Effect of dietary ractopamine on tenderness and postmortem protein degradation of pork muscle

Twenty-four finishing pigs with a mean starting weight of 82 kg were assigned to two dietary regimens: (1) a corn–soybean meal basal diet (control; n = 12), and (2) the basal diet supplemented with 20 ppm ractopamine HCl (RAC; n = 12). After 28–30 days on the feeding trial, pigs were slaughtered, and the growth and carcass characteristics were measured. Furthermore, the 3rd–13th rib section of longissimus muscle was excised at 48 h postmortem, sliced into 19-mm thick chops, vacuum packaged, stored at 2 °C, and subjected to Warner–Bratzler shear force (WBSF) and electrophoretic tests after 2, 4, 7, 10, 14, and 21 days (postmortem). RAC feeding increased (P < 0.01) pig carcass weight and percent lean, but it also increased the day-2 muscle WBSF by 20% (P < 0.01). The shear force difference between control and RAC pig muscles gradually decreased and vanished by day 10 (P > 0.05) when both muscle groups became more tender. The muscle from RAC-fed pigs exhibited a slower protein degradation rate than muscle from the control animals, notably for proteins in the 15–45 kDa range. The results suggested that the tenderness difference between ractopamine-treated and control pig muscles was related to the proteolysis rate, and could be diminished with adequate postmortem ageing.     

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).     

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.     

Effects of distribution packaging method and storage time on the physical properties and retail display characteristics of pork

The sensory characteristics of pork chops from bone-in loins and Boston butts (n = 65 each) were affected little by primal loin and the butt packaging method (paper wrap, vacuum pack and gas flush) and storage time (7, 10 and 14 days) under industry conditions. However, loin chops fabricated from vacuum-packaged loins after 14 days of storage had less (P < 0·05) discoloration and two-toning than chops fabricated from other loins. All loin chops were placed in retail display and overwrapped with a polyvinyl chloride film after fabrication at each storage time. Vacuum-packed butts stored for 10 and 14 days produced chops with less discoloration and two-toning, and higher overall appearance scores (P < 0·05) compared to chops from paper-wrapped or gas-flushed cuts. Vacuum-packaging resulted in higher quality retail cuts than paper-wrapped or gas-flushed packaging. Thus, it is recommended that the pork industry and retail distribution system utilize vacuum-packaging as the primary method to store and ship fresh pork before retail sale.     

Impact of muscle type and sodium chloride concentration on the quality, sensory, and instrumental color characteristics of solution enhanced whole-muscle beef

Beef biceps femoris (n = 10; muscle sections, n = 20; BF), infraspinatus (n = 10; muscle sections, n = 20; IS), and longissimus (n = 10; muscle sections, n = 20; LM) muscles were utilized to evaluate the effect of enhancement with phosphate and varying levels of sodium chloride in beef muscles differing in composition and palatability. Muscles were untreated or solution enhanced to 112% of raw product weight with sodium tripolyphosphate at 0.4% of product weight (STPP), or STPP and sodium chloride (NaCl) at 0.5%, 1.0% or 1.5% of product weight. There was a quadratic relationship (P = 0.04) for percent free water to decrease and a linear relationship (P < 0.01) for cook yield to increase as the level of NaCl increased. The IS steaks required less (P < 0.05) shear force than either the BF or LM, with the BF and LM having similar (P > 0.05) shear force values. There was a linear relationship (P < 0.01) for shear force values to decrease with increasing salt concentration. Steaks from all four enhancement treatments had lower (P < 0.05) shear force values than untreated steaks. Sensory overall tenderness ratings revealed that the IS and LM were similar (P > 0.05) and superior (P < 0.05) to the BF in tenderness. Steaks enhanced with STPP and 0.5%, 1.0%, or 1.5% NaCl all were rated more tender (P < 0.05) than untreated or STPP-only treated steaks. The BF exhibited the lowest (P < 0.05) L* (lightness) and a* (redness) values, as well as decreased (P < 0.05) vividness. The LM generally exhibited superior color to the other two muscle types. There was a linear relationship (P < 0.01) for L*, a*, b* (yellowness) values, and vividness to decline with increasing salt concentration, but steaks enhanced with STPP and 0.5% NaCl were similar (P > 0.05) in a* values and vividness to untreated steaks. These results suggest that across three different muscles varying in composition and palatability, enhancement with 0.4% STPP and 0.5% NaCl allowed for improvements in palatability while minimizing the color deterioration associated with phosphate/salt enhancement.     

Physicochemical and sensory properties of chicken nuggets with washed mechanically deboned chicken meat: Research note

The effects of different proportions (0%, 10%, 20%, 30%, 40%) of washed mechanically deboned chicken meat (WM) as a substitute for hand deboned chicken meat, on the physicochemical and sensory characteristics of chicken nuggets were evaluated. The addition of WM increased fat content, but it was only significant (P < 0.05) when 40% of WM was added, whereas the protein content was significantly (P < 0.05) reduced as from 20%. Significant differences (P < 0.05) were found in L^*, a^* and b^* values with different proportions of WM, however, these differences were evidently not discerned as shown by the no significant differences (P > 0.05) in ΔE^* color scores. The addition of WM did not affect (P > 0.05) sensory attributes of chicken nuggets. From a technical viewpoint, up to 40% WM could be incorporated into nugget formulation instead of hand deboned chicken meat without affecting sensory attributes of the product. Minor changes in composition were observed but they were probably not detrimental to the product.     

The influence of early post-mortem enhancement and accelerated chilling on pork quality

To improve pork quality, the effectiveness of early post-mortem enhancement and accelerated chilling were investigated. The four treatments evaluated were: Enhancement with Accelerated Chilling (ENAC), Accelerated Chilling Only (ACO), Enhancement with Conventional Chilling (ENCC), and Conventional Chilling Only (CCO). ENAC had a higher (P < 0.05) pH than all other treatments. CCO resulted in the highest (lightest; P < 0.05) L^*, while ENAC had the lowest L^* value (darkest; P < 0.05). Subjective color and striping did not differ (P > 0.05) between ENAC and ENCC, although ENAC was numerically higher for both parameters. Sensory analysis for juiciness and tenderness were not different (P > 0.05) between ENAC and ENCC, but both were higher (P < 0.05) than ACO and CCO. Enhancement early post-mortem coupled with accelerated chilling may be used to improve instrumental color and pH over conventional processing methods.     

Chemical, instrumental and sensory characteristics of cooked pork ham

Instrumental, chemical and sensory parameters of cooked pork ham were evaluated. Principal component analysis was carried out on the basis of the instrumental variables related to colour and texture. The four PCs account for almost 94% of the total variance in the data set. The PCA only separated 3 hams with a^* > 10. Hardness was correlated with non-collagen muscle protein (P  0.01), gumminess (P  0.01) and ash (P  0.05). Sensory evaluated tenderness showed positive significant correlation with L^* (P  0.01). The most important colour parameter seems to be a^*, which was negatively correlated with sensory evaluated parameter colour (P  0.01). The PCA performed on all parameters (sensory, chemical and textural) discriminated two groups of hams differing in non-collagen muscle protein content and hardness.     

Effect of different stunning systems on meat quality of light lamb

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

Effects of dietary magnesium and duration of refrigerated storage on the quality of vacuum-packaged, boneless pork loins

Quality data were initially collected on 78 pork loins from crossbred pigs fed diets containing 0, 1.25 or 2.5% magnesium mica (MM). Loins were then vacuum-packaged, and randomly assigned to either 4 or 8 weeks of storage at 2°C. Dietary MM had no (P > 0.05) effect on moisture loss/retention or subjective and objective color measurements. Purge volume increased (P<0.05) and drip loss decreased (P<0.05) as storage time increased. Moreover, longissimus thoracis et lumborum (LM) chops became lighter (P<0.05), redder (P<0.05), and more yellow (P<0.05) during 8 weeks of storage. Although TBARS values increased linearly (P<0.001) during extended storage, LM chops from pigs fed 2.5% MM tended to have lower (P<0.07) TBARS values after 4 weeks of storage than chops from pigs fed 0 and 1.25% MM. After 8 weeks of storage, however, there was a tendency for TBARS values of chops from pigs fed 1.25% MM to be lower (P<0.07) than chops from pigs fed 2.5% MM. Even though feeding swine diets containing MM did not affect color and water-holding capacity of pork loins during storage, the data indicated inclusion of MM in swine diets may retard onset of oxidative rancidity in vacuum-packaged pork loins.     

The impact of lactic acid concentration and sodium chloride on pH, water-holding capacity, and cooked color of injection-enhanced dark-cutting beef

The objectives of this study were to evaluate the effect of enhancement with 0.5%, 1.0%, 1.5%, or 2.0% lactic acid (LA), with or without 0.5% salt (NaCl), on pH, water-holding capacity, and resultant cooked color of dark-cutting (DC) beef. The pH of DC sections treated with LA decreased (P < 0.05), whereas water-holding capacity (WHC) increased (P < 0.05) with increasing concentrations of LA. Sensory panelists noted an increase (P < 0.05) in the degree of doneness (less pink internal color), whereas, a^* and chroma values were lower (P < 0.05), and hue angles were greater (P < 0.05), indicating the internal color of LA-treated DC sections was less red and appeared more well-done. Also, 630:580 nm reflectance ratios were similar (P > 0.05) among DC steaks treated with 0.5% and 1.0% LA and normal pH (NDC) steaks, likely caused by an increase (P < 0.05) in myoglobin denaturation in LA-enhanced DC steaks. These results indicate that the use of LA can reduce postmortem muscle pH and alter the cooked color of DC beef, ultimately resulting in a deletion of the persistent pinking condition.     

Augmented postmortem glycolysis does not occur early postmortem in AMPKγ3-mutated porcine muscle of halothane positive pigs

The objective of this study was to determine the effects of the halothane (HAL) and Rendement Napole (RN) genes on the rate-limiting reactions of glycolysis and their relationship to pork quality development. Samples were collected from the longissimus muscle at 0, 30, 60, and 120 min and 24 h postmortem from homozygous HAL and RN pigs (NN/rn⁺rn⁺, NN/RN⁻RN⁻, nn/rn⁺rn⁺, nn/RN⁻RN⁻). Muscle pH was recorded at 0, 15, and 45 min, and 24 h postmortem. HAL mutants, compared with HAL normal, had lower (P < 0.05) ATP concentrations at 0 and 30 min, lower (P < 0.05) pH at 45 min, and hastened glycogen degradation and lactate accumulation in the first 120 min postmortem (HAL × time, P < 0.0001). RN mutants had greater (P < 0.0001) glycolytic potentials than RN normal, and lower (P < 0.05) 24 h pH compared with the normal genotype, but not the HAL mutant genotype. The HAL mutation negatively affected (P < 0.05) L*, b* and color scores whereas both HAL and RN mutations independently decreased (P < 0.05) firmness, marbling and water holding capacity. RN mutant genotypes had higher (P < 0.0001) phosphocreatine concentrations than other genotypes at 0 min. Compared with HAL normal, HAL mutants had elevated (P < 0.05) muscle glucose concentrations at 30, 60, and 120 min, and 24 h. RN mutants had higher (P < 0.05) glucose levels than RN normal after 60 min. Glucose-6-phosphate (G6P) concentrations decreased (P < 0.05) during the first hour postmortem except in HAL/RN mutants, which had higher (P < 0.01) G6P concentrations than all other genotypes at 30 min. From 60 min to 24 h postmortem, G6P increased (P < 0.05) in HAL normal genotypes. Altogether, these data show that elevated muscle glycogen content does not further aggravate rapid early postmortem metabolism.     

Effects of rigor temperature and electrical stimulation on venison quality

The effects of rigor temperature and electrical stimulation on venison quality were assessed using venison longissimus dorsi muscle. In the first trial, effect of rigor temperature (0, 15, 25, 30, 35 and 42 °C) and time post-mortem (at rigor, 3, 7 and 14 days) on drip and cooking losses, % expressible water (water holding capacity, WHC), sarcomere length, protein solubility, meat tenderness and colour were investigated. In the second trial, the effects of rigor temperature (15 and 35 °C), electric stimulation (stimulated or not stimulated) and time (at rigor, 3 and 6 weeks post-mortem) on tenderness and colour were further investigated. Results of the first trial showed no clearly established trends of the effect of rigor temperature and time on the cooking and drip losses and protein solubility except venison muscles that went into rigor at 42 °C tended to have higher drip loss and lower protein solubilities compared to muscles that went into rigor at the other temperatures. Venison water holding capacity (WHC) decreased with the increase in rigor temperature (P < 0.001) and venison became more tender with time post-mortem. Venison colour improved with increasing rigor temperature. During display, samples that went into rigor at 15, 25 and 35 °C had the lowest and those at 0 and 42 °C had the highest rate of change of redness (a^*) value with time. In the second trial, tenderness was improved by stimulation (P = 0.01). Redness (a^*) values were affected by rigor temperature (P < 0.01) and post-mortem time (P < 0.001) but not by electrical stimulation. It is concluded that venison tenderness can be improved via the manipulation of rigor temperature to obtain acceptable level of tenderness early post-mortem with less damaging effect on colour stability.     

Meat quality of lambs of indigenous dairy Greek breeds as influenced by dietary protein and gastrointestinal nematode challenge

The effect of dietary protein and gastrointestinal (GI) parasitism on growth and meat quality of lambs was assessed using 60 animals. The lambs were randomly allocated to one of three treatment groups (n = 20): group A, which served as control, group B that was regularly treated with albendazole and group C, which was given supplementary feeding with dietary protein. The three groups of lambs grazed into a pasture (Lolium perenne), which was contaminated with L₃ larvae of GI nematodes. Lamb growth and condition score were assessed at 21-day intervals. After 126 days grazing all lambs were slaughtered and their carcasses were assessed for conformation and fatness and their ultimate pH was measured. Four carcasses from each group were randomly selected for meat quality measurements including physical analysis as well as colour, moisture, total fat, protein content and fatty acid composition. Parasitic challenge was assessed by means of faecal egg counts of lambs, pasture larvae and numbers of adult nematodes in the GI tract of lambs at slaughter. Growth rate of group B was higher (P < 0.01) than that of group A and resulted in significantly (P < 0.01) heavier carcasses. The produced carcasses had similar fatness, but differed significantly (P < 0.05), in their conformation; carcasses of group C scored higher than either those of group B or group A, respectively. There was a significant difference in the colour attributes (L^*) with group A being significantly lighter (P < 0.05) and in pH (P < 0.01); Group B had the highest values. Carcasses of group C had the highest (P < 0.05) amounts of intermuscular fat compared to those of group B and A, respectively. The proportion of C16:1n-7 and C18:2n-6 was higher (P < 0.05) in subcutaneous fat tissue whereas the proportion of C18:0 was higher (P < 0.05) in muscle tissue. In conclusion, the present results showed that the increased protein content in the diet of growing lambs, grazing on a pasture infected with GI nematode larvae, resulted in the production of acceptable carcasses.     

Prediction of intramuscular fat by impedance spectroscopy

Multiple multi-frequency impedance measurements during the computer controlled passage of a probe through the M. longissimus dorsi in pork and beef were applied. It was expected that the variability in impedance would correlate with the intramuscular fat (IMF) due to the inhomogeneous distribution of electrolytes and fat. We conducted our experiments in pig carcasses at different, well defined times post-mortem in varying directions of puncture (Experiment 1) and predicted the intramuscular fat in pork and beef by regression (Experiment 2). The highest correlations were obtained in experiment 1 for parameters characterising the variability of the impedance 24 h post-mortem and insertion of the probe through the back fat and muscle towards the body cavity (r = 0.54–0.79, P < 0.001). Both of these were chosen for the measurements in experiment 2. Regression for the prediction of IMF in pork and beef in experiment 2 resulted in R² values of 0.12 and 0.48, respectively; and in RMSE values of 0.67 and 0.64, respectively. The correlation between the predicted and the IMF analysed by n-hexane extraction or Near Infrared Transmission varied from 0.28 to 0.69 (P < 0.001) depending on species and breed. A selection of the carcasses for high IMF (above a certain threshold) using the impedance measurements agreed poorly with the analysed IMF. Depending on the level of IMF within a breed, low IMF contents were often over-predicted (3.4–92.7%) or high IMF contents were estimated as too low (0–80.9%). Breed specific regression equations could improve the accuracy. These data indicate that the selectivity of the impedance method in the configuration presented here is not yet sufficient for practical use.     

Effects of Dietary Rape Seed Oil, Copper(II) Sulphate and Vitamin E on Drip Loss, Colour and Lipid Oxidation of Chilled Pork Chops Packed in Atmospheric Air or in a High Oxygen Atmosphere

The effect of addition of rapeseed oil (canola), CuSO(4) and vitamin E (all-rac-α-tocopheryl acetate) to pig diets on pork meat quality (lipid oxidation, colour and drip loss) was studied. Pigs were reared on ten different diets, either a control diet (no supplementation of rapeseed oil, CuSO(4) or vitamin E) or 6% rapeseed oil diets supplemented with CuSO(4) (0, 35 or 175mg/kg) and vitamin E (0, 100 or 200mg all-rac-α-tocopheryl acetate/kg). The natural content of vitamin E originating from feed ingredients amounted to 9-23mg vitamin E (α-tocopherol) per kg feed. Muscle vitamin E levels reflected the dietary intake and pigs fed the control diet had significantly lower levels than pigs fed rapeseed oil diets. The quality of fresh pork chops packed in air or in 80% O(2):20% CO(2) was followed during chill storage for 8 and 13 days, respectively. Colour, as measured by tristimulus colorimetry of pork chops packed in 80% oxygen atmosphere, was significantly improved with respect to redness when compared to chops packed in air, regardless of dietary treatment. The low vitamin E content in pigs fed the control feed significantly decreased a values and the oxidative stability of pork chops during chill storage compared to the other feeding groups. Packing of chops in a high-oxygen atmosphere increased lipid oxidation, especially in chops with low levels of vitamin E. Supplementation of rapeseed oil diets with 100 or 200mg vitamin E significantly decreased lipid oxidation of chill stored chops. Supplementation with CuSO(4) did not influence meat quality attributes (drip loss, colour stability and lipid oxidation) for any of the storage conditions.     

Studies on tenderization and preparation of enrobed pork chunks in microwave oven

This study was conducted to develop technology for tenderization and production of enrobed pork chunks in a microwave oven. Meat chunks from shoulder cuts of pork were cured in a solution containing salt, sodium tripolyphosphate and sugar for 48 h at 4 ± 1 °C, enrobed with cream based batter and cooked in a microwave oven at 900 MHz. These enrobed chunks (control) were compared with tenderized (treated) enrobed chunks, for which 7.5% cucumis extract, 9% ginger extract and 0.50% papain powder were incorporated in the standard curing solution. Ginger and papain treatments caused significant (P < 0.01) increases in the moisture content and pH of the cooked products compared to the control and cucumis treated samples. Shear force values were significantly (P < 0.01) lower and overall acceptability scores were significantly (P < 0.01) higher in all treated samples compared to the control. During storage at 4 ± 1 °C, the moisture contents and sensory qualities decreased, but TBARS values and microbial counts increased significantly (P < 0.01). Although all products were acceptable up to 15 days of storage, the ginger treated samples had significantly (P < 0.01) lower TBARS and microbial loads and higher sensory attributes than the control, cucumis and papain treated samples. The magnitude of the storage changes were less and acceptability ranking was higher for the ginger treated samples compared with the others. The results indicated that microwaves could be used for the preparation of enrobed pork chunks. The overall acceptability and shelf life of microwave cooked enrobed pork chunk can be further improved using ginger extract in the curing solution.     

Effect of oxidized dietary lipid and vitamin E on the colour stability of pork chops

The effect of oxidized corn oil and vitamin E (α-tocopheryl acetate) in pig diets on the oxidative stability of muscle lipids and on the surface colour characteristics of fresh and previously frozen pork chops in refrigerated storage was investigated. Lipid oxidation (TBARS values) and surface redness (Hunter 'a' values) were significantly influenced (P < 0·01) by dietary α-tocopheryl acetate levels but not by degree of oxidation of dietary corn oil. Lipid oxidation and colour deterioration during refrigerated storage were greater in previously frozen chops compared to fresh chops. TBARS values were lower and Hunter 'a' values higher in pork chops from pigs fed 100 and 200 mg α-tocopheryl acetate/kg diet compared to pigs fed 10 mg/kg diet after 2, 4, 6 and 8 days of refrigerated storage. Hunter 'a' values were significantly correlated (P < 0·01) with the logarithm of TBARS values. The results suggest that oxidation of myoglobin precedes oxidation of muscle lipids in pork chops stored at 4°C.