Research On Quality Identification Model Of Fenjiu Base Liquor Based On Three-dimensional Fluorescence Spectroscopy

Three-dimensional fluorescence spectroscopy is a rapid analytical technique with high sensitivity,no pretreatment and good reproducibility.At present,it is widely used in food,drug detection and other fields.In the field of liquor,three dimensional fluorescence spectroscopy is used to identify different flavors,even different brands and different vintages.In this study,Fenjiu base liquor whose quality evaluated by the sensory mouth is selected different as the research object.The three-dimensional fluorescence spectrometer was used to measure the three-dimensional fluorescence spectrum data of the base liquor of different quality levels,and the fluorescence characteristics were analyzed.From the macro and micro two perspective,the mechanism of base liquor fluorescence is discussed.By collecting a large number of samples,support vector machine,partial least square discriminant analysis and BP neural network is used to establish a three-dimensional fluorescence-based liquor quality identification model,aiming to provide a new technology for the quality control of liquor production.(1)Various trace substances were added into the simulated liquor,and the fluorescence contribution of the main substances in the base liquor was discussed.It was found that alcohols contributed more to the fluorescence generation of base liquor,and ethanol mainly formed the fluorescence peak at 285 nm/330 nm(excitation wavelength/emission wavelength,Ex/Em).The fluorescence contribution of esters can be divided into two parts.One part is that the fluorescence contribution of esters with short carbon chains,such as ethyl acetate and ethyl lactate,is weak;the other part is that the fluorescence peak of higher fatty acid esters,such as ethyl oleate,is generated at 310 nm/330 nm,and its fluorescence contribution is strong.Among the acids,the acids with short carbon chains,such as acetic acid and butyric acid,played a weak role in the formation of fluorescence,but their fluorescence contribution was not large.However,acids with long carbon chains,such as hexanoic acid and heptanoic acid,contribute strongly to the formation of fluorescence.With the increase of carbon chain,the fluorescence contribution of ester substances and acid substances becomes stronger.This may be due to the increase of alkyl groups and the increase of hydrophobicity.When several substances are mixed,their different interactions between molecules lead to different fluorescence.With the increase of concentration,aldehydes have a quenching effect on the fluorescence of shortwave strength,but have a greater contribution to the fluorescence of high-wave strength.(2)Taking 11 fractions of distillate in the process of clear flavor distilling as samples,the fluorescence changes of distilling process were analyzed by using three-dimensional fluorescence spectrum for the first time,and the fluorescence characteristics of the fluorescence spectra of each fraction of distilling process were analyzed.The fluorescence spectra of each segment mainly showed two fluorescence peaks in the same position,which were 285 nm/310 nm and 310 nm/335 nm respectively.The distillate liquor of different time was detected by gas chromatography to obtain the distillation rule of the main components in the liquor.The parallel factor method was used to decompose the spectra and combine the distillation rule of each substance in the liquor body and the contribution of each monomer to the fluorescence.It was proved that the fluorescence peak at 285 nm/310 nm was formed by the combined action of alcohols and caproic acid,and the short carbon chain substances such as ethyl acetate and acetic acid had a slight increase effect on the fluorescence peak.The fluorescence peak at 310 nm/335 nm was mainly formed by higher fatty acid esters such as ethyl oleate.(3)Taking 390 base liquor samples with different grades after sensory oral evaluation as samples,the three-dimensional fluorescence spectra were measured and the fluorescence spectrum characteristics of each grade of liquor were analyzed.The results showed that there were two fluorescence peaks at 290 nm/310 nm and 310 nm/335 nm in the fluorescence spectrum of base liquor,but the fluorescence intensity of the two fluorescence peaks was different between different liquor samples.Based on the original spectral data of 390 samples,the classification effect is poor.Four emission spectra at excitation wavelengths of 290 nm,310 nm,340 nm and 360 nm were extracted from the original spectral data as new characteristic quantities.After dimensionality reduction by principal component analysis and linear discriminant analysis,390 base liquor fluorescence data were taken as the test set for modeling by support vector machine,and another 78 samples were taken as the external test set.The results showed that the accuracy of modeling training was 86.9%,and the classification accuracy of test set was decreased to 85.9%,which could provide a new identification method for the quality identification of base liquor.