Ultimate Pork Quality Research Articles

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.

Correlations among various blood parameters at exsanguination and their relationships to pork quality traits

The objectives of this study were to investigate the correlations between various blood parameters compared with cortisol and lactate levels under the standard pre-slaughter procedure and handling conditions and to assess their potential as indicators of pork quality traits. Despite there being no additional pre-slaughter stress treatment, there is considerable variation in blood parameters at exsanguination. Serum cortisol and blood lactate levels, widely used indicators of stress, were positively correlated with blood glucose and electrolytes, such as calcium, potassium and sodium. Moreover, these parameters were significantly correlated with a rapid rate of early postmortem glycolysis and reduced water-holding capacity. In particular, blood lactate and glucose levels significantly differed between porcine quality classes. However, other blood parameters including electrolytes did not significantly differ between quality classes though they significantly correlated with pork quality traits. Therefore, serum cortisol, blood lactate and glucose have potential as indicators of the rate and extent of postmortem metabolism and ultimate pork quality under the standard procedure and handling conditions of pre-slaughter.

The relation of blood glucose level to muscle fiber characteristics and pork quality traits

The purpose of this study was to examine the relationships between blood glucose level, muscle fiber characteristics, and pork quality. Muscle samples were classified into three groups based on blood glucose level measured at slaughter. Pigs with higher area percentages of fiber type IIB showed higher blood glucose levels compared to pigs with lower area percentages of fiber type IIB. The high blood glucose level group presented lower pH values at 45 min and 24 h postmortem, and also had higher L ∗ values and reduced water holding capacity. In addition, blood glucose level had a negative relationship with pH 45 min and the solubility of sarcoplasmic and myofibrillar proteins, whereas it had a positive relationship with drip loss and filter-paper fluid uptake. In conclusion, blood glucose level was related to muscle fiber area composition and could partially indicate ultimate pork quality.

The effect of ractopamine supplementation at 5 ppm of swine finishing diets on growth performance, carcass composition and ultimate pork quality

Five hundred thirty-six finishing pigs were placed on experiment for an average of 26 d prior to slaughter, to determine the effects of 5 mg ractopamine hydrochloride (RAC) per kg of diet on growth performance, carcass composition and the eating quality of pork. Treatments included a control diet similar to a western Canadian commercial finishing diet and a treatment diet containing 5 mg RAC kg-1 with elevated amino acids, vitamins and minerals. The experiment started when average animal weight was 86 kg; pigs were marketed at an average liveweight of 118 kg. Two pigs were selected from each of 32 pens in week 4 of the experiment, for detailed carcass and meat quality evaluation, providing 16 pigs per gender per treatment. RAC-fed pigs reached market weight 4 d sooner (P &lt; 0.05), grew 13 % faster (P &lt; 0.05) and had 13% better feed efficiency (P &lt; 0.05) than the controls. RAC-fed pigs also had 1 mm less backfat and 2.5 mm thicker loins (P &lt; 0.05). Ultimate pH, purge loss and visual colour scores were unaffected by treatment but RAC-fed pigs had lower CIE a* and b* measurements (P &lt; 0.05). RAC had no effect on juiciness, flavour, saltiness or overall acceptability (P &gt; 0.10), but increased Warner-Bratzler shear force and reduced taste panel tenderness slightly (P &lt; 0.05). The inclusion of 5 mg RAC kg-1 in a commercial finishing diet will increase the rate and efficiency of gain and improve carcass composition. Minimal impact on pork quality can also be expected with the use of RAC fed at this level. Key words: Ractopamine, swine, carcass composition, pork quality, beta-adrenergic agonist

Effect of Sodium Bicarbonate Injection in Pre-rigor Porcine M. Longissimus lumborum on Pork Quality

Effects of sodium bicarbonate (SBC) injection on meat quality and functionality of porcine M. longissimus lumborum were investigated. Fifteen pigs () were randomly selected at a commercial slaughter plant. After slaughtering the loins were dissected from the carcass before chilling at approximately 30 minutes post mortem. The loins were divided into four cuts for sample treatment, and SBC of 0.25 M, 0.40 M and 0.75 M was injected (2% w/w) using a syringe. As SBC injection level was increased, muscle pH increased significantly (p) values on the surface of muscle. Moreover, with injection of SBC, drip loss %, cooking loss % and shear force were significantly (p content were significantly (p0.05) were found in aroma, off-flavor and drip between injection of SBC at different levels and the control, although color and acceptability were significantly lower (p0.05) on all treatments, but tenderness and acceptability were significantly higher (p0.05) were found in sarcoplasmic protein solubility between the treatments. These results indicated that SBC injection into pre-rigor porcine M. longissimus lumborum could improve ultimate pork quality characteristics such as meat color, water-holding capacity, and could inhibit muscle protein denaturation due to an increase in muscle pH.

Objectively Predicting Ultimate Quality of Post-Rigor Pork Musculature: I. Initial Comparison of Techniques

A total of 290 pork loins were selected to include a wide variation of quality to investigate the quality categories into which most pork falls, selection criteria for these categories and methods to objectively assess ultimate pork quality. They were probed at 24 h postmortem (PM) for the following: A) light reflectance by Danish Meat Quality Marbling (MOM), Hennessy Grading Probe (HGP) and Sensoptic Invasive Probe (SIP); B) electrical properties by NWK LT-K21 conductivity (NLT) and Sensoptic Resistance Probe (SRP): and C) pH by NWK pH-K21 (NpH). Also, measurements of % drip loss (PDL) and filter paper wetness (FPW), color brightness (L*), ultimate pH (pHu), lipid content, subjective color (SC), firmness/wetness (SF) and marbling scores (SM) were assessed. Each loin was categorized as either pale, soft and exudative (PSE), reddish-pink, soft and exudative (RSE), reddish-pink, firm and non-exudative (RFN) or dark, firm and dry (DFD). Statistically comparing coefficients of determination (CD), the results indicated that overall, the HGP predicted quality groups slightly better than MQM (CD=71 and 62% respectively), NpH and SRP were less effective (CD= 56 and 44% respectively), and SIP and NLT had the lowest values (CD=36 and 5% respectively). Combining various independent variable did not greatly improve the variation accounted for. When the data was sorted into marbling groups based on lipid content, this was not accurately predicted by any of the probe measurements. The MQM probe remained the best predictor for marbling class and accounted for about 25% of the lipid content variation. This was slightly improved to 33% when pHu was combined with MQM.

The influence of dietary magnesium supplement type, and supplementation dose and duration, on pork quality and the incidence of PSE pork

Ninety crossbred (Large White × Landrace) female pigs were used to compare the effects on ultimate pork quality of different magnesium (Mg) compounds [magnesium aspartate (MgAsp) and magnesium sulfate (MgSO4)], Mg dose (1.6 and 3.2 g elemental Mg), and Mg supplementation period (2 and 5 days) in pigs subjected to an acute stressor pre-slaughter. Pigs fed the Mg-supplemented diets had lower muscle lactic acid concentrations at 24 h post-slaughter than pigs fed the control diet. There were no significant differences in muscle glycogen concentrations in the Longissimus thoracis (LT) at 5 min, 40 min, or 24 h post-slaughter between the control and Mg-supplemented diets. Pigs fed the Mg-supplemented diets produced less pale colour pork (i.e. darker colour) and had reduced drip loss and reduced incidence of pale, soft, exudative (PSE) pork in the LT muscle compared with pigs fed the control diet. Within the Mg diets, pigs fed the MgAsp-supplemented diet produced less pale LT muscle colour than pigs fed the MgSO4-supplemented diet. There were no significant differences in LT pork quality parameters (colour and percent drip loss) regardless of whether the high or low Mg dose or the 2- or 5-day supplementation period was used. This experiment has shown that the use of dietary MgAsp supplementation at a dose of 1.6 g elemental Mg (20 g MgAsp) for 2 days prior to slaughter significantly improved pork quality and reduced the incidence of PSE pork.

The Effect Of Handling Pre-Slaughter And Carcass Processing Rate Post-Slaughter On Pork Quality

Forty-eight male crossbred (Large White—Landrace) pigs were used in a 2×2 factorial design to determine the effect of pre-slaughter handling (minimal and negative handling prior to slaughter) and the rate of carcass processing post-slaughter [normal rate (45 min) and delayed rate (70 min) from time of exsanguination to carcass entering the chiller] on muscle glycolysis and pork quality. Pigs negatively (using an electric goad) handled at the abattoir just prior to slaughter had lower muscle glycogen concentrations in the Longissimus thoracis (LT) and the Biceps femoris (BF) at all times post-slaughter and lower lactic acid at 5, 45 and 70 min post-slaughter compared to pigs minimally (no use of electric goads) handled prior to slaughter. Negative handling of pigs just prior to slaughter also resulted in pork which had higher surface exudate and a higher incidence of PSE compared with pigs minimally handled prior to slaughter. A prolonged rate of carcass processing resulted in reduced muscle glycogen in the LT and BF at all times post-slaughter. Delays in carcass processing rate also affected pork quality, as the meat was paler in comparison with pig carcasses that were processed without any delays. The results from this experiment have indicated that the use of electric goads to move pigs at the abattoir, and delays in carcass processing post-slaughter, can have a detrimental influence on ultimate pork quality.

Causes for variation in pork quality

Research was carried out on 260 pigs that were slaughtered in 12 batches in the slaughter facilities of ID-DLO at Zeist. The practical circumstances were highly standardized. The ‘animals’ meat quality was good with only little variation; 46 animals showed a ‘slightly’ aberrant quality and 6 ‘slight’ DFD. Carcasses within the quality categories ‘PSE’ and ‘slight’ PSE did not occur. Statistically significant effects on meat quality could be shown for the duration of the resting period before slaughter and the muscular contractions occurring while stunning, shackling and exsanguination, despite the minor variation in pork quality under standardization. A longer resting period before slaughter induced significantly lower temperatures in the m. semimembranosus and the loin at 45 min post mortem and a slightly higher ultimate pH, accompanied by a somewhat darker colour (24hr post mortem). A connection between the animal's behaviour at the fattening station and ultimate pork quality could not be shown. The same counts for fighting in the resting pen of the slaughter house and the pig's behaviour in the stunning area. Muscular contractions during and after stunning had a negative effect on pork quality, causing a more rapid drop in pH, a faster development of rigor mortis and a reduced water holding capacity. An imperfect electrical stunning procedure caused an increase in muscular contractions.

Predictive value of slaughterhouse measurements of ultimate pork quality in seven halothane negative Yorkshire populations

An experiment with 1969 pigs, belonging to Yorkshire sire lines, was set up in cooperation with seven Dutch breeding organizations. The pigs, which were claimed to be halothane negative, were slaughtered in weekly batches. Light reflectance was determined with the Hennessy Grading Probe (HGP) and Fibre Optic Probe (FOP), in addition to pH 1 and rigor mortis at 45 min post mortem (p.m.). Further meat quality determinations were performed either in the slaughterhouse at 20 h p.m., or in the laboratory at 24 h p.m.. At first sight, both the scatter of light (HGP-PSE, FOP) and pH, measured at 45 min p.m., appeared to be indicative of the ultimate meat quality score. More accurate analyses, however, showed that the value of reflectance values is limited and less suitable in comparison to pH 1, especially with reference to the prediction of ultimate quality characteristics of water holding capacity. The correlations for pH 1 with drip loss were rather consistent, ranging from −0·34 to −0·52 per breeding population. In contrast, HGP-reflectance values ranged from −0·27 to 0·34, while those based on FOP 1 had a range from nearly zero (0·02) to 0·20. The proportion of variation ( R 2 × 100%) in drip loss, explained by a set of slaughterline measurements, ranged from 13 to about 28% per breeding population. The use of measurements carried out at 20 h p.m. improved the R 2 × 100% for drip loss to a range from 50 to 62%.

Effect of oral loading of acid or base on the incidence of pale soft exudative pork (PSE) in stress-susceptible pigs

Thirty-three halothane-positive pigs were assigned to one of three ad libitum water treatments 4 days prior to slaughter: control, sodium bicarbonate (12·6 g litre −1), or ammonium chloride (8 g litre −1) to study the effect of an oral acid or base load on post-mortem changes in the longissimus dorsi muscle and on ultimate pork quality. Eight halothane-negative pigs were also slaughtered as negative controls. Dietary ammonium chloride caused a metabolic acidosis as indicated by lower blood and urine pH, and lower blood bicarbonate in treated pigs. In halothane-positive pigs, dietary treatments had no significant effect on post-mortem muscle pH changes or on measurements of muscle quality (colour, drip loss, texture scores or protein solubility). There was a weak to modest relationship between the blood gas measurements and meat quality indicators. Blood pH ( r = 0·566) and bicarbonate ( r = 0·514) were positively correlated with subjective texture scores and a trend was seen for blood PCO 2 and bicarbonate to be positively related to 45 min pH and subjective colour. These observations suggest that pigs with increased blood pH and bicarbonate may show an improvement in meat quality. Further research is necessary to find the optimum time and level of treatment to maximize the response.

The effect of scalding on subcutaneous and ham temperatures and ultimate pork quality

Scalding of pig carcasses (n = 34) at 60°C for a period of at least 5·5 to 7·5 min gave satisfactory dehairing results, with the exception of autumn hair for which a longer period (9 mins) was required. Temperature curves were recorded for a subcutaneous position in the ham (n = 26) between the rind and the underlying fat layer. These showed a curve starting at about 30·8°C and increasing to an asymptotic value of 53°C during scalding. Results of calculations with a finite element model of a flat layer of muscle covered with a layer of 1·0 cm fat broadly showed the same temperature increase at about 0·5 cm below the surface as the actual values measured. Immediately after dehairing, about 1·5 mins after finishing scalding, the subcutaneous temperature had already dropped to 46·1 ± 3·0°C, which was considerably higher than the muscle temperature at the same position at a depth of 5 cm under the skin (40·6°C). The heat removal and temperatures during the cooling period after scalding were also calculated. It can be concluded that the increase in temperature due to scalding has only a minor influence on muscle temperature and that meat quality (pH, FOP) is not affected.

The effectiveness of examining early post-mortem musculature to predict ultimate pork quality

Variations in pork quality reflect value differentials. However, only when they can be easily, accurately, rapidly and cost-effectively detected, can swine producers expect to eliminate poor quality from their herds through genetic selection, and can the industry be expected to take the necessary environmental precautions to prevent poor quality. This study was designed to assess the effectiveness of various techniques thought to predict ultimate pork quality through the examination of the physical and chemical properties of early post-mortem (PM) musculature. Based on stiffness and pH 30, 285 carcasses were selected. This selection procedure ensured a wide variation in ultimate quality. Using 12 instruments simultaneously, temperature, stiffness, electrical properties, lightness properties, and pH 45 of the early PM longissimus thoracis et lumborum were recorded to predict ultimate quality. Based on post-rigor light reflection and water-holding capacity (WHC), quality was assigned to one of five arbitrary groups. Of all techniques tested, the only one with any potential for adequate prediction of quality categories was pH 45. Combination of different techniques did not significantly increase predictive values. For predicting quality of single carcasses, pH 45 should not be considered satisfactory. However, based on our success in selecting carcasses representing quality variation for this study and the results obtained from the study, using pH 45 and muscle stiffness to select groups of carcasses is feasible. We conclude that the techniques used early post mortem are not appropriate for predicting ultimate pork quality for single carcasses. At present we recommend that only post-rigor muscle be considered, and that ultimate pH, light reflection and a measure of WHC should be used.

The influence of pre-slaughter oral loading of acid or base on post-mortem changes in Longissimus Dorsi muscle of pork

Twenty-four pigs were assigned to one of four ad libitum water treatments: control, sodium bicarbonate (12·6 g/litre), low ammonium chloride (4 g/litre) or high ammonium chloride (8 g/litre) for 5 days, to study the influence of an oral acid or base load on post-mortem changes in longissimus dorsi muscle and ultimate pork quality. Physiological changes before slaughter were monitored by measuring blood pH, pCO 2 and HCO 3 −. The influence of dietary treatments on post-mortem changes and ultimate meat quality was determined by measuring glycolytic enzymes and intermediates, and muscle pH, color and water-holding capacity (WHC). As expected, sodium bicarbonate generated a metabolic alkalosis, whereas ammonium chloride resulted in a metabolic acidosis. Pre-slaughter acid-base status was positively correlated with muscle WHC (P < 0·05). However, no significant dietary treatment effect was observed in muscle quality traits such as color ( a, b, L) and WHC. Muscle pH 45 was significantly (P < 0·05) higher in bicarbonate than control and high ammonium chloride treatments. The activity of Ca 2+-dependent protein kinase was significantly (P < 0·05) higher at 45 min post-mortem but that of pyruvate kinase was significantly lower at 2 and 4 h post mortem in bicarbonate-treated pigs. At 45 min post mortem, the activity of fructose-1,6-diphosphatase in the control pigs was significantly higher (P < 0·05) than on other treatments. The concentration of glycogen was significantly (P < 0·05) higher in bicarbonate and high ammonium chloride pigs; bicarbonate-treated pigs also has significantly higher adenosine-5′-triphosphate (ATP) and pH values than other treatment groups (P < 0·05) at early post-mortem. It was concluded that pre-slaughter oral loading of acid or base could induce changes in muscle metabolism and post-mortem muscle pH. Further research is required to confirm that altering diet acidogenicity or alkalinogenicity may be a means of enhancing ultimate pork quality.