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September 2019 (published: 24.09.2019)
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The application of spectroscopy to assess the quality of grape wines
Korshunova N.A., Romanov V.A., Eveleva V.V.
Research have been conducted to assess the possibility of determining quality indicators of grape wines by spectroscopy in the middle IR range. Objects of the study were samples prepared on the basis of Chardonnay dry white wine of the Taman Peninsula. Samples were prepared by diluting the wine with distilled water with the subsequent addition of rectified ethyl alcohol and citric acid to the obtained solutions. In the samples the mass concentration of titratable acids and the volume fraction of ethyl alcohol were determined by the methods described in the current standards and the method of broken total internal reflection (BTIR) on ALPHA and VERTEX 70 IR-Fourier spectrometers by Bruker brand. Mass concentration of titratable acids in the test sample varied from 1.09 to 14.96%, the alcohol by volume – from 2.07 to 14.52% by volume. Spectral parameters were chosen taking into account the achievement the best results in terms of resolution and signal-to-noise ratio. In the obtained IR spectra absorption bands were selected that characterize the content of titratable acids and ethyl alcohol. Using the spectrometer software we established the calibration characteristics of the wine quality indicators studied from the area of the corresponding absorption band. Statistical indicators of established functional dependencies and indicators determined by them are estimated. Correlation coefficient of the calibration equation for ethanol content was 0.989, coefficient of determination – 0.977. The calibration equation for determining the content of organic acids was characterized by correlation coefficient 0.987 and coefficient of determination 0.975. In conclusion, the metrological characteristics of measuring the concentrations of ethanol and titrated acids by the proposed method are consistent with the standards. This method to determine the content of alcohol and organic acids can be recommended to analyze table wines of the corresponding type. The preparation of new series of samples and recalibration are required only when analyzing a new type of wine. It is recommended to use the data obtained in training courses at the Master's program Methods of Quality Control of Food Products.
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Keywords: spectroscopic analysis; dry white grape wine; quality indicators; alcohol by volume; mass concentration of titratable acids
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