Effect of Cooking and In Vivo Glycemic Response of Sri Lankan Traditional Rice: A Source of Sustainable and Underutilized Functional Food

Abstract

The availability of scientific information on the nutrient composition of cooked rice and glycemic responses of Sri Lankan traditional rice varieties with a high export potential is scarce. This study determined the nutrient composition (moisture, ash, crude fat, and protein, digestible (DC) and total carbohydrate (TC), resistant starch (RS), insoluble (IDF), soluble (SDF), and total dietary fiber (TDF)), amylose, amylopectin, and glycemic indices (GI) of sixteen cooked unpolished traditional rice varieties with standard methods. Cooked rice and rice flour contained 55.9-70.6% (fresh weight) and 6.2-9.5% (dry basis) moisture respectively. Ash, crude fat and protein contents were 1.1-1.6%, 4.1-6.0% and 4.8-9.5% respectively. Digestible carbohydrates comprised 73.8-83.8% with over 80% TC. Cooking increased the RS (1.3-5.5%) while IDF, SDF and TDF of cooked rice were 3.8-6.4%, 0.4-4.8%, and 5.4-9.8% respectively. All varieties contained high amylose (24.2-35.7%) except for one variety and elicited either low or medium GI (49-67). GI and amylose of cooked rice showed a significant (P=0.04) negative correlation. Significant (P≤0.05) positive correlation between moisture and rice portions containing 50g of carbohydrate allows the selection of rice that provides low glycemic loads. Unpolished traditional rice, rich in nutrients eliciting low or medium GI are highly suitable in diet plans for controlling the glycemic response and in achieving sustainable health benefits.