The main factors affecting mushroom preservation are as follows:
Temperature: The higher the temperature, the worse the preservation of mushrooms. 0-4℃ is the optimum temperature for mushroom preservation. In addition to quick freezing, freezing injury is easy to occur below 0℃.
Water quality: When the content of iron or copper in water exceeds 2 mg/L, the color of mushrooms will turn dark brown, so it is forbidden to use iron and copper utensils and tools.
Humidity: 95- 100%. Under 90%, the color becomes darker, and it is easy to open the umbrella and deteriorate.
Gas composition: an important cause of corruption, which can be suppressed by sterilization and PH adjustment.
Enzyme activity: Polyphenol oxidase is the main cause of mushroom browning.
Therefore, there are five fresh-keeping methods for mushrooms: controlled atmosphere, low temperature, radiation and chemical drugs. Low temperature and modified atmosphere have the best preservation effect.
1. Modified atmosphere preservation: PE bags with a thickness of 0.05 mm are treated by special physical methods. Mushrooms are kept fresh by simple air conditioning. The results showed that the mushrooms were fresh and tender within 3-5 days without opening the umbrella, and there was basically no browning, and the water loss rate was lower than 65438 0%. At present, breathable plastic film bags are used for packaging, and the oxygen concentration in the bags is 1%, and the carbon dioxide concentration is 10- 15%, which can keep the mushrooms white and fresh within 4 days.
2, cold storage: low temperature can keep mushrooms fresh and high quality. During storage and transportation, it is advisable to keep the temperature at 0-3℃ and the relative humidity at 90-95%.
3. Quick-freezing and fresh-keeping: within 30-40 minutes, the mushroom is quickly cooled from normal temperature to -30-40℃, the central humidity of the frozen mushroom should be -20℃, and then frozen to-18℃, which can maintain the original quality and flavor for a long time. The quick-freezing process is: raw material acceptance/cleaning/color protection/rinsing/manual sorting/air extraction/blanching/primary cooling/secondary cooling/quick-freezing/selection/icing/packaging/frozen storage/transportation.
4. Chemical medicine preservation: antiseptic cleaner: 10-20mg/L potassium sorbate and sodium benzoate; 20 mg/l sodium sulfite; 10 mg/l benzene et; 5- 10 mg/l carbendazim or thiophanate-methyl. Rinse whitening agent: rinse with 0. 1-0.5% sodium metabisulfite for 5-6 minutes; 0. 1-0.2% sodium metabisulfite plus 10 mg/l guanine solution. Anti-discoloration agent: soak in 0.0 1-0. 1% dimethylamine succinamic acid for 0/0 minute, take it out, drain it and seal it in a sterilized plastic bag, which can keep fresh for 6-8 days at 0-4℃. Soak in 0.02-0.05% ascorbic acid solution for 10-20 minutes, and the total time shall not exceed 4 hours. Spraying stable chlorine dioxide on mushrooms during fruiting period, fruiting period and before harvesting has a remarkable effect. In a word, the fresh-keeping liquid made of food additives with ascorbic acid and citric acid as the main components is added to the fresh-keeping liquid with the same weight, soaked in 0.25% pyrosulfurous acid solution for 10 minute, rinsed with clean water for 20-30 minutes, drained and stored, which not only solves the problem of deterioration in long-distance storage and transportation, but also brings economic benefits to the processing plant.
5. Salt water preservation: immediately put the cooked mushrooms into 19 pommel horse salt solution, add a proper amount of refined salt after a few days, and continue to maintain 19 pommel horse salt solution. After 4-6 days, it can be sealed and kept fresh after equal parts, weight and pH value are stable.