I hate to sound arrogant, but I was pretty sure I’d landed on the perfect roast potato recipe until about an hour ago.
The steps seemed so simple. Par-boil the spuds (I love roosters) for about ten minutes; put a shameful amount of olive oil in a tray to warm in a hot oven; chuff and season the spuds with semolina and herbs, and then roast. Right?
Wrong, it seems. Because while every other step might be legit (like, Mary Berry-approved legit), I’m making a serious mistake with my oil.
Beef tallow isn’t just a delicious, decadent addition to spuds, it turns out ― olive oil is among the worst oils you can roast your potatoes in, apparently. Specifically, extra-virgin olive oil.
What? Why?
It’s all to do with something called a smoke point.
The smoke point of extra-virgin olive oil is around 165-190°C, which pales in comparison to duck fat’s 190°C and rice bran oil’s 260°C.
Light or refined olive oil has a more impressive smoke point of 260°C, but it’s not as good as safflower oil’s 265°C.
In fact, Serious Eats puts extra-virgin olive oil right at the bottom of its smoke point chart ― meaning it’s better used as a dressing or dip than a cooking aid.
That’s because once you heat oil past its smoke point, its fats start to break down, releasing free radicals and a substance called acrolein.
Acrolein is responsible for that burned, acrid, bitter flavour we’re all trying to avoid ― so while flash-frying a quick meal in shallow levels of oil might be OK, leaving your veggies to essentially stew in split fats for an hour or more probably isn’t.
And given that most roast potato recipes call for a 200°C-ish (or 180°C fan) roasting temp for potatoes, it doesn’t seem likely that your 65-190°C-smoke-point extra-virgin olive oil will cut it.
I mean, even if you can stand the taste, a smoky oven is nobody’s idea of fun, right?
What should I use instead?
Duck fat, which has a smoke point of 190°C, could be suitable (and delicious) if you’re cooking on the slightly lower fan-assisted heat.
But good ol’ sunflower and vegetable oil, which can withstand temps of around 225°C, might be a cheaper (and perfectly tasty) option.
Avoid coconut oil and butter, which both have low smoke points of around 175°C. ― and if you’re craving that extra-rich taste, beef tallow has a high smoke point of 205°C.
Refined or light olive oil has a high smoke point of 260°C, so this should be fine to use too ― it’s just the extra-virgin type you need to worry about.
Ah, the joys of cooking...