Emulsion based on oil-in-water gel Pickering, preparation method and application

Abstract

The invention discloses an oil-in-water gel-based Pickering emulsion, a preparation method and application, and the preparation method comprises the following steps: step 1, dispersing liquid oil and beeswax to obtain oil gel; step 2, adding nano cellulose whiskers into the sodium alginate solution, and fully mixing to obtain a water phase solution; wherein the mass ratio of the sodium alginate to the nano cellulose whiskers is (2-10): 5; and step 3, fully mixing and dispersing the oil gel in the step 1 and the water phase solution in the step 2 to obtain the required oil-in-water gel Pickering emulsion. According to the invention, the oil-in-water gel Pickering emulsion obtained by adding sodium alginate and modified CNW as emulsifiers has significantly improved curcumin embedding and delivery capability, and the chemical stability and biological accessibility of curcumin are improved.

Description

Technical Field

[0001] The invention relates to the technical field of biomaterials, and in particular to a Pickering emulsion based on oil-in-water gel, a preparation method and application thereof. Background Art

[0002] Curcumin is a polyphenol compound belonging to the diphenylheptane class of substances, and is in the form of an orange-yellow crystalline powder. Studies have found that curcumin has functional properties such as anti-inflammatory, antioxidant, anti-tumor, free radical scavenging, and digestive system. In clinical trials, curcumin is relatively safe, and the safe dose can reach 12g per day. However, its low solubility, poor chemical stability, and low bioaccessibility limit its application in the fields of food and medicine. In particular, curcumin is easily degraded under acidic conditions. The curcumin ingested by the human body is destroyed during the digestion stage in the stomach, and only a very small amount can reach the small intestine for digestion and absorption, resulting in its extremely low bioaccessibility, so it is not widely used in clinical practice. Therefore, it is particularly important to find a method to deliver curcumin and give full play to its efficacy. Although the existing Pickering emulsion can improve the encapsulation and delivery capacity of curcumin to a certain extent, the effect is not ideal. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a Pickering emulsion based on oil-in-water gel, a preparation method and application thereof.

[0004] The technical solution adopted by the present invention is:

[0005] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0006] Step 1: Dispersing liquid oil and beeswax to obtain oil gel;

[0007] Step 2: adding nanocellulose whiskers to the sodium alginate solution and mixing them thoroughly to obtain an aqueous solution; wherein the mass ratio of the sodium alginate to the nanocellulose whiskers is 2 to 10:5;

[0008] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired water-in-oil gel Pickering emulsion.

[0009] Furthermore, the nanocellulose whiskers are modified nanocellulose whiskers that have been desulfurized with hydrochloric acid;

[0010] The preparation method of modified nanocellulose whiskers is as follows:

[0011] The hydrochloric acid and the nanocellulose whiskers are mixed, and oscillated and heated at 98-100° C. and 100 rpm for 0.5-1 h to fully react to obtain the modified nanocellulose whiskers; wherein the mass ratio of the hydrochloric acid to the nanocellulose is 9:10.

[0012] Furthermore, after the reaction of the hydrochloric acid and the nanocellulose whiskers is completed, the desired modified nanocellulose whiskers can be obtained by cooling, centrifuging, washing and dialysis; the centrifugal speed is 8000 rpm and the centrifugal time is 15 min.

[0013] Furthermore, in step 1, the gel preparation process is as follows:

[0014] Beeswax is added to soybean oil, wherein the concentration of the beeswax is 10.0% w / v; the mixture is stirred at a speed of 300 rpm and 80° C. for 15 minutes to obtain the desired oil gel.

[0015] Furthermore, in step 2, the aqueous solution is heated at 80° C. for 15 min.

[0016] Furthermore, the mixing and dispersing process in step 3 is as follows:

[0017] First, homogenize at an emulsifier speed of 10000 rpm for 2 min;

[0018] Then pulse ultrasound was applied at 525 W for 2 min;

[0019] During the ultrasound process, the ultrasound is cycled for N seconds and then paused for M seconds.

[0020] Furthermore, the aqueous phase solution in step 2 also contains NaCl, wherein the concentration of NaCl is 60 mM.

[0021] A Pickering emulsion based on an oil-in-water gel.

[0022] An application based on an oil-in-water gel Pickering emulsion, wherein the oil-in-water gel Pickering emulsion is used as an embedded delivery carrier for nutrition.

[0023] Furthermore, the nutrient is curcumin.

[0024] The beneficial effects of the present invention are:

[0025] The water-in-oil gel Pickering emulsion obtained by adding sodium alginate and modified CNW as emulsifiers in the present invention significantly improves the ability of emulsion embedding and delivering curcumin, and improves the chemical stability and bioaccessibility of curcumin.

[0026] The water-in-oil gel Pickering emulsion obtained by the invention can have a high embedding rate for nutrients with poor oil and water solubility. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the density of sulfonic acid groups on the surface of nanocellulose whiskers obtained in Examples 1 to 2 of the present invention and Comparative Examples 1, 2, and 3.

[0028] Figure 2 Schematic diagram of the microstructure of the water-in-oil gel Pickering emulsion obtained in Examples 1 to 2 of the present invention and Comparative Examples 1, 2, and 3, a is a schematic diagram of a laser confocal microscope, and b is a schematic diagram of the particle size distribution of the emulsion.

[0029] Figure 3 Schematic diagram of the stability test results of the water-in-oil gel Pickering emulsion obtained in Examples 1 to 2 of the present invention and Comparative Examples 1, 2, and 3, a is a macroscopic morphology diagram during storage, b is a CI test result diagram during storage, c is an optical microscope diagram during storage, and d is a schematic diagram of the average particle size statistical results during storage.

[0030] Figure 4 Schematic diagram of the stability test results of the water-in-oil gel Pickering emulsion obtained in Examples 1, 3 and 4 of the present invention and Comparative Example 4, a is a macroscopic morphology diagram during storage, b is a CI test result diagram during storage, c is an optical microscope diagram during storage, and d is a schematic diagram of the average particle size statistical results during storage.

[0031] Figure 5 The encapsulation comparison of curcumin by the water-in-oil gel Pickering emulsion obtained in Example 4 of the present invention and Comparative Example 4 is shown in FIG. 4 , where a is the encapsulation rate of curcumin and b is the retention rate during storage.

[0032] Figure 6 The release rate of curcumin during gastrointestinal digestion after curcumin is embedded in the water-in-oil gel Pickering emulsion obtained in Example 4 of the present invention and Comparative Example 4.

[0033] Figure 7 The bioaccessibility of curcumin after being embedded in the water-in-oil gel Pickering emulsion obtained in Example 4 of the present invention and Comparative Example 4. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0035] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0036] Step 1: Disperse liquid oil and beeswax to obtain oil gel; add beeswax into soybean oil, wherein the concentration of beeswax is 10.0% w / v; stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it, thereby obtaining the desired oil gel.

[0037] Step 2: Add nanocellulose whiskers to the sodium alginate solution, mix thoroughly to obtain an aqueous solution, and heat at 80° C. for 15 minutes; wherein the mass ratio of sodium alginate to nanocellulose whiskers is 2 to 10:5; the sodium alginate solution contains NaCl, and the concentration of NaCl is 60 mM.

[0038] The preparation process of nanocellulose whiskers is as follows:

[0039] The hydrochloric acid and the nanocellulose whiskers are mixed, and oscillated and heated at 98-100° C. and 100 rpm for 0.5-1 h to fully react to obtain the modified nanocellulose whiskers; wherein the mass ratio of the hydrochloric acid to the nanocellulose is 9:10.

[0040] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired oil-in-water gel Pickering emulsion;

[0041] The dispersion process is as follows:

[0042] The mixture was homogenized for 2 min at 10,000 rpm using an ultrafine homogenizer, and ultrasonicated for 2 min in pulse mode at 525 W pressure amplitude using a high-intensity ultrasonic processor, with 3 s of operation and 3 s of rest during the pulse process to obtain a water-in-oil gel Pickering emulsion. The temperature was maintained at 70-90 ° C during the dispersion process. The volume ratio of the oil gel to the aqueous phase solution was 3:7.

[0043] Example 1

[0044] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0045] Step 1: Add beeswax to soybean oil, stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it to obtain the desired oil gel. The concentration of beeswax in the oil gel is 10.0% w / v.

[0046] Step 2: Add nanocellulose whiskers to the sodium alginate solution and mix thoroughly to obtain an aqueous solution. The aqueous solution has a NaCl concentration of 60 mM, a sodium alginate concentration of 0.2% w / v, and a nanocellulose whisker concentration of 0.5% w / v. Heat at 80°C for 15 minutes.

[0047] The preparation process of nanocellulose whiskers is as follows:

[0048] 100mL of 5mol / L hydrochloric acid and 100mL of 20mg / mL nanocellulose whiskers were mixed and dispersed, and heated in a constant temperature oscillating water bath at 99°C and 100rpm for 0.5h to fully react and obtain modified nanocellulose whiskers. After desulfurization, first cool it, then centrifuge and wash it at 8000rpm for 15min; pour out the supernatant to remove the hydrochloric acid, repeat centrifugation until the upper liquid becomes turbid, and pour the upper turbid suspension into a dialysis bag with a molecular weight cutoff of 8000-14000Da for dialysis until the pH value of the dialysate is neutral. Use polyethylene glycol 20000 to concentrate the suspension in the dialysis bag, collect the concentrated sample suspension and save it.

[0049] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired oil-in-water gel Pickering emulsion (denoted as CNW0.5 in the figure); the volume ratio of the oil gel to the aqueous solution is 3:7.

[0050] The dispersion process is as follows:

[0051] The mixture was homogenized for 2 min at 10000 rpm using an ultrafine homogenizer, and ultrasonicated for 2 min in pulse mode at 525 W pressure amplitude using a high intensity ultrasonic processor, with 3 s of operation and 3 s of rest during the pulse process, to obtain an oil-in-water gel Pickering emulsion. The temperature was maintained at 80°C during the dispersion process.

[0052] Example 2

[0053] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0054] Step 1: Add beeswax to soybean oil, stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it to obtain the desired oil gel. The concentration of beeswax in the oil gel is 10.0% w / v.

[0055] Step 2: Add nanocellulose whiskers to the sodium alginate solution and mix thoroughly to obtain an aqueous solution. The aqueous solution has a NaCl concentration of 60 mM, a sodium alginate concentration of 0.2% w / v, and a nanocellulose whisker concentration of 0.5% w / v. Heat at 80°C for 15 minutes.

[0056] The preparation process of nanocellulose whiskers is as follows:

[0057] 100mL of 5mol / L hydrochloric acid and 100mL of 20mg / mL nanocellulose whiskers were mixed and dispersed, and heated in a constant temperature oscillating water bath at 99°C and 100rpm for 1h to fully react and obtain modified nanocellulose whiskers. After desulfurization, first cool it, then centrifuge and wash it at 8000rpm for 15min; pour out the supernatant to remove the hydrochloric acid, repeat centrifugation until the upper liquid becomes turbid, and pour the upper turbid suspension into a dialysis bag with a molecular weight cutoff of 8000-14000Da for dialysis until the pH value of the dialysate is neutral. Use polyethylene glycol 20000 to concentrate the suspension in the dialysis bag, collect the concentrated sample suspension and save it.

[0058] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired oil-in-water gel Pickering emulsion (denoted as CNW1 in the figure); the volume ratio of the oil gel to the aqueous solution is 3:7.

[0059] The dispersion process is as follows:

[0060] The mixture was homogenized for 2 min at 10000 rpm using an ultrafine homogenizer, and ultrasonicated for 2 min in pulse mode at 525 W pressure amplitude using a high-intensity ultrasonic processor, with 3 s of operation and 3 s of rest during the pulse process, to obtain an oil-in-water gel Pickering emulsion. The temperature was maintained at 70°C during the dispersion process.

[0061] Example 3

[0062] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0063] Step 1: Add beeswax to soybean oil, stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it to obtain the desired oil gel. The concentration of beeswax in the oil gel is 10.0% w / v.

[0064] Step 2: Add nanocellulose whiskers to the sodium alginate solution and mix thoroughly to obtain an aqueous solution. The aqueous solution has a NaCl concentration of 60 mM, a sodium alginate concentration of 0.5% w / v, and a nanocellulose whisker concentration of 0.5% w / v. Heat at 80°C for 15 minutes.

[0065] The preparation process of nanocellulose whiskers is as follows:

[0066] 100mL of 5mol / L hydrochloric acid and 100mL of 20mg / mL nanocellulose whiskers were mixed and dispersed, and heated in a constant temperature oscillating water bath at 99°C and 100rpm for 0.5h to fully react and obtain modified nanocellulose whiskers. After desulfurization, first cool it, then centrifuge and wash it at 8000rpm for 15min; pour out the supernatant to remove the hydrochloric acid, repeat centrifugation until the upper liquid becomes turbid, and pour the upper turbid suspension into a dialysis bag with a molecular weight cutoff of 8000-14000Da for dialysis until the pH value of the dialysate is neutral. Use polyethylene glycol 20000 to concentrate the suspension in the dialysis bag, collect the concentrated sample suspension and save it.

[0067] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired water-in-oil gel Pickering emulsion; the volume ratio of the oil gel to the aqueous solution is 3:7.

[0068] The dispersion process is as follows:

[0069] The mixture was homogenized at 10,000 rpm for 2 minutes using an ultrafine homogenizer, and ultrasonicated at 525 W pressure amplitude for 2 minutes using a high-intensity ultrasonic processor, with 3 seconds of operation and 3 seconds of rest during the pulse process, to obtain an oil-in-water gel Pickering emulsion. The temperature was maintained at 90°C during the dispersion process.

[0070] Example 4

[0071] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0072] Step 1: Add beeswax to soybean oil, stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it to obtain the desired oil gel. The concentration of beeswax in the oil gel is 10.0% w / v.

[0073] Step 2: Add nanocellulose whiskers to the sodium alginate solution and mix thoroughly to obtain an aqueous solution. The aqueous solution has a NaCl concentration of 60 mM, a sodium alginate concentration of 1.0% w / v, and a nanocellulose whisker concentration of 0.5% w / v. Heat at 80°C for 15 minutes.

[0074] The preparation process of nanocellulose whiskers is as follows:

[0075] 100mL of 5mol / L hydrochloric acid and 100mL of 20mg / mL nanocellulose whiskers were mixed and dispersed, and heated in a constant temperature oscillating water bath at 99°C and 100rpm for 0.5h to fully react and obtain modified nanocellulose whiskers. After desulfurization, first cool it, then centrifuge and wash it at 8000rpm for 15min; pour out the supernatant to remove the hydrochloric acid, repeat centrifugation until the upper liquid becomes turbid, and pour the upper turbid suspension into a dialysis bag with a molecular weight cutoff of 8000-14000Da for dialysis until the pH value of the dialysate is neutral. Use polyethylene glycol 20000 to concentrate the suspension in the dialysis bag, collect the concentrated sample suspension and save it.

[0076] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired water-in-oil gel Pickering emulsion; the volume ratio of the oil gel to the aqueous solution is 3:7.

[0077] The dispersion process is as follows:

[0078] The mixture was homogenized for 2 min at 10000 rpm using an ultrafine homogenizer, and ultrasonicated for 2 min in pulse mode at 525 W pressure amplitude using a high intensity ultrasonic processor, with 3 s of operation and 3 s of rest during the pulse process, to obtain an oil-in-water gel Pickering emulsion. The temperature was maintained at 80°C during the dispersion process.

[0079] Comparative Example 1

[0080] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0081] Step 1: Add beeswax to soybean oil, stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it to obtain the desired oil gel. The concentration of beeswax in the oil gel is 10.0% w / v.

[0082] Step 2: Add nanocellulose whiskers to the sodium alginate solution and mix thoroughly to obtain an aqueous solution. The aqueous solution has a NaCl concentration of 60 mM, a sodium alginate concentration of 0.2% w / v, and a nanocellulose whisker concentration of 0.5% w / v. Heat at 80°C for 15 minutes.

[0083] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired oil-in-water gel Pickering emulsion (denoted as CNW0 in the figure); the volume ratio of the oil gel to the aqueous solution is 3:7.

[0084] The dispersion process is as follows:

[0085] The mixture was homogenized for 2 min at 10000 rpm using an ultrafine homogenizer, and ultrasonicated for 2 min in pulse mode at 525 W pressure amplitude using a high intensity ultrasonic processor, with 3 s of operation and 3 s of rest during the pulse process, to obtain an oil-in-water gel Pickering emulsion. The temperature was maintained at 80°C during the dispersion process.

[0086] Comparative Example 2

[0087] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0088] Step 1: Add beeswax to soybean oil, stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it to obtain the desired oil gel. The concentration of beeswax in the oil gel is 10.0% w / v.

[0089] Step 2: Add nanocellulose whiskers to the sodium alginate solution and mix thoroughly to obtain an aqueous solution. The aqueous solution has a NaCl concentration of 60 mM, a sodium alginate concentration of 0.2% w / v, and a nanocellulose whisker concentration of 0.5% w / v. Heat at 80°C for 15 minutes.

[0090] The preparation process of nanocellulose whiskers is as follows:

[0091] 100mL of 5mol / L hydrochloric acid and 100mL of 20mg / mL nanocellulose whiskers were mixed and dispersed, and heated in a constant temperature oscillating water bath at 100°C and 100rpm for 3h to fully react to obtain modified nanocellulose whiskers. After desulfurization, first cool it, then centrifuge and wash it at 8000rpm for 15min; pour out the supernatant to remove the hydrochloric acid, repeat centrifugation until the upper liquid becomes turbid, and pour the upper turbid suspension into a dialysis bag with a molecular weight cutoff of 8000-14000Da for dialysis until the pH value of the dialysate is neutral. Use polyethylene glycol 20000 to concentrate the suspension in the dialysis bag, collect the concentrated sample suspension and save it.

[0092] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired oil-in-water gel Pickering emulsion (denoted as CNW3 in the figure); the volume ratio of the oil gel to the aqueous solution is 3:7.

[0093] The dispersion process is as follows:

[0094] The mixture was homogenized for 2 min at 10000 rpm using an ultrafine homogenizer, and ultrasonicated for 2 min in pulse mode at 525 W pressure amplitude using a high intensity ultrasonic processor, with 3 s of operation and 3 s of rest during the pulse process, to obtain an oil-in-water gel Pickering emulsion. The temperature was maintained at 80°C during the dispersion process.

[0095] Comparative Example 3

[0096] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0097] Step 1: Add beeswax to soybean oil, stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it to obtain the desired oil gel. The concentration of beeswax in the oil gel is 10.0% w / v.

[0098] Step 2: Add nanocellulose whiskers to the sodium alginate solution and mix thoroughly to obtain an aqueous solution. The aqueous solution has a NaCl concentration of 60 mM, a sodium alginate concentration of 0.2% w / v, and a nanocellulose whisker concentration of 0.5% w / v. Heat at 80°C for 15 minutes.

[0099] The preparation process of nanocellulose whiskers is as follows:

[0100] 100mL of 5mol / L hydrochloric acid and 100mL of 20mg / mL nanocellulose whiskers were mixed and dispersed, and heated in a constant temperature oscillating water bath at 98°C and 100rpm for 6h to fully react to obtain modified nanocellulose whiskers. After desulfurization, first cool it, then centrifuge and wash it at 8000rpm for 15min; pour out the supernatant to remove the hydrochloric acid, repeat centrifugation until the upper liquid becomes turbid, and pour the upper turbid suspension into a dialysis bag with a molecular weight cutoff of 8000-14000Da for dialysis until the pH value of the dialysate is neutral. Use polyethylene glycol 20000 to concentrate the suspension in the dialysis bag, collect the concentrated sample suspension and save it.

[0101] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired oil-in-water gel Pickering emulsion (denoted as CNW6 in the figure); the volume ratio of the oil gel to the aqueous solution is 3:7.

[0102] The dispersion process is as follows:

[0103] The mixture was homogenized for 2 min at 10000 rpm using an ultrafine homogenizer, and ultrasonicated for 2 min in pulse mode at 525 W pressure amplitude using a high intensity ultrasonic processor, with 3 s of operation and 3 s of rest during the pulse process, to obtain an oil-in-water gel Pickering emulsion. The temperature was maintained at 80°C during the dispersion process.

[0104] Comparative Example 4

[0105] A method for preparing an oil-in-water gel Pickering emulsion comprises the following steps:

[0106] Step 1: Add beeswax to soybean oil, stir at a speed of 300 rpm and 80° C. for 15 minutes to melt the beeswax and evenly disperse it to obtain the desired oil gel. The concentration of beeswax in the oil gel is 10.0% w / v.

[0107] Step 2: Prepare an aqueous solution with a NaCl concentration of 60 mM and a nanocellulose whisker concentration of 0.5% w / v. Heat at 80°C for 15 min.

[0108] The preparation process of nanocellulose whiskers is as follows:

[0109] 100mL of 5mol / L hydrochloric acid and 100mL of 20mg / mL nanocellulose whiskers were mixed and dispersed, and heated in a constant temperature oscillating water bath at 99°C and 100rpm for 0.5h to fully react and obtain modified nanocellulose whiskers. After desulfurization, first cool it, then centrifuge and wash it at 8000rpm for 15min; pour out the supernatant to remove the hydrochloric acid, repeat centrifugation until the upper liquid becomes turbid, and pour the upper turbid suspension into a dialysis bag with a molecular weight cutoff of 8000-14000Da for dialysis until the pH value of the dialysate is neutral. Use polyethylene glycol 20000 to concentrate the suspension in the dialysis bag, collect the concentrated sample suspension and save it.

[0110] Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired water-in-oil gel Pickering emulsion; the volume ratio of the oil gel to the aqueous solution is 3:7.

[0111] The dispersion process is as follows:

[0112] The mixture was homogenized for 2 min at 10000 rpm using an ultrafine homogenizer, and ultrasonicated for 2 min in pulse mode at 525 W pressure amplitude using a high intensity ultrasonic processor, with 3 s of operation and 3 s of rest during the pulse process, to obtain an oil-in-water gel Pickering emulsion. The temperature was maintained at 80°C during the dispersion process.

[0113] Figure 1Schematic diagram of the surface sulfonic acid group density of nanocellulose whiskers obtained in Examples 1 to 2 of the present invention and Comparative Examples 1, 2, and 3. It can be seen from the figure that the sulfonic acid groups can be effectively cut out from the surface of CNW by hydrochloric acid hydrolysis. When the hydrochloric acid hydrolysis time is 0.5, 1, 3, and 6 hours, the CNW sulfonic acid group density is (0.28±0.01)mmol / g, (0.12±0.01)mmol / g, (0.08±0.00)mmol / g, and (0.08±0.01)mmol / g, respectively. As the hydrochloric acid hydrolysis time increases, the CNW sulfonic acid group density decreases significantly, which is consistent with the decrease in the absolute value of the Zeta potential. When the hydrochloric acid hydrolysis time increases to 3h, stratification occurs in the CNW dispersion, and the degree of stratification increases as the hydrolysis time increases. By changing the hydrochloric acid hydrolysis time, CNWs with different sulfonic acid group densities but similar fiber lengths are obtained.

[0114] Figure 2 The microstructure diagram of the oil-in-water gel Pickering emulsion obtained in Examples 1 to 2 of the present invention and Comparative Examples 1, 2, and 3, a is a schematic diagram of a laser confocal microscope, and b is a schematic diagram of the emulsion particle size distribution. Figure 2 In figure a, it can be seen that the oil gel phase exists in the emulsion system as a dispersed phase, forming a water-in-oil gel Pickering emulsion. CNW is coated on the surface of each spherical oil gel, and CNW is successfully adsorbed on the oil-water interface to stabilize the emulsion. Figure 2 It can be seen from Figure b that the peak values ​​of the emulsion droplet size distribution obtained in Comparative Example 1 and Examples 1 to 4 are 3.7 μm, 4.4 μm, 4.7 μm, 5.2 μm, and 5.1 μm, respectively. As the density of the CNW sulfonic acid group decreases, the peak value of the emulsion particle size distribution increases and the distribution range shifts to the right. This indicates that as the hydrolysis time of hydrochloric acid increases, the droplet size of the emulsion increases. As the density of the sulfonic acid group on the CNW surface decreases, the electrostatic repulsion between the particles weakens, and the particles are easily aggregated, resulting in an increase in the emulsion particle size.

[0115] Figure 3 The schematic diagram of the stability test results of the water-in-oil gel Pickering emulsion obtained in Examples 1 to 2 of the present invention and Comparative Examples 1, 2, and 3, a is a macroscopic morphology during storage, b is a CI test result during storage, c is an optical microscope schematic diagram during storage, and d is a schematic diagram of the average particle size statistical results during storage. Figure 3 As can be seen in Figure a, on day 0, CNWs with different sulfonic acid group densities can be used to make uniform milky white emulsions. Water can be observed to precipitate from the emulsion on days 7 and 20. This is due to phase separation caused by gravity. Under the same storage days, as the density of CNW sulfonic acid groups decreases, the volume of water precipitated from the emulsion first decreases significantly and then increases significantly. Figure 3As can be seen in b, during the 20-day storage process, after 20 days of storage, as the density of CNW sulfonic acid groups decreases, the CI of the emulsion stabilizes at (41.7±2.1)%, (35.1±0.7)%, (40.0±2.1)%, (44.3±2.8)% and (43.9±0.6)%. As the density of CNW sulfonic acid groups decreases, its CI first decreases significantly and then increases significantly. Too large or too small a density of CNW sulfonic acid groups is not conducive to the storage stability of water-in-oil gel Pickering emulsions. The sulfonic acid group density obtained by the CNW sulfonic acid group preparation method selected in the present invention meets the requirements. Through the change of CI, it can be found that there are two stages of emulsion stability with the decrease of CNW sulfonic acid group density. In the first stage, the decrease of sulfonic acid group density weakens the electrostatic repulsion between CNWs, and CNWs are easy to aggregate. When the CNWs covered on the surface of the emulsion droplets are in an appropriate aggregation state, a relatively stable emulsion can be obtained. At the same time, the electrostatic repulsion of the emulsion is sufficient to overcome the van der Waals attraction and prevent the aggregation of oil droplets, thereby improving the stability of the emulsion. In the second stage, due to the decrease of sulfonic acid group density, the electrostatic repulsion between CNWs continues to decrease, and the repulsive interaction between droplets is no longer stronger than the attractive interaction, resulting in flocculation of emulsion droplets and reduced emulsion stability.

[0116] from Figure 3 As can be seen in Figure c, the droplet size of the emulsion increases significantly with the decrease in the density of the CNW sulfonic acid group. The degree of flocculation of the emulsion droplets increases after 7 days of storage. After 20 days of storage, the degree of flocculation of the emulsion droplets continues to increase. Under the same storage time, the density of the CNW sulfonic acid group decreases and the degree of flocculation of the emulsion droplets increases. This is because as the density of the CNW sulfonic acid group decreases, the electrostatic repulsion between the emulsion droplets decreases, resulting in an increase in the degree of droplet flocculation. Figure 3 In the figure, d is the particle size statistics. During storage, the average particle size of the emulsion droplets prepared by CNW with different sulfonic acid group densities did not change significantly. This is due to the electrostatic repulsion between the emulsion droplets, which can prevent the droplets from aggregating. In addition, the oil gel is a semi-solid state. Even if the emulsion droplets flocculate, they will not merge into larger droplets, but will remain at their original size and stick together, so that the average particle size of the emulsion droplets does not change significantly during storage.

[0117] In the preparation process step 1 of Examples 1, 3, 4 and Comparative Examples 1 to 4, curcumin was added at the same time, and the concentration of curcumin in the oil gel solution was 1.0% (w / v); a magnetic stirrer was used to stir for 1 h in a water bath heated at 60° C., and ultrasound was performed for 30 min to ensure that curcumin was dissolved as much as possible.

[0118] Figure 4Schematic diagram of the stability test results of the water-in-oil gel Pickering emulsion obtained in Examples 1, 3 and 4 of the present invention and Comparative Example 4, a is a macroscopic morphology during storage, b is a CI test result during storage, c is an optical microscope diagram during storage, and d is a schematic diagram of the average particle size statistics during storage. Figure 4 As can be seen in Figure a, on day 0, uniform milky white emulsions can be prepared at different sodium alginate concentrations. Water can be observed to precipitate from the emulsion on days 7 and 20. This is due to phase separation caused by gravity. Under the same storage days, as the sodium alginate concentration increases, the volume of water precipitated from the emulsion decreases significantly. Figure 3 It can be seen from Figure b that when the sodium alginate concentration is 0%, 0.2%, 0.5% and 1.0%, respectively, after storage at 25°C for 20 days, the CI of the emulsion is stabilized at (44.5±2.5)%, (41.7±2.1)%, (35.6±2.5)% and (15.7±2.0)%, respectively. The CI is significantly reduced, indicating that the increase in the sodium alginate concentration is beneficial to improving the storage stability of the emulsion. The addition of sodium alginate produces a stronger network structure in the continuous phase of the emulsion, and the increase in the sodium alginate concentration increases the viscosity of the continuous phase. This reduces the fluidity of the dispersed phase, prevents droplet flocculation and aggregation, and improves the stability of the emulsion. Figure 3 As can be seen in Figure c, the droplet size increases significantly with the increase of sodium alginate concentration. After 7 days of storage, the emulsion droplets of the emulsions with sodium alginate concentrations of 0% and 0.2% begin to flocculate. After 20 days of storage, no significant changes were found in the droplet state of the emulsions prepared under conditions of sodium alginate concentrations of 0.5% and 1.0%. Figure 4 It can be seen in Figure d that as the sodium alginate concentration increases from 0% to 1.0%, the average particle size of the Pickering emulsion droplets increases from (4.3±0.2)μm to (9.2±0.1)μm. There is no significant difference in the average particle size of the droplets of the emulsions prepared at different sodium alginate concentrations during storage. The average particle size of the emulsion droplets can remain relatively stable during storage because there is an electrostatic repulsion between the droplets to prevent the droplets from aggregating. The oil gel is a semi-solid state. Even if the emulsion droplets flocculate, they will not merge into larger droplets, but will remain at their original size and stick together. In addition, the increase in sodium alginate concentration increases the viscosity of the continuous phase, preventing the emulsion droplets from flocculating and agglomerating during storage. With the increase in sodium alginate concentration, the emulsion stability is significantly improved. The storage stability of the emulsion is excellent when the sodium alginate concentration is 1.0%.

[0119] Figure 5 The encapsulation comparison of curcumin by the water-in-oil gel Pickering emulsion obtained in Example 4 of the present invention and Comparative Example 4, a is the encapsulation rate of curcumin, and b is the retention rate during storage. Figure 5As can be seen in Figure a, the embedding rates of curcumin in the emulsions prepared at 0% and 1.0% sodium alginate concentrations were (80.9±0.7)% and (86.3±3.7)%, respectively, and the embedding rate of curcumin increased significantly. With the addition of sodium alginate, the embedding rate of curcumin increased significantly. Figure 5 It can be seen from b that during storage for 20 days, in the emulsion prepared under the conditions of sodium alginate concentration of 0% and 1.0%, as the storage time is extended, the retention rate of curcumin in the emulsion is significantly reduced. After storage for 20 days, it is observed that the retention rate of the emulsion with a sodium alginate concentration of 0% after storage for 20 days is (89.5 ± 0.7)%, and the retention rate of the emulsion with a sodium alginate concentration of 1.0% after storage for 20 days is (92.8 ± 0.9)%. Compared with the emulsion with a sodium alginate concentration of 0%, the retention rate of curcumin in the emulsion with a sodium alginate concentration of 1.0% is significantly improved, and chemical stability is significantly improved. This is because the addition of sodium alginate causes more droplets of large particle size to exist in the emulsion, and the presence of large droplets reduces the contact area between oxygen and curcumin in the oil droplets, slowing down the oxidative degradation of curcumin.

[0120] The water-in-oil gel Pickering emulsion obtained by the present invention has a high embedding rate for oil and water-poorly soluble nutrients. Curcumin can be uniformly dispersed and fixed in the three-dimensional network structure of the oil gel. The highly stable emulsion system can keep curcumin from being destroyed during the gastric digestion stage, thereby improving its bioavailability.

[0121] Figure 6 The release rate of curcumin during gastrointestinal digestion after the oil-in-water gel Pickering emulsion obtained in Example 4 of the present invention and Comparative Example 4 encapsulates curcumin. Figure 6It can be seen that the release of curcumin in the gastrointestinal tract gradually increases with the increase of digestion time. After 2 hours of digestion in the stomach stage, (41.5±2.0)% of the curcumin in the emulsion with 0% sodium alginate encapsulated curcumin was released, while the curcumin release rate of the emulsion prepared under the condition of 1.0% sodium alginate concentration was significantly reduced compared with it, only (11.9±0.3)%. This result shows that the emulsion prepared at a sodium alginate concentration of 1.0% can effectively protect curcumin in the stomach environment and deliver it to the next stage. Since the emulsion prepared at a sodium alginate concentration of 0% releases most of the curcumin in the stomach stage, the cumulative release of curcumin in this stage after 2 hours of intestinal digestion is only (30.9±1.0)%. In the first 30 minutes after the emulsion with a sodium alginate concentration of 1.0% enters the intestinal stage of digestion, (46.3±4.4)% of curcumin is rapidly released from the emulsion, and after 2 hours of intestinal digestion, the cumulative release of curcumin in this stage is (62.3±1.0)%. With the addition of sodium alginate, the release rate of curcumin in intestinal digestion is significantly improved. This is because the emulsion droplet interface membrane prepared at a sodium alginate concentration of 0% is relatively fragile. Under the acidic conditions of the stomach, a relatively large amount of the emulsion droplet interface membrane is destroyed after complete gastric digestion, and curcumin is released in large quantities in the gastric stage. As a result, only a small part of curcumin can be effectively embedded and delivered to the intestinal stage and then released. The emulsion droplet interface membrane prepared at a sodium alginate concentration of 1.0% is more stable, which can effectively protect the curcumin from being delivered to the intestine for release during gastric digestion. In the first 30 minutes of simulated intestinal digestion, lipase reacts rapidly with oil in the smaller droplets of the emulsion and destroys most of the emulsion droplet interface membranes, causing the release of a large amount of curcumin. Afterwards, the gel network structure of the oil gel can delay the reaction of lipase and oil, so that the release rate of curcumin in the later period tends to be gentle. The method for simulating the gastrointestinal environment used in the present invention is an existing method, and the test and calculation method of the release rate also adopts an existing method.

[0122] Figure 7 The bioaccessibility of curcumin after being embedded in the water-in-oil gel Pickering emulsion obtained in Example 4 of the present invention and Comparative Example 4. Figure 7It can be seen that the bioaccessibility of curcumin in the emulsion with a sodium alginate concentration of 0% is (38.6±2.1)%, and the bioaccessibility of curcumin in the emulsion with a sodium alginate concentration of 1.0% is (45.6±0.3)%, and the bioaccessibility is significantly improved. Digestible substances such as fatty acids, monoacylglycerols and bile salts can be integrated into mixed micelles to form, thereby promoting the solubility of curcumin. The release of a large amount of curcumin in the emulsion with a sodium alginate concentration of 0% in the stomach stage will cause the loss of curcumin, and only a small part of curcumin can be effectively encapsulated and delivered to the intestinal stage for digestion and absorption. The emulsion with a sodium alginate concentration of 1.0% can encapsulate and deliver most of the curcumin to the intestine and then release it. Therefore, the bioaccessibility of curcumin in the emulsion with a sodium alginate concentration of 1.0% is significantly improved compared with the bioaccessibility of curcumin in the emulsion with a sodium alginate concentration of 0%.

[0123] Sodium alginate is added to the water-in-oil gel Pickering emulsion of the present invention, and the particle size of the emulsion droplets increases from (4.3±0.2)μm to (9.2±0.1)μm. The particle size of the emulsion does not change significantly during storage, and CI decreases from (44.5±2.5)% to (15.7±2.0)%. The increase in the concentration of sodium alginate is conducive to improving the stability of the emulsion. Adding sodium alginate can improve the embedding capacity of the emulsion for curcumin, and at the same time help to improve the stability of curcumin during storage. Adding 1.0% of sodium alginate, the embedding rate of the water-in-oil gel Pickering emulsion for curcumin is increased by 5.4%, and the retention rate stored at 25°C for 20 days is increased by 3.3%. The increase in the concentration of sodium alginate is conducive to improving the protective ability of the water-in-oil gel Pickering emulsion for curcumin during in vitro digestion, and can more effectively deliver curcumin to the intestine for digestion and absorption. The release rate of curcumin in the stomach was significantly reduced, the release rate in the intestine was significantly increased, and the bioaccessibility was increased by 7.0%. The stability of the water-in-oil gel Pickering emulsion was further improved by adding CNW treated with hydrochloric acid.

Claims

1. A method for preparing an oil-in-water gel Pickering emulsion, characterized in that: The following steps are involved: Step 1: Dispersing liquid oil and beeswax to obtain oil gel; Step 2: adding nanocellulose whiskers to the sodium alginate solution and mixing them thoroughly to obtain an aqueous solution; wherein the mass ratio of the sodium alginate to the nanocellulose whiskers is 2 to 10:5; Step 3: The oil gel in step 1 and the aqueous solution in step 2 are fully mixed and dispersed to obtain the desired water-in-oil gel Pickering emulsion.

2. The method for preparing an oil-in-water gel Pickering emulsion according to claim 1, characterized in that: The nanocellulose whiskers are modified nanocellulose whiskers that have been desulfurized with hydrochloric acid; The preparation method of modified nanocellulose whiskers is as follows: The hydrochloric acid and the nanocellulose whiskers are mixed, and oscillated and heated at 98-100° C. and 100 rpm for 0.5-1 h to fully react to obtain the modified nanocellulose whiskers; wherein the mass ratio of the hydrochloric acid to the nanocellulose is 9:

10.

3. The method for preparing an oil-in-water gel Pickering emulsion according to claim 2, characterized in that: After the reaction of the hydrochloric acid and the nanocellulose whiskers is completed, the desired modified nanocellulose whiskers can be obtained by cooling, centrifuging, washing and dialysis; the centrifugal speed is 8000 rpm and the centrifugal time is 15 minutes.

4. The method for preparing an oil-in-water gel Pickering emulsion according to claim 1, characterized in that: In step 1, the gel preparation process is as follows: Beeswax is added to soybean oil, wherein the concentration of the beeswax is 10.0% w / v; the mixture is stirred at a speed of 300 rpm and 80° C. for 15 minutes to obtain the desired oil gel.

5. The method for preparing an oil-in-water gel Pickering emulsion according to claim 1, characterized in that: In the step 2, the aqueous phase solution is heated at 80° C. for 15 min.

6. The method for preparing an oil-in-water gel Pickering emulsion according to claim 1, characterized in that: The mixing and dispersing process in step 3 is as follows: First, homogenize at an emulsifier speed of 10000 rpm for 2 min; Then pulse ultrasound was applied at 525 W for 2 min; During the ultrasound process, the ultrasound is cycled for N seconds and then paused for M seconds.

7. The method for preparing an oil-in-water gel Pickering emulsion according to claim 1, characterized in that: The aqueous phase solution in step 2 also contains NaCl, wherein the concentration of NaCl is 60 mM.

8. The Pickering emulsion based on oil-in-water gel obtained by any one of the preparation methods of claims 1 to 7.

9. The use of an oil-in-water gel Pickering emulsion as claimed in claim 8, characterized in that: The oil-in-water gel Pickering emulsion is used as a nutrient embedding delivery vehicle.

10. The use of the oil-in-water gel Pickering emulsion according to claim 9, characterized in that: The nutrient is curcumin.

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