Ethanol Concentration in Chinese Liquors by Absolute Raman Difference Spectra
YU Lan1, MENG Sen-sen1, LIN Ke1,2*, DUAN Si-qi1, WANG Zhi-qiang1, ZHANG Rui-ting1
1. School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, China
2. Interdisciplinary Research Center of Smart Sensor, Xidian University, Xi’an 710071, China
Abstract：Because of the rapid development of Raman spectroscopy, especially the popularization of portable Raman spectrometer, Raman spectroscopy is particularly important in the rapid analysis of food safety. However, Raman spectroscopy is still less used to analyze the quality of liquor. Because the microstructures of aqueous ethanol solution are different at different concentrations, the Raman spectra are different at different concentrations. Here we proposed an absolute Raman difference spectra to quantify these spectral differences and the concentration of aqueous ethanol. The absolute Raman difference spectra are obtained through subtracting the normalized spectra of pure ethanol from the normalized spectra of solution. The intensity of the absolute Raman difference spectra related to the concentration of ethanol. Using the relationship, we measured the ethanol concentration of a series of bottled Chinese liquors. The measured values agree well with those marked on the bottle, which confirms the reliability of the absolute Raman difference spectra. Based on this method, we also measured the spectra of a series of bulk liquors in Xi’an. The results show that the ethanol concentration of bulk liquor is generally a few degrees lower than its identification value, which highlights the need for supervision of bulk liquors. Our results show significantly that the absolute Raman difference spectrum is a good method to detect the ethanol concentration of liquors rapidly.
Key words：Raman spectra; Difference spectra; Alcohol degree; Chinese liquor
