Betarubin color protection technology

Abstract

The invention belongs to the technical field of food additives, and provides a betacyanin color protection technology. Calcium ions are used as central ions, catechin and derivatives thereof are used as ligands, and the calcium ions are coordinated with phenolic hydroxyl groups to form unsaturated complexes; cross-linking carboxyl or hydroxyl of betacyanin with calcium ions through a coordination reaction to form a stable complex; the complexes are further crosslinked by non-covalent interaction to form an MOF network structure, and the betacyanin is fixed in the network structure to form a coordination compound with the particle size of 100-150nm; and then the polysaccharide is coated on the periphery of the nano coordination compound, so that a dual protection effect on the betacyanin is achieved. The coordination compound has a special core-shell structure, the stability of the betacyanin under stress of light, heat, an oxidizing agent, metal ions, strong acid and strong alkali is remarkably improved, slow release of the betacyanin is achieved, a new technology is provided for stabilization of natural pigments, and a high-stability betacyanin product is provided for the industries of food, cosmetics and medicine.

Description

Technical Field

[0001] This invention relates to the field of food additives technology, and in particular to a betalain color-protecting technology. Technical Background

[0002] Betanin (BT) is a natural, water-soluble, nitrogenous polyphenolic pigment, primarily derived from red beet roots, cactus fruit, and dragon fruit peels. BT is not only used as a natural colorant in the food and cosmetic industries, providing vibrant red or purplish-red hues, but also possesses beneficial properties such as anti-inflammatory, anti-cancer, and anti-diabetic effects, making it widely used in the pharmaceutical industry. However, BT exhibits poor stability and is easily degraded during extraction and processing due to factors such as temperature, light, pH, and metal ions, leading to fading, reduced bioavailability, and severely impacting its applications. The degradation reactions of BT mainly involve isomerization, decarboxylation, dehydrogenation, and oxidation. Therefore, modifying, encapsulating, and masking its easily degradable groups are effective means to improve BT's stability.

[0003] Chemical modification of biotin (BT) involves the generation of new functional groups, is complex, requires the introduction of chemical reagents, and necessitates a reassessment of the product's food safety. Therefore, physical modification, particularly non-covalent bonding and encapsulation techniques, has become the best option for improving BT stability. In recent years, macromolecular encapsulation has become a hot technology for improving BT stability, offering advantages such as simple processes, high product safety, and ease of large-scale application. Commonly used macromolecules are polysaccharides and proteins. Cai et al. (2000) used maltodextrin and starch to encapsulate BT in amaranth, effectively reducing BT's hygroscopicity and enhancing its storage stability. Combining BT with maltodextrin, chitosan, etc., improved its color stability (Chranioti et al., 2015). Soy protein isolate binds to BT through hydrophobic interactions, increasing BT's heat retention rate from 55.3% to 75.9% (Zhao et al., 2020). Rice-pea composite plant protein can non-covalently bind to BT, and the a* value retention rate of BT is over 65% after storage at 4 ℃ for 28 days (Geng et al., 2024). Whey protein and BT mainly form complexes through van der Waals forces and hydrogen bonds, increasing the retention rate of BT from 6.17% to 27.26% after heat treatment at 80 ℃ (Hu et al., 2022). In addition, some researchers have used a combined co-coloring and embedding technique to improve the stability of BT, with co-coloring agents mainly including oxalic acid, citric acid, lactic acid, acetic acid, tartaric acid, gallic acid, ascorbic acid, p-coumaric acid, ferulic acid, and malic acid. Studies have shown that when BT is loaded with chlorogenic acid or coumarin as co-coloring agents and protein as the embedding agent, its retention rate is 65.03% after heating in an 80 ℃ water bath for 1 hour (CN 118415292 A). Using sodium alginate and soy protein isolate as wall materials, calcium ion cross-linking was used to form gel beads for BT encapsulation, significantly improving its thermal stability, pH stability (5-7), and storage stability (CN 120898934 A). Encapsulating BT with a composite wall material of maltodextrin-rice protein-inulin significantly improved its storage stability (CN 113208111 A). BT liposomes prepared using chondroitin sulfate-chitosan multilayer modification technology achieved sustained release of BT and improved bioavailability (CN 114343214A). Therefore, using suitable wall materials to encapsulate BT can effectively improve its thermal, pH, and storage stability.

[0004] Although the aforementioned technologies have improved the stability and bioavailability of BT, especially its thermal and storage stability, its stability under alkaline conditions remains low. Furthermore, most studies have focused on the light, heat, pH, and storage stability of BT, with very little attention paid to its stability under metal ions. Metal ions, such as zinc, copper, and iron, are common in food systems and are essential trace elements for the human body. When BT is used in food or cosmetics, the presence of metal ions, especially beneficial minerals, is unavoidable in the ingredients. Numerous studies have found that BT is extremely sensitive to metal ions, and even after encapsulation or color enhancement, its stability under metal ions remains low. For example, after encapsulation in casein micelles, BT's stability under 0.01 mol / L Fe... 3+ The retention rate of BT after 120 min of treatment was less than 80%, and only about 10% higher than that of unencapsulated BT (Zeng et al., 2025); after whey protein encapsulation, the retention rate of BT at 0.5 mg / mL Zn 2+ The retention rate after 120 min of treatment was less than 80% at 0.5 mg / mL Cu. 2+ The retention rate after 120 min of treatment was less than 60% (Zhou Jinran et al., 2025). However, some studies have pointed out that Ca... 2+ Some studies have shown that calcium ions have no effect on the stability of BT (He et al., 2023), and may even protect betaine (Xu et al., 2014). This suggests that there may be a special interaction between calcium ions and BT.

[0005] Studies have shown that compounds with catechol and pyrogallol structures readily react with Ca. 2+ Formation of complexes (Wang et al., 2018). Ca 2+ It can form 4-coordinate complexes with guaiacol, and the coordination reaction proceeds stepwise (Yin Junjun, 2021). To date, the construction of complexes using Ca... 2+ There are few reports on the research of complexes with catechins and BT as common ligands, and no reports have been found on the technology of using complexes and macromolecules to stabilize BT and protect its color.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] This invention preferably uses catechins and their derivatives as ligands and co-colorants, with Ca being a preferred choice. 2+ Using Ca as the central ion, a catechin-type compound was constructed. 2+- By using betaine nano-MOF type complexes and edible polysaccharides as encapsulating agents, a coordination complex loaded with betaine was prepared, which significantly improved the thermal, pH, light, and oxidative stability of betaine, especially its metal ion stability. This provides a highly stable pigment for the food and cosmetics industries and offers new ideas and technologies for the color protection of natural pigments.

[0008] The objective of this invention is achieved through the following technical solution: A betalain color-protecting technology, characterized by the following steps and process conditions: (1) Dissolve catechin or its derivatives in deionized water, adjust the pH to 5.5-6.5 with 0.1-1 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 1-3 g / L; dissolve calcium chloride in deionized water and prepare an aqueous solution with a concentration of 0.5-1 g / L; dissolve betalain in deionized water, adjust the pH to 5.5-6.5 with 0.1-1 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 10-30 g / L; dissolve polysaccharide in deionized water, adjust the pH to 4.5-5.5 with 0.1-1 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 10-30 g / L for later use; (2) Mix the polyphenol solution and calcium chloride solution from step (1) at a volume ratio of 2:1 to 1:2, adjust the pH of the mixture to 5.5 to 6.5, and then perform ultrasonic treatment. The ultrasonic frequency is 20 kHz, the amplitude is 20 to 40%, the pulse mode is 2 to 4 seconds on and 4 to 8 seconds off, the ultrasonic temperature is 45 to 65 °C, and the ultrasonic time is 5 to 10 min to prepare polyphenol-Ca 2+ Complex solution; (3) The polyphenol-Ca prepared in step (2) 2+ The complex solution was placed in a water bath at 45-65℃ and preheated with magnetic stirring at 2000-3000 r / min. An appropriate amount of betaine solution from step (1) was taken and added to the polyphenol-Ca complex at a volume ratio of 1:1-5:1 at a rate of 8-12 mL / min. 2+ In the complex solution, heat for another 10-20 minutes, then slowly adjust the pH of the complex solution to 7-8 using 0.1-1 mol / L hydrochloric acid or sodium hydroxide to prepare polyphenol-Ca. 2+ -Betaine complex solution; (4) The polyphenol-Ca prepared in step (3) 2+- The betaine complex solution was placed in an ultrasonic processor, and 1-3 times the volume of polysaccharide aqueous solution was added at a rate of 8-12 mL / min under ultrasonic irradiation. The ultrasonic frequency was 20 kHz, the amplitude was 20-40%, the pulse mode was 2-4 seconds on and 4-8 seconds off, and the ultrasonic temperature was 25-45℃. Ultrasonication was then continued for 5-10 min to prepare polyphenol-Ca. 2+ -Betaine@polysaccharide coordination complex solution; (5) Spray dry the solution from step (4) to obtain highly stable polyphenol-Ca. 2+ -Betaine polysaccharide coordination complex powder.

[0009] Compared with the prior art, the present invention has the following advantages and effects: (1) In this invention, catechins and their derivatives with excellent coordination effects are preferred as auxiliary coordination agents, and Ca(II) which have no degradation effect on betalains are preferred. 2+ As the central ion, it promotes the formation of a coordination number of 1 to 2 between the two under ultrasonic driving; then, through coordination, betaine and catechin-type compounds -Ca 2+ The complex binds to form a catechin-type compound -Ca 2+ - The MOF network structure of betalains fixes betalains in the network structure, protecting them from degradation due to adverse environmental factors.

[0010] (2) Based on the construction of the coordination complex, this invention further protects betalains by encapsulating polysaccharide macromolecules. The preferred polysaccharide is a natural, edible, water-soluble polysaccharide, and its aqueous solution is basically colorless and transparent, which does not affect the color of betalains. Through polysaccharide encapsulation, a dual protection effect on betalains is achieved on the one hand, and excellent water solubility is given to the coordination complex on the other hand, ensuring that it has a wide range of applications.

[0011] (3) On the one hand, this invention utilizes catechin-type compounds, betaine, and Ca 2+ The coordination mechanism effectively protects the functional groups of betaine, while the co-coloring effect of catechin-type compounds further enhances the stability of betaine. Furthermore, the non-covalent interaction between betaine and catechins forms a multilayer network structure, which, while protecting the structural stability of betaine, achieves sustained release and significantly improves its bioavailability.

[0012] (4) This invention utilizes Ca 2+The coordination mechanism binds to the groups on the betaine molecule that readily coordinate with metal ions, preventing them from further coordinating with other metal ions in the processing environment due to steric hindrance. This effectively prevents betaine degradation due to exposure to metal ions, significantly improving its metal ion stability. Simultaneously, polysaccharide encapsulation significantly improves the stability of betaine under strong alkaline and acidic conditions, expanding its application range. This color-protecting technology is simple, environmentally friendly, and uses only food or food additives as raw materials, making it safe for consumption. Attached Figure Description

[0013] Figure 1 This is the appearance of the betaine red complex aqueous solution in the technical principle and Examples 1-4 of this invention.

[0014] Figure 2 Ca, a catechin-type compound in the embodiments of the present invention. 2+ - Particle size and potential of betaine@polysaccharide coordination complexes. Different capital letters indicate significant differences between samples. p<0.05 BT stands for free betaine.

[0015] Figure 3 The spray-dried catechin-type compound - Ca in the embodiments of the present invention 2+ - Morphology of betaine@polysaccharide coordination complex, wherein the BT magnification is 400×, and the magnification of the example sample is 10000×.

[0016] Figure 4 Ca, a catechin-type compound in the embodiments of the present invention. 2+ - Thermal stability of betaine@polysaccharide coordination complex; different capital letters indicate significant differences between different samples at the same treatment time, and different lowercase letters indicate significant differences between the same sample at different treatment times. p<0.05 (The same applies below.)

[0017] Figure 5 Ca, a catechin-type compound in the embodiments of the present invention. 2+ - pH stability of betaine@polysaccharide coordination complex.

[0018] Figure 6 Ca, a catechin-type compound in the embodiments of the present invention. 2+ - The photostability of the betaine@polysaccharide coordination complex.

[0019] Figure 7 Ca, a catechin-type compound in the embodiments of the present invention. 2+ - Oxidative stability of betaine@polysaccharide coordination complex.

[0020] Figure 8 Ca, a catechin-type compound in the embodiments of the present invention.2+ - Metal ion stability of betaine@polysaccharide coordination complex.

[0021] Figure 9 Ca, a catechin-type compound in the embodiments of the present invention. 2+ -Mimetic gastrointestinal fluid cumulative release rate of betaine@polysaccharide coordination complex. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise stated, the raw materials used in the embodiments of the present invention are conventionally purchased raw materials. Example 1

[0023] (1) Dissolve catechin in deionized water and adjust the pH to 6.5 with 0.1 mol / L hydrochloric acid or sodium hydroxide to prepare an aqueous solution with a concentration of 1 g / L; dissolve calcium chloride in deionized water to prepare an aqueous solution with a concentration of 0.5 g / L; dissolve betalain in deionized water and adjust the pH to 6.5 with 0.1 mol / L hydrochloric acid or sodium hydroxide to prepare an aqueous solution with a concentration of 10 g / L; dissolve sodium alginate in deionized water and adjust the pH to 5.5 with 0.1 mol / L hydrochloric acid or sodium hydroxide to prepare an aqueous solution with a concentration of 10 g / L for later use; (2) Take 100 mL of catechin solution and mix it with 50 mL of calcium chloride solution. Adjust the pH of the mixture to 6.5 and then perform ultrasonic treatment. The ultrasonic frequency is 20 kHz, the amplitude is 20%, the pulse mode is 2 seconds on and 4 seconds off, the ultrasonic temperature is 45 ℃, and the ultrasonic time is 10 min to prepare polyphenol-Ca 2+ Complex solution; (3) Catechins-Ca 2+ The complex solution was preheated in a 45°C water bath with magnetic stirring at 2000 rpm. 150 mL of betaine solution was then added to the catechin-Ca complex at a rate of 8 mL / min. 2+ The complex solution was heated for another 20 minutes, and then the pH of the complex solution was slowly adjusted to 7 using 0.1 mol / L sodium hydroxide to obtain catechin-Ca. 2+ -Betaine complex solution; (4) Catechins-Ca 2+ - The betaine complex solution was subjected to ultrasonic treatment in an ultrasonic processor at a frequency of 20 kHz, an amplitude of 20%, a pulse mode of 2 seconds on and 4 seconds off, and an ultrasonic temperature of 25℃. During the ultrasonication, 300 mL of sodium alginate aqueous solution was added at a rate of 8 mL / min, followed by continued ultrasonication for 10 min to obtain catechin-Ca.2+ - Aqueous solution of betaine@sodium alginate coordination complex; (5) Catechins-Ca 2+ - Betaine red pigment @ sodium alginate coordination complex aqueous solution was spray-dried to obtain catechin-Ca 2+ -Betaine@Sodium Alginate Coordination Complex Powder. Example 2

[0024] (1) Dissolve epigallocatechin gallate in deionized water, adjust the pH to 5.5 with 1 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 3 g / L; dissolve calcium chloride in deionized water and prepare an aqueous solution with a concentration of 1 g / L; dissolve betalain in deionized water, adjust the pH to 5.5 with 1 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 30 g / L; dissolve maltodextrin in deionized water, adjust the pH to 4.5 with 1 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 30 g / L for later use. (2) Take 25 mL of epigallocatechin gallate solution and mix it with 50 mL of calcium chloride solution. After adjusting the pH of the mixture to 5.5, perform ultrasonic treatment. The ultrasonic frequency is 20 kHz, the amplitude is 40%, the pulse mode is 4 seconds on and 8 seconds off, the ultrasonic temperature is 65 ℃, and the ultrasonic time is 5 min to obtain epigallocatechin gallate-Ca 2+ Complex solution; (3) Epigallocatechin gallate-Ca 2+ The mixed solution was placed in a 65°C water bath and preheated with magnetic stirring at 3000 rpm. 375 mL of betaine solution was then added to epicatechin gallate-Ca at a rate of 12 mL / min. 2+ In the complex solution, the mixture was heated for another 10 minutes, and then the pH of the complex solution was slowly adjusted to 8 using 1 mol / L hydrochloric acid or sodium hydroxide to obtain epigallocatechin gallate-Ca. 2+ -Betaine complex solution; (4) Epigallocatechin gallate-Ca 2+ - The betaine complex solution was subjected to ultrasonic treatment in an ultrasonic processor at a frequency of 20 kHz, an amplitude of 40%, a pulse mode of 4 seconds on and 8 seconds off, and an ultrasonic temperature of 45℃. During the ultrasonication, 1125 mL of maltodextrin aqueous solution was added at a rate of 12 mL / min, followed by continued ultrasonication for 5 min to obtain epigallocatechin gallate-Ca 2+ -Betaine@maltodextrin coordination complex solution; (5) Epigallocatechin gallate-Ca 2+-The betaine@maltodextrin coordination complex solution was spray-dried to obtain epigallocatechin gallate-Ca 2+ -Betaine@maltodextrin coordination complex powder. Example 3

[0025] (1) Dissolve gallic acid in deionized water, adjust the pH to 6 with 0.5 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 2 g / L; dissolve calcium chloride in deionized water and prepare an aqueous solution with a concentration of 0.8 g / L; dissolve betalain in deionized water, adjust the pH to 6 with 0.5 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 20 g / L; dissolve dextran in deionized water, adjust the pH to 5 with 0.5 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 20 g / L for later use; (2) Take 50 mL of gallocatechin solution and mix it with 50 mL of calcium chloride solution. After adjusting the pH of the mixture to 6, perform ultrasonic treatment. The ultrasonic frequency is 20 kHz, the amplitude is 30%, the pulse mode is 3 seconds on and 6 seconds off, the ultrasonic temperature is 55 ℃, and the ultrasonic time is 8 min to obtain gallocatechin-Ca 2+ Complex solution; (3) Gallic catechin-Ca 2+ The complex solution was preheated in a 55°C water bath with magnetic stirring at 2500 rpm. 200 mL of betaine solution was then added to gallocatechin-Ca at a rate of 10 mL / min. 2+ In the complex solution, the mixture was heated for another 15 minutes, and then the pH of the complex solution was slowly adjusted to 7.5 using 0.5 mol / L hydrochloric acid or sodium hydroxide to obtain gallocatechin-Ca. 2+ -Betaine complex solution; (4) Galla catechin-Ca 2+ - The betaine complex solution was subjected to ultrasonic treatment in an ultrasonic processor at a frequency of 20 kHz, an amplitude of 30%, a pulse mode of 3 seconds on and 3 seconds off, and an ultrasonic temperature of 35℃. Under ultrasonic treatment, 400 mL of dextran aqueous solution was added at a rate of 10 mL / min, followed by continued ultrasonication for 8 min to obtain gallocatechin-Ca. 2+ -Betaine@glucan coordination complex solution; (5) Galla catechin-Ca 2+ -The betaine@glucan coordination complex solution was spray-dried to obtain gallocatechin-Ca 2+ -Betaine@glucan coordination complex powder. Example 4

[0026] (1) Dissolve catechin in deionized water, adjust the pH to 6.5 with 0.3 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 1 g / L; dissolve calcium chloride in deionized water and prepare an aqueous solution with a concentration of 0.6 g / L; dissolve betalain in deionized water, adjust the pH to 6.0 with 0.3 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 20 g / L; dissolve pectin in deionized water, adjust the pH to 5.5 with 0.3 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 15 g / L for later use; (2) Take 25 mL of catechin solution and mix it with 75 mL of calcium chloride solution. After adjusting the pH of the mixture to 5.5, perform ultrasonic treatment. The ultrasonic frequency is 20 kHz, the amplitude is 20%, the pulse mode is 2s on and 5s off, the ultrasonic temperature is 50℃, and the ultrasonic time is 6 min to obtain catechin-Ca 2+ Complex solution; (3) Catechins-Ca 2+ The complex solution was preheated in a 50°C water bath with magnetic stirring at 2000 rpm. 300 mL of betaine solution was then added to catechin-Ca at a rate of 12 mL / min. 2+ The complex solution was heated for another 15 minutes, and then the pH of the complex solution was slowly adjusted to 7.5 using 0.3 mol / L hydrochloric acid or sodium hydroxide to obtain catechin-Ca. 2+ -Betaine complex solution; (4) Catechins-Ca 2+ The mixed solution was subjected to ultrasonic treatment in an ultrasonic processor at a frequency of 20 kHz, an amplitude of 20%, a pulse mode of 2 seconds on and 5 seconds off, and an ultrasonic temperature of 30℃. 500 mL of pectin aqueous solution was added at a rate of 8 mL / min, followed by continued ultrasonication for 6 min to obtain catechin-Ca. 2+ -Betaine@pectin coordination complex solution; (5) Catechins-Ca 2+ -The betaine@pectin coordination complex solution was spray-dried to obtain catechin-Ca 2+ -Betaine red pigment @ pectin coordination complex powder.

[0027] The technical principles and appearance of the betaine coordination complex aqueous solution after reconstitution are shown in the attached figure. Figure 1 As shown, polyphenols and betalains are combined using the coordination of hydroxyl and carboxyl groups with calcium ions to form a complex. Then, non-covalent interactions between polyphenol and betalain molecules are used to stack the complex, forming a MOF-structured complex. Finally, a macromolecular polysaccharide is used to encapsulate the complex, providing dual protection for betalains. Figure 1As shown in the example, the betaine coordination complex retains its original color after reconstitution and has a bright color.

[0028] The particle size and potential of the betaine coordination complexes in Examples 1-4 after reconstitution were determined using conventional methods, as shown in the appendix. Figure 2 As shown in the figure, the betaine particle size is 1121.11±16.18 nm, which is relatively large. The betaine coordination complex prepared by this invention has a particle size between 100 and 150 nm, making it a nanoscale complex. The betaine coordination complex carries a negative charge, and the negative charge is greater than that of the uncoated betaine, indicating that it has high stability and dispersibility.

[0029] The morphology of the betaine coordination complexes in Examples 1-4 was observed using scanning electron microscopy (SEM), see attached figures. Figure 3 As can be seen from the figure, betalains exhibit a large particle morphology, while the betalain coordination complex consists of uniform spherical particles with a particle size significantly smaller than that of betalains and a smoother surface.

[0030] The betaine red complex powders from Examples 1-4 were dissolved in water to prepare an aqueous solution with a concentration of 10 mg / mL. 200 mL of this solution was heated in water baths at 60°C and 80°C, respectively. The betaine red content was determined spectrophotometrically at 30, 60, 90, and 120 min, respectively. The retention rate was calculated using a standard curve to evaluate the thermal stability of betaine red. The results are shown in the appendix. Figure 4 As shown in the figure, after heating in a 60℃ water bath for 30 min, the retention rate of free betalains was 85.73±2.78%, and after heating for 120 min, the retention rate was 45.66±2.48%. The betalain coordination complexes prepared by the present invention showed a betalain retention rate greater than 98% after heating for 30 min and greater than 95% after heating for 120 min. After heating in an 80℃ water bath for 30 min, the retention rate of free betalains was 62.11±0.48%, and after heating for 120 min, the retention rate was 20.24±1.13%. The betalain coordination complexes prepared by the present invention showed a betalain retention rate greater than 97% after heating for 30 min and greater than 91% after heating for 120 min. It is evident that the thermal stability of the betalain coordination complexes is much higher than that of free betalains.

[0031] The betaine complex powders from Examples 1-4 were dissolved in water at pH 1, 5, 8, and 11, respectively, to prepare aqueous solutions with a concentration of 10 mg / mL. The betaine content was measured at 30, 60, 90, and 120 min, and the retention rate was calculated to evaluate the pH stability of betaine. The results are shown in the appendix. Figure 5As shown in the figure, after standing for 120 min in an aqueous solution at pH 1, the retention rate of free betalain was 43.58 ± 0.54%, while the retention rates of betalain in the betalain coordination complexes were all greater than 90%. After standing for 120 min in an aqueous solution at pH 5, the retention rate of free betalain was 73.58 ± 0.52%, while the retention rates of betalain in the betalain coordination complexes were all greater than 96%. After standing for 120 min in an aqueous solution at pH 8, the retention rate of free betalain was 72.66 ± 0.77%, while the retention rates of betalain in the betalain coordination complexes were all greater than 92%. After standing for 120 min in an aqueous solution at pH 11, the retention rate of free betalain was 23.58 ± 0.51%, while the retention rates of betalain in the betalain coordination complexes were all greater than 76%. It is evident that the color-protecting technology of this invention significantly improves the stability of betalains in strong acid and strong alkaline environments.

[0032] The betaine coordination complex powders from Examples 1-4 were dissolved in water to prepare a solution with a concentration of 10 mg / mL. The solution was placed in a diode illumination chamber and exposed to a 25 W light source (illumination distance of 40 cm). The betaine content was measured at 24, 48, 72, and 96 hours, and the retention rate was calculated to evaluate the photostability of betaine. The results are shown in the appendix. Figure 6 As shown in the figure, the retention rate of free betalain after 96 hours of light exposure was 55.24 ± 1.11%, while the retention rates of the betalain coordination complexes in the examples were all greater than 95%. This demonstrates that the technology of this invention significantly improves the photostability of betalain.

[0033] The betaine complex powders from Examples 1-4 were dissolved in water to prepare an aqueous solution with a concentration of 10 mg / mL. 1% hydrogen peroxide was added, and the betaine content was measured at 12, 24, 36, and 48 hours. The retention rate was calculated, and the oxidative stability of betaine was evaluated. The results are shown in the appendix. Figure 7 As shown in the figure, after standing in 1% hydrogen peroxide for 48 hours, the retention rate of free betalain was 67.24 ± 0.98%, while the retention rate of betalain in the betalain coordination complex was greater than 87%. This demonstrates that the technology of this invention significantly improves the oxidative stability of betalain.

[0034] The betaine coordination complex powders from Examples 1-4 were dissolved in a solution containing 0.01 mol / L Zn. 2+ Cu 2+ Fe 3+ A 10 mg / mL solution was prepared in an aqueous solution, and the betalain content was determined at 30, 60, 90, and 120 min. The retention rate was calculated, and the metal ion stability of betalain was evaluated. The results are shown in the appendix. Figure 8 As can be seen from the figure, in Zn 2+ After standing for 120 min, the retention rate of free betalains was 73.97 ± 1.26%, while the retention rate of betalains in the betalain coordination complex was greater than 89%. In Cu... 2+ After standing for 120 min, the retention rate of free betalains was 38.95 ± 1.09%, while the retention rate of betalains in the betalain coordination complex was greater than 77%. In Fe... 3+ After standing for 120 minutes, the retention rate of free betalain was 56.97±1.11%, while the retention rate of betalain in the betalain coordination complex was greater than 80%. This demonstrates that the metal ion stability of betalain is significantly improved after color protection using the technology of this invention.

[0035] The betaine coordination complex powders from Examples 1-4 were dispersed in simulated gastric and intestinal fluids, and the release rate of betaine was measured at different time points. The results are shown in the appendix. Figure 9 As shown in the figure, the cumulative release rate of free betaine in simulated gastric fluid over 2 hours was 73.34 ± 0.78%, while the cumulative release rate of betaine in the betaine coordination complex was approximately 15%. The cumulative release rate of betaine in simulated intestinal fluid was highest at 0.5 hours (74.67 ± 1.21%), and then rapidly decreased, indicating that free betaine degraded in the weakly alkaline intestinal fluid. In simulated intestinal fluid, the cumulative release rate of betaine in the betaine coordination complexes of Examples 1-4 gradually increased, with all exceeding 88% at 2 hours. In other words, the betaine coordination complex has high stability in gastric juice, with a low betaine release rate, while most of the free betaine is released due to dissolution in gastric juice. In intestinal juice, the betaine coordination complex has high stability, protecting betaine from degradation while achieving sustained release of betaine, while the release rate of free betaine decreases due to degradation as digestion time increases.

[0036] In summary, by employing a combined coordination-encapsulation process and co-coloring technology, the processing stability of betalains can be significantly improved, and their sustained release can be achieved, which is beneficial for enhancing the bioavailability of betalains. This invention not only provides a new color-protecting technology for betalains but also offers a highly stable natural pigment additive for the food and cosmetics industries, and a novel MOF raw material for the pharmaceutical industry.

[0037] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A betaine color-protecting technology, the mechanism of which involves using catechins or their derivative polyphenols as ligands, and reacting with Ca... 2+ First, an unsaturated complex with a coordination number of 1-2 is formed, which further forms a stable complex with a coordination number of 3-4 with betaine. Then, a multilayer MOF-type network structure is formed by non-covalent interactions between betaine and betaine, catechins and their derivatives, thereby fixing betaine inside the network. Finally, a macromolecular polysaccharide is used to encapsulate catechin-type -Ca 2+ -Betaine complexes further protect betaine.

2. A betalain color-protecting technology, characterized in that... This includes the following steps and process conditions: (1) Dissolve catechin or its derivatives in deionized water, adjust the pH to 5.5-6.5 with 0.1-1 mol / L hydrochloric acid or sodium hydroxide, and prepare a polyphenol aqueous solution with a concentration of 1-3 g / L; dissolve calcium chloride in deionized water and prepare an aqueous solution with a concentration of 0.5-1 g / L; dissolve betalain in deionized water, adjust the pH to 5.5-6.5 with 0.1-1 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 10-30 g / L; dissolve polysaccharide in deionized water, adjust the pH to 4.5-5.5 with 0.1-1 mol / L hydrochloric acid or sodium hydroxide, and prepare an aqueous solution with a concentration of 10-30 g / L for later use; (2) Mix the polyphenol solution and calcium chloride solution from step (1) at a volume ratio of 2:1 to 1:2, adjust the pH to 5.5 to 6.5, and then perform ultrasonic treatment. The ultrasonic frequency is 20 kHz, the amplitude is 20 to 40%, the pulse mode is 2 to 4 seconds on and 4 to 8 seconds off, the ultrasonic temperature is 45 to 65 °C, and the ultrasonic time is 5 to 10 min to prepare polyphenol-Ca 2+ Complex solution; (3) The polyphenol-Ca prepared in step (2) 2+ The complex solution was placed in a water bath at 45-65°C and preheated with magnetic stirring at 2000-3000 r / min. An appropriate amount of betaine solution from step (1) was taken and slowly added to the polyphenol-Ca complex at a volume ratio of 1:1 to 5:

1. 2+ In the complex solution, heat for another 10-20 minutes, then slowly adjust the pH of the complex solution to 7-8 using 0.1-1 mol / L hydrochloric acid or sodium hydroxide to prepare polyphenol-Ca. 2+ -Betaine complex solution; (4) The polyphenol-Ca prepared in step (3) 2+ - The betaine complex solution was subjected to ultrasonic treatment in an ultrasonic processor at a frequency of 20 kHz, an amplitude of 20-40%, a pulse mode of 2-4 seconds on and 4-8 seconds off, and an ultrasonic temperature of 25-45℃. During the ultrasonication process, 1-3 times the volume of polysaccharide aqueous solution was slowly added, followed by continued ultrasonication for 5-10 minutes to prepare polyphenol-Ca. 2+ -Betaine@polysaccharide coordination complex solution; (5) Spray dry the solution in step (4) to obtain the betalain coordination complex.

3. The preparation method according to claim 2, characterized in that: The betalain solution in step (3) and the polysaccharide solution in step (4) are added at a rate of 8~12 mL / min.

4. The polysaccharides described in claims 1, 2, and 3 are colorless and transparent edible polysaccharides such as maltodextrin, sodium alginate, pectin, sodium hyaluronate, and dextran.

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