High-yield Cultivation Techniques for Edible Fungi and Key Points for Storage and Fresh-keeping
1. Button Mushroom
1.1 Storage Characteristics
Button mushrooms have a very high water content and readily lose water, which reduces their storability. At the same time, they have vigorous metabolism and should be stored at a low temperature of 5°C; if the temperature is too low, chilling injury readily occurs. Button mushrooms harvested at different growth stages have different respiration intensities, and button mushrooms are prone to senescence after the caps open and do not keep well, so they should be harvested before the caps open and cooled promptly. Modified atmosphere has an obvious effect on storage results, and small-package methods are mostly used. Another storage characteristic of button mushrooms is that they readily brown; reducing mechanical injury and modified atmosphere storage have an obvious effect on reducing browning.
1.2 Harvesting and Pretreatment
The standard generally followed is: harvest when the mushrooms have grown to about 4 cm and the caps have not yet opened. Before harvesting, the harvesting tools should be disinfected in advance. It is best to cut the mushrooms off with a small knife and place them directly in plastic or bamboo baskets; each basket should not be filled too full, and the bottom of the basket should be lined with plastic film. Throughout the entire process from harvesting to leaving the warehouse for market, they must be handled gently. Reduce mechanical injury. Use the method of sorting while picking to reduce movement between different containers. Remove residual culture medium, and select mushrooms free of pests and diseases, free of mildew, and of normal growth for storage. Cooling the mushrooms promptly after harvest has a great influence on the fresh-keeping effect; generally they can first be pre-cooled in a pre-cooling room. The baskets can be placed flat on the floor of the room, not stacked, and may be left uncovered. If the harvest is large, where conditions permit, the vacuum pre-cooling method can be used, with even better results. Cooling the mushrooms in a short time has little effect on water loss from the mushrooms. However, the refrigerating capacity of the room is required to be large, so that the mushrooms can be cooled to 6°C in a short time.
1.3 Storage Conditions
The suitable storage temperature for button mushrooms is about 5°C, and the relative humidity is 80%-90%.
1.4 Storage Methods and Management
In a cold storage room that can ensure temperature and humidity, mushrooms can be stored directly in baskets. After the mushrooms are pre-cooled according to the above method, they do not need to be trimmed again, and the baskets can be stacked directly. Cover the surface of the stack with plastic film 0.06 mm thick to reduce water loss. Under these conditions, the mushrooms can be kept fresh for several days. This method can buffer the sales pressure during large harvests.
With the modified atmosphere storage method, mushrooms can be kept fresh for more than 10 d; place the mushrooms in polyethylene bags 0.03 mm thick, put about 0.5 kg in each bag, and seal the bag opening. If nitrogen and carbon dioxide are flushed into the bags, the effect is instead poor. When conditions permit, the gas composition in the bags can be monitored; the gas composition range to be maintained is an O2 concentration of 2%-5% and a CO2 concentration of 10%-15%, and ventilation for air exchange should be carried out when necessary.
2. Oyster Mushroom
2.1 Storage Characteristics
Oyster mushrooms are cultivated in many countries, and there are many varieties. Different varieties differ in storability. Among edible fungus varieties, oyster mushrooms do not keep well. After harvest at room temperature, white fuzz quickly grows at the stipe, the caps crack and the edges curl, until finally they brown and rot. In addition, oyster mushrooms have high oxidase activity after harvest and readily brown.
2.2 Harvesting and Pretreatment
The harvesting standard is: the caps are basically flattened and have not yet released spores in large quantities. When harvesting, they can be cut with a knife; take care to maintain the integrity of the mushrooms and reduce mechanical injury, and also take care not to affect the growth of the next crop of mushrooms.
2.3 Storage Conditions
The suitable storage temperature for oyster mushrooms is 0°C, and the relative humidity is 80%-90%.
2.4 Storage Methods and Management
Oyster mushrooms are mostly stored by the cold storage method; place the oyster mushrooms in polyethylene bags 0.03 mm thick, put about 0.5 kg in each bag, and seal the bag opening. If the storage time does not exceed 1 week, small packaging may be omitted. However, attention should be paid to heat preservation.
3. Shiitake Mushroom
3.1 Storage Characteristics
Shiitake mushrooms are a relatively storability-tolerant species among edible fungi, because during storage they can tolerate low temperatures and high carbon dioxide environments without suffering obvious injury; therefore, modified atmosphere storage can be used for shiitake mushrooms.
3.2 Harvesting and Pretreatment
Shiitake mushrooms should be harvested in batches; the suitable harvesting standard is: the cap is not fully opened, the edge of the cap is slightly incurved, and the gills have fully straightened. Shiitake mushrooms should be harvested on a clear morning, when the temperature is relatively low. When harvesting, they can be cut off one by one with a small knife and placed in containers such as bamboo baskets; the lower part of the container should be lined with a layer of plastic film, and during picking care should be taken to maintain the integrity of the shiitake mushrooms and avoid mechanical injury. After harvest, sorting should be carried out promptly to remove mushrooms unsuitable for storage.
3.3 Storage Conditions
The suitable storage temperature for shiitake mushrooms is 0°C, the relative humidity is 80%-90%, and the gas conditions are an O2 concentration of 2%-5% and a CO2 concentration of 10%-15%.
3.4 Storage Methods and Management
After shiitake mushrooms are harvested, the temperature should first be lowered before small packaging. Shiitake mushrooms are mostly stored by the small-package storage method, with a film thickness of 0.03 mm, 1 kg packed per bag, and the bag opening sealed, carrying out spontaneous modified atmosphere without treatments such as nitrogen flushing. This method can generally keep shiitake mushrooms for 2-3 weeks with relatively good quality.
4. Disease Control
Common diseases of button mushrooms include brown rot, brown blotch and rust spot, etc. Oyster mushrooms, however, are often infected by Penicillium and Botrytis. In addition, pest infestations often occur in edible fungus production. Control of the occurrence of pests and diseases in edible fungi is mainly approached from two aspects: first, in the processes of harvesting, transport and storage, etc., improve the disease resistance of the mushrooms through suitable operations; second, carry out preservative treatment by chemical methods.
According to some storage characteristics common to edible fungi, the following work should be done well to improve the rot resistance of edible fungi; the relevant tools used for harvesting and storage should be disinfected; timely harvesting is very important, as mushrooms harvested too late rot very easily, and selection should be carried out before storage to remove individuals already infected with disease; throughout the entire process from harvesting to sales, attention should be paid to reducing mechanical injury; attention should be paid to controlling storage conditions.
In terms of chemical preservation, the preservatives often used are: 20 mg/kg potassium sorbate, sodium benzoate, sodium bisulfite, and 10 mg/kg Benlate, thiophanate, etc. Because the surface of edible fungi has no protective tissue, the use of preservatives is generally not advocated.