The smoke point, also referred to as the burning point, is the temperature at which an oil or fat begins to produce a continuous bluish smoke that becomes clearly visible, dependent upon specific and defined conditions. [1] Smoke point values can vary greatly, depending on factors such as the volume of oil utilized, the size of the container, the presence of air currents, the type and source of light as well as the quality of the oil and its acidity content, otherwise known as free fatty acid (FFA) content. [2] The more FFA an oil contains, the quicker it will break down and start smoking. [2] [3] The lower the value of FFA, the higher the smoke point. [4] However, the FFA content typically represents less than 1% of the total oil and consequently renders smoke point a poor indicator of the capacity of a fat or oil to withstand heat. [4] [5] [6]
The smoke point of an oil correlates with its level of refinement. [7] [8] Many cooking oils have smoke points above standard home cooking temperatures: [9]
Smoke point decreases at a different pace in different oils. [10]
Considerably above the temperature of the smoke point is the flash point, the point at which the vapours from the oil can ignite in air, given an ignition source.
The following table presents smoke points of various fats and oils.
Fat | Quality | Smoke point [caution 1] | |
---|---|---|---|
Almond oil | 221 °C | 430 °F [11] | |
Avocado oil | Refined | 271 °C | 520 °F [12] [13] |
Avocado oil | Unrefined | 250 °C | 482 °F [14] |
Beef tallow | 250 °C | 480 °F | |
Butter | 150 °C | 302 °F [15] | |
Butter | Clarified | 250 °C | 482 °F [16] |
Castor oil | Refined | 200 °C [17] | 392 °F |
Coconut oil | Refined, dry | 204 °C | 400 °F [18] |
Coconut oil | Unrefined, dry expeller pressed, virgin | 177 °C | 350 °F [18] |
Corn oil | 230–238 °C [19] | 446–460 °F | |
Corn oil | Unrefined | 178 °C [17] | 352 °F |
Cottonseed oil | Refined, bleached, deodorized | 220–230 °C [20] | 428–446 °F |
Flaxseed oil | Unrefined | 107 °C | 225 °F [13] |
Grape seed oil | 216 °C | 421 °F | |
Lard | 190 °C | 374 °F [15] | |
Mustard oil | 250 °C | 480 °F [21] | |
Olive oil | Refined | 199–243 °C | 390–470 °F [22] |
Olive oil | Virgin | 210 °C | 410 °F |
Olive oil | Extra virgin, low acidity, high quality | 207 °C | 405 °F [13] [23] |
Olive oil | Extra virgin | 190 °C | 374 °F [23] |
Palm oil | Fractionated | 235 °C [24] | 455 °F |
Peanut oil | Refined | 232 °C [13] | 450 °F |
Peanut oil | 227–229 °C [13] [25] | 441–445 °F | |
Peanut oil | Unrefined | 160 °C [13] | 320 °F |
Pecan oil | 243 °C [26] | 470 °F | |
Rapeseed oil (Canola) | 220–230 °C [27] | 428–446 °F | |
Rapeseed oil (Canola) | Expeller press | 190–232 °C | 375–450 °F [28] |
Rapeseed oil (Canola) | Refined | 204 °C | 400 °F |
Rapeseed oil (Canola) | Unrefined | 107 °C | 225 °F |
Rice bran oil | Refined | 232 °C [29] | 450 °F |
Safflower oil | Unrefined | 107 °C | 225 °F [13] |
Safflower oil | Semirefined | 160 °C | 320 °F [13] |
Safflower oil | Refined | 266 °C | 510 °F [13] |
Sesame oil | Unrefined | 177 °C | 350 °F [13] |
Sesame oil | Semirefined | 232 °C | 450 °F [13] |
Soybean oil | 234 °C [30] | 453 °F | |
Sunflower oil | Neutralized, dewaxed, bleached & deodorized | 252–254 °C [31] | 486–489 °F |
Sunflower oil | Semirefined | 232 °C [13] | 450 °F |
Sunflower oil | 227 °C [13] | 441 °F | |
Sunflower oil | Unrefined, first cold-pressed, raw | 107 °C [32] | 225 °F |
Sunflower oil, high oleic | Refined | 232 °C | 450 °F [13] |
Sunflower oil, high oleic | Unrefined | 160 °C | 320 °F [13] |
Vegetable oil blend | Refined | 220 °C [23] | 428 °F |
Hydrolysis and oxidation are the two primary degradation processes that occur in an oil during cooking. [10] Oxidative stability is how resistant an oil is to reacting with oxygen, breaking down and potentially producing harmful compounds while exposed to continuous heat. Oxidative stability is the best predictor of how an oil behaves during cooking. [33] [34] [35]
The Rancimat method is one of the most common methods for testing oxidative stability in oils. [35] This determination entails speeding up the oxidation process in the oil (under heat and forced air), which enables its stability to be evaluated by monitoring volatile substances associated with rancidity. It is measured as "induction time" and recorded as total hours before the oil breaks down. Canola oil requires 7.5 hours, for example, whereas extra virgin olive oil (EVOO) and virgin coconut oil will last over a day at 110 °C (230 °F) of continuous heat. [9] The differing stabilities correlate with lower levels of polyunsaturated fatty acids, which are more prone to oxidation. EVOO is high in monounsaturated fatty acids and antioxidants, conferring stability. Some plant cultivars have been bred to produce "high-oleic" oils with more monounsaturated oleic acid and less polyunsaturated linoleic acid for enhanced stability. [9]
The oxidative stability does not directly correspond to the smoke point and thus the latter cannot be used as a reference for safe and healthy cooking. [36]
Olive oil is a liquid fat obtained by pressing whole olives, the fruit of Olea europaea, a traditional tree crop of the Mediterranean Basin, and extracting the oil.
Sautéing or sauteing is a method of cooking that uses a relatively small amount of oil or fat in a shallow pan over relatively high heat. Various sauté methods exist.
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of edible plants. Like animal fats, vegetable fats are mixtures of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fats from seeds. Olive oil, palm oil, and rice bran oil are examples of fats from other parts of plants. In common usage, vegetable oil may refer exclusively to vegetable fats which are liquid at room temperature. Vegetable oils are usually edible.
Rancidification is the process of complete or incomplete autoxidation or hydrolysis of fats and oils when exposed to air, light, moisture, or bacterial action, producing short-chain aldehydes, ketones and free fatty acids.
Coconut oil is an edible oil derived from the kernels, meat, and milk of the coconut palm fruit. Coconut oil is a white solid fat below around 25 °C (77 °F), and a clear thin liquid oil at higher temperatures. Unrefined varieties have a distinct coconut aroma. Coconut oil is used as a food oil, and in industrial applications for cosmetics and detergent production. The oil is rich in medium-chain fatty acids.
Hemp oil is oil obtained by pressing hemp seeds. Cold pressed, unrefined hemp oil is dark to clear light green in color, with a nutty flavor. The darker the color, the grassier the flavour. It should not be confused with hash oil, a tetrahydrocannabinol-containing oil made from the Cannabis flower.
Cottonseed oil is cooking oil from the seeds of cotton plants of various species, mainly Gossypium hirsutum and Gossypium herbaceum, that are grown for cotton fiber, animal feed, and oil.
Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish due to the presence of impurities. In chemical terms, oleic acid is classified as a monounsaturated omega-9 fatty acid, abbreviated with a lipid number of 18:1 cis-9, and a main product of Δ9-desaturase. It has the formula CH3−(CH2)7−CH=CH−(CH2)7−COOH. The name derives from the Latin word oleum, which means oil. It is the most common fatty acid in nature. The salts and esters of oleic acid are called oleates. It is a common component of oils, and thus occurs in many types of food, as well as in soap.
Shortening is any fat that is a solid at room temperature and is used to make crumbly pastry and other food products.
Omega−6 fatty acids are a family of polyunsaturated fatty acids that have in common a final carbon-carbon double bond in the n−6 position, that is, the sixth bond, counting from the methyl end.
In chemistry, acid value is a number used to quantify the acidity of a given chemical substance. It is the quantity of base, expressed as milligrams of KOH required to neutralize the acidic constituents in 1 gram of a sample. The acid value measures the acidity of water-insoluble substances like oils, fats, waxes and resins, which do not have a pH value.
Rice bran oil is the oil extracted from the hard outer brown layer of rice called bran. It is known for its high smoke point of 232 °C (450 °F) and mild flavor, making it suitable for high-temperature cooking methods such as stir frying and deep frying. It is popular as a cooking oil in East Asia, the Indian subcontinent, and Southeast Asia including India, Nepal, Bangladesh, Indonesia, Japan, Southern China and Malaysia.
Corn oil or maize oil (British) is oil extracted from the germ of corn (maize). Its main use is in cooking, where its high smoke point makes refined corn oil a valuable frying oil. It is also a key ingredient in some margarines. Corn oil is generally less expensive than most other types of vegetable oils.
Soybean oil is a vegetable oil extracted from the seeds of the soybean. It is one of the most widely consumed cooking oils and the second most consumed vegetable oil. As a drying oil, processed soybean oil is also used as a base for printing inks and oil paints.
Sunflower oil is the non-volatile oil pressed from the seeds of the sunflower. Sunflower oil is commonly used in food as a frying oil, and in cosmetic formulations as an emollient.
Avocado oil is an edible oil extracted from the pulp of avocados, the fruit of Persea americana. It is used as an edible oil both raw and for cooking, where it is noted for its high smoke point. It is also used for lubrication and in cosmetics.
Lard is a semi-solid white fat product obtained by rendering the fatty tissue of a pig. It is distinguished from tallow, a similar product derived from fat of cattle or sheep.
Shallow frying is a hot oil-based cooking technique. It is typically used to prepare portion-sized cuts of meat, fish, potatoes and patties such as fritters. Shallow frying can also be used to cook vegetables.
Cooking oil is a plant or animal liquid fat used in frying, baking, and other types of cooking. Oil allows higher cooking temperatures than water, making cooking faster and more flavorful, while likewise distributing heat, reducing burning and uneven cooking. It sometimes imparts its own flavor. Cooking oil is also used in food preparation and flavoring not involving heat, such as salad dressings and bread dips.
Rapeseed oil is one of the oldest known vegetable oils. There are both edible and industrial forms produced from rapeseed, the seed of several cultivars of the plant family Brassicaceae. Historically, it was restricted as a food oil due to its content of erucic acid, which in laboratory studies was shown to be damaging to the cardiac muscle of laboratory animals in high quantities and which imparts a bitter taste, and glucosinolates, which made many parts of the plant less nutritious in animal feed. Rapeseed oil from standard cultivars can contain up to 54% erucic acid.
Table 2-3 Smoke Points of Common Fats and Oils.