Characterization of the internal quality of turkey eggs according to their commercial grading

The present study aimed to determine the influence of egg weight and shape index on the internal quality of turkey eggs. To this aim, a total of 197 turkey eggs were measured including external and internal egg quality traits. Different egg categories were built attending to the weight terciles of the sample and the commercial shape index standards. A Discriminant Canonical Analysis (DCA) was performed using these categories as dependent variables, while the internal quality attributes acted as explanatory variables. The yolk percentage was the only variable reporting multicollinearity and was therefore removed from further analysis. The Pillai's trace criterion was significative (p < 0.05) and validated the performance of the DCA. Moreover, the cross-validation test reported a high accuracy of correct assignments (95.88 %), which validated the applicability of the statistic model. The diameter and lightness of the yolk, the proportion of shell in the overall weight, and the height and pH of the albumen were the variables reporting discriminatory ability across weight and shape index groups. Similar associations between the internal quality and egg weight were found in the literature, while the connections with the shape index were less frequent. The present work eases the efficient determination of increased-quality eggs from their external appearance. However, quality perception varies with the consumer preferences of each market. Therefore, heavier eggs will offer larger yolks and reduced shell percentage in weight, while lighter and rounder eggs will tend to present darker yolks, with taller albumen and lower gas exchange during storage.