Double-emulsion-based hydrogel capable of coating small-molecule flavor substances and preparation method thereof

Abstract

The invention discloses hydrogel based on double emulsions and capable of coating small-molecule flavor substances and a preparation method thereof.The preparation method comprises the following steps that S1, a nonionic surfactant solution and a sodium alginate solution containing a water-soluble emulsifier are mixed to be uniform, and a water phase is prepared; s2, mixing a small molecule flavor substance with the water phase prepared in the step S1 to prepare an O1 / W primary emulsion; s3, mixing the O1 / W primary emulsion prepared in the step S2 with edible oil containing an oil-soluble emulsifier to prepare an O1 / W / O2 dual emulsion; s4, mixing the O1 / W / O2 double emulsion prepared in the step S3 with a calcium chloride solution to promote crosslinking of sodium alginate, then centrifuging, and pouring out an upper-layer oil phase; and S5, mixing the emulsion treated in the step S4 with an aqueous solution containing a water-soluble emulsifier, washing and collecting hydrogel particles. An O1 / W / O2 type double emulsion is used as a template, a small amount of Ca < 2 + > solution is added, and the calcium alginate hydrogel coated with the small-molecule flavor substances is prepared, so that the fragrance retention time of the calcium alginate hydrogel is prolonged, and the release rate of the calcium alginate hydrogel is controlled.

Description

Technical Field

[0001] The invention relates to the technical field of flavor substance sustained release, in particular to a double emulsion hydrogel of small molecule flavor substances and a preparation method thereof. Background Art

[0002] Flavor substances give food a specific aroma and taste, and are an important indicator of food sensory evaluation. Flavor substances mainly include two types: natural and synthetic, such as various alcohols, esters, aldehydes, fatty acids, sulfides, nitrogen-containing substances and other organic substances. With the progress of society and the increase in consumer demand, people use some flavor substances as edible flavors, which are widely used in the food processing industry, greatly enriching the types and tastes of food.

[0003] Most flavor and fragrance ingredients are highly volatile and have a short fragrance retention time, which can easily have an adverse effect on product quality. In addition, the stability and solubility of flavor and fragrance substances are limited, which restricts their application in the food industry. Therefore, the sustained-release and controlled-release technology of flavors and fragrances has become a hot topic and a difficult point of research at home and abroad. Related research fields are committed to developing certain special materials to form a coating relationship between flavor molecules and materials through physical or chemical bonding, thereby improving the storage stability of flavors and fragrances, slowing down or controlling their volatility in application, and extending their fragrance retention time.

[0004] Double emulsion is a multiphase system formed by emulsifying a single emulsion (usually called primary emulsion) twice and dispersing it in another continuous phase. Double emulsions mainly include two types: water-in-oil-in-water (W / O / W) and oil-in-water-in-oil (O / W / O). Among them, W / O / W double emulsion is more common. Compared with single-phase emulsions, double emulsions have unique two-film (oil / water interface) and three-phase structure. They can be used as coating and delivery carriers for drugs, active ingredients, etc., and can relatively prolong the release time of the coated substances, thereby increasing the fragrance retention time of the flavor substances and maintaining relatively stable product quality. However, double emulsions are different from simple O / W or W / O emulsions. Due to the presence of two dispersed phases, two phase volumes, and at least two surfactants, double emulsions belong to complex multiphase thermodynamically unstable systems. The instability of this system is mainly manifested in: diffusion of internal phase encapsulation, Ostwald ripening, flocculation and coalescence of internal and external phase droplets, etc., which greatly affect the application of double emulsions in actual production processes. Therefore, in order to prepare a double emulsion with high stability and good reproducibility, and to achieve the encapsulation and release of flavor substances, high requirements are placed on the preparation process, type of emulsifier, and component ratio. Summary of the invention

[0005] In view of the problem that the double emulsion for encapsulating flavor substances has low stability, the present invention provides a hydrogel based on double emulsion that can encapsulate small molecule flavor substances and a preparation method. The O1 / W / O2 double emulsion hydrogel for encapsulating flavor substances prepared by the method has good stability and encapsulates the flavor substances in the inner oil phase, which helps to control their release rate and improve the sustained-release effect.

[0006] In order to achieve the above object, the present invention provides a method for preparing a hydrogel capable of encapsulating small molecule flavor substances based on a double emulsion, comprising the following steps:

[0007] S1. Evenly mixing a polymer surfactant and a sodium alginate solution containing a nonionic surfactant to obtain an aqueous phase;

[0008] S2, mixing the small molecule flavor substance with the aqueous phase obtained in step S1 to obtain an O1 / W primary emulsion;

[0009] S3, mixing the O1 / W primary emulsion prepared in step S2 with edible oil containing an oil-soluble emulsifier to obtain an O1 / W / O2 double emulsion;

[0010] S4, mixing the O1 / W / O2 double emulsion prepared in step S3 with a calcium chloride solution to promote cross-linking of sodium alginate, and then centrifuging to pour out the upper oil phase;

[0011] S5, mixing the emulsion treated in step S4 with an aqueous solution containing a nonionic surfactant, washing and collecting the hydrogel particles.

[0012] Sodium alginate is a natural high molecular weight polysaccharide that is non-toxic, non-irritating, and has good hydrophilicity. It is widely used as a thickener, gelling agent, etc. in the field of food and daily chemical industry. Sodium alginate has good bioadhesion and biocompatibility. Sodium alginate is added to the middle water phase (W) of the O1 / W / O2 double emulsion to increase the viscosity of the water phase to restrict the movement of the droplets and improve the stability of the inner oil phase droplets. In addition, using the double emulsion as a template, the external Ca 2+ Cross-linking is performed to further prepare calcium alginate hydrogel encapsulating flavor substances, which can further improve the stability and sustained-release effect of the system.

[0013] The invention uses small molecule flavor substances as the inner oil phase (O1) and edible oil as the outer oil phase (O2), and uses food-grade emulsifiers and surfactants to prepare an O1 / W / O2 double emulsion encapsulating flavor substances through two-step emulsification. On this basis, the O1 / W / O2 double emulsion is used as a template, and a small amount of Ca is added. 2+The solution is used to prepare calcium alginate hydrogels encapsulating small molecule flavor substances, so as to prolong the fragrance retention time, control the release rate, and improve the sustained release effect of flavor substances. The preparation method of the invention is simple, the raw materials are safe and reliable, the production cost is low, and it has broad application prospects in the field of food industry.

[0014] Preferably, in step S1, the water-soluble emulsifier is Tween 20, and the nonionic surfactant is Pluronic F127. The mass ratio of Tween 20 to Pluronic F127 is (3-5):(0.1-0.3).

[0015] Tween20 can be quickly adsorbed on the oil-water interface to generate small emulsion droplets, while Pluronic F127 can form a thicker interfacial film with a certain degree of viscoelasticity on the surface of the droplets. The compounding of Tween20 and Pluronic F127 in a certain ratio can help enhance the stability of the O1 / W interfacial film and prevent the rupture of the inner oil phase droplets through the synergistic effect between the two surfactants. In addition, the interaction between the hydrophobic chains of Tween20 and F127 can improve the thermodynamic stability of the system.

[0016] Preferably, in step S2, the small molecule flavor substance is ethyl butyrate.

[0017] Preferably, in step S2, the mass ratio of the small molecule flavor substance to the aqueous phase is 1:(4-6).

[0018] Preferably, in step S2, the mixing is performed by shearing with a high-speed shearing instrument for 180 to 240 seconds at a rotation speed of 12000 to 15000 rpm.

[0019] Preferably, in step S3, the oil-soluble emulsifier is polyglycerol castoryl ester, the edible oil is sunflower oil, and the concentration of polyglycerol castoryl ester in the edible oil containing the oil-soluble emulsifier is 0.5-2.5wt%; the mass ratio of the O1 / W primary emulsion to the edible oil containing the oil-soluble emulsifier is 1:(9-13); and the mixing is performed by shearing with a high-speed shearing instrument for 150-240s at a rotation speed of 3000-6000rpm.

[0020] The invention adds a high molecular weight emulsifier polyglycerol polyricinoleate (PGPR) to sunflower oil, which helps to enhance the hydrophobicity of the outer oil phase and can hinder the migration of water molecules in the middle water phase to a certain extent, thereby helping to improve the stability of the O1 / W / O2 double emulsion system, thereby achieving slow and lasting release of ethyl butyrate in the system.

[0021] In 10-14 g of freshly prepared O1 / W / O2 emulsion, slowly add 500 μL-1500 μL of 1.0 mol·L-1 Calcium chloride aqueous solution.

[0022] Sodium alginate was added to the middle aqueous phase (W) of the O1 / W / O2 double emulsion to restrict the movement of droplets by increasing the viscosity of the aqueous phase and improve the stability of the ethyl butyrate droplets in the oil phase of the small molecule flavor substance. 2+ Cross-linking is performed to further prepare calcium alginate hydrogel encapsulating ethyl butyrate, thereby ultimately improving the sustained-release effect of ethyl butyrate in the application system.

[0023] Preferably, in step S5, the aqueous solution containing the nonionic surfactant is a 0.05wt% to 0.1wt% Tween 20 aqueous solution. The addition of a very low concentration of Tween aqueous solution is to wash away the residual oil phase on the surface of the hydrogel. If the Tween concentration is too high, the encapsulation rate of the flavor substances in the hydrogel will decrease.

[0024] Another aspect of the present invention provides a double emulsion-based hydrogel prepared by the above method and capable of encapsulating small molecule flavor substances.

[0025] Through the above technical solution, the present invention achieves the following beneficial effects:

[0026] 1. The present invention uses small molecule flavor substances as the inner oil phase (O1) and edible oil as the outer oil phase (O2), and uses various food-grade emulsifiers to prepare an O1 / W / O2 double emulsion that encapsulates flavor substances through two-step emulsification. On this basis, the O1 / W / O2 double emulsion is used as a template, and a small amount of Ca is added. 2+ The solution is used to prepare calcium alginate hydrogels encapsulating small molecule flavor substances, so as to prolong the fragrance retention time, control the release rate, and improve the sustained release effect of flavor substances. The preparation method of the invention is simple, the raw materials are safe and reliable, the production cost is low, and it has broad application prospects in the field of food industry.

[0027] 2. The polymer surfactant F127 of the present invention can form a viscoelastic interfacial film with a certain thickness on the surface of the droplet. The nonionic surfactant Tween20 and F127 are compounded in a certain ratio, and the synergistic effect between the two surfactants helps to enhance the stability of the O1 / W interfacial film and prevent the rupture of the ethyl butyrate droplets in the inner oil phase.

[0028] 3. In the O1 / W / O2 double emulsion product obtained by the present invention, the droplets are evenly distributed in the oil continuous phase, and the dispersed droplets have a double structure containing one or more small droplets, and the average droplet particle size (D[4,3]) is 3.68±0.50μm. Compared with the droplet template, the average particle size of the hydrogel in water (5.09±0.40μm) is slightly larger than the average particle size of the water phase droplets in the double emulsion. The hydrogel is spherical and evenly distributed in water without agglomeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an optical microscope image of the calcium alginate hydrogel coated with ethyl butyrate in Example 1 of the present invention;

[0030] Figure 2 is a SEM image of calcium alginate hydrogel coated with ethyl butyrate in Example 1 of the present invention;

[0031] Figure 3 is a particle size distribution diagram of calcium alginate hydrogel coated with ethyl butyrate in Example 1 of the present invention;

[0032] Figure 4 It is an optical microscope image of the ethyl butyrate / Tween20 / H2O emulsion system prepared in Comparative Example 1 of the present invention;

[0033] Figure 5 It is an optical microscope picture of the ethyl butyrate / Tween20 / H2O / PGPR / sunflower oil emulsion system prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below in conjunction with the examples. It should be understood that the specific implementation described herein is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0035] Example 1

[0036] S1. Dissolve sodium alginate powder in deionized water, stir with a magnetic stirrer overnight, and put it in a refrigerator after it is completely dissolved and hydrated to obtain a sodium alginate aqueous solution with a concentration of 1wt%. Take an appropriate amount of sodium alginate aqueous solution and add Tween20, then mix and stir with Pluronic F127 to prepare a sodium alginate aqueous solution containing surfactants Tween20 and F127 as the aqueous phase, wherein the concentration of Tween20 is 3wt%, and the concentration of Pluronic F127 is 0.1wt%;

[0037] S2, mixing ethyl butyrate (O1) with the aqueous phase prepared in step S1 at a mass ratio of 1:5, placing the mixture in an ice water bath, and shearing the mixture at 12000 rpm for 180 s using a high-speed shearing instrument to prepare an O1 / W primary emulsion;

[0038] S3, taking 1 g of the O1 / W emulsion prepared in step S2, adding it to 9 g of sunflower oil containing 0.5 wt% PGPR, after preliminary vortex mixing, shearing for 150 s using a high-speed shearing instrument at 3000 rpm, and secondary emulsification to obtain an O1 / W / O2 double emulsion;

[0039] S4, slowly add 500 μL of 1.0 mol·L O1 / W / O2 double emulsion prepared in step S3 while stirring (800 rpm) -1 Calcium chloride aqueous solution. Continue stirring at room temperature for 1 hour to promote the full cross-linking of sodium alginate in the middle aqueous phase. Centrifuge the cross-linked emulsion at 8000 rpm for 5 minutes and pour out the upper oil phase;

[0040] S5. Add an aqueous solution containing 0.1 wt% Tween 20 to the emulsion treated in step S4 and shake well to mix, wash and collect the hydrogel particles.

[0041] Example 2

[0042] S1. Dissolve sodium alginate powder in deionized water, stir with a magnetic stirrer overnight, and put it in a refrigerator after it is completely dissolved and hydrated to obtain a sodium alginate aqueous solution with a concentration of 2wt%. Take an appropriate amount of sodium alginate aqueous solution and add Tween20, then mix and stir with Pluronic F127 to prepare a sodium alginate aqueous solution containing surfactants Tween20 and F127 as the aqueous phase, wherein the concentration of Tween20 is 5wt%, and the concentration of Pluronic F127 is 0.3wt%;

[0043] S2, mixing ethyl butyrate (O1) with the aqueous phase prepared in step S1 at a mass ratio of 1:6, placing the mixture in an ice water bath, and shearing the mixture at 15000 rpm using a high-speed shearing instrument for 240 s to prepare an O1 / W primary emulsion;

[0044] S3, taking 1 g of the O1 / W emulsion prepared in step S2, adding it to 13 g of sunflower oil containing 2.5 wt% PGPR, after preliminary vortex mixing, using a high-speed shearing instrument at 6000 rpm for shearing for 240 s, and secondary emulsification to obtain an O1 / W / O2 double emulsion;

[0045] S4. Slowly drop 1500 μL of 1.0 mol·L O1 / W / O2 double emulsion prepared in step S3 while stirring (600 rpm). -1 Calcium chloride aqueous solution. Continue stirring at room temperature for 1 hour to promote the full cross-linking of sodium alginate in the middle aqueous phase. Centrifuge the cross-linked emulsion at 8000 rpm for 5 minutes and pour out the upper oil phase;

[0046] S5. Add an aqueous solution containing 0.05 wt% Tween 20 to the emulsion treated in step S4 and shake well to mix, wash and collect the hydrogel particles.

[0047] Example 3

[0048] S1. Dissolve sodium alginate powder in deionized water, stir with a magnetic stirrer overnight, and put it in a refrigerator after it is completely dissolved and hydrated to obtain a sodium alginate aqueous solution with a concentration of 1.5wt%. Take an appropriate amount of sodium alginate aqueous solution and add Tween20, then mix and stir with Pluronic F127 to prepare a sodium alginate aqueous solution containing surfactants Tween20 and F127 as the aqueous phase, wherein the concentration of Tween20 is 4wt%, and the concentration of Pluronic F127 is 0.2wt%;

[0049] S2, mixing ethyl butyrate (O1) with the aqueous phase prepared in step S1 at a mass ratio of 1:5, placing the mixture in an ice water bath, and shearing the mixture at 13000 rpm using a high-speed shearing instrument for 200 s to prepare an O1 / W primary emulsion;

[0050] S3, taking 1 g of the O1 / W emulsion prepared in step S2, adding it to 11 g of sunflower oil containing 1.5 wt% PGPR, after preliminary vortex mixing, using a high-speed shearing instrument at 4000 rpm for 200 s, and secondary emulsification to obtain an O1 / W / O2 double emulsion;

[0051] S4. Slowly drop 1000 μL of 1.0 mol·L O1 / W / O2 double emulsion prepared in step S3 while stirring (1000 rpm). -1 Calcium chloride aqueous solution. Continue stirring at room temperature for 1 hour to promote the full cross-linking of sodium alginate in the middle aqueous phase. Centrifuge the cross-linked emulsion at 8000 rpm for 5 minutes and pour out the upper oil phase;

[0052] S5. Add an aqueous solution containing 0.1 wt% Tween 20 to the emulsion treated in step S4 and shake well to mix, wash and collect the hydrogel particles.

[0053] Comparative Example 1

[0054] The other conditions were the same as those in Example 1, except that Pluronic F127 was not added to the aqueous phase in step S1. The O1 / W emulsion was prepared without adding the polymer surfactant F127 and using only Tween 20 as the surfactant. Microscopic observation revealed that the droplet size in the obtained O1 / W emulsion was reduced and large pieces of agglomeration appeared, such as Figure 4 As shown. Other conditions remain unchanged, based on the O1 / W emulsion prepared above, an O1 / W / O2 double emulsion is prepared. Its morphology (such as Figure 5 As shown), it was found that the droplet size in the emulsion system was not uniform, the morphological characteristics of the double droplets were not obvious, and the stability of the droplets was poor.

[0055] Comparative Example 2

[0056] Other conditions were the same as those in Example 1, except that Tween 20 was not added to the aqueous phase in step S1.

[0057] Comparative Example 3

[0058] Other conditions are the same as those in Example 1, except that sodium alginate is not added to the aqueous phase in step S1.

[0059] Performance Testing

[0060] (1) Drop the hydrogel product prepared in Example 1 on a glass slide (76×26 mm 2 ) and covered with a cover glass (22×22mm 2 ) was covered, and the microscopic morphology of the product was observed using a Leica optical microscope (DMLM / P). Figure 1 As shown. Figure 1 It can be seen that the hydrogel is spherical and evenly distributed in water without agglomeration.

[0061] (2) The hydrogel product prepared in Example 1 was freeze-dried using a Telsatr freeze dryer (Lyoquest-55, Spain) (-58°C, 0.026 mBar). The freeze-dried sample was adhered to a conductive adhesive and subjected to vacuum gold spraying for 30 seconds. The surface morphology of the freeze-dried hydrogel was observed using a Zeiss supra55 field emission scanning electron microscope (accelerating voltage was 5.0 kV). Figure 2 shown.

[0062] (3) The particle size distribution of the hydrogel product prepared in Example 1 was measured by a Malvern laser diffraction particle size analyzer (Mastersizer 3000) equipped with a Hydro LV dispersion unit. The hydrogel was diluted with water to achieve an appropriate light shielding rate. The particle size distribution of the hydrogel coated with ethyl butyrate is shown in FIG. Figure 3 The average particle size of the hydrogel in water is 5.09±0.40 μm.

[0063] (4) Flavor substance sustained release test

[0064] 1 g of the substances prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were respectively placed in test tubes, and the release test of ethyl butyrate was carried out in a water bath. The water baths were set to room temperature (20°C) and 40°C, respectively. A group of the above test tubes were placed in each water bath and heated overnight, and another group was placed in a 4°C refrigerator as a reference. After the end, the ethyl butyrate content in the residue of each test tube was determined by chromatography, and the percentage was calculated by comparison with the content of the reference.

[0065] The experimental results are shown in Table 1 below.

[0066] Table 1. Ethyl butyrate release test results

[0067] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Reference 100％ 100％ 100％ 100％ 100％ 100％ normal temperature 98.3％ 99.0％ 97.2％ 96.7％ 95％ 94.3％ 40℃ 74.6％ 72.1％ 71.8％ 70.2％ 70％ 65.3％

[0068] The preferred implementation modes of the present invention are described in detail above in combination with the embodiments; however, the present invention is not limited to the specific details in the above implementation modes. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical scheme of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0069] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0070] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a hydrogel capable of encapsulating small molecule flavor substances based on double emulsion, characterized in that: The following steps are involved: S1. Evenly mixing a polymer surfactant and a sodium alginate solution containing a nonionic surfactant to obtain an aqueous phase; S2, mixing the small molecule flavor substance with the aqueous phase obtained in step S1 to obtain an O1 / W primary emulsion; S3, mixing the O1 / W primary emulsion prepared in step S2 with edible oil containing an oil-soluble emulsifier to obtain an O1 / W / O2 double emulsion; S4, mixing the O1 / W / O2 double emulsion prepared in step S3 with a calcium chloride solution to promote cross-linking of sodium alginate, and then centrifuging to pour out the upper oil phase; S5, mixing the emulsion treated in step S4 with an aqueous solution containing a nonionic surfactant, washing and collecting the hydrogel particles.

2. The preparation method according to claim 1, characterized in that: In step S1, the nonionic surfactant is Tween 20, and the polymer surfactant is Pluronic F127.

3. The preparation method according to claim 2, characterized in that: The mass ratio of Tween 20 to Pluronic F127 is (3-5): (0.1-0.3).

4. The preparation method according to claim 1, characterized in that: In step S2, the small molecule flavor substance is ethyl butyrate.

5. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of the small molecule flavor substance to the aqueous phase is 1:(4-6).

6. The preparation method according to claim 1, characterized in that: In step S2, the mixing is performed by shearing with a high-speed shearing instrument for 180 to 240 seconds at a rotation speed of 12,000 to 15,000 rpm.

7. The preparation method according to claim 1, characterized in that: In step S3, the oil-soluble emulsifier is polyglycerol castor oil ester, the edible oil is sunflower oil, the concentration of polyglycerol castor oil ester in the edible oil containing the oil-soluble emulsifier is 0.5~2.5 wt%; the mass ratio of the O1 / W primary emulsion to the edible oil containing the oil-soluble emulsifier is 1:(9~13); the mixing is performed by shearing with a high-speed shear instrument for 150~240 s at a rotation speed of 3000~6000 rpm.

8. The preparation method according to claim 1, characterized in that: In step S4, compared with the addition of 500 μL to 1500 μL of 1.0 mol·L O1 / W / O2 emulsion to 10∼14 g freshly prepared O1 / W / O2 emulsion, -1 Calcium chloride aqueous solution.

9. The preparation method according to claim 1, characterized in that: In step S5, the aqueous solution containing the non-ionic surfactant is a 0.05 wt% to 0.1 wt% Tween 20 aqueous solution.

10. A hydrogel based on double emulsion capable of encapsulating small molecule flavor substances, characterized in that: Prepared by the preparation method described in any one of claims 1 to 9.

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