Meat flavor sulfur compounds

Standards of typical meat flavor sulfur aliphatics and heterocyclics were made from 5 ng/pl to 500 ng/pl in hexane to determine response factors as well as reproducibility in the flame photometric detector. Background sulfur compounds were checked in concentrated reagent blanks. 

Herz and Chang (21) examined several furan compounds which had a wide variety of aromas, but none of them were meaty, Furans that do not contain sulfur are usually fruity, nutty, and caramel-like in odor. The furanones described above have burnt pineapple and roasted chicory odors, but these contribute to overall flavor impression of meat and important N and S meat flavor compounds might be formed from them during cooking. 

The Maillard reaction has received much attention since the 1950 s as the source of flavor chemicals in cooked foods. Numerous compounds produced by this reaction have been reported in the last two decades. The major flavor chemicals are nitrogen- and sulfur-containing heterocyclic compounds. For example, nitrogen-containing pyrazines contribute a characteristic roasted or toasted flavor to cooked foods. Sulfur-containing thiophenes and thiazoles give a characteristic cooked meat flavor. A striking property of these compounds is their extremely low odor thresholds. 

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). 

Most of the original patents referring to meat flavors utilizing Maillard technology vere claimed by Unilever (48-52 56,57). More recent patents are involved with the production of meat-like flavors. While a majority of patents are concerned vith cysteine, cystine, or methionine as the sulfur source, others claim alternatives such as mercaptoacetaldehyde, mercaptoalkamines, etc. Several patents (53,54), declare the contribution to meat-like flavors produced from thiamine in the Maillard reaction. Alternately, a technical report describes the volatile flavor compounds produced by the thermal degradation of thiamine alone (55). 

Hodge et al. (45) discussed mechanisms for formation of methyl furanones and related substances from Amadori compounds. They have been produced by heating D-ribose and D-ribose phosphate with ammonia (46 47). Hicks and Feather (48) demonstrated that the Amadori compound 1-benzylamino-l-deoxy-D-threo-pentulose dehydrates to 4-hy-droxy-5-methyl-3(2H)-furanone and it has also been identified as a degradation product of L-ascorbic acid. This compound is believed to be formed from ribose-5-phosphate, and gained prominence when it was isolated from beef by Tonsbeck et al. (49). It became more apparent as a precursor of meat flavor when Van den Ouweland and Peer (50) reacted it and its thio analog with HaS to produce a number of sulfur compounds, some of which had meaty odors. 

N, S and 0 heterocyclic compounds, along with noncyclic sulfur compounds and hydrocarbons, are predominant in "meaty" flavor volatiles. The mechanisms of heterocyclic formation by Maillard and pyrolysis reactions have been reviewed by Vemin and Parkanyi (57) and the Maillard reaction itself is a recurring subject of review (58). Since other speakers contributing to this volume will discuss these aspects of meat flavor, they will not be repeated in this presentation. 

The precursors used for process meat flavors are reviewed and also discussed will be non-Maillard interactions of ribose-5-phosphate and lipid degradation products with sulfur giving a real meaty odor and meat specie specific odor compounds, respectively. 

Heterocyclic compounds are dominant among the aroma compounds produced in the Maillard reaction, and sulfur-containing heterocyclics have been shown to be particularly important in meat-like flavors. In a recent review, MacLeod (6) listed 78 compounds which have been reported in the literature as possessing meaty aromas seven are aliphatic sulfur compounds, the other 71 are heterocyclic of which 65 contain sulfur. The Strecker degradation of cysteine by dicarbonyls is an extremely important route for the formation of many heterocyclic sulfur compounds hydrogen sulfide and mercaptoacetaldehyde are formed by the decarboxylation and deamination of cysteine and provide reactive intermediates for interaction with other Maillard products. 

A flame photometric detector specific for sulfur compounds revealed a mixture of sulfur compounds in the cooked meat extract which quantitatively changed with storage. Three nuyor sulfur compounds were identified as markers for flavor changes, namely methional, methyl sulfone, and benzothiazole. 

Since several studies identified the aliphatic and heterocyclic sulfur compounds as being important to cooked-beef flavor (9-11). the present report focuses upon a few key sulfur compounds that contribute to flavor of cooked meat as they change with time and temperature. Previous work has been directed to obtaining reliable correlation of sensory panel data with objective instrumental data describing meat flavor deterioration on storage (1). The present study is targeted toward obtaining a reliable, objective assay... 

Extraction. The sulfur compounds of interest and other meat flavor principles in the cooked meat patties were extracted and concentrated... 

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. 

Volatile profiles of raw and cooked-beef flavor samples, prepared by the procedures of Figure 1, were obtained after capillary GC and FPD. Although the identification of these sulfur containing compounds is as yet incomplete, the chromatograms demonstrated that there were a number of new sulfur compounds produced on cooking that were not present in the raw beef. Three prominent sulfur compounds were identified as markers in subsequent meat flavor deterioration experiments, namely, methional (13.2 min), methyl sulfone (13.8 min), and benzothiazole (25.3 min). Each compound produced an adequate mass spectrum for spectral library search and positive identification. 

There is no doubt that sulfur-containing components play a most important role in roasted and cooked meat flavors because only trace amounts of these compounds need be present to be aroma effective. 

By way of contrast, a total of 70 sulfur-containing compounds were identified in the volatile components isolated from our model meat flavor system. A rough survey of the chemical classes represented in the processed meat aroma is shown in Table I. 

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). 

Sun, B., Tian, H., Zheng, R, Liu, Y., Xie, J., Meaty aromas characteristic structural unit of sulfur-containing compounds with a basic meat flavor. Perf. Flav. 30(1), 36-45 (2003)... 

The Maillard reaction plays an important role in flavor development, especially in meat and savory flavor (Buckholz, 1988). Products of the Maillard reaction are aldehydes, acids, sulfur compounds (e.g., hydrogen sulfide and methanethiol), nitrogen compounds (e.g., ammonia and amines), and heterocyclic compounds such as furans, pyrazines, pyrroles, pyridines, imidazoles, oxazoles, thiazoles, thiophenes, di- and trithiolanes, di- and trithianes, and furanthiols (Martins et al., 2001). Higher temperature results in production of more heterocyclic compounds, among which many have a roasty, toasty, or caramel-like aroma. 

Among the major volatile sulfur compounds generated during the preparation of die ketopentose-L-cysteines are 2-methylfuran-3-thiol, 2-furfurylthiol and 3-mercapto-2-pentanone (13, Table I). These compoimds have also been identified as character impact compounds of boiled meat flavor (II, 12). This suggests that ketopentosese-L-cysteines are playing a role in the development of boiled meat flavor. Ketohexose-L-cysteines do not produce these character impact compounds in significant quantities (Table I) and are therefore unlikely to play a role in boiled meat flavor development. 

Golovnya R.V., Misharina T.A., Garbuzov V.G. and Medvedev F.A. (1983) Volatile sulfur-containing compounds in simulated meat flavor and comparison of their composition with volatile compounds of natural boiled beef. Nahrung 27(3), 237-49. (Chem. Abstr. 99, 4241w)... 

Meat flavor is due to a great number of volatiles from different chemical classes. However, most of the odorants described as meaty aroma contain sulfur. The two most important reactions which generate meaty aroma compounds are the reactions between sulfur containing amino acids and reducing sugars (Maillard reaction) and the thermal degradation of thiamin [35], Sulfur-containing furans are the basic chemicals responsible for the aroma of thermally treated meat. 

C,H OS, Mr 114.16. Liquid with an unpleasant, sulfur-like odor, coffee-like odor at high dilution (O.l-I ppb) bp. I60 C,D. 1.132. F. is long known as one of the important aroma constitutents of coffee flavor, but also contributes to the aroma of meat flavor The olfactory threshold is 5 ppt. F. is formed by the Maillard reaction and is thus considered as a secondary flavor compound. For production, see Ut.. Use in meat and coffee flavors. 

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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