Effects of vacuum and pressure infiltration of pollulan and chitosan coatings on the composition of interanl atmosphere (CO2, O2, ethanol and acetaldehyde), quality preservation and postharvest decay of "Wahington Navel" oranges

Citrus fruit are subjected to transpiration losses, chilling injury and postharvest decay due to fungus growth. In order to reduce these losses fruit are often coated with commercially formulated waxes with fungicides. In this study an effort was made to determine the suitability of some alternatives to commercial waxing and postharvest fungicides, using dipping, vacuum and pressure infiltration of edible coating materials. Orange fruit c.v. 'Washington Navel' was purchased from a commercial citrus distributor based in Central Macedonia and transferred to the Post Harvest Facilities, at the Pomology Laboratory of Aristotle University in Thessaloniki where the experiment was carried out and where fruit was stored until its use for the experiments. The aim of this study was to investigate: a) whether chitosan and pollulan coatings in different concentrations, applied with dipping, vaccum and pressure infiltration methods can promote the quality preservation of fuit during 2-3 months of storage at 5 deg C and by testing the coating permeability to oxygen and carbon dioxide; b) whether chitosan and pollulan coatings in different concentrations posses antifungal properties to control P. italicum (blue mold rot). The results were influenced by the method of application (dipping, vaccum and pressure) as well as the coating materials (chitosan and pollulan). Pressure and vacuum infiltration of coating materials resulted in greater weight loss than the pollulan coated fruits with dipping method. Application of edible coating materials did not cause any significant difference in total soluble solids content in ascorbic acid content even through there was a sligh decrease. During the storage period there was a decrease of titratable acidity. However, there were no statistically sigificant differences. Concerning the antifungal acidity of the coating materials towards P. italicum, chitosan displayed that it could inhibit fungal infection during cold storage and after, during shelf life. Pollulan on the other hand, showed antifungal capability but not to the same extent as chitosan.