Pasteurized Wheat Straw Prep TEK

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Pasteurized Wheat Straw Prep TEK


The following procedure is a simple method for pasteurizing wheat straw and is ideal for the small-scale home cultivator. The number one benefit of working with a bulk substrate like Pasteurized Wheat Straw (as far as the small-scale cultivator is concerned) is the impressive boost that it offers in terms of overall performance and cropping yields. Fruitbodies grown out on WS are typically much larger than ones that are grown out on grain or flour. Colonization (or Spawn Run) times are also decreased which means that the mycelium grows more rapidly in straw than it does in grain or flour.

Wheat straw is an ideal substrate for these particular mushrooms and for this particular application. In fact, given its cleanliness, ease of preparation, and nutritional benefits; it may be the best alternative for any indoor cultivation app where these (or other similar mushrooms) are concerned.

The type of straw that we will be using is known as Wheat Straw and is commonly used amongst commercial grow-ops for creating composts to be used with edible mushrooms that require it. For small-scale apps, straw can be used as a primary substrate for this particular kind of mushroom.

Wheat straw can be purchased at any feed store for approximately $5 for 1 bale. One Bale weighs approximately 40 lbs dried. That is a lot of substrate for the price! Other places that are likely to carry wheat straw are; gardening centers or nurseries (frequently used for landscaping). You should be able to find straw at any one of these places with little effort.

Note: Be sure not to use an Oat or Barley type straw. Make sure that you are purchasing "wheat" straw!


Below is a list of all the items you will need to carry out this procedure:


Large pot for boiling water (5-7 Qt.)
2 lbs or more of wheat straw
A metal grate or a heavy weight
(for holding the straw under water during pasteurization.)
1 Meat probe Thermometer
A pair of scissors for cutting up straw.
A large container
(for holding the chopped straw)

Wheat Straw Preparation:

Place the following items in your workspace:


Bag of Wheat Straw
2 large bowls or pans


Before you begin, you will want to fill the large pot with water (about 1/2 - 3/4 full) with tap water like so:


Place the pot of water on the stove top and turn the stove on to begin the boiling process:


The water water should be allowed to boil for 20-30 minutes before adding straw. (This gives us plenty of time to chop the straw down to size in preparation of the pasteurization process).

Chopping the straw:


The straw needs to be chopped down to a reasonable size so that it is easier to work with for our particular application. Generally, wheat straw should always be chopped down to 1-3 inch lengths which allows for a better substrate medium for both the cultivator and the mushrooms. The idea is to compact as much substrate mass as possible into a given area which increases your cropping efficiency while offering the mycelium a more ideal medium to colonize over. Cropping efficiency, in this case, is determined by how much substrate can be packed into a given area. This is essentially what determines the yield for a given substrate mass or "cake". In other words; a substrate/cake that is more compact or dense will produce greater yields than one that is less dense or compact.


Since we will be using such a small container to house our substrate/cakes, we will need to chop the straw down to the minimum possible length desirable. 1 inch is a good length for this particular application.

Start by grabbing a hand full of straw, and while working over your tray or bowl, begin cutting the loose pieces of straw off the end of the bushel like so:

Work your way down, one inch at a time, until you're able to get an even egde to work from (see pic below):

Continue to cut the bushel down to 1 inch lengths and repeat this procedure until you have at least 2.5 to 3 times the amount of mass that you plan to fill. Below is a picture of the final batch of straw ready for pasteurization:



In order for pasteurization to be completed, Wheat straw is bathed in a pot of water at 160-170'F for a total of 30-45 minutes.

The pot of water should have had plenty of time to come to a boil and remain for 20-30 minutes:

Before we can add the straw to the pot of water, we need to lower the temperature of the water to a point below boiling that is ideal for pasteurization to proceed. To do this; simply turn the stove dial down by 1/3 or 1/2. Using the Meat Thermometer Probe; periodically check the temperature of the water until it nears the ideal range for pasteurization (160-170'F):

Once the water temperature is down within range; you can begin to add the straw into the water. This is the point where you should start your 30-45 minute countdown:

After filling the pot with a portion of dry straw, force the floating straw down under the water with a heavy-duty utensil for total submersion:

Repeat this procedure of filling and sumberging the straw into the pot of water until you have added as much straw as necessary for your application (or as much as can possibly be contained in the pot your working with):

Using a grate (or some form of heavy-duty material that will alow you to hold the straw submerged under the water for the duration of the pasteurization process), force the straw down into the pot of water like so:

Here is a close up view of the type of grating that was modified to fit this pot for this particular purpose:

Now, you will need a heavy weight of some kind to place on top of the grate in order to keep the straw forced down into the pot of water. I used a couple of weights from a weight-lifting set and wrapped them in a heavy-duty plastic bag, like so:

Be sure to use the thermometer probe to gauge the temperature of the water. It's important to keep an eye on the gauge to make sure that the straw remains within the ideal range for the duration of the pasteurization process.

Draining water from straw:

Once the straw has been fully submerged and pasteurized for the 30-45 minute time period, the stove shouldbe turned off and allowed to cool down for about 10 minutes before draining the water out of the pot.

In the pic below, you can see how the leftover water from the pasteurization process was drained (and strained) into a 1 QT jar where it will be saved for another batch of grain:

Below is a picture of the final product of the drained wheat straw juice that will be used on the next batch of grain jars in place of bottled water, which will provide the spawn jar with a nutritional boost that will help to speed up the colonization cycle considerably.

Once the water has been drained from the pot, it's time to move the freshly pasteurized straw into a heavy-duty plastic bag where it can be allowed to cool down to room temperature before being spawned.

I recommend tying the bag up and poking about 20-30 holes into it with a clean nail or similar poking device and allowing it to hang for a 4-6 hour time period until it has had plenty of time to cool back down to room temperature. (see pic below)

Below is a picture of the final product after pasteurization and draining is completed:

Once the straw has cooled down to room temperature, you can proceed to the following TEK where you will find the necessary information for spawning the freshly pasteurized wheat straw with a pre-colonized jar of grain spawn:

Wheat Straw Spawning TEK

Edited by Mycotek on Dec. 21 2001,6:00