Nature of phase transitions of waxy maize starch in water-ionic liquid mixtures

Abstract

The nature of phase transitions of waxy maize starch heated in mixtures of water and ionic liquid (IL) was elucidated using a variety of analytical methods. The transition from a single endotherm to an exotherm followed by an endotherm, and then to a single exotherm was observed with the increasing concentration of IL. The results showed that at To of DSC phase transition no structural disruption had occurred. Except for the water/IL ratios of 1.5:1 and 1:1, there was considerable structural disruption of starch samples that were preheated to Tp or Tp2 of gelatinization transition. No residual structural order was observed at Tc of the gelatinization transition. An exothermic transition at water:IL ratios of 3:1 and 2:1 was attributed to the interaction of ionic liquid and amorphous regions in starch. The molecular disassembly of starch granules during gelatinization in different water:IL mixtures proceeded to completion at different rates.