High-temperature-resistant astaxanthin microcapsule as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature-resistant astaxanthin microcapsule and a preparation method and application thereof, and relates to the field of nutritional products, the microcapsule comprises: a, a core material: astaxanthin oil selected from haematococcus pluvialis or krill oil; b, double-layer wall materials: an inner-layer wall material is formed by crosslinking sodium alginate and whey protein through an ionic gel method; the outer-layer wall material is formed by electrostatic adsorption of chitosan and Arabic gum; and c, an antioxidant synergist: a rosemary extract. A double-layer embedding structure is adopted outside astaxanthin oil, sodium alginate on the inner layer is combined with whey protein to form a compact network structure through ionic bonds, chitosan on the outer layer and Arabic gum form a compact composite film on the surface of a primary embedded microsphere through electrostatic attraction, so that the double-layer embedded microcapsule has the advantages that the astaxanthin oil has good stability, and the astaxanthin oil has good stability. The temperature resistance limit of a traditional single-layer microcapsule is broken through, the stability of the astaxanthin in a high-temperature baking environment is remarkably improved, the astaxanthin can stably exist in high-temperature baked food, and the anti-oxidation effect and the like of the astaxanthin are fully exerted.

Description

Technical Field

[0001] The invention relates to the technical field of nutritional products, in particular to the manufacture of astaxanthin food, and specifically to a high temperature resistant astaxanthin microcapsule and a preparation method and application thereof. Background Art

[0002] Astaxanthin, as a naturally occurring powerful antioxidant, has attracted extensive attention in many fields such as food, health products and cosmetics due to its unique molecular structure and significant biological activities such as anti-oxidation, anti-inflammatory and immunity enhancement. Its unique antioxidant properties can effectively remove free radicals and protect cells from oxidative damage, thus having a positive impact on human health.

[0003] In the process of food processing, especially the production of baked goods, high temperature treatment (temperature is usually higher than 150°C) is usually required. Under such high temperature conditions, the stability of astaxanthin will be seriously challenged, and the degradation rate is as high as 50% or more. Specifically, due to the large number of conjugated double bonds in the molecular structure of astaxanthin, it is extremely sensitive to environmental factors such as light, oxygen, and heat. Especially in high temperature environments, its stability will drop sharply. This not only leads to a significant weakening of the antioxidant function of astaxanthin, but also limits its wide application in baked goods, making it difficult to give full play to the positive effects of astaxanthin on human health.

[0004] Therefore, how to improve the stability of astaxanthin in high temperature environment has become a key issue that needs to be urgently solved in the field of functional food processing technology. Summary of the invention

[0005] The invention overcomes the deficiencies of the prior art and provides a high temperature resistant astaxanthin microcapsule and a preparation method and application thereof.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a high temperature resistant astaxanthin microcapsule, comprising:

[0007] a. Core material: astaxanthin oil, selected from Haematococcus pluvialis or krill oil;

[0008] b. Double wall material:

[0009] Inner wall material: formed by cross-linking sodium alginate and whey protein through ion gel method;

[0010] Outer wall material: formed by chitosan and gum arabic through electrostatic adsorption;

[0011] c. Antioxidant synergist: rosemary extract.

[0012] In a preferred embodiment of the present invention, the particle size of the microcapsule is 20-50 μm.

[0013] In a preferred embodiment of the present invention, the content of rosmarinic acid in the rosemary extract is ≥ 40%.

[0014] The present invention provides a method for preparing high-temperature resistant astaxanthin microcapsules, comprising the following steps:

[0015] S1. Emulsification: Mix astaxanthin oil with sodium alginate, whey protein and rosemary extract, and perform high-shear homogenization to form primary emulsion.

[0016] S2. Primary encapsulation: Drop the primary emulsion into calcium chloride solution to form sodium alginate-whey protein microspheres.

[0017] S3. Double-layer encapsulation: Immerse the sodium alginate-whey protein microspheres in a mixed solution of chitosan and arabic gum, adjust the pH value to 5.0 - 5.5, and perform electrostatic adsorption for 20 - 40 min to form microspheres with a double-layer encapsulation structure.

[0018] S4. Drying: Spray-dry the microspheres after double-layer encapsulation to obtain microcapsule powder.

[0019] In a preferred embodiment of the present invention, in the step of S1, the mass ratio of astaxanthin oil, sodium alginate, whey protein and rosemary extract is 1:0.2 - 0.5:0.3 - 0.6:0.1 - 0.5; the rotation speed of the high-shear homogenization is 8000 - 12000 rpm, and the time is 3 - 10 min.

[0020] In a preferred embodiment of the present invention, in the step of S2, the concentration of the calcium chloride solution is 1.5 - 2.5 wt%; the dropping speed is 10 - 20 drops per minute.

[0021] In a preferred embodiment of the present invention, in the step of S3, the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:2 - 5; in the mixed solution, the concentration of chitosan is 1 - 3%, and the concentration of arabic gum is 2 - 4%.

[0022] In a preferred embodiment of the present invention, in the step of S4, the inlet air temperature of the spray drying is 150 °C, the outlet air temperature is 80 °C, and the drying time is 20 - 30 min.

[0023] The present invention provides an application of the high-temperature resistant astaxanthin microcapsules described in any one of the above, adding the astaxanthin microcapsules with an addition amount of 0.1 - 1 wt% to bakery foods, the baking temperature is 170 - 190 °C, and the time is 15 - 20 min.

[0024] In a preferred embodiment of the present invention, the bakery foods include one of bread, biscuits or cakes.

[0025] The present invention solves the defects existing in the background art, and the present invention has the following beneficial effects:

[0026] (1) The present invention provides a high-temperature resistant astaxanthin microcapsule, its preparation method and application. By adopting a double-layer embedding structure outside the astaxanthin oil, the combination of sodium alginate and whey protein in the inner layer forms a tight network structure through ionic bonds, and due to the good film-forming property of whey protein, the inner side can tightly wrap the astaxanthin oil droplets, effectively isolating high temperature and oxygen, thereby reducing the leakage caused by molecular thermal motion at high temperature. Moreover, by using the opposite charges of chitosan and arabic gum in the outer layer, they form a dense composite film on the surface of the primary embedded microspheres through electrostatic attraction, further enhancing the temperature resistance and structural stability of the microcapsules. Thus, the microcapsules with this double-layer embedding structure not only break through the temperature resistance limit of traditional single-layer microcapsules, but also significantly improve the stability of astaxanthin in the high-temperature baking environment, with its retention rate reaching over 85%, enabling astaxanthin to stably exist in high-temperature baked foods and fully exert its antioxidant and other effects.

[0027] (2) In the present invention, by providing an appropriate acidic condition during the electrostatic adsorption process of the outer layer embedding, the amino groups in chitosan can be fully protonated, and efficiently combined with the negative charges of the carboxylate groups of arabic gum through Coulomb force, making the electrostatic interaction reach the optimal state, avoiding film defects caused by local charge repulsion, and thus forming a stable and dense outer layer structure, enabling the microcapsules to maintain a complete structure during the high-temperature baking process and effectively protecting astaxanthin from being damaged.

[0028] (3) In the present invention, by using rosemary extract as an antioxidant synergist, the benzene ring structure of rosmarinic acid is directionally combined with the conjugated double bonds of astaxanthin through π-π stacking to form an electron delocalization system, and then it can produce a synergistic antioxidant effect with astaxanthin, effectively inhibiting the oxidative degradation of astaxanthin at high temperature and further enhancing the high-temperature resistance performance of the microcapsules.

[0029] (4) In the present invention, when the astaxanthin microcapsules are applied to baked foods, they will not bring bad flavors such as fishy smell to the foods, nor will they have a negative impact on the taste of baked foods. Whether it is the soft taste of bread, the crispy texture of biscuits or the delicate taste of cakes, they can all be well maintained, ensuring that consumers can obtain the health benefits brought by astaxanthin while enjoying delicious baked foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0031] Figure 1 It is a schematic cross-sectional structure diagram of astaxanthin microcapsules according to a preferred embodiment of the present invention;

[0032] Figure 2 It is a flow chart of a preparation method of a heat-resistant astaxanthin microcapsule according to a preferred embodiment of the present invention;

[0033] In the figure: 1, astaxanthin oil; 2, inner wall material; 3, outer wall material. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0035] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0036] Application overview:

[0037] In view of the problem that astaxanthin is easily degraded at high temperatures, microencapsulation technology is traditionally used to protect it. The applicant has found that traditional single-layer microencapsulation technology, such as the common single-layer gelatin embedding method, although can protect astaxanthin to a certain extent, its embedding effect is limited, and the temperature it can withstand is usually below 120°C. Once the temperature exceeds this value, the structure of the microcapsules is easily damaged, and it cannot effectively protect astaxanthin, resulting in a large amount of degradation of astaxanthin.

[0038] In addition, the applicant has also found that adding antioxidants (such as vitamin E) alone to protect astaxanthin also has unsatisfactory effects in practical applications. Specifically, due to the high temperature, high humidity and complex chemical reaction environment during the baking process, a single antioxidant cannot comprehensively resist the oxidative degradation of astaxanthin and is difficult to meet the strict requirements for the stability of astaxanthin in high-temperature baking.

[0039] In view of the above problems, the present invention proposes a new type of heat-resistant astaxanthin microcapsule, its preparation method and application. Through innovative double-layer embedding technology, specific process parameters and the addition of antioxidant synergists, high stability of astaxanthin in a high-temperature baking environment is achieved, providing a new solution for the development of functional baking foods.

[0040] It should be noted that: The raw materials, equipment, reagents, etc. used in the present invention can all be obtained through market purchase or by means of preparation in the prior art.

[0041] As Figure 1 shown, a heat-resistant astaxanthin microcapsule includes:

[0042] a. Core material: Astaxanthin oil 1, selected from Haematococcus pluvialis or krill oil;

[0043] b. Double-layer wall material:

[0044] Inner layer wall material 2: Formed by crosslinking sodium alginate and whey protein through the ion gel method;

[0045] Outer layer wall material 3: Formed by electrostatic adsorption of chitosan and arabic gum;

[0046] c. Antioxidant synergist: Rosemary extract.

[0047] In some specific embodiments, the particle size of the microcapsule is 20 - 50 μm.

[0048] In some specific embodiments, the rosmarinic acid content in the rosemary extract is ≥ 40%.

[0049] As Figure 2 shown, the present invention provides a preparation method of a heat-resistant astaxanthin microcapsule, including the following steps:

[0050] S1. Emulsification: Mix astaxanthin oil with sodium alginate, whey protein and rosemary extract, and form a primary emulsion through high-shear homogenization;

[0051] S2. Primary embedding: Drop the primary emulsion into a calcium chloride (CaCl2) solution to form sodium alginate - whey protein microspheres;

[0052] S3. Double-layer embedding: Immerse the sodium alginate - whey protein microspheres in a mixed solution of chitosan and arabic gum, adjust the pH value to 5.0 - 5.5, and perform electrostatic adsorption for 20 - 40 min to form microspheres with a double-layer embedding structure;

[0053] S4. Drying: Spray-dry the microspheres after double-layer embedding to obtain microcapsule powder.

[0054] In some specific embodiments, in the step of S1, the mass ratio of astaxanthin oil, sodium alginate, whey protein and rosemary extract is 1:0.2 - 0.5:0.3 - 0.6:0.1 - 0.5; the rotation speed of high-shear homogenization is 8000 - 12000 rpm, and the time is 3 - 10 min.

[0055] In some specific embodiments, in the step of S2, the concentration of the calcium chloride solution is 1.5-2.5 wt%; the dropping rate is 10-20 drops per minute.

[0056] In some specific embodiments, in the step of S3, the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:2-5; in the mixed solution, the concentration of chitosan is 1-3%, and the concentration of gum arabic is 2-4%.

[0057] In some specific embodiments, in the step of S4, the inlet air temperature for spray drying is 150 °C, the outlet air temperature is 80 °C, and the drying time is 20-30 min.

[0058] The present invention provides an application of any one of the above-mentioned high-temperature resistant astaxanthin microcapsules. The astaxanthin microcapsules are added to the baked food at an addition amount of 0.1-1 wt%, the baking temperature is 170-190 °C, and the time is 15-20 min.

[0059] In some specific embodiments, the baked food includes one of bread, biscuits or cakes.

[0060] To further make the object and effect of the present invention simple and easy to understand, the present invention is further described in combination with examples and comparative examples.

[0061] Example 1

[0062] A preparation method of high-temperature resistant astaxanthin microcapsules, comprising the following steps:

[0063] S1. Mix astaxanthin oil, sodium alginate, whey protein and rosemary extract with a mass ratio of 1:0.3:0.5:0.3, and stir with a high-shear homogenizer at a rotation speed of 10000 rpm for 5 min to form primary emulsion;

[0064] S2. Drop the primary emulsion into a CaCl2 solution with a concentration of 2 wt% at a speed of 15 drops per minute to form sodium alginate-whey protein microspheres;

[0065] S3. Immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% concentration of chitosan and 3% concentration of gum arabic. The mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:3, adjust the pH value to 5.2, and perform electrostatic adsorption for 30 min to form microspheres with a double-layer embedding structure;

[0066] S4. Spray dry the double-layer embedded microspheres at an inlet air temperature of 150 °C and an outlet air temperature of 80 °C for 25 min to obtain astaxanthin microcapsule powder.

[0067] Example 2

[0068] This example is basically the same as Example 1, except that: The specific steps of S3 are as follows: Immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% gum arabic. The mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:3. Adjust the pH value to 5.0 and perform electrostatic adsorption for 30 minutes to form microspheres with a double-layer embedding structure.

[0069] Example 3

[0070] This example is basically the same as Example 1, except that: The specific steps of S3 are as follows: Immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% gum arabic. The mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:3. Adjust the pH value to 5.5 and perform electrostatic adsorption for 30 minutes to form microspheres with a double-layer embedding structure.

[0071] Example 4

[0072] This example is basically the same as Example 1, except that: The specific steps of S3 are as follows: Immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% gum arabic. The mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:2. Adjust the pH value to 5.2 and perform electrostatic adsorption for 30 minutes to form microspheres with a double-layer embedding structure.

[0073] Example 5

[0074] This example is basically the same as Example 1, except that: The specific steps of S3 are as follows: Immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% gum arabic. The mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:5. Adjust the pH value to 5.2 and perform electrostatic adsorption for 30 minutes to form microspheres with a double-layer embedding structure.

[0075] Example 6

[0076] This example is basically the same as Example 1, except that: The specific steps of S1 are as follows: Mix astaxanthin oil, sodium alginate, whey protein and rosemary extract with a mass ratio of 1:0.3:0.5:0.1, and stir with a high-shear homogenizer at a rotation speed of 10,000 rpm for 5 minutes to form primary emulsion.

[0077] Example 7

[0078] This example is basically the same as Example 1, except that: The specific steps of S1 are as follows: Mix astaxanthin oil, sodium alginate, whey protein and rosemary extract with a mass ratio of 1:0.3:0.5:0.5, and stir with a high-shear homogenizer at a rotation speed of 10,000 rpm for 5 minutes to form primary emulsion.

[0079] Comparative Example 1

[0080] This comparative example is basically the same as Example 1, except that: there are no steps S3 and S4, and it specifically includes the following steps:

[0081] S1. Mix astaxanthin oil, sodium alginate, whey protein and rosemary extract with a mass ratio of 1:0.3:0.5:0.3, and stir with a high-shear homogenizer at a rotation speed of 10,000 rpm for 5 minutes to form primary emulsion;

[0082] S2. Drop the primary emulsion into a 2 wt% CaCl2 solution at a speed of 15 drops per minute to form sodium alginate-whey protein microspheres, and obtain astaxanthin microcapsule powder.

[0083] Comparative Example 2

[0084] This comparative example is basically the same as Example 1, except that: the specific operation of step S3 is: immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% arabic gum, and the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:3, adjust the pH value to 7, and perform electrostatic adsorption for 30 minutes to form microspheres with a double-layer embedding structure.

[0085] Comparative Example 3

[0086] This comparative example is basically the same as Example 1, except that: the specific operation of step S3 is: immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% arabic gum, and the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:3, adjust the pH value to 4.8, and perform electrostatic adsorption for 30 minutes to form microspheres with a double-layer embedding structure.

[0087] Comparative Example 4

[0088] This comparative example is basically the same as Example 1, except that: the specific operation of step S3 is: immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% arabic gum, and the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:3, adjust the pH value to 5.8, and perform electrostatic adsorption for 30 minutes to form microspheres with a double-layer embedding structure.

[0089] Comparative Example 5

[0090] This comparative example is basically the same as Example 1, except that: The specific steps of S3 are as follows: Immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% gum arabic, and the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:1. Adjust the pH value to 5.2 and perform electrostatic adsorption for 30 min to form microspheres with a double-layer embedding structure.

[0091] Comparative Example 6

[0092] This comparative example is basically the same as Example 1, except that: The specific steps of S3 are as follows: Immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan and 3% gum arabic, and the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:6. Adjust the pH value to 5.2 and perform electrostatic adsorption for 30 min to form microspheres with a double-layer embedding structure.

[0093] Comparative Example 7

[0094] This comparative example is basically the same as Example 1, except that: The specific steps of S1 are as follows: Mix astaxanthin oil, sodium alginate and whey protein with a mass ratio of 1:0.3:0.5, and pass through a high-shear homogenizer and stir at a speed of 10,000 rpm for 5 min to form a primary emulsion;

[0095] The specific steps of S3 are as follows: Immerse the sodium alginate-whey protein microspheres in a mixed solution of 2% chitosan, 3% gum arabic and rosemary extract. The mass ratio of astaxanthin oil to rosemary extract is 1:0.3, and the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:3. Adjust the pH value to 5.2 and perform electrostatic adsorption for 30 min to form microspheres with a double-layer embedding structure.

[0096] Comparative Example 8

[0097] This comparative example is basically the same as Example 1, except that: The specific steps of S1 are as follows: Mix astaxanthin oil, sodium alginate, whey protein and rosemary extract with a mass ratio of 1:0.3:0.5:0.07, and pass through a high-shear homogenizer and stir at a speed of 10,000 rpm for 5 min to form a primary emulsion.

[0098] Comparative Example 9

[0099] This comparative example is basically the same as Example 1, except that: The specific steps of S1 are as follows: Mix astaxanthin oil, sodium alginate, whey protein and rosemary extract with a mass ratio of 1:0.3:0.5:0.6, and pass through a high-shear homogenizer and stir at a speed of 10,000 rpm for 5 min to form a primary emulsion.

[0100] Performance detection: The astaxanthin microcapsule powders obtained in Examples 1-7 and Comparative Examples 1-9 were sieved to a particle size of 37 μm, and added to bread dough at an addition amount of 0.5 wt%, kneaded thoroughly and evenly, placed in an oven, and baked at a temperature of 180 °C for 18 min to make bread containing astaxanthin microcapsules; The breads containing astaxanthin microcapsules prepared in Examples 1-7 and Comparative Examples 1-9 were successively subjected to performance tests for astaxanthin retention rate, antioxidant activity and sustained release property, and the results are shown in Table 1.

[0101] Astaxanthin retention rate: The astaxanthin content in the baked bread was determined by high performance liquid chromatography (HPLC), and the astaxanthin retention rate was calculated:

[0102] Antioxidant activity: The sample was mixed with a free radical initiator (AAPH) and a fluorescent probe, and the change of fluorescence intensity with time was monitored to calculate the ORAC value.

[0103] Sustained release property: A pH 7.4 phosphate buffer solution (containing bile salts and pancreatin) was used to simulate the intestinal environment, samples were taken at regular intervals to measure the release amount, and the cumulative release rate in 24 h was calculated.

[0104] Table 1: Performance test results of breads containing astaxanthin microcapsules prepared in Examples 1-7 and Comparative Examples 1-9

[0105]

[0106]

[0107] As shown in Table 1:

[0108] It can be known from the comparison of Examples 1-7 that: by adopting a double-layer embedding structure of specific materials in the present invention, after the sodium alginate in the inner wall material is cross-linked by ionic gel, unreacted carboxylic acid groups will remain on the surface, and under the pH value of 5.0-5.5 of the double-layer embedding, part of the amino groups (-NH2) of whey protein are protonated to -NH 3+, a local positive charge region is formed. When the outer chitosan (with positively charged amino groups) and gum arabic (with negatively charged carboxylate groups) form a composite film through electrostatic adsorption, the positively charged amino groups of chitosan will electrostatically complementarily bind with the negatively charged carboxyl groups of the inner sodium alginate to form an interlayer ionic bond. Furthermore, the bonding driven by this charge gradient significantly enhances the interfacial binding force between the two wall materials, reducing the protection failure caused by interlayer delamination at high temperatures. At the same time, the carboxylate groups of gum arabic can also bind to the protonated amino groups of whey protein through Coulomb force to form crosslinking nodes, further stabilizing the bilayer structure. This not only makes it more resistant to shear force and thermal stress at high temperatures, but also inhibits oxygen penetration by reducing interfacial defects, and synergistically quenches free radicals through the π-π stacking network of rosmarinic acid and astaxanthin rich in rosemary extract to inhibit oxidation, ensuring a high retention rate (>80%), strong antioxidant activity (ORAC>3500 μmol TE / g), and slow release property (release rate>90%) of astaxanthin at high temperatures.

[0109] It can be known from the comparison between Example 1 and Comparative Example 1 that: single-layer embedding only relies on the ion gel network of sodium alginate - whey protein, lacking the dense composite film of the outer chitosan - gum arabic. The single-layer gel network cannot completely block high-temperature heat conduction and oxygen diffusion. The conjugated double bonds of astaxanthin molecules are directly exposed to the oxidative environment, and a double-layer "rigid inner layer + flexible outer layer" composite barrier is not formed. The molecular thermal motion intensifies at high temperatures, resulting in the leakage and degradation of astaxanthin.

[0110] It can be known from the comparison between Example 1 and Comparative Example 2 that: in a neutral environment, at pH 7.0, the amino groups of chitosan are deprotonated and lose their positive charges, and cannot efficiently bind to the carboxylate groups of gum arabic through electrostatic attraction, resulting in a loose and porous outer layer with decreased strength and easy cracking at high temperatures.

[0111] It can be known from the comparison between Examples 1 - 3 and Comparative Examples 3 - 4 that: when the treatment environment for double-layer embedding is overly acidic (pH 4.8), chitosan is overly protonated, resulting in too high a charge density and too strong electrostatic adsorption, leading to an increase in the rigidity of the membrane layer and easy brittleness; at the same time, the negative charge density of gum arabic is insufficient, the membrane structure is uneven, and the sodium alginate gel network may be partially dissociated due to + too high an H concentration, weakening the inner layer stability, and when the treatment environment is not acidic enough (pH 5.8), the degree of protonation of the amino groups of chitosan is insufficient, the electrostatic attraction with gum arabic is weakened, and the compactness of the outer layer membrane decreases, making it difficult to effectively resist high-temperature penetration.

[0112] It can be known from the comparison between Example 1 and Examples 4-5 and Comparative Examples 5-6 that when the chitosan-arabic gum mixture is too little, the surface of the microspheres cannot be completely coated, resulting in a low outer film coverage rate, a decline in oxygen barrier ability, and an excessive mixture is likely to cause the chitosan and arabic gum molecules to be overly dispersed, increasing the shrinkage stress during the drying process, making the microcapsules prone to rupture and the sustained release performance to deteriorate.

[0113] It can be known from the comparison between Example 1 and Comparative Example 7 that by mixing the antioxidant with astaxanthin oil in the emulsification stage, rosmarinic acid (polyphenol) binds to the conjugated double bond of astaxanthin through π-π stacking to form a local antioxidant microenvironment, directly inhibiting the free radical chain reaction. When rosemary extract is added in the outer embedding stage, it is only distributed on the surface of the microcapsules and cannot form a molecular-level contact with astaxanthin oil, so the synergistic antioxidant effect is limited.

[0114] It can be known from the comparison between Example 1 and Examples 6-7 and Comparative Examples 8-9 that at an appropriate dosage, rosemary extract acts synergistically with astaxanthin to both inhibit oxidation and not affect the structure of the microcapsules. When the antioxidant is too little, there is not enough rosmarinic acid to form a continuous π-π conjugate system with astaxanthin, resulting in a weak synergistic antioxidant effect and an accelerated oxidative degradation of astaxanthin. An excessive amount of rosmarinic acid may interfere with the ionic crosslinking of sodium alginate-whey protein, leading to a loose inner gel network and a decline in thermal barrier ability.

[0115] Based on the ideal embodiments of the present invention as inspiration, through the above description, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0116] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high temperature resistant astaxanthin microcapsule, characterized in that: include: a. Core material: astaxanthin oil, selected from Haematococcus pluvialis or krill oil; b. Double wall material: Inner wall material: formed by cross-linking sodium alginate and whey protein through ion gel method; Outer wall material: formed by chitosan and gum arabic through electrostatic adsorption; c. Antioxidant synergist: rosemary extract.

2. The high temperature resistant astaxanthin microcapsule according to claim 1, characterized in that: The particle size of the microcapsule is 20-50 μm.

3. The high temperature resistant astaxanthin microcapsule according to claim 1, characterized in that: The rosemary extract has a rosmarinic acid content of ≥40%.

4. A method for preparing a high temperature resistant astaxanthin microcapsule according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Emulsification: Mix astaxanthin oil with sodium alginate, whey protein and rosemary extract, and homogenize by high shear to form colostrum; S2, primary embedding: colostrum is added dropwise into calcium chloride solution to form sodium alginate-whey protein microspheres; S3, double-layer embedding: immerse the sodium alginate-whey protein microspheres in a mixed solution of chitosan and gum arabic, adjust the pH value to 5.0-5.5, and electrostatically adsorb for 20-40 minutes to form microspheres with a double-layer embedding structure; S4, drying: spray drying the double-layer embedded microspheres to obtain microcapsule powder.

5. The method for preparing a high temperature resistant astaxanthin microcapsule according to claim 4, characterized in that: In step S1, the mass ratio of astaxanthin oil, sodium alginate, whey protein and rosemary extract is 1:0.2-0.5:0.3-0.6:0.1-0.5; the rotation speed of the high shear homogenizer is 8000-12000 rpm, and the time is 3-10 min.

6. The method for preparing a high temperature resistant astaxanthin microcapsule according to claim 4, characterized in that: In step S2, the concentration of the calcium chloride solution is 1.5-2.5wt%; and the dropping speed is 10-20 drops per minute.

7. The method for preparing a high temperature resistant astaxanthin microcapsule according to claim 4, characterized in that: In step S3, the mass ratio of the sodium alginate-whey protein microspheres to the mixed solution is 1:2-5; in the mixed solution, the concentration of chitosan is 1-3%, and the concentration of gum arabic is 2-4%.

8. The method for preparing a high temperature resistant astaxanthin microcapsule according to claim 4, characterized in that: In the step S4, the inlet air temperature of the spray drying is 150° C., the outlet air temperature is 80° C., and the drying time is 20-30 minutes.

9. An application of the high temperature resistant astaxanthin microcapsule according to any one of claims 1 to 3, characterized in that: The astaxanthin microcapsules are added to baked food in an amount of 0.1-1 wt %, and the baking temperature is 170-190° C. and the baking time is 15-20 min.

10. The use according to claim 9, characterized in that: The baked food comprises one of bread, biscuits or cakes.

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