Total dietary fibre content of some green and root vegetables obtained at different ethanol concentrations

The effect of reducing ethanol concentration for the precipitation of soluble dietary fibre in the Association of Official Analytical Chemists (AOAC, 1990, 1992, Official Methods of Analysis) enzymatic-gravimetric method 985.29 for total dietary fibre (TDF) in food was investigated. Alcohol concentration was decreased from 76% to 41% and 56% in determining TDF of raw collard and mustard greens, sweet potato leaves and storage roots, and sugar beet leaves and roots. TDF contents of the vegetables at the reduced ethanol concentrations were generally not different from those at the AOAC recommended volume (P < 0.05). When there was a significant difference, the TDF means for the same vegetable varied within the range of the standard deviations. Reduction of ethanol volume can lower analysis cost, lessen environmental organic solvent contamination and shorten filtration time.