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.