Mussels that don’t open are OK to eat – sometimes they just hang on harder!!
A strong urban myth has been telling us since the 1970s to "discard mussels that don't open – that they are unsafe to eat". Mussel growers know – as do most good chefs, there is nothing wrong with a mussel that refuses to open while being cooked. Australians have thrown away around 370 tonnes a year of good mussels because of an old wives tale!
The advice to "throw away mussels that refuse to open", began in the 1970s when there were concerns over some European mussels being dredged from polluted mussel beds. This advice has been repeated without question by chefs and in many ‘how to cook fish’ cook books since then.
Just over 10% of mussels will stay closed after being cooked and depending on cooking time. As it is steamed, the mussel opens when the adductor muscle inside the shell breaks. If that adductor muscle does not sever or separate from the shell, then the mussel will not open. Closed mussels can be cooked a little longer or the shell prised open with a knife.
If buying fresh mussels, look for mussels that;
- are closed and full of water
- if open, will close their shells if tapped, or move if the shell is squeezed
- do not smell 'fishy' or look open and dried out (these have long since died)
Fresh live mussels can be stored out of water in a moist, cool environment eg covered in ice, for between 8-12 days depending on season. To keep them alive;
- cover them with ice, never soak mussels – always allow melted ice to drain away
- don't store mussels in airtight containers or plastic bags without holes or they will suffocate
"The bottom line is that if the mussel is fresh, you cook it and it doesn’t open, but it smells good, it's more than fine to eat" Chef Michael Bacash.
"I find that when a shellfish is reluctant to open it is often especially vigorous and has a very tight hold on its shell. I do not discard unopened mussels or clams without removing those that have opened and giving the reluctant ones another go!" The Cooks Companion, Stephanie Alexander.