Sterilize & Pasteurize
Get the recommended sterilization time for grain jars and sawdust blocks at 15 psi, and the temperature and time to pasteurize straw and bulk substrate — plus which one your substrate actually needs.
The rule is simple: anything supplemented — grain, or substrate with bran or soy hull — must be sterilized, because the added nutrition feeds contaminants as readily as mycelium. Plain straw only needs pasteurizing. These are recommended ranges from practice, not exact figures; denser or larger loads want the top of the range, and timing always starts once full pressure or temperature is reached.
These are recommended ranges from cultivation practice, not exact figures — denser or larger loads need the top of the range, and timing always starts once full pressure or temperature is reached. When in doubt, go longer.
How to use it
- Pick a method. Sterilize at 15 psi for grain and supplemented substrate, or pasteurize for straw and bulk.
- Pick the container or volume. Jar size and count, or the amount of substrate to pasteurize.
- Read the recommendation. Time, temperature or pressure, with the key reminders — when to start the clock, when to cool.
Questions
Should I sterilize or pasteurize?
Sterilize grain and supplemented substrate at about 15 psi — the added nutrition feeds contaminants. Plain straw only needs pasteurizing.
How long do I sterilize grain jars?
Roughly 90 minutes for pint or quart jars at 15 psi, longer for larger jars and denser loads. Start timing only once the gauge reaches full pressure.
What temperature do I pasteurize straw at?
Hold it at 65–80 °C for an hour to an hour and a half. Don't boil — too hot kills the beneficial competition too.
Do I need a pressure cooker?
For sterilizing, yes — you need 15 psi for ~121 °C. For pasteurizing straw, no: a hot-water bath or a cold lime bath works.