High-strength, antibacterial soybean protein isolate film and preparation method and application thereof
Patent Information
- Application Number
- CN202410232591.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-01
- Publication Date
- 2026-08-28
- Estimated Expiration
- 2044-03-01
AI Technical Summary
[0005]本发明的主要目的在于解决现有大豆分离蛋白基膜在机械强度和抗菌性方面的不足，尤其是不能同时兼顾良好的韧性和强度的问题
[0030]1、提高机械性能：本发明采用双醛淀粉与大豆分离蛋白结合，通过特定的交联作用，显著提高了膜的机械强度。另外，低温等离子体辅助制备的双醛淀粉醛基含量更高，溶解度提高，醛基含量高可以导致与大豆分离蛋白更多的交联反应，溶解度提高可以与大豆分离蛋白更好的融合减少相分离，从而增强膜的机械性能和热稳定性。这有助于提高膜的强度和耐久性，使其更适用于要求高机械性能的应用，如包装领域。这使得薄膜在更广泛的环境条件下都能保持其性能，例如在潮湿或酸碱性环境中。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of protein membrane technology, and more specifically, to a high-strength, antibacterial soybean protein isolate membrane, its preparation method, and its application. Background Technology
[0002] Currently, packaging materials on the market are mainly made of plastics and other synthetic materials. While these materials offer advantages such as mechanical strength and low cost, they are generally not biodegradable, placing a heavy burden on the environment. Biomass materials (primarily proteins, polysaccharides, and lignin) offer an effective solution to address significant environmental problems due to their sustainability and abundance, and can also reduce over-reliance on petroleum resources.
[0003] Soy protein, due to its low cost, non-toxicity, and environmental friendliness, has been widely used in adhesives, films, and hydrogels. However, in practical applications, the inherent hydrophilicity and strong molecular interactions of natural soy protein isolate result in limited mechanical strength and toughness. Although modification with small-molecule plasticizers such as glycerol may have great potential to increase protein chain migration, insufficient strength remains a challenge, and its poor antibacterial properties limit its widespread application. With increasing environmental awareness and the growing demand for sustainable development, developing a new packaging material that is both environmentally friendly and possesses high strength and excellent antibacterial properties has become an urgent priority. This need is particularly pressing in the food packaging sector.
[0004] Although some biodegradable packaging materials, such as polylactic acid (PLA) and polyhydroxyalkanoates (PHA), exist on the market, they are either too expensive or lack certain properties (such as water stability or antimicrobial properties). Furthermore, the production of these materials often requires the use of hazardous chemicals, which to some extent reduces their environmental advantages. Summary of the Invention
[0005] The main objective of this invention is to address the shortcomings of existing soy protein isolate membranes in terms of mechanical strength and antibacterial properties, particularly the inability to simultaneously achieve good toughness and strength. This invention proposes a novel high-strength, antibacterial soy protein isolate membrane composite material. This material combines the high strength of dialdehyde starch (DAS), the natural antibacterial properties of tea polyphenols, and the biodegradability of soy protein. This unique combination not only improves the mechanical strength and antibacterial effect of the membrane material while maintaining good toughness and strength, but also preserves its environmental friendliness.
[0006] This novel membrane material, due to its excellent performance and environmentally friendly properties, is particularly suitable for use in food packaging, medical product packaging, and biopharmaceutical materials. Its use can effectively reduce plastic pollution and improve the safety and sustainability of packaging materials. The composite film of this invention has minimal environmental impact during production and use, fully complying with current global requirements for environmental protection and sustainable development. Simultaneously, its natural antibacterial properties provide additional protection for food safety.
[0007] The objective of this invention is achieved through the following technical solutions.
[0008] A high-strength, antibacterial soy protein isolate membrane is prepared by using soy protein isolate as a base material, combined with plasticizers, reinforcing agents and antibacterial agents; the reinforcing agent is dialdehyde starch, which is prepared by plasma pretreatment of starch followed by oxidation.
[0009] Preferably, in the pretreatment preparation of dialdehyde starch, the plasma pretreatment voltage is 100-150kV, the frequency is 50-70HZ, the power is 45-60kW, and the treatment time is 1-5min.
[0010] More preferably, in the pretreatment preparation of dialdehyde starch, the plasma pretreatment voltage is 100kV, the frequency is 50HZ, and the power is 45kW.
[0011] Preferably, the plasma pretreatment device is a DBD plasma.
[0012] Preferably, in the plasma pretreatment of starch to dialdehyde starch, the concentration of the sodium periodate solution used is 0.5 mol / L to 1.2 mol / L, the molar ratio of starch to sodium periodate is 1:0.5 to 1:1.2, the pH value is 3 to 5, the reaction temperature is 25℃ to 60℃, the reaction time is 1h to 6h, and the drying temperature is 50℃ to 70℃.
[0013] Preferably, the amount of dialdehyde starch added is 5% to 20% of the soybean protein isolate.
[0014] Preferably, the starch is potato starch, corn starch, tapioca starch, or sweet potato starch.
[0015] Preferably, the plasticizer is glycerol, and the amount of glycerol added is 20% to 50% of the soybean protein isolate.
[0016] Preferably, the antibacterial agent is tea polyphenol, and the amount of tea polyphenol added is 1% to 10% of the soybean protein isolate.
[0017] A method for preparing a high-strength, antibacterial soy protein isolate membrane as described in any of the above-mentioned methods includes the following steps:
[0018] Soy protein isolate, plasticizer, dialdehyde starch and water are mixed and the pH is adjusted to 8.5-11. Then the mixture is stirred in a water bath at 60℃-90℃ for 30-60 minutes to obtain a soy protein isolate solution. After cooling to room temperature, an antibacterial agent is added and the mixture is stirred at room temperature to obtain a film-forming solution. The film-forming solution is poured onto an plexiglass plate and dried in a drying oven to form a film. The film is then softened in a constant temperature and humidity sealed box and peeled off to obtain a high-strength, antibacterial soy protein isolate film.
[0019] Preferably, the soy protein isolate solution contains 1% to 10% by mass.
[0020] Preferably, the pH is adjusted to 8.5-11 by adding an alkaline solution with a concentration of 0.05 mol / L to 0.3 mol / L; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.
[0021] Preferably, the drying is carried out in an oven at a temperature of 20°C to 60°C for a time of 10 to 30 hours.
[0022] Preferably, the preparation method includes the following steps:
[0023] (1) Starch was pretreated by plasma, and then oxidized with sodium periodate to obtain dialdehyde starch:
[0024] Weigh 1g of starch and spread it evenly in a reaction vessel for low-temperature plasma treatment. Weigh an appropriate amount of pretreated starch and add it to a 0.5mol / L to 1.2mol / L sodium periodate solution to make the molar ratio of starch to sodium periodate 1:0.5 to 1:1.2. Then adjust the pH value to 3 to 5 with 0.05mol / L to 0.15mol / L dilute sulfuric acid. React in the dark at 25℃ to 60℃ for 1h to 6h. Filter and wash with deionized water until neutral. Place in an oven and dry at 50℃ to 70℃ to obtain plasma-pretreated dialdehyde starch, which is CP-DAS.
[0025] (2) A high-strength, antibacterial soybean protein isolate membrane was prepared by solution casting.
[0026] Soy protein isolate, plasticizer glycerin, and CP-DAS are mixed and the pH is adjusted to 8.5–11. The mixture is then placed in a water bath at 60–90°C and stirred vigorously for 30–60 minutes to obtain a soy protein isolate solution. After cooling to room temperature, tea polyphenols are dissolved in the soy protein isolate solution and stirred at room temperature to obtain a film-forming solution. The film-forming solution is poured onto an plexiglass plate and dried in a drying oven to form a film. The film is then softened in a constant temperature and humidity sealed chamber and peeled off to obtain a high-strength, antibacterial soy protein isolate film.
[0027] The above describes the application of soy protein isolate film in food packaging.
[0028] Conventional methods for preparing DAS (dialdehyde starch) typically involve stirring in an acidic aqueous solution. This results in long reaction times and low reaction efficiency. Furthermore, sodium periodate is expensive, approximately ten times the price of starch. Improving the utilization efficiency of sodium periodate in DAS preparation is key to reducing production costs. Introducing plasma pretreatment of starch before DAS preparation not only shortens the reaction time but also yields DAS with high aldehyde content and excellent solubility. This enhances the mechanical properties of soy protein isolate membranes, resulting in a membrane that simultaneously maintains both toughness and strength, and possesses excellent antibacterial properties.
[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0030] 1. Improved Mechanical Properties: This invention utilizes a combination of dialdehyde starch and soy protein isolate, significantly enhancing the mechanical strength of the membrane through specific cross-linking processes. Furthermore, the dialdehyde starch prepared with low-temperature plasma assistance has a higher aldehyde content and improved solubility. The higher aldehyde content leads to more cross-linking reactions with soy protein isolate, while increased solubility allows for better integration and reduced phase separation, thereby enhancing the membrane's mechanical properties and thermal stability. This contributes to improved membrane strength and durability, making it more suitable for applications requiring high mechanical performance, such as packaging. This also allows the film to maintain its performance under a wider range of environmental conditions, such as humid or acidic / alkaline environments.
[0031] 2. Enhanced Antibacterial Properties: This invention imparts excellent antibacterial properties to soy protein isolate membranes by introducing tea polyphenols. As a natural antibacterial agent, tea polyphenols can effectively inhibit the growth of various bacteria and microorganisms, making this invention promising for wide applications in food packaging, medical devices, and other fields.
[0032] 3. Environmentally Friendly: All raw materials used in the preparation process are biodegradable, meaning the film can decompose naturally after disposal, reducing the burden on the environment. Furthermore, compared to traditional plastic packaging materials, the bio-based source of this invention is more environmentally friendly, contributing to the development of green packaging materials.
[0033] 4. Versatility of Applications: Due to its unique physical and chemical properties, the soy protein isolate film of this invention can be used in multiple fields, such as food packaging, biomedical materials, and even as a biodegradable agricultural film. This versatility provides it with a wider range of applications in the market.
[0034] 5. Innovation in preparation method: By optimizing the ratio of dialdehyde starch to tea polyphenols and adjusting the reaction conditions, this invention can precisely control the performance of the membrane to meet the needs of different application scenarios.
[0035] 6. Cost-effectiveness: Considering the wide availability of raw materials and the simplicity of the preparation process, this invention is also economically feasible. Compared to other high-performance materials, it provides a more cost-effective solution, especially for large-scale production. Attached Figure Description
[0036] Figure 1 Antibacterial zone diagrams of soybean protein isolate-based films prepared for examples and comparative examples.
[0037] Figure 2 Thermogravimetric analysis (TGA) of the soybean protein isolate-based films prepared for the examples and comparative examples.
[0038] Figure 3 Flowchart for the preparation of high-strength, antibacterial soy protein isolate membrane. Detailed Implementation
[0039] The present invention will be further described below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.
[0040] Example 1
[0041] (1) Take 1g of corn starch and spread it evenly in the reactor. Treat it with low-temperature plasma (voltage 100KV, frequency controlled at 50HZ, power controlled at 45KW) for 1min. Repeat the treatment 5 times and collect the samples for later use.
[0042] (2) Weigh 4.86g of CP-pretreated starch, add 50mL of 0.6mol / L sodium periodate solution, and then adjust the pH to 3 with 0.1mol / L dilute sulfuric acid; react in the dark at 25℃ for 3h, filter and wash with deionized water until neutral, and dry in an oven at 50℃ to obtain plasma-pretreated dialdehyde starch, which is CP1-DAS.
[0043] (3) By mass percentage, a 5% soy protein isolate solution was prepared by adding distilled water, followed by the addition of glycerol at 50% of the soy protein isolate mass and CP1-DAS at 5% of the soy protein isolate mass. The pH was adjusted to 10 using 0.1M sodium hydroxide solution. The solution was then stirred vigorously in a 70℃ water bath for 30 minutes to obtain the soy protein isolate solution. After cooling to room temperature, tea polyphenols at 5% of the soy protein isolate mass were dissolved in the soy protein isolate aqueous solution. The solution was then stirred at room temperature to obtain a soy protein isolate film-forming solution. The film-forming solution was poured onto an plexiglass plate and dried in a drying oven at 50℃ to form a film. The film was then softened in a constant temperature and humidity sealed chamber, and the film was peeled off to obtain the composite membrane. The composite membrane was completely degraded after being buried in soil for 40 days.
[0044] Example 2
[0045] (1) Take 1g of corn starch and spread it evenly in the reactor. Treat it with low-temperature plasma (voltage 100KV, frequency controlled at 50HZ, power controlled at 45KW) for 2min. Repeat the treatment 5 times and collect the samples for later use.
[0046] (2) Weigh 4.86g of CP-pretreated starch, add 50mL of 0.6mol / L sodium periodate solution, and then adjust the pH to 3 with 0.1mol / L dilute sulfuric acid; react in the dark at 25℃ for 3h, filter and wash with deionized water until neutral, and dry in an oven at 50℃ to obtain plasma-pretreated dialdehyde starch, which is CP2-DAS.
[0047] (3) By mass percentage, a 5% soy protein isolate solution was prepared by adding distilled water, followed by the addition of glycerol at 50% of the soy protein isolate mass and CP2-DAS at 10% of the soy protein isolate mass. The pH was adjusted to 10 using 0.1M sodium hydroxide solution. The solution was then stirred vigorously in a 70℃ water bath for 30 minutes to obtain the soy protein isolate solution. After cooling to room temperature, tea polyphenols at 5% of the soy protein isolate mass were dissolved in the soy protein isolate aqueous solution. The solution was then stirred at room temperature to obtain a soy protein isolate film-forming solution. The film-forming solution was poured onto an plexiglass plate and dried in a drying oven at 50℃ to form a film. The film was then softened in a constant temperature and humidity sealed chamber and peeled off to obtain the composite membrane. The composite membrane was completely degraded after being buried in soil for 40 days.
[0048] Example 3
[0049] (1) Take 1g of corn starch and spread it evenly in the reactor. Treat it with low-temperature plasma (voltage 100KV, frequency controlled at 50HZ, power controlled at 45KW) for 3min. Repeat the treatment 5 times and collect the samples for later use.
[0050] (2) Weigh 4.86g of CP-pretreated starch, add 50mL of 0.6mol / L sodium periodate solution, and then adjust the pH value to 3 with 0.1mol / L dilute sulfuric acid; react in the dark at 25℃ for 3h, filter and wash with deionized water until neutral, and dry in an oven at 50℃ to obtain plasma-pretreated dialdehyde starch, which is CP3-DAS.
[0051] (3) By mass percentage, a 5% soy protein isolate solution was prepared by adding distilled water, followed by the addition of glycerol at 50% of the soy protein isolate mass and CP3-DAS at 15% of the soy protein isolate mass. The pH was adjusted to 10 using 0.1M sodium hydroxide solution. The solution was then stirred vigorously in a 70℃ water bath for 30 minutes to obtain the soy protein isolate solution. After cooling to room temperature, tea polyphenols at 10% of the soy protein isolate mass were dissolved in the soy protein isolate aqueous solution. The solution was then stirred at room temperature to obtain a soy protein isolate film-forming solution. The film-forming solution was poured onto an plexiglass plate and dried in a drying oven at 50℃ to form a film. After softening in a constant temperature and humidity sealed chamber, the film was peeled off to obtain the composite membrane. The composite membrane was completely degraded after being buried in soil for 40 days.
[0052] Example 4
[0053] (1) Take 1g of corn starch and spread it evenly in the reactor. Treat it with low-temperature plasma (voltage 100KV, frequency controlled at 50HZ, power controlled at 45KW) for 4min. Repeat the treatment 5 times and collect the samples for later use.
[0054] (2) Weigh 4.86g of CP-pretreated starch, add 50mL of 0.6mol / L sodium periodate solution, and then adjust the pH to 3 with 0.1mol / L dilute sulfuric acid; react in the dark at 25℃ for 3h, filter and wash with deionized water until neutral, and dry in an oven at 50℃ to obtain plasma-pretreated dialdehyde starch, which is CP4-DAS.
[0055] (3) By mass percentage, a 5% soy protein isolate solution was prepared by adding distilled water, followed by the addition of glycerol at 50% of the soy protein isolate mass and CP4-DAS at 15% of the soy protein isolate mass. The pH was adjusted to 10 using 0.1M sodium hydroxide solution. The solution was then stirred vigorously in a 70℃ water bath for 30 minutes to obtain the soy protein isolate solution. After cooling to room temperature, tea polyphenols at 10% of the soy protein isolate mass were dissolved in the soy protein isolate aqueous solution. The solution was then stirred at room temperature to obtain a soy protein isolate film-forming solution. The film-forming solution was poured onto an plexiglass plate and dried in a drying oven at 50℃ to form a film. The film was then softened in a constant temperature and humidity sealed chamber and peeled off to obtain the composite membrane. The composite membrane was completely degraded after being buried in soil for 40 days.
[0056] Example 5
[0057] (1) Take 1g of corn starch and spread it evenly in the reactor. Treat it with low-temperature plasma (voltage 100KV, frequency controlled at 50HZ, power controlled at 45KW) for 5min. Repeat the treatment 5 times and collect the samples for later use.
[0058] (2) Weigh 4.86g of CP-pretreated starch, add 50mL of 0.6mol / L sodium periodate solution, and then adjust the pH to 3 with 0.1mol / L dilute sulfuric acid; react in the dark at 25℃ for 3h, filter and wash with deionized water until neutral, and dry in an oven at 50℃ to obtain plasma-pretreated dialdehyde starch, which is CP5-DAS.
[0059] (3) By mass percentage, a 5% soy protein isolate solution was prepared by adding distilled water, followed by the addition of glycerol at 50% of the soy protein isolate mass and CP5-DAS at 20% of the soy protein isolate mass. The pH was adjusted to 10 using 0.1M sodium hydroxide solution. The solution was then vigorously stirred in a 70℃ water bath for 30 minutes to obtain the soy protein isolate solution. After cooling to room temperature, tea polyphenols at 10% of the soy protein isolate mass were dissolved in the soy protein isolate aqueous solution. The solution was then stirred at room temperature to obtain a soy protein isolate film-forming solution. The film-forming solution was poured onto an plexiglass plate and dried in a drying oven at 50℃ to form a film. After softening in a constant temperature and humidity sealed chamber, the film was peeled off to obtain the composite membrane. The composite membrane was completely degraded after being buried in soil for 40 days.
[0060] Comparative Example 1
[0061] By mass percentage, a 5% soy protein isolate solution was prepared by adding distilled water, followed by the addition of glycerol at 50% of the soy protein isolate mass. The pH was adjusted to 10 using 0.1M sodium hydroxide solution. The solution was then stirred in a 70°C water bath for 30 minutes to obtain the soy protein isolate solution. After cooling to room temperature, a soy protein isolate film-forming solution was obtained. The film-forming solution was poured onto an plexiglass plate and dried in a drying oven at 50°C to form a film. The film was then softened in a constant temperature and humidity sealed chamber and peeled off.
[0062] Comparative Example 2
[0063] (1) Weigh 4.86g of starch, add 50mL of sodium periodate solution with a concentration of 0.6mol / L, and then adjust the pH value to 3 with 0.1mol / L dilute sulfuric acid; react in the dark at 25℃ for 3h, filter and wash with deionized water until neutral, and dry in an oven at 50℃ to obtain dialdehyde starch.
[0064] (2) By mass percentage, prepare a 5% soy protein isolate solution by adding distilled water, then add glycerol at 50% of the soy protein isolate mass and dialdehyde starch at 10% of the soy protein isolate mass, and adjust the pH to 10 using 0.1M sodium hydroxide solution. Then place it in a 70℃ water bath and stir vigorously for 30 minutes to obtain a soy protein isolate solution. After cooling to room temperature, pour the film-forming solution onto an plexiglass plate, dry it in a drying oven at 50℃ to form a film, soften it in a constant temperature and humidity sealed box, and then peel off the film.
[0065] Comparative Example 3
[0066] A 5% soy protein isolate solution was prepared by adding distilled water, followed by the addition of glycerol at 50% of the soy protein isolate mass. The pH was adjusted to 10 using 0.1M sodium hydroxide solution. The solution was then stirred in a 70°C water bath for 30 minutes to obtain the soy protein isolate solution. After cooling to room temperature, 5% of tea polyphenols at the soy protein isolate mass were dissolved in the soy protein isolate aqueous solution. The solution was then stirred at room temperature to obtain a soy protein isolate film-forming solution. The film-forming solution was poured onto an plexiglass plate and dried in a drying oven at 50°C to form a film. The film was then softened in a constant temperature and humidity sealed chamber and peeled off.
[0067] The mechanical properties of the soybean protein isolate-based films prepared in the above embodiments and comparative examples were measured, and the test results are shown in Table 1.
[0068] Mechanical property testing method: The film was cut into 70mm × 10mm sample strips and subjected to tensile testing using a universal testing machine equipped with a 10kg load cell. The tensile speed was set to 5mm / s, and the test was performed in parallel for 8 times. The tensile strength and elongation at break of different samples were measured and averaged.
[0069] Antibacterial performance testing: *Escherichia coli* and *Staphylococcus aureus* were tested using standard beef extract peptone agar medium. The bacterial plate method was employed, with bacterial suspensions of *Escherichia coli* and *Staphylococcus aureus* prepared at a concentration of 10-1. 7 CFU / mL, the bacterial suspension was spread onto the surface of a plate using the plate coating method; filter paper was made into 6mm circular pieces using a punch, the circular pieces were soaked in the mixed adhesive solution, lifted with sterile tweezers to drain, and no water droplets fell off, and then attached to the bacterial plate. Escherichia coli and Staphylococcus aureus were incubated at 30℃ for 24h, and the diameter of the inhibition zone was measured (mm). Each sample was repeated 3 times.
[0070] Thermal analysis was performed on a TG / DTAQ500 thermogravimetric analyzer. The sample weight was 7-8 mg, nitrogen was used as the carrier gas at a flow rate of 50 mL / min, the ambient temperature of the experimental sample ranged from 30℃ to 500℃, the temperature rise rate was 10℃ / min, and the thermogravimetric (TG) curve was recorded.
[0071] Table 1
[0072]
[0073] Table 1 clearly shows that the addition of plasma-pretreated dialdehyde starch significantly improves the mechanical properties of the film. In the preparation of soy protein isolate membranes, the added dialdehyde starch undergoes a cross-linking reaction with amino acid residues (such as lysine) in soy protein. This cross-linking reaction mainly involves the reaction of aldehyde and amino groups to form Schiff base structures, thereby creating stable chemical bonds between soy protein molecules. Through cross-linking, the interconnections between soy protein molecules increase, resulting in a more compact and stable membrane structure. This increased intermolecular interaction improves the mechanical strength of the membrane, including tensile strength and tear resistance. This makes the membrane more durable in practical applications and able to withstand greater physical stress. Plasma pretreatment improves the solubility of dialdehyde starch, which is beneficial for its integration with soy protein, reduces phase separation, and forms a film with excellent mechanical properties.
[0074] Depend on Figure 1 The inhibition zone analysis shows that the addition of tea polyphenols enhances the antibacterial properties of soy protein isolate membranes against *Escherichia coli* and *Staphylococcus aureus*. Tea polyphenols can disrupt the bacterial cell wall and cell membrane structure, leading to leakage of cell contents, thereby inhibiting or killing bacteria. Tea polyphenols can also interfere with bacterial metabolic pathways, including inhibiting enzyme activity and blocking DNA replication, further inhibiting bacterial growth. *Escherichia coli* is a Gram-negative bacterium with a thin peptidoglycan layer and an outer membrane. Tea polyphenols can penetrate its outer membrane, disrupting the bacterial cell structure and effectively inhibiting or killing *E. coli*. *Staphylococcus aureus*, a Gram-positive bacterium, has a thick peptidoglycan wall but no outer membrane. Tea polyphenols can penetrate the peptidoglycan layer, disrupting the cell wall and membrane, effectively combating *Staphylococcus aureus*. During the preparation of soy protein isolate membranes, tea polyphenols can be evenly distributed within the membrane and form a stable binding with soy protein. This even distribution and binding facilitates the sustained antibacterial effect of tea polyphenols on the membrane surface and inside. Since Escherichia coli and Staphylococcus aureus are common pathogens in the food industry and medical and health care, this soy protein isolate film with targeted antibacterial properties has important application value in the food packaging field.
[0075] Depend on Figure 2Thermogravimetric analysis (TGA) shows that adding dialdehyde starch during the preparation of soy protein isolate membranes improves their thermal stability. The aldehyde groups can chemically react with amino acid residues (such as lysine) in soy protein to form Schiff base structures. This cross-linking reaction creates stable chemical bonds between protein molecules, increasing the intermolecular cross-linking density of the membrane material. Increased cross-linking density means stronger intermolecular bonding, making the membrane less prone to morphological changes or decomposition when heated. The cross-linked structure reduces the influence of thermal motion on intermolecular interactions, improving the material's thermal stability. At high temperatures, the cross-linked structure prevents molecular chain slippage and disassembly, thus maintaining the membrane's integrity and function. The addition of dialdehyde starch also alters the microstructure of the soy protein isolate membrane, making it more compact and uniform. This structural stabilization further enhances the membrane's heat resistance.
[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A high-strength, antibacterial soy protein isolate membrane, characterized in that, It is prepared using soy protein isolate as a base material, combined with plasticizers, reinforcing agents and antibacterial agents; the reinforcing agent is dialdehyde starch, which is prepared by plasma pretreatment of starch followed by oxidation; In the pretreatment preparation of dialdehyde starch, the plasma pretreatment voltage is 100-150kV, the frequency is 50-70HZ, the power is 45-60kW, and the treatment time is 1-5min.
2. The high-strength, antibacterial soy protein isolate membrane according to claim 1, characterized in that, In the plasma pretreatment of starch to oxidize dialdehyde starch, the concentration of sodium periodate solution used is 0.5 mol / L to 1.2 mol / L, the molar ratio of starch to sodium periodate is 1:0.5 to 1:1.2, the pH value is 3 to 5, the reaction temperature is 25℃ to 60℃, the reaction time is 1h to 6h, and the drying temperature is 50℃ to 70℃.
3. The high-strength, antibacterial soy protein isolate membrane according to claim 1, characterized in that, The amount of dialdehyde starch added is 5% to 20% of the soybean protein isolate.
4. The high-strength, antibacterial soy protein isolate membrane according to claim 1, characterized in that, The starch is potato starch, corn starch, cassava starch, or sweet potato starch.
5. The high-strength, antibacterial soy protein isolate membrane according to claim 1, characterized in that, The plasticizer is glycerol, and the amount of glycerol added is 20% to 50% of the soybean protein isolate.
6. The high-strength, antibacterial soy protein isolate membrane according to claim 1, characterized in that, The antibacterial agent is tea polyphenol, and the amount of tea polyphenol added is 1% to 10% of the soybean protein isolate.
7. The high-strength, antibacterial soy protein isolate membrane according to any one of claims 1-6, characterized in that, The preparation method of this high-strength, antibacterial soy protein isolate membrane includes the following steps: Soy protein isolate, plasticizer, dialdehyde starch and water are mixed and the pH is adjusted to 8.5-11. Then the mixture is stirred in a water bath at 60℃-90℃ for 30-60 minutes to obtain a soy protein isolate solution. After cooling to room temperature, an antibacterial agent is added and the mixture is stirred at room temperature to obtain a film-forming solution. The film-forming solution is poured onto an plexiglass plate and dried in a drying oven to form a film. The film is then softened in a constant temperature and humidity sealed box and peeled off to obtain a high-strength, antibacterial soy protein isolate film.
8. The high-strength, antibacterial soy protein isolate membrane according to claim 7, characterized in that, The soy protein isolate solution contains 1% to 10% by mass.
9. The application of a high-strength, antibacterial soy protein isolate film according to any one of claims 1-8 in food packaging.