Storage and fresh-keeping Technology of Edible Fungi

After harvest, assimilation has stopped, respiration directly or indirectly affects various physiological and biochemical processes, so it also affects the changes of storability and disease resistance. How to keep the characteristics of fresh food is the problem to be solved in the storage and preservation of edible fungi. The first method used for edible fungi preservation is low temperature treatment. In recent years, the research on controlled atmosphere storage, radiation preservation and chemical preservation has been carried out. They are described below.

Storage and preservation technology of edible fungi

1. Low temperature preservation

The principle is that in the low temperature range where freezing does not occur, the respiratory metabolism of fresh edible fungi is inhibited by lowering the ambient temperature, so that the freshness and quality of the product can be maintained within a certain period of time, and the activity of spoilage microorganisms is inhibited.

As we all know, mushroom cap above there is no obvious surface protection structure, so water is easy to evaporate, so mushroom respiration and transpiration after harvest is very intense, is physiologically one of the most susceptible to deterioration and aging vegetables. The results showed that 100kg mushroom released 2215kJ(kilojoules) of energy at 10℃, but only 627kJ at 0℃ within 24h. The respiratory intensity of mushroom at 10℃ was 3.5 times higher than that at 0℃. Many studies have shown that the optimum temperature for low temperature storage of mushrooms is 0~3℃, and the optimum cold storage temperature is 0℃. Under this temperature, the storage life of Agaricus bisporus can reach 30 days.

After 4~5 hours of picking, the percentage of open umbrella of straw mushroom reached 20%~ 30%. Therefore, it is better to send it to cold storage at 15~20℃ within 1 hour after picking, which can improve the preservation effect and can be stored for 3~4 days. Under normal circumstances, the cold storage temperature of straw mushroom should not be lower than 10℃, and 15~20℃ is appropriate. When the mushroom production area is far away from the factory, you can use the production area precooked method. Boiling the washed mushroom in boiling water for 10min, adding 2% salt during boiling can keep the freshness of the mushroom. It can be stored at 0~4℃ for 1~2 days, and the quality changes little. - It can be stored at 18℃ for 7 days. If the mushroom is too late for processing, the storage temperature should be 0~4℃, and the storage time should not exceed 12h. If stored for more than 24h, volvella volvacea obviously softened and a large amount of brown liquid oozed out. The production of this liquid is related to peroxidase contained in straw mushroom.

3 days before harvest, Flammulina velutipes should be managed dry and harvested 1~2 days earlier. After harvest, Flammulina velutipes, because of the associated mycorrhiza with nutrients, life activities are still very active, easy to aging, discoloration, deterioration, change flavor. Flammulina velutipes can be stored for about 5 days at 4~5℃, and its color and flavor will deteriorate after 7 days. Of course, it can also be frozen storage, Flammulina velutipes in boiling water for 8 minutes, quickly cooled with cold water, and then frozen storage below 0℃.

Fresh mushroom cold storage temperature control in 0℃ above, 4℃ below. Because the temperature reaches above 5℃, the mushroom body tissue moves as usual, and it is easy to open the umbrella, but below 0℃, it will freeze and affect the quality. 8~10h before fresh mushroom transportation, mushroom stem pruning can be carried out. Such as cutting handle in advance, easy to black, affect the quality. Therefore, before shipment, we must concentrate on manpower assault shear handle. The length of mushroom stalk is 2~3cm, the pure mushroom rate is about 85% after cutting stalk, and then continue to store, waiting for loading and transportation.

II. Controlled atmosphere storage

Controlled atmosphere storage (CA) is a method of preservation by controlling the gas composition in the storage environment and appropriate storage temperature. The main preservation effects are as follows: under the condition of controlled atmosphere, the respiration intensity is inhibited, thus reducing the nutrient consumption rate of edible fungi, inhibiting the production of ethylene in edible fungi, delaying the process of post-ripening and aging, inhibiting the reproduction of harmful microorganisms, reducing the decay loss and improving the commodity rate.

The key of CA storage technology is to form and maintain suitable gas components required by edible fungi in the storage system. The initial gas composition of the storage system is atmospheric, i.e. oxygen is about 21%, nitrogen is about 78%, carbon dioxide is about zero. To achieve a controlled atmosphere in the storage system, first try to reduce the oxygen concentration and increase the carbon dioxide concentration.

When CO2 exceeded 5%, the growth of mushroom stem and lid was almost completely inhibited. When the oxygen concentration is lower than 1%, it has obvious inhibitory effect on umbrella opening and respiration. Therefore, the gas conditions required for mushroom storage are oxygen less than 1%, carbon dioxide greater than 5%.

Foreign experiments with 0.1% oxygen and 25% carbon dioxide storage, obtained good preservation effect. Special attention should be paid when using this storage method. When the oxygen concentration exceeds 1% or the carbon dioxide concentration is less than 5%, it may stimulate the growth of the cap, often causing the mushroom to open.