Response to different pathway interventions to improve pork eating quality consistency

For consistent delivery of high quality, boar-taint-free pork cuts in Australia, additional data is needed to quantify interactions between different pathway factors. Few studies have been conducted comparing eating quality traits of different pork cuts from entire male pigs immunised against gonadotrophin releasing factor (GnRF) (IM) with females, in combination with other pathway interventions, including ageing for 7 d and electrical stimulation (ES) previously shown to improve pork eating quality (Channon and Warner 2011). This study aimed to validate the effect of ES, ageing (A) and moisture infusion (MI) on eating quality attributes of five different pork cuts from female (F) and IM.

Large White × Landrace pigs (F, n = 50; IM, n = 50), raised from weaning in straw-based eco-shelters with access to feed on an ad libitum basis, were slaughtered at 21 weeks of age. For three weeks before slaughter, ractopamine hydrochloride was included in the feed at a rate of 5 ppm/tonne. Entire male pigs were vaccinated with Improvac^® (Zoetis Ltd., USA) at 10 and 15 weeks of age. Pigs were separated according to gender prior to transport and slaughtered at a commercial abattoir. Pigs were randomly allocated within gender to the ES treatment (control or 150 mA for 30 sec at 2 min after slaughter). A total of 25 pigs per gender were selected from the larger group in the chiller at 60 min after slaughter based on carcass specifications of 60–75 kg (Trim 1) and 8–13 mm P2. At 24 hours after slaughter, roast and stir fry portions were obtained from loin and silverside muscles from both carcase sides and steaks from the loin only. Ageing (2 or 7 days) was allocated to muscles from each carcase side (n = 10 sides per treatment) and frozen prior to thawing for sensory analysis. In addition, MI (no, or 10% extension) was applied to no-ES, 2-day-aged loin and silverside muscles from 10 sides per gender. Consumers (n = 400) rated 2,000 samples for quality grade (1 = unsatisfactory to 5 = excellent). Fail rate was determined (expressed as a percentage of evaluations achieving a quality grade score of 1 or 2). Data were analysed by ANOVA.

Ageing for 7 days increased (P < 0.05) quality grade scores across all cut × cooking method treatments compared with 2 days (3.38 versus 3.26; SED 0.046), with larger improvements in quality grade scores found due to MI (3.54 vs. 3.32, for MI and no-MI cuts respectively; SED 0.058; P < 0.05). Across all cut × cooking methods, neither gender nor ES influenced (P > 0.05) quality grade scores and no interactions across cut × cooking methods were found (data not presented). At the cut level, loin roasts from IM had higher quality grade scores (P = 0.034) and had lower fail rates than F (Table 1). Differences in quality grade scores between cuts evaluated in this study were greater in magnitude compared with other interventions imposed.

Table 1.  Quality grade scores (and fail rate, %) of pork from female (F) and entire male pigs immunised against GnRF (IM) for five cut × cooking treatments

As quality grade scores (and fail rates) of different pork cuts from IM were either comparable, or better, than those from F, this suggests that pork from IM may be included into any future eating quality system. Font i Furnols et al. (2008) also reported no differences in tenderness and juiciness of pork loin from F and IM pigs. Further investigations to understand mechanisms impacting on the ability of pork loin and silverside muscles to age are needed as ageing for 7 days after slaughter only caused very minor improvements in quality grade scores. The lack of response to ES in this study suggests that alternate options need to be explored for individual supply chains to enable an eating quality system for pork to be successful.