Influenza del confezionamento con film plastico sulla maturazione di frutti di avocado (Persea americanaMill.) cv Hass frigoconservati

Hass avocado fruit was harvested in mid April from a
commercial orchard located in the Eastern Sicily. The fruits
were transported under non-controlled conditions in Sardinia, where arrived the day after. Immediately after arrival, fruits were sorted out and were either wrapped individually in polystyrene trays with a 15 mm thick polyolefinic heat shrinkable film or not wrapped (group A), before being stored at 4 °C and 90 % RH for 0, 2, 4, 6, or 8 weeks. At the end of each storage period, when the fruit was transferred at 20°C for ripening, a lot of fruit was un-wrapped (group B), while one more lot was un-wrapped after 3 days of exposure at 20 °C (group C). At day interval respiration rate and ethylene production rate
were measured. Weight loss was releaved at the time of transferring and after 3 days at 20°C. When ripe the fruits were inspected for decay and internal browning, and the time required to reach the eating ripe stage was recorded. In addition, ten packaged fruits (group D) were used to measure the in-package concentration of CO2, 02and C2H4. The necessary time to reach the climacteric peak decreased
with time in storage, and since the fourth week of storage no rise was observed after transferring to 20°C. No important differences were observed among the no-wrapped fruit and the unwrapped ones in relation to C02, either at the moment of transfer
from storage to 20°C or after 3 days at 20°C. Ethylene production rate decreased very highly by the time in storage, and the greatest reductions were observed in no-wrapped fruits, while in general the pattern was similar for the un-wrapped groups. The in-package atmosphere, which ranged between 3% and 6% for C02and 16% and 12% for 02during storage, affected
neither the respiration rate nor the ethylene evolution, in
fact when fruit were transferred at 20°C the CO2and C2H4concentration inside the packages increased, reached the peaks and then decreased with the same timing of no-wrapped or unwrapped fruits. In addition ethylene concentration decreased by the time in storage, as observed both for no-wrapped and unwrapped fruit. The action of wrapping in reducing weight losses resulted very effective; after 3 days at 20°C following 8 weeks storage
the group A, B and C lost 15.5%,3.2% and 2.3% of the initial
weight respectively. Decay was mainly caused by anthracnose
but the incidence was low for all the treatments, in particular no differences were observed until the fruit were in storage, while after the transfer to 20°C it was significandy higher in group C. Wrapping also reduced internal browning, and the differences with the control became much more evident going on with the time in storage.
In fruit placed directly at 20°C, or after 2 week storage, the plastic film slighdy retarded the time required to reach the eating ripe stage; but since the fourth week of storage the time required to the eating ripe stage decreased, and after 8 weeks of storage most of the control failed to ripen while the un-wrapped fruit ripened in about 5 days. Film wrapping was not effective in prolonging postharvest life of Hass avocado fruit by slowing the physiological activity of the fruit, but was very effective in reducing chilling injury, as evidenced by the negligible incidence of internal browning, the higher ethylene production rate, and the shorter time required
to ripening following the fourth weeks of storage, when the severity of chilling injury appeared evident.Frutti di avocado della cultivar Hass sono stati raccolti
nella seconda decade di aprile e frigoconservati a 4 °C e 90% di umiditaà relativa (UR) per 0, 2, 4, 6 e 8 settimane, dopo essere stati in parte confezionati singolarmente con un film plastico termoretraibile di natura poliolefinica di 15 micron di spessore