Abstract
Meat colour data was collected from 4,953 lambs produced at 5 sites across Australia over a 5 year period (2007-2011) as part of the Sheep Cooperative Research Centre’s information nucleus flock experiment. Longissimus muscle samples were collected 24 h post-mortem, vacuum packaged, aged for 5 days and then placed under simulated retail display conditions for 3 days. At the end of this period light reflectance of the meat surface was measured with a Hunterlab reflectometer and a ratio was calculated (630 nm/580 nm reflectance) to represent redness, with higher values redder and hence more desirable. These ratios were analysed using linear mixed effects models. The base model included fixed effects for site, year of birth, kill group, sire type and dam breed. In a second analysis pH measured 24 h post-mortem was included in the base model as a covariate. Of the dam breeds, Merino progeny had 0.19 units lower redness than those of Maternal dam breed. Similarly the Merino sire type produced lower redness values than Maternal or Terminal sired lambs, with 0.39 units difference seen between lambs of Merino and Terminal sire types. pH was negatively associated with meat redness, with a 0.92 unit decrease (P<0.01) in redness across the pH range of 5.4 to 6. With pH included in the model, the effect of sire type was not significant, suggesting that differences in post-mortem muscle pH between sire types may underpin the observed variation in retail meat colour. Our findings suggest that by reducing the pH of lamb loins we can improve the redness of the meat whilst on retail display.