Jiang-Lin Li,Da-Wen Sun,Hongbin Pu,Digvir S. Jayas
Surface-enhanced Raman scattering (SERS) imaging coupling with multivariate analysis in spectral region of 200 to 1800 cm −1 was developed to quantify and visualize thiophanate-methyl (TM) and its metabolite carbendazim residues in red bell pepper ( Capsicum annuum L.). Least squares support vector machines (LS-SVM) and support vector machines (SVM) models based on seven optimized characteristic peaks that showed SERS effects of TM and its metabolite carbendazim residues were employed to establish prediction models. SERS spectra with first derivative (1st) and second derivative (2nd) method were subsequently compared and the optimized model of 1st-LS-SVM acquired showed the best performance (RPD = 6.08, R 2 P = 0.986 and RMSEP = 0.473). The results demonstrated that SERS imaging with multivariate analysis had the potential for rapid determination and visualization of the trace TM and its metabolite carbendazim residues in complex food matrices.
The contamination of spices with aflatoxin (AF) raises concerns regarding its health risks. In this study, 51 samples of dried red chili peppers (including 10 varieties collected from three regions) were used to investigate the AF contamination of dried red chili peppers sold in China, and the toxigenic characteristics of Aspergillus flavus strains isolated from chili peppers. AFs were identified using immunoaffinity column purification, derivatization, and high-performance liquid chromatography with fluorescence detection. The AF content in various types of dried red chili peppers sold in the Chinese market was generally low (≤ 7.19 µg/kg), below the limit of the relevant standard (10 µg/kg). The frequency of suspected A. flavus strains isolated from chili peppers was high (24/51), with a high toxigenic strain ratio of 29.17%. Further investigation revealed that 25–30 ℃ was the optimal temperature for toxin production by these toxigenic strains. This indicated that dried chilled peppers have a significant risk of AF contamination. Therefore, the findings of this study suggest that long-term storage of dried chili peppers should be conducted at temperatures below 25 ℃ or above 37 ℃ to mitigate the problem of AF contamination exceeding the levels allowed by the standards, providing new insights for the prevention and control of AF contamination of dried red chili peppers.
危险品化学品经营许可证（带存储）