Structural, thermal and rheological properties of small granule starch in 1-ethyl-3-methylimidazolium acetate and choline acetate

Three small granule starches (amaranth, quinoa and taro) and maize starch were treated with ionic liquids (ILs) at 20 °C using pure 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) and choline acetate ([Chol][OAc]), as well as their IL–water mixtures (molar ratios 1:25, 1:5 and 1:2.5). Small granule starches showed greater susceptibility to IL treatment than maize starch. [Chol][OAc] and its mixtures increased gelatinization temperatures by 2–10°C compared to native starches, while [Emim][OAc] systems exhibited smaller thermal shifts. The 1:5 [Emim][OAc]–water mixture (Em5) induced complete loss of endothermic transitions at 20°C for all three small granule starches (enthalpy change reduced to zero), whereas maize retained partial crystallinity (enthalpy change 3.3 J/g). Em5-treated quinoa starch uniquely preserved high elasticity (storage modulus at 25 °C: 3450 Pa) and showed increased yield point (72.5%) versus the native (43.1%), indicating enhanced shear resistance. Pure [Chol][OAc] (Ch0) at 85 °C caused extensive granule merging and produced soft gels with loss factor exceeding 1. Principal component analysis explained 73.2% of total variance, with Em5 and Ch0 samples separating distinctly. Hierarchical cluster analysis indicated greater structural diversity among IL ratios for quinoa and taro starches than for maize and amaranth. Among small granule starches, amaranth showed the highest sensitivity, quinoa preserved elasticity, and taro exhibited intermediate behaviors. These quantitative relationships enable rational selection of IL treatments for potential industrial applications including biodegradable packaging, biomedical hydrogels, and industrial adhesives.