Dietary creatine monohydrate affects quality attributes of Duroc but not Landrace pork

Increased creatine content in the muscle may delay post mortem lactate formation and postpone the pH decline, hence potentially improving the water-holding capacity (WHC). Duroc and Landrace pigs were supplemented with 0, 12.5, 25 or 50 g creatine monohydrate (CMH)/d for 5 days prior to slaughter. Meat from Longissimus dorsi (LD) of Duroc pigs had a higher WHC and pH at all times, lower colour determinants; a* (redness), b* (yellowness), L* (lightness) and was more juicy compared to that of Landrace pigs. Furthermore, higher pH_2 h, pH_24 h and decreased colour determinants were observed in carcass sides exposed to a faster cooling profile. Dietary supplementation with CMH increased the body weight gain of both breeds. However, only meat from Duroc pigs had higher pH_30 min and pH_45 min (at 50 g CMH/d) and WHC, but reduced redness (reduced in both breeds) and juiciness when supplemented with CMH compared to non-supplemented controls.     

Evaluation of lean meat quality in pigs using two electronic probes

The Danish Fat-O-Meater grading probe (FOM) and the Fibre Optic Probe (FOP) developed at IFR, Bristol, were evaluated for their potential ability to predict lean meat quality in a sample of 76 pig carcasses showing a wide range of quality in the M. longissimus dorsi. When probings were made after chilling at about 20 h post mortem the correlations between probe value (FOP_u and FOM_u) and reflectance (EEL value), drip loss during storage and subjective assessment score for colour-structure were high (FOP_u and reflectance, r = 0·89; drip loss, r = 0·78; subjective assessment, r = 0·90. FOM_u and reflectance, r = 0·88; drip loss, r = 0·73; subjective assessment r = 0·81). Nevertheless, probe values could not be used to unambiguously group samples into normal, pale, soft, exudative (PSE) or dark, firm, dry (DFD) classes. Correlations between probe values at 45 min post mortem and measures of ultimate meat quality were much lower. Neither probe could potentially differentiate between normal and DFD meat at this time and differentiation between normal and PSE meat was also poorer.     

Spray chilling of lamb carcasses

Two spray-chilling treatments were developed to improve appearance and reduce weight loss during lamb chilling. Rates of cooling and weight loss and meat quality were compared to conventionally chilled carcasses.

The first treatment was an intermittent spray during the first 3 h of chilling. The second consisted of only two sprays at 2 h and 10 h post mortem. The conventional control was a two-stage process, with air at 10°C and 1 m/s up to 10 h post mortem, followed by air at 0°C and 1 m/s for a further 14 h.

Both treatments significantly reduced weight loss at 24 h post mortem compared to conventional, from 2·20% to 0·86% and 1·20%, respectively. During a further 4 days storage, the savings were maintained, with weight losses being 3·97%, 2·97% and 3·19%, respectively.

There were small (<1 h) but significantly reductions in the cooling times of spray-chilled loins and legs, attributed to sustained evaporative cooling of the continually wetted surfaces.

No effects on texture or drip loss and only slight effects on surface lean and fat colour were found. Variation in texture between animals within treatments was far greater than between treatments and could not be accounted for by variations in cooling rates.     

Diverse lamb genotypes-2. Meat pH, colour and tenderness

The effect of genotype on meat ultimate pH, colour and tenderness was studied in 3 experiments involving 436 lambs. The lambs were sired by a selection of Texel (T), Poll Dorset (PD), Border Leicester (BL) and Merino (M) rams, crossed with Border Leicester × Merino (BLM) and Merino (M) ewes giving 6 genotypes (T × BLM, PD × BLM, T × M, PD × M, BLM and M × M). In experiment 1, pH data were obtained for 4 muscles (M. Semimembranosus (SM), M. Biceps femoris M. Semitendinosus and M. Longissimius thoracis et lumborum (LL)) from 198 carcasses representing two sexes (104 cryptorchid males, 94 ewes). There were significant differences for pH between genotypes in both sex groups. BL × M and M × M lambs tended to have higher pH values than the other genotypes.

In experiment 2, meat pH, colour using a chromameter, and tenderness data were obtained for 186 lambs representing two sexes (101 cryptorchid males, 85 ewes). There were few significant differences between genotypes for the various meat quality traits amongst the ewes. The PD × BLM ewes had a significantly lower (p < 0.05) pH than the BL × M ewes for the LL and SM muscles.

The BL × M crypt orchids had a higher LL muscle pH (p < 0.05) than the PD × BLM cryptorchids with other genotypes being intermediate. There were no significant differences between the genotypes for muscle shear force values. Within experiment 2, LL samples were taken from an additional 52 cryptorchid carcasses these being from 3 specific Poll Dorset sires (experiment 3). One of these sires (sire 3) was suspected of carrying a gene for increased muscling. Sire had a significant effect (p < 0.05) on shear force values, cooking loss and L^* colour values, but not a^* or b^* colour values or pH. Sire 3 progeny had significantly (p < 0.001) tougher LL muscles than those from the other 2 sires. Sire 3 also had the lowest L^* values, but was intermediate for cooking loss. There was no significant sire effect on LL area at the same carcass weight, but boneless loins from the progeny of Sire 3 were significantly (p < 0.05) heavier.

In a fourth experiment, meat colour was measured at three sites (LL, diaphragm and M. Obliquus externus abdominis) on 86 cryptorchid carcasses 24 hr post-mortem. There was little association between L^*, a^* and b^* values measured at the different sites.     

Objective assessment of pork quality

Several objective methods for estimating pork quality were studied: internal light scattering (FOP), electrical conductivity (EC), pH, colour, water holding capacity (WHC), soluble proteins (SP), pigment content, intramuscular fat (i.m. fat), and moisture. The measurements were made on the Semimembranosus and Longissimus thoracis at 45 min and 24 h post mortem in some cases and on the Semimembranosus in others.

Most of the measurements are significantly different between normal, PSE and DFD quality categories.

There is a good correlation between pH values in both muscles: pH₄₅SM-pH₄₅LT (r=0.74) and pH₂₄SM-pH₂₄LT (r=0.71). At 45 min the correlation of EC with FOP and pH was r=0.56 and r=0.48 respectively. Lower correlations were found in other parameters.

The results from principal component analysis (PCA) showed that the three first components explained 60.3% of the total variation and the most important variables for the first PC were pH₄₅ and EC₄₅.     

Objective meat quality measurements of ham: A practical classification method on the slaughterline

Meat quality is one of the principal problems in Spanish dry cured ham productuon. At the experimental level, there are well developed objective instrumental measurements which can be made on the slaughterline and then, by applying the correct statistical treatment, these measurements can be used to classify hams with an acceptable degree of accuracy. These treatments, however, are not easy to apply in the industry.

In this work, 312 pork carcasses were tested at three industrial abbatoirs. Ham meat quality was determined by internal light scattering (FOP), electrical conductivity (EC) and pH measurements in Semimembranosus (SM) muscle at 45 min and 24 h post mortem. The results obtained were: 21 (6.7%) DFD; 168 (53.9%) slightly DFD; 104 (33.3%) normal; 11 (3.5%) slightly PSE; and 8 (2.6%) PSE.

A simplified method has been developed for classifying hams into quality categories, by deriving a theoretical quality value (Q) based on a simple statistical treatment of values for FOP, EC and pH. The multiple linear regression coefficient of Q was R² = 0.85 (P<0.001) with respect to the experimental variables.     

Effect of different stunning systems on meat quality of light lamb

The present study was proposed to compare the effect that different types of stunning (TS) had on the quality of refrigerated meat from light lambs of the Spanish Manchega breed at 24 h and 7 days post-mortem. Lambs were electrically stunned (ESL; n = 10), using CO₂ (GSL; n = 10) or slaughtered without previous stunning (USL; n = 10). Measurements on meat quality were carried out by evaluating pH, colour coordinates (L^*, a^*, b^*), water holding capacity (WHC), cooking loss (CL), shear force (SF) and drip loss (DL). At 24 h post-mortem, no significant differences were found in any of the variables studied. However, at 7 days post-mortem, meat quality was affected by the different TS: pH, CL and DL were lower (P < 0.001) in the USL group and GSL obtained the lowest a^* (redness) and b^* (yellowness) values (P < 0.01) than in the other groups. Ageing of meat affected SF in the ESL group (P < 0.01), although there were no significant differences due to treatments at any of the ageing times.     

Colour of normal and high pH beef heated to different temperatures as related to oxygenation

The effects of oxygenation and thermal treatment (internal temperature, T_i: 45, 60, 75°C) on the colour and some colour related physical and biochemical properties of beef longissimus dorsi (LD) muscle, both normal (pH_u5.6) and DFD (pH_u>6.6), were studied. The colour components (L^*, a^*, b^* values) for the raw and heated LD, both before and after oxygenation, were instrumentally and sensorily evaluated. The colour of raw and heated (60°C) DFD beef before and after oxygenation differed significantly from the normal meat and contained more native muscle pigment (TMP). pH also influenced the depth of the oxygenated layer, specific activity of cytochrome c oxidase (SACCO) and the amount of oxygen consumed. An increase in internal temperature was usually accompanied by a lower SACCO and a significant decrease of TMP, as well as a change of all colour parameters. Oxygenation of the raw and heated slices (except at 75°C) of both types of meat led to higher L^*, a^* and b^* values.     

The influence of high post-mortem temperature and differing ultimate pH on the course of rigor and ageing in pig Longissimus dorsi muscle

This study was performed in order to assess the effect of temperature and differing ultimate pH (pH_u, 24 h post mortem) on the development of rigor mortis in pig Longissimus dorsi muscle. The rigor development (isometric tension and shortening) was measured continuously during the first 24 h post mortem, using an apparatus wherein muscle strips were held at constant temperatures of 12 or 35°C. pH_u was manipulated by adrenaline injections preslaughter.

The rates of pH fall, adenosine triphosphate (ATP) and creatine phosphate (CP) breakdown were markedly increased at 35°C compared to 12°C. For both temperatures, no delay phase was observed with regard to the development of shortening. Rigor resulted in higher maximum isometric tension and shortening and in shorter time needed to reach maximum values at 35°C than at 12°C. The results are discussed in connection with pH, ATP and CP data. The extent of ageing from 2 to 4 days post mortem, estimated through myofibrillar length determinations, was higher for 12°C than for 35°C.

pH_u affected significantly most of the traits under study, but its effect depended in some cases upon the rigor temperature. At 12°C, the traits related to the kinetics of rigor development were significantly affected by pH_u, but this was not the case at 35°C. Maximum isometric tension was significantly related to pH_u at 35°C (r = 0·86, P < 0·001), but such a relationship was not found at 12°C. Myofibrillar lengths were significantly affected by pH_u, but in an opposite manner from one temperature to another. A positive relationship was found at 12°C and a negative one at 35°C.

These results illustrate the importance of the interaction between the extent of pH fall and temperature with regard to post-mortem changes in pig muscle.     

Effect of electrical stimulation on post mortem biochemical characteristics and quality of Longissimus dorsi thoracis muscle from buffalo (Bubalus bubalis)

High voltage electrical stimulation (700 V, 1400 V peak, pulses 1 s on/1 s off, 60 Hz, 2 A) on buffalo carcasses resulted in a significantly more rapid pH fall in Longissimus dorsi thoracis muscle when compared to non stimulated controls (p < 0.01), during the first 24 h after slaughter. The IMP/ATP ratio on the same period showed a much more rapid increase for the stimulated muscles (1.07 and 1.16 at times 1 and 2.5 h post mortem vs control values of 0.77 and 0.83, respectively). Sensory and instrumental evaluation of texture of meat cooled by two distinct processes showed that tenderness at 24 h post mortem was higher in the stimulated muscles compared to non-stimulated controls, irrespective of the cooling process adopted. High voltage stimulation significantly decreases cohesiveness, increases myofibril fragmentation; and SDS polyacrylamide gel electrophoresis of the myofibrillar proteins showed a weakening of Troponin T band during 6 days of ageing in non-stimulated control muscles, whereas electrical stimulation accelerated the process of ageing over 3 days. This is the first report on acceleration of conditioning in buffalo muscle and the conditions described here have a high potential for application in meat industry for buffalo slaughter.     

Degradation of ubiquitin in beef during storage

Sarcoplasmic proteins were prepared from the quadriceps femoris muscle immediately after slaughter (2.5 hr) and from stored muscle samples at 10 days post mortem for SDS-PAGE analysis and Western blotting. Characterization with ubiquitin antiserum (Sigma, St. Louis, MO, USA) showed clear and strong recognition of ubiquitin (8.6 kDa) and another minor band (17 kDa) in purified ubiquitin (Sigma, St. Louis, MO, USA). Among the sarcoplasmic proteins prepared, this antiserum also reacted with the bands corresponding to purified ubiquitin (8.6 kDa and 17 kDa) and a small amount of some other higher-molecularmass proteins which were considered to be ubiquitin-protein conjugates. However, at 10 days post mortem, both ubiquitin and the ubiquitin-protein conjugates had almost disappeared, suggesting their degradation by proteinases.     

Changes affecting the Longissimus dorsi, Triceps brachii caput longum and Rectus femoris muscles of young Friesian bulls during meat ageing

The chemical composition and post-mortem changes during 3–14 days of ageing were studied on three muscles (Longissiums dorsi, Triceps brachii caput longum, Rectus femoris) from 13 young Friesian bulls. Chemical composition varied widely between animals (p < 0.001) and muscles (p < 0.001), and did not change during post-mortem storage. Significant changes affecting the non-protein nitrogen and soluble protein nitrogen contents were similar in all three muscles but differed from animal to animal. The increase in non-protein nitrogen can be considered as an indicator of proteolysis. Proteolysis extended to 14 days post mortem. The myofibril fragmentation index increased significantly (p < 0.001) between 3 and 7 days post mortem along the same pattern, irrespective of the muscle and animal. A ceiling was reached at around 7 days post mortem, by which time maximum breakdown of the structure had probably occurred.

No significant relationship was observed between chemical composition, changes in the soluble protein nitrogen, breakdown of structures and carcass characteristics.     

Effect of transport time and ageing on aspects of beef quality

Forty-eight bulls were transported by road in groups of eight for approximately 30 min, 3 or 6 h in two replicates. After slaughter, steaks from the longissimus dorsi thoracis of all transported animals were analysed in terms of pH, water-holding capacity, myoglobin concentration, texture at 7 and 14 days of ageing (compression and Warner-Bratzler analyses) and colour of the same surface of meat cut at 24 h post-mortem and allowed to bloom for 24 h and 7 d (L^*a^*b^*, chroma and hue). The myofibrillar resistance of the meat from animals transported 30 min was significantly greater at 20% compression (P<0.05). The maximum load and a^*b^* and chroma were all lower for meat aged 14 days.     

The effects of electrical stunning and percussive captive bolt stunning on meat quality of cattle processed by Turkish slaughter procedures

The effects of electrical and percussive captive bolt stunning both on initial and up to 14 days post mortem meat quality of Friesian young bulls were studied. The first group (NS; n=10) were slaughtered without stunning under Turkish slaughter procedure (these animals were slaughtered under conditions acceptable to the appropriate ethics committee) in a modern abattoir. In the second group (ES; n=10) animals were electrically stunned. In the third group (PS; n=10) animals were stunned with percussive captive bolt. Meat quality was assessed by examining muscle glycogen concentration, pH and WHC. Also cooking loss, texture parameters and consumer sensory properties were assessed at 24 h, 4, 7 and 14 days post mortem. Meat colour as L^*, a^*, b^*, C^*, h^* values were evaluated at 0, 48 h, 3, 5, 7, 9 and 14 days post mortem. Pre-slaughter handling affected muscle glycogen concentration (P<0.05). Animals in electrical and percussive captive bolt stunned groups had higher muscle glycogen concentrations compared to animals in the non-stunned group (P<0.05). Although pre-slaughter handling did not affect significantly pH_{24 h} and WHC, differences were significant for cooking loss, colour coordinates and texture parameters at some storage times. For all sensory attributes (odour, flavour, tenderness and overall acceptability) at all ageing periods (24 h, 4, 7 and 14 days) the percussive stunned (PS) group was significantly superior to the non-stunned (NS) group. The electrically-stunned (ES) group also tended to be superior to the NS group although not all differences were statistically significant. These results indicate that percussive captive bolt stunning of cattle improved meat quality compared with cattle electrically stunned using head only tongs and those non stunned under approved Turkish slaughter procedure.     

Non-destructive prediction of selected quality attributes of beef by near-infrared reflectance spectroscopy between 750 and 1098 nm

Heifers (n = 70) were slaughtered and hung conventionally in an industrial meat plant. Near infrared (NIR) spectroscopy was studied for its ability to predict selected meat quality attributes, i.e. Warner-Bratzler shear force (WBSF), sensory tenderness, texture, flavour and acceptability. Freshly cut steaks (2.5 cm thick) were taken from the longissimus dorsi (LD) muscle at 1, 2, 7 and 14 days post mortem for NIR analysis. Other samples (also 2.5 cm thick) were taken at 2, 7 and 14 days post mortem, vacuum-packaged in plastic bags and stored at −20 °C for WBSF measurement and sensory analysis. Heifers were slaughtered in two groups; between slaughterings, replacement of the spectrophotometer lamp and lamp assembly was necessitated by a bulb failure. Using principal component regression (PCR), correlation coefficients of 0.82 and 0.73 were obtained for the prediction of WBSF in sample sets 1 and 2, respectively. On merging both sample sets, this value was lowered slightly (r = 0.61). Correlation coefficients obtained for the prediction of tenderness, texture, flavour and acceptability were 0.67, 0.53, 0.51 and 0.46 respectively (set 1); 0.72, 0.71, 0.45 and 0.67 (set 2); 0.53, 0.54, 0.24 and 0.42 (combined sets).     

The influence of goat genotype on the production of Capretto and Chevon carcasses. 2. Meat quality

The effect of five goat genotypes, Boer×Angora (BA), Boer×Saanen (BS), Feral×Feral (FF), Saanen x Angora (SA) and Saanen x Feral (SF) on the meat quality of Capretto and Chevon carcasses obtained from 50 buck kids, was assessed. Genotype had an influence on cooking loss and longissimus thoracis muscle colour coordinates (CIE L^*, a^*, b^* values). BS kids from the Capretto group had paler muscle colour compared to other genotypes; pale muscle colour being required for Capretto carcasses. Total pigment concentration, fat colour, shear force values and sensory scores for flavour, tenderness, juiciness and overall acceptability did not differ significantly between genotypes. Muscle colour became darker and fat colour became more yellow with increasing animal age. Tenderness decreased with animal age as indicated by higher shear force values. Age had no significant influence on cooking loss and sensory scores.     

Effect of stunning conditions on occurence of PSE defects in hams of rn+/RN(-) pigs

Pigs of the same genetic type at the RN and HAL loci, i.e. rn⁺RN⁻/NN were reared in similar conditions of feeding and housing. They were slaughtered in two abattoirs (referred to as A1 and A2) using a mixture of air (30%) and CO₂ (70%), at a rate of 300 pigs per hour per slaughterline. One hundred and thirty-two pigs from 11 farms were slaughtered in A1 using a corusinga restrainer and 127 pigs from 5 farms were slaughtered in A2 with the backloading technique. pH at 40 min, 2.5 h and 24 h after slaughter and colour (L*, a*, b*) at 24 h after slaughter were measured in the semimembranosus muscle. Meat quality of the ham was scored as follows: 1, no PSE-zone; 2, doubtful; 3, PSE-zones in the semimembranosus and sometimes on the internal flexor muscles; 4, PSE-zones in all the flexor muscles. The muscle pH value was higher in A2 than in A1 at 40 min post mortem (P<0.01), but not at 2.5 and 24 h. L* (P<0.001) and b* (P<0.05) were higher in A1 than in A2. There was a remarkable difference in meat quality scores, with 50% of the hams scoring 3 or 4 in A1, vs 13% in A2. Lairage time before slaughter affected (P<0.01) the pH value at 2.5 h (5.69 vs 5.93). The values of pH1 and pH2.5 decreased with increasing the meat quality score. The values of L* and b* increased markedly with the score. The results of the present study indicate that the method of bringing the slaughter pigs to the stunning device affects the frequency and importance of PSE meat in the ham. The automated driving of groups of animals to the stunning machine combined with the backloading of a nacelle, compared to a traditional system driving pigs in single file using electrical goads and a restrainer was beneficial with respect to both meat quality and animal welfare.     

Colour stability of beef from different Spanish native cattle breeds stored under vacuum and modified atmosphere

Beef steaks from five Spanish cattle breeds were submitted to three packaging conditions: (a) 15 days under vacuum, (b) 15 days under modified atmosphere (MAP) (60% O₂, 30% CO₂ and 10% N₂), and (c) 10 days under vacuum plus 5 days more under MAP. CIE L^*a^*b^* coordinates, chroma (C^*) and hue (H^*), relative concentration of myoglobin, oxymyoglobin and metmyoglobin at the meat surface and sensory evaluation of colour were determined 0, 5, 10 and 15 days after packaging. Beef under MAP showed higher lightness (L^*) and hue (H^*) and lower redness (a^*) and chroma (C^*) than beef under vacuum. Colour of beef under MAP was not acceptable after 15 days of storage, due to the high metmyoglobin concentration. Yellowness (b^*) was the indicator of differences due to ageing and differences in colour between breeds were related to L^*, a^* and H^* values. Packaging conditions had a greater effect on beef colour than breed, but breed differences might change with packaging atmosphere. Both packaging and breed are major factors in packaged beef quality.     

Bos indicus-cross feedlot cattle with excitable temperaments have tougher meat and a higher incidence of borderline dark cutters

Temperament ratings based on a numerical scale (chute score) were assessed during weighing and handling of cattle at a feedlot. Breeds studied included Braford, Red Brangus and Simbrah. Cattle were fed to a constant fat thickness of 9 to 13 mm (target = 11 mm) over the 12th rib as determined by periodic ultrasound measurements. Cattle were slaughtered in a commercial slaughter plant and stunned by captive bolt. Temperament rating had a significant effect on the incidence of borderline dark cutters which were downgraded by a USDA grader (P = 0.01). Temperament score also had a significant effect on tenderness (P < 0.001) as evaluated by Warner-Bratzler Shear (WBS) force at day 14 post mortem. The calmest animals which stood still when restrained in a hydraulic squeeze chute had a mean WBS force of 2.86 ± 11 kg and cattle which became highly agitated and struggled violently during restraint averaged 3.63 ± 19 kg. Forty percent of these cattle had WBS force values which were over 3.9 kg which is a threshold value for acceptability in food service establishments. These data show that cattle with the most excitable temperament ratings produce carcasses with tougher meat and a higher incidence of borderline dark cutters than cattle with calm temperament ratings.     

Effects of age and/or weight at slaughter on longissimus dorsi muscle: Biochemical traits and sensory quality in pigs

The effect of increasing either age alone through feed restriction, or both age and weight at slaughter, on the quality of the longissimus dorsi muscle (LM) was investigated. Starting at 83 days of age and 32 kg, 80 pigs were allotted within litter to four experimental groups. All pigs were free of RYR1 mutated gene. Pigs were fed either ad libitum (A100, A130) or restricted 30% (R100, R130) and slaughtered at either 100 kg (A 100, R100) or 130 kg (A130, R130) body weight. Restricting feed intake in order to increase age at the same weight resulted in slower growth, better feed efficiency and increased leanness, whereas increasing age and weight simultaneously elicited slower growth, reduced feed efficiency and fatter carcasses. Intramuscular fat (IMF) and muscle collagen concentration were reduced by restricted feeding. Increase in both age and weight of pigs resulted in lower water, and higher protein and IMF concentrations. Although pigs were free of RYR1 gene, the PSE condition (defined as pH1 ≤ 5.9) developed in 25 carcasses, with a higher incidence in restricted pigs. PSE animals were excluded from the subsequent analysis of meat quality data. Feed restriction resulted in higher drip loss and lower a^* and c^* (saturation index) values. Longer myofibril fragments in muscle of restricted pigs on day 1 post mortem are indicative of slower maturation, while longer fragments on day 4 in heavier pigs, suggest that the extent of post mortem tenderisation could be negatively affected by the elevation of slaughter weight. Feed restriction had no significant effect on meat sensory quality, whereas increase in both age and weight resulted in lower tenderness, chewiness and mouth coating scores. Our results indicate that increasing age at a given body weight, via feed restriction, reduced IMF and collagen concentrations, and the rate of post mortem proteolysis, however, this had no significant impact on pork quality assessed after 4 days of ageing. On the other hand, increasing both age and weight at slaughter could alter pork texture, in spite of elevated IMF concentration.