Antioxidant activity and glycemic index of resistant starch from black glutinous rice

Abstract

Type 2 diabetes mellitus ((T2DM) is a global public health manifested by hyperglycemia due to insulin resistance. Rice is the main staple food for the world's population but has a high glycemia index (GI) value. Therefore, this research was aimed to produce resistance starch (RS) from black glutinous rice with different methods – autoclave and annealing, freeze-thawing, and acid methanol methods.  The RS content, total phenolic compound content, antioxidant activity, and estimated GI (pGI) were investigated.  Results showed that the autoclave and annealing method yielded highest RS content of 27.33±8.56%, followed by freeze-thawing, 15-day acid methanol, and 30-min acid methanol methods. The RS from the autoclave and annealing method also had highest total phenolic content (61.55±1.19 mg gallic acid/g sample) and antioxidant activity by 2,2-Diphenyil-picrylhydrazyl (DPPH, IC50 of 7.40±0.24 mg/ml) and ferric reducing antioxidant power (FRAP, 75.47±0.51 mg tocopherol equivalent/g extract). Moreover, The RS from the autoclave and annealing method also had the lowest pGI (57.32±0.74). In conclusion, the autoclave and annealing process gave the highest yield of RS with the highest total phenolic content and antioxidant activity; and with the lowest GI compared to the freeze-thawing and acid methanol methods.