Gelatin packaging film based on phenol crosslinking modification and preparation method and application thereof

Abstract

The invention relates to the technical field of packaging film materials, and discloses a gelatin packaging film based on phenol crosslinking modification and a preparation method and application thereof. According to the invention, 1-4wt% of grape skin polyphenol is added into a gelatin base material, and the grape skin polyphenol and the gelatin base material are crosslinked through hydrogen bonds to form a three-dimensional network structure, so that the packaging film taking gelatin as the base material has good moisture resistance; besides, due to the addition of the grape skin polyphenol, the grape skin polyphenol has antioxidant activity and can endow the packaging film with oxidation resistance, and other antioxidants do not need to be added in the preparation process of the packaging film; and after the grape skin polyphenol and the gelatin form a three-dimensional network structure, the mechanical property of the packaging film can be greatly improved, the problem that the gelatin film is easy to soften is solved, and the physical barrier packaging effect of the gelatin film is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging film materials, in particular to a phenol-crosslinked modified gelatin packaging film and a preparation method thereof. Background Art

[0002] Gelatin, a naturally biodegradable polymer, shows promising application prospects in food packaging due to its excellent film-forming properties, edibility, and biocompatibility. Traditionally, gelatin films are primarily produced through solution casting, but these conventional methods do not meet the multifunctional, high-performance requirements currently required for packaging films. Researchers are looking to improve the mechanical, antimicrobial, and antioxidant properties of gelatin films.

[0003] Chinese patent application publication number CN104194354A discloses an edible bio-preservative film. By modifying a film substrate, such as gelatin, with natural antioxidants and antimicrobial agents, as well as plasticizers and emulsifiers, the film improves its mechanical properties and imparts antimicrobial and antioxidant properties. However, the patented bio-preservative film suffers from the following issues: 1. Strong hygroscopicity: This patent ignores the inherent hygroscopicity of gelatin molecules. Gelatin molecules contain a large number of hydrophilic groups, such as -OH, -NH2, -COOH, etc., which will cause them to easily absorb water and soften in a high humidity environment, seriously affecting the packaging performance.

[0004] 2. Unstable mechanical properties: It is significantly affected by humidity. After absorbing water, the packaging film will soften and the tensile strength will decrease, making it difficult to meet the basic requirements of packaging materials.

[0005] 3. Poor antioxidant durability: Traditional gelatin film mainly relies on physical barrier effect and lacks active preservation function. Properties such as antioxidant and antibacterial require additional functional ingredients. Summary of the Invention

[0006] In order to solve the technical problems of the above-mentioned gelatin film, such as strong hygroscopicity and poor mechanical properties, the present invention provides a gelatin packaging film based on phenol cross-linking modification, and a preparation method and application thereof.

[0007] The specific technical solutions of the present invention are: On the one hand, the present invention provides a phenol-crosslinked modified gelatin packaging film, which includes a gelatin base material and grape skin polyphenols, wherein the mass ratio of the gelatin base material to the grape skin polyphenols is 100:(1~4); in the gelatin packaging film, the gelatin base material and the grape skin polyphenols are cross-linked by hydrogen bonds to form a three-dimensional network structure.

[0008] Because gelatin molecules contain numerous hydrophilic groups such as -OH, -NH2, and -COOH, packaging films based on gelatin are highly hygroscopic. Even with the addition of antioxidants and antimicrobial agents, existing gelatin packaging films still suffer from inherent hygroscopicity. This reduces their mechanical strength in high humidity environments, allowing moisture to easily penetrate the film and enter the packaging, causing the contents to deteriorate.

[0009] The present invention provides a gelatin packaging film based on phenol cross-linking modification. By adding 1-4%wt of grape skin polyphenols to a gelatin base material and cross-linking with the polyphenols to form a three-dimensional network structure, the packaging film based on the gelatin has good moisture barrier properties and greatly improves the mechanical properties of the packaging film.

[0010] The gelatin packaging film provided by the present invention has good moisture barrier properties through grape skin polyphenols. Its advantages include the following two points: first, grape skin polyphenols have antioxidant activity, and their addition can also give the packaging film antioxidant properties, and no other antioxidants need to be added during the preparation of the packaging film; second, after the grape skin polyphenols and gelatin form a three-dimensional network structure, the mechanical properties of the packaging film can be greatly improved, the problem of easy softening of the gelatin film is alleviated, and the physical barrier packaging effect of the gelatin film is ensured.

[0011] The amount of grape skin polyphenol added to the gelatin packaging film provided by the present invention must be controlled within a gelatin base material to grape skin polyphenol mass ratio of 100:1 to 4. Moisture barrier performance tests revealed that the film exhibited excellent moisture barrier properties when the gelatin base material to grape skin polyphenol mass ratio was within the range of 100:1 to 4. Omission of grape skin polyphenol or excessive addition of grape skin polyphenol resulted in poor moisture barrier properties.

[0012] In the moisture barrier performance test, it was found that when the mass ratio of gelatin base material to grape skin polyphenols was 50:1, the packaging film had the best moisture barrier performance. Therefore, as a preferred embodiment of the above-mentioned gelatin packaging film, the mass ratio of gelatin base material to grape skin polyphenols is 50:1.

[0013] As a preferred embodiment of the above-mentioned gelatin packaging film, the gelatin packaging film further comprises one or more of an opening agent, a plasticizer, a film-forming agent, a viscosity regulator and water.

[0014] As a preferred embodiment of the above-mentioned gelatin packaging film, the gelatin packaging film includes the following components, calculated by mass: 100 parts of gelatin, 1 to 4 parts of grape skin polyphenols, 4 to 7 parts of SiO2, 18 to 24 parts of glycerin, 4 to 8 parts of gellan gum, 0.1 to 1.5 parts of malic acid, and 12 to 20 parts of deionized water.

[0015] In the gelatin packaging film, gelatin is used as the base material, grape skin polyphenols are added and cross-linked with it through hydrogen bonds to form a three-dimensional network structure, SiO2 is added as an opening agent, glycerin is used as a plasticizer, gellan gum is used as an auxiliary film-forming agent, malic acid is added to adjust the pH viscosity of the system, and deionized water is used as a solvent. The final gelatin packaging film has good moisture barrier properties and mechanical properties.

[0016] On the other hand, the present invention provides a method for preparing a phenol-crosslinked modified gelatin packaging film, characterized in that it comprises the following steps: Step S1, mixing raw material components including a gelatin base material and grape skin polyphenols, wherein the mass ratio of the gelatin base material to the grape skin polyphenols is 100:(1-4), and stirring to obtain a membrane mixed base material; Step S2, extruding and granulating the membrane mixed substrate; Step S3: Casting the film mixed substrate after extrusion granulation to obtain a gelatin packaging film.

[0017] In the preparation method of the gelatin packaging film, gelatin is used as a base material, and grape skin polyphenol is added and mixed therewith, so that the gelatin base material and grape skin polyphenol form strong hydrogen bond cross-linking during the mixing and extrusion process, so that a granulated material with a three-dimensional network structure is obtained, and the gelatin packaging film of the present invention is obtained by cast film formation.

[0018] Compared with the traditional solution casting method, the film material obtained by the extrusion granulation method of the present invention has better mechanical properties.

[0019] As a preferred embodiment of the above preparation method, in step S2, the process temperature of the extrusion granulation is 65-95°C.

[0020] Further preferably, the extrusion granulation process is: along the conveying direction of the extruded material, different zones are included in sequence, and the zones include different temperatures, and the different temperatures are: 65~75℃, 75~85℃, 85~95℃, 85~95℃, 85~95℃, 80~90℃, and 75~85℃.

[0021] By optimizing the extrusion process with zoned temperature settings, an ordered three-dimensional network structure is formed, improving the mechanical properties of the resulting film. The tensile strength (TS) of the gelatin packaging film produced using this method can be increased to 16 MPa.

[0022] As a preferred embodiment of the above preparation method, in step S3, the temperature of the film casting is 65-95°C.

[0023] As a preferred embodiment of the above preparation method, in step S1, the raw material components are gelatin, grape skin polyphenols, SiO2, glycerol, gellan gum, malic acid, and deionized water.

[0024] Further preferably, the raw material components are, by mass, 100 parts of gelatin, 1-4 parts of grape skin polyphenols, 4-7 parts of SiO2, 18-24 parts of glycerin, 4-8 parts of gellan gum, 0.1-1.5 parts of malic acid, and 12-20 parts of deionized water.

[0025] Furthermore, in step S1, the mixing method is: Based on the gelatin packaging film provided by the present invention, or based on the gelatin packaging film prepared by the preparation method provided by the present invention, the present invention provides its use in food preservation or tobacco preservation.

[0026] Compared with the prior art, the present invention has the following technical effects: (1) The present invention adds 1-4%wt of grape skin polyphenols to a gelatin matrix and cross-links the polyphenols to form a three-dimensional network structure, thereby making the packaging film with gelatin as the matrix have good moisture barrier properties; in addition, due to the addition of grape skin polyphenols, it has antioxidant activity and can also give the packaging film antioxidant properties, and no other antioxidants need to be added during the preparation of the packaging film; and after the grape skin polyphenols and gelatin form a three-dimensional network structure, the mechanical properties of the packaging film can be greatly improved, the problem of easy softening of the gelatin film is alleviated, and the physical barrier packaging effect of the gelatin film is ensured.

[0027] (2) In the preparation method of the gelatin packaging film, gelatin is used as the base material, grape skin polyphenols are added and mixed with it, and extrusion granulation and cast film are combined. Furthermore, through the improved extrusion process with zoned temperature setting, gelatin and grape skin polyphenols are cross-linked to form an ordered three-dimensional network structure, thereby improving the mechanical properties of the prepared film material, and the tensile strength of the gelatin packaging film is increased to 16 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The figure shows the Fourier infrared spectrum of the phenol cross-linked modified gelatin packaging film of the present invention.

[0029] Figure 2 Shown are scanning electron micrographs of gelatin packaging films cross-linked and modified with different amounts of grape skin polyphenols. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the following embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only a portion of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0031] Example 1 A gelatin packaging film is provided, which is prepared according to the following method: (1) Base material blending: ① Prepare 5% SiO2 and set aside; ② Add 5% gellan gum to 20% glycerol, stir magnetically for 20 minutes, and set aside; ③ Add 1% grape skin polyphenols to a solution of 0.5% malic acid and 15% deionized water, sonicate for 10 minutes, and set aside. In steps ①, ②, and ③, the content of each component is expressed as a percentage of gelatin. Then, add the substances prepared in steps ①, ②, and ③ to the fish gelatin in sequence and stir to obtain a fluffy gelatin base material.

[0032] (2) Extrusion granulation: The gelatin base material is hot extruded and shaped, and then pelletized to obtain modified gelatin granules after cooling to room temperature. The hot extrusion molding is carried out using an LSSHJ-20 twin-screw extruder. Along the direction of extrusion, the LSSHJ-20 twin-screw extruder is divided into 7 zones. The processing temperatures of zones 1 to 7 are 70°C, 80°C, 90°C, 90°C, 85°C, and 80°C, respectively. The screw speed is 80 rpm.

[0033] (3) Cast film: The modified gelatin particles are passed through a casting machine to form a cast film. Along the material conveying direction, the processing temperatures of the barrel zones 1 to 8 in the casting machine are set to 70°C, 75°C, 80°C, 80°C, 85°C, 85°C, 90°C, and 90°C, the transition body is 90°C, the die zones 1 to 3 are 90°C, 85°C, and 80°C, and the screw speed is 50 rpm. Thus, a phenol cross-linked modified packaging film is obtained with a film thickness of 100 μm.

[0034] (4) FTIR measurements of the obtained packaging film were performed using an FTIR spectrometer (Nicolet iS10, Thermo Fisher, USA) in transmission mode at room temperature. Figure 1 . Figure 1 In the figure, 0%, 1%, 2%, 3% and 4% represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this example is 1%.

[0035] Depend on Figure 1 The Fourier transform infrared spectrum shows that the 3290 ~ 3280 cm −1 The amide A band in the range of 1628 cm is caused by the stretching vibration of NH and OH groups. −1 The amide I band is formed by C=O stretching / hydrogen bonding with COO. This indicates that grape skin polyphenols and gelatin cross-link through hydrogen bonding, without changing the peak position of the infrared spectrum.

[0036] (5) Using SEM (Phenom XL, Netherlands), the film was embrittled with liquid nitrogen to obtain a cross section and carefully glued to the sample tray. All samples were placed in an ion sputterer and sprayed with gold coating at 15 mA for 60 s to improve their conductivity. The surface and cross-sectional structure of the obtained packaging film were detected at 15 kV acceleration. The results are shown in Figure 2 . Figure 2 In the figure, 0%, 1%, 2%, 3%, and 4% below represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this example is 1%.

[0037] Depend on Figure 2 It shows that the packaging film obtained in this embodiment has fewer pores, which indicates that the packaging film has a relatively dense structure.

[0038] Example 2 A gelatin packaging film is provided, which is prepared according to the following method: (1) Base material blending: ① Prepare 5% SiO2 and set aside; ② Add 5% gellan gum to 20% glycerol, stir magnetically for 20 minutes, and set aside; ③ Add 2% grape skin polyphenols to a solution of 0.5% malic acid and 15% deionized water, sonicate for 10 minutes, and set aside. In steps ①, ②, and ③, the content of each component is expressed as a percentage of gelatin. Then, add the substances prepared in steps ①, ②, and ③ to the fish gelatin in sequence and stir to obtain a fluffy gelatin base material.

[0039] (2) Extrusion granulation: The gelatin substrate is hot extruded and formed, and then pelletized after cooling to room temperature to obtain modified gelatin granules. The hot extrusion molding is performed using an LSSHJ-20 twin-screw extruder. Along the direction of the extruded material conveying, the LSSHJ-20 twin-screw extruder is divided into 7 zones. The processing temperatures of zones 1 to 7 are 70°C, 80°C, 90°C, 90°C, 85°C, and 80°C, respectively, and the screw speed is 80 rpm.

[0040] (3) Cast film: The modified gelatin particles were melt-extruded through a single-screw extruder to form a cast film to obtain a phenol cross-linked modified packaging film with a thickness of 100 μm. The processing temperatures of the barrel zones 1 to 8 in the casting machine were set to 70°C, 75°C, 80°C, 80°C, 85°C, 85°C, 90°C, and 90°C, the transition zone was set to 90°C, the die zones 1 to 3 were set to 90°C, 85°C, and 80°C, and the screw speed was 50 rpm.

[0041] (4) FTIR measurements of the obtained packaging film were performed using an FTIR spectrometer (Nicolet iS10, Thermo Fisher, USA) in transmission mode at room temperature. Figure 1 . Figure 1In the figure, 0%, 1%, 2%, 3% and 4% represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this example is 2%.

[0042] (5) Using SEM (Phenom XL, Netherlands), the film was embrittled with liquid nitrogen to obtain a cross section and carefully glued to the sample tray. All samples were placed in an ion sputterer and sprayed with gold coating at 15 mA for 60 s to improve their conductivity. The surface and cross-sectional structure of the obtained packaging film were detected at 15 kV acceleration. The results are shown in Figure 2 . Figure 2 In the figure, 0%, 1%, 2%, 3%, and 4% below represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this example is 2%.

[0043] Depend on Figure 2 The cross-sectional electron micrograph of the packaging film shows that the packaging film obtained in this example has almost no pores, which indicates that the gelatin packaging film with a grape skin polyphenol content of 2% has a dense structure.

[0044] Example 3 A gelatin packaging film is provided, which is prepared according to the following method: (1) Base material blending: ① Prepare 5% SiO2 and set aside; ② Add 5% gellan gum to 20% glycerol, stir magnetically for 20 minutes, and set aside; ③ Add 3% grape skin polyphenols to a solution of 0.5% malic acid and 15% deionized water, sonicate for 10 minutes, and set aside. In steps ①, ②, and ③, the content of each component is expressed as a percentage of gelatin. Then, add the substances prepared in steps ①, ②, and ③ to the fish gelatin in sequence and stir to obtain a fluffy gelatin base material.

[0045] (2) Extrusion granulation: The gelatin substrate is hot extruded and formed, and then pelletized after cooling to room temperature to obtain modified gelatin granules. The hot extrusion molding is performed using an LSSHJ-20 twin-screw extruder. Along the direction of the extruded material conveying, the LSSHJ-20 twin-screw extruder is divided into 7 zones. The processing temperatures of zones 1 to 7 are 70°C, 80°C, 90°C, 90°C, 85°C, and 80°C, respectively, and the screw speed is 80 rpm.

[0046] (3) Cast film: The modified gelatin particles were melt-extruded through a single-screw extruder to form a cast film to obtain a phenol cross-linked modified packaging film with a thickness of 100 μm. The processing temperatures of the barrel zones 1 to 8 in the casting machine were set to 70°C, 75°C, 80°C, 80°C, 85°C, 85°C, 90°C, and 90°C, the transition zone was set to 90°C, the die zones 1 to 3 were set to 90°C, 85°C, and 80°C, and the screw speed was 50 rpm.

[0047] (4) FTIR measurements of the obtained packaging film were performed using an FTIR spectrometer (Nicolet iS10, Thermo Fisher, USA) in transmission mode at room temperature. Figure 1 . Figure 1 In the figure, 0%, 1%, 2%, 3% and 4% represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this example is 3%.

[0048] (5) Using SEM (Phenom XL, Netherlands), the film was embrittled with liquid nitrogen to obtain a cross section and carefully glued to the sample tray. All samples were placed in an ion sputterer and sprayed with gold coating at 15 mA for 60 s to improve their conductivity. The surface and cross-sectional structure of the obtained packaging film were detected at 15 kV acceleration. The results are shown in Figure 2 . Figure 2 In the figure, 0%, 1%, 2%, 3%, and 4% below represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this example is 3%.

[0049] Depend on Figure 2 It shows that the packaging film obtained in this embodiment has fewer pores, which indicates that the packaging film has a relatively dense structure.

[0050] Example 4 A gelatin packaging film is provided, which is prepared according to the following method: (1) Base material blending: ① Prepare 5% SiO2 and set aside; ② Add 5% gellan gum to 20% glycerol, stir magnetically for 20 minutes, and set aside; ③ Add 4% grape skin polyphenols to a solution of 0.5% malic acid and 15% deionized water, sonicate for 10 minutes, and set aside. In steps ①, ②, and ③, the content of each component is expressed as a percentage of gelatin. Then, add the substances prepared in steps ①, ②, and ③ to the fish gelatin in sequence and stir to obtain a fluffy gelatin base material.

[0051] (2) Extrusion granulation: The gelatin substrate is hot extruded and formed, and then pelletized after cooling to room temperature to obtain modified gelatin granules. The hot extrusion molding is performed using an LSSHJ-20 twin-screw extruder. Along the direction of the extruded material conveying, the LSSHJ-20 twin-screw extruder is divided into 7 zones. The processing temperatures of zones 1 to 7 are 70°C, 80°C, 90°C, 90°C, 85°C, and 80°C, respectively, and the screw speed is 80 rpm.

[0052] (3) Cast film: The modified gelatin particles were melt-extruded through a single-screw extruder to form a cast film to obtain a phenol cross-linked modified packaging film with a thickness of 100 μm. The processing temperatures of the barrel zones 1 to 8 in the casting machine were set to 70°C, 75°C, 80°C, 80°C, 85°C, 85°C, 90°C, and 90°C, the transition zone was set to 90°C, the die zones 1 to 3 were set to 90°C, 85°C, and 80°C, and the screw speed was 50 rpm.

[0053] (4) FTIR measurements of the obtained packaging film were performed using an FTIR spectrometer (Nicolet iS10, Thermo Fisher, USA) in transmission mode at room temperature. Figure 1 . Figure 1 In the figure, 0%, 1%, 2%, 3% and 4% represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this example is 4%.

[0054] (5) Using SEM (Phenom XL, Netherlands), the film was embrittled with liquid nitrogen to obtain a cross section and carefully glued to the sample tray. All samples were placed in an ion sputterer and sprayed with gold coating at 15 mA for 60 s to improve their conductivity. The surface and cross-sectional structure of the obtained packaging film were detected at 15 kV acceleration. The results are shown in Figure 2 . Figure 2 In the figure, 0%, 1%, 2%, 3%, and 4% below represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this example is 4%.

[0055] Depend on Figure 2 It shows that the packaging film obtained in this embodiment has fewer pores, which indicates that the packaging film has a relatively dense structure.

[0056] Comparative Example 1 A gelatin packaging film is provided. The preparation method is the same as that of Example 1, except that grape skin polyphenols are not added in step (1). Other steps are the same as those of Example 1.

[0057] The packaging film obtained in this comparative example was subjected to FTIR measurement using the same method as in the example. Figure 1 . Figure 1 0%, 1%, 2%, 3% and 4% represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this comparative example is 0%.

[0058] The same method as in Example 1 was used to test the surface and cross-sectional structure of the packaging film obtained in this comparative example. The results are shown in FIG. Figure 2 . Figure 2In the figure, 0%, 1%, 2%, 3%, and 4% below represent the grape skin polyphenol content in the film. The grape skin polyphenol content of the packaging film obtained in this comparative example is 0%.

[0059] Depend on Figure 2 It shows that the packaging film obtained in this comparative example contains more and larger pore structures, which indicates that the packaging film of this comparative example has a loose structure.

[0060] Comparative Example 2 A gelatin packaging film is provided. The preparation method is the same as that of Example 1, except that the 1% grape skin polyphenols added in step (1) is replaced with 1% tea polyphenols. Other preparation methods are the same as those of Example 1.

[0061] The surface and cross-sectional structures of the packaging film obtained in this comparative example were tested using the same method as in the example. The results showed that the packaging film obtained in this comparative example contained a relatively large number of pore structures, indicating that the packaging film of this comparative example had a loose structure.

[0062] Comparative Example 3 A gelatin packaging film is provided. The preparation method is the same as that of Example 1, except that the 1% grape skin polyphenols added in step (1) is replaced with 1% ferulic acid. Other steps are the same as those of Example 1.

[0063] The surface and cross-sectional structures of the packaging film obtained in this comparative example were tested using the same method as in the example. The results showed that the packaging film obtained in this comparative example contained a relatively large number of pore structures, indicating that the packaging film of this comparative example had a loose structure.

[0064] Performance Characterization (1) The packaging films obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were tested for tensile strength (TS) and elongation at break (EAB) to characterize the mechanical strength of the films. The packaging films obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were tested for water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) to characterize the physical barrier strength of the films. The results are shown in Table 1.

[0065] Mechanical strength was determined using an intelligent electronic tensile testing machine (Jinan XLW (EC)) at 25°C and 90% relative humidity (RH) according to ASTM-D882-12 (2012). The tensile strength (TS) and elongation at break (EAB) of the films were measured. A strip of film (15 mm × 100 mm) was placed between the grips with an initial grip distance of 60 mm and a test speed of 50 mm / min.

[0066] Oxygen transmission rate: According to the national standard GB / T1038-2000, the sample was cut into a circle with a special cutter and the OTR of the sample was tested using the G2 / 132 differential pressure gas permeometer with the initial test temperature set at 23°C.

[0067] Water vapor transmission rate was measured with a WVTR meter (WB-31E, Labstone, Guangxi, China) using the weight loss method at 38°C and 10% RH according to the principle of the weighing method and GB / T 1037.

[0068] Group TS (MPa) EAB (%) <![CDATA[OTR(cm 3 / m 2 ·24h·0.1MPa)]]> <![CDATA[WVTR(*10^11g·cm / cm 2 ·s·Pa)]]> Example 1 8.97 109.80 176.94 1.89 Example 2 16.24 76.93 130.84 0.89 Example 3 12.05 67.60 167.16 1.21 Example 4 15.53 55.83 155.71 1.57 Comparative Example 1 6.10 51.00 200.01 2.06 Comparative Example 2 5.86 50.74 225.26 2.42 Comparative Example 3 6.17 51.63 217.84 2.29

[0069] Table 1 As shown in Table 1, compared to films without grape skin polyphenols (Comparative Example 1), the addition of grape skin polyphenols (Examples 1 to 4) increased the mechanical strength of the gelatin films. The film containing 2% grape skin polyphenols had the highest TS (16.24 MPa), and the film containing 1% grape skin polyphenols had the highest EAB (109.80%). The EAB decreased when the grape skin polyphenol content increased from 1% to 2%. This may be due to the 2% grape skin polyphenols increasing the internal connections of the gelatin, resulting in a decrease in ductility. Compared to films containing other polyphenols (Comparative Examples 2 and 3), the addition of grape skin polyphenols significantly improved the mechanical strength and physical barrier properties of the gelatin films (Examples 1 to 4).

[0070] At the same time, as shown in Table 1, compared with the gelatin film without adding grape skin polyphenol (Comparative Example 1), the OTR and WVTR of the gelatin film decreased due to the addition of grape skin polyphenol (Examples 1 to 4). Combined with the electron microscopy images, it can be seen that the reason for the decrease in OTR and WVTR may be that the cross-linking modification of grape skin polyphenol makes the microstructure of the film more compact, reducing the channels for gas molecules. In addition, the gelatin film with 2% grape skin polyphenol added has the lowest WVTR, which may be due to the best and densest microstructure of the film under the cross-linking modification of 2% grape skin polyphenol.

[0071] (2) Characterization of tobacco preservation performance The packaging films obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were used to package tobacco, and samples were taken regularly to measure the moisture content of the tobacco. The results are shown in Table 2.

[0072] The moisture content of tobacco must be strictly controlled during the processing, as it directly affects the elasticity, toughness, filling and burning characteristics of tobacco, as well as its appearance and intrinsic quality such as color and gloss. In this step, the packaging film of the present invention is applied to the preserved tobacco to characterize its moisture barrier properties to tobacco. The test method is as follows: After packaging the packaging films obtained in Examples 1 to 4 and Comparative Examples 1 to 3, standard moisture tobacco shreds are packaged and placed in a constant temperature and humidity chamber at 25°C and RH 65%. The moisture content of the tobacco is measured on days 0, 5, 10, 15, 20, 25 and 30, with three replicates measured for each group. The moisture content is determined according to the method specified in YC / T 31-1996 "Oven Method for Determination of Moisture in Tobacco and Tobacco Products".

[0073] Table 2

[0074] As shown in Table 2, the moisture content of tobacco encapsulated in the packaging films cross-linked with grape skin polyphenols (Examples 1 to 4) remained around 13%, effectively keeping the tobacco dry and maintaining a relatively ideal moisture content. However, the moisture content of tobacco encapsulated in packaging films without grape skin polyphenols or with other cross-linked polyphenols increased rapidly, ultimately maintaining around 18%, indicating that these packaging films were ineffective in blocking water vapor.

[0075] In the embodiments of the present invention, the SiO2 anti-blocking agent used was purchased from Shanghai Maclean Biotechnology Co., Ltd., gellan gum was purchased from Shanghai Maclean Biotechnology Co., Ltd., glycerol was purchased from Shanghai Titan Biotechnology Co., Ltd., grape skin polyphenols were purchased from Shanghai Yuanye Biotechnology Co., Ltd., malic acid was purchased from Shanghai Yuanye Biotechnology Co., Ltd., and fish gelatin was purchased from Guangdong Odima Bioengineering Co., Ltd.

[0076] In the embodiments of the present invention, the screw extruder used was purchased from Foshan Jinzhonghe Machinery Co., Ltd.

[0077] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A gelatin packaging film based on phenol cross-linking modification, characterized in that: The invention comprises a gelatin base material and grape skin polyphenols, wherein the mass ratio of the gelatin base material to the grape skin polyphenols is 100:(1-4); in the gelatin packaging film, the gelatin base material and the grape skin polyphenols are cross-linked by hydrogen bonds to form a three-dimensional network structure.

2. The phenol cross-linked modified gelatin packaging film according to claim 1, characterized in that: The mass ratio of the gelatin base material to the grape skin polyphenols is 100:

2.

3. The phenol cross-linked modified gelatin packaging film according to claim 1 or 2, characterized in that: It also includes one or more of an opener, a plasticizer, a film former, a viscosity regulator and water.

4. The phenol cross-linked modified gelatin packaging film according to claim 3, characterized in that: The invention comprises the following components in parts by mass: 100 parts of gelatin, 1-4 parts of grape skin polyphenols, 4-7 parts of SiO2, 18-24 parts of glycerin, 4-8 parts of gellan gum, 0.1-1.5 parts of malic acid, and 12-20 parts of deionized water.

5. A method for preparing the phenol-crosslinked modified gelatin packaging film according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1, mixing raw material components including a gelatin base material and grape skin polyphenols, wherein the mass ratio of the gelatin base material to the grape skin polyphenols is 100:(1-4), and stirring to obtain a membrane mixed base material; Step S2, extruding and granulating the membrane mixed substrate; Step S3: Casting the film mixed substrate after extrusion granulation to obtain a gelatin packaging film.

6. The preparation method according to claim 5, wherein: In step S2, the process temperature of the extrusion granulation is 65-95°C.

7. The preparation method according to claim 6, wherein: The extrusion granulation process is as follows: along the conveying direction of the extruded material, different zones are sequentially included, and the zones have different temperatures, and the different temperatures are sequentially: 65~75°C, 75~85°C, 85~95°C, 85~95°C, 85~95°C, 80~90°C, and 75~85°C.

8. The preparation method according to claim 5, wherein: In step S3, the temperature of the film casting is 65-95°C.

9. The preparation method according to claim 5, wherein: In step S1, the raw material components are gelatin, grape skin polyphenols, SiO2, glycerol, gellan gum, malic acid, and deionized water.

10. Use of the gelatin packaging film according to any one of claims 1 to 4, or the gelatin packaging film prepared by the preparation method according to any one of claims 5 to 9, in food preservation or tobacco preservation.

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