A rapid detection method and kit for sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology

Abstract

The present invention relates to the technical field of food quality management, and in particular to a rapid detection method and kit for sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology. The principle that malachite green MG can be rapidly detected by a malachite green colloidal gold immunochromatography detection card, sulfur dioxide or sulfite can react with MG and its product cannot be detected by the malachite green colloidal gold immunochromatography detection card is used to obtain a reverse relationship between the sulfur dioxide content of the sample and the residual amount of malachite green, thereby adding MG to the candied fruit sample extract, reacting, and then using the malachite green colloidal gold immunochromatography detection card to detect the residual MG in the test liquid, thereby realizing the rapid detection of sulfur dioxide in the candied fruit sample by the immunochromatography colloidal gold detection method, and obtaining the kit of the present invention based on the immunochromatography colloidal gold detection method. The present invention solves the technical problems that the use of colorimetry is easily affected by the clarity and transparency of the sample liquid and the background color, and the sample processing speed is slow.

Description

Technical Field

[0001] The invention relates to the technical field of food quality management, and in particular to a rapid detection method and a kit for sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology. Background Art

[0002] Sulfur dioxide (including sulfite, pyrosulfite, hyposulfite, and bisulfite, all measured as sulfur dioxide when detecting content) is a food additive and processing aid and can be used in the production of designated foods. Because it is harmful to the human body, its ADI value is 0-0.7 mg / kg bw / day (milligrams per kilogram of body weight per day), so the national standard also stipulates the maximum allowable residue in designated foods.

[0003] The existing methods for determining sulfur dioxide mainly include spectrophotometry, distillation titration, and chromatography. Among them, spectrophotometry requires a spectrophotometer, and the detection process is relatively cumbersome; distillation titration takes at least 2 hours, and also requires equipment such as a distillation instrument, which cannot meet the needs of rapid detection; the chromatograph of the chromatography method is expensive, has high requirements for detection personnel, and cannot meet the needs of rapid detection. At present, in the field of rapid food safety detection, there are mainly colorimetry and immunochromatography colloidal gold rapid detection methods. So far, the rapid detection of sulfur dioxide in food has only applied colorimetry, which is judged by visual colorimetry or rapid detection instruments (using the principle of spectrophotometry). However, the colorimetric method has obvious disadvantages: (1) The sample liquid must be clear and transparent, and turbid liquid has a great influence on the results; and the processing methods such as filtration, centrifugation, and sedimentation cannot meet the timeliness requirements or the conditions of rapid detection occasions. (2) Different types of food have different colors. Their sample solutions often have a background color that seriously interferes with the interpretation of the results. However, it is difficult and time-consuming to remove the background color. In some cases, it cannot be removed at all, and cannot meet the conditions for time-limited or rapid testing. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a rapid detection method and kit for sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology, which solves the technical problems that the colorimetric method currently used for rapid detection of sulfur dioxide in food is easily affected by the clarity and transparency of the sample liquid and the background color, and the sample processing method cannot meet the timeliness requirements or the conditions of the rapid detection occasion.

[0006] (II) Technical solution

[0007] In a first aspect, the present invention provides a method for rapid detection of sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology, comprising the following steps:

[0008] S1. Prepare sample extract

[0009] Weigh the candied fruit sample, mix the candied fruit sample with water and sodium hydroxide or its solution, and then perform homogenization. If the candied fruit sample contains a core, remove the core first, then mix it with water and sodium hydroxide or its solution, and then perform homogenization. The weight of the candied fruit after core removal is the weighed sample mass.

[0010] After the homogenization treatment is completed, the mixture is allowed to stand, and the standing supernatant is centrifuged at a speed of ≥4000 rpm to obtain a centrifugal supernatant, which is the sample extract;

[0011] S2. Prepare the test solution

[0012] Measure a known volume of sample extract, adjust the pH of the sample extract to 6.0-7.0 with phosphate buffer, then add malachite green reagent to make the concentration of malachite green in the reaction system 30 ppb, react for 4-8 minutes, and obtain the test solution;

[0013] Taking the limit value of SO2 in the candied fruit sample as the assumed content, through the steps of preparing the sample extract and preparing the test solution in S1, the assumed content of SO2 in the test solution is finally diluted to 0.01 mg / mL;

[0014] S3. Detection

[0015] At room temperature of 15-30°C, drop the test solution into the sample well of the malachite green colloidal gold immunochromatographic test card and read the result after 8-10 minutes. The reading method is:

[0016] If the color of T line is darker than or the same as that of C line, it means that the concentration of malachite green is lower than the detection limit, which means that the SO2 in the candied fruit sample exceeds the limit value;

[0017] If the T line is lighter than the C line or the T line is not colored, it means that the concentration of malachite green is higher than the detection limit, which means that the SO2 in the candied fruit sample has not reached the limit value.

[0018] According to a preferred embodiment of the present invention, in S1, when the limit value of SO2 in the candied fruit sample is 100 mg / kg, 1 g of the candied fruit sample is mixed with water and sodium hydroxide or its solution into 5 mL of solution for homogenization;

[0019] When the limit value of SO2 in the candied fruit sample is 200 mg / kg, 1 g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form a 10 mL solution for homogenization;

[0020] When the limit value of SO2 in the candied fruit sample is 250 mg / kg, 1g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form 12.5 mL of solution for homogenization;

[0021] When the limit value of SO2 in the candied fruit sample is 300 mg / kg, 1g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form a 15mL solution for homogenization;

[0022] When the limit value of SO2 in the candied fruit sample is 350 mg / kg, 1 g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form 17.5 mL of solution for homogenization;

[0023] When the limit value of SO2 in the candied fruit sample is 500 mg / kg, mix 1g of the candied fruit sample with water and sodium hydroxide or its solution into 25mL of solution and homogenize it.

[0024] In this application, the limit value can be the limit value specified by the national standard of the candied fruit product, or it can be the internal control value set by the manufacturer itself. Generally, the internal control value is lower than the limit value specified by the national standard value to achieve better quality control.

[0025] According to a preferred embodiment of the present invention, in S1, the sodium hydroxide solution used is a sodium hydroxide solution with a mass concentration of 8%.

[0026] According to a preferred embodiment of the present invention, in S1, the volume of distilled water in mL = the weight of the candied fruit sample in g × 10-1.

[0027] According to a preferred embodiment of the present invention, in S1, the candied fruit sample is mixed with water and sodium hydroxide or a solution thereof, homogenized in a homogenizer for 1 min, and allowed to stand for 10 min to produce a stationary supernatant. 1.5 mL of the stationary supernatant is taken into a 2 mL centrifuge tube and centrifuged at a speed of 4000 rpm-8000 rpm for 4-5 minutes. The obtained centrifuged supernatant is the sample extract.

[0028] According to a preferred embodiment of the present invention, in S2, the volume of the sample extract, the volume of the phosphate buffer solution, and the volume of the malachite green reagent measured are 5:4:1; and the total volume of the test solution is 1 mL.

[0029] According to a preferred embodiment of the present invention, in S2, the phosphate buffer is prepared by dissolving sodium dihydrogen phosphate and disodium hydrogen phosphate in water, and its pH is 6.5-7.0, preferably 6.8; the concentration of malachite green (basic blue, MG) in the malachite green reagent is 300 ppb.

[0030] According to a preferred embodiment of the present invention, in S3, 100-150 μL of the test solution is taken into the gold-labeled microwell, blown to dissolve and reacted for 2 minutes, and all of it is dropped into the sample well of the malachite green colloidal gold immunochromatographic detection card, and the result is judged after 8-10 minutes.

[0031] In a second aspect, the present invention provides a rapid test kit for sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology; the kit comprises: sodium hydroxide or its solution, deionized water, phosphate buffer, malachite green reagent and malachite green colloidal gold immunochromatography test card.

[0032] The malachite green colloidal gold immunochromatographic test card is a commercially available product, for example, it can be purchased from Meicheng (Huzhou) Biotechnology Co., Ltd.

[0033] (III) Beneficial effects

[0034] Sulfur dioxide is a small molecule inorganic substance and has no antigen or antibody that specifically binds to it. The present invention adds MG (dominant malachite green) to the test liquid, utilizes sulfur dioxide to react with malachite green, and the sulfur dioxide content is inversely related to the residual amount of malachite green. Then, a malachite green colloidal gold immunochromatographic detection card is used to detect the residual MG (the product after the addition reaction cannot bind to the antigen and therefore cannot be detected), thereby achieving the purpose of rapidly detecting sulfur dioxide in candied fruit samples by immunochromatographic colloidal gold detection method.

[0035] The pH value of the extract of the fruit raw material candied fruit product is 2-5, but when preparing the extract sample containing sulfur dioxide from the candied fruit, sodium hydroxide solution needs to be used as the extractant, which ultimately makes the pH of the extract alkaline, and malachite green will generate alkaline malachite green in an alkaline solution (which cannot be detected by the malachite green colloidal gold test card). Considering that the optimal condition for the addition reaction of sulfur dioxide and malachite green is pH 7.0, the present invention uses a phosphate buffer (pH 6.5-6.8) to adjust the pH of the test solution to 6.0-7.0 when preparing the test solution. In addition, the correct interpretation of the results by the malachite green colloidal gold immunochromatographic test card is not affected at room temperature of 15-30°C.

[0036] The rapid detection method for sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology provided by the present invention adopts a fixed volume of pre-prepared malachite green reagent (fixed concentration) and phosphate buffer solution when preparing the test solution, even for different types of candied fruit products and sulfur dioxide limit values. This greatly simplifies the operation, reduces the workload of detection personnel, and is conducive to achieving fully automated detection. It has the advantages of simple and rapid sample processing, mild processing conditions, and accurate detection at room temperature. It can be used as a standardized rapid detection method for whether the sulfur dioxide content in candied fruit products is compliant. DETAILED DESCRIPTION

[0037] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods.

[0038] As a small molecule inorganic substance, sulfur dioxide has no antigen or antibody that specifically binds to it. However, sulfur dioxide or sulfite can react with malachite green MG. Before the reaction, malachite green MG can be detected by the malachite green colloidal gold immunochromatographic detection card, while the product of the addition reaction between sulfur dioxide and malachite green MG cannot be detected by the malachite green colloidal gold immunochromatographic detection card. Therefore, the sulfur dioxide content in the sample to be tested is inversely related to the residual amount of malachite green. Based on this principle, the present invention adds MG to the extract of the candied fruit sample, and after the reaction, uses the malachite green colloidal gold immunochromatographic detection card to detect the residual MG (the part that has not reacted with sulfur dioxide) in the test solution, thereby achieving the purpose of quickly detecting sulfur dioxide in the candied fruit sample by immunochromatographic colloidal gold detection method.

[0039] The reaction process of sulfite and malachite green MG is as follows:

[0040]

[0041] The following is a description of the solution according to the preferred embodiment of the present invention. The preparation method, concentration and consumables of each reagent in the following embodiments are described as follows:

[0042] (1) Sodium hydroxide solution: Accurately weigh 8.0 g of sodium hydroxide and dissolve it in 92 mL of distilled water. After cooling naturally, cover and seal the container and store it at room temperature. The sodium hydroxide solution is 8%.

[0043] (2) Malachite green reagent (concentration 300 ppb), the preparation process is as follows:

[0044] Accurately weigh 0.01 g of malachite green (MG), dissolve it in distilled water and transfer it to a 1000 mL volumetric flask, add distilled water to the mark, seal this solution with a brown glass bottle, store it at -18 ° C away from light, and it is valid for one month as a malachite green (MG) stock solution (10000ppm). Then, accurately measure 1 mL of the malachite green (MG) stock solution into a 1000 mL volumetric flask and add distilled water to the volume. This solution is prepared and used immediately as a malachite green (MG) intermediate solution (10ppm). Continue to accurately measure 3 mL of the malachite green (MG) intermediate solution into a 100 mL volumetric flask, add distilled water to the volume, and this solution is prepared and used immediately, with a concentration of 300 ppb, and is used to drop into the test solution for reaction detection.

[0045] (3) Phosphate buffer (pH 6.8): Accurately weigh 15.72 g of sodium dihydrogen phosphate dihydrate and 17.66 g of disodium hydrogen phosphate dihydrate, dissolve them and transfer them to a 1000 mL volumetric flask, and add distilled water to make up to volume. Store at room temperature.

[0046] (4) Materials and tools: Malachite green (MG) colloidal gold immunochromatographic test strip kit, with a sensitivity of 2 ppb (water sample), was purchased from Meicheng (Huzhou) Biotechnology Co., Ltd. The kit consists of: MG (water sample) test card, gold-labeled microwell, and disposable dropper.

[0047] (5) Homogenizers, micro centrifuges, pipettes (5-50μL, 10-1000μL), electronic scales (range: 500g, accuracy: 0.01g), etc. are commonly used products in laboratories.

[0048] Example 1

[0049] Take an appropriate amount of candied fruit and remove the core (its sulfur dioxide content is known to be 200 mg / kg), homogenize it with a homogenizer, weigh 2.0g of the homogenized sample into another sample cup (the sample cup equipped with the homogenizer), add distilled water and sodium hydroxide solution (mass concentration is 8%), homogenize for another minute, and let it stand for 10 minutes to prepare the sample extract. When preparing the sample extract, different volumes of distilled water and sodium hydroxide solution are used to make the concentration of SO2 contained in the sample extract different, and sample extract 1 and sample extract 2 are obtained respectively, wherein the concentration of sulfite (in terms of SO2) in sample extract 1 is 0.02 mg / mL, and the concentration of sulfite (in terms of SO2) in sample extract 2 is 0.019 mg / mL.

[0050] First, take 500 μL of sample extract 1, 400 μL of phosphate buffer (pH 6.8) and 100 μL of 300 ppb malachite green reagent for mixed reaction for 10 minutes. The concentration of sulfite (in terms of SO2) in the reaction system is 0.01 mg / mL. After the reaction, use a malachite green colloidal gold immunochromatographic test card (purchased from Meicheng (Huzhou) Biotechnology Co., Ltd.) for detection. The red color of the T line is slightly darker than that of the C line, and the malachite green is judged to be negative, that is, sulfur dioxide is positive. Then, 500 μL of sample extract 2, 400 μL of phosphate buffer (pH 6.8) and 100 μL of 300 ppb malachite green reagent were mixed and reacted for 10 minutes. The concentration of sulfite (in terms of SO2) in the reaction system was 0.0095 mg / mL. After the reaction, the malachite green colloidal gold immunochromatographic test card was used for detection. The red color of the T line was slightly lighter than that of the C line, and the malachite green was judged to be positive, that is, sulfur dioxide was negative. It can be seen that when the concentration of malachite green in the test solution is 30 ppb, the detection limit of the malachite green colloidal gold immunochromatographic test card for sulfite (in terms of SO2) in the test solution is 0.01 mg / mL. If the actual concentration of sulfur dioxide in the test solution is lower than this concentration, even if sulfite ions exist in the solution, it may still cause the detection result of sulfur dioxide to be false negative (lower than the detection limit).

[0051] Therefore, in the following testing process, the limit value of sulfur dioxide in the candied fruit sample is referred to, and the limit value is used as the assumed content of sulfur dioxide in the candied fruit sample. Then, the dilution multiple (i.e., the total volume of the homogenization treatment) in the sample extraction process is adjusted so that the assumed concentration of SO2 in the final test solution (reaction system with malachite green) is adjusted to the sensitivity of the colloidal immunochromatographic test card, i.e., 0.01 mg / mL. At this time, when the test result of the malachite green colloidal gold immunochromatographic test card is malachite green positive, it means that the content of sulfur dioxide in the candied fruit sample is lower than the limit value (the sulfur dioxide content is within the qualified range). Conversely, when the test result of the malachite green colloidal gold immunochromatographic test card is malachite green negative, it means that the content of sulfur dioxide in the candied fruit sample is higher than the limit value (the sulfur dioxide content exceeds the qualified range). The limit value of sulfur dioxide in candied fruit, the dilution multiple during extraction, and the composition of the test solution are shown in Table 1:

[0052] Table 1: Limit values ​​of sulfur dioxide in candied fruit, dilution multiples during extraction, and composition of the test solution

[0053]

[0054] Example 2

[0055] This example uses colloidal gold immunochromatography to detect whether the sulfur dioxide in Qingxin Banmei is compliant. The limit value of sulfur dioxide in this Qingxin Banmei product is 250 mg / kg. There are two types of samples to be tested (see Table 2):

[0056] Table 2: Two production batches of Qingxin Banmei products and the sulfur dioxide content detected by distillation method

[0057]

[0058] The detection method is as follows:

[0059] (1) Preparation of sample extract

[0060] Take the above 1# and 2# samples and process them in the following ways: Take 2 packages of fresh half-plum finished products and unpack them respectively, mix them evenly, randomly select about 100g, remove the cores one by one, and cut the pulp into thin slices with a thickness of 0.5-1mm with scissors. Homogenize with a homogenizer. Since the sample viscosity is very high, homogenize in a point-to-point manner. Accurately weigh 10.0g of the homogenized sample into another sample cup, add 1mL of sodium hydroxide solution (8%), and then measure 124mL of distilled water. Use the method of gradually adding distilled water to homogenize, mainly in a point-to-point manner during the period to avoid the sample liquid temperature from being too high, until there is no granular sample visible to the naked eye. Let it stand for another 10 minutes. Take about 1.5mL of sample extract into a 2mL centrifuge tube, centrifuge at 5000rpm for 5min, and the supernatant is the sample extract. The pH value of the extract was tested to be 2.3.

[0061] (2) Preparation of test solution

[0062] Take 500 μL of the sample extracts of 1# and 2# fresh half-plum prepared above, 400 μL of phosphate buffer (pH 6.8) and 100 μL of malachite green reagent (300 bbp), mix and react for 5 minutes to obtain a test solution.

[0063] (3) Detection

[0064] Take 120μL of the test solution into the gold-labeled microwell, blow and dissolve it, react for 2 minutes, and add all of it to the sample well of the malachite green colloidal gold immunochromatographic test card. Read the results after 10 minutes. The results are shown in Table 3:

[0065] Table 3: Results of the detection of sulfur dioxide in Qingxin Banmei by colloidal gold immunochromatography

[0066]

[0067] It can be seen that the present invention adopts colloidal gold immunochromatography technology to quickly detect whether the sulfur dioxide content in fresh half plum is within the limit value range.

[0068] Example 3

[0069] This example uses colloidal gold immunochromatography to detect whether the sulfur dioxide in red melon cubes is compliant. The limit value of sulfur dioxide in this red melon cube product is 200 mg / kg. There are two types of samples to be tested (see Table 4):

[0070] Table 4: Two production batches of red melon diced products and sulfur dioxide content detected by distillation method

[0071]

[0072] The detection method is as follows:

[0073] (1) Preparation of sample extract

[0074] Take the above 3# and 4# samples and process them in the following way: Take 2 packages of red melon diced finished products, unpack them and mix them evenly, randomly select about 100g, and cut the pulp into slices with a thickness of 0.5-1mm with scissors. Homogenize with a homogenizer, accurately weigh 10.0g of the homogenized sample into another sample cup, add 1mL of sodium hydroxide solution (concentration of 8%), and then measure 99mL of distilled water, and gradually add distilled water to homogenize, mainly in a jog manner during the process to avoid the sample liquid temperature being too high, until there is no granular sample visible to the naked eye, and then let it stand for 10 minutes.

[0075] Take about 1.5 mL of sample extract into a 2 mL centrifuge tube, centrifuge at 4000 rpm for 5 min, and the supernatant is the sample extract. The pH value of the extract is 6.94.

[0076] (2) Preparation of test solution

[0077] Take 500 μL of the sample extract of 3# and 4# fresh half-plum prepared above, 400 μL of phosphate buffer (pH 6.8) and 100 μL of malachite green reagent (300 bbp), mix and react for 5 minutes to obtain the test solution.

[0078] (3) Detection

[0079] Take 120μL of the test solution into the gold-labeled microwell, blow and dissolve it, react for 2 minutes, and add all of it to the sample well of the malachite green colloidal gold immunochromatographic test card. Read the results after 10 minutes. The results are shown in Table 5:

[0080] Table 5: Results of the detection of sulfur dioxide in Qingxin Banmei by colloidal gold immunochromatography

[0081]

[0082] It can be seen that the present invention adopts colloidal gold immunochromatography technology to quickly detect whether the sulfur dioxide content in red melon cubes is within the limit value range.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rapid detection method for sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology, characterized in that: The steps include: S1. Prepare sample extract Weigh the candied fruit sample, mix the candied fruit sample with water and sodium hydroxide or its solution, and then perform homogenization. If the candied fruit sample contains a core, remove the core first, then mix with water and sodium hydroxide or its solution, and then perform homogenization, and the weight of the candied fruit after core removal is the weighed sample mass. After the homogenization treatment is completed, the mixture is allowed to stand, and the standing supernatant is centrifuged at a speed of ≥4000 rpm to obtain a centrifugal supernatant, which is the sample extract; S2. Prepare the test solution Measure a known volume of sample extract, adjust the pH of the sample extract to 6.0-7.0 with phosphate buffer, then add malachite green reagent to make the concentration of malachite green in the reaction system 30 ppb, react for 4-8 minutes, and obtain the test solution; Taking the limit value of SO2 in the candied fruit sample as the assumed content, through the steps of preparing the sample extract and preparing the test solution in S1, the assumed content of SO2 in the test solution is finally diluted to 0.01 mg / mL; S3. Detection At room temperature of 15-30°C, drop the test solution into the sample well of the malachite green colloidal gold immunochromatographic test card and read the result after 8-10 minutes. The reading method is: If the color of T line is darker than or the same as that of C line, it means that the concentration of malachite green is lower than the detection limit, which means that the SO2 in the candied fruit sample exceeds the limit value; If the T line is lighter than the C line or the T line is not colored, it means that the concentration of malachite green is higher than the detection limit, which means that the SO2 in the candied fruit sample has not reached the limit value.

2. The rapid detection method according to claim 1, characterized in that: In S1, when the limit value of SO2 in the candied fruit sample is 100 mg / kg, 1 g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form a 5 mL solution for homogenization; When the limit value of SO2 in the candied fruit sample is 200 mg / kg, 1 g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form a 10 mL solution for homogenization; When the limit value of SO2 in the candied fruit sample is 250 mg / kg, 1g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form 12.5 mL of solution for homogenization; When the limit value of SO2 in the candied fruit sample is 300 mg / kg, 1g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form a 15mL solution for homogenization; When the limit value of SO2 in the candied fruit sample is 350 mg / kg, 1 g of the candied fruit sample is mixed with water and sodium hydroxide or its solution to form 17.5 mL of solution for homogenization; When the limit value of SO2 in the candied fruit sample is 500 mg / kg, mix 1g of the candied fruit sample with water and sodium hydroxide or its solution into 25mL of solution and homogenize it.

3. The rapid detection method according to claim 2, characterized in that: In S1, the sodium hydroxide solution used is a sodium hydroxide solution with a mass concentration of 8%.

4. The rapid detection method according to claim 3, characterized in that: In S1, the volume of distilled water in mL = the weight of the candied fruit sample in g × 10-1.

5. The rapid detection method according to claim 1, characterized in that: In S1, the candied fruit sample is mixed with water and sodium hydroxide or its solution, homogenized in a homogenizer for 1 min, and allowed to stand for 10 min to produce a stationary supernatant. 1.5 mL of the stationary supernatant is taken into a 2 mL centrifuge tube and centrifuged at a speed of 4000 rpm-8000 rpm for 4-5 minutes. The obtained centrifuged supernatant is the sample extract.

6. The rapid detection method according to claim 1, characterized in that: In S2, the volume of the sample extract, the volume of the phosphate buffer, and the volume of the malachite green reagent measured are 5:4:1; the total volume of the test solution is 1 mL.

7. The rapid detection method according to claim 1, characterized in that: In S2, the phosphate buffer is prepared by dissolving sodium dihydrogen phosphate and disodium hydrogen phosphate in water, and its pH is 6.5-7.0; the concentration of malachite green in the malachite green reagent is 300 ppb.

8. The rapid detection method according to claim 1, characterized in that: In S3, 100-150 μL of the test solution is taken into the gold-labeled microwell, and after being blown to dissolve, it reacts for 2 minutes, and then all of it is dropped into the sample well of the malachite green colloidal gold immunochromatographic detection card, and the result is judged after 8-10 minutes.

9. A rapid test kit for sulfur dioxide in candied fruit based on colloidal gold immunochromatography technology; It includes: Sodium hydroxide or its solution, deionized water, phosphate buffer, malachite green reagent and malachite green colloidal gold immunochromatographic test card; The rapid test kit is used to perform detection according to the rapid test method described in any one of claims 1 to 8.

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