Investigation Of Ions And Sugars On The Foaming Properties Of Egg White Proteins And Their Application In Cakes

This research was funded by National Natural Science Foundation of China（no.32101993）.Egg white protein is often used as a foaming agent in baked goods due to its excellent foaming properties.The mechanisms of salt ions and sugars,as common additives in food,on the functional properties of egg white proteins and their applications are not yet clear.Moreover,most of the current studies on the foaming ability of egg white proteins have focused on the basic characteristics of foaming behavior,such as the determination of foam volume,density and stability,so it is necessary to consider the final structural texture and digestive stability of foamed foods.In this paper,we analyzed the molecular mechanism of protein foaming ability enhancement from the perspective of structural properties,surface properties,and aggregation morphology,and determined the ion concentration for optimal foaming ability and stability by using egg white protein as the research object,and the effect of ion-induced foaming property of egg white protein.Based on the determined ion concentrations,low heat and low sugar cakes with erythritol substitution for sucrose were prepared,and the effects of different sugar alcohol substitution amounts on the baking properties of the cakes were analyzed from the perspectives of sensory morphology,baking quality,and internal structure.Finally,based on the prepared cake samples,the changes of digestion rates of proteins and sugars were investigated by using in vitro simulation digestion models,combined with gastric digestion kinetics and intestinal digestion kinetics,respectively,to elucidate the digestive characteristics of the samples.The aim of this thesis is to improve the foaming performance of egg white proteins,optimize the preparation of cake products,enhance their digestive characteristics,and then propose new directions for the production and processing of foamed foods.The main research contents and results of the full paper are as follows.（1）The mechanism of different ions on the enhancement of ovalbumin foaming performance was explored.Two salt ions of different valence,Na Cl and Mg Cl₂,were selected with ion-modulated concentrations of 0,50,100,150 and 200 m M.The changes of protein interfacial properties were analyzed by the determination of interfacial protein content,surface tension and zeta potential;the secondary and tertiary structures of proteins were characterized by circular dichroism,Fourier infrared spectroscopy and endogenous fluorescence spectroscopy.In addition,the relationship between the changes of egg white protein aggregation morphology and foaming properties was analyzed by the determination of particle size distribution,apparent viscosity,free sulfhydryl groups and other indexes.The results showed that the foaming properties reached a maximum of 136.67±11.55%（Na Cl）and 117.22±5.36%（Mg Cl₂）as the ionic strength increased to 200 m M;the stability of foaming was 89.41±8.61%（Na Cl）and 91.61±4.66%（Mg Cl₂）.This may be due to the fact that ions promote protein unfolding at the gas-water interface and enhance the adsorption rate by interacting with proteins,thus improving foaming performance;divalent ions(Mg²⁺)can bind charged amino acids more effectively than monovalent ions（Na⁺）and have a stronger electrostatic shielding effect by binding more strongly to proteins.（2）The effect of erythritol substitution for sucrose on the baking properties of the prepared low heat and low sugar cakes was investigated under different ionic matrices based on the determined ionic strength.The erythritol substitution content was selected as:0,20,40,50,60,80 and 100%.The baking characteristics and internal structure of the cake samples were characterized and corroborated with the sensory morphology results.The results showed that when the erythritol substitution amount was≤50%,the specific gravity of batter and specific volume of cake were slightly reduced,and the baking loss rate was basically unchanged;the change of moisture state was also small;the color,tissue texture and sensory taste of cake were not greatly affected.In addition,when the ratio of erythritol to sucrose was 1:1,the baking performance of the samples with Mg Cl₂ did not decrease significantly in terms of batter specific gravity,cake specific volume,and texture characteristics,and the acceptable degree was higher.（3）Based on the determination of the baking properties of the above sample,a subsequent analysis of the digestive properties of this sample was carried out.From the use of gastric digestion kinetics and intestinal digestion kinetics,mathematical models were constructed to analyze the digestion of the two major human nutrients protein and sugar.The results showed that the gastric digestion rate slowed down and both peptide concentrations decreased after erythritol substitution,and the bioavailability of protein decreased.Similarly,glucose release decreased with increasing erythritol content,which could be due to the decrease in sucrose content causing a decrease in glucose slow release;or it could be due to the competitive inhibition ofα-glucosidase by erythritol,allowing the samples to achieve a hypoglycemic effect after digestion.In addition,the two groups of samples with Mg Cl₂ and Na Cl added were controlled at the ratio of sucrose to erythritol of 1:1,and the results showed that the peptide concentration after gastric digestion was higher than that of the control group and the glucose release after intestinal digestion was lower than that of the control group in the samples with Mg Cl₂ as the substrate;it both weakened the degree of protein destruction after digestion and better exerted the glucose-lowering effect,which provided the development of green low-energy food It provides a new direction for the development of green low-energy food.