Hydrothermy. How to prepare a substrate for oyster mushrooms

Hydrothermy. How to prepare a substrate for oyster mushrooms

Hydrothermy is a method of heat treatment of raw materials for oyster mushrooms.

Dry raw materials are poured with water so as to completely cover the raw materials. Then the water is heated to a temperature of 70-75 degrees.

Raw materials must be kept at this temperature for several hours. Then the water must be drained and the substrate cooled.

The hydrothermal method is popular among novice mushroom growers, due to its apparent ease.

The content of the article
  1. What container is needed for the heat treatment of the substrate?

  2. How much water should be added to the substrate

  3. Hydrothermal equipment

  4. Instruction for heat treatment

  5. Substrate cooling with water

What container is needed for the heat treatment of the substrate?

The preparation of the substrate for oyster mushrooms by the hydrothermal method takes place in a container or barrel from 1 to 6 cubic meters.

The substrate, which is in one cubic meter of container, is used for 25-28 mushroom substrate blocks weighing 10-11 kg.

First, dry raw materials are soaked in a tank or barrel (in a container).

You pour dry raw materials not very tightly into polypropylene bags, tie them up. And put it in a tank. Then fill with water.

The best raw material for this heat treatment method is sunflower husk.

If you can’t find it, take chopped straw with 5-7% bean hay, or a mixture of straw with a little husk.

Straw in bags

Straw in bags stands near the steaming tank

Sunflower husk substrate

Sunflower husk substrate cools down after steaming

I do not recommend experimenting with complex plant compositions in hydrothermia.

Different plant materials need different modes of soaking and steaming. You cannot create the ideal mode for each component when mixing.

Therefore, you are more likely to have substrate overgrowth defects during incubation.

How much water should be added to the substrate

You will be using a lot of water.

Approximately 750 liters of water are required for each cubic meter of the container, in which bags of raw materials are already placed.

We need so much water to completely cover the bags of raw materials.

And the layer of water above the bags should be at least 10cm.

If the sides of the bags stick out of the water, they will not be able to steam well and there will be spots when the mycelium is overgrown.

How long should raw materials be in water in general?

It depends on the properties and structure of the raw material. You must set this time by experience.

The substrate after heat treatment should have a moisture content of 67-69%

If the substrate is dry (less than 66%) – the yield will be low due to the lack of nutrient solution for growing mushrooms
If the substrate is too wet (more than 70-71%) – this provokes the growth of bacteria and mold during the growth of mycelium. Ugly mushrooms may also form.

Can water be used a second time?

You can try.

Water must be passed through a sieve (filter) so that large debris and mud foam settle. And then use this purified water for heat treatment of raw materials.

But as soon as defects appear during the overgrowth of the mycelium, the reuse of water will have to be abandoned.

Hydrothermal equipment

plastic water tank for substrateThe low cost of equipment is an undoubted advantage of this technology.

All you need is an insulated iron tank with a lid for hydrothermal treatment.

Place an iron grate at a height of 10-15 cm from the bottom, you will put bags of raw materials on it. The grid cells will be 10 by 10 cm or so.
You can also use a plastic water tank like in the photo. This container is suitable if you fill the raw materials immediately with hot water.

How to heat water

Electricity is rarely used to heat water, it is too expensive. For a 2 cubic tank, for example, the power of the heating elements must be at least 40 kW.

To heat the same container with gas, you need about 25 cubic meters.

You can also heat water with wood.

To do this, an iron tank must be placed on brick walls in order to burn firewood under the tank.

You make this structure like a furnace – on the one hand you lay firewood, on the other hand you put a pipe to create traction.

Instruction for heat treatment

There are two ways:
1. You put dry raw materials in bags into the tank and immediately fill it with hot water. The water temperature is 85-90C. This method is described in detail here.
2. You pour warm water at 25-30C, and after a certain time you heat it up.

I will talk about this method now.

  • Raw materials must be kept in warm water for at least 8 hours. Mold and bacteria spores swell during this time. They become vulnerable and die during steaming.
    If the water is too cold, you pour it into the tank and at the same time heat it up to 20-30 degrees. Spores swell very actively at this temperature.
    If the water flow from the tap is slow, place an additional container of water to pump water from it at the same time as the water from the tap.
  • After 8-10 hours, start heating the container with water. Water must be heated to at least 80 degrees.

    You must always measure the temperature in the center of the raw material bag. It should be within 70-72 degrees. The water may be hot, but the raw material may be at a lower temperature than necessary.

Once you have fixed the temperature of 70-72C in the raw material, maintain it for 3-4 hours for sunflower husk substrate and 7-8 hours for straw-hay and/or husk mixture. If your tank is well insulated, you don’t need to heat up the water.

  • Drain the water from the tank when the steaming time is over. Leave the raw material bags in the tank for 5-6 hours.
    Excess water drains during this time, and the bags cool slowly, absorbing additional moisture into their structure.
    You can remove the bags from the tank as soon as the water drains.
    But! Then the bags should be stacked in a tight pile on a pallet in a clean area or in an adjoining room.
    After 6-7 hours, place the bags separately from each other for faster cooling.
  • When the temperature drops below 27 degrees, sowing (inoculation) can begin.
  • Do not store the cooled substrate for a long time!

    The longer it stays in bags, the more various microorganisms multiply in it. And definitely – these microorganisms are not friends for oyster mushroom mycelium.

Substrate cooling with water

Some mushroom growers pour cold water into the tank after draining the hot water – to quickly cool the substrate.

I don’t recommend this way.

Humidity changes uncontrollably with a sharp decrease in temperature. Condensation appears in the substrate. This liquid after inoculation flows into the corners of the bag.

I’ve read on mushroom forums that rinsing with cold water frees the raw material from readily available mold food.

But this is impossible!

If this “nutrition” did not dissolve in hot water, and did not go away with this water when drained, how can cold water wash these substances away? This is not dirt on a concrete path to wash it off …

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