Surfactin composite film, preparation method thereof and application of the film in fruit and vegetable preservation
The composite film prepared by combining chitosan, polyvinyl alcohol, and surfactin solves the problem of the single function of existing fruit preservation films, and improves the mechanical properties, antibacterial properties, and ultraviolet blocking properties, thus extending the preservation effect of fresh-cut fruits.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SANYA INSTITUTE OF NANJING AGRICULTURAL UNIVERSITY
- Filing Date
- 2026-04-16
- Publication Date
- 2026-06-09
AI Technical Summary
Existing fresh-cut fruit preservation films have limited functions and poor overall preservation performance, making it difficult to simultaneously meet the requirements for mechanical properties, antibacterial properties, and oxygen barrier properties.
A composite membrane was prepared by combining chitosan, polyvinyl alcohol, and the surfactant Surfactin. By adding glycerol as a plasticizer and citric acid as a crosslinking agent, a stable composite membrane structure was formed, which enhanced the mechanical and antibacterial properties. The addition of Surfactin further improved the UV blocking performance.
The prepared composite film has good film-forming properties, mechanical properties and antibacterial properties. It can effectively inhibit bacterial growth, reduce light-induced fruit and vegetable metabolism, delay water loss and quality deterioration, and extend the shelf life of fresh-cut fruits.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of preservation materials technology, specifically relating to a Surfactin composite film, its preparation method, and its application in fruit and vegetable preservation. Background Technology
[0002] Fresh-cut fruits often face problems such as moisture loss, accelerated browning, and rapid quality decline during commercial sales, significantly shortening their shelf life. Currently, commonly used preservation methods mainly include low-temperature refrigeration, modified atmosphere packaging, and chemical preservative treatment, but these methods still have certain limitations. For example, while low-temperature refrigeration can delay quality deterioration, it consumes a lot of energy and has limited preservation effects on some fruits; chemical preservatives may raise food safety concerns; and single-function packaging materials often cannot simultaneously meet multiple requirements such as antibacterial properties, oxygen barrier properties, and mechanical properties.
[0003] Polyvinyl alcohol (PVA) and chitosan (CS) have been widely used in food packaging materials due to their excellent film-forming properties, biocompatibility, and biodegradability. However, single PVA / CS composite films still suffer from limited mechanical properties, insufficient antibacterial activity, and limited functionality, making it difficult to meet the demand for high-efficiency preservation materials for fresh-cut fruits.
[0004] Surfactin is a cyclic lipopeptide bioactive substance produced by microorganisms. It has good antibacterial activity and biocompatibility, but its application in food packaging materials is still relatively limited, especially in terms of stable loading and improved preservation performance in PVA / CS composite systems, which still lacks systematic research.
[0005] Therefore, developing a functional composite film material that combines good mechanical properties, antibacterial properties, and preservation effects is of great significance for extending the shelf life of fresh-cut fruits. Summary of the Invention
[0006] To address the problem that existing fresh-cut fruit preservation films have limited functionality and poor overall preservation performance, this invention provides a composite film made from chitosan, polyvinyl alcohol, and surfactin, along with its preparation method and applications. The technical solution is as follows:
[0007] A Surfactin composite membrane comprising chitosan, polyvinyl alcohol and surfactant; the ultraviolet light transmittance of the composite membrane is not greater than 75%.
[0008] A method for preparing the above-mentioned Surfactin composite membrane includes the following steps:
[0009] (1) Add polyvinyl alcohol to water and heat and stir until dissolved to obtain a polyvinyl alcohol solution; dissolve chitosan in water containing acetic acid to obtain a chitosan solution;
[0010] (2) Mix the polyvinyl alcohol solution with the chitosan solution, add glycerol as a plasticizer, and add citric acid as a crosslinking agent. Stir continuously at 90~100℃ to make the system uniform and obtain a mixed solution.
[0011] (3) After the mixed solution is cooled to room temperature, add surfactant and stir evenly to disperse it in the system. After defoaming, a uniform film solution is obtained.
[0012] (4) The membrane liquid is poured into a mold and dried at 40~50℃ to form a membrane, thus obtaining the Surfactin composite membrane.
[0013] Furthermore, the mass concentration of the polyvinyl alcohol solution is 3-8%; the mass concentration of the chitosan solution is 0.5-1.5%.
[0014] Furthermore, the volume ratio of the polyvinyl alcohol solution to the chitosan solution is 1:1.5~2.5; and the amount of surfactant added is 256~1024 μg / mL.
[0015] Furthermore, the degree of polymerization of the polyvinyl alcohol is 1500~2000.
[0016] Furthermore, the degree of deacetylation of the chitosan is ≥95%, and the viscosity is 100~200 mPa·s.
[0017] Furthermore, the amount of glycerol added is 0.5-2% of the total mass of polyvinyl alcohol and chitosan.
[0018] Furthermore, the amount of citric acid added is 2-6% of the total mass of polyvinyl alcohol and chitosan.
[0019] Application of the above-mentioned Surfactin composite film in fruit and vegetable preservation.
[0020] Furthermore, the application of Surfactin composite film in fruit and vegetable preservation shows that the weight loss rate of fruits and vegetables is no more than 5% after 5 days of preservation.
[0021] By adopting the above scheme, the method of the present invention has the following advantages:
[0022] 1. The composite film prepared by the present invention has good film-forming properties and mechanical properties, and can be widely used for the preservation of fruits and vegetables, especially suitable for surface coating of fresh-cut fruits.
[0023] 2. The composite membrane of the present invention has significant antibacterial and ultraviolet blocking properties. While inhibiting bacterial growth, it can reduce the promoting effect of light on the metabolism of fruits and vegetables, so that fruits and vegetables can be kept at a low metabolic level as much as possible.
[0024] 3. In the application of the composite film of the present invention for the preservation of fresh-cut apples, it can effectively delay moisture loss and slow down quality deterioration, thereby extending its shelf life. Attached Figure Description
[0025] Figure 1 This is a comparison diagram showing the antibacterial effects of the composite membranes in the various embodiments and comparative examples against Escherichia coli.
[0026] Figure 2 This is a comparison diagram showing the antibacterial effects of the composite membranes of the various embodiments and comparative examples against Staphylococcus aureus.
[0027] Figure 3 A comparison diagram showing the UV blocking performance of the composite films in each embodiment and the comparative example;
[0028] Figure 4 Comparison of cross-sectional images of fresh-cut apples after 5 days of treatment with different films;
[0029] Figure 5 A comparison chart of weight loss rates in fresh-cut apples;
[0030] Figure 6 A comparison chart showing the changes in soluble solids content in fresh-cut apples;
[0031] Figure 7 A comparison chart showing the changes in titratable acid content in fresh-cut apples. Detailed Implementation
[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.
[0033] Example: (1) Weigh 5 g of polyvinyl alcohol 1799 type, add it to 95 mL of deionized water, and stir magnetically in a water bath at 95°C until completely dissolved to obtain a polyvinyl alcohol solution with a mass fraction of 5 wt%; Weigh 1 g of chitosan, add it to 100 mL of acetic acid solution with a mass fraction of 1%, and stir in a water bath at 45°C until completely dissolved to obtain a chitosan solution with a mass fraction of 1 wt%;
[0034] (2) Mix the above polyvinyl alcohol solution and chitosan solution at a volume ratio of 1:2, add glycerol, the amount of glycerol added is 1 wt% of the total mass of polyvinyl alcohol and chitosan; then add citric acid, the amount of citric acid added is 4 wt% of the total mass of polyvinyl alcohol and chitosan; stir continuously at 95°C for 30 min to make the system uniformly mixed; after the mixture cools to room temperature, add Surfactin to make its final concentration in the membrane solution 512 μg / mL, continue stirring for 20 min, and let stand to defoam for 30 min to obtain a uniform membrane solution;
[0035] (3) Pour the obtained film solution into a mold and dry it in a 45°C forced-air drying oven for 24 hours. After peeling off the film, you will get the Surfactin-polyvinyl alcohol / chitosan composite film (named PCS).
[0036] Comparative Example 1: The difference from Example 1 is that:
[0037] PVA membranes (named PVA) were prepared without adding chitosan solution and Surfactin.
[0038] Comparative Example 2: The difference from Example 1 is that:
[0039] Without adding Surfactin, a PVA / CS composite membrane (named PC) was prepared.
[0040] Comparative Example 3: The difference from Example 1 is that:
[0041] Without adding chitosan solution, a Surfactin-PVA composite membrane (named PS) was prepared.
[0042] Performance tests of the examples and comparative examples:
[0043] I. Antibacterial Rate Test: *Escherichia coli* and *Staphylococcus aureus* were selected as indicator bacteria, and the antibacterial performance of different component membrane solutions was evaluated using the colony counting method. 500 μL of each solution with a concentration of 1×10⁻⁶ was taken. 6 CFU / mL suspensions of E. coli and S. aureus were mixed with equal volumes of the membrane solutions used in Examples 2 and 3 before casting, with the pure PVA membrane solution used in Comparative Example 1 before casting serving as a control. The mixtures were incubated at 37°C and 180 rpm for 24 h, and the viable cell counts in each treatment group were determined using a serial dilution plating method.
[0044] Test results are as follows Figure 1 and Figure 2As shown, the inhibitory effects of PC membrane solution and PCS membrane solution on E. coli were significantly better than those of PVA membrane solution and PS membrane solution, indicating that chitosan has a good inhibitory effect on Gram-negative bacteria.
[0045] Meanwhile, the PCS membrane solution showed the most significant inhibitory effect on S. aureus, exhibiting superior antibacterial performance compared to other treatment groups. This result may be related to the synergistic antibacterial effect between chitosan and Surfactin.
[0046] II. Ultraviolet blocking performance test: The films obtained in Example 1 and Comparative Examples 1-3 were cut into films of the same size and fixed flat on the sample holder of the ultraviolet-visible spectrophotometer. With air as a blank control, the transmittance spectrum of each group of films was scanned and measured in the wavelength range of 200-800 nm. The focus was on analyzing the transmittance change of each film in the ultraviolet region of 200-400 nm to evaluate its ultraviolet-visible light shielding performance.
[0047] Test results are as follows Figure 3 As shown, the PCS composite film exhibits the lowest transmittance and best UV blocking performance in the 200–400 nm range; the PC composite film is second best; and the pure PVA film has the weakest UV blocking performance. Analysis suggests that, on the one hand, the introduction of CS improves the compactness of the membrane system. CS and PVA form a denser network structure through hydrogen bonding, reducing the transmission channels of UV light within the membrane. On the other hand, the addition of Surfactin enhances the intermolecular interactions within the membrane matrix, making the membrane structure more uniform and dense, thereby further reducing UV transmittance. The results indicate that the synergistic introduction of CS and Surfactin can significantly improve the UV shielding capability of PVA-based composite films, which is beneficial for reducing the impact of light on the quality of fresh-cut apples. Furthermore, visible light generally promotes fruit and vegetable metabolism and shortens their shelf life. In the visible light range, PS films with added Surfactin have higher transmittance than PVA films, but PCS does not exhibit this phenomenon compared to PC. Furthermore, the visible light transmittance of PS and PCS films differs by nearly 10%, indicating that CS and Surfactin can synergistically block visible light, reducing the impact of visible light on fruits and vegetables without affecting observation.
[0048] III. Storage Test of Fresh-Cut Apple Samples: Select fresh apples of similar size, uniform maturity, free from pests, diseases, and mechanical damage. Rinse them thoroughly with tap water, air dry them naturally, peel them, and cut them into uniform wedge-shaped apple pieces. The films obtained in Examples 1-3 and Comparative Examples 1-3 are uniformly coated onto the surface of the apple pieces. A blank control group without any film coating is also provided.
[0049] 1. Appearance changes: Apple samples from each treatment group were stored at 4℃ and 75% relative humidity, and their appearance and quality changes were observed and measured during storage.
[0050] Test results are as follows Figure 4 As shown, compared with the blank group and each comparative group, the PCS composite film treatment group obtained in Example 1 can more effectively maintain the color of apple pieces and slow down browning during storage, showing a better preservation effect.
[0051] 2. Determination of weight loss rate: Fresh-cut apple samples from different treatment groups were stored continuously at 4℃ and 75% relative humidity for 5 days, with samples weighed daily. The initial sample mass was recorded as M0, and the sample mass on day t was recorded as M. t Calculate the weight loss rate using the following formula:
[0052] Weight loss rate (%) = (M0 − M) t ) / M0×100%
[0053] Test results are as follows Figure 5 As shown, the weight loss rate of each group of fresh-cut apple samples gradually increased with the extension of storage time. The weight loss rate of the PCS composite film treatment group obtained in Example 1 was always the lowest, indicating that it can effectively inhibit moisture loss and delay quality deterioration.
[0054] 3. Determination of soluble solids: Fresh-cut apple samples from each treatment group were collected daily from day 0 to day 5 of storage. The samples were crushed in a mortar and pestle and filtered through gauze to extract the juice. A small amount of the filtrate was added to the surface of the prism of a handheld refractometer, and the soluble solids content was determined at 20°C.
[0055] Test results are as follows Figure 6 As shown, with prolonged storage time, the soluble solids content of fresh-cut apples in all groups except the blank control group showed a decreasing trend. The soluble solids content in the blank control group showed a continuous increasing trend, which is attributed primarily to the concentration effect caused by significant moisture loss during storage. In contrast, the soluble solids content of all film-treated groups decreased to varying degrees, with the PCS composite film treatment group obtained in Example 1 showing the smallest decrease. This indicates that it effectively preserves soluble sugars and flavor compounds in apples, contributing to the maintenance of fresh-cut apple quality.
[0056] 4. Determination of titratable acid content: On days 0-5 of storage, approximately 5g of fresh-cut apple samples from each treatment group were taken daily, placed in a mortar, and ground thoroughly with an appropriate amount of distilled water. The mixture was then transferred to a 100mL volumetric flask, diluted to volume with distilled water, and thoroughly mixed to obtain a sample homogenate. The homogenate was placed in an Erlenmeyer flask, and 2-3 drops of phenolphthalein indicator were added. Titration was performed with 0.1 mol / L NaOH standard solution until the solution changed from colorless to a slightly reddish color that did not fade within 30 seconds. The volume of NaOH consumed was recorded as V. Simultaneously, a blank titration was performed using distilled water instead of the sample under the same conditions, and the volume of NaOH consumed was recorded as V0.
[0057] Titratable acid content is calculated as malic acid, using the following formula:
[0058] TA(%)=C×(V−V0)×K / m×100%
[0059] In the formula, C is the concentration of NaOH standard solution (mol / L); V is the volume consumed in sample titration (L); V0 is the volume consumed in blank titration (L); K is the malic acid conversion factor; and m is the sample mass (g).
[0060] Test results are as follows Figure 7 As shown, the titratable acid content of fresh-cut apples in all treatment groups gradually decreased with prolonged storage time. The blank control group showed the fastest decrease, indicating that the consumption or degradation of organic acids in fresh-cut apples was more significant under no preservation treatment conditions. In contrast, all film treatment groups exhibited varying degrees of sustained-release effects. The PCS composite film treatment group obtained in Example 1 showed the smallest decrease in titratable acid content, indicating that it could better maintain the organic acid levels in apples, thereby delaying flavor deterioration and preserving the quality of fresh-cut apples.
[0061] For those skilled in the art, various other corresponding changes and modifications can be made based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of this invention.
Claims
1. A Surfactin composite membrane, characterized in that, It includes chitosan, polyvinyl alcohol, and surfactants; the ultraviolet light transmittance of the composite film is no more than 75%.
2. A method for preparing the Surfactin composite membrane according to claim 1, characterized in that, Includes the following steps: (1) Add polyvinyl alcohol to water and heat and stir until dissolved to obtain a polyvinyl alcohol solution; dissolve chitosan in water containing acetic acid to obtain a chitosan solution; (2) Mix the polyvinyl alcohol solution with the chitosan solution, add glycerol as a plasticizer, and add citric acid as a crosslinking agent. Stir continuously at 90~100℃ to make the system uniform and obtain a mixed solution. (3) After the mixed solution is cooled to room temperature, add surfactant and stir evenly to disperse it in the system. After defoaming, a uniform film solution is obtained. (4) The membrane liquid is poured into a mold and dried at 40~50℃ to form a membrane, thus obtaining the Surfactin composite membrane.
3. The method for preparing the Surfactin composite membrane according to claim 2, characterized in that, The polyvinyl alcohol solution has a mass concentration of 3-8%; the chitosan solution has a mass concentration of 0.5-1.5%.
4. The method for preparing the Surfactin composite membrane according to claim 2, characterized in that, The volume ratio of the polyvinyl alcohol solution to the chitosan solution is 1:1.5~2.5; the amount of surfactant added is 256~1024 μg / mL.
5. The method for preparing the Surfactin composite membrane according to claim 2, characterized in that, The degree of polymerization of the polyvinyl alcohol is 1500~2000.
6. The method for preparing the Surfactin composite membrane according to claim 2, characterized in that, The degree of deacetylation of the chitosan is ≥95%, and the viscosity is 100~200 mPa·s.
7. The method for preparing the Surfactin composite membrane according to claim 2, characterized in that, The amount of glycerol added is 0.5-2% of the total mass of polyvinyl alcohol and chitosan.
8. The method for preparing the Surfactin composite membrane according to claim 2, characterized in that, The amount of citric acid added is 2-6% of the total mass of polyvinyl alcohol and chitosan.
9. The application of the Surfactin composite film according to claim 1 in the preservation of fruits and vegetables.
10. The application of the Surfactin composite film according to claim 9 in fruit and vegetable preservation, characterized in that, The weight loss rate of fruits and vegetables after 5 days of preservation should not exceed 5%.