Look at the influential cookery books of the 1960s, such as Larousse Gastronomique in 1965 and Italian Food by Elizabeth David in 1966.
These books made absolutely no mention of discarding unopened mussels.
The myth seems to have been started by the English food writer, Jane Grigson in her 1973 publication, Fish Book. ...
By the 1970s, some 13 per cent of cookery books were agreeing with Jane Grigson; and by the 1980s, this had risen to 31 per cent.
By the 1990s, there was almost universal agreement among the cookbook writers — none of whom were fisheries biologists. ...
Nick Ruello got involved in this mussel myth because he was commissioned to write a report for Seafood Services Australia, on the rather specific topic of adding value to mussels. ...
Nick Ruello found that 1.9 per cent of mussels opened early. These mussels opened before they had been cooked long enough to kill any potential pathogens in them.
If you removed them from the stove once they opened and ate these mussels, you would be at risk of food poisoning.
But you would get a strong hint from the texture of the meat — it would be unappetizing, jelly-like, un-coagulated, and stuck to the perimeter of the shell.
At the other extreme, he found that some 11.5 per cent of mussels remained closed after a so-called "normal" cooking time.
When he forced them open with a knife, every single one was both adequately cooked and safe to eat.
So, according to Nick Ruello, even if the adductor muscles refuse to bow to the heat, the meat is still safe to eat.
But on the occasions when he cooked them for a further 90 seconds, about one-seventh of them still remained shut.
And in the mussels that finally did open, thanks to the overcooking, the meat was now shrunken and tough.
The best way to check the safety of mussels is to check them before you cook them.
Mussels have such a small mass that if they are invaded by a pathogen or germ, they will be overwhelmed almost immediately, and will smell bad.
--Karl Kruszelnicki, Australian Broadcasting Corporation, on how to increase your mussel yield by 10+ percent