Valorization of sunflower (Helianthus annuus L.) and canola (Brassica napus L.) meals through protein coprecipitation: Physicochemical, functional, and structural characterization

Abstract

Canola-sunflower protein coprecipitates (CSPoCos) were prepared with different flour ratios, and their physicochemical, functional, and structural properties were analyzed. The crude protein content of the CSPoCos ranged from 88.19% to 91.21%, higher than that of canola protein precipitates (CPoPc, 82.25%) and sunflower protein precipitates (SPoPc, 86.19 %). In addition, protein coprecipitation (PoC) increased the apparent and compact densities, Carr and Hausner indices, while decreasing the particle size and modifying the morphology measured through of dynamic light scattering and scanning electron microscopy, respectively. Glutelins (52.71-60.30%) were the major protein fraction in the CSPoCos. In addition, the PoC increased the properties of water holding capacity, oil holding capacity, last gelation concentration, emulsifying activity index, foam capacity and foam stability. The improvement of these functional properties could be due to the formation or combination of different covalent and non-covalent interactions between the individual protein sources. Moreover, PoC also modified the secondary and tertiary protein structures of the CSPoCos, which was manifested by a significant increase (p<0.05) on the surface hydrophobicity, in comparison to CPoPc and SPoPc. On the other hand, the values of in vitro antioxidant capacity, in vitro digestibility, sulfhydryl groups and disulfide bridges of the CSPoCos were higher than CPoPc. Electrophoresis revealed that CSPoCos had subunits with molecular weights ranging from 15 to 49 kDa. Overall, CSPoCos had better functional properties than single canola and sunflower proteins, making the application of PoC an attractive alternative for obtaining protein powders with improved qualities for use as food ingredients.