Preliminary googling says it turns water to steam, and the steam moves, but that still doesn’t explain in my head why the food gets moister.
Like, if the water is already in the food, why isn’t it moist in the first place? Where is all that water “hiding” in the fairly dry Muffin I am about to microwave, and after I microwave it the whole thing is very moist?
In: Chemistry
In something like a muffin or biscuit that you are reheating, the moisture is already there. When it started it was nice and moist (probably), as it sat and cooled, possibly was refrigerated, it started drying from the outside in. Also, as it cooled, the dough cooled becoming harder. When you pop it in the microwave the next day, there’s probably significantly less moisture and it is concentrated towards the middle (and probably bottom). The microwave turns what is there to steam which expands, so it moves through the bread heating and softening it back up. The actual dough softening adds to the moistness texture. So, if you compared your reheated muffin to an identical fresh one, it probably wouldn’t seem as moist because it has lost water. However, compared to its day old colder self, the water left was heated, redistributed, and soften the dough back up. But try reheating 3 day old pizza, and there’s no getting that crust moist again by microwave alone. There’s just not enough moisture left in it. Muffins or something with more volume to surface area will last longer though because the will lose the moisture slower.
It’s not so much that it turns the food moist, it was already moist. It turns it leaky.
Microwaving primarily works by heating water. The water becomes steam, the steam ruptures the cells and gets outside the fat/water/protein structures where it was trapped. As the water loses heat (by heating the other parts of the food) it then condenses back into water. So what used to be water inside the food is now water outside food that’s now a lot drier.
I mean, half the things I microwave dry out if anything. Rice, pasta, lasagna, etc. I usually add a little liquid and it all gets absorbed in.
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