Rheological and protein thermal denaturation properties of eggs from different farming systems

This study aimed to evaluate rheological characteristics and protein denaturation of eggs obtained from three
different types of laying poultry farms, intensive, dual purpose and extensive. The flow curves of both egg whites
and whole eggs, assessed by rotational rheometry, revealed a shear thinning behavior. Raw egg whites were more
viscous than whole eggs due to the higher protein content of the former. Lower steady shear viscosity was recorded
for the egg whites obtained from the intensive system, while the variability of values for the extensive system
was higher. Differential scanning calorimetry showed no differences among the farming systems in lysozyme and
ovalbumin denaturation temperatures of the egg white detected at ~ 65 and 80oC, respectively. The temperature
and enthalpy values of an endothermic transition at ~ 82oC of the egg yolk samples, was ascribed to the composite
mixture of lipids, lipoproteins and contaminant egg white proteins; these responses were similar among the
farming systems, whereas the enthalpy values had higher variability for eggs of the extensive system. Overall,
the farming system appeared to affect the variability rather than mean values of the rheological and thermal
parameters, with samples from the extensive system exhibiting higher heterogeneity in their physical properties.
However, due to the limited number of farms involved in the study and several substantial confounding factors
involved (e.g. breed, feed ration), the results should be interpreted cautiously. Funded by EU (HORIZON H2020)
under the acronym CodeReFarm Grant No: 101000216