Oh, The Perfect French Fry. Golden and crispy on the outside, tender and fluffy on the inside. One of life’s simple pleasures.

Comprised of just potatoes and fat, you’d think great fries would be easy to execute…so why are there so many sad, floppy, medicore fries out there in the world?

This was a question our students tackled in their recipe development workshop with Kenji Lopez-Alt, managing culinary director of Serious Eats and mastermind behind The Food Lab. Leaning on Kenji’s test kitchen background and angle on food science, the class deconstructed the different factors at play, came up with hypotheses, and tested away. And yes, there was a lot of blind French fry tasting involved! For science.

Potato Type

Not all potatoes are created equal. Team Potato had a singular focus on how different types of potatoes (and their varying levels of starch) resulted in different caliber fries.

The Variable: Russet / Yukon Gold / Red-Skinned Potatoes

The Constant: All fries were cut to the same size, rinsed, and double fried at the same temp for the same amount of time.

The Winner: Yukon Golds yielded fries that were crispiest on the outside, and fluffiest on the inside.

Surface Starch

So we now know that varying levels of starch in the potato themselves make a difference, but what about playing with the amount of surface starch? Team Surface Starch wondered whether rinsing or soaking the starch out of the potatoes would yield a more even fry.

The Variable: No Rinse / Rinse / Soak / Multiple Soak

The Constant: All fries were cut to the same size, and double fried at the same temp for the same amount of time.

The Winner: Multiple Soak — potatoes that were soaked in water that had been changed out twice until the water ran clear (removing the most amount of surface starch) resulted in fries with a more even golden color. In comparison, the No Rinse and Rinse fries browned too quickly.

Fat Type

All fries need to be…well, fried. The question is, fried in what kind of fat? This team examined three common types of frying oil, with varying levels of saturated fat to test ultimate crispiness. (More on the difference between saturated and unsaturated fats here if you want to get really sciencey).

The Variable (with corresponding grams of saturated fat per tablespoon): Canola Oil (1 g) / Peanut Oil (2.5 g) / Vegetable Shortening (3 g)

The Constant: All fries were cut to the same size, rinsed, and double fried at the same temp for the same amount of time.

The Winner: Shortening won in the crispy department, proving the hypothesis that the more saturated the fat, the crispier the fry.

Double Cooking Method

It was a given that a double fry would be better than single fry, but we wondered, would the method of that first par-cook make a difference?

The Variable: Blanch in Oil / Baked / Boiled in Water

The Constant: All fries were cut to the same size, rinsed, and cooked to the same doneness all the way through before frying at the same temp for the same amount of time.

The Winner: Blanch in Oil — the classic double fry, double oil combo gave us a consistently crispier fry, while the Baked version resulted in super disappointing hollow fries (nothing but air inside!), and Boiled ones were utterly lacking in the crispy department.

So there you have it! After a hard day’s work at the fryer, our perfect French fry was achieved with:

  • Yukon Gold Potatoes
  • Multiple Soak Method
  • Vegetable Shortening
  • Double Fry

Whether or not our students pursue a career in a test kitchen, this exercise in problem solving and recipe development is one that we think will prove useful in any kitchen. And, if there are some perfect fries along the way, we’re guessing there will be no complaints.


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at SF Cooking School.

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