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There are several questions which cover overboiling a potato, where you would excessively hydrate it. However when it's being steamed this seems to not occur, and in other overcooking settings you are prone to drying it out. What happens in this case, does a potato really overcook in a steaming setting and if so what happens?

Since it's very similar, lets also answer whether this occurs during pressure cooking (in the pressurized steam).

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  • I'm pretty certain it wouldn't still be pleasant if steamed for three weeks, but I can't speak from personal experience
    – Tristan
    Jul 21 at 14:49
  • Anything can be overcooked, it’s just a matter of how long is too long. For steaming a potato though, ’too long’ is probably on the order of at least multiple hours (probably less in a pressure cooker would be my guess), though this likely varies by variety of potato. Jul 21 at 20:48

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In a boiling setting, the full water immersion rinses away the structural pectin and starches, causing the waterlogged texture.

Serious Eats has a good explanation of potato pectin and starches.

An older research paper on pectin and potato texture - full text behind paywall.

In a steaming situation with potatoes raised above the cooking liquid, without the large amount of liquid water in contact with and penetrating the potatoes the starch gelatinization is limited to water already present within the cells and condensation on outer surfaces of potato pieces. The gelatinized starch tends to stay contained within the pieces as well since the pectin structure is not washed away by mechanical agitation and exposure to cooking liquid. The potatoes still release cellular fluid during cooking, and that collects at the bottom.

From personal experience pressure cooking only potatoes in my Instant Pot, yellow-fleshed potatoes such as Yukon Gold remain creamy throughout and Russets become a dry fluffy when cooked up to 50 minutes on high pressure with a natural release.

Given a long enough cooking time the potatoes would expel all the available internal liquid - waxier potatoes become gummy and starchier potatoes become powdery. After that, pectin and starches break down and turn to mush, though that would be on the scale of hours.

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  • I don’t know about steaming specifically, or pressure cooking, but you can over-bake a potato. It gets drier and shrinks, leaving cracks through the middle. When you slice it open. (I often toss a few potatoes in the oven to have to make hash later, when I’m baking other stuff, and sometimes forget to set a timer). It’s possible this might happen in a pressure cooker, no idea under just steaming
    – Joe
    Jul 21 at 12:31
  • @Skyler was aware of potatoes drying out in such conditions in the original post. The shrinking and cracking from evaporative losses due to the dry heating environment of an oven is significant reduced in steaming where relative humidity is at 100%, and almost nonexistent in a pressure cooker environment. Jul 21 at 15:16
  • With pectin content comparable to apples (~15% both?), can you make jam with those potatoes?
    – Cong Chen
    Jul 21 at 15:27
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    @CongChen there is a Japanese dish called warabi mochi that is a jelly sometimes made with potato starch. It is pretty tasty. There is also konnyaku, which is a jelly made by boiling sweet potatoes.
    – BlackThorn
    Jul 21 at 16:14
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    @CongChen while they have similar amounts of pectin on a weight/weight basis, the composition varies - they're all branching chains of simple sugars, but pectins in apples have different branching/ratios of sugars than in potatoes. Other components like starch as rumtscho noted will have an impact on texture, another major one being the amount of calcium present for cross-linking forming stronger gels. Apples on average have 6mg/100g while potatoes have double that at 12mg/100g, according to the USDA. ncbi.nlm.nih.gov/pmc/articles/PMC6404037/… Jul 23 at 11:35

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