Study On Traditional Fermented Dairy Products In Xilinguole League Mongolian And Preparation Of Milk-derived Peptides By Microbial Fermentation

The purpose of this paper is to study milk peptide and the High efficient preparation technology of peptide.Samples of Mongolian traditional fermented cow and horse milk were collected from Xilingol League Mongolia.By studying the basic biochemical indexes,bioactive dipeptides and the composition of fermentation microorganisms,the valuable functional microorganisms were screened by the traditional microbial separation method,and the fermentation mode of composite strains was adopted,and the fermentation conditions were optimized by orthogonal test to improve the hydrolysis rate of characteristic lactopeptides.The main conclusions of this study are as follows:(1)The results showed that there was no significant difference in the content of protein,fat and amino acids(P>0.05),the content of lactose and pH decreased,and the acidity increased.The content of protein,amino acid and fat in milk before and after fermentation was significantly higher than that in horse milk(P<0.05),while the content of lactose,acidity and pH in milk before and after fermentation was lower than that in horse milk(P<0.05).There was no significant difference(P>0.05).The acidity of the whole sample increased moderately,and there was no sign of over fermentation and obvious infection of putrefactive bacteria.(2)The proportion of molecular weight of milk protein hydrolysate increased significantly after microbial fermentation.37 peptides were identified from fermented cow and horse milk samples.The peptides with high labeling content and functional activity were characterized by VL,IR,VP and AF.The total and unique peptides identified in fermented horse milk samples were the most,and the potential ACE inhibitory peptides were the most.(3)Based on the sequencing technology of Illumina misq,the dominant bacteria of fermented cow and horse milk are Lactococcus,Lactobacillus,Streptococcus,etc.The dominant fungi are Dekkera,Trichosporon,Wickerhamsiches and so on.It can be seen from the cluster analysis that the composition and region of the samples are likely to affect the floristic composition of microorganisms.47 species of bacteria,39 species of bacteria and 8 species of fungi were screened from fermented milk samples of cattle and horses by traditional methods.The probiotics suitable for the subsequent fermentation of composite strains were selected:Lactobacillus helveticus and Lactococcus lactis.(4)Based on the protease activity and the proportion of protein hydrolysate with relative molecular weight less than 1000 Da,through single factor and L16(45)orthogonal experiments,the final combination scheme of the fermentation experiment of composite strains was determined as follows:temperature 40?,time 11 h,pH 8.0,inoculation amount 3%,and the ratio of strains 3:1.With the quantitative analysis of characteristic peptides and the determination of the inhibition rate of angiotensin-converting enzyme(ACE),it was significantly higher than that of single strain fermentation(P<0.05).The results showed that the co fermentation technology of composite strains was feasible to optimize the preparation process of milk-derived peptides.