The effect of dietary vitamin E supplementation on the quality of fresh and frozen lamb meat

Abstract

The effect of dietary α-tocopheryl acetate supplementation on the uptake of α-tocopherol in ewe plasma, lamb plasma, milk, organs and muscles was investigated. The oxidative stability and colour in fresh M. longissimus dorsi and frozen M. longissimus dorsi, M. psoas major and M. gluteus medius were also investigated. Ewes ( n = 12) were selected and scanned to assess pregnancy. They were divided into two groups ( n = 6). The control group was fed a diet containing 20 mg α-tocopheryl acetate/kg feed/day and the supplemented group fed a diet containing 1000 mg α-tocopheryl acetate/kg feed/day, for 9 weeks ante-parturition and 3 weeks post-parturition. The lambs were weaned at 3 weeks and fed supplemented or basal feed for 10 weeks before slaughter. Plasma α-tocopherol increased significantly ( p < 0.01) in ewes in the 9 weeks ante-parturition, and lamb plasma taken just before slaughter was significantly ( p < 0.01) higher for the supplemented group than the basal group, following 13 weeks of supplementation. Milk α-tocopherol levels were significantly ( p < 0.01) higher from ewes fed the supplemented diet at parturition and for the three weeks of supplementation post-parturition ( p < 0.05). Supplementation increased the α-tocopherol levels in all tissues sampled. The α-tocopherol concentrations in M. longissimus dorsi and M. psoas major were also determined after frozen storage at −20 °C for 34 weeks. Frozen storage resulted in a significant ( p < 0.01) reduction in mean α-tocopherol levels for M. longissimus dorsi but not M. psoas major. Dietary supplementation with α-tocopheryl acetate significantly ( p < 0.05) increased the oxidative stability of lamb muscle. Surface colour (Hunter L, a, b) was found to be negatively correlated with metmyoglobin content. Supplementation reduced surface discolouration in refrigerated display under fluorescent light over a 6–7 day storage period. The effect was more pronounced in frozen displayed muscles than in freshly displayed samples.