Chromatographic analysis of lypophilic compounds in eggs from organically fed hens

Egg yolks represent a common foodstuff in the human diet and are an important source of nutrients including lipids and carotenoids. The aim of this study was to compare the carotenoid, fatty acid and vitamin E contents of the yolk of eggs from nine hen breeds (Barred Plymouth Rock, Speckled Italian, Black Italian, Red Italian, Rhode Island, Silver Laced Wyandotte, Gold Araucana, Partridge Brahma and Yellow Cochin) raised in barns in an enclosed house. Gas chromatography-mass spectrometry (GC-MS) was used for the fatty acid analyses, and reversed phase-high performance liquid chromatography-photodiode array detection (RP-HPLC-PDA) for carotenoids and vitamin E quantification. The major carotenoids identified were lutein and zeaxanthin, which together represented more than 93% of the total carotenoids, followed by beta-cryptoxanthin and beta-carotene. The results indicated that the total carotenoid content of the eggs ranged from 16.84-87.31 mu g/g egg yolk (average value 49 mu g/g egg yolk). The most representative fatty acids found were palmitic acid, stearic acid, oleic acid and linoleic acid. Significant differences in the proportions of a-linolenic acid were observed among the samples. The a-tocopherol content was directly correlated with the total carotenoid content. The results show that the chemical composition of egg yolk varies greatly among hen breeds.