I’m sure this has already been asked, but when I tried searching, I couldn’t find anything…
When you cook mussels, everyone knows to throw out the ones that don’t open.
But why?
Well, because they’re bad.
But what specifically about them makes the bad ones not open, while “good” mussels do? What is the mechanism/cause that prevents them from opening?
Thanks in advance 
Bivalve shells are hinged with a ligament and kept closed by a strong muscle - on cooking, the animal inside is killed and the muscle cannot maintain its grip; the shell springs open. I think the implication is that shells remaining closed may have already been dead before the cooking process began, possibly for some time, and that something like rigor mortis is keeping the muscle in the tensed position.
Interesting article, but it isn’t exactly hard science, is it? He may be right, but I’d like to see some proper microbiology done on open and closed mussels before we come to a conclusion. His suggestion of a ‘nose’ test is potentially wrong too; stinky food isn’t always unsafe and unsafe food isn’t always stinky.
And his claim that the practice of discarding closed mussels originated in 1975 sounds highly suspect.
How does one gather mussels? Pick 'em off the pier pilings? Off of the rocks? Or do you have to gather them in depths where they are never out of the water?
Johnny, most mussels today are grown in a process called “rafting”. They’re basically cultivated on big nets that hang down into the water. The mussels are “seeded” onto the rope lines, they attach themselves with their tough “beard”, and they just kinda hang out and filter the water that passes by for their food. When it’s time to harvest, the ropes are pulled from the water and the mussels removed by big machines. The rafting process makes it easy to gather scads of quality mussels at one location.
The cooks I know don’t recommend you eat a closed mussel because they believe the mussel didn’t get steamed properly if it were protected by the shell. I know this isn’t scientific, because it is likely to be just as hot inside the shell as outside, but many mussel connousuiers report that prying open a closed/near closed mussel often reveals meat that is less than desirable, and I would have to agree.
Mussels are so inexspensive in my neck of the woods that I wouldn’t bother with the 2-3 closed ones in my big bowl. Six bucks should get you a huge bowl (the size a “big salad” for 4 people or more would be served in).
Mussels in white sauce, please. Extra bread for dipping.
Thanks, Max Torque. But I was wondering about collecting wild mussels. I’ve mostly lived by the water (San Diego, Los Angeles, Birch Bay) and I’ve always wondered about gathering wild mussels.
[sub]FWIW, Birch Bay has lots of clams and oysters. I’ll plan on getting my license next week.[/sub]
Sorry, I don’t buy this explanation. It’s more likely that the shell doesn’t open because it’s either full of sand or there is a hole somewhere.
You can freeze clams and mussels (which kills the bivalve) and still steam them open. I believe they open because the water inside the shell turns to steam and forces the shell open. If the shell is full of sand or has an opening for the steam to escape, the shell stays closed.
Chef fight…rrrrooooowr.
You may be right in that my explanation may not be correct, but I don’t buy your steam idea - the shells open wide when cooked - steam would only force them open a little, then the pressure would escape.
What about before cooking. I was always told to discard the ones that wouldn’t close because I guess they were presumed DOA and thus, bad.
Yes? No?
Mussels Yummmmmmy!
sigh
I really want some mussels now. In white sauce. With extra bread for dipping. Thanks, **Philster ** and Essured.
I think it can be related to the old pressure/temperature/volume equation. Water in a confined area that is suddenly turned to steam creates a small explosion of expansion, which would violently throw the shell back. Not all clams open fully or uniformly. Then again, I could be completely full of crap. 
My impression is that they open somewhat gradually, rather than with a pop.
Some empirical experimentation is required here and I am just the man to do it - that’s right, hard, empirical science. And white wine sauce. It’s a tough project, but I’m prepared to see it through. Maybe with some chunky granary bread.
This is turning into something realy needy of investigation, is The Master in the house? That article is interesting, but the writer did not do a scientific test and is hardly a neutral observer (his dad owns a mussle farm, he was hired by the Mussel board).
I think their are a few points that are related but need answering
Are mussles that are open before cooking, dangerous to eat?
Are mussels that remain closed through cooking, dangerous?
Are mussels that open during cooking less likely to be dangerous to eat, than those that fail to open during cooking?
Does the opening or not of a mussel effect the flavour?
Hey, you’re in the Pacific Northwest now. Take a spin down to Whidbey Island and check out Penn Cove near Coupeville, one of the premium mussel-harvesting locations in several states. Grab a table at an area restaurant and have a bowl of mussels fresh off the beach, prepared in red curry broth and served with some crusty bread and a little butter and maybe a nice glass of gamay rouge from
Sorry, I had to go replace my keyboard. I shorted out my last one by drooling on it.
Damn you people – now I’m hungry, too! There is a local pan-Asian place that does some really killer Vietnamese steamed mussels with some kind of citrusy sauce; I’m not sure whether it’s tamarind, or lemongrass, or both, or what, but it’s really yummy. Has anyone had something similar? Can I get a recipe?
Whoops. I thought you wanted to know about the commercial process.
In any case, from what I’ve heard, you’re better off going with commercially-grown mussels than harvesting them in the wild. Mussels in the wild take a long time to reach a decent size, and an older mussel means a tougher meat. Plus, since their wild existence is more precarious than that of a rafted mussel, they have to focus their energies more on growing a tough shell than growing large. So, you’ll probably get a better mussel at a shop than at the beach.