Yes they can.
Even after pasteurization, there are several reasons why unwanted mushrooms might grow on your substrate:

1 Incomplete pasteurization:

Incorrect temperature or duration:.
The substrate might not have been heated to a high enough temperature or for a long enough period to kill all unwanted fungi spores.

2 Uneven heating:.
Some parts of the substrate might not have reached the proper temperature for complete pasteurization, allowing unwanted spores to survive.

3 Contamination after pasteurization:.
The substrate might have been contaminated with unwanted spores after pasteurization, either through improper handling, inadequate airflow, or contaminated equipment.
Nutrient-rich substrate:

4 Excessive supplementation:.
A substrate with too much bran or other nutrients can be more attractive to unwanted fungi than the desired mushroom species.

5 Presence of unwanted nutrients:.
The substrate might contain trace nutrients that specifically favor the growth of unwanted fungi.

6 Competition between fungi:
Slow colonization of desired mushroom: If the desired mushroom takes too long to colonize the substrate, unwanted fungi might be able to outcompete it for resources.

7 Species-specific vulnerability: Some desired mushroom species are more susceptible to specific types of contamination than others.

**Some tips to prevent unwanted mushrooms from growing on your pasteurized substrate:.

*Ensure proper pasteurization:.
Use a reliable method and verify the temperature and duration.
*Maintain sterile conditions:.
Clean and sterilize all equipment and work surfaces before handling the substrate.
*Use a balanced substrate recipe:.
Avoid over-supplementation and use high-quality ingredients.
*Monitor the substrate closely:.
Look for early signs of contamination and discard any contaminated substrate immediately.
*Choose resistant mushroom species:.
If you are struggling with contamination, consider switching to a mushroom species that is more resistant to unwanted fungi.


**If you are still having trouble with unwanted mushrooms after observating the above, it is important to identify the specific type of contamination so you can take steps to prevent it in the future.

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