Maintaining your virginity: How to store your EVOO
EVOO or Extra Virgin Olive Oil is the highest quality olive oil. It is defined as having a free fatty acid (FFA) concentration of less than 0.8%. Unlike wine, olive oil starts to oxidize (go rancid) from the moment it is picked. In fact if left too long on the tree or if olives are harvested by picking them off the ground after they have fallen from the tree (as historically has been done in parts of Europe) then the olives may have already started to go rancid before they have been crushed.
From harvest, the optimum quality is achieved by eliminating, as much as possible, air (or oxygen as the key oxidizing component) and heat – as both air and heat allow rapid oxidation of the olive oil. That is why ‘cold pressed’ is important to maintain the quality of the EVOO.
Ideally the olives are cold crushed within hours of being picked and the oil stored in air-tight containers. This can be achieved by either storing the oil in flexible bags from which the air is excluded or storing in stainless steel tanks with a layer of inert gas (typically nitrogen or argon are used) to prevent oxygen mixing with the olive oil. During bottling, the very best approach is to fill the bottles with nitrogen first so that when the oil is filled into the bottle there is no mixing with air.
At Manna Hill Estate we harvest using a tree shaker so that the olives never touch the ground and then seek to cold press within hours of harvesting.
Consume the olive oil within 4-6 weeks of opening
Once bottled it is best to store the EVOO in the dark (light will also increase oxidation) and below 18 degrees C. (A cellar is a great place to store your EVOO). Stored in this way it will oxidise very slowly and will likely still be EV after 2 years (or possibly more). However once the bottle is opened the air will mix with the olive oil and it will start to oxidise quite quickly. As a result it is recommended that you use the EVOO within 4 to 6 weeks of opening to maintain the premium quality.
Quite often people store their EVOO in a cupboard above the stove (as it is convenient when cooking). However this is probably the worst place to store your EVOO as this cupboard will usually get quite warm. Similarly, storing your EVOO above the fridge is not a good idea for the same reason. It is not recommended that you store the EVOO in the fridge as some components of the oil will likely solidify and you will have to wait for the oil to reach room temperature before using. (Storing your EVOO in the fridge does not damage the oil – just inconvenient when you want to use it).
Virgin, Pure & other olive oils
Virgin oil is lower quality than EVOO (it can have a free fatty acid concentration up to 2%) It is more oxidized (started to go rancid) and will not have the same level of anti-oxidants, polyphenols and other healthy attributes. At FFA concentrations above 2.0% the olive oil is considered rancid and not fit for human consumption. Note that it is common industry practice to blend EVOO with olive oil that has a FFA above 2.0% (not fit for human consumption) to produce an oil that can be classified as Virgin Olive Oil (VOO).
Pure olive oil has been processed (usually using cyclohexane) to remove most of the anti-oxidants, polyphenols and other components of the oil that already have or are likely to create rancidity. Essentially many of the health giving attributes of olive oil are removed so that the remaining oil doesn’t easily oxidise.
I am unsure why you would use such an oil for human consumption when there are such brilliant, healthy and great tasting EVOOs available.