EDIBLE FILM WITH ENHANCED RELEASE EFFICIENCY OF ESSENTIAL OIL AND PREPARATION METHOD THEREOF

Abstract

The present invention discloses an edible film with enhanced release efficiency of essential oil and a preparation method thereof. The edible film is composed of at least one blank layer and at least one essential oil-rich layer; during casting, the blank layer serves as a substrate layer and the essential oil-rich layer serves as an intermediate layer or an external layer; wherein the blank layer is composed of an alcohol-soluble protein-water-soluble protein composite film, and the essential oil-rich layer is composed of an alcohol-soluble protein-water-soluble protein composite film loading with essential oil. The present invention provides a structure and a method of divisional enrichment of essential oil, wherein the essential oil of equal mass is enriched in a certain layer of the film. Compared with the existing edible film loading with essential oil, the essential oil is loaded to the entire film matrix in the present invention.

Claims

1. An edible film with enhanced release efficiency of essential oil, characterized in that, the edible film is composed of at least one blank layer and at least one essential oil-rich layer; during casting, the blank layer serves as a substrate layer and the essential oil-rich layer serves as an intermediate layer or an external layer; wherein the blank layer is composed of an alcohol-soluble protein-water-soluble protein composite film, and the essential oil-rich layer is composed of an alcohol-soluble protein-water-soluble protein composite film loading with essential oil.

2. The edible film according to claim 1, wherein the edible film is composed of 1 to 4 blank layers and 1 to 4 essential oil-rich layers.

3. The edible film according to claim 1, wherein in the blank layer, a total mass concentration of an alcohol-soluble protein and a water-soluble protein is 16-27 wt %, wherein a mass ratio of the alcohol-soluble protein to the water-soluble protein is 1:(1.3-2.7).

4. The edible film according to claim 3, wherein in the blank layer, the total mass concentration of the alcohol-soluble protein and the water-soluble protein is 18-22 wt %, wherein the mass ratio of the alcohol-soluble protein to the water-soluble protein is 1:(1.6-2.0).

5. The edible film according to claim 4, wherein in the essential oil-rich layer, the total mass concentration of the alcohol-soluble protein and the water-soluble protein is 16-27 wt %, wherein the mass ratio of the alcohol-soluble protein to the water-soluble protein is 1:(1.3-2.7), and a concentration of the essential oil accounts for 5-18% (v/w) of a solid matter content.

6. The edible film according to claim 5, wherein in the essential oil-rich layer, the total mass concentration of the alcohol-soluble protein and the water-soluble protein is 18-22 wt %, wherein the mass ratio of the alcohol-soluble protein to the water-soluble protein is 1:(1.6-2.0), and the concentration of the essential oil accounts for 7.5-16% (v/w) of the solid matter content.

7. A preparation method for the edible film with enhanced release efficiency of essential oil according to claim 1, characterized in that, the preparation method comprises the following steps: S1, compounding and dissolving an alcohol-soluble protein and a water-soluble protein in an acetic acid-water solution, adding a plasticizer, stirring to obtain a film-forming solution of the blank layer; S2, dissolving an alcohol-soluble protein and a water-soluble protein in an acetic acid-water solution, stirring to complete dissolution, adding a plasticizer and an essential oil, stirring evenly to obtain a film-forming solution of the essential oil-rich layer; and S3, casting the film-forming solutions of steps S1 and S2 to form films, wherein during casting, first casting the film-forming solution of the blank layer, to take the blank layer as a substrate layer, and taking the essential oil-rich layer as an intermediate layer or an external layer; after a first layer of film is dried, continuing to cast the next layer of film based on the first layer of film, then continuing to dry, and by repetition, the edible film of enhancing the release efficiency of essential oil with a multi-layer film structure is obtained.

8. The preparation method according to claim 7, wherein a cast temperature is 40° C. to 100° C., and a cast velocity is 0.01-0.5 m/min.

9. The preparation method according to claim 7, wherein a thickness of each blank layer is controlled to 50-500 μm; and a thickness of each essential oil-rich layer is controlled to 50-500 μm.

10. The preparation method according to claim 7, wherein the plasticizer is one or more of glycerol, water, oleic acid and polyethylene glycol; a concentration of the plasticizer in steps S1 and S2 is controlled to account for 5-20% (v/w) of a solid matter content.

11. A packaging article, characterized in that, the packaging article comprises or is produced by the edible film according to claim 1.

12. A preparation method for the edible film with enhanced release efficiency of essential oil according to claim 2, characterized in that, the preparation method comprises the following steps: S1, compounding and dissolving an alcohol-soluble protein and a water-soluble protein in an acetic acid-water solution, adding a plasticizer, stirring to obtain a film-forming solution of the blank layer; S2, dissolving an alcohol-soluble protein and a water-soluble protein in an acetic acid-water solution, stirring to complete dissolution, adding a plasticizer and an essential oil, stirring evenly to obtain a film-forming solution of the essential oil-rich layer; and S3, casting the film-forming solutions of steps S1 and S2 to form films, wherein during casting, first casting the film-forming solution of the blank layer, to take the blank layer as a substrate layer, and taking the essential oil-rich layer as an intermediate layer or an external layer; after a first layer of film is dried, continuing to cast the next layer of film based on the first layer of film, then continuing to dry, and by repetition, the edible film of enhancing the release efficiency of essential oil with a multi-layer film structure is obtained.

13. A preparation method for the edible film with enhanced release efficiency of essential oil according to claim 3, characterized in that, the preparation method comprises the following steps: S1, compounding and dissolving an alcohol-soluble protein and a water-soluble protein in an acetic acid-water solution, adding a plasticizer, stirring to obtain a film-forming solution of the blank layer; S2, dissolving an alcohol-soluble protein and a water-soluble protein in an acetic acid-water solution, stirring to complete dissolution, adding a plasticizer and an essential oil, stirring evenly to obtain a film-forming solution of the essential oil-rich layer; and S3, casting the film-forming solutions of steps S1 and S2 to form films, wherein during casting, first casting the film-forming solution of the blank layer, to take the blank layer as a substrate layer, and taking the essential oil-rich layer as an intermediate layer or an external layer; after a first layer of film is dried, continuing to cast the next layer of film based on the first layer of film, then continuing to dry, and by repetition, the edible film of enhancing the release efficiency of essential oil with a multi-layer film structure is obtained.

14. A preparation method for the edible film with enhanced release efficiency of essential oil according to claim 5, characterized in that, the preparation method comprises the following steps: S1, compounding and dissolving an alcohol-soluble protein and a water-soluble protein in an acetic acid-water solution, adding a plasticizer, stirring to obtain a film-forming solution of the blank layer; S2, dissolving an alcohol-soluble protein and a water-soluble protein in an acetic acid-water solution, stirring to complete dissolution, adding a plasticizer and an essential oil, stirring evenly to obtain a film-forming solution of the essential oil-rich layer; and S3, casting the film-forming solutions of steps S1 and S2 to form films, wherein during casting, first casting the film-forming solution of the blank layer, to take the blank layer as a substrate layer, and taking the essential oil-rich layer as an intermediate layer or an external layer; after a first layer of film is dried, continuing to cast the next layer of film based on the first layer of film, then continuing to dry, and by repetition, the edible film of enhancing the release efficiency of essential oil with a multi-layer film structure is obtained.

15. A packaging article, characterized in that, the packaging article comprises or is produced by the edible film according to claim 2.

16. A packaging article, characterized in that, the packaging article comprises or is produced by the edible film according to claim 3.

17. A packaging article, characterized in that, the packaging article comprises or is produced by the edible film according to claim 5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 shows a structural diagram of some edible films which are enriched in essential oil divisionally prepared by the embodiments of the present invention.

[0038] FIG. 2 shows release profiles of essential oil of the embodiments and comparative examples.

[0039] FIG. 3 shows the rotten rate of blueberries during the storage time packaged with the embodiments and comparative examples.

[0040] FIG. 4 shows cross-section microstructure of the embodiments and comparative examples.

DESCRIPTION OF THE EMBODIMENTS

[0041] The present invention is further described below in combination with the specific embodiments, but the present invention is not limited to the embodiments in any forms. Substitutions of general parameters in the implementations cannot be exhausted in the embodiments, but the present invention is not limited thereto. Any other changes, modification, substitution, combination and simplification made without departing from the spirit and principles of the present invention should be deemed as equivalent replacement and should be comprised in the scope of the present invention.

[0042] Unless specified, reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0043] Unless specified, reagents and materials used in the following embodiments are commercially available.

Embodiment 1

[0044] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0045] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2; and a concentration of the plasticizer glycerol was controlled to account for 8% of a solid matter content;

[0046] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2, a concentration of oregano essential oil accounts for 15% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 8% of the solid matter content;

[0047] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0048] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.25 mm;

[0049] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of blank layer was subsequently poured based on the first layer of film to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film, and finally the film was rolled up at the other end of the casting machine; and

[0050] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing and testing.

Embodiment 2

[0051] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0052] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2; and a concentration of the plasticizer glycerol was controlled to account for 8% of a solid matter content;

[0053] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2, a concentration of oregano essential oil accounts for 15% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 8% of the solid matter content;

[0054] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0055] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.25 mm;

[0056] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was subsequently poured based on the first layer of film to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of blank layer was added to form a third layer of film, and finally the film was rolled up at the other end of the casting machine; and

[0057] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing and testing.

Embodiment 3

[0058] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0059] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2; and a concentration of the plasticizer glycerol was controlled to account for 8% of a solid matter content;

[0060] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2, a concentration of oregano essential oil accounts for 7.5% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 8% of the solid matter content;

[0061] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0062] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.25 mm;

[0063] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was subsequently poured based on the first layer of film to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film, and finally the film was rolled up at the other end of the casting machine; and

[0064] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing and testing.

Embodiment 4

[0065] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0066] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, oleic acid was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2; and a concentration of the plasticizer glycerol was controlled to account for 8% of a solid matter content;

[0067] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, oleic acid was added followed by magnetic stirring for 15 minutes; thyme essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2, a concentration of thyme essential oil accounts for 15% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 8% of the solid matter content;

[0068] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0069] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.5 mm;

[0070] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a second layer of film, and finally the film was rolled up at the other end of the casting machine; and

[0071] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing.

Embodiment 5

[0072] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0073] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2; and a concentration of the plasticizer glycerol was controlled to account for 8% of a solid matter content;

[0074] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; cinnamon essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2, a concentration of cinnamon essential oil accounts for 7.5% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 8% of the solid matter content;

[0075] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0076] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.25 mm;

[0077] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film; after the third layer of film was dried, 100 mL of the film-forming solution of blank layer was added to form a fourth layer of film; and finally the film was rolled up at the other end of the casting machine; and

[0078] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing.

Embodiment 6

[0079] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0080] (1) preparation of a film-forming solution of a blank layer: zein, kafirin, gelatin A, and casein were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of alcohol-soluble proteins (zein+kafirin) and water-soluble proteins (gelatin A+casein) was controlled to 20 wt %, wherein a mass ratio of the alcohol-soluble proteins (zein+kafirin) to the water-soluble proteins (gelatin A+casein) was 1:2; a concentration of the plasticizer glycerol was controlled to account for 8% of a solid matter content; and a mass ratio of zein to kafirin was 1:1, and a mass ratio of gelatin A to casein was 1:1;

[0081] (2) preparation of a film-forming solution of an essential oil-rich layer: zein, kafirin, gelatin A, and casein were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol and water were added followed by magnetic stirring for 15 minutes; fingered citron essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of alcohol-soluble proteins (zein+kafirin) and water-soluble proteins (gelatin A+casein) was controlled to 20 wt %, wherein a mass ratio of the alcohol-soluble proteins (zein+kafirin) to the water-soluble proteins (gelatin A+casein) was 1:2, a concentration of fingered citron essential oil accounts for 7.5% (v/w) of a solid matter content; a concentration of the plasticizers, glycerol and water (a volume ratio of glycerol to water was 1:1), was controlled to account for 8% of the solid matter content; and a mass ratio of zein to kafirin was 1:1, and a mass ratio of gelatin A to casein was 1:1;

[0082] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0083] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.25 mm; 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film; after the third layer of film was dried, 100 mL of the film-forming solution of blank layer was added to form a fourth layer of film; and finally the film was rolled up at the other end of the casting machine; and

[0084] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing.

Embodiment 7

[0085] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0086] (1) preparation of a film-forming solution of a blank layer: oat prolamin and whey protein were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, polyethylene glycol was added followed by magnetic stirring for 15 minutes; a total mass concentration of oat prolamin and whey protein was controlled to 20 wt %, wherein a mass ratio of oat prolamin to whey protein was 1:2; and a concentration of the plasticizer polyethylene glycol was controlled to account for 8% of a solid matter content;

[0087] (2) preparation of a film-forming solution of an essential oil-rich layer: wheat gliadin and soybean protein were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, oleic acid was added followed by magnetic stirring for 15 minutes; sage essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of wheat gliadin and soybean protein was controlled to 20 wt %, wherein a mass ratio of wheat gliadin to soybean protein was 1:2, a concentration of sage essential oil accounts for 5% (v/w) of a solid matter content; and a concentration of the plasticizer oleic acid was controlled to account for 8% of the solid matter content;

[0088] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0089] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.25 mm; 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film; after the third layer of film was dried, 100 mL of the film-forming solution of blank layer was added to form a fourth layer of film; after the fourth layer of film was dried, 100 mL of the film-forming solution of blank layer was added to form a fifth layer of film; after the fifth layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a sixth layer of film; after the sixth layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a seventh layer of film; after the seventh layer of film was dried, 100 mL of the film-forming solution of blank layer was added to form an eighth layer of film; and finally the film was rolled up at the other end of the casting machine; and

[0090] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing.

Embodiment 8

[0091] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0092] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 18 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:1.6; and a concentration of the plasticizer glycerol was controlled to account for 5% of a solid matter content;

[0093] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 22 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:1.6, a concentration of oregano essential oil accounts for 7.5% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 5% of the solid matter content;

[0094] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0095] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 50° C., a cast velocity was 0.02 m/min, and a knife height was 0.2 mm;

[0096] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of blank layer was subsequently poured based on the first layer of film to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film, and finally the film was rolled up at the other end of the casting machine; and

[0097] (5) The above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing.

Embodiment 9

[0098] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0099] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 22 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:1.6; and a concentration of the plasticizer glycerol was controlled to account for 20% of a solid matter content;

[0100] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 18 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:1.6, a concentration of oregano essential oil accounts for 16% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 20% of the solid matter content;

[0101] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0102] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 80° C., a cast velocity was 0.15 m/min, and a knife height was 0.8 mm;

[0103] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of blank layer was subsequently poured based on the first layer of film to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film, and finally the film was rolled up at the other end of the casting machine; and

[0104] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing.

Embodiment 10

[0105] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0106] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 16 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:1.3; and a concentration of the plasticizer glycerol was controlled to account for 10% of a solid matter content;

[0107] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 16 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:1.3, a concentration of oregano essential oil accounts for 5% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 10% of the solid matter content;

[0108] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0109] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 40° C., a cast velocity was 0.01 m/min, and a knife height was 0.1 mm;

[0110] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of blank layer was subsequently poured based on the first layer of film to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film, and finally the film was rolled up at the other end of the casting machine; and

[0111] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing.

Embodiment 11

[0112] An edible film enriched in essential oil divisionally and enhancing the release efficiency of essential oil was prepared by the following steps:

[0113] (1) preparation of a film-forming solution of a blank layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 27 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2.7; and a concentration of the plasticizer glycerol was controlled to account for 10% of a solid matter content;

[0114] (2) preparation of a film-forming solution of an essential oil-rich layer: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 27 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2.7, a concentration of oregano essential oil accounts for 18% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 10% of the solid matter content;

[0115] (3) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0116] (4) film-forming by multi-layer casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 40° C., a cast velocity was 0.01 m/min, and a knife height was 1 mm;

[0117] 100 mL of the film-forming solution of blank layer was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution of blank layer was subsequently poured based on the first layer of film to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution of essential oil-rich layer was added to form a third layer of film, and finally the film was rolled up at the other end of the casting machine; and

[0118] (5) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing.

Comparative Example 1

[0119] A conventional edible film loading with essential oil was prepared by the following steps:

[0120] (1) preparation of a film-forming solution loading with essential oil: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2; a concentration of oregano essential oil accounts for 5% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 8% of the solid matter content;

[0121] (2) degasification: the above-prepared film-forming solution was degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0122] (3) film-forming by casting: the edible film was prepared with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.75 mm; 300 mL of the film-forming solution loading with essential oil was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; and finally the film was rolled up at the other end of the casting machine; and

[0123] (4) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing and testing.

Comparative Example 2

[0124] A conventional edible film loading with an active substance prepared by a multi-layer casting process was prepared by the following steps:

[0125] (1) preparation of a film-forming solution loading with active substance: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2; a concentration of oregano essential oil accounts for 5% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 8% of the solid matter content;

[0126] (2) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0127] (3) film-forming by casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.375 mm;

[0128] 150 mL of the film-forming solution loading with active substance was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 150 mL of the film-forming solution loading with active substance was poured based on the first layer of film to form a second layer of film; and finally the film was rolled up at the other end of the casting machine; and

[0129] (4) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing and testing.

Comparative Example 3

[0130] A conventional edible film loading with an active substance prepared by a multi-layer casting process was prepared by the following steps:

[0131] (1) preparation of a film-forming solution loading with active substance: zein and gelatin A were dissolved in an 80% (v/v) acetic acid; after stirring to complete dissolution, glycerol was added followed by magnetic stirring for 15 minutes; oregano essential oil was then added, followed by magnetic stirring for 1 hour; a total mass concentration of zein and the water-soluble protein gelatin A was controlled to 20 wt %, wherein a mass ratio of zein to the water-soluble protein gelatin A was 1:2; a concentration of oregano essential oil accounts for 5% (v/w) of a solid matter content; and a concentration of the plasticizer glycerol was controlled to account for 8% of the solid matter content;

[0132] (2) degasification: the above-prepared film-forming solutions were degassed ultrasonically for 5 minutes to remove the bubbles from the film-forming solutions;

[0133] (3) film-forming by casting: the edible film was prepared by multi-layer casting with a casting machine, and parameters of the casting machine were set as follows: an oven temperature was 60° C., a cast velocity was 0.05 m/min, and a knife height was 0.375 mm;

[0134] 100 mL of the film-forming solution loading with active substance was poured into a trough of the casting machine, and passed through an oven to accelerate solvent evaporation; after a first layer of film was dried, 100 mL of the film-forming solution loading with active substance was poured based on the first layer of film to form a second layer of film; after the second layer of film was dried, 100 mL of the film-forming solution loading with active substance was added to form a third layer of film; and finally the film was rolled up at the other end of the casting machine; and

[0135] (4) the above-prepared edible film was placed in a sealed container at a temperature of 25° C. to 30° C. with humidity of 45% to 55% for storing and testing.

Experimental Embodiment

[0136] 1. Products prepared by Embodiments 1, 2, 3 and Comparative Examples 1, 2, 3 were placed in the same condition to carry out determination of release profile of oregano essential oil.

[0137] (1) By putting the product in n-hexane for continuous stirring, a release profile of oregano essential oil was determined. First, 30 mL of n-hexane was placed in a sealed serum bottle, and 1 g of the film (cut into a 5 mm×5 mm square) was put in the n-hexane. Then, the serum bottle was placed on a magnetic stirrer for continuous stirring at a rotate speed of 600 rpm to accelerate the release of essential oil from the film. At regular intervals, 0.5 mL of solution was taken out and diluted with 3 mL n-hexane, and absorbance of the diluted solution was detected at 276 nm using an ultraviolet spectrophotometer, and the concentration of essential oil was calculated according to a standard curve. Finally, a release profile of the concentration of essential oil varying with time was depicted.

[0138] (2) Test results are shown in FIG. 2.

[0139] A part of the essential oil is left in a film matrix during the release of essential oil from the film matrix to the environment, wherein the less the concentration of essential oil, the more dispersive the essential oil distributes in the film matrix, and the easier the essential oil is left in the film matrix. With the method of divisional enrichment, retention of essential oil within the film matrix can be reduced, and a displacement distance of the essential oil released from the film matrix to the environment is decreased. Besides, essential oil of high concentration can generate a stronger driving force, reducing the retention of essential oil within the film matrix. It can be seen from FIG. 2 that compared to Comparative Examples 1, 2 and 3, the release of the essential oil in Embodiments 1, 2 and 3 increased, wherein the essential oil was enriched in an external layer of the film in Embodiment 1, with a rapid-release effect; and the essential oil was enriched in an intermediate layer of the film in Embodiment 2, with a sustained-release effect, indicating that the sustained release of essential oil can be achieved by taking the essential oil-rich layer as an intermediate layer, while the rapid release of essential oil can be achieved by taking the essential oil-rich layer as an external layer.

[0140] In the comparative examples, with a number of the film layers increasing, the release efficiency of essential oil was decreased. This is because the increasing number of film layers would require increasing number of casting, a high-temperature drying time of the film was increased which raised the volatilization loss of essential oil. Therefore, the number of essential oil-rich layers should not be excessive. The addition amount of essential oil in each volume of film in the comparative examples and embodiments was equal, but a preparation method of divisional enrichment of essential oil was used, the release efficiency of essential oil was significantly enhanced. Thus, better fresh-keeping effect and reduction on industrial cost can be achieved.

[0141] 2. Products prepared by Embodiments 1, 2, 3 and Comparative Examples 1, 2, 3 were placed in the same condition to determine the rotten rate of blueberries packaged with these films products during the storage time.

[0142] (1) Blueberries produced in Shandong China were chosen as the fruit object for fresh keeping. Fresh blueberries were washed clean and those with suitable size were selected, water drops on the surface were wiped off, and each culture dish was placed with 15 blueberries. The film was covered on the culture dish surface (with the upper essential oil-rich layer oriented towards fruits) and fixed with a double-side adhesive tape. Each film was subjected to three parallel experiments. All culture dishes were placed in a temperature-constant and humidity-constant oven, a temperature was controlled to 28±2° C., and relative humidity was controlled to 80%. The number of rotten blueberries was observed every two days, and a final result was calculated as the rotten rate of fruit.

[0143] (2) Test results are shown in FIG. 3.

[0144] It can be known from the data of FIG. 3 that the rotten rate of blueberries preserved by using the films of the embodiments are all lower than those of the comparative examples. Particularly, the fresh-keeping effect of Embodiment 1 is the best. In the above determination of release profile of essential oil, although the release efficiencies of essential oil of Embodiments 2 and 3 are slightly higher than Comparative Example 1, the release of essential oil in the comparative example is a two-way release during the release of essential oil. In the practical application in fresh keeping, the essential oil acting on the objects to be preserved comes from only one direction. According to the data of FIG. 3, the fresh-keeping effect of both Embodiments 2 and 3 is obviously higher than Comparative Example 1, thus indicating that the two-way release of essential oil can be effectively reduced and anti-microbial effect of the active film can be enhanced by using the preparation method of divisional enrichment of essential oil.

[0145] 3. Products prepared by Embodiments 1, 2, 3 and the comparative examples were placed in the same condition to carry out a mechanical properties test and a transparency test. The test results are shown in Table 1.

TABLE-US-00001 TABLE 1 Comparison of mechanical properties and transparency between different edible films Tensile strength Elongation at Thickness Sample (Mpa) break (%) (μm) Transparency Embodiment 1  26.9 ± 5.08.sup.a 23.46 ± 11.58.sup.a  93.4 ± 0.66.sup.a 1.72 ± 0.35.sup.a Embodiment 2 22.09 ± 5.91.sup.a 29.57 ± 11.58.sup.a 88.13 ± 7.61.sup.a 1.35 ± 0.21.sup.a Embodiment 3 20.86 ± 6.35.sup.a 31.46 ± 6.35.sup.a  84.11 ± 2.23.sup.a 1.27 ± 0.46.sup.a Comparative 21.34 ± 2.06.sup.a 28.98 ± 8.73.sup.a  93.12 ± 7.44.sup.a 1.56 ± 0.17.sup.a Example 1 Comparative 22.67 ± 8.09.sup.a 34.89 ± 9.57.sup.b  100.73 ± 4.92.sup.b  1.33 ± 0.21.sup.a Example 2 Comparative 22.23 ± 3.45.sup.a 34.6 ± 9.21.sup.b   91.6 ± 4.69.sup.a 1.30 ± 0.31.sup.a Example 3

[0146] It can be known from the data of Table 1 that there's no significant difference in the tensile strength between Embodiments 1, 2, 3 and Comparative Examples 1, 2, 3, and thus the mechanical properties of the film would not be significantly decreased by the method of divisional enrichment of essential oil. And there's no significant difference in the transparency between Embodiments 1, 2, 3 and Comparative Examples 1, 2, 3, and thus the optical properties of the film would not be affected either by the method of divisional enrichment of essential oil.

[0147] 4. Products prepared by Embodiments 1, 2, 3 and Comparative Examples 1, 2, 3 were placed in the same condition to carry out observation of cross-section microstructure with a scanning electron microscope. The test result is shown in FIG. 4.

[0148] As seen from the FIG. 4, the three-layer structures in Embodiments 1, 2, 3, have good adhesiveness between layers without obvious separation of layers. This is because the solution used for preparing the three-layer film is the 80% acetic acid-water solution, when casting the film-forming solution on a previous dried film, the 80% acetic acid-water solution would re-dissolve a part of the surface of the already dried film, thus resulting in good adhesiveness between layers.

[0149] 5. Products prepared by Embodiments 1 and Embodiments 4, 5, 6, 7, 8, 9, 10, 11 were placed in the same condition to carry out a test of release profile of oregano essential oil from the film, a mechanical property test and optical property test, and observation of cross-section microstructure.

[0150] It is found in the results that the products prepared by Embodiments 4, 5, 6, 7, 8, 9, 10, 11 have good adhesiveness between layers without obvious separation of layers, and the mechanical properties and transparency of the films are relatively good, meanwhile with greatly enhanced release efficiency of essential oil. Particularly, through comparison of the products prepared by Embodiments 8, 9, 10, 11 and the product prepared by Embodiment 1, in the aspect of the release efficiency of essential oil, Embodiment 1 is better than Embodiments 8 and 9, and Embodiments 8 and 9 are better than Embodiments 10 and 11.

[0151] It is stated by the applicant that the above specific implementations are preferred embodiments for the convenience of understanding the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected in the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the scope of protection and disclosure of the present invention.