Oxidative stability and lipid components of eggs from flax-fed hens: effect of dietary antioxidants and storage
An experiment was conducted to investigate the effect of dietary antioxidants and storage on fatty acid profile, oxidative stability, and vitamin E concentration of n-3 fatty acid-enriched eggs. Eggs (384, 48/diet) were collected from ISA Brown layers fed diets containing corn-soy (control) with 100 g/kg of flax seed and 2 types of antioxidants [α-tocopherols (α-TOC) and butylated hydroxytoluene (BHT)] at 0, 50, 100, or 150 IU or mg/kg. Eggs were stored at 4°C. On d 0, 20, 40, and 60 of storage, 2 eggs were selected randomly from each replicate (totaling 12 eggs per treatment) and analyzed. Eggs from hens fed flax had increased α-linolenic (18:3n-3), eicosapentaenoic (20:5n-3), and docosahexaenoic acids (DHA, 22:6n- 3) and decreased arachidonic acid (20:4n-6) and total n-6:n-3 ratio when compared with control eggs (P < 0.05). The n-6:n-3 fatty acid ratio was lowest in the flax + 50 IU of α-TOC, flax + 100 IU of α-TOC, and flax + BHT supplemented group when compared with the flax group (P < 0.05). With the exception of flax + 100 mg of BHT, addition of antioxidants led to a reduction in palmitic acid in fresh eggs (P < 0.05). During the first 20 d of storage, over a 17% reduction in total n-3 fatty acids was observed in eggs from flax + 50 mg of BHT supplemented groups (P < 0.05). Docosahexaenoic acid was the predominant long-chain n-3 fatty acid in egg and was stable during storage in the control, flax, flax + 100 IU of α-TOC, flax + 150 IU of α-TOC, and flax + 150 mg of BHT groups. However, antioxidant supplementation had no effect on DHA upon storage in flax + 50 IU of α-TOC and flax + 50 mg of BHT eggs where over 13 to 17% reduction in DHA content was observed during 20 to 60 d of storage (P < 0.05). Inclusion of α-TOC led to over 4.5- to 12-fold increases in α-TOC in eggs. Egg storage for 40 d or longer led to over 50% reduction in egg α-TOC (P < 0.05). Feeding flax seeds led to an increase in TBA reactive substances in eggs (P < 0.05). α-Tocopherol was better in preventing lipid oxidation than BHT at d 0 of storage. However, neither had a significant effect on egg TBA reactive substances upon 60 d of storage (P > 0.05). These studies demonstrate that the level and type of antioxidants and duration of egg storage significantly affected the fatty acid profile, α-TOC status, and oxidative stability of chicken eggs.
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