Pale, Soft And Exudative Condition Research Articles

A simple, reliable and reproductive method to obtain experimental pale, soft and exudative (PSE) pork

The inferior quality and economic risk of pale, soft and exudative (PSE) pork warrant continuing research. However, such research efforts are often hindered by the challenge to obtain reliable PSE muscle samples with similar quality characteristics. The objective of this study was to establish a reliable and convenient method to produce PSE-like pork. A PSE condition was induced by incubation of 30-min postmortem Longissimus muscle at 35°C for 7h followed by chilling to 4°C. Compared to normal red, firm and non-exudative (RFN) pork (kept at 4°C), PSE muscle had consistently lower pH2h (5.46 vs. 5.74) and pH4h (5.35 vs. 5.52), higher L* (lightness) value (56.5 vs. 51.0), and reduced protein solubility and thermal stability (enthalpy and temperature) than RFN muscle (P<0.05). The highly reproducible results indicate that incubation of muscle immediately postmortem at 35°C offers a simple and consistent method to produce PSE pork.

Development of an autonomous, wireless pH and temperature sensing system for monitoring pig meat quality

This paper focuses on the development of a unique wireless pH and temperature monitoring system to assess pig meat quality. Pale, soft and exudative (PSE) pig meat continues to be a major problem in the pig meat industry today. The PSE condition in pork is related to a number of factors including genetics, pre-slaughter stress and insufficient chilling of pig carcasses, which cause a rapid rate of glycolysis post-mortem (<1 h). As a result the pH drops to low levels while the muscle temperature is still high. A wireless dual channel system that monitors pH and temperature simultaneously has been developed to provide pH and temperature data of the carcass during the first 24 h after slaughter. We have demonstrated that this approach can distinguish in real time, pH and temperature profiles that are ‘non-normal’, and identify carcasses that are PSE positive quickly and easily.

Risk assessment of PSE condition due to pre-slaughter conditions and RYR1 gene in pigs

A polychotomous logistic regression model was used to identify and assess the risk factors for pork meat becoming pale, soft and exudative (PSE). A total of 116 deliveries, comprising 15,695 commercial pigs delivered from different commercial farms to five Spanish pig commercial abattoirs were surveyed. The PSE condition was described as an ordinal response variable (normal, prone to PSE and PSE) based on measurements of electrical conductivity in the Semimembranosus muscle 1–2 h post-mortem. The RYR1 genotype, the abattoir, the season, the gender, the floor surface in the lorry, the loading system, and the stocking density during transportation influenced the risk of PSE condition, as well as on-farm fasting time, loading time, transportation and lairage times. The effect of the RYR1 gene, determined in a subsample of 1331 pigs, was due to nn stress-susceptible pigs, in which the risk of PSE meat (PQM>6 μs) increased fourfold. Abattoirs should be especially careful in summer, when the risk of PSE meat was found to be double that of winter. The risk of PSE meat decreased with the time of transportation, though its effect depended on the stocking density. Thus, our results indicate that, for transits longer than 3 h, the risk of PSE increases with stocking density during transport, while the opposite occurs for shorter transits.

Using pork to teach students quality variations and how they are measured. 1998 UW-AS-305 Class.

Using a total of eight pork loins representing DFD (dark, firm, and dry) and PSE (pale, soft, and exudative) conditions, 35 students conducted a series of objective and subjective measurements to demonstrate extremes in meat quality in a single 2-h laboratory. Students learned to objectively assess appearance, water-holding and water-binding capacity, ultimate pH (pHu), and shear force (cooked samples) by operating seven commonly known laboratory instruments. They also learned how to prepare and present samples for organoleptic analysis using hedonic and triangle tests. Finally, the students learned the factors related to meat quality and how extremely they can vary. Within one laboratory, they observed that DFD, when compared with PSE, averaged 1.5 units higher in pHu, 4.7% (absolute) less drip loss, bound 136% (absolute) more water, was darker in color (26 units lower L* value), was firmer with a more attractive structure requiring 1 kg/cm less force to shear, and was superior in organoleptic properties (overall 21% more desirable). Having 35 replicates to use for the data set, the results illustrated statistically significant variations in meat-quality traits and how they could be objectively measured. Nine months later, 12 of the students were surveyed. It was their perception that the laboratory was not any more effective than other laboratories in the same class, but they were able to remember 85% of the methods used to measure quality; about twice that of other methods taught in other laboratory sessions.

GLYCOLYTIC POTENTIAL IN PORCINE LONGISSIMUS MUSCLE BEFORE AND AFTER TRANSPORT: AN IN VIVO STUDY

The purpose of this research was to study the effect of transport on the glycolytic potential (GP, very close to glycogen content) measured in vivo of porcine Longissimus muscle. Four groups of 9 (Landrace × Yorkshire) × Hampshire crossbred pigs, corresponding to 4 rearing pens, were transported unmixed for 2 h. Biopsy samplings were performed immediately before and after transport on each pig. GP did not vary significantly when compared before and after transport (–2.2%). As shown by postmortem pH and internal light scattering measurements, no tendency toward the PSE (pale, soft and exudative) or DFD (dark, firm and dry) conditions was observed. It was concluded that a relatively short transport time (2 h) without mixing unfamiliar animals, did not induce high stress, as shown by the stability of muscle glycogen stored in vivo and the lack of deviation in meat quality traits postmortem.

MEASURING RESEARCH BENEFITS FROM A REDUCTION OF PALE, SOFT AND EXUDATIVE PORK IN AUSTRALIA

In this paper, a closed‐economy model is developed for evaluating the size and the distribution of benefits from research that lowers the mean incidence of pork with pale, soft and exudative (PSE) syndrome. The major finding is that the Australian pig industry has the potential to derive gross research benefits of about A$7 million per year from a one percentage point reduction in the incidence of pork with PSE conditions. About 85 per cent of the total research benefits accrue to pork producers. The implication is that it is profitable for pork producers to invest large sums in order to reduce PSE syndrome in pork.

Phospholipase A 2 activity, calmodulin, Ca 2+ and meat quality in young and adult halothane-sensitive and halothane-insensitive British Landrace pigs

PSE (pale, soft and exudative) meat is the result of a developmental disorder and is not produced in meat from young (3–11 weeks) halothane-sensitive British Landrace pigs. Formation of the PSE condition is closely associated with the muscle mitochondrial phospholipase A 2 activity, which increases significantly from 12 weeks of age. The increase in phospholipase A 2 activity shows good correlation (r = 0·87) with the increase in post-mortem sarcoplasmic Ca 2+. In halothane-insensitive British Landrace both the phospholipase A 2 activity and sarcoplasmic Ca 2+ level remain constant throughout growth. Significant increases in the levels of endogenous mitochondrial calmodulin, fatty acids and phospholipase A 2 activity, and Ca 2+ (mitochondrial and sarcoplasmic) are observed in the M. longissimus dorsi of adult halothane-sensitive pigs when compared with either young halothane-sensitive or young and adult halothane-insensitive pigs. The enhanced mitochondrial phospholipase A 2 activity is calmodulin-dependent and the increase in activity is postulated to be due to increased endogenous calmodulin.

Infrared Fiber Optic Spectrophotometry of Meat

The absorbance of infrared light (700 to 1,000 nm) by the bovine longissimus muscle and by porcine vastus intermedius and semitendinosus muscles and subcutaneous adipose tissue was measured with a fiber optic probe. The primary objectives were: (1) to identify an optimum wavelength for the optical resolution of boundaries between adipose tissue and lean meat and (2) to examine the relationship between infrared absorbance and pH-dependent aspects of meat quality. The widest separation of the absorbance spectra of fat and lean was at 850 nm. The difference between muscle and fat was less pronounced at lower and higher wavelengths. The difference was enhanced when muscles were pale, soft and exudative (PSE). However, the wavelength that was best suited for the detection of boundaries between muscle and fat (850 nm) was the least suitable for the detection of PSE. Absorbance at 1,000 nm was correlated with several indices of the PSE condition: with electrical resistivity (r = −.83, P<.005), with capacitance (r = −.66, P<.01) and with pH at 45 min postmortem (r = −.63, P<.025). However, similar relationships were also found with red light at 700 nm.

Relationship between endogenous factor and decrease in color formation of low quality pork.

To clarify the reason for the decrease in CFR (color forming ratio) of pale, soft and exudative (PSE) porcine muscle, the effect of simulation of the PSE conditions on cooked cured meat color was investigated in fractionated components from porcine skeletal muscle, 24hr postmortem. Although the solubility of total proteins and heme pigments markedly decreased in sarcoplasm by this treatment, no decline in CFR of the sarcoplasm could be observed when compared to the controls. A similar tendency was observed in both high- and low-molecular weight fractions of sarcoplasm. On the other hand, myofibrils simulated the PSE conditions in the presence of myoglobin significantly decreased CFR, and the extent of this decline was nearly consistent with the case of whole muscle. The reasons for the decrease in CFR of PSE muscle are discussed.

Effect of porcine muscle conditions on the color of cooked cured meat products.

The effect of pale, soft and exudative (PSE) porcine muscles on the color of processed meat products was investigated in sausages prepared in the laboratory. Eighteen muscle samples obtained at 24hr postmortem were tested. CFR (color forming ratio) tended to decrease with decreasing pH value. Muscle samples with extreme PSE characteristics produced low CFR sausages. A significant difference was not observed in the amount of total heme pigments in normal and PSE muscle. The effect of pH (4.926.23) on laboratory sausage from normal muscle showed that CFR gradually increased at lower pH values. The PSE conditions were also simulated by incubation of normal muscle adjusted to low pH (5.45.0) for 90 min at 40°C. Laboratory sausages were prepared from the PSE-like muscle after adjustment to pH 6.0. The PSE-like muscles had changes in CFR similar to those obtained with PSE muscles. The reasons for the decrease in CFR are discussed.

Changes in solubility and enzymic activity of muscle glycogen phosphorylase in PSE-muscles

Comparison of the crude extracts of soluble proteins of PSE (pale, soft and exudative) and normal porcine muscles shows that the solubility and activity of muscle glycogen phosphorylase are diminished in PSE muscles. In the insoluble fractions of the muscle extract, however, an increased amount of a protein with the molecular weight of the phosphorylase subunit (92·500-95·000) can be found by means of SDS-electrophoresis. The PSE conditions with high temperatures of 36–40°C in the first hour post mortem and a low pH of 5·3–5·8 at the same time post mortem are simulated with normal porcine muscles at twenty-four hours post mortem which causes the same change in solubility and activity of muscle glycogen phosphorylase as in PSE muscles. This proves, for the first time, that low pH and high temperature in whole muscles cause a denaturation of phosphorylase, as indicated by both reduced activity and decreased solubility. Previous studies have looked only at one of these aspects. This supports the hypothesis of Bendall & Wismer-Pedersen (1962) that in PSE muscles a partial denaturation of sarcoplasmic protein occurs.

The trigger for PSE condition in stress-susceptible pigs.

AbstractTightly coupled mitochondria from M. longissimus dorsi (LD) muscle of different breeds of pigs showed variations in the rate of Ca2+ efflux during anaerobiosis. The initial fast efflux rate of Ca2+ could be used to relate the stress‐susceptibility of the pigs used. Mitochondria from LD muscle of stress‐susceptible (SS) Pietrain and Poland China pigs showed an anaerobic rate of Ca2+ efflux twice that of stress‐resistant (SR) Large Whites. Mitochondria from crossbreds (Large White x Saddleback) showed a Ca2+ efflux rate intermediate between that of purebred SS and SR pigs. Halothane enhanced the rate of Ca2+ efflux only in SS pigs, and this effect could be eliminated by MgCl2. The marked difference in the rate of Ca2+ efflux between SS and SR pigs, and the enhancement in the rate of Ca2+ efflux by halothane only in SS pigs, offers an ultimate explanation for the formation of PSE (pale, soft and exudative) muscle and malignant hyperthermia in SS pigs. The excess Ca2+ liberated from mitochondria of SS pigs is postulated to be the trigger for PSE meat and also the case of malignant hyperthermia.