Application of Yingtai Vacuum Freeze-Drying Technology in the Freeze-Drying of Codonopsis Radix
Codonopsis Radix is the dried root of Codonopsis pilosula, Codonopsis pilosula var. modesta, or Codonopsis tangshen from the Campanulaceae family. It is a commonly used tonic in traditional Chinese medicine (TCM) prescriptions, known for its effects in replenishing qi, quenching thirst, strengthening the spleen and lungs, and promoting fluid production. The post-harvest processing and drying of medicinal herbs are fundamental to the preparation of TCM decoction pieces. Except for a few cases where fresh herbs are used, most require preliminary processing and drying at the production site to remove impurities and moisture, ensuring medicinal efficacy and facilitating further processing.
01. Traditional Drying Methods for Codonopsis Radix
Post-harvest processing significantly impacts the quality of medicinal herbs, with drying being a critical step. Wild Codonopsis Radix typically requires minimal processing—simply removing soil and sun-drying. However, Codonopsis pilosula var. modesta and Codonopsis tangshen must be washed and briefly scalded in boiling water before drying. In rainy conditions, charcoal baking may be used, with the temperature controlled at around 60°C and frequent turning. The roots are baked until pliable, then kneaded and rebaked repeatedly until fully dried.
Different drying methods affect the quality of Codonopsis Radix differently. While drying techniques (shade-drying, sun-drying, and oven-drying) show no significant impact on major chemical components (alcohol-soluble extracts, Codonopsis polysaccharides, Codonopsis saponins, and lobetyolin), excessive drying temperatures (80–85°C) can notably alter the content of polysaccharides and saponins. During drying, Codonopsis polysaccharides may enzymatically convert into monosaccharides, influencing the "sweetness" of the dried product. Studies indicate that within the 45–65°C range, different chemical components are optimally preserved at varying temperatures. Low-temperature pretreatment helps maintain chemical stability even at higher drying temperatures.
02. Modern Drying Methods for Codonopsis Radix
Modern drying technologies for Codonopsis Radix include microwave drying, hot-air drying, gas jet impingement drying, combined gas jet-microwave drying, infrared drying, and heat pump drying. Research shows that microwave drying is fast, preserves volatile and aromatic compounds, and ensures uniform heating. Hot-air drying, however, leads to reduced extractable content and darker coloration as temperature increases. Gas jet impingement drying requires precise parameter control, as air temperature and moisture transition points significantly affect drying time, energy consumption, and product quality.
Advantages of Modern Drying Methods
Compared to traditional methods, modern drying techniques allow controlled temperature, humidity, and drying area, significantly shortening processing time. Automated equipment also facilitates standardized, large-scale production.
Comparison of the Two Methods
Traditional drying, with its gentle conditions, better preserves active ingredients, whereas modern methods are still optimizing parameters to avoid compromising quality. Additionally, modern quality assessments must integrate chemical analysis with traditional sensory evaluations (e.g., taste and aroma) for comprehensive quality control.
03. Freeze-Drying of Codonopsis Radix and Its Advantages
Traditional processing often leads to significant loss of active compounds, reducing market value and efficacy. Freeze-drying, which removes moisture under low-temperature vacuum conditions, effectively preserves the nutritional and medicinal properties of Codonopsis Radix.
The content of bioactive components, such as lobetyolin and polysaccharides, determines the herb’s quality. Factors like drying temperature and slice thickness influence these components. Compared to shade-drying, sun-drying, and oven-drying, freeze-drying better retains active ingredients. With growing demand for high-quality TCM products, vacuum freeze-drying technology addresses nutrient loss while enhancing product value. Freeze-dryers are also applicable to other herbs like Cordyceps, Panax notoginseng powder, and Dendrobium officinale.
Freeze-Drying Steps for Codonopsis Radix
1. Harvesting: Typically done in autumn when roots harden and turn yellowish. Care is taken to avoid root damage.
2. Cleaning: Gentle washing to remove soil and impurities without damaging the skin.
3. Pre-freezing: Low-temperature pretreatment acclimatizes the roots for subsequent freeze-drying.
4. Freezing: Rapid freezing below -20°C ensures uniform ice crystal formation, preserving cellular structure.
5. Vacuum Sublimation Drying: Ice sublimates directly into vapor under controlled vacuum, removing moisture.
6. Secondary Drying: Further moisture removal ensures ultra-low water content, extending shelf life.
7. Cutting/Grinding: Freeze-dried roots are lightweight and easily processed into desired forms.
8. Packaging & Storage: Moisture-proof, light-resistant materials protect quality during storage and transport.
Advantages of Freeze-Drying
1. Preservation of Bioactivity: Low-temperature freezing protects cellular structures, preventing degradation of active compounds. The vacuum environment minimizes oxidation, ensuring stable efficacy.
2. Extended Shelf Life: Ultra-low moisture content significantly prolongs preservation.
3. Efficiency & Quality Control: Batch processing improves productivity, while precise parameter control ensures consistency.
Freeze-drying maximizes the retention of medicinal properties, enhances storability, and boosts market competitiveness. As technology advances, freeze-drying will play an increasingly vital role in modernizing TCM processing, driving innovation in the industry.
