Does Oil Spoil?

Tuesday, July 2, 2013

By Greta Breskin, M.S., Guest Blogger

Have you ever looked at that old bottle of olive oil in your pantry and wondered, “does this stuff ever go bad?” I was pondering that very question when packing up my kitchen last week (I just moved to a new house). Some of my oils had been in the cabinet next to my stove for over a year – I ended up tossing most of them.

The Spoilage Story
Over time oils do spoil – they go rancid. You won’t get sick from eating rancid oil like you would from eating rotten meat, but the oil will have an off taste that can ruin recipes. Rancid oil may also lose some of its healthy properties, like the antioxidants found in olive oil.

Oils go rancid through a chemical reaction that causes the fat molecules in the oil to break down. The whole process is sped up by exposure to air, light and heat. For some oils (like sesame and walnut) the process happens faster because their chemical structure makes them more vulnerable to this breakdown.

You usually can tell if oil has gone rancid by taking a whiff. If it smells off (some people say it smells like crayons!), then it’s time to toss the bottle and buy a new one. If you’re not 100% sure, heat a few tablespoons in a pan and take another whiff. If there’s any odor from the hot oil that means it’s time to part ways.

Purchasing and Storing
When you’re at the grocery store, choose oils packaged in tinted glass containers. Try to avoid clear glass or plastic, which allows more light in and speeds up the spoilage process. If you do have to buy a clear container, you can cover the outside with foil to keep light out. Buying a smaller size more often instead of a huge bottle can help decrease the chances of spoilage, especially if those big bottles take you a long time to use up.

Store oils in a cool, dark pantry with the caps on tightly. Don’t store them right next to the stovetop (like I used to do!) or on the counter. Here are some guidelines on how to store commonly used oils:

Olive Oil
Store for up to 6 months in the pantry or up to 1 year in the fridge. Extra virgin olive oil will turn cloudy when stored in the fridge but that’s okay. Remove it from the fridge and let it sit at room temperature or run it under warm water and it will return to its original form.

Vegetable, Canola, Soybean, Corn, and Peanut Oil
Store up to 1 year in the pantry.

Walnut and Sesame Oil
These varieties go rancid much more quickly than other oils. Store in the fridge for up to 4 months.

TELL ME: What are your favorite oils to cook with?

Greta Breskin, M.S. received her Master’s degree in Nutrition Education from Teachers College, Columbia University. She will be completing her dietetic internship this July and plans to work as a registered dietitian in the New York City area.

Filed under Food Safety, Tips  |  Comments: more

4 Comments on “Does Oil Spoil?

Jamie Says:

Greta, nicely done! I’m sending this to my husband, the cook 😉

Wendy Says:

Who knew? I have now gone through the pantry . . . thrown away the bottles that have been around for awhile . . . and covered the others in foil. Thanks for the tip.

Laura Says:

I’m definitely going to cover my oil in foil. Thanks for the tip!

how to tell if food is fresh Says:

[…] of my cupboard after buying it two years ago. (You know the one?) Nutritionist Toby Amidor shares tips on how to tell if oil has gone rancid and also gives advice on how to prevent oil from spoiling with proper […]

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