Method for analyzing characteristic flavor substances in table vinegar and application thereof

Abstract

The invention provides a method for analyzing characteristic flavor substances in table vinegar and application of the method, and relates to the technical field of food flavor detection.The method comprises the steps that volatile compounds in the table vinegar are determined through comprehensive two-dimensional gas chromatography-smelling-mass spectrometry, and the characteristic flavor compounds are determined; the content of organic acid and reducing sugar in the table vinegar is determined by high performance liquid chromatography, and the content of characteristic taste compounds in the table vinegar is determined. According to the method, the volatile compounds in the table vinegar are determined by adopting comprehensive two-dimensional gas chromatography and smelling mass spectrometry, and the characteristic odor compounds are positioned and discriminated; the content of organic acid and reducing sugar in the table vinegar is determined by adopting a high performance liquid chromatograph, the content of characteristic taste compounds in the table vinegar is positioned, and discrimination is implemented. According to the method provided by the invention, the characteristic odor substances in the table vinegar can be rapidly and accurately detected, and meanwhile, the taste characteristics of the table vinegar can be objectively reflected.

Description

Technical Field

[0001] This invention relates to the field of food flavor detection technology, and in particular to a method for analyzing characteristic flavor substances in vinegar and its application. Background Technology

[0002] There are many types of vinegar, each with its own unique flavor characteristics. Flavor is a key indicator that not only influences consumer purchasing choices but also directly relates to a product's market competitiveness. Therefore, controlling the quality of vinegar during its production process requires identifying the characteristic flavor compounds within it.

[0003] For a long time, people have judged the flavor of vinegar based on their own senses. However, this judgment is often highly subjective, and the evaluation results vary considerably depending on age, experience, and other factors. Even the same person may arrive at different results due to physical condition and emotional changes. Moreover, olfactory identification involves the inhalation of volatile substances, and long-term experiments can harm human health. Furthermore, certain unpleasant odors can make evaluators particularly sensitive, leading to erroneous results. In addition, sensory evaluation often requires a large number of experienced evaluators to form an evaluation team, making the process cumbersome and the evaluation results often lack repeatability. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a method for analyzing characteristic flavor substances in vinegar and its application, which can quickly and accurately detect characteristic odor substances in vinegar, while objectively reflecting the taste characteristics of vinegar, thus achieving accurate analysis of characteristic flavor substances in vinegar.

[0005] A first aspect of the present invention provides a method for analyzing characteristic flavor compounds in vinegar, comprising: The volatile compounds in vinegar were determined by two-dimensional gas chromatography-olfactometry-mass spectrometry to identify characteristic odor compounds; the contents of organic acids and reducing sugars in vinegar were determined by high performance liquid chromatography to identify the contents of characteristic flavor compounds in vinegar. The gas chromatography conditions for the full two-dimensional gas chromatography-olfactometry-mass spectrometry are as follows: initial temperature 39~41℃, hold for 1.8~2.2 min, increase to 225~235℃ at 3~4℃ / min, hold for 5~6 min, injection port temperature 230℃, and carrier gas flow rate 1.2mL / min. The conditions for determining the content of the organic acids in vinegar by high performance liquid chromatography are as follows: Column selection: Aminex HPX-87H ion-exclusion column, 7.8 mm × 300 mm. The mobile phase was a 4.5–5.5 mmol / L sulfuric acid aqueous solution, and isocratic elution was performed. The flow rate is 0.55~0.65 mL / min; The conditions for determining the reducing sugar content in vinegar by high performance liquid chromatography are as follows: Column selection: Xbridge Amide, 4.6 mm × 150 mm, 3.5 μm. The mobile phase consists of an organic phase and an aqueous phase, with a volume ratio of (65:35) to (85:15). The organic phase is acetonitrile and triethylamine, with the triethylamine having a volume content of 0.18% to 0.22%. Gradient elution is performed. The flow rate is 0.45~0.55 mL / min.

[0006] As a preferred method, when determining volatile compounds in vinegar, the gas chromatography-mass spectrometry (GC) preparation method for vinegar samples is as follows: weigh the vinegar sample into a headspace vial, add sodium chloride and internal standard 2-methyl-3-heptanone, then place it in a metal bath of an autosampler at 55~65℃ for equilibration, use an SPME extraction head (CAR / PDMS / DVB) for adsorption, and desorb the extraction head in the injection port at 230℃.

[0007] As a preferred method, the qualitative analysis method for identifying characteristic odor compounds is as follows: the characteristic odor compounds in vinegar are identified and analyzed by combining mass spectrometry (MS), retention index (RI), olfaction (O), and standard compounds (STD). Mass spectrometry (MS) identification analysis involves matching the mass spectra of odor compounds in vinegar samples with the mass spectra of standard compounds in the NIST 17.0 library, and initially screening compounds with a matching degree ≥700. The retention index (RI) identification analysis is performed under the same instrument parameters by calculating the actual RI value of odor compounds in vinegar samples through a series of n-alkanes (C8-C25). If the difference between the actual RI value and the theoretical RI value of each odor compound is <50, it is considered retained. The olfactory (O) identification analysis utilizes the sensitivity of sensory evaluators to odor compounds. They smell the aroma compounds in the vinegar sample. While separating the volatile compounds in the vinegar sample in a two-dimensional gas phase, the olfactory evaluators smell the odor and record the smelling time, odor and intensity. The odor characteristics are then compared with those reported in the literature to further identify the aroma compounds in the vinegar sample. Standard compound (STD) identification analysis involves diluting a standard compound and injecting it under the same instrument parameters. The peak times of the standard compound and the corresponding compound in the sample are compared to determine the odor compounds in the vinegar sample.

[0008] Preferably, the mass spectrometry of the two-dimensional gas chromatography-olfactometry-mass spectrometry uses an electron impact ion source with an electron energy of 70 eV, an ion source temperature of 230℃, and a mass spectrometry scanning range of 15-300 m / z.

[0009] Preferably, the mass spectrometry parameters of the two-dimensional gas chromatography-olfactometry-mass spectrometry are as follows: electron impact ion source, electron energy of 70 eV, ion source temperature of 230℃, mass spectrometry scan range of 15-300 m / z, quadrupole temperature of 150℃, transfer line temperature of 280℃, and solvent delay of 4 min.

[0010] Preferably, the olfactometer conditions for the two-dimensional gas chromatography-olfactometer-mass spectrometry are as follows: the vinegar sample enters the capillary column through the injection port, enters the olfactometer in proportion through the splitter, and passes through pure water, resulting in humid air to ensure that the nose does not dry out during olfactometer use; the column temperature is set to 250°C.

[0011] Preferably, the conditions for determining the content of organic acids in vinegar by high performance liquid chromatography are as follows: Detector: Ultraviolet detector; Column selection: Aminex HPX-87H ion-exclusion column, 7.8 mm × 300 mm. The mobile phase was a 5 mmol / L sulfuric acid aqueous solution, and isocratic elution was performed. The flow rate was 0.6 mL / min. The column temperature is set to 30℃. The wavelength of the ultraviolet detector is 215 nm.

[0012] Preferably, the conditions for determining the reducing sugar content in vinegar by high performance liquid chromatography are as follows: Detector: Evaporative light scattering detector, Column selection: Xbridge Amide, 4.6 mm × 150 mm, 3.5 μm. The mobile phase consists of an organic phase and an aqueous phase. The organic phase is acetonitrile and triethylamine, with the triethylamine having a volume content of 0.2% in the organic phase. Gradient elution is performed. The flow rate was 0.5 mL / min. The column temperature is set to 35℃.

[0013] As a preferred method, when determining the content of organic acids and reducing sugars in vinegar, the liquid phase preparation method of the sample is as follows: vinegar and water are mixed in a volume ratio of 1:(8~10) to obtain a mixed solution.

[0014] Preferably, the gradient elution procedure is as follows: .

[0015] Preferably, the isocratic elution time is 30 min.

[0016] Preferably, the gradient elution time is 20 min.

[0017] As a preferred embodiment, a method for analyzing characteristic flavor compounds in vinegar includes: The volatile compounds in vinegar were determined by two-dimensional gas chromatography-olfactometry-mass spectrometry to identify characteristic odor compounds; the contents of organic acids and reducing sugars in vinegar were determined by high performance liquid chromatography to identify the contents of characteristic flavor compounds in vinegar. The gas chromatography conditions for the two-dimensional gas chromatography-olfactometry-mass spectrometry are as follows: initial temperature 39~41℃, hold for 1.8~2.2 min, increase to 225~235℃ at 3~4℃ / min, hold for 5~6 min, injection port temperature 230℃, carrier gas is helium, and carrier gas flow rate is 1.2 mL / min. The conditions for determining the content of the organic acids in vinegar by high performance liquid chromatography are as follows: Detector: Ultraviolet detector; Column selection: Aminex HPX-87H ion-exclusion column, 7.8 mm × 300 mm. The mobile phase was a 5 mmol / L sulfuric acid aqueous solution, and isocratic elution was performed. The flow rate was 0.6 mL / min. The column temperature is set to 30℃. The ultraviolet detector has a wavelength of 215 nm; The conditions for determining the reducing sugar content in vinegar by high performance liquid chromatography are as follows: Detector: Evaporative light scattering detector, Column selection: Xbridge Amide, 4.6 mm × 150 mm, 3.5 μm. The mobile phase consists of an organic phase and an aqueous phase. The organic phase is acetonitrile and triethylamine, with the triethylamine having a volume content of 0.2% in the organic phase. Gradient elution is performed. The flow rate was 0.5 mL / min. The column temperature is set to 35℃.

[0018] In a second aspect, the present invention provides the application of the above-described method for analyzing characteristic flavor substances in vinegar in the identification of vinegar.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows: Vinegar contains a wide variety of flavor compounds, so simply using instruments or sensory evaluation is not enough to identify its characteristic flavor compounds. Considering that vinegar is a food product, this invention combines instrumental analysis results with human sensory evaluation to provide a method for identifying the characteristic flavor compounds in vinegar.

[0020] Two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) is a novel chromatographic analysis technique developed based on traditional gas chromatography-mass spectrometry (GC-MS). Its main principle involves connecting two independent chromatographic columns with different separation mechanisms in series. A modulator in the middle concentrates and aggregates components that are not fully separated in the first dimension (co-distillates), releasing them in periodic pulses into the second column for further separation, achieving orthogonal separation. Due to its high resolution, high sensitivity, and peak capacity, GC×GC has been widely used to analyze volatile compounds in various foods. Compared to 1D-GC, GC×GC effectively improves the separation degree and identification accuracy of volatile compounds in food, with an identification capability 2-3 times that of 1D-GC.

[0021] Furthermore, two-dimensional gas chromatography-olfactometry (GC-O / GC-O-MS) is combined with olfactometry. Since the frequency of two-dimensional gas chromatography is too fast for olfactometry, it is switched to one-dimensional gas chromatography for olfactometry. GC-O / GC-O-MS measurements are performed by the human nose, with a human respiratory cycle of approximately 3-5 seconds and a compound recognition time of 700 milliseconds. The peak width of volatile compounds in GC×GC is approximately 30 to 140 milliseconds. Therefore, in practical applications, olfactometry cannot be directly connected to GC×GC-MS for analysis. By using a constant gas supply technique, the two-dimensional gas chromatography is switched to one-dimensional gas chromatography, enabling olfactometry. Therefore, this invention employs a switchable, fully two-dimensional gas chromatography-olfactometry-mass spectrometry (GC-O / GC-O-MS) technique, which can significantly improve the identification capability of aroma compounds, thereby facilitating quality control of food production and storage processes based on flavor analysis. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 Radar graphs of the nine sensory characteristics of vinegar in Examples 1-9.

[0024] Figure 2 Radar graphs showing the taste of vinegar based on nine sensory characteristics in Examples 1-9.

[0025] Figure 3 This is a heatmap showing the clustering of volatile compounds. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0028] Example 1 Methods for analyzing characteristic aroma compounds and taste in vinegar The vinegar used in this embodiment is Cangzhou rice vinegar, denoted as CZ. 1. Sensory evaluation analysis A sensory evaluation team of 20 trained personnel (10 men and 10 women, aged 22-25, all from Beijing Technology and Business University) was selected to smell and taste CZ, collecting sensory descriptive terms. Based on the statistical results, sensory terms appearing more than 10% of the total were used for subsequent sensory analysis. Finally, acetic acid, alcohol, fermentation, smokiness, bran, fruit, floral, herbal, and sour, sweet, bitter, astringent, salty, umami, mellow, and soy sauce aromas were selected as sensory descriptive terms for the sensory evaluation of nine vinegar samples. The scoring standard was 0-10, where 0 indicates no odor, 2 indicates a very weak odor, 4 indicates a weak odor, 6 indicates a moderate odor, 8 indicates a strong odor, and 10 indicates a very strong odor. To minimize unnecessary interference from other factors and ensure the validity and independence of the results, the sensory evaluators were not allowed to eat within one hour before the sensory evaluation, and there was no communication between the evaluators during the sensory evaluation process.

[0029] 2. Analysis of volatile compounds in vinegar using two-dimensional gas chromatography-olfactometry (GC×GC-O-MS). Weigh 3 g of vinegar sample into a headspace vial, add 1 g of sodium chloride and 1 μL of internal standard (2-methyl-3-heptanone, concentration 0.816 μg / μL), tighten the cap, and place the vial in the metal bath of a 60℃ autosampler for equilibration for 20 min. Use an SPME extraction head (CAR / PDMS / DVB) for adsorption for 40 min, and then desorb the extraction head in the injection port at 230℃ for 5 min.

[0030] The gas chromatography conditions for GC×GC-O-MS were as follows: initial temperature 40℃, held for 2 min, increased to 230℃ at 4℃ / min, held for 5 min, injection port temperature 230℃, helium as carrier gas, and carrier gas flow rate 1.2 mL / min. Mass spectrometry used an electron impact ion source with an electron energy of 70 eV, an ion source temperature of 230℃, and a mass spectrometry scan range of 15–300 m / z.

[0031] The mass spectrometry parameters for GC×GC-O-MS were as follows: electron impact ion source, energy 70 eV, ion source temperature 230℃, quadrupole temperature 150℃, transfer line temperature 280℃, and solvent delay 4 min.

[0032] The olfactory settings for the GC×GC-O-MS are as follows: the sample enters the capillary column through the injection port, passes through a splitter to the olfactory device in a specific ratio, and then passes through a purified water bottle, resulting in humid air to prevent the nose from drying out during olfaction. The column temperature is set to 250℃.

[0033] The odor compounds in CZ were identified and analyzed using a combination of mass spectrometry (MS), retention index (RI), olfaction (O), and standard compound (STD) methods. Specifically: (1) First, the mass spectra of the odor compounds in the sample are matched with the mass spectra of the standard compounds in the NIST 17.0 library, and the compounds with a matching degree ≥700 are initially screened.

[0034] (2) Secondly, under the same instrument parameters, the actual RI value of the odor compound in the sample is calculated by the n-alkanes (C8-C25). The difference between the actual RI value and the theoretical RI value of each odor compound is <50 and is retained.

[0035] (3) Then, using the sensory evaluation personnel’s sensitivity to odor compounds, the aroma compounds in the sample are smelled. That is, while the volatile compounds in the sample are separated in the full two-dimensional gas phase, the smellers smell the odor and record the smelling time, odor and intensity and compare it with the odor characteristics reported in the literature, and then the aroma compounds in the sample are qualitatively identified again.

[0036] (4) Finally, for aroma compounds that have not been accurately identified by the above qualitative methods, the standard compound is diluted 1000 times and injected under the same instrument parameters. The peak time of the standard compound is compared with the peak time of the compound in the sample, and the odor compounds in the sample are finally qualitatively analyzed.

[0037] 3. Determination of organic acid content in vinegar by high performance liquid chromatography (HPLC) The vinegar sample was diluted 10 times and centrifuged at 10,000 r / min for 5 min. The supernatant was collected, and the filtrate was filtered through a 0.22 μm filter membrane before HPLC analysis.

[0038] Table 1 High Performance Liquid Chromatography Conditions

[0039] 4. Determination of reducing sugar content in vinegar by high performance liquid chromatography (HPLC) Dilute the vinegar sample 10 times, centrifuge at 10000 r / min for 5 min, take the supernatant, filter the filtrate through a 0.22 μm filter membrane and then perform the test.

[0040] Table 2 High Performance Liquid Chromatography Conditions

[0041] The gradient elution procedure in Table 2 is shown in Table 3 below.

[0042] Table 3 Elution Procedure for Determination of Reducing Sugar Content by High Performance Liquid Chromatography

[0043] Example 2 Methods for analyzing characteristic aroma compounds and taste in vinegar The method is the same as in Example 1, except that the vinegar sample used is Sanhe rice vinegar, denoted as SH; Example 3 Methods for analyzing characteristic aroma compounds and taste in vinegar The method is the same as in Example 1, except that the vinegar sample used is Baoning vinegar, denoted as BN; Example 4 Methods for analyzing characteristic aroma compounds and taste in vinegar The method is the same as in Example 1, except that the vinegar sample used is Donghu vinegar, denoted as DH; Example 5 Methods for analyzing characteristic aroma compounds and taste in vinegar The method is the same as in Example 1, except that the vinegar sample used is Tianli Duliu aged vinegar, denoted as TLDL; Example 6 Methods for analyzing characteristic aroma compounds and taste in vinegar The method is the same as in Example 1, except that the vinegar sample used is Yongchun aged vinegar (acidity of 6.5°), denoted as YC1; Example 7 Methods for analyzing characteristic aroma compounds and taste in vinegar The method is the same as in Example 1, except that the vinegar sample used is Yongchun aged vinegar (acidity of 9.5°), denoted as YC2; Example 8 Methods for analyzing characteristic aroma compounds and taste in vinegar The method is the same as in Example 1, except that the vinegar sample used is Zhenjiang vinegar, denoted as ZJXC; Example 9 Methods for analyzing characteristic aroma compounds and taste in vinegar The method is the same as in Example 1, except that the vinegar sample used is Zhenjiang fragrant vinegar (premium grade), denoted as ZJZP.

[0044] 1. Sensory evaluation results analysis of vinegar Figure 1 and Figure 2 These are radar charts of the aroma and taste of vinegar, respectively. The axes in the radar charts indicate the intensity of the sensory flavor, a value obtained by sensory evaluators. Figure 1 and Figure 2 This indicates that the overall scores of the nine vinegars differed in sensory evaluation. In comparison, CZ vinegar exhibited a pronounced acetic acid aroma, but its floral and alcoholic notes were the weakest; SH vinegar had the weakest herbal aroma; BN vinegar had the strongest fermented aroma; DH vinegar had the most prominent smoky aroma; TLDL vinegar had a relatively strong bran aroma; YC1 had the lowest scores in smoky, fermented, and herbal aromas; YC2 had the strongest alcohol aroma; ZJXC had a relatively high score in herbal aroma; and ZJZP had the lowest score in alcohol aroma and a relatively high score in bran aroma. During tasting, CZ and SH vinegars showed similar characteristics, with neither saltiness nor astringency being prominent; DH had the most pronounced bitterness; TLDL had the strongest sweetness; YC1 had the most pronounced sourness; YC2 had the strongest mellow aroma; ZJXC had the weakest bitterness; and ZJZP had a relatively strong sourness.

[0045] 2. Analysis of key volatile compounds in vinegar Figure 3 The heatmaps for volatile compounds in Examples 1-9 provide a visual comparison of the differences in volatile compounds among different samples. Each row in the heatmap represents a sample, and each column represents the relative content of the same volatile compound in different samples. The graphs allow observation of the differences in volatile compound content among various types of vinegar and among different types of vinegar.

[0046] 3. Relative Odor Activity Value (r-OAV) Analysis The flavor contribution of volatile compounds depends not only on their concentration but also on their olfactory threshold. Therefore, the relative odor activity value (r-OAV) is used as a reasonable indicator to evaluate their contribution to the flavor of the sample. Based on the calculation results of r-OAV, the contribution of different aroma compounds to the overall aroma of the sample can be assessed. The larger the r-OAV value, the greater the contribution of the compound to the aroma of the sample. A total of 31 compounds were detected in nine vinegar samples. The r-OAV was calculated based on their olfactory thresholds, and the results are shown in Table 4.

[0047] Combination Figure 3 Table 4 analyzes the volatile compounds and r-OAV of vinegar: (1) Among the volatile compounds that contribute significantly to the aroma of CZ vinegar are phenethyl alcohol, 2,3-butanedione, isoamyl acetate, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, phenylacetaldehyde, 4-ethylguaiacol, 2,4,5-trimethyloxazole, and ethyl 3-methylthiopropionate. Among these, phenethyl alcohol, 2,3-butanedione, acetoin, and 4-ethylguaiacol have relatively high contents.

[0048] (2) Among the volatile compounds, the ones that contribute significantly to the aroma of SH vinegar are phenylethanol, 2,3-butanedione, isoamyl acetate, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, phenylacetaldehyde, 4-ethylguaiacol, furfural, and 3-methylthiopropanol. Among these, 3-methylthiopropanol, phenylethanol, and acetoin are present in relatively high amounts.

[0049] (3) Among the volatile compounds, the ones that contribute most to the aroma of BN vinegar are phenylethanol, 2,3-butanedione, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, phenylacetaldehyde, 4-ethylguaiacol, and furfural. Among these, furfural, phenylacetaldehyde, acetoin, and 4-ethylguaiacol have relatively high contents.

[0050] (4) Among the volatile compounds, the ones that contribute significantly to the aroma of DH vinegar are phenylethanol, 2,3-butanedione, isoamyl acetate, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, phenylacetaldehyde, 4-ethylguaiacol, furfural, and 3-methylcyclopentane-1,2-dione. Among these, phenylacetaldehyde and acetoin are present in relatively high amounts.

[0051] (5) Among the volatile compounds, the ones that contribute significantly to the vinegar-like aroma of TLDL are phenylethanol, 2,3-butanedione, isoamyl acetate, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, phenylacetaldehyde, furfural, methyl nonyl ketone, and isovaleric acid. Isovaleric acid has the highest content.

[0052] (6) Among the volatile compounds, the ones that contribute most to the vinegar-like aroma of YC1 are phenylethanol, 2,3-butanedione, isoamyl acetate, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, 4-ethylguaiacol, and ethyl 2-methylpropionate. Among them, isoamyl acetate, phenethyl acetate, phenylethanol, and acetoin have relatively high contents.

[0053] (7) Among the volatile compounds that contribute significantly to the aroma of YC2 vinegar, phenethyl alcohol, 2,3-butanedione, isoamyl acetate, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, 4-ethylguaiacol, 2,4,5-trimethyloxazole, furfural, ethyl phenylacetate, ethyl 2-methylpropionate, and methyl nonyl ketone are present in relatively high amounts.

[0054] (8) Among the volatile compounds that contribute significantly to the aroma of ZJXC vinegar, phenethyl alcohol, 2,3-butanedione, isoamyl acetate, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, phenylacetaldehyde, 4-ethylguaiacol, ethyl 3-methylthiopropionate, furfural, and diethyl succinate are the most abundant.

[0055] (9) Among the volatile compounds that contribute significantly to the aroma of ZJZP vinegar, phenethyl alcohol, 2,3-butanedione, isoamyl acetate, tetramethylpyrazine, ethyl acetate, phenethyl acetate, acetoin, phenylacetaldehyde, ethyl 3-methylthiopropionate, furfural, diethyl succinate, and ethyl 2-methylpropionate are present in relatively high amounts.

[0056] Table 4. Relative Odor Activity Values ​​(r-OAV) of Volatile Compounds

[0057] In Table 4, nd indicates that it was not detected.

[0058] 4. Analysis of organic acid and reducing sugar content in vinegar Table 5 shows the contents of organic acids and reducing sugars in Examples 1-9. The differences in the contents of organic acids and reducing sugars among different samples can be compared by significance analysis. Different letters in the same row of the table indicate that there are significant differences in the contents of organic acids and reducing sugars among different samples (p<0.05).

[0059] Table 5. Content of organic acids and reducing sugars in vinegar (μg / mL)

[0060] In Table 5, the content results are expressed as “mean ± standard deviation”; different letter labels indicate that the same index differs significantly between different samples (p<0.05).

[0061] Table 5 shows that CZ vinegar has a high content of maltotriose; SH vinegar has high levels of tartaric acid, citric acid, maltotriose, and maltose; BN vinegar has high levels of tartaric acid, malic acid, lactic acid, fructose, maltotriose, and maltose; DH vinegar is mainly characterized by high levels of malonic acid and oxalic acid; TLDL vinegar has high levels of malic acid, malonic acid, pyruvic acid, maltose, and glucose; YC1 vinegar has a high content of malonic acid; YC2 vinegar has high levels of malonic acid and citric acid; ZJXC vinegar has a high maltose content; and ZJZP vinegar has high levels of tartaric acid, malonic acid, oxalic acid, and maltose.

[0062] In summary, this invention provides a method for analyzing the characteristic flavor of vinegar, using sensory evaluation to obtain an objective evaluation grade; using GC×GC-O-MS to determine the volatile compounds in vinegar and the differences in the types and contents of volatile compounds in different samples; and combining qualitative and quantitative analysis of flavor substances (organic acids, reducing sugars) to achieve a comprehensive scientific evaluation and identification of the flavor of vinegar.

[0063] This invention provides a method for analyzing characteristic flavor compounds in vinegar. It employs sensory evaluation of the vinegar's aroma and taste, combining this with a sensory evaluation radar chart to determine the vinegar's sensory evaluation level. Two-dimensional gas chromatography-olfactometry (GC-MS / GC-MS) is used to determine volatile compounds in the vinegar, locating characteristic aroma compounds for identification. High-performance liquid chromatography (HPLC) is used to determine the content of organic acids and reducing sugars in the vinegar, locating the content of characteristic flavor compounds for identification. The method provided by this invention can rapidly and accurately detect characteristic aroma compounds in vinegar, while objectively reflecting the vinegar's flavor characteristics.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of analyzing a characteristic flavor substance in a food vinegar, characterized by, The application relates to a method for determining characteristic flavor and odor compounds in vinegar. The method comprises the following steps: determining characteristic odor compounds in vinegar by full two-dimensional gas chromatography-olfactometry-mass spectrometry; determining the content of characteristic flavor compounds in vinegar by high performance liquid chromatography; the gas chromatography conditions of the full two-dimensional gas chromatography-olfactometry-mass spectrometry are as follows: initial temperature 39-41 DEG C, holding for 1.8-2.2 min, increasing to 225-235 DEG C at a rate of 3-4 DEG C / min, holding for 5-6 min, injection port temperature 230 DEG C, and carrier gas flow rate 1.2 mL / min; the conditions for determining the content of the organic acid in vinegar by high performance liquid chromatography are as follows: the chromatographic column is selected as Aminex HPX-87H ion exclusion chromatographic column, 7.8 mm*300 mm, the mobile phase is 4.5-5.5 mmol / L sulfuric acid aqueous solution, and isocratic elution is carried out, the flow rate is 0.55-0.65 mL / min; the conditions for determining the content of the reducing sugar in vinegar by high performance liquid chromatography are as follows: the chromatographic column is selected as Xbridge Amide, 4.6 mm*150 mm, 3.5 mu m, the mobile phase is composed of an organic phase and an aqueous phase, the volume ratio of the organic phase to the aqueous phase is (65:35)-(85:15), the organic phase is acetonitrile and triethylamine, the volume content of the triethylamine in the organic phase is 0.18%-0.22%, and gradient elution is carried out, 2. The method of claim 1, wherein the characteristic flavoring substance in the vinegar is analyzed, characterized in that, the flow rate is 0.45-0.55 mL / min.

3. The method of analyzing a characteristic flavor substance in a food vinegar according to claim 1 or 2, characterized by, When the volatile compounds in vinegar are determined, the gas chromatography-mass spectrometry preparation method of the vinegar sample is as follows: vinegar samples are weighed in a headspace bottle, sodium chloride and an internal standard 2-methyl-3-heptanone are added, then the headspace bottle is placed in a 55-65 DEG C automatic injector metal bath for balance, a SPME extraction head is adsorbed, and the extraction head is desorbed in an injection port at 230 DEG C. The qualitative analysis method for determining the characteristic odor compounds is as follows: the characteristic odor compounds in vinegar are identified and analyzed by combining mass spectrometry, retention index, olfaction and standard compounds; the mass spectrometry identification and analysis is carried out by matching the mass spectrometry spectrum of the odor compounds in the vinegar sample with the mass spectrometry structure information of standard compounds in the NIST 17.0 spectrum library, and compounds with a matching degree greater than or equal to 700 are initially screened; the retention index identification and analysis is carried out by calculating the actual RI value of the odor compounds in the vinegar sample under the same instrument parameter conditions through normal C8-C25 series alkanes, and the difference between the actual RI value and the theoretical RI value of each odor compound is less than 50, that is, retention; the olfaction identification and analysis is carried out by using the sensitivity of sensory evaluation personnel to odor compounds, olfaction is carried out on the aroma compounds in the vinegar sample, the odor compounds in the vinegar sample are separated by full two-dimensional gas chromatography, at the same time, the olfaction personnel smell the odor and record the olfaction time, odor and intensity, and compare them with the odor characteristics reported in the literature, and the aroma compounds in the vinegar sample are qualitatively analyzed again. The standard compound identification analysis is performed by injecting the sample after dilution with a standard compound under the same instrument parameters, comparing the peak time of the standard compound with the peak time of the compound in the vinegar sample, and finally qualitatively analyzing the odor compounds in the vinegar sample.

4. The method of analyzing a characteristic flavor substance in a food vinegar according to claim 1 or 3, characterized by, The mass spectrometry parameters of the comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry are as follows: electron impact ion source, electron energy of 70 eV, ion source temperature of 230 DEG C, mass spectrometry scanning range of 15-300 m / z, quadrupole temperature of 150 DEG C, transmission line temperature of 280 DEG C, and solvent delay of 4 min.

5. The method of analyzing a characteristic flavor substance in a food vinegar according to claim 1 or 4, characterized in that, The olfactometry instrument conditions of the comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry are as follows: the vinegar sample enters the capillary chromatographic column through the inlet, enters the olfactometry instrument through the proportioner according to the proportion, and passes through pure water, and the humid air is discharged to ensure that the nose is not dry during olfaction, and the chromatographic column temperature is set to 250 DEG C.

6. The method of analyzing a characteristic flavor substance in a food vinegar according to claim 1 or 5, characterized by, The conditions for determining the content of the organic acid in the vinegar by the high performance liquid chromatography are as follows: Detector: ultraviolet detector; Chromatographic column selection: Aminex HPX-87H ion exclusion chromatographic column, 7.8 mm*300 mm, The mobile phase is 5 mmol / L sulfuric acid aqueous solution, and isocratic elution is performed, The flow rate is 0.6 mL / min, The column temperature is set to 30 DEG C, and the ultraviolet detector wavelength is 215 nm.

7. The method of analyzing a characteristic flavor substance in a food vinegar according to claim 1 or 6, characterized by, The conditions for determining the content of the reducing sugar in the vinegar by the high performance liquid chromatography are as follows: Detector: evaporative light scattering detector, Chromatographic column selection: Xbridge Amide, 4.6 mm*150 mm, 3.5 um, The mobile phase is composed of an organic phase and an aqueous phase, the organic phase is acetonitrile and triethylamine, the volume content of the triethylamine in the organic phase is 0.2%, gradient elution is performed, the flow rate is 0.5 mL / min, and the column temperature is set to 35 DEG C.

8. The method of analyzing a characteristic flavor substance in a food vinegar according to claim 1 or 7, characterized by, When the content of the organic acid and the reducing sugar in the vinegar is determined, the liquid phase preparation method of the sample is as follows: the mixed solution is obtained by mixing the vinegar and water in a volume ratio of 1:(8-10).

9. The method of analyzing a characteristic flavor substance in a food vinegar according to claim 1 or 8, characterized in that, The gradient elution program is as follows: 。 10. The use of the method for analyzing the characteristic flavor substances in vinegar according to any one of claims 1-9 in the identification of vinegar.

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