V.N. Skresanov, Z.E. Eremenko, V.V.Glamazdin, A.I. Shubnyj

Control of quality of wines is an important problem, due to their production and sale have multimillion incomes, and quality of these products influences the health of consumers. There is no universal method of wine authentication. Each of the known methods (the methods of analytical chemistry, wine sampling, physical-chemical methods) has its own advantages and disadvantages and assumes a definite area of application. Thus, the development of alternative methods of wine product quality determination remains actual. Until now the recommendations for the application of the complex permittivity (CP) measurement method in order to the authentication of wines are not worked out. One of reasons is that the data of the systematic measuring of influence of concentration of different components of wines on CP are absent. These data are necessary for the base of such recommendations. The aim of work is the precise CP measurement of model liquids that simulates the chemical composition of wines. Differential method based on the CP measurement of difference in CP of solution and solvent simplifies the precision CP measurement technique. The CP measurement of the musts and model liquids were carried out using the designed for these aims automated dielectrometer. It consists of the measurement block connected to the computer. The calculation of the CP is done by means of the computer program using measurement data of the difference in attenuation and phase coefficients for electromagnetic waves in two identical cells of the measurement cavity, one of that is filled with the solution under test, the other one - with the distilled water. Cells are cylindrical glasses with 20 mm diameter manufactured in a common copper body. The quartz cylinders are glued perpendicularly to the walls of every side body glasses. The solution under test and solvent are poured into glasses. The measurement technique is based on the dependence of the propagation coefficient of the electromagnetic wave excited in a cylinder on dielectric properties of liquid surrounding this cylinder. The attenuation and phase coefficients of the wave in the cell with the solvent are calculated using the characteristic equation and known CP of solvent. The difference of attenuation coefficients and difference of phase coefficients of waves in the cell with a solvent and the cell with the solution under test are measured. The attenuation coefficient and phase coefficients of waves in the cell with solution are calculated using attenuation and phase coefficients obtained from the characteristic equation and their measured differences, respectively. And, finally, we obtain the CP value from the characteristic equation for the solution under test using calculated attenuation and phase coefficients. A measurement scheme of our device is a microwave bridge with two measurement cells of in two its arms. The amplitude of signal in one of the bridge arms is controlled by a measurement P-I-N-attenuator. The measurement phase shifter is in the other bridge arm that is a movable short-circuiting plunger connected to a Y-circulator. The motion of the plunger is controlled by a step motor. The tuning of the attenuator and phase shifter is implemented by the microcontroller program in the measurement block. We measure the change in the attenuation of the P-I-N-attenuator and the change of the phase of the phase shifter at the microwave bridge balance point. The duration of a complete measurement cycle does not exceed three minutes. The detailed analysis of sources and sizes of random and systematic errors of measurements, the series of circuit technological and structural decisions were done to reduce random errors. As a result the differential sensibility of our device is 0,1% and 0,05% for the attenuation and phase coefficients, respectively. These values correspond to the differential sensibility better than 0,5% for the CP values that, in particular, allows solving the problem of wines authentication. The chemical composition of wines is the water solutions of organic and inorganic substances. Water, ethanol, sugar (glucose, fructose and saccharose), and glycerin are chemical components the most influencing on CP of wines and juices (musts) at 8-mm wavelength range. The results of the difference between the CP of water and the CP of water solutions of glucose, glycerin and ethanol are presented at frequency 31.82 GHz and at temperature 25°С. The CP measurements of different mixtures of ethanol, glucose, and glycerin were done. For fortified, dessert and lequeur wines the additivity of the chemical components contribution in CP of wines values is well presented, if the percentage of water-ethanol solution, as the solvent of wine components, is the same as in the wine under test. Thus, the additivity of the chemical components contribution in CP of wines values can be used at the development of the dielectrometry testing technique in the wine-making. Dependences of CP of solutions of different sugars (saccharose, fructose and glucose) in 10% ethanol solution in water on the mass concentration of sugars are presented. CP of such mixtures simulates demi-doux and demi-sec wines at the CP values first approximation. The dependence of CP of ethanol solution in water on the ethanol concentration (in volume percents) is shown. CP of different sugars solutions in water with an identical mass concentration differ a little from each other. The dependences of CP of apple, tartaric, and lemon acids solutions in 10% ethanol solution in water on the mass concentration of acids were also measured. The influence of the concentration change of organic acids on the CP of wines and juices (musts) is in several times less, and these dependences are not monotonous. The measurement data of model liquids presented in the article can be used for the development of the dielectrometry technique at 8-mm wavelength range in the wine-making. Now one of possible practical applications can be the added water detection in wine or in must. Positive results are also obtained the added water detection in must or squash before the fermentation process. The differential sensitivity of the dielectrometry testing technique at the detection of the added water is higher, than for the traditionally used chemical methods. The duration of our measurement cycle is much less than for the traditionally used chemical method.