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Guide to cooking oils

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When it comes to cooking oils, we are spoiled for choice these days. But which oil is the best option to use in specific situations? Nutritionist Vanessa Furlong investigates.

Cooking oils are one of the most frequently used items in the kitchen — from dressing salads to roasting, and almost everything in between. Not all oils, however, are suited to all uses.

Understanding the properties and composition of cooking oils will help you make the best choice for your dish — and for your health.

Nutritional composition

Oils are liquid fat derived from plants, nuts or seeds. All oils have similar energy content (roughly 3500kJ per 100ml, or about 520kJ per tablespoon), but oils can differ markedly in both the type of fats and the ratio of different fats they contain. It is this difference which makes some oils healthier than others.

Polyunsaturated and monounsaturated fats are often called ‘heart healthy’ because they lower total and LDL (‘bad’) cholesterol, whereas saturated fats increase total and LDL cholesterol.

Monounsaturated fats, which feature heavily in the Mediterranean diet, also increase HDL (‘good’) cholesterol.

Oils are a good source of antioxidants such as the carotenoids beta-carotene and lutein, vitamin E and a range of polyphenols. Antioxidants have been shown to slow the ageing process and reduce the risk of heart disease and some cancers.

Being an energy-dense food, oils should be used sparingly, even if they are the healthy kind. In an average 8700kJ day, it is recommended we have no more than 80g fat and 23g saturated fat. One tablespoon (15ml) of oil contains 13-14g total fat — around 16 per cent of the upper daily amount (the saturated fat content will vary depending on the type of oil). When cooking, 1-2 tablespoons of any type of oil at the most is usually enough.

Smoke point

The term ‘smoke point’ refers to the temperature at which oil starts to degrade. It is directly proportional to the amount of free fatty acids or acidity in the oil. At a certain temperature the free fatty acids become volatile and ‘smoke’, which affects both the quality of the oil and the flavour of the dish you’re cooking. The smoke point is determined both by the natural composition of the oil, and how the oil has been processed, and can vary between different brands of the same type of oil. For example, a poor quality olive oil with high acidity has a low smoke point, but a fresh New Zealand olive oil with low acidity has a high smoke point.

Oils with a low smoke point are best suited to little or no heat (making them good for salad dressings and dips). Oils with a high smoke point are well suited to high heat but can also be used for oven-cooked foods or in sauces, dips and dressings.

Which oil for…

Stir-frying and sautéing

Sunflower, canola and vegetable oil blends (canola and soybean oil) are good choices for sautéing and stir-frying food. They contain healthy fats, have a mild flavour and are not prohibitively expensive. Keep in mind that some oils are higher in saturated fat so be sure to read the label. Other good choices for high heat cooking include sesame oil, peanut oil, avocado oil and rice bran oil.

Grilling, baking and roasting

Olive oil is well suited to oven-cooking or barbecuing foods. Coconut and palm oils are widely used in commercially baked goods but best avoided because of their high saturated fat content. When lining baking tins, choose a vegetable oil rather than butter, and apply sparingly. If you are trying to cut back on your energy intake, use an oil spray which gives a fine mist of oil so you use less.

Adding flavour to salad dressings, marinades, sauces and dips

Some oils are very unstable and will deteriorate rapidly when exposed to heat. These types of oils tend to be derived from nuts and seeds and are best used as an ingredient in cold dishes.

Extra-virgin olive oil, flaxseed and walnut oils work well in dressings, sauces and dips.

Some of the most commonly used cooking oils

Avocado oil is produced from avocado pulp and is rich in monounsaturated fat and vitamins A, D and E. It has a mild flavour and can be used to sauté meat, fish or chicken or used in salad dressings.

Rice bran oil is extracted from the germ of rice grains. It is widely used in deep-fried Asian dishes. It has a higher saturated fat content compared with most other oils but is also rich in vitamin E, monounsaturated and polyunsaturated fats.

Vegetable oil is usually a blend of canola and soybean oils, which are well suited to high temperature cooking. Palm oil is sometimes used in vegetable oil blends but this is best avoided as it is almost 50 per cent saturated fat. It is not always possible to tell from the label if palm oil is included but check the nutrition: choose vegetable oil blends with 20g saturated fat or less per 100g.

Canola oil comes from the rapeseed plant, which is a member of the mustard family. It is high in monounsaturated fat and has one of the lowest saturated fat contents of all oils. It contains heart-friendly omega-3s and is suitable for both low and high heat cooking. Canola oil is also widely used to make dressings such as mayonnaise.

Light olive oil comes from the second pressing of the olives and is milder than extra-virgin olive oil. While many people mistake ‘light’ olive oil for being lower in fat, in this instance the word refers to its lighter colour and mild flavour. Light and extra-virgin olive oil have the same energy content. It is more refined than other olive oils and it is suitable for cooking at higher temperatures.

Peanut oil is well suited to stir-frying. It is moderately high in monounsaturated fat and does not absorb or transfer flavours during the cooking process. If you plan to cook with peanut oil, be sure that nobody has a peanut allergy.

Sunflower oil is rich in vitamin E, low in saturated fat, has little or no flavour and can be used in most types of cooking.

Sesame oil has a rich, nutty taste and is well suited to high heat dishes as well as cold Asian-style salads.

Grapeseed oil can be used in both high heat and cold dishes. It is rich in heart-healthy poly-unsaturated fats.

Macadamia oil has a strong, nutty flavour and is suited to both high heat cooking and as an ingredient in salad dressings. It is also very high in healthy monounsaturated fats.

Extra-virgin olive oil comes from the first pressing of the olives and contains primarily heart-healthy monounsaturated fats. It is best suited to dressings, marinades, sauces and low heat cooking. It is green in colour and usually has a strong, pleasant flavour.

Coconut oil Pressed from coconuts, this oil is almost 90 per cent saturated fat, so it is best to avoid.

Walnut oil is best for cold dishes such as dressings, sauces and dips, and has a rich, nutty flavour and contains one of the lowest saturated fat contents of all oils.

Flaxseed/linseed oil is loaded with heart-healthy omega-3s. Be sure to store it away from light. It is best suited for cold dishes and dressings.