Food Protection Trends - January/February 2015 - 38

about the purpose of the study. A rubric was developed
and used for recording observations from the videotaped
meal preparation sessions. A total hand washing score
and a cross-contamination score were calculated for each
participant based on his or her observed behaviors, and
these scores were used to determine differences associated
with group, type of meal prepared, and whether or not
cues were provided. A handwashing score was assigned (0
= no handwashing; 1 = washed less than 20 seconds with
no soap; 2 = washed 20 or more seconds with no soap; 3 =
washed less than 20 seconds with soap; 4 = washed 20 or
more seconds with soap) for each handwashing event (prior
to meal preparation, after handling raw meat, after handling
raw meat packaging, after throwing away trash, after
handling raw egg, and after handling fruits and vegetables).
The handwashing score could range from zero to 24. A
cross-contamination score was assigned based on eight
behaviors (washing hands after handling raw meat, washing
hands after handling raw meat packaging, washing counter
after handling raw meat, using a common hand towel, using
same utensil for raw and cooked meat, using same utensil
for raw meat and salad ingredients, washing cutting board
between uses, and washing bowls between uses). The crosscontamination score could range from zero to eight, based
on yes/no responses to each practice.
Microbiological analysis
Lactobacillus casei (ATCC 334; KWIK-STIK™) was obtained
from Microbiologics, Inc. (St. Cloud, MN) to serve as a
non-pathogenic "tracer" organism to gauge microbiological
cross-contamination associated with handling raw meat. The
culture was received at the K-State Food Safety and Defense
Laboratory (FSDL) and activated according to the supplier's
instructions. The activated culture was transferred onto
Tryptic Soy Agar with 5% Sheep Blood (TSA; Remel, Lenexa,
KS), incubated at 35oC under anaerobic conditions for 48
h, and stored at 4oC. Biochemical confirmation of the tracer
culture as received was done using API 50 CHL test strips
(bioMérieux, Inc., Durham, NC) at the time of receipt. This

working culture was propagated and biochemically confirmed
bi-weekly during the course of the study to ensure continued
viability and purity. To prepare a master inoculum for use on
each day of food preparation, a single colony of L. casei was
transferred into 9 ml of de Mann, Rogosa, Sharpe broth (MRS;
Oxoid Ltd, Basingstoke, Hampshire, UK) and incubated
at 35oC for 24 h. The inoculum was maintained at 4oC and
applied to the raw meat product within 12 h of scheduled
consumer food preparation activities.
Participants received packages of either two raw boneless
skinless chicken breasts or 90% lean ground beef, as
predetermined for their assigned treatment group. The raw
meat for each recipe was purchased at a local supermarket and
stored at 4oC for no more than 3 days prior to inoculation. At
the time of inoculation, raw products were removed from their
original packaging and placed onto new Styrofoam™ trays with
absorbent pads. Two mL of master inoculum was dispensed
onto two chicken breasts (0.5 mL to each side) and evenly
distributed using a L-shaped cell spreader to achieve a target
of 106-7 CFU. A one-pound brick of ground beef was bisected
horizontally with a sanitized knife, and both interior (bisected
middle) and exterior (top and bottom) surfaces were inoculated
evenly with 0.5 mL of culture (total of 2 mL applied) to achieve
a target of 106-7 CFU/g. The two inoculated meat portions were
joined to re-establish the single brick appearance. The trays of
both inoculated chicken breasts and inoculated ground beef
were wrapped with plastic film to appear as purchased from a
retail market and stored in the refrigerator (4oC) for no longer
than 12 h prior to each participant's meal preparation session.
In preliminary studies, meat products to be used in the L. casei
tracer studies with participants were inoculated as described,
trays containing the inoculated meat were overwrapped and
stored for 24 h at 4oC, and L. casei levels were confirmed to
consistently achieve the target level of 106 CFU/g of meat (data
not shown). A standard USDA-mandated safe handling label
(Fig. 1) was applied to each package. It should be noted that
these labels contain the basic food safety messages and so could
be considered external cues that all participants received.

Figure 1. Safe handling instructions for meat packages

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