A pH-responsive large galangal essential oil liposome composite film and a preparation method and application thereof

Abstract

The application discloses a pH response large galangal essential oil liposome composite film and a preparation method and application thereof, and belongs to the technical field of composite films.The preparation method steps are as follows: konjac glucomannan is subjected to octenyl succinic anhydride modification to obtain esterified konjac glucomannan; then, pH response large galangal essential oil liposomes are prepared; PVA, the esterified konjac glucomannan, the pH response large galangal essential oil liposomes and glycerol are stirred and mixed to obtain a mixed uniform film-forming emulsion; the film-forming emulsion is poured on a glass plate while hot, a hand-operated film scraper is used for scraping the film, then the glass plate is dried in an oven, and the upper composite film is carefully torn and placed in a self-sealing bag for storage and standby use.The application provides the pH response large galangal essential oil liposome composite film and the preparation method and application thereof, has the pH response controlled release characteristic, can realize accurate on-demand release of essential oil, and prolongs the shelf life of fruits and vegetables.

Description

Technical Field

[0001] This invention relates to the field of composite membrane technology, specifically to a pH-responsive galangal essential oil liposome composite membrane, its preparation method, and its application. Background Technology

[0002] As a synthetic biodegradable material, PVA is widely used as a packaging material due to its excellent film-forming ability, superior oxygen barrier properties, excellent mechanical properties, non-carcinogenicity, and good bioadhesive characteristics. Konjac glucomannan is a naturally abundant polysaccharide extracted from the perennial herbaceous plant konjac. Its main chain consists of D-mannose and D-glucose units linked by β-1,4- groups in a molar ratio of 1.6:1, and its side chains are linked by β-1,6-glycosyl groups. Because of its excellent biocompatibility, biodegradability, and good film-forming properties, konjac glucomannan is widely used in food packaging materials. Pure konjac glucomannan films have disadvantages such as low mechanical strength, poor antibacterial ability, and poor water resistance. The applicant's research has found that esterification modification can overcome these disadvantages. Therefore, blending PVA with esterified konjac glucomannan is a reasonable choice to improve the biodegradability of PVA and reduce the overall cost.

[0003] Packaging technology aims to extend the shelf life of food, making it more accessible, affordable, and attractive. Extended shelf life, guaranteed safety, and better quality are characteristics of packaging films, which can serve as a remedy to reduce post-harvest losses of fruits and vegetables. With the advent of the intelligent era, the function of food packaging has long since moved beyond its basic function. Due to the short shelf life of fresh food, shelf extension is necessary. Existing technologies utilize slow-release SO2 and other bactericides for fruit preservation. Various materials exhibiting physical stimulus responses (temperature, electricity, electrochemistry, light, magnetism, and ultrasound), chemical stimulus responses (pH, ion concentration, redox reactions), and biological stimulus responses (enzymes, glucose, inflammation) have been used to prepare efficient functional factor delivery systems. In the preparation of pH-responsive controlled-release systems, the introduction of ionizable functional groups—such as amino, carboxyl, and phosphate groups—allows these groups to be protonated or deprotonated at different pH levels, undergoing pH-dependent changes in physical or chemical properties (such as swelling rate or solubility), thereby achieving controlled release of functional factors. Preliminary research has shown promising results in the development of smart packaging films utilizing natural essential oils. However, there remains a gap in achieving precise, on-demand release of essential oils to extend the shelf life of fruits and vegetables, while simultaneously addressing the limitations of pH-responsive controlled-release properties and avoiding the volatility and instability inherent in antibacterial essential oils. Combining the release of essential oils with external environmental factors in the packaging process to create smart responsive packaging films holds significant application value. Summary of the Invention

[0004] Technical problems solved: In view of the technical problems of existing pure konjac glucomannan membranes, such as low mechanical strength, poor antibacterial ability, and poor water resistance, as well as the low level of intelligence of packaging films, the inability to accurately release essential oils on demand, and the volatile and unstable application limitations of antibacterial essential oils, this invention proposes a pH-responsive galangal essential oil liposome composite membrane, its preparation method and application, which has pH-responsive controlled release characteristics, can realize the accurate and on-demand release of essential oils, and extend the shelf life of fruits and vegetables.

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

[0006] Step 1. Octenyl succinic anhydride modification of konjac glucomannan: Konjac glucomannan and Na2CO3 were uniformly mixed, and ethanol solution and octenyl succinic anhydride were added under stirring to obtain a mixture. The mixture was placed in a microwave reactor and heated at 300W for 25 minutes, then cooled to room temperature. It was then mixed with an equal amount of ethanol solution, and the pH was adjusted to 6.5. The mixture was centrifuged and filtered, and washed with ethanol solution to remove octenyl succinic anhydride residue. The final solid part was dried at 40℃ to obtain esterified konjac glucomannan.

[0007] Step 2. The oil phase and its solvent were rotary evaporated at 35°C in a bottle to form a uniform lipid film layer. After being placed in a vacuum drying oven at room temperature for 12 hours, the aqueous phase and its solvent were mixed with the oil phase and its solvent at a volume ratio of 2:1. The mixture was fully hydrated in a water bath with ultrasound, centrifuged, and filtered to obtain pH-responsive Alpinia officinarum essential oil liposomes.

[0008] Step 3. Preparation of composite membrane: PVA solution, esterified konjac glucomannan solution, glycerol and pH-sensitive galangal essential oil liposome are stirred and mixed to obtain a uniform film-forming emulsion. The film-forming emulsion is poured onto a glass plate while hot and the film is scraped using a manual film scraper. The glass plate is then dried in an oven. The upper composite membrane is carefully torn off and placed in a self-sealing bag for storage.

[0009] Preferably, in step one, the amount of Na2CO3 added to the konjac glucomannan is 3wt%, the mass fraction of the ethanol solution is 30%, and the octenyl succinic anhydride is an octenyl succinic anhydride solution diluted five times with anhydrous ethanol (v / v). The volume ratio of the konjac glucomannan doped with Na2CO3, the ethanol solution, and the octenyl succinic anhydride solution in the mixture is 2:2:1.

[0010] Preferably, in step two, the oil phase consists of soybean lecithin, cholesterol, and galangal essential oil in a mass ratio of 2:1:1, with chloroform as the oil phase solvent and a ratio of 3g:100mL for the oil phase to the oil phase solvent; the aqueous phase consists of hexadecyltrimethylammonium bromide and γ-polyglutamic acid in a mass ratio of 2:1, with 0.1M PBS at pH=7 as the aqueous phase solvent and a ratio of 3g:800mL for the aqueous phase to the aqueous phase solvent.

[0011] Preferably, the PVA solution in step three is an 8 wt% PVA aqueous solution.

[0012] Preferably, in step three, the PVA solution is placed in a magnetic stirrer and stirred for 30 minutes at 90°C and 800 r / min before use.

[0013] Preferably, the esterified konjac glucomannan solution in step three is an aqueous solution of 1 wt% esterified konjac glucomannan.

[0014] Preferably, in step three, the mass ratio of PVA solution, esterified konjac glucomannan aqueous solution, glycerol and pH-sensitive galangal essential oil liposomes is 15:5:2:(2-6).

[0015] Preferably, the drying conditions in step three are: a drying temperature of 40°C and a drying time of 3 hours.

[0016] A pH-responsive galangal essential oil liposome composite membrane was prepared based on the above method. It is a biodegradable, controlled-release active packaging composite membrane using PVA and esterified konjac glucomannan as substrates and pH-sensitive liposomes as carriers to encapsulate galangal essential oil.

[0017] The above-mentioned pH-responsive galangal essential oil liposome composite membrane is used in the preparation of smart responsive packaging films. This membrane exhibits pH-responsive essential oil release properties, effectively extending the shelf life of citrus fruits and vegetables.

[0018] Beneficial effects:

[0019] (1) The composite membrane provided by the present invention exhibits particle aggregation due to incompatibility, resulting in higher roughness. Esterification of konjac glucomannan leads to a gradual decrease in the tensile strength and elongation at break of the composite membrane.

[0020] (2) The present invention improves the antibacterial properties of the composite membrane by adding pH-responsive galangal essential oil liposomes.

[0021] (3) The composite membrane provided by the present invention maintains certain mechanical properties while having pH-responsive essential oil release properties, which can realize precise on-demand release of essential oils and extend the shelf life of fruits and vegetables. Attached Figure Description

[0022] Figure 1 Surface characterization (Figure 1) (×1000) and cross-sectional view (Figure 2) (×5000) of the octenyl succinic anhydride esterified konjac glucomannan / PVA / pH-sensitive Alpinia galanga essential oil liposome composite membrane, where A: PVA; B: PVA-1PLip; C: P 75 K 25 D: P9K1; E: P 75 K 25 -1 PLip; F:P 50 K 50 ;G:P 25 K 75 ;H:P 75 K 25 -2PLip:I:P 75 K 25 -3 PLip;

[0023] Figure 2 Essential oil release curves for octenyl succinic anhydride esterified konjac glucomannan / PVA / pH-sensitive Alpinia galanga essential oil liposome composite membranes;

[0024] Figure 3 Octenyl succinic anhydride esterified konjac glucomannan / PVA / pH-sensitive galangal essential oil liposome composite membrane packaging of citrus fruit (A) and its effect on rot rate (B) and weight loss rate (C) of citrus fruit during storage. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] The raw materials used in the examples in this specification; PVA was purchased from Comio Biotech; other reagents, such as glycerol, anhydrous ethanol, etc., were all of analytical grade. All other products not mentioned are commercially available common products.

[0027] Example 1

[0028] A PVA solution of 8 wt% was prepared by mixing PVA with distilled water. The PVA aqueous solution was then placed in a magnetic stirrer at 90°C and 800 rad / min for 30 minutes to obtain a homogeneous and transparent PVA solution. The PVA solution was then mixed with glycerol at a volume ratio of 15:2 to obtain a homogeneous film-forming emulsion. 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°C oven for 3 hours. The top composite film was carefully peeled off and the plate was placed in a resealable bag for storage, labeled as PVA.

[0029] Example 2

[0030] Konjac glucomannan and Na₂CO₃ were uniformly mixed, with Na₂CO₃ added at 3 wt% to the konjac glucomannan. A 30 wt% ethanol solution was added under stirring, along with octenyl succinic anhydride (octenyl succinic anhydride solution diluted five times with anhydrous ethanol, v / v). The volume ratio of konjac glucomannan doped with Na₂CO₃, ethanol solution, and octenyl succinic anhydride solution in the mixture was 2:2:1. The mixture was placed in a microwave reactor and heated at 300 W for 25 min, then cooled to 25 °C. The mixture was then mixed with an equal volume of ethanol solution (30 wt%), and the pH was adjusted to 6.50. The mixture was centrifuged and filtered, and washed five times with ethanol solution (30 wt%) to remove octenyl succinic anhydride residue. The final solid fraction was dried at 40 °C to obtain octenyl succinic anhydride esterified konjac glucomannan.

[0031] A PVA solution of 8 wt% was prepared by mixing PVA with distilled water. The PVA aqueous solution 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. A 1 wt% esterified konjac glucomannan solution was prepared by mixing esterified konjac glucomannan with distilled water. The above PVA solution and esterified konjac glucomannan solution were mixed at 45℃ with magnetic stirring (700 rad / min) in ratios of 90:10, 75:25, 50:50, and 25:75 (V / V). The above solution was mixed with glycerol at a ratio of 10:1 to obtain a homogeneous film-forming emulsion. The film-forming emulsion was poured onto a glass plate while hot and coated using a manual film scraper. The glass plate was then dried in a 40℃ oven for 3 h. The upper composite film was carefully peeled off and the emulsion was placed in a resealable bag for storage. (P9K1, P) 75 K 25 P 50 K 50 and P 25 K 75 .

[0032] Example 3

[0033] After uniformly mixing konjac glucomannan and Na2CO3 (Na2CO3 added to konjac glucomannan at 3wt%), an equal volume of ethanol solution (30wt%) was added under stirring, along with octenyl succinic anhydride (octenyl succinic anhydride solution diluted five times with anhydrous ethanol, v / v). The volume ratio of konjac glucomannan doped with Na2CO3, ethanol solution, and octenyl succinic anhydride solution in the mixture was 2:2:1. The mixture was placed in a microwave reactor and heated at 300W for 25 min. After cooling to 25°C, it was mixed with an equal volume of ethanol solution (30wt%), and the pH was adjusted to 6.50. The mixture was centrifuged and filtered, and washed five times with ethanol solution (30wt%) to remove octenyl succinic anhydride residue. The final solid fraction was dried at 40°C to obtain octenyl succinic anhydride esterified konjac glucomannan.

[0034] The oil phase consisted of soybean lecithin, cholesterol, and galangal essential oil in a mass ratio of 2:1:1, with chloroform as the solvent. The ratio of oil phase to solvent was 3 g: 100 mL. The oil phase and solvent were rotary evaporated at 35 °C in a flask to form a uniform lipid film. After drying in a vacuum oven at room temperature for 12 h, the film was removed. The sample was then added to the aqueous phase and solvent, which consisted of hexadecyltrimethylammonium bromide and γ-polyglutamic acid in a mass ratio of 2:1, with 0.1 M PBS at pH 7 as the solvent. The ratio of aqueous phase to solvent was 3 g: 800 mL. The aqueous phase and solvent were mixed with the oil phase and solvent at a volume ratio of 2:1, and the mixture was fully hydrated in a water bath with ultrasound. After centrifugation and membrane extraction, pH-responsive galangal essential oil liposomes were obtained.

[0035] A PVA solution of 8 wt% was prepared by mixing PVA with distilled water. The PVA solution was then placed in a magnetic stirrer at 90°C and 800 rad / min for 30 minutes to obtain a homogeneous and transparent PVA solution. A 1 wt% esterified konjac glucomannan solution was prepared by mixing esterified konjac glucomannan with distilled water. The PVA solution and esterified konjac glucomannan solution were mixed at a ratio of 75:25 (v / v) at 45°C with magnetic stirring (700 rad / min). Subsequently, 10 wt%, 20 wt%, and 30 wt% pH-sensitive Alpinia galanga essential oil liposomes (the sum of the PVA and esterified konjac glucomannan solutions) were added, and stirring continued for 1 hour. The above solution was then mixed with glycerol at a mass ratio of 11:1 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 plates were placed in resealable bags for later use. The plates were labeled P. 75 K 25 -1 PLip, P 75 K 25 -2PLip and P75 K 25 -3 PLip.

[0036] Comparative Example 1

[0037] Similar to Example 1, except that 10 wt% pH-sensitive Alpinia galanga essential oil liposomes were added to the membrane solution. Specifically: The oil phase consisted of soybean lecithin, cholesterol, and Alpinia galanga essential oil in a mass ratio of 2:1:1, with chloroform as the solvent. The ratio of oil phase to solvent was 3 g:100 mL. The oil phase and solvent were rotary evaporated at 35°C in a bottle to form a uniform lipid membrane layer. After drying in a vacuum oven at room temperature for 12 hours, the membrane was removed. The sample was then added to the aqueous phase and solvent. The aqueous phase consisted of hexadecyltrimethylammonium bromide and γ-polyglutamic acid in a mass ratio of 2:1, with 0.1 M PBS at pH 7 as the solvent. The ratio of aqueous phase to solvent was 3 g:800 mL. The aqueous phase and solvent were mixed with the oil phase and solvent at a volume ratio of 2:1, and the mixture was fully hydrated in a water bath with ultrasound. After centrifugation and membrane extraction, pH-responsive Alpinia galanga essential oil liposomes were obtained.

[0038] A PVA solution of 8 wt% was prepared by mixing PVA with distilled water. The PVA solution was then placed in a magnetic stirrer at 90°C and 800 rad / min for 30 minutes to obtain a homogeneous and transparent PVA solution. Subsequently, 10 wt% pH-sensitive Alpinia galanga essential oil liposomes were added to the PVA solution, and stirring continued for 1 hour. The above solution was then mixed with glycerol at a mass ratio of 11:1 to obtain a homogeneous film-forming emulsion. 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°C oven for 3 hours. The top composite film was carefully peeled off and the emulsion was placed in a resealable bag for storage, labeled PVA-1PLip.

[0039] Comparative Example 2

[0040] Same as Example 3, except that 10 wt% of pH-sensitive liposomes without Alpinia galanga essential oil were added to the membrane solution, named P 75 K 25 -1 CK.

[0041] The membranes prepared in Examples 1-3 and Comparative Example 1 were subjected to performance tests.

[0042] 1. Characterize the membrane; see the characterization diagram below. Figure 1 ,from Figure 1As can be seen in Figure A (which includes A1 and A2 by default, and so on), the PVA membrane maintains its uniformity and density, with almost no particles or cracks detected. The pure PVA membrane exhibits a dense internal structure and a smooth, flat surface morphology. In Figure B, the addition of liposomes slightly reduces the smoothness of the membrane surface, but maintains the uniformity and density of the membrane, with almost no particles or cracks detected.

[0043] CDFG analysis revealed that with the addition of konjac glucomannan, the blended composite membrane exhibited particle aggregation due to incompatibility, resulting in higher roughness. Although the cross-sectional roughness of the membrane composite of esterified konjac glucomannan and PVA increased, no voids or cracks were observed, indicating that the prepared membrane was relatively continuous overall. When 25% esterified konjac glucomannan was used to replace PVA, undissolved white particles agglomerated on the surface of the composite membrane. With the gradual increase in the amount of esterified konjac glucomannan, the membrane surface showed slight roughness, inhomogeneity, and fluctuations, indicating that the compatibility between esterified konjac glucomannan and PVA had begun to deteriorate, leading to localized agglomeration and wrinkling of the membrane surface.

[0044] EHI analysis revealed that with the addition of konjac glucomannan, the blended composite membrane exhibited particle aggregation due to incompatibility, resulting in higher roughness. The addition of liposomes slightly reduced the smoothness of the membrane surface, maintaining the membrane's uniformity and density, with almost no detectable particles or cracks. Furthermore, no visible droplets were observed in the structure. With increasing liposome concentrations, especially at the highest dosage, the number of aggregated particles in the membrane increased. Excessive liposomes negatively impacted the membrane surface morphology due to the gradual increase in aggregated particles. Cross-sectional images showed no phase separation on the cross-sectional surfaces of all membranes, indicating good compatibility among liposomes, PVA, and esterified konjac glucomannan.

[0045] 2. The mechanical properties of the prepared composite membrane were tested.

[0046] 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:

[0047] TS(MPa)=p / bd

[0048] EB(%) = (G - G0) / G0) × 100

[0049] 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); G represents the distance of the gauge marks when the sample breaks (mm). The test results are shown in Table 1.

[0050] Table 1 Mechanical properties of octenyl succinic anhydride esterified konjac glucomannan / PVA / pH-sensitive galangal essential oil liposome composite membrane

[0051]

[0052] As can be seen from Table 1, the pure PVA film has good tensile strength and elongation at break; with the addition of esterified konjac glucomannan, the tensile strength and elongation at break of the composite film gradually decrease.

[0053] 3. To evaluate the sustained-release capacity of essential oils in the composite membrane under different pH conditions, the specific steps are as follows: The prepared membrane (experimental group P) was... 75 K 25 -1PLip and positive control group P 75 K 25 -1 CK; 2×2cm 2 The solution was completely immersed in 30 mL of release solutions at different pH values ​​(pH = 6 and 7) and then stored in the dark. Subsequently, 1 mL of solution was removed at each set time and replaced with the corresponding simulated solution. Finally, the amount of galangal essential oil released was calculated from a UV-Vis spectrophotometer at 300 nm. The following model was used to fit the release curve.

[0054] Zero-order release kinetic model: M t / M ∞ =kt

[0055] Among them, M t and M ∞ t and t represent the amount of galangal essential oil released at time t and equilibrium, respectively, and k is the release rate constant.

[0056] See results Figure 2 ,from Figure 2The results show that the release of essential oils from the polymer matrix can be divided into two stages: first, a rapid release, followed by a sustained and stable release. The release behavior of essential oils from the polymer film mainly involves two steps. In the first step, liquid molecules penetrate the polymer matrix, leading to the expansion and weakening of the polymer network structure. Then, essential oil molecules diffuse from the inside of the film into the simulated solution until a thermodynamic equilibrium is reached. The release was relatively slow in both the positive control group and the experimental group under neutral conditions. When the pH of the medium was further decreased, the release rate of the positive control group showed a slight increase, which may be due to the reaction of the polymer matrix under different medium conditions. The essential oils from the pH-responsive liposome composite membrane were released rapidly in a short time, exhibiting pH-responsive sustained-release behavior. The released results obtained indicate that under pH conditions... 25 K 75 Adding liposomes to composite membranes can prevent premature release.

[0057] 4. A storage and preservation experiment was conducted, as follows: Fresh and uniformly sized citrus fruits were selected as experimental materials, randomly divided into 5 groups, and the prepared composite film (PVA; P...) was used. 75 K 25 ;P 75 K 25 -1 CK; P 75 K 25 -1 PLip; P 75 K 25 -2 PLip; P 75 K 25 Packaging was done with -3PLip, and the packaging was sealed with a plastic sealer. After random grouping, the samples were stored at a relative humidity of 75±1% and a temperature of 20±10℃, and relevant indicators were analyzed.

[0058] (1) Determination of weight loss rate

[0059] The weight of each citrus sample was measured at each time point, and the calculation formula is as follows:

[0060] Weight loss rate (%) = (Initial weight of citrus - Weight at storage time) / (Initial weight of citrus × 100)

[0061] (2) Determination of decay rate

[0062] The presence of water stains or mold colonies on the surface of the fruit is considered rotten.

[0063] Rot rate (%) = (Number of rotten fruits) / (Total number of fruits × 100)

[0064] See results Figure 3 ,from Figure 3 All films in A can be used for citrus packaging.

[0065] from Figure 3 B shows that the citrus fruits under PVA packaging began to rot after 4 days of storage; P 25 K 75 The citrus fruits under the packaging began to rot after 4 days of storage, while P 25 K 75 Citrus fruits packaged in -1 CK packaging showed improvement after 8 days of storage. The pH-responsive liposome packaging material exhibited significant anti-corrosion and preservation advantages, maintaining a low level of spoilage even after 20 days of storage at room temperature. Furthermore, its effectiveness was related to the amount of liposomes added. Higher concentrations resulted in higher levels of released active ingredients and better effects on the fruit.

[0066] Figure 3 C indicates that PVA-packaged citrus fruits have a lower water loss rate in the early and middle stages of storage, but the rate accelerates in the later stages, offering no preservation effect; the weight loss rate of citrus fruits under various packaging materials gradually increases with the extension of storage time; during this period, P... 25 K 75 The group of citrus fruits showed the fastest increase in weight loss and poor preservation effect; after adding essential oil liposomes, the introduction of hydrophobic substances resulted in the film having better water vapor barrier properties, thereby reducing the evaporation of water and the consumption of nutrients in citrus fruits, and effectively extending the shelf life of citrus fruits and vegetables.

[0067] 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 pH-responsive galangal essential oil liposome composite membrane, characterized in that, The steps are as follows: Step 1. Octenyl succinic anhydride modification of konjac glucomannan: Konjac glucomannan and Na2CO3 were uniformly mixed, and ethanol solution and octenyl succinic anhydride were added under stirring to obtain a mixture. The mixture was placed in a microwave reactor and heated at 300W for 25 minutes, then cooled to room temperature. It was then mixed with an equal amount of ethanol solution, and the pH was adjusted to 6.

5. The mixture was centrifuged and filtered, and washed with ethanol solution to remove octenyl succinic anhydride residue. The final solid part was dried at 40 °C to obtain esterified konjac glucomannan. Step 2. The oil phase and its solvent were rotary evaporated at 35°C in a bottle to form a uniform lipid film. After being placed in a vacuum drying oven at room temperature for 12 hours, the film was removed. The aqueous phase and its solvent were mixed with the oil phase and its solvent at a volume ratio of 2:

1. The mixture was fully hydrated in a water bath with ultrasound, centrifuged, and filtered to obtain pH-responsive Alpinia galanga essential oil liposomes. The oil phase consisted of soybean lecithin, cholesterol, and Alpinia galanga essential oil in a mass ratio of 2:1:

1. The aqueous phase consisted of hexadecyltrimethylammonium bromide and γ-polyglutamic acid in a mass ratio of 2:1:

1. Step 3. Preparation of composite membrane: PVA solution, esterified konjac glucomannan solution, glycerol and pH-sensitive galangal essential oil liposome are stirred and mixed to obtain a uniform film-forming emulsion. The film-forming emulsion is poured onto a glass plate while hot and the film is scraped using a manual film scraper. The glass plate is then dried in an oven. The upper composite membrane is carefully torn off and placed in a self-sealing bag for storage.

2. The method for preparing a pH-responsive galangal essential oil liposome composite membrane according to claim 1, characterized in that, In step one, the amount of Na2CO3 added to konjac glucomannan is 3wt%, the mass fraction of the ethanol solution is 30%, and the octenyl succinic anhydride is an octenyl succinic anhydride solution diluted five times with anhydrous ethanol. The volume ratio of konjac glucomannan doped with Na2CO3, ethanol solution, and octenyl succinic anhydride solution in the mixture is 2:2:

1.

3. The method for preparing a pH-responsive galangal essential oil liposome composite membrane according to claim 1, characterized in that, In step two, the oil phase solvent is chloroform, and the ratio of oil phase to oil phase solvent is 3g:100mL; the aqueous phase solvent is 0.1 M PBS with pH=7, and the ratio of aqueous phase to aqueous phase solvent is 3g:800mL.

4. The method for preparing a pH-responsive galangal essential oil liposome composite membrane according to claim 1, characterized in that, In step three, the PVA solution is an 8 wt% PVA aqueous solution.

5. The method for preparing a pH-responsive galangal essential oil liposome composite membrane according to claim 1, characterized in that, In step three, the PVA solution is placed in a magnetic stirrer before use and stirred for 30 minutes at 90 ℃ and 800 r / min.

6. The method for preparing a pH-responsive galangal essential oil liposome composite membrane according to claim 1, characterized in that, In step three, the esterified konjac glucomannan solution is an aqueous solution of 1 wt% esterified konjac glucomannan.

7. The method for preparing a pH-responsive galangal essential oil liposome composite membrane according to claim 1, characterized in that, In step three, the mass ratio of PVA solution, esterified konjac glucomannan aqueous solution, glycerol and pH-sensitive galangal essential oil liposomes is 15:5:2:(2~6).

8. The method for preparing a pH-responsive galangal essential oil liposome composite membrane according to claim 1, characterized in that, The drying conditions in step three are: drying temperature of 40 ℃ and drying time of 3 h.

9. A pH-responsive galangal essential oil liposome composite membrane prepared according to any one of claims 1-8.

10. The application of the pH-responsive galangal essential oil liposome composite membrane according to claim 9 in the preparation of intelligent responsive packaging films.

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