Compared to the repellency data obtained in the preliminary bioassays
conducted with essential oils on filter paper, where the efficacy
decreased drastically after 3 hours from the beginning of the
experiments, coated films showed a durable efficacy, ranging around
60% for citronella- and oregano-based repellent packaging, and 87%
for the rosemary-based coated film. The retention of effectiveness is
due to the bonding of essential oil to the packaging film by the coating
matrix which, while immobilizing the essential oil preventing its loss
by evaporation, it guarantees a controlled release able to effectively
repel insects. As previous studies demonstrated this coated polymers
are stable for at more than 4 months and in some cases the activity
remains even for more than one year (Nerín, 2012). Further studies
should address the shelf life of repellent packaging by the release kinetics:
indeed it is required that the effectiveness of such systems is at
least as long as the product shelf life.