Thiazoles flavoring from

A heterocyclic sulfur-containing compound, 2-methyl-thiophene, was identified in boiled crayfish tail meat and pasteurized crabmeat. Thiazole and 3-methylthiopropanal were identified in the crayfish hepatopancreas. Heterocyclic sulfur-containing compounds play important roles in generating meaty aromas in a variety of meat products and are considered important volatile aroma components of marine crustaceans (12— 14). The 2-methylthiophene could be an important flavor cemponent in boiled crayfish tail meat. Both thiazole find 3-methylthiopropanal were important contributors to the desirable meaty aroma associated with crayfish hepatopancreas. The 3-methyl-thiopropanal, identified in boiled crayfish hepatopancreas, is derived from Strecker degradation of methionine (15), and has been considered to be an important cemponent in basic meat flavor (16). Pyridine was detected in the headspace of the hepatopancreas from freshly boiled crayfish. Pyridine and 2-ethylpyridine have been previously reported as components in the atmospheric distillate from a sample of crayfish hepatopancreas frozen for three months (2). 

Sulfur Compounds of Beef Flavor. Methional, which results from the degradation of methionine, is an important contributor to flavor in meat. Thiolanes, formed during the cooking of beef, have peculiar oniony flavors that also augment the quality of the meaty flavor. Thiophenes and thiofurans are also important to meaty flavors. Sulfides, such as methyl sulfide, are oxidized to methyl sulfoxide and methyl sulfone. Condensation reactions of Maillard browning products also result in thiazoles such as benzothiazole, an important component of meat flavor. 

There was no loss in flavorant at a 100 mg level when either whole soy or soy 7S protein was used, but there was a 14-24 percentage loss when 11S protein was used. Only soy 11S protein affected the substituted pyrazine content of the mixture at all addition levels. The higher the substituted pyrazine congener, the smaller was the percentage loss with any of the protein types. At the 500 mg level, only about 50% of the amount of any of the methyl pyrazines in the control was recovered from either soy 7S or 11S protein while 70% was recovered from whole soy protein. These results greatly extend the initial work reported by Palkert and Fagerson (11J who determined that about 75% of dimethyl thiazole, a sulfur-nitrogen heterocycle, was recovered from dry, textured soy protein. 

Pyruvaldehyde is a liquid at room temperature and boils at 72°C, thus when cysteine-pyruvaldehyde mixture was heated at 80°C, the components are in solution and flavor notes reminiscent of Japanese rice cracker developed. As reaction temperatures increased gradually other flavor notes developed. In the case of cysteine-glucose system, no reaction took place until the reaction temperature reached 130°C. The flavor of cysteine-glucose was comparable to that of cysteine-pyruvaldehde at 160°C, with one exception, the glucose system had a sweet note. As temperature increased the flavor impression of both systems increased in similarity. The volatile compounds produced at 160°C in the presence of pyruvaldehyde were different from those in presence of glucose. While thiazole and thazolines were absent in the volatiles of cysteine-glucose, cysteine-pyruvaldehyde volatiles were devoid of pyridines, picolines and furans (24). 

Thiazoles are a class of compounds possessing a flve-membered ring with sulfur and nitrogen in the 1 and 3 positions, respectively. The potential for thiazole derivatives as flavorants is evident from the work of Stoll et al. (24) who found the strong nut-like odor of a cocoa extract to be due to a trace amount of 4-methyl-5-vinylthla-zole. Since then, numerous thiazoles have been identified in food flavors. 

Nearly 1000 compounds have so far been identified in the volatile constituents of meat from beef, chicken, mutton and pork (6). The largest number of volatiles has been determined in beef and these were representative of most classes of organic compounds. Hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters, lactones, ethers, sulfur and halogenated compounds as well as different classes of heterocyclic substances (Figure 1) namely furans, pyrldlnes, pyrazines, pyrroles, oxazol(in)es, thiazol(in)es, thiophenes were present in cooked meat flavor volatiles as shown in Table I. Many of these compounds are unimportant to the flavor of meat and some may have been artifacts (16). 

Guava flavor G.f., resembling pear and quince flavor, contains )8- caryophyllene, numerous fruit esters, e.g., ethyl butanoate and ethyl hexanoate, cinna-myl acetate (see cassia oil) and the green notes from hexanal, ( )-2- hexenal, and (Z)-3- hexen-l-ol. Important trace components are C -C,g-dienals, Fura-neol, some pyrazines and thiazoles, as well as 6-mercapto-I-hexanol(CiHnOS, Mr 134.24,CAS [1633-78-9]) ... 

Several methods have been employed (20) in the extraction of flavor volatiles from their chemical and physical bonds in the complex muscle matrix. These methods include steam distillation, solvent extraction, headspace analysis and supercritical fluid extraction. Each method had specific advantages and shortcomings when used in the isolation of numerous compound types such as carbonyls, sulfur-containing compounds such as thiols and thiazoles, pyrazines, furans, and pyrroles (27, 22). The mechanisms responsible for the formation of these flavor volatiles have been proposed and developed based on such experimentation (25, 24). 

The acidic, basic and neutral flavor components of a YA were examined in the first published study, and 48 compounds were identified (5,7). Three sulfur compounds, i.e., 2-thiophenecarboxylic acid, its 5-methyl derivative and 4-methyl-5(2 -hydroxyethyl)thiazole were mentioned. Later, Golovnya et al. (8) identified 37 sulfur compounds from a simulated meat flavor produced by heating a bakery YA with sugar. They included aliphatic sulfides and thiols, alicyclic sulfur compounds, thiophenes and sulfur-substituted furans. 

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