Colour Traits Of Chicken Eggs With Different Eggshell Pigmentation

Abstract

The study was carried out with 11 purebred groups of chickens at 48 weeks of age, laying eggs with white, tint, blue-green and brown shell pigmentation to investigate the colour characteristics of eggshells in the CIE L*a*b* colour system. On the basis of L*, a* and b* values, * (Chroma), Hue o (the angle between b* and a* colour coordinates) and SCI (eggshell colour index) values were calculated. L* values decreased statistically significantly (<0.001) from 92.7 in white-shelled eggs to 40.2 in dark brown eggs. Brown eggs had a* values between 1.9 and 22.5, which increased from cream-coloured to dark brown shells. In bluegreen and tinted eggs, L* and b* values were similar. In blue-green eggs, the values of the a* colour coordinate were negative. There was a substantial variation in the colour of eggs not only within the groups, but also within the breed. The shell colour index (SCI) is suitable for reliable colour identification only in brown and non-pigmented eggs. SCI values lower than 70 could be recommended as reference values for brown pigmented shells whereas SCI values over 85for white-shelled eggs. Spectrophotometric analysis is appropriate for use in eggs with uniform pigmentation of the shell. The Hue angle is not suitable for colour analysis of eggshells due to the extremely large variations and the possibility to obtain similar values but with different sign in eggs with similar colour.