Study On Improving The Stability Of Egg Yolk Emulsion By Phytic Acid

Egg yolk integrates senses,nutrition and functions,and it is an important raw material for daily life and food production.Under acidic conditions,egg yolk(EY)can form the emulsion,which has been used in mayonnaise,seasonings and milk beverages.However,the egg yolk is not stable enough in the acid emulsion system,and the prepared emulsion is prone to stratificating or separating the oil,which limits its application in actual production.Therefore,it is of great significance to study how to improve the physical stability of egg yolk in the acid emulsion system.This thesis intends to study the effect of phytic acid concentration and pH on the physical stability of egg yolk,egg yolk plasmas,egg yolk granulars and their emulsions under acidic conditions,and we will analyze the physical and chemical properties,microstructure and interface properties of the egg yolk emulsion.Then we will explore the mechanism of phytic acid(PA)stabilizing egg yolk emulsion,and provide certain theoretical basis and data support for improving the production and application of acid egg yolk emulsion products.The results of the study are as follows:(1)At pH 3.0,the effect of different concentrations of phytic acid(0.0125-0.8%)on the physical stability of egg yolk and its emulsion was studied.The research results showed that,as the concentration of phytic acid increased,phytic acid would first form an insoluble electrostatic complex with the soluble protein in the egg yolk,then it chelated and destroyed the calcium phosphate bridge structure of the egg yolk,and combined with the released protein again to form more the insoluble electrostatic compound EY-PA.The stability of the modified egg yolk emulsion prepared by EY-PA was significantly better than that of the control emulsion;among them,the 0.2% concentration of phytic acid modified emulsion had the lowest particle size and emulsification index,and the adsorption amount of interfacial protein and emulsion viscosity was the highest,and the physical stability was the best.(2)When the concentration of phytic acid was 0.2%,the effect of different pH values(pH 3.0,4.0,5.0)on the stability of egg yolk and its composite emulsion was studied.Research results showed that when the pH was lower than the isoelectric point of egg yolk(approximately pH 5.35),phytic acid and egg yolk protein would electrostatically combine to form an insoluble electrostatic complex EY-PA;in addition,when the pH value was lower,the degree of interaction between phytic acid and egg yolk protein was higher,which would destroy the calcium phosphate bridge structure more effectively,produce more insoluble electrostatic complexes,and make more egg yolk protein adsorb to the oil-water interface,so as to better improve the physical stability of the egg yolk emulsion.(3)At pH 3.0,the effects of different concentrations of phytic acid(0%,0.05%,0.2%)on the stability of egg yolk plasmas(EP),egg yolk granules(EG)and their composite emulsions were studied,and we also discussed the mechanism of phytic acid in the preparation of acidic egg yolk emulsion.The research results showed that,the mechanism of phytic acid on egg yolk plasmas and egg yolk granulars was different,the soluble proteins in the egg yolk plasmas would electrostatically combine with phytic acid to form an insoluble complex EP-PA;After the calcium phosphate bridge in the egg yolk granules was chelated and destroyed by phytic acid,the encapsulated soluble proteins were released,and then phytic acid would combine with these released proteins to form an insoluble electrostatic complex EG-PA.The stability of the emulsion prepared from the electrostatic composites EP-PA and EG-PA was significantly better than that of the control emulsion;among them,the emulsion of the modified slurry had better emulsion stability than the modified particles under the same conditions.