Comparative study of the structural and functional properties of protein isolates prepared from edible vegetable leaves

Abstract

ABSTRACT Isoelectric precipitation was used to produce protein isolates (>90% protein contents) from three edible vegetable leaves. Amaranth (ALI), eggplant (ELI) and fluted pumpkin (FLI) leaf protein were isolated to study their conformational structures. Intrinsic fluorescence indicated a loose structural conformation for ELI at all the pH values, whereas FLI and ALI had more compact structures at pH 3.0 and pH 9.0. The surface hydrophobicity showed a greater distribution of hydrophobic amino acid groups of the protein isolates at the basic than the acidic regions. The SDS-PAGE results showed that the leaf isolates had similar polypeptide bonds characterized by 20, 25, 40 and 200 kDa and some distinct bands above 200 kDa. The ELI formed emulsions with significantly (p < .05) smallest oil droplet sizes (<3.3 µm) when compared to FLI and ALI. However, foaming capacity was mostly pH-dependent with significantly (p < .05) higher values at pH 7.0 and 9.0. The leaf protein isolates may be considered as potential functional food ingredients.