On many farms, but also in supermarkets, I regularly see that the stem of mushrooms turn brown or even almost black. How does this phenomenon occur? And, more importantly, how can you prevent it as a mushroom grower?
The brown discoloration is caused by excess moisture in the stem. This excess moisture contains many nutrients. Cell damage, bacterial growth or oxidation processes cause the stems to discolor.
I often discuss this subject with growers. It is often thought that the problem lies with evaporation in the growingroom. In my opinion, however, the real cause is too much moisture in the stem, despite a dry climate. Especially at high compost temperatures during the first flight, I see this problem occur.
Cause of Too Much Moisture in the Stalk
1. High compost temperature during the first flight
When compost temperatures are high, the mycelium is very active, causing increased moisture flow to the mushroom. The mushroom cannot handle this excess moisture, so it gets stuck in the stalk and causes discoloration.
2. Last day of harvest
On the last day of harvest, you often see that large quantities of mushrooms have been harvested the day before (6-7 kg per m²). The following day, only 1 to 1.5 kg per m² remains, causing the mycelium to continue the moisture supply to the remaining mushrooms. This leads to an accumulation of water in the remaining mushrooms, especially in the stems.
How Can You Prevent This?
As a mushroom grower, it is important to follow nature and keep the compost temperature in balance with mushroom growth. Here are some practical tips:
1. Set lower starting temperatures
Start a day before the first flight with a compost temperature of 19°C to a maximum of 20°C and an air temperature of 16°C to 17°C or even lower.
2. Warm up slowly during harvest
When you start harvesting, let the compost temperature rise slowly. Increase the air temperature by about 0.04°C per hour (about 1°C per day). This way, the compost temperature remains under control.
3. Control after several days of harvesting
After four days of harvesting, the compost temperature can rise to 24-25°C, while the air temperature is around 18-19°C. With a good spread of mushrooms and enough room for growth, you will see less moisture in the stems.
4. Extra attention for chestnut mushrooms
With chestnut mushrooms, peak harvest is more difficult to control. That’s why you see this problem more often with this variety. Good harvest management is even more important here.
By following this approach, you as a grower can significantly reduce the risk of moisture accumulation in the mushroom stems and improve the quality of your harvest.
Mark den Ouden | Mushroom Blog
