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.     

Evaluation of an optical microbiological method for rapidly estimating populations of aerobic bacteria, coliforms, and Escherichia coli from ground pork

The BioSys optical methods for estimating populations of aerobic bacteria, coliforms, and Escherichia coli from ground pork were evaluated. Ground pork samples were analyzed immediately, after temperature abuse at 25 degrees C for various periods of time, or after temperature abuse and dilution by mixing with pork that was prepared by grinding whole muscles that had the outer portion excised using a sterile scalpel. Each ground pork sample was tested using standard methods such as aerobic plate counts (APC), violet red bile (VRB) agar plate counts (coliforms), and three-tube most probable numbers (MPN--E. coli). Each sample was tested using the BioSys for total viable counts (TVC) by placing 2 ml of ground pork homogenate (25 g into 225 ml of sterile 1% buffered peptone water) into 8 ml of nutrient medium containing brom-cresol purple in a test vial and monitoring at 35 degrees C. Coliforms were enumerated by placing 5 ml of ground pork homogenate into 5 ml of coliform medium (CM) in a test vial and monitoring at 35 degrees C. E. coli were enumerated by placing 5 ml of ground pork homogenate into 5 ml of double-strength CM with 2% dextrose in a test vial and monitoring at 42 degrees C. The correlation coefficients for the regression lines comparing APC to BioSys TVC detection times (DT), VRB to BioSys coliform DT, and MPN to BioSys E. coli DT were -0.95, -0.94, and -0.93, and the line equations were logl0 CFU/ml = 8.94 - 0.40(DT), log10 CFU/ml = 8.77 - 0.43(DT), and log10 CFU/ml = 8.96 - 0.81(DT), respectively. These methods may allow pork producers to monitor equipment surfaces and products in less than 16 h and obtain microbiological results prior to shipment.     

Influence of processing schemes on indicative bacteria and quality of fresh aquacultured catfish fillets.

Fresh aquacultured catfish fillets were obtained from three processors using different processing protocols in summer, autumn, winter, and spring and evaluated for microbial quality. Twenty freshly processed fillets were randomly selected and each fillet was placed in a sterile polyethylene bag. The fillets were transported on ice-pack overnight by air immediately after processing. Five fillets were randomly selected for microbial assays. Each fillet was weighed and an equal volume of sterile 0.1% peptone water at 0 to 1 degrees C was added aseptically. The fillet was massaged (or rinsed) for 120 s and the rinse was used to determine microbial quality. Aerobes (incubation at 35 degrees C for 48 h) and psychrotrophs (incubation at 20 degrees C for 96 h) were enumerated using 3M Petrifilm Aerobic Count plates. Escherichia coli (incubation at 35 degrees C for 24 to 48 h) and total coliforms (incubation at 35 degrees C for 24 to 48 h) were enumerated on 3M Petrifilm E. coli Count plates. Staphylococcus aureus counts were determined on Baird-Parker agar (incubation at 35 degrees C for 48 h). Significant differences (P < or = 0.05) in aerobic, psychrotrophic, total coliform, E. coli, and S. aureus counts due to temperature effects during production and variations in processing protocols were observed. E. coli and S. aureus counts were significantly different during the four seasons. E. coli and S. aureus counts were high during summer and low during winter weather. There was a significant difference (P < or = 0.05) in aerobic, psychrotrophic, and total coliform counts among the three processors during warm weather; however, these differences were significantly (P < or = 0.05) reduced in cold weather.     

Use of a Shiga toxin (Stx)-enzyme-linked immunosorbent assay and immunoblot for detection and isolation of Stx-producing Escherichia coli from naturally contaminated beef

The purpose of this study was to evaluate an enzyme-linked immunosorbent assay (ELISA) and an immunoblot procedure for detection and isolation of Shiga toxin-producing Escherichia coli (STEC) from beef, and to correlate the presence of STEC in beef with E. coli and total coliform counts. A total of 120 samples of boneless beef supplied to a meat processor in southern Ontario were tested for the presence of STEC, E. coli, and total coliforms. Following enrichment in modified tryptic soy broth, samples were screened for Shiga toxin (Stx) by a Stx-ELISA and a Vero cell assay (VCA). Samples that were positive in the Stx-ELISA were subjected to the Stx-immunoblot for STEC isolation. Overall, 33.3% of samples were positive in the VCA, and 34.2% were positive in the Stx-ELISA. There was almost complete agreement between the Stx-ELISA and the VCA results (kappa = 0.98). The sensitivity and specificity of the Stx-ELISA with respect to the VCA were 100% and 98.75%, respectively. STEC were isolated by the Stx-immunoblot from 87.8% of the samples that were positive in the Stx-ELISA. The STEC isolates belonged to 19 serotypes, with serotype O113:H21 accounting for 10 of 41 isolates. No STEC of serotype O157:H7 were isolated. There was a significant correlation between E. coli counts and total coliform counts (Spearman correlation coefficient = 0.68, P < 0.01). The E. coli count was positively correlated with detection of STEC by both the Stx-ELISA and the VCA (P < 0.01).     

Methods to Detect the Occurrence of Various Indicator Bacteria on the Surface of Retail Poultry in Spain

ABSTRACT: Contamination levels (cfu/g and cfu/cm²) of indicator microorganisms in retail broiler chicken carcasses in León (Spain) were investigated. Counts (log₁₀ cfu/g) were 5.19, 3.04, 2.73, 3.38, and 3.16 for total aerobic counts ( TAC), Enterobacteriaceae , coliforms determined by the standard VRBA method (coliforms-VRBA), coliforms determined by the Hydrophobic Grid Membrane Filter method (coliforms-HGMF), and Escherichia coli (HGMF method), respectively. These values fit into the microbiological criteria for poultry meat consulted. A low correlation coefficient was found between TAC and Enterobacteriaceae counts (r = 0.308; P = 0.053) and between coliforms-VRBA and coliforms-HGMF counts ( r = 0.398; P = 0.048). The determination method had a significant influence on the coliform counts obtained. All broiler chicken carcasses harbored E. coli biotype I. E. coli biotype II was detected in 20% of the samples. The HGMF method was not completely specific for detecting E. coli since 11.25% of false positive colonies were found.     

Evaluation of the microbial quality of Tajik sambusa and control of Clostridium perfringens germination and outgrowth by buffered sodium citrate and potassium lactate

Clostridium perfringens spore destruction, aerobic plate counts (APCs), and counts of Enterobacteriaceae, coliforms, and Escherichia coli during baking of sambusa (a traditional Tajik food) were evaluated. Control of germination and outgrowth of C. perfringens spores in sambusa during cooling at room or refrigerated temperatures was evaluated using organic acid salts (buffered sodium citrate [Ional] and 1 and 2% potassium lactate, wt/wt). Sambusa were prepared with 40 g of either inoculated or noninoculated meat and baked for 45 min at 180 degrees C. For evaluation of destruction of C. perfringens spores during heating and germination and outgrowth of spores during cooling, ground beef was inoculated and mixed with a three-strain cocktail of C. perfringens spores. Aerobic bacteria, Enterobacteriaceae, coliforms, and E. coli were enumerated in noninoculated sambusa before and after baking and after cooling at room or refrigeration temperatures. After baking, APCs and Enterobacteriaceae and coliform counts were reduced by 4.32, 2.55, and 1.96 log CFU/g, respectively. E. coli counts were below detectable levels in ground beef and sambusa samples. Enterobacteriaceae, coliform, and E. coli counts were below detectable levels (< 0.04 log CFU/g) in sambusa after cooling by both methods. Total C. perfringens populations increased (4.67 log CFU/g) during cooling at room temperature, but minimal increases (0.31 log CFU/g) were observed during cooling under refrigeration. Incorporation of 2% (wt/wt) buffered sodium citrate controlled C. perfringens spore germination and outgrowth (0.25 log CFU/g), whereas incorporation of up to 2% (wt/wt) potassium lactate did not prevent C. perfringens spore germination and outgrowth. Incorporation of organic acid salts at appropriate concentrations can prevent germination and outgrowth of C. perfringens in improperly cooled sambusa.     

Efficacy of radio frequency cooking in the reduction of Escherichia coli and shelf stability of ground beef

The effectiveness of radio frequency (RF) cooking on the inactivation of Escherichia coli in ground beef and its effect on the shelf stability of ground beef were investigated with a comparison to hot water-bath cooking. E. coli K12 was used as a target bacterium instead of E. coli O157:H7. The ground beef samples inoculated with E. coli K12 (ampr) were heated until the centre temperature of each sample reached 72 degrees C. These samples were then stored at 4 degrees C for up to 30 days. The enumeration of E. coli K12, background E. coli and coliform counts in ground beef samples was carried out for shelf-life study. Although both methods significantly reduced E. coli K12 (ampr), E. coli and coliform counts and extended the shelf-life, RF cooking had a shorter cooking time, and more uniform heating. Thus, RF cooking of meat has a high potential as a substitute for the hot water-bath cooking.     

Microbial evaluation of selected fresh produce obtained at retail markets

The microbial quality of five types of fresh produce obtained at the retail level was determined by standard quantitative techniques. These techniques included aerobic plate count (APC), total coliform counts, Escherichia coli counts, and yeast and mold counts. Three different methods were used to determine total coliform counts, which consisted of MacConkey agar plate counts, Colicomplete most probable number counts, and Petrifilm E. coli (EC) plate counts. The mean APCs for sprouts, lettuce, celery, cauliflower, and broccoli were 8.7, 8.6, 7.5, 7.4. and 6.3 log10 CFU/g, respectively. MacConkey agar counts indicated that 89 to 96% of the APCs consisted of gram-negative bacteria. Yeast and mold counts were in a range expected of fresh produce. Fresh produce was also analyzed for human pathogens. Samples were analyzed for Staphylococcus spp., Bacillus spp., Salmonella spp., Listeria spp., and Campylobacter spp. One isolate of Staphylococcus was found to be enterotoxigenic, and one species of Bacillus was also toxigenic. Neither Salmonella spp. nor Campylobacter spp. were detected in any of the produce samples. A variety of Listeria spp., including Listeria monocytogenes, were found in fresh produce.     

Incidence of Salmonella on beef carcasses relating to the U.S. meat and poultry inspection regulations.

This article is part of a major study designed to collect baseline contamination data by sampling beef carcasses in seven slaughtering plants (four steer-heifer and three cow-bull plants) during both a dry season (November to January) and a wet season (May to June). Samples (n = 30) were excised from each of three carcass anatomical sites (brisket, flank, and rump) at each of three points in the slaughtering chain (pre-evisceration, following final carcass washing, after 24-h carcass chilling). A total of 3,780 samples (100 cm2 each) were analyzed for presence of Salmonella; aerobic plate counts, total coliform counts, and Escherichia coli counts were also made. After 24-h chilling, average incidence (expressed as a percentage) of Salmonella in the brisket, flank, and rump samples, respectively, for steer-heifer carcasses was 0.8+/-1.7, 0, and 2.5+/-5.0 for the wet season and 0.8+/-1.7, 0, and 0 for the dry season; the corresponding percentages for cowbull carcasses were 4.4+/-2.0, 2.2+/-3.9, and 1.1+/-1.9 for the wet season and 2.2+/-3.9, 1.1+/-1.9, and 0 for the dry season. Depending on plant and season, ranges of probabilities of chilled steer-heifer carcasses passing the U.S. regulatory requirements for Salmonella contamination were 0.24 to 1.0 for the brisket, 1.0 for the flank, and 0.002 to 1.0 for the rump; the corresponding ranges for the chilled cow-bull carcasses were 0.25 to 1.0, 0.25 to 1.0, and 0.70 to 1.0. When the number of positive brisket, flank, and rump samples were combined, the probabilities of passing the regulatory requirements were 0.242 to 1.0 and 0.772 to 1.0 for the wet and dry seasons, respectively, in steer-heifer plants and 0.368 to 0.974 and 0.865 to 1.0 in cow-bull plants. Correlation coefficients of aerobic plate counts, total coliform counts, and E. coli counts with Salmonella incidence were higher (P< or =0.05) for cow-bull samples that had increased incidence of the pathogen when compared to steer-heifer samples.     

Longitudinal microbiological survey of fresh produce grown by farmers in the upper midwest

Microbiological analyses of fruits and vegetables produced by farms in Minnesota and Wisconsin were conducted to determine coliform and Escherichia coli counts and the prevalence of E. coli, Salmonella, and E. coli O157:H7. During the 2003 and 2004 harvest seasons, 14 organic farms (certified by accredited organic agencies), 30 semiorganic farms (used organic practices but not certified), and 19 conventional farms were sampled to analyze 2,029 preharvest produce samples (473 organic, 911 semiorganic, and 645 conventional). Produce varieties included mainly lettuces, leafy greens, cabbages, broccoli, peppers, tomatoes, zucchini, summer squash, cucumber, and berries. Semiorganic and organic farms provided the majority of leafy greens and lettuces. Produce samples from the three farm types had average coliform counts of 1.5 to 2.4 log most probable number per g. Conventional produce had either significantly lower or similar coliform populations compared with the semiorganic and organic produce. None of the produce samples collected during the 2 years of this study were contaminated with Salmonella or E. coli O157:H7. E. coli contamination was detected in 8% of the samples, and leafy greens, lettuces, and cabbages had significantly higher E. coli prevalence than did all the other produce types in both years for the three farm types. The prevalence of E. coli contamination by produce type was not significantly different between the three farm types during these 2 years, with the exception of organic leafy greens, in which E. coli prevalence was one-third that of semiorganic leafy greens in 2003. These results indicate that the preharvest microbiological quality of produce from the three types of farms was very similar during these two seasons and that produce type appears to be more likely than farm type to influence E. coli contamination.     

Microbiological hazard identification and exposure assessment of street food vending in Johannesburg, South Africa

One hundred and thirty-two samples of beef, chicken, salad and gravy were collected from two street vendors over eleven replicate surveys to assess microbiological safety and quality. For each food type samples were collected during preparation and holding. Dish water was also collected and food preparation surfaces swabbed during preparation and display. Standard methods were used to determine aerobic plate counts, Enterobacteriaceae counts, coliform counts and spore counts. Six hundred and seventy-five predominant colonies were isolated from aerobic plate counts of all samples and characterised. The incidence of selected foodborne bacterial pathogens and non-pathogenic E. coli 1 was also determined. In most cases mean bacterial counts of the raw materials were significantly higher (P < 0.05) than those of corresponding cooked foods. No significant differences (P > 0.05) in all count types were observed between food samples collected during cooking and those collected during holding. In addition, no significant differences (P > 0.05) in all count types were observed between prepared salads and their raw materials. Mean bacterial counts of water and swab samples collected from vendor 1 were lower than those of water and swab samples collected from vendor 2.The predominant populations isolated from the aerobic plate counts were Bacillus spp., Staphylococcus spp., Enterobacteriaceae and Alcaligenes spp. Bacillus cereus was detected in 17%, Clostridium perfringens in 1%, Staphylococcus aureus in 3% and Vibrio metchnikovii in 2% of the food samples. Campylobacter jejuni, Listeria monocytogenes, and Escherichia coli O157:H7 were not detected. Non-pathogenic E. coli 1 was detected in 13% of food samples, in 86 and 36% of dish water samples collected from vendors 1 and 2, respectively, and in 36% of surface swab samples from vendor 2.     

EVALUATION OF A RIBOFLAVIN-METHIONINE MIXTURE TO IMPROVE THE QUALITY OF AQUACULTURED CATFISH FILETS DURING THE CHILLING PROCESS

An optimized riboflavin-methionine (RM) mixture with Escherichia coli (target organism) was evaluated for improving the quality of catfish filets during the chilling process. The RM mixture (pH 7.2) containing riboflavin (10μM), methionine (20 mM) and EDTA (1 mM) was photoactivated. E. coli cells grew in a medium containing l-methionine when exposed to fluorescent light and grew in a RM mixture in the dark. However, the activated RM mixture injured and killed E. coli cells. As the concentration of riboflavin increased, the number of survivors decreased. The concentration of methionine did not significantly decrease the survival rate of E. coli. As pH increased, the number of killed and injured E. coli cells increased. The RM mixture injured and/or killed a low load of E. coli cells faster than a high load. Methionine solution or RM mixture added to the suspension in phosphate buffer (15 mM, pH 7.2) and photoactivated at 0 and 24C for 8h to simulate the chilling water significantly reduced the total coliform counts but not the standard plate counts. However, when the catfish filets were suspended in a RM mixture at 0 and 24C for 2h to simulate the chilling process, there was no reduction in standard plate or total coliform counts.     

Spatial and annual variability in concentrations and sources of Escherichia coli in multiple watersheds

Nonpoint source fecal contamination is a concern for drinking water supplies worldwide. In this study, 4812 E. coli isolates were classified to source. Results of this experiment show that the fecal coliform (FC) counts varied by year, month, and site, for each of the watersheds sampled. For both years, the lowest FC counts tended to be at the highest elevation sites followed by the drinking water intake sites at the lowest elevation. The highest FC counts tended to be at the mid-elevation sites on BX, Deer, and Duteau Creeks. The sources of E. coli varied significantly with stream for 2003 and 2004 (P < 0.001, df = 39), although the main sources of E. coli (avian, deer/elk, canine, rodent, bovine, and bear) tended to be similar between watersheds. The dominant sources of E. coli changed from 2003 (avian, deer/elk, and canine) to 2004 (avian, bovine, and rodent). It is important to look at the results of more than 1 year of source tracking data to get a better picture of the dominant sources within a watershed. Overall, wildlife was the largest contributor of E. coli to the watersheds in both 2003 (> 84%) and 2004 (> 73%).     

Survival of Escherichia coli, strain W, during the manufacture of cottage cheese.

Cottage cheese was manufactured in 10-liter experimental vats by the direct-acid-set method from milk that was inoculated with a heat resistant strain of Escherichia coli. Growth or survival of Strain W (ATCC 9637) E. coli was determined at various stages of the cheese making operation after the cheese-skim milk was inoculated to give counts of 2.5 X 10(4) or 4.0 X 10(5) cells/ml. Numbers of coliform organisms remained constant at the inoculated concentration in the cheese milk up to a cooking temperature of 43 C. At 43 C, when curd was separated from the whey, the curd (not washed) had coliform counts that were two log cycles greater than the whey. These trends were in milks with both cell counts. Washing of the curd with acid and 10 ppm chlorine reduced the number of coliform cells in the curd at all cooking temperatures as compared with unwashed curd. Acid wash of the curd at pH 5 did not reduce the coliform counts below those of unwashed curd. Cooking temperatures of 54 C were necessary to destroy (less than 1 cell/ml) E. coli Strain W, in either the unwashed or acid-chlorine washed curd. Holding curd with an initial average log count of 6.26 coliform cells/ml at constant temperatures of 38, 43, 49, and 54 C confirmed that 54 C for 50 min was necessary to reduce the average count to less than 1 cell/ml in isolated curd. Coliforms in whey were reduced to that concentration after 10 min at 54 C.     

Microbial Assessment in School Foodservices and Recommendations for Food Safety Improvement

ABSTRACT:  This study evaluated microbial food safety in school foodservices. Five school foodservices were randomly selected, and samples from water, cooking utensils, tableware, foodservice surroundings, and linen were collected in summer and winter ( N = 420). Tap and drinking water samples were collected, samples of food contact surfaces were collected by swab-kit, and samples for foodservice workers' hands and gloves were prepared by glove juice method. Aerobic plate count (APC) and coliform bacterial populations were enumerated on plate count agar (PCA) and desoxycholate lactose agar, respectively. The presence of Escherichia coli , Salmonella , Listeria monocytogenes , and Staphylococcus aureus was also examined by biochemical identification tests. In addition, PCA agar for APCs and Baird-Parker agar for S . aureus were used to enumerate airborne microorganisms. Higher APCs (< 0 to 5.1 log CFU/mL) than acceptable level were generally observed in water samples, while low coliform counts were found in the samples. High APCs were enumerated in cooking utensils, foodservice workers, tableware, and foodservice surroundings, and coliforms were also found in the samples for both seasons. The presence of Salmonella was found from only 10% of plastic glove samples (summer), and the presence of L . monocytogenes was not observed in all samples. S . aureus was detected in some of water, cooking utensils, tableware, employees, and foodservice surroundings, and E . coli was observed in cooking utensils (10% to 20%; summer). No obvious airborne bacteria were detected. These results showed that sanitation practice in school foodservices should be improved, and the results may be useful in microbial assessment of school foodservices.     

MICROBIOLOGICAL QUALITY OF COLD MEALS SERVED BY AIRLINES

The microbiological quality of 675 cold meals prepared for serving on aircraft was studied in 1991–1994. The material consisted of appetizers, salads and desserts prepared in 33 countries. The geometric mean of aerobic colony counts , Escherichia coli and Staphylococcus aureus were significantly lower in desserts (p<0.05) than in salads and appetizers. Salmonella was not found in any of the samples. Staphylococcus aureus, Bacillus cereus and Clostridium perfringens were found in 50 samples (7%). In respect of E. coli, S. aureus and B. cereus, the samples exceeded the Routine microbiological standards for aircraft-ready food; Accepted by the Association of European Airlines by 14%, 7% and 3%, respectively. There were considerable differences in aerobic colony counts , E. coli and B. cereus counts between countries where the food was prepared.     

Efficacy of hypobromous acid as a hide-on carcass antimicrobial intervention

Escherichia coli O157:H7 and Salmonella on cattle hides at slaughter are the main source of beef carcass contamination by these foodborne pathogens during processing. Hypobromous acid (HOBr) has been approved for various applications in meat processing, but the efficacy of HOBr as a hide antimicrobial has not been determined. In this study, the antimicrobial properties of HOBr were determined by spraying cattle hides at either of two concentrations, 220 or 500 ppm. Treatment of hides with 220 ppm of HOBr reduced the prevalence of E. coli O157:H7 on hides from 25.3 to 10.1% (P < 0.05) and reduced the prevalence of Salmonella from 28.3 to 7.1% (P < 0.05). Treatment of hides with 500 ppm of HOBr reduced (P < 0.05) the prevalence of E. coli O157:H7 on hides from 21.2 to 10.1% and the prevalence of Salmonella from 33.3 to 8.1%. The application of 220 ppm of HOBr reduced (P < 0.05) aerobic plate counts, total coliform counts, and E. coli counts on hides by 2.2 log CFU/ 100 cm(2). The use of 500 ppm of HOBr resulted in reductions (P < 0.05) of aerobic plate counts, total coliform counts, and E. coli counts by 3.3, 3.7, and 3.8 log CFU/100 cm(2), respectively, demonstrating that the use of higher concentrations of HOBr on hides resulted in additional antimicrobial activity. These results indicate that the adoption of a HOBr hide wash will reduce hide concentrations of spoilage bacteria and pathogen prevalence, resulting in a lower risk of carcass contamination.     

Effect of prechill fecal contamination on numbers of bacteria recovered from broiler chicken carcasses before and after immersion chilling

Paired carcass halves were used to test whether fecal contamination of skin during processing of broiler chickens can be detected by increased bacterial counts in samples taken before and after immersion chilling. In each of three trials, six freshly defeathered and eviscerated carcasses were cut in half, and a rectangle (3 by 5 cm) was marked with dots of ink on the breast skin of each half. One half of each pair was chosen randomly, and 0.1 g of freshly collected feces was spread over the rectangle with a spatula. After 10 min, both halves were sprayed with tap water for 10 to 15 s until feces could no longer be seen in the marked area. Both halves were sampled with a 1-min carcass rinse and were then put in a paddle chiller with other eviscerated carcasses for 45 min to simulate industrial immersion chilling. Immediately after chilling, each carcass half was subjected to another 1-min rinse, after which the skin within the rectangle was aseptically removed from the carcass halves and stomached. Rinses of fecally contaminated halves had significantly higher Enterobacteriaceae immediately before chilling, but there were no differences in coliform and Escherichia coli counts. After chilling, there were no differences in Enterobacteriaceae, coliform, and E. coli counts in rinse or skin samples from the paired carcass halves. Correlations were generally poor between counts in rinse and skin samples but were significant between prechill and postchill rinses for both control and fecally contaminated halves. Correlations were also significant between counts in rinses of control and contaminated halves of the same carcass after chilling. Bacterial counts in postchill carcass rinses did not indicate that fecal contamination occurred before chilling.     

Relationship among fecal coliforms and <Emphasis Type="Italic"> Escherichia coli </Emphasis>in various foods

For much of the twentieth century, coliform bacteria and especially Escherichia coli have been used as indicators of possible post-processing contamination and the presence of E. coli as an indicator of fecal contamination in foods. In this study, 500 foods in 10 different groups, mainly dairy products, delicatessen products, salads, spices, cream cakes and fresh fruit and vegetable samples, were analyzed for the natural contamination of fecal coliforms and E. coli by the standard most probable number (MPN) method. The difference between weighted means of fecal coliforms and E. coli counts were only 0.246 log₁₀ MPN/g-ml (MPN/gram for solid samples, and MPN/milliliter for liquids). Enumeration results were also evaluated by Pearson's correlation coefficient ( r), Cronbach's alpha (f) and determination coefficient ( r ²) analysis. According to results, although 33 samples contained only non- E. coli fecal coliforms, the results of reliability analyses indicated that fecal coliform counts and E. coli counts may be used interchangeably ( P <0.0001). It can be said that fecal coliform or, preferably E. coli analysis is sufficient for rapid routine determination of fecal contamination, at least for those food groups analyzed in this research.     

Studies to evaluate chemicals and conditions with low-pressure applications for reducing microbial counts on cattle hides

Studies were conducted to identify effective antimicrobials and application parameters that could be used as decontamination interventions to reduce microbial loads on cattle hides before removal from carcasses. In study I, hide swatches inoculated with Escherichia coli O157:H7 were sprayed with 10% acetic acid (at 23 and 55 degrees C), 10% lactic acid (at 23 and 55 degrees C), 3% sodium hydroxide (at 23 degrees C) or 4 and 5% sodium metasilicate (at 23 degrees C). All antimicrobials were evaluated independently after being applied alone, being applied after a water rinse, or being followed by a water rinse. Antimicrobial treatments followed by a water rinse lowered E. coli O157:H7 populations by 0.6 to 2.4 log CFU/cm2 and resulted in hides with a surface pH of 6.3 to 9.2. Treatments in which a water rinse was followed by antimicrobial application lowered E. coli O157:H7 populations by 1.5 to 5.1 log CFU/cm2 but resulted in hides with a surface pH of 3.9 to 10.5. In study II, whole hides were treated with one of four antimicrobials (acetic acid, lactic acid, sodium hydroxide, or sodium metasilicate) followed by a water rinse. Hides were evaluated for aerobic bacterial counts, total coliform counts, and E. coli counts. Generally, all antimicrobials resulted in greater reductions (P < 0.05) of E. coli counts when compared with the control; however, only acetic and lactic acids resulted in greater reductions (P < 0.05) of aerobic bacterial counts and total coliform counts compared with the controls. These antimicrobials could be used to reduce microbial contamination on hides, potentially reducing microbiological contamination transferred to carcasses or to the plant environment.