Olive oil is a product of the fruit of the olive tree, Olea Europea. It has always been a valuable commodity for cooking but olive oil was also used in ancient times as an ointment for the body and hair and as a healing ointment. it was a vital ingredient in the production of terra-cotta lamps and then was the fuel to light them. Because of tese many qualities and uses the olive tree and its oil soon became an important source of income. The ancient trading routes encouraged a widespread growth of the tree throughout the Mediterranean and beyond.

Although the exact date and origin of the first olive tree is unknown, it is generally accepted to have been first cultivated in the Middle East and Crete as far back as the year 3000 BC, and possibly even earlier.

below "Path Between Olive Trees" by klausthebest on flickr

Even after so many centuries of production there is still no machine which can handle the harvesting process of olive oil. It is still mostly done by hand. Methods of harvesting vary from country to country. In some places the olives are left to ripen until they fall from the trees. More usually they are shaken off and nets are set a few inches above the ground to catch the olives in order to prevent the heat in the soil causing them ferment.

The olives are taken to the mills for "pressing." They are stored for up to three days. This storage helps with the eventual release of the oil. Knowing how short or long a time to store the olives is crucial - too long in the heat causes fermentation and the olives will be spoiled. The method of production varies both regionally and nationally. Today the majority of olive oil mills use machinery for pressing the olives, but in some parts of the Mediterranean more traditional methods prevail.

When te olives are ready to be pressed they are first washed and then crushed - this extracts the oil. Traditionally this was done by large stone wheels, today stainless steel crushers simultaneously crush, shear and rub the olives. The product of this crushing is ground to form a paste. This paste is spread out on fibre mats. which are piled up one on top of another and placed in a vertical press which extracts the oil.

This is called 'cold pressing' or the "first pressing" of the oil. There is an incresing use of a machine which revoles at high speed and forces the oil from the crushed fruit - but "pressing" is still the preserred method for te purists.

Water is separated from the stil-cloudy which is then transferred to large containers, or amphorae, where it is kept until spring. As the temperature rises the oil thins, leaving the cloudy sediment at the bottom. The clear, premium oil, extra-virgin oil, is then filtered off. The quality of an oil is determeined by the level of acidity, the higher the acidity the lower the quality. Extra-virgin olive oil must have an acidity level of less than 1%. About 90% of oil extracted in the 'cold pressing' is extra-virgin.

The average worldwide production of olive oil is approximately 2 million tons, with about 90% of that produced by Mediterranean countries. Spain and Italy are the largest producers, followed by Greece, Tunisia, Portugal, Morocco, Syria and France. The rest comes from the Middle East and the Americas.

It was the Ancient greeks who introduced olive trees to France and Italy and as the Roman Empire expanded the olive tree spread across southern europe. The Greeks had also introduced the tree into Spain who in turn, in the 16^th century, introduced this native Mediterranean tree to north and south America and the West Indies. Today the olive tree can be found in almost every country where the growing conditions suit it. It thrives in a climate with mild winters, a brief wet spring and autumn, and hot, dry summers. It can survive long droughts but does not tolerate extreme cold or wet. It can thrive in poor rocky soil where other crops cannot. The mountainous regions of Greece and Italy are ideal growing areas, as the trees require little attention, the limited access is not a problem.

Thomas Jefferson introduced the olive tree to his estate in Virginia in the 1770's but the trees did not survive. Conversely, when the Spanish introduced the trees to California in the mid-1800's the conditions were perfect and the olive trees soon established themeselves. The small amount of olive oil produced in the U.S today comes from California.

The olive tree is an evergreen, characterised by its rather gnarled trunk and unruly branches. It has thin, spiky leaves which are dark green on top and with silver scales underneath An olive leaf lives for about 3 years before being replaced with a new leaf. The tree bears fruit from 5 years, matures at 20 years and can live for over 100 years. When an olive tree dies, shoots sprout up from the base. If left they will replace the old tree - each shoot is capble of becomeing a new olive tree.

Olive trees produce bunches of white blossoms in early spring. About one flower in twenty actually produces an olive. A very wet spring can ruin an olive crop for that year. Fruition starts in June and continues until early October, when the pit turns hard, the pulp fills out, and it becomes the flesh of the pear-shaped or drop-shaped fruit which is an olive. Olives are harvested in late autumn and winter, depending on the variety of the tree and whether the olive is for eating or for oil production. Green olives are harvested from October and black olives from November to February.

The olive is a pit fruit and in terms of ripening there is no difference between the many green and black varieties. Olives are always green when unripe and turn black as they ripen with varying degrees of red, purple and brown in between.

Some varieties produce good eating olives. For example, the black Greek Kalamata or the green Spanish Manzanilla. Others are grown specifically for their oil such as the Italian Frantoio and the Spanish Cornicaba.

Olive varieties differ both from country to country and regionally. The label on a bottle of oil will state the grade of the oil, the level of acidity, country of origin, volume and the producer's name. 'First Pressing' or 'Cold pressing' can be seen on some bottles of extra-virgin olive oil, and if the bottle comes from a single estate, the grower's name will also be listed. This is only the case with oil produced by a small grower.

Italian Olive Oil : Italy, especially Tuscany, produces some of the finest oils in the world. The main olive varieties are Corantina, Cerasolo, Frantoio, Leccino and Moriolo. Italian oil is deep green with a peppery aftertaste. Many of the best oils come from single estates although cooperatives also produce fine oils.

Spanish Olive Oil : the main Spanish varieties are Cornicabra, Hojiblanca, Manzanilla, Picual and Picudo. Spanish oil tends to be pale gold-yellow with a heavy taste of the sun, and many are also slightly peppery. Spanish oils are more readily aceptable to a palate used to vegetable oil because their taste is less pronounced that many Italian oils.

Greek Olive Oil : Unlike in other countries, many small growers in Greece send their annual olive crop to large cooperatives to be milled. Greek oils tend to be green and are generally of good quality although they generally lack the superior flavour of their Italian and Spanish counterparts.

French Olive Oil : A relatively small producer of olive oil, France, southern France in particular, produces some fine oil. Far paler in colour and lighter in flavour, French oils are subtler than oils from more southerly countries.

Flavoured oils have been infused with either herbs, garlic, chillies or citrus peel. Some types are infused at the pressing stage, for instance where lemons are actually pressed with the olives. Other types of flavouring are added at a later stage. Most commonly this is done with a chemically produced essence added when the oil is bottled. 

In recent years the interest and demand for olive oil has increased enormously. Subsequently, a wider selection of oils is available in supermarkets. Being presented with shelves of different oils of varying quality from numerous countries is enough to make most shoppers make a hasty decision but with a small amount of knowledge it is easy to make a better choice for your culinary needs and personal tastes.

Supermarket brands are probably the first olive oils that many people buy and branded exta-virgin olive oil is sold at very reasonable prices. Unfortunately, these oils are often of mediocre quality and are typical of oils from different countries bleded together to produce a cheaper oil. On the other hand, although single-estate oils are expensive, they are the best quality and it is money well spent. For anyone who is interested in cooking and enjoys good food, a superior bottle of single-estate extra-virgin olive oil is essential.

There are plenty of olive oils that are neither the supermarket variety nor from single estates. The only way to decide which oils you particularly like is to begin tasting. If you live or visit an olive growing region yu can often visit the grower or estate for a tasting and to purchase directly from them – much like visiting vineyards. Some specialty stores and delicatessens hold tastings from time to time – if not, why not suggest such an event to your local deli ? Anyone interested in experimenting with olive oil should seek out these tastings. Start with oil from a particular country, become familiar with the flavours, then go on to experiment with oils from different regions and growers.

Unlike many culinary oils that are designed to have little or no flavour, olive oil is specifically produced with a pronounced olive flavour. Therefore, using an extra-virgin olive oil would be impractical and pointless at times. Oils break down at high cooking temperatures and even at lower temperatures there is a certain amount of flavour loss.

Keep two or three different oils in your kitchen cupboard. Use a single-estate extra-virgin olive oil to drizzle over salads and vegetable dishes, a good-quality extra-virgin olive il for low-temperature cooking and a good quality olive oil for cooking at higher temperatures, for baking and for making mayonnaise and herb infusions.

Extra-Virgin Olive Oil : this expensive oil has a rich, deep flavour. It is best used as a flavouring in its own right. The Italians use it as a sauce to pour over grilled, broiled or poached fish and meat. It is excellent for salad dressings and is added to soups as stews as a condiment.

Virgin Olive Oil : called either 'pure olive oil' or more commonly 'olive oil' this is best used for cooking if the temperature is not too high. It is ideal for braising meat, fish and vegetables and shuld be used when a recipe calls for olive oil. Its lack of astringency makes it the preferred olive oil for baking cakes and biscuits. French olive oil is particularly good for making mayonnaise as it does not overpower the other ingredients.

Polyunsaturated fats have long been considered healthier than saturated fats but recent research has found that monounsaturated fats, such as oleic acid, to be healthier still. Olive oil contains 80% oleic acid and a lower percentage of linoleic acid, a polyunsaturate. Research indicates that oleic acid is effective in reducing the amount of plasma cholesterol which is responsible for the high level of heart disease.

Olive oil is beneficial for maintaining a low cholesterol level and the rate of heart disease is lower in countries where olive oil is consumed daily. Research has also suggested that olive oil has further benefits. It contains Vitamin A and this, along with the high percentage of oleic acid, stimulates bone growth. Olive oil is belived to be claming on the stomach, reducng acid and the risk of stomach ulcers. It also reduces the chance of constipation by aiding the passage of foods through the intestine and bowel. Olive oil stimulates the secretion of bile in the gall bladder which can help to prevent gall stones. When olive oil is used as the main source of dietary fat it appears to be healthier than saturated fats.