Microbiological examination of ready-to-eat cold sliced meats and pâté from catering and retail premises in the UK

AIMS: To establish the microbiological quality of cold ready-to-eat sliced meats and paté from catering and retail premises, and investigate links hypothesized between foodborne Campylobacter infection and the consumption of cold sliced meats. METHODS AND RESULTS: A total of 4078 cold meat and paté samples were collected and examined according to a standardized protocol. Comparison with published microbiological guidelines revealed that most ready-to-eat meat and paté samples (75%) were of satisfactory/acceptable microbiological quality and 25% were of unsatisfactory/unacceptable quality. Two cold meat samples (<1%) were of unacceptable microbiological quality because of the presence of Campylobacter jejuni in 25 g and Listeria monocytogenes at 3.4 x 104 CFU g-1. CONCLUSIONS: Acceptable microbiological quality was associated with premises where the management was trained in food hygiene and those that had hazard analysis in place. Poor microbiological quality was associated with storage above 8 degrees C, presliced meats, infrequent cleaning of slicing equipment and poor control of practices that may lead to cross contamination. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides important information about the microbiological quality of cold ready-to-eat meats and paté. It also assists caterers, retailers, enforcement officers and policy makers to understand how different food safety practices affect microbiological quality.     

Microbiological examination of ready-to-eat stuffing from retail premises in the north-east of England. The 'Get Stuffed' survey

AIMS: To establish the microbiological quality of ready-to-eat stuffing from retail premises in the north-east of England. To establish threshold levels of bacteria in the product for acceptance as a ready-to-eat food. To determine the relationship between the microbiology of the product and production processes. METHODS AND RESULTS: A microbiological study of ready-to-eat stuffing using validated methods was performed on 147 samples from 139 retail premises. The determinants investigated were as follows: aerobic colony count, Escherichia coli, Enterobacteriaceae, Staphylococcus aureus, Bacillus spp., Salmonella spp. and Campylobacter spp. Results indicate that using current guidelines 76.3% were satisfactory, 15.6% were acceptable and 8.2% were of unsatisfactory quality. CONCLUSIONS: Unsatisfactory results were due to high aerobic colony counts, E. coli, Enterobacteriaceae and S. aureus. There were significant associations between bacteriological quality and temperature of storage, food hygiene training, product discard policy and confidence in management scores. SIGNIFICANCE AND IMPACT OF THE STUDY: The microbiology of ready-to-eat stuffing suggests that this is a relatively safe product. It is suggested that the product be placed in food category 3 in the current guidelines for ready-to-eat foods.     

Prevalence and level of Listeria monocytogenes and other Listeria sp. in ready-to-eat minimally processed and refrigerated vegetables

Minimally processed and refrigerated vegetables can be contaminated with Listeria species bacteria including Listeria monocytogenes due to extensive handling during processing or by cross contamination from the processing environment. The objective of this study was to examine the microbiological quality of ready-to-eat minimally processed and refrigerated vegetables from supermarkets in Osijek, Croatia. 100 samples of ready-to-eat vegetables collected from different supermarkets in Osijek, Croatia, were analyzed for presence of Listeria species and Listeria monocytogenes. The collected samples were cut iceberg lettuces (24 samples), other leafy vegetables (11 samples), delicatessen salads (23 samples), cabbage salads (19 samples), salads from mixed (17 samples) and root vegetables (6 samples). Listeria species was found in 20 samples (20 %) and Listeria monocytogenes was detected in only 1 sample (1 %) of cut red cabbage (less than 100 CFU/g). According to Croatian and EU microbiological criteria these results are satisfactory. However, the presence of Listeria species and Listeria monocytogenes indicates poor hygiene quality. The study showed that these products are often improperly labeled, since 24 % of analyzed samples lacked information about shelf life, and 60 % of samples lacked information about storage conditions. With regard to these facts, cold chain abruption with extended use after expiration date is a probable scenario. Therefore, the microbiological risk for consumers of ready-to-eat minimally processed and refrigerated vegetables is not completely eliminated.     

The microbiological examination of ready-to-eat organic vegetables from retail establishments in the United Kingdom.

AIMS: A microbiological study of uncooked ready-to-eat organic vegetables was undertaken to determine the microbiological quality of these vegetables on retail sale in the UK. METHODS AND RESULTS: Organic vegetables were collected and examined according to a standardized protocol. The majority (3185 of 3200; 99.5%) of samples were found to be of satisfactory/acceptable quality whilst only 15 (0.5%) were of unsatisfactory quality. Unsatisfactory results were due to Escherichia coli and Listeria spp. (not L. monocytogenes) levels in excess of 102 cfu g-1. CONCLUSIONS: The absence of pathogens (L. monocytogenes, Salmonella, Campylobacter and E. coli O157) and the low incidence (1.5%) of E. coli and Listeria spp. associated with these organic vegetables indicates that overall agricultural, hygiene, harvesting and production practices were good. SIGNIFICANCE AND IMPACT OF THE STUDY: There has been a significant expansion of the UK organic market since 1998/99. Of the various commodity sectors making up the organic market, fruit and vegetables is the largest sector and this has been reflected in an increased interest in their microbiological safety. This is the first study to provide information on the microbiological quality of organic vegetables.     

Fate of Listeria monocytogenes in processed meat products during refrigerated storage.

The fate of Listeria monocytogenes during refrigerated storage was determined on several processed meat products, including ham, bologna, wieners, sliced chicken, sliced turkey, fermented semidried sausage, bratwurst, and cooked roast beef. The meats were surface inoculated with a five-strain mixture of less than or equal to 200 or ca. 10(5) L. monocytogenes cells per package, vacuum packaged, and stored at 4.4 degrees C. Survival or growth of listeriae was determined for up to 12 weeks of storage or until the product was spoiled. The organism survived but did not grow on summer sausage, grew only slightly on cooked roast beef, grew well on some wiener products but not on others, grew well (10(3) to 10(5) CFU/g increase within 4 weeks) on ham, bologna, and bratwurst, and grew exceptionally well (10(3) to 10(5) CFU/g increase within 4 weeks) on sliced chicken and turkey. The rate of growth depended largely upon the type of product and the pH of the product. Growth was most prolific on processed poultry products. The organism generally grew well on meats near or above pH 6 and poorly or not at all on products near or below pH 5. These results indicate the importance of preventing postprocessing contamination of L. monocytogenes in a variety of ready-to-eat meat products.     

Estimates of heterocyclic amine intake in the US population

HA-specific meat concentration estimates using a method that combines laboratory data to predict HA concentrations from meat type, cooking method and meat doneness were used with national dietary data to estimate daily HA intake for segments of the US population. PhIP was found to comprise approximately 70% of US mean dietary intake of total HAs, with pan-frying and chicken being the single cooking method and meat type contributing the greatest to total estimated HA exposures. This analysis demonstrated significantly higher concentrations in grilled/barbecued meats than in other cooked meats. African-American males were estimated to consume nearly twofold and approximately 35 to 40% more PhIP (and total HAs) than white males at ages <16 and >30 years, respectively.     

Fate of Listeria monocytogenes in processed meat products during refrigerated storage

The fate of Listeria monocytogenes during refrigerated storage was determined on several processed meat products, including ham, bologna, wieners, sliced chicken, sliced turkey, fermented semidried sausage, bratwurst, and cooked roast beef. The meats were surface inoculated with a five-strain mixture of less than or equal to 200 or ca. 10(5) L. monocytogenes cells per package, vacuum packaged, and stored at 4.4 degrees C. Survival or growth of listeriae was determined for up to 12 weeks of storage or until the product was spoiled. The organism survived but did not grow on summer sausage, grew only slightly on cooked roast beef, grew well on some wiener products but not on others, grew well (10(3) to 10(5) CFU/g increase within 4 weeks) on ham, bologna, and bratwurst, and grew exceptionally well (10(3) to 10(5) CFU/g increase within 4 weeks) on sliced chicken and turkey. The rate of growth depended largely upon the type of product and the pH of the product. Growth was most prolific on processed poultry products. The organism generally grew well on meats near or above pH 6 and poorly or not at all on products near or below pH 5. These results indicate the importance of preventing postprocessing contamination of L. monocytogenes in a variety of ready-to-eat meat products.     

ASSESSMENT OF IMPEDANCE MICROBIOLOGICAL METHOD FOR THE DETECTION OF ESCHERICHIA COLI IN FOODS

This study was conducted to determine the sensitivity and specificity of the impedance-based microbiological method for the detection of Escherichia coli in foods within 24 h of testing. A Malthus Microbiological Analyzer system (Malthus System V, Malthus Instruments Ltd., Bury, United Kingdom), and a modified Malthus Coliform Broth Medium (MCBM), and an incubation temperature of 44C were used. The sensitivity of the impedance method was determined by testing E. coli-negative food samples spiked with different concentrations of E. coli. The specificity of the method was determined by testing E. coli -negative food samples spiked with Klebsiella pneumoniae, Enterobacter cloacae and Pseudomonas aeruginosa. The test results were compared with those obtained by the Most Probable Number (MPN) method. Milk, milk products, raw and ready-to-eat meats, and vegetables were tested for the presence of E. coli by both methods. The sensitivity of the impedance method and the MPN method for the detection of foods containing 10¹ CFU/g was 100% and 84.4%, respectively. Both methods had a specificity of 100% for food samples spiked with 10¹ CFU/g E. coli. The specificity of the impedance and the MPN methods for the detection of E. coli in naturally contaminated milk and meat samples was 100% and 95.7% respectively. E. coli was detected in foods by the impedance method within 4–24 h of testing at a detection limit of 1 CFU/mL. These results demonstrate that the impedance method can be used as a rapid and sensitive method for the detection of E. coli in foods.     

Public health investigations of Salmonella Enteritidis in catering raw shell eggs, 2002-2004

AIMS: In response to a dramatic change in the epidemiology of Salmonella Enteritidis in England and Wales thought to be associated with raw shell eggs, the Health Protection Agency initiated public health investigations to establish the incidence of Salmonella contamination and origin of eggs used by catering premises implicated in outbreaks of Salm. Enteritidis. METHODS AND RESULTS: Between October 2002 and November 2004, 16 971 eggs were sampled and Salmonella were recovered from 3.4%. Salmonella was isolated from 5.5% and 6.3% of Spanish and eggs of unknown origin, respectively, used in catering premises linked to outbreaks, a level significantly higher than that (1.1%) found in nonLion Quality UK eggs sampled. The small sample of UK Lion Quality eggs tested (reflecting their lack of use in premises visited) did not contain Salmonella. Several phage types of Salm. Enteritidis other than phage type 4 (PT 4) were identified with nonUK eggs. CONCLUSIONS: Eggs from Spain were implicated as a major source of infection. Eggs were contaminated more frequently with Salmonella when shells were dirty and/or cracked, and stored at above 8 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of Spanish eggs by the catering sector has been identified as a consistent significant factor in many of the outbreaks caused by Salm. Enteritidis nonPT4 in England and Wales during 2002-2004. Advice to caterers and hospitals that raw shell eggs should not be used in food that will either not be cooked or only lightly cooked should be reinforced.     

Series of incidents of Listeria monocytogenes non-invasive febrile gastroenteritis involving ready-to-eat meats

AIMS: A series of cases and outbreaks of febrile noninvasive gastrointestinal disease involving 31 identified cases was investigated in terms of the numbers and types of Listeria monocytogenes present in the suspect foods (ready-to-eat meats) and clinical samples from cases. METHODS AND RESULTS: Foods and faecal samples involved in the incidents were tested for the presence and number of L. monocytogenes. Isolates were typed by macrorestriction analysis using pulsed-field gel electrophoresis. The foods contained high levels of L. monocytogenes, in one case 1.8 x 10(7) g-1. Faecal samples contained L. monocytogenes for up to 15 d after the contaminated food was consumed. All isolates from the food and faecal samples were of serotype 1/2 and were indistinguishable from one another by macrorestriction typing. CONCLUSIONS: It is likely that the meats were contaminated either during their manufacture after they had been cooked or by underprocessing. The long shelf lives on these products would have allowed the contaminating L. monocytogenes to grow to the high numbers measured in this study, causing food poisoning as described. SIGNIFICANCE AND IMPACT OF THE STUDY: Outbreaks of febrile noninvasive listeriosis are relatively rare. This report adds ready-to-eat meats to the range of foods that have acted as vehicles for such outbreaks.     

A comparative in vitro investigation into the effects of cooked meats on the human faecal microbiota

Protein fermentation is one of the important microbial activities in the human colon. Meat foods rich in protein provide substantial resource for this metabolic activity. However, little information exists on the relative impact of different meats on the composition and activities of the human gut microbiota. Similarly, little information is available on the confounding effects of cooking on these activities. In this study, beef, chicken and fish (salmon) were examined in vitro for their impact on the human faecal microbiota. The influence of cooking method was also investigated by using either frying or boiling. Upon fermentation over 48 h the Clostridium perfringens/histolyticum group increased significantly in number in the beef fermentations, either fried (p = 0.023) or boiled (p = 0.017). Cooking method appeared to influence Clostridium spp. growth, with higher numbers in fried meat compared to boiled meats after 5 h (p = 0.024) and 48 h (p = 0.003) fermentation. Significant differences between meat types were also seen for numbers of Bifidobacterium spp. at 48 h (p = 0.028), Bacteroides group at 24 h (p = 0.016) as well as Coriobacterium/Atopobium group at 10 h (p = 0.038). Most types of short chain fatty acids increased significantly in concentration over the experiment (p < 0.05). Significant differences between meat types were found in n-butyric acid production at 24, 30 and 48 h (p = 0.015, p = 0.024 and p = 0.035 respectively) and in i-valeric acid production at 10, 24, 30 and 48 h (p = 0.026, p = 0.002, p = 0.019 and p = 0.022 respectively). The concentration of i-valeric acid differed significantly between cooking methods at 24 h (p = 0.042). These findings suggest that both the type of meat and cooking process can influence fermentation profiles within the human gut microbiota. Interactions between ingested cooked meats and the gut microbiota may represent a novel corollary to mechanisms underlying the observed increased risk of intestinal and systemic diseases associated with high intake of certain meats/processed meats.     

乳杆菌在模拟肉制品条件下结合苯并芘的效果

【背景】乳杆菌对众多致癌物具有吸附作用,但关于乳杆菌结合吸附苯并芘特性的研究并不多。【目的】探讨戊糖乳杆菌(Lactobacillus pentosus) ML32和植物乳杆菌(Lactobacillus plantarum)121对加工肉制品中苯并芘的吸附能力与吸附机制。【方法】基于HPLC检测菌体对不同模拟加工处理方式肉品中的苯并芘的吸附率。【结果】植物乳杆菌121和戊糖乳杆菌ML32对模拟油炸、烟熏或烧烤方式处理肉中苯并芘的吸附率均在30%以上。菌株121对直接烟熏肉中的苯并芘吸附率为41.21%,直接油炸肉中吸附率为38.71%,直接烧烤肉中吸附率为37.51%;菌株ML32对间接烟熏肉中的苯并芘吸附率为40.02%,间接烧烤肉中吸附率为38.01%。植物乳杆菌121适合于去除高温长时间加工肉中的苯并芘,戊糖乳杆菌ML32则相反。另外,乳杆菌细胞壁中的肽聚糖或许在吸附过程中发挥了主要作用。【结论】两株乳杆菌121和ML32具有吸附某些加工肉制品中苯并芘的效果,或许可以作为一种方法用于消除某些肉制品中因苯并芘过量带来的风险。     

Analysis and Prediction of the Effective Thermal Conductivities of Meats

Published data of the effective thermal conductivities of meats were analyzed in relation to approximate compositions of the meats. On the basis of series heat conduction model, the “intrinsic” thermal conductivity value of meat protein was estimated to be 0.342 [W/m · °C] when unfrozen, and 0.581 [W/m · °C] when frozen. Using these “intrinsic” values and the series heat conduction model, the effective thermal conductivities of meats were reversely predicted from the contents of water and fat. Standard deviations of the published data from the predictions were ± 7.0% for unfrozen meats and ± 15.4% for frozen meats. If heat flow is parallel to the meat grain, published data for frozen meats are higher than the predictions by about 20% as a mean.     

Incidence of Mesophilic Clostrodium Spores in Raw Pork, Beef, and Chicken in Processing Plants in the United States and Canada

The anaerobic film pouch technique was used to quantitate and isolate clostridial spores in 2,358 samples of raw meat (1,078 of chicken, 624 of beef, 656 of pork). Of 19,727 putrefactive anaerobic (PA) sporeformers isolated, 1 was confirmed by mouse protection testing to be Clostridium botulinum type C. This isolate was obtained from a Western Canada chicken sample which contained 5.33 clostridia per gram. These data indicate a very low incidence of botulinal contamination in raw meats at the packing-plant level (0.042% of 2,358 samples) and an almost 20,000:1 ratio of nonbotulinal PA sporeformers to mesophilic C. botulinum spores. The mean level of PA contamination was 2.8 PA sporeformers per gram of meat; 77% of the samples contained three or less PA sporeformers per gram. Small but statistically significant differences in the incidence of clostridial spores were noted for season, geographical region, and type of meat.     

Molecular identification of Salmonella isolates from poultry and meat productsin Irbid City,Jordan

The sensitivity and accuracy of molecular diagnosis of Salmonella from meat and poultry products using polymerase chain reaction (PCR) was compared with conventional microbiological methods. A total of 212 samples representing the most frequently used fresh and frozen meat and poultry products (whole, cut, ground, and processed) were collected from different locations within the city of Irbid. DNA was extracted directly from each food sample and amplified using Salmonella-specific primers. Samples were also analysed using conventional microbiological methods for the presence of Salmonella spp. Results showed that Salmonella was detected in 185 samples out of 212 (87%) by PCR technique, while 172 (81%) samples were detected Salmonella positive by conventional microbiological methods. On the other hand, 27 (12.7%) samples were negative by PCR and 40 (18.8%) samples were negative by conventional microbiological methods. PCR assay proved to be an effective method for Salmonella detection in meat and poultry products with high specificity and sensitivity and more importantly a less time-consuming procedure. Using PCR, Salmonella spp. detection could be achieved within 24–36 h compared to 3–8 days for the conventional microbiological methods.     

Quantitative Relationship between Alphα-tocopherol and Polyunsaturated Fatty Acids and Its Connection to Development of Oxidative Rancidity in Chicken Skeletal Muscle

Quantitative relationships were investigated between α-tocopherol and either polyunsaturated fatty acids (PUFA) or PUFA > 18:2 (PUFA with three or more double bonds) in chicken dark meat (thigh muscle) and light meat (M. pectoralis profundus). Their effects on the development of oxidative rancidity in precooked meats held at 5°C for 3 days were also investigated. Chicken dark meat had higher concentrations of α-tocopherol (μmol) per gram of PUFA or PUFA > 18 :2 than did chicken light meat. 2-Thiobarbituric acid (TBA) values for the cooked ground meats held at 5°C for 3 days tended to increase at both higher and lower concentrations of α-tocopherol than the concentration of about 1.5 μmol of α-tocopherol per gram of PUFA regardless of the type of chicken skeletal muscle.     

Association of Processed Meat Intake with Hypertension Risk in Hemodialysis Patients: A Cross-Sectional Study

In this cross-sectional study, we hypothesized that hemodialysis patients consuming greater processed meat is associated with hypertension risk, which can be partly explained by the high sodium content in processed meat. From September 2013 to May 2014, one hundred and four patients requiring chronic hemodialysis treatment were recruited from hemodialysis centers. Data on systolic blood pressure and diastolic blood pressure before receiving dialysis, and 3-day dietary records of the recruited patients were collected. HD patients with systolic and diastolic blood pressures greater than140 mmHg and higher than 90 mmHg, respectively, were considered hypertension risk. Protein foods were divided into 4 categories: red meat, white meat, soybeans, and processed meat (e.g., sausage and ham). In a model adjusted for energy intake and hypertension history, additional servings of processed meats was positively associated to systolic blood pressure >140 mmHg (odds ratio [95% confidence interval]: 2.1 [1.0–4.3]), and diastolic blood pressure > 90 mmHg (odds ratio: 2.5 [1.2–5.5]). After adjustment for dietary sodium contents or body mass index (BMI), most associations were substantially attenuated and were no longer significant. In systolic blood pressure greater than140 mmHg, one serving per day of red meats (β = -1.22, P < .05) and white meats (β = -0. 75, P = .05) was associated with a reduced risk compared with one serving per day of processed meats. Similarly, compared with one serving per day of processed meat, a reduced risk of diastolic blood pressure higher than 90 mmHg was associated with one serving per day of red meat (β = -1. 59, P < .05), white meat (β = -0. 62, P < .05). Thus, in these hemodialysis patients, intake of processed meat is significantly positively associated with higher blood pressure risk, and both sodium contents in processed meat and BMI significantly contributes to this association.     

Incidence and relationship of group D streptococci with other indicator organisms in meats.

Raw and processed meats were analyzed for presumptive group D streptococci using KF streptococcus agar. Counts were compared with coliform, presumptive Escherichia coli, and Enterobacteriaceae counts but no meaningful relationships were observed. Results indicated that group D streptococci and E. coli type I were principally contaminants from the packing plant, rather than at retail level. The predominating group D streptococcus in both beef and pork cuts was Streptococcus faecalis, while in processed meat (bologna), the predominating group D streptococci were Streptococcus faecium var. durans and Streptococcus faecium. Streptococcus bovis was not detected among the isolates from any meat samples. Marked differences were noted in numbers of group D streptococci in processed meat from different manufacturers. The results did not support the use of group D streptococci as alternative indicator organisms for meats. However, the association of group D streptococci with packing plant contamination may prove to be of value.     

Effect of Soy Proteins on the Growth of Clostridium perfringens

Proteins that are used to fabricate imitation foods such as synthetic meats were evaluated for stimulative or inhibitory effects on the growth of Clostridium perfringens. Growth rate and extent were measured in thioglycolate medium without dextrose. This liquid medium contains Trypticase (BBL) which served as the protein control. For comparison, various soy proteins, synthetic meats, beef, turkey, sodium caseinate, and combinations of each were substituted for Trypticase. Meat loaf systems were also employed to determine the effects of protein additives to meat under actual meat loaf conditions. Growth of C. perfringens type A, strain S40, was measured in the respective media at 45 C at a pH of 7.0 and an E(h) of below -300 mv. Viable populations were enumerated by agar plate techniques on Trypticase-sulfite-yeast-citrate-agar incubated anaerobically (90% N(2)-10% CO(2)) for 18 hr at 35 C. When compared to Trypticase, some soy proteins had stimulative effects on the growth of C. perfringens, whereas sodium caseinate and some soy proteins were inhibitory. In liquid medium in which meat or soy meat was the source of protein, there was a marked stimulation by beef, chicken, and soy beef. Soy chicken supported growth at a rate less than observed with Trypticase. Under actual meat loaf conditions, the addition of soy meat or protein additives to beef did not affect the growth of C. perfringens. The addition of protein additives to turkey meat loaves significantly enhanced the rate of growth of C. perfringens. The stimulative effects of some soy proteins are significant in relation to control of foodborne disease.     

Heat tolerance of Salmonella typhimurium DT104 isolates attached to muscle tissue

Aerobic and anaerobic plate counts were compared for routine monitoring of the microflora, dominated by lactic acid bacteria, developing on vacuum- and carbon dioxide-packaged raw meat during chilled storage. No statistical differences were observed between aerobic and anaerobic enumerations, made on plate count and blood agar plates, of the microflora developing on beef striploins packaged under vacuum or carbon dioxide during 14 weeks' storage at 0°C. With both techniques the spoilage microflora development differed between the two packaging regimes. The results indicate that there is no necessity for aerobic plate counts to be replaced by anaerobic plate counts in the routine microbiological examination of the spoilage microflora developing on chilled meats packaged under anoxic modified atmospheres.