Dendrobium, a traditional and precious Chinese medicinal herb, has its dried product processing techniques directly impacting its yield and quality. In the transformation of fresh dendrobium into dried product (Fengdou), the blanching temperature and kneading intensity are two core process parameters. These two parameters influence the physical state and chemical stability of the stems, jointly determining the final product's shape. This process requires a balance between traditional experience and modern technology to achieve standardized production.
Blanching is the first step in dendrobium processing. Its essence is to destroy the enzyme activity within the stems through high-temperature treatment, preventing the decomposition of active components such as polysaccharides and alkaloids, while simultaneously softening the tissue for subsequent shaping. Traditional processes often use charcoal or electric furnaces for baking, typically controlling the temperature range to a high degree.
High-temperature blanching can quickly deactivate enzyme activity, but if the temperature is too high, a hard shell easily forms on the stem surface, making it difficult for internal moisture to dissipate evenly, leading to breakage or loosening of the spiral structure during subsequent kneading. Conversely, insufficient temperature fails to thoroughly soften the stems, increasing resistance during kneading, making it difficult to peel off the leaf sheaths, and significantly reducing the yield. Therefore, the blanching temperature needs to strike a balance between enzyme inactivation and tissue softening, avoiding excessive scorching while ensuring moderate stem flexibility.
The kneading intensity is a crucial operation in shaping the Dendrobium officinale, its function being to mechanically form a spiral or spring-like structure in the stems. This process requires dynamic adjustment of the intensity based on the degree of stem softening: fully softened stems can be kneaded more intensely to promote leaf sheath shedding and the formation of a tight spiral structure; if the stems are not fully softened, forcibly increasing the intensity will lead to stem breakage or surface damage, thus reducing the shaping rate. Furthermore, the kneading direction and frequency must match the fiber orientation of the stems; kneading against the fibers easily causes breakage, while kneading with the fibers improves shaping efficiency. In traditional craftsmanship, artisans often judge the flexibility of the stems by feel; this experience-dependent operation method is a significant factor contributing to fluctuations in the yield of Dendrobium officinale.
The synergistic effect of blanching temperature and kneading intensity is directly reflected in the appearance and internal quality of the Dendrobium officinale. A suitable blanching temperature allows the stems to soften evenly, providing an ideal physical state for kneading. At this temperature, the stems possess sufficient extensibility without being easily damaged by excessive kneading. For example, when the blanching temperature reduces the moisture content of the stems to a specific range, the kneading intensity can be more precisely controlled to ensure the tightness of the spiral structure, preventing shaping failure due to stems that are too hard or too soft. Conversely, if the blanching temperature and kneading intensity are mismatched—for example, if the kneading intensity is not adjusted promptly after high-temperature blanching, or if the kneading intensity is forcibly increased after low-temperature blanching—it will lead to a rough surface, loose spirals, or an increased breakage rate in the dried peony.
Modern processing technology significantly improves the shaping rate of dried peony by precisely controlling process parameters. For example, using a segmented blanching process, first rapidly deactivating enzyme activity at a higher temperature, and then continuously softening the stems at a lower temperature, can avoid problems such as surface hardening and uneven internal moisture. Simultaneously, combining this with mechanized kneading equipment, by adjusting pressure and speed, standardizes the kneading intensity, reducing quality differences caused by human factors. These technological improvements not only increased production efficiency but also resulted in a more uniform spiral structure and smoother surface in dendrobium, meeting market demands for high-quality dendrobium products.
From the perspective of compositional changes, the blanching temperature and kneading intensity also affect the retention rate of active ingredients such as polysaccharides and alkaloids in dendrobium. High-temperature blanching may damage some heat-sensitive components, but losses can be minimized by optimizing the temperature profile. While the mechanical action during kneading does not directly decompose the components, excessive kneading can lead to cell wall rupture and accelerate component oxidation. Therefore, process optimization must balance the forming rate and component retention. For example, adding a low-temperature drying step after kneading can both fix the spiral structure and reduce component loss.
In the processing of dried dendrobium, precise control of blanching temperature and kneading intensity is key to improving the forming rate of dendrobium. Traditional processes rely on experience, while modern technology, through parameter standardization and equipment upgrades, has achieved process stability and reproducibility. In the future, with in-depth research into the composition and processing mechanism of dendrobium, process optimization will focus more on balancing component retention and molding efficiency, driving the dendrobium industry towards high-quality development.
