Low-moisture-absorption heat-sealing edible instant packaging film as well as preparation method and application thereof

Abstract

The invention relates to the field of food packaging, and discloses a low-moisture-absorption heat-sealing instant packaging film as well as a preparation method and application thereof. Pulullan and carrageenan serve as film forming matrixes, mannitol is added to serve as an auxiliary, after degassing and defoaming, the mixture is poured into a mold to form a film, and the film is dried, uncovered and balanced, the mass of the carrageenan accounts for 6-10% of the mass of the pulullan, and the mass of the mannitol accounts for 15-20% of the total mass of dry substances of the pulullan and the carrageenan. According to the present invention, the heat-sealability and the food safety are provided while the good instant solubility is maintained, the barrier property is improved, the hygroscopicity and the storage stability are improved, and the heat-sealability and the food safety are provided, such that the heat-sealability and the food safety are provided, and the heat-sealability and the storage stability are improved.

Description

Technical Field

[0001] This invention relates to the field of food packaging, specifically to a low-moisture-absorbing heat-sealable edible quick-dissolving packaging film, its preparation method, and its application. Background Technology

[0002] With the accelerating pace of modern food industry and urbanization, the demand for packaging materials for convenience foods is growing. Currently, the market is dominated by non-degradable plastic packaging. This type of packaging needs to be removed and discarded after use, which not only increases solid waste emissions but also poses food safety risks such as microplastic migration during high-temperature cooking or long-term storage, hindering the development of a green and safe food industry.

[0003] To reduce the use of traditional plastics, bio-based edible films have attracted widespread attention. Current technologies primarily utilize hydrophilic polymers such as starch, protein, and other polysaccharides to prepare films for encapsulating seasonings and functional powders. While these films can dissolve rapidly in hot water and exhibit some film-forming properties, their high hygroscopicity, stability, and poor storage properties are due to the hydrophilic nature of the bio-based material. Under high relative humidity, the films easily absorb water, soften, and clump together, leading to moisture absorption and clumping of the packaged goods, affecting consumer appearance and food safety. Furthermore, moisture fluctuations reduce the film's mechanical strength and barrier properties, limiting its application in room temperature circulation and long-term storage. On the other hand, industrial packaging production typically relies on heat sealing processes for bag shaping and sealing, thus placing certain requirements on the heat-sealing characteristics of the encapsulating film. Films capable of rapid heat sealing and possessing sufficient sealing strength are better suited to meet the requirements of food packaging.

[0004] Current research has attempted to improve the hygroscopicity and heat-sealing properties of edible films through methods such as composite hydrophobic substances, cross-linking modification, or multilayer structures. However, these methods often suffer from problems such as complex formulation systems, difficulty in scaling up processes, high raw material costs, or adverse effects on the solubility of the contents. Overall, existing technologies lack an edible, quick-dissolving packaging film that exhibits low hygroscopicity, can be adapted to conventional heat-sealing equipment while maintaining high sealing strength, and can rapidly dissolve and release the contents during use. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention proposes a low-moisture-absorbing, heat-sealable, edible, and quick-dissolving packaging film. This invention uses pullulan and carrageenan in a compound, with mannitol added as an additive. The resulting packaging film exhibits low moisture absorption and excellent barrier properties, making it highly valuable for use in convenience food packaging.

[0006] To solve the above-mentioned technical problems, the present invention is specifically implemented through the following technical solutions: The first aspect of this invention provides a low-moisture-absorbing heat-sealable edible instant packaging film. The film uses pullulan and carrageenan as film-forming matrices, and adds mannitol as an auxiliary agent. After degassing and defoaming, the film is poured into a mold to form a film, dried, peeled off, and balanced. The mass of carrageenan is 6-10% of the mass of pullulan, and the mass of mannitol is 15-20% (w / w) of the total dry matter of pullulan and carrageenan.

[0007] A second aspect of this invention provides a method for preparing a low-moisture-absorbing, heat-sealable, edible, and quick-dissolving packaging film, comprising the following steps: (1) Preparation of pullulan polysaccharide solution: Pullulan polysaccharide was added to deionized water and stirred evenly to obtain a pullulan polysaccharide solution with a concentration of 2-4%; (2) Preparation of carrageenan solution: Carrageenan is added to deionized water and stirred evenly at a temperature of 60-80℃ to obtain a carrageenan solution with a concentration of 0.5-1.5%; (3) Mix the pullulan polysaccharide solution obtained in step (1) and the carrageenan solution obtained in step (2), wherein the mass of carrageenan is 6-10% of the mass of pullulan polysaccharide, and add mannitol at 15-20% (w / w) of the total dry matter of pullulan polysaccharide and carrageenan, and stir evenly to obtain a compound film-forming solution. (4) The compound film-forming solution is degassed and defoamed by ultrasonic treatment to obtain a uniform compound film-forming solution.

[0008] (5) Pour the degassed and defoamed compound film-forming solution into a mold for drying and film formation. After peeling off the film, the pullulan polysaccharide / carrageenan low moisture absorption heat-sealing quick-dissolving packaging film is obtained.

[0009] Further, in step (3), the mass of the carrageenan solution is 6%-8% of the mass of the pullulan polysaccharide solution.

[0010] Further, in step (4), preferably, the ultrasonic treatment for degassing and defoaming is performed at 20-40 kHz and 200-400W for 10-20 minutes.

[0011] Further, the drying conditions in step (5) are: drying at 20-25℃ and 40-50% RH for 24-30 h; and equilibration conditions are equilibration at 20-25℃ and 45-55% RH for 48-50 h.

[0012] The third aspect of this invention provides the application of the pullulan / carrageenan edible low-hygroscopic quick-dissolving heat-sealable film prepared above in convenience food packaging.

[0013] According to the above scheme, the convenience food is a powdered or block-shaped food. Specifically, it can be peptide powder, such as bovine bone collagen peptide powder, solid beverage powder, coffee powder, milk powder, instant soup powder, seasoning powder and fortified powder, seasoning blocks, etc.

[0014] According to the above scheme, the specific application is as follows: the low moisture absorption heat-sealable edible instant packaging film is heat-sealed into a three-side sealed packaging bag, the convenience food is put into the packaging bag and then heat-sealed.

[0015] According to the above scheme, the heat sealing temperature is 145-165°C, the heat sealing time is 3.5-4.5 s, and the heat sealing pressure is 0.15-0.25 MPa. According to the above scheme, when the low moisture absorption heat-sealed edible quick-dissolving packaging film is put into hot water at 80-100℃, the packaging film can be fully dissolved within 30-60 seconds without leaving obvious film residue, without affecting the taste of the contents, and can realize the convenient use of convenience foods.

[0016] This invention aims to develop a low-hygroscopic, heat-sealable, edible, and quick-dissolving film suitable for convenience food packaging. While polyhygroscopic polymers (PULs) are suitable for edible film preparation due to their film-forming properties and water solubility, their high hygroscopicity limits their practical application in convenience food packaging. To address this, while ensuring water solubility and edibility, we selected a series of water-soluble, naturally edible biomolecules and aimed to reduce hygroscopicity through compounding, while maintaining the film's heat-sealing properties, water solubility, and edibility. Extensive research revealed that compounding CARs and PULs resulted in the most significant reduction in hygroscopicity while maintaining good water solubility and meeting packaging requirements for heat-sealing strength. Further research on the PUL / CAR compounding ratio showed that as the proportion of CARs in the film increased, the film's hygroscopicity decreased. Furthermore, when PUL and CARs were in a certain ratio (CAR mass being 6-10% of PUL mass), the interaction between PUL and CARs formed a specific network structure, which not only reduced the film's hygroscopicity but also enhanced its mechanical properties. Furthermore, further studies in the PUL and CAR systems using different additives revealed that films prepared with mannitol exhibited superior performance in all aspects, with a more compact structure that helped reduce moisture diffusion. The molecular symmetry of mannitol also facilitated the formation of microcrystalline domains, promoting a more ordered arrangement within the film and thus enhancing its mechanical strength and heat-sealing properties. Ultimately, this invention, through the synergistic effect of pullulan and carrageenan combined with mannitol, prepared a film with excellent heat-sealing properties, low moisture absorption, and good mechanical properties. The resulting film can completely dissolve within 30-60 seconds and possesses heat-sealing, water-soluble, and edible characteristics, along with good barrier properties, making it particularly suitable for convenience food packaging.

[0017] The beneficial effects of this invention are: This invention uses pullulan and carrageenan in combination, with mannitol added as an adjuvant. The resulting encapsulating film maintains good instant solubility while also possessing heat-sealability and food safety, and improves barrier properties. It is used for convenient food packaging and can improve hygroscopicity and storage stability. Attached Figure Description

[0018] Figure 1 Hygroscopicity of PUL composite films with different biomacromolecules; Figure 2 Hygroscopicity (A) and mechanical properties (B) of PUL and CAR films with different ratios, where EAB% is elongation at break and TS is tensile strength; Figure 3 Moisture absorption rate (A) and moisture content (B) of different types and contents of polyol P-CAR films; Figure 4 Water contact angles of different types of polyol P-CAR films; Figure 5 Water vapor permeability and oxygen permeability of different types of polyol P-CAR films; Figure 6 Heat-sealing strength of polyol P-CAR films of different types and contents; Figure 7 Microstructure of different types of polyol P-CAR films; Figure 8 FTIR spectra of different types of polyol P-CAR films; Figure 9 XRD patterns of different types of polyol P-CAR films; Figure 10 The application of different types of polyol P-CAR films in peptide powder packaging is shown in Figure A, which is the appearance of the packaging; Figure B is the solution state after dissolution; and Figure C is the dissolution time. Figures DE show the moisture absorption rates of the packaged peptide powder at ambient humidity of 53%RH and 81%RH, respectively. Figures F and G show the moisture absorption rates of the membranes packaging the peptide powder at ambient humidity of 53%RH and 81%RH, respectively.

[0019] Figure 1 , Figure 2 , Figure 3 , Figure 5 , Figure 6 and Figure 10 Different lowercase letters under the same indicator represent significant differences (P < 0.05). Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments in order to better understand the technical solution.

[0021] Implementation Case 1: PUL in combination with different biomacromolecules PUL was prepared into 3% solutions with selected biomolecules. 80 mL of PUL solution and 20 mL of the selected biomolecule solution were mixed thoroughly to prepare a film-forming solution. Then, 15% glycerol (dry weight) was added, and the mixture was stirred for 3 h. After stirring, the film-forming solution was defoamed using an ultrasonicator. 20 mL of the film-forming solution was poured into a mold (10 cm × 10 cm) and dried at 25°C and 40% (RH) for 24 h. After removing the film, it was equilibrated in a constant temperature and humidity chamber at 25°C and 50% (RH) for 48 h for further characterization. The selected biomolecules were soybean soluble polysaccharides, gelatin, soy protein isolate, pea protein, sodium alginate, carrageenan, carboxymethyl chitosan, and sodium carboxymethyl cellulose. The PUL-coated membranes were named PS, P-GEL, P-SPI, P-PP, P-SA, P-CAR, P-CMCS, and P-CNA, respectively.

[0022] Depend on Figure 1 It is evident that, compared to a single PUL membrane, most polysaccharides and proteins did not reduce the membrane's hygroscopicity. Only gelatin and CAR reduced the membrane's hygroscopicity, with CAR showing the most significant reduction. Under different environmental humidity conditions, CAR was chosen to be blended with PUL, and their blending ratio was further investigated.

[0023] Implementation Case 2: Different Ratios of PUL and CAR PUL was prepared into a 3% solution, and CAR into a 1% solution. The CAR concentration was 2-14% of the PUL concentration. The mixture was thoroughly mixed, and then 15% (dry weight) of glycerol was added. The mixture was stirred for 3 hours, and after stirring, it was defoamed using an ultrasonicator to obtain the film-forming solution. 20 mL of the film-forming solution was poured into a mold (10 cm × 10 cm) and dried at 25°C and 40% (RH) for 24 hours. After removing the film, it was equilibrated in a constant temperature and humidity chamber at 25°C and 50% (RH) for 48 hours for further characterization. The CAR concentration relative to PUL was set to 2%, 4%, 6%, 8%, 10%, 12%, and 14%, and named 2%CAR, 4%CAR, 6%CAR, 8%CAR, 10%CAR, 12%CAR, and 14%CAR, respectively.

[0024] As the proportion of CAR in the membrane increases, the hygroscopicity of the membrane decreases. Figure 2 A); At the same time, PUL and CAR interact to form a specific network structure. At a certain ratio (CAR mass is 6-10% of PUL mass), not only is the hygroscopicity of the membrane reduced, but the mechanical properties of the membrane are also enhanced. Figure 2 B). Therefore, the blending ratio of PUL to CAR in this invention is 50:3-50:5, that is, the mass of CAR is 6-10% of the mass of PUL.

[0025] Implementation Case 3: Types and Contents of Polyols Weigh 3 g of PUL and add it to 76 mL of deionized water. Stir at 270 r / min for 3 h to obtain a PUL solution. Weigh 1 g of CAR and dissolve it in 100 mL of deionized water. Stir at 65℃ and 270 r / min for 3 h to obtain a 1% CAR solution. P-CAR films and different types and amounts of polyols (according to the total percentage of pullulan and carrageenan dry matter) are prepared by casting, using distilled water as the solution. Mix 76 mL of PUL solution and 24 mL of CAR solution to prepare a film solution. Then add different amounts (0%, 10%, 15%, 20%) of glycerol, xylitol, sorbitol, and mannitol, stir for 3 h, and defoam using an ultrasonic machine after stirring. 20 mL of the film-forming solution was poured into a square film-forming dish (10 cm × 10 cm) and dried at 25 °C and 40% (RH) for 24 h. After removing the film, it was equilibrated in a constant temperature and humidity chamber at 25 °C and 50% (RH) for 48 h for further characterization. P-CAR films with added glycerol, xylitol, sorbitol, and mannitol were named xG-P-CAR, xX-P-CAR, xS-P-CAR, and xM-P-CAR, respectively, where x represents the corresponding polyol content in each film. For example, 10G-P-CAR represents a P-CAR film containing 10 wt% glycerol.

[0026] Experimental Example 1: Appearance, transmittance, and dissolution time Color difference: The color parameters of the film, including L* (brightness), a* (redness / greenness), and b* (yellowness / blueness), were measured using a colorimeter. A standard white plate was used as a control, and three points were randomly measured for each sample. The total color difference (ΔE) was calculated using the following formula:

[0027] In the formula: L* is the sample brightness, a* is the sample red-green hue, b* is the sample yellow-blue hue, L0 is the standard white plate brightness, a0 is the standard white plate red-green hue, and b0 is the standard white plate yellow-blue hue.

[0028] Transmittance: The membrane was cut into rectangular strips (5 mm × 40 mm) and placed in the test cell of a full-spectrum UV spectrophotometer. The UV-Vis transmission spectrum was recorded by scanning in the wavelength range of 200–800 nm.

[0029] Dissolution time: Cut the membrane sample into 20 cm × 20 cm pieces, add 30 mL of deionized water at 85℃ (the typical water temperature for brewing instant noodles, instant coffee and other fast food), and stir at a constant speed (700 rpm) until completely dissolved, and record the dissolution time.

[0030] All films exhibited UV blocking rates in the 200–280 nm wavelength range. In color difference experiments, the ΔE values ​​of all films were less than 5, indicating that color changes were difficult to distinguish with the naked eye. Furthermore, all samples dissolved completely within 60 seconds, demonstrating good water solubility. The color of the film directly affects its sensory quality in packaging materials. The prepared film exhibits good transparency and high visual quality, making it suitable for portable packaging materials and demonstrating good practical application potential.

[0031] Experimental Example 2: Hygroscopicity and Moisture Content The membrane was cut into 20 mm × 20 mm samples and weighed. The samples were then laid flat on a watch glass and placed in a desiccator with a relative humidity of 81% created using a saturated ammonium sulfate solution. Vaseline was applied to the ground glass joints to ensure a good seal. After 72 hours at room temperature (25°C), the mass of the samples was weighed. The moisture absorption rate was calculated as follows:

[0032] Where: W0, W n These represent the mass (g) of the sample before and after placement. Dry the weighing bottle to constant weight in a 105°C forced-air drying oven. Weigh 1 g of the membrane and place it in the weighing bottle, then dry it again to constant weight in a 105°C forced-air drying oven. The moisture content is calculated as follows:

[0033] In the formula: m1 is the initial weight of the weighing bottle containing the membrane, g; m2 is the weight of the weighing bottle containing the membrane after drying, g.

[0034] The moisture absorption rate and moisture content of P-CAR films with different types and amounts of polyols are shown in the figure. Figure 3 The moisture absorption rate of the P-CAR film is approximately 12.60%. The overall moisture absorption decreases after the addition of polyols, increasing with dosage (10–20 wt%), following the order of glycerol > xylitol > sorbitol > mannitol. Among the four polyols, glycerol and sorbitol have higher moisture content, while xylitol and mannitol have lower moisture content; for example, 15 wt% glycerol has an MC of approximately 13.41%, and 15 wt% mannitol has an MC of approximately 11.21%. In summary, mannitol inhibits moisture absorption and weight gain while maintaining a low initial water content, which is beneficial for improving the moisture barrier properties and storage stability of the film of this invention.

[0035] Experiment Example 3: Water Contact Angle The water contact angle of the membrane was measured using an optical contact angle meter. The membrane (10 mm × 20 mm) was placed on a glass slide, 10 μL of deionized water was added, and the image was recorded using a high-speed camera.

[0036] Water contact angle of P-CAR films with different types and amounts of polyols, such as Figure 4 As shown, the P-CAR film has a water contact angle of approximately 79°, exhibiting a moderately hydrophilic surface. Adding 10–20 wt% polyols reduces the overall water contact angle and enhances surface wettability. Adding glycerol and sorbitol lowers the water contact angle to approximately 58–60°. Adding xylitol and mannitol significantly modulates surface wettability, with an angle of approximately 62–66°. Comparatively, these methods improve processability while avoiding excessive hydrophilicity, thus enhancing storage and usage stability and demonstrating greater application potential.

[0037] Experiment Example 4: Water vapor transmission rate and oxygen transmission rate The membrane was cut into square samples (40 mm × 40 mm). 3 g of anhydrous silica gel was placed in a dried, constant-weight weighing bottle, and the membrane was attached to the bottle opening and sealed with a mixture of beeswax and paraffin. The weighing bottle was placed in a desiccator filled with distilled water (100% RH), and the weight of the bottle was recorded every 24 hours for one week. The water vapor transmission rate was calculated as follows:

[0038] In the formula: Δm is the increase in weight of the weighing bottle, g; x is the thickness of the film, cm; S is the test area of ​​the film, cm². 2 t is the time it takes for the weighing bottle to gain weight, in seconds; ΔP is the vapor pressure difference across the membrane, in Pa.

[0039] The oxygen permeability of the antibacterial membrane was determined using a reducing agent reaction method. The membrane was cut into square samples (40 mm × 40 mm) and attached to a weighing bottle (2.5 cm in diameter, 4.0 cm in height) containing 3 g of FeSO4·7H2O, then sealed with rubber and paraffin wax. The weighing bottle was placed in a desiccator containing saturated NaCl solution (75% RH), and the weight of the bottle was recorded every 24 hours for one week. The oxygen permeability was calculated as follows:

[0040] In the formula: Δm is the weight gain of the weighing bottle, g; x is the thickness of the film, cm; t is the time it takes for the weighing bottle to gain weight, s; S is the test area of ​​the film, cm². 2 .

[0041] For the water vapor transmission rate (WVP) and oxygen transmission rate (OP) of P-CAR films with different types of polyols, see [link to relevant data]. Figure 5 Among the four polyols, the P-CAR film with added mannitol exhibited the lowest WVP and lower OP, with a WVP of 1.34 × 10⁻⁶ at a 15 wt% addition. - ¹² g·cm / cm²·Pa·s, which is superior to other groups.

[0042] Experimental Example 5: Heat Seal Strength The film was cut into rectangles of 15 mm × 80 mm, and two films were aligned face to face. A heat-sealing tester was used to heat-seal the films, setting the parameters as follows: heat-sealing temperature 150°C, heat-sealing time 4 s, and heat-sealing pressure 0.2 MPa. The heat-sealed sample was unfolded 180° and fixed at both ends to the probe of a tensile testing machine. The initial distance between the clamps was 60 mm, and the testing speed was 300 mm / min. The maximum load at which the sample broke was recorded. The heat-sealing strength was calculated as follows:

[0043] In the formula: F is the maximum load, N; W is the membrane width, mm.

[0044] The heat-sealing strength of P-CAR films with different types and contents of polyols is as follows: Figure 6 As shown, the heat-sealing strength of the P-CAR film is approximately 0.76 N / 15 mm. The addition of polyols resulted in differentiated increases in heat-sealing strength depending on the type and amount: the glycerol group showed a smaller increase; the xylitol and sorbitol groups showed a continuous upward trend with increasing polyol content, reaching a maximum of approximately 1.45–1.94 N / 15 mm; the mannitol group performed best, achieving a stable heat-sealing strength of 2.34 N / 15 mm at 15 wt%, significantly better than the groups without added polyols and other polyols. These results indicate that mannitol can effectively improve the heat-sealing strength of the film of this invention, making it suitable for applications requiring high heat-sealing strength, such as instant food pouches.

[0045] Experimental Example 6: Thickness and Mechanical Properties Thickness measurement: Five locations were randomly selected on the membrane, and the thickness was measured using a thickness gauge. The average value of the results was taken.

[0046] The membrane was cut into rectangular strips of 20 mm × 80 mm. The initial clamping distance was 40 mm, and the testing speed was 50 mm / min. The maximum load and fracture deformation were recorded. The tensile strength and elongation at break were calculated using the following two formulas:

[0047]

[0048] In the formula: F is the maximum load that the membrane withstands at the instant of rupture, in N; S is the cross-sectional area of ​​the membrane, in m.2 L is the length of the membrane when it breaks, in mm; L0 is the original length of the membrane, in mm.

[0049] As shown in Table 1, the addition of different types and amounts of polyols significantly affects the mechanical properties of P-CAR films. Among them, the addition of mannitol has the most significant effect on improving the mechanical properties of the films. In the range of 15-20 wt%, the tensile strength and elongation at break of the films are significantly improved, showing superior overall mechanical properties compared to other polyols.

[0050] Table 1. Effects of polyol type and content on P-CAR film thickness and mechanical properties

[0051] Note: Different letters (a, b, c...) in the same column indicate significant differences. p <0.05).

[0052] Experimental Example 7: Structural Features of Membranes Microscopic morphology: The membrane sample was cut into 20 mm × 20 mm pieces, and the surface and cross-sectional morphology of the membrane were photographed at 2000x magnification using a scanning electron microscope. The cross-section was subjected to liquid nitrogen brittle fracture and gold sputtering treatment.

[0053] Fourier Transform Infrared (FTIR) spectroscopy: The membrane sample was dried, potassium bromide was added and thoroughly ground and mixed, then pressed into a transparent sheet. The potassium bromide sheet was used as a blank control. FTIR was performed using a Fourier transform infrared spectrometer in the wavenumber range of 4000–600 cm⁻¹. -1 The scan was performed 64 times.

[0054] X-ray diffraction (XRD): The film sample was analyzed using an X-ray diffractometer with a scanning diffraction angle range of 5° – 60° and a scanning rate of 2° / min.

[0055] The microstructure and molecular interactions of P-CAR films with different types of polyols, such as Figure 7 , Figure 8 and Figure 9 As shown. The PUL film without added polyols has a smooth and dense surface. Even after compounding with CAR, the P-CAR film still shows no obvious pores, indicating good compatibility. The film surface becomes smoother overall after adding polyols. The glycerol, xylitol, and sorbitol groups show uniformity without obvious delamination, but some microcracks appear locally. The mannitol group has a complete surface and the densest cross-section, which helps reduce moisture diffusion channels and thus lowers the film's moisture absorption rate. FTIR results show that the P-CAR film without added polyols has a moisture absorption rate of approximately 3611 cm⁻¹. -1 An OH stretching vibration peak appeared at the [location missing]. This peak showed a slight shift upon the introduction of polyols, with the peak shifting to approximately 3527 cm⁻¹ in the film containing mannitol (15M-P-CAR).-1 This indicates that it forms stronger hydrogen bonds with P-CAR and reconstructs the internal hydrogen bond network. In the XRD pattern, after the addition of mannitol, 15M-P-CAR shows a relatively broad peak at about 20°, indicating the existence of certain microcrystalline structural domains in the film. This may be due to the high molecular symmetry of mannitol, which helps to promote a more ordered arrangement of polymer chains, thereby giving the film better structural stability, barrier properties, as well as mechanical and heat-sealing properties.

[0056] Example 8: Application of membrane in peptide powder packaging Taking peptide powder as an example, specific packaging applications were studied using different films. The film samples were cut into 60 cm × 60 cm rectangular blocks, and 5 g of peptide powder was sealed in each film using a heat sealer. Figure 10 A represents the actual appearance of the packaging bag after the peptide powder was filled using the packaging film of this invention. Unsealed samples served as a control group. The sealed peptide powder was stored in two different relative humidity environments (53% RH and 81% RH) for 7 days, with sample weight recorded every 24 hours during this period. The average moisture absorption of the peptide powder was calculated using the following formula:

[0057] In the formula: W1 and W2 represent the weights of the peptide powder samples before and after moisture absorption, respectively, in g.

[0058] To simulate the convenient and rapid dissolution performance in actual use, a dissolution test was conducted on the packaging film containing peptide powder. The sealed film packaging was placed in 30 mL of deionized water at 85°C and stirred at 700 rpm / min until completely dissolved (no visible residue within 60 s). Figure 10 B illustrates the state where the membrane and peptide powder dissolve rapidly after the packaging bag is immersed in hot water.

[0059] Results of using P-CAR films with different types of polyols for peptide powder packaging: Figure 10 As shown in Figure C, all films and their encapsulated peptide powders completely dissolved within 2 minutes in hot water at 85°C, leaving a clear and transparent solution with no film residue. In the hygroscopicity test, the 15M-P-CAR film with added mannitol dissolved within 53% RH during a 7-day storage period. Figure 10 F) and 81%RH Figure 10 G) The moisture absorption rate was the lowest in both different humidity environments, and the packaged peptide powder also showed the lowest moisture absorption rate. Figure 10 (D and E). For example... Figure 10E. After 7 days of storage in a relative humidity environment (81% RH), compared with P-CAR film without additives, 15M-P-CAR film with added mannitol was used to package peptide powder. The moisture absorption rate of the peptide powder contents was significantly reduced from 11.40% to 5.87%, which was also better than other films.

[0060] This invention uses pullulan and carrageenan in combination, with mannitol added as an adjuvant. The resulting encapsulating film effectively inhibits the moisture absorption of the film itself and its contents, such as peptide powder, thus improving packaging stability. After 7 days of storage at room temperature (20-25°C) and relative humidity of 81%, the packaging film remains smooth and unadhesive, without significant softening or curling. The contents inside the packaging bag remain free of lumps and maintain good flowability. When used for convenience food packaging, it effectively reduces the risk of moisture absorption and clumping of the contents during storage, helping to maintain product quality during storage.

[0061] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A low-moisture-absorbing, heat-sealable, edible, and quick-dissolving packaging film, characterized in that: The membrane uses pullulan and carrageenan as the film-forming matrix, with mannitol added as an auxiliary agent. After degassing and defoaming, it is poured into a mold to form a film, dried, peeled off, and balanced. The mass of carrageenan is 6-10% of the mass of pullulan, and the mass of mannitol is 15-20% of the total dry matter of pullulan and carrageenan.

2. The method for preparing a low-moisture-absorbing, heat-sealable, edible, and quick-dissolving packaging film according to claim 1, characterized in that: Includes the following steps: (1) Preparation of pullulan polysaccharide solution: Pullulan polysaccharide was added to deionized water and stirred evenly to obtain a pullulan polysaccharide solution with a concentration of 2-4%; (2) Preparation of carrageenan solution: Carrageenan is added to deionized water and stirred evenly at a temperature of 60-80℃ to obtain a carrageenan solution with a concentration of 0.5-1.5%; (3) Mix the pullulan polysaccharide solution obtained in step (1) and the carrageenan solution obtained in step (2), wherein the mass of carrageenan is 6-10% of the mass of pullulan polysaccharide, and add mannitol at 15-20% (w / w) of the total dry matter of pullulan polysaccharide and carrageenan, and stir evenly to obtain a compound film-forming solution. (4) The compound film-forming solution is degassed and defoamed by ultrasonic treatment to obtain a uniform compound film-forming solution; (5) Pour the degassed and defoamed compound film-forming solution into a mold for drying and film formation. After peeling off the film, the pullulan polysaccharide / carrageenan low moisture absorption heat-sealing quick-dissolving packaging film is obtained.

3. The preparation method according to claim 2, characterized in that: In step (3), the mass of the carrageenan solution is 6%-8% of the mass of the pullulan polysaccharide solution.

4. The preparation method according to claim 2, characterized in that: In step (4), the ultrasonic treatment for degassing and defoaming is performed at 20-40 kHz and 200-400 W for 10-20 minutes.

5. The preparation method according to claim 2, characterized in that: The drying conditions in step (5) are: drying at 20-25℃ and 40-50% RH for 24-30 h; and equilibration conditions are: equilibration at 20-25℃ and 45-55% RH for 48-50 h.

6. The application of the edible, quick-dissolving heat-sealable film as described in claim 1 in convenience food packaging.

7. The application according to claim 6, characterized in that: The convenience food mentioned is in powder or block form. Specifically, it can be peptide powder, solid beverage powder, coffee powder, milk powder, instant soup powder, seasoning powder, and fortified powder or seasoning block.

8. The application according to claim 6, characterized in that: Low-moisture-absorbing heat-sealable edible instant packaging film is heat-sealed into a three-side sealed packaging bag, into which the convenience food is placed and then heat-sealed.

9. The application according to claim 6, characterized in that: The heat sealing temperature is 145-165°C, the heat sealing time is 3.5-4.5 s, and the heat sealing pressure is 0.15-0.25 MPa.

10. The application according to claim 6, characterized in that: When the aforementioned low-moisture-absorbing heat-sealed edible quick-dissolving packaging film is placed in hot water at 80-100℃, the packaging film will fully dissolve within 30-60 seconds, leaving no obvious film residue.

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