Scientists have gained special insight into how lamb production and processing factors can influence the key quality attributes important to consumers: tenderness and colour.
By basing their work on the Sheep CRC’s Information Nucleus flock, which is distributed at eight locations in 5 states across Australia, researchers have been able - for the first time - to separate environmental and genetic components of meat quality.
The study was conducted jointly by Robin Jacobs of DAFWA, Janelle Edwards of SARDI and
Robyn Warner of DPI Victoria, who says in the first year of the project, data from more than 2000 lambs was accumulated.
“We all know that consumers expect premium quality and value from their lamb meat purchases, and both of these are influenced by environmental and genetic factors.
“This work will deliver ways of improving meat yield, quality and nutritional value, and will be applicable to different breeds, regions and lamb management systems across Australia.”
Dr Warner, who was also part of a team that won a 2010 Museum of Australia Eureka Prize for science, says the study came to a number of key conclusions.
“For tenderness, the level of Intramuscular fat (IMF) and processing conditions are most important, as indicated by the chemically measured fat in the meat, and the ultimate pH and the rate of pH fall. The majority of lamb loin meat was acceptably tender after five days of ageing.
“The most important determinant of fresh colour appears to be ultimate pH. Most of the lamb loin meat was acceptable in terms of fresh meat colour.
“We also found that IMF and mineral content affect the browning of meat during retail display, hence playing a role in shelf-life management.
“Overall, the breeding and management practices that increase muscle IMF levels and the processing practices that optimise muscle pH post-slaughter do most to improve the tenderness of lamb.
“The confounding factor is that extension of retail colour stability may be antagonistic to traits associated with tenderness, particularly IMF level and the rate of pH decrease, though more work will help us to unravel this area,” she said.
Main results in detail:
- Meat colour: the majority of samples would be considered to have acceptable redness by 95% of consumers. Older lambs have more pigment, a darker colour and a higher level of myoglobin pigment than younger lambs. Carcasses from lambs finished using high-energy pelleted diets have less redness compared with those from lambs fed low-energy diets and pasture. Results suggest that colour stability during retail display has moderate heritability and that it is likely to be responsive to genetic selection.
- Tenderness: On day 1 post-slaughter, the proportion of acceptable tenderness among flocks ranged from 0.5% for flock 1 to 58% for flock 8. On day 5 post-slaughter (i.e., after 5 days of ageing), most flocks produced acceptably tender meat (71–95% of samples were acceptable). Females produced meat that had a lower shear force on days 1 and 5 post-slaughter and had a lower shear force difference than wethers, although, while the difference was significant, it would most likely not be detected by the consumer.
- Intramuscular fat: Australian lamb contains 4–5% IMF, and studies have demonstrated that this level of fat is required to achieve consumer satisfaction in Australia. An IMF content of less than 3% has a particularly detrimental effect on palatability. A new finding is that tenderness depended on IMF content and increased with IMF. Over the range of IMF in the flocks, the shear force at 5 days would be 10N lower from lambs with higher IMF. This means that a consumer eating the meat from lambs with higher IMF would require less ‘bite’ power to chew through the meat.
- Breed effects: In general, Merinos take more time to reach slaughter weight than other breeds at given nutritional regime and thus will generally be older than other breeds at slaughter and have darker meat.
