Freeze drying method for freeze-dried products

Freeze drying method for freeze-dried products
The quality requirements of the freeze-drying machine for freeze-dried products are: constant biological activity, uniform appearance and color, full shape, firm structure, fast dissolution rate and low residual moisture. To obtain high quality products, a comprehensive understanding of the theory and process of lyophilization should be obtained. The freeze-drying process of the freeze dryer includes three stages of pre-freezing, sublimation and re-drying. Reasonable surface effectively shortening the freeze-drying cycle has obvious economic value in industrial production.
Freeze dryer freezes freeze-dried products:
When the solution is frozen (10 to 50 ° C per minute), the crystal grains remain visible under the microscope; on the contrary, at slow freezing (1 ° C / min), the formed crystals are visible to the naked eye. The coarse crystal leaves a large gap in sublimation, which can improve the efficiency of lyophilization. The gap left by the fine crystal after sublimation is small, so that the sublimation of the lower layer is hindered, the finished frozen particles are fine, the appearance is uniform, the specific surface area is large, and the porous surface is porous. The structure is good, the dissolution rate is fast, and the wettability of the finished product is relatively stronger.
There are two ways to pre-freeze the drug in the freeze dryer: one is to cool the product and the drying box at the same time; the other is to cool the shelf to be dried to about -40 °C, and then put the product into the product, the former is equivalent to slow freezing, The latter is between frozen and slow-frozen and is often used to balance freeze-drying efficiency with product quality. The disadvantage of this method is that when the product enters the box, the water vapor in the air will quickly condense on the shelf, and in the early stage of sublimation, if the plate heats up faster, the large-area sublimation may exceed the normal load of the condenser. This phenomenon is particularly noticeable in summer.
The freezing of the product is at rest. Experience has shown that the phenomenon of supercooling is easy to occur until the temperature of the product has reached the eutectic point. However, the solute still does not crystallize. In order to overcome the phenomenon of supercooling, the freezing temperature of the product should be lower than the range below the eutectic point, and it needs to be maintained for a period of time to allow the product to completely freeze.