2.6.3. PL and bioactive coating
Coated or uncoated green bean samples (2.0
102 to
2.2
102 kg each), inoculated with L. innocua, were placed in
sterile Petri dishes and exposed to PL treatments at an energy dose
comprised between 3
104 and 1.2
105 J/m2 for each side.
The samples were exposed to PL treatments in a bench-top
RS-3000C SteriPulse-XL system (Xenon Corp., Wilmington, Mass.,
USA), which included a power/control module, a treatment
chamber equipped with an adjustable stainless steel tray, lamp
housing with a linear 1600 xenon
flash lamp and a fan. The system
generates 3 pulse/s (3.60
104 s width) of a polychromatic light in
the wavelength range between 100 and 1100 nm. The samples
were placed in the centre of the tray and aligned with their main
axis parallel to the lamp tube at the maximum possible vertical
distance (0.204 m) between the upper surface of the sample and
the lamp. At this distance, the surface of bean samples was
irradiated at an intensity of 2700 J/m2/pulse, for an input voltage of
3800 V, as per manufacture specification. During the treatment,
the samples were exposed to the desired energy dose, rotated 180
along their main axis and exposed again to the same dose. The
dosage applied to each side of the sample was of 3
104, 6
104
and 1.2
105 J/m2, thus within the maximum
fluence value
allowed by FDA (FDA, 1996).