Preliminary Investigation Of The Allergenic Capacity Of β-lactoglobulin By Covalent Conjugation With Plant Polyphenols

With the improvement of people’s material living conditions,dairy products become more and more important in people’s daily diet.However,milk proteins are major food allergens,Reducing the allergenicity of milk protein is an important research topic in nutrition and food science.At present,,many processing methods have been used to modify milk allgerens to decrease their allergenicity,such as heating,high hydrostatic pressure,and hydrolysis.However,these methods might destroy useful functions and nutritional values of the proteins.Therefore,it is important to find a novel approach to reduce protein allergenicity with improving the protein functional properties.In this paper,we examined covalent interactions between β-lactoglobulin(βLG)the main allergen component in milk protein and plant polyphenols and characterized the covalent conjugates.We used SDS-PAGE,matrix-assisted laser desorption ionization time-of-flight mass(MALDI-TOF-MS)and covalent complex group detection to verify that protein and plant polyphenols were covalently bonded.Circular dichroism(CD),fluorescence spectroscopy and infrared spectroscopy(FTIR)were used to analyze the effects of protein binding to plant polyphenols on the structure of proteins.According to the results of the enzyme-linked immunoassay(ELISA),we can analyze the change of the binding capacity of IgE after βLG binding to plant polyphenols.Furthermore,the resistance to gastrointestinal digestion of the protein and its conjugates was investigated by simulated gastric digestion.βLG is the main component of whey protein(WPI).WPI is a mixtureand used widely in food industry.According to our previous study,we choosed one of the polyphenols to conjugate with WPI to investigate the the changes in IgE-binding capacity,antioxidant activity,solubility,emulsibility,foaming,and thermal stability of the conjugate.This research provides a theoretical support for reducing the allergenicity of βLG,which might have potential in producing hypoallergenic foods.The main research results are as follows:1,The results of SDS-PAGE and MALDI-TOF-MS show that βLG are covalently bound to plant polyphenols.At the same time,the total phenolic contents of βLG–polyphenol conjugates increase,the contents of free amino and thiol groups and tyrosine residue reduce,these also demonstrate that plant polyphenols are covalently binded with the protein.2,The results of CD,fluorescence spectroscopy and FTIR indicate that βLG conformational structure change after polyphenol conjugation,the structure of the protein has an important relationship with its function.The result of ELISA shows that the covalent complex reduces the IgE-binding capacity of βLG compared with the native protein.3,The simulated gastrointestinal digestion shows that the conjugates showed higher digestibility than the native protein.The Western blot of the digested product of the conjugates reduce the IgE binding capacities.4,The functional properties of WPI are changed after covalently binding with chlorogenic acid(CHA).its solubility,emulsifying activity,foaming properties and antioxidant capacity of WPI are enhanced by covalent conjugation of CHA.The thermal stability reduce,WPI-CHA conjugates exhibited lower IgE-binding capacity than native WPI...