Study On Influencing Factors Of Glycosylation Based On Structure And Functional Properties Of Whey Protein Isolate

Whey protein isolate(WPI)has good emulsifying,gelling and foaming properties,and is often widely used as a natural food ingredient and additive in food systems.Glycosylation is one of the common methods for improving the functional properties of proteins.The glycosylation product can be widely used as a carrier of fat-soluble nutrients in the food industry to improve the storage and digestive stability of fat-soluble nutrients.The glycosylation is affected by many factors,such as: the type of sugar,the ratio of protein and sugar,pH,reaction temperature and reaction time,etc.These factors affect the structure of the protein and the ability of the protein to carry fat-soluble nutrients.In view of the above problems,this paper uses WPI as the raw material to study the influence of glycosylation conditions on the structure and functional characteristics of WPI,and analyzes the effect of glycosylation products on the digestion stability of the emulsion.It lays a theoretical foundation for WPI as a carrier of fat-soluble nutrients.The conclusion of the full text is as follows:(1)Different pH values(2-10)and types of sugar(glucose,lactose,and dextran)have certain effects on the structure and emulsifying properties of WPI-sugar conjugates(WPI-sugar).The results of degree of glycation,surface hydrophobicity,apparent viscosity and emulsifying properties show that alkaline conditions are favorable for the glycosylation reaction,and WPI-sugar has good emulsifying properties.When the pH values are 9 and 10,the degree of glycation,surface hydrophobicity,apparent viscosity,and emulsion stability of WPI-sugar are reduced.The small molecule glucose makes the WPI-glucose conjugates have a higher degree of glycation,while the large molecule dextran improves the surface properties of WPI,WPI-Dextran conjugate(WPI-D)has an increased apparent viscosity and enhanced emulsifying properties.(2)The glycosylation reaction has a certain effect on the structure and functional properties of WPI.Different reaction temperatures(50-90 ?)have a certain effect on the structure and functional properties of WPI-D.The results of FTIR,CD and endogenous fluorescence spectra showed that the secondary and tertiary structure of WPI changed after glycosylation.The emulsifying properties and ?-carotene embedding rate results show that,compared with WPI,the emulsifying properties and embedding rate of WPI-D have been improved.As the reaction temperature increases,the degree of glycation increases,the ?-sheet structure decreases,and it has better emulsifying properties and embedding rate.When the reaction temperature is too high(90 ?),aggregation occurs between WPI molecules,which is not conducive to the glycosylation reaction,and the emulsifying properties and embedding rate decrease.(3)Through the ratio of WPI to dextran(3:1-1:3),pH(7-9)and reaction time(1-5 h)single factor experiments on the structure and functional properties of WPI-D,orthogonal experiments were designed.The preparation method of WPI-D was optimized orthogonally with the ?-carotene embedding rate as an index.The best preparation method of WPI-D is that WPI: dextran is 3:1,pH is 8,reaction temperature is 70 ?,and reaction time is 3 h.(4)Glycosylation reaction(WPI and WPI-D)and different oil types(soybean oil,corn oil and coconut oil)have certain effects on in vitro digestion stability of ?-carotene emulsion.Emulsion structure and simulated in vitro digestion test results show that the glycosylation reaction and the type of oil will affect the structure and properties of the emulsion.Compared with WPI,WPI-D is beneficial for protecting the transportation of nutrients into the small intestine,and WPI-D is suitable for the transportation of nutrients that need to be slowly released in the small intestine.Coconut oil is better than soybean and corn oil as an oil phase for preparing nutrients emulsion to transport nutrients,and is more easily digested and absorbed by the body.