The sonication experiments were conducted at a laboratory
scale operation using a standard configuration of ultrasonic horn
operating at fixed frequency of 20 kHz. The initial trials during this
study showed that the ultrasound treatment at lower power levels
did not result in the desired reduction in the number of food borne
pathogens. Trials were conducted at different power levels ranging
from 20 W to 120 W at different treatment times. At power levels
below 100 W, maximum of 33.5 log reduction in the microorganisms which existed in the juice as the natural flora was achieved
by increasing the treatment time from 15 to 30 min and also by
decreasing the volume of the juice to about 100–150 ml. The lower
extent of disinfection at lower power dissipation can be attributed
to the lower cavitational intensity being generated in the liquid
which is not capable of completely disinfecting the microorganisms [30]. Thus it can be established that to definitely damage
the microbial cell walls to the required extent, higher ultrasound
energy input is necessary