Accelerated chilling of carcasses to improve pork quality

Exploring the multifaceted factors affecting pork meat quality

The significance of pork meat quality extends far beyond mere consumer satisfaction, encompassing crucial aspects such as health and nutrition, economic impact, reputation and branding, food safety, and sustainability within the global food system. Influenced by a multitude of factors, each playing a pivotal role in shaping its sensory attributes and consumer appeal, pork meat quality stands as a cornerstone of the meat industry. Thus, understanding these factors are imperative for ensuring consistent high-quality pork production, aligning with consumer preferences, and elevating overall satisfaction levels. In this review, we provide a comprehensive overview of the diverse factors affecting pork meat quality, including genetic characteristics, rearing systems, feed composition, gender differences, pre-slaughter handling, and meat aging processes.

Pork muscle profiling: pH and instrumental color of the longissimus thoracis is not representative of pH and instrumental color of shoulder and ham muscles

From a population of 351 pork carcasses, 3.0-cm thick chops from the 10th rib location of the longissimus thoracis, faced surfaces of the triceps brachii and serratus ventralis muscles from the boneless shoulder, and faced surfaces of the biceps femoris, semitendinosus, semimembranosus, adductor, rectus femoris, and vastus lateralis muscles from the boneless ham were evaluated for pH and instrumental color (Minolta CR-400). Evaluations were conducted for at least three different locations on each of the muscle samples and averaged before data analysis occurred. The longissimus thoracis had the lowest pH and the lightest and least red color compared with the other eight muscles evaluated in this study (mean differences ranged from 0.98 to 8.70 for L*, 3.98 to 12.56 for a*, and 0.026 to 0.409 for pH). Furthermore, regression analysis suggested that pH and color values for the longissimus thoracis were not adequate predictors for pH and color values obtained from other muscles and therefore consideration should be given to the individual muscles that are of interest.

Time of dehairing alters pork quality development

Studies investigating the effect of scald time on pork quality are confounded with time of dehairing. To understand better pork quality development and two-toning in hams, twenty-four carcasses were assigned to an 8- or 16-min dwell time prior to the dehairing, with or without scalding (n = 6 per trt). Semimembranosus (SM) muscles were collected following dehairing and at 24 h postmortem. Protracted time to dehair improved ultimate pH (pH_u; P < 0.005) and reduced (P < 0.05) color variation. One hundred forty-two carcasses were then subjected to protracted (control, 10-min) dwell times (15-min, or 20-min) in an industrial setting. Lightness was improved with 15-min dwell times compared to control, however 20-min dwell decreased the pH_u (P < 0.001), increased lightness (P < 0.05), and percent purge (P < 0.001) in the SM. Also, lightness of the longissimus muscle (LM) increased (P < 0.001) with dwell time. These data show time to dehairing impacts pork quality development and suggest dehairing may be critical to quality development in a muscle-dependent manner.

Reduced scald time does not influence ultimate pork quality

Fresh pork color is a function of pigment, and the pH and temperature conditions in the carcass postmortem. To explore the role of scald on color development, carcasses (n = 16) were subjected to either a 4- or 8-min scald. Semimembranosus (SM) muscle samples were collected before and after scalding, and at 24 h postmortem. A 50% reduction in scald time resulted in lighter color (L*) across the muscle early postmortem (P < 0.001), yet the 8-min scald treatment was lighter (P = 0.001) at 24 h. An interaction between scald time and sampling time showed in an increase in L* values at 4-min immediately following scald (P < 0.001). Two-hundred carcasses were then subjected to a modified scald time (6.5 min, or 7.5 min) in an industrial setting. Lowering scald time failed to recapitulate results. In fact, darker meat (L* value; P = 0.0166) was noted in the SM across longer scalds. These data suggest modest changes in scald time may not be responsible for changes in pork quality development.

Quantification of the Effects of Electrical and CO2 Stunning on Selected Quality Attributes of Fresh Pork: A Meta-Analysis

Stunning is a statutory pre-slaughter process that may affect the quality of pork. The objective of this study was quantification of the effects of stunning (ES vs. CO2 stunning) on selected quality attributes of pork, using a meta-analytical approach. Data from 18 publications with 46 individual experiments were combined using a random-effect model to estimate the effect size of stunning on the initial and ultimate pH (pH1, pHu); drip loss (DL); colour (lightness—L*, redness—a*, yellowness—b*); and tenderness (expressed as Warner–Bratzler shear force, WBSF) of pork. In overall, loins from ES showed significantly lower pH1 (by 0.08 units); greater DL (by 0.68 p.p.); higher L* (by 1.29 units); and a* (by 0.80 units) as they compared to those from CO2 stunning. In subgroups, a greater-than-overall negative change in pH1, pHu, DL, L* and a* was detected with the application of the head-to-back (HB) stunning method. Additionally, alterations in DL and L* may be magnified with the application of conventional chilling (Conv.) to ES pigs. There was no effect of stunning on WBSF but, due to a low number of research in the database, the reliability of these results may be misleading. These results provide evidence that the differences between these two stunning methods in DL and L* may be diminished by the application of the head-only (HO) or head-to-body (HBO) method, followed by the fast chilling of carcasses.

The Effect of Rapid Chilling of Pork Carcasses during the Early Postmortem Period on Fresh Pork Quality

The objective was to investigate the effects of blast chilling on pork quality in cuts from the Longissimus thoracic et lumborum (LM), Psoas major (PM), Semimembranosus (SM; both superficial [SMS] and deep [SMD] portions) and the Triceps brachii (TB). Forty carcasses (10 carcasses per replication) were split and sides were assigned to either blast chill (BC, –32°C for 90 min, followed by spray chill at 2°C for 22.5 h) or conventional chill (CC, spray chilled at 2°C for 24 h) regimens. The LM from BC sides had lower (P < 0.05) temperature at 2 h postmortem (CC 21.8°C, BC 9.7°C), 4 h (CC 13.3°C, 3.8°C BC), 22 h (CC 4.2°C, BC 1.4°C), and 30 h (CC 0.4°C, BC –0.2°C). The LM pH in BC sides was higher at 4 h (CC 6.09, BC 6.34), 22 h (CC 5.81, BC 5.89), and 30 h (CC 5.68, BC 5.74) postmortem. The BC resulted in higher (P < 0.05) 30 h postmortem pH in the SM compared to the CC regime (CC 5.68, BC 5.74). The BC sides had increased (P < 0.05) purge in the PM (CC 0.48%, BC 0.74%) and increased (P < 0.05) cook loss in chops from the LM (CC 22.37%, BC 24.24%). The PM from BC sides were more juicy (CC 7.50, BC 8.30), less chewy (CC 2.80, BC 2.10), and more tender (CC 7.90, BC 8.60). Chops from the LM of BC sides had greater Warner-Bratzler shear force (CC 2.00, BC 2.30). Color was affected in the SM with BC sides showing darker color score (CC 3.00, BC 3.20) and redder Hunter a value (CC 16.35, BC 16.02). Chilling treatment did not affect sarcomere length in the LM. Treatment did not affect postmortem proteolysis in any cut. The response to chilling regimen is different across different muscles which may be caused by location, rate of chilling, and fiber type.

Pork ham and belly quality can be estimated from loin quality measurements?

The aim of the study was to determine the relationships between the quality evaluation of loin and the quality evaluation of ham and belly from the same carcasses for trying to predict the quality parameters of ham and belly based on measurements made on the loin. The research material consisted of 105 pork carcasses, from which three elements were cut and marked: loin, ham and belly. Quality evaluation included: pH, color, water holding capacity (WHC), cooking loss (CL), and sensory analysis. All designated quadratic equations were characterized by low R² values from 0.06 to 0.43 for ham and from 0.00 to 0.28 for belly. However, it is possible to predict the quality parameters of ham or belly with different levels of accuracy (R² from 0.50 to 0.92 - depending on the measurement and the element), using measurements selected from all those tested on the loin. Those loin quality measurements most frequently used in equations were chewiness and CL.

Characterization of variability in pork carcass composition and primal quality,

The objective was to characterize the factors and production practices that contribute to variation in pork composition and quality. It is possible the variation in pork quality traits, such as color, marbling, and tenderness, contributes to reduced customer confidence in the predictability of finished product quality and, therefore, pork products becoming less competitive for consumer dollars. Pigs raised in 8 different barns representing 2 seasons (hot and cold) and 2 production focuses (lean and quality) were used in this study. Pigs were marketed in 3 groups from each barn and marketing procedures followed commercial marketing procedures. Data were collected on a total of 7,684 pigs. The mivque0 option of the VARCOMP procedure in SAS was used to evaluate the proportion of variation each independent variable (season, production focus, marketing group, sex, and random variation) contributed to total variance. Random variation including inherent biological differences, as well as factors not controlled in this study, contributed the greatest proportion to total variation for each carcass composition and quality trait. Pig and other factors contributed to 93.5% of the variation in HCW, and marketing group, sex, season, and production focus accounted for 4.1, 1.4, 0.8, and 0.3%, respectively. Variation in percent carcass lean was attributed to production focus (36.4%), sex (15.8%), and season (10.2%). Pig and other factors contributed the greatest percentage of total variation (39.4%). Loin weight variation was attributed to production focus (21.4%), sex (5.4%), season (2.7%), marketing group (1.8%), and pig (68.7%). Belly weight variation was attributed to pig (88.9%), sex (4.1%), marketing group (3.8%), production focus (3.0%), and season (0.1%). Variation in ham weight was attributed to pig and other factors (93.9%), marketing group (2.8%), production focus (2.2%), and season (1.1%). Ultimate pH variation was attributed to pig (88.5%), season (6.2%), production focus (2.4%), marketing group (2.2%), and sex (0.7%). Aside from pig (71.9%), production focus (14.0%) was the next largest contributor to variation in iodine value followed by sex (13.2%) and marketing group (0.9%). Variation in carcass quality and composition could be accounted for, but the greatest percentage of variation was due to factors not accounted for in normal marketing practices.

Effects of pork differentiation strategies in Canada on pig performance and carcass characteristics

Performance and quality traits were measured in carcasses from combinations of genotype, diet supplement, slaughter weight, and carcass chilling regime. Iberian-crossed pigs had lower live animal performance than Duroc and Lacombe. From 70 to 115 kg, Lacombe pigs grew slightly faster than Duroc. Duroc carcasses had a higher lean percentage, heavier ham and picnic primals, and lighter loins and bellies, compared with Lacombe and Iberian. Heavier carcasses had lower lean yield, except those from Iberian-crossed pigs, and bigger bellies. Meat from Duroc-crossed pigs was lighter in colour and higher in marbling, with intermediate values for fat hardness. Iberian carcasses displayed dark meat with intermediate marbling and the hardest fat. Meat from Lacombe pigs was the leanest although, like in all three breeds, marbling scores were higher in heavier carcasses. Generally, supplementing with canola and flax decreased and blast chilling increased fat hardness values. Dietary canola also seemed to affect meat colour traits, but these effects were not consistent among breeds and slaughter weights. The commercial combination of Duroc breed, control diet, and 115-kg slaughter weight showed a balance in terms of performance, carcass, and quality traits. Other combinations evaluated in this study showed potential to efficiently produce differentiated pork.

Techniques to reduce the temperature of beef muscle early in the post mortem period – a review

A review of the literature was conducted on the effects of high temperature and low pH (HTLP) on meat quality, with a focus on interventions that increase the rate of cooling post slaughter. HTLP can potentially change meat tenderness, water-holding capacity and colour due primarily to protein denaturation during the first 5 h post mortem. Deep muscles in large carcasses are susceptible to HTLP when cooled conventionally. Ante mortem and post mortem solutions that increase the rate of carcass cooling are discussed. Ante mortem solutions include access to feed and water, showering with water and provision of shade. Post mortem solutions included vascular flushing, hot fat trimming, opening seams, hot boning, spray chilling, blast chilling, immersion cooling, and very fast chilling. Accelerating rigor with electrical stimulation before HTLP remains controversial. Combinations of different techniques, that suit the specific requirements of a particular processing plant, is the likely best solution to HTLP, but further development of commercial solutions is suggested.

The effects of different chilling methods on meat quality and calpain activity of pork muscle longissimus dorsi

The objective of this study was to investigate the effects of conventional chilling (0 to 4 °C), rapid chilling (RC, -20 °C for 30 min, followed by 0 to 4 °C), and short-duration chilling (0 to 4 °C for 30 min, followed by 25 °C) on meat quality and calpain activity of pork muscle longissimus dorsi (LD). The muscle quality characteristics pH, color, cooking loss, pressing loss and tenderness, and calpain activities were measured 0-, 3-, 12-, and 24-h postmortem. Results show that the RC resulted in a faster temperature decline of the muscle, and prevented the meat pH and Commission Internationale de l'Eclairage L* value from declining during postmortem aging. RC also reduced meat cooking loss and pressing loss compared with the other two chilling methods. However, the chilling methods did not significantly affect meat shear force. During the first 24-h postmortem, there was not a noticeable change in the activity of m-calpain. But μ-calpain activity decreased regardless of chilling method. In the rapidly chilled carcasses, μ-calpain activity remained the same 3- and 12-h postmortem. However, in the short-duration chilled and conventionally chilled carcasses, the activity was visibly reduced. At 24-h postmortem, no clear zones on the gel were observed in all three treatments.

PRACTICAL APPLICATION

Conventional and RC methods are commonly used for pork in commercial practice nowadays. Compared with conventional chilling, the effect of RC on quality parameters of pork varies. In recent years, short-duration chilling (SC) is widely used in many Chinese pig slaughtering facilities. However, few researchers have studied the effect of SD on pork quality. Therefore, the present study investigated the effect of different chilling methods on functionalities or quality of chilled pork meat.

The influence of early post-mortem enhancement and accelerated chilling on pork quality

To improve pork quality, the effectiveness of early post-mortem enhancement and accelerated chilling were investigated. The four treatments evaluated were: Enhancement with Accelerated Chilling (ENAC), Accelerated Chilling Only (ACO), Enhancement with Conventional Chilling (ENCC), and Conventional Chilling Only (CCO). ENAC had a higher (P<0.05) pH than all other treatments. CCO resulted in the highest (lightest; P<0.05) L(∗), while ENAC had the lowest L(∗) value (darkest; P<0.05). Subjective color and striping did not differ (P>0.05) between ENAC and ENCC, although ENAC was numerically higher for both parameters. Sensory analysis for juiciness and tenderness were not different (P>0.05) between ENAC and ENCC, but both were higher (P<0.05) than ACO and CCO. Enhancement early post-mortem coupled with accelerated chilling may be used to improve instrumental color and pH over conventional processing methods.