Is Your Olive Oil Rancid?

Your Portuguese kitchen pantry is simply incomplete if it doesn’t contain Portuguese olive oil.   It is part of the source code for all Portuguese cuisine.  It’s likely to be rancid though and you may not know the difference because your taste buds have been programmed to accept this.  Like a bad string of characters in  source code the rancid olive oil is tainting your food.  Why can’t you tell the difference?  There are two reasons: (1) It is because most olive oil sold in the United States is left on store shelfs longer than its optimal peak.  Olive Oil can be expensive (especially the top shelf varieties) and most supermarkets will just leave it there until it is sold since there is no expiration date on the label. (2) The cheap olive oil is likely a mixture of several batches of oils (including vegetable as a filler) or it is “refined olive oil” “that has been refined using charcoal and other chemical and physical filters. If the label says Pure olive oil or Olive oil it is primarily refined olive oil, with a small addition of virgin for taste.” (Source: ).  To put it simply we have developed a tolerance for rancid olive oil.  Since the beginning of our appreciation for food we have been eating a lot of rancid olive oil in America.  So much so that we can’t taste it and for some people they actually prefer the rancid over the good.  The home cook isn’t the only one that has undergone this transformation.  Samin Nosrat, in her recent book entitled “Salt Fat Acid Heat” tells a story where Alice Waters of Chez Panisse held a contest for all her kitchen staff.  She offered $500 for the best tomato sauce and was shocked that almost everyone used rancid olive oil.  So, what makes olive oil rancid?  The passage of time is olive oil’s biggest enemy.  Over time olive oil is oxidized which is a fancy way of saying that the oil is exposed to oxygen sort of the way iron turns to rust when exposed to water.   Even though the bottle you purchased is sealed,  oxygen is present because our atmosphere contains 21 percent of it.  This oxygen needs help to ruin your olive oil and it usually comes from light exposure or storage problems (like storing it a warm place for long periods of time).  This causes peroxide to be formed. When those peroxides decompose, the olive oil gets rancid.  You can’t beat the system because over time this will happen to every ounce of olive oil that is produced no matter the origin, quality or vessel it is contained in.  How long?  It depends but within 2 years of production most olive oil is rancid.  Unlike another expensive liquid that comes in a fancy bottle (i.e. wine) olive oil does not get better with age.  How can you tell its rancid?  This is difficult since rancid olive oil tastes bitter and almost all extra virgin olive oil has a sort of bitter note to it.  The difference is subtle, but I have developed a way to differentiate the natural flavor note to its oxidized cousin.  Olive oil really isn’t bitter it is more pungent.   Good olive oil should be strong and bold like what it is made from: olives.  It isn’t good if you get a stinging or acrid hit after ingesting it.  Rancid olive oil tastes chemically like paint or turpentine.  Using rancid olive oil in your food while cooking will impart some bad flavors like banana.  Using the rancid oil for drizzling over food will make it taste bitter likely forcing you to add salt to mask it.  How can you avoid rancid olive oil and begin to re-train your palate?  Here are some suggestions:

  • Check the production date on the bottle. If it was within two years go ahead and purchase it. If there is no production date on it just leave it there and don’t buy it.
  • Expensive does not mean it is better. Remember I told you the supermarket wants to get rid of the expensive bottles and thus unlikely to take them off the shelf after its peak time.
  • Store the olive oil in a dark cool place. Not a cold place like the refrigerator (it will congeal and be useless to you when needed) more like the basement.  When you buy a bottle (or more) pour some of it into another container (I use sauce bottles) and place this near where you prep your food.
  • Look for bottles that are dark. The darker the better so as to filter out the light that will eventually induce oxidation.
  • Do not buy a huge jug of olive oil no matter how cheap it may seem. You may not be able to use it all within its two-year window.  Better to buy smaller bottles and use them as you go.  This also means that if you buy a brand and don’t like it or it in fact is already rancid you are not wasting 5 liters of it.
  • USE YOUR OLIVE OIL! I don’t get when people buy a nice bottle of olive oil and display this in their kitchen and using it only for special occasions like Christmas Eve Bacalhau (codfish) dinner. By the second Christmas it turns rancid!  I had a family member once tell my they were given a jug of homemade olive oil by a farmer friend in Portugal and he would only use it for special occasions.  The jug was almost 15 years old.  I tasted it and it was unpalatable.  I nearly choked on it.  I was too polite to say it sucked.
  • Before using any olive oil taste, it by pouring it into a shot glass.  How can you know what it is like or if it is rancid if you don’t try it straight up raw?  Pungent strong flavors that remind you of olives is good.  A chemical taste that reminds you of turpentine or paint is bad!  If it is rancid throw it out!