Made a jalfrezi curry and tossed in some mushrooms from the store. You know, the white button type. And it got me thinking: mushrooms are notoriously difficult to sort edible from toxic. Every year there’s a slew of stories of amateur mushroom hunters who get sick, or worse, die, from picking the wrong sorts of mushrooms.
How are mushrooms I buy in the store safeguarded against poisonous toadstools getting in the mix?
because they are raised under controlled conditions and not picked by amateur mushroom hunters from the wild.
How safe is store-bought ANYthing? Pretty safe, I’m thinking. Nothing I’ve ever purchased at a store has made me sick (except for overconsumption on my own part.)
Firstly, fungi aren’t generally any more difficult to identify than any other sort of lifeforms on this planet. The people who make fatal misidentification of wild fungi do so mostly through carelessness or ignorance - not because they are faced with an impossible task.
Commercial mushrooms are farmed by introducing known spawn to a sterilised compost - so they are usually a monoculture anyway. The number of poisonous species that could a) grow in exactly the same conditions and b) look similar enough to the crop as to be mistaken for it is very small, perhaps zero.
Wild-picked mushrooms sold on market stalls and directly from collectors to restaurants etc possibly pose a slight risk, as there is the potential for both parties to make a mistake - but it is worth re-emphasising - fatal poisoning from fungi happens because of avoidable mistakes, not because fungi are somehow impossible to properly identify.
From conversations with a mushroom hunting coworker - there are several varieties of tasty, safe to eat mushrooms look nearly identical to a deadly variety, and which grow under the same conditions. Old mushroom hunters (like him), just cross those off their list, and don’t even attempt to distinguish them. Bold mushroom hunters go through great effort to determine if they’re looking at the safe or deadly mushroom. There are few old, bold mushroom hunters. But most supermarket varieties of mushrooms don’t have poisonous lookalikes.
Mangetout has it right (as is usually the case on issues of food - and perhaps others as well). Commercial mushrooms are indeed produced as a monoculture - there is probably less chance of finding a strange variety mixed in than of encountering poison ivy among the supermarket lettuce.
Agree - if you know all the diagnostic features of a Chanterelle, you can’t possibly mistake it for a False Chanterelle, or anything else. If you know exactly how to identify a Morel, you won’t accidentally pick something else.
Most keen amateur fungus hunters are looking for maybe a couple of dozen good, usually common, edible species that they know they can absolutely reliably identify, and the rest is just scenery.
It is possible to identify fungi with the same degree of certainty as you can identify strawberries - but people seem to find this hard to believe - some sort of conflation between risk severity and risk likelihood, I think.
Basically, if you can tell what it is you’re looking at, there’s no problem. If you look at something and say “Ah, I know what that is, it’s a Chanterelle”, then you’re fine. The problem comes in when someone looks at something and says “Hm, I don’t know what that is, but it looks very similar to a Chanterelle; I’ll bet that, since Chanterelles are safe and tasty, this one probably is, too.”. Even there, it might well be something safe and tasty: There are a large number of mushrooms that are. But it might also be something that turns your liver into slush within a day of eating it.
People are often told, as small children, that “that might be poisonous, don’t eat it!”. They rarely care enough to find out as adults whether that was correct or not, and just pass on the information to their kids. I can’t tell you how many people think I’m trying to kill them when I encourage them to taste a violet flower or, god forbid, a serviceberry.
Mushrooms seem the most common victims, but red berries get picked on a lot, too.
But yes, storebought button mushrooms - and berries - are as safe as any other cultivated crop, because that’s exactly what they are. Cultivated. Farmed.
But really, fungi aren’t unique in this regard. Daffodil bulbs look like onions, Monkshood root looks like parsnips, laburnum pods look like green peas, etc.
I recall many stories of Europeans here in the US who have ended up poisoned by hand picked mushrooms. It was usually stated that they were unfamiliar with poisonous varieties here that resembled edible versions back home. These were reported in the news, but rarely with much detail, so I have no idea if that is representative of anything.
Just don’t eat anything from the nightshade family and you will be fine.
That seems a great tragedy. Not only are saskatoon berries (serviceberries) not poisonous, they’re the tastiest fruit in existence. And they grow wild all over the place here (Saskatoon, SK - one might suspect that’s not entirely coincidental) and no one local would think they were poisonous.
I don’t always disabuse them of their notions, however. More berries for me! 
First of all, the nightshade family are a group of plants, not fungi. Second of all, the nightshade family includes such plants as tomatoes, potatoes, bell peppers, and eggplant. If you open up a pack of smokes remember that tobacco is also in the nightshade family.
I was joking, referencing the ancient belief that plants from the nightshade family were poisonous.
Let’s make exceptions for bell & chili peppers, eggplant, potatoes, tomatillos, and tomatoes. Please? But you’re right that it’s much healthier to avoid Nicotiana.
Edit: Ninjaed by robert_columbia. Good show.
In Washington state, at least, all food that will be served to the public is required to be sourced from a USDA-approved producer, so buying and serving wild-picked or homegrown anything directly from individuals is just asking for trouble.
It happens a lot here in the UK - foragers sell directly to small restaurants - or restaurant owners go out and forage for their own. Not that it seems to cause a problem.
That’s definitely one thing about some (all?) of the Western European countries that’s pretty cool…say, a chef in France can go bag a brace of pheasants in the morning and be serving them in his restaurant that evening.
I trust the ability of a highly-trained culinarian to identify possible issues with meat, produce, etc than some guy in a suit from the Health Department armed with a pen and a meat thermometer.