素有“液体黄金”之称的橄榄油已成为健康食用油的代名词, 不仅身价陡增, 而且在非产地市场也已成为一种畅销油。 在橄榄油检测技术中光谱法与其他技术相比具有快速、 无损、 无样品处理等优势而备受关注, 而不同的光谱检测方法在检测的物质成分上各有侧重, 例如红外光谱法侧重于脂肪酸含量的检测、 拉曼光谱法侧重于分子的检测、 荧光光谱法侧重于光敏物质的检测以及吸收光谱法侧重于光敏物质和不饱和脂肪酸的检测等。 荧光及吸收光谱对光敏物质反应极其灵敏, 而橄榄油富含叶绿素等光敏物质, 因此荧光及吸收光谱成为一种鉴别橄榄油的有效技术手段。 叶绿素是一种含有环卟啉结构的有机分子, 该类分子结构具有吸光特性, 且不同的叶绿素吸收光谱各异, 其中绿色植物的叶绿素a含量最多。 为深入研究叶绿素的吸收光谱及荧光特性在橄榄油鉴别中的应用, 将特级初榨橄榄油中掺入不同比例的玉米油, 已达到间接调控橄榄油中叶绿素含量的目的, 测量不同掺伪比例橄榄油的荧光及吸收光谱并研究与叶绿素浓度的相关性, 以此来研究叶绿素浓度与掺伪量对橄榄油吸收光谱及荧光特性的影响。 取10份同批次的特级初榨橄榄油, 将其中9份按照等比例稀释, 并对10份样品按照掺伪量依次排序; 依次采集这10份样品的荧光及吸收光谱, 比较叶绿素浓度与掺伪量的相关性及对这两种光谱技术在橄榄油鉴别中的影响。 随着叶绿素浓度的上升, 荧光强度由弱变强, 并在某一时刻后会出现荧光强度急剧减弱的现象, 即聚集荧光猝灭。 这种现象主要是由于叶绿素的环卟啉分子结构引起的分子间π—π作用, 使未被激发的低能分子与高能分子堆叠在一起, 能量的辐射跃迁(荧光)也转变为分子间的能量转移(热能交换)。 对于吸收光谱, 随着叶绿素浓度的上升, 吸收光谱的强度也逐渐增强。 橄榄油中叶绿素吸收的能量主要去向包括镁电子辐射跃迁产生荧光以及分子间热能交换两部分, 而橄榄油的吸收光谱并未出现类似于聚集荧光猝灭的现象, 且吸收光谱强度与掺伪浓度间存在近似线性相关的关系。 结果表明: 当聚集荧光猝灭出现时, 叶绿素吸收的能量仍然与浓度呈线性相关, 此时高、 低能分子堆叠引起的热能交换效率提高。

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.