A photo-triggered starch-based galangal essential oil liposome composite membrane, its preparation method and application

Abstract

A phototriggered starch-based galangal oil liposome composite membrane, its preparation method, and its application are disclosed. The specific steps are as follows: Citric acid-modified starch is used to prepare esterified starch; essential oil liposomes are prepared by thin-film dispersion, where the oil phase consists of soybean lecithin, cholesterol, galangal oil, and pheophytic chlorophyll a; PVA solution, esterified starch emulsion, glycerol, and photoresponsive galangal oil liposomes are mixed and stirred to obtain a uniformly mixed film-forming emulsion. The film-forming emulsion is then poured onto a glass plate, and a manual film-forming machine is used to coat the film. After drying, the phototriggered starch-based galangal oil liposome composite membrane is obtained. The composite membrane prepared by this invention uses PVA and esterified starch as substrates, and photosensitive liposomes as carriers to encapsulate galangal oil, creating a biodegradable active packaging composite membrane with controlled-release properties. It exhibits phototriggered essential oil release performance and can effectively extend the shelf life of chilled pork.

Description

Technical Field

[0001] This invention relates to the field of composite membrane technology, specifically to a phototriggered starch-based Alpinia galanga essential oil liposome composite membrane, its preparation method, and its application. Background Technology

[0002] With changes in consumers' living standards and consumption patterns, the quality and shelf life of refrigerated foods have become increasingly important. Polyvinyl alcohol (PVA) possesses excellent film-forming ability, miscibility, good tensile strength, and elongation properties, making it suitable for use in the food industry as a protective barrier for food products. In recent years, the performance of PVA-based packaging materials has been improved by fusing polysaccharides, proteins, and lipids from natural or renewable resources to form biocomposite polymers. Starch, a biodegradable and renewable polymer, can be combined with PVA to prepare composite films, which can reduce the biodegradation cycle of packaging materials, lower material costs, and improve the performance of single films. Modification of starch weakens the association of hydroxyl groups in starch macromolecules, significantly improving processing heat resistance and addressing the poor water resistance of native starch.

[0003] Pure starch / PVA films lack antibacterial, antioxidant, and antifungal properties. Therefore, adding natural ingredients as fillers to the starch / PVA matrix has significant application value in the field of active food packaging. Among these, biodegradable packaging materials loaded with essential oils can effectively inhibit the growth of microorganisms in fresh foods (such as chilled meat), extending their shelf life. Compared to the early stages of food storage, the later stages require packaging materials with higher bactericidal activity. Developing intelligent responsive packaging films by combining the intelligent release of active substances with external environmental factors has significant application value. Summary of the Invention

[0004] Technical problems solved: Addressing the challenges of existing technologies such as the difficulty in degrading packaging materials, the lack of antibacterial, antioxidant, and antifungal properties in existing composite films, the inability to intelligently release higher bactericidal activity in later stages, and the difficulty in preserving chilled meat, this invention proposes a photo-triggered starch-based galangal essential oil liposome composite film, its preparation method, and its application. The prepared composite film exhibits photoresponsive essential oil release, antioxidant, and antibacterial properties. Photo-stimulated composite film samples can effectively slow down the quality deterioration of chilled pork, solving the problem of quality deterioration during long-term storage of chilled meat.

[0005] Technical solution: A method for preparing a light-triggered starch-based galangal essential oil liposome composite membrane, the steps of which are as follows:

[0006] Step 1: Starch modification. Mix starch with citric acid aqueous solution (the reaction conditions are optimal at pH=3.5) and equilibrate. Then dry the mixture and place it in a reactor for reaction. Then wash the dried material thoroughly with distilled water to remove unreacted citric acid. Finally, dry the material to obtain modified starch.

[0007] Step 2: Preparation of photoresponsive galangal essential oil liposomes. The essential oil liposomes were prepared using a thin-film dispersion method. The oil phase mixture was dissolved in an organic solvent at a ratio of 3 g:100 mL. The solution was then rotary evaporated in a container to form a thin film on the inner wall. A 0.1 M PBS solution (pH = 7.2) was then added to the container and stirred continuously to obtain the photoresponsive galangal essential oil liposomes. The oil phase mixture consisted of soybean lecithin, cholesterol, galangal essential oil, and pheophytic chlorophyll a in a mass ratio of 200:100:100:3. The total volume ratio of the oil phase mixture and organic solvent to the aqueous phase was 1:2.

[0008] Step 3: Preparation of the composite membrane. Modified starch is prepared into modified starch emulsion. Then, PVA solution, modified starch emulsion, glycerol and photoresponsive ginger essential oil liposomes are mixed and stirred to obtain a uniformly mixed film-forming emulsion. The film-forming emulsion is then poured onto a glass plate and coated with a manual film scraper, followed by drying.

[0009] Preferably, the concentration of the citric acid aqueous solution in step one is 0.24 g / mL, the starch is potato starch, and the ratio of potato starch to citric acid aqueous solution is 4 g: 5 mL.

[0010] Preferably, in step one, the equilibrium temperature is 25℃ and the time is 18h; the drying temperature is 60℃ and the drying time is 7h; the reaction temperature is 130℃ and the reaction time is 4h; the drying temperature is 45℃ and the drying is carried out until the moisture content is 10±1%, and the degree of substitution of citric acid esterified starch in the modified starch is 0.125%.

[0011] Preferably, in step two, after forming a film on the inner wall, 2.5 g / L PVP is dissolved in 0.1 M PBS solution and added to the container with continuous stirring; the organic solvent is chloroform, and the rotary evaporation temperature is 35°C.

[0012] Preferably, the PVA solution in step three is an 8 wt% PVA aqueous solution, which is prepared by stirring PVA and distilled water at a temperature of 90°C and a rotation speed of 800 rad / min for 30 min.

[0013] As a preferred method, the modified starch emulsion is prepared as follows: the modified starch is mixed with distilled water and gelatinized in a water bath at 75°C for 20 min, with a concentration of 10 wt%.

[0014] Preferably, in step three, the mass ratio of PVA solution, modified starch emulsion, photoresponsive ginger essential oil liposomes and glycerol is 15:5:(2-8):2.

[0015] Preferably, in step three, the stirring temperature is 45°C, the stirring time is 1 hour, and the rotation speed is 700 rad / min; the drying temperature is 40°C, and the drying time is 3 hours.

[0016] A photo-triggered starch-based galangal essential oil liposome composite membrane was prepared by the above method. This membrane, using PVA and esterified starch as substrates and photosensitive liposomes as carriers to encapsulate galangal essential oil, is a biodegradable active packaging composite membrane with controlled release properties. It exhibits photo-triggered essential oil release performance and can effectively extend the shelf life of chilled pork.

[0017] Based on the above, a light-triggered starch-based galangal oil liposome composite membrane is used in the preparation of responsive antibacterial packaging films.

[0018] The pheophytic acid a used in this invention is a chlorophyll metabolite with low toxicity and high activity. It can serve as an excellent photosensitizer. Phosphochlorophyll a can generate singlet oxygen under red light excitation. It is hypothesized that this singlet oxygen further oxidizes and destroys the phosphodiester bonds in liposomes, thereby disrupting the liposome structure. Photoresponsive Alpinia galanga essential oil liposomes were prepared and modified with pheophytic acid a liposomes. Their structure and functional activity were characterized, and their release mechanism was elucidated, providing a theoretical basis for the stable and precise release of Alpinia galanga essential oil. The stimulus-response controlled release system is an intelligent, active substance delivery system that can induce the encapsulated system to respond through stimulus-based decomposition or morphological changes.

[0019] Beneficial effects: (1) From Figure 1 It can be seen that no phase separation occurred on the surface of the composite membrane blended with modified potato starch, photoresponsive galangal oil liposomes, and PVA, but its roughness value increased. This indicates that there is an interaction between the components of the mixed composite membrane and that they have good compatibility.

[0020] (2) Figure 3 and 4 It can be seen that the substitution of esterified starch leads to the PVA-Lip composite film exhibiting good degradation performance, with a large number of pores and cracks appearing on the surface after being buried in the soil.

[0021] (3) Figure 2 , 6 As can be seen from Figures 7 and 8, the prepared composite membrane exhibits photostimulated release characteristics and photoresponsive essential oil release, antioxidant, and antibacterial properties. Furthermore, the photostimulated composite membrane sample can effectively slow down the quality deterioration of chilled pork. Attached Figure Description

[0022] Figure 1 The following are surface (subscript 1) (×1000) and cross-sectional (subscript 2) (×5000) views of the composite films prepared in the embodiments and comparative examples of this invention. A: PVA; B: PVA-1 Lip; C: P 75 S 25 D: P9S1-1Lip; E: P 75 S 25 -1Lip;F:P 50 S 50 -1 Lip; G:P 25 S 75 -1 Lip; H:P 75 S 25 -2Lip;I:P 75 S 25 -3Lip;

[0023] Figure 2 Essential oil release curves of photosensitive Alpinia galanga essential oil liposome composite membranes prepared by citric acid esterified starch / PVA;

[0024] Figure 3 Scanning electron microscope (SEM) images (×1000) of photosensitive Alpinia galanga essential oil liposome composite membranes prepared by citric acid esterified starch / PVA after 35 days of degradation. A: PVA; B: PVA-1 Lip; C: P 75 S 25 D: P9S1-1Lip; E: P 75 S 25 -1Lip;F:P 50 S 50 -1 Lip; G:P 25 S 75 -1 Lip; H:P 75 S 25 -2Lip;I:P 75 S 25 -3Lip;

[0025] Figure 4 Degradation curves of photosensitive Alpinia galanga essential oil liposome composite membranes prepared by citric acid esterified starch / PVA;

[0026] Figure 5 Photograph of pork packaged in a photosensitive Alpinia galanga essential oil liposome composite membrane prepared by citric acid esterified starch / PVA / .

[0027] Figure 6 The effect of photosensitive Alpinia galanga essential oil liposome composite membrane prepared by citric acid esterified starch / PVA on the pH of pork;

[0028] Figure 7 The effect of citric acid esterified starch / PVA / photosensitive galangal essential oil liposome composite membrane on total bacterial count in chilled pork. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] Unless otherwise specified, all raw materials used in the examples in this specification are from commercially available products.

[0031] Example 1

[0032] PVA was mixed with distilled water to prepare an 8 wt% PVA solution, which was then placed in a magnetic stirrer. The stirrer temperature was set to 90°C and the speed to 800 rad / min. After 30 min, a homogeneous and transparent PVA solution was obtained. The PVA solution and glycerol were mixed at a mass ratio of 15:2 and magnetically stirred at 45°C (700 rad / min). The film-forming emulsion was poured onto a glass plate while hot and coated using a manual film scraper. The glass plate was then placed in a 40°C oven to dry for 3 h. The top composite film was carefully peeled off and the product was placed in a resealable bag for storage and labeled as PVA.

[0033] Example 2

[0034] S1) Modified potato starch

[0035] The pH of the solution was adjusted to 3.5 using 0.24 g / mL citric acid with 10 M NaOH. Potato starch (40 g) was mixed with 50 mL of the citric acid solution, and the suspension was equilibrated at 25 °C for 18 h. The mixture was then dried at 60 °C for approximately 7 h until the moisture content was 10% (w / w). The mixture was then reacted at 130 °C for 4 h. The sample was then thoroughly washed with distilled water to remove unreacted citric acid. The starch was then placed in a 45 °C oven to remove excess moisture, yielding citric acid-modified starch (moisture content approximately 10%).

[0036] S2) PVA was mixed with distilled water to prepare an 8 wt% PVA solution, which was then placed in a magnetic stirrer. The magnetic stirrer temperature was set to 90℃ and the speed to 800 rad / min. After 30 min, a homogeneous and transparent PVA solution was obtained. Citric acid-modified starch was mixed with distilled water and gelatinized in a 75℃ water bath for 20 min to prepare a 10 wt% gelatinized starch emulsion. The PVA solution: starch emulsion: glycerol were mixed at a mass ratio of 15:5:2 and magnetically stirred at 45℃ (700 rad / min). The film-forming emulsion was poured onto a glass plate while hot and coated with a manual film scraper. The glass plate was then placed in a 40℃ oven to dry for 3 h. The upper composite film was carefully peeled off and placed in a self-sealing bag for storage. It was labeled P. 75S 25 .

[0037] Example 3

[0038] S1) Modified potato starch

[0039] The pH of a solution containing 0.24 g / mL citric acid was adjusted to 3.5 using 10M NaOH. Potato starch (40 g) was mixed with 50 mL of the citric acid solution, and the suspension was equilibrated at 25 °C for 18 h. The mixture was then dried at 60 °C for approximately 7 h until the moisture content was 5-10% (w / w). The mixture was then reacted at 130 °C for 4 h. The sample was then thoroughly washed with distilled water to remove unreacted citric acid. The starch was then placed in a 45 °C oven to remove excess moisture, yielding citric acid-modified starch (moisture content approximately 10%).

[0040] S2) Preparation of light-responsive galangal essential oil liposomes

[0041] The mass ratio of soybean lecithin, cholesterol, galangal essential oil, and pheophytic acid a in the oil phase mixture was 200:100:100:3, and the ratio of the oil phase mixture to chloroform was 3:100 (g / mL). The aqueous phase consisted of 2.5 g / L PVP dissolved in 0.1 M PBS solution. The total volume ratio of the oil phase mixture and chloroform to the aqueous phase was 1:2. Essential oil liposomes were prepared using a thin-film dispersion method. The oil phase mixture was dissolved in chloroform, and then rotary evaporated in a container to form a thin film on the inner wall. The aqueous phase was then added to the container and stirred continuously to obtain photoresponsive galangal essential oil liposomes.

[0042] Preparation of S3) Composite Membrane

[0043] PVA was mixed with distilled water to prepare an 8 wt% PVA solution, which was then placed in a magnetic stirrer. The magnetic stirrer temperature was set to 90 °C and the rotation speed to 800 rad / min. After 30 min, a homogeneous and transparent PVA solution was obtained. Citric acid-modified starch was mixed with distilled water and gelatinized in a water bath at 75 °C for 20 min to prepare a 10 wt% gelatinized starch emulsion. The PVA solution:starch emulsion:glycerol was mixed at a mass ratio of 90:10:10, 75:25:10, 50:50:10, and 25:75:10, respectively, and magnetically stirred at 45 °C (700 rad / min). Then, 10 wt% photosensitive Alpinia galanga essential oil liposomes, with the sum of the PVA solution and starch emulsion added, were added and stirred for another 1 h to obtain a homogeneous film-forming emulsion. The film-forming emulsion was poured onto a glass plate while still hot, and the film was applied using a manual film scraper. The glass plate was then placed in a 40°C oven to dry for 3 hours. The top composite film was carefully peeled off and the plate was placed in a resealable bag for later use. The emulsion was labeled P9S1-1 Lip, P 75 S 25 -1 Lip, P50 S 50 -1 Lip and P 25 S 75 -1 Lip.

[0044] Example 4

[0045] Same as Example 3, except that the ratio of PVA solution: starch emulsion: glycerol is 75:25:10; the amount of photosensitive Alpinia galanga essential oil liposomes added is 20wt%, 30wt%, and 40wt% of the sum of PVA solution and starch emulsion, respectively, and named P... 75 S 25 -2 Lip, P 75 S 25 -3 Lip and P 75 S 25 -4 Lip.

[0046] Comparative Example 1

[0047] Same as Example 1, except that 10wt% of photosensitive Alpinia galanga essential oil liposomes were added to the PVA solution, named PVA-1Lip.

[0048] Specifically, the mass ratio of soybean lecithin, cholesterol, galangal essential oil, and pheophytic acid a in the oil phase mixture was 200:100:100:3, and the ratio of the oil phase mixture to chloroform was 3:100 (g / mL). The aqueous phase consisted of 2.5 g / L PVP dissolved in 0.1 M PBS solution. The total volume ratio of the oil phase mixture and chloroform to the aqueous phase was 1:2. The essential oil liposomes were prepared using a thin-film dispersion method. The oil phase mixture was dissolved in chloroform, and then rotary evaporated in a container to form a thin film on the inner wall. The aqueous phase was then added to the container and stirred continuously to obtain the photoresponsive galangal essential oil liposomes.

[0049] PVA was mixed with distilled water to prepare an 8 wt% PVA solution, which was then placed in a magnetic stirrer. The magnetic stirrer temperature was set to 90℃ and the rotation speed to 800 rad / min. After 30 min, a homogeneous and transparent PVA solution was obtained. The mixture of PVA solution, photoresponsive galangal oil liposomes, and glycerol was stirred magnetically at 45℃ (700 rad / min) in a mass ratio of 15:1.5:2. The film-forming emulsion was poured onto a glass plate while still hot and coated using a manual film scraper. The glass plate was then dried in a 40℃ oven for 3 h. The top composite film was carefully peeled off and the product was placed in a resealable bag for storage and labeled PVA-1Lip.

[0050] Performance tests were conducted on the products prepared in Examples 1-4 and Comparative Example 1:

[0051] 1) See the surface and cross-sectional characterization diagrams of the prepared composite membrane. Figure 1,from Figure 1 As can be seen in A (including A1 and A2), the pure PVA sample exhibits a uniform, smooth, and dense morphology. PVA maintains the uniformity and density of the film, with almost no detectable particles or cracks;

[0052] Figure 1 As can be seen from C (including C1 and C2), the substitution of esterified starch leads to an increase in the roughness of the composite membrane. When citric acid esterified starch is incorporated into PVA, undissolved white particles aggregate on the surface of the composite membrane. Due to the low compatibility between the components of the blended composite membrane, a rough, uneven, and fluctuating surface is formed. With the addition of starch, the cross-sectional texture of the membrane becomes uneven, rough, and wrinkled.

[0053] Figure 1 B (including B1 and B2) shows that no phase separation occurred on the surface of the blended composite membrane. The addition of liposomes did not significantly affect the surface uniformity and smoothness of the PVA composite membrane, which remained relatively smooth and flat. This indicates that uniformly sized liposomes can be evenly distributed in PVA with minimal aggregation and good compatibility. Appropriate addition of liposomes can improve the compatibility between starch and PVA through esterification. The membrane exhibited a rough surface but maintained uniformity and density, with almost no detectable particles or cracks. The smaller size of the liposomes can fill in incompatible areas of starch / PVA, increasing its integrity. The cross-section of the citric acid-esterified starch, liposome, and PVA composite membrane showed a uniform cross-sectional structure, indicating interactions and good compatibility between the composite membrane components. For P... 75 S 25 -1 Lip films are smoother than P films 75 S 25 There has been a significant improvement, but for P... 75 S 25 -2Lip and P 75 S 25 -3Lip sample, its surface is more P 75 S 25 -1 Lip exhibits a rough surface, but still maintains the uniformity and density of the film, with almost no particles or cracks detected.

[0054] 2) Water absorption rate determination

[0055] Place a 2×2cm sample in an oven at 50±2℃ for 24 hours until constant weight is achieved, and record the mass of the sample at this point as m. l The sample was then immersed in 25°C deionized water for 24 hours, ensuring complete immersion during this period. Afterward, the sample was removed, its surface moisture was wiped off with filter paper, and it was quickly weighed to a volume of m². The water absorption rate was calculated using the following formula:

[0056] Water absorption rate (%) = (m2 - m1) / m1 × 100

[0057] Water vapor barrier performance test

[0058] The unwrinkled composite membrane sample was sealed flat at the mouth of a 5×5cm weighing bottle. The weighing bottle contained 3g of completely dried CaCl2 (CaCl2 needs to be dried in an oven at 130℃ for 8 hours beforehand). The weighing bottle was then placed in a desiccator containing distilled water, and the weight gain of the precision monitoring system was monitored at 25℃. The calculation methods for water vapor transmission rate (WVTR) and water vapor transmission coefficient (WVP) are as follows:

[0059] WVTR(gm 2 ·s)=Δm / A×Δt

[0060] WVP(g / m2·s·Pa)=Δm×d / A×Δt×ΔP

[0061] In the formula, Δm represents the increase in volume (g) of the sample weighing bottle before and after weighing; A is the effective permeation area of ​​water vapor (m²). 2 ); d is the membrane thickness (m); Δt is the measurement time interval (s); ΔP represents the water vapor pressure difference across the membrane (Pa).

[0062] The test results are shown in Table 1.

[0063] Table 1. Water absorption and water vapor permeability of the composite membranes prepared in the examples and comparative examples.

[0064]

[0065] Note: Experimental data are expressed as mean ± standard deviation, and the experiment was repeated 3 times. Differences in means within different letter columns were statistically significant (p < 0.05).

[0066] Table 1 shows that the water absorption rate of the pure PVA membrane is 170.98%. When the ratio of PVA to esterified starch decreases, the water absorption rate of the composite membrane first decreases and then increases. The membrane sample with the highest water absorption rate (276.29%) is obtained when esterified starch replaces 25% of the PVA without adding liposomes. PVA more readily absorbs water molecules, thus exhibiting good water solubility. As the starch ratio increases, the two phases become unevenly mixed, and the water absorption rate increases again. Adding liposomes reduces the water absorption rate of the PVA membrane to 152.82%. When the PVA / starch ratio is fixed, the water absorption rate of the PVA membrane... 75 S 25 -2Lip and P 75 S 25 -3Lip compared to P 75 S 25The water absorption rate of -1 Lip is significantly reduced. There are two main reasons for this: (I) the hydrophobic compounds in the essential oil and liposomes are difficult to bind with water molecules; (II) a large number of intermolecular hydrogen bonds are formed between the components of the essential oil and liposomes and the PVA / starch membrane matrix, which limits the interaction between the membrane matrix and water molecules.

[0067] 3) Measurement of mechanical performance parameters

[0068] The mechanical properties of the membrane were evaluated by measuring tensile strength (TS) and elongation at break (EB) using a physical property testing instrument. A rectangular membrane sample (1.5 cm × 1 cm) was fixed between the upper and lower metal handles of the instrument. An A / TG probe was used, with a clamp spacing of 20 mm. The initial and running speeds were both 1 mm / sec. The TS and EB of the membrane were calculated using the following formula:

[0069] TS(MPa)=p / bd

[0070] EB(%) = (G - G0) / G0 × 100

[0071] In the formula, p represents tensile strength (N); b represents film width (mm); d represents film thickness (mm); G0 represents the original gauge length of the sample (mm); and G represents the distance between the gauge marks when the sample breaks (mm).

[0072] The mechanical properties of the thin film are shown in Table 2.

[0073] Table 2 Mechanical properties of the composite films prepared in the examples and comparative examples

[0074]

[0075] Note: Experimental data are expressed as mean ± standard deviation, and the experiment was repeated 3 times. Differences in means within different letter columns were statistically significant (p < 0.05).

[0076] As shown in Table 2, the tensile strength and elongation at break of the pure PVA film are 56.54 N / m. 2 It has a purity of 291.70% and good mechanical properties.

[0077] With the addition of starch, the tensile strength and elongation at break of the PVA film both decreased significantly. Adding more starch to PVA resulted in a brittle structure without any significant plastic deformation. The increased starch content led to a significant decrease in the flexibility of the blend film.

[0078] The addition of Alpinia galanga essential oil liposomes reduced the tensile strength of the membrane samples. However, the elongation at break of the PVA / starch membrane was less affected by the liposome content because the smaller liposomes can promote the formation of a continuous polymer network structure, leading to relaxation and stretching of the PVA membrane structure, thereby increasing the flexibility of the molecular chains and contributing to a slight increase in elongation at break.

[0079] 4) Photoresponsive essential oil release test

[0080] Test method: The composite membrane sample was placed in 10% light-protected alcohol and tested under 650nm infrared light (0.5mW / cm²). 2 Irradiation was performed for 10 minutes, followed by the removal of 1 mL of solution at each set time point and replacement with a corresponding simulated solution. Finally, the release value of Alpinia galanga essential oil was calculated using a UV spectrophotometer at 300 nm. The release model is as follows:

[0081] M t / M ∞ =kt

[0082] Among them, M t and M ∞ , respectively, represent the amount of Alpinia galanga essential oil released at time t and equilibrium, k is the release rate constant, and n is the release index indicating the nature of the release mechanism.

[0083] See results Figure 2 , Figure 2 China P 75 S 25 -CK is P 75 S 25 Only PVA and esterified starch; P 75 S 25 -2 Lip and P 75 S 25 The difference between -2Lip Light and the latter is that the latter is irradiated with infrared light.

[0084] from Figure 2 The results show that the release rate of free essential oil in the composite membrane sample is significantly higher than that in the sample with essential oil encapsulated by liposomes, indicating that liposome-loaded essential oil can reduce the influence of external conditions to a certain extent, exhibiting better resistance and protection. Furthermore, when the membrane is irradiated with infrared light, the amount of essential oil released increases compared to before, indicating that the photoresponsive liposomes encapsulated in the composite membrane matrix can achieve photoresponsiveness, thereby rapidly releasing the essential oil.

[0085] 5) Composite membrane degradation test

[0086] Test Method: The biodegradability of the membrane was evaluated using the soil burial method (GB / T 1034-2008). Pre-dried samples (m1) were cut into 20×20mm pieces and buried 10cm deep in level, flat soil (with large gravel and debris removed). Samples were removed from the soil every week, washed with distilled water, and then dried in a 60℃ oven for 20min until constant weight (m2). The mass loss of the sample over time was used to indicate the membrane degradation rate, calculated using the following formula:

[0087] Degradation rate (%) = ((m1-m2) / m1) × 100

[0088] See results Figure 3 .

[0089] Figure 3 SEM images of the film surfaces after degradation of all samples are shown. The PVA film surface is relatively smooth. The degradation of PVA is due to the disordered breakage of polymer chains caused by microbial attack. In addition, tertiary carbon atoms in PVA also undergo oxidative degradation, producing 1,3 diketone groups. Due to the complete crystal structure of PVA, its degradation is relatively slow.

[0090] Adding starch can effectively improve the degradation rate of PVA films. The degraded film surface exhibits shrinkage and curling, accompanied by cavities and pores. Because starch is a good food source for microorganisms and is hydrophilic, it promotes water absorption within the film, further creating a more favorable environment for microbial growth. Esterified starch substitution results in the composite film exhibiting good degradation performance, with numerous pores and cracks appearing on the surface after burial in soil.

[0091] Compared to PVA, the degradation rate of esterified starch / PVA / liposome films is significantly increased. This is because the addition of these substances affects the crystallization of the PVA composite film, making it more susceptible to microbial attack and degradation when in contact with water and soil. The degraded film surface exhibits shrinkage and curling, accompanied by cavities and pores.

[0092] Figure 4 The degradation rate of the composite membrane was shown, with the PVA membrane exhibiting a degradation rate of 13.58% after 35 days of soil burial. The addition of liposomes did not negatively impact the degradation of the PVA membrane. Regardless of the presence of liposomes, the addition of starch effectively increased the degradation rate of the PVA membrane and improved the degradation of P... 75 S 35 -3 Lip was found to have the highest degradation rate, at 49.6%.

[0093] 6) Fresh pork preservation test

[0094] Test method:

[0095] (1) pH

[0096] Fresh chicken breast was immediately sterilized to remove excess connective tissue and fat. The chicken pieces were then cut into small, roughly equal-sized pieces (3cm x 3cm, approximately 10 ± 0.1g). The cut chicken samples were randomly divided into 9 groups. The prepared membrane samples were individually packaged and refrigerated at 4℃ for quality testing. 3g of meat sample was mixed with 25mL of distilled water and homogenized. The pH value of the supernatant was then measured.

[0097] The composite membrane sample was placed in 10% light-protected alcohol and subjected to 650nm infrared light (0.5mW / cm²). 2 Irradiate for 10 minutes.

[0098] (2) Total bacterial count

[0099] Meat samples were cultured and counted at appropriate dilution ratios, referring to GB / T 4789.2—2016 "National Food Safety Standard - Microbiological Examination of Food - Determination of Total Colony Count".

[0100] See results Figure 5 , 6 and 7, Figure 5 This is a diagram of meat packaging using composite film. Figure 6 and 7 The PVA in the middle is the composite film prepared in Example 1; P 75 S 25 The composite membrane prepared in Example 2; P 75 S 25 -2 Lip and P 75 S 25 -4 Lip is the composite membrane prepared in Example 4; P 75 S 25 -2 Lip-Light and P 75 S 25 -4 Lip-Light uses 650nm infrared light (0.5mW / cm²). 2 The composite membrane prepared in Example 4 after irradiation.

[0101] Changes in pH value of chilled pork packaged in different materials at 4℃ are as follows: Figure 6 As shown. pH value is an important indicator reflecting the quality of chilled pork, and it is affected by the metabolic activities of the meat itself and microorganisms. During storage, the pH value of all groups of pork samples showed an overall upward trend. This is because the microbial activity in the meat samples and the meat's own endogenous enzymes decompose the proteins in the meat into ammonia-like alkaline substances. Among them, P... 75 S 25 The pH of the medium-sized pork samples increased the fastest, especially during the later stages of storage, significantly (p < 0.05) higher than that of other pork samples. The pH of the PVA samples was higher than that of the P samples.75 S 25 The sample maintained its quality well, and its levels were significantly lower than P after 7 days of storage. 75 S 25 The packaged pork samples showed improved pH levels, attributed to the dense structure of the PVA membrane leading to low permeability and preventing severe microbial growth and oxidation. The addition of essential oil liposomes significantly delayed the pH increase in the pork samples, with a pH significantly lower (p < 0.05) than that of PVA and PVA after 3 days of storage. 75 S 25 The pH of pork. There are extensive reports of different essential oils delaying the rise in pork pH, attributed to their antioxidant and antibacterial properties. Furthermore, exposure to light further leads to the release of essential oils, thus increasing their effect in delaying pH rise.

[0102] Figure 7 It can be seen that the packaging material with added essential oils is beneficial for maintaining a low total bacterial count in pork samples. Compared with the PS and PVA groups, the pork samples wrapped with essential oil films showed stronger antibacterial ability, with the total bacterial count remaining at the lowest level. On the 9th day of storage, the total bacterial count was 5.46 log CFU / g, which is lower than the national standard hygiene requirement for fresh and frozen poultry products (1×10⁶ CFU / g). Galangal essential oil can effectively inhibit the growth and reproduction of various pathogens, and its antibacterial activity is further enhanced by light exposure, resulting in optimal antibacterial performance.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a light-triggered starch-based galangal oil liposome composite membrane, characterized in that, The steps are as follows: Step 1: Starch modification. After mixing starch with citric acid aqueous solution and equilibrating, the mixture is dried and placed in a reactor for reaction. The dried material is then thoroughly washed with distilled water to remove unreacted citric acid, and then dried to obtain modified starch. Step 2: Preparation of photoresponsive galangal essential oil liposomes. The essential oil liposomes were prepared using a thin-film dispersion method. The oil phase mixture was dissolved in an organic solvent at a ratio of 3 g:100 mL. The mixture was then rotary evaporated in a container to form a thin film on the inner wall. A 0.1 M PBS aqueous solution was then added to the container and stirred continuously to obtain the photoresponsive galangal essential oil liposomes. The oil phase mixture consisted of soybean lecithin, cholesterol, galangal essential oil, and pheophytic chlorophyll a in a mass ratio of 200:100:100:

3. The total volume ratio of the oil phase mixture and organic solvent to the aqueous phase was 1:

2. Step 3: Preparation of the composite membrane. Modified starch is prepared into modified starch emulsion. Then, PVA solution, modified starch emulsion, glycerol and photoresponsive ginger essential oil liposomes are mixed and stirred to obtain a uniformly mixed film-forming emulsion. The film-forming emulsion is then poured onto a glass plate and coated with a manual film scraper, followed by drying.

2. The method for preparing a light-triggered starch-based galangal oil liposome composite membrane according to claim 1, characterized in that, In step one, the concentration of the citric acid aqueous solution is 0.24 g / mL, the starch is potato starch, and the ratio of potato starch to citric acid aqueous solution is 4 g: 5 mL.

3. The method for preparing a light-triggered starch-based galangal oil liposome composite membrane according to claim 1, characterized in that, In step one, the equilibrium temperature is 25℃ and the time is 18h; the drying temperature is 60℃ and the drying time is 7h; the reaction temperature is 130℃ and the reaction time is 4h; the drying temperature is 45℃ and the moisture content is dried to 10±1%.

4. The method for preparing a light-triggered starch-based galangal oil liposome composite membrane according to claim 1, characterized in that, In step two, after forming a film on the inner wall, 2.5 g / L PVP is dissolved in 0.1 M PBS solution and added to the container with continuous stirring; the organic solvent is chloroform, and the rotary evaporation temperature is 35 °C.

5. The method for preparing a light-triggered starch-based galangal oil liposome composite membrane according to claim 1, characterized in that, In step three, the PVA solution is an 8 wt% PVA aqueous solution, which is prepared by stirring PVA and distilled water at a temperature of 90 ℃ and a rotation speed of 800 rad / min for 30 min.

6. The method for preparing a light-triggered starch-based galangal oil liposome composite membrane according to claim 1, characterized in that, The modified starch emulsion is prepared as follows: the modified starch is mixed with distilled water and gelatinized in a water bath at 75°C for 20 min, with a concentration of 10 wt%.

7. The method for preparing a light-triggered starch-based galangal essential oil liposome composite membrane according to claim 1, characterized in that, In step three, the mass ratio of PVA solution, modified starch emulsion, photoresponsive ginger essential oil liposomes, and glycerol is 15:5:(2~8):

2.

8. The method for preparing a light-triggered starch-based galangal oil liposome composite membrane according to claim 1, characterized in that, In step three, the stirring temperature is 45 ℃, the stirring time is 1 h, and the rotation speed is 700 rad / min; the drying temperature is 40 ℃, and the drying time is 3 h.

9. A phototriggered starch-based Alpinia galanga essential oil liposome composite membrane prepared by the method of claim 1.

10. The application of the light-triggered starch-based galangal essential oil liposome composite membrane according to claim 9 in the preparation of responsive antibacterial packaging films.

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