Abstract
BACKGROUND: This study attempts to compare two possibilities of enhancing the colour of egg yolk. One of them is based on the ecological rearing of laying hens on natural green grass whereas the other uses a feeding dose supplemented with natural pigments in laying hens reared in individual cages. Is it possible to distinguish these two technologies using yolk colour determination in the CIELAB system?
RESULTS: Yolk colour parameters such as L*, a*, and b* in the group of grazed hens are significantly different (α = 0.001) from those observed in hens reared in cages. The yolk colour shows a darker, redder and more yellow colour. The greatest difference was seen in the red colour parameter, a*, that increased more than twice. Visually, this means a shift towards a more orange colour. Compared to grazing in the meadow (Δ__E__* = 13.257), the addition of artificial pigments in the feed resulted in a more significant increase in the parameter Δ__E__* (CIE total colour difference), with the greatest value of Δ__E__* being observed with the use of both pigments (Δ__E__* = 24.265).
CONCLUSION: Grazing increases the parameter a* whereas the values of the parameter C*~ab~ remain relatively low. The parameter Δ__E__* is significantly lower in the case of grazing as compared to the supplementation of the feed with pigments. However, colourity parameters cannot be used as a specific standard to identify a particular grazing technology as their values vary during the laying period. Copyright © 2011 Society of Chemical Industry