Research round-up: Salmonella in pork, Listeria in lettuce and stopping aflatoxin

By Joseph James Whitworth

- Last updated on GMT

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Related tags Food safety Listeria monocytogenes

With more than a third of the year gone, we take our fourth look at food safety and quality research.

The National Food Institute, Technical University of Denmark​, has developed a method that they claim halves the time it takes slaughterhouses to test for Salmonella in pork meat.

Current testing methods take at least 10 hours to get results but the new method can be completed in less than five hours.

“This enables testing to be carried out within one working shift and the meat can be sent to market faster, which in turn reduces the slaughterhouses’ operating costs for meat chillers and extends the shelf life of the meat in the distribution chain,”​ said the researchers.

The workflow – which is being patented – is similar to current methods at the slaughterhouses.

It consists of a three hour enrichment in standard buffered peptone water and a real-time PCR compatible sample preparation method, based on filtration, centrifugation and enzymatic digestion, followed by fast cycling real-time PCR detection.

Massachusetts Institute of Technology​ (MIT) researchers have created a test based on a type of liquid droplet that can bind to bacterial proteins and be detected by the naked eye or a smartphone.

They said it could offer a faster and cheaper alternative to existing food safety tests.

To turn droplets into sensors, the researchers designed a surfactant molecule containing mannose sugar to self-assemble at the hydrocarbon–water interface, which makes up the top half of the droplet surface.

These molecules can bind to a protein called lectin, found on the surface of some strains of E. coli. When E. coli is present, the droplets attach to the proteins and become clumped together.

So light hitting them scatters in many directions and droplets become opaque when seen from above.

The team hope to adapt the technology into arrays of small wells, each containing droplets customized to detect a different pathogen and linked to a different QR code.

They hope to launch a company to commercialize the technology within the next 18 months.

Work on aflatoxin and Listeria

In other work, Monica Schmidt, a plant geneticist at the University of Arizona​, has engineered a strain of corn that shuts off the ability of a plant fungus to produce aflatoxin.

Schmidt said it has the potential to improve public health and save lives in Africa and prevent tens of millions of tons of grain being destroyed each year.

The procedure embeds a snippet of RNA from an aspergillus fungus into the corn plant. When the host plant and fungus exchange small bits of genetic information during infection, the ability to produce aflatoxin is shut down.

The research was conducted with a $100,000 grant from the Bill and Melinda Gates Foundation but was not awarded second phase funding.

A Purdue University​ study shows that Listeria monocytogenes could live within lettuce in every stage of the growth process inside the plant tissue.

L. monocytogenes can gain entry through cracked seed coats, small tears in root tissue during germination and damaged plant tissue. The researchers found exposing lettuce to the bacteria could lead to infection of plant tissue in 30 minutes.

Research led by Amanda Deering, clinical assistant professor in the Department of Food Science showed L. monocytogenes in romaine lettuce can persist up to 60 days or until harvest.

The study was in defined lab conditions that may not directly represent field conditions.

Not that type of modelling

A team from Cleveland State University​ has been awarded a three-year, $258,000 grant from the US Department of Agriculture for work to create better controls to reduce contamination.

They will develop a mathematical model designed to better assess how pathogens spread through the food supply.

“Ironically, the produce washing process has been identified as a key point of pathogen transfer in the food supply chain as contaminated produce mixes with uncontaminated food and pathogens ‘escape’ without being completely removed from all items," ​said Partha Srinivasan, associate professor of mathematics at CSU and principal project investigator.

The team will create a fully operational produce washing system in a laboratory environment to enable better prediction of pathogen cross-contamination and chemical analysis of sanitizer performance.

University of Maryland​ researchers have developed a model to understand the pathway of E. coli in leafy green production which simulates the effects of soil, irrigation, cattle, wild pig and rainfall in a hypothetical farm.

Results conclude the peak July to November timeframe is consistent with the prevalence of E. coli in cattle and wild pig feces in Salinas Valley, a leafy greens producing region in California.

Concentration of E. coli in leafy greens can be significantly reduced if feces contamination is controlled, said the research team.

The human factor

Meanwhile, Dr Derek Watson, a senior lecturer in the University of Sunderland’s​ Faculty of Business, Law and Tourism, has been investigating how manufacturers can develop a positive food safety culture by adopting a new industry model.

The model was devised for totrain, a North East based training business specialising in food safety, as part of a national research exercise.

Dr Watson designed the questionnaire which finds out issues affect businesses with regards to food safety compliance and offer validated feedback.

“What our model does is to look at clear information and data that demonstrates an organisation has buy-in from its own workforce and how effective are those systems running in the organisation in order to achieve continuous improvement.”

It is designed on the four C’s Model: Control, Co-operation, Communications and Competence.

Data is analysed, followed by one-to-one interviews and focus groups, before being validated and results presented at each stage before a final report.

John Husband, totrain CEO, said with new and emerging threats and the supply of manufactured ingredients becoming global food safety culture is more important than ever.

“We are used to the more tangible elements of food safety, process control, hazard analysis, food safety standards but a manufactures approach to food safety, the behavioural aspects and creating a culture of responsibility is now an important aspect of any food manufactures responsibilities.”

Three businesses are involved with one named as Fulwell Mill, a manufacturer of organic, Fairtrade and healthy foods. The findings will be documented into an academic paper to inform food manufacturers of the core issues they face and suggested solutions.

Finally, family and friends are the first source for food safety information, according to University of Florida​ Institute of Food and Agricultural Sciences research.

From the national online survey of 1,024 people, 64% said they got food safety information from family and friends. Health professionals were deemed the most trustworthy (45% of respondents).

“While most people trust professionals as an information source about food safety, they are more likely to reach out to families and friends for advice,”​ said Alexa Lamm, a UF/IFAS assistant professor of agricultural education and communication.

“The finding holds implications for the power of social media, as people can readily access one another and may be getting information from unreliable sources, rather than leaning on universities or health organizations.”

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