1, natural cooling storage
Natural cooling storage is a simple and convenient storage method. People's commonly used natural cooling storage mainly includes stacking (stacking), ditch storage (burying), frozen storage, false planting storage and ventilated cellar storage (kiln cellar, well cellar), all of which use external natural low temperature (air temperature or ground temperature) to adjust the temperature and humidity of the storage environment. The storage temperature cannot be controlled at an ideal level due to the geographical and seasonal restrictions. However, due to the simple structure of its facilities, some of which are temporary facilities (such as stacking, stacking and ditch storage), the required building materials are few and the cost is low, which can alleviate the supply and demand of products to a certain extent, so this simple storage method is very common in many fruit and vegetable producing areas in China.
It occupies a large proportion in the total storage capacity. Although the shelf life of refrigerated products is not too long, it has its special application value for some kinds of fruits and vegetables, such as ditch storage is suitable for storing radish; Spinach is suitable for frozen storage; False planting storage is suitable for celery, bamboo shoots and cauliflower; Chinese cabbage, apples, pears, etc. Can hoard; Cabbage and onion can be stacked or stacked. They are mostly used in winter and early spring when the outdoor temperature is low in the north, and the storage temperature of the products is around O℃. It can also be used in other places in China, such as citrus cellar storage in Nantong.
2, artificial cooling storage
Artificial cooling storage is a storage method that uses mechanical refrigeration to adjust the temperature of storage environment. When in use, it is not limited by seasons and regions, and the storage temperature can be controlled more accurately. Suitable for all kinds of fruits and vegetables, if properly managed, can achieve satisfactory storage effect. Although low temperature can effectively slow down the metabolic rate, refrigeration can not extend the shelf life indefinitely. So far, the economically developed countries in the world have taken mechanical refrigeration as a necessary means to store fresh fruits and vegetables. Due to the application of mechanical refrigeration, many fruits and vegetables, such as kiwi fruit, early and middle ripe apples, peaches, lychees, tomatoes and other products that are difficult to store at room temperature, can be stored for a long time or transported for a long distance.
Modified atmosphere storage is developed on the basis of cold storage. For some fruits and vegetables, the effect of modified atmosphere storage is better than that of cold storage. For example, frozen apples can only be stored for 6 months, while modified atmosphere storage can be stored for 10 months, and still maintain good hardness. This storage method of artificially controlling or changing the gas composition in the storage environment (reducing the oxygen concentration and increasing the carbon dioxide concentration) is called modified atmosphere storage, which is usually expressed by the English letter CA storage. This is one of the main means to store and ensure the long-term supply of apples and pears in developed countries. However, not all fruits and vegetables are suitable for modified atmosphere storage, and some products have no obvious effect of modified atmosphere storage, and even have side effects. Generally speaking, the effect of modified atmosphere storage of climacteric fruits is better, but the effect of non-climacteric fruits is not significant. In addition, different fruits and vegetables have different sensitivities to gases, and the ratio of oxygen and carbon dioxide required is also different. Because of the high cost and difficult operation and management of modified atmosphere storage, fruits and vegetables suitable for long-term storage or high economic value should be selected for modified atmosphere storage. At present, spontaneous modified atmosphere storage is widely used in our country, that is, the product itself is used to consume oxygen and accumulate carbon dioxide, so as to achieve the effect of modified atmosphere storage. Although this method is not as good as the real modified atmosphere storage, it is simple in operation, low in cost and low in risk. The storage of apples and garlic shoots in silicon window bags or small plastic bags belongs to spontaneous controlled atmosphere storage, and the storage effect is good. [Edit this paragraph] Third, the storage method of fruits must be harvested in batches according to maturity. It is best to pick fruit in sunny morning after the dew is dry; At the time of harvesting, fruits of different varieties and different maturity should be harvested, opened, packaged and stored respectively; Pests, rotten fruits, bruised fruits and unqualified fruits should be removed as soon as possible after harvest. In order to improve the storability of fruits, 0.2% calcium chloride solution, 150 times of high-fat film or 1000 times of thiophanate superphosphate solution can be sprayed on the crown half a month before harvesting to prevent the fruits from being infected with mold.
The humidity suitable for storage under cold storage conditions is 80%-95%. The temperature is controlled at about -5℃ ~+5℃, which is mainly suitable for fruit preservation.
Most fruits in northern China are stored at -3 ~+5℃. Such as apples, pears and winter dates. Late-maturing varieties and good-quality ones are easier to store.
Most fruits in southern Guangdong are stored at 3 ~ 15℃. Not every kind of fruit is suitable for keeping fresh in the refrigerator at low temperature. Some fruits are naturally afraid of cold, such as bananas, mangoes and papayas. , is a native product of the tropics. Putting it in the refrigerator will make the peel produce spots or turn dark brown, and the quality and flavor of fruit will also be destroyed.
1. southern storage method: store in a dry, cool and disinfected warehouse, preferably at 0 ~+5℃. Fruits are usually stored in cartons, cloth bags or sacks. Before leaving the cold storage, it should be moved to a slightly higher temperature for transition and gradually moved out of the warehouse. In order to prevent condensation of water droplets, they should not be repackaged after leaving the warehouse, but should be cold-paved and transported in new packaging after the condensed water droplets disappear.
2. North storage method: when a large number of sacks are used for storage, the stacking should be 50-60 cm away from the wall, and walkways should be left between piles to facilitate ventilation and personnel passage. In the rainy season, every bag of fruit should be covered with sacks to increase the moisture-proof effect. When the outside air temperature is low and dry, you can open the ventilation hole of the warehouse to pump away the air in the warehouse and replace it with dry air. When storing fruits, if you put a few small piles of lime powder in the warehouse, the humidity in the warehouse can be significantly reduced.
3. Simple family storage method, a small amount can be stored in the shade after being put in jars, bowls, jars, plastic bags, etc. Store with rice husk ash in a larger amount, which is pollution-free. The method is: choose a clean, dry and cool room with cement floor, clean the surroundings and sprinkle with lime powder, then spread rice husk ash with a thickness of 1 cm on the floor, and then spread a layer of fruit, so that the height of one layer of rice husk ash and one layer of fruit is 30-40 cm. This method is moisture-proof and sterilization, and can be stored for 2-3 months. [Edit this paragraph] 4. Several fresh-keeping techniques of fruits abroad Fruits are fresh food, which is easy to rot after harvesting. In order to prolong the shelf life, researchers from all over the world have invented a variety of new preservation technologies, and now 10 has been introduced.
1. Fresh-keeping carton: This is a new carton developed by Japan Food Circulation System Association in recent years. The researchers used a kind of "rectorite" (a silicate rock) as an additive for paper pulp. Because this kind of stone powder has a unique good adsorption effect on various gases, and its price is cheap, it does not need low-temperature and high-cost equipment, especially it has a long-term preservation effect, and the weight of fresh fruit will not be reduced, so merchants love to use it, which is more suitable for long-distance storage and transportation.
2. Microwave preservation: This is a method for a Dutch company to keep fruits fresh by low-temperature disinfection. After being heated to 72℃ by microwave for a short time (120s) and then put into the market at 0~4℃, the processed food can be preserved for 42~45 days without deterioration. It is very suitable for supplying "seasonal fruits" in the off-season and is favored by people.
3. Edible fruit preservative: This is an edible fruit preservative developed by the British Food Association. It is a "translucent emulsion" made of sucrose, starch, fatty acid and polyester. It can be sprayed, brushed, dipped and covered on the surface of watermelon, tomato, sweet pepper, eggplant, cucumber, apple and banana, and its preservation period can be as long as more than 200 days. This is because this preservative forms a "sealing film" on the surface of fruits and vegetables, which completely prevents oxygen from entering the interior of fruits and vegetables, thus achieving the purpose of prolonging the ripening process of fruits and enhancing the preservation effect.
4. New film preservation: This is a disposable moisture-absorbing and fresh-keeping plastic packaging film developed in Japan. It consists of two translucent nylon membranes with strong water permeability, and natural paste and syrup with high osmotic pressure are installed between the membranes, which can slowly absorb the water oozing from the surface of fruits and meat to achieve the effect of preservation.
5. Pressurized preservation: The method of making food by pressure was successfully developed by the Institute of Food Science, Kyoto University, Japan. After pressure sterilization, the fresh-keeping time of fruits can be prolonged and the fresh taste can be improved. But acid can't work under pressure, so it is ideal to keep the fruit in the best condition.
6. Ceramic fresh-keeping bag: This is a fruit fresh-keeping bag with far infrared effect developed by a Japanese company. It is mainly to coat a very thin layer of ceramic material on the inside of the bag, so that the infrared rays released by the ceramic can have a strong "* * * vibration" movement with the moisture contained in the fruit, thus promoting the preservation of the fruit.
7. Microbial preservation method: ethylene can promote the aging and ripening of fruits, so in order to achieve the purpose of fruit preservation, ethylene needs to be removed. Scientists isolated a "NH- 10 strain" through screening and research. The strain can be made into "ethylene remover NH-T" to remove ethylene, which can prevent grapes from browning, loosening and falling off during storage, prevent tomatoes and peppers from losing water, changing color and softening, and has obvious fresh-keeping effect.
8. decompression preservation method: it is a new method of fruit storage with good preservation effect, convenient management, simple operation and low cost. At present, some countries such as Britain, America, Germany and France have developed low-pressure containers with standard specifications, which are widely used in long-distance transportation of fruits.
9. Hydrocarbon mixture preservation method: This is a "natural edible preservative" developed by a British biotechnology company, which can extend the shelf life of pears, grapes and other fruits by 1 times. It uses a complex hydrocarbon mixture, which is dissolved in water to form a solution, and then the fruit to be preserved is soaked in the solution, so that the surface of the fruit is evenly coated with a layer of liquid agent. This greatly reduces the absorption of oxygen, and almost all the CO2 produced by fruits is discharged. Therefore, the role of preservatives is similar to that of "anesthetics" acting on fruits to make them dormant.
10, electronic technology preservation method: it uses negative oxygen ions and ozone generated by high-voltage negative electrostatic field to achieve the goal. Negative oxygen ions can inactivate enzymes that metabolize fruits, thus reducing the respiratory intensity of fruits and weakening the survival of ethylene, a fruit ripening agent. Ozone is a strong oxidant and a good disinfectant, which can not only kill and eliminate microorganisms and toxins secreted by fruits, but also inhibit and delay the hydrolysis of organic substances in fruits, thus prolonging the storage period of fruits.