Elsevier

Meat Science

Volume 61, Issue 2, June 2002, Pages 215-224
Meat Science

Tenderness of pork m. longissimus thoracis et lumborum after accelerated boning. Part II. Effect of post-slaughter ageing

https://doi.org/10.1016/S0309-1740(01)00189-9Get rights and content

Abstract

This research investigated the effect of ageing time (0–10 days) at 2 °C on tenderness of pork longissimus muscle after either rigor boning (RB) or accelerated boning (removal from carcass within 30 min post slaughter) and temperature conditioning at either 0 or 14 °C. Ageing occurred most rapidly in muscles conditioned at 14 °C– maximum tenderization occurred by 4 days post-mortem. RB muscles and muscles conditioned at 0 °C aged more slowly and took 8 and 10 days, respectively, to reach a comparable level of tenderness. Temperature conditioning at 14 °C, produced muscles which had lower drip loss and lighter surface colour.

Introduction

Accelerated boning of meat carcasses has been conducted for a number of years. Accelerated boning enables production costs to be reduced due to lower labour requirements, a reduction in chiller space and energy input and increased product turnover (Cross & Seideman, 1985, Powell et al., 1982). Accelerated boning of pork has been slow to be employed world wide, largely due to the logistics of changing to accelerated boning and also the potential detrimental impact on tenderness because of the rapid drop in muscle temperature that occurs when muscles are removed pre-rigor. Accelerated boning of pork loins followed by chilling at 0 °C results in cold toughening and higher drip loss (Rees, Trout, & Warner, 2001b). Furthermore, other researchers have also observed cold toughening of pork following accelerated boning (Cross & Seideman, 1985, Honikel & Reagan, 1987). Thus, alterations to the accelerated boning methods used for pork are required to overcome the problem of cold shortening and reduced proteolytic activity, the two factors that contribute to cold toughening. Dransfield, Jones, and MacFie (1980–1981) have shown post slaughter ageing can also be used to overcome increased toughness. The experiment in this study was designed to determine the rate of ageing of accelerated boned pork.

A method reported to improve meat tenderness is post slaughter ageing of the muscle (Dransfield et al., 1980–1981). However conflicting reports are presented on the ideal storage time and whether post slaughter storage of cold shortened muscle is effective in improving tenderness.

Meat becomes more tender during storage post rigor (Dransfield et al., 1980–1981), a process referred to as ageing. Tenderisation is believed to occur because of the degradation of some of the key structural proteins (desmin, titin and nebulin) by endogenous enzymes when meat is aged (Koohmaraie, Wheeler, & Shackelford, 1995). Furthermore, changes in the sarcoplasmic proteins, actomyosin and connective tissue have been observed during ageing along with myofibrillar fragmentation that occurs in or near the z disc (Bandman & Zdaris, 1988, Koohmaraie, 1994). This fragmentation has been related to increased tenderness (Bandman & Zdaris, 1988, Koohmaraie, 1994).

There are differing views on the optimum time of post mortem ageing to achieve pork tenderness following conventional boning. Harrison, Bowlers, Anderson, Tuma, and Kropf (1970) and Buchter and Zeuthen (1971) observed an increase in tenderness in pork LTL muscle up to the sixth and eighth days post mortem respectively. In contrast, Bennett, Bramblett, Aberle, and Harrington (1973) found that ageing more than one to two days did not significantly improve the tenderness of pork. Furthermore, Feldhusen and Kuhne (1992) found that the optimum shear force values were attained after two to three days of ageing. Dransfield et al. (1980–1981) used a model to predict that on average 50% of the tenderisation of pork occurs in two days relative to 4.2 days for beef and veal under their experimental conditions.

Conflicting views are presented in the literature on the degree of ageing of meat following accelerated boning. The lack of improvement in tenderness with post slaughter storage of muscle following accelerated boning is believed to be due to cold toughening. Davey, Kuttel, and Gilbert (1967) demonstrated that with increased muscle shortening the muscle demonstrates a decrease in tenderness improvements with ageing. The reduced tenderness improvement when muscles shorten is believed to be caused by structural changes in the myofibrils preventing the proteolysis by endogenous enzymes of proteins on or near the z line (Iversen, Henckel, Larsen, Monllao, & Moller, 1995). It is possible that the tougher muscle resulting from accelerated boning may require longer to reach its optimal tenderness. Therefore a closer examination of the rate of ageing is required.

Thus this experiment was designed to test the following hypotheses:

  • 1.

    muscles undergoing accelerated boning and chilling at 0 °C will not age due to cold shortening and a reduction in proteolytic activity

  • 2.

    muscles undergoing accelerated boning and chilling at 14 °C will tenderise rapidly due to the prevention of cold shortening and maximisation of proteolysis

  • 3.

    muscles undergoing rigor boning will undergo rapid ageing (80% of the improvements in tenderness within 4 days post slaughter) as previously observed in Rees et al. (2001b).

Section snippets

Methodology

Fifteen Large White × Landrace female pigs were slaughtered on three separate days following stunning with carbon dioxide (90% CO2 in air for 1.8 mm) and after splitting the carcass the sides were randomly allocated to one of three treatments:

  • 1.

    RB—rigor boning, placed in the chiller and boned at rigor;

  • 2.

    AB-0—accelerated boning within 0.5 hours of slaughter and placed in an ice water bath (0 °C) until rigor; and

  • 3.

    AB-14—accelerated boning within 0.5 hours of slaughter and temperature conditioned at

Rate of pH and temperature decline

The rates of pH and temperature decline for the three treatments can be seen in Fig. 1, Fig. 2, respectively. At 30 min, 1, 2, 4, 5, 6,7, 8 and 9 h post slaughter there was no difference in muscle pH between the three treatments (P>0.05). At 3 h post slaughter, the AB-0 muscles had a higher muscle pH than the AB-14 and RB muscles (<0.01). At 30 min post slaughter, no difference in muscle temperature was observed (P>0.05). By 1 h post slaughter and continuing to rigor, the AB-0 muscles had a

Discussion

Improvements in meat tenderness have been reported with post slaughter ageing. The tenderisation of meat occurs in two stages—an initial rapid phase followed by a slow phase (Takahashi, 1996). The rapid improvement in tenderness is mainly due to the structural weakening of myofibrils which begins at rigor mortis where tenderness is at its lowest. The slow improvement is due to the structural weakening of the endomysium and perimysium (Takahashi, 1996). However, when severe cold shortening

Conclusions

Post slaughter storage of pork appears to be effective at improving tenderness when severe chilling conditions are prevented. Under conditions that could result in cold shortening, ageing was prevented due to the shortening of the sarcomeres preventing proteolysis from occurring. As the AB-0 muscles did not appear to have completely entered rigor morris at initial sampling as indicated by the higher muscle pH, the true impact of this treatment on sarcomere length may have been missed.

Acknowledgements

The authors wish to acknowledge the financial assistance of the Pig Research and Development Corporation, Canberra, Australia and the assistance of D. D'Souza, P. Walker, C. Hofmeyr, H. Channon, M. Kerr, A. Payne, R. Biden, P. Weston and K. Butler.

References (36)

  • M.E. Bennett et al.

    Muscle quality, cooking method and ageing on palatability of pork loin chops

    Journal of Food Science

    (1973)
  • L. Buchter et al.

    The effect of ageing on the organoleptic qualities of PSE and normal pork loins

    Proceedings 2nd International Symposium on Condition of Meat Quality in Pigs

    (1971)
  • M. Candek-Potokar et al.

    Quality parameters of pig longissimus dorsi muscle as affected by slaughter weight and breed

    42nd International Congress of Meat Science and Technology

    (1996)
  • H.R. Cross et al.

    Use of electrical stimulation for hot boning of meat

  • R.D. Culler et al.

    Relationship of myofibril fragmentation index to certain chemical, physical and sensory characteristics of bovine longissimus muscle

    Journal of Food Science

    (1978)
  • C.L. Davey et al.

    Shortening as a factor in meat ageing

    Journal of Food Technology

    (1967)
  • Dransfield, E., Jones, R., & MacFie, H. (1980–1981). Tenderising in m longissimus dorsi of beef, veal, rabbit, lamb and...
  • P.F. Gould et al.

    Effect of aging on tenderness of pork loin chops

    Food Technology

    (1965)
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