Characterization of Resistant Starch from Autoclaved Wheat Starch

Abstract

Abstract The nature of a particular type of in vitro undigestible starch, i.e. resistant starch (RS), was studied. This type of undigestible starch is found in products processed at relatively high moisture contents, such as baking and autoclaving. The RS was concentrated by enzymic digestion of available starch and protein and recovered by centrifugation. RS from autoclaved wheat starch was evaluated by various methods. The crystallinity was studied by X‐ray diffraction and DSC. The degree of polymerization (DP) was evaluated with gel permeation chromatography and iodine binding and the starch content and linearity by enzymic methods. The results indicate that RS consist of crystallized, linear α‐glucans of relatively low molecular weight (DP approx. 65). The recovery of RS after various drying procedures, and the introduction of a thermostable amylase (Termamyl®) in the RS assay was also studied. Oven‐drying of the fibre residues used in the analysis had no significant effect on RS recovery, whereas freeze‐drying was accompanied by a slight increase in RS content. The use of Termamyl®, in the assay of RS in the fibre residues, decreased the yield of RS by 10–15%.