A method for preparing crab shell chitin without chemical decolorization and its application

Abstract

This invention discloses a method for preparing and applying crab chitin without chemical decolorization. The method includes: crushing the shells of Chinese mitten crabs to obtain shell powder; dissolving the shell powder in distilled water at a ratio of 1:10 to 1:30 (w / v) to obtain a shell powder solution; treating the shell powder solution with plasma jet (PJ), washing until neutral, and drying to obtain plasma-pretreated shell powder; dissolving the plasma-pretreated shell powder in 0.1-3M hydrochloric acid (HCl) solution at a ratio of 1:10 to 1:30 (w / v) for demineralization; washing the demineralized solid to neutral, performing deproteinization treatment with 0.1-3M sodium hydroxide (NaOH) solution, washing until neutral, and drying to obtain white solid crab chitin. This invention eliminates the need for a strong oxidizing agent (such as H2O2) for decolorization during the extraction of crab chitin, resulting in a color close to commercial chitin. The process is simple, environmentally friendly, and reduces production costs.

Description

Technical Field

[0001] This invention relates to the field of biomass processing technology, and more specifically, to a method for preparing and applying crab shell chitin without chemical decolorization. Background Technology

[0002] my country produces over one million tons of crab shell biomass annually, but the effective utilization rate is less than 20%. Taking the Chinese mitten crab (Malva spp.) as an example, its edible rate is only 30%–40%, and about 60% of the shell becomes waste after processing. Crab shells are rich in biomass, including minerals, proteins, and chitin.

[0003] Chitin is the second most abundant natural organic polysaccharide after cellulose, widely distributed in the exoskeletons of arthropods (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 severe environmental burden and economic costs.

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

[0005] (a) Technical problems to be solved

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing crab shell chitin without chemical decolorization, thus solving the problems of high production cost and serious pollution associated with traditional methods.

[0007] (II) Technical Solution

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

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

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

[0011] Step S3: The crab shell powder solution from step S2 is treated with plasma jet (PJ) power of 300-800W, gas flow rate of 0.1-2L / min, and stirring speed of 150-200rpm for 5-90min, washed until neutral, and dried (55-65℃) to obtain plasma pretreated crab shell powder.

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

[0013] Step S5: Wash the demineralized solids until neutral, dissolve them in 0.1-3M sodium hydroxide (NaOH) solution, stir at 90-105℃ for 1-6 hours, and perform deproteinization treatment;

[0014] Step S6: Wash the deproteinized solid material until neutral, and dry (55-65℃) to obtain white solid crab chitin.

[0015] As a preferred embodiment, step S1 specifically involves drying the shell of the Chinese mitten crab at 65°C, pulverizing it, and passing it 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 embodiment, 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 embodiment, in step S4, the HCl concentration, temperature, time, and liquid-to-material ratio are 1-2M, 55-65℃, 1-2h, and 1:10-1:30 (w / v), respectively.

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

[0020] As a preferred embodiment, in step S6, the drying temperature of crab shell chitin is 55-65°C.

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

[0022] (III) Beneficial Effects

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

[0024] This invention uses plasma jet (PJ) treatment as an auxiliary process for extracting chitin from crab shells. First, PJ is used for pretreatment, then HCl is used to remove minerals, and NaOH is used to remove proteins. Its advantages are that no chemical reagents (such as H2O2) are needed for decolorization, saving production costs, reducing energy consumption and pollution. This invention can make the color of crab shell chitin almost the same as that of commercial shells. Attached Figure Description

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

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

[0027] Figure 3 The effect of different treatment methods on the color of chitin in crab shells. Detailed Implementation

[0028] The present invention will be further described and illustrated below with reference to specific embodiments and the accompanying drawings:

[0029] Example 1

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

[0031] (1) Crab shell crushing: Wash the Chinese mitten crab shells after processing in the factory, dry them at 65℃, grind the dried crab shells and pass them through a 100-mesh sieve to make crab shell powder.

[0032] (2) Demineralization: Mix crab shell powder with 2M HCl solution at a ratio of 1:20 (w / v). Specifically, weigh 5g of crab shell powder into a beaker, add 100mL of HCl solution, and stir in a 60℃ water bath for 1h.

[0033] (3) Protein removal: 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 material until neutral, add 100 mL of 10% H2O2 solution, and stir in a water bath at 60°C for 1 h.

[0035] (5) Chitin preparation: The decolorized solid material is washed until neutral and dried at 65°C. The resulting white solid product is chitin.

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

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

[0038] Example 2

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

[0040] (1) Crab shell crushing: Wash the Chinese mitten crab shells after processing in the factory, dry them at 65℃, grind the dried crab shells and pass them through a 100-mesh sieve to make crab shell powder.

[0041] (2) Demineralization: Mix crab shell powder with 2M HCl solution at a ratio of 1:20 (w / v). Specifically, weigh 5g of crab shell powder into a beaker, add 100mL of HCl solution, and stir in a 60℃ water bath for 1h.

[0042] (3) Protein removal: 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) Chitin preparation: Wash the deproteinized solid material until neutral, dry at 65°C, and the solid product is chitin.

[0044] Depend on Figure 2 Infrared spectroscopy revealed that the chemical structure of the unbleached chitin extracted using traditional methods was basically consistent with that of the standard, with a chitin yield of 15.59% from crab shells.

[0045] Depend on Figure 3 It is evident that the color of the unbleached chitin extracted using traditional methods differs significantly from that of the standard, with the ΔE value of crab chitin being 12.40.

[0046] Traditionally extracted, unbleached chitin has a structure similar to the standard, but the decolorization step is crucial for improving chitin purity, appearance, and functional properties, as well as meeting the needs of various applications. For example, in food packaging, films made from white chitin have better visual appeal and market acceptance; in the pharmaceutical field, when used in wound dressings, decolorized chitin can better contact the skin, promoting wound healing, and its color does not affect wound observation and assessment; decolorization also removes some odor-causing substances from chitin, improving its taste and aroma in food and cosmetics.

[0047] Example 3

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

[0049] (1) Crab shell crushing: Wash the Chinese mitten crab shells after processing in the factory, dry them at 65℃, grind the dried crab shells and pass them through a 100-mesh sieve to make crab shell powder.

[0050] (2) Plasma jet (PJ) pretreatment: Crab shell powder and distilled water were mixed at a ratio of 1:20 (w / v) and pretreated with plasma jet (PJ). Specifically, the beaker containing the crab shell powder solution was placed on a magnetic stirrer at 180 rpm and treated for 60 min under the conditions of plasma jet (PJ) power of 750 W and gas flow rate of 1.2 L / min. After washing until neutral, the solution was 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, 5g of plasma-pretreated crab shell powder was weighed into a beaker, 100mL of HCl solution was added, and the mixture was stirred in a water bath at 60℃ for 1h.

[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) Chitin preparation: Wash the deproteinized solid material until neutral, dry at 65°C, and the resulting white solid product is chitin.

[0054] Depend on Figure 2 Infrared spectroscopy revealed that the chemical structure of the plasma-pretreated chitin was completely identical to that of the standard, with a yield of 15.31% for crab chitin. Furthermore, the plasma-pretreated chitin exhibited a distinct stretching vibration peak at 3250 cm⁻¹ (amino group), indicating that plasma pretreatment can promote the deacetylation of crab chitin.

[0055] Depend on Figure 3 It is evident that the color of the plasma-pretreated chitin is closer to that of the standard, and the ΔE value of the crab chitin is 1.50.

[0056] The present invention relates to a method for preparing crab chitin without chemical decolorization. In the process of extracting crab chitin, no chemical reagents (such as H2O2) are used for decolorization. The color is almost the same as that of commercial chitin. 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, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing crab shell chitin without chemical decolorization, characterized in that, Includes the following steps: Step S1: Crush the shell of the Chinese mitten crab to obtain crab shell powder; Step S2: Dissolve the crab shell powder from step S1 in distilled water at a ratio of 1:10 to 1:100 w / v to obtain a crab shell powder solution; Step S3: The crab shell powder solution from step S2 is treated in a plasma jet with a plasma jet power of 650~750W, a gas flow rate of 0.8~1.2 L / min, a stirring rate of 180~200 rpm, and a treatment time of 45~60 min. After washing until neutral, the solution is dried at a temperature of 55~65℃ to obtain plasma pretreated crab shell powder. Step S4: Dissolve the above plasma-pretreated crab shell powder in 0.1-3 M hydrochloric acid solution at a ratio of 1:10 to 1:100 w / v and stir at 25-80°C for 1-6 h to carry out demineralization treatment; Step S5: Wash the demineralized solids until neutral, dissolve them in 0.1-3 M sodium hydroxide solution, stir at 90-105℃ for 1-6 h, and perform deproteinization treatment; Step S6: Wash the deproteinized solid material until neutral, and dry it to obtain white solid crab chitin.

2. The method for preparing crab shell chitin without chemical decolorization according to claim 1, characterized in that... Step S1 specifically involves drying the shell of the Chinese mitten crab at 65°C and then pulverizing it. The dried shell is then ground and passed through a 100-mesh sieve to obtain shell powder.

3. The method for preparing crab shell chitin 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 chitin 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℃, the stirring time is 1~2 h, and the material-to-liquid ratio is 1:10~1:30 w / v.

5. The method for preparing crab shell chitin 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℃, the stirring time is 1~2 h, and the material-to-liquid ratio is 1:10~1:30 w / v.

6. The method for preparing crab shell chitin without a chemical decolorization step according to claim 1, characterized in that... In step S6, the drying temperature of crab shell chitin is 55~65℃.

7. The application of the method according to any one of claims 1 to 6 in chitosan decolorization.

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