Cooking without the use of oil is virtually impossible, but when edible oils are available in such wide varieties, each will have their own nutritional boons and disadvantages as well as practical uses. Picking the right oil might seem like an intimidating and expensive exercise to most, so we’ve endeavoured to make things simple by explaining some of the key properties in the most commonly used types of oil for cooking and dressing food.
All edible oils are sensitive to heat, oxygen exposure and light, and should be stored in a cool dry place when not in use. When we talk about the nutritional value of oils we are largely talking about two factors – their health benefits (or drawbacks) and their smoking point, the temperature at which the oil breaks down into free fatty acids and glycerol.
Oil and Health
The health benefits of different oils can vary depending on the brand and how they are made, but some oils are simply better than others. Oils with monounsaturated fats lower cholesterol in the body, especially the “bad” LDL cholesterol, while increasing the good HDL cholesterol, while those with polyunsaturated fats lower cholesterol as well as providing the body with much-need Omega 3 fatty acids. As a general rule, it is best to stay away from oils that are labelled as “hydrogenated” or “partially hydrogenated”, as they contain very high levels of trans-fats.
Bad oils on the other hand will contain high levels of saturated fats, which raise all the bad types of cholesterol, or trans-fats which raise LDL cholesterol while reducing the amount of HDL cholesterol. This means that nutritionally positive cooking oil will have high levels of monounsaturated or polyunsaturated fats while having little to no saturated or trans fats; olive oil is particularly fantastic for its monounsaturated fats, as are corn, safflower, soy, canola and sunflower oils. As a general rule, a tablespoon of most oils contains around 120 calories and 14 grams of fat – however, this doesn’t have to be bad fat.
Another major factor in the use of cooking oils is in their smoke point, which is connected to their nutritional value. As the level of free fatty acid decreases within the oil, the smoke point becomes higher – meaning that lighter, healthier and more refined oils have a much higher smoke point than their unrefined counterparts. This can also be affected by the product which is being cooked in oil, whether salt is used in the recipe and how the oil is stored.
For cooking at low temperatures such as baking or pan-frying over a low heat, unrefined fats and oils are the best for the job. Flaxseed oil smokes at the very low temperature of 225 degrees Fahrenheit, while unrefined walnut and olive oil begin to smoke at 320, and butter or lard at around 350. If using the oven, the temperature will affect which oil or fat is the best to use. If you only have one low-heat oil it should probably be a good olive oil, which can be used for salad dressing and gentle frying alike and is high in monounsaturated fat.
High temperature cooking such as grilling and deep frying must be done with oil which has a high smoke point – often refined oils. Peanut oil has a smoke point of over 400 Fahrenheit, palm oil at 450 and soybean oil at an impressive 495F, which is even higher than that for ghee (clarified butter). These can withstand the most heat and having direct contact with flames, but in terms of flavour they can vary quite wildly, and while some will impart their flavour to the food others will not.
Between these two categories of oil are the “all-purpose” oils which have a medium smoking point and can be used just as well cold for salads as for frying. These include vegetable, sunflower and grapeseed oil which all have a smoke point of around 400 degrees Fahrenheit.
Why is the smoke point so important?
You may think that a little smoke is no big deal – especially if you have fire safety equipment on hand – but breaking down the oil can decrease its nutritional value quite drastically. When it begins to smoke, it is being broken down into fatty acids and glycerol; if it continues to smoke at this temperature a bitter-smelling chemical named acrolein is released. Acrolein is responsible for the sensation of stinging eyes, and can be quite toxic, as well as ruining your food by eradicating flavour and nutrition.
But be aware – while general indications of smoking point temperature can be followed, the quality of the oil and how it was processed may change the results quite drastically.
If your head is spinning from the different types of fat and temperatures, here are some of the most commonly found cooking oils and what they are particularly good for.
Nut Oils – best used in cold cooking such as salad dressings, as the distinctive flavours can be ruined by heat, nut oils have a great source of both Omega-3 and vitamin E. Experiment with a few different flavours – walnut, almond and macadamia are particularly popular.
Canola Oil – one of the lowest in saturated fat, it is full of monounsaturated fat, omega-3 fatty acids, vitamin A and vitamin E. It doesn’t have a strong flavour so can be used for cooking, baking, and pan-frying over a low heat.
Peanut Oil – also known as groundnut oil, it has a substantial flavour and a high smoke point, making it perfect for a variety of cooking styles. While it is high in polyunsaturated fat it falls behind things like olive oil in terms of monounsaturated fats.
Olive Oil – great for monounsaturated fats and antioxidants, olive oils can be quite different depending on the type of olive used and the method of processing. Extra-virgin olive oil is the most highly refined and very expensive so is best kept for enjoying cold with salads or bread.
Vegetable Oil – this is usually a hybrid of oils, most commonly canola and soybean. It has comparatively high levels of unsaturated fat, but tends to be much cheaper and has quite a high smoke point. The two worst varieties of vegetable oil are palm and coconut oil, which have 50% and 90% fat respectively.
Choosing the right oil for your meal can mean the difference between a culinary masterpiece and a burning, toxic mess of little nutritional value. While there’s no need to have a dozen types of oil in the cupboard, having three with varied smoke points and applications can enhance your cooking more than you realised. Why settle for substandard food when a change in oil could make all the difference?