A calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging and its preparation method
Patent Information
- Application Number
- CN202611413184.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-11
- Publication Date
- 2026-10-20
AI Technical Summary
针对单一淀粉膜功能单一，物理化学稳定性不足及力学性能较差等问题，本发明以玉米淀粉、果胶为核心成膜物质，以功能型纳米粒子即海藻酸钠纳米粒子为抗菌与性能增强添加剂，并引入钙离子Ca2+作为交联剂通过配位作用强化膜结构，最终采用溶液共混、流延成膜的方法制备出保鲜包装用钙交联淀粉-果胶-海藻酸钠复合薄膜
[0013]本发明具有以下有益效果：本发明提供了一种保鲜包装用钙交联淀粉-果胶-海藻酸钠复合薄膜制备方法，原料便宜易得，工艺简单环保，淀粉源自天然淀粉，具有资源丰富、价格低廉、可再生且储量不可枯竭的特点，同时兼具生物可降解性，对环境污染小；果胶则具备无毒性、生物可降解性、优异的生物相容性及一定抗菌性，且成膜性能良好；二者复合成膜时，既能保留优异的生物降解性能；又通过与海藻酸钠相连的钙离子与淀粉中的羟基、果胶中的羧基形成稳定的配位键，使其形成更紧密的交联网络，成膜性显著优化；此外，添加的具有良好生物相容性与抗菌活性的海藻酸钠纳米粒子，不仅能进一步增强淀粉与果胶复合膜的力学性能（如拉伸强度、耐折性），还能大幅提升其抗菌效果，尤其使抗菌保鲜性能得到显著强化；在流延成膜过程中，钙离子成功交联淀粉、果胶、海藻酸钠三种组分，羧基与钙的配位作用以及多糖间氢键共同构筑复合薄膜的交联网络结构，这种特殊的化学交联结构，正是该保鲜包装用钙交联淀粉-果胶-海藻酸钠复合薄膜能够同时获得优异力学性能与抗菌保鲜性能的关键。本发明还提供了一种保鲜包装用钙交联淀粉-果胶-海藻酸钠复合薄膜，该复合膜充分融合了淀粉的可再生性与果胶的成膜优势，具有良好的生物降解性能，复合薄膜中的淀粉、果胶、钙离子与海藻酸钠纳米粒子协同作用，可有效提升膜的力学强度、抗菌活性与保鲜效果，能够为具有抗菌功能的可降解生物质包装膜的技术发展与产业化应用提供有力推动。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of green preservation packaging materials, specifically referring to a calcium ion crosslinked starch-pectin-sodium alginate composite film for preservation packaging and its preparation method. Background Technology
[0002] One of the major causes of food spoilage is the growth and reproduction of microorganisms (such as bacteria and molds). Therefore, packaging films with antibacterial and preservative functions have gradually become an industry hotspot and market mainstream in recent years. Some innovative products in this category can even effectively inhibit the growth and reproduction of microorganisms by slowly releasing antibacterial active ingredients, thus slowing down the rate of food spoilage and significantly extending the shelf life of food. Furthermore, in the food industry, new packaging materials that combine multiple functions such as extending storage periods, real-time detection of additive residues, and dynamic sensing of food freshness (such as the degree of spoilage and quality changes) are demonstrating extremely broad application prospects and development potential due to their crucial role in ensuring food quality and safety control.
[0003] In today's society, with the continuous improvement of environmental awareness and the pursuit of sustainable development, the development of green and degradable packaging materials has become an important research direction in the field of materials science. Traditional petroleum-based plastic packaging materials, for example, due to their difficult-to-degrade characteristics, accumulate in large quantities in the natural environment, causing serious pollution to the ecological environment, such as forming white pollution and threatening the survival of wild animals and plants. Therefore, it is urgent to find a new type of packaging material that can replace traditional plastics, and bio-based degradable materials have emerged. Recently, people have become increasingly interested in the development of biodegradable films, using natural renewable polymers as core raw materials, such as gelatin, chitosan, cellulose, pullulan, etc. (Wang Yang, Yu Yang, Jia Ze, et al. Preparation of gelatin / polyvinyl alcohol-chitosan double-layer antibacterial film and its application in the preservation of fresh pork [J]. Meat Research, 2025, 39(08): 50-56.). Because it addresses the pain points of traditional petroleum-based plastic films being "non-degradable and causing white pollution," while also taking into account "green raw materials, safe contact, and functional compatibility," it has become a core alternative material in fields such as food packaging, agricultural mulch film, and medical dressings. Currently, biodegradable plastics can be divided into: (1) natural polymer-based biodegradable plastics, such as pectin, starch, cellulose, gelatin, etc.; (2) synthetic polymer-based biodegradable plastics, such as polylactic acid (PLA), polyhydroxyalkanoates (PHA), polybutylene adipate-co-terephthalate (PBAT), polybutylene succinate (PBS), PLA / PBAT blends, starch / PBS composite plastics, etc.; (3) microbial synthetic-based biodegradable plastics, which are synthesized by microbial bacteria and fungi under specific conditions through fermentation. Currently, biodegradable plastics based on natural polymers are gradually attracting attention and have a broad market potential (Li Feng. Preparation and performance study of lignin / thermoplastic starch functional composite film [D]. Guangxi University, 2025).
[0004] Starch, as a common natural polymer material, boasts advantages such as wide availability, low cost, biodegradability, and non-toxicity, demonstrating enormous application potential in various fields such as food and medicine. Starch possesses certain film-forming properties, good transparency, extensibility, and oxygen barrier properties; however, starch films exhibit low flexibility and strength, limited functionality, and insufficient physicochemical stability. Modifying starch or compounding it with other biodegradable polymers can significantly improve the film-forming properties and mechanical strength of starch films, such as addressing the brittleness and poor wet strength of pure starch films, enhancing tensile and tear resistance, and further endowing starch-based composite film materials with more diverse functions. Pectin, as a natural polysaccharide, possesses biodegradability and excellent biocompatibility, along with good antiseptic and antibacterial properties and film-forming performance, demonstrating significant application value in biomedical materials and biodegradable packaging materials. By compounding starch and pectin, starch composite film materials with excellent mechanical properties, such as stable tensile strength, good folding resistance and water resistance, and antibacterial and preservative functions can be prepared. These materials not only align with the sustainable development trend of "degradable and environmentally friendly", but also meet the dual requirements of "practicality + functionality" for materials in scenarios such as food packaging and fresh food preservation. Therefore, they show extremely broad development prospects and industrialization potential in the field of green packaging materials.
[0005] This invention uses corn starch and pectin as a matrix, adding sodium alginate nanoparticles linked to calcium ions. The calcium ions successfully crosslink the three components: starch, pectin, and sodium alginate. The coordination of carboxyl groups with calcium and the hydrogen bonds between polysaccharides jointly construct the crosslinked network structure of the composite film, thereby optimizing the overall performance of the composite film, including its biodegradability, mechanical properties, and structural stability. Simultaneously, the added functional sodium alginate nanoparticles also endow the composite film with excellent antibacterial properties. The resulting calcium-crosslinked starch-pectin-sodium alginate composite film for food preservation packaging, prepared using a simple process, will provide a stronger impetus for the development of biodegradable plastics in the field of antibacterial food preservation packaging films. Summary of the Invention
[0006] To overcome the shortcomings of the prior art, the present invention aims to provide a calcium-crosslinked starch-pectin-sodium alginate composite film for food preservation packaging and its preparation method. Addressing the problems of single starch films having limited function, insufficient physicochemical stability, and poor mechanical properties, the present invention uses corn starch and pectin as the core film-forming substances, and functional nanoparticles, namely sodium alginate nanoparticles, as antibacterial and performance-enhancing additives, and introduces calcium ions (Ca). 2+As a crosslinking agent, calcium-crosslinked starch-pectin-sodium alginate composite film for food preservation packaging was prepared by solution blending and casting to strengthen the film structure through coordination. The prepared composite film effectively improves the brittleness of pure starch film, possessing not only high tensile strength but also excellent antibacterial and food preservation properties, while also exhibiting green and biodegradable characteristics, showing promising application prospects in the field of biodegradable antibacterial food preservation packaging.
[0007] The technical solution of the present invention is implemented according to the following steps: A calcium-crosslinked starch-pectin-sodium alginate composite film for food preservation packaging is provided. It uses starch and pectin as the framework, with sodium alginate nanoparticles uniformly dispersed in the system. Calcium ions successfully crosslink the three components of starch, pectin and sodium alginate. The coordination of carboxyl groups with calcium and the hydrogen bonds between polysaccharides jointly construct the crosslinked network structure of the composite film.
[0008] The preparation method of the calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging includes the following steps: (1) Preparation of sodium alginate nanoparticles: Sodium alginate nanoparticles are abbreviated as CANPs, and their preparation process is as follows: Figure 1 As shown, sodium alginate was dissolved in distilled water, cinnamon essential oil was added, and calcium chloride aqueous solution was slowly added dropwise. The mixture was continuously magnetically stirred at room temperature and then ultrasonically stirred to prepare a sodium alginate nanoparticle solution loaded with cinnamon essential oil. (2) Preparation of calcium cross-linked starch-pectin-sodium alginate composite film: The preparation process of calcium cross-linked starch-pectin-sodium alginate composite film is as follows: Figure 2 As shown, corn starch was taken, distilled water was added, and the mixture was gelatinized at high temperature. After naturally cooling to room temperature, pectin was added, and the mixture was magnetically stirred. Glycerin and sodium alginate nanoparticle solution from step (1) were added at room temperature, and the mixture was magnetically stirred. Then, the mixture was poured into a preheated mold and dried to form a film, thus obtaining a calcium cross-linked starch-pectin-sodium alginate composite film. Its infrared spectrum is shown below. Figure 3 As shown, the carbonyl peak is located at 1698 cm⁻¹ in pectin. -1 Significant blue shift to 1750 cm -1 This indicates that calcium ions undergo ionic cross-linking with the carboxyl groups of pectin and sodium alginate, forming carboxylate coordination bonds; 2926 cm -1 Methylene and 1000 cm -1 The retention of the characteristic peak of the alcohol hydroxyl group indicates that the main polysaccharide chemical structure of starch and pectin is preserved. The change in peak position and shape across the entire spectrum indicates that, in addition to calcium ion crosslinking, numerous intermolecular hydrogen bonds formed between starch, pectin, and sodium alginate molecules, proving that the three components successfully crosslinked, and the composite film was formed through chemical interactions. Therefore, calcium ions successfully crosslinked the three components of starch, pectin, and sodium alginate, and the coordination of carboxyl groups with calcium, along with the hydrogen bonds between polysaccharides, jointly constructed the crosslinked network structure of the composite film.
[0009] (3) Cut the composite film from step (2) into pieces for use in food preservation packaging.
[0010] In step (1), the sodium alginate used has a molecular weight of 100,000 to 250,000; the concentration of the calcium chloride aqueous solution is 0.1 mol / L; magnetic stirring is performed at 400 rpm for 1 hour; ultrasonic stirring is performed 3 times for 5 minutes each time; wherein 0.075 to 0.090 parts of sodium alginate are dissolved in 75 to 90 parts of distilled water, the mass ratio of sodium alginate to cinnamon essential oil is 1:186.7 to 1:88.9, and the molar ratio of sodium alginate to calcium chloride is 1:285 to 1:178.
[0011] The corn starch used in step (2) has a purity of 99.0% and a molecular weight of 200,000 to 400,000; the pectin added is commercially available and has a galacturonic acid content of ≥80.0%; the gelatinization temperature is 90 ℃ and the gelatinization time is 30 minutes; the magnetic stirring speed is 400 rpm and the stirring is continuous for 20 minutes; the mold preheating and drying film forming temperature are both 50 to 60 ℃; the amount of corn starch is 0.9 to 1.2 parts, the amount of distilled water is 23 to 30 parts, the amount of pectin is 0.09 to 0.12 parts, the amount of glycerol is 0.35 to 0.50 parts, and the amount of sodium alginate nanoparticle solution is 0.45 to 0.60 parts.
[0012] The calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging also includes a traction collection step, a cutting step of cutting to the required size, and a step of testing mechanical properties using a servo electronic tensile testing machine.
[0013] This invention offers the following advantages: It provides a method for preparing a calcium-crosslinked starch-pectin-sodium alginate composite film for food preservation packaging. The raw materials are inexpensive and readily available, and the process is simple and environmentally friendly. Starch, derived from natural starch, is abundant, inexpensive, renewable, and its reserves are inexhaustible. It also possesses biodegradability and minimal environmental pollution. Pectin, on the other hand, is non-toxic, biodegradable, has excellent biocompatibility, and certain antibacterial properties, and exhibits good film-forming performance. When the two are combined to form a film, excellent biodegradability is retained. Furthermore, the calcium ions linked to sodium alginate form stable coordination bonds with the hydroxyl groups in starch and the carboxyl groups in pectin, resulting in a tighter crosslinked network. The film-forming properties are significantly optimized. In addition, the added sodium alginate nanoparticles, which have good biocompatibility and antibacterial activity, not only further enhance the mechanical properties (such as tensile strength and folding resistance) of the starch and pectin composite film, but also significantly improve its antibacterial effect, especially enhancing its antibacterial and freshness-preserving properties. During the casting process, calcium ions successfully crosslink the three components of starch, pectin, and sodium alginate. The coordination of carboxyl groups with calcium and the hydrogen bonds between polysaccharides jointly construct the crosslinked network structure of the composite film. This special chemical crosslinked structure is the key to the excellent mechanical properties and antibacterial and freshness-preserving properties of the calcium crosslinked starch-pectin-sodium alginate composite film for freshness packaging. This invention also provides a calcium-crosslinked starch-pectin-sodium alginate composite film for food preservation packaging. This composite film fully integrates the renewability of starch and the film-forming advantages of pectin, and has good biodegradability. The starch, pectin, calcium ions and sodium alginate nanoparticles in the composite film work synergistically to effectively improve the mechanical strength, antibacterial activity and preservation effect of the film, which can provide a strong impetus for the technological development and industrial application of biodegradable biomass packaging films with antibacterial function. Attached Figure Description
[0014] To more clearly illustrate the embodiments or technical solutions of the present invention, the accompanying drawings used in the description of the embodiments or technical solutions will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0015] Figure 1 This is a schematic diagram of the preparation process of sodium alginate nanoparticles according to the present invention.
[0016] Figure 2 This is a schematic diagram of the preparation process of the calcium cross-linked starch-pectin-sodium alginate composite film of the present invention.
[0017] Figure 3 This is the infrared spectrum of the calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging of the present invention. Detailed Implementation
[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1
[0019] Take 1 part corn starch, add 25 parts distilled water, gelatinize at 90℃ for 30 minutes, cool, add 0.4 parts glycerin, pour into a mold preheated at 55℃, and dry at 55℃ to form a film, thus obtaining a starch film.
[0020] The mechanical properties were tested using a servo electronic tensile testing machine. The starch film was cut into 1 cm × 5 cm rectangular blocks with an initial clamping distance of 25 mm, a tensile speed of 1 mm / s, and a return speed of 10 mm / s. Each sample was tested in parallel five times. The tensile strength TS was calculated as follows: TS = F / D × d, where F is the maximum tensile force at break of the sample (unit: N), D is the width of the sample (unit: mm), and d is the thickness of the film (unit: mm). As shown in Table 1, the maximum tensile strength was found to be 10.2 MPa.
[0021] Referring to standard QB / T 2591-2003 "Antibacterial Plastics - Test Methods and Antibacterial Effects" and the 2002 "Disinfection Technical Specifications" issued by the Ministry of Health of the People's Republic of China, the prepared film was incubated with a certain amount of bacterial suspension for 72 hours, followed by colony counting. The results of the antibacterial performance test against *Escherichia coli* are shown in Table 2, with an inhibition zone diameter of 1 mm; the results of the antiseptic performance test against *Staphylococcus aureus* are shown in Table 3, with an inhibition zone diameter of 1 mm.
[0022] Fresh strawberries of uniform size were selected and grouped. The strawberries were placed in plastic trays and sealed with the prepared film. The decay index of the strawberries was tested after 72 hours of storage at room temperature. The results are shown in Table 4. The decay index was 4.
[0023] The above test data shows that the mechanical properties of conventionally prepared starch films are not high, and their antibacterial and preservative effects are also very limited. Example 2
[0024] A method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging includes the following steps: (1) Preparation of sodium alginate nanoparticles: Sodium alginate was dissolved in distilled water, cinnamon essential oil was added, calcium chloride aqueous solution was slowly added dropwise, and the mixture was continuously magnetically stirred at room temperature and then stirred with ultrasound to prepare a sodium alginate nanoparticle solution loaded with cinnamon essential oil. (2) Preparation of calcium cross-linked starch-pectin-sodium alginate composite film: Take corn starch, add distilled water, gelatinize at high temperature, cool naturally to room temperature, add pectin, stir magnetically, add glycerol and sodium alginate nanoparticle solution in step (1) at room temperature, stir magnetically, and then pour into a preheated mold to dry into a film to obtain calcium cross-linked starch-pectin-sodium alginate composite film; (3) Cut the composite film from step (2) into pieces for use in food preservation packaging.
[0025] In step (1), the sodium alginate used has a molecular weight of 100,000 to 250,000; the concentration of the calcium chloride aqueous solution is 0.1 mol / L; magnetic stirring is performed at 400 rpm for 1 hour; ultrasonic stirring is performed 3 times for 5 minutes each time; wherein 0.075 parts of sodium alginate are dissolved in 75 parts of distilled water, the mass ratio of sodium alginate to cinnamon essential oil is 1:106, and the molar ratio of sodium alginate to calcium chloride is 1:178.
[0026] The corn starch used in step (2) has a purity of 99.0% and a molecular weight of 200,000~400,000; the pectin added is commercially available and has a galacturonic acid content of ≥80.0%; the gelatinization temperature is 90 ℃ and the gelatinization time is 30 minutes; the magnetic stirring speed is 400 rpm and the stirring is continuous for 20 minutes; the mold preheating and drying film forming temperature are both 55 ℃; the amount of corn starch is 0.9 parts, the amount of distilled water is 23 parts, the amount of pectin is 0.09 parts, the amount of glycerol is 0.35 parts, and the amount of sodium alginate nanoparticle solution is 0.45 parts.
[0027] The calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging also includes a traction collection step, a cutting step of cutting to the required size, and a step of testing mechanical properties using a servo electronic tensile testing machine.
[0028] The mechanical properties were tested using a servo electronic tensile testing machine. A calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging was cut into 1 cm × 5 cm rectangular blocks. The initial distance between the clamps was 25 mm, the tensile speed was 1 mm / s, and the return speed was 10 mm / s. Each sample was tested five times in parallel. The tensile strength was calculated using the following formula: TS = F / D × d, where F is the maximum tensile force at break (unit: N), D is the width of the sample (unit: mm), and d is the thickness of the film (unit: mm). As shown in Table 1, the maximum tensile strength was found to be 40.5 MPa.
[0029] Referring to standard QB / T 2591-2003 "Antibacterial Plastics - Test Methods and Antibacterial Effects" and the 2002 "Disinfection Technical Specifications" issued by the Ministry of Health of the People's Republic of China, the prepared calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging was reacted with a certain amount of bacterial suspension for 72 hours, then cultured, and colony counted. The results of the antibacterial performance test against *Escherichia coli* are shown in Table 2, with an inhibition zone diameter of 10.3 mm; the results of the antiseptic performance test against *Staphylococcus aureus* are shown in Table 3, with an inhibition zone diameter of 10.4 mm.
[0030] Fresh strawberries of uniform size were selected and grouped. The strawberries were placed on plastic trays and sealed with a prepared calcium cross-linked starch-pectin-sodium alginate composite film. The decay index of the strawberries was tested after 72 hours of storage at room temperature. The decay index was calculated as (∑ grade number × number of strawberries in that grade) / total number of strawberries tested. Strawberries were graded according to their decay index: Grade 0: Fresh strawberries with no decay or damage; Grade 1: Fruits with rotten spots covering less than 1 / 4 of the strawberry area; Grade 2: Fruits with rotten spots covering more than 1 / 4 but less than 1 / 2 of the strawberry area; Grade 3: Fruits with rotten spots covering more than 1 / 2 but less than 3 / 4 of the strawberry area; Grade 4: Fruits with rotten spots covering more than 3 / 4 of the strawberry area. The test results are shown in Table 4. The decay index was grade 2.
[0031] The above test data demonstrate that the prepared calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging has excellent mechanical properties and antibacterial and preservation effects. Example 3
[0032] A method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging includes the following steps: (1) Preparation of sodium alginate nanoparticles: Sodium alginate was dissolved in distilled water, cinnamon essential oil was added, calcium chloride aqueous solution was slowly added dropwise, and the mixture was continuously magnetically stirred at room temperature and then stirred with ultrasound to prepare a sodium alginate nanoparticle solution loaded with cinnamon essential oil. (2) Preparation of calcium cross-linked starch-pectin-sodium alginate composite film: Take corn starch, add distilled water, gelatinize at high temperature, cool naturally to room temperature, add pectin, stir magnetically, add glycerol and sodium alginate nanoparticle solution in step (1) at room temperature, stir magnetically, and then pour into a preheated mold to dry into a film to obtain calcium cross-linked starch-pectin-sodium alginate composite film; (3) Cut the composite film from step (2) into pieces for use in food preservation packaging.
[0033] In step (1), the sodium alginate used has a molecular weight of 100,000 to 250,000; the concentration of the calcium chloride aqueous solution is 0.1 mol / L; magnetic stirring is performed at 400 rpm for 1 hour; ultrasonic stirring is performed 3 times for 5 minutes each time; wherein 0.075 parts of sodium alginate are dissolved in 90 parts of distilled water, the mass ratio of sodium alginate to cinnamon essential oil is 1:125, and the molar ratio of sodium alginate to calcium chloride is 1:205.
[0034] The corn starch used in step (2) has a purity of 99.0% and a molecular weight of 200,000 to 400,000; the pectin added is commercially available and has a galacturonic acid content of ≥80.0%; the gelatinization temperature is 90 ℃ and the gelatinization time is 30 minutes; the magnetic stirring speed is 400 rpm and the stirring is continuous for 20 minutes; the mold preheating and drying film forming temperature are both 55 ℃; the corn starch is 1 part, and 25 parts of distilled water, 0.10 parts of pectin, 0.40 parts of glycerol, and 0.50 parts of sodium alginate nanoparticle solution are added.
[0035] The calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging also includes a traction collection step, a cutting step of cutting to the required size, and a step of testing mechanical properties using a servo electronic tensile testing machine.
[0036] Mechanical properties were tested using a servo electronic tensile testing machine. The membrane was cut into 1 cm × 5 cm rectangular blocks with an initial clamping distance of 25 mm, a tensile speed of 1 mm / s, and a return speed of 10 mm / s. Each sample was tested in parallel five times. The tensile strength TS was calculated using the following formula: TS = F / D × d, where F is the maximum tensile force at break of the sample (unit: N), D is the width of the sample (unit: mm), and d is the thickness of the membrane (unit: mm). As shown in Table 1, the maximum tensile strength was found to be 35.2 MPa.
[0037] Referring to standard QB / T 2591-2003 "Antibacterial Plastics - Test Methods and Antibacterial Effects" and the 2002 "Disinfection Technical Specifications" issued by the Ministry of Health of the People's Republic of China, the prepared calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging was reacted with a certain amount of bacterial suspension for 72 hours, then cultured, and colony counted. The results of the antibacterial performance test against *Escherichia coli* are shown in Table 2, with an inhibition zone diameter of 10.9 mm; the results of the antiseptic performance test against *Staphylococcus aureus* are shown in Table 3, with an inhibition zone diameter of 10.8 mm.
[0038] Fresh strawberries of uniform size were selected and grouped. The strawberries were placed in plastic trays and sealed with the prepared calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging. The rot index of the strawberries was tested after 72 hours of storage at room temperature. The results are shown in Table 4. The rot index was 2, indicating that the prepared calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging has a good antibacterial and preservation effect.
[0039] The above test data demonstrate that the prepared calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging has excellent mechanical properties and antibacterial and preservation effects. Example 4
[0040] A method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging includes the following steps: (1) Preparation of sodium alginate nanoparticles: Sodium alginate was dissolved in distilled water, cinnamon essential oil was added, calcium chloride aqueous solution was slowly added dropwise, and the mixture was continuously magnetically stirred at room temperature and then stirred with ultrasound to prepare a sodium alginate nanoparticle solution loaded with cinnamon essential oil. (2) Preparation of calcium cross-linked starch-pectin-sodium alginate composite film: Take corn starch, add distilled water, gelatinize at high temperature, cool naturally to room temperature, add pectin, stir magnetically, add glycerol and sodium alginate nanoparticle solution in step (1) at room temperature, stir magnetically, and then pour into a preheated mold to dry into a film to obtain calcium cross-linked starch-pectin-sodium alginate composite film; (3) Cut the composite film from step (2) into pieces for use in food preservation packaging.
[0041] In step (1), the sodium alginate used has a molecular weight of 100,000 to 250,000; the concentration of the calcium chloride aqueous solution is 0.1 mol / L; magnetic stirring is performed at 400 rpm for 1 hour; ultrasonic stirring is performed 3 times for 5 minutes each time; wherein 0.080 parts of sodium alginate are dissolved in 90 parts of distilled water, the mass ratio of sodium alginate to cinnamon essential oil is 1:186.7, and the molar ratio of sodium alginate to calcium chloride is 1:255.
[0042] The corn starch used in step (2) has a purity of 99.0% and a molecular weight of 200,000~400,000; the pectin added is commercially available and has a galacturonic acid content of ≥80.0%; the gelatinization temperature is 90 ℃ and the gelatinization time is 30 minutes; the magnetic stirring speed is 400 rpm and the stirring is continuous for 20 minutes; the mold preheating and drying film forming temperature are both 55 ℃; the amount of corn starch is 1.1 parts, with 28 parts of distilled water, 0.11 parts of pectin, 0.45 parts of glycerol, and 0.55 parts of sodium alginate nanoparticle solution added.
[0043] The calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging also includes a traction collection step, a cutting step of cutting to the required size, and a step of testing mechanical properties using a servo electronic tensile testing machine.
[0044] Mechanical properties were tested using a servo electronic tensile testing machine. The membrane was cut into 2 cm × 5 cm rectangular blocks with an initial clamping distance of 25 mm, a tensile speed of 1 mm / s, and a return speed of 10 mm / s. Each sample was tested five times in parallel. The tensile strength TS was calculated using the following formula: TS = F / D × d, where F is the maximum tensile force at break of the sample (unit: N), D is the width of the sample (unit: mm), and d is the thickness of the membrane (unit: mm). As shown in Table 1, the maximum tensile strength was found to be 33.5 MPa.
[0045] Referring to standard QB / T 2591-2003 "Antibacterial Plastics - Test Methods and Antibacterial Effects" and the 2002 "Disinfection Technical Specifications" issued by the Ministry of Health of the People's Republic of China, the prepared calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging was reacted with a certain amount of bacterial suspension for 72 hours, then cultured, and colony counted. The results of the antibacterial performance test against *Escherichia coli* are shown in Table 2, with an inhibition zone diameter of 11.4 mm; the results of the antiseptic performance test against *Staphylococcus aureus* are shown in Table 3, with an inhibition zone diameter of 11.6 mm.
[0046] Fresh strawberries of uniform size were selected and grouped. The strawberries were placed in plastic trays and sealed with a prepared calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging. The rot index of the strawberries was tested after 72 hours of storage at room temperature. The results are shown in Table 4. The rot index was grade 1.
[0047] The above test data demonstrate that the prepared calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging has excellent mechanical properties and antibacterial and preservation effects. Example 5
[0048] A method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging includes the following steps: (1) Preparation of sodium alginate nanoparticles: Sodium alginate was dissolved in distilled water, cinnamon essential oil was added, calcium chloride aqueous solution was slowly added dropwise, and the mixture was continuously magnetically stirred at room temperature and then stirred with ultrasound to prepare a sodium alginate nanoparticle solution loaded with cinnamon essential oil. (2) Preparation of calcium cross-linked starch-pectin-sodium alginate composite film: Take corn starch, add distilled water, gelatinize at high temperature, cool naturally to room temperature, add pectin, stir magnetically, add glycerol and sodium alginate nanoparticle solution in step (1) at room temperature, stir magnetically, and then pour into a preheated mold to dry into a film to obtain calcium cross-linked starch-pectin-sodium alginate composite film; (3) Cut the composite film from step (2) into pieces for use in food preservation packaging.
[0049] In step (1), the sodium alginate used has a molecular weight of 100,000 to 250,000; the concentration of the calcium chloride aqueous solution is 0.1 mol / L; magnetic stirring is performed at 400 rpm for 1 hour; ultrasonic stirring is performed 3 times for 5 minutes each time; wherein 0.090 parts of sodium alginate are dissolved in 75 parts of distilled water, the mass ratio of sodium alginate to cinnamon essential oil is 1:88.9, and the molar ratio of sodium alginate to calcium chloride is 1:285.
[0050] The corn starch used in step (2) has a purity of 99.0% and a molecular weight of 200,000~400,000; the pectin added is commercially available and has a galacturonic acid content of ≥80.0%; the gelatinization temperature is 90 ℃ and the gelatinization time is 30 minutes; the magnetic stirring speed is 400 rpm and the stirring is continuous for 20 minutes; the mold preheating and drying film forming temperature are both 55 ℃; the amount of corn starch is 1.2 parts, with 30 parts of distilled water, 0.12 parts of pectin, 0.50 parts of glycerol, and 0.60 parts of sodium alginate nanoparticle solution added.
[0051] The calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging also includes a traction collection step, a cutting step of cutting to the required size, and a step of testing mechanical properties using a servo electronic tensile testing machine.
[0052] Mechanical properties were tested using a servo electronic tensile testing machine. The membrane was cut into 1 cm × 5 cm rectangular blocks with an initial clamping distance of 25 mm, a tensile speed of 1 mm / s, and a return speed of 10 mm / s. Each sample was tested in parallel five times. The tensile strength TS was calculated using the following formula: TS = F / D × d, where F is the maximum tensile force at break of the sample (unit: N), D is the width of the sample (unit: mm), and d is the thickness of the membrane (unit: mm). As shown in Table 1, the maximum tensile strength was found to be 31.5 MPa.
[0053] Referring to standard QB / T 2591-2003 "Antibacterial Plastics - Test Methods and Antibacterial Effects" and the 2002 "Disinfection Technical Specifications" issued by the Ministry of Health of the People's Republic of China, the prepared calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging was reacted with a certain amount of bacterial suspension for 72 hours, then cultured, and colony counted. The results of the antibacterial performance test against *Escherichia coli* are shown in Table 2, with an inhibition zone diameter of 16.3 mm; the results of the antiseptic performance test against *Staphylococcus aureus* are shown in Table 3, with an inhibition zone diameter of 20.5 mm.
[0054] Fresh strawberries of uniform size were selected and grouped. The strawberries were placed in plastic trays and sealed with a prepared calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging. The rot index of the strawberries was tested after 72 hours of storage at room temperature. The results are shown in Table 4. The rot index was 0.
[0055] The above test data show that the prepared calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging has excellent mechanical properties and very good antibacterial and preservation effects.
[0056] Table 1 Maximum tensile strength of films prepared in Examples 1-5
[0057] Table 2. Test results of the anti-Escherichia coli properties of the films prepared in Examples 1-5
[0058] Table 3. Test results of the anti-Staphylococcus aureus performance of the films prepared in Examples 1-5
[0059] Table 4. Rot index of strawberries after sealing with the film prepared in Examples 1-5
[0060] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.
Claims
1. A method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging, characterized in that: The composite film uses starch and pectin as the framework, with sodium alginate nanoparticles uniformly dispersed in the system. Calcium ions successfully crosslink the three components of starch, pectin, and sodium alginate. The coordination of carboxyl groups with calcium and the hydrogen bonds between polysaccharides jointly construct the crosslinked network structure of the composite film.
2. The method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging according to claim 1, characterized in that: Includes the following steps: (1) Preparation of sodium alginate nanoparticles: Sodium alginate was dissolved in distilled water, cinnamon essential oil was added, calcium chloride aqueous solution was slowly added dropwise, and the mixture was continuously magnetically stirred at room temperature and then stirred with ultrasound to prepare a sodium alginate nanoparticle solution loaded with cinnamon essential oil. (2) Preparation of calcium cross-linked starch-pectin-sodium alginate composite film: Take corn starch, add distilled water, gelatinize at high temperature, cool naturally to room temperature, add pectin, stir magnetically, add glycerol and sodium alginate nanoparticle solution in step (1) at room temperature, stir magnetically, and then pour into a preheated mold to dry into a film to obtain calcium cross-linked starch-pectin-sodium alginate composite film; (3) Cut the composite film from step (2) into pieces for use in food preservation packaging.
3. The method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging according to claim 2, characterized in that: In step (1), the sodium alginate has a molecular weight of 100,000 to 250,000; the calcium chloride aqueous solution has a concentration of 0.1 mol / L; the magnetic stirring is performed at 400 rpm for 1 hour; and the ultrasonic stirring is performed 3 times for 5 minutes each time.
4. The method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging according to claim 2, characterized in that: In step (1), 0.075 to 0.090 parts of sodium alginate are dissolved in 75 to 90 parts of distilled water. The mass ratio of sodium alginate to cinnamon essential oil is 1:186.7 to 1:88.9, and the mass ratio of sodium alginate to calcium chloride is 1:285 to 1:
178.
5. A method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging according to claim 2, characterized in that: The corn starch used in step (2) has a purity of 99.0% and a molecular weight of 200,000 to 400,000; the added pectin is commercially available and has a galacturonic acid content of ≥80.0%; the gelatinization temperature is 90℃ and the gelatinization time is 30 minutes; the magnetic stirring speed is 400 rpm and the stirring is continuous for 20 minutes; the mold preheating and drying film forming temperature are both 50 to 60℃.
6. The method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for preservation packaging according to claim 2, characterized in that: In step (2), the amount of corn starch is 0.9-1.2 parts, distilled water is added to 23-30 parts, pectin is added to 0.09-0.12 parts, glycerin is added to 0.35-0.50 parts, and sodium alginate nanoparticle solution is added to 0.45-0.60 parts.
7. A method for preparing a calcium cross-linked starch-pectin-sodium alginate composite film for food preservation packaging according to any one of claims 1 to 6, characterized in that: The composite film also includes a traction collection step, a cutting step of cutting to the required size, and a step of testing mechanical properties using a servo electronic tensile testing machine.
8. A calcium cross-linked starch-pectin-sodium alginate composite film obtained by the preparation method of claim 7.