No rancid oils, please and thank you.

Something happened last night and I just had to share. I’m currently on the road playing a string of Christmas shows. We’re finishing out the tour with a weekend in Fargo, ND. The shows have been great, the company, the hotels; all of it great.

I’m moving quickly through my self-stocked supply of whole foods so I ran down to the hotel restaurant for dinner last night. No surprise here: there’s ONE thing on the menu that I can have; a wicked-bland salad that I snazzed up with some salmon. They brought out the olive oil and vinegar and I was set to dig in.

I reached for the olive oil and noticed that the glass container was warm. Uh oh. I opened the cap and gave it a sniff. The oil smelled like crayons. Uh oh, again. Why the double “uh oh”? Those are just a few of the warning signs of rancid oil!

A few months ago, I wrote about the importance of fat in our diets. I eat VERY little sugar so my need for fat is slightly higher. I opt for fatty fish and healthy oils whenever I can. But fats can be finicky. Before we get too far into this, we should quickly dive into a very easy science lesson.

Fatty acids are made of carbon and hydrogen molecules. Different combinations create the three different types of fatty acids: saturated, monounsaturated, and polyunsaturated. If each carbon atom in the chain has bonded with two hydrogen atoms, this makes a fully saturated fat. The chains look like nice, sturdy, straight lines. Because of their straight shape, these stable acids fit together perfectly and form a solid at room temperature. Examples of saturated fats are butter and coconut oil.

Sometimes one of the carbon atoms is missing a hydrogen atom so it forms a double bond with the next carbon atom in the chain. That leaves one link unsaturated by hydrogen, or a monounsaturated fatty acid. This produces a slight kink at the site of the missing hydrogen bond so it’s not quite as sturdy. That kink doesn’t allow the acids to fit together quite as well so these are found in liquid form at room temperature, but can solidify in the refrigerator. Examples of monounsaturated fats are olive oil, avocado oil, and almond oil.

Lastly, there can be multiple sites missing a hydrogen bond. These are called polyunsaturated fatty acids and they have all sorts of kinks and curves at each unsaturated site. Because of all the kinks, these fatty acids are very unstable and also form a liquid at room temperature. A few examples of polyunsaturates are fish oils, flaxseed and most other seed oils, and most vegetable oils.

There’s a fourth type of fatty acid that I should include while we’re on the subject. Trans fatty acids begin as an unsaturated fat and are put through a treatment process with heat, chemicals and certain metals (like nickel) to make it fully and artificially saturated. Yum. This process is called hydrogenation. Avoid these fats at all costs. I’m looking at you, margarine.

All of these types of fat, aside from trans fats, are found in nature and are all necessary for the health of our bodies. But much like any other type of food, these fats can spoil, or rancidify.

Rancid fats are toxic when eaten. The more unsaturated/unstable the fats, the more easily they can spoil. Heating oils beyond their threshold can damage them and create free radicals (which can lead to cancer, heart disease, and all sorts of other issues). For this reason, it’s safest to cook with saturated fats like butter, lard, and coconut oil as they can withstand higher heats. Monounsaturated oils can be used at low heats. Polyunsaturates must never be heated.

In addition to heat, light and oxygen exposure can damage oils. Luckily, it’s pretty easy to detect rancid oils:

• Smell: Unrefined, un-heat-treated olive oil has a really wonderful olive-y aroma. If it smells like Elmer’s Glue, crayons or putty, fermenting fruit, rotten fruit, or just plain unpleasant, it’s probably rancid and should be thrown away.
• Taste: The taste of rancid oil is similar to the smells. It can be pretty obvious when an oil has gone bad. Additionally, if there’s absolutely no flavor at all, it has likely gone bad. Make sure you don’t swallow the oil if you detect a foul flavor.
• Feel: If you put a little oil in your mouth and swish it around, a greasy feeling is indicative of rancidity. Again, if you suspect the oil is past its prime, spit it out.

In my case, it was very clear from the smell alone that my oil had gone bad so I decided to eat my salad dry. Weeeee.

I know a lot of us are already on very restricted diets so I never like to add to the list of “don’ts”, but it is extremely important to examine the oils at restaurants before you use them. It is in your body’s best interest to avoid denatured, inappropriately heated, or rancid fats. You would never willingly eat a rotten piece meat or a slimy old vegetable, so why would you eat rancid fats?

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While You’re At Home: As I mentioned above, heat, light, and oxygen exposure can all damage delicate oils and fats so proper storage is key. Any mono- or polyunsaturated oils should be kept in airtight, darkened glass containers (plastic can leach BPA and other chemicals into the oil) away from direct light. Avoid storing your olive oil in the cupboard above the stove. The heat from the stove travels upward and can vastly reduce the shelf life of your oil. I like to keep my unsaturated oils in the refrigerator. When it’s time to use them, I run the bottle under warm water until the oil liquefies just enough to pour.