The composition of dietary fibre-rich extrudates from oat affects bile acid binding and fermentation in vitro

A series of extrudates was prepared from oat meal, oat bran and Novelose 330®, differing in concentrations of individual dietary fibre (DF) components, such as β-glucan and resistant starch, as well as total DF. After simulated digestion, the digested DF-rich oat-based extrudates were used to evaluate their physiological effects in vitro. A strong interaction occurred between the digested extrudates and bile acids (BA). The binding of BA increased with increasing proportions of oat bran, total DF, insoluble DF and β-glucan in the extrudates. Dihydroxy-BA was more strongly bound to the extrudates than trihydroxy-BA. Interactions at pH 5.0 were greater than at pH 6.5. During fermentation of digested extrudates with human faecal samples, concentrations of short-chain fatty acid (SCFA) formed and the molar proportion of butyrate increased continuously. Higher SCFA concentrations were found when extrudates contained more oat bran, soluble and insoluble DF and β-glucan. Extrudates, on the basis of oat, have several beneficial nutritional and protective effects in vitro. Therefore, physiological effects occurring in the small and large intestine are also related to the DF composition of the cereal products.