Precursors, meat flavor

In search for the key intermediates to meat flavor development in heated cysteine-sugar systems, it was found that in addition to thiazolidine derivatives also the tetrahydro-l,4-thiazine derivatives are being formed. These tetrahydro-l,4-thiazines, which are the cyclic form of Amadori compounds of cysteine, have excellent meat flavor precursor properties and are likely to play a prominent part in meat flavor development. Another major pathway to meat flavor development is the reaction of cysteine with the Amadori compounds of other amino acids. Model experiments showed that both pathways are probably of about equal importance for flavor development in boiled meat and process flavorings, this in spite of the low reactivity of cysteine with sugars. It seems that the first pathway is general-acid-catalyzed by the other amino acids, whereas the second pathway is inhibited by cysteine. 

C. Determination of Water-Soluble Meat Flavor Precursors... 

Another processing procediue that could involve supercritical fluid extraction with CO2 is the preparation of flavor concentrates from meat lipids for use in mixtures of other natural precursors for the preparation of tynthetic meat flavor additives that serve bofii as antioxidants that prevent warmed-over flavor (WOF) in cooked meat diuing storage and enhance the flavor of the natural products. 

Many desirable meat flavor volatiles are synthesized by heating water-soluble precursors such as amino acids and carbohydrates. These latter constituents interact to form intermediates which are converted to meat flavor compounds by oxidation, decarboxylation, condensation and cyclization. 0-, N-, and S-heterocyclics including furans, furanones, pyrazines, thiophenes, thiazoles, thiazolines and cyclic polysulfides contribute significantly to the overall desirable aroma impression of meat. The Maillard reaction, including formation of Strecker aldehydes, hydrogen sulfide and ammonia, is important in the mechanism of formation of these compounds. 

Raw meat has little desirable flavor, but each type of meat has a characteristic flavor due to the animal species and the temperature and type of cooking. Both water-soluble and lipid-soluble fractions contribute to meat flavor and the water-soluble components include precursors which upon heating are converted to volatile compounds described as "meaty."... 

Hornstein and Crowe (4) found that flavor precursors of meat were extractable with cold water and demonstrated that lyophilized... 

In their recent comprehensive review of natural and synthetic meat flavors, MacLeod and Seyyedain-Ardebili (20) listed 80 patents describing "reaction products" procedures that produced meat-like flavors upon heating. Approximately one-half of these precursor mixtures included amino acids and reducing sugars. Most of the mixtures described in patented procedures for synthetic meat flavor are modeled after ingredients found in the water-soluble dialy— zable fraction of fresh meat. These constituents serve as reagents for Maillard reactions. 

Even though many compounds discussed in the above presentation are thought to be important in meat flavor, a delicate blend of these compounds and other ingredients at the appropriate concentration is needed to synthesize acceptable flavor. In view of the possible instability of the flavor compounds themselves, precursors that supply the precise mixture of volatiles upon heating will be needed. Attempts have already been made to use this approach as judged by the numerous patented mixtures of precursors listed in the literature. More effort should be given to the quantitative aspects of meat flavor production and work must be continued on the qualitative aspects of the volatiles and the appropriate Maillard reaction precursors chosen. 

Cystine and other sulfur-containing amino acids are recognized as important precursors of food flavors, especially meat flavors (3, 11-12). DMHF, a cyclic-a-dicarbonyl, possesses a sweet, caramel and fruity aroma (13). It is found in many food sources (14-17) and is used extensively in many flavor applications (18-19). DMHF can be formed from sugar via either sugar enolization (caramelization) by a Maillard reaction then cyclization (20). 

There are tvo approaches to meat flavor analysis one is concerned vith the isolation and identification of volatile flavor components, and the other involves identification of non volatile flavor precursors. 

Further evidence of the importance of the Halliard reaction in the formation of volatile flavorants from meat precursors is gleaned by examining ingredients in reaction mixtures patented as synthetic meat constituents. Ching (31), examined 128 patents of meat flavor and found that 55 specified use of both amino acids and sugars. Cysteine, cystine, and glutamic acid were used in 39 such mixtures. Over 80 patents describe meat flavor "reaction products" (32). 

The flavor of raw fresh meat is bland, metallic and slightly salty, whereas desirable meaty flavor is apparent only after heating. The precursors of brothy-desirable meat flavor have been studied extensively. More than 700 volatile components have been identified from meat reaction systems and undoubtedly many others are formed. Despite these efforts, the elucidation of the precise compounds responsible for "meaty" flavor remains an attractive endeavor for food chemical researchers. 

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. 

The flavor industry has introduced, over the years, methods of developing meat flavors by processing appropriate precursors under carefully controlled reaction conditions. As a result, meat flavors having a remarkably genuine meat character in the beef, chicken and pork tonalities are available for the food industry. It has repeatedly been stated that the Maillard reaction is particularly important for the formation of meat flavors. However, of the 600 volatile compounds isolated from natural beef aroma, only 12% of them find their origin in sugar/amino acid interactions and of these 70% are pyrazine derivatives. 

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. 

In this study the physical parameters involved in interaction of a major class of meat flavorants, methyl pyrazines, with soy proteins were determined at meat roasting temperatures. Beef diffusate, the water soluble, low molecular weight fraction that constitutes about IX of beef, was shown to contain the necessary precursors to obtain a desirable, thermally generated meat aroma (8). Diffusate was heated under controlled conditions and generated volatiles were transferred to a gas chromatograph for separation and quantitation. Methyl pyrazines, either from heated diffusate or from standard solutions, were measured in the presence of purified soy proteins and the thermodynamics of binding were determined. 

The major precursors in meat flavors are die water-soluble components such as carbohydrates, nucleotides, thiamine, peptides, amino acids, and the lipids, and Maillard reaction and lipid oxidation are the main reactions that convert these precursors in aroma volatiles. The thermal decomposition of amino acids and peptides, and the caramelization of sugars normally require temperatures over 150C for aroma generation. Such temperatures are higher than those normally encountered in meat cooking. During cooking of meat, thermal oxidation of lipids results in the formation of many volatile compounds. The oxidative breakdown of acyl lipids involve a free radical mechanism and the formation of... 

Cysteine is an important precursor of meat flavor and is therefore often being used in precursor systems for the industrial production of meat process flavorings (1-4). Meat flavor development in these systems is usually based on the Maillard reaction of cysteine (and other amino acids) with sugars. Unfortunately, there are a few complications that prevent that high yields of volatile flavor compounds are obtained from these reactions. The first... 

---