Effect of different drying techniques on drying characteristics, physical quality, and active components of Citri reticulatae pericarpium, and the correlation between physiochemical quality

Drying characteristics and various quality attributes were investigated to assess the adaptability of four different drying techniques (hot air impingement drying (HAID), medium- and short-wave infrared drying (MSWID), hot air drying with temperature and humidity process control (HAD-THPC), and freeze drying (FD)) for Citri reticulatae pericarpium (CRP). HAID and MSWID had higher drying rate, total flavonoid content (TFC), total volatile oil content (TVOC), aldehydes, and alkenes than those of the other drying methods, among which HAID consumed the lowest energy. FD had the highest thickness, frangibility, and larger cavities of CRP due to the optimal structure retention as compared to the thermal drying methods. According to the fingerprints and principal component analysis (PCA), the volatile organic compounds (VOCs) differed between dried and fresh samples, as well as FD and thermal dried ones. Furthermore, the oil cell number can be used to forecast and determine the TVOC and various volatile components. The findings indicate HAID would be a promising drying method for CRP with better quality, shorter drying time, and lower energy consumption.