2.3.2. High intensity light pulses
Pulsed light treatment was applied using a pulsed light sterilization
system (Steri-Pulse XL 3000, Xenon Corp., MA, USA) consisting
of a control module, a lamp housing containing a Xenon
flashlamp, and a sterilization chamber. A continuous flow system
was developed in-house and located within the sterilization chamber.
Juice was pumped (Section 2.3.1) through two quartz tubes
(length 30 cm, 1 mm i.d) positioned at a distance of 1.9 cm from
the lamp (Fig. 1). The tubes were located on a grooved (300 mm
length 3 mm diameter) aluminium assembly through which
coolant (ethylene glycol at 10 C) was circulated to prevent overheating
of the juice. To minimise temperature rise, the product was
cooled pre- and post-processing with cooling coils submerged in
iced water, in addition to in-process cooling within the flow cell
system. The post-processing temperature typically did not exceed
30 C. The Xenon source produced light pulses of 360 ls width at
a frequency of 3 Hz and delivered radiant energy of 1.213 J/cm2
per pulse. The total cumulative length of exposed tubing was 40
(2 20 cm) cm and the total energy dosage was 3.3 J/cm2, based
on a sample flow rate of 20.8 ml/min.