Research On Portable Laser Spectrometer For Food Detection

In recent years,as people's living standards have been increasing,the field of food safety has attracted much attention.Food safety testing methods have also received more and more attention.In this thesis,liquor,water and edible oil,which are common in life,are studied as the main research targets in food detection.Based on portable spectrometer with 405 nm excitation wavelength,the alcohol content of liquor,the total nitrogen content of water and the spectral characteristics of edible soybean oil are studied by using Raman spectroscopy and fluorescence spectroscopy.The current status of international and domestic development are summarized,and several typical miniature spectrometers are briefly introduced.And several typical small-scale spectrometer are briefly introduced.At the same time,the characteristics and applications of fluorescence spectrum and Raman spectrum are studied.According to the results of this study,this paper decided to use Raman spectroscopy combined with fluorescence spectra are specific experimental analysis.First of all,the experiment uses the Raman spectra characteristics of ethanol and water molecules to realize the quantitative detection of alcohol content.By different concentration ethanol-water solution(20% ~ 100%)of laser induced Raman spectrum detection,has established the ethanol and water Raman peak ratio,the corresponding relationship between the concentration of ethanol to determine the linear fitting equation.At the same time,the background subtraction algorithm effectively reduces the fluorescence background interference in the sample Raman spectrum and realizes the quantitative detection of alcohol accuracy.Secondly,the thesis adopts the traditional alkaline potassium persulfate uv spectrophotometry for total nitrogen content in water samples.According to the fluorescence spectral characteristics of the DOM components,the content of total nitrogen and the corresponding relationship of the fluorescence characteristic peak is determined.By means of fluorescence spectrum peak intensity and total nitrogen content value fitting linear fitting equation,the thesis implements the total nitrogen content of quantitative detection of water.Finally,in order to further expand the application of portable laser spectrometer,the thesis makes an experimental analysis of edible soybean oil.Based on the fluorescence spectral characteristics of edible soybean oil of theoretical analysis.Three-dimensional fluorescence spectrum detection system is established by using portable spectrometer,and the three dimensional fluorescence spectrum edible soybean oil samples test obtains three-dimensional fluorescence spectrum with more comprehensive information and finds two characteristic fluorescence peak,then,the laser induced fluorescence spectrum detections using the same portable laser spectrometer for soybean oil samples of being measured for different heating time(10 minutes,15 minutes,20 minutes,25 minutes)of the same brand of soybean oil sample are induced,and the corresponding relationship of the fluorescence characteristic peaks of heating time to the sample is determines.The experimental results show that the first fluorescence spectrum characteristic peak intensity growth trend on the whole,the second characteristic peak keeps to decline,and the material composition changes may occur in the process of heating are analyzed.The soybean oil potentially harmful substances in the process is judged,and the basis for quality testing for soybean oil sample is provided.