Microbiology of charcoal-broiled European river lampreys (Lampetra fluviatilis) stored at 3 and 22 degrees C

The microbiological quality of 30 production lots of charcoal-broiled river lampreys was studied at three lamprey processing plants (plants A, B, and C). Samples were taken directly after charcoal broiling and stored at 22 and 3 degrees C. Lampreys were examined on the day of manufacture, and those kept at 22 degrees C were examined every second day for 6 days. Samples kept at 3 degrees C were examined every fourth day for up to 24 days. On the production day, the mean aerobic plate counts (APCs) for broiled lampreys from plants A, B, and C were 2.29 log CFU/g, 1.88 log CFU/g, and undetectable (1.67 log CFU/g), respectively. At 22 degrees C, the mean APCs for samples from plants A, B, and C increased markedly within 4 days, and after 6 days the counts for samples from these plants were 8.56, 5.04, and 6.23 log CFU/g, respectively. Chilling and storage at 3 degrees C remarkably improved the shelf life of the product. The levels of bacteria in charcoal-broiled river lampreys from plant A were higher than those in lampreys from plants B and C. No significant increases in APCs were observed during storage at 3 degrees C for 24 days; mean APCs did not exceed 2.80 log CFU/g for samples from any plant. Staphylococcus aureus was found in two samples. No lactic acid bacteria, thermotolerant coliforms, enterococci, Clostridium perfringens, or Listeria monocytogenes was detected. Microbiological data from this study will be used for the development of a hazard analysis for the determination of critical control points.     

Distribution and prevalence of airborne microorganisms in three commercial poultry processing plants

Airborne microbial contaminants and indicator organisms were monitored within three poultry processing plants (plants A, B, and C). In total, 15 cubic feet (c.f.) of air was sampled per location during 15 visits to each plant and quantitatively analyzed for total mesophilic and psychrophilic aerobic counts, thermophilic campylobacters, Escherichia coli, and Enterobacteriaceae. The prevalence of Salmonella spp. in air samples was also evaluated. Significant reductions in total aerobic counts were observed between defeathering and evisceration areas of the three plants (P < 0.05). Mesophilic plate counts were highest in the defeathering areas of all plants compared to equivalent psychrophilic plate counts. Enterobacteriaceae counts were highest in the defeathering areas of all three plants with counts of log10 1.63, 1.53, and 1.18 CFU/15 c.f. recovered in plants A, B, and C, respectively. E. coli enumerated from air samples in the defeathering areas exhibited a similar trend to those obtained for Enterobacteriaceae with log10 1.67, 1.58, and 1.18 CFU for plants A, B, and C, respectively. Thermophilic campylobacters were most frequently isolated from samples in the defeathering areas followed by the evisceration areas. The highest mean counts of the organism were observed in plant A at 21 CFU/15 c.f. sample with plants B and C at 9 and 8 CFU/sample, respectively. With the exception of low levels of Enterobacteriaceae recovered from samples in the on-line air chill in plant A, E. coli, Enterobacteriaceae, or Campylobacter spp. were not isolated from samples in postevisceration sites in any of the plants examined. Salmonella spp. were not recovered from any samples during the course of the investigation.     

Behaviour of log-phase Escherichia coli at temperatures near the minimum for growth

The behaviour of cold-adapted, log-phase Escherichia coli in broth cultures incubated at temperatures between 7 and 15 degrees C was examined by determinations of numbers of colonies recovered on plate count agar (PCA); absorbance at 600 nm (A600); cell lengths from photomicrographs; and cell size distributions by flow cytometry. Cultures incubated between 7 and 10 degrees C were evaluated for 8 days or until A600 values approached 1.0. Cultures incubated at > or =12 degrees C were subcultured to maintain them in the log phase for up to 8 days. Numbers of colonies recovered declined when cultures were incubated at 7 degrees C, but increased when cultures were incubated at higher temperatures. However, A600 values increased during incubation at all temperatures. The mean lengths of cells doubled during incubation at 7 degrees C for 8 days, but remained constant during incubation at 10 degrees C for 1.25 days. Forward angle light scatter (FALS) measurements obtained by flow cytometry indicated that the mean length of cells increased at < or = 8 degrees C, but not at 10 degrees C. A reference value at the 90th percentile of FALS measurements on day 0 was used to determine changes in the distribution of the lengths of cells. About 80% or 17% of the cells were above the reference value after 5 days of incubation at 7 degrees C or 1.25 days of incubation at 10 degrees C, respectively. Cultures that were maintained in the log phase at 12 degrees C became increasingly heterogeneous in cell size after 2 days, but cultures that were maintained at 13 degrees C remained constant in cell size for 8 days. The observations have implications for the prediction of mesophile proliferation at temperatures that approach their minima for growth.     

Comparison of sponging and excising as sampling procedures for microbiological analysis of fresh beef-carcass tissue

Sponging and excising were evaluated as sampling procedures for microbiological analysis of beef-carcass tissue. Brisket tissue portions (10 x 10 cm) were inoculated with 2 ml of an Escherichia coli ATCC 25922 cell suspension (3 x 10(8)CFU/ ml). After 30 min, the portions were sampled by excising (EX) or swabbing (SP) with a sterile sponge and were analyzed for aerobic plate counts on tryptic soy agar and for total coliform counts and E. coli counts on Petrifilm E. coli count plates. Another set of inoculated samples was analyzed after being spray washed, in sequence, with water (6 s, 35 degrees C, 3.4 bar), acetic acid (2%, 6 s, 35 degrees C, 2.1 bar), water (20 s, 42 degrees C, 20.7 bar), and acetic acid (2%, 6 s, 35 degrees C, 2.1 bar). Additional samples were sampled for analysis after chilling at 7 degrees C for 24 h. Bacterial counts recovered were influenced (P < or = 0.05) by procedure of sampling (EX versus SP), time of sampling (0.5 versus 24 h), and by their interactions. Counts recovered 0.5 h after inoculation from unwashed or spray-washed samples were similar between the two sampling procedures (EX and SP). However, counts recovered after 24 h of sample storage were significantly (P < or = 0.05) lower for the SP compared with the EX procedure. The results indicated that as the carcass tissue was stored, recovery of bacteria by SP was less efficient than was recovery by EX.     

Inhibition of nonproteolytic,psychrotrophic clostridia and anaerobic sporeformers by sodium diacetate and sodium lactate in cook-in-bag turkey breast

A nonproteolytic, psychrotrophic Clostridium isolate, designated strain OMFRI1, was recovered from cook-in-bag turkey breasts (CIBTB) that displayed an intense pink discoloration and an off-odor following extended refrigerated storage. The viability of strain OMFRI1 in CIBTB containing sodium diacetate (at 0, 0.25, and 0.5%) and/or sodium lactate (at 0, 1.25, and 2.5%) was subsequently evaluated. Raw CIBTB batter was inoculated with 9 to 30 spores of strain OMFRI1 per g, vacuum packaged, cooked to an instantaneous internal temperature of 71.1 degrees C, chilled, and incubated at 4 degrees C for up to 22 weeks. In the absence of food-grade antimicrobial agents, spoilage (i.e., an off-odor) occurred within 6 weeks, and anaerobic plate counts reached 6.6 log10 CFU/g. The CIBTB containing sodium diacetate (0.25%) and that containing sodium lactate (1.25%) required 12 weeks for spoilage to occur and for anaerobic plate counts to reach 7.0 and 6.0 log10 CFU/g, respectively. When sodium diacetate (0.25%) and sodium lactate (1.25%) were used in combination, no off-odor was detected and anaerobic plate counts did not exceed 2.3 log10 CFU/g over 22 weeks of storage at 4 degrees C. In related experiments, sodium diacetate (at 0, 0.25, and 0.5%), sodium lactate (at 0, 1.25, and 2.5%), and combinations of both ingredients were evaluated in uninoculated CIBTB incubated at 25 degrees C for up to 22 days. In the absence of antimicrobial agents and in CIBTB containing sodium diacetate (0.5%), spoilage occurred within 8 days and anaerobic plate counts reached 6.8 and 6.6 log10 CFU/g, respectively. Samples of CIBTB containing sodium lactate (2.5%) showed signs of spoilage within 22 days, and anaerobic plate counts for these samples ranged from < or = 1.0 to 6.3 log10 CFU/g. In CIBTB containing both sodium lactate (2.5%) and sodium diacetate (0.25%), spoilage was not evident and anaerobic plate counts were < or = 1.0 log10 CFU/g within 22 days. These data validate the efficacy of sodium lactate and sodium diacetate in extending the shelf life of CIBTB.     

Survival and recovery of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on lettuce and parsley as affected by method of inoculation, time between inoculation and analysis, and treatment with chlorinated water

The effects of method for applying inoculum and of drying time after inoculation on survival and recovery of foodborne pathogens on iceberg lettuce and parsley were studied. Five-strain mixtures of Escherichia coli O157:H7, Salmonella, or Listeria monocytogenes were applied to lettuce and parsley by dip, spot, or spray inoculation methods. Inocula were dried for 2 h at 22 degrees C or for 2 h at 22 degrees C and then 22 h at 4 degrees C before being treated with water (control) or chlorine (200 microg/ml). Significantly higher populations (CFU per lettuce or parsley sample) of E. coli O157:H7 and Salmonella (alpha = 0.05) were recovered from dip-inoculated produce than from spot- or spray-inoculated produce. This difference was attributed to larger numbers of cells adhering to lettuce and parsley subjected to dip inoculation. Populations of E. coli O157:H7 and Salmonella recovered from lettuce inoculated by spot and spray methods were not significantly different, but populations recovered from spot-inoculated parsley were significantly higher than those recovered from spray-inoculated parsley, even though the number of cells applied was the same. Significantly different numbers of L. monocytogenes were recovered from inoculated lettuce (dip > spray > spot); populations recovered from dip-inoculated parsley were significantly higher than those recovered from spot- or spray-inoculated parsley, which were not significantly different from each other. Populations of pathogens recovered from lettuce and parsley after drying inoculum for 2 h at 22 degrees C were significantly higher than or equal to populations recovered after drying for 2 h at 22 degrees C and then for 22 h at 4 degrees C. Significant differences (water > chlorine) were observed in populations of all pathogens recovered from treated lettuce and parsley, regardless of inoculation method and drying time. It is recommended that spot inoculation with a drying time of 2 h at 22 degrees C followed by 22 h at 4 degrees C be used to determine the efficacy of chlorine and other sanitizers in killing foodborne pathogens on lettuce and parsley.     

Ice immersion as a postharvest treatment of oysters for the reduction of Vibrio vulnificus

Vibrio vulnificus produces serious illnesses that are commonly associated with shellfish consumption, particularly raw oysters. Ingestion can result in fatal septicemia in susceptible individuals with hepatitis, cirrhosis, immune dysfunction, diabetes, or hemochromatosis (metabolic iron overload). Therefore, postharvest treatments to reduce vibrio levels in oysters have been recommended. In this study, rapid chilling by immersion of unwashed whole oysters in ice for 3 h was assessed as a postharvest treatment for reduction of V. vulnificus. Treated oysters were subsequently refrigerated at 45 degrees F (7.2 degrees C), whereas control oysters were not iced but were maintained at 45 degrees F throughout the study. Homogenized meats were monitored for total heterotrophic aerobic bacteria, V. vulnificus, and fecal coliform content before and after treatment over a 2-week period. V. vulnificus was enumerated by DNA probe hybridization of colonies from standard plate counts on nonselective medium, and recovery was compared for several media. Loss of plating efficiency was observed on standard selective and differential media compared with nonselective agars. Numbers of V. vulnificus generally declined in treated samples compared with controls; however, increases in total heterotrophic bacteria and fecal coliforms were also observed in treated samples at some time points. This study does not support the use of ice immersion as a postharvest method because of the relatively small declines in V. vulnificus numbers and the possibility of concomitant increases in fecal coliform and total bacterial contamination.     

A national survey of the microbiological quality of retail raw meats in Australia

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.     

A follow-up survey of Staphylococcus aureus contamination of commercial raw minced meat at supermarkets and characteristics of isolates

A survey of Staphylococcus aureus contamination of commercial raw minced meat at 3 supermarkets in Hyogo Prefecture was conducted over a period of half a year (January to June 2006). In total, the contamination rate was 77.8% (28/36) for beef, 91.7% (33/36) for pork and 91.7% (33/36) for chicken samples. In supermarket A, half or more of the positive samples had MPN values of >/=110/g for all 3 kinds of meat samples. In supermarkets B and C, most of the positive samples were less than 46/g for all 3 kinds of meat samples. Of the 94 isolates examined, 50 (53.2%) belonged to the human biotype, and 44 (46.8%) to animal biotypes. By coagulase typing, 64 (77.1%) of the 83 typable isolates were classified into types V (n=32) and VII (n=32). Seventeen (18.1%) of the 94 isolates produced staphylococcal enterotoxins C (n=16) and B (n=1). Pulse-field gel electrophoresis was applied for epidemiological analysis of the isolates in the 3 supermarkets. In supermarket A, the predominant type shifted during the term of the investigation. In supermarket B, the same type was isolated repeatedly from the meat throughout the investigation. In supermarket C, a variety of genotypes were detected from the meat throughout the investigation.     

Putrescine, cadaverine, and indole production by bacteria isolated from wild and aquacultured penaeid shrimp stored at 0, 12, 24, and 36 degrees C

Putrescine, cadaverine, and indole production capabilities of bacteria isolated from wild domestic and aquacultured Ni-caraguan penaeid shrimp in progressive decomposition states were evaluated. The numbers and types of microorganisms responsible for the production of putrescine, cadaverine, and indole in wild and aquacultured shrimp increased with increasing decomposition temperature and time. Throughout the storage experiments, mean aerobic plate counts (log/g) ranged from 4.5 to 9.7 and 4.5 to 9.0 for domestic and Nicaraguan shrimp, respectively. Vibrio spp. were more prominent in Nicaraguan shrimp (Litopenaeus vannamei) than in domestic shrimp (Litopenaeus setiferus and Litopenaeus brasiliensis). The only amine-producing (putrescine) microorganism isolated from wild and aquacultured shrimp at all temperatures of decomposition (0, 12, 24, and 36 degrees C) was Shewanella putrefaciens. On the basis of putrescine production by S. putrefaciens at 0 and 12 degrees C and putrescine production by S. putrefaciens, Vibrio spp., and Morganella morganii at 24 and 36 degrees C, putrescine should be considered a potential chemical indicator of decomposition in shrimp.     

Prediction of fertility by centrifugal countercurrent distribution (CCCD) analysis: correlation between viability and heterogeneity of ram semen and field fertility

The prediction of the fertilizing ability of a sire or a given insemination dose is a primary aim in the field of artificial insemination. Centrifugal countercurrent distribution analysis (CCCD) was used to determine the relationship between some sperm parameters and the in vivo fertility rate obtained with the same sample after cervical artificial insemination. A total of 522 ewes from 26 different farms was inseminated with 53 ejaculates obtained from 25 mature Rasa aragonesa rams. Semen was diluted to 1.6 x 10(9) cells ml-1 and doses of 0.25 ml were prepared and kept at 15 degrees C until used for insemination. The same ejaculates were used for analysis of standard semen parameters and CCCD analysis. Sperm motility, concentration and viability were determined before and after CCCD. Post-CCCD parameters were derived from the analysis of the profile obtained after CCCD. The recovered viability showed the highest correlation with fertility, especially in the central chambers (V2), r = 0.415, P < 0.005). The ejaculate heterogeneity also showed a positive correlation with field fertility (r = 0.23), with a tendency towards significance (P < 0.1). The mean fertility value of all ejaculates used in this study was 46.75%, ranging from 12.5% to 75.0%. Ejaculates were classified into two categories according to their fertility: higher and lower than the mean value. Only the viability recovered in the central chambers (V2) was a parameter with a predictive capacity to discriminate between the two groups (P < 0.05). A predictive equation for field fertility with a correlation coefficient r = 0.488 and a very high level of significance (P < 0.005) was deduced by multiple analysis: PF = 6.02 + 0.069V2 + 0.315H (where PF is predictive fertility, V2 is the recovered viability in the CCCD profile central chambers and H is heterogeneity).     

The effect of short-time microwave exposures on Escherichia coli O157:H7 inoculated onto chicken meat portions and whole chickens

Small portions of fresh chicken breasts weighting 20 g each and fresh whole chickens, weighting on average 1310 g each, were inoculated with Escherichia coli O157:H7 (10(5)-10(6) cfu/g) and cooked, using two different domestic microwave ovens at full power. The chicken portions were heated for 5, 10, 15, 20, 25, 30, and 35 s and the whole chickens for 22 min. Following exposures, viable counts and temperature measurements were performed. Although the chicken breast portions looked well-cooked after 30 s of MW heating at a mean end-point surface temperature of 69.8 degrees C, a mean concentration of 83 cfu/g E. coli O157:H7 cells was recovered. Elimination of E. coli O157:H7 cells occurred only after 35 s of MW exposure at 73.7 degrees C. When whole chickens were thoroughly cooked by MW heating, the final subsurface temperatures, measured in the thighs and wings, ranged from 60.2 degrees C to 92 degrees C and viable cells of E. coli O157:H7 were recovered from all samples of whole chicken. The results indicate that short time exposures of chicken portions to microwave heating do not eliminate E. coli O157:H7.     

Comparison of methods for enumeration of yeasts and molds in shredded low-moisture, part-skim mozzarella cheese

Two studies were conducted to compare established and new methods for enumerating yeasts and molds in shredded low-moisture, part-skim mozzarella cheese stored under refrigeration and temperature-abuse conditions. Yeast and mold counts covered a range of 6 log10 units. In study 1, the potato dextrose agar plus chlortetracycline (PDA) pour plate, dichloran rose bengal chloramphenicol (DRBC) spread plate, Petrifilm, and Iso-Grid hydrophobic grid-membrane filtration methods were used to analyze samples after < or = 1 day of unopened storage at 7 degrees C and after opening, resealing, and 2 days of storage at 25 degrees C. The results of all methods were highly correlated (r2 > or = 0.96). In study 2, the PDA, DRBC, and Iso-Grid methods were compared with the Simplate 2-day method in an analysis of 42 samples stored for various times at 8, 11, 15, and/or 22 degrees C. The results of all methods except the Simplate method were again highly correlated (r2 > or = 0.94), although yeasts and molds were not always detected by all methods. Compared with the PDA, DRBC, and Iso-Grid methods, the Simplate method most often (10 of 42 samples, 23.8%) failed to detect yeasts and molds when at least one other method did, and the results were less highly correlated with those of other methods (r2 = 0.88 to 0.90). Our results suggest that the PDA, DRBC, Petrifilm, and Iso-Grid methods are equivalent for enumerating yeasts and molds in shredded low-moisture, part-skim mozzarella cheese samples.     

Effect of freezing time on the quality of Indian mackerel (Rastrelliger kanagurta) during frozen storage

The present study aims to find the effect of freezing methods on the quality of mackerel (Rastrelliger kanagurta) in commercial plate and air blast freezers during freezing and subsequent frozen storage (-18 degrees C). Total time for freezing was significantly different (P < 0.05) between the plate and air blast freezers (90 and 220 min, respectively). This difference in the freezing time could be attributed to the varied quality of the 2 samples. Upon freezing, the moisture content decreased in air blast frozen samples compared to plate freezer where protein content decreased in both the samples. Upon freezing and during frozen storage, lipid oxidation products (peroxide value, thiobarbutiric acid value, and free fatty acid value) and volatile bases (total volatile base nitrogen and trimethyl amine nitrogen) showed an increasing trend in both the samples with values slightly higher in air blast frozen samples compared to plate frozen samples. The total plate counts showed a significantly (P < 0.05) decreasing trend in both the samples. K value did not show any significant (P < 0.05) difference between the samples where as the histamine formation was significantly (P < 0.05) increased in air blast frozen samples compared to plate frozen samples. The taste and overall acceptability was significantly different (P < 0.05) in plate frozen samples compared to air blast frozen samples on 3rd month. Both samples were in acceptable condition up to 3 mo but the plate frozen samples quality was slightly better than the air blast frozen samples.     

Effect of thiamine hydrochloride,pyridoxine hydrochloride and calcium-d-pantothenate on the patulin content of apple juice concentrate

Thiamine hydrochloride, pyridoxine hydrochloride and calcium-d-pantothenate were applied apple juice concentrates (AJC) at various doses in order to reduce the patulin content. AJC samples containing high levels of patulin were stored at 22 +/- 2 degrees C and 4 degrees C for 6 months after vitamins were added. Patulin was fully degraded at the end of a 6-month period in samples stored at 22 +/- 2 degrees C, on the other hand, other quality parameters diminished significantly. Without any considerable reduction on other quality parameters, applications of 1000 and 2500 mg/kg calcium-d-pantothenate resulted in reduction of patulin of 73.6 and 94.3%, respectively, however, 42.1% of patulin reduction was observed in the control sample of AJC stored for 1 month at 22 +/- 2 degrees C. Addition of thiamine hydrochloride (1000 mg/kg), pyrodoxine hydrochloride (625 or 875 mg/kg) and calcium-d-pantothenate (1000 or 2500 mg/kg) into the samples and storage at 4 degrees C for 6 months yielded 55.5 to 67.7% of patulin reduction which was only 35.8% for the control while the other quality parameters were protected adequately.     

Heterotrophic plate count methodology in the United States

In the United States (US), the history of bacterial plate counting (BPC) methods used for water can be traced largely through Standard Methods for the Examination of Water and Wastewater (Standard Methods). The bacterial count method has evolved from the original Standard Methods (1st edition, 1905) plate count which used nutrient gelatin and incubation at 20 degrees C for 48 h, to the HPC method options in the latest edition of Standard Methods that provide greater flexibility of application, depending on the data needs of the water analyst. The use of agar-agar as a gelling agent, replacing gelatin, allowed the use of higher incubation temperatures and resulted in the "body temperature count" (37 degrees C) found in the 3rd through the 8th edition of Standard Methods. The change from 37 degrees C incubation to 35+/-0.5 degrees C accommodated laboratories that did both milk and water analyses. By using a single temperature, fewer incubators were needed. The term "standard plate count" (SPC) first appeared in 1960 (11th edition) along with plate count agar. Incubation at 20 degrees C for the plate count was dropped from the 13th to 15th editions and few changes were made in the SPC method from the 11th edition through the 13th editions. Plate count analysis of bottled waters was included in the 14th edition (1975), calling for incubation at 35+/-0.5 degrees C for 72+/-4 h. Perhaps the most significant changes in plate count methods occurred with the 16th edition (1985). The term heterotrophic plate count replaced the standard plate count, and the spread plate (SP) and membrane filter (MF) methods were added along with new media for pour and spread plates (R2A agar and NWRI agar, both low nutrient) and for the membrane filter method (mHPC medium). The use of low nutrient media, lower incubation temperature, and longer incubation times, results in higher plate count results for most water samples. The options currently available, including low and high nutrient media, incubation temperatures (20 degrees C, 28 degrees C or 35 degrees C), plating methods (pour plate (PP), spread plate and membrane filter) and range of incubation times (24, 48, 72 h and 5-7 days) provide great flexibility in the application of the HPC analysis to drinking water.     

Comparison of the Baird-Parker agar and 3M Petrifilm Staph Express Count plate methods for enumeration of Staphylococcus aureus in naturally and artificially contaminated foods

The recently developed 3M Petrifilm Staph Express Count plate (PFSE) method was compared with the U.S. Food and Drug Administration Bacteriological Analytical Manual's Baird-Parker agar spread plate (B-P) method for enumeration of Staphylococcus aureus in naturally contaminated, mechanically separated poultry (MSP; n = 92) and raw milk (n = 12). In addition, mozzarella and Parmesan cheeses and hot-smoked rainbow trout and chub were surface inoculated with a three-strain mixture of S. aureus, stored at 5 degrees C, and periodically analyzed with both methods for numbers of S. aureus. For naturally contaminated raw milk and MSP samples, the PFSE method yielded counts that were not significantly different (P > 0.05) from counts obtained using the B-P method. From raw milk and MSP samples, 60% (21 of 35) and 55% (124 of 226), respectively, of confirmed (DNAse-positive) isolates from PFSE plates were identified by further testing as S. aureus. Corresponding S. aureus identification rates for isolates forming typical colonies on B-P plates were 53% (19 of 36) and 50% (125 of 248). For both methods, other staphylococci composed the vast majority of tested isolates that were not identified as S. aureus. For inoculated hot-smoked fish, S. aureus counts from the PFSE method were not significantly different from counts from the B-P method. Compared to the B-P method, significantly lower numbers of inoculated S. aureus were recovered using the PFSE method in analyses of mozzarella cheese stored 28 and 42 days at 4 degrees C. The PFSE and B-P methods were not significantly different for inoculated cheeses at all other sampling times. DNAse-positive isolates from PFSE analyses of inoculated cheeses and smoked fish were identified as S. aureus 98% (51 of 52) and 86% (36 of 42) of the time, respectively, as compared with 100% (58 of 58) and 95% (40 of 42) of the time for typical B-P isolates. Overall, the PFSE and B-P methods appeared to perform similarly in enumeration of S. aureus in animal-derived foods.     

Properties and stability of butter oil obtained from milk and yoghurt

The physical and chemical characteristics and thermal stability of butter oil produced from cow's milk by two different methods were studied. Butter oil samples from cow's milk were made (i) directly from milk and (ii) from yoghurt. Samples were autoxidized at 60, 70 and 80 degrees C in the dark and the reaction monitored by peroxide, thiobarbituric acid and free fatty acid values. Peroxide and thiobarbituric acid values increased as the temperature increased. The increase of the acid value was not significant. The thermal stability was highest in butter oil produced from yoghurt. Oxidative changes compared to hydrolytic changes are of greater significance in the thermal stability of butter oil samples. Arrhenius parameters and activation energies were calculated for the peroxide value data. The percent loss of linolenic acid was about 3 times faster than that of linoleic acid.     

Microbiological quality of chilled beef carcasses in Northern Ireland: a baseline survey

To standardize the assessment of the hygienic quality of beef carcasses in Northern Ireland (NI) abattoirs, swabbing techniques were evaluated. Six materials, including two commercially produced swabs, were compared for their ability to recover spoilage and pathogenic bacteria and for their ease of use as carcass swabs. A sponge retailed for domestic use was selected on the basis of efficiency of recovery of microorganisms, ease of use, and cost. On sample carcasses, 1,000 cm2 of the brisket was swabbed, since this site is normally readily contaminated. For 9 months, 420 carcasses in seven of the nine European Union-approved abattoirs in NI were sampled while in the chiller (24 to 48 h after kill). Total viable count (TVC), yeasts and molds, and Enterobacteriaceae were enumerated after incubation at 22 (48 h) and 37 degrees C (48 h), and the results were expressed as log CFU/cm2. The mean TVC results at 22 and 37 degrees C were 2.80+/-0.70 and 2.75+/-0.64, respectively. Although 63% of samples had yeasts that grew at 22 degrees C, only 35% were positive at 37 degrees C. The respective mean yeast counts were 1.12+/-0.59 and 0.46+/-0.51. Enterobacteriaceae were present in 15% of samples at 22 degrees C and 21% of samples at 37 degrees C. The mean counts for positive samples were 0.41+/-0.37 and 0.40+/-0.30, respectively. Molds were found in less than 4% of samples. Given that the brisket is normally one of the most heavily contaminated parts of the carcass, these results suggest that good hygienic practices are in operation in NI abattoirs. The results also enabled the abattoirs with the cleanest carcasses to be identified, hence permitting best practices to be found.     

A national survey of the microbiological quality of beef carcasses and frozen boneless beef in Australia

The third national baseline microbiological survey of Australian beef carcasses and frozen boneless beef was conducted in 2004. Carcasses (n=1155) sampled at 27 slaughter establishments had a mean aerobic plate count (at 25 degrees C) of 1.3 log CFU/cm2. Escherichia coli was isolated from 8.0% of the cacasses, with a mean count of -0.8 log CFU/cm2 for positive samples. On samples from 24 boning (fabrication) plants (n=1082), 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 1082 boneless samples. Salmonella was isolated from 0 of 1155 carcasses and from 1 of 1082 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.