Xanthophyll, β-carotene and α-tocopherol in yolk eggs through the whole laying period in a free-range system: a complex antioxidant that limits lipid oxidation during storage

Abstract

Egg, and particularly yolk, is rich in antioxidant compounds for human health and to protect the yolk during the storage. However their content could vary with the age of hens through the whole cycle of laying affecting the nutritional value and the potential antioxidant for the storage. In this sense, the objective of this work was to determined the content of xanthophyll, as lutein, zeaxanthin, astaxanthin, canthaxanthin, and β-carotene and α-tocopherol and the lipid oxidation in yolk eggs fresh and stored, at three ages of hens, coming from a free range system in Uruguay. Yolks (fresh and stored for 28 days at 4°C),  from Hy-Line Brown, at 34, 62, 84 weeks of age, coming from three Experimental Units (30 eggs each one) in a free range system receiving a conventional diet (corn-soybean), alfalfa silo pack and pasture (ryegrass and oak) in outdoor, were used. Yolks were extracted with methanol: THF:BHT (50:49.05:0.05) and filtered. Extract filtered with 0.45 μm was injected in a HPLC Prominence LC-20A, with diode array and column C30. Lipid oxidation was measured by TBARs and expressed as mg MDA/kg yolk. For fresh yolks, at 34, 62 and 84 weeks of age lutein was: 2246,1861,1664 µg/100g; zeaxanthin: 1382,1420,1250 µg/100g; astaxanthin: 145,115,88 µg/100g;  canthaxanthin: 574,717,439 µg/100g; carotene: 34,36,38 ug/100g and tocopherol:13,14,13 mg/100g. Age but no storage affect xanthophylls content. Carotene and tocopherol decreased with storage but not with age. Lipid oxidation did not vary with age of hens, except for stored yolks at 34 weeks of age that was higher than fresh ones (p<0.05). Yolks, fresh and stored, were rich in xanthophylls, still considering the decrease with age, for human health and for protection against yolk oxidation. β-carotene and α-tocopherol decrease with storage at all ages studied suggesting a crucial role for protecting the yolks from oxidation process.