The healthiest oils for frying are resistant to high-temperature cooking, have a high smoking point, and have a favorable fatty acid profile. These include olive, avocado, and peanut oil.
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Olive oil is the primary cooking oil in the Mediterranean diet. It contains more monounsaturated (MUFA) than polyunsaturated (PUFA) fat, making it less likely to produce harmful compounds. Extra virgin olive oil contains 69.2% MUFA, 9.07% PUFA, and 15.4% saturated fats.
Olive oil has a smoking point of 410 degrees Fahrenheit (210 degrees Celsius), while virgin olive oil has a lower smoking point of 320-338 degrees Fahrenheit (160-170 degrees Celsius). Olive oil is rich in antioxidants, increasing the oil’s resistance to creating harmful compounds.
Frying increases the oil’s free fatty acid content (FFA). FFAs can turn into harmful compounds through a process called oxidation, lowering the oil’s quality. In a study of FFA generation in olive, canola, and peanut oils during frying, the olive oil had the lowest FFA content of the three oils.
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Avocado oil contains 70.6% MUFA, 13.5% PUFA, and 11% saturated fats. It also has a high smoke point above 482 degrees Fahrenheit (250 degrees Celsius). Avocado oil’s stability is similar to olive oil.
In a study comparing potato chips fried with avocado, soybean, sesame seed, and almond oil, the antioxidant capacity in avocado oil remained the highest after five frying cycles.
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Rice bran oil is another healthier option for deep-frying foods. It has a high antioxidant capacity and a smoke point of 449 degrees Fahrenheit (232 degrees Celsius). Rice bran oil consists of 39.3% MUFA, 35% PUFA, and 19.7% saturated fats.
Rice bran oil can also be blended with other oils. A study looking at blends of rice bran oil with olive oil, sunflower oil, and palm oil found that the most stable (resistant to deterioration) blends were rice bran oil with olive oil and rice bran oil with palm oil.
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Peanut oil contains 57.1% MUFA, 19.9% PUFA, and 16.2% saturated fats. It also has a high smoke point of about 446 degrees Fahrenheit (230 degrees Celsius).
A study comparing the stability of peanut, canola, soybean, and corn oil during heating found that harmful compounds were highest in corn oil and lowest in peanut oil.
Highly refined peanut oil is safe for people with peanut allergies, but cold-pressed, expelled, and extruded peanut oils still contain allergens.
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Canola oil contains 63.3% MUFA, 28.1% PUFA, and 7.36% saturated fats, but deep-frying with canola oil may produce an undesirable taste. When buying canola oil, check for labels that state it contains high oleic acid, as canola oil blends with high oleic acid are more heat-resistant.
A study compared the changes in canola oil, corn oil, peanut oil, palm oil, and sunflower oil during the frying of French fries. The results showed that peanut and canola oils contain the least harmful compounds.
When you’re choosing oil for frying, consider:.
- Oil fatty acid profile: Oils with high PUFA cause more harmful compounds when heated, compared to oils with high MUFA or saturated fat. Although saturated fats (such as coconut oil) are stable in heat, it is not recommended to fry with high saturated fats because fried food absorbs the oil.
- Smoke point: A high smoke point (the temperature at which oil begins to evaporate) is desirable for frying. Evaporating oil causes chemical changes that result in an undesirable taste and the formation of harmful compounds.
- Processing method: Processing affects oil stability. Mechanical processes used to produce extra virgin olive oil preserve its natural antioxidant content. Refined oils (that may be bleached or heated) lose some antioxidants, so they’re generally added later as additives.
Shallow frying causes more lipid oxidation products. These compounds can cause DNA and cell damage, leading to health conditions.
For shallow frying, using MUFA-rich fats is still more suitable. A study compared lipid oxidation products in avocado oil, extra virgin olive oil, corn oil, and soybean oil in shallow frying. PUFA-rich oils (corn and soybean oil) resulted in the highest generation of lipid oxidation products compared to avocado and olive oil.
The fatty acid composition of oil changes when exposed to heat. Frying reduces PUFA content and increases saturated and trans fatty acids. Therefore, oils with high PUFA content are not suitable for frying.
High PUFA oils include:
- Corn oil: 52.9% PUFA, 13.4% saturated fats
- Sunflower oil: 62.4% PUFA, 9.4% saturated fats
- Sesame oil: 41.2% PUFA, 16.9% saturated fats
- Soybean oil: 57.6% PUFA, 14.9% saturated fats
- Safflower oil: 79.1% PUFA, 9.3% saturated fats
- Grape seed oil: 74.9% PUFA, 10.4% saturated fats
A study examined the changes in the composition of coconut, olive, rapeseed, and sunflower oils when heated. The results showed that coconut oil was the most resistant to heat, while sunflower oil was the least resistant.
Although saturated fats are stable at high temperatures, frequent consumption is not recommended because it’s associated with an increased risk of heart disease.
Oils high in saturated fat include:
- Coconut oil: 18.2% PUFA, 92.1% saturated fats
- Butter: 2.52% PUFA, 45.6% saturated fats
Use these oils in applications requiring little to no heating, such as salad dressings.
