Comparative studies on nutritional and functional properties of selected traditional rice varieties in Sri Lanka

Abstract

Non-communicable diseases are chronic metabolic diseases increasing rapidly around the world. Evaluation of natural food sources in terms of controlling or preventing non-communicable diseases is an immerging research area in food science and nutrition schemes. Traditional rice varieties are one of the food commodities currently becoming popular among health-conscious consumers, as they provide health benefits through bioactive compounds or functional food ingredients other than a variety of nutrients. This study aimed to assess the nutritional and functional properties of selected 20 traditional rice varieties in Sri Lanka. Proximate composition was analyzed for raw rice samples. Methanolic extracts of rice were analyzed for total phenolic content (TPC), total flavonoid content (TFC), carotenoid content (TC), antioxidant, anti-inflammatory and anti-diabetic properties. In vitro gastrointestinal digestion was performed to evaluate the bioavailability of bioactive compounds. Rice samples with higher anti-diabetic properties were tested for a postprandial glycemic response using healthy individuals. The results indicated fresh methanolic extracts of Rath Kadha had the significantly (p<0.05) highest TPC (9.94±0.01mgGAE/g FW) and TC (2.27±0.06 mg/g FW), Beheth Heenati have the highest DPPH% inhibition (84.93±0.81%), Sudu Heenati had the significantly (p<0.05) highest TFC (16.77±0.01mg RE/g FW), anti-diabetic properties (59.54±0.02%) and anti-inflammatory properties (65.85±0.01%). Among the rice varieties subjected to in vitro digestion, Suwadel showed highest significant (p<0.05) TPC (0.45±0.02 mg GAE/g FW) and TFC (2.01±0.02 mgRE/g FW), Ma Vee showed the highest TC (0.24±0.015 mg/g FW) and Pachchaperumal showed the highest DPPH% inhibition (61.77±0.02%) in the gastric phase. In the intestinal Phase Sudu Heenati showed the highest TPC (0.99±0.04 mgGAE/g FW), Ma Vee showed the highest TFC (0.8±0.01 mgRE/g FW) and TC (3.24±0.04 mg/g FW), Beheth Heenati showed the highest DPPH% inhibition (63.98±0.07%). Tested all cooked rice varieties exhibited a lower postprandial glycemic response than glucose. Among the cooked rice varieties Maa Vee showed the lowest peak (97mg/dl) concerning glucose. According to glycemic response, values were significantly (p<0.05) changed with the rice variety. The results highlighted that traditional rice verities are rich with a wide range of functional properties and useful in the management of non-communicable diseases and their complications.