Three physical modifications enhanced the binding interactions of Cyperus esculentus protein with proanthocyanidins and physicochemical properties of complexes: The contribution of non-covalent interactions

Abstract

This study investigated non-covalent interactions between unmodified/modified (ball-milling, BMP; high pressure homogenization, HPHP; cold plasma, CPP) Cyperus esculentus protein (CEP) and proanthocyanidins (PA and PB2) to evaluate structure, functionalities and potential in emulsions. The PA and PB2 addition significantly increased the turbidity and ζ-potential of CEP samples, as confirmed by aggregations observed via atomic force microscopy, validating the formation of protein-proanthocyanidin complexes. Fluorescence quenching and isothermal titration calorimetry revealed that procyanidins caused CEP sample static quenching, with CEP-proanthocyanidins binding affinity order as CPP > HPHP>BMP > CEP. The CEP-proanthocyanidins involve non-covalent interactions, driven by hydrogen bonding and electrostatic interactions, without altering CEP sample spectral bands and secondary structures, but enhancing thermal stabilities, antioxidant activities, and emulsifying properties. Then, the CPP-PA stabilized emulsion droplet size decreased with aqueous phase pH increasing, contrary to ζ-potential values. Conclusively, these findings illustrated that the modified CEP-proanthocyanidin complexes as a promising strategy for addressing these challenges and stabilizing emulsion.