Sweet Potato Fries – The Quest for Crispy (FAK Friday)

Perfect Sweet Potato Fries
Healthy Never Tasted So Good

I have a confession to make. I have never successfully made crispy sweet potato fries. Until now.

Every once and a while I come across a simple culinary task that renders me completely inept. I know plenty of people who turn out perfectly crisp sweet potato fries every time, with no fuss. Somehow, that’s not the case for me. Instead they turn out limp, soggy, or a little burnt in an over-zealous attempt to crank the heat and get them crispy once and for all. And I know I’m not the only one.

A quick search turns up nearly a dozen different methods suggesting how to make perfect fries. I agree with many of them, in principal, and yet few have proved to be at all helpful. Finally I decided it was time I set out once and for all to solve this problem – for myself, and hopefully everyone else in my situation.

It’s FAK Friday (Feeding my Appetite for Knowledge) and this week my diet has consisted primarily of sweet potatoes, as I attempted again and again to produce the perfect fry. Now that I’ve done my share of tests, I’m sharing my findings in the hope that my experiences may shed some light for anyone else struggling with this simple spud.


The Quest for Crispy
Sweet Potatoes
Sweet potatoes – not yams

First off, let’s get something straight. Sweet potatoes are not the same as yams. Here in the US, they are frequently (miss)labeled as yams – but just because the label says it doesn’t make it so. In fact, real yams, native to Africa and Asia, are of a completely different genus than sweet potatoes, and have an almost black outer skin similar to the bark of a tree.
While we’re at it, did you know that sweet potatoes aren’t even related to regular potatoes? They’re from two different families entirely, and while there are hundreds of varieties of potatoes, the sweet potato isn’t one of them. While regular potatoes find themselves sharing genes with tomatoes, peppers, and eggplants, sweet potatoes are more closely related to morning glories, a type of flowering vine. In other parts of the world sweet potatoes go by a range of different names, one of which being “batata”, a word which later morphed into the already well-known “potato”. Thus was born, the sweet potato. Who knew?

Okay, enough with the history lesson. On to the fries!

Crispy Sweet Potato Fries
Let me start by saying you can make sweet potato fries by deep frying them, just like regular french fries… but for this experiment, I’m going to focus on how to get them crispy in the oven. Not only are oven-baked fries significantly healthier, but who wants to burn a half gallon of oil just for a snack? Not me, that’s who.
Just to clarify, when I say crispy, I mean similar in texture to a regular french fry – a bit of crisp to the outside, with a soft interior. 
In order to figure out the best method, I went out and bought a bunch of sweet potatoes. I used a mix of both Garnet and Jewel, in case the variety made a difference. (It didn’t, though I found I liked the Garnet a bit better in flavor.) I researched every tip, trick, technique, and recipe I could find. Then I set to work testing each one. I tried them all with a range of different oven temperatures, as well as different thickness of potato, to see what would work the best.

Fry Test - How To Make Perfect Sweet Potato Fries
                       Mushy Inside                                   Burnt                                     Just About Right
I did a total of about seventeen tests. I won’t burden you with a detailed account of each one, but here are some of the highlights.

I started by doing what most people do – slice a potato, drizzle with olive oil, sprinkle with salt, and bake. Easy peasy, as it should be. I tried many variations on this, lining my tray with parchment or foil, using more or less oil, cutting the fries thicker/thinner, baking at different temperatures… I learned a lot about what worked and what didn’t, but I still wasn’t getting a crispy exterior. I even tried one method which suggested turning on the broiler for the final moments of baking, which turned my fries completely black (see the middle image above).

Next I tried a few different recipes which called for soaking the fries in cool water for awhile, then rinsing and drying them before baking. The idea behind this method is that soaking will draw out some of the starches from the potato. Starch holds on to moisture, so less starch means a less soggy fry, right? It made plenty of sense to me, but my sweet potatoes didn’t agree. I found zero difference in the crispiness of the fries, and am pretty sure the insides were actually a little soggier than before. Almost as if they’d been sitting in water for a long period of time… strange.

Next I moved on to coatings. There are two main “techniques” out there for coating the fries. The first is to toss the fries in a lightly beaten egg white before baking, the theory being that the egg white will do the crisping, and act as a shell on the outside of the fry. I don’t like this method for a few reasons: one, I don’t particularly want to whip an egg white just to make some fries; two, it takes a perfectly good treat that can be enjoyed by anyone and makes it off-limits to those on diets or with egg allergies; and three, it simply doesn’t work that well. The egg white does become crisp, but it ends up tasting more like over-cooked scrambled eggs with a soggy fry in the center. Not the desired result, in my opinion.

The second “coating” method is to dredge the fries very lightly in cornstarch. This goes by similar logic to the egg white version, but unlike the egg white the cornstarch actually clings to the fries and helps absorb some of the moisture that comes out of them. I played around with this technique for quite a while, trying to get just the right amount of cornstarch (too much means gummy, yucky fries), before finally getting it to work the way it’s supposed to. While the cornstarch did create a somewhat pleasant texture, I found it left the fries with an odd flavor similar to that of raw flour, and a very greasy feel. Perhaps with heavy enough seasoning, this would be acceptable. (I should note, making a batter of cornstarch is a great method for getting extra crunch on deep-fried fries, but I found it didn’t work nearly as well in the oven.)

Sweet Potato Fries - tips and tricks
Just when I thought I had run out of ideas, it occurred to me that the problem might lie not in the technique I used, but the equipment. Was it possible my oven was the issue? Surely a convection oven would do a better job, but that couldn’t be the only answer. What about water vapor, which can sometimes be an issue in gas ovens? That couldn’t be it, because mine is electric. Still, I couldn’t help but wonder…

So I called up a friend of mine – one of those lucky people who make sweet potato fries all the time with no problems – and asked if I could borrow his kitchen. Well, he did me one better, and not only let me use his kitchen but walked me through exactly how he did things.

And you know what? He did them exactly the same way I (normally) do. Cut the fries, toss ’em in oil, and bake. I measured the temperature of his oven, cut the fries as I had been, and baked them exactly the same way… and low and behold, they came out much more french-fry-like than the ones I had made before.

The biggest difference between the batch at my friend’s house and the batch at my house? The baking sheet. My baking sheets are rather thin, and have a black non-stick coating. His trays were much heavier-bottomed, and had no such coating. This created a much more even heat, and a much crisper caramelization on the outside of the fries.

Sweet Potato Fries - The Quest For Crispy
I wish there were some grander finale to this tale than a baking sheet, but sure enough, those fries were perfect. I made batch after batch, and each time was the same. So what about you – do you have trouble getting crispy fries, and if so, what type of tray do you bake them on? I’d love to know if my theory is right!

Along my little journey, I learned a lot about what did and did not work. I know I’ve been a little round-about in getting to it, but here are my top tips for making perfect sweet potato fries:

How To Make Perfect Sweet Potato Fries
Tips, Tricks, and Techniques
  1. Preheat the oven –  I found my fries baked perfectly between 425f. – 450f.. This temperature may vary depending on your oven, and also the pans you bake your fries on. I found with a black, non-stick coated pan, 425f. was plenty hot enough. With a thicker, non-coated pan, 450f. was the right temperature. Use an oven thermometer to make sure the temperature is correct – it isn’t uncommon for an oven to be as much as 30-40 degrees off.
  2. Use the right baking sheet – I found that a heavy-bottomed baking sheet with a shinier (not coated) surface did the best job making crispy fries. If you’re using a flimsier tray, try reducing the oven temperature a little and increasing the bake time.
  3. Cut the potatoes into evenly sized fries – this way they cook at an even rate. I found that the best size was just under half an inch thick. Much thicker and they didn’t get crisp, much thinner and they burned. Peeling the potato first is up to you, but keep in mind there’s a lot of good flavor (not to mention nutrients) in the skin. I also found the skin gave a better crunch to the fries. Just be sure to wash your potato and dry it well if you plan to leave the skin on.
  4. Use enough oil – one of the main reasons to make fries in the oven instead of the fryer is because they’re so much healthier, but that doesn’t mean you can avoid the oil all together. It does mean you can use healthier oil, though, like olive oil or coconut oil. Once the fries are cut, toss them in 1-2 TBSP to coat. Be sure to grease the pan, too, to keep them from sticking (or you could use parchment paper – I found it didn’t make much difference in terms of crispiness). 
  5. Seasoning – After coating the fries in oil is the perfect time to season them, because the oil will help it stick. A pinch of salt is a must, but the flavor possibilities are truly endless. If you’re in the mood for something spicy, try a bit of chili powder or cayenne pepper. Want something sweet? A dash of cinnamon goes a long way. Some of my favorites are cumin and coriander, rosemary or sage, curry powder, paprika, garlic powder, and even nutmeg. Use whatever flavors call to you!
  6. Spread the fries into an even layer – space the fries out on the baking sheet with a bit of room  between each one. If the fries are crowding the pan they’ll steam themselves and become soggy instead of crispy. If you’re making a lot of fries, use two trays, or do them in batches. (Don’t put more than two trays in the oven at once, or else the amount of steam may cause them to get soggy.)
  7. Bake in the upper 1/3rd of the oven – you want the oven to be hot, but if the fries are too close to the heating element (at the bottom of most ovens) they may get burnt. I found keeping them on the top, or second to top rack, helped tremendously.
  8.  Flip the fries every 10-15 minutes – this will help them cook evenly, and also ensure they get caramelized all ’round. The side of each fry touching the pan will have the most browning, while the side on top will have a chance to dry out and release steam. Both are important! If you’re using two trays, be sure to swap their positions in the oven at this time, too. (I found my fries took about 30-35 minutes, though your time may vary depending on your oven, baking sheet, and the thickness of your fries.)
  9. If you’re using a gas oven – depending on your oven, you may find it necessary to crack the door ever few minutes, just for a moment, to let some of the steam out. Don’t leave the door open for a long period of time, though, because you don’t want the heat to dissipate!
  10. Once the fries are out of the oven – move them immediately to a cooling rack so that air can circulate around them. Keep them spaced out in a single layer (not piled on top of each other) so that they’ll hold on to the crispy exterior.
  11. Devour immediately – it doesn’t need to be said, but fries are best eaten fresh. Fresh, and before anyone else has a chance to get to them. 
So there you have it… no fancy tricks, just a little practice and the right equipment. Do you have any tips for making fries? Have you struggled with them in the past, and if so, was any of this helpful to you? Oh, and what’s your favorite seasoning to use? I’d love to know in the comments below!

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23 Responses to Sweet Potato Fries – The Quest for Crispy (FAK Friday)

  1. From Valeries Kitchen April 6, 2013 at 2:50 am #

    I’m laughing as I read this because I too have always struggled with getting sweet potatoes to do what regular potatoes do in the oven. One of my boys was determined to make this work and he has found that using aluminum foil works for him so I totally think you’re on to something with the baking sheet thing. It does make a huge difference. Those broken in, old, black baking sheets result in black sweet potato fries. Love this post Willow. I’m seeing sweet potato fries in my future :)

    • Willow April 6, 2013 at 2:57 am #

      Thanks, Valerie! I think the thickness of the baking sheet made a big difference. Just a heavier metal to distribute the heat better. And the black non-stick coating just didn’t reflect the heat enough to get them crispy (only burnt). Hope some of my trial and error helps you!

    • Anonymous April 9, 2013 at 1:53 am #

      Cast iron makes a very crispy sweet potato fry and roasted potatoes are amazing from a cast iron pan. :)

    • Willow April 9, 2013 at 2:43 pm #

      You know, I never thought to try it in my cast iron… that’s a great idea, thanks for the tip!

  2. Hari Chandana April 6, 2013 at 4:20 am #

    Looks absolutely perfect !!

  3. Foodie Stuntman April 7, 2013 at 5:06 pm #

    Fascinating…Thank you for this series, Willow. I’ve learned a lot from it.

    • Willow April 9, 2013 at 2:42 pm #

      Thanks, glad to be helpful!

  4. Elly McCausland April 9, 2013 at 7:39 am #

    I really enjoyed this post! I too have been plagued by non-crispy sweet potato fries (I call them wedges though!) and this was fascinating – I’d never have thought of half the techniques you tried! Going to check my baking trays now…

    • Willow April 9, 2013 at 2:46 pm #

      Another thing I found helpful was cutting them a little thinner than I used to – I don’t know how thick your wedges are, but when I made thicker ones they never really crisped up.

  5. multiplesclerosisvent April 9, 2013 at 10:41 am #

    I have used a screen type pan so they cook evenly and I do not have to flip them, takes half the time to cook also!

    • Willow April 9, 2013 at 2:44 pm #

      Very interesting – I’ve never had the opportunity to use one of those screen pans before. Good to know they work well!

  6. Sunday Morning Banana Pancakes April 11, 2013 at 6:41 pm #

    The baking sheet makes complete sense! Like you I have tried the soaking method and cornstarch method- both fails…and I can’t tell you how many times I have ended up with burnt fries just like your middle pic from cranking the heat up – I just bought a new heavy gauge baking pan, I can’t wait to try this method to see if it has been the pan all along…I use a stoneware rimmed baking pan and that may be the culprit!

    • Willow April 11, 2013 at 6:45 pm #

      You’ll have to let me know if the new pan makes a difference! I’m looking into getting a new baking sheet soon, as well, but haven’t decided what I want yet. Good luck with your next batch of fries!

  7. shannon weber April 14, 2013 at 12:12 pm #

    this is like, Tim’s dream post, because he loves sweet potato fries but no, can never get them crispy; ours always end up like the mushy version you pictured. SEVENTEEN TESTS! girl, i admire your work. I would say i can’t believe that after all those experiments it was simply a matter of what type of baking sheet to use, but i CAN believe it: baking sheets are critical to the success or failure of many things, right? I have several types here, and i use certain ones for certain things, because i know which will work best (and it really does make a difference in cookies, roasting vegetables, etc). i’ve ditched all my old crappy thin sheets by now because they weren’t doing me any good at all.

    • Willow April 15, 2013 at 2:34 pm #

      So true! I have one heavier sheet, but it’s still non-stick coated (which is great for some things, but not for others). Looking into getting some new ones soon. :)

  8. Mikel Gainza January 19, 2014 at 1:30 pm #

    Great article, I have failed a few times trying to get them crispy too…

    Did you notice any differences between the oven shelves? I read that heat concentrates more at the top shelf, which makes it more suitable for crispiness…

    Have you tried frying + oven ? Like you do with meat . you sear it first and then you move it to the oven. Cast iron pans could be great for this


    • Willow Arlen January 21, 2014 at 12:31 pm #

      Thanks Mikel!

      I didn’t notice much difference with where the shelves were. In my oven the heating element is at the bottom, and if the fries were too close to it I found they burned more easily. I noticed no difference between the upper and middle shelves.

      I’ve never tried pan frying them first, but another commenter mentioned that they use a cast iron skillet and found it works well. I can’t speak for it myself, but it sounds like a good idea to me!

    • Mikel Gainza February 3, 2014 at 10:51 am #

      This comment has been removed by the author.

    • Willow Arlen February 3, 2014 at 12:36 pm #

      No, it wasn’t a grill tray, just a solid baking sheet. I’ve since purchased a better baking sheet for myself (this one, on Amazon: http://www.amazon.com/gp/product/B000G0KJG4/ref=oh_details_o09_s01_i02?ie=UTF8&psc=1 ) and find that it does quite well (much better than my old, nonstick coated one). Once they are out of the oven, it does help to transfer them immediately to a cooling rack, which is what that last picture is of.

      I’m sorry to hear the cast iron didn’t make a difference — it sounded like such a good idea. Thanks for stopping back to let me know, I really appreciate it!

    • Mikel Gainza February 3, 2014 at 12:37 pm #

      (I am just correcting typos… :-)

      Just to let you know, that last night I tried using a cast iron pan to cook the sweet potatoes, without frying them first.
      I just place the cast iron pan straight to the oven.

      I did 2 batches, and found no difference at all compared to a coated oven baking tray.

      Quick question, the tray that you used to make them perfect in your friend’s house, was it an Oven Grill Tray? The last pic of your article?


  9. Mikel Gainza February 3, 2014 at 12:40 pm #

    oopps… sorry… i deleted and re-published my last post… and in the meantime you replied…

    sorry for confusing the thread…

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