Rapid Freezing and Cold Storage Preservation Techniques for Edible Mushrooms

Shiitake mushroom production has flourished across both northern and southern regions of our country in recent years. Since the popularization of bag-cultivated shiitake in Fujian, the provinces of Zhejiang, Henan, Hubei and others have successively developed bag-cultivated shiitake with successful results. Quick-freezing storage of shiitake has become an indispensable and important preservation technique in @#@136@#@. Quick-freezing storage of shiitake is simpler and more convenient than that of button mushrooms. Generally, fresh mushrooms are pre-cooled in ice water, removed and drained, then rapidly placed in an ultra-low temperature freezer at -50 to -60°C for quick freezing, and then placed in a cold storage at -18 to -24°C for storage, entering consumers' homes through the "cold chain" system. It is said that the preservation period of quick-frozen shiitake reaches 1.5-2 years.

Quick-Freezing Storage of Enoki Mushroom (Flammulina velutipes)

After fresh enoki mushrooms are harvested, they are sorted and packed into special food bags, with each bag containing a fixed amount of 100 grams, 200 grams or 500 grams, and heat-sealed or vacuum-sealed, then immediately placed in a freezer at -20°C for storage. The preservation period reaches over 1 year, with excellent nutrition and flavor.

Quick-Freezing Storage of Oyster Mushroom (Pleurotus ostreatus)

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 stipe cut to 1 cm in length. Remove decayed and deteriorated fruiting bodies and remove substrate impurities. Rinse the fruiting bodies clean with running water, separate clustered fruiting bodies into individual ones, and grade them into 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 amount of oyster mushrooms added being 20%-30% of the blanching solution. Gently stir the fruiting bodies to ensure even heating. The blanching solution temperature is controlled at about 95°C, and blanching generally takes 5-8 minutes. After blanching is completed, immediately place in clean cold water for rapid cooling. After cooling, put the fruiting 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 grams 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.