Rheological measurements of yolk to characterise origin and processing properties of eggs

Egg proteins and lipoproteins are responsible of a wide range of interesting properties of many emulsions, foams, gels and other foods processed by industry. The modifications of functional properties of these proteins during food processing determine a complex behaviour that can result in structural changes of difficult prediction, and rheological measurements are a useful tool to study them. In this work, egg yolk samples coming from different species of fowls, different breeds of laying hens, and differently fed hens, have been analysed using steady state and dynamic tests in a rotational rheometer. Thermal transitions in egg yolk have been established by differential scanning calorimetry (DSC). The results have given valuable information about differences in egg yolk functional and structural properties that could be very useful to improve storage and processing conditions, as well as a tool to quality and fraudulence control in egg industry.