Effetti dell'applicazione per breve periodo di un'atmosfera a bassa concentrazione d'ossigeno sui parametri qualitativi dei frutti di tangelo "Page"

A brief prestorage treatment of Page tangelo [(Citrus paradisiMacf. xC. reticulata) xC. reticulata] with a low-O2atmosphere was performed, in order to assess if anaerobic conditions could delay senescence of the fruit. Freshly harvested fruits were randomly selected for minimal blemishes and omogenous size and divided into two plots. Fruits to be treated were put in a 250-liter plastic container at 20°C in which an atmosphere containing 99% N2+ 1 % O2was established within 1 hour by flushing water saturated N2from a cylinder at a flow rate of 5L/min and then sealing ermetically the container. Control fruits were placed in a container and flushed with water saturated air at the above cited conditions. After 24 hours from the beginning of the experiment containers were opened and fruit transferred immediately either at simulated shelf-life (SL) conditions at 20°C and 70% of relative humidity (RH) for 30 days, or in cold storage at 4°C and 95% RH for 4 or 8 weeks periods, each one followed by 1 week of SL. Fruits placed directly in SL were inspected at ten day intervals, while the cold stored fruits after each cold storage and subsequent SL periods. At each inspection the following parameters were monitored: weight loss and decay as percent, as well as firmness of the entire fruit, expressed as deformation in mm, by applying a 1 kg weight on the equatorial side of the fruit for 5 seconds. A visual test was assessed by five technicians, who were asked to rank the overall appearance of 60 undamaged fruit with a scale of 1 to 5 with 3 as the limit of saleability. The incidence of chilling injury simptoms (pitting) was also carried out. At each inspection time three replicates of 20 fruits taken at random were used for juice chemical analyses, which included pH, total soluble solid content (TSS) titratable acidity, vitamin C, ethanol and acetaldehyde content. Respiration rate and ethylene production were also monitored by TCD and FID gaschromatography. Presto rage anaerobic applications significandy reduced deformation of the fruit, probably due to a reduction of the enzimatic activity involved in the cell wall breakdown. Infact, cell turgor, the other important factor responsible for fruit firmness, would not be involved in firmness differences, as water loss leading to a diminution in water pressure of cells was quite similar between exposed and not exposed fruits. Moreover, in citrus fruits weight loss is mainly localized in the epicarp, that assumes a leather like aspect being in this way more resistant to deformation forces, alto ugh in this experiment this aspect was not encountered. The low-O2treated tangelos also maintained a better external appearance than the control fruit. In particular, fruit that had been exposed to anarobic conditions appeared more fresh, with the stem end greener and with a more shining epicarp than control fruits. The positive effects of the anaerobic treatment were recorded chiefly during the 30 days of SL, while during the cold storage regimes the beneficial role of the exposition could have been overlapped by the low temperature. Accumulation of acetaldehyde and ethanol in the fruit juice was registered at the end of the 24h-treatment, the amount of ethanol being 100 times higher than that of acetaldehyde. However, both acetaldehyde and ethanol content declined quickly by 10 days of SL. The level of ethanol, although very high in some cases, did not impart any off-flavour to fruits, as detected by an informal panel test of five persons.Frutti di tangelo Page [ibrido ottenuto dall'incrocio (Citrus paradisiMacf. xC. reticulata) xC. reticulata] sono stati esposti ad un'atmosfera contenente inizialmente il 99% di N2e l'1 % di O2alla temperatura di 20°C e trasferiti dopo 24 ore in condizioni di shelf-life (SL) a 20°C e 70% di umidità relativa (U.R.) per 30 giorni, oppure a 4 °C e 95% di U.R. per periodi di 4 e 8 settimane a ciascuno dei quali seguiva una settimana di SL. L'applicazione delle condizioni anaerobiche ha avuto degli effetti benefici sulla senescenza del frutto, rallentando sia il naturale peggioramento dell'aspetto esterno, sia il rammollimento rispetto ai frutti del controllo. I frutti trattati hanno fatto registrare un contenuto più alto in solidi solubili totali e in vitamina C. Tali risultati sono stati evidenti quasi esclusivamente nei frutti posti direttamente in SL. Il trattamento ha favorito l'accumulo di acetaldeide ed etanolo nel succo rispetto ai frutti non trattati. Si è registrato comunque un rapido declino della concentrazione dei due metaboliti già dopo 10 giorni di SL. Gli alti valori di concentrazione di etanolo nel succo raggiunti in alcuni casi non hanno comunque pregiudicato le caratteristiche organolettiche del prodotto. Infatti, i frutti all'assaggio non mostravano odori e sapori sgradevoli.