Grafted pectin composition

Abstract

The application provides a grafted pectin composition, and relates to the technical field of pectin.The grafted pectin composition is composed of grafted pectin and at least one of an acrylic polymer and a saccharide compound, the grafted pectin is a polyether structure chemically grafted on the pectin, the esterification degree of the pectin is 40-65%, and the mole proportion of polyoxyethylene in the polyether structure is not more than 30%.The grafted pectin and the grafted pectin composition can respectively become gels in an acidic environment.

Description

Technical Field

[0001] This invention belongs to the field of pectin technology and relates to a grafted pectin composition. Background Technology

[0002] Based on the degree of esterification, pectin can be divided into high-ester pectin (esterification degree > 50%) and low-ester pectin (esterification degree < 50%). Pectin can form gels and has a significant impact on its various applications, but pectin itself cannot form gels. High-ester pectin gel formation typically requires the addition of a high concentration of sucrose (>65%) and a pH < 3.5. Most of the carboxyl groups on high-ester pectin undergo methylation, acetylation, and amidation. In an acidic environment (pH < 3.5), the remaining carboxyl groups are converted to carboxyl groups, reducing the hydrophilicity of high-ester pectin. Furthermore, the added high concentration of sucrose draws away water molecules from the surrounding pectin, disrupting its hydration layer. This forces the molecular chains of high-ester pectin closer together and causes hydrophobic interactions, thus forming a gel. Low-ester pectin can form gels over a wider pH range (3-5). The principle is mainly based on the electrostatic interaction between divalent cations (such as calcium ions) and ionized carboxyl groups, forming an eggshell structure to create and stabilize the gel.

[0003] For some applications where high-ester pectin is in a gel state, high concentrations of sucrose are detrimental, such as in beverages. Therefore, pectin needs to be modified to form a gel independently, for example, in food applications where it can form a gel under gastric acid conditions, thereby increasing satiety or slowing down the rate at which food is broken down by gastric acid. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention provides a grafted pectin composition.

[0005] The technical solution of the present invention is as follows:

[0006] A grafted pectin composition, wherein the raw material components include grafted pectin, and at least one of an acrylic polymer and a sugar compound; The grafted pectin is a chemically grafted polyether structure onto pectin; The polyether structure is selected from polypropylene glycol monomethyl ether structure or copolymer structure of polyoxyethylene and polyoxypropylene. When the polyether structure is selected from the copolymer structure of polyoxyethylene and polyoxypropylene, the molar proportion of polyoxyethylene in the polyether structure does not exceed 30%; The 0.1-2wt% aqueous solution of the grafted pectin is in a gel state at 10-50℃ and pH≤3. The degree of esterification of the pectin is 40-65%.

[0007] Preferably, the grafting rate of the polyether structure is 3-15%.

[0008] Preferably, when the polyether structure is selected from polypropylene glycol monomethyl ether, the number-average molecular weight of the polyether structure is 600-6000 g / mol.

[0009] Preferably, when the polyether structure is selected from the copolymer structure of polyethylene oxide and polypropylene oxide, the number average molecular weight of the polyether structure is 800-3000 g / mol.

[0010] Preferably, the grafted pectin is obtained by reacting the pectin with a polyether of the structure shown in formula (1); R 1 (OCH2CH2) m (OCH2CHCH3) n R 2 (1) Among them, R 1 Selected from C1-C4 alkyl groups, R 2 Selected from hydroxyl or primary amino groups, m≥0, n>0.

[0011] Preferably, the acrylic polymer is selected from one or more of sodium polyacrylate, sodium acrylate / acrylate copolymer, sodium acrylate / methacrylate copolymer, polysodium methacrylate, and sodium methacrylate / methacrylate copolymer.

[0012] Preferably, the weight ratio of the grafted pectin to the acrylic polymer is 1:0.1-2.

[0013] Preferably, the carbohydrate compound is selected from one or more sugar alcohols and oligosaccharides.

[0014] More preferably, the sugar alcohol compound is selected from one or more of isomaltitol, maltitol, sorbitol and xylitol; The oligosaccharide is selected from one or more of maltose, fructooligosaccharides, stachyose, and dextran.

[0015] Preferably, the weight ratio of the grafted pectin to the carbohydrate compound is 1:0.1-1.

[0016] The beneficial effects of this invention are: (1) In this invention, a polyether structure is introduced into pectin with a certain degree of esterification through chemical grafting. The polyether structure reduces the hydrophilicity of pectin under acidic conditions and its ability to bind with water molecules, thus enabling it to form a gel on its own under acidic conditions without the need for the action of high concentrations of sucrose. Moreover, the introduced polyether structure has a certain degree of flexibility, which improves the flexibility of the gel-state pectin, resulting in better flexibility compared to gels formed by high-ester pectin and sucrose.

[0017] (2) The present invention adds acrylic polymers and / or sugar compounds to grafted pectin to form a grafted pectin composition. The obtained grafted pectin composition has better gel properties and the obtained gel has higher mechanical strength than the gel formed by grafted pectin alone. Attached Figure Description

[0018] Figure 1 The image shows the FT-IR spectrum of the ungrafted pectin in Example 1.

[0019] Figure 2 The image shows the FT-IR spectrum of the grafted pectin after grafting in Example 1. Figure 3 This is a comparison between the grafted pectin of Example 1 forming a gel and the high-ester pectin of Comparative Example 2 failing to form a gel. Detailed Implementation

[0020] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0021] This invention proposes a grafted pectin composition, wherein the raw material components include grafted pectin, and at least one of an acrylic polymer and a sugar compound; Grafted pectin is a chemically grafted polyether structure onto pectin; The polyether structure is selected from the polypropylene glycol monomethyl ether structure or the copolymer structure of polyoxyethylene and polyoxypropylene; When the polyether structure is selected from the copolymer structure of polyethylene oxide and polypropylene oxide, the molar proportion of polyethylene oxide (PEO) in the polyether structure shall not exceed 30%; A 0.1-2wt% aqueous solution of grafted pectin is in a gel state at 10-50℃ and pH≤3. The degree of esterification of pectin is 40-65%.

[0022] This invention involves chemically grafting a certain proportion of polyether structures onto pectin with a specific degree of esterification (40-65%). The polyether structures react with the carboxyl groups on the pectin, converting them into polyether structures. The polyoxyethylene content in the polyether structures is low (≤30%), resulting in poor hydrophilicity. When the pH of the aqueous environment containing the grafted pectin is low (pH ≤ 3), the carboxyl groups in the grafted pectin are converted to carboxyl groups, further reducing hydrophilicity. Hydrophobic interactions can occur between polyether structures and between the polyether structures and the pectin structures, allowing the grafted pectin to be directly converted into a gel without the need for high-concentration sucrose or other additives. Gels formed from high-ester pectin and high-concentration sucrose tend to be brittle. The grafted pectin in this invention, with its more flexible polyether structures, results in a gel with better flexibility.

[0023] The present invention also found that the combination of the above-mentioned grafted pectin with acrylic polymers and / or sugar compounds (grafted pectin composition) can further improve the mechanical strength of the formed gel, possibly because: (1) under acidic conditions, the carboxyl groups of acrylic polymers can form hydrogen bonds with the ether bonds on the polyether structure in the grafted pectin, thereby further destroying the binding force between the polyether structure and water molecules, enhancing the hydrophobic interaction between the grafted pectin molecular chains, which is equivalent to the grafted pectin molecular chains “shrinking” more obviously, thereby improving the gel strength; (2) the sugar compounds contain multiple hydroxyl groups in their structure, which can combine with water molecules around the grafted pectin, capture these water molecules, further destroy the hydration layer of the grafted pectin, promote the “shrinking” of the grafted pectin molecular chains, and achieve the effect of improving the mechanical strength of the gel without adding high concentrations of sugar compounds, or even low concentrations of sugar compounds.

[0024] The aqueous solution of the grafted pectin of the present invention can be in a gel state at concentrations of 0.1wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 2wt%, etc., temperatures of 10℃, 20℃, 30℃, 40℃, 50℃, etc., and pH values ​​of 3, 2, 1.

[0025] In this invention, the pectin can be either low-ester or high-ester pectin, and can be directly obtained from the market. For example, the degree of esterification of the pectin can be 40%, 45%, 48%, 50%, 52%, 55%, 57%, 60%, etc. The degree of esterification of the pectin should not be too high or too low. If it is too low, the overall degree of esterification is insufficient, the hydrophilicity is too high, and it cannot form a gel under acidic conditions. If it is too high, the overall degree of esterification is too high, the hydrophilicity is too low, and the solubility is poor. Furthermore, the molar proportion of polyoxyethylene (PEO) in the polyether structure does not exceed 20%.

[0026] In this invention, the degree of esterification of the grafted pectin is not less than 50%. The degree of esterification of the grafted pectin includes the original esterification of the pectin and the esterification formed by the grafted polyether structure, with one grafted polyether structure equivalent to one degree of esterification.

[0027] In some embodiments, the grafting rate of the polyether structure is 3-15%. The grafting rate of the polyether structure refers to the proportion of the weight of the grafted polyether structure to the weight of the pectin. The higher the grafting rate, the more polyether structures are grafted onto the pectin. However, both excessively high and low grafting rates are detrimental to gel formation. If the grafting rate is too high, the grafted pectin will be highly hydrophobic and have poor water solubility; if the grafting rate is too low, the polyether structure cannot function effectively. For example, the grafting rate of the polyether structure can be 3%, 5%, 7%, 8%, 10%, 12%, 15%, etc. Further, the grafting rate of the polyether structure can be 5-15%.

[0028] In some embodiments, when the polyether structure is selected from the polypropylene glycol monomethyl ether structure, the number-average molecular weight Mn of the polyether structure is 600-6000 g / mol.

[0029] Compared to the PEO structure, the PPO structure has lower hydrophilicity and better hydrophobicity, which can reduce the water activity of the grafted pectin aqueous solution. This reduces the interaction between the grafted pectin and water under acidic conditions, thus facilitating gel formation. For example, the number-average molecular weight Mn of the polyether structure can be 600 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, 5000 g / mol, 6000 g / mol, etc.

[0030] In some embodiments, when the polyether structure is selected from the copolymer structure of polyoxyethylene (PEO) and polypropylene (PPO) (PEO / PPO), the number-average molecular weight Mn of the polyether structure is 800-3000 g / mol. For example, the number-average molecular weight Mn of the polyether structure can be 800 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, etc. When the grafting rate of the polyether structure is high, such as 10-15%, although the presence of PEO structure in the polyether structure will increase the hydrophilicity of the polyether structure, the polyether structure as a whole still exhibits hydrophobicity, just not as high as that of the PPO structure alone. By increasing the grafting rate of the polyether structure, the water activity of the grafted pectin aqueous solution can also be reduced, thereby reducing the interaction between the grafted pectin and water under acidic conditions, which is beneficial for the grafted pectin to form a gel under acidic conditions.

[0031] In some embodiments, the grafted pectin is obtained by reacting a polyether with pectin as shown in formula (1); R 1 (OCH2CH2) m (OCH2CHCH3) n R 2 (1) Among them, R 1 Selected from C1-C4 alkyl groups, R 2 Selected from hydroxyl or primary amino groups, m≥0, n>0.

[0032] Some of the carboxyl groups on the pectin undergo methoxylation, leaving some carboxyl groups. The polyether structure shown in formula (1) has R... 2 The hydroxyl or primary amino group can undergo esterification or amidation reactions with the carboxyl group, thereby transforming the polyether structure R... 1 (OCH2CH2) m (OCH2CHCH3)n - It chemically bonds to pectin molecules to form grafted pectin.

[0033] The above-mentioned esterification or amidation reactions can be carried out according to existing technical methods, such as using lipases as catalysts, or combinations of dicyclohexylcarbodiimide (DCC) / 4-dimethylaminopyridine (DMAP), carbodiimide compound (EDC) / N-hydroxysuccinimide (NHS), EDC / DMAP, etc., as catalysts.

[0034] In some embodiments, the acrylic polymer is selected from one or more of sodium polyacrylate, sodium acrylate / acrylate copolymer, sodium acrylate / methacrylate copolymer, polysodium methacrylate, and sodium methacrylate / methacrylate copolymer.

[0035] In some embodiments, the weight ratio of grafted pectin to acrylic polymer is 1:0.1-2. In this invention, it is not necessary to add a high concentration of acrylic polymer; even a low concentration of acrylic polymer can achieve the effect of improving the mechanical strength of the gel. For example, the weight ratio of grafted pectin to acrylic polymer can be 1:0.1, 1:0.2, 1:0.3, 1:0.5, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.6, 1:1.8, 1:2, etc. Further, the weight ratio of grafted pectin to acrylic polymer can be 1:0.5-2.

[0036] In this invention, there are no particular restrictions on the Mn content of the acrylic polymers; for example, it can be 1000-100000 g / mol. The molar percentage of sodium acrylate in sodium acrylate / acrylate copolymers and sodium acrylate / methacrylate copolymers can be 30-80% respectively; the molar percentage of sodium methacrylate in sodium methacrylate / methacrylate copolymers can also be 30-80%.

[0037] In some embodiments, the carbohydrate compound is selected from one or more sugar alcohols and oligosaccharides.

[0038] In some embodiments, the sugar alcohol compound is selected from one or more of isomaltitol, maltitol, sorbitol, and xylitol; Oligosaccharides are selected from one or more of maltose, fructooligosaccharides, stachyose, and dextran.

[0039] In some embodiments, the weight ratio of grafted pectin to carbohydrate compounds is 1:0.1-1. For example, the weight ratio of grafted pectin to carbohydrate compounds may be 1:0.1, 1:0.2, 1:0.3, 1:0.5, 1:0.6, 1:0.8, 1:1, etc. Further, the weight ratio of grafted pectin to carbohydrate compounds is 1:0.3-1.

[0040] The grafted pectin and pectin composition of the present invention can be used in food, such as beverages.

[0041] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0042] Example 1 The weight ratio of pectin (65% esterification) to polypropylene glycol monomethyl ether MPPG (Mn 3500 g / mol) is 100:3.

[0043] Add pectin to deionized water to prepare an aqueous solution with a concentration of 1 wt%. MPPG was added to tetrahydrofuran to prepare a 5 wt% THF solution; Under ice-water bath conditions, the above THF solution was added to the above aqueous solution, followed by the addition of EDC (1.5 times the molar amount of MPPG) while stirring. After the addition was complete, DMAP (0.1 times the molar amount of MPPG) was gradually added. The mixture was stirred for 0.5 h after the addition was complete, then transferred to room temperature (25±2℃) and stirred for another 48 h. The product was precipitated with a large amount of anhydrous diethyl ether and dried to obtain grafted pectin.

[0044] The FT-IR spectrum of the pectin before grafting in this embodiment is shown in the attached figure. Figure 1 As shown in the attached figure, the FT-IR spectrum of the grafted pectin is as follows. Figure 2 As shown, it can be seen that the number of carboxyl groups on the grafted fruit gum is significantly reduced, while the number of carbonyl groups and ether bonds is significantly enhanced, at 2800-2900 cm⁻¹. -1 The characteristic peaks between these peaks are absorption peaks of CH, therefore... Figure 1 and attached Figure 2 The FT-IR spectrum comparison proved that the polyether structure was indeed grafted onto the pectin.

[0045] Example 2 The weight ratio of pectin (65% esterification) to polypropylene glycol monomethyl ether MPPG (Mn 2000 g / mol) is 100:5.

[0046] Example 3 The weight ratio of pectin (esterification degree 53%) to polypropylene glycol monomethyl ether MPPG (Mn 2000 g / mol) is 100:10.

[0047] Grafted pectin was prepared according to the method in Example 1.

[0048] Example 4 The weight ratio of pectin (40% esterification) to polypropylene glycol monomethyl ether MPPG (Mn 2000 g / mol) is 100:15.

[0049] Grafted pectin was prepared according to the method in Example 1.

[0050] Example 5 The weight ratio of pectin (48% esterification) to PEO / PPO copolymer (Mn 2500 g / mol, PEO molar percentage 20%, one end group of the copolymer is methoxy) is 100:15.

[0051] Comparative Example 1 The difference between this comparative example and Example 4 is that in Example 4, the weight ratio of pectin to MPPG was adjusted from 100:15 to 100:20. The remaining steps remained unchanged.

[0052] Comparative Example 2 The pectin in this comparative example is the high-ester pectin from Example 1.

[0053] Performance testing (1) Gel properties At 23℃, the grafted pectin to be tested (including the high-ester pectin of Comparative Example 2) was added to deionized water to prepare an aqueous solution with a concentration of 1wt%. Acetic acid was added to adjust the pH to 2.5-3.0, and the aqueous solution was converted into a gel.

[0054] In Comparative Example 1, a small amount of insoluble matter was observed in the grafted pectin, indicating that a high grafting rate of the polyether structure leads to decreased solubility of the grafted pectin. A comparison is provided below of the gel formed from the grafted pectin of Example 1 and the aqueous solution of the high-ester pectin of Comparative Example 2. Figure 3 As shown, Figure 3 In the example 1-1, the aqueous solution of high-ester pectin is still in a flowable solution state; Figure 3 In the example 1-2, the grafted pectin aqueous solution of Example 1 is in a non-flowing gel state.

[0055] SAG gelation degree: Tested according to the method in QB / T 2484-2000 "Food Additives Pectin". The higher the SAG gelation degree value, the higher the mechanical strength of the gel.

[0056] Deformation rate: The percentage of deformation a gel undergoes when it is compressed to the point of rupture. The higher the deformation rate, the better the flexibility of the gel.

[0057] The results are shown in Table 1 below.

[0058] Table 1

[0059] Therefore, as can be seen from the data results in Table 1 above, the grafted pectin of the present invention can be converted into gel on its own under acidic conditions. The gel with a concentration of 1 wt% has certain strength and resistance to deformation. Furthermore, as the grafting rate of the polyether structure increases, the flexibility of the gel increases, but the strength of the gel first increases or decreases as the grafting rate of the polyether structure increases.

[0060] (2) Effect of concentration on gel properties At 23°C, the grafted pectin of Example 4 was added to deionized water to prepare aqueous solutions with concentrations of 0.1wt%, 0.5wt%, 1wt%, and 2wt%, respectively. Acetic acid was added to adjust the pH to 2.5-3.0, and the aqueous solution was converted into a gel.

[0061] The results are shown in Table 2 below.

[0062] Table 2

[0063] Therefore, as can be seen from the data results in Table 2 above, the grafted pectin of the present invention can also form a gel on its own at a low concentration (0.1wt%), showing good gel-forming ability.

[0064] Example 6 The grafted pectin composition of this embodiment is composed of the grafted pectin of Example 3 and sodium polyacrylate (Mn is 6000 g / mol) in a weight ratio of 1:0.1.

[0065] Example 7 The difference between this embodiment and Embodiment 6 is that in Embodiment 6, the weight ratio of grafted pectin and sodium polyacrylate was adjusted from 1:0.1 to 1:0.6. The remaining steps remain unchanged.

[0066] Example 8 The grafted pectin composition of this embodiment is composed of the grafted pectin of Example 3 and sodium acrylate / acrylate copolymer (Mn is 10000 g / mol, and the molar percentage of sodium acrylate is 70%) in a weight ratio of 1:1.

[0067] Example 9 The difference between this embodiment and Embodiment 8 is that in Embodiment 8, the weight ratio of grafted pectin and sodium acrylate / acrylate copolymer was adjusted from 1:1 to 1:2. The remaining steps remain unchanged.

[0068] Example 10 The grafted pectin composition of this embodiment is composed of the grafted pectin of Example 4 and maltitol in a weight ratio of 1:0.1.

[0069] Example 11 The grafted pectin composition of this embodiment is composed of the grafted pectin of Example 4 and maltose in a weight ratio of 1:0.3.

[0070] Example 12 The grafted pectin composition of this embodiment is composed of the grafted pectin of Example 4 and maltose in a weight ratio of 1:1.

[0071] The results are shown in Table 3 below.

[0072] Table 3

[0073] Therefore, as can be seen from the data results in Table 3 above, the addition of acrylic polymers and sugar compounds to the grafted pectin of the present invention can further improve the strength and flexibility of the gel.

[0074] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A grafted pectin composition, characterized in that, The raw material components include grafted pectin, and at least one of acrylic polymers and sugar compounds; The grafted pectin is a chemically grafted polyether structure onto pectin; The polyether structure is selected from polypropylene glycol monomethyl ether structure or copolymer structure of polyoxyethylene and polyoxypropylene. When the polyether structure is selected from the copolymer structure of polyoxyethylene and polyoxypropylene, the molar proportion of polyoxyethylene in the polyether structure does not exceed 30%; The grafted pectin is obtained by reacting the pectin with the polyether shown in formula (1); R 1 (OCH2CH2) m (OCH2CHCH3) n R 2 (1) Among them, R 1 Selected from C1-C4 alkyl groups, R 2 Selected from hydroxyl or primary amino groups, m≥0, n>0; The 0.1-2wt% aqueous solution of the grafted pectin is in a gel state at 10-50℃ and pH≤3. The degree of esterification of the pectin is 40-65%.

2. The grafted pectin composition according to claim 1, characterized in that, The grafting rate of the polyether structure is 3-15%; The grafting rate of the polyether structure refers to the proportion of the weight of the grafted polyether structure to the weight of the pectin.

3. The grafted pectin composition according to claim 1, characterized in that, When the polyether structure is selected from polypropylene glycol monomethyl ether, the number-average molecular weight of the polyether structure is 600-6000 g / mol.

4. The grafted pectin composition according to claim 1, characterized in that, When the polyether structure is selected from the copolymer structure of polyoxyethylene and polyoxypropylene, the number average molecular weight of the polyether structure is 800-3000 g / mol.

5. The grafted pectin composition according to claim 1, characterized in that, The acrylic polymer is selected from one or more of sodium polyacrylate, sodium acrylate / acrylate copolymer, sodium acrylate / methacrylate copolymer, polysodium methacrylate, and sodium methacrylate / methacrylate copolymer.

6. The grafted pectin composition according to claim 1, characterized in that, The weight ratio of the grafted pectin to the acrylic polymer is 1:0.1-2.

7. The grafted pectin composition according to claim 1, characterized in that, The carbohydrate compound is selected from one or more sugar alcohols and oligosaccharides.

8. The grafted pectin composition according to claim 7, characterized in that, The sugar alcohol compound is selected from one or more of isomaltitol, maltitol, sorbitol and xylitol; The oligosaccharide is selected from one or more of maltose, fructooligosaccharides, stachyose, and dextran.

9. The grafted pectin composition according to claim 1, characterized in that, The weight ratio of the grafted pectin to the carbohydrate compound is 1:0.1-1.

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