Study On Characteristic Taste Substances And Isolation And Identification Of Key Umami Peptides In Preserved Egg Yolk

Preserved eggs are a traditional Chinese egg product,forming a unique flavor that is loved by consumers.According to the existing research,the study of volatile substances in preserved eggs white or yolks have been gradually improved.However,there are few researches on non-volatile flavor components of preserved eggs.In this study,preserved egg yolk was taken as the research object,and revealed its flavor characteristics and umami mechanism through a variety of technical means.The specific research content and results are as follows:Firstly,the characteristic taste of preserved egg yolk was studied by electronic tongue,UHPLC-MS/MS and multivariate statistical.Electronic tongue results showed that the distinctive taste characteristic of preserved egg yolk was umami,and UHPLC-MS/MS results showed that there were significant differences in metabolites between preserved egg yolk and fresh raw egg yolk.Combined with PCA and OPLSDA,the umami taste characteristics of preserved egg yolk were obtained.Glu,Asp and other free amino acids,IMP,GMP and other nucleotide,succinic acid and their derivatives were considered as the important umami components of egg yolk.Other substances such as carnosin,glutamine and lipids may contribute to the retention of its umami taste.Secondly,the contents of free amino acids,nucleotides and succinic acid in yolk during pickling were studied,and OPLS method was used to analyze the influencing factors of protein changes in preserved egg yolk.The results showed that the content of Asp acid increased gradually,while the contents of succinic acid,AMP,CMP,GMP and UMP decreased and then increased.The contents of IMP and other free amino acids were gradually decreased.It was found that succinic acid,a single umami substance,played a key role in the umami formation of preserved egg yolk by comparing the TAV of various umami substances.In addition,R2 and Q2 in OPLS model established by changes in TCA soluble peptide content and free amino acid content and p H value were both greater than 0.5,and R2 was close to 1,indicated that p H affected the change of substance content.Due to the increase of TCA soluble peptide content,it was also found that preserved egg yolk may contain umami peptides that promote the umami taste of preserved egg yolk.Finally,to further improve the theoretical basis of umami substance composition in preserved egg yolk.Five novel umami peptides,SLSSLMK,APYSGY,VAMNPVDHPH,PPMF and AGFMPLP,were isolated,identified and screened from preserved egg yolk by nano-HPLC-MS/MS combined with molecular docking technique.The amino acid sequence analysis of five umami peptides showed that hydrophobic amino acids affected the umami taste of long chain peptides.The docking results showed that Phe527 on T1R1/T1R3 was the key interaction site,and hydrogen bonding,electrostatic interaction and hydrophobic interaction were the main binding forces between T1R1/T1R3 and umami peptides.In conclusion,this study not only fills the blank in the study of umami peptides in preserved egg yolk,but also reduces the separation and purification steps of umami peptides by using molecular docking technology,which provides a premise for exploring umami peptides in other foods.