Heat-induced flavor formation

Heat-Induced Flavor Formation from Peptides... 

Rizzi, G.P. Heat-induced flavor formation from peptides. In Thermal Generation of Aromas, Parliment, T.H. McGorrin, R.J. Ho, C.-T., Eds. ACS Symp. Ser. 409 American Chemical Society Washington D.C., 1989 pp 172-181. 

The flavor compounds of the crust from the chemically leavened model bread were then compared to those recently identified (6) in the crust of a standard wheat bread which was leavened by addition of yeast (Table I). One striking difference was that Acp (No. 16), which showed the highest FD-factor in the yeast-leavened bread showed a very low FD-factor in the chemically leavened bread. This indicated, that the flour contained only minor amounts of the precursor (s) for the formation of Acp. On the other hand, 2(E),4(E)-decadienal, 2(E),4(E)-nonadienal, l-octen-3-one and 2(Z)-nonenal, which are undoubtedly formed by a heat-induced oxidative degradation of the flour lipids, became predominant odorants in the chemically leavened compared to the yeast-leavened bread. 

Heat-induced degradation leads to formation of furans, pyrones, cyclopentanones, carbonyls, pyrroles and acids which possess objectionable flavor qualities at low concentrations. Most have odors typically described as caramel-like and burnt sugar-like. 

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],... 

Peptides formed enzymically or by mineral acid hydrolysis or thermal degradation of higher molecular veight protein can also serve as flavor precursors in thermally induced reactions. The reactivity of peptides is evidenced by their behavior during pyrolysis/GC (9), heating in air (10), reactions vith mono- (11), and dicarbonyl (12, 13) compounds and reactions in hot acetic acid (1A). The types of reactions observed for peptides include side-chain thermolysis, fragmentation into amino acids, DKP formation and Halliard reaction vith ambient carbohydrates. 

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