STUDIES ON DIETARY FIBER .3. IMPROVED PROCEDURES FOR ANALYSIS OF DIETARY FIBER

Three related methods, A-C, are described for analysis of dietary fiber (DF). Homogenized and/or milled foodstuff is extracted with 80% ethanol and light petroleum ether. The extracted residue is analyzed directly for the DF and starch content (method B) or treated further with thermostable .alpha.-amylase at 96.degree. C and amyloglucosidase at 60.degree. C. Insoluble and soluble DF components were then separated by centrifugation and, respectively, dialysis and freeze-drying of the supernatant (method A). Alternatively, insoluble and soluble DF components were isolated together by precipitation of soluble fiber in 80% ethanol and subsequent centrifugation (method C). Neutral polysaccharide constituents were analyzed as alditol acetates, uronic acids by a decarboxylation method, and Klason lignin by gravimetric techniques. Starch was determined enzymatically. A satisfactory correlation between the different DF methods was observed for several food samples.