Analysis And Quantum Chemical Calculation Of Meat Flavor Substance In "Cysteine-glucose" Maillard Reaction System

The Maillard reaction of cysteine and reducing sugar is one of the important ways to prepare meat flavor.At present,relevant studies mainly focus on the types and contents of meat-like substances formed through Maillard reaction model research,but little research has been done on the formation of the final product,the arrangement between molecules and the changes in energy during the reaction.Based on the existing reaction paths for the formation of meat-like substances,quantum chemical calculation can be used to study the optimal molecular structure and energy changes of the meat-like substances formed in the reaction process.In this study,experimental chemistry and computational chemistry were combined to control the meat flavor substances formed in the reaction process,which provided theoretical guidance for the processing and quality control of meat flavor.(1)Process optimization and structural characterization of "cysteine-glucose" Maillard reaction to form meat flavorCysteine and glucose were used as reaction raw materials,and the optimal process conditions for forming meat flavor were determined by measuring browning degree,color difference and sensory evaluation.The optimal condition was as follows:total substrate concentration 10%(W/V),cysteine 0.242 g/1OmL,glucose 0.360 g/10 mL,reaction time 90 min reaction temperature 160℃,pH 6.On this basis,the differences in structural characteristics of Maillard reaction products at different reaction temperatures were studied by combining ultraviolet spectrum,fluorescence spectrum and Fourier transform infrared spectrum.The results showed that the characteristic peak of Maillard reaction products appeared at about 290 nm,and the ultraviolet absorption intensity was gradually increased with the increase of reaction temperature.At 423 nm,the fluorescence intensity of Maillard reaction product at 170℃ is the highest The Maillard reaction was confirmed by the observation of an absorption peak at 900 nm by Fourier transform infrared spectroscopy,and an absorption peak at 3300 nm was observed,indicating that the structure of the reaction product was related to the vibrational contraction of N-H,O-H and C-H.(2)analyze that volatile flavor components of the model system base on GC-MS and GC-IMSThe Maillard reaction products at different temperatures were detected by the combination of gas chromatography-mass spectrometry(GC-MS)and gas chromatography-ion mobility spectrometry(GCIMS),to screen and analyze the key flavor substances and formation causes.A total of 69 volatile components were identified by GC-MS.Among them,2-acetylthiazole,2-furfuryl mercaptan,2,5dimethylpyrazine,2-thienyl mercaptan and 2-methyl-3-(methylthio)furan were the key flavor substances for meat flavor.A total of 46 volatile components were identified by GC-IMS.1-Octene-3ol,furfuryl mercaptan,2-Acetylthiazole and 2-Acetylpyridine were the main components that formed the meat flavor.At the same time,it was found that GC-MS and GC-IMS had different detection abilities for Maillard flavor compounds.GC-MS was sensitive to mercaptans,and GC-IMS was sensitive to esters.(3)density functional theory study on the formation of 2-furfuryl mercaptan and 2-acetylthiazoleGC-MS and GC-IMS jointly identified that 2-furfuryl mercaptan and 2-acetylthiazole contributed greatly to the meat flavor.Therefore,the formation process of 2-furfuryl mercaptan and 2-acetylthiazole was calculated by quantum chemistry,and compared with experimental chemistry,which further explained the formation mechanism of meat flavor substances formed by Maillard reaction.The intermediates furfural,glyoxal and methylglyoxal were qualitatively analyzed by HPLC-MS,and the structure optimization,energy and vibration frequency of the molecules in the reaction path of forming 2-furfuryl mercaptan and 2-acetylthiazole were calculated by Gaussian software.The results show that Maillard reaction is a multi-step reaction,and the intermediates furfural,glyoxal and methylglyoxal identified in experimental chemistry can be calculated by density functional theory.The intermediate furfural forms 2-furfuryl mercaptan through reduction reaction,and the reaction process is endothermic.The intermediates glyoxal and methylglyoxal were dehydrated,cracked,condensed and deoxidized to further form 2-acetylthiazole.The reaction process was exothermic,and the atomic changes of reactants and intermediates during the reaction process could be further observed through computational chemistry.Experimental chemistry combined with computational chemistry further clarified the formation of meaty substance intermediates and products during Maillard reaction.