Preparation method of edible electrostatic spinning fiber membrane with good texture characteristics based on spirulina protein

Abstract

The invention provides a preparation method of an edible electrostatic spinning fiber membrane with good texture characteristics based on spirulina protein. According to the preparation method, the spirulina protein extract and the pullulan are adopted as raw materials, the obtained electrostatic spinning fiber membrane has good fiber structure and texture characteristics under the condition of proper viscosity and conductivity, and the application value of the electrostatic spinning fiber membrane is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of food engineering, and in particular relates to an edible electrostatically spun fiber membrane with good texture characteristics based on spirulina protein and a preparation method thereof. Background Art

[0002] In recent years, electrospinning technology has become the most effective and simplest method to prepare fiber membranes under mild operation mode. Compared with traditional fibers, fiber membranes prepared by electrospinning technology have the advantages of high porosity, good air permeability, and small fiber pore size, which makes this technology show broad application prospects in the field of edible food packaging materials. At present, the materials for preparing fiber membranes by electrospinning are mainly made of bio-based materials such as proteins and natural polysaccharides, which have the advantages of renewability, degradability and good biocompatibility. However, these raw materials and their fiber membranes still face many limitations in practical applications.

[0003] The protein materials commonly used in electrospinning still show many limitations in terms of texture, uniformity, antioxidant and antibacterial properties in the application of edible food packaging. First, the texture of this type of fiber membrane is usually loose, lacking sufficient toughness or elasticity, and is easy to break, break or fail to maintain its shape during use. Secondly, traditional fiber membranes are insufficient in uniformity, continuity and smoothness, making it difficult to tightly wrap food, especially when dealing with foods with complex shapes or irregular surfaces, which will affect the sealing and overall appearance quality of the packaging. At the same time, this type of fiber membrane has poor antioxidant properties and is easily affected by external factors and undergoes oxidation reactions, which will not only cause the material to discolor and deteriorate, but may also produce odors, thereby shortening the shelf life of the packaging material and affecting its practical application in food packaging. In addition, this type of fiber membrane usually lacks effective antibacterial properties and is difficult to inhibit the growth of microorganisms, increasing the risk of food being contaminated by bacteria or fungi during storage, thereby increasing the possibility of food deterioration.

[0004] Spirulina protein extracts are rarely used in the field of electrospinning. The main reason is that the spirulina protein extracted by the prior art usually contains more non-protein impurities (such as polysaccharides, lipids and pigments). These impurities will affect the functional properties of the protein, such as solubility, rheology and interfacial activity, thereby limiting its processability and film forming ability during the electrospinning process. At the same time, the existing extraction technology easily destroys the natural structure of the protein, making it prone to denaturation or aggregation. This structural degradation reduces the stability of the protein during the electrospinning process, resulting in uneven fiber membrane diameter and increased membrane surface roughness. In addition, the spirulina protein extracted on the market often shows problems of insufficient surface activity and uneven charge distribution, which is difficult to meet the requirements of electrospinning for preparing high-performance fiber membranes, and ultimately leads to loose membrane structure and poor mechanical properties. Summary of the invention

[0005] In view of the above problems, the present invention discloses a method for preparing an electrospun fiber membrane based on spirulina protein with good texture characteristics after purification.

[0006] Compared with other protein materials, the spirulina protein provided by the present invention contains more functional groups, such as carboxyl groups, amino groups and hydroxyl groups, after being extracted by a unique process. These groups can have stronger interactions with polysaccharide substances during the electrospinning process, forming synergistic effects such as hydrogen bonds and electrostatic attractions. Due to these groups of spirulina protein, it promotes multi-site binding between molecules, making the composite material of spirulina protein and polysaccharide show a higher degree of molecular entanglement during fiber formation. This method can effectively improve the performance of the fiber membrane in terms of fiber structure and texture characteristics, reduce the oxidative loss of food flavor, and ensure that the packaging material is not easily damaged.

[0007] The extraction and treatment method of spirulina protein provided by the present invention first includes the following steps: First, the fresh spirulina powder is pretreated with ultrasonic ethanol, and the treatment conditions are a solid-liquid ratio of 1:40 g / mL. Secondly, the pretreated spirulina powder is mixed with distilled water and the solution is adjusted to an alkaline condition (such as pH 8.0 - 10.0), and an ultrasonic cell disruptor is used to further break the cells. Subsequently, a unique enzymatic means is used to decompose the cell wall structure of spirulina, release more proteins and remove polysaccharide impurities. The specific steps are to add 1 - 1000 U / g of galactanase, hemicellulase and cellulase to the above-treated solution for enzymatic hydrolysis reaction. Finally, the enzymatic hydrolysis product is purified by ultrafiltration technology, and the fraction with a molecular weight cut-off greater than 50 kDa is collected to obtain the spirulina protein extract. The above method can effectively remove the organic small molecule substances in spirulina, thereby obtaining high-purity spirulina protein.

[0008] This study uses ethanol purification technology to effectively remove easily oxidized small molecule organic substances such as green pigments in spirulina, reduce the risk of photooxidation, and improve the stability of the material. And through ultrafiltration technology, the functional components such as bioactive peptides and polysaccharides in spirulina protein are further concentrated and purified, making it have higher biological activity. Therefore, the electrospun fiber membrane prepared from the treated spirulina protein has excellent antioxidant and antibacterial properties. It can not only reduce the oxidation reaction of food components (such as fats and vitamins), extend the shelf life of food, but also maintain the freshness of food, reduce the loss of flavor and nutritional components, thereby improving the flavor and nutritional value of food, and can effectively inhibit the growth of microorganisms on the surface or inside of food, significantly improving the anti-corrosion and fresh-keeping effects of the fiber membrane in food packaging, providing a strong guarantee for food safety.

[0009] Meanwhile, treatment with carbohydrate enzymes can release more protein fragments with surface-active or charge characteristics to improve the fiber surface morphology. And the treatment with carbohydrate enzymes can break hydrophobic interactions and some disulfide bonds, reduce protein aggregation, and enhance the uniformity of the spinning solution. This can significantly improve the phenomenon of uneven fiber diameter or fiber breakage during the electrospinning process, thus forming a more uniform, continuous, and smooth fiber membrane. Such a fiber membrane not only improves in terms of quality and appearance consistency, but also can better conform to food due to its smooth surface, improving the ductility and adaptability for packaging foods of different shapes and sizes, while reducing material waste during the packaging process and better protecting consumer health.

[0010] Generally speaking, the high-purity spirulina protein obtained by the above treatment method exposes more polar groups and can bind to polysaccharide molecules through hydrogen bonds and electrostatic interactions, which is beneficial to form a more compact molecular chain network with pullulan during the electrospinning process. At the same time, the effective interaction between spirulina protein and pullulan makes the fiber structure more stable, thus improving the texture properties such as the tensile strength, elasticity, and toughness of the fiber membrane, enabling it to maintain its structural integrity when subjected to external forces or environmental changes and protecting the food inside the package more effectively to prevent breakage.

[0011] To achieve the above object, the present invention develops a method for preparing an edible electrospun fiber membrane based on spirulina protein treated by a unique process. Using a spirulina protein extract and pullulan (PUL) as raw materials, under appropriate viscosity and conductivity, the obtained electrospun fiber membrane has good fiber structure and texture properties, enhancing its application value.

[0012] The main technical solutions adopted by the present invention include:

[0013] In the first aspect, the present invention provides a method for preparing an edible electrospun fiber membrane based on spirulina protein, comprising the following steps:

[0014] S1. Sample preparation: Mix a spirulina protein extract and pullulan in a certain proportion and dissolve them in distilled water, and dissolve under a magnetic stirrer to form a mixed solution.

[0015] S2. Electrospinning technology: Use a plastic syringe equipped with a needle to suck the mixed solution, and by adjusting spinning parameters such as voltage, solution flow rate, and the distance from the nozzle to the receiver, etc., make the solution stretch into fibers under the action of an electric field and form a thin film structure on the receiver.

[0016] The mechanism of using spirulina protein and pullulan to prepare electrospun fiber membrane is as follows: during the electrospinning process, pullulan can combine with spirulina protein through hydrogen bonds, thereby improving the spinnability of spirulina protein by changing the properties of the polymer solution. The final edible electrospun fiber membrane has good biocompatibility and degradability, and is suitable for use as food packaging materials and other fields.

[0017] As a preferred technical solution of the present invention, the spirulina protein extract described in step S1 is a substance with high purity obtained by carbohydrate complex enzyme treatment. If the purity of the spirulina protein extract is low, there are more impurities such as salt ions and polysaccharides in the extract, and it is impossible to form a strong interaction force between it and pullulan, and more defects will appear on the fiber. Moreover, the presence of these impurities will make the polymer solution have a higher conductivity, so that it will be subjected to a large traction force under the action of a strong voltage during the spinning process to form droplets, and electrostatic spinning cannot be formed.

[0018] In some preferred embodiments of the present invention, in step S1, when the total polymer concentration of pullulan and spirulina protein extract is 10wt%, the mass ratio of spirulina protein extract to pullulan in the mixed solution is (20-40): (60-80). If the proportion of spirulina protein extract in the mixed solution is too high, it may result in the inability to form fibers. Since the viscosity of the spirulina protein itself is relatively high, as the concentration increases, the viscosity of the polymer solution will gradually increase, which will cause the needle to be blocked during the spinning process, thereby preventing the formation of fibers.

[0019] In some preferred embodiments of the present invention, the plastic syringe equipped with a needle used in step S2 has an inner diameter of 0.9 mm and a volume of 10 mL.

[0020] The spinning parameters in the electrospinning technology are set as follows: voltage 5-50 kV, flow rate 0.05-1 mL / h, and the distance between the needle and the fiber collector is 10 cm.

[0021] Furthermore, the preparation of the Spirulina protein extract comprises the following steps:

[0022] (1) fresh spirulina powder and ethanol were mixed in a ratio of 1:40 g / mL and then subjected to ultrasonic treatment;

[0023] (2) mixing the ultrasonically treated spirulina powder with distilled water and adjusting the mixture to an alkaline state, further disrupting the cells using an ultrasonic cell disruptor, and then adding a carbohydrate complex enzyme to perform an enzymatic hydrolysis reaction;

[0024] (3) The retained components are collected by ultrafiltration technology to obtain the purified Spirulina protein.

[0025] Further, the carbohydrate complex enzyme is a complex of galactanase, hemicellulase, and cellulase.

[0026] Further, the mass ratio of galactanase, hemicellulase, and cellulase is (40 - 60):(20 - 30):(20 - 30).

[0027] Further, based on the mass of fresh spirulina powder, the dosage of the carbohydrate complex enzyme is 1 U / g - 1000 U / g.

[0028] Further, the components with a molecular weight cut-off greater than 50 kDa are collected by ultrafiltration technology.

[0029] Further, the edible electrospun fiber membrane prepared by the said preparation method has antibacterial properties against Escherichia coli and Staphylococcus aureus, and the diameter of the inhibition zone is 10 mm for both. Description of the Drawings

[0030] Figure 1 It is a columnar comparison chart of the average fiber diameter of the spinning products formed from the polymer solutions of Examples 1 - 12 and Comparative Examples 1 - 9, 19 - 20 of the present invention;

[0031] Figure 2 It is a scanning electron microscope (SEM) image of the spinning products formed from the polymer solutions of Examples 2, 4 - 5 and Comparative Examples 1 - 2 of the present invention;

[0032] Figure 3 It is a columnar comparison chart of the antibacterial activity of the spinning products formed from the polymer solutions of Examples 1 - 12 and Comparative Examples 1 - 9, 19 of the present invention;

[0033] Figure 4 It is a columnar comparison chart of the antioxidant activity of the spinning products formed from the polymer solutions of Examples 1 - 12 and Comparative Examples 1 - 9, 19 of the present invention. Detailed Description of the Specific Embodiments

[0034] The detailed information of the main instrument and equipment used in the embodiments of the present invention is described as follows:

[0035] The electrospinning instrument model is ET - 2535H, supplied by Beijing Yongkang Leye Technology Development Co., Ltd.;

[0036] The rotational rheometer model is Paar Physica MCR, supplied by Anton Paar (Shanghai) Trading Co., Ltd.;

[0037] The conductivity meter model is SX751, supplied by Shanghai Sanxin Instrument Factory;

[0038] The texture analyzer model is TA-XTplus, supplied by Stable Micro Systems, UK;

[0039] The scanning electron microscope model is NovaNanoSEM 230, supplied by FEI CZECH REPUBLIC S.R.O., Czech Republic;

[0040] The heating magnetic stirrer model is DS-101S, supplied by Shanghai Biaohe Instrument Co., Ltd.;

[0041] The preparation of the edible electrospun fiber membrane used in each embodiment of the present invention specifically includes the following steps:

[0042] Under the condition that the total polymer concentration is 10 wt%, pullulan (PUL) and spirulina protein extract (SPP) are mixed in a certain ratio and then dissolved under a magnetic stirrer to form a mixed solution; a 10 mL plastic syringe equipped with a needle with an inner diameter of 0.9 mm is used to suck the mixed solution. By adjusting the electrospinning parameters, for example, setting the voltage to 5 - 50 kV, the solution flow rate to 0.05 - 1 mL / h, and the distance from the nozzle to the receiver to 10 cm, the solution is stretched into fibers under the action of an electric field and a film-like structure is formed on the receiver.

[0043] Specifically, the preparation method of the spirulina protein extract (SPP) includes the following steps: First, fresh spirulina powder is pretreated with ultrasonic ethanol (ultrasonic power 100 W, time 30 min), and the treatment condition is a solid-liquid ratio of 1:40 g / mL. Second, the pretreated spirulina powder is mixed with distilled water at a solid-liquid ratio of 1:20 g / mL and then the solution is adjusted to an alkaline condition (pH = 8.0), and an ultrasonic cell disruptor is used to further break the cells (ultrasonic power 200 W, time 60 min). Subsequently, 1 - 1000 U / g of galactanase, hemicellulase, and cellulase are added to the above-treated solution for enzymatic hydrolysis reaction, wherein the mass ratio of galactanase, hemicellulase, and cellulase is (40 - 60):(20 - 30):(20 - 30). Finally, the enzymatic hydrolysis product is purified by ultrafiltration technology, and the fraction with a molecular weight cut-off greater than 50 kDa is collected to obtain the spirulina protein extract.

[0044] Specifically, the dosage composition of galactanase, hemicellulase, and cellulase in the carbohydrate complex enzyme required for purifying spirulina protein in each embodiment, the ratio of pullulan (PUL) to spirulina protein extract (SPP), the setting of electrospinning voltage, etc. are shown in Table 1.

[0045] Table 1 Raw materials, dosage ratio relationships, and reaction conditions used in Examples 1 - 12 and Comparative Examples 1 - 21

[0046]

[0047]

[0048] Note: The specific operation of the protein extraction method of Comparative Example 21 is as follows: Mix fresh spirulina powder with 0.1M NaOH solution at a solid-liquid ratio of 1:40 g / mL, and continuously stir and extract at 50°C for 2 hours; after the extraction is completed, centrifuge to collect the supernatant, and then repeat the above extraction steps for the precipitate residue to improve the total protein yield. After combining the two extraction solutions, slowly add 6M HCl solution to adjust the pH of the system to 4.0 - 4.5 to trigger isoelectric precipitation, let it stand at 4°C for 1 hour to fully aggregate the protein, then centrifuge to collect the precipitate, and wash it 3 times with deionized water to thoroughly remove the residual alkali solution; finally, freeze-dry the washed protein precipitate to obtain the spirulina protein extract.

[0049] The test indexes and test methods of the edible electrospun fiber membrane obtained in the above examples of the present invention are as follows:

[0050] (1) Determination of substance components

[0051] ① Dry matter content

[0052] Measure a volume V0 of the purified sample, add it to an aluminum foil dish with a weight of m1, place it in an oven, dry it at 60°C for 24 hours, and measure the weight m2 of the sample after drying to determine the dry matter content of the sample.

[0053]

[0054] ② Protein content, recovery rate and purity

[0055] Using potassium nitrate solution as the standard product, determine the nitrogen content (mg / L) in the sample by a total organic carbon analyzer (TOC), and then calculate the protein concentration in the sample according to the conversion factor of 4.44.

[0056] The protein purity is mainly calculated based on the mass m4 of the protein obtained by extraction and purification and its dry matter mass m5. The specific formula is as follows:

[0057]

[0058] ③ Polysaccharide content

[0059] The anthrone-sulfuric acid method is used to determine the carbohydrate content in the sample. By measuring the absorbance value at 625 nm and using glucose as the standard product, calculate the carbohydrate content of each sample.

[0060] ④ Green pigment

[0061] Referring to the method of Gilver Rosero - Chasoy et al., the absorbance values of the sample at 649 nm and 664 nm were measured, and the pigment content was calculated by the following formula.

[0062] C1 = 13.36A 664 - 5.69A 649

[0063] C2 = 27.43A 649 - 8.12A 664

[0064] Where C1 is chlorophyll a and C2 is chlorophyll b.

[0065] (2) Characterization of polymer solution

[0066] ① Viscosity

[0067] The viscosity of the polymer solution was mainly measured by an Anton Paar rotational rheometer. The sample was placed on the operating table, and the viscosity at a shear rate of 100 s⁻¹ was repeatedly measured at 25 °C. -1 The viscosity at a shear rate of 100 s⁻¹.

[0068] ② Conductivity

[0069] The conductivity of the solution was measured using a Mi 180Bench conductivity meter.

[0070] (3) Observation of fiber structure

[0071] The sample sputtered with a gold - palladium mixture was observed by scanning electron microscopy (SEM) at an acceleration voltage of 6 kV, with magnification factors of 5000 and 20000 times. The spinning diameter was measured from the SEM image obtained at a magnification of 20000 times using Image J - DiamaterJ software.

[0072] (4) Texture properties of the product

[0073] A texture analyzer was used to determine the hardness, elasticity, cohesiveness, adhesiveness, and chewiness of the spun product. The spun product with a height of 5 mm was compressed to 50% of its original thickness at a speed of 1 mm / min using a P / 6 probe; after the first bite, it was returned to the original position at a speed of 5 mm / min and the second bite was performed.

[0074] (5) Detection of antibacterial and antioxidant activities of the product

[0075] The antibacterial activity of the electrospun membrane was determined by the inhibition zone test. Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were selected as representative microorganisms and cultured in a medium in an incubator. The film was cut into 6 mm discs using a hole punch. 100 μl of the overnight cultures of Escherichia coli and Staphylococcus aureus suspensions were added to 25 ml of agar medium and evenly coated. The prepared film was placed on the inoculation plate. Then, the plate was cultured in an incubator at 37 °C for 24 hours, and the diameter of the inhibition zone was measured using a vernier caliper.

[0076] The antioxidant activity of the spun membrane was determined by the DPPH method. The spun membrane (0.1 g) was immersed in 5 ml of DPPH-ethanol solution (0.2 mM). The scavenging activity was determined by recording the absorbance of the DPPH solution at 517 nm within the first 20 minutes using a UV-visible spectrophotometer.

[0077] Please refer to Table 2 in detail. After treatment with carbohydrate complex enzymes I, II, and III (Examples 1-3), the removal of purity, impurity polysaccharides, and green pigment was significantly higher than that of the method without using complex enzymes (Comparative Example 1), the commonly used alkali extraction protein method on the market (Comparative Example 21), single enzymes (Comparative Examples 2-5), and other combined enzymes (Comparative Examples 6-9). Among them, the purity using carbohydrate complex enzyme II (Example 2) was the highest, reaching 90%. At the same time, the effect was better when the enzyme addition amount was 1 U to 1000 U. Excessive enzyme amount may lead to instability of protein content and purity (Comparative Example 17). When the cut-off amount of the ultrafiltration molecule was greater than 50 kDa, the content of polysaccharides and other impurities in the extract was lower, and the protein purity was higher.

[0078] Table 2 Substance components of examples and comparative examples

[0079]

[0080] Please refer to Table 3 in detail. After treatment with carbohydrate complex enzymes I, II, and III (Examples 1-3), there was no significant difference in the viscosity and conductivity of the solution. This may be because the complex enzymes can act synergistically to evenly degrade the carbohydrates in spirulina, maintaining a stable solution viscosity and conductivity. In contrast, for the solutions treated without using complex enzymes (Comparative Example 1) and single enzymes (Comparative Examples 2-5), due to the weak enzymatic hydrolysis effect, the molecular structure in the polymer solution could not be effectively adjusted, resulting in a decrease in viscosity and poor spinning and film-forming performance. Although other combined enzymes (Comparative Examples 6-9) have certain enzymatic hydrolysis ability, due to improper ratio or lack of synergistic effect, the solution viscosity is low.

[0081] When the mass ratio of SPP to PUL is changed beyond the range of (20 - 40):(60 - 80) (Comparative Examples 10 - 11), too high a proportion of SPP may increase the cohesion of the solution, resulting in too high viscosity and difficulty in being stretched by the electric field, while too high a proportion of PUL leads to a lack of necessary viscoelasticity in the solution, and the spinning solution cannot form continuous fibers. When the electrospinning voltage exceeds the set range (5 - 50 kV) (Comparative Examples 14 - 15), stable spinning cannot be achieved either. Specifically, when it is lower than 5 kV, the electric field force is insufficient to drive the solution to form a jet; while when it exceeds 50 kV, the electric field force is too strong, resulting in an unstable jet flow and even causing fiber breakage. When the set range of the flow rate exceeds 0.1 - 1 mL / h (Comparative Examples 12 - 13), the spinning process will also become unstable. When the flow rate is too low, the solution supply is insufficient, the jet flow is intermittent, and it is difficult to form continuous fibers; while when the flow rate is too high, too much solution accumulates, easily forming a droplet structure at the nozzle, resulting in fiber interruption or beading phenomenon. At the same time, too high an enzyme dosage (Comparative Example 17) leads to an excessive reduction in the viscosity of the solution, enhancing the fluidity of the spinning solution, but with insufficient cross-linking between molecular chains and a lack of sufficient viscoelastic support, ultimately making it difficult to form continuous and uniform fibers. In addition, when the ultrafiltration cut-off molecular weight is less than 50 kDa (Comparative Example 18), there are more impurities in the extract and the protein purity is lower, and spinning cannot be achieved.

[0082] Table 3 Influence of Polymer Solution Characteristics on Its Spinning Feasibility

[0083]

[0084]

[0085] Note: a: “+” indicates successful spinning, “-” indicates inability to spin.

[0086] Please refer in detail to Figure 1 ., as shown by the comparison results in the figure, compared with the commonly used proteins (Comparative Example 19) and polysaccharides (Comparative Example 20) on the market, the electrospun products of SPP with different proportions (Examples 2, 4, 5) show more delicate and compact characteristics. A moderate flow rate (Examples 6 - 7) can ensure a stable supply of the solution and maintain the balance between the stretching force and the fluidity of the electrospinning process. When the voltage is moderate (Examples 8 - 9), the electric field strength is sufficient to apply enough stretching force to the polymer solution. An appropriate amount of enzyme (Examples 10 - 11) can effectively regulate the degradation degree of spirulina protein, making the solution viscosity appropriate. The combined action of the above conditions helps to form stable, fine and uniform fibers during the spinning process. However, when the proportion of different enzymes is inappropriate (Comparative Examples 1 - 9), the enzymatic hydrolysis process is uneven, there are more impurities in the solution, resulting in a higher conductivity of the polymer solution, and the droplets are easily attracted by the voltage to form finer fibers, and even may lead to unstable spinning.

[0087] Please refer to in detail Figure 2 As shown by the comparison results in the figure, when using carbohydrase II within the range of SPP:PUL (20 - 40):(60 - 80) (Examples 2, 4, 5), the electrospun products are similar in fiber morphology to the commonly used protein on the market (Comparative Example 19), all showing smooth, tight and bead-free characteristics. When exceeding the proportion range (Comparative Examples 10 - 11), the fiber structure is disordered and a tight network cannot be formed. At the same time, the fibers of the electrospun product without carbohydrase treatment (Comparative Example 1) show irregular bending, and bead defects appear, while the tightness of fiber arrangement decreases.

[0088] Please refer to Table 4 in detail. The texture properties of the electrospun products treated with carbohydrase I, II, III (Examples 1 - 3) and the enzyme amount in the range of 1U - 1000U (Examples 10 - 11) are significantly better than those treated without carbohydrase (Comparative Example 1), single enzyme (Comparative Examples 2 - 5) and other combined enzymes (Comparative Examples 6 - 9), and are also better than WPI (Comparative Example 19) and dextran (Comparative Example 20) commonly used as raw materials on the market. Among them, the fiber membrane with a protein proportion of 60% (Example 5) has the highest hardness and chewiness, and shows the best elasticity, cohesiveness and adhesiveness. Mainly due to the removal of polysaccharides by carbohydrase, spirulina protein with higher purity is obtained. Its fiber membrane not only shows excellent strength and toughness in mechanical properties, but also has an advantage in taste, can provide a better use experience, and is suitable for a wider range of food packaging and functional food applications.

[0089] Table 4 Texture characteristics of electrospun products

[0090]

[0091]

[0092] Please refer to in detail Figure 3 The antibacterial activities of 11 examples and 10 comparative examples were compared. Under appropriate enzyme dosage conditions (Examples 10, 11), the fiber membranes showed significant inhibitory effects on Escherichia coli and Staphylococcus aureus. When the proportion of spirulina protein reached 60% (Example 5), the antibacterial performance of the fiber membrane was optimal. In the comparative experiment (such as Comparative Example 1), non-enzymatic hydrolysis would lead to weak antibacterial performance of the membrane, and the inhibition zone diameters for Escherichia coli and Staphylococcus aureus were only 5.5 mm and 6.7 mm, showing insufficient antibacterial property. In addition, the antibacterial performance of the raw material WPI (Comparative Example 19) was much lower than that of spirulina protein.

[0093] Please refer to in detail Figure 4The radical scavenging abilities of different comparative examples and example fiber membranes are shown. The experimental results indicate that with the change of enzyme dosage, the radical scavenging rate of the electrospun membrane shows a certain regular change. An appropriate amount of enzyme dosage (Examples 2 and 11) can promote the sufficient enzymatic hydrolysis of spirulina protein, releasing peptide segments with high antioxidant activity and showing a high radical scavenging rate (about 45%-55%). However, when no enzymatic hydrolysis treatment is used (Comparative Example 1), antioxidant peptide segments cannot be effectively released, resulting in a low radical scavenging rate (about 20%). At the same time, the inefficient enzymatic hydrolysis and uncoordinated enzyme ratios of other enzyme combinations (Comparative Examples 2-9) lead to low antioxidant and antibacterial properties. It can be seen that an appropriate enzyme dosage is crucial for improving the antioxidant and antibacterial properties of the fiber membrane. The present invention significantly improves the antioxidant performance of the spirulina protein membrane by precisely regulating the enzyme dosage, thus having important application value in the field of food packaging.

[0094] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A method for preparing an edible electrospun fiber membrane with good texture properties based on spirulina protein, characterized in that: The following steps are involved: S1. Sample preparation: Spirulina protein extract and pullulan are mixed and dissolved in distilled water in a certain proportion, and dissolved under a magnetic stirrer to form a mixed solution; S2. Electrospinning technology: Use a plastic syringe equipped with a needle to absorb the mixed solution. By adjusting the spinning parameters including voltage, solution flow rate and the distance from the nozzle to the receiver, the solution is stretched into fibers under the action of the electric field and forms a thin film structure on the receiver.

2. The preparation method according to claim 1, characterized in that: The mass ratio of spirulina protein extract to pullulan in the mixed solution is (20-40): (60-80).

3. The preparation method according to claim 1, characterized in that: The spinning parameters in the electrospinning technology are set as: voltage 5 ~ 50 kV.

4. The preparation method according to claim 1, characterized in that: The spinning parameters in the electrospinning technology are set as: solution flow rate 0.05~1 mL / h.

5. The preparation method according to claim 1, characterized in that: The preparation of the spirulina protein extract comprises the following steps: (1) Fresh spirulina powder and ethanol were mixed in a ratio of 1:40 g / mL and then subjected to ultrasonic treatment; (2) Mixing the ultrasonically treated Spirulina powder with distilled water and adjusting the mixture to alkaline, further disrupting the cells using an ultrasonic cell disruptor, and then adding a carbohydrate complex enzyme for enzymatic hydrolysis; (3) The retained components are collected by ultrafiltration technology to obtain purified Spirulina protein.

6. The preparation method according to claim 5, characterized in that: The carbohydrate complex enzyme is a complex of galactanase, hemicellulase and cellulase.

7. The preparation method according to claim 6, characterized in that: The mass ratio of galactanase, hemicellulase and cellulase is (40-60): (20-30): (20-30).

8. The preparation method according to claim 5, characterized in that: Calculated based on the mass of fresh spirulina powder, the dosage of carbohydrate complex enzyme is 1U / g to 1000U / g.

9. The preparation method according to claim 5, characterized in that: The fractions with a molecular weight cut-off greater than 50 kDa were collected by ultrafiltration.

10. The edible electrospun fiber membrane prepared by the preparation method according to any one of claims 1 to 9, characterized in that: It has antibacterial properties against Escherichia coli and Staphylococcus aureus, and the diameter of the inhibition zone is 10 mm.

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