Flavour changes of raspberries (Rubus idaeus L.) under different drying approaches by using HS-GC-IMS

Abstract The purpose of this study was to compare the flavour components of raspberries subjected to different drying methods in order to evaluate their impact on the fruit. By utilising headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), volatile organic compounds (VOCs) in raspberries were detected under fresh, 60 °C drying, 80 °C drying, and freeze drying conditions. The results of the HS-GC-IMS showed that in all raspberry samples, a total of 73 peak signals and 64 VOCs were identified, including 27 aldehydes, 9 ketones, 12 esters, 4 alcohols, 5 alkenes, and 5 other VOCs. In addition, the results of PCA analysis, Euclidean distance analysis, and hierarchical clustering heat map analysis showed that raspberry samples from different conditions can be effectively distinguished based on their VOCs, indicating their consistency and variability. Different drying methods have a significant impact on the flavour profile of raspberries. From the analyses, it can be seen that there was an increase in aldehydes and ketones in freeze-dried raspberry and a decrease in esters in oven-dried raspberries compared to fresh raspberry. This work provides valuable information on understanding the volatile flavour compounds in raspberries and offers some references for future raspberry processing.