Abstract
This study was designed to investigate the influence of cooking on the glycemic index (GI), amylose, and amylopectin contents of two rice varieties. Two rice varieties (foreign long rice and ofada) were sourced for, divided into two, one portion cooked and the other used raw. The sugar, starch, amylose, and amylopectin contents as well as glycemic indices, antioxidant properties, and the ability of the rice to inhibit carbohydrate‐hydrolyzing enzymes (α‐amylase and α‐glucosidase) were determined. In addition, polyphenol content was determined. The results revealed that cooking caused a significant increase in starch content of the rice varieties. In the same vein, cooking increases the amylopectin content but has no effect on the amylose content. In addition, cooking shows no effect on polyphenol content but significantly increases radical scavenging ability of rice varieties used in this study. Furthermore, cooking lower the α‐amylase and α‐glucosidase inhibitory properties of two rice varieties except for foreign rice. However, the inhibitory effect of both cooked and raw foreign and ofada rice on α‐amylase and α‐glucosidase coupled with their low GI may explain their important role in controlling blood glucose level.
Highlights
Carbohydrates are sole source of energy in human nutrition
The results showed that cooking slightly altered the glycemic index (GI) of two rice varieties used in this study: raw [foreign rice (48.4%) and ofada rice (49.2%)] and cooked [foreign rice (49.0%) and ofada rice (51.8%)]
The results revealed that cooking has no effect on total phenol, total flavonoid, and ferric reducing antioxidant property, whereas it significantly increases the ABTS radical scavenging ability of two rice varieties
Summary
Carbohydrates are sole source of energy in human nutrition. Some years back, hyperglycemia and obesity play front role in health problems affecting many lives. Alpha-amylase and alpha-glucosidase play crucial role in sudden rise in blood glucose level observed in diabetic patients after taking carbohydrate-rich foods due to hydrolysis of carbohydrate by these enzymes into simpler monomeric unit (glucose) (Kim, Jeong, Wang, Lee, & Rhee, 2005; Kwon, Vattem, & Shetty, 2006). Attenuation of these enzymes involved in the hydrolysis of starch can lower the postprandial increase in blood glucose after eating carbohydrate-rich food and this could be of importance in the management of type 2 diabetes. Having in mind the lack of scientific literatures on the effect of cooking on in vitro GI, α-amylase, and α-glucosidase inhibitory properties of grains, present study was designed to assess the effect of cooking on amylose and amylopectin contents, sugar and starch contents, GI, and antioxidant properties of two rice varieties, as well as their effects on starch hydrolyzing enzymes (α- amylase and α-glucosidase)
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