Acerola cherry vitamin C and fish collagen compound soft capsule and preparation method thereof

Abstract

The invention belongs to the field of nutritional health-care food, and provides an acerola cherry vitamin C and fish collagen compound soft capsule and a preparation method thereof. The core design of the antioxidant nano microgel spray powder formed by self-assembly of fish collagen peptide, vitamin C and nano microgel polysaccharide components under an acidic condition is adopted, the average particle size of nano microgel is controlled to be 150-400 nm, and the volume median particle size D50 of the spray powder is 5-20 [mu] m; the high embedding rate and antioxidant stability of vitamin C are achieved, the content maintains the low-viscosity filling performance of 0.8-2.0 Pa.s under the solid content of 55-75 wt%, the water activity is controlled within the range of 0.35-0.55, the long-term sealing stability is guaranteed, the technical problems that high solid content and low viscosity are difficult to consider, pH regulation and control conflict with shell-core interface plasticization, and spray drying efficiency conflict with activity retention are solved, and the preparation method is suitable for industrial production. And the method has wide application value.

Description

Technical Field

[0001] This invention relates to the field of nutritional and health food products, specifically to a soft capsule made from acerola cherry vitamin C and fish collagen, and its preparation method. Background Technology

[0002] Acerola cherry vitamin C and fish collagen are core functional ingredients in nutritional supplements, with widespread demand in applications such as beauty and anti-oxidation, immune regulation, and collagen supplementation. Acerola cherries are rich in natural vitamin C and antioxidants such as flavonoids, and their bioavailability and synergistic antioxidant effect are significantly superior to synthetic vitamin C. Fish collagen peptides are a preferred raw material for collagen supplementation due to their small molecular weight, easy absorption, and high bioactivity. In health supplement soft capsules, simultaneously meeting the requirements of high stability retention of vitamin C, maintenance of activity of fish collagen peptides, low viscosity filling performance of soft capsule contents, and long-term storage sealing stability has become a core performance requirement for product development. Especially in the design of high solid content formulations, it is necessary to consider the antioxidant protection of vitamin C, the uniform dissolution and dispersion of protein peptides, the rheological properties of the contents to match the soft capsule filling process window (solid content 55–75 wt%, viscosity 0.8–2.0 Pa·s), and the inhibition of microbial growth and long-term stability of the shell-core interface through water activity control (0.35–0.55).

[0003] However, existing technologies for combining acerola cherry vitamin C with fish collagen have significant shortcomings in meeting the aforementioned multiple performance requirements. First, vitamin C, as a highly reducing water-soluble vitamin, is highly susceptible to oxidative degradation in aqueous systems due to dissolved oxygen, metal ion catalysis, and light exposure. This is particularly pronounced in acidic to neutral pH environments where it coexists with protein peptides, where the oxidation rate intensifies, leading to an activity loss rate of 30–50% during storage. Existing technologies, by simply adding antioxidants or reducing water activity, struggle to achieve long-term protection in high-solids formulations. Second, fish collagen peptides readily undergo intermolecular hydrogen bonding and hydrophobic aggregation in high-concentration solutions, causing a sharp increase in system viscosity (typical formulations can reach 3–8 Pa·s), exceeding the process window (0.8–2.0 Pa·s) of soft capsule filling equipment. This makes stable filling and sealing impossible. For example, Chinese patent CN 112931203 A discloses a fish collagen vitamin soft capsule, but it suffers from difficulties in controlling content viscosity and poor filling stability. Furthermore, strategies employed to inhibit oxidation, such as low pH control (pH 3.8–4.5) and the use of polyols to reduce water activity, can lead to plasticization of the soft capsule shell material (gelatin or modified starch), decreased sealing strength, and long-term compatibility failure at the shell-core interface. For example, Chinese patent CN101700236A discloses a vitamin C soft capsule, but it suffers from insufficient stability at the shell-core interface and shelf-life sealing failure. Therefore, there is an urgent need for synergistic innovation in structural design and interface control to systematically address the multiple contradictions related to vitamin C's antioxidant protection, protein peptide dispersion stability, content rheological regulation, and shell-core interface compatibility. Summary of the Invention

[0004] The purpose of this invention is to provide a soft capsule made from acerola cherry vitamin C and fish collagen, and its preparation method, to resolve three core contradictions that are mutually constraining: First, achieving both high vitamin C encapsulation efficiency and shear-stable microstructure within a filling window of 55–75 wt% high solids content and 0.8–2.0 Pa·s low viscosity is difficult. Second, the acidic environment of pH 3.8–4.5, while inhibiting oxidation by reducing water activity of polyols, leads to plasticization of the shell-core interface, decreased sealing strength, and sealing failure. Third, the high yield, low residual water, and redispersibility of spray drying conflict with the thermal / oxygen stability and activity retention of vitamin C. This results in the inability to simultaneously optimize microstructure stability, batch-to-batch consistency, shelf-life antioxidant capacity, shell material compatibility, processing efficiency, and activity retention through a single parameter, requiring a cross-structural design, interface control, and a multi-stage processing synergy system.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A soft capsule containing a combination of acerola cherry vitamin C and fish collagen, with a single capsule weight of 1.6–2.4 g, comprises the following components by weight: 30–55 parts antioxidant nano-microgel spray powder; 20–35 parts polyol moisturizer; 3–10 parts of free polysaccharide components; 10–25 parts water; 0.5–3 parts buffer salt and antioxidant, wherein the sum of the mass parts of the buffer salt and antioxidant is 0.5–3; 1.0–5.0 parts acerola cherry extract; The antioxidant nano-microgel spray powder is composed of particles obtained by self-assembly of fish collagen peptides, vitamin C, and nano-microgel polysaccharide components under acidic conditions to form nano-microgels, and then spray drying. The nano-microgels encapsulate vitamin C through hydrogen bonds and electrostatic interactions. Based on the total mass of the solids in the spray powder, the mass fraction of fish collagen peptides is 50–80 wt%, the mass fraction of vitamin C is 5–20 wt%, and the mass fraction of nano-microgel polysaccharide components is 15–30 wt%.

[0006] Furthermore, the preparation method of the antioxidant nano-microgel spray powder includes the following steps: a) Dissolve fish collagen peptides, vitamin C and nano-microgel polysaccharide components in a citric acid and trisodium citrate buffer solution with a pH of 3.8–4.2 to obtain a solution with a solid content of 5–15 wt%, and stir at a temperature of 25–30℃ for 30–60 min to obtain a homogeneous mixed solution. b) Adjust the pH of the mixed solution to 4.0±0.2 and let it stand at room temperature for 0.5–2 h to allow the fish collagen peptides, vitamin C and nano-microgel polysaccharide components to self-assemble into nano-microgels, and control the average particle size of the obtained nano-microgels to be 150–400 nm. c) The nano-microgel dispersion is fed into a spray drying device and spray dried under the conditions of inlet temperature of 150–170℃, outlet temperature of 75–85℃, and atomization pressure of 0.8–1.5 MPa. The resulting spray powder has a median particle size D50 of 5–20 μm and a moisture content of no more than 5 wt%.

[0007] Furthermore, the antioxidant nano-microgel spray powder, based on the total mass of the spray powder solids, has a fish collagen peptide mass fraction of 50–80 wt%, a vitamin C mass fraction of 5–20 wt%, and a nano-microgel polysaccharide mass fraction of 15–30 wt%.

[0008] Furthermore, both the free polysaccharide component and the nano-microgel polysaccharide component are selected from one or more of resistant dextrin, pectin, and sodium alginate; The nano-microgel polysaccharide component is selected from one or more of resistant dextrin, pectin, and sodium alginate; Preferably, the nano-microgel polysaccharide component includes at least resistant dextrin and sodium alginate, and based on the total mass of the nano-microgel polysaccharide component, resistant dextrin accounts for 40–80 wt% and sodium alginate accounts for 20–60 wt%.

[0009] Furthermore, the polyol moisturizer is selected from one or more of glycerin, sorbitol and maltitol; preferably, the polyol moisturizer includes at least glycerin and sorbitol, and in the polyol moisturizer, glycerin accounts for 30-60 wt% and sorbitol accounts for 40-70 wt%.

[0010] Furthermore, the buffer salt comprises citric acid and trisodium citrate, which are prepared in a molar ratio of 1:(2.5–3.5) to adjust the pH of the soft capsule contents to 4.0±0.3. The antioxidant includes vitamin C and / or sodium ascorbate, wherein the conversion factor for sodium ascorbate to vitamin C is 0.89, and the total vitamin C content per soft capsule is 200–500 mg. The antioxidant may further include vitamin E acetate, with the amount of vitamin E acetate added relative to the total mass of the soft capsule contents being 0.01–0.20 wt%. The protein content provided by fish collagen peptides per single soft capsule is no less than 500 mg.

[0011] Furthermore, the contents of the soft capsules have a solid content of 55–75 wt%, a viscosity of 0.8–2.0 Pa·s, a pH of 3.8–4.5, and a water activity of 0.35–0.55 at a temperature of 25–35°C, wherein the water activity is preferably measured at a temperature of 25°C.

[0012] Furthermore, the antioxidant includes sodium ascorbate, which is added at an amount of 0.1–0.5 wt% relative to the total mass of the soft capsule contents, and may further include vitamin E acetate, which is added at an amount of 0.01–0.20 wt% relative to the total mass of the soft capsule contents.

[0013] As a concept of this invention, the present invention employs a design that utilizes fish collagen peptides, vitamin C, and nano-microgel polysaccharide components to self-assemble into nano-microgels under acidic conditions, followed by spray drying to prepare antioxidant nano-microgel spray powder. This design primarily aims to enhance the antioxidant stability of vitamin C, the uniform dispersion of protein peptides, and the rheological regulation properties of soft capsule contents. In a citric acid and trisodium citrate buffer system with a pH of 3.8–4.2, the degree of amino and carboxyl protonation of fish collagen peptides is controlled. Positively charged protein peptide segments and negatively charged nano-microgel polysaccharide components (resistant dextrin, sodium alginate) self-assemble through electrostatic interactions and hydrogen bond networks. Vitamin C molecules interact with the hydrophilic groups of the protein peptides and polysaccharides through hydrogen bonds, becoming embedded or complexed within the hydrophilic core or shell of the nano-microgel, forming a core-shell or network structure nano-microgel with an average particle size of 150–400 nm. This nanoscale embedded structure significantly reduces the probability of vitamin C contacting dissolved oxygen and metal ions, inhibiting free radical chain oxidation reactions. The spray drying process rapidly transforms the nano-microgel dispersion into spray-dried powder particles with a median particle size (D50) of 5–20 μm. The low moisture content (≤5 wt%) and solid matrix further isolate oxygen and moisture, forming a dual antioxidant protective barrier. When the spray-dried powder is rehydrated and dispersed in the soft capsule contents, the nano-microgel redisperses into nanoscale colloids. The fish collagen peptides exist in the form of nano-microgels rather than in a free molecular state. Intermolecular association and aggregation are inhibited by the nanostructure, significantly reducing the system viscosity. This maintains the viscosity of the high-solids formulation (55–75 wt%) within the 0.8–2.0 Pa·s filling window, which is 60–75% lower than that of conventional formulations that simply dissolve fish collagen peptides (viscosity 3–8 Pa·s), demonstrating the synergistic effect of the rheological regulation of the nano-microgel.

[0014] On the other hand, the present invention also discloses a method for preparing a soft capsule composed of acerola cherry vitamin C and fish collagen, comprising the following steps: S1. Prepare the antioxidant nano-microgel spray powder; S2. The antioxidant nano-microgel spray powder, polyol moisturizer, free polysaccharide component, buffer salt, antioxidant, and water are added to a mixing tank according to the specified ratio. The mixture is stirred at 25–35℃ for 1–2 h to obtain a homogeneous mixture. Vacuum degassing is then performed to ensure that the residual bubble volume fraction is not higher than 1 vol%. S3. Detect the solid content, viscosity and pH value of the soft capsule contents online, and adjust them to maintain a solid content of 55–75 wt%, a viscosity of 0.8–2.0 Pa·s and a pH value of 3.8–4.5. S4. The contents obtained in step S3 are transported to a soft capsule machine and filled and sealed under the conditions of shell temperature of 60–70℃ and contents temperature of 25–35℃ to obtain wet capsules. S5. Dry at a temperature of 20–25℃ and a relative humidity of 20–30% for 48–72 h to obtain the finished soft capsules.

[0015] In step S5, the drying process of the soft capsule controls the final water activity of the soft capsule contents to be 0.35–0.55, which is preferably measured at a temperature of 25°C.

[0016] As another aspect of this invention, a stepwise mixing, online detection and control, and gradient drying preparation method is designed to enhance the filling stability, shell-core interface compatibility, and long-term storage stability of soft capsule contents. In step S2, antioxidant nano-microgel spray powder is mixed with polyol humectant, free polysaccharide component, buffer salt, antioxidant, and water in a specific ratio and gently stirred at 25–35°C for 1–2 h to ensure that the nano-microgel in the spray powder is fully rehydrated and dispersed into nanoscale colloids, avoiding damage to the nanostructure due to high temperature or vigorous stirring. Vacuum degassing treatment reduces the residual bubble volume fraction to ≤1 vol%, preventing bubbles from causing sealing defects during filling. The online detection and control in step S3 is a key process innovation. By monitoring the solid content, viscosity, and pH value in real time and dynamically adjusting them, the contents are precisely controlled within a three-dimensional filling window of 55–75 wt% solid content, 0.8–2.0 Pa·s viscosity, and pH 3.8–4.5. This window takes into account the rheological requirements of the filling equipment, the pH stability of vitamin C, and the acid-base compatibility of the shell material. Step S5, gradient drying (20–25℃, relative humidity 20–30%, 48–72 h), employs a low-temperature, low-humidity, slow dehydration strategy, gradually reducing the water activity of the contents to 0.35–0.55. This water activity range inhibits microbial growth and prevents excessive water loss and embrittlement of the shell material. At the same time, the slow dehydration process makes the moisture gradient at the shell-core interface more gradual, reducing interfacial stress and uneven plasticization, ensuring long-term sealing stability. Compared with rapid drying (40℃, 24 h), the sealing strength of the shell material is increased by 30–50%, demonstrating the synergistic effect of process on improving product quality.

[0017] In this invention, the synergistic mechanism of fish collagen peptides and nano-microgel polysaccharide components (resistant dextrin and sodium alginate) in the composite system is manifested in the dual synergistic enhancement of antioxidant stability and rheological regulation performance. Fish collagen peptides focus on providing protein nutritional value and bioactivity. The amino acid residues such as glycine, proline, and hydroxyproline, which are rich in collagen peptides, are protonated and carry a positive charge under acidic pH conditions, forming hydrogen bond complexes with vitamin C. At the same time, the amphiphilic structure of the peptides (alternating arrangement of hydrophilic and hydrophobic amino acids) constructs a core-shell interface in the nano-microgel, encapsulating vitamin C through a hydrophobic core and forming a steric barrier, reducing the diffusion rate of oxygen and free radicals, and enhancing the antioxidant stability of vitamin C. The polysaccharide components of the nano-microgel focus on providing structural stability and rheological regulation. Resistant dextrin, as an enzymatic hydrolysis product of amylopectin, has a highly branched structure and good water solubility, forming a flexible supporting framework in the nano-microgel and reducing the viscosity of the system. Sodium alginate, as an anionic polysaccharide, is partially protonated under acidic conditions. The negatively charged carboxyl groups and the positively charged amino groups of fish collagen peptides form an ionic cross-linking network through electrostatic interactions, stabilizing the three-dimensional structure of the nano-microgel. The synergistic effect of fish collagen peptides and nano-microgel polysaccharide components is manifested in the following aspects: the protein peptides provide a dual antioxidant mechanism of hydrogen bonding and hydrophobic encapsulation, while the polysaccharide components provide a rheological regulation mechanism of electrostatic stabilization and branching viscosity reduction. The nano-microgel structure constructed by the two together enables the encapsulation rate of vitamin C to reach 85-95%, and the activity retention rate increases to 75-85% after 6 months of storage (compared to 50-60% in conventional formulations). At the same time, the viscosity of the high-solids formulation (55-75 wt%) is reduced by 60-75% (from 3-8 Pa·s to 0.8-2.0 Pa·s), demonstrating a significantly better synergistic effect than single components.

[0018] Beneficial technical effects 1. Significantly improves the antioxidant stability and activity retention of vitamin C: Through the core design of antioxidant nano-microgel spray powder formed by the self-assembly of fish collagen peptides, vitamin C and nano-microgel polysaccharide components under acidic conditions, vitamin C is encapsulated or complexed at the nanoscale (average particle size 150–400 nm), reducing the probability of contact with dissolved oxygen and metal ions, inhibiting free radical chain oxidation reactions, the encapsulation rate of vitamin C reaches 85–95%, and the activity retention rate increases to 75–85% after 6 months of storage, which is significantly better than the activity retention rate of 50–60% of conventional simple compounding technology.

[0019] 2. Effectively solves the viscosity control problem of high solids content formulations and meets the filling process window of soft capsules: The structured design of nano-microgels is adopted, so that fish collagen peptides exist in the form of nano-colloids rather than free molecules, which inhibits intermolecular hydrogen bonding and hydrophobic aggregation. Under the condition of 55-75 wt% high solids content, the viscosity of the contents is precisely controlled within the filling window of 0.8-2.0 Pa·s, which is 60-75% lower than the viscosity of conventional formulations of 3-8 Pa·s, thus achieving stable filling and sealing operations.

[0020] 3. Ensuring long-term compatibility and sealing stability at the shell-core interface: Through the synergistic configuration of polyol humectants, free polysaccharide components, and buffer salt systems, combined with a gradient drying process (20–25℃, relative humidity 20–30%, 48–72 h), the water activity of the soft capsule contents is precisely controlled within the range of 0.35–0.55. This water activity range inhibits microbial growth and prevents excessive water loss and embrittlement of the shell material. At the same time, the slow dehydration process makes the moisture gradient at the shell-core interface more gradual, reducing interfacial stress and uneven plasticization. The sealing strength of the shell material is increased by 30–50% compared to rapid drying, significantly improving the product's shelf-life stability.

[0021] 4. Achieve efficient synergistic supplementation of protein and vitamin C: Based on a single soft capsule (1.6–2.4 g), the protein content provided by fish collagen peptides is no less than 500 mg, and the total vitamin C content is 200–500 mg, meeting the functional requirements of nutritional health foods. At the same time, through the encapsulation and sustained-release effect of nano-microgels, the bioavailability and absorption efficiency of vitamin C and protein peptides in the gastrointestinal tract are improved.

[0022] 5. Excellent adaptability to industrial production and batch stability: The preparation method adopts a process route of stepwise mixing, online detection and control, and gradient drying. By monitoring the solid content, viscosity, and pH value in real time and making dynamic adjustments, the contents are precisely controlled within the three-dimensional filling window (55–75 wt% solid content, 0.8–2.0 Pa·s viscosity, pH 3.8–4.5). Vacuum degassing treatment reduces the residual bubble volume fraction to ≤1 vol%, ensuring batch consistency in filling and sealing. It is compatible with the process parameters and equipment capabilities of conventional soft capsule production lines and has good feasibility for large-scale production. Attached Figure Description

[0023] Figure 1 This invention relates to the effect of pH value on the particle size of nanogels and the encapsulation rate of vitamin C during self-assembly.

[0024] Figure 2 This invention investigates the effect of spray drying inlet temperature on vitamin C retention rate and spray powder D50 particle size.

[0025] Figure 3This invention investigates the effect of the dosage of antioxidant nano-microgel spray powder on the viscosity and protein content of the contents.

[0026] Figure 4 This invention investigates the effect of water activity of the soft capsule contents on vitamin C retention and product stability.

[0027] Figure 5 The ATR-FTIR spectrum of the fish collagen peptide in Example 1 of this invention is shown.

[0028] Figure 6 This is the ATR-FTIR spectrum of vitamin C (free) in Example 1 of the present invention.

[0029] Figure 7 The ATR-FTIR spectrum of the antioxidant nano-microgel spray powder in Example 1 of this invention is shown.

[0030] Figure 8 The ATR-FTIR spectrum of the contents of the soft capsule in Example 1 of this invention is shown.

[0031] Figure 9 Retention rate of vitamin C under different water activity conditions at 40 °C and 75% RH varies with time.

[0032] Figure 10 Morphology diagram of the antioxidant nano-microgel spray powder of Example 1 of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0034] Example 1 This embodiment provides a soft capsule containing a combination of acerola cherry vitamin C and fish collagen. With a single capsule weight of 2.0g, the contents of the soft capsule, by weight, include: 42 parts antioxidant nano-microgel spray powder; 28 parts polyol moisturizer; 6.5 parts free polysaccharide component; 17.5 parts water; 0.8 parts buffer salt; 0.7 parts antioxidant, wherein the total mass of buffer salt and antioxidant is 1.5; 3.0 parts acerola cherry extract.

[0035] The antioxidant nano-microgel spray powder of this embodiment is composed of particles obtained by self-assembly of fish collagen peptides, vitamin C, and nano-microgel polysaccharide components under acidic conditions to form nano-microgels, and then spray drying. In this embodiment, the nano-microgels encapsulate or complex vitamin C. Based on the total mass of solids in the spray powder of this embodiment, the mass fraction of fish collagen peptides is 65 wt%, the mass fraction of vitamin C is 12 wt%, and the mass fraction of nano-microgel polysaccharide components is 23 wt%.

[0036] The preparation method of the antioxidant nano-microgel spray powder in this embodiment includes the following steps: a) Dissolve fish collagen peptides, vitamin C, and nano-microgel polysaccharide components in a citric acid and trisodium citrate buffer solution with a pH of 4.0 to obtain a solution with a solid content of 10 wt%. Stir at 27°C for 45 min to obtain a homogeneous mixed solution. b) Adjust the pH of the mixed solution in this embodiment to 4.0, and let it stand at room temperature for 1 h to allow the fish collagen peptides, vitamin C, and nano-microgel polysaccharide components to self-assemble into nano-microgels, controlling the average particle size of the obtained nano-microgels to be 270 nm; c) The nano-microgel dispersion was fed into a spray drying device and spray dried under the conditions of an inlet temperature of 160℃, an outlet temperature of 80℃, and an atomization pressure of 1.1 MPa. The antioxidant nano-microgel spray powder with a median particle size D50 of 12 μm and a moisture content of 3.5 wt% was collected.

[0037] The free polysaccharide component of this embodiment is selected from resistant dextrin and sodium alginate; the nano-microgel polysaccharide component of this embodiment is selected from resistant dextrin and sodium alginate, and in the nano-microgel polysaccharide component of this embodiment, resistant dextrin accounts for 60 wt% and sodium alginate accounts for 40 wt%.

[0038] The polyol moisturizer in this embodiment is selected from glycerin and sorbitol; in the polyol moisturizer in this embodiment, glycerin accounts for 45 wt% and sorbitol accounts for 55 wt%.

[0039] The buffer salt in this embodiment includes citric acid and trisodium citrate, which are prepared in a molar ratio of 1:3.0 to adjust the pH of the soft capsule contents to 4.0. The antioxidant in this embodiment includes sodium ascorbate, which is added at an amount of 0.3 wt% relative to the total mass of the soft capsule contents, and further includes vitamin E acetate, which is added at an amount of 0.10 wt% relative to the total mass of the soft capsule contents. The total vitamin C content per soft capsule is 350 mg. The protein content provided by fish collagen peptides per soft capsule is 550 mg.

[0040] The contents of the soft capsules in this embodiment have a solid content of 65 wt%, a viscosity of 1.4 Pa·s, a pH of 4.1, and a water activity of 0.45 at a temperature of 30°C. The water activity in this embodiment was measured at a temperature of 25°C.

[0041] The preparation method of a soft capsule made from acerola cherry vitamin C and fish collagen in this embodiment includes the following steps: S1. Preparation of the antioxidant nano-microgel spray powder of this embodiment; S2. The antioxidant nano-microgel spray powder, polyol moisturizer, free polysaccharide component, buffer salt, antioxidant and water of this embodiment are added to a mixing tank according to the ratio, and stirred at 30°C for 1.5 h to obtain a uniform mixture. Vacuum degassing treatment is then performed to make the residual bubble volume fraction 0.5 vol%. S3. Online monitoring of the solid content, viscosity, and pH value of the soft capsule contents, adjusting to achieve a solid content of 65 wt%, a viscosity of 1.4 Pa·s, and a pH value of 4.1; S4. The contents obtained in step S3 are transported to a soft capsule machine, and filled and sealed at a shell temperature of 65°C and a contents temperature of 30°C to obtain wet capsules; S5. Dry the soft capsules for 60 h at a temperature of 22°C and a relative humidity of 25% to obtain the finished soft capsules. In step S5, the drying process of the soft capsules controls the final water activity of the soft capsule contents to be 0.45. In this embodiment, the water activity is measured at a temperature of 25°C.

[0042] Features of Example 1: This example employs moderately stable parameter configurations, with all component ratios falling within the central region of the claims, ensuring product stability and reproducibility. The spray powder contains a moderate amount of fish collagen peptides (65 wt%), a balanced ratio of vitamin C (12 wt%) and nano-microgel polysaccharide components (23 wt%), forming a stable nano-encapsulation structure. The ratio of glycerol to sorbitol in the polyol moisturizer (45:55) provides good moisturizing effects and soft capsule flexibility. The moderate parameter design of 65 wt% solid content and 1.4 Pa·s viscosity ensures both flowability during filling and product stability. The nano-microgel particle size of 270 nm falls within the optimal encapsulation range, and the spray powder D50 particle size of 12 μm ensures good dispersibility and solubility. This example is suitable for the daily health supplement market requiring long-term stability and standardized production, particularly for mass industrial production. It exhibits excellent process stability and product consistency, making it suitable for ordinary consumers with balanced vitamin C and collagen supplementation needs.

[0043] Example 2 This embodiment provides a soft capsule containing a combination of acerola cherry vitamin C and fish collagen. With a single capsule weight of 1.8g, the contents of the soft capsule, by weight, include: 36 parts antioxidant nano-microgel spray powder; 30 parts polyol moisturizer; 4.0 parts free polysaccharide component; 16 parts water; 1.0 part buffer salt; 1.2 parts antioxidant, wherein the sum of the weight of the buffer salt and antioxidant is 2.2; and 1.8 parts acerola cherry extract.

[0044] The antioxidant nano-microgel spray powder of this embodiment is composed of particles obtained by self-assembly of fish collagen peptides, vitamin C, and nano-microgel polysaccharide components under acidic conditions to form nano-microgels, and then spray drying. In this embodiment, the nano-microgels encapsulate or complex vitamin C. Based on the total mass of solids in the spray powder of this embodiment, the mass fraction of fish collagen peptides is 72 wt%, the mass fraction of vitamin C is 8 wt%, and the mass fraction of nano-microgel polysaccharide components is 20 wt%.

[0045] The preparation method of the antioxidant nano-microgel spray powder in this embodiment includes the following steps: a) Dissolve fish collagen peptides, vitamin C, and nano-microgel polysaccharide components in a citric acid and trisodium citrate buffer solution with a pH of 3.9 to obtain a solution with a solid content of 7 wt%. Stir the solution at 26℃ for 50 min to obtain a homogeneous mixed solution. b) Adjust the pH of the mixed solution in this embodiment to 3.9, and let it stand at room temperature for 1.5 h to allow the fish collagen peptides, vitamin C, and nano-microgel polysaccharide components to self-assemble into nano-microgels, controlling the average particle size of the obtained nano-microgels to be 200 nm; c) The nano-microgel dispersion was fed into a spray drying device and spray dried under the conditions of an inlet temperature of 155℃, an outlet temperature of 77℃, and an atomization pressure of 0.9 MPa. The antioxidant nano-microgel spray powder with a median particle size D50 of 8 μm and a moisture content of 4.2 wt% was collected.

[0046] The free polysaccharide component of this embodiment is selected from resistant dextrin, pectin and sodium alginate; the nano-microgel polysaccharide component of this embodiment is selected from resistant dextrin and sodium alginate, and in the nano-microgel polysaccharide component of this embodiment, resistant dextrin accounts for 48 wt% and sodium alginate accounts for 52 wt%.

[0047] The polyol moisturizer in this embodiment is selected from glycerin and sorbitol; in the polyol moisturizer in this embodiment, glycerin accounts for 34 wt% and sorbitol accounts for 66 wt%.

[0048] The buffer salt in this embodiment includes citric acid and trisodium citrate, which are prepared in a molar ratio of 1:2.7 to adjust the pH of the soft capsule contents to 3.9. The antioxidant in this embodiment includes sodium ascorbate, which is added at an amount of 0.45 wt% relative to the total mass of the soft capsule contents, and further includes vitamin E acetate, which is added at an amount of 0.15 wt% relative to the total mass of the soft capsule contents. The total vitamin C content per soft capsule is 280 mg. The protein content provided by fish collagen peptides per soft capsule is 520 mg.

[0049] The contents of the soft capsules in this embodiment have a solid content of 60 wt%, a viscosity of 1.0 Pa·s, a pH of 3.9, and a water activity of 0.42 at a temperature of 28°C. The water activity in this embodiment was measured at a temperature of 25°C.

[0050] The preparation method of a soft capsule made from acerola cherry vitamin C and fish collagen in this embodiment includes the following steps: S1. Preparation of the antioxidant nano-microgel spray powder of this embodiment; S2. The antioxidant nano-microgel spray powder, polyol moisturizer, free polysaccharide component, buffer salt, antioxidant and water of this embodiment are added to a mixing tank according to the ratio, and stirred at 28°C for 1.6 h to obtain a uniform mixture. Vacuum degassing treatment is then performed to make the residual bubble volume fraction 0.7 vol%. S3. Online monitoring of the solid content, viscosity, and pH value of the soft capsule contents, adjusting to achieve a solid content of 60 wt%, a viscosity of 1.0 Pa·s, and a pH value of 3.9; S4. The contents obtained in step S3 are transported to a soft capsule machine, and filled and sealed at a shell temperature of 63°C and a contents temperature of 28°C to obtain wet capsules; S5. Dry the soft capsules at a temperature of 21°C and a relative humidity of 27% for 65 h to obtain the finished soft capsules. In step S5, the drying process of the soft capsules controls the final water activity of the soft capsule contents to be 0.42. In this embodiment, the water activity is measured at a temperature of 25°C.

[0051] Example 2 Features: This example uses a high-protein, low-vitamin C formulation. The spray powder has a high content of fish collagen peptides (72 wt%) and a relatively low vitamin C content (8 wt%), highlighting the collagen supplementation effect. The small 1.8 g per capsule design is suitable for consumers requiring precise dosage control. It has a high content of polyol moisturizers (30 parts), with sorbitol accounting for 66%, providing excellent moisturizing properties and soft capsule softness. The total antioxidant content is high (1.2 parts, 1.35%), with 0.45 wt% sodium ascorbate added, combined with 0.15 wt% vitamin E acetate, forming a complex antioxidant system that effectively improves the stability of vitamin C. The free polysaccharide content is low (4.0 parts), reducing the viscosity of the formulation and lowering the content viscosity to 1.0 Pa·s, which is beneficial for filling operations and consumer swallowing. The nano-microgel particles have a diameter of 200 nm, which is within the small particle size range, improving bioavailability. This embodiment is suitable for beauty and health care people who focus on collagen supplementation and have relatively low vitamin C requirements. It is especially suitable for skin anti-aging and joint health maintenance applications. The small size design makes it easy to carry and take daily, making it suitable for office workers and fitness enthusiasts.

[0052] Example 3 This embodiment provides a soft capsule containing a combination of acerola cherry vitamin C and fish collagen. With a single capsule weight of 2.2g, the contents of the soft capsule, by weight, include: 50 parts antioxidant nano-microgel spray powder; 24 parts polyol moisturizer; 8.5 parts free polysaccharide component; 13 parts water; 0.3 parts buffer salt; 0.5 parts antioxidant, wherein the total mass of buffer salt and antioxidant is 0.8; 4.7 parts acerola cherry extract.

[0053] The antioxidant nano-microgel spray powder of this embodiment is composed of particles obtained by self-assembly of fish collagen peptides, vitamin C, and nano-microgel polysaccharide components under acidic conditions to form nano-microgels, and then spray drying. In this embodiment, the nano-microgels encapsulate or complex vitamin C. Based on the total mass of solids in the spray powder of this embodiment, the mass fraction of fish collagen peptides is 54 wt%, the mass fraction of vitamin C is 18 wt%, and the mass fraction of nano-microgel polysaccharide components is 28 wt%.

[0054] The preparation method of the antioxidant nano-microgel spray powder in this embodiment includes the following steps: a) Dissolve fish collagen peptides, vitamin C, and nano-microgel polysaccharide components in a citric acid and trisodium citrate buffer solution with a pH of 4.1 to obtain a solution with a solid content of 13 wt%. Stir the solution at 29°C for 35 min to obtain a homogeneous mixed solution. b) Adjust the pH of the mixed solution in this embodiment to 4.1, and let it stand at room temperature for 0.7 h to allow the fish collagen peptides, vitamin C, and nano-microgel polysaccharide components to self-assemble into nano-microgels, controlling the average particle size of the obtained nano-microgels to be 350 nm; c) The nano-microgel dispersion was fed into a spray drying device and spray dried under the conditions of an inlet temperature of 166℃, an outlet temperature of 83℃, and an atomization pressure of 1.35 MPa. The antioxidant nano-microgel spray powder with a median particle size D50 of 17 μm and a moisture content of 2.8 wt% was collected.

[0055] The free polysaccharide component of this embodiment is selected from resistant dextrin and sodium alginate; the nano-microgel polysaccharide component of this embodiment is selected from resistant dextrin and sodium alginate, and in the nano-microgel polysaccharide component of this embodiment, resistant dextrin accounts for 72 wt% and sodium alginate accounts for 28 wt%.

[0056] The polyol moisturizer in this embodiment is selected from glycerin and sorbitol; in the polyol moisturizer in this embodiment, glycerin accounts for 56 wt% and sorbitol accounts for 44 wt%.

[0057] The buffer salt in this embodiment includes citric acid and trisodium citrate, which are prepared in a molar ratio of 1:3.3 to adjust the pH of the soft capsule contents to 4.2. The antioxidant in this embodiment includes vitamin C and further includes vitamin E acetate, with the amount of vitamin E acetate added relative to the total mass of the soft capsule contents being 0.05 wt%. The total vitamin C content per soft capsule is 460 mg. The protein content provided by fish collagen peptides per soft capsule is 540 mg.

[0058] The contents of the soft capsules in this embodiment have a solid content of 70 wt%, a viscosity of 1.7 Pa·s, a pH of 4.3, and a water activity of 0.40 at a temperature of 32°C. The water activity in this embodiment was measured at a temperature of 25°C.

[0059] The preparation method of a soft capsule made from acerola cherry vitamin C and fish collagen in this embodiment includes the following steps: S1. Preparation of the antioxidant nano-microgel spray powder of this embodiment; S2. The antioxidant nano-microgel spray powder, polyol moisturizer, free polysaccharide component, buffer salt, antioxidant and water of this embodiment are added to a mixing tank according to the ratio, and stirred at 32°C for 1.2 h to obtain a uniform mixture. Vacuum degassing treatment is then performed to make the residual bubble volume fraction 0.3 vol%. S3. Online monitoring of the solid content, viscosity, and pH value of the soft capsule contents, adjusting to achieve a solid content of 70 wt%, a viscosity of 1.7 Pa·s, and a pH value of 4.3; S4. The contents obtained in step S3 are transported to a soft capsule machine, and filled and sealed at a shell temperature of 68°C and a contents temperature of 32°C to obtain wet capsules; S5. Dry the soft capsules for 52 hours at a temperature of 24°C and a relative humidity of 22% to obtain the finished soft capsules. In step S5, the drying process of the soft capsules controls the final water activity of the soft capsule contents to be 0.40. In this embodiment, the water activity is measured at a temperature of 25°C.

[0060] Example 3 Features: This example employs a high-vitamin C, low-moisture formulation design, highlighting the antioxidant effects of vitamin C. The spray powder has a high vitamin C content (18 wt%), a relatively low fish collagen peptide content (54 wt%), and a high content of nano-microgel polysaccharide components (28 wt%), forming a stronger encapsulation and protective structure. Acerola cherry extract is added in a high amount (4.7 parts), bringing the total vitamin C content per capsule to 460 mg, meeting the needs of high-dose vitamin C supplementation. The high content of free polysaccharide components (8.5 parts) provides better viscosity regulation and stability, while the moisture content is low (13 parts), resulting in a high solids content of 70 wt% and a water activity as low as 0.40, significantly improving product stability and shelf life. The polyol humectant has a high glycerol content (56%), effectively preventing drying and cracking in high-solids formulations. The nano-microgel particles, with a diameter of 350 nm, fall within a relatively large particle size range, providing a more stable encapsulation structure. The spray powder D50 particle size of 17 μm ensures good flowability and filling performance. The amount of buffer salt added is low (0.3 parts), but the acidity of the product is reduced by maintaining a high pH value (4.3). This embodiment is suitable for special populations that require high doses of vitamin C supplementation, such as people with low immunity, smokers, and high-intensity athletes. It is especially suitable for preventive health care during the peak season of seasonal influenza, as well as the high-end beauty market for whitening and anti-oxidation. The large size design of 2.2 g per capsule meets the high dose requirements.

[0061] Example 4 This embodiment provides a soft capsule containing a combination of acerola cherry vitamin C and fish collagen. With a single capsule weight of 2.3g, the contents of the soft capsule, by weight, include: 53 parts antioxidant nano-microgel spray powder; 21 parts polyol moisturizer; 9.2 parts free polysaccharide component; 11 parts water; 1.2 parts buffer salt; 1.6 parts antioxidant, wherein the total mass of buffer salt and antioxidant is 2.8; 4.8 parts acerola cherry extract.

[0062] The antioxidant nano-microgel spray powder of this embodiment is composed of particles obtained by self-assembly of fish collagen peptides, vitamin C, and nano-microgel polysaccharide components under acidic conditions to form nano-microgels, and then spray drying. In this embodiment, the nano-microgels encapsulate or complex vitamin C. Based on the total mass of the solids in the spray powder of this embodiment, the mass fraction of fish collagen peptides is 77 wt%, the mass fraction of vitamin C is 6 wt%, and the mass fraction of nano-microgel polysaccharide components is 17 wt%.

[0063] The preparation method of the antioxidant nano-microgel spray powder in this embodiment includes the following steps: a) Fish collagen peptides, vitamin C, and nano-microgel polysaccharide components were dissolved in a citric acid and trisodium citrate buffer solution with a pH of 3.85 to obtain a solution with a solid content of 14 wt%. The solution was stirred at 29.5℃ for 33 min to obtain a homogeneous mixed solution. b) Adjust the pH of the mixed solution in this embodiment to 4.15, and let it stand at room temperature for 0.6 h to allow the fish collagen peptides, vitamin C, and nano-microgel polysaccharide components to self-assemble into nano-microgels, controlling the average particle size of the obtained nano-microgels to be 370 nm; c) The nano-microgel dispersion was fed into a spray drying device and spray dried under the conditions of an inlet temperature of 168℃, an outlet temperature of 84℃, and an atomization pressure of 1.42 MPa. Antioxidant nano-microgel spray powder with a median particle size D50 of 18.5 μm and a moisture content of 2.2 wt% was collected.

[0064] The free polysaccharide component of this embodiment is selected from resistant dextrin; the nano-microgel polysaccharide component of this embodiment is selected from resistant dextrin and sodium alginate, and in the nano-microgel polysaccharide component of this embodiment, resistant dextrin accounts for 77 wt% and sodium alginate accounts for 23 wt%.

[0065] The polyol moisturizer in this embodiment is selected from glycerin and sorbitol; in the polyol moisturizer in this embodiment, glycerin accounts for 32 wt% and sorbitol accounts for 68 wt%.

[0066] The buffer salt in this embodiment includes citric acid and trisodium citrate, which are prepared in a molar ratio of 1:2.6 to adjust the pH of the soft capsule contents to 4.25. The antioxidant in this embodiment includes sodium ascorbate, which is added at an amount of 0.48 wt% relative to the total mass of the soft capsule contents, and further includes vitamin E acetate, which is added at an amount of 0.18 wt% relative to the total mass of the soft capsule contents. The total vitamin C content per soft capsule is 490 mg. The protein content provided by fish collagen peptides per soft capsule is 940 mg.

[0067] The contents of the soft capsules in this embodiment have a solid content of 73 wt%, a viscosity of 1.85 Pa·s, a pH of 4.4, and a water activity of 0.37 at a temperature of 34°C. The water activity in this embodiment was measured at a temperature of 25°C.

[0068] The preparation method of a soft capsule made from acerola cherry vitamin C and fish collagen in this embodiment includes the following steps: S1. Preparation of the antioxidant nano-microgel spray powder of this embodiment; S2. The antioxidant nano-microgel spray powder, polyol moisturizer, free polysaccharide component, buffer salt, antioxidant and water of this embodiment are added to a mixing tank according to the ratio, and stirred at 34°C for 1.1 h to obtain a uniform mixture. Vacuum degassing treatment is then performed to make the residual bubble volume fraction 0.2 vol%. S3. Online monitoring of the solid content, viscosity, and pH value of the soft capsule contents, adjusting to achieve a solid content of 73 wt%, a viscosity of 1.85 Pa·s, and a pH value of 4.4; S4. The contents obtained in step S3 are transported to a soft capsule machine, and filled and sealed at a shell temperature of 69°C and a contents temperature of 34°C to obtain wet capsules; S5. Dry the soft capsules for 50 h at a temperature of 24.5℃ and a relative humidity of 21% to obtain the finished soft capsules. In step S5, the drying process of the soft capsules controls the final water activity of the soft capsule contents to be 0.37. In this embodiment, the water activity is measured at a temperature of 25℃.

[0069] This embodiment employs boundary value verification in its formulation design, validating the applicability and feasibility of the technical solution through parameter combinations. The single-particle weight is 2.3 g, the amount of antioxidant nano-microgel spray powder is 53 parts, the free polysaccharide component is 9.2 parts, the water content is 11 parts, and the total amount of buffer salts and antioxidants is 2.8 parts. In the spray powder composition, the fish collagen peptide content is 77 wt%, the vitamin C content is 6 wt%, and the nano-microgel polysaccharide component is 17 wt%. The polyol moisturizer content is 21 parts, of which glycerol accounts for 32 wt%. The process parameters include a spray liquid-to-solid content of 14 wt%, a spray drying inlet temperature of 168℃, an outlet temperature of 84℃, an atomization pressure of 1.42 MPa, a spray powder D50 particle size of 18.5 μm, and a nano-microgel particle size of 370 nm. The content solid content is 73 wt%, and the viscosity is 1.85. With a Pa·s and a water activity of 0.37, each grain contains 940 mg of protein and 490 mg of vitamin C, providing a dual high-dose supplementation of protein and vitamin C. The high solids content combined with the low water activity design gives the product a long shelf life and high stability, making it suitable for applications requiring high-intensity nutritional supplementation, such as professional athletes, post-operative recovery patients, and malnourished patients. It is also suitable for long-term storage and use under extreme environmental conditions such as high temperature and high humidity, to verify its operability and finished product stability under stringent process conditions.

[0070] Comparative Example 1: It is basically the same as Example 1, except that only resistant dextrin is used for the nano-microgel polysaccharide component, and sodium alginate is not added. The amount of other components and preparation conditions remain unchanged.

[0071] Comparative Example 2: It is basically the same as Example 1, except that only 28 parts of glycerin are used as the polyol moisturizer, and no sorbitol is added. The amount of other components and the preparation conditions remain unchanged.

[0072] Comparative Example 3: It is basically the same as Example 1, except that the mass fraction of fish collagen peptide in the spray powder is 45 wt%, the mass fraction of vitamin C is 15 wt%, the mass fraction of nano-microgel polysaccharide component is 40 wt%, and the amount of other components and preparation conditions remain unchanged.

[0073] Comparative Example 4: It is basically the same as Example 1, except that only 0.7 parts of sodium ascorbate were used as antioxidants, and vitamin E acetate was not added. The amounts of other components and preparation conditions remained unchanged.

[0074] Comparative Example 5: It is basically the same as Example 1, except that the pH value of the buffer solution in step a) is 3.5, and the pH value of the mixed solution in step b) is adjusted to 3.5. The amounts of other components and preparation conditions remain unchanged.

[0075] Comparative Example 6: It is basically the same as Example 1, except that the spray drying inlet temperature is 180°C and the outlet temperature is 90°C in step c), while the amount of other components and preparation conditions remain unchanged.

[0076] Comparative Example 7: Basically the same as Example 1, except that the average particle size of the nanogel in step b) is 120 nm, which is achieved by shortening the standing time to 0.3 h, while the amount of other components and preparation conditions remain unchanged.

[0077] Comparative Example 8: It is basically the same as Example 1, except that the solid content of the solution in step a) is 18 wt%, while the amount of other components and the preparation conditions remain unchanged.

[0078] Comparative Example 9: It is basically the same as Example 1, except that the drying temperature in step S5 is 30°C and the relative humidity is 25%, while the amount of other components and the preparation conditions remain unchanged.

[0079] Comparative Example 10: It is basically the same as Example 1, except that the amount of antioxidant nano-microgel spray powder is 25 parts, the amount of polyol moisturizer is 32 parts, the amount of water is adjusted to 21.5 parts, and the amount of other components and preparation conditions remain unchanged.

[0080] Comparative Example 11: It is basically the same as Example 1, except that the amount of free polysaccharide component is 12 parts, the amount of water is adjusted to 15.5 parts, and the amount of other components and preparation conditions remain unchanged.

[0081] Comparative Example 12: Basically the same as Example 1, except that the amount of acerola cherry extract was 6.0 parts, the amount of antioxidant nano-microgel spray powder was adjusted to 39 parts, and the amounts of other components and preparation conditions remained unchanged.

[0082] Comparative Example 13: It is basically the same as Example 1, except that the relative humidity in step S5 is 40%, the drying time is extended to 80 h, and the amount of other components and preparation conditions remain unchanged.

[0083] Comparative Example 14: It is basically the same as Example 1, except that the final value of water activity in the drying process in step S5 is controlled to be 0.62, which is achieved by shortening the drying time to 40 h. The amount of other components and preparation conditions remain unchanged.

[0084] Performance testing: Experiment 1 / 6: Determination of Nanoparticle Size of Microgels Test Object: The nano-microgel dispersion after reconstitution of antioxidant nano-microgel spray powder. Test Objective: To evaluate the average particle size and particle size distribution of the nano-microgel and verify the uniformity of the self-assembled structure. Test Principle: Based on dynamic light scattering technology, the hydrodynamic diameter of the particles is calculated by analyzing the intensity fluctuations of scattered light caused by the Brownian motion of the nanoparticles. Experimental Method: An appropriate amount of spray powder was diluted with a pH 4.0 citric acid-trisodium citrate buffer solution to a solid content of 0.1 wt%. The powder was gently stirred at room temperature for 10 min to ensure complete dispersion. Dynamic light scattering was used to measure the dispersion at 25±1℃ and a backscattering angle of 173°. Each sample was measured in triplicate, and the Z-average particle size (Z-average) and polydispersity index (PDI) were recorded. Standard Basis: Refer to ISO 22412-2017 "Particle size analysis—Dynamic light scattering method". Key Parameters: Test temperature 25±1℃, fixed dilution factor, scattering angle 173°, measurement time 120 s per measurement. Data processing: The average particle size of the nanogel is expressed as Z-mean particle size. The mean ± standard deviation of three parallel measurements (n=3) is calculated; PDI<0.3 indicates uniform particle size distribution.

[0085] Experiment 2 / 6: Determination of Vitamin C Encapsulation Rate Test Subject: Antioxidant nano-microgel spray powder. Test Objective: To evaluate the encapsulation efficiency of vitamin C in the nano-microgel and verify the core technological innovations. Test Principle: Free vitamin C and encapsulated vitamin C are separated by centrifugation, and quantitatively determined by high-performance liquid chromatography (HPLC). Experimental Method: 0.5 g of spray powder was reconstituted with pH 4.0 buffer solution to 50 mL, centrifuged (10000 rpm, 20 min, 4℃) to separate free vitamin C. The supernatant was filtered through a 0.45 μm filter membrane, and the free vitamin C content was determined by HPLC. Separately, the same batch of spray powder was subjected to acid hydrolysis to destroy the nano-microgel structure, and the total vitamin C content was determined. HPLC Conditions: C18 column (250 mm × 4.6 mm, 5 μm), mobile phase 0.01 mol / L potassium dihydrogen phosphate solution (pH 2.5), flow rate 1.0 mL / min, detection wavelength 254 nm, column temperature 30℃. Standard Basis: Refer to GB 5009.86-2016 "Determination of Ascorbic Acid in Food". Key Parameters: Centrifugation conditions: 10000 rpm / 20 min / 4℃, HPLC flow rate: 1.0 mL / min. Data Processing: Encapsulation efficiency (%) = (Total Vitamin C - Free Vitamin C) / Total Vitamin C × 100%, n≥3, report mean ± standard deviation.

[0086] Experiment 3 / 6: Determination of the rheological properties of soft capsule contents Test Subject: Soft capsule contents mixture. Test Objective: To evaluate the viscosity and rheological properties of the contents at the filling temperature and verify processing suitability. Test Principle: Viscosity changes at different shear rates are measured using a rotational rheometer to evaluate the flow behavior type. Experimental Method: Freshly prepared soft capsule contents mixtures are sampled immediately after degassing and measured using a rotational rheometer at a constant temperature of 30±1℃. A conical plate clamp (40 mm diameter, 1° cone angle) is used, with a shear rate range of 0.1-100 s⁻¹. Steady-state flow curves and viscosity-shear rate curves are measured for each sample. The apparent viscosity at a shear rate of 1.0 s⁻¹ is recorded as the standard value. Standard Basis: Refer to GB / T 22235-2008 "Determination of Viscosity of Liquid Chemicals". Key Parameters: Test temperature 30±1℃, shear rate 1.0 s⁻¹, conical plate clamp gap 0.05 mm. Data processing: Express the viscosity value at a shear rate of 1.0 s⁻¹, in Pa·s, n≥3, and report the mean ± standard deviation; plot the viscosity-shear rate double logarithmic curve to determine the flow type.

[0087] Experiment 4 / 6: Accelerated Stability Test of Vitamin C Test Subject: Vitamin C in finished soft capsules. Test Objective: To evaluate the retention rate of vitamin C in soft capsules during storage and verify the effectiveness of the antioxidant design. Test Principle: Vitamin C residue was periodically measured during storage under accelerated conditions (40℃±2℃, RH 75%±5%). Experimental Method: Finished soft capsules were stored in a constant temperature and humidity chamber (40℃±2℃, RH 75%±5%), and samples were taken on days 0, 15, 30, 60, and 90. Storage continued under the same conditions until 180 days (6 months), with additional sampling at days 120 and 180. Ten capsules were cut open each time, and the contents were extracted with 0.5% metaphosphoric acid solution. The vitamin C content was determined using HPLC (C18 column, mobile phase pH 2.5 potassium dihydrogen phosphate solution, flow rate 1.0 mL / min, detection wavelength 254 nm). Key Parameters: Storage temperature 40±2℃, humidity 75±5%, sampling interval 15-30 days. Data processing: Vitamin C retention rate (%) = Ct / C0 × 100% (Ct is the content at day t, C0 is the initial content), n≥3, plot the retention rate-time curve, and calculate the 90-day retention rate.

[0088] Experiment 5 / 6: Water Activity Measurement Test Subject: Soft capsule contents. Test Objective: To evaluate the water activity of the contents and verify the microbial stability and shelf-life design rationality. Test Principle: Based on the dew point temperature method, the ratio of the partial pressure of water vapor in the gas phase above the sample to the saturated vapor pressure of pure water is measured. Experimental Method: Take 5 dried finished soft capsules, cut them open, and quickly transfer the contents to a sample cup for the water activity meter, filling it to 2 / 3 of its height. Immediately cover with a sealed cap. Place the cup in a water activity meter (dew point method) and equilibrate under a constant temperature of 25.0±0.1℃. Record the water activity value after the reading stabilizes (change <0.001 aw in 3 consecutive readings). Standard Basis: Refer to GB 5009.238-2016 "Determination of Water Activity in Food". Key Parameters: Test temperature 25.0±0.1℃, sample filling height 2 / 3 of the cup height, equilibrium criterion Δaw <0.001. Data processing: Read the aw value directly, accurate to 0.01, n≥3, and report the mean ± standard deviation; aw<0.6 indicates that microbial growth is inhibited.

[0089] Experiment 6 / 6: X-ray diffraction (XRD) structural characterization Test Subject: Antioxidant nano-microgel spray powder. Test Objective: To characterize the crystallinity and crystalline structure of the nano-microgel and verify the structural changes of fish collagen peptides during self-assembly. Test Principle: X-ray diffraction (XRD) was used to analyze the crystal structure of the sample, and the crystallinity and crystalline form were determined by the position and intensity of the diffraction peaks. Experimental Method: 0.5 g of spray powder was evenly spread in the sample trough and measured using an XRD instrument. The test conditions were: Cu Kα radiation source (λ=1.5406 Å), tube voltage 40 kV, tube current 40 mA, scanning range 5-50° (2θ), scanning rate 5° / min, and step size 0.02°. Key Parameters: Cu Kα radiation, scanning range 5-50°, step size 0.02°, scanning rate 5° / min. Data processing: Record the diffraction pattern, mark the position (2θ) and relative intensity of characteristic peaks; calculate the relative crystallinity by peak area integration method = (crystallization peak area / total area) × 100%, and export the CSV format data (2θ, Intensity) for Origin plotting and analysis.

[0090] Figure 1To investigate the effect of pH value on particle size and vitamin C encapsulation rate of the self-assembly of the antioxidant nanogel of this invention, the following parameters were fixed: fish collagen peptide mass fraction 65 wt%, vitamin C mass fraction 12 wt%, nanogel polysaccharide component mass fraction 23 wt%, mixed solution solid content 10 wt%, stirring temperature 27℃, stirring time 45 min, standing time 1 h, spray drying inlet temperature 160℃, outlet temperature 80℃, and atomization pressure 1.1 MPa. The variable parameter was the self-assembly pH value from 3.5 to 4.5. When the self-assembled pH value is between 3.9 and 4.1, the particle size of the nano-microgel is controlled between 258 and 282 nm, and the vitamin C encapsulation rate reaches 85.8% to 87.5%, showing a peak range. When the pH value is below 3.8, the fish collagen peptides are excessively protonated, which leads to enhanced electrostatic repulsion, causing the particle size to drop to 245 nm and the encapsulation rate to drop to 82.3%. When the pH value is above 4.2, the electrostatic attraction weakens, causing the particle size to increase to 295 nm and the encapsulation efficiency to drop to 84.7%. This proves that precise pH control can simultaneously achieve the structural stability of the nano-microgel and the efficient encapsulation of vitamin C.

[0091] Figure 2 To investigate the effect of spray drying inlet temperature on vitamin C retention rate and spray powder D50 particle size, the following parameters were fixed: fish collagen peptide 65 wt%, vitamin C 12 wt%, nano-microgel polysaccharide component 23 wt%, self-assembly pH 4.0, mixed solution solid content 10 wt%, nano-microgel particle size 270 nm, atomization pressure 1.1 MPa, and the outlet temperature and inlet temperature were linked to maintain a temperature difference of 80°C. The variable parameter was the spray drying inlet temperature ranging from 140°C to 180°C. When the spray drying inlet temperature is 155 to 165°C, the vitamin C retention rate reaches 95.2% to 95.8%, and the optimal balance is achieved when the spray powder D50 particle size is controlled between 11.2 and 13.5 μm. When the inlet temperature is below 150°C, the drying efficiency is insufficient, resulting in high residual moisture, particle adhesion, and a retention rate of 94.5%. When the inlet temperature is above 170°C, the thermal oxidation intensifies, leading to vitamin C degradation, causing the retention rate to plummet to 91.5%, and the D50 particle size to increase to 17.8 μm. This verifies that a moderate temperature can balance drying efficiency and vitamin C activity.

[0092] Figure 3To investigate the effect of the dosage of the antioxidant nano-microgel spray powder on the viscosity of the contents and the protein content of individual particles, the following parameters were fixed: 6.5 parts of free polysaccharide component, 0.8 parts of buffer salt, 0.7 parts of antioxidant, 3.0 parts of acerola cherry extract, mixing temperature 30°C, stirring time 1.5 h, shell temperature 65°C, contents temperature 30°C, drying temperature 22°C, and relative humidity 25%. The variable parameters were the dosage of the antioxidant nano-microgel spray powder, ranging from 25 parts to 65 parts. When the amount of antioxidant nano-microgel spray powder is 35 to 48 parts, the viscosity of the contents is controlled at 1.25 to 1.58 Pa·s and the protein content of a single capsule reaches 455 to 625 mg, showing a synergistic peak of processability and nutritional efficacy. When the amount of spray powder is less than 30 parts, the protein content is less than 390 mg and the viscosity drops to 1.12 Pa·s, resulting in a decrease in filling stability. When the amount of spray powder is more than 55 parts, the viscosity rises rapidly to 1.75 Pa·s, close to the upper limit of the filling window. This indicates that an appropriate amount of spray powder is the key to simultaneously meeting the requirements of soft capsule processing technology and nutritional supplementation efficacy.

[0093] Figure 4 To investigate the effect of the water activity of the soft capsule contents on vitamin C retention and product stability, the following parameters were fixed: 42 parts of antioxidant nano-microgel spray powder, 28 parts of polyol humectant, 6.5 parts of free polysaccharide component, 0.8 parts of buffer salt, 0.7 parts of antioxidant, and 3.0 parts of acerola cherry extract. The soft capsule preparation process was the same as in Example 1, with the variable parameter being the final water activity value controlled during the drying process, ranging from 0.30 to 0.62. When the water activity of the soft capsule contents was controlled between 0.35 and 0.50, the 90-day vitamin C retention rate remained between 90.5% and 94.5%, with excellent microbial stability. When the water activity was below 0.35, excessive drying led to brittleness and cracking of the capsule shell; although the retention rate slightly increased to 95.2%, the sealing performance was compromised. When the water activity was above 0.55, water migration intensified, leading to accelerated oxidative degradation of vitamin C, causing the retention rate to plummet to 87.2% and a decrease in sealing strength. This demonstrates that precise water activity control can balance vitamin C stability and soft capsule integrity.

[0094] Figure 5The ATR-FTIR spectrum (transmission mode) of fish collagen peptides was obtained. The fixed parameters were: ATR-FTIR test mode, resolution 4 cm⁻¹, number of scans 32, spectral range 4000–600 cm⁻¹, sample was freeze-dried fish collagen peptide powder, test temperature 25°C, relative humidity 45%, and the variable parameter was wavenumber decreasing from 4000 cm⁻¹ to 600 cm⁻¹. The spectrum shows a broad and strong N–H / O–H stretching vibration band near 3300 cm⁻¹, typical strong absorption peaks of amide I and amide II at 1650 cm⁻¹ and 1550 cm⁻¹ respectively, CH2 bending and amide III absorption are visible near 1450 cm⁻¹ and 1240 cm⁻¹, and characteristic C–O / C–N peaks appear near 1070 cm⁻¹. The overall spectrum is completely consistent with the collagen characteristics in the literature, proving that the fish collagen peptide backbone structure is intact, providing a stable protein peptide substrate for subsequent self-assembly of nanogels.

[0095] Figure 6 The ATR-FTIR spectrum (transmission mode) of vitamin C (free) was obtained. The fixed parameters were: test mode ATR-FTIR, resolution 4 cm⁻¹, number of scans 32, spectral range 4000–600 cm⁻¹, sample was crystalline vitamin C standard, test temperature 25°C, relative humidity 45%, and the variable parameter was wavenumber decreasing from 4000 cm⁻¹ to 600 cm⁻¹. The spectrum shows a broad O–H stretching vibration peak at 3420 cm⁻¹, a distinct strong C=O absorption peak of lactone near 1750 cm⁻¹, characteristic peaks of the C=O / C=C conjugated system in the range of 1670–1610 cm⁻¹, and multiple sets of C–O and C–C stretching absorptions in the region of 1320–1060 cm⁻¹. The strong peak at 1750 cm⁻¹ and the C–O band at 1060 cm⁻¹ are clearly distinguishable, indicating that free vitamin C is in a complete cyclic lactone configuration, providing a control basis for subsequent comparison of C=O vibrational behavior before and after encapsulation.

[0096] Figure 7The ATR-FTIR spectrum (transmission mode) of the antioxidant nano-microgel spray powder (Example 1) was obtained. The fixed parameters were: test mode ATR-FTIR, resolution 4 cm⁻¹, number of scans 32, spectral range 4000–600 cm⁻¹, sample was the nano-microgel spray-dried powder obtained in Example 1, spray powder moisture content 3.5 wt%, particle size D50 12 μm, test temperature 25°C, relative humidity 45%, and the variable parameter was wavenumber decreasing from 4000 cm⁻¹ to 600 cm⁻¹. The O–H / N–H band at 3300 cm⁻¹ in the spectrum is further broadened and slightly redshifted. The C=O peak of free vitamin C at 1650 cm⁻¹ transforms into a broad peak at approximately 1638 cm⁻¹ in the microgel, which overlaps with the COO⁻ stretching of collagenamide I and polysaccharide carboxylates. The characteristic absorption of lactone C=O at 1750 cm⁻¹ is significantly weakened and even difficult to distinguish. At the same time, obvious asymmetric / symmetric stretching double peaks of COO⁻ appear at 1608 / 1415 cm⁻¹. The absorption of C–O–C and C–O is enhanced in the 1145–1020 cm⁻¹ region. This indicates that vitamin C is partially ionized or undergoes structural changes under acidic conditions, and forms hydrogen bonds and electrostatic interactions with fish collagen peptides and nano-microgel polysaccharides through carboxyl or hydroxyl groups, thereby more stably embedding itself in the nano-microgel network. This effectively proves that vitamin C transforms from a free state to an embedded or complexed state in the nano-microgel network.

[0097] Figure 8The ATR-FTIR spectrum (transmission mode) of the soft capsule contents (Example 1) was obtained. The fixed parameters were: ATR-FTIR test mode, resolution 4 cm⁻¹, number of scans 32, spectral range 4000–600 cm⁻¹, sample was the soft capsule contents of Example 1 after mixing and degassing (solid content 65 wt%, viscosity 1.4 Pa·s, pH 4.1, water activity 0.45), test temperature 25°C, relative humidity 45%, and the variable parameter was wavenumber decreasing from 4000 cm⁻¹ to 600 cm⁻¹. The spectrum shows a broad O–H / N–H peak at approximately 3330 cm⁻¹, contributed by fish collagen peptides, polyol moisturizers, and polysaccharides. Overlapping broad peaks of amide I and carboxylate COO⁻ stretching are observed in the 1635–1605 cm⁻¹ range. These peaks are significantly weaker than the 1750 cm⁻¹ lactone peak of free vitamin C and shift towards lower wavenumbers. Symmetrical stretching of COO⁻ is enhanced near 1413 cm⁻¹, and the absorption intensities of C–O–C and C–O are further increased in the 1150–1030 cm⁻¹ region. Meanwhile, at 1735 cm⁻¹... The presence of a moderate-intensity C=O peak at cm⁻¹, originating from vitamin E acetate and some polyol esterification groups, indicates that in the actual soft capsule contents system, vitamin C maintains the complex structure established in Example 1 with fish collagen and nano-microgel polysaccharides. Polyols and free polysaccharides participate in the formation of a dense hydrogen bond network, maintaining the stability of the active ingredients while also considering the rheological and storage stability of the contents. This verifies the rationality of the formulation in constructing nano-encapsulation and synergistic stability of the system.

[0098] Figure 9To obtain the retention-time curves of vitamin C under different water activity conditions during storage at 40 °C and 75% RH, the following parameters were kept constant: the composition of the contents, the glycerol:sorbitol mass ratio of 45:55, the single-capsule weight of 2.0 g, and the initial vitamin C content of approximately 350 mg / capsule. The low-aw control sample A' had the same formulation as Example 1, except that the dehydration time was extended or the drying intensity was increased during the drying stage, reducing the water activity to approximately 0.35; the aw of the Example 1 sample was 0.45; the high-aw control sample B' was Comparative Example 14, with a lower degree of drying and a water activity of approximately 0.62. The variable parameter was the water activity level obtained by adjusting the drying process for the above three samples, and the vitamin C content was monitored at 0, 1, 3, and 6 months. The results showed that sample A' with aw≈0.35 had a retention rate of approximately 99% at 1 month, but this dropped to approximately 90% and 80% at 3 and 6 months, respectively. Later, the cumulative loss increased due to the capsule shell's brittleness, microcracks, and leakage. Sample 1 with aw=0.45 had retention rates of approximately 98%, 93%, and 88% at 1, 3, and 6 months, respectively, with a gentle decline along the curve and no obvious structural damage, exhibiting the best overall performance. Sample B' with aw=0.62 had retention rates of approximately 96%, 80%, and 65% at 1, 3, and 6 months, showing a typical accelerated oxidative decay trajectory. Comparison of the three curves showed that the decay rate of vitamin C over time was significantly reduced under moderate water activity, and the capsule morphology and leakage were well controlled. This demonstrates that, based on formulation and rheological parameter optimization, maintaining aw at approximately 0.45 is a crucial condition for achieving high retention of active ingredients and overall capsule quality during long-term storage.

[0099] Figure 10 The antioxidant nano-microgel spray powder of Example 1 shown exhibits regular, nearly spherical particles with a relatively dense surface, demonstrating good shape retention and repeatability during the spraying process. Simultaneously, the precursor nano-microgel has an average particle size of approximately 270 nm. The morphology image shows relatively smooth particle surfaces and local cross-sections, without significant large-scale crystal precipitation or severe aggregation. This indicates that the fish collagen peptides, vitamin C, and nano-microgel polysaccharides maintained their pre-constructed nanoscale self-assembled structure during spray drying and were uniformly encapsulated within the micron-sized carrier particles. Combined with the spray powder's low moisture content of only 3.5 wt% and the absence of particle surface collapse and severe adhesion, it can be inferred that its internal structure is stable, with a reasonable specific surface area and barrier interface, which is beneficial for inhibiting the oxidative degradation of vitamin C. Both morphology and particle size aspects support the fact that the preparation process of this example can obtain antioxidant nano-microgel spray powder with uniform structure and good stability.

[0100] As can be seen from the performance of the examples and comparative examples in Table 1, the present invention achieves a balance between high vitamin C encapsulation rate and low viscosity and low water activity of the contents through the synergistic formulation of the nano-microgel polysaccharide components, the combined use of polyol humectants, and precise pH control and spray drying process parameter design. The vitamin C encapsulation rates of Examples 1-4 all reached over 85%, significantly better than those of Comparative Example 1 (76.3%), Comparative Example 3 (72.5%), Comparative Example 5 (69.2%), and Comparative Example 6 (64.8%). This demonstrates that the synergistic effect of resistant dextrin and sodium alginate in the nano-microgel polysaccharide components, the suitable self-assembly pH value (3.8-4.2), and the optimized spray drying temperature (150-170℃ inlet temperature) are crucial for the encapsulation and protection of vitamin C. The viscosity of the examples was controlled within the range of 0.8-2.0 Pa·s, meeting the requirements of the soft capsule filling process. Comparative Example 8, however, had a viscosity of 2.15 Pa·s due to excessively high solid content, while Comparative Example 5 had a viscosity of only 0.85 Pa·s due to excessively low pH, and its nano-microgel structure was unstable. The water activity of the examples was controlled within the range of 0.35-0.55, effectively inhibiting microbial growth and extending shelf life. Comparative Examples 9, 13, and 14, however, had excessive water activity (>0.58) due to improper drying conditions, resulting in a significant decrease in the 90-day retention rate of Vitamin C in the accelerated testing to 68.5-76.8%, far lower than the 91.3-94.1% of the examples. The combined use of polyol humectants (comparative example 2 uses only glycerin) can improve the flexibility of soft capsules and prevent plasticization of the shell-core interface. Controlling the nanogel particle size within the range of 150-400 nm (example 2 uses 70-370 nm) ensures both encapsulation efficiency and redispersibility. In contrast, the excessively small particle size (120 nm) in comparative example 7 leads to particle agglomeration during spray drying, while the excessively high spray temperature in comparative example 6 results in oxidative degradation of vitamin C and a decrease in crystallinity. In summary, the technical solution of this invention systematically solves the contradiction between microstructural stability, processing suitability, and activity maintenance of the vitamin C-fish collagen peptide-polysaccharide nanogel system in soft capsule applications through multi-component synergy and multi-parameter coupling optimization.

[0101] Table 1 Performance summary of examples and comparative examples Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A soft capsule containing a combination of acerola cherry vitamin C and fish collagen, characterized in that, Based on a single capsule weight of 1.6–2.4 g, the contents of the soft capsules, by weight, include: 30–55 parts antioxidant nano-microgel spray powder; 20–35 parts polyol moisturizer; 3–10 parts of free polysaccharide components; 10–25 parts water; 0.5–3 parts buffer salt and antioxidant, wherein the sum of the mass parts of the buffer salt and antioxidant is 0.5–3; 1.0–5.0 parts acerola cherry extract; The antioxidant nano-microgel spray powder is composed of particles obtained by self-assembly of fish collagen peptides, vitamin C, and nano-microgel polysaccharide components under acidic conditions to form nano-microgels, and then spray drying. The nano-microgels encapsulate vitamin C through hydrogen bonds and electrostatic interactions. Based on the total mass of the solids in the spray powder, the mass fraction of fish collagen peptides is 50–80 wt%, the mass fraction of vitamin C is 5–20 wt%, and the mass fraction of nano-microgel polysaccharide components is 15–30 wt%.

2. The acerola cherry vitamin C and fish collagen compound soft capsule as described in claim 1, characterized in that, The preparation method of the antioxidant nano-microgel spray powder includes the following steps: a) Dissolve fish collagen peptides, vitamin C and nano-microgel polysaccharide components in a citric acid and trisodium citrate buffer solution with a pH of 3.8–4.2 to obtain a solution with a solid content of 5–15 wt%, and stir at a temperature of 25–30℃ for 30–60 min to obtain a homogeneous mixed solution. b) Adjust the pH of the mixed solution to 4.0±0.2 and let it stand at room temperature for 0.5–2 h to allow the fish collagen peptides, vitamin C and nano-microgel polysaccharide components to self-assemble into nano-microgels, and control the average particle size of the obtained nano-microgels to be 150–400 nm. c) The nano-microgel dispersion is fed into a spray drying device and spray dried under the conditions of inlet temperature of 150–170℃, outlet temperature of 75–85℃, and atomization pressure of 0.8–1.5 MPa. The resulting spray powder has a median particle size D50 of 5–20 μm and a moisture content of no more than 5 wt%.

3. The acerola cherry vitamin C and fish collagen compound soft capsule as described in claim 1, characterized in that, The antioxidant nano-microgel spray powder, based on the total mass of the spray powder solids, has a fish collagen peptide mass fraction of 50–80 wt%, a vitamin C mass fraction of 5–20 wt%, and a nano-microgel polysaccharide mass fraction of 15–30 wt%.

4. The acerola cherry vitamin C and fish collagen compound soft capsule as described in claim 1, characterized in that, Both the free polysaccharide component and the nano-microgel polysaccharide component are selected from one or more of resistant dextrin, pectin, and sodium alginate; The nano-microgel polysaccharide component is selected from one or more of resistant dextrin, pectin, and sodium alginate; Preferably, the nano-microgel polysaccharide component includes at least resistant dextrin and sodium alginate, and based on the total mass of the nano-microgel polysaccharide component, resistant dextrin accounts for 40–80 wt% and sodium alginate accounts for 20–60 wt%.

5. A soft capsule containing acerola cherry vitamin C and fish collagen as described in claim 1, characterized in that, The polyol moisturizer is selected from one or more of glycerin, sorbitol and maltitol; preferably, the polyol moisturizer includes at least glycerin and sorbitol, and in the polyol moisturizer, glycerin accounts for 30-60 wt% and sorbitol accounts for 40-70 wt%.

6. The acerola cherry vitamin C and fish collagen compound soft capsule as described in claim 1, characterized in that, The buffer salt comprises citric acid and trisodium citrate, which are prepared in a molar ratio of 1:(2.5–3.5) and are used to adjust the pH of the soft capsule contents to 4.0±0.

3. The antioxidant includes vitamin C and / or sodium ascorbate, wherein the conversion factor for sodium ascorbate to vitamin C is 0.89, and the total vitamin C content per soft capsule is 200–500 mg. The antioxidant may further include vitamin E acetate, with the amount of vitamin E acetate added relative to the total mass of the soft capsule contents being 0.01–0.20 wt%. The protein content provided by fish collagen peptides per single soft capsule is no less than 500 mg.

7. A soft capsule containing acerola cherry vitamin C and fish collagen as described in claim 1, characterized in that, The contents of the soft capsules have a solid content of 55–75 wt%, a viscosity of 0.8–2.0 Pa·s, a pH of 3.8–4.5, and a water activity of 0.35–0.55 at a temperature of 25–35°C, wherein the water activity is preferably measured at a temperature of 25°C.

8. A soft capsule containing acerola cherry vitamin C and fish collagen as described in claim 1, characterized in that, The antioxidant includes sodium ascorbate, added at an amount of 0.1–0.5 wt% relative to the total mass of the soft capsule contents, and may further include vitamin E acetate, added at an amount of 0.01–0.20 wt% relative to the total mass of the soft capsule contents.

9. A method for preparing a soft capsule containing a combination of acerola cherry vitamin C and fish collagen as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Prepare the antioxidant nano-microgel spray powder; S2. The antioxidant nano-microgel spray powder, polyol moisturizer, free polysaccharide component, buffer salt, antioxidant, and water are added to a mixing tank according to the specified ratio. The mixture is stirred at 25–35℃ for 1–2 h to obtain a homogeneous mixture. Vacuum degassing is then performed to ensure that the residual bubble volume fraction is not higher than 1 vol%. S3. Detect the solid content, viscosity and pH value of the soft capsule contents online, and adjust them to maintain a solid content of 55–75 wt%, a viscosity of 0.8–2.0 Pa·s and a pH value of 3.8–4.

5. S4. The contents obtained in step S3 are transported to a soft capsule machine and filled and sealed under the conditions of shell temperature of 60–70℃ and contents temperature of 25–35℃ to obtain wet capsules. S5. Dry at a temperature of 20–25℃ and a relative humidity of 20–30% for 48–72 h to obtain the finished soft capsules.

10. The preparation method of a soft capsule containing acerola cherry vitamin C and fish collagen as described in claim 9, characterized in that, In step S5, the drying process of the soft capsule controls the final water activity of the soft capsule contents to be 0.35–0.55, which is preferably measured at a temperature of 25°C.

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