A
biofilm is defined as a “microbially-derived sessile community which is
characterized cells that are irreversibly attached to a substratum or
interface, or to each other” are embedded in a matrix of extracellular
polymeric substances (EPS). More simply put, microorganisms attach to surfaces and develop biofilms. Biofilms can be found in natural environments, on surfaces around the home, but
more alarmingly, they can be found in food processing facilities.
Cells
in a biofilm have the ability to survive cleaning and sanitization. The
resistance to sanitizers increases with the maturity of the biofilm. In the
last decade, a number of studies have been conducted to determine a variety of
sanitizers’ efficacy against biofilms. In 2010, the Department of Food Science
at Purdue University compared the effect of chlorine dioxide gas, aqueous
chlorine dioxide, and aqueous sodium hypochlorite treatments on the
inactivation of listeria monocytogenes containing biofilms. Listeria
monocytogenes is a food-borne pathogen with the highest mortality rate. It
has the ability to adhere to and grow on a variety of surfaces found in
food processing plants. The study proved that the biofilm developed from the
five-strain mixture was more resistant to the sodium hypochlorite treatment
than either chlorine dioxide (CD) option. Aqueous CD resulted in significantly
greater log reduction of biofilm cells for shorter treatment times as compared
to CD gas treatment. However, once the CD gas dissolved in the water present,
it was similar in effectiveness.
This
comparison of chlorine dioxide’s efficacy against biofilms in both the gaseous
or aqueous state was taken a step further by the Republic of Korea’s Department
of Biotechnology and University of Georgia’s Center for Food Safety in 2014.
This team evaluated chlorine dioxide’s ability to kill Bacillus cereus
spores in biofilm formed on a stainless steel surface. Bacillus cereus
is a spore-forming bacterium that can cause foodborne diseases. The study
pointed out that while aqueous CD has “the advantage of being easy to produce
and handle compared to gaseous ClO2,” its residual moisture may
promote the growth of molds after treatment of food-contact surfaces. It was
determined that the antimicrobial activity of chlorine dioxide gas was higher
than that of the aqueous, and spores were inactivated within one hour.
Interested
in reading more? You can view the published articles here:
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