PROJECT
INCORPORATING COLD CHAIN
2. PASTEURISATION
Once the composting process is complete,
it is then transferred into a tunnel. The aim
of this step is to destroy pests, diseases,
and competing moulds in the compost.
Pasteurisation ensures that the substrate
delivered to the growing rooms is clean,
disease free, and absent of any other type
of fungus.
The process involves using the correct
balance of oxygen in the closed
environment of the tunnel to again raise the
temperature of the compost to 56–60°C for
a period of 8–10 hours. After the ‘kill’, the
compost is conditioned, which provides
additional nutrients for the mushrooms, and
then cooled.
3. SPAWN AND SPAWN RUNNING
Mushroom spawn (which is mushroom
mycelium germinated onto rye grain seeds)
is added to the pasteurised compost and
again filled into a tunnel. Humidity and
carbon dioxide are kept high to stimulate
the ‘spawn running’ process. This is
essentially where the mycelium grows from
the spawn kernels into the compost. This
transfer allows the whole tunnel of compost
to be colonised by the mushroom mycelium.
This process usually takes around 14–17 days.
4. CASE RUNNING
The spawned mushroom compost from
the tunnels is then delivered to the various
growing units. This compost is placed into
aluminium shelves and the bed of compost
is then topped with a 5cm layer of peat.
Peat has a high ability to absorb and hold
water. This provides water to the mushroom
once it starts growing.
Medallion imports peat from the northern
hemisphere, mainly Ireland, where it is
abundant and being removed from fields for
urban development. This is an environmental
decision in order to preserve the precious
wetlands in South Africa.
The growing room’s environment is set to
a high relative humidity, high carbon dioxide
level, and at the optimum temperature for
mushroom mycelium growth. This allows
the mushroom mycelium to grow from the
compost through the wet peat to the top
of the mushroom beds. This usually takes
six to seven days. And yes, this happens
in dark rooms, mainly because the rooms
have to be highly insulated, so the amount
of energy required is kept to a minimum.
Mushrooms do not contain chlorophyll and
so do not need light to grow, but extract
their food from the compost.
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5. AIRING
Airing is where the growing room
environment is changed over a period of
two to three days to simulate a change
in season. This causes the mycelium to
believe that the season is changing and
so the mycelium starts the reproductive
stage, producing fruit bodies, which are
mushrooms. Growers, with the assistance
of computers, reduce the air temperature,
carbon dioxide, and the humidity in the
growing room. This causes the mycelium to
‘pin’ or clump together, making the start of
the mushroom. Mushrooms then grow fast
and double in size every 24 hours.
6. CROPPING
The mushrooms are then grown to their
optimum size for quality, shelf life, and
taste. When ready, they are carefully hand
harvested by a picker, who gently twists
and plucks the mushroom from the growing
bed, trims the stem, and then places them
in punnets.
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1. Once the ‘bodies’ are formed
from the spawn, mushrooms
then grow fast and double in
size every 24 hours.
2. Medallion does its own
processing and packaging
in-house.
3. Once picked clean, the
mushrooms regrow quickly
and can be picked again.
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COLD LINK AFRICA • May 2018
www.coldlinkafrica.co.za
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