Family: OLACEAE
A hardy, evergreen tree, growing to a height of 25 - 30 m, the olive is widely distributed throughout the world especially in Mediterranean regions. It needs full sun and a long, comparatively dry season, with some winter chilling for good fruit production. The tree is frost hardy to about - 9.5°C, although the fruit is damaged below - 2°C. It prefers deep, rich, well - drained soil, but can tolerate poorer, shallower soils. Although the olive is very drought tolerant, occasional deep watering in arid climates increases fruit size and production. It will withstand strong winds, making it a useful species for windbreak, and has some salt resistance.
The olive tree is self - pollinating and will bear fruit after about 5 years and can continue for more than 2000 years. As with many trees, a heavy crop one year will often be followed by a light crop the next, although this tendency can be overcome by thinning the fruit. Average yield is about 4.8 tonnes/ha, the fruit having an oil content of between 18 - 25%. Between 225 - 270 litres of oil of all grades is usually obtained from pressing 1 tonne of olives. The fruits are green at first, but ripen to black during the winter months. They can be picked either green or black for both pickling and oil production.
Nutritional composition of the pickled green olive per 100 grams of edible portion is: Water - 86%, Energy - 116 calories, Carbohydrate - 1.3 g, Fat - 12.7g, Protein - 1.4 g, Ash - 6.4 g, Calcium - 61 mg, Potassium - 55 mg, Sodium - 2400 mg, Magnesium - 22 mg, Iron -1.6 mg, Phosphorous - 17 mg, Vitamin A - 300 I.U. and the digestion time is 1.75 hours.
Olive trees may be propagated by seed or cuttings, although raising from seed is slow, often taking up to a year to germinate. The hard stones can either be cracked or scarified to speed the process. The seedlings should then be grafted. Cuttings can be taken in summer. Strong shoots, 10 - 15 cm long are stripped of leaves to half their length and the bare portion inserted into sandy soil. Best results are obtained using bottom heat in a greenhouse. Most cultivated varieties are grafted onto seedling stock and as many as 5 varieties can be grafted onto one rootstock. Olives need little or no fertiliser. Corrective pruning may sometimes be required.
Processing
Olive oil: olives can either be picked green or left until they are fully ripe and starting to become wrinkled. The best quality oil is obtained from green olives, but a greater yield is produced from those allowed to ripen. The olives should then be dried on racks for a week or ten days, turning frequently, or in a food drier. Press the dried olives in an olive or cider press, but do not squeeze hard enough to crush the pits as the oil is of inferior quality and used to make soap. Strain the juice through cheesecloth into glass jars and allow it to separate from the remaining solids. Over the next 2 - 3 months the oil should be siphoned off as sediment builds up. This should be done every 2 weeks for as many as 5 times. Once the oil is clear it can be poured into sterilised jars and sealed. Refrigerate once opened.
Pickling olives: Olives can be picked either green or tinged black for pickling, depending on the variety. It is important that the fruit be handled carefully, as they bruise easily. The processing removes the unpalatable bitterness from the olives. Slitting the skins or pricking with a fork will help to speed the process.
Method: soak olives in fresh water, ensuring that they are fully immersed and rinsing every few days. Black olives should be rinsed and soaked for a week, green olives for two weeks. Then rinse olives and store in an airtight jar in a salt - water solution. The brine should be just strong enough to allow an egg to float in it. Fresh herbs such as fennel can be packed between the olives and the lid to ensure that they are fully immersed. The olives should be left in this solution for at least a month and can be left for up to 2 years. After thoroughly rinsing, the olives can then be flavoured with a herb and garlic dressing. Place them in a jar with plenty of garlic and herbs such as marjoram and thyme. Fill the jar with 3/4 boiled and cooled water, 1/4 cider or white wine vinegar and a thin layer of olive oil on top. Shake and leave for a month.