Super Eco

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Is your fancy imported olive oil supposed to taste like that—or has it gone rancid? Having always equated "rancid" with "spoiled," we were shocked to learn that rancidity is not a sudden, finite condition, as easy to spot as the furry green stuff on those back-of-the-shelf leftovers (not that we've ever experienced that ...).

Rancidity is the slow but inevitable result of oxidation. The million-dollar question: how long does it take? Extra-virgin and virgin olive oils keep at least nine months after opening. According to the Olive Oil Source, varieties containing more natural antioxidants may be good for up to three to four years, if properly stored in unopened containers. Other oils (especially particularly unfiltered oils) may be unpalatable within a year, even if stored properly. "A two-year-old olive oil may taste rancid to some, while others don't mind it," the Olive Oil Source notes. "Most people would be put off by the taste of any vegetable oil more than four to five years old."

Taste remains the best judge of whether or not an oil has gone rancid.

Preventing rancidity is essentially a game of keep-away. The Olive Oil Source advises you to keep your oils away from:

• Heat Don't store oil near or over a heat source in the kitchen. Store oil in a cool pantry or even the refrigerator.
• Light Opaque containers are best.
• Air A full, tightly capped bottle will oxidize less than a large, half-full bottle. You can help prevent large containers of oil from going rancid by spraying into the container some inert gas, available in small spray cans from well-stocked wine departments.
• Time The longer it sits, the more rancid it gets. The best prevention for rancidity is to use the oil—enjoy!