
So, since I am cooking with olive oil today I'll give you a quick guide on olive oil.
Olive oil is made out of olives (o'rly?). The production process is relatively simple:
The olives are being washed and hackled together with it's stone. This mixture will then be stirred and compressed. After the mixture settles, the oil can be used without further processing.
In the EU, there are 8 different quality grades for olive oil but you will only see 3 of these in a supermarket (at least in Germany).
Grade I - Extra Virgin:
comes from virgin oil production only, no more than 0.8% acidity, tastes really good. Used on salads, added at the table to soups and stews and for dipping.
Grade II - Virgin:
comes from virgin oil production only, has an acidity less than 2%, tastes good but not as good as Extra Virgin. Good for roasting meat etc. as long as you don't go over 180°C
Grade VI - Olive Oil:
a blend of virgin and refined production oil, of no more than 1.5% acidity. It commonly lacks a strong flavor.
But what's the big deal about olive oil anyway? Well, you will need it if you want to cook some decent Italian or Spanish food. It tastes good and it's very healthy. Why is that you ask? Olive oil contains a lot of monounsaturated fats, more than any other oil and thus reduces the risk of coronary heart disease.
http://en.wikipedia.org/wiki/Monounsaturated_fat#Relation_to_health
So, what's important when you go out to buy some olive oil?
First of all, the glass of the bottle has to be dark as olive oil is very sensitive to sunlight. Sunlight will start oxidation -> the oil will start to taste bitter.
Also important: No plastic bottles. Either glass or porcelain but no plastic.
Other than that? Trial and error
Keep your olive oil somewhere dark, with a constant temperature of roughly 20 °C. Don't worry if it gets colder for some reason (accidently putting it in the fridge for example) and the oil starts to flocculate or change it's color. This won't affect it's taste in any way.
See ya...