Ningxia eleutherine eleutherine essential oil microcapsule and preparation method thereof

Abstract

The invention discloses an eleutherine americana essential oil microcapsule and a preparation method thereof, and belongs to the technical field of food processing. The preparation method comprises the following steps: (1) preparing beta-cyclodextrin into a saturated solution, adding Ningxia eleutherine americana essential oil at 25-50 DEG C, and stirring to form a pre-inclusion compound so as to reduce volatilization of the essential oil; (2) adding natural vitamin E accounting for 0.5-5% of the mass of the essential oil into the pre-clathrate compound, and uniformly stirring to form an anti-oxidation protection layer; (3) dissolving Arabic gum and sodium alginate in water according to a mass ratio of (2-8): 1 to prepare a composite wall material solution; (4) adding the system obtained in the step (2) into the composite wall material solution, carrying out high-speed shearing emulsification, and then carrying out circulating high-pressure homogenization to obtain a stable O / W type emulsion with the average particle size of less than or equal to 1 mu m; and (5) carrying out spray drying on the emulsion at the air inlet temperature of 155-165 DEG C and the air outlet temperature of 78-82 DEG C to obtain the powdery microcapsule. The microcapsule prepared by the invention is high in embedding rate (greater than or equal to 85%) and good in oxidation stability, and can effectively retain the characteristic flavor and biological activity of the Ningxia eleutherine americana essential oil.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a Ningxia red shallot essential oil microcapsule and its preparation method. Background Technology

[0002] Ningxia red shallots, rich in active ingredients such as thioallyl compounds, possess strong natural antibacterial, antioxidant, and unique flavor properties. However, their essential oils are highly volatile and easily oxidized; light, heat, and oxygen can all cause rapid loss of activity, severely limiting their application in the food industry. Currently, most plant essential oil microcapsules use single wall materials or chemical cross-linking agents, resulting in low encapsulation rates (typically below 80%), and issues such as the use of organic solvents or high temperatures destroying activity, making it difficult to meet food-grade green safety requirements. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the technical solution adopted by this invention is: a method for preparing Ningxia red shallot essential oil microcapsules, comprising the following steps performed sequentially: (1) Dissolve β-cyclodextrin in water to make a saturated solution, and add Ningxia red shallot essential oil dropwise at 25-50℃ while stirring continuously. The main active and flavor substances of Ningxia red shallot essential oil are thioallyl compounds (such as diallyl disulfide and diallyl trisulfide), which are long-chain and highly hydrophobic. β-cyclodextrin is a truncated cone-shaped molecule with an inner cavity diameter of about 0.6-0.65nm, which can form a 1:1 or 1:2 host-guest inclusion complex with 1-2 thioallyl molecules. Through van der Waals forces, hydrophobic interactions and hydrogen bonds, volatile molecules are "locked" into the cavity. During subsequent shearing, homogenization and high-temperature spraying at 160℃, the unencapsulated free essential oil is easily vaporized and escaped, while the encapsulated part hardly volatilizes, forming a β-cyclodextrin / Ningxia red shallot essential oil pre-encapsulation complex. (2) Add natural vitamin E to the pre-encapsulated compound obtained in step (1) and stir evenly. Vitamin E (mainly α-tocopherol) is a lipid-soluble free radical scavenger. Its phenolic hydroxyl group can preferentially react with ROO• and RO• generated by lipid peroxidation, and generate stable tocopherol free radicals to terminate the chain reaction. The thioallyl compounds in shallot oil are easily stripped of allyl hydrogen by oxygen, forming thiofree radicals that trigger chain oxidation. When added after pre-encapsulation and before emulsification, 40% to 60% of the essential oil molecules are still exposed on the surface of the aqueous phase (the part not encapsulated by β-cyclodextrin), which is the most sensitive stage for oxidation. Once high-pressure homogenization is carried out, the oil droplets are broken into <1μm, and the surface area increases by hundreds of times. The vitamin E added in advance will preferentially adsorb on this part of the exposed essential oil surface, forming the first "molecular barrier". (3) Separately, dissolve gum arabic and sodium alginate in water to prepare a composite wall material solution. Gum arabic is a very strong emulsifier (containing 10% to 15% protein components, which can anchor the oil-water interface), but it has poor film-forming properties and is prone to cracking after drying. Sodium alginate has moderate emulsifying properties, but it will slowly crosslink with trace amounts of calcium ions (trace amounts of calcium in the air are sufficient during spray drying) to form a gel skeleton with high strength. The specific process is as follows: In the initial emulsion stage, the protein polypeptide chains of gum arabic extend into the surface of oil droplets, forming a thick and soft interfacial film. During the spray drying process, the water evaporates rapidly, and the sodium alginate molecular chains slowly cross-link with Ca²⁺ in the flexible network formed by gum arabic, forming a semi-interpenetrating network (IPN) structure that is "flexible on the outside and tough on the inside". The final dry powder particles have a smooth surface with few depressions (contributed by gum arabic) and an internal honeycomb gel skeleton (contributed by sodium alginate), with a wall thickness of about 1-3 μm, and are dense and non-porous. (4) The system obtained in step (2) is slowly added to the composite wall material solution in step (3), and high-speed shear emulsification is performed first, followed by high-pressure homogenization to obtain a stable O / W type emulsion with an average particle size ≤1μm. (5) Spray dry the emulsion obtained in step (4) at an inlet air temperature of 155-165°C and an outlet air temperature of 78-82°C to obtain powdered Ningxia red shallot essential oil microcapsules.

[0004] Preferably, in step (1), the mass ratio of β-cyclodextrin to Ningxia red shallot oil is 4-10:1, and the stirring time is 2-8 hours, so that the volatile sulfur allyl compounds enter the hydrophobic cavity of β-cyclodextrin, reducing the volatilization loss during subsequent emulsification and drying processes.

[0005] Preferably, in step (2), the amount of natural vitamin E added is 0.5-5% of the mass of Ningxia red shallot essential oil. After adding, continue stirring for 20-60 minutes so that vitamin E and essential oil molecules form an antioxidant protective layer before entering the wall material system, thereby inhibiting oxidative deterioration during processing.

[0006] Preferably, in step (3), the mass ratio of gum arabic to sodium alginate is 2 to 8:1, and the total solids content of the composite wall material is 10 to 30% (w / w). The gum arabic provides emulsifying properties, and the sodium alginate provides an ion gel framework. The two work together to form a highly stable wall material system.

[0007] Preferably, in step (4), the high-speed shear emulsification speed is 8000-15000 rpm and the time is 5-15 min, the high-pressure homogenization pressure is 80-150 MPa and the cycle is 2-5 times, so as to form a nano-sized emulsion with uniform particle size that does not separate into layers after standing at 4℃ for 30 days.

[0008] Preferably, in step (5), the inlet air temperature is 158–162°C and the outlet air temperature is 79–81°C, which causes the droplets to lose water rapidly and form a dense wall material layer. The specific structure is as follows: Outer layer: A dense membrane composed of arabinin and polysaccharides; Inner layer: Sodium alginate gel backbone + β-cyclodextrin inclusion complex filling, forming a multi-chamber structure (similar to a honeycomb). The overall wall thickness is 1.5–3 μm, the porosity is <5%, and the core material is completely sealed, thus preserving the characteristic flavor and bioactivity of Ningxia red shallot essential oil.

[0009] A microcapsule of Ningxia red shallot essential oil is prepared by the method described above. The microcapsule uses Ningxia red shallot essential oil as the core material and β-cyclodextrin, gum arabic, sodium alginate and natural vitamin E as wall material components. The oil loading of Ningxia red shallot essential oil is 8% to 20% (w / w), the natural vitamin E accounts for 0.5% to 5% of the total mass of the core material, and the mass ratio of gum arabic to sodium alginate in the wall material is 2 to 8:1.

[0010] Preferably, the microcapsules have an encapsulation rate of ≥85%, a surface oil content of ≤3%, an average particle size of ≤10μm, a moisture content of ≤5%, an angle of repose of ≤40°, and are completely dispersed within 30s after rehydration.

[0011] Preferably, after the microcapsules are stored at 40°C and 75% relative humidity for 90 days, the retention rate of the main sulfur allyl compounds in Ningxia red shallot essential oil is ≥80%.

[0012] The beneficial effects of this invention are as follows: The entire process uses GRAS substances such as β-cyclodextrin, gum arabic, sodium alginate, and natural vitamin E, without any chemical crosslinking agents or organic solvents. Through a five-stage synergistic process of "pre-encapsulation - source anti-oxidation - composite wall material - two-step homogenization - low-temperature precision spray drying", the active ingredients such as thioallyl compounds are systematically protected from the source to the end, significantly extending the shelf life. Attached Figure Description

[0013] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0015] Example 1 refer to Figure 1 100g of β-cyclodextrin was weighed and added to purified water at 60℃, stirring until completely dissolved to form a saturated solution. 12.5g of Ningxia red shallot essential oil (β-cyclodextrin: essential oil = 8:1) was added dropwise while stirring at 300r / min. After the addition was complete, stirring was continued for 4 hours to obtain the pre-inclusion complex.

[0016] Add 0.375g of natural vitamin E (3% of the essential oil mass) to the pre-encapsulated compound for antioxidant effects, and stir at 300r / min for 30min.

[0017] To prepare the composite wall material solution, weigh 72g of gum arabic and 18g of sodium alginate (mass ratio 4:1), dissolve them in purified water at 80℃ to prepare a composite wall material solution with a solid content of 20% (w / w), and cool it to 40℃ for later use.

[0018] The two-step emulsification process involves slowly adding the system obtained in step 2 to the composite wall material solution in step 3. First, the system is sheared at 10,000 rpm for 10 minutes, and then circulated three times at 100 MPa using a high-pressure homogenizer to obtain an O / W emulsion with an average particle size of about 680 nm and uniform distribution.

[0019] Spray drying was performed using a laboratory spray dryer with an inlet air temperature of 160℃, an outlet air temperature of 80℃, and a peristaltic pump feed rate of 25mL / min, yielding a white microcapsule powder with excellent flowability.

[0020] Test results: Encapsulation rate: 93.7%; Surface oil: 1.9%; Oil load: 15.8% (w / w); Average particle size: 7.4 μm; Moisture: 3.6%; Angle of repose: 36°; After 90 days of accelerated treatment at 40℃ and 75% RH, the retention rate of thioallyl compounds was 88.4%.

[0021] Example 2 β-Cyclodextrin:Essential oil = 6:1, Vitamin E added 1%, Gum arabic:Sodium alginate = 5:1, high-pressure homogenization at 120 MPa for 2 cycles, the rest is the same as in Example 1. The final encapsulation rate was 90.2%, the oil loading was 13.6%, and the 90-day retention rate was 84.6%.

[0022] Example 3 β-Cyclodextrin:Essential oil = 10:1, Vitamin E addition 5%, Gum arabic:Sodium alginate = 2:1, the rest is the same as in Example 1. The final encapsulation efficiency was 89.5%, the oil loading was 10.2%, and the 90-day retention rate was 86.9%.

[0023] Comparative Example 1 Without a pre-encapsulation step, essential oils, vitamin E, and composite wall material solutions are directly mixed, sheared, homogenized, and spray-dried. The encapsulation rate is only 71.3%, the surface oil content is 6.8%, and the 90-day retention rate is only 58.7%.

[0024] Comparative Example 2 No vitamin E was included; otherwise, it was the same as in Example 1. The encapsulation rate was 85.6%, the 90-day retention rate was 69.4%, and a slight oxidative odor was observed.

[0025] Comparative Example 3 When used as a single type of gum arabic wall material, the embedding rate was 77.9%, slight stratification of the emulsion occurred after 24 hours, and the retention rate was 62.3% after 90 days.

[0026] in conclusion: Only by using the five-step process in synergy can we obtain Ningxia red shallot essential oil microcapsules with an encapsulation rate of ≥85%, an oil loading of 8% to 20%, and a 90-day retention rate of ≥80%.

[0027] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described and explained in the present invention, unless otherwise specified or limited, shall be implemented according to conventional means in the art.

Claims

1. A method for preparing Ningxia red shallot essential oil microcapsules, characterized in that, The following steps are performed sequentially: (1) Dissolve β-cyclodextrin in water to prepare a saturated solution, add Ningxia red shallot essential oil dropwise at 25-50℃ and stir continuously to form a β-cyclodextrin / Ningxia red shallot essential oil pre-inclusion complex; (2) Add natural vitamin E to the pre-encapsulated compound obtained in step (1) and stir until well mixed; (3) Separately dissolve gum arabic and sodium alginate in water to prepare a composite wall material solution; (4) The system obtained in step (2) is slowly added to the composite wall material solution in step (3), and high-speed shear emulsification is performed first, followed by high-pressure homogenization to obtain a stable O / W type emulsion with an average particle size ≤1μm. (5) Spray dry the emulsion obtained in step (4) with an inlet air temperature of 155-165℃ and an outlet air temperature of 78-82℃ to obtain powdered Ningxia red shallot essential oil microcapsules.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of β-cyclodextrin to Ningxia red shallot oil is 4-10:1, and the stirring time is 2-8 hours, so that volatile sulfur allyl compounds can enter the hydrophobic cavity of β-cyclodextrin, reducing volatilization loss during subsequent emulsification and drying processes.

3. The preparation method according to claim 1, characterized in that, In step (2), the amount of natural vitamin E added is 0.5-5% of the mass of Ningxia red shallot essential oil. After adding, continue stirring for 20-60 minutes so that vitamin E and essential oil molecules form an antioxidant protective layer before entering the wall material system, thereby inhibiting oxidative deterioration during processing.

4. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of gum arabic to sodium alginate is 2 to 8:1, and the total solids content of the composite wall material is 10 to 30% (w / w). The gum arabic provides emulsifying properties, and the sodium alginate provides an ion gel framework. The two work together to form a highly stable wall material system.

5. The preparation method according to claim 1, characterized in that, In step (4), the high-speed shear emulsification speed is 8000-15000 rpm and the time is 5-15 min. The high-pressure homogenization pressure is 80-150 MPa and the cycle is 2-5 times, thereby forming a nano-sized emulsion with uniform particle size that does not separate into layers after standing at 4℃ for 30 days.

6. The preparation method according to claim 1, characterized in that, In step (5), the inlet air temperature is 158-162℃ and the outlet air temperature is 79-81℃, which causes the droplets to lose water quickly and form a dense wall material layer, thereby preserving the characteristic flavor and bioactivity of Ningxia red shallot essential oil.

7. A microcapsule of Ningxia red shallot essential oil, characterized in that, The microcapsules are prepared by the method described in any one of claims 1 to 6. The microcapsules use Ningxia red shallot oil as the core material and β-cyclodextrin, gum arabic, sodium alginate and natural vitamin E as wall material components. The oil loading of Ningxia red shallot oil is 8% to 20% (w / w), the natural vitamin E accounts for 0.5% to 5% of the total mass of the core material, and the mass ratio of gum arabic to sodium alginate in the wall material is 2 to 8:

1.

8. The Ningxia red shallot essential oil microcapsules according to claim 7, characterized in that, The microcapsules have an encapsulation rate of ≥85%, a surface oil content of ≤3%, an average particle size of ≤10μm, a moisture content of ≤5%, an angle of repose of ≤40°, and are completely dispersed within 30s after rehydration.

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