Interaction of pea protein isolate with betanin in red beet (Beta vulgaris L.) extract: Influence on structure, antioxidant properties and stability at pH 3

Betanin, the red pigment in red beet extract (RBE), is susceptible to degradation under acidic conditions, limiting its application as a colorant and ingredient in food products. This study investigated complex formation between betanin in RBE with pea protein isolate (PPI) to improve the stability of betanin at pH 3. Spectroscopic analysis showed that the interactions between PPI and RBE affected the secondary and tertiary structure of PPI, and a transition from α-helical to β-sheet conformation occurred. Gel-electrophoresis confirmed that PPI proteins were involved in PPI-RBE interactions. Furthermore, the size of PPI-RBE particles was found to increase with an increase in RBE concentration. As the PPI-RBE complex had improved antioxidant activity and long-term refrigerated stability compared to the RBE control, this indicates that PPI-RBE complexes could expand the applicability of betanin as a natural colorant and antioxidant in acidic foods while also increasing nutritional value with the added pea protein.