Effect Of Casein On Structure-activity Relationship Of Coagulated Yogurt

Casein has a high proportion in milk protein,accounting for about 80%.Its composition and structure have a great influence on the texture,microstructure and rheological properties of coagulated yogurt,but he effect and role of casein on yogurt gel properties and structure is not much reported.Understanding the structure of yogurt made from milk source containing different casein,analysing the effect of casein fraction and content on gel structure,finding out the best gel structure,and researching the effect of casein on the gel structure can solve the problems of whey precipitation and poor curd texture in the actual production,so as to provide theoretical basis for the further study of yogurt.In this study,commercially available whole milk,yak milk and buffalo milk were used as raw milk.By studying the change of water holding capacity,viscosity,texture and microstructure,to explore the relationship between the physical properties of the gel,microstructure and casein.The main results of this paper are as follows:(1)The effect of casein and whey protein ratio on the structure-activity relationship of coagulated yogurt was studied by using whole milk as raw material and 3% protein content of fixed raw milk.The results showed that with the increase of the ratio of casein and whey protein,the water holding capacity,viscosity,hardness and cohesion of the yogurt gel increased,but the continuity of the three-dimensional network structure gradually deteriorated.(2)On the basis of keeping the same content of total protein in the raw milk and maintaining the ratio of casein and whey protein as 4:1,this paper studied the effect of different milk caseins on the structure-activity relationship of coagulated yogurt gel.The results showed that whole milk milk casein had the greatest effect on the structure-activity relationship of coagulated yogurt gel.(3)The composition of the casein is the same for the three different milk sources,but the quality and proportion of casein are not the same.Three kinds of milk casein contain four secondary structures: ɑ-helix,β-fold,β-turn and irregular curl,the content and proportion of casein monomer components have a greater effect on coagulated yogurt,but the effect of casein structure is not obvious.(4)In this paper,the effects of casein fractions and structure on coagulated yogurt were investigated and the correlation analysis was performed.The results showed the effect of ɑ-casein on coagulated yogurt was significant in the four substances,and there was a positive correlation between the physical properties of coagulated yogurt.