The Interaction Mode Between Walnut Polyphenols And Protein And The Effect Of Depolyphenols On The Function Of Walnut Protein

In the processing of food or beverage,the plant tissue was destroyed,the intracellular compounds was in contact with the extracellular molecules,and polyphenols were combined with proteins across the membrane.Because of the interaction between walnut polyphenols and proteins,new structures and new biological functions were created,which affect the functional properties of proteins.In this study,the solvent was used to destroy the interaction between walnut polyphenols and walnut protein,and the bound mechanism between walnut polyphenols and proteins was clarified.The antioxidant activity of polyphenols in different combinations was determined to determine the types of polyphenols with antioxidant function and their binding to proteins.Preparation of walnut dephenolated protein by ultrasonic assisted extraction of polyphenols by ethanol,the effects of removing polyphenols on the functionality of walnut protein were investigated.The specific research results are as follows:1.The mechanism of chemical bonding between walnut phenolic compounds and walnut protein of the walnut were explored in this paper.The walnut protein solution was first treated by solvent under alkaline and acidic conditions,and then ultrafiltration was carried out,and five different bound polyphenols were obtained by destroying the interaction force between walnut protein-polyphenol compounds.The content of polyphenols were determined.The results showed that under the conditions of PH 3.5 and PH 11,the contents of non-covalently bound polyphenols were 11.31mg/g and 7.74 mg/g,accounting for 44.02%and 36.73%of total phenols.The contents of non-covalently bound flavones were 2.39 mg/g and 2.49 mg/g respectively,accounting for 38.61%and 40.36%of total flavones.Non-covalent binding is the main binding mode between walnut polyphenols and walnut protein.2.Different concentrations of sodium chloride and urea were used to destroy the interaction between walnut phenols and walnut protein,and the antioxidant activity of different bound polyphenols was determined.Under the conditions of pH 3.5 and pH11,the scavenging rates of DPPH free radicals by free polyphenols were 82.34%and43.68%,the chelating rates of Fe²⁺were 71.88%and 49.96%,the absorbance values of reducing power were 1.157 and 0.857,and the anti-peroxidation abilities of lipids were 47.71%and 32.69%respectively.Among the five different bound polyphenols,the antioxidant activity of free polyphenols was significantly higher than that of other bound polyphenols.3.The extraction process of walnut polyphenols by ethanol ultrasonic assisted method was as follows:ethanol volume fraction was 51%,ultrasonic power was 140W,ultrasonic time was 10 min,ultrasonic temperature was 30°C,and ratio of material to liquid was 1:30（w/v）.Under the optimal conditions,the polyphenol content was（32.81±1.252）mg/g,which reached 98.85%of the theoretical value of the regression model（33.189 mg/g）,the relative error value was 1.142%.The removal rate of polyphenols was the highest.4.The phenolic substances in walnut degreasing powder were removed by ultrasonic assisted method,and the dephenolated protein of walnut was prepared by alkali-soluble acid precipitation method to study the effect of polyphenols on protein functionality.The results showed that the walnut protein function of ultrasonic dephenolization was better than that of non-ultrasonic dephenolization,and the two walnut proteins had the worst function at pH 5,with the solubility were 5.31%and4.86%,the emulsifying properties were 24.95 m²/g and 19.91 m²/g,and the foaming properties were 3.66%and 2.94%respectively.At pH 11,the solubility were 82.35%and 73.55%,the emulsifying properties were 46.35 m²/g and 37.28 m²/g,the foaming properties were 35.85%and 18.87%,respectively.The removal of phenolics from walnut protein by ethanol ultrasound is helpful to improve the function of walnut protein.