Optical Sensing Platform Based on Liquid Crystal Droplets for the Detection of Hydrogen Peroxide and Catalase in Food Safety

With the large-scale development of the food industry, hydrogen peroxide (H₂O₂), a potent oxidizing agent, has been illicitly used by some manufacturers for bleaching, decolorization, and preservation, making it a significant potential risk in the field of food safety. Therefore, elucidating the hazardous mechanisms of H₂O₂ residues in food is of paramount importance for strengthening food safety monitoring systems and safeguarding public health. In this study, a label-free and highly sensitive sensing platform based on 4-cyano-4'-pentylbiphenyl (5CB) liquid crystal (LC) microdroplets was developed for the detection of H₂O₂ and catalase (CAT). The sensor enables the detection of H₂O₂ and CAT by monitoring the distinct optical pattern transitions of dodecanal-doped 5CB liquid crystal microdroplets under various conditions using polarized optical microscopy (POM). The results demonstrate that under pH 11 conditions, the limit of detection (LOD) for H₂O₂ is 0.01% (w/v), and for CAT is 0.01 ng/mL. Fourier Transform Infrared Spectroscopy (FTIR) was employed to characterize the post-reaction system, verifying the chemical transformations. Furthermore, simulated testing on food samples was successfully conducted, suggesting that this sensor holds significant potential for applications in food safety, biomedicine, and analytical detection. However, the optical sensing platform is sensitive to changes in ambient humidity and temperature, which may limit its direct application in complex food matrices. Although the system enables intuitive interpretation of POM textures, future work should investigate matrix interference, quantitative image analysis, portable readout integration, and validation using authentic food samples.