Rapid identification of gutter oil by detecting the capsaicin using surface enhanced Raman spectroscopy

Accurate determination of the gutter oil represents a major food safety challenge. Here, we propose to use the surface enhanced Raman spectroscopy (SERS) with silver nanorod array substrates to detect the capsaicin, a marker of the gutter oil that is difficult to remove. The capsaicin has several characteristic SERS peaks at v=807cm(-1), v=1, 264cm(-1), and so forth, which correspond to the C-39-C-37-C-43 stretching vibrational mode at the alkyl chain, the ring stretching vibrational mode, and so forth, confirmed by our density functional theory calculation. This SERS-based method enabled the rapid and highly sensitive detection of the gutter oil with minimum pretreatment. The concentration dependent SERS investigation shows that the SERS intensity of these characteristic peaks has a linear relationship with the capsaicin concentration when 1mg/L<C<60mg/L. By combining a liquid phase extraction method and the SERS detection strategy, the capsaicin concentration as low as 30mg/L can be detected from inoculated corn oil samples.