Dissolution Behavior of Maize Starch in Aqueous Ionic Liquids: Effect of Anionic Structure and Water/Ionic Liquid Ratio

摘要

The effect of the anionic structure of ionic liquids (ILs) and water/IL ratio on the dissolution behavior of maize starch at room temperature (22–23 °C) was investigated. The ILs used were 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), 1-ethyl-3-methylimidazolium formate ([C2mim][HCOO]), and 1-ethyl-3-methylimidazolium acetate ([C2mim][CH3COO]). The structural analysis indicated that the long- and short-range molecular order in the starch after treatment with water/[C2mim][Cl] and water/[C2mim][HCOO] mixtures decreased with the decreasing water/IL ratio from 10:1 to 2:1 and was completely disrupted at the 2:1 ratio. However, the ordered structure of starch was disrupted completely in the water/[C2mim][CH3COO] ratio of 5:1. The disruption extent of starch structures followed the order: [C2mim][CH3COO] > [C2mim][HCOO] > [C2mim][Cl] at water/IL ratios of 10:1 and 5:1, but the opposite was observed at lower water/IL ratio (2:1). Our results clearly showed that both the nature of the anion and water/IL ratio affected the dissolution behavior of maize starch. The hydrogen bonding capacity of IL anions and viscosity of water/IL mixtures were proposed to play the key roles in the structural disruption of starch. These findings would be of great importance for rationally designing “green and sustainable” processes for the utilization of promising natural biopolymers.