Is the farming method (cage, barn, organic) a relevant factor for marketed egg quality traits?

Abstract

• Farming method affected egg quality traits, but not odour and flavour attributes. • Barn and cage eggs had the heaviest yolk with the highest colour intensity. • Organic eggs showed distinctive physicochemical quality traits. • Barn and cage eggs quality traits changed with sampling period. The present study evaluated the physicochemical and sensory traits of marketed table eggs, deriving from different farming methods (cage, barn, and organic) and sampled in different marketing periods (June, July, September, October). A total of n=540 eggs (n=45 eggs/farming method/sampling period) of “medium” weight-grading were purchased and subjected to physical measurements (shell, yolk, and albumen physical traits), chemical evaluations (proximate composition, cholesterol content and fatty acid profile of the edible portion) and to a descriptive sensory analysis. Results highlighted that eggs physical traits often differed among the considered farming methods: organic eggs had the lowest albumen pH ( P < 0.001) and the highest albumen proportion ( P = 0.004), whereas barn and cage eggs had the highest yolk proportion ( P = 0.026). Barn eggs had the heaviest shell proportion ( P = 0.011), which did not however imply a higher resistance to penetration and compression tests. As expected, egg colour differed according to the farming method with cage eggs displaying the highest overall yolk colour intensity (a*, b* and yolk colour FAN; P < 0.001), followed by barn and organic eggs. The egg marketing period demonstrated to be a relevant factor in determining egg physical attributes too. Surprisingly, organic eggs showed constant albumen, yolk and shell physical characteristics, and yolk colour traits, whereas barn and cage eggs displayed a certain variability in these terms. Cage eggs showed the highest protein ( P = 0.001) and barn eggs the highest lipid ( P = 0.003) contents, whereas cholesterol content was only affected by the marketing period in all three farming methods. Organic eggs were the richest in moisture ( P = 0.003), in polyunsaturated fatty acids (FA) of both n-6 ( P = 0.011) and n-3 series ( P < 0.001), whereas cage ones had the highest saturated ( P = 0.030) and monounsaturated ( P = 0.018) FA. Among the considered sensory traits, farming method only affected the yolk colour intensity, which was the lowest in organic eggs and, for cage and barn eggs, it decreased along the marketing period. Results of the present research indicated that the overall quality of marketed table eggs effectively differs according to the farming method and to the marketing period time which is a relevant information, yet poorly investigated, from the consumer's point of view. Organic eggs were the most distinguishable, especially in terms of yolk colour and nutritional composition.