Effects of Different Drying Methods on the Quality of Amomum villosum Lour. Based on GC-MS and Chemometric Techniques

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