Effect of muscle type on the rate of post-mortem proteolysis in pigs

Impact of cooking temperature on pork longissimus, and muscle fibre type, on quality traits and protein denaturation of four pork muscles

Variations in pork quality impact consumer acceptance, and fibre type differences between muscles contribute to this variation. The aim was to investigate the influence of variations in muscle fibre types and protein denaturation peaks across four pork muscles and the influence of ageing and cooking temperature on longissimus quality traits. The longissimus, masseter, cutaneous trunci, and psoas major from 13 carcases were removed 1-day postmortem and subjected to 0- or 14-days ageing (d0, d14). Quality traits, protein denaturation peak temperature (DSC), fibre diameter and fibre type proportions were measured. Cook loss for longissimus was similar on d0 and d14, but was higher on d14 for masseter, cutaneous trunci, and psoas major. Warner-Bratzler shear force was highest, and ultimate pH was lowest, for longissimus, and similar among cutaneous trunci, masseter, and psoas major. Masseter had lowest L* and highest a* and longissimus and cutaneous trunci had highest L* and lowest a*. The DSC temperature peaks for longissimus occurred at lower temperatures relative to the other muscles. Fibre diameter was largest for type-IIb fibres relative to type-IIa and type-I. Longissimus and cutaneous trunci had predominantly type-IIb glycolytic (71%, 51% respectively), masseter had predominantly type-IIa intermediate (50%) and psoas major had predominantly type-I oxidative (48%) fibres. The glycolytic longissimus had the lowest DSC temperature peaks and the lowest quality meat. Masseter had the highest proportion of type-I fibres but was generally similar in quality traits to psoas major, and also similar to cutaneous trunci which had more glycolytic fibres than masseter.

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.

Effects of mitochondria on postmortem meat quality: characteristic, isolation, energy metabolism, apoptosis and oxygen consumption

Meat quality holds significant importance for both consumers and meat producers. Various factors influence meat quality, and among them, mitochondria play a crucial role. Recent studies have indicated that mitochondria can sustain their functions and viability for a certain duration in postmortem muscles. Consequently, mitochondria have an impact on oxygen consumption, energy metabolism, and apoptotic processes, which in turn affect myoglobin levels, oxidative stress, meat tenderness, fat oxidation, and protein oxidation. Ultimately, these factors influence the color, tenderness, and flavor of meat. However, there is a dearth of comprehensive summaries addressing the effects of mitochondria on postmortem muscle physiology and meat quality. Therefore, this review aims to describe the characteristics of muscle mitochondria and their potential influence on muscle. Additionally, a suitable method for isolating mitochondria is presented. Lastly, the review emphasizes the regulation of oxygen consumption, energy metabolism, and apoptosis by postmortem muscle mitochondria, and provides an overview of relevant research and recent advancements. The ultimate objective of this review is to elucidate the underlying mechanisms through which mitochondria impact meat quality.

Higher Protein Digestibility of Chicken Thigh than Breast Muscle in an In Vitro Elderly Digestion Model

This study investigated the protein digestibility of chicken breast and thigh in an in vitro digestion model to determine the better protein sources for the elderly in terms of bioavailability. For this purpose, the biochemical traits of raw muscles and the structural properties of myofibrillar proteins were monitored. The thigh had higher pH, 10% trichloroacetic acid-soluble α-amino groups, and protein carbonyl content than the breast (p<0.05). In the proximate composition, the thigh had higher crude fat and lower crude protein content than the breast (p<0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of myofibrillar proteins showed noticeable differences in the band intensities of tropomyosin α-chain and myosin light chain-3 between the thigh and breast. The intrinsic tryptophan fluorescence intensity of myosin was lower in the thigh than in the breast (p<0.05). Moreover, circular dichroism spectroscopy of myosin revealed that the thigh had higher α-helical and lower β-sheet structures than the breast (p<0.05). The cooked muscles were then chopped and digested in the elderly digestion model. The thigh had more α-amino groups than the breast after both gastric and gastrointestinal digestion (p<0.05). SDS-PAGE analysis of the gastric digesta showed that more bands remained in the digesta of the breast than that of the thigh. The content of proteins less than 3 kDa in the gastrointestinal digesta was also higher in the thigh than in the breast (p<0.05). These results reveal that chicken thigh with higher in vitro protein digestibility is a more appropriate protein source for the elderly than chicken breast.

Meat quality, post-mortem proteolytic enzymes, and myosin heavy chain isoforms of different Thai native cattle muscles

OBJECTIVE

This study investigated the meat quality characteristics, endogenous proteolytic enzymes, collagen content, and myosin heavy chain (MyHC) isoforms of different muscles of Thai native cattle (TNC).

METHODS

Infraspinatus (IF), Longissimus thoracis (LT), and Supraspinatus (SS) muscles were obtained from two TNC breeds, Kho-Lan (KL, n = 7) and Kho-Isaan (KI, n = 7). The muscle and meat characteristics of TNC breeds and their relationship with MyHC expression were examined.

RESULTS

Three MyHC isoforms namely MyHC I, MyHC IIa, and MyHC IIx were detected in the muscles. The KL had higher (p<0.05) MyHC IIx than the KI. The IF muscle had higher (p<0.05) MyHC I compared to other muscles. The LT muscle had the least MyHC I. The LT had higher (p<0.05) MyHC IIx than the IF and SS muscles. The IF presented the least MyHC IIx. The KL had higher (p<0.05) lightness and moisture content and lower crude protein, redness, cooking loss, shear force, and calpastatin than the KI. The glycogen, total collagen, soluble collagen, crude protein, ash contents, and troponin T degradation product of IF and SS were lower (p<0.05) than that of LT. Ether extract in LT was lower (p<0.05) than that of IF and SS. The percentage of MyHC I, MyHC IIa, and MyHC IIx were significantly correlated with muscle and meat characteristics of TNC.

CONCLUSION

These results suggest that the differences in the MyHC isoforms may partly account for the variation in meat quality between breeds and among muscles of TNC.

Postmortem Protein Degradation as a Tool to Estimate the PMI: A Systematic Review

Objectives: We provide a systematic review of the literature to evaluate the current research status of protein degradation-based postmortem interval (PMI) estimation. Special attention is paid to the applicability of the proposed approaches/methods in forensic routine practice. Method: A systematic review of the literature on protein degradation in tissues and organs of animals and humans was conducted. Therefore, we searched the scientific databases Pubmed and Ovid for publications until December 2019. Additional searches were performed in Google Scholar and the reference lists of eligible articles. Results: A total of 36 studies were included. This enabled us to consider the degradation pattern of over 130 proteins from 11 different tissues, studied with different methods including well-established and modern approaches. Although comparison between studies is complicated by the heterogeneity of study designs, tissue types, methods, proteins and outcome measurement, there is clear evidence for a high explanatory power of protein degradation analysis in forensic PMI analysis. Conclusions: Although only few approaches have yet exceeded a basic research level, the current research status provides strong evidence in favor of the applicability of a protein degradation-based PMI estimation method in routine forensic practice. Further targeted research effort towards specific aims (also addressing influencing factors and exclusion criteria), especially in human tissue will be required to obtain a robust, reliable laboratory protocol, and collect sufficient data to develop accurate multifactorial mathematical decomposition models.

Muscle fiber characteristics and postmortem quality of longissimus thoracis, psoas major and semitendinosus from Chinese Simmental bulls

Using Chinese Simmental cattle semitendinosus, psoas major, and longissimus thoracis samples, we assessed muscle fiber characteristics and postmortem quality. The type I, IIA, and IIB fiber diameters were greater in semitendinosus and longissimus thoracis relative to psoas major, with psoas major, semitendinosus, and longissimus thoracis having the highest respective percentages of type I, IIB, and IIA fibers. Psoas major had the highest R 248 and R 250 values and lowest R 258 values at 1- and 6-hr postmortem. Psoas major had the lowest Warner-Bratzler shear force (WBSF), hardness, and chewiness values. The trends of WBSF, hardness, and chewiness changes decreased with increasing aging time. Semitendinosus had higher changes in WBSF than psoas major, and the number % type I fibers was correlated negatively with % changes of WBSF. Therefore, muscles with a high proportion of type IIB fibers and a low proportion of type I had lower tenderness and higher tenderization rate. Further research should be done to seek the optimal composition of muscle fiber type in order to improve beef quality, as muscle fiber type has opposite effect of tenderness background and tenderization rate.

Calpain activation and proteolysis in postmortem goose muscles

Meat tenderness is considered as the most important criterion for meat quality by consumers and can be improved by the actions of endogenous proteases, mainly calpains, during postmortem storage at 0-5°C. The purpose of this study, therefore, was to examine the postmortem calpain activation and proteolysis in breast (BM) and leg and thigh (LM) muscles of White Roman goose. BM and LM were taken from goose carcasses (n = 15) at 0 (10-15 min postmortem), 1, 3, and 7 days of storage at 5°C. The decrease in postmortem pH, calpain-1 and -11 activities, and contents of the calpain-1 80 kDa subunit and desmin was more rapid (p < .05) in BM than in LM. Our results show that postmortem proteolysis was more extensive in BM than in LM of White Roman goose, not only because the difference in fiber type composition between two muscles, but because the rate and extent of calpain activation were greater in BM as well. These results may provide useful information to optimize meat processing for different muscles in goose industry.

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.

Characteristics of selected pork muscles 45 min and 24 h post mortem

The muscles of the pork topside – musculus adductor (AD) and m. semimembranosus (SM), and of the silverside – m. biceps femoris (BF) and m. semitendinosus (ST) were analysed and their properties compared with the m. longissimus thoracis (LT) and m. supraspinatus (SS) muscles. Colour (CIE L*a*b*), D/L-lactic acid content, and pH values were measured 45 min and 24 h post mortem. The basic chemical composition of muscles was analysed 24 h after slaughtering. A significant correlation (r = -0.61, P < 0.001) was found between the pH values and the level of lactic acid 45 min post mortem, though not 24 h after slaughter (r = -0.25, P > 0.05). The results confirmed that a direct comparison cannot be made between the fall in pH values in meat and the increase in the level of lactic acid. The lightness L* 24 h post mortem was higher (P < 0.05) in AD, BF, ST and LT muscles than those in samples measured 45 min after slaughter. The toughest muscle was biceps femoris, with a mean value of shear force of 90.5 N. The differences in shear force between the individual analysed muscles were significant (P < 0.05). There were significant differences in the intramuscular fat content between the topside and silverside muscles (P < 0.05). The results of the present study are of value to meat producers who might intend to substitute these parts of the leg with one another during the production, particularly in the case of whole-muscle meat products.

The changes in the proteolysis activity and the accumulation of free amino acids during chinese traditional dry-cured loins processing

Twelve pieces of longissimus dorsi were processed into Chinese traditional dry-cured loins. The changes in the proteolylic enzymes activities, myofibrillar proteins degradation, and free amino acids content were investigated during processing. Compared with fresh piece (0 day), the cathepsin B + L and calpains activities decreased after dry-curing and maintained potential activities values of 23.25 and 15.04% in the final products, respectively. The myosin heavy chain (MHC) and C protein were intensely degraded at the dry-ripened stage; the 50 kDa desmin increased at day 2 and then disappeared at day 11. The total free amino acids content increased from 333.18 mg/100 g in the raw to 1096.54 mg/100 g at the end of the dry-ripening. This work provided a mechanism for the accumulation of free amino acids and predicted the proteolysis extent of myofibrillar proteins by monitoring the changes of three marker proteins (MHC, C protein and 50 kDa desmin) during Chinese traditional dry-cured loins processing.

CE-TOF MS-based metabolomic profiling revealed characteristic metabolic pathways in postmortem porcine fast and slow type muscles

To determine key compounds and metabolic pathways associated with meat quality, we profiled metabolites in postmortem porcine longissimus lumborum (LL) and vastus intermedius (VI) muscles with different aging times by global metabolomics using capillary electrophoresis-time of flight mass spectrometry. Loading analyses of the principal component analysis showed that hydrophilic amino acids and β-alanine-related compounds contributed to the muscle type positively and negatively, respectively, whereas glycolytic and ATP degradation products contributed to aging time. At 168h postmortem, LL samples were characterized by abundance of combinations of amino acids, dipeptides, and glycolytic products, whereas the VI samples were characterized by abundance of both sulfur-containing compounds and amino acids. The AMP and inosine contents in the VI were approx. 10 times higher than those in the LL at 4h postmortem, suggesting different rates of inosine 5'-monophosphate (IMP) accumulation by adenylate kinase 7 and 5'-nucleotidase, and subsequent different production levels of IMP and hypoxanthine between these two porcine muscles.

A structural approach to understanding the interactions between colour, water-holding capacity and tenderness

The colour, water-holding capacity (WHC) and tenderness of meat are primary determinants of visual and sensory appeal. Although there are many factors which influence these quality traits, the end-results of their influence is often through key changes to the structure of muscle proteins and their spatial arrangement. Water acts as a plasticiser of muscle proteins and water is lost from the myofibrillar lattice structure as a result of protein denaturation and consequent reductions in the muscle fibre volume with increasing cooking temperature. Changes in the myofilament lattice arrangement also impact the light scattering properties and the perceived paleness of the meat. Causes of variation in the quality traits of raw meat do not generally correspond to variations in cooked meat and the differences observed between the raw muscle and cooked or further processed meat are discussed. The review will also identify the gaps in our knowledge and where further investigation would beneficial.

Characterization of Longissimus thoracis, Semitendinosus and Masseter muscles and relationships with technological quality in pigs. 1. Microscopic analysis of muscles

Three porcine muscles (Longissimus thoracis, Semitendinosus, Masseter), known to have large differences in biochemical and histological traits, were fully characterized and the link between muscle structure and quality evaluated. The oxidative Masseter had more pigment, higher content of metmyoglobin, haem iron, protein and collagen, and was redder with higher fibre numbers, fibre circularity, pH and water holding capacity than the glycolytic Longissimus. Fibre type distribution showed predominance of type IIB in Longissimus and Semitendinosus white, type I in Semitendinosus red and IIA in Masseter. Type I fibres were larger than type IIB and IIA in Semitendinosus and Masseter, respectively, but not in the Longissimus, indicating that fibre size is muscle dependent. Muscle redness was positively correlated with type I fibre traits, haem iron and metmyoglobin, and negatively associated with type II fibre characteristics, non-haem iron and oxymyoglobin. Expressible juice had positive correlation with fibre size and negative with fibre number and connective tissue.

Cleavage of desmin by cysteine proteases: Calpains and cathepsin B

The intermediate filament protein, desmin, was purified from pork longissimus dorsi and incubated with either μ-calpain, m-calpain or cathepsin B. Proteolysis of desmin was followed using SDS-PAGE and Western blotting. After incubation of desmin with the proteases, cleavage sites on the desmin molecule were identified by N-terminal sequencing of the different proteolytic fragments. Desmin incubated with either m-calpain or μ-calpain was primarily cleaved in the head and tail region leaving the rod domain relatively intact even after prolonged incubation. Incubation with cathepsin B produces a sequential C-terminal degradation pattern characteristic of this dipeptylpeptidase. The substrate primary structure was not found to be essential for regulation of the proteolytic activity of the cysteine peptidases studied. However, the degradation patterns obtained imply that calpains are involved in degradation of desmin early post-mortem, targeting the non-helical region of the desmin molecule and resulting in depolymerisation and initial disorganisation of the intermediate filament structures of the muscle cell.

Postmortem role of calpains in Pekin duck skeletal muscles

BACKGROUND

It is generally agreed that calpains are involved in postmortem proteolysis of skeletal muscle and improve meat tenderness. However, little information regarding the postmortem role of calpains in duck skeletal muscle is known. Therefore, the purpose of this study was to examine the role of calpains in Pekin duck postmortem breast muscles (BM) and leg and thigh muscles (LM) muscles at 5 °C.

RESULTS

The postmortem pH was lower (P < 0.05) in BM than in LM. Western blots indicated that postmortem desmin degradation and the 30/32 kDa troponin-T degradation product accumulation were more rapid in BM than in LM. Casein zymograms showed that at-death µ-calpain activity was higher in BM than in LM. As time post mortem increased, µ-calpain was activated and autolyzed more rapidly and extensively in BM than in LM, but µ/m-calpain was activated at a relative slower rate compared with µ-calpain. Correlation results showed that µ-calpain activity, rather than µ/m-calpain activity, in BM samples was highly correlated with the abundance of desmin and the 30/32 kDa troponin-T degradation components across the postmortem period. However, no such correlations were found with LM µ- and µ/m-calpains.

CONCLUSION

Therefore, our results suggest that BM µ-calpain with a faster and more extensive activation and autolysis would play a relatively dominant role in dictating degradation of desmin and troponin-T in postmortem duck muscle.

Postmortem degradation of desmin and calpain in breast and leg and thigh muscles from Taiwan black-feathered country chickens

BACKGROUND

Several studies have reported that the postmortem changes are more rapid in breast muscles (BM) than in leg and thigh muscles (LM) of chickens. However, the reasons for the differences in postmortem proteolysis of BM and LM are still uncertain. The purpose of this study was therefore to compare the postmortem degradation of desmin and calpains in BM and LM from Taiwan black-feathered country chickens at 5 °C.

RESULTS

The pH was lower (P < 0.05) in BM than in LM. Western blot indicated that postmortem desmin degradation was more rapid in BM than in LM. Casein zymograms showed that at-death µ-calpain activity was higher in BM than in LM. As postmortem time proceeded, µ-calpain was activated and autolyzed more extensively in BM than in LM. However, the µ/m-calpain activity remained stable during postmortem storage in both BM and LM.

CONCLUSION

Our results suggest that the more rapid postmortem proteolysis found in BM than in LM at 5 °C similar with the previous study could be mainly explained by both greater amounts and faster activation and autolysis of µ-calpain in BM.

The influence of giant fibres on utility for production of massaged products of porcine muscle longissimus dorsi

Musculus longissimus dorsi (L) originating from 6 genotype groups of pigs was examined. Three among these were parental lines: Pietrain (Pi), Duroc (D), Polish Large White x Polish Landrace (PLW x PL), the other three crossbreeds obtained by crossing the aforementioned parental lines: (PLW x PL) x Pi, (PLW x PL) x (PixD) and (PLW x PL) x (D x Pi). It was found that there exists a variety of numbers and sizes of giant fibres and sizes of muscle fibres in the L muscle of the groups of animals, which results in a diversity of quality and susceptibility to massaging. The largest number of giant fibres and the greatest sizes of normal and giant fibres, along with the largest losses after heat treatment, the highest hardness, shear force, the lowest juiciness and attractiveness were found in the L muscle of Pi. Muscle of this breed was characterised by the least change in quality indicators during massaging. The decrease of Pi breed genes in the crossbreed genotype, resulted in reduction in the quantity of giant fibres and fibre sizes in comparison with pure Pi breed, which increased quality of crossbreeds' muscles and their susceptibility to massaging.

Effects of available dietary carbohydrate and preslaughter treatment on glycolytic potential, protein degradation, and quality traits of pig muscles

The current study was conducted to determine the interactive effects of a glycogen-reducing diet fed to finishing pigs and length of preslaughter transportion on muscle metabolic traits, proteolysis of intermediate filament and costameric proteins, and meat quality traits. Large White gilts and barrows (n = 48) were selected at 88 kg of BW and individually fed for 21 d a diet (2.6 kg/d) either high (HC) or low (LC) in available carbohydrates. Six gilts and 6 barrows fed the HC and LC diets were subjected to 0 or 3 h of transportation on the day of slaughter. Muscle temperature and pH were measured at 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, and 24 h postmortem in the LM and 24 h postmortem in the dark (STD) and light (STL) portion of the semitendinosus. At 24 h postmortem, glycolytic potential (GP) was determined in the LM, STD, and STL, as well as proteolysis of titin, nebulin, desmin, vinculin, and talin in the LM and STD. The GP was lower (P < 0.05) in muscles from LC-pigs than in muscles from HC-pigs. The LC diet also resulted in lower (P < 0.05) pH, and a darker (P = 0.03), less (P < 0.01) yellow color in the STL. The LC diet decreased (P = 0.04) cooking losses in the STL and STD. The 3-h journey further decreased (P = 0.05) the GP in the STD, regardless of the diet, but transport had no effect (P > or = 0.67) on the GP of the LM and STL. Ultimate pH of the LM was lower (P = 0.02), and both portions of the semitendinosus were darker (P = 0.01) and less yellow (P < 0.01), in pigs transported 3 vs. 0 h. In pigs transported for 3 h, intact vinculin tended to be more (P = 0.08) degraded in the LM, which coincided with lower (P = 0.04) drip losses in the LM of pigs transported for 3 compared with 0 h. Increased (P < 0.01) proteolysis of titin paralleled lower (P = 0.02) shear force values in the STD of pigs transported 3 vs. 0 h. Although the present results demonstrated the potential of a glycogen-reducing diet to alter the GP of different porcine muscles, the effect of these changes on meat quality traits was limited to higher ultimate pH and darker color in the STL. The positive effects of length of transportation on water-holding capacity (LM and STD) and meat color (STD and STL) were only partially related to the resting muscle glycogen concentration because the 3-h transport lowered the GP only in the muscle with the lowest basal glycogen concentration.