Study Of Preparation And Gelation Capacity Of Soybean Polysaccharide Gel

Soybean polysaccharide gel is a kind of polysaccharides with similar capacity to low-methoxy pectin. It was prepared with okara which is rich, cheap and had good gelation capacity, so soybean polysaccharide gel had widely application prospect as a pectin substitute. In this thesis, the preparation, physicochemical properties and the gelation capacity of soybean polysaccharide gel were investigated, and then the gelation mechanism was discussed. A certain theoretical reference was offered for the further study and application of soybean polysaccharide gel. The main content and conclusions were as follows:1. Sodium hexametaphosphate-assited method was used. Through single factor and multiple-indicators orthogonal experimental designs, the impact of different conditions on the yield of gel, the concentration of galacturonic acid, gel strength was studied and we obtained the optimum processing conditions for the preparation of soybean polysaccharide gel:solid-liquid ration 1:15, sodium hexametaphosphate concentration 0.8%, pH 6.0, temperature 80℃, reaction time 1h. With the developed production process, the yield of soybean polysaccharide gel was 8.99%, the concentration of galacturonic acid was 50.78%, and the gel strength was 54.02g. The influence of various factors on the yield was as follows: influence of various factors on the content of galacturonic acid was as follows: the influence of various factors on gel strength was as follows:2. In this sector the composition, physicochemical properties, the water holding capacity and structure of soybean polysaccharide gel were mainly studied. The main conclusions were gotten as follows:the polysaccharide content was 56.53%, the esterification degree was 19.17%, and the character of soybean polysaccharide gel was similar to low-methoxy pectin. It mainly composed of fucose, galactose, arabinose and other monosaccharides. The net structure of gel could be observed through scanning electron microscope (SEM), and fourier transform infrared spectroscopy (FT-IR) was used to detect the sample, that soybean polysaccharide gel was a kind of non-pectin polysaccharide gels with some glycoprotein, and the water-holding capacity of soybean polysaccharide was better than carrageenan’s.3. Through studied the gelation capacity and structure of soybean polysaccharide gel which were prepared under different conditions of sodium hexametaphosphate, the main conclusions were gotten as follows:the influence of main forces on soybean polysaccharide gel formation was:hydrogen-bonding> electrostatic force> hydrophobic interaction, all of these forces were indispensable in the process of gel formation. The formation of soybean polysaccharide gel depended on the esterification reaction between sodium hexametaphosphate and polysaccharide, the soybean polysaccharide gel molecular chain was stretched and the network nodes were increased by sodium hexametaphosphate which were useful for gel network structure.4. The gel strength was increased as the concentration of soybean polysaccharide gel increased, and the gel strength was reached maximum by the concentration with 2.5%, but the elasticity was not significantly influenced by the concentration. The gel time was reduced as the concentration increased, and the gel time prolonged as the temperature increased. Through compared the structure of different gel concentrations, we found that the structure with higher gel concentration was more compact and stable.5. The gel strength of soybean polysaccharide gel was increased as the temperature increased and the gel strength was reached the maximum at 100℃. The viscous force and flexibility were increased as the temperature increased but not significantly. Through structure contrast, the rate and extent of hydration, and gel strength could be improved with increasing of the gel temperature.6. The pH range of soybean polysaccharide gel was 3.0-7.0, gel strength was reached the maximum with pH 6.0, the influence to elasticity and viscous force by pH was not significantly. Through structure contrast under acidic and alkaline conditions, the formation of gel would be impeded by both conditions:the hydrolysis of glycosidic bond and ester bond was occurred on acidic condition, alkaline condition susceptible to skim which the ester group would be destroyed by saponification reaction.7. The impact of sucrose on the gel strength of soybean polysaccharide gel was significant, the gel strength was decreased first and then was increased as the content of sucrose increased, but the elasticity was not influenced by sucrose significantly. The hydrophobic interaction of the system would be improved with the addition of sucrose, but the hydrogen-bonding would be reduced.8. The influence of various metal ions on the gel properties of soybean polysaccharide gel was as follows:Ca2+>Fe3+>K+. In a certain range of concentration, the formation of soybean polysaccharide gel would be improved with the addition of Ca2+ and Fe3+, but a downward trend of gelation capacity was occurred when the concentration increased, and the gelation capacity was not influenced significantly with concentration of K+. The hydrophobic interaction was increased with the addition of Ca2+, but over a certain extent, the gel strength would be reduced.