5.7. Estimation of Dietary Fibre Content

Total dietary fiber (TDF), soluble dietary fiber (SDF), and insoluble dietary fiber (IDF) were determined by using an enzymatic–gravimetric method with the fiber assay kit (AOAC 991.43) method [33,34]. In brief, one gram of sample suspended in Mes-Tris buffer was sequentially digested by heat stable α-amylase for 15 min in a boiling water bath, after which protease and amyloglucosidase were added and the mixture was held for 30 min at 60 °C. After filtration, the IDF was recovered from enzyme digestate, dried at 105 °C, and then weighed. SDF in the filtrate was precipitated with ethanol and filtered. The precipitate, referred to as SDF, was dried at 105 °C and weighed. IDF and SDF contents were corrected for residual protein and ash content. The TDF content was the sum of IDF and SDF.