Fast detection method and kit for sulfur dioxide in starch products based on colloidal gold immunochromatography technology

Abstract

The present application relates to the technical field of food quality detection, and particularly relates to a fast detection method and kit for sulfur dioxide in starch products based on colloidal gold immunochromatography technology. The fast detection method comprises the following steps: preparing a detection solution: quantitatively weighing the starch product, extracting sulfur dioxide at normal temperature or low temperature with a caustic solution, and centrifuging the extraction solution to obtain the upper clear liquid. Intermediate reaction: measuring the detection solution, calculating the limited molar amount of sulfur dioxide according to the limited value and extraction rate of sulfur dioxide, adding an equal molar amount of DDQ reagent and LMG reagent, and reacting at pH 6.5-7.5. Colloidal gold reaction: adding the reaction solution dropwise to a malachite green colloidal gold immunochromatography detection card. Judgment: if the redness of the T line is deeper than that of the C line or the same, the malachite green is negative, and the sulfur dioxide is over-limited; if the redness of the T line is lighter or not colored, the malachite green is positive, and the sulfur dioxide is not over-limited; and if the C line is not colored, the detection is invalid. The present application is suitable for rapid qualitative detection of sulfur dioxide in starch.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food quality detection technology, and particularly relates to a rapid detection method and kit for sulfur dioxide in starch products based on colloidal gold immunochromatography technology. BACKGROUND

[0002] Sulfur dioxide (including sulfite, pyrosulfite, subsulfite, bisulfite, and the detection content is calculated as sulfur dioxide) is used as a food additive and processing aid, and can be used in specified food production. Because sulfur dioxide is harmful to human body, the ADI value is 0-0.7 mg / kg bw, and therefore the maximum allowable residue of specified food is also regulated in the national standard.

[0003] With the establishment of food safety related regulations and the strengthening of food safety supervision, the innovation of detection technology and the application to the field of food safety rapid detection are increasingly strong. The characteristics of the food safety rapid detection method are as follows: allowing certain error (false negative and false positive rate), good sensitivity, fast detection speed (time requirement). The existing sulfur dioxide determination methods mainly include spectrophotometry, distillation titration method, and chromatography. The spectrophotometry needs to be equipped with a spectrophotometer, and the detection process is relatively complicated. The distillation titration method takes at least 2 hours or more, and also needs to be equipped with a distillation instrument and other equipment, which cannot meet the requirements of rapid detection. The chromatography method has high price of chromatograph and high requirements for detection personnel, and also cannot meet the requirements of rapid detection.

[0004] At present, the main methods in the field of food safety rapid detection are colorimetry and immunochromatography colloidal gold rapid detection method. At present, the rapid detection of sulfur dioxide only applies colorimetry, which is judged by visual colorimetry or rapid detection instrument (applying the principle of spectrophotometry). The colorimetry has some shortcomings: (1) the sample liquid must be clear and transparent, and the turbid liquid has a great influence on the result. The treatment methods such as filtration, centrifugation and sedimentation cannot meet the time requirement or the conditions of rapid detection. (2) Different types of food have different colors, and the sample liquid often has a background color, which seriously interferes with the result judgment. The removal of the background color is difficult and time-consuming, and cannot meet the time requirement or the conditions of rapid detection.

[0005] The colloidal gold method based on the technical principle of the addition reaction of sulfur dioxide and malachite green can rapidly detect sulfur dioxide, wherein the concentration of the malachite green reagent is only ppb level, but due to the photosensitivity of malachite green, the shelf life of the aqueous solution of malachite green at normal temperature or under refrigerated storage conditions is very short (2 hours at normal temperature), and the shelf life of the aqueous solution with low concentration is extremely short, and significant changes in concentration occur within 2 hours at normal temperature, thereby leading to opposite detection results, which cannot meet the rapid detection needs of daily samples. Malachite green that is not prepared into a solution is also unstable in chemical properties at normal temperature, and the half-life under natural light is less than 24 h, which limits the application of malachite green as an indicator in rapid detection. SUMMARY

[0006] (I) Technical problems to be solved

[0007] In view of the above-mentioned defects and deficiencies of the prior art, the present application provides a rapid detection method and kit for sulfur dioxide in starch products based on colloidal gold immunochromatography technology, which is based on the principle that leuco-malachite green (LMG) reacts with dichlorodicyanoquinone (DDQ) to generate malachite green (MG). The sample extract is mixed with DDQ and LMG reagents for reaction, and the solution after reaction is detected by a malachite green immunocolloidal gold detection card. Whether the solution generates MG is determined to determine the content of sulfur dioxide in the sample extract, so as to achieve the detection goal of qualitatively judging whether the sulfur dioxide in the starch product exceeds the standard.

[0008] (II) Technical solutions

[0009] In the first aspect, the present application provides a rapid detection method for sulfur dioxide in starch products based on colloidal gold immunochromatography technology, which comprises:

[0010] S1, preparing a sample liquid to be detected

[0011] The starch product is quantitatively weighed, and a caustic solution is used for sulfur dioxide extraction, which is carried out at normal temperature or low temperature. The extraction liquid is subjected to centrifugal treatment to obtain a clear supernatant, and the clear supernatant is the sample liquid to be detected;

[0012] S2, intermediate reaction

[0013] A predetermined volume of the sample liquid to be detected is measured, the limit molar amount of sulfur dioxide in the measured sample liquid to be detected is calculated according to the limit value of sulfur dioxide in the starch product and the extraction rate of sulfur dioxide in S1, and DDQ reagent and LMG reagent are added and reacted under the condition of pH 6.5-7.5. The DDQ molar amount contained in the added DDQ reagent is equal to the limit molar amount of sulfur dioxide;

[0014] S3, colloidal gold immunochromatography reaction

[0015] The reaction solution after S2 reaction is added dropwise into the sample adding hole of the malachite green colloidal gold immunochromatography detection card, and the result is interpreted; the interpretation method is as follows:

[0016] If the red color of the T line is deeper than that of the C line or is as deep as that of the C line, it indicates that the malachite green is negative, and the sulfur dioxide content in the starch product exceeds the limit value;

[0017] On the contrary, if the red color of the T line is shallower than that of the C line or the T line does not show color, it indicates that the malachite green is positive, and the sulfur dioxide content in the starch product does not exceed the limit value;

[0018] The C line does not show color, and the detection result of this time is invalid.

[0019] According to the preferred embodiment of the present application, in S1, the caustic solution is a sodium hydroxide solution (concentration of 30-50 g / L), and the extraction process is carried out in a nitrogen protection box, and the extraction temperature is 10-30℃.

[0020] The extraction process of S1 includes: accurately weighing the starch product with a mass of M, adding a sodium hydroxide solution and pure water to obtain an extraction system with a total volume of V0, mixing and oscillating the reaction for 0.5-1.5 min, and standing for 2-4 min; taking 1-2 mL of sample solution to a centrifugal tube, tightly covering the cap and performing centrifugal treatment, and obtaining the upper clear liquid as the sample solution to be detected.

[0021] According to the preferred embodiment of the present application, in S1, the extraction process is carried out under nitrogen protection, for example, in a nitrogen glove box, so as to avoid the oxidation of sulfur dioxide (sulfite).

[0022] According to the preferred embodiment of the present application, in S2, the volume V1 of the sample solution to be detected is taken, and the limit molar amount of sulfur dioxide in the taken sample solution to be detected is calculated according to the limit value a of sulfur dioxide in the starch product and the extraction rate b of sulfur dioxide in S1;

[0023] The limit molar amount = M × a × b × (V1 / V0) / 64 g / mol.

[0024] According to the preferred embodiment of the present application, in S2, M is in units of g, a is in units of mg / g; and b is the extraction rate of sulfur dioxide in the starch product.

[0025] According to the preferred embodiment of the present application, in S2, the pH of the reaction system is adjusted to 6.5-7.5 by using a phosphate buffer; the reaction system is composed of the sample solution to be detected, an LMG reagent, a DDQ reagent and a phosphate buffer; and the part less than 1000 microliters is supplemented to 1000 μL by the phosphate buffer, except for the sample solution to be detected, the LMG reagent and the DDQ reagent.

[0026] According to the preferred embodiment of the present application, in S2, the reaction system is 1000 μL, the solvent in the DDQ reagent is anhydrous ethanol, the concentration is 100 ppm, and the added amount is 20 μL; the volume of the sample to be detected is 40-42 μL; the solvent in the LMG reagent is anhydrous ethanol, the concentration is 100 ppm, and the added amount is 0.5-10 μL; and the rest is the phosphate buffer;

[0027] wherein, when the extraction rate of sulfur dioxide in the starch product is 0.9, M is 5 g;

[0028] For the food with the limit value of sulfur dioxide in the starch product being 50 mg / kg, the volume V0 of the extraction system is 15 mL;

[0029] For the food with the limit value of sulfur dioxide in the starch product being 100 mg / kg, the volume V0 of the extraction system is 30 mL;

[0030] For the food with the limit value of sulfur dioxide in the starch product being 200 mg / kg, the volume V0 of the extraction system is 60 mL.

[0031] According to the preferred embodiment of the present application, in S2, the pH of the phosphate buffer is 6.5-7.0.

[0032] According to the preferred embodiment of the present application, in S3, 80-120 μL of the reaction solution after the reaction in S2 is taken to the gold mark microwells at 15-30 ℃, mixed and blown for 2 min, then added dropwise to the sample well of the malachite green colloidal gold immunochromatography detection card, and the result is read after 5-6 min.

[0033] In the second aspect, the present application provides a fast detection kit for sulfur dioxide in starch products based on colloidal gold immunochromatography technology, which comprises:

[0034] sodium hydroxide or a solution thereof, LMG reagent, DDQ solid reagent, phosphate buffer, and malachite green colloidal gold immunochromatography detection card; the LMG reagent is anhydrous ethanol solution of LMG; the DDQ solid reagent is sealed with a constant-volume glass reagent bottle and stored in a vacuum bag, each constant-volume glass reagent bottle contains a certain mass of DDQ powder (dissolved with anhydrous ethanol before use); the fast detection kit is used for detection according to the above fast detection method.

[0035] (Three) beneficial effects

[0036] The reagent used in the fast detection method of sulfur dioxide in the starch product of the application has good stability at normal temperature, and the concentration of LMG used is relatively high (can reach 100 ppm or higher), and LMG has good stability at normal temperature, and in the detection process, LMG is added in excess, as long as there is residual DDQ in the S2 reaction system to cause LMG to be converted into MG, which can be recognized by the colloidal gold detection card (the sensitivity reaches 2 ppb level), so the method of the application has no strict requirement on the concentration of LMG, even if the concentration changes significantly during storage, it will not affect the final detection result, and the LMG mother liquor can be stored at normal temperature for 6 months and still meet the detection requirements.

[0037] The DDQ in the kit is sealed with a glass reagent bottle and stored in a vacuum bag, each glass reagent bottle contains a certain mass of DDQ powder, and each kit can be matched with 6-12 bottles of DDQ powder, which can be used by adding anhydrous ethanol for dissolution, so that the kit can meet the use requirement of 6-12 months. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The reaction formula for dehydrogenation of LMG to MG by DDQ.

[0039] Figure 2 The photos of the MG immune colloidal gold detection card showing negative (left photo) and positive (right photo) respectively. DETAILED DESCRIPTION

[0040] In order to better explain the application, so as to be understood, the application is described in detail in combination with the drawings through specific embodiments.

[0041] The principle of the fast detection method of sulfur dioxide in the starch product based on the colloidal gold immune chromatography technology of the application is as follows:

[0042] Sulfur dioxide (sulfite) has strong reducing property, and its reducing property is greater than that of leucomalachite green (LMG), so in the reaction system coexisting with sulfur dioxide, leucomalachite green (LMG) and dichlorodicyanoquinone (DDQ), sulfur dioxide (sulfite) is prior to LMG to react with DDQ by redox reaction; if sulfur dioxide is insufficient, leading to excess DDQ, then the remaining DDQ will oxidize LMG to obtain MG (malachite green) which can be detected by a malachite green immunocolloidal gold detection card, at this time, the detection result is malachite green positive, and sulfur dioxide is relatively insufficient; on the contrary, if sulfur dioxide is sufficient or even excessive, then DDQ in the reaction system will be consumed, at this time, even if sulfite is excessive, it cannot react with LMG, leading to no MG being generated, and the reaction system cannot detect MG, at this time, the detection result is malachite green negative, and sulfur dioxide is relatively sufficient or even excessive. Therefore, the residual DDQ in the reaction system and the content of sulfur dioxide are in inverse relationship, and the residual DDQ can be indirectly detected by malachite green, so that the positive and negative of malachite green detected by the malachite green immunocolloidal gold detection card can be used to indirectly determine whether sulfur dioxide is excessive.

[0043] DDQ is an excellent dehydrogenation reagent, and can quickly react with LMG to generate MG (the reaction process is as shown in Figure 1 ). Although conventional oxidants such as potassium permanganate or H2O2 have strong oxidizing property, the product after the reaction with LMG is not MG, and the purpose of being detected by the malachite green immunocolloidal gold detection card cannot be achieved. Tetrachloroquinone is also a dehydrogenation reagent, but its reaction rate is significantly lower than that of DDQ, and cannot meet the requirement of rapid detection. At the same time, the implementation of the present application is also based on the chemical property that the reducing property of sulfur dioxide (sulfite) is greater than that of LMG, and although sulfur dioxide also has certain oxidizing property, its oxidizing property is not enough to react with LMG to generate MG.

[0044] In addition, the above reaction process has certain requirements on pH. Although DDQ can dehydrogenate LMG to generate MG that can be detected, malachite green can further generate basic malachite green in a strong alkaline solution (this product cannot be detected by a malachite green colloidal gold detection card). Therefore, it is necessary to ensure that the reaction system in which sulfur dioxide, leuco-malachite green (LMG) and dichlorodicyanoquinone (DDQ) coexist cannot be a strong alkaline environment. Similarly, a strong acidic environment can accelerate the hydrolysis of DDQ and inhibit the conversion of LMG to MG (strong acid can easily cause the detection card to fail), so the reaction conditions are set to pH 6.5-7.5. Since caustic solution is used as an extractant when extracting sulfur dioxide from edible starch, the sample solution to be detected may be alkaline. In order to adjust the pH of the coexisting reaction system, the phosphate buffer (pH 6.5-7) is used to adjust the pH of the sample solution to be detected, so as to ensure that it is 6.5-7.5. Therefore, the reaction system is composed of the sample solution to be detected, LMG reagent, DDQ reagent and phosphate buffer. Among them, the LMG reagent and the DDQ reagent are anhydrous ethanol solutions of LMG and DDQ, respectively. In addition, the results of the malachite green immunocolloidal gold detection card read at 15-30℃ are more accurate, and do not affect the correct interpretation of positive and negative results.

[0045] The following is described in conjunction with the embodiments of the present application.

[0046] Example 1

[0047] The present embodiment provides a rapid detection kit for sulfur dioxide in starch products based on colloidal gold immunochromatography technology, which is composed of:

[0048] Extractant: sodium hydroxide solution with a concentration of 40 g / L. Reagent A: phosphate buffer solution with pH 6.8. Reagent B: 100 ppm LMG solution. Reagent C: DDQ powder in a 100 mL glass reagent bottle, sealed with a cover, and each bottle contains 0.01 g of DDQ powder. Anhydrous ethanol, pure water and malachite green immunocolloidal gold detection card (purchased from Guangzhou Ruisen Biotechnology Co., Ltd. The sensitivity is 2 ppb).

[0049] Preparation method of reagent A: weigh 0.786 g of NaH2PO4·2H2O and 0.88 g of Na2HPO4·2H2O, dissolve in a suitable amount of pure water, add 20 μL of Triton X-100, and dilute to 100 ml. The pH of the buffer reagent is 6.8.

[0050] Preparation method of reagent B: accurately weigh 0.01 g of LMG and dissolve in a suitable amount of anhydrous ethanol, and then dilute to 100 mL with ethanol to obtain a 100 ppm LMG reagent.

[0051] Reagent C: Open a glass reagent bottle cap, inject anhydrous ethanol to 100 mL with a syringe needle, and mix well by blowing and sucking to obtain 100 ppm DDQ reagent.

[0052] Example 2

[0053] This example is a method for extracting sulfur dioxide from a starch sample. The extraction process is as follows:

[0054] (1) Accurately weigh 5.0 g of the sample into a sample cup with a cover.

[0055] (2) Add 1 mL of the extraction agent, then use a pipette to add 14 mL of pure water, mix well by vigorous shaking for 1 min, and stand for 3 min. The extraction agent is a 40 g / L sodium hydroxide solution.

[0056] (3) Use a pipette to take 1.5 mL of the sample solution into a 2 mL centrifuge tube, cover tightly, and centrifuge at 1200 rpm for 1 min. The upper clear liquid is the sample solution to be tested. The extraction process is completed in a nitrogen glove box.

[0057] By adding a known precise mass of sodium sulfite to starch without sulfur dioxide (self-made sweet potato starch), the sample solution to be tested is prepared according to the above method. Then the content of sulfur dioxide in the sample solution to be tested is determined by spectrophotometry (actual recovery), compared with the actual amount added, the recovery rate (i.e. extraction rate) is calculated, and the sulfur dioxide extraction rate of the above extraction method is 90%. In the following experiments, 90% is taken as the extraction rate of sulfur dioxide extracted by alkali method in starch samples.

[0058] Example 3

[0059] Using the rapid detection kit of Example 1, taking the limit value of sulfur dioxide in starch products as 50 mg / kg, 100 mg / kg, and 200 mg / kg as examples, the addition amount of each reagent in the 1000 μL reaction system of the "intermediate reaction" is designed from the perspective of saving reagents and facilitating operation (accurate weighing or pipetting), and the calculation method is as follows:

[0060] (1) The sample amount of the starch product is 5 g, the limit value a of sulfur dioxide in the starch product is 50 mg / kg, and 1 mL of the extraction agent is added during the extraction process, then 14 mL of pure water is added with a pipette to make the extraction system volume reach 15 mL. Since the extraction rate b of sulfur dioxide in the starch product is 0.9, V1 is taken as 42 μL, and it is calculated that the limit molar amount of sulfur dioxide in 42 μL of the sample solution to be tested is 9.85 nmol, which requires 22 μL of the DDQ mother liquor with a concentration of 100 ppm to react completely.

[0061] (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, and then 28 mL of pure water is added using a pipette to make the volume of the extraction system reach 30 mL. Since the extraction rate b of sulfur dioxide in starch products is 0.9, V1 is taken as 42 μL. Similarly, the limit molar amount of sulfur dioxide in 42 μL of the sample liquid to be detected is 9.85 nmol, and these sulfur dioxide need 22 μL of DDQ mother liquor with a concentration of 100 ppm to react completely.

[0062] (3) If the limit value a of sulfur dioxide in starch products is 200 mg / kg, 4 mL of extractant is added during the extraction process, and then 56 mL of pure water is added using a pipette to make the volume of the extraction system reach 30 mL. Since the extraction rate b of sulfur dioxide in starch products is 0.9, V1 is taken as 42 μL. The limit molar amount of sulfur dioxide in 42 μL of the sample liquid to be detected is 9.85 nmol, and these sulfur dioxide need 22 μL of DDQ mother liquor with a concentration of 100 ppm to react completely.

[0063] Since the sensitivity of the malachite green immunocolloidal gold detection card is 2 ppb, whether MG can be detected depends only on the remaining amount of DDQ, and the LMG reagent is added in excess, so the amount of LMG reagent added is not strictly required, and can be conveniently measured, for example, 10 μL.

[0064] Therefore, taking 5 g of starch products as an example, the amount of each reagent in the kit during detection is shown in Table 1.

[0065] Table 1: Composition of the extraction system and the intermediate reaction system corresponding to 5 g of starch products

[0066]

[0067] Example 4

[0068] This example relates to a rapid detection method for the content of sulfur dioxide in starch products, and the steps are as follows:

[0069] (1) Accurately weigh 5.0 g of starch sample into a sample cup with a cover;

[0070] (2) Add extractant (40 g / L sodium hydroxide solution) and pure water according to the "extraction system composition" in Table 1, cover tightly, mix vigorously for 1 min, and stand for 3 min.

[0071] (3) Use a pipette to suck 1.5 ml of sample liquid into a 2 ml centrifuge tube, cover tightly, and centrifuge in a centrifuge for 1 min. The upper clear liquid is the sample liquid to be detected.

[0072] (4) Take 42 μL of the treated sample liquid into a 2 ml centrifuge tube with a pipette, and add 22 μL of reagent C, 926 μL of reagent A and 22 μL of reagent B into the 2 ml centrifuge tube according to the "intermediate reaction system composition" in Table 1, tightly cover and shake, and then detect after 3 min of reaction.

[0073] (5) Take out the Malachite Green immunocolloidal gold detection card and the microwell and place them on the table, use a disposable pipette to take the sample liquid in step (4), drop 4 drops (80-100 μL) into the microwell, strictly time for 2 min, and use the pipette to evenly blow the liquid in the microwell during the period. Drop all the liquid in the microwell into the S hole of the Malachite Green immunocolloidal gold detection card, time for 5 min, and read the result within 5-6 min.

[0074] (6) Read the detection result according to Table 2

[0075] Table 2: Reading method of the Malachite Green immunocolloidal gold detection card

[0076]

[0077] Example 5

[0078] In this example, two kinds of starch samples in Table 3 were detected, and the limit standard of sulfur dioxide was 50 mg / kg.

[0079] Table 3: Two kinds of starch samples

[0080]

[0081] The detection was carried out according to the method of Example 4, and the display result of the Malachite Green immunocolloidal gold detection card was shown in Table 4.

[0082] Table 4: Detection results of two kinds of commercially available starch samples in Example 5 (see Figure 2 )

[0083]

[0084] Example 6

[0085] In this example, two kinds of starch samples in Table 4 were detected, and the limit standard of sulfur dioxide was 50 mg / kg.

[0086] Table 3: Two kinds of starch samples

[0087]

[0088] The detection was carried out according to the method of Example 4, and the display result of the Malachite Green immunocolloidal gold detection card was shown in Table 5.

[0089] Table 5: Results of testing of two commercial starch samples of Example 6

[0090]

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements, or combinations of the technical features in the above embodiments, do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

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. The caustic soda 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, and obtaining the clear liquid in the upper layer is 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. The calculation method for the limit molar amount of sulfur dioxide is as follows: 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; Limit molar amount = M×a×b×(V1 / V0) / 64g / mol. 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 extraction process is carried out under nitrogen protection.

3. The rapid detection method according to claim 1, 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.

4. The rapid detection method according to claim 1, 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.

5. The rapid detection method according to claim 1, 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.

6. The rapid detection method according to claim 4 or 5, characterized in that, In S2, the pH of the phosphate buffer solution is 6.5-7.

0.

7. 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.

8. 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 vacuum-sealed in a vacuum 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 1-7.

Images