Solubility of the Corn Protein Zein in Imidazolium-based Ionic Liquids

The solubility of the corn protein zein is measured gravimetrically from 30 to 60 °C in seven imidazolium-based ionic liquids and three conventional solvents, acetic acid, 70 vol % aqueous ethanol, and 1-methylimidazole. At elevated temperatures the solubility of zein in six of the ionic liquids exceeds that of the current industry standard, 70 vol % aqueous ethanol. The ionic liquids 1-methylimidazolium acetate and 1-ethyl-3-methylimidazolium dicyanamide can dissolve 2.5 times more zein at 60 °C than 70 vol % aqueous ethanol. Single and multivariate regressions are used to model zein's solubility as a function of common solvent properties. Solvents able to dissolve more zein have small molecular volumes, low polarities, and act as a weak hydrogen bond acceptors.