Freeze drying and purification of traditional Chinese medicine liquids are two completely different but often used in combination in the modern processing of traditional Chinese medicine. Simply put, "purification" is for "removing impurities and extracting essence", while "freeze-drying" is for "preservation and shaping". The core differences between the two are as follows:
1. Different core purposes
Purification (separation and refinement): The purpose is to remove impurities and increase the concentration of active ingredients. Traditional Chinese medicine extract is usually a mixture containing active ingredients and a large amount of impurities such as starch, protein, tannins, colloids, heavy metals, etc. The process of purification is to use physical or chemical means to remove unwanted impurities, making the medicinal substance purer.
Freeze drying (vacuum freeze-drying): The purpose is to preserve activity to the greatest extent possible and facilitate long-term storage. It directly sublimates the water in traditional Chinese medicine solution into water vapor in a low-temperature vacuum environment. Its core advantage lies in avoiding the damage of heat sensitive components (such as volatile oils, polysaccharides, flavonoids) caused by high temperatures, and being able to inhibit microbial growth, allowing the product to be stored at room temperature for a long time.
2. Different processing objects and process principles
Purification process: mainly utilizing differences in substance solubility or molecular size for separation. Common techniques include precipitation methods (such as alcohol precipitation, water precipitation), flocculation techniques, macroporous adsorption resin adsorption, membrane separation techniques, etc. For example, through membrane separation technology, impurities can be effectively removed and active ingredients can be concentrated at room temperature and low pressure.
Freeze drying process: mainly utilizing the phase change principle of water. The process is divided into three stages: pre freezing (freezing the liquid medicine below -40 ℃), sublimation drying (directly sublimating ice into water vapor under vacuum), and desorption drying (removing some bound water). The entire process is carried out at low temperature and low pressure, without changing the original spatial structure of the material.
3. The final product has different forms and characteristics
Purified product: usually a high-purity extract (such as a paste, dry powder, or clear liquid). After purification, the efficacy of the product is more concentrated, but if it is in liquid or paste form, it still faces the problems of easy deterioration and difficult long-term storage.
Freeze dried product: usually a loose and porous solid powder or block. The freeze-dried product has excellent rehydration properties (it can quickly reduce to liquid after adding water), and due to the removal of over 95% of moisture, it can be stored at room temperature for 2-3 years without the need for preservatives.
Summary: The relationship between the two
In the actual production of high-end traditional Chinese medicine, these two are often in a sequential relationship. Usually, the traditional Chinese medicine extract is first purified to remove large molecular impurities and ineffective components, resulting in a high-purity medicinal solution; Then, the purified drug solution is subjected to freeze-drying treatment to produce high-quality freeze-dried powder or freeze-dried powder injections. This not only ensures the purity of the drug efficacy, but also achieves the stability and long-term preservation of the product

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