Lipid and protein oxidation and colour stability during display in high oxygen modified atmosphere packaging of beef from late-maturing bulls fed rumen protected fish oil

Increasing the concentration of polyunsaturated fatty acids (PUFA) in beef enhances its nutritional value but may compromise its oxidative shelf life. In this experiment, the impact of inclusion of rumen protected fish oil (PFO) in the finishing diet of late-maturing bulls on muscle fatty acid profile, antioxidant content, lipid stability, colour and protein oxidation was investigated. Charolais-sired suckler bulls were offered ad libitum, for 101 d pre-slaughter, a barley-based concentrate (C) or a concentrate containing rumen PFO. Following post-mortem ageing for 14 d, M. Longissimus thoracis muscle was subjected to simulated retail display (4°C, 1,000 lux for 12 h out of 24 h) for 3, 7 and 10 d in modified atmosphere packs (O2:CO2; 80:20). The concentrations of C22:6n-3, n-6 PUFA and total PUFA and the n-6:n-3 PUFA ratio were higher (P < 0.001) in muscle of PFO bulls compared to C bulls, while the α-tocopherol concentration was lower (P < 0.01). The concentrations of C18:3n-6, C20:4n-6, n-3 PUFA and highly peroxidisable PUFA were lower (P < 0.05) on day 14 compared to day 0 of display. Lipid oxidation after 10 d of display was higher (P < 0.05) in muscle of PFO bulls compared to C bulls but not to an extent that would be detected by a consumer. Colour stability was not affected. It is concluded that the increase in PUFA concentration achieved had minor effects on bull beef shelf life.