A sensitivity analysis has been also carried out to evaluate the
effect of the total number of contact points. The progress of the
average E. coli cell population xavg after a Dt ¼ 48 h period, for the leaf
ensemble L1-L2-L3 (Fig. 2), is reported in Fig. 6, when an external
contamination xi ¼ 4:8 log CFU/g was assumed, the external temperature
Te being 20 C. xavg was computed through a volume integration
extended to the considered leaves volume. As expected, a
reduction of the total number of contact points (with the same
pseudorandom distribution) prevents the onset of contamination,
therefore the average cell population decreases accordingly. But it is
seen that the dependence is nonlinear, as a mere 12% reduction in
xavg is found when the contact points total number is halved, while
the xavg decrement is 21% when the total number is brought to 1/3.
In order to focus on the most severe scenarios from the food
safety standpoint, and having assessed the relative importance of
the assumptions on food structure, the maximum number of contact
points have been considered in the results presented herein.