It is very important that the mussels are alive before cooking, dead mussels can be unsafe to eat and might be poisonous or will irritate your stomach.
Here's how to clean the mussels:
1. Thoroughly clean mussels by washing and scrubbing them to remove dirt and grains of sand.
2. Pull the beard from the mussels by using one's fingers, or use a kitchen knife as an alternative.
3. Tap mussels on the side to see if they are still alive. Mussels will either close or open when tapped.
4. Mussels that are already open prior to cooking should be discarded, they are already dead. On the other hand, discard mussels that remain closed even when cooked, they are also already dead and should not be consumed.