Study on Fluorescence Quenching and Absorption Spectra of Olive Oil
WANG Hong-peng, WAN Xiong*
Key Laboratory of Space Active Opto-Electronics Technology, Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, Shanghai 200083, China
Abstract：The olive oil, known as “liquid gold”, has become a synonym for healthy edible oil. It not only has a steep increase in its price, but also has become a best-selling oil in the non producing market. Spectral method has many advantages compared with other technologies, such as fast, nondestructive and non sample processing. Different spectral detection methods have a particular emphasis on the material components, for example, infrared spectroscopy focuses on the detection of fatty acid content, Raman spectroscopy focuses on the detection of molecules, fluorescence spectroscopy focuses on the detection of photosensitive substances, and absorption spectroscopy focuses on the detection of unsaturated fatty acids. Fluorescence and absorption spectra are very sensitive to photosensitive substances, and olive oil is rich in chlorophyll and other photosensitive substances. Therefore, fluorescence and absorption spectra have become an effective technique for identifying olive oil. Chlorophyll is an organic molecule containing the structure of cycloporphyrin. The molecular structure of this kind of molecular structure has the characteristics of absorption of light, and the absorption spectra of different kinds of chlorophyll are unique, among which the content of chlorophyll a in green plants is the most. In order to study the application of the absorption spectrum of chlorophyll and the fluorescence characteristics of the extra virgin olive oil, the content of chlorophyll in olive oil was indirectly regulated by mixing different proportion of corn oil in the special primary olive oil. The fluorescence and absorption spectra of different adulterated olive oil were measured and the phase of chlorophyll concentration was studied. The effecus of chlorophyll concentration and adulteration amount on the absorption spectra and fluorescence characteristics of olive oil were studied. 10 samples of the same batch of extra virgin olive oil were taken, 9 of them were diluted in equal proportion and 10 samples were sequentially ordered according to adulteration. The fluorescence and absorption spectra of the 10 samples were collected in turn, and the correlation between the concentration of chlorophyll and adulteration were compared and the effects of the two spectral techniques on the identification of olive oil were compared. With the increase of chlorophyll concentration, the fluorescence intensity becomes stronger and weakens sharply after a certain time, that is, the aggregation fluorescence quenching. This phenomenon is mainly due to the intermolecular π—π action caused by the molecular structure of the phyphyrphyrin, which makes the non excited low energy molecules and high energy molecules stacked together. The radiation transition of energy (Fluorescence) is also transformed into the energy transfer (heat exchange) between the molecules. As for the absorption spectrum, the intensity of absorption spectrum increases with the increase of chlorophyll concentration. The main energy of the absorption of chlorophyll in olive oil consists of two parts, including the emission of magnesium electron emission and the intermolecular heat exchange, while the absorption spectrum of olive oil does not appear like aggregation fluorescence quenching, and there is an approximate linear correlation between the absorption spectrum intensity and the adulteration concentration. The results show that when the fluorescence quenching occurs, the energy of the absorption of chlorophyll is still linearly related to the concentration, and the efficiency of heat exchange caused by the stacking of high and low energy molecules increases.
Key words：Chlorophyll; Fluorescence; Absorption spectrum; Extra virgin olive oil; Detection
王泓鹏，万 雄. 橄榄油的聚集荧光猝灭及吸收光谱特性的研究[J]. 光谱学与光谱分析, 2019, 39(08): 2421-2424.
WANG Hong-peng, WAN Xiong. Study on Fluorescence Quenching and Absorption Spectra of Olive Oil. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(08): 2421-2424.
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