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Mushroom kits

Preparing Jars of Grain Substrate for Mushroom Cultivation

Mushroom spawn: Definition: the mycelium, or primary filamentous growth, of the mushroom; also cakes of earth and manure containing this growth, which are used for propagation of the mushroom.

The Life Cycle of a Cultivated Mushroom:

First, one must grow the spawn of the mycelium. Grain such as rye is often used for this task. While the spawn is starting to grow, composting of the manure takes place. Components such as manure, straw, chicken droppings, and/or turkey droppings can all be added to the mixture (but not acidic pine needles). Once this compost reaches the proper temperature, mushrooms growers will add the spawn to the nutrient-rich compost.

In turn, the mycelium will run all throughout the compost eagerly digesting the organic material. In order to coerce the fungus into creating mushrooms, a low-nutrient casing is placed on top of the compost. Thinking it is about to run out of food, the fungus will produce fruiting bodies (mushrooms) to disperse spores. When just the right time has come, harvesters will come along and cut the mushrooms away from the mycelium.

What you need:

7 Qt. pressure cooker
Large pot for boiling water (5-7 Qt.)
7 ? 1 Qt. sized canning jars (w/lids)
1 cup measuring device
1 cup liquid measuring device
Industrial-grade masking tape (not shown in pic)
2 lbs or more of rye grain (rye berries)
1 gallon of spring, distilled, or drinking water

The first item of consideration when working with grain is a pressure cooker for sterilization. As far as I know (aside from an autoclave), a pressure cooker is the only way to get the grain hot enough in order for it to become properly sterilized. For this TEK, we will be using a 7 QT. capacity pressure cooker which holds 7 - 1 Qt. sized canning jars.

The type of grain that we will be using is known as rye grain and is the most commonly used type amongst commercial grow-ops for creating spawn used with bulk substrates and edible mushrooms. For small-scale opps, grain can be used as a primary substrate or can be used to spawn more prepared grain (which allows one to extend a live culture or spawn to create more substrate mass to fruit from). And, as with the commercial application of grain, it can also be used to spawn bulk substrates like compost or pasteurized wheat straw, etc? to achieve greater yield potential.

Below is a photo of the rye grain that we stock.

Initial Preparation:

Before we begin, it's always a good idea to wash your hands and clean the work space that you will be working in before you get started. However, for this procedure it's not nearly as crucial as some of the other procedures, so being overly cautious is not necessary at this point.

What is important for this procedure is to be sure that the jars that you are using are clean. If your jars are new, then it's a good idea to give them a simple washing and drying before carrying on. If your jars are used, then make sure that you get all the visible build-up eliminated and then clean them in a 10% bleach solution and rinse clean. If you don't have bleach, then you can spray Lysol directly into the jar to clean it and then rinse it clean. You may want to give them a final cleaning with an alcohol-saturated paper towel to be safe.

Once your jars are cleaned, then you will need to modify the lid so that you will be able to inoculate them with a syringe needle, without having to remove the lid entirely. To do this, we will need to drill, cut, punch, or melt a hole into the center of the lid.

A 3/16" hole would be the ideal minimum diameter to use for this app, while a 1/4" hole would be about as large as you would ever need. I prefer a 3/16" hole as it provides plenty of room for me to get the tip in and out without much effort.

Once you have modified all your lids to accommodate the syringe inoculation, then you can wash the lids clean and move onto the procedure.


Place the following items in your workspace:

7 ? 1 Qt. sized canning jars (w/lids)
1 cup measuring device
1 cup liquid measuring device
Industrial-grade masking tape (not shown in pic)
2 lbs or more of rye grain (rye berries, rye grass seed, etc?)
1 gallon of spring, distilled, or drinking water

Now you are ready to prepare the jars of grain for the pressure cooking session. First, scoop 1 cup of rye grain into each of the 7 jars:

And now, using a liquid measuring device (must be a liquid measuring cup!), pour 2/3-3/4 cup of the bottled water into the measuring device.

Add the water to the jar of grain:

Now, add the lid to the jar and tighten it:

Add a piece of industrial-grade masking tape over the hole (I am using hi-temp foil tape):

And shake until the water is mixed with the grain:

(be sure to wash off the grain that sticks to the insides of the jar by swirling the jar around until all the loose kernels have settled back down onto the bottom of the jar in one mass.) Below is a pic that shows the jar before the water is added and after the water has been added to the jar and shaken for proper mixing:

(If the jars are allowed to sit very long, the grain will soak up the water and it will appear differently than the freshly mixed one in the pic above.)

Once all the jars are mixed with the proper amount of grain and water, then you are almost ready to load them into the pressure cooker. First, we need to loosen the lids back a 1/4 - 1/2 turn to allow the jar to breathe and not blow up from pressure. Once you have loosened the lids accordingly, then you are ready to load them into the pressure cooker:

Now, you will need to boil several quarts of water in the large pot before adding it to the pressure cooker (see pressure cooker instructions for correct amount to add):

Once the water has boiled for 5-10 minutes, it's ready to add to the pressure cooker:

Now, secure the lid onto the pressure cooking unit and turn the stove top heat on "High":

After 5 minutes, you should begin to hear and see some steam coming out of the top hole of the pressure cooker lid. After another 5 minutes, the steam should be flowing pretty steadily, like so:

And after 10 minutes of steady flowing steam, it's time to add the stopper thingy to the lid (total duration of time up to this point = 15-20 min):

After 10-15 minutes of the stopper being on the unit, the psi should be up to 15 psi or so and this is when you need to start the 1 hour countdown for the sterilization process to occur. The ideal range for sterilization is typically 15-18 psi for a 1 hour duration.

It's very important to keep a very close eye on the steps involved and the duration of time spent on each step because, if you allow the cooker to run too long before adding the stopper for instance, then you will loose all the water needed for sterilizing the jars to steam, and they will dry out and get cooked or burnt! Once the cooker has reached the 1 hour mark, it's then time to turn the stove ?OFF? and let the cooker cool down on it's own for a matter of hours.

**Never let the pressure cooker run for more than 1 and a half hours - from start to finish (the entire procedure). If you do, then you will certainly cook your grain and it will be useless.

**It's important to mention that you will smell some grain cooking after about 15 minutes into the 15-18 psi range. That is okay so don't be alarmed if you smell your grain cooking.

After your pressure cooker has cooled back down to room temperature (at least 4-8 hours) then you can take the lid off of it and follow the procedure found below:

Checking for cracks
The first thing that you will want to do upon removing the freshly prepared jars of grain is to check the jars for any cracks that might have taken place while under the intense pressure of the cooker. You'll notice that after the jar is rotated and checked for cracks, the lid is then tightened to allow for shaking.

Shaking and Mixing
The first part of the shaking process is an effort to shake the grain loose from the jar, followed by an attempt to break the grain apart (you will notice a lot of banging and slapping going on to the jar during this part of the movie...a real good reason to check for cracks

Rolling and Twisting
Also, notice that once the grain is broken up from the shaking and banging, a final rolling (end-over-end) of the jar is applied to help mix the dryer kernals resting at the top of the jar with the very saturated kernels resting on the bottom of the jar. This is a very important part in the shaking process because it enables the top and bottom kernals to become mixed together which allows for a complete mixing of the kernals within the jar. The idea is to flip the jar from end-to-end while simultaneaously rolling or twisting the jar around with your wrists so that the grains cascade from top to bottom, and so on...

A final smack on the bottom of the jar should cause the grain to settle back down into place which will complete shaking process and make the jar ready for inoculation.

If you take a look at the pic below, you can see how a jar grain appears directly after it's removed from the pressure cooker (jar #3) as compared to a jar that has been shaken in preparation for inoculation (jar #4).

(Notice that the grain within jar #4 has increased it's size or mass by almost 3 times the initial dry grain mass of jar #1.)

That's it! The jars are now ready to inoculate!