Egg quality and food safety of table eggs: Egg quality and age of flock - A longitudinal study

Abstract

Eggs were collected from a cage and a free range flock at the ages of 25, 35 and 45 weeks and divided into 4 different groups after candling and scoring for translucency. Thirty eggs were used for the estimation of the amount of cuticle present on the egg shell using a hand held Konica Minolta spectrophotometer before and after MST Cuticle Blue staining. The cage system eggs were visually more uniformly stained than the free range eggs. Significant effects were recorded for production system and age for L*a*b* values, but there was no significant interaction between the two. Under the scanning electron microscope (SEM), unstained patches showed no cuticle whereas stained areas had intact cuticle irrespective of the rearing system. None of the egg shells showed 100% cuticle coverage. Traditional egg quality measurements were carried out using specialized equipment supplied by TSS (UK). A significant effect was recorded for flock age and production system for all the egg quality variables except shell breaking strength, while interaction between the two was significant for translucency score, egg weight, shell weight, shell thickness and yolk score. Shell ultrastructural features of thirty eggs per flock were scored using SEM following plasma etching. Shell ultrastructural variables significantly affected by production system and age were mammillary cap size, early fusion, late fusion and depression, while interaction between production system and flock age was recorded only for confluence, alignment, type A bodies, cuffing, changed membrane, depression and erosion. The remaining 60 eggs per flock were used for microbiological studies, which showed negative results for 'Salmonella' spp.