Comparative analyses of five drying techniques on drying attributes, physicochemical aspects, and flavor components of Amomum villosum fruits

Amomum villosum fruit is an attractive spice owing to its pleasant aromatic properties, and drying is an efficacious way to maintain its therapeutic and trading values. In this study, Amomum villosum fruits were dried using five drying technologies namely, freeze drying (FD), hot air impingement drying (HAID), hot air drying with temperature and humidity process control (HADTHPC), HADTHPC combined with radio frequency-vacuum drying (HADTHPC + RFVD), as well as medium-and short-wave infrared drying (MSWID). Quality and drying characteristics were compared. Result showed that FD achieved the best color retention, the lowest shell burst ratio, and the best retention of flavor profiles due to the complete glandular trichomes structure; however, it recorded the longest drying time and the highest energy consumption. HADTHPC + RFVD, combining the advantages of HADTHPC and RFVD, had the shortest drying time, the highest conservation of total flavonoids content (TFC), the best antioxidant activity, and low energy consumption compared with the other thermal drying methods. After drying, the content of esters decreased, while alcohols content increased. GC-IMS indicated the fingerprints of the four thermal dehydrated samples exhibiting similar signal intensities. Therefore, in terms of maintaining quality and saving energy, HADTHPC + RFVD would be a promising drying technology for Amomum villosum fruits.