Freeze-drying operates on the principle of sublimating solvents from solid samples directly into gas in a vacuum, achieving drying. As it dries samples at or even below room temperature, it preserves their biological activity, rendering them porous and easily soluble. Thus, freeze-drying is an excellent method for preserving bioactive samples.

Operating Procedure of Freeze Dryer:一. Pre-freezing Preparation:

1.Place the material evenly on the material tray, ensuring a thickness not exceeding 10mm. Position the material temperature sensor appropriately within the material and secure it.

2.Put the tray with the material onto the freeze-drying rack, then into the cold trap, and cover with the insulation cover.

3.Turn on the main power switch. If planning to introduce nitrogen (or other inert gas) into the drying chamber at the end of freeze-drying, first use nitrogen to purge the water inlet, then close the water inlet valve.

 Material Pre-freezingMaterial pre-freezing is a crucial step in the freeze-drying process, directly affecting the quality of the freeze-dried product. Pre-freezing can be done through slow freezing or rapid freezing, depending on specific needs. For example:

1.Slow Freezing: Place the prepared material into the cold trap, cover with the insulation cover, and start the compressor. Pre-freezing begins.

Rapid Freezing: Start the compressor first. Once the temperature in the2. cold trap chamber drops to a certain level, place the prepared material into the cold trap. Pre-freezing begins.

Freeze-drying Operation:

1.Remove the material rack from the cold trap chamber and place it on a spare hard plastic disc (all placed above the cold trap chamber). Then cover with the acrylic cover. If using a pressure cover device to freeze-dry the material, quickly transfer the material from the pre-freezing rack to the tray of the pressure cover device, then cover with the acrylic cover.

2.On the equipment operation screen, press the "Vacuum Pump" button to start the vacuum pump. Press the "Vacuum Gauge" button to display the vacuum level. Once the vacuum level reaches around 30Pa, press the "Heating" button to initiate the freeze-drying process, which runs according to the preset process program.

Note: The vacuum gauge zero has been calibrated, so users do not need to adjust it. After turning on the vacuum gauge, atmospheric pressure readings of 110×103～80×103Pa are normal and do not require adjustment. Recommendation: Only open the vacuum gauge when checking the vacuum level during freeze-drying. Close it when not in use to prolong its lifespan.

 Defrosting Operation:

1.On the equipment operation screen, press the defrost button to initiate the cold trap defrosting. Once defrosting is complete, the system will automatically stop the process. (This function should be available on selected models.)

Clean the ice, moisture, and impurities inside the cold trap, and maintain the equipment properly. After the ice in the cold trap chamber has melted, it can be drained out through the water inlet valve. When not in use, keep the main machine's water inlet valve in the open position.

"If you are interested in freeze-dried food making or would like to learn more about our products and services, please feel free to contact us. We are happy to provide you with advice and answer any questions you may have. Our team will be happy to serve you. Look forward to communicating and cooperating with you!"

article source: https://www.bothsh.com/news/how-does-a-freeze-dryer-work/

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