title: Effects of Temperature and Duration of Storage on the Stability of Antioxidant Compounds in Egg Yolk and Plasma.
abstract: Antioxidants help protect tissues from oxidative damage caused by reactive oxygen species. In view of the widespread interest in egg yolk and plasma antioxidants in relation to environmental and life-history variables, there is a need for knowledge on the necessary conditions for sample storage, which is currently lacking. In this study, our purpose was to examine the kinetics of the degradation of lutein, retinol, and tocopherol in egg yolk samples and the total antioxidant capacity in plasma samples stored at three different temperatures (-20°, -50°, and -80°C) for 24 mo. We found that yolk lutein was stable during the study period. Yolk retinol and tocopherol showed a steep early decline and then remained relatively stable, but retinol showed significant losses at the end of the study period too. In contrast to our expectations, there was no difference in the stability of antioxidant compounds of egg yolk samples stored at different temperatures. Plasma OXY level was stable during the first 6 mo, showed a slight decline between 6 and 12 mo, and declined more intensely after 12 mo of storage. We suggest that studies focusing on the analysis of egg yolk retinol or tocopherol concentrations and total plasma antioxidant capacity should analyze the samples in the first 6-7 mo after collection. For the analysis of yolk lutein, samples can be stored for 24 mo without significant degradation. The storage temperature of -20°C seemed to be sufficient, as a lower temperature did not significantly affect the slope of degradation of the samples.
authors.forename: Rita
authors.initials: R
authors.lastname: Hargitai
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Nyiri
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Eke
authors.forename: János
authors.initials: J
authors.lastname: Török
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002645:Chickens; D003080:Cold Temperature; D004530:Egg Yolk / Q000737:chemistry*; D014975:Lutein / Q000737:chemistry; D046109:Passeriformes / Q000097:blood*; D013997:Time Factors; D024505:Tocopherols / Q000737:chemistry; D014801:Vitamin A / Q000737:chemistry
chemical_list: D000975:Antioxidants; D014801:Vitamin A; D024505:Tocopherols; D014975:Lutein
keywords: OXY test; carotenoids; degradation; lutein; total antioxidant capacity; vitamins