shiitake log sterilization

Several important factors for shiitake log sterilization

1. Cold Air Exhaust  

no matter it is high-pressure  or normal-pressure sterilization, the cold air needs to be exhausted.

when shiitake logs are put into the cabinet,Both air and substrate inside shiitaek logs are cold. After hot steam comes in, it will form a cold and hot mixture with cold air. When this mixture amount increase to a certain level, the pressure rises very quickly, but the temperature cannot rise accordingly.

At this time, the exhaust duct must be opened to allow the cold air discharged along with the steam. When cold air meets hot air (steam),water will be formed. Therefore, in early stage of sterilization, we see water flowing out of the exhaust duct. The colder season, the more cold air, and the more water will be in the exhaust duct.

As time goes by, water will gradually become less and less. When a large amount of steam is sprayed out, it means the cold air has been exhausted, then We can close a bit the exhaust duct. After cold air is exhausted completely, the center temperature of shiitake log will quickly reach 100℃, then the boiler will be easily to control, and A small amount of steam can maintain a balance of 100℃ of the shiitake log center

2. Sterilization temperature & time

After cold air is exhausted, the center temperature of the shiitake logs quickly reaches 100℃. then time can be counted and this is the sterilization time. The sterilization time is closely related to the shiitake log quantity and substrate weight. This needs to be flexibly adjusted according to the specific situation.

High-temperature and high-pressure sterilization:

If the temperature is maintained at 121°C, sterilization time need 90 minutes, plus the time for pressure increase and pressure release, it will take about 4 hours totally. After the temperature drops to 80°C, open the sterilizer door, pre-cool to approximately 60°C, then rapidly cool (with cooling water) to over 20°C before inoculation.

If the temperature is maintained at 117°C, sterilization time need 8 hours (this is the sterilization time), excluding the heating time, stewing time and exhaust time.

If the temperature is maintained at 108°C without piercing small holes, it usually takes 14 hours, and the clip tying should be loosened a bit.

The small holes poked should not be too large, 6mm diameter is ok.

3.Altitude

The higher altitude, the lower temperature of saturated steam. Therefore, in areas with an altitude of more than 800 meters, the temperature at the center of shiitake log is difficult to reach 100℃. Therefore, in high-altitude areas, high-pressure sterilization is generally required. must refer to the reference table of temperature and corresponding saturated steam pressure to determine whether cold air is completely exhausted.