Study On Inhibiting Retrogradation Of Rice Starch And Improving Water Solubility Of Genistin By Thermostable Amylase

Thermostable amylase is a kind of enzyme protein that has a specific effect on starch,which come from microbial fermentation. Because of optimal enzyme activity under hightemperature, they meet the requirements of some high temperature food processing.Thermostable amylase has been widely used in the food industry in the lactic acid fermentation,beer, monosodium glutamate and other production and its application will be used moreextensively in the.future.Based on two kind of thermostable amylase0613and1458prepared by our laboratory，theyhave purified determined by SDS-PAGE electrophoresis. The paper investigates enzyme activityand kinetic parameters and research on rice degradation about amylose and amylopectin on theeffect of two enzymes.And else the application to food modification such as slowing the starchretrogradation and improving genistin water-solubility were conducted.The results show that: enzyme activity of amylase0613was7.859U/mL and enzymeactivity was28.247U/mL of amylase1458in this experiment used. Enzyme kinetic parameterswere measured by using γ-CD as substrate and concluded amylase0613on γ-CD affinity isgreater than1458on γ-CD affinity, but the catalytic of the1458effect on γ-CD is greater than0613of γ-CD. The enzyme kinetic parameters of0613and1458toward amylose andamylopectin were determined. The results showed that both0613and1458have more affinity toamylose than that of amylopectin. Both amylase0613and1458are more easily hydrolyzedamylase.By experiment of amylose and amylopectin were degraded by amylase0613and1458,theresult shows that two amylase have an effect on rice starch. About30%amylase of rice starchdecreased to7.33%and reducing sugar content were nearly unchanged and amyopectin changedfrom43.57%to66.71%in1hour after the recreation by amylase0613.The amylose of ricestarch were also decreased to11.50%, reducing sugar content were unchanged, amylopectinchanged from41.51%to60.88%in1hour after the recreation by amylase1458.The retrogradation of modified rice starch was determined using differential scanningcalorimetry. The result shows that retrogradation enthalpy of modified starch without amylase is3.56J/g. The retrogradation enthalpy of modified starch with enzyme0613is3.20J/g, andretrogradation enthalpy of modified starch with enzyme1458is1.97J/g during7days of storage at4℃, The retrogradation enthalpy of control starch is4.27J/g and modified starch withenzyme0613is3.50J/g, and retrogradation enthalpy of modified starch with enzyme1458is2.78J/g during14days of storage at4℃.We can conclude that amylases0613and1458inhibited the retrogradation of starch in some extent. The function of amylase1458was the moreobviously.Put amylase0613and1458apply to recreation of transfer glycosylation and analyzed withHPLC. The results showed: genistin retention time is about16min.There are some differentabsorption peaks before the retention time at16min. The conversion rate of genistin recreatingby amylase0613was40.24%, contrast to1458was24.87%.The result illustrate thatamylase0613and1458improved genistin water-soluble.