Applied Research On Detection Of Food Additive Based On LIBS

With the rapid development of food industry in China,the variety of food additives is increasing.Some undesirable merchants use some prohibited additives or excessively use additives in the process of food production,which leads to potential safety problems and brings serious threat to people's life and property.However,current safety research and techniques for food additives analysis are far from meeting the needs of the current development.Laser induced breakdown spectroscopy(LIBS)technique is a spectral analysis method based on laser ablation.We can use an ultrashort laser pulse to focus on the sample surface and produce plasma,and then analyze the plasma emission spectrum to determine the composition and content of the material in the sample quickly.LIBS has the advantages of simultaneous multiple elements detection,no sample pretreatment and simple operation,etc.Therefore,in this thesis,we attempted to apply LIBS technique to content detection of food additives.We built a LIBS-based detection system,and then explored its application in fast detection of food additive content.We carried out LIBS spectra detection and data analysis with two types of food additives,titanium dioxide(whitening agent)and aluminum potassium sulfate dodecahydrate(Ming Fan),which are commonly used in flour products,and realized fast semiquantitative analysis of these two additives in flour products.The work mainly includes the following aspects:1.We used an Nd:YAG nanosecond laser(1064 nm)as the excitation source,a spectrometer and an intensified charge-coupled device(ICCD)to set up a set of LIBS detection system.The system adopted single pulse excitation in vertical direction and the forward collecting detection method on the vertical pulse light path.2.By analyzing the signal intensity and signal to noise ratio of the LIBS spectra of the standard samples under different excitation energy,we optimized the experimental conditions and the parameter settings for the system to be used in the detection of food additive content in dough.For example,the optimum delay time and integral time of the ICCD were determined.3.We applied the detection system on the standard samples using direct spectral intensity calibration method and internal standard method respectively.Through data analysis,we obtained the calibration curves of titanium dioxide and aluminium potassium sulfate dodecahydrate in different flour products.The advantages and disadvantages of two different calibration methods were compared and analyzed.4.Using the calibration curves,we realized semi-quantitative analysis of the content of titanium dioxide and aluminium potassium sulfate dodecahydrate in various flour products from the market(real samples).The innovation points of this thesis are as follows:1.LIBS technology was applied to fast quantitative / semi-quantitative analysis of food additives in flour products.2.The calibration curves of titanium dioxide and aluminium potassium sulfate dodecahydrate in different kinds of flour products(wet dough,dry dough,fermented dough,fried dough)were set up,and used to detect the content of food additives in daily food products.