A high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives, its preparation method, and its application in preserving fresh chilled meat

Abstract

The present invention belongs to the field of fresh meat preservation technology, and in particular to a kind of high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives and its preparation method and application in chilled meat preservation. The present invention prepares a kind of cinnamaldehyde derivative (isophthalic acid acrolein) by raw materials such as 1,3-phthalaldehyde, malonic acid, pyridine, piperidine, ether, ethanol. When the obtained isophthalic acid acrolein is made into a hydrogel antibacterial packaging film and applied to chilled meat preservation, it shows a more excellent fresh-keeping effect than cinnamaldehyde hydrogel, and the shelf life of chilled meat can be effectively extended. Meanwhile, the method for preparing isophthalic acid acrolein of the present invention is mild in conditions and reaction by-products are few, meets the requirement of green manufacturing technology, and when making the antibacterial antiseptic preservation of hydrogel applied to chilled meat, it has the characteristics of easy operation and good fresh-keeping effect.

Description

Technical Field

[0001] The invention belongs to the technical field of fresh meat preservation, and particularly relates to a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives, a preparation method thereof, and application thereof in preserving chilled fresh meat. Background Art

[0002] Fresh meat is nutritious and delicious, and demand for it is rapidly growing. The rapid development of cold chain and fresh food e-commerce has further boosted its consumption. However, during processing, transportation, and storage, fresh meat is prone to spoilage due to its high water activity and rich protein content. Microbial growth and reproduction are a major cause of meat spoilage. Currently, commercially available fresh meat primarily uses relatively simple packaging methods such as plastic wrap and trays, which only provide a simple physical barrier with minimal antibacterial effect. This backward post-slaughter preservation technology severely restricts the processing and development of fresh meat, leading to significant resource waste and the occurrence of foodborne illnesses.

[0003] Active packaging, consisting of active ingredients and a substrate, actively interacts with its contents or environmental factors to maintain food quality and freshness. It is currently the most commonly used new cold meat preservation technology. Recent studies have found that wrapping frozen livestock and poultry meat with active packaging film can effectively reduce meat dryness loss, inhibit protein and fat oxidation, improve the quality of meat products, extend their shelf life, and prevent economic losses. However, the most commonly used synthetic antibacterial agents on the market today are highly toxic and pose a threat to human health. Furthermore, most existing cold meat packaging has only a limited antibacterial effect and a short shelf life. Therefore, developing an antibacterial packaging with effective antibacterial properties that is both green and safe is key to preserving cold meat.

[0004] Cinnamaldehyde is an aldehyde organic compound extracted from the bark, leaves, or roots of cinnamon. It is used in food storage and preservation due to its antimicrobial activity and environmental safety. However, its strong odor, high volatility, and difficulty in embedding have many drawbacks and limitations in its application. Some studies have found that cinnamaldehyde derivatives have higher antibacterial activity and excellent physical properties than cinnamaldehyde (JF Malheiro, JY Maillard, F. Borges, M. Evaluation of cinnamaldehyde and cinnamic acid derivatives in microbial growth control, Int. Biodeterior, 141 (2019) 71-78.). Therefore, the development of more cinnamaldehyde derivatives with high antibacterial effects has important application prospects.

[0005] At present, the main methods for preparing active packaging include melt extrusion, casting, and coating. The packaging films prepared by the first two methods have low elasticity and are difficult to fully cover irregular meat; the latter is prone to residue, which will affect the flavor of the packaged food and is not suitable for the storage and preservation of fresh chilled meat. Hydrogels are three-dimensional polymer networks formed by physical or chemical cross-linking of hydrophilic substances. They have good mechanical properties and ductility, and can provide sufficient capacity to accommodate various materials, thereby effectively encapsulating active ingredients (including small molecules, polymers, and particles, etc.). Among them, those that exhibit antibacterial properties by adding antibacterial agents are called antibacterial hydrogels. At the same time, hydrogels can better fit and cover the surface of fresh chilled meat, and uniform contact helps to improve its antibacterial effect.

[0006] In summary, it is necessary to construct an active packaging film based on cinnamaldehyde derivatives to effectively inhibit the proliferation of microorganisms during the storage of fresh meat, extend the shelf life of the product, ensure consumer health and promote the development of the fresh meat industry. Summary of the Invention

[0007] In order to overcome the above-mentioned shortcomings of the existing technology, the present invention constructs an active packaging film based on a cinnamaldehyde derivative (isophthalic acid propenal), which effectively inhibits the proliferation of microorganisms during the storage of fresh meat, extends the shelf life of the product, ensures consumer health and promotes the development of the fresh meat industry.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] The first aspect of the present invention provides a method for preparing a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives. Specifically, the method comprises the following steps: mixing 5-15% (mass percentage) of gelatin solution, 1-4% (mass percentage) of chitosan solution, and 5-10% (mass percentage) of PVA solution; then adding isophthalic acid propylene glycol and mixing evenly to form a film-forming liquid; and forming a film from the film-forming liquid to obtain a hydrogel packaging film.

[0010] The present invention synthesizes a cinnamaldehyde derivative (isophthalic acid propenal) with double side chains and uses it as a new type of high-efficiency antibacterial agent to load it into a hydrogel for embedding, thereby improving the antibacterial effect of the active packaging, enabling it to effectively inhibit the growth of microorganisms in fresh chilled meat, thereby extending the shelf life.

[0011] Preferably, the volume ratio of the gelatin solution, chitosan solution and PVA solution is 2-3:2-3:1-2.

[0012] Preferably, the amount of isophthalic acid acrolein used accounts for 0.5%-2% of the mixed solution by weight.

[0013] Preferably, the chitosan solution uses 2-6% citric acid as solvent.

[0014] Preferably, when preparing the membrane, the membrane-forming liquid is placed in a membrane-forming plate, first frozen at -18 to -80°C for 2 to 6 hours, then thawed at room temperature for 1 to 2 hours, and the freezing and thawing cycle is repeated 1 to 4 times.

[0015] Preferably, the preparation method of isophthalic acid acrolein comprises the following steps:

[0016] S1. After heating a suspension of 1,3-benzenedic acid, pyridine and piperidine to reflux, the pH value is adjusted to 1-2;

[0017] S2. Add ethanol and (2E, 2'E)-3,3'-(1,3-phenylene) diacrylate, then add Me3SiCl4 under an inert gas atmosphere, stir for 10-15 hours, and extract with ethyl acetate. After drying the extract, add the diester and diethyl ether, cool to -10°C to -30°C, and then add LiAlH4 under an inert gas atmosphere, and stir for 4-6 hours.

[0018] S3. After the stirring reaction is completed, diol, KMnO4 and MnO2 solution are added, and the mixture is stirred and reacted at room temperature for 10-15 hours. After filtering and washing, the crude product is purified by silica gel column chromatography to obtain isophthalic acid acrolein.

[0019] More preferably, in S1, the usage ratio of 1,3-benzenedicaldehyde, malonic acid, pyridine and piperidine is 450-550 mg:1-2 g:5-10 mL:80-120 μL.

[0020] More preferably, in S1, the heating reflux temperature is 110-130° C., and the time is 20-30 hours.

[0021] More preferably, in S2, the usage ratio of ethanol, (2E, 2'E)-3,3'-(1,3-phenylene)diacrylic acid, Me3SiCl, diester, ether and LiAlH4 is 15-25 mL: 0.5-1.5 g: 2-3 g: 6-7 g: 350-450 mL: 4-5 g.

[0022] More preferably, in S3, the usage ratio of the diol, KMnO4 and MnO2 solution is 1-2 g: 4-5 g: 70-80 mL, and the concentration of the MnO2 solution is 20-30 g / 70-80 mL.

[0023] More preferably, in S3, the crude product is purified by silica gel column chromatography using 10%-20% ethyl acetate / hexane as eluent.

[0024] The second aspect of the present invention provides a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives prepared by the preparation method described in the first aspect.

[0025] The third aspect of the present invention provides the use of the high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives described in the second aspect in preserving fresh chilled meat.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention uses 1,3-benzenedic acid, malonic acid, pyridine, piperidine, ether, ethanol, etc. as raw materials to prepare a cinnamaldehyde derivative (isophthalic acid propenal). At the same time, the obtained isophthalic acid propenal has a more efficient antibacterial property than cinnamaldehyde. It is made into a hydrogel antibacterial packaging film and exhibits a better preservation effect than cinnamaldehyde hydrogel when applied to the preservation of cold fresh meat, which can effectively extend the shelf life of cold fresh meat. Moreover, like cinnamaldehyde hydrogel, it also has good mechanical properties and strong ductility, can better fit the surface of meat to wrap meat in all directions, and is suitable for preserving and preserving cold fresh meat, and has the characteristics of wide application range, high sensitivity, stable performance, safety and biodegradability. In addition, the method for preparing isophthalic acid propenal of the present invention has mild conditions and few reaction by-products, meets the requirements of green manufacturing technology, and is easy to operate and has good preservation effect when it is made into hydrogel and applied to the antibacterial and antiseptic preservation of cold fresh meat. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The inhibition zones of cinnamaldehyde and isophthalic acid acrolein against Trichotheres thermocidal and Pseudomonas aeruginosa;

[0029] Figure 2 The packaging effect of the hydrogel packaging film of isophthalic acid acrolein based on Example 2 on chilled fresh chicken;

[0030] Figure 3 The preservation effect of different hydrogel packaging films on chilled fresh chicken, where (A) is volatile basic nitrogen and (B) is the total bacterial count. DETAILED DESCRIPTION

[0031] The following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0032] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0033] Example 1: Preparation method of cinnamaldehyde

[0034] Cinnamon bark (50 g) was soaked in 95% ethanol (150 mL), heated to 75°C for 1 h, and then filtered. The filtrate was collected and distilled to recover the ethanol. The solution was extracted with ether (100 mL) and repeated 3 times. Anhydrous calcium chloride (3 g) was then added and dried to remove the calcium chloride. The ether was then distilled off at 60°C to obtain cinnamaldehyde.

[0035] Example 2: Preparation of Cinnamaldehyde Derivatives (Isophthalic Acrylaldehyde)

[0036] (1) 1,3-Benzenedicarboxaldehyde (500 mg), malonic acid (1.5 g), pyridine (7 mL), and piperidine (100 μL) were mixed in a round-bottom flask to prepare a suspension. The suspension was heated under reflux at 120°C for 24 hours, and then the pH was adjusted to 1 with HCl solution.

[0037] (2) Anhydrous ethanol (20 mL) and (2E, 2'E)-3,3'-(1,3-phenylene) diacrylate (1 g) were added to a round-bottom flask, and Me3SiCl4 (2 g) was added under N2. After stirring for 8 h, the mixture was extracted with 100 mL of ethyl acetate at room temperature until no product was produced. After the extract was dried, the diester (6.3 g) and ether solution (400 mL) were added. After cooling to -20°C, LiAlH4 (4 g) was added under N2 and stirred for 5 h.

[0038] (3) After the stirring reaction is completed, diol (1.4 g), KMnO4 (4.6 g) and MnO2 (25 g, dissolved in 75 mL DCM) are added to form a solution. The resulting mixture is stirred and reacted at room temperature for 8 hours, then filtered through celite, washed, and finally purified by silica gel column chromatography (using 10% ethyl acetate / hexane as eluent) to obtain the crude product isophthalic acid acrolein.

[0039] Example 3: Preparation of Cinnamaldehyde Derivatives (Isophthalic Acrylaldehyde)

[0040] (1) 1,3-Benzenedicarboxaldehyde (500 mg), malonic acid (1.72 g), pyridine (7 mL), and piperidine (100 μL) were mixed in a round-bottom flask to prepare a suspension. The suspension was heated under reflux for 24 hours, and then the pH was adjusted to 1 with HCl solution.

[0041] (2) Anhydrous ethanol (20 mL) and (2E,2'E)-3,3'-(1,3-phenylene)diacrylate (1 g) were added to a round-bottom flask. Me3SiCl4 (2.2 g) was then added under N2. The mixture was stirred for 12 h and extracted with ethyl acetate. The extract was dried and then the diester (6.3 g) and ether solution (400 mL) were added. The mixture was cooled to -20°C and LiAlH4 (4.4 g) was added under N2. The mixture was stirred for 5 h.

[0042] (3) After the stirring reaction is completed, diol (1.4 g), KMnO4 (4.6 g) and MnO2 (25 g, dissolved in 75 mL DCM) are added to form a solution. The reaction mixture is stirred at room temperature for 12 hours, then filtered through celite, washed, and finally purified by silica gel column chromatography (using 10% ethyl acetate / hexane as eluent) to obtain the crude product isophthalic acid acrolein.

[0043] Example 4: Antibacterial activity of cinnamaldehyde derivatives (isophthalic acid acrolein)

[0044] Two dominant spoilage bacteria (Thermomyces pyrifer and Pseudomonas aeruginosa) screened from fresh chicken were used as indicator strains (the screening and identification of Thermomyces pyrifer and Pseudomonas aeruginosa refer to the literature "Zhou Binjing, Liu Xiaohua, Peng Jing, et al. Effects of Pseudomonas fluorescens and Thermomyces pyrifer on changes in pork quality during low-temperature storage [J]. Food Science, 2022, 43(19): 208-216.; Benie, Comoé Koffi Donatien, Dadié, Adjéhi, Guessennd N, et al. Characterization of Virulence Potential of Pseudomonas Aeruginosa Isolatedfrom Bovine Meat, Fresh Fish, and Smoked Fish [J]. European Journal ofMicrobiology&Immunology,2017,7(1):55-64.DOI:10.1556 / 1886.2016.00039."), the antibacterial activity of cinnamaldehyde in Example 1 and isophthalic acid acrolein in Examples 2 and 3 was tested by the inhibition zone test. 100 μL of bacterial suspension of the two strains with a concentration of 108 CFU / mL was taken and spread on nutrient agar medium respectively, and 100 μL of cinnamaldehyde or isophthalic acid acrolein was added to 8 mm wells. After incubation at 37°C for 24 h, the antibacterial zone was photographed and the size of the inhibition zone was measured.

[0045] from Figure 1 It can be seen that compared with the cinnamaldehyde in Example 1, the inhibition zone sizes of the isophthalic acid propionaldehyde in Examples 2 and 3 against C. thermophila were increased from 1.6 cm to 3.1 cm and 5.4 cm, respectively, and against Pseudomonas aeruginosa from 1.5 cm to 2.3 cm and 5.0 cm.

[0046] Example 5: Preparation and Application of Cold Meat Antibacterial Hydrogel Packaging Film Based on Cinnamaldehyde or Cinnamaldehyde Derivatives

[0047] (1) Preparation of a hydrogel antibacterial packaging film based on cinnamaldehyde according to Example 1: 2% gelatin aqueous solution, 1% chitosan solution (dissolved in 3% citric acid) and 10% PVA aqueous solution were mixed in a volume ratio of 3:3:2, and 0.5% (weight percentage) of cinnamaldehyde according to Example 1 was added and stirred evenly to form a film-forming liquid. 30 mL of the film-forming liquid was then placed in a 10×10 cm film-forming plate, frozen at -20°C for 3 h, and then thawed at room temperature for 2 h. This process was repeated for 3 times, and finally rinsed with distilled water to obtain a hydrogel packaging film.

[0048] (2) Preparation of a hydrogel antibacterial packaging film based on the cinnamaldehyde derivative of Example 2: 2% gelatin aqueous solution, 1% chitosan solution (dissolved in 3% citric acid) and 10% PVA aqueous solution were mixed in a volume ratio of 3:3:2, and then 0.1% (weight percentage) of isophthalic acid propionaldehyde of Example 2 was added and stirred evenly to form a film-forming liquid. Then, 30 mL of the film-forming liquid was placed in a 10×10 cm film-forming plate, frozen at -20°C for 3 h, and then thawed at room temperature for 2 h. This freeze-thaw cycle was repeated 3 times, and finally rinsed with distilled water to obtain a hydrogel packaging film.

[0049] (3) Preparation of a hydrogel antibacterial packaging film based on the cinnamaldehyde derivative of Example 3: 2% gelatin aqueous solution, 1% chitosan solution (dissolved in 3% citric acid) and 10% PVA aqueous solution were mixed in a volume ratio of 2:2:1, and 0.1% (weight percentage) of isophthalic acid propionaldehyde of Example 3 was added and stirred evenly to form a film-forming liquid. Then, 30 mL of the film-forming liquid was placed in a 10×10 cm film-forming plate, frozen at -40°C for 6 h, and then thawed at room temperature for 2 h. This freeze-thaw cycle was repeated 3 times, and finally rinsed with distilled water to obtain a hydrogel packaging film.

[0050] (4) Application of hydrogel antibacterial packaging film based on cinnamaldehyde or isophthalic acid propenal: 50 g of fresh chicken that has passed quarantine inspection was wrapped with the hydrogel antibacterial packaging film of (1) to (3), and then placed in a 5×5×3 cm packaging box and stored under refrigeration conditions ( Figure 2 During the refrigeration process, the total colony count and volatile basic nitrogen content of meat samples were determined using the methods in national standards GB4789.2-2016 and GB 5009.228-2016, and the measurements were performed every 1 day until the 7th day.

[0051] According to the provisions of GB 5009.228-2016 on the content of volatile basic nitrogen (TVB-N), the content of volatile basic nitrogen (TVB-N) in fresh meat shall not exceed 15mg / 100g. Figure 3It can be seen that the volatile basic nitrogen (TVB-N) content of the fresh meat wrapped in the cinnamaldehyde hydrogel packaging film based on Example 1 reached 16.48 mg / 100 g on the 4th day, reaching the level of corruption; while the volatile basic nitrogen (TVB-N) content of the fresh meat wrapped in the isophthalic acid acrolein hydrogel packaging film based on Examples 2 and 3 reached 15.03 mg / 100 g and 15.80 mg / 100 g on the 6th and 7th days, respectively, that is, the packaging period of the hydrogel antibacterial packaging film based on isophthalic acid acrolein was extended by 2-3 days compared with the hydrogel antibacterial packaging film based on cinnamaldehyde. At the same time, after storage for the seventh day, the total colony count of the fresh meat wrapped in the cinnamaldehyde hydrogel packaging film based on Example 1 was 12.05 log (CFU / g), while the total colony count of the fresh meat wrapped in the isophthalic acid acrolein hydrogel packaging films based on Examples 2 and 3 was 9.22 log (CFU / g) and 8.32 log (CFU / g), respectively, showing a better antibacterial effect.

[0052] In summary, compared with traditional cinnamaldehyde, the cinnamaldehyde derivative isophthalic acid propenal synthesized in the present invention is used as a new type of highly effective antibacterial agent and loaded into the hydrogel for embedding, which can make the active packaging more effective in inhibiting the growth of microorganisms in fresh chilled meat, thereby further extending the shelf life.

[0053] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and the changes still fall within the scope of protection of the present invention.

Claims

1. A method for preparing a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives, characterized in that: A 5-15% by weight gelatin solution, a 1-4% by weight chitosan solution, and a 5-10% by weight PVA solution are mixed, and then isophthalic acid diacrolein is added and mixed to form a film-forming solution. After film-forming, a hydrogel packaging film is obtained; the isophthalic acid diacrolein is used in an amount of 0.5% to 2% by weight of the film-forming solution; The preparation method of isophthalic acid acrolein comprises the following steps: S1. Heating a suspension of 1,3-benzenedic acid, pyridine, and piperidine under reflux, and adjusting the pH to 1-2; S2. Add ethanol and (2E, 2'E)-3,3'-(1,3-phenylene) diacrylate, then add Me3SiCl4 under an inert gas atmosphere, stir for 10-15 hours, and extract with ethyl acetate. After drying the extract, add the diester and diethyl ether, cool to -10°C to -30°C, and then add LiAlH4 under an inert gas atmosphere, and stir for 4-6 hours. S3. After the stirring reaction is completed, diol, KMnO4 and MnO2 solution are added, and the mixture is stirred and reacted at room temperature for 10-15 hours. After filtering and washing, the crude product is purified by silica gel column chromatography to obtain isophthalic acid acrolein.

2. The method for preparing a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives according to claim 1, characterized in that: The volume ratio of the gelatin solution, chitosan solution and PVA solution is 2-3:2-3:1-2.

3. The method for preparing a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives according to claim 1, characterized in that: In S1, the usage ratio of 1,3-benzenedicaldehyde, malonic acid, pyridine and piperidine is 450-550 mg:1-2 g:5-10 mL:80-120 μL.

4. The method for preparing a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives according to claim 1, characterized in that: In S1, the heating reflux temperature is 110-130° C. and the time is 20-30 hours.

5. The method for preparing a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives according to claim 1, characterized in that: In S2, the usage ratio of ethanol, (2E, 2'E)-3,3'-(1,3-phenylene) diacrylate, Me3SiCl, diester, ether, and LiAlH4 is 15-25 mL: 0.5-1.5 g: 2-3 g: 6-7 g: 350-450 mL: 4-5 g.

6. The method for preparing a high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives according to claim 1, characterized in that: In S3, the usage ratio of the diol, KMnO4 and MnO2 solution is 1-2 g: 4-5 g: 70-80 mL, and the concentration of the MnO2 solution is 20-30 g / 70-80 mL.

7. A highly effective antibacterial hydrogel packaging film based on cinnamaldehyde derivatives prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the high-efficiency antibacterial hydrogel packaging film based on cinnamaldehyde derivatives according to claim 7 in preserving fresh chilled meat.

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