Food Safety Developments Are in the Air
McGinnis July 22, 2008
An experimental treatment from the Agricultural Research Service (ARS) could
one day help protect some fresh produce from potentially dangerous microbes
such as Salmonella, Listeria and Escherichia coli O157:H7.
The treatment relies on cold plasma, which is generated when some form
of concentrated energy--in this case, electricity--is introduced into a gas
until free electrons are torn from the gas's atoms.
This plasma-forming process is related to the technology used to
create plasma for computer chips. But in addition to increasing conductivity,
the process of turning gas into plasma has an antimicrobial effect. The ARS
researchers aren't the first to harness this technology for food safety
purposes, but their method of production has the potential for increased
efficiency and lower costs when applied at a larger scale.
To make plasma, other food safety scientists use gas mixtures that
include exotic gases like helium or argon, but the ARS team is using the
cheapest gas mixture available: air.
In addition to its economic benefits, air--unlike other gases--doesn't
need to be confined to a closed chamber during plasma production. This means
that at a pilot scale, this particular method of plasma treatment could be done
continuously, on a conveyor belt, which would translate to better efficiency
and increased cost savings.
At the ARS
Regional Research Center in Wyndmoor, Pa., microbiologist
Niemira and engineer
Sites--who are developing the process--exposed Golden Delicious apple
samples to various microbial pathogens. Then they treated the samples with
The scientists observed that any exposure to the plasma resulted in a
significant reduction in pathogen numbers without harming the apples. Raising
the air flow rate and length of exposure increased the antimicrobial activity.
The research was conducted at a laboratory scale and is still in
experimental stages. Future studies will include other types of produce and
expand the scale of the plasma-creation process.
This research was published in the July 2008 issue of the
Journal of Food
ARS is a scientific research agency of the
U.S. Department of