RU2246108C2 - Wine-making product authenticity identification method - Google Patents

Abstract

FIELD: wine-making industry.

SUBSTANCE: vine to investigate is subjected to potentiometric titration of HCl contained in vine with alkali solution recording pairs of values: alkali solution volume - pH. Adapted formation function π is then calculated and dependence of formation function on pH of solution is fitted with sigmoid function, whose parameters are further used when taking decision about authenticity of acid composition of wine product. Dependence of free acidity on varying total acidity determines decision about authenticity of wine product itself.

EFFECT: accelerated and simplified identification procedure due to omitting determination of such characteristics as volume fraction of ethanol, weight concentration of titrated acids and reduced extract.

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Description

The invention relates to the wine industry and can be used to identify the authenticity (naturalness) of wines of various types.

A known method (analogue) of the identification of naturalness based on the analysis of electrophoretic profiles of wines (RF Patent 2156976, 2000, Ageeva N.M., Guguchkina T.I., Yakuba Yu.F.). The disadvantage of this method is the need for capillary electrophoresis devices and profile identification according to witnesses.

A known method (analog) of the identification of naturalness by the chromatographic profile of volatile aromatic compounds (Simpkins W. Detection of illicit spirits. Wine Anal. Berlin etc. - 1998. - S.317-338). The method is quite effective, but does not allow to reveal the falsification of a number of products. In addition, this identification method does not reflect the content of non-volatile components.

Closest to the claimed is a method for determining the naturalness of wines (Regyeil des methods Internationales d'analyse des vins et des mouts. Paris, 1990), based on the establishment of calculated coefficients or ratios (adopted by us for the prototype). The essence of the method lies in the fact that the methods of chemical analysis establish the concentration of free and bound organic acids, the value of which is used in the calculation of the Blarez, Gauthier or Ross criteria.

The advantages of the method include the ability to objectively identify falsified products.

To calculate these criteria, in addition to the concentrations of free and bound organic acids, it is necessary to determine the volume fraction of ethyl alcohol, the mass concentration of titratable acids and the reduced extract. The disadvantages of the method are the complexity, duration of the analysis, the need for ion exchange, the use of expensive equipment, such as chromatographs, etc.

The technical result when using the proposed method is achieved due to the fact that in the method for identifying the authenticity of wine products, including the assessment of the acid composition of wine, the assessment of the acid composition of wine is carried out on the basis of analysis of the dependence of free acidity on changing total acidity. The technical result is to accelerate the process of identifying the authenticity of wine products while maintaining its reliability and its cost reduction through the use of widespread equipment and reagents. In addition, to establish the fact of falsification, it is not necessary to determine other indicators of the chemical composition of wine or to compare with the characteristics of a similar sample of genuine products.

The method is as follows.

, равную среднему количеству ионов Н⁺, связанных одним кислотным остатком, и определяемой изменением свободной и общей кислотности смеси в ходе титрования (Бек М., Надьпал И. Исследование комплексообразования новейшими методами. М., Мир, 1989, с.71). Применительно к нашему конкретному случаю формула для расчета в каждой точке кривой титрования имеет следующий вид:A sample of wine with a volume of 10 cm ^{3 was} mixed with the same volume of acid, for example hydrochloric, with a concentration of 0.1 mol / dm ³ . The introduction of hydrochloric acid is necessary to convert the bound organic acids into free form. After that, the mixture was titrated with a solution of a base, for example, sodium hydroxide concentration of 0.1 mol / dm ³ to a pH of about 9.5-10. In this case, pairs of values “volume of sodium hydroxide - pH of the mixture” were recorded every 0.2 pH units. Figure 1 presents the results of titration - titration curves of samples of genuine (a) and falsified (b) wine. Then, for each pH value of the pair, the Bierrum formation function was calculated

equal to the average number of H ⁺ ions bound by one acid residue and determined by the change in the free and total acidity of the mixture during titration (Beck M., Nagypal I. Investigation of complexation by the latest methods. M., Mir, 1989, p. 71). For our particular case, the formula for calculating at each point of the titration curve has the following form:

where n _H = C _NaOH · V _i ; n _HA = n _H —C _HCL · V _HCl ; With _DOS - the concentration of the base, mol / DM ³ ; V _t - base volume corresponding to the equivalence point, cm ³ ; With _HCl - the concentration of hydrochloric acid, mol / DM ³ ; V _HCl is the volume of added hydrochloric acid, cm ³ ; V _DOS - the volume of the added sodium hydroxide solution at this point, cm ³ ; V ₀ - the initial volume of the titrated solution (the sum of the volumes of wine and acid), cm ³ .

позволяет выявить не только зависимости между свободными и общими кислотами, но и несет информацию о подлинности продукта.The need to establish this dependence is explained by its information content. So, in natural wines, the amount of bound acids significantly exceeds the amount of free acids, and in falsified products, mostly free acids are present. Therefore, the calculation of the adapted education function

allows you to identify not only the relationship between free and common acids, but also carries information about the authenticity of the product.

- рН”, которая и применялась для идентификации. На фиг.2 представлены зависимости функции образования

от рН исследуемых проб для подлинного (а) и фальсифицированного (б) вина.Thus, for each sample, the dependence was determined ”

- pH ”, which was used for identification. Figure 2 presents the dependence of the education function

from the pH of the test samples for genuine (a) and falsified (b) wine.

- рН”. Поэтому для точной идентификации анализируемой пробы вина использовали уравнение (программа Sigmaplot, SРSS inc.) зависимости

от рН, т.е. проводили аппроксимацию найденной зависимости

от рН сигмоидной кривой, описываемой уравнением (2) путем подбора параметров k₁-k₆ таким образом, чтобы сумма квадратов отклонений рассчитанных от найденных экспериментально величин

для каждого значения рН была минимальной.Comparing the curves is a rather difficult task that requires additional restrictions (for example, fixed pH values or the total number of points in each experiment, etc.). It is more convenient to compare the parameters of the equations of the curves describing the dependence

- pH ”. Therefore, for the accurate identification of the analyzed wine samples, the equation (Sigmaplot program, SPSS inc.) Was used

from pH, i.e. carried out the approximation of the found dependence

from the pH of the sigmoid curve described by equation (2) by selecting the parameters k ₁ -k ₆ so that the sum of the squared deviations calculated from the experimentally found values

for each pH value was minimal.

where k ₁ -k ₃ - parameters for assessing the authenticity of wine products,

k ₄ -k ₆ are the parameters of the sigmoid curve characterizing its form;

е≈ 2.718 - the base of natural logarithms;

The results showed that to make a decision about the naturalness of the wine being studied, only 3 parameters are used: k ₁ , k ₂ and k ₃ . Based on the experimental data, the standard of genuine products under these experimental conditions are the values of parameter k ₁ in the range from 1.4 to 2.8 units, parameter k ₂ in the range of minus 2.3 to minus 0.9 units, parameter k ₃ in ranging from 3.2 to 5.3 units. The deviation of any parameter beyond the specified ranges indicates the falsification of wine.

Figure 3-5 presents a graphical comparison of the results of the study of samples of wine materials (1-Garnet, 2-Kakheti, 3-Cabernet, 4-Smile, 5-Merlot, 6-Chardonnay, 7-Cabernet) according to the calculated parameters k ₁ , k ₂ , k ₃ assessments of its authenticity, where the regions in which the samples of genuine (outlined by an oval) and falsified wines are grouped are clearly visible. A significant difference in the values of these parameters allows us to confidently distinguish between genuine and falsified wines. For calculations, we used the Microsoft Excel and other similar programs for mathematical data processing.

Thus, the claimed method has advantages both in terms of the conditions of its implementation, and in the degree of objectivity in assessing the authenticity of products. In the claimed method, the identification procedure is performed by converting the pH-metric titration data, while, in contrast to the prototype, not one point is used in the calculation (in the prototype, the point of equivalence), but all experimental data to the point of equivalence. Therefore, the inventive method allows to obtain a larger amount of information regarding the authenticity of wine products, including the ratio of bound and free acids.

Checking the correctness of the results obtained using the proposed method is confirmed by numerous analyzes of natural and falsified wines selected from the distribution network. In total, more than 100 samples were analyzed.

Examples of specific applications of the method.

Example 1

An unknown sample of natural dry white wine is presented for analysis. To establish its authenticity, the methods described in the prototype are applied.

In accordance with the prototype in the test sample was determined: the mass concentration of free and bound acids using eluent chromatography (passing the sample through a cation exchanger and anion exchanger); reduced extract, titratable acids, volume fraction of ethyl alcohol. Based on the data obtained, the relations of Blarez, Gauthier and Ross were calculated, the values of which were 3.2 13.8 and 3.6, respectively, which is similar to the values of the reference sample - natural wine.

для каждой точки титрования. Также указывали ячейки, содержащие сумму квадратов отклонений, рассчитанных от найденных экспериментально величин

и начальные значения параметров k₁-k₆ уравнения (2), в качестве которых применяли значения параметров предыдущего образца. После этого выполнялась процедура “Поиск решения” программы Microsoft Ехсеl. В результате расчета определяли параметры k₁-k₆ уравнения (2) для данного образца. Значение параметра k₁=1,6, k₂=-1,1, k₃=4,6, k₄=0,5, k₅=0,4, k₆=-0,1. Значения параметров k₁-k₃ попадают в диапазон значений, соответствующих подлинным винам. Таким образом, вино считают подлинным.In accordance with the claimed method, to 10 cm ^{3 the} sample add 10 cm ³ hydrochloric acid solution with a concentration of 0.1 mol / DM ³ . We titrate the resulting mixture with a base solution (sodium hydroxide) with a concentration of 0.1 mol / dm ³ to pH ≈ 10, recording the volume of the added base solution through 0.2 pH units: when adding acid, the pH of the mixture was 1.8; the volume of alkali was fixed at pH 2.0, 2.2, 2.4 ... 10.0. Based on the results obtained, by determining the inflection point of the titration curve, an equivalence point (complete neutralization of acids) was found, which in this example was 18.4 cm ³ . At each point of the titration, the values of the formation function were found by substituting the values of the volume of the sodium hydroxide solution and pH into the formula (1). Pairs of pH values and the formation function of all points of the experimental titration curve were recorded on a Microsoft Excel program sheet. In accordance with the conditions of the “Solution Search” procedure of Microsoft Excel, the values of the calculated formation function (2) and the squares of deviations calculated from the experimentally found values were additionally determined

for each titration point. Cells containing the sum of squared deviations calculated from experimentally found values were also indicated.

and initial values of the parameters k ₁ -k _{6 of} equation (2), for which the values of the parameters of the previous sample were used. After that, the “Solution Search” procedure of Microsoft Excel was performed. As a result of the calculation, the parameters k ₁ -k _{6 of} equation (2) for this sample were determined. The value of the parameter k ₁ = 1.6, k ₂ = -1.1, k ₃ = 4.6, k ₄ = 0.5, k ₅ = 0.4, k ₆ = -0.1. The values of the parameters k ₁ -k ₃ fall into the range of values corresponding to genuine wines. Thus, the wine is considered genuine.

Example 2

An unknown sample of natural dry white wine is presented for analysis. To establish its authenticity, the methods described in the prototype are also applied.

In accordance with the prototype in the test sample was determined: the mass concentration of free and bound acids using eluent chromatography (passing the sample through a cation exchanger and anion exchanger); reduced extract, titratable acids, volume fraction of ethyl alcohol. Based on the data obtained, the relations of Blarez, Gauthier and Ross were calculated, the values of which were 3.0 10.8 and 4.6, respectively, which does not allow making an unambiguous decision on the naturalness of the product. Therefore, for an objective assessment, it is necessary to carry out additional calculations and measurements.

для каждой точки титрования. Также указывали ячейки, содержащие сумму квадратов отклонений, рассчитанных от найденных экспериментально величин

, и начальные значения параметров k₁-k₆ уравнения (2), в качестве которых применяли значения параметров предыдущего образца. После этого выполнялась процедура “Поиск решения” программы Мicrosoft Ехсеl. В результате расчета определяли параметры k₁-k₆ уравнения (2) для данного образца. Значение параметра k₁=1,6, k₂=-2,7, k₃=2,8, k₄=1,1, k₅=2,5, k₆=-0,2. Значения параметра k₁ попадает в диапазон значений, отвечающих подлинным винам, но параметры k₂ и k₃ не соответствуют параметрам подлинных вин. Таким образом, вино считают фальсифицированным.In accordance with the claimed method, to 10 cm ^{3 the} sample add 10 cm ³ hydrochloric acid solution with a concentration of 0.1 mol / DM ³ . We titrate the resulting mixture with a base solution (sodium hydroxide) with a concentration of 0.1 mol / dm ³ to pH≈10, registering the volume of the added base solution through 0.2 pH units: when adding acid, the pH of the mixture was 1.6; the volume of alkali was fixed at pH 1.8, 2.0, 2.2 ... 10.0. Based on the results obtained, by determining the inflection point of the titration curve, an equivalence point (complete neutralization of acids) was found, which in this example was 16.1 cm ³ . At each point of the titration, the values of the formation function were found by substituting the values of the volume of the sodium hydroxide solution and pH into the formula (1). Pairs of pH values and the formation function of all points of the experimental titration curve were recorded on a Microsoft Excel program sheet. In accordance with the terms of the “Solution Search” procedure of Microsoft Excel, the values of the calculated formation function (2) and the squares of deviations calculated from the experimentally found values were additionally determined

for each titration point. Cells containing the sum of squared deviations calculated from experimentally found values were also indicated.

, and the initial values of the parameters k ₁ -k _{6 of} equation (2), for which the values of the parameters of the previous sample were used. After that, the “Solution Search” procedure of Microsoft Excel was performed. As a result of the calculation, the parameters k ₁ -k _{6 of} equation (2) were determined for this sample. The value of the parameter k ₁ = 1.6, k ₂ = -2.7, k ₃ = 2.8, k ₄ = 1.1, k ₅ = 2.5, k ₆ = -0.2. The values of the parameter k ₁ fall into the range of values corresponding to genuine wines, but the parameters k ₂ and k ₃ do not correspond to the parameters of genuine wines. Thus, the wine is considered falsified.

Claims (1)

A method for identifying the authenticity of wine products, including an assessment of the acid composition of wine, characterized in that the assessment of the acid composition of wine is carried out on the basis of an analysis of free acidity from changing total acidity.

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