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How long does an extra vir­gin olive oil stay that way?

This ques­tion is first asked by olive oil pro­duc­ers who would dis­play ​‘Best By Date’ infor­ma­tion on their label. And then, by retail­ers and buy­ers (con­sumers included) who would also like to have a rea­son­able answer.

Well, as usual, the answer is: It depends. And it causes con­ster­na­tion in every­one that there is no straight, sim­ple answer.

First, as we well know, olive oils are very dif­fer­ent. Their antiox­i­dant con­tent, usu­ally mea­sured as polyphe­nols, varies greatly among oils, as much as two- to three-fold. These polyphe­nols are not only ben­e­fi­cial to human health, they also con­tribute to an oil’s longer shelf-life.

There are also ​‘fil­tered’ and ​‘unfil­tered’ olive oils in the mar­ket, with pro­po­nents of one or the other argu­ing end­lessly about their mer­its. Filtration removes resid­ual veg­e­ta­tion water from the oil, as well as any fine sed­i­ment remain­ing from the olive fruit. These two ele­ments are usu­ally asso­ci­ated with ​‘fresh­ness’ of oils that are sold as Olio Nuovo. However, if water or sed­i­ment is left in con­tact with the oil, in a short time the oil qual­ity will suf­fer. That’s why Olio Nuovo is meant to be con­sumed soon after har­vest: in three to six months at the lat­est.

However, if the same oil had been ​“racked,” caus­ing fine par­ti­cles to sed­i­ment from the oil over time, or bet­ter yet, ​“fil­tered,” the same oil can sus­tain its extra-vir­gin­ity very likely for a year or two.

Secondly, stor­age con­di­tions, either in the ware­house, store shelf or kitchen pantry will shorten the lifes­pan of an olive oil’s extra vir­gin sta­tus. Two major cul­prits are light expo­sure, espe­cially if the olive oil is in a clear bot­tle, and expo­sure to tem­per­a­tures higher than 70 degrees Fahrenheit.

But a major trig­ger of qual­ity decay is air con­tact, which results in oxi­da­tion.

So, based on sci­en­tific research and obser­va­tions in our lab, what are the esti­mates for the real Best By Date for an olive oil?

• Olio Nuovo, unfil­tered or non-racked oils: 3 to 6 months
• Low polyphe­nol, fil­tered or racked oils: 1 to 2 years. But, if exposed to air, light or high tem­per­a­ture, its life may be short­ened to between 6 and 12 months.
• High polyphe­nol, fil­tered oils: 18 months to 3 years. But, if exposed to high tem­per­a­tures, its life may be short­ened to 6 months.

In con­clu­sion, let’s not be mis­guided by overly promis­ing Best By Dates if the con­tainer offers no clues as to the polyphe­nol con­tent in the oil.

Consume unfil­tered oil soon after its har­vest date. And fol­low the advice of keep­ing the oil stored in a cool, dark place. Once opened, use the oil promptly. Do not buy big jugs that will not be con­sumed within weeks after open­ing. And, of course, the oil must be a good oil to begin with, at the mill.