Higher Ultimate pH Values Research Articles

Characterization of Carcass Color Differences Between Hen (Small Birds) and Meat-Type (Large Birds) Pheasant Lines Associated with Freezing

ObjectivesThe aim of this study was to determine the cause of why hen carcasses turn red on freezing in contrast to meat-type male pheasants.Materials and MethodsHen pheasant carcasses (n = 5) that were visibly red on the outside and larger meat-type pheasants (n = 5, not red) from the same harvest day at a commercial plant were obtained. The frozen carcasses in their original, sealed plastic bag were brought to the University of Wisconsin Meat Science Laboratory and stored in a –25°C freezer prior to being semi-thawed for about 24 h (4°C). Breast muscles (M. pectoralis major) were collected, cut into similar sections (approx. 2.5 cm × 2.5 cm × 1.5 cm), vacuum-packaged in a Nylon/PE vacuum bag, and stored in the –25°C freezer. The frozen samples were ground (9.5 mm plate). Skins were trimmed of excessive fat prior to pulverization in liquid nitrogen. Instrumental color, pH, proximate composition, myoglobin content (myoglobin-based methodology, Mb), and muscle fiber type determination were conducted. All data were analyzed using the PROC MIXED procedure of the SAS statistical analysis software. Dependent variable means were separated (P < 0.05) by pairwise comparisons using the PDIFF option.ResultsHens exhibited greater redness (CIE a*, 4.87) and were darker (CIE L*, 53.33) than the meat-type pheasants (CIE a*, 4.31 and CIE L*, 55.74) on frozen/semi-thawed breast muscles (P < 0.05), whereas no difference was observed in the yellowness (CIE b*) between the different pheasant types (P > 0.05). The highest pH (6.38) and Mb (1.89 mg/g) values were obtained from the skin of the hen carcasses compared to the skin of the meat-type pheasants (pH 6.21, Mb 1.22 mg/g). In addition, the breast muscle of the hens had a higher pH and Mb content. The hen skin exhibited the highest moisture and protein content as well as a lower fat content than the skin from meat-type pheasants. The intermediate fiber (IIA) type was the only type found in the pectoralis major muscles, regardless of the different pheasant types.ConclusionThe results of the current study reveal that hen carcasses had more red pigmentation and exhibited significantly higher pH values, redness, and Mb level than the meat-type pheasants. In this regard, a higher pH might suggest hens were more stress-susceptible which produced the darker red meat. Also, higher ultimate pH values could protect myoglobin and hemoglobin from denaturation. A major part of the darkening might be related to the lower amount of fat within the skin which may have facilitated transparency to the darker, more red breast muscle. Genetics or production practices differences did not appear to alter muscle fiber types. Our findings suggest that the more intense red appearance may be associated with the presence of hemoglobin rather than myoglobin. Future evaluation of the effects of soaking pheasant skin with various pH solutions and scalding variations on the physicochemical properties of collagen may merit investigation.

Implications of white striping and spaghetti meat abnormalities on meat quality and histological features in broilers

During the past few years, there has been an increasing prevalence of broiler breast muscle abnormalities, such as white striping (WS) and wooden breast conditions. More recently, a new muscular abnormality termed as spaghetti meat (SM) because of the altered structural integrity of the Pectoralis major muscle often associated with WS has emerged. Thus, this study aimed at evaluating the effects of WS and SM conditions, occurring alone or combined within the same P. major muscle, on meat quality traits and muscle histology. In two replications, 96 P. major muscles were classified into four classes: normal (N), WS, SM and WS/SM. The whole fillet was used for weight assessment and morphometric measurements, then each sample was cut in order to separate the superficial layer from the deep one and used to evaluate proximate composition, histological features, nuclear magnetic resonance relaxation times, functional properties and both myofibrillar and sarcoplasmic proteins profile. Fillets affected by WS and SM abnormalities exhibited higher weights and increased thickness and length. SM condition was associated with a relevant decrease in protein content coupled with a significant increase in moisture level, whereas fat content was affected only by the simultaneous presence of WS. Histological evaluations revealed that abnormal samples were characterized by several degenerative aspects that almost completely concerned the superficial layer of the fillets. White striped fillets exhibited necrosis and lysis of fibers, fibrosis, lipidosis, loss of cross striation and vacuolar degeneration. Moreover, SM samples were characterized by poor fiber uniformity and a progressive rarefaction of the endo- and peri-mysial connective tissue, whereas WS/SM fillets showed intermediate histological features. Nuclear magnetic resonance relaxation analysis revealed a higher proportion of extra-myofibrillar water in the superficial section of all the abnormal fillets, especially in SM samples, which consequently led to a reduction of the water holding capacity of meat. As for functional properties, abnormal fillets exhibited a lower protein solubility and higher ultimate pH values on both the superficial and deep sections. Although abnormal fillets exhibited higher yellowness values, no relevant effect on meat color was observed. The occurrence of WS and SM abnormalities led to increased carbonylation levels and more intense proteolytic processes. Overall, muscle abnormalities mainly affect the superficial layer of P. major muscle and particularly the occurrence of SM myopathy seems to implicate a more pronounced modification of meat quality traits than the mere presence of WS.

Breast meat quality of chickens with divergent growth rates and its relation to growth curve parameters

Abstract. The effects of the increase of body weight of contemporary broilers during growth on functional meat quality and color characteristics of the chicken breast muscle are controversially debated. Therefore, male chickens (n = 264) of a fast-growing commercial broiler (Ross 308) and two slow-growing experimental meat-type chicken lines were compared at equal age and at similar body weight in order to investigate the effect of growth rate on selected functional breast meat traits and meat color. Additionally, the breast meat characteristics of birds with different growth profiles were compared within lines. When the body weight of commercial broilers reached about 40 to 60 % of their growth potential, they exhibited particularly high ultimate pH values compared with slow-growing lines. The ability of the meat of fast-growing broilers to retain water during cooking was impaired (5 to 16 percentage points increased cooking loss compared to slow-growing lines), which, in contrast to pH, was only marginally affected by body weight and/or age at slaughter. No unfavorable correlations of breast meat quality traits with the growth profile, represented by growth curve parameters derived from the Gompertz–Laird equation, were detected within any of the investigated chicken lines. It is noteworthy that the associations of ultimate pH and cooking loss with maximum growth speed indicate a non-linear relationship. Thus, some of the functional characteristics of breast meat of the fast-growing broiler resembled the white-striping defect described for poultry meat, but the hypothesis that selection on increased growth rates is detrimental for meat quality per se could not be confirmed. In fact, an elevated growth potential in particular, i.e., body weight at maturity, could have some beneficial effects for the water-holding capacity of breast meat, regardless of the genotypic growth rate.

Varying the Temperature of the Liquid Used for High‐Pressure Processing of Prerigor Pork: Effects on Fresh Pork Quality, Myofibrillar Protein Solubility, and Frankfurter Textural Properties

The objective was to evaluate high-pressure processing (HPP) with varying liquid (water) temperatures on pork quality and textural properties of frankfurters. HPP pressurization liquid temperatures were 15.5 °C (HPP Low) and 29.4 °C (HPP Med). Analyses were conducted using paired boneless loins and paired boneless hams. Loins were evaluated for pH, purge loss, objective color, subjective color, firmness; and changes in color after a bloom period. Eight independent batches (2 batches each of HPP Low, paired untreated, HPP Med, and paired untreated) of frankfurters were manufactured from the outside portion of the ham and the knuckle. Both HPP treatments resulted in higher (P < 0.05) ultimate pH and less (P < 0.05) purge loss of the loin. Loin tenderness was not different among either HPP treatment temperature groups when compared to untreated controls except HPP Med chops were more tender (P = 0.02) than untreated controls. Salt-soluble protein extractability of inside ham muscles was lower (P < 0.05) for both HPP treatment levels when compared to untreated controls, but was not different between the 2 HPP treatment levels. Textural properties of frankfurters were not different for either HPP treatment group when compared to its respective untreated control for any parameter except springiness. HPP Low frankfurters had lower (P = 0.10) springiness values than untreated controls. Fracturability of HPP Med samples was lower (P = 0.12) than untreated controls. Overall, HPP caused higher ultimate pH and increased water-holding capacity, but did not affect tenderness of fresh meat or textural properties of frankfurters. HPP can be used on prerigor pork as means to improve fresh pork quality. Loins from HPP-treated pork sides had higher ultimate pH values and less package purge loss. Tenderness values were not affected positively or negatively by HPP treatment. The high pH and water-holding capabilities of treated samples have positive implications for further processing applications. Frankfurter textural properties suggest emulsified products can be made with pressurized pork without sacrifice to the textural profile.

The effects of high pressure processing on pork quality, palatability, and further processed products

The objective was to evaluate high pressure processing (HPP) on postmortem metabolism and pork quality. Six pigs were randomly selected immediately after slaughter. After splitting, one side was randomly designated for HPP of 215 MPa for 15 s with water temperature at 33 °C and the other side (non-pressure treated) served as the control. Chilled sides were fabricated into loins, boneless picnic, boneless Boston butt, and ham. Samples were cut from the loin, inside portion of the ham and cushion ( M. triceps brachii). Pork quality, lipid oxidation, connective tissue solubility, protein functionality, sensory analysis, and processed characteristics of restructured hams were evaluated. HPP partially inhibits postmortem metabolism, indicated by lower muscle lactate levels and higher ultimate pH values. Cook and drip loss were both reduced in HPP treated muscles compared to controls. HPP treated sides were more tender than controls. Collagen content was not different between HPP and control groups.

Effect of ante- and postmortem hide clipping on the microbiological quality and safety and ultimate pH value of beef carcasses in an EC-approved abattoir

Effect of ante- and postmortem hide clipping on the microbiological quality of beef carcasses. Bovine carcasses (362) were tested for indicator micro-organisms and the presence of pathogens. Prior to slaughter, hide cleanliness of each animal was categorized on a scale of 1-5 (clean to dirty). Lowest mean aerobic colony counts (ACC) (log(10) 3.0 CFU cm(-2)) came from carcasses where clipping had been performed in lairage, antemortem. ACC from animals clipped online (log(10) 3.2 CFU cm(-2)) were significantly higher (P < 0.05) than those clipped in lairage, but comparable to those carcasses from Category 1 and 2 animals. There were no significant differences in the detection of pathogens from any of the carcass groups. Ultimate pH values for carcasses from Category 3 and 4 animals showed clipping animals in lairage, as opposed to online, resulted in a small, but significant increase (P < 0.05) in pH value (mean pH 5.66 and 5.59, respectively). Hide clipping does not adversely affect microbiological quality of carcasses, although higher ultimate pH values indicate increases in antemortem stress. Hide clipping carcasses both ante- and postmortem appears to be an effective intervention to minimize transfer of hide microflora to carcasses during slaughtering operations. Online clipping offers advantages for animal welfare and improves safety for operatives.

The influence of seasonal temperatures on meat quality characteristics of hot-boned, m. psoas major and minor, from goats and sheep

Samples of psoas major and minor muscles were randomly collected weekly from 203 (99 hot and 104 cool seasons) Omani goats, 215 (106 hot and 109 cool seasons) Omani sheep, 212 (104 hot and 108 cool seasons) Somali goats, 242 (127 hot and 115 cool seasons) Somali sheep and 211 (110 hot and 101 cool seasons) Australian Merino sheep slaughtered at the Central Slaughterhouse in Oman to investigate the effect of season on meat quality. The collection period was during November 2004–October 2005 and divided into two seasons according to ambient temperatures and relative humidity. These were termed: cool season (average temperature of 21°C and 59% relative humidity and hot season (average temperature of 35°C and 47% relative humidity). Muscles collected during the hot season had significantly (P<0.05) higher ultimate pH values (5.78) than those collected during the cool season (5.65). Myofibrillar fragmentation index was significantly (P<0.05) higher for hot season samples (86.88%) than for cool season samples (85.59%). Expressed juice was significantly (P<0.05) higher for cool season samples (36.84) than for hot season samples (35.74). Goat meat from the hot seasonal group was significantly (P<0.05) darker than the cold season group based on L∗ (37.6 vs. 39.6), a∗ (20.0 vs. 23.3) and b∗ (3.6 vs. 4.2) colour measurements. These results indicated that high ambient temperatures had caused an increase in muscle ultimate pH leading to significant effects on meat quality.

Performances and meat quality of two Italian pig breeds fed diets for commercial hybrids

The effects of specific diets for commercial hybrids were investigated on 6 Casertana and 11 Mora Romagnola, two endangered Italian pig breeds. Average daily gain (ADG), feed conversion index (FCI), dressing percentage and meat and fat quality of animals bred under similar environmental and nutritional conditions were compared to define their optimal slaughtering weight. Animals were fed the same diets assuming that requirements of Mora Romagnola and Casertana did not differ, and changed every 30 kg of weight gain. ADG and FCI were calculated every 15 days. Weight gains, divided into 5 groups based on live weight (LW) of animals (⩽60 kg, 60 < kg ⩽ 90, 90 < kg ⩽ 120, 120 < kg ⩽ 160, >160 kg), showed higher values for Casertana than Mora Romagnola, particularly from 121 to 160 kg LW (687 g/d). Average FCI from 50 to 160 kg LW was similar in both breeds (4.2). After 403 days of trial, animals were slaughtered at about 195 kg LW. Carcass measurements showed that Casertana had higher dressing percentage and lean cuts than Mora Romagnola. Both breeds showed extraordinary high ultimate pH values of M. longissimus thoracis (5.96 and 6.15 for Casertana and Mora Romagnola, respectively) M. semimembranosus (6.37 and 6.30), showing an incomplete post mortem glycolysis. Colour of M. longissimus thoracis did not differ between breeds and was particularly dark. Chemical analysis of Casertana meat showed lower percentage of water and fat; the total amount of fatty acids (SFA, MUFA and PUFA) and the SFA/UFA ratio did not show significant differences between breeds. Results showed that from a growth point of view the optimal slaughtering weight of Casertana and Mora Romagnola should not exceed 160 kg LW. Both breeds had an uncommon reactivity to stress probably due to interactions of genetic, nutritional and management factors.

Effects of dietary α-lipoic acid on glycolysis of postmortem muscle

The effects of dietary α-lipoic acid (α-LA) on the pH value, AMP-activated protein kinase (AMPK) activation, and the activities of glycogen phosphorylase and pyruvate kinase in postmortem muscle were investigated. Eighteen C57BL/6J mice were fed diets containing 0%, 0.5%, and 1.0% α-LA. At the end of 2-week feeding trial, the mice were killed and longissimus muscles were sampled at 0-, 1-, and 24-h postmortem for pH determination and enzyme assay. The results showed that dietary α-LA treatment significantly slowed down the decrease of pH values in postmortem muscle. The ultimate pH values in postmortem muscle of mice receiving 0.5% and 1.0% α-LA treatments were 6.40 and 6.63, respectively, significantly higher than that (6.21) of no α-LA treatment ( p < 0.05). AMPK was activated at the early postmortem stage. Dietary α-LA can suppress the activation of AMPK in postmortem muscle. At 1- and 24-h postmortem, activities of AMPK were much lower in postmortem muscle of mice receiving 0.5% and 1.0% α-LA treatments than that with no α-LA treatment. Between these two dietary α-LA treatments, however, no difference in AMPK activity was observed, indicating that 0.5% dietary α-LA is enough to suppress AMPK in postmortem muscle. Similar to AMPK, glycogen phosphorylase activity was higher in the treatment without dietary α-LA than those with 0.5% and 1.0% dietary α-LA supplements. No difference in the activity of glycogen phosphorylase was observed between the 0.5% and 1.0% dietary α-LA treatments. Dietary α-LA had no significant influence on the activity of pyruvate kinase in postmortem muscle. All these results indicate that AMPK plays a role in glycolysis in postmortem muscle. Dietary α-LA supplementation can suppress the activation of AMPK in postmortem muscle, down-regulate the activity of glycogen phosphorylase, resulting in a higher ultimate pH values in postmortem muscle. Therefore, dietary α-LA supplementation is a potential way to reduce the incidence of pale, soft, exudative (PSE) meat.

Preslaughter handling effects on pork quality and glycolytic potential in two muscles differing in fiber type composition

The objective of the present experiment was to investigate the effects of transportation, lairage, and preslaughter stressor treatment on glycolytic potential and pork quality of the glycolytic longissimus and the oxidative supraspinatus (SSP) or serratus ventralis (SV) muscles. In a 2 x 2 x 2 factorial design, 384 pigs were assigned randomly either to short (50 min) and smooth or long (3 h) and rough transport, long (3 h) or short (< 45 min) lairage, and minimal or high preslaughter stress. Muscle samples were taken from the LM at 135 min and from the SSP at 160 min postmortem for determination of the glycolytic potential and rate of glycolysis. At 23 h postmortem, pork quality was assessed in the LM and the SV. Effects of transport and lairage conditions were similar in both muscle types. Long transport increased (P < 0.01) the glycolytic potential and muscle lactate concentrations compared with short transport. Both long transportation and short lairage decreased (P < 0.01) redness (a* values) and yellowness (b* values) of the LM and SV. In combination with short lairage, long transport decreased (P < 0.05) pork lightness (lower L* values), and electrical conductivity was increased (P < 0.05) after long transport. Several interactions between stress level and muscle type (P < 0.001) were observed. High preslaughter stress decreased (P < 0.001) muscle glycogen in both the LM and SSP, but this decrease was greater in the LM. Lactate concentrations were increased (P < 0.001) only in the LM by high preslaughter stress. Increases in ultimate pH (P < 0.001) and decreases in a* values (P < 0.01) were greatest in the SV, whereas increases in electrical conductivity (P < 0.001) were greatest in the LM. The lack of interactions among transportation, lairage, and muscle type was attributed to the relatively minor differences in stress among treatments. It was concluded that, in glycolytic muscle types such as the LM, the high physical and psychological stress levels associated with stress in the immediate preslaughter period have a greater effect on the water-holding capacity of the meat and may promote PSE development. Conversely, oxidative muscle types tend to have higher ultimate pH values and produce DFD pork in response to intense physical activity and/or high psychological stress levels preslaughter.

The influence of season on quality characteristics of hot-boned beef m. longissimus thoracis

Samples of m. longissimus thoracis (LT) muscle were randomly collected from 70 Omani beef cattle 1 h after slaughter between August 2001 and July 2002 in the Muscat Municipality central slaughterhouse to investigate the effect of seasonal parameters on meat quality during the hot and cool seasons of Oman. The collection period (12 months) was divided into two seasons according to ambient temperatures and relative humidity and termed: Cool Season (November–March with average temperature of 21.2±1.40 °C and 57.9±1.61% relative humidity) and Hot Season (April–October with average temperature of 34.3±1.67 °C and 48.8±7.57% relative humidity). The season had a significant effect on meat quality characteristics of the LT muscle. Muscles collected during the hot season had significantly ( P<0.001) higher ultimate pH values (6.24) with significantly ( P<0.001) lower Warner–Bratzler (WB) shear force values (10.12) than those collected during the cool season (5.54 and 15.58). In these hot-boned samples, there was a linear relationship between ultimate pH and WB shear values. Cooking loss was significantly ( P<0.001) higher for cool season samples (26.01%) than from hot season samples (19.75%). Beef from the hot season group had significantly ( P<0.001) darker meat than that of the cold season group, based on L* (31.45 vs 35.58), a* (18.53 vs 23.19) and b* (4.16 vs 6.40) colour measurements. There was a linear relationship between ultimate pH and cooking loss, L*, a* and b*. These results indicated that heat stress (>30 °C) lead to physiological stress in beef cattle, which in turn increased muscle ultimate pH and influenced related meat quality characteristics.

Effects of preslaughter management on the quality of carcasses from porcine stress syndrome heterozygous market hogs.

The objectives of this study were to determine whether two preslaughter management treatments, rest and mixing, influence the muscle quality of porcine stress syndrome (PSS) heterozygous (Nn) market hogs and to verify the expected quality characteristics of carcasses produced from PSS-normal (NN) and PSS-susceptible (nn) animals. Twenty-nine Nn, 14 NN, and 9 nn market hogs were randomly assigned to preslaughter handling treatments. One-half of the animals in each genotype group received 16 h of rest before slaughter, and the remaining pigs were slaughtered immediately upon arrival at the Iowa State University Meat Laboratory. Within each group, half of the Nn animals were mixed with unfamiliar pigs during transport and lairage. Length, backfat, and loin muscle area (LMA) were not affected by mixing and rest treatment. The carcasses from nn pigs had less fat (P < .05) measured at the 10th rib (off midline) and last lumbar vertebra (midline) and possessed larger LMA than carcasses from NN pigs. Heterozygous pigs were intermediate for most carcass traits. Carcass pH values among heterozygous groups were not significantly different, except that the rested animals had higher ultimate pH values (P < .01) and higher 45-min pH values. Resting had no effect on pH of NN or nn pigs. The 45-min pH values of nn carcasses were lower (P < .01) than those of NN carcasses, but ultimate pH values were similar. Values of unrested Nn animals were between those of NN and nn genotypes but with rest approached values of NN pigs. Loin muscle Minolta-Y and Hunter-L values from unrested Nn animals were higher ( P < .05) than those of rested Nn animals. Mixing did not influence these traits. The longissimus muscle lipid content was not influenced by treatment but differed among genotypes (P < .01). Glycogen levels of rested Nn animals tended to be lower than those of NN animals and approached those of nn pigs. Mixing of Nn animals resulted in higher (P < .05) chewiness scores of cooked loin chops. No significant cooking loss or InstronTM tenderness differences were observed between the PSS-Nn treatment groups. Even though 16 h of rest before slaughter improved the color and water-holding capacity of Nn pigs, effects were small and were much less than those that were due to the PSS gene.

Contribution ofrigorshortening and cold shortening to variability in the texture ofPectoralis majormuscle from commercially‐processed broilers

Abstract 1. Three experiments were conducted to establish the degree to which cold shortening and rigor shortening contribute to variability in the texture of Pectoralis major (PM) muscles of commercially processed broiler carcases chilled at different rates. 2. In the first experiment, free range and standard broiler carcases were air‐chilled under normal commercial conditions at 0°C. Strong negative correlations between pH values 15 min post‐mortem (pH15 min) and sarcomere length indicated that some cold shortening had occurred, while evidence supporting the occurrence of rigor shortening was much weaker. Regardless of the cause of muscle shortening, weak negative correlations between shear force and sarcomere length indicated that shorter sarcomeres were associated with tougher meat. In addition, strong negative correlations between pH values 24 h post‐mortem (pH24 h) and cooking losses suggested that increased juiciness is associated with higher ultimate pH values. 3. In the second experiment, carcase...

Ultimate pH values in reindeer meat with particular regard to animal sex and age, muscle and transport distance

The distribution of ultimate pH values and the frequency of high pH values in three reindeer muscles (AL longissimus, M. biceps femoris and M. triceps brachii) from bulls, cows and calves after short and long distance transport were studied. About 3400 reindeer carcasses from 12 different herds were included in this study. The post mortem processes in reindeer meat seemed to develop very rapidly, and therefore an early measurement (approx. 15h post mortem) of ultimate pH can be done without electrical stimulation of the carcasses. In a comparison between muscles, M. triceps brachii had a higher ultimate pH value than M. longissimus and M. biceps femoris. Meat from reindeer calves had higher ultimate pH values than meat from adult animals, indicating that calves are more susceptible to stress than adult animals and hence deplete their energy stores more readily. Road transport by lorry did not cause any increase in ultimate pH values in bulls and calves. Reindeer cows, however, did have an increase in ultimate pH, while more borderline cases of DFD (5.80&amp;lt;pH&amp;lt;6.20) were observed when cows were transported over more than 500 km. The physical condition and energy balance of the animals before transport were suggested to determine their ability to tolerate transport stress.

Electrical Stimulation and 48 Hours Aging of Bull and Steer Carcasses

ABSTRACTBull (n = 30) and steer (n = 30) carcasses were measured for meat quality in the longissimus muscle after 48 hr on electrically stimulated (ES) sides or after 6 days on their unstimulated counterparts. Electrical stimulation and 48 hr aging had the same tenderizing effect as a 6 day aging period on both bulls and steers. Compared to meat from steers, that from bulls was tougher and had higher ultimate pH values and collagen contents. On an overall quality basis however, ES meat aged for 48 hrs was equivalent to nonstimulated meat aged for 6 days.

Cattle handling at abattoirs. II. The effects of rest in transit and duration of the resting period before slaughter on carcass weight, bruising and muscle properties

In two experiments, we examined the effects on carcass weight, bruising and muscle properties of resting cattle during a long rail journey and for various periods at an abattoir before slaughter. In experiment 1, 170 Shorthorn bullocks (mean liveweight 556 kg) were transported 90 km by road and 650 km by rail, with three groups (34 per group) going directly to an abattoir and two groups resting once for one day midway during the rail journey. The resting periods at this abattoir were 2, 3, 4,2 and 3 days, respectively. In experiment 2, 240 cows (mean liveweight 424 kg) were transported 190 km by road and 965 km by rail, with three groups (40 per group) going directly to another abattoir, two groups resting once for one day and one group twice for one day during the rail journey. The resting periods at this second abattoir were 1.5, 2.5, 3.5, 1, 2 and 1 day(s), respectively. All cattle had access to feed and water during resting periods and to water until slaughter. As the total resting period after the start of the rail journey and before slaughter increased, the percentage of carcasses with high pH values for M. longissimus dorsi decreased (P &lt; 0.05); correlations for pH 24 h post mortem and ultimate pH were -0.97 and -0.71, respectively. The correlation between total resting period and shear values (initial yield and peak force) were c. -0.5. A resting period during the rail journey was as effective as that time spent resting at the abattoir. Cattle transported directly by rail to the abattoir had a greater bruise score than those rested en route, although cows rested twice were as bruised as those going direct. Treatment had no significant effect on carcass weight or systematic effect on cooking loss. Very high incidences of high ultimate pH values in one group of bullocks (29.4%) and another of cows (20.5%) occurred following periods of stress when slaughtering was interrupted by unavoidable stoppages.

Cross-sectional studies of ultimate pH in lambs.

The ultimate pH of the longissimus muscle was measured in 1536 lambs routinely slaughtered at a meat export works in the southern part of the North Island during the 1981/82 season. The mean ultimate pH of ail samples was 5.60, and 7.2 percent of the carcases had values equal to, or above, 6.00 whereas 85.3 percent of carcases had values below 5.80 which is considered to be optimal. The ultimate pH values of samples from lambs slaughtered during the summer period was significantly higher than those obtained during three other seasonal sampling periods and Perendale lambs had significantly higher ultimate pH values as compared to Iambs of other breeds. There was no statistical association between distance travelled before slaughter and the ultimate pH of carcases but there was a highly significant direct correlation between holding periods of lambs in the stockyards and ultimate pH of their meat. There was also a highly significant inverse correlation between fleece weight and ultimate pH and it is suggested that both this effect and the seasonal pattern of ultimate pH values indirectly reflect the major role that nutrition may play in the development of high ultimate pH meat in lambs. It is further suggested that washing of animals prior to slaughter and the length of subsequent resting periods are important factors in relation to the development of undesirably high ultimate pH values.

Tenderness of exercise-stressed lambs

Abstract Rested and exercise-stressed lambs were slaughtered and dressed. The carcasses from half of the rested and exercise-stressed groups were electrically stimulated 30 min after slaughter and all carcasses were moved into a freezer 2 h postmortem. Tenderness was assessed on legs and loins roasted from the frozen state. The rested lambs were extremely tough unless the carcasses had been electrically stimulated but, if stimulated, were moderately tender. The exercise-stressed Iambs went into rigor rapidly with high ultimate pH values in leg and loin muscles. The legs and loins of exercise-stressed, non-stimulated animals were tender but the legs were toughened by stimulation. It is likely that this toughening is the result of rigor occurring during or soon after stimulation so that no relaxation of muscles can occur when the stimulating current is switched off.