Lipid and colour stability of beef from grazing heifers supplemented with sunflower oil alone or with fish oil

The effect of sunflower and fish oil supplementation of grazing heifers on lipid oxidation and colour stability in beef was investigated. For 150 days, heifers were assigned unsupplemented grazing (G) or restricted grazing with 2.5 kg concentrates containing 1250 I.U. α-tocopheryl acetate and 290 g sunflower oil (S1), 415 g sunflower oil (S2), 290 g sunflower + 85 g fish oil (FS1) or 415 g sunflower + 85 g fish oil (FS2). Longissimus dorsi muscle was excised 24 h post-mortem and stored at −30 °C prior to analysis. Muscle α-tocopherol in the oil-supplemented groups was higher (P < 0.05) than the G group. Lipid oxidation in refrigerated, minced raw or cooked beef was not significantly affected by diet but metmyoglobin was higher (P < 0.05) in raw beef from oil-supplemented groups compared to the G group. Lipid oxidation and metmyoglobin formation increased (P < 0.001) during refrigerated storage. Vitamin E supplementation together with pasture grazing appeared to offset any potential deleterious effect of oil supplementation on lipid and colour stability.