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.

Allow the pressure cooker to cool to room temperature before removing the lid. Shake the jars when removing them to mix up the grains. The grains on the bottom will have a greater moisture content than the rest and will need redistributed. Allow the jars to cool for 24 hours before attempting to inoculate them.

When you inoculate your jars, it is best to work in a clean area to prohibit bacteria from contaminating your substrate. Cleanse the area well and nuke the air with Lysol. Using a culture syringe, insert the needle through the self-healing injection site and administer 1 cc of solution per jar. Shake up the grains to distribute the solution and incubate at between 82-86 degrees F. After five days, you can shake the jar one more time to aid in speeding up colonization time. If the jars have not colonized within 14-21 days the jar is most likely contaminated or the temperatures are too low.

Grain to Grain Transfer

When a Quart Rye Jar is fully colonized it can be used to inoculate up to 10 more jars to expand your mycelium and increase substrate mass thus increasing yields. Inoculating a grain jar with colonized substrate is faster than using a Liquid Culture because there is more mycelium to reproduce and proliferate. The procedure is fairly simple. The main concern is sterility when opening the uncolonized substrate jars.

First thing. You should wait approximately 1 week after the jar has colonized to ensure the interior has colonized as well and allow the mycelium to digest the substrate in preparation for fruiting. A rye jar usually colonized in about 3-4 weeks. Sometimes this can take longer if the temperature is not between 82-86 degrees during incubation.

When you are sure colonization is complete you will need to break up the grain so that you can inoculate your other substrates. Using a tire is perfect for this. Just make sure there are no cracks in the jar or it could break. You should also use safety goggles when doing this. After the grains have broken up, place it back in your incubation area and wait 24 hours. This will help rule out contaminations. The next day, mycelium should be growing again. If it has not within 24 hours the jar is considered contaminated by bacteria and should be thrown out. If you use it then you are potentially contaminating all of your new substrate jars.

The following day when you are ready to inoculate your jars, you should clean your work area, table and air with some cleaner. Any automatic air should be turned off one hour before the procedure. This helps calm the air and reduce the risk of airborne contaminates entering the jar when you open it. Ideally, you should be working in front of a Flow Hood but a Sterilized Glovebox will work as well. If you are using a glovebox, load the jars at this time.

The Procedure: Reshake the colonized jar to break up the grains. To inoculate the new rye jars, remove the lid from your colonized jar and the lid from the fresh substrate jar. Shake some colonized rye grains into the fresh substrate. There should be enough to divide the 1 colonized jar into 10 new ones.

Continue with the rest of the jars. Remove the lid, quickly inoculate with rye grain and replace the lid. The less time the lid is off the better. Incubate your jars the same way you did the first one. After these have colonized you can do several things with the grain.

• Use each jar to inoculate 10 more jars each

• Fruit the mushrooms right out of the top of the jar (depending on your species; not all mushrooms fruit directly from grain)

• Use the colonized grain to inoculate any of our 3 lb Substrate Spawn Bags. In most cases these can be fruited directly using our grow chambers or a humidity tent.

• Use the colonized grain to inoculate Pasteurized Straw