Modified starch composition as well as preparation method and application thereof

Abstract

The invention discloses a modified starch composition as well as a preparation method and application thereof, and relates to the technical field of new materials. Comprising the following steps: adding oxidized amylopectin, modified chitosan and kappa-carrageenan into deionized water, heating to 70-90 DEG C while stirring, continuously stirring, sequentially adding anthocyanin, epsilon-polylysine, catechin, ferulic acid, composite zinc nanoparticles, modified montmorillonite, a sodium alginate compound and synergistic particles, uniformly stirring, and carrying out ultrasonic treatment, so as to obtain a finished product. The modified starch composition is obtained. The tea tree essential oil is introduced into the synergistic particles, so that the fresh-keeping capability of the modified starch composition is effectively improved; and by adding the components such as the composite zinc nanoparticles and the sodium alginate compound, the thermal stability and the mechanical property of the material are further improved. Therefore, the modified starch composition disclosed by the invention has a wider application prospect in the fresh-keeping aspect of fruits, vegetables and fresh meat.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and particularly relates to a modified starch composition, a preparation method thereof and an application thereof. Background Art

[0002] Starch is a high-molecular compound formed by the polymerization of glucose molecules, which is divided into two categories: amylose and amylopectin. It exists in the form of granules in the tubers, roots, seeds and other parts of various plants, and is composed of three elements: carbon, hydrogen and oxygen. Its high-molecular polymer long chain can be decomposed into small-molecule monosaccharides under the action of microorganisms in the environment, and the final metabolites are carbon dioxide and water. Starch is rich in nature, has the advantages of large particle size, low gelatinization temperature, strong water absorption, etc., and has high economic value and development potential. Due to the easy aging of starch, poor thermal stability, shear resistance and large viscosity, and strong hydrogen bonds between and within molecules, its thermal stability and mechanical properties are poor, and the aging property is high, which hinders its application in the fields of food and packaging industry.

[0003] In order to improve the properties of starch, researchers have carried out modification treatments on starch through physical modification, chemical modification, enzymatic modification and multiple modification methods. For example, a modified starch film and its preparation and application proposed in the patent technical literature CN115322448B. The modified starch film described in this invention is prepared by mixing octenyl succinic acid tapioca starch ester, chitosan, glycerol, nano-ZnO and ε-polylysine; among them, the mass ratio of octenyl succinic acid tapioca starch ester: chitosan: glycerol: nano-ZnO: ε-polylysine is 1-1.2: 1-1.2: 0.09-0.10: 0.03-0.04: 0.04-0.16.

[0004] However, the thermal stability and mechanical properties of the modified starch compositions prepared by these existing technical methods still need to be improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a modified starch composition, a preparation method thereof and an application thereof, and solve the following technical problems: There are still problems with the unsatisfactory thermal stability and mechanical properties of the existing modified starch compositions.

[0006] The purpose of the present invention can be achieved by the following technical solutions: A preparation method of a modified starch composition, comprising the following steps: Add oxidized branched starch, modified chitosan, κ-carrageenan to deionized water, then stir and heat to 70-90 °C, continue to stir and sequentially add anthocyanin, ε-polylysine, catechin, ferulic acid, composite zinc nanoparticles, modified montmorillonite, sodium alginate complex, synergistic particles, and after stirring evenly, perform ultrasonic treatment to obtain a modified starch composition.

[0007] Preferably, the mass ratio of the deionized water, oxidized branched starch, modified chitosan, κ-carrageenan, anthocyanin, ε-polylysine, catechin, ferulic acid, composite zinc nanoparticles, modified montmorillonite, sodium alginate complex, and synergistic granules described in is 200-300:5-10:2-4:1-2:0.5-1:0.3-0.6:0.2-0.4:0.2-0.4:0.5-1:0.5-1:0.3-0.6:7.5-11.5.

[0008] Preferably, the preparation method of the oxidized branched starch is as follows: Disperse the branched starch in deionized water, then dropwise add hydrogen peroxide solution while stirring, react at 40-60 °C for 2-4 h, then adjust the pH to 6.5-7.5, and then perform filtration, washing, and drying treatments to obtain oxidized branched starch; The dosage ratio of the branched starch, deionized water, and hydrogen peroxide solution is 10-20 g:200 mL:10-20 mL; The mass fraction of the hydrogen peroxide solution is 30%.

[0009] Preferably, the preparation method of the modified chitosan is as follows: Step A1: Add chitosan to an aqueous acetic acid solution, stir for 20-30 min, then adjust the pH to 10-12, and continue stirring for 1-2 h to obtain a pretreated chitosan solution; Step A2: Dissolve 2,3-epoxypropyltrimethylammonium chloride in isopropanol, then dropwise add it to the pretreated chitosan solution while stirring, and then stir and react at 60-80 °C for 8-10 h. After cooling to room temperature, adjust the pH to 6.5-7.5, and then perform dialysis, drying, washing, and drying treatments to obtain modified chitosan.

[0010] Preferably, the dosage ratio of the aqueous acetic acid solution and chitosan in Step A1 is 100 mL:1-2 g; The mass fraction of the aqueous acetic acid solution in Step A1 is 2%; The dosage ratio of 2,3-epoxypropyltrimethylammonium chloride, isopropanol, and the pretreated chitosan solution in Step A2 is 1.9-4.7 g:100 mL:100 mL.

[0011] Preferably, the preparation method of the composite zinc nanoparticles is as follows: Add chlorogenic acid to absolute ethanol, stir for 30-60 min, then dropwise add zinc chloride solution while stirring, then adjust the pH to 7-9, stir and react for 1-3 h, then perform ultrasonic treatment, and then perform centrifugation, washing, and drying treatments to obtain composite zinc nanoparticles; The dosage ratio of the absolute ethanol, chlorogenic acid, and zinc chloride solution is 50 - 100 mL : 0.1 - 0.5 g : 50 mL; The concentration of the zinc chloride solution is 0.005 mol / L.

[0012] Preferably, the preparation method of the modified montmorillonite is as follows: Disperse the montmorillonite in deionized water, then add cetyltrimethylammonium bromide while stirring at 70 - 90 °C and continue stirring and reacting for 4 - 6 h, and then obtain the modified montmorillonite through filtration, washing, and drying; The dosage ratio of the montmorillonite, deionized water, and cetyltrimethylammonium bromide is 2 - 10 g : 200 mL : 1 - 2 g.

[0013] Preferably, the preparation method of the sodium alginate composite is as follows: Dissolve sodium alginate in deionized water, then add calcium chloride and dropwise add the titanium dioxide dispersion while stirring, react at 50 - 70 °C for 2 - 3 h, and then obtain the sodium alginate composite through centrifugation, washing, and drying; The dosage ratio of the sodium alginate, deionized water, calcium chloride, and titanium dioxide dispersion is 1 - 3 g : 100 mL : 0.1 - 0.2 g : 50 - 100 mL; The titanium dioxide dispersion is obtained by mixing nano - titanium dioxide and deionized water with a dosage ratio of 0.5 - 1.5 g : 50 - 100 mL.

[0014] Preferably, the preparation method of the synergistic granules is as follows: Dissolve hydroxypropyl - β - cyclodextrin in an ethanol solution, raise the temperature to 45 - 50 °C, then dropwise add tea tree essential oil, stir at 45 - 50 °C for 3 - 4 h, then cool at 3 - 4 °C for 12 - 15 h, and then perform filtration and freeze - drying under vacuum conditions to obtain the synergistic granules; The dosage ratio of the hydroxypropyl - β - cyclodextrin, ethanol solution, and tea tree essential oil is 20 - 30 g : 100 - 150 mL : 3 - 5 g; The mass fraction of the ethanol solution is 1%.

[0015] An application of a modified starch composition, where the modified starch composition is used for the preservation and packaging of fruits, vegetables, and fresh meat.

[0016] As a further aspect of the present invention.

[0017] The beneficial effects of the present invention: The present invention provides a modified starch composition, its preparation method, and application. The present invention effectively improves the thermal stability, preservation ability, antibacterial property, and mechanical strength of the modified starch composition through the following methods.

[0018] (1) The groups such as 2,3-epoxypropyltrimethylammonium chloride introduced by the modification of the present invention further enhance the antibacterial ability of chitosan. Moreover, the modified chitosan molecule has a certain flexibility and viscosity, can interact with components such as oxidized branched starch, and plays a role in enhancing the toughness and strength of the film during the film-forming process. It can be filled between other molecules to form a relatively tight network structure, improve stability, hinder the permeation of oxygen, moisture and other gases, and at the same time enable the formed modified starch composition film to have better tensile properties and tear resistance, so as to better play the barrier role of the film, reduce the gas permeability and water permeability of the film, and improve the freshness preservation ability.

[0019] (2) The composite zinc nanoparticles of the present invention combine zinc nanoparticles with chlorogenic acid to produce a synergistic antibacterial effect and enhance the antibacterial ability of the modified starch composition. And the addition of the composite zinc nanoparticles can make chlorogenic acid better dispersed in the modified starch composition and act as physical cross-linking points to enhance the interaction between starch molecular chains, form a more stable structure, and prevent the movement and rearrangement of starch molecular chains, thereby improving the antioxidant ability, thermal stability, storage stability, freshness preservation ability, tensile strength, elastic modulus and other mechanical properties of the modified starch composition sample.

[0020] (3) In the sodium alginate complex of the present invention, sodium alginate undergoes a cross-linking reaction with calcium chloride to form a gel structure. This structure has good stability. Nano-titanium dioxide is dispersed in this structure as a reinforcing phase and interacts with sodium alginate molecules to play a filling and reinforcing effect. Then, in the modified starch composition, it forms a relatively dense structure together with other components, improving the thermal stability, freshness preservation ability, antibacterial performance and mechanical strength of the modified starch composition sample.

[0021] (4) The tea tree essential oil in the synergistic granules of the present invention has antibacterial effects and contains a variety of antioxidant components, which can enhance the antioxidant ability of the modified starch composition and can also cooperate with other components to better maintain the freshness and quality of the items to be preserved. The present invention uses hydroxypropyl-β-cyclodextrin to encapsulate the tea tree essential oil to improve its stability and slow-release performance.

[0022] Therefore, the modified starch composition prepared by the present invention has more excellent thermal stability, freshness preservation ability, antibacterial performance and mechanical strength, as well as a broad application prospect. Detailed implementation mode

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] The properties and sources of some raw materials in the present invention are as follows: Amylopectin was purchased from Shanghai Qincheng Biotechnology Co., Ltd., CAS: 9037-22-3; nano-titanium dioxide was purchased from Shanghai Yunfu Nano Technology Co., Ltd., CAS: 13463-67-7; tea tree essential oil was purchased from Jiangxi Hairui Natural Plants Co., Ltd., CAS: 285-377-1.

[0025] Example 1: A preparation method of a modified starch composition is as follows: S1: Disperse 10 g of amylopectin in 200 mL of deionized water, and then dropwise add 10 mL of hydrogen peroxide solution with a mass fraction of 30% at a rate of 1 mL / min while stirring. After reacting at 40 °C for 2 h, adjust the pH to 6.5 with a sodium hydroxide solution with a concentration of 0.1 mol / L, and then perform filtration, washing, and drying treatments to obtain oxidized amylopectin; S2: Add 1 g of chitosan to 100 mL of acetic acid aqueous solution with a mass fraction of 2%. After stirring for 20 min, adjust the pH to 10 with a sodium hydroxide solution with a mass fraction of 20%, and continue stirring for 1 h to obtain a pretreated chitosan solution; S3: Dissolve 1.9 g of 2,3-epoxypropyltrimethylammonium chloride in 100 mL of isopropanol, and then dropwise add it to 100 mL of the pretreated chitosan solution at a rate of 2 mL / min while stirring. Then stir and react at 60 °C for 8 h. After cooling to room temperature, adjust the pH to 6.5 with a hydrochloric acid solution with a concentration of 0.1 mol / L, dialyze with deionized water for 3 d (change deionized water 3 times a day), dry at 40 °C, wash 3 times with absolute ethanol, and dry again at 40 °C to obtain modified chitosan; S4: Add 0.1 g of chlorogenic acid to 50 mL of absolute ethanol, stir at 300 r / min for 30 min, and then dropwise add 50 mL of zinc chloride solution with a concentration of 0.005 mol / L at a rate of 1 mL / min while stirring. Then adjust the pH value to 7 with a sodium hydroxide solution with a concentration of 0.1 mol / L, stir and react for 1 h, perform ultrasonic treatment at a power of 100 W for 15 min, then centrifuge at a speed of 8000 r / min for 10 min, wash the precipitate 3 times with deionized water and absolute ethanol respectively, and dry at 40 °C for 6 h to obtain composite zinc nanoparticles; S5: Disperse 2 g of montmorillonite in 200 mL of deionized water. Then, add 1 g of cetyltrimethylammonium bromide while stirring at 70 °C and continue stirring and reacting for 4 h. After filtration, washing, and drying, modified montmorillonite is obtained. S6: Disperse 0.5 g of nano-titanium dioxide in 50 mL of deionized water to obtain a titanium dioxide dispersion. S7: Dissolve 1 g of sodium alginate in 100 mL of deionized water. Then, add 0.1 g of calcium chloride and dropwise add 50 mL of the titanium dioxide dispersion at a rate of 2 mL / min while stirring. After reacting at 50 °C for 2 h, perform centrifugation, washing, and drying to obtain a sodium alginate composite. S8: Dissolve 20 g of hydroxypropyl-β-cyclodextrin in 100 mL of an ethanol solution with a mass fraction of 1%. After heating to 45 °C, add 3 g of tea tree essential oil dropwise. Stir at 45 °C for 3 h, then cool at 3 °C for 12 h. Then, perform filtration and freeze-drying under vacuum conditions to obtain a synergistic granule. S9: Add 5 g of oxidized branched starch, 2 g of modified chitosan, and 1 g of κ-carrageenan to 200 mL of deionized water. Then, heat to 70 °C while stirring, continue stirring, and sequentially add 0.5 g of anthocyanin, 0.3 g of ε-polylysine, 0.2 g of catechin, 0.2 g of ferulic acid, 0.5 g of composite zinc nanoparticles, 0.5 g of modified montmorillonite, 0.3 g of sodium alginate composite, and 7.5 g of synergistic granules. Stir at 70 °C at 400 r / min for 20 min, then perform ultrasonic treatment at a power of 200 W for 10 min to obtain a modified starch composition.

[0026] Example 2: A method for preparing a modified starch composition is as follows: S1: Disperse 15 g of branched starch in 200 mL of deionized water. Then, add 15 mL of a 30% hydrogen peroxide solution dropwise at a rate of 1.5 mL / min while stirring. After reacting at 50 °C for 3 h, adjust the pH to 7 with a 0.3 mol / L sodium hydroxide solution. After filtration, washing, and drying, oxidized branched starch is obtained. S2: Add 1.5 g of chitosan to 100 mL of an aqueous acetic acid solution with a mass fraction of 2%. Stir for 25 min, then adjust the pH to 11 with a 20% sodium hydroxide solution. Continue stirring for 1.5 h to obtain a pretreated chitosan solution. S3: Dissolve 3.3 g of 2,3-epoxypropyltrimethylammonium chloride in 100 mL of isopropanol, and then dropwise add it to 100 mL of the pretreated chitosan solution at a rate of 2.5 mL / min while stirring. Then stir and react at 70 °C for 9 h. After cooling to room temperature, adjust the pH to 7 with a 0.3 mol / L hydrochloric acid solution, dialyze with deionized water for 4 days (changing deionized water 4 times a day), dry at 45 °C, wash with absolute ethanol 4 times, and dry again at 45 °C to obtain modified chitosan; S4: Add 0.3 g of chlorogenic acid to 75 mL of absolute ethanol, stir at 400 r / min for 45 min, then dropwise add it to 50 mL of a 0.005 mol / L zinc chloride solution at a rate of 1.5 mL / min while stirring. Then adjust the pH value to 8 with a 0.5 mol / L sodium hydroxide solution, stir and react for 2 h, perform ultrasonic treatment at a power of 200 W for 25 min, then centrifuge at a speed of 10,000 r / min for 15 min and wash the precipitate 4 times with deionized water and absolute ethanol respectively, and dry at 50 °C for 9 h to obtain composite zinc nanoparticles; S5: Disperse 6 g of montmorillonite in 200 mL of deionized water, then add 1.5 g of cetyltrimethylammonium bromide while stirring at 80 °C and continue to stir and react for 5 h. Then, after filtration, washing, and drying, obtain modified montmorillonite; S6: Disperse 1 g of nano-titanium dioxide in 75 mL of deionized water to obtain a titanium dioxide dispersion; S7: Dissolve 2 g of sodium alginate in 100 mL of deionized water, then add 0.15 g of calcium chloride and dropwise add it to 75 mL of the titanium dioxide dispersion at a rate of 2.5 mL / min while stirring. After reacting at 60 °C for 2.5 h, perform centrifugation, washing, and drying to obtain a sodium alginate complex; S8: Dissolve 25 g of hydroxypropyl-β-cyclodextrin in 125 mL of a 1% ethanol solution by mass, raise the temperature to 48 °C, then add 4 g of tea tree essential oil dropwise, stir at 48 °C for 3.5 h, cool at 3.5 °C for 14 h, and then perform filtration and freeze-drying under vacuum conditions to obtain synergistic granules; S9: Add 7.5 g of oxidized branched starch, 3 g of modified chitosan, and 1.5 g of κ-carrageenan to 250 mL of deionized water, then stir and heat to 80 °C, continue to stir and sequentially add 0.75 g of anthocyanin, 0.45 g of ε-polylysine, 0.3 g of catechin, 0.3 g of ferulic acid, 0.75 g of composite zinc nanoparticles, 0.75 g of modified montmorillonite, 0.45 g of sodium alginate complex, and 9.5 g of synergistic granules. Stir at 80 °C at 450 r / min for 25 min, then perform ultrasonic treatment at a power of 250 W for 15 min to obtain a modified starch composition.

[0027] Example 3: A preparation method of a modified starch composition is as follows: S1: Disperse 20 g of amylopectin in 200 mL of deionized water, then while stirring, dropwise add 20 mL of a 30% hydrogen peroxide solution at a rate of 2 mL / min. After reacting at 60 °C for 4 h, adjust the pH to 7.5 with a 0.5 mol / L sodium hydroxide solution, and then perform filtration, washing, and drying treatments to obtain oxidized amylopectin; S2: Add 2 g of chitosan to 100 mL of a 2% acetic acid aqueous solution. After stirring for 30 min, adjust the pH to 12 with a 20% sodium hydroxide solution, and continue stirring for 2 h to obtain a pretreated chitosan solution; S3: Dissolve 4.7 g of 2,3-epoxypropyltrimethylammonium chloride in 100 mL of isopropanol, then while stirring, dropwise add it to 100 mL of the pretreated chitosan solution at a rate of 3 mL / min. Then stir and react at 80 °C for 10 h. After cooling to room temperature, adjust the pH to 7.5 with a 0.5 mol / L hydrochloric acid solution, dialyze with deionized water for 5 d (changing deionized water 4 times a day), dry at 50 °C, wash 5 times with absolute ethanol, and dry again at 50 °C to obtain modified chitosan; S4: Add 0.5 g of chlorogenic acid to 100 mL of absolute ethanol, stir at 500 r / min for 60 min, then while stirring, dropwise add 50 mL of a 0.005 mol / L zinc chloride solution at a rate of 2 mL / min. Then adjust the pH value to 9 with a 1 mol / L sodium hydroxide solution, stir and react for 3 h, perform ultrasonic treatment at a power of 300 W for 30 min, then centrifuge at a speed of 12,000 r / min for 20 min, and wash the precipitate 5 times with deionized water and absolute ethanol respectively. After drying at 60 °C for 12 h, obtain composite zinc nanoparticles; S5: Disperse 10 g of montmorillonite in 200 mL of deionized water, then while stirring at 90 °C, add 2 g of cetyltrimethylammonium bromide and continue stirring and reacting for 6 h. Then perform filtration, washing, and drying treatments to obtain modified montmorillonite; S6: Disperse 1.5 g of nano-titanium dioxide in 100 mL of deionized water to obtain a titanium dioxide dispersion; S7: Dissolve 3 g of sodium alginate in 100 mL of deionized water, then add 0.2 g of calcium chloride and while stirring, dropwise add it to 100 mL of the titanium dioxide dispersion at a rate of 3 mL / min. After reacting at 70 °C for 3 h, perform centrifugation, washing, and drying treatments to obtain a sodium alginate complex; S8: Dissolve 30 g of hydroxypropyl-β-cyclodextrin in 150 mL of 1% ethanol solution by mass, heat it to 50 °C, then add 5 g of tea tree essential oil dropwise, stir at 50 °C for 4 h, cool at 4 °C for 15 h, and then filter and freeze-dry under vacuum conditions to obtain the synergistic granules; S9: Add 10 g of oxidized branched starch, 4 g of modified chitosan, and 2 g of κ-carrageenan to 300 mL of deionized water, then heat to 90 °C while stirring, continue to stir and sequentially add 1 g of anthocyanin, 0.6 g of ε-polylysine, 0.4 g of catechin, 0.4 g of ferulic acid, 1 g of composite zinc nanoparticles, 1 g of modified montmorillonite, 0.6 g of sodium alginate complex, and 11.5 g of synergistic granules. Stir at 90 °C at 500 r / min for 30 min, then perform ultrasonic treatment at a power of 300 W for 20 min to obtain the modified starch composition.

[0028] Comparative Example 1: Compared with Example 1, in this comparative example, only the "pretreated chitosan solution" added in the preparation process of modified chitosan in S3 was replaced with "add 1 g of chitosan to 100 mL of deionized water and stir for 2 h", and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally the modified starch composition was obtained.

[0029] Comparative Example 2: Compared with Example 1, in this comparative example, only the "oxidized branched starch" added in the preparation process of the pretreated starch solution in S9 was replaced with "branched starch", and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally the modified starch composition was obtained.

[0030] Comparative Example 3: Compared with Example 1, in this comparative example, only the "modified chitosan" added in the preparation process of the pretreated starch solution in S9 was replaced with "chitosan", and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally the modified starch composition was obtained.

[0031] Comparative Example 4: Compared with Example 1, in this comparative example, only the "composite zinc nanoparticles" added in the preparation process of the pretreated starch solution in S9 was replaced with the "sodium alginate complex" prepared in S7 of Example 1 of the present invention, and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally the modified starch composition was obtained.

[0032] Comparative Example 5: Compared with Example 1, in this comparative example, only the "modified montmorillonite" added in the preparation process of the pretreated starch solution in S9 was replaced with "montmorillonite", and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally the modified starch composition was obtained.

[0033] Comparative Example 6: This comparative example is the same as Example 1 except that the "sodium alginate complex" added in the preparation process of the pretreated starch solution in S9 is replaced with "sodium alginate", and the remaining steps and parameters are the same. This comparative example will not be repeated here, and finally a modified starch composition is obtained.

[0034] Comparative Example 7: This comparative example is the same as Example 1 except that the "synergistic granules" added in the preparation process of the pretreated starch solution in S9 is replaced with "hydroxypropyl-β-cyclodextrin", and the remaining steps and parameters are the same. This comparative example will not be repeated here, and finally a modified starch composition is obtained.

[0035] Performance detection: The modified starch compositions prepared in Examples 1 - 3 and Comparative Examples 1 - 7 of the present invention were respectively poured into molds of the same specification and dried into films at 50 °C to obtain specimens of each modified starch composition (with a thickness of 0.5 mm); Determination of antibacterial property: Escherichia coli (bacterium 1) and Staphylococcus aureus (bacterium 2) were respectively cultured in LB solid medium for 12 h at 37 °C. When the strains grew to the exponential growth phase, the strains were taken and diluted with sterile water to prepare a bacterial suspension with a concentration of 106 CFU / mL. The specimens of the modified starch composition were made into discs with a diameter of 6 mm using a puncher and placed in a clean bench for ultraviolet sterilization for 30 min. Each bacterial suspension (30 μL) was respectively inoculated on an agar solid medium plate and spread evenly, and then each modified starch film disc was placed on the medium. The plate was placed in a biochemical incubator and cultured at 37 °C for 24 h. An electronic vernier caliper was used to measure the diameter (mm) of the antibacterial zone of each modified starch film disc. According to this method, the antibacterial properties (mm) of the modified starch compositions prepared in Examples 1 - 3 and Comparative Examples 1 - 7 of the present invention were determined, and the test results are shown in Table 1 below.

[0036] Determination of tensile strength and elongation at break: The specimens of the modified starch composition were made into dumbbell shapes with a width of 0.5 cm and a length of 3 cm using a film press. An electronic universal material testing machine was used to stretch and measure the corresponding tensile strength and elongation at break at a speed of 30 mm / min. According to this method, the tensile strength (MPa) and elongation at break (%) of the modified starch compositions prepared in Examples 1 - 3 and Comparative Examples 1 - 7 of the present invention were determined, and the test results are shown in Table 1 below.

[0037] Determination of antioxidant property: Refer to the standard GB / T 45178-2024 "Chemical Fibers - Determination of Antioxidant Activity - DPPH and ABTS Methods". Use an ultraviolet spectrophotometer to measure the absorbance at a wavelength of 517 nm to test the DPPH scavenging rate of the modified starch composition (the higher the DPPH scavenging rate, the stronger the antioxidant performance). According to this method, the antioxidant properties (%) of the modified starch compositions prepared in Examples 1 - 3 and Comparative Examples 1 - 7 of the present invention were measured, and the test results are shown in Table 1 below.

[0038] Determination of thermal stability: Refer to the standard GB / T 6680-2001 "Determination of Thermal Stability of Starch". Cut the modified starch composition sample into pieces, take 5 g, add 100 mL of deionized water to prepare a starch paste. Then heat it to 95 °C at a rate of 1 °C / min and keep it for 30 min. Then cool it to 50 °C, and use a rotational viscometer to measure the viscosity of the starch paste at this temperature. Record the viscosity after 1 h and calculate the viscosity change rate (the smaller the viscosity change, the better the thermal stability). According to this method, the thermal stability (%) of the modified starch compositions prepared in Examples 1 - 3 and Comparative Examples 1 - 7 of the present invention was measured, and the test results are shown in Table 1 below.

[0039] Determination of freshness preservation effect: Randomly select 50 blueberries with similar maturity, size and shape and no damage. Then wrap them with the modified starch composition sample, measure their mass M1. After 12 days at 25 °C, measure their mass M2 again and count the number of rotten blueberries, and calculate the corresponding decay rate (the ratio of the number of rotten blueberries to the total number of blueberries) and weight loss rate (the ratio of M1 - M2 to M1). According to this method, the freshness preservation effect (%) of the modified starch compositions prepared in Examples 1 - 3 and Comparative Examples 1 - 7 of the present invention was measured, and the test results are shown in Table 1 below.

[0040] Table 1: Performance test results of Examples 1 - 3 and Comparative Examples 1 - 7

[0041] Data analysis: As can be seen from Table 1, the modified starch compositions prepared in the examples of the present invention have more excellent antibacterial properties, mechanical properties, antioxidant properties, thermal stability and freshness preservation ability.

[0042] This may be due to: (1) The oxidation treatment of the present invention can break some glycosidic bonds in amylopectin molecules, break the molecular chains, and reduce the relative molecular mass, thereby improving its solubility in water, and then ensuring the uniformity and stability of the entire modified starch composition. And after the oxidation treatment, the molecular structure of amylopectin changes, and more polar groups such as carboxyl groups and aldehyde groups are introduced on the molecular chains, making the oxidized amylopectin better combine with components such as modified chitosan, anthocyanins, and ε-polylysine, and more likely to form a continuous film structure during the drying process, thereby improving the film-forming performance and reaction activity of the modified starch composition.

[0043] (2) The groups such as 2,3-epoxypropyltrimethylammonium chloride introduced by the modification of the present invention further enhance the antibacterial ability of chitosan. And the modified chitosan molecule has certain flexibility and viscosity, can interact with components such as oxidized amylopectin, and plays a role in enhancing the toughness and strength of the film during the film-forming process. It can be filled between other molecules to form a relatively tight network structure, improve stability, hinder the permeation of oxygen, moisture and other gases, and at the same time, the formed modified starch composition film can have better tensile properties and tear resistance, so as to better play the barrier role of the film, reduce the gas permeability and water permeability of the film, and improve the freshness preservation ability.

[0044] (3) The composite zinc nanoparticles of the present invention combine zinc nanoparticles with chlorogenic acid to produce a synergistic antibacterial effect and enhance the antibacterial ability of the modified starch composition. And the addition of the composite zinc nanoparticles can make chlorogenic acid better dispersed in the modified starch composition, and serve as physical cross-linking points to enhance the interaction between starch molecular chains, form a more stable structure, and prevent the movement and rearrangement of starch molecular chains, thereby improving the antioxidant ability, thermal stability, storage stability, freshness preservation ability, tensile strength, elastic modulus and other mechanical properties of the modified starch composition sample.

[0045] (4) After the modification treatment of montmorillonite in the present invention, its compatibility with other components is improved, it can be better dispersed in the system, play a role in heat insulation and hindering heat transfer, and form tortuous channels, thereby improving the barrier properties of the product to oxygen, water vapor, etc., and at the same time serving as physical cross-linking points to limit the movement of polymer molecular chains, thereby improving the thermal stability, freshness preservation ability, tensile strength, hardness and other mechanical properties of the modified starch composition sample.

[0046] (5) In the sodium alginate complex of the present invention, sodium alginate undergoes a cross-linking reaction with calcium chloride to form a gel structure. This structure has good stability. Nano-titanium dioxide is dispersed in this structure as a reinforcing phase and interacts with sodium alginate molecules, playing a role in filling and strengthening. Subsequently, in the modified starch composition, it forms a relatively dense structure together with other components, improving the thermal stability, freshness preservation ability, antibacterial property, and mechanical strength of the modified starch composition sample.

[0047] (6) The tea tree essential oil in the synergistic granule of the present invention has antibacterial effects and contains various antioxidant components, which can enhance the antioxidant ability of the modified starch composition and can also cooperate with other components to better maintain the freshness and quality of the item to be preserved. In the present invention, hydroxypropyl-β-cyclodextrin can be used to encapsulate the tea tree essential oil, improving its stability and sustained-release performance.

[0048] (7) The addition of specific proportions of κ-carrageenan, anthocyanin, ε-polylysine, catechin, and ferulic acid in the present invention further improves the freshness preservation ability, antioxidant property, antibacterial property, stability, and mechanical properties of the modified starch composition sample.

[0049] The above has described a detailed description of an embodiment of the present invention, but the content described is only the preferred embodiment of the present invention and cannot be considered as defining the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for preparing a modified starch composition, characterized in that: The following steps are involved: Oxidized amylopectin, modified chitosan and κ-carrageenan are added to deionized water, and then heated to 70-90° C. while stirring, and anthocyanidins, ε-polylysine, catechins, ferulic acid, composite zinc nanoparticles, modified montmorillonite, sodium alginate complex and synergistic particles are added in sequence, stirred evenly and then ultrasonically treated to obtain a modified starch composition.

2. The method for preparing the modified starch composition according to claim 1, characterized in that: The mass ratio of the deionized water, oxidized amylopectin, modified chitosan, kappa-carrageenan, anthocyanin, epsilon-polylysine, catechin, ferulic acid, composite zinc nanoparticles, modified montmorillonite, sodium alginate complex, and synergistic particles is 200-300: 5-10: 2-4: 1-2: 0.5-1: 0.3-0.6: 0.2-0.4: 0.2-0.4: 0.5-1: 0.5-1: 0.3-0.6: 7.5-11.

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3. The method for preparing the modified starch composition according to claim 1, characterized in that: The preparation method of the oxidized amylopectin is as follows: The amylopectin is dispersed in deionized water, and then a hydrogen peroxide solution is added dropwise while stirring, and the reaction is carried out at 40-60° C. for 2-4 hours, and then the pH is adjusted to 6.5-7.5, and then filtered, washed, and dried to obtain oxidized amylopectin; The ratio of pullulan, deionized water and hydrogen peroxide solution is 10-20 g: 200 mL: 10-20 mL; The mass fraction of the hydrogen peroxide solution is 30%.

4. The method for preparing the modified starch composition according to claim 1, characterized in that: The preparation method of the modified chitosan is as follows: Step A1: adding chitosan to an aqueous solution of glacial acetic acid, stirring for 20-30 minutes, adjusting the pH to 10-12, and continuing stirring for 1-2 hours to obtain a pretreated chitosan solution; Step A2: dissolving 2,3-epoxypropyltrimethylammonium chloride in isopropanol, then adding dropwise to the pretreated chitosan solution while stirring, and then stirring and reacting at 60-80°C for 8-10 hours. After cooling to room temperature, adjusting the pH to 6.5-7.5, and then dialyzing, drying, washing, and drying to obtain modified chitosan.

5. The method for preparing the modified starch composition according to claim 4, characterized in that: The usage ratio of the glacial acetic acid aqueous solution and chitosan in step A1 is 100 mL: 1-2 g; The mass fraction of the glacial acetic acid aqueous solution in step A1 is 2%; The usage ratio of 2,3-epoxypropyltrimethylammonium chloride, isopropanol and pretreated chitosan solution in step A2 is 1.9-4.7 g: 100 mL: 100 mL.

6. The method for preparing the modified starch composition according to claim 1, characterized in that: The preparation method of the composite zinc nanoparticles is as follows: Add chlorogenic acid to anhydrous ethanol, stir for 30-60 minutes, then drop a zinc chloride solution while stirring, adjust the pH to 7-9, stir for 1-3 hours, perform ultrasonic treatment, and then centrifuge, wash, and dry to obtain composite zinc nanoparticles; The dosage ratio of the anhydrous ethanol, chlorogenic acid and zinc chloride solution is 50-100 mL: 0.1-0.5 g: 50 mL; The concentration of the zinc chloride solution is 0.005 mol / L.

7. The method for preparing the modified starch composition according to claim 1, characterized in that: The preparation method of the modified montmorillonite is as follows: Dispersing montmorillonite in deionized water, then adding hexadecyltrimethylammonium bromide at 70-90°C with stirring and continuing to stir for 4-6 hours, and then filtering, washing and drying to obtain modified montmorillonite; The usage ratio of the montmorillonite, deionized water and hexadecyltrimethylammonium bromide is 2-10g:200mL:1-2g.

8. The method for preparing the modified starch composition according to claim 1, characterized in that: The preparation method of the sodium alginate complex is as follows: Dissolve sodium alginate in deionized water, then add calcium chloride and drop titanium dioxide dispersion while stirring, react at 50-70°C for 2-3h, centrifuge, wash and dry to obtain a sodium alginate complex; The dosage ratio of the sodium alginate, deionized water, calcium chloride and titanium dioxide dispersion is 1-3 g: 100 mL: 0.1-0.2 g: 50-100 mL; The titanium dioxide dispersion is obtained by mixing nano titanium dioxide and deionized water in a dosage ratio of 0.5-1.5 g:50-100 mL.

9. The method for preparing the modified starch composition according to claim 1, characterized in that: The preparation method of the synergistic granules is as follows: Dissolve hydroxypropyl-β-cyclodextrin in an ethanol solution, heat it to 45-50°C, then drop tea tree essential oil, stir at 45-50°C for 3-4 hours, cool at 3-4°C for 12-15 hours, filter and freeze-dry under vacuum conditions to obtain synergistic particles; The dosage ratio of hydroxypropyl-β-cyclodextrin, ethanol solution and tea tree essential oil is 20-30 g: 100-150 mL: 3-5 g; The mass fraction of the ethanol solution is 1%.

10. Use of the modified starch composition according to claims 1-9, characterized in that: The modified starch composition is used for preserving and packaging fruits, vegetables and fresh meat.

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