The overall goal of this procedure is to demonstrate the potential cross-contamination mechanism of the foodborne pathogen, listeria monocytogenes. In a retail deli setting. This is accomplished by first designing a mock deli kitchen to simulate the retail environment.
In the second step, deli meat is inoculated with a fluorescent compound, and then volunteers are asked to slice, package and store the coated meat in the refrigerator. In the final step, the potential cross-contamination will be tracked by observing the fluorescent compound under black light. Ultimately, spectrometry can be used to quantify the fluorescent compound illustrating how cross-contamination occurs in the retail deli environment.
The main advantage of this technique over methods that use microorganisms is that with this technique, the fluorescent compound can be quantified quickly by spectral photometry. Though this method can provide insight into retail, food safety can also be applied to other systems such as small farms, food processing plants, and other food service operations. Begin by placing clean gloves and 70%ethanol on the counter for use during the procedure.
Then use a clean knife and cutting board to slice the deli meat into three approximately 100 millimeter thick samples. Then use a slightly damp clean sponge to evenly coat one sample with freshly prepared fluorescent powder. Next, wrap all of the samples with plastic wrap and use tape to label the fluorescent powder coated sample as a and the remaining two samples as b and c.
Then place the samples at four degrees Celsius and mount black compact fluorescent lights with 13 watt bulbs around the slicer area. Cut a five by five centimeter of aluminum foil to serve as a template for swabbing and fill 1315 milliliter tubes with six milliliters of 95%ethanol at this time as well. Then mount three video cameras in strategic locations to observe all the areas of the mock deli at the same time.
To track the contamination of the deli meat by fluorescent powder, turn the cameras on to videotape the participants during the procedure and take a before picture of the mock deli under black fluorescent light. Then have each participant do the following. First, remove the A labeled meat sample from the refrigerator.
Next, unwrap the meat, saving the plastic wrap, and place the sample on the carriage tray of the slicer. Secure the sample with the meat grip, and then turn the slicer on and adjust the slicer index knob to two. Next, slice and dispense five pieces of meat onto the deli paper, and then turn the power off and release the meat grip.
Place the slices of the meat in a plastic bag labeled A, and then rewrap the meat sample and return it to the refrigerator after slicing samples B and C as just demonstrated taken after photograph of the mock kitchen. To quantify the fluorescent powder contamination, place the sterile aluminum foil template onto each area indicated in the image. Then swab each area with a sterile calcium alginate cotton swab, soaked in 95%Ethanol and place one cotton swab in each of the tubes of 95%Ethanol.
Vortex each tube thoroughly, and then transfer the contents to individual glass cuvettes. Read the absorbance of each swab sample at 370 nanometers, and then use the formula to calculate the amount of fluorescent powder swabbed from each area. Finally, watch the video to quantify the number of times the various surfaces of the mock de were touched.
In this representative experiment, volunteers were videotaped to analyze the average frequency of hand contact on various surfaces of the meat slicer during the preparation of the deli slices. For different viewers then analyzed the video and the frequency of hand contacts was averaged. The data indicate that as expected, the meat grip deli, meat wrapper, deli meat and deli paper had the highest rates of hand contact with an average of eight to 14 contacts per participant.
Surfaces, such as the refrigerator, grip table, meat grip, slicer blade, and various components of the carriage tray were then swabbed, and the amount of fluorescent powder on the various components of the slicer and the mock kitchen were quantified. As just demonstrated as expected. The results indicated that the highest levels of contamination were found on the refrigerator, grip, meat grip, and back plates.
While attempting this procedure, it's important to remember to turn on the video cameras at the same time to ensure that the pictures are synchronized. This method can help answer key questions in the field of food safety, such as how cross contamination occurs, and effective training practices can be developed based on our results.
