April 2019Cooking with Fats and Oils: Can they withstand the heat?
By Anita Bancroft
An assortment of fats and oils are available at your local grocery store to use in all types of cooking applications. Some are better to use than others, especially when the heat is involved, so it is necessary to select the right tool for the job. Many oils are suitable for dressings or garnishes, while others are preferable for grilling or stir-frying with higher heat.
It’s important to avoid the smoke point (the temperature a fat or oil begins to smoke), as this can produce toxic compounds and bitter or ‘off’ flavors. Exceeding the smoke point can also destroy valuable nutrients. When selecting your oil, it is important to note that food cooked on the stove top rarely exceeds 350°F. However, this temperature can be exceeded with other cooking techniques such as baking, grilling, and frying.
Understanding Types of Fats
SATURATED FATS
Saturated fats typically come from animal products, but some plants are high in this type of fat as well. These fats are solid at room temperature. Saturated fats commonly used in cooking include: butter, coconut oil, palm oil, and lard. Although saturated fats can add flavor to your dish, they should be consumed in small amounts, as they can raise blood cholesterol levels, which is associated with an increased risk for heart disease. The 2015-2020 Dietary Guidelines for Americans recommend limiting saturated fat to less than 10% of daily calories (example – less than 200 calories from saturated fat for a diet of 2000 calories per day, or less than 22 grams/day).
UNSATURATED FATS
Plant oils, and some animal products, are high in both mono- and poly-unsaturated fats. Unsaturated fats commonly used in cooking include canola, flaxseed, avocado, peanut, and olive oil. These fats are associated with a reduced risk for many conditions, including heart disease and stroke. Unsaturated fats lower bad cholesterol, blood pressure, and inflammation while providing nutrients that are essential for building and maintaining cells in the body. The DGA recommends replacing saturated fats with healthier unsaturated fats.
TRANS FATS
Trans fats are created through hydrogenation, a process that takes oil that is liquid at room temperature (unsaturated) and turns it into solid fat (saturated). These are commonly found in margarine and shortenings. Like saturated fats, trans fats also have the ability to raise blood cholesterol levels and increase the risk of heart disease. The DGA recommends avoiding trans fats.
Storage
Storage is essential when it comes to oils. The quickest way to damage stored oil is to expose it to heat, air, and light. This causes oil to break down, which leads to a loss of nutrients. Oil should be stored in a cool, dark area and replaced if it has a bitter odor. Some oils (polyunsaturated oils such as flaxseed, grapeseed, and walnut) become rancid quicker than others and should be stored in the refrigerator to extend their shelf life.
Olive Oils
Olive oils are a heart-healthy choice. They are high in antioxidants and omega-9 fatty acid (Oleic acid). Virgin oils provide the most antioxidants. There is controversy regarding the use of olive oils in cooking. Compared to many other oils, they are actually more stable during heating, making them excellent for all cooking methods.
FAQs
When heated repeatedly, changes in physical appearance of the oil will occur such as increased viscosity and darkening in colour [1], which may alter the fatty acid composition of the oil. Heating causes the oil to undergo a series of chemical reactions like oxidation, hydrolysis and polymerization [2].
What is the temperature at which oils or fats begin to break down? ›
The smoke point is also called the burning point of oil and can range from relatively low 325 F to very high (520 F).
What is the effect of heating on fats and oils with respect to smoke point? ›
Heated past its smoke point, that fat starts to break down, releasing free radicals and a substance called acrolein, the chemical that gives burnt foods their acrid flavor and aroma. Think watering eyes, a stinky kitchen, and bitter, scorched food. Free Radicals.
Why should cooking oils and fatty foods be kept in a dark cool place? ›
"Extra virgin olive oil, vegetable oils, peanut oils, and coconut oils should be stored in a cool, dark place that's also dry—preferably a pantry away from appliances and sunlight because exposure to heat breaks down the oils, and, in turn, can make them rancid."
Are fats destroyed by heat? ›
Fats are incredibly fragile. Heat, light and oxygen break down and destroy the nutrients in fat. So, the less they are processed, the more beneficial they will be. But, processing is how they are made to withstand high heats for cooking.
What happens to cooking oil when its heated? ›
Research reveals that heating the vegetable oils up to the level of 180 °C changes their chemical composition and reduces the quality of oil by decomposing the heat-labile vitamin E [10]. Thermal oxidation and auto-oxidation are well-defined reaction in heated cooking oil that affect the stability of cooking oil.
What cooking oil is best for high heat? ›
Refined oils recommended for high-heat cooking and deep-frying are “high oleic” safflower, sunflower, and peanut oil.
What is the maximum temperature for cooking oil? ›
Vegetable oil has a high smoke point of 400-450°F (204-230°C), so it fall right in the perfect frying oil temp of 350-375°F. Corn oil is similar to vegetable oil coming in at 410-450°F (210-230°C).
What is the healthiest oil to cook with? ›
Oil Essentials: The 5 Healthiest Cooking Oils
- Olive Oil. Olive oil is popular for a reason. ...
- Avocado Oil. Avocado oil boasts a lot of the same benefits as extra virgin olive oil, but with a higher smoking point, making it great for sauteing or pan frying. ...
- Coconut Oil. ...
- Sunflower Oil. ...
- Butter.
As a result of heating fats, three types of degradative changes can occur: (a) autoxidation; (b) thermal polymerization; and (c) thermal oxidation.
When heat is applied to fats, they melt, rather than evaporate or solidify. Fats can take the form of a solid, liquid, or a variation of both. However, they all become liquid when heated. Fats are used as a medium for cooking and baking because they are less likely to burn than other substances.
Why overheating or repeated heating of fats or oils is harmful? ›
Reactions like oxidation, hydrolysis, and polymerisation occur upon reheating oil, which forms volatile compounds and toxic monomeric and polymeric products. These compounds and products are responsible for giving the oil a bad flavour and for many negative effects on our health.
What oils are not carcinogenic when heated? ›
The 5-second cheat sheet:
- Extra-virgin, Expeller- or Cold-pressed, Unrefined, Organic Olive Oil (medium heat)
- Organic Ghee (high heat)
- Organic, Extra-virgin, Unrefined Coconut Oil (medium heat)
- Organic, Expeller- or Cold-pressed Avocado Oil (medium-high heat)
- Refined Safflower Oil (high heat)
Even healthy oils can turn bad in quality, taste and healthiness when stored near a stove or exposed to heat and light, so it's important to know how to store them properly. In general, you want to store cooking oils with polyunsaturated fats (PUFAs) in the fridge.
What oils go rancid? ›
Oils like vegetable or olive oil are especially susceptible to going rancid. And if you're dealing with toasted versions like Asian sesame oil or toasted nut oils, the reaction happens especially quickly, since these oils were already been exposed to heat when they were made.
What happens when you heat olive oil? ›
The flavor compounds in olive oil are delicate and will evaporate when heated. Heating olive oil does not damage the health benefits but it will make the olive oil lose some flavor. Some people consider this to be a good thing as they do not want their foods to taste like olive oil.
What happens to fats at high temperatures? ›
It's important to avoid the smoke point (the temperature a fat or oil begins to smoke), as this can produce toxic compounds and bitter or 'off' flavors. Exceeding the smoke point can also destroy valuable nutrients. When selecting your oil, it is important to note that food cooked on the stove top rarely exceeds 350°F.
Why is heated oil bad for you? ›
Smoke points and harmful free radicals
When an oil is heated past its smoke point, it releases free radicals – it reacts with oxygen to form harmful compounds. You definitely don't want to be consuming or breathing in these. Free radicals can injure cells and DNA in your body.
What happens when fats melt? ›
Most fats melt somewhere between 90° and 130°F (30°–55°C). As they melt, trapped air and water escape from the fat. Water evaporates as steam vapor, and the air and steam expand, pushing on cell walls so that baked goods increase in volume. In other words, melting fat contributes to leavening.
