French fries and double frying

Why

During the first fry at a lower temperature, around 150–160 °C, the starch inside the fry gelatinises and softens and the surface starts to dry out while the fry stays pale; as it rests, more steam escapes and the surface firms up. In the second, short fry this dried layer quickly becomes a crisp golden crust, whereas with a single fry a thicker chip either burns outside while staying raw inside, or ends up soft and greasy. Browning also produces acrylamide, which forms from sugars and the amino acid asparagine above about 120 °C and increases quickly as the colour darkens. EU Regulation 2017/2158 therefore requires food businesses to fry chips at no more than 175 °C and recommends soaking or blanching the potatoes beforehand, because the water washes some of the sugars off the surface. The UK FSA advises cooking starchy foods at home, whether fried, baked or toasted, only to a golden yellow, so fries cooked until brown are not only bitter but also carry needless acrylamide.

How to do it

• Cut the potatoes into fries of even thickness, about 10–12 mm, rinse them and soak them in cold water for 30 minutes to 2 hours.
• Before frying, drain and rinse them and dry them thoroughly in a tea towel; wet fries pull down the oil temperature and the water makes the oil spit.
• Fry them the first time in small batches at 150–160 °C for about 5–8 minutes, until soft but still pale (for safety see the Deep-frying in oil card).
• Drain the fries on a rack and let them rest for at least 10 minutes; meanwhile heat the oil for the second fry.
• Fry them the second time at 170–175 °C, no hotter, for just 2–4 minutes, and take them out as soon as they are golden yellow, not brown.
• Salt them in a bowl after frying and serve at once; fries from the oven or an air fryer should also be cooked only until golden.

If it goes wrong

Soft, greasy fries were fried in oil that was too cool or in too large a batch; let the oil heat up again and briefly refry them in smaller batches. Fries golden outside and raw inside were fried only once or in oil that was too hot; finish them for a few minutes in the oven. Dark brown, bitter fries cannot be fixed; discard the darkest ones and fry for a shorter time next time. Put fries that have gone limp back into hot oil or a hot oven for 1–2 minutes.