Structural and functional characterization of kidney bean and field pea protein isolates: A comparative study

Protein isolates were prepared from different kidney bean (KB) and field pea (FP) lines and their physicochemical (protein content, colour, electrophoretic profile & zeta potential), structural (thermal & conformational), dynamic rheological and functional (emulsification, foaming, water and fat absorption) properties were evaluated. These isolates differed significantly in colour-, structural-, thermal- and functional-properties. SDS-PAGE and size exclusion chromatography revealed that vicilins (∼150 kDa) were prominent proteins in KB isolates, while FP protein isolates contained both legumins and vicilins (∼330 and ∼155 kDa, respectively) as major components. FTIR spectroscopy revealed that β-sheets, β-turns and α-helix were main secondary structures in the KB and FP proteins. KB proteins had relatively more β-sheets (38.6%) while less α-helix (22.8%) than FP proteins (30.0 and 28.0%, respectively). The rheological properties of the protein isolates were measured as gelation temperature (Tgel), gel reinforcement (Greinforcement) and tan δ. KB proteins had higher thermal denaturation temperature (Td), Tgel and Greinforcement while lower tan δ than FP proteins. Principal component analysis (PCA) revealed that Td, Tgel and Greinforcement related positively, whereas tan δ related negatively with the proportion of β-sheets. Protein solubility, emulsion stability, foaming capacity and stability were positively related to the charge on the proteins.