Formation Mechanism Of Meat Flavors From Peptide Maillard Reaction

In this paper, formation mechanism of meat flavors formed from peptide（glutathione and glutathione-relatived oligopeptides）-xylose Maillard reaction wasstudied, including the impact of the composition and the amino acid sequence of thepeptide chain to the Maillard reaction. In the optimal condition,¹³C₅-Xyl and Xyl （1:1）and peptides or free amino acid run the Maillard reaction, then the key meat flavorcompounds were analyzed and identified with the technologies of GasChromatograph-Olfactometry-Mass Spectrometer （GC-O-MS）, High Performance LiquidChromatography （HPLC） and High Performance Liquid Chromatography-MassSpectrographic （HPLC-MS）, and their formation ways were concluded. Furthermore, theproducts in liquid were detected, which were used to infer the cleaving capability andposition of the oligopeptide paticipating in the Maillard reaction, thus, the reaction courseand mechanism of the key meat flavor compounds formed from oligopeptide-xyloseMaillard reaction.Glutathione （GSH）-xylose Maillard reaction mechanism: At the first, GC-O-MSwas used to identify the key meat flavors formed from GSH and its constituent aminoacid and dipeptide （Cys-Gly） participating in the Maillard reaction. Then, with¹³Cisotope labeling method, the carbon skeletons of many aroma compounds, such asfurfural,2-furfurylthiol, thiophene,2-methyl-3-furanthiol,2-methyl-thiophene and2-pentyl-thiophene were inferred to derive from xylose carbon. What’s more, HPLC andLC/TOF MS were used to detect the products in liquid, and the cleaving capability andposition of GSH in the Maillard reaction were researched.Tetrapeptides-xylose Maillard reaction mechanism: In order to make thetetrapeptides-xylose Maillard reaction to produce more meat flavors, the reaction systemand conditions were optimized firstly. The best combination of reactants of tetrapeptides–xylose Maillard reaction was tetrapeptides+Cys+xylose+V_B1, and the best reactioncondition was25mL phosphate buffer, pH4.8, the incubation temperature140℃andreaction time60min. Volatiles, especially the aroma-active compounds, were analyzedwith GC-O-MS. There were many thiophenes, thiaoles, funans and lipids, in which being9kinds of compounds with roasted or meaty in total. With the qualitative andsemi-quantitative analysis to meat flaor compounds, it was found that Cys in the C-terminal of tetrapeptides can promote the generation of meat flavors. In the system oftetrapeptides-xylose Maillard reaction, it also formed other procucts of xylosedegradation, such as funan,3-methyl-funan,2-methoxy-5-methyl-thiophene,3-thiophenecarboxaldehyde,2-thiophene carboxaldehyde and5-methyl-2-thiophene carboxaldehyde.What’s more, LC/TOF MS were used to detect the nonvolatiles in liquid, and the cleavingcapability and position of GSH in the Maillard reaction were researched.2,2’-[carbonothioyl bis （thio）] bis-acetic acid was inferred to be the specific product of thetetrapeptides-xylose Maillard reaction. What’s more, in the tetrapeptides’ chains, it waseasy to cleave when Glu and Cys connected, and beneficial to form aroma compounds.Pentapeptides to heptapeptides-xylose Maillard reaction mechanism:52kinds ofvolatiles were detected by GC-O-MS, and there being36kinds of compounds can bedetected using sniffing. In term of the content of sulfur-containing compounds and meatflavors, arginine contained in the peptide chain can promote the formation ofsulfur-containing compounds and meat flavors. In addition, according to the proportionof the isotope labeling, it was inferred that benzene, styrene, phenylpropyl aldehyde,2-methyl-funan,2,5-Pyrrolidinedione,2-Pyrrolidone and3-hexylamine derived fromxylose degradation. According to liquid product, it was concluded that when Gly and Alaconnected, the peptide bond was easy cleave here. Furthermore, when Arg was linked atthe end of the peptide chain, it was liable to form hydrogen bonds between Arg and otheramino acid, especially Gly, then promoting the peptide bond cleavage here to form cyclicdipeptide compounds. And peptide bond cleavage promoted the generation ofsulfur-containing compounds and meat flavor compounds.In tetrapeptide to heptapeptide-xylose Maillard reaction, there also were otherinternediates and nonvolatile products, such as cysteine,2-methoxy-5-methyl-4-pyrimidinamine,3-methylamino-2-butene, diglycerol and2,4-bis（acetylamino）-phenethyl, and these products can further cleavge to generate volatileMaillard products.Formation mechanism of meat flavors formed from Peptides （glutathione andglutathione-relatived oligopeptides） as the precursor participating in the Maillard reactionwas studied, including the impact of the composition and the amino acid sequence of thepeptide chain to the Maillard reaction. This rearch had a guiding role to make meat flavorcompounds, and would significantly improve our nation’s research level in the field topromote the development of the food industry.