Characteristics and application of vacuum precooli

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The characteristics and application of vacuum precooling device for fruit and vegetable food

in China, the sales link of fruit and vegetable food is generally to directly market after picking, and then consumers buy it home and clean it before eating, while the remaining inedible parts are transported and processed in a centralized manner. This consumption method is not only time-consuming and laborious, increases repeated transportation and treatment, but also pollutes the environment, and does not meet the requirements of food hygiene. Obviously, this is different from modernization The fast-paced, highly civilized and developed society is becoming increasingly incompatible

industrialized processing of fruits and vegetables has been achieved in developed countries since the 1970s, and has developed to large-scale production by the early 1980s. The harvested fruits and vegetables are selected, stripped, cleaned, pre cooled, packaged, refrigerated and transported to the refrigerated shelves of supermarkets. Consumers buy them back and put them into refrigerators for refrigeration. When eating, they can cook directly without cleaning. This consumption mode undoubtedly has many advantages compared with China's traditional consumption mode:

industrialized centralized processing will inevitably bring a profound change to agriculture, The processing of agricultural and sideline products is bound to develop in the direction of industrialization, scale and standardization; It can provide consumers with agricultural and sideline products that fully meet the food hygiene standards, and the freshness is greatly improved; Greatly reduce urban garbage and environmental pollution; Reduce repeated transportation; Consumers save time and effort to meet the requirements of a fast-paced lifestyle

the Chinese government has always vigorously advocated the "vegetable basket" project, especially in the period of China's economic development, the industrialized processing of fruits and vegetables has been highly valued by governments at all levels, and the marketing of clean vegetables has become an inevitable trend. In recent years, there will be great development. In addition, the export of fresh fruits and vegetables is restricted by pre cooling and fresh-keeping technology, which has become increasingly unable to meet the growing requirements of international trade

The concept of precooling is different from that of cooling. The so-called precooling refers to the process in which the food rapidly decreases from the initial temperature (about 30 ℃) to the desired end temperature (0 ~ 15 ℃). The process of cooling and rapid cooling before rapid freezing is called precooling; Cooling is the process of reducing the food temperature to higher than the freezing temperature. Cooling is mainly used in the following types:

cooling storage. It is used for high-temperature cold storage (fresh-keeping cold storage) of fruits, vegetables and other foods in order to keep fresh and prolong their storage time

pure cooling. A certain temperature required for complete use in certain liquids. During pure cooling, the fluid temperature drops without state change, that is, it only absorbs its own latent heat, such as cooling beer, seasoning, milk, water, wine, sodium hydroxide solution, salt water, etc

precipitation cooling. Generally, it refers to multiphase liquid, that is, one or more liquid components solidify and precipitate when cooling. Such as processing oil, paraffin, zinc barium stone, sulfur dioxide, acetone recovered by pharmaceutical factories, frozen concentrated sea water, fruit juice, salt water, wine, etc., tartar precipitation and some chemical treatment methods

solidification cooling. Solidification cooling refers to the transformation of a substance from liquid to solid, such as margarine, vegetable oil, animal oil, palm oil, chocolate, stearin, gel, etc

due to the influence of ambient temperature, the surface temperature of fruits and vegetables is generally relatively high after harvest. In addition to its strong respiration, the heat released does not match the chemical products. If you want to open up new markets in this field and continuously increase the market share, the temperature will continue to rise, and the higher temperature will accelerate its respiration, continuously release heat, and a large amount of water evaporation, The continuous consumption of its own nutrition and water will rapidly wilt and reduce its freshness, greatly shortening the shelf life

in order to prolong the shelf life of fruits and vegetables, reduce their dry consumption and various losses in circulation, and enable consumers to obtain high freshness and clean fruits and vegetables, a series of post harvest processing must be carried out in the factory, such as selecting, peeling roots and leaves, cleaning and pre cooling, filtering, packaging, etc., and the pre cooling process is essential

principle of vacuum precooling method

common precooling methods include air precooling, water precooling, ice water precooling and vacuum precooling

heat the water to 100 ℃ under normal pressure to start boiling, and freeze when the temperature drops to 0 ℃. When the pressure decreases, the boiling point of water also decreases, and the boiling point at 613.28pa is 0 ℃. According to the physical property that the boiling point of water decreases with the decrease of pressure, the pre cooled food is placed in a vacuum tank for vacuum pumping. When the pressure reaches a certain value, the water on the food surface begins to evaporate. The advantages of vacuum precooling method are:

the food surface contains a lot of water, and its water vapor pressure also changes due to its high temperature. The evaporation of water is relatively slow under atmospheric pressure, and the evaporation speed is accelerated under vacuum due to the reduction of resistance, so the cooling speed of food is fast. The initial temperature of food is 35 ℃, and it takes about 20min to drop to 3 ℃; In the vacuum tank, the pressure at each point is uniform, so the food precooling is uniform; Large cooling capacity, including loading and unloading time, which can be operated twice per hour; Precooling is clean and sanitary, without cross contamination

vacuum precooling device

there are four types of vacuum precooling devices: intermittent, continuous, mobile and spray. The intermittent vacuum precooling device is used for small-scale production, the continuous vacuum precooling device is used for large-scale processing plants, and the mobile vacuum precooling device is expected to pass the certification and be supplied in batches within this year. Its integration is flexible and can be used in different places. The spray device is used for precooling fruit and rhizome foods with small surface moisture. For example, the dy series vacuum precooling device designed by Shenyang Refrigeration Technology Research Institute and manufactured by Shenyang Bingtian refrigeration equipment Co., Ltd. is mainly composed of vacuum tank, water trap, vacuum pump, refrigeration unit, loading and unloading mechanism, control cabinet and other components

vacuum tank. The vacuum tank is generally made of Q235B steel or I cy18m9t1 stainless steel. The small vacuum tank is cylindrical and reinforced with stiffeners. Groove welding is adopted for all welded junctions, and X-ray flaw detection is carried out. When Q235B material is used, the inner side should be treated with anti-corrosion treatment, and the outer side should be sprayed with high-strength anti rust material. The tank door shall be electric or manual, and the processing and fine washing system has good sealing performance. A track mechanism is set at the bottom of the vacuum tank to facilitate loading and unloading of materials. The vacuum tank is equipped with drainage device and cleaning system to ensure internal cleanliness

water trap. The water catcher, also known as the cold tank, has the same function as the water catcher in the vacuum freeze-drying device, that is, it is used to concentrate the water in the air, so as to prevent the water from entering the vacuum pump and emulsifying the lubricating oil to damage the vacuum pump components. The water catcher of the intermittent vacuum precooling device is generally designed to solve the problems found above well, which is calculated as a cylindrical structure

vacuum pump. Vacuum pump is the key component of vacuum system, and its selection should be determined according to different specifications of vacuum precooling devices and specific conditions, such as rotary vane vacuum pump group, water ring booster pump group, water vapor jet pump group, etc

refrigeration unit. For small intermittent or continuous vacuum precooling device, water-cooled or air-cooled Freon wire anti swing rack condensing unit should be selected, and ammonia system should be used for large devices. For hotter climates, freon water-cooling units are generally selected, and the refrigeration units are assembled on a common chassis with vacuum pump units and control cabinets

loading and unloading mechanism. The loading and unloading mechanism shall be determined according to the user's loading and unloading method. The conveyor belt or track shall be used for single package loading and unloading, and the battery forklift or hydraulic propeller shall be used for overall loading and unloading. The control system is equipped with manual and automatic system engineering. When any system fails, it will be operated by another system

source: China food processing machinery and packaging e-commerce platform

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