Method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor

Abstract

The present invention discloses a method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor, and belongs to the technical field of carbon isotope analysis. In order to simplify the detection operation and ensure the accuracy of the result, the present invention uses the dynamic relationship between ethanol, caproic acid and ethyl caproate in the esterification hydrolysis equilibrium reaction to provide a method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor, comprising: determining the original ethyl caproate δ 原 13 C; react ethanol, caproic acid and ethyl caproate in the liquor to be tested, and determine the δ of ethyl caproate after the reaction 后 13 C; through δ 原 13 C and δ 后 13 The standard deviation of C can be used to judge whether ethanol, caproic acid and / or ethyl caproate are added exogenously. The method of the present invention only detects the δ of ethyl caproate before and after the reaction. 13 C, small workload, not dependent on "real liquor samples", greatly simplifies the detection operation, and the results are accurate and reliable.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon isotope analysis and specifically relates to a method for 13 C. Hexanoic acid delta 13 C, ethyl hexanoate δ 13 C. A method for detecting whether exogenous caproic acid, ethanol, or ethyl caproate is added to liquor. Background Art

[0002] Liquor is obtained by fermentation and distillation of one or more grains, of which more than 98% are water and ethanol, while the remaining less than 2% of trace components determine the flavor and quality of liquor, which are collectively referred to as flavor substances. Driven by the pursuit of illegal profits, in recent years, there have been frequent incidents of exogenously added liquor impersonating solid-state fermented high-quality liquor, which has seriously damaged the legitimate rights of consumers and the brand reputation of regular enterprises. Therefore, the current liquor identification field urgently needs to establish an effective detection method for exogenous additives in liquor.

[0003] CN105445429A and CN105424897A disclose a method for detecting exogenously added ethyl caproate in liquor. Both methods utilize the delta-stable relationship between the target compound (ethyl caproate or ethyl lactate) in liquor and the internal standard (n-propanol). 13 The average difference and standard deviation of C values ​​were used to determine whether ethyl caproate or ethyl lactate was added exogenously. Before judging the sample to be tested, the δ 13 C value, and then calculate the average difference and standard deviation as the judgment standard. The accuracy of the judgment results of the tested samples depends on the authenticity of the real liquor samples, that is, it depends on the authenticity of the "real base liquor of newly produced distilled liquor without additives collected from traditional liquor production enterprises". The collection and detection of real liquor is similar to establishing a database, which requires a lot of work, and when the real liquor samples are not necessarily authentic, these methods will be limited. Summary of the invention

[0004] In view of the problems of the prior art, the present invention simplifies the detection operation and ensures the accuracy of the detection result. By utilizing the mutual influence and interaction of ethanol, caproic acid and ethyl caproate in the esterification hydrolysis equilibrium reaction, a method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor is provided, which comprises the following steps:

[0005] A. Determination of the original ethyl hexanoate δ in the liquor to be tested 原 13 C;

[0006] B. Make the ethanol, caproic acid and ethyl caproate in the liquor to be tested react, and measure the δ of ethyl caproate after the reaction. 后 13 C;

[0007] C. Calculate the original ethyl hexanoate δ 原 13 C and ethyl hexanoate after reaction δ 后 13 C; if the standard deviation STD≤0.3‰, it means that no ethanol, hexanoic acid and ethyl hexanoate are exogenously added to the tested liquor; if the standard deviation STD>0.3‰, it means that at least one of ethanol, hexanoic acid and ethyl hexanoate is exogenously added to the tested liquor.

[0008] Among them, in the above method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor, the liquor to be tested is a Luzhou-flavor liquor.

[0009] Among them, in the above method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor, in step B, concentrated sulfuric acid is used as a catalyst to catalyze the reaction of ethanol, caproic acid and ethyl caproate in the liquor to be tested.

[0010] Among them, in the above-mentioned method for detecting exogenously added caproic acid, ethanol, and ethyl caproate in liquor, in step B, concentrated sulfuric acid is slowly dripped into the liquor to be tested under vortex oscillation conditions, and the volume ratio of the liquor to be tested to the concentrated sulfuric acid is controlled to be 1:0.13-0.14.

[0011] Among them, in the above method for detecting exogenously added caproic acid, ethanol, and ethyl caproate to liquor, in step B, the liquor to be tested is placed in a water bath at 38-42°C until the reaction reaches dynamic equilibrium.

[0012] Among them, in the above-mentioned method for detecting exogenously added caproic acid, ethanol, and ethyl caproate in liquor, in step B, after the reaction is completed, the system is cooled to room temperature, water and a water-insoluble organic solvent are added to the system for extraction, the system is allowed to stand and the layers are separated to obtain the organic phase, which is used to determine the stable carbon isotope value of ethyl caproate after the reaction.

[0013] Among them, in the above method for detecting exogenously added caproic acid, ethanol, and ethyl caproate in liquor, during extraction, the amount of water used is to dilute the system to an ethanol concentration of 10-15 Vol%; the amount of the water-insoluble organic solvent used is 40-60% of the volume of the liquor to be tested.

[0014] Beneficial effects of the present invention:

[0015] The present invention utilizes the mutual influence and interaction relationship between ethanol, caproic acid and ethyl caproate in liquor in the esterification hydrolysis equilibrium reaction to compare the δ 13 The standard deviation of C value is used to judge whether ethanol, caproic acid and / or ethyl caproate are added to the liquor. The method of the present invention directly detects and calculates the δ of ethyl caproate before and after the reaction. 13The C value standard deviation is used for judgment, and there is no need to detect other sample substances, so the workload is small and it does not rely on "real liquor samples", which greatly simplifies the detection operation. The test results are accurate and reliable, providing new ideas for liquor identification research. DETAILED DESCRIPTION

[0016] Specifically, the method for detecting exogenously added caproic acid, ethanol, and ethyl caproate in liquor comprises the following steps:

[0017] A. Determination of the original ethyl hexanoate δ in the liquor to be tested 原 13 C;

[0018] B. Make the ethanol, caproic acid and ethyl caproate in the liquor to be tested react, and measure the δ of ethyl caproate after the reaction. 后 13 C;

[0019] C. Calculate the original ethyl hexanoate δ 原 13 C and ethyl hexanoate δ after reaction 后 13 C; if the standard deviation STD≤0.3‰, it means that no ethanol, hexanoic acid and ethyl hexanoate are exogenously added to the tested liquor; if the standard deviation STD>0.3‰, it means that at least one of ethanol, hexanoic acid and ethyl hexanoate is exogenously added to the tested liquor.

[0020] In liquor, ethanol is the main substance, and ethyl hexanoate and hexanoic acid are the main flavor substances. In the absence of exogenous addition, ethanol, ethyl hexanoate, and hexanoic acid are all derived from the fermentation metabolism of brewing raw materials by microorganisms. Their stable isotopes (ethanol δ 13 C. Hexanoic acid delta 13 C, ethyl hexanoate δ 13 C) will have a metabolic homology relationship. And in the presence of water, there is a dynamic reaction between ethanol, caproic acid, and ethyl caproate: ethanol + caproic acid ← → ethyl caproate + water, that is, in the liquor without exogenous addition, ethanol δ 13 C. Hexanoic acid delta 13 C, ethyl hexanoate δ 13 The relationship between δ C is dynamically stable. As long as ethanol, caproic acid and / or ethyl caproate are added to the liquor, this stable relationship will be destroyed. Based on this principle, the present invention accelerates the dynamic reaction and then compares the δ C of ethyl caproate before and after the reaction. 13 C, and established a method for identifying exogenous added substances in liquor.

[0021] In step B of the method of the present invention, concentrated sulfuric acid can be used as a catalyst to catalyze the dynamic reaction between ethanol, caproic acid, and ethyl caproate in the liquor to be tested. The specific operation is: put the liquor to be tested in a water bath at 38-42°C, slowly drip concentrated sulfuric acid into the liquor to be tested under vortex oscillation conditions, control the volume ratio of the liquor to be tested to the concentrated sulfuric acid to be 1:0.13-0.14, and wait until the reaction reaches dynamic equilibrium after the dripping is completed (generally 58-62 minutes).

[0022] In the method of the present invention, after the reaction is completed, the system is cooled to room temperature, water and a water-insoluble organic solvent are added to the system for extraction, and the organic phase is taken for stratification and determination of the stable carbon isotope value of ethyl hexanoate. In order to improve the extraction degree, the ethanol concentration of the water-insoluble organic solvent (normal hexane, dichloromethane, etc.) should be lower than 15% during extraction. Therefore, during extraction, the amount of water is controlled to dilute the system to an ethanol concentration of 10-15 Vol%, and then the water-insoluble organic solvent is used in an amount of 40-60% of the volume of the liquor to be tested for extraction.

[0023] In the method of the present invention, the stable carbon isotope value of ethyl hexanoate can be determined by gas chromatography-combustion-stable isotope ratio mass spectrometry using conventional methods in the art.

[0024] The present invention is further described in detail below by way of examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0025] Example 1

[0026] 1) Determination of the original ethyl caproate δ in the Luzhou-flavor liquor to be tested 原 13 C.

[0027] 2) Under vortex oscillation, slowly drop 0.66 mL of concentrated sulfuric acid into 5 mL of the sample at a rate of 1 d / s, then place in a 40°C water bath to react for 60 min. After cooling to room temperature, add 15 mL of water and 2 mL of n-hexane, vortex oscillate and extract for 2 min, let stand to separate the layers and take the supernatant.

[0028] 3) Detection of ethyl hexanoate δ after reaction 后 13 C.

[0029] A total of 10 samples of Luzhou-flavor liquor with different alcohol content and different brands (high-end, mid-to-high-end) from different wineries were tested. The experimental results are shown in Table 1.

[0030] Table 1 Experimental results

[0031]

[0032]

[0033] Table 1 shows the δ of ethyl hexanoate before and after reaction of high-end and mid-to-high-end brand Luzhou-flavor liquors with different alcohol content from different wineries 原 13 C and δ 后 13 There was no obvious difference in C, and the standard deviations STD were all less than 0.3‰, indicating that these samples had no exogenous addition of ethanol, caproic acid, or ethyl caproate.

[0034] Example 2

[0035] 1) Determine the Luzhou-flavor liquor to be tested (52% vol, ethanol δ 13 C is -14.31‰, hexanoic acid δ 13 C is -26.43‰) in the original ethyl hexanoate δ 原 13 C.

[0036] 2) Add cassava alcohol (52% vol, ethanol δ 13 C is -28.82‰), exogenous hexanoic acid (hexanoic acid δ 13 C is -34.01‰), exogenous ethyl hexanoate (ethyl hexanoate δ 13 C is -28.74‰).

[0037] 3) Under vortex oscillation conditions, slowly drop 0.66 mL of concentrated sulfuric acid into 5 mL of the sample at a speed of 1 d / s, then place in a 40°C water bath to react for 60 min. After cooling to room temperature, add 15 mL of water and 2 mL of n-hexane, vortex oscillate and extract for 2 min, let stand to separate the layers, and take the supernatant.

[0038] 4) Detection of ethyl hexanoate δ after reaction 后 13 C.

[0039] The experimental results are shown in Table 2.

[0040] Table 2 Experimental results

[0041]

[0042]

[0043] Table 2 shows that after adding different amounts of exogenous cassava alcohol, caproic acid, and ethyl caproate, the δ 后 13 In this embodiment, as the addition content of cassava alcohol, caproic acid, and ethyl caproate increases, ethyl caproate δ 原13 C and δ 后 13 The difference in C gradually becomes larger, and when the addition amount of cassava alcohol exceeds 10%, the addition amount of caproic acid exceeds 10%, and the addition amount of ethyl caproate exceeds 15%, the standard deviation is greater than 0.3‰, indicating that this method can effectively detect whether there is exogenous addition of ethanol, caproic acid, and ethyl caproate in Luzhou-flavor liquor.

Claims

1. A method for detecting exogenously added caproic acid, ethanol, and ethyl caproate in liquor, characterized in that: The following steps are involved: A. Determination of the original ethyl hexanoate δ in the liquor to be tested 原 13 C; B. Make the ethanol, caproic acid and ethyl caproate in the liquor to be tested react, and measure the δ of ethyl caproate after the reaction. 后 13 C; C. Calculate the original ethyl hexanoate δ 原 13 C and ethyl hexanoate δ after reaction 后 13 C; if the standard deviation STD≤0.3‰, it means that no ethanol, caproic acid and ethyl caproate are added to the tested liquor; if the standard deviation STD>0.3‰, it means that at least one of ethanol, caproic acid and ethyl caproate is added to the tested liquor; In step B, concentrated sulfuric acid is used as a catalyst to catalyze the reaction of ethanol, caproic acid, and ethyl caproate in the liquor to be tested; In step B, concentrated sulfuric acid is slowly added dropwise to the liquor to be tested under vortex oscillation conditions, and the volume ratio of the liquor to be tested to the concentrated sulfuric acid is controlled to be 1:0.13-0.14; In step B, the liquor to be tested is placed in a water bath at 38-42°C until the reaction reaches dynamic equilibrium.

2. The method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor according to claim 1, characterized in that: The liquor to be tested is a Luzhou-flavor liquor.

3. The method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor according to claim 1, characterized in that: In step B, after the reaction is completed, the system is cooled to room temperature, water and a water-insoluble organic solvent are added to the system for extraction, and the system is allowed to stand for stratification to obtain an organic phase for determining the stable carbon isotope value of ethyl hexanoate after the reaction.

4. The method for detecting exogenously added caproic acid, ethanol and ethyl caproate in liquor according to claim 3, characterized in that: During extraction, the amount of water used is to dilute the system to an ethanol concentration of 10-15 Vol%; the amount of the water-insoluble organic solvent used is 40-60% of the volume of the liquor to be tested.

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