Fats and cooking. There is a lot of different information out there about what the best fats and oils are for cooking with. Some fats are bad for us, but not the ones that mainstream media may have us believe. To understand fats, you need to know something about the chemistry of fats. Fats ( or lipids) are a class of organic substances. Simply put, fatty acids are chains of carbon atoms which have hydrogen atoms filling the available bonds. Most fat that is in our bodies and that we eat is in the form of triglycerides, which is three fatty acid chains attached to a glycerol molecule.It is true that elevated triglycerides in the blood have been positively linked to heart disease, but what is not commonly known is that these triglycerides do not come directly from dietary fats. They are actually made in the liver from any excess sugars that have not been used for energy. Foods containing carbohydrates, particularly refined sugar and white flour are the source of these triglycerides.
Fats are classed in 3 different ways according to their chemical structures. All fats and oils are some combination of saturated fatty acids, monounsaturated fatty acids and polyunsaturated linoleic acid.
1/ Saturated. A fatty acid is saturated when all available carbon bonds are occupied by a hydrogen atom. This makes saturated fats highly stable as there are no free carbon bonds for any other atoms to bond with. The hydrogen atoms keep saturated fats intact and also help protect it against oxidation and binding of free radicals.This means that they do not normally go rancid, even when heated for cooking.They are straight in form, hence packed together easily, which is why they are solid or semi solid at room temperature. Saturated fatty acids are mostly found in animal fats and tropical oils, your body also makes them from carbohydrates.
2/ Monounsaturated. Monounsaturated fatty acids have one double bond in the form of two carbon atoms double-bonded to each other and therefore lack two hydrogen atoms. Monounsaturated fats have a bend at the position of this double bond, so they do not pack together as well as saturated fats and are therefore liquid at room temperature. This double bond also makes them less stable than saturated fats as there is one (hence the term ‘mono’) free bond for other atoms to potentially bond with. They are still relatively stable and may still be heated but not to as high temperatures as saturated fats. Your body makes monounsaturated fats from saturated fats and uses them in many ways. The one most commonly found in our food is called oleic acid, the main component of olive oil and also found in oils from avocados, peanuts, almonds, cashews and pecans.
3/ Polyunsaturated. Polyunsaturated fatty acids have two or more pairs of double bonds and therefore lack four or more hydrogen atoms. These unpaired electrons at the double bonds makes these oils highly reactive and therefore unstable as there are many (hence the term ‘poly’) free bonds for other atoms to potentially bond with. For this reason they should never be heated or used in cooking as they become oxidized and rancid when subjected to heat, oxygen and moisture. Rancid oils are characterized by free radicals, which attack the unbound carbon bonds.These produce compounds which are extremely reactive chemically. They attack cell membranes and red blood cells causing damage that can trigger mutations in tissue, blood vessels and skin. This may lead to an array of problems ranging from wrinkles and premature ageing to tumors in organs and the build up of plaque in arteries. Some common oils which are composed primarily of polyunsaturated fatty acids are flax seed, sunflower, soybean, corn and safflower.
So, what are the best oils to cook with? Well, it depends on the temperature of the cooking and the composition of the different oils available. All fats and oils have a certain temperature that they may be heated to before oxidation occurs. Once oxidation occurs the chemical structure of the fat changes and it becomes rancid. This is not to be confused with the ‘smoke point’ of fats and oils. The smoke point is the temperature at which an oil or fat begins to burn and give off smoke and many people are led to believe that this is when the structure changes. It is the ratio of fatty acids of the oil that determines when the chemical structure changes though. For example coconut oil has a relatively low smoke point of approximately 170 degrees, but as it is over 80% saturated fatty acids it is safe from oxidation until approximately 220 degress. On the other end of the scale are all oils composed primarily of polyunsaturated fatty acids such as flax seed and safflower oil. These oils have a smoke point of approximately 107 degrees, but oxidation occurs as soon as any heat is applied.
When buying oils, always choose unrefined and cold pressed (preferably organic too!). This means that there is the least amount of processing involved. Many refined oils are marketed as having a higher smoke point. This may be true, but does not mean they are healthy to cook with. Many refined oils are treated, often involving bleaching, deodorizing and the use of toxic chemicals. This removes many of the healthy nutrients such as natural antioxidants, which then makes the oil more oxidatively sensitive. Oils such as grapeseed and rice bran which are promoted as healthy, high temperature cooking oils are already rancid by the time you buy them in the bottle.
Safflower, sunflower, corn, soybean and cottonseed oils all contain over 50 percent omega-6, a polyunsaturated oil. Research continues to accumulate on the dangers of excess omega-6 in the diet, whether rancid or not. So consumption of these oils should be strictly limited and they should never be consumed once they have been heated as in cooking, frying or baking. High oleic safflower and sunflower oils are available. They have a similar composition to olive oil, therefore a lower amount of polyunsaturates and thus are more stable than the traditional priorities. Only use these if you can find truly cold-pressed versions of these oils.
Canola oil is over 50% monounsaturated fatty acids and for this reason is often promoted as a healthy cooking oil. It was developed from the rape seed however, which is considered unsuited to human consumption as it contains erucic acid. Canola oil was bred to contain little if any erucic acid but it still presents dangers of its own. It has a high sulphur content and goes rancid easily. During the deodorizing phaze when canola oil is processed, the omega-3 acids are transformed into trans fatty acids, similar to those in margarine. These damaged trans fat molecules behave differently in the human body than natural fatty acids; they are taxing on the liver and prevent the body from absorbing good fat.
So as far as cooking goes, the best fats and oils to use are ones that are high in saturated fat. For high heat cooking, the best fats to use are; coconut oil, lard, duck fat, palm oil and ghee. These may all be heated up to approximately 220 degrees celsius and are therefore great for all types of cooking; baking, frying, stewing etc.
Fats and oils which have high levels of monounsaturated fats such as olive, avocado, macadamia, peanut, sesame and butter may be used for lower temperature cooking such as frying or sautéing, or low temperature baking in the oven. They should not be heated over 160 degrees celsius.
Polyunsaturated fats should not be heated at all. Flax seed is the most health beneficial and should be kept in the refridgerator and used raw, in small amounts.