Lean turkey had "blubber" white stuff, what is it?

I put my lean turkey in the crook pot and some organic tomato sauce and put it on low, headed to the gym. I come back and there was this weird white blubber in it. I almost would have guessed fat at first, but its like 99% fat free and there is very little in the tomato sauce, think 6–8g or so?

What the heck is it? Should I be worried? It is still sitting in crook pot just never seen that before that I can remember….

I don’t cook much, or should say been cooking more now so I have no idea is this is normal or not.
EDIT: I’ll try and get a picture up ASAP for y’all.