The Flavor Characterization of ‘Huyou’ ( Citrus changshanensis ) Essential Oils Extracted by Conventional and Novel Methods

The aroma of citrus is among the most appealing natural flavors. ‘Huyou’ (HY) is a hybrid citrus with a unique flavor compared to grapefruit (GF), but few studies have analyzed its characteristic flavor comprehensively. In this study, we extract six essential oils (EOs) from HY and GF peels by cold pressing (CP) and microwave-assisted hydrodistillation (MADH) and spinning cone column (SCC). Further, the flavor of six EOs was investigated by using flavoromics analysis, including e-nose, GC-MS and GC-O combined with chemometric approaches. The results showed that CP EOs exhibited a stronger citrus characteristic flavor, while MADH and SCC EOs contained more diverse volatiles. A total of 23 key odorants were identified in the GC-O-MS analysis, 12 of which were specific to HY. The flavor wheel and partial least squares regression (PLSR) revealed that floral, sweet and fruity odors were positively correlated with linalool, α-terpineol and geraniol, while fatty, green and woody odors with germacrene D, germacrene B and nootkatone. Additionally, based on orthogonal partial least squares discriminant analysis (OPLS-DA), six aroma-active compounds were screened as aroma markers to distinguish HY from GF; i.e., γ-terpinene, D-limonene, germacrene D, nootkatone, germacrene B and terpinolene. The extraction methods and citrus varieties both impact the flavor characterization of citrus EOs, and our study provides guidance on the extraction and application for citrus EOs.