title: Possibilities of enhancing the colour of egg yolk.
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 (ΔE* = 13.257), the addition of artificial pigments in the feed resulted in a more significant increase in the parameter ΔE* (CIE total colour difference), with the greatest value of ΔE* being observed with the use of both pigments (ΔE* = 24.265).
  
  
  CONCLUSIONS
  Grazing increases the parameter a* whereas the values of the parameter C*(ab) remain relatively low. The parameter ΔE* 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.
authors: Department of Biochemistry, Chemistry and Biophysics, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Brno, Czech Republic. dvorakp@vfu.cz
authors: Petr
authors: P
authors: Dvořák
authors: Pavel
authors: P
authors: Suchý
authors: Eva
authors: E
authors: Straková
authors: Vladimír
authors: V
authors: Kopřiva
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000822:Animal Husbandry; D000818:Animals; D017849:Animals, Inbred Strains; D002645:Chickens; D018153:Czech Republic; D004530:Egg Yolk / Q000378:metabolism*; D005260:Female; D035264:Flowers / Q000737:chemistry; D010860:Pigments, Biological / Q000008:administration & dosage* / Q000378:metabolism*; D006109:Poaceae / Q000378:metabolism; D031686:Tagetes / Q000737:chemistry; D024341:Xanthophylls / Q000008:administration & dosage / Q000378:metabolism
chemical_list: D010860:Pigments, Biological; D024341:Xanthophylls