Strategy for enhancing Cistanche deserticola drying efficiency and quality based on novel freeze-infrared hybrid drying: moisture transition points control.

Background: Fresh Cistanche deserticola, a valuable medicinal and dietary ingredient with exceptional functional properties, exhibits a high moisture content and is susceptible to deterioration due to its high moisture content. Therefore, it is imperative to identify an appropriate dehydration method. This study primarily focuses on enhancing the efficiency and quality of dried C. deserticola, through a hybrid drying process that combines freeze-drying (FD) and infrared drying (IRD). The samples were first dehydrated by FD and then transferred to IRD until the end of drying, with different moisture transition points (based on FD durations of 5.5, 6.0, 6.5, and 7.0 h, and the corresponding groups are marked as FD5.5h-IR, FD6.0h-IR, FD6.5h-IR, and FD7.0h-IR).

Results: The FD6.5h-IR method proved to be 32.08% more energy efficient than the sole FD method. The microscopic examination revealed that the surfaces of samples treated using the FD6.5h-IR and FD7h-IR techniques were smoother and clearer with smaller and more uniform pores, similar to the microstructure of the solely FD sample. Furthermore, the FD6.5h-IR treatment has been demonstrated to be highly effective in maintaining the retention of active ingredients in products.

Conclusion: Given the disadvantage of FD7h-IR treatment in terms of energy consumption, FD6.5h was identified as the best moisture transition point. This investigation offers a theoretical basis for enhancing quality control and refining the process during the FD-IRD processing of newly harvested C. deserticola slices. © 2025 Society of Chemical Industry.