Oral adhesive enzyme-responsive synergistic sweetening microcapsules, and preparation method and application thereof

Abstract

The present application relates to a kind of oral mucous-adhesion type enzyme response synergistic sweetening microcapsules and its preparation method and application, the microcapsule includes core material and the enzyme response adhesion type wall material coated in the outer layer of core material, the wall material is obtained by ring-opening esterification reaction of anhydride and the polysaccharide or oligosaccharide capable of being decomposed by saliva amylase, and the surface of wall material has carboxyl group.The preparation method is as follows: anhydride is added dropwise to polysaccharide or oligosaccharide dispersion, and ring-opening esterification reaction is carried out, and enzyme response adhesion type wall material powder is obtained after treatment;Core material is slowly added to the aqueous solution containing the wall material, and homogeneous emulsion is obtained to obtain oil-in-water emulsion;Then, oil-in-water emulsion is prepared into the microcapsule of the application by freeze drying etc..The present application is based on the hydrogen bond, electrostatic interaction and molecular entanglement effect formed by carboxyl and mucin, to realize the sustained stay in oral cavity, and utilize the step-by-step decomposition of wall material by saliva amylase, to produce oligosaccharide sweet taste and release sweetening aroma substance core material synchronously, so as to realize long-acting synergistic sweetening.

Description

Technical Field

[0001] This invention relates to the field of microcapsule preparation technology, and in particular to an oral adhesive enzyme-responsive synergistic sweetening microcapsule, its preparation method, and its application. Background Technology

[0002] With the growing health awareness of global consumers, metabolic diseases such as obesity and diabetes caused by excessive sugar intake are receiving increasing attention, driving the food industry into a "sugar reduction" era. High-intensity sweeteners are widely used as sucrose substitutes, but they often have unpleasant flavors such as metallic taste and bitter aftertaste, and their sweetness is weak, affecting consumer acceptance. Research shows that food flavor is a comprehensive experience across membrane states; even without taste input, posterior nasal olfaction can trigger taste perception. Therefore, adding aroma compounds with sweetening effects can achieve olfactory-gustatory synergy to enhance the body's perception of sweetness. However, these aroma compounds generally suffer from poor stability and short residence time in the oral cavity, making it difficult to meet consumers' demand for long-lasting, mild, and sustained sweetness.

[0003] Currently, to prolong flavor retention time, researchers are exploring microencapsulation technology to protect and slow-release sweetening aroma substances. Existing microencapsulation systems primarily rely on the physical barrier of the wall material for controlled release; the wall material typically acts only as a carrier and does not participate in sweetness formation. Furthermore, most microcapsules have limited residence time in the oral cavity, making sustained release difficult. On the other hand, oral adhesion technology is widely used in drug delivery, enhancing residence time through hydrogen bonds, electrostatic interactions, or molecular entanglement between materials and the oral mucosa; however, related technologies are rarely used in food sweetening systems. In particular, an effective solution remains lacking for how to organically combine oral adhesion, enzymatic release, and synergistic sweetening mechanisms to achieve an integrated function of long-lasting residence, continuous enzymatic hydrolysis, and synergistic sweetening.

[0004] Therefore, developing a microcapsule system that can adhere for a long time in the oral cavity and continuously release sweetness under the action of salivary amylase is of great significance for improving sweetness utilization efficiency, improving the sweetness time curve, and reducing the amount of high-intensity sweeteners used. Summary of the Invention

[0005] The purpose of this invention is to provide an oral-adhesive enzyme-responsive synergistic sweetening microcapsule, its preparation method, and its application. By constructing an enzyme-responsive wall material with oral adhesion capabilities, the microcapsule can be continuously retained in the oral cavity. The wall material is gradually decomposed by salivary amylase to produce oligosaccharide sweetness and simultaneously release sweetening aroma substances into the core material, thereby achieving long-lasting synergistic sweetening.

[0006] The objective of this invention can be achieved through the following technical solutions: On one hand, the present invention provides an oral adhesive enzyme-responsive synergistic sweetening microcapsule, comprising a core material and an enzyme-responsive adhesive wall material coated on the outer layer of the core material. The enzyme-responsive adhesive wall material is obtained by ring-opening esterification reaction of acid anhydride with polysaccharides or oligosaccharides that can be decomposed by salivary amylase. The surface of the enzyme-responsive adhesive wall material has carboxyl groups.

[0007] Preferably, the anhydride includes any one of maleic anhydride, succinic anhydride, itaconic anhydride, and octenyl succinic anhydride.

[0008] In this invention, acid anhydrides introduce carboxyl structures onto the surface of microcapsules by undergoing ring-opening esterification with hydroxyl groups in polysaccharides or oligosaccharides. These carboxyl structures act as "hooks" for adhesion, forming hydrogen bonds, electrostatic interactions, and molecular entanglement with mucins in the oral mucosa, thereby enhancing the bioadhesion ability of the microcapsules.

[0009] Preferably, the polysaccharide includes any one of natural starch, porous starch, and oxidized starch, and the oligosaccharide includes any one of maltodextrin or cyclodextrin.

[0010] In this invention, the polysaccharides or oligosaccharides can be gradually hydrolyzed by salivary amylase in the oral environment to generate sweet substances such as maltose, oligosaccharides and glucose.

[0011] Preferably, the core material is a sweetening aroma substance found in each fragrance.

[0012] Preferably, the fragrance includes one or more of the following: fruity fragrance, sweet fragrance, floral fragrance, sour fragrance, green fragrance, and aldehyde fragrance.

[0013] More preferably, the sweetening aroma substance with fruity aroma includes one or more of octyl acetate, terpinene, ethyl butyrate, ethyl propionate, ethyl 2-methylbutyrate, ethyl hexanoate, butyl hexanoate, acetophenone, and γ-terpinene.

[0014] More preferably, the sweet aroma-enhancing substance includes any one or more of carvone, citronellol, carvone, furanone, propyldecyl lactone, propylnonyl lactone, butyldecyl lactone, ethyl phenylacetate, benzyl alcohol, citronellol acetate, citral, 1-nonanol, trans-ethyl ocimene, myrcene, farnesol, nonanal, and citronellol formate.

[0015] More preferably, the sweetening aroma substance with floral notes includes one or more of α-ionone, β-ionone, nerol acetate, nerol, nerolidol, terpinene alcohol, methyl dihydrojasmone, and farnesene.

[0016] More preferably, the sweetening aroma substance with a sour aroma includes one or more of hexanoic acid, octanoic acid, 2-methylbutyric acid, 3-methylbutyric acid, and trans-2-hexenoic acid.

[0017] More preferably, the sweetening aroma substance with a green aroma includes β-pinene.

[0018] More preferably, the sweetening aroma substance with aldehyde aroma includes one or more of myristaldehyde and lauryl alcohol.

[0019] In this invention, the aroma substances described above can enhance the perception of sweetness through olfactory-gustatory synergy, thereby reducing the amount of sugar or sweeteners used.

[0020] Preferably, the microcapsules have an irregular near-spherical structure and a particle size of 300~500 nm.

[0021] More preferably, the surface of the microcapsule has a wrinkled and porous structure, which facilitates the entry of moisture and salivary amylase from the oral environment into the interior of the wall material, thereby promoting subsequent enzymatic degradation and core material release.

[0022] Secondly, the present invention provides a method for preparing the oral adhesive enzyme-responsive synergistic sweetening microcapsules, comprising the following steps: S1: Under heating conditions, polysaccharides or oligosaccharides are dispersed in deionized water to obtain a dispersion; S2: Under pH conditions of 7.5 to 9.0, acid anhydride is added dropwise to the dispersion to carry out a ring-opening esterification reaction. The pH is kept stable during the reaction. After the reaction is completed, the pH is adjusted to 6.5 to 7.5. After post-processing, enzyme-responsive adhesive wall material powder is obtained. S3: Disperse the enzyme-responsive adhesive wall material powder in deionized water to obtain an enzyme-responsive adhesive wall material solution. Slowly add the core material to the enzyme-responsive adhesive wall material solution and homogenize and emulsify it under a high-speed shear machine to obtain an oil-in-water emulsion. S4: Prepare the oil-in-water emulsion into the microcapsules by any one of spray drying, freeze drying or polycondensation.

[0023] Preferably, in step S1, the concentration of the dispersion is 5 wt% to 30 wt%, and the heating temperature is 40 to 70 °C.

[0024] More preferably, in step S1, in addition to dispersing the polysaccharide or oligosaccharide in deionized water under heating conditions to obtain a dispersion, high-speed shearing or ultrasonic treatment can be used for 5 to 20 minutes to improve the uniformity of polysaccharide or oligosaccharide dispersion.

[0025] Preferably, in step S2, the mass of the acid anhydride is 0.5% to 15% of the mass of the polysaccharide or oligosaccharide, the temperature of the ring-opening esterification reaction is 25 to 55°C, and the reaction time is 1 to 6 h.

[0026] More preferably, in step S2, the pH of the system is maintained stable using an alkaline solution during the reaction.

[0027] More preferably, in step S2, the alkaline solution is an aqueous solution of sodium hydroxide.

[0028] More preferably, in step S2, after the reaction is complete, the pH is adjusted to 6.5-7.5 using hydrochloric acid.

[0029] More preferably, the post-processing includes first purifying the product obtained from the reaction, then drying it at 40-45°C to a moisture content of 8-12%, and pulverizing it to the required particle size to obtain the enzyme-responsive adhesive wall material powder.

[0030] More preferably, the purification process involves removing unreacted reactants and byproducts through any one of centrifugation, filtration, dialysis, or precipitation.

[0031] More preferably, the particle size is 100~300 nm.

[0032] Preferably, in step S3, the concentration of the enzyme-responsive adhesive wall material solution is 10–25 wt%.

[0033] Preferably, in step S3, the mass ratio of the core material to the enzyme-responsive adhesive wall material powder is 1:5 to 1:20.

[0034] Preferably, in step S3, the shearing rate of the high-speed shearing machine is 10,000 to 14,000 rpm, and the time is 3 to 10 minutes.

[0035] More preferably, in step S3, after homogenization and emulsification under a high-speed shearing machine, high-pressure homogenization is performed 1 to 3 times to form an oil-in-water emulsion with uniform particle size.

[0036] Preferably, in step S4, when the water-in-oil emulsion is prepared into the microcapsules by spray drying, the process parameters are as follows: inlet air temperature is 130-180℃, outlet air temperature is 65-95℃, feed rate is 3-10 mL / min, and atomization pressure is 0.1-0.5 MPa.

[0037] Preferably, in step S4, when preparing the microcapsules from the oil-in-water emulsion using freeze-drying, the process parameters are as follows: First, the oil-in-water emulsion is pre-frozen at a temperature of -20 to -80 °C for 4 to 24 h; then, it is freeze-dried under vacuum at a cold trap temperature of -40 to -60 °C, a vacuum degree of 5 to 50 Pa, and a drying time of 12 to 48 h to obtain the oral-adhesive enzyme-responsive synergistic sweetening microcapsules.

[0038] Preferably, in step S4, when preparing the microcapsules from the oil-in-water emulsion using complex coagulation, the process parameters are as follows: a complex coagulation inducing agent is added to the oil-in-water emulsion to cause phase separation of the wall material and form a coagulated layer, wherein the amount of complex coagulation inducing agent added is 0.5% to 10% of the wall material mass; the pH of the system is adjusted to 3.0 to 5.5; the reaction temperature is 30 to 50 °C; the stirring speed is 200 to 800 rpm; and the reaction time is 30 to 180 min. Subsequently, the microcapsule structure is stabilized by cooling and curing or cross-linking treatment, and the microcapsules are obtained after centrifugation, washing, and drying.

[0039] Thirdly, this invention provides an application of the oral adhesive enzyme-responsive synergistic sweetening microcapsules in the preparation of oral sweetening products. The carboxyl structure on the surface of the microcapsule wall material forms hydrogen bonds and molecular entanglement with the mucins in the oral mucosa to enhance the retention capacity of the microcapsules in the oral cavity. After the microcapsules remain in the oral cavity, salivary amylase gradually hydrolyzes the wall material, causing it to disintegrate and releasing maltose and oligosaccharides to produce sweetness. As the wall material gradually disintegrates, the sweetening aroma substances in the core material are released simultaneously and transmitted through the posterior nasal pathway, forming a staged synergistic sweetening effect of taste and smell.

[0040] The core mechanism of this invention lies in the coupling effect between oral adhesion, enzyme-responsive degradation, and synergistic sweetening: By introducing carboxyl groups onto the surface of the wall material through ring-opening esterification of the hydroxyl groups in the polysaccharide or oligosaccharide with acid anhydrides, the microcapsules can form hydrogen bonds and molecular entanglements with mucins in the oral mucosa, thereby enhancing their oral retention capacity. Once the microcapsules are in the oral cavity, α-amylase in saliva gradually hydrolyzes the α-1,4 glycosidic bonds in the wall material (polysaccharide or oligosaccharide), causing the wall material to gradually disintegrate and release maltose and oligosaccharides to produce sweetness. As the wall material gradually degrades, sweetening aroma substances in the core material are released simultaneously, forming a synergistic sweetening effect through the posterior nasal pathway, involving both olfactory and gustatory stages. The entire process forms a continuous mechanism of action: oral retention – enzyme-responsive degradation – wall material sweetening – core material release – synergistic sweetening effect, achieving long-lasting sweetness maintenance.

[0041] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention provides an oral adhesive enzyme-responsive synergistic sweetening microcapsule, its preparation method, and its application. The microcapsule uses anhydride-modified starch polysaccharide or oligosaccharide as the wall material. The surface of the wall material contains carboxyl groups, which can form hydrogen bonds and molecular entanglement with the oral mucosa, giving the microcapsule good oral adhesion properties and significantly prolonging its retention time in the oral cavity. At the same time, the wall material can be gradually degraded by salivary amylase to generate maltose and oligosaccharides to provide sweetness, and simultaneously release the sweetening aroma substances in the core material, realizing the synergistic sweetening effect of sweetening by the wall material and the core material, overcoming the technical limitations of traditional microcapsules that lack oral adhesion, have inert wall materials that do not participate in sweetening, and release sweetness instantaneously.

[0042] (2) The present invention introduces a carboxyl structure on the surface of the wall material by modifying it with anhydride, so that the microcapsules can form a stable adhesion with the oral mucosa, thereby significantly prolonging the residence time of the microcapsules in the oral cavity and breaking through the limitation of traditional sweeteners being released immediately upon ingestion.

[0043] (3) This invention breaks through the technical limitation of traditional microcapsule wall materials only serving as inert protective layers. It proposes for the first time a functional wall material strategy that involves wall material participation in sweetening. This invention uses starch polysaccharide or oligosaccharide wall materials that can be decomposed by salivary amylase. During the enzymatic hydrolysis process, maltose and oligosaccharide sweet substances are generated, so that the wall material itself participates in the formation of sweetness.

[0044] (4) The present invention constructs a synergistic release mechanism of sweetening of wall material and sweetening of core material. After the microcapsule adheres in the oral cavity, salivary amylase triggers the gradual degradation of wall material. While continuously producing oligosaccharide sweetness, the sweetening aroma substance core material is slowly released. The aroma and sweetness are synergistically enhanced in time and space through the olfactory pathway, achieving a long-lasting, gentle and natural overall sweetening effect.

[0045] (5) The microcapsule system provided by the present invention can effectively improve the oral utilization efficiency of sweet substances, prolong the duration of sweetness perception, improve the smoothness and persistence of the sweetness time course curve, and provide a feasible path to reduce the amount of high sweeteners used. It has important application value in the field of sugar-reduced foods. Attached Figure Description

[0046] Figure 1 This is the infrared spectrum of Embodiment 1 of the present invention; Figure 2 This is a SEM image of Embodiment 1 of the present invention; Figure 3 Sensory evaluation diagrams of synergistic sweetening in Examples 1, 2, 3, Comparative Examples 1-4, and the blank control of the present invention; Figure 4 This is an adhesion effect diagram of Embodiment 1 of the present invention; Figure 5 This is an adhesion effect diagram of Embodiment 2 of the present invention; Figure 6 This is an adhesion effect diagram of Embodiment 3 of the present invention. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0048] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0049] Example 1: Preparation of starch-octenyl succinic anhydride (OSA) modified microcapsules The starch is dispersed in deionized water at a mass fraction of approximately 35%, and stirred thoroughly until a uniform starch slurry is formed. The pH of the starch slurry is adjusted to 8.5–9.0 using sodium hydroxide solution. A certain amount of OSA (1%–5% of the dry weight of starch) is slowly added dropwise while continuously stirring. During the addition, the system temperature is maintained at 30–35°C, and the pH is kept stable by adding sodium hydroxide solution. The reaction continues for approximately 4 hours, allowing OSA to undergo esterification with the starch hydroxyl groups. After the reaction is complete, the pH of the system is adjusted to 6.5–7.0 using hydrochloric acid. The reaction product is washed by centrifugation or filtration, first with deionized water multiple times to remove unreacted OSA and byproducts; ethanol can be used as an auxiliary washing agent if necessary. The washed product is dried at 40–45°C to a moisture content of approximately 10%, and then pulverized to the desired particle size to obtain OSA-modified starch. The degree of substitution (DS) of the OSA starch can be determined by acid-base titration, generally controlled within the range of 0.01–0.03 to ensure good emulsifying properties and amphiphilicity.

[0050] Weigh the above-mentioned OSA-modified starch wall material and add it to deionized water to prepare a wall material dispersion with a mass concentration of 10-25 wt%. Stir at 40-60℃ until completely dispersed to obtain an enzyme-responsive adhesive wall material solution. Then, according to a core-to-wall mass ratio of 1:5-1:20, add the sweetening aroma substance as the core material slowly to the wall material solution and emulsify under high-speed shear conditions. The shear rate is 10000-14000 rpm and the emulsification time is 5-10 min to form a uniform and stable oil-in-water emulsion.

[0051] The obtained oil-in-water emulsion was placed in a freeze-drying container and pre-frozen at -40℃ for 12 h to ensure complete freezing. It was then transferred to a vacuum freeze-drying apparatus for drying, with the cold trap temperature set at -50℃, the vacuum degree controlled at 20 Pa, and the freeze-drying time at 36 h. After drying, the sample was removed, pulverized, and sieved to obtain oral adhesive enzyme-responsive synergistic sweetening microcapsules.

[0052] Example 2: Preparation of γ-cyclodextrin-maleic anhydride modified microcapsules γ-Cyclodextrin was dispersed in deionized water at approximately 20% by mass and stirred thoroughly at 50–60°C until homogeneous, forming a γ-cyclodextrin dispersion. The pH of the γ-cyclodextrin dispersion was adjusted to 8.0–8.5 using sodium hydroxide solution. A certain amount of maleic anhydride, at 2%–8% of the dry weight of the γ-cyclodextrin, was slowly added while continuously stirring. During the addition process, the system temperature was maintained at 35–45°C, and the pH was stabilized by dropwise addition of sodium hydroxide solution. The reaction lasted approximately 3–5 days. h, maleic anhydride is reacted with the hydroxyl group in the γ-cyclodextrin molecule to undergo a ring-opening esterification reaction, introducing a carboxyl-containing maleic acid monoester group into the γ-cyclodextrin molecule structure; after the reaction, the pH of the system is adjusted to 6.5-7.0 with hydrochloric acid; unreacted maleic anhydride and byproducts are removed by dialysis, precipitation or other suitable purification methods, and ethanol is used to assist precipitation and washing if necessary; the purified product is dried at 40-45℃ to obtain maleic anhydride modified γ-cyclodextrin.

[0053] The maleic anhydride-modified γ-cyclodextrin was weighed as the wall material and added to deionized water to prepare a wall material dispersion with a mass concentration of 10–20 wt%. The dispersion was stirred thoroughly at 40–60°C until homogeneous, yielding an enzyme-responsive adhesive wall material solution. Subsequently, a sweetening aroma-enhancing substance was slowly added to the wall material solution as the core material at a core-to-wall mass ratio of 1:5–1:20. Emulsification was then performed under high-speed shear conditions at a shear rate of 10,000–14,000 rpm for 5–10 min, forming a homogeneous and stable oil-in-water emulsion.

[0054] The obtained oil-in-water emulsion was placed in a freeze-drying container and pre-frozen at -40℃ for 12 h to ensure complete freezing of the emulsion system. It was then transferred to a vacuum freeze-drying apparatus for drying, with the cold trap temperature set at -50℃, the vacuum degree controlled at 20 Pa, and the freeze-drying time at 36 h. After drying, the sample was removed, pulverized, and sieved to obtain oral-adhesive enzyme-responsive synergistic sweetening microcapsules with maleic anhydride-modified γ-cyclodextrin as the wall material.

[0055] Example 3: Preparation of maltodextrin-succinic anhydride modified microcapsules Maltodextrin was dissolved in deionized water at a mass fraction of approximately 25%, and stirred thoroughly at 50–60°C until homogeneous to form a maltodextrin solution. The pH of the maltodextrin solution was adjusted to 8.0–8.5 using sodium hydroxide solution. A certain amount of succinic anhydride was slowly added dropwise under continuous stirring. The amount of succinic anhydride added was 2%–10% of the dry weight of the maltodextrin. During the addition, the system temperature was maintained at 35–45°C, and the pH of the system was kept stable by adding sodium hydroxide solution dropwise. The reaction was carried out for approximately 3–5 hours, allowing the succinic anhydride to undergo a ring-opening esterification reaction with the hydroxyl groups in the maltodextrin molecule, introducing a carboxyl-containing succinic acid monoester group into the maltodextrin molecule structure. After the reaction was completed, the pH of the system was adjusted to 6.5–7.0 using hydrochloric acid. Unreacted succinic anhydride and byproducts were removed by dialysis, ethanol precipitation, or filtration. The purified product was dried at 40–45°C to obtain succinic anhydride-modified maltodextrin.

[0056] The succinic anhydride-modified maltodextrin described above was weighed as the wall material and added to deionized water to prepare a wall material solution with a mass concentration of 10–25 wt%. The solution was stirred thoroughly at 40–60°C until completely dissolved or uniformly dispersed, yielding an enzyme-responsive adhesive wall material solution. Subsequently, a sweetening aroma substance was slowly added to the wall material solution as the core material at a core-to-wall mass ratio of 1:5–1:20. Emulsification was then performed under high-speed shear conditions at a shear rate of 10,000–14,000 rpm for 5–10 min, forming a uniform and stable oil-in-water emulsion.

[0057] The obtained oil-in-water emulsion was placed in a freeze-drying container and pre-frozen at -40℃ for 12 h to ensure complete freezing of the emulsion system. It was then transferred to a vacuum freeze-drying apparatus for drying, with the cold trap temperature set at -50℃, the vacuum degree controlled at 20 Pa, and the freeze-drying time at 36 h. After drying, the sample was removed, pulverized, and sieved to obtain oral-adhesive enzyme-responsive synergistic sweetening microcapsules with succinic anhydride-modified maltodextrin as the wall material.

[0058] Comparative Example 1: The difference between this comparative example and Example 1 is that the wall material was not modified, and starch was used directly for microcapsule preparation. The remaining preparation steps and process parameters were the same as in Example 1.

[0059] Comparative Example 2: The difference between this comparative example and Example 2 is that the wall material was not modified, and γ-cyclodextrin was used directly for microcapsule preparation. The remaining preparation steps and process parameters were the same as in Example 2.

[0060] Comparative Example 3: The difference between this comparative example and Example 3 is that the wall material was not modified, and maltodextrin was used directly for microcapsule preparation. The remaining preparation steps and process parameters were the same as in Example 3.

[0061] Comparative Example 4 Free sweetening and aroma-enhancing substances.

[0062] Sensory evaluation of synergistic sweetening by microcapsules A standardized low-sugar model solution was prepared as the evaluation matrix. Under the same matrix conditions, the microcapsules of this invention, an equal amount of free sweetening aroma substances, unmodified microcapsules, and a blank control sample were added respectively. Sensory evaluation was conducted by five subjects who had received basic taste training. All subjects were able to accurately identify basic tastes and were familiar with the sensory evaluation methods. The evaluation employed an instantaneous sweetness intensity perception test method. Subjects immediately rated the sweetness intensity after tasting the sample, using a 1-10 scale (1 point indicates no sweetness perception, 10 points indicates extremely strong sweetness perception upon tasting). All samples were randomly coded and tested in a double-blind manner in a random order to reduce subjective bias.

[0063] Microcapsule Adhesion Performance Determination A standard curve for porcine gastric mucosal protein type II was constructed using UV-Vis spectrophotometry. Porcine gastric mucosal protein type II was dissolved in PBS buffer at pH 7.0, and the maximum absorption wavelength was obtained by full-spectrum scanning using a UV-Vis spectrophotometer (U-3900, Japan). Different concentrations (0.5–2 mg / mL) of porcine gastric mucosal protein type II solutions were mixed with microcapsule dispersions (1 mg / mL), and the microcapsule-mucosal protein mixtures were incubated at 250 rpm for 1 hour at 37°C in a large-capacity CO2 shaking incubator. The mixtures were then centrifuged at 10,000 rpm for 30 minutes, and the concentration of free mucosal protein in the supernatant was determined using a UV-Vis spectrophotometer. The oral adhesion ability of the microcapsules was expressed as the mass percentage of mucosal protein adsorbed on the nanoparticle surface relative to the total mucosal protein.

[0064] like Figure 1 The image shows the Fourier transform infrared spectra of starch, OSA-modified starch, and OSA-modified starch microcapsules. Compared to the original starch, OSA-modified starch exhibits higher wavelengths at approximately 1727.9 cm⁻¹. -1 A new absorption peak appears nearby, attributed to the stretching vibration of the ester carbonyl group (C=O), indicating that the carboxylic anhydride group in OSA undergoes a ring-opening esterification reaction with the hydroxyl group in the starch molecule, successfully introducing the succinate group into the starch molecule structure. Simultaneously, at approximately 3336.2 cm⁻¹... -1The change in the nearby hydroxyl stretching vibration peak indicates that the hydrogen bonding environment between starch molecules was affected, further proving the occurrence of the OSA modification reaction. The prepared OSA-modified starch microcapsules also retained the above-mentioned characteristic absorption peaks, indicating that the freeze-drying process did not damage the chemical structure of the wall material, and that OSA-modified starch can stably construct the microcapsule wall layer.

[0065] like Figure 2 The image shown is a scanning electron microscope image of OSA-modified starch microcapsules. As can be seen from the image, the obtained microcapsule particles exhibit an irregular, near-spherical structure with a continuous and intact surface. No obvious breakage or core material leakage was observed, indicating that OSA-modified starch can form a stable coating layer during emulsification, effectively encapsulating sweetening and aroma-enhancing substances. Simultaneously, the microcapsule surface exhibits certain wrinkles and porous structures. This is due to the porous network structure formed by the sublimation of ice crystals during freeze-drying, which facilitates the entry of moisture and salivary amylase from the oral cavity into the wall material, thereby promoting subsequent enzymatic degradation and core material release.

[0066] like Figure 3 As shown, the sweetness perception scores of OSA-modified starch microcapsules, maleic anhydride-modified γ-cyclodextrin microcapsules, and succinic anhydride-modified maltodextrin microcapsules were approximately 8.6, 8.4, and 8.6, respectively, all higher than the corresponding unmodified microcapsules. The sweetness perception score of free phenylethanol was approximately 7.6, with the lowest score (approximately 2.6) in the blank control group.

[0067] The above results indicate that anhydride modification can enhance the synergistic sweetening effect of different polysaccharide or oligosaccharide microcapsules. This may be because anhydride modification introduces carboxyl groups into the wall material, enhancing the interaction between the microcapsules and oral mucoproteins, thereby prolonging their residence time in the oral cavity; simultaneously, the polysaccharide or oligosaccharide wall material is gradually degraded and releases sweetening aroma substances under the action of salivary amylase, achieving a synergistic effect of sweetening by the wall material and sweetening by the core material.

[0068] like Figure 4 The figure shows the mucin adsorption performance of starch microcapsules and OSA starch microcapsules at different mucin concentrations. With increasing mucin concentration, the mucin adsorption capacity of both microcapsules gradually increased and tended to stabilize at higher concentrations. Compared to unmodified starch microcapsules, OSA starch microcapsules exhibited higher mucin adsorption capacity at all concentrations, reaching approximately 9.2 × 10⁻⁶ at a mucin concentration of 4 mg / mL. 4 μg, significantly higher than starch microcapsules (approximately 5.8 × 10 μg). 4 The results indicate that OSA modification can effectively enhance the interaction between microcapsules and mucins, and the introduced carboxyl structure can improve the oral adhesion properties of microcapsules through hydrogen bonding, electrostatic interactions, and molecular entanglement.

[0069] like Figure 5 The figure shows the mucin adsorption performance of γ-cyclodextrin microcapsules and maleic anhydride-modified γ-cyclodextrin microcapsules under different mucin concentrations. With increasing mucin concentration, the adsorption capacity of both microcapsules gradually increased, indicating that increased mucin concentration is beneficial for the binding between the microcapsules and mucin. Compared with unmodified γ-cyclodextrin microcapsules, maleic anhydride-modified γ-cyclodextrin microcapsules exhibited higher mucin adsorption capacity under all concentration conditions. When the mucin concentration reached 4 mg / mL, the mucin adsorption capacity of maleic anhydride-modified γ-cyclodextrin microcapsules was approximately 9.0 × 10⁻⁶. 4 μg, while unmodified γ-cyclodextrin microcapsules are approximately 4.5 × 10 μg. 4 μg. The results showed that maleic anhydride modification could improve the oral adhesion properties of γ-cyclodextrin microcapsules. This may be because the ring-opening esterification reaction between maleic anhydride and the hydroxyl groups in the γ-cyclodextrin molecule introduces carboxyl groups onto the wall surface, enhancing the interaction between the microcapsules and mucins, thereby improving their oral adhesion ability.

[0070] like Figure 6 The figure shows the mucin adsorption performance of maltodextrin microcapsules and succinic anhydride-modified maltodextrin microcapsules under different mucin concentrations. With increasing mucin concentration, the mucin adsorption capacity of both microcapsules gradually increased, with the succinic anhydride-modified maltodextrin microcapsules consistently exhibiting higher adsorption capacity. When the mucin concentration was 4 mg / mL, the mucin adsorption capacity of the succinic anhydride-modified maltodextrin microcapsules reached approximately 7.2 × 10⁻⁶. 4 μg, higher than that of unmodified maltodextrin microcapsules (approximately 5.0 × 10 μg). 4 The results above indicate that succinic anhydride modification can enhance the binding ability between maltodextrin microcapsules and mucin. Due to the introduction of carboxyl groups on the modified wall material surface, the interaction between the microcapsules and the oral mucosa can be enhanced through hydrogen bonding and electrostatic interactions, thereby improving the adhesion and retention capacity of the microcapsules in the oral cavity.

[0071] comprehensive Figures 4-6 The results showed that modifying different oligosaccharide or polysaccharide wall materials with different acid anhydrides resulted in microcapsules exhibiting enhanced mucin adsorption capacity, indicating that the acid anhydride modification strategy has good universality. The carboxyl structure introduced by the acid anhydride can effectively enhance the interaction between the wall material and mucin, enabling the microcapsules to achieve better oral adhesion properties, providing a basis for subsequent salivary amylase-responsive degradation and sustained synergistic sweetening.

[0072] In summary, this invention provides an oral-adhesive enzyme-responsive synergistic sweetening microcapsule, its preparation method, and its application. The microcapsule wall material is composed of anhydride-modified starch polysaccharides or oligosaccharides. Carboxyl groups are introduced onto the surface through a ring-opening esterification reaction, giving the wall material excellent oral mucosal adhesion properties and significantly prolonging the microcapsule's residence time in the oral cavity. Simultaneously, the wall material itself can be gradually enzymatically hydrolyzed in the oral cavity to generate maltose and oligosaccharides, releasing its own sweetness. Furthermore, as the wall material gradually disintegrates, the encapsulated sweetening aroma substances are simultaneously released via the posterior nasal pathway, thus constructing a synergistic sweetening mechanism where the wall material produces sweetness and the core material enhances sweetness. This invention overcomes the technical limitations of traditional microcapsule wall materials serving only as inert protective layers, achieving an organic unity of oral residence, enzyme-responsive release, and olfactory-flavor synergy. It provides a long-lasting, gentle, and natural sweetening solution for the low-sugar food industry, possessing excellent application prospects and market value.

[0073] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A type of oral adhesive enzyme-responsive synergistic sweetening microcapsule, characterized in that, The invention includes a core material and an enzyme-responsive adhesive wall material coated on the outer layer of the core material. The enzyme-responsive adhesive wall material is obtained by ring-opening esterification of acid anhydrides with polysaccharides or oligosaccharides that can be decomposed by salivary amylase. The surface of the enzyme-responsive adhesive wall material has carboxyl groups.

2. The oral adhesive enzyme-responsive synergistic sweetening microcapsule according to claim 1, characterized in that, The anhydride includes any one of maleic anhydride, succinic anhydride, itaconic anhydride, and octenyl succinic anhydride.

3. The oral adhesive enzyme-responsive synergistic sweetening microcapsule according to claim 1, characterized in that, The polysaccharide includes any one of natural starch, porous starch, and oxidized starch, and the oligosaccharide includes any one of maltodextrin or cyclodextrin.

4. The oral adhesive enzyme-responsive synergistic sweetening microcapsule according to claim 1, characterized in that, The core material comprises sweetening aroma compounds found in various fragrance aromas, including one or more of fruity, sweet, floral, sour, green, and aldehyde aromas. The fruity sweetening aroma compounds include one or more of octyl acetate, terpinene, ethyl butyrate, ethyl propionate, ethyl 2-methylbutyrate, ethyl hexanoate, butyl hexanoate, acetophenone, and γ-terpinene. The sweetening aroma compounds include carvone, citronellol, carvone, furanone, propyldecyl lactone, propylnonyl lactone, butyldecyl lactone, ethyl phenylacetate, benzyl alcohol, citronellol acetate, citral, 1-nonanol, and trans-ethylhexyl alcohol. The sweetening aroma compounds with floral notes include any one or more of leucene, myrcene, farnesol, nonanal, and citronellol formate; the sweetening aroma compounds with floral notes include any one or more of α-ionone, β-ionone, nerol acetate, nerol, nerolidol, terpinenol, methyl dihydrojasmone, and farnesene; the sweetening aroma compounds with acidic notes include any one or more of hexanoic acid, octanoic acid, 2-methylbutyric acid, 3-methylbutyric acid, and trans-2-hexenoic acid; the sweetening aroma compounds with green notes include β-pinene; and the sweetening aroma compounds with aldehyde notes include any one or more of myristaldehyde and lauryl alcohol.

5. A method for preparing oral adhesive enzyme-responsive synergistic sweetening microcapsules as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Under heating conditions, polysaccharides or oligosaccharides are dispersed in deionized water to obtain a dispersion; S2: Under pH conditions of 7.5 to 9.0, acid anhydride is added dropwise to the dispersion to carry out a ring-opening esterification reaction. The pH is kept stable during the reaction. After the reaction is completed, the pH is adjusted to 6.5 to 7.

5. After post-processing, enzyme-responsive adhesive wall material powder is obtained. S3: Disperse the enzyme-responsive adhesive wall material powder in deionized water to obtain an enzyme-responsive adhesive wall material solution. Slowly add the core material to the enzyme-responsive adhesive wall material solution and homogenize and emulsify it under a high-speed shear machine to obtain an oil-in-water emulsion. S4: Prepare the oil-in-water emulsion into the microcapsules by any one of spray drying, freeze drying or polycondensation.

6. The preparation method according to claim 5, characterized in that, In step S1, the concentration of the dispersion is 5 wt% to 30 wt%, and the heating temperature is 40 to 70°C.

7. The preparation method according to claim 5, characterized in that, In step S2, the mass of the acid anhydride is 0.5% to 15% of the mass of the polysaccharide or oligosaccharide, the temperature of the ring-opening esterification reaction is 25 to 55°C, and the reaction time is 1 to 6 h.

8. The preparation method according to claim 5, characterized in that, In step S3, the concentration of the enzyme-responsive adhesive wall material solution is 10-25 wt%, the mass ratio of the core material to the enzyme-responsive adhesive wall material powder is 1:5-1:20, the shearing rate of the high-speed shearing machine is 10000-14000 rpm, and the time is 3-10 min.

9. The preparation method according to claim 5, characterized in that, In step S4, when preparing the microcapsules from the oil-in-water emulsion using freeze-drying, the process parameters are as follows: First, the oil-in-water emulsion is pre-frozen at a temperature of -20 to -80 °C for 4 to 24 h; then, it is freeze-dried under vacuum at a cold trap temperature of -40 to -60 °C, a vacuum degree of 5 to 50 Pa, and a drying time of 12 to 48 h to obtain the oral-adhesive enzyme-responsive synergistic sweetening microcapsules.

10. The application of the oral adhesive enzyme-responsive synergistic sweetening microcapsule as described in any one of claims 1 to 4 in the preparation of oral sweetening products, characterized in that, The carboxyl structure on the surface of the microcapsule wall material forms hydrogen bonds and molecular entanglements with the mucin in the oral mucosa to enhance the retention capacity of the microcapsule in the oral cavity. After the microcapsule is retained in the oral cavity, salivary amylase gradually hydrolyzes the wall material, causing it to disintegrate and releasing maltose and oligosaccharides to produce sweetness. As the wall material gradually disintegrates, the sweetening aroma substances in the core material are released simultaneously and transmitted through the posterior nasal pathway, forming a staged synergistic sweetening effect of taste and smell.

Images