One-step extraction of oat protein by choline chloride-alcohol deep eutectic solvents: Role of chain length of dihydric alcohol

The aim of this study is to investigate the effect of dihydric alcohol chain length (1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol) on the structure of deep eutectic solvents (DESs) and the properties of the extracted oat proteins. Herein, five anhydrous and nine hydrated DESs were successfully prepared by mixing choline chloride, dihydric alcohol, and/or water in a heating method. The structures of DESs were confirmed by FTIR and 1H NMR. Among them, only four anhydrous and six hydrated DESs were able to extract oat proteins from flours by one-step extraction. SDS-PAGE and FTIR analyses indicated that the structural properties of the oat proteins were highly reliant on the composition of the DESs; while physicochemical properties were primarily ruled by the environmental pH. Overall, the hydrated DES composing of all food-grade compounds, including choline chloride, 1,3-propanediol, and water at a molar ratio of 1:3:1, demonstrated its great potential for one-step biorefinery of oat proteins.