Preparing grains

How To Prepare Grains


Grain is a media used to expand mycelium. Different type of grains can be used, such as rye, birdseed, oat, wheat and corn seeds. Some use other type of seeds or media, such as cardboard or wood chips. This is one of the aspects of the hobby that is a matter of personal preference, and depends on the items we have at hand.

The basic steps are to: cook the grains, bag the grains, sterilize the bags and once cooled, inoculate the grains using agar, liquid culture or other grains, and then waiting a few weeks for it to be ready to use.

Before the hobbyist gets to the cooking part, the grains need to be prepared. Grains can be soaked 12 to 24 hours before cooking. This will allow the grains to get hydrated, which in turn reduces the time needed to cook.

When we soak the grains, we use a small amount of gypsum, but this is not a must; we only use it because we have huge bags available to us at an inexpensive cost. Keep in mind that the grains will continue to cook once they are in the pressure cooker. In fact, some hobbyist skip the cooking part, do a soak and then put the grains into the pressure cooker. To know if the grains are cooked, the hobbyist can use the fingernail method by taking a single grain and trying to crush the grain with the fingernail. If the grain gets crushed, then it’s cooked enough to be in grain spawn production.

The goal is to have a grain that is just cooked enough to be hydrated and soft. If the grain becomes like a paste, then that batch of grains is overcooked and should not be used. Overcooked grains usually become contaminated so should be discarded.

If the grains were soaked, then about 10 minutes in boiling water is enough; otherwise, 20 minutes is good, and the time starts once the water is boiling. We use oat, since it is the grain that is easily available to us where we live.

Once the grains are cooked, they need to be taken out of the pan to drain and cool. Allowing the grains to sit for five minutes in a colander is enough for the grains to cool down and lose a good portion of the excess water. At this point, the grains need to lose more humidity. The rule of thumb is that if the hobbyist takes a handful of grains, the palm of the hand should be be dry. If not, then the grains are still too wet. Some humidity in the hand is okay, but wet is not. The grains need to be put on table and dried even more ideally allowing two hours to sit and lose the excess humidity. We use a fan to expedite this process.

Too much humidity on the grains will cause contamination, which will result in failure and waste of time and resources. The hobbyist must ensure that the grains have just the right amount of humidity before putting the grains in bags or jars.

After some time, the grains are ready to be bagged or put into jars, in which case it is important to properly set the bags into the pressure cooker. The aluminium foil around the bags ensures the plastic bags will not get in contact with the body of the pressure cooker; otherwise, the bag could melt and become waste in the pressure cooker. A bag that melts is lost and the grains are no longer useful.

In order to sterilize properly, the hobbyist must cook for 90 minutes at 15 PSI.

Once the grains are sterilized, they can be taken out of the pressure cooker and properly sealed for storage.

In this case, the plastic bags are properly sealed with tape. It is important not to block the filter patch since this allows for air exchange. Without proper air exchange mycelium will not grow.

As soon as the grains are cooled, they can be inoculated by grain-to-grain, liquid culture or agar.

Grain-to-grain means that the hobbyist takes existing grain with mycelium and mixes about a tablespoon of the mixture with a new batch of sterile grains.

Liquid culture means the hobbyist injects liquid culture directly into the bag through the tape or injection port. Some bags have built-in injection ports, but these bags cost much more. If injection is done through a tape, then we use another piece of tape to cover the needle hole we made on the first tape.

Agar inoculation means the hobbyist cuts pieces of agar and puts them into the bag of grains.

Now the hobbyist has to wait for mycelium to expand on the new batch of sterilized grains.

Please see our other blogs covering on more specific subjects about the fun world of growing mushrooms.