I notice that when I prepare stews or soups with potatoes (e.g. beef stew, Japanese curry, etc.), they have a tendency to have a somewhat-off "stale" taste when reheated the next day, after taking it out of the refrigerator. The other vegetables in the same dish (e.g. carrots, onions, etc.) are usually still good.
Does anyone what the reason for this could be, or how to prevent this?
I suspect that the issue is that starches change when cooked and then chilled. (Called retrogradation)
This is why long grain rice is always a bit dry and hard when refrigerated (but makes for better fried rice as it’s less sticky, and it’s lower glycemic index as it’s now resistant starch)
Bread also undergoes retrogradation when chilled, which is what we refer to as ‘stale’ when it happens.
Most people don’t find chilled and reheated potatoes objectionable like you do, but they might notice the changes. For instance, you can’t easily mash a refrigerated potato, even after warming it back up.
I’m not aware of any way to prevent it.
You can try using vinegar to revive and liven up an old stew or soup. A little goes a long way, so try reheating a small amount and slowly add it to see how the flavor changes. Depending on what you made a particular flavor (apple cider, balsamic, etc) might work better than others but regular white vinegar is a good place to start.
