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 in contenitori di polistirolo. Alla raccolta e dopo i succitati periodi di frigoconservazione i frutti sono stati trasferiti a 20°C e sono stati sconfezionati in parte subito ed in parte dopo tre giorni di permanenza a 20°C per seguirne la produzione di anidride carbonica e di etilene, il calo peso e valutare soggettivamente l'incidenza dei marciumi, l'imbrunimento interno ed il tempo medio impiegato per raggiungere la maturazione di consumo. Inoltre un gruppo di frutti posto a 20°C non è stato mai sconfezionato in modo da poter monitorare giornalmente l'evoluzione della composizione dell'atmosfera interna al confezionamento. II confezionamento con il film plastico ha contribuito in modo significativo alla riduzione delle perdite di peso. L'incidenza dei marciumi è stata molto contenuta in tutti i trattamenti ed è stata principalmente causata da antracnosi. II film plastico non ha esercitato alcuna influenza sullo sviluppo dei marciumi durante it periodo di frigoconservazione, ma nei frutti trasferiti a 20°C la presenza del film plastico ha favorito lo sviluppo della malattia. Molto efficace è stata l'azione del film plastico nel ridurre l'imbrunimento interno dei tessuti, espressione del danno da freddo, e tale influenza è diventata sempre più marcata con il procedere della frigoconservazione. Scarsa è stata l'influenza del film nel rallentare il processo di maturazione. Al contrario, a partire dalla 4a settimana di frigoconservazione i frutti confezionati hanno impiegato meno tempo per raggiungere lo stadio di maturazione di consumo rispetto ai frutti non confezionati, evidenziando una chiara azione positiva di riduzione delle alterazioni fisiologiche conseguenti all'esposizione alle basse temperature. All'interno dei confezionamenti non sono stati mai raggiunti valori di CO2e di O2tali da interferire sull'attività respiratoria o sulla produzione di etilene.