Identification of volatile and non-volatile components of two lemons based on sensory characteristics, electronic sensing evaluation and untargeted metabolomics

China's Citrus × limon Eureka (EU) and Citrus × limon Rosso (RO) have similar powder colors; however, EU is pricier, leading to instances of forgery. This study aimed to differentiate the two lemons by combining sensory characteristics, electronic sensing evaluation and untargeted metabolomics. Results showed that the electronic nose (E-nose) and electronic tongue (E-tongue) effectively distinguished the two varieties. EU's TPC (7.13 ± 0.16 mg GAE/g DW) and TFC (1.87 ± 0.03 mg RE/g DW) are twice RO's. EU demonstrates excellent antioxidant activity. UPLC-QTOF/MS untargeted metabolomics identified 251 non-volatile compounds, among which 73 differential metabolites mainly included flavonoids and terpenoids. Further KEGG analysis revealed that it was mainly related to the phenylpropanoid biosynthesis pathway. Correlation analysis revealed taxifolin's potential role in EU antioxidant properties. HS-GC-Orbitrap/MS analysis revealed nine significant volatile differences between two lemons, with 1-hexanol, hexanal, α-Terpineol, and perillaldehyde being the main substances for EU to exert antioxidant effects. Combined with sensory analysis, it can be concluded that camphor and isovaleraldehyde might potentially contribute to the bitterness and sourness of RO. Collectively, these findings suggested that EU had a higher nutritional value, and that electronic sensing evaluation could be effective tools to distinguish both species.