Study On Fluorescence Spectroscopy Technology And Mechanism Of Two Dairy Additives

In view of the increasingly serious problem of dairy products security and theineffectively controlled phenomenon of dairy additives abuse, the characteristics andmechanisms of the three-dimensional fluorescence spectra, the time-resolved fluorescencespectra, the polarized fluorescence spectra and the quantum efficiency of pure milk, yogurt,carrageenan and potassium sorbate are systematically studied in this article. The deep studyand exploration of the spectra characteristics and mechanisms of the pure milk mixed withcarrageenan and the yogurt and apple juice mixed with potassium sorbate are conducted. Atthe same time, a method of measuring the content of carrageenan and potassium sorbate isproposed in the paper. The results are as follows.1. The three-dimensional reflection fluorescence spectra of pure milk and yogurt areobtained. Results show that the similarity of the fluorescence spectra of yogurt and pure milkare very strong. The fluorescence emission peak wavelengths are not only at336nm but alsoat530nm.Two best excitation wavelengths,377nm and470nm, are obtained of the latter. The530nm fluorescence peak wavelength of milk is mainly contributed by vitamin B2andvitamin C. The fluorescence intensity of the yogurt is lower than that of the pure milk. Maybeit is related to the hydrolysis of the protein in the fermentation process. Obtain an exponentialcurve and a function between fluorescence intensity and the concentration of pure milk. Thestudy results can be used to pure milk composition analysis and detection of pure milk purity.2. The three-dimensional fluorescence spectra and the time-resolved fluorescence spectraof the carrageenan are obtained by using the method of transmission fluorescence spectra. Thepeak emission wavelengths of the carrageenan are at430nm and660nm and they both havetwo fluorescence lifetime. Thus the conclusion that the emission wavelength of thecarrageenan may consist of many fluorophores can be drawn. The linear relationship betweenfluorescence intensity and the concentration of carrageenan in aqueous solution is shown inthe paper. It can be used to estimate the contents of carrageenan.3. The667nm characteristic emission wavelength of carrageenan can be apparentlyobserved in the diluted pure milk mixed with carrageenan. The intensity is linear with theconcentration of carrageenan. Based on this, the concentration of carrageenan in milk can bedetected. The characteristic emission wavelength of carrageenan shifts red because of theinteraction of the carrageenan and the protein. Meanwhile, that leads to the quenching of the336nm peak wavelength of the protein. The667nm characteristic emission wavelength ofcarrageenan can also be apparently observed in different concentrations of pure milk mixedwith the equivalent carrageenan.4. The three-dimensional fluorescence spectra of the potassium sorbate are obtained by using the method of transmission fluorescence spectra. The485nm and565nm peak emissionwavelengths are obtained. The mechanism of the spectra is that the transition of the potassiumsorbate molecules and the oxidation of potassium sorbate molecules. The polynomialrelationship of the fluorescence intensity under the excitation of485nm and theconcentrations from0.05mg/ml to100mg/ml are obtained. Results show that the fluorescencewill quench when the concentration surpasses30mg/ml and the red shift will appear. Thereason may be the resonance energy transition of molecules.5. The three-dimensional fluorescence spectra, the polarized fluorescence spectra and thetime-resolved fluorescence spectra of the yogurt mixed with the potassium sorbate areobtained by using the method of transmission fluorescence spectra. Results show that thepotassium sorbate can quench the fluorescence of the yogurt and change the fluorescenceanisotropies of yogurt, but it doesn’t change the fluorescence life time. That may because ofthe interactions of the potassium sorbate and the yogurt. The relationship between thefluorescence intensity and the concentration of the potassium sorbate and the relationshipbetween the fluorescence anisotropies and the concentration of the potassium sorbate aregiven in the paper. Thus an indirect detection method of the potassium sorbate is proposed.6. The fluorescence spectra of the apple juice are obtained by using the method oftransmission fluorescence spectra. The relationship between the fluorescence intensity and theconcentration of the potassium sorbate are given in the paper. Therefore the concentration ofthe potassium sorbate in the apple juice can be detected directly using the method offluorescence spectra.