Rapid detection method and kit for sulfur dioxide in starch product based on colloidal gold immunochromatography technology

Abstract

The invention relates to the technical field of food quality detection, in particular to a rapid detection method for sulfur dioxide in a starch product based on a colloidal gold immunochromatography technology and a kit. The rapid detection method comprises the following steps: preparing a to-be-detected solution: quantitatively weighing a starch product, extracting sulfur dioxide by using a caustic alkali solution at normal temperature or low temperature, and centrifuging an extracting solution to take an upper-layer clear solution; intermediate reaction: measuring the solution to be detected, calculating the limited molar weight according to the sulfur dioxide limited value and the extraction rate, adding a DDQ reagent and an LMG reagent with equal molar weight, and reacting under the condition that the pH value is 6.5-7.5. Colloidal gold reaction: dropwise adding the reaction liquid into a sample adding hole of a malachite green colloidal gold immunochromatography detection card for interpretation: if T line red is deeper than or equal to C line red, malachite green is negative, and sulfur dioxide exceeds the limit; t line red is light or does not develop color, malachite green is positive, and sulfur dioxide does not exceed the limit; if the C line does not develop color, the detection is invalid. The method is suitable for rapid qualitative detection of sulfur dioxide in starch.

Description

Technical Field

[0001] This invention relates to the field of food quality testing technology, specifically to a rapid detection method and kit for sulfur dioxide in starch products based on colloidal gold immunochromatography. Background Technology

[0002] Sulfur dioxide (including sulfites, metabisulfites, hyposulfites, and bisulfites, all measured as sulfur dioxide) can be used as a food additive and processing aid in the production of designated foods. However, due to its harmfulness to the human body, the acceptable intake (ADI) value is 0-0.7 mg / kg bw. Therefore, the national standard also specifies the maximum allowable residue level for designated foods.

[0003] With the establishment of food safety regulations and the strengthening of food safety supervision, the demand for innovation in testing technologies and their application in the field of rapid food safety testing is becoming increasingly strong. Rapid food safety testing methods are characterized by: allowing for a certain degree of error (false negative and false positive rates), good sensitivity, and fast detection speed (time-sensitive requirements). Existing methods for determining sulfur dioxide mainly include spectrophotometry, distillation titration, and chromatography. Spectrophotometry requires a spectrophotometer, making the detection process relatively cumbersome; distillation titration takes at least 2 hours and also requires equipment such as a distillation apparatus, which cannot meet the needs of rapid detection; chromatographic methods require expensive chromatographs and demand highly skilled personnel, also failing to meet the needs of rapid detection.

[0004] At present, the main rapid detection methods for food safety are colorimetric and immunochromatographic colloidal gold rapid detection. However, the rapid detection of sulfur dioxide currently only uses colorimetric methods, which are interpreted by visual colorimetry or by rapid detection instruments (using the principle of spectrophotometry). Colorimetric methods have some disadvantages: (1) The sample solution must be clear and transparent. Turbid liquids have a great impact on the results. The processing methods such as filtration, centrifugation, and sedimentation cannot meet the time requirements or conditions for rapid detection. (2) Different types of food have different colors, and their sample solutions often have a background color. The background color seriously interferes with the interpretation of the results. The removal of the background color is difficult and time-consuming, which cannot meet the conditions for time-sensitive or rapid detection.

[0005] The colloidal gold method, based on the addition reaction of sulfur dioxide with malachite green, can rapidly detect sulfur dioxide. However, the concentration of malachite green reagent is only at the ppb level. Due to its photosensitivity, malachite green's aqueous solution has a very short shelf life (2 hours at room temperature) under both room temperature and refrigeration conditions. Low-concentration aqueous solutions have an extremely short shelf life; significant concentration changes occur within 2 hours at room temperature, leading to contradictory detection results, which cannot meet the needs of rapid testing of routine samples. Furthermore, malachite green in its unresolved form is chemically unstable at room temperature, with a half-life of <24 hours under natural light. These factors limit its application as an indicator in rapid detection. Summary of the Invention

[0006] (a) Technical problems to be solved 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 starch products based on colloidal gold immunochromatography. This method is based on the principle of reacting leucomalleite green (LMG) with dichlorodicyanobenzoquinone (DDQ) to generate malachite green. The sample extract is mixed with DDQ and LMG reagents and reacted. The resulting solution is detected using a malachite green immunochromatographic colloidal gold test card. The presence or absence of MG in the solution is used to determine the sulfur dioxide content in the sample extract, thus achieving the qualitative detection objective of whether sulfur dioxide in starch products exceeds the standard. The LMG and DDQ reagents have good stability, meeting the needs of rapid detection of large numbers of samples in daily practice.

[0007] (II) Technical Solution In a first aspect, the present invention provides a rapid detection method for sulfur dioxide in starch products based on colloidal gold immunochromatography, comprising: S1. Prepare the sample solution to be tested. The starch product was weighed quantitatively, and sulfur dioxide was extracted using a caustic soda solution at room temperature or low temperature. The extract was centrifuged to obtain the clear supernatant, which was the sample solution to be tested. S2, intermediate reaction Take a predetermined volume of the sample solution to be tested. Calculate the limit molar amount of sulfur dioxide in the measured sample solution according to the limit value of sulfur dioxide in starch products and the extraction rate of sulfur dioxide in S1. Add DDQ reagent and LMG reagent and react under pH 6.5-7.5 conditions. The molar amount of DDQ contained in the added DDQ reagent is equal to the limit molar amount of sulfur dioxide. S3, Colloidal gold immune layer reaction After the S2 reaction is complete, add the reaction solution dropwise into the sample well of the malachite green colloidal gold immunochromatographic assay card and interpret the results. The interpretation method is as follows: If the T line is redder than or the same as the C line, it indicates that the malachite green is negative and the sulfur dioxide content in the starch product exceeds the limit. Conversely, if the T line is lighter in color than the C line or the T line is not colored, it indicates that malachite green is positive and the sulfur dioxide content in the starch product does not exceed the limit value. The C line showed no color, therefore the test result is invalid.

[0008] According to a preferred embodiment of the present invention, in S1, the caustic soda solution is a sodium hydroxide solution (concentration of 30-50 g / L), and the extraction process is carried out in a nitrogen-protected chamber at an extraction temperature of 10-30°C. The extraction process of S1 includes: accurately weighing the starch product with a mass of M, adding sodium hydroxide solution and pure water to obtain an extraction system with a total volume of V0, covering and vigorously shaking to mix for 0.5-1.5 min, and letting it stand for 2-4 min; taking 1-2 mL of sample solution into a centrifuge tube, tightening the cap and centrifuging to obtain the clear liquid in the upper layer, which is the sample solution to be tested.

[0009] According to a preferred embodiment of the present invention, in S1, the extraction process is carried out under nitrogen protection, for example, in a nitrogen glove box, to prevent sulfur dioxide (sulfite) from being oxidized.

[0010] According to a preferred embodiment of the present invention, in S2, a volume V1 of the sample liquid to be tested is taken, and the limit molar amount of sulfur dioxide in the sample liquid to be tested is calculated according to the limit value a of sulfur dioxide in starch products and the extraction rate b of sulfur dioxide in S1. The limit molar quantity = M × a × b × (V1 / V0) / 64 g / mol.

[0011] According to a preferred embodiment of the present invention, in S2, M is in g, a is in mg / g, and b is the extraction rate of sulfur dioxide from starch products.

[0012] According to a preferred embodiment of the present invention, in S2, the pH of the reaction system is adjusted to 6.5-7.5 using phosphate buffer; the reaction system consists of the sample solution to be tested, LMG reagent, DDQ reagent and phosphate buffer; except for the sample solution to be tested, LMG reagent and DDQ reagent, the portion less than 1000 μL is supplemented to 1000 μL by phosphate buffer.

[0013] According to a preferred embodiment of the present invention, in S2, the reaction system is 1000 μL, wherein the solvent in the DDQ reagent is anhydrous ethanol with a concentration of 100 ppm and an addition amount of 20 μL; the volume of the sample to be tested is 40-42 μL; the solvent in the LMG reagent is anhydrous ethanol with a concentration of 100 ppm and an addition amount of 0.5-10 μL; the remainder is phosphate buffer. When the extraction rate of sulfur dioxide in starch products is 0.9, M is taken as 5g; For foods with a sulfur dioxide limit of 50 mg / kg in starch products, the volume V0 of the extraction system is 15 mL. For foods with a sulfur dioxide limit of 100 mg / kg in starch products, the volume V0 of the extraction system is 30 mL. For foods with a sulfur dioxide limit of 200 mg / kg in starch products, the extraction system volume V0 is 60 mL.

[0014] According to a preferred embodiment of the present invention, in S2, the pH of the phosphate buffer solution is 6.5-7.0.

[0015] According to a preferred embodiment of the present invention, in S3, at 15-30°C, 80-120 μL of the reaction solution after the completion of the S2 reaction is taken into the microwell of the gold label, mixed by suction and blowing for 2 min, and then dropped into the sample well of the malachite green colloidal gold immunochromatographic detection card. The result is read after 5-6 min.

[0016] Secondly, the present invention provides a rapid detection kit for sulfur dioxide in starch products based on colloidal gold immunochromatography technology, comprising: Sodium hydroxide or its solution, LMG reagent, DDQ solid reagent, phosphate buffer, and malachite green colloidal gold immunochromatographic assay card; the LMG reagent is an anhydrous ethanol solution of LMG; the DDQ solid reagent is stored in a sealed glass reagent bottle with a cap and vacuum-sealed in a vacuum bag, each glass reagent bottle containing a defined mass of DDQ powder (dissolved in anhydrous ethanol before use); the rapid test kit is used to perform the test according to the rapid test method described above.

[0017] (III) Beneficial Effects The rapid detection method for sulfur dioxide in starch products of the present invention uses reagents with good stability at room temperature and uses a high concentration of LMG (up to 100 ppm or higher). LMG also has good stability at room temperature. In addition, LMG is added in excess during the detection process. As long as there is residual DDQ in the S2 reaction system that causes LMG to be converted into MG, it can be detected by the colloidal gold detection card (sensitivity reaches 2 ppb level). Therefore, the method of the present invention does not have strict requirements on the concentration of LMG. Even if the concentration changes significantly during storage, it will not affect the final detection result. The LMG mother liquor still meets the detection requirements after being stored at room temperature for 6 months.

[0018] The DDQ in the kit is stored in a sealed glass reagent bottle with a cap and then in a vacuum-sealed bag. Each glass reagent bottle contains a defined mass of DDQ powder. Each kit can be used with 6-12 bottles of DDQ powder. When using, anhydrous ethanol is added to dissolve the powder before use, so that the kit can meet the needs of 6-12 months. Attached Figure Description

[0019] Figure 1 The reaction formula is for the dehydrogenation of LMG to MG by DDQ.

[0020] Figure 2 The images show malachite green immunogold test strips displaying negative (left) and positive (right) results for MG. Detailed Implementation

[0021] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The principle of the rapid detection method for sulfur dioxide in starch products based on colloidal gold immunochromatography is as follows: Sulfur dioxide (sulfite) has strong reducing properties, greater than leucomalleite green (LMG). Therefore, in a reaction system where sulfur dioxide, leucomalleite green (LMG), and dichlorodicyanobenzoquinone (DDQ) coexist, sulfur dioxide (sulfite) preferentially reacts with DDQ over LMG. If sulfur dioxide is insufficient, leading to an excess of DDQ, the remaining DDQ will oxidize LMG to produce MG (malachite green), which can be detected by the malachite green immunochromatographic gold test card. In this case, the test result is positive for malachite green, while sulfur dioxide is relatively insufficient. Conversely, if sulfur dioxide is sufficient or even excessive, it will consume all the DDQ in the reaction system. In this case, even if sulfite is excessive, it cannot react with LMG, resulting in no MG formation. The reaction system will not detect MG, and the test result is negative for malachite green, while sulfur dioxide is relatively sufficient or even excessive. Therefore, the residual DDQ in the reaction system is inversely related to the sulfur dioxide content. The residual DDQ can be indirectly detected by malachite green. Thus, the positive or negative result of malachite green detected by the malachite green immunochromatographic gold test card can be used to indirectly determine whether sulfur dioxide exceeds the standard.

[0023] DDQ is an excellent dehydrogenating agent that can rapidly react with LMG to dehydrogenate it, producing MG (the reaction process is as follows). Figure 1 While conventional oxidants such as potassium permanganate or H2O2 possess strong oxidizing properties, their reaction with LMG does not produce MG, thus failing to achieve the detection goal of the malachite green immunogold assay card. Tetrachlorobenzoquinone is also a dehydrogenating reagent, but its reaction rate is significantly lower than that of DDQ, which cannot meet the requirements for rapid detection. Furthermore, the implementation of this invention is also based on the chemical characteristic that sulfur dioxide (sulfite) has a greater reducing power than LMG. Although sulfur dioxide also possesses some oxidizing properties, its oxidizing power is insufficient to react with LMG to generate MG.

[0024] Furthermore, the above reaction process has certain pH requirements. Although DDQ can dehydrogenate LMG to generate detectable MG, malachite green will further generate basic malachite green in a strongly alkaline solution (this product cannot be detected by the malachite green colloidal gold test card). Therefore, the reaction system in which sulfur dioxide, leucomalleite green (LMG), and dichlorodicyanobenzoquinone (DDQ) coexist must not be a strongly alkaline environment. Similarly, a strongly acidic environment will accelerate the hydrolysis and inactivation of DDQ and inhibit the protonation of LMG to MG (strong acidity easily leads to test card failure). Therefore, this invention sets the reaction conditions to a pH of 6.5-7.5. Since edible starch requires a caustic soda solution as an extractant when extracting sulfur dioxide, the sample solution to be tested may be alkaline. In order to adjust the pH of the coexisting reaction system, this invention uses phosphate buffer (pH 6.5-7) to adjust the pH of the test solution to ensure it is between 6.5 and 7.5. Therefore, the reaction system consists of the sample solution to be tested, LMG reagent, DDQ reagent, and phosphate buffer. The LMG reagent and DDQ reagent are anhydrous ethanol solutions of LMG and DDQ, respectively. Furthermore, the malachite green immunogold test strip provides accurate results at 15-30℃, without affecting the correct interpretation of positive or negative results.

[0025] The following description is based on embodiments of the present invention.

[0026] Example 1 This embodiment provides a rapid detection kit for sulfur dioxide in starch products based on colloidal gold immunochromatography technology, the composition of which is as follows: Extraction solvent: 40 g / L sodium hydroxide solution. Reagent A: pH 6.8 phosphate buffer solution. Reagent B: 100 ppm LMG solution. Reagent C: 0.01 g of DDQ powder in 100 mL sealed glass reagent bottles. Anhydrous ethanol, pure water, and malachite green immunogold assay strips (purchased from Guangzhou Ruisen Biotechnology Co., Ltd., with a sensitivity of 2 ppb).

[0027] Preparation method of reagent A: Weigh 0.786g of NaH2PO4·2H2O and 0.88g of Na2HPO4·2H2O, dissolve them in an appropriate amount of purified water, add 20μL of Triton X-100, and make up to 100ml. The pH of this buffer reagent is 6.8.

[0028] Preparation method of reagent B: Accurately weigh 0.01g of LMG and dissolve it in an appropriate amount of anhydrous ethanol, then make up to 100mL with ethanol to obtain 100ppm of LMG reagent.

[0029] Before using reagent C, open the cap of a glass reagent bottle, inject anhydrous ethanol to 100 mL using an injection needle, and mix by blowing and aspiration to obtain 100 ppm DDQ reagent.

[0030] Example 2 This embodiment describes a method for extracting sulfur dioxide from starch samples. The extraction process is as follows: (1) Accurately weigh 5.0g of sample into a sample cup with a lid.

[0031] (2) Add 1 mL of extraction solvent, then add 14 mL of pure water using a pipette, cover and shake vigorously for 1 min, and let stand for 3 min. The extraction solvent is a sodium hydroxide solution with a concentration of 40 g / L.

[0032] (3) Use a pipette to draw 1.5 mL of sample solution into a 2 mL centrifuge tube, tighten the cap, and centrifuge at 1200 rpm for 1 min. The clear liquid in the upper layer is the sample solution to be tested. The extraction process is completed in a nitrogen glove box.

[0033] The sample solution was prepared by adding a known precise mass of sodium sulfite to sulfur dioxide-free starch (homemade sweet potato starch) according to the method described above. The sulfur dioxide content (actual recovery amount) in the sample solution was then determined spectrophotometrically. The recovery rate (i.e., extraction rate) was calculated by comparing the actual amount added, yielding a sulfur dioxide extraction rate of 90% using the above extraction method. In subsequent experiments, 90% was used as the extraction rate for the alkaline extraction of sulfur dioxide from starch samples.

[0034] Example 3 Using the rapid detection kit of Example 1, taking the limits for sulfur dioxide in starch products as 50 mg / kg, 100 mg / kg, and 200 mg / kg as examples, the amount of each reagent in the 1000 μL reaction system of the "intermediate reaction" was designed from the perspective of saving reagents and facilitating operation (accurate weighing or measuring), and the calculation method is as follows: (1) The sample size of starch product is 5g. The limit value a of sulfur dioxide in starch product is 50mg / kg. During the extraction process, 1mL of extractant is added, and then 14mL of pure water is added with a pipette to make the volume of the extraction system reach 15mL. Since the extraction rate of sulfur dioxide in starch product is b=0.9, if V1 is taken as 42μL, it is calculated that the limit molar amount of sulfur dioxide in 42μL of the sample solution to be tested is 9.85nmol. This sulfur dioxide needs to be reacted with 22μL of DDQ mother liquor with a concentration of 100ppm.

[0035] (2) If the limit value a of sulfur dioxide in starch products is 100 mg / kg, 2 mL of extractant is added during the extraction process, followed by 28 mL of pure water using a pipette to bring the extraction system volume to 30 mL. Since the extraction rate b of sulfur dioxide in starch products is 0.9, V1 can be taken as 42 μL. Similarly, the limit molar amount of sulfur dioxide in 42 μL of the sample solution to be tested is 9.85 nmol, and this sulfur dioxide requires 22 μL of DDQ mother liquor with a concentration of 100 ppm to react with it.

[0036] (3) If the limit value a of sulfur dioxide in starch products is 200 mg / kg, add 4 mL of extractant during the extraction process, and then add 56 mL of pure water using a pipette to make the extraction system volume reach 30 mL. Since the extraction rate b of sulfur dioxide in starch products is 0.9, if V1 is taken as 42 μL, the limit molar amount of sulfur dioxide in 42 μL of the sample solution to be tested is 9.85 nmol. This sulfur dioxide needs to be reacted with 22 μL of DDQ mother liquor with a concentration of 100 ppm.

[0037] Since the sensitivity of the malachite green immunogold assay card is 2 ppb, and whether MG can be detected depends only on the remaining amount of DDQ, while LMG reagent is added in excess, there is no strict requirement for the amount of LMG reagent added. The amount should be based on what is convenient to measure, such as 10 μL.

[0038] Therefore, taking 5g of starch product as an example, the dosage of each reagent in the kit during testing is shown in Table 1.

[0039] Table 1: Composition of the extraction system and intermediate reaction system for 5g starch products Example 4 This embodiment relates to a rapid detection method for sulfur dioxide content in starch products, the steps of which are as follows: (1) Accurately weigh 5.0 g of starch sample into a sample cup with a lid; (2) Add the extractant (40 g / L sodium hydroxide solution) and pure water according to the “Composition of Extraction System” in Table 1, cover and shake vigorously for 1 min, and let stand for 3 min.

[0040] (3) Use a pipette to draw 1.5 ml of sample solution into a 2 ml centrifuge tube, tighten the cap, centrifuge for 1 min, and the clear liquid in the upper layer is the sample solution to be tested.

[0041] (4) Use a pipette to measure 42 μL of the prepared sample solution into a 2 ml centrifuge tube. According to the “Composition of Intermediate Reaction System” in Table 1, use a pipette to add 22 μL of reagent C, 926 μL of reagent A and 22 μL of reagent B to the aforementioned 2 ml centrifuge tube respectively. Cover tightly and shake well. After reacting for 3 min, wait for testing.

[0042] (5) Take out the malachite green immunogold test card and microwells and place them flat on the table. Use a disposable pipette to draw 4 drops (80-100 μL) of the test solution from step (4) into the microwells and time it strictly for 2 minutes. During this time, use the pipette to blow the liquid in the microwells evenly. Add all the liquid in the microwells into the S well of the malachite green immunogold test card and time it for 5 minutes. Read the results within 5-6 minutes.

[0043] (6) Read the test results according to Table 2. Table 2: Methods for reading results from the Malachite Green Immunocolloid Gold Detection Card Example 5 This embodiment tested two starch samples as shown in Table 3, where the limit for sulfur dioxide was 50 mg / kg.

[0044] Table 3: Two starch samples The results of the malachite green immunochromatographic gold test card, obtained by testing according to the method in Example 4, are shown in Table 4.

[0045] Table 4: Detection results of two commercially available starch samples in Example 5 (see Table 4) Figure 2 ) Example 6 This embodiment tested two starch samples as shown in Table 4, where the limit for sulfur dioxide was 50 mg / kg.

[0046] Table 3: Two starch samples The results of the malachite green immunogold test card, obtained by performing the test according to the method in Example 4, are shown in Table 5.

[0047] Table 5: Detection results of two commercially available starch samples in Example 6 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 or all of the technical features. These modifications or substitutions, or combinations of technical features in the above embodiments that do not conflict with each other, can be made in accordance with the manner described in the embodiments. These modifications, substitutions or combinations 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 starch products based on colloidal gold immunochromatography, characterized in that, It includes: S1. Prepare the sample solution to be tested. The starch product was weighed quantitatively, and sulfur dioxide was extracted using a caustic soda solution at room temperature or low temperature. The extract was centrifuged to obtain the clear supernatant, which was the sample solution to be tested. S2, intermediate reaction Take a predetermined volume of the sample solution to be tested. Calculate the limit molar amount of sulfur dioxide in the measured sample solution according to the limit value of sulfur dioxide in starch products and the extraction rate of sulfur dioxide in S1. Add DDQ reagent and LMG reagent and react under pH 6.5-7.5 conditions. The molar amount of DDQ contained in the added DDQ reagent is equal to the limit molar amount of sulfur dioxide. S3, Colloidal gold immune layer reaction After the S2 reaction is complete, add the reaction solution dropwise into the sample well of the malachite green colloidal gold immunochromatographic assay card and interpret the results. The interpretation method is as follows: If the T line is redder than or the same as the C line, it indicates that the malachite green is negative and the sulfur dioxide content in the starch product exceeds the limit. Conversely, if the T line is lighter in color than the C line or the T line is not colored, it indicates that malachite green is positive and the sulfur dioxide content in the starch product does not exceed the limit value. The C line showed no color, therefore the test result is invalid.

2. The rapid detection method according to claim 1, characterized in that, In S1, the caustic alkali solution is sodium hydroxide solution. The extraction process is carried out in a nitrogen-protected chamber at an extraction temperature of 10-30℃. The extraction process of S1 includes: accurately weighing the starch product with a mass of M, adding sodium hydroxide solution and pure water to obtain an extraction system with a total volume of V0, covering and vigorously shaking to mix for 0.5-1.5 min, and letting it stand for 2-4 min; taking 1-2 mL of sample solution into a centrifuge tube, tightening the cap and centrifuging to obtain the clear liquid in the upper layer, which is the sample solution to be tested.

3. The rapid detection method according to claim 1, characterized in that, In S1, the extraction process is carried out under nitrogen protection.

4. The rapid detection method according to claim 2, characterized in that, In S2, take a volume V1 of the sample solution to be tested, and calculate the limit molar amount of sulfur dioxide in the sample solution to be tested according to the limit value a of sulfur dioxide in starch products and the extraction rate b of sulfur dioxide in S1. The limit molar quantity = M × a × b × (V1 / V0) / 64 g / mol.

5. The rapid detection method according to claim 4, characterized in that, In S2, M is in g, a is in mg / g, and b is the extraction rate of sulfur dioxide from starch products.

6. The rapid detection method according to claim 4, characterized in that, In S2, the pH of the reaction system is adjusted to 6.5-7.5 using phosphate buffer. The reaction system consists of the sample solution to be tested, LMG reagent, DDQ reagent, and phosphate buffer. Except for the sample solution to be tested, LMG reagent, and DDQ reagent, any remaining amount less than 1000 μL is supplemented to 1000 μL with phosphate buffer.

7. The rapid detection method according to claim 4, characterized in that, In S2, the reaction system is 1000 μL, in which the solvent of DDQ reagent is anhydrous ethanol with a concentration of 100 ppm and an addition amount of 20 μL; the volume of the sample to be tested is 40-42 μL; the solvent of LMG reagent is anhydrous ethanol with a concentration of 100 ppm and an addition amount of 0.5-10 μL; the remainder is phosphate buffer. When the extraction rate of sulfur dioxide in starch products is 0.9, M is taken as 5g; For foods with a sulfur dioxide limit of 50 mg / kg in starch products, the volume V0 of the extraction system is 15 mL. For foods with a sulfur dioxide limit of 100 mg / kg in starch products, the volume V0 of the extraction system is 30 mL. For foods with a sulfur dioxide limit of 200 mg / kg in starch products, the extraction system volume V0 is 60 mL.

8. The rapid detection method according to claim 6 or 7, characterized in that, In S2, the pH of the phosphate buffer solution is 6.5-7.

0.

9. The rapid detection method according to claim 1, characterized in that, In S3, at 15-30℃, take 80-120μL of the reaction solution after the S2 reaction is completed and put it into the microwell of the gold label. Mix it by suction and blow for 2 minutes, and then add it dropwise into the sample well of the malachite green colloidal gold immunochromatographic assay card. Read the result after 5-6 minutes.

10. A rapid detection kit for sulfur dioxide in starch products based on colloidal gold immunochromatography, characterized in that, It comprises: sodium hydroxide or a solution thereof, LMG reagent, DDQ solid reagent, phosphate buffer, and malachite green colloidal gold immunochromatographic assay card; wherein the LMG reagent is an anhydrous ethanol solution of LMG; the DDQ solid reagent is stored in a sealed glass reagent bottle with a cap and a vacuum-sealed bag, each glass reagent bottle containing a defined mass of DDQ powder; the rapid test kit is used to perform the test according to the rapid test method described in any one of claims 1-9.

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