A method for extracting double products from penaeus vannamei shrimp shell

Abstract

The application discloses a kind of South American white prawn shell double-product extraction method, belong to the field of bioactive substance extraction, steps include, South American white prawn shell is soaked with the pre-treatment solution containing curcumin, citric acid and ethanol, then drying and crushing, shrimp shell powder is soaked with acid solution, organic solvent is added and extracted, solid-liquid separation obtains astaxanthin organic solution and insoluble matter, astaxanthin organic solution is purified, and astaxanthin is obtained, insoluble matter is soaked with protease, and chitin is separated, chitin is treated with alkali solution for deacetylation, and chitosan is purified.The method is aimed at the characteristics of South American white prawn shell, uses specific processing flow, reduces the damage, degradation of target product and target product precursor in the extraction process, and is conducive to more thoroughly removing impurities such as fatty acid, calcium, realizes the joint efficient extraction of astaxanthin and chitosan in shrimp shell, the extraction rate and purity of astaxanthin are high, and the quality of astaxanthin and chitosan product is excellent.

Description

Technical Field

[0001] This invention relates to a method for extracting two products from the shell of Litopenaeus vannamei, belonging to the field of bioactive substance extraction. Background Technology

[0002] The whiteleg shrimp is an important farmed shrimp species in my country, possessing extremely high economic and nutritional value. Shrimp shells, as a major byproduct of aquatic product processing, contain abundant bioactive substances such as astaxanthin and chitin, and have significant industrial, pharmaceutical, and food applications.

[0003] Currently, the main methods for extracting astaxanthin from shrimp shells include alkaline extraction, oil-soluble extraction, organic solvent extraction, and supercritical CO2 fluid extraction. Traditional astaxanthin extraction processes suffer from serious environmental pollution, high energy consumption, and low product purity.

[0004] The common method for extracting chitin from shrimp shells is the chemical acid-base method, which mainly involves removing proteins with concentrated alkali and then removing calcium from the shrimp shells with hydrochloric acid. While this method is simple and efficient, it consumes large amounts of acid and alkali, is energy-intensive, and pollutes the environment. Although microbial fermentation and enzymatic hydrolysis methods exist, they suffer from problems such as long processing times and high costs.

[0005] In existing technologies, astaxanthin and chitin are usually extracted separately, which fails to achieve comprehensive and efficient utilization of shrimp shell resources. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a method for extracting two products from the shell of Litopenaeus vannamei, which can simultaneously achieve efficient separation and extraction of astaxanthin and chitin from the shell of Litopenaeus vannamei.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A method for extracting two products from the shell of Litopenaeus vannamei includes the following steps:

[0009] The shells of whiteleg shrimp were soaked in a pretreatment solution, then dried and pulverized to obtain shrimp shell powder; the pretreatment solution contained curcumin, citric acid and ethanol;

[0010] The shrimp shell powder was soaked in an acidic solution to obtain an acidic suspension;

[0011] An organic solvent was added to the acid suspension, and the mixture was extracted under reflux conditions. Solid-liquid separation was performed to obtain an organic solution of astaxanthin and insoluble matter.

[0012] The astaxanthin organic solution was purified to obtain astaxanthin;

[0013] The insoluble matter was soaked in a protease, and the solid was separated to obtain chitin.

[0014] The chitin was deacetylated with an alkaline solution, washed with water until neutral, and then purified to obtain chitosan.

[0015] The dual-product extraction method for shrimp shells of Litopenaeus vannamei provided in this application can achieve efficient separation and extraction of astaxanthin and chitosan from shrimp shells, reduce energy consumption during the extraction process, reduce environmental pollution from extraction wastewater, and improve product purity and resource utilization.

[0016] Furthermore, the preparation step of the pretreatment solution includes:

[0017] Citric acid is dissolved in water to prepare a citric acid solution with a pH of 3-4;

[0018] The ethanol and the citric acid solution were mixed in a volume ratio of 3:1 to obtain a mixed solvent;

[0019] Curcumin is dissolved in the mixed solvent to prepare the pretreatment solution with a curcumin concentration of 0.05wt%~0.1wt%.

[0020] In the step of soaking the shells of whiteleg shrimp in a pretreatment solution, the soaking time is 10 min to 15 min.

[0021] Furthermore, the step of soaking the shells of the whiteleg shrimp in the pretreatment solution is carried out in an ultrasonic environment with an ultrasonic power of 300W and a frequency of 40kHz.

[0022] Furthermore, the step of soaking the shells of the whiteleg shrimp in the pretreatment solution is carried out in a microwave environment, with microwave radiation applied intermittently in a pattern of 10 seconds on and 20 seconds off, and the microwave radiation power during application is 500W.

[0023] Furthermore, the acidic solution is a mixture of phosphoric acid, citric acid, and lactic acid, with a pH of 3-4. In the step of soaking the shrimp shell powder in the acidic solution, the temperature is 45℃-60℃ and the time is 2 hours.

[0024] The mixture of multiple acids can provide a richer ionic environment. Compared with a single acid, they can work synergistically to dissolve components such as calcium carbonate in shrimp shells more effectively. They can also react more comprehensively with various minerals and organic components in shrimp shells, promoting the destruction of shrimp shell structure and the dissolution of components, thus creating better conditions for the extraction of astaxanthin.

[0025] Furthermore, the mass ratio of the phosphoric acid, the citric acid, and the lactic acid is 2:4~6:2~3.

[0026] This optimized mass ratio improves the proportions of acids in the acidic solution, allowing them to exert the best synergistic effect in dissolving shrimp shell components. It also has a unique role in the dissolution of certain organic components and good permeability to shrimp shells, thereby improving the selectivity of the entire extraction process and the quality of the product.

[0027] Furthermore, in the step of adding an organic solvent to the acid suspension, the volume ratio of the acid suspension to the organic solvent is 6-7:5; the organic solvent is a mixture of ethanol and acetone, and the volume mixing ratio of ethanol to acetone is 7:3 to 8:2.

[0028] The process eliminates the need for solid-liquid separation between acid washing and organic extraction, reducing wastewater to some extent and accelerating the dissolution of organic components through acid corrosion. The organic solvent, a mixture of ethanol and acetone, further facilitates the separation and purification of astaxanthin by utilizing their different volatility and other physical properties, thereby improving the quality of the astaxanthin product.

[0029] Furthermore, the requirement for extraction under reflux conditions is to rotary evaporate at 35°C for 2 hours.

[0030] This temperature ensures that the organic solvent is in a suitable state of volatilization and circulation, allowing astaxanthin to be continuously extracted during solvent reflux, while preventing the decomposition or oxidation of astaxanthin due to excessive temperature, thus achieving effective separation of astaxanthin from insoluble matter. By precisely controlling the temperature and time of reflux extraction, the extraction efficiency of astaxanthin can be improved, providing favorable preconditions for subsequent purification to obtain high-purity astaxanthin.

[0031] Further, the step of soaking the insoluble matter with protease includes: soaking it in a flavor protease hydrolysate with a pH of 6.5 at 40°C to 45°C for 2 to 3 hours, wherein the enzyme activity of the flavor protease hydrolysate is 1000 U / g.

[0032] Furthermore, in the step of deacetylation treatment of chitin with alkaline solution, the temperature is 110℃~120℃, the time is 3h~4h, and the alkaline solution is a 40wt%~50wt% sodium hydroxide solution.

[0033] Within this temperature and time range, chitin can fully react with sodium hydroxide solution to achieve deacetylation, converting chitin into chitosan. Ensuring the complete deacetylation reaction yields a chitosan product with a suitable degree of deacetylation. Following the previous pretreatment-acid washing-enzymatic hydrolysis process, this alkali concentration allows the reaction to proceed smoothly without degrading the quality of the chitosan product. By precisely controlling the concentration, temperature, and reaction time of the alkali solution, high-quality chitosan products can be stably prepared, further enhancing the comprehensive utilization value of shrimp shell resources.

[0034] The beneficial effects of this invention are as follows: The dual-product extraction method for Litopenaeus vannamei shells of this invention is tailored to the characteristics of Litopenaeus vannamei shells and employs a specific processing procedure, which reduces the damage and degradation of the target product and its precursors during the extraction process. It also facilitates the more thorough removal of impurities such as fatty acids and calcium, achieving the combined and efficient extraction of astaxanthin and chitosan from the shells. The extraction rate and purity of astaxanthin are high, and the astaxanthin and chitosan products are of excellent quality. The energy consumption during the extraction process is low, and less wastewater is generated during the extraction process, which is in line with the concept of green environmental protection. Attached Figure Description

[0035] Figure 1 This is an electron microscope image of the shrimp shell after pretreatment in Example 1.

[0036] Figure 2 This is an electron microscope image of the shrimp shells in Comparative Example 1 after cleaning. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this invention.

[0038] It should be understood that, without conflict, any and all embodiments of the present invention can be combined with technical features of any other embodiment or multiple other embodiments to obtain other embodiments. The present invention includes such combinations to obtain other embodiments.

[0039] Unless otherwise specified, all technical and scientific terms used herein have the standard meaning in the field to which the claimed subject matter pertains. Where multiple definitions exist for a term, the definition herein shall prevail.

[0040] Most existing methods can only extract one useful substance. A few methods extract multiple substances simultaneously. A common process in these methods is: enzymatic deproteinization – acid washing – organic extraction to separate astaxanthin and chitin. The main purpose of acid washing is decalcification. Acid washing is usually time-consuming and requires heating. Enzymatic deproteinization before acid washing leads to premature decomposition of the astaxanthin-protein complex, exposing free astaxanthin. Although this makes astaxanthin easier to extract in subsequent organic extraction, the free astaxanthin is easily oxidized during prolonged acid washing, affecting product quality. For this reason, some methods have been modified to directly perform organic extraction without acid or alkali washing after enzymatic deproteinization. However, shrimp shells are natural biocomposite materials with a very dense microstructure, filled with amorphous or crystalline calcium carbonate nanoparticles. The astaxanthin-protein complex is encapsulated in this dense network structure composed of chitin and calcium carbonate. The calcium carbonate mineral forms a strong physical barrier, hindering the entry of solvents and reagents. Although this method does not cause astaxanthin oxidation, the organic extraction efficiency is very low, and the astaxanthin yield is also low.

[0041] This application provides a method for extracting two products from the shell of Litopenaeus vannamei, including the following steps:

[0042] S1: The shells of Litopenaeus vannamei were soaked in a pretreatment solution, then dried and pulverized to obtain shell powder. (Hereinafter referred to as pretreatment.) The pretreatment solution contains curcumin, citric acid, and ethanol.

[0043] S2: Shrimp shell powder is soaked in an acidic solution to obtain an acid suspension. (Hereinafter referred to as acid washing.)

[0044] S3: An organic solvent is added to the acid suspension, and extraction is performed under reflux conditions. Solid-liquid separation yields an organic solution of astaxanthin and insoluble matter. (Hereinafter referred to as organic extraction.)

[0045] S4: Purify the organic solution of astaxanthin to obtain astaxanthin.

[0046] S5: The insoluble matter was soaked in protease, and the solid was separated to obtain chitin. (Hereinafter referred to as enzymatic hydrolysis.)

[0047] S6: Chitin was deacetylated with an alkaline solution, washed with water until neutral, and then purified to obtain chitosan.

[0048] Due to the high-fat diet ingested in the aquaculture environment, the shells of Litopenaeus vannamei (whiteleg shrimp) have a high content of free fatty acids. In the embodiments of this application, the phenolic hydroxyl groups of curcumin can act as a natural antioxidant for astaxanthin, improving the storage stability of astaxanthin in the shrimp shell and achieving the dual functions of deodorizing and anti-oxidation. Curcumin also forms fat-soluble complexes with the fatty acids in the shells of Litopenaeus vannamei, simultaneously removing fishy odor substances and fatty acids through subsequent organic extraction processes, reducing wastewater discharge and lowering the COD value of wastewater. Combined with the acidity of citric acid and its complexing effect with calcium ions, the shrimp shell becomes porous, allowing organic solvents to penetrate more deeply during subsequent organic extraction, simultaneously dissolving astaxanthin and fat-soluble fishy odor substances.

[0049] In most shrimp and crabs, the calcium carbonate in the shell is mainly crystalline calcite. In the shell of the whiteleg shrimp, the calcium carbonate is mainly amorphous calcium carbonate. Amorphous calcium carbonate is more easily dissolved under acidic conditions, but it also easily forms a "calcium-protein complex gel" with proteins, leading to a decrease in the efficiency of subsequent enzymatic hydrolysis. Therefore, in this embodiment, preliminary decalcification is performed in the pretreatment stage, followed by concentrated decalcification in an acidic suspension. Citric acid is introduced in the pretreatment stage to enhance the decalcification effect on amorphous calcium carbonate. Then, astaxanthin is extracted organically. This eliminates the need for enzymatic hydrolysis of proteins to expose astaxanthin. The concentrated decalcification by acid washing can be performed in a shorter time and at a lower temperature, reducing astaxanthin oxidation and breaking down the barrier of calcium carbonate minerals, allowing the solvent to penetrate the shrimp shell more effectively for astaxanthin extraction.

[0050] In step S1, the drying method can be, for example, baking or freeze-drying. In order to reduce the oxidation of astaxanthin, freeze-drying is preferred.

[0051] Specifically, the preparation steps of the pretreatment solution include:

[0052] S01: Dissolve citric acid in water to prepare a citric acid solution with a pH of 3-4.

[0053] SO2: Mix ethanol and citric acid solutions in a volume ratio of 3:1 to obtain a mixed solvent.

[0054] S03: Dissolve curcumin in a mixed solvent to prepare a pretreatment solution with a curcumin concentration of 0.05wt%~0.1wt%.

[0055] The pretreatment solution prepared in this way not only ensures good solubility of curcumin but also guarantees the solution's effectiveness in treating shrimp shell components. Curcumin forms a fat-soluble complex with free fatty acids, thereby removing fishy odor substances and fatty acids. This concentration of curcumin effectively exerts its deodorizing and antioxidant effects.

[0056] Accordingly, in step S1, the soaking time is 10-15 minutes. This process removes the fishy smell and complexes with free fatty acids, without causing premature excessive dissolution of shrimp shell components due to prolonged soaking in an acidic environment. This ensures the efficiency and stability of the pretreatment step, providing a good raw material foundation for subsequent steps such as the extraction of astaxanthin and chitin.

[0057] Specifically, the acidic solution in step S2 is a mixture of phosphoric acid, citric acid, and lactic acid with a pH of 3-4. In the step of soaking the shrimp shell powder in the acidic solution, the temperature is 45℃-60℃ and the time is 2 hours.

[0058] With pretreatment, using a specific compound acid, at a lower pickling temperature and shorter time, it is possible to ensure that the acid reacts fully with the shrimp shell, thus avoiding the oxidation or decomposition of components such as astaxanthin.

[0059] Preferably, the mass ratio of phosphoric acid, citric acid, and lactic acid is 2:4~6:2~3.

[0060] This mixed acid is highly effective at dissolving calcium carbonate in the shells of Litopenaeus vannamei, and its pH is stable and easily adjustable. The mixed acid components can complex with some components in the shell, for example, preventing calcium ions from re-binding with proteins to form calcium-protein complex gels. By precisely controlling the ratio of the three acids, calcium in the shell can be removed more effectively, ensuring that the target products are not damaged or have their purity reduced due to excessive acidic solution treatment during subsequent extraction of astaxanthin and chitin.

[0061] In some embodiments, the step of soaking the shells of Litopenaeus vannamei in a pretreatment solution is carried out in an ultrasonic environment with an ultrasonic power of 300W and a frequency of 40kHz.

[0062] Ultrasound can accelerate the interaction between the components in the pretreatment solution and the shrimp shell. On one hand, the cavitation effect of ultrasound can generate tiny cavitation bubbles on the shrimp shell surface. When these cavitation bubbles rupture, they generate localized high pressure, which helps to open the shell structure, allowing curcumin, citric acid, and ethanol to enter the shell more quickly. This accelerates the removal of odor substances, the complexation of free fatty acids with curcumin, and the initial dissolution of shrimp shell components. On the other hand, ultrasound can also promote molecular vibration and diffusion, resulting in a more uniform distribution of the pretreatment solution within the shrimp shell, thereby improving the effectiveness and consistency of the pretreatment.

[0063] In some embodiments, the step of soaking the shells of Litopenaeus vannamei in a pretreatment solution is carried out in a microwave environment, with microwave radiation applied intermittently in a pattern of 10 seconds on and 20 seconds off, and the microwave radiation power during application is 500W.

[0064] Microwave radiation induces high-frequency vibrations in shrimp shell molecules, accelerating the reaction between the pretreatment solution and the shrimp shell. Intermittent microwave application ensures sufficient energy input to promote the reaction while avoiding excessive reaction or denaturation of shrimp shell components that might occur with continuous heating. Under these microwave conditions, the effects of curcumin in removing fishy odor, complexing with free fatty acids, and the dissolution and modification of shrimp shell components by citric acid and ethanol can be carried out more efficiently.

[0065] In some embodiments, ultrasonic and microwave-assisted pretreatment can be used simultaneously. Ultrasonic waves create microscopic cracks in the shrimp shell. Microwaves open these cracks, increasing the shell's porosity and providing unobstructed pathways for subsequent acid and solvent entry. Ultrasonic waves accelerate the diffusion of H⁺ ions into the shell and continuously shed surface reaction products (Ca²⁺) through cavitation, exposing fresh reaction interfaces. Microwaves double the decalcification rate, enhancing the initial decalcification effect during pretreatment. The deep disruption of the shrimp shell's physical structure maximizes the contact area between fat-soluble substances and curcumin solution, improving fatty acid removal and deodorizing effects.

[0066] In step S3, the volume ratio of the acid suspension to the organic solvent is 6-7:5; the organic solvent is a mixture of ethanol and acetone, with a volume ratio of ethanol to acetone of 7:3 to 8:2. This volume ratio ensures sufficient extraction of astaxanthin from the acid suspension after the addition of the organic solvent. The organic solvent is uniformly dispersed in the acid suspension, allowing for thorough contact with the astaxanthin, thereby improving extraction efficiency and ensuring that as much as possible of astaxanthin is transferred to the organic solvent phase, laying the foundation for obtaining a high-purity astaxanthin organic solution. Specifically, the extraction under reflux conditions requires rotary evaporation at 35°C for 2 hours.

[0067] For example, the specific process of step S4 is as follows: concentrate the organic solution of astaxanthin, perform column chromatography and membrane separation, elute and recrystallize (4℃, 12h~24h), separate by preparative chromatography, freeze dry and vacuum package.

[0068] The specific requirements for step S5 can be: soaking in a flavor protease hydrolysate with a pH of 6.5 at 40℃~45℃ for 2h~3h, with the enzyme activity of the flavor protease hydrolysate being 1000U / g.

[0069] After pretreatment and acid washing, this enzymatic hydrolysis environment effectively decomposes proteins in insoluble substances, accelerates the hydrolysis reaction of proteins, and breaks them down into smaller molecules, facilitating subsequent separation from chitin. Protein removal occurs under mild conditions. The pretreatment-acid washing-enzymatic hydrolysis process minimizes damage to the chitin structure, resulting in high-quality chitin products, while also reducing the amount of acid and alkali used and minimizing environmental impact.

[0070] In step S6, the temperature is 110℃~120℃, the time is 3h~4h, and the alkaline solution is a 40wt%~50wt% sodium hydroxide solution.

[0071] The purification process after washing with water until neutral can be as follows: wash with 65%~95% ethanol 1~3 times, 15min~30min each time, then centrifuge and spray dry (60℃, 12h), and finally vacuum package.

[0072] Example 1

[0073] Fresh whiteleg shrimp shells were washed with clean water and soaked in a pretreatment solution for 15 minutes. The pretreatment solution was a 3:1 volume ratio mixture of citric acid solution (pH=4) and ethanol, with a curcumin concentration of 0.1 wt%. The shells were then freeze-dried and pulverized to obtain shrimp shell powder with a particle size of approximately 5 mm. The shrimp shells were observed under an electron microscope before pulverization. Figure 1 As shown.

[0074] Add 100g of pretreated shrimp shell powder to 600ml of hydrochloric acid solution (pH=3) and stir at 45℃ for 2 hours. This step can both preliminarily decalcify and promote the release of astaxanthin from the shrimp shell matrix.

[0075] The acid-treated mixture was cooled to room temperature, and 500 ml of an ethanol-acetone mixture (volume ratio 7:3) was added. Extraction was carried out under reflux for 2 hours. The extract (astaxanthin organic solution) and shrimp shell residue (insoluble matter) were separated by filtration.

[0076] Astaxanthin organic solution was purified by silica gel column chromatography using petroleum ether-acetone (85:15 v / v) as the eluent. The red fraction was collected, evaporated under reduced pressure, dissolved in a small amount of acetone, and allowed to crystallize overnight at 4°C. The crystals were then vacuum-dried at 60°C for 4 hours to obtain astaxanthin with a purity of over 95%, which was then vacuum-packed and stored.

[0077] The shrimp shell residue after astaxanthin extraction was soaked in a flavor protease hydrolysate with pH 6.5 at 40°C for 3 hours to obtain chitin. The enzyme activity of the flavor protease hydrolysate was 1000 U / g.

[0078] Chitosan was added to a 45% NaOH solution and treated at 115°C for 3.5 hours. The product was washed with water until neutral, then washed twice with 65% ethanol to remove impurities and residual reagents. It was then dried at 70°C for 12 hours to obtain the chitosan product, which was then sealed and packaged.

[0079] Example 2

[0080] Fresh whiteleg shrimp shells were washed with clean water and then soaked in a pretreatment solution for 15 minutes under ultrasonic conditions. The pretreatment solution was a 3:1 volume ratio mixture of citric acid solution (pH=4) and ethanol, with a curcumin concentration of 0.1 wt%. The ultrasonic power was 300 W and the frequency was 40 kHz. The shells were then freeze-dried and pulverized to obtain shrimp shell powder with a particle size of approximately 5 mm.

[0081] Add 100g of pretreated shrimp shell powder to 600ml of a mixed acid solution and stir at 45℃ for 2 hours. The mixed acid solution is a mixture of phosphoric acid, citric acid, and lactic acid in a 2:4:3 ratio.

[0082] The acid-treated mixture was cooled to room temperature, and 500 ml of an ethanol-acetone mixture (volume ratio 7:3) was added. Extraction was carried out under reflux for 2 hours. The extract (astaxanthin organic solution) and shrimp shell residue (insoluble matter) were separated by filtration.

[0083] The astaxanthin organic solution was purified by silica gel column chromatography using petroleum ether-acetone (85:15 v / v) as the eluent. The red fraction was collected, evaporated under reduced pressure, dissolved in a small amount of acetone, and allowed to crystallize overnight at 4°C. The crystals were then vacuum-dried at 60°C for 4 hours, yielding astaxanthin that was 16% heavier than in Example 1. The astaxanthin was then vacuum-packed and stored.

[0084] The shrimp shell residue after astaxanthin extraction was soaked in a flavor protease hydrolysate with pH 6.5 at 40°C for 3 hours to obtain chitin. The enzyme activity of the flavor protease hydrolysate was 1000 U / g.

[0085] Chitosan was added to a 45% NaOH solution and treated at 115°C for 3.5 hours. The product was washed with water until neutral, then washed twice with 65% ethanol to remove impurities and residual reagents. It was then dried at 70°C for 12 hours to obtain the chitosan product, which was then sealed and packaged.

[0086] Comparative Example 1

[0087] Fresh whiteleg shrimp shells were washed with clean water, then dried and pulverized to obtain shrimp shell powder with a particle size of approximately 5 mm. The shrimp shells were observed under an electron microscope before pulverization. Figure 2 As shown.

[0088] Add 100g of pretreated shrimp shell powder to 600ml of hydrochloric acid solution (pH=3) and stir for 2 hours at 45℃.

[0089] The acid-treated mixture was cooled to room temperature, and 500 ml of an ethanol-acetone mixture (volume ratio 7:3) was added. Extraction was carried out under reflux for 2 hours. The extract (astaxanthin organic solution) and shrimp shell residue (insoluble matter) were separated by filtration.

[0090] Astaxanthin organic solution was purified by silica gel column chromatography using petroleum ether-acetone (85:15 v / v) as the eluent. The red fraction was collected, evaporated under reduced pressure, dissolved in a small amount of acetone, and allowed to crystallize overnight at 4°C. The crystals were then vacuum-dried at 60°C for 4 hours and stored in vacuum packaging.

[0091] The shrimp shell residue after astaxanthin extraction was soaked in a flavor protease hydrolysate with pH 6.5 at 40°C for 3 hours to obtain chitin. The enzyme activity of the flavor protease hydrolysate was 1000 U / g.

[0092] Chitosan was added to a 45% NaOH solution and treated at 115°C for 3.5 hours. The product was washed with water until neutral, then washed twice with 65% ethanol to remove impurities and residual reagents. It was then dried at 70°C for 12 hours to obtain the chitosan product, which was then sealed and packaged.

[0093] contrast Figure 1 and Figure 2 As can be seen, after the pretreatment in Example 1, there are more pores on the shrimp shell, while the untreated shrimp shell is more dense. Figure 1 These pores facilitate the full reaction of various washing and extracting solutions inside the shrimp shell, hence the astaxanthin and chitosan obtained in Example 1 were more than those in Comparative Example 1.

[0094] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0095] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for extracting two products from the shell of Litopenaeus vannamei, characterized in that, Includes the following steps: The shells of whiteleg shrimp were soaked in a pretreatment solution, then dried and pulverized to obtain shrimp shell powder; the pretreatment solution contained curcumin, citric acid and ethanol; The shrimp shell powder was soaked in an acidic solution to obtain an acidic suspension; An organic solvent was added to the acid suspension, and the mixture was extracted under reflux conditions. Solid-liquid separation was performed to obtain an organic solution of astaxanthin and insoluble matter. The organic solvent was a mixture of ethanol and acetone. The astaxanthin organic solution was purified to obtain astaxanthin; The insoluble matter was soaked in a protease, and the solid was separated to obtain chitin. The chitin was deacetylated with an alkaline solution, washed with water until neutral, and then purified to obtain chitosan. The preparation steps of the pretreatment solution include: Citric acid is dissolved in water to prepare a citric acid solution with a pH of 3-4; The ethanol and the citric acid solution were mixed in a volume ratio of 3:1 to obtain a mixed solvent; Curcumin is dissolved in the mixed solvent to prepare the pretreatment solution with a curcumin concentration of 0.05wt%~0.1wt%. In the step of soaking the shells of whiteleg shrimp in a pretreatment solution, the soaking time is 10 min to 15 min. The acidic solution is a mixture of phosphoric acid, citric acid, and lactic acid, with a pH of 3-4. In the step of soaking the shrimp shell powder in the acidic solution, the temperature is 45℃-60℃ and the time is 2 hours.

2. The method for extracting two products from the shell of Litopenaeus vannamei according to claim 1, characterized in that, The step of soaking the shells of whiteleg shrimp in a pretreatment solution is carried out in an ultrasonic environment with an ultrasonic power of 300W and a frequency of 40kHz.

3. The method for extracting two products from the shell of Litopenaeus vannamei according to claim 1, characterized in that, The step of soaking the shells of whiteleg shrimp in a pretreatment solution is carried out in a microwave environment. The microwave radiation is applied intermittently with a pattern of 10 seconds on and 20 seconds off, and the microwave radiation power during application is 500W.

4. The method for extracting two products from the shell of Litopenaeus vannamei according to claim 1, characterized in that, The mass ratio of the phosphoric acid, the citric acid, and the lactic acid is 2:4~6:2~3.

5. The method for extracting two products from the shell of Litopenaeus vannamei according to claim 1, characterized in that, In the step of adding an organic solvent to the acid suspension, the volume ratio of the acid suspension to the organic solvent is 6-7:5; and the volume mixing ratio of ethanol to acetone in the organic solvent is 7:3 to 8:

2.

6. The method for extracting two products from the shell of Litopenaeus vannamei according to claim 1, characterized in that, The step of soaking the insoluble matter with protease includes: soaking it in a flavor protease hydrolysate with a pH of 6.5 at 40℃~45℃ for 2h~3h, wherein the enzyme activity of the flavor protease hydrolysate is 1000U / g.

7. The method for extracting two products from the shell of Litopenaeus vannamei according to claim 1, characterized in that, In the step of deacetylation treatment of chitin with alkaline solution, the temperature is 110℃~120℃ and the time is 3h~4h, and the alkaline solution is a 40wt%~50wt% sodium hydroxide solution.

Images