[Advances in Food Research] Advances in Food Research Volume 10 Volume 10 || Aroma and Flavor of Japanese Soy Sauce

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<ul><li><p>AROMA AND FLAVOR OF JAPANESE SOY SAUCE </p><p>BY TAMOTGU YOKOTSUKA No&amp; Institute for Scientific Re.rcnrch, atld Research ltlstitirtc of </p><p>Noda Soy Sauce Company. Lfd., Nocla.shf. Chfba.ken. Japan </p><p>Page I . Introduction . . . . . . . . . . . . . 75 I1 . Composition . . . . . . . . . . . . . 77 </p><p>A . Analysis . . . . . . . . . . . . . 77 B . Nitrogen-containing Compounds . . . . . . . . 78 C . Carbohydrates. Sugar. Alcohols. and Extractive . . . . . 82 D . Acids. Salts. and Related Compounds . . . . . . . &amp;3 E . Color . . . . . . . . . . . . . . 87 </p><p>I11 . Chemical Components of Flavor . . . . . . . . . 87 A . Fraction I . . . . . . . . . . . . . 96 B . Fraction I1 (b.p. &lt; 78C.) . . . . . . . . . 97 C . Fraction I11 (b.p. &gt;78C.) . . . . . . . . . 99 D . Fraction IV (The Aretal Fraction) . . . . . . . g9 E . Fraction VI . . . . . . . . . . . . 1 0 </p><p>IV . Sources of Aroma and Flavor Development . . . . . . 104 A . Raw Materials . . . . . . . . . . . . 104 B.Processing . . . . . . . . . . . . . loFl C . Koji . . . . . . . . . . . . . . 108 D . Mash (Moromi) . . . . . . . . . . . 111 E . Pasteurization . . . . . . . . . . . . 115 </p><p>V . Flavor Ingredients as Natural Preservatives . . . . . . 119 A . Natural Yeast-static and Bactericidal Compounds . . . . . 119 B . Artificial Preservatives for Soy Sauce . . . . . . . 121 </p><p>VI . Summary . . . . . . . . . . . . . 121 Acknowledgments . . . . . . . . . . . . 123 References . . . . . . . . . . . . . 123 </p><p>I . INTRODUCTION The four major characteristics of Japanese soy sauce. which differs </p><p>from other types produced in the Orient. are aroma. flavor. color. and stability . About 60 years ago. certain chemical procedures were intro- duced into the Japanese soy sauce industry. and since then the fermen- tation period has been shorter . Although these chemical procedures have come into general use. the basic method of manufacture is almost unchanged . </p><p>75 </p></li><li><p>76 T A M OTSU Y OKOTSU K A </p><p>Oiir ancestors knew tlici tcwhnicliies of enzymatically hydrolyzing cer- tain protein foods into amino acids to make them more appealing. For example, since ancient times the people in the Orient have enriched the flavor of fish and meiit by fermenting it in the presence of high salt concentrations. These foods, formerly cidled fish soy or merely SOY, can still be seen today in nuoc-mam in Java, or shottsuru in Japan, and itre believed to be antecedents of the soy sniice now in use. Years ago several kinds of pulses and corn were used as raw materials; now, however, only soybeans and wheat are used. </p><p>The mold Aspergillrts soyne is the source of the proteolytic enzymes. The first soy sauce produced was cnlled soy, sho, or mislio, and was very different from soy sauce produced today. It resembled the present day miso ( Ilitrtl mitsh ) or moromi (miish ) and W B S consumed without further treatment. During the Muromachi period ( 1~28-1573), much research was done on the kinds and relative quantities of raw materials and on the fermentative process, with the result that the product was improved considerably. </p><p>Today three types of soy sauce are available in Japan: koikuchi, usukuchi, and tamari. About 90% of the Japanese soy sauce produc- tion is of the koikiichi type. In China, most of the soy sauces belong to the tamari type; that is, thcy are made of soybeans or with a greater amount of soybeans than wheat. High-quality Japanese fermented soy sauce is made from equitl amounts of soybeans and wheat. The product consists not only of amino acids, but also of many flavor inpedients derived from the alcoholic fermentation which is part of the manufac- turing process. Wheat bran also plays an importiint role in the develop- ment of flavor and aroma. </p><p>Chemical studies begitn to supplement sensory methods during the period from 1867 to 1912. In addition, autoclaves and hydraulic presses came into iise in its manufacture. At that time, the soy mash was usually fermented at ambient temperatures for 1 to 3 years. Next various lots of sauce (which had been fermented for different periods) were blended and sold. Several attempts were made to shorten the long fermentation period and hence lower the cost of production. Thus, dur- ing the last decade there hits been a growing tendency to make soy siiiice by acid hydrolysis, in order to increase the yield and reduce pro- duction time. A chemical method, announced by the Noda Soy Sauce Co., Ltd. (1955), is now being commonly used by soy sauce manu- factiircrs. Even where the fermentation method is still used, soybean Iiydrolyzates are added to the fermented soy sauce as a flavor booster. </p><p>The flavor siibstanccs of true Jiipancse soy saiice produced by the traditional fermentation method will be discussed in this review, </p></li><li><p>AROMA AND FLAVOR OF JAPANESE SOY SAUCE 77 </p><p>II. COMPOSITION </p><p>A. ANALYSIS Most of the Japanese soy sauces are the koikuchi type, containing </p><p>5@% or more of i\ chemical hydrolyzatc of defatted soybeans. Only a few of the large manufacturers produce the bestquality product, which requires aging for more than a year. Good-quality fermented soy sauce contains 1.5 g. of total nitrogen, and 18 g. of sodium chloride per 100 ml., and appropriate proper amounts of amino acids, sugar, alcohol, glycerin, and organic acids. It should have a high buffer capacity, stability, and good aroma, flavor, and color. Typical composition of koikuchi soy sauce samples is shown in Table I and of a high-quality </p><p>TABLE I COMPOSITION OF KOIKUCHI SOY SAIJCI?' </p><p>Specific Year and gravity Sodium Total Amino Total Alcohol </p><p>grade BC Extract" chlorideb nitrogenh nitrogcnb Sugarb acidsb (% vol. ) </p><p>1937 23.84 20.50 18.46 1.52 0.65 5.19 0.63 1.63 1949 19.10 7.16 17.70 0.73 0.39 0.79 0.30 0.41 1957 </p><p>Grade A 22.75 18.15 18.50 1.49 0.79 4A5 0.90 2.00 1957 </p><p>Grade B 22.38 16.19 18.25 1.28 0.68 3.02 0.86 0.88 </p><p>From Nuda Soy Sauce Company, 1,iniitcd ( 1958). Data cxprcsscd a'i g./lM nil. </p><p>fermented soy SilUCe in Table 11. The composition of tamari and usukuclii soy swces is shown in Tables I11 and IV. </p><p>Sodium chloride in soy sauce is usunlly determined by titration with silver nitrate, using potassium chromate as nn indicator. Accurate re- </p><p>TABLE 11 COMPOSITION OF A TYPICAL HIGH-QLMLITY FERMENTED SOY SAUCE" </p><p>Specific gravity, B6 24.00 Extract, g./100 ml. Total nitrogen, g./lOO ml. 1.51 Protein nitrogen. g./100 ml. Amino nitrogen, g./lOO ml. 0.70 Reducing sugar, g.1100 ml. Dextrin, g./lOO ml. 1.06 Viscosity Total acid as lactic, g./lOO ml. Alcohol, % 2.00 Glycerin, g./lOO ml. Inorganic substances, % 19.70 Sodium chloride, g./lOo ml. PH 4.02 </p><p>0.48 Volatile arid, g./lOO ml. </p><p>From No&amp; Soy Snwe Company, Limitrd (1957). </p><p>38.13 0.09 5.99 3.50 0.17 1.00 </p><p>18.02 </p></li><li><p>78 TAMOTSU YOKOTSUKA </p><p>specific gravity Sodium Total ( n o chlorideb nitrogen* Extracth </p><p>Sample 1 25.90 16.43 2.86 31.78 Sample 2 23.45 19.29 1.80 19.42 </p><p>From Noda Soy Sauce Company, Limited ( 1957). b Data expressed as g./lOO ml. </p><p>sults are obtainable only when the sample is first ashed; otherwise, cer- tain corrections are necessary, depending on the nature of the sample. Sato (1955) proposed the use of bromophenol blue as an indioator for </p><p>TABLE IV cOhfPOSI1 ION OF LrSUKUCIXI SOY SAW</p></li><li><p>AROMA AND FLAVOR OF JAPANESE SOY SAUCE 79 </p><p>These investigators reported also that almost 9&amp; of the total nitrogen was easily converted by the ordinary Kjeldahl method, in which only cuproiis srilfate was used as the catalyst; however, the remaining 2% was very resistant to digestion. They attributed this resistance to the nitrogen-containing phenolic fraction, which increases when soy saiice is heated. Since the quality of a soy sauce may be relnted to its total nitro- gen content, this observation is important. Accordingly, faster and more accurate methods of analysis are needed. </p><p>The nitrogen compounds consist of about 40 to 50% amino acids, 10 to 15% ammonia, 40 to !50% peptides and peptones, and less than 1% proteins. Takada (1934) stated that 45% subpeptone and peptone, but no protein or metaprotein are present. Tsunoda and Ishizuka (1952) also claimed the absence of protein on the basis that no precipitate was obtained with sodium tungstate or trichloroacetic acid. These workers are believed to have studied commercially pasteurized soy sauce in which the proteins would have been precipitated by heat. </p><p>Sakasai and Yokotsuka (1957) divided the total nitrogen of unheated soy sauce into: ( 1) tannin-coagulatable, ( 2) phosphomolybdate-pre- cipitable, and (3) residual nitrogen. The quantity of each fraction was 0.2 to 1.5%, 45.9 to 46.88, and 52.6 to 53.3%, respectively. The ammonia content was 8.8 to 11.2%, the difference between formol nitrogen and ammonia nitrogen was 34.1 to 43.11, and the free glutamic nitrogen was 3.8 to 4.9% of the total nitrogen. These ratios varied depending on the extent to which the raw materials had been cooked. </p><p>The ratio of amino nitrogen to total nitrogen has been considered as a criterion for judging quality, with a high ratio indicating high quality. Usiially the amino nitrogen content has been reported to be 50 to 6oR, of the total; however, the imperfect formol titration method that has been used has caused erroneous results because of the ammonia present. Moreover, because of the intense color of soy sauce, it is difficult to obtain a sharp end point by formol titration. Ohara and Moriguchi (1954) tried to determine formol nitrogen by electrometric titration at pH 8.0 without adjusting the pH of the sample. Sakasai and Yokotsuka (1957) also reported a method of determining the formol nitrogen in soy sauce by electrometric titration; the ammonia nitrogen con- tent was determined by the Conway diffusion method. The difference between the formol and ammonia nitrogen was regarded as amino nitro- gen. By using this method, the amino nitrogen content of ordinary soy sauces was found to be about 40 to 45% and ammonia nitrogen about 10 to 15% of the total nitrogen. Sakasai &amp; Yokotsuka (1958) recovered almost loolxI of the amino acids from a synthetic mixhire (similar to natural soy sauce) by formol titration at pH 8.5. </p></li><li><p>80 TAMOTSIJ YOKOTSUKA </p><p>The pH value seems to be important with the Conway method of determining ammonia. These same authors rcprted that lower alkalinity failed to recover all of the ammonia conjugated to the weak acids present in soy sauce, such as benzoic or isovaleric. On the other hand, with higher alkalinity (pH values above 12), glutamine decomposes into ammonia. The Van Slyke gasometric method for amino acid deter- mination is used with good results; however, it recovers only 25% of the ammonia nitrogen present and does not measure proline or oxyproline nitrogen. Form01 titration, on the other hand, measures all of the am- monia nitrogen and 25% of the nitrogen present in proline and oxypro- line. Yoshino and Takano (1956) proposed a colorimetric method for measuring amino acids using ninhydrin, and obtained results similar to those using the Van Slyke method. However, since the color developed with ninhydrin varies with the kind of amino acid, these results are subject to question. </p><p>1. Amino A&amp; The individual amino acids present in soy sauce have been identified </p><p>and are the subject of many reports. Alanine, proline, leucine, glutamic acid, oxyglutamic acid, aspartic acid, lysine, arginine, cystine, phenyl- alanine, and methionine were detected by Omura ( 1931), Udo (1931a), and Kaneko (1939). Glutamic acid was identified for the first time by Udo (1931b), who also showed its importance as a flavoring agent in soy sauce. He isolated crystalline dutamic acid and aspartic acid, which were mostly in the conjugated form, and concluded that the chief in- gredient responsible for the delicious taste of soy sauce is glutamic acid and its salt. Tomiyasu (1939) claimed the existence of P-hydroxy- glutamic acid in unpasteurized soy sauce. Yoshino ( 1951a,c), using paper chromatography, found threonine, valine, glycine, and histidine by precipitating them as carbamino acid mercurous acetates. </p><p>Tsunoda and Ishizuka (1952) determined the amino acids present in soy sauce by bioassay (see Table V). According to their results, 50% or more of the total nitrogen present is in the form of free amino acids. They also studied the peptides of glutamic acid, aspartic acid, and glycine. Fifty per cent of the glutamic and 40% of the aspartic acid were ehimated to be in the conjugated form. Yoshino (1953) identified 14 amino acids, excepting serine and tryptophan, from 16 amino acids which had been identified by Tsunoda and Ishizuka. Hori et al. (1956) reported that the peptide form of glutamic acid present is less than 10%, and that 50% of the gliitamic acid in the hydrolyzate is pyroglutamic acid. They found almost equal amounts of glutamine and free glutamic acid in the mash at the beginning of the fermentation but hardly any </p></li><li><p>AROMA AND FLAVOR OF JAPANESE SOY SAUCE a1 </p><p>glutamine in commercial soy sauce. They concluded that glutamic acid is changed into pyroglutamic acid in the earlier stage of fermentation. The asparagine content of commercial soy sauces was about 0.1%. Fuji- wnra et ul. (1958) reported on the amino acids content of many kinds of soy sauce as measured by a microbioassay method. </p><p>TABLE V ALflNO ACID CONTENT OF SOY SAUCE" </p><p>Filtrate after sodium tungstate </p><p>Amino acid Before hydrolysisb After hydrolysisb precipitntionb </p><p>Arginine 6.60 6.39 6.43 Aspartic 4.73 7.60 6.96 Cystine 0.26 0.93 0.59 Glutamic 12.08 21.10 20.00 </p><p>Histidine 1.42 1.62 1.52 Isoleucine 3.88 3.34 3.78 Leucine 8.78 7.04 7.04 Lysine 3.68 5.67 5.76 Methionine 1.99 1.38 1.36 Phenylalanine 3.70 3.4s 3.45 Proline 6.97 8.87 5.89 Serine 9.40 4.76 4.85 Threonine 3.08 3.01 2.99 Tryptophan 0.61 0.15 0.08 Tyrosine 0.72 0.96 0.79 Valine 4.93 5.21 5.35 </p><p>GI ycine 2.90 4.15 3.44 </p><p>From Tsunoda and Ishizuka ( 1952). b Total nitrogen of the sample 1.62 g./lOO ml.; all data based on bioassay, and </p><p>Ion exchangers, chromatography, bioassay, and enzymes have been widely used for determining glutamic acid. Among these, the enzymatic method, using microbial cells, seems to be most convenient and reliable (Seidman and Blish, 1957). </p><p>expressed as mg./ml. </p><p>2. Orgunic Bases Yamada (1926) obtained 0.16 g. of putrescine and 0.4 g. of cadaver- </p><p>ine from 2 liters of soy sauce (as picrates). Udo (1931b) identified lysine, putrescine, cadaverine, a base with the empirical formula C,H,N,, adenine, choline, and betaine, as picrate or platinum salts in the fraction containing glutamic acid. Yukawn ( 191%) identified tyra- mine ( p-hydroxyphenylethylamine ) , and Kuninaka ( 195458) detected adenine, hypoxanthine, xanthine, guanine, cytosine, and uracil as the </p></li><li><p>82 TAMOTSIJ YOKOTSUKA </p><p>constituents of soy sauce by using chemical methods, electrophoresis, paper chromatography, and ultraviolet spectroscopy. These compounds were considered to be derived from nucleic acid, produced by the en- zymes present in the mold. </p><p>C. CARBOHYDRATES, SUGAR, ALCOIIOLS, AND Exrrtrcrm Yoshino (1951a,b) s...</p></li></ul>

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