Tailoring foaming properties of pea vicilin by pH-shift, heat, and their combined treatments

Abstract: Recently, pea protein as a functional food ingredient has received increasing attention because of its competitive price and allergen-free nature. The major pea seed storage proteins are hexameric structure of legumin (11S) and trimeric structure of vicilin (7S). Our previous study found that pea vicilin (PV) had an appreciably higher foaming capacity (FC) than pea globulin and legumin, but still compares unfavorably with commonly used foaming agents like casein. Considering foaming properties are crucial to making certain foods, the aim of this study was to enhance foaming properties of PV by moderate and simple physical methods including pH-shift, heat, and their combined treatments. In addition, the mechanisms of the abovementioned treatments on the modification of PV’s foaming properties were elucidated by measuring structural properties and air-water surface behaviors (i.e., kinetic adsorption properties, rheological air-water interfacial properties) of modified PV. The results showed that while the foaming stability (FS) of all treated PV samples remained stable, their FC was significantly higher compared to casein, but this increase arose via different mechanisms in different samples. The FC order of PV is combined treatment > pH-shift = heat > control. Because noticeably higher amounts of α-helix structures in combined treated PV (20.23% vs 17.05%) were identified, it had the highest FC (153.97%) among all treated samples. Regarding single treatment effect, the higher FC of pH-shift treated PV was not only attributed to its improved surface hydrophobicity, but was also due to the enhanced dilatational viscoelasticity (40 mN/m vs 34 mN/m) which can form a thicker protein film at the air/water interface. The heat treatment also dramatically improved the dilatational viscoelasticity (44 mN/m vs 34 mN/m) and penetration rate (9.12 s^-1 vs 7.19 s^-1). These findings could broaden the application of PV as a new foaming agent in food industries.