The effect of exercise stress, adrenaline injection and electrical stimulation on changes in quality attributes and proteins in Semimembranosus muscle of lamb

Exercise pre-slaughter has previously been shown to increase drip loss and tenderness in the longissimus muscle of lambs. The mechanism causing higher water loss in post-mortem muscle of lambs is not well understood. This experiment examines the effects of exercise stress, adrenaline injection and electrical stimulation (ES) on meat tenderness and water holding capacity. Forty crossbred lambs (20±2 kg live weight) were used in this study. Meat quality measurements were carried out on the Semimembranosus muscle (SM). The ultimate pH was higher with exercise stress (pH 5.93) compared to controls (pH 5.55; P<0.01). As expected the glycogen levels 30 min and 24 h post-mortem in the exercise stressed (P<0.01) muscle were lower. Lactate concentration at 30 min post-mortem in the electrical stimulation (ES: P<0.05) treated muscle was higher than all other treatment combinations. Myofibrillar protein denaturation, measured by protein solubility, was higher (P<0.05) and the rate of proteolysis of muscle proteins titin and troponin-T, as observed with western blots, increased with exercise stress. However, there were no treatment effects on Warner-Braztler shear force (WBSF). Exercise stress and an interaction with adrenaline caused increased drip loss (P<0.05) and purge (P<0.01) from the muscle. Muscle drip from the exercise stress treatment group had lower Mg(2+) (P<0.01) and K(+) (P<0.01) than controls. The main findings were that exercise stress pre-slaughter increased water loss and the rate of titin breakdown but had no effect on tenderness measured by WBSF. Together the different rates of proteolysis, protein denaturation and ionic conditions may have caused the reduced capacity of the muscle proteins to hold water, despite their relatively high ultimate pH.     

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.     

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.     

基于低场核磁共振研究不同解冻方式对冻猪肉食用品质的影响

本研究旨在从低场核磁共振（low field-nuclear magnetic resonance,LF-NMR）T2弛豫的角度探究不同解冻方式对冻猪肉食用品质的影响。以冷鲜肉（半腱肌,宰后27 h）作对照,测定冷藏解冻、微波-1解冻和微波-2解冻3 种解冻方式下冷冻猪肉的品质特性（解冻损失、蒸煮损失、持水能力（water holding capacity,WHC）、pH值、色泽、水溶性和盐溶性蛋白含量）,T2弛豫时间的水分分布情况及感官品质特性的变化。结果表明：微波-2解冻耗时最短,为5 min;微波解冻与冷藏解冻相比,具有更低的解冻损失率（P＜0.01）,其中微波-2的解冻损失率最低（5.31%）;并且相比于鲜肉,微波-2具有更高的WHC（30.99%）和更低的剪切力（19.49 N）;3 种解冻方式对肉样pH值无显著影响（P＞0.05）;微波解冻对肉样L*值、a*值、b*值、水溶性蛋白含量和盐溶性蛋白含量的影响均优于冷藏解冻,且与冷鲜肉更加接近;NMR T2弛豫的水分分布情况显示,冷藏解冻使冻猪肉中的不易流动水向自由水进行迁移,微波-1解冻则使冻猪肉中的自由水向不易流动水迁移,而微波-2解冻更倾向于使不易流动水向结合水迁移,这一定程度上解释了以上品质特性指标的差异性;感官评价结果显示微波-2解冻肉样各项评估指标评分与鲜肉更接近。由此可见,微波-2解冻能够更好地保持猪肉的食用品质。     

Comparison of functional and sensory attributes of high pH values in Semimembranosus and Longissimus dorsi of bull muscles during aging

Functional and sensory attributes were evaluated during aging for 96 h of high ultimate pH (pH > 6.2) Semimembranosus (Sm) from bulls. To investigate if type of muscle has an influence on these factors from dark, firm and dry (DFD) meat, the Sm muscle was compared with the Longissimus dorsi (Ld) muscle. Significant changes in pH and water holding capacity (WHC), dominant wavelength, lightness and viscosity were found between these muscles. The remaining functional and sensory properties between these muscles did not change signifi-cantly during storage. Bull's Sm muscle had lower pH (after 24, 48 and 72 h), WHC (after 24 and 48 h) and viscosity (after 24, 48, 72 and 96 h). However, the Sm muscles had higher cooking losses, less inten-sive flavour, less juiciness, tenderness and firmness.     

Nitrite-cured color and phosphate-mediated water binding of pork muscle proteins as affected by calcium in the curing solution

Calcium is a mineral naturally present in water and may be included into meat products during processing thereby influencing meat quality. Phosphates improve myofibril swelling and meat water-holding capacity (WHC) but can be sensitive to calcium precipitation. In this study, pork shoulder meat was used to investigate the impact of calcium at 0, 250, and 500 ppm and phosphate type [sodium pyrophosphate (PP), tripolyphosphate (TPP), and hexametaphopshate (HMP)] at 10 mM on nitrite-cured protein extract color at various pH levels (5.5, 6.0, and 6.5) and crude myofibril WHC at pH 6.0. Neither calcium nor phosphates present in the curing brines significantly affected the cured color. Increasing the pH tended to promote the formation of metmyoglobin instead of nitrosylmyoglobin. The ability of PP to enhance myofibril WHC was hampered (P < 0.05) by increasing the calcium concentration due to PP precipitation. Calcium also decreased the solubility of TPP but did not influence its enhancement of WHC. On the other hand, HMP was more tolerant of calcium but the soluble Ca-HMP complex was less effective than free HMP to promote water binding by myofibrils. The depressed muscle fiber swelling responding to added calcium as evidenced by phase contrast microscopy substantiated, to a certain extent, the deleterious effect of calcium, suggesting that hardness of curing water can significantly affect the quality of cured meat products. PRACTICAL APPLICATION: Although not affecting nitrite-cured color, calcium hampers the efficacy of phosphates to promote water binding by muscle proteins, underscoring the importance of water quality for brine-enhanced meat products.     

THE EFFECT OF SODIUM POLYPHOSPHATES AND OF DIVALENT CATIONS ON THE WATER HOLDING CAPACITY OF PRE-AND POST-RIGOR CHICKEN BREAST MUSCLE

The water holding capacity (WHC) of natural actomyosin (NAM), of both contracted and uncontracted glycerinated myofibrils and of pre- and post-rigor chicken meat was investigated in the presence and/or absence of sodium pyrophosphate (PP_i), Kena, CaCl₂ and MgCl₂. In these experiments PP_i caused a small decrease in the WHC of NAM which was further decreased either by Ca or even further by Mg. PP_i with or without Ca or Mg had almost no effect on the WHC of glycerinated myofibrils. Pre-rigor meat showed a slight decrease in WHC of PP_i which was further decreased with Mg or even further by Ca. With post-rigor meat the WHC increase with PP_i was decreased by the addition of Mg or even further decreased by the addition of Ca. The actual WHC of pre-rigor meat was almost twice that of post-rigor meat. Once rigor had occurred no major changes in WHC were observed up to 5 days. Kena caused a slight decrease in the WHC of NAM. Using myofibrils and the meat samples, Kena gave an increase in WHC. The addition of Ca and Mg again tended to decrease this WHC.     

The influence of pre-slaughter oral loading of acid or base on post-mortem changes in Longissimus Dorsi muscle of pork

Twenty-four pigs were assigned to one of four ad libitum water treatments: control, sodium bicarbonate (12·6 g/litre), low ammonium chloride (4 g/litre) or high ammonium chloride (8 g/litre) for 5 days, to study the influence of an oral acid or base load on post-mortem changes in longissimus dorsi muscle and ultimate pork quality. Physiological changes before slaughter were monitored by measuring blood pH, pCO(2) and HCO(3)(-). The influence of dietary treatments on post-mortem changes and ultimate meat quality was determined by measuring glycolytic enzymes and intermediates, and muscle pH, color and water-holding capacity (WHC). As expected, sodium bicarbonate generated a metabolic alkalosis, whereas ammonium chloride resulted in a metabolic acidosis. Pre-slaughter acid-base status was positively correlated with muscle WHC (P < 0·05). However, no significant dietary treatment effect was observed in muscle quality traits such as color (a, b, L) and WHC. Muscle pH(45) was significantly (P < 0·05) higher in bicarbonate than control and high ammonium chloride treatments. The activity of Ca(2+)-dependent protein kinase was significantly (P < 0·05) higher at 45 min post-mortem but that of pyruvate kinase was significantly lower at 2 and 4 h post mortem in bicarbonate-treated pigs. At 45 min post mortem, the activity of fructose-1,6-diphosphatase in the control pigs was significantly higher (P < 0·05) than on other treatments. The concentration of glycogen was significantly (P < 0·05) higher in bicarbonate and high ammonium chloride pigs; bicarbonate-treated pigs also has significantly higher adenosine-5'-triphosphate (ATP) and pH values than other treatment groups (P < 0·05) at early post-mortem. It was concluded that pre-slaughter oral loading of acid or base could induce changes in muscle metabolism and post-mortem muscle pH. Further research is required to confirm that altering diet acidogenicity or alkalinogenicity may be a means of enhancing ultimate pork quality.     

滩羊肉宰后成熟期间ATPase活力变化对微观结构及保水性的影响

为研究宰后成熟期间ATPase活力变化对滩羊肉微观结构以及保水性的影响,以6 月龄滩羊背最长肌（Longissimus dorsi）为研究对象,分析其4 ℃成熟0、1、2、4、8 d时Na＋-K＋-ATPase、Ca2＋-ATPase、Caspase-3活力以及肌肉微观结构、pH值与滴水损失率的变化情况。结果表明：随成熟时间延长,Na＋-K＋-ATPase与Ca2＋-ATPase活力先升高后降低,成熟1 d时达到最大值;Caspase-3活力先升高后降低,成熟2 d时达到最大值;滴水损失率先升高后降低,pH值先降低后有所回升;总蛋白、低盐溶性蛋白及高盐溶性蛋白质量浓度均逐渐减少,水溶性蛋白质量浓度成熟2 d后显著降低（P＜0.05）;成熟至8 d时,肌原纤维断裂,肌纤维之间、肌束之间、肌纤维及肌膜之间形成间隙,Z线断裂,H带消失;相关性分析结果表明Na＋-K＋-ATPase活力与各指标均呈极显著相关性（P＜0.01）,Ca2＋-ATPase活力与pH值、Na＋-K＋-ATPase及Caspase-3活力均呈极显著相关性（P＜0.01）。结论：滩羊肉宰后成熟过程中Na＋-K＋-ATPase与Ca2＋-ATPase活力变化可能促使下游Caspase-3激活,Caspase-3水解结构蛋白可能导致肌肉组织在不同部位形成间隙,在重力作用下肌肉中的水分流入间隙中,引起滩羊肉滴水损失升高,保水性变差。     

Ultrasonic-assisted phosphate curing: a novel approach to improve curing rate and chicken meat quality

The effects of ultrasound-assisted phosphate curing (UPC), phosphate curing (PC), and deionised water curing (DC) on the quality of chicken breast meat were investigated. The analysis of tissue sections, low-field nuclear magnetic resonance (LF-NMR), and headspace solid-phase microextraction gas-phase mass spectrometry (HS-SPME-GC-MS) of water distribution, myofibrillary structure, and volatile components of the meat samples were performed to reveal the mechanism. Also, the curing rate, water holding capacity (WHC), and shear force of meat were assessed. The results revealed that ultrasonic-assisted salting improved the meat salting rate, WHC, and tenderness by mechanically destroying the muscle fibre structure, increasing the space between the muscle fibre bundles, promoting water migration and uniform distribution, and reducing water freedom in the treated samples. In addition, HS-SPME-GC-MS analysis revealed that PC significantly reduced the content of volatile flavour components in the chicken breast meat compared with DC (P < 0.05); however, the combination treatment with PC and ultrasonic curing could reconstruct the flavour loss caused by phosphate. Thus, our cumulative results suggest that the ultrasonic technology may effectively assist the processing technology in improving the quality of meat and reconstructing the flavour loss in meat products.     

Postmortem changes in muscle electrical properties of bovine M. longissimus dorsi and their relationship to meat quality attributes and pH fall

Heifers (n=47) were slaughtered and hung conventionally in an industrial meat plant. Electrical impedance (Py) and conductivity (EC) were studied for their ability to indicate or predict selected meat quality attributes i.e. Warner-Bratzler shear force (WBSF), sensory tenderness, texture, flavour and acceptability, water holding capacity (WHC) and colour. pH, electrical impedance (meat check) and electrical conductivity (pork quality meter) measurements were taken at hourly intervals up to 8 h and again at 1 and 2 days postmortem. Electrical measurements were taken again at 7 and 14 days postmortem. Freshly cut steaks (2.5 cm thick) were taken from the longissimus dorsi (LD) muscle at 2, 7 and 14 days postmortem, vacuum-packaged in plastic bags and stored at -20°C for WBSF and sensory analysis. Freshly cut steaks were used for WHC and colour measurements. During the development of rigor and over the ageing period, electrical changes occur in muscle tissue. Electrical measurements were found to change significantly between 1 and 14 days postmortem and when measured over the ageing period (at 2, 7 and 14 days postmortem) were significantly correlated to WBSF, sensory tenderness and Hunter 'a' and 'b' values (r=±0.56-±0.68, p<0.001) and weakly to moderately correlated to other sensory attributes (r=±0.31-0.58, p<0.001) measured at the same times postmortem; thus showing potential for these rapid physical measurements as indicators of meat quality if both electrical measurements and quality attributes are measured at the same times postmortem and correlations are calculated over the ageing period. However, electrical measurements taken at specific times at the early postmortem period (i.e. at 1 or 2 days) showed only a few weak relationships with meat quality attributes measured at later times postmortem (i.e. 7 or 14 days) demonstrating that early postmortem electrical measurements are not suitable for the prediction of ultimate meat quality. Py values taken between 7 h and 7 days postmortem were significantly correlated with all pH measurements with the exception of 1 day values. Two day Py measurements showed the highest correlations (r=0.45-0.62, p<0.01-0.001) with pH. EC was also found to be moderately correlated with pH although correlations were slightly lower than those obtained for Py. Highest correlations (r=0.47-0.59, p<0.01) were obtained for 7 h values.     

Fragmentation of myofibrils, limited proteolysis and water holding capacity of meat

Protein changes in ageing meat result in increased vulnerability of the myofibrils to fragmentation, caused possibly by limited proteolysis. It was investigated which groups of muscle proteases, if any, were involved and what was the relation between fragmentation and hydration of beef meat. In samples ranging in natural pH from 5.4 to 7.0 the least fragmentation after 3 days at 2 degrees C was at pH 6. This could suggest the role of both the cathepsins and neutral proteases. In samples aged in the presence of EDTA fragmentation was significantly lower than in the controls. This could indicate the role of Ca2+ activated neutral proteases, or support the hypothesis on the nonenzymatic mechanism involving Ca2+. The results of PAG electrophoresis could not have been due to the neutral proteases, as the 30,000 g X mol-1 component, resulting from the hydrolysis of troponin T, did not accumulate at pH 7 until the 9th day of ageing, but at pH 5.4 the intensity of this band increased markedly already after 3 days. There was no correlation between the fragmentation and the hydration of the aged meat after cooking. The addition of 0.001% of trypsin or 0.0005% of papain to minced meat did not cause after 9 days any increase in the contents of free amino acids and peptides or significant changes in the PAGE pattern as compared to those in the controls. However, the fragmentation and hydration of the raw meat was larger in the samples containing added enzymes. After cooking the hydration of the samples did not differ.(ABSTRACT TRUNCATED AT 250 WORDS)     

微冻贮藏对牛肉保水性的影响

本实验以冷藏（2 ℃）和冷冻（－18 ℃）作为对照组,从肌原纤维蛋白结构和水分迁移等方面分析了微冻（－4 ℃）贮藏条件下牛肉保水性变化的机制。结果表明：微冻贮藏牛肉的汁液损失率和蒸煮损失率显著高于冷藏和冷冻处理组（P＜0.05）,保水性最差。微冻贮藏过程中,牛肉中的水分弛豫时间逐渐变长,结合水相对含量无明显变化,不易流动水相对含量显著下降,自由水相对含量显著上升（P＜0.05）。随着贮藏时间的延长,3 种贮藏方式下牛肉的总巯基含量和活性巯基含量均显著下降,蛋白质表面疏水性显著上升（P＜0.05）,且贮藏温度越低,变化速率越慢。微冻贮藏过程中,牛肉肌原纤维蛋白降解程度较低,贮藏后期蛋白质变性程度较高,提升了肌原纤维蛋白网络中不易流动水的自由度,使得部分不易流动水转化为自由水,导致了微冻牛肉较差的保水性。     

Dietary creatine monohydrate has no effect on pork quality of Danish crossbred pigs

Creatine content in the muscle may delay postmortem lactate formation and postpone the pH decline, hence potentially improving the water-holding capacity (WHC) as shown in a previous study including purebred Duroc pigs, although the same study did not find any effect on meat from purebred Landrace pigs. In the present study Danish D(LY) crossbreeds were supplemented with 0 or 50g creatine monohydrate (CMH)/d for five days prior to the slaughter. CMH supplementation had no effect on meat quality indicators (pH and temperature), meat quality attributes (WHC and colour) or eating quality (juiciness and tenderness) of meat from the D(LY) crossbred pigs. As a consequence the D(LY) crossbreed was classified as a non-responder to CMH supplementation.     

The relationship between water-holding capacity and cooked meat tenderness in some beef muscles as influenced by acidic conditions below the ultimate pH

Previous studies have indicated the beneficial influence of higher than normal ultimate pH (pH(u)) on the tenderness of cooked meat. Such benefits have been indirectly linked to the influence of increased pH on the water-holding capacity (WHC) of meat above the iso-electric point (IEP) of the myofibrillar proteins. In the present study, relationships between WHC and the tenderness of some beef muscles were investigated under pH conditions within and below the IEP of the myofibrillar proteins, such that the maximum range of meat swelling was achieved. It was found that increased WHC, as measured by swelling ratio in both raw and cooked meat, markedly influenced cooked meat tenderness, irrespective of the connective tissue content of the muscles. The results fitted a series of exponential decay equations relating swelling ratio to cooked meat toughness. Additionally, strong linear decreases in toughness were apparent over the pH range 4·6 to 4·1 for the three muscle types studied.     

Biochemical studies on fast glycolysing bovine muscle

Of the psoas major muscles from 1395 carcasses of young bulls 64% showed pH(1) values (30 min post mortem) below 6·0. In 100 muscle samples (selected so that a normal distribution of the pH(1) values was obtained), water-holding capacity (WHC), brightness of colour and the concentration of all glycolytic metabolites were determined. There were correlations between pH(1) and the other characteristics of meat quality, lower pH(1) values were associated with lower WHC, paler colour, lower glycogen levels and higher levels of lactate (30 min post mortem). All these correlations were highly significant. The accelerated breakdown of glycogen-and a simultaneous accumulation of hexose monophosphates-indicate an activation of the phosphorylase system in fast glycolysing bovine muscle. In fast glycolysing muscle, creatine phosphate was almost absent by 1 h post mortem and the ATP level was very low, indicating a high rate of breakdown of high-energy phosphates. The quality deviation of fast glycolysing beef is much less severe than that of PSE pork and therefore might not present a serious economic problem.     

Colour of muscle from 18-month-old steers given long-term daily exercise

Darker beef from pasture-fed compared with grain-fed cattle may result from differences in physical activity rather than differences in nutrition. The objective was to determine if steers that were exercised produced darker meat than non-exercised steers and whether any effect was muscle-related. Exercised steers were walked 4.41 km daily in a single bout, six days per week for 18 weeks at an average speed of 5.2 kmh(-1). All steers were fed grass silage on an ad libitum basis plus 6 kg concentrates. Following slaughter, muscle colour coordinates ('L' (lightness), 'a' (redness) and 'b' (yellowness) values) of M. longissimus dorsi (LD), M. semimembranosus (SM) and M. extensor carpi radialis (ECR) were recorded at 48 h postmortem and redness and yellowness were used to calculate muscle hue ('H') and colour intensity/saturation ('C'). The pH of all muscles was measured at 1.5, 3, 6, 22 and 48 h postmortem and LD samples were recovered (90 min postmortem) for glycolytic potential (GP) assessment. Exercise did not affect muscle lightness, yellowness, hue or colour intensity. However, LD was the darkest (P<0.001) and SM the most saturated (P<0.001) muscle. Exercise affected muscle redness in a muscle-dependent manner (muscle×exercise, P=0.038) whereby ECR became more red with exercise but LD and SM were unaffected. There were muscle×time (P<0.001) and time×exercise (P=0.045) interactions for muscle pH. The ECR muscle had the highest pH at all times. The exercised steers had higher (P<0.05) LD muscle pH than control steers at 3 and 6 h postmortem. Exercise did not affect myoglobin concentration, which was muscle dependent, decreasing in the order: SM (6.72 mg/g)>ECR (6.33 mg/g)>LD (5.48 mg/g), which were all different (P<0.001). Exercise had no effect on GP in LD muscle (111 vs. 99 μmol/g for control and exercised steers, respectively; SED=6.6 μmol/g). It was concluded that although application of exercise did not affect muscle lightness and thus, did not cause 'darker' meat, it did affect muscle redness in a muscle-dependent manner.     

Aging-induced changes in microstructure and water distribution in fresh and cooked pork in relation to water-holding capacity and cooking loss - A combined confocal laser scanning microscopy (CLSM) and low-field nuclear magnetic resonance relaxation study

Confocal laser scanning microscopy (CLSM) and low-field nuclear magnetic resonance (LF-NMR) relaxometry were combined to characterize microstructural changes and water distribution in fresh and cooked pork during an aging period of 14 days. At day 1 (24 h postmortem) a few muscle fibres, which appear swollen, were observed in both fresh and cooked meat. An identical microstructure was still apparent after 14 days, however, the number of muscle fibres showing distinguished characteristics was found to increase throughout the aging period. Hence, it was apparent that during aging the individual fibres swell and disintegrate at different rates. Development in water-holding capacity (WHC) was followed during the aging period using gravimetric methods, and an increase in the WHC in the fresh meat was observed, which resembled the amount of extramyofibrillar water measured by NMR relaxometry (T₂₂ population). This was consistent with the CLSM images, as a substantial increase in the number of myofibrils that appeared swollen, capable of holding more water, was observed during aging. In the cooked meat the width of the T_21c population, reflecting the myofibrillar water in the cooked meat, was seen to decrease during the entire storage period, which corresponds to the development of a more homogeneous structure. In the CLSM data a continuous degradation during the storage period was observed, which could resemble a shift to a more homogeneous structure. Comparison of CLSM of transverse sections of fresh and cooked pork revealed a pronounced shrinkage of muscle fibres upon cooking. This resulted in large gaps between the cooked muscle fibres, which also was visible as shrinkage at the level of the individual myofibrils. This pattern was also reflected in the NMR relaxation data. The cooking-induced shrinkage of the myofibrils occurred concomitantly with a decrease in the amount of intermyofibrillar water within the individual fibre and an increase in the larger extramyofibrillar spaces between fibres, i.e. water is expelled from the myofibrillar matrix upon cooking. Accordingly, the present study demonstrated that the use of CLSM together with NMR relaxometry can provide further information on the relationship between structural characteristics of meat and resultant water distribution.     

Strategic finishing feeding as a tool in the control of pork quality

A standard diet and two finishing feeding strategies known to reduce muscle glycogen stores were investigated in combination with exercise immediately prior to slaughter in pigs. The objective was to determine the influence of muscle glycogen at slaughter on temperature and pH in post-mortem muscle, the colour, drip loss and Warner–Bratzler shear force of the meat. The muscle glycogen stores were reduced by strategic finishing feeding. In general, pH_{45 min} was higher in muscles from strategically fed pigs compared with control pigs. Exercise also resulted in higher pH_{45 min} in control pigs compared to non-exercised control pigs, while the opposite was seen in muscles from strategically fed pigs. Exercise resulted in higher muscle temperatures in the carcasses irrespective of feeding strategy. pH_{24 h} were higher in M. biceps femoris and M. semimembranosus from exercised, strategically fed pigs compared with the corresponding controls. In contrast, irrespective of feeding strategy no difference in pH_{24 h} was registered in the meat of non-exercised pigs. Drip loss was lower in meat of strategically fed pigs compared with meat of control pigs. Moreover the drip loss was lowest in the meat of non-exercised pigs. The present study shows that strategic finishing feeding has high potential for the control of pork quality.     

Post mortem energy metabolism and meat quality of porcine M. longissimus dorsi as influenced by stunning method - A (31)P NMR spectroscopic study

Post mortem changes in phosphorus metabolites and pH were studied in M. longissimus dorsi from pigs (n=10) stunned either by CO(2) (n=3), electrical (n=2), captive bolt pistol (n=2) or by anesthesia (ketamine) (n=3). (31)P-NMR spectroscopy revealed significant effects of stunning method on changes of the various phosphorus metabolites in the muscle post mortem, with the effect being most pronounced on the degradation of phosphocreatine (PCr). Moreover, the four stunning methods gave rise to large differences in the progress of pH as determined by (31)P-NMR spectroscopy. Using anesthesia as the reference showed that the captive bolt pistol caused the highest rates of post mortem degradation of phosphorus metabolites, electrical stunning intermediate, and CO(2)-stunning causing the lowest post mortem degradation rates, even though CO(2)-stunning also was associated with higher post mortem degradation rates compared with anesthesia. Finally, it was demonstrated that the water-holding capacity (WHC) of the meat was affected by the applied stunning method, as CO(2)-stunning, electrical stunning and captive bolt pistol resulted in mean drip losses of 6.4, 8.3 and 8.6%, respectively (P=0.02). The result displays the significance of induction and progress in post mortem changes on WHC in meat.