Fiber

Method Description

This method determines insoluble and soluble dietary fiber, which are summed to calculate total dietary fiber content. Samples (defatted if necessary) are enzymatically digested with α-amylase, protease, and amyloglucosidase to remove starch and protein. The remaining insoluble residue is filtered, dried, and measured gravimetrically as insoluble dietary fiber. The filtrate is collected, and ethanol is added to precipitate soluble dietary fiber, which is then filtered, dried, and measured gravimetrically. All residues are corrected for ash and protein content. Total dietary fiber is calculated as the sum of insoluble and soluble fiber. This method is applicable to most food products; however, samples containing psyllium or fructans should be submitted under specific test codes. High-fat (>5%) samples require special handling.