Our Mushroom Growing Process
Mushroom growing is a highly complicated production process involving both nature’s processes and technology. To simplify it can be broken down into the following main steps:
- Step 1 Compost Making
- Step 2 Pasteurization
- Step 3 Spawn Running
- Step 4 Case Running
- Step 5 Airing
- Step 6 Cropping
- Step 7 Packing and Delivering
- Step 8 End of Crop and Compost Disposal
Compost is the substrate that the mushroom feeds off and is made from wheat straw, chicken manure, gypsum and water. Compost is made following a recipe which is constantly altered based on the structure and quality of the raw materials. At our farms we use large bunkers which are at the forefront of composting technology. One main advantage is that air is supplied through holes in the floor. This ensures that the composting process occurs aerobically (meaning with oxygen) and so odour is limited. The converse is anaerobic compost making which is without oxygen and that is when bad odour generated. This process takes approximately 2 – 3 weeks depending on the time of year. Interestingly, the internal compost temperatures during this process can go as high as 85oC as a result of the chemical and microbiological reactions that are taking place.
Once the composting process is complete it is then transferred into tunnels. The aim of this step is to destroy and pests, diseases and competing moulds in the compost. Pasteurization 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 oC for a period of 8 to 10 hours. After the “kill”, the compost is conditioned and then cooled.
Spawn and Spawn Running
Mushroom spawn (which is mushroom mycelium germinated onto rye grain seeds) is added to the pasteurized compost and again filled into a tunnel. Humidity and carbon dioxide is 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 to 17 days.
The spawned mushroom compost from the tunnels is then delivered to our various growing units. This compost is placed into wooden trays, or aluminium shelves depending on the technology employed at our different sites. The bed of compost is then topped with a 5 centimetre layer of peat. Peat has a high ability to absorb and hold water. This provides water to the mushroom once it starts growing as we can’t water mushrooms once the mushrooms start forming as water will damage their beautiful white appearance.
On our farms we import peat from the Northern Hemisphere, mainly Germany, where it is abundant and being removed from fields for urban development. This is an environmental decision in order to preserve our 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 9 – 11 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 this means so no windows and mushrooms do not contain chlorophyll and so not need light to grow, but extract their food from the compost.
Airing is where the growing room environment is changed over a period of 2 -3 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.
Our 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. In order to protect quality we try to only touch a mushroom once, that is when being harvested. Pickers are highly specialised and trained people making sure that mushrooms are picked carefully and at great speed. Punnets are placed into trays and taken immediately to the pack house for final quality grading and packing.
Packing and Delivery
Mushrooms are delivered to our pack houses, blast chilled and then await final quality and weight checking. Punnets are then wrapped, labelled, given a sell by dates and placed into lugs and stored in our large refrigerator awaiting delivery.
As mushrooms have a very short shelf life we store our mushrooms for the minimum amount of time. This means that our processes are designed to get your mushrooms to you in the store on the day, or the day after they have been harvested.
On order from customers mushrooms are placed in refrigerated vehicles and delivered to the retailer’s central distribution area or direct to your store.
End of Crop and Compost Disposal
A mushroom compost will deliver three weeks of mushrooms. Thereafter most of the food has been used from the compost. Mushroom growing houses are then steamed out to ensure any mushroom diseases are killed and that a clean waste product is available to be disposed of. Spent mushroom compost is then sold by our farms under contract to nurseries, landscapers etc. to be used as a wonderful soil additive for gardens putting nutrition back into the earth.