A method for extracting condensed tannins in dry red wine

Abstract

This invention relates to the field of wine testing technology, specifically to a method for extracting condensed tannins from dry red wine. First, the treated dry red wine is subjected to solid-phase extraction to obtain a condensed tannin extract. Then, the condensed tannin extract is analyzed by high-performance liquid chromatography (HPLC). The eluent for solid-phase extraction is a mixed solution of acetone, water, and acetic acid. In the mixed solution, the volume ratio of acetone, water, and acetic acid is 60–90:9.5–39.5:0.5. The condensed tannin extract contains condensed tannins of various degrees of polymerization. This method can specifically identify and detect condensed tannins of various degrees of polymerization, and can also obtain the content of condensed tannins at each degree of polymerization. The analytical results are good, achieving the enrichment and detection of condensed tannins with different degrees of polymerization. The operation is simple and highly reproducible.

Description

Technical Field

[0001] This invention relates to the field of wine testing technology, and more specifically, to a method for extracting condensed tannins from dry red wine. Background Technology

[0002] Astringency is an important sensory attribute of dry red wine, and its intensity and texture affect its flavor quality. Condensed tannins are important phenolic substances in dry red wine. They enter the wine from the grape skins and seeds during fermentation through maceration and are polymers linked by flavan-3-ol monomers as basic units.

[0003] Condensed tannins bind to salivary proteins in the oral cavity to form precipitates, thereby causing the contraction and wrinkling of oral epithelial cells. Their content and composition are crucial to the astringent quality of dry red wines. However, due to the diverse structures of condensed tannins, it is difficult to fully analyze their content and structure in dry red wines with complex matrix compositions, especially some high-molecular-weight tannins that are present in lower amounts.

[0004] Currently, some chemical methods can be used to detect the total phenol content in dry red wine, but these methods cannot specifically identify condensed tannins. The specific limitations of these methods are as follows:

[0005] (a) Traditional methods for detecting total phenols (such as the Folin-Schönbrunn method)

[0006] Traditional total phenol detection methods detect phenolic substances including condensed tannins, anthocyanins, and phenolic acids. Compared to the present invention, it cannot specifically distinguish condensed tannins, thus the results will overestimate the true condensed tannin content of the wine sample.

[0007] (II) Gel Chromatography

[0008] Gel chromatography typically uses dextran gel (Sephadex LH-20) and macroporous resin (TSK HW-50(F)) as packing materials, and organic reagents, such as methanol, are used to elute condensed tannins adsorbed on the packing material. Compared to this invention, this method requires a larger volume of dry red wine sample, is more cumbersome and time-consuming, and is better at separating oligomeric condensed tannins (degree of polymerization 2-5), but is difficult to elute high-polymer tannins (degree of polymerization greater than 5).

[0009] (III) Mass Spectrometry

[0010] Mass spectrometry can directly detect condensed tannins in dry red wine samples, requiring a small sample volume (3-5 μL). In contrast, this method can only determine the content of flavanol monomers and condensed tannin dimers. The content of condensed tannins with high degree of polymerization is relatively low and the molecular structure is complex, making it difficult to quantify them in the complex matrix of untreated dry red wine. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a method for extracting condensed tannins from dry red wine.

[0012] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0013] This invention provides a method for extracting condensed tannins from dry red wine. First, the treated dry red wine is subjected to solid-phase extraction to obtain a condensed tannin extract, and then the condensed tannin extract is detected by high-performance liquid chromatography.

[0014] The eluent for solid-phase extraction is a mixed solution of acetone, water, and acetic acid; the volume ratio of acetone, water, and acetic acid in the mixed solution is 60–90:9.5–39.5:0.5; the condensed tannin extract contains condensed tannins of various degrees of polymerization.

[0015] Furthermore, the volume ratio of the treated dry red wine to the eluent is 1:4.

[0016] Furthermore, the condensed tannins include flavanol monomers, condensed tannin dimers, condensed tannin trimers, condensed tannin tetramers, condensed tannin pentamers, condensed tannin hexamers, condensed tannin heptamers, and condensed tannin octamers.

[0017] Furthermore, the extraction method includes the following steps:

[0018] S1-1. Centrifuge the dry red wine to remove insoluble precipitates and retain the supernatant.

[0019] S1-2. The solid phase extraction column is activated sequentially with methanol and water. After activation, the packing material in the solid phase extraction column is dried.

[0020] S1-3. Add the supernatant obtained in step S1 to the solid phase extraction column. After the supernatant is completely adsorbed onto the packing material, blow the packing material dry.

[0021] S1-4. Rinse the solid-phase extraction column with distilled water;

[0022] S1-5. Elute the solid-phase extraction column with the eluent and collect the eluent;

[0023] S1-6. Remove acetone from the eluent, freeze-dry the remaining liquid, and then reconstitute it in the simulated wine to obtain the condensed tannin extract. The simulated wine is an aqueous solution of ethanol, tartaric acid, and sodium chloride, wherein the volume percentage of ethanol is 12% of the total volume of the simulated wine, the mass ratio of tartaric acid to the volume of the simulated wine is 5 g / L, and the concentration of sodium chloride is 0.2 M sodium chloride.

[0024] Furthermore, in step S1-1, the centrifugation speed is 8000 r / min and the centrifugation time is 5 min.

[0025] Furthermore, the solid-phase extraction column is an Oasis HLB column with a specification of 3cc / 60mg;

[0026] In step S1-2, the volume of both methanol and water is 2 mL; in step S1-3, the amount of supernatant added is 5 mL; and in step S1-6, the amount of elution solution used is 20 mL.

[0027] Furthermore, the high-performance liquid chromatography detection includes the following steps:

[0028] S2-1. Perform high performance liquid chromatography on the condensed tannin extract and determine the condensed tannin corresponding to each chromatographic peak in the chromatogram based on the retention time of each condensed tannin.

[0029] S2-2, Perform the same high-performance liquid chromatography (HPLC) detection as in step S2-1 on epicatechin standard solutions with multiple concentration gradients to obtain the standard equation for epicatechin; the standard equation is a linear equation between concentration and peak area.

[0030] S2-3. Substitute the peak area of ​​each condensed tannin in the chromatogram of step S2-1 into the standard equation in step S2-2 to calculate the content of each condensed tannin.

[0031] Furthermore, in step S2-1, the retention time of the flavanol monomer is 4.90 min, the retention time of the condensed tannin dimer is 10.91 min, the retention time of the condensed tannin trimer is 19.51 min, the retention time of the condensed tannin tetramer is 27.00 min, the retention time of the condensed tannin pentamer is 35.58 min, the retention time of the condensed tannin hexamer is 40.61 min, the retention time of the condensed tannin heptamer is 46.77 min, and the retention time of the condensed tannin octamer is 51.24 min.

[0032] Furthermore, the high-performance liquid chromatography detection conditions are as follows:

[0033] The chromatographic column was Develosil Diol. The chromatographic column has dimensions of 250×4.6mm and 5μm; the column temperature is 40℃.

[0034] The fluorescence excitation wavelength is 230 nm, and the emission wavelength is 321 nm.

[0035] The injection volume was 5 μL, the flow rate was 1 mL / min, and the run time was 10 min.

[0036] The mobile phase includes mobile phase A and mobile phase B; mobile phase A is an acetonitrile-acetic acid solution with a volume ratio of acetonitrile to acetic acid of 98:2; mobile phase B is a mixed solution of methanol, water and acetic acid with a volume ratio of methanol, water and acetic acid of 95:3:2; the elution method is gradient elution.

[0037] Furthermore, the gradient elution procedure is as follows:

[0038] At 0 min, the volume ratio of mobile phase A to mobile phase B is 93:7;

[0039] After 3 minutes, the volume ratio of mobile phase A to mobile phase B is 93:7.

[0040] After 60 minutes, the volume ratio of mobile phase A to mobile phase B was 62.4:37.6.

[0041] At 63 min, the volume ratio of mobile phase A to mobile phase B was 0:100;

[0042] At 70 min, the volume ratio of mobile phase A to mobile phase B is 0:100;

[0043] After 76 minutes, the volume ratio of mobile phase A to mobile phase B is 93:7.

[0044] The beneficial effects of this invention are as follows:

[0045] (1) The extraction method of condensed tannins in dry red wine of the present invention adopts a combination of solid phase extraction and high performance liquid chromatography, and the solid phase extraction eluent used is a mixed solution of acetone, water and acetic acid, which can specifically identify and detect condensed tannins with multiple degrees of polymerization.

[0046] (2) The extraction method of condensed tannins in dry red wine of the present invention can also obtain the content of condensed tannins with different degrees of polymerization, and the analysis results are good. It realizes the enrichment and detection of condensed tannins with different degrees of polymerization.

[0047] (3) The extraction method of condensed tannins in dry red wine of the present invention can accurately and stably analyze the composition of condensed tannins in dry red wine and eliminate the interference of complex matrix components in dry red wine.

[0048] (4) The extraction method of condensed tannins in dry red wine of the present invention is simple to operate and highly reproducible. Attached Figure Description

[0049] Figure 1 In the extraction method of condensed tannins from dry red wine of the present invention, in Example 1, the high performance liquid chromatogram of the experimental group is shown.

[0050] Figure 2 In the method for extracting condensed tannins from dry red wine according to the present invention, Figure 1 A magnified view of part A in the image;

[0051] Figure 3 In the extraction method of condensed tannins from dry red wine of the present invention, in Example 1, the high performance liquid chromatogram of the control group is shown.

[0052] Figure 4 In Example 3 of the extraction method of condensed tannins in dry red wine of the present invention, a comparison diagram of the peak areas of condensed tannins at different degrees of polymerization is shown.

[0053] Figure 5 In Example 4 of the extraction method of condensed tannins in dry red wine of the present invention, a comparison diagram of the peak areas of condensed tannins at different degrees of polymerization is shown.

[0054] Figure 6 This is a comparison diagram of the peak areas of condensed tannins at different degrees of polymerization in Example 5 of the extraction method of condensed tannins in dry red wine of the present invention. Detailed Implementation

[0055] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0056] The present invention discloses a method for extracting condensed tannins from dry red wine. First, a solid-phase extraction column is used to elute the treated dry red wine to obtain a condensed tannin extract. Then, the condensed tannin extract is analyzed by high-performance liquid chromatography (HPLC). The eluent is a mixed solution of acetone, water, and acetic acid. The volume ratio of acetone, water, and acetic acid in the mixed solution is 80:19.5:0.5. The condensed tannin extract contains condensed tannins with various degrees of polymerization.

[0057] The extraction method for condensed tannins in dry red wine using this invention can accurately and stably analyze the composition of condensed tannins in dry red wine, eliminating interference from complex matrix components. Specifically, the extraction method includes elution and high-performance liquid chromatography (HPLC) detection, which can specifically identify and detect condensed tannins with multiple degrees of polymerization, and can also obtain the content of condensed tannins at each degree of polymerization. The analytical results are good, achieving the enrichment and detection of condensed tannins with different degrees of polymerization. The operation is simple and highly reproducible.

[0058] Preferably, the volume ratio of the treated dry red wine to the eluent is 1:4.

[0059] Preferably, the tannin monomers are condensed tannin dimers, condensed tannin trimers, condensed tannin tetramers, condensed tannin pentamers, condensed tannin hexamers, condensed tannin heptamers, and condensed tannin octamers.

[0060] The method and effects of the present invention will be specifically described below through specific embodiments.

[0061] Example 1

[0062] This embodiment verifies the effect of whether solid-phase extraction is performed before high-performance liquid chromatography (HPLC) detection on the extraction results.

[0063] This embodiment is divided into an experimental group and a control group. The experimental group uses the extraction method of the present invention to perform solid-phase extraction and detection on dry red wine, while the control group uses high-performance liquid chromatography (HPLC) to detect the same dry red wine. The HPLC conditions of the control group are the same as those of the experimental group.

[0064] The extraction method for the experimental group specifically includes the following steps:

[0065] S1-1. Centrifuge the dry red wine, remove the insoluble precipitate after centrifugation, and retain the supernatant; the centrifugation speed is 8000 r / min, and the centrifugation time is 5 min.

[0066] The dry red wine used in this experimental group was Cabernet Sauvignon dry red wine from Xinjiang.

[0067] S1-2. The solid-phase extraction column was activated sequentially with methanol and water. After activation, the packing material in the solid-phase extraction column was dried. The volume of both methanol and water was 2 mL. The solid-phase extraction column used in this example was an Oasis HLB column with specifications of 3cc / 60mg, 100 / box (wat094226).

[0068] S1-3. Add the supernatant obtained in step S1 to the solid phase extraction column. After the supernatant is completely adsorbed onto the packing material, blow the packing material dry. The amount of supernatant added is 5 mL.

[0069] S1-4. Rinse the solid-phase extraction column with 5 mL of distilled water.

[0070] S1-5. Elute the solid-phase extraction column with eluent and collect the eluent; the volume of eluent used is 20 mL.

[0071] S1-6. Remove acetone from the eluent, freeze-dry the remaining liquid, and then reconstitute it in the simulated wine to obtain the condensed tannin extract.

[0072] Preferably, rotary evaporation is used to remove acetone from the eluent. The rotary evaporation temperature is 30°C and the pressure is 50 mbar. When there is no liquid in the condenser, the acetone has been completely removed. In actual operation, the volume of the remaining liquid at this point is approximately 4–5 ml.

[0073] It should be noted that the lyophilized substance can only be completely dissolved and used for subsequent high-performance liquid chromatography detection by dissolving it in simulated wine.

[0074] Preferably, the simulated wine is an aqueous solution of ethanol, tartaric acid and sodium chloride, wherein the volume percentage of ethanol is 12% of the total volume of the simulated wine, the mass ratio of tartaric acid to the volume of the simulated wine is 5 g / L, and the concentration of sodium chloride is 0.2 M sodium chloride.

[0075] In the method of this invention, the high-performance liquid chromatography detection includes the following steps:

[0076] S2-1. The condensed tannin extract was subjected to high performance liquid chromatography to obtain chromatograms of each condensed tannin peak in the condensed tannin extract.

[0077] The condensed tannin content of S2-2 dry red wine was calculated using epicatechin as an equivalent. High-performance liquid chromatography (HPLC) was performed on epicatechin standard solutions of multiple concentration gradients, similar to step S2-1, to obtain the standard equation for epicatechin; the standard equation is a linear equation between concentration and peak area.

[0078] S2-3. Substitute the peak area of ​​each condensed tannin in the chromatogram of step S2-1 into the standard equation in step S2-2 to calculate the content of each condensed tannin.

[0079] The high-performance liquid chromatography (HPLC) detection conditions are as follows:

[0080] The chromatographic column was Develosil Diol. The chromatographic column has dimensions of 250×4.6mm and 5μm; the column temperature is 40℃.

[0081] The fluorescence excitation wavelength is 230 nm, and the emission wavelength is 321 nm.

[0082] The injection volume was 5 μL, the flow rate was 1 mL / min, and the run time was 10 min.

[0083] The mobile phase includes mobile phase A and mobile phase B; mobile phase A is an acetonitrile-acetic acid solution with a volume ratio of acetonitrile to acetic acid of 98:2; mobile phase B is a mixed solution of methanol, water, and acetic acid with a volume ratio of methanol, water, and acetic acid of 95:3:2; the elution method is gradient elution.

[0084] The gradient elution procedure is as follows:

[0085] At 0 min, the volume ratio of mobile phase A to mobile phase B was 93:7;

[0086] After 3 minutes, the volume ratio of mobile phase A to mobile phase B was 93:7.

[0087] After 60 minutes, the volume ratio of mobile phase A to mobile phase B was 62.4:37.6.

[0088] At 63 min, the volume ratio of mobile phase A to mobile phase B was 0:100.

[0089] At 70 min, the volume ratio of mobile phase A to mobile phase B was 0:100.

[0090] After 76 minutes, the volume ratio of mobile phase A to mobile phase B was 93:7.

[0091] After extraction, the chromatograms obtained by the experimental group are as follows: Figure 1 and Figure 2 As shown, the chromatogram obtained from the control group is as follows. Figure 3 As shown.

[0092] according to Figure 1 and Figure 2 It can be seen that after solid-phase extraction, the outlines of condensed tannins with different degrees of polymerization in dry red wine are clear, and the elution time of flavanol monomers and oligomeric tannins is slightly advanced.

[0093] According to Figure 3 It can be seen that without solid-phase extraction, high-performance liquid chromatography detection cannot yield other condensed tannins with high polymerization degrees, except for flavanol monomers, and it is impossible to distinguish condensed tannins with different polymerization degrees.

[0094] Example 2

[0095] This embodiment verifies the retention times of condensed tannins at each degree of polymerization obtained in the experimental group in Example 1, to prove that the obtained chromatographic peaks do indeed correspond to condensed tannins at each degree of polymerization.

[0096] To determine the substances contained in each chromatographic peak, this embodiment performed a qualitative analysis of the composition of each peak, and the mass spectrometry information is shown in Table 1:

[0097] Table 1. Mass Spectrometry Information of Condensed Tannin Extracts from Dry Red Wine

[0098]

[0099] Upon identification, the mass spectrometry information of the substances in each chromatographic peak was consistent with the reported mass spectrometry information of condensed tannins with different degrees of polymerization, indicating that the chromatographic peaks obtained by the method of the present invention correspond to the aforementioned condensed tannins with different degrees of polymerization. The reported mass spectrometry information can be found in the literature “Ma W, Waffo-Teguo P, Jourdes M, Li H, Teissedre P L. Chemical Affinity between Tannin Size and Salivary Protein Binding Abilities: Implications for Wine Astringency[J]. PLoS One, 2016, 11(8):e0161095.” and “Cave J R, Waterhouse A L. Combinatorics of proanthocyanidins in wine[J]. Analyst, 2019, 144(14):4395-4399.”

[0100] Example 3

[0101] This embodiment compares and verifies the effect of the loading amount on the extraction results of solid phase extraction.

[0102] In this embodiment, solid-phase extraction was performed using sample loading volumes of 2 mL, 3 mL, 4 mL, and 5 mL, respectively. All other extraction and high-performance liquid chromatography conditions were the same as those in the experimental group in Example 1.

[0103] The peak areas of condensed tannins at different degrees of polymerization were compared by high performance liquid chromatography (HPLC) after analyzing the condensed tannin extracts obtained from the above-mentioned sample loading amounts. Figure 4 As shown.

[0104] according to Figure 4 It can be seen that when the sample loading amount is 5 mL, the peak area of ​​condensed tannins of each degree of polymerization is the largest and has a significant difference from other sample loading amounts. This indicates that solid phase extraction with a sample loading amount of 5 mL can extract condensed tannins of each degree of polymerization to the maximum extent.

[0105] Additionally, it should be noted that the maximum sample loading volume for the solid-phase extraction column used in this invention is 5 mL.

[0106] Example 4

[0107] This embodiment compares and verifies the effect of the eluent volume of solid-phase extraction on the extraction results, wherein the sample loading volume is 5 mL.

[0108] In this embodiment, solid-phase extraction was performed using eluent volumes of 10 mL, 20 mL, and 30 mL, respectively. All other extraction and high-performance liquid chromatography conditions were the same as those in the experimental group in Example 1.

[0109] The peak areas of condensed tannins obtained from each of the above eluent volumes were compared by high performance liquid chromatography (HPLC) and the peak areas of condensed tannins at each degree of polymerization are shown in Figure 5.

[0110] according to Figure 5 It can be seen that when the eluent volume is 20 mL, the peak area of ​​condensed tannins of each degree of polymerization is the largest and has a significant difference from other eluent volumes. This indicates that solid phase extraction with an eluent volume of 20 mL can extract condensed tannins of each degree of polymerization to the maximum extent.

[0111] Example 5

[0112] This embodiment compares and verifies the effect of the volume ratio of acetone in the eluent on the extraction results in solid phase extraction. The sample loading volume is 5 mL and the eluent volume is 20 mL.

[0113] This embodiment specifically sets up experimental groups I, II, III, and IV. Specifically, the eluent used in experimental group I had a volume ratio of acetone, water, and acetic acid of 60:39.5:0.5; the eluent used in experimental group II had a volume ratio of acetone, water, and acetic acid of 70:29.5:0.5; the eluent used in experimental group III had a volume ratio of acetone, water, and acetic acid of 80:19.5:0.5; and the eluent used in experimental group IV had a volume ratio of acetone, water, and acetic acid of 90:9.5:0.5.

[0114] All other extraction and high-performance liquid chromatography conditions were the same as those in the experimental group in Example 1.

[0115] The peak areas of condensed tannins at different degrees of polymerization were compared by high performance liquid chromatography after the condensed tannin extracts obtained from the above eluents were analyzed. Figure 6 shows the comparison of condensed tannin peak areas at different degrees of polymerization.

[0116] according to Figure 5 It can be seen that the experimental group with a volume ratio of acetone, water and acetic acid of 80:19.5:0.5 in the eluent had the largest peak area of ​​condensed tannins of each degree of polymerization and showed significant differences from other eluents. This indicates that solid-phase extraction with the above eluent can maximize the extraction of condensed tannins of each degree of polymerization.

[0117] Example 6

[0118] Since there are no independent standards for condensed tannins at each degree of polymerization, the effectiveness of this method cannot be verified by specifically detecting the extraction and recovery rates. Therefore, this embodiment uses a linear evaluation method for verification.

[0119] This embodiment uses the same extraction and detection methods as in Example 1. The sample tested in this embodiment is a blend of six wines, specifically a blend of Merlot, Cabernet Sauvignon, and Marselan, which come from the Ningxia region.

[0120] The standard curve in this embodiment uses epicatechin as a standard, and the gradient solutions used are 0.01, 0.05, 0.25, 0.5, 1.5, 3.0, 4.0, and 5.0 mmol / L. The dilution ratios, standard equations corresponding to condensation tannins at each degree of polymerization, and R0 of the standard equations are also provided in this embodiment. 2 The limits of detection and limits of quantitation are shown in Table 2.

[0121] Table 2. Regression equations and R values ​​for condensed tannins in wine. 2 Dilution ratio, limit of detection and limit of quantitation

[0122]

[0123] As can be seen from Table 2, the method of the present invention has good detection effect when detecting condensed tannins at various degrees of polymerization.

[0124] Example 7

[0125] This embodiment measures the intraday and interday accuracy of the method to verify its stability and repeatability.

[0126] This embodiment uses the same extraction and detection methods as in Example 1, and tests were conducted on six wines. The six wines are: Merlot (W1), Merlot (W2), Cabernet Sauvignon (W3), Cabernet Sauvignon (W4), Cabernet Sauvignon (W5), and Marselan (W6); all of the above wines are from the Ningxia production area, and the two Merlots and three Cabernet Sauvignons are from different wineries.

[0127] The intraday and interday accuracy was evaluated using relative standard deviation (RSD), and the results are shown in Table 2. The intraday and interday accuracy of this method are both less than 5%, indicating that the method has good stability and repeatability and can effectively evaluate the content of condensed tannins in dry red wine.

[0128] Table 3. Intra-day and inter-day detection precision of condensed tannin extracts from 6 dry red wine samples.

[0129]

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for extracting condensed tannins in dry red wine, characterized by, First, solid-phase extraction was performed on the treated dry red wine to obtain a condensed tannin extract, and then the condensed tannin extract was analyzed by high-performance liquid chromatography. The condensed tannins include flavanol monomers, condensed tannin dimers, condensed tannin trimers, condensed tannin tetramers, condensed tannin pentamers, condensed tannin hexamers, condensed tannin heptamers, and condensed tannin octamers. The eluent for the solid-phase extraction is a mixed solution of acetone, water, and acetic acid; the volume ratio of acetone, water, and acetic acid in the mixed solution is 60-90:9.5-39.5:0.5; the condensed tannin extract contains condensed tannins with various degrees of polymerization. The volume ratio of the treated dry red wine to the eluent is 1:4; the solid phase extraction column is an Oasis HLB column; The high-performance liquid chromatography detection includes the following steps: S2-1. Perform high performance liquid chromatography on the condensed tannin extract, and determine the condensed tannin corresponding to each chromatographic peak in the chromatogram according to the retention time of each condensed tannin. The retention times of the flavanol monomers were 4.90 min, the condensed tannin dimer was 10.91 min, the condensed tannin trimer was 19.51 min, the condensed tannin tetramer was 27.00 min, the condensed tannin pentamer was 35.58 min, the condensed tannin hexamer was 40.61 min, the condensed tannin heptamer was 46.77 min, and the condensed tannin octamer was 51.24 min. S2-2, Perform the same high-performance liquid chromatography (HPLC) detection as in step S2-1 on epicatechin standard solutions with multiple concentration gradients to obtain the standard equation for epicatechin; the standard equation is a linear equation between concentration and peak area. S2-3. Substitute the peak area of ​​each condensed tannin in the chromatogram of step S2-1 into the standard equation in step S2-2 to calculate the content of each condensed tannin. The high-performance liquid chromatography detection conditions are as follows: The chromatographic column was a Develosil Diol 100 Å column with dimensions of 250 × 4.6 mm and 5 µm; the column temperature was 40℃. The fluorescence excitation wavelength is 230 nm, and the emission wavelength is 321 nm. The injection volume was 5 μL, the flow rate was 1 mL / min, and the run time was 10 min. The mobile phase includes mobile phase A and mobile phase B; mobile phase A is an acetonitrile-acetic acid solution with a volume ratio of acetonitrile to acetic acid of 98:2; mobile phase B is a mixed solution of methanol, water and acetic acid with a volume ratio of methanol, water and acetic acid of 95:3:2; the elution method is gradient elution. The gradient elution procedure is as follows: At 0 min, the volume ratio of mobile phase A to mobile phase B is 93:7; After 3 minutes, the volume ratio of mobile phase A to mobile phase B is 93:7; After 60 min, the volume ratio of mobile phase A to mobile phase B is 62.4:37.6; At 63 min, the volume ratio of mobile phase A to mobile phase B was 0:100; For 70 minutes, the volume ratio of mobile phase A to mobile phase B is 0:

100. After 76 minutes, the volume ratio of mobile phase A to mobile phase B is 93:

7.

2. The method of claim 1, wherein the condensed tannins are extracted from a dry red wine. The extraction method includes the following steps: S1-1. Centrifuge the dry red wine to remove insoluble precipitates and retain the supernatant. S1-2. The solid phase extraction column is activated sequentially with methanol and water. After activation, the packing material in the solid phase extraction column is dried. S1-3. Add the supernatant obtained in step S1 to the solid phase extraction column. After the supernatant is completely adsorbed onto the packing material, dry the packing material. S1-4. Rinse the solid-phase extraction column with distilled water; S1-5. Elute the solid-phase extraction column with the eluent and collect the eluent; S1-6. Remove acetone from the eluent, freeze-dry the remaining liquid, and then redissolve it in the simulated wine to obtain the condensed tannin extract. The simulated wine is an aqueous solution of ethanol, tartaric acid, and sodium chloride, wherein the volume percentage of ethanol is 12% of the total volume of the simulated wine, the mass ratio of tartaric acid to the volume of the simulated wine is 5 g / L, and the concentration of sodium chloride is 0.2 M sodium chloride.

3. The method for extracting condensed tannins from dry red wine according to claim 2, characterized in that, In step S1-1, the centrifugation speed is 8000 r / min and the centrifugation time is 5 min.

4. The method for extracting condensed tannins from dry red wine according to claim 2, characterized in that, The Oasis HLB cartridges are available in 3cc / 60mg form. In step S1-2, the volume of both methanol and water is 2 mL; in step S1-3, the amount of supernatant added is 5 mL; and in step S1-5, the amount of eluent used is 20 mL.

Images