CN115368640B - Preparation method of pullulan polysaccharide loaded with tea polyphenol and seaweed candy and vegetable preservative film - Google Patents
Preparation method of pullulan polysaccharide loaded with tea polyphenol and seaweed candy and vegetable preservative film Download PDFInfo
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- CN115368640B CN115368640B CN202211063905.4A CN202211063905A CN115368640B CN 115368640 B CN115368640 B CN 115368640B CN 202211063905 A CN202211063905 A CN 202211063905A CN 115368640 B CN115368640 B CN 115368640B
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Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
- C08J2305/04—Alginic acid; Derivatives thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2401/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2401/08—Cellulose derivatives
- C08J2401/26—Cellulose ethers
- C08J2401/28—Alkyl ethers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/05—Alcohols; Metal alcoholates
- C08K5/053—Polyhydroxylic alcohols
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/15—Heterocyclic compounds having oxygen in the ring
- C08K5/151—Heterocyclic compounds having oxygen in the ring having one oxygen atom in the ring
- C08K5/1545—Six-membered rings
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
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- Polymers & Plastics (AREA)
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- Jellies, Jams, And Syrups (AREA)
Abstract
The invention discloses a preparation method of pullulan loaded with tea polyphenol and a seaweed candy and vegetable preservative film, and relates to the technical field of food packaging material preparation. The pullulan and trehalose are blended in an aqueous solution, and stirred at room temperature for 1h until the pullulan and trehalose are completely dissolved, so as to prepare a polysaccharide solution. Adding plasticizer and tea polyphenol with certain mass concentration into the polysaccharide solution, placing the blend into a water bath constant temperature magnetic stirrer, and stirring for 30min at 50 ℃ to obtain film forming solution. And (3) placing the film forming liquid in a sealed bag, placing the sealed bag in a multi-mode ultrasonic treatment device at room temperature, and taking out the sealed bag after ultrasonic treatment. Taking a film forming liquid, forming a film by adopting a tape casting method, and drying for 8 hours by blowing at 60 ℃; and taking out the film after the film is formed, and cooling to room temperature to obtain the preservative film. The obtained composite film can meet the requirements of active packaging of food, is favorable for developing green and environment-friendly food packaging materials, and has important academic value and application prospect.
Description
Technical Field
The invention relates to the technical field of food packaging material preparation, in particular to a pullulan/trehalose composite film packaging material for loading tea polyphenol, which is prepared by taking pullulan and trehalose as raw materials, adding a plasticizer and a tea polyphenol bacteriostat and adopting an ultrasonic treatment method.
Background
In the last decades, traditional petrochemical packaging has attracted attention because of its non-biodegradable deadly defects, causing irreversible damage to the environment. In recent years, development of biodegradable food packaging films has attracted attention. At present, various functional food packaging materials, such as antibacterial and antioxidant active packages, are developed, and synthetic materials are generally derived from natural degradable polymers such as proteins, polysaccharides and lipids. Many food technicians advocate the addition of natural antimicrobial agents or antioxidants to these packaging materials to inhibit, retard the growth of microorganisms.
Tea Polyphenols (TP) are compound of polyhydroxy phenols in tea, and comprise more than 30 phenols, and have physiological activities such as antioxidant and antibacterial. TP, which is an antioxidant, contains more than two ortho-hydroxyl groups and has strong hydrogen supply capacity. In addition, TP has inhibitory activity on nearly 100 natural bacteria such as Escherichia coli and staphylococcus aureus, and shows broad-spectrum antibacterial performance. TP is used as a food preservative, and can slow down biochemical activities of picked fruits and vegetables and delay the later maturation stage of the fruits and vegetables. TP has been currently used as a natural active ingredient for developing active food packages based on biopolymer materials. However, TP has been found to be less stable to light, temperature and oxygen, greatly limiting its use in food products. In previous studies, we found that trehalose (Tre), which is a commonly used adjuvant to protect/stabilize active substances, can form a tight molecular packing around the active substances due to its low molecular weight. Trehalose, however, is a poor film-forming precursor, and is prone to crystallization during air-drying of the film, resulting in its loss of stability. Therefore, the addition of pullulan to trehalose is a good choice. Pullulan (Pul) is a high molecular weight polysaccharide that can increase the stiffness and strength of the membrane material. In addition, pullulan has a relatively high glass-rubber transition temperature. Thus, tea polyphenol @ pullulan/trehalose (TP @ pul/Tre) blends are ideal film forming materials because they have no tendency to crystallize while also guaranteeing TP stability. To ensure intimate contact and high physical stability between them, we have introduced an ultrasonic process during blending.
Ultrasonic technology is considered as an effective green method because it does not produce secondary pollution, and has been widely used for extraction of active substances, homogenization and degradation of various polymers such as polysaccharide. In liquid media, ultrasound involves the formation, growth and collapse of tiny cavities. The micro-flow and local shear forces caused by the collapse of the cavity can be used to thoroughly agitate the heterogeneous biopolymer aggregates. In recent years, ultrasonic technology has been increasingly applied to solve the problem of mixing film-forming liquids, forming a uniform base film during evaporation of water. Yuan et al found that the ultrasonic treatment enhanced the compatibility of gulfweed polysaccharide with chitosan and improved the functional performance of the membrane. (D.Yuan, H.Meng, Q.Huang, C.Li, X.Fu, preparation and characterization of chitosan-based edible active films incorporated with Sargassum pallidum polysaccharides by ultrasound treatment, international Journal of Biological Macromolecules,183 (2021) 473-480) likewise, cheng et al demonstrated that ultrasound reduced pea protein aggregation and eliminated cracks on the membrane surface. (J. Cheng, L. Cui, effects of high-intensity ultrasound on the structural, optical, mechanical and physicochemical properties of pea protein isolate-based edible film, ultrasonics Sonochemistry,80 (2021) 105809.) furthermore, we believe that sonication does not blindly improve the functional performance of the composite membrane, depending on the time, power and frequency of the ultrasound.
To our knowledge, the research on preparing the pullulan/trehalose composite membrane by ultrasonic synergistic tea polyphenol has not been reported. In the invention, pullulan and trehalose are used as raw materials, a plasticizer is added, a tea polyphenol bacteriostat is added, and meanwhile, an advanced multi-mode ultrasonic technology is adopted, so that the mechanical property, optical property, barrier property, structural property, thermal stability and bacteriostatic activity of the composite film are improved, and the requirements of food packaging are met.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a green physical processing mode for preparing a tea polyphenol@pullulan/trehalose (TP@Pul/Tre) composite membrane, and the influence of an ultrasonic preparation technology on the mechanical property, barrier property, structural property, thermal stability and antibacterial activity of the TP@Pul/Tre composite membrane is researched.
The ultrasonic preparation method of the TP@Pul/Tre composite fruit and vegetable preservative film comprises the following steps:
(1) Pullulan and trehalose were mixed according to 1:1, stirring at room temperature for 1h to completely dissolve to obtain polysaccharide solution.
(2) Adding plasticizer and tea polyphenol with certain mass concentration into the polysaccharide solution in the step (1), placing the blend into a water bath constant temperature magnetic stirrer, and stirring for 30min at 50 ℃ to obtain a film forming solution.
(3) And (3) placing the film forming liquid in a sealed bag, placing the sealed bag in a multi-mode ultrasonic treatment device at room temperature, and taking out the sealed bag after ultrasonic treatment.
(4) Taking a film forming liquid, forming a film by adopting a tape casting method, and drying for 8 hours by blowing at 60 ℃; and taking out the film after the film is formed, and cooling to room temperature to obtain the preservative film.
The concentration of the polysaccharide solution in the step (1) is 2g/50mL.
The plasticizer in the step (2) is sodium carboxymethyl cellulose and glycerol, and the mass ratio of the sodium carboxymethyl cellulose to the glycerol is 2:3.
the adding amount of sodium carboxymethyl cellulose in the step (2) is 5-25% of the total mass ratio of pullulan polysaccharide and trehalose, and the preferable adding amount is 10%.
The glycerol added in the step (2) accounts for 5-25% of the total mass ratio of the pullulan polysaccharide and the trehalose, and the preferable adding amount is 15%.
The adding amount of the tea polyphenol in the step (2) is 1-9% of the total mass ratio of the pullulan polysaccharide and the trehalose, and the preferable adding amount is 5%.
The specific parameters of the ultrasonic treatment in the step (3) are that the ultrasonic power density is 20W/L-100W/L, and the ultrasonic power density is preferably 40W/L; the ultrasonic treatment time is 5min-30min, preferably 15min; the ultrasonic frequency is one of 20kHz, 35kHz, 50kHz, 20/35kHz, 20/50kHz, 35/50kHz or 20/35/50kHz, and preferably the ultrasonic frequency is 20/35kHz.
The invention has the beneficial effects that:
(1) The ultrasonic treatment technology used in the process of preparing the tea polyphenol@pullulan/trehalose composite film is a physical method, ultrasonic waves are an environment-friendly physical processing mode, are widely applied in the food industry, and are a novel physical treatment method for preparing food packaging materials.
(2) Under the conditions of 40W/L ultrasonic power density, 15min ultrasonic time and 20/35kHz ultrasonic frequency, the mechanical property, the barrier property, the structural property and the thermal stability of the composite membrane are effectively improved.
(3) The loading of tea polyphenol provides excellent antibacterial performance for the composite membrane, and takes escherichia coli and staphylococcus aureus as examples.
(4) The invention provides a theoretical basis for the application of ultrasonic technology in preparing the composite film, and the obtained composite film can meet the requirements of active packaging of food, is favorable for developing green and environment-friendly food packaging materials, and has important academic value and application prospect.
Drawings
FIG. 1 is a diagram showing a multi-mode ultrasonic apparatus according to the present invention, which is provided with a computer program controller for controlling three ultrasonic controllers respectively for setting ultrasonic operation parameters (ultrasonic power density, frequency, pulse operation time, intermittent time and total treatment time), and is connected with three ultrasonic vibration plates of different frequencies respectively, so that single frequency/two frequencies/three frequencies ultrasonic treatment can be realized; and (3) putting the sample to be treated into a liquid container for single-frequency/double-frequency/multi-frequency ultrasonic treatment, and starting a circulating pump to circulate the solution. The automatic control of the solution temperature is realized through a water bath kettle and a temperature probe. Wherein 1 is a display, 2 is a frequency mode controller, 3 is a water bath controller, 4 is a water bath, 5 is an ultrasonic reaction chamber, 6 is a circulating pump, 7 is a 20kHz ultrasonic generator, 8 is a 35kHz ultrasonic generator, and 9 is a 50kHz ultrasonic generator.
FIG. 2 shows the effect of sodium carboxymethylcellulose addition on the mechanical properties of composite membranes.
FIG. 3 shows the effect of glycerol addition on the mechanical properties of the composite membrane.
FIG. 4 shows the effect of tea polyphenol addition on the mechanical properties of the composite film.
FIG. 5 is a graph showing the effect of ultrasonic power density on the mechanical properties of a composite membrane.
FIG. 6 is a graph showing the effect of ultrasonic time on the mechanical properties of a composite membrane.
FIG. 7 is a graph showing the effect of ultrasonic frequency on the mechanical properties of a composite membrane.
Figure 8 is a bar graph of the mechanical properties of different composite films. The drawing from left to right is respectively: pullulan/trehalose composite film (Pul/Tre), tea polyphenol@pullulan/trehalose composite film (tp@pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-tp@pul/Tre).
Fig. 9 is a bar graph of moisture content and water vapor transmission rate for various composite films. The drawing from left to right is respectively: pullulan/trehalose composite film (Pul/Tre), tea polyphenol@pullulan/trehalose composite film (tp@pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-tp@pul/Tre).
Fig. 10 is an ultraviolet full-band scan of different composite films. The figures are respectively from top to bottom: pullulan/trehalose composite film (Pul/Tre), tea polyphenol@pullulan/trehalose composite film (tp@pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-tp@pul/Tre).
FIG. 11 is a Raman spectrum of soybean oil treated with different composite films. The figures are respectively from top to bottom: control group (Control), pullulan/trehalose complex film (Pul/Tre), tea polyphenol@pullulan/trehalose complex film (TP@Pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose complex film (U-TP@Pul/Tre).
FIG. 12 shows the characteristic peak intensity ratio (I) (970) /I (1438) And I(1656) /I (1746) ). The drawing from left to right is respectively: control group (Control), pullulan/trehalose complex film (Pul/Tre), tea polyphenol@pullulan/trehalose complex film (TP@Pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose complex film (U-TP@Pul/Tre).
Fig. 13 is a plan (left) and cross-sectional (right) sem image of different composite films. The figures are respectively from top to bottom: pullulan/trehalose composite film (Pul/Tre), tea polyphenol@pullulan/trehalose composite film (tp@pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-tp@pul/Tre).
Figure 14 is an XRD diffractogram of the different composite films. The figures are respectively from top to bottom: pullulan/trehalose composite film (Pul/Tre), tea polyphenol@pullulan/trehalose composite film (tp@pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-tp@pul/Tre).
Fig. 15 is a fourier transform attenuated total reflection infrared spectrum of a different composite film. The figures are respectively from top to bottom: pullulan/trehalose composite film (Pul/Tre), tea polyphenol@pullulan/trehalose composite film (tp@pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-tp@pul/Tre).
FIG. 16 is a thermogravimetric diagram of a different composite membrane. The drawing from left to right is respectively: pullulan/trehalose composite film (Pul/Tre), tea polyphenol@pullulan/trehalose composite film (tp@pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-tp@pul/Tre).
FIG. 17 is a graph of the primary differential of the thermal weights of different composite films. The figures are respectively from top to bottom: pullulan/trehalose composite film (Pul/Tre), tea polyphenol@pullulan/trehalose composite film (tp@pul/Tre), ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-tp@pul/Tre).
Fig. 18 shows the bacteriostatic effect (time-dependent) of different composite membranes against e.coli and s. In the figure, TP@Pul/Tre represents a tea polyphenol@pullulan/trehalose composite membrane, and U-TP@Pul/Tre represents an ultrasonic-tea polyphenol@pullulan/trehalose composite membrane.
FIG. 19 is a scanning electron microscope topography of E.coli and Staphylococcus aureus before and after treatment with an ultrasonic-tea polyphenol@pullulan/trehalose complex film (U-TP@pul/Tre).
Fig. 20 is a schematic view showing the fresh-keeping effect of the fresh-cut apples under different conditions. In the figure, from left to right, a film-free covering group (CON), a pullulan/trehalose composite film covering group (Pul/Tre), a tea polyphenol@pullulan/trehalose composite film covering group (TP@Pul/Tre), and an ultrasonic-tea polyphenol@pullulan/trehalose composite film covering group (U-TP@Pul/Tre) are respectively arranged.
Fig. 21 is a schematic view of the fresh-keeping effect of pears under different conditions. The figure shows from left to right that the coating-free group (CON), the pullulan/trehalose coating group (Pul/Tre), the tea polyphenol@pullulan/trehalose coating group (TP@Pul/Tre), and the ultrasonic-tea polyphenol@pullulan/trehalose coating group (U-TP@Pul/Tre) are respectively arranged.
Detailed Description
The terms used in the present invention generally have meanings commonly understood by those of ordinary skill in the art unless otherwise indicated. The invention will be described in further detail below in connection with specific examples and with reference to the data. It should be understood that these examples are intended to illustrate the invention and are not intended to limit the scope of the invention in any way.
FIG. 1 is a diagram showing a multi-mode ultrasonic apparatus according to the present invention, which is provided with a computer program controller for controlling three ultrasonic controllers respectively for setting ultrasonic operation parameters (ultrasonic power density, frequency, pulse operation time, intermittent time and total treatment time), and is connected with three ultrasonic vibration plates of different frequencies respectively, so that single frequency/two frequencies/three frequencies ultrasonic treatment can be realized; and (3) putting the sample to be treated into a liquid container for single-frequency/double-frequency/multi-frequency ultrasonic treatment, and starting a circulating pump to circulate the solution. The automatic control of the solution temperature is realized through a water bath kettle and a temperature probe.
In the following examples, the Chinese names, english names or abbreviations of the following nouns may be used, but whether the Chinese names, english names or abbreviations are used, they represent a compound or a pharmaceutical or an agent. Specifically as shown in table 1:
table 1 Chinese and English control abbreviation table
Experimental materials:
pullulan is available from Shanghai Ara Ding Shenghua technologies Inc. Glycerol (purity 99%), D (+) -anhydrous trehalose, agar powder, and sodium chloride were purchased from national pharmaceutical chemicals limited. Sodium carboxymethyl cellulose (CMC) was purchased from Sigma. Tea polyphenols (TP, purity. Gtoreq.98%) were purchased from Nanjing Dulai biotechnology Co. Tryptone (LP 0042) and yeast powder (LP 0021) were purchased from beijing orchid bordetella biotechnology limited. Coli cic 10389 and staphylococcus aureus cic 10201 are both purchased from the chinese industrial microbiological bacterial collection center.
The mechanical property measuring method of the film material prepared in the embodiment and the experimental example comprises the following steps: the film was cut into 20mm by 60mm strips, and its Tensile Strength (TS) and Elongation At Break (EAB) were measured with a physical property meter at a test speed of 1mm/s and a grip distance of 30mm.
Tensile strength calculation formula: ts=f/(d×w)
Wherein: TS-tensile Strength (N/mm) 2 ) The method comprises the steps of carrying out a first treatment on the surface of the F-maximum tensile force (N0; d-film thickness (mm); W-film width (mm)) to which the film is subjected when broken.
Elongation at break calculation formula: eab= (L-L 0 )×100/L 0
Wherein: EAB-elongation at break (%); l-distance between the reticles at break (mm); l (L) 0 Film original reticle distance (mm).
Young's modulus (E) is obtained by calculating the ratio of TS to EBA, MPa.
Example 1: optimization of CMC (CMC) addition in preparation of pullulan/trehalose composite film
(1) Pullulan 1g and trehalose 1g were blended in an aqueous solution, and stirred at room temperature for 1 hour until they were completely dissolved, to prepare a polysaccharide solution having a concentration of 2g/50mL.
(2) Adding glycerol accounting for 15% of the total mass of pullulan and trehalose as a plasticizer, and uniformly mixing.
(3) Adding CMC accounting for 5%, 10%, 15%, 20% or 25% of the total mass of pullulan and trehalose, and placing in a water bath constant temperature magnetic stirrer for sealing and stirring for 30min, wherein the water bath temperature is 50 ℃, so as to obtain uniform Pul/Tre film forming liquid.
(4) Taking 15mL of film forming liquid, casting on a disposable plastic flat plate to form a film, standing for 10min, drying by air blast at 50 ℃ for 8h, and placing in a drying dish with a relative humidity of 43% for use (saturated K is placed in the drying dish) 2 CO 3 A solution).
The CMC addition was optimized with TS, EBA and E as indicators of mechanical properties, the results are shown in FIG. 2. As can be seen from FIG. 2, the addition of CMC significantly increases TS and E (P.ltoreq.0.05) in the film and EBA significantly decreases. This is due to the increased intermolecular forces between the complex chains caused by the carboxymethyl substituents in CMC. In addition, the sugar ring structure in the CMC provides a good skeleton effect for the Pul/Tre composite membrane structure, improves the stability of the internal structure and increases TS. From the comprehensive index point of view, 10% of CMC addition is selected for the optimization of the next glycerol addition.
Example 2: optimization of glycerol addition in preparation of pullulan/trehalose composite film
(1) Pullulan 1g and trehalose 1g were blended in an aqueous solution, and stirred at room temperature for 1 hour until they were completely dissolved, to prepare a polysaccharide solution having a concentration of 2g/50mL.
(2) Adding CMC accounting for 10 percent of the total mass of the pullulan and the trehalose, and uniformly mixing.
(3) Adding glycerol accounting for 5%, 10%, 15%, 20% or 25% of the total mass of pullulan and trehalose, and placing in a water bath constant temperature magnetic stirrer for sealing and stirring for 30min, wherein the water bath temperature is 50 ℃, so as to obtain uniform Pul/Tre film forming liquid.
(4) Taking 15mL of film forming liquid, casting on a disposable plastic flat plate to form a film, standing for 10min, drying by air blast at 50 ℃ for 8h, and placing in a drying dish with a relative humidity of 43% for use (saturated K is placed in the drying dish) 2 CO 3 A solution).
The effect of glycerol concentration in 10% CMC film-forming solution on the mechanical properties of Pul/Tre films is shown in FIG. 3. Films prepared with low doses of glycerol plasticizer are too brittle to be tested. The film prepared at the glycerol concentration of 15% has good mechanical properties and has strength and flexibility. As can be seen from a comparison of fig. 2 and 3, the effect of CMC on the mechanical properties of the Pul/Tre film is quite opposite to the effect of glycerol added as a plasticizer to the film on the mechanical properties of the Pul/Tre film. The glycerol in the film reduces acting force among molecules and internal hydrogen bonds among polymer chains, increases molecular volume and mobility of the polymer chains, and enables the film to be more flexible. Therefore, the resistance and rigidity of the Pul/Tre film can be reduced and the ductility of the Pul/Tre film can be improved by properly adjusting the addition amount of CMC and glycerol.
Example 3: optimization of tea polyphenol addition amount in preparation of tea polyphenol@pullulan/trehalose composite film
(1) Pullulan 1g and trehalose 1g were blended in an aqueous solution, and stirred at room temperature for 1 hour until they were completely dissolved, to prepare a polysaccharide solution having a concentration of 2g/50mL.
(2) Adding CMC accounting for 10 percent of the total mass of pullulan and trehalose and glycerin accounting for 15 percent of the total mass of pullulan and trehalose, and uniformly mixing.
(3) Adding tea polyphenol accounting for 1%, 3%, 5%, 7% or 9% of the total mass of pullulan and trehalose, and placing in a water bath constant temperature magnetic stirrer for sealing and stirring for 30min, wherein the water bath temperature is 50 ℃, so as to obtain uniform TP@Pul/Tre film forming liquid.
(4) Taking 15mL of film forming liquid, casting on a disposable plastic flat plate to form a film, standing for 10min, drying by air blast at 50 ℃ for 8h, and placing in a drying dish with a relative humidity of 43% for use (saturated K is placed in the drying dish) 2 CO 3 A solution).
FIG. 4 shows the effect of different TP additions on Pul/Tre films TS and EBA. The addition of lower levels of TP significantly increases the EBA value of the film, while the addition of higher levels of TP decreases the EBA value of the film. Also, the addition of small amounts of TP increases the tensile strength of the film. These results clearly show that the addition of TP has a significant effect on the mechanical properties of the film and that this effect depends on the amount added. The most likely reason for this effect is that the addition of TP weakens the internal hydrogen bonds between the Pul/Tre matrix molecules, forming new hydrogen bonds. However, excess TP molecules limit the binding of Pul to Tre, and it appears that an intermediate amount of TP (5%) is required to produce a strong flexible film.
Example 4: optimization of ultrasonic power density in preparation of ultrasonic-tea polyphenol@pullulan/trehalose composite film
(1) Pullulan 1g and trehalose 1g were blended in an aqueous solution, and stirred at room temperature for 1 hour until they were completely dissolved, to prepare a polysaccharide solution having a concentration of 2g/50mL.
(2) Adding CMC accounting for 10 percent of the total mass of pullulan and trehalose, 15 percent of glycerol and 5 percent of tea polyphenol, and placing the mixture into a water bath constant temperature magnetic stirrer for sealing and stirring for 30min, wherein the water bath temperature is 50 ℃, thus obtaining uniform TP@Pul/Tre film forming liquid.
(3) And (3) taking a proper amount of film forming liquid in a plastic package bag, and performing ultrasonic treatment at room temperature for 15min, wherein the ultrasonic frequency is 20/35kHz, and the ultrasonic power density is 20, 40, 60, 80 or 100W/L.
(4) Taking 15mL of film forming liquid, casting on a disposable plastic flat plate to form a film, standing for 10min, drying by air blast at 50 ℃ for 8h, and placing in a drying dish with a relative humidity of 43% for use (saturated K is placed in the drying dish) 2 CO 3 A solution).
FIG. 5 shows TS and EBA of the TP@Pul/Tre composite film under different ultrasonic conditions. When the ultrasonic power density is 40W/L, TS reaches the maximum value of 19.6MPa, which is improved by 6.4MPa compared with untreated ultrasonic power density, but the influence on EBA is not obvious. Cavitation is directly controlled and generated by ultrasonic power, and with the gradual increase of early power density, the formation of pullulan-trehalose polymer is favored, resulting in an increase of TS. There is evidence that ultrasound can produce smaller particles in the film-forming solution and lead to larger molecular interactions. However, with increasing power density (> 40W/L), excessive cavitation destroys the molecular structure, resulting in a decrease in TS of the film. Also, when the ultrasonic power density reached 100W/L, the EBA increased significantly, reaching a maximum of 152%. This is because with a slight increase in cavitation effect, the polymer structure becomes more ordered. The result shows that the optimal ultrasonic power density is 40W/L, which is beneficial to improving the mechanical property of the film.
Example 5: optimization of ultrasonic time in preparation of ultrasonic-tea polyphenol@pullulan/trehalose composite film
(1) Pullulan 1g and trehalose 1g were blended in an aqueous solution, and stirred at room temperature for 1 hour until they were completely dissolved, to prepare a polysaccharide solution having a concentration of 2g/50mL.
(2) Adding CMC accounting for 10 percent of the total mass of pullulan and trehalose, 15 percent of glycerol and 5 percent of tea polyphenol, and placing the mixture into a water bath constant temperature magnetic stirrer for sealing and stirring for 30min, wherein the water bath temperature is 50 ℃, thus obtaining uniform TP@Pul/Tre film forming liquid.
(3) And (3) taking a proper amount of film forming liquid in a plastic package bag, and performing ultrasonic treatment at room temperature for 5, 10, 15, 20, 25 or 30min, wherein the ultrasonic frequency is 20/35kHz, and the ultrasonic power density is 40W/L.
(4) Taking 15mL of film forming liquid, casting on a disposable plastic flat plate to form a film, standing for 10min, drying by air blast at 50 ℃ for 8h, and placing in a drying dish with a relative humidity of 43% for use (saturated K is placed in the drying dish) 2 CO 3 A solution).
As can be seen from FIG. 6, TS was significantly reduced at 5min of ultrasound. When ultrasound is applied to a liquid, the intermolecular van der Waals forces cannot maintain the cohesion of the liquid, so that gas-filled microbubbles are formed near the surface of the liquid and implode occurs, and various effects such as particle breakdown and erosion are generated. That is, the cavitation of the ultrasonic wave breaks the original hydrogen bond between molecules, so that the acting force between the molecules is reduced. Along with the extension of ultrasonic time, the molecules are rearranged by the mixing action of ultrasonic waves, so that a compact and uniform network structure is formed. From this point of view, it can be assumed that the reduction of the particles promotes the formation of new chemical bonds between TP and Pul/Tre, and thus the enhancement of EBA and TS at 15 min. In addition, as the ultrasound time is prolonged, cavitation effects increase the polysaccharide molecular conformation, increasing the volume of the polymer, and decreasing the TS value of the TP@Pul/Tre membrane. In addition, continuous ultrasound can accumulate excessive thermal effects, which are unfavorable for crosslinking of the composite membrane, thereby reducing the mechanical properties of the composite membrane. On the other hand, the increase of molecular movement leads to disorder of molecular arrangement, resulting in degradation of mechanical properties of the film. Notably, EBA is insensitive to ultrasound. This finding shows that TS and EBA are not always relevant when evaluating film mechanical properties. In summary, an ultrasonic treatment for 15 minutes is sufficient to obtain a dense and uniform polymer matrix.
Example 6: optimization of ultrasonic frequency in preparation of ultrasonic-tea polyphenol@pullulan/trehalose composite film
(1) Pullulan 1g and trehalose 1g were blended in an aqueous solution, and stirred at room temperature for 1 hour until they were completely dissolved, to prepare a polysaccharide solution having a concentration of 2g/50mL.
(2) Adding CMC accounting for 10 percent of the total mass of pullulan and trehalose, 15 percent of glycerol and 5 percent of tea polyphenol, and placing the mixture into a water bath constant temperature magnetic stirrer for sealing and stirring for 30min, wherein the water bath temperature is 50 ℃, thus obtaining uniform TP@Pul/Tre film forming liquid.
(3) And (3) taking a proper amount of film forming liquid in a plastic package bag, and performing ultrasonic treatment at room temperature for 15min, wherein the ultrasonic frequency is 20, 35, 50, 20/35, 20/50, 35/50 or 20/35/50kHz, and the ultrasonic power density is 40W/L.
(4) Taking 15mL of film forming liquid, casting on a disposable plastic flat plate to form a film, standing for 10min, drying by air blast at 50 ℃ for 8h, and placing in a drying dish with a relative humidity of 43% for use (saturated K is placed in the drying dish) 2 CO 3 A solution).
The effect of single, double and triple frequency ultrasonic frequencies on the mechanical properties of the composite film is shown in figure 7. The frequency is an important factor in determining the ultrasonic characteristics, and ultrasonic waves generate different cavitation effects at different frequencies, which also lead to no trend in TS and EBA. Clearly, sonication increases the TS value, and in addition to the 20/35/50 kHz-enhanced cavitation effect, reduces the toughness of the film under the excessive influence of ultrasound. Single and double frequencies (representing moderate cavitation effects) facilitate the formation of denser structures between the film-forming components during drying. That is, shear and shock waves generated by moderate cavitation can result in greater molecular interactions between the film-forming components, resulting in higher TS values. In addition, more inclusions are formed during ultrasound, which may provide greater strength to the polymer matrix. From the mechanical indexes of TS and EAB, the ultrasonic treatment of 20/35kHz is beneficial to improving the mechanical properties of the film.
Experimental example, performance test of ultrasonic-tea polyphenol @ pullulan/trehalose-loaded composite film
The preparation method of the composite membrane of different types in the experimental example is as follows:
pullulan/trehalose complex film (Pul/Tre): reference example 1, wherein the glycerol addition amount was 15% and the CMC addition amount was 10%;
tea polyphenol@pullulan/trehalose composite film (TP@Pul/Tre): reference example 3 wherein tea polyphenol was added in an amount of 5%.
Ultrasonic-tea polyphenol@pullulan/trehalose composite film (U-TP@Pul/Tre): reference example 4, in which the ultrasonic power density was 40W/L, the ultrasonic treatment time was 15min, and the ultrasonic frequency was 20/35kHz.
Experimental example 1: mechanical properties of different composite membranes
The results of the mechanical properties after optimization are shown in FIG. 8. Polyphenols are natural cross-linking agents that can bind to Pul/Tre via hydrogen bonds. The formation of hydrogen bonds limits the mobility of the polysaccharides and enhances the interaction between them, thereby improving the mechanical properties of the composite membrane. The mechanical properties of the material are further improved by ultrasonic treatment (40W/L, 15min,20/35 kHz). The mechanical property of the film after ultrasonic treatment is integrally improved, and the requirements of food packaging are met.
Experimental example 2: moisture content and Water vapor Transmission Rate of different composite films
The experimental method comprises the following steps: gravimetrically evaluate WVP of film, film sample was tightly placed on the opening of a weighing flask, which had been loaded with 10g CaCl 2 Particles (0% RH). Subsequently, the weighing flask is placed in a container containing saturated KNO 3 (93% RH) in a desiccator. The weighing flask was weighed at 25℃for 12h, once every 2 h. WVP (g.m/m) 2 s.Pa) is calculated as:
wherein Deltam is mass increment, g; a is the water vapor permeation area, m 2 The method comprises the steps of carrying out a first treatment on the surface of the Δt is the time interval, s; Δp= 2.945kPa. MC is measured by drying a film to constant weight at 105 ℃, and the calculation formula is as follows:
wherein M is 1 Is the weight of wet basis; m is M 2 Is the dry weight.
FIG. 9 shows WVP and MC of the composite membrane. Generally, packaging films for food are waterproof to prevent moisture loss from the food. The water vapor can be divided into three steps of adsorption, diffusion and dissolution through the composite membrane, which are closely related to the hydrophobicity, hydrophilicity and spatial structure of the raw materials. As can be seen from FIG. 9, after TP addition, the WVP of the composite membrane was 7.151 ×10 -12 g cm -1 s -1 Pa -1 Increased to 7.85×10 -12 g cm -1 s -1 Pa -1 . The combination of the film forming matrix and TP may change the original molecular structure and raise the permeability of water molecule. In addition, the introduction of hydrophilic groups in TP increases the hydrophilicity of the membrane, resulting in faster diffusion of water molecules and an increase in WVP. After sonication, the WVP values were significantly reduced to 3.49×10 -12 g cm -1 s -1 Pa -1 . Moderate ultrasound promotes the formation of hydrogen bond interaction between polyphenol and polysaccharide, reduces the hydrophilicity and diffusion coefficient of the membrane, increases the crosslinking degree, and makes the U-TP@Pul/Tre membrane compact and complex to form a 'curved path', thereby limiting the escape and permeation of water vapor and greatly reducing WVP.
The Pul/Tre films have a downward trend in MC after binding to TP, which is related to the phenolics in TP. The carboxyl and hydroxyl of the phenolic substance have stronger binding capacity to pullulan and trehalose molecules, thereby inhibiting the binding of polysaccharide and water molecules. Sonication had no significant effect on MC (p > 0.05).
Experimental example 3: transmittance of different composite films
The experimental method comprises the following steps: an ultraviolet-visible spectrophotometer UV-1601 was used to measure the light transmittance of the film in the wavelength range of 260-800 nm.
Clarity of films is an important optical property for many food packaging applications. The transmittance of visible and ultraviolet light at selected wavelengths of 260-800nm was measured (fig. 10), and the Pul/Tre films exhibited good transmittance in the 260-800nm range. The addition of TP reduces the transparency and uv transmittance of the film, mainly due to the selective absorption of light by the phenol groups in TP. The ultraviolet absorption peak at 280nm proves that the TP@Pul/Tre film can effectively prevent ultraviolet light transmission. The transmittance is improved by ultrasonic treatment. The ultrasonic treatment is favorable for the compatibility of film forming components, and the light transmittance of the film is improved. In addition, the small cavities created by cavitation may also be responsible for the high light transmittance.
Experimental example 4: oxygen transmission rate of different composite membranes
The experimental method comprises the following steps: a50 mL sample of soybean oil was placed in a 250mL Erlenmeyer flask, sealed with a film sample, and placed in a 60℃incubator to accelerate oxidation of the oil for 7d. Using DXR TM 3 Raman spectrometer (Thermo Scientific DXR) TM United states) for oil-like spectroscopic acquisition. Collecting condition parameters: the excitation wavelength is 532nm, the laser power is 10mW, the temperature is room temperature, the scanning time is 10s, the scanning is carried out for 3 times on average, and the scanning range is 500-2000cm -1 。
The raman spectrum of an oil sample mainly contains spectral peaks caused by vibrations of the hydrocarbon chain. Fig. 11 shows raman spectra of different film-coated oils. In the Raman spectrum, each peak may display molecular structure information of its component, for example, 970cm -1 (trans- = C-H bending vibration), 1080cm -1 (-(CH 2 ) n -stretching vibration), 1264cm -1 (cis- = C-H bending vibration), 1300cm -1 (in-phase-CH) 2 Bending vibration), 1438cm -1 (CH 2 Shear bending vibration) 1656cm -1 (cis-C=C stretching vibration), 1746cm -1 (c=o stretching vibration), and the like. During lipid oxidation, as the oxidation time increases, the cis double bonds continually isomerize and rearrange into stable trans double bond configurations. Variation of the trans double bond as I (970) /I (1438) Characterised by the change in unsaturation being denoted by I (1656) /I (1746) Is a feature (fig. 12). Wherein I is (970) /I (1438) In a downward trend (less trans structure is indicated), I (1656) /I (1746) There was an upward trend (indicating reduced loss of cis double bonds). The results show that the Pul/Tre, TP@Pul/Tre and U-TP@Pul/Tre films can effectively block O 2 And the oxidation of grease is delayed. The addition of TP reduces the OP of the blend membrane, and a large amount of TP plays a role in blocking the oxygen molecule from passing throughBarrier function across the membrane. The ultrasonic treatment has a positive effect on the oxygen barrier properties of the film, probably because the ultrasonic treatment forms a uniform network structure and a dense microstructure of the film matrix, and creates a vertical layer to prevent diffusion and transfer of gases in the composite film.
Experimental example 5: scanning electron microscope observation of different composite films
The experimental method comprises the following steps: the microstructure of the surface and the section of the film was observed by a scanning electron microscope at an acceleration voltage of 15 kV. And (3) placing the film in liquid nitrogen for natural fracture to obtain the cross section of the film.
The microstructure and biopolymer compatibility of the film is shown in figure 13. The surfaces and cross sections of the various films are smooth and continuous, which shows that the matrix has good compatibility with TP, and the transmittance of the films also proves the same. The addition of TP maintains the initial fluidity and viscosity of the composite film unchanged. The difference between the two groups after ultrasonic treatment is not statistically significant.
Experimental example 6: x-ray diffraction analysis of different composite films
The experimental method comprises the following steps: XRD spectra of the films were obtained using an X-ray diffractometer at 5-80, 5/min in the 2 theta range.
FIG. 14 shows the X-ray diffraction patterns of Pul/Tre, TP@Pul/Tre and U-TP@Pul/Tre films. As shown in fig. 14, there is a broad diffraction peak at 2θ=19.80°, which is the result of crystallization of pullulan, indicating that pullulan is encapsulated around trehalose in the form of macromolecules. The diffraction peak is slightly wider and is of an amorphous structure. The amorphous film is formed mainly due to the presence of significant covalent bonds between Pul and Tre. The addition of TP has no significant effect on crystallization properties, indicating that TP is encapsulated in the network structure formed by trehalose and pullulan as active filler materials. In addition, the sonicated film had a broader, flatter peak with better compatibility. However, all composite films exhibited similar curves, indicating that the addition of TP and the action of ultrasound did not alter the crystallization pattern of the polymer film.
Experimental example 7: fourier transform attenuated total reflection infrared spectroscopy of different composite films
ExperimentThe method comprises the following steps: at 4000-600cm using ATR-FTIR spectrometer -1 FTIR spectra of the film were recorded in the range of (2) and scanned 16 times with a resolution of 4cm -1 。
FIG. 15 shows FTIR spectra of Pul/Tre, TP@Pul/Tre and U-TP@Pul/Tre composite membranes. In the Pul/Tre spectrum, characteristic peaks respectively appear at 3348cm due to O-H stretching vibration, C-H bending vibration and c=o stretching vibration -1 、2932cm -1 、1596cm -1 And 1031cm -1 (amide I). 994cm -1 The absorption peak at this point is due to the hydrogen bond formed by the oxygen atom on the glycosidic bond with the O-H in the glycerol molecule. After TP was added to the Pul/Tre film, an absorption peak of-OH from 3348cm was observed -1 Offset to 3343cm -1 Indicating that new hydrogen bonds are formed between TP and the matrix molecule. The addition of TP can weaken the intramolecular hydrogen bond, and C-O in TP forms new hydrogen bond with-OH in polysaccharide. In addition, no significant wavelength shift or additional peaks were observed, indicating no covalent bonds between TP and Pul/Tre. After ultrasonic treatment, the TP@Pul/Tre film is 1596cm -1 The absorption peak at the location shifts to 1600cm -1 Where it is shown that the ultrasonic treatment enhances the covalent bonding ability of the film-forming matrix. This is advantageous in improving the crosslinkability of the polymer and making the polymer structure denser.
Experimental example 8: thermal characterization of different composite films
The experimental method comprises the following steps: the thermal stability of the film was carried out on a comprehensive thermal analyzer STA 449 F3 Jupiter, at N 2 The atmosphere was heated from 30deg.C to 500deg.C (flow rate 20 mL/min) at a rate of 10deg.C/min.
TGA and DTG (30-500 ℃) of Pul/Tre, TP@Pul/Tre and U-TP@Pul/Tre films are shown in FIGS. 16 and 17. The first stage of thermal degradation occurs at 30-170 c, mainly due to evaporation of the moisture in the film. It can be indirectly derived that MC of Pul/Tre is higher than TP@Pul/Tre and U-TP@Pul/Tre films, which are consistent with the results of MC testing. DTG curves show that the water loss temperature of the TP@Pul/Tre and U-TP@Pul/Tre films is obviously higher than that of Pul/Tre, so that a denser hydrogen bond network is formed by adding TP, and the water diffusion is limited. The second stage of thermal degradation is observed at 170-350 ℃, mainly due to degradation and decomposition of TP and polysaccharide molecules. Their breakdown is associated with intermolecular/intramolecular hydrogen bonds, electrostatic interactions and cleavage of covalent bonds. The thermal decomposition of polysaccharide molecules mainly refers to the degradation of glycosidic bonds. FIG. 16 shows that the mass loss of the film after sonication is significantly reduced. Similarly, fig. 17 shows the higher thermal decomposition temperature of the film treated by ultrasonic waves. This explains the more ordered, more stable structure of the film-forming matrix and the stronger covalent binding capacity. In conclusion, the crosslinking degree of the film under ultrasonic treatment is higher, the structure is more ordered and more stable, and the thermal stability is better.
Experimental example 9: antibacterial properties of different composite membranes
The experimental method comprises the following steps: the antibacterial properties of the different samples were studied using standard colony counting methods. Fresh E.coli was obtained by incubation at 37 ℃. Then the E.coli suspension was brought to 10 with 0.9% sodium chloride solution 7 CFU/mL. The different samples (2 g) were immersed in 50mL of the prepared E.coli suspension and placed in a Erlenmeyer flask. The supernatants were taken after 0h, 2h, 4h, 6h, 8h and diluted to appropriate concentrations with 0.9% NaCl solution. 0.1mL of the solution is smeared on the surface of LB solid medium, and is cultured for 24 hours at 37 ℃. Coli suspension without any sample was used as a control on LB medium. Each experiment was repeated 3 times. The above procedure is equally applicable to staphylococcus aureus.
As shown in FIG. 18, TP@Pul/Tre and U-TP@Pul/Tre are time dependent on the antibacterial effect of E.coli and Staphylococcus aureus. Bacterial mortality achieved 100% and 99.47% when E.coli and Staphylococcus aureus were incubated with TP@Pul/Tre and U-TP@Pul/Tre for 4h and 6h, respectively, due to incorporation of TP.
As shown in fig. 19, the untreated bacterial surface was plump and smooth in SEM images, and the shape was complete, without deformation or defects. After treatment with U-TP@Pul/Tre, E.coli and Staphylococcus aureus were deformed and dented. Specifically, the surface morphology of E.coli becomes wrinkled, damaged and porous, and the cell surface morphology of Staphylococcus aureus becomes severely distorted. In contrast, E.coli is more damaged, its cytoplasm leaks and collapses completely, probably because of its thinner cell wall.
Application example 1: test of fresh-keeping effect of composite film on fresh-cut apples
In the application examples, the preparation of the Pul/Tre, TP@Pul/Tre and U-TP@Pul/Tre composite films is referred to in experimental examples. Cutting intact or moldy apple into 1cm pieces 3 Is color protected with 0.9% sodium chloride solution. After draining off the surface moisture, the material was placed in a plastic petri dish. The prepared composite film is covered on a plastic culture dish. Finally, the samples were stored at 25℃for 4 days, photographed at regular intervals and weighed. Fresh apple pieces without film coating served as control.
From the digital photographs in FIG. 20, the group covered by the U-TP@Pul/Tre film showed more weight retention and minimal oxidative browning compared to the CON, pul/Pre and TP@Pul/Tre groups. The fresh apple pieces of the CON, pul/Pre, TP@Pul/Tre and U-TP@Pul/Tre groups had weight loss rates of 84.95%, 54.12%, 42.57% and 38.99%, respectively, on day four. The composite membrane is proved to be denser after ultrasonic treatment, and the loss of moisture and the permeation of oxygen can be effectively delayed.
Application example 2: testing of pear fresh-keeping effect of composite film coating
In the application example, pul/Tre, TP@Pul/Tre and U-TP@Pul/Tre film forming liquid are the same as film forming liquid before drying in the preparation of the Pul/Tre, TP@Pul/Tre and U-TP@Pul/Tre composite film in the experimental example. The method of accelerating pear rot by using artificial wound is adopted to determine the anti-corrosion effect of the composite film. The artificial wound was made using a sterile needle to make a wound 15 mm deep and 4 mm in diameter. Soaking fructus Pyri in the film-forming solution at 25deg.C for 2min. After removal, the pears were dried in a fume hood at 25℃for 3min to form film-coated pears, which were then stored at 25℃for 7 days and photographed periodically. The decay diameter was measured on day 7 of storage. Uncoated pears were used as controls.
As can be seen from fig. 21, the rot diameter around the pear wound after the U-tp@pul/Tre film coating treatment is the smallest compared with the CON, pul/Pre and tp@pul/Tre groups, indicating that the effect of U-tp@pul/Tre in delaying fruit rot is most remarkable compared with the other three groups.
Claims (5)
1. The preparation method of the pullulan loaded with tea polyphenol and the seaweed candy and vegetable preservative film is characterized by comprising the following steps of:
(1) Pullulan and trehalose were mixed according to 1:1, stirring at room temperature for 1h to completely dissolve to prepare polysaccharide solution;
(2) Adding plasticizer and tea polyphenol with certain mass concentration into the polysaccharide solution in the step (1), placing the blend into a water bath constant temperature magnetic stirrer, and stirring for 30min at 50 ℃ to obtain film forming solution;
(3) Placing the film forming liquid in a sealed bag, placing the sealed bag in a multi-mode ultrasonic treatment device at room temperature, and taking out the sealed bag after ultrasonic treatment;
(4) Taking a film forming liquid, forming a film by adopting a tape casting method, and drying for 8 hours by blowing at 60 ℃; taking out the film after the film is formed, and cooling to room temperature to obtain the preservative film;
the concentration of the polysaccharide solution in the step (1) is 2g/50mL; the plasticizer in the step (2) is sodium carboxymethyl cellulose and glycerol, and the mass ratio of the sodium carboxymethyl cellulose to the glycerol is 2:3, a step of;
the adding amount of the sodium carboxymethyl cellulose in the step (2) is 5-25% of the total mass ratio of the pullulan polysaccharide and the trehalose;
the glycerol addition amount in the step (2) accounts for 5% -25% of the total mass ratio of pullulan to trehalose;
the adding amount of tea polyphenol in the step (2) is 1-9% of the total mass ratio of pullulan to trehalose;
the specific parameters of the ultrasonic treatment in the step (3) are that the ultrasonic power density is 20W/L-100W/L; the ultrasonic treatment time is 5min-30min; the ultrasonic frequency is one of 20kHz, 35kHz, 50kHz, 20/35kHz, 20/50kHz, 35/50kHz, or 20/35/50 kHz.
2. The method for preparing the tea polyphenol-loaded pullulan and seaweed candy and vegetable preservative film according to claim 1, wherein the adding amount of sodium carboxymethyl cellulose in the step (2) is 10% based on the total mass ratio of the pullulan to the seaweed.
3. The method for preparing the tea polyphenol-loaded pullulan and seaweed candy and vegetable preservative film according to claim 1, wherein the glycerol addition amount in the step (2) is 15% based on the total mass ratio of the pullulan to the seaweed candy and vegetable preservative film.
4. The method for preparing the pullulan loaded with tea polyphenol and seaweed candy and vegetable preservative film according to claim 1, wherein the tea polyphenol added in the step (2) accounts for 5% of the total mass ratio of the pullulan to the seaweed candy and vegetable preservative film.
5. The method for preparing pullulan loaded with tea polyphenol and seaweed candy and vegetable preservative film according to claim 1, wherein the specific parameter of the ultrasonic treatment in the step (3) is that the ultrasonic power density is 40W/L; the ultrasonic treatment time is 15min; the ultrasonic frequency is 20/35kHz.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1723803A (en) * | 2005-07-18 | 2006-01-25 | 南京雨润食品有限公司 | Natural membrane forming preservation agent used for crystal-like delicious meat |
| CN106854300A (en) * | 2016-12-02 | 2017-06-16 | 中国肉类食品综合研究中心 | A kind of poly-blended film and preparation method and application |
| CN112409649A (en) * | 2020-11-25 | 2021-02-26 | 华南理工大学 | Artemisia apiacea crude polysaccharide/chitosan edible composite film and preparation method and application thereof |
| CN113214514A (en) * | 2021-04-27 | 2021-08-06 | 江苏大学 | Ultrasonic preparation method of oat protein and pullulan composite fruit and vegetable preservative film |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1723803A (en) * | 2005-07-18 | 2006-01-25 | 南京雨润食品有限公司 | Natural membrane forming preservation agent used for crystal-like delicious meat |
| CN106854300A (en) * | 2016-12-02 | 2017-06-16 | 中国肉类食品综合研究中心 | A kind of poly-blended film and preparation method and application |
| CN112409649A (en) * | 2020-11-25 | 2021-02-26 | 华南理工大学 | Artemisia apiacea crude polysaccharide/chitosan edible composite film and preparation method and application thereof |
| CN113214514A (en) * | 2021-04-27 | 2021-08-06 | 江苏大学 | Ultrasonic preparation method of oat protein and pullulan composite fruit and vegetable preservative film |
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