Quantitative Determination And Preparation Of Indica Rice Resistant Starch

Resistant starch (RS) is defined as the total dietary starch that does not digest in the small intestine and can be fermented in the large intestine. The determination of RS and the factors influencing formation of RS were investigated, and RS preparation by use of twin screw extrusion was also examined.RS is determined mainly by the methods of Englyst, Berry, Siljestrom & Asp (S.A.) and Goni. The methods of SA. and Goni were comparatively studied through testing the content of RS in treated rice flour. Goni method showed great advantages in reliability and simplicity in operation compared with S.A. method. Enzymatic treatment and optimum pH for enzymatic reaction are key factors for both methods.The influence of retrogradation factors (ratio of amylose to amylopectin, ratio of starch to water, time of gelatinization, time of cycle, pH, time of retrogradtion, temperature of retrogradation, Ca²⁺) on rice RS preparation was investigated. Two linearity factors (ratio of amylose to amylopectin, time of cycle) and six non-linearity factors (ratio of starch to water, time of gelatinization, pH, time of retrogradation, temperature of retrogradation, Ca²⁺) were obtained. Four different pastes (30%, g/g, based on paste: 40 min and 60 min; 25%, g/g, based on paste: 40 min and 60 min) were respectively prepared from rice starch as the test materials. Factorial test with orthogonalization (4×3) shows that rice starch paste made from gelatinization of 30 min in 30% (g/g, based on paste) starch solution was retrograded under the optimized conditions of pH 7, 1% (g/g, based on rice starch) Ca²⁺, 60℃ for 24 h, resulting in 19% (g/g, based on rice starch) of RS, the highest yield of the tested samples. The four factors influencing RS preparation were ranked as time > temperature > Ca²⁺ > pH.RS preparation with twin screw extrusion was conducted. Two samples with...