Posted by kathryn in Shopping Basket and Fat

After missing a month due to the 31 Days to a Better Diet series, Q & A Thursday is back.

The first question is from Maja who asks which is the healthiest oil for frying and roasting?

Why do we use oil in cooking?

Oil has to be one of the most frequently used cooking ingredients. We use it in dressings and when marinating foods. However it’s also the foundation of several cooking techniques: sautéing, roasting and stir frying.

Cooking in oil is different from cooking in water, because it heats to a higher temperature. While water turns to gas at 100°C, oils remain liquid at temperatures above 200°C.

This temperature gives food a crisper texture and more intense flavour.

What makes an oil more or less healthy?

There are three factors which affect the health quota of an oil:

1. The type of fat it contains
2. How the oil reacts to heat
3. How much of the oil you use

1. The type of fat

There are three distinct groups of fat found in oils: saturated, poly-unsaturated and mono-unsaturated fatty acids. While all three are present in both animal and plant foods, different oils tend to be dominated by one group.

While we need each of these fatty acids in our diet, most people eat too much of the saturated kind. Here in Australia, on average people eat twice the recommended daily intake. And a high saturated fat diet is a problem, because it’s associated with an increased risk of cardiovascular disease, cancer and diabetes.

In contrast mono- and poly-unsaturated fatty acids are associated with health benefits. These include reducing cardiovascular risk and cognitive decline in old age, and improving mental health.

2. How the oil reacts to heat

The amount of saturated, poly-unsaturated and mono-unsaturated fatty acids varies considerably between different oils. This affects the stability of the oil and how it responds to heat.

Heat can change the structure, composition and flavour of an oil. All oils have a smoking point, although the temperature at which this occurs varies. If you heat an oil beyond it’s smoking point it will burn and the flavour deteriorate. More concerning for your health though, heating an oil beyond its smoking point encourages the production of free radicals.

To prevent this it’s important to choose an oil which remains stable at a high enough temperature for the cooking method you’re using.

3. How much of the oil you use

Even the healthiest of oils can be over-consumed. Oils are basically 100 percent fat. Which makes them a concentrated energy source and therefore high in kilojoules. Too much of even the best oils can contribute to weight gain. Quantity counts.

How to use some of the most common oils

• Olive oil: high in mono-unsaturated fats and has a lowish smoking point of 190°C. Therefore suitable for cooking at lower temperatures. Use for sautéing foods, adding at the end of cooking to flavour a dish, roasting foods in the oven at a lower temperature.
• Canola oil: high in mono-unsaturated fatty acids and has lowest saturated fat content of all the common oils. Has a higher smoke point than olive oil (240°C). Therefore suitable for higher temperature cooking, without affecting flavour or increasing free radical damage. Blander flavour makes it a good multi-purpose oil. Use in baked goods and for stir frying where a medium – high temperature is required.
• Sesame, peanut and sunflower seed oils: high in poly-unsaturated fatty acids and have distinct amounts of mono-unsaturates. At 232°C they have a higher smoking point than olive oil and are in a similar range to canola oil. Excellent for stir-frying or frying.
• Macadamia oil: different fatty acid profile from the other nut and seed oils. 85 percent mono-unsaturates, 14 percent saturates and virtually no poly-unsaturates. Has a distinctive flavour and medium smoking point of 210°C. Excellent for stir fries and roasting.

Five tips for using the healthies oil in your diet

1. There is no one perfect oil. As with other parts of your diet, variety is the key. Use olive oil some nights, but also include canola, sesame, macadamia and so on. It’s the best way to ensure you’re getting the fatty acids you need.
2. Buy cold pressed. Cold pressed and extra virgin oils are the first pressings from the nut and seed, which are extracted without heat or chemical solvents. These are purer, better oils, with a fuller flavour.
3. Don’t exceed the smoking point. If you exceed the smoking point, you’re damaging the oil and increasing free radicals, so use the right oil for the cooking job.
4. Avoid using too much. Find ways to reduce the overall amount of oil you use. While a recipe may specify tablespoons and cupfuls, it’s usually possible to reduce this down.
5. Replace saturated fatty acids. Rather than adding mono- and poly-unsaturated fatty acids to your diet, use them to replace some of the existing saturates you use. Add canola oil to baking and dip your bread in olive oil, rather than using butter.

What about trans fats?

I specifically haven’t mentioned trans fats in this post, as they’re not regularly found in the oils we use at home. If you want to know more about trans then see my previous posts on the subject:

• Trans fats: what’s the problem
• What foods contain them
• Why manufacturers use them
• A reality check

If you want to know more about cooking oils, then I have an article coming up in Wellbeing magazine. It will be published in the November issue.

What oils do you most commonly cook with?

04 September, 2008