Differences in the dietary fiber content of fruits and their by-products quantified by conventional and integrated AOAC official methodologies

Accurate determination of total dietary fiber (DF) and its soluble (SDF) and insoluble (IDF) fractions is relevant for food analysis research and nutritional labelling. AOAC integrated DF methodology (AOAC 2011.25, IM) has procedure differences compared to the traditionally used AOAC method (991.43, TM), resulting in different DF quantification. However, IM has been mostly performed for cereal-based products and its application in sources such as fruit products needs to be studied. The aim of this study was to compare the DF content obtained by TM with that achieved using IM in pulps and peels of banana (Musa paradisiaca), mamey sapote (Pouteria sapota), mango (Mangifera indica), Meyer lemon (Citrus meyeri), orange (Citrus sinensis), prickly pear (Opuntia ficus-indica), tamarind (Tamarindus indica), and watermelon (Citrullus lanatus). Samples containing high starch (banana and its peel, mamey sapote and mango pulp) showed higher IDF values when IM was used. Differences were observed when pectinaceous fruits (orange, Meyer lemon, mango and prickly pear) were assayed, since soluble and insoluble pectins are underestimated by TM. Fruits with a high content of non-digestible oligosaccharides showed higher SDF values when assayed by IM. The use of IM in fruits and their by-products provides relevant information about DF fractions and reduces DF underestimations typically observed when assayed by TM.