Creating Grain Spawn

When growing mushrooms at home, cereal grains such as wheat, rye, millet, maize, amaranth, quinoa, etc. can be used as a vehicle to expand your substrate mass into bulk substrates. If you’ve mastered half-pint jars, making grain spawn is the next logical step. When a jar of grain is completely colonized it can be used to inoculate other jars of grain using what’s called a grain to grain transfer. G2G for short. Paul Stamet’s explains that 1 jar of colonized grain can inoculate 10 more jars of grain. Each of these jars in turn can inoculate 10 more jars and finally those can inoculate 10 bags of bulk substrate each. Do the math and you are expanding your mycelial mass up to 10,000 times the original jar. (Growing Gourmet and Medicinal Mushrooms, 2000).

If you would like to create your own Rye jars, simply follow these instructions and start making your own grain spawn to experiment with.

There are many lid designs that can be used with your quart jars. We recommend drilling four ¼” holes as you normally would in half-pint jar lids. Then drill one larger hole in the center. This will be filled with a High Temp Gasket sealer to create a self-healing injection site. If you are using the quart jars for grain to grain transfers you can leave out the injection site.

Depending on the size of your pressure cooker you will want to adjust the amount of ingredients to suit how many quart size jars you will be able to sterilize at one time. For each quart jar measure out 200g or 250 ml of organically grown rye. You can use the quart jars for measuring. Simply pour the rye into each jar to the 250 ml level. We will need to set a pot large enough to hold enough water to cover all of the rye grains put together.

Fill your pot with enough water and heat to boiling. Immerse your grains in the water and then lower the heat. Keeping it up high will cause the grains to break open and this can lead to contamination later on. We want to steep the grains for one hour stirring now and then. For my stove I lower the heat from level 8 to level 3 when putting the grains in and then on down to level 1 after twenty minutes. Your stove will be different but I included these settings to show an example. The grains will start to swell from absorbing water as time goes on.

After your hour of steeping is up you will want to drain off the excess water and then pour the grains through a strainer. I usually rinse off the grains before loading them in the quart jars. Scoop enough grain so that each jar is evenly filled. Place your lids on loosely and cover them with a square of aluminum foil to keep water droplets from landing on the lid and seeping through to the interior.

Load your pressure cooker with the jars and fill it up to the desired water level. Now, take your jars back out and preheat your pressure cooker water to boiling. This will help prohibit more grains from exploding during the heating process. After the water has started to boil, load the pressure cooker again and place the lid on. After the pressure cooker starts to sizzle at 15 p.s.i., set your timer for 90 minutes.

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