Preparation method and application of zein / gelatin-based edible film loaded with lotus seed core extract

Abstract

The present invention discloses a method for preparing a zein / gelatin-based edible film loaded with lotus seed pith extract, comprising the steps of dissolving zein and lotus seed pith extract in ethanol, then adding the mixture dropwise to a gelatin solution, stirring to obtain a uniform lotus seed pith extract-zein-gelatin film-forming solution, homogenizing and degassing the solution, and applying the hot solution to form a film. The present invention has the advantages of being easy to operate, low cost, and having good biocompatibility of the prepared edible film, which can be removed by washing. Zein is used as a carrier to encapsulate the biologically active lotus seed pith extract, thereby enhancing the antibacterial and antioxidant properties of the edible film.

Description

Technical Field

[0001] The invention relates to the field of edible packaging films, in particular to a preparation method and application of a zein / gelatin-based edible film carrying a lotus seed core extract. Background Art

[0002] Since traditional plastic packaging films are difficult to degrade in the natural environment, they pose a serious threat to the ecological environment and also pose a potential hazard of migrating carcinogens. Therefore, the use of degradable bio-based packaging films to replace traditional plastic packaging films has become a development trend in the food packaging industry. On the one hand, edible bio-based packaging films are usually made of non-toxic, edible biomass macromolecules (such as polysaccharides, proteins, and lipids, etc.) as raw materials, and are made into films through suitable film-forming methods, with advantages such as biodegradability. On the other hand, improving the mechanical resistance of edible films and their ability to block oxygen and water vapor, and developing functional edible films with antibacterial and antioxidant properties have received increasing attention.

[0003] Gelatin is one of the most common natural protein-based biopolymers used in food, primarily derived from cartilage in animal bones, connective tissue, and skin. Gelatin is widely used in the preparation of edible films due to its biodegradability, bioactivity, and non-toxicity. However, the main drawbacks of gelatin-based edible films include low mechanical strength, weak water vapor barrier properties, and unsuitability for encapsulating active substances such as antimicrobials and antioxidants with poor water solubility.

[0004] Zein, the primary protein in corn endosperm, is a recognized safe food-grade ingredient. Its biodegradability, film-forming properties, and adhesiveness make it an ideal food packaging material. Its hydrophobic nature also facilitates the encapsulation of less water-soluble active ingredients such as antimicrobials and antioxidants. However, edible films made from zein suffer from poor mechanical properties, making them unsuitable for long-term food storage or long-distance transportation.

[0005] Lotus seed pith, the green embryo from the mature seed of the lotus (Nelumbo nucifera Gaertn), a plant of the Nymphaeaceae family, is a medicinal and edible ingredient with a history of over 400 years in my country. Modern research has shown that lotus seed pith contains a variety of chemical components, with over 130 compounds isolated and identified, including alkaloids, flavonoids, polysaccharides, and volatile oils. Extracts and related components of lotus seed pith have demonstrated biological activity both in vitro and in vivo. Currently, research on the effects of lotus seed pith and its components focuses on the cardiovascular and nervous systems, anti-inflammatory and anti-tumor effects, and the liver. Summary of the Invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a zein / gelatin-based edible film loaded with lotus seed core extract. The solvent casting method used in the preparation of zein / gelatin-based films is a simple and low-cost method for preparing edible films. Based on the above characteristics, the present invention provides a method for preparing PNE@GZF and its application. In the present invention, zein can reduce the water permeability of gelatin films and improve the water solubility of films. At the same time, given the hydrophobic properties of zein, it can be used to encapsulate the main hydrophobic components such as alkaloids and flavonoids in lotus seed core extract, and can reduce the negative effects of the addition of lotus seed core extract, such as the reduction in film mechanical properties.

[0007] Technical solution: The method for preparing the edible film of the present invention comprises the following steps: dissolving zein and lotus seed core extract in ethanol, then adding the mixture dropwise to a gelatin solution, stirring to obtain a uniform lotus seed core extract-zein-gelatin film-forming solution, homogenizing and degassing the solution, and then coating the solution into a film.

[0008] The method for preparing the edible film comprises the following steps: stirring at 800-1000 rpm, stirring for 1-3 hours, and a temperature of 70-90°C.

[0009] The preparation method of the edible film comprises the following raw materials in parts by weight: 0.8-7.2 parts of zein, 72.8-79.2 parts of gelatin, and 0.4-1.6 parts of lotus seed core extract.

[0010] In the method for preparing the edible film, the ethanol has a volume fraction of 80 to 85%.

[0011] In the method for preparing the edible film, the mass concentration of zein in the ethanol is 0.16-1.44%, preferably 0.8%; the mass concentration of the lotus seed core extract solution in the ethanol is 5-15%, preferably 10%.

[0012] The preparation method of the edible film comprises dissolving gelatin in water at 60-90 DEG C and stirring to obtain a gelatin solution.

[0013] In the method for preparing the edible film, the mass concentration of the gelatin solution is 16.2-17.6%, preferably 16.9%.

[0014] The method for preparing the edible film, wherein the preparation of the lotus seed core extract comprises the following steps:

[0015] (1) Dry lotus seed core powder was sieved, soaked with ethanol, and subjected to continuous cycle extraction with ethanol at 60-75°C;

[0016] (2) distilling the ethanol extract under reduced pressure, adding sulfuric acid solution to the residue and adjusting the pH to 2-3;

[0017] (3) The suspension is filtered, and the filtrate is washed with a small amount of ether to remove non-alkaline components; the acid solution is alkalized to pH 9-10 with aqueous ammonia, and extracted with aqueous ammonia several times;

[0018] (4) removing the ether solvent to obtain the lotus seed core extract.

[0019] In the method for preparing the edible film, the ethanol used for soaking and continuous circulation extraction in step (1) is 80-85% ethanol by volume; and the sulfuric acid solution in step (2) has a volume fraction of 5-15%.

[0020] The zein / gelatin-based edible film loaded with lotus seed core extract is prepared by the preparation method.

[0021] Application of the zein / gelatin-based edible film carrying lotus seed core extract in food packaging materials.

[0022] In some embodiments, a uniform hot solution of lotus seed pith extract, zein, and gelatin is obtained after stirring, homogenized, degassed, and poured into a mold, where it is naturally formed into a film by casting, and then dried. Preferably, the drying temperature is 25° C., the relative humidity is 30-55%, and the drying time is 24-48 hours.

[0023] In some embodiments, the volume ratio of the gelatin solution to the zein alcohol solution is 9:1.

[0024] The present invention provides a fresh-keeping application of PNE@GZF as a food packaging material.

[0025] Beneficial Effects: Compared with existing technologies, the present invention offers the following advantages: The edible film constructed based on a zein / gelatin matrix can conveniently and effectively disperse the bioactive lotus seed core extract within the film. The gelatin, zein, and lotus seed core extract used are all renewable biomass resources, and their degradation products are harmless to the environment and human health, and the film can be removed by washing. Furthermore, the edible film is biocompatible and safe, making it suitable as a food packaging material for preserving fruits and vegetables. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 3 is a morphological diagram of zein / gelatin-based edible films prepared in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 of the present invention;

[0027] Figure 21 is an infrared spectrum test chart of the zein / gelatin-based edible film prepared in Example 2, Comparative Example 1 and Comparative Example 2 of the present invention;

[0028] Figure 3 1 is a test chart of water absorption performance of zein / gelatin-based edible films prepared in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 of the present invention;

[0029] Figure 4 Graphs showing the hydrophobicity / hydrophilicity of zein / gelatin-based edible films prepared in Example 1, Example 2, Example 3, and Comparative Example 1 of the present invention, using contact angle measurements;

[0030] Figure 5 These are the test results of the antioxidant properties of the gelatin zein edible films prepared in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 of the present invention;

[0031] Figure 6 These are the test results of the antioxidant properties of the gelatin / zein edible films prepared in Examples 2, 4, 5 and 6 of the present invention;

[0032] Figure 7 2 is a test graph showing the inhibition of Escherichia coli activity by PNE@GZF prepared in Examples 4, 7, and 8 of the present invention (wherein the values ​​of PNE@GZF in Examples 7, 8, and 4 are 0);

[0033] Figure 8 The results of the antibacterial activity test of lotus seed core extract against Aspergillus niger, Botrytis cinerea, Alternaria alternata and Aspergillus terreus;

[0034] Figure 9 The statistical results of the antibacterial activity test of lotus seed core extract against Aspergillus niger, Botrytis cinerea, Alternaria alternata and Aspergillus terreus;

[0035] Figure 10 This is a graph showing the results of using PNE@GZF prepared in Examples 4, 5, and 6 of the present invention to preserve strawberries for 7 days. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto. The materials involved in the following examples can all be obtained from commercial channels.

[0037] Example 1

[0038] The preparation method of the zein / gelatin-based edible film of this embodiment comprises the following steps:

[0039] Zein was dissolved in 85% (v / v) ethanol to prepare a 0.16% (w / v) zein solution, which was then added dropwise to a 17.6% (w / v) hot gelatin solution to a total volume of 100 mL and a total solid content of 16% (w / v). After stirring at 80°C for 2 h, a zein / gelatin-based membrane-forming solution was obtained.

[0040] The prepared film-forming solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 h, and then the dry film was peeled off from the Petri dish.

[0041] The dried film was stored in a desiccator at a temperature of 25° C. and a relative humidity of 53% for about 40 hours to obtain a zein / gelatin-based edible film.

[0042] The edible film prepared in this embodiment is uniform and transparent (such as Figure 1 shown).

[0043] Example 2

[0044] The preparation method of the zein / gelatin-based edible film of this embodiment comprises the following steps:

[0045] Zein was dissolved in 85% (v / v) ethanol to prepare a 0.8% (w / v) zein solution, which was then added dropwise to a 16.9% (w / v) hot gelatin solution to a total volume of 100 mL and a total solid content of 16% (w / v). After stirring at 80°C for 2 h, a zein / gelatin-based membrane-forming solution was obtained.

[0046] The prepared film-forming solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 h, and then the dry film was peeled off from the Petri dish.

[0047] The dried film was stored in a desiccator at a temperature of 25° C. and a relative humidity of 53% for about 40 hours to obtain a zein / gelatin-based edible film.

[0048] The edible film prepared in this embodiment is uniform and transparent (such as Figure 1 Infrared spectroscopy showed that zein / gelatin-based edible films were successfully prepared ( Figure 2 ).

[0049] Example 3

[0050] The preparation method of the zein / gelatin-based edible film of this embodiment comprises the following steps:

[0051] Zein was dissolved in 85% (v / v) ethanol to prepare a 1.44% (w / v) zein solution, which was then added dropwise to a 14.6% (w / v) hot gelatin solution to a total volume of 100 mL and a total solid content of 16% (w / v). After stirring at 80°C for 2 h, a zein / gelatin-based membrane-forming solution was obtained.

[0052] The prepared film-forming solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 h, and then the dry film was peeled off from the Petri dish.

[0053] The dried film was stored in a desiccator at a temperature of 25° C. and a relative humidity of 53% for about 40 hours to obtain a zein / gelatin-based edible film.

[0054] The edible film prepared in this embodiment is opaque light yellow and has a rough surface (such as Figure 1 shown).

[0055] Example 4

[0056] The preparation method of PNE@GZF in this embodiment includes the following steps:

[0057] The dried lotus seed core powder is passed through a 40-mesh sieve, soaked in 80% (v / v) ethanol for 24 hours, and extracted with 80% (v / v) ethanol in a continuous cycle at 75°C. The ethanol extract is distilled under reduced pressure, and the residue is added with 10% (v / v) sulfuric acid solution to adjust the pH to 2-3. The suspension is filtered through a nylon filter, and the filtrate is washed with a small amount of ether to remove non-alkaline components. The acid solution is alkalized to a pH of 9-10 with aqueous ammonia and extracted multiple times with aqueous ammonia. The ether solvent is removed to obtain the lotus seed core extract.

[0058] Dissolve zein in 85% (v / v) ethanol to prepare a 0.8% (w / v) zein solution, dissolve the lotus seed heart extract in 85% (v / v) ethanol to obtain a 10% (w / v) solution, slowly drip the lotus seed heart extract solution into the zein solution, stir at room temperature for 2 hours, and obtain a lotus seed heart extract-zein mixed solution.

[0059] The above-mentioned zein solution containing lotus seed heart extract was slowly added dropwise to a gelatin solution with a concentration of 16.9% (w / v), so that the volume ratio of the alcohol solution to the gelatin solution was 1:9, the total solid content was 16% (w / v), and the final concentration of lotus seed heart extract was 0.08% (w / v). After stirring at 80°C for 2 hours, a uniform lotus seed heart extract-zein-gelatin film-forming solution was obtained.

[0060] The prepared film-forming solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 h, and then the dry film was peeled off from the Petri dish.

[0061] The dry film was stored in a desiccator at a temperature of 25 °C and a relative humidity of 53% for about 40 h to obtain PNE@GZF.

[0062] Example 5

[0063] The preparation method of PNE@GZF in this embodiment includes the following steps:

[0064] Dissolve zein in 85% (v / v) ethanol to prepare a 0.8% (w / v) zein solution, dissolve the lotus seed heart extract in 85% (v / v) ethanol to obtain a 10% (w / v) solution, slowly drip the lotus seed heart extract solution into the zein solution, stir at room temperature for 2 hours, and obtain a lotus seed heart extract-zein mixed solution.

[0065] The above-mentioned zein solution containing lotus seed heart extract was slowly added dropwise to a gelatin solution with a concentration of 16.9% (w / v), so that the volume ratio of the alcohol solution to the gelatin solution was 1:9, the total solid content was 16% (w / v), and the final concentration of lotus seed heart extract was 0.16% (w / v). After stirring at 80°C for 2 hours, a uniform lotus seed heart extract-zein-gelatin film-forming solution was obtained.

[0066] The prepared film-forming solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 h, and then the dry film was peeled off from the Petri dish.

[0067] The dry film was stored in a desiccator at a temperature of 25 °C and a relative humidity of 53% for about 40 h to obtain PNE@GZF.

[0068] Example 6

[0069] The preparation method of PNE@GZF in this embodiment includes the following steps:

[0070] Dissolve zein in 85% (v / v) ethanol to prepare a 0.8% (w / v) zein alcohol solution, dissolve the lotus seed heart extract in 85% (v / v) ethanol to obtain a 10% (w / v) alcohol solution, slowly drip the lotus seed heart extract alcohol solution into the zein alcohol solution, stir at room temperature for 2 hours, and obtain a lotus seed heart extract-zein alcohol solution.

[0071] The above-mentioned zein alcohol solution containing lotus seed heart extract was slowly added dropwise to a gelatin solution with a concentration of 16.9% (w / v), so that the volume ratio of the alcohol solution to the gelatin solution was 1:9, the total solid content was 16% (w / v), and the final concentration of lotus seed heart extract was 0.32% (w / v). After stirring at 80°C for 2 hours, a uniform lotus seed heart extract-zein-gelatin hot solution was obtained.

[0072] The prepared film-forming solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 hours, after which the dry film was peeled off from the Petri dish.

[0073] The dry film was stored in a desiccator at a temperature of 25 °C and a relative humidity of 53% for about 40 h to obtain PNE@GZF.

[0074] Example 7

[0075] The preparation method of PNE@GZF in this embodiment includes the following steps:

[0076] Dissolve zein in 85% (v / v) ethanol to prepare a 0.8% (w / v) zein alcohol solution, dissolve the lotus seed heart extract in 85% (v / v) ethanol to obtain a 10% (w / v) alcohol solution, slowly drip the lotus seed heart extract alcohol solution into the zein alcohol solution, stir at room temperature for 2 hours, and obtain a lotus seed heart extract-zein alcohol solution.

[0077] The above-mentioned zein alcohol solution containing lotus seed heart extract was slowly added dropwise to a gelatin solution with a concentration of 16.9% (w / v), so that the volume ratio of the alcohol solution to the gelatin solution was 1:9, the total solid content was 16% (w / v), and the final concentration of lotus seed heart extract was 0.02% (w / v). After stirring at 80°C for 2 hours, a uniform lotus seed heart extract-zein-gelatin hot solution was obtained.

[0078] The prepared film-forming solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 hours, after which the dry film was peeled off from the Petri dish.

[0079] The dry film was stored in a desiccator at a temperature of 25 °C and a relative humidity of 53% for about 40 h to obtain PNE@GZF.

[0080] Example 8

[0081] The preparation method of PNE@GZF in this embodiment includes the following steps:

[0082] Dissolve zein in 85% (v / v) ethanol to prepare a 0.8% (w / v) zein alcohol solution, dissolve the lotus seed heart extract in 85% (v / v) ethanol to obtain a 10% (w / v) alcohol solution, slowly drip the lotus seed heart extract alcohol solution into the zein alcohol solution, stir at room temperature for 2 hours, and obtain a lotus seed heart extract-zein alcohol solution.

[0083] The above-mentioned zein alcohol solution containing lotus seed heart extract was slowly added dropwise to a gelatin solution with a concentration of 16.9% (w / v), so that the volume ratio of the alcohol solution to the gelatin solution was 1:9, the total solid content was 16% (w / v), and the final concentration of lotus seed heart extract was 0.04% (w / v). After stirring at 80°C for 2 hours, a uniform lotus seed heart extract-zein-gelatin hot solution was obtained.

[0084] The prepared film-forming solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 hours, after which the dry film was peeled off from the Petri dish.

[0085] The dry film was stored in a desiccator at a temperature of 25 °C and a relative humidity of 53% for about 40 h to obtain PNE@GZF.

[0086] Comparative Example 1

[0087] The method for preparing the zein film of this embodiment comprises the following steps:

[0088] Zein was dissolved in 85% (v / v) ethanol to prepare a zein alcohol solution with a concentration of 16% (w / v).

[0089] The prepared zein alcohol solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 h, after which the dry film was peeled off from the Petri dish.

[0090] The dried film was stored in a desiccator at a temperature of 25° C. and a relative humidity of 53% for about 40 hours to obtain a zein film.

[0091] The edible film prepared in this comparative example is opaque light yellow, and the surface is uneven and rough (such as Figure 1 shown).

[0092] Comparative Example 2

[0093] The method for preparing the gelatin film of this embodiment comprises the following steps:

[0094] Gelatin was dissolved in water to prepare a gelatin solution with a concentration of 16% (w / v).

[0095] The prepared hot gelatin solution was poured into a plastic Petri dish and then kept at ambient temperature for 48 h before peeling the dry film from the Petri dish.

[0096] The dried film was stored in a desiccator at a temperature of 25° C. and a relative humidity of 53% for about 40 hours to obtain a gelatin film.

[0097] The edible film prepared in this comparative example is uniform and transparent (such as Figure 1 shown).

[0098] Next, the water absorption, hydrophilicity, hydrophobicity, oxygen permeability, antioxidant and antibacterial properties of the PNE@GZF prepared in the present invention were tested.

[0099] Water absorption performance test

[0100] The films of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 were cut into squares (5×5 cm) and then placed in a dryer containing water for 48 hours, and their moisture absorption capacity was calculated. Figure 2 The water absorption of different edible films is shown. Comparative Example 1 has the lowest water absorption due to its hydrophobicity. As the percentage of gelatin increases, the water absorption of the film also increases. Comparative Example 2 has a water absorption similar to that of Example 1, reaching more than 15%. A slight decrease in the water absorption of Examples 2 and 3 is observed here, which is due to the stronger hydrophobicity of zein and the hydrogen bonding interaction between the hydroxyl groups of gelatin and gelatin ( Figure 3 ).

[0101] Hydrophilicity and hydrophobicity test

[0102] The water contact angle (WCA) is related to the microstructure and chemical properties of the film. It is also related to the wettability, roughness, porosity and pore size of the film. Comparative Example 2 has a hydrophobic surface with a WCA of more than 90°. Comparative Example 1, on the other hand, has a hydrophilic surface with a WCA of 65.13°, which is opposite to the expected WCA value trend based on the hydrophobicity of gelatin and zein. It shows that surface roughness and pore size can significantly affect the WCA value. Compared with gelatin, zein is more unevenly distributed in the film and has a rougher surface, while gelatin has a smoother surface, which may affect the contact angle of the film. The water contact angles of Example 1, Example 2, and Example 3 are 73.47°, 77.30°, and 71.40°, respectively. The hydrophilicity of the zein / gelatin edible film is between that of gelatin and zein films ( Figure 4 ).

[0103] Antioxidant performance test

[0104] The antioxidant activity of GZF and PNE@GZF was determined using the DPPH free radical scavenging method. Comparative Example 2 had no antioxidant activity, while Examples 1, 2, and 3 showed increased antioxidant activity as the proportion of zein increased. Comparative Example 1 had the strongest antioxidant activity ( Figure 5 ). The PNE@GZF obtained in Examples 4 to 6, after conversion, contained 0.08-0.32% (w / v) of lotus seed core extract in the film, equivalent to 0.8-3.2 mg / mL, and all showed significant antioxidant activity. The free radical scavenging rate of Example 4 could reach 55.33%, the free radical scavenging rate of Example 5 could reach 90.22%, and the free radical scavenging rate of Example 6 could reach 87.40% ( Figure 6 ).

[0105] Antibacterial performance test

[0106] The antibacterial activity of PNE@GZF was evaluated by plate diffusion method ( Figure 7 ). Using free lotus seed heart extract of the same concentration as in Example 7, Example 8 and Example 4 as a control, the lotus seed heart extract group showed the highest inhibitory effect on bacterial growth, and 0.02-0.08% (w / v) of lotus seed heart extract in the film was equivalent to 0.2-0.8 mg / mL. Among them, Example 7 showed obvious antibacterial activity and achieved an inhibition rate of 100%. Compared with lotus seed heart extract, the inhibitory effect of PNE@GZF was enhanced, which may be due to its hydrophobic structure that makes zein have antibacterial ability ( Figure 7 ).

[0107] Antifungal performance test

[0108] The in vitro antifungal activity test selected strawberry pathogenic fungi: Aspergillus niger, Botrytis cinerea, Alternaria alternata and Aspergillus terreus as experimental subjects. The lotus seed heart extract in the film was converted to 0.08-0.64% (w / v) equivalent to 0.8-6.4 mg / mL. After 7 days, compared with the control group, the lotus seed heart extract at concentrations of 3.2 mg / mL and 6.4 mg / mL had a significant inhibitory effect on the mycelial growth of four different pathogenic fungi. The lotus seed heart extract at a concentration of 1.6 mg / mL had significant inhibitory activity against Botrytis cinerea, Alternaria alternata and Aspergillus terreus ( Figures 8-9 ).

[0109] Strawberry freshness test

[0110] Perishable strawberries were selected to evaluate the performance of PNE@GZF in preserving fruits. The strawberries were divided into 4 groups, and the freshness at 25°C was recorded after storage for 1, 3, 5, and 7 days. Photographs taken within 7 days showed that untreated strawberries began to be contaminated by microorganisms on the 3rd day, and severe mold contamination was observed on the 6th day. Compared with untreated strawberries, strawberries coated with PNE@GZF were not contaminated by mold. Films containing lotus seed heart extract at different concentrations were able to effectively inhibit biological contamination before the 7th day, indicating that the films of Example 4, Example 5, and Example 6 have long-lasting antibacterial activity ( Figure 10 ).

Claims

1. A method for preparing an edible film, characterized in that: The following steps are involved: Dissolve zein and lotus seed pith extract in ethanol, then add dropwise to a gelatin solution, stir to obtain a uniform lotus seed pith extract-zein-gelatin film-forming solution, homogenize and degas, and then apply the hot solution to form a film; the raw materials comprise the following parts by weight: 0.8-7.2 parts zein, 72.8-79.2 parts gelatin, and 0.4-1.6 parts lotus seed pith extract; The preparation of the lotus seed core extract comprises the following steps: (1) The dried lotus seed core powder was sieved, soaked with ethanol, and subjected to continuous cycle extraction with ethanol at 60-75°C; (2) Distill the ethanol extract under reduced pressure, add sulfuric acid solution to the residue, and adjust the pH to 2-3; (3) The suspension is filtered and the filtrate is washed with a small amount of ether to remove non-alkaline components; the acid solution is alkalized to pH 9-10 with aqueous ammonia and extracted with aqueous ammonia several times; (4) Remove the ether solvent to obtain the lotus seed core extract.

2. The method for preparing an edible film according to claim 1, wherein: The ethanol used to dissolve the zein and lotus seed core extract has a volume fraction of 80-85% ethanol.

3. The method for preparing an edible film according to claim 1, wherein: The mass concentration of the zein in the ethanol is 0.16-1.44%; the mass concentration of the lotus seed core extract solution in the ethanol is 5-15%.

4. The method for preparing an edible film according to claim 1, wherein: Dissolve gelatin in water at 60-90°C and stir to obtain a gelatin solution.

5. The method for preparing an edible film according to claim 4, wherein: The mass concentration of the gelatin solution is 16.2-17.6%.

6. The method for preparing an edible film according to claim 1, wherein: The ethanol used for soaking and continuous circulation extraction in step (1) is 80-85% ethanol by volume; the sulfuric acid solution in step (2) has a volume fraction of 5-15%.

7. A zein / gelatin-based edible film loaded with lotus seed core extract, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the zein / gelatin-based edible film containing lotus seed core extract according to claim 7 in food packaging materials.

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