Effect of salts and pH on selected ketone flavours binding to salt-extracted pea proteins: The role of non-covalent forces

• Addition of salts and adjustment of pH modified flavour headspace volatility.
• A low salt system generally weakened protein-flavour binding.
• Position of salt in lyotropic series related to the extent of flavour binding.
• Ketone binding was increased by hydrophobic association and physical adsorption.
• Extent of protein-flavour association is a function of the charge on protein systems.

The effects of salts and pH on a mixture of homologous ketone flavours (2-hexanone, 2-heptanone and 2-octanone) binding to salt-extracted pea protein isolates (PPIs) were studied using GC/MS in an aqueous model system. Ionic strength, the specific flavour compound and pH were found to significantly affect protein-flavour binding. Comparing the univalent (NaCl) and divalent (CaCl2) cations, higher concentrations of NaCl (0.25-1 M) greatly promoted protein-flavour binding compared to CaCl2, while lower concentrations (0.05-0.1 M NaCl and 0.25 M CaCl2) decreased flavour retention. Considering the effect of anions (0.5 M), flavour binding by PPIs was dependent upon the position of the anions in the lyotropic series such that binding decreased in the order: Na2SO4 >> NaCl > NaCH3COO = no salt > NaSCN. In terms of the effect of pH, overall flavour binding followed the order: pH 5 > pH 7 > pH 9 > pH 11 > pH 3. Competitive binding between the selected flavour mixture and PPIs was also observed as evidenced by 2-octanone more effectively binding to PPIs than 2-heptanone and 2-hexanone. This research supported existing knowledge on the effects of salts and pH on flavour partitioning with and without protein present. This further promotes utilization of plant proteins in aqueous food systems to achieve desired flavour attributes.