Colorimetric detection of edible oil oxidation using PAN–Congo red nanofiber mats

Lipid oxidation significantly compromises the safety, nutritional quality, and shelf life of edible oils, while conventional analytical methods are costly, time-consuming, and unsuitable for real-time monitoring. This study presents a novel nanofiber-based colorimetric sensor for rapid visual detection of lipid oxidation in soybean oil (SBO) and extra virgin olive oil (EVOO) under accelerated storage conditions (70 °C for 35 days). Polyacrylonitrile (PAN) nanofiber mats containing Congo red dye (CR, 0.0025%, 0.005%, and 0.01%, w/w) were fabricated via solution-blowing spinning and characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Oxidative deterioration was evaluated through conjugated diene (CD) and triene (CT) values, para-anisidine value (p-AnV), total polar compounds (TPC), volatile oxidation compounds, Rancimat induction period (IP), FTIR analysis, and cytotoxicity assays. Among the developed sensors, Mat_III (0.01% CR) exhibited the highest sensitivity, showing distinct color responses with ΔE values of 12.83 ± 0.20 in SBO and 9.83 ± 0.15 in EVOO, and rapid response times of 2.94 s and 4.71 s, respectively. After 35 days, CD, CT, and TPC increased to 3.83%, 0.96%, and 12.17% in SBO and 2.49%, 0.62%, and 7.83% in EVOO, while IP values decreased markedly, particularly in SBO, from 7.89 h to 2.04 h. Overall, these sensors offer a low-cost, rapid, and user-friendly approach for real-time oil oxidation monitoring.