Study On Characteristics Of Egg White Protein Gel

Gelating and foaming properties are the most important functional properties of egg white, which is used in food industry. But it is still lack of systematic studies on properties of egg white gel. In this experiment, gel strength was used as the main index. DSC, SEM and other analytic methods were also used to study the basic gel properties of egg white and the effect of processing conditions and ingredients systematically. On this basis, tried to modify egg albumin by ionic polysaccharide, and explore the reaction mechanism to develop a kind egg white powder white high gel and foaming properties in order to provide a new type of food ingredients for the food industry. The major findings are as follows:The optimum conditions of gel preparation used in analysis were determined through experiment, which were that concentrations of egg white was 10%, gel temperature was 90℃,and gel time was 30min. There were 3 endothermic peaks in DSC curve induced by protein denaturation. The effect of pH on gel strength of egg white was very significant. Gel strength was strongest when pH was 4 and 8. There were two minimum peaks at the point of pH 4 and 8. The gel strength of egg white firstly increased with the increasing concentration of NaCl, CaCl2, and MgCl2, Sodium algimate, and Xanthan gum, and then decreased. When the concentration of ethanol and Konjac flour was less than 6% and 0.2% respectively, the gel strength enhanced. The effect of EDTA (<0.25%0), NaNO3 (<0.5‰) and NaNO2 (<0.5‰) on the gel strength of egg white was not significant. Various kinds of phosphate had different effect gel strength of egg white. But gel strength of egg white decreased white increasing concentration of sucrose and glucose. The study showed that the gel strength of egg white could be enhanced to get the best quality food, by using of some ingredients.Combination of starch and egg white are widely used in food. The gel strength of egg white increased with the addition of corn starch, potato starch and hydroxypropyl starch. SEM analysis showed that the three egg white-starch blending gel is embedded-type gel. And some starch gelatinization occurred. There are some difference between the effect of pH, sucrose, NaCl, CaCl2 and MgCl2 on gel strength of egg white-starch blending gel and pure egg white gel. Gel strength of egg white-corn starch blending gel (ECSG) and egg white-hydroxypropyl corn starch blending gel (EHPG) decreased with the increasing concentration sucrose. But the gel strength of egg white-potato starch blending gel (EPSG) increased when the concentration of sucrose was less than 10%. And there was maximum value when the concentration of sucrose was 4%. Effect of pH on the three blending gels was also very significant. The minimum value and maximum value appeared respectively at different pH. The effect of kinds of inorganic salt on the three blending gel were as same as the effect on egg white gel. The study showed that the gel strength of starch-egg blending gel could also be enhanced to get the best quality food, by using of some ingredients.The study on Egg white was blending with sodium carboxymethyl cellulose (CMC-Na) and carboxymethyl cellulose (CMC) respectively showed that when the reaction temperature was 60℃and reaction time was 2 days, the gel strength of egg white increased significantly, and the network structure of gel was much more uniform and compact, the content of proteins of small molecularweight reduced significantly. Analysis for foaming properties showed that respective samples enhanced significantly after 2d reaction. And excessive cross-linking may lead to the egg white powder of large molecular weight, decreasing solubility and deepening color.And the foaming of samples was best, when added CMC(0.25%) and CMC-Na(0.25%) to them. Then the foaming ability increased, and foaming stability also increased significantly. It showed that egg white powder of good gelating and foaming properties could be obtained under this condition.