Cooking with Vegetable Oils
I’m frequently hearing of another vegetable oil with superior properties to canola oil, olive oil, or whatever. So, what is the best vegetable oil, how much better is one cooking oil than another, and which properties are important?
Vegetable oil is defined as oil extracted from plants that are liquid at room temperature, however, for this article I’ll include both liquids and semi solids. These oils are extracted from seeds, fruits, or nuts.
The properties that affect cooking and health are flavor, percentages of different types of fats, smoke point, and shelf life. Cooking technique, such as deep frying, stir frying or baking, is another important consideration when choosing cooking oil. Vegetable oils have many properties and can be used in a variety of cooking methods so there isn’t a single oil for everything.
Oil Extraction and Processing
There are a variety of methods to separate the oil from the seeds, nuts, or fruit. The oldest method is to simply squeeze or press the ground material, generally without the addition of heat. This is referred to as “cold-pressed”. Countries and industry groups have laws and regulations covering processing and labeling. An example; for olive oil there is a maximum allowable temperature (less than 86°F, 30°C) during pressing in order to be labeled “extra virgin”.
A common cold-press nomenclature is expeller pressed. This uses a mechanical screw to compress and move the material. The process does create heat which must be monitored to maintain a sufficiently low temperature. Cold pressing removes the oil and the natural flavors, without altering taste or chemistry.
It may seem ideal to always use cold pressing for extraction but some oils can’t be removed using this process or for cost reasons the producer may choose to use higher temperatures or solvents. Adding heat can increase the yield and may also have negative effects on flavor.
Flavor can be either neutral, meaning the oil imparts very little flavor to the dish being prepared, or it may range from mild to strong. Some oils such as walnut oil or hazelnut oil have a nutty flavor. This can be enhanced by carefully roasting the seeds or nuts prior to extracting the oil.
One of the most popular oils, olive oil, may have a strong, mild, or no flavor depending on the extraction process, the source, or type of olives. Sesame seed oil is a good example of oil that has a very strong flavor from roasted (or toasted) seeds and a very mild flavor from the cold-pressed variety.
The smoke point is the temperature that oil begins to smoke when heated. At this temperature the oil begins to break down and the flavor and chemical properties change so, you’ll want to keep the cooking temperature below the smoke point. There is also greater danger of fire even though the smoke point is well below the flash point. Oils with a higher smoke point are better for frying, sautéing, and stir frying. Deep frying occurs above 325°F (163°C) so choose oil with a smoke point at least 20°F above the frying temperature. Oils with low smoke points should not be used for frying or sautéing and are best used for dressings, marinades, or baking. This often works well as many of the more flavorful oils have lower smoke points. Flavorful oils can be used on food, such as vegetables or starches, after they have been cooked.
The smoke point is not a precise number; it is dependent upon the degree of refinement, the variety of seed used, and upon the percentages of the various fats in the oil. It can also change depending upon how hot and for how long the oil has been previously heated. Oil that has already been used for frying may have a lower smoke point than oil that hasn’t been previously used. There are recommendations on the number of times frying oils can be reused but they are difficult to find.
I’ve divided the cooking techniques for oils into four groups. They are frying, stir-frying, baking, and dressings. For each usage the smoke point and flavor should be considerations for your choice of oil. Most vegetable oils are liquids at room temperature, but a few are a semi solid (like vegetable shortening) which also enters into your choice. Using a semi solid such as coconut oil for a dressing or marinade wouldn’t be a good usage choice, even if it did impart a desired flavor.
Baking provides the greatest latitude in the choice of cooking oil. Smoke point shouldn’t be an issue since for all commonly used cooking oils; it is above the boiling point of water and below any temperature that a baked good would reach.
Flavor desired is often neutral but additional flavor may be desired – the choice is yours. Replacing a neutral flavored vegetable oil, in a desert such as cookies, with hazelnut or coconut oil may make your version stand out from others.
Some baked dishes require a semi solid such as, butter, shortening, or lard. To make vegetarian versions, remove cholesterol, or to change the fat profile a semi solid vegetable oil such as palm oil may be substituted.
Roasting is similar to baking because the main ingredient will not reach a very high temperature.
Baking pie crusts is a special baking case. This is due to the complex interaction between the flour and the shortening. For this reason substitution of butter or shortening may have unpredictable results.
This cooking technique refers to deep frying or immersion frying where the food is completely submerged in the oil. Pan frying is similar to deep frying but the food is only partially submerged and the considerations are the same as those for deep frying.
The primary property to consider when choosing an oil for deep frying is the smoke point. Other considerations include cost, health, and flavor. Deep frying is generally done between 345°F and 375°F (174°C and 191°C). Oils chosen should have a smoke point at least 20°F higher than the frying temperature. Commercial frying may use oils that are solids at room temperature. These have high smoke points, greater reusability and are higher in saturated fats.
Deep frying doesn’t impart significant oil to the food when done properly. Proper preparation includes correct temperature, not over-crowding, and not over cooking. While the oil shouldn’t impart flavor to the ingredients if the oil has been previously used flavors may be infused.
Many traditional foods are deep fried. In the American south fried chicken or catfish are commonly prepared. French fries are found internationally while dishes such as tempura are traditionally Japanese. Sweets such as donuts and beignets are deep fried.
Safety is a huge concern when deep frying. You should be aware of the dangers and be prepared to safely extinguish an oil fire. Never use water to attempt to extinguish an oil fire. It will cause the fire to expand with near explosive force.
Stir frying is cooking in a pan, usually a wok, over a high heat with a small amount of oil. It is a healthy and flavorful way to prepare foods. Traditionally an Asian technique stir frying can also be used to prepare fresh vegetables.
Oils used for stir frying must have a high smoke point and may be either flavored, neutral, or a mixture of both.
For stir frying and similar cooking techniques always heat the pan first then add oil. As soon as the oil reaches the desired temperature begin cooking. Oils begin to break down when heated and flavor will begin to degrade if oil remains in a hot pan.
Sautéing and Searing
Sautéing is very similar to stir frying but it uses a lower heat and even less oil. It is most often used in the preparation of foods that have been thinly sliced such a cutlet. The purpose is to brown and heat the food.
This group includes salad dressings, marinades, emulsions such a mayonnaise, and dipping sauces.
The purpose of this group is to flavor the food rather than cook it; therefor smoke point is not a consideration. Marinades for foods that will eventually be cooked may use oils with a low smoke point. This is because the marinade will be absorbed by the food. A different oil with a high smoke point can then be used for cooking. This is often done when preparing meats. Flavorful oils, such as extra virgin olive oil, may be used in marinades and then the meat would be roasted. Another example would be the use of roasted sesame seed oil in a marinade and then stir frying in a wok with a neutral flavored oil.
Oils are composed of many types of fatty acids. These fatty acids are divided into three groups for listing on food labels. The three that you will see on vegetable oils in the US are saturated fats, monounsaturated fats, and polyunsaturated fats.
The fatty acid profile can have an effect on your health. You should research this to determine which to use in your diet. Information given here is to inform that there are risks and considerations. For information on how to mitigate those risks consult health professionals.
Vegetables and vegetable oils do not contain cholesterol. Some labels may state “cholesterol-free”; this is just marketing since none contain cholesterol.
Trans fats are not naturally occurring in vegetables. In vegetable oils they are a product of partial hydrogenation. The important point is that unprocessed vegetable oils will not contain trans fats.
Saturated Fatty Acids
Saturated fatty acids occur naturally and oils with higher amounts of saturated fats generally have a higher melting points and longer shelf life. Saturated fats are considered unhealthy compared to unsaturated fats. Since it would be very difficult to eliminated saturated fats from your diet you should try to limit their intake.
Also consider the net effect, replacing an animal sourced cooking oil that contains cholesterol and trans fats with one that has a higher portion of saturated fat, than say olive oil, may still yield a net benefit.
Monounsaturated Fatty Acids
Recommendations from many sources, including the CDC, state that most of the fats eaten should come from unsaturated fats. Monounsaturated fats tend to reduce LDL cholesterol levels. they are primarily composed of omega-9 oleic acid.
Monounsaturated fatty acids have a higher melting point than polyunsaturated and lower than saturated.
Polyunsaturated Fatty Acids
Polyunsaturated fats are composed primarily of Omega-3, and Omega-6 fatty acids with traces of Omega-9. They are healthier than saturated fats, but their intake should still be a limited portion of your diet.
Omega-3 fatty acids are a part of human cell membranes and the body can’t make them. So, some Omega-3 fatty acids must come from food. Sources for Omega-3 include vegetable oils, nuts, fish, and leafy vegetables.
Omega-6 fatty acids are also an essential fatty acid. This means that the body requires them but can’t make them. They are found in many seeds, nuts, and eggs. Linoleic acid is the most common Omega-6 fatty acid.
There are many health claims and research on the ratio of Omega-6 to Omega-3 fatty acids. Most recommendations seem to be in the range of 1:1 to 10:1. There are many variables and various health effects. The purpose here is to inform you that this may be important, not to recommend a particular ratio.
Trans fats may be either monounsaturated or polyunsaturated. They are formed when natural fatty acids are hydrogenated. That means they don’t occur naturally. Some brands of shortening contain trans fats, so check the label. If the label includes any “partially hydrogenated” or “hydrogenated” oil then the product contains trans fats. Trans fats are linked to coronary and heart disease. For this reason most dietary and medical sources recommend avoiding trans fats.
In America products labeled “zero trans fats” can have up to 0.5 grams of trans fat per serving. Check the percentages on the ingredients label to determine if there are none. If the label has any “hydrogenated” or “partially hydrogenated” oil then zero isn’t zero.
Vegetable oils may keep anywhere from a few months to several years. Dates given here are based on recommendations from producers. The best judge is you. Oils will have a rancid smell when bad. Some oils such as flaxseed (linseed) oil and walnut oil are drying oils and have shelf lives of just a few months after opening. Shelf life statements from manufacturers may include both opened and unopened times or an expiration date.
Oils that are higher in saturated fats have longer shelf lives. The amount of refinement will also affect shelf life with refined oils having a longer shelf life than unrefined.
To increase the shelf life of vegetable oils they can be stored in a cool dark place or refrigerated. Oils can also be placed in the freezer. This may make them solidify or become cloudy but this will go away after they are warmed. Keeping excess air from the oil is also advantageous. If available you can purge with nitrogen to extend life.
Vegetable Oil Properties
|Vegetable Oil||Type||Smoke Point||Fatty Acids||Cooking Technique|
|(°C)||(°F)||Saturated||Monoun- saturated||Polyun-saturated||Bake||Stir Fry||Fry||Sauté||Dressing|
|Coconut||Refined||232||450||92%||6%||2 – 3%||✔||✔||No|
|Macadamia||Unrefined||210||410||13%||84%||2 – 4%||✔||✔|
|Sunflower||High Stearic, High Oleic||232||450||24%||69-71%||5%||✔||✔||No|
|Sunflower||High Oleic||227||440||9%||84%||2 – 9%||✔|
Note: All values are typical and derived from a variety of sources including product web sites, labels, and research papers. “✔” means that this is a recommended usage, blank is neutral, and “No” means that it is not recommended.
Almond oil extracted from sweet almonds Prunus Amygdalus Dulcis is the species used for cooking. It is a very good choice for cooking because it has high smoke point, low percentage of saturated fats, and a high percentage of monounsaturated fats. Note that there is a bitter almond oil Prunus amara which is poisonous.
Two versions are available; cold-pressed and refined. Cold pressed has a light color and a mild nutty almond taste. Cold-pressed almond oil is best used for flavor and not for any method that requires high heat. There are also roasted versions of cold-pressed almond oil. Good uses would include baking or in dressings. To add an almond flavor to any recipe a portion of the original oil can be replaced with almond oil. Refined almond oil is almost clear and has little taste. It also has a higher smoke point.
Both cold-pressed and refined almond oil have smoke points sufficiently high for frying but the refined version would be preferred because heat ruins the flavors of the cold-pressed variety.
Avocado oil is extracted from the partially dried flesh, not the seed, of several cultivars of avocados. The most common oil comes from the Hass variety but Fuerte is also used. Oil is extracted mechanically. Avocado oil has the highest smoke point of any vegetable oil used for cooking. This makes it superb for high temperature frying. As with any vegetable oil the refined variety has a higher smoke point. Refined and unrefined varieties are available.
The fatty acid profile is one of the lowest in saturated fats and highest in monounsaturated fats. Only macadamia nut oil exceeds avocado oil in these percentages.
Unrefined versions have a deep green color and a mild to medium avocado flavor while the refined avocado oil has little flavor. The green color is mainly from chlorophyll. The avocado flavor can go well in salad dressings. In many cases it can be used in place of olive oil.
Canola oil is extracted from a cultivar of rapeseed, a member of the Brassicaceae family. The extraction process first begins by crushing the seeds and then pressing them while heating. Further processing using heated water, filtering, and crushing is performed. It is then degummed and filtered. Rapeseed contains a toxin erucic acid. This is reduced in canola oil by genetic selection of the seeds and may also be removed chemically using an alkali.
There are three types of canola oil available cold pressed, high oleic, and refined. Cold pressed oil has a good balance of properties. It is low in saturated fats and has a 275°F smoke point. Refined canola oil has a 400°F smoke point with a fatty acid profile the same as cold pressed. The high oleic acid version was developed to replace oils with trans fats in food that require a long shelf life. It is higher in monounsaturated fatty acids and has a smoke point of 375°F.
The neutral taste, fatty acid profile, and high smoke point make canola oil a good choice for general cooking.
Coconut oil is extracted from the coconut pulp by a variety of processes that can be divided into wet or dry processes. Both yield a thick oil that can be used in place of shortening.
Refining coconut oil removes bacteria and other impurities. It is then bleached and deodorized. Refined coconut oil has a neutral flavor. Some refined coconut oils are hydrogenated which removes some healthy benefits. Refined coconut oil has a longer shelf life than unrefined. The smoke point is 450°F.
Coconut oil is a solid below 70°F and a liquid above 76°F. It is high in saturated fats resulting in stable oil with long self-life. Although high in saturated fats it may still be used without adverse heath effects. This is true for coconut oils that haven’t been hydrogenated. The main saturated fat in coconut oil is lauric acid, which has been shown to increase both LDL and HDL. Although this may not be the healthiest vegetable oil, when used in moderation or to replace an animal fat it can be a good choice.
Extra virgin coconut oil has a definite coconut flavor. Use this variety in baking deserts and in curries. Some of this flavor will dissipate during baking.
The oil’s property of being a liquid or a solid near room temperature can be creatively used. For example use it in place of butter to make whipped frosting or add to melted chocolate to make it harden on ice cream or any frozen fruit. Another flavorful possibility is to make a coconut powder for topping a desert.
Most corn oil is extracted from corn germ using the expeller process followed by solvent extraction. Further processing may include degumming and an alkali treatment. There may also be steps to remove odors and waxes.
Corn oil that is produced using only the expeller process is also available.
This is a good general purpose oil, but better choices are available.
Cotton Seed Oil
Cotton seed oil is higher in saturated fats than other liquid vegetable oils. This gives it a longer shelf life making it a good choice for food when the manufacturer desires longer storage. In food processing it is used to make mayonnaise, salad dressing, and to fry potato chips. It has a high ratio of polyunsaturated fat to monounsaturated fat which is claimed to be less healthy than a balanced ratio. Cotton seed oil may be partially hydrogenated adding to the health concerns.
Cotton seed oil has a light golden color and refined versions have very little taste. This oil isn’t normally used in home cooking.
A light green oil with a very light nutty flavor. its moderately high smoke point makes it suitable for frying or sautéing. It is low in saturated fats but the monounsaturated fats are low compared to the polyunsaturated.
This oil is extracted from grape seeds after they have been pressed for wine making.
Hazelnut oil is extracted by crushing and then roasting hazelnuts in large cast-iron pans then pressed. It may then be filtered.
It is a strongly flavored oil
useful for adding flavor to pasta, dressings, or cooked vegetables. If you are substituting this oil for another you may want to replace only a portion to get the desired taste.
Macadamia Nut Oil
A light oil with the slightly nutty macadamia nut flavor. It has an very good fat profile low in saturated fats and high in monounsaturated fats.
The combination of good fatty acid profile and a smoke point of 410°F make this oil useful for any cooking use. But its flavor is best used for dressing and stir-frying.
Mustard Seed Oil
An oil made by pressing any of three species (white, brown, or black) of mustard seeds. It has a pungent flavor. Commonly used for cooking in parts of India, Nepal, and other countries in the region.
The most widely used vegetable oil. It is available in at least four varieties; extra virgin, virgin, pure, and extra light. The top grades are defined by the method of extraction and the oleic acid content. Oils with lower acid content are of higher quality.
Extra virgin olive oil is produced by cold pressing olives. There are several requirements that must be met to qualify as extra virgin. Some of these are; pressed at temperatures below 86°F (30°C), oleic acid less than 0.8%, a clean olive flavor, and pass a chemical analysis. Flavor can vary greatly depending on the type of olives, the orchard they are sourced from, and handling. Extra virgin olive oil must have the country (or countries) of origin on the label.
Virgin olive oil is similar to extra virgin olive oil but with a higher acid content. Oleic acid must be less than 1.5%.
Olive oil without any other designation is generally of lower quality and has a higher acid content than virgin olive oil. For this designation acid must be below 2%.
Refined or a blend of refined and virgin olive oil is often labeled “pure”. It is generally odorless, colorless, and tasteless. The refining process usually involves filtering and must not alter the glyceridic (oil and fat) structure.
Extra light olive oil is a highly refined olive oil that is light in flavor, not calories. This variety of olive oil has a higher smoke point than others making it good for sautéing and stir-frying. Due to the refining process there is little nutrition left in refined or extra light olive oil. This variety of olive oil isn’t regulated so check the back label carefully to see if it is 100% olive oil.
Oil extracted from the fruit of the African oil palm (Elaeis guineensis) yields a highly saturated vegetable oil that is semi-solid at room temperature. The oil is extracted from the red mesocarp (the fleshy part of the fruit) resulting in a reddish colored oil. Palm oil is a solid at room temperature.
Palm oil and palm kernel oil are not the same. Palm oil comes from the palm fruit and palm kernel oil comes from the seed. Palm oil is 50% saturated fatty acids and palm kernel oil is over 80%.
Although it doesn’t contain cholesterol (like all vegetable oils) it is high (41 to 52%) in saturated fats. Palm oil is not a healthy substitute for oils with trans fats.
Palm oil may have been harvested from areas where natural vegetation was destroyed. Check country of origin and manufacturer’s web sites to avoid purchasing oil that leads to deforestation.
Refined peanut oil has a mild flavor while the roasted variety has a distinct peanut flavor. It doesn’t absorb the flavors of food fried in it so it can be used for multiple foods. Its high smoke point makes it well suited for frying.
Refined peanut oil has been bleached and deodorized. This process removes the allergic protein component of the oil, making it non-allergenic. Refined peanut oil is the main type of oil utilized in major US fast-food chains.
Pumpkin Seed Oil
Pumpkin seed oil is made from roasted pumpkin seeds. It has a light to dark green or dark red color. It has an intense nutty flavor.
This oil is traditionally used in parts of Austria, Slovenia, Croatia and other countries in the region. It is used in dressings and deserts. It shouldn’t be used for cooking because heating destroys the flavor.
Rice Bran Oil
A mild flavored vegetable oil extracted from rice bran and the kernel. This oil is popular in Japan and in some parts of China. Its high smoke point makes it suitable for frying.
It has equal parts monounsaturated and polyunsaturated fats but 55% more saturated fat than olive oil.
The moderate level of saturated fat and no hydrogenation results in a stable oil with good fry life. This makes rice bran oil a popular choice for frying tempura in America. In Japan tempura is fried in a blend of oils, with each restaurant closely guarding its recipe.
There are two types of safflower oil but only the high oleic variety is used in foods and cooking. It is a light, colorless, odorless oil.
Its neutral flavor, good fatty acid profile, and high smoke point make safflower oil a good general purpose oil.
Cold pressed and black sesame oils
Sesame oil is available in several variations including unrefined, partially refined, black, and roasted.
Cold pressed sesame oil is a light yellow color and has a mild sesame taste. It may be refined or partially refined.
Sesame seed oil is also made from black sesame seeds and their hulls. Unroasted the color is darker than sesame seed oil and roasted it may be almost black. It has a stronger flavor than oil from the white seeds.
Roasted sesame oil is often used in Asian cooking because of its very strong nutty flavor. It has a dark brown color with a lower smoke point than other sesame seed oils.
Soybean oil is extracted by crushing soybeans and using hexane as a solvent.
Some soybean oils are hydrogenated. Soybean oil is a drying oil which limits the shelf life.
A very light neutrally flavored oil with a high smoke point making it suitable for frying. There are at least four varieties available. Each variety is a result of breeding to optimize a desired fatty acid profile.
High linoleic sunflower oil is the original type of sunflower oil. It is susceptible to oxidation, making it less desirable for frying.
Mid Oleic sunflower oil is a stable variety that is produced without hydrogen stabilization. It is low in saturated fats with a neutral taste.
High Stearic, High Oleic sunflower oil was developed by breeding to obtain a very stable oil that is relatively low in saturated fats (for a solid), no trans fat and a solid at room temperature. It is a solid at 39°F (4°C) temperature. It is marketed under the Nutrisun brand.
High oleic sunflower oil is higher in monounsaturated (oleic) fats. It has a neutral taste and longer shelf life than other sunflower oil varieties.
Tea Seed Oil
Tea seed oil also known as Camellia is a light amber oil with a sweet herbal aroma. Some varieties have a nutty or olive flavor. It has a high smoke point making it useful for stir frying. It is widely used for cooking in Southern China.
It has a long shelf life.
Walnut oil comes from the Persian walnut Juglans regia which is now often called the English walnut. Much of the walnut oil comes from France but there are several California suppliers as well. It is light colored and light flavored.
There roasted and unroasted varieties with roasted having a more pronounced walnut flavor. Both varieties are best used for flavor in dressings and marinades rather than frying or baking because it loses flavor and nutrition when heated.
Walnut oil is a drying oil and has a limited shelf life of about 6 months after opening. However with refrigeration it may last much longer.