You can't control what happens to your mussels once you start cooking, but you can control which mussels you buy. So if possible, make sure you don't buy any that are open when alive. After cooking, for the ones that are closed, I still open them up to take a look. If they look normal, I still eat them (or spit them out if it tastes funky).
I ended up buying mussels from Superstore (on Marine & Main) last Friday cuz that was the most convenient. They had 2 2-lb bags left, but those were going bad. Fortunately, they had a lot of loose mussels to choose from, so it must have been a recent shipment. I was there again earlier this week, and most of their loose mussels had been purchased.
For those curious, I had the day off and was going to cook mussels in white wine for my wife for our anniversary dinner as a surprise while she was at work. She was unwell that morning so she called in sick, ruining my plans in a way. After sleeping the morning away, she got better so in the end, I bought & prepped the ingredients and she did the cooking.
