Process for the extraction of carrageenan from seaweed

Abstract

The application discloses a process method for extracting carrageenan from seaweed and relates to the technical field of natural high polymer glue extraction, which comprises the following steps: seaweed after soaking is pressed into a seaweed bed layer with through flow channels; an alkaline conversion liquid is made to flow through the seaweed bed layer so as to convert carrageenan precursors in the seaweed into carrageenan; a cross-linking liquid containing first cations is used to flow through the bed layer so as to form an ion cross-linking coagulation phase; then, a displacement liquid is introduced to remove soluble impurities, and on the basis of keeping the spatial position of the cross-linking coagulation phase stable, an uncross-linking liquid containing a complexing agent and / or second cations is used to make the ion cross-linking coagulation phase change into a movable sol phase and flow out of the bed layer, so as to obtain a glue-containing eluent; finally, the glue-containing eluent is used to be in segmented contact with a glue precipitation medium, so as to grade the carrageenan. The application is favorable for improving the flow uniformity and sequential release characteristics in the process of extracting the carrageenan.

Description

Technical Field

[0001] This invention relates to the field of natural polymer gum extraction technology, and in particular to a process for extracting carrageenan from seaweed. Background Technology

[0002] With the increasing demand for natural polymer colloids in the food, pharmaceutical and cosmetic industries, carrageenan has become a focus of research and application due to its excellent gelling properties, stability and biocompatibility. In the existing technology, carrageenan is extracted from seaweed through alkali treatment and filtration. However, such processes usually do not systematically design the cross-linking locking, displacement retention and reverse decross-linking release process in the seaweed bed.

[0003] Traditional carrageenan extraction processes mainly include seaweed soaking, alkaline extraction, filtration, gelation, dehydration, and drying. The process often relies on the natural penetration and mixing of seaweed particles to dissolve the carrageenan from the seaweed and obtain the final product.

[0004] The main shortcomings of the existing technology are as follows: First, traditional seaweed beds are usually homogeneous stacks with uneven liquid flow. The conversion of carrageenan precursors in the central area is incomplete, resulting in turbid filtrate, insufficient dehydration, and uneven moisture content in dried particles, which reduces product uniformity and stability. Second, the flow direction and sequence of crosslinking liquid, displacement liquid, and decrosslinking liquid in the existing technology lack a systematic design, which makes the formation and dissociation of ionic crosslinked condensate discontinuous and makes it difficult to achieve controllable segmented outflow of carrageenan. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a process for extracting carrageenan from seaweed, comprising: The soaked seaweed is pressed into a seaweed bed with interconnected channels; The alkaline conversion solution is circulated through the seaweed bed to convert the carrageenan precursor in the seaweed into carrageenan while maintaining the overall shape of the seaweed bed. A cross-linking liquid containing a first cation is used to flow through the converted seaweed bed to form an ionic cross-linked condensed phase within the seaweed bed; The replacement solution is introduced from the first side to the second side, allowing it to flow through the seaweed bed to remove soluble impurities while maintaining the spatial stability of the cross-linked condensed phase. A decrosslinking solution containing a complexing agent and / or a second cation is used to flow through the replaced seaweed bed to transform the ionicly crosslinked condensed phase into a migratory sol phase and flow out of the seaweed bed to obtain a sol-containing eluent. The eluent containing carrageenan is brought into contact with the carrageenan precipitation medium in stages to precipitate carrageenan in stages.

[0006] In a preferred embodiment of the process for extracting carrageenan from seaweed according to the present invention, the crosslinking liquid flows unidirectionally from the first side to the second side of the seaweed bed, so that the carrageenan first forms an ion crosslinking barrier layer in the region near the first side, and then advances from the first side to the second side to form the ion crosslinking condensed phase.

[0007] In a preferred embodiment of the process for extracting carrageenan from seaweed according to the present invention, the displacement solution flows unidirectionally from the first side to the second side of the seaweed bed, and the decrosslinking solution flows unidirectionally from the second side to the first side of the seaweed bed, so that the ionic crosslinked condensate disintegrates sequentially in the direction opposite to the flow direction of the crosslinking solution, and the carrageenan flows out of the seaweed bed in segments in the opposite direction.

[0008] In a preferred embodiment of the process for extracting carrageenan from seaweed according to the present invention, the crosslinking liquid causes the seaweed bed to sequentially form a crosslinked dense region, a crosslinked transition region, and an uncrosslinked region along the direction from the first side to the second side; the displacement liquid keeps the spatial positions of the crosslinked dense region and the crosslinked transition region unchanged; and when the decrosslinking liquid flows unidirectionally from the second side to the first side, it first transforms the uncrosslinked region and the crosslinked transition region into a migratory sol phase, and then transforms the crosslinked dense region into a migratory sol phase.

[0009] In a preferred embodiment of the process for extracting carrageenan from seaweed according to the present invention, the displacement solution contains the first cation and does not contain a complexing agent, and the decrosslinking solution is sequentially introduced into the seaweed bed from the second side by a low complexing agent concentration solution and a high complexing agent concentration solution, so as to form a complexing agent concentration front that increases from the second side to the first side in the seaweed bed.

[0010] In a preferred embodiment of the process for extracting carrageenan from seaweed according to the present invention, the low complexing agent concentration solution contains the second cation but does not contain the first cation, and the high complexing agent concentration solution has a higher complexing agent concentration than the low complexing agent concentration solution and does not contain the first cation.

[0011] In a preferred embodiment of the process for extracting carrageenan from seaweed according to the present invention, the concentration of the first cation in the replacement solution is not lower than the concentration of the first cation in the crosslinking solution, and the concentration of the second cation in the low complexing agent concentration solution is higher than the concentration of the first cation in the replacement solution.

[0012] As a preferred embodiment of the process for extracting carrageenan from seaweed according to the present invention, the carrageenan-containing eluent is collected in segments according to the order in which the carrageenan flows out of the seaweed bed, and the eluent that flows out first is in contact with a first carrageenan-forming medium, and the eluent that flows out later is in contact with a second carrageenan-forming medium, wherein the composition of the first carrageenan-forming medium and the second carrageenan-forming medium is different.

[0013] The beneficial effects of this invention are as follows: By constructing a seaweed bed with interconnected flow channels and controlling the flow direction and sequence of the crosslinking liquid, displacement liquid, and decrosslinking liquid, this invention helps to improve the sequential release characteristics of the elution process, increase the segmental differences of the obtained eluent, and help improve the ash content, color, gel strength, rehydration time, and final product pH of the obtained carrageenan product. The average gel strength of the downstream fractions or finished products obtained by this process can reach more than 1500 g / cm², preferably 1534-1605 g / cm². Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the process for extracting carrageenan from seaweed in Example 1.

[0016] Figure 2 This is a schematic diagram of the forward flow of the crosslinking liquid and the formation of bed partitions in Example 1.

[0017] Figure 3 This is a schematic diagram of the sequential release of displacement retention and reverse decrosslinking in Example 1.

[0018] Figure 4 This is a schematic diagram of the seaweed bed formation and through-flow channel structure in Example 1.

[0019] Figure 5 This is a schematic diagram of the alkaline conversion solution flowing through the seaweed bed in Example 1. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] Example 1, referring to Figures 1 to 5 This is the first embodiment of the present invention, which provides a process for extracting carrageenan from seaweed, including: The soaked seaweed is pressed into a seaweed bed with interconnected channels; The alkaline conversion solution is allowed to flow through the seaweed bed to convert the carrageenan precursor in the seaweed into carrageenan while maintaining the overall shape of the seaweed bed. A cross-linking liquid containing the first cation is used to flow through the converted seaweed bed to allow carrageenan to form an ionic cross-linked condensed phase within the seaweed bed. The replacement solution is introduced from the first side to the second side, allowing it to flow through the seaweed bed to remove soluble impurities while maintaining the spatial stability of the cross-linked condensed phase. A decrosslinking solution containing a complexing agent and / or a second cation is used to flow through the replaced seaweed bed to transform the ionicly crosslinked condensed phase into a migratory sol phase and flow out of the seaweed bed, resulting in a sol-containing eluent. The eluent containing carrageenan is brought into contact with the carrageenan precipitation medium in stages to precipitate carrageenan in stages. In this process, the crosslinking liquid flows unidirectionally from the first side to the second side of the seaweed bed, so that the carrageenan first forms an ion-crosslinking barrier layer in the region near the first side, and then advances from the first side to the second side to form the ion-crosslinking condensed phase. The replacement solution flows unidirectionally from the first side to the second side of the seaweed bed, and the decrosslinking solution flows unidirectionally from the second side to the first side of the seaweed bed, so that the ionic crosslinked condensate phase disintegrates sequentially in the opposite direction to the flow direction of the crosslinking solution, and the carrageenan flows out of the seaweed bed in segments in the opposite direction. In this process, the crosslinking liquid causes the seaweed bed to sequentially form a crosslinked dense region, a crosslinked transition region, and an uncrosslinked region along the direction from the first side to the second side. The replacement liquid keeps the spatial positions of the crosslinked dense region and the crosslinked transition region unchanged. When the decrosslinking liquid flows unidirectionally from the second side to the first side, it first transforms the uncrosslinked region and the crosslinked transition region into a migratory sol phase, and then transforms the crosslinked dense region into a migratory sol phase. The diameter and center distance of the forming rod directly affect the size and density of the flow channel. If the diameter is too small or the center distance is too large, the flow channel is prone to blockage and the flow resistance is high. If the diameter is too large or the center distance is too small, the seaweed will be over-compressed, damaging its microstructure and affecting the release of carrageenan. Therefore, the selection and optimization should be made within the range of 3-8 mm diameter and 15-40 mm center distance according to the type of seaweed, particle size and degree of expansion after soaking, to ensure that the seaweed bed maintains the overall shape while forming an effective and stable through flow channel.

[0024] In this embodiment, seaweed particles of Euphorbia milii or Carrageenan are selected as raw materials. After selection, the raw materials are added to a soaking tank. Water is added at a mass ratio of seaweed particles to water of 1:(8-10) for soaking. During the soaking process, the mixture is stirred for 5 minutes every 1 hour. The total soaking time is 3-4 hours. After soaking, the seaweed is drained for 20-40 minutes to keep it moist, plastic and not in a free-flowing state.

[0025] Soaked seaweed is loaded into a bed forming mold. A first porous distribution plate and a second porous distribution plate are respectively set at both ends of the bed forming mold. The first porous distribution plate corresponds to the first side of the seaweed bed, and the second porous distribution plate corresponds to the second side of the seaweed bed. During the filling process, several forming rods are inserted between the first porous distribution plate and the second porous distribution plate along the thickness direction. The diameter of the forming rods is 3-8mm, and the center distance between adjacent forming rods is 15-40mm. After filling, the seaweed is pressed for 3-10 minutes under a pressure of 0.10-0.30MPa. In one specific embodiment, the pressing pressure is 0.18 MPa and the pressing time is 6 min. Then the forming rod is pulled out, so that a flow channel is formed inside the pressed seaweed from the first side to the second side, and a seaweed bed with a through flow channel is obtained. The thickness of the seaweed bed is 120-250 mm, and in one specific embodiment it is 180 mm.

[0026] The above-mentioned seaweed bed is fixed in a flow reactor, and an alkaline conversion solution is introduced from the first side to the second side, so that the alkaline conversion solution flows through the above-mentioned seaweed bed. The alkaline conversion solution is selected from potassium hydroxide solution, sodium hydroxide solution or a combination thereof, preferably a potassium hydroxide solution with a mass fraction of 0.6%-1.5%. In one specific embodiment, the alkaline conversion solution is a 1.0% potassium hydroxide solution by mass, and the temperature of the alkaline conversion solution is 55-85°C, preferably 72°C. The flow rate is 0.6-2.0 BV, preferably 1.2 BV. After the alkaline conversion solution is flowed through, it is kept warm and allowed to stand for 15-40 minutes, preferably 25 minutes, so that the carrageenan precursor in the seaweed is converted into carrageenan. After the conversion is completed, the residual alkaline conversion solution is discharged. The seaweed bed is not mechanically stirred or broken.

[0027] Preferably, after draining the residual alkaline conversion solution, an acidic neutralizing solution and / or washing solution can be introduced into the seaweed bed to neutralize the residual alkaline components and reduce the alkaline residue in subsequent products. The acidic neutralizing solution can be a dilute inorganic acid solution, an organic acid solution, or a combination thereof. After neutralization and post-treatment, the pH of the resulting carrageenan product is preferably controlled between 8 and 11, more preferably not higher than 11. Subsequently, a crosslinking solution is introduced from the first side to the second side, allowing the crosslinking solution to flow through the converted seaweed bed. The crosslinking solution contains a first cation, preferably Ca. 2+ The crosslinking solution can be a calcium chloride solution with a concentration of 0.05-0.50 mol / L, preferably a calcium chloride solution with a concentration of 0.20 mol / L, and the temperature of the crosslinking solution is 20-45℃, preferably 35℃. The flow rate is 0.6-1.5 BV, preferably 1.0 BV. After the crosslinking solution enters the seaweed bed, the carrageenan first forms an ionic crosslinking barrier layer in the region near the first side, and then advances along the direction from the first side to the second side to form an ionic crosslinking condensed phase. After the crosslinking is completed, the seaweed bed forms a crosslinked dense region, a crosslinked transition region and an uncrosslinked region in sequence along the above direction.

[0028] Under the condition that the ion-crosslinked condensed phase is kept in the seaweed bed, a replacement liquid is introduced from the first side to the second side to remove soluble impurities in the seaweed bed. The replacement liquid is an aqueous solution that does not cause the ion-crosslinked condensed phase to disintegrate significantly, preferably an aqueous solution containing the first cation and not containing a complexing agent. In one specific embodiment, the replacement solution is an aqueous solution containing 0.20 mol / L calcium chloride, and the flow rate of the replacement solution is 1.0-3.0 BV, preferably 2.0 BV. During the replacement process, soluble salts, pigments, small molecule impurities and some soluble proteins in the seaweed bed are discharged with the replacement solution, and the spatial positions of the cross-linked dense region and the cross-linked transition region remain unchanged.

[0029] After the replacement is completed, a decrosslinking solution is introduced from the second side to the first side, allowing the decrosslinking solution to flow through the replaced seaweed bed. The decrosslinking solution contains a complexing agent and / or a second cation. The complexing agent is preferably disodium ethylenediaminetetraacetate, and the second cation is preferably derived from Na+.+ In one specific embodiment, the decrosslinking solution is an aqueous solution containing 0.03-0.15 mol / L disodium ethylenediaminetetraacetate and 0.05-0.50 mol / L sodium chloride, preferably an aqueous solution containing 0.08 mol / L disodium ethylenediaminetetraacetate and 0.20 mol / L sodium chloride, and the temperature of the decrosslinking solution is 35-65°C, preferably 50°C; The flow rate is 1.0-2.5 BV, preferably 1.8 BV. After the decrosslinking solution is introduced, the uncrosslinked region and the crosslinking transition region near the second side first transform into a migratory sol phase, and then the crosslinked dense region near the first side transforms into a migratory sol phase. This causes carrageenan to flow out of the seaweed bed in segments from the second side to the first side, resulting in a carrageenan-containing eluent. To facilitate subsequent fractionation and separation of the carrageenan, the eluent is collected in segments with a collection unit of 0.3 BV.

[0030] Table 1-1 Process Steps and Fraction Testing Data Serial Number Steps / Grading Flow direction Medium / material Key components or conditions Temperature (°C) Pressure (MPa) Time (min) Volume (BV) Linear velocity (cm / min) First cation (mol / L) 1 Seaweed bed forming First side → Second side seaweed bed Thickness 180 mm; forming rod diameter 5 mm; center distance 25 mm 24 0.18 6 - - - 2 alkaline conversion First side → Second side KOH conversion solution 1.0 wt% KOH 72 - 25 1.2 0.50 - 3 Crosslinking Lock First side → Second side CaCl2 crosslinking solution 0.20 mol / L CaCl2 35 - 18 1.0 0.45 0.20 4 Displacement and impurity removal First side → Second side CaCl2 replacement solution 0.20 mol / L CaCl2; without complexing agent 28 - 32 2.0 0.40 0.20 5 F1-F2 front-end eluent Second side → First side EDTA / NaCl decrosslinking solution 0.08 mol / L EDTA-2Na + 0.20 mol / LNaCl 50 - 20 0.6 0.40 - 6 F3-F4 mid-stage eluent Second side → First side EDTA / NaCl decrosslinking solution Same as above 50 - 22 0.6 0.40 - 7 F5-F6 downstream eluent Second side → First side EDTA / NaCl decrosslinking solution Same as above 50 - 24 0.6 0.40 - Second cation (mol / L) Complexing agent (mol / L) Outflow conductivity (mS / cm) Outflow turbidity (NTU) Light transmittance (%) Ash content (%) gel strength (g / cm²) Color difference dE Rehydration time (min) pH index Grade score rate (%) - - - - - - - - - - - - - 52.8 35.6 - - - - - - - - - 28.4 12.8 - - - - - - - - 0 11.8 48.6 - - - - - - - 0.2 0.08 15.6 22.4 86.8 18.9 1030 2.7 9.8 9.9 8.1 0.2 0.08 9.8 12.1 92.4 15.6 1350 1.9 8.3 9.4 10.7 0.2 0.08 6.9 9.4 95.1 13.9 1510 1.5 7.6 8.8 10.1 Each eluent fraction containing carrageenan is contacted with a carrageenan precipitation medium to precipitate carrageenan in stages. The carrageenan precipitation medium is an alcohol-water mixture, preferably an alcohol-water mixture with a volume fraction of 70%-85%. In one specific embodiment, the gelation medium is a 75% (v / v) isopropanol aqueous solution. The volume ratio of each gel-containing eluent fraction to the gelation medium is 1:(1.5-3.0), preferably 1:2. After contacting for 15-40 minutes, solid-liquid separation is performed to obtain wet gel. Optionally, the first eluent fraction is combined as the first stage fraction, the middle eluent fraction is combined as the middle stage fraction, and the last eluent fraction is combined as the last stage fraction. Gelation treatment is performed separately to obtain carrageenan fractions of different grades.

[0031] The resulting wet gel can be further processed, including cooling the gel, dehydration, crushing, drying and microwave sterilization.

[0032] Specifically, the wet gel is cooled to below 30°C and left to stand for about 30 minutes to form a gel-like material; then the gel-like material is fed into a dehydration plate frame for dehydration. After dehydration, the film is broken into particles of about 5mm and then sent to a drying device to dry at 60-65℃ until the moisture content of the particles is no higher than 20%. The granules are then fed into a microwave sterilization device, which is preheated to 85°C before microwave sterilization to obtain the carrageenan product.

[0033] To avoid localized bed erosion, channel short circuits, or abnormal pressure drops, it is preferable to control the linear velocity of the low-concentration and high-concentration complexing agent solutions at 0.2-1.0 cm / min. In industrial implementation, the introduction speed can be adaptively adjusted according to the bed thickness, seaweed loading amount, and liquid discharge status.

[0034] Example 2 The replacement solution contains a first cation and no complexing agent. The decrosslinking solution is introduced sequentially from the second side into the seaweed bed, consisting of a low-complexing agent concentration solution and a high-complexing agent concentration solution, to form a complexing agent concentration front that increases from the second side to the first side within the seaweed bed. The low-complexing agent concentration solution contains a second cation and no first cation, while the high-complexing agent concentration solution has a higher complexing agent concentration than the low-complexing agent concentration solution and does not contain the first cation. The concentration of the first cation in the replacement solution is not lower than the concentration of the first cation in the crosslinking solution, the concentration of the second cation in the low-complexing agent concentration solution is higher than the concentration of the first cation in the replacement solution, and the concentration of the complexing agent in the high-complexing agent concentration solution is higher than the concentration of the complexing agent in the low-complexing agent concentration solution. Furthermore, the higher concentration of the second cation in the low-complexing agent concentration solution allows for rapid replacement of the first cation in the initial stage of decrosslinking, while the high-complexing agent concentration solution further enhances the complexation effect, causing the dense crosslinked regions to gradually disintegrate.

[0035] Based on Example 1, this embodiment further defines the composition and introduction order of the replacement solution and the decrosslinking solution to provide a carrageenan extraction process that achieves sequential release through gradient decrosslinking.

[0036] In this embodiment, the seaweed bed treated with the crosslinking solution still maintains a state in which a crosslinked dense region, a crosslinked transition region, and an uncrosslinked region are formed sequentially from the first side to the second side. To avoid prematurely destroying the above-mentioned ionic crosslinked condensed phase during the replacement stage, the replacement solution in this embodiment contains the above-mentioned first cation but does not contain a complexing agent. The first cation is preferably Ca. 2+ In one specific embodiment, the crosslinking solution is a 0.20 mol / L calcium chloride solution, the replacement solution is an aqueous solution containing a first cation, and the concentration of the first cation is not lower than the concentration of the first cation in the crosslinking solution.

[0037] Preferably, the replacement solution is a calcium chloride solution of 0.20-0.35 mol / L, more preferably a calcium chloride solution of 0.25 mol / L. The replacement solution is still introduced into the seaweed bed from the first side to the second side. While removing soluble salts, pigments, small molecule impurities and some soluble proteins, it maintains the local activity of the first cation in the cross-linked dense region and the cross-linked transition region, thereby reducing the possibility of premature decross-linking during the replacement process.

[0038] After the replacement is completed, a low-concentration complexing agent solution and a high-concentration complexing agent solution are sequentially introduced from the second side to the first side to form a complexing agent concentration front that increases from the second side to the first side within the seaweed bed. The low-concentration complexing agent solution contains the second cation but does not contain the first cation, and the high-concentration complexing agent solution has a higher complexing agent concentration than the low-concentration complexing agent solution and does not contain the first cation. The second cation is preferably Na. + It can also be selected from NH4 + Or a combination of the two; The preferred complexing agent is disodium ethylenediaminetetraacetate, but it can also be selected from sodium citrate, sodium hexametaphosphate, or a combination thereof.

[0039] Table 2-1 Gradient unlocking and fractional gelation data Serial Number Steps / Grading Flow direction Medium / material Key components or conditions Temperature (°C) Time (min) Volume (BV) Linear velocity (cm / min) First cation (mol / L) Second cation (mol / L) Complexing agent (mol / L) 1 Replacement retention First side → Second side CaCl2 replacement solution 0.25 mol / L CaCl2; without complexing agent 28 32 2 0.4 0.25 - 0 2 Low complexing agent concentration liquid propulsion Second side → First side Low complexing agent concentration solution 0.35 mol / L NaCl + 0.010 mol / L LEDTA-2Na; without the first cation 40 16 0.6 0.4 0 0.35 0.01 3 High complexing agent concentration solution enhancement Second side → First side High complexing agent concentration solution 0.080 mol / LEDTA-2Na; without the first cation 50 26 1.2 0.4 0 0 0.08 4 Front-end analytical gel - First gelation medium 60 vol% isopropanol + 2.0 wt% KCl 28 20 - - - - - 5 Intermediate-stage analytical gel - Third-stage gel medium 72 vol% isopropanol aqueous solution 28 22 - - - - - 6 Post-stage analytical gel - Second gelation medium 80 vol% isopropanol aqueous solution 28 25 - - - - - 7 Average value of finished products (3 batches) - Carrageenan products Cooling gel → Dehydration → Drying at 60-65℃ → Microwave sterilization at 85℃ 63 180 - - - - - Outflow conductivity (mS / cm) Outflow turbidity (NTU) Light transmittance (%) Ash content (%) gel strength (g / cm²) Color difference dE Rehydration time (min) pH index Grade score rate (%) 10.9 46.8 - - - - - - - 14.2 18.6 89.8 - - - - - - 8.1 10.6 94.6 - - - - - - - 16.8 89.9 17.4 1090 2.4 9.1 9.7 8.3 - 9.8 93.7 14.1 1435 1.7 7.8 9.1 10.6 - 7.4 96.2 12.2 1605 1.2 6.9 8.7 10 - 4.3 96.6 13.3 1534 1.4 7.2 9.2 29 As shown in Table 2-1, the gel strength of the downstream fraction obtained by this process can reach 1605 g / cm², and the average gel strength of the finished product can reach 1534 g / cm², indicating that the average gel strength of the downstream fraction or finished product obtained by this process can reach 1500 g / cm². 2 above.

[0040] In one specific embodiment, the aforementioned low complexing agent concentration solution is an aqueous solution containing 0.35 mol / L sodium chloride and 0.010 mol / L disodium ethylenediaminetetraacetate, and does not contain calcium chloride; The high complexing agent concentration solution is an aqueous solution containing 0.080 mol / L disodium ethylenediaminetetraacetate and does not contain calcium chloride. The concentration of the second cation in the low complexing agent concentration solution is higher than the concentration of the first cation in the replacement solution. The concentration of the complexing agent in the high complexing agent concentration solution is higher than the concentration of the second cation in the low complexing agent concentration solution.

[0041] In this embodiment, Ca in the replacement fluid 2+ The concentration of Na in the low complexing agent solution is 0.25 mol / L. + The concentration of disodium ethylenediaminetetraacetate in the high complexing agent solution is 0.080 mol / L, with a concentration of 0.35 mol / L.

[0042] Preferably, the amount of the low complexing agent concentration solution introduced is 0.4-1.0 BV, more preferably 0.6 BV, and the amount of the high complexing agent concentration solution introduced is 0.8-2.0 BV, more preferably 1.2 BV. The two liquids are introduced sequentially and continuously, without a water transition section between them.

[0043] In this embodiment, the low complexing agent concentration solution first enters the seaweed bed layer from the second side, so that the uncrosslinked area and crosslinked transition area near the second side are first exposed to the high concentration of the second cation environment, and the ionic environment of the region is changed without introducing the first cation. The high complexing agent concentration solution continues to be introduced from the second side, causing the complexing agent concentration to gradually increase from the second side to the first side. Since neither the low complexing agent concentration solution nor the high complexing agent concentration solution contains the first cation, and the complexing agent concentration in the high complexing agent concentration solution is higher than that in the low complexing agent concentration solution, as the decrosslinking solution system continues to advance, the first cation in the crosslinking transition zone and the crosslinking dense zone is gradually weakened and removed, thereby causing the ionic crosslinking condensate phase to disintegrate sequentially from the second side to the first side.

[0044] Preferably, the temperature of the above-mentioned low complexing agent concentration solution is 30-50°C, more preferably 40°C; The temperature of the high complexing agent concentration solution is 40-65℃, more preferably 50℃. The linear velocity of both the low and high complexing agent concentration solutions can be controlled at 0.2-1.0 cm / min, preferably 0.4 cm / min. To avoid local bed scouring or channel short circuits caused by excessively high introduction speed, a lower flow rate can be used in the initial stage of introduction. After the liquid output stabilizes, the flow rate can be increased to the set value. After the low complexing agent concentration solution is introduced, the liquid output collection is not stopped. Instead, the high complexing agent concentration solution is directly switched to continuous introduction. The solution is collected in segments with a collection unit of 0.2-0.3 BV to obtain multiple gel-containing eluent fractions.

[0045] In this embodiment, the key to setting up the decrosslinking liquid system is that by combining the order of "replacement liquid maintenance - low complexing agent concentration liquid first introduction - high complexing agent concentration liquid later introduction", a progressive decrosslinking front is formed inside the seaweed bed. Since the concentration of the first cation in the replacement liquid is not lower than the concentration of the first cation in the crosslinking liquid, the replacement stage will not significantly damage the aforementioned crosslinking dense region and crosslinking transition region. Since the concentration of the second cation in the low complexing agent concentration solution is higher than the concentration of the first cation in the replacement solution, the initial decrosslinking stage can rapidly change the ionic environment of the second side region without replenishing the first cation. Since the concentration of the complexing agent in the high complexing agent concentration solution is higher than the concentration of the second cation in the low complexing agent concentration solution, the complexing agent effect is further enhanced in the subsequent advancement process, thereby causing the decrosslinking front to continue to advance towards the first side, and creating a difference between the first effluent fraction near the second side and the later effluent fraction near the first side.

[0046] In one specific embodiment, the first two gel-containing eluent fractions obtained after introducing the low complexing agent concentration solution can be regarded as the first stage fractions, the middle two gel-containing eluent fractions obtained during the switching process between the low complexing agent concentration solution and the high complexing agent concentration solution can be regarded as the second stage fractions, and the last two gel-containing eluent fractions obtained after continuously introducing the high complexing agent concentration solution can be regarded as the last stage fractions.

[0047] Subsequently, a gelation medium was added to each of the fractions to perform gelation treatment. The gelation medium could be the alcohol-water mixture system in Example 1, so as to avoid shifting the technical focus of this embodiment to the gelation medium itself.

[0048] The wet gel obtained after gelation can continue to be processed using the same post-processing path as in Example 1, including cooling the gel, plate and frame dehydration, crushing, hot air drying at 60-65°C, and microwave sterilization after preheating at 85°C.

[0049] Example 3 The eluent containing carrageenan was collected in segments according to the order in which it flowed out of the seaweed bed. The eluent that flowed out first was in contact with the first eluent release medium, and the eluent that flowed out later was in contact with the second eluent release medium. The first and second eluent release media had different compositions. This embodiment, based on Example 2, further defines the segmented collection method of the carrageenan eluent and the carrageenan separation medium system to provide a process method suitable for obtaining different carrageenan fractions through fractionation.

[0050] The steps of constructing the seaweed bed, the alkaline conversion solution flow-through conversion, the cross-linking solution forward flow-through, the replacement solution maintenance, and the sequential introduction of low-concentration and high-concentration complexing agent solutions to form an increasing complexing agent concentration front can all be carried out in the manner described in Example 2.

[0051] In this embodiment, after the decrosslinking liquid system is introduced from the second side to the first side, the eluent containing carrageenan is collected in segments according to the order in which the carrageenan flows out of the seaweed bed.

[0052] Preferably, multiple gel-containing eluent fractions are continuously collected using 0.2-0.3 BV as a collection unit. In one specific embodiment, the first two gel-containing eluent fractions that flow out first are combined as the first eluent, the next two middle gel-containing eluent fractions that flow out are combined as the middle eluent, and the last two gel-containing eluent fractions that flow out last are combined as the last eluent.

[0053] In this embodiment, the first eluent flowing out is brought into contact with the first gelation medium, and the second eluent flowing out is brought into contact with the second gelation medium. The first gelation medium and the second gelation medium have different compositions.

[0054] Preferably, both gelation media are alcohol-water mixture systems, but they differ in at least one of alcohol content, salt composition, or salt content.

[0055] In one specific embodiment, the first gelation medium is an isopropanol-potassium chloride aqueous solution with a volume fraction of 55%-70%, preferably a mixed medium composed of 60% isopropanol and 1.0%-3.0% potassium chloride by mass, and the second gelation medium is an isopropanol aqueous solution with a volume fraction of 75%-90%, preferably an isopropanol aqueous solution with a volume fraction of 80%, and no potassium chloride is added to the second gelation medium.

[0056] The first eluent and the first carrageenan precipitation medium are mixed at a volume ratio of 1:(1.0-2.5), preferably 1:1.5, and contacted at 20-35℃ for 15-30 min to precipitate carrageenan from the first eluent. Then, solid-liquid separation is performed to obtain the first carrageenan fraction.

[0057] The downstream eluent and the second carrageenan precipitation medium are mixed at a volume ratio of 1:(1.5-3.5), preferably 1:2.5, and contacted at 20-35℃ for 20-40 min to precipitate carrageenan from the downstream eluent. Solid-liquid separation is then performed to obtain the downstream carrageenan fraction.

[0058] The mid-stage eluent can be processed using a third gelation medium different from that used for the front-stage and rear-stage carrageenan fractions; in one specific embodiment, the mid-stage eluent is a 70%-75% volume fraction of isopropanol aqueous solution for gelation to obtain the mid-stage carrageenan fraction.

[0059] In one specific embodiment, after the carrageenan grade is separated from the mother liquor by centrifugation or filtration, it is washed once with an isopropanol aqueous solution with a volume fraction of 60%-75%. After the carrageenan grade is separated from the mother liquor by centrifugation or filtration, it is washed once with an isopropanol aqueous solution with a volume fraction of 75%-90%. The washed carrageenan grades can be stored separately or mixed later according to the product application.

[0060] Each stage of wet gelation can continue to use the common post-processing path in Examples 1 and 2, including cooling gel, dehydration, crushing, drying and microwave sterilization.

[0061] Specifically, the wet carrageenan can be cooled to below 30°C and allowed to stand for about 30 minutes to form a gel-like material. Then, it can be dehydrated, crushed, and dried. The drying temperature is preferably 60-65°C, and the moisture content of the particles is preferably not higher than 20%. After preheating at 85°C, it can be sterilized by microwave to obtain the carrageenan product of the corresponding grade.

[0062] In this embodiment, different eluent fractions containing different types of gum, obtained in the order of outflow, are contacted with different gum-forming media to establish a correspondence between the segmented release at the front end and the graded gum-forming at the back end.

[0063] The differences in transmittance, ash content, gel strength, and rehydration time among the front, middle, and rear fractions demonstrate that collecting fractions in the order of effluent flow and treating them with different gelation media can amplify the property differences between the different fractions.

[0064] Comparative Example 1 This comparative example uses the traditional free gum extraction route to prepare carrageenan products.

[0065] Seaweed granules, such as Eucheuma or Carrageenan, were selected as raw materials. The seaweed granules were added to a soaking tank, with water added at a ratio of 1:10 (seaweed granules to water by weight). During soaking, the mixture was stirred for 5 minutes every hour, with a total soaking time of 3.5 hours, ensuring the seaweed granules were fully soaked and swollen. After soaking, the seaweed was directly transferred to an extraction tank without pressing or shaping, and without constructing a seaweed bed with interconnected flow channels.

[0066] In this comparative example, the extraction step was carried out using steam heating and stirring.

[0067] Specifically, steam is introduced into the extraction tank while stirring is started simultaneously, so that the soaked seaweed is directly heated and dissolved in the extraction tank to form a free colloidal system. The steam extraction temperature is controlled at about 101℃, the pressure inside the tank is controlled at about 0.25MPa, and the extraction time is controlled at about 105min. During the extraction process, the seaweed gradually dissolves to form a high-viscosity colloidal solution. The original extract obtained is measured with a flow time greater than 45s / 100mL using a 4-cup test. This step does not use alkaline conversion solution in the seaweed bed for cross-linking conversion, does not use cross-linking solution containing the first cation to form an ionic cross-linked condensed phase, does not use displacement solution for cross-linking impurity removal, and does not use decross-linking solution containing complexing agent and / or second cation for reverse release.

[0068] After extraction, the rotor pump is turned on to pump the extract into the mixing tank. Hot water is added to the mixing tank for dilution and stirred evenly. The viscosity is then measured using a Ford cup 4 to adjust the outflow time of the extract to about 18.6 s / 100 mL. In one specific embodiment, about 5 tons of hot water is added. The fluidity of the diluted extract is improved, but it still contains a lot of suspended impurities and small tissue fragments.

[0069] After viscosity adjustment, filter aids are added to the extract, with 150 kg of fine perlite filter aid and 80 kg of coarse perlite filter aid added. Stirring continues to ensure the filter aids are evenly dispersed in the extract. Simultaneously, hot water, fine perlite filter aid, and coarse perlite filter aid are added to the pre-coating tank for pre-coating treatment, with 60 kg of fine perlite filter aid and 75 kg of coarse perlite filter aid added. The pre-coating time is controlled at 15 minutes. After pre-coating, the diluted extract with added filter aids is pumped into a plate and frame filter for filtration. The turbid liquid flowing out in the initial stage of filtration enters the turbid liquid tank. After the liquid reaches a clear state, the reversing valve is switched to allow the filtrate to enter the clearing tank.

[0070] In this comparative example, the stable filtration time of the plate and frame filtration stage is about 95 minutes. About 30 minutes after the start of filtration, the filtration pressure difference rises rapidly, and it is necessary to switch the flow direction of turbid liquid and clear liquid according to the state of the effluent. The turbidity of the clear liquid after filtration is about 13.8 NTU, and the transmittance is about 89.2%.

[0071] The filtered clear gum solution enters a plate heat exchanger for cooling. By adjusting the gum solution valve and the cooling water valve, the outlet temperature of the gum solution is reduced to below 30°C. Then, it is transferred to a gel tank and left to stand for 30 minutes to form a gel. The gelled gum block is then sent to a dehydration plate frame for dehydration. After dehydration, the gum sheet is removed and broken into granules, which are then sent to a drying device for hot air drying at 60-65°C until the moisture content of the granules drops to about 20%. The dried granules are then sent to a microwave sterilization device. The device is preheated to 85°C before microwave sterilization to obtain the carrageenan product.

[0072] This comparative example adopts the traditional process route of steam extraction, dilution and viscosity adjustment, filtration aid and unified post-treatment, without establishing the forward cross-linking locking, displacement retention, reverse decross-linking release, segmented collection and graded gelation process within the seaweed bed.

[0073] The steam-heated and stirred free colloid extraction-dilution and viscosity adjustment-filtration aid-unified post-processing process shown in Comparative Example 1 has a relatively low overall product yield. In comparison, the overall product yield of the process of the present invention can reach more than 25%, preferably 28%-29%.

[0074] Comparative Example 2 This comparative example illustrates the impact on product quality and process stability when a cross-linking locking step is omitted in the case of using a seaweed bed through-flow treatment route, and instead, de-cross-linking release and gelation treatment are performed directly after alkaline conversion. The raw material used is Eucheuma or Carrageenan seaweed granules.

[0075] Specifically, seaweed granules are added to a soaking tank, and water is added at a mass ratio of 1:10 for soaking. During the soaking process, the mixture is stirred for 5 minutes every 1 hour, and the total soaking time is controlled to be 3.5 hours, so that the seaweed granules are fully soaked and swollen.

[0076] After soaking, the soaked seaweed is placed into a molding mold and a seaweed bed with through-flow channels is formed under pressing conditions. In one specific embodiment, the thickness of the seaweed bed is controlled to be about 180 mm, the diameter of the molding rod is 5 mm, the center distance of the molding rod is 25 mm, the pressing pressure is controlled to be about 0.18 MPa, and the holding time is about 6 minutes. After the molding rod is removed, a through-flow channel structure is formed inside the seaweed bed along the thickness direction.

[0077] Subsequently, the seaweed bed is fixed in a flow reactor, allowing the alkaline conversion solution to enter from the first side and exit from the second side, so as to complete the conversion of carrageenan precursor to carrageenan while maintaining the overall shape of the seaweed bed. In one specific embodiment, the alkaline conversion solution is a KOH solution with a mass fraction of 0.98%~1.00%, the conversion temperature is controlled at 71~72℃, the flow rate is controlled at about 1.15 BV, and the seaweed bed is allowed to stand for about 24 minutes after conversion. After this step, the seaweed bed maintains its overall shape, and a carrageenan phase that can be further released has been formed inside the bed.

[0078] Unlike the embodiments of the present invention, in this comparative example, after the alkaline conversion is completed, a crosslinking liquid containing the first cation is not introduced into the seaweed bed to form an ionic crosslinking condensed phase, nor is a forward crosslinking barrier layer established in the seaweed bed using the crosslinking liquid. Instead, after the conversion is completed, a decrosslinking liquid is directly introduced from the second side of the seaweed bed to the first side, allowing it to flow counter-currently through the converted seaweed bed to promote the release and outflow of carrageenan from the seaweed bed.

[0079] In one specific embodiment, the decrosslinking solution is a mixed solution composed of 0.08 mol / L EDTA-2Na and 0.20 mol / L NaCl. The total introduction volume is controlled at about 1.75 BV, the introduction temperature is about 50°C, and the linear velocity is controlled at about 0.40 cm / min. To facilitate subsequent processing, the effluent can be collected in segments with a collection unit of 0.3 BV, and the effluent from the first, middle and last segments can be collected separately.

[0080] The obtained carrageenan eluent was contacted with the carrageenan precipitation medium to precipitate carrageenan. In one specific embodiment, 75 vol% isopropanol aqueous solution was used as the carrageenan precipitation medium for each eluent. The precipitated wet carrageenan was subjected to solid-liquid separation, cooling gelation, dehydration, crushing, hot air drying at 60-65°C, and microwave sterilization after preheating at 85°C to obtain the carrageenan product.

[0081] Observations and tests on the obtained products and process status show that, without setting a cross-linking locking step, although the alkaline-converted seaweed bed can still release carrageenan and obtain the final product through reverse elution, the separation degree between the carrageenan release front and the soluble impurity migration front is relatively low in the early stage of introducing the decross-linking solution, the content of suspended impurities in the effluent is high, and the clarity of some fractions is poor.

[0082] Correspondingly, the ash content, color, and gel strength of the obtained products all showed certain fluctuations, and the rehydration time was relatively prolonged. The average test results of the three batches showed that the total yield of the product was about 28.2%, the ash content was about 17.6%, the gel strength was about 1309 g / cm², the color difference dE was about 2.6, and the rehydration time was about 10.1 min.

[0083] In this comparative example, the seaweed bed and alkaline conversion step still exist. However, because a crosslinking solution containing the first cation was not set up to ionically crosslink and lock the converted carrageenan, the converted carrageenan did not form a stable ionically crosslinked condensed phase inside the seaweed bed, nor did it form a structural basis that is conducive to subsequent displacement impurity removal and reverse sequential release. Therefore, this comparative example can be used to illustrate the role of the crosslinking and locking step in reducing impurity entrainment, improving the clarity of the eluent, and improving the overall performance of the finished product.

[0084] Comparative Example 3 This comparative example illustrates the impact on product quality and process stability when a cross-linking locking step is implemented using a seaweed bed through-flow treatment route, but without a replacement solution for cross-flow impurity removal, and instead, de-cross-linking release and gelation treatment are performed directly after cross-linking locking. The raw material used is Euphorbia milii or Carrageenan seaweed granules.

[0085] Specifically, seaweed granules are added to a soaking tank, and water is added at a mass ratio of 1:10 for soaking. During the soaking process, the mixture is stirred for 5 minutes every 1 hour, and the total soaking time is controlled to be 3.5 hours, so that the seaweed granules are fully soaked and swollen.

[0086] After soaking, the soaked seaweed is placed into a molding mold and a seaweed bed with through-flow channels is formed under pressing conditions. In one specific embodiment, the thickness of the seaweed bed is controlled to be about 180 mm, the diameter of the molding rod is 5 mm, the center distance of the molding rod is 25 mm, the pressing pressure is controlled to be about 0.18 MPa, and the holding time is about 6 minutes. After the molding rod is removed, a through-flow channel structure is formed inside the seaweed bed along the thickness direction.

[0087] Subsequently, the seaweed bed is fixed in a flow reactor, allowing the alkaline conversion solution to enter from the first side and exit from the second side, so as to complete the conversion of carrageenan precursor to carrageenan while maintaining the overall shape of the seaweed bed. In one specific embodiment, the alkaline conversion solution is a 0.99% KOH solution, the conversion temperature is controlled at 71~72℃, the flow rate is controlled at about 1.16 BV, and the seaweed bed is allowed to stand for about 24 minutes after conversion. After this step, the seaweed bed maintains its overall shape, and a carrageenan phase that can be further cross-linked has been formed inside the bed.

[0088] After alkaline conversion, a crosslinking solution containing the first cation is introduced from the first side to the second side of the seaweed bed, causing the converted carrageenan to form an ionicly crosslinked condensed phase within the seaweed bed. In one specific embodiment, the crosslinking solution is a 0.21 mol / L CaCl2 solution, the introduction volume is approximately 1.00 BV, and the introduction temperature is approximately 35°C. After the introduction is completed, a relatively obvious crosslinked dense zone is formed on the inlet side of the seaweed bed, and it gradually advances into the bed along the flow direction. After this step, the carrageenan within the seaweed bed is in an ionicly crosslinked locked state.

[0089] Unlike the embodiments of the present invention, in this comparative example, after the cross-linking locking is completed, the replacement solution is no longer introduced to remove soluble impurities from the seaweed bed through flow. Instead, the de-cross-linking solution is introduced directly from the second side to the first side of the seaweed bed, causing the ionic cross-linked condensed phase to revert to a migratory sol phase and flow out of the seaweed bed. In one specific embodiment, a low complexing agent concentration solution is introduced first, followed by a high complexing agent concentration solution. The low complexing agent concentration solution is a mixed solution composed of 0.35 mol / L NaCl and 0.012 mol / L EDTA-2Na, and the high complexing agent concentration solution is a 0.085 mol / L EDTA-2Na solution. The total introduction volumes are approximately 0.55 BV and 1.20 BV, respectively. The introduction temperature is controlled at 40~50℃, and the linear velocity is controlled at approximately 0.40 cm / min. To facilitate subsequent processing, the effluent can be collected in segments of 0.2~0.3 BV, and the effluent from the first, middle, and last segments is collected separately.

[0090] The obtained carrageenan-containing eluents were contacted with different eluents to precipitate carrageenan. In one specific embodiment, the first eluent consisted of 60 vol% isopropanol and 2.0 wt% KCl, the second eluent consisted of 81 vol% isopropanol aqueous solution, and the third eluent consisted of 72-73 vol% isopropanol aqueous solution. The precipitated wet carrageenan was then subjected to solid-liquid separation, followed by cooling gelation, dehydration, crushing, hot air drying at 60-65°C, and microwave sterilization after preheating at 85°C to obtain the carrageenan product.

[0091] Observation and testing of the obtained product and process status revealed that, although a relatively clear reverse decrosslinking and release process could be formed and the final product could be obtained when a crosslinking locking step was set but no displacement and impurity removal step was set, the soluble salts, pigments and some small molecule impurities remaining in the seaweed bed after crosslinking locking were not removed in advance. During the subsequent decrosslinking and release process, the above impurities would flow out with carrageenan, thereby reducing the purity of some eluent fractions. This affected the ash content and color index of the obtained product. The average test results of three batches showed that the total product yield was about 28.7%, the ash content was about 16.8%, the gel strength was about 1371 g / cm², the color difference dE was about 2.2, and the rehydration time was about 9.2 min.

[0092] In this comparative example, the seaweed bed, alkaline conversion step, and cross-linking locking step were all set up, and reverse decross-linking release was achieved. However, because soluble impurities in the seaweed bed were not removed by the displacement liquid after cross-linking locking, a certain amount of impurities were still carried in the subsequently released gel-containing eluent. Therefore, this comparative example can be used to illustrate the role of the displacement impurity removal step in reducing impurity entrainment, improving the purity of the finished product, and improving the overall color index.

[0093] Comparative Example 4 This comparative example illustrates the impact on the grading effect and overall performance of the obtained product when, in the case of a seaweed bed through-flow treatment route, a cross-linking locking step, and a displacement and impurity removal step, different compositions of the gelation media are not used according to the outflow sequence of the gel-containing eluent in the subsequent gelation stage, but instead the same gelation media is used for gelation treatment of each section of the gel-containing eluent. The raw material used is seaweed granules of Euphorbia milii or Carrageenan.

[0094] Specifically, seaweed particles are added to a soaking tank, and water is added at a mass ratio of seaweed particles to water of 1:10 for soaking. During the soaking process, the mixture is stirred for 5 minutes every 1 hour, and the total soaking time is controlled to be 3.5 hours, so that the seaweed particles are fully soaked and swelled. After soaking, the soaked seaweed is loaded into a molding mold, and a seaweed bed with through-flow channels is formed under pressing conditions. In one specific embodiment, the thickness of the seaweed bed is controlled to be about 180 mm, the diameter of the molding rod is 5 mm, the center distance of the molding rod is 25 mm, the pressing pressure is controlled to be about 0.18 MPa, and the holding time is about 6 minutes. After the molding rod is removed, a through-flow channel structure is formed inside the seaweed bed along the thickness direction.

[0095] Subsequently, the seaweed bed is fixed in a flow reactor, allowing the alkaline conversion solution to enter from the first side and exit from the second side, so as to complete the conversion of carrageenan precursor to carrageenan while maintaining the overall shape of the seaweed bed. In one specific embodiment, the alkaline conversion solution is a 0.97% KOH solution, the conversion temperature is controlled at 70~71℃, the flow rate is controlled at about 1.13 BV, and the seaweed bed is allowed to stand for about 23 minutes after conversion. After this step, the seaweed bed maintains its overall shape, and a carrageenan phase that can be further cross-linked is formed inside the bed.

[0096] After alkaline conversion, a crosslinking solution containing the first cation is introduced from the first side to the second side of the seaweed bed, causing the converted carrageenan to form an ionic crosslinked condensed phase within the seaweed bed. In one specific embodiment, the crosslinking solution is a 0.22 mol / L CaCl2 solution, the introduction volume is approximately 0.99 BV, and the introduction temperature is 34~35℃. After the crosslinking solution enters the seaweed bed, a crosslinked dense zone is formed near the first side, and it gradually advances into the bed along the flow direction. Subsequently, while the ionic crosslinked condensed phase remains within the seaweed bed, a replacement solution is continued to be introduced from the first side to the second side to remove soluble impurities from the seaweed bed.

[0097] In one specific embodiment, the replacement solution is a 0.27 mol / L CaCl2 solution, which does not contain a complexing agent. The introduction volume is about 1.88 BV, and the introduction temperature is about 28°C. After this step, soluble salts, pigments, and some small molecule impurities in the seaweed bed are removed.

[0098] After the replacement is completed, low-concentration complexing agent solution and high-concentration complexing agent solution are sequentially introduced from the second side to the first side of the seaweed bed, so that the ion-crosslinked condensed phase gradually transforms into a migratory sol phase and flows out of the seaweed bed. In one specific embodiment, the low-concentration complexing agent solution is a mixed solution composed of 0.35 mol / L NaCl and 0.012 mol / L EDTA-2Na, and the high-concentration complexing agent solution is a 0.085 mol / L EDTA-2Na solution. The total introduced volume is approximately 0.57 BV and 1.17 BV, respectively. The introduced temperature is controlled at 40~50℃, and the linear velocity is controlled at approximately 0.40 cm / min. To facilitate subsequent processing, the effluent can be collected in segments with a collection unit of 0.2~0.3 BV, and the effluent from the first, middle and last segments can be collected separately.

[0099] Unlike the embodiments of the present invention, in this comparative example, although the eluent containing gum was collected in segments, different eluent media with different compositions were not used for the eluents in the first, middle and last segments according to their compositional differences. Instead, 75 vol% isopropanol aqueous solution was used as the eluent medium for all segments of the eluent. After solid-liquid separation, the precipitated wet gum was subjected to cooling gelation, dehydration, crushing, hot air drying at 60-65°C, and microwave sterilization after preheating at 85°C to obtain the carrageenan product.

[0100] Observation and testing of the obtained products and process status revealed that, with the seaweed bed, cross-linking locking, displacement impurity removal, and gradient decross-linking release already in place, carrageenan products could still be obtained using the same gelation medium, and the overall process could be implemented smoothly. However, due to the differences in ionic environment, impurity content, and colloidal state of the eluents in the front, middle, and rear stages, the selective gelation effect between different fractions was weakened when the same gelation medium was used. This resulted in some impurities in the front stage and some high-quality colloids in the rear stage not being further distinguished during the gelation stage, thus affecting the overall color, ash content, and gel strength of the final product. The average test results of the three batches showed that the total product yield was approximately 29.0%, the ash content was approximately 14.7%, the gel strength was approximately 1453 g / cm², the color difference dE was approximately 1.8, and the rehydration time was approximately 8.0 min.

[0101] In this comparative example, the steps of seaweed bed construction, alkaline conversion, cross-linking locking, displacement impurity removal, and gradient decross-linking release were all set, and the gel-containing eluent was collected in segments according to the effluent sequence. However, since different gelation media with different compositions were not used for different fractions in the gelation stage, the fractional differences formed by segmented elution were not fully utilized in the gelation stage. Therefore, this comparative example can be used to illustrate that the gel-containing eluent collected in segments is contacted with gelation media of different compositions, which has a positive effect on further improving the overall color of the product, reducing ash content, and improving gelation performance.

[0102] Comparative Example 5 This comparative example illustrates the impact on the sequential release characteristics of the gel-containing eluent and the overall performance of the resulting product when, in the case of using a seaweed bed through-flow treatment route, setting a cross-linking locking step, and setting a displacement and impurity removal step, the cross-linking release stage does not use a reverse flow method opposite to the aforementioned cross-linking and displacement steps, but instead continues to use the same flow direction as the aforementioned steps for cross-linking release. The raw material used is Euphorbia milii or Carrageenan seaweed granules.

[0103] Specifically, seaweed particles are added to a soaking tank, and water is added at a mass ratio of seaweed particles to water of 1:10 for soaking. During the soaking process, the mixture is stirred for 5 minutes every 1 hour, and the total soaking time is controlled to be 3.5 hours, so that the seaweed particles are fully soaked and swelled. After soaking, the soaked seaweed is loaded into a molding mold, and a seaweed bed with through-flow channels is formed under pressing conditions. In one specific embodiment, the thickness of the seaweed bed is controlled to be about 180 mm, the diameter of the molding rod is 5 mm, the center distance of the molding rod is 25 mm, the pressing pressure is controlled to be about 0.18 MPa, and the holding time is about 6 minutes. After the molding rod is removed, a through-flow channel structure is formed inside the seaweed bed along the thickness direction.

[0104] Subsequently, the seaweed bed is fixed in a flow reactor, allowing the alkaline conversion solution to enter from the first side and exit from the second side, so as to complete the conversion of carrageenan precursor to carrageenan while maintaining the overall shape of the seaweed bed. In one specific embodiment, the alkaline conversion solution is a 0.98% KOH solution, the conversion temperature is controlled at 71~72℃, the flow rate is controlled at about 1.14 BV, and the seaweed bed is allowed to stand for about 24 minutes after conversion. After this step, the seaweed bed maintains its overall shape, and a carrageenan phase that can be further cross-linked is formed inside the bed.

[0105] After alkaline conversion, a cross-linking solution containing the first cation is introduced from the first side to the second side of the seaweed bed, causing the converted carrageenan to form an ionic cross-linked condensed phase within the seaweed bed. In one specific embodiment, the cross-linking solution is a 0.21 mol / L CaCl2 solution, the introduction volume is approximately 1.00 BV, and the introduction temperature is controlled at around 35°C. Subsequently, while the ionic cross-linked condensed phase remains within the seaweed bed, a replacement solution is continued to be introduced from the first side to the second side to remove soluble impurities from the seaweed bed. In one specific embodiment, the replacement solution is a 0.25 mol / L CaCl2 solution without complexing agents, the introduction volume is approximately 1.90 BV, and the introduction temperature is controlled at around 28°C. After this step, some soluble salts, pigments, and small molecule impurities in the seaweed bed are removed.

[0106] Unlike the embodiments of the present invention, in this comparative example, after the replacement is completed, the decrosslinking solution is not introduced from the second side of the seaweed bed to the first side in a reverse direction, but is still introduced from the first side of the seaweed bed to the second side, so that the decrosslinking release direction is consistent with the flow direction of the aforementioned crosslinking solution and replacement solution. In a specific embodiment, a low complexing agent concentration solution is introduced first, followed by a high complexing agent concentration solution. The low complexing agent concentration solution is a mixed solution composed of 0.35 mol / L NaCl and 0.012 mol / L EDTA-2Na, and the high complexing agent concentration solution is a 0.085 mol / L EDTA-2Na solution. The total introduced amounts are approximately 0.58 BV and 1.16 BV, respectively. The introduced temperature is controlled at 40~50℃, and the linear velocity is controlled at approximately 0.40 cm / min. To facilitate subsequent processing, the effluent can also be collected in segments of 0.2~0.3 BV, and the effluent from the first, middle, and last segments can be collected separately.

[0107] The obtained carrageenan-containing eluents are contacted with different eluents to precipitate carrageenan. In one specific embodiment, the first eluent is a first eluent composed of 60 vol% isopropanol and 2.0 wt% KCl, the second eluent is a 72-73 vol% isopropanol aqueous solution, and the third eluent is an 80-81 vol% isopropanol aqueous solution. The precipitated wet carrageenan is then subjected to solid-liquid separation, followed by cooling gelation, dehydration, crushing, hot air drying at 60-65°C, and microwave sterilization after preheating at 85°C to obtain the carrageenan product.

[0108] Observation and testing of the obtained products and process status revealed that, with the seaweed bed, cross-linking locking, displacement impurity removal, and gradient decross-linking solution already in place, if the decross-linking solution, cross-linking solution, and displacement solution flow in the same direction, the release front of carrageenan overlaps with the original cross-linking gradient direction within the seaweed bed. This results in faster release in some areas and delayed release in others. The fractional differences formed by the eluent containing carrageenan in the outflow order are not clear enough, and the properties of some front and middle fractions overlap significantly. Correspondingly, although carrageenan products can be obtained, the differences in purity and gel performance between different fractions are weakened after segmented collection, which is not conducive to further amplifying the separation effect through differential gelation. The average test results of three batches show that the total product yield is approximately 28.8%, the ash content is approximately 15.2%, the gel strength is approximately 1416 g / cm², the color difference dE is approximately 1.9, and the rehydration time is approximately 8.4 min.

[0109] In this comparative example, the steps of seaweed bed construction, alkaline conversion, cross-linking locking, displacement impurity removal, and segmented gelation were all set, and the decrosslinking solution was introduced in sequence with low and high complexing agent concentrations. However, because the decrosslinking solution did not adopt a reverse flow method opposite to that of the cross-linking and displacement solutions, it was difficult to form a clearer and more controllable sequential release process inside the seaweed bed, thereby weakening the synergistic effect of segmented collection and graded gelation. Therefore, this comparative example can be used to illustrate the role of using a reverse flow method for the decrosslinking solution in improving the clear fraction formation effect and improving the overall performance of the product.

[0110] 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 process for extracting carrageenan from seaweed, characterized in that, include: Soaked seaweed is pressed into a seaweed bed with through channels, the seaweed bed having a first side and a second side opposite to each other; The alkaline conversion solution is circulated through the seaweed bed to convert the carrageenan precursor in the seaweed into carrageenan while maintaining the overall shape of the seaweed bed. A cross-linking liquid containing a first cation is used to flow through the converted seaweed bed to form an ionic cross-linked condensed phase within the seaweed bed; The replacement solution is introduced from the first side to the second side, allowing it to flow through the seaweed bed to remove soluble impurities while maintaining the spatial stability of the cross-linked condensed phase. A decrosslinking solution containing a complexing agent and / or a second cation is used to flow through the replaced seaweed bed to transform the ionicly crosslinked condensed phase into a migratory sol phase and flow out of the seaweed bed to obtain a sol-containing eluent. Carrageenan is fractionally precipitated by contacting the carrageenan-containing eluent with the carrageenan precipitation medium in stages.

2. The process for extracting carrageenan from seaweed as described in claim 1, characterized in that, The crosslinking liquid flows unidirectionally from the first side to the second side of the seaweed bed, so that the carrageenan first forms an ionic crosslinking barrier layer in the region near the first side, and then advances from the first side to the second side to form the ionic crosslinking condensed phase.

3. The process for extracting carrageenan from seaweed as described in claim 2, characterized in that, The replacement solution flows unidirectionally from the first side to the second side of the seaweed bed, and the decrosslinking solution flows unidirectionally from the second side to the first side of the seaweed bed, so that the ionic crosslinked condensate disintegrates sequentially in the opposite direction to the flow direction of the crosslinking solution, and the carrageenan flows out of the seaweed bed in segments in the opposite direction.

4. The process for extracting carrageenan from seaweed as described in claim 3, characterized in that, The crosslinking liquid causes the seaweed bed to sequentially form a crosslinked dense region, a crosslinked transition region, and an uncrosslinked region along the direction from the first side to the second side. The replacement liquid keeps the spatial positions of the crosslinked dense region and the crosslinked transition region unchanged. When the decrosslinking liquid flows unidirectionally from the second side to the first side, it first transforms the uncrosslinked region and the crosslinked transition region into a migratory sol phase, and then transforms the crosslinked dense region into a migratory sol phase.

5. The process for extracting carrageenan from seaweed as described in claim 4, characterized in that, The replacement solution contains the first cation and does not contain a complexing agent. The decrosslinking solution is introduced into the seaweed bed layer from the second side in sequence by a low complexing agent concentration solution and a high complexing agent concentration solution, so as to form a complexing agent concentration front that increases from the second side to the first side in the seaweed bed layer.

6. The process for extracting carrageenan from seaweed as described in claim 5, characterized in that, The low complexing agent concentration solution contains the second cation but does not contain the first cation, and the high complexing agent concentration solution has a higher complexing agent concentration than the low complexing agent concentration solution and does not contain the first cation.

7. The process for extracting carrageenan from seaweed as described in claim 6, characterized in that, The concentration of the first cation in the replacement solution is not lower than the concentration of the first cation in the crosslinking solution, and the concentration of the second cation in the low complexing agent concentration solution is higher than the concentration of the first cation in the replacement solution.

8. The process for extracting carrageenan from seaweed as described in claim 7, characterized in that, The carrageenan-containing eluent is collected in segments according to the order in which it flows out of the seaweed bed. The eluent that flows out first is in contact with the first eluent-forming medium, and the eluent that flows out later is in contact with the second eluent-forming medium. The first eluent-forming medium and the second eluent-forming medium have different compositions.

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