阅读说明：本技术 去除燕窝中亚硝酸盐的方法 (Method for removing nitrite in cubilose ) 是由 徐建强 于 2021-09-14 设计创作，主要内容包括：本发明公开了去除燕窝中亚硝酸盐的方法,将燕窝浸泡在水中,采用电渗析手段,经过过滤、低压干燥后,得到脱硝燕窝。本发明的去除燕窝中亚硝酸盐的方法效率高、成本低、制造与使用过程中无毒安全环保,可由其获得亚硝酸盐含量极低的燕窝。(The invention discloses a method for removing nitrite in cubilose, which comprises the steps of soaking cubilose in water, adopting an electrodialysis means, filtering, and drying at low pressure to obtain the denitrified cubilose. The method for removing nitrite from cubilose has high efficiency, low cost, no toxicity, safety and environmental protection in the manufacturing and using process, and cubilose with extremely low nitrite content can be obtained by the method.)

1. The method for removing the nitrite in the cubilose is characterized by comprising the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

2. The method for removing nitrite in bird's nest according to claim 1, which is characterized in that: the bath ratio of the cubilose to the water is 1kg (4-6) L; in the electrodialysis treatment, a nitrate removal filter membrane and direct current with the current of 1.6-1.95A are adopted, the flow rate of water is 30-50mL/s, the water temperature is 32-38 ℃, and the time duration is 40-60 min.

3. The method for removing nitrite in bird's nest according to claim 1, which is characterized in that: the low-pressure drying temperature is 43-47 ℃, the air pressure is 15-25kPa, and the time duration is 5-7 h.

4. The method for removing nitrite in cubilose according to claim 2, wherein the method for preparing the nitrate removal filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

5. The method for removing nitrite in bird's nest according to claim 4, characterized in that: the pore-forming agent is one or a mixture of two of vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester.

6. The method for removing nitrite in bird's nest according to claim 4, characterized in that: the cross-linking agent is one or a mixture of two of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal.

7. The method for removing nitrite in bird's nest according to claim 4, characterized in that: the wetting agent is one or a mixture of two of isopropanol and n-butanol.

8. The method for removing nitrite in bird's nest according to claim 4, characterized in that: in the step D1, the mass ratio of the polyacrylamide, the pore-forming agent, the cross-linking agent and the wetting agent is (4-6): (0.7-0.9): (0.8-1.2): (2.8-2.7); the temperature of the mixing technological conditions is 65-70 ℃, the pressure is 45-50MPa, the rotating speed is 70-100rpm, and the time duration is 50-80 min.

9. The method for removing nitrite in bird's nest according to claim 4, characterized in that: the defoaming treatment is stirring under a vacuum condition.

10. The method for removing nitrite in bird's nest according to claim 4, characterized in that: in the step D2, the discharge temperature of the film scraping machine is 68-72 ℃, and the film scraping speed is 0.08-0.2 m/s; the thickness of the film coating is 85-115 μm; the hot air drying and forming temperature is 55-65 ℃, the air speed is 4-6m/s, and the time duration is 70-85 min;

in the step D3, the bath ratio of the semi-finished product A to water is 1kg (7-9) L, and the soaking time is 35-50 min; the vacuum drying condition is that the vacuum degree is 10-15Pa, the temperature is 45-52 ℃, and the duration is 8-11 h.

Technical Field

The invention relates to the technical field of cubilose, in particular to a method for removing nitrite in cubilose.

Background

The bird's nest, commonly called swallow vegetable, swallow root, swallow vegetable, is a nest formed by mixing saliva secreted by some of the swallows of the family Ramaridae and the genus swiftlet with other substances, such as soil, branches, etc. In China, the cubilose has been one of the traditional famous and precious foods sought after by people since the Ming dynasty. Nowadays, with the economic development and the increasing consumption living standard, more consumers have selected the bird's nest as the first choice nutritional supplement. The edible bird's nest can be used for achieving the nutritional and health-care effects of skin care, face nourishing, yin nourishing, lung moistening, disease resistance improvement and the like. In the prior art, the processing mode of the cubilose mainly comprises cooking, and the cubilose product obtained by the rough processing mode often contains a large amount of nitrite residues which are harmful to human health. The traditional washing and drying modes have the problems of weak capability of removing nitrite, easy loss of nutrient substances and oxidative deterioration.

The electrodialysis method has the characteristics of high efficiency and low energy consumption for separating and enriching nitrite, but in the prior art, no report that the electrodialysis method is used for removing nitrite in cubilose is found.

Patent CN102362637B discloses a method for removing nitrite in edible bird's nest by using microorganism viable bacteria suspension and/or crude enzyme liquid and application thereof, wherein one or two of microorganism viable bacteria suspension which is prepared by edible microorganisms and has the capability of removing nitrous acid or crude enzyme liquid which is prepared by edible microorganisms and has the capability of removing nitrous acid are mixed with bird's nest, oscillated and washed to obtain the bird's nest from which the nitrite is removed, but the method has higher energy consumption, unnecessary new impurities are often introduced into the obtained bird's nest, the capability of removing the nitrite is limited, and the problem of nutrient loss in the treatment process is not solved.

Disclosure of Invention

In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for removing nitrite from bird's nest.

The traditional washing and drying modes have the problems of weak capability of removing nitrite, easy loss of nutrient substances and oxidative deterioration. The bird's nest obtained in the prior art often contains a large amount of nitrite residues, which are harmful to human health; in the prior art, no report that the electrodialysis method is used for removing nitrite in cubilose exists, and the electrodialysis method has the advantages of high efficiency and low energy consumption for separating and enriching nitrite.

In order to solve the technical problems, the invention adopts the technical scheme that:

the method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The preferable proposal is that the bath ratio of the cubilose and the water is 1kg (4-6) L; in the electrodialysis treatment, a nitrate removal filter membrane and direct current with the current of 1.6-1.95A are adopted, the flow rate of water is 30-50mL/s, the water temperature is 32-38 ℃, and the time duration is 40-60 min; the low-pressure drying temperature is 43-47 ℃, the air pressure is 15-25kPa, and the time duration is 5-7 h.

Preferably, the preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

The method comprises the steps of mixing polyacrylamide, a vinyl pyrrolidone-vinyl acetate copolymer, coconut oil fatty acid ester, N-dimethyl formamide N-butyl acetal, butyraldehyde diethyl acetal, isopropanol and N-butyl alcohol, removing bubbles to obtain a membrane liquid, blade coating the membrane liquid by a membrane scraping machine to obtain a membrane coating, carrying out gel phase change on the membrane liquid during hot air drying to form a filter membrane phase with good toughness, and soaking and cleaning in water to obtain the denitrification filter membrane for electrodialysis.

Preferably, in the step D1, the mass ratio of the polyacrylamide to the pore-forming agent to the cross-linking agent to the wetting agent is (4-6): (0.7-0.9): (0.8-1.2): (2.8-2.7); the temperature of the mixing technological conditions is 65-70 ℃, the pressure is 45-50MPa, the rotating speed is 70-100rpm, and the time duration is 50-80 min.

Preferably, the defoaming treatment is stirring under vacuum condition.

The invention adopts a vacuum stirring means as a means for removing redundant bubbles in the membrane liquid when preparing the membrane liquid, because the existence of large bubbles can lead nitrite to flow back to the side loaded with the bird's nest under the action of driving force generated by concentration gradient during electrodialysis, so that the denitration effect is greatly reduced, and the vacuum and stirring are combined to effectively lead the large bubbles to be separated from the membrane liquid and escape.

More preferably, the vacuum degree is 12-18Pa, the temperature is 62-67 ℃, the stirring speed is 220-310rpm, and the time duration is 18-25 min.

In the preferable scheme, in the step D2, the discharge temperature of the film scraping machine is 68-72 ℃, and the film scraping speed is 0.08-0.2 m/s; the thickness of the film coating is 85-115 μm; the hot air drying and forming temperature is 55-65 ℃, the air speed is 4-6m/s, and the time duration is 70-85 min.

Preferably, in the step D3, the bath ratio of the semi-finished product A to water is 1kg (7-9) L, and the soaking time is 35-50 min; the vacuum drying condition is that the vacuum degree is 10-15Pa, the temperature is 45-52 ℃, and the duration is 8-11 h.

Preferably, the pore-forming agent is one or a mixture of two of vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester; the cross-linking agent is one or a mixture of two of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal; the wetting agent is one or a mixture of two of isopropanol and n-butanol.

The selected pore-forming agent, the vinylpyrrolidone-vinyl acetate copolymer and the coconut oil fatty acid ester have specific topological molecular surface area and molecular electronegativity, so that the specific topological molecular surface area and the specific molecular electronegativity can generate fine holes on a polyacrylamide substrate, which is beneficial to the fact that nitrite ions migrate to the other side of a membrane under the guiding action of current in the electrodialysis process, and simultaneously prevents diffusion and loss of various macromolecular nutrient substances such as sialic acid, amino acid and the like, so that the cubilose subjected to electrodialysis treatment with the denitration filter membrane prepared by the specific method provided by the invention has extremely low nitrite residual quantity, and simultaneously, various nutrient components are greatly reserved. When the two pore-forming agents are compounded and used according to specific dosage, the chemical shift is generated between the specific electronegativity of the two pore-forming agents, so that the inner cavity of the hole formed on the polyacrylamide substrate is more round, the microstructure and the charge distribution of the obtained inner cavity are more beneficial to the dialysis effect on nitrite, and various nutrient components are better retained.

The spatial position and the carbon chain configuration of nitrogen and oxygen atoms in N, N-dimethylformamide di-N-butyl alcohol and the equivalent negative charge center formed by two oxygen atoms in butyraldehyde di-N-butyl acetal lead to that the two substances can improve the distribution condition of the pore-forming agent on a polyacrylamide substrate when compounded and used as a cross-linking agent in the raw material system, thereby obtaining the denitrification filter membrane with proper pore size and shape, uniform pore distribution and stronger toughness. The carbon chain structures and the dosage proportion of the isopropanol and the n-butanol enable the pore-forming agent, the cross-linking agent and the polyacrylamide to be fully fused with each other, so that the denitrification filter membrane with better structure and performance uniformity is obtained.

More preferably, the pore-forming agent is a mixture of vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester in a mass ratio of (1-3) to (1-3); the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of (1-3) to (1-3); the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of (1-5) to (1-5).

Most preferably, the pore-forming agent is a mixture of vinylpyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester in a mass ratio of 2: 1; the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of 1: 1; the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of 1: 4.

Preferably, carbon dioxide and/or nitrogen are used as the gaseous medium.

More preferably, carbon dioxide is used as the gaseous medium.

In the invention, carbon dioxide is preferably used as a hot air medium in the hot air drying and forming process, because the molecular weight, surface tension and polarizability of the carbon dioxide are favorable for the membrane liquid to form a cavity structure and holes which are favorable for nitrite to pass through during drying, so that the separation effect on nitrite in the electrodialysis process can be further enhanced.

The method for removing nitrite from cubilose well solves the problems of weak capability of removing nitrite, easy loss of nutrient substances and oxidative deterioration in the traditional washing and drying mode.

The invention has the beneficial effects that:

1. the invention provides a method for removing nitrite from cubilose, which adopts an electrodialysis means and a nitrate removal filter membrane prepared by the specific method of the invention to obtain the cubilose with extremely low nitrite residual quantity and higher nutrient content after filtration and low-pressure drying.

2. The invention adopts a specific method to prepare a denitration filter membrane, which takes polyacrylamide as a matrix, vinyl pyrrolidone-vinyl acetate copolymer and/or coconut oil fatty acid ester as a pore-forming agent, N-dimethylformamide di-N-butyl alcohol and/or butyraldehyde diethyl acetal as a cross-linking agent, isopropanol and/or N-butyl alcohol as a wetting agent, and obtains the denitration filter membrane which can efficiently and selectively pass through nitrite under the condition of electrodialysis without greatly losing cubilose nutrition after blade coating by a film scraping machine and hot air drying and forming.

Detailed Description

The above summary of the present invention is described in further detail below with reference to specific embodiments, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples.

Introduction of some raw materials in this application:

bird's nest, purchased from Cihua trade company, Inc., Guangzhou, produced: malaysia.

Polyacrylamide, CAS: 25085-02-3, purchased from Tianmen Ganchang chemical Co., Ltd, molecular weight: 580 million.

Vinylpyrrolidone-vinyl acetate copolymer, CAS: 25086-89-9, available from mairei chemical technologies, inc, molecular weight: 5 million, the molar ratio of vinylpyrrolidone to vinyl acetate is 7: 3.

Coconut oil fatty acid ester, CAS: 68553-02-6, available from Michelle chemical technology, Inc., Shanghai.

N, N-dimethylformamide di-N-butanol, CAS: 18503-90-7, available from Sahn chemical technology (Shanghai) Co., Ltd.

Butyraldehyde diacetal, CAS: 3658-95-5, available from Bailingwei technology Limited.

Example 1

The method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The bath ratio of the cubilose to the water is 1kg to 5L; in the electrodialysis treatment, a denitrification filter membrane and direct current with the current of 1.8A are adopted, the flow rate of water is 40mL/s, the water temperature is 35 ℃, and the time duration is 50 min; the temperature of the low-pressure drying is 45 ℃, the air pressure is 20kPa, and the time duration is 6 h.

The preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

In the step D1, the mass ratio of the polyacrylamide to the pore-forming agent to the cross-linking agent to the wetting agent is 5:0.8:1: 2; the temperature of the mixing technological conditions is 70 ℃, the pressure is 50MPa, the rotating speed is 100rpm, and the time duration is 70 min; the pore-forming agent is a mixture of a vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester in a mass ratio of 2: 1; the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of 1: 1; the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of 1: 4.

The defoaming treatment is stirring under a vacuum condition; the vacuum degree is 15Pa, the temperature is 65 ℃, the stirring speed is 300rpm, and the time duration is 20 min.

In the step D2, the discharge temperature of the film scraping machine is 70 ℃, and the film scraping speed is 0.1 m/s; the thickness of the film coating is 100 μm; the hot air drying and forming temperature is 60 ℃, the air speed is 5m/s, carbon dioxide is used as a gas medium, and the time duration is 80 min.

In the step D3, the bath ratio of the semi-finished product A to water is 1kg to 8L, and the soaking time is 40 min; the vacuum drying condition is that the vacuum degree is 12Pa, the temperature is 50 ℃, and the time duration is 10 h.

Example 2

The method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The bath ratio of the cubilose to the water is 1kg to 5L; in the electrodialysis treatment, a denitrification filter membrane and direct current with the current of 1.8A are adopted, the flow rate of water is 40mL/s, the water temperature is 35 ℃, and the time duration is 50 min; the temperature of the low-pressure drying is 45 ℃, the air pressure is 20kPa, and the time duration is 6 h.

The preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

In the step D1, the mass ratio of the polyacrylamide to the pore-forming agent to the cross-linking agent to the wetting agent is 5:0.8:1: 2; the temperature of the mixing technological conditions is 70 ℃, the pressure is 50MPa, the rotating speed is 100rpm, and the time duration is 70 min; the pore-forming agent is a vinyl pyrrolidone-vinyl acetate copolymer; the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of 1: 1; the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of 1: 4.

The defoaming treatment is stirring under a vacuum condition; the vacuum degree is 15Pa, the temperature is 65 ℃, the stirring speed is 300rpm, and the time duration is 20 min.

In the step D2, the discharge temperature of the film scraping machine is 70 ℃, and the film scraping speed is 0.1 m/s; the thickness of the film coating is 100 μm; the hot air drying and forming temperature is 60 ℃, the air speed is 5m/s, carbon dioxide is used as a gas medium, and the time duration is 80 min.

In the step D3, the bath ratio of the semi-finished product A to water is 1kg to 8L, and the soaking time is 40 min; the vacuum drying condition is that the vacuum degree is 12Pa, the temperature is 50 ℃, and the time duration is 10 h.

Example 3

The method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The bath ratio of the cubilose to the water is 1kg to 5L; in the electrodialysis treatment, a denitrification filter membrane and direct current with the current of 1.8A are adopted, the flow rate of water is 40mL/s, the water temperature is 35 ℃, and the time duration is 50 min; the temperature of the low-pressure drying is 45 ℃, the air pressure is 20kPa, and the time duration is 6 h.

The preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

In the step D1, the mass ratio of the polyacrylamide to the pore-forming agent to the cross-linking agent to the wetting agent is 5:0.8:1: 2; the temperature of the mixing technological conditions is 70 ℃, the pressure is 50MPa, the rotating speed is 100rpm, and the time duration is 70 min; the pore-forming agent is coconut oil fatty acid ester; the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of 1: 1; the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of 1: 4.

The defoaming treatment is stirring under a vacuum condition; the vacuum degree is 15Pa, the temperature is 65 ℃, the stirring speed is 300rpm, and the time duration is 20 min.

In the step D2, the discharge temperature of the film scraping machine is 70 ℃, and the film scraping speed is 0.1 m/s; the thickness of the film coating is 100 μm; the hot air drying and forming temperature is 60 ℃, the air speed is 5m/s, carbon dioxide is used as a gas medium, and the time duration is 80 min.

In the step D3, the bath ratio of the semi-finished product A to water is 1kg to 8L, and the soaking time is 40 min; the vacuum drying condition is that the vacuum degree is 12Pa, the temperature is 50 ℃, and the time duration is 10 h.

Example 4

The method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The bath ratio of the cubilose to the water is 1kg to 5L; in the electrodialysis treatment, a denitrification filter membrane and direct current with the current of 1.8A are adopted, the flow rate of water is 40mL/s, the water temperature is 35 ℃, and the time duration is 50 min; the temperature of the low-pressure drying is 45 ℃, the air pressure is 20kPa, and the time duration is 6 h.

The preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

In the step D1, the mass ratio of the polyacrylamide to the pore-forming agent to the wetting agent is 5:0.8: 2; the temperature of the mixing technological conditions is 70 ℃, the pressure is 50MPa, the rotating speed is 100rpm, and the time duration is 70 min; the pore-forming agent is a mixture of a vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester in a mass ratio of 2: 1; the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of 1: 4.

The defoaming treatment is stirring under a vacuum condition; the vacuum degree is 15Pa, the temperature is 65 ℃, the stirring speed is 300rpm, and the time duration is 20 min.

In the step D2, the discharge temperature of the film scraping machine is 70 ℃, and the film scraping speed is 0.1 m/s; the thickness of the film coating is 100 μm; the hot air drying and forming temperature is 60 ℃, the air speed is 5m/s, carbon dioxide is used as a gas medium, and the time duration is 80 min.

In the step D3, the bath ratio of the semi-finished product A to water is 1kg to 8L, and the soaking time is 40 min; the vacuum drying condition is that the vacuum degree is 12Pa, the temperature is 50 ℃, and the time duration is 10 h.

Example 5

The method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The bath ratio of the cubilose to the water is 1kg to 5L; in the electrodialysis treatment, a denitrification filter membrane and direct current with the current of 1.8A are adopted, the flow rate of water is 40mL/s, the water temperature is 35 ℃, and the time duration is 50 min; the temperature of the low-pressure drying is 45 ℃, the air pressure is 20kPa, and the time duration is 6 h.

The preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

In the step D1, the mass ratio of the polyacrylamide to the pore-forming agent to the cross-linking agent is 5:0.8: 1; the temperature of the mixing technological conditions is 70 ℃, the pressure is 50MPa, the rotating speed is 100rpm, and the time duration is 70 min; the pore-forming agent is a mixture of a vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester in a mass ratio of 2: 1; the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of 1: 1.

The defoaming treatment is stirring under a vacuum condition; the vacuum degree is 15Pa, the temperature is 65 ℃, the stirring speed is 300rpm, and the time duration is 20 min.

In the step D2, the discharge temperature of the film scraping machine is 70 ℃, and the film scraping speed is 0.1 m/s; the thickness of the film coating is 100 μm; the hot air drying and forming temperature is 60 ℃, the air speed is 5m/s, carbon dioxide is used as a gas medium, and the time duration is 80 min.

In the step D3, the bath ratio of the semi-finished product A to water is 1kg to 8L, and the soaking time is 40 min; the vacuum drying condition is that the vacuum degree is 12Pa, the temperature is 50 ℃, and the time duration is 10 h.

Example 6

The method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The bath ratio of the cubilose to the water is 1kg to 5L; in the electrodialysis treatment, a denitrification filter membrane and direct current with the current of 1.8A are adopted, the flow rate of water is 40mL/s, the water temperature is 35 ℃, and the time duration is 50 min; the temperature of the low-pressure drying is 45 ℃, the air pressure is 20kPa, and the time duration is 6 h.

The preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

In the step D1, the mass ratio of the polyacrylamide to the pore-forming agent to the cross-linking agent to the wetting agent is 5:0.8:1: 2; the temperature of the mixing technological conditions is 70 ℃, the pressure is 50MPa, the rotating speed is 100rpm, and the time duration is 70 min; the pore-forming agent is a mixture of a vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester in a mass ratio of 2: 1; the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of 1: 1; the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of 1: 4.

In the step D2, the discharge temperature of the film scraping machine is 70 ℃, and the film scraping speed is 0.1 m/s; the thickness of the film coating is 100 μm; the hot air drying and forming temperature is 60 ℃, the air speed is 5m/s, carbon dioxide is used as a gas medium, and the time duration is 80 min.

In the step D3, the bath ratio of the semi-finished product A to water is 1kg to 8L, and the soaking time is 40 min; the vacuum drying condition is that the vacuum degree is 12Pa, the temperature is 50 ℃, and the time duration is 10 h.

Example 7

The method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The bath ratio of the cubilose to the water is 1kg to 5L; in the electrodialysis treatment, a denitrification filter membrane and direct current with the current of 1.8A are adopted, the flow rate of water is 40mL/s, the water temperature is 35 ℃, and the time duration is 50 min; the temperature of the low-pressure drying is 45 ℃, the air pressure is 20kPa, and the time duration is 6 h.

The preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing the polyimide, the pore-forming agent, the cross-linking agent and the wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

In the step D1, the mass ratio of the polyimide to the pore-forming agent to the cross-linking agent to the wetting agent is 5:0.8:1: 2; the temperature of the mixing technological conditions is 70 ℃, the pressure is 50MPa, the rotating speed is 100rpm, and the time duration is 70 min; the pore-forming agent is a mixture of a vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester in a mass ratio of 2: 1; the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of 1: 1; the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of 1: 4.

The defoaming treatment is stirring under a vacuum condition; the vacuum degree is 15Pa, the temperature is 65 ℃, the stirring speed is 300rpm, and the time duration is 20 min.

In the step D2, the discharge temperature of the film scraping machine is 70 ℃, and the film scraping speed is 0.1 m/s; the thickness of the film coating is 100 μm; the hot air drying and forming temperature is 60 ℃, the air speed is 5m/s, carbon dioxide is used as a gas medium, and the time duration is 80 min.

In the step D3, the bath ratio of the semi-finished product A to water is 1kg to 8L, and the soaking time is 40 min; the vacuum drying condition is that the vacuum degree is 12Pa, the temperature is 50 ℃, and the time duration is 10 h.

Example 8

The method for removing the nitrite in the cubilose specifically comprises the following steps:

soaking the bird's nest in water, performing electrodialysis treatment, filtering, and drying at low pressure to obtain the denitration bird's nest.

The bath ratio of the cubilose to the water is 1kg to 5L; in the electrodialysis treatment, a denitrification filter membrane and direct current with the current of 1.8A are adopted, the flow rate of water is 40mL/s, the water temperature is 35 ℃, and the time duration is 50 min; the temperature of the low-pressure drying is 45 ℃, the air pressure is 20kPa, and the time duration is 6 h.

The preparation method of the denitrification filter membrane comprises the following steps:

d1, mixing polyacrylamide, a pore-forming agent, a cross-linking agent and a wetting agent, and removing bubbles to obtain a membrane liquid;

d2, coating the membrane liquid on non-woven fabric by a membrane scraping machine to form a membrane coating, drying and forming by hot air, and scraping to obtain a semi-finished product A;

d3, soaking the semi-finished product A in water, and drying in vacuum to obtain the nitrate removal filter membrane.

In the step D1, the mass ratio of the polyacrylamide to the pore-forming agent to the cross-linking agent to the wetting agent is 5:0.8:1: 2; the temperature of the mixing technological conditions is 70 ℃, the pressure is 50MPa, the rotating speed is 100rpm, and the time duration is 70 min; the pore-forming agent is a mixture of a vinyl pyrrolidone-vinyl acetate copolymer and coconut oil fatty acid ester in a mass ratio of 2: 1; the cross-linking agent is a mixture of N, N-dimethylformamide N-butyl acetal and butyraldehyde diethyl acetal in a mass ratio of 1: 1; the wetting agent is a mixture of isopropanol and n-butanol in a mass ratio of 1: 4.

The defoaming treatment is stirring under a vacuum condition; the vacuum degree is 15Pa, the temperature is 65 ℃, the stirring speed is 300rpm, and the time duration is 20 min.

In the step D2, the discharge temperature of the film scraping machine is 70 ℃, and the film scraping speed is 0.1 m/s; the thickness of the film coating is 100 μm; the hot air drying molding temperature is 60 ℃, the air speed is 5m/s, nitrogen is used as a gas medium, and the time duration is 80 min.

In the step D3, the bath ratio of the semi-finished product A to water is 1kg to 8L, and the soaking time is 40 min; the vacuum drying condition is that the vacuum degree is 12Pa, the temperature is 50 ℃, and the time duration is 10 h.

Test example 1

Testing the content of nitrite: the nitrite content in the denitrified bird's nest obtained by each example of the invention is tested according to the spectrophotometry in the national standard GB 5009.33-2016 (determination of nitrite and nitrate in food safety national standard food). 40.0mL of the filtrate was aspirated into a 50mL stoppered cuvette, and 0.00mL, 0.20mL, 0.40mL, 0.60mL, 0.80mL, 1.00mL, 1.50mL, 2.00mL, and 2.50mL of the standard use solution of sodium nitrite were aspirated into a 50mL stoppered cuvette, respectively. Respectively adding 2mL of sulfanilic acid solution with the concentration of 4g/L into a standard tube and a sample tube, uniformly mixing, standing for 5min, then adding 1mL of naphthyl ethylenediamine hydrochloride solution with the concentration of 2g/L, adding water to scale, uniformly mixing, standing for 15min, adjusting the zero point by using a 1cm cuvette and a zero tube, measuring the absorbance at the wavelength of 538nm, drawing a standard curve, comparing, and making a reagent blank. Two control groups were set: one group directly tests the nitrite content of the commercially available bird's nest; the other group is prepared by soaking commercially available nidus Collocaliae in 35 deg.C water at a bath ratio of 1g:5mL for 50min, filtering, and oven drying at 50 deg.C for 2 h.

The test results are shown in table 1.

TABLE 1 nitrite content of bird's nest

Test example 2

Sialic acid content testing: the sialic acid content of the denitrified bird's nest obtained by each example of the invention was tested according to GB/T30636-. Drying the cubilose obtained by each example of the invention at 105 ℃ for 60min, cooling in a drier, grinding into fine powder by a mortar, and uniformly mixing; weighing 0.1g of sample, placing the sample in a 25mL colorimetric tube, adding 10mL of 50% acetic acid solution, covering a glass plug, placing the sample in a water bath at 100 ℃ for hydrolysis for 10min, taking out the colorimetric tube, and cooling to room temperature; transferring the hydrolysate to a 100mL volumetric flask, fixing the volume to the scale with the mobile phase, mixing uniformly, taking the supernatant, and filtering with a 0.45-micrometer syringe filter for testing. For each bird's nest 5 different samples were measured and the results were averaged over five results. Two control groups were set: one group directly tests the nitrite content of the commercially available bird's nest; the other group is prepared by soaking commercially available nidus Collocaliae in 35 deg.C water at a bath ratio of 1g:5mL for 50min, filtering, and oven drying at 50 deg.C for 2 h.

The test results are shown in table 2.

TABLE 2 sialic acid content of bird's nest

Test example 3

And (3) testing the amino acid content: the content of amino acids in the denitrated bird's nest obtained in examples 1 to 3 of the present invention was tested according to national standard GB 5009.124-2016 "determination of amino acids in food safety national standard food". The test results are shown in table 3.

TABLE 3 amino acid content of bird's nest

It is apparent that embodiment 1 of the present invention is superior to the other examples.

The method comprises the steps of mixing polyacrylamide, a vinyl pyrrolidone-vinyl acetate copolymer, coconut oil fatty acid ester, N-dimethyl formamide N-butyl acetal, butyraldehyde diethyl acetal, isopropanol and N-butyl alcohol, removing bubbles to obtain a membrane liquid, blade coating the membrane liquid by a membrane scraping machine to obtain a membrane coating, carrying out gel phase change on the membrane liquid during hot air drying to form a filter membrane phase with good toughness, and soaking and cleaning in water to obtain the denitrification filter membrane for electrodialysis. The selected pore-forming agent, the vinylpyrrolidone-vinyl acetate copolymer and the coconut oil fatty acid ester have specific topological molecular surface area and molecular electronegativity, so that the selected pore-forming agent, the vinylpyrrolidone-vinyl acetate copolymer and the coconut oil fatty acid ester can generate fine pores on a polyacrylamide substrate, which is beneficial to nitrite ions to migrate to the other side of a membrane under the guiding action of current in the electrodialysis process, and simultaneously prevents diffusion and loss of various macromolecular nutrient substances such as sialic acid, amino acid and the like, so that the cubilose subjected to electrodialysis treatment with the denitration filter membrane prepared by the specific method provided by the invention has extremely low nitrite residual quantity, and greatly retains various nutrient components; when the two pore-forming agents are compounded and used according to specific dosage, the chemical shift is generated between the specific electronegativity of the two pore-forming agents, so that the inner cavity of the hole formed on the polyacrylamide substrate is more round, the microstructure and the charge distribution of the obtained inner cavity are more beneficial to the dialysis effect on nitrite, and various nutrient components are better retained.

The spatial position and the carbon chain configuration of nitrogen and oxygen atoms in N, N-dimethylformamide di-N-butyl alcohol and the equivalent negative charge center formed by two oxygen atoms in butyraldehyde di-N-butyl acetal lead to that the two substances can improve the distribution condition of the pore-forming agent on a polyacrylamide substrate when compounded and used as a cross-linking agent in the raw material system, thereby obtaining the denitrification filter membrane with proper pore size and shape, uniform pore distribution and stronger toughness. The carbon chain structures and the dosage proportion of the isopropanol and the n-butanol enable the pore-forming agent, the cross-linking agent and the polyacrylamide to be fully fused with each other, so that the denitrification filter membrane with better structure and performance uniformity is obtained. The invention adopts a vacuum stirring means as a means for removing redundant bubbles in the membrane liquid when preparing the membrane liquid, because the existence of large bubbles can lead nitrite to flow back to the side loaded with the bird's nest under the action of driving force generated by concentration gradient during electrodialysis, so that the denitration effect is greatly reduced, and the vacuum and stirring are combined to effectively lead the large bubbles to be separated from the membrane liquid and escape. In the invention, carbon dioxide is preferably used as a hot air medium in the hot air drying and forming process, because the molecular weight, surface tension and polarizability of the carbon dioxide are favorable for the membrane liquid to form a cavity structure and holes which are favorable for nitrite to pass through during drying, so that the separation effect on nitrite in the electrodialysis process can be further enhanced. The method for removing nitrite from cubilose well solves the problems of weak capability of removing nitrite, easy loss of nutrient substances and oxidative deterioration in the traditional washing and drying mode.