CN106478839A - Pretreatment method of shrimp and crab shells and method for preparing alpha-chitin - Google Patents

Abstract

The invention provides a pretreatment method of shells of shrimps and crabs and a method for preparing alpha-chitin. The pretreatment method of the shrimp and crab shells is characterized in that after the water content of the shrimp and crab shells is improved, the pressure is instantaneously released under a high-temperature and high-pressure environment, so that the water in the shrimp and crab shells is quickly evaporated and released, the inner skin layer structure of the shrimp and crab shells is directly damaged to generate a plurality of layer films, and a porous structure is formed among the layer films. The invention also provides a method for preparing alpha-chitin, which comprises the main steps of the pretreatment method of the shells of the shrimps and crabs. The invention can form the shrimp and crab shells into a porous structure on the basis of maintaining the shapes of the raw materials and the products, increase the reaction surface area, further improve the reaction rate, shorten the processing time and avoid the browning of the shrimp and crab shells.

Description

Shrimp and crab shell pretreatment method and method for preparing α-chitin

technical field

The present invention relates to a pretreatment method of shells of shrimp and crabs, in particular to a method of pretreating shells of shrimps and crabs by means of expansion, and a method for further preparing α-chitin (α-chitin).

Background technique

Chitin is abundant in nature and exists in the exoskeleton of arthropods, squid cartilage and cell walls of fungi and yeasts. Chitin is a high molecular polymer formed by N-acetylglucosamine sugar as a monomer and linked by β-1,4 bonds. Chitin and its derivatives can be used in a wide range of fields, such as agriculture, food nutrition, biomedicine, material science, nanotechnology, cosmetics, wastewater treatment, papermaking, textiles and other fields.

The chitin, protein, calcium carbonate and calcium phosphate in the shell of shrimp and crab are tightly combined from the outside to the inside like a sandwich pie. The chitin layer is sandwiched by two carrier protein (CP) layers, and the CP layer The outer layer is the mineralization matrix (mineralization matrix, MM) layer, the outermost layer is the calcium phosphate layer, the MM layer is an acidic polypeptide chain with a strong affinity for calcium ions, and the CP is a A layered or sheet-like chitin-protein complex that has no affinity for calcium ions.

In detail, crab shells can be divided into three layers. The outermost layer is the epicuticle, which is a waxy layer that blocks moisture. The second layer is the denser exocuticle. The third layer is the endocuticle with lower density. The thickness of the inner epidermis is about three times that of the outer skin, and its volume accounts for 90% of the exoskeleton of the crab. The outer skin and the inner epidermis are hard and rough, and both are made of Composed of Bouligand structure (or twisted plywood), the chitin-protein complex (the above-mentioned layered structure of chitin and two layers of carrier protein) will be stacked into Bouligand structure in a parallel rotation manner, The void in the Bouligand structure is called the pore canal, which forms a twisted cavity similar to a honeycomb, which has the function of transmitting nutrients and ions to synthesize the exoskeleton. There are soft and elastic pore canal tubes (pore canal tubes) ribbon-shaped tubes in the pores, which can increase the toughness and elasticity of the carapace (see Chen et al., 2008; Xu et al., 2013).

The main components of the crustacean shell are minerals, chitin and protein. For example, the dry part of the crab shell has a general composition of 29.19% crude protein, 40.60% ash, 28.86% chitin, and 1.35% crude fat (Kim , 2003), so when using crustacean shells as raw materials to prepare chitin, protein and minerals must be removed first.

Calcium carbonate is the main component of the minerals in shrimp and crab shells. There are two ways to remove calcium carbonate. One method is to utilize dilute acid (such as aqueous hydrochloric acid or aqueous acetic acid) with a concentration of 3% by weight (hereinafter referred to as "wt%") to 5wt% to act at room temperature for 6 to 24 hours to react with carbonate to generate carbon dioxide , thereby removing calcium carbonate. Strong acids are not used to avoid degradation of chitin due to the reaction. Another method is to use ethylenediaminetetraacetic acid (EDTA) to chelate metals. EDTA can remove minerals under neutral conditions. Although chitin molecular chains are less likely to degrade when treated with EDTA, Chitin with a larger molecular weight can be produced, but its ability to remove minerals is poor, and the action time is also longer.

There are chemical methods and biological methods to remove protein, and chemical methods are mostly used at present. The chemical method is to use lye to treat, usually use 3-5wt% sodium hydroxide aqueous solution, and react at 80-100°C for 2-4 hours. The method is relatively simple, the reaction time is short and the effect is good, but it will cause chitin deacetylation reaction. In order to avoid this phenomenon, a two-stage lye treatment can be adopted, first using 0.5N low-concentration sodium hydroxide (0.5mol /L low-concentration sodium hydroxide) aqueous solution to remove the protein outside the shell, and then use 2-5N high-temperature and high-concentration sodium hydroxide (2-5mol/L high-temperature and high-concentration sodium hydroxide) aqueous solution to treat the protein as much as possible. Remove and avoid the occurrence of deacetylation reaction, and get chitin in a more original state. The biological method is the enzyme method, which uses protease to remove protein. Its advantages are that it will not cause damage to chitin, the processing temperature is low and there is no lye pollution. However, due to the long acting time and the difficulty in completely removing the protein, it is rarely used.

In addition, organic solvents (such as ethanol, acetone, etc.), or potassium permanganate and oxalic acid can be used to remove lipids and pigments.

Chitin is currently produced commercially, mainly by acid-base treatment to remove minerals and proteins from shrimp, crab shells or squid cartilage. However, in order to prevent adulteration, in commercial production, it is often necessary to react with large particles (tablets) or even the original size of raw materials, resulting in long production time and difficulties in purification. Therefore, there is an urgent need to develop a pretreatment method for shrimp and crab shells to shorten the reaction time and facilitate purification to prepare α-chitin in large quantities.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for pretreatment of shrimp and crab shells and a method for preparing α-chitin, aiming at the above-mentioned deficiencies in the prior art, by using explosive expansion to substantially maintain the consistency of raw materials and products. However, it can make the material form a porous structure and increase the reaction surface area, which can shorten the reaction time and solve the problem of difficult purification.

The technical solution adopted by the present invention to solve the technical problems is to provide a pretreatment method for shrimp and crab shells, which at least includes the following steps:

(a) Utilize an aqueous solution to adjust the moisture of a shrimp and crab shell to a predetermined water content, and the predetermined water content is calculated by the total weight of the shrimp and crab shell (that is, the total weight of the shrimp and crab shell containing the predetermined water content) Calculated as 100 weight percent (wt%), it is greater than or equal to 10 weight percent;

(b) placing the shrimp and crab shells in an airtight container;

(c) adding a first volume of deionized water to the closed container;

(d) heating to make the pressure in the airtight container reach a first pressure value, wherein the first pressure value is 4-14kg/cm ² gauge pressure, and when the pressure in the airtight container reaches the first pressure value , the temperature in the airtight container is 150-199°C; and

(e) releasing the pressure in the airtight container to a second pressure value, so that the moisture in the shell of the shrimp and crab is quickly evaporated and released, directly causing the inner epidermis structure of the shell of the shrimp and crab to be destroyed to produce multiple layers of film, And a porous structure is formed between the multiple layers of films; wherein, the second pressure value is less than or equal to the atmospheric pressure of the environment where the airtight container is located.

Preferably, in the step (a), the shrimp and crab shells are at least one of granular, flake, and complete crab and shrimp shells.

Preferably, in the step (e), the distance between adjacent films is greater than or equal to 8 μm.

Preferably, in the step (e), the distance between adjacent layers is 8-14 μm.

Preferably, in the steps (b)-(e), the airtight container is a pressure container, and the atmospheric pressure of the environment where the pressure container is located is 1 atmosphere.

Preferably, in the steps (b)-(e), the pressure vessel is an expansion gun.

Preferably, in the step (a), the predetermined water content of the shell of the shrimp and crab is 35%-75%.

Preferably, in the step (a), the aqueous solution is deionized water, pure water, reverse osmosis water or a liquid aqueous solution.

Preferably, in the steps (b)-(e), the airtight container has an airtight accommodating space for placing the shell of the shrimp and crab.

Preferably, the volume of the airtight accommodating space is 1.4L, and the first volume of deionized water in the step (c) is 40mL of deionized water.

Preferably, the added volume of the deionized water in the step (c) is sufficient to make the water content of the shrimp and crab shells obtained through the treatment of the steps (d) to (e) greater than or equal to 6 weight percent, and no Cases of browning.

Preferably, before the step (a), the pretreatment method also includes the following steps:

(z1) Soak the shrimp and crab shells in 0.5N sodium hydroxide solution and act at room temperature for 24 hours; and

(z2) Wash the shell of the shrimp and crab with water to make the pH value 6.5-7.5.

Preferably, the shrimp and crab shells are at least one of shrimp shells and crab shells.

Preferably, in the step (d), the first pressure value is 9-14 kg/cm ² gauge pressure, and when the pressure in the airtight container reaches the first pressure value, the temperature in the airtight container is 180 ~199°C.

The present invention also provides a method for preparing α-chitin, which at least includes the following steps:

(a) using an aqueous solution to adjust the moisture content of a shell of a shrimp and crab to a predetermined water content, and the predetermined water content is greater than or equal to 10% by weight based on the total weight of the shell of the shrimp and crab being 100% by weight;

(b) placing the shrimp and crab shells in an airtight container;

(c) adding a first volume of deionized water to the closed container;

(d) heating to make the pressure in the airtight container reach a first pressure value, wherein the first pressure value is 4-14kg/cm ² gauge pressure, and when the pressure in the airtight container reaches the first pressure value , the temperature in the airtight container is 150-199°C;

(e) releasing the pressure in the airtight container to a second pressure value, so that the moisture in the shell of the shrimp and crab is quickly evaporated and released, directly causing the inner epidermis structure of the shell of the shrimp and crab to be destroyed to produce multiple layers of film, And a porous structure is formed between the multiple layers of films; wherein, the second pressure value is less than or equal to the atmospheric pressure of the environment where the airtight container is located;

(f) Soak the shrimp and crab shells in 2N hydrochloric acid solution, and act at room temperature for 2 hours;

(g) Soak the shrimp and crab shells in 2N sodium hydroxide solution, and act at 80°C for 1 hour;

(h) washing the shell of the shrimp and crab with water, so that the pH value is 6.5-7.5;

(i) Soak the shell of the shrimp and crab in a potassium permanganate solution with a concentration of 1 wt%, and act at room temperature for 1 hour; and

(j) Soak the shrimp and crab shells in oxalic acid solution with a concentration of 1 wt%, and act at 80° C. for 1 hour.

Preferably, in the step (a), the shrimp and crab shells are at least one of granular, flake, and complete crab and shrimp shells.

Preferably, in the step (e), the distance between adjacent films is greater than or equal to 8 μm.

Preferably, in the step (e), the distance between adjacent layers is 8-14 μm.

Preferably, in the step (d), the first pressure value is 9-14 kg/cm ² gauge pressure, and when the pressure in the airtight container reaches the first pressure value, the temperature in the airtight container is 180 ~199°C.

Preferably, the added volume of the deionized water in the step (c) is sufficient to make the water content of the shrimp and crab shells obtained through the treatment of the steps (d) to (e) greater than or equal to 6 weight percent, and no Cases of browning.

By adjusting the water content of the shrimp and crab shells and controlling the pressure of explosive expansion, the present invention can generally maintain the shape of raw materials and products, but make the shrimp and crab shells form a porous structure, increase the reaction surface area, further increase the reaction rate, and shorten the processing time , and can avoid the browning of shrimp and crab shells and make inferior products. Shrimp and crab shells are pretreated according to the method of the present invention, which can save 20%-30% of the reaction time in the step of acid treatment and demineralization in the subsequent chitin purification and manufacturing process, and the step of alkali treatment and removal of protein can save 30%. %-50% response time. Moreover, the final chitin obtained can be seen from FTIR and X-ray diffraction patterns, and the functional group, degree of deacetylation and crystallinity of the product are not significantly different from those of the untreated group.

Description of drawings

Fig. 1: is the flowchart according to the pretreatment method of shrimp and crab shell of the present invention.

Figure 2: It is a schematic diagram of a bulking gun.

Fig. 3: is a flowchart of the method for preparing α-chitin according to the present invention.

Figure 4A: is a photograph of crab shells undergoing browning.

Figure 4B: is a photograph of crab shells without browning.

Figure 5A: is a scanning electron micrograph of the inner epidermis of an untreated crab shell.

Fig. 5B: is a scanning electron micrograph of the inner epidermis of crab shells pretreated by expansion (expansion pressure 4kg/cm ² ).

Fig. 5C is a scanning electron micrograph of the inner epidermis of crab shells pretreated by expansion (expansion pressure 14kg/cm ² ).

Figure 6: FTIR spectra of α-chitin obtained from crab shells pre-expanded under different pressures (4 and 14kg/cm ² ) and then purified.

Figure 7: X-ray diffraction patterns of α-chitin obtained from crab shells expanded under different pressures (4 and 14 kg/cm ² ).

detailed description

In view of the defects of the prior art, the present invention provides a pretreatment method for shells of shrimp and crabs, and provides a method for preparing α-chitin. Using the method of the present invention to pretreat shells of shrimps and crabs can greatly shorten the processing time in subsequent chitin processing without affecting the degree of deacetylation and crystallinity of products.

The following uses the detailed description of the embodiments of the present invention to illustrate the technology and features of the present invention. However, this embodiment is not intended to limit the present invention, and any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall be included in the patent protection scope of the present invention .

Please refer to FIG. 1 for the pretreatment method of shrimp and crab shells according to the present invention, which shows a flow chart of the pretreatment method of shrimp and crab shells according to the present invention. As shown in Fig. 1, at first carry out step (a), utilize an aqueous solution to adjust the moisture of shell of shrimp and crab to a predetermined water content, and this predetermined water content, with the gross weight of this shell of shrimp and crab (water content) be 100wt% , greater than or equal to 10wt%. In a preferred embodiment, step (a) soaks the shrimp and crab shells in the aqueous solution, then filters off the excess solution, and finally lowers the moisture to a predetermined moisture content in an oven at 50°C, but is not limited to this step and method , and other steps, temperature or methods can also be used to adjust the moisture content of shrimp and crab shells to a predetermined moisture content. The aqueous solution may be deionized water, but not limited thereto, and may also be pure water, reverse osmosis water (RO water) or other liquid aqueous solutions. The predetermined water content is greater than or equal to 10wt%, preferably 35wt% to 75wt%. The moisture content can be measured using an infrared moisture analyzer (IR-35, Denver Instrument, Germany), but not limited thereto. In a preferred embodiment, the shrimp and crab shells in step (a) are at least one of granular, flaked, or whole shells of crabs and shrimps.

Next, step (b) is performed, and the shrimp and crab shells are placed in an airtight container. The airtight container has an airtight accommodating space for placing shells of shrimps and crabs. The airtight container can be a pressure vessel, such as a puffing gun (puffing gun), which can be heated to release the pressure instantly to puff the shell of the shrimp and crab, but the puffing method and tools are not limited to this, and other types of puffing guns can also be used. Pressure vessel for instant pressure relief safety protection. Figure 2 shows a schematic diagram of the structure of the bulking gun. The expansion gun structure includes a rotating tank 2 and its cover 4 , a pressure sensor 6 , a heater 8 and a controller 10 .

Then, proceed to step (c), add deionized water in a closed container. The added volume of deionized water is enough to make the water content of the obtained shrimp and crab shells greater than or equal to 6wt% after the subsequent steps (d)-(e) treatment, so that browning does not occur. For example, when the volume of the airtight accommodating space of the airtight container is 1.4 L, the volume of the deionized water may be, for example, 40 mL.

Then, carry out step (d), heating to make the pressure in the airtight container reach a first pressure value, wherein, the first pressure value is gauge pressure 4-14kg/cm ² , and when the pressure in the airtight container reaches the first pressure value At a pressure value, the temperature in the airtight container is 150-199°C. Preferably, the first pressure value is a gauge pressure of 9-14 kg/cm ² , and when the pressure in the airtight container reaches the first pressure value, the temperature in the airtight container is 180-199°C. During the heating process, the pressure in the airtight container reaches the first pressure value due to the moisture contained in the shell of the shrimp and crab and the steam generated by the evaporation of deionized water added in step (c), and there is a pressure in the airtight container. corresponding temperature. For example, when the aqueous solution is deionized water, pure water, RO water or other liquid aqueous solutions, when the first pressure value reaches a gauge pressure of 4kg/ ^cm2 , the corresponding temperature is 152°C; when the first pressure When the value reaches the gauge pressure of 5kg/ ^cm2 , the corresponding temperature is 159°C; when the first pressure value reaches the gauge pressure of 6kg/ ^cm2 , the corresponding temperature is 165°C; when the first pressure value reaches the gauge pressure When the pressure is 7kg/ ^cm2 , the corresponding temperature is 170°C; when the first pressure value reaches the gauge pressure of 8kg/ ^cm2 , the corresponding temperature is 175°C; when the first pressure value reaches the gauge pressure of 9kg/ ^cm2 , the corresponding temperature is 180°C; when the first pressure value reaches a gauge pressure of 10kg/cm ² , the corresponding temperature is 184°C; when the first pressure value reaches a gauge pressure of 11kg/cm ² , the corresponding The temperature is 188°C; when the first pressure value reaches the gauge pressure of 12kg/ ^cm2 , the corresponding temperature is 191°C; when the first pressure value reaches the gauge pressure of 13kg/ ^cm2 , the corresponding temperature is 195 °C; when the first pressure value reaches a gauge pressure of 14kg/cm ² , the corresponding temperature is 198 °C.

Then, carry out step (e), release the pressure in the airtight container to a second pressure value, make the moisture in the shrimp and crab shell quickly evaporate and release, drop from the first pressure value to the moment of the second pressure value, directly cause shrimp The structure of the inner epidermis of the crab shell is destroyed to produce multiple layers of membranes, and a porous structure is formed between the layers of membranes; wherein, the second pressure value is less than or equal to the atmospheric pressure of the environment where the airtight container is located. In steps (b) to (c), the airtight container can be a pressure container, and the atmospheric pressure of its environment can be, for example, 1 atmosphere, so that the airtight container reaches a second pressure value equal to atmospheric pressure after depressurization. And under the condition of safety and equipment permission, the second pressure value can even be less than atmospheric pressure, for example, the airtight container is placed in a negative pressure or near vacuum environment, after making the airtight container depressurize, reach the first pressure value less than atmospheric pressure. Two pressure values.

The pretreatment of the shrimp and crab shells through the above steps can destroy the structure of the inner epidermis of the shrimp and crab shells to produce multiple layers of films, and a porous structure is formed between the layers of films. The distance between adjacent layers may be, for example, greater than or equal to 8 μm. Preferably, the distance between adjacent layers may be, for example, 8-14 μm.

Before performing step (a) to adjust the water content of shrimp and crab shells, step (z1) can be performed to soak the shells of shrimp and crabs in 0.5N sodium hydroxide solution and act at room temperature for 24 hours to remove residual meat and tissue; And step (z2) washing the shells of the shrimps and crabs with water to make them roughly neutral, for example, the pH value is about 6.5-7.5.

In another aspect of the present invention, the method for preparing α-chitin according to the present invention includes the steps of the pretreatment method for shrimp and crab shells according to the present invention and other steps. Please refer to FIG. 3 , which shows a flowchart of the method for preparing α-chitin according to the present invention. As shown in FIG. 3 , steps (a) to (e) are the same as steps (a) to (e) shown in FIG. 1 above for processing shrimps and crabs, and will not be repeated here. After steps (a) to (e), the expanded shrimp and crab shells are obtained, and then step (f) is performed, the shrimp and crab shells are soaked in 1-4N hydrochloric acid solution (1-4mol/L hydrochloric acid solution), Act at room temperature for 1-3 hours to remove minerals. Preferably, shells of shrimps and crabs are soaked in 2N hydrochloric acid solution (2mol/L hydrochloric acid solution) and acted at room temperature for 2 hours to remove minerals.

Then proceed to step (g), soak the shrimp and crab shells in 1-4N sodium hydroxide solution (1-4mol/L sodium hydroxide solution), and act at 50-100° C. for 1-3 hours to remove protein. Preferably, shells of shrimps and crabs are soaked in 2N sodium hydroxide solution (2mol/L sodium hydroxide solution) and acted at 80° C. for 1 hour to remove protein.

Then proceed to step (h), washing the shrimp and crab shells with water, so that the pH value is 6.5-7.5, which is roughly neutral.

Then proceed to step (i), soak the shrimp and crab shells in 0.5-2 wt% potassium permanganate solution, and act at 20-50° C. for 0.5-2 hours to remove the pigment. Preferably, shells of shrimps and crabs are soaked in a potassium permanganate solution with a concentration of 1 wt%, and acted at room temperature for 1 hour to remove pigment.

Then proceed to step (j), soak the shrimp and crab shells in 0.5-2wt% oxalic acid solution, and act at 50-100° C. for 0.5-2 hours to reduce potassium permanganate. Preferably, shells of shrimps and crabs are soaked in oxalic acid solution with a concentration of 1 wt%, and acted at 80° C. for 1 hour to reduce potassium permanganate.

Each of the above solutions may be an aqueous solution, but not limited thereto, or may include solutions in other suitable solvents. Other substances can also be added to the solution as needed.

Then, it can be further washed with water until almost neutral, and can be further dried to obtain α-chitin.

The following examples according to the present invention are used to illustrate the present invention, but the present invention is not limited by these specific examples.

Example 1

Collect crab shells (collect crab shells from restaurants in Wanli District, New Taipei City, China, collected crab shells are the crab shells of flower crabs (Portunus pelagicus), but the present invention is not limited thereto), clean it up, remove After most of the viscera and impurities, soak in 0.5N NaOH (0.5mol/L NaOH) aqueous solution, and let it work at room temperature for one day to remove residual meat and tissue, wash with water until neutral, dry at room temperature before use. First soak 100g of the crab shell raw material in 1000mL of water for 1 hour, and the water content of the crab shell after rehydration is about 35% (using an infrared moisture analyzer (IR-35, Denver Instrument, Germany) and a water activity analyzer (AquaLab., Devices, CX2, the United States) to measure), wipe off excess water on the surface for later use. After 50g of rehydration, the crab shells were put into a swelling gun (PRM-014, Wang Pioneer Enterprise Co., Ltd., Taichung, Taiwan, China) with a volume of 1.4 liters in a rotating drum (rotating drum), and then added 40mL of deionized water, lock the tank cover (lid), heat to increase the pressure of the expansion gun to the set pressure of 4kg/cm ² , then open the tank cover instantly, causing high temperature and high pressure water to suddenly turn into water vapor, causing crab shells Due to the external heat energy and strong water vapor pressure, its structure is destroyed, and large holes are formed in the inner epidermis, and a pretreated crab shell in Example 1 is obtained. The pretreated crab shells are collected and processed for subsequent purification.

Add 50 g of the crab shells pretreated in Example 1 to 500 mL of 2N HCl (2mol/L HCl) aqueous solution, and act at room temperature for 2 hours until no bubbles (such as CO ₂ ) are generated to fully remove minerals. Then act with 500mL 2N NaOH (2mol/L NaOH) aqueous solution at 80°C for 1 hour to remove the protein in the crab shell, wash with water until neutral, and then act with 500mL 1wt% potassium permanganate aqueous solution at room temperature for 1 hour to Remove the pigment, wash with water, and then act with 500mL 1wt% oxalic acid aqueous solution at 80°C for 1 hour to reduce potassium permanganate, then wash with water until neutral, and dry at 50°C to obtain α-chitin.

Example 2

Proceed in the same manner as Example 1, but heat to increase the pressure of the expansion gun to reach the set pressure of 14kg/cm ² instead of 4kg/cm ² , and obtain a crab shell after pretreatment in Example 2.

Comparative Example 1 No Added Water Group

The crab shells were pretreated in the same manner as in Example 1, but no water was added to the rotating tank of the expansion gun (that is, 40 mL of deionized water was not added), and a pretreated crab shell of Comparative Example 1 was obtained.

Comparative example 2 untreated group

Collect crab shells (collect crab shells from restaurants in Wanli District, New Taipei City, China, collected crab shells are the crab shells of flower crabs (Portunus pelagicus), but the present invention is not limited thereto), clean it up, remove After most of the viscera and impurities were soaked in 0.5N NaOH (0.5mol/L NaOH) aqueous solution, and acted at room temperature for one day to remove residual meat and tissue, washed with water until neutral, dried at room temperature, and obtained a comparison Example 2 Crab shells of the untreated group. 50 g of the crab shells of the untreated group in Comparative Example 2 were added to 500 mL of 2N HCl (2mol/L HCl) aqueous solution for 2 hours until no bubbles (such as CO ₂ ) were generated, so as to fully remove minerals. Then act with 500mL 2N NaOH (2mol/L NaOH) aqueous solution at 80°C for 1 hour to remove the protein in the shrimp shell, wash with water until neutral, and then act with 500mL 1wt% potassium permanganate aqueous solution at room temperature for 1 hour to Remove the pigment, wash with water, and then act with 500mL 1wt% oxalic acid aqueous solution at 80°C for 1 hour to reduce potassium permanganate, then wash with water until neutral, and dry at 50°C to obtain α-chitin.

detection

The crab shells after pretreatment in Example 1 and the crab shells after pretreatment in Comparative Example 1 were subjected to browning analysis, that is, whether browning occurred was observed with the naked eye. The crab shells after the pretreatment of Example 1, the crab shells after the pretreatment of Example 2, and the crab shells of the untreated group of Comparative Example 2 were observed with a scanning electron microscope (SEM). For the experimental method, see Mi et al. (2002) and Rinki and Dutta (2010). The crab shells after the pretreatment of example 1, the crab shells after the pretreatment of example 2, and the crab shells of the untreated group of comparative example 2 are carried out to remove calcium (Ca), magnesium (Mg), the reaction of protein and calcium, magnesium, protein Determination of content to calculate the reaction rate constant when removing calcium, magnesium, protein, etc. The crab shells after the pretreatment of example 1, the crab shells after the pretreatment of example 2, and the crab shells of the untreated group of comparative example 2 are carried out to Fourier transform infrared spectroscopic analysis (Fourier transform infrared, FTIR; be to use Fourier transform infrared spectrometer to analyze (Fourier transform infrared spectroscopy, FTS-155, BIO-RAD, California, USA)), see Baxter et al. (1992) for the experimental method. Carry out X-ray (X-ray) diffraction analysis (using Bruker D2 phaser x-ray power diffractometer, the crab shell after the example 1 pretreatment, the crab shell after the example 2 pretreatment, and the crab shell of the untreated group of comparative example 2 Germany), see Rinki and Dutta (2010) for experimental methods.

result

The present invention has two main key operations, one of which is to adjust the water content of crab shells. Table 1 below shows the effect of adding deionized water (40mL) on the water content and browning of crab shells after expansion in the expansion gun. influences. It can be seen from Table 1 that if no additional deionized water is added to the expansion gun, the water content of the crab shell after expansion is only 1.4% to 2.7% (please refer to the left column of Table 1: crab shell after pretreatment in Comparative Example 1) , will cause browning of the crab shell, as shown in Figure 4A, the crab shell lacks texture and is brown, so that white chitin cannot be produced; and an additional 40mL deionized water is added to the expansion gun, and after expansion The water content of the crab shell is 6.0%～6.5% (please refer to the right column of Table 1: the crab shell after the pretreatment of Example 1), and the browning of the crab shell will not occur, as shown in Figure 4B, there are red and white patterns of flower crab crab shell. Therefore, Example 1 puts 57.5g of water (17.5g of water in the raw material) into the rotating tank (1.4L) to ensure that the moisture in the system is sufficient and maintains a hot and humid state, so that the system will not become Browning of crab shells caused by dry heat.

Table 1

The second key operation of the present invention is the control of the expansion pressure. We set the maximum pressure of the first pressure value at gauge pressure 14kg/cm ² (at this moment, the temperature in the rotating tank is 198°C), mainly because we It was found that when the temperature in the rotating tank was higher than 200°C, the crab shells were prone to browning.

The inner epidermis of the crab shell was observed with a scanning electron microscope (SEM), as shown in Figures 5A, 5B and 5C. Figure 5A is a scanning electron micrograph of the inner epidermis of the untreated crab shell of Comparative Example 2, taken at a magnification of 4200 times, and the rotating splint structure of the inner epidermis can be observed, the structure is tight, and only in parallel rotating strips There are small gaps (pores) between them. Fig. 5B is a scanning electron micrograph of the inner epidermis of the crab shell subjected to expansion pretreatment (expansion pressure 4kg/cm ² ) of Example 1, taken at a magnification of 4200 times, and it can be observed The distance (from the center of one film to the center of the adjacent film) is about 8.64 μm, and the hole diameter formed between the two layers is about 4.72 μm. Figure 5C is a scanning electron micrograph of the inner epidermis of the crab shell that has been pretreated by expansion (expansion pressure 14kg/cm ² ) in Example 2, and the shooting magnification is 4200 times, and the gap between adjacent layers of film can be observed The distance is about 13.67 μm, and the hole diameter formed between the two layers is about 8.90 μm. It can be seen from Figures 5B and 5C that after the inner skin structure undergoes explosive expansion at 4 and 14 kg/cm ² , the pores will become larger as the expansion pressure increases. The increase of the pores will increase the total surface area of the reaction, which can accelerate the reaction rate of the subsequent purification process.

Table 2 below shows the reaction rate constants (k, the unit is min ^-1 ) for the removal of calcium, magnesium, and protein when preparing chitin from crab shells pre-expanded under different pressures (4 and 14 kg/cm ² ). ). The larger the value of k, the faster the reaction rate. As can be seen from Table 2, the reaction rate constants of the crab shells after expansion pretreatment of examples 1 and 2 are all greater than the untreated group (or called control group (control)) of comparative example 2, and the reaction rate constants will increase with the expansion. This result is consistent with the result of SEM. It shows that after the explosive expansion pretreatment of the inner epidermis of the crab shell, the pores will become larger and the total surface area of the reaction will increase, thereby increasing the reaction rate constant of the reaction of removing calcium, magnesium and protein.

Among them, the crab shells (4kg/cm ² ) after expansion pretreatment in Example 1 and the crab shells (14kg/cm ² ) after expansion pretreatment in Example 2, the reaction rate constants for removing calcium are 0.0783min ^-1 and 0.0783min -1 respectively. 0.0843min ^-1 ; the reaction rate constants of the crab shells (4kg/cm ² ) after expansion pretreatment in Example 1 and the crab shells (14kg/cm ² ) after expansion pretreatment in Example 2 were 0.0609min respectively ^-1 and 0.0694min ^-1 ; the crab shells (4kg/cm ² ) after expansion pretreatment in Example 1 and the crab shells (14kg/cm ² ) after expansion pretreatment in Example 2, the reaction rate constants for removing protein were respectively 0.0766min ^-1 and 0.1092min ^-1 .

Table 2

Preferably, the reaction rate constant of removing calcium from the crab shell pretreated by expansion of the present invention is greater than 0.07min ^-1 ; preferably, the reaction rate constant of calcium removal from the crab shell pretreated by expansion of the present invention is Greater than 0.08min ^-1 . Preferably, the reaction rate constant of removing magnesium from the crab shell pretreated by expansion of the present invention is greater than 0.05min ^-1 ; preferably, the reaction rate constant of removing magnesium from the crab shell pretreated by expansion of the present invention is Greater than 0.06min ^-1 . Preferably, the reaction rate constant of removing protein from the crab shell pretreated by expansion of the present invention is greater than 0.06min ^-1 ; preferably, the reaction rate constant of protein removal from the crab shell pretreated by expansion of the present invention is greater than 0.07min ^-1 ; preferably, the reaction rate constant of removing protein from crab shells pretreated by expansion of the present invention is greater than 0.1min ^-1 .

Fig. 6 is the FTIR spectra of α-chitin obtained from crab shells pretreated by swelling under different pressures (4 and 14 kg/cm ² ) and then purified. After calculating the degree of deacetylation of α-chitin made from crab shells of the untreated group (comparative example 2) or the expanded pretreatment group (examples 1 and 2) from the map data, it was found that the degree of deacetylation was about 25%. In addition, it can be seen from the spectrum that the main peaks of the functional groups of the prepared α-chitin include 3450cm ^-1 (OH group stretching (stretching)), 2870–2880cm ^-1 (CH stretching), 1650–1655cm ^-1 ( Amide I), 1550–1555cm ^-1 (amide II), and 1315–1320cm ^-1 (amide III) have no significant difference, indicating that swelling pretreatment will not affect the functional groups of chitin in crab shells .

Fig. 7 is the X-ray diffraction patterns of α-chitin obtained from crab shells after swelling pretreatment (Examples 1 and 2) and untreated (Comparative Example 2) under different pressures (4 and 14kg/cm ² ) . It can be seen from the spectrum that no matter whether the crab shell is pretreated by swelling or not, the purified α-chitin produces obvious peaks at about 9.6°, 19.6°, 21.1°, and 23.7°, and the intensity is similar, showing that its chitin There was no significant difference in crystallization properties.

Table 3 below is the result of calculating the reaction time (minutes) required for the reaction of purifying α-chitin and the percentage of the reduced reaction time using the reaction rate constants in Table 2. After calculation, it was found that when α-chitin was purified from unexpanded crab shells (comparative example 2), the time required to remove calcium, magnesium, and protein were 126.31, 125.56, and 42.25 minutes, respectively, and these reaction endpoints were set as standard Endpoint to calculate the percentage of purification reaction time reduced by swelling crab shells. After calculating the required reaction time with the crab shells processed by different pressure expansion, it was found that the reaction time for removing calcium, magnesium and protein in the 4kg/ ^cm2 group (Example 1) was about 98.08, 99.58 and 29.84 minutes respectively, and the reduced reaction The time percentages are 22.34%, 20.68% and 29.37%, respectively. The reaction times of the 14kg/cm ² group (Example 2) were 91.10, 87.39 and 20.93 minutes, respectively, and the reaction times were reduced by about 27.87%, 30.40% and 50.45%, respectively. It can be seen from the above that the pretreatment of crab shells by explosive expansion reaction can significantly accelerate the purification reaction time of α-chitin, and the higher the expansion pressure, the more purification reaction time can be saved.

table 3

The above Table 2 and Table 3 are the data obtained from the same experiment, and Table 2 is sampling and measuring calcium, magnesium, and protein content at different time points, and then calculating the reaction rate constant. Table 3 uses the reaction rate constant to deduce when calcium, magnesium, and protein will be completely reacted, and then obtain the total reaction time and the percentage of the reduced reaction time.

The technology of the present invention has two main key operations, one is to adjust the water content of the shrimp and crab shell, and the other is to control the pressure of explosive expansion. Properly controlling the variables to perform these two operations can make the shrimp and crab shells form a porous structure, increase the reaction rate, shorten the processing time, and avoid the browning of the shrimp and crab shells and produce inferior products. Shrimp and crab shells are pretreated according to the method of the present invention, which can save 20%-30% of the reaction time in the step of acid treatment and demineralization in the subsequent chitin purification and manufacturing process, and the step of alkali treatment and removal of protein can save 30%. %-50% response time. Moreover, the final chitin obtained can be seen from FTIR and X-ray diffraction patterns, and the functional group, degree of deacetylation and crystallinity of the product are not significantly different from those of the untreated group.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of the claims of the present invention. Therefore, all other changes or modifications that do not deviate from the spirit disclosed in the present invention should be included. Within the scope of patent protection of the present invention.

Table 4 References

Claims (20)

1. a pretreatment method for shrimp and crab shells, characterized in that it at least comprises the following steps: (a) using an aqueous solution to adjust the moisture content of a shell of a shrimp and crab to a predetermined water content, and the predetermined water content is greater than or equal to 10% by weight based on the total weight of the shell of the shrimp and crab being 100% by weight; (b) placing the shrimp and crab shells in an airtight container; (c) adding a first volume of deionized water to the closed container; (d) heating to make the pressure in the airtight container reach a first pressure value, wherein the first pressure value is 4-14kg/cm ² gauge pressure, and when the pressure in the airtight container reaches the first pressure value , the temperature in the airtight container is 150-199°C; and (e) releasing the pressure in the airtight container to a second pressure value, so that the moisture in the shell of the shrimp and crab is quickly evaporated and released, directly causing the inner epidermis structure of the shell of the shrimp and crab to be destroyed to produce multiple layers of film, And a porous structure is formed between the multiple layers of films; wherein, the second pressure value is less than or equal to the atmospheric pressure of the environment where the airtight container is located. 2. The pretreatment method of shrimp and crab shells as claimed in claim 1, characterized in that, in the step (a), the shrimp and crab shells are at least one of granular, flaky, and complete crab and shrimp shells. 3. The pretreatment method of shrimp and crab shells as claimed in claim 1, characterized in that, in the step (e), the distance between adjacent layers is greater than or equal to 8 μm. 4. The method for pretreatment of shrimp and crab shells as claimed in claim 3, characterized in that, in the step (e), the distance between adjacent layers is 8-14 μm. 5. The pretreatment method of shrimp and crab shells as claimed in claim 1, characterized in that, in the steps (b) to (e), the airtight container is a pressure vessel, and the atmospheric pressure of the environment where the pressure vessel is located is 1 atmosphere. 6. The method for pretreatment of shrimp and crab shells as claimed in claim 5, characterized in that, in the steps (b) to (e), the pressure vessel is an expansion gun. 7. The pretreatment method of shrimp and crab shells according to claim 1, characterized in that, in the step (a), the predetermined water content of the shrimp and crab shells is 35% to 75%. 8. The pretreatment method of shrimp and crab shells as claimed in claim 1, characterized in that, in the step (a), the aqueous solution is deionized water, pure water, reverse osmosis water or liquid aqueous solution. 9. The pretreatment method of shrimp and crab shells as claimed in claim 1, characterized in that, in the steps (b) to (e), the airtight container has an airtight accommodating space for placing the shrimp and crab shells . 10. The pretreatment method of shrimp and crab shells as claimed in claim 9, wherein the volume of the airtight accommodating space is 1.4L, and the deionized water of the first volume of the step (c) is 40mL Deionized water. 11. The pretreatment method of shrimp and crab shells as claimed in claim 1, characterized in that, the added volume of the deionized water in the step (c) is enough to make the processed obtained in the steps (d)～(e) The water content of the shell of shrimp and crab is greater than or equal to 6 weight percent, and browning will not occur. 12. the pretreatment method of shrimp and crab shell as claimed in claim 1, is characterized in that, before this step (a), this pretreatment method also comprises the following steps: (z1) Soak the shrimp and crab shells in 0.5N sodium hydroxide solution and act at room temperature for 24 hours; and (z2) Wash the shell of the shrimp and crab with water to make the pH value 6.5-7.5. 13. The pretreatment method of shrimp and crab shells as claimed in claim 1, wherein the shrimp and crab shells are at least one of shrimp shells and crab shells. 14. The method for pretreatment of shells of shrimp and crabs according to claim 1, characterized in that, in the step (d), the first pressure value is 9-14 kg/cm ² gauge pressure, and when the airtight container When the pressure reaches the first pressure value, the temperature in the airtight container is 180-199°C. 15. A method for preparing α-chitin, characterized in that it at least comprises the following steps: (a) using an aqueous solution to adjust the moisture content of a shell of a shrimp and crab to a predetermined water content, and the predetermined water content is greater than or equal to 10% by weight based on the total weight of the shell of the shrimp and crab being 100% by weight; (b) placing the shrimp and crab shells in an airtight container; (c) adding a first volume of deionized water to the closed container; (d) heating to make the pressure in the airtight container reach a first pressure value, wherein the first pressure value is 4-14kg/cm ² gauge pressure, and when the pressure in the airtight container reaches the first pressure value , the temperature in the airtight container is 150-199°C; (e) releasing the pressure in the airtight container to a second pressure value, so that the moisture in the shell of the shrimp and crab is quickly evaporated and released, directly causing the inner epidermis structure of the shell of the shrimp and crab to be destroyed to produce multiple layers of film, And a porous structure is formed between the multiple layers of films; wherein, the second pressure value is less than or equal to the atmospheric pressure of the environment where the airtight container is located; (f) Soak the shrimp and crab shells in 2N hydrochloric acid solution, and act at room temperature for 2 hours; (g) Soak the shrimp and crab shells in 2N sodium hydroxide solution, and act at 80°C for 1 hour; (h) washing the shell of the shrimp and crab with water, so that the pH value is 6.5-7.5; (i) Soak the shell of the shrimp and crab in a potassium permanganate solution with a concentration of 1 wt%, and act at room temperature for 1 hour; and (j) Soak the shrimp and crab shells in oxalic acid solution with a concentration of 1 wt%, and act at 80° C. for 1 hour. 16. The method for preparing α-chitin as claimed in claim 15, characterized in that, in the step (a), the shrimp and crab shells are at least one of granular, flake, and complete crab and shrimp shells . 17. The method for preparing α-chitin according to claim 15, characterized in that, in the step (e), the distance between adjacent layers is greater than or equal to 8 μm. 18. The method for preparing α-chitin according to claim 17, characterized in that, in the step (e), the distance between adjacent layers is 8-14 μm. 19. The method for preparing α-chitin according to claim 15, characterized in that, in the step (d), the first pressure value is 9-14 kg/cm ² gauge pressure, and when the airtight container When the pressure reaches the first pressure value, the temperature in the airtight container is 180-199°C. 20. The method for preparing α-chitin as claimed in claim 15, characterized in that, the added volume of the deionized water in the step (c) is enough to make the obtained The water content of the shrimp and crab shells is greater than or equal to 6% by weight, and browning will not occur.