I live a far distance from any body of salt water, so the only mussels available are packaged frozen mussels.
I have always heard that cooked mussels must open or they are not good to eat, but when we cooked the frozen mussels only a few opened. I went ahead and ate them anyways, they tasted fine and did not make me sick.
Is it normal for frozen mussels to not open their shells when cooked? If it is normal, is there a way to tell if they are safe to eat?