Assessing a new technique for ensuring fresh produce remains Salmonella-free

September 17, 2012
Electron micrograph showing Salmonella in the pores of a lettuce leaf (photo has been colored). Credit: Kathryn Cross, Institute of Food Research

Researchers at the Institute of Food Research have tested a new technique to ensure fresh produce is free of bacterial contamination.

Plasmas are a mix of highly created when gases are excited by an energy source. They can be used to destroy bacteria but as new research shows, some can hide from its effects in the microscopic of different foods.

Eating fresh fruit and vegetables is promoted as part of a , and consumers are responding to this by eating more and in a greater variety. Ensuring fruit and vegetables are free from contamination by poisoning bacteria is crucial, as they are often eaten raw, without cooking or processing that kills off bacteria.

A move away from current chlorine-based decontamination is driving the search for new, safe ways of ensuring fresh fruit and vegetables are free from without reducing quality or flavour. One technique being investigated is cold plasma technology.

Plasmas can effectively inactivate microorganisms, and as they don't involve such as high temperature they have been suggested for use in decontaminating food surfaces without affecting the structure. Dr Arthur Thompson has been investigating how well cold atmospheric plasmas (CAP) inactivate Salmonella under different conditions and on different foods at the Institute of Food Research, which is strategically funded by the Biotechnology and Biological Sciences Research Council.

Publishing in the journal Food Microbiology, Dr Thompson found Salmonella could be effectively inactivated by plasmas, but the length of exposure varied greatly depending on the type of produce. Other variables, such as the ambient temperature of the produce or the growth phase of the Salmonella had no significant effect. Inactivation on food surfaces took longer than on an artificial membrane filter surface.

To understand why, the researchers looked at the food surfaces with an electron microscope. At this microscopic level of detail, it was possible to see how Salmonella could 'hide' from the effects of the plasmas. Different structures, such as the bumps on the strawberries, the pores in lettuce leaves or the cell walls of potatoes create shadowed zones that block plasma reaching bacteria.

This study was conducted using a laboratory scale plasma device, used as part of ongoing research at IFR to study operational parameters and investigate precisely how cold plasma's destroy bacteria.

"The results suggest scaled up devices or combinations with other mild treatments could provide a very effective solution for destroying bacteria with little or no effect on the produce itself." said Dr Thompson. "What this study shows is that it will be important to take into account the type of food and its surface structure."

Explore further: Food scientists confirm commercial product effectively kills bacteria in vegetable washwater

More information: Inactivation of Salmonella enterica serovar Typhimurium on fresh produce by cold atmospheric gas plasma technology, Food Microbiology, doi: 10.1016/j.fm.2012.08.007

Related Stories

Light, photosynthesis help bacteria invade fresh produce

September 28, 2009

Exposure to light and possibly photosynthesis itself could be helping disease-causing bacteria to be internalized by lettuce leaves, making them impervious to washing, according to research published in the October issue ...

Plasma therapy: An alternative to antibiotics?

December 15, 2010

Cold plasma jets could be a safe, effective alternative to antibiotics to treat multi-drug resistant infections, says a study published this week in the January issue of the Journal of Medical Microbiology.

A zap of cold plasma reduces harmful bacteria on raw chicken

February 2, 2012

A new study by food safety researchers at Drexel University demonstrates that plasma can be an effective method for killing pathogens on uncooked poultry. The proof-of-concept study was published in the January issue of the ...

The time is ripe for Salmonella

March 26, 2012

The ripeness of fruit could determine how food-poisoning bacteria grow on them, according to scientists presenting their work at the Society for General Microbiology's Spring Conference in Dublin this week. Their work could ...

Recommended for you

Ancient walnut forests linked to languages, trade routes

September 4, 2015

If Persian walnut trees could talk, they might tell of the numerous traders who moved along the Silk Roads' thousands of miles over thousands of years, carrying among their valuable merchandise the seeds that would turn into ...

Huddling rats behave as a 'super-organism'

September 3, 2015

Rodents huddle together when it is cold, they separate when it is warm, and at moderate temperatures they cycle between the warm center and the cold edges of the group. In a new study published in PLOS Computational Biology, ...

Fighting explosives pollution with plants

September 3, 2015

Biologists at the University of York have taken an important step in making it possible to clean millions of hectares of land contaminated by explosives.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.