An environmentally friendly biphasic shellac coating agent and its application in promoting flavor release.

Abstract

This invention relates to the field of food coating materials technology, providing an environmentally friendly two-phase shellac coating agent and its application in promoting flavor release. The coating agent is an oil-in-water emulsion. The aqueous phase contains modified shellac salt, a glycerol-sorbitol complex, and an octenyl succinate-sodium starch-cellulose nanocrystal complex; the oil phase contains a hydrophobic shellac resin, medium-chain triglycerides, and an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin. An interfacial functional layer is constructed through hydrogen bonding and multiple interactions, achieving a smart response of high barrier properties during storage and rapid release upon wetting. This invention is entirely aqueous, contains no organic solvents, has an elongation at break of 235%, a flavor release rate of 82%, and also possesses antibacterial properties. It can be used for the preservation and flavor control of fruits, vegetables, nuts, and other foods.

Description

Technical Field

[0001] This invention belongs to the field of food coating materials technology, and in particular relates to an environmentally friendly two-phase shellac coating agent and its application in promoting flavor release. Background Technology

[0002] Shellac resin is a naturally derived resin commonly used as a food coating agent. However, traditional shellac coating agents have the following problems: High brittleness and poor film continuity: Pure shellac resin has a strong molecular chain rigidity and a high glass transition temperature. The elongation at break of a single shellac film is generally low. After film formation, it is easy to crack and fall off, and cannot form a continuous and complete protective barrier, thus directly losing its preservation effect.

[0003] Strong flavor barrier: After shellac resin forms a film, its dense structure provides strong barrier properties against volatile flavor substances inside food. While this can prevent flavor loss during storage, it can also hinder the release of flavor substances during consumption, resulting in a bland taste and reduced sensory experience.

[0004] Solvent residue issue: Shellac resin is naturally hydrophobic, and traditional shellac coating agents require the use of organic solvents such as ethanol and acetone or high-concentration alcohol solutions to achieve dissolution and film formation. This not only poses food safety risks due to solvent residue, but also does not conform to environmental protection trends.

[0005] Limitations of single-phase systems: Existing shellac coating agents are all single-phase systems with a single aqueous phase or a single oil phase, which cannot simultaneously meet the contradictory requirements of high barrier properties during storage and rapid release during consumption. While a dense structure can achieve high barrier properties during storage, it will inevitably lead to poor flavor release; while a loose structure can improve flavor release, it will inevitably lose its barrier properties during storage.

[0006] Existing technologies, such as CN103843881A, disclose a milk protein-based natural fruit and vegetable preservative coating agent, which uses a combination of shellac and milk protein. While this improves film-forming properties, it requires the use of organic solvents and fails to solve the flavor blocking problem. Another example is CN110251679A, which discloses a compound coating agent using white oil, caprylic / capric acid oil, carnauba wax, and other components. Although it is a solvent-free system, all components are single-phase structures, making intelligent control of flavor release impossible. These existing technologies fail to resolve the contradiction between the high brittleness and strong flavor blocking properties of shellac films, and struggle to simultaneously meet the dual requirements of flavor blocking and release. Summary of the Invention

[0007] This invention provides an environmentally friendly two-phase shellac coating agent and its application in promoting flavor release, aiming to solve the following technical problems of existing shellac coating agents: (1) high brittleness and poor film continuity; (2) dense film structure leads to strong flavor barrier, making it difficult to achieve controllable release; (3) organic solvent residue does not conform to the environmental protection trend; (4) single-phase system cannot meet the contradictory needs of film protection and controllable flavor release.

[0008] The modified shellac salts mentioned in this article refer to water-soluble shellac salts obtained by neutralizing and modifying dewaxed shellac resin with alkaline substances (such as ammonia, sodium hydroxide, potassium hydroxide, etc.). The form of the modified shellac salts can be an aqueous solution or a solid powder obtained by spray drying. The hydrophobic shellac resins mentioned refer to dewaxed and decolorized shellac resins that have not undergone neutralization modification, with an acid value ≥70mgKOH / g and a softening point ≥75℃. The dewaxed shellac resin used in this article is all food grade with a purity of ≥95%; chitosan is food grade with a degree of deacetylation of 85%~95%; carboxymethyl-β-cyclodextrin is food grade with a degree of substitution of 3~6; sodium octenyl succinate starch (SSOS) is food grade with a degree of substitution of 0.02~0.05; microcrystalline cellulose is food grade with a particle size of 200~300 mesh; and the remaining raw materials are all food grade and comply with relevant national food safety standards.

[0009] This invention is achieved by providing an environmentally friendly two-phase shellac coating agent, comprising the following components by weight: Aqueous phase: Modified shellac salt: 20-35 parts A complex of glycerol and sorbitol: 2-6 parts Complex of sodium octenyl succinate starch and cellulose nanocrystals: 0.1–0.8 parts Deionized water: 50-70 parts Oil phase: Hydrophobic shellac resin (unneutralized): 5-15 parts Medium-chain triglycerides (MCT): 2-8 parts Electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin: 1-4 parts; The glycerol-sorbitol complex is a complex formed by the hydrogen bond network of glycerol and sorbitol under heating conditions. The complex of sodium octenyl succinate starch and cellulose nanocrystals is formed by ultrasonic co-dispersion of sodium octenyl succinate starch and cellulose nanocrystals. The electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin is a nanocomposite formed by the electrostatic self-assembly of chitosan and carboxymethyl-β-cyclodextrin under pH 4.0–5.0 conditions.

[0010] Preferably, the aqueous phase comprises 25-30 parts by weight of modified shellac salt, 3-5 parts by weight of a complex of glycerol and sorbitol, 0.3-0.6 parts by weight of a complex of sodium octenyl succinate starch and cellulose nanocrystals, and 55-65 parts by weight of deionized water; The oil phase comprises 8-12 parts by weight of hydrophobic shellac resin, 3-7 parts by weight of medium-chain triglycerides, and 2-3 parts by weight of an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin.

[0011] Preferably, the aqueous phase comprises 27.5 parts by weight of modified shellac salt, 4 parts by weight of a complex of glycerol and sorbitol, 0.5 parts by weight of a complex of sodium octenyl succinate starch and cellulose nanocrystals, and 60 parts by weight of deionized water. The oil phase comprises 10 parts by weight of hydrophobic shellac resin, 5 parts by weight of medium-chain triglycerides, and 2.5 parts by weight of an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin.

[0012] Preferably, the modified shellac salt refers to a water-soluble salt formed by neutralizing dewaxed shellac resin with an alkaline substance. The preparation method is as follows: the dewaxed shellac resin is pulverized to 100-200 mesh, 3-5 times its weight of deionized water is added, and an alkaline substance (one or more of 20%-28% ammonia, sodium hydroxide, potassium hydroxide, or morpholine) is slowly added while stirring to adjust the pH to 6.5-7.5. The mixture is stirred and dissolved at 50-70°C for 1-2 hours, and insoluble matter is removed by filtration to obtain a modified shellac salt aqueous solution with a solid content controlled at 20-35%. The modified shellac salt powder can be further obtained by spray drying for easy storage and use.

[0013] Preferably, the complex of glycerol and sorbitol is prepared by mixing glycerol and sorbitol in a mass ratio of 1:1 to 2:1, stirring at 60 to 80°C for 20 to 40 minutes until a homogeneous transparent liquid is formed, and then cooling to room temperature. Both glycerol and sorbitol are polyols, and the combination of the two forms a gradient hydrogen bond network that runs through the aqueous shellac salt, significantly reducing the glass transition temperature of the shellac film and improving its flexibility.

[0014] Preferably, the preparation method of the composite of sodium octenyl succinate starch and cellulose nanocrystals is as follows: 1. Preparation of cellulose nanocrystals: Food-grade microcrystalline cellulose was slowly added to a 64% sulfuric acid solution pre-cooled to 4-10℃. The mass-to-volume ratio of microcrystalline cellulose to sulfuric acid solution was 1:8-1:12 g / mL. The mixture was stirred and hydrolyzed in a water bath at 40-50℃ for 45-75 minutes. After hydrolysis, 8-12 times the volume of ice water was added to terminate the reaction, and the mixture was allowed to stand overnight. The supernatant was discarded, and the lower turbid liquid was transferred to a dialysis bag with a molecular weight cutoff of 12000-14000 Da. The mixture was dialyzed with deionized water until the conductivity of the dialysate was <5 μS / cm, resulting in a cellulose nanocrystal suspension. The suspension was ultrasonically dispersed in an ice-water bath for 10-20 minutes and then freeze-dried to obtain cellulose nanocrystals with a particle size of 50-200 nm, an aspect ratio >20, and a Zeta potential of -40 to -50 mV. 2. Preparation of the complex: Sodium octenyl succinate starch and the above-mentioned cellulose nanocrystals were mixed at a mass ratio of 1:1 to 1:3, 5 to 10 times the mass of deionized water were added, and the mixture was ultrasonically dispersed at a power of 200 to 400 W for 15 to 30 minutes. The dispersion was freeze-dried or spray-dried to obtain the complex of sodium octenyl succinate starch and cellulose nanocrystals. Sodium octenyl succinate starch is amphiphilic, with its hydrophobic segments (octenyl groups) anchored in the oil phase and its hydrophilic portion (starch backbone) extending into the aqueous phase. Cellulose nanocrystals bind to the hydrophilic portion of sodium octenyl succinate starch via hydrogen bonds, which helps to form a stable and mechanically strong Pickering interface layer at the oil-water interface, enhancing the mechanical strength of the interface. The hydroxyl groups on the surface of the cellulose nanocrystals form hydrogen bonds with the hydroxyl groups of the glycerol-sorbitol complex, connecting the aqueous plasticizing network and the interface reinforcement layer into a continuous reinforcing phase, thereby simultaneously improving the emulsion stability and film-forming mechanical properties.

[0015] In the oil-in-water emulsion of the present invention, the medium-chain triglyceride (MCT) used in the oil phase not only serves as a green solvent for hydrophobic shellac resin, but its moderate polarity and medium-chain molecular structure also give it certain interfacial activity. It can participate in and promote the anchoring and arrangement of hydrophobic segments of sodium octenyl succinate starch at the oil-water interface, thereby synergistically enhancing the compactness and stability of the interfacial functional layer.

[0016] Preferably, the preparation method of the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin is as follows: chitosan is dissolved in a 1-2% aqueous acetic acid solution to prepare a 0.5-1.5% chitosan solution, and the pH is adjusted to 4.0-5.0 with sodium hydroxide; carboxymethyl-β-cyclodextrin is dissolved in deionized water to prepare a 1.0-2.5% carboxymethyl-β-cyclodextrin solution; under stirring conditions of 20-30℃ and 300-600 rpm, the carboxymethyl-β-cyclodextrin solution is slowly added dropwise to the chitosan solution, controlling the dropping rate to 1-5 mL / min; the mass ratio of chitosan to carboxymethyl-β-cyclodextrin is 1:1-1:3; after the addition is complete, stirring is continued for 1-2 hours; the resulting suspension is centrifuged (8000-12000 rpm, 10-20 min), the precipitate is collected, and washed 2-3 times with deionized water; freeze-drying is performed to obtain electrostatic complex powder with a particle size of 200-400 nm; Under pH conditions of 4.0–5.0, chitosan carries a positive charge (amino protonation) and carboxymethyl-β-cyclodextrin carries a negative charge (carboxyl ionization). The two form a nanocomposite with a particle size of 200–400 nm through electrostatic self-assembly. During emulsification and film formation, the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin, along with the sodium octenyl succinate starch-cellulose nanocrystal complex, are synergistically distributed in the oil-water interface region through multiple interactions (including hydrogen bonding, hydrophobic interactions, and residual electrostatic interactions), forming a stable interfacial functional layer. Specifically, the hydroxyl groups on the surface of the cellulose nanocrystals form a hydrogen bond network with the hydroxyl / amino groups on the chitosan molecular chain, while the hydrophobic segments of the sodium octenyl succinate starch are anchored to the oil phase, collectively achieving the stability and functionalization of the interfacial layer. The interfacial functional layer of this invention exhibits environmentally responsive characteristics: under dry storage conditions, the interfacial layer presents a dense structure, effectively blocking water vapor and flavor substances. When the coating is in a high-humidity environment (such as the oral cavity, relative humidity >90%), the hydrophilic components in the interfacial layer (including the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin) absorb water and undergo volume expansion, causing a reversible loosening transformation of the interfacial layer structure, forming channels that facilitate the diffusion of flavor substances; the cyclic stability data of Experimental Example 3 verify that this response mechanism has good reversibility.

[0017] The present invention also provides a method for preparing the above-mentioned environmentally friendly two-phase shellac coating agent, comprising the following steps: (1) Oil phase premixing: Hydrophobic shellac resin was dissolved in medium-chain triglycerides, and an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin was added. The mixture was homogenized at 5000-8000 rpm for 5-10 min to obtain an oil phase suspension.

[0018] (2) Aqueous phase preparation: Dissolve the modified shellac salt in deionized water, add the complex of glycerol and sorbitol and the complex of sodium octenyl succinate starch and cellulose nanocrystals, adjust the pH to 6.0-7.0, and ultrasonically disperse for 10-20 min to obtain an aqueous dispersion.

[0019] (3) Two-phase assembly: Under the conditions of 20-30℃ and 6000-8000rpm shear, the oil phase is slowly added to the aqueous phase in a thin stream (flow rate 10-20mL / min). After mixing, the pH is maintained at 5.5-6.5, and shearing is continued for 10-15min to obtain an oil-in-water emulsion, i.e. the coating agent.

[0020] In the above preparation method, adjusting the pH to 6.0-7.0 during aqueous phase preparation is beneficial for the full dissolution and stability of modified shellac salt; maintaining the pH at 5.5-6.5 after mixing the two phases provides a suitable weakly acidic environment for the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin in the oil phase, which helps maintain its structural stability and functional activity at the oil-water interface.

[0021] The resulting emulsion can be sprayed onto the surface of food and dried with hot air at 35–45°C to form a film. For heat-sensitive foods, low-temperature drying at 25–35°C or extending the drying time to 30–60 minutes can be used to avoid deterioration of food quality.

[0022] This invention prepares an oil-in-water emulsion through a specific shear emulsification process. During the drying and film formation process of the emulsion, the water in the aqueous phase gradually evaporates, and the aqueous phase component, mainly modified shellac salt, forms a continuous and dense matrix. The oil phase component does not evaporate with the water and remains stably in the continuous aqueous matrix in the form of uniformly dispersed microspheres, ultimately forming a typical oil-in-water two-phase structure.

[0023] Meanwhile, the sodium starch-cellulose nanocrystal complex of octenyl succinate has amphiphilicity and interfacial activity, and can spontaneously anchor itself at the oil-water interface; the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin has multiple interactions with the former, and the two are synergistically enriched at the oil-water interface between the oil phase microspheres and the aqueous matrix, forming a stable interfacial functional layer, which provides a structural basis for emulsion stability, film-forming performance and humidity-responsive flavor release.

[0024] The coating agent of this invention also possesses excellent antibacterial properties. Its antibacterial mechanism stems from the synergistic effect of three aspects: First, the protonated amino groups on the chitosan molecular chain can bind to the negatively charged groups on the surface of bacterial cell membranes, disrupting the integrity of bacterial cell membranes and achieving bacteriostasis; second, carboxymethyl-β-cyclodextrin can adsorb toxins produced by bacterial metabolism, disrupting the bacterial survival environment; third, shellac resin itself can form a physical barrier on the food surface, blocking the contact between bacteria and the food matrix and inhibiting bacterial reproduction. The synergistic effect of these three factors effectively inhibits common Escherichia coli in food without the need for additional chemical preservatives, further improving food preservation and food safety.

[0025] Compared with the prior art, the embodiments of this application have the following main advantages: The environmentally friendly two-phase shellac coating agent provided by this invention utilizes a gradient hydrogen bond network formed by a complex of glycerol and sorbitol to penetrate the aqueous phase, enhancing the flexibility of the shellac salt phase. A complex of sodium octenyl succinate starch and cellulose nanocrystals anchors at the oil-water interface, forming a rigid reinforcing layer that improves interfacial stability and film continuity. An electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin synergistically works with the interfacial reinforcing layer to construct a humidity-responsive flavor release channel. The three components form an interfacial functional layer through hydrogen bond bridging and multiple interactions, achieving a smart response function of high barrier properties during storage and rapid release during consumption, while maintaining excellent mechanical properties. Attached Figure Description

[0026] Figure 1 This is a flowchart of the preparation method of the environmentally friendly two-phase shellac coating agent provided by the present invention. Detailed Implementation

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] Example 1 This invention provides an environmentally friendly two-phase shellac coating agent, such as... Figure 1 As shown, its preparation method includes the following steps: 1. Preparation of modified shellac salt Take 30g of dewaxed shellac resin, pulverize it to 100 mesh, add 70g of deionized water, and slowly add 25% ammonia water while stirring to adjust the pH to 7.0. Stir and dissolve at 60℃ for 1.5 hours, filter to remove insoluble matter, and obtain a modified shellac salt aqueous solution. Concentrate the obtained solution under reduced pressure at 50℃ to a solid content of about 20%, and then spray dry (inlet air temperature 160℃, outlet air temperature 80℃) to obtain modified shellac salt powder for later use.

[0030] 2. Preparation of the glycerol-sorbitol complex Take 2g of glycerin and 1g of sorbitol, mix them, and stir at 70℃ for 30 minutes to obtain a homogeneous and transparent liquid.

[0031] 3. Preparation of sodium octenyl succinate starch-cellulose nanocrystal composite 3.1 Preparation of cellulose nanocrystals Take 10g of commercially available food-grade microcrystalline cellulose and slowly add 100mL of 64% sulfuric acid solution pre-cooled to 10℃ (the mass-to-volume ratio of microcrystalline cellulose to sulfuric acid is 1:10g / mL). Hydrolyze the solution in a water bath at 45±2℃ for 60 minutes with stirring. After hydrolysis, add 10 times the volume of ice water to terminate the reaction and let it stand overnight. Discard the supernatant and transfer the lower turbid layer to a dialysis bag (molecular weight cutoff 12000~14000Da). Dialyze with deionized water until the conductivity of the dialysate is <5μS / cm (indicating complete removal of sulfuric acid). Disperse the dialyzed suspension ultrasonically in an ice-water bath (200W, 15 minutes), then freeze-dry (-50℃, pressure <10 Pa, 48 hours) to obtain white powdery cellulose nanocrystals. The average particle size of the obtained cellulose nanocrystals was determined to be 100~200nm, and the Zeta potential was approximately -40~-50mV.

[0032] 3.2 Preparation of the complex Sodium octenyl succinate starch (degree of substitution 0.02~0.05) was mixed with the above cellulose nanocrystals at a mass ratio of 1:2, and 8 times the mass of deionized water was added. The mixture was ultrasonically dispersed for 25 minutes (power 300W, working / intermittent mode). The dispersion was freeze-dried (-50℃, 48 hours) to obtain a composite powder of sodium octenyl succinate starch and cellulose nanocrystals.

[0033] 4. Preparation of the chitosan-carboxymethyl-β-cyclodextrin electrostatic complex Take 0.8 g of chitosan and dissolve it in 100 mL of 1% acetic acid aqueous solution. Adjust the pH to 4.5 with sodium hydroxide. Take 1.5 g of carboxymethyl-β-cyclodextrin and dissolve it in 100 mL of deionized water. Under stirring at 25 °C and 400 rpm, add the cyclodextrin solution dropwise to the chitosan solution at a rate of 3 mL / min. Continue stirring for 1.5 hours after the addition is complete. Centrifuge (10000 rpm, 15 min), wash the precipitate three times with deionized water, and freeze-dry to obtain electrostatic complex powder with a particle size of about 300 nm.

[0034] 5. Preparation of coating agents (1) Oil phase premixing: Take 10g of hydrophobic shellac resin, dissolve it in 5g of medium-chain triglycerides, add 2.5g of the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin, and homogenize at 7000rpm for 8min to obtain an oil phase suspension.

[0035] (2) Aqueous phase preparation: Take 30g of the modified shellac salt powder prepared in step 1, dissolve it in 70g of deionized water, add 3g of glycerol-sorbitol complex and 0.4g of sodium starch-cellulose nanocrystal complex of octenyl succinate, adjust the pH to 6.5, and ultrasonically disperse for 15min to obtain an aqueous dispersion.

[0036] (3) Two-phase assembly: Under the conditions of 25℃ and 7000rpm shearing, the oil phase is slowly added to the aqueous phase at a flow rate of 15mL / min. After mixing, the pH is maintained at 6.0, and shearing is continued for 12min to obtain an oil-in-water emulsion, namely the coating agent.

[0037] (4) Emulsion properties: The obtained emulsion has a uniform appearance and no stratification or precipitation after standing at room temperature for 24 hours; the average particle size measured by dynamic light scattering is 280±45nm, and the polydispersity index PDI=0.21; no oil-water stratification was observed after centrifugation at 3000rpm for 10min.

[0038] 6. Application of film formation Spray the emulsion onto the surface of fresh blueberries and dry it with hot air at 40°C to form a uniform film.

[0039] 7. Performance Testing (1) Elongation at break: The elongation at break of the coated sample was determined according to GB / T 1040.3-2006 (dumbbell-shaped sample, tensile speed 50 mm / min, temperature 23±2℃, relative humidity 50±5%), and the elongation at break of the coated sample was 235%.

[0040] (2) Flavor release rate: The release of characteristic aroma substances under different humidity conditions was detected by electronic nose. 5g of coated blueberry sample was placed in a sealed test bottle and kept at 37℃. The relative humidity was controlled at 30% (simulating dry storage), 60% (simulating room temperature storage), and 90% (simulating high humidity environment in the oral cavity). The cumulative release of characteristic aroma substances (limonene, hexenal, etc.) was detected by headspace sampling. Flavor release rate (%) = (cumulative release within 30 min / total aroma substance content in the sample) × 100%. The results showed that the flavor release rate within 30 min was 12% under RH 30% conditions, 18% under RH 60% conditions, and 82% under RH 90% conditions. This indicates that the coating agent has good barrier properties for flavor substances under dry storage conditions, while achieving efficient release under high humidity eating conditions.

[0041] (3) Organic solvent residues: Gas chromatography was used to detect organic solvents such as ethanol and acetone.

[0042] (4) Antibacterial activity: Paper disc diffusion method, 20 μL of the film emulsion was dropped onto an agar plate containing Escherichia coli and incubated at 37°C for 24 h. The diameter of the inhibition zone was 12.5 mm.

[0043] (5) Barrier performance: The water vapor transmission rate was determined according to GB / T 1037-2021, and the water vapor transmission rate of the membrane was 98 g / m. 2 • 24h, with commercially available shellac alcohol solution coating agent (95g / m 2 The performance was comparable to that of 24h, indicating that the barrier performance was not reduced during storage.

[0044] Example 1A: Optimization of the ratio of glycerol-sorbitol complex Referring to the formulation and preparation process of Example 1, only the mass ratio of glycerol to sorbitol was changed, setting five ratios of 1:0.5, 1:1, 1.5:1, 2:1, and 3:1 respectively. The elongation at break of the film was measured, and the results are as follows: The results showed that the plasticizing effect of the complex was optimal when the mass ratio of glycerol to sorbitol was 1:1 to 2:1, with the elongation at break exceeding 258%. Beyond this range, the plasticizing effect decreased significantly. Therefore, the preferred mass ratio of the glycerol to sorbitol complex of the present invention is 1:1 to 2:1.

[0045] Example 2 Formula: 20 parts modified shellac salt, 2 parts glycerol-sorbitol complex, 0.1 parts octenyl succinate starch sodium-cellulose nanocrystal complex, 70 parts deionized water; 5 parts hydrophobic shellac resin, 2 parts medium-chain triglycerides, 1 part electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin, the rest are the same as the preparation process in Example 1.

[0046] Performance test: Elongation at break 192%, flavor release rate (RH 90%) 74%, average particle size of emulsion 410nm, PDI=0.29, no stratification after centrifugation at 3000rpm for 10min.

[0047] Example 3 Formula: 35 parts modified shellac salt, 6 parts glycerol-sorbitol complex, 0.8 parts octenyl succinate starch sodium-cellulose nanocrystal complex, 50 parts deionized water; 15 parts hydrophobic shellac resin, 8 parts medium-chain triglycerides, 4 parts electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin; the rest are prepared in the same way as in Example 1.

[0048] Performance test: Elongation at break 268%, flavor release rate (RH 90%) 79%, average particle size of emulsion 305nm, PDI=0.24, no stratification after centrifugation at 3000rpm for 10min.

[0049] Comparative Example 1 The aqueous phase contained only modified shellac salt and water (without the addition of glycerol-sorbitol complex and sodium starch-cellulose nanocrystal complex of octenyl succinate), and the oil phase contained hydrophobic shellac resin, medium-chain triglycerides and an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin, the rest being the same as in Example 1; the elongation at break was measured to be 45%, the flavor release rate (RH 90%) was 75%, the average particle size of the emulsion was 410 nm, the PDI was 0.32, and no stratification was observed after centrifugation at 3000 rpm for 10 min, but the film formed was brittle.

[0050] Comparative Example 2 The oil phase did not contain the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin, and the rest was the same as in Example 1. The elongation at break was 270%, the flavor release rate (RH 90%) was 23%, the average particle size of the emulsion was 265 nm, the PDI was 0.19, and no stratification was observed after centrifugation at 3000 rpm for 10 min.

[0051] Compared with Example 1, Comparative Example 2 had a slightly higher elongation at break, but its flavor release rate (RH 90%) (23%) was much lower than that of Example 1 (82%). This indicates that the core contribution of the chitosan-carboxymethyl-β-cyclodextrin electrostatic complex lies in constructing a reversible flavor release channel, achieving a breakthrough improvement in flavor release performance.

[0052] Comparative Example 3 The aqueous phase contained modified shellac salt and a glycerol-sorbitol complex (without the addition of sodium starch-octenyl succinate-cellulose nanocrystal complex), and the oil phase contained hydrophobic shellac resin and medium-chain triglycerides (without the addition of electrostatic complex). The rest was the same as in Example 1. The elongation at break was measured to be 120%, the flavor release rate (RH 90%) to be 35%, the average particle size of the emulsion to be 680 nm, and the PDI to be 0.45. After centrifugation at 3000 rpm for 10 min, clear stratification was observed.

[0053] Comparative Example 4 The aqueous phase contained modified shellac salt and sodium starch-cellulose nanocrystal complex of octenyl succinate (without glycerol-sorbitol complex), and the oil phase contained hydrophobic shellac resin and medium-chain triglycerides (without electrostatic complex). The rest was the same as in Example 1. The elongation at break was 78%, the flavor release rate (RH 90%) was 32%, the average particle size of the emulsion was 340 nm, the PDI was 0.30, and there was no stratification after centrifugation at 3000 rpm for 10 min. The film formed was relatively brittle.

[0054] Comparative Example 5 The aqueous phase contained only modified shellac salt and water (without the addition of glycerol-sorbitol complex and sodium starch-cellulose nanocrystal complex), and the oil phase contained only hydrophobic shellac resin and medium-chain triglycerides (without the addition of electrostatic complex). The rest was the same as in Example 1. The measured elongation at break was 38%, the flavor release rate (RH 90%) was 28%, the average particle size of the emulsion was 850 nm, the PDI was 0.52, and obvious stratification was observed after centrifugation at 3000 rpm for 10 min. The film formed was brittle and prone to cracking.

[0055] Comparative Example 5A Meanwhile, the sodium starch-cellulose nanocrystal complex and chitosan-carboxymethyl-β-cyclodextrin electrostatic complex were missing: the aqueous phase contained 30g of modified shellac salt, 4g of glycerol-sorbitol complex, and 60g of deionized water; the oil phase contained 10g of hydrophobic shellac resin and 5g of medium-chain triglycerides; the rest were prepared in the same way as in Example 1.

[0056] Performance test: Elongation at break 142%, flavor release rate (RH 90%) 19%, average particle size of emulsion 720nm, PDI=0.49, obvious stratification after centrifugation at 3000rpm for 10min.

[0057] Compared with Example 1 (235% elongation at break, 82% flavor release (RH 90%), emulsion stability), all properties of Comparative Example 5A were significantly reduced.

[0058] Comparative Example 6 Commercially available conventional shellac alcohol solution coating agent, with a solid content of 10%, mainly consists of shellac and edible alcohol; the measured elongation at break is 52%, the flavor release rate (RH 90%) is 11%, the ethanol residue is about 1200ppm, and there is no antibacterial activity.

[0059] Comparative Example 7 In the aqueous phase, a room-temperature physical mixture of 2g glycerol and 1g sorbitol was used to replace the glycerol-sorbitol complex prepared by heating at 70°C for 30min in Example 1. The remaining components and preparation process were the same as in Example 1.

[0060] The measured elongation at break was 218%, the flavor release rate (RH 90%) was 79%, the average particle size of the emulsion was 315 nm, the PDI was 0.26, and no stratification was observed after centrifugation at 3000 rpm for 10 min.

[0061] Compared with Example 1 (elongation at break 235%), the elongation at break of Comparative Example 7 was significantly reduced, indicating that the plasticizing and reinforcing effect of glycerol and sorbitol forming a hydrogen bond network complex after heating is significantly better than that of simple physical mixing of the two.

[0062] Comparative Example 8 In the aqueous phase, a room-temperature physical mixture of 2g sodium octenyl succinate starch and 1g cellulose nanocrystals was used to replace the sodium octenyl succinate starch and cellulose nanocrystals complex prepared by ultrasonic dispersion for 20 min followed by freeze drying in Example 1. The remaining components and preparation process were the same as in Example 1.

[0063] The measured elongation at break was 241%, the flavor release rate (RH 90%) was 80%, the average particle size of the emulsion was 365 nm, the PDI was 0.33, and slight stratification occurred after centrifugation at 3000 rpm for 10 min.

[0064] Compared with Example 1 (stable emulsion without stratification), the emulsion stability of Comparative Example 8 decreased significantly and slight stratification occurred, indicating that the complex formed by ultrasonic co-dispersion of sodium octenyl succinate starch and cellulose nanocrystals has a significantly better effect on interface enhancement and emulsion stabilization than simple physical mixing of the two.

[0065] Comparative Example 9 In the oil phase, a room-temperature physical mixture of 0.8 g chitosan and 1.5 g carboxymethyl-β-cyclodextrin was used to replace the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin prepared by electrostatic self-assembly in Example 1. The remaining components and preparation process were the same as in Example 1.

[0066] The measured elongation at break was 273%, the flavor release rate (RH 90%) was 58%, the average particle size of the emulsion was 420 nm, the PDI was 0.38, and stratification occurred after centrifugation at 3000 rpm for 10 min.

[0067] Compared with Example 1 (flavor release rate 82%, emulsion stability), Comparative Example 9 showed a significantly reduced flavor release rate and decreased emulsion stability, indicating that the electrostatic self-assembly of chitosan and carboxymethyl-β-cyclodextrin to form a complex has a significantly better effect on promoting flavor release and stabilizing the emulsion than simple physical mixing of the two.

[0068] Comparative Example 10 Simultaneously, alternative methods are used in comparisons 7, 8, and 9: Aqueous phase: The glycerol-sorbitol complex was replaced with a room-temperature physical mixture of glycerol and sorbitol; Aqueous phase: The complex of sodium octenyl succinate starch and cellulose nanocrystals was replaced with a room-temperature physical mixture of sodium octenyl succinate starch and cellulose nanocrystals. Oil phase: The electrostatic complex was replaced by a room-temperature physical mixture of chitosan and carboxymethyl-β-cyclodextrin; The remaining components and preparation process are the same as in Example 1.

[0069] The measured elongation at break was 187%, the flavor release rate (RH 90%) was 51%, the average particle size of the emulsion was 580 nm, the PDI was 0.48, and the emulsion showed obvious stratification after centrifugation at 3000 rpm for 10 min.

[0070] Compared to Example 1 (235% elongation at break, 82% flavor release (RH 90%), and emulsion stability), all properties of Comparative Example 10 were significantly reduced. Combined with the results of Comparative Examples 7-9, it is clear that the superiority of this invention stems from the specific compounding treatment of each complex and the synergistic combination of the three, rather than from the simple selection of raw materials.

[0071] The performance test results are shown in Table 1 below: Experiment Example 1: Long-term storage stability verification The emulsions prepared in Example 1 were stored at 4°C, 25°C, and 37°C, respectively, and their particle size distribution, pH, and centrifugal stability were tested periodically.

[0072] Storage at 4℃: After 12 months of storage, the emulsion has a uniform appearance, an average particle size of 295nm, PDI=0.24, pH=6.0, and no stratification after centrifugation.

[0073] Storage at 25℃: After 6 months of storage, the emulsion has a uniform appearance, an average particle size of 310nm, PDI=0.28, pH=5.9, and no stratification after centrifugation.

[0074] Accelerated at 37℃: After 60 days of storage, the average particle size was 335nm, PDI=0.32, pH=5.8, and no stratification occurred during centrifugation; this is equivalent to 6 months of stability at room temperature.

[0075] Experiment Example 2: Verification of Multi-Scenario Adaptability Adjust the spraying process according to different food substrates: Walnuts (nuts): Spraying amount 1.5mL / cm 2 2 times, dried at 40℃; good film adhesion, flavor release rate (RH 90%) 76%.

[0076] Soft candy (candy type): Spraying amount 1.0 mL / cm 2 One pass, dried at 35℃; improved moisture resistance, flavor release rate (RH90%) 79%.

[0077] Cookies (baked goods): Spraying amount 0.8mL / cm 2 Drying at 45℃ for 3 cycles; shelf life extended by 3 days, flavor release rate (RH90%) 71%.

[0078] Strawberries (high-moisture fruit): Spraying amount 1.2 mL / cm 2 One pass, dried at 30℃; weight loss reduced by 45%, flavor release rate (RH 90%) 80%, and inhibition zone diameter 11.8mm.

[0079] Experimental Example 3: Verification of the Stability of Reversible Channel Cyclic Circulation The film samples prepared in Example 1 were tested in alternating humidity environments: high humidity (RH 90%, 37℃, 30min) simulated consumption, and low humidity (RH 30%, 25℃, 2h) simulated storage, for 10 cycles.

[0080] Results: The flavor release rate (RH 90%) was 82% after the first high-humidity treatment and 76% after the 10th treatment, with a retention rate of 92.7%; the water vapor transmission rate in the dry state was initially 98 g / m³. 2 • 24h, 105g / m² after the 10th time 2 • After 24 hours, the retention rate was 93.1%, indicating that the reversible channel mechanism has good cyclic stability.

[0081] As a control, the coated sample prepared in Comparative Example 9 (using a physical mixture of chitosan and carboxymethyl-β-cyclodextrin) was subjected to the same cyclic test. After the first high-humidity treatment, the flavor release rate was 58%, which decreased to 31% after the 10th treatment, with a retention rate of only 53.4%; the water vapor transmission rate was initially 112 g / m³. 2 • 24h, 178g / m² after the 10th time 2 • After 24 hours, the retention rate was only 63.4%, indicating that the composite formed by electrostatic self-assembly is the key structural basis for achieving reversible channel cycle stability.

[0082] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. An environmentally friendly two-phase shellac coating agent, characterized in that, It is an oil-in-water emulsion, consisting of an aqueous phase and an oil phase: The aqueous phase comprises 20-35 parts by weight of modified shellac salt, 2-6 parts by weight of a complex of glycerol and sorbitol, 0.1-0.8 parts by weight of a complex of sodium octenyl succinate starch and cellulose nanocrystals, and 50-70 parts by weight of deionized water. The oil phase comprises 5-15 parts by weight of hydrophobic shellac resin, 2-8 parts by weight of medium-chain triglycerides, and 1-4 parts by weight of an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin. The glycerol-sorbitol complex is a complex formed by the hydrogen bond network of glycerol and sorbitol under heating conditions. The complex of sodium octenyl succinate starch and cellulose nanocrystals is formed by ultrasonic co-dispersion of sodium octenyl succinate starch and cellulose nanocrystals. The electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin is a nanocomposite formed by the electrostatic self-assembly of chitosan and carboxymethyl-β-cyclodextrin under pH 4.0–5.0 conditions.

2. The environmentally friendly two-phase shellac coating agent as described in claim 1, characterized in that, The aqueous phase comprises 25-30 parts by weight of modified shellac salt, 3-5 parts by weight of a complex of glycerol and sorbitol, 0.3-0.6 parts by weight of a complex of sodium octenyl succinate starch and cellulose nanocrystals, and 55-65 parts by weight of deionized water. The oil phase comprises 8-12 parts by weight of hydrophobic shellac resin, 3-7 parts by weight of medium-chain triglycerides, and 2-3 parts by weight of an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin.

3. The environmentally friendly two-phase shellac coating agent as described in claim 2, characterized in that, The aqueous phase comprises 27.5 parts by weight of modified shellac salt, 4 parts by weight of a complex of glycerol and sorbitol, 0.5 parts by weight of a complex of sodium octenyl succinate starch and cellulose nanocrystals, and 60 parts by weight of deionized water. The oil phase comprises 10 parts by weight of hydrophobic shellac resin, 5 parts by weight of medium-chain triglycerides, and 2.5 parts by weight of an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin.

4. The environmentally friendly two-phase shellac coating agent as described in claim 1, characterized in that, The modified shellac salt is prepared as follows: Crush the dewaxed shellac resin to 100-200 mesh and add 3-5 times its weight of deionized water; Add an alkaline substance while stirring to adjust the pH to 6.5-7.5, dissolve at 50-70℃ for 1-2 hours, and filter to obtain a modified shellac salt aqueous solution with a solid content of 20-35%.

5. The environmentally friendly two-phase shellac coating agent as described in claim 1, characterized in that, The mass ratio of glycerol to sorbitol in the glycerol-sorbitol complex is 1:1 to 2:

1.

6. The environmentally friendly two-phase shellac coating agent as described in claim 1, characterized in that, The preparation method of the composite of sodium octenyl succinate starch and cellulose nanocrystals is as follows: Sodium octenyl succinate starch and cellulose nanocrystals were mixed at a mass ratio of 1:1 to 1:

3. Add 5 to 10 times the weight of deionized water, ultrasonically disperse for 15 to 30 minutes, and then dry.

7. The environmentally friendly two-phase shellac coating agent as described in claim 1, characterized in that, The preparation method of the electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin is as follows: Chitosan was dissolved in a 1-2% aqueous acetic acid solution to prepare a 0.5-1.5% chitosan solution, and the pH was adjusted to 4.0-5.0 with sodium hydroxide. Dissolve carboxymethyl-β-cyclodextrin in deionized water to prepare a 1.0-2.5% carboxymethyl-β-cyclodextrin solution; Under stirring conditions, the carboxymethyl-β-cyclodextrin solution was added dropwise to the chitosan solution at a rate of 1 to 5 mL / min, and the mass ratio of chitosan to carboxymethyl-β-cyclodextrin was 1:1 to 1:

3. After the addition is complete, continue stirring for 1 to 2 hours, centrifuge at 8000 to 12000 rpm for 10 to 20 minutes to collect the precipitate, wash and dry it.

8. A method for preparing the film-coating agent according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Dissolve hydrophobic shellac resin in medium-chain triglycerides, add an electrostatic complex of chitosan and carboxymethyl-β-cyclodextrin, and homogenize at 5000-8000 rpm for 5-10 min to obtain an oil phase suspension; (2) Dissolve the modified shellac salt in deionized water, add the complex of glycerol and sorbitol and the complex of sodium starch octenyl succinate and cellulose nanocrystals, adjust the pH to 6.0-7.0, and ultrasonically disperse for 10-20 min to obtain an aqueous dispersion. (3) Under the conditions of 20-30℃ and 6000-8000rpm shearing, the oil phase is slowly added to the aqueous phase at a rate of 10-20mL / min. After mixing, the pH is maintained at 5.5-6.

5. Shearing is continued for 10-15min to obtain an oil-in-water emulsion, i.e. the coating agent.

9. The application of the two-phase shellac coating agent according to any one of claims 1 to 7 or the two-phase shellac coating agent prepared by the method of claim 8 in food preservation and flavor control.

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