Effect of Raw and Heat-Moisture Treated High-Amylose Corn Starch on Fermentation by the Rat Cecal Bacteria

Abstract

Resistant starch content of high-amylose corn starch (HAS) was doubled by heat-moisture treatment. Resistant starch content of HAS and heat-moisture treated high-amylose corn starch (HMT-HAS) were 31.8 and 67.3%, respectively, as determined by enzymatic-gravimetric method. Effects of the two types of high-amylose corn starches, HAS and HMT-HAS, on starch fermentation, microflora, pH, short chain fatty acid (SCFA) content and β-glucuronidase activity in the cecal content have been investigated. Rats were given ordinary corn starch (OCS; control), HAS or HMT-HAS at 10% level for 10-13 days. The cecal and colorectal content's weights were larger in HAS and HMT-HAS groups than in the OCS group. The cecal content's weight did not differ between HAS and HMT-HAS groups, while the colorectal content's weight was higher in the HMT-HAS group than in the HAS group. The upper and lower small intestinal and cecal starch contents were significantly higher in the HAS and HMT-HAS groups than in the OCS group, whereas there were no differences between colorectal starch content in group OCS and HAS. Starch excretion in feces was significantly higher in groups HAS and HMT-HAS than in group OCS, the increase in the HMT-HAS group was especially remarkable. The composition of the cecal microflora was not effected by the diet. β-Glucuronidase activities in rats fed HAS or HMT-HAS decreased. SCFA concentration was higher in groups HAS and HMT-HAS than in group OCS, and the cecal pH was lower in groups HAS and HMT-HAS than in group OCS.