Have you ever noticed that sometimes reheated meat has a bit of a funky flavour, even though it's only been in the fridge a day or two? Well, that's called "Warmed Over Flavour" (WOF). There are chemical reactions that happen inside the meat after it's cooked and chilled and then reheated. Here's an article that explains the science and ways to help prevent or limit it.
Meet Warmed-Over Flavor, the Phenomenon That Turns Leftovers Funky
Meet Warmed-Over Flavor, the Phenomenon That Turns Leftovers Funky