Study On The Preparation And Properties Of Indica Rice Resistant Starch Of Type RS₃

Resistant starch can not be digested in the small intestine of healthy individuals,with the similar physiological function of dietary fiber can improve intestinal metabolism,reduce the risk of colorectal cancer,obesity,and its physiological function is similar to a certain degree of insulin can regulate blood sugar,made of functional food for diabetic patients to eat.Most food scientists and nutritionists are concerned with the RS₃（retrogradation or recrystallization starch）,which is difficult to be digested by amylase even when heated.In this study the indica broken rice as raw material to prepare rice starch.Rice starch were pregelatinized by microwave technology.The indica resistant starch of type RS₃ was prepared by combining with crystal seed indution and dual enzymatic hydrolysis and the ultrasonic intermittent auxiliary and step debranching enzymatic hydrolysis of isoamylase and pullulanase.The solubility,swelling degree,water retention and other physicochemical properties of indica resistant starch of type RS₃ were studied.The main research contents and conclusions are as follows:1、Indica starch pregelatinized by microwave as a material and the yield of RS₃ was investigated.Through the single factor experiments and two response surface tests.Optimization of the ultrasonic intermittent auxiliary and step debranching enzymatic hydrolysis of isoamylase and pullulanase of RS₃.The results showed that under the conditions:starch mass fraction,10%;isoamylase hydrolysis temperature,50℃;isamylase hydrolysis pH,5.0;pullulanase hydrolysis temperature,60℃;pullulanase hydrolysis pH,4.5;ultrasonic power,70 W,the optimal parameters were obtained as follows:isoamylase amount,16 U/g,isoamylase hydrolysis time,3 h;pullulanase amount,8 U/g,pullulanase hydrolysis time,2.2 h;ultrasonic treatment time,7 min;ultrasonic intermittent time,2.7 h.Under these conditions,the yield of indica rice resistant starch of type RS₃ was 18.19%.2、Indica starch pregelatinized by microwave as a material and the yield of RS₃ was investigated.Through the single factor experiments and response surface tests.Optimization of crystal seed induction combined with step debranching enzymatic hydrolysis of isoamylase and pullulanase of RS₃.The results showed that under the conditions:starch mass fraction,10%;isoamylase hydrolysis temperature,50℃;isamylase hydrolysis pH,5.0;pullulanase hydrolysis temperature,60℃;pullulanase hydrolysis pH,4.5;crystal seed adding temperature,40℃,isoamylass hydrolysis time,4h,the optimal parameters were obtained as follows:crystal seed 5%;isoamylase 0.8 U/g;pullulanase 0.8 U/g;pullulanase hydrolysis time 3.50 h.Under this optimum preparation condition the yield of indica rice resistant starch of type RS₃ was 27.42%.3、The effect of ultrasonic auxiliary-dual enzyme method and seed induced-dual enzyme method on the structure and physicochemical properties of indica rice resistant starch of type RS₃ were researched in this study.The results showed that the structure of the raw starch was polyhedron,the edge of the surface was distinct,the crystal form was type A,and the crystallinity was only 8.9%.While the structure of RS₃ were made by ultrasonic auxiliary-dual enzyme method and seed induced-dual enzyme method became rough and uneven,the solubility,swelling degree and water holding capacity were decreased,the crystal forms were dense and stable type B or type B+V,and the highest crystallinity was20.10%.There was no new functional group was formed during the formation process of RS₃ and their chemical structure has not changed.The enzyme addition sequence showed that pullulanase was added before isoamylase better to promote starch crystal formation of ordered structure.