Nutritional and antioxidant properties of selected traditional rice (Oryza sativa L.) varieties of Sri Lanka

Five traditional red and white rice varieties of Sri Lanka namely Kurulu Thuda, Nilkanda, Heeneti, MaaWee and Suwadal were studied for a range of nutritional and antioxidant properties (AP). Whole grain flour of the selected varieties were studied for moisture, crude fat, crude protein, crude ash, available carbohydrates, total dietary fiber (TDF) and sugar contents using standard analytical techniques (n=3), while oil extracted from rice bran was studied for the fatty acid profile using gas chromatographic technique (n=3). Antioxidant properties were studied using ferric reducing antioxidant power (FRAP) and 2-azino-bis (3-ethylbenzothiazoline-6-sulfonic) acid (ABTS) radical scavenging activity for the 70% ethanolic extracts of the rice bran (n=3 each). Results showed significant (P < 0.05) differences for both nutritional and AP among the varieties tested. However, between red and white rice varieties variation was significant (P < 0.05) only for the AP. Among the selected varieties, Suwadal had the highest TDF, Heeneti had the highest crude ash content while Maa Wee had the highest protein and sugar contents. Both Suwadal and Kurulu Thuda showed the highest fat content. Oleic acid was the most predominant fatty acid in all rice bran oil types. The highest oleic and palmitic acids were observed in Kurulu Thuda while MaaWee had the highest linoleic acid content. For AP, the highest activities for both FRAP and ABTS radical scavenging activity was observed for the red rice variety Kurulu Thuda while white rice variety Suwadal had the lowest. In conclusion, nutritional and AP vary significantly among the varieties and only AP varies significantly between the red and white rice types.