Physicochemical properties and volatile compounds of whole lotus root powders prepared by different drying methods

This research aimed to evaluate the effects of freeze-drying (FD), hot air drying (HAD), hot air drying combined with baking (HADB) on the color, antioxidant activity, thermal and pasting properties, as well as volatile compounds of whole lotus root powders (WLRPs). The highest browning degree and antioxidant activity of WLRP was obtained by HAD at 80°C for 6 h. The gelatinization temperatures of the FD sample were higher than those of the HAD and HADB samples. WLRP prepared by HADB at 120°C for 5 min had the highest trough and final viscosities. Furthermore, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) analysis showed that 125 and 97 volatile compounds were detected from WLRPs in dried and hydrated states, respectively. The types of identified compounds were the most in dried HADB, followed by dried HAD and FD, which were also affected by the drying temperature and time. The hydration treatment led to an increase in the detected compounds from the FD sample and a decrease in those from the HAD and HADB samples. These observations indicated that the quality of WLRPs depended on the drying technique and conditions, which could be useful for selecting an appropriate drying method to prepare desirable WLRPs products.