一. How does a freeze dryer work
A freeze dryer is a device that removes water from materials through sublimation in a vacuum. Once freeze-dried, products can be stored long-term without preservatives while retaining all their original nutrients.
二. Components of a Freeze Dryer
The freeze-drying machine is generally composed of a freeze-drying bin, a heating system, a vacuum system and a cold trap.
1. Freeze-drying Bin: It is used to place materials to be freeze-dried; the material is placed on the tray first, and then the tray is placed in the compartment of the freeze-drying bin.
2. Heating system: it is used to provide the problem of sublimation of the internal moisture of materials under a vacuum state. It is generally the temperature generated by heating water with an electric heating tube.
3. Vacuum system: used to maintain the vacuum degree of the freeze-drying bin, which is generally composed of two vacuum pumps or a combination of a vacuum pump and a roots pump.
4. Cold trap: it is used to capture the water vapor sublimated from the freeze-drying bin. The water vapor is splashed on the cold trap coil to release heat and then condensed into ice. According to the condenser in the cooling system, the cooling mode of the cold trap to the Freon compressed by the compressor is water-cooled and air-cooled, and the water-cooled type is used to cool the Freon through circulating cold water, which needs to be used with the water tower; the air-cooling type cools the Freon through the cooling fan, but it will be affected by the temperature of the use environment.
三. How to make freeze-dried products with a freeze dryer
The premise of making freeze-dried products is not only to understand what the freeze-drying machine does, but also to understand the characteristics of the materials to be processed. The water content of different materials is different, the freeze-drying time is different, and the pre-treatment method is also different. For example, the freeze-dried fruit can be put into the freeze-drying machine for freeze-drying treatment after the center temperature is -18°C to 25°C.
In general, the production of freeze-dried products is divided into three steps:
1. The first step is to put raw materials cut into specific sizes into quick-freezing equipment for quick freezing. The reason for quick freezing is to freeze the water inside and on the surface of the material into ice. The quick freezing time is about 30-40 minutes, ensuring that the center temperature is -18°c to -25°c, and the quick freezing is completed.
2. The second step is to put the frozen materials into the freeze-drying bin of the freeze-drying machine. The water content frozen into ice in the materials is sublimated into water vapor under vacuum. This process is called sublimation drying, which can remove about 90% of the water content.
3. The third step is called analytical drying, which is to deal with the remaining moisture of materials after the sublimation drying stage. This process usually takes a long time and a high temperature, but the temperature cannot exceed the allowable value of the product. The whole analytical drying process is very important for temperature control.
Corresponding to different materials, the continuous stage of sublimation drying, the temperature, and the time of each stage; and the continuous stage of analytical drying, the temperature, and the time of each stage can be set in the freeze-drying machine control system. These parameters can be classified and stored one by one, which is the freeze-drying machine formula.
四.Operating Notes for Freeze Dryers
1. Please make sure that the power supply specifications match the power supply specifications required by the machine.
2. When defrosting the cold trap, take out all the freeze-dried materials before defrosting.
3. Check whether there is leakage in the heating sandwich plate, hot water pipeline, and cold trap pipeline of the freeze-drying bin.
4. Before starting the machine, start the cold trap, and after the temperature of the cold trap is close to the set temperature, put the materials in the freeze-drying bin.
5. The product after freeze-drying should be tested and recorded with the water content inspection instrument so as to adjust the machine parameters.
6. Some materials need to be pretreated before freeze-drying, such as the liquid needs to be concentrated before freeze-drying and the fungi need to be processed by ultrasonics before scalding.
7. Check the vacuum pump oil regularly to prevent the vacuum pump from burning due to oil-free operation.
五.Summary
Due to the high nutritional value and easy storage of freeze-dried products in daily life, they are deeply loved by people. Moreover, freeze-dried products have much higher value than other drying products, which indicates that freeze-drying products have a good prospect in the food processing market. High-quality freeze-drying products require high-quality freeze-drying equipment. As a professional freeze-drying equipment manufacturer, Orange Mech will provide you with high-quality equipment and services. If you want to learn more about freeze-drying equipment, please contact us.
