Conducting porphyrin-based multivariate impedance platform for hexanal detection in lipid-rich foods

Hexanal is a well-established early marker of lipid oxidation and can be used as an indicator to assess food freshness and quality. However, re-useable sensors that can be integrated into portable detectors for rapid and selective detection of hexanal in complex food matrices are still lacking. This study presents the design and development of an impedance-based multivariable sensing approach for detecting hexanal in various lipid-rich food samples. An impedimetric sensor was fabricated by electropolymerizing tetrakis(4-aminophenyl) porphyrin polymer (p-TAPP) on an interdigitated gold electrode (IDE), and its impedance spectrum, spanning a frequency range of 100 Hz to 8 MHz, was utilized for sensing studies. The developed sensor exhibits high sensitivity and selectivity towards hexanal, with rapid response (9 s) and recovery (21 s), over a practical concentration range of 1-100 ppm. Furthermore, the sensor was successfully tested on fat-rich food samples (solid, semi-solid, liquid and processed emulsified) at different hexanal concentrations, demonstrating its effectiveness in assessing lipid degradation. Principal component analysis (PCA) showed clear discrimination between safe and spoiled samples across different food matrices, with more than 97% variance, confirming the robustness of the sensor. The p-TAPP sensor, in conjunction with multivariate data analytics, offers a rapid, selective, sensitive, and matrix-independent analytical tool to monitor hexanal in diverse food systems and assess its quality in terms of oxidative degradation.