Analysis of dietary fibre of boiled and canned legumes commonly consumed in the United Kingdom

• The fibre content of legumes consumed in the UK was analysed by the AOAC method.
• Canning reduces the fibre content of legumes by 30% compared to boiling.
• Two thirds of fibre in cooked legumes is insoluble fibre.
• An NSP to AOAC-fibre conversion factor of 1.43 has been generated.

The use of different analytical methods to measure the dietary fibre content of foods complicates the interpretation of epidemiological studies. The aim of this study was to determine the total (TDF) and insoluble (IDF) fibre content of 14 boiled and canned legumes commonly consumed in the UK using the Association of Official Analytical Chemists (AOAC) enzymatic gravimetric method. The fibre values obtained were compared to non-starch polysaccharide (NSP) values. The results showed that mean values for TDF (2.7–11.2 g/100 g) were higher than NSP (2.6–6.7 g/100 g), with a mean NSP:TDF ratio of 1:1.43. TDF was correlated with NSP (r = 0.6; p = 0.02). Canning significantly reduced TDF and IDF by an average of 30% and 26% compared to boiling respectively. However, IDF represented at least 60% of the TDF in both boiled and canned samples. In conclusion, fibre values are affected by the processing and analytical method used.