Effects of Endpoint Temperature on the Internal Color of Pork Loin Chops of Different Quality

ABSTRACT: The effects of 5 endpoint temperatures for cooked, internal color were determined for boneless pork longissimus muscle from 4 treatment groups: normal, normal-injected, PSE, and DFD. Visual and instrumental color, myoglobin denaturation, and acid phosphatase (ACP) of raw and cooked samples were evaluated. Visual internal color became (P < 0.05) less pink as endpoint temperature increased; however, DFD chops were more pink (P < 0.05) and PSE chops were less pink (P < 0.05) than other treatments at most endpoint temperatures. Cooked color was similar (P > 0.05) for chops from normal and normal-injected groups. Myoglobin denaturation increased as endpoint temperature increased. ACP activity in raw chops was not affected by treatment group and it was a good indicator of doneness at 71.1 °C.     

External Fat Cover Influence on Raw and Cooked Beef 2. Cooking Time, Losses, Press Fluid and Shear Force Values

SUMMARY: The semitendinosus muscle was used in a study of the influence of the external fat cover and the oven temperature on the characteristics of cooked beef. Roasts were cooked either with or without the external fat cover to an internal temperature of 58°C (rare). Two oven temperatures, 163° or 218°C, were used. The roasts cooked at 218°C required a shorter time in the oven than did the roasts cooked at 163°C but the presence or absence of the external fat cover had very little effect on the min per lb. Roasting at an oven temperature of 218°C caused significantly greater total cooking losses than roasting at 163°C. The cooking losses were increased significantly by cooking the roasts with the fat cover on, as compared with removing the external fat The increase was mainly due to an increase in the drip losses. The presence or absence of the external fat cover had a significant influence on the quantity of press fluid obtained from the samples. A greater amount of fluid was pressed from the roasts without the fat cover. The posterior ends of the muscle were more tender (as indicated by Warner Bratzler shear force values) than the anteriomr ends. The lower oven temperature also caused significantly more tender roasts.     

Response of Striated Muscle to Electrical Stimulation

SUMMARY— The response of striated muscle to electrical stimulation was studied in 30 Duroc pigs at two weights; and in 14 Poland China, 11 Yorkshire and 8 Yorkshire-Duroc crossbred pigs of market weight. The Duroc pigs in the heavyweight group were more responsive to electrical stimulation, had a slower rate of post-mortem pH decline and higher color-morphology ratings than the light weight group of Durocs.
The sex of the animal had only a slight effect on the response of the muscle to electrical stimulation. Muscles with a slow rate of glycolysis were significantly more responsive to electrical stimulation than those with an intermediate rate of glycolysis.
The initial lactic acid concentration, unless present in excessive quantities, appeared to have little influence on the responsiveness of the muscle to electrical stimulation. Lactic acid increased significantly, accompanied by a lowering of pH, during the electrical stimulation of the muscle.
Stimulation of the spinal cord caused a significantly lower color-morphology rating and pH in the Poland China and Yorkshire, but not in the Duroc animals. Electrical stimulation in animals other than Poland China did not produce pale, soft, exudative (PSE) musculature.
The electrical stimulatory response of red and white muscle was not significantly (P > .05) different; however, the data indicate that white muscle and PSE muscle do not respond in a similar manner to electrical stimulation.     

Early Post Mortem pH decrease in porcine M. longissimus dorsi of PSE, Normal and DFD quality

The purpose of this investigation was to compare the muscle pH at exsanguination and the rate of pH changes in porcine M. longissimus dorsi (LD) of normal, DFD (Dark, Firm, Dry) and PSE (Pale, Soft, Exudative) quality. The pH was continuously measured in the LD in 116 carcasses during the first 50 min post mortem. Calculations were made both on measured pH-values and on pH-values transformed to hydrogen ion concentrations. A regression of pH or hydrogen ion concentration on time was made for each animal. These individual regressions were then combined, using a multivariate analysis to estimate regression curves for each meat quality class. The two methods for expressing pH gave somewhat different results. The relationship between the hydrogen ion concentration and time was found to be linear for normal and DFD muscles and quadratic for PSE muscles. As a consequence of the mathematical properties of pH, the relationship between pH and time was found to be quadratic for the normal and DFD qualities, and linear for the PSE quality. For both methods of calculations the slopes for the regression curves were significantly different between PSE and the other two quality classes with both calculating methods, while the slopes did not differ between normal and DFD muscle qualities. The intercepts of the regression curves differed significantly between PSE and the other two quality classes only when the calculations were made on measured pH-values without transformation. A temporary increase in pH was seen in some normal and PSE carcasses during the measured time period. Development of muscles with PSE characteristics thus seems to be initiated by a combination of a lower muscle-pH already at exsanguination and a faster pH decrease. It is also of importance to consider the special mathematical properties of the pH-value.     

Water Extractable Proteins of Porcine Muscle

SUMMARY: The study was performed on 31 samples of porcine muscle (m. longissimus dorsi) of different qualities, ranging from extremely pale, soft and exudative (PSE) to dark red in color, firm in structure and dry in appearance (DFD) in order to determine the water solubility of muscle proteins 24 hr post mortem. It was found that the water solubility of muscle proteins depends on the quality of the muscle, and is lowest in extremely PSE muscle. It was demonstrated, with the aid of electrophoresis on agar and acrylamide gels, that some sarcoplasmic proteins which undergo precipitation 30 min after adding a citrate-phosphate buffer (pH 4.6) at temperature of 20°C are extracted in smaller amounts from PSE muscle than from normal muscle. One of these fractions was benzidine positive.     

CONSUMER EVALUATION OF PORK APPEARANCE WITH DIFFERING PHYSIOLOGICAL AND PACKAGING CONDITIONS

Consumers (n = 116) evaluated color (pink intensity), appearance (wet/dry), overall acceptability and purchase intent of normal, PSE and DFD pork loin slices in PVC and in vacuum packages. Packaging x muscle condition affected (p < 0.05) appearance, overall acceptability and consumer purchase intent of pork slices. Color differences were perceptible to consumers between packaging treatments. PVC-packaged pork was pinker than vacuum-packaged pork. Vacuum-packaged, PSE pork appeared drier than PVC-packaged PSE pork. Normal pork was more acceptable than PSE pork regardless of packaging. DFD pork acceptability was not different from that of normal pork when vacuum packaged. In general purchase intent paralleled consumer evaluation of overall acceptability. Instrumental color data and pH for samples evaluated are also presented.     

Effects of pork muscle quality on bacterial growth and retail case life

The effects of muscle quality (PSE, normal, DFD) upon the bacteriology and retail case life of pork chops were determined. Pork loin chops were processed from boneless backs after 90 days of frozen storage at -30°C. Variation in bacterial numbers was due to a highly significant (p < 0·001) storage time by muscle quality interaction. During simulated retail display, total psychrotrophs, Pseudomonas spp., Brochothrix thermosphacta and Enterobacteriaceae were lowest on PSE pork and highest on DFD pork in comparison to normal pork. Differences in bacterial densities were due to a longer lag phase in PSE pork and a shorter lag phase in DFD pork than in normal pork. Of the three muscle quality groups, DFD was most susceptible to the development of spoilage odours, while PSE pork was most sensitive to deterioration in appearance.     

Sensory Properties of Rib and Round Muscle Roasts from Two Beef Breed-Types on Two Feeding Regimes

Roasts from the rib and three round muscles obtained from Angus and Simmental Angus (SA) steers on two feeding regimes, high concentrate (HC) and pasture followed by short term HC, were roasted to an internal temperature of 65–68°C. Time of roasting, cooking losses, shear values, and pressed juice were determined. A trained sensory panel evaluated flavor, tenderness, juiciness, and overall acceptability. Sensory panelists scored flavor acceptability higher in SA roasts (P < 0.05) than in roasts from Angus steers. Flavor acceptability, overall acceptability, and tenderness were found to be higher in round muscle roasts from the HC feeding regime (P < 0.05) than in round roasts from the cattle fed pasture followed by short term HC.     

EFFECTS OF INJECTION OF A DILUTE PHOSPHATE-SALT SOLUTION ON PORK CHARACTERISTICS FROM PSE, NORMAL AND DFD CARCASSES

Phosphate-salt pump effects were evaluated on sensory characteristics of pale, soft, exudative (PSE) pork, normal and dark, firm and dry (DFD) pork. Water-holding capacity, instrumental color (L*, a*, b*), pH, and muscle color scores were determined at 24 h postmortem on pork loin pairs (n=21 pairs). Based on color score, paired loins were assigned to PSE, normal or dark, firm, dry groups. PSE muscles were lighter, redder and more yellow than normal or DFD muscles; hue angle indicated that DFD muscles were actually closer to the true red axis of the CIE Lab Color Space. Drip and purge losses were higher (p<0.05) in PSE muscles. Paired loins were pumped with water (controls) or 0.3% tripolyphosphate solution (0.25% salt) to 110% of original weight, vacuum packaged, frozen, cut into chops, and cooked to 70 or 80C. Phosphate-salt pumped loins were juicier and more tender (p<0.05) than water-pumped loins regardless of muscle condition. Loins cooked to 70C were juicier, were more tender (sensory) but required more force to shear than those cooked to 80C.     

CONSUMER EVALUATION OF SODIUM REDUCED, RESTRUCTURED LAMB ROASTS

The longissimus dorsi (LD) and psoas major (PM) muscles were removed from the racks and loins of nine lamb carcasses (18 sides). Each LD was cut in half to yield 36 pieces of each muscle. Three defatted LD pieces and one PM were randomly grouped together (4 replications) and assigned to the following treatments at 1.5% of the fresh muscle weight: (1) 100% NaCl (control); (2) 75% NaCl + 25% KCl; (3) 50% NaCl + 50% KCl. Water (5%) and sodium tripolyphosphate (.3%) were also added. Muscle pieces were tumbled for 2 h, tied into roasts, cooked and smoked. Proximate analysis results showed no significant differences (P > 0.05) among treatment groups for percentage moisture and fat. The 100% NaCl control had significantly higher (P < 0.05) cooking yields than the 50% KCl replacement treatment. A consumer sensory panel found no consistent differences among treatments for juiciness, flavor desirability, off-flavor, or overall acceptability among treatments. Consumer panel responses indicate that the low-fat (5.3–6.8%), low-sodium (455–744 mg/100g), restructured lamb roasts evaluated in this experiment would be an acceptable new processed lamb product.     

The Effects of Marination and Cooking Regimes on the Waterbinding Properties and Tenderness of Beef and Bison Top Round Roasts

ABSTRACT: The combined effect of marination and different cooking regimes on the cooking yield and palat-ability of bison and beef top round roasts was investigated. Semimembranosus (SM) muscles from beef and bison top rounds were injected with a marinade to achieve 20% extension by weight and 0.5% sodium chloride and 0.3% sodium tripolyphosphate levels and then subdivided into 4 roasts and cooked by following 4 cooking regimes: cooking at a constant temperature of 75°C (control; C); similar to the control treatment except that roasts were held at an internal temperature of 55°C for 45 min (Hold45) or 90 min (Hold90) prior to final cooking at 75°C; initial cooking at 55°C with a 5°C increase in oven temperature every hour (Step-up) until the 71°C internal temperature was achieved. Cooking yield, expressible moisture, purge, and shear force of processed roasts were determined. Marination by injection improved the yield and tenderness of beef and bison SM roasts. The cooking yield for injected samples (78%) was significantly (P < 0.05) higher compared with noninjected controls (68%). Injected SM roasts from bison had lower cooking losses than those from beef, whereas control samples from these 2 species did not differ in their cooking yields. Injected beef SM was more tender than bison SM; however, marination significantly reduced the shear force values of SM roasts for both species (i.e., shear force values of 82 N in control samples was reduced to 63 N in injected ones). The cooking regimes, Hold45, Hold90, and Step-up (which allowed a longer time at 55 to 60°C), gave products with lower ( P < 0.05) shear force values than those of the controls. Based on the cooking yield and time involved, the Hold 45 treatment performed the best.     

EFFECTS OF INHERENT MUSCLE QUALITY DIFFERENCES UPON THE PALATABILITY AND COOKING PROPERTIES OF VARIOUS FRESH, CURED AND PROCESSED PORK PRODUCTS

Ham steaks, loin chops, bacon slices, shoulder roasts and sausage patties fabricated from three muscle quality groups were utilized to evaluate the effects of muscle quality on palatability and cooking properties. Irrespective of muscle quality (pale, soft, exudative (PSE) versus normal versus dark, firm, dry (DFD)) all pork cuts evaluated were well within the acceptable range in palatability. In addition, results indicated that inherent muscle quality differences were of little relevance to the eating quality of pork. However, meaningful differences in cooking losses were observed from loin chops and bacon slices.     

Effects of low voltage electrical stimulation on mature cow carcasses: Part 1-Selected quality attributes of beef

The quality characteristics of semitendinosus (ST) and longissimus dorsi (LD) roasts obtained from mature carcasses subjected to extra low voltage (50-100 V) electrical stimulation (ES) were determined. ES was applied for 2 min with voltage increases to either 50 V (ES1) or 100 V (ESII). Evaluationss were conducted on meat obtained from control sides (no ES) aged for either 48h or 7 days and from ES carcasses aged for 48h. ES caused a reduction (P < 0·1) in pH values 1 and 4h post mortem. At 24h, the pH of each of the muscles from ES and control carcasses was similar. There were no differences in raw rib-eye muscle colour, firmness or texture due to ES. Cooking losses of ST and LD did not appear to be affected by either ES or increased ageing of control roasts. For both ST and LD roasts, trained panellists generally detected no significant effects of ES or ageing time (for no ES roasts) on palatability. Consumer panel judgements of ST roasts were similar to those of the trained judges. Water-holding capacity, tenderness (OTMS) and softness (penetrometer) data for ST and LD roasts generally support findings from sensory evaluation. Cooking and eating quality characteristics of ST and LD roasts from mature cow carcasses subjected to ES were similar to those of the controls.     

The relationship of sarcoplasmic and myofibrillar protein solubility to colour and water-holding capacity in porcine longissimus muscle

In order to investigate the relationship of sarcoplasmic and myofibrillar protein solubility to colour and water-holding capacity (WHC) in pork, 60 loins were selected to represent the quality classes: PSE (pale, soft, exudative), RSE (reddish-pink, soft, exudative), RFN (reddish-pink, firm, non-exudative) and DFD (dark, firm, dry). PSE samples exhibited lower (p<0.05) protein solubility (sarcoplasmic, myofibrillar and total) compared to the other quality classes. RSE samples exhibited lower (p<0.05) sarcoplasmic protein solubility compared to DFD samples. RSE, RFN and DFD samples had similar myofibrillar and total protein solubilities. Sarcoplasmic protein solubility explained 71% of the variation in lightness with a linear decrease in L* value. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) gels of the sarcoplasmic and myofibrillar samples distinctly showed the association of some sarcoplasmic proteins with the myofibrillar protein fractions in PSE and RSE samples. The sarcoplasmic proteins which precipitated were phosphorylase, creatine kinase, triose phosphate isomerase and myokinase for PSE and phosphorylase for RSE samples. Pork colour is highly correlated with precipitation of sarcoplasmic proteins while WHC is affected by denaturation of myofibrillar proteins (PSE samples) and lower ultimate pH (PSE and RSE samples).     

The colour of the adductor muscle as a predictor of pork quality in the loin

The relation between measurements of colour made in the m. adductor (AD) at 45 min or 20 h post mortem and the quality, assessed subjectively in terms of colour and waterholding capacity, of the m. longissimus (LD) in the loin was examined. The study used data from 100 pig carcasses exhibiting a wide range of meat quality from extreme PSE (pale, soft and exudative) to extreme DFD (dark, firm and dry). The subjective assessments were confirmed by objective measures of paleness (reflectance) and waterholding capacity (drip loss in storage) in the LD. Lightness (L^*) measured at 20 h post mortem in the AD was the best potential predictor of loin muscle quality, explaining 59% of the variation in subjective and objective quality measures. Comparable measurements at 45 min post mortem explained between 21% and 44% of the variation. The equation that described the relation between AD Lightness (L^*) and subjectively assessed LD quality was derived. This could be used to transpose the AD L^* values from a population of slaughtered pigs into nominal subjective scores for the LD, allowing the frequency of the five subjective quality groups (extremely DFD, slightly DFD, normal, slightly PSE, and extremely PSE) in the population of carcasses to be defined.     

Metmyoglobin Reducing Capacity of Fresh Normal, PSE, and DFD Pork During Retail Display

Fresh pale, soft, exudative (PSE), dark, firm, dry (DFD), and normal pork were stored under light or dark conditions at 4°C for 7 days. Sample pH, metmyoglobin reductase activity, oxygen consumption rate, and relative surface metmyoglobin and oxymyoglobin contents were determined. DFD pork had the highest metmyoglobin reductase activity and oxygen consumption rate. Enzyme activity of PSE was lower than that of normal pork, but no difference existed in oxygen consumption rate between PSE and normal samples. Metmyoglobin reductase activity dropped slowly during meat storage; oxygen consumption rate sharply decreased during the first day of storage. Both metmyoglobin reductase activity and oxygen consumption rate declined more rapidly in the light. Results can help develop guidelines for display and packaging of pork.     

Consumer-rated Quality Characteristics as Related to Purchase Intent of Fresh Pork

Consumers (n=556) rated pink color, wet/dry appearance, overall acceptability and purchase intent of normal, pale, soft and exudative (PSE), and dark, firm and dry (DFD) pork loin slices in PVC packages in five retail supermarkets. DFD samples appeared driest and PSE samples appeared wettest. Samples in the higher ranked two purchase intent categories appeared more wet than those in the lower three categories. The pinker PSE samples and all DFD samples were in the higher ranked purchase intent categories. Purchase intent generally paralleled overall acceptability; however, prediction equations indicated that wet/dry appearance, color and overall acceptability all contributed to purchase intent decision depending on muscle condition.     

Effect of ionizing radiation on quality characteristics of vacuum-packaged normal,pale–soft–exudative,and dark–firm–dry pork

Normal, pale–soft–exudative (PSE), and dark–firm–dry (DFD) pork Longissimus dorsi muscles were vacuum-packaged, irradiated at 0, 2.5 or 4.5 kGy, and stored at 4 °C for 10 days. The pH, color and lipid oxidation of pork were determined at 0, 5 and 10 days of storage. Volatile production from pork loins was determined at Day 0 and Day 10, and sensory characteristics at Day 7 of storage. Irradiation increased the redness of vacuum-packaged normal, PSE and DFD pork. However, the 2-thiobarbituric acid reactive substances (TBARS) values of three types of pork were not influenced by irradiation and storage time. Irradiation increased the production of sulfur (S)-containing volatile compounds, such as mercaptomethane, dimethyl sulfide, carbon disulfide, methyl thioacetate, and dimethyl disulfide, as well as total volatiles in all three types of pork. Normal pork produced higher levels of total and S-containing volatile compounds than the PSE and DFD pork did. The volatiles produced by irradiation were retained in the vacuum packaging bag during storage. Although the odor preference for the three meat types of pork was not different, the panelists could distinguish irradiated meat from the non-irradiated. Industrial relevance: Several US meat companies have already started test-marketing irradiated meat products. Irradiation and the subsequent storage of pork improved the color of PSE and DFD pork, and showed generally similar effects on the production of volatiles, except that there appeared to be a lower level of S-volatiles in the PSE than in the other two samples. This indicated that irradiation can increase the utilization of low-quality pork (PSE and DFD). DFD pork, in particular, which has shorter shelf-life than the others, could benefit the most from irradiation because the shelf-life of DFD meat can be extended significantly by both the methods of vacuum packaging and irradiation.     

External Fat Cover Influence on Raw and Cooked Beef. 1. Fat and Moisture Content

SUMMARY: The fat content of beef semitendinosus muscle, raw and cooked at two oven temperatures, with and without the external fat cover, has been determined. Each muscle was divided into two, an anterior and a posterior roast. The external fat cover was removed from half of the total number of roasts, and all roasts were then cooked to an internal temperature of 58°C at an oven temperature of either 163° or 218°C. Two types of samples were analyzed for their moisture and fat content. These were a separable lean sample and a total sample. The total sample was composed of both the separable lean and the external fat cover. The moisture content of the lean samples was not affected by the oven temperature, the external fat cover or the end of the muscle used. The total samples had moisture contents that reflected the amount of crude fat present. The yield of crude fat from raw or cooked meat was not significantly altered by the use of a polar solvent in place of a nonpolar one. Both of the fat determination methods extracted significantly more fat from the cooked lean samples than from the comparable raw ones. The lean samples from meat roasted at 163°C contained significantly more extractable fat than the samples roasted at 218°C. The presence or absence of the external fat cover did not affect the amount of fat extracted from the cooked lean.     

Muscle protein changes post mortem in relation to pork quality traits

The relationship between post-mortem traits of muscle proteins and water loss traits was investigated using 84 pork loins representing the four quality traits of PSE, RSE (reddishpink, soft, exudative), RFN (reddish-pink, firm, non-exudative) and DFD. Protein solubility measurements (sarcoplasmic, myofibrillar and total) were lower and myosin denaturation (quantified by myofibrillar ATPase activity) was higher for PSE samples compared with samples from the other quality classes. RSE samples were similar to RFN samples in protein solubility and myosin denaturation, although RSE had lower values then DFD samples for protein solubility measurements. RFN samples had lower drip, thaw, cook and total water loss than RSE samples and all water loss traits were lowest for DFD samples and highest for PSE samples. Insoluble phosphorylase was the only characteristic that differentiated among PSE, RSE and RFN samples. SDS-PAGE and Western blots indicated that in PSE and RSE samples, the myofibrillar protein titin was less degraded and nebulin was more degraded compared with RFN and DFD samples. SDS-PAGE of extracted and unextracted myofibrils showed that the reduced myofibrillar solubility of PSE samples was caused by decreased extractability of the myosin heavy chain in these samples. In conclusion, although RSE samples have unacceptably high water loss, muscle protein denaturation was minimal and did not explain the low water-holding capacity.