This standard specifies the determination method (enzymatic-gravimetric method) of dietary fiber in foods.
This standard is applicable to the determination of total soluble and insoluble dietary fibers in all kinds of vegetable foods and their products, excluding such dietary fiber components as fructooligosaccharide, galactooligosaccharide, polydextrose, resistant maltodextrin and resistant starch.
2 Terms and Definitions
2.1
dietary fiber (DF)
a kind of healthy carbohydrate polymers with the degree of polymerization DP ≥3, including cellulose, hemicellulose, pectin and other monome components, which are found naturally in foods or made through extraction/synthesis and cannot be digested and absorbed by small intestine of human body
2.2
soluble dietary fiber (SDF)
dietary fiber soluble in water, including oligosaccharide and some indigestible polysaccharide
2.3
insoluble dietary fiber (IDF)
dietary fiber insoluble in water, including lignin, cellulose and some hemicelluloses
2.4
total dietary fiber (TDF)
the sum of soluble dietary fiber and insoluble dietary fiber
3 Theory
Remove protein and starch from the dry specimen through enzymatic digestion by thermostable α-amylase, protease and glucosidase, after which precipitate the specimen with ethanol, filter it by suction, then rinse the residue with ethanol and acetone and dry it for weighing to get the total dietary fiber residue. Take the same specimen for enzymolysis, directly filter it by suction, rinse it with hot water and dry the residue for weighing to get the insoluble dietary fiber residue; precipitate the filtrate with ethanol which is 4 times of the filtrate volume, filter it by suction and dry it for weighing to get the soluble dietary fiber residue. The contents of total insoluble and soluble dietary fibers in the specimen may be calculated by deducting the corresponding contents of protein, ash content and reagent blank in the residues of various dietary fibers.
