Correct storage is critical to preserve nutritional qualities of extra virgin olive oil.
The rule number one to get olive oil when its nutritional qualities are the highest level is to buy the most recent harvest. The rule number two is buying from a trusted producer, whenever possible.
Great! Now that you got a high quality extra virgin olive oil, how do you preserve its nutritional qualities? Storage is the most important element to preserve its qualities for a longer period of time.
Olive oil enemies are: Oxigen, Light and Heat. If we protect it from these three elements we are doing the right thing.
Oxygen - Freshly milled olive oil is packed with antioxidants (polyphenols), an indicator of quality. If you expose it to air/oxygen these qualities degrade quickly due to the oxidation process. So, always keep your olive oil well sealed. If you buy it in packaging bigger than one litre it is strongly recommended you bottle it in smaller and sealed containers.
Light - Exposure to light causes a chemical reaction called photo-oxidation. Good practice is to keep it away from sunlight and always in dark colored containers. Dark glass, stainless steel or porcelain are ideal, certainly not plastic.
Heat - Ideal temperature for olive oil is around 15C, it should never be stored in a warm environment above all if temperatures can go above 20C. Heat could turn it rancid. A sound practice is keeping just daily or weekly consumption in the kitchen if the environment is constantly warm.
Remember! Olive oil is not wine. Its qualities degrade with age.
In conclusion, always buy the current year harvest and to preserve its nutritional qualities, store olive oil in a dark and cool place.