For olive oil production, it is very important not to irrigate for the weeks leading up to harvest as the moisture content of the fruit can be too high, the optimum moisture content is 50%. Plump olives are sometimes full of water, not oil. The high water content makes the extraction of oil more difficult as the malaxing process is meant to rub and work the paste, collecting the tiny particles of oil together into globules that can be separated in the later stages. In fruit with very high water (moisture) content this does not happen as well and the paste slops around instead of kneading properly. In order to produce Extra Virgin Olive Oil (EVOO), it is necessary to use freshly-picked olives (i.e. no longer than 48 hours from picking to the processor). Another factor which is very important is the correct time of harvesting which should not be too early as this results in low oil yields. Immature fruit will give less oil. Even though the skin can be dark in colour the flesh on the inside of the fruit may still be classed as green. In Southern Queensland we have intense sunlight and therefore the skin tends to colour much faster than in the Southern states than the Mediterranean olive growing countries. Many growers actually allow up to 5% of the ripe fruit to drop to the ground and be wasted before harvesting the remaining fruit and processing it into oil. This ensures that the bulk of the fruit is fully ready for the extraction process and the resultant oil yield will be greater.
When do you harvest your olives?
The IOC (International Olive Council) Maturation index gives a guide as to the stages of ripening olives.
0=Olives the skin of which is a deep or dark green colour.
1=Olives the skin of which is a yellow or yellowish-green colour.
2=Olives the skin of which is a yellowish colour with reddish spots.
3=Olives the skin of which is a reddish or light violet colour.
4=Olives the skin of which is black and the flesh is still completely green.
5=Olives the skin of which is black and the flesh is a violet colour halfway through. 6=Olives the skin of which is black and the flesh is a violet colour almost right through to the pit or stone.
7=Olives the skin of which is black and the flesh is completely dark.
For Olive Oil Production, growers must decide whether to harvest for quality or quantity. Many Australian growers harvest early for quality and may harvest earlier than normal say somewhere around 3. If growers are after quantity then they may harvest late at say 5 – 6. For Table Olive Production, growers should pick when the olives are looking the nicest at the green or black stage. Methods of harvesting There are many different styles of harvesting. (Your trees must be pruned to suit the style of harvesting).
Different methods may include:
- Beating the olives off the tree. (Traditional method not recommended)
- Hand Harvesting includes the aid of small hand rakes, picking bags with harness, Pneumatic & Electric Olive Harvesters and Limb shakers.
- Mechanical Harvesting including Trunk Shakers, Limb Shakers, Straddle Harvesters and Oscillating Combs (singular or dual models available).
All methods depend on the fruit removal force required. Usually, the greener the olive the higher the fruit removal force.
Storing and Transporting Your Olives
Make sure you have crates or bins that allow the fruit to breathe and will not cause damage to the fruit.