A number of recipes call for foods to be cooked in varying amounts of hot fat. Usually, your choice of a fat won't matter much because ordinary frying takes place at moderate temperatures, well below 400 degrees Fahrenheit. However, some preparations require higher temperatures and oils that can handle the heat without breaking down. Peanut oil, for example, has a relatively high smoke point.
Smoke Point 101
When you heat a pot of water, you'll see vapors rising from the surface well before it boils. The same is true for oils, which will visibly release acrid, strong-smelling gases and vapors well before they boil. This happens at a temperature referred to as that oil's "smoke point." At that temperature the oil begins to break down and change its chemical structure, creating off flavors and potentially carcinogenic compounds. This is undesirable for both culinary and health reasons, so when you must cook at high temperatures it's important to choose an oil with a correspondingly high smoke point.
A Moving Target
All measures of oils' smoke points are only approximations, because the temperature itself is a moving target. There are several obstacles to accurate measurement of smoke points. First, the term itself is subjective because oils begin emitting vapors at relatively low temperatures. Identifying the point at which they become problematic is difficult. Second, oils from different manufacturers can vary widely even when they're the same type of oil. Finally, the more refined an oil is the higher its smoke point.
The smoke point for pure peanut oil depends on how you define "pure." An unrefined, cold-pressed peanut oil has a rich peanut flavor, but its smoke point is approximately 320 degrees Fahrenheit. That's quite low, and not well-suited to frying. The smoke point of a highly refined peanut oil is approximately 440 F to 450 F, suitable for almost any purpose. In comparison, canola oil's smoke point is approximately 400 F; grapeseed oil's is approximately 420 F, refined soy oil smokes at 450 F; extra-light olive oil at over 460 F; and safflower oil at an estimated 510 F.
In practial terms, oils with a smoke point of at least 400 F are suitable for most uses. Deep frying usually requires temperatures ranging from 350 F to 375 F, and seldom exceeds that level for most foods. Ordinary pan-frying and sauteing are usually carried out at temperatures ranging from 350 F to 400 F, again well below the smoke point of most oils. Only a few common cooking chores, such as stir-frying, searing a steak or rapidly crisping breaded oysters, require temperatures in the 400 F to 450 F range. Refined peanut oil is well suited to those uses. Still, for safety, cooks should closely monitor any high-temperature cooking to minimize the risk of burns or fire.
- On Food and Cooking: The Science and Lore of the Kitchen; Harold McGee
- The Washington Post: Where There's Smoke, There's a Fryer; Robert L. Wolke
- Cooking For Engineers: Smoke Points of Various Fats
- Photo Credit Creatas Images/Creatas/Getty Images