THE three main objectives of harvesting olives are: Pick when ready for preparing eating olives or making olive oil, to cause as little bruising as possible and cause as little damage to the trees as possible. Olives for eating need to be picked while still firm. Olives for oil can be picked at the same stage or left to fully swell to maximise the overall yields.
Some high quality producers still pick by hand. However most olives are allowed to fall naturally or racked, knocked off with long canes, or shaken off with mechanical tree shakers onto nets and then transferred to plastic boxes.
In some areas, to reduce harvesting costs, the ground under trees is laid bare by using weed killers two weeks before shaking the olives onto the ground when they are blown or brushed into heaps for sacking.
Yields can vary from 10 to 110 kilos or more per tree depending on the age, health and pruning of the tree, and the summer and autumn sunshine and rainfalls.
Pickling olives to eat
See chapter 78 of ‘Growing Healthy Fruit in Spain’ for our favourite methods and recipes.
Producing olive oil
To extract high quality oil from olives they need to be processed as soon after their harvesting as possible to minimise the onset of fermentation that can spoil the taste of the product.
The process follows the following process. Riddling to remove leaves and stones, washing if allowed to fall on the ground before harvesting, the picking out of obviously bad olives, milling/ mashing the olives to create a paste, pressing of the paste to extract the oil and water and then the separation of the oil from the oil/water mix and pouring into storage vessels. These days quality plastic bottles or storage tanks are used.
There are four ways to process olive to oil.
1. Purchase a manually or power operated mill/masher and press yourself or with a group of friends.
2. Arrange for a friend or local villager to do the pressing for you on in a historic or new old style press.
3. Arrange for a larger agricultural cooperative mill to process your olives mixed in with those of other growers.
Old mills will still use a cold process and you will get good quality extra virgin olive oil.
Commercially olive oils are classified in descending quality order as Extra Virgin, Virgin, Ordinary Virgin Olive Oil, Olive Oil, Refined Olive oil, Lamp Oil.
The standard maximum acceptable acidity levels are 1.0 per cent for extra virgin, 2.0 per cent for virgin and 3.3 per cent for ordinary virgin. A good yield is a litre of oil from five kilos of olives. A poor yield from poor olives can be as little as a litre from seven or eight kilos.
Bottled olive oil is best stored in a cool dark place. Good quality oil can be stored for many years. It is not usual or desirable to add preservatives.
Coastal harvesting will now be complete but it will continue in colder inland and northern areas.
(c) Dick Handscombe
www.gardenspain.com February 2015.