| Food, as one of the essential material conditions of human existence, its safety has become the focus of public and governments. However, most of the food safety detection technology have the disadvantage of high cost, tedious pretreatment, specific component detection. Thus, it is badly in need of a low cost and rapid on-site detection in a holistic manner for dealling with the large negotiability of food industry. In this research work, we adopted a Tri-step infrared spectroscopy（Fourier Transform Infrared Spectroscopy, Second derivative Infrared spectroscopy and Two dimensional correlation infrared spectroscopy） coupled with chemometrics to identify and quantitate three common inedible materials in a holistic manner in order to provide theoretical basis for the development of rapid on-site detection equipments.We chosed the most common fluorescent whitening agent in the market, fluorescent brightener DMS, as detect object. And Tri-step infrared spectroscopy was used to detect fluorescent brightener DMS in wheat flour. First, computer vision technology and colourimetry were employed to investigate the color trend among different concentrations of fluorescent brightener DMS in wheat flour for speculating the content range of fluorescent brightener DMS in wheat flour. The concentration of fluorescent brightener DMS may added in wheat flour was less than 100mg/g. Then the characteristic absorption peaks of fluorescent brightener DMS were analyzed. With the increase of the fluorescent brightener DMS concentration, Second derivative Infrared spectrum peaks at 115 cm-1, 1141 cm-1, 1112 cm-1, 1085 cm-1 and 1025 cm-1 attributed to fluorescent brightener DMS was regularly enhanced. The detection limits of fluorescent brightener DMS determination was 0.05mg/g by using Two dimensional correlation infrared spectroscopy. A quantitative prediction model based on Second derivative Infrared spectrum was established successfully. The correlation coefficient of the model was more than 0.988 and RMSEP was 5.73. T-test was employed to verify the accuracy of the model. And there was no significant difference with true values.Benzoyl peroxide was chosed as research object for forbidden to use as wheat flour brightening agent since 2011 by Ministry of Public Health of China. Tri-step infrared spectroscopy was employed to identify and quantitative benzoyl peroxide in wheat flour. The difference of benzoyl peroxide characteristic absorption peaks in wheat flour before and after storage was analyzed by second derivatives spectroscopy. It is proved that benzoyl peroxide changed into benzoic acid after storage. Then a quantitative prediction model combined Partial Least Squares was established and the correlation coefficient of the model was more than 0.97 and RMSEP was 17.5. when using two-dimensional correlation infrared spectroscopy to track changes of benzoyl peroxide in wheat flour, the phenomenon of benzoyl peroxide changed into benzoic acid was observed with the concentration of 0.05mg/g during six days. For simulating the industry process of wheat flour products, samples were heating under 100°C. And spectral subtraction analysis was employed. It was confirmed that benzoyl peroxide in wheat flour not only decomposed into benzoic acid and benzoate, but also produced other deleterious substances, like ethyl benzoate, poly-m-methyl styrene or toluene.After stimulating the sulphur fumigation of tremella, sulfite in tremella was detected. Based on X Ray Fluorescence analytical method, the content of elemental sulphur was detected. The effect of standard curve was available, and the correlation coefficient was 0.992. Using Tri-step infrared spectroscopy for analyzed the tremella after fumigation, as the concentration of sulfur increased, peaks particularly at 980 cm-1 was intensified gradually which correspond with the antisymmetric stretching vibration of sulphurous acid group. The evidence showed that the peak at 983 cm-1 belonged to sulfite was enhanced with the improvement of concentration of sulfur. However, when tremella was fumigated by sulphur, the strength of peak 3506 cm-1 and other peaks nearly it which belonged to vitamin B2 were becoming weaker during the concentration of sulfur increased. The evidence proved sulphur fumigation damaged hydroxyl radicals of vitamin B2. During the improvement of concentration of sulfur, cross peak of peak 963 cm-1 and 983 cm-1 were positive correlation. It means that the two peaks had the same variation trend. And the strength improvement of the peak 983 cm-1 did not influence the strength decrease of the peak 963 cm-1. In consideration of the peak 963 cm-1 belonged to the vibration of C=O, sulphur fumigation was not damaged polysaccharides of tremella. |
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