Recipes engineered for perfection—what exactly does that mean? We take you inside Cook’s Illustrated’s science experiments.
THE BACKSTORY
We normally store sweet potatoes away from the light at a cool room temperature. But we couldn’t help wondering if that was really the best way. We set out to see if storing them in the refrigerator would make them last longer, or if it would do more harm than good.
THE EXPERIMENT
We bought a case of sweet potatoes and divided it into two batches. We kept each batch for four weeks, one at room temperature (in a cabinet, between 55 and 65 degrees) and one in the refrigerator (between 34 and 38 degrees). When the time was up, we took the potatoes out of the refrigerator, allowed them to come to room temperature, then cut up both batches and roasted them in a 400-degree oven for 45 minutes. We tasted them blindly to see if we could tell the difference between the refrigerated and non-refrigerated potatoes.
While the room temperature potatoes were creamy and soft all the way through, the refrigerated ones remained hard at the center. To see if another cooking method would produce different results, we repeated the test, this time slicing both batches and boiling them for 40 minutes. The outcome was the same: the refrigerated potatoes had tough centers.
Why does refrigerating sweet potatoes make them tough? It turns out that the vegetable contains an enzyme called demethylase. The enzyme normally lies dormant, but if the potato is subjected to temperatures below 55 degrees for a prolonged period, it kicks into gear. The enzyme then weakens the pectin that holds the potatoes’ cells together, causing the pectin to bind with the calcium ions that are also present. The calcium ends up strengthening the cells’ walls so that they can’t be broken down—even by prolonged cooking.
The bottom line? If you keep your sweet potatoes in the fridge, it’ll be a tough situation to recover from. For the best possible spuds, keep them in a cool, dark place.
MAKE IT NOW: Our recipe for Roasted Sweet Potatoes is free through February 28, 2013.
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really love this tip. also — I wonder if this is why some supermarket bought sweet potatoes are rock hard no matter how long you cook them. when’s optimal sweet potato season?
My tip for storing sweet potatoes is to cook them in boiling water. Peel, slice, and store in freezer. Great idea for a quick meal. Take out what you need and put in shallow pan. Sprinkle with cinnamon and maple syrup.
It takes quite a bit longer than 45 minutes to bake a sweet potato. I don’t time it, because it depends on how large the potato is. I just squeeze with a hot pad to see if it feels soft.
~ Southern Girl
Made sweet potato spicy salmon cakes with a sweet potato I stored in the cabinet. When I cooked the potato, it was nice and fluffy!
I grew my own sweet potatoes last summer, and though the subterranean rodents enjoyed a fair share – I finished the last of my September harvest this Sunday (early March)! Though some of the smallest ones were a little soft on the outside and a little woody inside, they boiled up just fine and mashed into beautiful sweet potato rolls.
I stored them in my basement (about 65F, with consistently medium humidity) in an open wire basket. My regular potatoes grew all over the place, but these guys did really well!