The relationships between physicochemical properties and conformational features of succinylated and acetylated kidney bean (Phaseolus vulgaris L.) protein isolates

The effects of succinylation and acetylation on some physicochemical properties and conformational features of kidney bean protein isolate (KPI) were investigated. The extent of N-acylation progressively increased up to 93–94% with increasing anhydride-to-protein ratio (0–1.0 g g−1), while the O-acylation occurred only after extensive blocks of ε-amino groups. Zeta potential and size exclusion chromatography analyses indicated that the acylation and the succinylation in particular led to decreases in isoelectric point and zeta potential at neutral pH, in an extent of acylation dependent manner, while the association/dissociation state of the vicilin was slightly affected by the acylation. The surface hydrophobicity was also remarkably affected by the acylation, but the influence varied with the type and extent of acylation. Differential scanning calorimetry (DSC), intrinsic fluorescence and near-UV and/or far-UV CD spectroscopic analyses showed significant changes in tertiary and/or secondary conformations of the proteins in KPI, with extent of acylation, especially extent of succinylation. These phenomena suggest close relationships between the physicochemical properties and tertiary and/or secondary conformational features of the proteins in acylated KPI samples. It is also suggested that the physicochemical and conformational properties of KPI could be modulated by selecting the type and level of the applied anhydrides.