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The Science Behind Cooking With Oil

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Oil is an essential ingredient in every single kitchen. We all use different type of oils – some of us decide what type of oil to use depending on what is available at our local shops. Some of us make our oil selections depending on what we are cooking or which oil is more affordable. The thought process is a little different nowadays. People are becoming more aware and thus are buying oils that they believe are good for their health. There are types of oils that are better for certain uses than the others. Today I want to talk about oil safety, the science behind cooking with oil, and offer you some ideas about what type of oil would be more appropriate for different cuisines.

What happens to oil in the cooking process?

Oil gets heated up to different temperatures during a cooking process. It is heated almost up to its smoking point for deep-frying and to lower temperatures for other types of cooking process. Oil starts to smoke when it is over-heated and starts to form aldehydes, ketones, alcohols, dienes, and acids. As a result, if you continue to cook something in the same oil, the food product will taste poorly. More importantly, the smoke of rapeseed, soybean, peanut oil and lard can cause serious mutagenicity and genetic toxicity. A few culprits to consider are an aldehyde called acrolein, as well as alkenals and alkadienals (unsaturated aldehydes) – they are formed during the burning/smoking process of the above-mentioned oil. There are quite a few fast food restaurants that use peanut oil to deep-fry their fries. Lard is widely used in pie crusts, and soybean is popular is households. Acrolien in very toxic to our cells and genes – they degrade our cells and genes; they also generate free radicals. Free radicals are responsible for cell aging. Recent studies have shown an increased amount of acrolein in Alzheimer’s disease patients’ brains. I strongly encourage you to read the two references listed below, they’re such eye openers!

In a nutshell, oils with low smoking point (rapeseed, soybean, peanut oil, and lard) ⇒ acrolein ⇒ free radical ⇒ Alzheimer’s disease + premature aging.

What can you do?

Avoid the oils I mentioned above. Don’t buy them, don’t use them. I have started to avoid canola oil as well, because it is made from genetically modified rapeseed oil. I’ve talked about the negative side effect of rapeseed oil above. I know its very hard not to deep fry this and that, but try at least. If you must deep fry your favorites, use grapeseed oil – its my personal favorite for everyday use. The following oils are okay to use on a daily basis:

Grapeseed oil http://fatsecret.com/calories-nutriti...
Olive oil http://fatsecret.com/calories-nutriti...
Safflower oil http://www.nutrientfacts.com/foodpage...

Now you have an idea of what sort of oil you should and should not use. Then there is the question of using refined or unrefined oil. Refined oils have a higher smoking point and unrefined oils have a lower smoking point. Refined oils have their impurities cleaned out and unrefined oils don’t. Unrefined oil might have tiny tiny bits and part of whatever it is made from (i.e. olive oil might have bits of olive); these tiny bits might burn as you heat up the oil to a high temperature. You’ll have to decide whether to use refined or unrefined oil for yourself.

What type of oil to use for a certain type of cuisine

Each oil has its own smoking point, here’s a quick link to Wikipedia for you to look it up: http://en.wikipedia.org/wiki/Smoke_point

If you cook the type of cuisine that requires you to heat up the oil to a high temperature and then proceed with the following step, I’d recommend that you cook with grapeseed or safflower oil. For example, Indian cooking requires that you heat up the oil, splatter whole spices in the hot oil, and then proceed. So grapeseed or safflower oil’s high smoking point perform very well for that. French cooking sometime requires that you sear a piece of meat or fish. You need your oil temperature to be really high for that. Grapeseed or safflower oil will do beautifully for that as well.

If you don't need your oil to be really hot all by itself in the pan in the very first step of your cooking process, then you may cook with olive oil; it has a lower smoking point. For example, for some Italian recipes, you can add the oil, onion, and vegetables right in the pan at the same time. This prevents the oil from reaching its smoking point, because the heat has something to disperse into, the vegetables or whatever have you.

Some folks like mixing oil and butter together to achieve the taste of both. Butter has a lower smoking point than the three above-mentioned oils. If you mix an oil and butter, the smoking points of the two will equilibrate. That basically means that the butter will bring the overall smoking point down a little bit. So, if you’re using this oil/butter hybrid, don’t allow it to sit on the stove all by itself for too long. Add whatever you’re cooking before it starts to smoke, so that the heat will be dispersed.
I hope this long long article has been helpful and informative. Happy cookin’!

References:
Emissions of volatile aldehydes from heated cooking oils http://webcache.googleusercontent.com...

Acrolein, the toxic endogenous aldehyde, induces neurofilament-L aggregation http://webcache.googleusercontent.com...

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  1. I know you mean well, but the amount of actual/strong science in your post is minimal. Even a basic, such as the scientific process, is lacking in that you're equating a basic chemical reaction to a disease causation. Not only those, but it also goes against basic culinary knowledge, such as peanut oil being excellent for frying and avoiding olive oil for heating purposes. Top top it off, you continue to perpetuate myths such as mixing butter with oil for cooking purposes, which doesn't work since it's the milk protein that burns before anything else.

    1 Reply
    1. re: ediblover

      I appreciate your opinion on my post. It is meant to be a light-weight article and these are certainly my take on using oil. It isn't a scientific paper, neither is it my PhD thesis. I kept it simple, but did include references that contain in-depth discussions.