Influence of far‐infrared vacuum drying on drying kinetics and quality characteristics of Cistanche slices

Abstract

AbstractIn order to improve the drying efficiency and quality of Cistanche, the effects of far‐infrared vacuum drying on drying rate, active component content and microstructure of Cistanche slices were studied with drying temperature, slice thickness and irradiation height as experimental indexes. The results showed that the drying process of Cistanche was mainly concentrated in the deceleration stage. When the drying temperature was 55°C, the slice thickness was 4 mm, the irradiation height was 150 mm, and the time to reach the safe water content (10% w.b.) of Cistanche was the shortest. With the increase in drying temperature, slice thickness and irradiation height, the contents of phenylethanoid glycosides, iridoids, polysaccharides, total phenols and total flavonoids in dried products increased first and then decreased. Compared with natural drying, the samples dried by far‐infrared vacuum have more pores and better structural integrity. Phenylethanol glycosides and iridoid compounds, such as echinacoside and verbascoside, in Cistanche have significant effects in anti‐inflammatory and analgesic, tonifying kidney yang, anti‐Alzheimer's disease and protecting various organs and systems of the body. In this study, the slices of Cistanche were processed by far infrared vacuum drying, and the effects of different drying conditions on drying rate, effective moisture diffusion coefficient, active ingredient content, antioxidant activity, color and microstructure of dried Cistanche were studied. The drying process was fitted by a drying model, in order to obtain dried Cistanche products with better quality, and provide theoretical basis and technical support for the actual production of Cistanche.Novelty impact statement Midilli model could better describe the variation law of water content in the drying process of Cistanche. Compared with natural drying, the surface samples dried by far‐infrared vacuum have no cracks and good boundary integrity. The optimal process parameters (55°C, 4 mm, 310 mm) for far‐infrared vacuum drying of Cistanche slices were determined by the entropy value method.