S. Typhi was a common foodborne pathogen that often enters the human body through food and caused illness. In order to achieve the rapid detection of S. Typhi, surface enhanced Raman spectroscopy (SERS) had been studied by more and more people. To prepare an efficient, stable, and simple signal enhancer, the signal enhancement effects of Au NPs, Ag NPs, and Au @ Ag NPs on S. Typhi were compared. Because of the good enhancement effect and stability, Au @ Ag NPs was used as the research object. The influence of SERS substrates with the same gold core size and different silver shell thickness on bacterial signal enhancement was investigated. Au @ Ag NPs with different thickness silver layers were prepared by changing the concentration of silver nitrate, and colloids were characterized by UV spectroscopy. After de-noising, smoothing and de-baselining of SERS spectra, the characteristic peak intensity information was used to analyze the detection limit and detection stability of S. Typhi. The experimental results showed that when the silver layer thickness was prepared by 4 mM silver nitrate, Au @ Ag NPs had the best amplification effect on S. Typhi Raman signal, which could achieve a detection limit of 104 CFU/mL, and the coefficient of variation of SERS characteristic peak was less than 7%. In addition, the quantitative prediction model of S. Typhi with 105 CFU/mL - 108 CFU/mL was established by MLR, which achieved a correlation coefficient (Rc) of 0.99 and a root mean square error (RMSEC) of 100.0364 CFU/mL.
Problems with “clenbuterol”, a synthetic β2-adrenergic stimulant that includes clenbuterol, ractopamine, and albuterol, have been increasing in recent years. This article focuses on the detection of albuterol, chemically called 3,6-dihydroxy1-methyl-5-oxo-3,5-dihydro-2H-indolium betaine. It is difficult to directly measure the content of clenbuterol in pork due to its messy and uneven composition, which requires a destructive pre-treatment process that takes time and effort. In this study, a method for subsurface food inspection was presented based on a newly developed line-scan spatially scattering Raman spectroscopy technique. A spatially offset Raman spectroscopy system based on line-scan Raman chemical imaging system was built, which was used to collect spatially offset Raman spectra from the samples. Under the condition of one CCD exposure, the spatially offset Raman spectroscopy system can collect a series of Raman spectra simultaneously in a narrow space interval and a wide offset range. Through data analysis, the rare clenbuterol species in the sample can be determined by the position of characteristic peaks. The system was used to collect salbutamol Raman signal, and the results showed that the characteristic peaks of salbutamol were consistent with the standard characteristic peaks, so it was possible to use the system to detect lean meat in meat.
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