Changes Of Properties And Their Mechanisms Of Protein And Polysaccharide Colloids After Ultra High Pressure Treatment

Ultrahigh pressure (UHP) treatment is a new technology for food processing and storage. As the base of the application of this technology, we should not only to understand the effects of UHP treatment on microorganisms, enzymes in food, but also to know the changes of foods' physicochemical properties after the treatment. Protein and polysaccharide are two main components of foods, and they have important functional properties. In this dissertation, protein colloid solutions of soybean milk, isolated soybean protein (ISP), milk powders and gelatin, polysaccharide colloid solutions of carrageenin, agar, high methoxyi pectin, etc. were used as research objects, at the condition of ≤ 500MPa pressure, normal temperature, 0~30min, to study the changes of physicochemical properties after the UHP treatment.The results showed that the turbility of soybean milk slightly decreased after the treatment of pressure more than 200MPa, but its settling stability and heat stability increased, oil or fat, pH and sugar affected the changes. UHP treatment greatly improved the solubility of ISP. The results of SEM observation showed that the particle size of protein in soybean milk and ISP solution decreased, and that of fat in soybean milk increased after UHP treatment. The viscosity of soybean milk and ISP solution increased as the result of decreasing of particle size and increasing concentration of protein particles. Solutions of bovine milk powder had similar changes after the treatment. The elasticity of the solutions also increased, but when the pressure was ≥ 200MPa, the elasticity of soybean milk decreased. The chemical analysis and infrared absorption spectrum of the solutions displayed that the protein disassociated and unfolded with the treatment of ≤ 400MPa, disulphar bonds were partially disrupted, and the internal hydrophobic groups demasked. These made the contents of -SH groups and hydrophobicity increasing, which improved the proteins' surface properties and ability for gelatification, and formed gel was fine and with a high water holding capacity, lower gel strength. The gel strength...