Method for detecting content of ethanol in condiment

Abstract

The invention relates to the technical field of condiment analysis, in particular to a method for detecting the content of ethanol in condiments. The method for detecting the ethanol content in the condiment comprises the following steps: preparing a series of ethanol standard solutions, respectively carrying out redox reaction on the ethanol standard solutions and potassium dichromate to obtain a series of reaction standard solutions, testing the absorbance value of each reaction standard solution, and establishing a standard curve between the ethanol content and the absorbance; mixing the seasoning to be detected and Tween, and performing distillation treatment to obtain a condensate; carrying out redox reaction on the condensate and potassium dichromate to obtain a solution to be detected; and testing the absorbance value of the to-be-tested solution, and substituting the absorbance value into the standard curve to obtain the content of ethanol in the to-be-tested seasoning. According to the method, the content of ethanol can be rapidly and accurately detected, the error range is as low as + / -0.02% vol, the content of ethanol as low as 0.2 muL / mL can be detected, and the method is suitable for analysis and detection of many seasonings with low ethanol content.

Description

Technical Field

[0001] The present application relates to the technical field of condiment analysis, and in particular to a method for detecting ethanol content in condiments. Background Art

[0002] Ethanol is a common food additive that can be used not only in alcoholic beverages but also in many condiments to provide a unique flavor and taste. Many countries and regions have strict regulations on the ethanol content in food, and accurate ethanol content information is also very important to consumers.

[0003] However, unlike the detection of ethanol in alcoholic beverages, the concentration of ethanol in condiments is relatively low, and the condiments themselves have complex ingredients and different colors. How to accurately detect the ethanol content in condiments is a key issue. Summary of the invention

[0004] Based on this, the first aspect of the present application provides a method for detecting the ethanol content in a condiment, and its technical solution is as follows:

[0005] A method for detecting ethanol content in condiments comprises the following steps:

[0006] A series of ethanol standard solutions are prepared, and the solutions are respectively subjected to redox reactions with potassium dichromate to obtain a series of reaction standard solutions, and the absorbance values ​​of the reaction standard solutions are tested to establish a standard curve between ethanol content and absorbance;

[0007] Mix the seasoning to be tested and Tween, and perform distillation to obtain a condensate;

[0008] causing the condensate to undergo an oxidation-reduction reaction with potassium dichromate to obtain a solution to be tested;

[0009] The absorbance value of the solution to be tested is measured and substituted into the standard curve to obtain the ethanol content in the seasoning to be tested.

[0010] Compared with the traditional solution, this application has the following beneficial effects:

[0011] The present application establishes a method for detecting the ethanol content of condiments. The condiments to be tested are first distilled to separate the ethanol into the condensate, and Tween is added during the distillation process. On the one hand, it plays a role in defoaming during the distillation process, avoiding the foam generated during the distillation of the condiments to entrain other ingredients in the condiments to be substituted into the condensate, affecting the ethanol redox reaction or affecting the color development, causing inaccurate test results; on the other hand, using Tween for defoaming, compared with adding other defoaming agents, can also ensure the clarification of the condensate, avoiding the subsequent influence on the absorbance value, causing inaccurate test results. After the ethanol in the condiments to be tested is distilled into the condensate, the present application uses the redox reaction of ethanol and potassium dichromate, ethanol is oxidized to acetic acid, hexavalent chromium is reduced to green trivalent chromium, and then the standard curve is constructed by colorimetry to complete the quantitative detection of ethanol. The above method can quickly and accurately detect the content of ethanol, with an error range as low as ±0.02%vol, and can detect ethanol content as low as 0.2μL / mL, which is suitable for the analysis and detection of many condiments with low ethanol content. At the same time, after the oxidation reaction between ethanol and potassium dichromate, the test solution turns green, and its color stability is good, which is beneficial to the stability of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0013] Figure 1 This is a real-life diagram of the condensate of Example 1;

[0014] Figure 2 It is a real-life diagram of the condensate of Comparative Example 1;

[0015] Figure 3 This is a real-life diagram of the condensate of Comparative Example 2;

[0016] Figure 4 This is a real-life diagram of the condensate of Comparative Example 3;

[0017] Figure 5 This is a real-life diagram of the condensate of Comparative Example 4;

[0018] Figure 6 This is a real-life diagram of the condensate of Comparative Example 5;

[0019] Figure 7 This is a real-life diagram of the condensate of Comparative Example 6. DETAILED DESCRIPTION

[0020] The present application will be further described in detail below in conjunction with specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly understood.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0022] the term

[0023] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0024] In this application, "optionally", "optional" and "optional" refer to optional, that is, to any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0025] In this application, in the "first aspect", "second aspect", "third aspect", "fourth aspect", etc., the terms "first", "second", "third", "fourth", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0026] In the present application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1 to 10, indicating that t is any integer selected from the integer group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0027] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0028] In the present application, the percentage content, unless otherwise specified, refers to mass percentage for solid-liquid mixing and solid-solid mixing, and volume percentage for liquid-liquid mixing.

[0029] In this application, when it comes to percentage concentration, unless otherwise specified, it refers to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of the component.

[0030] In the present application, %(w / w) and wt% both represent weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass volume percentage.

[0031] The first aspect of the present application provides a method for detecting the ethanol content in a condiment. In one embodiment, the detection method comprises the following steps:

[0032] A series of ethanol standard solutions are prepared, and the solutions are respectively subjected to redox reactions with potassium dichromate to obtain a series of reaction standard solutions, and the absorbance values ​​of the reaction standard solutions are tested to establish a standard curve between ethanol content and absorbance;

[0033] Mix the seasoning to be tested and Tween, and perform distillation to obtain a condensate;

[0034] causing the condensate to undergo an oxidation-reduction reaction with potassium dichromate to obtain a solution to be tested;

[0035] The absorbance value of the solution to be tested is measured and substituted into the standard curve to obtain the ethanol content in the seasoning to be tested.

[0036] The above implementation method establishes a method for detecting the ethanol content of condiments. The condiments to be tested are first distilled to separate the ethanol into the condensate, and Tween is added during the distillation process. On the one hand, it plays a role in defoaming during the distillation process, avoiding the foam generated during the distillation of the condiments to entrain other ingredients in the condiments to be substituted into the condensate, affecting the ethanol redox reaction or affecting the color development color, causing inaccurate test results; on the other hand, using Tween for defoaming, compared with adding other defoaming agents, can also ensure the clarification of the condensate, avoiding the subsequent influence on the absorbance value, causing inaccurate test results. After the ethanol in the condiments to be tested is distilled into the condensate, the present application utilizes the redox reaction of ethanol and potassium dichromate, ethanol is oxidized to acetic acid, hexavalent chromium is reduced to green trivalent chromium, and then the standard curve is constructed by colorimetry to complete the quantitative detection of ethanol. The above method can quickly and accurately detect the content of ethanol, with an error range as low as ±0.02%vol, and can detect ethanol content as low as 0.2μL / mL, which is suitable for the analysis and detection of many condiments with low ethanol content. At the same time, after the oxidation reaction between ethanol and potassium dichromate, the test solution turns green, and its color stability is good, which is beneficial to the stability of the test results.

[0037] Traditional ethanol detection methods include density bottle method, alcohol meter method, gas chromatography, infrared spectroscopy, gas diffusion method, etc., among which the density bottle method requires repeated constant weight, which is time-consuming and labor-intensive; the reading of the alcohol meter in the alcohol meter method is unstable, with a minimum error of up to ±0.1%vol, a large error, poor repeatability, and a large influence of temperature on the reading, making it difficult to accurately quantify the sample to be tested with a low ethanol content, and the alcohol meter is prone to deviation during long-term use, resulting in inaccurate results; gas chromatography and infrared spectroscopy have defects such as high requirements for equipment, high requirements for the ability of detection personnel, and long detection time; although the gas diffusion method is fast in ordering, it has poor accuracy. Different from the above method, the new ethanol detection method provided by the above implementation method has good repeatability, high accuracy, few restrictions on sampling conditions, few requirements on operators, less reliance on large precision instruments, rapid redox reaction time, and good color stability of the solution to be tested after color development. It can be used for the analysis and detection of many condiments with low ethanol content and complex ingredients, with wide applicability and high sensitivity.

[0038] Optionally, the condiments to be tested include one or more of soy sauce, soy sauce crude oil, cooking wine, brine juice, oyster sauce, soybean paste and column sauce. Compared with alcoholic beverages, the above condiments to be tested have complex ingredients, different colors, and relatively low ethanol content. This embodiment can detect the ethanol content in the above condiments to be tested, and has high accuracy and stability.

[0039] Optionally, the mass volume ratio of the Tween to the seasoning to be tested is (0.04~0.16) g:100 mL.

[0040] Further, for the condiments to be tested with different solid contents, the mass of Tween added can be adjusted. When the solid content of the condiments to be tested is less than 20wt%, the mass of the Tween added to each 100mL of the condiments to be tested is 0.04g~0.08g. For example, the mass of the Tween added to each 100mL of the condiments to be tested is 0.04g, 0.05g, 0.06g, 0.07g, 0.08g. When the solid content of the condiments to be tested is greater than or equal to 20wt%, the mass of the Tween added to each 100mL of the condiments to be tested is 0.12g~0.16g. For example, the mass of the Tween added to each 100mL of the condiments to be tested is 0.12g, 0.13g, 0.14g, 0.15g, 0.16g. It can be understood that the condiments to be tested with a solid content less than 20wt% can be cooking wine, brine juice, fish juice, etc. The condiments to be tested with a solid content greater than or equal to 20wt% may be soy sauce, crude soy sauce, oyster sauce, soybean paste, column sauce, etc. The above detection method can determine the ethanol content in the condiments to be tested with a solid content of 60wt% to 70wt%.

[0041] Condiments are prone to foaming during the distillation process. If other ingredients in the condiments enter the condenser with the foam, impurities will be introduced into the condensate, which may affect the redox reaction of ethanol and cause inaccurate test results. At the same time, some condiments themselves are darker in color. If they are substituted into the condensate, they will also affect the color of the color development reaction and the absorbance value, causing inaccurate test results. In this embodiment, Tween is added during the distillation of the condiments to be tested. Through the above-mentioned improvement, it can play a role in defoaming, avoid interfering components of the redox reaction and colored components from entering the condensate, and ensure the accuracy of the test results. At the same time, using Tween for defoaming can also ensure the clarity of the condensate compared to adding other defoaming agents, avoid subsequent influences on the absorbance value, and cause inaccurate test results. Optionally, Tween can be Tween 80.

[0042] The distillation process is performed until the ethanol in the condiment to be tested is fully separated into the condensate. Whether the ethanol is fully separated into the condensate can be judged according to the theoretical content of ethanol in the condiment to be tested. On the one hand, it can be judged whether the ethanol has been fully collected according to the volume of the collected condensate. For the condiments to be tested as exemplified above, when the volume of the condensate is 80mL~100mL. For example, the volume of the condensate is 80mL, 85mL, 90mL, 95mL, 100mL. It can be judged that the distillation process is terminated. On the other hand, it can also be judged whether the ethanol has been fully collected according to the time of the distillation process. For the condiments to be tested as exemplified above, when the time of the distillation process is 2min~5min. For example, the time of the distillation process is 2min, 2.5min, 3min, 3.5min, 4min, 4.5min, 5min. It can be judged that the distillation process is terminated.

[0043] The distillation process can be carried out in a Kjeldahl nitrogen analyzer. Optionally, the distillation power in the Kjeldahl nitrogen analyzer can be set to 100%.

[0044] It can be understood that the principle of the redox reaction between the condensate and potassium dichromate is the same as the principle of the redox reaction between a series of ethanol standard solutions and potassium dichromate, that is, the redox reaction between ethanol and potassium dichromate is used, ethanol is oxidized to acetic acid, and hexavalent chromium is reduced to green trivalent chromium.

[0045] Wherein, the reaction conditions for the redox reaction between the condensate and the potassium dichromate are the same as the reaction conditions for the redox reaction between a series of the ethanol standard solutions and the potassium dichromate. Optionally, the reaction temperature is 80°C to 120°C. For example, the reaction temperature is 80°C, 90°C, 100°C, 110°C, 120°C. Optionally, the reaction time is ≥12min. At this time, the redox reaction is basically completed. For example, the reaction time is 12min, 14min, 16min, 18min, 20min.

[0046] The reaction system of the condensate and the potassium dichromate is acidic, and the reaction system of the series of the ethanol standard solutions and the potassium dichromate is acidic. To keep the reaction system acidic, this embodiment includes the step of adding an acid agent to the reaction system. Optionally, the acid agent includes sulfuric acid. Wherein, the sulfuric acid can be provided by concentrated sulfuric acid.

[0047] The initial concentration of potassium dichromate in the reaction system of the condensate is the same as the initial concentration of potassium dichromate in the reaction systems of a series of the ethanol standard solutions, and optionally, the initial concentration is 0.005 g / mL to 0.015 g / mL. For example, the initial concentration is 0.005 g / mL, 0.01 g / mL, and 0.015 g / mL.

[0048] Optionally, the concentration of ethanol in a series of ethanol standard solutions includes 0 μL / mL, 0.1 μL / mL to 0.3 μL / mL, 0.4 μL / mL to 0.6 μL / mL, 0.9 μL / mL to 1.1 μL / mL, 1.4 μL / mL to 1.6 μL / mL, and 1.9 μL / mL to 2.1 μL / mL. It can be understood that the solvent in a series of ethanol standard solutions is water.

[0049] Optionally, the wavelength for testing the absorbance value of the test solution is the same as the wavelength for testing the absorbance value of each of the reaction standard solutions, and the wavelength is 580nm~600nm. For example, the wavelength is 580nm, 590nm, and 600nm. At the above wavelengths, the absorption of trivalent chromium is relatively large, wherein trivalent chromium has a maximum absorption at a wavelength of 590nm.

[0050] This embodiment utilizes the fact that the ethanol content is proportional to the absorbance value, and constructs a standard curve by colorimetry to complete the quantitative detection of ethanol. The spectrophotometer has high precision and good accuracy, with an error range as low as ±0.02%vol, and good detection repeatability and reproducibility.

[0051] The following is further described in conjunction with specific embodiments and comparative examples. The raw materials involved in the following specific embodiments and comparative examples, unless otherwise specified, can all be commercially available, the instruments used, unless otherwise specified, can all be commercially available, and the processes involved, unless otherwise specified, are all routinely selected by those skilled in the art.

[0052] Example 1

[0053] This embodiment provides a method for detecting the ethanol content in a condiment, and the steps are as follows:

[0054] 1. Instruments and reagents

[0055] Kjeldahl nitrogen analyzer (VAP 300), UV-visible spectrophotometer (UV-1800).

[0056] Potassium dichromate, analytical grade, concentrated sulfuric acid, analytical grade, ethanol, analytical grade.

[0057] 2. Preparation of standard curve

[0058] 2.1 Preparation of ethanol standard stock solution

[0059] Take 1 mL of ethanol and add water to make up to 100 mL to obtain a standard ethanol stock solution with a concentration of 1000 μL / 100 mL.

[0060] 2.1 Preparation of a series of ethanol standard solutions

[0061] 0 mL, 0.2 mL, 0.5 mL, 1.0 mL, 1.5 mL and 2.0 mL of the ethanol standard stock solution were respectively taken and placed in 10 mL colorimetric tubes, and 1 mL of water was added to prepare a series of ethanol standard solutions with concentrations of 0 μL / mL, 0.2 μL / mL, 0.5 μL / mL, 1.0 μL / mL, 1.5 μL / mL and 2.0 μL / mL.

[0062] 2.3 Preparation of a series of reaction standard solutions

[0063] Weigh 5 g of potassium dichromate, add water to dissolve it, add 10 mL of concentrated sulfuric acid, and add water to make the volume to 100 mL to obtain an acidic potassium dichromate solution with a potassium dichromate concentration of 5 g / 100 mL.

[0064] Add 2 mL of acidic potassium dichromate solution to 10 mL colorimetric tubes containing a series of ethanol standard solutions, add water to the scale, mix well, place in a 100°C water bath to react for 15 minutes, take out and cool to room temperature to obtain a series of reaction standard solutions.

[0065] 2.4 Preparation of standard curve

[0066] A series of reaction standard solutions were placed in a spectrophotometer, and the absorbance values ​​were measured at a wavelength of 590 nm. The results are shown in Table 1. A standard curve between ethanol concentration and absorbance value was prepared.

[0067] Table 1

[0068]

[0069] Conclusion: The linear coefficient R of the standard curve 2 =0.99983, good linear relationship.

[0070] 3. Preparation of test solution

[0071] Take 100mL of the straw mushroom aged soy sauce sample and place it in a distillation tube. Add about 0.15g of Tween 80 to the distillation tube. Place the distillation tube containing the sample and Tween 80 in a Kjeldahl nitrogen analyzer for distillation. Set the distillation parameters as follows: steam power 100%, distillation time 3 minutes and 30 seconds. The content of the obtained liquid is close to 100mL. Add water to the obtained liquid to make it 100mL to obtain a condensate. See the actual picture of the condensate for details. Figure 1 , the condensate is clear and transparent.

[0072] Take 1mL of condensate in a 10mL colorimetric tube, add 2mL of the acidic potassium dichromate solution (5g / 100mL) in item 2.3, add water to the scale, mix well, place in a 100℃ water bath to react for 15min, take out and cool to room temperature to obtain the solution to be tested.

[0073] 4. Measurement and result calculation

[0074] Place the solution to be tested in a spectrophotometer, measure the absorbance value at a wavelength of 590 nm, substitute it into the standard curve under item 2.4, and obtain the concentration of ethanol in the sample to be tested.

[0075] Once the ethanol concentration in the sample is known, the alcohol content (in terms of volume ratio) in the sample can be further calculated according to formula (1), with the calculation result retaining two significant figures after the decimal point.

[0076] (1)

[0077] Where:

[0078] X represents alcohol content (by volume), in %vol;

[0079] c represents the concentration of ethanol in the sample to be tested, in moles per liter (μL / mL);

[0080] V1 represents the fixed volume of the machine: 10mL;

[0081] V2 represents the sampling volume of the condensate, in milliliters (mL).

[0082] 5 Methodological Validation

[0083] 5.1 Investigation of redox reaction time

[0084] Take 1mL of 1000μL / 100mL ethanol standard stock solution and place it in a 10mL colorimetric tube, then add 2mL of the acidic potassium dichromate solution under Item 2.3, add water to the scale, mix well, place it in a 100℃ water bath to react for 5min, 8min, 10min, 12min, 15min, and 20min, take it out and cool it to room temperature, then place it in a spectrophotometer, and measure the absorbance at a wavelength of 590nm. The results are shown in Table 2.

[0085] Table 2

[0086]

[0087] Conclusion: After 12 minutes of water bath time, the absorbance value is basically stable, indicating that the reaction is basically completed.

[0088] 5.2 Study on the color stability of the reaction standard solution

[0089] Take 0.5mL of 1000μL / 100mL ethanol standard stock solution and place it in a 10mL colorimetric tube, then add 2mL of the acidic potassium dichromate solution under Item 2.3, add water to the scale, mix well, place it in a 100℃ water bath to react for 15min, take it out and cool it to room temperature, place it for 10min, 20min, 30min, 60min, 90min, and 120min, then place it in a spectrophotometer, and measure the absorbance value at a wavelength of 590nm. The results are shown in Table 3.

[0090] Table 3

[0091]

[0092] Conclusion: The color of the reaction solution is stable within 2 hours after the heating color development reaction, and the absorbance value is stable.

[0093] 5.3 Reproducibility study

[0094] The day when 1000 μL / 100mL ethanol standard stock solution and the acidic potassium dichromate solution under item 2.3 are prepared is recorded as day 0. On day 0, 1, 4, 5, 10, and 13, 0.5mL of 1000 μL / 100mL ethanol standard stock solution is placed in a 10mL colorimetric tube, and then 2mL of the acidic potassium dichromate solution under item 2.3 is added. Water is added to the scale, and the mixture is mixed. The mixture is placed in a water bath at 100°C for reaction for 15 minutes. The mixture is taken out, cooled to room temperature, placed in a spectrophotometer, and the absorbance is measured at a wavelength of 590nm. The results are shown in Table 4.

[0095] Table 4

[0096]

[0097] Conclusion: The test results can be reproduced within 13 days, and the ethanol standard solution and acidic potassium dichromate solution did not expire within 13 days after preparation.

[0098] 5.4 Repeatability Study

[0099] Take 6 portions of 0.5 mL of 1000 μL / 100 mL ethanol standard stock solution and place them in 10 mL colorimetric tubes, then add 2 mL of the acidic potassium dichromate solution in item 2.3 to each tube, add water to the scale, mix well, place in a 100°C water bath to react for 15 minutes, take out and cool to room temperature, then place in a spectrophotometer and measure the absorbance at a wavelength of 590 nm. The results are shown in Table 5.

[0100] Table 5

[0101]

[0102] Conclusion: The same concentration of ethanol standard solution was measured 6 times with a coefficient of variation of 0.9%, indicating good repeatability.

[0103] 5.5 Recovery rate investigation

[0104] Take two portions of straw mushroom soy sauce, record them as straw mushroom soy sauce 1 and straw mushroom soy sauce 2, and prepare the test solution according to item 3. Take 1 mL of straw mushroom soy sauce 1 condensate and 1 mL of straw mushroom soy sauce 2 condensate and place them in 10 mL colorimetric tubes respectively, then add 2 mL of the acidic potassium dichromate solution in item 2.3, add water to the scale, mix well, place in a 100°C water bath to react for 15 minutes, take out and cool to room temperature, then place in a spectrophotometer, measure the absorbance at a wavelength of 590 nm, and calculate the alcohol content according to formula (1) in item 4. Repeat the redox reaction and determination 6 times for straw mushroom soy sauce 1, and repeat the redox reaction and determination 6 times for straw mushroom soy sauce 2. The results are shown in Table 6.

[0105] Add 0.5 mL of ethanol to 100 mL of straw mushroom dark soy sauce 1, and add 0.4 mL of ethanol to 100 mL of straw mushroom dark soy sauce 2, and prepare the test solution according to item 3. Take 1 mL of the condensate of the spiked straw mushroom dark soy sauce 1 and 1 mL of the condensate of the spiked straw mushroom dark soy sauce 2, and place them in 10 mL colorimetric tubes respectively, then add 2 mL of the acidic potassium dichromate solution in item 2.3, add water to the scale, mix well, place in a 100°C water bath to react for 15 min, take out and cool to room temperature, then place in a spectrophotometer, measure the absorbance at a wavelength of 590 nm, and calculate the alcohol content according to formula (1) in item 4. Repeat the redox reaction and determination 6 times for the spiked straw mushroom dark soy sauce 1, and repeat the redox reaction and determination 6 times for the spiked straw mushroom dark soy sauce 2. The results are shown in Table 6.

[0106] Table 6

[0107]

[0108] Conclusion: The recovery rate basically falls within the range of 94%~106%. The same sample was measured six times with an absolute range of ≤0.02% vol.

[0109] Comparative Example 1

[0110] This comparative example provides a method for detecting the ethanol content in a condiment, which is basically the same as Example 1, except that when preparing the test solution, Tween 80 is replaced with corn oil of equal mass. The actual picture of the obtained condensate is shown in FIG. Figure 2 .

[0111] Comparative Example 2

[0112] This comparative example provides a method for detecting the ethanol content in a condiment, which is basically the same as Example 1, except that when preparing the test solution, Tween 80 is replaced with an equal mass of tributyl phosphate. The actual picture of the obtained condensate is shown in FIG. Figure 3 .

[0113] Comparative Example 3

[0114] This comparative example provides a method for detecting the ethanol content in a condiment, which is basically the same as Example 1, except that when preparing the test solution, Tween 80 is replaced with dimethyl silicone oil of equal mass. The actual picture of the obtained condensate is shown in FIG. Figure 4 .

[0115] Comparative Example 4

[0116] This comparative example provides a method for detecting the ethanol content in a condiment, which is basically the same as Example 1, except that when preparing the test solution, Tween 80 is replaced by polydimethylsiloxane of equal mass. The actual picture of the obtained condensate is shown in FIG. Figure 5 .

[0117] Comparative Example 5

[0118] This comparative example provides a method for detecting the ethanol content in a condiment, which is basically the same as Example 1, except that when preparing the test solution, Tween 80 is replaced by polyacrylamide of equal mass. The actual picture of the obtained condensate is shown in FIG. Figure 6 .

[0119] Comparative Example 6

[0120] This comparative example provides a method for detecting the ethanol content in a condiment, which is basically the same as Example 1, except that when preparing the test solution, Tween 80 is replaced by polyvinyl alcohol of equal mass. The actual picture of the obtained condensate is shown in FIG. Figure 7 .

[0121] Conclusion: In combination with Example 1 and Comparative Examples 1 to 6, it can be seen that for the same sample to be tested, under the premise that the reaction conditions and the apparatus are unchanged, the use of different defoaming agents in the distillation process has a great influence on the color of the condensate obtained by distillation. The use of many defoaming agents is not conducive to the subsequent use of color development reaction to determine the absorbance value and thus obtain the ethanol content.

[0122] Comparative Example 7

[0123] This comparative example provides an alcohol meter method for detecting the ethanol content in condiments, and the steps are as follows:

[0124] Take the straw mushroom dark soy sauce 1 and straw mushroom dark soy sauce 2 under item 5.5, use the minimum range alcohol meter (0-6% vol) to measure the alcohol content of straw mushroom dark soy sauce 1 and straw mushroom dark soy sauce 2, and repeat the measurement 6 times for straw mushroom dark soy sauce 1 and straw mushroom dark soy sauce 2 respectively. The results are shown in Table 7.

[0125] 0.5 mL of ethanol was added to 100 mL of straw mushroom dark soy sauce 1, and 0.4 mL of ethanol was added to 100 mL of straw mushroom dark soy sauce 2. The alcohol content of the straw mushroom dark soy sauce 1 spiked sample and the straw mushroom dark soy sauce 2 spiked sample was measured using an alcohol meter with a minimum range (0-6% vol). The straw mushroom dark soy sauce 1 spiked sample and the straw mushroom dark soy sauce 2 spiked sample were measured 6 times, respectively. The results are shown in Table 7.

[0126] Table 7

[0127]

[0128] Compared with Example 1, it can be seen that even if the minimum range alcohol meter (0-6% vol) is used to measure the straw mushroom soy sauce 1 and the straw mushroom soy sauce 2, the ethanol content in the straw mushroom soy sauce 1 and the straw mushroom soy sauce 2 is too low, the alcohol meter reading is unstable, and the stability and recovery rate of the results of repeated measurements of the same sample for 6 times are poor.

[0129] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0130] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for detecting ethanol content in condiments, characterized in that: The following steps are involved: A series of ethanol standard solutions are prepared, and the solutions are respectively subjected to redox reactions with potassium dichromate to obtain a series of reaction standard solutions, and the absorbance values ​​of the reaction standard solutions are tested to establish a standard curve between ethanol content and absorbance; Mix the seasoning to be tested and Tween, and perform distillation to obtain a condensate; causing the condensate to undergo an oxidation-reduction reaction with potassium dichromate to obtain a solution to be tested; The absorbance value of the solution to be tested is measured and substituted into the standard curve to obtain the ethanol content in the seasoning to be tested.

2. The method for detecting ethanol content in condiments according to claim 1, characterized in that: The condiments to be tested include one or more of soy sauce, crude soy sauce, cooking wine, brine, sauce, oyster sauce, soybean sauce and column sauce.

3. The method for detecting ethanol content in condiments according to claim 2, characterized in that: The mass volume ratio of the Tween to the seasoning to be tested is (0.04-0.16) g:100 mL.

4. The method for detecting ethanol content in condiments according to claim 3, characterized in that: The solid content of the seasoning to be tested is less than 20wt%, and the mass of the Tween added to each 100mL of the seasoning to be tested is 0.04g~0.08g; or the solid content of the seasoning to be tested is greater than or equal to 20wt%, and the mass of the Tween added to each 100mL of the seasoning to be tested is 0.12g~0.16g.

5. The method for detecting ethanol content in condiments according to claim 1, characterized in that: The distillation process is performed until the ethanol in the seasoning to be tested is fully separated into the condensate.

6. The method for detecting ethanol content in condiments according to claim 5, characterized in that: The distillation process satisfies at least one of the following conditions: (1) distilling the condensate until the volume of the condensate is 80 mL to 100 mL; (2) The distillation treatment time is 2min~5min.

7. The method for detecting ethanol content in condiments according to any one of claims 1 to 6, characterized in that: The reaction conditions for the redox reaction between the condensate and the potassium dichromate are the same as the reaction conditions for the redox reaction between a series of the ethanol standard solutions and the potassium dichromate, and the reaction conditions include at least one of the following: (1) The reaction temperature is 80℃~120℃; (2) Reaction time ≥ 12 min.

8. The method for detecting ethanol content in condiments according to any one of claims 1 to 6, characterized in that: The reaction system of the condensate and the potassium dichromate is acidic, and the reaction system of a series of the ethanol standard solutions and the potassium dichromate is acidic.

9. The method for detecting ethanol content in condiments according to any one of claims 1 to 6, characterized in that: The initial concentration of the potassium dichromate in the reaction system of the condensate is the same as the initial concentration of the potassium dichromate in the reaction systems of a series of the ethanol standard solutions, and the initial concentration is 0.005 g / mL to 0.015 g / mL.

10. The method for detecting ethanol content in condiments according to any one of claims 1 to 6, characterized in that: The wavelength for testing the absorbance value of the test solution is the same as the wavelength for testing the absorbance value of each of the reaction standard solutions, which is 580nm~600nm.

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