采用降温扰动二维相关拉曼光谱鉴别掺假橄榄油

doi:10.3964/j.issn.1000-0593(2020)12-3727-05

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Abstract The doping of inferior or low-priced oils into the edible oil infringes consumers’ rights and harms public health. Therefore, the anti-counterfeiting identification of edible oils is of great significance. When the content of counterfeit components in the adulterated oil decreases, the similarity between the genuine oil and the adulterated oil becomes higher so that the identification of low-doping oil is generally difficult. In this paper, synchronous two-dimensional Raman correlation spectroscopy with cooling as a perturbation factor was used for the identification of the pure and the low-doping (5%, 10%, 20%) olive oils. Soybean oil with high similarity to the olive oil was selected as a counterfeit component. In the range of 15 to 0 centigrade degree, the Raman spectra of the pure and the adulterated olive oils were similar and changed slightly when the temperature decreased. The characteristic peaks appeared at 2 850，2 874，2 906，2 933，2 958，3 005 cm^-1. The characteristic peak at 2 850 cm^-1 corresponding to the symmetric stretching vibration of methylene (CH₂) was the strongest peak. When the temperature dropped below 0 centigrade degree, the Raman spectra of the pure and the adulterated olive oils changed significantly along with the decrease of temperature. In the range of -5 to -20 centigrade degree, the characteristic peaks appeared around 2 848, 2 883, 2 933, 2 956, 3 005 cm^-1. The peak at 2 848 cm^-1 was attributed to the redshift of the peak (2 850 cm^-1) of the symmetric stretching vibration of CH₂, and its relative peak strength decreased with the dropping of temperature; meanwhile, the peak at 2 883 cm^-1 corresponding to the asymmetrical stretching vibration of CH₂ gradually increased and became the strongest peak. Synchronous two-dimensional Raman correlation spectra showed that the strength of the auto peak around 2 925 cm^-1 and that of the negative cross peak at (2 925, 2 883 cm^-1) remarkably decreased with the increase of doping ratio, and the two-dimensional spectral difference among the pure and the low-doping (5%, 10%, 20%) olive oils was significant. Hierarchical clustering analysis based on the synchronous two-dimensional Raman correlation spectra showed that the blind samples of the pure and the low-doping olive oils were all accurately identified. Synchronous two-dimensional Raman correlation spectroscopy with cooling as a perturbation factor is efficient to distinguish the low-doping oils from the genuine olive oil and can be also helpful for the identification of other kinds of oils.

Key words：Raman spectroscopy; Two-dimensional correlation; Clustering analysis; Edible oil

Received: 2019-10-25 Accepted: 2020-02-12

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O657.37

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)12-3727-05 OR https://www.gpxygpfx.com/EN/Y2020/V40/I12/3727