Identification of characteristic volatiles in three different varieties of Citri Reticulatae Pericarpium during aging processes using HS-SPME-GC-MS and GC-IMS

Abstract

Citri Reticulatae Pericarpium (CRP), commonly referred to as Chenpi in China, has been extensively studied for its physicochemical properties. However, the characteristic volatile changes in different CRP varieties during the aging process remain unclear. In this study, three varietal CRP (G-CRP, C-CRP, and Z-CRP) aged from 1 to 10 years were collected, and their characteristic volatiles and aroma profiles were analyzed using electronic nose (E-nose), gas chromatography-ion mobility spectrometry (GC-IMS), combined with headspace-solid phase microextraction-GC-mass spectrometry (HS-SPME-GC-MS). The results revealed significant differences in the characteristic flavor profiles both among the three varieties and across different aging periods. A total of 33 and 37 volatiles were identified by GC-IMS and HS-SPME-GC-MS, respectively, with 11 substances co-identified. Twenty-four key common aroma compounds were screened based on a relative odor activity value (ROAV) threshold ≥1. ᴅ-Limonene, myrcene, linalool, 2,3-butanedione, and methyl-2(methylamino)benzoate were identified as key aroma contributors common to all three CRP varieties, with the greatest contribution from linalool oxide to G-CRP, vanillin to C-CRP, and α-pinene to Z-CRP. During aging, the aroma of G-CRP tended to develop spicy notes, C-CRP exhibited herbal characteristics, and Z-CRP displayed woody traits. Using the combined volatile organic compound (VOC) dataset, a two-step machine-learning framework preliminarily predicted the variety with 95.56% accuracy. Then, utilizing a subset of six VOC markers, it predicted the aging year for each variety, achieving accuracies of 93.33% for C-CRP and 80.00% for both G-CRP and Z-CRP. This study comprehensively characterizes the volatile compounds of three major CRP varieties in China and their dynamic changes during the aging process, providing valuable insights for further research on other CRP varieties and supporting high-value industrial applications.