ABSTRACT
A general scheme has been developed to determine sugars, starches, total dietary fiber, and dietary fiber polysaccharides in a half-gram freeze-dried food sample. Triplicate samples are weighed into teflon tubes; free sugars (mono-and disaccharides) are extracted into 80% methanol and analyzed on a gas-liquid chromatograph (GLC). The residues after 80% methanol extraction are incubated with amyloglucosidase and hydrolysates are removed for glucose determination by GLC. Starch content is calculated as glucose (g/100 g)×0.9. The remaining hydrolysates are diluted with 95% ethanol, filtered through glass crucibles matted with Celite filter aid. The residues are dried and weighed. One of the triplicate residues is analyzed for crude protein, and the second one for ash. The third residue is hydrolyzed in H2SO4; analyzed for neutral sugars on GLC and uronic acids spectrophotometrically. Total dietary fiber content is calculated as the residue weight corrected for residual protein and ash, and dietary fiber polysaccharides are the sum of neutral sugars and uronic acids. According to this scheme, complex carbohydrates are found in the fractions represented by starch, total dietary fiber, and dietary fiber polysaccharides. Data will be presented on the contents of these complex carbohydrate fractions of some frequently consumed foods.
