Kinetic study on the digestibility of lactose and lactulose using small intestinal glycosidases

Abstract

Lactose is mostly hydrolysed in the small intestine, whereas lactulose, recognised prebiotic carbohydrate, reaches the colon to be fermented by the intestinal microbiota. Digestibility of these substrates was investigated by an in vitro digestion model using a Rat Small Intestine Extract (RSIE). A kinetic study of lactose digestion showed levels of hydrolysis (82.8%) at 0.2 mg*mL−1 and the highest hydrolysis rate constant (kobt). Considering these conditions, lactulose showed high resistance to intestinal digestion by RSIE, resulting in low hydrolysis degrees (20.4%) after 5 h reaction. These results underline the suitability of these intestinal extracts under the studied conditions, as a reliable tool to evaluate carbohydrate digestion and support the evidences towards the higher resistance of galactosyl-fructose linkages during its intestinal degradation.