| The annual output of buffalo milk is about 9×10~8 tons,accounting for 13%of the world's milk production.Protein,fat,lactose,total solids,vitamins and minerals are higher than Holstein milk.These differences make the flavor and taste of buffalo milk conducive to the manufacture of various types of dairy products such as cheese and yogurt.By 2016,more than 23 million buffaloes have been farmed in China,and buffalo milk production ranks third in the world.Buffalo milk production is inconsistent with the lack of basic research on the nutritional composition and production characteristics of buffalo milk,and it is impossible to process high-value-added,high-yield diversified buffalo milk products.The basic research and processing technology of buffalo milk is in urgent need of transformation and upgrading.The study on the effect of different casein phenotypes on the quality of buffalo milk is particularly lacking.Therefore,based on the results of buffalo milk protein polymorphism analysis,this study isolated and purified active?-casein phenotypes from buffalo milk.The secondary structure of each phenotype of?-casein was analyzed by circular dichroism spectrumand fluorescence spectroscopy,and it's digestive performance in the gastrointestinal tract was analyzed using an in vitro digestion model;the release of bioactive peptide was analyzed based on the antioxidant activity of the hydrolysate.The results of the study are as follows:1.The results of High-performance liquid chromatography(HPLC)showed that the milk protein polymorphism of 160 buffaloes was:?-casein has A and B genotypes,of which A genotype accounted for 21.50%of the total.The proportion of B genotypes was 78.50%.There were three genotypes of?-casein:AA,AB,and BB.BB phenotype accounted for 64.38%of the total;AB phenotype accounted for 28.12%;AA phenotype accounted for only 7.5%.2.The correlation between?-casein phenotypes and milk components showed that there were significant differences in the protein content and fat content of buffalo milk with different phenotypes of?-casein(P<0.05).The protein content of BB phenotype buffalo milk was higher.In AA phenotype,the fat content of AA phenotype buffalo milk was higher than BB phenotype.There was no significant difference in buffalo milk of different?-casein phenotypes in total solid,non-fat,and lactose content.3.The secondary structure of?-casein results showed that the randomcoil of the three?-casein phenotypes accounted for a larger proportion,followed by the?-turn,the least was the?-helix.Except for randomcoil,all other contents of BB genotype were smaller than AA phenotype.The maximum emission wavelength and emission intensity of the three?-casein phenotypes at both the excitation wavelengths of 280 nm and 295 nm had extremely significant differences(P<0.01).4.The digestion results of?-casein showed that the digestibility of AB phenotype was fastest,followed by AA phenotype.BB phenotype were the most difficult to digest.5.The results of antioxidant activity showed that the DPPH scavenging ability of AA phenotype in?-casein was better than that of BB phenotype;the OH radical scavenging ability of BB phenotype was better than that of AA phenotype;The reductive ability of the BB genotype was better than that of the AA phenotype.The results showed that?-casein in buffalo milk had both A and B alleles and three genotypes(AA,AB and BB).The three phenotypes of buffalo milk differed in milk composition and casein particle size.The genetic polymorphisms of?-casein were closely related to the differences in milk composition,and even cause differences in in vitro digestive function and antioxidant activity.These results provided a theoretical basis for the directional breeding of buffalo milk and the precise design of functional milk dairy products. |
PDF Full Text Request