Preparation method and application of crab shell chitin without chemical decoloration

Abstract

The invention discloses a preparation method and application of crab shell chitin without chemical decolorization, and the preparation method comprises the following steps: crushing the crab shell of Eriocheir sinensis to obtain crab shell powder; dissolving crab shell powder in distilled water according to a ratio of 1: 10-1: 30 (w / v) to obtain a crab shell powder solution; treating the crab shell powder solution by using plasma jet (PJ), washing to be neutral, and drying to obtain plasma pretreated crab shell powder; dissolving the crab shell powder pretreated by the plasma into 0.1-3M hydrochloric acid (HCl) solution according to the ratio of (1: 10)-(1: 30) (w / v), and carrying out demineralization treatment; washing the demineralized solid matter to be neutral, performing deproteinization treatment by using 0.1-3M sodium hydroxide (NaOH) solution, washing to be neutral, and drying to obtain white solid crab shell chitin. In the extraction process of the crab shell chitin, a strong oxidant (such as H2O2) is not required to be used for decoloring, the color is close to that of commercial chitin, and the process is simple, green and environment-friendly; meanwhile, the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass processing, in particular to a method for preparing crab shell chitosan without chemical decolorization and application thereof. Background Art

[0002] my country produces over one million tons of crab shell biomass annually, but the effective utilization rate is less than 20%. For example, the Chinese mitten crab (hairy crab) has an edible rate of 30% to 40%, while approximately 60% of the shells become waste after processing. Crab shells are rich in biomass, including minerals, protein, and chitin.

[0003] Chitin is the second most abundant natural organic high-molecular polysaccharide after cellulose. It is widely distributed in arthropod exoskeletons (such as crab and shrimp shells), fungi, and mollusks. However, traditional acid-base extraction processes rely on multiple steps, including decalcification with high-concentration hydrochloric acid (HCl), deproteinization with sodium hydroxide (NaOH), and decolorization with hydrogen peroxide (H2O2), resulting in significant environmental and economic costs.

[0004] Existing patented technologies (such as CN114409826B microbial fermentation method, CN112062875B ultrasonic-assisted method, CN112920290B water bath heating method) partially reduce the amount of acid and alkali or improve the extraction rate, but the decolorization process relies on high concentrations of strong oxidants (such as 10% to 30%, H2O2) and requires treatment at an environment above 60°C for 1 to 6 hours, increasing production costs and energy consumption. Therefore, it is of great significance to find a simple process for preparing chitin that does not require a decolorization step. Summary of the Invention

[0005] (1) Technical problems solved

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art, provide a method for preparing crab shell chitosan without chemical decolorization, and solve the problems of high production cost and serious pollution in traditional methods.

[0007] (2) Technical solution

[0008] To achieve the above object, the present invention provides the following technical solution: a method for preparing crab shell chitosan without chemical decolorization, comprising the following steps:

[0009] Step S1: crushing the Chinese mitten crab shell to obtain crab shell powder;

[0010] Step S2: dissolving the crab shell powder in step S1 into distilled water at a ratio of 1:10 to 1:100 (w / v) to obtain a crab shell powder solution;

[0011] Step S3: treating the crab shell powder solution in step S2 for 5 to 90 minutes under the conditions of a plasma jet (PJ) power of 300 to 800 W, a gas flow rate of 0.1 to 2 L / min, and a stirring rate of 150 to 200 rpm, washing to neutrality, and drying (55 to 65° C.) to obtain plasma pretreated crab shell powder;

[0012] Step S4: dissolving the plasma pretreated crab shell powder in a 0.1-3 M hydrochloric acid (HCl) solution at a ratio of 1:10-1:100 (w / v) and stirring at 25-80° C. for 1-6 hours for demineralization;

[0013] Step S5: washing the demineralized solid matter to neutrality, dissolving it in a 0.1-3 M sodium hydroxide (NaOH) solution at 90-105° C. and stirring for 1-6 hours to perform deproteinization;

[0014] Step S6: washing the deproteinized solid matter to neutrality and drying (55-65° C.) to obtain white solid crab shell chitosan.

[0015] As a preferred solution, the step S1 specifically comprises: drying the Chinese mitten crab shell at 65° C., crushing the shell, and passing the shell through a 100-mesh sieve to obtain crab shell powder.

[0016] As a preferred embodiment, in step S2, the ratio of crab shell powder to distilled water is 1:10 to 1:30 (w / v).

[0017] As a preferred solution, in step S3, the plasma jet (PJ) power, gas flow rate, stirring rate and processing time are 650-750 W, 0.8-1.2 L / min, 180-200 rpm and 45-60 min respectively.

[0018] As a preferred solution, in step S4, the HCl concentration, temperature, time, and material-liquid ratio are 1-2 M, 55-65° C., 1-2 h, and 1:10-1:30 (w / v), respectively.

[0019] As a preferred solution, in step S5, the NaOH concentration, temperature, time, and material-liquid ratio are 0.5-1 M, 90-100° C., 1-2 h, and 1:10-1:30 (w / v), respectively.

[0020] As a preferred solution, in step S6, the crab shell chitosan is dried at a temperature of 55-65°C.

[0021] The application of the preparation method in chitin decolorization.

[0022] (3) Beneficial effects

[0023] Compared with the prior art, the present invention provides a method for preparing crab shell chitosan without chemical decolorization and its application, which has the following beneficial effects:

[0024] The present invention uses plasma jet (PJ) treatment as an auxiliary process for crab shell chitin extraction. First, PJ is used for pretreatment, then HCl is used for demineralization, and NaOH is used for deproteinization. The advantage is that no chemical reagents (such as H2O2) are needed for the decolorization step, which saves production costs, reduces energy consumption and pollution. The present invention can make the color of crab shell chitin almost consistent with that of commercial shells. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 Infrared spectra of crab shell chitin prepared by different treatment methods;

[0027] Figure 3 Effects of different treatments on the color of crab shell chitin. DETAILED DESCRIPTION

[0028] The present invention will be further described and explained below in conjunction with specific embodiments and accompanying drawings:

[0029] Example 1

[0030] The present invention relates to a method for preparing crab shell chitosan without chemical decolorization, comprising the following steps:

[0031] (1) Crab shell crushing: The crab shells of Chinese mitten crab processed in the factory were cleaned and dried at 65°C. The dried crab shells were ground and passed through a 100-mesh sieve to make crab shell powder.

[0032] (2) Demineralization: Crab shell powder was mixed with 2M HCl solution at a ratio of 1:20 (w / v). Specifically, 5 g of crab shell powder was weighed into a beaker, 100 mL of HCl solution was added, and the mixture was stirred in a 60°C water bath for 1 h.

[0033] (3) Deproteinization: Wash the demineralized solids until neutral, add 100 mL of 1 M NaOH solution, and stir in a 95 °C water bath for 1 h.

[0034] (4) Decolorization: Wash the deproteinized solid matter until it is neutral, add 100 mL of 10% H2O2 solution, and stir in a 60°C water bath for 1 h.

[0035] (5) Preparation of chitosan: The decolorized solid material is washed to neutrality and dried at 65°C to obtain a white solid product, which is chitosan.

[0036] Depend on Figure 2Infrared spectrum shows that the chemical structure of chitin extracted by traditional extraction method is completely consistent with that of the standard, indicating that the traditional extraction method can effectively extract chitin from crab shells, and the yield of crab shell chitin is 15.40%.

[0037] Depend on Figure 3 It can be seen that the color of chitin after decolorization by traditional extraction method is close to that of the standard, and the ΔE value of crab shell chitin is 2.29.

[0038] Example 2

[0039] The present invention relates to a method for preparing crab shell chitosan without chemical decolorization, comprising the following steps:

[0040] (1) Crab shell crushing: The crab shells of Chinese mitten crab processed in the factory were cleaned and dried at 65°C. The dried crab shells were ground and passed through a 100-mesh sieve to make crab shell powder.

[0041] (2) Demineralization: Crab shell powder was mixed with 2M HCl solution at a ratio of 1:20 (w / v). Specifically, 5 g of crab shell powder was weighed into a beaker, 100 mL of HCl solution was added, and the mixture was stirred in a 60°C water bath for 1 h.

[0042] (3) Deproteinization: Wash the demineralized solids until neutral, add 100 mL of 1 M NaOH solution, and stir in a 95 °C water bath for 1 h.

[0043] (4) Preparation of chitosan: The deproteinized solid matter is washed to neutrality and dried at 65°C to obtain a solid product, which is chitosan.

[0044] Depend on Figure 2 Infrared spectrum showed that the chemical structure of chitin extracted by traditional method without decolorization was basically consistent with that of the standard product, and the yield of crab shell chitin was 15.59%.

[0045] Depend on Figure 3 It can be seen that the color of traditionally extracted undecolorized chitin is significantly different from that of the standard product, and the ΔE value of crab shell chitin is 12.40.

[0046] While the structure of traditionally extracted, unbleached chitin is similar to that of the standard product, the bleaching step is crucial for increasing chitin's purity, improving its appearance and functional properties, and meeting the demands of various applications. For example, in food packaging, films made from white chitin offer better visual appeal and market acceptance. In the pharmaceutical field, bleached chitin, when used in wound dressings, allows for better contact with the skin, promoting wound healing without affecting wound observation and interpretation due to color issues. Decolorization also removes some odorous substances from chitin, improving its taste and odor in food and cosmetics.

[0047] Example 3

[0048] The present invention relates to a method for preparing crab shell chitosan without chemical decolorization, comprising the following steps:

[0049] (1) Crab shell crushing: The crab shells of Chinese mitten crab processed in the factory were cleaned and dried at 65°C. The dried crab shells were ground and passed through a 100-mesh sieve to make crab shell powder.

[0050] (2) Plasma jet (PJ) pretreatment: Crab shell powder was mixed with distilled water at a ratio of 1:20 (w / v) and pretreated using a plasma jet (PJ). Specifically, the beaker containing the crab shell powder solution was placed on a 180 rpm magnetic stirrer and treated for 60 min under a plasma jet (PJ) power of 750 W and a gas flow rate of 1.2 L / min. The mixture was washed to neutrality and dried at 65°C to obtain plasma-pretreated crab shell powder.

[0051] (3) Demineralization: The plasma-pretreated crab shell powder was mixed with 2M HCl solution at a ratio of 1:20 (w / v). Specifically, 5 g of plasma-pretreated crab shell powder was weighed into a beaker, 100 mL of HCl solution was added, and the mixture was stirred in a 60 °C water bath for 1 h.

[0052] (4) Deproteinization: Wash the demineralized solids until neutral, add 100 mL of 1 M NaOH solution, and stir in a 95°C water bath for 1 h.

[0053] (5) Preparation of chitin: The deproteinized solid material is washed to neutrality and dried at 65°C. The obtained white solid product is chitin.

[0054] Depend on Figure 2 Infrared spectroscopy showed that the chemical structure of the chitin obtained from plasma pretreatment was identical to that of the standard product, with a crab shell chitin yield of 15.31%. Furthermore, plasma pretreatment of chitin exhibited a significant stretching vibration peak at 3250 cm-1 (amino group), indicating that plasma pretreatment promoted the deacetylation of crab shell chitin.

[0055] Depend on Figure 3 It can be seen that the color of chitin pretreated by plasma is closer to that of the standard product, and the ΔE value of crab shell chitin is 1.50.

[0056] The method for preparing crab shell chitosan without chemical decolorization disclosed by the present invention does not require the use of chemical reagents (such as H2O2) for decolorization during the crab shell chitosan extraction process. The color is almost consistent with commercial chitosan. The process is simple, green and environmentally friendly, and the production cost is about 16% lower than that of traditional extraction methods.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing crab shell chitosan without chemical decolorization, characterized in that: The following steps are involved: Step S1: crushing the Chinese mitten crab shell to obtain crab shell powder; Step S2: dissolving the crab shell powder in step S1 into distilled water at a ratio of 1:10 to 1:100 (w / v) to obtain a crab shell powder solution; Step S3: treating the crab shell powder solution in step S2 in a plasma jet (PJ), washing to neutrality, and drying at a temperature of 55 to 65° C. to obtain plasma pretreated crab shell powder; Step S4: dissolving the plasma pretreated crab shell powder in a 0.1-3 M hydrochloric acid (HCl) solution at a ratio of 1:10-1:100 (w / v) and stirring at 25-80° C. for 1-6 hours for demineralization; Step S5: washing the demineralized solid matter to neutrality, dissolving it in a 0.1-3 M sodium hydroxide (NaOH) solution at 90-105° C. and stirring for 1-6 hours to perform deproteinization; Step S6: washing the deproteinized solid matter to neutrality and drying to obtain white solid crab shell chitosan.

2. The method for preparing crab shell chitosan without chemical decolorization according to claim 1, characterized in that The step S1 specifically comprises: drying the Chinese mitten crab shell at 65° C. and then crushing it, grinding the dried crab shell and passing it through a 100-mesh sieve to obtain crab shell powder.

3. The method for preparing crab shell chitosan without chemical decolorization according to claim 1, characterized in that : In step S2, the ratio of crab shell powder to distilled water is 1:10 to 1:30 (w / v).

4. The method for preparing crab shell chitosan without a chemical decolorization step according to claim 1, characterized in that : In step S3, the plasma jet (PJ) power is 650-750 W, the gas flow rate is 0.8-1.2 L / min, the stirring rate is 180-200 rpm, and the processing time is 45-60 min.

5. The method for preparing crab shell chitosan without a chemical decolorization step according to claim 1, characterized in that In step S4, the HCl concentration is 1-2 M, the reaction temperature is 55-65° C., the stirring time is 1-2 h, and the material-liquid ratio is 1:10-1:30 (w / v).

6. The method for preparing crab shell chitosan without a chemical decolorization step according to claim 1, characterized in that : In step S5, the NaOH concentration is 0.5-1 M, the reaction temperature is 90-100° C., the stirring time is 1-2 h, and the material-liquid ratio is 1:10-1:30 (w / v).

7. The method for preparing crab shell chitosan without a chemical decolorization step according to claim 1, characterized in that : In step S6, the crab shell chitosan drying temperature is 55-65°C.

8. Use of the method according to any one of claims 1 to 7 in decolorization of chitin.

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