Fatty acid profile and oxidative stability of egg yolks from hens under different production systems
This study was carried out to compare the egg quality, fatty acid (FA) profiles, and oxidative stability of yolks from hens maintained in cages and fed a conventional diet (CON), those fed a conventional diet with free access to outdoor grassy area (5 m2/hens) under free-range conditions (FR), and those fed an organic diet and free access to outdoor grassy area (10 m2/hens) under in organic system (ORG). Heavier eggs were produced by CON, while percentages of yolk and eggshell were greater in eggs of FR and ORG hens. The FR and ORG hens produced eggs that contained significantly more monounsaturated fatty acids (MUFAs) but less polyunsaturated fatty acids (PUFAs) than CON hens. Eggs from FR and ORG hens had a lower concentration of PUFA n-6 because of less C18:2 n-6 (linoleic acid) and a higher percentage of PUFA n-3 (eicosapentaenoic acid). Consequently, the ratio of PUFA n-6 to n-3 for eggs from FR and ORG hens was healthier for consumers compared with CON. However, eggs from the ORG hens had a similar FA profile to those from the FR hens. No significant differences were noted in hypocholesterolaemic (HI), atherogenic (AI) and thrombogenic indexes. Antioxidant concentration was greatest in eggs from ORG hens (retinol-14.32 μg/g and α-tocopherol-98.7 μg/g/yolk). Thus, the oxidative stability of eggs measured after storage at 4°Cfor 15 or 30 days was improved. The best eggs in terms of nutritional value were from the ORG system in which hens lived in their natural environment.
Keywords: antioxidants, conventional production, egg quality, free range production, malonaldehyde, organic production