The Science of French Fries

Thin and crispy, with its subtle aroma and the grainy feel of salt: just one bite makes you want to take another, immediately. What are we talking about? French fries, of course. Simple, unsurpassable, French fries. However, when it comes to actually making them well, it seems that cooking French fries requires a kind of shamanic ritual. The ingredients and technique may be simple, but we can never be sure about the final result.

This is not actually the case: frying a good fry is within everybody’s power, but ensuring that they are crisp and thin requires knowing a few secrets and tricks. And a few laws of chemistry and physics. Let’s begin with an obvious consideration. French fries – in any variant – aren’t among the healthiest of foods, so it’s quite useless to try and make them into something they’re not. Once you’ve decided to make delicious French fries, it’s better to just follow the classic steps instead of trying to tweak them into something healthier that simply makes them less tasty – and they’ll never be as healthy as a salad, so why bother? If you’re concerned about health, eat and enjoy your fries… and then eat broccoli the next day.

From a chemical point of view, the potato is about 80% water, 15% carbohydrates and 4% protein. Starch is a principal component: made of many connected glucose molecules, it’s the carbohydrate most responsible for the chemical reactions that take place when the potato undergoes frying. And because starch is a carbohydrate, it’s susceptible to the famous Maillard reaction, which we’ve already discussed in past articles. This series of reactions involves carbohydrates and proteins when exposed to temperatures higher than 140°C.

So first, let’s look at the temperature factor: to fry a chip well, the heat needs to be between 162°C and 164°C – and to ensure this, a cooking thermometer is indispensible. Then there’s the matter of the oil: for a long series of reasons, the crispiest and driest frying is done with saturated fats – yes, the unhealthy kind. What can make this unhealthy choice much less problematic, is ensuring that you only use the oil once, changing it with new oil for every new batch. The ideal solution would be to fry the chips in melted, heated butter, but you can achieve perfection with two parts coconut oil and one part butter. Now let’s discuss the actual chips. Once they’ve been slices, they need to be soaked in salted water for about twenty minutes and then rinsed well and dried with paper towels, which serves to eliminated the extra starch – making them crunchy and golden.

To make the classic “French” versions, in longish sticks, you’ll need to cook them in two phases: first for about 4-5 minutes at 163°C, then after draining them, heat the fat to 192°C – 198°C and fry them again for a couple of minutes to achieve the delicious crust. This will provide that unmistakable “crunch” at the first bite – an immediate reward for your considerable efforts.