The in vitro digestion of differently structured starch gels with different amylose contents

Abstract

The present study investigated starch in-vitro digestibility in differently structured starch gels formed by corn starches with different amylose contents. Gels formed using normal corn starch (NCS), waxy corn starch (WCS) and high-amylose corn starch (HCS) were subjected to an in vitro sequential dynamic digestion, including an in vitro oral step followed by a dynamic human gastric simulation and an intestinal digestion step. Compared with the WCS gels, the harder gels (formed with NCS and HCS) had lower degrees of swelling, higher degrees of fragmentation and smaller gel particles in the gastric digesta, resulting in greater release of glucose and greater starch hydrolysis in the oral‒gastric step. In the intestinal step, the WCS gel (released from the stomach within 60 min) had the lowest release of glucose because of its lower starch content in the gastric digesta. Also, the native compact granular structure of the HCS gastric digesta resulted in the least starch hydrolysis. The oral‒gastric digestion of these starch gels was more dependent on the gel structure than on the granular characteristics (e.g. amylose content, degree of swelling) of the starch. These findings provide information for manipulating the digestibility of starch through the design of the gel structure.