In vitro fermentation of different types of α-amylase resistant corn starches

Three types of alpha-amylase resistant corn starches were in vitro fermented (72 h) using cecal content of rat as inoculum. Resistant starches were prepared from native (NCS), retrograded (RSA), and retrograded and boiled (RSB) corn starch by treatment with alpha-amplase to remove digestible starch. Short-chain fatty acid (SCFA) production, molar ratios (acetate: propionate: butyrate), fermentability with respect to lactulose and dry matter disappearance were measured. SCFA production was significantly correlated with non-fermented residue (P < 0.001). The three starches showed a similar fermentability, although the rate of SCFA production and disappearance of substrate were slower for retrograded starches. NCS was fermented early while RSA and RSB prolonged their degradation to 72 h. There were slight differences in the molar ratios of acetate, propionate and butyrate. Structural changes in the materials were observed by scanning electron microscopy (SEM). In summary, commonly utilised domestic cooking and technological treatments modified the in vitro fermentative characteristics of resistant corn starches probably due to structural changes.