The best oil to fry in? – A reader’s question

I can keep on being surprised by discovering that some sort of basic food such as rosemary, apples, or, in this case, frying oils has been researched extensively! When diving into ‘frying with oil’ I found complete books dedicated on the topic and loads of articles. Who would have thought that?

It’s a perfect example of food science applied in real life. And all thanks to a reader’s question I received a little while ago (I love receiving reader’s questions by the way). This time the question was as follows:

When frying oliebollen for our new year’s celebrations it seemed as if using peanut oil made for a higher quality oliebol, than sunflower oil. Could that be true? Or is it just imagination?

Of course, this question can be applied to frying any type of food. As usual, no deep-dive into health benefits here, but we w

Frying & Oliebollen

For the non-Dutch readers, a quick reminder, oliebollen are similar to donuts, but not they’re same. They are essentially fried dough balls made from a yeast risen dough and often filled with raisins or apple (or anything you like).

The oliebollen are fried in oil at about 180ºC until they’re a nice golden brown and cooked on the inside. Frying in oil is a skills by itself. It’s important to get the temperature just right so you don’t burn the product, but don’t undercook it either. You generally prefer a crispy, not an oily product either.

oliebollen, ready to be eaten

Frying oils

I’ve always thought that deep frying oliebollen or anything similar is best done in sunflower oil. However, when diving into the question from my reader I discovered this might not be true.

There are a lot of different oils  that can be used for frying in some way or the other. Common examples are sunflower, canola, rapeseed, soybean or peanut oil. The main differences between these oils is their composition.

The oils are mostly made up of so called triglycerides. These are a specific group of molecules. A triglyceride consists of three fatty acid chains on a backbone. Different oils have different fatty acid chains on this backbone. These fatty acids determine the behaviour of the oil.

Fatty acid chains

Fatty acid chains can be different in various ways. They are always chains of carbon atoms. However, the length of the chains can differ. Some are long (>20 atoms) whereas others can be very short (only 4 carbon atoms). Longer chains tend to intertangle more easily than shorter ones.

Another important difference is how these carbon atoms are attached to one another. They can be attached through a single bond or a double bond. If a chain contains these double bonds (1 or more), it will be called an unsaturated fatty acids. If it doesn’t, it’s a saturated fatty acid.

Health benefits

A lot of research on the best oils to use for frying focus on the health benefits of the various frying oils, not necessarily flavour. I’ve found a lot of attempts to make healthier oils.

Healthier oils are generally regarded as those having more unsaturated fatty acids vs saturated fatty acids. Some are mixtures of oils, but let’s not dive any deeper into this aspect.

Flavour & taste

For this question, we want to know whether the type of oil influences your final fried result. Short answer first: yes!

Oils all tend to taste slightly different. So yes, they can and will influence taste and flavour. However, that is kind of where the research outcomes stop. Which tastes better and why is not as objective as I might have hoped.

I found some research that states peanut oil is generally regarded as giving a better tasting product. But then again, I read that this taste tends to be pretty country dependent. Apparently the French are really used to using peanut oil whereas the Americans prefer soybean oil. So if you’d do this research in France, you’ll probably get different results than in the US.

Overall, it seems that you prefer what you’re used to, as long as the oil you’re using is fresh and of a high quality. Some oils simply aren’t suitable for frying such as Virgin Olive Oil since it tends to smoke at temperatures around frying temperature.

Another aspect making comparison more complex is that oils are processed and ‘cleaned’ quite a bit. This can again influence their flavour and taste profile.

Stability of peanut oil vs sunflower

When discussing flavour, I’ve assumed we’re using fresh new oil. Things tend to shuffle around a little once the oil has been used for a while, this is where differences between oils can really show up.

A prolonged heat treatment of an oil will always somehow affect the oil. One of the things that will happen is oxidation. Essentially an oxidation reaction is a reaction of the fatty acids with the oxygen in the air. Too much oxidation will lead to off flavours (think of rancid butter). Other reactions occuring are hydrolysis and polymerization, here‘s an article digging deep into the chemistry of these reactions, it’s fun!

So will peanut oil behave differently than sunflower oil? Yes. it can for sure. Peanut oil happens to be very stable over time during frying. It has one of the longest ‘fry shelf lifes’. In other words, you can use it quite long before you really have to change it for new one.

This is due to the type of fatty acids in the oil. Unsaturated fatty acids tend to be less stable under high temperatures, but peanut oil consists of most saturated fatty acids. These tend to be more stable.

So which is better?

There are a lot of reasons why one oil might be more suitable for frying than the other. There’s costs, flavour but also fry stability. We know for a fact that the type of oil can certainly impact flavour as well as its characteristics over time while frying. Which is best though is hard to tell though.

Peanut oil tends to be more expensive than sunflower oil, but has a different flavour (which is appreciated by certain countries/people) and is more stable during frying. Sunflower oil on the other hand is generally cheaper, but less stable during frying.

This search through literature has definitely triggered a new project in our kitchen: using different frying oils. It’s added to the ever growing list!

 

If you’d like a more detailed look into frying oil science, have a look at the resources below or ask a question in the comments below! There’s so much detail in there that I’ve tried keeping it quite top level for today.

Sources

Yes, they’ve done research on the effect of the type of frying oil used for frying chips.

A complete book on deep frying.

Of course, a book all about peanuts praises the flavour of peanuts.

I’m not a health expert, but if you want some information on health, have a look at this bbc website.

Fats & Oils book

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