Commercial-quality evaluation of different weight-grade eggs

The European market offers to the consumers grade-A eggs classified in different weight classes. Egg price is largely influenced by egg size; a study was therefore carried out to evaluate the commercial quality of S, M, L, and XL eggs, in order to provide tools for an informed choice to the consumers. Twenty seven samples of commercial grade-A eggs, laid by cage hens and purchased in different retail shops in Northern Italy, were analysed. Each sample included 36 eggs from the same lot, corresponding to more than 970 eggs evaluated. The following parameters were measured: egg weight, percentage of eggs outside the declared weight range; shell, albumen and yolk percentage; Haugh Units (HU) and air cell height; yolk colour, and whipping capacity of whole egg. Tolerance limits of egg weight compliance to the declared size were widely exceeded: L and XL samples often contained eggs of lower weight grade, while S and M samples included overweight eggs. The absolute weight of all egg fractions increased with size grade, but in different proportions: S eggs presented the highest albumen percentage, while XL eggs the lowest shell percentage. The freshness indexes HU and air cell height were influenced by egg size: HU values of S eggs and air cell height of XL eggs resulted significantly higher than in other egg classes; moreover, a direct correlation (p£0.05) between egg size and air cell height was observed. Unexpectedly, no correlations between these parameters and egg age (calculated from the dates reported on the packs) were found. Whipping tests highlighted a significantly higher overrun for XL eggs, and a higher foam consistency for S eggs. The relationship between egg quality and price is discussed.