NEWS & BLOG
Why is the rotary vane vacuum pump so widely used in cooked food processing and fruit and vegetable preservation?
Category: Industry News
Time: 2021-01-19
Summary: First, the fruits and vegetables we harvest are still living organisms. They obtain essential substances and energy through respiration. On the one hand, respiration sustains the life of the organism; on the other hand, it consumes stored substances, thereby accelerating the aging process of fruits and vegetables. Thus, the goal of preservation is to slow down this aging process. To achieve this, we must control respiration, and the factor most closely related to respiration is temperature. Respiration not only releases energy but also raises the product’s temperature. In turn, this elevated temperature further promotes respiration, hastening the aging of fruits and vegetables. Clearly, if we can lower the temperature of fruits and vegetables, we can effectively control respiration and delay aging. Therefore, after harvesting, fruits and vegetables must be pre-cooled as quickly as possible to remove heat and reduce respiratory heat generation, thus creating favorable conditions for extending their shelf life. Currently, natural cooling is widely used, but it has several drawbacks: it requires a large area, takes a long time, and not only struggles to meet the demands of rapid pre-cooling but is also unsuitable for industrial-scale production. Some facilities directly place produce into cold storage for cooling, which is both costly and fails to ensure quick, uniform cooling. After cooked food is processed, it must be cooled before packaging. Traditional cooling methods include indoor cooling, natural cooling, forced-air ventilation cooling, and air-conditioned room cooling. These methods not only take a long time, have slow turnover rates, and occupy large spaces, but also result in uneven cooling—often with significant temperature differences between the surface and the center of the product. More importantly, they can compromise food hygiene and safety. During the cooling process, bacteria from the air inevitably adhere to the food, causing “secondary contamination.” Especially when the temperature is inappropriate, bacteria can multiply rapidly. If bacteria pass through this temperature range too quickly, the number of generations required for bacterial reproduction can be drastically reduced, making it easier to control the initial bacterial load and enhancing food safety while extending shelf life. This is of great significance for implementing food safety laws. It’s evident that the food processing industry needs advanced methods and equipment to achieve rapid cooling of its products. The principle behind vacuum cooling is to utilize the heat absorption generated by water evaporation. Consequently, water vapor is produced during the cooling process. If this water vapor were to enter the rotary vane pump directly, it would emulsify the pump oil, not only impairing pump performance but also potentially damaging the pump itself. The solution is to install a water trap upstream of the pump, which condenses the water vapor at low temperatures and drains the resulting liquid. To accomplish this, the refrigeration system must be reconfigured to allow the vacuum pump to exhaust air that has been stripped of water vapor. Under the action of a rotary vane vacuum pump, a vacuum cooler for fruits and vegetables can keep vegetables fresh and lock in their moisture, achieving an effective pre-cooling effect. In short, vacuum cooling enables vegetables to cool down more rapidly after harvest without losing their original moisture content—this is precisely where the advantages of the rotary vane vacuum pump become fully apparent.
First of all, the fruits and vegetables we harvest are still living organisms. They obtain the necessary substances and energy through respiration. On the one hand, respiration sustains the life of the individual; on the other hand, it consumes stored substances, thereby accelerating the aging process of fruits and vegetables. Thus, the goal of preservation is to slow down this aging process. To achieve this, it’s essential to control respiration—and the factor most closely linked to respiration is temperature. Respiration not only releases energy but also raises the product’s temperature. In turn, this higher temperature further stimulates respiration, speeding up the aging of fruits and vegetables. Clearly, if we can lower the temperature of fruits and vegetables, we can effectively slow down respiration and delay aging. Therefore, after harvesting, fruits and vegetables must be pre-cooled promptly to quickly remove excess heat and reduce respiratory heat production—thus creating favorable conditions for extending their shelf life. Currently, natural cooling methods are widely used, but they have several drawbacks: they require large areas, take a long time, and not only struggle to meet the demands of rapid pre-cooling but are also unsuitable for industrial-scale production. Some people directly place harvested produce into cold storage for cooling, which is both costly and fails to ensure quick, uniform cooling.
After cooked food is processed, it must be cooled before being packaged. Traditional cooling methods include indoor cooling, natural cooling, forced-air ventilation cooling, and air-conditioned room cooling. These cooling methods not only take a long time, have slow turnover rates, and occupy large spaces, but also result in uneven cooling, with significant temperature differences between the surface and the center of the food. More importantly, they can compromise food hygiene and safety. During the cooling process, bacteria in the air inevitably adhere to the food, causing “secondary contamination.” Particularly when the temperature is inappropriate, bacteria can multiply rapidly. If bacteria pass through this temperature range quickly, the number of generations required for their reproduction can be greatly reduced, making it easier to control the initial bacterial load and thereby enhancing food safety and extending shelf life. This has significant implications for the implementation of food safety laws. It is evident that samples used in the food processing industry also require advanced methods and equipment for rapid cooling.
The principle behind vacuum cooling is the endothermic effect produced by water evaporation. Consequently, water vapor is generated during the cooling process. If this water vapor directly enters the rotary vane pump, it can cause emulsification of the pump oil, which not only impairs pump performance but also damages the pump itself. To address this issue, a water trap should be installed upstream of the pump to condense the water vapor at low temperature and discharge the resulting liquid water. As a result, the refrigeration system must be reconfigured to remove the water vapor-laden air via a vacuum pump.
Under the action of a rotary vane vacuum pump, fruit and vegetable vacuum coolers can keep vegetables fresh, lock in their moisture, and achieve a pre-cooling effect. In short, vacuum cooling enables vegetables to cool down more quickly after harvest without losing their original moisture content—this is precisely when the role of the rotary vane vacuum pump becomes fully apparent.