Rapid Geographical Discrimination of Wenzhou Ougan via GC-IMS: A Comparison of Peel and Juice Volatile Fingerprints

As a National Geographical Indication (GI) product, Wenzhou Ougan (WZ) is difficult to distinguish visually from mandarins of other origins. In this study, 34 peel samples and 47 juice samples from WZ and three external origins were analyzed by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS), and their VOC fingerprints were compared. A total of 59 and 68 VOC signal variables were extracted from peel and juice samples, respectively; compound assignments were tentative annotations based on retention index and drift time matching with the GC-IMS library. Gallery plots and two-dimensional spectra revealed distinct differences in several VOC signal regions among origins. Principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and variable importance in projection (VIP) values were used to evaluate grouping trends and screen discriminant VOC signal variables. For WZ-origin samples, the main WZ-high discriminant VOC signal variables in peel included furfuryl alcohol, 3-octanone, pentanal, n-nonanal, ethyl 2-methylbutyrate, butyl hexanoate, alpha-pinene, and 3-methylbutyric acid, while those in juice mainly included beta-ocimene, limonene, furfuryl alcohol, 2-acetylfuran, 2-methylfuran, butyric acid, and pentanoic acid. These findings indicate that integrated VOC fingerprints show potential for rapid geographical discrimination of Wenzhou Ougan, while further independent validation and complementary chemical confirmation are required.