Food Protection Trends - May/June 2023 - 220

Figure 3. Boxplot of transfer rate rankings from chicken
to masks based on inoculation level (low vs. high).
highlighting the heightened interest. It is vital that safe food
handling practices be communicated to consumers and food
handlers during health emergencies, particularly if consumer
behavior changes significantly, such as wearing masks.
Cross-contamination is one of the most common
problematic food handling practices in residential and
commercial foodservice establishments and has been
investigated by many studies. Some studies have noted
gloves or hands as vehicles for bacterial transfer and
characterized or quantified contamination on surfaces and
utensils. These studies showed that cross-contamination
and bacterial transfer easily occur when food handlers do
not appropriately change gloves, towels, or utensils between
some food preparation tasks, but the degree to which this
occurs is affected by surface, bacteria, or material (7). Crosscontamination
or breaches in aseptic practices is of great
interest outside the food industry, such as in healthcare and
dental industries. In a study to determine whether bacteria
could be transferred from masks to gloved hands, masks
were contaminated during aerosol-causing dental procedures
(9). Researchers recovered contaminants (Streptococci spp.
and Staphylococci spp.) from masks, as well as gloves that
touched the contaminated masks. Most masks worn by the
public throughout the pandemic in the United States were
disposable medical masks or reusable cloth masks that are
not designed to have a tight fit, requiring frequent manual
adjustment to cover the nose, mouth, and chin. It was
unknown whether or how bacteria transfer to and from these
masks in the context of food preparation. Therefore, the
authors of the present study were intrigued by the potential
of cross-contamination via disposable medical masks
220 Food Protection Trends May/June
Figure 4. Ranking of transfer rates grouped by chicken slicing times.
Letters of significance show significant differences in slicing times
(number of times the mask was touched) for chicken to mask A
(A and B) and for mask B to lettuce (C and D). Mask B to lettuce
resulted in no significant differences in the rank of transfer rates
based on initial chicken slicing time.
commonly worn during the COVID-19 pandemic while
handling raw and RTE foods (Fig. 1). The results highlighted
that food handlers, when wearing a mask to prevent disease
transmission, must change the mask between tasks or wear
a properly fitting mask to prevent the need to adjust it
periodically.
Because initial inoculation level (high vs. low) did not
have a significant impact, the results indicate that even if the
natural contamination level is low, cross-contamination may
still occur and lead to foodborne illness. Other studies have
shown or suspected impacts of inoculation level, calling into
question whether a high inoculation level should be used
in studies such as these (11). For example, Montville and
Schaffner (14) found that inoculum size or concentration
had a significant effect on the percent transfer rate of bacteria
from surfaces (cutting boards, hands, gloves, and spigot)
to foods (chicken and lettuce) and from foods to surfaces.
They stated that studies determining cross-contamination
might be affected significantly enough by the inoculum
size to confound conclusions. Others have pointed out that
bacterial transfer studies that examine stepwise or cumulative
transfer run the risk of overestimating (22). These points,
as well as the unlikelihood of natural contamination as high
as 5 log CFU/g pathogen in these scenarios, spotlight the
criticism of using only high inoculation levels in laboratory
studies. Therefore, two inoculation levels were chosen for
the present study to see whether trends in bacterial transfer
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