Nutritionally important starch fractions and estimated glycemic index of selected South Indian rice varieties

Abstract

The nutritionally important starch fractions and in vitro starch digestibility index (SDI) were studied in three commercially available rice varieties and a millet which were subjected to four different cooking methods to validate the claim of low glycemic index. The Hydrolysis index was analyzed to compute Estimated Glycemic Index (EGI) and correlated with SDI. In addition, carbohydrate profile, amylose content, the degree of gelatinization and ultra-structural analysis were also done. The starch fractions differed according to the cooking methods. Samples with high Rapidly Available Glucose (RAG) showed higher Starch Digestibility Index (SDI). The SDI ranged from 17-46, samples cooked by pressure and steaming method had higher SDI. The degree of gelatinization (DG) correlated with total starch (TS) content. The Estimated Glycemic Index ranged from 53-65 categorizing them as medium GI foods. The nutritional properties of rice starch fractions are of immense interest due to their digestion characteristics (slowly digested and absorbed) and therefore, the identification of foods with low glycemic index and low RDS and SDI values could be useful for target population.

Keywords

• commercial rice varieties
• processing methods
• starch fractions
• digestibility
• glycemic responses