Analysis of the Effect of Drying Methods on Volatile Components of Toona sinensis Based on GC-IMS and GC-MS Combined with Chemometrics

To investigate the effect of drying methods on the volatile flavor substances of Toona sinensis, the volatile components of vacuum freeze-dried, heat pump-dried, hot air-dried, and microwave vacuum-dried Toona sinensis samples were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS) coupled with relative odor activity values, and the differences of volatile components among samples were further explored by combining the stoichiometric principal component analysis and partial least square discriminant analysis. The results showed that 78 peaks were detected and 59 compounds were identified by GC-IMS. 94 kinds of volatile compounds were identified by GC-MS, and the main volatile components were sulfides, olefins and aldehydes. The content of total volatile compounds was significantly reduced after drying. The key aroma compounds in Toona sinensis samples were identified by ROAV method, such as (E,Z)-di-1-propenyldisulfide, 2-mercapto-3,4-dimethyl-2,3-dihydrothiophene, hexanal, 2-hexenal and eugenol. The PCA and PLS-DA results showed that the samples with different drying methods were not only clearly separated from the raw samples, but also significantly different from each other. The raw samples and vacuum freeze-dried samples were grouped, and the other three dried Toona sinensis samples were grouped. According to the variable importance in projection score, a total of 10 (VIP>1) labeled volatile compounds were selected. The drying method had significant effect on the flavor characteristics of Toona sinensis, and the vacuum freeze-dried group was the closest to the raw sample, while heat pump-drying was the most suitable dehydration method for Toona sinensis, considering the practical application. This study provides some theoretical references for flavor quality control in the thermal processing process.