When a potato cooks, the starches contained in each cell are released as the cell walls break down. These starches absorb the potato’s internal moisture and swell and soften. These two processes are what transform a raw, hard potato into a cooked, softer potato fit for mashing.
If you cut your potatoes up before boiling them, the starches absorb the internal potato moisture as well as the water in which they’re being boiled. If they boil for too long, they absorb too much water and your mashed potatoes will become gummy. The difference between perfectly cooked potato pieces and soggy pieces can sometimes be as little as a minute or two.
An easy workaround is to boil potatoes whole. They’ll take a bit longer to cook but you can leave them in the hot water after boiling without undesirable effects, keeping them warm until it’s time to mash them. I start my potatoes boiling as soon as I begin cooking and mash them immediately before dinner.
If they need more moisture, you can add a bit of hot potato boiling water or another liquid. This way, you have more control of their moisture content.
To be totally transparent, I never had gummy mash until my wife and I got together. She used to boil her potatoes, let them sit in the hot water until closer to dinner, then whip them with beaters. She’s from Ireland, I joke that the potato blight was a failed preemptive strike to prevent her from ever touching a potato.
So I don’t have to do any of what you’re saying in your post, I just have to not do the weird stuff your wife does. Cool.
Pretty sure it’s the beaters (assuming that’s an electric hand mixer type-thing, i’ve never heard them referred to by that term) that made them gummy. Over mashing will break up the cell walls too much, releasing the starches and ruining the texture. Cooking chopped or whole doesn’t matter as much, since the number of cells broken by chopping is negligible. And the skin is water permeable anyway.
You gotta mash by hand, that’s all.
Every couple months I make the mistake of thinking that I’ll speed up mash the potatoes by using an emulsion blender. Then it’s just potato snot
You are correct, op has no idea what they are talking about. Potatoes contain two different types of starch, in differing amounts depending on the kind of potato. Amylase, and Amylopectin, the second when overworked will make gummy potatoes. Overworking them is what makes them gummy.
1" dice, fork tender, food mill, ricer, or fork, perfect. If you want them extra smooth simmer in milk or cream (not water), strain and mash, then fold in the drained liquid gently with a spatula.
And the ‘hot potato boiling water’ contains mostly Amylase. If you add that it will make them more slippery/slimey.
This person potatoes
It’s the beaters making it gummy. Mash by hand, it’s too easy to overdo with an electric mixer.