Phytic acid content may affect starch digestibility and glycemic index value of rice (Oryza sativa L.).

Phytic acid (PA) is an anti-nutrient present in cereals and pulses. It is known to reduce mineral bioavailability and inhibit starch digesting α-amylase (which requires calcium for activity) in the human gut. In principle, higher the PA, lesser is the rate of starch hydrolysis. It is reflected in the lower glycemic index (GI) value of the food. People leading sedentary life and consuming rice as a staple food are likely to develop type-II diabetes. Hence, this study was planned to understand how PA content of different rice varieties affects their GI.The rice Khira and Mugai which had very low PA (0.30, 0.36g/kg respectively) had higher GI and α-amylase activity, while Nua Dhusara and the pigmented rice Manipuri black rice (MBR) which had high PA (2.13, 2.98g/kg respectively) showed low α-amylase activity and GI values. This relationship was statistically significant, though a weak relationship was found in the pigmented rice. Expression levels of MIPSI, IPKI and GBSSI dramatically increased in the middle stage of grain development in all of the six genotypes having contrasting PA and GI. Maximum expression of MIPSI and IPKI was observed in Nua Dhusara and MBR (which had high PA) while GBSSI in Khira and Mugai (with higher GI) at middle stage showing a negative correlation between PA and GI.The data indicate that high PA content in rice might have an adverse effect on starch digestibility resulting in slower starch digestion in human gut and consequently low glycemic response. This article is protected by copyright. All rights reserved.