Research Of Soy Protein With High Dispersibility And High Solubility

At present, among the domestic and foreign commercial soybean protein products, thesoybean protein with high solubility usually has poor dispersibility, forming “lump”; and highdispersibility soybean protein often has poor solubility, limiting the function. Therefore, themarket needs soybean protein with high dispersibility and high solubility (mainly used fordairy drink) desperately. This subject focuses on the enzymatic hydrolysis and heat treatment,exploring the use of hydrothermal cooking and spray granulation lecithin processing to furtherimprove the dispersibility and solubility of the soybean protein, aiming at producing thesoybean protein products with both high solubility and high dispersibility.First of all, in the soybean protein fabrication process, after alkali soluble acid sinking,five enzymes are used to improve the solubility and dispersibility of soy protein. The resultsshowed that enzymatic hydrolysis of soybean protein could increase the dispersibility anddecrease the solubility, apparent viscosity, gel strength respectively. In comparison, soybeanprotein hydrolysed by0.2%bromelain (B2) has the best dispersibility, its20s dispersibility is94.8%, and the solubility is40.0%; and soybean protein hydrolysed by0.05%alcalase (A2)has the best solubility, and good dispersibility at the same time, the solubility of84.3%,20sdispersibility is58.6%. Through the relevant analysis between the insoluble aggregate contentand dispersibility, we found that they are significantly positively related (r=0.915, p <0.05);In addition, SDS-PAGE and HPLC results show that different enzymes and DH can producedifferent number of small molecular peptide, through the correlation analysis, we canconclude that small molecular peptide content and soybean protein dispersibility has asignificant positive correlation (r=0.806, p <0.05). Furthermore, in order to explore thereason why the papain hydrolyzate have so poor solubility, we measure the solubility of thepapain-induced insoluble precipitation in different buffer solution, and the aggregations couldcompletely dissolve in the buffer solution containing1%(w/v) SDS and8mol/L urea, so weconcluded that the noncovalent bonding, such as hydrophobic force and hydrogen bonding, isthe main force to promote the forming of the precipitation.Then, the paper studies the heat treatment conditions (pH, temperature) during theproduction process of soybean protein on product’s dispersibility and solubility. The resultsshow that after the heat treatment of soybean protein, the dispersibility significantly improved,but the solubility significantly reduced. In pH4-7and heat treatment temperature60-90°Crange, at pH approaching isoelectric point and the higher the temperature, the product hasbetter dispersibility and more poor solubility. In comparison, the soybean protein after heattreatment for30min at pH5.0and90°C (H509) has the best dispersibility, whose20sdispersibility is95.6%and the solubility is15.3%. Through the relevant analysis between theinsoluble aggregate content and dispersibility, we found that they are significantly positivelyrelated (r=0.992, p <0.05), and the results are consistent with enzymatic hydrolysis section.Through the enzymatic hydrolysis and heat treatment, we get the soy protein with highdispersibility (B2and H509), in order to enhance their solubility, we performed hydrothermalcooking processing. The results show that hydrothermal cooking could translate the insoluble aggregate into soluble aggregation, improving the solubility of samples, but the dispersibilityhave declined at different degree.At last, the paper explores a method to prepare soy protein with both high dispersibilityand high solubility. Hydrolyze the soy protein with0.05%（w/w）alcalase (A2) first, then spraysoy lecithin on the surface of the protein powder. The final product we get has both highdispersibility(20s dispersibility=83.6%) and high solubility(94.6%).