The peroxide added to mushroom cultures decomposes entirely to water and oxygen as the mushroom mycelium occupies the substrate. As a result, there can be no trace of the added peroxide left in the mushroom crop, beyond what is naturally there due to metabolic processes. Moreover, hydrogen peroxide itself is found naturally in all aerobic living organisms and in a variety of natural environments. From time immemorial, honeybees have secreted enzymes which add peroxide to their nectar, protecting it from bacteria, yeasts, and mold, and imparting antibacterial properties to the resulting honey. The mycelia of certain mushrooms produce their own peroxide to help break down the woody substrates the organisms encounter. And peroxide is even a part of the healing defenses of the human organism. Indeed, around the world, thousands of proponents of a system of healing called oxygen therapy ingest peroxide solution on a daily basis to cure various ills and promote vitality, and some people have done so for many years. Much of the peroxide found in nature is created spontaneously by ultraviolet light falling on water.

There is some question as to the effect peroxide oxidation may have on the mushroom substrate itself. Chlorine, when it reacts with organic materials like paper pulp, produces small amounts of dioxin, a very dangerous, cancer-causing chemical. Hydrogen peroxide does not produce dioxin, and as a result, environmentalists are campaigning to get paper companies to bleach their paper fiber with peroxide rather than chlorine. Still, it is conceivable that peroxide could produce some other harmful substance when it reacts with the organic materials in mushroom substrates. I have not ruled out this possibility, but I consider it unlikely. For one thing, living organisms have evolved for millions of years with hydrogen peroxide both in and around them. This means that aerobic organisms most likely have developed metabolic machinery to deal safely with the oxidation products that result from the reaction of peroxide with biological materials. In addition, hydrogen peroxide is chemically quite stable in sterilized mushroom substrates, and the concentration of peroxide we're using is so low that the amount of substrate oxidation going on has to be very low indeed. Finally, I have seen absolutely no evidence of any mutagenic or toxic effect of peroxide-treated mushroom substrate on the mycelium or fruiting bodies. Agar cultures containing hydrogen peroxide give fine, healthy halos of mycelium, and the final fruiting cultures produce mushrooms as beautiful as any grown by traditional methods.

Can peroxide be used for certified "organic" growing of mushrooms?