Oleocellosis
Oleocellosis (sometimes known as ‘oil spotting or burn’) occurs following mechanical injury to the fruit (Figure 4).
It is caused by the rupturing of oil glands releasing toxic oil during harvest and/or transport from the field to the packing house. This oil kills the nearby cells of the flavedo and can also cause spotting on the surface of adjacent fruit.
It is more common when fruit is turgid and the weather is cold and/or wet at harvest.
Oleocellosis predisposes fruit to storage rots, chilling injury and burning from ozone (when used to control diseases that develop during storage).
The oil from the ruptured cells inhibits degreening and discolours the rind. Careful harvesting, transport and use of GA helps reduce the problem.
Rind quality
GA maintains rind quality by strengthening the rind which helps keep the texture looking younger. Rind ageing is delayed in late harvested varieties by preventing collapse due to weakening of the cell walls and subsequent dehydration of mature fruit.
Some climatic and storage conditions can accelerate the ageing process, such as:
- heavy rains plus high humidity, followed by very cold conditions
- dehydration of the fruit in the orchard during hot conditions
- holding fruit too long between harvest and packing (low humidity storage in the packing shed)
- warm and dry conditions when trees are under water stress — this leads to dehydration of the stem end of the fruit.
Other benefits
Other benefits of using GA include:
- better rind firmness at harvest
- fruit appears less prone to postharvest decay (this may be because of greater resistance to injury due to the firmer rind)
- fruit treated with GA seems to better withstand adverse weather (hot, wet or windy), rough handling and staining
- lower incidence of both rind puffiness in mandarins and splitting in varieties with thin rind.
Note: GA has no effect on internal fruit quality or maturity but may delay external colour development.