Preservative film with antibacterial effect and preparation process thereof

Abstract

The invention relates to a preservative film with an antibacterial effect and a preparation process thereof, the preservative film comprises the following components: curcumin, chlorogenic acid, protein and a preservative film base material, and after the components are prepared by the process disclosed by the invention, the preservative film not only has a long-term antibacterial effect, but also can still keep an excellent antibacterial effect under the action of strong light.

Description

Technical Field

[0001] The present invention relates to the field of packaging materials, in particular to a fresh-keeping film with antibacterial function and a preparation process thereof. Background Art

[0002] As an important material for food packaging, plastic wrap primarily protects food, extends its shelf life, and maintains its freshness. Currently, plastic wrap on the market is divided into two main categories: traditional plastic wrap and new biodegradable plastic wrap. While traditional plastic wrap, such as polyethylene (PE) film, is relatively low-cost, it is difficult to degrade and poses a potential threat to the environment. New biodegradable plastic wrap, such as those based on polysaccharides, proteins, and lipids, offers a wide variety of raw material sources, is non-toxic, and environmentally friendly, making it a viable alternative to non-degradable plastic wrap.

[0003] Traditional plastic wrap mainly protects food through physical isolation, but it cannot effectively inhibit the growth of bacteria.

[0004] It can be seen from this that it is necessary to develop cling film with stronger antibacterial properties to effectively inhibit the growth and reproduction of microorganisms in food and extend the shelf life of food. At the same time, how to extend the antibacterial time of cling film and how to ensure that cling film still plays an antibacterial role under the action of light are important issues that need to be solved at present. Summary of the Invention

[0005] In order to solve the problem of insufficient antibacterial efficacy of existing cling films, the present invention provides an antibacterial cling film, which improves the light stability of curcumin by adding a stabilizer, thereby improving the antibacterial duration of the cling film and the antibacterial performance under strong light.

[0006] The technical solution adopted in the present invention is as follows: A fresh-keeping film with antibacterial effect comprises the following ingredients: curcumin, chlorogenic acid, protein and a fresh-keeping film base material.

[0007] Furthermore, the cling film substrate is selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polymethylpentene (PMP), or a combination thereof. Preferably, the cling film substrate is polyethylene (PE).

[0008] Furthermore, the protein is selected from the group consisting of soy protein isolate (SPI), zein, wheat gluten, whey protein, casein, or a combination thereof. Preferably, the protein is zein.

[0009] Furthermore, curcumin and chlorogenic acid were mixed with proteins and prepared into nanoparticles through nanoemulsion technology.

[0010] Furthermore, the mass ratio of curcumin, chlorogenic acid, protein and plastic wrap base material is 1-2: 2-4: 5-10: 500-1000. Preferably, the mass ratio of curcumin, chlorogenic acid, protein and plastic wrap base material is 1:2:5:500.

[0011] The present invention provides a preparation process of a fresh-keeping film with antibacterial efficacy, which comprises the following steps: Preparation of nanoparticles Dissolve 1 g of curcumin and 2 g of chlorogenic acid in 100 ml of water to obtain a solution; 5 g of protein was dissolved in the above solution and treated by ultrasound for 30 min to obtain a mixed solution; The mixed solution was processed by a high-pressure homogenizer to obtain particles with a diameter of 100-200 nanometers.

[0012] Preparation of plastic wrap The nanoparticles were mixed with 500 g of polyethylene and added to a film blowing machine; The film is blown at 200°C to obtain an antibacterial fresh-keeping film with a thickness of 10-15 microns (μm).

[0013] Furthermore, the thickness of the plastic wrap can be selected from three types: 10 microns, 12 microns, and 15 microns.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. Improved antibacterial properties: Curcumin, as a photosensitizer, can produce active oxygen under light conditions, effectively inhibiting the growth of microorganisms and improving the antibacterial properties of plastic wrap.

[0015] 2. Improved stability of curcumin: The addition of chlorogenic acid significantly improved the photostability of curcumin and prolonged its half-life under light conditions.

[0016] 3. Enhanced food safety: Since curcumin and chlorogenic acid are both natural ingredients, the plastic wrap of the present invention has good biocompatibility and food safety.

[0017] 4. Protein addition: 1) Improves solubility. Zein can bind to curcumin through non-covalent interactions, forming a stable nanocomplex, significantly increasing curcumin's water solubility. 2) Sustained release: Protein-based nanoparticles can provide a sustained release effect, controlling the release rate of curcumin and extending the duration of the antibacterial wrap. 3) Improves oxidative stability: Nanoencapsulated curcumin exhibits superior oxidative stability compared to curcumin alone, primarily due to the protein's shielding effect on curcumin and the protein's inherent strong antioxidant properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1The inhibitory effect of the fresh-keeping films prepared in different embodiments on Escherichia coli at different times.

[0019] Figure 2 The inhibitory effects of the fresh-keeping films prepared in different embodiments on Staphylococcus aureus at different times.

[0020] Figure 3 The inhibitory effect of the plastic wrap prepared in different embodiments on Escherichia coli over time under strong light. DETAILED DESCRIPTION

[0021] The present invention is further described below by means of specific examples and comparative examples. It should be understood that these examples and comparative examples are merely provided for more detailed and specific description and should not be construed as limiting the present invention in any form.

[0022] Example 1

[0023] A fresh-keeping film with antibacterial efficacy comprises the following ingredients: curcumin, chlorogenic acid, zein, and polyethylene (PE), wherein the mass ratio of the above ingredients is 1:2:5:500.

[0024] The preparation method of the fresh-keeping film is as follows: Preparation of nanoparticles Dissolve 1 g of curcumin and 2 g of chlorogenic acid in 100 ml of water to obtain a solution; 5 g of protein (zein) was dissolved in the above solution and treated by ultrasound for 30 min to obtain a mixed solution; The mixed solution was processed through a high-pressure homogenizer to obtain particles with a diameter of 100-200 nm; Preparation of plastic wrap The nanoparticles were mixed with 500 g of polyethylene and added to a film blowing machine; The film was blown at 200°C to obtain an antibacterial fresh-keeping film with a thickness of 12 microns (μm).

[0025] Example 2

[0026] A fresh-keeping film with antibacterial efficacy comprises the following ingredients: curcumin, zein, and polyethylene (PE), wherein the mass ratio of the above ingredients is 1:5:500.

[0027] Dissolve 1 g of curcumin in 100 ml of water to obtain a solution; 5 g of protein (zein) was dissolved in the above solution and treated by ultrasound for 30 min to obtain a mixed solution; The mixed solution was processed through a high-pressure homogenizer to obtain particles with a diameter of 100-200 nm; Preparation of plastic wrap The nanoparticles were mixed with 500 g of polyethylene and added to a film blowing machine; The film was blown at 200°C to obtain an antibacterial fresh-keeping film with a thickness of 12 microns (μm).

[0028] Example 3

[0029] A fresh-keeping film with antibacterial efficacy comprises the following ingredients: curcumin, chlorogenic acid, and polyethylene (PE), wherein the mass ratio of the above ingredients is 1:2:500.

[0030] The preparation method of the fresh-keeping film is as follows: Preparation of nanoparticles Dissolve 1 g of curcumin and 2 g of chlorogenic acid in 100 ml of water to obtain a solution; The above solution was processed by a high-pressure homogenizer to obtain particles with a diameter of 100-200 nm; Preparation of plastic wrap The nanoparticles were mixed with 500 g of polyethylene and added to a film blowing machine; The film was blown at 200°C to obtain an antibacterial fresh-keeping film with a thickness of 12 microns (μm).

[0031] Effect Example 1: Antibacterial Duration Test Test samples: The cling film prepared in Examples 1-3 was used as the experimental group, and the cling film directly prepared from polyethylene (ie, no other ingredients were added except polyethylene) was used as the control group.

[0032] Bacteria selection: Escherichia coli and Staphylococcus aureus were tested separately.

[0033] Activation and preparation of bacterial strains: Inoculate the standard test strain on nutrient agar (NA) slant medium, culture at (37±1)℃ for 24 hours, then transfer to fresh slant medium and culture at (35±1)℃ for 20 hours. Prepare NB medium with a concentration of 1 / 500, transfer the activated bacterial strain to NB medium, and make a concentration of about 10 8 -10 9 CFU / mL of bacterial suspension.

[0034] Test sample preparation: Cut the plastic wrap sample to be tested into 2cm × 2cm pieces, and evenly apply the prepared bacterial suspension on the plastic wrap sample to ensure that the entire sample surface is covered.

[0035] Incubation and elution: Place the inoculated sample in a constant temperature and humidity incubator and incubate at (37±1)°C. After 24 hours of incubation, use physiological saline to vigorously shake the sample to elute the bacteria from the sample.

[0036] Calculation of viable bacteria count and antibacterial rate: After the eluate is appropriately diluted, spread it on an agar plate and count the colonies after incubation. The antibacterial rate is calculated according to the following formula: Antibacterial rate = [(number of colonies in the control group − number of colonies in the experimental group) / number of colonies in the control group]) × 100% Test data: The antibacterial rates were tested at the initial, 1, 2, 3, 4, 5, 6, 7, and 8 months. The above-mentioned cling films were all stored in the same indoor non-light environment. Each group was tested 3 times and the average value was calculated. Figure 1 and Figure 2 .

[0037] Conclusion: According to Figure 1 It can be seen that the inhibition rate of the cling film prepared in Example 1 on E. coli remained between 95% and 100% from the initial test period to the 8-month test period, showing an excellent long-term inhibition effect.

[0038] The cling film prepared in Example 3 showed a rapid decrease in its effect on E. coli starting from the third month due to the lack of a protein base. At the eighth month, its antibacterial rate was only about 10%. This indicates that the absence of the protein-based zein allows the rapid release of curcumin, further demonstrating that the protein-based zein can provide a sustained-release effect, control the release rate of curcumin, and prolong the duration of action of the antibacterial cling film.

[0039] The antibacterial rate of the cling film prepared in Example 2 dropped below 90% starting from the fifth month. This indicates that although the above experiment was conducted by storing the cling film in an indoor non-illuminated environment, the presence of weak indoor light and the absence of chlorogenic acid caused curcumin to decompose under weak light. Therefore, Example 2 shows that the addition of chlorogenic acid significantly improves the photostability of curcumin and prolongs its half-life under light conditions.

[0040] Figure 2 It has an inhibitory effect on Staphylococcus aureus. Figure 1 The inhibitory effect on Escherichia coli is similar in trend, except that the inhibition rate on Staphylococcus aureus is different from that on Escherichia coli.

[0041] Effect Example 2: The inhibitory effect of light on plastic wrap Test samples: The cling film prepared in Examples 1-3 was used as the experimental group, and the cling film directly prepared from polyethylene was used as the control group. Bacterial strain: Escherichia coli. Other preparation steps are as described in Example 1.

[0042] Test data: The antibacterial rate was tested at the initial, 2nd, 4th, 6th, 10th, 15th and 20th day. The above plastic wrap was irradiated under 8000 lux light conditions for 6 hours every day. Each group was tested 3 times and the average value was calculated. Figure 3 .

[0043] Conclusion: According to Figure 3 It can be seen that the inhibition rate of the plastic wrap prepared in Example 1 against Escherichia coli under strong light was maintained at above 90% from the initial stage to the 20-day test period. That is, the addition of chlorogenic acid significantly improved the photostability of curcumin and prolonged its half-life under light conditions.

[0044] The inhibition rate of the plastic wrap prepared in Example 2 against E. coli under strong light began to decrease significantly from the 4th day. On the 20th day, the inhibition rate was less than 10%. It can be seen that curcumin is extremely unstable under strong light conditions.

[0045] The inhibition rate of the plastic wrap prepared in Example 3 against E. coli under strong light began to decline from the 6th day. On the 20th day, the inhibition rate was only about 50%. It can be seen that although chlorogenic acid can improve the photostability of curcumin, the lack of protein base accelerates the release of curcumin under the action of strong light, resulting in a rapid decrease in the release of curcumin content.

[0046] It can be seen that curcumin, as a photosensitizer, can produce reactive oxygen species under light conditions, effectively inhibit the growth of microorganisms, and improve the antibacterial properties of plastic wrap.

[0047] The addition of chlorogenic acid significantly improved the photostability of curcumin and prolonged its half-life under light conditions.

[0048] Protein-based nanoparticles can provide a sustained-release effect, control the release rate of curcumin, and prolong the duration of action of the antibacterial plastic wrap.

[0049] Without departing from the scope of the present invention, those skilled in the art may modify and change the present invention. In addition, it should be understood that the aspects of each embodiment can be interchangeable as a whole or in part. The above description is also only exemplary and is not intended to limit the present invention further described in the appended claims.

Claims

1. A fresh-keeping film with antibacterial effect, comprising the following ingredients: curcumin, chlorogenic acid, protein and a fresh-keeping film base material.

2. The cling film according to claim 1, wherein The plastic wrap substrate is selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polymethylpentene (PMP) or a combination thereof.

3. The cling film according to claim 2, wherein The protein is selected from: soy protein isolate (SPI), zein, wheat gluten, whey protein, casein, or a combination thereof.

4. The cling film according to claim 3, wherein The plastic wrap base material is selected from polyethylene (PE), and the protein is selected from zein.

5. The fresh-keeping film according to claim 4, wherein The mass ratio of curcumin, chlorogenic acid, protein and plastic wrap base material is: 1-2: 2-4: 5-10: 500-1000.

6. The cling film according to claim 5, wherein The mass ratio of curcumin, chlorogenic acid, protein and plastic wrap base material is 1:2:5:

500.

7. The fresh-keeping film according to claim 6, comprising the following preparation steps: Preparation of nanoparticles Dissolve 1 g of curcumin and 2 g of chlorogenic acid in 100 ml of water to obtain a solution; 5 g of protein was dissolved in the above solution and treated by ultrasound for 30 min to obtain a mixed solution; The mixed solution was processed through a high-pressure homogenizer to obtain particles with a diameter of 100-200 nm; Preparation of plastic wrap The nanoparticles were mixed with 500 g of polyethylene and added to a film blowing machine; Film blowing is performed at 200°C to obtain an antibacterial cling film with a thickness of 10-15 μm; the thickness of the cling film is prepared in three types: 10 μm, 12 μm and 15 μm.

8. The method for preparing the fresh-keeping film according to any one of claims 1 to 7, comprising the following steps: Preparation of nanoparticles Dissolve 1 g of curcumin and 2 g of chlorogenic acid in 100 ml of water to obtain a solution; 5 g of protein was dissolved in the above solution and treated by ultrasound for 30 min to obtain a mixed solution; The mixed solution was processed through a high-pressure homogenizer to obtain particles with a diameter of 100-200 nm; Preparation of plastic wrap The nanoparticles were mixed with 500 g of polyethylene and added to a film blowing machine; Film blowing is performed at 200°C to obtain an antibacterial cling film with a thickness of 10-15 μm; the thickness of the cling film is prepared in three types: 10 μm, 12 μm and 15 μm.

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