because, in addition to retarding crystallization, it also retains water and retards the drying out of baked goods, The results of these functional applications are an icing surface that is smooth and velvety and protects the moisture of the cake, thus improving appearance, quality, and over-all texture. Another de- cided advantage of CMC in icings is that the icings will not separate when properly stored for as long as twenty-four hours, and can be rewhipped for reuse. As little as 0.1% of high-viscosity CMC in butter cream icings, flat boiled icings, or marshmallow cooked icings is sufficient to give the desired results.

CMC has been used in a thickening capacity in many prepared icing formulations. Wagner (1954) prepared a stable, boiled icing-base dry mix

304 MARTlN GLICIiSMAN

with a blend of egg albumen, calcium sulfate, sodium aluminum sulfate, powdered sugar, starch, flavor, and CMC. Butler (1959a) used CMC as a stabilizer in a noncook instant icing composition employing primarily sugar and a whipping agcnt. Ganz (1961), in a more recent patent, combined a protein and CMC. The protein is water-insoluble but hydrates when incorporated into the icing composition.

An unusual attribute of CMC in dry-mix icing formulations was reported by Grossi (1958), who claimed the use of CMC as a color stabilizer in dry powder foods. Thus, the addition of 0.25-1.0% CMC to a typical chocolate icing mix was claimed to give a product of improved color-stability.

For use in glaze icings on sweet rolls and “brown and serve” rolls, CMC is an effective stabilizer and will give glazes that have very attractive surface and eye appeal. About 0.1-0).2% CMC added to 2070 sugar glaze is sufficient to give a hard, glossy, attractive finish to products of this type.

S. Meringues

Meringue textures are very popular balced-goods toppings. A con- sistent and unchanging texture from the time of preparation until eating requires a proper stabilizer in most meringue formulations. The addition of CMC to starch and agar meringues gives products that show no syneresis after twenty-four hours. In addition, these products have excellent volume, cut easily, and have a tender, smooth, shiny, and finely textured surface. Another stated advantage of these meringues is that they can be rewhipped in case a portion is reused. A typical hot-process meringue stabilizer will consist of 63% dextrose, 15% cornstarch, 15% high-viscosity CMC, and 7% agar. For a cold-process meringue, the agar can be eliminated and a formulation can be prepared using 69% dextrose, 18% cornstarch, and 13% high-viscosity CMC. Prepared dry meringue powders have also been formulated for application with regular meringue, cold marshmallow meringues, and boiled marshmallow meringues. A formulation for dry mix suggested by Hercules Powder Co. (1962b) consists of the following ingredients: dried egg whites, 30.0%; powdered sugar, 32.0% ; dextrose, 13.1% ; cornstarch, 20.07’0 ; CMC (high-viscosity) , 2.0% ; gum karaya, 0.75% ; salt, 1.25% ; citric acid monohydrate, 0.9% ; and sufficient vanillin for flavor (about 3 ounces per 100 pounds).

4, Breads and Cakes

The use of hydrophilic colloids as anti-staling agents for bread and cakes has been investigated by many workers in the food field with some


evidence that hydrophilic colloids as additives do enhance the shelf life of white bread.

Early work by Schuurink (1947) showed that the water-retaining capacity and volume of flours or doughs are increased by the addition of 1-276 of CMC. This was reconfirmed and expanded by Bayfield (1958), who found that the addition of different-viscosity types of CMC produced significant changes in the mixing behavior of the dough. Dif- ferent amounts of water were required for optimum absorption. The breads with CMC, after 5 days’ storage, possessed approximately 1.4% more moisture than the control and were definitely softer. It was postu- lated that the CMC plus water possibly served to coat the starch granules and, by forming this coating, slowed the changes normal during staling. Although not a proved staling preventive, CMC appeared promising as an aid in retarding staling.

5. Miscellaneous

In doughnut mixes of both the cake type and the yeast-raised type, CMC is used in order to give improved yield, less fat absorption, enhanced tenderness, improved glaze adherence, and longer shelf life. About 0.25% of CMC added to each 100 pounds of doughnut mix is sufficient to produce doughnuts that show these more tender textures with better eating qualities and shelf storage life.

The addition of .05 to .lo% high-viscosity CMC to baker’s jelly will improve the quality by decreasing tendency to melt, inhibiting syneresis, and making the product more spreadable. In addition, the solids content of the jelly can be reduced by 2 to 3% and the gel will still be firm and tender.

Roundy and Osmond (1960) utilized CMC in improving the baking characteristics of a spray-dried baker’s type of cheese. This was made by spray-drying, under proper conditions, an acidified milk-cream mixture containing a stabilizer compound of 3.3% CMC and 6.7% instant starch. The final product had very desirable baking properties and could be used satisfactorily in many heat-processed cheese-based foods.

In emulsions used for whipped toppings, about .015% of high-viscosity CMC contributes body and desirable textural properties to the final product.

E. SALAD DRESSINGS, SAUCES, AND GRAVIES

1. Salad Dressings

The thickening ability and emulsification properties of CMC have been used to stabilize salad dressings, both regular and French, as well


as mayonnaises and similar products (Anonymous, 1952 ; Fouassin, 1957) and is a permitted optional emulsifying ingredient for salad dressings, including French dressings, under the standards of identity for food products of this type.

In some applications, CMC is used in combination with low-methoxy pectin and a sparingly soluble calcium salt as the emulsion stabilizer. Bondi and Spitzer (1959) suggested the use of 0.5-0.8% CMC in combination with 0.2M.40% agar or related gums in the formulation of a low-calorie Italian salad dressing having oleaginous characteristics.

Levin (1960) prepared a cream salad dressing having a whipped cream appearance but containing no vegetable oil or egg yolks by using CMC as a stabilizer for the butterfat base used. The base was composed of vinegar, sugar, salt, and water, stabilized with CMC and mixed with heavy cream. When used as an aerosol product, the composition is ejected in a semipermanent mass of tiny globules having physical characteristics similar to those of whipped cream and the taste qualities of a cream salad dressing.

2. Relishes and Sauces

Anderson et al. (1954) found that small amounts of CMC (0.25- 0.75%) and carrageenan (0.15-0.45%) were very effective in reducing the bothersome separation of syrup from sweet-pickle relishes during storage. I n addition, they produced a more uniform finished product that was organoleptically better than the untreated product. Experimental packs prepared with CMC and carrageenan produced more desirable relishes than the controls, with respective drained-weight values (as percent of original weights) averaging 96.8% and 98.9%, compared to 92% for the controls.

In addition, i t was observed that the relishes made with the gums appeared to be less dry and brighter in color than the controls. This was attributed to the increased total syrup retention, i.e., to the thicker film of syrup surrounding each particle of relish. It was also felt that, by eliminating syrup separation, syrups containing thickeners could be spiced somewhat less, with a consequent saving in flavoring cost.

3. Gravies

Beef pot pies and turkey and chicken pies can be improved with the use of 0.5% high-viscosity CMC as a thickening agent for the gravy. CMC gives products that have improved flavor appeal and more con- sistent gravy body in addition to better stability.


F. CONFECTIONERY In confectionery products, as in ice cream, control of sugar crystalli-

zation is an important factor in the manufacture of high-quality items. The inhibition of sugar crystallization is necessary in order to achieve the desired properties of gloss, body, mouthfeel, shelf life, and related textural attributes. The mechanics of sugar crystal growth is dependent upon two concurrent processes: the dissolution of small sugar crystals simultaneous with the growth of the larger crystals.

Crystal size and growth are normally controlled by the introduction of ingredients known as “doctors,” which commonly include such materials as corn syrup, invert sugar, milk solids, fats, emulsifiers, gelatin, and various other hydrocolloids. In addition to having specific functions of their own, these “doctors” inhibit sugar crystallization either by in- terfering with the growth of the large crystals or by preventing the dissolution of small crystals.

Desmarais and Ganz (1962) and Desmarais (1962) investigated the use of CMC in controlling sucrose crystal growth either as a substitute for other “doctors” or as an adjunct to increase “doctor” efficiency. In experiments with supersaturated sugar solutions, measurements were made on the growth of crystals in solutions with and without “doctors.” The results (Table V) show that all the “doctors” (corn syrup, invert syrup, and CMC) were effective in inhibiting crystal growth, but that the low-viscosity CMC was most effective as shown by the high percentage of small crystals over a four-month storage period.

TABLE V

GROWTH OF CRYSTALS IN SATURATED SUGAR SOLUTIONS’

Crystal sizes (p)

1 day 1 month 4 months

% 70 % Composition Range below 16 Range below 16 Range below 16

Control 2-1 10 25 10-140 20 8-240 1-2 15% corn syrup 2-60 55 4-75 50 10-85 20 5% invert syrup 2-60 40 4-75 40 10-125 15 0.2% CMC-7HP 4-100 70 4-100 GO 8-180 40 0.2 % CMC-7LP 4-100 85 4-100 85 8-110 75 0.2% CMC-7AP 4-80 90 4-80 90 8-120 40

Uesmarltis and Cans, 1962.

308 MARTIN GLICXSMAN

In addition to work with purc sucrose solutions, Desinarais and Ganz (1962) investigated the effect of CMC in typical fondant preparations. The shelf life of all sucrose fondants, which is normally short, could be lengthened by low-viscosity CMC. The CMC was more effective when added before or during boiling than when added just before creaming, and operated by producing smaller initial sugar crystals and slowing the rate of growth (Table VI) .

TABLE VI

INITIAL SIZES AND GROWTH RATE OF CRYSTALS IN FONDANT CONTAINING 3.0% CORN SYRUP’

~~ ~ ~

Crystal sizes ( p )

1 day 1 week 1 month Beating t,emp. % % %

Composition (OF) Range below 16 Range below 16 Range below 16

Control 107 2-16 98 7-20 95 5-70 45 150 2-16 98 3-50 50 7-80 30 246 3-30 90 10-70 20 10-120 5

0.370 CMC-7LP 107 2-14 100 2-20 98 4-20 95 140 2-16 98 2-20 95 4-20 95 150 2-20 97 2-20 95 4-25 90 246 2-25 95 2-30 70 5-55 45

Desmarais and Ganz, 1962.

In fondants containing a small amount of corn syrup (376), CMC broadens up to 150°F the range of temperatures a t which the fondant is creamed on a slab-type beater, and does not impart any odor or flavor to the finished product. In fondants containing high concentrations of corn syrup (20%) and invert syrup ( lo%) , the effect of adding CMC is “markedly less noticeable.”

This confirmed results obtained by Algemene Kunstzijde Unie N. V. (1953) in the preparation of commercial fondants with glucose and sucrose. It proved advantageous to add 0 . 1 4 3 % by weight of a CMC with a viscosity of more than 50 cps in 1% aqueous solution to the sugar after the boiling process and preferably after its tabling. CMC helpcd control the crystallization of sucrose in the final product.

G. DIETETIC FOODS As with many gums, CMC has pronounced bulking properties and has

found several uses in the field of dietetic or low-calorie foods. AR early

UTILIZATION OF SYNTHETIC GUMS I N THE FOOD INDUSTRY 309

application to reduce appetite was developed by Ferguson (1955). This composition, about 4 : l CMC and tartaric acid, was dissolved slowly in the mouth, whereby the inner mouth surfaces, including the tongue, became coated with a mild, taste-insulating coating that temporarily covered the taste buds and destroyed keenness of taste and appreciation of food. It thereby, presumably, cut down the desire of the individual to stuff himself with calories.

In 1962, Pfizer & Company entered the dietary food field with the introduction of a low-calorie creme-filled biscuit containing the “bulking agent sodium carboxymethyl cellulose to allay hunger and a t the same time satisfy the desire for solid foods.” These biscuits, which sold under the name of “Limmits,” each contained 175 calories. The standard diet consisted of four biscuits per day plus two glasses of whole or skimmed milk together with one normal low-calorie meal. The function of the 2.6% sodium carboxymethylcellulose, according to the promotional literature (Pfizer & Company, 1962a,b), was to supply the bulk, “thereby helping to appease the appetite, counteracting a frequent cause of failure in weight control programs.” On contact with the stomach digestive juices, the CMC expands slowly to produce a bulk effect. This is supplemented by sufficient fat, which is digested slowly and gives the diet “staying power.”

In the area of low-calorie beverages, CMC has been commonly used for several years. Brenner (1954) suggested its use as a bodying agent in sugarless beverages containing sodium cyclohexylsulfaniate instead of sugar. In this application, the CMC bodying agent is necessary to impart the syrupy texture that is normally supplied by the high sugar concentration.

In a similar way, many low-calorie food products are based on hydro- colloid gels to supply the bulk and body usually furnished by sugar. These products frequently lack stability and tend to weep readily. Die- tetic jams and jellies have these inherent faults, which can be overcome with a combination of high-viscosity CMC and low-methoxy pectin to produce a spreadable product. A recommended combination is 0.8% low- methoxy pectin, 0.37% high-viscosity CMC, and 0.25% calcium chloride (Hercules Powder Company, 1961a).

The same base can also be uscd to prepare low-calorie mayonnaise- type salad dressing. I t is usually necessary to add starch to the gums to produce the heavy, smooth paste-like consistency that is a desired texture.

Other related low-calorie applications are in pharmaceutical wafers, low-calorie cakes, and low-calorie canned fruits. Representative formulations can usually be obtained from the gum manufacturers or suppliers.


H. PROCESSED FOODS

1. Frozen Foods

The use of CMC in frozen foods was discussed earlier in some detail with respect to its biggest application in ice cream and related frozen confections. As shown, the primary function of CMC is to control ice crystal size and thereby maintain a uniform, smooth texture. In addition, the excellent water-retention properties of CMC under drastic freeze- thawing conditions have led to its use in other prepared frozen food products. Glicksman (1962b) used CMC in an alginate dessert gel system for the preparation of a gelatin dessert or aspic that could be frozen and thawed without textural degradation or other quality deterioration.

Perry (1961) prepared a novel frozen confection product using CMC to form the candy masses based on the sweetening constituents.

Burt (1955) developed a food preservation method composed of drawing a vacuum on apple slices, blanching the slices in a thickened aqueous sugar solution containing 0.2-1.0% CMC to maintain the firni- ness and natural color of the apple slices, and then preserving the blanched slices in the aqueous sugar solution by freezing.

Akuta and Koda (1954) used CMC to preserve the organoleptic qualities and the ascorbic acid content of frozen strawberries.

The use of CMC to improve texture and prevent syneresis in frozen pie fillings has also been discussed in the section on bakery products.

2. Dehydrated Foods

Dehydrated foods, such as fruit juices, vegetable powders, and dry soup powders, are more easily reconstituted in water and have a better texture and more palatable properties if CMC is added prior to dehydration. The addition of CMC to foods prior to dehydration is said to improve the retention of natural ff avors (Karabinos and Hindert, 1954).

Bogin and Feick (1951a,b) used CMC in aqueous fatty and oily systems, which could then be converted to dry, stable, nongreasy, solid food products by dehydration. These stable fatty-food products could then be used in dry packaged commodities such as noodle soup, etc.

Perech (1946a,b) used CMC to convert vegetable and fruit juices into dry, stable powders by dehydration and for its subsequent thickening properties in the reconstituted products.

3. Canned Foods

CMC has found some novel applications in canned food products. When added to canned fish and meat products, CMC prevented separation


of the liquid portions of the products. This was particularly effective in sterilizing fresh fish a t 110-115°C in closed cans (Algemene Kunstzijde Unie N. V., 1951). In canned agar fruit gels, Kojima e t aE. (1959a,b) found CMC to be an effective gel-strength reinforcing agent. Agar gels reinforced with 0.1% CMC and packed with fruits and heavy sugar syrup in canned mitsumame showed no change of taste and odor after 80 days a t 30°C and had higher gel strengths than agar controls containing no CMC.

Ronold (1952) prepared various fruit j ams-orange, strawberry, raspberry and plum-containing CMC as the gelatinizing agent. Berglund (1948) also used CMC to prepare sugar jelly products.

The use of CMC in canned pie fillings is discussed in a previous section.

4. Beverages

CMC has been used in several beverage applications. Wallerstein e t al. (1951) found that the incorporation in beer of small amounts of the alkali metal salts of CMC forms highly stable foams. CMC has been shown to be effective as a protective colloid in beverage flavor emulsions. Horikoshi (1954) prepared a stable lemon flavor emulsion by treating 6.3 kg of a paste containing 3% CMC and 1% nonionic surfactant with 1.5 kg lemon oil.

I. DRY PACKAGE MIXES

Pudding mixes, both the cooked and instant types, can use CMC to improve textural qualities by reducing syneresis and preventing or mini- mizing retrogradation of the starch base. A dry cooked pudding mix can be improved by adding about 0.25% high-viscosity CMC with 19% starch. Instant pudding mixes based on pregelatinized potato starch and phosphates can use about 0.3 t o .75% high-viscosity CMC.

Prepared cake mixes of the shortening-containing variety use 0.01- 1.0% CMC, based on dry weight of the mix, to give products that have greatly improved ease of batter preparation and produce cakes of improved quality and high volume (Elsesser, 1961).

Other dry mix preparations, such as instant fluffy frosting mixes, instant butter cream icing mixes, white icing bases, etc., make use of small amounts of CMC (less than 1% usually) to improve the quality of the product.

Dry beverage powders that must be reconstituted with water sometimes utilize CMC as a bodying ngcnt.

Huffman and Moore (1961) made an instant-type oatmeal composed of quick-cooking rolled oats and about 0.1-1.0% CMC. When boiling


water was added, the product acquired the flavor and texture characteristics of cooked oatmeal.

J. FOOD PRESERVATION APPLICATIONS

1. Preservative Food Coatings

The film-forming properties of CMC have been utilized to good advantage in the protection of perishable foodstuff s from bacterial attack and decay. Cornwell (1951) used CMC in conjunction with antimycotic agents to coat meats, fruits, and vegetables and thus protect them from bacteria and molds. In a similar way, eggs were also protected by a film of CMC containing a preservative (Algemene Kunstzijde Unie N. V., 1952). Improvements in this technique were made by Vale (1953), who formulated a solution consisting of about 1.0% of an alkyl quaternary ammonium halide, 0.1% CMC, and glycerol as an optional plasticizer. This composition was effective as a temporary preservative coating for fruits and vegetables for a period of about six weeks, i.e., between picking and canning, and could be removed by washing with water a t final processing.

CMC has also been used to form water-resistant films that can be used as a harmless vehicle for food, tobacco, antiseptics, etc. Rosenberg and Bandel (1961) mixed 5 lb CMC dispersed in 145 lb water with 50 Ib of 5% of periodate oxidized starch (dialdehyde starch). Then 2.5 lb glycerol was added, and the mixture was coated on a stainless-steel surface to form a cross-linked, tough, water-resistant film.

Shinn and Childs (1955) used CMC in a meat-coating preparation comprising an emulsion consisting of 30-60% fat, 3040% water, 2-12% edible gelatin, and 0.05-30/0 CMC.

Eggs can be preserved by treatment with formaldehyde, followed by a dip in oil or a film-forming substance such as CMC to decrease the rate of evaporation of water by 10-15% of that of the untreated eggs (Ulsen- heimer, 1956).

Brown e t al. (1958) dissolved a dry mix of 2 parts sorbic acid and 3 parts medium-viscosity CMC in 95 parts water to form a dip or spray that formed an antifungal coating on food products. In a similar manner, Nikkila et al. (1960) used CMC to thicken a preservative solution containing soluble phosphates that was used to treat fresh foods prior to or during freezing.

2. P r e s l ~ Fish Pvesewution

Several years ago it was discovered that fish could be preserved for substantially longer periods when treated with an antibiotic, chlorte-


tracycline (CTC) . The economic advantages of this were evident: fishing vessels could remain a t sea longer and return with a bigger catch with much smaller risk or degree of spoilage. In addition, the residual CTC was readily destroyed by heating, and therefore was not ingested by the consumer.

The CTC was usually applied in the form of an antiseptic ice containing 1 ppm CTC uniformly distributed throughout the ice blocks used for icing down the fish catch. During normal preparation of ice blocks, the CTC had a disturbing tendency to migrate during the freezing process and thereby give an unevenly distributed antibiotic concentration. Boyd e t al. (1955) found that the addition of CMC or carrageenan resulted in comparative uniform distribution of the antibiotic in ice blocks prepared by conventional slow-freezing procedures. I n addition, these gums also improved the distribution of certain food colors, acridine dyes, and aniline dyes in ice blocks (Gillespie e t al., 1955).

Less exotic preservative methods of fish preservation utilized the freezing of fish in salt solutions thickened with CMC (Aktieselskabet Protan, 1955). Inagaki and Iechika (1953) found that the freshness of fresh fish could be maintained by soaking them for 20 seconds in a 1-276 ascorbic acid solution. CMC used together with ascorbic acid improved the penetration of the acid into the fish, enhancing the preservative action.

5. Nontoxic Preservative

Perech (1955) prepared a novel nontoxic preservative by passing an electric current through silver or silver alloys immersed in a solution of CMC. After sufficient time, the solution is evaporated to yield the residual silver-CMC complex, which has a high germicidal action. Perech suggested its use in foods and beverages because of its nontoxicity.

K. MISCELLANEOUS Matsumoto and Matsuura (1954) invented a fortified artificial rice

molded under pressure from a dough of flour, soybean flour, and potato flour with CMC as a binder, and containing the appropriate nutrients of vitamins B1, Bt, and calcium lactate. A subsequent process by Taninaka and Hori (1958) eliminated the need for pressure treatment and produced a similar product by heating a mixture of starch and flour for 10 minutes a t 120°C, coating with CMC, and then drying.

Moore (1954) improved the settling rates of first carbonation juice in bcet-sugar manufacture by the addition of 2 ppni CMC based on the amount of juice.

Frieden and Stern (1956) increased the efficiency of feed utilization by

314 MAltTIN GLICKSMAN

nonruminant animals by adding a small amount of CMC to the feed. They believed that this addition slowed the progress of the feed through the digestive tract, thereby permitting the digestive juices to act more completely on the feed substances.

1. Tablet Coatings

In a related but not strictly food use, CMC, because of its lack of toxicity and its good film-forming properties, has been used in various tablet coating applications. Spradling (1954a,b) used it in a sugar syrup to give an elastic and fracture-resistant subcoating for medicinal tablets. Claims were made that fewer and thinner coatings were needed in this way, and that chipping a t the corners of the tablets was reduced. Oral tablets of activated carbon were coated with a thin CMC layer (<0.1 mm) in order to allow easier handling without staining or smearing of the hands, as well as making swallowing easier (Algemene Norit Maat- schappij, 1955). Awe (1957) used an emulsion of CMC, sugar, and starch to form a pill coating having a slow rate of decomposition.

IV. METHYLCELLULOSE AND HYDROXYPROPYLMETHYLCELLULOSE

A. BACKGROUND The modification of cellulose by chemical means to produce water-

soluble gums has been accomplished in many different ways. One of the most common chemical modifications is the preparation of the methyl ester of cellulose, whereby the methyl groups are substituted upon the hydroxyls of the cellulose. The effect of such modifications or the addition of these groups, is to separate the cellulose chains so that water or other solvents can enter and thereby dissolve the product. The properties of the modified cellulose ethers vary with the various degrees of treatment, such as degree of substitution, uniformity of substitution, and type of substituent group. Thus, i t has been shown that products with few methoxyl groups are soluble only in aqueous alkali solutions whereas highly substituted products are soluble in polar organic solvents. Also, a decrease in the molecular weight of the product as indicated by intrin- sic viscosity will improve solubility. The introduction of groups other than the methoxyl can also affect the solubility and other properties of cellulose. Other groups, such as ethoxyl, carboxyl, hydroxyethyl, and hydroxypropyl, have been used for these purposes.

The preparation of methylcellulose is comparatively simple. Cellulose fibers, usually cotton linters or wood pulp, are treated and swelled by caustic-soda solutions to yield an alkali cellulose:


R-OH + NaOH + R-ONa + HzO

This is then treated with methyl chloride to yield the methyl ether of cellulose or methylcellulose:

R-0 Na + CH3C1+ R-OCH, + NaCl

I n addition to this methoxyl substitution, the further reaction with propylene oxide will also give a hydroxypropyl substitution, thus yielding mixed ethers of cellulose:

R-ONa + H,C-CH-CH, R - O C H r CH-CH, I

'0' OH

Varying the ratios and amounts of methoxyl and hydroxypropoxyl units gives a vast number of cellulose ethers of differing physical and chemical properties. The main properties modified in this way affect organic solubility and thermo-gel point temperature, as shown in Table VII. In the United States, the Dow Chemical Company is the sole pro-

TABLE VII COMMERCIAL TYPES OF METHYLCELLULOSE AND HYDROXYPROPYLMETHYLCELLULOSE

Methoxyl Hydroxypropylb Thermal

Trade names % D.S. % D.S. gel pointo

Methocel, MC 27.5-31.5 1.64-1.92 - - 50-55°C Methocel, GOHG 28-30 I .68-1.82 7-12 0.17-0.3 5540°C Methocel, 65HG 27-29 1.61-1.75 4-7.5 0.1-0.18 (iO45"C MethoceI, 70HG 24-27 3.42-1.61 3-5.5 0.07-0.13 66-72°C Methocel, 90HC 19-24 1.08-1.42 4-12 0.1-0.3 85°C

a Fach of these types is available in a wide range of viscoeitiep. b Dow Chemical Company, 1962.

Windover, 1962.

ducer of these materials, which are sold under the trade name "Methocel." The number of substituent groups on the cellulose and anhydroglucose

unit determines the properties of the methylcellulose products. It has been found that a degree of substitution ranging from 1.64 to 1.92 yields the maximum water solubility. A lower degree of substitution gives products soluble only in alkali, whereas higher degrees of substitution produce materials soluble only in organic solvents.


B . PROPERTIES Methylcellulose and hydroxypropylmethylcellulose have a unique

property that distinguishes them from all other commercial gums. Whereas most gums will decrease in viscosity as the temperature of solution is increased, methylcellulose does the reverse; methylcellulose is soluble in cold water, and upon heating thickens and gels a t elevated temperatures, depending on the degree of substitution and other structural modifications. This novel property has led to its extensive use both in the food industry and in other industrial applications.

Thc gelling temperature, while dependent upon the degree and ratio of methoxyl and hydroxypropoxyl substituent groups, is also affected by other additives. The gel point is usually depressed by most electrolytes, as well as by sorbitol, sucrose, and glycerol. Conversely, i t is raised by ethanol, propylene glycol, and polyethylene glycol 400. These materials also counteract the depressive action of the former additives (Levy and Schwarz, 1958).

Methylcellulose is nonionic, and therefore is not affected by other salts or inorganic ions. However, methylcellulose materials can be salted out of solution when the concentration of electrolytes or other dissolved materials exceeds certain limits. This is usually affected by the ability of the soluble inorganic salts to take up water and decrease the hydration properties of the cellulose ether.

Methylcellulose can be used to prepare watcr-soluble films. These films can be cast from water solutions or by mixed solvent systems, such as methanol-water or methanol-benzene. Although water-soluble, methylcellulose films are unaffected by oil, greases, and hydrocarbons and also have excellent resistance to most organic solvents.

The methylcellulose products (Methocel, MC, U.S.P. series) have been approved by the FDA, and appear on the GRAS list as methylcellulose U.S.P. having a methoxyl content of not less than 27.5% and not more than 31.5% on a dry-weight basis. Hydroxypropylinethylcel- lulose (Methocel HG series) is also permitted as a food additivc for use as an emulsifier, film former, protective colloid, stabilizer, suspending agent, or thickener, in accordance with good manufacturing practice.

Under the Definitions and Standard of Identity for French and salad dressings, both methylcellulose and hydroxypropylnicthylcellulose are allowed as an optional emulsifying ingredient (Dow Chemical Co., 1961).

In general, the properties of methylcellulose have been long utilized by the food industry, and for many years the methylcellulose and hydroxypropylmethylcellulose products have been used as emulsifiers, film- formers, protective colloids, stabilizers, thickeners, suspending agents,

UTILIZATION O F SYNTHETIC GUMS I N THE FOOD INDUSTRY 317

etc., in food products (Greminger, 1957). Table VIII is a partial listing of some of the more common applications.

TABLE VIII FOOD APPLICATIONS O F METHYLCELLULOSE PRODUCTS

Bakery products Batter dip Beer stabilizer Confections Canned pie fillings Dehydrated foods Dietetic foods Edible packaging Flavor emulsions French dressings Frozen foods Ice rream and ice pope Milk stabilizer Pie fillings Preservative food coatings Salad dressings Whipped toppings

C. BAKERY PRODUCTS Methylcellulose has found a use in both chemically and yeast-leavened

doughnut mixes, sweet rolls, and coffee cake, as well as in bread and dietetic products. It has been used in white bread and spoonbread dry mixes (Greminger and Savage, 1959).

The contributions of Methocel are increased water absorption and mixing tolerance, particularly with low-gluten or gluten-free flours, improving the uniformity and quality of the finished products. Machining and handling of the doughs is also improved.

Other noted advantages are increased volume during baking or frying, controlled fat absorption in fried products, improved flavor retention, and lengthened shelf life from slower staling (Dow Chemical Co., 1955).

1. Functional Properties

The functional properties of the methylcelluloses that are helpful in broadening the tolerances of doughs and batters are the following (Dow Chemical Co., 1962) :

a. Gelat ion and Binding Characteristics. Some of the properties of the methylcelluloses are similar to the gluten present in flour, but they are not affected by proteases, mineral salts, or acids, and are affected only

318 MARTIN CLICKSMAN

mildly by common oxidizing agents. In addition, methylcellulose gels during elevated baking temperatures, thus assisting gas retention during baking without increasing the toughness of the finished product.

b. Emulsifying Properties. The methylcellulose materials are effective emulsifying agents when used in batters, and appear to retard retrogradation of starch or the onset of staling, They are also effective in low-pH batters because of their excellent pH stability.

c. Moisture Retention. The ability of the methylcelluloses to imbibe up to forty times their weight of water yields improved mixing tolerances and a finished product with better water retention and a greater resistance to staling.

d. Oil Resistance. The methylcelluloses, being insoluble in fats and oils, absorb less fa t and improve product quality when used in doughnuts and fried cakes.

2. Chemically Leavened Systems

a. Doughnuts and Fried Cakes. Studies on the functional effect of methylcellulose in cake and doughnut batters led to the development of cake mixes in which the normal egg content could be partially replaced by these gums. Weaver et al. (1957) found that an optimum level of 0.2- 0.4% Methocel, 65 HG, 4,000 cps, based on the total mix weight, in a commercial low-egg formula gave the following effects:

a ) Increased water absorption by the dough b) More uniform batter viscosity c) Gelation characteristics similar to those of the native starch and

In addition, Methocel improved the dough’s standing tolerance and allowed production of quality doughnuts from undermixed or overmixed batters. Samples with Methocel bubbled much less in the deep-fat bath and provided a smoother surface and a more tender doughnut texture.

b. Cakes. The gas retention characteristics of cake batters depend upon the formulation of stable, uniform, emulsified mixes. The emulsifying and moisture-retention properties of the methylcelluloses yield batters with the desired qualities and cakes with increased freshness retention.

These surface-active properties are particularly usable in prepared mixes that require the addition only of milk, water, and possibly fresh eggs. The whipping properties of methylcellulose can partially replace dry or liquid egg whites in the production of cake mixes, as patented by Weaver and Greminger (1957). Total replacement gives an overly moist cake, tending toward sogginess ; approximately 10-50% replacement is

protein in the batter


usually beneficial. Recommended replacement levels are 0.5 oz methylcellulose in place of 1 oz egg white solids or 39 oz liquid egg whites.

3. Yeast-Leavened Systems

a. Coffee Cake and Sweet Rolls. Measurements of specific volumes and compressibility as well as subjective taste tests were made on the dough and post-bake characteristics of coffee cakes and sweet rolls containing methylcellulose. Farinogram results indicated that thc addition of 0.28% Methocel, 65 HG, 4,000 cps (0.2% of total recipe) increased water absorption of the flour and its mixing tolerance. In the same system, the viscosity is increased without other effects on the gel properties. Other tests indicated that retrogradation of the starch was also retarded by the addition of Methocel, and compression tests on coffee cakes showed increased elasticity a t all times.

The gas retention properties of doughs stabilized with Methocel can be judged by the increase in specific volume achieved in the baked goods. Volume increased 8% while moisture loss remained constant.

Taste-panel tests indicated that coffee cakes containing Methocel remained moist, sweet, and tender and retained full flavor for periods up to 48 hours, while cakes without Methocel had begun to lose moisture, tenderness, and flavor (Dow Chemical Co., 1962).

b. Raised Doughnuts. Results with typical yeast-raised doughnuts showed marked improvement by the addition of 0.2% Methocel, 65 HG, 4,000 cps. Although the specific volume of the doughnuts was increased by lo%, fat abeorption was decreased by 17%. This was attributed to the improved gas retention quality of the dough, together with the oil- insolubility of the methylcellulose products (Dow Chemical Co., 1962).

c. Bread. Methylcelluloses have functional properties that are of advantage in baked goods, particularly in food made of flours such as rice, corn, and rye, which are low in or lacking in gluten. The methylcelluloses, which are available in a wide range of gel points, contribute to cell structure and reduce crumbling. The use of methylcellulose allows more water to be carried in a dough, permitting more complete gelatinization of the starch.

Methocel, 65 HG, 4,000 cps, in low-gluten nonstandardized breads showed increased water absorption of the doughs and improved crumb texture of the baked goods. The reversible thermal gelation characteristics of Methocel products play an important role in strengthening the dough during the gas evolution stage in baking without contributing t o toughness. Methocel also appears to retard migration of moisture t o the loaf surface during storage, thus tending to retard the amount of mold


growth on stored loaves that were wrapped while still warm (Dow Chemi- cal Co., 1962).

d. Pie Fillings. The ability of niethylcellulose solutions to gel a t elevated temperatures common in baking operations suggests its use in jelly and fruit pie filling. Methylcellulose is used in pie fillings to reduce the absorption of water into the pie crust during baking. In addition, its thickening properties stabilize the system after baking and result in a fruit filling that retains its full natural flavor during baking. Since these gums are nonionic, they are unaffected by fruit acids and function effec- tively in acid media (Windover, 1962).

More specifically, the clarity and sheen of pie fillings is improved when hydroxypropylmethylcellulose, 1,500 or 4,000 cps a t a level of 0.5% based upon the weight of the filling, including drained fruit juices and additional water, is addcd to cherry, blueberry, and raspberry products. The stabilizing properties of the nonionic methylcelluloses are not affected by the fruit acids (Greniinger and Savage, 1959).

D. DIETETIC FOODS

The dramatic expansion of the market for dietetic foods in recent years has led to increased use of inethylcellulose and hydroxypropylmethylcellulose in low-calorie foods as well as in specialty foods for diabetics, allergic individuals, and those on salt-free diets.

The properties that make these cellulose ethers useful in this application are the following (Dow Chemical Co., 1960) :

1) Are colorless, odorless, and tasteless 2) Have no caloric value 3) Are nontoxic and nonallergenic 4) Are low-ash nonionic materials and will not react with acids or

5 ) Are effective as thickeners, emulsifiers, stabilizers, mechanical alkalis present in foods

foamers, and moisture retainers

1 . Diabetic Syrups

Sugar-free items for diabetics require a bodying or viscosity agent to improve palatability, and methylcellulose found an early use in this application. Bauer and Wasson (1948) investigated a number of sugar- free recipes that were supposedly safe for diabetic individuals. These so- called ‘‘safe and reliable preparations” were found to be unsafe because of significant amounts of glycogenetic materials such as alcohol, glycerin, and propylcne glycol. These m:tterinls could be replaced, however, hy aqueous methylcellulose in proper concentrations, which would act ns satisfactory vehicles for various electrolytes in the concentrations nor-


mally used. Synthetic fruit essences could be used, along with saccharin, to help mask the taste of thc active ingredients.

Good-quality nonsugar inaple syrups and soft drinks have been made with methylcellulose and syntlictic sweetencrs. Concentrations for synthetic maple syrup vary from 0.75 to 1.0% of the total formula weight, and those for the synthetically sweetened soft drinks vary from 0.15 to 0.3%, based on the weight of the final drink. The methylcellulose provides the body required to obtain good consumer acceptance (Greminger and Savage, 1959).

2. Jams and Jellies

Dietetic jams and jellies that do not exhibit syneresis, such as occurs with low-methoxyl pectin, can be prepared with methylcellulose. The nonionic methylcelluloses can be used with calcium salts of cyclamate sweeteners (Windover, 1962).

3. Wafers and Crackers

For many years, methylcellulose has been used commercially in the manufacture of crackers or wafers designed for reducing diets. In this application, i t served two functions: 1) it produced a feeling of fullness or satiety due to its ability to hold many times its own weight in water, and 2) i t served as a bulking agent that stabilized moisture content during passage of the food through the digestive tract.

This property of stabilizing water content in the digestive tract has found a broad use in pharmaceutical preparations designed to overcome constipation. The strong water-holding demulcent and nonmetabolizable properties also make i t very effective as a treatment for diarrhea. It has also been suggested that methylcellulose added to concentrated food products, such as army rations, would provide bulk to offset the restricted volume of the concentrates and would help control constipation and intestinal upsets due to extreme nervous and physical tension (Dow Chemi- cal Co., 1956).

4 . Gluten-Free Flours

Rice, barley, tapioca, soya, potato, and cottonseed flours are often used in baked goods for persons allergic to wheat. Use of these flours in place of wheat in the preparation of baked goods often yields products that lack desirable texture and cutting properties because of the absence of wheat gluten. Certain methylcelluloses, such as Methocel, 65 HG, 4,000 cps, have a gel point in the same range as the gelation temperature of the starches and the coagulation temperature of the wheat proteins: 65-70°C. There- fore, its use in place of wheat flour gives dietetic baked products that

322 MARTIN GLICICSMAN

resemble standard goods in texture and cutting properties (Windover, 1962). Levels of 0.2% based on flour have been reported to improve the volume, lightness] texture, crumb, and keeping qualities of baked goods made from these gluten-free flours (Dow Chemical Co., 1960).

5. Salad Dressings

In cream salad dressings of the mayonnaise type and French type, the smoothness and texture achieved by a high level of oil can be obtained by replacement of oil with hydroxypropylmethylcellulose to give an equivalent low-calorie product. The caloric values of salad dressings containing these methylcellulose materials can be reduced as much as 90% below those of standard dressings, and formulations can be made with caloric values of as low as one calorie per gram (Dow Chemical Co., 1960). For this application, a hydroxypropylmethylcellulose with a 90°C gel point and 4,000 cps viscosity is suggested a t a concentration of 1.0- 1.5%, depending on the consistency desired (Greminger and Savage, 1959).

Low-calorie Italian and French dressings that can be made with methylcellulose have been patented recently. For Italian dressing, Bondi and Spiteer (1959) suggested 0.548% by weight methylcellulose in combination with 0.25-0.40% of a gelling gum, such as agar. For French dressing, Nasarevich and Spiteer (1959) recommended a three-gum system utilizing 1.2-1.576 methylcellulose, 0.2-4.3570 agar or derivatives, and 0 . 2 4 5 % pectin or derivatives, together with 1.0% kaolin.

6. Soft Drinks

Soft drinks usually contain large amounts of sugar, not only for sweetness and flavor but for the body and texture required for good consumer acceptance. In these beverages, sugar can be satisfactorily replaced with saccharin and cyclamate for sweetness, and methylcellulose for body and texture. Methocel, 65 HG, 400 or 4,000 cps, has been recommended for this purpose a t levels of O.lM.20% based on total weight of the product. This methylcellulose product is completely compatible with all sweeteners, and, since i t is nonionic, it is possible to formulate a low- sodium beverage as well. It also does not cause cloudiness during chilling] since it has excellent cold-water solubility (Dow Chemical Co., 1960).

E. DEHYDRATED FOODS

1. Fruit and Vegetable Juices

The expanding field of dehydrated foods has found a broad use for methylcellulose products. Several processes for the preparation of dehy-


drated fruit and vegetable juices use i t for improving the resuspension and reconstitution properties of the dehydrated juices (Windover, 1962).

Low-viscosity methylcelluloses (15-25 cps) a t a concentration of 0.5- 1.0%, based upon the weight of solids in the dehydrated fruit or vegetable products, aid in redispersion and provide better consistency in the reconstituted product. The reversible thermal gel point, together with the viscosity and suspending properties, improves product performance (Greminger and Savage, 1959).

Eddy (1950) reported that the difficulty normally encountered in the production of free-flowing fruit and vegetable powders by spray-drying or drum-drying could be overcome by methylcellulose used as a drying aid. In the preparation of spray-dried grapefruit and orange juice powders, Eddy prescribed 0.14.0% methylcellulose, based on dry weight of solids, ranging in viscosity from 15 to 4,000 cps, added prior to drying.

A more recent process for the dehydration of fruit and vegetable juices is the foam-mat drying method. In this procedure, stable foains are created by incorporating air or other gases (by whipping) in a liquid concentrate of the food product containing suitable edible stabilizers. The foam is air-dried or oven-dried in belt-type dryers to give extremely porous sheets or mats that can easily be crumbled into free-flowing powders. This technique was originally applied to tomato paste and orange juice, but has since been extended to milk, coffee, lemonade, apri- cot puree, pineapple juice, grape juice, and prune juice.

The original work as reported by Morgan et al. (1959) found suitable stabilizers to be egg albumen, fatty acid monoglycerides, mixtures of mono- and diglycerides, aiid fatty esters of sucrose a t levels of about 1% of the diy solids in the product.

Subsequent work by Gold (1961) on the foam-mat drying of tomato paste and apple sauce found certain methylcellulose stabilizers to be effective in this application. Specifically, for these two food products, 1.5% Methocel, 60 HG, 50 cps, was reported to be effective from the standpoint of foam development and stability. This was attributed to Methocel’s compatibility characteristics coupled with a low gel point. It was also found that the low-viscosity methylcelluloses provided a faster rate of foam development.

A more recent review of the status of the foam-mat drying process for making orange juice powder, as being developed by the Florida Citrus Commission and the U.S.D.A. Fruit and Vegetable Laboratory a t Winter Haven, Florida, reported the use of small amounts of soya protein and methylcellulose to form the stable foam of concentrated orange juice for drying (Anonymous, 1962e). After forming, the stable, spaghetti-like strips of the foam are forced onto a moving belt by a press and dried in


a stream of heated air, after which the strips are ground to a powder. Bissett e t al. (1961) reviewed progress in the use of foam stabilizers

in foam-mat drying of orange juice a t the Citrus Processing Conference in September, 1961. The prime requirement of a good foam stabilizer was to permit the formation of a stable foam that could be handled in the feeders without breaking down, would retain its shape on the drying belt, and would give a satisfactory reconstituted product. Of the various foam stabilizers evaluated, only two showed promise: 1) a glyceryl monostearate and 2) a modified soybean protein when combined with about one-fourth its weight of methylcellulose. The soybean-methylcellulose product had the advantage of yielding a more natural color in the reconstituted product and reconstituting more readily. I n addition i t gave n denser foam, which permitted a heavier belt-loading rate and also did not contribute appreciably to flavor.

Specific experimental data reported by Wagner (1961) utilized a preferred ratio of 0.8% soya protein and 0.2% methylcellulose, on a solid basis, for stabilization of orange juice.

The most recent studies of foam-mat-dried orange juice by Bissett et nl. (1963) report the preferred proportions of the foam stabilizer used. To 2,386 grams of frozen Valencia orange concentrate of 59" Brix is added 60 grams of a 16.7% solution of modified soya protein and 60 grams of a 4.8% suspension of 10 cps methylcellulose. The dry weight of the added foam stabilizers equaled 0.9% of the total solids present, and the final Brix was 56.7".

2. Chocolate Milk

In the manufacture of dry chocolate drinks, several factors reduce consumer acceptance: surface scumming, poor color, variable consistency, and segregation of chocolate solids. Methylcellulose has been used as a stabilizer for spray-dried chocolate milk drinks containing skim milk solids. It functions both as a suspending agent for the cocoa solids and as a bodying agent to simulate the consistency of whole milk. Love (1959) reported the preferred stabilizer to be a hydroxypropylmethylcellulose (Methocel, 90 HG, 100 cps) used a t 1% concentrations based on the weight of milk solids.

F. FROZEN FOODS Methylcellulose materials possess the very desirable property of sta-

bility a t temperatures near freezing and resistance to syneresis a t sub- zero temperatures. These properties were recently used by Rivoche (1957, 1959, 1960) in a series of food-product patents, The foods were patties containing a mixture of cooked meat, fish, or fowl with vegetables, and


combinations of frozen fruits and vegetables were also possible. The function of the methylcellulose materials was to hold these patties together by gelation during frying and to provide the moisture required to prevent burning of the vegetable components.

1. Fruit Products

Rivoche (1961) also used the properties of methylcellulose in an improved process for preserving foods by dehydration and freezing. This process was claimed to have advantages whereby the treated food products substantially retained their initial shape and appearance after freezing and thawing or cooking. The process essentially consisted of partially dehydrating the moisture-containing food products by subjecting them to a series of subatmospheric pressure changes a t elevated temperatures. During these vacuum treatments the partially dehydrated foods were immersed in methylcellulose or methylcellulose-sugar solutions, where the foods gradually became impregnated with the hydrophilic colloid. This adsorption treatment was repeated a number of times, alternately between dehydrating steps. The treated foods could then be preserved indefinitely by freezing or canning and would retain the original shape and texture of the product without becoming soft and mushy. This process was especially applicable to fruits and berries but could be used for vegetables, meats, and fish.

The freeze-thaw-resistant gel properties of methylcellulose were again uhed by Rivoche (1962) in the preparation of frozen fruit pies. I n this procedure, the frozen fruit to be used was thaxved and the juice drained off. Part of the juice was mixed with methylcellulose, and the rest mixed with starch to form a suspension. The starch suspension was brought to a boil to form R partially gelled starch mass, which was then mixed with thc methylcellulose solution. This suspension was then added t o the thawed fruit to provide a pie filling for frozen pies. In some instances, methylcellulose was used alone, without the starch. The advantages cited were that the pies could be cut without cooling, and the filling was in attractive gel-like form, with firm, plump fruits and berries, and no leakage of juice. In addition, the methylcellulose in the filling prevented the juices from soaking through the bottom of the pie during cooking.

2. French-Fried Potatoes

Methylcellulose has found important use in the production of high- quality frozen French-fried potatoes. Product color is a serious quality control problem and is dependent in great part upon the procurement of raw potatoes of relatively high solids content and low reducing sugar content. And even with good-quality tubers, normal storage conditions


are not optimum for control of color, and the resulting high conversion of starch to reducing sugar tends to produce dark-colored products. In addition to color, textural firmness of the product also is related to the raw potato solids content (and to the amount of oil absorbed during fat- frying).

It was found that treatment of potato strips by a dip into a methylcellulose solution, following blanching of the potato strips, gave drier, firmer products having lighter, more even colors when fried (Gold, 1962). Gold (1962) reported that although all Methocel (methylcellulose) products are generally suitable for this application (because of their ability to form oil-resistant thermal gels) , products of the Methocel 90 HG type were more suitable from the standpoint of the processing temperatures involved. In addition, these products form tender thermal gels a t relatively high temperatures that are less prone to rupture due to migration of water from the strips during frying. Under proper processing conditions, vegetable-oil absorption was reduced 20-3070.

A typical production procedure described by Gold (1962) consists of the following steps:

1 ) Peeling, sorting, and slicing 2) Water blanching a t about 190°F for 7-10 minutes to partially cook

the potatoes, to inactivate certain enzymes, and to leach out a portion of the natural sugars

3) Sugar solution dip to replace leached sugars 4) Methocel solution dip using 2.5% Methocel, 90 HG, 100 cps, solu-

5 ) Deep-fat frying a t 375°F for about one minute 6) Packaging, freezing, and storage

tion a t about 150°F

3. Frozen Confections

As with most hydrophilic gums, the methylcelluloses were evaluated as ice cream stabilizers but were not found to be particularly suitable for this application. An early evaluation by Pompa (1945) found Metho- cel 4,000 to be helpful in contributing viscosity to ice cream mixes but not effective in preventing “wheying-off” in the finished ice cream.

In a related application, however, methylcellulose was reported to be very effective as a binder and thickener in improving the stability of frozen ice pops. Windover (1960) used methyIcelIuIose to minimize the objectionable fast meltdown and color and flavor drainage that are common in ice pop confections. Recommended levels were 0.5-2.0% by weight of the higher-viscosity inethylcellulose or hydroxypropylmethylcellulose, based on the total weight of the composition.


G. EDIBLE PROTECTIVE COATINGS

The film-forming properties of the methylcelluloses have been utilized in protective coatings for various food applications. A Russian article discusses the possible use of methylcelluloses in the meat industry for the coating of various meat products (Lyaskovskaya et al., 1955). Ulsen- heimer (1956) used it for the preservation of eggs. The eggs were first treated with formaldehyde and then coated with methylcellulose to decrease the evaporation of water (a reduction of only 1&15% below that of untreated eggs is desired).

Eppell (1955) developed an edible film made of a mixture of methylcellulose and low-methoxyl pectin modified by a calcium salt. This film composition was designed to be used as a coating for compressed cereal bars, compressed fruit and nut bars, candy bars, jelly bars, and other foodstuffs (in either piece or bar form) that require protective coatings. The advantages claimed for the coating are that i t is edible, adds strength to fragile food bars, is grease resistant, and tends to prevent sticking of the bars even when unwrapped.

The Watson Flour Company, Woodside, New York, has used hydroxypropylmethylcellulose in the preparation of cold-water-dissolving edible pouches for functional single-use transparent containers for a dough conditioner and for a vitamin supplement used in the bakery industry. The pouch is made by a coating process using the cellulose ether com- pounded with various food-grade plasticizers that improve the film- forming characteristics of the material and allow it to be heat-sealed. The two products packaged in the film are Do-Con, a powdered dough conditioner, and Sol-U-Pak, a bread-enrichment mixture packaged for Charles Pfieer & Company (Anonymous, 1962f).

These new pouch packs, distributed in a convenient dispenser carton, save the baker time and waste in measuring ingredients from bulk quantities and eliminate the trouble of opening small unit packages. Upon dropping into a dough-mixing machine, the film dissolves, releasing the contents for thorough mixing in the batch.

H. MISCELLANEOUS

1. Batter Dips

The best gelation, adhesive, and grease-resistant properties of the methylcelluloses provide a combination of functions especially suitable in a dipping batter for deep-fried breaded foods. Thermal gelation of the methylcelluloses when they come into contact with the hot fat creates a


barrier around the fried article that greatly reduces fat absorption. Sug- gested use level is 1% hydroxypropylcellulose based on the total weight of the wet batter. In addition, i t can be used in a conventional batter to control viscosity and to permit dipping a t lower batter solids (Greminger and Savage, 1959).

Of course, the adhesive properties of the methylcellulose are of prime importance and serve excellently in the application to assist the adherence of the bread crumbs and other granulated material. Use has been a t 1-1$% levels in breading batters for fresh and frozen fish and meat products.

2. Toppings

The whipping properties of inethylcellulose have been used frequently in the preparation of bakery and confectionery toppings. A recent patent for a whipped sugar topping (General Foods Corp., 1958) uses a blend of methylcellulose, sugar, and an alginate foam stabilizer.

V. OTHER CELLULOSE DERIVATIVES

The cellulose derivatives discussed so far-carboxymethylcellulose, methylcellulose, and hydroxypropylmethylcellulose-are the only cellulose derivatives that have FDA approval for direct food use. They enjoy widespread application in this field.

Other cellulose derivatives are commercially available (Machell, 1961) and have interesting properties, but do not find much use in food products, although some of these have limited approval in pharmaceutical tableting and in food-coating applications. A short review of these is made in order to complete the picture.

A. HYDROXYETHYLCELLULOSE (HEC) Hydroxyethylcellulose is produced by the reaction of ethylene oxide

with alkali-treated cellulose as follows (Windover, 1962) :

R-OH + NaOH -+ R-ONa + HzO R-ONa + CH?-O-CH2 + R-OCH2CH2-OH

In the United States i t is manufactured and sold by Hercules Powder Company as Natrosol 250, and hy Union Carbide Chemicals Co. as Cellosiee.

Hydroxyethylcellulose is a nonionic, synthetic, hydrophilic colloid with good thickening power and fine film-forming properties. It is readily soluble in hot or cold water, and, being nonionic, exhibits excellent tolerance for dissolved electrolytes and is unaffected by pH changes. The

UTILIZATION OF SYNTHETIC GUMS IN THE FOOD IKDUSTRY 329

films formed from hydroxyethylcellulose are water-soluble, and can be made water-insoluble if desired. This material is completely organic, containing no mineral constituent, and therefore leaves a minimum of ash upon ignition (Butler, 1959b).

Hydroxyethylcellulose is compatible with synthetic and natural guins and resins, and functions well as a colloidal stabilizer and protective colloid. It is a nonfoaming material with a very low B.O.D. value. It has excellent freeze-thaw stability and a good shelf life, with little change in viscosity during the storage of sterile solutions.

Early toxicity feeding studies were made by Smyth et al. (1947), who conducted a 2-year test feeding rats diets containing 5, 1, and 0.270 hydroxyethylcellulose. The results were published as “indirect evidence that the compound is neither absorbed nor hydrolyzed in the gastro-intestinal tract.”

More recent work confirmed the low oral toxicity of the product. In- clusion in the rat diet a t a level of 5% for 10 days caused no detectable harm, though long-term feeding information sufficient to determine the safety of this product in food or food packaging is not yet available (Union Carbide Chemicals Co., 1960d).

Because of the recent stringent FDA regulations requiring long-term feeding tests, there are few instances of the use of hydroxyethylcellulose in food or pharmaceutical products. However, there are some instances where the film-forming properties of this gum have found some use in related applications designed for oral ingestion. Duninire (1954) employed hydroxyethylcellulose as a protective coating for grain. Whole, cracked, or ground grain pellets, as well as extruded wafers of hardened fa t or similar edible substances, were spray-coated with a solution of hydroxyethylcellulose. The coating was digestible yet impervious to oxidation, and thus protected the vitamin content of the pellets. Spradling (195413) used 2-7 parts hydroxyethylcellulose in a syrup of 200 parts by weight sugar and 100 parts water, to form an elastic and fracture-resistant subcoating for medicinal tablets. Advantages claimed were the need for fewer and thinner coatings and a rcduction in the chipping of tablet corners.

Levy and Jones (1958) found hydroxyethylcellulose extremely eff ec- tive in preparing a stable, flavored aspirin suspension that could be reconstituted from a prepared dry powder mix. Because of its nonionic nature, the hydroxyethylcellulose was not affected by the acidic nature of the suspension, and results with hydroxyethylcellulose showed that the constituted aspirin suspension could be kept a t room temperature for 1 month without excessive hydrolysis. The unreconstituted powder mix was stable indefinitely and could be stored for a long time without deterioration.


B. ETHYLCELLULOSE (EC) Replacement of the hydroxyl groups on the basic anhydroglucose unit

of cellulose by ethoxyl instead of methoxyl groups gives a water-insoluble polymer instead of a water-soluble one. Normally this would be of little interest in a discussion of food applications. However, ethyl- ceIlulose has excellent film-forming properties that have found certain specialized edible applications in the food and drug industry.

Ethylcellulose is made by the reaction of ethyl chloride with alkali cellulose as follows:

R-0-Na + CzH&l+ R-0-C2H6 + NaCl

Complete substitution gives a material with poor strength and flexibility and limited applicability. The commercial materials are partially substituted, having a D.S. of 2.15 to 2.60 (or 43 to 50% ethoxyl content) (Hercules Powder Co., 1955).

Ethylcellulose is distinguished primarily by its versatility. It is very tough, is soluble in a wide range of solvents, and retains flexibility a t extreme ranges of temperature. In general i t is characterized by low inflammability, freedom from discoloration by sunlight, heat resistance, solubility in varied solvents, wide range of compatibility, and flexibility a t low temperatures.

As previously indicated, the most important property of ethylcellulose is its ability to form films having a high tensile strength combined with excellent flexibility over a wide temperature range. This toughness a t both high and low temperatures has been a principal factor in its use as a protective coating in certain food applications. In addition, ethylcellulose has no taste of its own and has been used as a coating for paper, film, or foil in contact with food.

It is nontoxic and has been cleared by the Food and Drug Adminis- tration (1962a) for use as a binder and filler in dry vitamin preparations and as a component of protective coatings for vitamin and mineral tablets.

Childs (1957) conceived of using ethylcellulose as a protective coating on sausages to prevent the undesirable “salt rust.,’ He used a double- coating procedure whereby the sausage was first coated with a gelatin, algin, or pectin film, and then an outer coating was applied of 13% ethylcellulose and 87% ethylacetate. This procedure was also claimed to lengthen the shelf life of the sausage.

Improved hot-melt food-conting compositions suitable for dip-coating fresh or frozen foods were developed by Wirt et al. (1958), who used ethylcellulose in refined mineral oil, together with plasticizers such :is


glyceryl monostearate, and antioxidants. Other compositions also utilized higher levels of antioxidants, together with color stabilizers (Wirt and Kelly, 1958). Further improvements in this technique were made by Patten and Kelly (1959) , who found the preferred type of ethylcellulose to be one having an ethoxyl content of 47.5-50% by weight. Addition of a nontoxic antioxidant was also recommended. This coating was especially effective in coating meat products, either by dipping into the molten coating preparation or by spraying on.

Subsequent work by Kelly and Wirt (1960) led to ethylcellulose coating compositions that were especially suitable for enveloping meat and meat products in tightly adhering protective coatings that could be readily stripped off. These coating compositions, applied by brushing, spraying, or dipping, produced films that were transparent even a t -20°F or below. These coatings also had the claimed advantages of not being sticky, oily, or greasy, and not causing oleaginous deposits.

In typical pharmaceutical applications, Blaugh et at. (1958) found ethylcellulose to be a superior granulating agent for ascorbic acid formulations. Granulation with an alcoholic solution of ethylcellulose accelerated drying, prevented contact with water, and coated the granules with a protective film. Greminger and Windover (1959) found that mixtures of ethylcellulose and hydroxypropylmethylcellulose with ratios ranging from 1:3 to 3:l could be used to make enteric coatings having controllable rates of dissolution in the alimentary canal of humans and animals.

C. ETHYLHYDROXYETHYLCELLULOSE (EHEC) Chemically modifying ethylcellulose to produce a close relative,

ethylhydroxyethylcellulose (EHEC) , results in different functional properties. It possesses the same toughncss, clarity, and stability as ethylcellulose, and is also soluble in aliphatic hydrocarbons although ethylcellulose is not. By further chemical manipulation of this cellulose- mixed ether, a polymer (Natrosol 75H) is obtained that has unusual solubility characteristics in that it is soluble in both water and organic solvents (Hercules Powder Co., 1959, 1962~) . It is soluble in water below 30"C, but gels a t 40°C and is insoluble in hot water.

These newer derivatives do not have any food uses or toxicity clearance, but their interesting properties are indicative of the variety of functional qualities that can be built into a basic cellulose structure, and illustrate the broad potentials of synthetic gums in the future.

D. CARBOXTMETHYLI-IYDROXTETHYLCELLULOSE (CMHEC) A very unusual hydrophilic colloid is the mixed ether, sodium car-

boxymethylhydroxyethylcellulosc (with the sodium salt formed on the


carboxyniethyl groups). It is available in two different grades, indi- cating differing ratios of the two substituent groups.

Carboxymethyl Hydroxyethyl CMHEC-37 0.3 D.S. 0.7 D.S. CMHEC-43 0.4 D.S. 0.3 D.S.

The functional properties, therefore, are a combination of those common to both carboxymethylcellulose and hydroxyethylcellulose, and in general these products show a broad tolerance for acids, alkalis, and salts. They are especially useful for their variable ionic-nonionic ratios, which give many of the advantages of a polyelectrolyte as well as a wider tolerance for multivalent cations (Hercules Powder Co., 1961b).

’ As mentioned, one of the outstanding properties of carboxymethylhydroxyethylcellulose is broad compatibility with various salts. It is compatible with as much as ten times its weight (or concentration) of salt. It can also be used to thicken acid solutions, down to a pH of about 2.1 with some acids. It is quite inert to almost all organic solvents: ketones, esters, pure alcohols, ethers, hydrocarbons, and chlorinated solvents.

Both types are compatible with CMC, methylcellulose, and gelatin, but are miscible only with natural gums such as arabic, Karaya, tragacanth, and sodium alginate, giving hazy combinations.

E. KLUCEL-MIXED CELLULOSE ETHER

In 1962, Hercules Powder Co. introduced a new, more versatile cellulose ether-ealled “Klucel.” The exact chemical composition was not re- vealed, but it was described as a nonionic ether with unusual solubility characteristics, i.e., soluble in cold water but insoluble in hot water, indi- cating functional properties similar to those of the well-known methylcellulose products (Hercules Powder Co., 1962~1).

As stated, i t produces sparkling clcar solutions in water a t temperatures below 5OoC, but becomes insoluble a t 50°C or above. It is also solid in a wide range of anhydrous polar organic solvents. It is described as an effective thickener, binder, emulsion stabilizer, film former, adhesive, and protective colloid.

The solid is a true thermoplastic and has a very low equilibrium moisture content. The films formed from Klucel are water-soluble, tough, in- flexible, and transparent, suggesting its use in packaging and protective coating applications.

Klucel has varying compatibility with inorganic salts in water solution and is compatible with most common salts below 5% concentration. It forms clear, smooth solutions in anhydrous lower alcohols and in many


other polar solvents, and is considered to he an efficient thickener for aqueous organic systems.

Preliminary studies indicate that it has a very low order of toxicity, similar to that of other physiologically inert cellulose derivatives. Addi- tional investigations are currently being conducted by the manufacturer.

Vl. POLYVINYLPYRROLIDONE (PVP)

A. BACKGROUND

Polyvinylpyrrolidone is a coiiiparative newcomer to the field of industrial water-soluble polymers. It was developed by W. Reppe, in Ger- many in the late 1 9 3 0 ’ ~ ~ and was first used during the second World War, as a blood plasma expander. After the war, other uses, primarily in nonfood fields, were developcd, and in 1956 the General Aniline and Film Corporation began full-scale production of this material in the United States (Azorlosa and Martinelli, 1962a).

Polyvinylpyrrolidone is a polymeric N-vinyl lactam, known chemically as poly-l-vinyl-2-pyrrolidone, but more generally as PVP. I ts chemical structure is as follows:

It is produced conimercially by a purely synthetic route involving acetylene, formaldehyde, ammonia, and hydrogen (p. 334).

Domestically the General Aniline and Film Corp. (1960) produces four different viscosity grades, which are offered in both powder form and aqueous solutions. These differ primarily in molecular weight, and are designated as follows:

A pproxiniate molecular weight PVP K-15 10,000 PVP K-30 40,000 PVP K-60 1 G0,OOO PVP K-00 360,000

In addition, special pliariuaceutical grades of PVP are available under the trade name “Plasdone,” and beverage-clarification grades are supplied as “Polyclar.”

At present these materials range in price froin a lorn of about $1.25 per pound to $3.20 for the highest pharmaceutical grade. But i t is felt that its physiological inertness and its protective colloid function re-


HCZCH t 2 HCHO HOCH2- C=C-CH,OH Acetylene Formaldehyde 1,4 -Butynediol

Butyrolactone l,4-Butanediol

2 - Pyrrolidone N -Vinylpyrrolidone PVP

main to be exploited in the food field, and that only a fraction of the market potential for PVP has been realized to date. With the growth of markets and long-range development of PVP, the price may eventually come down to the range of 60-70 cents per pound and offer severe competition to other water-soluble gums in this price range.

B. PROPERTIES Polyvinylpyrrolidone is very versatile and offers various functional

properties for a multitude of applications. PVP has a wide solubility and compatibility range. It is an excellent protective colloid and suspending agent, and has very good film-forming properties. It is also a good binder and stabilizing agent and has desirable adhesive properties. It is a complexing agent and can be used for detoxification purposes.

The commercial versatility of PVP, which has led to the increasing use of this polymer in a wide variety of fields, is due primarily to these outstanding properties (Azorlosa, 1958, 1959) :

1) Wide solubility and compatibility range 2) Complexing and detoxifying ability 3) Physiological acceptability 4) Protective colloid action

UTILIZATION OF SYNTHETIC GUMS I N THE FOOD INDUSTHY 335

5 ) Film-forming ability 6) Adhesive qualities,

1. Solubility

PVP is readily soluble in cold water and gives fairly viscous solutions. With lower-molecular-weight material, concentrations as high as 60% can be dissolved in aqueous media. The viscosity of PVP is not affected by pH over the broad range of 0 to 10. Solutions of PVP also have a high tolerance for many inorganic salts, particularly the lower-molecular- weight types. PVP solutions are stable over long periods if they are protected from mold growth by antimycotics such as sorbic acid.

In comparison with other commercially available water-soluble gums, PVP has unusual solubility in organic solvents. It is soluble in the lower alcohols, glycols, nitroparaffins, methylene dichloride, amines, and organic acids, and when it is anhydrous the solubility range is increased to include ketones, esters, and aromatic hydrocarbons.

The complexing action of PVP is demonstrated by its ability to form molecular adducts with other substances. In some cases the result is a solubilizing action, as with iodine; in other cases the result is a precipi- tating action, as with tannins in beverages.

2. Film Forming

One of the most unusual properties of PVP is in its film-forming nature. PVP can be cast from a variety of solvents to give films that are clear, glossy, and hard a t low humidities. They are very hygroscopic and exhibit excellent adhesion to a wide variety of surfaces, such as glass, metals, plastics, and human hair. As with most water-soluble resins, PVP films are hygroscopic and the degree of water adsorption is a function of relative humidity. Because of its unique properties, PVP film has found widespread application in the cosmetic field, where i t is used extensively in the formulation of various hair sprays and hair fixative preparations. In this field i t has also been used in barrier creams, hand cleaners, hand lotions, dentifrices, and shaving preparations as well as in deodorant sprays and after-shave lotions (Freifeld et al., 1962).

Insoluble films having the same physiological stability, compatibility, and other properties of soluble PVP can be made by reacting PVP with polymeric carboxylic acid compounds (Stoner and Wright, 1959).

3. Toxicology

The physiological background of PVP has been well explored because of its earlier uses as a blood plasma extender, and a long history of use has shown it to be essentially a physiologically inert material. PVP is

336 MARTIN GLlCKSiMAN

essentially nontoxic by oral administration, skin absorption, inhalation, or intravenous or intraperitoneal injection; it is not a primary irritant, skin-fatiguing material, or sensitizer; and i t is nonantigenic (General Aniline and Film Coip., 1960).

The acute oral toxicity is ADo greater than 100 grams per kilogram of body weight. Acute intravenous toxicity is LD50 equal to 12 to 15 grams per kilogram of body weight. Chronic oral toxicity was also investigated by feeding rats and dogs l- lO% PVP K-30 by weight of their total diet for up to 24 months. No toxic effects or significant pathological changes attributable to the PVP were observed (Freifeld et al., 1962; Azorlosa and Martinelli, 1962a).

C. FOOD APPLICATIONS In the food industry, with which we are primarily concerned, PVP

has found a good application in beverage manufacture as a clarifying agent. It is known that PVP forms insoluble complexes with certain tannins. Therefore, this principle is applied to clarification and chill proofing of vegetable and fruit beverages, such as beer, whiskey, wine, vinegar, and fruit juices (Anonymous, 1958a,b). Usually, taste and clarity are improved and other desirable properties are enhanced. The trade name for PVP offered for beverage uses is “Polyclar” in the United States, and PVP has been approved for use as a clarifying agent in beverages under prescribed conditions by the Food and Drug Administration (1963).

1. Beer

The use of polyvinylpyrrolidone as a selected precipitant for tannins in beer was discovered by MacFarlane et al. (1954) and MacFarlane (1954). In efforts to find a method of getting rid of the tannins in beer in order to extend shelf life, MacFarlane e t al. conducted a long search for these selective precipitants, and found that PVP was the most effective and useful. Chill haze is generally regarded as being due to a protein- tannin complex formed by a slow reaction between barley protein, beta- globulin, and a tannin of unknown structure but probably of high molecular weight. Proteolytic enzymes such as papain, which is the active ingredient of most chill-proofing agents, break down and solubilize the protein of the protein-tannin complex. The chill stability imparted to the beer by this process may be of a temporary nature because nothing is removed from the beer, so that upon storage for long periods the components of the protein-tannin complex may recombine and consequently reform a haze. On the other hand, PVP is concerned with a tannin rather than the protein component, and since PVP removes all the tannins it would appear that selective precipitation will result in a more permanent


chill proofing of the beer. MacFarlane e t aE. found that under certain specified conditions PVP permanently removed the chill haze material from beer without harming palate fullness, flavor, or head retention. They found the optimum requirement to be about one pound of PVP per hundred barrels, but this varied for beers brewed under different conditions. Insufficient PVP failed to give adequate protection, whereas an excess caused the appearance of haze during pasteurization. However, a method was described whereby the optimum amount of PVP for a given beer could be easily determined before proceeding to full-scale brewing trials. In addition, the use of PVP to remove these tannins improved taste and taste stability, foam retention, chill-haze stability, and filtration ease, and gave cleaner worts from the cooler, cleaner, better-tasting storage beer, shorter storage time, a saving on hops, and lower enzymatic chill-proof requirements.

The optimum amount of PVP used generally falls within the range of 120 to 200 parts per million, or about three to five pounds of PVP per 100 barrels of beer; but the optimum must be determined experimentally for a given brewery. The usual practice in breweries is to boil the malt cereals and hops with water for a specified period, after which the hot liquid, called “hot wort,” is strained free of hops. It is recommended that the PVP be added a few minutes before the end of the kettle boil. At this stage after filtration the PVP content of the finished beer is almost non- existent and the further addition of up to 100 parts per million of PVP to the beer in storage may improve stability further (Azorlosa and Marti- nelli, 1962a),

Stone (1962), in a recent patent, claimed that MacFarlane’s clarification procedure could be improved by using the low-molecular-weight PVP polymers (K-16), or copolymers of PVP with olefinic compounds such as vinyl acetate or vinyl alcohol. These additives would stabilize the beer or ale without causing precipitation of the protein-tannin complex.

Hoggan (1962) reported a recent advance in the brewing technology field whereby an insoluble form of PVP was used. This material, known as AT-496, was reported to combine the advantages of water-soluble PVP, such as the high selectivity for tannins (anthocyanogens), and none of the disadvantages that may be associated with the presence of residual PVP in the finished beer. In addition, the AT-496 appeared to possess a partic- ular affinity for the part of the anthocyanogens that combine specifically with protein to form chill-haze materials. Other advantages recommended or stated were that AT-496 did not adsorb bittering substances and that there was 110 effect on the foam propertics of treated beer. In addition, copper content was reduced significantly and the flavor was not adversely affected. In fact i t was reported that beers treated with AT-496 possess


less astringent after-bitterness, which seems to help accentuate the bitterness associated with the isohumulones. The levels of AT-496 recommended were about three to four pounds per 100 barrels.

Bertsson (1959) showed that the haxe-forming constituents in beverages are precipitated by the use of 0-8 g PVP per hectoliter of beverage, with the preferred PVP having a molecular weight of 550 to 2,500,000.

General developments in this field led to the production and sale of a specialized PVP product, “Polyclar H,” for use in the fining and stabilizing of beer (General Aniline and Film Corp., 1958). Polyclar H, currently sold by the General Aniline and Film Corporation for specific use as a clarifying and stabilizing agent for the brewing industry, is claimed to contribute the following desirable attributes:

1) Markedly increases the amount of trub removed as hot-break 2) Modifies the characteristics of trub, facilitating removal by de-

3) Reduces potential haze materials in the beer 4) Significantly reduces the amount of chill proof required 5) Enhances the flavor and foam properties of finished beer 6) Improves the clarity and stability of beer 7) Exerts a hop-sparing action 8) Improves stability to taste

canting, filtering, or centrifuging

2. Wines

Along the same lines, the wine industry investigated the use of PVP for the clarification of wines. The same essential conditions occur in wines: Tannin-like materials are introduced during the grape crushing and fermenting operations and must be removed in order to obtain a clear wine. Clemens and Martinelli (1958) investigated use of a special grade of PVP (AT-380) in wine clarification. These studies, made with port and blackberry wine, showed an advantage for this use in cost and performance. No added capital investment was required, and no changes in major processing conditions were needed. PVP could be evaluated or utilized a t any stage to obtain the desired results without changes in established processes or equipment. Fast action and a rapid settling, with a resulting clear supernatant wine, could be obtained, and these advantages showed up as a much faster filtration, fewer production slowdowns to change filters, and a more compact sediment in the vats, giving larger yields from fewer rackings. I n addition, storage stability improved and after-tastes were cleaner.

LaRosa (1958) reported observations on PVP in wine clarification. He found that not all wines reacted with PVP, and that more red wines than white wines gave precipitates. This difference could not be explained,

UTILIZATION O F SYNTHETIC GUMS I N THE FOOD INDUSTRY 339

since i t was believed that all wines contain some tannins. LaRosa felt that, possibly, the PVP reacted only when certain constitutional groups in the polyphenols were free. In those cases where PVP did give a precipitate, the addition of &l+ pounds of PVP to 1,000 gallons was usually sufficient to effect clarification.

In wines, the complexing action of PVP is utilized in removing tannin- like materials that result from the grape crushing and fermentation operations. It is believed that the PVP acts as both a complexing and a flocculating agent for the haze-forming substances in wine. In addition to improving the clarity, PVP seems to reduce the harsh after-taste of some wines. The best procedure is to add the PVP after fermentation, although it can be added a t various stages of the process.

The optimum amount varies with the type of wine, and must be determined experimentally. This is important because, when excess PVP is used, a solubilizing action occurs that gives less precipitate. Thus, for port wine it has been recommended that PVP be used in the range of up to 4 pounds per 1000 gallons (Azorlosa and Martinelli, 1962a).

The chill proofing of 100 proof whiskey can be accomplished by as little as .004% PVP. This is accomplished most easily by the simple addition of an aqueous solution of PVP with gentle stirring, followed by filtration through a filter aid (General Aniline and Film Corp., 1960).

3. Fruit Juices

The clarity of various fruit products is also affected by naturally occurring tannins. PVP may find use in the processing of such products as grape juice, cider, apple juice, vinegar, and jellies because of complexing action to remove these tannins. In experimental studies on grape juice, 0.2% added PVP followed by filtration after 24 hours a t 4°C produced a clear product. Control juice without PVP was cloudy. A jelly prepared from the treated juice gave a sparkling clear product and there was no apparent loss of pectin or change in taste from control samples (General Aniline and Film Corp., 1960).

4. Dehydrated Foods

Tiedemann (1962) recently patented a new application of PVP to improve soluble coffee and tea extracts. According to this patent the addition of small amounts of PVP greatly improved the process of con- centrating coffee, yielded a coffee of superior flavor and aroma, and gave a product outstandingly superior in solubility in that a “clear satisfactory solution of maximum flavor, taste and aroma is easily secured without the requirement for vigorous ebullition on the part of the dissolving water.” The preferred level of PVP was l - lO% by weight of the solids

340 MARTIN GLICXSMAN

present in the brew. The PVP was to be added to the coffee or tea brew prior to dehydration, by preferred procedures such as spray-drying or drum-drying.

Neumann (1962) improved the freeze-drying processing of certain aqueous food extracts by increasing the eutectic point of the extracts through the addition of PVP or some other hydrophilic materials.

Azorlosa and Martinelli (196213) found a novel use for PVP as a dialysis medium in a process for dehydrating aqueous food products such as coffee, tomato juice, and orange juice. When cellophane dialysis bags containing fruit juices or coffee are immersed in aqueous solutions containing a t least 25% by weight of a water-soluble polymer such as PVP, the internal water will diffuse out of the dialysis bag, and i t was claimed that 85-90% of the water could be removed from tomato juice and orangc juice in 3 hours a t room temperature. The advantage cited, of course, is the removal of large quantities of water from food products a t room temperature without affecting the quality or taste of the resulting dehydrated product.

5. Miscellaneous

A recent German patent (Naturin-Werk Becker & Co., 1962) claimed that sausage casings made from animal skin collagen are rendered easily removable from the sausage by coating the inner casing walls with layers of PVP or similar hydrophilic gums.

In the dietetic field, PVP has been found to be a valuable adjunct in the preparation of highly stable preparations capable of being dispensed dropwise for sweetening foods or beverages. Riffkin and Cyr (1958) utilized this property of PVP in the preparation of a low-calorie sweetening product of this type.

PVP has found use in the Preparation of highly stable oil-soluble vitamins (A, D, E) . These vitamins are prepared as solid solutions in hydrogenated oils or waxes, and subscquently dispersed within a gellable colloid plasticized with PVP. These vitamin products are quite stable even on exposure to air a t relatively high temperatures for prolonged periods (Bavley e t al., 1954; Bavley and Timreck, 1955).

VII. CARBOPOL

A. BACKGROUND

A new series of interesting water-soluble gums was introduced for industrial applications by the B. F. Goodrich Corp. (1957, 1962) a few years ago. These materials, sold under the tradename of Carbopol, are carboxy vinyl polymers of extremely high molecular weight. These arc

UTILIZATION OF SYNTHETIC GCMS IN THE FOOD INDUSTRY 341

available in three different types-Carbopol 934, 940, and 941-and are supplied as dry fluffy powders in the acid form. These materials must be neutralized in order to develop optimum thickening properties. The major characteristic of interest is the fact that highly viscous mucilages can be produced with very low concentrations of Carbopol resins when they are mixed with water or various organic solvents and then neutralized with a suitable base. The high viscosity tends to give to the Carbopol mucilages a fluid gel structure very similar to thick, salve-like masses, with good body and resistance to flow. A neutralized Carbopol resin offers this combination of reported properties and characteristics:

1. Thickening efficiency-extremely high thickening properties ob- tainable

2. Product uniformity-affords reproducibility unobtainable with natural gums

3. Toxicity-comparatively safe and approved for drug and cosmetic applications

4. Stability-relatively unaffected by temperature variation 5. Unaffected by aging-not subject to attack by hydrolysis or oxida-

6. Bacteria-resistantnot attacked by and will not support mold

7. Versatility-wide choice of neutralizing agents allows broad and

The industrial product has the following physical properties (B. F.

Appearance-fluffy white acid powder Bulk density-13 pounds per cubic foot (approximately) Specific gravity--1.41 Moisture equilibrium as shipped-2% maximum Equilibrium moisture content, room temperature a t 50% RH-8% pH of 1% water solution-3 As stated previously, three types of Carbopol are offered for indus-

trial uses. The structural or chemical differences of these materials have not been made public, although i t is probably a molecular-weight difference that is responsible for the varying properties among these materials. The properties differ as follows:

Carbopol 934 is used for the production of thick formulations such as heavy gel emulsions and suspensions. It gives permanent stability a t high viscosity.

Carbopol 940 forms clear, sparkling water gels or watcr-alcohol gels and has excellent thickening efficiency a t high viscosities.

Carbopol 941 can bc uscd at relatively low viscosities to form pcrmn-

tion

growth

diversified applications

Goodrich Corp., 1962) :


nent emulsions and suspensions, and is effective even in ionic systems. It produces high viscosity a t extremely low concentrations.

Although these Carbopol resins have been known for several years and used for various industrial applications, they have not found use in the food industry for the simple reason that they have not yet met the approval of any official agencies. However, it has been shown in feeding and other animal tests that these materials are harmless and will eventually be cleared, so eventual use should be considered in a review such as the following. In an earlier brochure published by the manufacturer of this material (B. F. Goodrich Corp., 1957) it was suggested that Carbopol could be used in various food applications such as the following: ice cream, sherbet, cheese spreads, bread and pastry mixes, confectionery, jellies, jam, salad dressings, animal feeds, shortenings, margarines, and beer. Although to the author’s knowledge none of this has taken place, i t is felt that the applications suggested will be explored further and that Carbopol will find some uses in the food industry. It is from this viewpoint that Carbopol must be considered as a potential raw material for consideration within the future growth and development of the food industry.

B. PROPERTIES

1. E’ffect of p H

The acid character of the Carbopol resins is primarily responsible for their versatility and applicability. Users of these materials can select the salt form and the pH best suited for each application. As mentioned previously, neutralization of the resins is necessary for full use of their maximum thickening or functional properties. There is a wide range of suitable neutralizing agents, and the agents used in most water systems are potassium, sodium, or ammonium hydroxide, and certain amines are preferred. Dry neutralizing agents such as sodium carbonate or sodium tetraborate can also be used, but these are generally less effective. The maximum use efficiency obtained with Carbopol 934 is usually in the pH range of 5.5-11. With Carbopol 940 and 941, the range is somewhat broader.

The thickening efficiency of Carbopol can best be illustrated by an example. A 1% dispersion of Carbopol 934 has a viscosity of 390 cps. Upon neutralization to pH 7 with sodium hydroxide the mucilage viscosity rises to 55,000-60,000 cps. Similar effects are also found with Carbopol 940 and 941, although these display significant thickening abilities even in the unneutralized form (B. F. Goodrich Corp., 1962).


2. Compatibility

Carbopol resins are compatible with most materials uscd frequently in cosmetic, pharmaceutical, and industrial products in water-base dispersions. Soluble salts decrease the efficiency of Carbopol mucilages, and all monovalent salts, such as sodium chloride, affect them similarly. Divalent salts cause an even more drastic loss in efficiency; however, solutions containing divalent ions can be thickened with Carbopol if pH is adjusted to 8 or above before the divalent materials are added.

In general, Carbopol 941 exhibits better resistance to ionic effects than Carbopols 934 and 940. Often this property reverses the gelling efficiencies of Carbopol934 or 940 and 941.

3. Aging Characteristics

Carbopol polymers are not subject to hydrolysis or oxidation under conditions of normal use. Carbopol 934 and 940 are unaffected by extended aging of mucilages a t temperatures of 160"F, whereas Carbopol 941 does lose viscosity. In general, Carbopol mucilages resist viscosity loss a t elevated temperatures. In addition, Carbopol systems where Carbopol is used as a primary emulsifier are stable to low temperatures and are freeze-thaw resistant.

Carbopol polymers are not attacked by bacteria or fungi, but do allow their growth on nutrients present in aqueous systems. Therefore, when biocides are used, the compatibility of Carbopol with these materials is an important factor in its utilization.

4. Toxicology

The toxicity of Carbopol resins is negligible, and this has been an important factor in the acceptance of Carbopol resins for use in a variety of specialty applications. Although Carbopol has not been used in the food industry, because of lack of clearance, it has been tested extensively and is currently being used in pharmaceutical preparations for oral uses under an OTC label (B. F. Goodrich Corp., 1962).

The utility of the Carbopol resins in food products and processing is under continuing study by the manufacturer, and the most recent communication from D. L. Secard (1962) , of the B. F. Goodrich Corp., states the following: "Of the Carbopol resins, only Carbopol 934 has been subjected to the rigorous toxicity studies. As a result of these studies Carbopol 934 has been approved for use in B number of oral and topical pharmaceutical applications. The toxicity studies indicate that Carbopol 934 has a very low ordcr of toxicity and we see no rcason why Carbopol


934 would not be acceptable for food use. At this time, however, we have not received clearance for the use of this resin in food products. The same holds for Carbopol 940 and 941.”

In addition to animal feeding studies, some clinical studies have been reported where Carbopol 934 was test,ed as a bulk laxative over a period of several months. Hospitalized patients were given tablets of Carbopol 934 for several months, and no deleterious effects were noted (B. F. Goodrich Corp., 1962).

c. APPLICATIONS Since Carbopol has not yet found use in the food industry, potential

applications and functional properties are indicated by experience in the two industries most closely related to foods-the pharmaceutical and cosmetic industries-where oral toxicity is also an important factor that must be considered.

I . Pharmaceuticals

In the pharmaceutical industry, Carbopol is used as a general thickening and suspending agent, as a binder and slow-release agent in tablets, and as a bulk laxative.

a. Tablets. In pharmaceutical tablets Carbopol 934 contributes no off taste and in some cases masks undesirable flavors. It gives tablet surfaces that are smooth and resist dusting, and tablet strength is improved by using small amounts of Carbopol 934. In addition, the drug potency can be preserved by the acid nature and nioisture-scavenging properties of Carbopol 934. Tableting methods can be wet granulation, or direct compression in a dry-blend technique. In addition, Carbopol 934 is used to advantage as a control release agent in certain types of tablets. The advantage of this is that fewer tablets are needed and less frequent dosing is requircd. The total amount of drug needed is reduced, and the desired concentration of the drug in the blood stream can be maintained over an extended period. In certain cases i t is desirable to form Carbopol salts of amino drugs in order to obtain controlled release properties.

b. Laxatives. Effectivc bulk laxatives can also be formulated with Carbopol 934 as the bulking agent. When the Carbopol dose reaches the alkaline intestine i t swells into a soft gel and establishes the proper moisture content in the colon. Paradoxically, the same property of controlling the moisture content of the colon makes it possible to prepare Carbopol doses that are useful in treating diarrhea (Anonymous, 1962g).

c . Emulsions and Suspensions. Soon aftcr its coinniercial introduction in 1954, Carbopol was found to be effective as a suspending, emulsifying, and stabilizing agent, and a good review of its effectiveness as an emulsion


stabilizer was made by Wolff and Meyer (1961). Swafford and Nobles (1955) found Carbopol to be useful as a suspending agent for calamine lotions, and for the preparation of palatable kaolin-pectin suspensions. Misek et al. (1956) undertook a study of Carbopol 934 to determine the suspending and emulsifying properties of Carbopol in combination with various medicinal agents. They found i t to be very effective for the preparation of suspensions of a number of common pharmaceuticals, with some difficulty encountered only with polyvalent metal ions such as bismuth and zinc. Carbopol is also found to be effective as an emulsifier for cod liver oil, cottonseed oil, and various other oils under proper emulsification conditions.

In 1959 Lee and Nobles (1959) modified Carbopol and used a dry sodium salt to prepare satisfactory suspensions and emulsions of a number of common medicinal preparations. They found the optimum concentration for suspensions to be around 0.5% whereas for emulsions the preferred concentrations were in the range of 0.25-2.0%, depending on the nature of the oil phase.

d. Salves and Jellies. In non-oral topical applications, investigations by Caver et al. (1957) found Carbopol to be extremely effective as a base for pharmaceutical jellies. I n a wide range of concentrations the color, viscosities, and spreadability of 17 commonly prescribed dermatological agents were found to be satisfactory.

Further investigations by Swafford (1960) utilized Carbopol 934 as a jelly base for the preparation of ephedrine sulfate jelly. Neutralization of the Carbopol base with triethanolaniine gave a gel material that could be spread smoothly and had good shelf stability.

2. Cosmetics

The utilization of Carbopol in cosmetics took place soon after it became available commercially. Dittmar (1957) reviewed the thickening propertics and rheology of Carbopol 934 and discussed its use in glycerol and glycerol-water systems. The improvement of viscosity in glycerol systems for cosmetic applications was felt to be a very important functional property of Carbopol 934 (Cohen, 1956). This characteristic resulted in its use in various cosmetic lotions, creams, ointments, etc.

It found a highly desirable application in toothpaste formulations, where, used as a binder, Carbopol 934 gave a high gloss, smooth texture, and excellent viscosity stability t o the toothpaste. In addition to its thickening and suspending powers, Carbopol 934 imparted plastic or sheer-thinning flow, and formulations with this binder could exhibit high apparent viscosity but still flow easily under slight pressure. Carbopol is therefore recommended for use in both tube and pressure-pack products.


An important related fact is that since Carbopol has recognized negligible toxicity it has been accepted for use in toothpaste by the FDA, with the official FDA statement allowing up to 1.5% Carbopol 934 as an inert compounding ingredient in order not to require a new drug application (B. F. Goodrich Corp., 1962).

VIII. GANTREZ AN

A. BACKGROUND

Another important newcomer to the ranks of synthetic water-soluble polymers is Gantrez An, a copolymer of methyl vinyl ether and maleic anhydride (PVM/MA) . Gantrez An, the trade name selected by General Aniline and Film Corp., is a polymeric acid anhydride with a linear structure having alternating units of methyl vinyl ether and maleic anhydride.

It is manufactured from the basic raw materials of acetylene, methanol, and maleic anhydride. Methanol is reacted with acetylene a t about 150°C, using an alkaline catalyst such as KOH to yield methyl vinyl ether. The ether is then reacted with maleic anhydride, in the presence of a free radical peroxide catalyst, to produce the polymer, with the following structure (Anonymous, 1961b) :

Three different grades of material are available commercially, differing basically in molecular weight (General Aniline and Film Corp., 1961) :

Gantrez An 119-low molecular weight, specific viscosity 0.1-0.5 Gantrez An 139-medium molecular weight, specific viscosity 1 .O-1.4 Gantrez An 149-medium molecular weight, specific viscosity 1.5-2.0 Gantree An 169-high molecular weight, specific viscosity 2.6-3.5 The outstanding physical characteristics of these new hydrophilic gums

1) Solubility and stability in water over entire pH range 2) Wide compatibility with other water-soluble gums, resins, plasti-

3) Effective thickening properties in either aqueous or organic solvent

4) Effective dispersing, stabilizing, and other protective colloid func-

include:

cizers, and most metallic salts

systems

tions

UTILIZATION OF SYNTHETIC GUMS IR’ THE FOOD INDUSTRY 347

5) Fine film-forming ability, yielding highly polar films 6) Insolubilization by certain polyfunctional compounds

B. PROPERTIES

1. Solubility

Gantrea An is soluble in water and several organic solvents, including alcohols, phenols, pyridine, aldehydes, ketones, lactams, and lower aliphatic esters. It is essentially insoluble in aliphatic, aromatic, or halo- genated hydrocarbons, ethyl ether, and nitroparaffins.

The solubility of Gantrez An in water is limited only by the viscosity of its solutions. The anhydride slowly hydrolyzes in the presence of water to form the free acid, which is readily soluble:

OCH, I

CH,- CH- CH- CH I

- CH I

Solutions of up to 50% concentrations can be prepared by adding the anhydride to water and allowing the mixture to stand 2448 hours a t room temperature with occasional stirring. Faster solutions can be made by using hot water and high-speed agitation. But in all cases time is needed for the anhydride to be hydrolyzed to the free acid, and thus, complete solution is strikingly indicated by an almost instantaneous change in appearance from milky white to colorless transparent.

2. Viscosity

At any given concentration, the viscosity of aqueous solutions of Gan- trez An is a logarithmic function of the molecular weight of the copolymer. As with most gums, the effect of temperature is to decrease the viscosity logarithmically as the temperature is raised.

Although Gantrez An is stable a t all pH levels, the viscosity is affected markedly by the addition of alkali and the type of alkali, but in gcncral follows a fairly typical pattern. At pH 2, the viscosity of Gantrez is a t its lowest point; upon the addition of alkali (NaOH or NHIOH), the viscosity increases rapidly to a maximum a t about p H 5, then drops gently to pH 7-8, rises to a second (lower) maximum a t about pH 11, and decreases sharply through pH 12. I n general, the viscosity is fairly level between pH 5 and 11, and shows wide changes only a t pH’s below 5 and above 11. With organic bases or amines, this relation is different,


and wide viscosity changes are cyident a t all pH’s and are dependent on the specific amine used (General Aniline and Film Corp., 1961).

3. Com,patibility

Gantrez An is conipatible with high concentrations of acids, so concentrations of sulfuric, hydrochloric, phosphoric, and acetic acids as high as 25% do not affect the clarity of aqueous solutions. It will tolerate most inorganic salts in concentrations equal to a t least 10 times that of the copolymer, except for ferric, lead, and mercury ions, which produce gelat- inous precipitates upon the addition of as little as 1% in some cases. Gantrez An solutions are compatible with a wide variety of water-soluble resins and gums.

4. Films

Gantrez films can be easily prcpared by casting from aqueous or organic solvent solutions. Thc unmodified films are nontacky and posscss high tensile and cohesive strength, and thc inherent brittleness of these films can be modified rcadily by the addition of compatible plasticizers. The films are normally soluble in water but can easily be insolubilized by reacting thcni with polyfunctional compounds such as polyhydroxy coni- pounds as glycols. They can also be insolubilized with severe heat treatment, but some discoloration takes place a t higher temperatures. Normal films have excellent stability upon aging for several days a t temperatures up to 150°C.

5. Toxicology

Gantrcz An is a bland material, and acute oral toxicity tests indicate that the copolymer is relatively nontoxic. Tests made with Gantrcz An 139 showed it to have an LDso of 8-9 g/kg. In addition, neither the dry powder nor aqueous solutions appear to be primary irritants or sensitizers, as indicated by patch tests made on 200 unselected human subjects (Gen- eral Aniline and Film Corp., 1961). Additional toxicological and physiological studies, a t the Alfred I. du Pont Institute of the De Nemours Foundation, in Wilmington, Delaware, have indicated a relative lack of toxicological effects on specific organs of the body (Hoyt, 1961).

Eventual clearance of this material by the FDA for food use is fore- seen by the manufacturer, and a t this date it has been approved as a component of food-packaging adhesives (Food and Drug Administration, 1962b).

C. APPLICATIONS As with other new synthetic gums, Gantrez An, lacking thc necessary

FDA clearance a t this time, has not found any active uses in the food


industry, but has been employed in diverse industrial applications in the fields of lithography, textiles, paper, adhesives and coatings, paints, detergents, ore processing, etc. I n addition, because of its lack of toxicity it has found limited application in the food-related fields of pharinaceuticals and cosmetics.

1. Pharmaceuticals

Early pharmaceutical applications for Gantrez An were as a thickening and suspending agent for medicinal agents used in topical salves and ointments (Skauen, 1955).

Because of its essentially low toxicity, it has more recently been evaluated for use in enteric and sustained-release coatings (Lappas and Mc- Keehan, 1962).

2. Cosmetics

The attractive film-forming, bodying, suspending, and emulsifying properties of Gantrez An have found uses in various cosmetic preparations such as hair sprays, detergent bars, shampoos, and lotions.

A particularly novel effect was obtained in its use as a stabilizer for dentures, where some physical ingestion might occur. Germann et al. (1961) found Gantrez to be an excellent substitute for the natural gum Karaya, normally used in such products, and claimed to have made a superior, improved product with Gantrez An.

IX. POLYOX

A. BACKGROUND Among the new synthetic water-soluble gums, the Polyox group of

compounds is one of the more important ones and should eventually find widespread use in the food industry. At present, Polyox has not been used widely, because of difficulty in meeting FDA requirements, although it is a nontoxic, harmless material.

Ethylene oxide polymers have been known for a long time commercially, and have been sold by Union Carbide Chemicals Co. under the trade name of Carbowax. These have usually been called polyethylene glycols, and varied in molecular weight from 200 to 20,000. The lower- molecular-weight members of the family are liquids, whereas those with molecular weights of 4,000 and above are waxy solids. When polymers of very high molecular weight are produced (in the range of 200,000 or more), entirely new products are obtained. These liigh-molecular-weight polymers of ethylene oxide, which arc called Polyox resins, arc tough, extensible, highly crystallinc, rrsinous, thermoplastic, watcr-soluble ma-


terials. In appearance, they are very similar to the low-density polyethylene resins, but they have the unusual property of being soluble in water, These Polyox resins were first brought to public attention in 1957, and offered in commercial quantities in 1958 by the Union Carbide Chemicals Co. The materials were offered in four established grades of resins, with prices around $.85 per pound (Mellecker, 1960).

An interesting review of market research activities leading up to com- niercialization of these materials is given by Bateman and Tenney (1959).

Some of the more important properties of the Polyox resins are as follows :

1) Complete water solubility 2) Increased thickening power with concentration 3) Low atmospheric pick-up in dry form 4) Good compatability with other types of polymers 5) High resistance to biological attack (no B.O.D.) 6) Ability to be calendered, molded, extruded, or cast 7) Ability to be heat-sealed 8) Inherent flexibility and toughness 9) Resistance to most oils and greases Although very few food applications have been developed so far, these

materials have found use in industrial applications such as textile warp sizes, paper coatings, detergents, aerosol hair sprays, toothpaste, water- soluble packaging films, and adhesives. It is strongly felt that approval by the FDA will eventually be obtained and applications will be found for these materials in the food field (Bergcr and Ivison, 1962; Powell and Bailey, 1960).

B. PREPARATION

Ethylene oxide, starting material for the preparation of Polyox, can be polymerized readily in the presence of a caustic and a suitable catalyst, such as water, ethylene glycol, or alcohol. Under these conditions, the highest practical molecular weights are usually of the order of 10,000. Increasing this polymerization to much higher molecular weights is usually difficult, and was not very successful in the period before 1958. It was found that other catalysts could increase the polymerization rate and allow the preparation of high-molecular-weight polymers. In the presence of an alkaline earth carbonate, polyethylene oxides of very high molecular weight could be formcd. The reaction was unpredictable, however, and still very slow, although faster than previously. Work by Hill et al. (1958) with various alkalinc earth carbonates was responsible for the development of mcthods for producing high-molecular-weight poly- oxyethylene products on a commercial basis.


At present, four grades of Ucar Polyox resins are offered by Union

1) WSR-35, molecular weight of approximately 200,000 2) WSR-205, molecular weight of 600,000 3) WSR-301, molecular weight of 4,000,000 4) Coagulant-grade, highest molecular weight In general, thickening power increases as the molecular weight of the

resin increases. The low-molecular-weight grades are used primarily in plastic applications such as production of water-soluble films and sheets and in solution applications where high concentrations of solids are required without excessive increases in viscosity. The high-molecular- weight grades are used for their thickening, coagulating, and flocculating ability (Union Carbide Chemicals Co., 1960a, 1962a).

Carbide, as follows:

C. PROPERTIES

1. Viscosity

The viscosity of aqueous solutions of Polyox water-soluble resins de- pends upon the grade and concentration of the resin, temperature of the solution, shear-rate applied during mixing, and nature and concentration of the dissolved salts.

The thickening power of the Polyox resins increases sharply with rising concentration. With respect to the highest-molecular-weight material, the WSR-301 product, every 0.1 % increase in concentration brings large increases in viscosity. In aqueous concentrations of 5-15% by weight, this material forms firm gels that are rubbery and elastic and have a dry, nontacky surface.

The Polyox resins are completely miscible with water a t room temperature, and the viscosity of solutions of the resins decreases as the temperature is raised. However, the degree of change of viscosity is less than for solutions of many other water-soluble resins.

In concentrations of a few tenths of a percent more, Polyox resins have an upper solution-temperature limit just below the boiling point of water. At this temperature there is a definite precipitation of the resin, but this phenomenon is reversible and the resin can be redissolved by simple stirring or agitation a t a lower temperature.

Polyox resin solutions show a permanent viscosity loss when subjected to high-shear mixing. Thcse materials are non-Newtonian or pseudoplastic, and do not exhibit thixotropic properties.

Electrolytes reduce the room-temperature viscosity and lower the temperature a t which resins will precipitate or salt-out. As an example, a 2% concentration of Polyox in two-tenths molar potassium carbonate


solution produces only one-quarter the viscosity that results from the concentration of resin in pure water. In addition, a t the same time, the upper temperature limit of solubility is lowered from 97°C to 69°C. The solubility of Polyox resins decreases nearly linearly with salt concentration.

Polyox has the unusual property of being able to thicken certain mineral acids. These acids are hydrochloric, phosphoric, and nitric, and, in addition, Polyox can thicken ammonium hydroxide, but not the sodium or potassium hydroxide. Sulfuric acid can also be thickened (Union Carbide Corp., 1962b).

Polyox is soluble not only in water but also in various organic solvents, such as chlorinated hydrocarbons, alcohol, acetone, and other related solvents. In many cases, the resins can be dissolved by the addition of a coupler such as methanol, and in this manner they can be made solublc in materials in which they are normally insoluble.

Dilute solutions of Polyox arc typically non-Newtonian and show a great dependence of viscosity on shear rate. This is apparent even in aqueous solutions containing as little as a few hundredths percent polymer, and in highly dilute solutions i t is necessary to measure the reduced viscosity as a function of both concentration and shear rate.

At higher concentrations, solutions of Polyos are rheologically classed as pseudoplastic, exhibit a mucous-like stringiness, and show enormous dependence of the viscosity of the solutions on shear rate.

The great thickening powers of these Polyox polymers in water can best be seen by comparing (see Table IX) the viscosities a t 0 rate of

TABLE IX VISCOSITIES AT ZERO RATE OF SHEAR AT 25°C (lY0 SOLUTIONS)

Polyox polymer 460 poises Sodium alginate (highest,

molecular weight) 20 poises Hydroxy eth ylcellulose 4 poises Carboxymethy lcellulose

(highest molecular weight) 12 poises

shear, of 1% aqueous solutions with 1% solutions of several familiar water-soluble polymers a t 25°C (Bailey e t al., 1958).

2. Plasticit3

Thermoplastic propcrtics characteristic of the Polyox resins are unusual for most water-soluble resins. These plastic properties are funrln- mentally characterized as follows (Smith and Van Cleve, 1958) :


1) Exceptionally high molecular weight 2) Very high degree of crystallinity under most conditions 3) Highly mobile nature of the ethylene oxide chain The high molecular weight is important in producing a ductile, very

strong, tough, and readily extensible material with good flexibility and thermoplasticity. The extraordinary degree of crystallinity in a solid state is responsible for the high tensile strengths reached by the oriented polymer, the sharpness of the melting point, and the low degree of moisture sorption. The highly mobile nature of the ethylene oxide chain has its overtones, as shown by the ductile flow under stress, which is sharply shear-dependent. Shear effect is found to be common to flow in the solid, liquid, and solution forms of the resins.

9. Toxicology

The Polyox water-soluble resins have apparently low oral toxicity. Inclusion of Polyox in the diet of rats a t 5% concentrations caused no detectable harm. These resins are believed to be nonirritating to the human skin and to have low sensitizing potential. Eye injury is also believed to be slight. Tests performed by flooding rabbits eyes with 5% Polyox resin in water caused only moderate inflammation.

In patch tests on human subjects, water solutions of 3% Polyox resins by weight were applied to discs of 1.3 inches diameter. These discs were applied to the backs of 50 male subjects and allowed to remain for 24 hours. This procedure was repeated every other day for 12 consecutive applications with fresh discs, and a final application was made two weeks after the last of the 12 consecutive applications. The results showed no cutaneous reaction after each application, and indicate that Polyox resins in 3% aqueous solution exert no primary cutaneous irritant action, no fatiguing action, and no allergenic action (Berger and Ivison, 1962; Union Carbide Chemicals Co., 1962a).

Earlier tests showed that Polyox administered orally to rats had a low order of toxicity. For example, the LDFio dose to rats is in the same general quantitative range as that of lactic acid. The resin was fed to rats for a 90-day period, and 4% in the diet of rats was without effect (Union Carbide Chemicals Co., 1960b, 1960~) .

At the writing of this report, the author has been informed that applications for clearance of Polyox for food uses have been submitted to the FDA and that clearance is expected within a very short time.

D. APPLICATIONS

The novel functional properties of Polyox have resulted in its application in various industrial products and processes. In the food industry,


because of the need for FDA clearance, the usefulness of Polyox resins has not been fully explored. However, i t is possible to consider the applications in the related cosmetic and drug industry to find and review the potential usability of Polyox in the food field a t some future time.

An important factor in the potential usefulness of the Polyox resins is that they have no significant B.O.D. Industrial applications of Polyox are therefore advantageous, because treatment of waste is an important economic factor and has been shown to be of special interest t o textile and mining industries. This lack of B.O.D. means that aqueous solutions of these resins do not have to contain preservatives during periods of storage or as additives to formulated products, and this, of course, is an important factor in its use in drug, cosmetic, and, eventually, food products.

Another important property of Polyox is its film-forming characteristics. Polyox resins form tough, flexible films that are resistant to most oils and greases and can thus be utilized advantageously for protective coatings and packaging applications. In the cosmetic area, i t has been found to be advantageous in spray-on hair preparations, where the film- forming characteristics have been a positive advantage.

In general, i t would be advantageous to discuss the applications of Polyox in those areas that could lead to an understanding of potential uses in related food fields.

1. Water-Soluble Packaging Films

Polyox resin films are tough and pliable, and also flexible. Since these materials are also thermoplastic, interest was substantial in their use for the production of water-soluble films by extrusion or calendering. Previously available water-soluble resins could be cast into satisfactory films, but difficulties were normally encountered in fabricating these materials into good water-soluble films with useful packaging properties. Polyox films, however, can be milled, calendered, extruded, or cast, with or without plasticizers. The flexibilities, surface slips, and strengths of films based on these resins are changed only slightly by variations in relative humidity below 90%.

The final films have a number of interesting properties. They are readily water-soluble but retain a dry feel even a t high relative humidities. The films have high moisture-vapor transmission properties and are heat- sealable, tough, resilient, and highly resistant to bacterial attack.

Packaging applications for this material have been suggested where the packaged product is to be dissolved or dispersed in water. The item to be packaged can actually be wrapped in a Polyox resin film and heat- sealed, or a dip coating can be utilized to form the protective film. As


mentioned before, food applications for this material have been littIe investigated, but products suggested for evaluation in packaging made from Polyox films include starches, auto radiator compounds, adhesives, bleaches, dyes, industrial cleaning compounds, water-treatment chemicals, inks, paints, detergent powders, greases and oils, herbicides, photo- graphic chemicals, fungicides, fire-fighting chemicals, insecticides, disin- fectants, plant food, drain cleaners, and many others (Berger and Ivison, 1962).

In the area of water-soluble films, Polyox was introduced, under the trade name Hylox, to compete with the established polyvinyl alcohol (PVA) and also with methylcellulose (Methocel). Hylox has several important properties differing from those of PVA, which may enable i t to receive preference for certain applications. Hylox film begins to soften a t a lower temperature (about 150°F) than PVA film (250°F), but remains flexible over a wide temperature range down to -50°F. While other soluble films must be cast from a water solution, Hylox is more versatile and can be fabricated by either calendering or extrusion. Hylox is permeable to organic vapors and would require an outer wrap in applications where an odor barrier is required; but, on the other hand, i t is suitable for wrapping materials that are perfumed for consumer appeal (Anonymous, 1960b).

Within the immediate future, i t is probable that Hylox will not be used for food packaging, but will find its greatest outlets in industrial applications such as soluble packages for detergents, dry bleaches, chemicals, dyes, etc. With FDA clearance, these markets will certainly be broadened to include diverse food uses such as protective edible coatings, prepackaged additives for food-processing operations, and other yet-to-be developed needs.

2. Cosmetics

Complete water-solubility, thickening efficiency, and the soft, silky feel imparted to cosmetic preparations are among the properties that made Polyox a functional component in many creams, lotions, shampoos, powders, and other cosmetic preparations. Outstanding properties of these gums in cosmetic applications include the extrcniely high lubricity they impart to formulated compositions and the compatibility of these gums with detergent compositions, electrolytes, and many organic solvents (Osipow and Berger, 1958).

Osipow and Berger (1958) employed Polyox to advantage in many types of toothpaste compositions. It was shown to be a good binder for the abrasives and was compatible with a high ratio of humectants to water used in toothpaste, and, in addition, its behavior was not adversely


affected by the presence of water-soluble salts such as fluorides and others commonly employed in toothpaste compositions. The most important contribution of these gums to toothpaste, as stated by Osipow and Berger, is improved mouth feel, presumably due to the lubrication quality of the gum solutions. This effect was not observed with other gums.

The use of Polyox in the development of synthetic detergent bars for toilet use contributed creaminess of lather and skin feel. Berger and Osipow found that these factors were substantially improved by the use of 1 or 2% of Polyoxes in detergent formulations.

As mentioned previously, the film-forming characteristics of the Polyoxes show them to be excellent for the preparation of high-quality hair sprays. An important feature of these hair sprays was the low hy- groscopicity of the films and the high silky effect given to the hair.

3. Pharmaceuticals

The one area most closely related to the food industry, where Polyox is used in products that are ingested and utilized by the human body, is in the field of pharmaceuticals, where Polyox is used as tablet coatings, tablet binders, and related applications. Polyox is reported to be ideal for pharmaceutical applications because of its excellent film-forming properties and the resultant high degree of flexibility and strength and low toxicity in the final film. Coating of tablets is a well-known pharmaeeuti- cal procedure, and coatings are used primarily to mask taste, improve appearance, protect from moisture, smooth the coatings for ease of swallowing, and protect the tablets from physical damage during handling and shipping. The requirements for a material to coat tablets are that it must be relatively nontoxic; white to colorless in order to allow the use of dyes; solid and stable to the effects of heat, light, air, and humidity; chemically nonreactive; rapidly soluble in the gastrointestinal system; soluble in volatile quick-drying solvents, such as alcohols, which are used in coating procedures and to protect water-soluble components of tablets ; odorless; tasteless; low in cost; and easy to apply. All these requirements are mct by the Polyox resins (Berger and Ivison, 1962). The tablet coating process reported by Berger and Ivison (1962), based on work done a t the University of Iowa, gives tablet coatings that are smooth, uniform, resistant to chipping, nonhygroscopic, noncaloric, and sugar-free. Tablet disintegration time is affected only slightly by the Polyox coating, and is well within the U.S.P. limits for coated tablets.

In a related application, Awe (1957) used Polyox for the preparation of coated pills having a low rate of decomposition. He coated the piIls with an emulsion of sugar, starch, and cellulose derivatives in water and then

UTILIZATION OF SYNTHETIC GUMS IN THE FOOD INDUSTRY 35i

polished the coating with a 10% solution of Polyox in chloroform solution. This retarded decomposition rate substantially.

Polyox has also been used as a tablet binder. Berger and Ivison (1962) reported the use of Polyox and gum arabic as binding agents with effective disintegration, hardness, and stability properties. Polyox WSR-301 a t 0.5%, together with 0.5% gum arabic in water, was effective in binding various tablet medicaments. Up to about 10% of starch was used in all cases as a filler and granulating agent. The prepared tablets gave satisfactory tests for hardness, and had a glossy appearance and smooth texture. The rate of disintegration could be varied by adjusting the ratio of Polyox to starch in any specific formulation. The use of Polyox improves the granulation process and makes it simpler and faster.

Other pharmaceutical applications that have benefited from Polyox are rubbing-alcohol compounds, dental adhesives, calamine lotions, pro- tectivc hand lotions, aerosol-applied plastic bandages, face creams, etc.

There has also been a report from Russia of the use of a polymer of polyethylene oxide as a binding agent in tablet manufacture (Nosovit- zkaya and Korotenko, 1957). This material, described as a yellowish wax-like, dense mass (m.p. 54-6OC), appears to be an impure version of domestic Polyox resins. It was reported to be nontoxic and easily eliminated, and its use made unnecessary the preliminary moistening and subsequent drying of the tablet mass. It was used best in combination with starch and talc, and preferred ratios for the preparation of Strepto- cide and phenacetin tablets were 3% poly (ethylene oxide), 1.5% starch, and 1% talc.

X. RESEARCH NEEDS

Within the food industry, this article has reviewed and discussed current and potential applications of the various synthetic and semisynthetic gums that havc been developcd over the last 2 or 3 decades, and particularly within the last few years. These gums have replaced many of the older, established natural gums in various food applications, and the development and commercialization of improved synthetic gums has given natural gums severe competition in recent years.

There are some organic chemists who believe that the day will come when every natural product will be synthesized in the laboratory, and a t the same time improved functionally in such a way as to overcome inherent undesirable properties. On the other hand, there are those who believe that synthetic gums will never economically replace the cheaper natural gums such as starch (10-15$/lb), gum arabic (20-25$/1b), and guar and locust bean gum (30$/lb), and that a t best the semisynthetics (chemically modified starches, celluloses, etc.) would be the limit of


practicality as a target for the synthetic chemist. But in all cases the economic incentive will be the guiding force behind these decisions.

In the synthetic gum field at present, most research efforts seem to be directed toward two objectives:

1) Synthesis and development of gums having properties identical to and superior to those of the well-known natural gums.

2) Synthesis and development of gums having completely new and novel properties for completely new and different applications.

With respect to the first objective, the most important research needed is related to the target rather than to the synthetic counterpart. The structural and chemical compositions of most of the natural gums are still incompletely defined, and, in most cases, basic knowledge of these materials is based on empirical findings. It is essential that the funda- mental composition of these gums be determined so that the functional properties of the various gums can be understood and correlated on a meaningful, scientific basis. In this way, by a better understanding of the target, the synthetic chemist will have a better chance of reaching it.

The second objective (new and novel gums) is a broader and more empirical area, with research needs that cannot be readily defined. In this area most research efforts are directed a t producing polymers that are an extension of the chemical commodity line of the respective company, and then determining whether these polymers have a place in the water- soluble gum field.

Sometimes serendipity plays a part, with new gums being discovered somewhat accidentally, such as Polyox. And then again, gums are sometimes produced as a means of utilizing surplus commodities or cheap industrial by-products. The Northern Regional Laboratory of the United States Department of Agriculture has developed a whole series of interesting “microbial gums” based on a search for new ways of utilizing the ever-present corn and corn syrup surpluses available in this country. A recent report from Russia reports the development of a new process for the extraction of a water-soluble cellulose ether from low-cost cotton waste from cotton ginning operations (Anonymous, 1963). It is said that this product may replace similar polymers such as those based on wood cellulose.

It is obvious that research needs in this area will depend on the specific area under investigation, and will be defined within the narrow, specific scope of the research effort itself.

In general it can be said that the overriding research need of the industry is a more complete basic knowledge of the chemistry of the natural gums and a correlation of the chemistry with functional properties. This would then offer a clearer understanding of the ultimate targets


of the synthetic gum industry, and of the best potential means for reaching these targets.

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