Yolk Color Characteristics, Xanthophyll Availability, and a Model System for Predicting Egg Yolk Color Using Beta-Apo-8′-Carotenal and Canthaxanthin

The egg yolk pigmenting ability of beta-apo-8′-carotenaI and canthaxanthin was evaluated using reflectance colorimetry to both describe the color and determine relative biological availability. Laying hens, previously depleted of xanthophylls, were fed diets containing 0, 2.2, 4.4, 8.8, and 17.6 mg/kg, of each of the two xanthophylls, in a 5 × 5 factorial arrangement of treatments. The yolk color was evaluated for the YCIE values of dominant wavelength (DWL), excitation purity (EP), and luminosity (Lum) when undiluted or diluted with a white diluent for each treatment. Selected treatment combinations of egg yolks were blended and also evaluated undiluted and diluted. DWL increased from 572.8 nm for the 0 level to 577.9 and 590.6 nm for the 17.6 mg/kg levels of beta-apo-8′-carotenal and canthaxanthin, respectively. Analysis of the diluted EP values indicated that beta-apo-8′-carotenal was 82.2% as available as canthaxandiin while the pigmentation efficiency of beta-apo-8′-carotenal was 92.1% that of canthaxanthin. Blended samples yielded similar color scores when compared at the same level of xanthophyll concentration as fed. From these data a model was formulated from which yolk color could be predicted from the feed concentrations of these two xanmophylls. It is suggested that egg yolks of a desired color could be obtained by using the model to predict either the feed concentration of the two test xanthophylls required in the diet or by blending yolks produced from feeds with known xanthophyll concentration.