Structural characterization and functional properties of safflower seed protein extracted by natural deep eutectic solvents

In this study, betaine-based natural deep eutectic solvents (NADES) were formulated for the extraction of safflower seed protein (SSP). Among the five NADES screened, betaine-glycerol (1:2 M ratio) was identified as optimal, achieving a protein purity of 85.66% and an extraction yield of 56.66%. Using response surface methodology, the extraction yield was further increased to 66.45% ± 0.43% under optimized conditions (29% water content, 52 °C, solid-to-liquid ratio of 1:24). Compared with protein extracted by alkaline solubilization–acid precipitation (AEAP), NADES-extracted SSP exhibited a lighter color, higher α-helix content (23.86%), and lower β-sheet content (34.16%), with better preservation of subunit integrity. Functionally, it demonstrated superior solubility (85.00%), emulsifying activity (93.23 m 2 /g), and foaming capacity (209.73%) at pH 3.0, along with higher oil-holding capacity. The betaine-glycerol NADES system was therefore established as a green and efficient approach for SSP extraction.