A rapid search on the Internet or the advice of a friend who is an expert cook will confirm that, when you have some delicious mushrooms, one of the few things you can be absolutely sure of is that they should never be washed. So, go home with your basket full of excellent porcini mushrooms and, one by one, cut off the harder bits and simply remove the soil with a knife.
Stop. In fact, it would be disastrous to wash them under running water because this would very likely cause the mushrooms to absorb water and “boil” when cooked. This rule contains half a truth and a whopping lie but, in order to clarify the issue, you need to know exactly what a mushroom is. Basically, we are already familiar with them. So familiar, in fact, that the mere thought makes our mouths water. However, with regard to their composition, things are less obvious.
Do you need to wash mushrooms?
To make it simpler, we can say that mushrooms are similar to sponges, consisting of densely packed lattices of polysaccharides which encapsulate an enormous quantity of water molecules: more than 90% of a mushroom is made up of water. Being devoid of a proper fluid circulation system, mushrooms collect nutrients by absorbing them directly through their wall structures. So, we are not wrong in thinking that mushrooms tend to absorb water and we realize this when we put them out to dry in the sun: in just a few hours their volume reduces by half and this is also the reason why they can be stored for a long time when dried.
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The fact that mushrooms soak up so much water has led, in the course of time, to the deeply rooted belief that they should not be washed but this is not at all true: it is only a question of method. Certainly, we cannot leave them to soak in a basin of water, in the same way as salad leaves. Champignon mushrooms do not have very compact fibres and, in actual fact, can withstand rapid washing under running water, but this is the typical exception that proves the rule.
For all other mushroom varieties, especially the noble porcini, the right method to follow is slower and more painstaking. It is necessary to procure a suitable brush. After removing the harder parts and most of the residual soil with a knife, dampen the brush and pass it over the entire surface of the mushroom. Every now and then, rinse the brush in water and repeat the operation. If you wish to speed up the process, you can replace the brush with a piece of a damp cloth, to be rinsed when dirty.
The importance of cooking method
Yes, we know, it is a particularly tedious job but it is the best way to do justice to prized mushrooms.
Alternatively, if you are sure of the source of your product and the cleanliness of the soil, you may clean it with a cloth only, without using water. If, on the other hand, you are dealing with smaller mushrooms, such as honey fungus, once all of the visible soil has been removed, you can use a high-pressure nebulizer filled with water, so long as you dry them immediately.
Finally, the cooking method is also extremely important. Excellent quality mushrooms should be cooked as little as possible but, if you realize that they have absorbed too much water and you wish to toss them in the pan, remember to use a very high-temperature setting so that the moisture evaporates rapidly without sacrificing too much taste and aroma. Besides, this method enables us to wash mushrooms in water without excessive concerns.