GASTROINTESTINAL OR SIMULATED IN-VITRO DIGESTION CHANGES DIETARY FIBER PROPERTIES AND THEIR FERMENTATION

This study evaluated the effect of digestion on the chemical and physi cochemical characteristics of dietary fibre and on its behaviour durin g fermentation. Three dietary fibre sources (wheat bran, barley bran a nd beet fibre) were recovered from ileal cannulated pigs after in vivo digestion and prepared by in vitro enzymatic treatment simulating dig estion. Raw substrates and fibre residues were analysed for their chem ical and physicochemical properties as well as their potential ferment ation by human colonic bacteria. In vitro and in vivo treatments led t o insoluble residues, enriched in cell wall polysaccharides, with simi lar cell wall sugar composition and physicochemical properties. Degrad ations of cell wall polysaccharides with losses of sugar residues occu rred mainly after in vivo digestion, especially for pectins from beet fibre and B-glucans from barley bran. Solubilisation of B-glucans remo ved highly fermentable substrates for further fermentation. For beet f ibre, removal of pectins led to increased hydration properties and fas ter fermentation of cell-wall polysaccharides. Enzymatic treatment sim ulated correctly the passage of fibre through the digestive tract, mod ifying the cell-wall matrix and predisposing the fibre to further ferm entation. (C) 1998 SCI.