Sterilising Rye Grain

The following example details how to prepare 1kg of sterilised rye grain for use as growing medium in bulk spawn production. The measurements can then be scaled according to the type of container you are using for the grain. One of the simplest containers to use is a jam jar. In this example we are using 2lb jars. It is important to note that once hydrated rye increases in weight by approximately 30% and at least doubles in volume.

Sterilising Rye Grain

The following example details how to prepare 1kg of sterilised rye grain for use as growing medium in bulk spawn production. The measurements can then be scaled according to the type of container you are using for the grain. One of the simplest containers to use is a jam jar. In this example we are using 2lb jars. It is important to note that once hydrated rye increases in weight by approximately 30% and at least doubles in volume.

Materials:

  • Rye Grain 600g
  • gypsum 10g
  • water
  • micro pore tape or cotton wool
  • tin foil

Equipment:

  • 5x Jam jar 770ml/2lb
  • Drill and 2mm drill bit
  • Pressure cooker

Method:

  • wash rye grain repeatedly until water runs clear
  • soak rye grain for 24hr with gypsum
  • boil until hydrated be careful to ensure the grain kernals don’t burst
  • drain and steam off excess moisture but don’t dry out
  • place into jars
  • put jars in pressure cooker, off the bottom of the pot, use inner pan or improvise metal spacer
  • sterilise at 15psi for 90mins, start counting when at 15psi
  • move into sterilised area when pressure at 0psi
  • allow to cool for 6-9 hours

 

Notes:

Firstly a note on preparing you jar lids. You need to create a filtered air exchange. Do this by making a 2mm hole in you jar lid and then filling with cotton wool or cover with micropore tape.

  1. Wash the grain: you need to get all the dust and any chaff from the grain, 4 -5 washes should do the trick.
  2. Add gypsum and leave to soak overnight. Use enough water to cover the top of the grain by 2-3cm.
  3. Bring to boil and simmer until the rye grain is hydrated, don’t over cook, when this happens the grain kernals burst and increases the risk of contamination.
  4. Drain and steam off excess moisture. You do not want the grain kernals dripping wet. Just stir the drained hydrated rye grain and allow the steam to evaporate. At the same time you don’t want the kernals to dry out. Find a balance. The aim is to avoid any excess moisture in the containers after sterilisation.
  5. Place into the jars. Fill only a third. In this example 200g in each jar should be sufficient. If you overfill the jars you will have problems when it comes to shaking up the mycellium.
  6. Put on the lid lightly, with the prepared hole, filled by cotton wool or micropore tape. Cover with the lid with tin foil. This prevent excess moisture getting into the jar during the sterilisation process.
  7. Place jars in pressure cooker, off the bottom of the pan, use an inner pan or improvise a metal spacer.
  8. Sterilise at 15psi for 90mins. Start counting when at 15psi.
  9. Once sterilised wait until the pressure returns to 0psi then carefully move the pressure cooker to sterilised work area for innoculation. Leave here until cool, about 6-9 hours.

You can now inoculate you sterilised grain with grain, agar or liquid inoculation.

For further detailed instructions be sure to get a copy of at least one of the essential mushroom grower books in our resources page.

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