Key Technical Points for Quick-Freezing and Cold Storage Preservation of Edible Fungi
Quick-frozen storage of shiitake mushrooms: In recent years, shiitake mushroom production has flourished across both northern and southern parts of China. Since the popularization of bag-cultivated shiitake mushrooms in Fujian, provinces such as Zhejiang, Henan, and Hubei have successively developed bag-cultivated shiitake mushrooms with success. Quick-frozen storage of shiitake mushrooms has become an indispensable and important preservation technique in the production and@#@136@#@chain. Quick-frozen storage of shiitake mushrooms is simpler and more convenient than that of button mushrooms. Generally, fresh mushrooms are pre-cooled in ice water, removed and drained, then quickly placed in an ultra-low-temperature ice storage at -50 to -60°C for quick-freezing, and then placed in a cold storage at -18 to -24°C for preservation, entering consumers' homes through the "cold chain" system. It is said that the preservation period of quick-frozen shiitake mushrooms reaches 1.5 to 2 years.
Quick-frozen storage of enoki mushrooms (Flammulina velutipes): After fresh enoki mushrooms are harvested, they are sorted and packed into special food bags, with each bag containing a measured amount of 100 g, 200 g, or 500 g, and heat-sealed or vacuum-sealed, then immediately placed in an ice storage at -20°C for preservation, with a preservation period of over 1 year, and excellent nutrition and flavor.
Quick-frozen storage of oyster mushrooms:
1. Process flow: Raw material selection → sorting and grading → blanching → cooling → draining → bagging → quick-freezing → low-temperature storage.
2. Raw material selection and grading: Oyster mushroom raw materials should be fresh and intact, with normal grayish-white color, shallow cracks on the cap edge, cap diameter of 3 cm or more, and the stem cut to a length of 1 cm. Remove rotten and deteriorated mushroom bodies and remove substrate impurities. Rinse the mushroom bodies clean with running water, separate clustered mushroom bodies into individual ones, and grade them into three sizes (large, medium, and small) according to cap diameter.
3. Blanching and cooling: Add clean water to the blanching tank, with the water amount at about 2/3 of the tank capacity, and add 0.05%-0.1% citric acid to the water. After the blanching solution is heated to boiling, pour the oyster mushrooms into the tank for blanching, with the added amount of oyster mushrooms at 20%-30% of the blanching solution. Gently stir the mushroom bodies to ensure even heating. The blanching solution temperature is controlled at about 95°C, and blanching generally takes 5 to 8 minutes. After blanching is completed, immediately place in clean cold water for rapid cooling. After cooling, put the mushroom bodies into clean gauze bags and place in a centrifuge for dehydration.
4. Bagging and quick-freezing: According to the graded sizes, put the oyster mushrooms into clean plastic bags, 500 g per bag. After sealing, send the oyster mushrooms into the quick-freezing machine chamber and rapidly freeze at a low temperature of -25 to -30°C.
5. Low-temperature storage: After quick-freezing, the oyster mushrooms are packed together with the bags into cardboard boxes, tightly packaged, and placed in a -18°C low-temperature warehouse for storage until consumption.