Why you should differentiate between oils for cooking and for cold dishes!
Nowadays, the variety of different oils in the supermarket is overwhelming. Have you ever heard that not all oils are suitable for frying and cooking? I will tell you what you should look out for when buying. Plus, I’ll show you the indicators of overheated and misused oils. I will also provide you with a list of the different smoke points of different cooking oils. This list will help you find the right oil for your purpose. Let’s go!
Oils are sensitive to light, oxygen and heat
In my blog post on fats, I’ve already explained that we characterize fats based on their double bonds and bonds to hydrogen atoms. This is what the classification of saturated, monounsaturated, and polyunsaturated fatty acids is based on. If the first double bond in the fatty acid chain is after the third carbon atom, we speak of omega-3 fatty acids. The omega-6 and omega-9 fatty acids are classified according to the same scheme. The more double bonds a fatty acid has, the more sensitive it is to oxygen, light, and heat. Thus, it is also less durable at the same time.
Therefore, oils with particularly high amounts of omega-3 fatty acids (e.g. linseed oil) can only be kept for about a month after opening and should be stored in the refrigerator. In contrast, oils with predominantly saturated fatty acids (e.g. coconut oil) last for months and can be stored away from light in the cupboard. The light sensitivity of fats and oils is also the reason why you should buy oils mainly in dark glass bottles. Long before the oil is harmful to your health, your sense of taste and smell will tell you that it is rancid. So, you can rely on your senses for the durability check.
Which oil is best for which preparation?
Since oils change their nutritional content depending on how they are prepared and how they are heated, different oils are suitable for different uses. Depending on whether you want to fry, steam, or prepare your food cold, a different sort of oil is better or worse.
The first rule of thumb is:
Edible oils that are rich in saturated or monounsaturated fatty acids (e.g. coconut oil) are suitable for cooking, baking, steaming, and frying. In contrast, you should use fats with predominantly polyunsaturated fatty acids only for cold preparation (e.g. linseed oil).
My second rule of thumb is:
The more saturated fatty acids an oil has, the more solid it is at room temperature (coconut oil). The more monounsaturated or polyunsaturated fatty acids it contains, the more liquid it is even in the refrigerator (linseed oil).
Olive oil is an absolute all-rounder. Often you hear that you shouldn’t use olive oil for frying.
But even with native, cold-pressed quality with a smoke point of 170-210 °C, it is heat-resistant enough to be suitable for frying.
What does “smoke point” mean for oils?
The smoke point stands for the temperature from which an oil begins to develop smoke. Edible oils begin to smoke from this temperature and harmful substances are produced. In addition, the oil becomes darker, begins to foam, smells rancid to pungent, and becomes tougher. A little hint: The correct frying temperature is usually around 130 °C. Searing can reach up to 200 °C and ideal temperatures for deep-frying are between 160 and 170 °C.
The third rule of thumb is:
The higher the proportion of free and polyunsaturated fatty acids (linseed oil), the lower the smoke point.
Therefore, oils with predominantly polyunsaturated fatty acids such as hemp or linseed oil are not suitable for frying and cooking. You should only use them for cold dishes, salad dressings, for refining and seasoning, as well as for smoothies or antipasti. In general, refined oils can usually be heated more strongly before they reach the smoke point due to strong processing. However, you should never heat oils so much that they exceed their smoke point. Since this would result in harmful or even highly carcinogenic trans fatty acids. I’ve already told you what trans fatty acids are here.
How do I know if I have overheated an oil?
First, the oil begins to smoke more and smells rancid/pungent. You have reached or exceeded the smoke point. In addition, the oil turns significantly darker. Plus, it begins to foam, gets thicker and tougher. The main problem is the formation of harmful substances through to carcinogenic trans fatty acids. In addition, the smoke that is created and released into the air is also toxic, carcinogenic, and mutagenic, i.e. it can attack the DNA. Above all, the development of lung cancer is strongly promoted.
In fact, scientists agree on this: Passive smoking is much less carcinogenic than the permanent overheating of oils and fats when preparing food (!). For example, a study in China found that the risk of developing lung cancer among women smokers who cook meat every day was almost three times the risk of developing lung cancer than women who smoked foods other than meat. Particularly when roasting meat, highly toxic heterocyclic amines (HCA) and polycyclic aromatic hydrocarbons (PAH) are generated. These are classified as highly carcinogenic. One less reason to eat and prepare meat.
Olive, coconut and avocado oil are the handymen
You can see from the graphic that olive oil, coconut oil, and avocado oil are the all-rounders. However, since olive oil is the only one of the three that is most affordable in terms of price-performance ratio, even in organic quality, I would personally recommend olive oil. When buying, look for organic quality or even for the Demeter-label and cold pressing.
In one of my following blog posts, I will list the advantages and properties of the different fats and oils for you. Olive oil is an all-rounder, but linseed oil, pumpkin seed oil, and other types of oil shouldn’t be removed from your shopping list! I conclude with my fourth rule of thumb:
Use oils sparingly since it is a processed food.
Therefore, it is better if you prefer to use the more natural variants in the form of nuts and seeds. In addition to the fats, you also get important proteins, fiber, and other nutrients that are bound to the solid components of the food and are therefore missing in the extracted oil. And finally, don’t forget:
A balanced, wholesome diet is always varied!
Chiang, T.A. et al. 1997: Mutgenicity and polycyclic aromatic hydrocarbon content of fumes from heated cooking oils produced in Taiwan, in: Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, Vol. 381, 1997, No. 2, pp. 157-161.
De Alzaa, F./Guillaume, C./Ravietti, L. 2018: Evaluation of Chemical and Physical Changes in Different Commercial Oils during Heating, in: Acta Scientific, Vol. 2, 2018, No. 6, pp. 2-11.
Seow, A. et al. 2000: Fumes from meat cooking and lung cancer risk in Chinese Woman, in: Cancer Epidemiol Biomarkers, in: Cancer Epidemiology, Biomarkers & Prevention, Vol. 9, 2000, No. 11.
The Vegetarian Health Institute, 2012: Smoke points of oils.