The mushroom is rich in nutrients, especially lysine and arginine. It also contains active substances such as mucopolysaccharides. It has important functions such as inhibiting tumor growth and improving immunity. It also has physiological functions such as anti-cancer, lowering plasma cholesterol, enhancing body's ability to resist stress, and resisting fatigue.
The Agaricus bisporus has a good quality after quick-frozen and is a kind of quick-frozen vegetable that people like to eat. The quality of frozen mushrooms is mainly determined by several factors such as mushroom color, mushroom size uniformity, tenderness and flavor. All mushrooms are light yellow, uniform in size, delicious in taste, and tender in texture. The quality of frozen mushrooms depends on the quick-freezing process.
First, the quick-frozen process of Agaricus bisporus: raw material selection → color protection → rinsing → blanching → cooling → draining → quick freezing → grading → checking → icing → packaging → inspection → refrigeration.
1, raw materials selection. Bisporus raw material requirements: fresh, white or light yellow, cap diameter within 5-12cm, hemispherical, edge in the roll, no deformity, allowing slight thin mushroom, but the pleats can not be black hair, no spots, no scales . Mushroom stalks cut flat, without mud, no hollow, no discoloration. The quality of the raw materials of Agaricus bisporus has a direct relation with the breeding, cultivation conditions, technical management, harvesting methods, storage and transportation conditions.
2, Aconite mushroom color protection. The freshly picked A. bisporus was placed in the air. After a period of time, brown mushroom finger prints and mechanical scars appeared on the surface of the mushroom cover. The main cause of this discoloration is the result of the oxidation of phenolic compounds contained in mushrooms under the catalysis of polyphenol oxidase, called enzymatic browning. The occurrence of enzymatic browning requires three conditions: proper phenolic substrate, phenol oxidase and oxygen. The control of enzymatic browning mainly starts with the control of enzymes and oxygen. Common methods include the following:
(1) Sulfite solution method. Commonly used sodium sulfite (na2s03), sodium metabisulfite (na2s2o3) and so on. Sulphite is a preservation agent for fruits and vegetables. It has a strong ability to inhibit polyphenol oxidase. When the so2 concentration reaches 10 mg/kg, the activity of the enzyme is almost completely suppressed, and the residual amount of s02 must not exceed 20 mg/kg.
Specific methods: immersing the picked mushrooms in 300mg/kg of na2s03 solution or 500mg/kg of na2s203 solution for 2min, immediately soak the mushrooms in clean water below 13°C and transport them to the factory. Can also be soaked in na2s03 or na2s203 solution for 2 min, then remove and drain, and then put it into a plastic film bag. Put it in a bag and put it into a wooden barrel or bamboo basket and transport it to the factory. Immediately after entering the factory, the temperature is below 13°C. Soaking in a clear water tank for 30 minutes, remove the coloring solution remaining on the mushroom body. This method can make the mushroom color change within 24h, so that processed mushroom products can meet the quality standards.
(2) Cysteine ​​solution method. The immersed mushrooms were immersed in a 0.4 mmool/l cysteine ​​solution for 30 minutes and then removed, which also had a good color protection effect.
The mushrooms that have been protected by this method have remained white for 4-6 hours, basically keeping the true color of the mushrooms. After the cysteine ​​color treatment, the color of the mushroom was not as white as that of the sodium sulfite treatment. It was slightly dark, but it had a strong sense of realism. The soup was clear, pale yellow, and tasted good, basically maintaining the flavor of the mushroom.
Cysteine ​​has a complex effect on polyphenol oxidase and can also act as a reducing agent to inhibit the occurrence of non-enzymatic browning, manifesting as delayed browning and reducing the rate of browning. At the same time, the mushroom is treated with cysteine ​​to supplement part of the nutritional requirements of the postharvest mushroom, which can delay the aging process and reduce the proportion of open umbrellas and thin-shelled mushrooms. Moreover, cysteine ​​is a kind of essential amino acid for the human body. It is harmless to the human body and has no residual problem. It is safe and reliable for food production. So cysteine ​​is also practical for mushroom color protection.
(3) film modified atmosphere packaging. Immediately put the newly picked mushrooms into a 0.06-0.08mm polyethylene bag. Place 20kg into each bag to fasten the bag. Because the mushroom is basically isolated from the outside air, it can also inhibit the enzymatic browning reaction. On the other hand, because the thin film bag is relatively thin, there is still a certain degree of breathability, which can maintain a low o2 concentration and a high c02 concentration in the bag. The mushroom can still maintain minimal respiration for a period of time without reaching a limit. Harmful effect. However, the time must be strictly controlled within 4-6 h. At this time, the gas composition in the film bag is determined to be: o2: 2-3%, and co2: 20%. If this time is exceeded, due to lack of oxygen in the bag, the mushroom cannot maintain minimal respiration and may result in the growth of Staphylococcus aureus.
3, hot. The purpose of mushroom blanching is mainly to destroy the activity of polyphenol oxidase, inhibit the enzymatic browning, and at the same time drive away the air in the mushroom tissue, make the tissue shrink, ensure the requirement of solids, increase the elasticity, reduce brittleness, and facilitate packaging. . When using sulphite to protect color, the use of blanching can also play a role in desulfurization. In order to reduce non-enzymatic browning, an appropriate amount of citric acid is often added to the blanching liquor to increase the reducibility of the blanching liquor and to improve the mushroom color.
The blanching method includes two kinds of hot water or steam, and the method of using steam is rich in flavor due to less loss of soluble components. The hot water temperature is 96-98°C and the ratio of water to mushrooms should be greater than 3:2. Under normal conditions, the mushrooms turned from white to light yellow after blanching, which is the reason for non-enzymatic browning. With the prolonged blanching time, the color is deeper and the weight loss is more. Generally, 0.1% citric acid solution is added to the hot water to adjust the acidity to inhibit non-enzymatic browning. The time of blanching is controlled within 4-6 minutes according to the size of the cap. However, the time for blanching should not be too long, so as to prevent the organization from being too old, lose water and lose its elasticity. In order to prevent the darkening of the mushroom color, the acidity of the blanching solution should be adjusted frequently and pay attention to the periodic replacement of the hot water.
4, cooling. Immediately after the blanching, the mushrooms are fed into the cooling water tank to be completely cooled, without overheating the quality. The cooling water contains 0.4-0.7mg/kg of residual chlorine.
5, drain. Mushrooms must be drained before quick freezing. If the moisture content on the surface of the mushroom is too large, it will freeze into clumps, which is not conducive to packaging and affects the appearance. Moreover, excessive moisture will increase the freezing load. Leaching can be done with vibrating screens, dryers (centrifuges) or fluidized bed pre-cooling devices.
6, quick-frozen. The greatest damage to frozen vegetables is the destruction of the organization. This is mainly due to the volume expansion after the formation of ice crystals, and the shrinkage of solid components in vegetables, resulting in partial pressure, resulting in rupture of the cell wall of vegetables and destroy its organizational structure, cell dehydration, protein and colloidal structure irreversible changes, when the thawing The generated water can not be restored to its original state with protein, and can only be allowed to flow out. The loss of water also includes water-soluble proteins, vitamins, organic acids, pigments, sugars, inorganic salts and other nutrients. In order to minimize the influence of ice crystals on the quality of vegetables, rapid freezing can be used to make the ice crystals in the quick-frozen vegetables to be small and evenly distributed in the cells, so that the reorganization of ice crystals and the ice crystals on the cells can be reduced. Local pressure and dehydration damage.
The quick freezing of mushrooms should adopt the fluidized bed quick freezing device. The cooled, drained mushroom is evenly placed on the fluidized bed conveyor belt. Because the mushroom can only form a semi-fluidized state in the fluidized bed, the mushroom layer thickness of the conveyor belt is 80-120 cm, and the air temperature in the fluidized bed apparatus Requirements -30 to -35 °C, cold air flow rate 4-6m / s, quick-freezing time 12-18min, mushroom center temperature below -18 °C.
Second, classification. The quick-frozen mushrooms should be graded according to the size of the cap shape and the length of the stipe using a roller-type grading machine or a mechanical oscillating-type grading machine.
Third, check. Remove mushrooms that do not meet the criteria for quick-frozen mushrooms: such as deformity, spots, rust collapse, hollow, off handle, open umbrella, color mushroom, thin mushroom and so on.
Fourth, pack ice clothing. In order to ensure the quality of quick-frozen mushrooms and to prevent the products from drying and oxidative discoloration during refrigerating, mushrooms must be covered in ice after classification and selection. Ice-cladding has a certain degree of technicality, and it is necessary to make the product covered with a thin layer of ice without thawing or agglomeration of the product. The specific approach is to pour 5kg of mushrooms into perforated plastic baskets or stainless steel wire baskets and immerse them in clean water of 1-3°C for 2-3 seconds. After shaking out, stir and drain them, and then do another operation. The cooling water needs to be clean and contains 0.4-0.7mg/kg of residual chlorine.
Fifth, packaging. Packaging must be performed in a low temperature environment below -5°C. When the temperature is -1 to -4°C, refrigerated mushrooms will recrystallize, which greatly reduces the quality of quick-frozen mushrooms. The packaging room must be sterilized by ultraviolet light at 1h before packaging. All work tools and workers' working clothes, caps, shoes, and hands must be regularly sterilized.
The inner package can be used for polyethylene bags with low temperature resistance, low permeability, impervious to water, no peculiar smell, no toxicity, and a thickness of 0.06-0.08mm. Packaging cartons, net mass 10kg per carton, carton surface must be oiled, good moisture resistance, lined with clean wax paper, taped with external tape. All packaging materials must be pre-cooled at temperatures below -10°C before packaging.
Frozen mushrooms should be inspected according to specifications prior to packaging. Care should be taken when handling bags to exclude air and prevent oxidation. The bag is sealed with a heat sealer, and the conditional vacuum packaging machine is available for bagging. After packing, the whole box is replenished. Qualified persons print the name, specifications, weight, production date, storage conditions and time limit, batch number, and manufacturer on the carton. Sealed with sealing strips, immediately into the cold storage.
Sixth, refrigeration. Quickly frozen mushrooms that meet the quality standards after inspection are quickly put into the refrigerator for refrigerated storage. Refrigerated temperature -18 to -20 °C, the temperature fluctuation range should be as small as possible, generally controlled within 1 °C, frozen mushrooms should be placed in a special store dedicated to frozen vegetables. At this temperature, the refrigeration period is 8-10 months.
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