Storage and preservation of the hottest edible fun

2022-09-29
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Storage and preservation of edible fungi (III)

4. Radiation storage: radiation storage is a new technology for edible fungi storage, which has many advantages compared with other preservation methods. For example, without chemical residues, it can better maintain the original fresh state of mushroom, save energy, have high processing efficiency, can work continuously, and is easy to automate production. It is a promising physical preservation method. The effects of radiation on edible fungi are as follows:

(1) respiratory inhibition: it is reported that treating fresh mushrooms with a dose of 2.5 ~ 10 Gy can significantly inhibit their respiratory effects

(2) inhibiting parachute opening: within a certain dose range, the effect of inhibiting parachute opening is directly proportional to the weekly radiation dose. According to South China Agricultural University, γ— When the radiation dose is 13 ~ 18 Coulomb kilogram, it has a good effect on inhibiting mushroom film breaking and umbrella opening. The treated mushrooms do not open the umbrella within 5 days, while the control mushrooms all open the umbrella. "60Co" for oak, etc γ— Radiation dose of 5.0 ~ 20 Gy can reduce the rate of canopy opening

(3) delaying the discoloration process: the darkening of fresh mushrooms is related to the enhancement of polyphenol oxidase and autolyase activities. After treatment with 10 ~ 30 Gy, the enzyme activity was inhibited and the discoloration process of mushroom was delayed

(4) kill or inhibit the activities of putrefactive microorganisms and pathogenic microorganisms: the test shows that radiation with a dose of 10 Gy can inhibit the growth of miscellaneous bacteria such as Verrucaria. Usually, the radiation is stored in the dose range of 5 ~ 60 Gy. Among them, 60 Gy is the best. But 20 Gy is more suitable for business. According to the results released by FAO, IAEA and the World Health joint expert meeting, when the total dose is 100 Gy, it has no toxic effect on food

the specific method of radiation treatment is: after picking the mature fruiting body without opening the umbrella, put it into porous polyethylene plastic bags, irradiate it according to the dose, and then store it at 15 ℃± 1 ℃. Generally, 90% of the fruiting bodies can not open the umbrella within 2 weeks (while the control opens the umbrella within 3 days), and at the same time, it also maintains its commodity value in terms of hardness, color, etc

a large number of tests have shown that irradiated food is non-toxic, but in order to ensure people's health, it is necessary to carry out experimental analysis to confirm that it is harmless before commodity production. China has approved the sale of radiation mushrooms

5. Film packaging storage: film packaging storage is a way of controlled atmosphere storage. This method is used for short-term storage, transportation and as a temporary storage method for fresh sales because the concentration of oxygen and carbon dioxide changes indefinitely during storage. Film packaging can reduce the evaporation of water in mushrooms and protect products from mechanical damage. In addition, packaging materials come from a wide range of sources, with low storage costs, and are both hygienic and beautiful. It is a good method for fresh packaging and storage

(1) types and properties of films: there are many kinds of packaging films with different characteristics. The biggest impact on the storage performance of edible fungi is the permeability and moisture permeability of the film. The former is related to whether the packaging system can maintain a more appropriate gas composition, and the latter is related to the freshness of products

materials used for edible fungus film packaging should be materials with high permeability and poor moisture permeability, such as low-density polyethylene, polypropylene, etc. At present, a new film of vinyl acetate resin has been used in vegetable packaging. Its air permeability and moisture permeability are better than low-density polyethylene. After packaging, there will be no water droplets in the bag, and it is not easy to cause carbon dioxide poisoning. It is an ideal packaging film

(2) film packaging technology: use film to pack edible fungi. If it is for fresh sale, each model of each series of the experimental machine can have its own precise standard to be packed in small bags, each bag containing 200 ~ 300 grams; If it is used for storage or transportation packaging, it can be packed in large bags, with each bag containing 5 ~ 10kg

in the packaging bag, the proportion of gas can only automatically reach an equilibrium concentration by the permeability of the film itself. The film has different permeability to different gases, and its permeability to carbon dioxide is 4 ~ 9 times greater than that to oxygen. Therefore, when the gas balance is reached, the oxygen partial pressure difference inside and outside the bag is several times larger than the carbon dioxide partial pressure difference inside and outside the bag, so as to maintain the low oxygen or high carbon dioxide level in the bag. However, this equilibrium concentration in the bag is not suitable for many products, and sometimes even harmful. Because most films still have the problem of insufficient air permeability, manual air conditioning of film packaging must be considered

the first way to improve the permeability of the film is to reduce the thickness of the film, which is usually 0.01 ~ 0.03 mm thick; Second, the "silicon window" is embedded on the ordinary packaging film. "Silicon window" is made of silicone rubber, a membrane material with strong permeability. Its permeability coefficient to oxygen and carbon dioxide is 200 ~ 300 times greater than that of polyethylene. Controlling the area of "silicon window" can adjust the permeability of the whole system; The third is to strengthen the free diffusion of gas. The method is to use a perforated film with an aperture of several microns to several millimeters. The size and number of pores should be determined according to the type of edible fungi, service conditions and specific requirements. It is better to meet the ventilation requirements. It should be pointed out that this method destroys the unique selective permeability of the membrane to different gases. When the gas inside and outside the membrane is balanced, the oxygen partial pressure difference inside and outside the membrane 3. It has good weather resistance; It is basically the same as the differential pressure of carbon dioxide, so there is no longer a low oxygen and high carbon dioxide environment in the membrane. A method similar to this method is to loosen the mouth of the bag, that is, leave a small hole with a diameter of 10mm at the mouth of the bag to strengthen the diffusion of gas

in order to reduce the oxygen concentration in the bag, you can also fill the bag with nitrogen to dilute the oxygen, or you can add deoxidant to quickly remove the oxygen

6. Chemical storage: the above methods are physical methods. Are many effective waste plastics easy to decompose? Physical methods require special equipment, high requirements and large investment. Therefore, recently, people pay more and more attention to using chemical methods to store edible fungi. The main chemicals that can be used to store edible fungi are 0.1% sodium pyrosulfite, 0.6% sodium chloride, 4 mg/L Triacontanol, 20 mg/L chlormequat, 50 mg/L penicillin, 50 mg/L ethephon, 0.05% salicylic acid, 0.05% potassium permanganate and 0.1% oxalic acid, 0.05% potassium permanganate and 0.1% sodium sulfite, etc

however, its development has accelerated the pace of transformation and upgrading of key materials in the raw material industry. The specific measures are as follows: after trimming the picked fresh mushrooms, immerse them in the above-mentioned liquid for 1-5 minutes, fish them out, absorb the water on the surface, put them into 0.03 mm thick polyethylene film bags, and tie them tightly for storage. The method is:

(1) sodium pyrosulfite treatment: first rinse the fresh mushrooms with 0.01% sodium pyrosulfite (na2s205) solution for 3 ~ 5 minutes, then soak them with 0.1% sodium pyrosulfite for 30 minutes, take them out and drain them, and be careful not to damage the mushrooms. The effect of preservation at room temperature of 10 ~ 15 ℃ is good, and the color of the mushroom body can be kept white for a long time, but when the storage temperature is higher than 30 ℃, the mushroom body will gradually change color

(2) salt water treatment: soak the fresh mushrooms in 0.6% salt water for about 10 minutes, remove them and drain them, and put them into plastic bags for storage. At the temperature of 10 ~ 25 ℃, the fresh mushrooms in the bag turn bright white after 4 ~ 6 hours. Fresh mushrooms treated with salt water can usually be kept fresh for 3 to 5 days

(3) spray ascorbic acid solution: in the peak harvest period of Flammulina velutipes, in order to prevent the fresh mushrooms from browning, spray 0.1% ascorbic acid (vitamin C) solution on the fresh mushrooms, and then put them into non-ferrous containers, refrigerate at -5 ~ 0 ℃ low temperature, and keep them fresh for 24 ~ 30 hours, with the freshness and color unchanged

(4) bijiu (B9) treatment: bijiu (n-dimethylaminosuccinamide) is a plant growth retarder. Soak the fresh mushrooms in 0.001% - 0.1% aqueous solution for 10 minutes, take them out and drain them, put them in plastic bags, and keep them fresh for 8 days at room temperature (5 ~ 22 ℃). This method can effectively prevent mushroom browning, delay aging and keep fresh. It can be used for the preservation of mushroom, Lentinus edodes, Pleurotus ostreatus and Flammulina velutipes

(5) excitin preservation: soak fresh mushrooms in 0.01% 6-aminopurine solution for 10 ~ 15 minutes, take them out and drain them, and put them into plastic bags for storage, which can delay aging and keep them fresh

(6) fresh keeping of Maifan stone: put the fresh straw mushroom into a plastic box, immerse the mushroom body in Maifan stone water, and store it at a low temperature of -22 ~ -20 ℃. Its fresh-keeping period is up to 70 days, and the content of amino acids in the mushroom is not different from that of the fresh mushroom body, with good color and taste

7. Other storage methods: in addition to the above fresh-keeping methods, there are also methods such as decompression fresh-keeping, anion preservation, microwave fresh-keeping, etc

(1) vacuum preservation: the vacuum preservation method is to reduce the air pressure in the mushroom storage place or storage container, resulting in a certain vacuum (the absolute pressure is 39 ~ 3923 PA). Its principle is: under vacuum, the oxygen partial pressure in the container is very low, which inhibits the respiration of the mushroom body, and also promotes the diffusion rate of harmful gases such as ethylene and acetaldehyde produced by the life activities of the mushroom body to the environment, reducing the physiological poisoning of the mushroom body itself. Decompression can not only prolong the storage period of fresh edible fungi, but also maintain the color of mushrooms and prevent tissue softening

(2) negative ion preservation: negative ions have a good fresh-keeping effect on mushrooms. The mechanism is that the negative ion generator produces both negative ions and ozone (O3). The ozone ions released by ozone have strong oxidizing power, which can kill microorganisms on the surface of mushrooms and in the environment, inhibit the metabolic activities of the body, and delay the aging and withering process

the specific method is: put the newly harvested mushroom body into a 6mm thick polyethylene bag without washing, store it at a temperature of 15 ~ 18 ℃, treat it with a negative ion generator 1 ~ 2 times a day, 20 ~ 30 minutes each time, and the negative ion concentration is lxl05/cm3

(3) microwave preservation: Yueyang Zhengrong edible fungus factory uses microwave to treat fresh Pleurotus ostreatus, fresh Lentinus edodes, etc., and packs them in composite plastic bags. They are stored at a temperature of 14 ~ 29 ℃, which can maintain the original shape, color and flavor of the mushrooms, and the preservation period can reach 90 days. The fresh mushrooms after fresh-keeping treatment meet the national health standards. Microwave is an electromagnetic wave with a frequency of 300 MHz to 300 GHz. Microwave preservation of edible fungi is mostly carried out in microwave ovens. Put the fresh bacteria in it, the microwave can penetrate the mushroom body from all directions, and the depth can reach 3 ~ 4 cm. Heat the inside and outside at the same time, and the mushroom body will be heated and dried instantly. Strictly control the heating time, so that the microorganisms and pests in the mushroom body are completely killed, so as to ensure that the mushroom body remains fresh within a certain period of time, so as to extend the shelf life

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