The sad truth is that most people in the US, for example, are accustomed to the flavor of rancid olive oil. Olive oil is no longer an occasional presence in the kitchen so it is time to change that.
Any discussion of defects must start with rancidity
Olive oil tastes best when it is fresh. Think of olive oil on a freshness continuum that goes from just-made, harvest-fresh at one end to completely rancid at the other.
How long it takes an olive oil to go from one end of this freshness continuum to the other depends on many factors: storage temperature, exposure to air and light, and the amount of natural antioxidants in the olive oil in the first place.
A good image for many people is the smell of crayons. Another helpful item — something that almost everyone has tasted — is rancid nuts. Rancid is fat gone bad, something we have encountered at some time.
Do you have a clear sense of what rancid oil smells and tastes like?
Most oils, if unopened and stored in a cool dark place, will still be good for up to two years, but they steadily lose the fresh fruitiness you want in olive oil.
Olive oil is best consumed within a year of harvest.
The second most common defect of olive oil is called “fusty.”
Fustiness is caused by fermentation in the absence of oxygen; this occurs within the olives before milling. This is why it is so important for olives to be processed into oil within as short a time as possible after harvest.
Start with freshness. Look for dates on olive oil bottles. Try local producers if you are lucky enough to live in an area where olive oil is made. Learn as much as you can about the grower.
How does a shopper use their knowledge of this chamber of horrors?