As temperature increased during the Dynashock wave ultrasound
treatment, heat liberation due to cavitation must have contributed to
inactivation of E. coli O157:H7. In apple juice (Fig. 2c), the temperature
reached 54.5 C by the end of the 50-min treatment. From the
heat inactivation studies summarized in Fig. 1 and the heat penetration
data presented in Fig. 2c, the contribution of heat to the total
lethality in the ultrasound treated apple juice was calculated. The
lethal rate for a given time interval, L, due to heat was calculated
using Equation (1), where T is the process temperature (C) at time t,
and Tr is the reference temperature, in this case 54.5 C. The z value is
the heat resistance parameter calculated in Fig. 1f.