How to Sterilize Grain Without Pressure Cooker?

If you can make spawn yourself, it allows you to grow any type of mushroom you want. This article will share, how to sterilize grain without a pressure cooker?

How To Sterilize Grain Without Pressure Cooker?

Sterilizing grain is an important part of the brewing process, as it removes any potential contaminants that could spoil the batch or cause illness. The most common method of sterilization is using a pressure cooker, but this isn’t always possible or practical. 

Here is an alternative method for sterilizing grain without a pressure cooker. Making grain spawn can be broken down into 6 easy steps.

  • Hydrate Grain By Soaking
  • Make Specialized Lids
  • Simmer, Drain and Dry The Grain
  • Sterilize
  • Inoculate With Liquid Culture
  • Colonize

1. Soak The Grain

The first step to making grain spawn is to soak some cereal grain. Soak the grain by simply placing it in a bucket or bowl with water and leaving it for 12 to 24 hours. Do not let it soak for more than 24 hours as it will eventually sprout.

This step is necessary as the grains absorb water and become hydrated. As grains absorb water, the volume increases just like when we cook rice. Depending on the grain, it should increase in size by 2 or 3 times. In terms of quantity, if you’re making 10-quart jars of spawn then you’ll need 3 jars of dry grain.

2. Making The Lids

Whole grains are soaked, you can make special lids. These lids will help you inoculate the sterilized grain. Follow the following steps to prepare the lids:

How To Sterilize Grain Without Pressure Cooker holes on lid
  • Drill 2 holes on top of the lid, one in the center (1/4” diameter) and the other on the edge of the lid (1/8” diameter).
  • A smaller hole is for creating a seal healing injection port. Once drilled cover it with a small dab of high-temperature silicone sealant and leave it to dry overnight. With this, you can inject right through the silicone.
  • Add a small wad of pillow stuffing as this allows mycelium to breathe as it is working its way through the grain.

3. Simmer, Drain, And Dry

Now you need to simmer the grains on a stove. This way the grain will be thoroughly hydrated and easier for the mushroom mycelium to consume. You’ll need to cook it for about 15 minutes and be careful to not overcook as grains will start to crack and become mushy.

After simmered on a low boil, drain the water and fill the jar about 2/3 or 3/4. It will be easy to shake your jars during the process.

4. Sterilize

This is an important step as it will help to get rid of any contaminants that may be present on the grains or in the jars. You can either use an oven or a pot with boiling water.

If using an oven, preheat it to 250 degrees Fahrenheit. Once at temperature, place the jars on the middle rack and leave them for 10 to 20 minutes. Keep in check from time to time that the water does not boil away. 

How To Sterilize Grain Without Pressure Cooker boil

After turning off the oven but do not open the door as this will let all the heat out. Leave the jars in the oven until they’re cooled. Whichever method you choose, make sure that the jars and lids are completely dry before proceeding to the next step.

5. Inoculate With Liquid Culture

Once the jars have cooled down, it’s time to inoculate them with your liquid culture. This is done by taking a needle or toothpick, dipping it into the culture, and then injecting it into the grain. Make sure to inoculate all the jars in a clean environment.

How To Sterilize Grain Without Pressure Cooker

6. Colonize

After you have inoculated the jars, it’s time to let them sit and colonize under sunlight. Check once in a while to see how mycelium is growing and becarful of contamination. Bacteria will look like wet brown sludge, and Trichoderma mold looks green. Either one of those things is a sign that you probably didn’t sterilize properly or your culture was bad.

You can speed up colonization by shaking once it is 1/2 colonized. After 1 to 2 weeks the jars will be completely colonized and you’ll have your grain spawn. Grain spawn can be used to inoculate larger bags of substrate or logs.

How To Sterilize Grain Without Pressure Cooker – Conclusion 

Now you know how to sterilize grain without a pressure cooker. This process is not as complicated as it may seem and with a little care and attention you can produce your grain spawn. With this method, you can also be sure that your grain spawn is free of contaminants. So go ahead and try it out for yourself. You may be surprised at just how easy it is to do.


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