Ratio of Amylose and Amylopectin as indicators of glycaemic index and in vitro enzymatic hydrolysis of starches of long, medium and short grain rice

Abstract

Background: Rice (Oryzasativa L.) is the staple food of over half the world’s population. The major carbohydrate of rice is starch, which is about 72 to 75%. Rice can be classified into three different types: long-grain, medium-grain and short-grain rice based upon their length as compared to their width. Aim of the study was to predict the glycemic index of long, medium and short grain rice based on amylose, amylopectin ratio and to study in vitro hydrolysis of starch of long, medium and short grain rice by salivary and pancreatic amylases and formulate the right type of rice to be consumed by diabetics. Methods: Starches were isolated from long, medium and short grain rice. Amylose and amylopectin from the isolated starches were estimated. Starches isolated were subjected to enzymatic hydrolysis by salivary amylase and pancreatic amylase under optimum in vitro conditions and reducing sugars released after hydrolysis and incubation period of   0, 5, 10, 15, 20 and 30 minutes were estimated by Folin-Wu method. Results were analysed using unpaired t-test and statistical significance was established.Results: Long grain rice was found to have high amylose and low amylopectin content as compared to medium and short grain rice. Long grain rice showed slow release of reducing sugars as compared to medium and short grain rice.Conclusions: Long grain rice because of its high amylose content is a low glycemic food and can be consumed by diabetics. Sustained slow release of reducing sugars given by long grain rice is desirable in diabetics.