Thursday, 22 March 2012


Sterilization in simple terms is to keep away insects and moulds.
It is very important not to confuse sterilization and pasteurization.
Pasteurization is never used in spawn making, but it is generally used for
cultivating mushrooms. Sterilization requires a pressure vessel called a retort
or autoclave.Sterilization requires a minimum of 121°C (250°F)
steam (2 atmospheres pressure) for 20 minutes. That short time is only
adequate if nothing contains more than 20 ml of liquid and all glass vessels
or other equipment is thin and easily heated. Longer times are necessary for
greater volumes of liquid, heavier equipment, and especially for anything
solid that occupies a substantial volume. Containers with 200 ml of liquid
will require 30 minutes. Grain used as substrate for spawn will require many
hours. The exact time will depend on the size and shape of the containers.
Another means of sterilizing is to heat things in a flame. Wires, needles
and many other things are heated until they are cherry red. Usually that method
is only practical with small metal items and then only to about 3 cm above
the area that is actually used. Although they have been sterilized, the openings
of tubes and bottles are normally put in a flame as soon as they are opened,
kept open for only a few seconds and put in a flame again, just before they
are closed. Knives and some other utensils, are generally first dipped in 70%
alcohol and then put in a flame, just to ignite the alcohol, and used as soon as
the alcohol flame goes out.

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