Effects of stimulation on tenderness of lamb with a focus on protein degradation

K. M. Martin; D. L. Hopkins; G. E. Gardner; J. M. Thompson

doi:10.1071/EA06010

RESEARCH ARTICLE

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Effects of stimulation on tenderness of lamb with a focus on protein degradation

K. M. Martin ^A ^B ^E , D. L. Hopkins ^A ^C , G. E. Gardner ^A ^D and J. M. Thompson ^A ^B

+ Author Affiliations

- Author Affiliations

^A Australian Sheep Industry Cooperative Research Centre, Chiswick, New England Highway, Armidale, NSW 2350, Australia.

^B School of Rural Sciences and Natural Resources, University of New England, Armidale, NSW 2351, Australia.

^C NSW Department of Primary Industries, Centre for Sheep Meat Development, Cowra, NSW 2794, Australia.

^D School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, WA 6150, Australia.

^E Corresponding author. Email: kirstie.martin@une.edu.au

Australian Journal of Experimental Agriculture 46(7) 891-896 https://doi.org/10.1071/EA06010
Submitted: 26 November 2005 Accepted: 8 May 2006 Published: 8 June 2006

Abstract

Past studies have identified that electrical stimulation systems not only affect the pH–temperature decline of lamb carcasses, but also affect the tenderness of the product. It is unknown whether these differences are due to the effects of an optimal pH–temperature decline path by which the occurrence of shortening is decreased and proteolytic enzyme activity is increased, or by another mechanism, such as disruption of the muscle myofibres. This study attempted to elucidate this by placing control and mid-voltage electrically stimulated samples of the M. longissimus thoracis et lumborum in a water bath to prevent shortening by imposing an even pH–temperature decline on all samples. In order to obtain a complete understanding of the effects of stimulation on the muscle, samples were taken for indicators of tenderness, myofibre degradation and protein breakdown. No effect of stimulation was seen on tenderness and structural degradation measures aside from the expected rapid lowering of muscle pH. Interesting relationships were observed, however, between the different methods of meat tenderness assessment, with muscle structural protein degradation, shear force and muscle fibre and myofibre breakdown comparisons. These results suggest that the effects of electrical stimulation seen in mid-voltage systems as applied in this study are due only to the prevention of shortening conditions.

Additional keywords: fibre breaks, lamb, myofibrillar protein, tenderness.

Acknowledgments

The technical assistance of David Stanley and Leonie Martin (NSW DPI), and Sheridon Moll (UNE) is gratefully acknowledged. The study was funded by NSW Department of Primary Industries, Meat and Livestock Australia, the Australian Sheep Industry Cooperative Centre and UNE. The assistance of Paul Weston (DPI, Vic.) in the slaughter and processing of the lambs at Werribee is noted with appreciation. Development of the histology method has been undertaken under the guidance of Steve Parkinson, School of Anatomy and Human Biology, University of Western Australia and the work of his group in preparing images is gratefully acknowledged.

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