A kind of crayfish shell chitosan and extraction method thereof

Abstract

The present invention belongs to the technical field of chitosan extraction, and specifically relates to a crayfish shell chitosan and an extraction method thereof. The method first crushes the crayfish shell to obtain shrimp shell powder; then adds citric acid solution and stirs until no gas is generated, stands, filters, and washes to neutrality; then places in NaOH solution, heats in a water bath and ultrasonicates until discoloration, filters, washes to neutrality; performs high-energy ion radiation treatment; finally, adds hydrogen peroxide and heats in a water bath and stirs until white, then filters, washes to neutrality, and dries to finally obtain chitosan. The preparation process of the present invention is simple, greener than the prior art, and chitosan is obtained without alkalization. The chitosan particle size is reduced, the shrimp shell powder is more delicate, the chitosan purity is higher, the structure of the chitosan shows higher looseness, and its active sites are significantly increased. In addition, the sample treated with methanol as the medium has lower nitrogen content and protein content, and a higher chitosan yield.

Description

Technical Field

[0001] The invention belongs to the technical field of chitosan extraction, and particularly relates to crayfish shell chitosan and an extraction method thereof. Background Art

[0002] Crayfish, scientifically known as Procambarus clarkii, is an important freshwater shrimp farmed in the middle and lower reaches of the Yangtze River in my country. In addition to rich proteins and lipids, crayfish shells are also rich in calcium, as well as active ingredients such as chitin and astaxanthin. In recent years, the deep processing of crayfish has developed steadily, mainly extracting chitin, aminoglucosamine, chitosan and astaxanthin from discarded shrimp shells. Chitosan is a deacetylated product of chitin. As a naturally derived polysaccharide, it has a wide range of applications and has multiple functions such as biodegradability, antibacterial properties, hygroscopicity and moisture retention. At present, chitosan is mainly prepared by three methods: chemical method, biological method and microwave method. The chemical method uses concentrated alkaline solution to remove the acetyl group of chitin, which has the defect of large amount of alkali, and the discharge of a large amount of alkaline solution, the pollution generated and the treatment cost have an impact on the environment and the economy. The biological method includes enzyme method and fermentation method, which has high requirements for the environment in which enzymes and microorganisms survive, and the reactants present in itself lead to poor quality of chitosan products.

[0003] At present, there have been a lot of studies on the deacetylation of chitin to prepare chitosan. For example, the existing technology uses 40% sodium hydroxide and 110°C for 4 h to obtain chitosan. Moreover, with the increase of NaOH solution concentration, treatment temperature and treatment time, the purity of chitosan will become higher and higher, and the final deacetylation degree will increase from 67.3% to 95.7%. However, this method uses a large amount of alkali, and the quality of chitosan will decrease with the increase of reaction time. Therefore, some researchers use intermittent alkali leaching method to treat chitin for a short time under certain alkali concentration and reaction temperature conditions, and then repeat 3 times to prepare chitosan. For example, chitosan with a purity of 89.07% was obtained by intermittent alkali leaching method. Although the above two methods are simple and easy to operate, they use a large amount of alkali and are easy to cause environmental pollution. Some scholars have studied mixing concentrated alkali with other solvents while using the intermittent method to reduce the amount of alkali. For example, the existing technology uses 19% sodium hydroxide, the reaction temperature is 90°C, the reaction is intermittent for 2 h+2 h+2 h, and a small amount of antioxidant sodium borohydride is added. This method can save a lot of sodium hydroxide usage, and there is no alkali liquid discharge, which is beneficial to environmental protection. Therefore, finding a new green method for preparing crayfish shell chitosan has always been a technical problem that needs to be solved in research. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art and provide a crayfish shell chitosan and an extraction method thereof, which specifically adopts the following technical scheme:

[0005] In one aspect of the present invention, a method for extracting chitosan from crayfish shells is provided, comprising the following steps:

[0006] S1: Crush the crayfish shells, and then pass through a 50-200 mesh sieve to obtain crayfish shell powder;

[0007] S2: adding the citric acid solution to the crayfish shell powder three times, stirring until no gas is generated, then standing until there is no crayfish shell powder suspended in the supernatant, filtering, and washing until neutral;

[0008] S3: Place the crayfish shell powder treated in S2 in a NaOH solution, heat in a water bath and sonicate until it changes color, filter, and wash until neutral;

[0009] S4: placing the crayfish shell powder treated in S3 in a high-energy ion radiation treatment device for high-energy ion radiation treatment to obtain shrimp shell powder;

[0010] S5: adding hydrogen peroxide solution to the shrimp shell powder treated in S4, heating in a water bath and stirring until it turns white, then filtering, washing until it is neutral, and drying to finally obtain chitosan.

[0011] The present invention crushes and screens shrimp shells, removes calcium with citric acid, removes protein with sodium hydroxide, and finally removes chitosan acetyl groups by high-energy ion radiation. The results show that the larger the number of shrimp shell powder sieves, the smaller the chitosan particle size is, and the better the protein removal effect is. In addition, the particle size of shrimp shell powder treated with high-energy ion radiation will decrease compared with the particle size of untreated shrimp shell powder. High-energy ion treatment may have a further crushing effect on shrimp shell powder. The particle size of shrimp shell powder treated with high-energy ion radiation with water as the medium is generally about 20 μm lower than that of shrimp shell powder with methanol as the medium. The particle size of the sample treated with high-energy ions with water as the medium is the smallest, which is 81.248 μm. The chitosan yield of 200 mesh is 5.0~11.7% higher than that of 100 mesh. In addition, the higher the degree of crushing of shrimp shell powder, the more active sites, and the higher the number of sieves, the higher the chitosan content and the lower the protein content of the shrimp shell powder.

[0012] As a further preferred embodiment, the crayfish shells are pre-treated before being crushed, and the specific steps are as follows:

[0013] The crayfish shells were ultrasonically cleaned in acetic acid solution for 3 times, each time for 30 min with an interval of 10 min, and then dried.

[0014] As a further preferred embodiment, the ratio of crayfish shell to acetic acid solution is 1 g: 10 mL, and the concentration of acetic acid solution is 0.5%.

[0015] As a further preferred embodiment, the specific process of high energy ion radiation treatment is as follows:

[0016] The crayfish shell powder is spread flat on the iron plate of the high-energy ion radiation treatment device, the high-energy ion radiation device is clamped with a butterfly clip, a medium is added, and then the iron plate is moved so that the high-energy ion radiation device is swept sequentially and the shrimp shell powder is evenly treated; the above-mentioned medium is water or methanol. More preferably, the medium is methanol.

[0017] Compared with the samples without high-energy ion irradiation, the particle size of the samples after high-energy ion irradiation is reduced, the shrimp shell powder is more delicate, the purity of chitosan is higher, the structure of chitosan shows higher looseness, its active sites are significantly increased, and the characteristic peaks of the samples are highly overlapped with the characteristic peaks of the chitosan standard. Compared with the products obtained by the high-energy ion treatment method with methanol as the medium and the high-energy ion treatment method with water as the medium, the samples obtained by methanol as the medium have lower nitrogen and protein content and higher chitosan yield. The method of selecting methanol as the medium for high-energy ion treatment has better effect.

[0018] As a further preferred embodiment, the ratio of the citric acid solution to the shrimp shell powder in S2 is 1020 mL:120 g, wherein the concentration of the citric acid solution is 120 g / L.

[0019] As a further preferred embodiment, the concentration of the NaOH solution in S3 is 3%; the concentration of the hydrogen peroxide solution in S5 is 30%.

[0020] As a further preferred embodiment, the temperature of the water bath heating is 60°C-70°C.

[0021] Another aspect of the present invention provides chitosan extracted by the above extraction method. The chitosan product is in the form of fine white crystals, with fine powder and gloss. After high-energy ion radiation treatment, the structure of the chitosan shows higher looseness, its active sites are significantly increased, and the particle size is reduced.

[0022] The beneficial effects of the present invention are as follows: the preparation process of the present invention is simple, the method uses high-energy ion radiation to treat chitin to remove the acetyl group, the process is greener than the prior art, and chitosan is obtained without alkalization. At the same time, the chitosan provided by the present invention is treated with high-energy ion radiation, the particle size is reduced, the shrimp shell powder is more delicate, the purity of chitosan is higher, the structure of chitosan shows higher looseness, and its active sites are significantly increased. In addition, the sample treated with methanol as the medium has lower nitrogen content and protein content, and a higher chitosan yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is a diagram of a high energy ion radiation treatment device;

[0024] Figure 2 Shown is a picture of a chitosan product;

[0025] Figure 3 Shown is the particle size of shrimp shell powder after being treated with different conductive media by high-energy ion radiation;

[0026] Figure 4 Shown is the infrared absorption spectrum of shrimp shell powder after being treated with different conductive media by high-energy ion radiation;

[0027] Figure 5 Shown are scanning electron microscope images of shrimp shell powder particles after treatment with different conductive media by high-energy ion radiation. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0029] Example 1

[0030] A method for extracting chitosan from crayfish shells, which specifically comprises the following steps:

[0031] Step 1: Sample processing:

[0032] The prepared crayfish were separated from the shells to remove the residual meat, and 0.5% acetic acid was added according to the material-liquid ratio of 1:10 (g / mL), and ultrasonic-assisted cleaning was performed for 3 times (after ultrasonic cleaning for 30 minutes, the cleaning solution was changed and continued to be cleaned for 30 minutes, and stirred once every 10 minutes), and then the processed shrimp shells were placed at 55°C for drying until the net weight did not change, and the shrimp shells were crushed by a grinder, and finally sieved with a 50-mesh sieve to collect the shrimp shell powder;

[0033] Step 2: decalcification:

[0034] Weigh 120 g of the shrimp shell powder obtained in step 1 and place it in a 2000 mL beaker, then prepare 1020 mL of 120 g / L citric acid solution, add the solution to the beaker containing the shrimp shell powder three times, stir with a glass rod until no gas is generated, then stand and wait for the calcium precipitation to be completed, until there is no shrimp shell powder suspended in the supernatant, and then filter and wash the shrimp shell powder until it is neutral;

[0035] Step 3: Deproteinization:

[0036] Place the shrimp shell powder treated in step 2 in a beaker again, and prepare 1200 mL of a 3% NaOH solution, heat in a water bath and ultrasonicate for 5 h at an ultrasonic working power of 300 W and a temperature of 70 °C until the color changes. After deproteinization, filter and wash the shrimp shell powder until it is neutral;

[0037] Step 4: High-energy ion radiation treatment:

[0038] Spread the shrimp shell powder processed in step 3 thinly on the iron plate of the high energy ion radiation treatment device (such as the attached Figure 1 As shown in the figure), use a butterfly clip to clamp the high-energy ion radiation instrument, then add water into the instrument as a medium to treat the shrimp shell powder with high-energy ion radiation. Before the experiment, the needle can be touched to the iron plate to confirm whether there is a microcurrent passing through. During the experiment, move the iron plate to allow the high-energy ion radiation instrument to sweep over the shrimp shell powder in turn and treat the shrimp shell powder evenly.

[0039] Step 5: Decolorization

[0040] Place the shrimp shell powder treated with high-energy ion radiation in step 4 in a 500 mL beaker, pour in 300 mL of 30% hydrogen peroxide solution, and place in a magnetic stirring water bath at 60°C for heating until the sample turns white. Finally, filter and wash the decolorized sample again until it is neutral, and dry it in an oven at 60°C until the net weight does not change to obtain chitosan.

[0041] Example 2

[0042] A method for extracting chitosan from crayfish shells, wherein the preparation process is different from that of Example 1 in that the 50-mesh sieve in step 1 is replaced with a 100-mesh sieve, and the other steps remain unchanged to obtain chitosan.

[0043] Example 3

[0044] A method for extracting chitosan from crayfish shells, wherein the preparation process is different from that of Example 1 in that the 50-mesh sieve in step 1 is replaced with a 200-mesh sieve, and the other steps remain unchanged to obtain chitosan.

[0045] Example 4

[0046] A method for extracting chitosan from crayfish shells, wherein the preparation process is different from that of Example 1 in that methanol is used as the medium instead of water in step 4, and the other steps remain unchanged to obtain chitosan.

[0047] Example 5

[0048] A method for extracting chitosan from crayfish shells, wherein the preparation process thereof is different from that of Example 2 in that methanol is added as the medium instead of water in step 4, and the other steps remain unchanged to obtain chitosan.

[0049] Example 6

[0050] A method for extracting chitosan from crayfish shells, wherein the preparation process is different from that of Example 3 in that methanol is used as the medium instead of water in step 4, and the other steps remain unchanged to obtain chitosan.

[0051] Example 7

[0052] This experiment used three kinds of shrimp shell powder without high-energy ion radiation treatment as a comparative experiment.

[0053] (1) Protein content determination

[0054] Put 0.3 g of shrimp shell powder of different mesh sizes in Example 1-Example 6 and shrimp shell powder treated with different conductive media after high-energy ion radiation into the digestive tube, and add 10 mL of concentrated sulfuric acid, 0.2 g of cuprous sulfate, and 3 g of potassium sulfate. Set up three control groups, and only add drugs but no samples to the digestive tube. After mixing evenly, put it into the digestion furnace and digest for 2 hours. After the digestion is completed, cool the digestive tube to room temperature and place it on the fully automatic Kjeldahl nitrogen analyzer. Start the instrument. The instrument automatically adds liquid, distills and titrates according to the set program. After the program is completed, record the titration volume V. The protein content calculation formula is as follows:

[0055]

[0056] Where: X is the protein content, g / 100 g; V1 is the volume of hydrochloric acid consumed by the test solution, mL; V2 is the volume of hydrochloric acid consumed by the reagent blank, mL; C is the concentration of the hydrochloric acid standard titration solution, mol·L -1 ; m is the sample mass in g.

[0057] The result data are shown in Table 1 below:

[0058] Table 1 Protein and chitosan contents of shrimp shell powder after high energy ion irradiation with different conductive media

[0059]

[0060] From the above table, we can see that after high-energy ion treatment, the impurities in the shrimp shell powder are treated more cleanly. The chitosan products of three kinds of shrimp shell powder with different mesh sizes treated with high-energy ion radiation and different conductive media are shown in Figure 2. Figure 2 The chitosan product is in the form of fine white crystals, with fine powder and glossy texture.

[0061] The experimental results show that high-energy ion treatment significantly improves the deproteinization degree of chitosan. In the process of deproteinization, the larger the mesh size, the better the deproteinization effect. The reason for this phenomenon may be that as the number of sieving increases, the particle size of shrimp shell powder decreases, making the shrimp shell powder easier to break under the bombardment of high-energy ions, which in turn causes its structure to become looser and its activity to increase. This structural change helps to promote the removal of chelated protein and calcium in chitosan, thereby achieving a more efficient deproteinization effect. The protein content of chitosan prepared from 50, 100 and 200 mesh shrimp shell powder treated with high-energy ions decreased with the increase of mesh size. This may be because the surface of large particles was hardened after high-energy ion radiation treatment, and the hardened layer was not conducive to the subsequent decalcification and deproteinization. The purity of the extracted chitosan was low, and the thermal conductivity of methanol was larger. When the shrimp shell powder was sieved through 100 mesh and 200 mesh sieves to obtain powder with smaller particle size, more reaction sites were exposed, and ion flow could more easily reach the reaction sites of various shrimp shell powder particles. The protein content of the chitosan product treated with methanol as the conductive medium was lower than that with water as the conductive medium.

[0062] (2) Particle size determination

[0063] The sample was mixed evenly with distilled water to form a suspension, and the diameter of chitin particles was measured using a laser scattering particle size distribution analyzer. The change in chitin particle size was observed by comparing it with the original structure shape.

[0064] The sample particle sizes of three kinds of crayfish shell powder were treated with high-energy ion radiation and the ultrasonic-assisted weak acid and weak base method were as follows: Figure 3 As shown, Note: T-50: 50 mesh shrimp shell powder has not been treated with high-energy ion radiation; PT-50-1: 50 mesh shrimp shell powder high-energy ion radiation-water medium; PT-50-2: 50 mesh shrimp shell powder high-energy ion radiation-methanol medium; T-100: 100 mesh shrimp shell powder has not been treated with high-energy ion radiation; PT-100-1: 100 mesh shrimp shell powder high-energy ion radiation-water medium; PT-100-2: 100 mesh shrimp shell powder high-energy ion radiation-methanol medium; T-200: 200 mesh shrimp shell powder has not been treated with high-energy ion radiation; PT-200-1: 200 mesh shrimp shell powder high-energy ion radiation-water medium; PT-200-2: 200 mesh shrimp shell powder high-energy ion radiation-methanol medium.

[0065] Compared with the 50 mesh without high-energy ion radiation treatment, the P <0.05), 31.48% ( P <0.05), 100 mesh decreased by 2.87% ( P <0.05), 0% ( P <0.05), 200 mesh decreased by 0% ( P<0.05), 10.11% ( P <0.05). The experimental results show that high-energy ion radiation treatment can reduce the particle size of shrimp shell powder, and the particle size decreases with the increase of sieve mesh number. Among them, the particle size obtained by methanol treatment is smaller than that of water treatment. This may be because high-energy ion radiation treatment can make the surface structure of shrimp shell powder looser and looser, so it is easier to form material components with smaller particles. Compared with the previous process of strong acid and strong alkali extraction, the chitosan extracted by high-energy ion radiation treatment has higher properties, better performance, and is more conducive to human absorption. The particle size of shrimp shell powder changes with different treatment methods. Previous studies have found that the sample is powdered after liquid nitrogen pulverization, and the average particle size is 120 μm measured by electron microscopy. Under the continuous bombardment of high-energy ions, shrimp shell powder is easily broken into smaller particle components, and the degree of refinement is higher than that of samples not treated with high-energy ion radiation. Therefore, the larger the sieve mesh number, the smaller the particles of the obtained product. At the same time, high-energy ion radiation will also have a certain effect on the particle size.

[0066] (3) Infrared spectroscopy

[0067] Take 1-2 mg of the sample and 200 g of pure potassium bromide and grind them into fine powder in an agate mortar. Press them into transparent thin slices on a tablet press. -1 Infrared absorption spectrum was measured.

[0068] Chitosan is obtained by removing calcium and protein from shrimp shell powder, and then removing acetyl from chitosan. The purity is affected by this, and chitosan extraction is difficult. Using chitosan standard as a reference, 50, 100, and 200 meshes were sieved, and then irradiated with high-energy ions in water and methanol as the medium. A total of 10 groups of shrimp shell powder with different mesh sizes were subjected to infrared spectroscopy. The results are shown in Figure 4 1600, 1480, 1280 cm -1 They represent the three spectral bands of amide I, amide II, and amide III, corresponding to CO stretching vibration (-COO- group), NH bending (NH 3+ ), NH bending and CN stretching. The infrared spectra of the three samples treated with high-energy ion radiation using methanol as the medium are very similar to those of the commercial chitosan samples at the typical absorption peak, and the treatment effect is the best. The samples treated with water as the medium are better than those without treatment. There are differences in infrared spectra between shrimp shell powders after sieving with different mesh sizes. Among them, the chitosan treated with 200 mesh methanol is the best, which is almost consistent with the infrared spectrum of commercial chitosan, so it is inferred that its purity is relatively high. It may be because the larger the mesh size of the sample, the smaller the particles, the more exposed sites of the particles, the more thoroughly bombarded by high-energy ions, and the more obvious the deacetylation effect. The samples treated with 100 mesh and 50 mesh have a peak at 866 cm-1 The absorption peak at 1400-1540 cm -1 The absorption peak of the segment is obviously more relaxed. The absorption peak of the shrimp shell powder treated with high-energy ion radiation with water as the medium is more compact in this segment, which is lower than the compactness of the sample treated with high-energy ion radiation with methanol as the medium. This shows that the deacetylation degree of the sample treated with high-energy ion with methanol as the medium is the best, the deacetylation degree of the sample with water as the medium is second, and the sample without high-energy ion treatment is poor. Therefore, high-energy ion radiation treatment may have the effect of removing the acetyl group of chitin in shrimp shells, and the experimental results show that the deacetylation degree of the sample treated with methanol as the medium is better than that of the sample treated with water as the medium, which may be related to the better thermal conductivity of methanol. At the same time, the experimental results show that the 2900-3000 cm -1 There are also some smaller absorption peaks due to the 2900 cm -1 Nearby are the absorption peaks of the CH bonds in CH3 and CH2. Therefore, it may be due to the presence of some unremoved proteins in the sample, which affects the infrared absorption of chitosan.

[0069] Affected by the different conductive medium treatment methods of high-energy ion radiation, the infrared absorption spectra of the obtained chitosan are different. Previous studies have found that the shrimp shell structure is based on chitosan as the core, with protein and calcium wrapped on its surface, and the three components exist by mutual chelation and penetration. In addition to using acid and alkali reagents to remove protein and calcium from shrimp shells, plasma treatment can promote the removal of protein and calcium, but it has not been shown whether it has an effect on the removal of acetyl groups in chitosan. High-energy ions have a stronger penetrating effect and can bombard the shrimp shell structure. At this time, the shrimp shell powder has been deproteinized and calcium removed using acid and alkali reagents, and chitosan can be better exposed for treatment. By comparing with the infrared chromatogram of commercially available standards, it is found that the characteristic peaks of chitosan are highly consistent. In summary, high-energy ion radiation treatment is effective in removing acetylation from chitosan in shrimp shell powder.

[0070] (4) Scanning electron microscopy

[0071] The microstructure of the sample was observed using a scanning electron microscope (SEM). The sample was dried before observation, and then the dried sample was attached to the sample stage with conductive tape. After being coated with a gold film by an ion sputtering instrument, it was placed under the SEM for observation, and the acceleration voltage was adjusted according to the magnification required for observation.

[0072] Scanning electron microscope photos of samples treated by different methods are shown in Figure 5As shown. Under 10K magnification, the tight network structure of chitosan can be clearly identified, indicating that protein, fat and calcium have been basically removed. Compared with the 50-mesh sample, the surface structure of the chitosan sample extracted from the 100-mesh shrimp shell powder is smoother, but contains more voids. This structure is more likely to form a stack of planar structures when the number of sieves increases. In particular, the 100-mesh sample ( Figure 5 d) It shows more uniform-sized flake crystal structures, indicating a higher chitosan purity. The structure of the 50-mesh sample without high-energy ion treatment is relatively compact, and the surface of the sample treated with water and methanol is smoother, reflecting the destructive effect of high-energy ion treatment on the structure of the chitosan sample, which makes it easier for citric acid and sodium hydroxide to erode and strip the calcium and protein therein. Compared with the 50-mesh sample, the chitosan sample extracted from the 100-mesh shrimp shell powder has a looser structure, and the 200-mesh sample has the loosest structure. The 100-mesh and 200-mesh shrimp shell powders treated with high-energy ions show a higher degree of fragmentation, forming clustered small pieces and block crystals, with finer particles, looser structures, and higher activity. This change may be the sample fragmentation effect caused by high-energy ion bombardment, which makes the extracted components of chitosan richer.

[0073] In summary, after high-energy ion radiation treatment, the structure of chitosan showed a higher looseness, its active sites increased significantly, and the particle size decreased. This change may be due to the strong bombardment of the chitosan surface by the high-energy ion radiator, which caused the surface structure to collapse, thereby affecting the binding of chitosan and protein, causing the protein to denature.

[0074] In the above data analysis, each sample was measured three times, and the data were expressed as mean ± standard deviation. The data analysis and result drawing were performed using one-way analysis of variance (ANOVA) and Duncan multiple range method in SPSS17.0 software for multiple significance analysis, and the significance level was set to P <0.05.

[0075] Although the description of the present invention has been quite detailed and specifically describes several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but should be regarded as providing a broad possible interpretation of these claims in view of the prior art by reference to the appended claims, thereby effectively covering the intended scope of the present invention. In addition, the above description of the present invention is based on the embodiments foreseeable by the inventor, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that have not yet been foreseen may still represent equivalent changes to the present invention.

Claims

1. A method for extracting chitosan from crayfish shells, characterized in that: The following steps are involved: S1: Crush the crayfish shells, and then pass through a 100-200 mesh sieve to obtain crayfish shell powder; S2: adding the citric acid solution to the crayfish shell powder three times, stirring until no gas is generated, then standing until there is no crayfish shell powder suspended in the supernatant, filtering, and washing until neutral; S3: Place the crayfish shell powder treated in S2 in a NaOH solution, heat in a water bath and sonicate until it changes color, filter, and wash until neutral; S4: placing the crayfish shell powder treated in S3 in a high-energy ion radiation treatment device for high-energy ion radiation treatment to obtain shrimp shell powder; S5: adding hydrogen peroxide solution to the shrimp shell powder treated in S4, heating in a water bath and stirring until white, then filtering, washing until neutral, and drying to finally obtain chitosan; The specific process of high energy ion radiation treatment is as follows: Spread the crayfish shell powder flat on the iron plate of the high-energy ion radiation treatment device, clamp the high-energy ion radiation device with a butterfly clip, add the medium, and then move the iron plate so that the high-energy ion radiation device sweeps through it in sequence and evenly treats the shrimp shell powder; The medium is methanol.

2. The extraction method according to claim 1, characterized in that The crayfish shells are pre-processed before being crushed. The specific steps are as follows: The crayfish shells were ultrasonically cleaned in acetic acid solution for 3 times, each time for 30 min with an interval of 10 min, and then dried.

3. The extraction method according to claim 2, characterized in that The ratio of crayfish shell to acetic acid solution was 1 g:10 mL.

4. The extraction method according to claim 3, characterized in that The concentration of the acetic acid solution was 0.5%.

5. The extraction method according to claim 1, characterized in that The dosage ratio of citric acid solution and shrimp shell powder in S2 is 1020 mL:120 g.

6. The extraction method according to claim 5, characterized in that The concentration of the citric acid solution was 120 g / L.

7. The extraction method according to claim 1, characterized in that The concentration of the NaOH solution in S3 is 3%; the concentration of the hydrogen peroxide solution in S5 is 30%.

8. The extraction method according to claim 1, characterized in that The water bath is heated at 60°C-70°C.

9. A chitosan, characterized in that: The extract is obtained by the extraction method according to any one of claims 1 to 8.

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