Lipid microcapsules with improved oxidation resistance, and methods of making and using the same

Abstract

This invention provides a lipid microcapsule with enhanced antioxidant properties, its preparation method, and its application. The microcapsule comprises at least one wall material and a content encapsulated by the wall material; the wall material is selected from at least one of OSA modified starch and corn starch; the content comprises lipids and at least one of an emulsifier and an antioxidant; the lipids are selected from at least one of algal oil, fish oil, and krill oil; the emulsifier is a mono- or diglyceride fatty acid ester; and the antioxidant is selected from at least one of citric acid, ascorbic acid, and vitamin E. The lipid microcapsule provided by this invention has strong antioxidant properties.

Description

Technical Field

[0001] This invention relates to a lipid microcapsule with enhanced antioxidant properties, its preparation method, and its application, belonging to the field of food engineering. Background Technology

[0002] Lipids such as algal oil, fish oil, and krill oil are rich in DHA (docosahexaenoic acid). DHA has high chemical activity and easily participates in various biochemical reactions, playing a vital role in the human body, such as promoting nerve cell growth, maintaining normal physiological activities of nerve cells, and improving memory.

[0003] However, the aforementioned lipids have some unpleasant flavors, and polyunsaturated fatty acids are easily oxidized during storage, producing more fishy odors and generating harmful oxidation products such as aldehydes and free radicals. This leads to a loss of functionality, safety, and nutritional value, as well as a reduction in product stability and shelf life, which is detrimental to the application of algal oil in food.

[0004] Therefore, developing a lipid-containing product with strong antioxidant properties has become a research direction. Summary of the Invention

[0005] This invention provides a lipid microcapsule with enhanced antioxidant properties, which is characterized by strong stability and the ability to inhibit the oxidation of nutrients.

[0006] This invention also provides a method for preparing lipid microcapsules, which can produce the above-mentioned lipid microcapsules. This method is characterized by its simple preparation process.

[0007] The present invention also provides a food product that has high nutritional value.

[0008] The present invention provides a lipid microcapsule with enhanced antioxidant properties, comprising at least one wall material and contents encapsulated by the wall material;

[0009] The wall material includes at least one of OSA modified starch and corn starch;

[0010] The contents include lipids.

[0011] The antioxidant-enhanced lipid microcapsules as described above, wherein the contents further include an emulsifier; and / or,

[0012] The contents also include antioxidants; and / or,

[0013] The lipids include at least one of algal oil, fish oil, and krill oil.

[0014] The antioxidant-enhanced lipid microcapsules as described above, wherein the emulsifier is selected from at least one of mono- and diglyceride fatty acid esters and soybean lecithin; and / or,

[0015] The antioxidant is selected from at least one of citric acid, ascorbic acid, and vitamin E.

[0016] The lipid microcapsules with enhanced antioxidant properties as described above, wherein the wall material accounts for 66.7–79.5 wt% of the microcapsule mass fraction; the lipid accounts for 20–33 wt% of the microcapsule mass fraction; the emulsifier accounts for 0.26–1.06 wt% of the microcapsule mass fraction; and the antioxidant accounts for 0.003–0.182 wt% of the microcapsule mass fraction.

[0017] The antioxidant-enhanced lipid microcapsules described above, wherein the mass ratio of the wall material to the lipid is 2:1 to 4:1; and / or,

[0018] The emulsifier is 0.79 to 3.17 wt% of the lipid mass.

[0019] The lipid microcapsules with enhanced antioxidant properties as described above, wherein the lipid microcapsules comprise, from the inside out, the contents, a first wall material, and a second wall material;

[0020] The first wall material is OSA modified starch, and the second wall material is corn starch.

[0021] The antioxidant-enhanced lipid microcapsules described above are prepared using a method comprising the following steps:

[0022] A first mixture comprising water and the wall material is mixed with a second mixture comprising the lipid to obtain a third mixture;

[0023] The third mixture was subjected to dispersion treatment and at least one homogenization treatment in sequence to obtain a lipid emulsion;

[0024] The lipid emulsion is granulated to obtain the lipid microcapsules;

[0025] The granulation process is either spray drying or double-spray drying.

[0026] The first mixture further includes an emulsifier; and / or,

[0027] The first mixture further includes at least one of citric acid and ascorbic acid; and / or,

[0028] The second mixture also includes at least one of vitamin E and tea polyphenol palmitate.

[0029] This invention also provides a method for preparing lipid microcapsules with enhanced antioxidant properties, comprising the following steps:

[0030] The first mixture comprising the wall material is mixed with the second mixture comprising the lipid to obtain a third mixture;

[0031] The third mixture was subjected to dispersion treatment and at least one homogenization treatment in sequence to obtain a lipid emulsion;

[0032] The lipid emulsion is granulated to obtain the lipid microcapsules;

[0033] The granulation process is either spray drying or double spray drying.

[0034] The first mixture further includes an emulsifier; and / or,

[0035] The first mixture further includes at least one of citric acid and ascorbic acid; and / or,

[0036] The second mixture also includes at least one of vitamin E and tea polyphenol palmitate.

[0037] The method for preparing lipid microcapsules with enhanced antioxidant properties as described above, wherein the dispersion treatment is performed at a rotation speed of 9000-10000 rpm for 6-8 min;

[0038] The homogenization process is carried out at a pressure of 20–50 MPa.

[0039] In the method for preparing lipid microcapsules with enhanced antioxidant properties as described above, the inlet air temperature of the spray drying process is 130–165°C; and / or,

[0040] The double-spray drying process uses corn starch as the second wall material, with an inlet air temperature of 130°C, an outlet air temperature of 50°C, an inlet air temperature of 130°C for the fluidized bed, and an internal tower temperature of 70°C.

[0041] The present invention also provides a food product comprising any of the above-mentioned lipid microcapsules with enhanced antioxidant properties.

[0042] The lipid microcapsules provided by this invention have high antioxidant properties. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced one by one below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 The image shows the particle size test results of the sample microcapsules.

[0045] Figure 2 The graph shows the test results of the microcapsule encapsulation efficiency of the samples.

[0046] Figure 3 The image shows the acid resistance test results of the sample microcapsules. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Currently, lipids such as algal oil, fish oil, and krill oil have some unpleasant flavors, and their polyunsaturated fatty acids are easily oxidized during storage, producing a stronger fishy odor and generating harmful oxidation products such as aldehydes and free radicals. This leads to a loss of functionality, safety, and nutritional value, as well as a reduction in product stability and shelf life, hindering the application of algal oil in food. The inventors believe this may be due to oxidation caused by contact with oxygen during storage. Isolating lipids from oxygen could solve these technical problems.

[0049] Based on this, the first aspect of the present invention provides a lipid microcapsule with enhanced antioxidant properties, the capsule comprising at least one wall material and contents encapsulated by the wall material;

[0050] The wall material includes at least one of OSA modified starch and corn starch;

[0051] The contents include lipids.

[0052] The lipid microcapsule provided in the first aspect of the present invention comprises a content and at least one wall material, wherein the wall material covers the outer surface of the content. The present invention does not limit the number of wall material layers; it can be one layer, two layers, or multiple layers. When the wall material has two or more layers, the first wall material is located between the content and the second wall material; or the wall material closer to the content is the first wall material, and the wall material closer to the outer surface of the lipid microcapsule is the second wall material.

[0053] In the lipid microcapsules provided by this invention, the wall material refers to the material that encapsulates the lipid contents, including at least one of OSA modified starch or corn starch. OSA modified starch is octenyl succinate starch ester. The wall material forms a robust protective layer, inhibiting the oxidation of lipids in the contents. The contents are the substances encapsulated by the wall material, and the contents include lipids. This invention does not limit the specific selection of lipids; commonly used lipids in the art can be used. Besides lipids, this invention does not limit other components of the contents; commonly used contents components in the art can also be used.

[0054] The inventors have discovered that the lipid microcapsules provided by this invention have strong antioxidant properties. The inventors speculate that this may be because the wall material, selected from specific substances, encapsulates the contents, effectively isolating oxygen and moisture from the outside and inhibiting the oxidation reaction of lipids in the contents, thereby significantly improving the antioxidant performance of the lipid microcapsules. Thus, the lipid microcapsules provided by this invention have strong antioxidant properties.

[0055] In one embodiment, the lipid microcapsules provided by the present invention contain lipids including at least one selected from algal oil, fish oil, and krill oil. These lipids, as the core contents of the microcapsules, are rich in nutrients such as DHA. Furthermore, the contents also include an emulsifier. The emulsifier helps form a stable emulsion by reducing the oil-water interfacial tension, thereby enhancing the integrity of the microcapsule structure. The present invention does not limit the specific type of emulsifier and can use common emulsifiers in the art. Furthermore, the contents also include an antioxidant. Since lipids are easily oxidized, resulting in a decrease in nutritional value, antioxidants can slow down this process. The present invention does not limit the specific selection of antioxidants and can use common antioxidants in the art. For example, in one embodiment, the antioxidant is selected from at least one selected from water-soluble antioxidants and oil-soluble antioxidants.

[0056] To enhance the antioxidant properties of the lipid microcapsules provided by this invention, in one embodiment, the emulsifier is selected from at least one of mono- and diglyceride fatty acid esters and soybean lecithin, preferably mono- and diglyceride fatty acid esters. Mono- and diglyceride fatty acid esters help form a stable and uniform emulsion during microcapsule preparation, resulting in a more uniform distribution of lipid particles and enhancing the overall stability of the microcapsules. Furthermore, the antioxidant is selected from at least one of citric acid, ascorbic acid, and vitamin E. These components can scavenge free radicals. In addition, citric acid can chelate metal ions, further inhibiting lipid oxidation. The synergistic effect of these factors significantly improves the antioxidant performance of the lipid microcapsules.

[0057] In one embodiment, the wall material accounts for 66.7–79.5 wt% of the microcapsule mass fraction; the lipid accounts for 20–33 wt% of the microcapsule mass fraction; and the emulsifier accounts for [missing information - likely a percentage].

[0058] 0.26–1.06 wt%; antioxidants account for 0.003–0.182 wt% of the microcapsule mass.

[0059] Specifically, an appropriate percentage of wall material forms a complete coating layer, providing a sufficient physical barrier to effectively isolate external environmental factors such as oxygen and moisture. This reduces the risk of lipid oxidation while increasing the structural strength of the microcapsules, ensuring their stability during processing, storage, and transportation, and preventing microcapsule rupture or leakage. An appropriate percentage of lipids ensures that the microcapsules contain sufficient lipids to meet functional requirements, such as providing nutrients like DHA, while avoiding oxidative instability caused by excessive lipids. Furthermore, controlling the lipid content within this range facilitates good bonding with the wall material, forming a stable core content and improving the overall stability and antioxidant properties of the microcapsules. An appropriate percentage of emulsifier reduces the oil-water interfacial tension during preparation, helping to form a stable and uniform emulsion, preventing lipid aggregation within the wall material, maintaining the dispersion stability of the microcapsules during storage, preventing the leakage or migration of lipid contents, and extending the shelf life of the microcapsules. An appropriate percentage of antioxidants avoids affecting the flavor of the microcapsules and reduces costs while maintaining antioxidant effects. The specific mass fraction ratio of the above components, through synergistic effect, achieves high antioxidant properties, excellent structural stability, and long-term storage stability of the microcapsules.

[0060] Furthermore, the content of citric acid in algal oil can be controlled at 0.03–0.63 wt%, vitamin E at 0.01–0.04 wt%, ascorbic acid at 0.05–0.2 wt%, and tea polyphenol palmitate at 0.015–0.06 wt%. Lipid microcapsules with these characteristics possess higher antioxidant properties.

[0061] In one specific embodiment, the wall material is OSA modified starch, and the oxidant consists of citric acid, ascorbic acid, and vitamin E. OSA modified starch possesses excellent hydrophilicity and emulsifying properties, forming a dense coating layer on the surface of the microcapsules. This effectively isolates external oxygen and moisture, significantly reducing the risk of lipid oxidation. Simultaneously, the structural characteristics of OSA modified starch allow the wall material to form a robust protective layer on the lipid particle surface, improving the mechanical strength of the microcapsules and ensuring they are not easily damaged or leaked during storage, processing, and transportation. Citric acid, by complexing with metal ions, reduces metal-catalyzed oxidation reactions and prevents the generation of free radicals. As a water-soluble antioxidant, ascorbic acid effectively captures free radicals in the aqueous phase, inhibiting lipid oxidation reactions. Vitamin E, as a fat-soluble antioxidant, directly acts on lipids, protecting lipid molecules in the oil phase and preventing their oxidation. This combination not only effectively scavenge free radicals but also inhibits the auto-oxidation chain reaction of lipids, thereby improving the overall antioxidant stability and shelf life of the microcapsules.

[0062] Furthermore, the mass ratio of wall material to lipids can be controlled to be 2:1 to 4:1. A higher proportion of wall material relative to lipids results in a thicker and denser wall layer, providing a stronger physical protective barrier for the lipids. This reduces the lipids' contact with the external environment and further isolates them from oxidizing factors such as oxygen and moisture in the air, thereby improving the lipids' shelf life and antioxidant properties. In addition, this thick-walled structure increases the mechanical strength of the microcapsules during storage, processing, and transportation, making them less prone to rupture or leakage and ensuring the integrity of the microcapsules. More specifically, the emulsifier can be controlled to be 0.79 to 3.17 wt% of the lipid mass. An appropriate proportion of emulsifier can effectively reduce the oil-water interfacial tension, forming a more stable emulsion. The uniformly distributed emulsifier forms a protective film on the oil droplet surface, preventing oil droplet aggregation or stratification.

[0063] To further enhance the antioxidant properties of the lipid microcapsules provided by the present invention, in one embodiment, the lipid microcapsules comprise, from the inside out, contents, a first wall material, and a second wall material; the first wall material is OSA modified starch, and the second wall material is corn starch.

[0064] First, this structure enhances the antioxidant properties of the microcapsules. Specifically, the first wall material (OSA modified starch) tightly encapsulates the lipid contents, forming an initial barrier that significantly reduces the contact between lipids and external oxygen, thus slowing down the oxidation process. The second wall material (corn starch) further enhances the outer layer protection, providing additional isolation and preventing the penetration of external moisture and oxygen, thereby greatly improving the antioxidant properties of the lipids. The double-layer wall structure increases the mechanical strength of the microcapsules, making them less prone to rupture during processing, storage, and transportation, thus preventing leakage of the contents. At the same time, the presence of the second corn starch wall material provides the microcapsules with stronger physical support, allowing them to maintain structural integrity in application scenarios and making them suitable for long-term storage.

[0065] Secondly, this structure improves the structural stability of the microcapsules. Specifically, the double-layer wall structure increases the mechanical strength of the microcapsules, making them less prone to rupture during processing, storage, and transportation, thus preventing leakage of the contents; the presence of the second cornstarch wall material provides the microcapsules with stronger physical support, allowing them to maintain structural integrity in application scenarios and making them suitable for long-term storage.

[0066] Third, this structure improves the sustained-release effect of lipids. Specifically, this bilayer structure helps control the release rate of the contents, with the combination of the first and second wall layers providing a gradual release effect. The sustained-release properties allow lipids to be released into the target medium more persistently, making it suitable for products such as foods and nutritional supplements that require sustained release of active ingredients.

[0067] Fourth, this structure can improve the encapsulation efficiency and protective effect of microcapsules. Specifically, OSA modified starch, as the inner wall material, has good emulsifying and encapsulating properties, ensuring that lipids are uniformly encapsulated in the microcapsules, improving the encapsulation rate, and reducing the generation of surface oil; corn starch, as the outer wall material, further blocks moisture and air from the external environment, protecting the quality and functional components of the lipid contents.

[0068] Finally, this structure also improves the applicability and consumer acceptance of microcapsules. Specifically, the double-layer wall material can effectively mask the fishy or unpleasant odor of lipids, enhancing the flavor suitability of microcapsules; in addition, this structure is suitable for scenarios with high flavor requirements, such as food and beverages, resulting in a better user experience for microcapsules in consumer products.

[0069] Therefore, lipid microcapsules with inner and outer double-walled structures not only improve antioxidant properties and structural stability, but also achieve effects such as sustained release, improved encapsulation efficiency, and enhanced flavor, thereby significantly improving the overall performance and application value of microcapsules.

[0070] In one embodiment, the lipid microcapsules provided by the present invention are prepared using a method comprising the following steps:

[0071] A first mixture comprising water and wall material is mixed with a second mixture comprising lipids to obtain a third mixture;

[0072] The third mixture was subjected to dispersion treatment and at least one homogenization treatment in sequence to obtain a lipid emulsion;

[0073] The lipid emulsion was granulated to obtain lipid microcapsules;

[0074] The granulation process is either spray drying or double spray drying.

[0075] The first mixture is used to dissolve the water-soluble raw material. When the lipid microcapsules to be obtained include an emulsifier, the first mixture also includes an emulsifier; when the lipid microcapsules to be obtained include a water-soluble antioxidant (ascorbic acid, citric acid), the first mixture also includes the aforementioned water-soluble antioxidant.

[0076] The second mixture is used to dissolve the oil-soluble raw material. When the lipid microcapsules to be obtained include an oil-soluble antioxidant (vitamin E), the second mixture also includes the aforementioned oil-soluble antioxidant.

[0077] The first mixture and the second mixture are combined to obtain the third mixture. Dispersion treatment involves stirring the third mixture to achieve a homogeneous texture. This invention does not limit the specific processing conditions for dispersion treatment; common processing conditions in the art can be used.

[0078] Homogenization, achieved through high-pressure homogenization, refines lipid particles, resulting in a more uniform particle size and facilitating the formation of a stable emulsion. Smaller, more uniform lipid particles are better encapsulated by the wall material, improving the overall stability of the microcapsules. Simultaneously, homogenization reduces the tension at the oil-water interface, preventing oil droplet aggregation and stratification, thus enhancing the emulsion structure. This is crucial for subsequent spray drying or dual-spray drying processes, ensuring uniform lipid distribution during drying and preventing microcapsule inhomogeneity due to separation. This invention does not limit the specific conditions of the homogenization process; common processing conditions in the art can be used. Multiple homogenization processes, through multiple improvements in particle size, stability, encapsulation efficiency, and antioxidant properties, ensure high-quality performance of the lipid microcapsules in all aspects, making them suitable for products with high requirements for stability and uniformity. A lipid emulsion is obtained after homogenization.

[0079] Granulation transforms the lipid emulsion into lipid microcapsules. Granulation can be achieved through spray drying or a dual-spray drying process. Spray drying involves forming a stable lipid emulsion from the contents. The lipids are atomized into small droplets by spray drying, and the droplets rapidly evaporate moisture in a high-temperature gas flow, forming lipid microcapsules with a structure where the contents are encapsulated by a first wall material.

[0080] Double-spray drying is similar to spray drying, but it adds an extra step: after the first spray drying process, a second spray is applied to form the outer wall material (i.e., the second wall material). Specifically, double-spray drying can be accomplished through two implementation methods:

[0081] In the first embodiment, the emulsion is first spray-dried to form lipid microcapsules, and then the second wall material is mixed with water to form a slurry. The slurry is then deposited onto the surface of the microcapsules in a fluidized bed to obtain lipid microcapsules with both a first and a second wall material. The innermost layer of the lipid microcapsule is the contents, the middle layer is the first wall material, and the outermost layer is the second wall material.

[0082] In the second embodiment, the lipid emulsion and the second wall material are placed in two nozzles respectively. During the preparation process, the two nozzles spray out the substances they store. After the lipid emulsion is sprayed out, it forms lipid microcapsules (the inner layer is the contents and the outer layer is coated with the first wall material). The microcapsules are then coated with the second wall material to obtain lipid microcapsules with the contents as the innermost layer, the first wall material as the middle layer, and the second wall material as the outermost layer.

[0083] Since the lipids in the second embodiment are prone to nutrient degradation when heated, and the lipids in the second embodiment are less affected by heat, the lipid microcapsules prepared using the second embodiment have higher nutritional value.

[0084] This invention does not limit the equipment used in the above process, as long as it meets the requirement of completing the above process. In one embodiment, the above process can be carried out using the WLG-1 microcapsule granulation dryer manufactured by Changzhou Yisite Drying Equipment Co., Ltd.

[0085] This second coating layer not only further enhances the antioxidant properties of the core material, but also improves the storage stability of the microcapsules by forming a bilayer structure.

[0086] A second aspect of the present invention provides a method for preparing lipid microcapsules with enhanced antioxidant properties, the method comprising the following steps:

[0087] A first mixture comprising wall material is mixed with a second mixture comprising lipids to obtain a third mixture;

[0088] The third mixture was subjected to dispersion treatment and at least one homogenization treatment in sequence to obtain a lipid emulsion;

[0089] The lipid emulsion was granulated to obtain lipid microcapsules;

[0090] Granulation is performed by spray drying or double spray drying.

[0091] The first mixture also includes an emulsifier; and / or,

[0092] The first mixture also includes at least one of citric acid and ascorbic acid; and / or,

[0093] The second mixture also includes at least one of vitamin E and tea polyphenol palmitate.

[0094] The meanings of the first mixture, the second mixture, the third mixture, dispersion treatment, homogenization treatment, lipid emulsion, spray drying treatment, and double spray drying treatment are the same as those mentioned above, and will not be repeated here.

[0095] The method for preparing lipid microcapsules with enhanced antioxidant properties provided by this invention involves multiple homogenization processes and double-layer wall material coating to obtain microcapsules with high antioxidant properties, good structural stability, and high encapsulation efficiency, and the process is simple.

[0096] In one embodiment, the dispersion treatment speed is 9000–10000 rpm, and the treatment time is 6–8 min; the homogenization treatment pressure is 20–50 MPa. A suitable dispersion speed refines and uniformly disperses the lipids in the wall material solution, forming a stable mixture. High speed ensures sufficient dispersion of lipids in the wall material, preventing lipid aggregation into large particles and improving emulsion uniformity. Furthermore, an appropriate treatment time ensures sufficient lipid particle dispersion without reducing emulsion stability due to excessive treatment. This dispersion effect is beneficial for subsequent homogenization, maintaining a uniform distribution of lipid particles and improving microcapsule quality. A suitable homogenization pressure further refines the lipid particles, making their particle size more uniform and resulting in stable, fine emulsion particles. This refinement helps improve emulsion stability, prevents oil-water separation, and ensures the uniformity of microcapsules during subsequent drying. Meanwhile, homogenization not only helps to completely encapsulate lipid particles in the wall material, but also increases the contact area between lipids and the wall material, thereby improving the encapsulation efficiency of microcapsules, so that lipids are completely sealed in microcapsules and reducing the generation of surface oil.

[0097] In one specific embodiment, the inlet air temperature for the spray drying process can be controlled between 130 and 165°C. A suitable temperature ensures that the emulsion dries rapidly into powdered microcapsules during spraying, effectively avoiding problems such as microcapsule adhesion or irregular shape caused by slow drying, thus guaranteeing the integrity and stability of the microcapsule structure. Furthermore, this temperature range is sufficient to allow for rapid moisture evaporation while preventing microcapsule rupture or deformation due to excessively high temperatures, ensuring that the microcapsules maintain a good morphology during the drying process.

[0098] Furthermore, the dual-spray drying process can use corn starch as the second wall material, controlling the inlet air temperature at 130℃, the outlet air temperature at 50℃, the fluidized bed inlet air temperature at 130℃, and the tower temperature at 70℃. The 130℃ inlet air temperature ensures rapid drying and shaping of the emulsion during the second spray, while the moderate temperature prevents damage to the first layer's structure and avoids inner layer instability caused by excessively high temperatures. The 50℃ outlet air temperature ensures gradual cooling during the drying process, reducing the impact of thermal stress on the microcapsules and preventing cracking or deformation of the outer layer. The 130℃ fluidized bed inlet air temperature and 70℃ tower temperature together control the final drying of the microcapsules within the tower, ensuring complete and stable coating of the outer corn starch layer, forming a dense and uniform double-layer wall material, and ensuring good flowability and storage stability of the microcapsule particles.

[0099] A third aspect of this invention provides a food product comprising the lipid microcapsules with enhanced antioxidant properties provided in the first aspect of this invention. Because the lipid microcapsules with enhanced antioxidant properties provided in the first aspect of this invention have strong antioxidant properties and the lipids therein are not easily oxidized, this food product has high nutritional value.

[0100] The preparation method of the lipid microcapsules with improved antioxidant properties provided by the present invention will be described below through specific embodiments.

[0101] The OSA modified starch used in all experimental cases was of the type Ingredion HI-CAP 100Starch.

[0102] Experimental Example 1

[0103] This example uses the following method to prepare microcapsules:

[0104] 1) Dissolve mono- and diglyceride fatty acid esters in water, and add OSA modified starch to dissolve and obtain a first mixture. Add algal oil to the first mixture and dissolve to obtain a second mixture. The mass ratio of OSA modified starch to algal oil in the first mixture is 2:1, and the mass fraction of mono- and diglyceride fatty acid esters in the algal oil is 3.17 wt%.

[0105] 2) The second mixture was sheared at 9600 rpm for 6 min to obtain emulsion 1;

[0106] 3) Immediately homogenize emulsion 1 three times under a pressure of 50 MPa to obtain emulsion 2; this emulsion is a1;

[0107] 4) Emulsion 2 was spray-dried at an inlet air temperature of 165℃ and an outlet air temperature of 100℃ to obtain microcapsules A1.

[0108] Experimental Example 2

[0109] This experimental example is basically the same as Experimental Example 1, except that in step 1, ascorbic acid is used instead of mono- and diglyceride fatty acid esters, and the mass fraction of ascorbic acid in algal oil is 0.2 wt%. In step 3, the resulting emulsion 2 is a2; microcapsules A2 are prepared.

[0110] Experimental Example 3

[0111] The microcapsules in this experimental example were prepared using the following method:

[0112] 1) OSA modified starch was dissolved in water to obtain a first mixture. Vitamin E was added to algal oil and dissolved to obtain a second mixture. The mass ratio of OSA modified starch in the first mixture to algal oil in the second mixture was 2:1, and the mass fraction of vitamin E in the algal oil was 0.03 wt%. The first and second mixtures were combined to obtain a third mixture.

[0113] 2) The third mixture was sheared at 9600 rpm for 6 min to obtain emulsion 1;

[0114] 3) Immediately homogenize emulsion 1 three times under a pressure of 50 MPa to obtain emulsion 2; this emulsion is a3;

[0115] 4) Emulsion 2 was spray-dried at an inlet air temperature of 165℃ and an outlet air temperature of 100℃ to obtain microcapsules A3.

[0116] Test Example 4

[0117] This example uses the following method to prepare microcapsules:

[0118] 1) Dissolve mono- and diglycerides of fatty acids, ascorbic acid, and citric acid in water, and add OSA-modified starch to obtain a first mixture. Dissolve vitamin E in algal oil to obtain a second mixture. The mass ratio of OSA-modified starch in the first mixture to algal oil in the second mixture is 2:1. The mass fraction of mono- and diglycerides of fatty acids in algal oil is 3.17 wt%, vitamin E is 0.03 wt%, ascorbic acid is 0.2 wt%, and citric acid is 0.06 wt%. Combine the first and second mixtures to obtain a third mixture.

[0119] 2) The third mixture was sheared at 9600 rpm for 6 min to obtain emulsion 1;

[0120] 3) Immediately homogenize emulsion 1 three times under a pressure of 50 MPa to obtain emulsion 2; this emulsion is a4;

[0121] 4) Emulsion 2 was spray-dried at an inlet air temperature of 165℃ and an outlet air temperature of 100℃ to obtain microcapsules A4.

[0122] Experimental Example 5

[0123] This embodiment is basically the same as Experimental Example 4, except that in step 4, a double-spray drying process is used instead of spray drying. Corn starch and water are mixed to form a slurry, which is then used as a second wall material in a fluidized bed to encapsulate the microcapsules A4, including the contents and the first wall material, for a second time. The inlet air temperature is 130°C, the outlet air temperature is 50°C, the fluidized bed inlet air temperature is 130°C, and the tower temperature is 70°C. Microcapsules A5 are thus obtained.

[0124] Experimental Example 6

[0125] This embodiment is basically the same as Experimental Example 1, except that in step 1, the mass fraction of mono- and diglyceride fatty acid esters in the algal oil is 0.79 wt%. In step 3, the resulting emulsion 2 is a6; microcapsules A6 are prepared.

[0126] Experimental Example 7

[0127] This embodiment is basically the same as Experimental Example 2, except that in step 1, the ascorbic acid accounts for 0.05 wt% of the algal oil. In step 3, the resulting emulsion 2 is a7; microcapsules A7 are prepared.

[0128] Experimental Example 8

[0129] This experimental example is basically the same as Experimental Example 3, except that in step 1, vitamin E accounts for 0.04 wt% of the algal oil. In step 3, the resulting emulsion 2 is a8; microcapsules A8 are prepared.

[0130] Experimental Example 9

[0131] This experimental example is basically the same as Example 1, except that in step 1, soybean lecithin is used instead of mono- and diglyceride fatty acid esters. In step 3, the resulting emulsion 2 is b1; microcapsules B1 are prepared.

[0132] Experimental Example 10

[0133] This experimental example is basically the same as Experimental Example 3, except that in step 1, tea polyphenol palmitate is used instead of vitamin E, and the mass fraction of tea polyphenol palmitate in algal oil is 0.015 wt%. In step 3, the resulting emulsion 2 is b2; microcapsules B2 are prepared.

[0134] Experimental Example 11

[0135] This experimental example is basically the same as Experimental Example 4, except that citric acid is not used in step 1. In step 3, the resulting emulsion 2 is b3; microcapsules B3 are prepared.

[0136] Test case

[0137] 1) The particle size of emulsion samples a1-3, a6-8, and b1-2 in Test Examples 1-3, 6-8, and 9-10 was determined using a Malvern particle size analyzer. The samples were diluted 500 times before measurement.

[0138] Test results are shown Figure 1 Different letters in the figure represent significant differences (P<0.05).

[0139] Smaller particle size indicates a more stable emulsion, which in turn contributes to improving the stability of microcapsules.

[0140] Depend on Figure 1 It can be seen that the particle size of emulsion sample a2 is the smallest, with a particle size of 274.70±3.90 nm. At the same time, the particle sizes of emulsion samples a1 and b2 are also less than 300 nm.

[0141] 2) The encapsulation efficiency of microcapsule samples A1-8 and B1-3 from Test Examples 1-8 and Test Examples 9-11 was determined. The oil content X (%) on the surface of the microcapsules was measured according to the method specified in SC / T3505-2006 "Fish Oil Microcapsules". The encapsulation efficiency E (%) was calculated using the formula: E (%) = (1 - X / oil content) × 100.

[0142] Test results are shown Figure 2 Different letters in the figure represent significant differences (P<0.05).

[0143] The higher the encapsulation rate, the better the OSA modified starch encapsulates the algal oil, the less surface oil there is, the better it can block the algal oil from contacting external oxygen and moisture, and the stronger its inhibitory effect on algal oil oxidation.

[0144] Depend on Figure 2 It can be seen that microcapsule sample A2 has the highest encapsulation efficiency, at 99.78±0.02%, which corresponds to the smallest particle size of emulsion sample a2. Meanwhile, the encapsulation efficiencies of microcapsule samples A4, A7, and B3 are all higher than 99%.

[0145] 3) The peroxide value of microcapsule samples A2-5, A7-8, and B2-3 from Test Examples 2-5 and 7-8, and Test Examples 10-11 was determined. After microcapsule preparation, the microcapsules were stored under nitrogen and placed in a constant temperature oven at 55℃. Samples were taken on days 0-10, 12, and 15 to determine the peroxide value. The extraction method of the oil from the microcapsules was the same as that used in "4.3.4 Peroxide Value of Oils" in SC / T 3505-2006 "Fish Oil Microcapsules". The peroxide value of the extracted oil was determined by the "First Titration Method" in GB 5009.227-2016 "National Food Safety Standard for Determination of Peroxide Value in Food".

[0146] The test results are shown in Table 1. The lower the peroxide value recorded in Table 1, the lower the degree of oxidation of the algal oil in the microcapsules and the higher the oxidative stability of the microcapsules.

[0147] Table 1

[0148]

[0149]

[0150] Table 1 shows that the peroxide value of microcapsule sample A5 was lower than that of all other samples within 15 days. The difference between microcapsule samples A4 and A5 lies in whether they were prepared by spray drying or a dual-spray method. The peroxide value of A4 on day 15 was lower than that of all other samples except A5, indicating that the emulsifier and antioxidant formulation of sample A4 improved the oxidative stability of the microcapsules to a greater extent than the other groups. A5, prepared by the dual-spray method, further improved the oxidative stability of the microcapsules.

[0151] Furthermore, comparing samples B2 and A3 revealed that before day 5, the peroxide value of B2 was lower than that of A3, while after day 5, the peroxide value of B2 was higher than that of A3. This may be because tea polyphenol palmitate was used instead of vitamin E in the preparation of B2. The long-term antioxidant capacity of tea polyphenol palmitate is inferior to that of vitamin E, thus leading to the aforementioned phenomenon.

[0152] Comparison of samples B3 and A4 revealed that before day 6, the peroxide value of B3 was lower than that of A4, while after day 6, the peroxide value of B3 was higher than that of A4. This may be because citric acid, a metal complexing agent, was not added during the preparation of B3, resulting in the microcapsules of B3 having a lower long-term antioxidant capacity than A4.

[0153] Observation of sample A7 shows that it has a lower peroxide value compared to other samples before day 7, but a higher peroxide value after day 7. This may be because the amount of antioxidant added during the preparation of sample A7 was relatively low, and the peroxide value increased significantly after the antioxidant was oxidized and consumed around day 7.

[0154] Observation of sample A4 shows that it has a higher peroxide value than other samples before day 7, and a lower peroxide value after day 7. This may be because the antioxidant and metal complexing agent citric acid added during the preparation of sample A4 can significantly reduce the long-term peroxide value of the sample.

[0155] On day 15, the peroxide values, from lowest to highest, were: A5 < A4 < A3 < B2 < A2 < B3 < A8 < A7.

[0156] 4) The acid value of the microcapsules prepared in Examples 4, 5, and 11 was determined. The storage conditions and oil extraction methods for the microcapsules were the same as above. Samples were taken on the 15th day of storage to determine the acid value. The method for determining the acid value was in accordance with GB 5009.229-2016, "National Food Safety Standard - Determination of Acid Value in Food".

[197] The “first method, cold solvent indicator titration method” in the text.

[0157] Test results are shown Figure 3 Different letters in the figure represent significant differences (P<0.05).

[0158] The lower the acid value, the lower the degree of oxidative rancidity of the algal oil in the microcapsules, and the higher the oxidative stability of the microcapsules.

[0159] Depend on Figure 3 It can be seen that the microcapsule sample A5 had the lowest acid value on day 15, at 2.25 ± 0.05 mg. This is significantly lower than that of sample A4, which was spray-dried with the same formulation, indicating that the dual spraying process significantly contributes to the oxidative stability of the microcapsules. Sample A4 also had a lower acid value than B3, indicating that the addition of citric acid also significantly improved the oxidative stability of the microcapsules.

[0160] Finally, it should be noted that the above test examples are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments and comparative examples, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lipid microcapsule with improved oxidation resistance, characterized in that, It includes at least one layer of wall material, and contents covered by the wall material; The wall material includes at least one of OSA modified starch and corn starch; The contents include lipids.

2. The lipid microcapsule according to claim 1, characterized in that, The contents also include emulsifiers; and / or, The contents also include antioxidants; and / or, The lipids include at least one of algal oil, fish oil, and krill oil.

3. The lipid microcapsule according to claim 1 or 2, characterized in that, The emulsifier is selected from at least one of mono- and diglyceride fatty acid esters and soybean lecithin; and / or, The antioxidant is selected from at least one of citric acid, ascorbic acid, and vitamin E.

4. The lipid microcapsule according to any one of claims 1-3, characterized in that, The wall material accounts for 66.7–79.5 wt% of the microcapsule mass; the lipid accounts for 20–33 wt% of the microcapsule mass; the emulsifier accounts for 0.26–1.06 wt% of the microcapsule mass; and the antioxidant accounts for 0.003–0.182 wt% of the microcapsule mass.

5. The lipid microcapsule according to any one of claims 1-4, characterized in that, The mass ratio of the wall material to the lipid is 2:1 to 4:1; and / or, The emulsifier is 0.79 to 3.17 wt% of the lipid mass.

6. The lipid microcapsule according to any one of claims 1-5, characterized in that, The lipid microcapsule comprises, from the inside out, the contents, a first wall material, and a second wall material; The first wall material is OSA modified starch, and the second wall material is corn starch.

7. The lipid microcapsule according to any one of claims 1-6, characterized in that, The lipid microcapsules were prepared using a method comprising the following steps: A first mixture comprising water and the wall material is mixed with a second mixture comprising the lipid to obtain a third mixture; The third mixture was subjected to dispersion treatment and at least one homogenization treatment in sequence to obtain a lipid emulsion; The lipid emulsion is granulated to obtain the lipid microcapsules; The granulation process is either spray drying or double-spray drying. The first mixture further includes an emulsifier; and / or, The first mixture further includes at least one of citric acid and ascorbic acid; and / or, The second mixture also includes at least one of vitamin E and tea polyphenol palmitate.

8. A method for preparing lipid microcapsules with enhanced antioxidant properties as described in any one of claims 1-7, characterized in that, Includes the following steps: The first mixture comprising the wall material is mixed with the second mixture comprising the lipid to obtain a third mixture; The third mixture was subjected to dispersion treatment and at least one homogenization treatment in sequence to obtain a lipid emulsion; The lipid emulsion is granulated to obtain the lipid microcapsules; The granulation process is either spray drying or double-spray drying. The first mixture further includes an emulsifier; and / or, The first mixture further includes at least one of citric acid and ascorbic acid; and / or, The second mixture also includes at least one of vitamin E and tea polyphenol palmitate.

9. The method according to claim 8, characterized in that, The dispersion treatment is carried out at a speed of 9000-10000 rpm for 6-8 minutes. The homogenization process is carried out at a pressure of 20–50 MPa.

10. The method according to claim 8 or 9, characterized in that, The inlet air temperature for the spray drying process is 130–165°C; and / or, The double-spray drying process uses corn starch as the second wall material, with an inlet air temperature of 130°C, an outlet air temperature of 50°C, an inlet air temperature of 130°C for the fluidized bed, and an internal tower temperature of 70°C.

11. A food product, characterized in that, The lipid microcapsules with enhanced antioxidant properties include any one of claims 1-7.

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