Sugars meat flavors

In mixtures of amino acids and sugars, meat flavor can be developed via different pathways. Cysteine does not only generate meat flavor via keto-L-cysteines but it reacts also with (the decomposition products of) the Amadori compounds of other amino acids to produce meat flavors that are of comparable intensity (5). This means that there are at least two major pathways to meat flavor development in such Maillard reaction systems ... 

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. 

Lipid decomposition volatiles. Reactions of sugar and amino acids give rise to odor profiles that are, at best, common to all cooked or roasted meats. The water soluble materials extracted from chicken, pork, or beef give reasonably similar meat flavor. To develop a species specific aroma one needs to study the lipid fraction and the volatiles produced from those lipids. The work of Hornstein and Crowe (10) reported that the free fatty acids and carbonyls generated by heating will establish the specific species flavor profiles. 

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). 

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 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 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... 

Continuing our evolution of reaction flavors brings us to the reaction of materials, which are themselves, isolated from amino acids and sugars to produce unique materials which are frequently very different than the reaction of the parent amino acids and sugar. The reaction of D-Xylose and L-Cysteine is a good example of this principle. A complex meaty tasting mix is obtained from the sugar and amino acid. The mixture contains small amoimts of 2-Methyl-3-furanthiol, a potent meat flavor (equation 5). 

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. 

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... 

The objective of the present work was to learn more about the initial stages of die reaction between cysteine and sugars to meat flavor compounds. This information can provide a clue to a more efficient conversion of the precursors into meat flavor compounds. 

In theory, a crude cysteine-sugar reaction product with a high content of Amadori compoimd can also be used as a flavor precursor system. However, to avoid off-flavor formation, the cysteine-xylose reaction has already to be discontinued before 75% of the maximum Amadori compound concentration has been achieved. Moreover, dilution with other precursors and/or a flavor carrier is necessary for acceptable stability. In some cases, the use of mixtures of cysteine with Amadori compounds of other amino acids (5) can also be a suitable alternative for the in situ generation of meat flavors. 

Flavor can be produced by thermal reactions between naturally occurring compounds in foods, such as the creation of meat flavor by the thermal reactions of certain amino acids and sugars (the so-called Maillard reactions). These types of materials have been used by the industry for more than 100 years in savory applications [4]. Flavors generated during heating or processing by enzymatic reactions or by fermentation are generally considered to be natural flavors [45]. 

The economical value and high popularity of meat lead to the production of meat-like flavors through process chemistry. Several heat-induced reactions lead to the formation of meat flavors. These reactions are the pyrolysis of peptides and amino acids, the degradation of sugars, the oxidation, dehydration, and decarboxylation of lipids, the degradation of thiamin and ribonucleotides, and interactions involving sugars, amino acids, fats, H2S, and NH3 [110],... 

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. 

The origin of meat flavor has been shown to arise from the combination of two primary sources. The first is the tissue fat, both extracellular and intracellular, which produces carbonyl and other lipid and lipid-oxidation products. The fat component of meat flavor is viewed as being responsible for the species specific flavor in meat (9). The second major component of meat flavor is the lean portion. The proteins, peptides, and amino acids of the lean, add not only to the muscle food s general meaty flavor, but also undergo Maillard reactions with sugars to produce Amadori and Heyns compounds having meat flavor characteristics. 

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