Determination Of Industrial Pigment In Food With Surface-enhanced Raman Spectroscopy(SERS)

With the rapid development of Chinese food industry and wide application of pigment in food products, food safety issues are also becoming increasingly prevalent, in which case that illegally adding pigment in food is not uncommon. China has set a strict limit to the species, dosage and application ranges of edible pigment. It is strictly prohibited to add industrial pigment as food additives due to its carcinogenicity. Therefore, how to quickly and effectively detect pigment in food becomes a research focus. Surface-enhanced Raman spectroscopy(SERS) with advantages of simple operation, rapid analysis, etc. has been gradually applied in the study of food safety. Based on this, in order to provide a feasible way to detect food pigment quickly and efficiently, SERS is used as a detection method to qualitative and quantitative study of auramine II, basic orange II, metanil yellow, dimethyl yellow, diethyl yellow in food. The study is divided into four chapters. The specific content of each chapter is as follows:In chapter 1:On the basis of food safety issues and edible pigment, the conventional detection methods and their applications of pigment in food were summarized and SERS was introduced. In the end, the significance, innovation points and prospects of this research were also summarized.In chapter 2: SERS and Normal Raman spectroscopy techniques were adopted to respectively detect auramine II, basic orange II and metanil yellow in bean products and liquid chromatography-tandem mass spectrometry(LC-MS) was also used to verify the accuracy. In this study, with methanol–water(7+3)as the extraction liquid, samples were accelerated by solvent extraction(ASE) and the extract was purified by gel permeation chromatography(GPC). Compared with Normal Raman Spectroscopy, it turned out that SERS technique was more precise and sensitive. By the analysis of the SERS spectras, the quantitative characteristic peaks of auramine II, basic orange II and metanil yellow were respectively 652cm-1, 995cm-1 and 983cm-1. By taking quantitative characteristic peak intensity and dye concentration of auramine II, basic orange II and metanil yellow pigments from different matrices(dried bean milk cream, skin of bean curd, soybean milk powder) as ordinate and abscissa respectively, the standard curve was drawn. The results showed a good linear relationship. Average recoveries of auramine II, basic orange II and metanil yellow pigments in the three samples were 83.48~92.59% with a relative standard deviation(RSD) of 4.3~7.2%.In chapter 3: In this, acetonitrile was used as the extraction liquid; ASE is adopted for sample extraction; dimethyl yellow and diethyl yellow in Dougan were quickly detected by SERS Liquid, and Chromatography-Mass Spectrometry(LC-MS) was used to qualitative confirmation. The results showed that the characteristic peaks of dimethyl yellow and diethyl yellow pigment appeared respectively at 724 cm-1,990 cm-1. On the basis, two standard quantitative curves of dimethyl yellow and diethyl yellow pigment were established. According to the results, detection limits of the method were respectively 3.0 mg/kg and 1 mg/kg; Linear ranges were 4~80mg/kg and 2~32 mg/kg, respectively; Recovery range was 72.18~106.2%; the relative standard deviation(RSD) was in range of 5.1~8.8%.In chapter 4: The basic orange II in cold noodles was detected rapidly using SERS method. Meanwhile, initial configuration was set up by Gaussview5.0; Using Gaussian 09 program package with HF/3-21 g basis set to fully optimize the initial configuration, a stab molecular structure and theoretical Raman spectra of basic orange II were obtained. By comparing the experimental Raman spectra and theoretical Raman spectra, ten characteristic peaks were identified. They were 477 cm-1, 517 cm-1, 733 cm-1, 995 cm-1, 1164 cm-1, 1288 cm-1, 1374 cm-1,1489 cm-1,1529 cm-1,1590 cm-1, of which 995 cm-1 was confirmed as the quantitative characteristic peak of basic orange II. Based on the above efforts, the quantitative standard curve was established. The results showed the detection limit was 1.5 mg/kg, the linear range was 2~100 mg/kg, and the dye recovery of Basic orange ? in cold noodles was in range of 70.83~101.7%, RSD was in range of 4.7~8.7%.