I used to go along with the conventional wisdom that you should only use a neutral pure vegetable oil for frying. I had just accepted the idea that other fats would be harmfully compromised by high temperatures and that only this cooking oil was suitable for the job. Now, having belatedly researched this bland oil, I simply won’t have it in my kitchen.
The whole vegetable tag is misleading. It doesn’t come from vegetables – with all their healthy associations – but oil seeds, a different proposition entirely. Some of this cooking oil is single-crop, like sunflower or groundnut, but most is an anonymous blend made from rapeseed, corn, safflower, soya and cotton seed.
These bulk oils are known in the trade as RBD, short for ‘refined, bleached and deodorised’, in other words, industrially refined. The seeds are crushed with heat and chemical solvents, such as hexane, to extract the maximum yield. The oil is then de-gummed with acids or enzymes. To make it presentable it also has to be bleached because all these processing stages give it an unattractive colour. Next, the oil has to be deodorised because it now smells bad. This usually involves heating it above 200 degrees centigrade – twice the temperature of boiling water – at least two times. Far from cool and pure, I have relabelled this ubiquitous cooking oil as ‘hot and bothered’.
This process destroys the notionally healthy unsaturated fatty acids in the seeds and constitutes extreme ultraprocessing by any measure. A handful of healthy sunflower or pumpkin seeds, full of their fresh, natural, untreated oil, should not be confused with this omnipresent cooking medium.
Food factories and restaurants use the same basic cooking oil as home cooks, but in commercial deep-frying, other improving agents are added to the bulk catering oil to extend its fry-life. Chemical additions include antioxidants (preservatives by another name), anti-foaming and anti-spattering agents, and mineral filters. These slow down the build-up of tacky, sticky deposit inside the deep-fryers so that businesses don’t have to change their oil so often.
There’s a growing school of thought that it’s this modern type of highly refined cooking oil that helps drive disease – not the natural, much more chemically stable, mainly saturated fats found in butter, lard, dripping. I find that a pretty plausible theory. A body of scientific research now associates repeatedly heated industrial seed oils with high blood pressure, heart disease, and intestinal and liver damage.
So, what do I use instead? I don’t ever deep-fry, but I do a fair amount of shallow frying and sautéing. I mostly use extra virgin olive oil for this; I’m just careful not to let it reach the smoke point (the temperature it begins to burn) before I put the food in the pan. For something like falafel, I use more oil than normal, somewhere between shallow and deep-frying. If you buy extra virgin olive oil in three or five-litre cans, it makes it quite affordable.
Increasingly, I’ve been using cold-pressed (unrefined) coconut oil for spicy dishes, like curries or pilau rice. I prefer to fry fish in breadcrumbs in it, too: you get a crisp crust this way. Ghee brings a wonderful richness, just right for French toast. Every scrap of duck, goose, dripping and lard that I accumulate is used to start off another dish, too. So you can keep your cooking oil, thanks. For my lunch, I’m off to fry up last night’s potatoes in leftover fat from the weekend’s pork roast.
The view from our nutritionist Kerry Torrens
At BBC Good Food we appreciate that heating fats and oils at high temperatures (approx. 180C and above) cause structural changes, which is why we aim to:
- Fry less, especially at high temperatures, opting for dry-frying, baking or grilling instead.
- When we do fry, we minimise the amount of oil we use and drain the cooked food (e.g. on a paper towel) before serving.
- We choose to use olive or cold pressed rapeseed oil, both being rich in mono-unsaturated fats; or saturated fats, like butter, coconut or ghee, which are more stable at high temperatures because they have a higher ‘smoke point’.
- We store our oils in a cool, dark place, out of direct sunlight and once used, we discard.
Read more articles by Joanna Blythman
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Good Food contributing editor Joanna is an award-winning journalist who has written about food for 25 years. She is also a regular contributor to BBC Radio 4.