Postharvest processing plays an important role in improving the quality and storage stability of mature fresh Amomum villosum Lour. (A. villosum). We investigated the effects of seven common drying methods (electric baking drying (EBD), heat pump drying, sun drying after heat pump drying, shade drying, hot air drying, sun drying, and freeze drying) on the volatile components of Amomum villosum. To discriminate different samples and identify key markers, chemometric techniques, including principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA), were applied to Chromatography–Mass Spectrometer (GC-MS) data of 70 identified metabolites. As an unsupervised method, PCA was first utilized to observe the overall clustering tendency of 21 samples, showing clear dispersion among seven groups with a slight overlap in the samples from sun drying after heat pump drying and hot air drying. To improve discrimination accuracy, the OPLS-DA model was further established as a supervised method. Its reliability was verified by permutation tests and cross-validation, which confirmed the absence of overfitting (R2 and Q2 intercepts with the vertical axis were <1 and <0, respectively). S-plots combined with variable importance in projection (VIP) values greater than 1 were used to screen differential metabolites, and camphor, borneol, and bornyl acetate were identified as the key discriminant markers for the samples obtained by different drying methods. Consequently, camphor, borneol and bornyl acetate, which are regarded as quality markers of A. villosum, were determined by gas chromatography (GC) to identify the optimal drying method for fresh A. villosum. The results showed that the content of the quality markers in A. villosum obtained by the seven drying methods outclass the standards of the Chinese Pharmacopoeia.Comprehensively considering the experimental results and the convenience and operability of the drying process, EBD is the most suitable drying process of A. villosum for popularization and application. It is on account of the shortest drying time among the seven drying methods, which only took 21.63 h to complete the drying of fresh A. villosum. Besides that, the quality control parameters in the content of bornyl acetate, camphor, borneol and the essential oil of A. villosum obtained by EBD were far more than the standards stipulated in the pharmacopeia.
Deng et al. (Fri,) studied this question.