Honor Calnan

Brown discolouration of lamb meat on retail display reduces consumer appeal, limiting the shelflife and value of the product. The rate of change in colour from red to brown, known as colour stability, is increased in short aged meat with high intramuscular fat (IMF) content (Calnan et al 2014). Therefore genotypic selection for IMF to improve sensory appeal may reduce lamb meat colour stability. Extended aging of lamb meat also reduces colour stability of lamb meat (Jose et al, 2008), a concern for chilled meat shipped for 35 - 70 days to distant markets. High intramuscular vitamin E (a-tocopherol) concentration, achieved by dietary supplementation, slows the loss of redness in lamb aged 5 - I 0 days (Jose et al, 2008). Given that colour stability worsens with aging, the impact of a-tocopherol may be greater in long-aged and high IMF meat. We hypothesised that high muscle a-tocopherol concentration in lambs will retain redness during display of the longissimus, particularly in long-aged and high IMF meat.

The brown discolouration of lamb meat reduces its appeal to consumers, costing the Australian Lamb industry considerably due to the discounting of product. Lamb meat browning is caused by the oxidisation of myoglobin pigments into the brown metmyoglobin form. The rate of this oxidisation is greater in more aerobic muscles (O'Keeffe and Hood 1982), with aerobicity quantified by the measurement of isocitrate dehydrogenase activity (ICDH). High intramuscular fat percentages (IMF) have been associated with high ICDH levels, so if industry moves to increase IMF we can hypothesise that there will be an ICDH linked increase in the brownness of lamb meat after 3 days of retail display..