Probing the molecular forces involved in binding of selected volatile flavour compounds to salt-extracted pea proteins

•Molecular forces were probed using various bond disturbing agents.•Aromatic, ketone and ester flavours bound pea proteins non-covalently.•Aldehyde and disulfide flavours covalently interacted with pea proteins.•Sulfhydryl–disulfide interchange reactions contributed to disulfide retention.•A combination of forces was required to explain binding mechanisms. Molecular interactions between heterologous classes of flavour compounds with salt-extracted pea protein isolates (PPIs) were determined using various bond disrupting agents followed by GC/MS analysis. Flavour bound by proteins decreased in the order: dibutyl disulfide>octanal>hexyl acetate>2-octanone=benzaldehyde. Benzaldehyde, 2-octanone and hexyl acetate interacted non-covalently with PPIs, whereas octanal bound PPIs via covalent and non-covalent forces. Dibutyl disulfide reacted with PPIs covalently, as its retention was not diminished by urea and guanidine hydrochloride. Using propylene glycol, H-bonding and ionic interactions were implicated for hexyl acetate, benzaldehyde, and 2-octanone. A protein-destabilising salt (Cl3CCOONa) reduced bindings for 2-octanone, hexyl acetate, and benzaldehyde; however, retention for octanal and dibutyl disulfide increased. Conversely, a protein-stabilising salt (Na2SO4) enhanced retention for benzaldehyde, 2-octanone, hexyl acetate and octanal. Formation of a volatile flavour by-product, 1-butanethiol, from dibutyl disulfide when PPIs were treated with dithiothreitol indicated occurrence of sulfhydryl–disulfide interchange reactions.