Tag Archives: tomato

Preharvest treatment improves tomato food safety

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Technology Networks reports that when vegetable farmers harvest crops, they often rely on postharvest washing to reduce any foodborne pathogens, but a new University of Georgia study shows promise in reducing these pathogens — as well as lowering labor costs — by applying sanitizers to produce while it is still in the fields.
Salmonella, Shiga toxin-producing E. coli and Listeria monocytogenes are major causes of foodborne diseases and of public health concern in the U.S. Tomato-associated salmonella outbreaks reported to the Centers for Disease Control and Prevention have increased in frequency and magnitude in recent years, and fresh produce accounted for 21% of E. coli outbreaks reported to the CDC over a 20-year span.

Initially researchers were going to study the use of a nonchlorine-based sanitizer made of two food additives approved by the U.S. Food and Drug Administration — levulinic acid and sodium dodecyl sulfate — as a postharvest wash solution. However, at the suggestion of a producer involved in the study — Bill Brim of Lewis Taylor Farms in Tifton, Georgia — they designed the study using the solution in a preharvest spray, said Tong Zhao, associate research scientist with the Center for Food Safety on the UGA Griffin campus.

While producers commonly use chlorine-based disinfectants — including chlorine gas, sodium hypochlorite, calcium hypochlorite and chlorine dioxide — to treat produce postharvest, the preharvest application of bactericides is not a common practice, Zhao said.

Building on previous studies of levulinic acid and sodium dodecyl sulfate that showed the combination substantially reduces both salmonella and E. coli on romaine lettuce without adversely affecting lettuce quality, Zhao hoped to prove the combination’s effectiveness on reducing foodborne pathogens on tomato plants contaminated with salmonella, Shiga toxin-producing E. coli and Listeria monocytogenes.

In the field studies, the spray treatment significantly reduced the total bacterial population on the surface of tomatoes, determining that this preharvest treatment is a practical, labor-cost effective and environmentally friendly approach for the control and reduction of foodborne pathogens. The study was recently published in the journal Food Control.

“This combination of chemicals had never been used for preharvest treatment,” said Zhao, who studied the combination 10 years ago as an alternative to chlorine treatment as a postharvest wash. “Free chlorine is easily neutralized by organic

71 now sick from Salmonella in Sweden linked to tomatoes

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Outbreak News Today reports Swedish health authorities, or Folkhalsomyndigheten are reporting 17 additional Salmonella Typhimurium cases in the current outbreak, bringing the total outbreak cases to 71 since August.

The Swedish National Food Agency and the Public Health Agency continue to investigate the outbreak to identify the source of the infection. The investigation shows that small tomatoes are the likely source of the outbreak. The tomatoes are no longer left in grocery stores, the outbreak has subsided and the risk of being infected is very small.

Uh-huh.

We’re all hosts on a viral planet

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About 1986, I was a MSc graduate student working on Verticillium (that’s a fungus) in tomatoes), published a couple of peer-revived papers, and then became the editor of the student newspaper (circ 25,000) after writing a science column about cats for a year because they were the first warm-blooded pets I had ever had.

I think my friend Mary knows what I’m talking about.

I also spent a lot of time looking through the electron microscope, which was also a great place to have sex.

I had a lot of sex there.

Researchers in the Agriculturpal Research Service (ARS) Electron and Confocal Microscopy Unit can magnify a cell’s internal structures to 200,000 times their size, flash freeze mites in liquid nitrogen to create striking “snapshots” as they feed, and create color-enhanced images that show a virus infecting its host. The resulting images help scientists determine how agricultural pests and pathogens feed, reproduce, respond to threats, and survive.

A sampling of the unit’s digital photo album shows the eclectic nature of its efforts.

The team also has a unique 3D printing capability that allows them to transform the images they create into hand-size 3D models that are the most structurally accurate models of mites and other organisms currently available. The researchers hope that one day they will be able to upload the 3D files to an online database so that anyone with a 3D printer can reproduce them to use as instructional aids, in research, or for scientific outreach.

Safe food, farm to fork

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It’s been my lab’s moto for over 20 years.

Nice to see the American Society for Microbiology catch up (nothing personal, Randy, just idle academic chirping, but at least you get paid).

Fresh produce supply chains present variable and diverse conditions that are relevant to food quality and safety because they may favor microbial growth and survival following contamination. This study presents the development of a simulation and visualization framework to model microbial dynamics on fresh produce moving through postharvest supply chain processes.

The postharvest supply chain with microbial travelers (PSCMT) tool provides a modular process modeling approach and graphical user interface to visualize microbial populations and evaluate practices specific to any fresh produce supply chain. The resulting modeling tool was validated with empirical data from an observed tomato supply chain from Mexico to the United States, including the packinghouse, distribution center, and supermarket locations, as an illustrative case study. Due to data limitations, a model-fitting exercise was conducted to demonstrate the calibration of model parameter ranges for microbial indicator populations, i.e., mesophilic aerobic microorganisms (quantified by aerobic plate count and here termed APC) and total coliforms (TC). Exploration and analysis of the parameter space refined appropriate parameter ranges and revealed influential parameters for supermarket indicator microorganism levels on tomatoes. Partial rank correlation coefficient analysis determined that APC levels in supermarkets were most influenced by removal due to spray water washing and microbial growth on the tomato surface at postharvest locations, while TC levels were most influenced by growth on the tomato surface at postharvest locations. Overall, this detailed mechanistic dynamic model of microbial behavior is a unique modeling tool that complements empirical data and visualizes how postharvest supply chain practices influence the fate of microbial contamination on fresh produce.

IMPORTANCE Preventing the contamination of fresh produce with foodborne pathogens present in the environment during production and postharvest handling is an important food safety goal. Since studying foodborne pathogens in the environment is a complex and costly endeavor, computer simulation models can help to understand and visualize microorganism behavior resulting from supply chain activities. The postharvest supply chain with microbial travelers (PSCMT) model, presented here, provides a unique tool for postharvest supply chain simulations to evaluate microbial contamination. The tool was validated through modeling an observed tomato supply chain. Visualization of dynamic contamination levels from harvest to the supermarket and analysis of the model parameters highlighted critical points where intervention may prevent microbial levels sufficient to cause foodborne illness. The PSCMT model framework and simulation results support ongoing postharvest research and interventions to improve understanding and control of fresh produce contamination.

Postharvest supply chain with microbial travelers: A farm-to-retail microbial simulation and visualization framework

American Society for Microbiology, 10.1128/AEM.00813-18

Claire Zoellner, Mohammad Abdullah Al-Mamun, Yrjo Grohn, Peter Jackson, Randy Worobo

Organic BS: Hucksters make a buck, plead guilty to fraud in Canada

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Chapman and I toured southern Ontario tomato farms and processors 16 years ago, and shot youtube video, but youtube didn’t exist, so we didn’t know what to do with the video.

Here it is.

Trevor Wilhelm of the Windsor Star reports that bankrupt Maidstone tomato processing company received a controversial $3- million provincial grant is expected to plead guilty next month to purposely mislabelling products as organic.

An order signed by a Toronto judge states that William (Bill) Thomas, owner of Thomas Canning, has agreed to plead guilty on behalf of the company and pay a $40,000 fine. In exchange, several other charges against the company and Thomas himself will be withdrawn.

The judge’s order states the guilty plea must be entered no later than Nov. 23. Thomas’s next scheduled court appearance in Windsor is Nov. 6.

The guilty plea and $40,000 fine is part of a joint submission from prosecution and defence lawyers. But the judge’s order states the court is not bound by that submission.

According to documents previously filed in Ontario court by the Canadian Food Inspection Agency, Thomas and his company are accused of 11 offences in contravention of the Food and Drug Act, the Consumer Packaging Act and the Canada Agricultural Products Act.

Thomas Canning and its owner are accused of labelling regular canned tomato products as organic.

The company and Thomas were also charged with falsifying the country of origin on their products between September 2013 and July 2015, passing off American tomato products as Canadian with labels that read “Product of Canada.”

Thomas was also charged personally with lying to a federal food inspector on Jan. 8, 2015, about canned tomato paste sold under the brand Tree of Life.

The company’s website, which is no longer accessible, previously stated that Thomas Canning charged a 20 per cent premium for organic products.

Thomas Canning received a $3-million grant from the province in 2014 to build a new fruit and vegetable processing facility. The plant was never built.

Farmers planted additional crops, signing contracts with Thomas Canning to supply tomatoes to the new plant. Those additional tomatoes rotted in the field.

Before the company went into receivership earlier this year, nine farmers were suing Thomas Canning for $2.85 million for reneging on contracts to grow tomatoes in 2016.

The Ontario Ministry of Agriculture, Food and Rural Affairs has said it’s fine with the way Thomas Canning used the money. The ministry said the money was used to create and retain jobs, rebrand its Utopia products and open up markets in Nigeria and China.

After receiving the $3 million, Thomas Canning went bankrupt. That process is still winding its way through court.

Going public: FDA not liable for $15 million in damages sought by tomato grower for food safety warning error

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I remember. I was in Quebec City with a pregnant Amy when all this went down. Doing hour-long iradio interviews where midnight callers asked about aliens and Salmonella.

tomato

Michael Booth of the National Law Journal reports the U.S. Food and Drug Administration cannot be held liable for financial damages suffered by farmers when it issues emergency, but erroneous, food safety warnings, the U.S. Court of Appeals for the Fourth Circuit has ruled.

In its Dec. 2 ruling, the Fourth Circuit refused to allow a South Carolina tomato farmer to seek more than $15 million in damages from the federal government under the Federal Tort Claims Act after the FDA issued a warning that an outbreak of Salmonella Saintpaul was caused by contaminated tomatoes, when it was later determined that the outbreak was caused by contaminated peppers imported from Mexico.

A South Carolina tomato farm, Seaside Farm on St. Helena Island, sued the federal government, claiming that the incorrect warnings issued by the FDA, beginning in May 2008 and later corrected, cost it $15,036,294 in revenue. The Fourth Circuit agreed with a trial court that the FDA was acting within its authority to issue emergency food safety warnings based on preliminary information in order to protect public health.

“We refuse to place FDA between a rock and a hard place,” wrote Judge J. Harvie Wilkinson for the panel, sitting in Richmond.

“One the one hand, if FDA issued a contamination warning that was even arguably overbroad, premature, or of anything less than perfect accuracy, injured companies would plague the agency with lawsuits,” he said.

“On the other hand, delay in issuing a contamination warning would lead to massive tort liability with respect to consumers who suffer serious or even fatal consequences that a timely warning might have averted,” Wilkinson said.

Judges Paul Niemeyer and Dennis Shedd joined in the Dec. 2 ruling.

The medical crisis arose on May 22, 2008, when the New Mexico Department of Health notified the Centers for Disease Control and Prevention (CDC) that a number of residents had been diagnosed as having Salmonella Saintpaul, a strain that causes fever, diarrhea, nausea and, if left untreated, death. Soon after, similar reports came in from Texas.

The CDC determined that a “strong statistical” analysis determined that the illnesses were caused by people eating raw tomatoes. By June 1 of that year, CDC was investigating 87 illnesses in nine states.

tomato-irradiationThe FDA then issued a warning to consumers in New Mexico and Texas. By June 6, 2008, however, reported cases grew to 145 incidents in 16 states. In New Jersey, three people were reported to have been diagnosed with the illness. On June 7, the FDA issued a blanket nationwide warning telling consumers that they should be wary of eating raw tomatoes. (New Jersey tomatoes were not implicated, since they do not ripen until later in the season.)

The warning listed a number of countries and states, including South Carolina, that were not included and were not implicated, but those states were not listed in media reports. Eventually, 1,220 people were diagnosed as having Salmonella Saintpaul.

Raw tomatoes were not the cause of the illnesses, however. The contamination was traced to imported jalapeño and serrano peppers imported from Mexico.

Seaside Farm, which had just harvested a large crop of tomatoes, sued in May 2011. The farm claimed the erroneous FDA warning about tomatoes cost it $15 million-plus damages in revenue. 

First world problems: ‘People feel very strongly about their tomatoes’ Fruit flies are a factor in warm climates like Brisbane and Florida

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Michael Pollan is an entertainer from a long line of American hucksters.

He’s not a professor, he’s a decent writer of food porn.

powell-tomato(Those with the least qualifications most actively seek the perceived credibility of a title.)

When his biggest soundbite is “I’d never eat a refrigerated tomato,” the absolutism shines through like any other spoiled demagogue.

Dan Charles of NPR fell into the gotta-be-cool trap without knowing shit, but eventually admitted it.

Charles says, There’s a laboratory at the University of University of Florida, in Gainesville, that has been at the forefront of research on tomato taste. Scientists there have been studying the chemical makeup of great-tasting tomatoes, as well as the not-so-great tasting ones at supermarkets.

“There’s a lot of things wrong with tomatoes right now,” says Denise Tieman, a research associate professor there. “We’re trying to fix them, or at least figure out what’s going wrong.”

These researchers studied this refrigeration question. They looked at what happened when a tomato goes into your kitchen fridge, or into the tomato industry’s refrigerated trucks and storage rooms.

Some components of a tomato’s flavor were unaffected, such as sugars and acids. But they found that after seven days of refrigeration, tomatoes had lower levels of certain chemicals that Tieman says are really important. These so-called aroma compounds easily vaporize. “That’s what gives the tomato its distinctive aroma and flavor,” she says.

The researchers also gave chilled and unchilled tomatoes to dozens of people to evaluate, in blind taste tests, “and they could definitely tell the difference,” says Tieman. The tomatoes that weren’t chilled got better ratings.

The scientists also figured out how chilling reduced flavor; cold temperatures actually turned off specific genes, and that, in turn cut down production of these flavor compounds.

Tieman speculates that someday scientists will figure out how to keep those genes turned on, even when chilled, so the tomato industry can have it both ways: They can refrigerate tomatoes to extend shelf life, without losing flavor.

tomatoThankfully, chilling didn’t seem to affect nutrition – the chilled tomatoes were just as nutritious as the non-refrigerated ones.

The new findings appear in this week’s issue of the Proceedings of the National Academy of Sciences.

As significant as the results are, they probably won’t end the great tomato refrigeration debate.

“It’s not so clear cut,” says Daniel Gritzer, culinary director at SeriousEats.com, a food website. Two years ago, he did a series of blind taste tests with many different tomatoes, in New York and in California.

“Sometimes I found that the refrigerator is, in fact, your best bet,” says Gritzer.

That’s especially true for a tomato that’s already ripe and at peak flavor, he says. If you let that tomato sit on your counter, it’ll end up tasting worse.

Gritzer wrote a long blog post, detailing his results, and got a flood of reaction. “Some people wrote to say, ‘Hey, this is what I’ve always found, I’m so glad you wrote this,'” Gritzer says. “And then, a lot of people pushed back saying, ‘You’re insane, you don’t know what you’re talking about.'”

And when the hockey kids call me Doug, I say that’s Dr. Doug, I didn’t spend six years in evil hockey coaching land to be called Mister.

We’re all hosts on a viral planet, plants too

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I studied Verticillium in tomato plants in my aborted MSc degree.

Journalism was more fun, and my hands were black from the printing press instead of green (yes, I am that old).

tomato.cmvLaurel Hamers of Science News writes that instead of destroying its leafy hosts, one common plant virus takes a more backhanded approach to domination. It makes infected plants more attractive to pollinators, ensuring itself a continued supply of virus-susceptible plant hosts for generations to come.

The strategy might be a way for the virus to discourage resistance from building up in the plant population, University of Cambridge biologist John Carr and colleagues report online August 11 in PLOS Pathogens.

“It looks like the pathogen is cheating a little bit —but in a way that helps its host,” says Carr.

Plants give off cocktails of volatile chemicals that send signals to pollinators, predators and other plants. Carr and his team found that tomato plants infected with cucumber mosaic virus gave off a different cocktail of these chemicals than non-infected plants — and that bumblebees preferred the infected plants’ brew.

That’s a small consolation for plants that have been stunted and blemished by cucumber mosaic virus. When infected tomato plants relied on self-fertilization, they produced fewer seeds on their own than their healthy counterparts. But when bumblebees helped out, infected plants’ seed production matched healthy ones.

The virus benefits, too, Carr says. By ensuring that sick plants can still reproduce, “those genes enabling susceptibility to the virus will stay in the population.” And plants that are resistant to the virus can’t gain the foothold that they could if all the sick plants died too soon.

The team also found that cucumber mosaic virus changes plants’ chemicals by disrupting their natural defenses against disease.

Normally, plants can identify when bits of foreign genetic material (like those from a virus) have worked their way inside. Specialized silencing enzymes snap into action and chop up the foreign invaders. But a cucumber mosaic virus protein called 2b disrupts this process by binding to the silencing molecules so that they can’t do their job, Carr and his colleagues found.

That lets the virus infect the plant more easily— and it also changes the way the plant turns its genes on and off. When the researchers tested a virus that didn’t have the gene for the 2b protein, the infected plants didn’t shift the chemicals they gave off like the plants infected with the fully functioning virus did.

The link between the 2b protein and volatile production is a major finding that could help scientists to better understand how viruses manipulate their hosts, says Andrew Stephenson, a biologist at Penn State University who wasn’t involved in the work.

But further research is needed to convincingly show that the increased pollination is really a fitness benefit for the plant, Stephenson says. Even though the infected plants produced more seeds, those seeds could be smaller and less likely to germinate, he says. And the shift in chemical production could lure aphids (which transmit the virus from plant to plant) just as much as bumblebees.  

Ya ain’t gonna wash it off, so breed it off: Salmonella growth on – not in – tomato plant surfaces

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Foodborne illness-causing enteric bacteria are able to colonize plant surfaces without causing infection. We lack an understanding of how epiphytic persistence of enteric bacteria occurs on plants, possibly as an adaptive transit strategy to maximize chances of reentering herbivorous hosts.

wax.on.wax.offWe used tomato (Solanum lycopersicum) cultivars that have exhibited differential susceptibilities to Salmonella enterica colonization to investigate the influence of plant surface compounds and exudates on enteric bacterial populations.

Tomato fruit, shoot, and root exudates collected at different developmental stages supported growth of S. enterica to various degrees in a cultivar- and plant organ-dependent manner. S. enterica growth in fruit exudates of various cultivars correlated with epiphytic growth data (R2 = 0.504; P = 0.006), providing evidence that plant surface compounds drive bacterial colonization success. Chemical profiling of tomato surface compounds with gas chromatography-time of flight mass spectrometry (GC-TOF-MS) provided valuable information about the metabolic environment on fruit, shoot, and root surfaces. Hierarchical cluster analysis of the data revealed quantitative differences in phytocompounds among cultivars and changes over a developmental course and by plant organ (P < 0.002). Sugars, sugar alcohols, and organic acids were associated with increased S. enterica growth, while fatty acids, including palmitic and oleic acids, were negatively correlated.

We demonstrate that the plant surface metabolite landscape has a significant impact on S. enterica growth and colonization efficiency. This environmental metabolomics approach provides an avenue to understand interactions between human pathogens and plants that could lead to strategies to identify or breed crop cultivars for microbiologically safer produce.

Importance: In recent years, fresh produce has emerged as a leading food vehicle for enteric pathogens. Salmonella-contaminated tomatoes represent a recurrent human pathogen-plant commodity pair. We demonstrate that Salmonella can utilize tomato surface compounds and exudates for growth. Surface metabolite profiling revealed that the types and amounts of compounds released to the plant surface differ by cultivar, plant developmental stage, and plant organ.

food-art-tomatoDifferences in exudate profiles explain some of the variability in Salmonella colonization susceptibility seen among tomato cultivars. Certain medium- and long-chain fatty acids were associated with restricted Salmonella growth, while sugars, sugar alcohols, and organic acids correlated with larger Salmonella populations. These findings uncover the possibility of selecting crop varieties based on characteristics that impair foodborne pathogen growth for enhanced safety of fresh produce.

Environmental metabolomics of the tomato plant surface provides insights on Salmonella enterica colonization

Appl. Environ. Microbiol. May 2016 vol. 82 no. 10 3131-3142

Sanghyun Han and Shirley A. Micallef

http://aem.asm.org/content/82/10/3131.abstract?etoc

Ain’t gonna wash it off: On-farm food safety for produce is where it starts

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Tomatoes have been implicated in various microbial disease outbreaks and are considered a potential vehicle for foodborne pathogens.

food-art-tomatoTraceback studies mostly implicate contamination during production and/or processing. The microbiological quality of commercially produced tomatoes was thus investigated from the farm to market, focusing on the impact of contaminated irrigation and washing water, facility sanitation, and personal hygiene.

A total of 905 samples were collected from three large-scale commercial farms from 2012 through 2014. The farms differed in water sources used (surface versus well) and production methods (open field versus tunnel). Levels of total coliforms and Escherichia coli and prevalence of E. coli O157:H7 and Salmonella Typhimurium were determined. Dominant coliforms were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. No pathogens or E. coli were detected on any of the tomatoes tested throughout the study despite the high levels of coliforms (4.2 to 6.2 log CFU/g) present on the tomatoes at the market. The dominant species associated with tomatoes belonged to the genera Enterobacter, Klebsiella, and Citrobacter. Water used on the farm for irrigation considered not fit for purpose according to national agricultural irrigation standards, with high E. coli levels resulting from either a highly contaminated source water (river water at 3.19 log most probable number [MPN]/100 ml) or improper storage of source water (stored well water at 1.72 log MPN/100 ml). Salmonella Typhimurium was detected on two occasions on a contact surface in the processing facility of the first farm in 2012. Contact surface coliform counts were 2.9 to 4.8 log CFU/cm2.

Risk areas identified in this study were water used for irrigation and poor sanitation practices in the processing facility. Implementation of effective food safety management systems in the fresh produce industry is of the utmost importance to ensure product safety for consumers.

Microbiological food safety status of commercially produced tomatoes from production to marketing

Journal of Food Protection, Number 3, March 2016, Pages 392-406, DOI: http://dx.doi.org/10.4315/0362-028X.JFP-15-300

N. van Dyk, W. de Bruin, E. M. du Plessis, and L. Korsten

http://www.ingentaconnect.com/content/iafp/jfp/2016/00000079/00000003/art00006