Effect of globular pea proteins fractionation on their heat-induced aggregation and acid cold-set gelation

This report focuses on cold-set gelation of pea (Pisum sativum L.) proteins and related globulin fractions, namely Vicilin 7S and Legumin 11S. Protein thermal denaturation and aggregation were investigated using differential scanning calorimetry (DSC) sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis, and sulfhydryl (S^-)/disulfide (S-S) bond assessment. While the denaturation temperature (T_d) of pea proteins increased from about 69 to 77°C with increasing legumin content, the disulfide-linked acidic (α) and basic (β) legumin subunits (56-58kDa) denatured and aggregated in a temperature range of 75-85°C. Dissociation of legumin oligomers and their rearrangements via hydrophobic interactions and sulfhydryl/disulfide bonds exchange reactions would occur concomitantly during the heat-treatment, giving rise mainly to high-molecular weight aggregates of random structure. However thermal denaturation and aggregation of vicilin molecules would involve solely non-covalent interactions. Then glucono-δ-lactone (GDL) acid-induced gelation of protein thermal aggregates was evaluated by means of G' and G″ moduli. The preheated mixed pea globulins and vicilin-enriched samples gave rise to increased final moduli values of the acid gels, while legumin-enriched samples displayed low gelling properties. Improving functional properties of pea proteins would help to promote their application in plant-based gelled products such as tofu, alternatively to their soy counterparts.