Small freeze-drying machines are widely used in fields such as biopharmaceuticals, food preservation, and scientific research experiments due to their advantages of low-temperature dehydration and retention of material activity. To help users standardize operations and improve freeze-drying efficiency, this article takes the commonly used -50 ℃ freeze-drying machine in the laboratory as an example to systematically sort out the key points of the entire process from material preparation to equipment maintenance.

　　1、 Preparation before operation: Double inspection of materials and equipment

1. Material pretreatment

① Packaging control: Package the materials to be freeze-dried (such as solutions, suspensions) into shallow culture dishes or specialized freeze-drying bottles, with a liquid level thickness not exceeding 1.5cm, to ensure uniform heat transfer;

② Pre freezing treatment: Place the packaged materials in a -40 ℃ freezer for 4-6 hours until they are fully solidified, avoiding direct placement in a freeze dryer that may cause excessive ice crystals and damage to cell structure;

③ Moisture content control: High sugar and high protein materials require the addition of protective agents (such as seaweed sugar) to prevent collapse during the freeze-drying process.

2. Equipment inspection and pre cooling

① Check whether the oil level of the vacuum pump is above the centerline of the oil mirror and whether the temperature of the cold trap has dropped below -50 ℃;

② Turn on the equipment and run it without load for 30 minutes to test the sealing of the vacuum system (target vacuum degree ≤ 10Pa).

　　2、 Freeze drying process: precise control in stages

1. Primary Drying stage

① Quickly transfer the pre frozen material to the cold trap, close the hatch and start the vacuum pump;

② Maintain a cold trap temperature of -50 ℃ and a vacuum degree of 10-30Pa for 12-24 hours (adjusted according to material thickness), during which more than 90% of the upstream free water is removed.

2. Analyze the Secondary Drying Stage

① Gradually increase the shelf temperature to 25-30 ℃, maintain a vacuum degree of 5-10Pa, and continue for 4-8 hours;

② Monitor the surface temperature of materials through infrared thermometers to avoid overheating and deactivation of active ingredients.

3. Termination criteria

① Observe that there is no new frost formation inside the cold trap;

② The material temperature is approaching the shelf temperature;

③ The vacuum degree is stable and has no fluctuations.

　　3、 Shutdown and post-processing: details determine the quality of finished products

1. Pressure relief sampling

① First, turn off the vacuum pump and slowly fill it with dry nitrogen gas to atmospheric pressure to prevent the material from absorbing moisture;

② Use tweezers to gently remove the freeze-dried block, avoiding severe vibration that may cause powdering.

2. Equipment cleaning and maintenance

① Wipe the inner wall and shelf of the cold trap with 75% alcohol to remove any residue;

② Regularly replace the vacuum pump oil (every 50 runs or 3 months) to prevent the deterioration of oil quality from affecting the vacuum degree;

③ When not in use for a long time, keep the cold trap dry and store it with power off.

Conclusion

The operation of a small freeze-drying machine needs to take into account the three core elements of "low temperature, vacuum, and temperature control". By strictly following the pre-treatment, staged drying, and standardized shutdown procedures, the efficiency of freeze-drying and the quality of finished products can be significantly improved. Experiments have shown that the optimized operation process can increase the activity retention rate of biologics to over 92%, providing reliable support for scientific research and production.