Growing Shrooms is an activity that combines science, dedication, and a deep respect for nature. These fascinating life forms require a controlled environment to thrive, as any imbalance can affect their growth in the form of the dreaded contamination. Thus, one of the most critical aspects in this process – as we always remind you – is hygiene, especially when the grower wants to prepare his substrate to inoculate it later.
Mushrooms grow from mycelium, which develops in a nutrient-rich substrate. This environment, if not managed properly, is also ideal for the growth of bacteria, molds, and other contaminants that can compete with the mycelium and destroy the crop. Therefore, ensuring that materials, tools, and the workspace are clean is an essential step for successful cultivation.
When preparing a grain jar to inoculate spores or a substrate for mycelium to grow, and beyond basic hygiene, it is essential to apply sterilization or pasteurization methods to minimize the presence of unwanted microorganisms in the substrate and utensils. Understanding these techniques and applying them correctly is the basis for obtaining a healthy and abundant harvest, otherwise, the mycelium will most likely end up contaminated. Today we will tell you how to sterilize or pasteurize your materials to minimize the appearance of this problem.
Why is it so important to use sterile material?
In mushroom cultivation, the mycelium must colonize the entire substrate to develop healthy fruiting. However, if the material used is contaminated, the microorganisms present will compete with the mycelium for nutrients. In most cases, these contaminants are more aggressive and colonize the substrate faster than the mycelium, resulting in crop loss.
The most common contaminants in mushroom cultivation include:
- Bacteria: Such as Bacillus spp. , which can emit unpleasant odors and acidify the substrate. Also, watch out for the appearance of Pseudomonas spp .
- Molds: Such as Trichoderma harzianum, which grows quickly and often covers the mycelium with a greenish or bluish spore layer (which is why we always advise you to keep your plants away from your mushroom crop!). Other molds to look out for are Penicillium spp., Aspergillus spp., Geotrichum spp., or Hypomyces spp.
- Yeasts: They can ferment the nutrients in the substrate and generate an unfavorable environment for the development of mushrooms.
In addition to compromising the quality of the crop, some contaminants can produce mycotoxins or toxic compounds that affect the safety of the final product. Therefore, using properly sterilized or pasteurized materials and tools not only improves the chances of success but also guarantees a safe final product for consumption. Yes, it is a somewhat cumbersome step, but we assure you that skipping it will only bring you problems!
Sterilization or pasteurization?
When preparing materials for mushroom cultivation, it is important to decide whether sterilization or pasteurization is required, depending on the type of material and the context of cultivation:
- Sterilization: This is a process that eliminates virtually all microorganisms, including bacteria, spores, and fungi. It is essential for materials that are extremely nutritious and prone to contamination, such as grains used to inoculate mycelium. It is also critical for tools or closed containers where the environment must remain completely free of contaminants.
- Pasteurization: In this case, most pathogenic microorganisms are eliminated, but less aggressive microorganisms are allowed to be present. It is ideal for substrates such as straw, manure, or sawdust, where a completely sterile environment is not necessary since the mycelium can coexist with certain non-competitive organisms.
As you can see, the choice between both methods depends on the materials and the level of control required for the culture, so sterilization is normally used for grains or very nutritious materials (where the mycelium will develop before mixing it with the substrate), and pasteurization for basic substrates such as straw or sawdust.
Sterilization methods
Sterilization is performed by applying high-pressure heat to kill any living organisms. There are two main methods for performing this:
Sterilization with pressure cooker
A pressure cooker, also known as a pressure cooker, is a kitchen utensil designed to cook food quickly by generating high-pressure steam inside it. In addition to its culinary use, it is a widely used tool in mushroom cultivation to sterilize materials such as jars with grain or small tools, thanks to its ability to reach temperatures and pressures similar to those of an autoclave.
This method is accessible, efficient, and widely used by home growers. The pressure cooker can reach temperatures of up to 121°C, necessary to eliminate the most resistant spores of bacteria and fungi.
Steps to sterilize with a pressure cooker:
- Fill the pot with enough water to generate steam, but without covering the jars or utensils.
- Place the jars or tools inside, making sure they are well sealed or covered. The jars should be about halfway up the water level, and ideally, they should be separated from the bottom of the pot so that they are not in direct contact with the metal (a very common solution is to use stainless steel microwave racks).
- Close the pot and cook at high pressure (15 psi) for 60-90 minutes.
- Allow to cool completely before opening to avoid accidental contamination.
Autoclave sterilization
An autoclave is a specialized device used to sterilize materials by applying high-pressure, high-temperature steam. It is widely used in laboratories, hospitals, and mushroom cultivation to eliminate microorganisms such as bacteria, viruses, fungi, and spores, ensuring the complete sterility of the treated objects or materials.
In mushroom cultivation, autoclaves are ideal for sterilizing grains and nutrient-rich substrates, where sterility is crucial to avoid contamination that could ruin the crop. Although autoclaves can be more expensive and less accessible than other methods, they offer superior and consistent results in larger-scale or professional cultivation projects.
Basic steps for autoclaving :
- Place the materials in the autoclave, leaving enough space for proper steam circulation.
- Set the cycle to 15 psi and 121°C for about 120 minutes, depending on volume.
- Wait for it to cool before removing the materials (1-2 hours).
Spore prints and syringes of magic mushrooms
Today we are going to tell you how to prepare a spore syringe from prints or vials, a simple process that requires maximum hygiene to minimize the risk of contamination. In addition, we will present you the different options you have to reproduce the mycelium and get a copious harvest of mushrooms.
Pasteurization methods
Pasteurization uses moderate heat to reduce the number of microorganisms in the substrate, allowing the mycelium to develop without significant competition. This is usually the most commonly used method to pasteurize the substrate before starting the culture:
Bucket with boiling water
This is one of the simplest and most effective methods for pasteurizing substrates such as straw or composted manure.
Steps to pasteurize with boiling water:
- Prepare the substrate, cutting it into small pieces to ensure uniform pasteurization.
- Fill a large bucket or heatproof container with boiling water.
- Place the substrate in cloth bags or directly into the water. Make sure it is completely submerged and stir the mixture well.
- Keep the temperature between 60-65°C for approximately 1 hour. Avoid exceeding 80°C to avoid accidentally sterilizing the material.
- After an hour, stir again, drain the substrate well, and let it cool before using it (3-4 hours).
- This method is economical and effective, making it ideal for those who are just starting out in mushroom growing.
You’ve already seen how sterilization and pasteurization are fundamental pillars for successful mushroom cultivation. Choosing the right method and applying it correctly not only prevents contamination but also maximizes the efficiency of the cultivation and the quality of the final product, saving you a lot of trouble in the process. With good preparation and attention to detail, you can enjoy healthy and abundant harvests, making this activity an experience that is as rewarding as it is productive.
Happy harvest!
References:
- The psilocybin mushroom bible, Virginia Haze, Dr. K, Mandrake
- Magic mushroom growing guide, Principium Quaesitor
- Growing psilocybin mushrooms at home, Paul Geis
