Can you use canola oil in a deep fryer?

In this article, we will answer the question “Can you use canola oil in a deep fryer?”, and how does deep-frying work?

Can you use canola oil in a deep fryer?

Yes, you can use canola oil in a deep fryer. Canola oil or rapeseed oil is inexpensive, readily available, and has a neutral taste. The average smoke point of most types of canola oil is around 400℉-430°F which is pretty high. Smoke point is the temperature at which a fat or oil produces a continuous wisp of smoke when heated. For frying purposes, the smoke point should be above 392°F. This provides a useful characterization of its suitability for frying (2).

The higher the smoke point of an oil, the more it is resistant to oxidative damage at a high temperature. Most of the foods deep fry at temperatures between 350 to 375℉. 

Deep frying involves the caramelization of the starches and sugars present in the food. Caramelization turns the food golden or brown and high temperatures make them crispy. The frying process relies on high temperatures and can change the structure of labile nutrients, such as proteins, vitamins and antioxidants. Some water-soluble molecules, such as ascorbic acid can be lost during the water evaporation (3).

During 1997–2011, animal cooking fat consumption at household level gradually declined from 22.4% in 1997 to 11.6% in 2011, whereas plant cooking oil consumption rose from 77.6% in 1997 to 88.5% in 2011. Peanut oil, soybean oil, and canola oil were the top 3 most widely consumed plant cooking oils followed by refined blended plant oil, sesame oil, and other plant oils (1).

How does deep-frying work?

Deep frying involves submerging the food in oil and heating it at 350–375°F (176–190°C). When food is exposed to such high temperatures, it forms an outer crust that is impermeable to oil. However, a portion of frying oil and polar compounds produced by oil degradation are absorbed by the food (3).

Meanwhile, steam forms in the core of the food that eventually cooks the food from the inside. The accuracy of the deep-frying temperature is very important. However, the temperature in the frying is very heterogeneous: the highest temperatures (which are close to oil temperatures) are observed in the peripheral region of the food while the core of the food, rich in water, shows temperatures around 212°F (100°C). Consequently, the rate of nutrient degradation in the peripheral region is higher than in the center (3).

The food will turn out soggy and greasy if the temperature is too low. If the temperature is too high, the food will turn out dry and the oil will oxidize.  Extended exposure of oil to high temperatures and atmospheric air can generate highly oxidized, potentially toxic products (3).

The stability of cooking oils is key

A stable oil that does not undergo oxidation easily and that has a high smoke point is the perfect choice for deep frying. 

Oils with a high concentration of saturated fats tend to be more stable than others. The degree of unsaturation of the fatty acids is the main factor affecting the oxidative stability of oil/fat. In general, oils that are more unsaturated oxidize more rapidly than less unsaturated ones (3).

Oils that have a high polyunsaturated content are unstable due to the presence of double or triple bonds. 

When exposed to a high temperature, such oils bond quickly with oxygen due to gain stability. Last but not the least, always opt for neutral flavor oils for deep frying.

In addition, retinol, carotenoids and tocopherols (which are vitamins that may be present in plant oils) are destroyed, changing oil flavor and color. However, preferential oxidation of tocopherols has a protective (antioxidant) effect which is particularly important, since the majority of the frying oils is of vegetable origin, showing great amounts of unsaturated, rapidly oxidized fats (3).

Coconut oil is a healthy choice

According to studies, coconut oil can withstand 8 hours of continuous deep frying at 365°F (180°C) without forming harmful compounds. However, virgin coconut oil (VCO) is less stable, thus VCO has lower smoke point (170°C) compared to coconut oil (above 200 °C), mainly due to the higher content of free short and medium-chain fatty acids in the VCO (4).

This remarkable tolerance to high heat is ascribed to the high(more than 90%) saturated content of coconut oil. Coconut oil may have excellent oxidative stability at high temperature due to high content of saturated fatty acids (>95%). Furthermore, this oil has a distinct coconut smell which may give good flavor to the fried food (4)

The research on the benefits and disadvantages of saturated fats is underway. As per the American Heart Association guidelines, saturated fats should only comprise 5-6% of the total calories of a healthy individual.

Lard, tallow, ghee, and drippings

Animal fats such as lard, tallow, ghee, and drippings can withstand high temperatures and add a lot of flavor and texture to the deep-fried food. Saturated fats comprise a major portion of the saturated fatty acid content of animal fats.

The fatty acid content of each type of animal is unique and depends upon the diet of the animal. Grain-fed animals may have a higher polyunsaturated fat content than grass-fed or pasture-raised animals.

However, scientists affirm that deep-frying, and other industrial processes for food preparation, require fats and oils with high thermo-oxidative stability. In these applications, due to easy storage and pouring, oils are better than fat. In addition, animal fats are considered unhealthy by many authors and the World Health Organization (5).

A useful way to determine the suitability of an oil for frying is to consider its inherent stability to oxidation. Inherent stability numbers relate to relative reaction rates of unsaturated fatty acids with oxygen. Therefore, an oil with a low inherent stability number is less susceptible to oxidation during frying. Lard and tallow have relative low inherent stability (6).

Unlike most animal fats, butter is undesirable for deep frying due to the presence of minute quantities of protein and carbs that tend to burn at a high temperature. Butter has a low smoke point of 230°F (110°C) (8). Clarified butter and ghee have a better heat tolerance than butter. Using ghee for frying for short periods did not cause the presence of cholesterol oxides; however, they were present after frying for 15 min (7).

Other good choices

Olive oil

Olive oil is one of the healthiest oils due to its high monounsaturated fats and its ability to withstand high temperatures for prolonged periods without oxidizing. The smoke point of olive oil is high, of 410°F or 210°C (8).

Avocado oil

Avocado oil is a bit expensive but it is a good choice for deep frying due to its high smoke point of 482°F (250°C) (9).. Just like olive oil, avocado oil contains a major portion of monounsaturated fats with a small ratio of saturated and polyunsaturated fats. 

Peanut oil

The smoke point of peanut oil or groundnut oil is 428°F or 220°C (8). Such a high smoke point coupled with the neutral taste of peanut oil makes it the perfect choice for deep frying. Groundnut oil-being high in oleic acid (monounsaturated fat), possesses greater thermal stability. Due to high smoke point (~230°C) and neutral taste, groundnut oil is considered more suitable for frying foods. However, studies show that frying with peanut oil greatly affects the oil quality by producing trans fats and other degradation products which can pose adverse health effects (10).

However, peanut oil is more prone to oxidative damage at a high temperature due to the presence of 32% polyunsaturated fats.

Palm oil 

Unrefined version of the palm oil, known as red palm oil, is considered best for deep frying due to its neutral taste and oxidative stability. But there are debates about the cultivation and sustainability of palm oil. Palm oil and palm kernel oil have relative low inherent stability when compared to other vegetable oils (6). 

Unsuitable options 

Vegetable oils with a high polyunsaturated fatty acid content are unsuitable for deep frying. These oils include soybean oil, corn oil, canola oil or rapeseed oil, cottonseed oil, safflower oil, rice bran oil, sunflower oil, sesame oil, etc. The smoke points of some of the unsuitable deep-frying oils are given in the table below (6).

Type of oil	Smoke point
Extra virgin olive oil	410 °F
Unrefined coconut oil	350℉
Vegetable shortening	302 °F
Lard	356 °F
Butter	230°F

Conclusion

In this article, we answered the question “Can you use canola oil in a deep fryer?”, and how does deep-frying work?

References