Dry heat thermal inactivation of Listeria innocua on deli slicer components
Posted: October 11th, 2010 - 7:23am
a thermal kill step was evaluated as a method of obtaining an additional margin of safety for retail deli meat slicers following cleaning and sanitizing. Retail deli slicers were cut into coupons or marked off in grids, cleaned and sanitized. Listeria innocua, an established thermal-resistant Listeria species, was inoculated at 107 CFU/cm2. The inoculated components or stainless steel coupons were placed in a dry heat oven at 66°C or 80°C and sampled at 0.5, 1, 3 and 15 h. There was no statistically significant difference in survival between the stainless steel and the cast aluminum portions of the slicer. at 66oC, there was an initial drop of approximately 1.5 log CFU after 30 min of treatment, but recovery of L. innocua remained at more than 4 log CFU even after 15 h.When temperatures were increased to 80oC, the decrease was over 4 log, but the thermal treatment times (15 h) were longer than an overnight treatment that might be considered practical for a retail deli. From these results, it appears that dry thermal treatments at temperature of 80oC and times up to 15 h are not sufficient to produce a 5-log reduction of residual L. innocua that may have survived improper cleaning and sanitizing of the deli slicer.