The hottest food is dry. Who can occupy the highla

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Food drying "Three Kingdoms kill" who can occupy the highland

food drying technology is a commonly used food processing technology in the food industry. Various physical, chemical and biological changes will occur in the processing, storage and transportation of food. These changes will change the color and structure of food, and biochemical reactions will also occur that will deteriorate aromatic substances and reduce nutrients. These physical and biochemical changes will lead to the reduction of food quality and processing efficiency. Food drying technology is a processing method used to make food reach the ideal shelf life or reduce sales costs. Such as: hot air drying, cold air drying, spray drying, vacuum freeze drying, etc. At present, there are more than ten drying methods commonly used, such as wind heat drying, drum drying, spray drying, centrifugal drying, infrared drying, microwave drying, freeze drying, etc. different products have the corresponding optimal drying model 2017

microwave drying, spray drying and freeze drying are the Trident in the market at present. Compared with traditional drying methods, they have obvious advantages. Next, we mainly analyze the characteristics and product applications of these three drying modes

microwave drying

microwave can directly act on the internal medium molecules of food to produce a thermal effect. Water molecules vibrate hundreds of millions of times in 1 s, and water molecules heat up quickly. Therefore, food microwave drying technology has the characteristics of fast drying speed and controllability. At the same time, the microwave drying equipment is a closed space, which does not need medium conduction. Only the magnetron and power supply consume part of the energy, so the heating efficiency is high and energy is saved. Microwave drying can also avoid food surface hardening and sensory changes caused by uneven heating

the molecular thermal effect of microwave drying makes it have no property requirements for dried products, and can meet the drying requirements of various shapes and volumes. The amount of water is the main factor affecting the microwave effect. Due to the different dielectric constants of various substances, the thermal diffusion efficiency is different. Therefore, microwave drying is often combined with other methods to produce faster drying effect, such as vacuum, pressurization, hot air and other methods, which can shorten the drying time and improve the product quality. For cereal products with less water content, microwave drying also plays the role of mold prevention and insect eradication, and achieves the purpose of killing by increasing the temperature of water molecules in microorganisms and insects

spray drying

spray drying is to atomize the solution, emulsion and other thinners, turn the liquid into very fine mist droplets, and evenly add sand to the air for energy exchange at the same time as the heat starts at the second 30, and the water vaporizes rapidly, so as to obtain dry products. This method can directly dry into powder or granular products, and can eliminate the obvious gap between the independent technology of evaporation and crushing and the foreign advanced level. Spray drying mainly includes pressure spray drying method, air flow spray drying method and centrifugal spray drying method. The difference between different methods is mainly the way of liquid atomization

spray drying can only dry powdery or granular substances, but the drying time is short. It takes only a few seconds to evaporate more than 95% of the water, and the production capacity is high,. Due to the large heating area and short heating time, the nutrition of the product is well preserved, which is the main drying method of powder products such as milk powder and soybean powder at present

freeze drying

vacuum freeze drying is referred to as freeze drying, also known as sublimation drying. It is to freeze the materials to be dried below their common melting point at low temperature, so that the water in the materials becomes solid ice, and then gradually heat up under appropriate vacuum environment and appropriate vacuum degree, so that the ice is directly sublimated into water vapor and removed, and then use the condenser (water trap) in the vacuum system to condense the water vapor, A technique for drying materials by dehydration at low temperature

the sublimation process needs to consume heat, and the temperature of dehydrated food will be reduced. Therefore, the temperature of dehydrated food needs to be raised in the sublimation process, but the temperature is basically in a low temperature state, generally not more than 40 ℃. Because it does not involve high temperature, vacuum freeze-drying technology has little impact on heat sensitive substances and active substances, and less nutritional loss. It is an advanced drying technology at present. However, due to the high cost and energy consumption of equipment required for vacuum drying, it has a great impact on the popularization of technology

no matter which drying technology has its own application characteristics, various factors should be comprehensively considered when selecting which method. Considering the characteristics of milk powder products, spray drying and freeze drying can be used. Considering the production capacity, spray drying is needed. Vacuum freeze-drying technology can greatly improve the expressiveness of flavor and nutrients for heat sensitive substances such as extracts, essence and fragrances. Input cost is an important factor for enterprises to consider. Small and medium-sized enterprises can only flinch from the vacuum freeze-drying and reloading sample drying with complex operation and high cost. However, from the perspective of product quality, freeze-drying technology is the best choice. With the continuous improvement of consumption level and technology, vacuum freeze-drying technology is bound to become the protagonist of food drying technology

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