CN115340712A - A functional edible composite film based on pullulan and its preparation method - Google Patents

Abstract

The application of the present invention belongs to the technical field of food packaging, and specifically discloses a functional edible composite film based on pullulan polysaccharide and a preparation method thereof. Edible glycerin is used as a plasticizer, and after degassing and defoaming, it is poured into a mold to form a film, and the film is dried and peeled off to obtain a balance; the advantages of the present invention are: the black fungus protein and polysaccharides are extracted from the black fungus and residues as raw materials, It greatly reduces the waste treatment and the preparation cost of black fungus protein/polysaccharide. The source of raw materials is extensive, non-toxic and has a health care effect on the human body; Waste of resources and environmental pollution caused by the discarding of defective fungus products.

Description

A functional edible composite film based on pullulan and its preparation method

technical field

The invention belongs to the technical field of food packaging, and specifically discloses a pullulan-based functional edible composite film and a preparation method thereof.

Background technique

Plastic packaging film is inedible, non-degradable, and difficult to recycle. Discarded plastic packaging is likely to cause waste of resources and pollute the environment. Edible films made of natural polymer biomaterials are more environmentally friendly and easy to decompose. Edible film is a degradable multifunctional film with a porous network structure formed through the interaction of different molecules by adding film-forming aids such as cross-linking agents and plasticizers using edible materials. It can be wrapped, impregnated, Coating and microcapsules are used to cover the surface/inside of food to maintain food safety, quality and extend shelf life. According to the film-forming materials, the films can be divided into polysaccharides, proteins, lipids and complex types, among which polysaccharide-based edible films have high film-forming properties, functional nutritional properties, good mechanical and barrier properties, and chemical stability .

Pullulan (Pullulan, PUL) is a non-ionic exopolysaccharide obtained from the fermentation medium of black yeast. It is an odorless, tasteless, edible water-soluble polymer without any toxicity And mutagenicity, its molecular weight is in the range of 4.5×10 ⁴ ~6×10 ⁵ Da, and its characteristic molecular formula is (C ₆ H ₁₀ O ₅ ) _n . It consists of α-(1,6) repeating maltotriose units linked by α-(1,4) glycosidic bonds, PUL has unique physicochemical properties due to the presence of nine hydroxyl groups on the glucopyranose ring of the G3 unit, such as Good film-forming properties, high water solubility, oxygen barrier properties and degradability. Pullulan film surface is transparent, colorless, odorless, non-toxic, has good oil resistance, oxygen resistance, high thermal stability and biodegradability, and can be used as food packaging materials. The brittleness, fragility, high cost, and lack of active functions of pullulan films limit its wider application. The design of pullulan-based blends and composite films is the route of choice to overcome these inherent limitations and obtain bioactive edible packaging systems for improved shelf life, safety, and quality of food products. Different kinds of bioactive compounds with antioxidant and antibacterial activities (such as polyphenolic compounds, nanomaterials, peptides, plant essential oils, and fungal extracts) have been added to polysaccharide membrane matrices to develop innovative active membranes.

Black fungus (Auricularia auricula), also known as tree chicken, light fungus, wood pistil, etc., is a colloid fungus of the family Auriculariaceae, and is widely used as health food and traditional medicine. The fruit body of black fungus has high colloid content, soft and smooth texture, and delicious taste. According to traditional Chinese medicine, black fungus has the functions of moistening lung and relieving cough, nourishing kidney and stomach, moistening dryness, nourishing qi and nourishing blood, etc. Carbohydrates and protein are the main active ingredients of black fungus. Through the determination of the dry fruiting body of black fungus, it can be known that the black fungus polysaccharide (Auricularia auricula polysaccharide, AAP) accounts for 61%, and the black fungus protein (Auricularia auricula protein, AAPR) accounts for 11.38%. Black fungus has potential value in functional food, cosmetics and medicine. During the picking and sorting process of black fungus, there are a large number of defective products that are not moldy. Among them, ear roots, broken fungus, and undeveloped defective black fungus account for 5% to 10% of the total output. These defective black fungus are mainly used as waste. Disposal of waste not only causes environmental pollution, but also wastes resources.

Contents of the invention

The object of the present invention is to provide a functional edible composite film based on pullulan and a preparation method thereof, so as to solve the problems of waste of resources and environmental pollution caused by discarding defective black fungus products.

In order to achieve the above object, the technical solution of the present invention is: a functional edible composite film based on pullulan, with pullulan and black fungus polysaccharide/protein as film-forming matrix, adding edible glycerin as plasticizer After degassing and defoaming, it is poured into a mold to form a film, dried and peeled off to balance.

Further, a preparation method of a functional edible composite film based on pullulan comprises the following steps:

(1) Preparation of pullulan solution: dissolving pullulan in distilled water to prepare a pullulan solution with a mass concentration of 1.6%-2.4%;

(2) adding a plasticizer: adding edible glycerol with a mass fraction of 18%-22% to the pullulan solution obtained in step (1) to obtain a mixed solution;

(3) Preparation of black fungus polysaccharide/protein solution: dissolving black fungus polysaccharide and black fungus protein in distilled water to prepare black fungus polysaccharide and black fungus protein ratio is 20% of the pullulan quality in step (1): 0% -0%: 20% black fungus polysaccharide/protein solution;

(4) Preparation of black fungus polysaccharide/protein/pullulan composite film-forming solution: mix the mixed solution obtained in step (2) with the black fungus polysaccharide/protein solution obtained in step (3), heat and stir in a water bath, Until the mixed solution is completely dissolved and uniform, and then magnetically stirred to obtain a film-forming solution;

(5) degassing and defoaming: the film-forming solution obtained in step (4) is subjected to ultrasonic degassing and defoaming;

(6) Cast film formation: pour the film-forming solution into an acrylic plate mold to cast a film to obtain a composite film;

(7) drying and peeling off the film: the composite film obtained in step (6) is heated and dried, and after being cooled to normal temperature, the film is peeled off;

(8) Balance: place the composite film in a constant temperature and humidity box to balance for 36-60 hours.

The working principle of this technical solution is: extract black fungus polysaccharide and black fungus protein from defective black fungus and residues as raw materials, prepare it together with pullulan polysaccharide as a film-forming matrix, add edible glycerin as a plasticizer, and degas Defoaming, casting into a film, and drying to obtain a functional edible composite film based on pullulan.

The beneficial effects of this technical solution are:

(1) Black fungus polysaccharide and black fungus protein are natural polymer substances extracted from the fungus black fungus, and the prepared black fungus polysaccharide/protein/pullulan polysaccharide-based composite film is safe and edible;

(2) Black fungus polysaccharides and black fungus proteins have antioxidant and antibacterial activities, and have the potential to become natural polymer antioxidants and antibacterial agents, which can endow black fungus polysaccharide/protein/pullulan-based composite films with better functions Activity, which is beneficial to play a better fresh-keeping effect;

(3) Black fungus polysaccharide and black fungus protein are substances with special nutritional value. Black fungus polysaccharide has a wide range of physiological activities, and black fungus protein has 8 kinds of essential amino acids, which have beneficial health effects on promoting human health;

(4) Black fungus polysaccharide, black fungus protein and pullulan polysaccharide are natural polymers, and the prepared black fungus polysaccharide/protein/pullulan polysaccharide-based composite film can be eaten or degraded by microorganisms after use, and will not affect the environment create pollution;

(5) The production process of black fungus polysaccharide and black fungus protein is simple and efficient, and the production process of pullulan polysaccharide is mature, which can continuously provide raw materials for the preparation of black fungus polysaccharide/protein/pullulan-based composite film;

(6) Black fungus protein and polysaccharides were extracted from defective black fungus and residues, which greatly reduced the cost of waste treatment and black fungus protein/polysaccharide preparation, and the black fungus polysaccharide, protein/pullulan polysaccharide-based composite film It can be degraded by itself after use, further reducing recycling costs.

Further, in step (4), the temperature of the water bath is 35-45° C., and the magnetic stirring time is 10-20 min.

Further, the ultrasonic treatment condition in step (5) is a power of 120-180W and a time of 5-15min.

Further, the heating condition in step (7) is 40-50° C., and the drying time is 6-10 hours.

Further, the equilibrium conditions in step (8) are 55-65% relative humidity and 20-30° C. temperature.

Description of drawings

Fig. 1 is a kind of pullulan-based functional edible composite film of the present invention and its preparation method embodiment, the pullulan polysaccharide-based composite film containing different proportions of black fungus polysaccharide (AAP) and black fungus protein (AAPR) Surface and cross-sectional scanning electron micrographs of the membrane;

Fig. 2 is the infrared spectrogram of the pullulan base composite film containing different proportions of AAP and AAPR in the embodiment;

Fig. 3 is the differential scanning calorimetry thermal characteristic curve of the pullulan base composite film containing different proportions of AAP and AAPR in the embodiment;

Fig. 4 is the X-ray diffraction spectrogram of the pullulan-based composite film containing different ratios of AAP and AAPR in an embodiment;

Fig. 5 is the contrast figure of DPPH and ABTS free radical scavenging activity of AAP and AAPR composite film of different proportions in the embodiment;

Fig. 6 is a comparison chart of antibacterial activity of pullulan-based composite films containing different proportions of AAP and AAPR in the examples.

Detailed ways

Below by specific embodiment and accompanying drawing, further describe in detail:

Fig. 1 is a kind of pullulan-based functional edible composite film of the present invention and its preparation method embodiment, the pullulan polysaccharide-based composite film containing different proportions of black fungus polysaccharide (AAP) and black fungus protein (AAPR) Surface and cross-sectional scanning electron micrographs of the membrane;

Fig. 2 is the infrared spectrogram of the pullulan base composite film containing different proportions of AAP and AAPR in the embodiment;

Fig. 3 is the differential scanning calorimetry thermal characteristic curve of the pullulan base composite film containing different proportions of AAP and AAPR in the embodiment;

Fig. 4 is the X-ray diffraction spectrogram of the pullulan-based composite film containing different ratios of AAP and AAPR in an embodiment;

Fig. 5 is the contrast figure of DPPH and ABTS free radical scavenging activity of AAP and AAPR composite film of different proportions in the embodiment;

Fig. 6 is a comparison chart of antibacterial activity of pullulan-based composite films containing different proportions of AAP and AAPR in the examples.

A functional edible composite film based on pullulan and a preparation method thereof, comprising the following steps:

(1) Preparation of pullulan solution: dissolving pullulan in distilled water to prepare a pullulan solution with a mass concentration of 1.6%-2.4%;

(2) adding a plasticizer: adding edible glycerol with a mass fraction of 18%-22% to the pullulan solution obtained in step (1) to obtain a mixed solution;

(3) Preparation of black fungus polysaccharide/protein solution: dissolving black fungus polysaccharide and black fungus protein in distilled water to prepare black fungus polysaccharide and black fungus protein ratio is 20% of the pullulan quality in step (1): 0% -0%: 20% black fungus polysaccharide/protein solution;

(4) Preparation of black fungus polysaccharide/protein/pullulan composite film-forming solution: mix the mixed solution obtained in step (2) with the black fungus polysaccharide/protein solution obtained in step (3), heat and heat at 35-45°C Stir in a water bath until the mixed solution is completely dissolved and uniform, then magnetically stir for 10-20 minutes to obtain a film-forming solution;

(5) degassing and defoaming: the film-forming solution obtained in step (4) is subjected to 120-180W ultrasonic degassing treatment, defoaming for 5-15min;

(6) Cast film formation: pour the film-forming solution into an acrylic plate mold to cast a film to obtain a composite film;

(7) Drying and removing the film: dry the composite film obtained in step (6) at 40-50°C for 6-10 hours, and gently peel off the film after cooling to normal temperature;

(8) Balance: place the composite film in a constant temperature and humidity (relative humidity 55-65%, 20-30° C.) box to balance for 36-60 hours.

The specific implementation process is as follows:

Example 1

1. Preparation of functional edible composite film based on pullulan

(1) Preparation of pullulan solution: dissolving pullulan in distilled water to prepare a pullulan solution with a mass concentration of 2%;

(2) Adding a plasticizer: adding a mass fraction of 20% edible glycerin to the pullulan solution obtained in step (1) to obtain a mixed solution;

(3) Preparation of black fungus polysaccharide/protein solution: dissolving black fungus polysaccharide and black fungus protein in distilled water to prepare black fungus polysaccharide and black fungus protein ratio is 20% of the pullulan quality in step (1): 0% black fungus polysaccharide/protein solution;

(4) Preparation of black fungus polysaccharide/protein/pullulan composite film-forming solution: mix the mixed solution obtained in step (2) with the black fungus polysaccharide/protein solution obtained in step (3), heat and place in a water bath at 40°C Stir until the mixed solution is completely dissolved and uniform, then magnetically stir for 15 minutes to obtain a film-forming solution;

(5) Degassing and defoaming: the film-forming solution obtained in step (4) is subjected to 150W ultrasonic degassing treatment, and defoaming for 10 minutes;

(6) Cast film formation: pour 20mL of the film-forming solution into an acrylic plate mold (5cm×10cm×1cm) (polymethyl methacrylate) to cast a film;

(7) Drying and removing the film: dry the composite film obtained in step (6) at 45°C for 8 hours, and then gently peel off the film after cooling to normal temperature;

(8) Equilibration: the composite film was placed in a constant temperature and humidity (60% relative humidity, 25° C.) box to equilibrate for 48 hours.

2. Structural characterization of functional edible composite films based on pullulan

The surface and cross-sectional microstructure of the film of Example 1 were observed using a scanning electron microscope (SEM): the film was dried at 50°C for 4h; the film was frozen in liquid nitrogen and ruptured to observe the cross-sectional structure; the film was fixed on the platform with conductive tape , and sprayed gold layer (10nm); the accelerating voltage was 5kv; the surface and cross-sectional morphology of the film were observed at 1000× and 800×. The result is shown in Figure 1.

Use Fourier Transform Infrared Spectroscopy (FT-IR) to study the functional groups and structural changes of the film of Example 1: the film and potassium bromide are dried in an oven until the water is completely evaporated, mixed (mass ratio is 1:100), uniform Grind and tablet. The scanning wavelength range, resolution and scanning times are 400-5000cm ^-1 , 4cm ^-1 and 32, respectively. The result is shown in Figure 2.

The thermal stability of the film of Example 1 was analyzed using differential scanning calorimetry (DSC): the film was weighed (3-5 mg) and placed in an aluminum crucible; using an empty crucible as a reference, the heating rate was controlled at 10 °C/min, and increase the temperature from 25 °C to 170 °C. The result is shown in Figure 3.

Use X-ray diffractometer (XRD) to investigate the crystal structure and compatibility of embodiment 1 film: the film was dried for 24 hours, and in the 2θ range of 10°-60° by XRD, with a scan rate of 5°/min, The analysis was performed using a copper Ka radiation source, a voltage of 40 kV and a current of 40 mA. The result is shown in Figure 4.

3. Performance test of functional edible composite film based on pullulan

Thickness and density test: use a screw micrometer (accuracy 0.001mm), take ten points for each film to measure the film thickness (ten points are randomly and evenly distributed on the sample, one of which is the center point), and take the average value as the test sample film thickness;

Cut the film into a size of 2cm×2cm, and weigh the mass of the film (2×2cm) with an electronic balance. The formula for calculating the film density is as follows:

In the formula: m is the weight (g) of the film, s is the area (cm ³ ) of the film, and d is the thickness (mm) of the film. The thickness and density test results of Example 1 are shown in Table 1.

Solubility and swelling test: Dry the film (2×2cm) at 105°C to constant weight (m ₁ ), immerse the film in 30mL of distilled water, dissolve at 25°C for 24h, remove the distilled water on the surface with filter paper, place the film in Dry to constant weight at 105°C and weigh (m ₂ ). The formula for calculating solubility is as follows:

The weight (m ₁ ) of the film (2×2 cm) was weighed, then immersed in 30 mL of distilled water for 24 hours, and the residual water on the surface was removed with filter paper, and the weight (m ₂ ) was weighed. The calculation formula of swelling degree is as follows:

The solubility and swelling test results of Example 1 are shown in Table 1.

Moisture content (MC) and water vapor transmission rate (WVP) tests: Weigh the film (m ₁ ) and dry it in an oven at 105°C to constant weight (m ₂ ). The moisture content calculation formula is as follows:

Use a rubber band to seal the film on the mouth of a 50mL conical flask filled with 10g of color-changing silica gel, and then place the conical flask in a desiccator filled with distilled water at a temperature of 25°C. The Erlenmeyer flasks were weighed hourly until constant weight was reached. The formula for calculating water vapor transmission rate is as follows:

In the formula: Δm is the weight change of the Erlenmeyer flask (g), D is the thickness of the film (mm), A is the permeation area (m ² ), t is the permeation time (h), and ΔP is the water vapor pressure difference on both sides of the film (3.168kPa). The moisture content and water vapor transmission rate test results of Example 1 are shown in Table 2.

Tensile Strength (TS) and Elongation at Break (EAB) Tests: The film was initially cut into strips (15mm x 80mm) with a minimum induced force of 5.0g. The initial gripper distance and detector speed were set at 30 mm and 5 mm/s, respectively. The calculation formulas of tensile strength and elongation at break are as follows:

In the formula: F is the maximum tension (N), S is the cross-sectional area of the film (width×thickness, mm ² ), L ₁ is the initial length of the film (mm), and L is the length of the film when it breaks (mm). The tensile strength and elongation at break test results of Example 1 are shown in Table 2.

Color parameters and opacity test: Film color (L*, a*, b*) parameters were measured on a white background (L=99.9, a=0, b=0.02) using a colorimeter. The calculation formula of total color difference (ΔE) is as follows:

ΔE＝[(L ^* -L) ² +(a ^* -a) ² +(b ^* -b) ² ] ^0.5

Cut the film into strips (40mm×10mm) and measure its thickness (D), then attach it tightly to the inner wall of a cuvette, and measure the absorbance at 600nm (Abs ₆₀₀ ) by a UV-Vis spectrophotometer. The formula for calculating opacity (O) is as follows:

The color parameters and opacity test results of Example 1 are shown in Table 3.

Antioxidant performance test: immerse 50 mg of the film in a test tube filled with ethanol (5 mL) for 24 hours to obtain a film extract. Then, the membrane extract solution (0.1mL) or absolute ethanol (0.1mL) as a control was added to 3.9mL DPPH (0.2mM) ethanol solution, and shaken, after 30min incubation in the dark at ambient temperature, Absorbance was measured at 517nm. The calculation formula of DPPH free radical scavenging rate is as follows:

In the formula: A ₀ is the absorbance of the control, A ₁ is the absorbance of the film extract solution and the DPPH solution.

Mix ABTS solution (7.4mM) and potassium persulfate (2.6mM) at a ratio of 1:1, and keep away from light for 16h, dilute the mixture with ethanol, and measure the absorbance of the mixture at 734nm to 0.70±0.001, 4°C Save the stock solution. The film extract (0.1 mL) or absolute ethanol as a control (0.1 mL) was mixed with the ABTS stock solution (1.0 mL), and incubated in the dark for 10 min, and the absorbance of the mixture was measured at 734 nm. The calculation formula of ABTS free radical scavenging rate is as follows:

In the formula: A ₀ is the absorbance of the control, and A ₁ is the absorbance of the film extract containing the ABTS solution. The results of the antioxidant performance test of Example 1 are shown in FIG. 5 .

Antibacterial performance test: The antibacterial performance of the film was evaluated by the solid assay method, and the diameter of the inhibition zone was measured. The stock solid culture of bacterial species is stored in a refrigerator at 4°C, and the test microorganisms Escherichia coli (G-) and Staphylococcus aureus (G+) are inoculated into LB broth liquid medium, cultivated and activated at 37°C For 24 hours, inoculate the bacterial suspension (0.1 mL) of Escherichia coli (5×10 ⁶ CFU/mL) and Staphylococcus aureus (2×10 ⁶ CFU/mL) on the surface of the agar plate of the medium, and then spread evenly , cut the film sample into discs with a diameter of 10 mm and sterilize them under ultraviolet light, place the discs on plate culture medium and incubate at 37°C for 24 hours, then measure the diameter of the inhibition zone around the film discs with a vernier caliper . The antibacterial performance test results of Example 1 are shown in FIG. 6 .

Example 2

1. Preparation of functional edible composite film based on pullulan

(1) Preparation of pullulan solution: dissolving pullulan in distilled water to prepare a pullulan solution with a mass concentration of 2%;

(2) Adding a plasticizer: adding a mass fraction of 20% edible glycerin to the pullulan solution obtained in step (1) to obtain a mixed solution;

(3) Prepare black fungus polysaccharide/protein solution: black fungus polysaccharide and black fungus protein are dissolved in distilled water to prepare black fungus polysaccharide and black fungus protein. The ratio is 15%:5% of the pullulan quality in step (1). black fungus polysaccharide/protein solution;

(4) Preparation of black fungus polysaccharide/protein/pullulan composite film-forming solution: mix the mixed solution obtained in step (2) with the black fungus polysaccharide/protein solution obtained in step (3), heat and place in a water bath at 40°C Stir until the mixed solution is completely dissolved and uniform, then magnetically stir for 15 minutes to obtain a film-forming solution;

(5) Degassing and defoaming: the film-forming solution obtained in step (4) is subjected to 150W ultrasonic degassing treatment, and defoaming for 10 minutes;

(6) Cast film formation: pour 20mL of the film-forming solution into an acrylic plate mold (5cm×10cm×1cm) (polymethyl methacrylate) to cast a film;

(7) Drying and removing the film: dry the composite film obtained in step (6) at 45°C for 8 hours, and then gently peel off the film after cooling to normal temperature;

(8) Equilibration: the composite film was placed in a constant temperature and humidity (60% relative humidity, 25° C.) box to equilibrate for 48 hours.

2. Structural characterization of functional edible composite films based on pullulan

The method and parameters of the structural characterization of the functional edible composite film based on pullulan polysaccharide are the same as in Example 1, the results of scanning electron microscope are shown in Figure 1, the results of Fourier transform infrared spectroscopy are shown in Figure 2, and the results of differential scanning The calorimetric results are shown in FIG. 3 , and the X-ray diffraction results are shown in FIG. 4 .

3. Performance test of functional edible composite film based on pullulan

The method and condition of the performance test of the functional edible composite film based on pullulan polysaccharide are the same as in Example 1, and the test results of moisture content, water vapor transmission rate, tensile strength elongation at break are as shown in Table 2, and the color parameters The results of the and opacity tests are shown in Table 3, the results of the antioxidant performance test are shown in Figure 5, and the results of the antibacterial performance test are shown in Figure 6.

Example 3

1. Preparation of functional edible composite film based on pullulan

(1) Preparation of pullulan solution: dissolving pullulan in distilled water to prepare a pullulan solution with a mass concentration of 2%;

(2) Adding a plasticizer: adding a mass fraction of 20% edible glycerin to the pullulan solution obtained in step (1) to obtain a mixed solution;

(3) Preparation of black fungus polysaccharide/protein solution: dissolving black fungus polysaccharide and black fungus protein in distilled water to prepare black fungus polysaccharide and black fungus protein ratio is 10% of the pullulan quality in step (1): 10% black fungus polysaccharide/protein solution;

(4) Preparation of black fungus polysaccharide/protein/pullulan composite film-forming solution: mix the mixed solution obtained in step (2) with the black fungus polysaccharide/protein solution obtained in step (3), heat and place in a water bath at 40°C Stir until the mixed solution is completely dissolved and uniform, then magnetically stir for 15 minutes to obtain a film-forming solution;

(5) Degassing and defoaming: the film-forming solution obtained in step (4) is subjected to 150W ultrasonic degassing treatment, and defoaming for 10 minutes;

(6) Cast film formation: pour 20mL of the film-forming solution into an acrylic plate mold (5cm×10cm×1cm) (polymethyl methacrylate) to cast a film;

(7) Drying and removing the film: dry the composite film obtained in step (6) at 45°C for 8 hours, and then gently peel off the film after cooling to normal temperature;

(8) Equilibration: the composite film was placed in a constant temperature and humidity (60% relative humidity, 25° C.) box to equilibrate for 48 hours.

2. Structural characterization of functional edible composite films based on pullulan

The method and parameters of the structural characterization of the functional edible composite film based on pullulan polysaccharide are the same as in Example 1, the results of scanning electron microscope are shown in Figure 1, the results of Fourier transform infrared spectroscopy are shown in Figure 2, and the results of differential scanning The calorimetric results are shown in FIG. 3 , and the X-ray diffraction results are shown in FIG. 4 .

3. Performance test of functional edible composite film based on pullulan

The method and condition of the performance test of the functional edible composite film based on pullulan polysaccharide are the same as in Example 1, and the test results of moisture content, water vapor transmission rate, tensile strength elongation at break are as shown in Table 2, and the color parameters The results of the and opacity tests are shown in Table 3, the results of the antioxidant performance test are shown in Figure 5, and the results of the antibacterial performance test are shown in Figure 6.

Example 4

1. Preparation of functional edible composite film based on pullulan

(1) Preparation of pullulan solution: dissolving pullulan in distilled water to prepare a pullulan solution with a mass concentration of 2%;

(2) Adding a plasticizer: adding a mass fraction of 20% edible glycerin to the pullulan solution obtained in step (1) to obtain a mixed solution;

(3) Preparation of black fungus polysaccharide/protein solution: dissolving black fungus polysaccharide and black fungus protein in distilled water to prepare black fungus polysaccharide and black fungus protein ratio is 5% of the pullulan quality in step (1): 15% black fungus polysaccharide/protein solution;

(4) Preparation of black fungus polysaccharide/protein/pullulan composite film-forming solution: mix the mixed solution obtained in step (2) with the black fungus polysaccharide/protein solution obtained in step (3), heat and place in a water bath at 40°C Stir until the mixed solution is completely dissolved and uniform, then magnetically stir for 15 minutes to obtain a film-forming solution;

(5) Degassing and defoaming: the film-forming solution obtained in step (4) is subjected to 150W ultrasonic degassing treatment, and defoaming for 10 minutes;

(6) Cast film formation: pour 20mL of the film-forming solution into an acrylic plate mold (5cm×10cm×1cm) (polymethyl methacrylate) to cast a film;

(7) Drying and removing the film: dry the composite film obtained in step (6) at 45°C for 8 hours, and then gently peel off the film after cooling to normal temperature;

(8) Equilibration: the composite film was placed in a constant temperature and humidity (60% relative humidity, 25° C.) box to equilibrate for 48 hours.

2. Structural characterization of functional edible composite films based on pullulan

The method and parameters of the structural characterization of the functional edible composite film based on pullulan polysaccharide are the same as in Example 1, the results of scanning electron microscope are shown in Figure 1, the results of Fourier transform infrared spectroscopy are shown in Figure 2, and the results of differential scanning The calorimetric results are shown in FIG. 3 , and the X-ray diffraction results are shown in FIG. 4 .

3. Performance test of functional edible composite film based on pullulan

The method and condition of the performance test of the functional edible composite film based on pullulan polysaccharide are the same as in Example 1, and the test results of moisture content, water vapor transmission rate, tensile strength elongation at break are as shown in Table 2, and the color parameters The results of the and opacity tests are shown in Table 3, the results of the antioxidant performance test are shown in Figure 5, and the results of the antibacterial performance test are shown in Figure 6.

Example 5

1. Preparation of functional edible composite film based on pullulan

(1) Preparation of pullulan solution: dissolving pullulan in distilled water to prepare a pullulan solution with a mass concentration of 2%;

(2) Adding a plasticizer: adding a mass fraction of 20% edible glycerin to the pullulan solution obtained in step (1) to obtain a mixed solution;

(3) Preparation of black fungus polysaccharide/protein solution: dissolving black fungus polysaccharide and black fungus protein in distilled water to prepare black fungus polysaccharide and black fungus protein ratio is 0% of the pullulan quality in step (1): 20% black fungus polysaccharide/protein solution;

(4) Preparation of black fungus polysaccharide/protein/pullulan composite film-forming solution: mix the mixed solution obtained in step (2) with the black fungus polysaccharide/protein solution obtained in step (3), heat and place in a water bath at 40°C Stir until the mixed solution is completely dissolved and uniform, then magnetically stir for 15 minutes to obtain a film-forming solution;

(5) Degassing and defoaming: the film-forming solution obtained in step (4) is subjected to 150W ultrasonic degassing treatment, and defoaming for 10 minutes;

(6) Cast film formation: pour 20mL of the film-forming solution into an acrylic plate mold (5cm×10cm×1cm) (polymethyl methacrylate) to cast a film;

(7) Drying and removing the film: dry the composite film obtained in step (6) at 45°C for 8 hours, and then gently peel off the film after cooling to normal temperature;

(8) Equilibration: the composite film was placed in a constant temperature and humidity (60% relative humidity, 25° C.) box to equilibrate for 48 hours.

2. Structural characterization of functional edible composite films based on pullulan

The method and parameters of the structural characterization of the functional edible composite film based on pullulan polysaccharide are the same as in Example 1, the results of scanning electron microscope are shown in Figure 1, the results of Fourier transform infrared spectroscopy are shown in Figure 2, and the results of differential scanning The calorimetric results are shown in FIG. 3 , and the X-ray diffraction results are shown in FIG. 4 .

3. Performance test of functional edible composite film based on pullulan

The method and condition of the performance test of the functional edible composite film based on pullulan polysaccharide are the same as in Example 1, and the test results of moisture content, water vapor transmission rate, tensile strength elongation at break are as shown in Table 2, and the color parameters The results of the and opacity tests are shown in Table 3, the results of the antioxidant performance test are shown in Figure 5, and the results of the antibacterial performance test are shown in Figure 6.

Fig. 1 shows the embodiment of the functional edible composite film based on pullulan and its preparation method, the pullulan-based composite film containing different proportions of black fungus polysaccharide (AAP) and black fungus protein (AAPR) The surface and cross-section SEM micrographs of, wherein Control represents contrast film, P1, P2, P3, P4 and P5 represent embodiment 1, embodiment 2, embodiment 3, embodiment 4 and embodiment 5 respectively, and a represents 1000 × lower surface cross-section, b represents the cross-section under 800×. Compared with the control film, the surface of P1 (20%:0%) was improved, no wrinkling, and small insoluble particles were observed in the cross-section. The addition of AAPR made the surface of P2(15%:5%) relatively flat, uniform and smooth. As the proportion of AAPR increased, the composite film formed a denser structure, which increased the TS of the film, and at the same time, the molecular mobility of the film components decreased, resulting in a decrease in the EAB of the PUL-based composite film. The surface and cross-section of P3(10%:10%) were smooth and uniform, without visible pores and cracks, indicating that the AAP/AAPR/PUL-based composite membrane had good compatibility and mechanical properties at this ratio. The surface structure of P4 (5%:15%) is smooth and uniform, with small insoluble particles in the cross-section. The surface of P5 (0%:20%) is continuous but not smooth, with different criss-cross patterns and raised cross-sections.

Fig. 2 is the infrared spectrogram of the pullulan base composite film containing different proportions of AAP and AAPR in the embodiment, wherein Control represents the contrast film, P1, P2, P3, P4 and P5 respectively represent embodiment 1, embodiment 2, implementation Example 3, Example 4 and Example 5.

Fig. 3 is the DSC thermal characteristic curve of the pullulan base composite film containing different proportions of AAP and AAPR in the embodiment, wherein Control represents the contrast film, P1, P2, P3, P4 and P5 represent embodiment 1, embodiment 2 respectively , embodiment 3, embodiment 4 and embodiment 5. The addition of AAP and AAPR significantly enhanced the melting peak of the PUL-based composite membrane.

Fig. 4 is the XRD spectrogram of the pullulan base composite membrane that contains different proportions AAP and AAPR in the embodiment, wherein Control represents contrast membrane, P1, P2, P3, P4 and P5 represent embodiment 1, embodiment 2, implementation respectively Example 3, Example 4 and Example 5.

Fig. 5 is the contrast figure of AAP and AAPR composite film of different proportions in the embodiment to DPPH and ABTS free radical scavenging activity, and wherein Control represents contrast film, P1, P2, P3, P4 and P5 represent embodiment 1, embodiment 2, In Example 3, Example 4 and Example 5, compared with the control membrane, the addition of AAP and AAPR significantly improved the scavenging ability of the composite membrane to DPPH and ABTS free radicals.

Fig. 6 is the comparison figure of the antibacterial activity of the pullulan polysaccharide-based composite film containing different proportions of AAP and AAPR in the embodiment, wherein Control represents the control film, P1, P2, P3, P4 and P5 respectively represent embodiment 1, embodiment 2 , embodiment 3, embodiment 4 and embodiment 5, a, b have expressed the impact on escherichia coli (G-) and Staphylococcus aureus (G+) to the addition of AAP and AAPR, and the addition of AAP/AAPR has significantly improved Antibacterial activity of pullulan-based composite membranes.

Table 1: Thickness, density, solubility and swelling degree of pullulan polysaccharide-based composite films containing different proportions of AAP and AAPR

With the addition of AAP and AAPR, the thickness and density of the pullulan polysaccharide-based composite membrane increased significantly, the solubility of the pullulan polysaccharide-based composite membrane gradually increased, and the swelling degree increased significantly.

Table 2: Moisture content, water vapor transmission rate, tensile strength and elongation at break of pullulan polysaccharide-based composite films containing different proportions of AAP and AAPR

Compared with the control film, the MC content of the composite film first increased and then decreased with the decrease of the ratio of AAP/AAPR, and the addition of AAP increased significantly from P1 (20%:0%) to P3 (10%:10%) However, with the decrease of AAP and the increase of AAPR, the WVP value of the pullulan-based composite membrane decreased significantly. The WVP value of P5(0%:20%) film was not significantly different from that of pullulan control film. Meanwhile, the addition of AAP/AAPR and glycerol improved the flexibility and fluidity of the pullulan-based composite membrane structure.

Table 3: Color parameters and opacity of pullulan polysaccharide-based composite films containing different proportions of AAP and AAPR

The addition of AAP/AAPR intensified the black, green and yellow color of the pullulan-based composite film, and reduced the transparency of the composite film.

What is described above is only an embodiment of the present invention, and common knowledge such as specific structures and characteristics known in the scheme are not described here too much. It should be pointed out that for those skilled in the art, under the premise of not departing from the structure of the present invention, several modifications and improvements can also be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation of the present invention. Effects and utility of patents.

Claims (6)

1. A functional edible composite film based on pullulan is characterized in that pullulan and auricularia auricula polysaccharide/protein are used as film forming matrixes, edible glycerol is added to be used as a plasticizer, degassing and defoaming are carried out, the mixture is poured into a mold to carry out tape casting, drying and film uncovering are carried out, and the functional edible composite film is obtained.

2. The method for preparing the pullulan-based functional edible composite film according to claim 1, wherein the method comprises the following steps:

(1) Preparing a pullulan solution: dissolving pullulan in distilled water to prepare a pullulan solution with the mass concentration of 1.6-2.4%;

(2) Adding a plasticizer: adding edible glycerol with the mass fraction of 18% -22% into the pullulan solution obtained in the step (1) to obtain a mixed solution;

(3) Preparing a black fungus polysaccharide/protein solution: dissolving black fungus polysaccharide and black fungus protein in distilled water to prepare a black fungus polysaccharide/protein solution, wherein the ratio of the black fungus polysaccharide to the black fungus protein is 20% to 0% to 20% of the mass of the pullulan polysaccharide in the step (1);

(4) Preparing a black fungus polysaccharide/protein/pullulan composite film-forming solution: mixing the mixed solution obtained in the step (2) with the auricularia auricula polysaccharide/protein solution obtained in the step (3), heating and stirring in a water bath until the mixed solution is completely and uniformly dissolved, and then magnetically stirring to obtain a film-forming solution;

(5) Degassing and defoaming: performing ultrasonic degassing and defoaming treatment on the film forming solution obtained in the step (4);

(6) Casting and film forming: pouring the film forming solution into an acrylic plate mold for casting and film forming to obtain a composite film;

(7) Drying and uncovering the film: heating and drying the composite film obtained in the step (6), and stripping the film after cooling to normal temperature;

(8) Balancing: and (3) placing the composite membrane in a constant temperature and humidity box for balancing for 36-60h.

3. The preparation method of the pullulan-based functional edible composite film according to claim 2, wherein the water bath temperature in the step (4) is 35-45 ℃, and the magnetic stirring time is 10-20min.

4. The preparation method of the pullulan-based functional edible composite film according to claim 2, wherein the ultrasonic treatment in the step (5) is performed under the power of 120-180W for 5-15min.

5. The preparation method of the pullulan-based functional edible composite film according to claim 2, wherein the heating condition in the step (7) is 40-50 ℃ and the drying time is 6-10h.

6. The method for preparing the pullulan-based functional edible composite film according to claim 2, wherein the equilibrium conditions in the step (8) are 55-65% of relative humidity and 20-30 ℃.

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