Elsevier

Meat Science

Volume 142, August 2018, Pages 14-22
Meat Science

Validating post-slaughter interventions to produce consistently high quality pork cuts from female and immunocastrated male pigs

https://doi.org/10.1016/j.meatsci.2018.03.021Get rights and content

Abstract

Eating quality attributes of pork loin (M. longissimus thoracis et lumborum) and silverside (M. biceps femoris) from female and immunocastrated male carcases hung from either the Achilles tendon or aitchbone, aged for either 2 or 7 days post-slaughter and cooked as roasts, stir fry and steak (loin only) (n = 25/gender) was assessed. A positive control treatment of moisture infusion (10% injection rate) was applied to Achilles hung sides with cuts aged for 2 d post-slaughter. Neither gender nor ageing period influenced consumer sensory scores. Beneficial effects of aitchbone hanging on eating quality compared with Achilles hanging were largely observed after 2 d ageing, with improvements (P < 0.05) in overall liking scores found for loin stir fry and silverside stir fry and roasts. Overall liking scores of all cuts, except silverside stir fry, were increased (P < 0.05) when moisture infused compared with those from aitchbone-hung sides. However, targeted fail rates of <10% were not consistently achieved across all cuts evaluated.

Introduction

For a pork eating quality system to be commercially acceptable, supply chains must be able to have flexibility in the choice of pathway interventions that are implemented to best suit the genetic and other management backgrounds of pigs and to meet their customer requirements. The use of aitchbone hanging, otherwise referred to as pelvic suspension or tenderstretching, where carcase sides are hung from the obturator foramen in the pelvis prior to rigor onset, to improve tenderness has been reported in beef (Bouton, Fisher, Harris, & Baxter, 1973; Hostetler, Link, Landmann, & Fitzhugh, 1972), lamb (Hopkins & Thompson, 2001; Thompson et al., 2005), pork (Bertram & Aaslyng, 2007; Channon, Taverner, D'Souza, & Warner, 2014; Møller, Kirkegaard, & Vestergaard, 1987; Rees, Trout, & Warner, 2003; Taylor, Perry, & Warkup, 1995) and in deer (Hutchison, Mulley, Wiklund, Flesch, & Sims, 2014). Aitchbone hanging results in stretching of the topside (M. semimembranosus), rump (M. gluteus medius) and silverside muscles in the hind leg and also straightens the vertebral column (Hostetler, Landmann, Link, & Fitzhugh, 1970), stretching the posterior section of the loin (Bertram & Aaslyng, 2007; Hopkins & Thompson, 2001). This results in an increase in sarcomere length of myofibrils due to reduced overlap between actin and myosin consequently, reducing muscle fibre density.

Aitchbone hanging has been included as a pathway intervention in both the Beef and Sheepmeat MSA programs as a means to effectively improve eating quality performance (Watson, Polkinghorne, & Thompson, 2008). Whilst improvements to tenderness have been reported for both pork loin steaks and topsides (M. semimembranosus) from aitchbone hung carcases (Channon et al., 2014; Dransfield, Ledwith, & Taylor, 1991), the requirement for abattoir personnel to manually change how pork carcases are suspended together with loss of chiller space and changes to muscle shape have contributed to the lack of adoption of aitchbone hanging to date. Aitchbone hanging may be an appropriate intervention to use to achieve eating quality improvements in cuts from pig carcases from particular supply chains in which a rapid rate of muscle pH decline, assessed from 45 min to 6 h post-slaughter, has previously been identified, rather than using electrical stimulation which may further exacerbate the rates of post-mortem muscle pH decline (Channon, Walker, Kerr, & Baud, 2003; Rees et al., 2003).

Recent studies involving different Australian supply chains have not shown any eating quality improvements resulting from ageing for 7 days compared with 2 days across a number of different cut type x cooking method combinations (Channon, D'Souza, & Dunshea, 2016; Channon, D'Souza, & Dunshea, 2018b). Further, no differences due to ageing for 7 or 28 days post-slaughter were found for eating quality attributes of both loin steaks and silverside roasts, indicating that maximal ageing occurred by 7 days post-mortem (Channon, D'Souza, & Dunshea, 2018a). For ageing period to be included as a recommended intervention to improve eating quality, further data is required to validate whether it can be reliably applied to pork cuts. Hanging carcases from the aitchbone may also negate the requirement for extended ageing to optimize pork quality as it has been shown that increasing ageing period from 2 to 7 days in pork (Channon et al., 2014) and from 7 to 14 days in beef (Ahnström, Hessle, Johansson, Hunt, & Lundström, 2009) hung from the aitchbone did not further improve tenderness. Moisture infusion (enhancement) of pork loin has been shown to improve eating quality traits without requiring extended ageing for 7 days post-slaughter compared with 24 h (Moore, Mullan, & D'Souza, 2012) or aitchbone hanging compared with Achilles (Walker, Channon, Baud, & Warner, 2005).

Previous benefits identified from aitchbone hanging on pork eating quality therefore warranted its inclusion in this study involving a current Australian pig genotype. The hypotheses tested, across all cut type × cooking method treatments investigated, were that the eating quality of pork from immunocastrated male pigs would be comparable, or better, than from females and be improved by: i. aitchbone hanging compared with hanging from the Achilles tendon; ii. ageing for 7 days post-slaughter rather than 2 days; and iii. moisture infusion (when applied to 2 day aged cuts from Achilles-hung carcases) compared with no moisture infusion. It was also hypothesised that these interventions, when applied in combination, would result in fail rate targets of <10% for both quality grade and re-purchase intention to be met across pork cuts sourced from the loin and silverside.

This study was conducted to determine whether hanging method, ageing period and moisture infusion can improve consumer eating quality scores of various cuts prepared from the loin and silverside, either as main effects or as interactions, and result in fail rates of <10% for both quality grade and re-purchase intention being achieved at a cuts level.

Section snippets

Animal management

The experimental protocols in this study were managed through CHM Alliance Pty. Ltd.'s Animal Ethics Committee (Protocol CHM PP 54/13). A total of 72 Large White × [Landrace × (Duroc × Large White)] entire male and female pigs (n = 36 per gender group) were managed on-farm within gender until slaughter at 22 weeks of age. All males were immunised against gonadotrophin releasing factor (GnRF) using Improvac® (Zoetis Ltd., USA), with injections administered at 10 and 17 weeks of age. As gilts had

Growth performance and carcase characteristics

No differences due to gender of the pig were observed in final liveweight of pigs (Table 2). Immunocastrated male carcases were 1.1 mm fatter (P = 0.015) at the P2 site and 3.2 kg lighter (P = 0.002) compared with female carcases. The average dressing percentage of carcases from immunocastrated males was 2.1 percentage units lower (P < 0.001) than females.

Objective measurements

Muscle pH of the loin, measured at 45 min, 90 min and 6 h post-slaughter, was not influenced by gender of the pig (Table 3). Average muscle

Discussion

Whilst flavour was the most highly correlated sensory trait with overall liking of pork in this study, tenderness must also be delivered to satisfy consumer expectations for a quality meat meal. The variation in tenderness of meat following post-mortem storage can be due to sarcomere length, connective tissue content and proteolysis of myofibrils and associated proteins, with the relative contribution of each of these components being muscle dependent (Koohmaraie, Kent, Shackelford, Veiseth, &

Conclusion

The lower overall fail rate for quality grade of pork cuts from immunocastrated males compared with females and the comparability in eating quality performance of cuts between these two genders supports the inclusion of immunocastrated males into an eating quality system for pork. The main effects of aitchbone hanging and moisture infusion each significantly improved pork eating quality attributes. However, these processing interventions did not achieve a consistently low fail rate (for either

Acknowledgements

Funding provided by the High Integrity Australian Pork Co-operative Research Centre (3A-109) and the support from Australian Pork Limited to undertake this work is acknowledged. The authors gratefully acknowledge both the producer and processor for their involvement, support, co-operation and assistance in the conduct of this study. Dr. Cameron Jose from the Department of Agriculture and Food Western Australia is acknowledged for his assistance. Dr. Richard Jarrett, Jessica Tan and Dr. Anna

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    1

    Aspects of this work has been previously published as: Channon, H.A., D'Souza, D.N., & Dunshea, F.R. (2015). Aitchbone hanging or moisture infusion, but not ageing, influenced eating quality of pork cuts. Animal Production Science, 55, 1474.

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