Plant oils |
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Types |
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Cooking oil (also known as edible 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.
Cooking oil is typically a liquid at room temperature, although some oils that contain saturated fat, such as coconut oil, palm oil and palm kernel oil are solid. [1]
There are a wide variety of cooking oils from plant sources such as olive oil, palm oil, soybean oil, canola oil (rapeseed oil), corn oil, peanut oil and other vegetable oils, as well as animal-based oils like butter and lard.
Oil can be flavored with aromatic foodstuffs such as herbs, chilies or garlic. Cooking spray is an aerosol of cooking oil.
While consumption of small amounts of saturated fats is common in diets, [2] meta-analyses found a significant correlation between high consumption of saturated fats and blood LDL concentration, [3] a risk factor for cardiovascular diseases. [4] Other meta-analyses based on cohort studies and on controlled, randomized trials found a positive, [5] or neutral, [6] effect from consuming polyunsaturated fats instead of saturated fats (a 10% lower risk for 5% replacement). [6]
Mayo Clinic has highlighted certain oils that are high in saturated fats, including coconut, palm oil and palm kernel oil. Those having lower amounts of saturated fats and higher levels of unsaturated (preferably omega-3) fats like olive oil, peanut oil, canola oil, soy and cottonseed oils are generally healthier. [7] The US National Heart, Lung and Blood Institute [8] urged saturated fats be replaced with polyunsaturated and monounsaturated fats, listing olive and canola oils as sources of healthier monounsaturated oils while soybean and sunflower oils as good sources of polyunsaturated fats. One study showed that consumption of non-hydrogenated unsaturated oils like soybean and sunflower is preferable to the consumption of palm oil for lowering the risk of heart disease. [9]
Cashew oil and other nut-based oils do not present a danger to persons with a nut allergy, because oils are primarily lipids, and allergic reactions are due to surface proteins on the nut. [10]
The seeds of most cultivated plants contain higher levels of omega-6 fatty acids than omega-3, with some notable exceptions. Growth at colder temperatures tends to result in higher levels of omega-3 fatty acids in seed oils. [11]
Unlike other dietary fats, trans fats are not essential, and they do not promote good health. [12] The consumption of trans fats increases one's risk of coronary heart disease [13] by raising levels of LDL cholesterol and lowering levels of HDL cholesterol. [14] Trans fats from partially hydrogenated oils are more harmful than naturally occurring oils. [15]
Several large studies [16] [17] [18] [19] indicate a link between the consumption of high amounts of trans fat and coronary heart disease, and possibly some other diseases. The United States Food and Drug Administration (FDA), the National Heart, Lung and Blood Institute and the American Heart Association (AHA) all have recommended limiting the intake of trans fats. In the US, trans fats are no longer "generally recognized as safe", and cannot be added to foods, including cooking oils, without special permission. [20]
Heating, as well as heating vessels rapidly change characteristics of cooking oil. [21] Oils that are healthy at room temperature can become unhealthy when heated above certain temperatures, especially when heating repeatedly. The toxic risk is linked to oxidation of fatty acids and fatty acids with higher levels of unsaturation are oxidized more rapidly during heating in air. [22] So, when choosing a cooking oil, it is important to match the oil's heat tolerance with the temperature which will be used. [23] and to change frying oil a few times per week. [22] Deep-fat frying temperatures are commonly in the range of 170–190 °C (338–374 °F), less commonly, lower temperatures ≥ 130 °C (266 °F) are used. [24]
Palm oil contains more saturated fats than canola oil, corn oil, linseed oil, soybean oil, safflower oil, and sunflower oil. Therefore, palm oil can withstand deep frying at higher temperatures and is resistant to oxidation compared to high-polyunsaturated vegetable oils. [25] Since the 1900s, palm oil has been increasingly added into food by the global commercial food industry because it remains stable in deep frying, or in baking at very high temperatures, [26] [27] and for its high levels of natural antioxidants, though the refined palm oil used in industrial food has lost most of its carotenoid content (and its orange-red color). [28]
The following oils are suitable for high-temperature frying due to their high smoke point:
Less aggressive frying temperatures are frequently used. [30] A quality frying oil has a bland flavor, at least 200 °C (392 °F) smoke and 315 °C (599 °F) flash points, with maximums of 0.1% free fatty acids and 3% linolenic acid. [31] Those oils with higher linolenic fractions are avoided due to polymerization or gumming marked by increases in viscosity with age. [30] Olive oil resists thermal degradation and has been used as a frying oil for thousands of years. [30]
All oils degrade in response to heat, light, and oxygen. [32] To delay the onset of rancidity, a blanket of an inert gas, usually nitrogen, is applied to the vapor space in the storage container immediately after production – a process called tank blanketing.[ citation needed ] [33]
In a cool, dry place, oils have greater stability, but may thicken, although they will soon return to liquid form if they are left at room temperature. To minimize the degrading effects of heat and light, oils should be removed from cold storage just long enough for use.[ citation needed ]
Refined oils high in monounsaturated fats, such as macadamia oil, [32] keep up to a year, while those high in polyunsaturated fats, such as soybean oil, keep about six months. Rancidity tests have shown that the shelf life of walnut oil is about 3 months, a period considerably shorter than the best before date shown on labels. [32]
By contrast, oils high in saturated fats, such as avocado oil, have relatively long shelf lives and can be safely stored at room temperature, as the low polyunsaturated fat content facilitates stability. [32]
Cooking oils are composed of various fractions of fatty acids. [34] For the purpose of frying food, oils high in monounsaturated or saturated fats are generally popular, while oils high in polyunsaturated fats are less desirable. [24] High oleic acid oils include almond, macadamia, olive, pecan, pistachio, and high-oleic cultivars of safflower and sunflower. [35]
Oils and fats | Saturated fatty acids | MUFA | PUFA | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
4:0 | 6:0 | 8:0 | 10:0 | 12:0 | 14:0 | 16:0 | 18:0 | 20:0 | 22:0 | 24:0 | 16:1 | 18:1 | 20:1 | 22:1 | 18:2 | 18:3 | |
Almond [36] | 6.5 | 1.7 | 0.6 | 69.4 | 17.4 | ||||||||||||
Almond [37] | 1 | 5 | 77 | 17 | |||||||||||||
Apricot kernel [36] | 5.8 | 0.5 | 1.5 | 58.5 | 29.3 | ||||||||||||
Avocado [36] | 10.9 | 0.7 | 2.7 | 67.9 | 12.5 | 1 | |||||||||||
Basil [38] | 8.5 | 11 | 24.5 | 54.5 | |||||||||||||
Brazil nut [39] | 0.1 | 13.5 | 11.8 | 0.5 | 0.3 | 29.1 | 0.2 | 42.8 | 0.2 | ||||||||
Butter [40] | 5.3 | 2.8 | 1.6 | 3.1 | 3.4 | 10.8 | 28.1 | 10.6 | 1.4 | 20.8 | 0.3 | 2 | |||||
Butter, anhydrous [36] | 3.2 | 1.9 | 1.1 | 2.5 | 2.8 | 10 | 26.2 | 12.1 | 2.2 | 25 | 2.2 | 1.4 | |||||
Canola [36] | 4.3 | 2.1 | 0.7 | 0.3 | 0.2 | 61.7 | 1.3 | 19 | 9.1 | ||||||||
Canola [41] | 3.9 | 1.9 | 0.6 | 0.2 | 0.2 | 0.2 | 64.1 | 1 | 18.7 | 9.2 | |||||||
Cashew [38] | 11.5 | 9 | 61 | 17 | |||||||||||||
Cocoa butter [36] | 0.1 | 25.4 | 33.2 | 0.2 | 32.6 | 2.8 | 0.1 | ||||||||||
Coconut [42] | 0.4 | 7.3 | 6.6 | 47.8 | 18.1 | 8.9 | 2.7 | 0.1 | 6.4 | 1.6 | |||||||
Corn [36] | 10.6 | 1.8 | 0.4 | 0.1 | 27.3 | 0.1 | 53.5 | 1.2 | |||||||||
Cottonseed [43] | 0.9 | 25.5 | 2.5 | 0.3 | 0.2 | 0.6 | 17.7 | 52.2 | 0.1 | ||||||||
Grapeseed [36] | 0.1 | 6.7 | 2.7 | 0.3 | 15.8 | 69.6 | 0.1 | ||||||||||
Hazelnut [39] | 0.1 | 5.8 | 2.7 | 0.2 | 0.3 | 79.3 | 0.2 | 10.4 | 0.5 | ||||||||
Hemp [38] | 6.5 | 3 | 11.5 | 56.5 | 20 | ||||||||||||
Lard [44] | 0.1 | 0.2 | 1.4 | 24.9 | 14.1 | 2.8 | 43.1 | 10.7 | 1 | ||||||||
Macadamia nut [39] | 1 | 8.4 | 3.2 | 2.3 | 17.3 | 65.1 | 2.2 | 2.3 | 0.1 | ||||||||
Olive [36] | 11.3 | 2 | 0.4 | 0.1 | 1.3 | 71.3 | 0.3 | 9.8 | 0.8 | ||||||||
Olive, Virgin [45] | 13.8 | 2.8 | 0.1 | 1.9 | 69 | 12.2 | |||||||||||
Palm kernel [46] | 0.3 | 3.6 | 3.3 | 48 | 16.7 | 8.5 | 2.1 | 14.9 | 2.5 | ||||||||
Palm [47] | 0.3 | 1.1 | 43.5 | 4.3 | 0.2 | 0.2 | 39.8 | 10.2 | 0.3 | ||||||||
Palm [36] | 0.1 | 1 | 43.5 | 4.3 | 0.3 | 36.6 | 0.1 | 9.1 | 0.2 | ||||||||
Peanut [41] | 0.1 | 11.6 | 3.1 | 1.5 | 3 | 1 | 0.2 | 46.5 | 1.4 | 31.4 | |||||||
Rapeseed [45] | 4.8 | 1.9 | 60.5 | 22.5 | 9.5 | ||||||||||||
Rice bran [48] | 0.4 | 19.8 | 1.9 | 0.9 | 0.3 | 0.2 | 42.3 | 0.5 | 31.9 | 1.2 | |||||||
Safflower, high oleic [36] | 0.1 | 4.9 | 1.9 | 0.4 | 0.3 | 0.1 | 74.8 | 0.3 | 12.7 | 0.1 | |||||||
Safflower [49] | 7.3 | 2.5 | 13.6 | 75.7 | 0.5 | ||||||||||||
Sesame [50] | 0.1 | 9.2 | 5.8 | 0.7 | 0.2 | 0.1 | 40.6 | 0.2 | 42.6 | 0.3 | |||||||
Soybean [36] | 10.5 | 4.4 | 0.4 | 0.4 | 22.6 | 0.2 | 51 | 6.8 | |||||||||
Soybean [41] | 0.1 | 11 | 4 | 0.3 | 0.1 | 0.1 | 23.4 | 53.2 | 7.8 | ||||||||
Soybean, low linolenic [43] | 10.8 | 4.5 | 0.4 | 0.4 | 26.1 | 55.4 | 2 | ||||||||||
Soybean, high oleic [note 1] | 7.3 | 3.4 | 0.4 | 0.4 | 85.1 | 1.3 | 2 | ||||||||||
Sunflower [41] | 0.5 | 0.2 | 6.8 | 4.7 | 0.4 | 0.1 | 18.6 | 68.2 | 0.5 | ||||||||
Sunflower, high linoleic [36] | 5.9 | 4.5 | 19.5 | 65.7 | |||||||||||||
Sunflower, linoleic [36] | 5.4 | 3.5 | 0.2 | 45.3 | 39.8 | 0.2 | |||||||||||
Sunflower, mid-oleic [36] | 0.1 | 4.2 | 3.6 | 0.3 | 0.8 | 0.1 | 57 | 0.2 | 28.9 | ||||||||
Sunflower, high oleic [36] | 0.1 | 3.7 | 4.3 | 1 | 0.1 | 82.6 | 1 | 3.6 | 0.2 | ||||||||
Sunflower, high oleic I [51] | 5 | 3 | 82 | 9 | |||||||||||||
Sunflower, high oleic II [51] | 5 | 4 | 90 | 1 | |||||||||||||
Tallow, beef [36] | 0.9 | 3.7 | 24.9 | 18.9 | 4.2 | 36 | 0.3 | 3.1 | 0.6 | ||||||||
Tallow, mutton [36] | 3.8 | 21.5 | 19.5 | 2.3 | 37.6 | 5.5 | 2.3 | ||||||||||
Walnut [39] | 0.1 | 6.7 | 2.3 | 0.1 | 0.2 | 21 | 0.2 | 57.5 | 11.6 | ||||||||
[52] Parts per hundred |
The smoke point is marked by "a continuous wisp of smoke". [53] It is the temperature at which an oil starts to burn, leading to a burnt flavor in the foods being prepared and degradation of nutrients and phytochemicals characteristic of the oil. [54]
Above the smoke point are flash and fire points. [53] The flash point is the temperature at which oil vapors will ignite but are not produced in sufficient quantities to stay lit. The flash point generally occurs at about 275–330 °C (527–626 °F). [55] The fire point is the temperature at which hot oil produces sufficient vapors they will catch on fire and burn. [55] As frying hours increase, all these temperature points decrease. [55] They depend more on an oil's acidity than fatty-acid profile. [56]
The smoke point of cooking oils varies generally in association with how oil is refined: a higher smoke point results from removal of impurities and free fatty acids. [54] Residual solvent remaining from the refining process may decrease the smoke point. [56] It has been reported to increase with the inclusion of antioxidants (BHA, BHT, and TBHQ). For these reasons, the published smoke points of oils may vary. [56]
Fat | Quality | Smoke point [caution 1] | |
---|---|---|---|
Almond oil | 221 °C | 430 °F [57] | |
Avocado oil | Refined | 271 °C | 520 °F [58] [59] |
Avocado oil | Unrefined | 250 °C | 482 °F [60] |
Beef tallow | 250 °C | 480 °F | |
Butter | 150 °C | 302 °F [61] | |
Butter | Clarified | 250 °C | 482 °F [62] |
Castor oil | Refined | 200 °C [63] | 392 °F |
Coconut oil | Refined, dry | 204 °C | 400 °F [64] |
Coconut oil | Unrefined, dry expeller pressed, virgin | 177 °C | 350 °F [64] |
Corn oil | 230–238 °C [65] | 446–460 °F | |
Corn oil | Unrefined | 178 °C [63] | 352 °F |
Cottonseed oil | Refined, bleached, deodorized | 220–230 °C [66] | 428–446 °F |
Flaxseed oil | Unrefined | 107 °C | 225 °F [59] |
Grape seed oil | 216 °C | 421 °F | |
Lard | 190 °C | 374 °F [61] | |
Mustard oil | 250 °C | 480 °F [67] | |
Olive oil | Refined | 199–243 °C | 390–470 °F [68] |
Olive oil | Virgin | 210 °C | 410 °F |
Olive oil | Extra virgin, low acidity, high quality | 207 °C | 405 °F [59] [69] |
Olive oil | Extra virgin | 190 °C | 374 °F [69] |
Palm oil | Fractionated | 235 °C [70] | 455 °F |
Peanut oil | Refined | 232 °C [59] | 450 °F |
Peanut oil | 227–229 °C [59] [71] | 441–445 °F | |
Peanut oil | Unrefined | 160 °C [59] | 320 °F |
Pecan oil | 243 °C [72] | 470 °F | |
Rapeseed oil (Canola) | 220–230 °C [73] | 428–446 °F | |
Rapeseed oil (Canola) | Expeller press | 190–232 °C | 375–450 °F [74] |
Rapeseed oil (Canola) | Refined | 204 °C | 400 °F |
Rapeseed oil (Canola) | Unrefined | 107 °C | 225 °F |
Rice bran oil | Refined | 232 °C [48] | 450 °F |
Safflower oil | Unrefined | 107 °C | 225 °F [59] |
Safflower oil | Semirefined | 160 °C | 320 °F [59] |
Safflower oil | Refined | 266 °C | 510 °F [59] |
Sesame oil | Unrefined | 177 °C | 350 °F [59] |
Sesame oil | Semirefined | 232 °C | 450 °F [59] |
Soybean oil | 234 °C [75] | 453 °F | |
Sunflower oil | Neutralized, dewaxed, bleached & deodorized | 252–254 °C [76] | 486–489 °F |
Sunflower oil | Semirefined | 232 °C [59] | 450 °F |
Sunflower oil | 227 °C [59] | 441 °F | |
Sunflower oil | Unrefined, first cold-pressed, raw | 107 °C [77] | 225 °F |
Sunflower oil, high oleic | Refined | 232 °C | 450 °F [59] |
Sunflower oil, high oleic | Unrefined | 160 °C | 320 °F [59] |
Vegetable oil blend | Refined | 220 °C [69] | 428 °F |
Oils are extracted from nuts, seeds, olives, grains or legumes by extraction using industrial chemicals or by mechanical processes. Expeller pressing is a chemical-free process that collects oils from a source using a mechanical press with minimal heat. Cold-pressed oils are extracted under a controlled temperature setting usually below 105 °C (221 °F) intended to preserve naturally occurring phytochemicals, such as polyphenols, tocotrienols, plant sterols and vitamin E which collectively affect color, flavor, aroma and nutrient value. [54] [78]
Type of oil or fat | SFA | MUFA | PUFA | Omega- | Smoke point | Uses | |
---|---|---|---|---|---|---|---|
3 | 6 | ||||||
Almond | 8% | 66% | 26% | 0 | 17% | 221 °C (430 °F) | Baking, sauces, flavoring |
Avocado oil | 12% | 74% | 14% | 0.95% | 12% | 271 °C (520 °F) | Frying, sautéing, dipping oil, salad oil |
Butter | 66% | 30% | 4% | 0.3% | 2.7% | 150 °C (302 °F) | Cooking, baking, condiment, sauces, flavoring |
Butter, clarified, Ghee | 65% | 32% | 3% | 0 | 0 | 190–250 °C (374–482 °F) | Deep frying, cooking, sautéing, condiment, flavoring |
Canola oil | 6% | 62% | 32% | 9.1% | 18% | 225 °C (437 °F) [73] | Frying, baking, salad dressings |
Coconut oil (virgin) | 92% | 6% | 2% | 0 | 1.8% | 177 °C (351 °F) | Cooking, tropical cuisine, beauty products |
Corn oil | 13% | 25% | 62% | 1.1% | 53% | 235 °C (455 °F) [81] | Frying, baking, salad dressings, margarine, shortening |
Cottonseed oil | 24% | 26% | 50% | 0.2% | 50% | 216 °C (421 °F) | Margarine, shortening, salad dressings, commercially fried products |
Diacylglycerol (DAG) oil | 3.05% | 37.95% | 59% | 0 | - | 215 °C (419 °F) | Frying, baking, salad oil |
Linseed oil [82] | 11% | 21% | 68% | 53% | 13% | 107 °C (225 °F) | Salad dressings, nutritional supplement |
Grapeseed oil | 12% | 17% | 71% | 0.1% | 69% | 204 °C (399 °F) | Cooking, salad dressings, margarine |
Hemp oil | 9% | 12% | 79% | 18% | 55% | 165 °C (329 °F) | Cooking, salad dressings |
Lard | 41% | 47% | 2% | 1% | 10% | 183–205 °C (361–401 °F) | Baking, frying |
Macadamia oil | 12.5% | 84% | 3.5% | 0 | 2.8% | 210 °C (410 °F) | Cooking, frying, deep frying, salads, dressings. A slightly nutty odour. |
Margarine (hard) | 80% | 14% | 6% | 2% | 22% | 150 °C (302 °F) | Cooking, baking, condiment |
Margarine (soft) | 20% | 47% | 33% | 2.4% | 23% | 150–160 °C (302–320 °F) | Cooking, baking, condiment |
Mustard oil | 13% | 60% | 21% | 5.9% | 15% | 254 °C (489 °F) | Cooking, frying, deep frying, salads, dressings. Very clean flavoured & palatable. |
Olive oil (extra virgin) | 14% | 73% | 11% | 0.7% | 9.8% | 190 °C (374 °F) | Cooking, salad oils, margarine |
Olive oil (virgin) | 14% | 73% | 11% | 0.7% | 9.8% | 215 °C (419 °F) | Cooking, salad oils, margarine |
Olive oil (refined) | 14% | 73% | 11% | 0 | 0 | 225 °C (437 °F) | Sautee, stir frying, deep frying, cooking, salad oils, margarine |
Olive oil (extra light) | 14% | 73% | 11% | 0 | 0 | 242 °C (468 °F) | Sautee, stir frying, frying, deep frying, cooking, salad oils, margarine |
Palm oil | 52% | 38% | 10% | 0.2% | 9.1% | 230 °C (446 °F) | Frying, [83] cooking, flavoring, vegetable oil, shortening |
Peanut oil | 18% | 49% | 33% | 0 | 31% | 231 °C (448 °F) | Frying, cooking, salad oils, margarine, deep frying |
Pumpkin seed oil | 8% | 36% | 57% | 0% | 64% | 121 °C (250 °F) | Salad oils |
Rice bran oil | 20% | 47% | 33% | 1.6% | 33% | 213 °C (415 °F) [48] | Cooking, frying, deep frying, salads, dressings. Very clean flavoured & palatable. |
Safflower oil (high oleic) [84] [85] | 6% | 75% | 13% | 242 °C (468 °F) [81] | Frying, cooking | ||
Safflower oil (linoleic) [86] | 6% | 14% | 75% | 242 °C (468 °F) [81] | Cooking, salad dressings, margarine | ||
Sesame oil (unrefined) | 14% | 43% | 43% | 0.3 | 41% | 177 °C (351 °F) | Cooking |
Sesame oil (semi-refined) | 14% | 43% | 43% | 0.3 | 41% | 232 °C (450 °F) | Cooking, deep frying |
Soybean oil | 15% | 24% | 61% | 6.7% | 50% | 240 °C (464 °F) [81] | Cooking, salad dressings, vegetable oil, margarine, shortening |
Sunflower oil (high oleic, refined) [87] | 9% | 82% | 9% | 0.2% | 3.6% | 244 °C (471 °F) [81] | Frying, cooking [88] |
Sunflower oil (linoleic, refined) [87] | 11% | 20% | 69% | 0% | 56% | 240 °C (464 °F) [81] | Cooking, salad dressings, margarine, shortening |
Sunflower oil (mid-oleic, refined, NuSun) [87] | 9% | 65% | 26% | 211 °C (412 °F) [81] | Commercial food manufacturing | ||
Tea seed oil [89] | 22% | 60% | 18% | 0.7% | 22% | 252 °C (486 °F) | Cooking, salad dressings, stir frying, frying, margarine |
Tallow [90] | 43% | 50% | 4% | 1% | 3% | Cooking, shortening, pemmican, deep frying | |
Walnut oil (semi-refined) | 9% | 23% | 63% | 10% | 53% | 204 °C (399 °F) [91] | Salad dressings, added to cold dishes to enhance flavor |
[92] |
This section needs additional citations for verification .(July 2021) |
Cooking oil extraction and refinement are separate processes. Extraction first removes the oil, typically from a seed, nut or fruit. Refinement then alters the appearance, texture, taste, smell, or stability of the oil to meet buyer expectations.
There are three broad types of oil extraction:
In large-scale industrial oil extraction you will often see some combination of pressing, chemical extraction and/or centrifuging in order to extract the maximum amount of oil possible. [104]
Cooking oil can either be unrefined, or refined using one or more of the following refinement processes (in any combination): [105]
Filtering, a non-chemical process which screens out larger particles, could be considered a step in refinement, although it doesn't alter the state of the oil.
Most large-scale commercial cooking oil refinement will involve all of these steps in order to achieve a product that's uniform in taste, smell and appearance, and has a longer shelf life. [104] Cooking oil intended for the health food market will often be unrefined, which can result in a less stable product but minimizes exposure to high temperatures and chemical processing.
Proper disposal of used cooking oil is an important waste-management concern. Oil can congeal in pipes, causing sanitary sewer overflow. [108] Because of this, cooking oil should never be dumped in the kitchen sink or in the toilet bowl. The proper way to dispose of oil is to put it in a sealed non-recyclable container and discard it with regular garbage. [109] Placing the container of oil in the refrigerator to harden also makes disposal easier and less messy.
Cooking oil can be recycled. It can be used in animal feed, soap, make-up, clothes, rubber, detergents, directly as fuel, and to produce biodiesel. [110] [111] [112]
In the recycling industry, used cooking oil recovered from restaurants and food-processing industries (typically from deep fryers or griddles) is called yellow grease, recycled vegetable oil (RVO), used vegetable oil (UVO), or waste vegetable oil (WVO). [113]
Grease traps or interceptors collect fats and oils from kitchen sinks and floor drains. The result is called brown grease, and unlike yellow grease its severe contaminants make it much harder to recycle.
Gutter oil and trench oil are terms used in China to describe recycled oil processed to resemble virgin oil, but containing toxic contaminants and sold illegally for cooking; its origin is frequently brown grease from garbage. [114]
In Kenya, thieves sell stolen electric transformers to operators of roadside food stalls for reuse of the oil in deep frying, suitable for prolonged use longer than regular cooking oil, but a threat to consumer health due to the presence of PCBs and polycyclic aromatic hydrocarbons. [115]
In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.
α-Linolenic acid, also known as alpha-linolenic acid (ALA), is an n−3, or omega-3, essential fatty acid. ALA is found in many seeds and oils, including flaxseed, walnuts, chia, hemp, and many common vegetable oils.
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. 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 fruits. In common usage, vegetable oil may refer exclusively to vegetable fats which are liquid at room temperature. Vegetable oils are usually edible.
Margarine is a spread used for flavoring, baking, and cooking. It is most often used as a substitute for butter. Although originally made from animal fats, most margarine consumed today is made from vegetable oil. The spread was originally named oleomargarine from Latin for oleum and Greek margarite. The name was later shortened to margarine.
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 in warmer climates. 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.
A saturated fat is a type of fat in which the fatty acid chains have all single bonds. A fat known as a glyceride is made of two kinds of smaller molecules: a short glycerol backbone and fatty acids that each contain a long linear or branched chain of carbon (C) atoms. Along the chain, some carbon atoms are linked by single bonds (-C-C-) and others are linked by double bonds (-C=C-). A double bond along the carbon chain can react with a pair of hydrogen atoms to change into a single -C-C- bond, with each H atom now bonded to one of the two C atoms. Glyceride fats without any carbon chain double bonds are called saturated because they are "saturated with" hydrogen atoms, having no double bonds available to react with more hydrogen.
An unsaturated fat is a fat or fatty acid in which there is at least one double bond within the fatty acid chain. A fatty acid chain is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond.
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.
Grape seed oil is a vegetable oil derived from the seeds of grapes. A by-product of the winemaking industry, it is typically used for edible applications.
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. 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.
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 biochemistry and nutrition, a monounsaturated fat is a fat that contains a monounsaturated fatty acid (MUFA), a subclass of fatty acid characterized by having a double bond in the fatty acid chain with all of the remaining carbon atoms being single-bonded. By contrast, polyunsaturated fatty acids (PUFAs) have more than one double bond.
Peanut oil, also known as groundnut oil or arachis oil, is a vegetable oil derived from peanuts. The oil usually has a mild or neutral flavor but, if made with roasted peanuts, has a stronger peanut flavor and aroma. It is often used in American, Chinese, Indian, African and Southeast Asian cuisine, both for general cooking and in the case of roasted oil, for added flavor. Peanut oil has a high smoke point relative to many other cooking oils, so it is commonly used for frying foods.
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.
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. 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. The more FFA an oil contains, the quicker it will break down and start smoking. The lower the value of FFA, the higher the smoke point. 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.
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.
In biochemistry and nutrition, a polyunsaturated fat is a fat that contains a polyunsaturated fatty acid, which is a subclass of fatty acid characterized by a backbone with two or more carbon–carbon double bonds. Some polyunsaturated fatty acids are essentials. Polyunsaturated fatty acids are precursors to and are derived from polyunsaturated fats, which include drying oils.
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.
The smoke point of an oil depends primarily on its free fatty acid content (FFA) and molecular weight. Through repeated use, as in a deep fryer, the oil accumulates food residues or by-products of the cooking process, that lower its smoke point further. The values shown in the table must therefore be taken as approximate, and are not suitable for accurate or scientific use
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