Visible contamination on animals and carcasses and the microbiological condition of meat

It is generally assumed that preventing visible contamination of or removing visible contamination from carcasses will enhance the microbiological safety of meat. Visible contamination of carcasses can be reduced by washing or otherwise cleaning animals before slaughter, by dehairing hides before carcasses are skinned or dressed with the skin on, or by performing skinning and eviscerating operations in manners that avoid the transfer of filth from the hide to the meat or the spillage of gut contents. Visible contamination can be removed by washing, trimming, or vacuuming carcasses. The available data appear to indicate that, of the various actions that can be taken to obtain carcasses that are free of visible contamination, only minimizing the visible contamination of meat during skinning and eviscerating operations may also ensure a degree of control over the microbiological contamination of meat. It might be preferable for visible contamination to be controlled largely by superior skinning and eviscerating practices rather than by animal or carcass cleaning treatments, which may not prevent the depositing of bacteria on or the removal of substantial numbers of bacteria from carcasses.     

Performance characteristics of three different pre-evisceration wash regimes applied to the forequarters of ovine carcasses in an inverted dressing system

The performance of three pre-evisceration wash regimes applied to the forequarters of ovine carcasses in an inverted dressing system was assessed. Washing regimes consisted of a high-pressure jet wash, a low-pressure sluice wash, and both washes applied in series. Visible contamination incidences prior to the wash were between 64 and 71% at the carcass level; wool was the predominant contaminant, while faecal material and ingesta were rare. All wash regimes reduced the incidence of carcass contamination by 62·8 to 70·5%, primarily through the removal of wool. A secondary effect was the redistribution of some wool from other areas of the forequarter to the inside leg. The sluice wash was superior to the jet wash in removing visible contamination. Bacterial numbers ranged from 3·64 to 4·03 log(10)CFU/cm(2) prior to washing and were reduced to between 3·24 and 3·75 log(10)CFU/cm(2) immediately after the pre-evisceration wash; the three wash regimes performed in an equivalent, but commercially non-significant manner. Further reductions of between 0·20 and 0·58 log(10)CFU/cm(2) were effected by post-dressing events, including 12 h chilling. The low-pressure wash performance was considered superior to that of the jet wash, and no further improvement in carcass quality was demonstrated by the use of both washes in series.     

Microbiological conditions of sheep carcasses from conventional or inverted dressing processes

At a small abattoir, 25 sheep carcasses were dressed conventionally, with the carcass suspended by the rear legs, and 25 carcasses were dressed while inverted, with the carcasses suspended by the forelegs. Two swab samples were obtained from randomly selected sites on each carcass, and total aerobic, coliform, and Escherichia coli counts were enumerated for each sample. Each type of count was arranged in two sets of 25 counts for each type of dressing process, and a log mean number and/or log total number recovered was calculated for each set of counts. The log mean number of total aerobic counts for one set of counts from carcasses dressed while inverted was less than the corresponding log mean numbers for both sets from the conventionally dressed carcasses and the other set from the carcasses dressed while inverted, and differed from them by about 0.7 log units. The coliforms recovered from carcasses were largely E. coli. The log total numbers of coliform or E. coli counts recovered from carcasses dressed while inverted were about 1.5 log units less than the corresponding log total numbers recovered from conventionally dressed carcasses. Those data indicate that the substitution of inverted for conventional dressing might serve to reduce the numbers of E. coli on sheep carcasses by reducing the microbiological contamination of the hindquarters but that the general microbiological condition of the carcasses would be little improved unless some means of preventing or removing contamination of the forequarters was also used.     

Determination of the principal points of product contamination during beef carcass dressing processes in Northern Ireland

To determine the principal points of microbial contamination of carcasses during beef carcass dressing in Northern Ireland, 190 carcasses were sampled by swabbing 1,000 cm2 of the brisket. A detailed survey of one abattoir was initially conducted, with sampling of a total of 100 carcasses immediately after hide removal (H), after carcass splitting (S), and immediately after washing (W) before dispatch to the chiller. The total bacterial counts after incubation at both 22 and 37 degrees C indicated that there was no significant increase in the numbers of bacteria after the first sampling point, H (P > 0.05). To determine whether this was the case in the majority of Northern Ireland abattoirs, 15 carcasses were then sampled at each of an additional six abattoirs, at points H and W only. Total bacterial counts were significantly higher (P < 0.05) at H than at W, indicating that hide pulling was the major point of bacterial contamination of beef carcasses and hence a critical control point for the final microbiological quality of the carcasses. Mean counts of Enterobacteriaceae at both incubation temperatures were very low (< 10 CFU/cm2) but were higher at W than at H, probably indicating that washing was redistributing bacteria from the posterior to the anterior region.     

Microbial populations on animal hides and beef carcasses at different stages of slaughter in plants employing multiple-sequential interventions for decontamination

Multiple-sequential interventions were applied commercially to reduce beef carcass contamination in eight packing plants. The study evaluated microbial populations on animal hides and changes in carcass microbial populations at various stages in the slaughtering process. Sponge swab samples yielded mean (log CFU/100 cm2) total plate counts (TPC), total coliform counts (TCC), and Escherichia coli counts (ECC) on the exterior hide in the ranges of 8.2 to 12.5, 6.0 to 7.9, and 5.5 to 7.5, respectively, while corresponding contamination levels on carcass surfaces, after hide removal but before application of any decontamination intervention, were in the ranges of 6.1 to 9.1, 3.0 to 6.0, and 2.6 to 5.3, respectively. Following the slaughtering process and application of multiple-sequential decontamination interventions that included steam vacuuming, pre-evisceration carcass washing, pre-evisceration organic acid solution rinsing, hot water carcass washing, postevisceration final carcass washing, and postevisceration organic acid solution rinsing, mean TPC, TCC, and ECC on carcass surfaces were 3.8 to 7.1, 1.5 to 3.7, and 1.0 to 3.0, respectively, while corresponding populations following a 24 to 36 h chilling period were 2.3 to 5.3, 0.9 to 1.3, and 0.9, respectively. The results support the concept of using sequential decontamination processes in beef packing plants as a means of improving the microbiological quality of beef carcasses.     

The development of a 'clean sheep policy' in compliance with the new Hygiene Regulation (EC) 853/2004 (Hygiene 2)

The aim of this research was to identify the risk factors associated with the transfer of bacterial contamination from the fleece to the ovine carcass thereby providing the scientific basis for the development and validation of a clean sheep policy. Two hundred sheep in lairage were graded into five categories each consisting of 40 sheep. The categories were as follows; (A) clean and dry; (B) clean and wet; (C) dirty and dry; (D) dirty and wet and (E) visible dags (dung-clotted tufts of wool) categorized by the chief veterinary inspector at the slaughter plant based on the visual inspection of the hygienic status of the fleece. Microbiological evaluations of the carcasses were conducted using swab sampling methods. Total viable counts (TVCs), Enterobacteriaceae and coliform counts were obtained from 40 animals per category at four separate sites (brisket, shoulder, flank and rump) immediately after pelt removal. Statistical analysis of TVC data obtained from the carcass indicated that the dirt level of the fleece had a significant effect on contamination levels when the fleece was dry. Enterobacteriaceae and coliform counts suggest that dirt was a contributing risk factor regardless of wetness or dryness of the animal. The clean sheep policy should therefore differentiate between clean and dirty sheep and mandate additional hygiene measures for the latter.     

Microbiological conditions of detained beef carcasses before and after removal of visible contamination

The microbiological conditions of carcasses detained for the removal of visible contamination at four beef packing plants were examined. The numbers of aerobes and Escherichia coli recovered from most visibly contaminated sites did not exceed numbers generally regarded as acceptable for beef carcasses. The numbers of bacteria at visibly contaminated sites were reduced when those sites were trimmed, but additional and/or routine decontaminating treatments after trimming gave greater reductions in numbers at three of the plants. At each plant, at the end of the dressing process, the microbiological condition of the carcasses that had been detained was similar or superior to the condition previously determined for carcasses routinely produced from the process.     

SOURCES OF CONTAMINATION DURING SLAUGHTER AND MEASURES FOR CONTROL

This paper is concerned with processes and procedures involved in the contamination of beef, lamb and pork carcasses during slaughter. The hides of beef and the fleece of sheep are major sources of carcass contamination. The spread of pathogens from beef hides to the carcass, operatives and surfaces in the abattoir is demonstrated. Efforts to clean the hide of cattle and the fleece of sheep are outlined, with reference to the success of these treatments in reducing carcass contamination. The effect of bringing very dirty or dungy animals to slaughter is considered in terms of the effect on carcass contamination after slaughter. The influence of tying the bung (or rectum) in reducing carcass contamination is discussed, as is the use of plastic bags as an additional control in preventing pathogen spread on pig carcasses. The relationship of this revised procedure in reducing the occurrence of yersiniosis in Norway is shown. The use of a commercially automated system to tie beef bungs is discussed in relation to reducing carcass contamination. A comparison between the removal of faecal contamination on carcasses by trimming or using a new steam-vacuumized system is presented. The effect of preevisceration washing of beef carcasses is described and the rationale relating to bacterial removal using this treatment is discussed. The influence of evisceration as a source of carcass contamination is demonstrated in relation to sheep slaughter. The processes of carcass decontamination using washing with water at different temperatures, steam pasteurization and hot lactic acid are compared in relation to their ability to remove bacteria from beef carcass surfaces. Finally, the effect of line speed and the impact of technology advances on beef and sheep carcass contamination is reviewed.     

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.     

FECAL COLIFORM CONTAMINATION OF BEEF CARCASSES DURING THE SLAUGHTERING PROCESS

The purpose of this study was to determine the fecal coliform counts of beef carcasses during different stages in the slaughter process. A total of nine carcasses were selected at random in the abattoir. The samples were taken by excision from three different sites; rump, brisket and shoulder. The samples were collected from the same carcasses at four different stages of processing; after dressing, after evisceration, after washing and after chilling for 24 h in a chilling room. The processing steps did not increase the fecal coliform counts on the rump samples. There were no significant differences in the samples of rump and shoulder among different processing steps. The contamination level of the brisket after washing was significantly higher than other processing steps. Brisket and shoulder parts are critical points for microbiological sampling as these sites showed higher microbial counts after chilling steps. The data obtained have relevance for the planning of washing methods for the production of clean and safe carcasses.     

Comparison of stunning methods in the dissemination of central nervous system tissue on the beef carcass surface

Beef carcasses were examined to explore the effects of stunning methods on central nervous system tissue (CNST) dissemination on the surface during the slaughtering process. The frequency of occurrence of CNST contamination on four defined parts, each on the interior and exterior surfaces of the split carcass, and their level of the contamination were measured by an ELISA test. The effect of hot carcass weight was also examined. The results showed that the frequency of contamination occurrence was not affected by the stunning method. However, the penetrating captive bolt stunning method resulted in a higher level of CNST contamination than non-penetrating sledge-hammer stunning (P < 0.001). The higher level of contamination occurred on the interior surface of carcasses along the vertebral area. Therefore, the dissemination of CNST on carcasses seemed to be affected by the stunning method, carcass splitting, and carcass washing. The carcass weight significantly affected the level of CNST contamination on the carcass (P < 0.01) but there was no interaction with the stunning method.     

MICROBIOLOGICAL CONDITIONS OF SHEEP CARCASSES DURING THE SLAUGHTERING PROCESS

This study was undertaken to determine the microbiological quality of sheep carcasses during different stages in the slaughtering process. A total of eleven carcasses were selected at random in an abattoir. The samples were taken by excision from four different sites; leg, brisket, shoulder and neck. The samples were collected from the same carcasses at four different stages in the slaughtering process; after dressing, after evisceration, after washing and chilling. The aerobic mesophilic bacteria, coliforms and Enterobacteriaceae recovered from each sample were enumerated. Chilling reduced the aerobic mesophilic and coliform counts of carcasses, significantly. Levels of carcass microbial load after chilling were 1.69, 0.11 and 0.11 log cfu/cm² for aerobic mesophilic counts, coliform counts and Enterobacteriaceae counts, respectively. According to data obtained in the present study, chilling of carcasses was the most important step in improving the hygienic quality of carcasses. Processing stages changed significantly both aerobic mesophilic and coliform counts of neck, therefore, among different sites of carcass, neck should be the only critical site for microbiological sampling for sheep carcasses.     

基于ADAMS的倾斜式羊扯皮机运动仿真分析

基于运动学仿真软件ADAMS,对倾斜式羊扯皮机进行了虚拟建模并进行运动仿真分析,得到了主要部件的位移曲线和角速度曲线等。通过对两种扯皮机水平方向运动分别与羊胴体运行曲线进行比较,得出倾斜式扯皮机水平方向运动与羊胴体运动曲线接近程度更高一些,相对运动曲线更接近于零线;从而得出倾斜式扯皮机更适合用于连续羊屠宰生产线上。     

Microbiological condition of horse meat prepared at a North American packing plant, and control of the temperatures of product air freighted to Europe

To obtain information about the microbiological quality of horse meat exported from North America, the microbiological conditions of hot or cold boned primal cuts and carcass quarters from horse carcasses processed at a North American packing plant were examined. In addition, temperature histories were obtained from boxes of hot boned meat during cooling, and from horse carcass quarters air freighted to Europe. The log mean numbers of aerobes recovered from horse carcasses after dressing were >2 logcfu/cm(2). Log total numbers of coliforms and Escherichia coli recovered from 25 samples from such carcasses were >2 log and <2 logcfu/2500 cm(2), respectively. Numbers of bacteria generally similar to those were recovered from cooled carcasses or hot or cold boned cuts. The cooling process for hot boned meat met with standards for hot boned beef cooling processes based on calculated growth of E. coli at box centres. The deep tissues of carcass quarters cooled and the temperatures of their surfaces rose during air freighting, but surface temperatures mostly remained below 7 °C. The microbiological condition of horse carcass quarters delivered to plants in Europe would likely be comparable with the microbiological conditions of hanging beef delivered from packing plants to distant customers within North America.     

Microbial contamination on beef in relation to hygiene assessment based on criteria used in EU Decision 2001/471/EC

Thirty-six carcasses were sampled over a 12-month period at an Irish beef abattoir. Between one and five carcass sites (including the hock, brisket, cranial back, bung, inside round and outside round) were sampled after hind leg skinning, hide removal, bung tying, evisceration, splitting, washing, chilling for 24 h and boning, using a wet and dry, cotton wool swab technique. For each sample, total viable counts (TVC), Escherichia coli, total coliforms and Enterobacteriaceae were enumerated. The results are considered in relation to European Union Decision 2001/471/EC which sets performance criteria for TVCs and Enterobacteriaceae in samples taken by excision. Though not explicitly stated in the Decision, it has been proposed that microbiological performance criteria for samples taken by swabbing be set at 20% of the values set for excision samples. Therefore, log mean TVCs in carcass swab samples taken before chilling are acceptable, marginal and unacceptable when they are <2.8, 2.8-4.30 and >4.30 cm(-2), respectively. By these criteria, TVCs on carcasses in the present study were in the marginal range. The marginal result for TVCs was due in the most part to hide removal operations, particularly at the hock and brisket sites. Bacterial contamination on post-chill carcasses was similar or lower to that on pre-chill carcasses, while boning resulted in general increases in TVCs and in E. coli, total coliform and Enterobacteriaceae numbers. In Decision 2001/471/EC, the effects of chilling and boning are not included in the assessment of process control. Data from this study indicate that performance criteria based on log mean Enterobacteriaceae values are unsuitable because of the infrequent occurrence of these organisms on the carcass.     

Management of risk of microbial cross-contamination from uncooked frozen hamburgers by alcohol-based hand sanitizer

This research was undertaken to determine the effectiveness of an alcohol-based hand sanitizer on hands contaminated with a nonpathogen surrogate for Escherichia coli O157:H7, where the source of the contamination was frozen hamburger patties. A nonpathogenic nalidixic acid-resistant food-grade strain of Enterobacter aerogenes was used to inoculate frozen hamburger patties composed of 76% lean beef and 24% fat. Thirty-two individuals participated to produce the data used in this study. Each participant handled nine patties at least three times, a sample for microbiological analysis was collected from the surface of one hand, the participant sanitized both hands, and a sample was collected from the other hand. Burger handling created perceptible and visible food debris on the hands of most participants. Computer simulations also were used to perform a variety of risk calculations. The average reduction in bacteria from the use of sanitizer on hands contaminated by frozen burgers containing E. aerogenes was 2.6 +/- 0.7 log CFU per hand. An experiment designed to simultaneously test the effect of sanitizer on E. aerogenes and E. coli O157:H7 also revealed no significant difference in sanitizer effectiveness against the two organisms. The results of the real-world risk estimation calculations (using the actual prevalence and concentration of E. coli O157:H7 in ground beef) predict that once in 1 million trials, a single pathogen cell will be transferred to a single lettuce piece. The effectiveness of this sanitizer intervention was similar to that for hand washing and glove use previously reported. The person-to-person microbial reduction variability from sanitizer use is similar to published data for glove use and was less variable than published data on hand washing effectiveness.     

The Microbiological Status of Carcasses from Wild Boar in Serbia

In this study, the microbiological status of wild boar carcass meat and the likely sources of its contamination were investigated. Wild boar carcasses (125) were analysed for Total Viable (TVC) and Enterobacteriaceae Count (EBC). The mean TVC and EBC on the skin were 3.5 and 2.1 log₁₀ cfu/cm², whereas higher levels of 4.3 and 2.9 log₁₀ cfu/cm² were determined on carcass meat, respectively. No difference was determined when TVC and EBC were compared between animals shot in the abdominal region and those shot elsewhere, indicating that inadequate hygiene in carcass handling was the reason for high level of microbiological contamination.     

Assessing the hygiene of pig carcasses using whole-body carcass swabs compared with the four-site method in EC Decision 471

An investigation was carried out in a pig abattoir to determine the microbiological status of carcasses being produced after slaughter and dressing. The carcasses were sampled in accordance with EC Decision 471 in relation to the application of hazard analysis critical control point (HACCP) criteria to the slaughter of animals. In this regard, four sites on the animals were examined on five consecutive carcasses during each of 10 visits for the presence of total viable counts and Enterobacteriaceae. A comparison of the EC four-site method, with a whole-body swab technique, as a means of measuring carcass contamination found that the two methods gave significantly different results for both groups of organisms. A comparison of the mean of the individual data from the four sites with the data from the pooled samples revealed that there was a poor relationship between the two. Samples may be taken by excision or swabbing and allocated to three categories of process control, which, in turn, are based on microbiological criteria that are different, depending on whether sampling is by excision or swabbing. The influence of these changes in microbiological criteria is discussed in relation to the categorization of samples as acceptable, marginal, or unacceptable and the influence this has on process control. Finally, the proposed introduction of Salmonella as a safety indicator in the EC HACCP system is discussed.     

Evaluation of control over the microbiological contamination of carcasses in a lamb carcass dressing process operated with or without pasteurizing treatment

The aim of this study was to quantify the hygienic status of a lamb slaughterhouse by means of multivariate statistical analysis, to demonstrate how the microbiological data could be exploited to improve the lamb slaughter process by constructing control charts and to evaluate the potential effect of an intervention step such as steam application on the microbiological quality of lamb carcasses. Results showed that pelt removal and evisceration were hygienically uncontrolled. TVC and Enterobacteriaceae progressively increased from the stage ‘after pelt removal of hind and forelegs/before final pulling’ to the stage ‘after evisceration/before pluck removal’ thus indicating possible deposition of microorganisms during these operations. It seems that the processing stages of freshly produced carcasses were better distinguished by Enterobacteriaceae, with evisceration contributing mostly to the final Enterobacteriaceae counts. Application of steam during the lamb slaughter process reduced microbial counts without adverse effects on the organoleptic characteristics of the carcasses. Moreover, the construction of control charts showed that decontamination with steam contributed to the maintenance of an in control process compared to that before the application of steam, suggesting the potential use of steam as an intervention step during the lamb slaughter process.     

CONTAMINATION AND DECONTAMINATION OF POULTRY CARCASS NECK TISSUE

Water absorption and changes in surface microtopography are major determinants of contamination of the underside of neck tissue. Salmonella cells adhere firmly to this tissue but cannot be effectively removed because of the major contribution of physical entrapment to the overall level of contamination. Heat and/or sorbate treatments can bring the bacteriological quality of neck tissue to that of the rest of the carcass but removal of this tissue is the most effective means of decontamination.