Study On Functional Properties And Phase Behavior Of Egg White Protein/Konjac Glucomannan Composite System

As a hot issue in the field of food science recently, the protein-polysaccharide interaction is an important factor to regulate the texture and rheological behaviors of food. In view of the insufficiency of research on the interaction between egg white protein and neutral polysaccharide, in this study, Konjac glucomannan (KGM) was chosen as a representative of a neutral polysaccharide to explore the effect of KGM on the functional properties of egg white protein/KGM composite system. Besides, a high-abundant protein (OVA) in egg white was selected to study the phase behavior of OVA/KGM composite system, trying to reveal the mechanism of phase separation phenomena. On one hand, this study provided fundamental resources for intensive studies on the protein-polysaccharide interaction; on the other hand, the new features found in the composite system were expected to provide theoretical basis for the development of food ingredients with special functions of egg source.The main contents and results indicated as follows:1. The functional properties, thermal properties and rheological properties of egg white protein/KGM mixed system were studied. It was manifested that the addition of KGM improved the foam stability, emulsifying ability and emulsion stability of the mixed system, yet reduced the foam ability. From TPA analysis, KGM at a certain concentration could increase the hardness, chewiness and elasticity of the gel sample. Creaming analysis showed that the emulsion stability increased with the rising KGM concentration, while reducing the degree of separation of emulsion. In addition, the results of thermal and rheological properties showed that the addition of KGM improved the thermal stability of the mixed system, and had a significant influence on the sol-gel transition temperature of samples.2. The water distribution and micro structure characteristics of the egg white protein/KGM composite gel were studied by NMR techniques. The gel strength generally increased at first and then decreased with increasing the concentration of KGM. It was found that the values of gel strength and WHC reached the summit as the addition of KGM at0.06wt.%, and the holes appeared in the gel according to SEM. Irregular holes appeared in the gel may be due to the presence of KGM promoting the enfoldment of egg white protein chain before ordered aggregation. NMR results revealed that there were at least two categories of water with different states or mobility in the composite gels, defined as bound water and immobile water respectively. Besides, the concentration of KGM had an insignificant effect on the stability of bound water, yet a considerable influence on the fluidity of immobile water.3. The phase behavior and microstructure of OVA/KGM mixtures were studied. When the concentration of OVA and KGM were sufficiently high, the mixture transformed into two phases, meant that phase separation occurred. Turbidity results show that OVA had a pronounced effect on turbidity of OVA/KGM mixtures, but KGM had not significant effects on the turbidity of OVA/KGM mixtures. As observed in CLSM, the association of protein aggregates occurred gradually in the sample system, which further confirmed the occurrence of phase separation.