Beef longissimus eating quality increases up to 20 weeks of storage and is unrelated to meat colour at carcass grading

Abstract

Optimal beef meat colour is associated with increased consumer acceptance, whereas dark or pale meat has a reduced desirability. Dark beef also has a variable eating quality and reduced shelf-life. We hypothesised that a poor meat colour at carcass grading would generate an unacceptable eating quality after vacuum-packed chilled storage for up to 20 weeks, due to the unfavourable pH conditions commonly associated with light and dark muscles. At three beef processing plants, beef longissimus muscles from 81 pasture- and grain-fed cattle (mix of Bos taurus and Bos indicus × Bos taurus) were graded at ~24 h post-slaughter for meat colour. The carcasses were allocated to light, medium and dark colour groups, with n = 27 carcasses per colour group. From the 81 carcasses, a total of 162 longissimus lumborum (LL) muscles was collected and half LLs were randomly allocated to three ageing times (2, 12, 20 weeks) within colour group and six half LLs were used per colour group within storage period and plant. Vacuum-packed muscles were stored at –1.0 ± 0.5°C for the designated period and sampled for biochemical and sensory assessments. The effects of colour group, storage week and carcass traits were analysed. Dark muscles had higher pH than the lighter ones (P < 0.05). The carcass trait dentition, feed type and fat depth did not influence the eating quality (P > 0.05). After 2, 12 and 20 weeks of vacuum-packed chilled storage; eating quality was similar for all 3 meat-colour groups (P > 0.05). With increasing storage time, all eating-quality attributes improved (P < 0.001 for all). Lipid oxidation increased with storage time and although values at 20 weeks were slightly above accepted levels for rancidity detection, MQ4 scores indicated that the meat would still be categorised as a three-star product, indicative of the opportunity to store the longissimus lumborum (LL) for this length of time, while maintaining an acceptable eating quality, regardless of meat colour at carcass grading.