Pork Quality Attributes Research Articles

Effects of pre-rigor injection of sodium citrate or acetate, or post-rigor injection of phosphate plus salt on post-mortem glycolysis, pH, and pork quality attributes

Forty pork carcass sides were assigned to one of four treatments: pre-rigor citrate (CIT) or acetate injection (ACE); post-rigor phosphate and salt injection (PHOS); and non-injected control (CON). Loins in 20 sides were injected at 50 min post-mortem with 4% solutions of CIT or ACE to approximately 110% of projected loin weights, and 10 loins were injected at 24 h post-mortem to 106.6% with a solution of 4.4% PHOS and 2.2% salt. Although CIT increased pH ( P < 0.05), neither CIT nor ACE altered ( P > 0.05) glycolytic metabolite concentrations. The pH increase in muscles from the CIT treatment was most likely due to its buffering ability rather than to its glycolytic inhibition. Pre-rigor CIT injection improved tenderness without the detrimental effects on color or flavor found with PHOS, but neither CIT nor ACE altered glycolytic metabolites or improved firmness, wetness, or fresh visual color over CON. Poor flavor attributes of the ACE treatment will hinder its use as an ingredient for pork enhancement solutions.

Comparison of histochemical characteristics in various pork groups categorized by postmortem metabolic rate and pork quality1

The purpose of the present study was to investigate the variations in histochemical characteristics of muscle samples segregated according to metabolic rates (MR) and pork quality attributes. A total of 231 crossbred Duroc x (Yorkshire x Landrace) pigs was evaluated. Samples of the LM were taken to evaluate histochemical characteristics, postmortem MR, and meat quality. Samples were classified into fast, normal, and slow MR groups based on muscle pH at 45 min and R-value. Drip loss and lightness (L*) were used to assign samples to 1 of 4 quality classes. Pale, soft, and exudative pork belonging in the fast group had the greatest (P < 0.05) percentage of type IIb fibers, and RSE (reddish-pink, soft, and exudative) pork belonging in the fast group had a similar tendency. Additionally, RFN (reddish-pink, firm, and nonexudative) pork belonging in the normal group showed a lower (P < 0.05) percentage of type IIb fibers than PSE or RSE, regardless of MR, and DFD pork had the lowest (P < 0.05) percentage of type IIb fibers. In general, the fast-glycolyzing PSE pork with the lowest pH at both 45 min and 24 h had greater percentages of type IIb fibers than the fast-glycolyzing RFN pork. There were more fiber-type composition differences between quality classes in pork undergoing a fast rate of metabolism compared with pork undergoing a normal rate of metabolism. It can be concluded that muscle histochemical characteristics are associated with early postmortem MR, the extent of glycolysis, and, thereby, pork quality; however, these effects are limited to the pigs exhibiting a fast glycolytic rate.

Negative effects of stress immediately before slaughter on pork quality are aggravated by suboptimal transport and lairage conditions

The objectives of the present experiment were 1) to study the effects of transport conditions and lairage duration on stress level, muscle glycolytic potential, and pork quality; and 2) to investigate whether the negative effects of high stress immediately preslaughter are affected by preceding handling factors (transport and lairage). In a 2 x 2 x 2 factorial design, halothane-free pigs (n = 384) were assigned to either 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. Pigs were processed in eight groups (48 pigs per group) on various days at a commercial plant. Blood samples were taken at exsanguination to measure plasma cortisol and lactate concentrations. Muscle pH and temperature were measured at 30 and 40 min, respectively, and both were measured at 3 h, postmortem. A LM sample was taken 135 min postmortem to estimate glycogen content and rate of glycolysis. Pork quality attributes were assessed 23 h postmortem. Short transport increased cortisol when followed by short lairage (transport x lairage; P < 0.01). Long transport, but not lairage (P > 0.30), tended to increase (P = 0.06) muscle glycolytic potential. Long transport tended to increase (P = 0.08) electrical conductivity, and decreased a* (P < 0.01) and b* (P < 0.02) values. Decreasing lairage from 3 h to <45 min decreased (P < 0.05) the L* value, but it did not (P > 0.10) affect other pork quality traits. High stress decreased (P < 0.001) muscle glycolytic potential, and increased (P < 0.001) plasma lactate, cortisol, muscle temperature, rate of pH decline, and ultimate pH. Except for decreased (P < 0.001) b* values, pork color was not (P > 0.40) affected by high stress, but water-holding properties (measured by electrical conductivity, filter paper moisture, and drip loss) were impaired (P < 0.001) by high stress. Fiber optic-measured light scattering and Warner-Bratzler shear force were not (P > 0.12) affected by any treatment. Comparisons with the "optimal" handling (short transport, long lairage, and minimal stress) revealed that, with regard to water-holding properties, the negative effects of high stress were aggravated by suboptimal transport and lairage conditions. High stress alone increased electrical conductivity by 56%, whereas high stress in combination with short lairage led to an 88% increase. However, high preslaughter stress contributed most and was the major factor responsible for reductions in pork quality.

Effects of oral administration or feeding of sodium citrate or acetate to pigs on post-mortem glycolysis, pH decline, and pork quality attributes (2005)

Previous studies have shown that citrate has the potential to inhibit phosphofructokinase (PFK), a key enzyme in post-mortem glycolysis. The objective of our study was to determine the effects of oral administration and feeding of citrate or acetate to pigs on post-mortem glycolysis, pH, and pork quality attributes. In Experiment 1, citrate, acetate, or water was orally administered to 30 pigs 45 min before stunning (electric plus captive bolt). In Experiment 2, citrate or acetate was fed to 30 gilts in 454 g of feed 60 min before stunning. Ante-mortem treatment had no effect (P > 0.05) on muscle pH or post mortem concentrations of glycolytic metabolites: glucose- 6 phosphate, fructose-6 phosphate, fructose-1,6 bisphosphate, glyceraldehyde-3 phosphate, dihydroxyacetone phosphate, or lactate. Minor, but inconsistent, differences in quality attributes were found in longissimus chops and inside and outside semimembranosus quality attributes among treatments (P>0.05). The reason for the lack of PFK inhibition is not known. Glycolytic-metabolite data indicate that PFK was a main regulatory enzyme in post-mortem muscle.; Swine Day, 2005, Kansas State University, Manhattan, KS, 2005

Effects of pre-rigor injection of sodium citrate or acetate, or post-rigor injection of phosphate plus salt, on post-mortem glycolysis, pH decline, and pork quality attributes (2005)

Effects of pre-rigor injection of sodium citrate or acetate, or post-rigor injection of phosphate plus salt, on post-mortem glycolysis, pH decline, and pork quality attributes (2005)

Effect of radio frequency (RF) heating on the texture, colour and sensory properties of a comminuted pork meat product

Radio frequency (RF) cooking is a form of dielectric heating in which products are heated by subjecting them to an alternating electromagnetic field between two parallel electrodes. Although similar in some respects to Microwave heating, RF has been proposed to be more suitable for industrial heating of meats because of the greater penetration depths possible with this technology. In this study an RF cooking protocol was developed and its effect on selected quality attributes of pork based white pudding was examined. Whilst cooking of the product in air proved unfeasible due to arcing, use of a polyethylene cell with circulating hot water (80 °C) facilitated successful heating of the product. Application of RF using an optimised cooking protocol (RF power = 450 W, cell volume = 500 ml and continuous circulation) resulted in a mean end-point temperature of 73 °C after 7 min 40 s. Similar mean end-point temperatures in water bath and steam oven heated products were achieved after 29 and 33 min, respectively. A factorial experiment was conducted to assess selected quality attributes of the cooked puddings. Results show that RF heated puddings were not significantly different ( P > 0.05) from water bath and steam oven heated products with regard to instrumental colour, instrumental texture (Kramer shear and texture profile analysis) and expressible fluid. Furthermore, results of a sensory similarity test involving 60 panellists indicated that panellists were not able to detect differences between puddings cooked by RF and conventional methods. Overall this suggests that RF heating technology could have potential in pasteurisation of meat products though further work is needed to verify this.

Preslaughter stress and muscle energy largely determine pork quality at two commercial processing plants.

The objective of the present experiment was to study physiological changes elicited in response to stress in the immediate preslaughter period and to link them to pork quality characteristics. Crossbred, halothane-free pigs (n = 192) were processed in eight groups (24 pigs per group) on various days at one of two commercial processing plants operating different stunning systems (electrical and CO2 stunning in Plants A and B, respectively). In each group, half the pigs were exposed to either minimal or high preslaughter stress. Blood samples were taken at exsanguination, and lactate, cortisol, and catecholamines, as well as blood pH and temperature, were assessed and linked to various longissimus muscle quality attributes. Additionally, muscle pH and temperature were measured 30 min postmortem, and muscle glycolytic potential was determined 22 h postmortem. At both processing plants, high preslaughter stress resulted in higher (P < 0.05) blood cortisol and lactate; however, the effects of preslaughter stress on catecholamines and blood pH were believed to be biased by the different stunning methods employed at the plants. High preslaughter stress increased (P < 0.05) blood temperature at Plant A but not at Plant B. At both plants, high stress increased (P < 0.05) 30-min muscle temperature and decreased (P < 0.05) 30-min muscle pH. Ultimate pH was increased (P < 0.05) and muscle glycolytic potential was decreased (P < 0.05) by high preslaughter stress. At both plants, high stress resulted in inferior pork quality attributes (P < 0.05), including reflectance, electrical conductivity, filter paper moisture, drip loss, and L* value. The effect of stress was greater on water-holding capacity than on pork color, with drip losses increased by 56%. Of all stress indicators measured at exsanguination, only blood lactate was strongly correlated with pork quality attributes. Regression analyses revealed that blood lactate and glycolytic potential accounted for 52 and 48% of the variation in drip loss and L* value, respectively. In combination with high preslaughter stress, high glycolytic potentials were related to increased drip losses. We conclude that high preslaughter stress leads to impaired pork quality, with high muscle energy levels aggravating the negative effects of preslaughter stress. Monitoring stress level by blood lactate measurement in combination with strategies to control muscle energy present at slaughter may help to improve meat quality.

The effects of gender and slaughter weight on the growth performance, carcass traits, and meat quality characteristics of heavy pigs.

Crossbred pigs (n = 192) from Piétrain x Large White sires mated to Landrace x Large White dams, with a mean BW of 75 +/- 1.3 kg, were used to investigate the effects of gender and slaughter weight (SW) on growth performance, carcass characteristics, and meat quality. Pens of pigs (eight pigs/pen) were assigned randomly to one of six treatments arranged in a 2 x 3 factorial design with two genders (barrows or gilts) and three SW (116, 124, or 133 kg). Each treatment was replicated four times. Over the entire trial, barrows had higher (P < 0.001) ADFI (as-fed basis) and ADG than gilts; however, gilts had higher (P < 0.05) gain-to-feed ratios (G:F) than barrows. Barrows had lower (P < 0.01) dressing percents than gilts and produced fatter (P < 0.001) carcasses that had lower trimmed shoulder (P < 0.10) and ham (P < 0.001) yields than gilts. There was a trend for the semimembranosus muscle (SM) from barrows to have a higher (P < 0.10) 45-min pH than that of gilts, but 24-h pH was 0.11 pH unit higher (P < 0.01) in the SM of barrows than gilts. Gender had no (P > 0.10) effect on the moisture and lipid content of the longissimus muscle (LM), nor did gender affect (P > 0.10) LM color, myoglobin content, or thaw loss percentage. However, the LM from barrows had lower (P < 0.05) cooking loss percentages and tended to have lower (P < 0.10) shear force values than the LM from gilts. Pigs slaughtered at 116 kg had higher (P < 0.05) ADG than pigs slaughtered at 124 and 133 kg. Daily feed intake (as-fed basis) was not (P > 0.10) different among SW; however, pigs slaughtered at 116 and 124 kg had higher (P < 0.001) G:F than those slaughtered at 133 kg. Dressing percent, backfat depth, carcass length, and ham and shoulder weights increased (P < 0.001) as SW increased from 116 to 133 kg. The initial (45-min) pH of the SM from pigs slaughtered at 133 kg was higher (P < 0.05) than from pigs slaughtered at 116 or 124 kg; however, 24-h pH was not (P > 0.10) affected by SW. The LM from pigs slaughtered at 133 kg was darker (lower L* values; P < 0.001), redder (higher a* value; P < 0.01), and had more (P < 0.001) myoglobin than the LM of pigs slaughtered at 116 and 124 kg. Barrows and gilts of this particular crossbreed can be used to produce acceptable quality fresh pork when slaughtered at 116 kg; however, increasing SW to 124 kg, or more, decreased live pig performance and carcass leanness without any additional benefits to pork quality attributes.

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.

Effect of low voltage electrical stimulation of pig carcasses and ageing on sensory attributes of fresh pork

The effect of electrically stimulating pig carcasses and ageing on sensory attributes of pork was evaluated in this study. A total of 48 female pigs [Duroc×Large White/Landrace (A; n=24) and Large White/Landrace (B; n=24)] were randomly allocated immediately prior to slaughter to one of two low voltage stimulation treatments; no stimulation or 150 mA applied for 30 s at 2 min post-exsanguination. Each side of the carcass was then randomly allocated to an ageing treatment of either 2 or 7 days post-slaughter. Muscle pH of the M. longissimus lumborum was lower ( P<0.001) in electrically stimulated carcasses when measured from 40 min to 8 h post-slaughter compared with non-stimulated carcasses. Percentage drip loss, muscle lightness and PSE incidence were not influenced ( P>0.05) by electrical stimulation. Electrical stimulation of pig carcasses and ageing pork for 7 days post-slaughter both improved ( P<0.001) consumer scores for tenderness, juiciness, overall liking and quality category, however the interaction term of electrical stimulation and ageing was not significant for any of the sensory attributes. Pork from non-stimulated carcasses that was aged for 2 day post-slaughter was less tender ( P<0.01) compared with pork in all other treatments. These results indicate that electrical stimulation (150 mA applied for 30 sec at 2 min post-exsanguination) was effective in improving eating quality attributes of pork, particularly when pork was aged for only 2 days post-slaughter, without detrimentally affecting colour or drip loss.

The effect of pig genetics on palatability, color and physical characteristics of fresh pork loin chops

The objective of this study was to characterize the quality attributes of pork derived from pigs of the following backgrounds: Duroc, Pietrain (Halothane negative, NN), Pietrain (Halothane positive, nn), Berkshire, Hampshire (rn+), Hampshire (RN−), and a synthetic line. A 10-member panel was trained to evaluate visual appearance of uncooked lean and fat, and flavor and texture of cooked chops. Hunter L*, a*, and b* values, hue angle, cookloss and Warner–Bratzler shear force were also determined. Visual color differences occurred due to genetic background. Chops from Duroc, Berkshire, Pietrain-nn, and the synthetic line were least pink. Chops from Berkshire carcasses appeared to have the most marbling in the lean and those from Pietrain-nn pigs appeared to have the least. Chops from Pietrain-nn and Hampshire-rn+ carcasses had the highest a* values while chops from Duroc, Pietrain-NN, and Hampshire-RN- carcasses had the lowest. Cook loss from chops from Duroc carcasses was lower than that from Hampshire rn+, Pietrain-NN and synthetic line carcasses. Shear force was highest for chops from Pietrain-nn and Hampshire-rn+ carcasses. Chops from Hampshire-RN− carcasses were most juicy followed by those from Hampshire-rn+, Pietrain-NN, Berkshire and Duroc carcasses. Shear force was positively correlated with abnormal flavor intensity, metallic taste, and chewiness ( r=0.72, 0.94, and 0.69, respectively), and negatively correlated with sweetness ( r=−0.73). Overall, genetic background had significant effects on many of the quality characteristics evaluated.

Microbial and Quality Attributes of Ground Pork Prepared from Commercial Pork Trim Treated with Combination Intervention Processes

The effects of combination intervention treatments of commercial pork trim on microbial and quality attributes of the subsequent ground pork were examined. Fresh commercial pork trim was inoculated with swine feces and subjected to five different intervention treatments: (i) control (untreated), (ii) water (15°C, 120 s), (iii) water followed by 2% lactic acid wash (15°C, 75 s), (iv) Combination 1 (water plus lactic acid plus hot air [510°C, 90 s]), and (v) Combination 2 (hot air plus water plus hot air). Following treatment, the pork trim was stored at 4°C for 24 h, then ground, stuffed, vacuum packaged, and stored at 4°C for 21 days. Populations of aerobic bacteria, coliforms, Escherichia coli, and lactic acid bacteria in the ground pork were monitored before treatment, after treatment (day 0), and at 2, 7, 14 and 21 days. In addition, uninoculated pork trim was treated as described above, and the color and emulsion stability of the ground product was evaluated. Ground pork prepared from trim treated with any of the treatment processes had lower initial microbial populations compared to the untreated samples. The applications of water plus lactic acid or Combination 1, which included a lactic acid wash, were more effective than water or Combination 2 at both reducing initial populations and suppressing the growth of aerobic bacteria, coliforms, and E. coli in ground pork during refrigerated storage. By day 21, populations of aerobic bacteria in ground pork prepared from control, water-treated, and Combination 2–treated trim were 8.22 to 8.32 log CFU/g, but in water plus lactic acid and Combination 1 ground pork, populations were 6.32 and 4.90 log CFU/g, respectively. Among the trim interventions examined, Combination 1 was most detrimental to the color and emulsion stability of the ground pork. The water plus lactic acid treatment provided the greatest microbial reduction and inhibition without large negative effects on quality attributes of the ground pork.

Comparison of CO 2 stunning with manual electrical stunning (50 Hz) of pigs on carcass and meat quality

The effects of carbon dioxide stunning on carcass and pork quality attributes were compared with the effects of manual electrical stunning using either head-only or head-to-brisket electrodes. A total of 30 Large White×Landrace boars (homozygous dominant for the halothane gene) were randomly allocated immediately prior to slaughter to one of three stunning treatments: carbon dioxide (90% CO 2), head only (HO; 1.3 A for 4 s at a frequency of 50 Hz) or head to brisket (HBR; 1.3 A for 4 s at a frequency of 50 Hz) electrical stunning. The pH of the M. longissimus thoracis (LT) muscle measured at two sites [between the fifth and sixth thoracic vertebrae (Site 1) and the last thoracic rib (Site 2)] at 40 min post-slaughter was lower ( P<0.001) in HBR stunned pigs compared with both CO 2 and HO stunned pigs. No differences in ultimate pH of the LT at either measurement site were found due to stunning method. However, a faster ( P<0.05) relative rate of pH decline was found in the LT at Site 1 from HBR stunned pigs compared with CO 2 stunned pigs. No difference in the relative rate of muscle pH decline ( P>0.05) between stunning methods was found in the LT muscle at Site 2. Pork from HBR stunned pigs was paler ( P<0.05) and had a higher ( P<0.001) percentage drip loss compared with pork from HO and CO 2 stunned pigs. LT muscles from HBR stunned pigs had lower ( P<0.001) WB shear force values compared with pork from HO stunned pigs (6.57 vs. 8.12 kg, S.E.D. 0.49). Carcass quality was improved by CO 2 stunning, with less ( P<0.05) ecchymosis-affected pork trimmed from shoulder primals compared with electrically stunned pigs. These results indicate that manual electrical stunning of pigs using HO tongs and CO 2 stunning reduced percentage drip loss, reduced muscle lightness and reduced the rate of muscle pH decline compared with pigs manually electrically stunned using HBR tongs.

Creatine monohydrate supplemented in swine finishing diets and fresh pork quality: II. Commercial applications.

The objectives of this study were to determine the value of supplementing creatine monohydrate (CMH) in a complete swine finishing ration and determining its effects on meat quality. Crossbred barrows (n = 59) were allotted five pens per treatment with three pigs per pen. Dietary treatments, including 20 g CMH x pig(-1) x d(-1) fed for 5, 10, or 15 d before slaughter, were compared to control pigs that received no CMH. The basal diet was a corn-soybean meal finishing diet. At 123.5 kg, pigs were delivered to a commercial packing plant (80 km) and slaughtered according to industry practices. After a 24-h chill at 4 degrees C, right-side loins were collected from the fabrication line and vacuum-packaged for delivery to the University of Missouri Meat Lab. Hams were scanned for lean content by a primal cut electromagnetic scanner. After scanning, ham pH and light reflectance (L*, a*, b*) were obtained on the gluteus medius muscle. Loin pH and light reflectance were obtained at the 10/11th-rib juncture. The posterior section of the boneless loin was weighed, vacuum-packaged, and stored for 7 d at 1 degree C. After aging, light reflectance, weights, and Warner/Bratzler shear force measurements were taken. A linear trend (P = 0.071) was observed for ham 24-h L* values, and a cubic trend was observed for ultimate loin pH (P = 0.102). Hunter L* values of the longissimus possessed a negative linear contrast (P = 0.009) after aging, revealing that the loins of those animals treated for 10 and 15 d exhibit higher L* values. A cubic trend (P = 0.057) was shown for percentage of moisture lost as purge; 5- and 10-d treatments were intermediate to control and 15-d treatments. Warner/Bratzler shear force measurements for chops aged 7 d increased in a linear fashion (P = 0.024). This data suggests that 5-d supplementation of CMH before slaughter improves several pork quality attributes. However, it seems that supplementing CMH in swine diets for 10 or 15 d could reduce the quality of fresh pork.

Conjugated linoleic acid improves feed efficiency, decreases subcutaneous fat, and improves certain aspects of meat quality in stress-genotype pigs.

Conjugated linoleic acid (CLA) was supplemented to crossbred growing-finishing barrows (n = 60) at 0.75% of the total diet. Pigs were randomly assigned to the CLA or control diets based on stress genotype (negative, carrier, or positive). Gain:feed was higher for CLA diet animals (350 g/kg feed) than for control diet animals (330 g/kg feed) independent of genotype (P < 0.05). No differences were observed for ADG for the diets (P = 0.71) or genotype classes (P = 0.40). Postmortem pH was lower (P < 0.01) by 3 h for CLA-supplemented pigs, with no differences in ultimate pH. No differences (P = 0.16) were observed for ultimate pH between the three genotypes. Conjugated linoleic acid-supplemented pigs exhibited less 10th rib fat depth (2.34 cm vs 2.84 cm) and last rib fat depth (2.46 cm vs 2.72 cm) than control pigs (P < 0.05). Loin muscle area (LMA) was not affected (P = 0.18) by CLA supplementation, but LMA was different (P < 0.02) for genotype; positive genotype carcasses had the largest LMA (45.02 cm2) and negative carcasses had the smallest LMA (36.44 cm2). Carrier carcasses were intermediate for LMA (40.76 cm2). Subjective scores for color were not affected (P = 0.98) by CLA but color was different (P < 0.01), with scores of 1.50, 2.40, and 3.1 for positive, carrier, and negative genotypes, respectively. Subjective marbling scores were increased (P < 0.03) in all genotypes with CLA supplementation. Subjective firmness scores were higher (P < 0.06) for CLA-supplemented pigs and were highly correlated (0.89) to marbling scores. The L* values were higher (P < 0.01) for stress-positive pigs at 24 h postmortem. Also, L* values were higher (P < 0.01) for CLA-fed pigs over 7 d of shelf storage. Sensory characteristics were not different with CLA supplementation for tenderness (P = 0.24), juiciness (P = 0.35), or flavor intensity (P = 0.14). This study showed that LMA was increased with stress-carrier and stress-positive genotypes, but lean color was negatively affected with the presence of the stress gene. Conjugated linoleic acid supplementation improves feed efficiency, decreases backfat, and improves pork quality attributes of marbling and firmness of the longissimus muscle. Furthermore, there is seemingly no interaction between the stress-genotype status of pigs and the subsequent effect of CLA on their growth and performance.

Impact of the hydrodyne process on tenderness, microbial load, and sensory characteristics of pork longissimus muscle.

Paired, boneless pork loin muscles were obtained from 76 market hogs to evaluate tenderness, meat quality characteristics, sensory attributes, and microbial characterization of pork muscle exposed to the Hydrodyne Process (H) compared with untreated control (C) loin. A subset of 16 paired loins was randomly selected for use in sensory evaluation and microbial characterization. Loins were vacuum packaged and immersed in a heat shrink tank prior to the H treatment. The Hydrodyne treatment exposed the loin to the pressure equivalent of a 150-g explosive, generating a pressure distribution of approximately 703 kg/cm2 at the surface of the samples. Meat quality assessments taken following treatment included subjective color, firmness/wetness, marbling scores (1 to 5 scale), Minolta reflectance and color readings, drip loss, and lipid content. The P-value for statistical significance for main effects and interactions was set at <.05 in all analyses. Administration of H resulted in a 17% improvement in Warner-Bratzler shear force (2.69 vs. 3.24 kg), with the shear force similar at two end-point cooking times (11 and 16 min) corresponding to approximately 75 and 83 degrees C, respectively. No differences between H and C were observed for color score, firmness score, Minolta L, Minolta Y, or drip loss on uncooked samples. The H loins had lower marbling scores (P<.05) and intramuscular lipid (P<.05) content than the paired C loin. Sensory evaluation on the randomly selected (n = 16) paired loins samples showed no improvement in Warner-Bratzler shear force. Sensory panelists were also unable to detect a difference between H and C loins for both initial and sustained tenderness scores. No differences between H and C loins were found for pork flavor, off-flavor, cohesiveness, or number of chews before swallowing, but H loins had a significantly lower juiciness score and more cooking loss than C loins. Microbial analysis results showed no differences in coliform bacteria counts, aerobic plate counts, and no detectable levels of Escherichia coli bacteria in any loins. The findings support the ability of the Hydrodyne procedure to improve tenderness without impacting other muscle quality attributes of pork.

Economic Values of Pork Attributes: Hedonic Price Analysis of Experimental Auction Data

Many fresh foods, such as fruits, vegetables, and meats, exhibit nearly continuous quality differences that cause consumers to value similar, but not identical, packages or lots of the food differently. Fresh pork chops are among the foods that typically exhibit these quality differences. Thus, although several packages of pork chops may be available at a particular price per pound, consumers will typically select among them based on perceived or expected quality differences. How consumers perceive and value these quality differences is of great interest to pork producers and grocery store managers. For example, it is unclear whether consumers perceive the same attributes when viewing advertising as they perceive in the actual product. Also unclear is how appearance relates to consumers' perceptions of taste or how attribute values change as consumers obtain new information (advertising versus appearance versus taste) about the product. Answers to these questions might signal changes in genetics and management of pork production and in the type of pork that grocery stores stock in meat counters. This may also provide advertisers, retailers, and other pork marketers with new information about fresh pork demand and how consumers perceive and value pork quality attributes. Such information is essential to effective pork advertising and marketing programs, such as the Other White Meat? campaign of the National Pork Producer's Council (NPPC). Methods of experimental economics the structured application of experimental methods to analyses of economic phenomena have recently become popular among economists as an effective means of examining consumer preferences and valuations (e.g., Hoffman et al.; Buhr et al.). However, these methods have historically been limited to binomial consumer choices (e.g., Shogren). In these studies, consumers have considered a single characteristic or set of characteristics which they observe at only one of two levels. As a result, experimental economics has been of limited use in valuing the multiple attributes that contribute to the nearly continuous variation observed in fresh pork quality. Melton et al., however, have extended the methods of experimental economics to analyze consumer preferences for multidimensional products. They integrated statistical methods of experimental design and methods of experimental economics so that it is possible to identify differences in consumers' preferences for products that exhibit continuous variance in multiple quality attributes or characteristics. They illustrated the method with an experimental auction of fresh pork chops that vary in color, marbling, and size. In this study, methods of hedonic price analysis are applied to derive new estimates of the economic value of these particular pork traits. Going a step beyond traditional approaches, the effects of socioeconomic variables on an attribute's economic value are also considered.

Cryogenic chilling of pork carcasses: Effects on muscle quality, bacterial populations and palatability

Two experiments were conducted to determine the effects of cryogenic chilling on the carcass shrinkage, meat quality, bacterial condition and palatibility of pork. In experiment I, pork sides were chilled at 1°C ( n = 20), or immersed in liquid nitrogen (LN) for 1 or 3 min prior to placement in a 1°C cooler. Muscle temperature in the loin was significantly lower at 2 and 6 h post mortem in treated compared to control sides, and loin muscle pH was higher ( P < 0·05) at 6 h post mortem in sides immersed for 3 min in LN. Carcass side shrinkage was reduced from 29·3 g kg −1 in control sides to 20·9 and 13·5 g kg −1 in sides dipped in LN for 1 and 3 min. Chilling treatment had no significant effect on the survival of mesophilic bacteria on carcass sides, on meat colour, drip loss, protein solubility or sarcomere length, but sides dipped for 1 min in LN has a higher muscle shear value than control sides. In experiment II, carcass sides from halothane positive (H+) and negative (H−) pigs were conventionally chilled ( n = 49), immersed in LN for 3 min ( n = 23), or electrically stimulated and chilled in LN for 3 min ( n = 26). Similar results for temperature, pH, colour, protein solubility and drip loss in loin muscle were found to those in experiment I. Laboratory taste panel results showed that chilling treatment had no effect on palatability. Genotype produced meaningful differences in most palatability attributes with H+ pigs having less tender, less juicy and less desirable flavour than pork from H− pigs. Laboratory studies with inoculated fresh muscle slices showed that a 3 min immersion in LN resulted in a 10-fold reduction in the aerobic spoilage pseudomonads, but effects upon other spoilage bacteria and potential human pathogens were less pronounced. It was concluded that cryogenic chilling using LN reduced carcass shrinkage during cooling, but had no consistent effects on meat quality, palatability or bacterial numbers on the carcass. In contrast, genotype had a significant effect on most pork quality and palatability attributes.