Purpose: Using cucumbers and zucchini squash as model products based on their inherent compositional differences, this study aimed to evaluate the impact of mechanical slicing speed on Listeria transfer.
Methods: Locally obtained zucchini squash and cucumbers were dip-inoculated with a 3-strain avirulent cocktail of Listeria monocytogenes to contain ~ 5 log CFU/g, and air-dried for 1 h. After artificially contaminating a modified NEMCO slicer (Model # 59155491) by slicing one inoculated zucchini or cucumber, 15 uninoculated zucchini or cucumbers were cut at a speed of either 3.3 cm/s or 2 cm/s. The first, middle and last slice from each of 15 samples was collected and analyzed for Listeria by surface-plating on MOX. Texture was measured using a texture analyzer TA-XT2i and water content was determined using a forced-air oven overnight at 100°C.
Results: After slicing one inoculated sample, the pusher and blades each yielded ~3 log CFU/component. After slicing, the 1st and 15th uninoculated zucchini yielded statistically similar (P < 0.05) Listeria populations at the high (3.5±1.1 and 2.7±0.6 log CFU/g) and low (3.4±0.4 and 2.5±0.6 log CFU/g) slicing speeds, respectively. However, for cucumbers significant reductions in Listeria transfer (P < 0.05) were observed between the 1st and 15th cucumber at both the high (3.4±0.3 and 2.2±0.4) and low (3.2±0.2 and 2.7±0.2) slicing speeds. Although water content for zucchini (95.6%) and cucumber (94.1%) was similar, the peak positive force for zucchini (11.78 N) was significantly (P < 0.05) lower than for cucumbers (29.43 N).
Significance: The extent of fresh produce cross-contamination is affected by slicing speed. These findings should prove useful in developing improved predictive models for bacterial transfer based on product composition and expanding current risk assessments across a wider range of products.