Sterilizing and pasteurizing mushroom substrates
When
growing mushrooms, your goal is to get your mycelium to colonize a new
substrate as quickly as possible --- definitely within two weeks.
As every gardener knows, nature abhors a vaccuum. Just as your
garden beds will quickly become coated with weeds if you don't plant
your veggies thickly or mulch them, your mushroom substrate will be
full of harmful contaminants if you don't make sure your mushrooms get
a head start.
The best way to
jump-start your mycelium in a new substrate is to
sterilize or pasteurize the material to kill off the harmful
competitors. Heat is the primary method used, but you have to be
sure not to raise the temperature of your substrate over 200 F or
you'll do more harm than good by waking up bad molds.
Sterilization sounded
very difficult to me until I realized that the methods
used at the home scale are basically the same as canning. Want to
sterilize jars of grain? Just boil the grain in water for an
hour, put it in clean quart jars, and then cook the whole thing in a
pressure cooker for another hour at 15 psi. I soaked my
cardboard substrate in hot water before inoculating, which I assume
did a bit of sterilization at least.
Of course, if you want to
inoculate masses of wood chips or straw, they
probably won't fit in your pressure cooker. Paul Stamets offers
an alternative method for pasteurizing bulk substrates at home --- fill
a big pot or metal drum with water, put your substrate in a wire basket
inside, and place over a propane burner or a fire. Straw needs to
cook at 150 to 180 degrees Fahrenheit for an hour while wood chips
should be cooked for twice as long. If you've enriched your wood
chips, you may need to cook for as long as 5 hours.
No matter how you
sterilize your substrate, let it cool, then inoculate
it with that
mycelium you carefully grew according to last week's
instructions.
The fungus will do most of the rest for you!
This post is part of our Growing Gourmet Mushrooms lunchtime series.
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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.
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Hi there,
We have just started growing mushrooms at home and are looking at trying Oysters on a coffee/woodchip mix.
We want to sterilise the woodchips- how is best to do this without a pressure cooker? We'll buy one if we decide to carry on with the mushrooms, but this early on we want to do it cheaply until we know whether we want to continue! THanks!