I'm not sure how many of you have ever pulled a piece of meat out of the freezer that has been in there for a while. This happened to me a couple months back with a roast. Found a nice easy way to tenderize it back up (it had some freezer burn): I grabbed a can of pineable chucks, minced them up and put them in a bag with the meat (juices also). I let it sit for a couple days (rotating a few times a day) and what I pulled out what was good. I ended up cooking the juice and making a glaze out of it. I'm sure you could do it with oranges, limes, lemon, or any type of fruit with a good amount of acid in it.