A comparison of three methods for analyzing dietary fiber in 38 foods

Abstract A rapid gravimetric method for determining dietary fiber has enabled the repetitive analysis of 101 foods in a total diet study covering five Canadian cities. In the present work, 38 samples representing all categories of foods thought to contain dietary fiber were selected among the 101 foods. They were analyzed using the rapid method and two other recognized methods: the AOAC total dietary fiber method and the Englyst gas-chromatography method which measures the nonstarch polysaccharides (NSP). Dietary fiber values using the rapid method ( y ) and the AOAC method ( x ) were closely correlated ( y = 1.02 ξ – 0.13, r 2 = 0.98, n = 38). The Englyst method was in agreement with the latter gravimetric methods for two-thirds of the foods and particularly the vegetables but yielded some lower values, mainly in cereal products. Adding lignin to NSP values improved the agreement between methods. Overall, the values using the rapid method ( y ) were closely correlated with those using the Englyst method plus lignin ( x ): y = 1.07 ξ – 0.31, r 2 = 0.96, n = 38. Results showed that the rapid method provides an accurate and quick estimation of dietary fiber in various foods. This method has been shown to have good precision in a recent collaborative study.