How to choose and reuse cooking oil by following these important safety guidelines to avoid the creation of free radicals and carcinogens in the oil and your food.
If you talk with anyone who has ever worked at a fast-food joint, chances are that one of the things they will tell you is how gross the commercial vegetable oil used for frying gets as it is repeatedly reused.
Even if procedures are supposedly in place to prevent the continual reuse of disgustingly rancid cooking oil, restaurant managers frequently ignore them and push the envelope as much as possible to keep cooking oil costs down.
While this vegetable oil is great for fueling some types of automobiles, it’s not at all good for your health, certainly not as a healthy cooking oil!
Commercial Cooking Oil Truth Bomb
The scary truth is that restaurant cooking oil is rancid before it is used even one time.
This is because the oils of choice in the restaurant industry are highly refined at extreme temperatures. What’s more, the polyunsaturate-heavy fatty acid profile of commercial vegetable oil makes it prone to rancidity from the factory processing, so much so, that edible oil companies have to deodorize them afterward (sometimes multiple times) because they smell so bad!
These types of oils that were never designed to be heated at all much less fried in.
The cheap oils restaurants use for frying, primarily canola or soybean oil, also contain trans fat even if marketed as “trans fat free“.
Adding insult to injury, both soy and canola oil are most likely genetically modified unless organic. What restaurant uses organic cooking oil? Not even Chick-fil-A or Chipotle last time I checked, although, to their credit, these restaurant chains respectively use refined peanut oil and rice bran oil for cooking, neither of which are GMO.
You see, it doesn’t really matter if a restaurant serves a meal of sustainable organic fare sourced locally.
If the food is cooked in commercial cooking oil (sometimes falsely called an “olive oil blend” which is mostly canola), the meal is probably still going to make you feel terrible later anyway.
But Wait! Isn’t Canola Monounsaturated Like Olive Oil?
Some might argue that canola and peanut oil have a high amount of monounsaturated fats which are more stable for frying than a predominantly polyunsaturated oil like soy.
However, canola also has a large percentage of delicate omega-3 and omega-6 polyunsaturated fats. And, peanut oil is nearly one-third omega-6 polyunsaturated. These heat-sensitive fatty acids are almost certainly rancid upon leaving the factory. Then, they are denatured further when used for frying and potentially reused.
As mentioned earlier, if a restaurant claims to be using olive oil (which is low in polyunsaturates) for cooking, you should still be on the alert. It is most likely not 100% olive oil. Restaurant grade olive oil is cut with GM canola oil or another cheap polyunsaturated oil.
Selecting a Healthy Cooking Oil
Even though fried foods at restaurants have a bad rap and for very good reason, do not despair. Frying at home can be a much healthier experience!
All that is required to safely cook and fry in oils at home is selecting the correct type of fat and keeping the heat below the smokepoint.
Traditional cultures seemed to know instinctively which fats were best for cooking. These revered fats are almost without exception of animal origin.
If you are uncertain about whether a fat is safe to cook in or not, just note the percentages of saturated, monounsaturated, and polyunsaturated fats it contains. All fats and oils contain varying ratios of the three.
If the percentage of polyunsaturates is very low (10% or less) as is the case with animal fats, then it is a good bet that the oil is fine to cook or even fry in.
For example, I am asked frequently about grapeseed oil for cooking. It’s even considered a traditional fat. It is certainly marketed as heart-healthy. But, is it good for frying?
The answer is that grapeseed oil is not a good oil to cook in and certainly not to fry in. It is very high in polyunsaturates (nearly 75%) which most Americans are already overdoing with their predilection for processed foods.
A better choice would be a traditional fat like pastured lard or tallow which is the usual fat I use for making French fries.
Tallow is less than 5% polyunsaturated.
In a nutshell, as a general rule of thumb, if you are not sure about a particular cooking oil, make sure it is very low in polyunsaturates before you select it for cooking or frying.
Guidelines for Safely Reusing Cooking Oil
You may remember Grandma reusing bacon grease or leaving a dish of used cooking oil by the side of the stove for later use. However, be aware that even healthy oils can have plenty of free radicals after cooking that can harm your health.
Here are the two things to keep in mind before reusing any cooking fat – even if traditional:
- Stay Below Smokepoint. Be sure to know what the smokepoint of your cooking oil is and even test it with a digital food thermometer before starting to cook the food with it. Exceeding the smokepoint ensures that free radicals will be in your food even if you cooked with a very healthy, traditional fat. If you did exceed the smokepoint, it’s definitely best to not reuse the oil! Even high smokepoint oils like avocado oil and clarified butter (ghee) can be damaged when the heat gets too high.
- Remove Bits of Cooked Food. Are there bits of food in the oil after you finished cooking? Even if you were careful to stay below the smokepoint for the particular oil you used, having food particles left in the oil will reduce the smokepoint of the oil if it is used again. If you want to be super safe, it is best to not reuse the oil at that point. If budget reasons require the use of the oil again, be sure to filter out the food particles as best you can. Besides negatively affecting the smokepoint, they contain carcinogenic acrylamides. By ensuring that the reused cooking oil does not contain food residue, you will avoid a significant drop in the smokepoint of the reused cooking oil and also decrease the chance of excessive free radical production.
More Information on Healthy Fats
Cooking with Olive Oil: Yay or Nay?
Why Pumpkin Seed Oil is Not Good for Cooking
Chicken Fat for Cooking
How Argan Oil Benefits Health
Red Palm Oil Benefits Rival Coconut Oil
Walnut Oil: Healthy Sub for Flax Oil
The Many Shades of Palm Oil
Just reuse it until it gets particularly grimy, cook fish in it and replace the oil! Fish should always be the last thing you fry, otherwise all your food will taste fishy.
Is peanut oil healthy to use in frying?
When I fry pastured bacon I save the bacon fat to cook in later – there are usually little bits of bacon in there so should I be straining those out or does it not matter with the animal fats?
Sarah, about testing the smoke point, I’m confused: Can I use a regular cooking thermometer instead of a frying/oil/candy thermometer to take the temperature of my oil? You said to test it before frying, but this is confusing because don’t you take the temperature while it is frying? Do I just keep the thermometer in the oil the whole time I am cooking to make sure it doesn’t go above the smoke point? This is all new to me. Please clarify the whole process. Thanks.
Thanks Sarah for sharing! That makes a lot of sense about reusing the oil. I am sensitive to gluten and to vegetable and canola oils. I get a more severe digestive reaction from consuming vegetable oil than gluten. My guess is the rancidity of the oil that makes me so sick. My biggest frustration with eating out is I have to ask every time I order if they cook with vegatable oil, if it is in the sauce, dressing or mayo. It really limits my food selection unfortunately 🙁 . I hope that more people step up and start cooking with only healthy animal fats. Most restaurants, even good, local organic ones, use some form of vegetable oil in their cooking.
I use rice bran oil and just googled it and found it’s 33% polyunsaturated fat! Seems high! However the blurb under the table of data said “Rice Bran Oil: The most balanced and versatile oil on the market and closest to the AHA recommendations. Rice bran oil is a superior salad, cooking, and frying oil which leaves no lingering after taste. The high smoke point prevents fatty acid breakdown at high temperatures. Its light viscosity, allows less oil to be absorbed in cooking, reducing overall calories. It mixes better in salad dressings and improves the taste of baked goods, providing cholesterol reduction, nutritional and anti-oxidant value.”
Now I’m a little confused.
mmmm Chipotle is sooooo good! I wish it were closer. I choose not to be THIS picky about my occasional eating out.
This is good to know. My son and I just ate there the other day and I was thinking I found a healthy alternative to some of the other popular places. But it did leave us feeling heavy for a day after. I’ll need to question our local place to see what oil they use. Thanks for the info!