Why does turkey breast get hard after you microwave it a couple times?

Perhaps because you have boiled off all the moisture?

(What would I object to here?)

You are drying it out in the microwave. It is sucking all the moisture out of the turkey. I only use my microwave to heat water/soup.

I think it is advisable to reheat leftovers one time only. Cut off only as much as you want to eat, keep the rest frozen or at least refrigerated. Reheat on a lower setting. You are about to set the turkey on fire and/or poison yourself.

Oh dear, I agree with @gailcalled and @chyna then @rooeytoo in great measure! Yes, the water is being heated, so steam escaping reduces the water content, but as you heat the meat, the proteins are also being ‘hear-shocked’ repeatedly. This shortens the protein chains… Sorry to get technical, but you did ask! It makes the meat tougher each time it is heated.

BUT: each time you have ‘leftovers’, the bacteria that are naturally around in the food and the air get a chance to grow. So as @rooeytoo says, you must only heat what you need to eat at the time. Do NOT keep re-heating the same food in total, all kinds of nasties may be breeding in it and you may eventually get sick. Not to mention that each episode of heating destroys vitamin content. Keep the food at a constant cool temperature until you need some, then ONLY heat what you need. Or invite some friends over and have a party. Just don’t keep doing that stuff with this Turkey! :O(

“a coupke times”? Sounds like your on the way to making turkey jerky,

You nuked a fairly lean piece of meat two or three times in a row. I’m surprised it was edible.

Turkey has a very high moisture content, and as previously said, multiple heatings evaporates much of it. Like Ron Says Turkey Jerkey

The microwave boils meat. Boiling meat is how you make it tough. It is a bad idea to cook any meat in the microwave. It is a bad idea to reheat it in the microwave. If you must reheat that way, then cut off only that which you want to eat then, and reheat it the minimum amount possible. You only want to warm it. You do not want to cook the meat any further.

Very, very interesting, thank you all. and auntydeb the more scientific the better!