Carrageenan and carrageenan-based gel as well as preparation method and application thereof

Abstract

The present invention relates to carrageenan comprising sodium ions, the amount of sodium ions being 1-10% w / w or 2-6% w / w based on the carrageenan, the pH of the carrageenan solution being in the range of 5-9, 7-9 or 7.8-9 when 1% w / w of the carrageenan is dissolved in water to form the carrageenan solution, the hydrogen ions and the sodium ions being bound to the sulfuric acid groups of the carrageenan, and the sodium ions being bound to the sulfuric acid groups of the carrageenan, the amount of sodium ions being in the range of 1-10% w / w or in the range of 2-6% w / w based on the carrageenan. Carrageenan-hydrogen sulfate and carrageenan-sodium sulfate are respectively formed. The present invention also relates to a carrageenan-based gel comprising the carrageenan in question, starch, a first salt, glycerol and water.

Description

Technical Field

[0001] The present invention relates to the technical field of carrageenan-based gels, and more particularly to capsule membranes containing carrageenan-based gels. Background Art

[0002] In recent years, natural, healthy, and green plant-based soft capsules have become a market hot spot. Compared with animal-source soft capsules, plant-based soft capsules have a wider application market and are suitable for consumer groups with other dietary habits including halal, vegetarian, and kosher. In the future, with the continuous strengthening of national health awareness and the continuous expansion of the vegetarian consumer group, the plant-based soft capsule market will have greater development potential.

[0003] However, common carrageenan in the market has high viscosity and high gelling temperature when used in soft capsules. Common carrageenan in the market has many disadvantages, such as high requirements for production equipment, poor reversibility, poor reusability of the gel film, and high cost.

[0004] Existing solutions in this field involve reducing the molecular weight (Mw) of carrageenan to lower its viscosity and gelling temperature, such as US Patent 7816341. In Europe, the term "carrageenan" refers to non-hydrolyzed or chemically degraded polymers (i.e., carrageenan degradation product poligeenan). There are concerns about the content of substances with a molar mass less than 50,000 Da (carrageenan degradation product poligeenan) in carrageenan. Some studies have shown that reducing the molecular weight of carrageenan poses health risks. For example, reducing Mw by degrading carrageenan (poligeenan) can lead to risks of gastrointestinal ulcers and gastrointestinal cancers.

[0005] Therefore, there is a need in the market to provide a carrageenan-based gel that does not require reducing the molecular weight of carrageenan. Summary of the Invention

[0006] The present invention relates to a carrageenan comprising sodium ions, wherein the content of sodium ions is 1-10% w / w, or 2-6% w / w of the carrageenan, and when 1% w / w of the carrageenan is dissolved in water to form a carrageenan solution, the pH range of the carrageenan solution is 5-9, 7-9, or 7.8-9, wherein hydrogen ions and sodium ions combine with the sulfate groups of the carrageenan to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate, respectively.

[0007] The present invention relates to a carrageenan-based gel, the carrageenan-based gel comprising carrageenan, starch, preferably modified starch, a first salt, glycerol and water, wherein the carrageenan comprises sodium ions, the content of the sodium ions being 1-10% w / w, or preferably 2-6% w / w, of the carrageenan, and wherein when 1% w / w of the carrageenan is dissolved in water to form a carrageenan solution, the pH range of the carrageenan solution is 5-9, 7-9 or 7.8-9, and wherein hydrogen ions and sodium ions bind to the sulfate groups of the carrageenan to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate, respectively.

[0008] The present invention relates to the use of the carrageenan or carrageenan-based gel discussed in soft capsule membranes.

[0009] The present invention relates to a method for manufacturing carrageenan, the method comprising: (a) gelling seaweed pulp, preferably with KCl, to obtain crude carrageenan; (b) applying a solution to the crude carrageenan to obtain carrageenan, wherein the solution comprises an acid, preferably an organic acid, a second salt other than potassium salts and calcium salts, and an alcohol, and the method does not reduce the molecular weight of the carrageenan. Description of the Drawings

[0010] Figure 1 Showing the conversion of colloids to Gel I and further to Gel II and its reversibility.

[0011] Figure 2 is a schematic diagram of the preparation process of carrageenan. Detailed Description

[0012] Unless otherwise specified, all dimensions, weights, lengths, etc. are in metric units and all temperatures are in degrees Celsius. It should be understood that unless otherwise specifically stated, the materials, compounds, chemicals, etc. described herein are generally commercially available and / or industry standard items that can be obtained from various suppliers and sources around the world.

[0013] In this document, a value expressed in a range format should be interpreted in a flexible manner to include not only the explicitly recited values that are the limits of the range but also all individual values or sub-ranges subsumed within that range, as if each individual value and sub-range were explicitly recited. For example, the range "from about 0.1% to about 5%" or "from about 0.1% to 5%" should be interpreted to include not only from about 0.1% to about 5%, but also individual values (e.g., 1%, 2%, 3%, and 4%) and sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. As another example, "95 - 121 °C" includes not only 95 - 121 °C, but also individual values (e.g., 95 °C, 96 °C, 97 °C, etc.) and sub-ranges (e.g., 95 - 97 °C, 96 - 100 °C, 100 - 121 °C, etc.) within the range of 95 - 121 °C. For example, the range "C2 - C16" should be interpreted to include C2, C3, C4, C5…C14, C15, and C16. Unless otherwise specified, the statement "about X to Y" has the same meaning as "about X to about Y". Similarly, unless otherwise specified, the statement "about X, Y or about Z" has the same meaning as "about X, about Y or about Z".

[0014] As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to "a substituent" includes a single substituent as well as two or more substituents, etc. It should be understood that any term in the singular form may include its plural counterpart, and vice versa.

[0015] Unless otherwise specified, the term "or" is used to mean non-exclusive "or". The statement "at least one of A and B" has the same meaning as "A, B, or A and B".

[0016] As used herein, the terms "for example", "such as", "like", or "including" are intended to introduce examples that further clarify a broader subject. Unless otherwise explicitly stated, providing such examples is for the sole purpose of assisting in understanding the applications shown in this disclosure and is not meant to be limiting in any way.

[0017] As used herein, the term "about" may allow for a degree of variability in, for example, a numerical value or a range, such as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% of a specified numerical value or a specified range limit, and includes the exact specified numerical value or range.

[0018] The term "the average molecular weight of carrageenan is greater than 500,000" means that the average molecular weight of carrageenan is greater than 500,000 g / mol. Based on the weight of carrageenan, the amount of carrageenan with a molecular weight Mw less than 50,000 daltons is less than 10 wt% or preferably less than 5 wt%.

[0019] The term "at least a part" means 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 100% of a substance.

[0020] The term "melting temperature" refers to the temperature at which the solid phase melts into the liquid phase, and in one embodiment, it refers to the temperature at which the gel / membrane transforms into a gel mass.

[0021] The term "setting temperature", also known as "gelling temperature" or "gelling point", refers to the temperature at which the liquid phase turns into the solid phase. In one embodiment, it refers to the temperature at which the gel mass transforms into the gel / membrane. In one example, the melting temperature is slightly higher than the setting temperature.

[0022] In one aspect, the long chains of carrageenan molecules exist in the form of a random cluster in the solution. As it cools, a three-dimensional polymer network structure is first formed, and the hydrogen bonds between galactose O-2 and O-6 are distorted into double helices, which generates the binding points of the polymer chains, that is, gel I (helix) with a preliminary gel state is formed. As Figure 1 shown, when the carrageenan colloid cools, the carrageenan colloid will form gel I, and compared with the carrageenan colloid, the gel strength of gel I will increase. Further cooling of gel I will cause these binding sites to aggregate to form bundles of double helices, forming a hard gel, that is, gel II (aggregate) is formed.

[0023] In one aspect, cations such as potassium ions are removed or reduced from carrageenan. Hydrogen ions and sodium ions (instead of potassium ions) are introduced into carrageenan. In one aspect, introducing hydrogen ions and sodium ions into carrageenan does not damage the molecular structure and molecular weight of carrageenan, and at least a part of the hydrogen ions and at least a part of the sodium ions bind to the sulfate groups. In one aspect, in the presence of hydrogen ions and sodium ions, most of the carrageenan is in the form of a colloid. This will maintain its reversibility and make it less likely to form gel II or carrageenan superchains, thereby reducing the gelling temperature and viscosity of the carrageenan-based gel or gel mass.

[0024] In one aspect, the presence of sodium ions can prevent the conformational change of carrageenan from a coil to a double helix, while the presence of potassium ions can promote the conformational change of carrageenan from a coil to a double helix.

[0025] In one aspect, a portion of hydrogen ions and a portion of sodium ions combine with the sulfate groups to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate, respectively. The remaining hydrogen ions and sodium ions float in the carrageenan solution. In one aspect, all of the hydrogen ions and sodium ions combine with the sulfate groups to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate, respectively.

[0026] In one aspect, the present invention provides a carrageenan (or carrageenan-based gel) and a method for preparing the same, in which hydrogen ions and sodium ions are introduced into carrageenan without reducing the molecular weight of carrageenan, while avoiding / reducing the formation of Gel II. Introducing hydrogen ions and sodium ions into carrageenan reduces the viscosity and gelling temperature of the carrageenan-based gel / gel solution to a level where the carrageenan-based gel has properties similar to those of gelatin.

[0027] The present invention provides a carrageenan comprising sodium ions, wherein the content of sodium ions is 1-10% w / w, or 1-9% w / w, or 1-8% w / w, or 1-7% w / w, or 2-7% w / w, or 2-6% w / w of carrageenan. When 1% w / w of carrageenan is dissolved in water to form a carrageenan solution, the pH range of the carrageenan solution is 5-9, 7-9 or 7.8-9, wherein hydrogen ions and sodium ions combine with the sulfate groups of carrageenan to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate, respectively.

[0028] In one aspect, the carrageenan is in powder form. In one aspect, the carrageenan comprises sodium ions and hydrogen ions. In one aspect, when the carrageenan is dissolved in an aqueous solution, at least a portion of the hydrogen ions and at least a portion of the sodium ions combine with the sulfate groups of the carrageenan. In one aspect, the remaining hydrogen ions and sodium ions are present in the aqueous solution.

[0029] In one aspect, at least a portion of the sodium ions and at least a portion of the hydrogen ions combine with the sulfate groups of the carrageenan. In one aspect, introducing hydrogen ions and sodium ions makes it difficult for carrageenan to form a bridge structure as shown in the following chemical structure, thereby avoiding or reducing the formation of Gel I and Gel II bundles (as Figure 1 shown), making the carrageenan or carrageenan-based gel more suitable for, for example, soft capsule membranes.

[0030]

[0031] In one aspect, the carrageenan is derived from seaweed, preferably from red seaweed. In one aspect, the carrageenan is κ-carrageenan, ι-carrageenan or a combination thereof.

[0032] In one aspect, the content of salt ions other than sodium ions (such as potassium ions and calcium ions) in carrageenan is less than 6% w / w based on carrageenan, or less than 5%, or less than 4%, or less than 3.8% w / w, or less than 3%, or less than 1% w / w, or in the range of 0.1 - 6% w / w, or in the range of 0.1 - 5% w / w, or in the range of 0.1 - 4% w / w. In one aspect, except for sodium ions, carrageenan has a low salt content, such as less than 6% w / w, or less than 5%, or less than 4%, or less than 3.8% w / w, or less than 3%, or less than 1% w / w, or in the range of 0.1 - 6% w / w, or in the range of 0.1 - 5% w / w, or in the range of 0.1 - 4% w / w.

[0033] The present invention provides a carrageenan-based gel, and the carrageenan-based gel contains the carrageenan as described above. The carrageenan-based gel may further contain additional components such as starch, a first salt, glycerol, and water. In one aspect, the carrageenan-based gel contains 6 - 10 wt% of carrageenan, 25 - 35 wt% of starch (preferably modified starch), 0.5 - 1.5 wt% of the first salt, and 15 - 25 wt% of glycerol, and water, and the amount of water is such that all components add up to 100 wt%. In one aspect, the carrageenan-based gel is obtained by mixing carrageenan, starch, the first salt, glycerol, and water. In one aspect, the first salt contains sodium phosphate. In one aspect, the starch contains modified starch. In one aspect, the modified starch contains hydroxypropyl starch.

[0034] The molecular weight of carrageenan is measured by the method disclosed by Uno Y. et al. (Uno Y, Omoto T, Goto Y, Asai I, Nakamura M, Maitani T. Molecular weight distribution of carrageenans studied by a combined gel permeation / inductively coupled plasma (GPC / ICP) method. Food Addit Contam. 2001 Sep;18(9):763 - 72) in 2001.

[0035] In one aspect, the average molecular weight of carrageenan in the carrageenan-based gel is greater than 500,000 g / mol, or preferably greater than 600,000 g / mol, or preferably greater than 700,000 g / mol. In one aspect, the average molecular weight of carrageenan in the carrageenan-based gel is in the range of 500,000 - 900,000 g / mol, or in the range of 600,000 - 900,000 g / mol, or in the range of 600,000 - 800,000 g / mol, or in the range of 500,000 - 800,000 g / mol, or in the range of 500,000 - 750,000 g / mol, or in the range of 620,000 - 745,000 g / mol.

[0036] In one aspect, the carrageenan having a molecular weight greater than 100,000 g / mol in the carrageenan-based gel is at least 60 wt%, or preferably at least 70 wt%, or preferably at least 80 wt%, or preferably at least 90 wt%, or preferably at least 95 wt% of the carrageenan.

[0037] In one aspect, the carrageenan having a molecular weight less than 50,000 g / mol in the carrageenan-based gel is less than 1.0 wt%, 0.75 wt%, 0.73 wt%, 0.70 wt% by weight of the carrageenan, or is in the range of 0.1 - 0.75 wt%. In one aspect, the carrageenan having a molecular weight less than 100,000 g / mol is less than 4 wt%, 3.5 wt%, 3 wt% by weight of the carrageenan, or is in the range of 2 - 4 wt%.

[0038] In one aspect, all components in the carrageenan-based gel are dissolved and stirred at high speed under pressure to reach a final temperature of 90 °C. The gelation temperature and viscosity are measured using a device called HAAKE viscoester IQ. The rotor is P60. The gelation temperature and viscosity are measured by an oscillating temperature ramp, with the temperature set to decrease from 100 °C to 50 °C, a frequency of 1 Hz, and a shear stress of 1 Pa. The viscosity at 90 °C is read. The temperature at which the storage modulus is equal to the loss modulus is read as the gelation temperature.

[0039] In one aspect, the viscosity of the carrageenan-based gel solution at 90 °C is less than 1,800,000 cPs, or less than 1,500,000 cPs, or less than 1,300,000 cPs, or less than 1,000,000 cPs, or less than 800,000 cPs, or less than 600,000 cPs, or less than 500,000 cPs, or less than 400,000 cPs, or less than 300,000 cPs. The viscosity of the gel solution at 90 °C is in the range of 100,000 - 1,800,000 cPs, or in the range of 100,000 - 1,500,000 cPs, or in the range of 100,000 - 1,300,000 cPs, or in the range of 200,000 - 1,300,000 cPs, or in the range of 200,000 - 1,000,000 cPs, or in the range of 200,000 - 1,100,000 cPs, or in the range of 200,000 - 1,000,000 cPs, or in the range of 200,000 - 800,000 cPs.

[0040] In one aspect, the gelling temperature of the carrageenan-based gel solution is in the range of 40 - 75 °C, or 40 - 70 °C, or 40 - 65 °C, or 45 - 70 °C, or 40 - 65 °C, or 45 - 60 °C, or 40 - 60 °C, or 40 - 50 °C, or 50 - 60 °C, or 45 - 55 °C.

[0041] In one aspect, the present invention provides the use of carrageenan or carrageenan-based gel in a capsule membrane. In one aspect, the capsule is a soft capsule. In one aspect, the capsule is for drugs, cosmetics or food. In one aspect, the capsule membrane contains a carrageenan-based gel and optionally further contains fillers (such as starch, cellulose) and plasticizers (such as polyols, such as glycerol, sorbitol or starch).

[0042] In one aspect, the present invention provides a method for manufacturing carrageenan, comprising: (a) gelling seaweed pulp preferably with KCl to obtain crude carrageenan; (b) applying a solution to the crude carrageenan to obtain carrageenan, wherein the solution contains an acid (preferably an organic acid), a second salt other than potassium salt and calcium salt (preferably sodium salt) and an alcohol. Relative to the average molecular weight of carrageenan without sodium salt, the method reduces the average molecular weight by less than 40% or less than 30%, or less than 20%, or less than 15%, or less than 10%, or less than 5%, or less than 3%. Preferably, relative to the average molecular weight of carrageenan without sodium salt, the method does not reduce the average molecular weight of carrageenan. Preferably, relative to carrageenan without sodium salt, the method does not reduce the molecular weight of carrageenan.

[0043] In one aspect, applying the solution to crude carrageenan includes washing the crude carrageenan with the solution, or soaking the crude carrageenan in the solution, or mixing the solution with the crude carrageenan, or spraying the solution onto the crude carrageenan. In one aspect, in step (b), the solution is applied to the crude carrageenan.

[0044] In one aspect, the acid is an organic acid. In one aspect, the acid is a natural organic acid or a chemically synthesized acid. In one aspect, the acid comprises citric acid, malic acid, tartaric acid, acetic acid, or any combination thereof.

[0045] In one aspect, the second salt in the solution is a sodium salt. In one aspect, the second salt is an organic acid salt. In one aspect, the second salt in the solution is a sodium organic acid salt. In one aspect, the second salt comprises sodium citrate, trisodium phosphate, sodium tartrate, or any combination thereof.

[0046] In one aspect, the alcohol comprises C2-C16 alkanols, C3-C16 unsaturated alcohols, C3-C20 alicyclic alcohols, C6-C20 aromatic alcohols, or any combination thereof. In one aspect, the alcohol comprises a monohydric or polyhydric alcohol of C2-C16 alkanols, C3-C16 unsaturated alcohols, C3-C20 alicyclic alcohols, C6-C20 aromatic alcohols, or any combination thereof. In one aspect, the C2-C16 alkanols comprise C2 alkanol (such as ethanol), C3 alkanol (such as propanol or isopropanol), C4 alkanol (such as butanol or isobutanol), C5 alkanol, C6 alkanol, C7 alkanol, C8 alkanol, C9 alkanol, C10 alkanol, C11 alkanol, C12 alkanol, C13 alkanol, C14 alkanol, C15 alkanol, C16 alkanol, or any combination thereof. In one aspect, the alcohol is ethanol. In one aspect, the alcohol is an aqueous alcohol solution.

[0047] In one aspect, the C3-C16 unsaturated alcohols comprise C3 unsaturated alcohols to C16 unsaturated alcohols, or any combination thereof. The C3-C20 alicyclic alcohols comprise C3 alicyclic alcohols to C20 alicyclic alcohols, or any combination thereof. The C6-C20 aromatic alcohols comprise C6 aromatic alcohols to C20 aromatic alcohols, or any combination thereof.

[0048] In one aspect, the method further comprises: before step (a), boiling the seaweed at a temperature above 85 °C to obtain a dissolved seaweed paste, and filtering the dissolved seaweed paste to obtain a seaweed slurry. In one aspect, boiling the seaweed is carried out at a temperature of about 90 °C. In one aspect, the seaweed slurry is a syrupy seaweed.

[0049] In one aspect, crude carrageenan is preferably further gelled with KCl to obtain a wet cake. In one aspect, in step (a), the crude carrageenan is obtained in the form of a wet cake, and in step (b), the wet cake is washed with a solution to obtain refined carrageenan, and the refined carrageenan is preferably dried to obtain carrageenan. In one aspect, hydrogen ions and sodium ions are introduced into the carrageenan by washing the wet cake of the crude carrageenan with a solution.

[0050] In one aspect, in step (a), the crude carrageenan is obtained in the form of a wet cake, and in step (b), the wet cake is washed with a solution, wherein the weight ratio of the wet cake to the solution is 1:0.1 to 1:50, preferably 1:1 to 1:10, or more preferably 1:0.5 to 1:10.

[0051] In one aspect, the solution comprises a 10 - 80% w / w alcohol solution, or preferably a 10 - 50% w / w alcohol solution. In one aspect, the solution comprises an acid of 0.005M - 0.2M or preferably 0.01M - 0.1M. In one aspect, the solution comprises a second salt of 0.005M - 0.2M or preferably 0.01 - 0.1M.

[0052] In one aspect, the dried carrageenan is further pulverized into carrageenan powder. In one aspect, the amount of sodium ions is 1 - 10% w / w of the carrageenan powder, or 2 - 9% w / w, or 2 - 8% w / w, or 2 - 7% w / w or 2 - 6% w / w. In one aspect, based on the carrageenan powder, Ca 2+ and K + amounts are below 6% w / w, or below 5% w / w, or below 4% w / w, or below 3.8% w / w, or below 3% w / w, or below 2% w / w. Based on the carrageenan powder, Ca 2+ and K + amounts are in the range of 0.1 - 6% w / w, in the range of 0.1 - 5% w / w, or in the range of 0.1 - 4% w / w, or in the range of 0.1 - 3% w / w.

[0053] Without being bound by theory, the inventors of the present invention have found that when hydrogen ions and sodium ions are introduced, the hydrogen ions and sodium ions can combine with the sulfate groups of carrageenan without destroying the molecular structure and molecular weight of carrageenan. The inventors have found that the combination of hydrogen ions, sodium ions and sulfate groups makes it difficult to form --o--K + --o or o--Ca 2+ --o bridge structures, so that the colloid of carrageenan is not easy to form gel I, and gel I is not easy to form gel II, thus maintaining its reversibility, and at the same time not easy to form carrageenan superchains, thereby reducing the gelling temperature and viscosity of the carrageenan-based gel liquid. Therefore, the carrageenan-based gel does not involve reducing the molecular weight of carrageenan, and at the same time can reduce the gelling temperature and viscosity, which makes the gel suitable for application in capsules, especially soft capsule membranes.

[0054] The inventors found that when K + or Ca 2+ is introduced into the carrageenan solution, binding points are generated through potassium bridges or calcium bridges, which helps to form a helix (gel I) and ultimately form a firm gel II; however, when hydrogen or sodium ions are introduced into the carrageenan solution, no binding points are generated and the formation of gel II is prevented. The inventors also found that when the pH is higher than 10, the carrageenan-sodium sulfate form mainly exists; when the pH is in the range of 5-9, the carrageenan-sodium sulfate and carrageenan-hydrogen sulfate forms exist. This will result in weak gels and good film-forming ability; when the pH is lower than the said range, such as lower than 4.6, the carrageenan-hydrogen sulfate form mainly exists, but autohydrolysis will start and the carrageenan will decrease.

[0055] In one aspect, the method comprises using dry carrageenan, preferably carrageenan powder, to produce a carrageenan-based gel. The method comprises combining carrageenan, preferably carrageenan powder, with starch, a first salt, glycerol, and water. In one aspect, the carrageenan-based gel comprises 6-10 wt% carrageenan, 25-35 wt% starch (preferably modified starch), 0.5-1.5 wt% first salt, and 15-25 wt% glycerol and water, the amount of water being such that all components add up to 100 wt%. In one aspect, the carrageenan-based gel is obtained by mixing carrageenan, starch, a first salt, glycerol, and water.

[0056] Examples

[0057] The following examples are provided to further illustrate and explain the present invention and should not be construed as limiting in any way.

[0058] Example 1

[0059] Materials and Preparation Method of Carrageenan and Carrageenan-Based Gel

[0060] As Figure 2 shown, the red seaweed is boiled in hot water at 90 °C to dissolve the seaweed to obtain a paste. The paste is filtered to obtain a pulp (carrageenan concentration of 20 g / l). KCl is mixed with the seaweed pulp and gelled to obtain crude carrageenan. The crude carrageenan is further gelled with KCl to obtain a wet cake. The wet cake is washed with a solution (i.e., a buffered salt alcohol solution) to obtain refined carrageenan. The refined carrageenan is dried to obtain carrageenan.

[0061] The components of the solution and the ratio of the wet cake to the solution are listed in Table 1. The pH value of the carrageenan in Table 1 is obtained by dissolving 1 wt% carrageenan in water to form a carrageenan solution and measuring the pH value of the carrageenan solution.

[0062] The carrageenan-based gel solution comprises 7.5 wt% of carrageenan, 23.5 wt% of hydroxypropyl starch, 1 wt% of sodium phosphate, 20 wt% of glycerol and 48 wt% of water.

[0063] The results including the setting temperature (i.e., the gelling temperature) of the gel solution and the viscosity of the gel solution are also listed in Table 1.

[0064] All the components in the carrageenan are dissolved and stirred at high speed under pressure to reach a temperature of 90 °C. The setting temperature and viscosity are measured using a device called HAAKE viscoester IQ. The setting temperature and viscosity are measured by oscillating temperature ramp, where the temperature is set from 100 °C to 50 °C, the frequency is 1 Hz, and the shear stress is 1 Pa. The viscosity at 90 °C is read, and the temperature when the storage modulus = loss modulus is read as the gelling temperature.

[0065] The molecular weight and source of the samples are listed in Table 2.

[0066] Table 1

[0067]

[0068]

[0069] Table 2

[0070]

[0071] As shown in Table 2, Samples 1-3 and Control Group 1 are from red seaweed 1, and Samples 4-5 and Control Group 2 are from red seaweed 2. Red seaweed 1 is E. Cottonii, which is used to manufacture k-carrageenan, and red seaweed 2 is E. Spinosum, which is used to manufacture i-carrageenan.

[0072] As shown in Table 1, in Sample 1, the solution contains 50% ethanol, 0.04 M sodium citrate and 0.06 M citric acid. In Sample 1, the ratio of the wet cake to the solution is 1:4 (w / w). The wet cake is washed with the solution and dried to obtain the final carrageenan with a pH of 7.8. The sodium ion content is 3.1% (w / w), and the Ca 2+ and K + ion content is 0.5% (w / w). The setting temperature of the gel solution of Sample 1 and the viscosity of the gel solution at 90 °C are 40.5 °C and 210,000 cps, respectively. As shown in Table 2, the average molecular weight of Sample 1 is 621,000 g / mol. The percentage of Sample 1 with a molecular weight less than 50,000 g / mol is 0.73%. The percentage of Sample 1 with a molecular weight less than 100,000 g / mol is 2.95%.

[0073] As shown in Table 1, in Control 1, based on the conventional process, red seaweed undergoes the following steps: alkali treatment (6% KOH, 67 °C, 4 h), hot water extraction (95 °C, 2 h), filtration, gelling with KCl by cooling, first pressing, washing the cake with KCl solution, second pressing, drying the cake, grinding / sieving, and packaging into bags. In Control 1, the ratio of the wet cake to the 30 g / l KCl solution is 1:1 (w / w). The wet cake is washed with 30 g / l KCl solution and dried to obtain the final carrageenan, with a pH of 9.6. The sodium ion content is 0.2% w / w, and the Ca 2+ and K + ion contents are 6.3% w / w. The setting temperature of the gel solution of Sample 1 and the viscosity at 90 °C are 84.0 °C and 1,830,000 cps, respectively. As shown in Table 2, the average molecular weight of Control 1 is 618,000 g / mol. The percentage of Sample 1 with a molecular weight less than 50,000 g / mol is 0.74%. The percentage of Sample 1 with a molecular weight less than 100,000 g / mol is 3.23%.

[0074] From the comparison between the samples and the control group, it can be seen that the pH value of the carrageenan in the samples is lower than that in the control group, and the sodium ion content of the carrageenan in the samples is higher than that in the control group, indicating that a higher level of hydrogen ions and sodium ions has been added to the samples compared to the control group. The Ca 2+ and K + contents in the samples are lower than those in the control group. These results show that, compared with the control group, the addition of hydrogen ions and sodium ions results in a lower setting temperature and lower viscosity without reducing the molecular weight of the carrageenan, indicating that the method of the present invention and the obtained carrageenan-based gel are more suitable for the capsule membrane.

[0075] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the present invention belong. It should also be understood that, unless explicitly defined herein, terms such as those defined in common dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and should not be interpreted in an idealized or overly formal sense.

[0076] Although the present disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes can be made and elements therein can be replaced with equivalents without departing from the scope of the present disclosure. In addition, various modifications can be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the basic scope of the present disclosure. Therefore, the present disclosure is not limited to the specific embodiments disclosed as the best mode for carrying out the present disclosure, but the present disclosure will include all embodiments falling within the scope of the appended claims.

[0077] The representative features of the present invention are set forth in the following clauses, which are independent, or may be combined, or may be combined arbitrarily with one or more features disclosed in the specification.

[0078] The present invention is as described in the following clauses:

[0079] Clause 1: A carrageenan, the carrageenan containing sodium ions,

[0080] wherein the amount of sodium ions is 1-10% w / w or 2-6% w / w based on the carrageenan,

[0081] wherein, when 1% w / w of the carrageenan is dissolved in water to form a carrageenan solution, the pH range of the carrageenan solution is 5-9, 7-9 or 7.8-9,

[0082] wherein hydrogen ions and sodium ions combine with the sulfate groups of the carrageenan to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate, respectively.

[0083] Clause 2: A carrageenan-based gel, the carrageenan-based gel containing carrageenan, starch preferably modified starch, a first salt, glycerol and water,

[0084] wherein the carrageenan contains sodium ions, and the content of the sodium ions is 1-10% w / w of the carrageenan, or 2-6% w / w,

[0085] wherein, when 1% w / w of the carrageenan is dissolved in water to form a carrageenan solution, the pH range of the carrageenan solution is 5-9, 7-9 or 7.8-9,

[0086] wherein hydrogen ions and sodium ions combine with the sulfate groups of the carrageenan to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate, respectively.

[0087] Clause 3: The carrageenan or carrageenan-based gel according to any one of the preceding clauses, wherein the amount of Ca 2+ and K + in the carrageenan is less than 6% w / w, or less than 3.8% w / w, or in the range of 0.1-4% w / w based on the carrageenan.

[0088] Clause 4: The carrageenan or carrageenan-based gel according to any one of the preceding clauses, wherein the average molecular weight of the carrageenan is greater than 500,000 g / mol.

[0089] Clause 5: The carrageenan or carrageenan-based gel according to any one of the preceding clauses, wherein the viscosity of the carrageenan-based gel liquid at 90 °C is less than 1,800,000 cPs, or less than 1,300,000 cPs, or in the range of 100,000-1,800,000 cPs, or in the range of 200,000-1,300,000 cPs.

[0090] Clause 6: The carrageenan or carrageenan-based gel according to any one of the foregoing clauses, wherein the gelling temperature of the carrageenan-based gel solution is in the range of 40 - 75 °C or 40 - 60 °C.

[0091] Clause 7: Use of the carrageenan or carrageenan-based gel according to any one of the foregoing clauses in a capsule membrane.

[0092] Clause 8: A method for manufacturing carrageenan, wherein the method comprises:

[0093] (a) Gelatinizing the seaweed pulp preferably with KCl to obtain crude carrageenan;

[0094] (b) Applying a solution to the crude carrageenan to obtain carrageenan, wherein the solution contains an acid, preferably an organic acid, a second salt other than potassium salt and calcium salt, and an alcohol, and the method does not reduce the molecular weight of the carrageenan.

[0095] Clause 9: The method according to Clause 8, wherein the acid is a natural organic acid.

[0096] Clause 10: The method according to Clause 8 or 9, wherein the acid comprises citric acid, malic acid, tartaric acid, acetic acid or any combination thereof.

[0097] Clause 11: The method according to any one of Clauses 8 - 10, wherein the second salt is a sodium salt.

[0098] Clause 12: The method according to any one of Clauses 8 - 11, wherein the second salt is an organic acid salt, preferably the second salt comprises sodium citrate, trisodium phosphate, sodium tartrate or any combination thereof.

[0099] Clause 13: The method according to any one of Clauses 8 - 12, wherein the alcohol includes C2 - C16 alkanols, C3 - C16 unsaturated alcohols, C3 - C20 cycloaliphatic alcohols, C6 - C20 aromatic alcohols or any combination thereof.

[0100] Clause 14: The method according to any one of Clauses 8 - 13, wherein the method further comprises:

[0101] Before step (a), boiling the seaweed at a temperature above 85 °C to obtain a dissolved seaweed paste, and filtering the dissolved seaweed paste to obtain seaweed pulp.

[0102] Clause 15: The method according to any one of Clauses 8 - 14, wherein in step (a), the crude carrageenan is obtained in the form of a wet cake, and in step (b), the wet cake is washed with the solution to obtain refined carrageenan, and preferably the refined carrageenan is dried to obtain carrageenan.

[0103] Clause 16: The method according to any one of Clauses 8-15, wherein in step (a) the crude carrageenan is obtained in the form of a wet cake, and in step (b) the wet cake is washed with a solution, wherein the weight ratio of the wet cake to the solution is 1:0.1 to 1:50, or 1:0.5 to 1:10.

[0104] Clause 17: The method according to any one of Clauses 8-16, wherein the solution comprises 10-80% or 10-50% of an alcohol solution, and 0.005M-0.2M or 0.01M-0.1M of an acid, and 0.005M-0.2M or 0.01-0.1M of a salt.

[0105] Clause 18: A carrageenan-based gel, the carrageenan-based gel comprising the carrageenan according to any one of Clauses 1, 3-6, and further comprising starch, preferably modified starch, a first salt, glycerol and water.

Claims

1. A carrageenan, the carrageenan containing sodium ions, wherein the amount of sodium ions is 1-10% w / w or 2-6% w / w based on the carrageenan, Among them, when 1% w / w of the carrageenan is dissolved in water to form a carrageenan solution, the pH range of the carrageenan solution is 5-9, 7-9 or 7.8-9, wherein hydrogen ions and sodium ions combine with the sulfate groups of the carrageenan to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate respectively.

2. A carrageenan-based gel, the carrageenan-based gel containing carrageenan, starch preferably modified starch, a first salt, glycerol and water, wherein the carrageenan contains sodium ions, and the content of the sodium ions is 1-10% w / w of the carrageenan, or 2-6% w / w, wherein when 1% w / w of the carrageenan is dissolved in water to form a carrageenan solution, the pH range of the carrageenan solution is 5-9, 7-9 or 7.8-9, wherein hydrogen ions and sodium ions combine with the sulfate groups of the carrageenan to form carrageenan-hydrogen sulfate and carrageenan-sodium sulfate respectively.

3. The carrageenan or carrageenan-based gel according to any one of the preceding claims, wherein the amounts of Ca 2+ and K + in the carrageenan are less than 6% w / w, or less than 3.8% w / w, or in the range of 0.1 - 4% w / w, based on the carrageenan.

4. The carrageenan or carrageenan-based gel according to any one of the preceding claims, wherein the average molecular weight of the carrageenan is greater than 500,000 g / mol.

5. The carrageenan or carrageenan-based gel according to any one of the preceding claims, wherein the viscosity of the carrageenan-based gel solution at 90 °C is lower than 1,800,000 cPs, or lower than 1,300,000 cPs, or in the range of 100,000-1,800,000 cPs, or in the range of 200,000-1,300,000 cPs.

6. The carrageenan or carrageenan-based gel according to any one of the preceding claims, wherein the gelling temperature of the carrageenan-based gel solution is in the range of 40-75 °C or 40-60 °C.

7. Use of the carrageenan or carrageenan-based gel according to any one of the preceding claims in a capsule membrane.

8. A method for manufacturing carrageenan, wherein the method comprises: (a) gelling seaweed pulp preferably with KCl to obtain crude carrageenan; (b) applying a solution to the crude carrageenan to obtain carrageenan, wherein the solution contains an acid, preferably an organic acid, a second salt other than potassium salts and calcium salts, and an alcohol, and the method does not reduce the molecular weight of the carrageenan.

9. The method according to claim 8, wherein the acid is a natural organic acid.

10. The method according to claim 8 or 9, wherein the acid comprises citric acid, malic acid, tartaric acid, acetic acid or any combination thereof.

11. The method according to any one of claims 8-10, wherein the second salt is a sodium salt.

12. The method according to any one of claims 8-11, wherein the second salt is an organic acid salt, or the second salt comprises sodium citrate, trisodium phosphate, sodium tartrate or any combination thereof.

13. The method according to any one of claims 8-12, wherein the alcohol includes C2-C16 alkanols, C3-C16 unsaturated alcohols, C3-C20 cycloaliphatic alcohols, C6-C20 aromatic alcohols or any combination thereof.

14. The method according to any one of claims 8-13, wherein the method further comprises: Before step (a), the seaweed is boiled at a temperature above 85°C to obtain a dissolved seaweed paste, and the dissolved seaweed paste is filtered to obtain a seaweed pulp.

15. The method according to any one of claims 8 - 14, wherein in step (a) the crude carrageenan is obtained in the form of a wet cake, and in step (b) the wet cake is washed with a solution to obtain refined carrageenan, and preferably the refined carrageenan is dried to obtain carrageenan.

16. The method according to any one of claims 8 - 15, wherein in step (a) the crude carrageenan is obtained in the form of a wet cake, and in step (b) the wet cake is washed with a solution, wherein the weight ratio of the wet cake to the solution is 1:0.1 to 1:50, or 1:0.5 to 1:

10.

17. The method according to any one of claims 8 - 16, wherein the solution comprises 10 - 80% or 10 - 50% of an alcohol solution, and 0.005M - 0.2M or 0.01M - 0.1M of an acid, and 0.005M - 0.2M or 0.01 - 0.1M of a salt.

18. A carrageenan-based gel, the carrageenan-based gel comprising the carrageenan according to any one of claims 1, 3 - 6, and further comprising starch, preferably modified starch, a first salt, glycerol, and water.

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