Abstract: The effects of alkaline pH-shifting (pH 11) combined with heat treatment (50 and 60 ℃) on the structural and functional properties of rice bran protein were investigated. The results indicated that the secondary structures of rice bran protein were transformed from an ordered state to a disordered one by alkaline pH-shifting treatment. Alkaline pH-shifting combined with heat treatment led to complex changes in the protein’s secondary structures from folding to unfolding to refolding, which was accompanied by oxidation of sulfhydryl groups. Alkaline pH-shifting treatment resulted in unfolding of rice bran protein. As the treatment time increased, the protein re-aggregated, which was aggravated by heat treatment. Alkaline pH-shifting treatment resulted in a significant decrease in the water-holding capacity, foaming capacity, foam stability, emulsifying activity, and emulsion stability of rice bran protein, but a significant improvement in the oil-holding capacity. As the treatment time increased, the water-holding capacity, foaming stability, emulsifying activity, and emulsion stability gradually increased, with the emulsifying activity showing the most significant increase. Alkaline pH-shifting combined with heat treatment could significantly improve the water-holding capacity, foaming capacity, foam stability and emulsion stability of rice bran protein while reducing its oil-holding capacity and emulsifying capacity.

Key words: rice bran protein; alkaline pH-shifting; heat treatment; structure; functional properties