Effect of Using Some Essential Oils Instead of Fungicides in Wax on the Storability of "Valencia" Orange Fruits

Abstract

This study was performed during 2005 and 2006 seasons. "Valencia" orange fruits treated with various treatments [dipping for 10 sec in (1) wax; (2) wax + Eucalyptus oil 1%; (3) wax + Eucalyptus oil 2%; (4) wax + Peppermint oil 0.5%; (5) wax + Peppermint oil 1%; (6) wax +Cinnamon oil 0.5%; (7) wax + Cinnamon oil 1%; (8) wax + Thiabendazole (TBZ) 0.5% + Imazalil (IMZ) 0.25% and (9) tap water (control)]. Thereafter, fruits were stored for 6 weeks at room temperature (20-26C and 80-90% RH).As the storage period prolonged, the percentages of unmarketable fruits and weight loss were significantly increased. At the end of storage period, the initial percentages of titratable acidity (TA) and fruit juice and the values of ascorbic acid (V.C) decreased, while the percentages of total soluble solids (TSS) and the TSS/ TA ratios increased. However, the differences of TSS and V.C were insignificant, as an average for all treatments.As an average for all storage periods, when wax was used alone or combined with either the essential oils (Eucalyptus, Peppermint or Cinnamon) or the fungicides (TBZ + IMZ), gave a great effect on reducing the percentage of unmarketable fruits (10-20% in first experimental season and 10-22.5% in the second) compared with unwaxed ones (45% in both seasons) and reducing the percentages of weight loss (5.401-7.037% in the first season and 5.601-6.354% in the second) compared with unwaxed fruits (11.096 and 11.863% in first and second season, respectively). However, the superiority of wax treatments on improving physical properties, was not greatly obvious on chemical ones (TSS; TA; fruit juice %; TSS/TA and V.C).Generally, neither essential oils nor fungicides influenced the percentages of weight loss by themselves, when both of them were added to the wax.The essential oils were more effective on reducing the percentages of unmarketable fruits than the fungicides (when both were combined with wax). Except, Eucalyptus oil 1% (in both experimental seasons) and Peppermint oil 1% (in first one), as their efficient were similarly to the fungicides, as an average for all storage periods.The unmarketable fruits were noticed for the first time at only 2 weeks of storage, in unwaxed orange fruits. Using wax alone retarded their appearance two weeks later. The addition of fungicides to wax delay their appearing till the end of storage period (6 weeks). When essential oils were used instead of fungicides, the unmarketable fruits appeared after 4-6 weeks of storage. Despite, most of their percentages were significantly lower than those of wax + fungicides, as an average for all storage periods.