Structural transformations at different organizational levels of ethanol-treated starch during heating

Abstract

Heating ethanol-treated starch (ETS) is the simplest method to produce granular cold-water swelling starch. Structural transformations of ethanol-treated maize and potato starch (ETMS and ETPS) at the crystalline, lamellae and granular structural levels during heating were investigated through in situ wide- and small-angle X-ray scattering (WAXS and SAXS) combined with light microscopy (LM). The result of in situ WAXS indicated that the native crystalline structure was slowly disrupted up to 82 and 60 °C for ETMS and ETPS, respectively. The initial temperature for the formation of a V-type crystalline structure of ETMS was observed to be 86 °C. The result of paracrystalline analysis suggested that the crystalline lamellae of ETS realigned toward a more ordered register when heated to 80 °C and 70 °C for ETMS and ETPS, respectively. The granular forms of ETMS and ETPS were still preserved at 100 °C, although the characteristic of Maltese cross was not observed. A model was proposed to elucidate transformations of ETS at the three structural levels of starch during heating.

Keywords: Crystalline structure; Ethanol-treated starch; Lamellae and granular levels; Structural transformations.