A method for reducing fluorine in food using natural ingredients

Abstract

The present invention discloses a method for reducing fluorine in food using natural ingredients, belonging to the technical field of selective removal of fluoride ions, including the extraction of natural ingredients and the adsorption of fluoride ions. Specifically, it includes tea pretreatment, extraction of natural ingredients, and defluorination of natural ingredients, etc. The tea leaves are dried, crushed and sieved to prepare tea powder, then the tea powder is mixed with ethanol, shaken at a constant temperature, and then filtered to remove alcohol and this step is repeated 3 times, and the tea powder is dried to a constant weight; then the tea powder obtained by pretreatment is ultrasonically extracted, the extract is filtered and collected, the supernatant obtained by centrifuging the extract is then concentrated under reduced pressure, mixed with absolute ethanol, allowed to stand, and the ethanol is removed to collect the precipitate; the precipitate is purified to remove fluoride ions, dried in an oven to a constant weight, and finally the treated precipitate is used to adsorb fluoride ions in food to achieve the defluorination effect. This method does not require additional addition of metal adsorption, has strong safety, low toxicity and side effects, and the operation process is simple and can achieve batch production.

Description

Technical Field

[0001] The present invention relates to the technical field of selective removal of fluoride ions, and particularly relates to a method for reducing fluoride in food using natural ingredients. Background Art

[0002] Fluoride is an important element in nature. Fluoride has a dual effect on the human body. Appropriate intake of fluoride can maintain the normal calcium and phosphorus metabolism of the body. However, when the human body ingests excessive fluoride for a long time, it is prone to suffer from dental fluorosis and skeletal fluorosis. In addition, excessive fluoride can also inhibit the activities of lipase, urease and bone phosphatase, causing metabolic disorders and resulting in chronic systemic poisoning. Tea drinking and diet are important supplementary sources of fluoride intake for the human body. Tea trees are plants with strong fluoride enrichment ability. Especially, the leaves have special accumulation characteristics of fluoride, and the old leaves have a higher fluoride content than the young leaves. When people ingest fluoride from tea leaves in an amount of 2.7 - 5.9 mg·d -1 fluorosis may occur; therefore, effectively reducing the excessive fluoride ions in high-fluoride foods has always been a research hotspot and difficulty.

[0003] At present, there are many methods for reducing the fluoride content in food, mainly including chemical precipitation method, ion exchange method, membrane filtration method, electrolysis method and adsorption method. The highly selective adsorption method has attracted much attention due to its advantages such as simple operation, high efficiency and low cost; in the prior art and literature, good fluoride reduction effects have been achieved by using metal-based biosorbents and MOFs materials. However, the use of metal-based biosorbents and MOFs materials has a high cost and is not convenient for large-scale promotion. Moreover, the reported methods for reducing the fluoride content in brick tea soup utilize the characteristics of fluoride reacting with some chemical reagents (mainly aluminum salts, calcium salts and iron salts) to undergo adsorption and precipitation reactions, converting the free fluoride in brick tea into inactive fluoride that is difficult to be absorbed by the human body. However, the treatment effects of these adsorbents need to be improved, the required treatment time is long, and there may be metal residue hazards, which pose great problems in practical applications.

[0004] Therefore, developing a method for reducing fluoride in food using natural ingredients, which does not require additional metal adsorption, has strong safety, low toxicity and side effects, and is simple in production operation and convenient for large-scale promotion, is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] To this end, the present invention provides a method for reducing fluoride in food using natural ingredients to solve the problems in the prior art that the treatment effect needs to be improved due to the conversion of free fluoride into inactive fluoride that is difficult to be absorbed by the human body by using the characteristics of fluoride reacting with some chemical reagents (mainly aluminum salts, calcium salts and iron salts), and there may be metal residue hazards, as well as the problems of high material cost and inconvenience for large-scale promotion.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for reducing fluorine in food using natural ingredients provided by the present invention includes the following steps:

[0008] (1) Tea pretreatment: Dry the tea leaves, crush and sieve them to prepare tea powder. Mix the tea powder with 80% ethanol, place it on a shaker for constant-temperature oscillation treatment, then filter by suction to discard the alcohol and repeat the above steps 3 times. Dry the pretreated tea powder to a constant weight for standby;

[0009] (2) Natural ingredient extraction: Add primary water to the tea powder obtained by pretreatment and perform ultrasonic extraction. Then, preliminarily filter to collect the extract. Centrifuge the collected extract, and concentrate the obtained supernatant under reduced pressure; At 4°C, mix the concentrated sample with absolute ethanol, let it stand to remove ethanol and collect the precipitate;

[0010] (3) Defluorination of natural ingredients: Purify the fluoride ions in the natural ingredients with a 1000Da dialysis bag in deionized water, freeze-dry and grind. Dry the obtained substance in an oven to a constant weight for standby;

[0011] (4) Adsorption of fluoride ions by natural ingredients: Place the defluorinated natural ingredients in an ultrafiltration tube, and perform oscillating adsorption through a water bath shaker. Then, measure and analyze the fluoride ion content using the fluoride ion selective electrode method.

[0012] Further, in the step (1), the shaker is set at a constant temperature of 25°C and 200 r / min, and the treatment duration is 6 h.

[0013] Further, in the step (1), the mixing ratio of the tea powder to 80% ethanol is 1 g:10 ml.

[0014] Further, in the step (2), the ultrasonic extraction duration is 30 min, the centrifugation duration of the extract is 10 min, and the standing duration of the mixed sample is 12 h.

[0015] Further, the specific steps of the adsorption of fluoride ions by the natural ingredients in the step (4) are as follows:

[0016] (1) Accurately weigh the defluorinated natural ingredients by dialysis, place them in the inner tube of a 1000Da ultrafiltration tube with a fluorine-containing reagent in the outer tube, place the ultrafiltration tube in a water bath shaker for oscillating adsorption. After the adsorption is completed, take the solution in the outer tube and measure the fluoride ion content using the fluoride ion selective electrode method;

[0017] (2) Analysis of the morphological characteristics of natural ingredients. Take an appropriate amount of natural ingredient samples before and after adsorption, adhere them to the sample stage, then place them in a vacuum sputtering instrument to coat a conductive film, and place them under a scanning electron microscope to observe their morphological structure and take pictures under a high-power microscope;

[0018] (3) Infrared spectrum analysis of natural components: The potassium bromide tablet pressing method is used to perform infrared spectrum analysis on the natural components before and after adsorption; the sample is mixed with dry potassium bromide, ground evenly, made into a tablet, and scanned and analyzed on an infrared spectrometer.

[0019] Further, in the step (1), the fluorine-containing reagent is a sodium fluoride solution, and the concentration of the sodium fluoride solution is 100 mg / L.

[0020] Further, in the step (1), the temperature of the water bath shaker is 40 °C, and the oscillation adsorption duration is 30 minutes to 1 hour.

[0021] Further, in the step (2), the duration of coating the conductive film by the vacuum evaporator is 20 min.

[0022] Further, in the step (3), the mixing ratio of the sample and dry potassium bromide is 1:100.

[0023] Further, in the step (3), the measurement range of the infrared spectrometer is 4000 cm -1 ~400 cm -1 。

[0024] The present invention has the following advantages:

[0025] 1. A new type of fluoride reduction method that is green and healthy: By extracting natural components from tea leaves to adsorb fluoride ions, there is no need to add additional metal adsorption, with strong safety, low toxicity and side effects, and the natural components can achieve green and pollution-free.

[0026] 2. Using natural components as fluoride reducing agents can achieve efficient utilization of low-efficiency resources: Coarse and old tea leaves have a high fluoride content and cannot be consumed for a long time, so their price is relatively low. Using natural components extracted from coarse and old tea leaves for defluorination of tea soup can avoid waste of resources, and this method hardly affects the original flavor and nutrients in the tea soup.

[0027] 3. It can be made into a tea bag for convenience and speed: The natural components are made into a tea bag with a small molecule pore size material of <1000 Da, which adsorbs excessive fluoride ions in the tea soup during the tea brewing process. Since it can be mass-produced and the operation process is simple, it has a high application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0029] The structures, ratios, sizes, etc. shown in this specification are only used to match the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the conditions for the implementation of the present invention. Therefore, they do not have substantial technical significance. Any modification of the structure, change in the ratio relationship, or adjustment of the size, without affecting the efficacy that the present invention can produce and the purpose that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention.

[0030] Figure 1 For the method for reducing fluorine in food using natural components provided by the present invention, A is the SEM morphological characterization of the natural component before adsorbing fluoride ions for 1 hour at 40°C, and B is the SEM morphological characterization after adsorbing fluoride ions for 1 hour at 40°C.

[0031] Figure 2 For the present invention, A is the infrared spectrum of the natural component before adsorbing fluoride ions, and B is the infrared spectrum of the natural component after adsorbing fluoride ions. Specific embodiments

[0032] The following specific embodiments illustrate the implementation manners of the present invention. Those familiar with this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0033] According to the first aspect of the present invention, a method for reducing fluorine in food using natural components is provided, including the following steps:

[0034] (1) Tea pretreatment: Bake the tea in an oven at 105°C until it reaches a constant weight, crush it through a 60-mesh sieve to prepare tea powder, mix the tea powder with 80% ethanol at a ratio of 1 g:10 ml, place it on a shaker at 25°C and 200 r / min for constant-temperature oscillation treatment for 6 h, then filter by suction to discard the alcohol and repeat the above steps 3 times to remove most of the pigments, monosaccharides, and small-molecule substances. Spread the pretreated tea powder evenly on a tray and dry it in an oven at 45°C with forced air until it reaches a constant weight for standby.

[0035] (2) Natural component extraction: Add 1 g of the tea powder prepared by pretreatment to 20 ml of primary water, perform ultrasonic extraction at an ultrasonic power of 200 W and an ultrasonic temperature of 40°C for 30 min, then preliminarily filter the extract to collect the extract, centrifuge the collected extract at 4°C and 8000 r / min for 10 min, and concentrate the obtained supernatant under reduced pressure. At 4°C, mix the concentrated sample with absolute ethanol at a volume ratio of 1:3, let it stand for 12 h, and then remove the ethanol to collect the precipitate.

[0036] (3) Defluorination of natural components: The precipitate was purified by a dialysis bag with a molecular weight cut-off of 1000 Da in deionized water to remove fluoride ions in the natural components, and then freeze-dried and ground. The obtained defluorinated mixture was first dried in an oven at 60 °C for 30 min, and then dried in an oven at 75 °C to constant weight for standby.

[0037] (4) Adsorption of fluoride ions by natural components: The defluorinated natural components were placed in an ultrafiltration tube, and oscillating adsorption was carried out through a water bath shaker. Then, the fluoride ion content was measured by the fluoride ion selective electrode method and analyzed.

[0038] Among them, the adsorption experiment of natural components on fluoride ions was as follows:

[0039] (1) Accurately weigh 0.3 g of the natural components after dialysis defluorination, and place them in the inner tube of a 1000 Da ultrafiltration tube with a fluoride-containing reagent in the outer tube. The ultrafiltration tube was placed in a water bath shaker at a temperature of 40 °C for oscillating adsorption for 30 minutes to 1 hour. After the adsorption was completed, the solution in the outer tube was taken, and the fluoride ion content was measured by the fluoride ion selective electrode method. The adsorption situation is shown in Table 1.

[0040] Table 1 Fluoride binding ability of natural components

[0041]

[0042] (2) Analysis of the morphological characteristics of natural components: Take an appropriate amount of the samples before and after adsorption, adhere them to the sample stage, and then place them in a vacuum sputtering instrument. After sputtering a conductive film for 20 min, observe their morphological structure under a scanning electron microscope and take pictures under a high magnification of 10000×. See Figure 1 . It can be seen from Figure 1 the SEM morphological characterization of the natural components before and after adsorbing fluoride ions at 40 °C for 1 h. As shown in Figure 1 A, before adsorption, the natural components showed a loose, irregular blocky porous structure under the scanning electron microscope. Figure 1 After adsorption as shown in

[0043] (3) Infrared spectrum analysis of natural components: The potassium bromide tablet method was used to analyze the infrared spectra of the samples before and after adsorption. 1 mg of the sample was mixed with 100 mg of dry potassium bromide, ground evenly, and then made into a tablet for scanning analysis on an infrared spectrometer, as shown in Figure 2 . It can be obtained from the comparison between Figure 2 A before adsorption and Figure 2 B after adsorption that the main differences in the natural components were manifested in the changes of the group absorption peaks after adsorbing fluoride ions, mainly concentrated in the hydroxyl groups at 3600 - 3200 cm -1 and the amino groups at 1070 - 1060 cm -1 , followed by those at 1311 - 1417 cm -1The carboxyl group. On the one hand, it shows that natural components can adsorb fluoride ions, and on the other hand, it further confirms that the adsorption of fluoride ions by natural components is related to active groups such as hydroxyl, amino, and carboxyl groups.

[0044] Specifically, in step (1), the fluorine-containing reagent is a sodium fluoride solution, and the concentration of the sodium fluoride solution in step (1) is 100 mg / L. Sodium fluoride is an important fluoride salt and is a raw material for manufacturing other fluorides. It is used in the experiment to detect the adsorption effect of natural components on fluoride ions.

[0045] Specifically, an infrared spectrometer usually consists of a light source, a monochromator, a detector, and a computer information processing system, and can study the structure and chemical bonds of molecules. In step (3), the measurement range of the infrared spectrometer is 4000 cm -1 ~400 cm -1 .

[0046] In order to better illustrate the technical solutions and technical effects of the present application, the following embodiments are provided.

[0047] Example 1

[0048] The method for reducing fluorine in dark brick tea using natural components is as follows:

[0049] Tea pretreatment: The tea leaves are dried to a constant weight in an oven at 105 °C, crushed and passed through a 60-mesh sieve to prepare tea powder. The tea powder is mixed with 80% ethanol in a ratio of 1 g:10 ml, placed on a shaker at 25 °C and 200 r / min for constant-temperature oscillation for 6 h, and then filtered to discard the alcohol, and the above steps are repeated 3 times to remove most of the pigments, monosaccharides, and small-molecule substances. The pretreated tea powder is spread out flat in a tray and dried to a constant weight in an oven at 45 °C with forced air, and reserved for use;

[0050] Extraction of natural components: 1 g of the tea powder prepared by pretreatment is added with 20 ml of primary water, and ultrasonic extraction is carried out at an ultrasonic power of 200 W and an ultrasonic temperature of 40 °C for 30 min. Then the extract is preliminarily filtered to collect the extract, and the collected extract is centrifuged at 4 °C and 8000 r / min for 10 min, and the supernatant is concentrated under reduced pressure. Under the condition of 4 °C, the concentrated sample is mixed with absolute ethanol in a volume ratio of 1:3, allowed to stand for 12 h, and then the ethanol is removed to collect the precipitate;

[0051] Defluorination of natural components: The precipitate is purified with a 1000 Da dialysis bag in deionized water to remove fluoride ions in the natural components, freeze-dried and ground. The obtained defluorinated mixture is first dried in an oven at 60 °C for 30 min, and then dried to a constant weight in an oven at 75 °C, and reserved for use.

[0052] Defluorination of dark brick tea: Accurately weigh 1.0 g of dark brick tea into 500 mL of deionized water. Accurately weigh 0.3 g of natural ingredients and place them in a dialysis bag with a molecular weight cut-off of 1000 Da. Then place the dialysis bag in the brick tea solution and shake and adsorb at 40 °C for 30 minutes. Use a fluoride ion selective electrode to measure the fluoride ion content in the tea soup before and after adsorption. The changes in the fluoride ion content of the brick tea soup before and after the natural ingredients adsorb fluoride are shown in Table 2. From the data in the table, it can be seen that the fluoride concentration in the brick tea soup before adding the natural ingredients is 5.64 ± 0.22 mg / L, and the fluoride concentration in the brick tea soup after adding the natural ingredients is 4.37 ± 0.18 mg / L. The natural ingredients have an obvious adsorption effect on the fluoride in the brick tea, and the adsorption rate in this experiment is 22.51%.

[0053] Table 2 Adsorption effect of natural ingredients on brick tea

[0054]

[0055] Example 2

[0056] The method for reducing fluoride in flower brick tea using natural ingredients is as follows:

[0057] Pretreatment of tea leaves: Bake the tea leaves in an oven at 105 °C until they reach a constant weight, crush them through a 60-mesh sieve to prepare tea powder. Mix the tea powder with 80% ethanol at a ratio of 1 g:10 ml, place it on a shaker at 25 °C and 200 r / min for constant-temperature oscillation for 6 h, then filter by suction to discard the alcohol and repeat the above steps 3 times to remove most of the pigments, monosaccharides, and small-molecule substances. Spread the pretreated tea powder evenly in a tray and dry it in an oven at 45 °C with forced air until it reaches a constant weight for standby;

[0058] Extraction of natural ingredients: Add 1 g of the tea powder prepared by pretreatment to 20 ml of primary water, and perform ultrasonic extraction at an ultrasonic power of 200 W and an ultrasonic temperature of 40 °C for 30 min. Then, preliminarily filter the extract to collect the extract. Centrifuge the collected extract at 4 °C and 8000 r / min for 10 min, and concentrate the obtained supernatant under reduced pressure. At 4 °C, mix the concentrated sample with absolute ethanol at a volume ratio of 1:3, let it stand for 12 h, and then remove the ethanol to collect the precipitate;

[0059] Defluorination of natural ingredients: Purify the precipitate with a 1000 Da dialysis bag in deionized water to remove fluoride ions in the natural ingredients, freeze-dry and grind it. The obtained defluorinated mixture is first baked in an oven at 60 °C for 30 min, and then dried in an oven at 75 °C until it reaches a constant weight for standby.

[0060] Fluoride reduction in Huazhuan tea: Accurately weigh 1.0 g of Huazhuan tea and dissolve it in 500 mL of deionized water. Accurately weigh 0.3 g of the natural component and place it in a dialysis bag with a molecular weight cut-off of 1000 Da. Then place the dialysis bag in the tea solution and shake it for adsorption at 40 °C for 30 minutes. Use a fluoride ion-selective electrode to measure the fluoride ion content in the tea soup before and after adsorption. The changes in the fluoride ion content of the tea soup of Huazhuan tea before and after the adsorption of the natural component are shown in Table 3. From the data in the table, it can be seen that the fluoride concentration in the tea soup of Huazhuan tea before adding the natural component is 5.08 ± 0.26 mg / L, and the fluoride concentration in the tea soup of Huazhuan tea after adding the natural component is 3.91 ± 0.18 mg / L. The natural component has an obvious adsorption effect on fluoride in Huazhuan tea, and the adsorption rate in this experiment is 23.03%.

[0061] Table 3 Adsorption effect of natural components on Huazhuan tea

[0062]

[0063] Although the present invention has been described in detail above with general descriptions and specific embodiments, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection of the present invention.

Claims

1. A method for reducing fluorine in food using natural ingredients, characterized in that, It includes the following steps: (1) Tea pretreatment: Dry the tea leaves, crush and sieve them to prepare tea powder. Mix the tea powder with 80% ethanol, place it on a shaker for constant-temperature oscillation treatment, then filter by suction to discard the alcohol and repeat the above steps 3 times. Dry the pretreated tea powder to a constant weight for standby; (2) Extraction of natural components: Add primary water to the tea powder obtained by pretreatment and perform ultrasonic extraction. Then, preliminarily filter to collect the extract. Centrifuge the collected extract and concentrate the obtained supernatant under reduced pressure. At 4°C, mix the concentrated sample with absolute ethanol, let it stand to remove ethanol and collect the precipitate. Among them, the ultrasonic extraction time is 30 min, the extract centrifugation time is 10 min, and the sample standing time after mixing is 12 h; (3) Defluorination of natural components: Purify the fluoride ions in the natural components from the precipitate with a 1000 Da dialysis bag in deionized water, freeze-dry and grind it. Dry the obtained substance in an oven to a constant weight for standby; (4) Adsorption of fluoride ions by natural components: Place the defluorinated natural components in an ultrafiltration tube and perform oscillatory adsorption through a water bath shaker. Then, measure the fluoride ion content by the fluoride ion selective electrode method and analyze it.

2. The method for reducing fluorine in food using natural ingredients as claimed in claim 1, wherein In step (1), the shaker is set at a constant temperature of 25°C and 200 r / min, and the treatment time is 6 h.

3. The method for reducing fluorine in food using natural ingredients as claimed in claim 1, characterized in that, In step (1), the mixing ratio of tea powder to 80% ethanol is 1 g:10 ml.

4. The method for reducing fluorine in food using natural ingredients according to claim 1, characterized in that, The specific steps for the adsorption of fluoride ions by natural components in step (4) are as follows: (1) Accurately weigh the defluorinated natural components by dialysis and place them in the inner tube of a 1000 Da ultrafiltration tube with a fluoride-containing reagent in the outer tube. Place the ultrafiltration tube in a water bath shaker for oscillatory adsorption. After the adsorption ends, take the solution in the outer tube and measure the fluoride ion content by the fluoride ion selective electrode method; (2) Analysis of the morphological characteristics of natural components: Take an appropriate amount of natural component samples before and after adsorption, adhere them to the sample stage, then place them in a vacuum sputtering instrument to coat a conductive film, and then observe their morphological structure under a scanning electron microscope and take pictures under a high-power microscope; (3) Infrared spectrum analysis of natural components: Perform infrared spectrum analysis on the natural components before and after adsorption by the potassium bromide tablet pressing method; Mix the sample and dry potassium bromide evenly, then make a tablet and scan and analyze it on an infrared spectrometer.

5. The method for reducing fluorine in food using natural ingredients as claimed in claim 4, wherein In step (1), the fluoride-containing reagent is a sodium fluoride solution, and the concentration of the sodium fluoride solution is 100 mg / L.

6. The method for reducing fluorine in food by using natural ingredients according to claim 4, characterized in that, In step (1), the temperature of the water bath shaker is 40°C, and the oscillatory adsorption time is 30 minutes to 1 hour.

7. The method for reducing fluorine in food using natural ingredients according to claim 4, characterized in that, In step (2), the time for coating the conductive film by the vacuum sputtering instrument is 20 min.

8. The method for reducing fluorine in food using natural ingredients as claimed in claim 5, characterized in that, In step (3), the mixing ratio of the sample to dry potassium bromide is 1:

100.

9. The method for reducing fluorine in food using natural ingredients according to claim 4, characterized in that, In step (3), the measurement range of the infrared spectrometer is 4000 cm -1 ~400 cm -1 .

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