Puzzling Parchment Paper Potato Patterns

[DaveD]

I made a side dish of roasted Yukon Gold taters to go with dinner last night. After scrubbing them clean, I cut them up into chunks, tossed with EVOO, and seasoned with salt, pepper, and Rancho Gordo's "Sabor Vaquero" blend (dried chiles, garlic, cumin, oregano, salt). Laid them out on parchment paper and roasted in a 425F/220C oven for 40 minutes, flipping halfway through. They came out great, really tasty and creamy, although lacking the crispy exteriors I would have liked.

Prepped for the oven:

At the halfway point:

Finished.


After serving, we noticed the rather striking uniformity in the patterns left behind on the parchment paper:


Those lineations pretty much line up from one spot to the next, regardless of the (random) orientation of the tater chunks.

We think we have it figured out, but I thought I'd pose it as a brain teaser here, see what y'all come up with for explanations! I recommend clicking on the image to embiggen so that you can see all the details...

[Panhead John]

Looks good Dave! I don’t have an explanation for your question but…….A few years ago I saw an online article about this predicament [non crispy exteriors]. I always made mine the same as you did. The article said to boil your whole potatoes to almost done, then cut them into your preferred pieces and bake as usual. I tried it and man, I’ve been making my best oven baked potatoe wedges ever since. Always crispy skin/exterior.

https://www.southyourmouth.com/2021/05/perfect-roasted-potato-wedges.html

Heres the important stuff in the article…..
WHY DO YOU BOIL POTATOES FIRST WHEN MAKING ROASTED OR BAKED POTATO WEDGES?


One reason is taste. When we boil the potatoes in salted water, they absorb the salt which flavors them from the inside out.

Boiling the potatoes first ensures creamy, fluffy, potato-flavor-packed insides with crispier, crunchier outsides.

Boiling the potatoes also helps create a thin crust from the starchy mash that will coat the wedges (see those little bubbled up areas? that’s potato gold!). If you really love that, add a teaspoon of baking soda when boiling the potatoes as it will cause the starch to break down more quickly

[N227GB]

The marks seem to show the paper's manufacturing process. The best analogy I can think of is machining marks on a piece of flat aluminum if that makes sense.

[Andrrr]

It's the parchment paper. I notice it wrinkles like that when we make keto crackers. Why? I don't know, but I'd have to imagine it has something to do with moisture trapped between the paper and whatever you're cooking.

[RonB]

If you were south of the equator, the would run in the opposite direction.

[MBMorgan]

Clearly slickensides resulting from slight lateral potato movement due to cooking during the nearby earthquake in New York yesterday. Please remember to cite me in your paper ...

[Troutman]

So professor, if you’re hypothesis is that the indication refers to a slickensided failure of the hydrous aluminium phyllosilicates, then I would heartily concur 🤔🤔

[DaveD]

MBMorgan I like the way you think! Very gneiss.

[DaveD]

Sure as I'm sitting here, I never in my wildest expected to hear anyone drop the term "phyllosilicates" in this forum. Bless you, Troutman !

[Troutman]

I do mine an air fryer all the time and they come out super crispy Cook them at 400°F for about 25 minutes.

[DaveD]

N227GB and Andrrr got it, I'm sure it is something to do with how the paper is made. The lineations are also parallel to the faint grid printed on the paper, which you can just see when viewing the pic at full size. That can't be a coincidence...

In terms of crispy taters, I've got a great recipe that I found from Jess Pryles, which we refer to now as Them Taters. Chunks of peeled tater get par-boiled until the outer few mm start to soften, then tossed in a colander to rough up the surface, then roasted in the oven (preferably in beef tallow). Perfect, crispy outsides and creamy insides. We have those pretty often though, so I was trying a different recipe to see how we liked it on these here.

[FireMan]

Looks great! Just a couple of too many P’s in the title though. Got worn out at potato. 🕶

[Jerod Broussard]

Still working on it......

[Oak Smoke]

Those are the lines that are on the baking sheet that was below the potatoes. Watson.

[DaveD]

But, my dear Holmes, there are no lines on the baking sheet... just a plain aluminum pan, with a very irregular surface from years of use.

[fzxdoc]

Adding a little baking soda to the water as you par-boil the potatoes, then roughing them up a bit in the colander as they drain before putting on the other toppings before baking will be a game changer.

Here's Kenji's take in his "Best roast potatoes ever" recipe:

Why It Works
Large chunks of potato maximize the contrast between exterior and interior.

• Parboiling the potatoes in alkaline water breaks down their surfaces, creating tons of starchy slurry for added surface area and crunch.
• Offering you the choice of oil, duck fat, goose fat, or beef fat means you can get whichever flavor you want.
• Infusing the oil or fat with garlic and herbs gives the potato crust extra flavor.

Kathryn

[barelfly]

Roughing them up was what I thought of as well, gaining that extra surface texture.

[Old Glory]

This is how I make them.

[DaveD]

This is very similar to the Jess Pryles approach I've used often - roughing up the parboiled layer is truly the gamechanger. Found I was getting into a bit of a tater rut doing it that way every time, so I was changing it up on purpose this time...