Articles
EVALUATING THE EFFECT OF α-FARNESENE ON THE SYMPTOMS OF SUPERFICIAL SCALD IN ‘GRANNY SMITH’ APPLES
-Farnesene is a slightly volatile sesquiterpene formed on the surface of pome fruit during cool storage.Autoxidation of
-farnesene to trienes is thought to cause the storage disorder “superficial scald”, characterized by browning or blackening of the fruit skin.Ventilation of fruit reduces the amount of
-farnesene and the degree of scald (Anet, 1972). If – farnesene and scald are related, then application of -farnesene to fruit during storage should increase the amount of scald.-Farnesene was applied to one side of individual fruits as vapour.
Fruit were sealed with tape onto plastic containers, with or without added -farnesene, stored for 27 weeks at 2°C, then assessed for scald after a further 7 days at 20°C. The amounts of -farnesene and triene were determined at two weekly intervals.
For control fruit, the enclosed skin surface had a significantly greater area of scald in 1993 (15%) and 1994 (23%), (p<0.005) than skin open to the atmosphere (<4%). The concentrations of -farnesene on the enclosed side of the fruit were up to ten times higher than those on the open side.
Similarly, the triene concentrations on the enclosed side were twice those on the open side.
The greater incidence of scald on the enclosed skin, and the greater concentrations of -farnesene and triene support the hypothesis (Anet, 1972) that -farnesene autoxidation is associated with superficial scald.
Application of -farnesene, prior to the apples being placed in storage, had no significant effect on the concentrations of either -farnesene or triene (p<0.05), except after two weeks at 2°C, when -farnesene concentrations were higher in the treated skin.
In a separate experiment, application of deuterated -farnesene (Fielder et al., 1993) was used to show that 7% of the applied -farnesene had diffused onto the apple surface after 7 days and 56% after 13 weeks.
Addition of -farnesene reduced the area of skin with scald symptoms in both years, significantly in 1994 by 81% (p<0.05). This reduction in scald might be explained by -farnesene acting as an antioxidant, in which case the amount of triene associated with scalding is greater due to the antioxidative role of -farnesene.