Genotype and age at slaughter influence the retail shelf-life of the loin and knuckle from sheep carcasses
R. D. Warner A B F , E. N. Ponnampalam B , G. A. Kearney C , D. L. Hopkins D and R. H. Jacob EA Australian Sheep Industry Cooperative Research Centre, Armidale, NSW 2350, Australia.
B Animal Production Sciences Platform, Department of Primary Industries, 600 Sneydes Road, Werribee, Vic. 3030, Australia.
C 36 Paynes Road, Hamilton, Vic. 3300, Australia.
D NSW Department of Primary Industries, Centre for Sheep Meat Development, PO Box 129, Cowra, NSW 2794, Australia.
E Department of Agriculture and Food Western Australia, 3 Baron-Hay Court, South Perth, WA 6151, Australia.
F Corresponding author. Email: robyn.warner@dpi.vic.gov.au
Australian Journal of Experimental Agriculture 47(10) 1190-1200 https://doi.org/10.1071/EA07077
Submitted: 16 March 2007 Accepted: 31 July 2007 Published: 19 September 2007
Abstract
This study was conducted to determine the effect of genotype and age at slaughter (8, 14 and 22 months) on the retail display life of lamb chops [boneless loin (M. longissimus thoracis) and boneless leg steaks from the knuckle (M. rectus femoris)]. The genotypes represented were Poll Dorset × Border Leicester Merino, Poll Dorset × Merino, Merino × Merino (M × M) and Border Leicester × Merino. The colour and retail shelf-life of lamb cuts were assessed objectively, using a HunterLab Miniscan, at 24 h postslaughter and at 0, 2 (midpoint of commercial retail display life) and 4 (endpoint of commercial retail display life) days for overwrapped product in a simulated retail display. M × M had a higher ultimate pH (pHu) in the knuckle, but not the loin, at 8, 14 and 22 months of age relative to the other three genotypes. Generally, at 1 day postslaughter and over the 4 days of retail display, the loin from the M × M genotype was lighter, less red and more brown with a lower oxymyoglobin : metmyoglobin (oxy : met) ratio, a faster time to discolouration and a higher percentage change in the oxy : met ratio during retail display. Conversely for the knuckle, the M × M genotype was generally less brown (more red) and less yellow with a higher oxy : met ratio, a slower time to discolouration and a lower percentage change in the oxy : met ratio. There were few differences between the other genotypes in surface meat colour either at 1 day postslaughter or during retail display for either muscle. At 14 and 22 months of age, the loin was darker, redder and yellower with a higher oxy : met ratio relative to the previous age than meat from the 8- and 14-month-old sheep, respectively. In conclusion, the loin from Merinos was most susceptible to discolouration in retail display and thus would be least acceptable to the consumer. In spite of the higher pHu in the knuckle of the Merino genotype, the meat was less susceptible to discolouration during retail display compared with the other genotypes.
Acknowledgements
The sheep used in this study were bred by NSW DPI at Cowra as part of a collaborative study within the Australian Sheep Industry Cooperative Centre. A large number of people contributed to the study including the slaughters and collection of data. The authors would like to thank Tony Markham, Jayce Morgan, Andrew Roberts, Sally Martin, Brent McLeod, Steve Sinclair, Joe Brunner, Stuart McClelland and Amanda Lang (NSW Department of Primary Industries), Peter Allingham (CSIRO) and Tracy Lamb and Rachel McGee funded by CSIRO, Drs Danny Suster and Matt McDonagh, Dete Hasse, Erin Rutty and Fahri Fahri (DPI, Victoria), Dr Greg Nattrass (SARDI) and Dr Martin Cake and Mal Boyce (Murdoch University). Special thanks for data collection associated with this paper are extended to Matthew Kerr and Oliver Ferdinando (DPI, Victoria) and for the biometrical input from Kym Butler. Funding provided by the Australian Sheep Industry Cooperative Centre and by the Victorian Department of Primary Industries is gratefully acknowledged.
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