Since burning your food isn't exactly seen as the marker of a good cook, going past an oil's smoke point (literally the point at which it starts to produce smoke) is something you want to avoid. Besides being a major faux pas in the kitchen, it tastes terrible which means you might have to start over, which is like burning cash. To truly understand how to use all the different oils glistening in your pantry, it helps knowing the science behind how smoke points work and what other ingredients can affect them,
The science of oil smoke points
The definition of is pretty straightforward. "An oil smoke point is the temperature of when an oil starts to smoke and the oil starts to degrade," says Nik Sharma, a chef who studied science and the author of The Flavor Equation ($26), a book that focuses on the science of flavor.
When an oil starts to smoke, that's a signal that it's starting to break down. At that point, the oil starts losing both its flavor and health benefits. "When an oil reaches its smoke point, the molecules start ripping themselves apart under the heat," says Stuart Farrimond, MD, a medical doctor who is the food scientist for BBC's "Inside The Factory" and the author of The Science of Cooking ($21).
If you continue heating something (in this case an oil) past its smoke point then you have put so much energy into the oil that particles within it will start to break down and the oil itself may even catch fire, explains Dr. Farrimond. For this reason he says an oil smoke point is the maximum temperature you can cook at and ideally you want to do your cooking before it reaches that point.
The experts say there are a few different reasons for different oils having different smoke points. One is due to varying ratios of fatty acids. All oils have fatty acids, but the ratios of the types of fatty acids—such as unsaturated and saturated—differ from oil to oil, which affects the smoke point, says Sharma. For example, flaxseed oil's ratio of omega-6s to omega-3s is 1:4 and it has a smoke point of 225°F while avocado's ratio is 12:1 and its smoke point is much higher at 520°F. When it comes to saturated fatty acids, each carbon is bound to two carbons with two hydrogens forming bonds on either side. But when the carbons bond with each other creating double bonds, it becomes an unsaturated fatty acid.
The number of free fatty acids—which determines the acid content in oils—is yet another piece to the smoke point puzzle. The lower the number of free fatty acids in an oil, the lower the smoke point, says Sharma.
But that's not all. Dr. Farrimond says there's also the factor of all the particles in an oil that gives its flavor, for example the particles from olives, walnuts, corn, or whatever plant the oil is being sourced from. The particles from olives break down differently than corn, for example. Dr. Farrimond says that in science-speak, these particles are called "impurities." Despite the name, you want an oil to maintain its impurities because that's where the flavor is.
A guide to the smoke points of the most commonly used oils
Both Dr. Farrimond and Sharma say it's impossible to give uniform smoke points for each type of oil because how they are processed and stored makes a difference too. "For example, if you have an oil that's sitting on your kitchen counter being exposed to direct sunlight, the chemical makeup of that oil is going to be different from one that's stored in a dark pantry," says Sharma. (For the record, he recommends storing all oils in a cool, dark place, where sunlight can break down molecules.)
That said, there is a general hierarchy of when oils tend to reach their smoke point. The list below can be used as a guide:
Avocado oil: 520°F
Coconut oil: 350°F
Extra-virgin olive oil: 331°F (Note: When it comes to extra-virgin olive oil, some scientific studies have shown that it can actually withstand temperatures over 475°F.)
Grapeseed oil: 475°F
Macadamia nut oil: 410°F
Peanut oil: 450°F
Sesame oil: 410°F
Soybean oil: 450°F
Sunflower oil: 450°F
Watch the video below to learn about the health benefits of olive oil:
Is cooking an oil past its smoke point "dangerous"?
If you have a rebellious nature in the kitchen, you may view the above chart as a mere suggestion. "Rules are for bakers, not chefs!" you may think. Well, if you ignore an oil's smoke point, it will eventually catch fire. So, if you're into burnt food, go ahead and blow right past it.
When an oil reaches its smoke point, the molecules start to break down. That means you're getting less flavor and nutrients. But is it 'dangerous"? Will inflammation-causing free radicals really form? Dr. Farrimond says there is some scientific evidence to suggest this. "There's some evidence showing that carcinogens—specifically one called acrolein—are produced when oil is heated past a certain point," he says. "So, yes, it is potentially harmful."
This intel is enough to make any health-conscious cook to always want to be aware of an oil's temperature. But Sharma says the only true way to know is by using a thermometer. If you notice your oil is starting to smell rancid while you're cooking, that's another sign. And if your pan has caught on fire, yeah, you're past the oil's smoke point.
How smoke point matters depending on what you're cooking
Of course you're never just cooking with oil and, of course, that affects its smoke point. Let's say you're making a sauce and decide to add a few of your favorite herbs to the mix. The antioxidants in herbs have been linked to protecting oils from being degraded as easily. "The other ingredients you're cooking with definitely matter," Sharma says.
You may wonder how the oil smoke point changes with the cooking method. For example, can an oil withstand a higher smoke point in the oven as opposed to on the stove? Dr. Farrimond says no. A smoke point is a smoke point and it's the same regardless of the way you're reaching that temperature.
With all this in mind, both experts say they tend to save their precious oils—the ones full of flavor that cost considerably extra—to add to food after it's cooked; that's the best way to really taste the flavors of the oil. For the actual cooking, both say they lean toward a neutral oil. Sharma favors grapeseed oil. "It has a high smoke point, it's cheap, and it's readily available," he says.
In this way, saving more expensive oils for after the cooking is done saves more than just money—it preserves the nutrient density and flavor, too. Whenever you're cooking with oil, that's good information to keep on the back burner.
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