Proteomic and peptidomic differences and similarities between four muscle types from New Zealand raised Angus steers.

Four muscles from New Zealand-raised Angus steers were evaluated (musculus semitendinosus, m. longissimus thoracis et lumborum, m. psoas major and m. infraspinatus) to test their differences and common features in protein and peptide abundances. The ultimate goal of such a comparison is to match muscle types to products with targeted properties. Protein profiling based on two-dimensional electrophoresis showed that the overall profiles were similar, but, between muscle types, significant (p<0.05) intensity differences were observed in twenty four protein spots. Profiling of endogenous peptides allowed characterisation of 346 peptides. Quantitative analysis showed a clear distinction between the muscle types. Forty-four peptides were identified that showed a statistically significant (p<0.05) and substantial (>2-fold change) difference between at least two muscle types. These analyses demonstrate substantial similarities between these four muscle types, but also clear distinctions in their profiles; specifically a 25% difference between at least two muscles at the peptidomic level, and a 14% difference at the proteomic level.

Altered post-mortem metabolism identified in very fast chilled lamb M. longissimus thoracis et lumborum using metabolomic analysis.

The aim of this experiment was to use metabolomic techniques to investigate the energy metabolism in lamb M. longissimus thoracis et lumborum subjected to very fast chilling (VFC) post-mortem. The tissue was prepared by 2 different operators and subjected to very fast chilling (less than 0°C within 1.5h of slaughter) or typical chilling regimes (Control; 0°C within 22h of slaughter). Non-targeted metabolomic analysis ((1)H NMR) and targeted analysis ((31)P NMR, HPLC-PDA and HPLC-MS/MS) were used to examine the change in muscle metabolites post-mortem. One VFC treatment, which resulted in a colder core temperature and more tender meat, had higher levels of glycolytic intermediate metabolites pre-rigor as well as more of the end-products of adenosine and nicotine nucleotide metabolism pre-rigor, relative to conventionally chilled treatments. In conclusion, VFC to less than 0°C within 1.5h of slaughter causes considerable changes in metabolism and rigor onset, which are associated with tender meat.

Early on-line classification of beef carcasses based on ultimate pH by near infrared spectroscopy.

Prediction of ultimate pH (measured 48 h post mortem; pH(u)) in beef from Visible-near infrared (VIS-NIR) spectra collected 20 to 40 min post mortem was assessed. Spectra were collected from carcasses (cows: n = 86, bulls: n = 170, steers: n = 363, and heifers: n = 38) in a commercial hot boning abattoir under routine conditions. Partial Least Squares (PLS) models showed limited accuracy with RMSE for validation equal to 0.26, 0.20 and 0.36 for the All-animals, Non-bulls and Bulls models, respectively. The pH(u)-PLS-predicted values were used to segregate carcasses as normal (pH(u)<5.8) or high (pH(u) ≥ 5.8) showing better performance, by correctly classifying at least 90% of high pH(u) carcasses. The Non-bulls model was equivalent to the current technology used in the abattoir to classify carcasses based on pH(u). Thus near infrared spectroscopy (NIRS) could be used for on-line classification of beef carcasses based on pH(u).

Pre rigor processing, ageing and freezing on tenderness and colour stability of lamb loins.

Forty eight lamb carcasses with temperature and pH monitored were obtained from two commercial plants. At 24h post mortem both loins (M. longissimus) from each carcass were randomly allocated to a) unaged frozen at -18°C, (b) aged at -1.5°C for 2weeks before freezing, (c) aged for 3 weeks before freezing and (d) aged for 9 weeks without freezing. Shear force, colour stability and proteolysis were analyzed. Carcasses with a slower temperature and more rapid pH decline had more calpain autolysis, slightly higher shear force and less colour stable compared to that counterpart in general (P<0.05). However, the shear force values of the loins were all acceptable (<6 kgF) regardless of different pre rigor processing and ageing/freezing treatments. Furthermore, the loins aged for 2 weeks-then-frozen/thawed had a similar shear force to the loins aged only for 9 weeks suggesting that ageing-then-freezing would result in equivalent tenderness compared to aged only loins for the long-term storage.

Rapid tenderisation of lamb M. longissimus with very fast chilling depends on rapidly achieving sub-zero temperatures.

A study was undertaken to determine whether variations within the defined temperature-by-time profile for very fast chilling (VFC), might explain variations in tenderness found with VFC. Loins from 32 lambs were subjected to one of five cooling regimes; defined by the average temperature between the meat surface and centre reached at a specific time post mortem. These were: -0.3 °C at 22 h (Control), 2.6 °C at 1.5 h (Fast(supra-zero)), 0.7 °C at 5.5 h (Slow(supra-zero)), -1.6 °C at 1.5 h (Fast(sub-zero)) and -2.3 °C at 5.5 h (Slow(sub-zero)), respectively. Shear force values considered very tender by consumers (less than 50 N, MIRINZ tenderometer) were found 2 days post mortem in Fast(sub-zero) loins only. Both time and temperature at the end of the cooling period contributed to variations in shear force. To achieve low shear force, the loins needed to be cooled to less than 0 °C at 1.5 h post mortem.

High pre rigor temperature limits the ageing potential of beef that is not completely overcome by electrical stimulation and muscle restraining.

Two simultaneous trials were conducted to determine the effects of electrical input [electrical stunning and stimulation (ES)], wrapping, pre rigor temperature (15 °C and 38 °C) and different post rigor chilling rates on beef quality using M. longissimus lumborum (n=100). The high pre rigor temperature induced a faster pH decline than ES. The loins at 38 °C had significantly greater protein denaturation, more purge and drip loss, higher shear force values and less desmin degradation compared with the loins at 15 °C. No difference in sarcomere length was determined between the pre rigor temperatures regardless of ES and wrapping. Different post rigor chilling rates did not play a substantial role in water-holding capacity, proteolysis, or shear force values during ageing. These results suggest that high pre rigor temperature induces temperature-related toughness of muscle due to protein denaturation with subsequent limitation of proteolysis by µ-calpain, regardless of ES and wrapping treatments.

Effect of lamb age and retail packaging types on the quality of long-term chilled lamb loins.

The objective of this study was to determine the impact of lamb age and packaging types on meat quality. Paired loins (M. longissimus dorsi) were obtained from 36 carcasses that included 4-month-old (New season; NS) and 11-month-old lambs (Old season; OS). The loins were vacuum-stored for eight weeks at -1.5°C. After storage, the loins were cut into subsamples and were randomly assigned to either high-oxygen modified atmosphere packaging (HiOx-MAP) or PVC-overwrapping for further display for 8 days. No differences between the age classes in shear force and drip loss were found (P>0.05). OS loins had significantly higher myoglobin and redness compared with NS loins. HiOx-MAP initially induced a more intense red colour compared with PVC (P<0.05), but resulted in severe discolouration at the end of display regardless of the age class. This observation suggests that the retail packaging type is the dominant factor over the age on lamb colour stability.

Water distribution and mobility in meat during the conversion of muscle to meat and ageing and the impacts on fresh meat quality attributes--a review.

This paper reviews current knowledge on the distribution and mobility of water in muscle (myowater) ante- and post mortem and factors affecting these in relation to fresh meat quality parameters; water-holding capacity (WHC), tenderness and juiciness. NMR transverse relaxometry (T(2)) using bench-top Low-Field Nuclear Magnetic Resonance (LF-NMR) has characterised myowater distribution and mobility as well as structural features in meat which directly affect WHC. The current literature demonstrates that WHC is correlated to the water located outside the myofibrillar network (extra-myofibrillar). This review identifies the critical stages which affect the translocation of water into the extra-myofibrillar space and thus the potential for decreased WHC during proteolysis (the conversion of muscle to meat). This review discusses how the intrinsic properties of the water held within the meat could contribute to juiciness and tenderness. Tenderness has been shown to correlate to T(2), however breed and species differences made it difficult to draw firm conclusions. Further understanding of the inherent water properties of fresh meat and the factors affecting water distribution and mobility using NMR technologies will increase the understanding of WHC and tenderisation of fresh meat.

Effect of ageing prior to freezing on colour stability of ovine longissimus muscle.

The effect of different ageing periods (0, 2 and 3 weeks at -1.5°C) of lamb loins (n=24) prior to freezing (9, 7 and 6 weeks at -18°C, respectively) compared to the aged-only (never frozen) lamb for 9 weeks postmortem on colour stability during display was assessed under high-oxygen modified atmosphere (HiOx-MAP; 80% O(2)) and oxygen permeable overwrap packaging conditions. The aged/frozen loins and aged-only loins in HiOx-MAP had similar (P>0.05) surface redness, colour intensity, and discolouration. Further, no significant difference found in shear force between the loins aged 3 weeks/frozen 6 weeks and the aged-only loins. However, more lipid oxidation (P<0.05) was found in the aged-only compared to the aged/frozen loins in HiOx-MAP throughout display. These results suggest that ageing loins prior to freezing would provide equivalent tenderness and colour stability, and better lipid oxidation stability compared to the aged-only loins under HiOx-MAP.

Retail colour display life of chilled lamb as affected by processing conditions and storage temperature.

This study explored the impact of i) processing conditions (electrical stimulation and pre rigor temperatures), and ii) storage temperature prior to retail display on the colour stability of lamb which had been vacuum-packaged for seven weeks before retail packaging in high-oxygen modified atmosphere (80% O(2)/20% CO(2)). A high pre rigor temperature (42°C) reduced colour stability while differences in colour stability between pre rigor temperatures of 5°C, 15°C and 25°C were limited. It was not affected by electrical stimulation, and did not interact with pre rigor temperature. In contrast, an increase in the storage temperature from the ideal temperature of -1.5°C to 2°C significantly decreased the colour stability of lamb loins. Even one week at 2°C at the end of the storage period had a substantial negative impact on the retail colour display life. The variability in colour increased over time, and the variability increased more for the temperature abuse treatments.

Temporal, biochemical and structural factors that influence beef quality measurement using near infrared spectroscopy.

This study included simultaneously measured pre and post-rigor meat quality indicators and attributes, using near infrared (NIR) spectroscopy and reference methods, to understand the temporal, biochemical and structural factors that influence beef quality and use this knowledge to build calibrations for measurement of meat quality using NIR. Eighty beef M. longissimus lumborum (LL) were measured from early pre-rigor (pH, glycogen concentration, and temperature) through to completion of post-rigor ageing (pH, shear force, and water holding capacity (WHC)). To create a range in the attributes, the LLs were subjected to various pre-rigor treatments, including electrical stimulation, restraint wrapping and cooling temperature (5°C, 15°C, or 35°C). Alongside the reference quality measurements and throughout the pre and post-rigor period, the LLs were measured with a diode array NIR spectroscopy system. NIR reflectance measurements were shown to be correlated to reference measurements of pre and post-rigor pH (R(validation)(2)=0.84), pre-rigor glycogen content (R(validation)(2)=0.70), post-rigor shear force (R(validation)(2)=0.58) and post-rigor WHC (R(validation)(2)=0.68). The shape of the NIR and reference plots over time and the ability of NIR to correctly measure differences in treatments indicated that NIR was not merely measuring changes that occur over time, but was measuring specific biochemical and physical changes, most likely changes in glycolytic metabolites, muscle shortening and/or proteolysis. Accounting for the reference method variance showed NIR measurement accuracy to be as good as or slightly better than that of the reference method.

The protective effect of electrical stimulation and wrapping on beef tenderness at high pre rigor temperatures.

A three factorial experimental design involving electrical stimulation (ES/NES), wrapping (wrapped/unwrapped) and pre rigor temperature (15°C or 35°C) was applied to 70 beef M. longissimus lumborum muscles to obtain a wide variation in shear force and drip loss. The shear force of all treatment groups decreased during ageing. As anticipated, wrapping and electrical stimulation had positive effects on shear force. However, high pre rigor temperature (35°C) did not result in higher shear force values if the muscles were electrically stimulated, wrapped or both. The results suggested that electrical stimulation protects against the negative effects of high pre rigor temperatures. The drip loss of all treatment groups increased during ageing in a manner that was unrelated to treatment but was correlated to tenderness (r(2)=0.70; p<0.0001). It was concluded that the application of electrical stimulation, whatever the pre rigor temperature, protects beef from toughening through the prevention of rigor shortening and the avoidance of inhibition of ageing enzymes.

Formation of mutagenic heterocyclic aromatic amines in fried pork from Duroc and Landrace pigs upon feed supplementation with creatine monohydrate.

Heterocyclic aromatic amines (HAA) have been shown to induce tumours at various organ sites in experimental animal studies and high levels of dietary intake of HAA have been associated with increased cancer risk in humans. These HAA are formed in meat upon heating from precursors such as amino acids, reducing sugars and creatine or creatinine. Groups of ten Duroc and ten Landrace pigs received feed supplemented with creatine monohydrate (CMH) for five days prior to slaughter at dose levels of 12.5, 25 and 50 g per animal per day. Ten control animals of each breed received the non-supplemented feed. Meat from Duroc pigs had been shown to respond to CMH supplementation with regard to waterholding capacity, juiciness, post slaughter pH and colour parameters, meat from Landrace pigs was unaffected. Indeed, while creatine phosphate levels in meat from Duroc pigs increased in a dose-dependent manner with CMH supplementation, no effect was observed in meat from Landrace pigs. Meat slices from longissimus dorsi were fried and considerable mutagenic activity was detected in meat extracts in Salmonella typhimurium YG1019 in the presence of rat-liver homogenate. However, no effect of breed or CMH supplementation was observed in fried pork on the formation of HAA determined as mutagenic activity. It may be concluded that feed supplementation with CMH at levels up to 50 g per day for five days prior to slaughter does not increase the level of heterocyclic aromatic amines detected as mutagenic activity formed upon frying of pork.

Significance of vitamin E supplementation, dietary content of polyunsaturated fatty acids, and preslaughter stress on oxidative status in pig as reflected in cell integrity and antioxidative enzyme activities in porcine muscle.

The present study investigates the combined effects of feed-induced increase in polyunsaturated fatty acids (PUFA) content and/or alpha-tocopherol content in pig muscles and preslaughter stress on cell integrity. Cell integrity was determined by plasma lactate dehydrogenase (LDH) activity, and antioxidative status of muscle was measured by activities of the antioxidative enzymes catalase, superoxide dismutase, and glutathione peroxidase. Preslaughter stress increased LDH activity, reflecting loss in cell membrane integrity independent of increased content of PUFA and/or alpha-tocopherol. However, feed-induced increase of PUFA decreased the LDH activity in plasma immediately after slaughter. Catalase activity in the muscle tissue increased as a consequence of the high-PUFA diet, which may indicate an increased demand caused by introduction of oxidative labile PUFA.

Physical changes of significance for early post mortem water distribution in porcine M. longissimus.

The post mortem changes in water mobility and distribution were followed in porcine muscle (M. longissimus dorsi) samples using continuous low-field NMR relaxation measurements and simultaneous measurement of changes in muscle impedance as an indirect measure of membrane integrity as well as muscle contraction measurements using a rigormeter instrument. Distributed exponential fitting analysis of NMR T(2) relaxation data revealed the presence of three distinct water populations (T(20), T(21), T(22)) within the muscle during its conversion to meat. Comparison of T(2) relaxation patterns and contraction data indicates that rigor development affects the attributes of the T(21) water population and thereby contributes to myofibrillar water characteristics post mortem, as the T(21) water population is believed to reflect inter/intra-myofibrillar water. The volume of the water population believed to reflect extra-cellular water (T(22)) in the living muscle. Early post mortem T(22) decreased slightly within the first 2-3 h post mortem followed by an increase and a change in its characteristic time constant. This was ascribed to an initial muscle cell swelling followed by water being expelled from the cellular space into the extra-myofibrillar space. Comparison of changes in the T(22) water population and impedance characteristics within the muscle during its conversion to meat revealed close relationship between progresses in the two attributes. Obtained data strongly support that the post mortem reorganization of water is closely associated with membrane properties, which moreover was found to affect the final water-holding capacity of the meat. Finally, a model for early post mortem events leading to changes in the distribution of water within muscles is proposed.

Postmortem proteome changes of porcine muscle related to tenderness.

Proteome analysis was used to investigate the relation between changes in postmortem proteome of porcine muscle and tenderness development. Muscle samples were taken at slaughter and 72 h postmortem, and the registered changes in the proteome were related to Warner-Bratzler shear force. One hundred and three protein spots were found to change significantly (P < 0.01) over time, and of these the 27 most pronounced changes were identified. Eleven out of the 27 changes were fragments of actin. Other identified myofibril proteins or fragments included myosin heavy chain, titin, myosin light chain I, myosin light II, CapZ, and cofilin. Correlation analysis revealed significant correlations between three of the identified actin fragments and the myosin heavy chain fragment to shear force. Moreover, myosin light chain II and triose phosphate isomerase I were also found to correlate significantly to shear force. The results clearly demonstrate that postmortem degradation of actin and myosin heavy chain is related to meat tenderness.

Significance of preslaughter stress and different tissue PUFA levels on the oxidative status and stability of porcine muscle and meat.

Polyunsaturated fatty acids (PUFAs) and exercise-induced stress are known to increase the oxidative susceptibility of lipids in muscle tissue. In contrast, antioxidative enzymes, e.g., catalase, superoxide dismutase, and glutathione peroxidase, are known to help sustain the delicate oxidative balance in biological tissue upon the application of stressors. The present study investigates the combined effect of different diet-induced muscle PUFA contents and preslaughter stress on the activity of antioxidative muscle enzymes and the oxidative stability of cooked meat. An increased content of unsaturated fatty acids in the tissue led to a decreased activity of lactate dehydrogenase in the plasma, indicating increased cell integrity. Catalase activity in the muscle tissue increased with increasing PUFA levels. However, this upregulation in antioxidative status of the muscle could not counteract the subsequent development of accelerated lipid oxidation in cooked meat as measured in terms of thiobarbituric acid reactive substances. Moreover, preslaughter stress induced increasing oxidative changes with elevated PUFA levels in the muscle tissue.

The significance of pre-slaughter stress and diet on colour and colour stability of pork.

The influence of pre-slaughter stress and a diet known to affect post mortem muscle metabolism or a standard diet (control pigs) on colour and colour stability of m. longissimus dorsi, m. biceps femoris and m. semimembranosus from 112 female pigs, free of the Halothane gene, was investigated. Pre-slaughter stress increased the early post mortem temperature in the three muscles, as well as the pH decline in control pigs, but not in pigs fed the experimental diet. Colour was measured on sliced samples after 0, 2 and 5 days retail display (1, 3 and 6 days post mortem, respectively) from the three muscles aged 1 day before cutting as well as on sliced m. longissimus dorsi samples aged 8 days before cutting (8, 10 and 13 days post mortem, respectively). Early post mortem pH was not a main determinant of the colour and colour stability, while the degree of pre-slaughter stress and especially its influence on temperature early post mortem was crucial in relation to colour development and colour stability. The discoloration rate was enhanced in m. longissimus dorsi aged for 8 days prior to retail display compared with samples aged for 1 day. However, the extent of the discoloration after 5 days of retail display was not inferior in muscle samples aged for 8 days due to a higher degree of blooming. Finally, present data indicate that 3-4 days ageing of pork prior to retail display results in the optimal colour stability.

Factors of significance for pork quality-a review.

This paper reviews current knowledge about factors of importance for pork quality with special emphasis on technological quality attributes. It is evident that production and slaughter factors can be used to control technological quality traits. However, most of the present knowledge is based on studies investigating the influence of a single or at the most two factors. This survey reveals that: -Most important, an understanding of how production and slaughter factors interact in relation to pork quality is a must to give the maximum number of tools to control pork quality and hereby meat quality demands of tomorrow. -The existence of a new genetic pool (elimination of the halothane and RN(-) genes in the commercial pig populations of tomorrow) force the meat science into a renaissance, as the influence of production and slaughter factors on pork quality may be fundamentally different in this new genetic pool. -A basic understanding on how muscle glycogen stores are influenced by genotype and feeding regime and the interaction with pre-slaughter handling might be the next major breakthrough in controlling technological pork quality. -Introduction of new production systems claim parallel studies to prevent unforseen negative effect on quality. -A holistic approach is needed to give an overall understanding of the influence of production, peri and post mortem factors on pork quality.

Physiological and structural events post mortem of importance for drip loss in pork.

Early post mortem metabolism and structural changes from 3 to 24 h, together with pH, temperature and impedance Py development were investigated in 37 Duroc×Landrace×Large White (DLY) pigs covering a range of drip loss from 2.2 to 12.6%. Multivariate statistical analysis was used to assess the impacts of different metabolites, pH and temperature, impedance, cytoskeletal protein degradation and extracellular cross-sectional area on drip loss. Taken as single factors, the concentration of lactate could explain 80% of the variation in drip, inosine monophosphate (IMP) and adenosine triphosphate (ATP) concentration explained 71 and 68%, respectively, whereas inosin and glycogen levels explained only 59 and 60%. The extracellular area was found to explain 39% of the variation in drip. The area between fibres provided more significant information than did the area between fibre bundles. The degradation of the cytoskeletal proteins was not related to drip loss. Impedance Py development over 24 h could explain 66% of the variation in drip, whereas pH and temperature explained 85 and 87%, respectively. A model including all measured variables could explain 83% of the variation in drip. However, only pH, temperature, impedance, [ATP](1 h) and [lactate](1 h and 2 h) were significant in relation to drip. By reducing the variables in the multivariate analysis, 89% of the variation in drip could be explained by a model containing only pH(2 h) and temperature(1 min). To explain variation in drip loss, pH and temperature measurements at significant time points were sufficient. Variation in post-mortem metabolites did, however, explain why variation in pH and temperature occurred. Development of drip channels was ruled by pH and temperature while impedance development was highly correlated to pH. This multi-faceted study shows those parameters, which can best be used to indicate or predict WHC, as well as those indicating the basic mechanism underlying variations in drip.