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4, vacuum packaging (vacuumpackaging)
Vacuum packaging is a kind of packaging method in which after the articles are packed into the airtight containers, the vacuum is taken before the containers are sealed so that there is substantially no air in the sealed containers. Vacuum packaging is also called decompression packaging or exhaust packaging. This kind of package can block the outside moisture from entering the packaging container, and can also prevent the presence of moist air inside the closed moisture-proof packaging and dew condensation when the temperature drops. With vacuum packaging, care should be taken to avoid excessive vacuum.
General raw grain and processed food products can be vacuum-packed. Vacuum packaging not only avoids or reduces the oxidation, discoloration, and taste deterioration of food, but also inhibits the growth of certain molds and bacteria.
At present, the processing and preservation of foodstuffs, oils, etc. are still in a low-level, extensive state, and China's refrigerated conditions cannot be compared with the United States, Japan, and other developed countries, thus causing a great deal of loss of agricultural products and waste of resources. Vacuum packaging can maintain the quality and nutrient content of food and agricultural products and is highly valued by the food industry.
In addition to controlling external temperature and sterility, vacuum packaging is more important to control the proper gas environment for food and achieve the desired preservation purpose. Its main methods are mechanical extrusion, straw degassing and other methods. Either way, the air inside the bag must be extracted and then heat-sealed. Its main characteristics are: reducing the oxygen content in the bag, inhibiting the growth and development of moulds and bacteria, controlling the deterioration of food, and achieving the purpose of freshness preservation. In addition, after being vacuum-packed, it can also resist mechanical pressure and reduce vibration, which is beneficial to long-distance transportation and facilitates sales.
5, vacuum storage (vacuumstorage)
Vacuum storage technology is also called low-pressure storage and vacuum storage. Vacuum storage is the use of suction decompression method, with the suction device to extract the air in the well-closed grain pile, reduce the concentration of oxygen in the grain pile and even make it close to the state of oxygen, and maintain for a long time to reach the storage The purpose of food preservation and pest control and pest control. In contrast to controlled atmosphere storage, decompression storage only changes the total air content and density in the storage environment and does not change the air composition and the combination ratio. Vacuum storage is essentially a pressure-controlled storage method. It is beneficial to inhibit the occurrence and spread of enzymes, bacteria, diseases, and insects.
Vacuum storage is to store grain in an enclosed warehouse (container), extract air from the storage (container) during the cooling process, and depressurize and reduce oxygen. As the pressure continues to decrease, some gases harmful to the storage It also decreased or almost disappeared, creating favorable conditions for the long-term storage and preservation of food. In normal operation, the vacuum decompression library can simultaneously and continuously complete the vacuum pre-cooling and decompression refrigeration process, which reduces the storage process. Since the stored grain in the warehouse does not require airtight packaging and has a wide range of applications, it has become a research hotspot for food scientists. .
6, vacuum bursting shell (vacuumbursting)
The shelled agricultural products (such as chestnuts, sunflower seeds, etc.) are washed into a vacuum sheller after rinsing and selecting processes (mainly picking moldy and insect raw materials). Under vacuum conditions, the wetted materials will have considerable moisture content. Heated to a certain temperature, under the action of vacuum pumping, the material absorbs heat and causes the moisture of the shell to continuously evaporate and is removed. The toughness and strength of the material are reduced, and the brittleness is greatly increased. The role of vacuum can reduce the pressure outside the shell and the shell will be in a relatively high pressure state. When the outer shell is heated and dried to generate stress strain, the kernels are also heated and vaporize their internal moisture. The nuts shrink due to water loss, which causes them to separate from the endothelium and the outer shell; because the nuts' moisture does not evaporate Escape from the shell, so that the pressure inside the shell is further increased, when it reaches a certain value, it will burst the shell and the endothelium.
Vacuum crust shell processing technology is not only efficient but also hygienic. It not only adapts to large-scale production, but also maintains the original shape, original color, and original taste of the kernels. Compared with milling, rolling, and extrusion processes, it greatly reduces crushing and loss of nuts. The blasting rate is more than 90%, which improves product quality and has broad application value.
7, vacuum drying (vacuumdrying)
The vacuum drying process is to place the material to be dried in a closed and dry room, and vacuum is used to continuously heat the material to be dried, so that the moisture inside the material is diffused to the surface through a pressure difference or concentration difference, and the water molecules are on the surface of the material. Get enough kinetic energy to overcome the mutual attraction between molecules, escape to the vacuum chamber of the low-pressure space, which was pumped away by the vacuum pump process. Vacuum drying makes it easy to recover useful and harmful substances and seals well. In the sense of environmental protection, some people claim that vacuum drying is “green dryingâ€.
In the vacuum state, the boiling point of the moisture of the material is reduced, and the vaporization process is accelerated. Therefore, it is particularly suitable for a material that is sensitive to temperature and easily decomposed. Vacuum drying is mainly performed in a low vacuum area. In the process of vaporization of grain moisture, the boiling evaporation temperature is directly proportional to the ambient pressure, and the high-moisture grain is placed in a closed drying cylinder, so that the drying cylinder forms and maintains a certain degree of vacuum, and the food in the drying cylinder is continuously heated. The moisture inside the grain is diffused to the surface by the pressure difference, vaporized and then pumped away by the vacuum pump to achieve continuous dehydration and drying of the high moisture grain under vacuum and low temperature. Vacuum drying causes the boiling evaporation temperature of the water to decrease from 100° C. to below 40° C. Since the evaporation temperature is lower than the gelatinization temperature of the starch, no damage is caused to the grain. It avoids the swelling and explosion of grain grains and ensures the quality of dried grains. It guarantees that the original color, fragrance, taste, nutrient composition and quality of the material after drying are basically the same. It is a true low-temperature drying, which is completely different from the general hot-air and low-temperature drying.
The vacuum freeze-drying technique is to freeze the materials first, then raise the temperature under vacuum conditions to sublimate the ice to achieve the final drying purpose. The heating methods used are infrared heating, microwave heating, etc. The provided heat must not only sublimate the ice but also damage the surface of the product. Vacuum freeze-drying technology can maintain the original color, aroma, taste, shape and nutrient content of the product, especially the drying of heat-sensitive materials. It is a promising drying method for producing green food.
8. Concluding remarks
China's grain transportation, drying and processing industries have huge market potential. How to use vacuum technology scientifically, reasonably and effectively in the food industry, vacuum workers should use their own professional advantages and new theoretical research to vigorously develop new and practical new ones. Technology, new processes, and new equipment will make due contributions to China's food industry.
The development of vacuum science and technology is rapid and involves a wide range of content. This article only briefly discusses several aspects of the application of vacuum technology in the food industry, and there are many items that are not involved. Please understand the readers.
Vacuum packaging is a kind of packaging method in which after the articles are packed into the airtight containers, the vacuum is taken before the containers are sealed so that there is substantially no air in the sealed containers. Vacuum packaging is also called decompression packaging or exhaust packaging. This kind of package can block the outside moisture from entering the packaging container, and can also prevent the presence of moist air inside the closed moisture-proof packaging and dew condensation when the temperature drops. With vacuum packaging, care should be taken to avoid excessive vacuum.
General raw grain and processed food products can be vacuum-packed. Vacuum packaging not only avoids or reduces the oxidation, discoloration, and taste deterioration of food, but also inhibits the growth of certain molds and bacteria.
At present, the processing and preservation of foodstuffs, oils, etc. are still in a low-level, extensive state, and China's refrigerated conditions cannot be compared with the United States, Japan, and other developed countries, thus causing a great deal of loss of agricultural products and waste of resources. Vacuum packaging can maintain the quality and nutrient content of food and agricultural products and is highly valued by the food industry.
In addition to controlling external temperature and sterility, vacuum packaging is more important to control the proper gas environment for food and achieve the desired preservation purpose. Its main methods are mechanical extrusion, straw degassing and other methods. Either way, the air inside the bag must be extracted and then heat-sealed. Its main characteristics are: reducing the oxygen content in the bag, inhibiting the growth and development of moulds and bacteria, controlling the deterioration of food, and achieving the purpose of freshness preservation. In addition, after being vacuum-packed, it can also resist mechanical pressure and reduce vibration, which is beneficial to long-distance transportation and facilitates sales.
5, vacuum storage (vacuumstorage)
Vacuum storage technology is also called low-pressure storage and vacuum storage. Vacuum storage is the use of suction decompression method, with the suction device to extract the air in the well-closed grain pile, reduce the concentration of oxygen in the grain pile and even make it close to the state of oxygen, and maintain for a long time to reach the storage The purpose of food preservation and pest control and pest control. In contrast to controlled atmosphere storage, decompression storage only changes the total air content and density in the storage environment and does not change the air composition and the combination ratio. Vacuum storage is essentially a pressure-controlled storage method. It is beneficial to inhibit the occurrence and spread of enzymes, bacteria, diseases, and insects.
Vacuum storage is to store grain in an enclosed warehouse (container), extract air from the storage (container) during the cooling process, and depressurize and reduce oxygen. As the pressure continues to decrease, some gases harmful to the storage It also decreased or almost disappeared, creating favorable conditions for the long-term storage and preservation of food. In normal operation, the vacuum decompression library can simultaneously and continuously complete the vacuum pre-cooling and decompression refrigeration process, which reduces the storage process. Since the stored grain in the warehouse does not require airtight packaging and has a wide range of applications, it has become a research hotspot for food scientists. .
6, vacuum bursting shell (vacuumbursting)
The shelled agricultural products (such as chestnuts, sunflower seeds, etc.) are washed into a vacuum sheller after rinsing and selecting processes (mainly picking moldy and insect raw materials). Under vacuum conditions, the wetted materials will have considerable moisture content. Heated to a certain temperature, under the action of vacuum pumping, the material absorbs heat and causes the moisture of the shell to continuously evaporate and is removed. The toughness and strength of the material are reduced, and the brittleness is greatly increased. The role of vacuum can reduce the pressure outside the shell and the shell will be in a relatively high pressure state. When the outer shell is heated and dried to generate stress strain, the kernels are also heated and vaporize their internal moisture. The nuts shrink due to water loss, which causes them to separate from the endothelium and the outer shell; because the nuts' moisture does not evaporate Escape from the shell, so that the pressure inside the shell is further increased, when it reaches a certain value, it will burst the shell and the endothelium.
Vacuum crust shell processing technology is not only efficient but also hygienic. It not only adapts to large-scale production, but also maintains the original shape, original color, and original taste of the kernels. Compared with milling, rolling, and extrusion processes, it greatly reduces crushing and loss of nuts. The blasting rate is more than 90%, which improves product quality and has broad application value.
7, vacuum drying (vacuumdrying)
The vacuum drying process is to place the material to be dried in a closed and dry room, and vacuum is used to continuously heat the material to be dried, so that the moisture inside the material is diffused to the surface through a pressure difference or concentration difference, and the water molecules are on the surface of the material. Get enough kinetic energy to overcome the mutual attraction between molecules, escape to the vacuum chamber of the low-pressure space, which was pumped away by the vacuum pump process. Vacuum drying makes it easy to recover useful and harmful substances and seals well. In the sense of environmental protection, some people claim that vacuum drying is “green dryingâ€.
In the vacuum state, the boiling point of the moisture of the material is reduced, and the vaporization process is accelerated. Therefore, it is particularly suitable for a material that is sensitive to temperature and easily decomposed. Vacuum drying is mainly performed in a low vacuum area. In the process of vaporization of grain moisture, the boiling evaporation temperature is directly proportional to the ambient pressure, and the high-moisture grain is placed in a closed drying cylinder, so that the drying cylinder forms and maintains a certain degree of vacuum, and the food in the drying cylinder is continuously heated. The moisture inside the grain is diffused to the surface by the pressure difference, vaporized and then pumped away by the vacuum pump to achieve continuous dehydration and drying of the high moisture grain under vacuum and low temperature. Vacuum drying causes the boiling evaporation temperature of the water to decrease from 100° C. to below 40° C. Since the evaporation temperature is lower than the gelatinization temperature of the starch, no damage is caused to the grain. It avoids the swelling and explosion of grain grains and ensures the quality of dried grains. It guarantees that the original color, fragrance, taste, nutrient composition and quality of the material after drying are basically the same. It is a true low-temperature drying, which is completely different from the general hot-air and low-temperature drying.
The vacuum freeze-drying technique is to freeze the materials first, then raise the temperature under vacuum conditions to sublimate the ice to achieve the final drying purpose. The heating methods used are infrared heating, microwave heating, etc. The provided heat must not only sublimate the ice but also damage the surface of the product. Vacuum freeze-drying technology can maintain the original color, aroma, taste, shape and nutrient content of the product, especially the drying of heat-sensitive materials. It is a promising drying method for producing green food.
8. Concluding remarks
China's grain transportation, drying and processing industries have huge market potential. How to use vacuum technology scientifically, reasonably and effectively in the food industry, vacuum workers should use their own professional advantages and new theoretical research to vigorously develop new and practical new ones. Technology, new processes, and new equipment will make due contributions to China's food industry.
The development of vacuum science and technology is rapid and involves a wide range of content. This article only briefly discusses several aspects of the application of vacuum technology in the food industry, and there are many items that are not involved. Please understand the readers.
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