THE EFFECT OF FIBER SOURCE AND FERMENTATION ON THE APPARENT HYDROPHOBIC BINDING-PROPERTIES OF WHEAT BRAN PREPARATIONS FOR THE MUTAGEN 2-AMINO-3,8-DIMETHYLIMIDAZO[4,5-F]QUINOXALINE (MEIQX)

Preparations of dietary fibre have an ability to bind potentially toxi c compounds in vitro, but it is unclear how the measured binding prope rties are a reflection of either the relative affinity of such compoun ds for fibre or the saturation binding capacity of the fibre. Cooking and processing of foods and fermentation activity in the colon can res ult in significant modification of the structure of the fibre matrix. Hence, binding properties measured in vitro may be significantly alter ed from those at the proposed site of fibre activity. Using cell wall material (CWM) prepared from three distinct wheat fibre sources, the e ffects of fermentation have been monitored and the consequences on the binding properties assessed. The CWM preparations were fermented for either 0, 6, 18 or 24 h in vitro, using a human faecal inoculum. The c oarse bran CWM was also subjected to a simulated gastric treatment. Fe rmentation resulted in a loss of material from each CWM preparation, t he loss being consistent with the bran source, and the maximum extent of fermentation was reached within 18 h. The in vitro binding of the m utagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) to the un fermented and fermented fibre fractions showed fine bran CWM had a muc h higher affinity for MeIQx than coarse bran. A 6 h fermentation had l ittle effect on the binding affinity to fine bran, but the affinity fo r coarse bran became similar to that of the fine bran. Further ferment ation for 18 h or 24 h resulted in a further slight increase in the bi nding affinity for coarse and fine bran, but, more significantly, the binding capacity of each was increased. The binding properties of the beeswing bran were not significantly affected by fermentation. Wheat b ran has the potential to bind hydrophobic mutagens in the diet and thi s potential can be enhanced after fermentation under colonic condition s.