Retrograded resistant starch (RS3), as a prebiotic, has attracted great attention owing to a good stability and an edible feature. This study aims to demonstrate how molecular weights, structural properties, in vitro digestibility and hydrothermal behaviors of RS3 are influenced by gradient ethanol fractionation assisted with annealing. Waxy maize dextrin (WMD) was sequentially precipitated by different volume ratios of dextrin solution to absolute ethanol in an order of 0.5:1, 1:1, and 1.5:1. RS3 prepared from WMD through tertiary precipitation (RWMD 1.5) exhibited higher resistance to digestibility and hydrothermal stability. This was attributed to the high production of slowly digestible starch (SDS, 63.1 %) and resistant starch (RS, 32.1 %), together with the highest peak temperature (101.3 °C) and gelatinization enthalpy (16.2 J/g). Moreover, RWMD 1.5 was largely formed by uniform and short WMD (weight-average molecular weight, 2.990 kDa), which thus caused the formation of homogeneous A-type crystals with ordered structures.
Keywords: Digestibility; Gradient ethanol fractionation; Hydrothermal stability; Retrograded starch; Waxy maize dextrin.
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