Efficacy of Some Essential Oils on Controlling Green Mold of Orange and their Effects on Postharvest Quality Parameters

The effect of lime, thyme, comphore oils against Penicillium digitatum, the causes of green mould disease of orange fruits, was evaluated for their inhibitory effect in vitro and in vivo during storage conditions. In vitro experiments, different concentration of each essential oil at 1, 5 and 10% (v/v) was tested on the growth of P. digitatum. The best concentration at 10% showed the highest inhibition growth of P. digitatum for all tested oils. In vivo experiments, in 2009 and 2010 seasons, treating fruits 15 days before harvest and after harvest or only after harvest (natural and artificial infection of fruits) by essential oils at conc. of 10% (v/v) significantly reduced the disease severity of fruits compared with untreated fruits (control) at 5C. There was no significant difference found between the two tested methods of applying oils on fruits (natural and artificial infection of fruits). All treatments significantly reduced the undesirable fruits percentage, fruit weight loss percentage during cooling storage for 14 weeks compared with control during the two investigated seasons. Also preceding harvest and post harvest spraying with lime essential oil at conc. of 10% caused significant increase in TSS% during cold storage for 14 weeks compared with control. Prolonged cooling storage at 5C for nine weeks slightly increased total soluble solids percentage of both controls and decline towards the end of storage period (14 weeks) of both treatments and control. At the end of storage period, there was no significant difference on Total Acidity (TA) between all tested treatments and controls. Vitamin C was gradually decreased as storage prolonged, for both control and all treatments.