# How to Pasteurize Mushroom Substrate with Steam

Source: [https://www.stilsan.com/en/blog/mantar-substrati-buharla-pastorizasyon](https://www.stilsan.com/en/blog/mantar-substrati-buharla-pastorizasyon)

Published: 2026-08-14

Last updated: 2026-08-14

Pasteurization and sterilization are not the same process for mushroom substrate. The room, load, distribution, temperature measurement, and cooling plan must be designed together.

## First define the target process: pasteurization or sterilization?

These two concepts should not be used interchangeably. The target temperature, duration, pressure, and expected microbiological outcome vary according to the production protocol. Before selecting a generator, the mushroom species, substrate recipe, and process step validated by the facility must be clarified.

## The determining factor is not room volume but the total load to be heated

In two rooms of the same size, the number of bags, substrate mass, starting temperature, and rack arrangement may differ. Wall and door insulation, outdoor conditions, cycle frequency, and door opening also change heat losses. Therefore, recommending a model based only on square or cubic meters is not reliable.

## Steam distribution and air evacuation

Steam must be able to circulate between the racks and bags, the initial air must be removed in a controlled manner, and the condensate formed must be drained. If the distribution line heats only the area near the inlet, hot and cold zones may form in the room.

## According to which temperature should the holding time begin?

The holding time should not be started solely when the generator is activated or based on a single thermometer near the door. Measurement must show that the reference condition defined by the protocol has been reached, particularly in the part of the load that heats most slowly. The number and placement of sensors are determined according to the room-load arrangement.

## Cooling and recontamination are also part of the cycle

Uncontrolled air entry, contaminated surfaces, or improper handling after the thermal process is complete may create new risks. Cooling, unloading, and transfer to the next stage should be addressed together with the facility's hygiene plan. The generator alone does not guarantee the microbiological outcome.

## Frequently asked questions

**How many kg/h of steam is required for mushroom substrate pasteurization?**

A reliable flow rate cannot be provided without knowing the total substrate mass, starting and target conditions, duration, room losses, and cycle program.

**Is the number of bags sufficient to select a generator?**

No. The mass per bag, material, starting temperature, arrangement, room insulation, and target protocol are also required.

**Is a single temperature sensor sufficient?**

It may be sufficient in a small, validated setup; however, in dense or large loads, temperature distribution may vary, so multiple points should be evaluated.

**Can a steam generator be added to an existing room?**

Suitability can be assessed after examining the insulation, door, distribution, air evacuation, drainage, sensors, and electrical infrastructure.

## Technical sources

1. FAO. [Mushroom Cultivation Guide: Pasteurizing Bags](https://www.fao.org/4/AB497E/ab497e07.htm)
2. FAO AGRIS. [Inactivation of Human Pathogens during Phase II Composting of Mushroom Growth Substrate](https://agris.fao.org/search/en/records/65de516a0f3e94b9e5cd653d)

## Related solution

[Mushroom Substrate Steam Pasteurization](https://www.stilsan.com/en/solutions/mantar-substrati-pastorizasyonu-icin-buhar-jeneratoru)