Chitosan-pickering emulsion composite, and preparation method and application thereof

Abstract

The application discloses a chitosan-Pickering emulsion compound and a preparation method and application thereof. The chitosan-Pickering emulsion compound comprises a chitosan solution and a Pickering emulsion, chitosan in the chitosan solution is adsorbed on the surface of the Pickering emulsion droplet, and the Pickering emulsion is prepared from a microcrystalline cellulose aqueous solution and a curcumin soybean oil solution. The chitosan-Pickering emulsion compound has the advantages of good stability, low cost, safety and environmental protection, and the like, and is suitable for being applied to the field of intelligent packaging materials, and can endow the packaging materials with long-acting antioxidant properties and food freshness indication functions.

Description

Technical Field

[0001] This invention relates to the field of Pickering emulsion technology, specifically to a chitosan-Pickering emulsion complex, its preparation method, and its application. Background Technology

[0002] Emulsions are systems composed of two immiscible liquids. Due to the high surface energy between the two immiscible phases, emulsion systems are generally considered thermodynamically unstable. Therefore, emulsions are typically prepared in the presence of surfactants or stabilizers. Pickering emulsions are emulsions stabilized by solid particles. Due to the irreversible adsorption of solid particles at the interface of the two immiscible liquids, their resistance to deformation is significantly improved compared to emulsions stabilized with traditional surfactants. They have found wide applications in petroleum recovery, pharmaceutical delivery, food, and cosmetics.

[0003] With the development of the food packaging industry, people have higher requirements for the mechanical properties, barrier properties, and printability of packaging materials. Curcumin is a natural polyphenol compound with various effects such as anti-oxidation, anti-inflammation, and anti-cancer properties. It also exhibits different absorption spectra at different pH values, displaying different colors, and has broad application prospects in the field of smart packaging. However, curcumin has hydrophobic and lipophilic properties and is easily decomposed by light, which severely limits its industrial application in the food packaging field. Summary of the Invention

[0004] The purpose of this invention is to provide a chitosan-Pickering emulsion complex, its preparation method, and its application.

[0005] The technical solution adopted in this invention is:

[0006] A chitosan-Pickering emulsion complex comprises a chitosan solution and a Pickering emulsion; the chitosan in the chitosan solution is adsorbed onto the surface of Pickering emulsion droplets; the Pickering emulsion is made from an aqueous solution of microcrystalline cellulose and a soybean oil solution of curcumin.

[0007] Preferably, the volume ratio of the chitosan solution to the Pickering emulsion is 1:0.9 to 1.1.

[0008] Preferably, the volume ratio of the microcrystalline cellulose aqueous solution to the curcumin soybean oil solution is 1 to 9:1.

[0009] Preferably, the mass percentage of microcrystalline cellulose in the microcrystalline cellulose aqueous solution is 0.5% to 2.5%.

[0010] Preferably, the pH value of the microcrystalline cellulose aqueous solution is 3 to 11.

[0011] Preferably, the microcrystalline cellulose aqueous solution is prepared by adding microcrystalline cellulose to water and stirring overnight at a stirring speed of 200 r / min to 500 r / min.

[0012] Preferably, the curcumin content in the soybean oil solution is 0.1% to 0.5% by mass.

[0013] Preferably, the curcumin soybean oil solution is prepared by the following method: adding curcumin to soybean oil, then placing it in an ice bath and stirring overnight at a stirring speed of 200 r / min to 500 r / min under light-protected conditions, then centrifuging for 10 min to 20 min at a centrifuge speed of 8000 r / min to 10000 r / min, and taking the supernatant.

[0014] Preferably, the chitosan solution is an acetate buffer containing chitosan.

[0015] Preferably, the chitosan solution contains 0.1% to 0.5% chitosan by mass.

[0016] Preferably, the chitosan solution is prepared by adding chitosan to an acetate buffer solution with a concentration of 90 mmol / L to 110 mmol / L, and then stirring overnight at a stirring speed of 200 r / min to 500 r / min.

[0017] A method for preparing the chitosan-Pickering emulsion complex as described above includes the following steps:

[0018] 1) The microcrystalline cellulose aqueous solution and the curcumin soybean oil solution were mixed and homogenized by ultrasonication to obtain Pickering emulsion;

[0019] 2) Add the Pickering emulsion to the chitosan solution and mix to obtain the chitosan-Pickering emulsion complex.

[0020] Preferably, the ultrasonic power for ultrasonic homogenization in step 1) is 250W to 550W, and the ultrasonic time is 1min to 5min.

[0021] Preferably, the mixing method in step 2) is stirring, with a stirring speed of 200 r / min to 500 r / min and a stirring time of 20 min to 40 min.

[0022] A packaging material comprising the above-mentioned chitosan-Pickering emulsion complex.

[0023] The beneficial effects of the present invention are: the chitosan-Pickering emulsion complex of the present invention has the advantages of good stability, the encapsulated curcumin is not easily degraded, good and long-lasting antioxidant properties, low cost, safety and environmental protection, etc., and is suitable for use in the field of smart packaging materials. It can endow packaging materials with long-lasting antioxidant properties and food freshness indication function.

[0024] Specifically:

[0025] 1) This invention encapsulates curcumin in Pickering emulsion and adsorbs chitosan on the surface of Pickering emulsion droplets, which greatly reduces the degradation of curcumin and significantly improves the utilization rate of curcumin, thus exerting long-lasting antioxidant properties.

[0026] 2) The chitosan-Pickering emulsion complex of the present invention uses inexpensive and abundant raw materials, and the preparation process is environmentally friendly and simple. Attached Figure Description

[0027] Figure 1 This is an appearance diagram of the chitosan-Pickering emulsion complex of Example 1.

[0028] Figure 2 This is an optical microscope image of the chitosan-Pickering emulsion complex from Example 1.

[0029] Figure 3 This is a particle size distribution diagram of the emulsion droplets in the chitosan-Pickering emulsion complex of Example 1.

[0030] Figure 4 This is a laser confocal microscope image of the chitosan-Pickering emulsion complex from Example 1.

[0031] Figure 5 The graph shows the retention rate test results of curcumin in the chitosan-Pickering emulsion complex of Example 1. Detailed Implementation

[0032] The present invention will be further explained and described below with reference to specific embodiments.

[0033] Example 1:

[0034] A chitosan-Pickering emulsion complex is prepared by the following steps:

[0035] 1) Add chitosan to a 100 mmol / L acetate buffer solution and stir overnight at a stirring speed of 300 r / min to obtain a chitosan solution with a mass fraction of 0.1%.

[0036] 2) Add curcumin to soybean oil, then place it in an ice bath and stir overnight at a stirring speed of 300 r / min in the dark. Then centrifuge at a speed of 8000 r / min for 10 min, and take the supernatant to obtain a soybean oil solution with a mass fraction of 0.1% curcumin.

[0037] 3) Add microcrystalline cellulose to deionized water to prepare a suspension with a mass fraction of 1%. Then adjust the pH of the suspension to 7 with 1 mol / L HCl solution and 1 mol / L NaOH solution. Stir overnight at a stirring speed of 300 r / min to obtain an aqueous solution of microcrystalline cellulose.

[0038] 4) Mix the microcrystalline cellulose aqueous solution and the curcumin soybean oil solution at a volume ratio of 9:1, and then place them in an ultrasonic cell disruptor and sonicate at 450W for 4 minutes to obtain Pickering emulsion.

[0039] 5) Slowly add the Pickering emulsion dropwise to an equal volume of chitosan solution while stirring at a speed of 300 r / min. After the addition is complete, continue stirring for 30 min to obtain the chitosan-Pickering emulsion complex.

[0040] Performance testing:

[0041] 1) The appearance of the chitosan-Pickering emulsion complex in this embodiment is shown in the figure below. Figure 1 (a is the freshly prepared chitosan-Pickering emulsion complex, and b is the chitosan-Pickering emulsion complex after being stored at room temperature for 40 days.)

[0042] Depend on Figure 1 It can be seen that the chitosan-Pickering emulsion complex did not separate after being stored at room temperature for 40 days, indicating its excellent stability.

[0043] 2) An optical microscope image of the chitosan-Pickering emulsion complex in this embodiment is shown below. Figure 2 As shown in the figure, the particle size distribution of the emulsion droplets is as follows: Figure 3 As shown.

[0044] Depend on Figure 2 It can be seen that the particle size of the emulsion droplets (chitosan adsorbed on the surface of the Pickering emulsion droplets) in the chitosan-Pickering emulsion complex is not much different, and the droplets are round and uniform in size.

[0045] Depend on Figure 3It can be seen that the droplet size of the emulsion maintains a single-peak distribution, indicating that the droplet size is very uniform. The average droplet size of the emulsion is 20.09 μm, which is not much different from the droplet size of Pickering emulsion without chitosan adsorption. The small droplet size is conducive to the stability of the emulsion.

[0046] 3) The laser confocal microscope image of the chitosan-Pickering emulsion complex in this embodiment is shown below. Figure 4 (a is an image of the Nile Blue-labeled chitosan-Pickering emulsion complex in the oil phase under 633 nm laser excitation; b is an image of the Rhodamine-labeled chitosan-Pickering emulsion complex in the chitosan phase under 543 nm laser excitation.) The retention rate test results of curcumin are shown in the following figure. Figure 5 As shown.

[0047] Depend on Figure 4 It can be seen that the Nile Blue-labeled oil phase droplets are relatively uniform in size; the Pickering emulsion droplets adsorbed by chitosan emit yellow fluorescence under laser irradiation, indicating that chitosan has been successfully adsorbed onto the surface of the Pickering emulsion droplets.

[0048] Depend on Figure 5 It can be seen that the retention rate of curcumin in the chitosan-Pickering emulsion complex was 88.90% after 40 days of storage at room temperature, which is very high (the dense interface layer formed by chitosan adsorbed on the surface of Pickering emulsion droplets is equivalent to a spatial barrier, which can prevent oxidants and free radicals from diffusing into the oil droplets, thus enhancing the stability of the Pickering emulsion and preventing oxidation from diffusing from one oil droplet to another).

[0049] Example 2:

[0050] A chitosan-Pickering emulsion complex is prepared by the following steps:

[0051] 1) Add chitosan to a 100 mmol / L acetate buffer solution and stir overnight at a stirring speed of 300 r / min to obtain a chitosan solution with a mass fraction of 0.1%.

[0052] 2) Add curcumin to soybean oil, then place it in an ice bath and stir overnight at a stirring speed of 300 r / min in the dark. Then centrifuge at a speed of 8000 r / min for 10 min, and take the supernatant to obtain a soybean oil solution with a mass fraction of 0.1% curcumin.

[0053] 3) Add microcrystalline cellulose to deionized water to prepare a suspension with a mass fraction of 2%. Then adjust the pH of the suspension to 7 with 1 mol / L HCl solution and 1 mol / L NaOH solution. Stir overnight at a stirring speed of 300 r / min to obtain an aqueous solution of microcrystalline cellulose.

[0054] 4) Mix the microcrystalline cellulose aqueous solution and the curcumin soybean oil solution at a volume ratio of 4:1, and then place them in an ultrasonic cell disruptor and sonicate at 450W for 5 minutes to obtain Pickering emulsion.

[0055] 5) Slowly add the Pickering emulsion dropwise to an equal volume of chitosan solution while stirring at a speed of 300 r / min. After the addition is complete, continue stirring for 30 min to obtain the chitosan-Pickering emulsion complex.

[0056] The test results (using the same method as in Example 1) showed that the chitosan in the chitosan-Pickering emulsion complex of this example was successfully adsorbed onto the surface of the emulsion droplets. After 40 days of storage at room temperature, there was no stratification. The retention rate of curcumin was 81.67%, the average particle size of the emulsion droplets was 25.23 μm, and the droplets varied in size.

[0057] Example 3:

[0058] A chitosan-Pickering emulsion complex is prepared by the following steps:

[0059] 1) Add chitosan to a 100 mmol / L acetate buffer solution and stir overnight at a stirring speed of 300 r / min to obtain a chitosan solution with a mass fraction of 0.1%.

[0060] 2) Add curcumin to soybean oil, then place it in an ice bath and stir overnight at a stirring speed of 300 r / min in the dark. Then centrifuge at a speed of 8000 r / min for 10 min, and take the supernatant to obtain a soybean oil solution with a mass fraction of 0.5% curcumin.

[0061] 3) Add microcrystalline cellulose to deionized water to prepare a suspension with a mass fraction of 0.5%. Then adjust the pH of the suspension to 3 with 1 mol / L HCl solution and 1 mol / L NaOH solution. Stir overnight at a stirring speed of 300 r / min to obtain an aqueous solution of microcrystalline cellulose.

[0062] 4) Mix the microcrystalline cellulose aqueous solution and the curcumin soybean oil solution at a volume ratio of 1:1, and then place them in an ultrasonic cell disruptor and sonicate at a power of 250W for 2 minutes to obtain Pickering emulsion.

[0063] 5) Slowly add the Pickering emulsion dropwise to an equal volume of chitosan solution while stirring at a speed of 300 r / min. After the addition is complete, continue stirring for 30 min to obtain the chitosan-Pickering emulsion complex.

[0064] According to the test (the test method is the same as in Example 1), the chitosan in the chitosan-Pickering emulsion complex of this example was successfully adsorbed onto the surface of the emulsion droplets. The adsorption was not very uniform. After being stored at room temperature for 40 days, there was no stratification. The retention rate of curcumin was 76.45%, the average particle size of the emulsion droplets was 28.53 μm, and the size of the emulsion droplets was uniform.

[0065] Example 4:

[0066] A chitosan-Pickering emulsion complex is prepared by the following steps:

[0067] 1) Add chitosan to a 100 mmol / L acetate buffer solution and stir overnight at a stirring speed of 300 r / min to obtain a chitosan solution with a mass fraction of 0.1%.

[0068] 2) Add curcumin to soybean oil, then place it in an ice bath and stir overnight at a stirring speed of 300 r / min in the dark. Then centrifuge at a speed of 8000 r / min for 10 min, and take the supernatant to obtain a soybean oil solution with a mass fraction of 0.5% curcumin.

[0069] 3) Add microcrystalline cellulose to deionized water to prepare a suspension with a mass fraction of 2.5%. Then adjust the pH of the suspension to 7 with 1 mol / L HCl solution and 1 mol / L NaOH solution. Stir overnight at a stirring speed of 300 r / min to obtain an aqueous solution of microcrystalline cellulose.

[0070] 4) Mix the microcrystalline cellulose aqueous solution and the curcumin soybean oil solution at a volume ratio of 9:1, and then place them in an ultrasonic cell disruptor and sonicate at 350W for 5 minutes to obtain Pickering emulsion.

[0071] 5) Slowly add the Pickering emulsion dropwise to an equal volume of chitosan solution while stirring at a speed of 300 r / min. After the addition is complete, continue stirring for 40 min to obtain the chitosan-Pickering emulsion complex.

[0072] The test results (using the same method as in Example 1) showed that the chitosan in the chitosan-Pickering emulsion complex of this example was successfully adsorbed onto the surface of the emulsion droplets. After 40 days of storage at room temperature, there was no stratification. The retention rate of curcumin was 80.63%, the average particle size of the emulsion droplets was 23.53 μm, and the droplet size was uniform.

[0073] Comparative Example 1:

[0074] A Pickering emulsion, the preparation method of which includes the following steps:

[0075] 1) Add curcumin to soybean oil, then place it in an ice bath and stir overnight at a stirring speed of 300 r / min in the dark. Then centrifuge at a speed of 8000 r / min for 10 min, and take the supernatant to obtain a soybean oil solution with a mass fraction of 0.1% curcumin.

[0076] 2) Add microcrystalline cellulose to deionized water to prepare a suspension with a mass fraction of 1%. Then adjust the pH of the suspension to 7 with 1 mol / L HCl solution and 1 mol / L NaOH solution. Stir overnight at a stirring speed of 300 r / min to obtain an aqueous solution of microcrystalline cellulose.

[0077] 3) Mix the microcrystalline cellulose aqueous solution and the curcumin soybean oil solution at a volume ratio of 9:1, and then place them in an ultrasonic cell disruptor and sonicate at 450W for 4 minutes to obtain Pickering emulsion.

[0078] 4) Slowly add Pickering emulsion dropwise to an equal volume of 100 mmol / L acetate buffer while stirring at 300 r / min. After the addition is complete, continue stirring for 30 min to obtain Pickering emulsion.

[0079] After testing (using the same method as in Example 1), the Pickering emulsion (without chitosan adsorption) of this comparative example showed obvious stratification after being stored at room temperature for 40 days. The retention rate of curcumin was 67.45%, the average particle size of the emulsion droplets was 19.83 μm, and the droplet size was uniform.

[0080] Comparative Example 2:

[0081] A chitosan-Pickering emulsion complex is prepared by the following steps:

[0082] 1) Add chitosan to a 100 mmol / L acetate buffer solution and stir overnight at a stirring speed of 300 r / min to obtain a chitosan solution with a mass fraction of 0.1%.

[0083] 2) Add curcumin to soybean oil, then place it in an ice bath and stir overnight at a stirring speed of 300 r / min in the dark. Then centrifuge at a speed of 8000 r / min for 10 min, and take the supernatant to obtain a soybean oil solution with a mass fraction of 0.1% curcumin.

[0084] 3) Add microcrystalline cellulose to deionized water to prepare a suspension with a mass fraction of 1%. Then adjust the pH of the suspension to 7 with 1 mol / L HCl solution and 1 mol / L NaOH solution. Stir overnight at a stirring speed of 300 r / min to obtain an aqueous solution of microcrystalline cellulose.

[0085] 4) Mix the microcrystalline cellulose aqueous solution and the curcumin soybean oil solution at a volume ratio of 9:1, and then place them in an ultrasonic cell disruptor and sonicate at 150W for 4 minutes to obtain Pickering emulsion.

[0086] 5) Slowly add the Pickering emulsion dropwise to an equal volume of chitosan solution while stirring at a speed of 300 r / min. After the addition is complete, continue stirring for 30 min to obtain the chitosan-Pickering emulsion complex.

[0087] Testing revealed that the comparative sample prepared in this study was not a chitosan-Pickering emulsion complex (the ultrasonic power was too low, the homogenization effect was not obvious, and a Pickering emulsion was not formed), but rather a dispersion containing chitosan, curcumin, and microcrystalline cellulose.

[0088] Comparative Example 3:

[0089] A chitosan-Pickering emulsion complex is prepared by the following steps:

[0090] 1) Add chitosan to a 100 mmol / L acetate buffer solution and stir overnight at a stirring speed of 300 r / min to obtain a chitosan solution with a mass fraction of 0.1%.

[0091] 2) Add curcumin to soybean oil, then place it in an ice bath and stir overnight at a stirring speed of 300 r / min in the dark. Then centrifuge at a speed of 8000 r / min for 10 min, and take the supernatant to obtain a soybean oil solution with a mass fraction of 0.1% curcumin.

[0092] 3) Add microcrystalline cellulose to deionized water to prepare a suspension with a mass fraction of 1%. Then adjust the pH of the suspension to 13 with 1 mol / L HCl solution and 1 mol / L NaOH solution. Stir overnight at a stirring speed of 300 r / min to obtain an aqueous solution of microcrystalline cellulose.

[0093] 4) Mix the microcrystalline cellulose aqueous solution and the curcumin soybean oil solution at a volume ratio of 9:1, and then place them in an ultrasonic cell disruptor and sonicate at 450W for 4 minutes to obtain Pickering emulsion.

[0094] 5) Slowly add the Pickering emulsion dropwise to an equal volume of chitosan solution while stirring at a speed of 300 r / min. After the addition is complete, continue stirring for 30 min to obtain the chitosan-Pickering emulsion complex.

[0095] The test (using the same method as in Example 1) showed that the chitosan in the chitosan-Pickering emulsion complex of this comparative example was successfully adsorbed onto the surface of the emulsion droplets, but the adsorption was uneven. After being stored at room temperature for 40 days, obvious stratification occurred. The retention rate of curcumin was 58.33%, the average particle size of the emulsion droplets was 40.61 μm, and the droplet sizes were inconsistent.

[0096] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A chitosan-Pickering emulsion complex, characterized in that, The composition includes a chitosan solution and a Pickering emulsion; the chitosan in the chitosan solution is adsorbed onto the surface of the Pickering emulsion droplets; the Pickering emulsion is prepared by ultrasonic homogenization of a mixture of microcrystalline cellulose aqueous solution and curcumin soybean oil solution; the volume ratio of the chitosan solution to the Pickering emulsion is 1:0.9–1.1; the volume ratio of the microcrystalline cellulose aqueous solution to the curcumin soybean oil solution is 1–9:1; the mass percentage of microcrystalline cellulose in the microcrystalline cellulose aqueous solution is 0.5%–2.5%; the pH value of the microcrystalline cellulose aqueous solution is 3–11; the mass percentage of curcumin in the curcumin soybean oil solution is 0.1%–0.5%; the mass percentage of chitosan in the chitosan solution is 0.1%–0.5%; and the ultrasonic power for ultrasonic homogenization is 250W–550W.

2. A method for preparing the chitosan-Pickering emulsion complex as described in claim 1, characterized in that, Includes the following steps: 1) A mixture of microcrystalline cellulose aqueous solution and curcumin soybean oil solution was ultrasonically homogenized to obtain Pickering emulsion; 2) Add the Pickering emulsion to the chitosan solution and mix to obtain the chitosan-Pickering emulsion complex.

3. The preparation method according to claim 2, characterized in that: Step 1) The ultrasonic power for ultrasonic homogenization is 250W to 550W, and the ultrasonic time is 1min to 5min.

4. A packaging material, characterized in that, It comprises the chitosan-Pickering emulsion complex of claim 1.

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