Preparation method and application of a flour pretreatment solution

Abstract

The present invention relates to the technical field of flour quality detection, and specifically discloses a preparation method and application of a flour pretreatment solution. By mixing flour with nitric acid solution and perchloric acid solution in a specific volume ratio, microwave digestion treatment is carried out, and after cooling, a primary treatment solution is obtained. Further, dilute hydrochloric acid is added to the primary treatment solution, and the flour treatment product obtained through filtration and washing is then added with hydrofluoric acid solution, and impregnated and kept warm at a specific temperature to obtain the flour pretreatment solution. The preparation method of the flour pretreatment solution provided by the present invention is simple to operate and can be completed within only three hours. The RSD value of the detection result of the present invention is smaller than that of the national standard, and the detection result is more accurate than the national standard, and can meet the requirements of large-scale production analysis and inspection.

Description

Technical Field

[0001] The present invention relates to the technical field of flour quality detection, and particularly relates to a preparation method and application of a flour pretreatment solution. Background Art

[0002] The main component of talcum powder is magnesium silicate containing crystal water, with the molecular formula of Mg 3 [Si 4 O 10 (OH) 2 , and long-term intake of a large dose of magnesium silicate is likely to cause renal silicate stones. For patients with renal insufficiency, phenomena such as dizziness, fainting, arrhythmia or mental symptoms, and abnormal fatigue may occur. The national standard method for detecting talcum powder in food is mainly GB5009.269-2016 "National Food Safety Standard - Determination of Talcum Powder in Food". This pretreatment method has steps such as weighing the sample → adding acid and heating (about 3h) → cooling (about 2h) → filtering and washing (about 1h) → adding acid, heating, removing acid, and volume fixing (about 5h). This method is cumbersome to process, time-consuming, and the accuracy of the detection results. Therefore, providing a simple operation method for preparing a flour pretreatment solution is of great significance for achieving accurate detection of talcum powder in flour. Summary of the Invention

[0003] In view of this, the present invention provides a preparation method of a flour pretreatment solution to solve the problems of long time consumption, cumbersome processing, and low detection accuracy in the preparation of the existing flour pretreatment solution. The present invention further improves the detection accuracy of talcum powder in flour by optimizing the pretreatment method.

[0004] To solve the above technical problems, the technical solution provided by the present invention is as follows:

[0005] A preparation method of a flour pretreatment solution includes the following steps:

[0006] Step a: Mix the flour and mixed acid evenly, perform microwave digestion treatment, and cool down to obtain a primary treatment solution; wherein, the mixed acid is a mixed solution of a nitric acid solution and a perchloric acid solution, the mass concentration of the nitric acid solution is 68%-70%, the mass concentration of the perchloric acid solution is 30%-35%, and the volume ratio of the nitric acid solution to the perchloric acid solution is 2.5-3.5:1;

[0007] Step b: Add dilute hydrochloric acid to the primary treatment solution, stir, filter, and wash to obtain a flour treatment product;

[0008] Step c: Add a hydrofluoric acid solution to the flour treatment product, heat up to 150°C-180°C, and keep warm for impregnation to obtain a flour pretreatment solution.

[0009] Compared with the prior art, the preparation method of the flour pretreatment solution provided by the present invention adds a mixed solution of nitric acid solution and perchloric acid solution to the flour. By limiting the specific ratio of the nitric acid solution and the perchloric acid solution and combining with a specific microwave digestion procedure, the organic matter in the flour can be decomposed to the greatest extent without affecting the talc content in the flour. Further, after cooling the primary treatment solution, adding a specific dilute hydrochloric acid can further remove the Mg element in the flour improver, and at a specific temperature, it can also ensure that the Mg in the talc will not be digested, improving the accuracy of the final detection result. Finally, by adding a specific hydrofluoric acid and heating, the Mg in the talc can be fully dissolved. The preparation method provided by the present invention is simple to operate and can meet the needs of large-scale production analysis and inspection. 3 The Mg element of

[0010] Preferably, in step a, the condition for cooling is that the end temperature is 20°C - 30°C.

[0011] Preferably, the volume concentration of hydrofluoric acid in the hydrofluoric acid solution is 28% - 32%.

[0012] Preferably, the concentration of the dilute hydrochloric acid is 1.5 - 2 mol / L.

[0013] Preferably, the mass-volume ratio of the flour to the mixed acid is 1:31 - 35, where the unit of mass is grams and the unit of volume is milliliters.

[0014] By limiting the specific mass-volume ratio of the flour to the mixed acid, the organic matter in the flour can be digested to the greatest extent, which is beneficial to the continuation of the subsequent reaction.

[0015] Preferably, the mass-volume ratio of the flour to the dilute hydrochloric acid is 1:15 - 20, where the unit of mass is grams and the unit of volume is milliliters.

[0016] By limiting the mass-volume ratio of the flour to the dilute hydrochloric acid, the Mg element in the flour improver can be further removed, ensuring that the dilute hydrochloric acid can remove the Mg element in the flour except for talc to the greatest extent. 3 of

[0017] Preferably, the mass-volume ratio of the flour to the hydrofluoric acid solution is 1:10 - 15, where the unit of mass is grams and the unit of volume is milliliters.

[0018] Preferably, in step a, the specific steps of the microwave digestion treatment are as follows: first, heat up to 110°C - 120°C within 2 min - 3 min and maintain for 3 min - 5 min, then heat up to 140°C - 145°C within 3 min - 5 min and maintain for 7 min - 8 min, and finally heat up to 160°C - 165°C within 2 min - 3 min and maintain for 18 min - 20 min.

[0019] The preferred microwave digestion treatment step can accelerate the reaction of the mixed acid, make the reaction more complete, and improve the efficiency and accuracy of the reaction.

[0020] It should be noted that after the flour and the mixed acid are mixed evenly, they are transferred to a sealed device for microwave digestion treatment.

[0021] Preferably, in step b, the stirring rate is 30 r / min - 50 r / min, and the stirring time is 30 min - 40 min.

[0022] Furthermore, in step b, the washing condition is to rinse until the water body is transparent.

[0023] Preferably, in step c, the heat preservation and impregnation are stopped when the remaining solution is 25% - 30% of the total volume of the added hydrofluoric acid solution.

[0024] The present invention provides a flour pretreatment solution, which is prepared by the preparation method of any one of the above flour pretreatment solutions.

[0025] The present invention also provides the application of the above flour pretreatment solution in detecting talcum powder.

[0026] The preparation method of the flour pretreatment solution provided by the present invention is simple to operate, and the operation can be completed within only three hours. Moreover, the RSD value of the detection result of the present invention is smaller than that of the national standard, and the detection result is more accurate than the national standard, and can meet the requirements of large-scale production analysis and inspection. Specific Embodiments

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with implementation cases. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Example 1

[0029] A preparation method of a flour pretreatment solution includes the following steps:

[0030] Weigh 0.5 g of flour and mix it evenly with 15.5 mL of mixed acid (the volume ratio of a nitric acid solution with a mass concentration of 68% and a perchloric acid solution with a mass concentration of 30% is 2.5:1), and carry out microwave digestion treatment; after cooling to 20 °C, add 7.5 mL of dilute hydrochloric acid with a concentration of 1.5 mol / L, stir at a speed of 30 r / min for 30 min, filter to obtain a flour treatment product; wash the obtained flour treatment product until the water body is transparent, add 5 mL of hydrofluoric acid solution with a volume concentration of 28%, and heat at 150 °C until the remaining solution is 30% of the total volume of the added hydrofluoric acid solution to obtain a flour pretreatment solution.

[0031] Among them, the conditions for microwave digestion treatment are as follows: In the first step, the temperature is raised to 120 °C within 3 minutes and maintained for 3 minutes. In the second step, the temperature is raised to 150 °C within 3 minutes and maintained for 8 minutes. In the third step, the temperature is raised to 165 °C within 2 minutes and maintained for 15 minutes.

[0032] Example 2

[0033] A method for preparing a pretreatment solution for flour includes the following steps:

[0034] Weigh 0.5 g of flour and 17.5 mL of mixed acid (the volume ratio of a nitric acid solution with a mass concentration of 70% and a perchloric acid solution with a mass concentration of 35% is 3.5:1), mix them evenly, and carry out microwave digestion treatment; after cooling to 30 °C, add 10 mL of dilute hydrochloric acid with a concentration of 2 mol / L, stir at a speed of 50 r / min for 40 min, filter to obtain a flour treatment product; wash the obtained flour treatment product until the water body is transparent, add 7.5 mL of hydrofluoric acid solution with a volume concentration of 30%, and heat at 180 °C until the remaining solution is 25% of the total volume of the added hydrofluoric acid solution to obtain a pretreatment solution for flour.

[0035] Among them, the conditions for microwave digestion treatment are as follows: In the first step, the temperature is raised to 110 °C within 2 minutes and maintained for 5 minutes. In the second step, the temperature is raised to 160 °C within 5 minutes and maintained for 7 minutes. In the third step, the temperature is raised to 160 °C within 3 minutes and maintained for 20 minutes.

[0036] Example 3

[0037] A method for preparing a pretreatment solution for flour includes the following steps:

[0038] Weigh 0.5 g of flour and 16 mL of mixed acid (the volume ratio of a nitric acid solution with a mass concentration of 69% and a perchloric acid solution with a mass concentration of 33% is 3:1), mix them evenly, and carry out microwave digestion treatment; after cooling to 26 °C, add 9 mL of dilute hydrochloric acid with a concentration of 1.8 mol / L, stir at a speed of 40 r / min for 33 min, filter to obtain a flour treatment product; wash the obtained flour treatment product until the water body is transparent, add 6 mL of hydrofluoric acid solution with a volume concentration of 29%, and heat at 156 °C until the remaining solution is 28% of the total volume of the added hydrofluoric acid solution to obtain a pretreatment solution for flour.

[0039] Among them, the conditions for microwave digestion treatment are as follows: In the first step, the temperature is raised to 115 °C within 2.5 minutes and maintained for 4 minutes. In the second step, the temperature is raised to 155 °C within 4 minutes and maintained for 7.5 minutes. In the third step, the temperature is raised to 163 °C within 2.5 minutes and maintained for 18 minutes.

[0040] Comparative Example 1

[0041] In this comparative example, compared with Example 1, the difference is that the mixed acid is a nitric acid solution with a mass concentration of 68% and a perchloric acid solution with a mass concentration of 30%, and the volume ratio is 4:1; other steps are the same as those in Example 1.

[0042] Comparative Example 2

[0043] In this comparative example, compared with Example 1, the difference is that the addition of dilute hydrochloric acid is omitted, and the specific operation is as follows:

[0044] Weigh 0.5 g of flour and mix it evenly with 15.5 mL of mixed acid (the volume ratio of nitric acid solution with a mass concentration of 68% and perchloric acid solution with a mass concentration of 30% is 2.5:1), and carry out microwave digestion treatment; after cooling to 20 °C, filter to obtain the flour treatment product; wash the obtained flour treatment product until the water body is transparent, add 5 mL of hydrofluoric acid solution with a volume concentration of 28%, and heat it at 150 °C until the remaining solution is 30% of the total volume of the added hydrofluoric acid solution to obtain the pre-treated flour solution.

[0045] Among them, the conditions for microwave digestion treatment are as follows: in the first step, heat up to 120 °C within 3 minutes and maintain it for 3 minutes; in the second step, heat up to 150 °C within 3 minutes and maintain it for 8 minutes; in the third step, heat up to 165 °C within 2 minutes and maintain it for 15 minutes.

[0046] Take the flour ground from fresh wheat and add 0.4% of talcum powder by the mass of the flour. Then take 0.5 g of the flour added with talcum powder, and prepare the pre-treated flour solutions according to Examples 1-3 and Comparative Examples 1-2 respectively. Dilute the pre-treated flour solutions prepared in Examples 1-3 and Comparative Examples 1-2 to 100 mL in a volumetric flask with strontium chloride solution to obtain the sample solutions; detect according to the method in GB5009.269-2016, and take 0.5 g of the same batch of flour and use 5.2.2 in GB5009.269-2016 to prepare the control sample solution. Among them, both the control sample solution and the sample solution are set with 5 replicates; detect them, and the detection results of talcum powder are shown in Table 1:

[0047] Table 1 Detection Results of Talcum Powder

[0048] Test Items Test Results RSD / % National Standard Test 4.3 g / kg 4.2％ Example 1 3.8 g / kg 1.8％ Example 2 4.1 g / kg 1.5％ Example 3 3.95 g / kg 2.0％ Comparative Example 1 4.26 g / kg 3.8％ Comparative Example 2 5.9 g / kg 4.5％

[0049] As can be seen from Table 1, compared with the national standard, the detection method of this application is more convenient, and this operation can be completed in only three hours. Moreover, the RSD value of the detection result of the present invention is smaller than that of the national standard, and the detection result is more accurate than the national standard. The preparation method provided by the present invention is simple in operation and can meet the needs of large-scale production analysis and inspection.

[0050] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a pretreatment solution for flour, characterized in that, it comprises the following steps: Step a: Mix the flour and the mixed acid evenly, carry out microwave digestion treatment, and cool down to 20°C - 30°C to obtain a primary treatment solution; wherein, the mixed acid is a mixed solution of a nitric acid solution and a perchloric acid solution, the mass concentration of the nitric acid solution is 68% - 70%, the mass concentration of the perchloric acid solution is 30% - 35%, and the volume ratio of the nitric acid solution to the perchloric acid solution is 2.5 - 3.5:1; Step b: Add dilute hydrochloric acid with a concentration of 1.5 - 2 mol / L to the primary treatment solution, stir, filter, and wash to obtain a flour treatment product; Step c: Add a hydrofluoric acid solution to the flour treatment product, heat up to 150°C - 180°C, and keep it warm and impregnated to obtain a pretreatment solution for flour; The mass - volume ratio of the flour to the dilute hydrochloric acid is 1:15 - 20, where the unit of mass is grams and the unit of volume is milliliters; In step a, the specific steps of the microwave digestion treatment are: first heat up to 110°C - 120°C within 2 min - 3 min and keep it for 3 min - 5 min, then heat up to 140°C - 145°C within 3 min - 5 min and keep it for 7 min - 8 min, and finally heat up to 160°C - 165°C within 2 min - 3 min and keep it for 18 min - 20 min.

2. The method for preparing a pretreatment solution for flour according to claim 1, characterized in that, in step a, the volume concentration of hydrofluoric acid in the hydrofluoric acid solution is 28% - 32%.

3. The method for preparing a pretreatment solution for flour according to claim 1, characterized in that, the mass - volume ratio of the flour to the mixed acid is 1:31 - 35, where the unit of mass is grams and the unit of volume is milliliters.

4. The method for preparing a pretreatment solution for flour according to claim 1, characterized in that, the mass - volume ratio of the flour to the hydrofluoric acid solution is 1:10 - 15, where the unit of mass is grams and the unit of volume is milliliters.

5. The method for preparing a pretreatment solution for flour according to claim 1, characterized in that, in step b, the stirring rate is 30 r / min - 50 r / min and the stirring time is 30 min - 40 min; and / or in step c, stop impregnation when the remaining solution is 25% - 30% of the total volume of the added hydrofluoric acid solution.

6. A pretreatment solution for flour, characterized in that, it is prepared by the method for preparing a pretreatment solution for flour according to any one of claims 1 - 5.

7. Use of the pretreatment solution for flour according to claim 6 in detecting talcum powder in flour.