Electrical stimulation or moisture infusion improves the eating quality attributes of loin and silverside cuts from female and immunocastrated male pigs.

This study validated the effect of gender (female, immunocastrated male; n = 50), electrical stimulation (none or 150 mA constant current for 30 s at 2 min post-slaughter) and ageing period (2 or 14 d) on the eating quality of pork roast and stir fry sourced from the loin (M. longissimus thoracis et lumborum) and silverside (M. biceps femoris) and steak from the loin only. Moisture infusion was applied to 2 d aged, non-stimulated primals as a positive control treatment. Neither gender nor ageing period influenced (P > 0.05) eating quality. Electrical stimulation and moisture infusion were each effective interventions in improving pork eating quality, but their effects were inconsistent between the five cuts evaluated. No interventions achieved the fail rate target of <10% for quality grade for all cuts, indicating that additional interventions are needed to enable industry to consistently deliver high quality pork.

Guaranteeing the quality and integrity of pork - An Australian case study.

The Australian pork industry is strongly committed to assuring the integrity of its product, with substantial research investment made over the past ten years to develop and implement systems to assure the consistency and quality of fresh pork and to enable accurate tracing of unpackaged fresh pork back to property of origin using trace elemental profiling. These initiatives are pivotal to allow Australian pork of guaranteed eating quality to be successfully positioned as higher value products, across a range of international and domestic markets, whilst managing any threats of product substitution. This paper describes the current status of the development of a predictive eating quality model for Australian pork, utilizing eating quality datasets generated from recent Australian studies. The implementation of trace elemental profiling, by Physi-Trace™, to verify and defend provenance claims and support the supply of consistently high eating quality Australian pork to its customers, is also discussed.

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

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.

Eating quality traits of shoulder roast and stir fry cuts outperformed loin and silverside cuts sourced from entire and immunocastrated male pigs.

This study investigated the effects of ageing period (2 or 7days), endpoint temperature (70 or 75°C), cut type (loin (M. longissimus thoracis et lumborum), silverside (M. biceps femoris), blade (M. triceps brachii) and chuck tender (M. supraspinatus)), cooking method (roast and stir fry (all cuts) and steak (loin only)) on eating quality attributes of pork from entire and immunocastrated male pigs. Higher intramuscular fat levels were found in all cuts from immunocastrated males compared with entire males. Of the seven cut type×cooking method combinations evaluated, shoulder cuts had the lowest fail rate (P<0.001) and loin steak and silverside cuts scored lowest (P<0.001) for tenderness, juiciness, overall liking, quality grade and re-purchase intention. Although no differences in sensory scores due to gender were observed, boar taint was identified in 10% of entire males. Minimising adverse risks in eating quality due to boar taint in males remains a key industry issue to ensure consistent delivery of high quality pork.

Diet composition and slaughter age up to 24weeks have minimal impact on pork eating quality of loin steaks and silverside roasts from female pigs.

Female crossbred pigs were randomly allocated at 16weeks of age to one of three dietary treatments (A: corn and soybean meal; B: wheat and canola meal; C: wheat and sorghum) matched for digestible energy (13.6MJ DE/kg) and total lysine (0.93-0.95%) and fed for 4, 5 or 8weeks, respectively, prior to slaughter. Loin (M. longissimus thoracis et lumborum) and silverside (M. biceps femoris) were obtained from 20 pigs per dietary treatment group and prepared into steaks and roasts, respectively, for consumer evaluation with ageing treatments of 7 and 28days post-slaughter allocated within muscle. Neither dietary treatment/age at slaughter nor ageing treatment influenced sensory traits of either cut. Intramuscular fat levels were also not influenced by dietary treatment. Higher (P<0.001) fail rates for silverside roasts compared with loin steaks indicate that different interventions are needed at a cut level to optimise pork eating quality consistency and consumer expectations.

Quantifying production, processing and post-slaughter effects on pork eating quality using random effects meta-regression.

Random effects meta-regression techniques, analyzed using a restricted maximum likelihood (REML) approach, was used to determine the influence of various factors that may be experienced or imposed on pigs, carcases and pork on pork eating quality attributes and shear force of the M. longissimus dorsi (loin). This was done to inform the development of a pathway based eating quality system for pork. Estimated means of explanatory variables were obtained for those pathway factors where sufficient published studies met the criteria for inclusion in the analysis. Due to a lack of data for interactions between factors investigated, only single factors were included as fixed terms in the REML models. This analysis identified that moisture infusion (P < 0.001), ageing for more than 2 d post-slaughter (P = 0.006) and tenderstretching (P = 0.006) each resulted in significant improvements in tenderness. Cooking loins to an endpoint temperature of ≥ 80°C negatively impacted both tenderness (P = 0.022) and juiciness (P < 0.001) scores compared with 70 to 74°C. It was not possible to develop algorithms to reliably estimate the effects of multiple factors on pork eating quality attributes to a cuts-based level due to limited studies reporting data for treatment interactions.

Developing a cuts-based system to improve consumer acceptability of pork: Impact of gender, ageing period, endpoint temperature and cooking method.

The effect of gender (entire male, female and castrate), ageing period (2 or 7days) and endpoint temperature (70 or 75°C) on consumer perceptions of cuts from the loin (Musculuslongissimus thoracis et lumborum), silverside (Musculus biceps femoris) and shoulder (Musculus triceps brachii (roast) and Musculus supraspinatus (stir fry)) when roasted or stir fried (all primals) or grilled as steaks (loin only) was investigated. Higher scores for juiciness (P=0.035), flavour (P=0.017), overall liking (P=0.018), quality grade (P=0.026) were obtained from castrates than entire males, with females intermediate. Neither ageing period nor endpoint temperature, as main effects, influenced sensory scores. Loin steaks and silverside roasts obtained lower (P<0.001) scores for all sensory traits except aroma; scores for shoulder cuts were highest (P<0.001). Cooking to 70°C improved (P<0.05) juiciness, flavor and overall liking scores of loin steaks compared with 75°C. Different pathway interventions are required to optimize eating quality of different pork cuts and the cooking methods used to prepare them.

Estimating the impact of various pathway parameters on tenderness, flavour and juiciness of pork using Monte Carlo simulation methods.

Monte Carlo simulation was investigated as a potential methodology to estimate sensory tenderness, flavour and juiciness scores of pork following the implementation of key pathway interventions known to influence eating quality. Correction factors were established using mean data from published studies investigating key production, processing and cooking parameters. Probability distributions of correction factors were developed for single pathway parameters only, due to lack of interaction data. Except for moisture infusion, ageing period, aitchbone hanging and cooking pork to an internal temperature of >74°C, only small shifts in the mean of the probability distributions of correction factors were observed for the majority of pathway parameters investigated in this study. Output distributions of sensory scores, generated from Monte Carlo simulations of input distributions of correction factors and for individual pigs, indicated that this methodology may be useful in estimating both the shift and variability in pork eating traits when different pathway interventions are applied.

Aitchbone hanging and ageing period are additive factors influencing pork eating quality.

The effects of abattoir, carcase weight (60 or 80 kg HCW), hanging method (Achilles or aitchbone) and ageing period (2 or 7 day post-slaughter) on eating quality attributes of pork were investigated in this 3×2×2×2 factorial study. A total of 144 Large White×Landrace female pigs were slaughtered at one of three abattoirs and sides hung from either the Achilles tendon or the aitchbone. After 24 h chilling, loin (M. longissimus thoracis et lumborum) and topside (M. semimembranosus) muscles were individually vacuum packaged and aged for 2 or 7 days post-slaughter. Consumers (n=852) evaluated eating quality. Neither abattoir nor carcase weight influenced tenderness, flavour or overall liking of pork. Improvements in tenderness, flavour and overall liking were found due to aitchbone hanging (P<0.001) and ageing (P<0.001) for 7 days compared with Achilles-hung carcases and pork aged for 2 days, respectively. This study demonstrated that aitchbone hanging and 7 day ageing can improve eating quality, but these effects were additive as the interaction term was not significant.

Effect of Duroc content, sex and ageing period on meat and eating quality attributes of pork loin.

This study was conducted to determine the effect of percentage Duroc content of entire male and female pigs and ageing period on meat and eating quality attributes of pork loin (M. longissimus thoracis et lumborum). A total of 84 pigs [entire males (n=42) and female (n=42)] of 0% Duroc (100% Large White), 50% Duroc (Duroc×Large White) or 100% Duroc (n=14 pigs per sex×genotype combination) were slaughtered at a liveweight of ∼100 kg. Steaks from the M. longissimus lumborum of female pigs were aged for either 2 or 7 days post-slaughter and evaluated using a consumer taste panel. Eating quality attributes of tenderness, flavour and overall liking of pork loin steaks from female pigs were not (P>0.05) influenced by Duroc content. Pork from 100% Duroc pigs was juicier (P=0.05) and had a higher (1.84%, P=0.05) intramuscular fat content than pork from 0 and 50% Duroc pigs (1.40 and 1.25%, respectively). Pork from entire male pigs had a lower (P<0.001) intramuscular fat content, was darker (P<0.01) in colour and recorded higher (P<0.01) Warner Bratzler shear force values compared with pork from female carcasses. Ageing pork loin steaks in vacuum bags for 7 days improved tenderness (P<0.01), flavour (P<0.05) and overall liking (P<0.05) compared with steaks aged for 2 days post-slaughter. Ageing of pork steaks for 7 days post-slaughter improved eating quality attributes far more effectively than increasing percentage Duroc content of pigs, which only influenced consumer scores for juiciness.

Application of constant current, low voltage electrical stimulation systems to pig carcasses and its effects on pork quality.

This study examined the effectiveness of a constant current, low voltage electrical stimulation system on improving pork quality when applied to pigs at 2 min post-exsanguination. A total of 48 female Duroc×Large White/Landrace pigs of 85-90 kg liveweight were randomly allocated immediately prior to slaughter to one of four constant current electrical stimulation treatments: control (no electrical stimulation), 50, 200 and 400 mA. Stimulation was applied to pig carcasses at 2 min post-exsanguination for 30 s. No differences (P>0.05) in WB shear force values, muscle lightness or PSE incidence of pork M. longissimus lumborum (LL) was found due to electrical stimulation treatment. Muscle pH of the LL muscle was lower (P<0.001) in carcasses in the 200 and 400 mA treatments compared to those from carcasses in both the 50 mA and control treatment groups, when measured at the various time points from 40 min to 8 h post-slaughter. Although carcasses stimulated with 200 and 400 mA had higher percentage drip loss (P<0.05) and purge (P<0.001), this was not found to impact WB shear force values, muscle lightness or PSE incidence.

Effect of low voltage electrical stimulation of pig carcasses and ageing on sensory attributes of fresh pork.

The effect of electrically stimulating pig carcasses and ageing on sensory attributes of pork was evaluated in this study. A total of 48 female pigs [Duroc×Large White/Landrace (A; n=24) and Large White/Landrace (B; n=24)] were randomly allocated immediately prior to slaughter to one of two low voltage stimulation treatments; no stimulation or 150 mA applied for 30 s at 2 min post-exsanguination. Each side of the carcass was then randomly allocated to an ageing treatment of either 2 or 7 days post-slaughter. Muscle pH of the M. longissimus lumborum was lower (P<0.001) in electrically stimulated carcasses when measured from 40 min to 8 h post-slaughter compared with non-stimulated carcasses. Percentage drip loss, muscle lightness and PSE incidence were not influenced (P>0.05) by electrical stimulation. Electrical stimulation of pig carcasses and ageing pork for 7 days post-slaughter both improved (P<0.001) consumer scores for tenderness, juiciness, overall liking and quality category, however the interaction term of electrical stimulation and ageing was not significant for any of the sensory attributes. Pork from non-stimulated carcasses that was aged for 2 day post-slaughter was less tender (P<0.01) compared with pork in all other treatments. These results indicate that electrical stimulation (150 mA applied for 30 sec at 2 min post-exsanguination) was effective in improving eating quality attributes of pork, particularly when pork was aged for only 2 days post-slaughter, without detrimentally affecting colour or drip loss.

A national audit of retail lamb loin quality in Australia.

A retail audit of lamb loin tenderness was conducted over a 12-month period to determine the variation in tenderness of Australian lamb. Tenderness was objectively measured using Warner-Bratzler (WB) shear force. Muscle pH and cooking loss were determined on all samples and colour was measured on a sub-sample of loins. A total of 909 midloins from retail butcher shops and supermarkets located in four Australian capital cities (Sydney, Canberra, Melbourne, and Perth) were evaluated at four sampling times (December 1997 and March, June, and October 1998). Overall, 20.3% of all midloins purchased had a WB shear force value above the threshold level of 5 kg. Generic samples from Melbourne butcher shops were similar for WB shear force on average to the generic samples from Canberra and Sydney, whereas those from Melbourne supermarkets had significantly (P<0.001) higher WB shear force and were in line with generic samples from Perth. In both Canberra and Perth, alliance (branded) lamb had a greater WB shear force (P<0.05) than generic lamb. No relationship was found between price per kg and shear force (r=0.02) for loins purchased in Sydney (n=220). Price per kg differed between months (P<0.001) and suburbs (P<0.001), but not between retail butcher shops and supermarkets. Of the midloins tested, 10.3% had a pH above the critical point of 5.8. Midloins from the December 1997 sampling had a lower pH (P<0.01) than those sampled at other months. Those sampled in Melbourne and Perth had a similar mean pH, which were lower (P<0.001) than Canberra and Sydney samples. The findings from this quality audit suggest that there is room to improve the tenderness of Australian lamb sold in the domestic market. A lamb eating quality assurance system, based on set protocols, is one approach that is currently being investigated in Australia to ensure the supply of consistently high eating quality lamb to consumers.

Comparison of CO(2) stunning with manual electrical stunning (50 Hz) of pigs on carcass and meat quality.

The effects of carbon dioxide stunning on carcass and pork quality attributes were compared with the effects of manual electrical stunning using either head-only or head-to-brisket electrodes. A total of 30 Large White×Landrace boars (homozygous dominant for the halothane gene) were randomly allocated immediately prior to slaughter to one of three stunning treatments: carbon dioxide (90% CO(2)), head only (HO; 1.3 A for 4 s at a frequency of 50 Hz) or head to brisket (HBR; 1.3 A for 4 s at a frequency of 50 Hz) electrical stunning. The pH of the M. longissimus thoracis (LT) muscle measured at two sites [between the fifth and sixth thoracic vertebrae (Site 1) and the last thoracic rib (Site 2)] at 40 min post-slaughter was lower (P<0.001) in HBR stunned pigs compared with both CO(2) and HO stunned pigs. No differences in ultimate pH of the LT at either measurement site were found due to stunning method. However, a faster (P<0.05) relative rate of pH decline was found in the LT at Site 1 from HBR stunned pigs compared with CO(2) stunned pigs. No difference in the relative rate of muscle pH decline (P>0.05) between stunning methods was found in the LT muscle at Site 2. Pork from HBR stunned pigs was paler (P<0.05) and had a higher (P<0.001) percentage drip loss compared with pork from HO and CO(2) stunned pigs. LT muscles from HBR stunned pigs had lower (P<0.001) WB shear force values compared with pork from HO stunned pigs (6.57 vs. 8.12 kg, S.E.D. 0.49). Carcass quality was improved by CO(2) stunning, with less (P<0.05) ecchymosis-affected pork trimmed from shoulder primals compared with electrically stunned pigs. These results indicate that manual electrical stunning of pigs using HO tongs and CO(2) stunning reduced percentage drip loss, reduced muscle lightness and reduced the rate of muscle pH decline compared with pigs manually electrically stunned using HBR tongs.

Meat quality of mixed sex lambs grazing pasture and supplemented with, roughage, oats or oats and sunflower meal.

The meat quality of 8-9-month-old cryptorchid, wether and ewe lambs (Poll Dorset×Border Leicester×Merino) was assessed. These lambs were grazed over summer and autumn from weaning (November) on lucerne (Medicago sativa) or ryegrass/clover (Lolium rigidum/trifolium subterranean) pasture at two locations (A or B). After 72 days lambs grazed on lucerne were supplemented with either ad lib clover hay or clover silage. Those grazed on the ryegrass/clover pasture were supplemented from weaning with either oat grain (400-600 g/h day and clover hay ad lib) or oat grain (200-400 g/h day) plus sunflower seed meal (200 g/h day) and clover hay ad lib. Lambs were slaughtered in April and May after they reached 48 kg liveweight. Lambs supplemented solely with roughage produced muscle (m. longissimus thoracis et lumborum; LTL) with a higher (P<0.05) pH, but there was no effect of nutrition or sex on meat colour or tenderness. Slaughter day affected tenderness of the topside (m. semimembranosus). Assessment of aroma, flavour and acceptability was undertaken on the m. biceps femoris from wether and cryptorchid lambs using an experienced taste panel. There was no clear effect of sex or nutrition on the assessment of the sensory attributes. However, panellists considered meat from cryptorchid lambs fed the oats/sunflower supplement and grazed at location B, to have a stronger aroma and flavour (P<0.05) and in some cases to be less acceptable than meat from other combinations of sex, diet and location. The most acceptable meat came from lambs supplemented with oats, irrespective of sex or location. As such, these effects could not be attributed solely to either the diet or sex, but suggest there are conditions where meat from cryptorchids can be less acceptable.

Halothane genotype, pre-slaughter handling and stunning method all influence pork quality.

Seventy-six Landrace and four Large White × Landrace pigs (n=80) of 90-134 kg liveweight were randomly allocated to a 2×2×2 factorial experiment to determine the effect of halothane genotype [heterozygous for the halothane gene (Nn) and homozygous dominant (NN)], pre-slaughter handling (minimal and negative) and stunning method (CO(2) stunning and electrical) on pork quality. The rate of muscle pH decline post-slaughter of the m. longissimus thoracis et lumborum (LTL) muscle was faster in Nn pigs compared with NN pigs (0.86 and 0.30 pH units/h, respectively). Pork from Nn pigs was also paler in colour, had higher percentage drip loss and purge and lower sarcoplasmic and myofibrillar protein solubility compared with NN pigs. Pork from CO(2) stunned pigs had a lower drip loss compared to pork from electrically stunned pigs (5.80 and 7.28%, respectively - means of both genotypes combined). Tenderness of pork assessed at 24 h post-slaughter was not influenced by genotype, pre-slaughter handling or stunning method. However, pork from Nn pigs aged for 5 days post-slaughter was less tender than NN pigs (5.84 and 4.84 kg, respectively). Pale, soft and exudative pork was produced in all negatively handled Nn pigs, regardless of stunning method. The average amount of ecchymosis-affected muscle trimmed from carcasses of electrically stunned pigs was higher compared to pigs stunned with CO(2) (65 and 0.7 g, respectively). These data indicate that although halothane status was the most important factor influencing pork quality, pre-slaughter handling and stunning method also influenced meat and carcass quality.