Choosing cooking oils
Image by Honglin Mu from Pixabay
With so many different oils available on the market, which ones are the best to use?
What is the healthiest cooking oil?
When it comes cooking, it is important that we choose the right oil for the job. When we cook at high temperatures (such as when frying), some oils can become unstable and begin to breakdown. Once an oil starts to ‘smoke’ and burn (a bluish-coloured smoke), it has started to produce chemicals, such as peroxides and aldehydes. This is referred to as an oil’s ‘smoke point’. The chemical compounds which are released at the smoke-point, can be harmful to our health if we are exposed over the long-term. However, an oils smoke point is not the most important factor when choosing a cooking fat. It is more important to look at the overall stability of an oil when it is heated. How stable or unstable an oil is depends on a number of factors such as it’s chemical structure and the level of antioxidants that may be present.
Saturated fats
Saturated fats have no double bonds in their chemical structure, meaning they are very stable when heated. However, saturated fats have been shown to increase our levels of cholesterol and therefore increase our risk of heart disease. The Heart Foundation recommends that we should continue to replace saturated fats in our diets with unsaturated fats.
Saturated fats are usually solid at room temperature. Common saturated fats include coconut and palm oil, butter and lard.
Photo by jonathan ocampo on Unsplash
Monounsaturated fats
Monounsaturated fats and oils have only a single double-bond in their chemical structure, meaning they are more stable when they are heated. Some common oils which are high in monounsaturated fats include olive, avocado, peanut, rice bran, canola and almond oils.
Because these oils are more stable at higher cooking temperatures, it is best to use these oils for frying, barbecuing and stir-frying at home.
While these oils may ‘smoke’, this is usually from steam (a white smoke), rather than the blueish smoke that is associated with unstable oils breaking down.
Polyunsaturated fats
Polyunsaturated fats and oils have more than one double-bond in their chemical structure, meaning they are more unstable when they are heated. Oils rich in polyunsaturated fats include sesame, sunflower, grapeseed, flaxseed and wheatgerm.
Because these oils are more unstable than monounsaturated fats, they are best kept for use as dressings or sauces, rather than using them to cook or fry with.
Extra virgin olive oil (EVOO)
EVOO, in particularly locally produced NZ EVOO, is an ideal multi-purpose cooking oil. It is predominately monounsaturated fat meaning that it is more heat-stable. It has a smoke-point of around 200C, which is higher than what we would typically cook with at home. For example, roasting is usually around 180C and deep-frying between 160C - 180C. In addition to having a higher smoke point, extra virgin olive oil also contains a high level of antioxidants (including phenolics), which help to prevent the fats being broken down. These antioxidants are also good for our health.
When it comes to imported olive oils, the quality can sometimes be questionable and the amount of antioxidants may not be as high as found in NZ produced EVOO. Therefore, they may not be as stable as what we produce in NZ. However, evidence still suggests that European olive oil is safe for frying.
What is the difference between EVOO and light olive oil
EVOO has undergone as little processing as possible. Therefore, it has more flavour and colour, as well as containing more health-promoting antioxidants. Light olive oil has undergone the most processing and is highly refined. It is lighter in colour and flavour but not lighter on calories (or energy). Because a light oil has a less distinct flavour, it is best used in baking or when you do not want to have a strong olive flavour in your cooking. Regular olive oils are often a combination of both virgin olive oils and refined olive oils. Whether you should use EVOO or regular olive oil, comes down to your budget, the temperatures you will be cooking at, personal preference and whether you are after an oil with a strong or light flavour.
Oils and health
Monounsaturated and polyunsaturated oils are generally liquid at room temperature, rather than solid. Both monounsaturated and polyunsaturated fats can help to lower the ‘bad’ LDL cholesterol levels in your blood and thereby help to reduce your risk of heart disease and stroke.
The best sources of heart-healthy fats and oils are from whole foods, such as nuts, seeds, avocado, olives and oily fish. When using vegetable oils, it is recommended to use them sparingly as part of a heart-healthy diet alongside plenty of vegetables, fruit, nuts, seeds, legumes and whole grains. The Heart Foundation recommends choosing the right oil for your budget and taking good care of it to prevent damage.
Is coconut oil healthy?
While these oils may ‘smoke’, this is usually steam (a white smoke), rather than the blueish smoke that is associated with unstable oils.
Despite the hype, coconut oil is far from a superfood. Coconut (and palm) oil are made up of predominately saturated fats, which is why this oil is often solid at room temperature - just like lard and butter. Saturated fats have been shown to raise our blood pressure and therefore increase our risk of heart disease. Research suggests coconut oil is better than butter for cholesterol levels, but not as good as other plant oils that are lower in saturated fat. Therefore, the Heart Foundation recommends that we choose to use other unsaturated liquid plant oils as the main cooking oil at home and that we only use a little coconut oil for flavour.
Seven ways to get the most out of your vegetable oil
Here are some helpful tips from the Heart Foundation to help you get the most out of your cooking oil:
Avoid stock-piling oil. Keep an eye on the 'use by' date and ideally use within 12 months.
Oils prefer cool, dark places. Where possible choose oil in a dark glass bottle or tin and store it away from direct light.
Use the right oil for higher heat cooking. Olive, canola and rice bran oils are all good choices.
Avoid overheating oil when cooking. When an oil is over-heated it produces unwanted chemicals. An oil's smoke point is the point at which the oil starts burning and smoking, which signals that damage to the oil has started.
Avoid reusing heated oils. As the oil darkens it develops off-flavours and becomes rancid.
Avoid deep-fried foods. If you do need to deep fry, corn and sunflower oils are unstable at high temperatures. Refined olive oil (light olive oil) and rice bran oils are better choices.