Why does mashed potato turn to glue?

Now We Know: Selecting the right spud and boiling in cold water help process

Often times with food, it is the seemingly straightforward dishes that can trip up the intrepid cook. Mastering the perfect boiled egg, say, or cooking spaghetti for the right amount of time. And so it is with the humble mashed potato.

Done right, or when elevated to posh nosh by way of sieving and buttering, this comfort food can be a glorious indulgence. Get it wrong, however, and mashed potatoes can be a culinary nightmare. Have you ever ended up with a glue-like mulch where your mashed potatoes were supposed to be? How could you have messed up something as easy as boiling a few spuds? Well, it has happened to me, and now I know why.

According to the experts, there are a few key factors in reaching peak creamy mashed potatoes as opposed to sticky spuds. Susan Chen, writing for PopSugar.co.uk, says selecting the right spud is essential. “Either one high in starch, like a tough-skinned russet, or waxy (like a thin-skinned, yellow potato),” writes Chen. She recommends Yukon Gold for their flavour and consistency.

Uneven cooking

Over on TheKitchn.com, Kelli Foster recommends starting the boiling process with cold water to avoid uneven cooking. If you add your spuds to a pot of boiling water, says Foster, “The outside of the potato will end up overcooked, while the inside will remain firm and underdone.” She also recommends bringing the milk and butter – essential to any good bowl of mashed spuds – to room temperature before adding to the hot, drained spuds.


The next, and perhaps most crucial step, is the mashing, and Martha Stewart gives us a clue into the science-y bit in an article on her website called How to make mashed potatoes – and how to fix them when things go wrong. "For mashing, use a ricer, a food mill, or a hand masher, but never use a food processor; the sharp blades break down a potato's starch granules, making it gluey."

You can have the same effect without a food processor if you get too carried away with mashing, which is easier than you think, particularly if you’re trying to get rid of lumps in your mash.

Let’s just say you do get carried away and your mash has become a bit of a gluey mess. Top tips regularly point to pairing the spuds with cheese, to create a topping for gratin, as grilled cheese has a remarkable ability to cover a multitude of sins.