Hydrogel capable of covering peculiar smell of monascus pigment and improving stability of monascus pigment and preparation method of hydrogel
By encapsulating red yeast rice pigment in a double cross-linked hydrogel of gelatin and pectin, the off-flavor problem of red yeast rice pigment in food was solved, its stability was improved, and its application range was expanded.
Patent Information
- Application Number
- CN202511229247.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-29
- Publication Date
- 2025-12-02
AI Technical Summary
The application of red yeast rice pigment in food is limited by off-flavors (such as alcoholic, musty, woody, sour, and burnt flavors). Existing hydrogel carriers cannot effectively mask these off-flavors and lack stability.
Using gelatin and pectin as matrices, and transglutaminase and calcium salt as cross-linking agents, a double-crosslinked interpenetrating network structure was formed to embed red yeast rice pigment, and hydrogels were prepared by low-temperature gelation method.
It effectively masks the off-flavor of red yeast rice pigment, significantly improves its light and heat stability, and expands its application prospects in food.
Smart Images
Figure BDA0005573412680000111 
Figure BDA0005573412680000112 
Figure BDA0005573412680000121
Abstract
Description
Technical Field
[0001] This invention relates to the food industry, specifically to a hydrogel capable of masking the off-flavor of red yeast rice pigment while improving its stability, and its preparation method. Background Technology
[0002] Red yeast rice pigment is a natural food coloring produced by the fermentation of Monascus purpureus. Due to its excellent bioactivity, it is widely used in food processing, cosmetics development, and pharmaceuticals. However, because Monascus purpureus produces a large number of volatile compounds during fermentation, most commercially available red yeast rice pigment mixtures exhibit different off-flavors, such as fruity, wine-like, or creamy aromas. Existing research shows that the flavor components of red yeast rice pigment differ in vinegar, wine, and pasta products, but the main components all include esters and fatty acids. These off-flavors limit the application of red yeast rice pigment. Currently, using natural macromolecules such as proteins and polysaccharides to construct hydrogels and other carriers to load flavor components such as fragrances has become a research direction with great application value. Constructing appropriate hydrogel materials can improve the stability and application prospects of the loaded material from multiple perspectives.
[0003] Therefore, there is a need in the art to provide a carrier that can mask the off-flavor of red yeast rice pigment and is easy to use in food. Summary of the Invention
[0004] The purpose of this invention is to provide a novel hydrogel that can mask the off-odor of red yeast rice pigment while improving its stability, and a method for preparing the same.
[0005] In a first aspect, the present invention provides a hydrogel comprising:
[0006] (a) The hydrogel matrix comprises: 1-10 parts by weight of gelatin and 0.5-5 parts by weight of pectin, 0.2-1 parts by weight of transglutaminase, and 0.1-1 parts by weight of calcium salt;
[0007] (b) Red yeast rice pigment dispersed in the hydrogel matrix; and
[0008] (c) Water.
[0009] In another preferred embodiment, the red yeast rice pigment comprises: red yeast rice red pigment, red yeast rice yellow pigment, red yeast rice orange pigment, or a combination thereof.
[0010] In another preferred embodiment, the gelatin in the hydrogel matrix is 2-8 parts by weight, more preferably 2.5-6 parts by weight, such as 2.5, 3, 3.75, 4 or 5 parts by weight.
[0011] In another preferred embodiment, the pectin in the hydrogel matrix is 0.8-4 parts by weight, more preferably 1-3.5 parts by weight, such as 1.5, 2, 2.25 or 3 parts by weight.
[0012] In another preferred embodiment, the amount of transglutaminase in the hydrogel matrix is 0.3-0.8 parts by weight, more preferably 0.35-0.75 parts by weight, such as 0.375, 0.4, 0.5, 0.6 or 0.7 parts by weight.
[0013] In another preferred embodiment, the calcium salt in the hydrogel matrix is 0.01-0.2 parts by weight, more preferably 0.05-0.18 parts by weight, such as 0.08, 0.1, 0.12 or 0.15 parts by weight.
[0014] In another preferred embodiment, the gelatin is selected from the group consisting of bovine bone gelatin, pork bone gelatin, bovine hide gelatin, pork hide gelatin, fish skin gelatin, sheep hoof gelatin, or combinations thereof.
[0015] In another preferred embodiment, the gelatin has a glue strength of 100-200, preferably 100-150.
[0016] In another preferred embodiment, the calcium salt is selected from the group consisting of CaCl2, Ca(NO3)2, calcium gluconate, calcium carbonate, or combinations thereof.
[0017] In another preferred embodiment, the pectin has 50-100% galacturonic acid groups, more preferably 60-90%, and even more preferably 70-80%.
[0018] In another preferred embodiment, the mass ratio of gelatin to pectin is 1:(0.2-1.0); more preferably 1:(0.4-0.8), even more preferably 1:(0.5-0.7), such as 1:0.55, 1:0.6, 1:0.65.
[0019] In another preferred embodiment, the mass ratio of gelatin to transglutaminase is 1:(0.075-0.3); more preferably 1:(0.12-0.18), and even more preferably 1:(0.14-0.16).
[0020] In another preferred embodiment, the mass ratio of gelatin to calcium salt is 1:(0.05-0.3); more preferably 1:(0.06-0.2), and even more preferably 1:(0.08-0.18), such as 1:0.08, 1:0.12, or 1:0.18.
[0021] In another preferred embodiment, the mass ratio of the red yeast rice pigment to gelatin is 1:(2-20), more preferably 1:(4-15); and even more preferably 1:(6-13), on a dry weight basis, such as 1:5, 1:6, 1:6.25, 1:7, 1:8, 1:9, 1:9.5, 1:10, 1:11, 1:12, or 1:12.5.
[0022] In another preferred embodiment, the total mass percentage of components (a) and (b) in the hydrogel is (3-20) wt%, more preferably 4-15 wt%, and more preferably 5-10 wt%.
[0023] In another preferred embodiment, the content of red yeast rice pigment in the hydrogel is 1-10 mg / g, preferably 2-6 mg / g.
[0024] In another preferred embodiment, the water content in the hydrogel is 80-97 wt%, more preferably 85-96 wt%, and even more preferably 90-95 wt%.
[0025] In a second aspect, the present invention provides a method for preparing a hydrogel as described in the first aspect of the present invention:
[0026] (i) Provide a mixed aqueous solution containing gelatin and pectin; and
[0027] (ii) Add transglutaminase solution and crosslink under stirring at 40-60℃. After crosslinking is completed, inactivate the enzyme in the reaction solution at 100±5℃.
[0028] (iii) Then add calcium salt solution and crosslink under stirring at 40-60℃;
[0029] (iv) Then add the red yeast rice pigment solution, stir evenly at 40-60℃, and then place at 2-8℃ to form a gel.
[0030] In another preferred embodiment, step (iv) includes stirring the resulting solution at 45-55°C until homogeneous and gelling it at 3-5°C.
[0031] In another preferred embodiment, in step (ii), the crosslinking time is 10 min-30 h, preferably 15-20 min.
[0032] In another preferred embodiment, in step (ii), the enzyme inactivation time is 10 min-30 h, preferably 15-20 min.
[0033] In another preferred embodiment, in step (iii), the crosslinking time is 1 min to 4 h, preferably 2 to 3 min.
[0034] In another preferred embodiment, in each step, 40-60°C is independently preferred to be 45-55°C, more preferably 50°C.
[0035] In a third aspect, the invention provides the use of the hydrogel as described in the first aspect in the preparation of colored edible hydrogels in which the off-flavor of red yeast rice pigment is reduced or masked.
[0036] In another preferred embodiment, the odor is derived from one or more of the following: isopropanol, acetic acid, crotonic acid, methyl hexanoate, ethyl oleate, ethyl hexanoate, caprylic acid, 2-nonanone, propionic acid, methyl decanoate, hexadecanoic acid, 1-heptanol, ethyl lactate, benzothiazole, and ethyl levulinate.
[0037] In another preferred embodiment, the odor comes from one or more of the following groups: isopropanol, acetic acid, and crotonic acid.
[0038] In another preferred embodiment, the odor is selected from the group consisting of: alcoholic odor, musty odor, woody odor, sharp sour odor, burnt odor, pineapple odor, strawberry odor, banana odor, oily odor, waxy odor, banana odor, putrid odor, creamy odor, earthy odor, fresh grass odor, pungent sour odor, cheese odor, wine odor, fruity odor, floral odor, oily odor, waxy odor, musty odor, sharp sour fruit odor, buttery odor, vegetal odor, coffee odor, rubber odor, floral odor, and berry odor.
[0039] In another preferred embodiment, the odor is selected from the group consisting of: alcoholic odor, musty odor, woody odor, sour odor, and burnt odor.
[0040] In a fourth aspect, the present invention provides a food product, characterized in that the food product comprises a hydrogel as described in the first aspect of the present invention.
[0041] In another preferred embodiment, the food is jelly, gummy candy, pudding, sausage, canned meat, etc.
[0042] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Attached Figure Description
[0043] Figure 1 The results show the hardness, adhesiveness, and chewiness of different hydrogels;
[0044] Figure 2 The photostability of different hydrogels loaded with red yeast rice pigments was demonstrated;
[0045] Figure 3 The thermal stability of different hydrogels loaded with red yeast rice pigments was demonstrated;
[0046] Figure 4 The thermal maps of the main flavor compounds in different hydrogels are shown. Detailed Implementation
[0047] Through extensive and in-depth research, including numerous screenings and tests, the inventors have developed a novel hydrogel capable of masking the off-flavor of red yeast rice pigment while simultaneously enhancing its stability, along with its preparation method. The use of red yeast rice pigment in food is limited by the presence of distinct alcoholic, musty, woody, sour, and burnt flavors in certain flavor compounds. This application utilizes gelatin and pectin as raw materials, and employs transglutaminase (TG enzyme) and Ca2+... 2+ As a crosslinking agent, a uniform interpenetrating network structure is formed through double crosslinking. A red yeast rice pigment solution is added before gelation, and a hydrogel is formed using a low-temperature gelation method. Surprisingly, this novel hydrogel effectively masks the off-odor of red yeast rice pigment, thus expanding its applications, and significantly improves the photostability and thermal stability of the pigment. Based on this, the present invention was completed.
[0048] the term
[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0050] As used herein, the terms “containing” or “including (comprise)” can be open-ended, semi-closed, or closed. In other words, the terms also include “consistently made of” or “made of”.
[0051] As used herein, the term “room temperature” or “normal temperature” refers to a temperature of 4–40°C, preferably 25 ± 5°C.
[0052] Red yeast rice pigment
[0053] Red yeast rice pigment, also known as red yeast rice, red yeast red, or gibberellin, is a natural pigment produced by Monascus spp. during fermentation. It is widely used in the food, pharmaceutical, and cosmetic industries and is highly favored for its safety and natural origin.
[0054] The red yeast rice pigment referred to in this invention is food-grade red yeast rice pigment (preferably with a pigment molecule content ≥98wt%, preferably ≥99wt%), which typically contains a mixture of pigments, including red yeast rice red pigment, red yeast rice orange pigment, red yeast rice yellow pigment, and microbial metabolites.
[0055] Commercially available red yeast rice pigment products can achieve a purity of around 99%. However, the fermentation process of red yeast rice pigment produces some odorous substances that can still be detected even at low concentrations, thus affecting the flavor of the final food product. In particular, these substances can produce alcoholic, musty, woody, sour, and burnt flavors, which limits the application of red yeast rice pigment in food to some extent.
[0056] In another preferred embodiment, the odor originates from one or more substances selected from the group consisting of: isopropanol, acetic acid, crotonic acid, methyl hexanoate, ethyl oleate, ethyl hexanoate, octanoic acid, 2-nonanone, propionic acid, methyl decanoate, hexadecanoic acid, 1-heptanol, ethyl lactate, benzothiazole, and ethyl acetylpropionate.
[0057] In another preferred embodiment, the odor originates from one or more substances selected from the group consisting of isopropanol, acetic acid, and crotonic acid.
[0058] In another preferred embodiment, the odor is selected from the group consisting of: alcoholic odor, musty odor, woody odor, sharp sour odor, burnt odor, pineapple odor, strawberry odor, banana odor, oily odor, waxy odor, banana odor, putrid odor, creamy odor, earthy odor, fresh grass odor, pungent sour odor, cheese odor, wine odor, fruity odor, floral odor, oily odor, waxy odor, musty odor, sharp sour fruit odor, buttery odor, vegetal odor, coffee odor, rubber odor, floral odor, and berry odor.
[0059] In another preferred embodiment, the odor is selected from the group consisting of: alcoholic odor, musty odor, woody odor, sour odor, and burnt odor.
[0060] Those skilled in the art will understand that food is an odor-sensitive product category, and therefore, the ability to mask off-flavors in food colorings is important for their application.
[0061] hydrogel
[0062] This invention provides a hydrogel comprising:
[0063] (a) The hydrogel matrix comprises: 1-10 parts by weight of gelatin and 0.5-5 parts by weight of pectin, 0.2-1 parts by weight of transglutaminase, and 0.1-1 parts by weight of calcium salt;
[0064] (b) Red yeast rice pigment dispersed in the hydrogel matrix; and
[0065] (c) Water.
[0066] In another preferred embodiment, the food coloring is selected from the group consisting of red yeast rice red pigment, red yeast rice yellow pigment, red yeast rice orange pigment, or combinations thereof.
[0067] In another preferred embodiment, the gelatin in the hydrogel matrix is 2-8 parts by weight, more preferably 2.5-6 parts by weight, such as 2.5, 3, 3.75, 4 or 5 parts by weight.
[0068] In another preferred embodiment, the pectin in the hydrogel matrix is 0.8-4 parts by weight, more preferably 1-3.5 parts by weight, such as 1.5, 2, 2.25 or 3 parts by weight.
[0069] In another preferred embodiment, the amount of transglutaminase in the hydrogel matrix is 0.3-0.8 parts by weight, more preferably 0.35-0.75 parts by weight, such as 0.375, 0.4, 0.5, 0.6 or 0.7 parts by weight.
[0070] In another preferred embodiment, the calcium salt in the hydrogel matrix is 0.01-0.2 parts by weight, more preferably 0.05-0.18 parts by weight, such as 0.08, 0.1, 0.12 or 0.15 parts by weight.
[0071] In another preferred embodiment, the gelatin is selected from the group consisting of bovine bone gelatin, pork bone gelatin, bovine hide gelatin, pork hide gelatin, fish skin gelatin, sheep hoof gelatin, or combinations thereof.
[0072] In another preferred embodiment, the gelatin has a glue strength of 100-200, preferably 100-150.
[0073] In another preferred embodiment, the calcium salt is selected from the group consisting of CaCl2, Ca(NO3)2, calcium gluconate, calcium carbonate, or combinations thereof.
[0074] In another preferred embodiment, the pectin has 50-100% galacturonic acid groups, more preferably 60-90%, and even more preferably 70-80%.
[0075] In another preferred embodiment, the relative molecular mass of the pectin is 20,000 to 400,000.
[0076] In another preferred embodiment, the mass ratio of gelatin to pectin is 1:(0.2-1.0); more preferably 1:(0.4-0.8), even more preferably 1:(0.5-0.7), such as 1:0.55, 1:0.6, 1:0.65.
[0077] In another preferred embodiment, the mass ratio of gelatin to transglutaminase is 1:(0.075-0.3); more preferably 1:(0.12-0.18), and even more preferably 1:(0.14-0.16).
[0078] In another preferred embodiment, the mass ratio of gelatin to calcium salt is 1:(0.05-0.3); more preferably 1:(0.06-0.2), and even more preferably 1:(0.08-0.18), such as 1:0.08, 1:0.12, or 1:0.18.
[0079] In another preferred embodiment, the mass ratio of the red yeast rice pigment to gelatin is 1:(2-20), more preferably 1:(4-15); and even more preferably 1:(6-13), on a dry weight basis, such as 1:5, 1:6, 1:6.25, 1:7, 1:8, 1:9, 1:9.5, 1:10, 1:11, 1:12, or 1:12.5.
[0080] In another preferred embodiment, the total mass percentage of components (a) and (b) in the hydrogel is (3-20) wt%, more preferably 4-15 wt%, and more preferably 5-10 wt%.
[0081] In another preferred embodiment, the content of red yeast rice pigment in the hydrogel is 1-10 mg / g, preferably 2-6 mg / g.
[0082] In another preferred embodiment, the water content in the hydrogel is 80-97 wt%, more preferably 85-96 wt%, and even more preferably 90-95 wt%.
[0083] Experiments have shown that embedding red yeast rice pigment in the hydrogel matrix of this invention can effectively mask the off-flavor of the red yeast rice pigment and significantly improve its photostability and thermal stability. Furthermore, the hardness, adhesiveness, and chewability of the pigment hydrogel can be adjusted and it exhibits excellent performance, making it suitable for various applications.
[0084] Hydrogel matrix composition
[0085] The present invention also provides a hydrogel matrix composition comprising:
[0086] (a) The hydrogel matrix comprises: 1-10 parts by weight of gelatin and 0.5-5 parts by weight of pectin, 0.2-1 parts by weight of transglutaminase, and 0.1-1 parts by weight of calcium salt.
[0087] The hydrogel matrix composition can be used to prepare the hydrogel of the present invention together with red yeast rice pigment and water.
[0088] The hydrogel matrix composition can be used to reduce or mask the odor of red yeast rice pigment.
[0089] Preparation method
[0090] This application uses gelatin and pectin as gelling agents, and transglutaminase (TG enzyme) as a gelatin cross-linking agent. 2+ As a pectin crosslinking agent, a uniform interpenetrating network structure is formed through double crosslinking. Before gelation, the red yeast rice pigment solution is thoroughly mixed with it, and then the gel is formed. This invention does not impose special requirements on the preparation method of the hydrogel, as long as the above-mentioned hydrogel can be formed. Specific solution concentrations, reaction temperatures, and times can be selected as needed.
[0091] This invention provides a preferred method for preparing the hydrogel, comprising the following steps:
[0092] (i) Provide a mixed aqueous solution containing gelatin and pectin; and
[0093] (ii) Add transglutaminase solution and crosslink under stirring at 40-60℃. After crosslinking is completed, inactivate the enzyme in the reaction solution at 100±5℃.
[0094] (iii) Then add calcium salt solution and crosslink under stirring at 40-60℃;
[0095] (iv) Then add the red yeast rice pigment solution, stir evenly at 40-60℃, and then place at 2-8℃ to form a gel.
[0096] In another preferred embodiment, step (iv) includes stirring the resulting solution at 45-55°C until homogeneous and gelling it at 3-5°C.
[0097] In another preferred embodiment, in step (ii), the crosslinking time is 10 min-30 h, preferably 15-20 min.
[0098] In another preferred embodiment, in step (ii), the enzyme inactivation time is 10 min-30 h, preferably 15-20 min.
[0099] In another preferred embodiment, in step (iii), the crosslinking time is 1 min to 4 h, preferably 2 to 3 min.
[0100] In another preferred embodiment, in each step, 40-60°C is independently preferred to be 45-55°C, more preferably 50°C.
[0101] application
[0102] In a third aspect, the invention provides the use of the hydrogel as described in the first aspect in the preparation of colored edible hydrogels in which the off-flavor of red yeast rice pigment is reduced or masked.
[0103] In another preferred embodiment, the odor is derived from one or more of the following: isopropanol, acetic acid, crotonic acid, methyl hexanoate, ethyl oleate, ethyl hexanoate, caprylic acid, 2-nonanone, propionic acid, methyl decanoate, hexadecanoic acid, 1-heptanol, ethyl lactate, benzothiazole, and ethyl levulinate.
[0104] In another preferred embodiment, the odor comes from one or more of the following groups: isopropanol, acetic acid, and crotonic acid.
[0105] In another preferred embodiment, the odor is selected from the group consisting of: alcoholic odor, musty odor, woody odor, sharp sour odor, burnt odor, pineapple odor, strawberry odor, banana odor, oily odor, waxy odor, banana odor, putrid odor, creamy odor, earthy odor, fresh grass odor, pungent sour odor, cheese odor, wine odor, fruity odor, floral odor, oily odor, waxy odor, musty odor, sharp sour fruit odor, buttery odor, vegetal odor, coffee odor, rubber odor, floral odor, and berry odor.
[0106] In another preferred embodiment, the odor is selected from the group consisting of: alcoholic odor, musty odor, woody odor, sour odor, and burnt odor.
[0107] In another preferred embodiment, the odor masking refers to the fact that after equal masses of red yeast rice pigment and the hydrogel of the present invention (based on the red yeast rice pigment load) are placed in sealed containers of equal volume for the same period of time, the odor substances in the air of the container of the hydrogel group are independently and optionally reduced by more than 80% relative to the red yeast rice pigment group, preferably independently and optionally reduced by more than 85%, more than 90%, more than 95%, more than 96%, more than 97%, more than 98%, or even more than 99%.
[0108] The present invention also provides a food product comprising the hydrogel as described in the present invention.
[0109] In another preferred embodiment, the food is jelly, gummy candy, pudding, sausage, canned meat, etc.
[0110] The hydrogel of the present invention can be loaded with other desired flavor ingredients, nutrients, etc., as needed before gelation.
[0111] The main advantages of this invention include:
[0112] 1. This invention provides a novel hydrogel that can mask the off-odor of red yeast rice pigment while improving its stability.
[0113] 2. Due to the distinct alcoholic, musty, woody, sour, and burnt flavors of certain flavor compounds in red yeast rice pigment, its application in food has been somewhat limited. Surprisingly, the hydrogel of this invention not only effectively masks the off-flavors of red yeast rice pigment but also improves its stability, thus offering better application prospects.
[0114] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.
[0115] Example 1
[0116] (1) Mixing of gelatin and pectin solutions: 5.00 g, 3.75 g, and 2.50 g of bovine bone gelatin (gel strength 100 g) were dissolved in 20 mL of deionized water under heating at 85 °C, and the pH was adjusted to 7.0 to obtain gelatin solutions No. 1, No. 2, and No. 3. 3.00 g, 2.25 g, and 1.50 g of pectin (galacturonic acid group ≥74%) were dissolved in 73 mL of deionized water under heating at 85 °C, and the pH was adjusted to 7.0 to obtain pectin solutions No. 1, No. 2, and No. 3. Under heating at 50 °C, gelatin solutions No. 1, No. 2, and No. 3 were poured into pectin solutions No. 1, No. 2, and No. 3 respectively and stirred for 15 min to obtain gelatin-pectin solutions with concentrations of 8%, 6%, and 4% (w / v) respectively, which were then refrigerated at 4 °C for later use.
[0117] (2) TG enzyme cross-linking: TG enzyme solution was added according to the ratio of TG enzyme: gelatin = 15u: 1g. 0.750g, 0.563g, and 0.375g of soybean meal TG enzyme (activity 100u / g) were dissolved in 5mL of deionized water to obtain TG enzyme solutions No. 1, No. 2, and No. 3, respectively. The gelatin-pectin solution was preheated at 50℃ for 30min. TG enzyme solutions No. 1, No. 2, and No. 3 were added to 8%, 6%, and 4% (w / v) gelatin-pectin solutions, respectively. The mixture was stirred at medium speed at 50℃ for 15min and then quickly placed in a boiling water bath at 100℃ for 15min to inactivate the enzyme, thus obtaining TG enzyme monocrosslinked gelatin-pectin solutions.
[0118] (3)Ca 2+ Crosslinking: Add Ca to the gelatin-pectin solution at a concentration of 0.04 mol / L. 2+ Solution. Dissolve 2.22 g of anhydrous CaCl2 in 5 mL of deionized water to obtain Ca... 2+ Solution. The TG enzyme monocrosslinked gelatin-pectin solution was placed in a 50℃ water bath for 30 min. 1 mL of Ca was added to each of the 8%, 6%, and 4% (w / v) gelatin-pectin solutions. 2+ The solution was stirred at medium speed at 50℃ for 2 hours to obtain TG enzyme-Ca. 2+ Double cross-linked gelatin-pectin solution.
[0119] (4) Preparation of a novel hydrogel loaded with red yeast rice pigment: 4g of red yeast rice pigment was added to 10mL of deionized water and dissolved completely to obtain a concentrated red yeast rice pigment solution. The solution was then loaded with 8%, 6%, and 4% (w / v) TG enzyme-Ca... 2+ 1 mL of red yeast rice pigment concentrate was added to the double crosslinked gelatin-pectin solution and stirred at high speed at 50°C for 15 min. The mixture was then poured into a mold, sealed, and placed in a refrigerator at 4°C overnight to form a gel, resulting in a novel hydrogel with a red yeast rice pigment concentration of 4 mg / g.
[0120] (5) Preparation of blank hydrogel without red yeast rice pigment: The TG enzyme-Ca obtained in step (3) 2+ The double crosslinked gelatin-pectin solution was poured directly into the mold, sealed, and placed in a 4°C refrigerator overnight to form a gel, resulting in a blank hydrogel without red yeast rice pigment.
[0121] Example 2
[0122] Characterization of the mechanical properties of hydrogels:
[0123] The blank hydrogels without red yeast rice pigment were named 8%-empty, 6%-empty, and 4%-empty, respectively. The novel hydrogels loaded with red yeast rice pigment were named 8%-MPS, 6%-MPS, and 4%-MPS, respectively. The differences in hardness, adhesiveness, and chewiness of the hydrogels before and after loading with red yeast rice pigment were measured using a TA.XTplus texture analyzer from SMS manufacturer [manufacturer name missing]. The textural results of the different hydrogels are shown below. Figure 1 As shown, the hardness, adhesiveness, and chewiness of the hydrogel all increase with increasing hydrogel concentration. This is because the high concentration of proteins and polysaccharides makes the interpenetrating network structure formed inside the hydrogel more compact. Meanwhile, it can be observed that the texture of the hydrogel also shows an increasing trend after loading with red yeast rice pigment. This may be related to the interaction between red yeast rice pigment and gelatin and pectin, such as the large number of hydrogen bonds.
[0124] Example 3
[0125] The effect of improving the stability of red yeast rice pigment:
[0126] The UV absorption OD value at 420 nm of the hydrogel was measured after continuous irradiation at 7000 lux for 6 h. The retention rate of red yeast rice pigment in different hydrogels was calculated with 0 h of irradiation as the initial value. Figure 2 The results show the photostability of different hydrogels loaded with Monascus pigment. Compared to the aqueous solution of Monascus pigment, hydrogels of different concentrations significantly slowed down the photodegradation rate of the pigment. The retention rates of 8%-MPS and 6%-MPS hydrogels after 48 hours of light exposure reached 76.66±1.51% and 75.23±0.95%, respectively, while the retention rate of the aqueous solution was only 48.11±0.55%. When the light exposure time was extended to 96 hours, the pigment retention rate of the aqueous solution decreased to a minimum of 17.75±0.07%, while the 8%-MPS hydrogel still maintained a high retention rate of 66.78±2.61%. Therefore, the interpenetrating network structure hydrogel formed by gelatin and pectin can significantly improve the photostability of Monascus pigment.
[0127] The results of the thermal stability test were obtained using a method similar to that of the photostability test. Figure 3 Different hydrogels loaded with red yeast rice pigment were subjected to TG enzyme and Ca...2+ The double-crosslinked gelatin-pectin hydrogel exhibits good thermal stability, and its interpenetrating network structure provides excellent physical protection for red yeast rice pigment, significantly enhancing its thermal stability. It was observed that the hydrogel's thermal stability protection effect on the pigment increases with increasing gelatin and pectin concentrations. After a 3-hour water bath at 100°C, the pigment retention rate of the red yeast rice pigment aqueous solution decreased to 56.16±2.43%, while the pigment retention rates of 8%-MPS, 6%-MPS, and 4%-MPS hydrogels were 88.66±2.85%, 76.58±1.44%, and 72.07±1.49%, respectively. This demonstrates that the interpenetrating network structure within the hydrogel significantly improves the stability of red yeast rice pigment at high temperatures.
[0128] Example 4
[0129] The masking effect of hydrogels on the odor of red yeast rice pigments:
[0130] Different hydrogels with a red yeast rice pigment concentration of 4 mg / g were weighed into 20 mL headspace vials, and 16 mg of red yeast rice pigment powder was weighed into a 20 mL headspace vial as a control. These were stored at 4℃ for SPME-GC-TOF-MS analysis. Before analysis, 5 μL of 1,2-dichlorobenzene at a concentration of 100 μg / mL was added to the sample as an internal standard (IS). The SPME-GC-TOF-MS analysis procedure was as follows: the sample was equilibrated at 100℃ for 15 min. Volatile compounds in the headspace vial were extracted using a 50 / 30 μm, DVB / CAR / PDMS three-phase composite fiber extraction head (model 57299-U, Supelco) at the same temperature for 30 min. The extracted volatile compounds were desorbed in the GC for 5 min and injected at 250℃ in splitless mode. Separation was performed using a DB-wax column (30 m × 0.25 mm × 0.25 μm, Agilent Technologies), with a helium carrier flow rate of 1 mL / min. The column temperature was maintained at 40 °C for 5 min, then increased to 220 °C at 5 °C / min, followed by an increase to 250 °C at 20 °C / min, and held for 15.5 min. The separated volatile compounds were transferred to a gas chromatography-time-of-flight mass spectrometer (7890B-Pegsus BT, LECO Corporation, USA). Ionization was performed using EI+, with an ion source temperature of 230 °C and an interface temperature of 290 °C. The full scan range was 33–450 m / z, and the scan frequency was 10 spectra / s.
[0131] Different hydrogels and red yeast rice pigment powders were tested three times each. Volatile compounds were preliminarily identified by comparing MS spectra with the NIST 17 standard reference database. The retention index (RI) of volatile compounds was calculated using C6-C29 saturated alkanes under the same GC-TOF-MS conditions. calc, with the RI in the retained index database lib The volatile compounds were further identified through comparison. By comparing the peak area ratio of each compound to the IS (Intense Precipitation) peak, and multiplying it by the IS concentration, the relative concentration of volatile compounds above each headspace vial was calculated for semi-quantitative analysis. The calculation formula is as follows.
[0132]
[0133] Table 1. SPME-GC-TOF-MS results of major flavor compounds in different hydrogels.
[0134]
[0135]
[0136] SPME-GC-TOF-MS analysis revealed 156 volatile compounds coexisting in the red yeast rice pigment powder and different hydrogels. Among them, 15 were major flavor compounds with high content and distinct odors, including 6 ester compounds, 5 acid compounds, 2 alcohol compounds, 1 ketone compound, and 1 heterocyclic compound. The results are shown in Table 1. Figure 4Thermal analysis of the main flavor compounds in different hydrogels revealed that the three most abundant flavor compounds in red yeast rice pigment powder were isopropanol, acetic acid, and crotonic acid. These compounds are likely metabolic byproducts produced by microorganisms during fermentation. Due to the distinct alcoholic, musty, woody, sour, and burnt flavors of these compounds, the application of red yeast rice pigment in meat products has been somewhat limited. Compared to red yeast rice pigment powder, the relative content of isopropanol in 4%-MPS hydrogel decreased from 61.9000±6.5666 ng / g to 0.0799±0.0273 ng / g, a reduction of approximately 99.87%; the relative content of acetic acid in 4%-MPS hydrogel decreased from 32.7364±0.6652 ng / g to 1.6273±0.7002 ng / g, a reduction of approximately 95.03%; and the relative content of crotonic acid in 8%-MPS hydrogel decreased from 31.0003±1.8650 ng / g to 0.0037±0.0009 ng / g, a reduction of approximately 99.99%. This demonstrates that the novel double-crosslinked gelatin-pectin hydrogel can effectively mask the off-flavor components in red yeast rice pigment powder. This is likely due to the numerous hydrogen bonds and ionic bonds formed between the abundant hydroxyl (-OH), carboxyl (-COOH), carbonyl (C=O), and ester (-COO-) groups in the flavor compounds (mainly alcohols, esters, and acids) and the gelatin and pectin within the hydrogel. This significantly reduces the relative content of flavor compounds in the red yeast rice pigment powder within the hydrogel. Furthermore, the interpenetrating network structure within the hydrogel also provides excellent physical encapsulation, effectively isolating volatile compounds within the hydrogel and thus masking the off-flavor of the red yeast rice pigment.
[0137] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.
Claims
1. A hydrogel, characterized in that, include: (a) The hydrogel matrix comprises: 1-10 parts by weight of gelatin and 0.5-5 parts by weight of pectin, 0.2-1 parts by weight of transglutaminase, and 0.1-1 parts by weight of calcium salt; (b) Red yeast rice pigment dispersed in the hydrogel matrix; and (c) Water.
2. The hydrogel as described in claim 1, characterized in that, The red yeast rice pigment includes: red yeast rice red pigment, red yeast rice yellow pigment, red yeast rice orange pigment, or a combination thereof.
3. The hydrogel as described in claim 1, characterized in that, The mass ratio of gelatin to pectin is 1:(0.2-1.0); preferably 1:(0.4-0.8), more preferably 1:(0.5-0.7), such as 1:0.55, 1:0.6, 1:0.
65.
4. The hydrogel as described in claim 1, characterized in that, The content of red yeast rice pigment in the hydrogel is 1-10 mg / g, preferably 2-6 mg / g.
5. The hydrogel according to claim 1, characterized in that, The total mass percentage of components (a) and (b) is (3-20) wt%, preferably 4-15 wt%, and more preferably 5-10 wt%.
6. The hydrogel according to claim 1, characterized in that, The water content in the hydrogel is 80-97 wt%, preferably 85-96 wt%, and more preferably 90-95 wt%.
7. The method for preparing the hydrogel according to claim 1, comprising the steps of: (i) Provide a mixed aqueous solution containing gelatin and pectin; and (ii) Add transglutaminase solution and crosslink under stirring at 40-60℃. After crosslinking is completed, inactivate the enzyme in the reaction solution at 100±5℃. (iii) Then add calcium salt solution and crosslink under stirring at 40-60℃; (iv) Then add the red yeast rice pigment solution, stir evenly at 40-60℃, and then place at 2-8℃ to form a gel.
8. The application of the hydrogel as described in claim 1 in the preparation of colored edible hydrogels in which the off-flavor of red yeast rice pigment is reduced or masked.
9. The use as described in claim 8, characterized in that, The odor is derived from one or more of the following groups: isopropanol, acetic acid, crotonic acid, methyl hexanoate, ethyl oleate, ethyl hexanoate, octanoic acid, 2-nonanone, propionic acid, methyl decanoate, hexadecanoic acid, 1-heptanol, ethyl lactate, benzothiazole, and ethyl acetylpropionate.
10. A food product, characterized in that, The food product includes the hydrogel as described in claim 1.