Storage preservation, or preservation, is the main content of preservation, that is, to maintain the original quality and freshness of some agricultural products for a long period of time, that is, fresh agricultural products. After a period of preservation and storage, it is still Just picked or near freshly picked and live

one. Relationship between temperature and preservation of fresh produce

After harvesting, the agricultural product is still a living body. In the course of storage, it must maintain the insulation plate of life cold storage, and it must continuously consume its own storage nutrition, thereby gradually losing its nutritional value and living quality. In addition, diseases and insect pests can also use the stored nutrients of agricultural products as food. As a result, the agricultural products will spoil and deteriorate and lose their freshness and food value. How to make the livelihood of agricultural products keep the nutrition and live quality, temperature is the most important influencing factor. Generally speaking, the lower the temperature, the less nutrient consumption of the product, the worse the pest and disease, and the longer it takes to maintain fresh quality. At the same time, the smaller the temperature change, the better the preservation effect. Preservation temperature is not unrestricted low, because the temperature is so low that the product can not endure, cold injury or freezing injury will occur. Therefore, fresh storage requires a relatively stable and suitable low temperature condition. The optimum preservation temperature for most agricultural products is around 0°C.

two. Maintaining the Optimum Temperature for Preserving Fresh Storage of Agricultural Products

The temperature is changing with the season of the year and the time of the day. Most of the seasons of traditional agricultural products harvest and cultivation are of high temperature and large variations in day and night, which are extremely unsuitable for fresh preservation of the product. Many simple solutions are to find a place where the natural temperature is relatively low and stable to store agricultural products to extend the shelf life of products, such as caves, crypts, shady areas, etc. These methods can not arbitrarily control the temperature, the preservation effect is poor, and the preservation period is also Shorter. According to the temperature required for long-term storage and preservation of products, the ultimate solution is to rely on manual production of a relatively stable low-temperature condition, that is, through mechanical equipment and electronic equipment, within a certain range of cold storage insulation board, can artificially control the temperature, common A variety of cold storage is such a facility.

three. What is cold storage

Cold storage generally refers to facilities that use various types of equipment for refrigeration, human control, and stable low temperatures. Its basic components are: refrigeration systems; electronic control devices; warehouses with certain insulation properties; ancillary buildings, etc.

The refrigeration system mainly includes all kinds of refrigeration equipment. The refrigeration equipment is the heart cold storage insulation board of the cold storage. It produces a cold storage insulation board to ensure the cold source supply in the warehouse. The electronic control device is the brain of the cold storage. It directs the refrigeration system to ensure the supply of cold.

The warehouse with certain thermal insulation properties is a cold storage thermal insulation board for storage of fresh agricultural products. Its role is to maintain the stability of the low-temperature environment, and the thermal insulation performance is usually referred to as thermal insulation. The good thermal insulation structure of the warehouse can minimize the leakage of refrigeration equipment manufacturing to the outside. In other words, it is to minimize the leakage of heat from outside the library to the inside of the warehouse. This is also the main reason for cold storage and general housing. the difference.

four. Types of cold storage and selection of rural production sites

There are many types of cold storage in China, and the classification lacks uniform standards. According to the types commonly used in production areas are briefly introduced as follows:

(1) According to the size of the storage capacity, there are large, medium, and small points. The large and medium sized commercial libraries mentioned in the general information are relatively large. According to the characteristics of the relatively cold storage areas in our country and the habitual appellations of the masses, a library with a storage capacity of 1,000 tons or more can be called a large-scale library, a library with a capacity of 1,000 tons or more and a volume of 100 tons or more can be called a medium-sized library, and a library with a capacity of 100 tons or less can be called Small library. The village of origin is most suitable for building a small cold storage of 10 tons to 100 tons.

(2) The refrigerant used by the refrigerator can be divided into ammonia refrigerating machine bank and fluorine refrigerating machine, and the high-automated fluorine refrigerating machine can be used to build small refrigerated warehouses in rural areas.

(3) According to the temperature of the cold storage, there is a distinction between low-temperature storage and high-temperature storage. The storage of fresh fruits and vegetables is generally a high-temperature storage, with a minimum temperature of -2°C. Aquatic and meat-based fresh-keeping warehouses are low-temperature libraries with temperatures below -18°C.

(4) There are cold storage and cold storage cold storage in the form of cold distributor inside the cold storage. Fresh fruits and vegetables are generally used for cooling, commonly known as cold storage.

(5) According to the construction method of the warehouse, it is divided into a civil cold storage, an assembly cold storage, and a civil and assembly composite cold storage. The civil cold storage is generally a sandwich wall thermal insulation structure, which covers a large area. The construction period is long and cold storage insulation board cold storage insulation board. Early cold storage is such a method.

Prefabricated cold storage is a prefabricated insulated sheet warehouse. The construction period is short and can be disassembled, but the investment is large. The civil engineering and assembly complex cold storage, the load-bearing and peripheral structure of the warehouse are civil construction forms, and the heat preservation structure is a form of polyurethane spray foaming or polystyrene foam board assembly. The civil construction and assembly type cold storage of polystyrene foam board insulation is the most economical application, and it is the preferred form of cold storage in the production area.

Fives. Refrigeration equipment for small refrigerators

Cold storage refrigeration equipment is the heart of cold storage. It is very important. The most critical condition for a cold storage operation is cooling equipment.

The main part of the refrigeration equipment is a refrigerator. There are many types of refrigeration equipment. There are two types of refrigerants: ammonia and fluorine. Some fluoro-engines are general models of cold storage insulation boards for various refrigerants, and advanced fluoro-engines use more refrigerants R22 and other new refrigerants that have a small impact on the environment. Fluorine machine is generally small, low noise, safe and reliable, high degree of automation, a wide range of cold storage insulation board, suitable for rural small cold storage.

The combination of refrigerators and condensers is often referred to as a refrigeration unit, and the refrigeration unit is divided into a water-cooled unit and an air-cooled unit. The air-cooled unit is the preferred form of the small cold storage. It has the advantages of simplicity, compactness, easy installation, convenient operation and less auxiliary equipment.

The chiller of a refrigeration unit is the heart of refrigeration equipment. Common compression chillers are divided into open, semi-enclosed and totally enclosed types. The hermetic compressor is small in size, low in noise, less in power consumption, and highly energy-efficient. It is the preferred type of cold storage insulation board for large-scale rural cold storage. The air-cooled refrigeration unit consisting mainly of totally-enclosed compressors can be made into the form of a split air conditioner and mounted on the wall.

The relatively good closed-circuit refrigeration compressors on the market nowadays are more reliable in terms of the quality of imported or Sino-foreign joint ventures in developed countries, but their prices are more than 50% higher than those of domestically-made confidential ones.

six. The benefits of building a small cold storage in rural areas

The small-scale cold storage with a capacity of 10 tons to 20 tons in rural areas is most suitable for cold storage insulation boards for cold storage, and the cold storage investment is between 20,000 yuan and 40,000 yuan, which is an acceptable range for general farmers. This small cold storage unit has a small capacity, is easy to control, and is convenient for storage and unloading. A product can be easily stored, the temperature can be quickly reduced, the temperature can be kept stable, the cold storage thermal insulation board can be used, and the power consumption can be low. The degree of automation is high, just like home air conditioners and refrigerators. Easy to manage. A number of such small cold storages have formed a small cold storage complex with a total capacity of several hundred tons and thousands of tons, and its total investment is similar to that of large and medium-sized cold storages of the same scale. But it can keep more products and varieties of cold storage insulation board, according to its different preservation temperature requirements, can achieve arbitrary control, which is not easy to do large-capacity cold storage. In short, the flexibility, operability, degree of automation, energy-saving effect, and operating effectiveness of the small cold storage group are much better than that of the medium- and large-scale cold storage.