Moisture Losses During Chilling from the Skin Surface of Scalded Pork Carcasses

The proportion of cooler shrinkage attributable to moisture loss from the skin of scalded, dehaired pork carcasses was estimated. Mean carcass cooler shrinkage was 1.91% during a 24 hr chill at —2°C. Approximately 80% of the cooler shrinkage was moisture endogenous to the skin. Thus, only 20% of total cooler shrinkage originated from the muscle and adipose tissue. Moisture was not absorbed in significant quantities by the skin during the scalding, dehairing and carcass washing process. Greater cooler shrinkage reported for scalded than for skinned pork carcasses was mostly a consequence of the widely different moisture content of the skin surface of scalded carcasses versus that of the adipose tissue surface of skinned carcasses.     

Physical and sensory attributes of hot-processed and conventionally chilled hams and bellies from electrically stimulated and non-stimulated pork carcasses

Forty-eight fresh hams and bellies were obtained from 24 market weight hogs (x = 94·5 kg) of which twelve were electrically stimulated (ES) by pulsing current immediately after exsanguination. The left side of each non-stimulated (NS) carcas was fabricated after conditioning for 3h post mortem at 17°C (NS hot-processed). The left sides of ES carcasses were fabricated 1 h pm. The right sides were fabricated following a 24 h cooler chill at 2°C (conventionally chilled: CP). Hams from ESCP carcasses had higher (P < 0·05) smokehouse yields than hams from NS carcasses. Hams that were hot-processed had higher smokehouse yields than the NSCP hams. Time of fabrication (1, 3 or 24h post mortem) did not affect smokehouse yields. Conventionally chilled bellies obtained from ES carcasses showed higher (P < 0·05) residual nitrite levels than those front electrically stimulated hot-processed (ESHP) carcasses. No differences were found for residual nitrite levels in the non-electrically stimulated sides. Panelists were unable to detect any sensory differences from the bacon strips. Sensory scores of ham slices were more juicy for non-stimulated hot-processed carcasses (NSHP) than those from ESHP carcasses. Panelists found the ham slices from NSCP carcasses to be more tender (P < 0·05) than those from electrically stimulated cold-processed (ESCP) carcasses. Results from this study clearly indicated that hot-processing of pork can provide hams and bellies that are acceptable for the production of cured hams and bacon of comparable quality and yield to those currently being produced under conventional processing methods.     

Hot water and organic acid interventions to control microbiological contamination on hog carcasses during processing

Pork skin and muscle tissue were washed with water at temperatures from 25 to 80 degrees C. Water temperatures of 65 and 80 degrees C resulted in greater population reductions of Enterobacteriaceae on pork muscle tissue than lower water temperatures. There was no observable effect of water temperature on population reductions of Enterobacteriaceae on pork skin. Water temperatures of 55, 65, and 80 degrees C reduced the populations of Enterobacteriaceae on inoculated scalded carcasses processed in a university abattoir by 1 to 1.5 log/cm2. Following the water wash with an organic acid rinse resulted in further numerical reductions in populations, although these were not statistically different from the water wash alone. The jowls of both scalded and skinned carcasses processed in a commercial establishment were directly inoculated with a fecal material slurry and then processed with organic acid rinsing only, hot water washing only, or a combination of hot water washing followed by organic acid rinsing. The hot water and acid treatment reduced the populations of mesophilic aerobic bacteria and Escherichia coli by approximately 2 log cycles on both scalded and skinned hog carcasses. The combined treatment resulted in 60% of the scalded carcasses and 40% of the skinned carcasses with undetectable levels of E. coli after direct fecal inoculation of the carcasses. Hot water washing followed by organic acid rinsing can significantly improve the microbiological quality of pork carcasses.     

Effectson carcass weight and meat quality of pigs dehaired by scalding or singering post-mortem

Two experiments were designed to compare the effects of two pig dehairing techniques. In the first experiment, 120 pigs were slaughtered in the same abattoir in five weekly sereis. One half of each series was dehaired by singeing (the usual technique in this abattoir), while the other half was dehaired in a scalding-dehairing combination. In the second experiment, 48 pigs were slaughtered in two series, one-half of each series in an abattoir practising singeing, the other half in an abattoir practising scalding. Temperature and pH were measured 30 min after slaughter in the longissimus lumborum. Meat quality was assessed the day after slaughter in various muscles. One ham was cured and cooked, while the other one was processed by dry-curing. In both experiments, carcass weights and yields were noticeably higher after singeing. Hams were heavier in singed carcasses, but their proportions in the carcasses were little or not at all affected by the dehairing technique. Proportions of loins, shoulders and bellies were similar with both dehairing techniques. The dehairing technique affected neither temperature nor rate of post-mortem pH fall. Meat quality as assessed on fresh meat was slightly better in singed carcasses. Weights of cooked ham and dry ham per side were higher in singed carcasses, due to the higher initial ham weight, but processing yields were not affected by the dehairing technique.     

Prediction of pork carcass composition based on cross-sectional region analysis of dual energy X-ray absorptiometry (DXA) scans

Dual energy X-ray absorptiometry (DXA) was used to measure pork carcass composition by performing a total scan of the right half of 262 pork carcasses (42.7±5.2 kg). The DXA scans were analyzed for percentage fat in the entire half-carcass as well as the shoulder, ham, loin, and side regions. In addition, a total of 14 cross-sections (57.6 mm wide) were analyzed: six in the shoulder/thoracic region, three in the loin region, and five in the ham region. Relative to the DXA measurement of total fat content, the coefficient of determination (R(2)) for a single cross-sectional slice ranged from 0.908 to 0.976. Relative to chemical analysis, a single slice from the ham region predicted the percentage of fat or lean in the half-carcass with an R(2) of 0.81 and a standard error of the estimate of 2.04. Prediction equations were used to analyze a separate group of 65 half-carcasses. These results indicate that carcass fat and lean percentages can be measured by performing a single-pass cross-sectional scan that would be compatible with on-line processing.     

Predicting pork carcass and primal lean content from electromagnetic scans

Fifty-four whole, pre-rigor, eviscerated carcasses (74.1±kg) were selected over a 5-week period to represent carcasses marketed to a Northwest Iowa packing plant during the fall season. Carcasses (spanning 40.7-65.2% carcass lean) were electromagnetically (EM) scanned before entering the chiller. Carcass right sides were fabricated and weights were recorded for each jowl, ham, loin, Boston butt, picnic shoulder, neckbone, sparerib, and belly. Each component was skinned and dissected into external fat, internal (seam) fat, bone, and lean with corresponding weights recorded. Regression equations were derived from points and areas taken from the EM scan curve. The best 5-variable equations were developed for total carcass lean (R(2)=0.9502; RMSE=1.31 kg), percentage carcass lean (R(2)=0.8789; RMSE=1.88%), ham lean (R(2)=0.8475; RMSE=0.755 kg), loin lean (R(2)=.8511; RMSE=0.781 kg), Boston butt lean (R(2)=.7251; RMSE=0.505 kg), picnic lean (R(2)=0.7387; RMSE=0.464 kg), and commodity, component carcass value (R(2)=0.9458; RMSE=$3.24).     

Prediction of lean and fat composition in swine carcasses from ham area measurements with image analysis

Video images of ham cross-sections were recorded from 71 pork carcasses (ranging in weight from 72 to 119 kg). Three sets of prediction equations were developed to estimate pork carcass lean and fat composition from video image analysis (VIA) of ham cross-sectional area measurements, 10th rib back fat depth (TENFAT) and hot carcass weight (HCKg). Carcass data of dissected lean and fat in the four primal cuts (ham, loin, Boston button and picnic shoulder) were used as dependent variables in establishing regression equations. The first set of equations combined VIA ham measurements and total ham weight (HTKg). Regression models containing the single variable HTKg times ham percentage lean area (Vol. 1) or HTKg times ham percentage fat area (Vol. 2) accounted for 88% and 68% of the variation in total carcass lean weight (CLKg) and total carcass fat weight (CFKg) from the right side of each carcass, respectively. The second set of equations combined VIA ham measurements and TENFAT (cm). Multiple regression models involving TENFAT, Vol. 1, and Vol. 2 accounted for 91% and 90% of the variation in CLKg and CFKg. The third set of equations used VIA ham measurements, TENFAT and HCKg. Carcass lean weight was best predicted by HCKg, TENFAT, and ham lean area (HLA) (R² = .92). Carcass fat weight was best predicted by HCKg, TENFAT, and Vol. 2 (R² = .91). Overall correlations showed a high association between Vol. 1 and CLKg (r = .94, P < .0001) and Vol. 2 and CFKg (r = .83, P < .0001). Ham lean area was related to CLKg (r = .74, P < .0001) and ham fat area to CFKg (r = .81, P < .0001). The results of this study indicated video image analysis of ham cross-section slices combined with backfat depth at the 10th rib can be used for accurate estimation of total carcass lean or fat composition.     

Contamination of pig hindquarters with Staphylococcus aureus.

Swab specimens from 4357 pig hindquarters provided for production of cured raw ham were contaminated with Staphylococcus aureus in 22.7%. The bacterial counts for S. aureus on the rind surface of the raw, uncured ham were between 10(1) and 10(3) cfu/cm2 in 89% of the positive samples. In the remaining 11% of contaminated ham counts of 10(3) to 10(6) cfu/cm2 were determined. There were major differences in the rate of contamination between pork from different suppliers. Questioning the suppliers revealed that pork highly contaminated with S. aureus could be traced back to certain abattoirs. This suggests that the technique of slaughter, concomitant hygiene precautions and the subsequent refrigeration of the carcasses affect the contamination of the meat with staphylococci.     

Nutrient Composition of Fresh Retail Pork

The nutrient composition of fresh pork was studied in samples from 71 carcasses. On separable lean, nutrient composition was determined for 7 raw retail cuts from one side of each of 11 carcasses, and nutrient retention was determined on the 7 matching cuts from the other side that had been cooked by common household methods. Loins from 60 additional carcasses were analyzed to determine whether USDA grades 1, 2, and 3 and region of production affected nutrient composition. The data indicated that variation in nutrient composition of pork is more dependent on the retail cut within the carcass than either the grade or the region of production of the carcass. Cooking method significantly affected retention of most of the nutrients analyzed.     

Improvement of the hygienic performance of the hindquarters skinning operations at a beef packing plant

The hindquarters skinning operations in a commercial beef carcasses dressing process were modified, and for short trial periods reorganized for the purpose of reducing the numbers of bacteria deposited on the carcasses. During performance of modified or reorganized operations, samples were obtained from randomly selected carcasses, by swabbing specified sites related to opening cuts, rump skinning or flank skinning operations, randomly selected sites along the lines of the opening cuts, randomly selected sites on the skinned hindquarters of carcasses, or randomly selected sites on carcass sides leaving the dressing process. For each form of the hindquarters skinning operations, a set of 25 samples of each type was collected, with a single sample being obtained from each selected carcass or side. Aerobic counts, coliforms and Escherichia coli were enumerated in each sample, and a log mean value was estimated for each set of 25 counts on the assumption of a log normal distribution of the counts. The data indicated that the log numbers of total aerobes, coliforms and E. coli that were deposited on carcasses during the modified hindquarters skinning operations were generally about 0.5, 1.0 and 1.0 log unit less, respectively, than the log numbers that had been deposited on the carcasses during the unmodified operations. Reorganization of the modified operations gave further small but consistent reductions in the numbers of bacteria. It, therefore, appears that changes to dressing procedures which are guided by appropriate microbiological data can produce consistent reductions in the microbiological contamination of carcasses.     

HOT-FAT TRIMMING OF PORK CARCASSES TO REDUCE PALE, SOFT AND EXUDATIVE PORK

Eighty market hogs were allotted to stressed and unstressed treatment groups, and one side of each carcass was conventionally chilled while the counterparts were hot-fat trimmed to 6.4 mm immediately postmortem. Temperature and pH declines were monitored after slaughter. At 2 h postmortem, internal ham temperatures from the hot-fat trimmed carcasses were about 3C lower (P < 0.05) than the control sides in both the stressed and unstressed groups but, no differences were found after 4 h. Muscle from stressed carcasses had a lower pH at 2 and 4 h postmortem with no differences after 4 h. Purge loss from vacuum packaged loins was evaluated after 7 and 14 days of storage. Hot-fat trimming reduced the incidence of PSE by 50%. The stressed carcasses had a 20% higher incidence of PSE. These results indicate that PSE can be reduced by decreasing muscle temperatures immediately postmortem through hot-fat trimming.     

不同屠宰工艺(剥皮和烫毛)对猪胴体表面微生物的多样性影响及关键点的控制研究

应用变性梯度凝胶电泳(Denaturinggradientgelelectrophoresis(DGGE))和经典微生物培养相结合的方法研究了剥皮和烫毛工艺中猪胴体表面污染的微生物数量和细菌多样性的变化以及3.5%乳酸处理后细菌总数和大肠菌群的变化。结果显示:不同猪胴体屠宰工艺中的微生物种类并不完全一致,微生物的污染多是由于前期的屠宰工艺引入;与剥皮工艺相比,烫毛后污染的微生物种类多,初始污染程度也较为严重;乳酸处理显著降低了剥皮工艺中的细菌总数,使出库猪胴体表面细菌总数降低到2.95logCFU/cm2,完全达到HACCP微生物的控制要求,但是没有降低烫毛工艺出库时的细菌总数,因此对不同的屠宰工艺应采取不同的关键点控制措施。     

Microbial assessment of an upward and downward dehiding technique in a commercial beef processing plant

Preventing microbial contamination during dehiding is challenging, and skinning methods are of critical importance for the hygienic status of beef carcasses. Two skinning methods are usually employed: upward hide pulling (UHP) and downward hide pulling (DHP). This study has compared the microbiological contamination of carcasses using both systems in a beef processing plant in the process of changing its dehiding method from UHP to DHP. 100 cm² areas from eight carcass sites (ham, chuck, rump, bung, flank, brisket, shin and neck) were sampled on 36 skinned carcasses dehided by each technique. Total viable counts (TVCs) and Enterobacteriaceae counts for each site were determined. No significant differences were observed in total (pooled-samples) carcass contamination regardless of the method used. However, significant differences (p < 0.05) in TVCs were observed at the flank, shin, brisket and neck. These differences can be attributed to possible deficiencies in the implementation of the HACCP pre-requisite programmes, and are not necessarily associated with the skinning method per se.     

Effect of pre-scalding brushing on contamination level of pork carcasses during the slaughtering process

The number of aerobic bacteria on the skin of pork carcasses was measured at seven different points on the slaughtering line in order to study the hygienic effect of pre-scalding brushing on the contamination level of carcasses. Eighty carcasses were investigated, of which 40 were brushed before scalding and 40 served as controls. Samples were excised from three sites: back, abdomen and ham. The total number of samples was 1368. The cleaning monitoring of the pre-scalding brushing machine and the blackscraping machine was done at the same time. After singeing and blackscraping there were significant differences (P<0·05) between brushed and non-brushed ham sites. After singeing, brushed ham sites had a contamination level of 2·11 (log(10) cm(-2)) and non-brushed ham sites a level of 1·57. After blackscraping the contamination of brushed ham sites was 3·45 (log(10) cm(-2)) and that of non-brushed ham sites 3·26. At the end of the slaughtering line brushed carcasses were more contaminated than those not brushed, although this difference was not significant.     

雾化喷淋冷却对猪半胴体干耗及品质的影响

为了解决实际生产中猪半胴体在冷却过程中干耗较严重的问题,选取宰后45min内的猪半胴体,研究了不同持续时间(4、8、12、16h)的雾化喷淋冷却处理对猪半胴体干耗及各项品质指标的影响。结果表明:雾化喷淋冷却能显著降低胴体24h冷却干耗,半胴体表面微生物数量稍有上升,喷淋对背最长肌货架期的影响并不显著。随着喷淋持续时间的延长,肌肉保水性降低,但对背最长肌L*、a*、b*值影响不大,脂肪L*值略有上升,且喷淋时间超过12h后脂肪颜色变亮、变灰。各处理组间半胴体冷却速率基本没有差异(p>0.05),16h喷淋组在冷却结束时pH偏低。     

Characterization of the Arcobacter contamination on Belgian pork carcasses and raw retail pork

In the present study, the occurrence of Arcobacter was assessed at four sites on 169 porcine carcasses (foreleg, chest, pelvis and ham) at different stages of slaughter and 47 pork products at retail. Carcass swab samples were enriched in Arcobacter broth containing 5-fluorouracil, amphotericine B, cefoperazone, novobiocine and trimethoprim as selective supplement. After microaerobic incubation, arcobacters were isolated using Arcobacter selective agar plates, containing the selective supplement described above. Some carcass samples and all pork samples were also examined quantitatively. All 862 isolates were identified by a species-specific m-PCR-assay and 182 isolates were further characterized by ERIC-PCR. Arcobacters were isolated from one or more sampling places on 96.4% of the carcasses, with the foreleg and the chest area as the two most contaminated sites. Furthermore, A. cryaerophilus was the most common species. Chilling decreased the number of positive carcasses, but did not eliminate all arcobacters. Direct isolation revealed that only a few carcasses were contaminated with arcobacters on foreleg and/or chest at levels higher than 10(2 )cfu/100 cm(2). Characterization demonstrated a large heterogeneity among the isolates, with ten genotypes present on more then one site per carcass. Fourteen genotypes were simultaneously present on carcasses from different herds slaughtered on the same day, which may indicate cross-contamination. Arcobacters were present in 21% of the pork samples taken at retail, but contamination levels did not exceed 100 cfu per gram. Characterization of the A. butzleri and A. cryaerophilus isolates indicated an additional contamination during processing at retail.     

Estimation of Canadian and European lean yields and composition of pig carcasses by dual-energy X-ray absorptiometry

Dual-energy X-ray absorptiometry (DEXA) was used on 110 pig carcasses to estimate fat, lean, bone mineral content and total tissue masses of the major primal cuts and overall carcasses. The DEXA estimations were compared and used to predict the dissected lean, fat (including skin), bone and weight of primal cuts and carcasses, as well as to predict the Canadian and the European lean yields. The best relationships were obtained when predicting the weight of ham (R(2)=0.99), loin (R(2)=0.99), shoulder (R(2)=0.96), belly (R(2)=0.93), half carcass (R(2)=0.98), ham lean (R(2)=0.89), loin lean (R(2)=0.89), shoulder lean (R(2)=0.87), and the meat weight used in the estimation of the Canadian (R(2)=0.92) and the European lean yield (R(2)=0.82). While the weight of fat in the carcass and primal cuts was accurately estimated by DEXA (R(2)>0.72), DEXA carcass composition estimations were less accurate when predicting dissected bone weights (R(2)<0.54).     

Evaluation of some objective methods for measuring pork quality

Several objective methods for estimating pork quality were evaluated, by correlating instrument values against visual scores by an experienced panel. The measurements examined were reflectance, fibre optic probe, pH, drip and Kapillarvolumeter values. Measurements were made on intact carcasses or after cutting across at the shoulder, mid-loin and ham. In chilled pork cuts, the fibre optic probe (FOP(u) value) and reflectometer agreed most closely with panel scores (r = 0·71 and 0·78, respectively). The probe has the added advantage of providing a useful indication of meat quality in the uncut carcass. Drip loss was about equally correlated with FOP(u), reflectance and Kapillarvolumeter values (r = 0·7 in all cases). In hot carcasses, the fibre optic probe (FOP(l) value) was superior to the pH(l) value for predicting panel score (r = 0·76 and -0·53 respectively) and reflectance (r = 0·80 and -0·60), whereas pH(l) was better than FOP(l) for predicting drip loss (r = -0·65 and 0·55).     

Chemical and structural changes in dry-cured hams (Bayonne hams) during processing and effects of the dehairing technique

Pigs of similar genetic backgrounds and feeding regimes were slaughtered in two abattoirs, one carrying out dehairing by scalding and the other by singeing. One ham from each of 80 carcasses was retained. Sixteen fresh hams (8 from each dehairing technique) were used for analysis while 64 hams were processed into dry-cured ham. Sixteen hams (8 from each dehairing technique) were taken for analysis at end of salting (day 14), end of rest (day 78), mid-processing (day 127) and end of processing (day 251). During processing, the water content of all muscles decreased while the salt content increased. The salt concentration in muscle water tended to equalize in all muscles. The nitrogen content of desalted dry matter (i.e. dry muscle tissue) decreased in both Biceps femoris and Semimembranosus. The content of every free amino acid increased with time, except for taurine and glutamine. Electrophoresis of the low ionic strength-soluble fractions showed all protein bands decreased during processing. Electrophoresis of the myofibrillar fractions indicated changes in all bands except actin (42kDa). These changes were more marked in the Semimembranosus than the Biceps femoris in the earlier processing steps. Ultrastructural changes were more marked in Semimembranosus than Biceps femoris. Hardness and chewiness increased in both muscles during the first half of processing then returned to values close to the initial ones in Semimembranosus but changed little in Biceps femoris. The scalded hams lost more weight than the singed ones during processing. The salt content was higher in scalded hams. Water-soluble nitrogen and NPN were higher in singed hams at the end of processing. The scalded hams were saltier and pungent. They had more pronounced aromas of dry ham, rancidity and hazelnut, and less aroma of fresh meat. Their texture was drier and less mellow.     

猪肉色泽和保水性的相关性研究

以猪瘦肉为原料展开猪肉色泽和保水性之间的相关性研究,一部分以来源于同一猪胴体的肉样为原料,另一部分采用从市场上随机抽样的样品为原料,研究肉样的保水性和肉色之间的相关性。结果表明：对于来源于同一个体的肉样而言,保水性与色泽无关;而来源于不同个体的肉样,加压系水力(WHC)与亮度(L 值)呈负相关,蒸煮损失与L 值和黄度(b 值)呈正相关,即L 越大,b 越大,保水性越差;在实验测定的范围内,pH 值与蒸煮损失呈负相关,与加压系水力呈正相关,表明pH 值越高的肉样,保水性越好;来源于同一个体的肉样,随着宰后时间的延长,其保水性有增强的趋势,表现为蒸煮损失与时间呈负相关,加压系水力与时间呈正相关。