These short but safe time limits for home-refrigerated foods will keep them from
spoiling or becoming dangerous to eat. The guidelines for freezer storage are
for quality only. Frozen foods remain safe indefinitely.
KSWFoodWorld
Category Archives: Methods
USA – Leftover Food Storage Tips Chart
Posted in Bacteria, Food Hygiene, Food Inspections, Food Safety, Food Testing, Foodborne Illness, Methods, Microbiology, Research
Tagged egg safety, freezer storage
Culture Better Than Rapid?
Tests for foodborne pathogens in which a culture is not grown in a lab may be necessary for produce companies, but they can’t replace traditional culture tests, industry leaders and government officials say.
Nonculture diagnostic tests have been around since the early 1980s, said David Gombas, senior vice president of food safety and technology for the Washington D.C.-based United Fresh Produce Association.
But there has been a recent push, Gombas said, to use them to replace culture tests that the Centers for Disease Control and Prevention, the Food and Drug Administration and other agencies and organizations rely on to accurately diagnose cases of salmonella, E. coli and other foodborne illnesses.
That trend was highlighted in a recent article in Scientific America magazine, which found that many clinics and state-run labs are turning to nonculture tests, which are faster than culture tests.
They’re faster, but are they better?
“Right now, the answer is no,” Gombas said. “CDC, FDA, and those in the produce industry I talk to — they want a live bug.”
Research Articles – Pulsed Electronic Field Milk – PCR Method Vibrio – Listeria Detection Culture Methods
Abstract
Lethal and sublethal injury of two Gram-positive (Staphylococcus aureus and Listeria monocytogenes) and one Gram-negative (Escherichia coli) bacteria in milk by pulsed electric fields (PEF) were determined using non-selective and selective media. PEF inactivation kinetics including lethal and sublethal injury fractions was also studied. The proportion of the sublethally injured microbial cells depended on the microorganisms, electric field strength and treatment time. The proportion of sublethally injured microbial cells reached maximum after a specific PEF treatment, and it kept constant or progressively decreased at greater electric field strengths and with longer PEF treatments. For the strain of L. monocytogenes, the proportion of sublethally injured cells increased from 18.98% to 43.64% with the increasing electric field strength from15 to 30 kV/cm. While for the strains of E. coli and S. aureus, the proportion of sublethally injured cells achieved the maximum (40.74% and 36.51%, respectively) at 25 kV/cm and then decreased. The proportion of the sublethally injured microbial cells reached maximum at 400 μs (S. aureus and L. monocytogenes) or 500 μs (E. coli), and decreased at longer treatments at 30 kV/cm. The PEF inactivation kinetics including lethal and sublethally injured fractions was analyzed by the Hülsheger model, and the model parameters (EC, tC, kE, bt) for lethal and sublethal injury were also calculated.
Abstract
A previously developed multiplex PCR targeting gyrB of Vibrios at genus level and pntA genes for specific detection of Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus was evaluated. The sensitivity of the multiplex PCR on spiked seafood was 1.5 × 103 CFU g−1. One hundred and fifty seafood samples were collected from retail stores and hypermarkets in different locations in Kuala Lumpur, Petaling Jaya and Seri Kembangan. The prevalence of V. parahaemolyticus was 29% (43/150). The pntA primers for V. parahaemolyticus detection were 100% specific and comparable to the toxR gene-based PCR. Six (12%) and 2 (4%) isolates contained trh and tdh genes, respectively. Repetitive Extragenic Palindromic PCR (REP-PCR) was used to genetically characterize the V. parahaemolyticus isolates in which 41 REP profiles were observed and all the isolates were categorized into 11 distinct clusters at the similarity of 80%. tdh-positive isolates shared a low level of similarity with trh-positive isolates. The prevalence of V. parahaemolyticus and particularly the presence of virulent gene such as trh and tdh among the isolates reiterate a high risk of contamination for seafood consumers in Malaysia. DNA fingerprinting of V. parahaemolyticus in this study indicates a high genetic diversity among the isolates and REP-PCR was able to distinguish the isolates with different virulotypes.
Abstract
The objectives of this study were to determine the prevalence of Listeria spp., specifically Listeria monocytogenes in ready-to-eat (RTE) foods and ascertain the efficiency of detecting L. monocytogenes with different selective culture media. A total of 396 RTE food samples were purchased from hypermarkets and streetside hawker stalls to examine the presence of Listeria spp. and L. monocytogenes. The presumptive isolates were characterized biochemically and were further confirmed by Polymerase Chain Reaction (PCR). Out of 396 samples, Listeria spp. was detected in 71 (17.9%) samples in which 45 (11.4%) were positive for L. monocytogenes. Among the studied RTE foods, salads and vegetables had the highest prevalence (14.7%) of L. monocytogenes, followed by chicken and chicken products (13.2%), beverages (10%), eggs and egg products (9.5%), beef and beef products (6.7%), lunch boxes (6.7%) and seafood and seafood products (6.7%). Both Listeria selective agar and PALCAM agar displayed a low sensitivity and specificity in L. monocytogenes detection compared to CHROMagar™ Listeria which demonstrated 96.9% of sensitivity and 99.1% of specificity in L. monocytogenes detection in naturally-contaminated foods. In conclusion, this work revealed consumption of RTE foods as a potential risk of listeriosis in this region. The high contamination rate of L. monocytogenes in salads and vegetables from hypermarkets and streetside hawker stalls was of great concern due to emerging fresh produce-borne L.monocytogenes globally. The scenario warrants further surveillance and action by the local authority to control the incidence of L. monocytogenes contamination in RTE foods.
USA – Foodborne Illness Outbreaks Database 1984 – 2012
Welcome to outbreakdatabase.com, a searchable database of illness outbreaks caused by one or more of the following
- consumption of contaminated foods or beverages,
- exposure to animals,
- exposure to contaminated recreational water,
- person-to-person contact with someone whose illness initiated from animal exposure or consumption of contaminated foods and beverages.
The database describes outbreaks occurring since 1984.
The Centers for Disease Control and Prevention (CDC) defines an outbreak as “two or more ill persons linked to a common source” and this serves as the basis of outbreakdatabase.com. To be included in outbreakdatabase.com, the outbreak must have supporting documentation from public health agencies, journal articles, media reports, etc. Names of stores, brands, restaurants, or other sources are listed if they have been publicly identified previously.
The database is a work in progress. It will continually be updated and revised. Significant effort has been made to ensure the data are accurate. We welcome contributions, corrections, comments, etc. Please use the contact form for comments.
Canada Research – Peracetic Acid for Fresh Produce
Up to 10,000 pounds of spinach are washed and packaged every day in iVeg Pak’s Toronto, Ontario plant. No matter where the spinach originates – Mexico, Texas, New Jersey or Ontario – the end product goes into a Pop-i package. That brand must be protected, not only for the Carnevale family owners but for the entire food chain.
To meet those standards, Taylor McCarthy’s full-time job is quality assurance, taking water samples every hour and making sure that the spinach is in the peracetic acid bath for a minimum of 45 seconds before proceeding to a drum dryer.
“This sanitizer has proven to be very effective,” says McCarthy. “We are an industry leader in using this product instead of chlorine. It’s not as corrosive on the stainless steel equipment.”
Posted in Bacteria, Food Hygiene, Food Poisoning, Food Safety, Methods, Microbiology, Research
Tagged restaurants, water
USA – Research -STEC Sampling and Listeria Outbreaks 1998-2008
This notice provides new instructions to inspection program personnel (IPP) for verifying and documenting the sample source (beef, veal, or mixed) in the Public Health Information System (PHIS) when collecting raw beef samples under FSIS’s verification testing programs for Shiga toxin-producing Escherichia coli (STEC).
Listeria monocytogenes, a bacterial foodborne pathogen, can cause meningitis, bacteremia, and complications during pregnancy. This report summarizes listeriosis outbreaks reported to the Foodborne Disease Outbreak Surveillance System of the Centers for Disease Control and Prevention during 1998–2008. The study period includes the advent of PulseNet (a national molecular subtyping network for outbreak detection) in 1998 and the Listeria Initiative (enhanced surveillance for outbreak investigation) in 2004. Twenty-four confirmed listeriosis outbreaks were reported during 1998–2008, resulting in 359 illnesses, 215 hospitalizations, and 38 deaths. Outbreaks earlier in the study period were generally larger and longer. Serotype 4b caused the largest number of outbreaks and outbreak-associated cases. Ready-to-eat meats caused more early outbreaks, and novel vehicles (i.e., sprouts, taco/nacho salad) were associated with outbreaks later in the study period. These changes may reflect the effect of PulseNet and the Listeria Initiative and regulatory initiatives designed to prevent contamination in ready-to-eat meat and poultry products.
Research – Grape Seed Extract Effect on Virus and E.coli on Fresh Cut Lettuce
Grape seed extract (GSE) is reported to have antibacterial properties with few current studies on antiviral activity. Recently, we reported the effects of GSE against foodborne viral surrogates in vitro. This study evaluated the application of GSE (commercial Gravinol-S) against hepatitis A virus (HAV) and human norovirus surrogates, feline calicivirus (FCV-F9) and murine norovirus (MNV-1), on model produce. Washed and air-dried lettuce (3 × 3 cm2) and jalapeno peppers (25–30 g) were inoculated with FCV-F9, MNV-1, or HAV at high (∼7 log10 PFU/ml) or low (∼5 log10 PFU/ml) titers, and treated with 0.25, 0.5, 1 mg/ml GSE or water for 30 s to 5 min. Treatments were stopped/diluted with cell-culture media containing 10% heat-inactivated fetal bovine serum and evaluated using plaque assays. At high titers, FCV-F9 was reduced by 2.33, 2.58, and 2.71 log10 PFU on lettuce; and 2.20, 2.74, and 3.05 log10 PFU on peppers after 1 min using 0.25, 0.50, and 1 mg/ml GSE, respectively. Low FCV-F9 titers could not be detected after 1 min at all three GSE concentrations. Low titer MNV-1 was reduced by 0.2–0.3 log10 PFU on lettuce and 0.8 log10 PFU on peppers, without reduction of high titer. GSE at 0.25–1 mg/ml after 1 min caused 0.7–1.1 and 1–1.3 log10 PFU reduction for high and low HAV titers, respectively on both commodities. Instrumental color analysis showed no significant differences between treated and untreated produce. GSE shows potential for foodborne viral reduction on produce as part of hurdle technologies.
Fresh-cut iceberg lettuce inoculated with Escherichia coli O157:H7 was submitted to chlorine washing (150 mg/mL) and modified atmosphere packaging on laboratory scale. Populations of E. coli O157:H7 were assessed in fresh-cut lettuce stored at 4, 8, 13 and 16 °C using 6–8 replicates in each analysis point in order to capture experimental variability. The pathogen was able to grow at temperatures ≥8 °C, although at low temperatures, growth data presented a high variability between replicates. Indeed, at 8 °C after 15 days, some replicates did not show growth while other replicates did present an increase. A growth primary model was fitted to the raw growth data to estimate lag time and maximum growth rate. The prediction and confidence bands for the fitted growth models were estimated based on Monte-Carlo method. The estimated maximum growth rates (log cfu/day) corresponded to 0.14 (95% CI: 0.06–0.31), 0.55 (95% CI: 0.17–1.20) and 1.43 (95% CI: 0.82–2.15) for 8, 13 and 16 °C, respectively. A square-root secondary model was satisfactorily derived from the estimated growth rates (R2 > 0.80; Bf = 0.97; Af = 1.46). Predictive models and data obtained in this study are intended to improve quantitative risk assessment studies for E. coli O157:H7 in leafy green products.
Posted in Bacteria, E.coli O157, Food Hygiene, Food Illness, Food Inspections, Food Poisoning, Food Safety, Food Technology, Food Testing, Food Virus, Hepatitis A, Hygiene, Illness, Methods, Microbiology, Norovirus, Pathogen, Research, STEC
Tagged cell culture media, fetal bovine serum, plaque assays, science
Research – E.coli O157 Testing in Water
The performances of three chromogenic agars were evaluated for the recovery of Escherichia coli O157:H7 from spiked de-chlorinated tap, ground and surface water, and treated drinking water samples. The chromogenic agars: ChromAgar O157 (CHROM), Rainbow Agar O157 (RB) and HiCrome EC O157 (HC) were compared to cefixime-tellurite Sorbitol MacConkey (CT-SMAC), commonly used for the isolation of E. coli O157:H7. Confirmation of suspect E. coli O157:H7 colonies were performed by colony real-time PCR (C-RTi-PCR) based on the presence of Shiga-toxin genes (stx1 and stx2). Recovery of inoculated E. coli O157:H7 from de-chlorinated tap water indicated that RB and CHROM agars demonstrated improved recovery when compared to HC or CT-SMAC. There was a significant drop in recovery on all agars tested after 120 hours (day 5). Twenty de-chlorinated tap and/or treated drinking water samples were inoculated with a pure culture of E. coli O157:H7 (ATCC 43894), and a mixed culture of E. coli O157:H7 (ATCC 43894), E. coli strain K-12, and Enterococcus faecalis (ATCC 063589). After a 48 hour holding time, the recovery using CHROM (99 %) and HC (12 %) from samples contaminated with the pure culture were found to be significantly different (p < 0.05). Recovery results using CHROM (39 %) and CT-SMAC (32 %) from samples contaminated with the mixed culture after 48 hour holding time were not significantly different (p > 0.05). Analysis by C-RTi-PCR of forty five environmental water samples (surface, sewage, and final effluents) which were negative for E. coli O157:H7 showed an incidence of false suspect positive colonies of 38 % (CHROM), 53 % (RB), 58 % (HC), and 91 % (CT-SMAC). Further analysis of eight of the environmental samples inoculated with E. coli (ATCC 43894) showed 100% recovery when utilizing CHROM, 50% when using RB and 40 % when using HC. In addition, the C-RTi-PCR positive confirmation rate was 100% for CHROM and HC and 65% for RB. CHROM demonstrated improved recovery of E. coli O157:H7 over RB, HC, and CT-SMAC in terms of sensitivity and specificity.
Posted in E.coli, E.coli O157, Methods, Microbiology, Pathogen, Research
Tagged science
Research – Safer Spinach Combined Microbiological Control
University of Illinois scientists have found a way to boost current industry capabilities when it comes to reducing the number of E. coli 0157:H7 cells that may live undetected on spinach leaves.
“By combining continuous ultrasound treatment with chlorine washing, we can reduce the total number of foodborne pathogenic bacteria by over 99.99 percent,” said Hao Feng, a U of I professor of food science and human nutrition.
Research – Inhibition of Clostridium and Detection of Enterotoxigenic Staph.
Abstract: Inhibition of Clostridium perfringens spore germination and outgrowth in reduced sodium roast beef by a blend of buffered lemon juice concentrate and vinegar (MoStatin LV1) during abusive exponential cooling was evaluated. Roast beef containing salt (NaCl; 1%, 1.5%, or 2%, w/w), blend of sodium pyro- and poly-phosphates (0.3%), and MoStatin LV1 (0%, 2%, or 2.5%) was inoculated with a 3-strain C. perfringens spore cocktail to achieve final spore population of 2.5 to 3.0 log CFU/g. The inoculated products were heat treated and cooled exponentially from 54.4 to 4.4 °C within 6.5, 9, 12, 15, 18, or 21 h. Cooling of roast beef (2.0% NaCl) within 6.5 and 9 h resulted in <1.0 log CFU/g increase in C. perfringens spore germination and outgrowth, whereas reducing the salt concentration to 1.5% and 1.0% resulted in >1.0 log CFU/g increase for cooling times longer than 9 h (1.1 and 2.2 log CFU/g, respectively). Incorporation of MoStatin LV1 into the roast beef formulation minimized the C. perfringens spore germination and outgrowth to <1.0 log CFU/g, regardless of the salt concentration and the cooling time.
Practical Application: Cooked, ready-to-eat meat products should be cooled rapidly to reduce the risk of Clostridium perfringens spore germination and outgrowth. Meat processors are reducing the sodium chloride content of the processed meats as a consequence of the dietary recommendations. Sodium chloride reduces the risk of C. perfringens spore germination and outgrowth in meat products. Antimicrobials that contribute minimally to the sodium content of the product should be incorporated into processed meats to assure food safety. Buffered lemon juice and vinegar can be incorporated into meat product formulations to reduce the risk of C. perfringens spore germination and outgrowth during abusive cooling.
Abstract: The aim of this study was to investigate the prevalence of enterotoxigenic Staphylococcus aureus in 122 samples, including 60 raw milk, 32 white cheese, 10 kashar cheese, 10 butter, and 10 ice cream samples obtained from Samsun province, Turkey. In this study, S. aureus was detected in 64 samples, including raw milk (45/60; 75%), white cheese (12/32; 37.5%), kashar cheese (3/10; 30%), butter (3/10; 30%), and ice cream (1/10; 10%) samples. A total of 81 isolates were identified as S. aureus by PCR with the presence of 16S rRNA and nuc genes. The presence of genes encoding the staphylococcal enterotoxins (SEs) SEA, SEB, SEC, and SED was detected by multiplex PCR. According to the analysis, seven isolates from the raw milk samples (7/51; 13.7%) were enterotoxigenic; five of them produced SEA (5/7; 71.4%), one produced SEB (1/7; 14.2%), and one produced SEA+SEB (1/7; 14.2%). Four isolates from the white cheese samples (4/21; 19%) produced the SEA (1/4; 25%), SEC (1/4; 25%), SED (1/4; 25%), and SEA+SED (1/4; 25%) toxins. Two isolates from the kashar cheese samples (2/4; 50%) were found to be enterotoxigenic; one produced SEA (1/2; 50%) and the other produced SED (1/2; 50%). One isolate from the butter samples (1/4; 25%) showed enterotoxigenic character (SEB, 1/1; 100%). The products were found to be potentially hazardous to public health because of the fact that levels of contamination were higher than 105–106 cfu/g ml in 39% (25/64, 17 raw milk, 7 white cheese, and 1 butter) of the analyzed samples.
Posted in Bacteria, Clostridium perfringens, Eurofins Laboratories, Food Hygiene, Food Illness, Food Inspections, Food Poisoning, Food Safety, Food Safety Alert, Food Technology, Food Testing, Foodborne Illness, Methods, Microbiology, Pathogen, Research, Staphylococcus aureus, Toxin
Tagged clostridium perfringens, food, lemon juice concentrate, restaurants, staphylococcus aureus
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