I'm often struck by the prevalence of rancid olive oil in American restaurants, even very high-end restaurants that otherwise emphasize quality ingredients. Too often, that little puddle of oil proudly presented with the bread is unmistakably rancid.
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It may have started out as an oil fully as delicious as the one I've described above, but bad handling, at a series of points, from the time it leaves the producer's tender care until the oil arrives in the user's kitchen, have corrupted a glorious product.
Heat and light are sworn enemies of oil, which should be kept in a cool, dark place, preferably in a metal container that light can't penetrate.
But what, you might ask, is rancid? What does it taste like? It's actually hard to describe, but all too easy to sample. Walnuts, for instance, because they're full of oil (and good-for-you oil, too), go rancid very quickly.
If you come across a jar of walnuts forgotten in the back of a pantry shelf, open it and take a good deep sniff - that's rancid. Whole wheat flour, for the same reason - oil in the germ of the wheat - will rancidify quite quickly, too, while regular flour, with the germ removed before milling, will remain stable much longer.
Rancid food, apart from its nasty flavor (reminiscent of cat's pee, some say), is not good for you; too much of it can be outright damaging to your health. Which is why cooking authorities recommend refrigerating or freezing walnuts, whole wheat flour and similar ingredients if you must keep them for a couple of months.
Should extra virgin olive oil be refrigerated? It's a question I'm often asked and I don't have a hard-and-fast answer. Typically, if you can keep oil in a cool pantry or even a cellar, it will be fine for up to two years from harvest; well-kept oil may lose its bright flavors, but it won't spoil. After all, there was no refrigeration at all in Mediterranean countries until recently and olive oil kept very well in cool, dark places from one year to the next.
But if you live in a hot climate, in the southern or southwestern U.S., and you don't have that ideal cool pantry, then it's not a bad idea, if there's room in your refrigerator, to store your fine oil there, only bringing out small quantities for daily use.
Nancy Harmon Jenkins is the author of several books, including "Cucina del Sole: A Celebration of the Cuisines of Southern Italy" and "The Essential Mediterranean."
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