Preventing mushroom darkening: Simple tricks to retain fresh colour

The beautiful smell and taste of mushrooms are not everything since their impeccable presentation also matters. The effect of the hard work put into preparing the delicacy can be spoiled by the fact that our mushrooms have started to darken – whether after being sliced or dried. Why does this happen? And how can you prevent it?

Mushrooms lose their colour, darken, and sometimes become almost black due to the oxidation process. It’s a natural process that – in simple terms – results from mushrooms coming into contact with oxygen. The same happens with potatoes, which we grate for potato pancakes and which, once turned into potato mass, take on a grey colour.

In both cases, you can prevent the product from darkening. To keep mushrooms' beautiful colour, it is worth using the same method as with darkening potatoes, which is to treat them with citric acid or lemon juice, for example, during soaking or boiling. A tried-and-true classic is also to add a tablespoon of vinegar to the boiling mushrooms. It is also worth adding some citric acid or lemon juice to the vinegar marinade used for pickling mushrooms. This guarantees that the preserves will not darken.

Dried mushrooms will certainly change colour somewhat, and there’s nothing alarming about it. Only genuinely dark, almost black colour can indicate that something went wrong during the drying process. If the mushrooms are black after drying, it may mean that they were dried at too high a temperature. Too high a temperature would be above 60°C.

The optimal temperature for drying mushrooms is considered to be between 40°C and 50°C. However, it is worth remembering that mushrooms containing a lot of water, such as slippery jacks, should be dried at even lower temperatures – around 30°C. After evaporating a large amount of water, the temperature can be gradually increased to a maximum of 50°C.