Is the water released from mushrooms during stir-frying edible?

The water from cooking mushrooms is good for flavour.

When making vegetarian pasta sauces, I often add mushrooms and their cooking water to the sauce, for example. These get well-fried, but not typically until the water evaporates, which of course concentrates the flavour - that's still good.

The only time I waste it (and it does feel like a waste, perhaps I should freeze it for pasta sauce) is when I cook them to add to an omelette, either by frying or in the microwave. That's because I don't want the water in the omelette.

I do lightly rinse mine before use, but let them dry for a few minutes so they add very little water to the pan. I find this more effective in removing dirt than wiping, and don't have a soft enough brush.

As an aside, plants are quite good at turning dirty water into clean juice (and sap etc.). Mushrooms aren't plants, but I would expect something similar. Anyway, they're usually grown under very controlled conditions, so the water isn't likely to be contaminated.

Some of the water may hail from the tap water + salt that I cleaned the mushrooms with.

True. But depending on where you are, if your tap water is safe to drink after boiling, then it wouldn't be a problem, and the mushroom water will be perfectly edible.

If you have any soup lying around, you can pour the mushroom water in to add extra flavor. Or vaporize it by turning up the heat (I would've suggested turning up the heat before the mushrooms went into the pan, but we're dealing with already soggy mushrooms in this post).

The water FROM the mushrooms is a product used in making mushroom ketchup. Not that it's common nowadays (or even the last 200 years...), but it is made, commercially and at home.

A point for judging the answer you should expect is that commercially produced and sold mushrooms can be reasonably counted upon to have been grown and handled professionally enough that anything inside them (as opposed to surface contamination) should be safe unless it is a well-known situation.

(And these are mushrooms: after all is said and done, while SOME mushrooms may be grown in manure, none of the industry is the cesspit that the chicken industry is and not too many worry about what they eat from their offerings, flesh-wise or internal liquids-wise.)

Not to mention but anything the liquid brings out with it SURELY had some left behind so if there were anything of concern, some would still be there when you ate the mushrooms and so the concern would be somewhat moot.

Of course, if you are still concerned, just dispose of it. Or stick an instant read into it and make sure it rises to a safe-seeming temp before you allow it to follow the food.

As to washing, mushrooms do NOT absorb any water from washing. While rubbing them clean (if done intelligently which... well, most people are pretty careless) ought to be perfectly fine and many are happy with them rubbed clean, I wash them any time I am not frying them. If frying in some manner, one doesn't need to increase water in the pan, even if it is surface water that was not fully dried off. Washing is easier and more complete (who wants ANY peat?) but drying is tougher. So judge your skills and act accordingly.

Mushrooms grow their cells but leave them "flat" or "uninflated" waiting for the right moment (and plenty of moisture) to suddenly fill them all with water and grow incredibly quickly. And reasonably quickly. Just depends upon the mushroom. Point is that the growers wait until they are just about done doing that so they are as big and heavy as possible before picking and shipping. So they are pretty much done taking in water by the time they hit the store. And surface absorption isn't their biggest source anyway. So not only do tests show you won't add water in prep, but the way they are grown and shipped ensures it won't happen either.

Naturally, if you have a special kind, or they were marketed at some special slice of the market ("baby mushrooms"?), there may be special circumstances about them.

And ALL bets are off if you (or anyone else) "picked them" (as opposed to grew them and sold them). Good luck with those.

If you're concerned about pesticides, there are a few that are commonly found in mushrooms. From What's On My Food, the main culprit is Thiabendazole; that's found in about half of conventional mushrooms tested. Thiabendazole is primarily soluble only in organic solvents (see for example this reference), and wouldn't dissolve very much into water.

You can look at the list and see what others you might be concerned about; most of the others are pretty low dosages, so nothing I'm particularly concerned about (as someone who mostly eats organic). I do prefer organic mushrooms though, to avoid this concern, but they're not nearly on the level of some of the bigger risks like strawberries.

Sure it's fine, it's not like you're drying that cooked mushroom water before eating the cooked mushroom, right? Even if you were drying your food after cooking for fear of contaminants then why did you cook it to begin with?

If you were to use it then use it right away; much like au jus from meat.

If you want to save it for a stock then make the stock as soon as possible. Do not let that wok water sit at room temperature for very long. Follow proper stock procedures and boil it for several minutes before storing it.