CN105295072B - The modification hydrogel of pineapple bran fibre grafting soybean protein and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of composite hydrogel, and discloses a modified hydrogel grafted with soybean protein by pineapple skin residue fiber, as well as its preparation method and application. The present invention extracts cellulose through pineapple pomace, then uses soybeans to separate out protein, then adds pineapple pomace cellulose and soybean protein isolate into a reaction vessel, oscillates and mixes evenly, then quickly adds ionic liquid, stirs and mixes, and seals to form Gel reaction, cooling, adding isopropanol aqueous solution for soaking, pouring off the soaking solution, adding distilled water to continue soaking, changing the water until the soaking solution does not contain ionic liquid, pre-freezing, vacuum freeze-drying, and obtaining a modified hydrogel. The modified hydrogel of the present invention forms a dense three-dimensional network structure due to the reaction of cellulose and soybean protein. The performance is strong, and the performance in terms of texture is superior, and it has potential applications in wound dressings and other aspects.

Description

Modified hydrogel of pineapple pomace fiber grafted with soybean protein and its preparation method and application

technical field

The invention belongs to the technical field of composite hydrogels, and in particular relates to a modified hydrogel grafted with pineapple pomace fiber and soybean protein, as well as its preparation method and application.

Background technique

Pineapple is a typical tropical fruit with characteristic flavor, which is widely planted in tropical regions. Most pineapple is processed into canned and preserved fruit, but its pomace accounts for 30-50% of the weight of the whole fruit. If it can be used well, it can not only achieve the purpose of high value, but also effectively solve the problem of annual processing of canned pineapple. The problem of environmental pollution caused by a large number of discarded peels. Therefore, the development of high-value deep processing and comprehensive utilization of pineapple by-products is an effective entry point to solve the problems in the current pineapple industry chain. Pineapple pomace is mainly composed of cellulose, hemicellulose, lignin, pectin and other substances. Through experimental determination, the cellulose content in the pineapple pomace accounts for 20-25% of the dry weight. Although pineapple pomace is rich in cellulose, there are few studies on the high-value utilization of cellulose in pineapple pomace. The chemical structure of cellulose is a linear polymer compound composed of D-glucopyranose rings linked by β-1,4-glycosidic bonds. Structural studies have found that cellulose is formed by interlacing crystalline and non-crystalline phases; the non-crystalline phase is amorphous when tested by X-ray diffraction techniques, because most of the hydroxyl groups on the glucose rings are in the Free state; while a large number of hydroxyl groups in crystalline phase cellulose form a large number of hydrogen bonds, and these hydrogen bonds form a huge hydrogen bond network, which directly leads to the formation of a dense crystal structure. The dense crystal structure seriously hinders the effective contact and interaction of chemical reagents or biological enzymes with the cellulose surface, which is also an important reason why natural cellulose is very difficult to hydrolyze.

As an important economic crop, soybean has a wide range of sources of raw materials. Soybean protein isolate is a protein extracted from soybean seeds by "alkali dissolution and acid precipitation". Soybean protein isolate (SPI) has uniform components, strong functional properties, and the ability to improve texture, as well as a variety of functional properties, among which gelation is one of the most important functional properties of soybean protein. Proteins can form a gel network structure with other substances or themselves through heat or other effects, in which hydrogen bonds, hydrophobic interactions, electrostatic interactions, disulfide bonds, etc. participate in the formation.

Cellulose can be dissolved in ionic liquid at slightly higher than room temperature to form a cellulose solution; but the formed glue is not tough enough and easy to break. However, the protein cannot form a gel under the ionic liquid system, and the protein itself undergoes some side reactions under heating conditions. How to combine the two to prepare a better hydrogel and cast it into a film requires us to explore and study. This also provides a new idea for the application of pineapple peel residue, which is of great significance.

Contents of the invention

In order to overcome the shortcomings and deficiencies in the prior art, the object of the present invention is to provide a method for preparing a modified hydrogel grafted with pineapple pomace fiber and soybean protein. In the ionic liquid system, the invention prepares a modified hydrogel with good performance through the modification of cellulose and soybean protein, and realizes the maximum utilization rate of raw materials.

Another object of the present invention is to provide a modified hydrogel prepared by the above preparation method. The hydrogel membrane prepared by the invention has smooth surface, low water permeability and good mechanical properties.

Another object of the present invention is to provide the application of the above-mentioned modified hydrogel.

The object of the present invention is achieved through the following technical solutions:

A preparation method of a modified hydrogel grafted with pineapple pomace fiber and soybean protein, specifically comprising the following steps:

(1) Preparation of pineapple pomace fiber

Pretreat the pineapple peel dregs to obtain pineapple peel fibrils; add distilled water to the pineapple peel fibrils, shake and wash at 75-80°C for 2-3 hours, adjust the pH to 3.8-4.0, filter, and add sodium chlorite The solution is bleached, filtered, washed, and dried to obtain bleached fibers; a strong alkali solution is added to the bleached fibers for alkalization, and finally subsequent processing is performed to obtain pineapple pomace cellulose;

(2) Preparation of soybean protein isolate

Grinding soybeans, sieving, adding distilled water, stirring to dissolve, adjusting the pH to 9.0-9.5 with an alkaline regulator, oscillating on a shaker, centrifuging, taking the supernatant, adding the second part of distilled water to the precipitate and repeating the above operations to obtain For the second supernatant, combine the two supernatants; use an acid regulator to adjust the pH of the supernatant to 4.0-4.5, let it stand, centrifuge, remove the supernatant, adjust the pH of the precipitate to neutral, and pre-freeze , vacuum freeze-drying to obtain soybean protein isolate;

(3) Preparation of modified hydrogel

Add pineapple husk cellulose and soybean protein isolate into the reaction container, shake to mix evenly, then quickly add ionic liquid, stir and mix evenly, seal, gel reaction, cool, add isopropanol aqueous solution for soaking, pour out soaking Then add distilled water to continue soaking, change the water until the soaking solution does not contain ionic liquid, pre-freeze, and vacuum freeze-dry to obtain a modified hydrogel.

The mass fraction of sodium chlorite in the sodium chlorite solution described in step (1) is 5%～7.5%, and the mass ratio of described pineapple peel fibrils and sodium chlorite is 1:2～1:2.5; (1) The bleaching treatment conditions described in 60 ~ 85 ℃ for 2 ~ 4h;

The washing described in the step (1) refers to first washing with distilled water for 3 to 5 times, and then washing the filtrate with an ethanol solution with a volume fraction of 80% to 95% for 2 to 3 times, and the drying condition is at 45 to 55° C. Drying treatment for 12 to 16 hours;

The strong alkali solution described in the step (1) is potassium hydroxide solution or sodium hydroxide solution; The solution mass volume ratio is 1g: (15-20)mL;

The condition of the alkalization treatment described in the step (1) is stirring at room temperature for 10-15 hours; the subsequent treatment described in the step (1) refers to washing with distilled water to neutrality, and then using a volume fraction of 80% to 95% ethanol The solution was washed 1-2 times, and finally dried at 45-55°C for 12-16 hours.

The mass volume ratio of pineapple peel fibrils and distilled water described in step (1) is 1g: (15～20) mL; The speed of described shaker oscillation is 100～150r/min; The substance that described pH adjustment is mass fraction 10% to 15% glacial acetic acid;

The pretreatment in the step (1) refers to washing the pineapple skin dregs with distilled water to remove soil residues, adding a small amount of water for preliminary crushing and filtering, drying the residues at 45-55° C. for 12-16 hours, and further pulverizing them with a high-speed pulverizer. Pass through a 60-100 mesh sieve to obtain pineapple peel fibrils (RPPF).

The mesh number of the sieve in step (2) is 60-100 mesh, the mass ratio of the soybean powder to the volume of distilled water is 1g: (10-20)mL, the speed of stirring and dissolving is 20-30r/min, The temperature for stirring and dissolving is room temperature, and the time for stirring and dissolving is 30 to 60 minutes; the alkaline regulator is sodium hydroxide solution, and its concentration is 1mol/L;

The speed of shaker oscillation described in step (2) is 100～150r/min, the temperature of shaker oscillation is 40～60 ℃, the time of oscillation in shaker is 50～75min; Described centrifugal speed is 3000～5000r/min min, the centrifugation time is 5-15 min;

The acid regulator described in step (2) is hydrochloric acid solution, and its concentration is 1mol/L;

The resting time in step (2) is 1 to 3 hours, the centrifugal speed is 3000 to 5000 r/min, and the centrifugation time is 5 to 15 minutes;

The temperature of pre-freezing described in step (2) is-20～-18 ℃, and the pre-freezing time is 20～25h; The temperature of described vacuum freeze-drying is-58～-50 ℃, and the time of vacuum freeze-drying is 30～ 35 hours; the amount of the second part of distilled water is 0.5-1 times of the amount of distilled water.

The rotating speed of stirring and mixing described in step (3) is 10～20r/min, and the time of stirring and mixing is 2～5min; The temperature of described cooling is room temperature; Virahol and water volume ratio 1 in the described isopropanol aqueous solution : (1～2.5), the time of adopting isopropanol aqueous solution soaking is 24h; Said water change refers to changing water once every 12h; Does not contain ionic liquid in the soaking liquid and refers to not containing oil in the soaking liquid, eluent Clear and transparent, the color of the glue is basically white to light yellow, and the glue with a large amount of protein added is light yellow, and the color is lighter than the glue just prepared; the temperature of the pre-freezing is -20 ~ -18 ° C, and the pre-freezing time is 20～25h; the temperature of the vacuum freeze-drying is -58～-50℃, and the time of vacuum freeze-drying is 30～35h;

The ionic liquid described in the step (3) is [AMIm]Cl (1-allyl-3-methylimidazole chloride) or [BMIm]Cl (1-butyl-3-methylimidazole chloride) or [ EMIm] Cl (1-ethyl-3 methylimidazole chloride). The glass tube is cylindrical with a flat bottom, and the diameter ratio of the rotor to the glass tube is 1:1.2-1:3.

The protein addition in step (3) is 0.5～20% of the ionic liquid quality, and the cellulose addition is 0.5～20% of the ionic liquid quality; The volume ratio is (5-10) g: (15-40) mL.

The specific process of the gelling reaction described in step (3) is: the initial stage of the reaction: stirring and reacting at 50-70°C for 1-3 hours, and the rotating speed is 10-18r/min; the second stage: stirring at 75-85°C Reaction for 2 to 4 hours, with a rotation speed of 22 to 28r/min; the third stage: stirring and reacting at 90 to 120°C for 3 to 6 hours, with a rotating speed of 15 to 22r/min; the fourth stage: stirring and reacting at 60 to 75°C for 1 to 2h, the speed is 10~18r/min.

The modified hydrogel is prepared by the above preparation method.

The application of the modified hydrogel in the field of medicine (wound dressing, drug loading) and filter membrane material.

Compared with the prior art, the present invention has the following advantages and beneficial effects: the cellulose-grafted soybean protein isolate modified hydrogel provided by the present invention forms a dense three-dimensional network structure due to the reaction of cellulose and soybean protein, so that its After the film-forming material is prepared, the surface is smooth and flat, the water permeability is low, and it has strong water-proof performance. At the same time, the overall water-holding performance of the colloid is strong, and the performance in terms of texture is also superior. It has potential applications in wound dressings, etc. .

Description of drawings

Fig. 1 is the FT-AR collection of illustrative plates of the modified hydrogel prepared in embodiment 1;

Figure 2 is a scanning electron microscope SEM image of the modified hydrogel prepared in Example 3.

Detailed ways

The implementation of the present invention will be further illustrated and described below in conjunction with the drawings and examples, but the implementation of the present invention is not limited thereto.

Example 1

(1) Extract pineapple pomace cellulose:

(1-1) Wash the pineapple skin residue to remove the soil residue, add a small amount of water and use a beater to crush and filter initially, elute the water-soluble components such as sugar and pigment, dry the residue in an oven at 50°C for 16 hours, and use a high-speed pulverizer Pulverize further, cross 80 mesh sieves, obtain pineapple peel fibril (RPPF);

(1-2) Add RPPF to distilled water (the mass volume ratio of distilled water of pineapple skin fibrils is 1g: 20mL), shake on a shaker at 80°C (speed 120r/min) for 2 hours, and use glacial acetic acid with a mass fraction of 13%. Adjust the pH to 3.8, filter, and treat the filter residue with sodium chlorite solution (mass fraction: 7.5%, the mass ratio of leather fibrils and sodium chlorite: 1:2.5) at 75°C for 2 hours, filter, and wash with distilled water for 3 times. After the filtrate was clear in color, it was washed twice with ethanol (95% by volume), and dried in an oven at 50°C for 15 hours to obtain bleached fibers;

(1-3) Add potassium hydroxide solution (mass fraction is 10%, the mass volume ratio of bleached fiber to potassium hydroxide solution is 1g: 15mL) to the bleached fiber, shake the table at room temperature (120r/min) 10h, stir slowly with a glass rod for half a minute every 1h to remove other impurities such as hemicellulose, filter, wash with distilled water until neutral, then wash twice with ethanol (volume fraction: 95%), and store at 50°C Dry in an oven for 15 hours to obtain pineapple pomace cellulose.

(2) Extraction of soybean protein isolate:

Take mature, dry, plump soybean grains, grind them with a high-speed grinder, pass through an 80-mesh sieve, add distilled water (soybean flour: water = 1g: 10mL), dissolve and stir (30r/min) at room temperature for 30min to reach Fully dissolve, adjust the pH to 9.5 with sodium hydroxide solution (1mol/L), shake (120r/min) in a shaker at 45°C for 50min, centrifuge at 4000r/min for 10min, take the supernatant, and repeat the above operation once for precipitation. Combine the supernatant, adjust the supernatant to pH 4.5 with hydrochloric acid solution (1mol/L), let it stand for 1h, centrifuge at 4000r/min for 10min, discard the supernatant, return the precipitate to pH 7.0, pre-freeze (temperature- 20°C, 20h) and then vacuum freeze-drying (temperature -58°C, 30h) to obtain soybean protein isolate;

(3) Preparation of modified hydrogel:

Take by weighing 0.05g pineapple pomace fiber and soybean protein isolate (0.5g, 0.25g, 0.05g respectively), join in a glass tube, put into a magnetic rotor (rotor diameter and glass tube diameter ratio are 1 : 1.5), shake it by hand to make it mix evenly, then quickly add 10g of ionic liquid [BMIm]Cl, stir and mix evenly (speed 10r/min, time 2min), seal the sealing glue, place the glass tube in the oil bath magnetic In a stirring pot, carry out a gelling reaction, the gelling reaction is as follows: the temperature at the initial stage of the reaction is 65°C, the rotating speed is 15r/min, and the time is 2h (discrimination is based on the formation of a homogeneous mixture of protein, fiber, and ionic liquid); The temperature of the second stage is 85°C, the rotating speed is 25r/min, and the time is 3h, so that the reactants are fully mixed, and the temperature preparation is made for gelling; the temperature of the third stage is 100°C, the rotating speed is 18r/min, the time is 6h, and the gelling is formed ; The fourth stage is mixed at 75°C, the rotating speed is 15r/min, and the time is 1h. The air whipped in during the gelation process is discharged; The ratio is 1:1, the amount added is about 30mL, just make it submerged), soak for 24 hours, pour off the soaking solution, then add distilled water to continue soaking, change the water every 12 hours until the eluent does not contain ionic liquid, time 7 days; pre-freezing (temperature -20°C, 20h) and then vacuum freeze-drying (temperature -58°C, 30h) to obtain a modified hydrogel.

Fig. 1 is the FT-AR image of the hydrogel prepared in Example 1, it can be seen from the figure that the grafting is obviously successful. Among them, Nos. 1-3 (No. 1-3 correspond to the gels with 0.5g, 0.25g, and 0.05g of protein added respectively) reached peaks at 3277cm ^-1 , 3347cm ^-1 , and 3348cm ^-1 respectively, which represent hydrogels. On the stretching vibration of -OH and -CH-, at the same time, the characteristic absorption peaks of pineapple peel fiber at 1058cm ^-1 , 1025cm ^-1 , and 1024cm ^-1 are the ether bonds between sugar units. All of the above It shows that the prepared hydrogel contains cellulose base. The peaks at 2924cm ^-1 , 2924cm ^-1 , and 2925cm ^-1 represent the absorption peaks of the carbon-nitrogen triple bond, while the vibrational absorption peaks at 2854cm ^-1 , 2854cm ^-1 , and 2854cm ^-1 are the vibrational absorption peaks of -CH-, and at 1744cm The absorption peaks at ^-1 , 1742cm ^-1 , and 1740cm ^-1 are the vibrational absorption peaks of carbonyl bonds. These three absorption peaks strongly prove the existence of protein in the hydrogel, which means that the grafting is successful.

Example 2

(1) Extract pineapple pomace cellulose:

(1-1) Wash the pineapple skin residue to remove the soil residue, add a small amount of water and use a beater to crush and filter initially, elute the water-soluble components such as sugar and pigment, dry the residue in an oven at 50°C for 16 hours, and use a high-speed pulverizer Pulverize further, cross 80 mesh sieves, obtain pineapple peel fibril (RPPF);

(1-2) Add RPPF to distilled water (the mass volume ratio of distilled water of pineapple skin fibrils is 1g: 15mL), shake the shaker at 80°C (speed 120r/min) for 2h, and use glacial acetic acid with a mass fraction of 13%. Adjust the pH to 3.9, filter, and treat the filter residue with sodium chlorite solution (mass fraction is 7.5%, the mass ratio of skin fibrils and sodium chlorite is 1:2.5) at 75°C for 2 hours, filter, and wash the filter residue with distilled water for 3 hours. After the filtrate was clear in color, it was washed twice with ethanol (95%), and the filter residue was dried in an oven at 50°C for 15 hours to obtain bleached fibers;

(1-3) Add potassium hydroxide solution (mass fraction is 10%, the mass volume ratio of bleached fiber to potassium hydroxide solution is 1g: 15mL) to the bleached fiber, shake the table at room temperature (120r/min) 10h, stir slowly with a glass rod for half a minute every 1h to remove other impurities such as hemicellulose, filter, wash with distilled water until neutral, then wash twice with ethanol (volume fraction: 95%), and store at 50°C Dried in an oven for 15 hours to obtain pineapple pomace cellulose;

(2) Extraction of soybean protein isolate:

Take mature, dry, plump soybean grains, grind them with a high-speed grinder, pass through an 80-mesh sieve, add distilled water (soybean flour: water = 1g: 10mL), dissolve and stir (30r/min) at room temperature for 30min to reach Fully dissolve, adjust the pH to 9.5 with sodium hydroxide solution (1mol/L), shake (120r/min) in a shaker at 45°C for 50min, centrifuge at 4000r/min for 10min, take the supernatant, and repeat the above operation once for precipitation. Combine the supernatant, adjust the supernatant to pH 4.5 with hydrochloric acid solution (1mol/L), let it stand for 1h, centrifuge at 4000r/min for 10min, discard the supernatant, return the precipitate to pH 7.0, pre-freeze (temperature- 20°C, 20h) and vacuum freeze-drying (temperature -58°C, 30h) to obtain soybean protein isolate;

(3) Preparation of modified hydrogel:

Weigh 0.05g of pineapple pomace fiber and 0.05g of soybean protein isolate, add them into a glass tube, put a magnetic rotor (the ratio of the diameter of the rotor to the diameter of the glass tube is 1:1.5), and mix them evenly. Prepare three such glass tubes, and quickly add 5g of ionic liquids [AMIm]Cl, [BMIm]Cl, [EMIm]Cl respectively to mix evenly, seal with sealing glue, and place the glass tubes in an oil bath magnetic stirring pot In, carry out gelling reaction, described gelling reaction is: the temperature of initial stage of reaction is 65 ℃, and rotating speed is 15r/min, time 2h (discrimination basis is that protein, fiber, ionic liquid have formed homogeneous mixture); Second The temperature of the stage is 85°C, the speed is 25r/min, and the time is 3h, so that the reactants are fully mixed, and the temperature preparation is made for gelling; the temperature of the third stage is 100°C, the speed is 18r/min, and the time is 6h, gelling; The four-stage temperature is 75°C, the rotating speed is 15r/min, and the time is 1h. The air whipped in during the gelation process is discharged; 1:1, the addition amount is about 30mL, just make it submerged), soak for 24 hours, pour out the soaking solution, then add distilled water to continue soaking, change the water every 12 hours until the eluent does not contain ionic liquid, the time is 7 day, pre-freezing (temperature -20°C, 20h) and vacuum freeze-drying (temperature -58°C, 30h) to obtain a modified hydrogel.

A group of hydrogels prepared in Example 2 were washed for 3 days and found that the three groups of samples had clear boundaries between two phases, the upper layer was an oily aqueous solution, and the lower layer was a non-flowing hydrogel colloid. The three groups of samples could not be completely eluted, the color of the ionic liquid [AMIm]Cl was the darkest, which was yellowish brown, the color of the ionic liquid [BMIm]Cl was the lightest, transparent and slightly white, and the color of the ionic liquid [EMIm]Cl Cl is white and opaque. Compared with the hydrogel just prepared 3 days ago, the order of color lightening from large to small is [BMIm]Cl, [EMIm]Cl, [AMIm]Cl. Continue soaking and find that the time required for complete elution of [AMIm]Cl, [BMIm]Cl, [EMIm]Cl is 12 days, 7 days, 10 days in turn. And [AMIm]Cl, [BMIm]Cl, [EMIm]Cl are all white and slightly transparent after elution. If they are cast into a film before soaking, they will be transparent and slightly white. The above phenomenon shows that [BMIm]Cl is the easiest to elute.

Example 3

(1) Extract pineapple pomace cellulose:

(1-1) Wash the pineapple skin residue to remove the soil residue, add a small amount of water and use a beater to crush and filter initially, elute the water-soluble components such as sugar and pigment, dry the residue in an oven at 50°C for 16 hours, and use a high-speed pulverizer Pulverize further, cross 80 mesh sieves, obtain pineapple peel fibril (RPPF);

(1-2) Add RPPF to distilled water (the mass volume ratio of distilled water of pineapple skin fibrils is 1g: 15mL), shake the shaker at 80°C (speed 120r/min) for 2h, and use glacial acetic acid with a mass fraction of 13%. Adjust the pH to 3.8, filter, and treat the filter residue with sodium chlorite solution (mass fraction is 7.5%, the mass ratio of skin fibrils and sodium chlorite is 1:2.5) at 75°C for 2 hours, filter, and wash the filter residue with distilled water for 3 hours. After the filtrate was clear in color, it was washed twice with ethanol (95%), and the filter residue was dried in an oven at 50°C for 15 hours to obtain bleached fibers;

(1-3) Add potassium hydroxide solution (mass fraction is 10%, the mass volume ratio of bleached fiber to potassium hydroxide solution is 1g: 15mL) to the bleached fiber, shake the table at room temperature (120r/min) 10h, stir slowly with a glass rod for half a minute every 1h to remove other impurities such as hemicellulose, filter, wash with distilled water until neutral, then wash twice with ethanol (volume fraction: 95%), and store at 50°C Dried in an oven for 15 hours to obtain pineapple pomace cellulose;

(2) Extraction of soybean protein isolate:

Take mature, dry, plump soybean grains, grind them with a high-speed grinder, pass through an 80-mesh sieve, add distilled water (soybean flour: water = 1g: 10mL), dissolve and stir (30r/min) at room temperature for 30min to reach Fully dissolve, adjust the pH to 9.5 with sodium hydroxide solution (1mol/L), shake (120r/min) in a shaker at 45°C for 50min, centrifuge at 4000r/min for 10min, take the supernatant, and repeat the above operation once for precipitation. Combine the supernatant, adjust the supernatant to pH 4.5 with hydrochloric acid solution (1mol/L), let it stand for 1h, centrifuge at 4000r/min for 10min, discard the supernatant, return the precipitate to pH 7.0, pre-freeze (temperature- 20°C, 20h) and then vacuum freeze-drying (temperature -58°C, 32h) to obtain soybean protein isolate;

(3) Preparation of modified hydrogel:

Weigh 0.05g of pineapple pomace fiber and 0.05g of soybean protein isolate, add them into a glass tube, put a magnetic rotor (the ratio of the diameter of the rotor to the diameter of the glass tube is 1:1.5), and mix them evenly. Prepare three such glass tubes, and quickly add 5 g of ionic liquid [BMIm]Cl to them, mix them evenly, and seal them with sealing glue. Place the glass tube in an oil-bath magnetic stirring pot to carry out the gelation reaction. The gelation reaction is as follows: the temperature at the initial stage of the reaction is 65°C, the rotation speed is 15r/min, and the time is 2h (the basis for discrimination is protein, fiber, ion The liquid forms a homogeneous mixture); the temperature of the second stage is 85°C, the rotating speed is 25r/min, and the time is 3h; the temperature of the third stage is 100°C, the rotating speed is 18r/min, and the time is 6h; the temperature of the fourth stage is 75°C, The rotation speed is 15r/min, and the time is 1h; after the reaction is completed, after cooling to room temperature, add isopropanol aqueous solution (the volume ratio of isopropanol to water is 1:1, the addition amount is about 30mL, just make it submerged), soak 24h, pour out the soaking solution, then add distilled water to continue soaking, change the water every 12h, until the eluent does not contain ionic liquid, the time is 7 days, pre-freeze (temperature -20°C, 20h) and vacuum freeze-dry (temperature -58°C, 30h), to obtain a modified hydrogel.

Fig. 2 is a scanning electron microscope image of the hydrogel prepared in Example 3. It can be seen from the figure that the microscopic morphology of the hydrogel film is a three-dimensional network structure, the surface is smooth and flat, and there are few protrusions.

For the hydrogel prepared according to the conditions in Examples 1 and 2, totally 5 samples (the samples with protein addition in Example 1 being 0.5g, 0.25g, and 0.05g are numbered as ①, ②, ③ in sequence, and will be implemented The samples prepared with ionic liquids [AMIm]Cl and [EMIm]Cl in Example 2 are sequentially numbered ④, ⑤), and after they were eluted, they were not freeze-dried temporarily, and were subjected to TPA texture analysis. After the hydrogel sample is reshaped (cut its shape into a cylinder with a diameter of about 2.5cm and a height of about 1.5cm with a knife), the model is P36-R cylindrical compression probe, the compression force is 5g, and the compression amount is 30%. The speed before compression is 5mm ^-1 , the speed during compression is 1mm s ^-1 , and the speed after compression is 5mm s ^-1 . After compression, the texture data shown in Table 1 were obtained.

Table 1: Texture data

It can be seen from Table 1 that compared with samples ③, ④, and ⑤, the hydrogel prepared with the ionic liquid [AMIm]Cl has the highest hardness and the lowest adhesion, while [EMIm]Cl has the second hardness and the highest adhesion. [BMIm]Cl are both in the middle. The hydrogel prepared with the ionic liquid [AMIm]Cl is relatively brittle, although it is relatively hard, it is also easy to break, while [EMIm]Cl and [BMIm]Cl are more tough and not as easy to break as [AMIm]Cl . And it can also be seen from the recovery value that [BMIm]Cl is easier to return to its original shape when subjected to external forces, while [AMIm]Cl is prone to fracture, and [EMIm]Cl continues to maintain deformation, although no deformation occurs. Broken and broken, but also difficult to return to its original form. Based on these values and the actual situation, the hydrogel prepared with [BMIm]Cl is superior to the other two in terms of flexibility and recovery.

Comparing samples ①, ②, and ③, when the amount of protein added increases, the hardness increases, the recovery performance also increases, and the mechanical performance indicators in all aspects are enhanced. However, when the amount of protein added is too much, it will decrease again, and when the amount of protein added increases, the color of the obtained sample hydrogel will become darker. These factors should be considered in the actual preparation of products.

The above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (8)

1. A kind of 1. preparation method of the modification hydrogel of pineapple bran fibre grafting soybean protein, it is characterised in that：Specifically include Following steps：

   (1) preparation of pineapple bran fiber

   Pineapple bran is pre-processed, obtains pineapple peel fibrillation；Distilled water is added into pineapple peel fibrillation, in 75~80 DEG C shaking table vibration 2~3h of washing, it is 3.8~4.0 to adjust pH, filtering, adds sodium chlorite solution and carries out bleaching, filtering, Washing, dry, the fiber after being bleached；Strong base solution is added into the fiber after bleaching and carries out basification, is finally carried out Subsequent treatment, obtains pineapple bran cellulose；

   (2) preparation of soybean protein isolate

   Soybean is crushed, is sieved, adds distilled water, stirring and dissolving, uses alkaline conditioner to adjust pH as 9.0~9.5, shake Bed vibration, centrifugation, takes supernatant, and Part II distilled water is added into precipitation and repeats aforesaid operations, obtains secondary supernatant, will Supernatant merges twice；The pH that acid regulator adjusts supernatant is used to be stood for 4.0~4.5, centrifugation, removes supernatant, will The pH of precipitation is adjusted to neutrality, and pre-freeze, vacuum freeze drying, obtains soybean protein isolate；

   (3) preparation of modified hydrogel

   Pineapple bran cellulose and soybean protein isolate are added in reaction vessel, concussion is uniformly mixed it, then rapidly joins Ionic liquid, is uniformly mixed, sealing, and plastic reaction, cooling, adds isopropanol water solution and soaked, outwell soak, Add distilled water to continue to soak, change water, until being free of ionic liquid in soak, pre-freeze, vacuum freeze drying, is modified Hydrogel；

   Protein addition described in step (3) is the 0.5~20% of ionic liquid quality, and the cellulose addition is ion The 0.5~20% of liquid quality；

   Ionic liquid described in step (3) is chlorination 1- pi-allyl -3- methylimidazoles, chlorination 1- butyl -3- methylimidazoles or chlorine Change -3 methylimidazole of 1- ethyls；

   Plastic described in step (3) reaction specific embodiment be：React initial period：In 50~70 DEG C stirring reaction 1~ 3h, rotating speed are 10~18r/min；Second stage：In 75~85 DEG C of stirring 2~4h of reaction, rotating speed is 22~28r/min；3rd Stage：In 90~120 DEG C of stirring 3~6h of reaction, rotating speed is 15~22r/min,；Fourth stage：In 60~75 DEG C of stirring reactions 1 ~2h, rotating speed are 10~18r/min.
2. 2. the preparation method of the modification hydrogel of pineapple bran fibre grafting soybean protein according to claim 1, its feature It is：The mass fraction of sodium chlorite is 5%~7.5% in sodium chlorite solution described in step (1), the pineapple peel fibril Dimension is 1 with sodium chlorite mass ratio：2~1：2.5；The condition of bleaching described in step (1) be in 60~85 DEG C handle 2~ 4h；

   Strong base solution described in step (1) is potassium hydroxide solution or sodium hydroxide solution；The matter of highly basic in the strong base solution It is 8%~10% to measure percentage, and the fiber filter residue quality and strong base solution liquor capacity ratio after the bleaching are 1g：(15~20) mL；

   The condition of basification described in step (1) is 10~15h of stir process at room temperature；Pineapple peel described in step (1) The mass volume ratio of fibrillation and distilled water is 1g：(15~20) mL；The speed of the shaking table vibration is 100~150r/min.
3. 3. the preparation method of the modification hydrogel of pineapple bran fibre grafting soybean protein according to claim 1, its feature It is：Bean powder quality described in step (2) and distilled water volume ratio are 1g：(10~20) mL, the rotating speed of the stirring and dissolving are 20~30r/min, the temperature of the stirring and dissolving is room temperature, and the time of stirring and dissolving is 30~60min；

   The speed of the vibration of shaking table described in step (2) is 100~150r/min, and the temperature of shaking table vibration is 40~60 DEG C, shaking table The time of middle vibration is 50~75min；The centrifugal rotational speed is 3000~5000r/min, and centrifugation time is 5~15min；

   Time of repose described in step (2) is 1~3h, and the centrifugal rotational speed is 3000~5000r/min, and the centrifugation time is 5~15min.
4. 4. the preparation method of the modification hydrogel of pineapple bran fibre grafting soybean protein according to claim 1, its feature It is：The material that pH is adjusted described in step (1) is the glacial acetic acid that mass fraction is 10%~15%；

   Subsequent treatment described in step (1) refers to be washed to neutrality with distilled water, then molten with 80%~95% ethanol of volume fraction Liquid washs 1~2 time, most after 45~55 DEG C of dry 12~16h；

   Washing refers to first be washed with distilled water 3~5 times described in step (1), uses volume fraction 80% after filtrate color is limpid again ~95% ethanol solution washs 2~3 times, and the drying condition is in 45~55 DEG C of 12~16h of drying process.
5. 5. the preparation method of the modification hydrogel of pineapple bran fibre grafting soybean protein according to claim 1, its feature It is：Alkaline conditioner described in step (2) is sodium hydroxide solution, its concentration is 1mol/L；It is acid described in step (2) to adjust Section agent is hydrochloric acid solution, its concentration is 1mol/L；

   The temperature of pre-freeze described in step (2) is -20~-18 DEG C, and the pre-freeze time is 20~25h；The vacuum freeze drying Temperature is -58~-50 DEG C, and the time of vacuum freeze drying is 30~35h；The dosage of the Part II distilled water is distilled water 0.5~1 times of dosage.
6. 6. the preparation method of the modification hydrogel of pineapple bran fibre grafting soybean protein according to claim 1, its feature It is：The rotating speed being stirred described in step (3) is 10~20r/min, and the time being stirred is 2~5min；It is described cold But temperature is room temperature；Isopropanol and water volume ratio 1 in the isopropanol water solution：(1~2.5), using isopropanol water solution The time of immersion is 24h；The water that changes refers to that every 12h changes a water；The temperature of the pre-freeze is -20~-18 DEG C, the pre-freeze time For 20~25h；The temperature of the vacuum freeze drying is -58~-50 DEG C, and the time of vacuum freeze drying is 30~35h；

   Pretreatment described in step (1) refers to that pineapple bran is carried out cleaning using distilled water removes soil residue, adds few The filtering of water preliminary crushing is measured, by residue in 45~55 DEG C of dry 12~16h, is further crushed using high speed disintegrator, mistake 60~ 100 mesh sieves, obtain pineapple peel fibrillation.
7. 7. a kind of modified hydrogel is prepared by claim 1~6 any one of them method.
8. 8. application of the hydrogel in field of medicaments and filter membrane material field is modified according to claim 7.