Effect of heat-moisture treatment on the in vitro digestibility and physicochemical properties of starch-hydrocolloid complexes

Abstract

The effect of heat-moisture treatment (HMT) on the in vitro digestibility and physicochemical properties of starch-hydrocolloid complexes of various structures was investigated, employing Gum Arabic, Xanthan Gum, and Guar Gum. HMT was performed at 120 °C for 4 h with a starch moisture content of 20%. HMT was shown to increase the slowly digestible starch content from 6.89% to 11.41%, and that of resistant starch from 7.02% to 18.04%. After blending with hydrocolloids, digestibility can be further reduced, with a Guar Gum-starch complex (1:40 ratio) showing the lowest rate of digestion. Scanning electron microscopy (SEM) and particle size analysis revealed that starch granules aggregated due to hydrogen bond interactions. Starch granules formed larger aggregates in the presence of Xanthan Gum or Guar Gum than Gum Arabic. SEM also demonstrated that the surface of starch granules became smoother after HMT. Rapid viscosity analysis and differential scanning calorimetry revealed that HMT significantly reduced the peak viscosity and setback of starch and significantly delayed gelatinization onset, peak, and conclusion temperatures. Finally, X-ray diffraction revealed that the A-type crystal form of the complexes was unaltered, but the relative crystallinity decreased. Overall, this study provides useful information for the development of healthful, low-GI, functional foods.