Guide to cooking oils
HFG senior nutritionist Rose Carr has a look at the oil shelf to see what’s new.
Oils are liquid fat derived from plants, nuts or seeds. Canola and olive oils seem to be the most abundant on our shelves but we can also buy oils of sesame, peanut, rice bran, sunflower, safflower, walnut, avocado, macadamia, grapeseed as well as less specifically-named products such as vegetable oil or salad and cooking oil. Oil is liquid, so coconut oil and palm oil, although usually described as oils, are more accurately described as fats since they’re solid below about 21 degrees Celsius.
Oils differ in both the type of fats they contain and the ratio of those fats. Polyunsaturated and monounsaturated fats are often referred to as ‘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. Just like other types of fat, all oils are high in kilojoules and have around 500-550kJ in one tablespoon. It’s generally easier to use small portions with liquid oils than with solid fats.
How are they produced?
Most of our cooking oils are refined oils. During refining, the oil most commonly undergoes solvent extraction first then it’s bleached and the final stage is deodorisation. Each of these steps reduces the flavour, odour and colour of the original oil. This processing also makes the oil more stable, meaning it won’t oxidise as quickly as unrefined oils which more readily go rancid with exposure to light, air or heat. Overall, refined oils tend to have less flavour and a higher smoke point (see In the kitchen, below), as well as being cheaper.
Unrefined oils, often referred to as virgin or extra-virgin oils, use mechanical rather than chemical extraction methods. The oil is usually extracted from a pulp by pressure or in a centrifuge. This processing retains most of the flavours and colour of the oil.
While refined oils are more stable, the quality of all oils will deteriorate over time with exposure to light, heat and air. The end result of this is rancid oil which smells and tastes off. Oils are best stored in a cool dark place and where possible choose oil in a dark glass bottle which helps protect it.
In the kitchen
The smoke point is the temperature at which oil starts to break down and smoke. This affects the nutrition and flavour of the oil and your dish. Using oils at temperatures higher than their smoke point damages the antioxidants and the structure of the beneficial fats. Refining an oil increases its smoke point, so a refined olive oil or coconut oil will have a higher smoke point than its unrefined or virgin counterpart.
As a general rule of thumb for seed oils, the lighter the colour of the oil the higher the smoke point. When choosing which oil to use we need to consider their suitability for the task at hand.
High-heat cooking: Stir-frying and sautéing
Canola and rice bran oils are good choices for sautéing and stir-frying food. They contain healthy fats, have a mild flavour and are not expensive. Sesame and peanut oils, which add their distinctive flavours, are also good choices for high-heat cooking.
Low-medium heat cooking: Grilling, baking and roasting
Olive oil and vegetable oil sprays are well suited to oven-cooking or barbecuing foods. Virgin coconut oil, palm oil and butter also fall into the low-medium heat category but are best kept to a minimum 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.
No cooking: Salad dressings, marinades, sauces and dips
Oils with a low smoke point tend to have a rich flavour and are best suited to little or no heat, making them good for salad dressings and dips. Extra-virgin olive oil, avocado, flaxseed and walnut oils are flavoursome ingredients in dressings, sauces and dips.
Olive oil by many names
Extra-virgin olive oil is premium quality oil from the first pressing with no more than 0.8% acidity. The next grade is virgin olive oil which may have minor imperfections and a slightly higher acidity level. If it’s labelled pure olive oil, it will be a mix of virgin oil plus oil that has been refined. Light olive oil is light in colour and aroma because it has a higher content of refined oil. It is not light in kilojoules.
Most of the research on olive oil has been done on the minimally processed extra-virgin oil. It’s important to note that refining the oil removes most of its natural antioxidants.
Oil questions answered
Q. I’ve read online that seed oils are bad for us and we shouldn’t have them. Is this true?
We’re sometimes told we’re consuming too much of the omega-6 poly-unsaturated fats from seed oils but that’s really not the case. Polyunsaturated fats have been linked with a lower risk of heart disease, although it is known that very large doses can be detrimental for health, as they can lead to cell damage.
Nutritionist Dr Elisabeth Weichselbaum says: “While we need these fats in our diet for heart health, and to make sure we get enough of the polyunsaturated fatty acids our bodies can’t produce, a safe range of intake is recommended at six to 11 per cent of our total energy intake. But in fact, an intake of 11 per cent would be difficult to reach through our normal diet. In New Zealand, the average contribution of poly-unsaturated fat to total energy intake is less than five per cent.”
Q. Should I use coconut oil instead of other oils for cooking? I’ve heard it’s healthier?
Coconut oil is not as bad for us as butter, but ‘less bad’ is not the same as ‘healthy’. There are better choices.
Cardiovascular disease (CVD) remains a very serious problem in New Zealand. While there is such good evidence that diets high in saturated fats play a significant role in the development of CVD it is disturbing that people may be adding saturated fat to their diets in the belief that it is healthy.
Coconut oil is over 90 per cent saturated fat and while there are many claims made about health benefits of using coconut oil, they remain unsubstantiated.
Advocates of coconut oil tell us it contains beneficial medium-chain triglycerides (MCTs). However, oils and fats expert Laurence Eyres says:
“The MCTs with possible beneficial effects are not the same as the ones present in coconut oil.” More research is needed, so we recommend that if you do choose to use coconut oil you treat it like other saturated fats and use in very small amounts.
Q. Isn’t butter better than vegetable oil because of all the essential vitamins it contains?
No. While butter does contain trace amounts of a number of vitamins and minerals, vitamin A is the only vitamin it provides in any significant amount. One tablespoon of butter provides 128mcg vitamin A, which is 14 per cent of the recommended intake each day. Spreads used instead of butter are fortified with vitamin A to similar levels. We can get plenty of vitamin A from other foods such as carrots, pumpkin, green vegetables and capsicum. Seed oils are considered a better alternative to butter as they are low in saturated fats.
Here are some oils we like to use in our kitchens
Sunfield Oils — Canola
A great all-rounder for stir-fries, baking or salads that won’t add flavour to cooking.
Alfa One Rice Bran Oil Cooking Spray
An oil spray is a great way to cut down on the amount of oil added to cooking.
Olivado Extra Virgin Avocado Oil — Lemon Zest
250ml, from $9.99
A delicious full-flavoured oil with added lemon zing. The cost facilitates moderate use but a little is all that’s needed anyway.
The Village Press Manzanillo Extra Virgin Olive Oil
A full-flavoured, high-quality oil that adds flavour your salads will love.