1. The effect of high or low solution concentration on the first product on the surface of liquid Y during the drying process. When the concentration of the solution is too high: dry to form a densely structured surface layer. The surface layer has small pores and poor T gas. The water inside passes through the surface layer, so it rises along the bottle wall, causing the product to leave the wall and shrink. In addition, when the concentration is too high, Y liquid is easy to agglomerate during the freeze-drying process, and the resulting product The appearance is uneven. When the concentration is too low: the mechanical strength is low, and the product structure is relatively loose after packaging and transportation to become a powder, which affects the appearance of the product
2. The thickness of the product is too thick. Generally, it should be 10-15mm. The situation where the product is too thick is similar to that when the concentration is too high. It does not dry for a long time, and it collapses and agglomerates.
3. The temperature rises and falls quickly and it is easy to cause the product to leave the wall and slow. Pre-freezing speed: The product that cools by 10-15°C per minute is called quick freezing, and the one that cools by 1°C per minute during the freeze-drying process is called slow freezing. Generally, the first stage of sublimation and drying: the temperature of the product should be reduced to 5-6 ℃. Below the eutectic point, the temperature rise should be slow, preferably at 5°C per hour, and the 90% moisture should be removed from the end of the first-stage sublimation drying. Second-stage sublimation and drying: This stage is mainly to remove crystal water and solid adsorbed water. The heating rate can be accelerated, preferably 5-10℃/h, but the temperature of the product cannot exceed the temperature of the product, otherwise the activity of the product will decrease. Caking and poor solubility
4. Deflation speed. In front of cabinet C, the deflation speed should not be too fast, otherwise the vacuum in the box will suddenly change greatly, and a turbulent flow will be formed into the container, causing the products to become flocculent or powder, which affects the appearance.