GROWING GOURMET - Anto2ni.it

GROWING GOURMET MUSHROOMS ON ENRICHED SAWDUST 169
Swing Gauge
posing the needs of production and the dangers
of uneven sterilization due to heavy loading.
Packing an autoclave deeper than 4 bags (32
inches deep) runs other contradictory risks. In
the attempt to achieve full colonization, sterilization
time is typically extended, potentially
causing other problems: over-sterilization of
the outer zones and bag-fatigue. Over-sterilization
usually occurs when wood substrates are
subjected to steam pressure (15-18 psi) for
more than five hours. The sawdust takes on a
dark brown color, has a distinctly different odor
signature and, most importantly, resists decomposition
by mushroom mycelium.
Prolonged steam sterilization results in complex
chemical transformations. (I have yet to
find a chemist who can adequately explain
what happens from prolonged exposure). Sufflee
it to say that turpentines, changes in
Gate Valve
Micron Filter
Breaking the vacuum to equalize
pressure in the autoclave without
introducing contamination.
Air from
Laboratory
Figure 137. A microporous filter canister is attached to a pipe equipped with a gate valve which in turn is
connected to a one-way check valve leading directly into the autoclave. Located on the clean-room side, this design
allows pressure to be equalized in the autoclave after the sterilization cycle without introducing contaminants.
volatile oils, and toxic by-products are responsible
for this radical shift in sawdust's
myco-receptivity. In the end, the substrate is
rendered entirely inhospitable to mushroom
mycelium.
After the autoclave has been packed, the displacement
of the cold air by introducing steam
and top-venting is absolutely critical. The cold
air, if not vented, gives a false temperature!
pressure reading. At 15 psi, the temperature
within the autoclave should be 252° F. (12 1°
C.). This arithmetic relationship between temperature
and pressure is known as Boyle's Law.
When a cold mass is introduced into an autoclave
or pressure cooker, Boyle's Law does not
come into play until the thermal inertia of the
affected mass is overcome. In other words, as
hot steam is being forcibly injected into the
vessel, there is a lag time as the heat is absorbed
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