Olives & Olive Oil: The Basics
Olive oil is healthy if it is of good quality. It contains lots of phenols and other healthy micronutrients. Looking at supermarket shelves, it seems difficult to obtain good quality olive oil, but in the age of the Internet, that's no excuse. If you really like Mediterranean cooking you need to invest in some good quality olive oil. Many olive oil producers have internet shops nowadays and are set up to deliver retail. In the US take a look at the California Olive Oil Council website, in Australia it's the Australian Olive Association, both list quality producers, who ship retail. In Europe I would buy directly from the oil mills, just google for "olive oil producers [the country you are looking for]".
You need roughly 30 - 60 kg (60 - 120 lbs) olives to produce 10 litres (2 1/2 gallons) of extra virgin olive oil from the first pressing. Harvest time depends on the variety and the growing region. It starts in September in some regions and in November in others. The photo shows an ancient olive tree near the Pont du Gard in the Gard Provençal. It is probably over 200 years old. Olive trees are carefully cultivated. They are regularly pruned after the harvest so more flower-bearing shoots can grow the next year. The spaces between the trees are regularly fertilized and trees need to be sprayed against pests. In France only biological pesticides are allowed from 2009 onwards. Mature olive trees bear olives every year, but there is often a two year cyle: a substantial harvest in the first year is followed by a meager harvest in the second year. Quality olives are harvested by hand using a small rake or an electric rake. The US and Australia have developed harvesting machines, which shake the tree, a method frowned upon by many European growers.
No wonder that cold pressed olive oil is expensive. 1 liter (2 pints) A.O.C Vierge Extra from the Cooperative du Nyonsais or from Moulin Jean Marie Cornille in Maussane les Alpilles will cost you €21 plus shipping costs.
Given its cost it is important to use the right quality of olive oil. You don't need to use the highest quality for all dishes, but I am afraid there are recipes where only the Extra Virgin olive oil will do. Look at it this way: in the mediterranean cuisine you spend less on meat, therefore you can invest a bit in good quality olive oil.
There are many varietes of olives resulting in a wide range of aromas and tastes of olive oil. Familiarize yourself first with Olive Oil Grades, i.e. the quality classifications. You may also want to read here how to taste olive oil.