
doi: 10.3382/ps.0591059
Abstract Experiments were conducted to evaluate and compare several methods of egg yolk color analysis. Egg yolks of various colors and intensities were produced either by feeding known concentrations of synthetic xanthophylls to color depleted hens or by mixing the xanthophylls directly into depleted egg yolks. The yolk samples were then analyzed for color using the AOAC procedure, visual comparisons using the Roche Color Fan, and by reflectance colorimetry to describe color in the CIE and L*a*b* systems. The AOAC procedure of beta-carotene equivalents was found to be inadequate in describing yolk colors produced from different xanthophyll sources. Yolks blended to approximate the same total xanthophyll concentration from natural feed sources or from canthaxanthin resulted in about the same beta-carotene equivalent values of 14.3 and 14.2 μg/g, respectively. Visual scoring resulted in a Roche Color Fan value of 7 for the natural yolks and 15 for the canthaxanthin blended yolk. The colorimetric analysis indicated that the natural yolk was more yellow and less red (578.4 dominant wavelength, 2.74 a* and 56.7 b*) than the canthaxanthin yolk (591.9 dominant wavelength, 25.60 a* and 34.7 b*). The AOAC procedure, however, shows good agreement with increases in a monopigment source of color. These results would indicate that the AOAC procedure is an adequate procedure for describing egg yolk color from a monopigment source. However, it is a very poor procedure for describing egg yolk color from a variety of pigments.
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