Association of phospholipids with pea globulins: effect on structure and foaming properties

The presence of lipids after pea protein isolation was related to changes in protein structure and functionality. The aim of this study is to investigate the effects of the presence of lipids, specifically polar endogenous lipids (phospholipids), on pea globulins' (including legumin and vicilin) structure and functionality. Pea globulins were extracted by isoelectric precipitation from defatted and non-defatted pea protein concentrates and further fractionated into legumin and vicilin. Non-defatted pea globulin contained 6.8 ± 0.3 % lipids, mostly consisting of polar endogenous lipids. After selective pH precipitation, legumin contained significantly more lipid than vicilin, suggesting their co-precipitation. Synchrotron radiation CD spectroscopy revealed that legumin contained higher α-helix structure (18 %) compared to vicilin (12 %), and comparable β-sheet structure. The greater structural order in legumin accounted for the higher denaturation temperature (83 °C), relative to vicilin (70 °C). The presence of lipid did not affect the structure of the proteins, but the protein extracted from defatted flour exhibited superior solubility and better foaming properties. Furthermore, Vicilin showed better solubility and foaming compared to legumin. It was concluded that the lipid present in the fraction competed for the interface, affecting the overall foaming properties. These findings contribute to a better understanding of the isolation of pea proteins and their structure-function relationships.