Effects of different storage temperatures on the intra- and intermolecular retrogradation and digestibility of sago starch

Three different storage temperatures including room temperature (RT), 4 degrees C and & minus;20 degrees C were investigated in this study, with respects to their effects on the retrogradation property and in vitro digestibility of gelatinized sago starch. Storage at & minus;20 degrees C resulted in the highest amount of both intra-and intermolecular double helices and a fracture-like structure under scanning electron microscopy (SEM). These crystallites were more homogenous while less thermally stable than that from RT and 4 degrees C storage conditions. Storage at RT significantly increased the stability and heterogeneity of the formed crystallites, resulting in a sponge-like structure under SEM. Causally, the digestion rate of retrograded sago starch by alpha-amylase was significantly lowered after storage at & minus;20 degrees C compared to that at RT and 4 degrees C. The crystallite heterogeneity, thermal stability, and ratio of inter-to intramolecular double helices were possibly the main driven factors for the observed digestion rates instead of the amount and micro-morphology of the crystallites. These results supply potential tools for the manufacture of food products with slower starch digestibility. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the effects of different storage temperatures on the retrogradation property and in vitro digestibility of gelatinized sago starch. Lower storage temperature (-20°C) resulted in higher amount of double helices but less thermal stability, whereas room temperature storage increased the stability and heterogeneity of crystallites. The digestion rate was significantly lowered after -20°C storage, possibly due to crystallite heterogeneity, thermal stability, and ratio of inter-to intramolecular double helices.