Application Of Time-resolved Fluorescence Technique In Quality Inspection Of Edible Vegetable Oil

In this study,time-resolved fluorescence technique was used to collect the fluorescence decay spectrum with HORIBA Scientific time-resolved fluorescence spectrometer.The excitation wavelength and the emission wavelength were set respectively at 405 nm and 675 nm,and DAS6 and Origin Pro8.5 were used as the data processing platforms.Four kinds of edible vegetable oil(i.e.camellia oil,peanut oil,sunflower oil and rapeseed oil)were chosen as the test objects to study methods for discriminating different varieties of edible vegetable oil.The quality of purity was analyzed with mixture samples of two components(i.e.camellia oil-peanut oil,camellia oil-sunflower oil,and camellia oil-rapeseed oil)and of three components(i.e.camellia oil-peanut oil-sunflower oil).The fluorescence decay spectra of camellia oil,peanut oil and sunflower oil produced by different processes were tested,and the volatile organic compounds in vegetable oil were detected and classified by gas chromatography-mass spectrometry(GC-MS).The study explored the change regularity between oil processing technology and the volatile organic compounds by comparing fluorescence decay spectrum and the results of GC-MS,which provided theoretical support for distinguishing the process identification of edible vegetable oil.The main research work and conclusions are as follows:1.In order to simplify test process and ensure accuracy and reliability of the test results,the thermostatic system was connected with the instrument detection cavity to ensure stability of the detection temperature.Simultaneously,the important parameters such as the receiving wavelength,the scanning slit and the detection temperature were analyzed and discussed to determine more reasonable parameters for time-resolved fluorescence spectroscopy.As a result,the excitation wavelength of 405 nm,the receiving wavelength of 675 nm,the scanning slit of 4 nm,and the detection temperature of 25 ? were set as the parameters for time-resolved fluorescence spectroscopy.2.A novel method for rapidly identifying different kinds of edible vegetable oil based on time-resolved fluorescence technique was proposed.Four kinds of edible vegetable oil were selected and the fluorescence decay spectra of different vegetable oils were collected under the selected experimental parameters.Then,the average fluorescence lifetime of each vegetable oil was calculated according to the related formula.The results showed that there were remarkable differences in the fluorescence decay spectra between four kinds of edible vegetable oil.Further comparison on their fluorescence lifetime revealed that the difference in fluorescence lifetime between different kinds of vegetable oil was more intuitive and obvious.3.A rapid detection method based on time-resolved fluorescence technique for camellia oil purity was proposed to solve the problem of lacking a rapid purity analysis method for edible vegetable oil.The mixed oil samples of camellia oil-peanut oil,camellia oil-sunflower oil,camellia oil-rapeseed oil and camellia oil-peanut oil-sunflower oil were analyzed in this study.Through comparing the time-resolved fluorescence decay spectra and fluorescence lifetime,it was found that when the camellia oil was mixed with other edible vegetable oils,its fluorescence decay spectrum and fluorescence lifetime changed.Specifically,when camellia oil was mixed with peanut oil or sunflower oil or different proportions of them,the average fluorescence lifetime of camellia oil was shortened and the addition of rapeseed oil prolonged its fluorescence lifetime,which was not changed with doping amount.These data further explained that the fluorescence lifetime is related to the type and environment of the fluorescent groups in edible vegetable oil,and is not related to the doping amount.4.In order to explore the influence of processing technology of edible vegetable oil on change of time-resolved fluorescence,GC-MS and time-resolved fluorescence technique were combined to analyze the changes of fluorescence decay spectrum,fluorescence lifetime and volatile organic components with processing technology of edible vegetable oil,and the composition of the fluorescent groups was preliminarily analyzed.The results showed that the time-resolved fluorescence decay spectrum and volatile organic compounds were different among camellia oil,peanut oil,and sunflower oil produced with different processes.It was found that the difference of the processing technology could influence the composition of volatile organic components in vegetable oil,which caused difference in composition of the fluorescent groups and the microenvironment,and led to significant change in fluorescence decay spectrum and fluorescence lifetime of the vegetable oil.In summary,to apply the time-resolved fluorescence technology in quality inspection of edible vegetable oil is an innovative idea and method.It provides a novel solution for identifying the variety,the purity and the process of edible vegetable oil.The main fluorescent groups of edible vegetable oil were further analyzed through combining with GC-MS.Time-resolved fluorescence has the advantages such as fast detection speed,low sample quantity,intuitive and accurate results,indicating that this technology has a broad application prospect for quality testing of edible vegetable oil and for quality inspection in producing food and agricultural products.