Abstract:
Riceberry rice (Oryza sativa L.), is a crossbreed of Kao Hom Nin, a local non-glutinous purple rice and Khoa Dawk Mali 105. Its pigment contains high amount of antioxidant compounds, especially anthocyanins. Previously, riceberry rice exhibited its food application with high antioxidant activity. However, the potential of food application of riceberry rice extract (RBE) in yogurt and beverage products and its postprandial effect on humans remains unknown. In this study, RBE was prepared from a mixture of riceberry rice and distilled water in 1:2 w/v ratio following the freeze-drying process. The results showed that RBE contained phenolic compounds and anthocyanins mainly cyanidin-3-glucoside and peonidin-3-glucoside. The supplementation of RBE to yogurt significantly increased total phenolic (TPC) content, anthocyanin content and antioxidant activity. Furthermore, yogurt representing a reduction of syneresis and firmness can be achieved by RBE. In gastrointestinal digestion, yogurt supplemented with RBE resulted in higher level of TPC, anthocyanin content and antioxidant activity than the control yogurt. The addition of 0.125-0.25% (w/w) RBE into yogurt did not negatively influence the overall acceptability, compared to the control yogurt. The higher TPC and antioxidant activity of yogurt supplemented with 0.125-0.25% (w/w) RBE was observed during 21 days of refrigerated storage. Moreover, acute consumption of yogurt enriched with 0.25% RBE significantly suppressed postprandial plasma glucose and improved postprandial antioxidant status in healthy subjects. The rating scores of hunger, fullness, desire to eat, and satiety were similarity in all types of yogurts. Interestingly, consumption of high-carbohydrate, moderate-fat (HCMF) meal with RBE beverage (0.5% w/v) significantly attenuated postprandial glucose, insulin, triglyceride, free fatty acid and MDA level in overweight and obese subjects. In addition, it significantly reduced inflammatory cytokines (IL-1β, IL-6 and TNF-α) after 3 and 6 h of HCMF-meal consumption. However, there were no significant differences in the rating scores of hunger, fullness, desire to eat, and satiety among tested meals. This study suggests that RBE offers a promising natural ingredient to produce novel yogurt and functional drink in order to reduce glycemic response, improve antioxidant capacity and reduce inflammatory cytokine in humans.
