Pickering emulsion containing cellulose nanofibers as well as preparation method and application of Pickering emulsion

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a Pickering emulsion containing cellulose nanofibers as well as a preparation method and application of the Pickering emulsion. The method comprises the following steps: dissolving cellulose nanofibers in water, carrying out ultrasonic treatment, and then mixing with corn oil to obtain an oil-phase-containing emulsion; the emulsion containing the oil phase is placed in a dispersion machine to be dispersed, then dynamic high-pressure microjet treatment is carried out, and the Pickering emulsion containing the cellulose nanofibers is obtained. According to the invention, the cellulose nanofiber is used as a stabilizer to prepare the Pickering emulsion, and the emulsion has good emulsification stability. In addition, the emulsion can be applied to beta-carotene loading and has good light stability. The application of the Pickering emulsion in a complex food system is promoted, the Pickering emulsion has a good application prospect in the aspect of nutrient substance conveying carriers, and meanwhile, a new direction is provided for high-value utilization of agricultural by-products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of food processing, and particularly relates to a Pickering emulsion containing cellulose nanofiber and a preparation method and application thereof. BACKGROUND

[0002] The Pickering emulsion is an emulsion system stabilized by solid particles instead of traditional surfactants, and has the advantages of high stability, low toxicity and environmental friendliness compared with traditional emulsions. At present, the most commonly used colloidal particles for stabilizing the Pickering emulsion are proteins, starch particles, polysaccharides and their complexes; however, these colloidal particles all have corresponding defects and cannot well meet the requirements of stabilizing emulsions, thereby limiting the application of the Pickering emulsion in complex food systems. SUMMARY

[0003] The purpose of the application is to solve the problems of the prior art, and provide a Pickering emulsion containing cellulose nanofiber and a preparation method and application thereof. The following technical solutions are specifically adopted: In a first aspect, the application provides a preparation method of a Pickering emulsion containing cellulose nanofiber, comprising the following steps: The cellulose nanofiber is dissolved in water, ultrasonicated, and then mixed with corn oil to obtain an oil-containing emulsion; The oil-containing emulsion is placed in a disperser for dispersion, and then subjected to dynamic high-pressure microjet treatment to obtain the Pickering emulsion containing cellulose nanofiber.

[0004] The Pickering emulsion is prepared by using cellulose nanofiber, wherein the cellulose nanofiber is a renewable and biodegradable natural nanomaterial, has a high specific surface area, excellent mechanical properties and surface activity, can be effectively adsorbed on the oil-water interface to form a stable interface film, thereby preventing the coalescence and delamination of emulsion droplets, and can better solve the problems existing in the application of the Pickering emulsion in food systems.

[0005] As a further preferred embodiment, the cellulose nanofiber is obtained by the following steps: S1, crushing the agricultural and sideline products, dissolving them in water, heating in a water bath and adding high-temperature alpha-amylase for enzymolysis, cooling to 50 DEG C after the enzymolysis is completed, adjusting the pH to 10.5, then adding alkaline protease for enzymolysis, heating and boiling to inactivate the enzyme after the enzymolysis is completed, adjusting the pH to 4.5 and adding saccharifying enzyme for enzymolysis, filtering, washing, drying and obtaining residues; S2, mixing and reacting the residues with a sodium hydroxide solution, and washing to obtain insoluble residues after the reaction is completed; S3, mixing the insoluble residue with sodium chlorite aqueous solution, then adjusting pH to 4, bleaching, washing, freeze-drying to obtain a white sample; S4, dissolving the white sample in water, mixing in a disperser, then treating with a dynamic high-pressure microfluidizer to obtain the cellulose nanofiber.

[0006] As a further preferred embodiment, the agricultural by-products include rice bran, wheat bran or bean dregs.

[0007] The present application promotes the application of Pickering emulsion in complex food systems by treating rice bran, wheat bran and bean dregs to obtain corresponding food-grade cellulose nanofiber for Pickering emulsion stabilization and functional material loading application. Rice bran, wheat bran and bean dregs are common agricultural by-products, with annual production reaching tens of thousands of tons, but their high-value utilization rate is generally low, causing serious resource loss and environmental pollution. The present application also provides a new direction for the high-value utilization of agricultural by-products.

[0008] As a further preferred embodiment, the ratio of agricultural by-products to water in S1 is 1:10. The temperature of water bath heating is 90-100℃, and the temperature of enzymatic hydrolysis by adding saccharifying enzyme is 60℃.

[0009] As a further preferred embodiment, the temperature of reaction in S2 is 60-80℃, and the reaction time is 3-5h.

[0010] As a further preferred embodiment, the ratio of insoluble residue to sodium chlorite aqueous solution in S3 is 1:20, and the concentration of sodium chlorite aqueous solution is 1.5%.

[0011] As a further preferred embodiment, the volume ratio of oil phase in the emulsion containing oil phase is 15-30%.

[0012] As a further preferred embodiment, the rotation speed of the disperser is 13000-16000 rpm, and the dispersion time is 1-3 min; the pressure of the dynamic high-pressure microfluidizer is 40-50 MPa.

[0013] In a second aspect, the present application provides a Pickering emulsion containing cellulose nanofiber, which is prepared by the above preparation method.

[0014] In a third aspect, the present application provides the application of the above Pickering emulsion containing cellulose nanofiber in loading β-carotene.

[0015] The present application has the following advantages: The present application uses agricultural by-products (rice bran, wheat bran, bean dregs) to prepare cellulose nanofibers, and then uses the cellulose nanofibers as stabilizers to prepare Pickering emulsions, the Pickering emulsions have good emulsification stability. In addition, the Pickering emulsions can be applied to β-carotene loading, so that the β-carotene has good light stability in the Pickering emulsion. The present application promotes the application of Pickering emulsion in complex food systems, has good application prospect in nutrient delivery carriers, and also provides a new direction for high-value utilization of agricultural by-products. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0017] Figure 1 The figure shows the comparison of different cellulose nanofiber solutions before and after being placed for 30 days; Figure 2 The figure shows the micro-morphology observation results of Pickering emulsions stabilized by different cellulose nanofibers; Figure 3 The figure shows the dynamic interfacial tension of corn oil and different cellulose nanofiber suspensions (A), different concentrations of bean dregs cellulose nanofiber suspensions (B); Figure 4 The figure shows the rheological property results of Pickering emulsions stabilized by different concentrations and different cellulose nanofibers; Figure 5 The figure shows the emulsification and emulsion stability results of different cellulose nanofibers; Figure 6 The figure shows the appearance pictures of Pickering emulsions stabilized by different cellulose nanofibers at different time periods (1 day, 7 days, 14 days, 30 days); Figure 7 The figure shows the ultraviolet transmittance of different cellulose nanofiber suspensions (0.1%, w / v); Figure 8 The figure shows the retention rate of β-carotene loaded in Pickering emulsions stabilized by different cellulose nanofibers at different ultraviolet irradiation times; Figure 9 The figure shows the DPPH free radical scavenging rate of Pickering emulsions loaded with β-carotene and stabilized by different cellulose nanofibers. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0019] Embodiment 1 A preparation method of a rice bran source cellulose nanofiber (RBCNF) stabilized Pickering emulsion, which specifically comprises the following steps: (1) Preparation of rice bran source cellulose nanofiber The defatted rice bran is crushed by a crusher and then sieved. Then, the defatted rice bran is mixed with distilled water at a solid-liquid ratio of 1:10. The mixture is heated to 95°C in a water bath, and then high-temperature α-amylase is added. The mixture is enzymatically hydrolyzed at 95°C for 1 h. The solution is cooled to 50°C, and then alkaline protease is added after adjusting the pH to 10.5. The mixture is enzymatically hydrolyzed at 50°C for 1 h. After the enzymatic hydrolysis is completed, the solution is boiled to inactivate the enzyme. The solution is heated to 60°C, and then glucoamylase is added after adjusting the pH to 4.5. The mixture is enzymatically hydrolyzed at 60°C for 1 h. Then, the enzymatic hydrolyzate is filtered, washed with 95% ethanol solution, and finally washed with distilled water until the filtrate is clear. The residue is collected and dried. Then, 4% (w / v) sodium hydroxide solution is added to the residue, and the mixture is reacted at 70°C for 4 h. After the reaction is completed, the remaining residue is washed with a large amount of distilled water. The insoluble residue is mixed with 1.5% (w / v) sodium chlorite aqueous solution at a solid-liquid ratio of 1:20, and then the pH is adjusted to 4 with acetic acid. The mixture is bleached at 70°C to obtain a white sample. The white sample is washed with distilled water until it is neutral and then freeze-dried. The white sample is dispersed in distilled water, and then the solution is mixed uniformly with a T18 dispersing machine. The cellulose dispersion solution is treated with a dynamic high-pressure microfluidization homogenizer to obtain a viscous gelatinous fluid, i.e., a cellulose nanofiber solution.

[0020] (2) Preparation of Pickering emulsion The cellulose nanofiber solution obtained in step (1) is mixed with distilled water to adjust the concentration of the cellulose nanofiber solution to 0.1% (w / v), and then ultrasonic treatment is performed for 15 min. The cellulose nanofiber solution is mixed with corn oil to prepare an emulsion system containing 20% of oil phase by volume. The emulsion system is dispersed with a dispersing machine at a speed of 15000 rpm for 2 min, and then treated with dynamic high-pressure microfluidization. The emulsion system is treated with dynamic high-pressure microfluidization twice at 50 MPa to prepare a stable Pickering emulsion (denoted as RBCNF 0.1%).

[0021] Embodiment 2 A method for preparing a Pickering emulsion stabilized by rice bran-derived cellulose nanofiber (RBCNF), the specific method of which is similar to that of Example 1, with the only difference being that the "adjust the concentration of the cellulose nanofiber solution to 0.1% (w / v)" in step (2) is replaced by "adjust the concentration of the cellulose nanofiber solution to 0.3% (w / v)", and the other steps are the same, to obtain a Pickering emulsion (denoted as RBCNF 0.3%).

[0022] Example 3 A method for preparing a Pickering emulsion stabilized by rice bran-derived cellulose nanofiber (RBCNF), the specific method of which is similar to that of Example 1, with the only difference being that the "adjust the concentration of the cellulose nanofiber solution to 0.1% (w / v)" in step (2) is replaced by "adjust the concentration of the cellulose nanofiber solution to 0.5% (w / v)", and the other steps are the same, to obtain a Pickering emulsion (denoted as RBCNF 0.5%).

[0023] Example 4 A method for preparing a Pickering emulsion stabilized by wheat bran-derived cellulose nanofiber (WBCNF), the specific method of which is similar to that of Example 1, with the only difference being that the "defatted rice bran" in step (1) is replaced by "wheat bran", and the other steps are the same, to obtain a Pickering emulsion (denoted as WBCNF 0.1%).

[0024] Example 5 A method for preparing a Pickering emulsion stabilized by wheat bran-derived cellulose nanofiber (WBCNF), the specific method of which is similar to that of Example 4, with the only difference being that the "adjust the concentration of the cellulose nanofiber solution to 0.1% (w / v)" in step (2) is replaced by "adjust the concentration of the cellulose nanofiber solution to 0.3% (w / v)", and the other steps are the same, to obtain a Pickering emulsion (denoted as WBCNF 0.3%).

[0025] Example 6 A method for preparing a Pickering emulsion stabilized by wheat bran-derived cellulose nanofiber (WBCNF), the specific method of which is similar to that of Example 4, with the only difference being that the "adjust the concentration of the cellulose nanofiber solution to 0.1% (w / v)" in step (2) is replaced by "adjust the concentration of the cellulose nanofiber solution to 0.5% (w / v)", and the other steps are the same, to obtain a Pickering emulsion (denoted as WBCNF 0.5%).

[0026] Example 7 A preparation method for preparing a Pickering emulsion stabilized by cellulose nanofiber (OCNF) from bean dregs, the specific method of which is similar to that of Example 1, with the only difference being that "defatted rice bran" in step (1) is replaced by "bean dregs", and the other steps are the same, to obtain a Pickering emulsion (denoted as OCNF 0.1%).

[0027] Example 8 A preparation method for preparing a Pickering emulsion stabilized by cellulose nanofiber (OCNF) from bean dregs, the specific method of which is similar to that of Example 7, with the only difference being that "adjust the concentration of the cellulose nanofiber solution to 0.1% (w / v)" in step (2) is replaced by "adjust the concentration of the cellulose nanofiber solution to 0.3% (w / v)", and the other steps are the same, to obtain a Pickering emulsion (denoted as OCNF 0.3%).

[0028] Example 9 A preparation method for preparing a Pickering emulsion stabilized by cellulose nanofiber (OCNF) from bean dregs, the specific method of which is similar to that of Example 7, with the only difference being that "adjust the concentration of the cellulose nanofiber solution to 0.1% (w / v)" in step (2) is replaced by "adjust the concentration of the cellulose nanofiber solution to 0.5% (w / v)", and the other steps are the same, to obtain a Pickering emulsion (denoted as OCNF 0.5%).

[0029] Comparative Example 1 A preparation method for preparing a Pickering emulsion stabilized by bacterial cellulose nanofiber (BCNF), the specific method of which is similar to that of Example 1, with the only difference being that step (1) is different, specifically: bacterial cellulose hydrogel (coconut fruit) is mixed with 2% sodium hydroxide aqueous solution at a mass ratio of 1:1, boiled, washed with distilled water to neutral after alkali boiling for 2 h, and then freeze-dried, then dispersed in distilled water, and treated with a T18 dispersing machine and a dynamic high-pressure microfluidizer in sequence to obtain a bacterial cellulose nanofiber solution, and the remaining steps are the same as those of Example 1, to obtain a Pickering emulsion (denoted as BCNF 0.1%).

[0030] Comparative Example 2 A preparation method for preparing a Pickering emulsion stabilized by bacterial cellulose nanofiber (BCNF), the specific method of which is similar to that of Comparative Example 1, with the only difference being that "adjust the concentration of the bacterial cellulose nanofiber solution to 0.1% (w / v)" in step (2) is replaced by "adjust the concentration of the bacterial cellulose nanofiber solution to 0.3% (w / v)", and the other steps are the same, to obtain a Pickering emulsion (denoted as BCNF 0.3%).

[0031] Comparative Example 3 A Pickering emulsion stabilized by bacterial cellulose nanofiber (BCNF) was prepared according to the similar procedure of Comparative Example 1, except that the concentration of the bacterial cellulose nanofiber solution in step (2) was adjusted to 0.5% (w / v) instead of 0.1% (w / v). The Pickering emulsion was denoted as BCNF 0.5%.

[0032] Example 10 The zeta potentials of the cellulose nanofiber solutions (RBCNF, WBCNF, OCNF) and the bacterial cellulose nanofiber solution (BCNF) prepared in the above examples and comparative examples were determined according to the following procedure. The zeta potential is obtained by measuring the mobility distribution of nanoparticles under the action of an electric field, and is used to evaluate the surface charge of the nanofiber, which is a key factor determining the stability of the CNF suspension in water. The zeta potential of the four cellulose nanofibers was determined using a Nano-ZSE Malvern particle potential instrument. The concentration of the cellulose nanofiber was diluted to 0.1 mg / mL using distilled water, and the test was performed after ultrasonic treatment for 10 min, and the test was stable at 25°C.

[0033] The results are shown in Table 1 and Figure 1. Figure 1 As shown in Table 1 and Figure 1, the average zeta potential of the cellulose nanofiber was in the range of -21.60 mV to -35.23 mV. The cellulose nanofiber has a negative potential due to the presence of a large number of hydroxyl groups on the surface of the cellulose. In general, if the absolute value of the zeta potential is greater than 25 mV, the solution is considered to be stable. Therefore, in addition to OCNF, the three cellulose nanofiber solutions are relatively stable, especially RBCNF, with a zeta potential of -35.23 mV.

[0034] Table 1 Zeta potential of each cellulose nanofiber solution Example 11 The Pickering emulsions prepared in the above examples and comparative examples were observed under a microscope according to the following procedure. 5 μL of the emulsion was dropped onto a glass slide, and then a cover glass was placed on the sample. The microstructure of the droplets was observed under an optical microscope. The shape and arrangement of the sample droplets were observed at a magnification of 10x objective lens and 40x objective lens.

[0035] The results are shown in Table 1 and Figure 1. Figure 2 As shown in Table 1 and Figure 1, the average zeta potential of the cellulose nanofiber was in the range of -21.60 mV to -35.23 mV. The cellulose nanofiber has a negative potential due to the presence of a large number of hydroxyl groups on the surface of the cellulose. In general, if the absolute value of the zeta potential is greater than 25 mV, the solution is considered to be stable. Therefore, in addition to OCNF, the three cellulose nanofiber solutions are relatively stable, especially RBCNF, with a zeta potential of -35.23 mV.

[0036] Example 12 The cellulose nanofiber solutions (RBCNF, WBCNF, OCNF) and bacterial cellulose nanofiber solution (BCNF) prepared in the above examples and comparative examples were subjected to oil-water interfacial tension determination, and the specific process was as follows: The change of oil-water interface was recorded by optical contact angle meter, the dynamic interfacial tension between cellulose nanofiber (0.5%, w / v) and corn oil was determined by pendant drop method, distilled water was used as blank control (DS), and the interfacial tension was calculated by Young-Laplace equation. By detecting the change trend of interfacial tension (IFT) with time, the dynamic adsorption behavior of cellulose nanofiber on the oil / water interface was studied.

[0037] The results are shown in Figure 3 The results show that the cellulose nanofiber of the application has the ability to reduce the IFT of oil-water interface and improve the stability of emulsion. When distilled water is added to corn oil, the interfacial tension of the two phases decreases slowly with time; compared with distilled water and bacterial cellulose nanofiber (BCNF), the three cellulose nanofibers (WBCNF, RBCNF and OCNF) derived from agricultural and sideline products can greatly reduce the interfacial tension, especially OCNF, which has the greatest degree of reducing interfacial tension. This may be due to the fact that OCNF has less charge, so the electrostatic repulsion between fibers is weaker, which is more conducive to the adsorption of fibers. On this basis, the ability of OCNF suspension with different concentrations to reduce the oil-water interfacial tension was further discussed, and it was found that the higher the mass fraction of the suspension, the faster the interfacial tension was reduced, and the lower the stable interfacial tension. The possible reason is that small size and amorphous shape may lead to higher surface activity and lower interfacial tension.

[0038] Example 13 The Pickering emulsion prepared in the above examples and comparative examples was subjected to rheological property determination, and the specific process was as follows: The rheological properties of the emulsion were determined by DHR-2 rotary rheometer. First, the linear viscoelastic region of the emulsion was determined by stress sweep, the strain interval was set to 0.1%-100%, and the frequency was set to 1 Hz; then the dynamic viscoelasticity of the emulsion was determined by frequency sweep, the frequency sweep range was set to 0.1-10 Hz, and the fixed strain was set to 1%; at the same time, the emulsion sample was subjected to static scanning, and the shear rate parameter was set to 0.1-100 s -1 .

[0039] The results are shown in Figure 4As shown, oscillation amplitude scanning was performed at a frequency of 1 Hz, with the scanned strain range from 0.1% to 100%. Below 1% strain, all emulsions exhibited typical linear viscoelastic (LVE) behavior. Throughout the LVE region, the storage modulus (G') of all Pickering emulsions was greater than the loss modulus (G"), indicating that the cellulose nanofiber-stabilized Pickering emulsions of this invention are elastic materials. Furthermore, most Pickering emulsions yielded at oscillation strain close to 1%, thus defining 0-1% as the linear viscoelastic region of the emulsion, and frequency scanning was performed. The frequency scanning range for small oscillation amplitudes was 0.1 to 10 Hz. The G' and G" curves of the Pickering emulsion stabilized by 0.5% cellulose nanofibers were almost horizontal within the test frequency range, indicating that G' and G" are not frequency-dependent. Simultaneously, the G' of all Pickering emulsions was higher than G" throughout the entire frequency range, consistent with the amplitude scanning curves, indicating that the Pickering emulsions possess a solid-like elastic texture. Furthermore, the higher the concentration of cellulose nanofibers, the larger the G' of the emulsion, indicating that increasing the concentration of cellulose nanofibers can improve the gel strength of Pickering emulsions. Static scanning analysis of the apparent viscosity of Pickering emulsions in response to shear rate showed that the viscosity of all Pickering emulsion samples decreased with increasing shear rate, indicating that the emulsions exhibit typical shear-thinning behavior.

[0040] Example 14 The cellulose nanofiber solutions (RBCNF, WBCNF, OCNF) and bacterial cellulose nanofiber solutions (BCNF) prepared in the above examples and comparative examples were subjected to emulsifying activity (EAI) and emulsifying stability (ESI) determinations. The specific procedures are as follows: Weigh 0.01 g of fiber sample, add 10 mL of distilled water, and disperse using a homogenizer. Add 3.34 g of corn oil to the fiber dispersion and homogenize at high speed (10,000 rpm) for 1 min. Then, transfer the sample base liquid after standing for 0 min and 10 min, and add it to 10 mL of 0.1% sodium dodecyl sulfate (SDS) solution, and shake and stir until homogeneous. Measure the absorbance of the SDS solution at 500 nm (A500 nm). EAI (m 2 The formulas for calculating (g) and ES (%) are: EAI = (2.303 × 2 × B × A0) / [C × (1 - D) × L] ES = (100 × EAI) 0) / ( EAI0-EAI 10 ) In the formula, B is dilution multiple (1.01); C is sample concentration (g / mL); D is the volume fraction of oil phase (0.2); A0 is the absorbance at 0 min; EAI0 is the emulsifying activity index at 0 min, EAI 10 is the emulsifying activity index at 10 min. Wherein EAI refers to the ability of fiber to form emulsion, and ESI represents the ability of the emulsified oil droplets to maintain dispersion without flocculation, coalescence and maturation.

[0041] The results shown by Figure 5 , the EAI and ESI of RBCNF are significantly higher than those of WBCNF and OCNF, indicating that the emulsifying activity and emulsifying stability of RBCNF are the best. Among them, there is no significant difference in emulsifying activity index between RBCNF and BCNF, indicating that BCNF also has good emulsifying activity, but the emulsifying stability of BCNF is significantly lower than that of RBCNF, WBCNF and OCNF, indicating that the emulsifying stability of BCNF is not as good as that of the other three cellulose nanofibers.

[0042] Example 15 The Pickering emulsion prepared in the above examples and comparative examples was stored and the creaming index was determined, and the specific process was as follows: 10 mL of emulsion was taken in a glass bottle, and it was stored in a 4 ℃ refrigerator, and the height of the separated clear liquid layer was measured at 0, 7, 14 and 28 days. The calculation formula of creaming index (CI) is as follows: CI (%) = Hs / Ht x 100 Wherein, Hs represents the height of the separated water (cm); Ht represents the total height of the emulsion in the glass bottle (cm).

[0043] The physical stability of the Pickering emulsion was evaluated by recording the appearance of the emulsion under different storage days (1, 7, 14 and 30 days) and calculating the corresponding CI value.

[0044] The results are shown in Figure 6 and Table 2 below. The emulsion stabilized by 0.1% CNF showed obvious emulsion layering on the first day, while the emulsion stabilized by 0.5% CNF only showed slight layering. With the extension of storage time, the emulsion did not show significant layering again, indicating that the emulsion stabilized by the cellulose nanofiber of the application reached a relatively stable state within one day. After significant difference analysis, it was found that the emulsion stabilized by 0.5% CNF had no significant difference after 30 days of storage, and could maintain good emulsifying stability.

[0045] Table 2 Creaming index (%) of emulsion after 30 days Example 16 The cellulose nanofiber solutions (RBCNF, WBCNF, OCNF) and bacterial cellulose nanofiber solution (BCNF) prepared in the above examples and comparative examples were subjected to ultraviolet transmittance determination, and the specific process was as follows: The ultraviolet-visible spectrometer was used to determine the light transmittance of the cellulose nanofiber solution. The cellulose nanofiber solution was subjected to ultrasonic treatment of the suspension for 10 min at 200 w, and then it was placed in a quartz cuvette, and the light transmittance in the wavelength range of 230-800 nm was recorded. When the light passes through the cellulose nanofiber solution, due to the presence of randomly dispersed particles in the suspension, the light will be scattered, and finally the refractive index transparency will be reduced.

[0046] The results are shown in Figure 7 The three cellulose nanofiber solutions (RBCNF, WBCNF, OCNF) from agricultural and sideline products have lower light transmittance than the bacterial cellulose nanofiber solution (BCNF), which may be due to the presence of nanocellulose agglomerates in the suspension, thereby causing light scattering, which has a positive significance for inhibiting the photosensitive oxidation of oil and fat after stabilizing the emulsion and avoiding the photodegradation of the natural active ingredients loaded.

[0047] Example 17 A method for preparing a Pickering emulsion containing cellulose nanofiber and loaded with β-carotene, the preparation process is similar to examples 1-9, the only difference is that: β-carotene is dissolved in the corn oil used in advance (0.1wt%), stirred overnight to make it fully dissolved, then mixed with the cellulose nanofiber solution, the rest of the steps are the same, and the Pickering emulsion is prepared.

[0048] Example 18 Determination of the ultraviolet light stability of β-carotene in the Pickering emulsion prepared in example 17 The emulsion loaded with β-carotene (10 mL) was added to a transparent glass bottle, and then the emulsion was irradiated with ultraviolet light from the ultraclean table, and the β-carotene content of the emulsion samples at 0-4 h was determined. The β-carotene was extracted by an extraction solution composed of ethanol and n-hexane (1:2, v / v), and centrifuged at 10000 rpm for 10 min. The absorbance value of the upper solution at 450 nm was determined, and the retention rate of β-carotene was determined by the ratio of the absorbance values at different time periods to the absorbance value at 0 h.

[0049] The results are shown in Figure 8It can be seen that, in the absence of emulsifiers, the retention rate of β-carotene is only 75.41% after the oil-water mixture is irradiated by ultraviolet light for 4 h; while the emulsion stabilized by 0.5% CNF, the retention rate of β-carotene is more than 90% after 4 h of ultraviolet light irradiation. This shows that cellulose nanofiber can play a certain shielding effect on ultraviolet light, and higher concentration of CNF is conducive to improving the ultraviolet stability of β-carotene. The ultraviolet light stability of the Pickering emulsion prepared by the three cellulose nanofibers (RBCNF, WBCNF, OCNF) derived from agricultural and sideline products is better than that of the Pickering emulsion prepared by bacterial cellulose nanofiber (BCNF).

[0050] Example 19 The Pickering emulsion prepared in Example 17 was subjected to DPPH free radical scavenging rate determination, and the specific process was as follows: 1 mL of cellulose nanofiber emulsion (0.5% CNF) was mixed with 1 mL of 0.2 mM DPPH ethanol solution, and vortexed uniformly, and then centrifuged (4500 rpm, 20 min) after 30 min of light shielding reaction; the absorbance value of the middle purple solution at 517 nm was measured. Distilled water was used as a blank control, and the DPPH free radical scavenging rate (%) was calculated according to the following formula: DPPH scavenging rate = (A0-A1) / A0x100 In the formula, A0 represents the absorbance value after DPPH is mixed with distilled water for reaction; and A1 represents the absorbance value after DPPH is mixed with the emulsion for reaction.

[0051] As shown in Figure 9 , each cellulose nanofiber stabilized Pickering emulsion has good DPPH free radical scavenging capacity, and the DPPH free radical scavenging capacity of the Pickering emulsion prepared by the three cellulose nanofibers (RBCNF, WBCNF, OCNF) derived from agricultural and sideline products is significantly better than that of the Pickering emulsion prepared by bacterial cellulose nanofiber (BCNF).

[0052] The embodiments of the present application are described above in combination with the drawings, and the principles and implementation modes of the present application are described by applying specific examples. The above example is only used to help understand the core idea of the present application, but the present application is not limited to the above specific implementation mode. The above specific implementation mode is only illustrative, not restrictive, and those skilled in the art can make many forms without departing from the scope of the present application under the guidance of the present application, which are all within the protection scope of the present application.

Claims

1. A method for preparing a Pickering emulsion containing cellulose nanofibrils, characterized by, The method comprises the following steps: The cellulose nanofiber is dissolved in water, ultrasonic treatment, and then mixed with corn oil to obtain an oil phase emulsion; The oil phase emulsion is placed in a disperser for dispersion, and then subjected to dynamic high-pressure microfluidization treatment to obtain the cellulose nanofiber-containing Pickering emulsion.

2. The production method according to claim 1, characterized by, The cellulose nanofiber is obtained by the following steps: S1, crushing the agricultural and sideline products, dissolving in water, heating in a water bath, and adding high-temperature alpha-amylase for enzymolysis; after the enzymolysis is completed, cooling to 50℃, adjusting the pH to 10.5, then adding alkaline protease for enzymolysis; after the enzymolysis is completed, heating and boiling to inactivate the enzyme, and after the inactivation is completed, the pH is 4.5 and glucoamylase is added for enzymolysis; after the enzymolysis is completed, filtering, washing, drying, and obtaining a residue; S2, mixing the residue with a sodium hydroxide solution for reaction, and after the reaction is completed, washing to obtain an insoluble residue; S3, mixing the insoluble residue with a sodium chlorite aqueous solution, then adjusting the pH to 4, bleaching, washing, and freeze-drying to obtain a white sample; S4, dissolving the white sample in water, mixing uniformly in a disperser, and then treating with a dynamic high-pressure microfluidization homogenizer to obtain the cellulose nanofiber.

3. The production method according to claim 2, characterized by, The agricultural and sideline products include rice bran, wheat bran, or bean dregs.

4. The production method according to claim 2, characterized by, The ratio of the agricultural and sideline products to water in S1 is 1:10; The temperature of the water bath heating is 90-100℃; and the temperature of the enzymolysis with the glucoamylase is 60℃.

5. The preparation method according to claim 2, characterized in that, The reaction temperature in S2 is 60-80℃, and the reaction time is 3-5 h.

6. The preparation method according to claim 2, characterized in that, The ratio of the insoluble residue to the sodium chlorite aqueous solution in S3 is 1:20; and the concentration of the sodium chlorite aqueous solution is 1.5%.

7. The preparation method according to claim 1, characterized in that, The volume ratio of the oil phase in the oil phase emulsion is 15-30%.

8. The method of claim 1, wherein, The rotation speed of the disperser is 13000-16000 rpm, and the dispersion time is 1-3 min; and the pressure of the dynamic high-pressure microfluidization is 40-50 MPa.

9. A Pickering emulsion comprising cellulose nanofibrils, characterized in that, Prepared by the preparation method of any one of claims 1-8.

10. The cellulose nanofiber-containing Pickering emulsion of claim 9 is used for loading β-carotene.

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