Identification of gas-producing components in different varieties of Phaseolus vulgaris by in vitro fermentation

Phaseolus vulgaris consumption has been limited as part of the occidental d iet owing to flatulence production. Raffinose, stachyose and verbascose hav e been shown to be the main components responsible for flatulence; however, it is thought that soluble fibre could also be involved in this phenomenon . The aim of the present study was to identify the main components of beans influencing flatus. Ten varieties of P vulgaris originating from South Ame rica were first analysed for their main nutrient and carbohydrate fractions . Three of the varieties were then fractionated to extract soluble and inso luble fibres. Various combinations of alpha -galactosides and soluble and i nsoluble fibre fractions, in similar proportions to those contained in cook ed grains, were used as substrates for in vitro fermentation studies using human faecal inoculum to determine the fermentative capacity of each of the three fractions. Considering the white varieties, total gas production and acidification of the medium were correlated with fermented organic matter from soluble fibre (R-2=1)) and with alpha -galactosides (R-2=0.75). On the other hand, tannins present in pigmented varieties did not seem to interfe re significantly in fermentation of soluble fibre. The total production of gas per gram of mixed fractions of soluble fibre and alpha -galactosides in proportions found in cooked grains was lower than that expected from each substrate separately. It can be concluded that soluble fibre and alpha -gal actosides are good substrates for endogenous colonic flora subjected to in vitro fermentation studies and are thus responsible for flatulence induced by legume consumption. (C) 2001 Society of Chemical Industry.