Studies on the in vitro starch digestibility and the glycemic index in rice cultivars differing in amylose content

Abstract

Starch digestibility was studied in eight rice cultivars with four levels of amylose content.An in vitro digestion method with α-amylase was applied to estimate the glycemic index in vivo based on kinetics of starch hydrolysis. The pattern of digestibility was described by using the Ørskov and McDonald's equation. The results indicated that amylose and non-digestible oligo saccharide contents affected the pattern of starch digestion. The content of amylose was significantly correlated with the amount of the digestible fraction and the content of non-digestible oligo saccharide with the rate of starch hydrolysis. Starch tends to be hydrolyzed more rapidly and completely in the waxy and low-amylose types of rice varieties than in intermediate- and high-amylose types. The estimated glycemic index was significantly correlated with the break-down value measured with a rapid visco analyzer.