This assay determines the total dietary fiber content of food using a combination of enzymatic and gravimetric methods. Samples of dried, fat-free foods are gelatinized with heat stable α-amylase and then enzymatically digested with protease and amyloglucosidase to remove the protein and starch present in the sample. Ethanol is added to precipitate the soluble dietary fiber. The residue is then filtered and washed with ethanol and acetone. After drying, the residue is weighed. Half of the samples are analyzed for protein and the others are ashed. Total dietary fiber is the weight of the residue less the weight of the protein and ash.
Uses a combination of enzymatic and gravimetric methods. This procedure is based on the method published in Official Methods of Analysis, 15th ed., AOAC, Arlington, VA, Vol. II, Sec. 985.29, 1105 (1990).