[4-1600-A] Postharvest/Food Technology and Process Engineering (3)

[4-1600-A-08] In Vitro Examination of Starch Digestibility and Antioxidant Activities of Amaranth Grains

*Xiaoyan Xiong¹, Florencio Jr. Collado Reginio^1,2, Sukanya Thuengtung¹, Sunantha Ketnawa¹, Yukiharu Ogawa¹ (1. Graduate School of Horticulture, Chiba University(Japan), 2. Institute of Food Science and Technology, College of Agriculture and Food Science, University of the Philippines Los Baños(Philippines))

Keywords:Amaranth grain, In vitro digestion, Antioxidant activities

Amaranth grain is a pseudo-cereal crop which is rich in both macro- and micronutrients. Apart from having high starch content, the phytochemicals in amaranth grains are abundant especially phenolic acids. In this study, the digestibility of starch in amaranth was examined by means of an in vitro simulation and the total phenolics, flavonoids, and antioxidant activities of two different solvent extracts from raw and cooked grains were determined. Whole grain and slurry states of cooked amaranth were subjected to simulated in vitro gastrointestinal digestion and starch hydrolysis (%) was computed based on the free glucose content of the digested fractions collected at different time periods. Additionally, raw and cooked whole amaranth grains were evaluated for their total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activties (ferric reducing antioxidant power [FRAP], DPPH and ABTS free-radical scavenging activity, and metal ion chelating [MIC] activity) using sodium phosphate buffer (100mM, pH 7.4) and 80% (v/v) methanol as extracting solvents. Results showed that after 360 min of in vitro gastrointestinal digestion, the whole grain cooked amaranth grain showed a relatively lower starch hydrolysis (66.82±1.60%) than the slurry state (80.44±3.91%)., This was accounted to the differences in morphological structure. It was also found that raw amaranth grain showed higher TPC, TFC, and antioxidant activity values when compared to cooked grain, except for DPPH, and these phenolic compounds were released more in sodium phosphate buffer than in methanol solvent possibly due to more water-soluble compounds of the grain. The results indicated that amaranth grain could be regarded as a healthy food as it can be a potential source of natural antioxidant and, at the same time, whole amaranth grain could help in controlling blood glucose level changes because of its slow rate of digestion.