Identification of the chili powder with illegal additive Sudan I by shifted-excitation Raman difference spectroscopy system.

This study developed a Shifted-Excitation Raman Difference Spectroscopy (SERDS) system integrated with a microscopic Raman system (μRaman) to reduce background interference in Raman spectroscopy. By using slightly shifted excitation laser wavelengths, two spectra are captured consecutively at the same sample position, allowing background noise to be subtracted and leaving only the Raman peaks. The reconstructed spectra showed a significant improvement in signal-to-noise ratio, effectively removing both broadband and ambient light interference. The system was applied to identify chili powder containing the illegal additive Sudan I, demonstrating enhanced performance in both Raman and surface-enhanced Raman spectroscopy (SERS).