Morphological signs of myopathy in pork that show no drastic decrease in pH after slaughter

High pH value 45 minutes after slaughter (рН45) has so far been the most frequently used indicator to select pig carcasses with normal course of autolysis. However, in practice, this does not provide meat quality homogeneity. Therefore, carcasses with рН45 > 6.0 were examined for signs of myopathy, which are characteristic for PSE meat, using the histological method. To perform the study, we randomly selected 320 individuals for slaughter out of 1,059 individuals of mixed swine grown in the same conditions. After slaughter, we selected 18 fresh carcasses that demonstrated low рН45. The results of the examination of the muscular tissue (L. dorsi) samples revealed that pork varied in microstructural characteristics. Only 44% of the samples had no signs of myopathy: no contracture nodes and destructive changes in the muscle fibers were present. A total of 39% of the samples were identified to the muscular tissue with mildly expressed myopathy, 17% of the samples – to the muscular tissue with acute myopathy. Thus, among the carcasses with рН45 > 6.0, 56% of the carcasses had signs of mild and acute myopathy, which explains quality homogeneity of meat selected using this criterion. Statistical analysis of the results suggested that the increase in the diameter of the muscle fibers of glycolytic type was related to appearance of signs of mild and acute myopathy – “giant fibers”. Increase in the weight of animals is not a risk factor. The obtained results allowed us to conclude the necessity of developing new approaches to assessing meat quality immediately after the slaughter with the purpose of increasing efficiency in predicting technological properties of meat. Promising directions of developing quick methods in histology allow us to hope that such approaches may be based on the data on microstructure of fresh muscular tissue.

Analysis of selected parameters influencing the technological and sensory quality of pork

The aim of the study was to analyze selected parameters influencing the technological and sensory quality of pork. The material for the study was pork from the ham muscle and the ribeye muscles. The raw material came from a meat processing plant located in north-eastern Poland. The research was carried out on 80 porkers from various farms and farms. The tests included pH in 45 minutes and 24 hours from slaughter, meat color, water holding capacity, and the chemical composition of meat. It was found that half of the porkers had a lean content of more than 50%, and the best distinction between meat of normal quality and other quality classes results from the use of two or three different evaluation methods. The measurements of color and pH are most useful in assessing the quality of meat, but for the classification to be precise, some of them must be carried out immediately on the slaughter and as soon as the carcasses have cooled down. The brightness of the meat and the final pH values enable distinguishing between DFD meat and PSE meat. The color of normal meat is very similar to that of meat with the RSE defect. Significant (P ≤ 0.01) relationships were found between the protein content and the pH of the meat measured 45 minutes and 24 hours after slaughter. Significant relationships (P ≤ 0.01) also occurred between the values of the parameter a* and b* (trichromaticity coordinates).

The Effect of Point Mutations in the RYR-1 Gene on the Physicochemical Properties of Meat

The impact of gene mutations in the RYR-1 gene on the physicochemical qualities and nutritional value of homozygous and heterozygous stress-resistant NOR carcasses with RSE and DFD defects was studied using molecular genetics methods. NOR, which is meat of homozygous cross-breeding pigs, had a 0.44 higher pH level, 2.62% higher water-holding ability, 2.36 units×103 higher color and 0.37% higher content of organic matter; the tryptophan content and protein-quality index were lower by 0.3 mmol/g and 0.29, respectively. This low acidity caused the denaturation of some sarcoplasmic proteins, which contributed to the loss of the meat’s water-holding ability. A sharp decrease in pH led to partial denaturation of the sarcoplasmic proteins, which determined the pale color of the PSE meat. It was found that, compared to the heterozygous stress-sensitive animals with DFD defects, the NOR pH level was 0.55 lower, the water-holding ability was 4.05% lower, and the color intensity was 4.97 units×103 lower; the protein-quality indicator amounted to 8.24, which was 1.12 higher than that in the heterozygous stress-sensitive animals with DFD defects. The defects had a significant impact on other physicochemical properties of the meat. Defects of PSE meat worsened meat color. The intensity of staining of muscle tissue with PSE defects was lower than in normal pork by 11.5, 8.7 and 6.4 units×103 , respectively. DFD-pork exceeded normal meat in color by 13.7 (P> 0.99), 9.5 (P> 0.99) and 7.4 units×103 . Keywords: stress tolerance, stress sensitivity, genotype, meat defects PSE and DFD-, RYR-1 gene, pH, water-holding ability, meat coloring

Comparative Study on Pale, Soft and Exudative (PSE) and Red, Firm and Non-Exudative (RFN) Pork: Protein Changes during Aging and the Differential Protein Expression of the Myofibrillar Fraction at 1 h Postmortem

In this paper, the protein changes during aging and the differences in the myofibrillar protein fraction at 1 d postmortem of pale, soft and exudative (PSE), and red, firm and non-exudative (RFN) pork longissimus thoracis (LT) were comparatively studied. The PSE and RFN groups were screened out based on the differences in their pH and lightness (L*) at 1 h, and their purge loss at 24 h postmortem. Based on the measured MFI, desmin degradation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, PSE meat presented more significant changes in the myofibrillar protein fraction compared to RFN meat during postmortem aging. Through liquid chromatograph-mass spectrometer/mass spectrometer (LC-MS/MS) analysis, a total of 172 differential proteins were identified, among which 151 were up-regulated and 21 were down-regulated in the PSE group. The differential proteins were muscle contraction, motor proteins, microfilaments, microtubules, glycolysis, glycogen metabolism, energy metabolism, molecular chaperones, transport, and enzyme proteins. The AMP activated protein kinase (AMPK) signaling pathway, HIF-1 signaling pathway, calcium signaling pathway, and PI3K-Akt signaling pathway were identified as the significant pathways related to meat quality. This study suggested that the different changes of the myofibrillar protein fraction were involved in the biochemical metabolism in postmortem muscle, which may contribute to the molecular understanding of PSE meat formation.

Fasting Finisher Pigs before Slaughter Influences Pork Safety, Pork Quality and Animal Welfare

The final phase in pork production is the transport of finisher pigs to the slaughterhouse. Fasting is one of the parameters that influence the stress coping ability of the pigs during transport and lairage. When implemented correctly with attention to the local factors, pre-slaughter fasting can improve animal welfare, pathogen risk and carcass hygiene. The length of pre-slaughter feed withdrawal time is important to the success of the production practice. In practice, a fasting time before slaughter between 12 and 18 h enhances pork safety, pork quality, and animal welfare. This means that communication between producer and slaughterhouse is essential when planning the fasting and lairage times to avoid carcass and technological pork quality problems (such as pale, soft, and exudative (PSE) meat or dark, firm and dry (DFD) meat).

Temporal dominance of sensations and check-all-that-apply analysis of restructured cooked hams elaborated with different salt content and pork quality meats

This study aimed to evaluate the effects of salt (NaCl) content of 1.2%, 1.6%, and 2.0% in the sensory characteristics of restructured cooked hams, formulated with abnormal (PSE; pale, soft, and exudative) and normal (RFN; reddish pink, firm, and non-exudative) meats. The products with 1.2% added salt had higher ( P < 0.05) acceptance scores for flavor, regardless of the type of meat used. Hams manufactured with PSE meat and 1.2% salt content had higher ( P < 0.05) overall impression scores and were associated with the terms “characteristic ham flavor”, “juicy”, and “soft” in the check-all-that-apply analysis. RFN meat samples with 1.6% and 2.0% salt content were respectively associated to “rubbery” and “firm” texture. The ham flavor was always reported at the beginning of the temporal dominance of sensation test, followed by the term “salty” for the samples with 2.0% salt and “meaty” in the samples with 1.2% salt. The term “umami taste” appears to be associated to that samples made with PSE meat. These results led to the conclusion that PSE meat had a positive effect on the sensory profile of restructured cooked hams, especially in those formulated with 1.2% salt.

Comparison of plasma corticosterone concentration, muscle fibre diameter, and apoptotic markers between normal and pale, soft, exudative (PSE) turkey breast muscles

The increasing production potential of birds is correlated with a lower health and immune potential, resulting in the appearance of numerous meat quality defects. The greatest concern for gallinaceous poultry (chickens and turkeys) is PSE meat, which is characterized by light colour, soft texture and a reduced water-binding capacity. The aim of the study was to compare plasma corticosterone concentration, muscle fibre diameter, and the apoptotic markers between normal and pale, soft, exudative (PSE) turkey breast muscles. The results show, that the PSE group is characterized by a significantly higher plasma corticosterone concentration and a significantly greater muscle fibre diameter at 30 min post mortem compared to the normal group. The time of refrigerated storage (4°C) of meat contributes significantly to reducing muscle fibre diameter in the PSE group at 24 h post mortem compared to 30 min post mortem. Additionally, the results obtain showed that the caspase-3 activity at 30 min post mortem increased significantly in the turkey breast muscles of PSE compared with the normal group. Moreover, the PSE group demonstrated the higher apoptotic potential measured in the breast muscle of turkey compared with the normal group. It is stated from the obtained results that the incidence of PSE meat in turkeys may be associated with their higher susceptibility to stress factors and stressinduced pathological states.