Binding of selected volatile flavour mixture to salt-extracted canola and pea proteins and effect of heat treatment on flavour binding

• Competitive binding was observed among selected ketones and aldehydes.
• Canola and pea proteins bound differently with aldehydes while same for ketones.
• Degree of protein denaturation by flavours correlated well with flavour bindings.
• Heat-induced protein association released previously bound flavours.
• Heating demonstrated aldehyde bound irreversibly while ketone was reversibly bound.

Binding of homologous and heterological classes of flavours with salt-extracted canola protein isolates (CPIs) and pea protein isolates (PPIs) and the effect of heat treatment on their binding were investigated using GC/MS. Competitive binding was observed when homologous ketones were added to CPIs and PPIs and when homologous aldehydes were mixed with CPIs. Ketone mixtures performed differently than aldehydes in that 2-octanone retained more effectively than 2-heptanone and 2-hexanone by CPIs and PPIs, whereas CPIs exhibited incremental affinity to hexanal rather than heptanal and octanal. For PPIs, the presence of aldehydes increased the proteins' overall flavour-binding capacities probably due to partial unfolding of proteins revealing more binding sites as manifested by the decreased ΔH from the DSC studies. Binding of hexanal to CPIs was significantly increased with increased heating time at 95 °C, while a transition of 2-octanone retention from increasing to decreasing inferred heat-induced protein association released previously bound 2-octanone. Heat treatment at 95 °C for 30 min promoted greater competitive binding when mixed ketones and hexanal and 2-hexanone mixtures interacted with CPIs and PPIs, respectively, while dramatic increases of binding of aldehyde mixtures was observed thought out the heating processes.

Percentage retention of homological series of ketone and aldehyde flavours at 250 ppm in a competitive binding environment with and without heat treatment (95 °C, 30 min) (A) flavour binding to CPIs; (B) flavour binding to PPIs. a∼j In each figure, bar values followed by the same superscript are not significantly different (P < 0.05). Note: control represents the percentage of bound flavour when the protein was mixed with a single flavour. The dashed lines have been included to clearly identify the two types of flavours such that the ketones are shown in Figs. a and c and the aldehydes in b and d.Figure optionsDownload as PowerPoint slide