Why it's (almost) impossible to make Crispy Sweet Potato Fries in the oven.

there's many a recipe out there touting crispy baked sweet potato fries but chances are if you've actually tried one or many versions like i did you've ended up with a thick orange stick that is browned and it may even have some crispy edges but it still unquestionably has the sweet potato sog so let's stop kidding ourselves due to the carbohydrate makeup of sweet potatoes compared to a regular potato like a russet it's basically impossible to make crispy sweet potato fries in the oven or is it hey everyone i'm ethan a home cooking nerd who likes to find better ways to cook and share them with all of you today is all about the sweet potato specifically we'll be trying to make a crispy sweet potato frie that is baked in the oven before i actually get to the science behind the techniques and the recipe let's first go over what i'm looking for in the ideal final product you see i want a sweet potato fry with a nice golden orange and brown appearance that has a balance between a crisp exterior and a fluffy interior with that nice potato bite i also want a long and thin french fry that holds together no thick wedges or falling apart thin ones for me lastly i want all of this while minimizing the amount of oil used which is why i'll specifically be focusing on low oil methods as i assume most of us who are baking sweet potato fries are probably doing so for a lower calorie option compared to deep fried or oven fried methods that use quite a bit of oil so let's answer the question why don't sweet potato fries crisp up like regular potato fries this one is simple it all comes down to starch versus sugar and as we've touched on multiple times on the channel starches in things like french fries or bagels hydrate and then gel on the surface which is what gives us a crisp crust sugar on the other hand gets black and burnt for potato called sweet it's an easy bet that has more sugar than your typical potato specifically from the usda's food database 100 grams of a raw russet potato has 18 grams of carbs which is made up of 16 grams of starch 1.3 grams of fiber and just .7 grams of sugar compare that to 100 grams of raw sweet potato which has 20 grams of carbs and is made up of 13 grams of starch 3 grams of fiber and 4 grams of sugar now you may be thinking does roughly 3 grams of sugar really make that big of a difference well if the sweet potatoes stayed at those levels of sugar and starch while cooking it probably wouldn't but they don't stay at those levels while cooking because of amylase where have we heard that before hoagie rolls the amylase enzyme was present in the diastatic malt powder that we added to the dough the amylase converts starches in the flour into sugar providing the yeast with more to feed on and this enzyme is also in sweet potatoes and does the exact same thing this is why if you munch on a raw sweet potato it's not exactly sweet but if you compare that to one that's been roasted the sweetness is off the charts specifically from on food and cooking by harold mcgee we learned that amylase attacks the starch and breaks it down to maltose as sugar when cooked this starts to happen at 135 degrees fahrenheit and it stops around 170 degrees fahrenheit when the enzyme is killed harold also notes that in certain varieties of sweet potatoes up to 75 percent of the starch can be turned to sugar let's take another look at those numbers for a sweet potato with 75 percent of the starches turned to sugar we are now looking at just 4.25 grams of starch 3 grams of fiber and 13.75 grams of sugar that lack of starch is what makes it basically impossible to achieve crispness regardless of if you are deep frying or cooking in the oven but you've probably had crispy sweet potato fries out at a restaurant so how is it possible once again this is simple we need more starch there's two options that we can try here one is limiting the amount of starch that gets turned to sugar or two is add starch back in remember how i said the amylase stops working at above 170 degrees fahrenheit well if we put the sweet potato fries in boiling water which is energy dense it will spend less time in that 135 to 170 range compared to slow roasting it in the oven meaning less starch is turned to sugar i tested two fries one was baked without boiling and one was baked with boiling and as we can see the one that was boiled does hold its structure better and is slightly crispy but it's still not what we're looking for this is where adding starch comes to the rescue and makes a big difference as dan souza from america's test kitchen explains adding hot potatoes to a cornstarch slurry will hydrate the starches and gel on the exterior of the sweet potato when fried in hot oil this creates a delectably crisp crust and the slurry is key as just adding a sprinkle of cornstarch on the potatoes doesn't allow those starches to hydrate and gel on the surface which is what we are after now here is a crunch test for one that has boiled in a cornstarch slurry and then fried in peanut oil i also would like to point out that i will not be boiling my fries in baking soda like dan did to weaken the pectin but instead i will be boiling with a splash of vinegar to strengthen the pectin because i want a thin french fry that holds together when a thin french fry is boiled in baking soda it leads to this [Music] so now that we know how to make crispy deep fried sweet potato fries is it possible to get them crispy in the oven absolutely for my oven this is the method that i found works best for a low oil option i place a wire rack over a baking sheet and evenly space out the slurried sweet potatoes to promote air flow and even cooking then for my oil choice it's peanut as you may remember from the oven fries recipe it crisps more efficiently due to the extra saturated fat and i just give a very light drizzle over the top of fries and for the whole sheet i use just 15 grams of oil and actually that's counting the oil that dripped down so it's probably more like 10 grams and i was able to get them plenty crispy with just 15 grams of oil total so it's definitely a low caloric option now if you do have a convection setting on your oven or an airfryer i would absolutely use those as they are more efficient at heat transfer than my basic oven due to the air movement so you likely need a little less time when you make yours that being said let's quickly walk through the step-by-step recipe and then do a little taste test to start set a large pot of water on medium-high heat to bring to a boil meanwhile you can peel the sweet potatoes and slice them into roughly 1 3 inch sheets then into roughly 1 3 inch thick fries once those are all cut up preheat the oven to 475 degrees fahrenheit once the water has boiled add a large three finger pinch of salt and a nice splash of vinegar stirring to dissolve the salt then add in the sweet potato fries to the boiling water and set a timer for six minutes and again the vinegar is used to slow down the breakdown of pectin so the fries do not fall apart easily while those are boiling add 50 grams of corn starch and 80 grams of cold water to a bowl stir that together until it is completely combined with no clumps remaining when the timer is up drain the fries into a colander and then immediately add them to the corn starch slurry and toss it until it starts to thicken and stick to the fries if you need a little more cornstarch feel free to add it and feel free to rough up the edges of the french fries with your fork if you would like the mixture should lightly coat the fries once coated set a wire rack over top of a baking sheet and move the fries to the wire rack evenly spacing them so none of them are touching then using a squirt bottle or spoon just drizzle the peanut oil over the fries trying to get an even coating over each one then add the sweet potatoes to the oven and set a timer for 15 minutes pull the baking sheet out and flip over the fries with a spatula and at this point you should be able to notice some blistering on the outside but the fries won't be overly crisp if they do look a little bit dry feel free to drizzle over more peanut oil but add them back to the oven and bake for another 10 to 15 minutes at this point they should be slightly brown and crispy though it could take longer depending on the size of the fry how crowded the pan is or the oil used if they aren't crispy just let them go a little bit longer slide the baked fries into a metal bowl and immediately add a pinch of salt and a couple cranks of fresh ground pepper then just toss the fries to absorb the seasoning and you can feel free to add anything like spices or fresh herbs if you would like at this stage finally turn them out to a serving bowl and serve with whatever dipping sauces you would like and ladies and gents this is the sweet potato fry i will be using from now on when i want to do them in the oven and i couldn't be more floored with the results and initially i did think this was going to be a pretty easy video to film i had like one or two key methods that i wanted to try but then there were so many nuances that i just wasn't getting the final product and i think i ended up doing like seven or eight different batches between the oven temperature and times my oven rack setup with the baking sheet versus down low on no baking sheet or on no wire rack and then when did how to do the cornstarch whether it was better in slurry form or just a sprinkle and eventually i got here and i couldn't be more happy and i mean the results speak for themselves like the crunch and sure some of these bigger ones aren't going to be like super crispy but it's miles better than any other method or recipe that i have tried for baked sweet potato fries and this is what i love so much about cooking because there wasn't a recipe that was making the product that i wanted to make i wanted thin french fries i wanted them with minimal oil but i still wanted them crunchy and you know through the science of cooking and learning about sweet potatoes which i didn't know about the amylase i didn't know about how it can convert it into sugars and how low the starch content is actually when they're baked so all that was really eye opening for me and hopefully it was for you too because it really does affect how and what you're trying to do with your final product which for me is like the coolest part about cooking is learning those basic techniques and science concepts and then putting them into practice to come up with the product that you want and this was mine so hopefully you guys enjoyed the video i'll have the link to the recipe up on my website and down in the description below if you guys want to check it out and if you do want to make these deep fried they're so good deep fried literally you just pop them in 350 degree peanut oil for 50 seconds let them dry off then pop them in for like three and a half minutes and you'll have the best like sweet potato fries ever they're better than restaurant so hopefully you guys enjoyed the video i'll catch you in the next one peace you

Channel: Ethan Chlebowski

Views: 929,517

Rating: 4.9369931 out of 5

Keywords: Ethan Chlebowski, sweet potato fries, crispy baked sweet potato fries, baked sweet potato fries, sweet potato, sweet potato fries in the oven, crispy sweet potato fries oven, crispy sweet potato fries air fryer, oven fries, baked sweet potato fries recipe, recipe

Id: ZCXX7Dea6eA

Length: 11min 3sec (663 seconds)

Published: Thu Aug 06 2020

Reddit Comments

[u/spakattak]

Great video, longer than it needs to be but I learnt something.

[u/Cg407]

Trying this tomorrow. I’ll let you know how it goes

Edit: a word

[u/paoper]

I really liked how he researched and explained what causes the difficulty with making crispy sweet potato fries, and how it can be done. It is rare that you actually learn something from a cooking video, but I would want all the cooking videos to be like this. Because this way, I can actually know how to apply this technique in other situations for example. Cheers!

[u/DeHofnar]

Thanks for sharing! Great stuff, gonna try this sometime.

[u/adreamofhodor]

That "subscribe" button that's in the bottom right is so obnoxious.

[u/KL1P1]

And here is the normal potatoes oven baked episode.
https://youtu.be/MvnYBCDaEKU

[u/clarkkentshair]

Isn't the premise completely bunk that deep frying is less healthy just because it "uses a lot of oil"?

Drizzling on oil and baking that, such that you will eat all that oil is close to the same thing as deep frying: because you're not soaking it in oil when you deep fry, but hot oil only has some residuals on the food when deep fried properly. At proper deep frying temperatures, steam escaping from deep fried food keeps pushing oil mostly out.