The effects of ascorbic acid, taurine, carnosine and rosemary powder on colour and lipid stability of beef patties packaged in modified atmosphere

This research was aimed at evaluating the inhibition of oxidative changes of beef patties packaged in modified atmosphere (70% O₂+20% CO₂+10% N₂) by natural antioxidants: ascorbic acid (500 ppm), taurine (50 mM), carnosine (50 mM), rosemary powder (1000 ppm) and their combinations with the first. Beef patties stored at 2±1°C for 20 days were evaluated for colour (L*, a*, b*, C* and H*), TBARS, metmyoglobin formation (% of total myoglobin), psychrotrophic microbial counts and sensory odour and discolouration. Rosemary, either alone or with ascorbic acid, was highly effective in inhibiting both metmyoglobin formation and lipid oxidation; sensory analysis was in agreement with these results. Ascorbic acid, ascorbic acid+taurine and ascorbic acid+carnosine treatments showed a limited inhibitory effect of myoglobin oxidation, while carnosine and carnosine+ascorbic acid were effective in inhibiting lipid oxidation. Taurine alone failed to exert any antioxidant effect. Principal components analysis confirmed these results.     

Development of a Model System to Mimic Beef Bone Discoloration

ABSTRACT: Some current practices used in the meat industry (blast chilling, enhancement, modified atmosphere packaging [MAP]) appear to result in darkening of the bone in fresh meat. The objective of this study was to develop a model system that could be used to evaluate intervention strategies to prevent this discoloration. Beef rib bones were removed from carcasses, split along the transverse plane from the proximal to the distal end of the rib, and then frozen (−20 °C) or held at 4 °C for 24 h. Half were exposed to a phosphate/salt enhancement solution while half served as the control. Samples were packaged in air or modified atmosphere packaged (MAP: 80% O₂/20% CO₂) and displayed in a retail case (4 °C, 24 h). Visual discoloration occurred during the 1st 10 h of display. More darkening (brown, green/black) was observed in previously frozen samples, whereas samples held at refrigeration temperature were redder. CIE L *, a *, and b * values determined after 24 h indicated that samples held in refrigeration before packaging were lighter and redder. After 24 h at 4 °C, previously frozen samples contained more methemoglobin/g protein in the bone marrow than did bone samples that had never been frozen.     

Effect of modified atmospheres on microbiological, color and sensory properties of refrigerated pork

Pork loin samples were stored (4 °C) in nylon polyethylene plastic bags using different modified atmospheres packaging (MAP): vacuum, 100% CO₂ 99% CO₂ + 1% CO, 100% O₂ or 100% CO followed by vacuum. Throughout the storage period Pseudomonas growth was limited in loins packaged in all MAPs evaluated, except for 100% O₂. Psychrotrophs reached 10⁷ CFU g⁻¹ after 20 days of storage except for the loin samples in 100% O₂ MAP that present count above 10⁸ CFU g⁻¹. The 1% CO/99% CO₂ atmosphere was best for preserving the desirable pork loin color and the L* and a* values remained similar to the fresh meat values using this MAP. Pork loins in 99% CO₂/1% CO MAP obtained the highest consumer acceptance scores after 24 h of storage. These samples and those treated with CO and then vacuum packaged received the greatest acceptance scores even after 20 days of storage.     

Effect of Antioxidant Solubility and Concentration on Discoloration of Beef Vertebrae Marrow during Display

ABSTRACT:  Two experiments were conducted to assess the role of aqueous- and lipid-based antioxidants in preventing or limiting beef lumbar vertebrae marrow discoloration. In experiment 1, lumbar vertebrae ( n = 8 replications) were treated with either 0%, 1.5%, or 2.5% (wt/wt) of ascorbic acid or ascorbate-6-palmitate. Vertebrae color (visual and L*a*b*) was evaluated during 5 d of display at 1 °C in high-oxygen modified atmosphere packaging (MAP; 80% oxygen/20% carbon dioxide). Ascorbic acid treatments minimized ( P < 0.05) discoloration compared with ascorbate-6-palmitate. In experiment 2, lumbar vertebrae ( n = 8 replications) were treated with 0, 0.06 M, or 0.10 M ascorbic acid and ascorbate-6-palmitate, packaged in high-oxygen MAP, and displayed for 5 d (1 °C). During display, vertebrae treated with ascorbic acid had a redder color ( P < 0.05) than those treated with ascorbate-6-palmitate, and both treatments were redder ( P < 0.05) than untreated controls. To better understand the mechanism of beef bone marrow discoloration, future work might address the hydrophobic antioxidants' lack of effectiveness and the potential localization of components responsible for bone discoloration within the aqueous phase of erythropoietic marrow.     

Growth of Listeria monocytogenes on vacuum-packaged horsemeat for human consumption

In order to investigate the likelihood of Listeria monocytogenes (serotype 4b, ATCC 19115) growth on vacuum-packaged horsemeat at refrigeration temperature, fourteen horsemeat surface/volume homogeneous 150 g weight pieces were superficially inoculated with serotype 4b L. monocytogenes and vacuum packaged. The samples were stored at 4 ± 1 °C. Two pieces (one for pH determination and one for L. monocytogenes counts) were examined at days 0, 7, 14, 21, 28, 35 and 42. Surface pH did not show significant variations during the experiment. The average L. monocytogenes initial contamination level was 1.77log₁₀ CFU/g. A lag phase of 7 days was recorded. The exponential growth rate between day 7 to day 35 was 0.125log₁₀ CFU/day, corresponding to 3.51log₁₀ CFU/g in 28 days. At the end of the experiment the mean L. monocytogenes log₁₀ CFU/g was 5.78.     

Bacteriological quality assurance (BQA) of mechanically deboned meat (MDM)

Adequacy of bacteriological quality assurance during the commercial production of mechanically deboned meat (MDM) was assessed. Lax standards of hygiene during production were observed, resulting in high numbers of Staphylococcus aureus, viz. 10⁴ to 10⁵ cfu g⁻¹, and severe contamination with Enterobacteriaceae: 10⁵ to 10⁶ cfu g⁻¹. These data indicate that measures of hygiene observed during boning of carcasses and during collection, storage and transport of bones or poultry parts should be markedly tightened, while conditions of refrigerated storage of raw materials and MDM should be improved. Use of bones of poor sensory quality (discoloration, abnormal smell) generally resulted in MDM of inferior bacteriological quality.

Phage typing, biotyping and assessment of enterotoxin production was carried out with 136 St. aureus cultures, isolates from mechanically deboned pork produced at one plant. Fifty-five per cent of the isolates was not typable, 28% was typable with human phages, 8% with bovine phages. The majority of the strains could not be explicitly assigned to any Meyer and/or Hájek and Mar álek types. Applying the simplified system of Devriese to eighteen strains isolated in our investigation, ten were found to belong to the poultry ecovar, one to the bovine ecovar, while seven strains were non-host specific. None of the isolates produced enterotoxins A–E.

Microbiological inspection of end products is recommended as part of an integrated quality assurance system. The following reference values for the final product (maximal colony counts to be expected under GMP conditions expressed as 95th percentile) were calculated: Pig MDM: log₁₀ mesophilic colony count 6·8 and log₁₀ cfu mesophilic Enterobacteriaceae g⁻¹ 4·8; Poultry MDM: log₁₀ mesophilic colony count 6·6 and log₁₀ cfu mesophilic Enterobacteriaceae g⁻¹ 4·7.     

Effect of carbon monoxide in modified atmosphere packaging, storage time and endpoint cooking temperature on the internal color of enhanced pork

The objective of this research was to evaluate the effects of gas atmosphere, refrigerated storage time, and endpoint temperature on internal cooked color of injection-enhanced pork chops. Enhanced chops were packaged in 0.36% CO/20.34% CO₂ (CO-MAP), 80% O₂/20% CO₂ (HO-MAP), or PVC-overwrapped (PVC-OW; controls), stored at 4 °C for 0, 12, 19 or 26 days, displayed for 2 days then cooked to six endpoint temperatures (54, 60, 63, 71, 77, and 82 °C). L^*, a^*, and b^* values, hue angle and chroma were determined on the internal cut surface of cooked chops. Chops packaged in CO-MAP had the highest a^* values; a^* value began increasing on day 14. The lowest hue angles occurred in chops cooked to lower endpoint temperatures. Chops in CO-MAP had lower hue angles and higher chroma than those in HO-MAP and PVC-OW. Above 71 °C, hue angle and chroma increased. Overall, CO-MAP packaged chops stored for longer time periods then cooked to lower endpoint temperatures appeared reddest. HO-MAP packaged chops were less red, did not change over time, and appeared more well done at lower endpoint temperatures than those in other gas atmospheres. CO-MAP packaged chops retained redness even after cooking at 82 °C.     

Meat quality characteristics of springbok (Antidorcas marsupialis). 1: Physical meat attributes as influenced by age, gender and production region

Springbok is the most extensively cropped game species in South Africa. The effects of age (adult, sub-adult, lamb), gender and production region on the physical attributes (pH₂₄, cooking and drip loss, Warner Bratzler shear force and colour) were determined using samples of the M. longissimus dorsi (LD) muscles of 166 springbok. Stressed animals had a higher (P < 0.05) pH₂₄ (6.3 ± 0.07), as observed in the meat originating from the Caledon region. This meat had lower (P < 0.05) cooking loss (27.2 ± 0.62%) and drip loss (1.8 ± 0.08%) values in comparison to meat originating from the other regions. Inverse correlations were noted between pH₂₄ and drip loss (r = −0.26, P < 0.01) and cooking loss (r = −0.42, P < 0.001). Shear force values (kg/1.27 cm diameter) correlated positively (r = 0.25, P < 0.01) with pH₂₄. Age-related effects on tenderness were small in comparison with pH₂₄ effects. CIELab colorimetric values were typical of game meat and venison (L^* < 40, high a^* and low b^* values). It was noted that pH₂₄ correlated negatively (r = −0.51, P < 0.001) and positively (r = 0.33, P < 0.001) with the hue-angle and the chroma value of colour, respectively. Springbok originating from Caledon had a significantly (P < 0.05) higher a^* value, indicating meat to be more red with higher colour saturation.     

The effects of residual oxygen concentration and temperature on the degradation of the colour of beef packaged under oxygen-depleted atmospheres

Samples of beef longissimus dorsi (LD), approximately 5 × 5 × 1 cm, were packaged in pairs under 10 litre volumes of N₂ or CO₂ containing O₂ at concentrations between 100 and 1000 ppm. The packaged samples were stored at temperatures of 5, 1, 0 or −1·5°C, for times between 4 and 48 h. Samples of beef psoas major (PM) were packaged under N₂ or CO₂ containing O₂ at between 100 and 600 ppm, and stored at −1·5°C for 24 or 48 h. After storage, each sample was assessed for colour deterioration and discoloration, and for the fraction of metmyoglobin in the surface pigment.

The results obtained with N₂ and CO₂ atmospheres were similar. The colours of all LD samples had deteriorated after 4 h storage at 5 or 1°C, although the degree of deterioration increased with increasing O₂ concentration. All LD samples stored for 12 h at 5 or 1°C were extensively discoloured, with metmyoglobin fractions generally exceeding 60%, but those stored at −1·5°C for 48 h or less, under O₂ concentrations ≤ 400 ppm had undergraded colours. The colours of some LD samples stored at −1·5°C under about 600 ppm of O₂ were also undergraded, but the colours of samples stored under 800 or 1000 ppm had deteriorated by 24 h. The colours of LD samples stored at 0°C under > 200 ppm had deteriorated after 24 h storage, and the colours of samples stored under 100 ppm O₂ had deteriorated after 48 h storage. All PM samples were wholly discoloured after storage at −1·5°C. Evidently, the colour of beef muscle of high colour stability is resistant to degradation by atmospheres containing < 600 ppm of O₂ when the meat is stored at sub-zero temperatures, but not when the storage temperature is at or above 0°C. Beef muscle of low colour stability, such as the PM, will discolour at all low concentrations of O₂ irrespective of the storage temperature.     

A novel use of modified atmospheres: Storage insect population control

The research described here aimed to establish the feasibility of using modified atmospheres (MA) to protect commodities throughout their storage life by using oxygen (O₂) levels that disrupt the life cycles of the target beetle species. Rather than achieving complete mortality of all stages, the aim was to identify more easily obtainable MAs that would kill the most susceptible stage and prevent population growth. Simulated burner gas and nitrogen (N₂) atmospheres with O₂ contents between 3% and 6%, were tested, along with a N₂-based MA with elevated carbon dioxide (CO₂) (10–20%).

Laboratory tests were carried out on five species of stored-product beetles, Cryptolestes ferrugineus, Oryzaephilus surinamensis, Sitophilus granarius, S. oryzae and Tribolium castaneum. After exposure to the MAs for 28 d an assessment was made of the mortality of adults, the number of adults from progeny produced under the MAs and, for the simulated burner gas, the number of adults from progeny produced in a 28-d period after exposure to the MA. The tests were carried out at 20 and 25 °C with 75% and 85% r.h. at each temperature.

The O₂ content preventing population growth varied with species and temperature. For simulated burner gas or N₂ it was about 4% for O. surinamensis, S. granarius and S. oryzae, and about 3% for C. ferrugineus and T. castaneum at 25 °C. At 20 °C it was about 3% for all species tested. When CO₂ was increased to 10% or 20%, reducing O₂ to 5% was sufficient to eliminate emergence of S. granarius at 20°C, but a few individuals emerged at 25 °C. For C. ferrugineus there was a 95% reduction with 5% O₂ plus 20% CO₂ at 20 °C, but not at 25 °C.     

Dietary vitamin E supplementation and discoloration of pork bone and muscle following modified atmosphere packaging

The effects of modified atmosphere (80% O₂: 20% CO₂) and illumination on the discoloration rate of pork bone (lumbar vertebrae) and muscle (longissimus lumborum), and on muscle lipid stability were studied in vitamin E-supplemented and unsupplemented pigs. Bone-in pork chops were placed in 80% O₂: 20% CO₂ at 0 °C and stored for 5 days in the dark. The chops were then displayed under (a) fluorescent light in air or modified atmosphere or (b) in air with or without illumination. Lipid oxidation was increased by the modified atmosphere packaging but this detrimental effect was offset by vitamin E supplementation. Higher supplementation levels (198 and 207mg/kg) improved bone color stability regardless of the packaging atmosphere or the lighting conditions. Although vitamin E supplementation improved muscle color stability during display in air or modified atmosphere, the benefit of supplementation on muscle color was detectable only for illuminated storage.     

Significance of storage time on degree of blooming and colour stability of pork loin from different crossbreeds

The objective was to investigate the effect of ageing time (1 day vs. 8 days postmortem) and sire breed used in the crossbreed (Duroc sired vs. Landrace sired pigs) on blooming ability and colour stability of pork M. longissimus dorsi (LD). The colour was measured during blooming (0, 10, 30, 60, 90 min and 24 h after cutting) and during subsequent display (1, 2, 3 and 6 days) at 3 °C. The contents of deoxymyoglobin (Mb), oxymyoglobin (MbO₂) and metmyoglobin (MetMb) were calculated. Ageing improved the blooming of LD from both crossbreeds with increased content of MbO₂ and decreased content of Mb, resulting in increased lightness, redness and yellowness. Ageing had smaller effect on colour stability with slightly lower MetMb in aged meat. Crossbreed affected both blooming and colour stability. LD from Landrace-sired pigs bloomed more than LD from Duroc-sired pigs, but more MetMb was formed during subsequent storage, although at a low level in both crossbreeds. The present data show superior colour characteristics of fresh pork aged for 8 days.     

Conventional freezing plus high pressure-low temperature treatment: Physical properties, microbial quality and storage stability of beef meat

Meat high-hydrostatic pressure treatment causes severe decolouration, preventing its commercialisation due to consumer rejection. Novel procedures involving product freezing plus low-temperature pressure processing are here investigated. Room temperature (20 °C) pressurisation (650 MPa/10 min) and air blast freezing (−30 °C) are compared to air blast freezing plus high pressure at subzero temperature (−35 °C) in terms of drip loss, expressible moisture, shear force, colour, microbial quality and storage stability of fresh and salt-added beef samples (Longissimus dorsi muscle). The latter treatment induced solid water transitions among ice phases. Fresh beef high pressure treatment (650 MPa/20 °C/10 min) increased significantly expressible moisture while it decreased in pressurised (650 MPa/−35 °C/10 min) frozen beef. Salt addition reduced high pressure-induced water loss. Treatments studied did not change fresh or salt-added samples shear force. Frozen beef pressurised at low temperature showed L, a and b values after thawing close to fresh samples. However, these samples in frozen state, presented chromatic parameters similar to unfrozen beef pressurised at room temperature. Apparently, freezing protects meat against pressure colour deterioration, fresh colour being recovered after thawing. High pressure processing (20 °C or −35 °C) was very effective reducing aerobic total (2-log₁₀ cycles) and lactic acid bacteria counts (2.4-log₁₀ cycles), in fresh and salt-added samples. Frozen + pressurised beef stored at −18 °C during 45 days recovered its original colour after thawing, similarly to just-treated samples while their counts remain below detection limits during storage.     

Inactivation of polyphenol oxidases in cloudy apple juice exposed to supercritical carbon dioxide

The inactivation of polyphenol oxidase (PPO) in cloudy apple juice exposed to supercritical carbon dioxide (SCCO₂) treatment was investigated. Higher pressure, higher temperature, and longer treatment time caused more inactivation of PPO. The maximum reduction of PPO activity reached more than 60% at 30 MPa and 55 °C for 60 min. The experimental data followed first-order reaction kinetics; the kinetic rate constant k and the decimal reduction time D were closely related to the pressure and temperature of SCCO₂ treatment. Higher pressures or higher temperatures resulted in lower D values (higher k), the D value of PPO was minimized to 145 min treated by the combination of 30 MPa and 55 °C. Activation energy of 18.00 kJ /mol, was significantly reduced by SCCO₂ treatment at 30 MPa, as compared to activation energy of 72.0 kJ/mol for identical treatment at atmospheric pressure. Pressure and temperature sensitivity of kinetic parameters were studied. Z_P at 55 °C was 66.7 MPa and Z_T at 30 MPa was 108 °C.     

Thermal inactivation of lectins (PHA) isolated from Phaseolus vulgaris

The influence of the thermal process on the loss of ability to bind a carbohydrate target was studied on lectins (PHA) purified from Phaseolus vulgaris seeds. Thermal inactivation of aqueous solutions of pure PHA occurred according to a biphasic first-order mechanism, the thermodynamic parameters, at pH 7·3, being as follows: ΔH*₁ = ΔH*₂ = 86·2 kcal mole⁻¹, ΔS*₁ = − 54·04 cal deg⁻¹ and ΔS*₂ = − 56·71 cal deg⁻¹. The first-order rate constants appeared to be dependent on pH (minimal around 7) and divalent cations. All different subunits constituting the whole PHA were inactivated at the same rate. The biphasic nature of this process is independent of the presence of 10 m Ca⁺⁺ or Mg⁺⁺ and appeared to indicate a discrete aggregation of PHA molecules.     

Beef shelf life in low O(2) and high CO(2) atmospheres containing different low CO concentrations

The use of atmospheres with low concentrations of CO (0.1 to 1%), in combination with O₂ (24%), high CO₂ (50%) and N₂ (25 to 25.9%), for preserving chilled beef steaks was investigated. The atmosphere used as reference contained 70% O₂+20% CO₂+10% N₂. Bacterial counts showed that all atmospheres containing CO greatly reduced total aerobic population numbers, including Brochothrix thermosphacta. Lactic acid bacteria, however, were not affected. CO concentrations of 0.5–0.75% were able to extend shelf life by 5–10 days at 1±1°C, as demonstrated by delayed metmyoglobin formation (less than 40% of total myoglobin after 29 days of storage), stabilisation of red colour (no change of CIE a* and hue angle after 23 days), maintenance of fresh meat odour (no variation of sensory score after 24 days) and significant (P<0.01) slowing of oxidative reactions (TBARS).     

The display life of retail-packaged beef steaks after their storage in master packs under various atmospheres

Beef strip loins were divided into four portions. One portion of each loin was vacuum-packaged and then stored at −1·5°C. The other portions were each divided into three steaks, which were retail-packaged. The retail packs were master-packaged under atmospheres of N₂, CO₂, or O₂ + CO₂ (2 : 1, v/v) and then stored at 2°C. Product was assessed after storage times of up to 60 days. At each assessment, a vacuum pack and a master pack of each type, each containing product from the same loin, were withdrawn from storage. The vacuum-packaged product was cut into three steaks, which were retail-packaged. The newly prepared retail packs and those from the master packs were displayed in a retail cabinet, at air temperatures that averaged between 3 and 5·7°C, and were assessed twice daily until the product was judged to be unacceptable. When first assessed, steaks cut from vacuum-packaged product were generally considered desirable, with little metmyoglobin in the surface pigment, although the edges of same steaks were discoloured. Steaks stored under N₂ or CO₂ for 4 days or less were only slightly desirable at best, with metmyoglobin forming relatively large fractions of the surface pigment. However, after storage under N₂ or CO₂ for 6 days or more, metmyoglobin fractions were low, and the steaks bloomed to a desirable red colour. Steaks stored under O₂ + CO₂ had lower metmyoglobin fractions, and were desirable after storage for up to 8 days. However, the fractions of metmyoglobin increased, and steaks were judged to be less desirable after longer storage times. Steaks stored under O₂ + CO₂ for 20 days were unacceptable. After storage, the numbers of bacteria on steaks from vacuum packs and N₂, CO₂, and O₂ + CO₂ atmospheres were, respectively, <10⁴, <10⁶, <10⁵, and <10⁴ CFU/cm². The flora from steaks stored under CO₂ were composed wholly of lactic acid bacteria. Other flora were dominated by lactic acid bacteria, but contained fractions of enterobacteria and/or Brochothrix thermosphacta.

The appearance of product from vacuum packs generally was unacceptable after 72 h of display. The display life of steaks stored under N₂ or CO₂ was shorter than that of the product from vacuum packs when product was stored for 2 days or less, or 46 days or more. After other storage times, the product from vacuum packs or master packs with N₂ or CO₂ atmospheres had a similar display life. The display life of product stored under O₂ + CO₂ was similar to that of product from vacuum packs or CO₂ or O₂ + CO₂ was similar to that of product from vacuum packs after storage times of 8 days or less but was shorter after storage times of 12 or 16 days. The flora on displayed product from vacuum packs or CO₂ or O₂ + CO₂. atmospheres did not attain the maximum number of 10⁷ CFU/cm². and the product did not develop off-odours of microbial origin. However, numbers of 10⁷ CFU/cm² were approached or attained during display of product stored under N₂ for 28 days or longer, and some of that product developed moderate off-odours. It then appears that, under temperature regimes that are common in commercial practice, retail-packaged strip-loin steaks with a display life of 2 days or longer can be obtained from master packs after storage periods of up to about 2, 4, or 7 weeks, respectively, with master-pack atmospheres of O₂ + COPin2 (2 : 1, v/v), N₂, or CO₂.     

Production of cured meat color in nitrite-free Harbin red sausage by Lactobacillus fermentum fermentation

Lactobacillus fermentum was substituted for nitrite to produce cured pink color in a Chinese-style sausage. Treatments included inoculations (10⁴, 10⁶, and 10⁸ CFU/g meat) followed by fermentation at 30 °C for 8 h and then at 4 °C for 16 h. Control sausage (with sodium nitrite, 60 mg/kg meat) was cured at 4 °C for 24 h without L. fermentum. The UV–Vis spectra of pigment extract from L. fermentum-treated sausage were identical to that of nitrosylmyoglobin (NO-Mb) formed in nitrite-treated control. The NO-Mb concentration and the colorimetric a^* value of sausage treated with 10⁸ CFU/g meat of L. fermentum essentially replicated those in nitrite-cured meat. Free amino acid content in sausage treated with L. fermentum was greater and the pH slightly lower compared with the nitrite-cured control sample. This study showed that L. fermentum has the potential to substitute for nitrite in the sausage production.     

Frozen storage stability of antioxidant-treated raw restructured beef steaks made from mature cows

Previous research has shown that beef quality decreased with the age of cattle. In this study, beef trimmings from nine mature cows (n = 9), equally representing three animal age groups (2–4, 6–8, and 10–12 yr), were restructured into steaks formulated with propyl gallate, alone or in combination with a beefy flavoring agent, to enhance palatability and stability during 6 months of frozen storage at −29 °C. Lipid oxidation, rancidity, and loss of beefy flavor in restructured steaks during extended storage were reduced by propyl gallate. The beefy flavoring agent inclusion masked mature, forage-fed beef off-flavors, intensified beefy flavor, and improved steak tenderness, juiciness and cooking yield. Thus, the combination of propyl gallate and beefy flavoring offers an effective means to enhance the palatability and storage stability of restructured beef prepared from mature cows.     

Influences of dietary conjugated linoleic acid (CLA) and total lysine content on growth, carcass characteristics and meat quality of heavy pigs

To assess the effects of dietary CLA, lysine and sex on performance, blood metabolites, carcass characteristics, meat quality and skeletal development, seventy-two pigs (initially 105.3 ± 6.6 kg live weight) barrows and gilts, were assigned to one of four diets in a 2 × 2 × 2 factorial arrangement. The diets contained 0% or 0.75% CLA, and 0% or 0.16% of l-lysine–HCl. All pigs were slaughtered at an average weight of 153.4 ± 11.0 kg. Neither CLA nor lysine supplementation influenced growth, blood metabolites or carcass characteristics. CLA reduced (P < 0.05) pH₂₄ and increased (P < 0.01) yellowness (b^*) of the Longissimus muscle. Lysine increased (P < 0.01) pH₂₄ and reduced (P < 0.01) muscle ash content. CLA reduced (P < 0.05) collagen synthesis, and lysine increased (P < 0.05) collagen synthesis in Longissimus muscle, but no influence on intramuscular collagen maturity or muscle hydroxylysylpyridinoline crosslink concentration were observed. In addition, metacarpal bone diameter was reduced (P < 0.05) by CLA. Barrows had higher ADG, final weight (P < 0.01), carcass weight, lean percentage (P < 0.05), serum cholesterol (P < 0.05) and triacylglycerol (P < 0.001) than gilts. Metatarsal diameter was larger in gilts than barrows (P < 0.05).