Phase Behavior And Glycosylation Of Ovalbumin-Cmc Mixtures

The interaction between protein and polysaccharide was hot scientific topics and frontiers in the field of Food Science. Ovalbumin was the most widely used model protein. In view of the poor research of interaction between Ovalbumin and the ionic polysaccharide, the relatively low price anionic polysaccharide sodium carboxymethylcellulose (CMC) was chosen to explore the influence that the physical blend and glycosylation modification of ovalbumin and CMC on the structure and functional properties of products. So as to further reveal the mechanism of interaction between ovalbumin with CMC. The study enriched the theoretical frame of interaction between protein and polysaccharide and provided fundamental resources for intensive study; at the same time, it also offered guidance on usage of mixture of food ingredients from egg source and polysaccharide, and theory evidence on developing tailored egg powder.The main contents and results indicated as follows:1. The influence that the pH value, CMC concentration and salt ion concentration exerted on the phase behavior of the OVA-CMC mixtures was researched. Under the neutral condition, phase separation occurred in mixtures because like charges between protein and polysaccharide repelled each other. When the pH was below the isoelectric point of protein, localized adsorption between OVA and CMC would happen in the system, electrostatic interactions played the dominated role, and the milky white uniform solution formed. The phase separation was easy to occur in mixtures where the CMC concentration was below0.4%and NaCl was absent. The addition of NaCl stabilized the composite system to some extent and narrowed the phase separation range of the composite system where the pH was under the isoelectric point of the OVA. Rheological analysis showed that OVA-CMC complex solution was pseudoplastic fluid and the pseudoplastic became more and more obvious with the decreasing of pH. Salt ion concentration influenced the viscosity of composite solution significantly. The phase behavior of the composite system was observed microscopicly by CLSM. The microscopic phase behavior of the composite system was observed by CLSM. The particle size distribution and UV spectral analysis were consistent with the CLSM result. A structure similar to nanometer gel particle was found in the transmission electron microscopic.2. CMC with three different degrees of substitution were chosen to modify OVA with the reaction of glycosylation grafting. The degree of substitution and molecular weight of the three kinds of CMC was determined. The effects that the reaction time, pH value and the reaction substrate ratio exerted on the extent of grafting reaction were studied by measuring the grafting degree and browning degree. The optimal modification conditions for forming three grafting polymer were:1#, reaction time of8d, reaction pH value of7, substrate ratio of4:1;2#reaction time of8d, reaction pH value of7, substrate ratio of4:1;3#, reaction time of8d, reaction pH value of8, substrate ratio of4:1. The browning kinetics of three kinds of grafting reaction was consistent with the zero order reaction kinetics model.3. The properties, including emulsibility and emulsion stability, foamability and foaming stability, rheological behavior, and surface hydrophobicity of the three different glycosylation grafted products were discussed. It was observed that the emulsibility strengthened with the increase of the grafting degree. The peak value of the foamability was less than that of the native protein. However, foaming stability improved with the extending of incubation time, and was larger than that of the native protein. The rheological behaviors of all the three grafted products were similar. It took more time for the formation of the protein gel when the incubation time was longer, and the thermal denaturation temperature of protein became higher. It also indicated that the temperature where the G’value of3#inflected was much lower than that of1#and2#, while the G’ values were the inverse. The research of surface hydrophobicity could account for the phenomenon with emulsibility as well as rheological behaviour.4. The SDS-PAGE analysis, fourier transform infrared analysis, amino acid analysis and CD spectrum analysis were introduced to characterize the glycosylation reaction. The results of SDS-PAGE and infrared analysis proved that the glycosylation grafting reaction happened. Amino acid analysis showed that lysine, arginine were involved in the glycosylation reactions, but did not cause significant damage to the nutritional value. CD spectrum analysis showed that the grafted CMC affected the secondary structure of protein to some extent, mainly the reduction of the a-helix structure and the increase of random coil content. The change of the secondary structure of the protein was more obvious when the molecular mass of the polysaccharide was much smaller.