Post-mortem modelling of pH and temperature in related lamb carcases

Exponential decay models have been used to model pH and temperature decline in lamb carcases post mortem. Such models, once fitted to carcase data, can then be used to predict a carcase's pH at a temperature of 18 °C and its temperature when the pH equals 6. Unfortunately, these models frequently fail when fitted to limited pH/temperature data, because of either insufficient data or inappropriateness of the exponential decay model. To overcome these problems an alternative though similar modelling approach is proposed. This alternative approach replaces the exponential decay model with a more flexible spline modelling approach for the average trend and includes in the model, as random effects, individual deviations from average trend. Including the individual deviations from average trend as random effects in the model allows information on individual carcases to be shared across carcases.     

Post-mortem evolution of non-protein nitrogen and its peptide composition in growing lamb muscles

Twenty-two 4-month-old lambs were used in two experiments to assess the effects of growth rate, induced by different feeding levels, and ageing (21 days, 4°C) on non-protein nitrogen (NPN) contents and their peptide composition. Muscle (Longissimus dorsi, Semimembranosus) and sex (male, female) effects were also studied. During ageing, NPN contents increased (15–20%). This variation represented 1.6–2.8% of total nitrogen. Peptides extracted from fresh muscles were in the range of molecular weight (MW) up to 12 kDa, the majority being less than 2.4 kDa (45–48%). During ageing, peptide average MW decreased (11.5–27.6%). High growth rate increased NPN contents at slaughter (+6–14%) and during ageing. Peptide average MW and post-mortem proteolysis rate as with to NPN variations were also higher. Differences between sex were observed at the end of the ageing period. Muscle effects were observed on the peptide class from 6.8 to 3.4 kDa.     

The cumulative effect of nutritional, shearing and preslaughter washing stresses on the quality of lamb meat

Carcass and meat characteristics were measured in lambs exposed to combinations of nutritional, shearing and preslaughter washing treatments. Both shearing and a low plane of nutrition reduced carcass weight (P < 0·001) and increased carcass leanness (P < 0·01). Tenderness and colour of M. longissimus dorsi were not significantly influenced by treatments even though there were substantial responses in meat pH. In lambs subjected to all three stressors pH was 0·40 units above control levels, significantly more than the sum of individual effects (P < 0·05), demonstrating a cumulative effect of stressors on meat pH.     

Post-mortem kinetics of meat tenderness and the components of the calpain system in bull skeletal muscle

Eight strip loins (M. longissimus dorsi) from pasture fed Friesian bulls were aged at 15 °C for a range of times from 1 to 120 h. pH declined from 6.29 (SE 0.119) one hour post slaughter to an ultimate pH of 5.48 (SE 0.013). The activities of the components of the calpain system (μ-calpain, m-calpain and calpastatin) were determined after separation on a DEAE-sephacel column. There was a dramatic decline in μ-calpain activity post slaughter with a complete disappearance within 48 h. The rates of decline in m-calpain and calpastatin activity were slower with 30% and 50% remaining 120 h post slaughter, respectively. The rapid decline in μ-calpain activity relative to the calpastatin activity is likely to reduce the degree of tenderisation and ultimate tenderness of the meat.     

Effects of dietary clenbuterol and salbutamol on meat quality in veal calves

Sixty male calves were assigned to one of four treatments, including (1) an untreated control, (2) clenbuterol; 1·6 mg/(calf.day), (3) and (4) salbutamol: 60 and 100 mg/(calf.day). Animals were milk-fed during 24 weeks, and β₂-agonists (BA) treatment occurred during the last 4 weeks including a 3-day withdrawal period before slaughter. Under identical feed intake amongst groups, treatments with BA had significantly positive effects on carcass weights and dressing percentages. BA induced muscle hypertrophy as evidenced by an improved EUROP carcass classification, 1 19–24% higher m. longissimus loin eye area and higher muscle protein/DNA and protein/RNA ratios. Through a dilution effect, this might explain the lower haem content of the m. semimembranosus and m. longissimus lumborum (LL) and diminished Hunter a^* value (redness) of the latter muscle. A higher ultimate pH was found in the m. semitendinosus and m. psoas major of BA-treated calves. The m. longissimus thoracis glycogen content appeared to be lowered by salbutamol. No effects of BA were encountered for water-holding properties of this muscle. Significantly higher shear force values (31–45%) for treated animals were measured for the LL which were parallelled by higher initial values for the calpain-inhibiting activity of calpastatin and a decrease of the μ-calpain/calpastatin ratio. EUROP fatness of carcasses and LL intramuscular fat content tended to be lowered by both BA. Effects of clenbuterol and of the higher salbutamol dose, which on a molecular base was administered at a 70 times higher level, were roughly of a comparable order. The lower dose mostly had intermediate effects. This means that in veal calves, clenbuterol is biologically more potent than salbutamol.     

宰后初期pH-温度窗口对牛肉品质的影响

嫩度、肉色及保水性是牛肉较为重要的食用品质,pH-温度下降关系对牛肉品质（尤其是嫩度）具有一定影响,但我国目前仍缺乏系统全面的牛肉嫩度数据库以及pH-温度窗口对牛肉品质差异的分析研究。基于此,该研究对我国两家具有代表性的大型屠宰企业肉牛宰后24 h内pH值与温度的下降关系（n=581）及宰后成熟过程中的品质指标（n=60）进行测定和分析。结果显示,A工厂88.1%的胴体处于理想的pH-温度窗口 [当pH值为6时的温度（Temp@pH6）处于12℃～35℃]内,而B工厂37.7%的胴体发生了热收缩现象,这种热收缩并未对B工厂牛肉的嫩度产生影响,两个工厂牛肉成熟21 d后嫩度仍未达到中国消费者的理想阈值。两工厂牛肉成熟期间均保持较高的a*值,B工厂胴体pH值的快速下降对保水性造成不利影响。此外,B工厂黑切（dark,firm and dry,DFD）肉发生率高达17.1%。因此,建议牛肉生产企业加强肉牛宰前管理、改进电刺激参数,以减少DFD牛肉及热收缩现象的发生。     

Formation of polycyclic aromatic hydrocarbons in beef and lamb kokorec: Effects of different animal fats

Traditional kokorec, which is one of the products of offal (edible by-products) and consumed enthusiastically in Turkey, is produced from fresh and washed lamb and calf small intestines. Some health risks can occur unless hygiene and sanitation rules are followed and proper cooking procedures are applied during the production process of kokorec. One of the most important among these risks is the microbial origin hazard and another is the formation of polycyclic aromatic hydrocarbons. In this study, the aim was to determine the concentrations of eight polycyclic aromatic hydrocarbons formed during the cooking of kokorec produced from beef and lamb small intestines by adding various animal fats. Polycyclic aromatic hydrocarbonformation was specified in ready-to-consume kokorec samples in which eight polycyclic aromatic hydrocarbon concentrations varied between 3.07 and 40.11 µg/kg. The consumption of lamb kokorec could be recommended to consumers because its average total eight polycyclic aromatic hydrocarbon concentration was lower than that of beef kokorec.     

Reduction of the olfactory cognitive ability in horses during preslaughter: stress-related hormones evaluation

As horses may perceive several odour signals of danger at slaughter, application of mentholated ointment to their nostrils may limit their perception of danger. To assess the effect of the application of a mentholated ointment to horse nostrils on the stress response during pre-slaughter handling, plasma levels were evaluated for cortisol, beta-endorphin, epinephrine and norepinephrine prior to and after stunning. Twenty draught-type horses were divided into control (n = 10) and treated (n = 10) groups and a mentholated ointment applied to the nostrils of the treated horses following blood sampling in lairage 45 min prior to slaughter. Treatment did not affect plasma concentrations of beta-endorphin or cortisol but significantly reduced the concentrations of epinephrine and norepinephrine observed in post-stun plasma. These results indicated that mentholated ointment applied to the nostrils of horses pre-slaughter reduced their adrenergic response to the slaughter environment, implying that the stress response may be reduced with this technology.     

Effects of two transport systems on lamb welfare and meat quality

The aim of this study was to analyse the effect of a direct transport system (DTS) versus transport with a logistic stopover system (TLS) on lamb welfare and meat quality at two seasons. A total of 96 lambs were sampled in a 2 × 2 × 2 factorial design, testing two transport systems and two seasons (summer and winter), with two replicates in each season. Significant interactions (P ≤ 0.05) between transport system and season in both welfare and meat quality were found. In general, lambs subjected to direct transport and logistic stopover during winter had a more intense stress response and poorer meat quality than lambs transported during summer. However, direct transport during the cold season seemed to be the most stressful, compared to the rest of the groups, which was reflected in significantly higher levels of cortisol, lactate, glucose, ratio of N/L, higher pH24 and darker and tougher meat.     

Effects of two transport systems on lamb welfare and meat quality

The aim of this study was to analyse the effect of a direct transport system (DTS) versus transport with a logistic stopover system (TLS) on lamb welfare and meat quality at two seasons. A total of 96 lambs were sampled in a 2×2×2 factorial design, testing two transport systems and two seasons (summer and winter), with two replicates in each season. Significant interactions (P≤0.05) between transport system and season in both welfare and meat quality were found. In general, lambs subjected to direct transport and logistic stopover during winter had a more intense stress response and poorer meat quality than lambs transported during summer. However, direct transport during the cold season seemed to be the most stressful, compared to the rest of the groups, which was reflected in significantly higher levels of cortisol, lactate, glucose, ratio of N/L, higher pH24 and darker and tougher meat.     

Post-mortem changes in cytoskeletal proteins of muscle

Progressive changes have been identified in the solubility of muscle-cell proteins during post-mortem muscle ageing, particularly the cytoskeletal proteins, desmin and connectin. Ox sternomandibularis muscle was sampled immediately post mortem and up to six days later. It was homogenised and separated into three salt-soluble fractions: phosphate soluble, concentrated KI soluble and guanidine-HCl soluble. Proteins in each fraction were analysed on sodium dodecylsulphate polyacrylamide gels. Changes reported previously by other authors were confirmed. In addition desmin, which was restricted to the guanidine fraction, disappeared, apparently due to proteolysis during storage. Connectin was also partly lost from the guanidine fraction, possibly through increased solubility in the KI fraction. In this respect an unidentified polypeptide of 110 000 D appeared during storage. Desmin extracted from ox muscle was partially purified and identified by amino acid analysis. It apparently occurs in vivo as a network of linked collars around the Z-discs and its loss during post-mortem storage probably accounts for the ease with which stored muscle disintegrates into individual myofibrils on homogenisation. The disintegration of the cytoskeletal network can account for the post-mortem changes in the physical properties of muscle for the increased tenderness after cooking of stored meat. However, factors other than those related to changes in cytoskeletal proteins are responsible for the toughness of cooked, cold-shortened muscle since cold shortening prior to storage did not affect the distribution of proteins among the three salt fractions, nor the patterns obtained in gel analyses.     

Effect of preslaughter events on the prevalence of Salmonella in market-weight turkeys

The goal of this study was to determine if preslaughter events, such as transport to and holding at the slaughterhouse, affect Salmonella prevalence in turkeys. Floors of transport crates were swabbed after loading and prior to transport at the farm (time 1, n = 100 swabs per trial) and after transport to and holding at the abattoir (time 2, n = 100 swabs per trial). In addition, environmental samples were taken at each of the six premises (n = 25 per premises) as well as in the holding shed at the abattoir (n = 25 samples per trial). At slaughter, the crops, ceca, and spleens were cultured (n = 50 each per flock). As shown from the culture of the crate floor swabs collected pre- and posttransport, when individual farms were analyzed, samples from only one premises exhibited a statistically significant change, as seen by the decline in Salmonella prevalence posttransport (P < 0.01). When the data from all farms were combined, Salmonella was recovered more frequently from swabs collected pretransport at loading on-farm (time 1, 47.6%) than from swabs collected after transport (time 2, 39.7%, P < 0.01). This suggests that transport to and holding at the abattoir do not increase the prevalence of Salmonella in turkeys. This observation contrasts with the increase in Salmonella prevalence reported for hogs and some broilers.     

Effects of shearing and fleece cleanliness on microbiological contamination of lamb carcasses

The meat industry in Norway has developed national guidelines for Good Hygiene Practices for slaughtering and skinning, based on categorisation of animals. These include shearing sheep and lambs in the abattoirs immediately before slaughter. The aim of this study was to investigate microbiological carcass contamination associated with: (i) different shearing regimes; (ii) fleece cleanliness; and (iii) the slaughter process. In addition, the efficacy of the national guidelines in reducing microbial contamination was evaluated. A total of 280 swab samples were collected from the brisket areas (100 cm(2)) of 140 naturally contaminated lamb carcasses in a commercial abattoir. Half the samples were collected at skinning of brisket areas at the start of the slaughter-line and half of them were collected at the end of slaughter-line, just before chilling. The lambs were divided into four groups (n=35) according to the duration of the period between shearing and slaughter: (i) 0 days (shorn at the abattoir immediately before slaughter); (ii) three days; (iii) seven days; and (iv) not shorn. Mean log colony forming units (CFU) per 100 cm(2) at skinning were 5.78 and 6.95 for aerobic plate count (APC) (P<0.05), 1.65 and 2.78 for Escherichia coli (P<0.05) for shorn and unshorn lambs, respectively. For shorn lambs, divided according to the period between shearing and slaughter, the mean log CFU per 100 cm(2) were 5.45, 5.75, 6.12 (APC) and 1.77, 1.46, 1.71 (E. coli) for the 0-days, 3-days and 7-days groups, respectively (P<0.05 for the difference between 0- and 7-days groups in APC results). A four-category scale (0-3) was used for assessing fleece cleanliness before skinning. Visually clean lambs (score '0') had lower levels of APC on the carcass surfaces than those categorised as dirty (score '2-3') (P<0.05). The carcasses at the end of the slaughter-line had lower levels of APC than they had at skinning. However, the statistical significant reduction of E. coli on carcass surfaces at skinning point for shorn lambs, were impaired and no longer significantly different from the unshorn group at the end of the slaughter-line. The increased E. coli level at the end of the slaughter-line might be explained by weaknesses related to slaughter hygiene in particular suboptimal evisceration in the abattoir which was used as a basis for our trial, and thus the national guidelines concerning shearing had not the fully intended effect on reducing microbial carcass contamination.     

Effects of lactate on ground lamb colour stability and mitochondria-mediated metmyoglobin reduction

Previous research suggests that lactate’s colour stabilizing effect in beef is through NADH production and antioxidant activity. However, no research has assessed lactate’s role in lamb colour. Hence, our objectives were to evaluate the effects of lactate on lamb surface discolouration, oxygen consumption, and metmyoglobin reduction. In experiment 1, lactate (final meat concentration = 2.5% w/w) was added to ground lamb (n = 20 carcasses) and patties were stored for 3 days at 1 °C in PVC packaging. Surface colour (CIE L∗ and a∗) and metmyoglobin reducing activity of ground lamb patties were measured. Addition of lactate improved colour stability and metmyoglobin reducing activity (p < 0.05). In experiment 2, mitochondria were isolated from lamb longissimus muscle (n = 3). Addition of lactate–LDH–NAD to mitochondria resulted in significant oxygen consumption and metmyoglobin reduction compared with mitochondrial controls without lactate (p < 0.05). Lactate can improve the colour stability of lamb, possibly by increasing metmyoglobin reducing activity.     

Studies in electrical stimulation: Post-mortem decline in nervous response in lambs

A study has been made of the effects of electrical stimulation, either indirectly through the nerves or directly through the muscles, on glycolysis in lamb hind leg muscles. Responses were affected by delay before application and the stimulating voltage. At 5 min post mortem the same fall in pH during stimulation (ΔpH) and subsequent increased rate of pH fall (dp H/dt) occurred in muscles stimulated both directly and indirectly with 12 V. With 200V, ΔpH was 50% greater in muscles stimulated directly and 30% less if stimulated indirectly. At 30 min post mortem there was very little effect of stimulation at either voltage on glycolysis when muscles were indirectly stimulated, indicating that the nerves had lost their capacity to trigger muscles to contract. In contrast, if the legs were stimulated directly, maximum ΔpH and dpH/dt values were achieved with 200 V pulses. The significance of these findings to the application of electrical stimulation to commercial meat processing is discussed.     

Endurance-exercised growing sheep: I. Post-mortem and histological changes in skeletal muscles

A study was conducted with Suffolk ram lambs to determine whether chronic endurance exercise would affect post-mortem changes in muscle tissue. Muscle fibre diameters, sarcomere lengths, fibre types, and pH and temperature declines were measured in five skeletal muscles (semimembranosus, SM: vastus lateralis, VL; semitendinosus, ST; psoas major, PM; gastrocnemius, G). The exercise had no significant effect on muscle size or muscle fibre diameter in any of the muscles studied. However, endurance-exercised sheep had significantly shorter sarcomeres in all five muscles than their non-exercised counterparts. The pH decline curves differed among muscles; those having the highest proportion of glycolytic fibres had the slowest rates of pH decline. The increased proportion of slow-twitch fibres in the SM, VL, ST and G associated with the exercise regime had little effect on the post-mortem pH decline. However, the ST also had a significant exercise-associated increase in the proportion of oxidative-glycolytic fibres (intermediate) and was the only muscle in which exercise influenced the rate of pH decline significantly.     

Effects of breeds on the formation of heterocyclic aromatic amines in smoked lamb

Heterocyclic aromatic amines (HAAs) are mutagenic and carcinogenic compounds, which are commonly detectable in cooked meat products. The objective of this study was to evaluate the effect of sheep breeds on the formation of HAAs in smoking cooked lamb. The results showed that HAAs in smoked lamb meat products were generally low (2.74–5.42 ng g^?1), with most being Harman and Norharman. IQ, MeIQx, 4,8‐DiMeIQx, Trp‐p‐2, PhIP and MeAaC were not detected in smoked lamb meat products in the present study. The total content of HAAs differed between meat products of different sheep breeds, but no difference in the order of magnitude was determined. Smoking altered the content of protein, fat, moisture and free amino acids in lamb meat products, which was probably mostly contributed by the reduction in meat moisture. Free tryptophan decreased in all breeds after smoking, which was probably used to synthesise HAAs. In summary, HAAs were low in smoked lamb meat products of all sheep breeds; thus, consumption of smoked lamb meat products should contribute very limited intake of HAAs.     

Effects of cooling temperature and hot carcass weight on the quality of lamb

The effects of cooling temperature (CT) (0–2, 2–4, or 4–6 °C) and hot carcass weight (HCW) (either 10.5 or 12.0 kg) on weight loss (WL) and meat quality were evaluated in 60 lamb carcasses of Rasa Aragonesa breed. Carcasses were exposed to CT throughout 90 h. WL was assessed at 18, 42, 66, and 90 h post-slaughter. pH, colour, instrumental measurement of texture, oxidation, and sensory parameters were evaluated in longissimus thoracis et lumborum aged for 96 h following standard methods. Sensory test involved a trained test panel. No significant interactive effects among the parameters evaluated were detected in the study. The lower the CT, the higher the WL after 90 h in storage (0.25% lost each 2 °C decrease), the higher final pH, and the lower lightness, the higher hue and chroma of the meat. Toughness was higher in meat cooled at 2–4 °C than in meat cooled at temperatures above or below this range. Neither oxidation nor sensory variables were affected by CT. Regarding on HCW, light carcasses exhibited higher WL (2.39% versus 2.04% after 90 h of cooling), higher final pH, and lower levels of oxidation than did heavier carcasses. Neither colour nor instrumental measurement of texture was affected by HCW. Lamb and fat odour and metallic and acid flavour intensities were significantly greater in the heavier carcasses, although it did not affect overall acceptability. Both CT and HCW should be considered as main effects on lamb quality, especially CT.     

Post-mortem Changes in Breast Muscles of Mule Duck

Post-mortem changes in myofibril fragmentation index and degradation of myofibrillar proteins of duck breast muscles at 5°C was investigated. Muscle samples were collected immediately after killing and from the stored carcasses at 5°C for 1, 3, 7, and 14 days post mortem . The results showed that the MFI of the breast muscles increased with time post mortem . SDS-PAGE of myofibrils indicated that the disappearance of troponin-T accompanied concurrently with the appearance of 32–30 kDa components. After 7 days of storage, α-actinin was degraded, and a 98 kDa component appeared. Titin 1 and nebulin also disappeared after post-mortem storage for 3 days.