Stabilizer for pickering emulsion and application thereof

Abstract

This invention provides a stabilizer for Pickering emulsions and its application, relating to the field of Pickering emulsion preparation technology. The stabilizer for Pickering emulsions is 6'- O It is obtained by compounding α-caffeoyl arbutin and cellulose nanocrystals, and in specific applications, 6'- O Pickering emulsions are prepared by mixing caffeoyl arbutin and cellulose nanocrystals in an aqueous phase with an oil phase. This invention overcomes the shortcomings of existing technologies, effectively improves the stability of Pickering emulsions, and further enhances their antioxidant effects, thereby increasing their application value.

Description

Technical Field

[0001] This invention relates to the field of Pickering emulsion preparation technology, and more specifically to a stabilizer for Pickering emulsions and its application. Background Technology

[0002] With the growing demand for green and sustainable materials in the cosmetics, food, and drug delivery systems industries, Pickering emulsions based on natural polymers and nanoparticles have gradually become a research hotspot. Pickering emulsions are emulsions stabilized by solid particles as emulsifiers, and compared with traditional emulsions using surfactants, they have better thermodynamic stability, lower toxicity, and superior performance in multiphase systems.

[0003] The stability of Pickering emulsions stems from the irreversible adsorption of solid particles, which form a dense film at the oil-water interface, effectively preventing droplet aggregation and co-growth. Compared to traditional surfactant emulsions, Pickering emulsions exhibit superior physicochemical stability, particularly under heat treatment and pH variations. Due to this enhanced stability, Pickering emulsions have wide applications in cosmetics, food, and pharmaceuticals. Especially in active molecule delivery and food packaging, Pickering emulsions act as carriers to stabilize the release of bioactive substances, increasing their bioavailability and shelf life.

[0004] To improve the stability of Pickering emulsions, stabilizers are typically added. However, most existing stabilizers are micron or nano-sized solid particles. These particles stabilize the emulsion by forming a physical barrier at the oil-water interface, preventing droplet aggregation. However, these stabilizers have limited applications in current fields. Furthermore, the antioxidant effect of the Pickering emulsion itself is a key research focus at this stage. Therefore, enhancing the antioxidant effect of Pickering emulsions while improving their stability is the main research direction at present. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a stabilizer for Pickering emulsions and its application, which effectively improves the stability of Pickering emulsions and further enhances their antioxidant effects, thereby increasing the application value of Pickering emulsions.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A stabilizer for Pickering emulsions, said stabilizer comprising the following components in parts by weight: 6'- O- 5-20 parts of caffeoyl arbutin (CA) and 30-50 parts of cellulose nanocrystals (CNCs).

[0008] The above-mentioned stabilizer for Pickering emulsions is used in the preparation of Pickering emulsions by preparing the stabilizer into an aqueous phase and then mixing it with an oil phase to prepare the Pickering emulsion.

[0009] Preferably, the method of formulating the stabilizer into an aqueous phase includes the following steps:

[0010] S1-1. Cellulose nanocrystals were added to deionized water and prepared into a cellulose nanocrystal suspension using an ultrasonic cell disruptor.

[0011] S1-2, Add 6'- to the cellulose nanocrystal suspension O - Caffeoyl arbutin was stirred at 7000-10000 r / min for 1-3 min, followed by ultrasonic treatment to obtain a CA / CNCs composite aqueous suspension as the aqueous phase.

[0012] Preferably, the ultrasonic treatment in step S1-2 is performed at 200W for 3 minutes.

[0013] Preferably, in the aqueous phase, 6'- O - The mass concentration of caffeoyl arbutin is 0.05%-0.2%, and the mass concentration of cellulose nanocrystals is 0.3%-0.5%.

[0014] Preferably, the specific method for preparing the Pickering emulsion by mixing the stabilizer in an aqueous phase with the oil phase includes the following steps:

[0015] S2-1. Mix the aqueous phase and oil phase and stir to pre-emulsify, and then prepare a pre-emulsion for later use.

[0016] S2-2. The pre-emulsion is ultrasonically treated under ice-water bath conditions to obtain Pickering emulsion.

[0017] Preferably, the volume ratio of the aqueous phase to the oil phase in step S2-1 is 3-5:1.

[0018] Preferably, the pre-emulsification process in step S2-1 involves stirring at a speed of 1000-1400 r / min for 1-3 minutes.

[0019] Preferably, the ultrasonic treatment power in step S2-2 is 200-300W, and the treatment time is 3-8min.

[0020] This invention provides a stabilizer for Pickering emulsions and its application, which has the following advantages compared with the prior art:

[0021] This invention uses 6'- O The preparation of an aqueous phase by combining caffeoyl arbutin and cellulose nanocrystals, followed by mixing with the oil phase, can significantly improve the static storage stability and dynamic mechanical stability of the prepared O / W Pickering emulsion. Furthermore, it enhances the antioxidant effect of the Pickering emulsion, making it a promising candidate for applications in functional cosmetics, health foods, and drug delivery systems where stability and oxidative protection are critical. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of CA suspensions and CA / CNCs suspensions with different CA mass concentrations in Example 1 of the present invention. From left to right, the mass concentrations of CA in the CA suspension and CA / CNCs suspension are 0 wt.%, 0.025 wt.%, 0.05 wt.%, 0.1 wt.%, and 0.2 wt.%, respectively.

[0023] Figure 2 This is a schematic diagram of the zeta potential of CA suspensions with different CA mass concentrations in embodiments of the present invention;

[0024] Figure 3 This is a schematic diagram of the zeta potential of CA / CNCs suspensions with different CA mass concentrations in Example 1 of the present invention;

[0025] Figure 4 This is a schematic diagram of CNCs suspensions and CA / CNCs suspensions with different CNCs mass concentrations in Example 1 of the present invention. From left to right, the mass concentrations of CNCs in the CNCs suspension and CA / CNCs suspension are 0 wt.%, 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, and 0.5 wt.%.

[0026] Figure 5 This is a schematic diagram of the zeta potential of CNCs suspensions with different CNCs mass concentrations in Example 1 of the present invention;

[0027] Figure 6 This is a schematic diagram of the zeta potential of CA / CNCs suspensions with different CNCs mass concentrations in Example 1 of the present invention;

[0028] Figure 7This is a schematic diagram showing the layering of Pickering emulsions prepared from aqueous phases with different CNCs mass concentrations after 7 days of storage in Example 2 of the present invention. The CNCs mass concentrations from left to right are 0 wt.%, 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, and 0.5 wt.%.

[0029] Figure 8 This is a schematic diagram showing the emulsification rate, PDI, and zeta potential of Pickering emulsions prepared in aqueous phase with different CNCs mass concentrations and stored for 7 days in Example 2 of the present invention.

[0030] Figure 9 This is a schematic diagram of Pickering emulsions prepared by different aqueous phases in Example 2 of the present invention. From left to right, the aqueous phases are deionized water, CA suspension, CNCs suspension and CA / CNCs suspension, respectively.

[0031] Figure 10 This is a schematic diagram showing the droplet diameters of Pickering emulsions prepared with different aqueous phases in Example 2 of the present invention;

[0032] Figure 11 These are micrographs (images under an optical microscope at 400x magnification) showing the morphological changes of Pickering emulsions prepared with different aqueous phases in Example 2 of the present invention, where a is the blank group, b is the CA group, c is the CNCs group, and d is the CA / CNCs group.

[0033] Figure 12 This is a schematic diagram of the spatial structure of Pickering emulsions prepared with different aqueous phases in Example 2 of the present invention; where a is the blank group, b is the CA group, c is the CNCs group, and d is the CA / CNCs group;

[0034] Figure 13 This is a schematic diagram of the staining results of Pickering emulsions prepared with different aqueous phases in Example 2 of the present invention (images at 630x magnification using a laser scanning confocal microscope); where a is the blank group, b is the CA group, c is the CNCs group, and d is the CA / CNCs group;

[0035] Figure 14 The images shown are TIP measurement images of Pickering emulsion after 7 days of storage in Example 3 of the present invention, where a is the blank group, b is the CA group, c is the CNCs group, and d is the CA / CNCs group.

[0036] Figure 15 This is a schematic diagram showing the viscosity changes of emulsions prepared with different aqueous phases under different shear stresses in Example 4 of the present invention;

[0037] Figure 16This is a schematic diagram of the storage modulus and loss modulus of emulsions prepared with different aqueous phases in Example 4 of the present invention;

[0038] Figure 17 This is a schematic diagram of the DPPH scavenging ability of each group of emulsions in Example 5 of the present invention;

[0039] Figure 18 ABTS of each group of emulsions in Example 5 of this invention + • Diagram illustrating clearance capabilities;

[0040] Figure 19 This is a schematic diagram showing the change in curcumin encapsulation rate in Pickering emulsion under different light conditions in Example 6 of the present invention;

[0041] Figure 20 This is a schematic diagram showing the changes in particle size, PDI, and zeta potential of Pickering emulsion under different temperature conditions in Example 6 of the present invention.

[0042] Figure 21 This is a schematic diagram showing the changes in particle size, PDI, and zeta potential of Pickering emulsion under different pH conditions in Example 6 of the present invention. Detailed Implementation

[0043] 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 in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The specific preparation method of cellulose nanocrystals used in the following examples is as follows:

[0045] First, lignin and hemicellulose in wood were removed using microwave-assisted eutectic solvent (DES) in conjunction with hydrogen peroxide (H2O2) to prepare cellulose. A choline chloride / lactic acid (ChCl / LA) DES system was prepared at a molar ratio of 1:2. Wood flour was mixed with DES at a solid-liquid ratio of 1:20 (g / mL), and the mixture was stirred at 200 W microwave power and 130℃ for 30 min. After the reaction, the mixture was filtered, and the filter cake was washed with deionized water until neutral. After preliminary decolorization with anhydrous ethanol, it was further treated with 30% H2O2 at 75℃ until white, washed with deionized water until neutral, and then freeze-dried under vacuum to constant weight to obtain wood cellulose with lignin and hemicellulose removed. Then, the wood cellulose was mixed with deionized water at a mass concentration of 0.2 wt.% to prepare a suspension. This suspension was ultrasonically treated at a frequency of 20 kHz and an output power of 1200 W for 30 min to obtain a CNCs suspension. Finally, the CNCs were obtained by filtration to remove water, washing the filter cake, and freeze-drying. Example 1:

[0046] 1. Preparation of CA / CNCs aqueous suspension:

[0047] (1) CNCs were added to deionized water and then an aqueous suspension of CNCs was prepared using an ultrasonic cell disruptor (450 W, 30 min).

[0048] (2) Add CA to the CNCs aqueous suspension, first stir at 8000 r / min for 1 min, then use 200 W ultrasonic treatment for 3 min to prepare CA / CNCs aqueous suspension;

[0049] 2. Following the preparation method described above, CNCs with a constant mass concentration (0.2 wt.%) were prepared, 6'- O - CA / CNCs suspension with caffeoyl arbutin concentrations of 0 wt.%, 0.025 wt.%, 0.05 wt.%, 0.1 wt.%, and 0.2 wt.%;

[0050] Additionally, 6'- O - Caffeoyl arbutin was directly added to deionized water and stirred at 8000 r / min for 1 min, followed by ultrasonic treatment at 200 W for 3 min to prepare CA suspensions with CA mass concentrations of 0 wt.%, 0.025 wt.%, 0.05 wt.%, 0.1 wt.%, and 0.2 wt.%.

[0051] 3. Detect the morphology and stability of CA suspensions and CA / CNCs suspensions with different CA mass concentrations:

[0052] (1) The morphology of CA suspensions and CA / CNCs suspensions with different CA mass concentrations is as follows: Figure 1 As shown (and the mass concentrations of CA from left to right are 0 wt.%, 0.025 wt.%, 0.05 wt.%, 0.1 wt.%, and 0.2 wt.%).

[0053] For CA suspensions: no obvious flocculation was observed in the suspensions, and because CA is slightly soluble in water, a suspension was only formed when the CA mass concentration reached 0.1 wt.%.

[0054] For CA / CNCs suspensions: as CA increases from 0 wt.% to 0.05 wt.%, the transparency of CA / CNCs suspensions increases significantly. This is because hydrogen bonds are formed between water-soluble CA and the CNCs network, which makes the partially aggregated nanoparticles uniformly dispersed.

[0055] Comparing the CA suspension and the CA / CNCs suspension in the figures above and below, the addition of CNCs makes the suspension more transparent and milky white, and more uniform overall, at CA concentrations of 0.1 wt.% and 0.2 wt.%. This indicates that even water-insoluble CA particles can form hydrogen bonds with the CNCs network, improving the dispersibility of the suspension.

[0056] (2) Zeta potential of CA suspensions and CA / CNCs suspensions with different CA mass concentrations:

[0057] Zeta potential, as a core electrochemical parameter for the stability of colloidal systems, directly characterizes the electrostatic repulsion potential energy between dispersed phase particles. The smaller the molecules or dispersed particles, the higher the absolute value of the zeta potential, which effectively inhibits Ostwald ripening and heterogeneous aggregation. Conversely, the lower the absolute value of the zeta potential, the greater the tendency for coagulation or agglomeration, leading to irreversible flocculation of the dispersed phase. When the absolute value of the zeta potential exceeds 30 mV, the emulsion exhibits high stability.

[0058] Specific zeta potential detection results are as follows: Figure 2 and Figure 3 As shown:

[0059] In CA suspension ( Figure 2 The stability of CA suspension increases with increasing CA concentration, and the zeta potential of the suspension tends to stabilize when the CA concentration reaches 0.1 wt.%.

[0060] In CA / CNCs suspension ( Figure 3In a 0.2 wt.% CNCs suspension, appropriately increasing CA (0-0.1 wt.%) can improve the stability of the suspension. However, when CA reaches 0.2 wt.%, the stability of the suspension decreases.

[0061] 4. Following the preparation method in step 1 above, prepare CA / CNCs suspensions with constant CA mass concentration (0.1 wt.%) and different CNCs mass concentrations (CNCs mass concentrations of 0 wt.%, 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, and 0.5 wt.%).

[0062] In addition, CNCs of different masses were added to deionized water, and CNCs suspensions of different mass concentrations were prepared by ultrasonic cell disruptor (450 W, 30 min) (CNCs mass concentrations were 0 wt.%, 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%).

[0063] 5. Detect the morphology and stability of CNCs suspensions and CA / CNCs suspensions with different CNCs mass concentrations:

[0064] (1) The morphology of CNCs suspensions with different CNCs mass concentrations and CA / CNCs suspensions are as follows: Figure 4 As shown (and the mass concentrations of CNCs from left to right are 0 wt.%, 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, and 0.5 wt.%).

[0065] Figure 4 When the mass concentration of CNCs is 0.05 wt.% or 0.1 wt.%, the CNCs suspension exhibits slight flocculation and stratification. However, with the addition of CA, the stratification of the CA / CNCs suspension is significantly improved, and the overall suspension becomes more uniform.

[0066] (2) Zeta potential of CNCs suspensions with different CNCs mass concentrations and CA / CNCs suspensions:

[0067] Specific results are as follows Figure 5 and Figure 6 As shown, Figure 5 The stability of the CNCs suspension gradually increased with the increase of CNCs mass concentration, and the zeta potential trend tended to stabilize after CNCs reached 0.3 wt.%. Figure 6The stability of the CA / CNCs suspension at the corresponding CNCs mass concentration improved compared to the CNCs suspension when a fixed mass concentration of CA (0.1 wt.%) was added.

[0068] The above tests show that the CA / CNCs suspension is most stable when the CA mass concentration is 0.1 wt.% and the CNCs mass concentration is 0.3 wt.%. Example 2:

[0069] Referring to Example 1 above, a CA / CNCs suspension was prepared as an aqueous phase for later use;

[0070] Mix 0.025 g curcumin with 50 g olive oil and stir magnetically at 60°C for 3 h until curcumin dissolves; this mixture is the oil phase.

[0071] The aqueous phase and oil phase were mixed at a volume ratio of 4:1 and stirred at 12,000 rpm for 1 min for pre-emulsification, followed by ultrasonic treatment at 250 W for 5 min to obtain Pickering emulsion.

[0072] 1. Limiting the ratio of CA to CNCs in the aqueous phase to 1:3, and using the mass concentration of CNCs as the standard, prepare different Pickering emulsions by preparing aqueous phases with CNCs mass concentrations of 0 wt.%, 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, and 0.5 wt.%.

[0073] The emulsion performance and emulsion phase volume fraction of Pickering emulsions with different CNCs mass concentrations in the aqueous phase were detected after 7 days of storage. Specific results are as follows: Figure 7 and Figure 8 As shown:

[0074] Figure 7 From left to right, the images show the layering of Pickering emulsions prepared with CNCs concentrations of 0 wt.%, 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, and 0.5 wt.% in the aqueous phase after 7 days of storage. As the CNCs concentration in the aqueous phase increases, the emulsification rate of the emulsion gradually increases. When the CNCs concentration is 0.3 wt.% (CA 0.1 wt.%), the emulsion layer tends to stabilize.

[0075] Figure 8 As the mass concentration of CA / CNCs increases, the absolute value of the zeta potential increases and the PDI decreases, indicating that the emulsion is more stable and the droplet size is more uniform. Uniformity is the key to ensuring the consistency of Pickering emulsion quality and performance.

[0076] 2. Using 0.3 wt.% CNCs suspension, 0.1 wt.% CA suspension, and CA / CNCs suspension with CA concentration of 0.1 wt.% and CNCs concentration of 0.3 wt.% as the aqueous phase, Pickering emulsions with different aqueous phases were prepared according to the preparation method described above.

[0077] (1) Observe the volume fraction of the emulsion phase in each group of Pickering emulsions, specifically as follows: Figure 9 As shown in the figure, the aqueous phases of the Pickering emulsion from left to right are deionized water (NC), CA suspension, CNCs suspension, and CA / CNCs suspension, respectively. As can be seen from the figure, CNCs can be absorbed at the oil-water interface without the introduction of CA. Due to the charge repulsion between CNCs, their hydrogen bond network is unstable, resulting in relatively poor emulsion stability. After adding CA to CNCs, CNCs flocculate, the particle size increases, more connections are formed at the oil-water interface, the shell is more compact, and the stability of the Pickering emulsion is further improved. CA is not suitable as a dispersant alone for preparing Pickering emulsions.

[0078] (2) Based on this, a nanoparticle size potentiometer was used to detect the droplet diameter of each group of Pickering emulsions. The specific results are shown in [the table below]. Figure 10 The diameter of the emulsion droplets decreased with the addition of CA, and the same trend was observed when CA was added to CNCs. This is because hydrogen bonds were formed between CA and CNCs, causing CA to adsorb onto the surface of CNCs, which weakened the electrostatic repulsion between CNCs and improved the stability of the emulsion.

[0079] (3) Observe the morphological changes of Pickering emulsions prepared with different aqueous phases using an optical microscope, specifically as follows: Figure 11 As shown, Figure 11 Figure a shows that when deionized water is in the aqueous phase (blank group), the emulsion droplets are small in size but exhibit significant heterogeneity in distribution; Figure 11 Figure b shows that when CA suspension is used as the aqueous phase (CA group), the droplet size is reduced and the dispersion uniformity is improved; Figure 11 The data in the middle section shows that when the CNCs suspension is in aqueous phase (CNCs group), the average droplet diameter increases, but it exhibits better monodispersity and dense packing characteristics. Figure 11 The data in the middle section shows that when the CA / CNCs suspension is used as the aqueous phase (CA / CNCs group), the droplet diameter is smaller and the uniformity of distribution is further improved. At this time, the average droplet diameter is 3.26 μm, the emulsion stability is the best, and the emulsification rate is the highest.

[0080] (4) Microscopic analysis of each group of Pickering emulsions was performed using cryo-scanning electron microscopy and laser confocal scanning microscopy:

[0081] After the prepared sample was left to stand for one week and shaken, the spatial structure of the emulsion was observed under a cryo-scanning electron microscope. Figure 12 As shown; among which CA group ( Figure 12 (b) The emulsion, after one week of storage, compared to the control group ( Figure 12 The emulsion in group a) did not have a large area of ​​dispersed oil layer, indicating that CA has a certain emulsifying effect; the CNCs group ( Figure 12 In emulsion c), most droplets are entangled together to form a network structure through connection and dispersion. This is because the charge repulsion between CNCs causes them to disperse into the aqueous phase. CNCs tend to be discretely distributed in the aqueous system, resulting in a significant reduction in their interfacial coverage at the oil-water interface; CA / CNCs group ( Figure 12 Cryo-scanning electron microscopy characterization of the emulsion (d) revealed a high-density monodisperse droplet arrangement. Compared to the CA and CNCs groups, the three-dimensional network structure formed by CNCs dissociated in this composite system, with residual fiber bundles observed only in local droplet gaps. The droplet size uniformity within the system was significantly improved, and the CA / CNCs composite formed heterogeneous adsorption domains at the interface, thereby endowing the emulsion with excellent long-term stability.

[0082] The microstructure and distribution characteristics of Pickering emulsions were further characterized using CLSM; Nile red (488 / 539) and Nile blue (365 / 435) were used to stain the aqueous and oil phases of stable emulsions from different aqueous groups (blank group, CA group, CNCs group, and CA / CNCs group), respectively. The results are as follows: Figure 13 As shown:

[0083] In the blank group ( Figure 13 The droplets in group a) exhibited trailing flow dynamics, showing extreme instability; the CNCs group ( Figure 13 (c) and CA / CNCs group ( Figure 13 The emulsion in group d) exhibits a larger droplet size, mainly due to the presence of CNCs, but it also has good interfacial coverage and stability, forming a robust and uniquely shaped structure with a tightly ordered interfacial structure; the CA group ( Figure 13 Although the droplet size of the emulsion in group b) was smaller than that in the CNCs group and the CA / CNCs group, the distribution was relatively dispersed, and no obvious blue interface ring was observed. In particular, a clear blue interface ring was observed in the CA / CNCs group by CLSM. Figure 13(d). The blue interfacial rings demonstrate particle adsorption and interfacial film formation at the interface. The blue rings are more pronounced in the CA / CNCs group and completely cover the oil droplets, indicating that the adsorption of CA and CNCs promotes the formation of a dense structure, which helps to form a strong physical barrier to prevent droplet aggregation. The hydrogen bonding interaction between CA and CNCs is the reason for the stronger interfacial film induced. In addition, the formation of a hydrogen bond network in the continuous phase ensures the high stability of the emulsion, with particles simultaneously anchored and adsorbed between two or more oil droplets, forming an emulsion network structure. Example 3:

[0084] Interfacial tension identification of each emulsion group:

[0085] The interfacial tension (IFT) between the aqueous phase (deionized water, CA suspension, CNCs suspension, and CA / CNCs suspension) and the oil phase (olive oil) was measured using a surface tension meter (SZ-CAMC32). Figure 14 )

[0086] The experiment investigated the effect of varying the aqueous phase composition on interfacial tension by fixing the CNCs mass concentration at 0.3 wt.% and the CA mass concentration at 0.1 wt.%. The results are shown in Table 1. When the CA suspension served as an aqueous-phase stable emulsion, the interfacial tension (122.43 mN / m) was significantly higher than that of the blank group (5.65 mN / m) and the CNCs suspension system (12.15 mN / m). Compared to the CNCs system without CA, the oil-water interfacial tension of the CA / CNCs system with added CA also increased (29.19 mN / m), but it was still much lower than the interfacial tension between the aqueous and oil phases in the CA suspension. This indicates that CA and CNCs were effectively combined. Theoretical derivation suggests that increased oil-water interfacial tension weakens emulsion stability, but this study found that the CA-modified CNCs system exhibited an anomalous synergistic effect. This contradictory phenomenon stems from the regulatory advantage of the hydrogen bond network between CA and CNCs on interfacial adsorption kinetics, whose dominant role significantly outweighs the effect of simple interfacial tension changes on stability.

[0087] The specific results are shown in Table 1 below:

[0088] Table 1

[0089] Example 4:

[0090] Rheological testing:

[0091] Pickering emulsions prepared with different aqueous phases were tested. All emulsions exhibited shear thinning under steady shear stress.

[0092] See details Figure 15The emulsion viscosities of the CA, CNCs, and CA / CNCs groups were all higher than the control group. The emulsion viscosity of the CA / CNCs group was lower than that of the CA and CNCs groups, reflecting the interaction between CA and CNCs. Furthermore, considering that the emulsification rates of the control and CA groups were far lower than those of the CNCs and CA / CNCs groups, the emulsification rate significantly improved with increasing shear viscosity. The viscosity of the CNCs and CA / CNCs groups changed more linearly with shear rate. Overall, the addition of CNCs significantly improved the emulsification rate. The addition of CA to CNCs weakened the hydrogen bond network between CNCs due to the hydrogen bonding between them, resulting in a decrease in emulsion shear viscosity and better flowability.

[0093] Rheological property characterization data such as Figure 16 As shown, the viscoelastic response of the Pickering emulsion is revealed: the storage modulus (G') is consistently higher than the loss modulus (G") across the entire frequency domain, confirming that the system possesses solid-like viscoelastic response characteristics. In the CA group, the values ​​of G' and G" are close, indicating that the system is in a dynamic equilibrium between elastic recovery and viscous dissipation during deformation, leading to a relatively weakened structural stability. In the CNCs group and the CA / CNCs group, the viscoelastic modulus of the emulsion increases, and the increase in G' is significantly higher than that in G", which confirms that CNCs can effectively enhance the structural stability of the emulsion. Example 5:

[0094] Verification of the effect of water in CA / CNCs suspension on the antioxidant effect of Pickering emulsion:

[0095] A 0.3 wt.% CNCs suspension, a 0.1 wt.% CA suspension, and a CA / CNCs suspension with a CA mass concentration of 0.1 wt.% and a CNCs mass concentration of 0.3 wt.% were prepared as the aqueous phase, referring to the above embodiments.

[0096] Different Pickering emulsions were prepared using olive oil with or without curcumin as the oil phase (see Example 2 for specific preparation methods and parameters).

[0097] Evaluation of DPPH· and ABTS of Pickering emulsions (with / without curcumin) formulated with different aqueous phases + ·;

[0098] Specific results are as follows Figure 17The diagram shows the DPPH· scavenging capacity of each emulsion group, indicating that the DPPH· scavenging capacity is related to the addition of curcumin, CA, and CNCs. The Pickering emulsion encapsulated with curcumin showed a better DPPH· scavenging rate than the emulsion without curcumin encapsulation. CNCs did not show a significant DPPH· scavenging capacity, but their addition improved the DPPH· scavenging capacity of the curcumin-encapsulated Pickering emulsion. When CA was used alone as a stabilizer, the Pickering emulsion stabilized by CA did not effectively encapsulate curcumin in terms of DPPH· scavenging capacity. However, the overall DPPH· scavenging capacity of the CA suspension as an aqueous phase was not high. This is because CA degrades rapidly and loses its antioxidant activity when stored in a natural environment without any protective mechanism. Regardless of whether curcumin was encapsulated, the Pickering emulsion stabilized by CA / CNCs showed the best DPPH· scavenging capacity in its group, indicating that the CA / CNCs system can effectively protect CA and enable it to exert its corresponding antioxidant activity.

[0099] Figure 18 ABTS for each emulsion group + • Schematic diagram of scavenging ability, in which the CA / CNCs suspension as a Pickering emulsion prepared in aqueous phase shows better ABTS. + • Scavenging rate and curcumin loading rate. Among these, compared to curcumin, CA showed higher loading rates for ABTS. + The scavenging ability of · accounts for a higher proportion of the antioxidant activity of the emulsion. Furthermore, CNCs did not exhibit significant ABTS. + • Scavenging ability, but like DPPH·, the scavenging rate is higher than that of the blank control group. This is because ultrasonic treatment can enhance the antioxidant capacity of the sample, and the turbulence caused by cavitation effect and physical shearing leads to changes in the emulsion conformation. Example 6:

[0100] Verify the effect of Pickering emulsion with CA / CNCs suspension in aqueous phase on stability:

[0101] Prepare a CA / CNCs suspension as the aqueous phase (CNCs mass concentration is 0.3 wt.%, CA mass concentration is 0.1 wt.%); mix 0.025 g curcumin with 50 g olive oil, and stir magnetically at 60℃ for 3 h until curcumin dissolves, as the oil phase;

[0102] The aqueous phase and oil phase were mixed at a volume ratio of 4:1 and stirred at 12,000 rpm for 1 min for pre-emulsification, followed by ultrasonic treatment at 250 W for 5 min to obtain Pickering emulsion.

[0103] 1. The time-dependent changes in curcumin encapsulation efficiency in Pickering emulsions under different light conditions were detected. Specific results are as follows: Figure 19 As shown:

[0104] During the 30-day observation period, the curcumin encapsulation efficiency of the light-protected emulsion remained consistently above 85% with minimal fluctuations. This stability highlights the positive role of the light-protected environment in maintaining the structural integrity of the emulsion and its curcumin loading capacity. In contrast, the curcumin encapsulation efficiency of the emulsion exposed to natural light gradually decreased after 3 days, dropping to 71.35% by day 15, before stabilizing. This decrease stems from the poor photostability of CA itself. Although the CNCs network initially mitigated CA oxidation at the oil-water interface, prolonged exposure to natural light led to CA degradation. Oxidized CA weakened the intermolecular interactions with CNCs, reducing the emulsion's ability to retain curcumin and thus decreasing the encapsulation efficiency. These findings clearly demonstrate that light exposure disrupts the interfacial interactions between CA and CNCs, which are crucial for curcumin retention. Therefore, light-protected storage is crucial for maintaining high encapsulation efficiency and long-term stability of the emulsion. It preserves the molecular synergy between CA and CNCs, ensuring the stability of curcumin-loaded emulsions. This is of key significance for optimizing shelf life and functional efficacy in antioxidant delivery applications.

[0105] 2. Changes in particle size, PDI, and zeta potential of Pickering emulsions at different temperatures were detected. Specific results are as follows: Figure 19 As shown:

[0106] Within the temperature range of 30-80℃, the average droplet diameter of the Pickering emulsion remained stable at approximately 3.5 μm, and the zeta potential also remained stable at approximately -36 mV. Only the PDI showed a slight upward trend, increasing from approximately 0.22 at 30℃ to approximately 0.32 at 80℃, indicating that temperature primarily affects the uniformity of droplet size distribution. High temperatures weaken hydrogen bonding between CAs and CNCs, as well as within the CNCs network, while enhancing hydrophobic interactions, leading to slight droplet aggregation and a wider droplet size distribution. At 90℃, the static stability of the emulsion was disrupted, with the average droplet diameter increasing to approximately 4 μm and the zeta potential decreasing to approximately -31 mV. The CA-CNCs network at the oil-water interface lost its spatial constraint on the droplets, triggering significant aggregation and partial droplet breakage. Therefore, the temperature range of 30-80℃ better maintains the structural integrity of the emulsion, indicating its good thermal stability.

[0107] 3. Changes in particle size, PDI, and zeta potential of Pickering emulsions at different pH values ​​were detected. Specific results are as follows: Figure 20 As shown:

[0108] As the pH value increases from 3.0 to 7.0, the droplet diameter of the emulsion gradually increases, and the stability decreases. Homogenizing after adjusting the pH value from 7.0 to 11.0 reduces the droplet size but does not improve stability. In an acidic environment, some water-soluble phenolic compounds (CA) undergo protonation, enhancing hydrogen bonding with hydroxyl groups on the surface of cellulose nanofibers (CNCs). Transitioning from acidic to neutral conditions triggers emulsion stratification because CNCs detach from the interface, leading to droplet coarsening and system instability. At pH 11.0, phenolic compounds may react with biopolymers in the suspension, and plant polyphenols are prone to oxidation and oligomerization in dissolved oxygen, forming high-molecular-weight products with low solubility. CA, which already has poor water solubility, further decreases in solubility. CA promotes CNC deposition on the surface through its affinity with nanocellulose via hydrogen bonding, inducing nanofiber crosslinking and constructing a continuous network around the oil droplets, thereby stabilizing the discrete droplets. Therefore, acidic conditions (pH 3.0→7.0) induce oil droplet aggregation and interfacial film weakening, while alkaline conditions (pH 11.0) allow for partial droplet reconstruction. Despite its pH responsiveness, Pickering emulsions maintain better stability in acidic environments, supporting optimization for specific applications and storage conditions.

[0109] In summary, Pickering emulsions with CA / CNCs suspension as the aqueous phase are most stable under light-protected, 30-80℃, and acidic conditions.

[0110] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. Use of a stabilizer for Pickering emulsions in the preparation of a Pickering emulsion, characterized in that: The stabilizer consists of the following parts by mass of the substances: 6' O - caffeoyl arbutin 5-20 parts and cellulose nanocrystal 30-50 parts; The stabilizer is used to prepare Pickering emulsion, and the method of application is to prepare Pickering emulsion by preparing the stabilizer into an aqueous phase and then mixing it with the oil phase. The aqueous phase contained 0.1% by mass of 6'-O-caffeoylarbutin and 0.3% by mass of cellulose nanocrystals. The method of preparing the stabilizer into an aqueous phase includes the following steps: S1-1. Cellulose nanocrystals were added to deionized water and prepared into a cellulose nanocrystal suspension using an ultrasonic cell disruptor. S1-2. 6'-O-caffeoylarbutin was added to the cellulose nanocrystal suspension and stirred at 7000-10000 r / min for 1-3 min, followed by ultrasonic treatment to obtain a 6'-O-caffeoylarbutin / cellulose nanocrystal composite aqueous suspension as the aqueous phase.

2. Use according to claim 1, characterized in that, The specific method for preparing Pickering emulsion by mixing the stabilizer in an aqueous phase with an oil phase includes the following steps: S2-1. Mix the aqueous phase and oil phase and stir to pre-emulsify, and then prepare a pre-emulsion for later use. The volume ratio of the aqueous phase to the oil phase is 3-5:

1. S2-2. The pre-emulsion is ultrasonically treated under ice-water bath conditions to obtain Pickering emulsion.

3. Use according to claim 1, characterized in that: In step S1-2, the ultrasonic treatment method is 200W for 3 minutes.

4. Use according to claim 2, characterized in that: In step S2-1, the pre-emulsification process involves stirring at a speed of 1000-1400 r / min for 1-3 minutes.

5. Use according to claim 2, characterized in that: In step S2-2, the ultrasonic treatment power is 200-300W, and the treatment time is 3-8 minutes.

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