Betarubin microcapsule as well as preparation method and application thereof

Abstract

The invention relates to the technical field of preparation of food additives, in particular to a betacyanin microcapsule as well as a preparation method and application thereof. The preparation method comprises the following steps: jointly dissolving sodium alginate and soybean protein isolate in water to obtain an SA-SPI compound; the SA-SPI compound, CaCO3 and betacyanin are mixed, and a water phase is formed; mixing liquid paraffin, glacial acetic acid and Tween 80 to obtain an acetic acid-containing oil phase; mixing the water phase with the acetic acid-containing oil phase to form a water-in-oil emulsion, and standing to form calcium alginate gel beads; the calcium alginate gel beads are subjected to pre-freezing-freeze-drying treatment, and the betacyanin microcapsules are obtained. The prepared betacyanin microcapsule has the characteristics of controllable particle size, high stability and easiness in industrialization, and the application range of betacyanin is widened. In addition, the preparation method disclosed by the invention is safe and simple to operate, has the advantages of low cost and high benefit, and can be directly applied to large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food additive preparation, in particular to a betalain microcapsule and a preparation method and application thereof. BACKGROUND

[0002] With the economic development and social progress, the concept of green and environmental protection is gradually accepted by the public. In recent years, the safety of artificial synthetic pigments has been increasingly valued. Natural pigments are more and more popular in the food, printing and pharmaceutical industries due to their non-toxic side effects, pleasing color and health benefits.

[0003] Betalain is mainly derived from red beetroot, red pitaya and red amaranth, and has a color from rose red to purple red. It was officially approved for use in the food industry in 2010. Betalain has higher hydrophilicity and coloring intensity than anthocyanin, and has a wider application range. In addition, betalain has high free radical scavenging, anti-inflammatory, antibacterial, anti-anxiety and weight loss effects. It also has the advantages of being natural, nutritious and multifunctional. The betalain in pitaya avoids the earthy odor problem caused by high nitrate, geosmin and pyrazine derivatives in beetroot, and has great potential in the food and cosmetic industries. However, natural pigments are unstable, and how to improve their stability while maintaining their color and function is a key problem that needs to be solved in the practical application of natural pigments.

[0004] In the prior art, the research on improving the stability of betalain mainly focuses on adding a single color developer, an antioxidant and a microencapsulation method. Among them, single wall material is commonly used for microencapsulation, and the betalain microcapsules prepared by single wall material coating still have the problems of short stability maintenance time and fast degradation rate. In addition, the commonly used microencapsulation methods are mainly spray drying, sharp hole method and complex coagulation method. Among them, the spray drying method has a high preparation temperature, and betalain is sensitive to heat, so the stability after preparation is poor; the sharp hole method produces betalain microcapsule particles with large size and short stability maintenance time. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a betalain microcapsule and a preparation method and application thereof. The present application uses a SA-SPI compound as a composite wall material and betalain as a core material. The composite wall material, CaCO3 and the core material are mixed and uniformly dispersed in an oil phase containing acetic acid to form a water-in-oil emulsion. At the same time, the acetic acid in the oil phase containing acetic acid initiates the dissociation of CaCO3 to form Ca 2+ , Ca 2+The betalain microcapsule prepared by the method has controllable particle size, high stability and easy industrialization, and widens the application range of the betalain.

[0006] To achieve the above object, the technical scheme adopted by the present application is: The first object of the present application is to provide a preparation method of betalain microcapsule, comprising the following steps: S1, dissolve sodium alginate and soybean protein isolate in water to obtain SA-SPI complex; sodium alginate interacts with soybean protein isolate through electrostatic interaction, steric hindrance and hydrogen bond, which improves the dispersion degree and reduces molecular aggregation, thereby improving the stability of the SA-SPI complex; meanwhile, the electrostatic and hydrophobic interaction between sodium alginate and soybean protein isolate promotes the conversion of free thiol groups in soybean protein isolate into intermolecular disulfide bonds, shortens the distance between amino acid residues in the peptide chain, and promotes the folding of the peptide chain to form a stable spatial structure. In addition, the hydrogen bond in the SA-SPI complex is also conducive to the formation of a more ordered and rigid structure, thereby improving the stability of the SA-SPI complex.

[0007] S2, mix the SA-SPI complex, CaCO3 and betalain to form an aqueous phase. The CaCO3 is the most commonly used calcium ion carrier, which has good spherical gel bead and stable properties, and can usually obtain gel beads with narrow size distribution. In addition, calcium carbonate is safe, convenient and economical.

[0008] S3, use liquid paraffin as the oil phase raw material, mix the liquid paraffin and Tween 80 to form a liquid paraffin emulsion; mix the liquid paraffin, glacial acetic acid and the liquid paraffin emulsion to obtain an acetic acid-containing oil phase.

[0009] S4, mix the aqueous phase and the acetic acid-containing oil phase, the aqueous phase is dispersed in the oil phase in the form of droplets, and a water-in-oil emulsion is formed, and then it is left to stand, during which the SA-SPI complex coats the betalain, and the glacial acetic acid in the acetic acid-containing oil phase initiates the dissociation of CaCO3 to form Ca 2+ , Ca 2+ In the water-in-oil emulsion, sodium alginate is crosslinked to form calcium alginate gel beads; the calcium alginate gel beads are pre-frozen and freeze-dried to obtain betalain microcapsules.

[0010] Preferably, the mass ratio of sodium alginate to soybean protein isolate is 1-2:0.5-1.

[0011] Preferably, the mass ratio of the total mass of sodium alginate and soybean protein isolate to the mass of betalain in the aqueous phase is 2.5-5:0.5-1, and the mass ratio of the total mass of sodium alginate and soybean protein isolate to the mass of CaCO3 is 3.75-7.5:1.

[0012] Preferably, the mass ratio of liquid paraffin to glacial acetic acid is 2100-2700:3.

[0013] Preferably, the mass ratio of sodium alginate to liquid paraffin is 0.2-0.6:95-110.

[0014] Preferably, the standing condition is standing at 4℃ for 21h-28h.

[0015] Preferably, the operation of pre-freezing and freeze-drying is that the calcium alginate gel beads are pre-frozen at-25℃ to-18℃ for 3h-6h, and then vacuum dried at-25℃ to-18℃ and 5Pa for 22h-27h.

[0016] The second object of the present application is to provide betalain microcapsules prepared by the above method.

[0017] The third object of the present application is the use of the above betalain microcapsules in the preparation of food additives.

[0018] Compared with the prior art, the present application has the following beneficial effects: 1. The present application provides a preparation method of betalain microcapsules. Sodium alginate and soybean protein isolate are dissolved in water together. Sodium alginate interacts with soybean protein isolate through electrostatic interaction, steric hindrance and hydrogen bonding to obtain a SA-SPI complex. The SA-SPI complex, CaCO3 and betalain are mixed to form an aqueous phase. Liquid paraffin is used as an oil phase, and liquid paraffin, Tween 80 and glacial acetic acid are mixed to obtain an acetic acid-containing oil phase. The aqueous phase and the acetic acid-containing oil phase are mixed, the aqueous phase is dispersed in the oil phase in the form of droplets, and a water-in-oil emulsion is formed. Then, the mixture is allowed to stand. During the standing process, the SA-SPI complex coats the betalain, and the glacial acetic acid in the acetic acid-containing oil phase triggers the dissociation of CaCO3 to form Ca 2+ , which is then coated by the SA-SPI complex. 2+The betalain microcapsule is prepared by the method of the present application, which is safe and simple in operation, controllable in particle size, high in stability and easy to be industrialized, has the advantages of low cost and high efficiency, and can be directly applied to large-scale production.

[0019] 2、The betalain microcapsule of the present application has high stability, which is due to the fact that the betalain is wrapped by the wall material sodium alginate and soybean protein isolate, which blocks its contact with oxygen and water and slows down the oxidation process. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a physical diagram and a particle size diagram of the betalain microcapsule, wherein a is a physical diagram, b is a particle size diagram, and the magnification is 20 times.

[0021] Figure 2 It is an embedding rate diagram of the betalain microcapsule of Example 1 to Example 6 and Comparative Example 1 to Comparative Example 3; wherein different lowercase letters represent significant differences, that is p <0.05.

[0022] Figure 3 It is a water content diagram of the betalain microcapsule of Example 1 to Example 6 and Comparative Example 1 to Comparative Example 3; wherein different lowercase letters represent significant differences, that is p <0.05.

[0023] Figure 4 It is a SEM diagram of the betalain microcapsule of Example 1 to Example 6 and Comparative Example 1 to Comparative Example 3, wherein a is Comparative Example 1, b is Example 1, c is Example 2, d is Comparative Example 2, e is Example 3, f is Example 4, g is Comparative Example 4, h is Example 5, i is Example 6, the magnification of e, f and g is 50x, and the others are 30x.

[0024] Figure 5The SEM images of betalain microcapsules of Example 1~Example 6 and Comparative Example 1~Comparative Example 3 are shown below, with a magnification of 100x, wherein a is Comparative Example 1, b is Example 1, c is Example 2, d is Comparative Example 2, e is Example 3, f is Example 4, g is Comparative Example 4, h is Example 5, and i is Example 6.

[0025] Figure 6 The SEM images of betalain microcapsules of Example 1~Example 6 and Comparative Example 1~Comparative Example 3 are shown below, with a magnification of 300x, wherein A is Comparative Example 1, B is Example 1, C is Example 2, D is Comparative Example 2, E is Example 3, F is Example 4, G is Comparative Example 4, H is Example 5, and I is Example 6.

[0026] Figure 7 The retention rate of betalain under different light exposure times and the retention rate of betalain in Example 1 betalain microcapsules are shown in the following chart, wherein different lowercase letters represent significant differences, i.e. p <0.05.

[0027] Figure 8 The retention rate of betalain under different temperatures and the retention rate of betalain in Example 1 betalain microcapsules are shown in the following chart, wherein different lowercase letters represent significant differences, i.e. p <0.05.

[0028] Figure 9 The retention rate of betalain under different pH values and the retention rate of betalain in Example 1 betalain microcapsules are shown in the following chart, wherein different lowercase letters represent significant differences, i.e. p <0.05.

[0029] Figure 10 The retention rate of betalain under different storage times and the retention rate of betalain in Example 1 betalain microcapsules are shown in the following chart, wherein different lowercase letters represent significant differences, i.e. p <0.05. DETAILED DESCRIPTION

[0030] The technical solutions of the present application will be described in detail below in combination with the data in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] It should be noted that the professional terms used in the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the protection scope of the present application. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present application can be purchased on the market or prepared by existing methods. Betacyanin is denoted as BC; sodium alginate is denoted as SA; soybean protein isolate is denoted as SPI.

[0032] In the prior art, microencapsulation generally uses single wall material coating, and is mostly spray drying, sharp hole or complex coagulation process; the obtained betacyanin microcapsules have the common defects of "short stability maintenance time and fast degradation rate", and the high temperature of spray drying easily causes the inactivation of the pigment, and the sharp hole method has large particles and short duration, which restricts the large-scale application of betacyanin.

[0033] In view of the problems existing in the prior art, the present application uses sodium alginate and soybean protein isolate as wall materials, first prepares a composite wall material, and uses endogenous emulsification to coat betacyanin, thereby successfully preparing betacyanin microcapsules with high stability, overcoming the defects of single wall material, heat-sensitive loss and particles in the prior art. 2+ , Ca 2+ In-situ cross-linking of sodium alginate inside the water-in-oil droplets to form calcium alginate gel beads solves the problems of easy oxidation of betacyanin, fast degradation upon heating, uncontrollable particle size and poor storage stability in traditional processes.

[0034] In order for those skilled in the art to have a clearer understanding of the technical solutions of the present application, the following will be described in detail in combination with specific embodiments: Example 1 A preparation method of betacyanin microcapsules, comprising the following steps: S1, preparing an aqueous phase: 0.25g of SA and 25mL of water are placed in a 100mL beaker, placed in a constant temperature magnetic stirrer, stirred at 25℃ with a stirring speed of 600r / min, after uniform stirring, 0.125g of SPI is added dropwise, and the stirring is continued, to obtain a SA-SPI composite; 0.1g of CaCO3 powder is weighed and added to the above SA-SPI composite, stirred uniformly, 0.075g of BC is weighed according to the core-wall ratio of 1:5, and the stirring is continued, to form an aqueous phase. The core material is BC, and the wall material is the SA-SPI composite.

[0035] S2, preparation of oil phase: take 100 mL of liquid paraffin in a 250 mL beaker, placed into a constant temperature magnetic stirrer, add 1 mL of Tween 80 to form a liquid paraffin emulsion; take 25 mL of liquid paraffin in a 50 mL beaker, and add 150 μL of glacial acetic acid, stir evenly at 25°C, then mix with the above emulsion to form an oil phase containing acetic acid.

[0036] S3, preparation of betalain microcapsules: the water phase is added to the oil phase containing acetic acid and stirred evenly, sealed and placed in a refrigerator at 4°C for 24 hours, then the water phase and the oil phase containing acetic acid are separated, the water phase is collected and placed in a 50 mL centrifuge tube, centrifuged at 4°C and 8000 rpm for 15 min, then placed in a refrigerator at -20°C for 4 hours, taken out and quickly placed on a freeze-drying machine shelf at -20°C, covered with a vacuum cover, the vacuum pump is started, the vacuum degree is reduced to 5 Pa, vacuumed for 24 hours, then taken out to obtain betalain microcapsules, recorded as BC-MC.

[0037] Example 2 A method for preparing betalain microcapsules, comprising the following steps: S1, preparation of water phase: 0.25 g of SA and 25 mL of water are placed in a 100 mL beaker, placed in a constant temperature magnetic stirrer, stirred at room temperature at a stirring speed of 600 r / min, after stirring evenly, 0.25 g of SPI is added dropwise, and stirring is continued to obtain SA-SPI complex; 0.1 g of CaCO3 powder is weighed and added to the above SA-SPI complex, stirred evenly, 0.1 g of BC is weighed according to the core-wall ratio of 1:5, and stirring is continued to form the water phase. The core material is BC and the wall material is SA-SPI complex.

[0038] S2, preparation of oil phase: take 100 mL of liquid paraffin in a 250 mL beaker, placed into a constant temperature magnetic stirrer, add 1 mL of Tween 80 to form a liquid paraffin emulsion; take 25 mL of liquid paraffin in a 50 mL beaker, and add 150 μL of glacial acetic acid, stir evenly at 25°C, then mix with the above emulsion to form an oil phase containing acetic acid.

[0039] S3, preparation of betalain microcapsules: the water phase is added to the oil phase containing acetic acid and stirred evenly, sealed and placed in a refrigerator at 4°C for 24 hours, then the water phase and the oil phase containing acetic acid are separated, the water phase is collected and placed in a 50 mL centrifuge tube, centrifuged at 4°C and 8000 rpm for 15 min, then placed in a refrigerator at -20°C for 4 hours, taken out and quickly placed on a freeze-drying machine shelf at -20°C, covered with a vacuum cover, the vacuum pump is started, the vacuum degree is reduced to 5 Pa, vacuumed for 24 hours, then taken out to obtain betalain microcapsules, recorded as BC-MC.

[0040] Example 3 A preparation method of betalain microcapsules, comprising the following steps: S1, preparing an aqueous phase: 0.375 g of SA and 25 mL of water are placed in a 100 mL beaker, which is placed in a constant temperature magnetic stirrer, stirred at a stirring speed of 600 r / min at room temperature, after uniform stirring, 0.125 g of SPI is added dropwise, and the stirring is continued, to obtain an SA-SPI compound; 0.1 g of CaCO3 powder is weighed and added to the SA-SPI compound, and stirred uniformly, 0.1 g of BC is weighed according to a core-wall ratio of 1:5, and the stirring is continued, to form an aqueous phase. The core material is BC, and the wall material is the SA-SPI compound.

[0041] S2, preparing an oil phase: 100 mL of liquid paraffin is placed in a 250 mL beaker, which is placed in a constant temperature magnetic stirrer, 1 mL of Tween 80 is added and stirred to form a liquid paraffin emulsion; 25 mL of liquid paraffin is taken in a 50 mL beaker, and 150 μL of glacial acetic acid is added, which is stirred uniformly at 25°C, and then mixed uniformly with the above emulsion, to form an acetic acid-containing oil phase.

[0042] S3, preparing betalain microcapsules: the aqueous phase is added dropwise to the acetic acid-containing oil phase and stirred uniformly, sealed and placed in a 4°C refrigerator for 24 h, then the aqueous phase and the acetic acid-containing oil phase are separated, the aqueous phase is collected and placed in a 50 mL centrifuge tube, which is centrifuged at 8000 rpm at 4°C for 15 min, then placed in a-20°C refrigerator for 4 h, taken out and quickly placed on a shelf of a freeze dryer at-20°C, covered with a vacuum cover, the vacuum pump is started, the vacuum degree is reduced to 5 Pa, and then vacuumized for 24 h, to obtain betalain microcapsules, which are recorded as BC-MC.

[0043] Example 4 A preparation method of betalain microcapsules, comprising the following steps: S1, preparing an aqueous phase: 0.375 g of SA and 25 mL of water are placed in a 100 mL beaker, which is placed in a constant temperature magnetic stirrer, stirred at a stirring speed of 600 r / min at room temperature, after uniform stirring, 0.125 g of SPI is added dropwise, and the stirring is continued, to obtain an SA-SPI compound; 0.1 g of CaCO3 powder is weighed and added to the SA-SPI compound, and stirred uniformly, 0.1 g of BC is weighed according to a core-wall ratio of 1:5, and the stirring is continued, to form an aqueous phase. The core material is BC, and the wall material is the SA-SPI compound.

[0044] S2, preparation of oil phase: take 100 mL of liquid paraffin in a 250 mL beaker, placed into a constant temperature magnetic stirrer, add 1 mL of Tween 80 to form a liquid paraffin emulsion; take 25 mL of liquid paraffin in a 50 mL beaker, and add 150 μL of glacial acetic acid, stir evenly at 25°C, then mix with the above emulsion to form an oil phase containing acetic acid.

[0045] S3, preparation of betalain microcapsules: the water phase is added to the oil phase containing acetic acid and stirred evenly, sealed and placed in a refrigerator at 4°C for 24 hours, then the water phase and the oil phase containing acetic acid are separated, the water phase is collected and placed in a 50 mL centrifuge tube, centrifuged at 4°C, 8000 rpm for 15 min, then placed in a refrigerator at -20°C for 4 hours, taken out and quickly placed on the shelf of a freeze dryer at -20°C, covered with a vacuum cover, the vacuum pump is started, the vacuum degree is reduced to 5 Pa, vacuumed for 24 hours, then taken out to obtain betalain microcapsules, marked as BC-MC.

[0046] Example 5 A method for preparing betalain microcapsules, comprising the following steps: S1, preparation of water phase: 0.5 g of SA and 25 mL of water are placed in a 100 mL beaker, placed in a constant temperature magnetic stirrer, stirred at room temperature at a stirring speed of 600 r / min, after stirring evenly, 0.125 g of SPI is added dropwise, and stirring is continued to obtain a SA-SPI complex; 0.1 g of CaCO3 powder is weighed and added to the above SA-SPI complex, stirred evenly, 0.125 g of BC is weighed according to a core-wall ratio of 1:5, and stirring is continued to form a water phase. The core material is BC, and the wall material is the SA-SPI complex.

[0047] S2, preparation of oil phase: take 100 mL of liquid paraffin in a 250 mL beaker, placed into a constant temperature magnetic stirrer, add 1 mL of Tween 80 to form a liquid paraffin emulsion; take 25 mL of liquid paraffin in a 50 mL beaker, and add 150 μL of glacial acetic acid, stir evenly at 25°C, then mix with the above emulsion to form an oil phase containing acetic acid.

[0048] S3, preparation of betalain microcapsules: the water phase is added to the oil phase containing acetic acid and stirred evenly, sealed and placed in a refrigerator at 4°C for 24 hours, then the water phase and the oil phase containing acetic acid are separated, the water phase is collected and placed in a 50 mL centrifuge tube, centrifuged at 4°C, 8000 rpm for 15 min, then placed in a refrigerator at -20°C for 4 hours, taken out and quickly placed on the shelf of a freeze dryer at -20°C, covered with a vacuum cover, the vacuum pump is started, the vacuum degree is reduced to 5 Pa, vacuumed for 24 hours, then taken out to obtain betalain microcapsules, marked as BC-MC.

[0049] Example 6 A preparation method of betalain microcapsules, comprising the following steps: S1, preparing an aqueous phase: 0.5 g of SA and 25 mL of water are placed in a 100 mL beaker, which is placed in a constant temperature magnetic stirrer, stirred at a stirring speed of 600 r / min at room temperature, after uniform stirring, 0.25 g of SPI is added dropwise, and the stirring is continued, to obtain an SA-SPI compound; 0.1 g of CaCO3 powder is weighed and added to the SA-SPI compound, and stirred uniformly, 0.15 g of BC is weighed according to a core-wall ratio of 1:5, and the stirring is continued, to form an aqueous phase. The core material is BC, and the wall material is the SA-SPI compound.

[0050] S2, preparing an oil phase: 100 mL of liquid paraffin is placed in a 250 mL beaker, which is placed in a constant temperature magnetic stirrer, 1 mL of Tween 80 is added and stirred to form a liquid paraffin emulsion; 25 mL of liquid paraffin is taken in a 50 mL beaker, and 150 μL of glacial acetic acid is added, which is uniformly stirred at 25°C, and then mixed with the above emulsion to form an acetic acid-containing oil phase.

[0051] S3, preparing betalain microcapsules: the aqueous phase is added to the acetic acid-containing oil phase and stirred uniformly, sealed and placed in a 4°C refrigerator for 24 h, then the aqueous phase and the acetic acid-containing oil phase are separated, the aqueous phase is collected and placed in a 50 mL centrifuge tube, which is centrifuged at 8000 rpm at 4°C for 15 min, then placed in a-20°C refrigerator for 4 h, taken out and quickly placed on a shelf of a freeze dryer at-20°C, covered with a vacuum cover, the vacuum pump is started, the vacuum degree is reduced to 5 Pa, and then vacuumized for 24 h, to obtain betalain microcapsules, which are recorded as BC-MC.

[0052] Comparative Example 1 A preparation method of betalain microcapsules, comprising the following steps: S1, preparing an aqueous phase: 0.25 g of SA and 25 mL of water are placed in a 100 mL beaker, which is placed in a constant temperature magnetic stirrer, stirred at a stirring speed of 600 r / min at room temperature, after uniform stirring, to obtain an SA solution; 0.1 g of CaCO3 powder is weighed and added to the SA solution, stirred uniformly, and then 0.05 g of BC is added and stirred, to form an aqueous phase.

[0053] S2, preparing an oil phase: 100 mL of liquid paraffin is placed in a 250 mL beaker, which is placed in a constant temperature magnetic stirrer, 1 mL of Tween 80 is added and stirred to form a liquid paraffin emulsion; 25 mL of liquid paraffin is taken in a 50 mL beaker, and 150 μL of glacial acetic acid is added, which is uniformly stirred at 25°C, and then mixed with the above emulsion to form an acetic acid-containing oil phase.

[0054] S3, preparation of betalain microcapsules: the water phase is added dropwise to the oil phase containing acetic acid, stirred evenly, sealed and placed in a refrigerator at 4°C for 24h, then the water phase and the oil phase containing acetic acid are separated, the water phase is collected and placed in a 50mL centrifuge tube, centrifuged at 8000rpm at 4°C for 15min, then placed in a refrigerator at -20°C for 4h, taken out and quickly placed on the shelf of a freeze dryer at -20°C, covered with a vacuum cover, the vacuum pump is started, the vacuum degree is reduced to 5Pa, vacuumed for 24h, then taken out, and betalain microcapsules are obtained.

[0055] Comparative example 2 A method for preparing betalain microcapsules, comprising the following steps: S1, preparation of water phase: 0.375g of SA and 25mL of water are placed in a 100mL beaker, placed in a constant temperature magnetic stirrer, stirred at a stirring speed of 600r / min at room temperature, after stirring evenly, SA solution is obtained; 0.1g of CaCO3 powder is weighed and added to the above SA solution, stirred evenly, then 0.075g of BC is added and stirred to form the water phase.

[0056] S2, preparation of oil phase: 100mL of liquid paraffin is placed in a 250mL beaker, placed in a constant temperature magnetic stirrer, 1mL of Tween 80 is added and stirred to form a liquid paraffin emulsion; 25mL of liquid paraffin is taken in a 50mL beaker, 150μL of glacial acetic acid is added, stirred evenly at 25°C, then mixed evenly with the above emulsion to form an oil phase containing acetic acid.

[0057] S3, preparation of betalain microcapsules: the water phase is added dropwise to the oil phase containing acetic acid, stirred evenly, sealed and placed in a refrigerator at 4°C for 24h, then the water phase and the oil phase containing acetic acid are separated, the water phase is collected and placed in a 50mL centrifuge tube, centrifuged at 8000rpm at 4°C for 15min, then placed in a refrigerator at -20°C for 4h, taken out and quickly placed on the shelf of a freeze dryer at -20°C, covered with a vacuum cover, the vacuum pump is started, the vacuum degree is reduced to 5Pa, vacuumed for 24h, then taken out, and betalain microcapsules are obtained.

[0058] Comparative example 3 A method for preparing betalain microcapsules, comprising the following steps: S1, preparation of water phase: 0.375g of SA and 25mL of water are placed in a 100mL beaker, placed in a constant temperature magnetic stirrer, stirred at a stirring speed of 600r / min at room temperature, after stirring evenly, SA solution is obtained; 0.1g of CaCO3 powder is weighed and added to the above SA solution, stirred evenly, then 0.075g of BC is added and stirred to form the water phase.

[0059] S2. Preparation of the oil phase: Take 100 mL of liquid paraffin and place it in a 250 mL beaker. Place it in a constant temperature magnetic stirrer and add 1 mL of Tween 80. Stir until a liquid paraffin emulsion is formed. Take 25 mL of liquid paraffin and place it in a 50 mL beaker. Add 150 μL of glacial acetic acid. Stir at a constant temperature of 25 °C until homogeneous. Then mix it evenly with the above emulsion to form an acetic acid-containing oil phase.

[0060] S3. Preparation of betaine microcapsules: The aqueous phase was added dropwise to the acetic acid-containing oil phase and stirred evenly. The mixture was then sealed and allowed to stand for 24 hours in a refrigerator at 4°C. The aqueous phase and the acetic acid-containing oil phase were then separated. The aqueous phase was collected and placed in a 50 mL centrifuge tube. After centrifugation at 8000 rpm for 15 minutes at 4°C, the tube was placed in a freezer at -20°C for 4 hours. The tube was then quickly placed on the shelf of a freeze dryer at -20°C, the vacuum cover was closed, the vacuum pump was turned on, and the vacuum degree was reduced to 5 Pa. After vacuuming for 24 hours, the tube was removed to obtain betaine microcapsules.

[0061] When sodium alginate in Example 1 was replaced with equal masses of gelatin, maltodextrin, and β-cyclodextrin, the results showed that none of them could gelatinize into microcapsules.

[0062] Table 1 shows the material ratios of the wall and core materials in the betaine microcapsules of Examples 1-6 and Comparative Examples 1-3.

[0063] Depend on Figure 1 This invention successfully prepared betalain microcapsules using sodium alginate and soy protein isolate as composite wall materials. The betalain microcapsules of this invention have a diameter of 345.51 µm, which is at the micron level, and exhibit good dispersibility. Microcapsule diameters are generally between 5 µm and 400 µm; if the diameter is too small, the core material is not encapsulated sufficiently, and if it is too large, the contents are released too slowly, resulting in poor dispersibility and uneven coloring. Microcapsules of this particle size exhibit good dispersibility, rapid dissolution, and high stability.

[0064] test: a. Determination of microcapsule encapsulation efficiency: Dissolve 0.1 g of BC-MC in 9.9 mL of 5% sodium citrate solution to decapsulate the microcapsules. Allow to stand until completely dissolved, filter, and centrifuge at 8000 rpm for 15 min to obtain a microcapsule solution free of impurities. Measure the absorbance at a wavelength of 538 nm. The calculation formula is as follows: Formula 1.

[0065] In the formula: E —Encapsulation rate, % c 1 — BC sample concentration, mg / mL; c 2BC-MC filtrate concentration, mg / mL.

[0066] b. Measurement of the moisture content of the microcapsules: The moisture content is a key factor affecting the stability of the microcapsules, and too high a moisture content will promote microbial growth and accelerate the oxidative degradation of the core material. BC is sensitive to heat, and its stability is poor: it changes from red to yellow when the temperature exceeds 60℃, and it will obviously brown when treated at 100℃ for 15 min. Based on the above reasons, the drying temperature is determined to be 60℃ in the present application.

[0067] The betalain microcapsules of Examples 1-6 and Comparative Examples 1-3 were respectively taken and placed in a weighing bottle, which was opened and placed in a constant temperature oven, dried at 60℃ for 5h, taken out and cooled to room temperature, and the weight was recorded. The above operation was repeated until the weight no longer changed, and the calculation formula was as follows: ω Formula 2.

[0068] In the formula: ω - water content, %; m 0 Weighing bottle mass, g; m 1 Weighing bottle and betalain microcapsule mass before drying, g; m 2 Weighing bottle and betalain microcapsule mass after drying, g.

[0069] c. Morphology observation: A small amount of betalain microcapsules was taken, placed on conductive glue and placed in a vacuum dryer, and after removing the surface moisture, scanning electron microscope test was carried out at an acceleration voltage of 5kV, and the morphology was observed and recorded.

[0070] d. Stability detection: The degradation behavior of betalains during storage conforms to the first-order kinetics law, and the degradation rate is independent of the initial concentration. The present application evaluates the improvement effect of microencapsulation treatment on the stability of pigments by measuring the retention rate (%) of betalains and betalain microcapsules during storage.

[0071] e. Light stability: BC and BC-MC were placed at a distance of 1.5m from a 60W D65 light source at room temperature, and the BC content was detected and calculated at 0h, 4h, 8h and 12h, respectively.

[0072] u Formula 3.

[0073] In the formula: u—— Retention rate, %; c 0 Initial betalain or microcapsule concentration, mg / mL; c 1 Betalain microcapsule mass concentration after treatment, mg / mL.

[0074] ① Thermal stability: BC and BC-MC were stored in the dark at 4℃, 10℃, 30℃ and 50℃ for 8 hours, and the BC content was detected and calculated according to Equation 3.

[0075] ② Acid resistance: At room temperature, buffer solutions with pH values ​​of 3, 5, 7 and 9 were prepared respectively. 0.1g of BC and betalain microcapsules were weighed respectively, with the betalain mass concentration being consistent. After centrifugation in centrifuge tubes with corresponding pH buffers for 4h, the pH was adjusted to neutral. Sodium citrate stock solution was added and the capsules were ruptured. The betalain content was detected and calculated according to Equation 3.

[0076] ③Time stability: BC and BC-MC were stored in the dark for 1 week, 2 weeks, 3 weeks and 4 weeks at 4℃ or room temperature, respectively, and the BC content was detected and calculated according to Equation 3.

[0077] e. Data Processing: Each treatment was performed in triplicate. Data analysis was conducted using SPSS 27.0, and Duncan's method was used for significance analysis. All results are expressed as mean ± standard deviation. Electron micrographs were processed using Photoshop CC. p <0.05 indicates a significant difference.

[0078] result: a. Effect of wall material ratio on the encapsulation efficiency of betalain microcapsules: Table 2 shows the encapsulation efficiency of betalain microcapsules in Examples 1-6 and Comparative Examples 1-3, n=3.

[0079] As shown in Table 2 and Figure 2 As shown, the encapsulation rates of betaine microcapsules prepared in Examples 1-6 and Comparative Examples 1-3 were generally between 75% and 95%. Among them, the betaine microcapsules prepared in Example 5 had the best encapsulation rate, reaching 94.27% ± 0.95%, which is 16.89% higher than the encapsulation rate of 77.38% for a single SA wall material in the prior art. This is mainly attributed to the introduction of SPI: betaine binds to the CO, CN, and NH groups in soy protein isolate, while sodium alginate enhances the solubility of soy protein isolate. The synergistic effect of these two factors promotes the increase in encapsulation rate. In addition, compared with the prior art methods that only use SPI or soy protein isolate fiber, the encapsulation rates of the betaine microcapsules of the present invention are increased by 29.37% and 18.37%, respectively. This is mainly related to the changes in the secondary structure of the betaine microcapsules during their formation.

[0080] b. Effect of wall material ratio on the water content of betalain microcapsules: Table 3 shows the effect of different wall material concentration ratios on moisture content, n=3

[0081] Moisture content is a crucial factor affecting the storage quality and stability of BC-MC. Higher moisture content accelerates product deterioration and shortens shelf life. Furthermore, BC is highly sensitive to heat, light, and water activity; therefore, strict control and reduction of the moisture content in betalain microcapsules are necessary during preparation. (See Table 3 and...) Figure 3 The results showed that the water content of the betaine microcapsules in Examples 1-6 and Comparative Examples 1-3 was all below 9%. When sodium alginate was used alone as the wall material, its water content was significantly higher than that of the SA-SPI composite wall material. p <0.05; When the SA concentration was 2%, the water content of the microcapsules prepared by combining SA and SPI all decreased to below 4%, with the betaine microcapsules of Example 6 having the lowest water content at 3.54% ± 0.42%, followed by the betaine microcapsules of Example 5 at 3.81% ± 0.39%. This indicates that the composite gel membrane structure formed by SA and SPI is more compact and can effectively block water from penetrating inward, thereby significantly improving the stability of betaine.

[0082] c. Observation of betaine microcapsule morphology: Depend on Figure 4 The results showed that the betaine microcapsule particles were all irregularly shaped, nearly spherical, with varying degrees of surface wrinkling. Overall, the betaine microcapsules encapsulated by different proportions of composite wall materials had different particle sizes. Figure 4 The particle size in figures a, b, c, d, f, and i is slightly larger. Figure 4 The particle sizes in the e, g, and h diagrams are relatively small. At the same SA content, with increasing SPI addition, the surface wrinkles of the betaine microcapsules gradually decrease, becoming closer to a regular sphere. This is mainly because the electrostatic and hydrophobic interactions between SA and SPI promote the conversion of free thiol groups in the protein into intermolecular disulfide bonds, shortening the distance between amino acid residues in the peptide chain and promoting peptide chain folding to form a stable spatial structure. Furthermore, the hydrogen bonds in the SA-SPI particles also contribute to the formation of a more ordered and rigid structure, improving its stability. When encapsulated with a single SA wall material, some betaine on the surface of the betaine microcapsules is not completely encapsulated, such as... Figure 4 As shown in Figures a, d, and g, after coating with 2% SA + 1% SPI as the wall material, the particle shape is closest to spherical, but the surface pores become more numerous, such as... Figure 4 As shown in Figure i, this is mainly because some protein molecules migrate with water to the surface of the droplets during drying, and the film strength is insufficient to maintain its spherical shape, leading to rupture. The corresponding magnified SEM image is shown below. Figure 5 and Figure 6 As shown.

[0083] In summary, when the SA content is 2% and the SPI content is 0.5%, the prepared betalain microcapsules have better embedding effect and better stability.

[0084] d. Stability detection of microcapsules: Table 4 is a table of the effect of light time on the stability of the betalain microcapsules of Example 1 and betalain

[0085] According to Table 4 and Figure 7 It is concluded that, compared with the BC original sample, the retention rate of BC-MC is significantly improved as the light time is prolonged, p <0.05. After 12 h, the retention rate of BC-MC is 92.17% ± 0.68%, and the retention rate of BC is 85.33% ± 1.63%. The slope of the trend line of the retention rate of BC is significantly higher than that of BC-MC, indicating that microencapsulation treatment can slow down the degradation of pigments caused by light damage and significantly improve the stability of BC. This is mainly due to the excellent film-forming property of SA and the improved solubility of SPI; in addition, the addition of SA changes the conformation of SPI, the complexation of SPI with polysaccharides in sodium alginate promotes the transformation of SPI from disordered structure to ordered structure, and the presence of SA makes the structure of SPI more compact, which isolates light and oxygen and reduces the influence of the environment on the stability of the core material BC.

[0086] Table 5 is a table of the effect of temperature on the stability of the betalain microcapsules of Example 1 and betalain

[0087] According to Table 5 and Figure 8 It is concluded that temperature is also a key factor affecting the stability of betalain. When the temperature exceeds 60°C, the color of BC will change significantly from red to yellow. In order to select a suitable storage temperature, the stability changes of BC and BC-MC at different temperatures are investigated. Figure 8 It can be seen that, as the temperature rises, the retention rates of BC and BC-MC samples both decrease. Compared with the original sample, the thermal stability of BC-MC is better after being stored at 50°C for 8 h, and the retention rate is higher than 85%, which is significantly higher than the retention rate of the BC sample, p <0.05, and the retention rate of BC is lower than 80%. At 30°C, the retention rates of BC and BC-MC are higher than those of the light treatment group for 8 h, which also indicates that light can accelerate the degradation of BC. Overall, BC and BC-MC have the highest retention rate when stored at 4°C in the dark. After 8 h, the retention rate of BC-MC is 99.26% ± 0.52%, and the retention rate of BC is 98.96% ± 0.30%, indicating that both BC and BC-MC should be stored at low temperature and in the dark.

[0088] Table 6 is the effect of pH on the stability of betalain microcapsules and betalains of Example 1

[0089] The stability of BC is highly dependent on pH, which is manifested in the transition to purple at lower pH or to yellow at higher pH. Combined with Table 6 and Figure 9 It is concluded that the retention rates of BC and its microcapsules are significantly decreased under alkaline conditions, i.e., pH = 9, which is mainly related to the degradation of BC to accelerate the generation of betalamic acid, 17-decarboxylated isobetanidin, or neobetanidin after the breakage of aldimine bond, dehydrogenation, or reaction of carboxyl group in the molecular structure of BC under alkaline environment. The retention rate at pH 5 is significantly higher than that under other pH conditions, i.e., p <0.05, which is consistent with the inherent chemical properties of BC, and its microcapsules also maintain good stability under this condition, indicating that BC and its microcapsules are suitable for storage under weak acidic conditions, and the storage effect is best at pH 5.

[0090] Table 7 is the effect of storage time on the stability of betalain microcapsules and betalains of Example 1

[0091] In the present application, 4℃-BC-MC is the abbreviation of 4℃ betalain microcapsules of Example 1, 4℃-BC is the abbreviation of 4℃ betalains, and 25℃-BC-MC is the abbreviation of 25℃ betalain microcapsules of Example 1, and 25℃-BC is the abbreviation of 25℃ betalains.

[0092] Storage stability is crucial for pigments used as colorants. Combined with Table 7 and Figure 10 It is concluded that with the increase of storage time, BC and BC-MC are partially degraded, and compared with BC, the degradation rate of BC-MC is significantly reduced. After 28 days of storage, under 4℃ conditions, the retention rate of BC-MC is as high as 97.96% ± 0.20%, and the retention rate of BC is reduced to 81.01% ± 0.34%. At room temperature, the retention rate of BC-MC is 87.42% ± 1.10%, which is significantly higher than the retention rate of BC, 73.78% ± 0.76%, p <0.05, indicating that microencapsulation and low-temperature preservation are crucial factors for maintaining the stability of BC. BC is easily affected by external factors during storage, causing oxidative stress and degradation. After microencapsulation, a composite protective layer is formed on the surface of BC, which inhibits the degradation of oxygen, light, and moisture on the core material BC, prolonging its stability period. Therefore, to ensure the storage stability of BC, embedding or encapsulation treatment is required, and it should be stored in low-temperature and light-proof place.

[0093] It should be noted that when the present application refers to a numerical range, it is understood that both the end points of each numerical range and any number between the two end points can be selected. Since the same procedure and examples are used, in order to prevent repetition, the present application describes a preferred embodiment. Although a preferred embodiment of the present application has been described, those skilled in the art will be able to make additional changes and modifications to these embodiments once they have been given the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiment and all changes and modifications falling within the scope of the present application.

Claims

1. A method for preparing betalain microcapsules, characterized in that, The method comprises the following steps: Sodium alginate and soybean protein isolate are dissolved in water, and the sodium alginate interacts with the soybean protein isolate through electrostatic interaction, steric hindrance and hydrogen bond to obtain a SA-SPI compound; The SA-SPI compound, CaCO3 and betacyanin are mixed to form an aqueous phase; Liquid paraffin, Tween 80 and glacial acetic acid are mixed to obtain an acetic acid-containing oil phase; The water phase is mixed with the oil phase containing acetic acid, the water phase is dispersed in the oil phase in the form of droplets, and a water-in-oil emulsion is formed, and then is left to stand, during which the SA-SPI complex coats betalain, and the glacial acetic acid in the oil phase containing acetic acid initiates the dissociation of CaCO3 to form Ca 2+ , Ca 2+ is crosslinked with sodium alginate inside the water-in-oil emulsion to form calcium alginate gel beads; the calcium alginate gel beads are subjected to pre-freezing and freeze-drying treatment to obtain betalain microcapsules.

2. The method for preparing betalain microcapsules according to claim 1, characterized in that, The mass ratio of sodium alginate to soybean protein isolate is 1-2:0.5-1.

3. The method for preparing betalain microcapsules according to claim 1, characterized in that, In the aqueous phase, the mass ratio of the total mass of sodium alginate and soybean protein isolate to the mass of betacyanin is 2.5-5:0.5-1, and the mass ratio of the total mass of sodium alginate and soybean protein isolate to the mass of CaCO3 is 3.75-7.5:

1.

4. The method of preparing betalain microcapsules according to claim 1, characterized in that, The mass ratio of liquid paraffin to glacial acetic acid is 2100-2700:

3.

5. The method of preparing betalain microcapsules according to claim 1, characterized in that, The mass ratio of sodium alginate to liquid paraffin is 0.2-0.6:95-110.

6. The method of preparing betalain microcapsules according to claim 1, characterized in that, The standing condition is standing at 4°C for 21-28 hours.

7. The method of preparing betalain microcapsules according to claim 1, characterized in that, The operation of pre-freezing and freeze-drying treatment is that the calcium alginate gel beads are pre-frozen at-25°C to-18°C for 3-6 hours, and then vacuum dried at-25°C to-18°C and 5 Pa for 22-27 hours.

8. A betalain microcapsule characterized in that, Prepared by the preparation method of any one of claims 1-7.

9. Use of the betacyanin microcapsule of claim 8 in the preparation of a food additive.

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