Retention of propanal in protein-stabilised tuna oil-in-water emulsions

Propanal concentrations in the static headspace (HS) above water, aqueous protein solutions and freshly made tuna oil-in-water emulsions spiked with propanal (an indicator of omega-3 fatty acid oxidation) were compared. In the presence of proteins, HS propanal concentration was reduced and its decrease above aqueous hydrolysed whey protein isolate (HWPI) solutions was significantly greater than that above whey protein isolate (WPI) solutions. Similar trends were found for emulsions stabilised by HWPI and WPI. The results suggested that there was stronger binding of propanal to HWPI compared to WPI. Emulsification decreased the HS propanal concentration even further for both the WPI and HWPI matrices, but its effect was less in comparison to the protein type. Phosphate buffer decreased the HS propanal concentration, but this effect was minor. The difference in the release of propanal from protein stabilised tuna oil-in-water emulsions was interpreted in terms of the chemical interaction between propanal and protein.