Acute exercise stress and electrical stimulation influence the consumer perception of sheep meat eating quality and objective quality traits
R. D. Warner A C , D. M. Ferguson B , M. B. McDonagh A , H. A. Channon A , J. J. Cottrell A and F. R. Dunshea AA Department of Primary Industries, 600 Sneydes Road, Werribee, Vic. 3030, Australia.
B CSIRO Livestock Industries, FD McMaster Laboratory, Locked Bag 1, Armidale, NSW 2350, Australia.
C Corresponding author. Email: Robyn.Warner@dpi.vic.gov.au
Australian Journal of Experimental Agriculture 45(5) 553-560 https://doi.org/10.1071/EA03270
Submitted: 8 December 2003 Accepted: 4 June 2004 Published: 27 June 2005
Abstract
The effects of acute exercise stress and electrical stimulation on lamb eating quality and objective measurements of quality were evaluated on the Longissimus thoracis et lumborum (LTL) and the Gluteus medius (GM) muscles. Meat quality attributes were also assessed on the LTL, Semimembranosus (SM) and the Semispinalis capitis (SC) muscles. Forty-eight Poll Dorset × Border Leicester–Merino ewes of about 6 months old were randomly allocated to treatments in a 2 × 2 factorial design, with the respective factors being exercise (Ex, 0 v. 15 min) and post-slaughter low voltage electrical stimulation (control v. ES). In general, exercise reduced the rate of pH fall and increased the ultimate pH of all 3 muscles (P<0.05). This effect was more pronounced in the SM than in the LTL and SC. Exercised LTL and SM muscles also had lower surface lightness (L*) values and higher muscle total water content, indicating an increased incidence of dark cutting meat. Exercised LTL steaks were rated higher for tenderness and juiciness by the taste panelists and had lower Warner-Bratzler shear force values, as is often observed with high ultimate pH meat. Electrical stimulation reduced initial pH (pH0.5) values, but resulted in a slower rate of pH fall in the LTL and SM thereafter. Electrical stimulation resulted in an elevation of temperature at rigor in the SM by 10°C (15 v. 25°C) and in the LTL by 3.1°C (7.4 v. 10.5°C). While no effect of electrical stimulation was observed with instrumental analysis, electrical stimulation reduced sensory tenderness scores and overall liking for the GM, and tended to reduce flavour and juiciness of both the GM and LTL. In conclusion, acute exercise pre-slaughter improved eating quality, but caused dark cutting meat. The negative effect of low voltage stimulation on the eating quality of the GM was probably due to a high rigor temperature and associated heat toughening.
Acknowledgments
The tremendous assistance beyond the call of duty given by Matthew Kerr is gratefully acknowledged. The technical assistance of Paul Meredith, Paul Weston, Tamara Hauke, Karen Brisco, Peter Walker, Doug Kerton, Rebecca Cibej and the biometrical input of Kym Butler is acknowledged. Funding was provided by the Sheep Co-operative Research Centre and also by the Sheep Meat Eating Quality Program of Meat and Livestock Australia.
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