Mixed product ready to be packed.
value of 2 grams/kg of air with a maximum of 4 grams/kg of air. When evaporation levels are too low (small difference AH growing room – AH inlet air), the computer will decrease the required RH , while when evaporation is too high ( large diffe- rence AH growing room – AH inlet air ) the com- puter will increase the required RH. However, the bandwidth of the RH must be set wide enough to allow the computer to make this adjustment. When the air volume flow is measured, or measu- red once and entered in the computer, the system can calculate evaporation in grams per m2
per
hour. This control/measurement is particularly beneficial in the second and third flushes. In the second flushes the aim is to evaporate about 30 grams per m2
per hour, but with inactive com-
post, it is sometimes necessary to lower the RH to 75% to achieve this. Since more attention has been paid to evaporation, there have hardly been any problems with bacterial blotch, no more moisture blemishes and fewer sticky mushrooms.
Other varieties
At present, the company grows oyster mushrooms, king oyster mushrooms, shiitake and nameko. The oyster mushrooms are grown on blocks of 40 x 60 cm, which weigh about 18 kg, on straw-based substrate. The other three varie- ties are grown on blocks of approximately 3 kg using a substrate based mainly on sawdust. The company used to produce pom pom blanc (erina- ceus) and maitake (grifola frondosa), but the market demand for these varieties is too unpre- dictable and relatively too small to justify a permanent supply.
The strain of oyster mushroom they grow is Spoppo, a variety that does not produce spores.
This means that face masks do not need to be worn at picking or processing. When growing oyster mushrooms, a constant RH level is very important. This is about 90% in the first flush. Any higher gives a greater risk of bacterial blotch, and any lower is detrimental to quality. Supplying enough fresh air is another important factor. The aim is to achieve a low CO2
content of 700 – 800
ppm which requires a lot of fresh air circulation. The plastic is removed immediately from the substrate blocks for shiitake at filling and they are cooled to 12-13oC air temperature with an RH of 95% until the pinheads have formed. Shiitake doesn't need the same level of fresh air as oyster mushrooms. With king oysters, the plastic bag is left in place until the pinheads have formed. The air temperature is also low at 12-13oC during pin- head formation and 14 – 15oC in the first flush. Plenty of fresh air is necessary.
Nameko is grown in a similar way to shitake, with little circulation of fresh air. The air temperature is continually maintained at 16.5oC with an RH of 94-100%.
In summer, a high cooling capacity is required for the oyster mushrooms and the king oyster mushrooms to maintain the low air temperature and high circulation of fresh air. With the exotic varieties there are often more problems with the substrate or mushrooms themselves than with the white mushrooms, so production fluctuations of 30% are no exception. But on the other hand, there are no problems with sciarids and phorids, although green mould does occur in or on the substrate used for shiitake and nameko, which negatively affects production. Green mould is only an occasional issue with oyster mushrooms.
MUSHROOM BUSINESS 29
Photos: Jos Hilkens and Oakfield Champignons
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