Functional jelly product free of artificially synthesized pigment and capable of slowly releasing curcumin

Abstract

The invention discloses a preparation method of a functional jelly product free of artificially synthesized pigment and capable of slowly releasing curcumin, and belongs to the technical field of food processing. The jelly comprises the following components in percentage by weight: 8%-10% of jelly powder, 3%-5% of white granulated sugar, 0.2%-0.4% of citric acid and 0.2%-0.8 mg / g of soybean protein isolate-curcumin-kappa-carrageenan aggregate particles. According to the invention, the soybean protein isolate and kappa-carrageenan composite agglomerate is utilized to encapsulate curcumin, so that curcumin particles have excellent illumination stability and bioavailability, and further the jelly is endowed with excellent color, elasticity, longer shelf life and excellent oxidation resistance. In addition, the soybean protein used in the method is low in cost and rich in essential amino acid, and belongs to complete protein. After digestion, carrageenan can be subjected to glycolysis by large intestine bacteria to form short-chain fatty acids such as formic acid, acetic acid and propionic acid, and the short-chain fatty acids become an energy source of probiotics. The preparation method provided by the invention is of great significance to design and manufacture of a functional jelly formula.

Description

Technical Field

[0001] This invention relates to a method for preparing a functional jelly product that does not contain artificial synthetic pigments and can release curcumin slowly, belonging to the field of food processing technology. Background Technology

[0002] Jelly, a popular snack, is known for its delicious taste, attractive appearance, and vibrant colors. It is primarily made from fruit juice, sweeteners, thickeners, and flavorings. Edible jellies are categorized by purpose into regular jellies and functional jellies. Regular jellies can be further divided into fruit-flavored jellies, fruit-based jellies, milk-containing jellies, and other types (non-fruit-based). Functional jellies are classified by their ingredient source into herbal, traditional Chinese medicine, grain, tea, and other types. Currently, commercially available jellies tend to have high sugar and fat content, but low nutritional value and health benefits. Since children and young women are the primary consumers of jelly, many manufacturers use excessive amounts of artificial colors and sweeteners to enhance taste and appearance, which is detrimental to children's health. With the improvement of people's living standards and the enhancement of health awareness, consumers' demand for jelly is increasing day by day, and their requirements for snack foods are also getting higher and higher. They not only require good taste, but also certain nutritional and functional properties. Therefore, the research and development of functional jelly will become a future research trend.

[0003] Curcumin, the main bioactive polyphenolic compound in turmeric, is widely used as a yellow pigment in the food industry. It possesses numerous bioactive functions, including anticancer, antibacterial, antioxidant, and anti-inflammatory activities. Curcumin is considered "generally recognized as safe" by the U.S. Food and Drug Administration and is listed as an permitted food additive with maximum allowable levels ranging from 20 mg / kg to 500 mg / kg, depending on the food type, with a maximum of 200 mg / L in beverages. Furthermore, there is increasing interest in fortifying foods with bioactive substances; however, directly adding curcumin powder to jellies, beverages, and other foods during processing remains challenging due to its low water solubility, high sensitivity to processing conditions (especially high-temperature alkaline conditions), and low bioavailability under human gastrointestinal conditions. Therefore, stable encapsulation and delivery systems are needed to improve the stability and bioavailability of curcumin in jellies.

[0004] Protein / polysaccharide-based complexes offer numerous advantages in protecting and delivering bioactive compounds in functional foods due to their safety, biocompatibility, and high encapsulation efficiency. Soy protein isolate (SPI) possesses high nutritional value and amphiphilic properties, enabling it to participate in strong electrostatic interactions and hydrogen bonding, making it highly compatible with polysaccharides in complex cophase systems. κ-carrageenan (κ-CG), a negatively charged hydrophilic polysaccharide, can form a uniform film to protect the core material and enhance the controlled release of bioactive compounds during digestion. The interaction between the two oppositely charged biopolymers, protein and polysaccharide, and intermolecular electrostatic interactions can lead to macroscopic phase separation, considered a "complex aggregate." The formation of this complex requires controlling various external parameters, such as pH, ionic strength, biopolymer ratio, total biopolymer concentration, and temperature, to impart excellent stability. The complex aggregate encapsulation of easily oxidized and / or degraded bioactive components (e.g., curcumin, enzymes) in the food and pharmaceutical industries represents the most important industrial application of complex synergy. Therefore, preparing a stable proteoglycan complex coagulation system and using the complex coagulation to encapsulate curcumin to improve the stability of curcumin in jelly, giving the jelly excellent color, avoiding the addition of chemical pigments, and effectively improving the bioavailability of curcumin are urgent technical bottlenecks. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing a functional jelly product that is free of artificial colorings and can release curcumin in a sustained-release manner. This invention utilizes a natural pigment (curcumin) to replace artificial colorings (such as tartrazine) in traditional jellies, aligning with the current market trend of "clean labeling" and the pursuit of natural ingredients. Furthermore, by encapsulating curcumin with soy protein isolate-carrageenan composite aggregate particles, the problems of instability, poor dispersibility, and low oral bioavailability of curcumin in jelly are solved.

[0006] The technical solution of the present invention:

[0007] A method for preparing a functional jelly product that is free of artificial colorings and has a sustained-release curcumin content, the method comprising the following steps:

[0008] Step 1: Dissolve soy protein isolate powder in deionized water to prepare soy protein isolate solution, stir at room temperature for 2 hours to prepare a protein solution with a concentration of 1% (w / v);

[0009] Step 2: Dissolve κ-carrageenan powder in deionized water and stir in a 75°C water bath for 1 hour to prepare a 1% (w / v) κ-carrageenan stock solution;

[0010] Step 3: Dissolve curcumin in anhydrous ethanol and stir thoroughly on a magnetic stirrer in the dark to prepare a 2 mg / mL curcumin-ethanol solution;

[0011] Step 4: 1 mL of curcumin-ethanol solution was slowly added dropwise to 10 mL of 1.0% (w / v) soy protein isolate solution and magnetically stirred for 2 h. Then, the ethanol was removed from the solution using a rotary evaporator to prepare a soy protein-curcumin (SPI-Cur) composite solution. Subsequently, the pH of the SPI-Cur solution was adjusted to 7.0 using 0.5 mol / L HCl, and then thoroughly stirred magnetically (200 rpm) for 2 h to obtain soy protein-curcumin granule samples, which were named SPC-7.0.

[0012] Step 5: Add a certain amount of κ-carrageenan solution (1.0%, w / v) to 10 mL of SPI-Cur composite solution. The ratio of SPI-Cur to κ-carrageenan in the mixed solution is 1:1, 5:1, 10:1, and 15:1. Adjust the pH of the mixed solution to 7.0, 5.5, and 4.0 using 0.5 mol / L HCl. Then, stir thoroughly for 2 hours using magnetic stirring (200 rpm) to obtain soy protein isolate-curcumin-κ-carrageenan (SKC) composite particles at different pH values.

[0013] Step 6: Add 8%-10% jelly powder, 3%-5% white sugar, and 0.2%-0.4% citric acid to boiling distilled water according to the mass fraction, and continue heating and stirring at a uniform speed for 10 minutes to ensure complete dissolution. Then, add SKC-4.0 composite particles to the jelly composite liquid according to the mass fraction of 0.2-0.8 mg / g, and continue heating and stirring for 10 minutes. Afterward, pour the mixed jelly liquid into a mold, keep it at 85℃ for 10 minutes, and then cool it to room temperature to form jelly samples. The jelly samples without SKC-4.0 composite particles, the jelly samples with SKC-4.0 composite particles (SKC-4.0 concentration of 0.2 mg / g, 0.4 mg / g, and 0.8 mg / g), and the jelly samples with curcumin powder (0.2 mg / g) are named 0, 2, 4, 8, and Cur-gel, respectively.

[0014] Furthermore, the optimal pH value for preparing SPC nanoparticles in step four is 7, and the optimal pH value for preparing SKC composite particles in step five is 4.

[0015] Furthermore, in step five, the ratio of SPI-Cur to κ-carrageenan in the preparation of SKC composite particles is 10:1, and the content of curcumin is 0.2 mg / g.

[0016] Furthermore, in step six, the amount of SKC-4.0 added to the jelly is 0.4 mg / g, the mass fraction of jelly powder is 10%, the mass fraction of white sugar is 5%, and the mass fraction of citric acid is 0.4%.

[0017] This invention offers the following advantages: It utilizes soy protein isolate and κ-carrageenan to form nanoparticles for stable encapsulation of curcumin, thereby increasing the light stability of curcumin, enhancing its storage resistance, significantly improving its bioavailability, enhancing its dispersibility in jelly, and imparting excellent antioxidant, water-holding, and elastic properties to the jelly. The preparation method provided in this application is of significant importance for the design and manufacture of jelly product formulations, and even for the development of jelly products with certain unique functions. Furthermore, the method provided by this invention also has the following advantages;

[0018] (1) The soybean protein used in this method is inexpensive and contains abundant essential amino acids. It is a complete protein, which gives the jelly product prepared by this invention excellent nutritional characteristics.

[0019] (2) The curcumin used in this method has anti-tumor, antioxidant, antibacterial, liver-protecting and lipid-lowering effects. It can replace artificial synthetic pigments and give jelly products excellent color.

[0020] (3) The carrageenan used in this method makes the resulting jelly elastic and non-aqueous, and it also has the basic characteristics of soluble dietary fiber. After degradation in the body, carrageenan can form soluble complexes with fibrin. It can be fermented by E. coli into short-chain fatty acids such as formic acid, acetic acid, and propionic acid, becoming an energy source for probiotics. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0022] Figure 1 Here are the FT-IR plots for Cur, SPI, SPC, and SKC.

[0023] Figure 2 Microstructure images of SPC composite particles and SKC composite particles

[0024] Figure 3 The photodegradation stability of curcumin in the composite particles.

[0025] Figure 4 The simulated gastrointestinal digestion curves of the composite particles.

[0026] Figure 5 This is an image of the jelly product.

[0027] Figure 6 The antioxidant properties of the jelly. Detailed Implementation

[0028] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred practices. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0030] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0031] Example 1:

[0032] (1) Dissolve soy protein isolate powder in deionized water to prepare soy protein isolate solution, stir at room temperature for 2 hours to prepare a protein solution with a concentration of 1% (w / v);

[0033] (2) Dissolve κ-carrageenan powder in deionized water and stir for 1 h in a water bath at 75°C to prepare 1% (w / v) κ-carrageenan stock solution;

[0034] (3) Dissolve curcumin in anhydrous ethanol and stir thoroughly on a magnetic stirrer in the dark to prepare a 2 mg / mL curcumin-ethanol solution;

[0035] (4) 1 mL of curcumin-ethanol solution was slowly added dropwise to 10 mL of 1.0% (w / v) soy protein isolate solution and magnetically stirred for 2 h. Then, the ethanol in the solution was removed by rotary evaporation to prepare a soy protein-curcumin (SPI-Cur) composite solution. Subsequently, the pH of the SPI-Cur solution was adjusted to 7.0 with 0.5 mol / L HCl, and then magnetically stirred (200 rpm) for 2 h to obtain soy protein-curcumin particle samples, which were named SPC-7.0.

[0036] (5) Add 1 mL of κ-carrageenan solution (1.0%, w / v) to 10 mL of SPI-Cur composite solution, and adjust the pH of the mixed solution to 7.0, 5.5 and 4.0 with 0.5 mol / L HCl. Then stir thoroughly for 2 h with magnetic stirring (200 rpm) to obtain soy protein isolate-curcumin-κ-carrageenan (SKC) composite particles at different pH values, and name them SKC-7.0, SKC-5.5 and SKC-4.0 respectively.

[0037] (6) Add 10% jelly powder, 5% white sugar, and 0.4% citric acid to boiling distilled water according to the mass fraction, and continue heating and stirring at a constant speed for 10 minutes to ensure complete dissolution. Then add SKC-4.0 composite particles to the jelly composite solution at a mass fraction of 0.4 mg / g, and continue heating and stirring for 10 minutes. Subsequently, pour the mixed jelly solution into a mold, keep it at 85℃ for 10 minutes, and then cool it to room temperature to solidify, thus obtaining a jelly sample. Name the sample 4.

[0038] Comparative Example 1: The difference between this example and Example 1 is as follows: (6) 10% jelly powder, 5% white sugar, and 0.4% citric acid were added to boiling distilled water according to the mass fraction, and the mixture was heated continuously and stirred at a constant speed for 10 minutes to fully dissolve it. Then the mixed jelly liquid was poured into a mold, kept at 85°C for 10 minutes, and then cooled to room temperature to form a jelly sample. The sample was named 0.

[0039] Comparative Example 2: The difference between this example and Example 1 is as follows: (6) 10% jelly powder, 5% white sugar, and 0.4% citric acid were added to boiling distilled water according to the mass fraction and heated continuously while stirring at a constant speed for 10 minutes to ensure complete dissolution. Then, curcumin powder was added to the jelly compound liquid according to the mass fraction of 0.2 mg / g, and the mixture was heated and stirred for another 10 minutes. Subsequently, the mixed jelly liquid was poured into a mold, kept at 85°C for 10 minutes, and then cooled to room temperature to form a jelly sample. The sample was named Cur-gel.

[0040] Comparative Example 3: The difference between this example and Example 1 is as follows: (6) 10% jelly powder, 5% white sugar, and 0.4% citric acid were added to boiling distilled water according to the mass fraction and heated continuously while stirring at a uniform speed for 10 minutes to ensure complete dissolution. Then, SKC-4.0 composite particles were added to the jelly composite liquid according to the mass fraction of 0.2 mg / g, and the mixture was heated and stirred for another 10 minutes. Subsequently, the mixed jelly liquid was poured into a mold, kept at 85°C for 10 minutes, and then cooled to room temperature to form a jelly sample. The sample was named 2.

[0041] Comparative Example 4: The difference between this example and Example 1 is as follows: (6) 10% jelly powder, 5% white sugar, and 0.4% citric acid were added to boiling distilled water according to the mass fraction and heated continuously while stirring at a uniform speed for 10 minutes to ensure complete dissolution. Then, SKC-4.0 composite particles were added to the jelly composite liquid at a mass fraction of 0.8 mg / g, and the mixture was heated and stirred for another 10 minutes. Subsequently, the mixed jelly liquid was poured into a mold, kept at 85°C for 10 minutes, and then cooled to room temperature to form a jelly sample. The sample was named 8.

[0042] Results and Analysis:

[0043] (1) Interactions of soybean protein, carrageenan and curcumin in composite particles

[0044] The interaction mechanism between SPI, κ-CG, and Cur was analyzed using FT-IR spectroscopy, such as Figure 1 As shown. Curcumin at 961, 1026, 1282, 1428, 1602, 1628 and 3507 cm⁻¹. -1 Characteristic peaks are present at isowavenumbers, attributed to the trans-CH vibration of benzoic acid esters, the COC stretching and in-plane bending vibrations of the aromatic ring CCH connected to the enol moiety, the out-of-plane bending vibration of CH3, the CCC and C=CH bending vibrations of the aromatic ketone moiety, the COH bending vibration of the ketone moiety, the benzene ring stretching vibration, the C=C and C=O stretching vibrations, and the phenol (benzene ring) -OH stretching vibration. These characteristic peaks disappear in the SPC and SKC composite particle spectra, confirming that the Cur molecule is completely embedded. SPI at 3296 cm⁻¹ -1 The characteristic peak in the vicinity is caused by the OH stretching vibration. After SPI and SPI / κ-CG encapsulate Cur, this characteristic peak shifts towards a lower wavenumber, indicating that hydrogen bonding is involved in the Cur encapsulation. At pH 4.0, SPI / κ-CG reaches a peak at 2927 cm⁻¹. -1 The characteristic peak of α undergoes a red shift, and combined with the hydrophobic properties of Cr, hydrophobic interactions under this pH condition are involved in the construction of SKC. (1539 cm⁻¹ in SPI) -1 and 1397cm -1 The characteristic peaks at the locations correspond to the NH deformation vibration (amide II band) and CN stretching vibration (amide III band), respectively. After embedding Cur, the above characteristic peaks shifted, confirming that embedding Cur affects the SPI conformation.

[0045] (2) Microstructure of composite particles

[0046] The microstructures of SPC-7.0, SKC-7.0, SKC-5.5, and SKC-4.0 were observed using field emission scanning electron microscopy. For example... Figure 2As shown, all particles exhibit an irregular spherical shape. The SPC-7.0 and SKC-7.0 composite particles are relatively small. The denser distribution and more uniform size of SKC-7.0 can be attributed to κ-CG enhancing the electrostatic repulsion within the system, reducing particle aggregation, and promoting uniform particle distribution. pH value has a significant impact on the microstructure of SKC. Lowering the pH value increases the particle size of SKC-5.5 and SKC-4.0, and some particles exhibit obvious cross-linking. The boundaries between SKC-5.5 composite particles are unclear, and some even show partial adhesion forming a layered structure, which may be due to aggregation caused by electrostatic interactions between the composites.

[0047] (3) Photostability of curcumin in composite particles

[0048] The photoprotective effect of the encapsulation system on curcumin was analyzed and evaluated by measuring the curcumin retention rate under ultraviolet light irradiation. Figure 3 The retention rates of free curcumin, SPC, and SKC under 40W UV irradiation from 0 to 150 min were observed. The results showed that free curcumin was the most unstable under UV irradiation, with the retention rate dropping to 44.56% after 30 min and almost completely degrading (retention rate of 0.84%) after 150 min, confirming the instability of curcumin under light. Furthermore, all encapsulation systems could mitigate the photodegradation of curcumin. After 90 min of UV irradiation, the curcumin retention rates of SPC-7.0, SKC-7.0, SKC-5.5, and SKC-4.0 were 8.8%, 19.74%, 30.28%, and 48.26%, respectively. These results indicate that SKC can effectively inhibit the degradation of curcumin under light, possibly because κ-carrageenan covering the surface of the nanoparticles provides a physical barrier, protecting curcumin from degradation. After 150 min of UV irradiation, the curcumin retention rates of SPC-7.0, SKC-7.0, SKC-5.5, and SKC-4.0 were 2.3%, 6.08%, 11.34%, and 39.88%, respectively. SKC-4.0 had the highest retention rate and exhibited good protective performance throughout the entire UV irradiation period. Therefore, the dense structure formed by SKC-4.0 can effectively block light radiation.

[0049] (4) Digestion characteristics of composite particles

[0050] Free curcumin often has reduced bioavailability due to gastrointestinal metabolism, while the sustained release of encapsulated curcumin can enhance its resistance to metabolism. Figure 4This study demonstrates the release behavior of curcumin in simulated gastrointestinal fluids. During the simulated gastric digestion phase (SGF), free curcumin showed a rapid release trend, with a cumulative release rate of 47.23±2.36%. Release continued during the simulated intestinal digestion phase (SIF), reaching a total release rate of 82.65±2.13% after 180 minutes of digestion, confirming its susceptibility to enzymatic metabolism. SPC release was slower, possibly due to the hydrophobic interaction and hydrogen bonding between curcumin and SPI, leading to a sustained release. Furthermore, the SKC complex system further delayed curcumin release. At 60 minutes of digestion, the curcumin release rate in SKC-4.0 was only 12.86±0.64%, indicating that SKC has a protective effect on curcumin in SGF. During the SIF phase, both SPC and SKC exhibited rapid release from 60-120 minutes and sustained release from 120-180 minutes, with SKC showing a more significant sustained-release effect on curcumin. The results showed that, under simulated gastrointestinal conditions, κ-carrageenan optimized the release of curcumin, enhanced its stability, and improved its bioavailability and bioactivity. After 180 min of digestion, the cumulative curcumin release rate of SKC-4.0 was 59.87 ± 1.94%, significantly lower than that of other samples. This can be attributed to the strong electrostatic interaction between the protein and the polysaccharide, resulting in a dense structure.

[0051] (5) Appearance analysis of jelly

[0052] Based on the previous experimental results, SKC-4.0, which exhibits significantly improved stability and enhances the bioavailability of curcumin, was selected for further research. Jelly samples containing added SKC and curcumin were prepared to evaluate the feasibility and advantages of SKC composite particles in practical food applications. Figure 5 The images show macroscopic photographs of the jelly samples. From left to right, they represent the control group sample, SKC jelly samples (SKC concentrations of 0.2 mg / g, 0.4 mg / g, and 0.8 mg / g), and Cur-gel jelly sample (0.2 mg / g). As shown in the figures, jelly samples 0-8 have a uniform color, are clear and transparent, and exhibit a certain color gradient, directly reflecting the positive correlation between SKC concentration and color intensity. As the SKC addition increases to 0.8 mg / g, the jelly color gradually changes from colorless to light yellow, then dark yellow, and finally golden yellow, a phenomenon consistent with the color development pattern of curcumin. The curcumin jelly sample has a uniform color, exhibiting an orange-yellow hue, and shows slight turbidity. Furthermore, observations revealed that all five jelly samples had high formability, a certain gel strength, good elasticity, and no significant bubbles or cracks. Therefore, it can be preliminarily concluded that the addition of SKC has a relatively small impact on the quality of the jelly processing.

[0053] (6) Texture properties of jelly

[0054] The textural parameters of the jelly samples were obtained by testing with a texture analyzer and are shown in Table 1. Compared with the control group, it was found that the hardness of the jelly increased with increasing SKC concentration, with Cur-gel jelly exhibiting the highest hardness. This phenomenon may be related to the total curcumin content in the jelly. Elasticity was defined as the rate at which the jelly returns to its original shape after deformation, while chewiness and adhesiveness were defined as the energy required to chew a solid or semi-solid food suitable for swallowing. Observations showed that the adhesiveness and chewiness of SKC jelly exhibited similar trends to its hardness. Cohesion refers to the degree of internal adhesion strength, and the results showed no significant difference in cohesion among all jelly samples, indicating that curcumin does not affect this textural property.

[0055] Table 1. Texture properties of the jelly

[0056]

[0057] Note: Different letters in the same column represent significant differences.

[0058] (7) Water-holding properties of jelly

[0059] The water retention rates of the jelly samples within 24 hours are shown in Table 2. The results show that SKC and Cur improved the water retention rate of the jelly. The jelly exhibited the best water retention rate when the SKC concentration was 0.8 mg / g. This is attributed to the enhanced interaction of the gel network by the pigment-encapsulated wall material, which in turn improved the gel strength and thus the water retention properties of the jelly.

[0060] Table 2. Water-holding properties of the jelly

[0061]

[0062] Note: Different letters in the same column represent significant differences.

[0063] (8) Antioxidant properties of jelly

[0064] To assess the bioactive value of the jelly, commercially available jelly was selected as a control for antioxidant experiments. Figure 6 The study showed the DPPH and ABTS+ free radical scavenging rates of the jelly. Results indicated that the control group exhibited the lowest antioxidant activity, with DPPH and ABTS+ free radical scavenging rates of 11.88% and 13.65%, respectively. The addition of Cur significantly improved the antioxidant activity of the jelly; the jelly demonstrated the strongest antioxidant capacity at a SKC concentration of 0.4 mg / g, with DPPH and ABTS+ free radical scavenging rates of 46.71% and 39.02%, respectively. Furthermore, Cur-gel jelly also showed some improvement in antioxidant properties. Compared to commercial jelly, SKC jelly exhibited stronger antioxidant activity, and its mechanism is closely related to the functional properties of Cur. These results confirm the development potential of SKC as a functional food ingredient.

[0065] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a functional jelly product containing no artificial colorings and capable of sustained-release curcumin, characterized in that, The method includes the following steps: Step 1: Dissolve soy protein isolate powder in deionized water to prepare soy protein isolate solution, stir at room temperature for 2 hours to prepare a protein solution with a concentration of 1% (w / v); Step 2: Dissolve κ-carrageenan powder in deionized water and stir in a 75°C water bath for 1 hour to prepare a 1% (w / v) κ-carrageenan stock solution; Step 3: Dissolve curcumin in anhydrous ethanol and stir thoroughly on a magnetic stirrer in the dark to prepare a 2 mg / mL curcumin-ethanol solution; Step 4: Slowly add 1 mL of curcumin-ethanol solution to 10 mL of 1.0% (w / v) soy protein isolate solution and stir magnetically for 2 h. Then, remove the ethanol from the solution using a rotary evaporator to prepare a soy protein-curcumin (SPI-Cur) composite solution. Subsequently, adjust the pH of the SPI-Cur solution to 7.0 using 0.5 mol / L HCl, and then stir thoroughly with magnetic stirring (200 rpm) for 2 h to obtain soy protein-curcumin particle samples, which are named SPC-7.

0. Step 5: A certain amount of κ-carrageenan solution (1.0%, w / v) was added to 10 mL of SPI-Cur composite solution. The ratio of SPI-Cur to κ-carrageenan in the mixed solution was 1:1, 5:1, 10:1, and 15:

1. The pH of the mixed solution was adjusted to 7.0, 5.5, and 4.0 using 0.5 mol / L HCl. The mixture was then stirred thoroughly for 2 h using magnetic stirring (200 rpm) to obtain soy protein isolate-curcumin-κ-carrageenan (SKC) composite particles at different pH values, which were named SKC-7.0, SKC-5.5, and SKC-4.0, respectively. Step 6: Add 8%-10% jelly powder, 3%-5% white sugar, and 0.2%-0.4% citric acid to boiling distilled water according to the mass fraction, and continue heating and stirring at a constant speed for 10 minutes to ensure complete dissolution. Then, add SKC-4.0 composite particles to the jelly composite solution at a mass fraction of 0.2-0.8 mg / mL, and continue heating and stirring for 10 minutes. Pour the mixed jelly solution into a mold, keep it at 85℃ for 10 minutes, and then cool it to room temperature to form jelly samples. The jelly samples without SKC-4.0 composite particles, the jelly samples with SKC-4.0 composite particles (SKC-4.0 concentration of 0.2 mg / g, 0.4 mg / g, and 0.8 mg / g), and the jelly samples with curcumin powder (0.2 mg / g) are named 0, 2, 4, 8, and Cur-gel, respectively.

2. The method for preparing a functional jelly product containing no artificial coloring and capable of sustained-release curcumin according to claim 1, characterized in that, The optimal pH value for preparing SPC nanoparticles in step four is 7, and the optimal pH value for preparing SKC composite particles in step five is 4.

3. The method for preparing a functional jelly product containing no artificial coloring and capable of sustained-release curcumin according to claim 1, characterized in that, In step five, when preparing SKC composite particles, the ratio of SPI-Cur to κ-carrageenan is 10:1, and the curcumin content is 0.2 mg / g.

4. The method for preparing a functional jelly product containing no artificial coloring and capable of sustained-release curcumin according to claim 1, characterized in that, In step six, the amount of SKC-4.0 added to the jelly is 0.4 mg / g, the mass fraction of jelly powder is 10%, the mass fraction of white sugar is 5%, and the mass fraction of citric acid is 0.4%.

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