Many exotic mushrooms can be cultivated on sterilised substrates in plastic bags, like shiitake, maitake, Hericium, King oyster, bunashimeji and nameko. Choosing the right bag depends on many factors: sterilisation method, preferred size of substrate block, top spawning or through spawning, chosen mushroom and required aeration. Large filter bag companies like Unicorn (US) and Sakato (Japan) typically have more than 100 different bag types. Many entrepreneurs wish to experiment with new bag types, however, choosing a bag that is routinely used may actually be the best choice. Using standard bags means quicker delivery, a lower price and using ‘proven technology’.

Material: PE, HDPE or PP

The sterilisation method in particular determines the choice of the plastic. (See image)

Currently, HDPE is  cheaper than PP, and growers in Japan mainly use HDPE to grow shiitake, maitake and nameko. In general PP is more brittle than PE, but by adding plasticisers PP is softened to avoid cracking at side folds and gussets.

Thickness

The thickness of the bags determines part of the bag price, as more material is needed for thicker bags. Most growers in Japan use 50 - 55μ, European growers prefer thicker bags of 65-70μ. Japanese use top spawning; the bags are handled carefully. European companies often apply through spawning; the bags are tumbled after spawning, putting more stress on the bags. Therefore thicker bags are chosen.

Aeration

The type of filter and the surface of the filter determine the aeration. Both Sakato and Unicorn use three different filters, with increasing aeration: A higher aeration however may also increase contamination risk, as there is more gasexchange. The substrate may dry out when using filters with the highest aeration. The bags should always be filled at 2 cm below the filter, to avoidlocally dried out substrate.

Size matters

Smaller bags (e.g. 1,2 kg substrate) in general give a higher yield but the handling cost is higher, too. The efficiency in the farm may be lower as well, for shiitake production the bags need space on all sides; other mushrooms like King oyster or nameko can be forced to have only pinning on top of the bags and can thus be spaced close to each other.

Typical bag sizes range from 1,2 to 2,5 kg in Japan and up to 5 kg in Europe.

Specials

Another special feature is to have pigments added to the bags. Black bags are used in nameko cultivation to limit pinning on the sides of the bag.