THERMAL SANITIZING IN A COMMERCIAL DISHWASHING MACHINE

This paper presents an experimental investigation on the thermal sanitization of food contact surfaces in a pilot dishwashing machine. The reduction of counts for Escherichia coli inoculated on clean glass surfaces was assayed in several tests performed under different conditions of temperature and duration of the washing cycles. The main aim of the measurements was to establish the relationship between operating conditions and sanitizing performance. The experimental results show that reduction of microbial counts clearly increases with the volume of water used for rinsing. On the other hand, the effect of the rinsing water temperature is less remarkable. It is inferred from these results that the reduction of microbial counts on food contact surfaces is mainly due to the mechanical elution of water jets rather than to thermal inactivation. The experimental results are analyzed using available kinetic data for reference organisms. The kinetic analysis confirms that the thermal effect is not sufficient to obtain a significant reduction of microbial counts on food contact surfaces under typical conditions of temperature and washing cycle length