Water distribution in porcine M. longissimus dorsi in relation to sensory properties

The water distribution in M. longissimus dorsi (LD) from purebred Hampshire and Swedish Yorkshire pigs was recorded by proton-pulse-NMR. Three domains of water were seen with this type of method, designated as free, extracellular and intracellular water, respectively. The relative proton population for the free water increased from 1·8% in raw, to 3·3% in fried, samples from Hampshire and to 4·2% for the Yorkshire samples. The relaxation time of the extracellular water increased for Hampshire samples from 100 ms, when raw, to 108 ms and 114 ms for samples fried to centre temperatures of 68°C and 80°C, respectively. For Yorkshire samples it decreased from 122 to 108 and 109 ms, respectively. The relative proton population of the extracellular water decreased after frying (raw: 24·5%, 68°C: 18·6% and 80°C: 13·9%) for Hampshire samples, whereas the corresponding populations of protons for those of Yorkshire were 16·5%, 19·2% and 16·6%. The intracellular water had relaxation times of about 40 ms (raw), 30 ms (68°C) and 28 ms (80°C) for both breeds. The relative proton populations were: for Hampshire, 74·1% (raw), 77·7% (68°C), 83·4% (80°C) and, for Yorkshire, 81·6% (raw), 75·5% (68°C) and 77·2% (80°C). On average, the samples of Hampshire were more juicy and tender than those of Yorkshire. The sensory properties were related to the water distribution, but obvious influences of breed and end-point temperature at frying were noted for the relationships. In general, the juiciness and tenderness of fried LD samples could fairly well be predicted by the water distribution in raw meat. However, due to the influence of breed and temperature, different variables are best for the prediction. Also, when the sensory properties were related to the water distribution in fried samples, the influences of breed and end-point temperatures were noted.     

Physico-chemical and processing quality of porcine M. longissimus dorsi frozen at different temperatures

Longissimus dorsi muscle from six pigs (24 h post-mortem) was cut into portions of similar size and shape (c. 700 g) and vacuum-packed in polyfilm. The muscle specimens were divided into three samples, one frozen at -20°C, another at -80°C and the third served as the control (not frozen). The meat sample frozen at -80°C was transferred to the -20°C freezer. After one month, both frozen pork samples were thawed at -2°C and drip loss (%) was measured. Hunter colour, metmyoglobin (MetMb) formation (%), water-holding capacity (WHC), TBA value, transmission value (TM) and myofibril fragmentation were also determined. There was no significant difference in drip loss for the two frozen samples. No MetMb formation could be detected and Hunter values were basically the same for all three samples. WHC, TBA value and TM were essentially the same for all three samples. TBA value was quite low for each frozen sample, indicating that lipid oxidation did not occur during freezing. Histological examination of both frozen samples indicated inter- and intracellular ice crystal formation at -20°C, and intracellular ice at -80°C, the extent being less than at -20°C. At -20°C, ice crystals were larger and muscle fibre diameter smaller than for the control or -80°C sample. Myofibril fragmentation in both frozen samples was significantly higher than in the control. Pork sausage was prepared from all three samples by adding 2% NaCl and 100 ppm NaNO(2). Cooking loss and colour forming ratios were essentially the same. The sausage sample made from the -20°C frozen meat was harder than that of the other two samples according to rheological measurement.     

Drip loss sampling in porcine m. longissimus dorsi

The effect of the sampling position is investigated when measuring drip loss in porcine longissimus dorsi muscle. Measuring in biological tissue often includes an assumption of homogeneity of the muscle under investigation, an assumption that only applies to a certain extent. However, this assumption is particularly critical when measuring drip loss. In the present experiment two different methods for measuring drip loss were applied. The two methods use a considerably different sample size and thus a difference in sensitivity to the heterogeneity of the object to be measured may be expected. In other words, when measuring drip loss a large sample size may blur information about biological variations in the parameter under investigation. The influence of the sampling position on the drip loss measurement 34 pigs were selected from a random group of 204 pigs. The right and the left longissimus dorsi were excised and used as objects for measuring drip loss with two different methods. Each longissimus dorsi muscle was sliced in 11–15 slices of 2.5 cm thickness. The left longissimus dorsi was sampled in three positions for each slice and the drip loss was measured in each position applying the EZ-DripLoss method. The longissimus dorsi from the right side of the carcasses was measured with the bag method.

Our measurements showed a substantial variation in the influence of the sampling position on the result of determination of drip loss. The influence is calculated as the standard deviation (SD) between measurements performed in different positions in transverse and longitudinal direction along the longissimus dorsi muscle.

Our work showed that the optimum position of sampling for drip loss determination was 5 cm cranial to the start of the fourth lumbar vertebra, where we found a SD between neighbouring sampling positions of less than 0.74%. We found a high correlation (0.85) between the methods applied even though this value included differences between the right and the left side of the carcass. From one single measurement of drip loss performed on the left longissimus dorsi with the EZ-DripLoss method, we were able to predict the average drip loss of the right longissimus dorsi with a very high correlation (>0.9). We are still searching for an explanation for the 1.2% offset between the two methods employed in this experiment.     

Procedure for determination of glycolytic potential in porcine m. longissimus dorsi

The aim of this work was primarily to work out a procedure for removal of samples from LD for determination of glycolytic potential in connection with experiments at commercial abattoirs and secondly to determine the correlation between glycolytic potential and ultimate-pH in Danish pigs. Samples of LD were taken immediately after exsanguination and 30 h post mortem. All samples were analysed for the content of glycogen, glucose, glucose-6-phosphate and lactate to be able to calculate the glycolytic potential. The results showed no difference in glycolytic potential in LD irrespective of sampling time. Samples removed after exsanguination contained a higher amount of glycogen and less lactate than samples removed the day after slaughter, where most of the glycogen had been transformed into lactate. These results show that samples for determination of glycolytic potential in LD can be removed the day after slaughter in the chilling room instead of being removed immediately after sticking at the slaughter line, which is less practical and hygienic. There was a significant correlation (-0.61) between glycolytic potential in LD and ultimate pH in LD.     

Metmyoglobin reductase activity in porcine m. longissimus dorsi muscle

Reduction of metmyoglobin by metmyoglobin reductase extracted from porcine m. longissimus dorsi was found to depend on the presence of NADH and to a lesser degree on the presence of an electron transfer mediator (ferrocyanide). The porcine metmyoglobin reductase was found to reduce equine metmyoglobin and metmyoglobin isolated from pigs hearts using a method described for bovine metmyoglobin. A linear increase in the rate of reduction as a function of amount of enzyme extract was observed, while the rate as a function of NADH concentration increased to a saturation level. In the pH range 6.0-7.1, the rate of reduction of porcine metmyoglobin by porcine metmyoglobin reductase increased at decreasing assay pH, apparently approaching a maximal rate around pH 6. From the temperature dependence of the maximal rate of the enzyme catalyzed reduction of porcine metmyoglobin an apparent activation energy of 33 kJ mol(-1) was calculated. Porcine metmyoglobin was also reduced by NADH in a non-enzymatic reaction, with a rather similar activation energy showing (i) that porcine metmyoglobin is more closely associated with the reductase complex than bovine metmyoglobin and not so easily separated, or (ii) that porcine metmyoglobin reduction is more facile as a non-enzymatic reaction and less dependent on electron transfer mediators compared to bovine metmyoglobin reduction.     

Preliminary investigations on the effects of ageing and cooking on the Raman spectra of porcine longissimus dorsi

The influence of ageing and cooking on the Raman spectrum of porcine longissimus dorsi was investigated. The rich information contained in the Raman spectrum was highlighted, with numerous changes attributed to changes in the environment and conformations of the myofibrillar proteins.Predictions equations for shear force and cooking loss were developed from the Raman spectra of both raw and cooked pork. Good correlations and standard errors of prediction were obtained for both WB shear force and cooking loss, with the raw and the cooked samples showing almost identical results R² = 0.77, root mean standard error of prediction (RMSEP)% of mean = 12% for shear force; R² = 0.71, RMSEP% of mean = 10% for cooking loss. The Raman spectra were also able to predict the extent of cooking that occurred within the pork (R²_val = 0.94, RMSEP% of range = 5.5%).Raman spectroscopy has considerable potential as a method for non-destructive and rapid determination of pork quality parameters such as tenderness. Raman spectroscopy may provide a means of determining changes during cooking and the extent to which foods have been cooked.     

Preliminary investigations on the effects of ageing and cooking on the Raman spectra of porcine longissimus dorsi

The influence of ageing and cooking on the Raman spectrum of porcine longissimus dorsi was investigated. The rich information contained in the Raman spectrum was highlighted, with numerous changes attributed to changes in the environment and conformations of the myofibrillar proteins.Predictions equations for shear force and cooking loss were developed from the Raman spectra of both raw and cooked pork. Good correlations and standard errors of prediction were obtained for both WB shear force and cooking loss, with the raw and the cooked samples showing almost identical results R² = 0.77, root mean standard error of prediction (RMSEP)% of mean = 12% for shear force; R² = 0.71, RMSEP% of mean = 10% for cooking loss. The Raman spectra were also able to predict the extent of cooking that occurred within the pork (R²_val = 0.94, RMSEP% of range = 5.5%).Raman spectroscopy has considerable potential as a method for non-destructive and rapid determination of pork quality parameters such as tenderness. Raman spectroscopy may provide a means of determining changes during cooking and the extent to which foods have been cooked.     

Practical use of surimi-like material made from porcine longissimus dorsi muscle for the production of low-fat pork patties

This study evaluates the effect of replacing fat with surimi-like material (SLM) made from the porcine longissimus dorsi muscle on the physicochemical and sensory characteristics of pork patties. Pork patties were produced with different levels of fat and SLM using a commercial method. Pork patties produced with 20% SLM had the lowest fat content (1.76%, P < 0.001), and had a higher cooking yield (87.41 vs. 78.57%, P < 0.05) and less shrinkage (4.01 vs. 9.02%, P < 0.001) than patties produced with 20% back-fat (control). Moreover, patties produced with SLM exhibited more acceptable organoleptic characteristics, including tenderness (P < 0.01) and overall acceptability (P < 0.001), than full-fat control patties. These results indicated that SLM cannot only be used as a fat replacer, but that it also improves the physicochemical and sensory characteristics of low-fat pork patties.     

Early Post Mortem pH decrease in porcine M. longissimus dorsi of PSE, Normal and DFD quality

The purpose of this investigation was to compare the muscle pH at exsanguination and the rate of pH changes in porcine M. longissimus dorsi (LD) of normal, DFD (Dark, Firm, Dry) and PSE (Pale, Soft, Exudative) quality. The pH was continuously measured in the LD in 116 carcasses during the first 50 min post mortem. Calculations were made both on measured pH-values and on pH-values transformed to hydrogen ion concentrations. A regression of pH or hydrogen ion concentration on time was made for each animal. These individual regressions were then combined, using a multivariate analysis to estimate regression curves for each meat quality class. The two methods for expressing pH gave somewhat different results. The relationship between the hydrogen ion concentration and time was found to be linear for normal and DFD muscles and quadratic for PSE muscles. As a consequence of the mathematical properties of pH, the relationship between pH and time was found to be quadratic for the normal and DFD qualities, and linear for the PSE quality. For both methods of calculations the slopes for the regression curves were significantly different between PSE and the other two quality classes with both calculating methods, while the slopes did not differ between normal and DFD muscle qualities. The intercepts of the regression curves differed significantly between PSE and the other two quality classes only when the calculations were made on measured pH-values without transformation. A temporary increase in pH was seen in some normal and PSE carcasses during the measured time period. Development of muscles with PSE characteristics thus seems to be initiated by a combination of a lower muscle-pH already at exsanguination and a faster pH decrease. It is also of importance to consider the special mathematical properties of the pH-value.     

The use of visible and near infrared reflectance spectroscopy to predict beef M. longissimus thoracis et lumborum quality attributes

Visible and near infrared reflectance spectroscopy was used to predict pH at 24 h (pH24) post-mortem, sarcomere length (SL), cooking loss (CL), Warner–Bratzler Shear Force (WBSF) and colour parameters (L^∗, a^∗, b^∗) in beef cattle samples. Samples from M. longissimus thoracis et lumborum from 30 bulls were aged at 4 °C for 1, 3, 7 and 14 days and analysed for pH, SL, CL, WBSF and colour. NIRS calibrations for pH24, luminosity at 0 (L^∗t0) and 60 min (L^∗t60) showed good predictability (R² = 0.97, 0.85 and 0.82; SECV = 0.10, 1.16, 1.36, respectively), whereas those related to the rest of the parameters were poorer.     

The estimation of beef carcass muscle using cross-sectional area of M. longissimus dorsi at the fifth rib

The improvements in the accuracy of prediction of side muscle (weight and proportion) using measurements of eye muscle area at the 10th rib (EMA(10)) and eye muscle area at the 5th rib (EMA(5)), were compared in 48 steers, grain-fed for the Japanese market. For side muscle proportion the addition of EMA(10) to hot side weight and a fat thickness measurement did not improve prediction but the addition of EMA(5) did. P8 fat thickness together with hot side weight and EMA(5) (each, P<0·001) predicted side muscle proportion with an SEE of 2·05% and an R(2) of 61%, while the values for 10th rib thickness together with hot side weight and EMA(5) (each, P<0·001) were 2·09% and 68%, respectively. For the prediction of side muscle weight a fat thickness measurement and hot side weight (both, P<0·001) explained 77-84% of variance; the addition of an eye muscle area measurement further improved prediction with the most accurate being P8 fat thickness together with hot side weight and EMA(5).     

Ultrastructural Variation in Beef M. longissimus dorsi as an Explanation of the Variation in Beef Tenderness

ABSTRACT: The objective of this experiment was to quantify variation in bovine M. longissimus dorsi tenderness and determine the extent such variation is explained by variation in the ultrastructure of muscles after different postmortem treatments. Eight muscles were hot-boned and aged for 2 d at 2 °C (T1) to achieve very contracted actomyosin crossover and tough beef. Eight carcass sides were tenderstretched for 10 h at 10 °C and a further 38 h at 2 °C (T2) to achieve lengthened actomyosin crossover and tender beef. Both T1 and T2 were compared with conventionally hung carcasses, which underwent similar chilling regimes, C1 ( n = 8) and C2 ( n = 8), respectively. Measurements of sarcomere length, pH, Warner Bratzler shear force (WBSF), and sensory tenderness were taken, and transmission electron microscopy images analyzed. Variances of attributes were analyzed on Bartlett's test. Variances of the 4 groups were homogenous for all attributes except for pH after 24 h postmortem (with T1 [0.00] having lower variances than C1 = 0.04, T2 = 0.06, and C2 = 0.05) and WBSF after 2 d aging (with T2 [74.33] having lower variances than T1 = 236.76, C1 = 398.82, and C2 = 856.74). The variation in the tenderness of beef was quantified through ultrastructural variation in bovine muscle, with tenderstretched moderately chilled beef having the least variable tenderness as a result of more uniform overlap between actin and myosin filaments. Variation in the eating quality of beef was not reduced by hot-boning with fast chilling or conventional hanging with fast or moderate chilling. The development of the uniformity within filaments of tenderstretched muscle requires further analysis as residual variation remains.     

Effect of high pressure, temperature, and storage on the color of porcine longissimus dorsi

The color of pork longissimus dorsi high pressure (HP) treated at 200 to 800MPa at 5 and 20°C for 10min was determined to a high degree by pressure level and to a lesser degree by temperature. Severe color changes appeared up to a threshold pressure at 400MPa. HP treatment at 20°C compared to 5°C resulted in meat, which was less red and slightly lighter. Storage at 2°C for 6days had no effect on lightness due to no further protein denaturation, but meat HP treated above 300MPa became significantly less red and more yellow within the first day of storage. Reflectance spectra showed that a short-lived ferrohemochrome myoglobin species was formed during HP treatment at 300 to 800, but transformed into a brown, ferric form of the pigment within the first day of storage. This explains the observed changes in the redness and yellowness after one day of storage.     

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 T₂ relaxation data revealed the presence of three distinct water populations (T₂₀, T₂₁, T₂₂) within the muscle during its conversion to meat. Comparison of T₂ relaxation patterns and contraction data indicates that rigor development affects the attributes of the T₂₁ water population and thereby contributes to myofibrillar water characteristics post mortem, as the T₂₁ water population is believed to reflect inter/intra-myofibrillar water. The volume of the water population believed to reflect extra-cellular water (T₂₂) in the living muscle. Early post mortem T₂₂ 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 T₂₂ 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.     

Effects of nutritional planes and brees on intramuscular-lipid deposition in M. longissimus dorsi of steers

The influences of nutritional planes and breeds on intramuscular-lipid (IML) deposition in M. longissimus dorsi were investigated by comparing the relationships between intramuscular lipid percentages (IMLP) in the muscle and side-carcass weight (SCW), carcass-fat percentage (CFP), and slaughter age (SA). Japanese Black (JB) and Japanese Shorthorn (JS) steers were fattened under two (medium-high and high) nutritional planes, which were different only in JB and when the adjusted IMLPs were compared on the basis of SCW or CFP. Breed effects on IML deposition were investigated by using three pure breeds and four crossbred-steer groups. The means of IMLPs in the muscle adjusted to three criteria were significantly different among breeds, the IMLPs of JB and their backcrosses being higher than those of JS and Charolais crosses. IML deposition in steers was highly dependent on the genetic potential of the breeds or bulls used.     

Effect of high pressure,temperature, and storage on the color of porcine longissimus dorsi

The color of pork longissimus dorsi high pressure (HP) treated at 200 to 800 MPa at 5 and 20 °C for 10 min was determined to a high degree by pressure level and to a lesser degree by temperature. Severe color changes appeared up to a threshold pressure at 400 MPa. HP treatment at 20 °C compared to 5 °C resulted in meat, which was less red and slightly lighter. Storage at 2 °C for 6 days had no effect on lightness due to no further protein denaturation, but meat HP treated above 300 MPa became significantly less red and more yellow within the first day of storage. Reflectance spectra showed that a short-lived ferrohemochrome myoglobin species was formed during HP treatment at 300 to 800, but transformed into a brown, ferric form of the pigment within the first day of storage. This explains the observed changes in the redness and yellowness after one day of storage.     

Tenderising in M. longissimus dorsi of beef, veal, rabbit, lamb and pork

The decrease in toughness of M. longissimus dorsi with storage time at 1°C was effectively described by an exponential decay equation. The average rate constant for beef, veal and rabbit was 0·17 whilst that for lamb was 0·21 and that for pork, 0·40 days(-1). However, the rate constants were not significantly different due to variations both within muscles and between animals. On average, 50% of the tenderising occurred in 2 days for pork and in 4·2 days for beef, veal and rabbit, and 80% in 4·9 and 9·5 days, respectively. At the completion of tenderising, beef and rabbit were the toughest and pork the most tender, whilst the greatest tenderising occurred in beef and lamb.     

High-oxygen packaging atmosphere influences protein oxidation and tenderness of porcine longissimus dorsi during chill storage

The effect of modified atmosphere packaging (70% O(2)/30% CO(2)) and skin packaging (no oxygen) on protein oxidation and texture of longissimus dorsi was investigated during storage for 14 days at 4°C. High oxygen atmosphere resulted in reduced tenderness and juiciness and SDS-PAGE revealed cross-linking of myosin heavy chain through disulfide bonding, and the content of protein thiols was reduced indicating protein oxidation. Myofibril fragmentation was reduced in meat stored in high oxygen atmosphere indicating less proteolysis and/or cross-linking of proteins. Protein carbonyl content was not affected by the packaging atmospheres. This study shows that packaging in modified atmosphere containing a high level of oxygen can result in protein cross-linking and reduced tenderness and juiciness of the meat.     

Quantifying the extent of variation in the eating quality traits of the M. longissimus dorsi and M. semimembranosus of conventionally processed Irish beef

The aim of this investigation was to quantify the scale of variation in the eating quality of two commercial beef muscles, M. longissimus dorsi (LD) and M. semimembranosus (Sm). Both the LD and Sm were excised from steers (n=81) and heifers (n=81) (classification grade O4H, O4L, R4H, R4L) within 48 h postmortem, vacuum packaged and stored at 4?°C until tested for eating quality at 14 days postmortem. Quality measurements analysed were: pH, Warner Bratzler shear force, sensory attributes, sarcomere length, Hunter L a b muscle and subcutaneous fat colour and chemical composition. Extent of variation in many eating quality measurements, with the exception of most sensory attributes and subcutaneous fat colour, depended on gender, classification grade or a combination of both. The LD was more variable than the Sm for most quality attributes and heifers were more variable than steers. No one carcass grade was more variable over all attributes analysed; with different grades causing higher or lower variances within certain attributes. Knowledge of the current scale of variation in the eating quality of beef is required by the meat industry, and is one that requires further research.