In vitro fermentation of beet fibre and barley bran, of their insoluble residues after digestion and of ileal effluents

The main objective of this study was to determine the form in which beet and barley bran fibres reach the colon, and to evaluate the influence of endogeneous compounds on their patterns of fermentation. Raw fibres (RF), corresponding ileal effluents (IE) from pigs, and insoluble fibre residues (IR) extracted from IE, were fermented with human faecal inoculum for 24 h in an in vitro batch system. For beet fibre, rate but not extent of cell wall sugars degradation was increased (+ 34% at 6 h, P < 0.05) after oroileal transit, due to a more porous structure. For barley bran, oroileal conditions degraded endosperm compounds such as beta-glucans, leading to a lower extent of cell wall glucose fermentation compared with RF (-22% at 24 h, P < 0.05). In the presence of endogeneous substances, degradation of beet fibre polysaccharides was delayed (P < 0.05) at each incubation time but that of barley bran fibre was unaltered. Compared to RF, IR and IE significantly exhibited lower acetate production for beet fibre, and higher propionate and lower butyrate production for barley bran after 24 h. It is concluded that in vivo digestion modified fermentation patterns of both fibres in a manner depending on botanical structure.