A liquid crystal-based sensor for real-time, selective, and visual detection of vanillin over coumarin in food samples

Abstract

This study reports the fabrication of a liquid crystal (LC)-based sensor for detecting and quantifying vanillin, a widely used food flavoring agent, and distinguishing it from the toxic adulterant coumarin. The sensing mechanism relies on host–guest interactions between β-cyclodextrin (β-CD) and sodium dodecyl sulfate (SDS), influencing LC alignment. Vanillin displaces SDS from the β-CD cavity, restoring homeotropic alignment observable under cross-polarizers and quantifiable via image analysis. The sensor detects vanillin at 60.0 ppm in water and 62.0 ppm in a food sample, both below the World Health Organization (WHO) and Food and Agriculture Organization (FAO) daily intake limit of 70 ppm.