3.3. Effect of UV-C light treatment applied after packaging in PA/PE
pouches
The efficacy of UV-C light treatment in extending the shelf life of
pineapple sticks could be impaired by the occurrence of posttreatment
contamination before packaging. Packaging the pineapple
sticks in a highly UV-C light transparent material before UV-C
light treatment could significantly reduce this risk. To verify this
hypothesis, PA/PE film was selected since it is characterised by an
80% UV-C light permeability and has been previously used to
package different samples before UV-C light treatment (Manzocco,
Panozzo, & Nicoli, 2012). Pineapple sticks were thus individually
packaged into PA/PE pouches and exposed to 200 J/m2 UV-C light.
Additional samples were prepared by UV-C light treating pineapple
sticks before packaging into PA/PE pouches. Differently from the
trays, each pouch contained only one pineapple stick. Samples were
then stored at 6 C up to 15 days and analysed for total viable
bacteria, yeast, mould and lactic acid bacteria counts. As shown in
Fig. 5, yeast counts of pineapple sticks submitted to UV-C light
treatment before packaging into PA/PE pouches showed the same
behaviour already observed in the case of PET/EVOH/PE trays
(Fig. 2). Also mould and lactic acid bacteria counts showed the same
behaviour observed in PET/EVOH/PE trays (data not shown). The
similar performance of the plastic materials was also confirmed by
head space analysis showing that oxygen in the pouches was
completely consumed within 5 days, mimicking the trend observed
for the PET/EVOH/PE trays (Fig. 3). No significant differences were
detected in yeast (Fig. 5), mould and lactic acid bacteria counts of
pineapple sticks exposed to UV-C light after packaging into PA/PE
pouches as compared to samples packaged before UV-C light
treatment. Although the lower radiation fluence (80%) on the