Dietary Fiber Content of Cross-linked Phosphorylated Resistant Starch (RS4) Determined by the Prosky and McCleary Methods. Part II. Comparison of Assay Data,

Abstract

Cross-linking normal starch with a low level of phosphate groups (≈1/30 anhydroglucose units) is a general method used to dramatically increase the resistant starch (RS) content of a starch. Currently, total dietary fiber is recognized by Codex Alimentarius to be the sum of nondigestible polysaccharides, resistant oligosaccharides, and RS. Determining total dietary fiber in a food containing a substantial level of RS is difficult. RS is chemically equivalent to digestible starch, including the majority (≈97%) of the sparsely cross-linked phosphorylated (CLP) RS4-type starches. Resistance to digestion arises principally from variations in microstructure that limit the diffusion of alpha-amylase to starch molecules. For CLP (≈0.4% P) wheat starch, the McCleary method for measurement of total dietary fiber (AACCI Approved Methods 32-45.01 and 32-50.01 or AOAC Methods 2009.01 and 2011.25) gives a total dietary fiber content of ≈25% compared with ≈85% given by the Prosky method (AACCI Approved Methods 32-05.01...