There are roughly three types of refrigeration temperature ranges and condensing temperatures of freeze dryer shelves. The refrigeration system adopts a single-stage refrigeration compression cycle. The refrigeration temperature of layers of shelfis about – 35 ~ – 40 ℃, and the refrigeration temperature of the condenser is about – 50 ℃. This freeze dryer is suitable for the production of some products that are easy to freeze dry,such as food, meat, etc. The refrigeration system adopts a two-stage refrigeration compression cycle.The refrigerating temperature of the layers of shelf is about – 45 to – 50 ℃, and the refrigerating temperature of the condenser is about – 65 ℃. This freeze dryer is suitable for the freeze drying of most pharmaceutical products. The refrigeration system adopts a cascade refrigeration cycle, the refrigeration temperature of the layers of shelf is about -55 to -60 ℃, and the refrigeration temperature of the condenser is about -75 ℃. This freeze dryer is suitable for the freeze drying of some special products. The selection of the above temperature range is determined by the eutectic point of the freeze-dried product. Products with a low eutectic point require that the cooling temperature of the shelf is low, and the temperature of the condenser is correspondingly lower. Regarding the vacuum degree of the freeze-drying chamber, the past view believed that the higher the vacuum degree, the better, and the current view believes that the vacuum degree should be within a reasonable range. The vacuum degree is too high, which is not conducive to heat transfer, and the drying speed decreases, but in any case, the no-load ultimate vacuum degree of the freeze-drying box should reach more than 1 × 10 – 2 mbar. If a high degree of vacuum is not required during use, the vacuum degree can be controlled by the vacuum degree adjustment device, so that the vacuum degree can be controlled within the required range. Therefore, the vacuum adjustment device should be selected. The emptying speed of the lyophilization chamber should be evacuated from atmospheric pressure to 1 × 10 – 1 mbar within half an hour. 2 hours to a vacuum of more than 1 x 10 – 2 mbar.
Lyophilization (freeze dry) is the technique of protection through a process called sublimation for drying the material. Water contained in the products is frozen at the very beginning and while in this situation, the water is expelled by sublimation. Sublimation is the transition of the material from solid (ice) state to gas (water vapor) state, by skipping the liquid state of the material, that is, without allowing the ice to melt. The iced water directly evaporates in low-pressure environment, in the event of a slight increase in temperature. In this way, high temperatures are not needed for obtaining preservation. Thus, it does not cause changes like cleavages and so on in products’ molecule and cell structure. Their inner and outer structures are not spoiled, they preserve almost their original states. Areas of uses of lyophilization Chemistry and biochemistry Pharmacy Cosmetics Food Industries Less common practices Books damaged by water Documents and manuscripts Animal by-products Dairy products yeasts Preservation of various archaeological excavation outputs Museum exhibition objects such as plants and animals
Strawberry fruit has a short shelf life. If stored at ambient temperature only lasts 1 day, so it needs to be dried into a frozen product so that its shelf life is longer. Freeze dried strawberries are favored by consumers because they still have properties like fresh fruit. It can have a half year of shelf life. A freeze vacuum dryer is an effective tool for producing high-quality freeze-dried products when compared to other dryers . This freeze vacuum dryer has been used extensively to obtain high-quality dry products .Frozen vacuum dryers can be applied to strawberries and other fruits. Frozen products produced are in line with the desires and needs of consumers for quality processed products that are hygienic and quality. If you have any project that requires the freeze dryer, please feel free to contact us. We will offer the know how and give you quote as soon as possible.
Durian freeze-drying technology mainly uses the principle of solid-state sublimation into gaseous state, and processes the durian through freeze-drying equipment. In the process of processing freeze-dried durian, firstly, the durian is pretreated or prepared, and the durian pulp to be technically treated is cleaned, graded and sliced. The second is the process of cooling and solidification, which is to freeze the water in the durian, so that the water-containing substances and free water in the durian are completely frozen into a solid state, and then the durian is sublimated and dried for the first time, using the physical principle of solid sublimation. Heating at low temperature promotes the decomposition of solid water molecules into water vapor, thereby achieving the purpose of durian dehydration. This sublimation drying process will sublime 90% of the water in the durian pulp. Finally, the secondary drying process are carried out, and the reprocessing is to use a higher physical temperature to dry the frozen water on the capillary wall of the durian pulp, thereby forming a durian dry that has a longer storage time after freeze-drying. The moisture content of durian pulp in the state is basically below 5%. The total production proess time can be reduced to 13 hours per batch, since we have done many trial tests and finally optimize the production process.
When the vacuum freeze dryer is used for freeze drying of graphene, the principle of sublimation is used to first freeze the graphene solution into ice crystals, and then vacuumize the water to sublime out, and finally obtain flocculent solid graphene. The cold trap has a pre-freezing function, which can quickly pre-freeze the graphene solution, with fast cooling speed, low noise and high freeze-drying efficiency. Graphene freeze-drying process and method: 1. The main engine and the vacuum pump are connected; 2. Pre-freeze the sample in a cold trap or other low temperature refrigerator; 3. When the pre-frozen samples are placed in the drying room, ensure that the air release valve is sealed, and turn on the vacuum pump; 4. Pay attention to the falling speed of the vacuum degree to determine whether the vacuum degree can reach below 20pa; 5. When vacuuming, be sure to keep the refrigerator turned on to ensure that the cold trap captures the sublimated moisture; 6. After the freeze-drying is completed, please release the air first (to prevent the vacuum pump from returning to the oil), then turn off the vacuum pump, turn off the refrigerator and power supply, and take out the dry product; 7. After defrosting in the cold trap, release the water, wipe off the residual water, and keep the table and the cold trap dry.