Preparation And Characterization Of Whey Protein-Polyphenol Complex And Chitosan-polyphenol Complex And Their Effects On The In Vitro Digestion Of Emulsion Oil

In this paper,free radical induction method and carbodiimide method were used to prepare Whey Protein-polyphenols with different structures(quercetin,kaempferol,quercetin,epigallocatechin gallate(EGCG))Covalent and physical complexes with chitosan(CS)-polyphenols(EGCG,gallic acid(GA)),and to explore the mechanism of complex formation by comparing the differences in structure and functional properties of the above complexes.On the evaluation of its impact on the physicochemical properties of the emulsion,antioxidant capacity and the digestion of emulsion fat in the process of simulated digestion in vitro,the purpose was to explore the close relationship between proteins,polysaccharides and polyphenols and the formation of complexes Functional characteristics.The research provided scientific basis and theoretical basis for the development of new multi-functional foods,realizing the steady state of functional factors,and the application of protein-polyphenol and polysaccharide-polyphenol covalent compounds in new functional foods.The main findings of this study are as follows:1.In the ascorbic acid/hydrogen peroxide reduction system,whey protein can be covalently bound to polyphenols with different structures such as EGCG,quercetin,kaempferol and myricetin,and the number and position of polyphenolic hydroxyl groups are the main factors affecting covalent bonding with whey protein.In terms of functional properties,the thermal denaturation temperature order of the whey protein-polyphenol complex is:WPI-EGCG>WPI-quercetin>WPI-kaempferol>WPI-myricetin,and all protein-polyphenol The thermal denaturation temperature of the valence complex is higher than that of the corresponding physical complex;in terms of antioxidant capacity,the WPI-EGCG covalent complex has the highest antioxidant capacity,and the quercetin,kaempferol and WPI covalent complex Following this,the WPI-myricetin covalent complex has the lowest antioxidant capacity.2.Before simulating in vitro digestion,the particle size of the emulsion containing whey protein-polyphenol covalent complex was smaller than that of the control whey protein,and all the emulsions were negatively charged except the whey protein emulsion was positively charged;in vitro digestion process In the medium,the addition of WPI-EGCG/quercetin/kaempferol/myricetin covalent compounds gradually increased the emulsion particle size and reached the maximum value in the small intestine,and the absolute value of the potential decreased from increasing to increasing.;Due to the dilution of the digestive juice,the viscosity of the emulsion gradually decreases.The emulsions containing WPI-EGCG,quercetin,kaempferol,and myricetin have different microstructure changes during the effect process.On the one hand,the degree of change in the degree of aggregation of the emulsion droplets increases with the increasing particle size the results echo,on the other hand,it can also reflect the effect on the digestibility of emulsion lipid droplets.The above WPI-polyphenol covalent compounds can always digest the emulsion lipid droplets,and the inhibitory effect of the WPI-EGCG covalent complex is the most significant.3.The covalent binding of whey protein and polyphenol can significantly improve the storage stability and antioxidant capacity of the emulsion,and its antioxidant capacity is related to the structure of the polyphenol and the amount of grafting;protein-polyphenol covalent compound in the simulated in vitro digestion process The substance exhibits different antioxidant capacity at different digestive stages.In general,the antioxidant capacity of the emulsion in the small intestine is stronger than that of the stomach.4.XRD and SEM results show that the physical recombination and covalent bonding between CS and EGCG and GA can affect the physical structure of chitosan such as crystal morphology and surface morphology,and the effect of covalent effect on chitosan is most obvious.The covalent complex formed by EGCG,GA and CS has high antioxidant activity,and at the same time,the antioxidant capacity of the CS-EGCG covalent complex is stronger than that of the CS-GA covalent complex.5.Compared with the emulsion containing control chitosan,the addition of CS-EGCG/GA increased the emulsion particle size and potential value to a certain extent;in the simulated in vitro digestion process,the emulsion particle size gradually increased with the transfer of the digestion site,Its potential is converted to:negative(oral)-positive(stomach)-negative(small intestine);the distribution and aggregation degree of emulsion droplets in the microstructure of each digestion site of each emulsion microscopically also confirms the change of its physical and chemical characteristics;Introducing EGCG and GA into CS can make the copolymer have various properties.On the one hand,GA can reduce the intramolecular and intermolecular hydrogen bonding network and eliminate the crystal structure.On the other hand,grafting provides sites for forming covalent bonds,which further affects the solubility and rheology of CS.The results show that GA-g-CS has potential as a thickener or gel-forming material in the food industry.6.The experimental results show that the CS-EGCG/GA complex can effectively inhibit lipid oxidation,and the order of its inhibitory ability from high to low is:CS-EGCG covalent complex>CS-GA covalent complex>CS-EGCG physical complex>CS-GA physical complex>Control CS;during the digestion of emulsion,the covalent combination of EGCG,GA and chitosan can effectively improve the antioxidant capacity of phenols during digestion,the main reason depends on the protective effect of chitosan on phenols;CS-EGCG/GA covalent complex inhibits the digestion and absorption of lipids by inhibiting the combination of bile salts and lipid droplets,lipase activity,and increasing the viscosity of the digestive tract.