Biologically calibrated and quantitative spiciness measurement based on a TRPV1-Responsive biosensing platform

The Scoville Heat Unit (SHU) scale has long been regarded as the standard for measuring pungency. However, its reliance on subjective human sensory panels inherently limits its accuracy and reproducibility. To overcome this limitation, we developed a biologically grounded spiciness assessment platform based on the activation of the transient receptor potential vanilloid 1 (TRPV1) channel, a key pain receptor triggered by capsaicinoids and mediates the burning sensation associated with pungency. To establish a physiologically relevant spiciness index, we investigated the quantitative correlation between TRPV1-mediated calcium influx in primary sensory neurons and nocifensive behavior in mice, following exposure to both pure capsaicin and chili pepper extracts. By analyzing patterns in the conversion factor, we defined five biologically relevant spiciness ranges: undetectable, minimal response, transitional range, pungent, and oversaturation. To implement this index, we engineered a label-free, live cell-free biosensor by incorporating nanovesicles (NVs) containing functional TRPV1 receptors into an electrode. This sensor detected capsaicin-induced ionic flux through TRPV1 channels, producing voltage shifts with femtomolar sensitivity and high molecular specificity. Notably, the biosensor showed a strong correlation with cellular and behavioral assays and enabled the quantitative classification of chili extracts into five spiciness categories. Integration with a portable electronic reader enabled real-time, on-site classification of spiciness, offering an objective alternative to the subjective SHU scale. This study establishes a reproducible and physiologically relevant framework for quantifying spiciness based on receptor-level molecular recognition, offering alternative to traditional sensory and analytical methods with broad applications in food science, quality control, and consumer product development.