The use of ultrasound in food technology I: inactivation of peroxidase by thermosonication

The combined effect of high power ultrasound and temperature on the activit y of peroxidase type VI from horseradish suspended in water was studied. Th e tests were performed at 80 degrees C using power ultrasounds having frequ encies of 20, 40, and 60 kHz. Accordingly, the actual ultrasonic powers var ied in the range from 0 to 120 W. Combined treatments were carried out by u sing a laboratory scale plant operating in continuous and in batch mode. In continuous experiments, 46 mi of suspension was circulated in the plant ha ving a sanitation chamber of 20 mi. In the other case, two sets of experime nts were carried out by using a sanitation chamber of 100 mi treating 40 or 80 mi of suspensions, respectively. It was found that the decimal reductio n time of peroxidase at 80 degrees C, D-80, reduces from 65 to 10 min ca. w hen ultrasounds are applied. In particular, D-80 varies with ultrasonic pow er, sonotrode geometry and volume of suspensions submitted to the treatment . It has been demonstrated that the influence of these variables on the dec imal reduction time can be grouped by considering the ultrasound power dens ity, i.e. the ultrasound power per unit area of tip of the probe and unit v olume of suspension. (C) 1999 Elsevier Science Ltd. All rights reserved.