Fresh-keeping Technology of Mushroom after Harvest

Fresh mushrooms are easy to change color, taste, deformation, weight loss and quality decline at room temperature, which reduces the sales price and edible value of fresh mushrooms. In order to prolong the fresh-keeping time of fresh mushrooms, the following techniques can be adopted for fresh-keeping storage.

? 1. Low temperature preservation technology:

Low temperature storage is to inhibit the metabolism of fresh mushrooms and inhibit the activities of rotting microorganisms by lowering the environmental temperature, and to maintain the freshness, color and flavor of mushrooms in a certain period of time. Low temperature storage is a common storage technique for mushrooms. There are usually two ways.

Ice storage: In the cold season, by collecting naturally frozen ice, centralized ice storage. In warm seasons, ice cubes are obtained by mechanical refrigeration for preservation and storage. It can also be cooled by air conditioning to cultivate mushrooms and kept fresh by machine ice. The specific method is: use silicon window bag packaging, each bag volume is 1--2.5 kg is appropriate, the oxygen concentration in the bag is adjusted to 1%, the carbon dioxide concentration is adjusted to 2.5%, and then put into the box with vent holes, each box contains 10 kg, so as to facilitate ventilation.

2. Refrigeration: After harvesting mushrooms, trim the stems, grade them, and rinse them with clean water. If it is necessary to protect the color, it can be rinsed with 0.01% sodium metabisulfite aqueous solution for 3--5min, and then pre-cooled with vacuum cold or ice water to reduce the temperature of the mushroom body to 3--5℃, and drained into the warehouse to reduce the pressure of a large amount of storage and avoid too large temperature fluctuation in the cold storage. General cold storage temperature should always be maintained at 1--3℃, relative humidity in 90%--95%. At the same time, pay attention to regular ventilation, control the carbon dioxide concentration of the cold storage does not exceed 0.3%, so that the mushrooms stored in the cold storage can be kept fresh for about 1 week.

???? II. Modified atmosphere preservation technology:

Fresh mushrooms are rinsed and graded, drained and packed in plastic bags or ventilated plastic boxes. Adjust the oxygen concentration in the bag or cold storage to 1% and the carbon dioxide concentration to 2.5%, so that the oxygen concentration is moderately reduced and the carbon dioxide is increased. In this environment, mushroom cap and stalk elongation is very slow, growth is obviously inhibited, umbrella opening is rare, mushrooms are white, controlled atmosphere preservation can be used for mushroom sales activities.

? III. Radiation preservation technology:

Fresh mushrooms after rinsing are packed in porous polyethylene plastic bags and irradiated with 66Co rays at a dose of 2000- 3000 Gy. Store at 10℃ after irradiation. After irradiation, the mushroom water evaporation was less, and the browning, membrane breaking and umbrella opening of fresh mushroom were inhibited obviously. After irradiation with 3000 Gy, it can be stored for 4- 5 days at room temperature of 16- 18 ℃ and relative humidity of 65%, and longer at lower temperatures. Radiation preservation is a new technology for mushroom preservation, which has many advantages compared with other preservation technologies. It can keep mushroom fresh, has no chemical residue, saves energy, has high processing rate, can work continuously, is suitable for automatic production, and is a fresh-keeping method with broad prospects.

? IV. Chemical preservation technology

Chemical preservation Mushrooms are only used for short-term storage or color preservation of mushrooms. The following are commonly used:

1. Dilute hydrochloric acid preservation: Soak mushrooms in 0.05% dilute hydrochloric acid solution, and the acid solution gradually penetrates into the mushroom tissue, so that the pH value in the mushroom body drops below 6 to inhibit the activity of enzymes, reduce the metabolic level of mushrooms, slow down the browning and umbrella opening speed, and also inhibit the propagation and growth of rot causing microorganisms.

2, salt water treatment: the fresh mushrooms washed into 0.6% salt water soaked for 10 minutes, drained water, in 10--25 degrees Celsius after 4--6h, mushrooms can be white, so that can reduce the opening of umbrellas.

3. Rinse the mushroom body with 0.05% sodium pyrosulfite aqueous solution for 3--5min, then soak it with 0.1% sodium pyrosulfite for 30min, remove and drain, put it into plastic bag for storage, and keep it fresh at room temperature of 10--15℃. The color can be kept white for a long time. However, it should be noted that when eating or processing mushrooms preserved by sodium pyrosulfite solution, they should be washed 2-3 times with water in advance until the sulfur content is below 20mg/kg.