Effect Of Semi-dry Modification On The Characteristics Of Soy Protein Isolate

Original protein could be modified with special modification technologies to satisfy the need of food processing industry for high quality soy protein, provide the soy protein which possesses excellent characteristics and expand the application of protein products. Protein glycosylation modification is a green and effective chemical modification technology although traditional methods including dry heat and wet heat possess certain limitations. This could be improved by semi-dry method and controllable manufacture could also be realized. Therefore, semi-dry method is utilized here to process glycosylation modification on soy protein isolate. Solubility, emulsibility and gelation are key indexes which are used for evaluating the nutrition and usage value of protein. Glycosylation is capable of significantly improving such functional properties. The effect of semi-dry modification on the characteristics of soy protein isolate is investigated in this experiment and main conclusions are as follows.1. The emulsification activity and stability of soy protein isolate is increased remarkably through combining the protein and maltodextrin covalently with the semi-dry method. The influences of different conditions including reaction temperature, reaction time, maltodextrin addition amounts and water contents of the reaction system on the emulsification property of soy protein isolate are discussed separately and the optimal process conditions includes the reaction temperature of 60 centigrade, the reaction time of 7 hours, the maltodextrin addition amounts of 25 % and the water content of 17 %. The primary and secondary sequence of various factors on the emulsification property of soy protein isolate is maltodextrin addition amounts>reaction time> water contents of the reaction system>reaction temperature through the optimizing experiment based on single factor experiments.2. The gelation of soy protein isolate is notably improved through combining the protein and maltodextrin covalently with the semi-dry method. Taking measured values of gel strength as the standards, the influences of different conditions including reaction temperature, reaction time, maltodextrin addition amounts and water contents of the reaction system on the gelation of soy protein isolate are discussed separately and the optimal process conditions includes the reaction temperature of 60 centigrade, the reaction time of 16 hours, the maltodextrin addition amounts of 30 % and the water content of 15 %. The primary and secondary sequence of various factors on the gelation of soy protein isolate is reaction temperature >reaction time> maltodextrin addition amounts> water contents of the reaction system through the optimizing experiment based on single factor experiments.3. Compared with unmodified soy protein isolate, the Solubility, hydratability, foaming capacity and foaming stability of soy protein isolate modified with semi-dry method are outstandingly improved. The solubleness value of modified product is optimized at 13 h of reaction time and then gradually decreased. The foaming capacity, foaming stability and solubleness values are minimized at isoelectric point around p H 4.5.4. The heat stability of soy protein-polysaccharose is more desirable than that of untreated soy protein isolate especially under higher temperature(80 centigrade-100 centigrade) when the difference of heat stability of both is more obvious. The glycosylation degree of soy isolate product with semi-dry method is around 20.31-23.72 % which indicates that glycosylation occurs to a certain extent during the saccharification reaction of soy protein isolate and maltodextrin.