The Study On Properties Of Aggregated Soybean Protein And Mixed Gelation With Native Soybean Protein

Aggregate properties of soybean protein and effect on its gelation properties were discussed in this paper. The purpose is studying the aggregate mechanism in protein gelation and effect on phase-separated process in a new way. Five aggregated proteins (5%, 10%, 30% heat-induced aggregated protein, acid-induced aggregated protein and ethanol-induced aggregated protein ) were prepared with different physical and chemical methods. Mixed gels with native soy protein and its aggregated protein were measured with texture,rheology,water holding capability and electron microscope. In order to research on the effect of aggregate, the properties of aggregated protein include solubility,turbidity,molecular weight,particle radius and secondary structure were measured. The result showed that the aggregated protein have poor solubility, high turbidity and great partical radius except induced-aggregated protein in 5% concentration. These indicated that a great proportion of aggregated proteins are insoluble. Heat and acid-induced aggregated protein have a small decrease in theα-helix component and an increase in the proportion of theβ-sheet at Second structure level. The regular-structure of the ethanol-induced aggregated protein increased. Water holding capability decend with the increasing of aggregated protein proportion, which indicated its compact structure. Hardness increase with the increasing of soluble aggregated protein. The gelation added ethanol-induced aggregated protein have the max hardness. There are lower gel temperature and less fracture stress with gelation added more aggregated protein except those added lower concentration heated-induced and ethanol-induced aggregated protein. A theoretical model for linear viscoelastic behaviour of composite biopolymer gels was used to calculate upper and lower bounds for gel moduli. Then the test value compared with theoretical value in order to analyse the effect of phase-separate on gel structure properties. Native soybean protein gel have symmetrical net work through SEM's observation .Gelation with different concentration of aggregated protein have colorful microstructure. The hardness of acid-induced gelation is greater than heated-induced gelation. With the enhanced proportion of aggregated protein ,when the heating speed was rapid, the water holding capability decreased, but when heating speed was slow, the result were otherwise. controlling the gelation texture with aggregate was mainly in the aspect of microcosmic phase-separate and gel speed.