A few weeks back, we came across a hotline question that rocked our worlds:
“I am wondering: Is it really necessary to prick potatoes and sweet potatoes before baking them? In what context? Or is this just a cooking myth from days of yore?”
Our team Slack channel lit up like a Christmas tree. Between two recipe developers and three food editors with more than 100 years of collective cooking experience/obsession, we had zero hard answers—and zero incidents of potato explosion among us. So we turned to science.
Initially, we thought that an experiment could provide the answer. We scoured the produce bins for two white potatoes and two sweet potatoes of equal sizes. Into the oven they went, at 425° F, one of each variety pricked all around with the tines of a fork about an inch and a half deep. The sweet potatoes took about 45 minutes to fully cook through, while the Russets (aka Idaho potatoes) took a little over an hour.
The results of this "experiment" were largely underwhelming—no explosions occurred, and all four potatoes had a very similar internal texture. (The only real difference was the darkening of the flesh of the Russet I'd pricked, due to an oxidizing reaction that occurred when I let it sit out for a half hour before baking.) If anything, the pricked Russet potato had a slightly less soft center, which I think would've been mitigated by another five minutes in the oven.
With a sample size of four, we're not surprised that we didn't get conclusive information. But greater experiments, like the one Cook's Illustrated ran in its journey to the perfect baked potato, have yielded equally blurry answers:
Everyone knows that you have to prick potatoes before baking them so steam doesn’t build up inside and cause them to explode. Well, we baked 40 potatoes without doing this, and not one exploded. But since it takes so little effort, here’s one time we’ll err on the side of caution. It could be the 41st one that explodes.Cook's Illustrated
Unsatisfied with the results of our great potato bake-off, we called in the big guns, straight from potato country.
"Yes, it’s good to prick them," says Brennan Smith, a faculty member of the School of Food Science at University of Idaho. "It pokes holes in the skin, which allows steam to escape. Otherwise, they could explode—it doesn’t happen all the time, but it happens every once in a while. The potato is full of water it’s trying to turn to steam, or water vapor. The skin acts like a pressure vessel. If you don’t let the steam escape, it builds up pressure—if it gets to a certain point of pressure from the water trying to become water vapor, it can pop the skin."
According to Smith, this is more likely to happen in a microwave than in an oven, because the rate of heating is faster, and there's less time for the pressure to escape naturally.
There's no material difference, he says, when it comes to the type of potato—sweet, or one of the white- or yellow-fleshed varieties. Both should get pricked.
And the tiny ones, like fingerlings or new potatoes?
"They have more surface area—more than likely, they’ll be less prone to explode," Smith tells me.
So, will a baked potato explode if you don't prick it? The answer's a firm "maybe." Or more accurately, "sometimes." If you don't want to risk it, just prick it.
Which kitchen theories would you like to see debunked? Let us know in the comments!