Enhanced molecular flexibility of α -zein in different polar solvents

alpha-Zein is the most abundant prolamin of zein; a specified molecular model of its structure has been proposed. alpha-Zein was modified by alkali and heat treatment in 70% ethanol aqueous solutions and ultrapure water to characterize the improvement in its amphiphilic property. The globular-structured aggregates formed by native alpha-zein were broken up after alkali and heat treatment. The size of the resulting particles was significantly reduced. The improved emulsifying stability and emulsifying activity of the modified alpha-zein were observed. The best emulsifying stability and emulsifying activity were observed for alpha-zein modified by alkali and heat treatment in ultrapure water. The enhanced amphiphilic property of alpha-zein resulted from the structure inversion ability achieved during treatment, which was confirmed by the recovery and unfolding of the alpha-helix secondary structure as the solvent polarity changed. The deamidation reaction improved the alpha-zein molecular flexibility, which was the fundamental reason for its structural inversion ability. Finally, a solvent-responsive pathway model was developed for alkali-heat modified alpha-zein.