CN115895050A - Method for directionally regulating and controlling performance of starch-based edible film - Google Patents
Method for directionally regulating and controlling performance of starch-based edible film Download PDFInfo
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Images
Classifications
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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
Abstract
The invention discloses a method for directionally regulating and controlling the performance of a starch-based edible film, and belongs to the technical field of food packaging. The edible film is prepared by using an enzymatic method for modifying starch, and alpha, 1-4 and alpha, 1-6 glycosidic bonds in a starch molecular structure are adjusted by using starch branching enzyme through the action of starch hydrolysis and transglycosylation, so that the preparation of the highly branched starch-based film is realized. Through the transformation of the enzyme action process conditions, the structural basis and the molecular mechanism of the film forming of the highly branched starch are explored, the performance optimization and dynamic regulation and control of the edible film are realized, the foundation is laid for the application of the starch film in different food fields, and a new idea and a new means are provided for the environment-friendly degradable packaging and application of food.
Description
Technical Field
The invention relates to a method for directionally regulating and controlling the performance of a starch-based edible film, belonging to the technical field of food packaging.
Background
The food packaging film is wrapped on the surface of the food, so that microorganisms and bacteria can be isolated, and external pollutants can be prevented from entering, thereby realizing the effect of prolonging the shelf life of the food. Plastic films, however, have a critical position in food packaging films due to their excellent mechanical properties and good chemical stability. However, the non-degradability of plastics poses environmental hazards, which limits the use of plastic films. The development of degradable and renewable films prepared from natural biomacromolecules as raw materials has attracted attention.
Due to the advantages of wide sources, environmental protection, degradability, renewability and the like, the starch becomes one of ideal choices for replacing plastics as food packaging materials. The inherent properties of starch determine that the mechanical property and the barrier property of the starch film are poor, the brittleness of the film is high, and the hydrophilicity of the starch enables the stability of the starch film to be poor in an environment with high relative humidity, so that the application of the starch film is severely limited; and the research on the performance of the starch film is less by changing the structure of the starch, so that the precise multi-dimensional application of the starch film in different food fields cannot be realized.
Disclosure of Invention
The invention provides a method for directionally regulating and controlling the performance of an edible film by modifying a starch structure through starch branching enzyme, which dynamically regulates the content of alpha-1, 4 and alpha-1, 6 glycosidic bonds in starch by utilizing the starch branching enzyme to realize the dynamic change of the film performance.
The invention provides a method for preparing an edible film, which carries out hyperbranched modification treatment on starch by starch branching enzyme so as to directionally regulate and control the performance of the edible film, and comprises the following steps:
(1) Size mixing
Dissolving starch in water to prepare starch milk, and uniformly stirring the starch milk at the temperature of between 25 and 50 ℃ for later use;
(2) Gelatinizing
Heating the starch milk to swell and collapse starch grains to form a viscous and uniform transparent paste solution;
(3) Enzymolysis
Adding starch branching enzyme into starch milk at 45-55 ℃, catalyzing starch to hydrolyze and transglycosidically, so as to realize the modification of starch structure by enzyme method;
(4) Plasticising
Adding a plasticizer into the starch emulsion subjected to enzymolysis in the step (3), so that the micromolecule plasticizer is doped among starch molecules, and the distance among the starch molecules is increased to form a gel solution;
(5) Pouring
Casting the gel solution obtained in the step (4) in a casting way in a polypropylene watch glass to form a film by adopting a casting method, and controlling the level to ensure that the film thickness is uniform;
(6) Drying by baking
Drying the gel solution in a horizontal vacuum drying oven, and drying for a certain time to obtain a highly branched starch film;
(7) Preservation of
And storing the highly branched starch film in a constant temperature and humidity box for later use.
In one embodiment of the present invention, the starch in step (1) is selected from the group consisting of corn starch, pea starch, tapioca starch and wheat starch.
In one embodiment of the present invention, the mass concentration of the starch milk in the step (1) is in a range of 3% to 5%.
In one embodiment of the invention, the temperature range for heating the starch milk in the step (2) is 90-100 ℃; the heating time is 30 min-1 h.
In one embodiment of the present invention, the starch branching enzyme of step (3) is added in an amount of 25 to 200U/g starch on a dry basis; adding starch branching enzyme, adjusting pH to 6.0-7.5, and reacting at 50-70 deg.C for 3-24 hr.
In one embodiment of the present invention, the starch branching enzyme of step (3) is added in an amount of 25 to 200U/g starch on a dry basis; adding starch branching enzyme, adjusting pH to 6.5-7.5, and reacting at 65-70 deg.C for more than 6 hr.
In one embodiment of the present invention, the starch branching enzyme used in step (3) refers to an enzyme having an EC number of 2.4.1.18.
In one embodiment of the present invention, the plasticizer in the step (4) is at least one of glycerin, polyhydric alcohol and glycol.
In one embodiment of the invention, in the step (4), after the plasticizer is added, the mixture is kept at 90-100 ℃ for 30 min-1 h, so that the small molecular plasticizer is doped between starch molecules.
In one embodiment of the present invention, the thickness of the cast in the step (5) is 0.050mm to 0.200mm.
In one embodiment of the present invention, the polypropylene cell area in step (5) is 33cm 2 The gel amount of the pouring is 20-40 g, and the thickness is 0.050mm-0.200mm.
In one embodiment of the invention, the temperature range for drying in the vacuum drying oven in the step (6) is 40-60 ℃, and the drying time is 8-12 h.
In one embodiment of the present invention, the temperature condition for storing in the constant temperature and humidity chamber in the step (7) is 25 ℃, the relative humidity is 50%, and the storage time is 24h.
The invention has the beneficial effects that:
the invention pretreats starch by size mixing and pasting to achieve the effects of disappearance of the crystal structure of starch grains, disconnection of hydrogen bonds, dispersion in water into colloidal solution and convenience for enzymatic modification; then, qualitatively modifying the structure of the starch by enzymolysis treatment of starch branching enzyme so as to achieve the effects of increasing the branching degree of the starch and realizing the reconstruction of starch molecules; and plasticizing the modified starch, pouring and drying to obtain the edible film.
The invention utilizes a biological enzyme method to carry out high-branching regulation and control on starch, uses a starch branching enzyme to cut alpha-1.4 glycosyl bonds in starch molecules, and transfers the cut chain segments to a receptor chain through the alpha-1, 6 glycosyl bonds to form new branches (see figure 1), the relative content of the alpha-1, 6-glycosidic bonds is improved, thereby increasing the starch branching degree, regulating the reconstruction of the glycosidic bonds in the starch molecules to realize the rearrangement of the original starch molecular structure, and compacting the structural basis for the preparation of a high-branching starch-based film.
The surface of the starch-based edible film obtained by the invention is changed from rough and porous to flat and smooth surface, and is uniform and continuous, compared with a film which is not modified by the branching enzyme, the tensile strength is obviously improved, and the starch-based edible film is convenient to apply in different food packaging fields.
Drawings
FIG. 1 is a schematic diagram of starch modified by starch branching enzyme.
FIG. 2 is a molecular structure diagram of amylopectin.
FIG. 3 influence of GBE modification on starch chain length distribution.
FIG. 4GBE modified starch 1 H NMR spectrum.
FIG. 5 scanning electron micrograph of starch-based film.
FIG. 6 tensile strength of corn starch film.
FIG. 7 thermogravimetric curve (left) and microperimetric thermogravimetric analysis curve (right) of corn starch film.
Detailed Description
In order to make the objects, features and technical solutions of the present invention more comprehensible, and in particular to highlight the beneficial effects of the synergistic effect of the processes of the present invention, the present invention is described in more detail below with reference to specific examples.
Example 1: regulation of highly branched starch structure by adding amount of starch branching enzyme
Specific steps for preparing high-branched starch
(1) Size mixing: dissolving pea starch in deionized water to obtain 3% starch milk, stirring at 50 deg.C, and storing for 30 min.
(2) Pasting: heating the starch milk to 95 ℃ for constant reaction for 1h to swell and collapse starch grains to form a viscous and uniform transparent paste solution.
(3) Enzymolysis: at 50 ℃, adding 25, 50, 100 and 200U/g of Geobacillus stearothermophilus-derived starch branching enzyme into starch milk respectively to perform constant temperature reaction for 3 hours, so that the starch is hydrolyzed and transglycosidated, and the high-branching modification of the starch structure by an enzyme method is realized.
Example 2: regulation of starch type to highly branched starch structure modified by starch branching enzyme
(1) Size mixing: dissolving pea starch and corn starch in deionized water to obtain 3% starch milk, stirring at 50 deg.C, and storing for 30 min.
(2) Pasting: heating the starch milk to 95 ℃ for constant reaction for 1h to swell and collapse starch grains to form a viscous and uniform transparent paste solution.
(3) Enzymolysis: adding 25U/g of Geobacillus stearothermophilus-derived starch branching enzyme into starch milk at 50 ℃ for carrying out constant temperature reaction for 3 hours, so that the starch is hydrolyzed and transglycosidated, and the enzymatic method is used for carrying out hyperbranched modification on the starch structure.
Example 3: regulation of starch branching enzyme modification time on highly branched starch structure
(1) Size mixing: dissolving pea starch in deionized water to obtain 3% starch milk, stirring at 50 deg.C, and storing for 30 min.
(2) Pasting: heating the starch milk to 95 ℃ for constant reaction for 1h to swell and collapse starch grains and form a viscous and uniform transparent paste solution.
(3) Enzymolysis: at 50 ℃, 25U/g of starch branching enzyme from Geobacillus stearothermophilus is added into starch milk to carry out constant temperature reaction for 3h, 6h and 9h respectively, so that the starch is hydrolyzed and transglycosidated, and the high-branching modification of the starch structure by an enzyme method is realized.
Control group 1:
the step (1) and the step (2) are the same as the example 1;
and (3) replacing GBE enzyme with deionized water, and reacting at a constant temperature of 50 ℃ for 3 hours.
Control group 2:
the step (1) and the step (2) are the same as those in the example 1; step (3) of example 1 is omitted.
The following tests were carried out for examples 1-3 and the control group:
1. determination of branched chain Length distribution
Measuring the chain length distribution of the sample by adopting a high-performance anion exchange chromatography-pulse amperometric detector (HPAEC-PAD), wherein the chromatographic analysis conditions are as follows: and (3) carrying out ternary gradient elution by using ultrapure water, 0.25M NaOH and 1M NaAC solution, carrying out chromatographic column CarboPacPA 200 at the flow rate of 0.5mL/min, at the column temperature of 30 ℃, and carrying out sample injection of 20 mu L.
Amylopectin is a highly branched polysaccharide formed by connecting glucose through alpha-1, 4 glycosidic bond to form main chain and connecting glucose through alpha-1, 6 glycosidic bond to form side chain, and its structure is shown in FIG. 2. The chain length distribution refers to that a series of linear short chains with different polymerization Degrees (DP), namely glucan chains with different lengths, are obtained after alpha-1, 6 glycosidic bonds of the starch are cut by debranching enzyme, and the contents of the glucan chains with different polymerization degrees are analyzed by high-efficiency anion exchange chromatography.
Table 1 and FIG. 3 show the results of the chain length distribution of the enzymatic hydrolysate obtained in example 1. To further analyze the branched fine structure (i.e., the specific ratio of glucan chains of different lengths) of hyperbranched corn starch, the side chain segments of amylopectin separated by debranching enzyme were classified according to their lengths, which are DP 3-12, DP 13-24, DP 25-36, and DP >36, and the content of each segment is shown in Table 1 and FIG. 1.
TABLE 1 branched chain segment content of pea starch acted on by different addition amounts of starch branching enzyme
Different letters on the same column of data in Table 1 indicate that the mean values between groups were significantly different at the p < 0.05 level.
As can be seen from FIG. 1, the chain length distribution of pea starch is approximately normal, wherein the DP <13 and DP 13-24 have a high segment content, and the GBE treatment changes the segment structure of the modified starch, but the whole distribution is still approximately normal. After modification, the contents of the segments DP <13 and DP 24-36 increased with increasing enzyme addition, and the contents of DP 12-24 and DP >36 decreased, indicating that GBE as a whole tends to hydrolyze longer molecular segments in amylopectin and reconnect the cut molecules, resulting in a decrease in the long chain content and an increase in the short chain content.
2. Determination of the content of alpha-1, 6-glycosidic linkages
Hydrogen spectrometer using nuclear magnetic resonance (1 H NMR) the degree of branching of the starch was investigated. Freeze-drying the high-branched starch sample after enzymolysis, and then grinding and sieving. Dissolving highly branched starch in heavy water (D) 2 O) to obtain a 20mg/mL solution, carrying out boiling water bath for 30min, freeze-drying the gelatinized sample for 72h, and dissolving in heavy water (20 mg/mL) again for a nuclear magnetic resonance hydrogen spectrometer (1 H NMR).
By using 1 H NMR measured the relative content of alpha-1, 6-glucosidic bonds in the samples before and after the starch had been modified, and the results are shown in FIG. 2. Chemical shifts of the alpha-1, 6-glycosidic bond and the alpha-1, 4-glycosidic bond were 4.97ppm and 5.37ppm, respectively. The relative content of the alpha-1, 6-glycosidic bond can be obtained according to the peak areas of the absorption peaks corresponding to the alpha-1, 4-glycosidic bond and the alpha-1, 6-glycosidic bond in the sample. As a result, the relative content of alpha-1, 6-glycosidic bonds of the starch modified by the branching enzyme in example 3 is obviously increased along with the prolonging of the modification time, which shows that the starch branching enzyme modification can obviously improve the branching degree of the starch.
Example 4: regulation and control of starch branching enzyme adding amount on performance of highly branched starch film
(1) Plasticizing: and (3) adding 30% of glycerol of the dry starch basis into the starch milk enzymolysis liquid obtained in the step (3) in the embodiment 1, and reacting for 30min at 95 ℃ to ensure that the micromolecule plasticizer is doped among starch molecules and the space among the starch molecules is increased.
(2) Pouring: casting 20g of gel solution into a polypropylene watch glass by a casting method to form a film, and controlling the level to ensure the film thickness to be uniform.
(3) Drying: drying in a horizontal vacuum drying oven at 60 deg.C for 8 hr to obtain the highly branched starch film.
(4) And (3) storage: the dried film was taken out from the vacuum drying oven and stored in a constant temperature and humidity cabinet at 25 ℃ and a relative humidity of 50% for 24 hours.
Example 5: regulation influence of starch branching enzyme on performance of different types of highly branched starch films
(1) Plasticizing: and (3) adding 30% of glycerol of the dry starch basis into the starch milk enzymolysis liquid obtained in the step (3) in the embodiment 2, and reacting for 30min at 95 ℃ to ensure that the micromolecule plasticizer is doped among starch molecules and the distance among the starch molecules is increased.
(2) Pouring: casting 20g of gel solution into a polypropylene watch glass by a casting method to form a film, and controlling the level to ensure the film thickness to be uniform.
(3) And (3) drying: drying in a horizontal vacuum drying oven at 60 ℃ for 8h to obtain the high-branched starch film.
(4) And (3) storage: the dried film was taken out from the vacuum drying oven and stored in a constant temperature and humidity cabinet at 25 ℃ and a relative humidity of 50% for 24 hours.
Example 6: regulation and control influence of starch branching enzyme modification time on performance of highly branched starch film
(1) Plasticizing: and (3) adding 30% of glycerol of the dry starch basis into the starch milk enzymolysis liquid obtained in the step (3) in the embodiment 3, and reacting for 30min at 95 ℃ to ensure that the micromolecule plasticizer is doped among starch molecules and the distance among the starch molecules is increased.
(2) Pouring: and casting 20g of gel solution into a polypropylene watch glass by adopting a casting method to form a film, and controlling the level to ensure that the film thickness is uniform.
(3) And (3) drying: drying in a horizontal vacuum drying oven at 60 deg.C for 8 hr to obtain the highly branched starch film.
(4) And (3) storage: the dried film was taken out from the vacuum drying oven and stored in a constant temperature and humidity cabinet at 25 ℃ and a relative humidity of 50% for 24 hours.
Control group 3:
no plasticizer was added, and the rest was the same as in example 6.
The following tests were carried out for examples 4-6 and control 3:
1. observation with a scanning electron microscope
The sample was sliced and stuck on a sample stand, and a layer of gold powder was uniformly sprayed on the surface, and observed at a voltage of 3.0kV, and the result is shown in FIG. 3.
FIG. 3 shows the observation results of each group of starch-based films by a scanning electron microscope. From the results of comparison between the groups of the control group 3 and the example 6, it can be seen that the addition of glycerol, whether or not the starch branching enzyme modification is added, improves the plasticity of the starch molecules, and increases the flexibility of the starch material due to the attraction between the spacer polymer molecules between the starch molecules, thereby gradually smoothing the surface of the starch film. Comparison of control 3 with that of example 6 shows that the surface of the starch film is changed from rough and porous to smooth and even by the modification of the starch branching enzyme, regardless of the plasticizing effect of glycerol, and the phenomenon obviously occurs along with the prolonging of the modification time of the amylase. The cavities and the rough surface are greatly reduced, the improvement of the film performance is facilitated, and the conjecture is that the chain structure of the starch molecules is recombined after the starch molecules are modified by the branching enzyme, so that the surface structure of the starch film is more compact and smooth.
2. Mechanical properties
The film is cut into rectangular sample strips with the size of 20 multiplied by 80mm, the distance between two frame plates is set to be 20mm, the stretching speed is set to be 20mm/min, and the mechanical strength of the starch-based film is measured.
As a result, as shown in fig. 4, the tensile strength of the starch film tended to increase and then decrease as the amount of enzyme added increased, and the tensile strength of the starch film reached a peak at 25U/g and then started to decrease; in combination with the chain length distribution results, GBE as a whole tends to hydrolyze longer molecular segments in amylopectin and reconnect the cut molecules, resulting in a decrease in the long chain content and an increase in the short chain content, compared to the native starch film (the product of control 1 is formed into a film by the method of reference example 6), in which the tensile strength is increased by 100.09%, 69.58%, 49.75%, and 9.68%, respectively. The increase in hyper-branching increases the short-range order of starch crystallization, thereby increasing the tensile strength of the starch film.
3. Thermodynamic properties
Detection was performed using TGA 8000. About 3mg of the starch film was loaded into a crucible pan and then heated from 30 ℃ to 500 ℃ at a heating rate of 15 ℃ under a nitrogen atmosphere at a gas flow rate of 20mL/min.
As shown in FIG. 5, the degradation temperature of the GBE-treated starch-based film gradually decreased with the increase of the enzyme addition amount, and the linear chains of the debranched starch were rearranged after the starch was modified with the GBE enzyme, but the crystalline region was decreased as compared with the original starch, resulting in a decrease in the decomposition temperature, and in addition, the decrease in the thermal stability may be associated with a decrease in the molecular interaction between the starch chains and the amorphous crystal structure of the starch.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method of making an edible film, comprising the steps of:
(1) Size mixing
Dissolving starch in water to prepare starch milk, and uniformly stirring at 25-50 ℃ for later use;
(2) Gelatinizing
Heating the starch milk to swell and collapse starch grains to form a viscous and uniform transparent paste solution;
(3) Enzymolysis
Adding starch branching enzyme into starch milk at 45-55 ℃, catalyzing starch to hydrolyze and transglycosidically, so as to realize the modification of starch structure by enzyme method;
(4) Plasticising
Adding a plasticizer into the starch emulsion subjected to enzymolysis in the step (3), so that the micromolecule plasticizer is doped among starch molecules, and the distance among the starch molecules is increased to form a gel solution;
(5) Pouring
Casting the gel solution obtained in the step (4) in a casting way in a polypropylene watch glass to form a film by adopting a casting method, and controlling the level to ensure that the film thickness is uniform;
(6) Drying by baking
Drying the gel solution in a horizontal vacuum drying oven, and drying for a certain time to obtain a highly branched starch film;
(7) Preservation of
And storing the highly branched starch film in a constant temperature and humidity box for later use.
2. A method of preparing an edible film according to claim 1 wherein the starch of step (1) is selected from the group consisting of corn starch, pea starch, tapioca starch and wheat starch.
3. A method of preparing an edible film according to claim 1, wherein the mass concentration of starch milk in step (1) is in the range of 3% to 5%.
4. A method of preparing an edible film according to claim 1, wherein the starch milk is heated in step (2) at a temperature in the range of 90 to 100 ℃; the heating time is 30 min-1 h.
5. A method of preparing an edible film according to claim 1, wherein the starch branching enzyme of step (3) is added in an amount of 25-200U/g starch on a dry basis; adding starch branching enzyme, adjusting pH to 6.0-7.5, and reacting at 50-70 deg.C for 3-24 hr.
6. The method of claim 1, wherein the plasticizer in step (4) is at least one of glycerin, a polyhydric alcohol, and a dihydric alcohol.
7. A method of preparing an edible film according to claim 1, wherein in step (4), after the plasticizer is added, the mixture is maintained at 90-100 ℃ for 30 min-1 h to allow the small molecule plasticizer to be incorporated between starch molecules.
8. A method of preparing an edible film according to claim 1, wherein the thickness cast in step (5) is 0.050mm to 0.200mm.
9. A starch-based edible film obtainable by the method of any one of claims 1 to 8.
10. Use of the starch-based edible film of claim 9 in food packaging.
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|---|---|---|---|---|
| JP2001294601A (en) * | 2000-04-11 | 2001-10-23 | Akita Prefecture | Highly branched starch and method for producing the same |
| CN1349544A (en) * | 1999-04-30 | 2002-05-15 | 罗凯脱兄弟公司 | Branched glucose soluble polymers and method for the production thereof |
| CN105199005A (en) * | 2015-11-11 | 2015-12-30 | 江南大学 | Preparation method of high-performance starch slurry |
| CN112852906A (en) * | 2021-01-13 | 2021-05-28 | 江南大学 | Method for synergistically preparing slowly digestible maltodextrin by using two starch branching enzymes |
| CN115058466A (en) * | 2022-07-29 | 2022-09-16 | 江南大学 | Freeze-thaw stable type biological modified starch and preparation method thereof |
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2022
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Patent Citations (5)
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| CN1349544A (en) * | 1999-04-30 | 2002-05-15 | 罗凯脱兄弟公司 | Branched glucose soluble polymers and method for the production thereof |
| JP2001294601A (en) * | 2000-04-11 | 2001-10-23 | Akita Prefecture | Highly branched starch and method for producing the same |
| CN105199005A (en) * | 2015-11-11 | 2015-12-30 | 江南大学 | Preparation method of high-performance starch slurry |
| CN112852906A (en) * | 2021-01-13 | 2021-05-28 | 江南大学 | Method for synergistically preparing slowly digestible maltodextrin by using two starch branching enzymes |
| CN115058466A (en) * | 2022-07-29 | 2022-09-16 | 江南大学 | Freeze-thaw stable type biological modified starch and preparation method thereof |
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