Postmortem pH Decline Research Articles

Young Blond d’Aquitaine, Angus and Limousin bulls differ in emotional reactivity: Relationships with animal traits, stress reactions at slaughter and post-mortem muscle metabolism

The present study investigated relationships between reactivity during tests, stress reactions at slaughter and animal traits in young Blond d’Aquitaine (BA), Limousin (LI) and Angus (AN) bulls. Behavioural and physiological reactivity of animals was evaluated during rearing using a “Human test” (exposure to human presence and handling) and an “Umbrella test (exposure to a sudden event, the opening of an umbrella). During both tests, bulls were also subjected to social isolation and novelty. Three weeks after the tests, bulls were slaughtered in an experimental abattoir and stress reactions were evaluated using ante-mortem behavioural and physiological measurements, and indicators of post-mortem muscle (Longissimus dorsi: LD and Semitendinosus: ST) metabolism. Animal traits (morphological measures, basal cortisol level and testosterone level) were also recorded. BA reacted more strongly to the tests than AN, while LI had often intermediate levels. In the Human test, BA and LI spent more time vigilant than AN. In the Umbrella test, BA turned their head backwards more often, were further away from the umbrella and expressed more startle responses than AN. At slaughter, AN showed lower LD pH3h and higher LD and ST pH30h after bleeding. Regression analyses showed that up to 25.3 and 39.7% of the variability between individuals in early post-mortem ST and LD pH40min was explained by differences in heart rate minutes before slaughter, and stress reactions during the reactivity tests, respectively, at least partly removing breed effects. Ultimate pH was more strongly related to physical traits, specifically dressing percentage. Models are in accordance with existing knowledge on the biological relationships between these traits and post-mortem metabolism. Overall, results show that the breeds differed in stress reactions during reactivity tests and in post-mortem pH decline. A considerable part of the breed effects on early post-mortem pH decline was explained by certain stress reactions during the reactivity tests or immediately before slaughter (pH40min, pH3h) and physical traits (pH30h).

Altered AMP deaminase activity may extend postmortem glycolysis

Postmortem energy metabolism drives hydrogen accumulation in muscle and results in a fairly constant ultimate pH. Extended glycolysis results in adverse pork quality and may be possible with greater adenonucleotide availability postmortem. We hypothesized that slowing adenonucleotide removal by reducing AMP deaminase activity would extend glycolysis and lower the ultimate pH of muscle. Longissimus muscle samples were incorporated into an in vitro system that mimics postmortem glycolysis with or without pentostatin, an AMP deaminase inhibitor. Pentostatin lowered ultimate pH and increased lactate and glucose 6-phosphate with time. Based on these results and that AMPK γ3R200Q mutated pigs (RN−) produce low ultimate pH pork, we hypothesized AMP deaminase abundance and activity would be lower in RN− muscle than wild-type. RN− muscle contained lower AMP deaminase abundance and activity. These data show that altering adenonucleotide availability postmortem can extend postmortem pH decline and suggest that AMP deaminase activity may, in part, contribute to the low ultimate pH observed in RN− pork.

Meat quality, proximate composition and muscle fatty acid profile of young llamas (Lama glama) supplemented with hay or concentrate during the dry season

Thirty llamas were used to study the effect of a 90day feed supplementation on meat quality, chemical composition and muscle fatty acid profile. Treatments were: GR=llama on native pasture until slaughter; GR+SH=like GR, but with overnight free access to barley/alfalfa hay; and GR+SC=like GR, but with overnight free access to a wheat bran/sorghum grain concentrate. The supplementation had no effect on postmortem pH and temperature decline in the Longissimus lumborum muscle (LLM), cooking losses nor Warner–Bratzler shear force values (P>0.05). Meat from GR+SC llama had higher fat content in LLM (P<0.05) compared to GR and GR+SH llama. Intramuscular fat from GR+SH llama showed higher (P<0.01) proportions of polyunsaturated fatty acids, higher (P<0.05) polyunsaturated fatty acids/saturated fatty acids and desirable fatty acids ratio, lower (P<0.05) omega-6/omega-3 (n−6/n−3) ratio, and higher (P<0.01) conjugated linoleic acid.

AMP-activated protein kinase (AMPK) α2 subunit mediates glycolysis in postmortem skeletal muscle

Postmortem glycolysis is directly linked to the incidences of PSE (pale, soft and exudative) and DFD (dark, firm and dry) meats which cause significant loss to meat industry. AMP-activated protein kinase (AMPK) is a major regulator of postmortem glycolysis. However, there are two isoforms of the AMPKα catalytic subunit, and their roles in glycolysis of postmortem muscle remain unclear. The objective was to identify the isoform specific roles of AMPK in postmortem glycolysis. Wild type, AMPKα1, and AMPKα2 knockout (KO) mice were used in the current study. AMPK in Longissimus muscle was activated shortly after death. AMPKα2 but not AMPKα1 KO abolished the activity of AMPK in postmortem muscle. In addition, AMPKα2 KO reduced postmortem pH decline and the generation of lactate, while AMPKα1 KO had no significant effect. Finally, the glycogen content of skeletal muscle was reduced in AMPKα2 KO but not AMPKα1 KO mice. Data clearly demonstrate that AMPKα2 catalytic subunit mainly regulates postmortem glycolysis in muscle.

High glycolytic potential does not predict low ultimate pH in pork

Extent of postmortem pH decline influences meat quality development. To better understand physiological determination of ultimate pH (pHu), we utilized female and castrated male pigs from a line whose selection index includes differentiated pHu. All genotypes of AMP-activated protein kinase γ3 subunit (AMPKγ3) V199I site were present. The mutant 199II genotype increased pHu, but only in castrated males. Genotype affected glycolytic potential (GP), but GP was weakly associated with pHu. A subset of animals was selected based on low (−Gly) and high (+Gly) residual glycogen content, and compared with AMPKγ3 200Q, which is associated with low pHu. Both +Gly and 200Q muscle contained glycolytic substrate at 24h; however, 200Q muscle generated low pHu and greater lactate compared to +Gly. Additionally,−Gly and +Gly groups exhibited similar pHu despite a large difference in GP. In conclusion, high GP does not appear to directly impact the extent of postmortem pH decline.

Effects of low-voltage electrical stimulation and aging on lamb meat quality

Pouliot, E., Gariépy, C., Thériault, M., Avezard, C., Fortin, J., Simmons, N. J. and Castonguay, F. W. 2012. Effects of low-voltage electrical stimulation and aging on lamb meat quality. Can. J. Anim. Sci. 92: 59–66. The aim of this study was to evaluate the effect of electrical stimulation (ES) and aging time on meat quality of heavy lamb as produced in Quebec. Seventy-six Suffolk-sired crossbred male lambs were slaughtered at a target weight of 50±2 kg. Half of them were electrically stimulated (ES vs. control) at 5–10 min postmortem (21 V; 0.25 A; 60 s). Postmortem pH decline and temperature were monitored. After carcass cutting, longissimus dorsi sections were assigned to aging periods of 1, 3 or 8 d. Temperature decline was the same for both treatments (P=0.749). However, ES carcasses always had a lower pH value than controls during the first 24 h (P&lt;0.001) while the ultimate pH was equivalent (P=0.803). Tenderness, as assessed by either Warner-Bratzler shear force (39 carcasses) or sensory evaluation (35 carcasses) was enhanced by both ES (P&lt;0.001) and aging (P&lt;0.001). At each aging time, tenderness was greater for ES meat. In addition, only 3 d of aging were necessary for ES meat to achieve the tenderness level attained by the controls after 8 d. Sarcomeres were longer (P&lt;0.001) in ES meat than in controls while myofibrillar fragmentation index was not affected by ES treatment (P=0.743). Electrical stimulation also had small effects on color parameters (a*, b* and L*; P&lt;0.01) and flavor (P=0.04). These results provide the first evidence that tenderness of the meat from heavy lambs produced and processed in Quebec could be enhanced by ES, mostly through cold shortening reduction.

Mitochondrial treason: a driver of pH decline rate in post-mortem muscle?

The rate and extent of post-mortem pH decline is an important determinant of meat quality, influencing among other things the incidence of pale, soft, exudative meat. In this perspective I argue two things. First, the accuracy of our modelling of pH decline rates might be improved by incorporation of a muscle mitochondrial content parameter. Second, that high mitochondrial content might help explain the surprisingly rapid pH decline that has sometimes been reported in red, oxidative muscles. The proposed physiological mechanism relates to the fact that mitochondria are known to act as net consumers, rather than producers, of ATP during periods of anoxia – a process called mitochondrial treason. To the best of my knowledge, the implications of the phenomenon of mitochondrial treason have never previously been applied or discussed in a meat science context.

Duration of transport and holding in lairage at constant postprandial delay to slaughter—Effects on fatty liver and breast muscle quality in mule ducks

The present study was designed to evaluate the effect of preslaughter transport (30 vs. 150 min) and holding of mule ducks in lairage in their transport crates (15 vs. 120 min) on the quality of the meat and fatty liver. A total of 120 birds were allocated in a 2 × 2 factorial design with a constant postprandial delay to slaughter (8 h), to avoid the confounding between the effects of the experimental treatments and those of fasting duration. Under such conditions, extending the transport or holding duration did not induce a loss in preslaughter live weight or liver weight. Similarly, breast muscle glycogen stores were not affected by the treatments, nor was the kinetics of postmortem pH decline affected. The mechanical resistance of raw meat obtained by the compression test significantly increased with holding duration. The gross chemical composition of the livers did not differ significantly among the preslaughter treatments. Residual blood in the liver, as indicated by heme pigment concentration, was enhanced with a longer transport, but this effect was more pronounced after the longest holding duration, as shown by a significant interaction. This, however, did not significantly affect the incidence of appearance defects or the commercial grading of the livers. The percentage of fat loss during the cooking of canned livers was significantly reduced when the transport duration was increased. This effect could not be explained on the basis of the current knowledge for determining the technological quality of fatty liver. The identification of biological markers of liver quality is currently underway in our laboratory. Further investigations studying the differential expression of these biological markers according to preslaughter conditions would provide a better understanding of the effect of transport duration on liver processing yield.

Consumption of Oxidized Oil Increases Oxidative Stress in Broilers and Affects the Quality of Breast Meat

A total of 120 4-week-old broiler chickens were allotted to 12 pens and fed one of three diets including control, oxidized diet (5% oxidized oil), or antioxidant-added diet (500 IU vitamin E) for 2 weeks. Blood samples were collected at the end of feeding trial, and breast muscles were sampled immediately after slaughter. Breast meats were also collected 24 h after slaughter and used for meat quality measurements. Oxidative stress in blood, lipid and protein oxidation, and sarcoplasmic reticulum Ca²(+)-ATPase (SERCA) activity of breast muscle were determined. The oxidized diet increased oxidative stress in blood and increased carbonyl content in breast meat compared with the other two dietary treatments (P < 0.05). Lipid oxidation of breast muscles with the antioxidant-supplemented diet was lower than that with the oxidized and control diet groups (P < 0.05). Meat from birds fed the oxidized diet showed higher drip loss after 1 and 3 days of storage and greater 0-1 h post-mortem pH decline (P < 0.05). Significant differences in specific SERCA activity in breast muscles from birds fed control and oxidized diets (P < 0.05) were detected. This suggested that dietary oxidized oil induced oxidative stress in live birds and increased lipid and protein oxidation in breast muscle. Decrease in SERCA activity in breast muscles due to oxidative stress in live animals accelerated post-mortem glycolysis, which sped the pH drop after slaughter and increased drip loss, indicating that oxidation of diet can cause PSE-like (pale, soft, and exudative) conditions in broiler breast muscles.

Influence of early pH decline on calpain activity in porcine muscle

This study investigated the influence of post-mortem pH decline on calpain activity and myofibrillar degradation. From 80 pigs, 30 Longissimus dorsi (LD) muscles were selected on the basis of pH values at 3h post-mortem and classified into groups of 10 as fast, intermediate and slow pH decline. The rate of pH decline early post-mortem differed between the three groups, but the ultimate pH values were similar at 24h. Calpain activity and autolysis from 1 to 72h post-mortem were determined using casein zymography and studied in relation to myofibrillar fragmentation. Colour and drip loss were measured. A faster decrease in pH resulted in reduced level of mu-calpain activity and increased autolysis of the enzyme, and hence an earlier loss of activity due to activation of mu-calpain in muscles with a fast pH decline. Paralleling the mu-calpain activation in muscles with a fast pH decline a higher myofibril fragmentation at 24h post-mortem was observed, which was no longer evident in the later phase of the tenderization process. In conclusion, the rate of early pH decline influenced mu-calpain activity and the rate but not the extent of myofibrillar degradation, suggesting an early effect of proteolysis on myofibril fragmentation that is reduced during ageing due to an earlier exhaustion of mu-calpain activity.

Comparison of fresh beef and camel meat proteolysis during cold storage

The objective of this research was to determine the difference in myofibrillar fragmentation of camel meat and beef during postmortem aging. Semitendinosus muscle was excised at slaughter and muscle pH was measured at 6, 12, 24, 48, and 72 h postmortem. Myofibril fragmentation index was measured on 1, 3, 5, and 7 days postmortem. Also, myofibrils isolated from semitendinosus muscles of camel and cattle at 1, 3, 5 and 7 days postmortem storage were analyzed using sodium dodecyl sulfate (SDS)–polyacrylamide gel electrophoresis. Results showed that the camel semitendinosus muscle had significantly higher myofibril degradation values compared to that in beef which was supported by a difference in troponin-T degradation and appearance of a 30 kDa band. Postmortem pH decline of camel meat was significantly slower than that of beef. This study demonstrated that the semitendinosus protease activity of camel meat was superior to that of beef, which may have been due to the difference in pH decline.

Mechanisms controlling pork quality development: The biochemistry controlling postmortem energy metabolism

Pale, soft and exudative (PSE) pork represents considerable economic losses for the industry due to its limited functionality and undesirable appearance. During the past several decades, exhaustive research covering various aspects of the food chain has established genotyping procedures, recommended handling practices, and quality indicators in order to reduce the incidence of inferior pork quality. Despite these efforts, there is still a relatively high occurrence of PSE pork. Development of pork quality attributes is largely governed by the rate and extent of postmortem pH decline. The combination of high temperature at low pH or abnormally low ultimate pH causes denaturation of sarcoplasmic and myofibrillar proteins, resulting in paler color and reduced water holding capacity. The pH decline is closely related to muscle energy availability and demand at or around slaughter. The postmortem degradation of glycogen through glycogenolysis and glycolysis provides ATP to help meet energy demand and decreases pH by generating lactate and H+. Therefore, the flux of metabolites through glycolysis, the involvement of energy signaling pathways that modulate glycolytic activity, and the inherent metabolism of different fiber types are critical factors influencing pH decline and pork quality. Further, recent work implicates adenosine monophosphate-activated protein kinase (AMPK) as a major energy sensor for the cell, and thus may be involved in the control of postmortem metabolism. The intent of this paper is to review the biochemistry controlling postmortem energy metabolism in pig muscle and explore new information generated using genetic mutations in order to define the fundamental mechanisms controlling the transformation of muscle to meat.

Rate and extent of pH decline affect proteolysis of cytoskeletal proteins and water-holding capacity in pork

The objective of this study was to determine the extent to which early postmortem (PM) pH decline influences proteolysis of the intermediate filament protein desmin, the costameric proteins vinculin and talin and autolysis of μ-calpain in the longissimus muscle (LM) of pigs from two genetic lines. Based on the LM 3 h pH (H = 3 h pH of LM > 6.0; L = 3 h pH of LM pH < 5.7) PM, 10 carcasses per line and pH group were selected. The average 3 h pH within pH group was 6.23 (H) and 5.44 (L). The LM samples were collected 24, 48, 72, and 120 h PM and percent drip loss was measured after 1, 2, and 4 d of storage. Samples collected at 24, 48, 72, and 120 h PM were used to monitor desmin, vinculin, and talin degradation and samples collected at 24 h PM were used to determine the extent of μ-calpain autolysis by immunoblotting. Higher ( P < 0.01) pH values at 45 min, 6 h, and 24 h PM and lower ( P < 0.01) drip losses after 1, 2, and 4 d of storage were recorded in the H-compared to the L-group. Abundance of the 76 kDa μ-calpain autolysis product was greater ( P < 0.01), proteolysis of talin at all measured time points and proteolysis of desmin after 24 and 48 h PM was greater ( P ⩽ 0.03) in the H-group than in the L-group. The current findings indicate activation rate of μ-calpain may be associated with proteolysis of desmin and talin and could play a role in the development of drip loss. The rate of early PM pH decline can partly explain the variation of desmin and talin degradation by affecting the activation of μ-calpain.

Difference in tenderness and pH decline between water buffalo meat and beef during postmortem aging

The objective of this research was to determine the difference in tenderness and some characteristics of water buffalo meat and beef during postmortem aging. Five female crossbred water-buffalo (Philippine Carabao × Bulgarian Murrah) and five female crossbred cattle (Brahman × Philippine Native), were finished on the same diet for 6 months and slaughtered at 30 months of age. The muscle pH was measured at 40 min, 3 h, 7 h, 24 h, and 48 h postmortem. Longissimus thoracis (LT) and semimembranosus (SM) muscles were excised at 2 d postmortem, and shear force was measured at 2, 4, 7, and 14 d postmortem. Glycogen and lactate concentrations were determined from 0, 2, and 4 d LT samples, and myosin heavy chain type of buffalo and cattle LT was determined by ELISA methods. Myofibrillar protein degradation was also observed by SDS–PAGE and Western blotting of fast-type troponin T. Results showed that the buffalo meat had significantly lower shear force values compared to beef for LT and SM muscles, which was supported by a difference in troponin T degradation. Postmortem pH decline of buffalo meat was significantly slower than that of beef, which was confirmed by lactic acid concentrations, but was not explained by glycogen content. In addition, there was no significant difference in the ratio of slow to fast type muscle fibers in buffalo and cattle, indicating that myosin heavy chain type was not responsible for the difference in pH decline and tenderness between the buffalo meat and beef. This study demonstrated that the tenderness of water buffalo meat was superior to that of Brahman beef, which may have been due to the difference in pH decline and the subsequent effect on muscle protease activity.

Impact of RN genotype and ageing time on colour characteristics of the pork muscles longissimus dorsi and semimembranosus

The effect of RN genotype on pH decline, ultimate pH, pigment content, blooming and colour stability during 6 days of display at 5 °C was studied in two pig muscles, M. longissimus dorsi (LD) and M. semimembranosus (SM), and furthermore the effect of anaerobic storage time (2 days vs. 9 days of ageing) on the same parameters was examined. The postmortem pH decline was faster and the ultimate pH lower in LD and SM of the RN − genotype compared with corresponding muscles from the rn + genotype. Pork of the RN − genotype was initially lighter and more red and yellow than pork of the rn + genotype due to a higher degree of blooming, which might be explained by the faster pH decline and/or lower ultimate pH. The level of oxymyoglobin (MbO 2) was decisive for the redness of both muscles during display in air despite a higher presence of metmyoglobin (MetMb). Pork of the RN − genotype was thus redder than that of the rn + genotype throughout display in air despite higher oxidation to MetMb. Ageing for 9 days in chill improved the blooming potential in pork of both genotypes compared with 2 days of ageing, resulting in superior meat colour. However, only in pork from the RN − genotype, the colour was not negatively affected by ageing time upon display in air.

Low birth weight is associated with enlarged muscle fiber area and impaired meat tenderness of the longissimus muscle in pigs1,2

The objective of this study was to determine the relationships between birth-weight-associated modifications in histological or chemical muscle characteristics and meat quality traits in pigs. At 68 d of age, Pietrain x (Large White x Landrace) female littermates were allocated into 2 groups on the basis of low birth weight (LW = 1.05 +/- 0.04 kg; n = 15) or high birth weight (HW = 1.89 +/- 0.02 kg; n = 15). Pigs were reared in individual pens with free access to a standard diet up to slaughter at approximately 112 kg of BW. During the growing-finishing period, LW and HW pigs had a similar daily feed consumption, whereas G:F was lower (P = 0.009) for LW pigs than for HW littermates. At final BW, LW pigs were 12 d older (P < 0.001) than HW littermates. Estimated lean meat content, relative proportions of loin and ham in the carcass, and weights of LM and semitendinosus muscle (SM) were decreased (P < 0.05) in LW pigs compared with HW pigs. Conversely, the LW pigs exhibited a fatter carcass, greater activity levels of fatty acid synthase and malic enzyme in backfat (n = 15 per group), and enlarged subcutaneous adipocytes (n = 8 per group) compared with the HW pigs. Similarly, lipid content was increased by 25% (P = 0.009), and mean adipocyte diameter was 12% greater (P = 0.008) in the SM from LW pigs compared with that from HW pigs, whereas lipid content did not vary in the LM of either group. Mean myofiber cross-sectional areas were 14% greater in the LM (P = 0.045) and the SM (P = 0.062) of LW pigs than of HW pigs. Conversely, the total number of myofibers was less (P = 0.003) in the SM of LW vs. HW pigs. There were no differences between groups for glycolytic potential at slaughter and rate and extent of postmortem pH decline in both muscles, as well as for LM drip losses. A trained sensory test panel judged the roast loin meat to be less tender (P = 0.002) in LW pigs relative to HW pigs. Scores for juiciness, flavor, flouriness, and fibrousness of meat did not differ between groups. Overall, negative but somewhat low correlation coefficients were found between LM tenderness score and ultimate pH (r = -0.36; P = 0.06) and between LM tenderness and mean cross-sectional area of myofibers (r = -0.34; P = 0.07). This study demonstrates a lower tenderness of meat from pigs that had a LW, partly as a result of their enlarged myofibers at market weight.

Influence of harvest processes on pork loin and ham quality1

The purpose of this study was to determine the specific effects of extending the interval between dwell time and the duration of scalding on pork quality attributes. Sixty-four Duroc x Yorkshire pigs were randomly assigned to a 2 x 2 factorial treatment arrangement. Treatments included extending the dwell duration from 5 to 10 min and extending the scald duration from 5 to 8 min. All carcasses entered the cooler 50 min after exsanguination. At exsanguination, blood was collected for three 1-min intervals and then for a final 2-min period. Temperature and pH of the LM and semimembranosus muscle (SM) were measured at 45 min, and at 2, 4, 6, and 24 h postmortem (PM). Hunter L*, a*, and b* values were determined on the LM, SM, and biceps femoris (BF). Purge loss was measured on the SM, BF, and the sirloin end of the loin. Drip loss was measured in duplicate from LM chops after 1 and 5 d of storage. Warner-Bratzler shear force (WBS) measurements were determined on LM chops aged 1, 3, 5, and 7 d PM. Over 99% of the collected blood was obtained during the first 3 min after sticking. Carcasses scalded for 8 min had greater (P < 0.05) semi-membranosus 2 h temperature (28.8 degrees C) than carcasses scalded 5 min (27.3 degrees C). An 8-min scald process resulted in longissimus dorsi chops with lower hue angle and greater WBS values than the 5-min scald process. Increasing dwell time from 5 to 10 min resulted in biceps femoris chops with greater hue angle and loin chops with greater WBS values at 3 d PM. Harvest processes did not significantly affect subjective quality scores, Hunter L* values, purge or drip loss. Lengthening the duration of dwell and scalding may result in a more rapid PM pH decline. Reducing the duration of scalding may lead to increased time for manual removal of hair. Because of differences in facilities, it is recommended that individual facilities monitor dwell and scald durations to determine how to best minimize time of entry into the cooler.

Effects of feeding different levels of conjugated linoleic acid and total oil to pigs on subsequent pork quality and palatability

The objective of the present study was to compare pork quality, composition and palatability of pigs fed different levels of conjugated linoleic acid (CLA) and total oil (TO). A 3 × 2 factorial design was used feeding three levels of CLA (0, 0.25, and 0. 5%) and two levels of TO (2 and 5% made up with canola oil). Thirty-six pigs were allotted per diet and diets were fed from 35 to 115 kg liveweight. TO had no effect on longissimus thoracis (LT) moisture or intramuscular fat contents, but feeding CLA decreased LT moisture (P = 0.04) and increased LT intramuscular fat (P = 0.04). CLA and TO had no effect on LT subjective color, structure or marbling scores. Post-mortem LT temperature was also unaffected by feeding CLA or TO. Pigs fed 0.5% CLA had a marginally higher muscle pH (P = 0.01), a tendency toward lower post-mortem lactate levels (P = 0.06) and had higher glycogen concentrations (P = 0.03) at 30 min post mortem. Feeding CLA may thus offer limited protection against rapid post-mortem pH decline. Adding CLA to the diet increased subcutaneous fat hardness (P = 0.01), which was related to increased saturated (P = 0.01) and reduced monounsaturated fatty acid levels (P = 0.01). Increasing TO had an opposite effect resulting in softer fat with lower saturated and higher mono- and polyunsaturated fatty acid levels (P = 0.01). Supplementing diets with CLA in combination with canola oil did not have any detrimental effect on pork quality, composition or palatability. Feeding CLA does, however, have the potential to improve pork quality by increasing intramuscular fat levels, reducing post-mortem glycogen utilization rates and increasing subcutaneous fat hardness. Key words: Conjugated linoleic acid, canola oil, pork quality, palatability, marbling, fat composition

Injection marination strategies for remediation of pale, exudative broiler breast meat

Pale, soft, and exudative (PSE) breast meat is caused by a rapid postmortem pH decline while carcass temperatures are still warm. The resulting protein denaturation leads to a pale color and a decrease in water-holding capacity, causing excessive yield losses to producers. If some of this protein damage could be prevented or reversed, and water-holding capacity increased, these excessive yield losses could be avoided. Therefore, this study evaluated the use of prerigor injection of broiler breast fillets with sodium phosphates (STPP) and sodium bicarbonate to determine the effects on PSE and normal meat. A total of 200 prerigor broiler breast fillets were collected at 2 h postmortem (PM) at a commercial processing plant and were classified by L* value as pale (L* >54) or normal (L*<51). The fillets were then injected (about or less than 3 h postmortem) with 7% (wt/wt) of 0.54% NaCl + 0.42% PO4 (pH 9), 0.54% NaCl + 0.42% PO4 (pH 11), 0.30 M sodium bicarbonate (pH 12), or left as noninjected controls. The pH and L* value at 2 and 24 h postmortem, marinade uptake, water-holding capacity, and expressible moisture were evaluated. As expected, the pale fillets had lower pH and higher L* values at 2 h postmortem and lower water-holding capacity than the normal fillets. Prerigor marination with NaCl and STPP (pH 9) reduced cook loss in breast fillets. The pH 11 marinade increased 24 h pH of pale fillets compared to that of normal fillets and reduced cook loss. Sodium bicarbonate increased pH at 24 h PM of pale fillets but not to that of normal fillets. These results indicate that marinating prerigor PSE meat with the high-pH phosphate marinade used in this study can improve PSE meat quality.

Effect of L-carnitine and paylean (ractopamine⋅HCl) supplementation on growth performance, carcass characteristics, and postmortem pH decline (2002)

Growth performance, carcass characteristics, and meat quality were evaluated from 126 pigs fed combinations of Paylean and Lcarnitine arranged in a 2 × 3 factorial. Dietary L-carnitine (0, 25, or 50 ppm) and Paylean (0 or 9 g/ton) were fed the last 4 weeks prior to slaughter. Feeding Paylean to pigs improved (P 0.46) ADG, but there was a trend for improved (quadratic, P<0.07) F/G in pigs fed increasing carnitine. A carnitine × Paylean interaction (P<0.05) was observed for dressing percentage and visual firmness, percentage transmission (soluble protein), temperature measured 1.5 h postmortem, and percentage drip loss. Dressing percentage was higher for pigs fed 25 ppm carnitine with no Paylean and lower for pigs fed 25 ppm carnitine with Paylean. Visual firmness scores decreased in pigs fed increasing carnitine and no Paylean but increased when adding carnitine to diets containing Paylean. Soluble protein increased (more soluble protein indicates higher quality muscle) and drip loss decreased when pigs were fed increasing L-carnitine with Paylean. A trend (P<0.07) was observed for pigs fed increasing carnitine to have lower 10 rib and average backfat. Feeding Paylean to pigs increased (P<0.01) percentage lean, L*, and hue angle, and decreased (P<0.02) visual color scores and a*/b* values. Pigs fed Paylean had higher temperature and lower pH measured 3 h postmortem (P<0.01) and tended (P<0.06) to have lower pH measured 6 h postmortem. These results suggest that Paylean improves growth performance when fed to finishing pigs. Carnitine decreased drip loss and improved meat quality when fed to pigs in combination with Paylean.