1. Insufficient fermentation temperature and time
The fermentation process in the process of oyster mushroom fermentation material is equivalent to the sterilization process of clinker. Because the fermentation temperature does not reach above 60 °C, or the time to reach above 60 °C is insufficient, a lot of mold and eggs will remain in the culture medium, which is easy to contaminate later.
Note: Because the fermentation material itself is an extensive cultivation method, the fermentation time should be determined according to the actual fermentation temperature, which is also related to the raw materials.

2. The water content is too high
After the fermentation, the water content of the medium before inoculation is too high, and the excessive water content after inoculation can easily lead to bacterial contamination, which is not conducive to the growth of mycelium.
The water content after fermentation is not easy to be too high, and the recommended water content is 63-65%.

3. Inappropriate pH
After the fermentation, the pH is too high or too low, which is not conducive to the growth of bacteria, is not conducive to the growth of mycelium, and it is easy to breed miscellaneous bacteria.
Compared with clinker cultivation, the pH value of oyster mushroom fermentation material cultivation can be a little higher, and the recommended pH value before inoculation is 6.5-7.5.

4. Small amount of inoculation
If the inoculation amount is too small, the oyster mushroom mycelium cannot quickly control the material surface and bacteria, increasing the probability of contamination.
Ensuring a certain amount of inoculum is determined by the cultivation method of fermented material.

5. The quality of the bacteria is not good
The oyster mushroom cultivar itself has miscellaneous bacteria, or the cultivar is not well developed, has poor activity, or the cultivar stored for a long time, or the cultivar that has been subjected to high temperature, etc., it is easy to cause pollution.
The quality of cultivated species is very important for clinker cultivation, and even more important for oyster mushroom fermented cultivation.

6. The culture temperature is too high
For the cultivation method that the medium is not completely sterilized, once the high temperature occurs during the growth of bacteria, the bacteria in the medium will quickly and actively multiply, and even the phenomenon of fever (burning) may occur, resulting in pollution.
If the temperature is too high, it will also have an adverse effect on the germination of oyster mushroom strains. It is recommended that the temperature of the oyster mushroom fermentation material after inoculation (the temperature between the fungus packs) should not exceed 22 °C.

7. The culture temperature is too low
Many people know that the fermentation material temperature is too high will lead to pollution, but they do not know that if the temperature is too low, it will also lead to pollution, because the temperature is so low that it will affect the germination and growth of oyster mushroom mycelium, which is bound to increase pollution.
After the oyster mushroom fermentation material is inoculated, it is recommended to control the culture temperature before 15-22 °C, which also refers to the temperature between the bacteria packs.

8. Too many nutrients
Too much nutrient material can easily lead to contamination of fermentation material, especially in the presence of the above 7 points, it is more likely to cause contamination and increase the degree of contamination.
For fermented materials, successful fermentation and growth are more important than increasing yield.

Finally, it should be emphasized that the fermentation material is a kind of oyster mushroom cultivation process under the condition of lack of equipment. If the conditions are available, it is recommended to use the clinker cultivation method.