A 1500 W ultrasonic processor (VC 1500, Sonics and Materials
Inc., Newtown, USA) with a 19 mm diameter probe was used for
sonication (Fig. 1). Samples (80 ml) were processed at a constant
frequency of 20 kHz. The energy input was controlled by setting
the amplitude of the sonicator probe. Extrinsic control parameters
of amplitude level (24.4–61 lm) and treatment time (2–10 min)
were varied with pulse durations of 5 s on and 5 s off. Tomato
juice samples of 80 ml were placed in a 100 ml jacketed vessel
through which water at 25 ± 0.5 C, with a flow rate of 0.5 l/min
was circulated. Juice temperature during sonication varied from
32 to 45 C. The ultrasound probe was submerged to a depth of
25 mm in the sample. All sonication treatments were carried
out in triplicate.