Olive oil comes from the fruit of the olive tree. The olive tree is not strictly a tree as, left to its own devices, it will sprout branches all the way up its trunk, which makes it, officially, a bush. Olive trees can live for 700 years or more. This is a pretty meaningless statement, but it just adds weight to the idea that olives can have incredible longevity.
For eating purposes freshly picked olives are invariably bitter and are traditionally soaked in regular changes of water or brine for up to two weeks, after which they are pickled and put into oil with herbs and spices. For oil, ripened fruits in perfect condition are pressed to yield their oil. The first pressing is dark, thick and very low in acid. This is the extra-virgin olive oil, of which the cold-pressed, stoneground is the best. The second pressing has a higher acid content and is slightly thinner. The cheapest, lightest and most acidic of the oils is extracted from the skins and pulp left over from the second pressing and needs to be balanced with the addition of an alkali. Olive oils are labelled according to their quality. Look for low percentage acidity.
The choice of when to harvest an olive is up to the taste of the grower. The oil is held in the fruit long before harvest, so taste, or economics, are the dictators of when the harvest occurs. Olives picked early make a greener, stronger flavoured oil with a little more bitterness and freshness. Some people prefer it, especially for dressing salads. People with their own small number of trees, often dispersed amongst vines, might beat a few early in the season to give them some of this type of oil and then, when the olives have ripened further, beat more to provide oil for cooking. The one thing that seems to be agreed upon is that olives should not be left on the tree to drop of their own accord. By this time they will have other juices than oil in them and the quality will be less good. As a rough guide olives picked for oil are usually harvested around January, while green olives for eating are harvested in September/October and black in November/December.
The method of harvesting will make a lot of difference to the final oil; hand-picked fruit with little damage will make the finest oils, and cost an arm and a leg. Mechanical harvesting involves shaking the trees which can cause damage. Oils may or may not be filtered, and this too will make a difference. Unfiltered oil can contain dark vegetable water on top of which the oil will float. Keeping this oil for any length of time will result in flavour from the bitter water transferring to the oil. If you will use your oil rapidly there is no need to buy it filtered but, if you are likely to keep it for any time, make sure that it is. Age is another issue and, though it is often said that you should use oil fast, Marcella Hazan prefers an oil at around 3-6 months when the edge has worn off and the flavour is more mellow. She also points out that it will start to go rancid during its second year. Ageing doesn’t suit olive oils.
Flavours of oils are also affected by region, so that Tuscan oils are often peppery, those of Liguria are light and grassy, whilst those of Umbria are warm, creamy, fruity. Those of Lazio are great meaty, gutsy oils like those of Kalamata in Greece. Lake Gada produces elegant, but rare oils and I once tasted an oil from Sicily that tasted of tomatoes. This being said, most ‘Italian’ olive oil will come from olives grown all over Italy and in North Africa, with the darkness possibly coming from additives.
Ultimately, the flavour of olive oil is dependent on climate, terrain, the soil, the harvesting timing and methods and processing, the freshness and the storage. Once you have possession of a good oil you can tip a little into soups, over cooked vegetables, into salads or over fresh seafood, or just dip some good fresh bread into it, the way my husband does when he gets home from work.
