Taste-like perception of citrus essential oils: Roles of taste receptors and retronasal aroma-taste integration

Citrus essential oils (EOs) can evoke taste-like perceptions, but whether these arise from direct taste receptor activation or aroma-driven flavor perception remains unclear. This study evaluated grapefruit and orange EOs using human taste receptor assays, volatile profiling, and nose-clip check-all-that-apply (CATA) sensory analysis. Neither EO activated umami, sweet, salty, or sour taste pathways, including TAS1R1/TAS1R3, TAS1R2/TAS1R3, ENaC, and OTOP1. Grapefruit EO activated multiple bitter taste receptors, whereas orange EO activated only TAS2R8. GC–MS analysis showed limonene-dominant volatile profiles in both EOs and grapefruit-specific constituents, including nootkatone, carvone-related compounds, and β-caryophyllene. Sourness selection increased significantly without a nose clip, despite the absence of detectable OTOP1 activation. These findings suggest that citrus EO-induced taste-like perception is attribute-dependent, with grapefruit bitterness associated with TAS2R activation and citrus sourness shaped mainly by retronasal aroma. This integrated approach provides a framework for distinguishing receptor-mediated taste activity from aroma-driven flavor perception in citrus flavor systems.