Mixed whey protein isolate-egg yolk or yolk plasma heat-set gels: Rheological and volatile compounds characterisation

•WPI gel structure was reinforced following incorporation of egg yolk or yolk plasma.•WPI-yolk lipoprotein interaction was found to be of synergistic nature.•Odour of the mixed gels is affected by compounds originating from both WPI and EY.•The unpleasant odour of butanoic acid was not detected in the EY-WPI mixed gels.

The influence of egg yolk (EY) or yolk plasma addition on the rheological properties and flavour characteristics of heat-set gels based on whey protein isolate (WPI) was the objective of this study. Large deformation compression tests and small deformation oscillatory measurements have shown that WPI gel structure-strengthening may take place following the incorporation of either EY or yolk plasma, indicating a possible synergistic effect between the yolk constituents on one hand and those of WPI on the other. Headspace solid-phase microextraction technique, coupled to gas chromatography-mass spectrometry (GC-MS) analysis, was applied to characterise the volatile compounds of the gels. A total of 29 compounds were identified. Furthermore, GC-Olfactometry analysis revealed that the major contributors to the overall odour quality of the mixed gels were 2,3-butanedione (buttery, caramel-like odour), hexanal (green), heptanal (fishy), 2-acetyl-1-pyrroline (cooked/milky), 1-hexanol (cooked) and methional (boiled potato-like odour), compounds originating either from WPI or EY.