A study was undertaken to examine hygienic control of the slaughter and dressing process for beef cattle at Australian export processing establishments. Samples were collected from two points during the process: immediately after hide removal and at the completion of dressing before the commencement of chilling. Hindquarter (HQ) and forequarter (FQ) samples were collected from 24 establishments, half of which (n=12) employed some form of microbial intervention (in addition to trimming). The overall contamination level on carcass sides was low and was reduced between hide-removal and entering the chiller. The concentration and prevalence of indicator bacteria were higher on samples from HQ than on FQ. Application of an intervention, such as hot water, in addition to trimming resulted in a greater reduction in the concentration and prevalence of indicator bacteria than trimming alone, although the level of E. coli and coliform bacteria on all samples was too low to allow meaningful comparisons to be made. Salmonellae were isolated from 2.09% and 0.56% of post-hide removal and pre-chill samples, respectively. Application of an intervention in addition to trimming did not result in a significant reduction (p=0.4) of Salmonella prevalence on pre-chill carcasses. Low levels of bacteria were found on carcasses after hide removal. This, combined with small reductions as a result of trimming and sometimes other interventions, resulted in carcasses with very low levels of bacterial contamination . If performance metrics were to be applied to the slaughter and dressing process, a measure of the expected contamination at the end of the process would provide a more unequivocal measure of the process than either contamination on the carcass after hide removal or any reduction achieved as a result of the dressing process.
Australia exports about 150,000 to 200,000 tons of manufacturing beef to the United States annually. Each lot is tested for Escherichia coli O157 using the N-60 sampling protocol, where 60 small pieces of surface meat from each lot of production are tested. A risk assessment of E. coli O157 illness from the consumption of hamburgers made from Australian manufacturing meat formed the basis to evaluate the effect of sample size and amount on the number of illnesses predicted. The sampling plans evaluated included no sampling (resulting in an estimated 55.2 illnesses per annum), the current N-60 plan (50.2 illnesses), N-90 (49.6 illnesses), N-120 (48.4 illnesses), and a more stringent N-60 sampling plan taking five 25-g samples from each of 12 cartons (47.4 illnesses per annum). While sampling may detect some highly contaminated lots, it does not guarantee that all such lots are removed from commerce. It is concluded that increasing the sample size or sample amount from the current N-60 plan would have a very small public health effect.
The fourth national baseline microbiological survey of Australian beef was conducted in 2011, including frozen boneless beef and, for the first time, samples from selected beef primal cuts. Cartons of frozen boneless beef ( n = 1,165) sampled at 29 boning (fabrication) plants were found to have a mean total viable count of 2.2 log CFU/g, and the mean count for the 2.1% of samples with detectable Escherichia coli was 1.3 log CFU/g. The mean total viable counts for striploins (longissimus dorsi, n = 572) and outsides (biceps femoris, n = 572) were 1.3 and 1.5 log CFU/cm 2 respectively. E. coli isolates were obtained from 10.7 and 25.2% of striploins and outsides, respectively, with mean counts of −0.5 and −0.3 log CFU/cm 2 on positive samples. E. coli O157:H7, Salmonella , and Campylobacter were not isolated from any primal cut samples, and Salmonella was not isolated from any of the boneless product ( E. coli O157:H7 and Campylobacter were not tested for). Listeria spp. were not detected in any of the boneless product, and one Listeria isolate was obtained on 1 (0.2%) of 572 striploin samples. Coagulase-positive staphylococci were isolated from 3.4% of boneless beef samples, 7.7% of beef striploins, and 8.4% of beef outsides, with positive samples having mean log counts of 1.9 CFU/g, 0.2 CFU/cm 2 , and 0.2 CFU/cm 2 , respectively.
When vacuum-packed striploins and cube rolls processed by six Australian establishments were stored at −0.5°C to determine their shelf life, all product was acceptable organoleptically for at least 26 weeks. The aerobic plate counts and counts of lactic acid bacteria over the storage period did not accord with those established by previous studies, i.e., stationary phase attained at 7 to 8 log CFU/cm 2 after 5 to 8 weeks followed by the development of negative sensory characteristics around 12 to 16 weeks. Rather, counts rarely progressed to 7 log CFU/cm 2 even after 30 weeks. It is believed that the combined effects of meat pH, temperature, and CO 2 concentration may combine to create conditions in which little or no growth occurs.
A national survey of the microbiology of meat (ground beef and diced lamb) at the retail level in Australia was undertaken. For ground beef samples ( n = 360), the mean aerobic plate count (APC) was 5.79 log CFU/g, and Escherichia coli was detected in 17.8% of samples; the mean population for these positive samples was 1.49 log CFU/g. Enterobacteriaceae were detected in 96.9% of samples (mean for positive samples, 3.01 log CFU/g), and coagulase-positive staphylococci were detected in 28.1% of samples (mean for positive samples, 2.18 log CFU/g). For diced lamb samples ( n = 360), the mean APC was 5.71 log CFU/g, and E. coli was detected in 16.7% of samples (mean for positive samples, 1.67 log CFU/g). Enterobacteriaceae were detected in 91.1% of samples (mean for positive samples, 2.85 log CFU/g), and coagulase-positive staphylococci were detected in 22.5% of samples (mean for positive samples, 2.34 log CFU/g). Salmonella was recovered from 4 (1.1%) of the 360 ground beef samples (isolates were Salmonella Typhimurium phage types), and E. coli O157 was recovered from 1 (0.3%) of 357 samples; Campylobacter and Clostridium perfringens were not recovered from any of the 91 and 94 samples tested, respectively. Salmonella was recovered from 2 (0.6%) of the 360 diced lamb samples (serovars were Salmonella Infantis and Salmonella Typhimurium), Campylobacter was recovered from 1 (1.1%) of 95 samples, and C. perfringens was recovered from 1 (1.1%) of 92 samples.
Australian regulations for microbiological testing of carcasses specify a number of incubation temperatures and media for meat processed at both domestic and export establishments. Accordingly, the effect of incubation temperature and media on aerobic plate counts of samples from beef and sheep carcasses was investigated. For both species, aerobic plate counts on Petrifilm incubated at 35°C were significantly lower than those counts on Petrifilm and pour plates incubated at 25 and 30°C, reflecting the inability of many psychrotrophs to grow at 35°C. When samples were taken from carcasses that had been stored in abattoir chillers for periods between 16 h and 5 days, difference between counts at 35°C versus those incubated at 25 and 30°C became greater as the period of refrigerated storage increased. For export beef carcasses, the effect of this difference is minimal, since the vast majority of counts incubated at 35°C are done on carcasses that have been chilled for less than 24 h and will not have a large proportion of psychrotrophs.
The third national baseline microbiological survey of Australian beef carcasses and frozen boneless beef was conducted in 2004. Carcasses ( n = 1,155) sampled at 27 slaughter establishments had a mean aerobic plate count (at 25°C) of 1.3 log CFU/cm2. Escherichia coli was isolated from 8.0% of the carcasses, with a mean count of −0.8 log CFU/cm2 for positive samples. On samples from 24 boning (fabrication) plants ( n = 1,082), the mean aerobic plate count for frozen boneless beef was 1.3 log CFU/g, and the mean count for the 1.8% of samples with detectable E. coli was 1.5 log CFU/g. E. coli O157: H7 was isolated from 1 of 1,143 carcasses and from 0 of 1,082 boneless samples. Salmonella was isolated from 0 of 1,155 carcasses and from 1 of 1,082 samples of boneless product. No Campylobacter spp. were isolated from carcasses or boneless beef. Coagulase-positive staphylococci were isolated from 28.7% of beef carcasses and 20.3% of boneless beef samples, and positive samples had a mean count of 0.3 log CFU/cm2 and 0.8 log CFU/g, respectively.
A survey of the microbiological quality of beef carcasses and boneless beef produced in Australia was conducted during the period June to November 1998. Sponge samples were collected from 1,275 carcasses, and meat samples were drilled from 990 cartons of frozen boneless beef. Carcass and boneless beef samples were respectively collected from 21 and 27 establishments that concentrated on export and from 38 and 3 establishments supplying the Australian domestic market of which 31 were very small plants slaughtering no more than 150 cattle equivalents per week. The mean log total viable counts (TVCs) were 2.42/cm 2 and 2.52/g for carcasses and boneless meat, respectively. Escherichia coli was detected on 10.3% of carcasses and 5.1% of boneless beef samples and coagulase-positive staphylococci on 24.3% of carcasses and 17.5% of boneless beef. Salmonella was detected on 0.2% of carcasses and 0.1% of boneless beef and E. coli O157:H7 recovered from 0.1% of carcasses but not detected on 990 boneless beef samples. Mean log TVCs/cm 2 differed significantly ( P < 0.05) between establishment types. They were lower on carcasses from export establishments (2.20) compared with domestic (2.61) and very small plants (3.10). There were no significant differences in prevalence of Salmonella or E. coli O157:H7 between establishment types. Excision samples were taken from 670 carcasses to make comparisons with the first baseline study of Australian meat, carried out in 1993 to 1994. While there were differences in sampling and microbiological techniques between the two studies that require detailed consideration, there were small but significant improvements in several microbiological criteria for carcasses and boneless meat.
Microbiological quality of sheep carcasses and boneless sheep meat produced in Australia was surveyed during the period June to November 1998. Sponge samples were collected from 917 carcasses, and meat samples were drilled from 467 cartons of frozen boneless meat. Carcass and boneless meat samples were respectively collected from 7 and 10 establishments that concentrated on export, and from 36 and 5 establishments supplying the Australian domestic market of which 31 were very small plants slaughtering cattle and sheep but no more than 1,200 sheep equivalents per week. The mean log total viable counts were 3.55/cm 2 and 3.30/g for carcasses and boneless meat, respectively. Escherichia coli was detected on 29.2% of carcasses and 24.5% of boneless meat samples and coagulase-positive staphylococci on 24.1% of carcasses, and 38.6% of boneless meat samples. Salmonella was detected on 0.1% of carcasses and 1.3% of boneless meat samples. E. coli O157:H7 was recovered from 0.7% of carcasses and 1.3% of boneless sheep meat. There were statistically significant differences between establishment types for some microbiological criteria, although there were no significant differences in prevalence of Salmonella or E. coli O157:H7 between establishment types. While there were differences in sampling and microbiological techniques between this study and another conducted in 1993 to 1994 that require detailed consideration, there were small but significant improvements in several microbiological criteria for boneless meat. While data that would allow for comparison of carcass data were not gathered, it is unlikely that improvements in the microbiological quality of boneless sheep meat could accrue without improvements to carcasses.