Inhibition of protease activity. Part 1. The effect on tenderness and indicators of proteolysis in ovine muscle

To examine the effect of particular enzyme groups on tenderness specific cysteine protease inhibitors were injected into muscle early post-mortem. The protease enzyme inhibitor E-64 was injected into the m. longissimus thoracis et lumborum (LTL) on the right side of 12 lamb carcasses within 15 min of death and in another 12 carcasses with the protease inhibitor Z-Phe-Ala-CHN(2). The left LTL (control) was injected with saline (0.25 M NaCl). To create variation in the rate of pH decline alternate carcasses were electrically stimulated (low voltage). The LTL was divided into cranial and caudal portions and aged for 1 or 2 days. Muscle samples at 1 day post-mortem were used for measurement of osmolality and sarcomere length (n=48), and others at 1 and 2 days post-mortem for shear force determination (n=96). The myofibrillar fragmentation index (MFI) was determined on samples taken at pH 6.2 and 1 and 2 days post-mortem (n=144). Other muscle samples were obtained at death, pH 6.2 and 6.0 and then at 1 and 2 days post-mortem (n=215). These samples were used for determination of protein solubility and the concentration of free amino acids. Stimulation caused a faster (P<0.05) decline in pH. There was no effect of stimulation (P>0.05) on shear force values, but injection of inhibitor and ageing both had effects (P<0.001). The inhibitor E-64 prevented any improvement in tenderness with ageing, whereas the inhibitor Z-Phe-Ala-CHN(2) and the control samples showed a similar ageing response. In the latter two treatments there was an average reduction of 1 kg in shear between 1 and 2 days post-mortem, whilst the inhibitor E-64 maintained shear force on average 2 kg higher than control samples. Injection and ageing had an effect on MFI (P<0.001) and there was an interaction (P<0.05) between stimulation and ageing for MFI, such that as stimulated muscle aged the rate of change of MFI was greater. There was an interaction between injection and ageing (P<0.05) for protein solubility such that samples treated with E-64 showed a minimal increase in protein solubility with ageing, whereas in samples treated with Z-Phe-Ala-CHN(2) and the control samples there was a significant increase. There was also an interaction between stimulation and ageing such that between sampling at pH 6.0 and 2 days post-mortem, stimulated muscle exhibited greater solubility (P<0.05). There were no effects (P>0.05) on the concentration of free amino acids. The evidence indicated that the cysteine proteases were responsible for post-mortem proteolysis and tenderisation, in particular the calpains, whereas the cathepsins (B and L) were unlikely to contribute to proteolysis and subsequent tenderisation in meat.     

Variation in the response to manipulation of post-mortem glycolysis in beef muscles by low-voltage electrical stimulation and conditioning temperature

The aim of this study was to investigate how manipulation of glycolytic rate by post-mortem processing conditions influences quality of aged beef of two bovine muscles of different physiological character, longissimus dorsi (LD) and adductor (AD). Post-mortem glycolysis was manipulated by low-voltage electrical stimulation (LV-ES) of half carcasses and by chilling rate of the muscles. Multivariate statistical analysis was used to visualise the data, while ANOVA was used to identify significant effects and interactions. As expected there was a significant effect of LV-ES on the pH decline in the first hours post-mortem in both muscles. Moreover, significant effects of LV-ES on WB shear force measured 2 and 8 days after slaughter were observed for LD at both chilling temperatures, while for AD no effect on WB shear force was observed. Furthermore, the results revealed a large individual variation in the response of LV-ES on both pH decline and WB shear force, and this variation did not always correlate for the two responses. Some animals showed no response of LV-ES on pH decline, but still had an improved WB shear force, and vice versa. The results from this study indicate that there probably are other mechanisms than accelerated pH decline and prevention of cold-shortening, by which LV-ES can affect meat tenderness.     

The influence of post-mortem ageing and roasting on the microstructure, texture and collagen solubility of bovine semitendinosus muscle

Bovine semitendinosus (ST) muscles aged for 5 and 12 days at 4?°C were roasted at 170?°C to internal temperatures of 50, 60, 70, 80 and 90?°C. Microstructural changes in meat were evaluated using a scanning electron microscope (SEM). Texture profile analysis (TPA) and measurements of the shear force values of samples were conducted using a texture analyser. The cooking losses and quantity of total and soluble collagen were also estimated. The structure of intramuscular connective tissue and myofibrillar structure of meat after 5 days of ageing was very regular. In 12-day-aged samples fibrous and myofibrillar structures were less distinct, damages of endomysium tubes appeared and fibres of perimysium were swelled. Ageing of ST muscle for 12 days caused a two-fold increase in the quantity of soluble collagen and a two-fold decrease in the value of TPA parameters-hardness and chewiness, as compared to 5-day-aged samples. The decrease in fibre diameter and sarcomere length during roasting started at 60?°C in 5-day-aged meat and at 50?°C in 12-day-aged samples. The shear force values measured after roasting were lower for 12-day-aged meat than for 5-day-aged samples. The quantity of soluble collagen in roasted meat increased at an internal temperature of 80?°C. At a higher temperature of meat this variable depended on the degree of meat ageing. The cooking losses during roasting of meat were about 3% lower for 12-day-aged than for 5-day-aged samples. In the examined range of internal temperature of meat the cooking losses and the sarcomere length were negatively correlated.     

Effect of muscle restraint on sheep meat tenderness with rigor mortis at 18°C

The effect on shear force of skeletal restraint and removing muscles from lamb m. longissimus thoracis et lumborum (LT) immediately after slaughter and electrical stimulation was undertaken at a rigor temperature of 18°C (n=15). The temperature of 18°C was achieved through chilling of electrically stimulated sheep carcasses in air at 12°C, air flow 1-1.5 ms(-2). In other groups, the muscle was removed at 2.5 h post-mortem and either wrapped or left non-wrapped before being placed back on the carcass to follow carcass cooling regimes. Following rigor mortis, the meat was aged for 0, 16, 40 and 65 h at 15°C and frozen. For the non-stimulated samples, the meat was aged for 0, 12, 36 and 60 h before being frozen. The frozen meat was cooked to 75°C in an 85°C water bath and shear force values obtained from a 1 × 1 cm cross-section. Commencement of ageing was considered to take place at rigor mortis and this was taken as zero aged meat. There were no significant differences in the rate of tenderisation and initial shear force for all treatments. The 23% cook loss was similar for all wrapped and non-wrapped situations and the values decreased slightly with longer ageing durations. Wrapping was shown to mimic meat left intact on the carcass, as it prevented significant prerigor shortening. Such techniques allows muscles to be removed and placed in a controlled temperature environment to enable precise studies of ageing processes.     

Changes in the Tenderness of Meat Cooked at 50–65°C

Warner-Bratzler (WB) shear force values obtained for stretched veal muscles decreased as cooking temperatures were increased from 50 to 60°C. Increased proteolytic enzyme activity at these temperatures to give accelerated aging did not appear to explain the effects since there was still a substantial decrease in shear force with increase in cooking temperature from 50 to 60°C, even when well aged (7 wk at 5–6°C) meat and meat cooked for 24 hr was used. A more likely explanation was that, even at these relatively low temperatures, changes in connective tissue were involved since (a) the magnitude and direction of the change in shear force with increasing temperature was dependent on animal age and cooking time; (b) the effect of recooking at 80°C was dependent on animal age; and (c) the effects of increasing the cooking temperature and/or time on adhesion between the meat fibres was significantly greater for the samples from the younger animals.     

Effect of selection for growth rate on the ageing of myofibrils, meat texture properties and the muscle proteolytic potential of m. longissimus in rabbits

The effect of selection for growth rate on the degradation of the myofibrillar proteins and on meat texture properties of rabbit longissimus muscle at two ageing times (1 and 7 days) was studied as well as its effect on the proteolytic potential of the muscle. Two groups of contemporary animals (20 rabbits per group), one selected for growth rate (S) for 14 generations and the other unselected control group (C) were compared. The control group was formed from the offspring of the embryos belonging to the 7th generation and was compared with selected animals belonging to 21st generation. Myofibrillar protein degradation was studied by SDS-PAGE electrophoresis (12.5% and 4-15% polyacrylamide gels) followed by densitometric analysis of the pherograms. Texture properties were evaluated by Warner-Bratzler (WB) test and Texture profile analysis (TPA). The activities of proteolytic enzymes calpains and cathepsins and of their inhibitors were determined in the muscle at 24h. Densitometric analysis of the pherograms of samples aged 7 days showed an extra 30kDa band and the disappearance of a band with higher molecular weight than the myosin heavy chain with respect to samples aged 24h in both groups of rabbits. TPA results showed that cohesiveness was significantly lower in meat at 7 days than at 24h (P<0.0001), whereas springiness and chewiness presented a clear tendency to be lower at 7 days than at 24h (P=0.0646 and P=0.0764, respectively). Regarding the genetic type, S animals presented higher hardness and chewiness than C rabbits. Shear firmness (WB test) was significantly (P<0.0001) higher for S group, whereas no significant differences in shear force and area were found. No significant effect (P>0.05) of ageing time was detected using WB test. Selection for growth rate did not affect the activities of proteolytic enzymes or their inhibitors.     

Post-mortem calpain-system kinetics in lamb: Effects of clenbuterol and preslaughter exercise

The effect of dietary supplementation with clenbuterol for either 8 days or 55 days in lambs was studied. The 55-day treatment was combined with an immediate preslaughter exercise regime. The effect of these treatments on post-mortem calpain system activities, meat ageing and meat quality was studied. Neither short-nor long-term supplementation had an effect on the rate of pH fall post mortem. Short-term supplementation had no effect on the initial nor the final shear force values but these were higher at intermediate times. In contrast, prolonged supplementation increased shear force values at all times post mortem. Preslaughter exercise, while influencing the rate of pH decrease in both control and supplemented groups, did not affect meat tenderness. After short-term clenbuterol-supplementation, the in-vitro μ-calpain activity was significantly lower in the supplemented group at 6 and 24 hr post mortem, while m-calpain and calpastatin activities were largely unaffected. In contrast, 55-day clenbuterol supplementation resulted in significantly higher levels of calpastatin activity at all times post mortem. These data imply that clenbuterol results in toughened meat due to alterations in the calpain/calpastatin system, the mechanisms of which are dependent upon the duration of supplementation.     

Possible mechanism for the effect of the RN(-) allele on pork tenderness

The effect of the dominant RN⁻ allele on rigor development, ageing and tenderness was studied in M. longissimus dorsi (LD) from 11 heterozygous carriers and five non-carriers of the RN⁻ allele. Rigor development was followed by measurements of muscle shortening, isometric tension, pH and FOP. During ageing the myofibrillar length and Warner–Bratzler shear force were measured in the meat. Sensory analysis was performed at 4 days post-mortem using a trained expert panel. It was found that the decrease in pH was faster for RN⁻ carriers than non-carriers during the first 5 h post-mortem, after which the pH-time slope was similar for the two groups. This resulted in a significantly lower mean ultimate pH in LD from RN⁻ carriers than non-carriers. During rigor development the isometric tension was lower in RN⁻ carriers than in non-carriers, while contraction (shortening and sarcomere length) did not differ significantly between the two genotypes. The myofibrillar length, which is an indirect measure of the proteolytic activity that has occurred in the meat, was shorter for the RN⁻ carriers than for the non-carriers. The difference in myofibrillar lengths between the genotypes was significant at 1 and 4 days post-mortem but not at 7 days post-mortem, which indicates that the RN⁻ carriers have a higher proteolytic activity earlier post-mortem. The results from the Warner–Bratzler shear force measurements showed that the meat from the RN⁻ carriers was significantly more tender, 1 and 4 days post-mortem, than the meat from the non-carriers. The meat from non-carriers needed 7 days to reach the tenderness attained by that from the RN⁻ carriers 4 days post-mortem. The greater tenderness in LD from RN⁻ carriers than that from non-carriers was also confirmed by a sensory panel at 4 days post-mortem. In conclusion, differences observed in the course of rigor and ageing in muscle from carriers and non-carriers of the RN⁻ allele suggest that proteolytic action, as initiated by a more rapid fall in pH, is the most important factor governing the variation in tenderness of the two genotypes.     

The roles of the proteasome, and cathepsins B, L, H and D, in ostrich meat tenderisation

As very little research has been conducted on ostrich meat tenderisation, this study aims at investigating the roles of the proteasome and cathepsins B, L, H, and D in the tenderisation process. The enzyme activities in meat from eight ostriches during a 12-day ageing period and the corresponding physical characteristics (e.g. pH, shear force) and myofibril patterns were determined. After 12 days, substantial high remaining activities were found, especially of the proteasome, thus implicating their possible roles in the tenderisation process. The mean shear force values, however, showed no improvement in tenderness, but the myofibril patterns showed the appearance of a M(r) 32 K component. Myofibril degradation studies of the proteasome, analysed electrophoretically, also revealed a possible role of the proteasome, but under activating conditions. This study provides further insights into the tenderisation process, particularly of ostrich meat, which may ultimately be used for the advantageous manipulation of the process.     

Pre-slaughter stress arising from on-farm handling and its interactions with electrical stimulation on tenderness of lambs

The effect of electrical stimulation of lamb carcasses (n=269) or its absence (n=257) on shear force of m. longissimus thoracis et lumborum (LT) was monitored during ageing in pasture-fed merino lambs (n=526). The lambs were slaughtered on four different days allowing durations of between one to 10 days of recovery from pre-slaughter handling (yarding, weighing and crutching) that affected ultimate pH (pH(u)). The right LT was removed 20-40min post-slaughter, tightly-wrapped in cling film (prevents the muscle cross-section increasing and thus minimising shortening) and rapidly cooled to 15°C to enter rigor mortis and age. At 0, 4, 24 and 72h post-slaughter, pH measurements and samples for shear force measurement were taken. Pre-slaughter handling had a significant negative effect on pH(u) and several days recovery were required for pH(u) to reach values associated with optimal meat quality as reflected by pH(u). Lambs with one and three days recovery (no significant difference between them) had a pH(u)>5.7 in 50% of the muscles and 19.4%>pH(u) 5.8. Whereas, in lambs with 8-10 days recovery (no significant difference between them), only 8% had a pH(u)>5.7 and 3.1%>pH(u) 5.8. Within each slaughter day electrically stimulated lambs were always more tender than non-stimulated lambs. For non-stimulated muscles at 72h, shear force values >40N occurred for 11.2% of the muscles: for electrically stimulated muscles at 72h, shear force values >40N occurred for 1.9% of the muscles. The rates of tenderisation were slower for intermediate pH(u) values resulting in higher shear force values at all ageing durations. With ageing at 72h for intermediate pH(u), non-stimulated muscles (n=38) 17.64% were >40N and for stimulated muscles (n=34), 7.9% were >40N.     

Injection of marinade with actinidin increases tenderness of porcine M. biceps femoris and affects myofibrils and connective tissue

BACKGROUND: Marination of beef muscles with brine solutions containing proteolytic enzymes from fruit extracts has been shown to tenderize meat. However, the effect of marination with actinidin on tenderness of pork muscles has not been investigated. Tenderness and eating quality of porcine M. biceps femoris was investigated by Warner–Bratzler (WB) shear test and sensory evaluation after injection of brine containing up to 11 g L^?1 actinidin‐containing kiwi fruit powder and 2, 5 or 9 days of storage. RESULTS: Actinidin decreased WB shear force, increased tenderness and did not affect flavour and juiciness. Injection of 2.8 g L^?1 actinidin powder and storage for 2 days resulted in WB shear force values similar to control samples stored for 5 or 9 days. In samples injected with 10 g L^?1 actinidin powder, degradation of desmin and percentage of heat‐soluble collagen (P < 0.05) increased compared to control samples. Myofibrillar particle size tended to decrease (P < 0.1) with increasing actinidin concentration. No major changes were observed by proteome analysis. Atomic force microscopy showed actinidin‐induced damage of endomysium surrounding isolated single muscle fibres. CONCLUSION: Our results indicate that actinidin tenderizes pork M. biceps femoris by affecting both the myofibrils and connective tissue. Copyright © 2009 Society of Chemical Industry     

Singular and combined effects of electrical stimulation, post-mortem ageing and blade tenderisation on the palatability attributes of beef from young bulls

Thirty Santa Gertrudis bulls (approximately 15-18 months old) were slaughtered, dressed and split into siides. The right side of each carcass was electrically stimulated (ES) with seventeen impulses (1·8s impulse duration; 1·8s interval between impulses) of 550 V (AC) and 5 A while the left side served as a non-stimulated control (not-ES). At 24h post morten, USDA quality and yield grade data were obtained from each side. On the second day post mortem, all sides were fabricated and strip loins, top sirloin butts and ribeyes were obtained from each side for post-mortem ageing and blade tenderisation studies. Steaks were removed after a post-mortem ageing period of 4 or 18 days and before (not-BT) or after blade tenderisation (BT) for sensory panel evaluations or shear force determinations. ES sides had more youthful lean maturity (P < 0·0001), higher marbling (P < 0.·002), higher USDA quality grades (P < 0·0.0001) and finer-textured lean (P < 0·002) than did not-stimulated (not-ES) sides. ES significantly improved (P < 0·05) palatability traits in two of twenty-four comparisons; BT significantly improved palatability traits in twelve of twenty-four comparisons and 18-day post-mortem ageing significantly improved palatability traits in seven of twelve comparisons. No significant reductions (P < 0·05) in shear force values were observed for steaks from ES versus not-ES sides while significant reductions (P < 0·05) were observed for steaks from BT versus non-BT cuts (four of six comparisons) and for steaks from cuts aged for 18 versus 4 days (ten of twelve comparisons). BT and 18-day post-mortem ageing were more effective for increasing palatability or for decreasing shear force requirements than was ES; however, ES greatly improved lean colour of meat from bulls.     

The significance of the activity of glycogen debranching enzyme in glycolysis in porcine and bovine muscles

The purpose of the study was to examine the activity of glycogen debranching enzyme, GDE, in porcine and bovine muscles differing in rate of contraction and oxidative capacity. The activity of GDE, the activity of phosphorylase, total glucose content, lactate content and pH were measured from meat samples taken 35min post-mortem and ultimate pH 24 or 48h post-mortem. Both GDE and phosphorylase are needed for the complete degradation of glycogen. In porcine muscles the activities of these glycogen degrading enzymes were higher than in bovine muscles. The activities were increasing with the increasing fast twitch and glycolytic character of a muscle of a given species. However, the increase in the activity of phosphorylase was greater than the increase in the activity of GDE. It was concluded that the GDE may restrict the rate of glycolysis in fast twitch muscles.     

The effect of ageing on the water-holding capacity of pork: role of cytoskeletal proteins

The water-holding capacity (WHC) of pork decreases post-mortem but has been shown to increase during subsequent ageing. In order to test a hypothesis that water-holding capacity increases during ageing due to degradation of the cytoskeleton, WHC was followed 10 days post-mortem and related to the extent of proteolysis of cytoskeletal proteins. A fast method for measuring WHC in small meat samples was developed by the use of centrifugation. The WHC of fresh pork decreases in the first part of post-mortem storage after which it increases to the level of 1 day PM. No changes in total water content of the meat were observed which could explain changes in WHC during ageing. Vinculin and desmin degrade gradually during ageing while talin degrades rapidly. These observations are consistent with the hypothesis that degradation of the cytoskeleton slowly removes the linkage between lateral shrinkage of myofibrils and shrinkage of entire muscle fibres, so removing the force that causes flow into the extracellular space. Inflow of previously expelled water is then possible, so increasing WHC as observed in later periods of storage.     

Effects of ultrarapid chilling and ageing on length of sarcomeres, and tenderness of pork

In this study, the m. longissimus dorsi and the m. semimembranosus of pigs with normal and accelerated glycolysis (pale, soft and exudative, PSE) were used to evaluate the effect of ultrarapid chilling methods (with short-term freezing of the muscle surface) and ageing up to 72 h post-mortem on length of sarcomeres, Warner Bratzler shear force and firmness. The short-term freezing after ultrarapid chilling of musculature with normal glycolysis led to cold shortening with contraction of the sarcomeres by 33·5% (m. longissimus dorsi) and 38·3% (m. semimembranosus). At the same time, a massive increase in shear force and firmness was observed. After ageing up to 48h post-mortem the sarcomeres increased in length, whereby, in comparison with the measurements before the beginning of the chilling, 88 and 84% of the original length was attained, respectively. In addition, ageing led to a significant improvement of tenderness. After ageing for more than 72h the shear force and the firmness of meat specimens chilled under normal and ultrarapid conditions became more similar. The lenghts of the sarcomeres and the shear force of musculature with accelerated glycolysis were glycolysis were not affected by the chilling procedure.     

Fresh beef tumbling at different post-mortem times to improve tenderness and proteolytic features of M. longissimus lumborum

The aim of this study was to determine the effects of tumbling at different post-mortem times on the proteolytic features and quality attributes of beef loins (M. longissimus lumborum). Loins (n = 12) were cut into 4 sections and assigned to tumbling at 1, 6 or 11 days post-mortem or non-tumbled control. Upon tumbling, additional ageing was applied to a common post-mortem time of 16 days. In general, tumbling had no considerable impacts on water-holding ability of samples. Tumbling resulted in an immediate decrease in shear force values (WBSF) of beef samples. Tumbling at 1 day post-mortem with no ageing had similar WBSF compared to the non-tumbled controls at 16 days (P > 0.05). With ageing, tumbling increased amounts of protein degradation, myofibrillar fragmentation and calpain-1 autolysis of samples. These results suggest that early post-mortem tumbling coupled with ageing can synergistically impact the tenderness development of beef loins and shorten the necessary ageing period.     

SHEAR PROPERTIES AND WARNER-BRATZLER TENDERNESS MEASUREMENT OF BEEF 1

The shear properties of raw and cooked beef and their relationship with Warner-Bratzler (WB) tenderness measurement were evaluated. Shear tests were performed on four muscles, biceps femoris (BF), longissimus dorsi (LD), semimembranosus (SM), and semitendinosus (ST), with three different aging treatments (0, 1, and 2 weeks), using a specially designed device and the WB shear device. Raw beef exhibited a nonlinear behavior characterized by linearity at small deformations, stress yield at intermediate deformations, and work hardening at large deformations. Cooked beef had a different nonlinear behavior with the slope of the force-displacement curve increasing with displacement before the peak force. Cooking resulted in a large increase (p=0.01) in maximum shear force and strain energy. The effect of muscle type and aging on shear properties was mostly significant (p=0.05). The maximum shear force of cooked beef was correlated with WB measurement with the R² value ranging from 0.65 to 0.34 for LD, SM, and BF except for ST with a R² value of 0.10. Correlations of the shear properties of raw meat with WB measurement were low (R²<0.36), indicating the difficulty of predicting WB tenderness from the shear properties of raw meat.     

Effect of finishing and ageing time on quality attributes of loin from the meat of Holstein–Fresian cull cows

The effects of finishing time, (T0 = 0, T1 = 30 and T2 = 60 days), on Holstein–Friesian cull cows (n = 18) and post-mortem ageing, (1, 7, 14, 21, 35 and 42 days), under vacuum conditions of Longissimus thoracis (LT) muscles were investigated. The objective of this research was to study how finishing feeding (based on a commercial concentrate and corn silage), following a pasture period of 90 days, affected carcass and meat quality. Ageing time effect was also evaluated on the main quality attribute of added value pieces, such as “striploin of ox” from cull cows. Finishing treatment affected intramuscular fat content (IMF), moisture percentage, water-holding capacity (WHC), colour parameters and shear force of meat at 24 h post-mortem, whereas ageing time enhanced meat tenderness, when this was measured by two textural tests, Warner–Braztler (WB) and textural profile analysis (TPA). A minimum shear force was achieved at 7 and 14 days of ageing for T1 and T2, respectively. No differences (P > 0.05) could be found in colour parameters from 7 to 42 days. The results show that a finishing time of two months is very beneficial, due to the increase in meat fatness, improved overall carcass quality and luminosity (L*). Furthermore, 14 ageing days were sufficient to improved tenderness. Ageing time did not have an effect on lipid oxidation (P > 0.05) and this leads us to conclude that meat shelf life exceeded 42 days under vacuum conditions’.     

Effects of electrical stimulation, chilling temperature and hot-boning on the tenderness of bovine muscles

The objective of this study was to determine the effects of hot-boning, low voltage electrical stimulation (ES) and chilling temperature on the tenderness of bovine M. longissimus dorsi (LD) and M. semimembranosus (SM) muscles. LD (n=32) and SM (n=32) muscles were subjected to different post-mortem treatments; hot-boning (before 90min post-mortem), cold-boning (at 48h post-mortem), low voltage ES and rapid or slow chilling. Hot-boned muscles which were not electrically stimulated (NES) had higher Warner Bratzler shear force (WBSF) values (P<0.001) and shorter sarcomeres (P<0.001) than cold-boned muscles. Hot-boned muscles subjected to ES had lower pH values (P<0.001) post-stimulation and up to 8h post-mortem than NES muscles. At both chilling temperatures WBSF values were lower in ES hot-boned LD and SM muscles at days 2, 7 and 14 post-mortem than NES muscles. Hot-boned muscles subjected to slow chilling had longer sarcomeres (P<0.001) than those subjected to fast chilling. In hot-boned SM muscles, ES resulted in longer sarcomere lengths (P<0.001). However, ES did not have a significant effect on the sarcomere length of LD muscles. As indicated by WBSF values all muscles tenderised during ageing, including muscles which were 'cold shortened'. Proteolysis was not the main reason for differences in WBSF values between ES and NES muscles as judged by qualitative sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). A combination of slow chilling and ES had a positive effect on hot-boned muscles with respect to WBSF values.     

Investigation on CAST, CAPN1 and CAPN3 porcine gene polymorphisms and expression in relation to post-mortem calpain activity in muscle and meat quality

This study aimed to detect variability in CAST, CAPN1 and CAPN3 porcine genes and to investigate the effect of CAST and CAPN1 polymorphisms on the activity of native and autolyzed μ-calpain and m-calpain, measured from 1 to 72 h post-mortem in Longissimus dorsi (LD) muscle of 30 pigs. Effects of polymorphisms on meat quality parameter such as pH, color and drip loss were also evaluated. Samples carrying CAST EU137105:g.76,872AA genotype showed higher autolyzed μ-calpain activity 24 and 72 h post-mortem, as well as lower drip loss values. Expression of CAST, CAPN1 and CAPN3 was assessed in LD muscles divergent for shear force. Higher CAST and CAPN3 expression was found in LD with high shear force (P<0.2), confirming a direct role for calpastatin but not for calpain 3 in meat tenderization. In conclusion, CAST gene affected post-mortem activation time of calpain and drip loss.