Polygonatum sibiricum dietary fiber-perilla frutescens essential oil composite fresh-keeping microemulsion and preparation method thereof

Abstract

The invention provides a rhizoma polygonati dietary fiber-perilla essential oil composite fresh-keeping microemulsion and a preparation method thereof. The microemulsion consists of a water phase and an oil phase, wherein the water phase consists of a rhizoma polygonati polysaccharide solution, glycerol, sodium caseinate and chitinase immobilized by sodium alginate microspheres; the oil phase is composed of sealwort dietary fiber-perilla essential oil microcapsules and olive oil. The preparation method comprises the following steps: performing two-step fermentation on polygonatum sibiricum residues through thermoactinomycetes and lactic acid bacteria to form a dietary fiber wall material embedded with polygonatum sibiricum polysaccharides and polyphenols, modifying by grafting salicylic acid, and encapsulating perilla essential oil to realize slow release, so as to construct the microcapsule with antibacterial, antioxidant and disease-resistant inducing functions; secondly, fungal cell walls are damaged in a targeted mode through immobilized chitinase, permeation synergistic sterilization of the perilla essential oil on cell membranes is enhanced, finally, the emulsion is prepared through a low-temperature self-emulsifying technology, the bacteriostatic and fresh-keeping effects are achieved in a multi-angle synergistic mode, and the shelf life of fruits and vegetables is prolonged.

Description

Technical Field

[0001] The invention belongs to the field of emulsion preparation and food preservation, and particularly relates to a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion and a preparation method thereof. Background Art

[0002] In the field of fruit and vegetable preservation, existing technologies face multiple challenges. Although plant essential oils have broad-spectrum antibacterial properties, their volatilization, oxidative inactivation, and off-flavor interference with the flavor of fruits and vegetables limit their application. For example, ingredients such as perilla essential oil have poor stability in light, heat, and oxygen environments, resulting in a decrease in antibacterial effect. At the same time, polysaccharide coating preservatives (such as polygonatum polysaccharide) can only provide a physical barrier and have limited antibacterial activity, making it difficult to meet the needs of efficient preservation. Studies have shown that polygonatum polysaccharide has limited inhibitory effect on common bacterial species, and although its extraction process has been optimized (such as microwave-assisted method), its antibacterial strength is insufficient in actual application. In addition, when polygonatum polysaccharide is applied to nanoemulsion systems, its lack of stability may cause emulsion aggregation and stratification, and conventional high-shear emulsification processes easily destroy the structure of the active ingredients, restricting the synergistic enhancement of functional ingredients.

[0003] To overcome the above-mentioned defects, microencapsulation technology has been introduced to improve the stability of essential oils, but existing methods still have limitations. For example, although microcapsules prepared by β-cyclodextrin or double emulsion-spray drying (such as thyme essential oil or Polygonatum sibiricum polysaccharide microcapsules) can slowly release the core material, the wall material has a single function and cannot synergistically improve the antibacterial and antioxidant properties. In addition, the process is complex and costly, and the large amount of surfactant used may introduce toxicity risks. Although microemulsion technology can enhance the water solubility and stability of essential oils, it is difficult to optimize the component ratio, relies on a large amount of emulsifiers, and fails to effectively integrate the synergistic antibacterial mechanism of polysaccharides and essential oils, resulting in a short-lasting preservation effect. Therefore, an innovative solution is urgently needed to solve the bottleneck of existing technologies through the synergistic action of multiple mechanisms to form a multifunctional preservation system to extend the shelf life of food. Summary of the Invention

[0004] Technical problem to be solved: In response to the above technical problems, the purpose of the present invention is to provide a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion and a preparation method thereof. The microemulsion consists of an aqueous phase and an oil phase: the aqueous phase is composed of a polygonatum polysaccharide solution, glycerol, sodium caseinate and chitinase immobilized on sodium alginate microspheres, and polygonatum dietary fiber-perilla essential oil microcapsules with antibacterial, antioxidant and disease-inducing functions are constructed, and the oil phase is formed with olive oil. Finally, a low-temperature self-emulsification process is used to prepare the emulsion, which synergistically exerts antibacterial and fresh-keeping effects from multiple angles to extend the shelf life of fruits and vegetables.

[0005] Technical solution: A polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion, comprising an aqueous phase and an oil phase: the aqueous phase is composed of a polygonatum polysaccharide solution, glycerol, sodium caseinate and immobilized chitinase; the oil phase is composed of polygonatum dietary fiber-perilla essential oil microcapsules and olive oil.

[0006] The preparation method of the above-mentioned polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion comprises the following specific preparation steps: S1. The Polygonatum polysaccharide was dissolved in deionized water and heated to 50-60 ° C to dissolve to obtain a Polygonatum polysaccharide solution with a concentration of 3-4wt%; S2. Add 3-5vt% glycerol, 1-1.5wt% sodium caseinate and 0.5-1wt% immobilized chitinase to the Polygonatum polysaccharide solution, adjust the pH to 5.5-6.5, stir well, and obtain an aqueous phase; S3. The 6-8wt% Polygonatum dietary fiber - Perilla essential oil microcapsules were dispersed in olive oil, 0.2-0.3% Span80 and 0.02% BHT were added, vortexed for 2min, and ultrasonically dispersed at 100W for 5-10min to obtain the oil phase; S4. Add the oil phase dropwise to the aqueous phase at a rate of 0.8 mL / min, with a volume ratio of 1:(3-3.5). Stir at a constant temperature of 30°C for 20-30 min, and then let it stand at 30°C for 2-2.5 h to obtain the Polygonatum dietary fiber-Perilla essential oil composite preservative microemulsion.

[0007] Furthermore, the preparation steps of the immobilized chitinase in step S2 are as follows: sodium alginate is dissolved in 0.05M pH 6 phosphate buffer to prepare a 1.5-2wt% sodium alginate solution, chitinase is added, and stirred evenly to obtain a mixed solution; the mixed solution is dropped into a 0.1M CaCl2 solution, solidified for 30 minutes, and the microspheres are collected and washed to obtain immobilized chitinase.

[0008] Furthermore, the added amount of the chitinase is 5000-10000 U / g sodium alginate.

[0009] Furthermore, the preparation steps of the polygonatum dietary fiber-perilla essential oil microcapsules in step S3 are as follows: Step 1. Grind the dried polygonatum sibiricum residue into 40-60 mesh, introduce saturated steam under reduced pressure of 12-20 kPa, and treat at 50-60°C for 1-2 hours to obtain pretreated polygonatum sibiricum residue; Step 2. Inoculate the pretreated Polygonatum sibiricum residue with a suspension of thermophilic actinomycetes, ferment at 55-60°C for 20-24 hours, steam inactivate at 105°C for 10-15 minutes, and cool to 30-35°C; Step 3. Inoculate the Lactobacillus plantarum suspension again into step 2, perform anaerobically fermentation at 30-35°C for 36-40 hours, sterilize, centrifuge, take the supernatant, add 4 times the volume of anhydrous ethanol, let stand at 4°C for 12 hours, centrifuge, take the precipitate, wash, and dry to obtain the polygonatum dietary fiber embedded with polygonatum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60-65°C to prepare a microcapsule wall material solution, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, high-speed shear at 6000-8000 rpm for 10-15 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in a 0.1 g / mL salicylic acid ethanol solution, add 1.2 mol / L 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 0.6 mol / L N-hydroxysuccinimide (NHS), adjust the pH to 5.5, react at 50°C for 2-4 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules.

[0010] Furthermore, the concentration of the thermophilic actinomycetes suspension in step 2 is 10 7 -10 8 CFU / mL, with an inoculum size of 5-8%.

[0011] Further, the concentration of the plant lactobacillus suspension in step 3 is 10 8 -10 9 CFU / mL, the inoculum size is 3-5%.

[0012] Furthermore, the concentration of the microcapsule wall material solution in step 4 is 5-8 wt %; and the volume ratio of the perilla essential oil to the microcapsule wall material solution is 1:(3-4).

[0013] Furthermore, in step 5, the mass volume ratio of the microcapsules to the salicylic acid ethanol solution is 1 g: (5-10) mL.

[0014] Application of the polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion prepared by the above preparation method in the preservation of fruits and vegetables. Beneficial effects

[0015] The invention adopts a low-temperature self-emulsification method to prepare a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion. The microemulsion consists of an aqueous phase and an oil phase, wherein the aqueous phase contains a polygonatum polysaccharide solution, glycerol, sodium caseinate, and chitinase immobilized on sodium alginate microspheres; the oil phase consists of polygonatum dietary fiber-perilla essential oil microcapsules and olive oil. The aqueous phase is slowly dripped into the oil phase, and an emulsion is formed by the self-assembly of polygonatum polysaccharide and sodium caseinate at the oil-water interface, thereby avoiding high shear damage to the microcapsule structure, ensuring the structural integrity of the microcapsule, and improving the stability of the emulsion, thereby achieving the antibacterial and fresh-keeping effects of the microcapsules and the microemulsion.

[0016] Polygonatum dietary fiber-perilla essential oil microcapsules are added to the microemulsion prepared by the present invention, and the Polygonatum sibiricum residue is fermented in two steps by thermophilic actinomycetes and lactic acid bacteria. First, the Polygonatum sibiricum residue is pretreated with reduced pressure steam to make the steam more easily penetrate into the microporous structure of the Polygonatum sibiricum residue, destroy the crystalline area of ​​the Polygonatum sibiricum residue fiber, increase the specific surface area, and improve the accessibility of microorganisms to the substrate; then, the Polygonatum sibiricum residue is pretreated by thermophilic actinomycetes fermentation to secrete a complex enzyme system such as cellulase, hemicellulase, endo-β-glucanase, pectinase, etc., to efficiently degrade insoluble fiber (IDF) into soluble dietary fiber (SDF), thereby increasing the content of soluble dietary fiber. However, if cellulase is directly added for enzymatic hydrolysis pretreatment of the Polygonatum sibiricum residue, the single cellulase only targets the hydrolysis of β-1,4-glycosidic bonds and cannot efficiently degrade cross-linked structures such as hemicellulose and lignin, resulting in a low SDF content and a loose fiber structure generated by enzymatic hydrolysis, which is not conducive to microcapsules. The core material is embedded and adsorbed, and the fermentation of thermophilic actinomycetes will also release the bound polysaccharide fragments synchronously; then, Lactobacillus plantarum is introduced into the system for continued fermentation. Lactobacillus plantarum hydrolyzes the residual bound polyphenol glycosidic bonds by secreting hydrolases such as β-glucosidase and converts them into free polyphenols, thereby forming a soluble Polygonatum dietary fiber wall material embedded with Polygonatum polysaccharide and polyphenol in the overall fermentation system, and is modified by grafting salicylic acid. The hydroxyl groups on the Polygonatum polysaccharide chain form a hydrogen bond network with the hydroxyl groups of cellulose, and the carboxyl groups of Polygonatum polyphenols are protonated under acidic conditions and undergo esterification reaction with the primary hydroxyl groups at the C6 position of cellulose to form ester bonds; salicylic acid contains carboxyl groups and phenolic hydroxyl groups, and its carboxyl groups can form ester bonds with the primary hydroxyl groups of SDF under acidic conditions and be fixed on the cellulose skeleton; at the same time, perilla essential oil is encapsulated to achieve sustained release, and a triple-functional synergistic microcapsule with antibacterial, antioxidant and disease-resistant functions is constructed.

[0017] The polygonatum soluble dietary fiber on the microcapsule wall material prepared by the present invention is water-soluble. Directly dispersing it in hydrophobic olive oil will cause severe aggregation and flocculation due to the huge interfacial tension, and it cannot form a stable dispersion. Therefore, the present invention adds Span 80, an oil-soluble surfactant, to the system. Under the combined action of vortex oscillation and ultrasonic dispersion, Span 80 molecules will be adsorbed to the hydrophilic wall material surface of the microcapsule. The lipophilic long chains of Span 80 will extend outward and be exposed to the surrounding olive oil. In this way, Span 80 forms an interfacial film on the surface of the microcapsule. This film significantly reduces the interfacial tension between the microcapsule and the olive oil, making the originally hydrophilic particle surface lipophilic. At the same time, Span 80 The adsorption of molecules on the particle surface can also provide a certain amount of steric hindrance or electrostatic repulsion, which can prevent the particles from aggregating close to each other. In addition, after the microcapsules are modified by grafting salicylic acid, since the benzene ring of salicylic acid is a significant hydrophobic group, it is covalently linked to the hydrophilic wall material surface, which overall reduces the hydrophilicity of the microcapsule surface and also assists and enhances the dispersion effect of Span80.

[0018] The polygonatum dietary fiber and polygonatum polysaccharide on the microcapsule wall material prepared by the present invention both have antibacterial effects, and the polygonatum polyphenols scavenges free radicals and has antioxidant capacity; the salicylic acid grafted on the wall material induces the activity of antioxidant enzymes such as superoxide dismutase and peroxidase after contact with fruits and vegetables, reduces the accumulation of reactive oxygen species, and delays the aging of fruits and vegetables; salicylic acid can also delay the ripening of fruits by reducing the respiration rate of fruits and vegetables and delaying the time of the respiratory peak; in addition, the porous structure of the polygonatum dietary fiber can realize the sustained release of the perilla essential oil in the core material, achieving a broad-spectrum antibacterial effect, and microencapsulation solves the defects of the essential oil being easy to volatilize, unstable, and having an odor, and the sustained release through the wall material prolongs the antibacterial time, thereby comprehensively improving the antibacterial and fresh-keeping effects.

[0019] Chitinase immobilized by sodium alginate microspheres is further added to the microemulsion prepared by the present invention. Free enzyme is easily inactivated in an emulsion environment. Immobilizing chitinase by sodium alginate microspheres can ensure enzyme activity and achieve sustained release of chitinase. Chitinase can specifically hydrolyze chitin, destroy the integrity of fungal cell walls, and cause cell lysis and death. After destroying the fungal cell walls, chitinase exposes the cell membrane, greatly enhancing the permeability and destruction ability of perilla essential oil on the cell membrane, and producing a significant synergistic bactericidal effect. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 The microscopic morphology of the composite fresh-keeping microemulsion prepared in Examples 9-10 and Comparative Examples 6-8; Figure 2 The particle size and potential diagrams of the composite fresh-keeping microemulsions prepared in Examples 9-10 and Comparative Examples 6-8. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments. The following embodiments are intended to explain the present invention, but the present invention is not limited to the following embodiments: The preparation steps of immobilized chitinase are as follows: Sodium alginate was dissolved in 0.05M pH 6 phosphate buffer to prepare a 2wt% sodium alginate solution, and chitinase was added at a concentration of 10,000 U / g sodium alginate. The mixture was stirred evenly to obtain a mixed solution. The mixed solution was dropped into a 0.1M CaCl2 solution and solidified at room temperature for 30 minutes. The microspheres were collected and washed to obtain immobilized chitinase.

[0021] The polygonatum sibiricum residue is obtained by freeze-drying the polygonatum sibiricum polysaccharide after extraction from the polygonatum sibiricum powder.

[0022] Example 1 The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 9 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Example 2

[0023] The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 9 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 6 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Example 3

[0024] The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 9 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 7 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Example 4

[0025] The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 9 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 8 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Example 5

[0026] The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 9 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:4, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Example 6

[0027] The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 9 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:6 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Example 7

[0028] The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 9 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:8 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Example 8

[0029] The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 109 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:10 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Comparative Example 1

[0030] The difference between this comparative example and Example 1 is that no thermophilic actinomycetes were added for fermentation, specifically as follows: The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 9 CFU / mL of Lactobacillus plantarum suspension, inoculated at 4%, anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, and the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the microcapsule wall material; Step 3. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 4. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Comparative Example 2

[0031] The difference between this comparative example and Example 1 is that the thermophilic actinomycete fermentation is replaced by cellulase enzymolysis, as follows: The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Add 1.5 wt% cellulase to the pretreated Polygonatum sibiricum residue, enzymolyze at 55°C for 24 hours, and cool to 30°C; Step 3. Inoculate the solution in step 2 at a concentration of 10 9 A suspension of Lactobacillus plantarum with a CFU / mL inoculation rate of 4% was anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the Polygonatum sibiricum dietary fiber embedded with Polygonatum sibiricum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Comparative Example 3

[0032] The difference between this comparative example and Example 1 is that no plant lactobacillus fermentation was added, specifically as follows: The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, with an inoculation size of 5%, fermented at 55°C for 24 hours, steam inactivated at 105°C for 10 minutes, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, and the suspension was allowed to stand at 4°C for 12 hours. The precipitate was collected by centrifugation, washed, and dried to obtain the microcapsule wall material; Step 3. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 4. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Comparative Example 4

[0033] The difference between this comparative example and Example 1 is that no salicylic acid modification is added, specifically as follows: The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 8 CFU / mL of thermophilic actinomycete suspension, inoculation size 5%, fermented at 55℃ for 24h, steam inactivated at 105℃ for 10min, and cooled to 30℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 9 CFU / mL of Lactobacillus plantarum suspension, inoculated at 4%, anaerobically fermented at 30°C for 36 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, and the suspension was allowed to stand at 4°C for 12 hours, centrifuged, the precipitate was collected, washed, and dried to obtain the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to obtain a microcapsule wall material solution with a concentration of 5wt%, add 2wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules. Comparative Example 5

[0034] The difference between this comparative example and Example 1 is that plant lactobacillus fermentation is performed first, and then thermophilic actinomycete fermentation is performed, specifically as follows: The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules are as follows: Step 1. Grind the dried Polygonatum sibiricum residue into 60 mesh, introduce saturated steam under 20kPa reduced pressure, and treat at 60℃ for 2h to obtain the pretreated Polygonatum sibiricum residue; Step 2. Inoculate the pre-treated Polygonatum sibiricum residue with a concentration of 10 9 CFU / mL of Lactobacillus plantarum suspension, inoculated at 4%, anaerobic fermentation at 30℃ for 36h, steam inactivation at 105℃ for 10min, and then heated to 55℃; Step 3. Re-inoculate the solution in step 2 at a concentration of 10 8CFU / mL of thermophilic actinomycete suspension, with an inoculation size of 5%, fermented at 55°C for 24 hours, sterilized, centrifuged, the supernatant was collected, 4 times the volume of anhydrous ethanol was added, and the suspension was allowed to stand at 4°C for 12 hours. The precipitate was collected by centrifugation, washed, and dried to obtain the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60°C to prepare a microcapsule wall material solution with a concentration of 5 wt%, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, the volume ratio of perilla essential oil to microcapsule wall material solution is 1:3, high-speed shearing at 6000 rpm for 10 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution with a mass volume ratio of 1 g:5 mL, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50°C for 2 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules.

[0035] Performance testing: (1) Soluble dietary fiber (SDF) yield Accurately record the mass of the original dried Polygonatum sibiricum residue used in step 1 (W0), take the dried microcapsule wall material powder (W1) from step 3, and determine the soluble dietary fiber content (C) in the dried microcapsule wall material powder using the AOAC 991.43 standard method. Calculate the soluble dietary fiber yield according to the following formula:

[0036] (2) Encapsulation rate of perilla essential oil Weigh 0.2 g of microcapsules, add 10 mL of petroleum ether, vortex for 2 min, centrifuge at 4000 rpm for 10 min, collect the supernatant, repeat washing three times, combine the supernatants, rotary evaporate, and weigh to obtain the free oil mass (m1); add the washed precipitate to a 50 mL round-bottom flask, add 10 mL of distilled water, steam distill for 2 h, extract the distillate with ether, dehydrate with anhydrous sodium sulfate, and rotary evaporate to remove the ether. The total oil mass (m0) is weighed and the perilla essential oil encapsulation efficiency is calculated according to the following formula:

[0037] (3) DPPH free radical scavenging rate Preparation of DPPH solution: Accurately weigh 25 mg of DPPH, dilute to 250 mL (0.1 mM) with anhydrous ethanol, and store in the dark. Sample solution preparation: 10 mg of microcapsules were added to 10 mL of anhydrous ethanol, ultrasonically disrupted for 10 min, centrifuged (8000 rpm, 5 min), and the supernatant was collected for later use; A blank group (2 mL DPPH + 2 mL ethanol), a sample group (2 mL DPPH + 2 mL sample supernatant), and a control group (2 mL ethanol + 2 mL sample supernatant) were set up respectively. After 30 min of reaction in the dark, the absorbance was measured at 517 nm, and the DPPH radical scavenging rate was calculated according to the following formula:

[0038] Table 1 SDF yield, perilla essential oil encapsulation efficiency and DPPH free radical scavenging rate

[0039] As shown in Table 1, the SDF yield of the microcapsules prepared in Examples 1-8 was 38.4-39.5%, the perilla essential oil encapsulation efficiency was 92.1-93.2%, and the DPPH free radical scavenging rate was 93.2-94.5%. In Comparative Example 1, no thermophilic actinomycete fermentation was added, and the SDF yield was low, and the encapsulation efficiency was also reduced. In Comparative Example 2, the thermophilic actinomycete fermentation was replaced by complex enzyme hydrolysis, and the SDF yield, perilla essential oil encapsulation efficiency and DPPH free radical scavenging rate were slightly lower than those of the examples. In Comparative Example 3, no plant lactobacillus fermentation was added, and cellulose degradation was Insufficient, and polygonatum polysaccharide and polyphenol are also correspondingly missing, so the perilla essential oil encapsulation efficiency and DPPH free radical scavenging rate are both reduced; Comparative Example 4 does not add salicylic acid modification, the microcapsule wall material is loose, and the perilla essential oil encapsulation efficiency and DPPH free radical scavenging rate are reduced; Comparative Example 5 is first fermented with Lactobacillus plantarum and then fermented with thermophilic actinomycetes. The high temperature of thermophilic actinomycete fermentation causes the plant lactobacillus to lose its activity, the fermentation is not thorough, the SDF conversion rate is low, and the same perilla essential oil encapsulation efficiency and DPPH free radical scavenging rate are also lower than those of the embodiment.

[0040] Therefore, the polygonatum dietary fiber-perilla essential oil microcapsules prepared in Example 1 were selected for the subsequent preparation of the polygonatum dietary fiber-perilla essential oil composite preservative microemulsion.

[0041] Example 9 The preparation method of polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion comprises the following specific preparation steps: S1. The Polygonatum sibiricum polysaccharide was dissolved in deionized water and heated to 50 ° C to dissolve to obtain a 3 wt% Polygonatum sibiricum polysaccharide solution; S2 was added to the Polygonatum polysaccharide solution 3vt% glycerol, 1.5wt% sodium caseinate and 0.5wt% immobilized chitinase, adjusted to pH 6, stirred, and the aqueous phase was obtained; S3. The 6wt% Polygonatum dietary fiber prepared in Example 1 - Perilla essential oil microcapsules were dispersed in olive oil, 0.3% Span 80 and 0.02% BHT were added, vortexed for 2min, and ultrasonically dispersed at 100W for 5min to obtain the oil phase; S4. The oil phase was added dropwise to the aqueous phase at a rate of 0.8 mL / min, with a volume ratio of 1:3. After stirring at a constant temperature of 30°C for 30 min, the mixture was transferred to a constant temperature box and allowed to stand and mature at 30°C for 2 h to obtain a composite preservative microemulsion of Polygonatum dietary fiber and Perilla essential oil.

[0042] Example 10 The preparation method of polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion comprises the following specific preparation steps: S1. The Polygonatum sibiricum polysaccharide was dissolved in deionized water and heated to 50 ° C to dissolve to obtain a 3 wt% Polygonatum sibiricum polysaccharide solution; S2 was added to the Polygonatum polysaccharide solution 3vt% glycerol, 1.5wt% sodium caseinate and 0.5wt% immobilized chitinase, adjusted to pH 6, stirred, and the aqueous phase was obtained; S3. 8wt% of the Polygonatum dietary fiber prepared in Example 1 - Perilla essential oil microcapsules were dispersed in olive oil, 0.3% Span 80 and 0.02% BHT were added, vortexed for 2min, and ultrasonically dispersed at 100W for 5min to obtain the oil phase; S4. The oil phase was added dropwise to the aqueous phase at a rate of 0.8 mL / min, with a volume ratio of 1:3.5. After stirring at a constant temperature of 30°C for 30 min, the mixture was transferred to a constant temperature box and allowed to stand at 30°C for 2 h to obtain a composite preservative microemulsion of Polygonatum dietary fiber and Perilla essential oil.

[0043] Comparative Example 6 The difference between this comparative example and Example 9 is that no immobilized chitinase was added, specifically as follows: The preparation method of polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion comprises the following specific preparation steps: S1. The Polygonatum sibiricum polysaccharide was dissolved in deionized water and heated to 50 ° C to dissolve to obtain a 3 wt% Polygonatum sibiricum polysaccharide solution; S2. Add 3vt% glycerol and 1.5wt% sodium caseinate to the Polygonatum polysaccharide solution, adjust the pH to 6, and stir to obtain an aqueous phase; S3. The 6wt% Polygonatum dietary fiber prepared in Example 1 - Perilla essential oil microcapsules were dispersed in olive oil, 0.3% Span 80 and 0.02% BHT were added, vortexed for 2min, and ultrasonically dispersed at 100W for 5min to obtain the oil phase; S4. The oil phase was added dropwise to the aqueous phase at a rate of 0.8 mL / min, with a volume ratio of 1:3. After stirring at a constant temperature of 30°C for 30 min, the mixture was transferred to a constant temperature box and allowed to stand and mature at 30°C for 2 h to obtain a composite preservative microemulsion of Polygonatum dietary fiber and Perilla essential oil.

[0044] Comparative Example 7 The difference between this comparative example and Example 9 is that the polygonatum dietary fiber-perilla essential oil microcapsules prepared in Example 1 are not added, specifically as follows: The preparation method of polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion comprises the following specific preparation steps: S1. The Polygonatum sibiricum polysaccharide was dissolved in deionized water and heated to 50 ° C to dissolve to obtain a 3 wt% Polygonatum sibiricum polysaccharide solution; S2 was added to the Polygonatum polysaccharide solution 3vt% glycerol, 1.5wt% sodium caseinate and 0.5wt% immobilized chitinase, adjusted to pH 6, stirred, and the aqueous phase was obtained; S3. Olive oil was added dropwise to the aqueous phase at a rate of 0.8 mL / min, with a volume ratio of 1:3. After stirring at a constant temperature of 30°C for 30 min, the mixture was transferred to a constant temperature box and allowed to stand and mature at 30°C for 2 h to obtain a composite preservative microemulsion of Polygonatum dietary fiber and Perilla essential oil.

[0045] Comparative Example 8 The difference between this comparative example and Example 9 is that perilla essential oil was directly added without being made into microcapsule form, as follows: The preparation method of polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion comprises the following specific preparation steps: S1. The Polygonatum sibiricum polysaccharide was dissolved in deionized water and heated to 50 ° C to dissolve to obtain a 3 wt% Polygonatum sibiricum polysaccharide solution; S2 was added to the Polygonatum polysaccharide solution 3vt% glycerol, 1.5wt% sodium caseinate and 0.5wt% immobilized chitinase, adjusted to pH 6, stirred, and the aqueous phase was obtained; S3. The perilla essential oil was dispersed in olive oil (the amount of perilla essential oil added was 85% of the Polygonatum dietary fiber - perilla essential oil microcapsules prepared in Example 1), 0.02% BHT was added, vortexed for 2 min, and ultrasonically dispersed at 100W for 5 min to obtain the oil phase; S4. The oil phase was added dropwise to the aqueous phase at a rate of 0.8 mL / min, with a volume ratio of 1:3. After stirring at a constant temperature of 30°C for 30 min, the mixture was transferred to a constant temperature box and allowed to stand and mature at 30°C for 2 h to obtain a composite preservative microemulsion of Polygonatum dietary fiber and Perilla essential oil.

[0046] Performance testing: (1) Micromorphology Depend on Figure 1 It can be seen that the droplets of the composite fresh-keeping microemulsions prepared in Examples 9 and 10 are all round, small in size, and evenly dispersed, while the droplets of the emulsion prepared in Comparative Example 6 without adding immobilized chitinase are slightly larger, and the dispersion is slightly worse than that of the examples; the emulsion prepared in Comparative Example 8 by directly adding perilla essential oil has significantly larger droplets, different sizes, and the overall dispersion is not as good as that of the emulsions of Examples 9-10.

[0047] (2) Particle size and potential Depend on Figure 2 It can be seen that the particle size of the composite fresh-keeping microemulsion prepared in Examples 9-10 is smaller, significantly smaller than that of Comparative Examples 6-8. The smaller the droplet size and the more uniform the distribution, the more stable the emulsion. This shows that the addition of immobilized chitinase and polygonatum dietary fiber-perilla essential oil microcapsules enhances the emulsification of the emulsion.

[0048] The absolute value of the zeta potential is a key parameter for evaluating emulsion stability. Its magnitude directly reflects the strength of the electrostatic repulsion between oil droplets. A larger absolute value indicates stronger electrostatic repulsion between emulsion particles, effectively preventing aggregation and significantly improving the electrostatic stability of the emulsion. The absolute values ​​of the zeta potential of the composite preservative microemulsions prepared in Examples 9 and 10 were higher than those of the composite preservative microemulsions prepared in Comparative Examples 6-8, indicating that the addition of microcapsules can enhance interfacial stabilization.

[0049] (3) Antibacterial properties Table 2 MIC and MBC of the composite fresh-keeping microemulsions prepared in Examples 9-10 and Comparative Examples 6-8

[0050] As shown in Table 2, the composite fresh-keeping microemulsions prepared in Examples 9 and 10 have significantly better inhibitory effects on Escherichia coli and Staphylococcus aureus than those in Comparative Examples 6-8, indicating that the synergistic effect of the microcapsule sustained-release perilla essential oil and the immobilized chitinase is more conducive to improving the antibacterial properties of the emulsions. In addition, the prepared emulsions have a better inhibitory effect on Staphylococcus aureus than on Escherichia coli.

[0051] (4) Fruit rot rate The decay rate of fruits and vegetables is one of the most intuitive indicators for judging the preservation effect. Strawberries were immersed in the composite fresh-keeping microemulsions prepared in Examples 9-10 and Comparative Examples 6-8 and placed at room temperature for 5 days. The fresh-keeping effect of the fresh-keeping microemulsion was evaluated according to the calculation formula of the decay rate. The calculation formula is as follows: Decay rate = (X1 / X2) × 100% Where: X1 is the number of rotten fruits; X2 is the total number of fruits.

[0052] Table 3 Fruit rot rate of the composite fresh-keeping microemulsions prepared in Examples 9-10 and Comparative Examples 6-8

[0053] As can be seen from Table 3, the composite fresh-keeping microemulsions prepared in Examples 9-10 have a low decay rate. This shows that the addition of polygonatum dietary fiber-perilla essential oil microcapsules and immobilized chitinase in the fresh-keeping microemulsion can exert a synergistic effect. The addition of perilla essential oil alone (Comparative Example 8) lacks the synergistic effect of polygonatum dietary fiber, polysaccharides, polyphenols and salicylic acid on the microcapsule wall material, and cannot achieve multi-party synergistic antibacterial effect. Therefore, the fruit decay rate is correspondingly increased.

[0054] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion, characterized in that: The invention comprises an aqueous phase and an oily phase: the aqueous phase is composed of polygonatum polysaccharide solution, glycerol, sodium caseinate and immobilized chitinase; and the oily phase is composed of polygonatum dietary fiber-perilla essential oil microcapsules and olive oil.

2. The method for preparing a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion according to claim 1, characterized in that: The specific preparation steps are as follows: S1. The Polygonatum polysaccharide was dissolved in deionized water and heated to 50-60 ° C to dissolve to obtain a Polygonatum polysaccharide solution with a concentration of 3-4wt%; S2. Add 3-5vt% glycerol, 1-1.5wt% sodium caseinate and 0.5-1wt% immobilized chitinase to the Polygonatum polysaccharide solution, adjust the pH to 5.5-6.5, stir well, and obtain an aqueous phase; S3. The 6-8wt% Polygonatum dietary fiber - Perilla essential oil microcapsules were dispersed in olive oil, 0.2-0.3% Span 80 and 0.02% BHT were added, vortexed for 2min, and ultrasonically dispersed at 100W for 5-10min to obtain the oil phase; S4. Add the oil phase dropwise to the aqueous phase at a rate of 0.8 mL / min, with a volume ratio of 1:(3-3.5). Stir at a constant temperature of 30°C for 20-30 min, and then let it stand at 30°C for 2-2.5 h to obtain the Polygonatum dietary fiber-Perilla essential oil composite preservative microemulsion.

3. The method for preparing a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion according to claim 2, characterized in that: The preparation steps of the immobilized chitinase in step S2 are as follows: sodium alginate is dissolved in 0.05M pH 6 phosphate buffer to prepare a 1.5-2wt% sodium alginate solution, chitinase is added, and the mixture is stirred evenly to obtain a mixed solution; the mixed solution is dropped into a 0.1M CaCl2 solution, solidified for 30 minutes, and the microspheres are collected and washed to obtain the immobilized chitinase.

4. The method for preparing a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion according to claim 3, wherein: The added amount of the chitinase is 5000-10000 U / g sodium alginate.

5. The method for preparing a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion according to claim 2, characterized in that: The preparation steps of polygonatum dietary fiber-perilla essential oil microcapsules in step S3 are as follows: Step 1. Grind the dried polygonatum sibiricum residue into 40-60 mesh, introduce saturated steam under reduced pressure of 12-20 kPa, and treat at 50-60°C for 1-2 hours to obtain pretreated polygonatum sibiricum residue; Step 2. Inoculate the pretreated Polygonatum sibiricum residue with a suspension of thermophilic actinomycetes, ferment at 55-60°C for 20-24 hours, steam inactivate at 105°C for 10-15 minutes, and cool to 30-35°C; Step 3. Inoculate the Lactobacillus plantarum suspension again into step 2, perform anaerobically fermentation at 30-35°C for 36-40 hours, sterilize, centrifuge, take the supernatant, add 4 times the volume of anhydrous ethanol, let stand at 4°C for 12 hours, centrifuge, take the precipitate, wash, and dry to obtain the polygonatum dietary fiber embedded with polygonatum polysaccharides and polyphenols as the microcapsule wall material; Step 4. Dissolve the microcapsule wall material in water, stir and dissolve at 60-65°C to prepare a microcapsule wall material solution, add 2 wt% gum arabic, stir for 10 minutes, then add perilla essential oil, high-speed shear at 6000-8000 rpm for 10-15 minutes, and spray dry to obtain microcapsules; Step 5. Immerse the microcapsules in 0.1 g / mL salicylic acid ethanol solution, add 1.2 mol / L LEDC and 0.6 mol / L NHS, adjust the pH to 5.5, react at 50° C. for 2-4 h, dialyze, and freeze-dry to obtain polygonatum dietary fiber-perilla essential oil microcapsules.

6. The method for preparing a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion according to claim 5, characterized in that: The concentration of the thermophilic actinomycetes suspension in step 2 is 10 7 -10 8 CFU / mL, with an inoculum size of 5-8%.

7. The method for preparing a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion according to claim 5, characterized in that: The concentration of the plant lactobacillus suspension in step 3 is 10 8 -10 9 CFU / mL, the inoculum size is 3-5%.

8. The method for preparing a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion according to claim 5, characterized in that: The concentration of the microcapsule wall material solution in step 4 is 5-8 wt %; the volume ratio of the perilla essential oil to the microcapsule wall material solution is 1:(3-4).

9. The method for preparing a polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion according to claim 5, characterized in that: In step 5, the mass volume ratio of the microcapsules to the salicylic acid ethanol solution is 1 g: (5-10) mL.

10. Use of the polygonatum dietary fiber-perilla essential oil composite fresh-keeping microemulsion prepared by the preparation method according to any one of claims 1 to 9 in the preservation of fruits and vegetables.

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