Method for regulating and controlling gel strength

Abstract

The invention discloses a method for regulating and controlling the gel strength of colloid. The preparation method comprises the following steps: uniformly mixing agar, carrageenan or sodium alginate with an ethanol-water solution, adding an esterifying agent, and modifying under an alkaline condition; filtering the modified agar, carrageenan or sodium alginate, washing with an ethanol-water solution, drying, and crushing to obtain solid powder; adding distilled water and heating to completely dissolve to obtain a colloidal solution; if the solution is a carrageenan solution, potassium chloride needs to be added; if the solution is a sodium alginate solution, adding calcium chloride; adding an alkali solution into the colloidal solution, and cooling to form gel; or after the colloidal solution is cooled to form gel, adding the gel into an alkaline solution for soaking. The gel strength of the agar, the carrageenan and the sodium alginate can be changed to different degrees, the gel with the adjustable gel strength is obtained, various processing requirements can be met, the application range of the agar, the carrageenan and the sodium alginate is widened, and the additional value of the agar, the carrageenan and the sodium alginate is improved.

Description

Technical Field

[0001] The invention relates to the field of gel, and in particular to a method for regulating gel strength. Background Art

[0002] Agar, carrageenan and sodium alginate are polysaccharides extracted from Gelidium amansii, Gracilaria and brown algae. They have many excellent properties and are widely used in food, biology, daily chemicals, medicine and other industries. In the biological field, they are often used as coagulants for biological solid culture media, and can also be used to fix cells and separate nucleic acids. They are mainly used in the food industry as food additives such as gelling agents, clarifiers, thickeners and suspending agents.

[0003] The above-mentioned polysaccharides are just a type of hydrophilic colloids after the initial processing of seaweed. With the renewal and iteration of the food industry, polysaccharide derivative products have become popular, that is, some physical and chemical properties of agar are changed by physical or chemical methods, such as gel strength, dissolution temperature, solidification temperature, water retention, elasticity, etc., to make it more suitable for actual applications in food production. However, there are currently few studies on regulating the strength of colloidal gel. The controllable strength of colloidal gel can make the application of polysaccharides more extensive. Summary of the invention

[0004] In summary, the present invention utilizes a variety of acid anhydrides to chemically modify agar, carrageenan and sodium alginate to different degrees, and then adds alkali or soaks them in an alkali solution, and different types or concentrations of alkalis are used to treat the modified agar solution or modified agar gel, which can change the gel strength to different degrees, and obtain a colloid with adjustable gel strength, which can meet various processing requirements, broaden the application range of agar, carrageenan and sodium alginate, and improve their added value.

[0005] The object of the present invention is to provide a method for regulating gel strength.

[0006] To achieve the above object, the present invention provides a method for regulating the strength of a colloidal gel, characterized in that it comprises the following steps:

[0007] S1. Mix agar or carrageenan or sodium alginate with an ethanol-water solution, and then add an esterifying agent to modify it under alkaline conditions;

[0008] S2. The modified agar or carrageenan or sodium alginate is filtered, then washed with an ethanol-water solution, dried and crushed to obtain a solid powder;

[0009] S3. Add the obtained solid powder to distilled water and heat it to completely dissolve it to obtain a colloidal solution; if it is a carrageenan solution, potassium chloride needs to be added; if it is a sodium alginate solution, calcium chloride needs to be added;

[0010] S4. adding an alkaline solution to the colloidal solution and allowing it to cool to form a gel; or,

[0011] After the colloidal solution is cooled to form a gel, the gel is added into an alkaline solution for soaking.

[0012] Furthermore, in steps S1 and S2, the volume concentration of ethanol in the ethanol-water solution can be independently 75-90 v / v%, preferably 80 v / v%.

[0013] Furthermore, in step S1, the esterifying agent is at least one of an organic acid, an acid anhydride, and an acid chloride; the esterifying agent is prepared into an organic solution and added dropwise or directly in batches;

[0014] Preferably, the organic acid is valeric acid; the acid anhydride is any one of succinic anhydride, glutaric anhydride and maleic anhydride; the acyl chloride is acetyl chloride;

[0015] The alkaline condition has a pH value of 8.0-8.5.

[0016] Furthermore, in step S1, the weight-to-volume ratio of the agar, carrageenan or sodium alginate to the esterifying agent is 3 g:1 mL.

[0017] Furthermore, in step S1, the concentration of the esterification agent is 2%-4%.

[0018] Furthermore, in step S3, 0.2 g of potassium chloride or calcium chloride is added to 100 mL of the system.

[0019] Furthermore, in step S4, the base is one or a complex of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0020] Furthermore, in step S4, the concentration of the alkaline solution is 0.05M-0.4M.

[0021] Furthermore, in step S4, the amount of the alkaline solution added is (3 ml-12 ml) alkaline solution: 1.5 g modified agar, carrageenan or sodium alginate.

[0022] Furthermore, in step S4, the soaking time is 18h-24h.

[0023] The ethanol used in the present invention (ethanol contained in the ethanol-water solution when washing the sample) can be recycled by a rotary evaporation method, thereby reducing the waste of reagents and the pollution to the environment, and being green and environmentally friendly.

[0024] The inventors of the present invention creatively discovered that both modification and alkali treatment can regulate the gel strength of the colloid. Modification can reduce the gel strength of the colloid, and alkali treatment can reduce or increase the gel strength of the colloid.

[0025] The present invention can improve or reduce the gel strength of the colloid by adding different volumes or different types of alkaline solutions to polysaccharides modified by different esterifying agents or to modified colloid solutions, or by immersing the colloid solution in alkaline solutions of different types or concentrations after the colloid solution has gelled, thereby achieving the effect of effectively regulating the gel strength of the colloid.

[0026] The present invention proposes a method for regulating the strength of colloid gel. After being modified by an esterifying agent, the dissolution temperature, solidification temperature and transparency of the colloid are effectively improved, which can meet various processing requirements, broaden the application range of the colloid and improve its added value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the infrared spectrum of the modified agar solution or gel treated with 0.2M alkali solution in Comparative Example 2 and Examples 2-4 of the present invention. DETAILED DESCRIPTION

[0028] Embodiments of the present invention are described in detail below, and the examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by reference to the accompanying drawings are exemplary, are intended to be used to explain the present invention, and are not to be construed as limitations of the present invention. Those who do not indicate specific techniques or conditions in the embodiments are carried out according to the techniques or conditions described in the documents in this area or according to the product specification. Those who do not indicate the manufacturer of reagents or instruments used are all conventional products that can be obtained commercially.

[0029] Comparative Example 1: Preparation of Succinic Anhydride Modified Agar and Its Gel

[0030] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V); set the stirring temperature to 30° C. and dissolve the agarose suspension by stirring to form a stable agar suspension;

[0031] While stirring continuously, add 5 ml of 2% succinic anhydride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0032] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0033] S2. After the reaction is completed, wash and filter several times with 80 v / v% ethanol (i.e., ethanol: water is 80 ml: 20 ml) and a vacuum filter to obtain a filter residue;

[0034] The filter residue was placed in a 55°C forced air drying oven and dried for 12 h, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0035] S3, heat and dissolve 1.5 g of modified agar powder in 100 mL of water until it is completely dissolved;

[0036] S4. Pour the obtained modified agar solution into a plate and cool it to gel at room temperature.

[0037] Comparative Example 2: Preparation of Succinic Anhydride Modified Agar and Its Gel

[0038] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0039] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0040] While stirring continuously, add 5 ml of 4% succinic anhydride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0041] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0042] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0043] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0044] S3, heat and dissolve 1.5 g of modified agar powder in 100 mL of water until it is completely dissolved;

[0045] S4. Pour the obtained modified agar solution into a plate and cool it to gel at room temperature.

[0046] See Figure 1 Succinic anhydride modified agar in.

[0047] Comparative Example 3: Method for alkali treatment of succinic anhydride modified agar solution

[0048] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0049] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0050] While continuing to stir, add 5 ml of 4% succinic anhydride-ethanol solution to the agar suspension, and add 3M NaOH solution to make the pH value of the system 8-8.5; after the succinic anhydride-ethanol solution is added within 1 hour, continue stirring for 1 hour and the reaction is completed;

[0051] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0052] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0053] S3, weigh 1.5g of modified agar powder, add it to 100ml of water, heat and dissolve until it is completely dissolved;

[0054] S4. Pour the obtained modified agar solution into a plate and cool it into a gel. Then, soak the gel in 0.01M, 1M and 5M sodium carbonate, 0.01M, 1M and 5M sodium hydroxide solutions for 24 hours.

[0055] Example 1: Method for alkaline treatment of succinic anhydride modified agar solution

[0056] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0057] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0058] While stirring continuously, add 5 ml of 4% succinic anhydride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0059] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0060] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0061] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0062] S3, weigh three portions of 1.5 g of modified agar powder, add them into water and heat to dissolve them until they are completely dissolved;

[0063] S4. Add 3 ml, 9 ml, and 12 ml of 0.2 M sodium hydroxide solution to the obtained modified agar solution to make the total system 100 ml, mix by ultrasonication, pour into a plate and cool to gel at room temperature.

[0064] Example 2: Method for alkali treatment of succinic anhydride modified agar solution

[0065] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0066] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0067] While stirring continuously, add 5 ml of 4% succinic anhydride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0068] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0069] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0070] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0071] S3, weigh three portions of 1.5 g of modified agar powder, add them into water and heat to dissolve them until they are completely dissolved;

[0072] S4. Add 3 ml, 9 ml and 12 ml of 0.2 M sodium carbonate solution to the obtained modified agar solution to make the total system 100 ml.

[0073] Mix by ultrasonication, pour into a plate and cool to form a gel at room temperature.

[0074] Example 3: Method for treating succinic anhydride-modified agar and its gel alkali

[0075] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0076] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0077] While stirring continuously, add 5 ml of 4% succinic anhydride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0078] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0079] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0080] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0081] S3, weigh 1.5g of modified agar powder, add it to 100ml of water, heat and dissolve until it is completely dissolved;

[0082] S4. Pour the obtained modified agar solution into a plate and cool it into a gel. Then soak the gel in 0.05M, 0.1M, 0.2M, 0.3M, or 0.4M sodium carbonate solutions for 24 hours.

[0083] Example 4: Method for treating succinic anhydride-modified agar and its gel alkali

[0084] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0085] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0086] While stirring continuously, add 5 ml of 4% succinic anhydride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0087] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0088] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0089] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0090] S3, weigh 1.5 g of modified agar powder, add it into water and heat to dissolve until it is completely dissolved;

[0091] S4. Pour the obtained modified agar solution into a plate and cool it into a gel. Then soak the gel in a 0.1M or 0.2M sodium hydroxide solution for 24 hours.

[0092] Example 5: Method for treating succinic anhydride-modified agar and its gel alkali

[0093] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0094] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0095] While stirring continuously, add 5 ml of 4% succinic anhydride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0096] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0097] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0098] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0099] S3, weigh 1.5 g of modified agar powder, add it into water and heat to dissolve until it is completely dissolved;

[0100] S4. Pour the obtained modified agar solution into a plate and cool it into a gel. Then soak the gel in a mixed solution of 0.2 M potassium hydroxide and 0.2 M sodium hydroxide for 24 hours.

[0101] Comparative Example 4: Preparation of glutaric anhydride modified agar and its gel

[0102] The following steps are involved:

[0103] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0104] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0105] While stirring continuously, add 5 ml of 4% glutaric anhydride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0106] After the glutaric anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0107] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0108] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0109] S3, heat and dissolve 1.5 g of modified agar powder in 100 mL of water until it is completely dissolved;

[0110] S4. Pour the obtained modified agar solution into a plate and cool it to gel at room temperature.

[0111] Comparative Example 5: Preparation of maleic anhydride modified agar and its gel

[0112] The following steps are involved:

[0113] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0114] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0115] While stirring continuously, add 5 ml of 4% maleic anhydride-ethanol solution to the agar suspension, and add 3M NaOH solution to adjust the pH value of the system to 8-8.5;

[0116] After the maleic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0117] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0118] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and sieved to obtain modified agar powder;

[0119] S3, heat and dissolve 1.5 g of modified agar powder in 100 mL of water until it is completely dissolved;

[0120] S4. Pour the obtained modified agar solution into a plate and cool it to gel at room temperature.

[0121] Comparative Example 6: Preparation of acetyl chloride-modified agar and its gel

[0122] S1. Disperse 15 g of agar in 200 mL of 80 v / v% ethanol to prepare an agar suspension with a mass concentration of 7.5% (W / V);

[0123] The stirring temperature was set to 30°C, and the agarose suspension was dissolved by stirring to form a stable agar suspension;

[0124] While stirring continuously, add 5 ml of 4% acetyl chloride-ethanol solution to the agar suspension, and add 3 M NaOH solution to adjust the pH value of the system to 8-8.5;

[0125] After the acetyl chloride-ethanol solution is added within 1 hour, continue stirring for 1 hour and the reaction is completed;

[0126] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0127] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified agar powder;

[0128] S3, heat and dissolve 1.5 g of modified agar powder in 100 mL of water until it is completely dissolved;

[0129] S4. Pour the obtained modified agar solution into a plate and cool it to gel at room temperature.

[0130] Comparative Example 7: Preparation of Succinic Anhydride Modified Carrageenan and Its Gel

[0131] The following steps are involved:

[0132] S1. Disperse 15 g of carrageenan in 200 mL of 80 v / v% ethanol to prepare a carrageenan suspension with a mass concentration of 7.5% (W / V); set the stirring temperature to 30° C., and dissolve the carrageenan suspension by stirring to form a stable carrageenan suspension; continue stirring, add 5 ml of 4% succinic anhydride-ethanol solution to the carrageenan suspension, and add 3 M NaOH solution to make the pH value of the system 8-8.5;

[0133] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0134] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0135] The filter residue was placed in a blast drying oven at 55°C and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified carrageenan powder;

[0136] S3, heating and dissolving 1.5 g of modified carrageenan powder in 100 mL of water (containing 0.2% wt% KCl) until it is completely dissolved;

[0137] S4. Pour the obtained modified carrageenan solution into a flat plate and cool it to form a gel at room temperature.

[0138] Comparative Example 8: Preparation of glutaric anhydride modified carrageenan and its gel

[0139] The following steps are involved:

[0140] S1. Disperse 15 g of carrageenan in 200 mL of 80 v / v% ethanol to prepare a carrageenan suspension with a mass concentration of 7.5% (W / V);

[0141] The stirring temperature was set to 30°C, and the carrageenan suspension was dissolved by stirring to form a stable carrageenan suspension;

[0142] While stirring continuously, add 5 ml of 4% glutaric anhydride-ethanol solution to the carrageenan suspension, and add 3M NaOH solution to adjust the pH value of the system to 8-8.5;

[0143] After the glutaric anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0144] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0145] The filter residue was placed in a blast drying oven at 55°C and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified carrageenan powder;

[0146] S3, heating and dissolving 1.5 g of modified carrageenan powder in 100 mL of water (containing 0.2% wt% KCl) until it is completely dissolved;

[0147] S4. Pour the obtained modified carrageenan solution into a flat plate and cool it to form a gel at room temperature.

[0148] Comparative Example 9: Preparation of Succinic Anhydride Modified Sodium Alginate and Its Gel

[0149] The following steps are involved:

[0150] S1. Disperse 15 g of sodium alginate in 200 mL of 80 v / v% ethanol to prepare a sodium alginate suspension with a mass concentration of 7.5% (W / V);

[0151] The stirring temperature was set to 30°C, and the sodium alginate suspension was dissolved by stirring to form a stable sodium alginate solution; while continuing to stir, 5 ml of 4% succinic anhydride-ethanol solution was added to the sodium alginate solution, and 3 M NaOH solution was added at the same time to make the pH value of the system 8-8.5;

[0152] After the succinic anhydride-ethanol solution is added within 1 hour, the reaction is completed after stirring for 1 hour;

[0153] S2. After the reaction is completed, the mixture is washed and filtered several times with 80 v / v% ethanol and a vacuum filter to obtain a filter residue;

[0154] The filter residue was placed in a 55°C forced air drying oven and dried for 12 hours, then crushed and passed through an 80-mesh sieve to obtain modified sodium alginate.

[0155] S3, heat and dissolve 1.5 g of modified sodium alginate powder in 100 mL of water (containing 0.2% wt% CaCl2) until it is completely dissolved;

[0156] S4. Pour the obtained modified sodium alginate solution into a flat plate and cool it to form a gel at room temperature.

[0157] Characterization of anhydride-modified agar, carrageenan and sodium alginate and their gel properties

[0158] The physicochemical properties of anhydride-modified agar, carrageenan and sodium alginate, including degree of substitution, transparency, solidification temperature and dissolution temperature, were tested using conventional testing methods. Unmodified agar, carrageenan and sodium alginate were used as controls.

[0159] Comparative Examples 1-2, Comparative Examples 4-6: Determination of the strength of agar gel modified by anhydride and acetyl chloride - Table 1

[0160] Prepare 1.5wt% original agar solution, original carrageenan solution, original sodium alginate solution, anhydride modified agar solution, carrageenan solution (containing 0.2wt% KCl), sodium alginate solution (containing 0.2wt% CaCl2), heat in a boiling water bath until they are completely dissolved, pour the gel solution into a plate until it is just full, cool at room temperature, solidify, and stand overnight (the method for preparing gel in the above embodiment or comparative example). Place the plate on the left tray of the tray balance, and place a cross-sectional area of ​​1cm 2 The plunger is fixed after just touching the gel, a beaker is placed on the tray on the right side of the balance, and distilled water is poured evenly and slowly. When the surface of the gel breaks, the pouring of water is stopped immediately, and the weight of the beaker and distilled water is recorded. The value is the gel strength of agar, carrageenan and sodium alginate after acid anhydride modification. Unmodified agar, carrageenan and sodium alginate are used as controls.

[0161] Table 1 Experimental results

[0162]

[0163] Table 2 Comparative Examples 7-8: Results of Anhydride Modified Carrageenan

[0164]

[0165] Table 3 Comparative Example 9: Results of Acid Anhydride Modified Sodium Alginate

[0166] Sodium alginate Comparative Example 9 Degree of substitution 0 0.049 <![CDATA[Gel strength (g / cm 2 )]]> 502.03±27.03 294.12±30.34 transparency(%) 82.3±0.6 87.8±0.2 Dissolving temperature(℃) 98.7±0.15 96.5±0.28 Solidification temperature(℃) 38.3±0.2 35.1±0.4

[0167] The results show that the gel strength of agar, carrageenan and sodium alginate modified by anhydride and agar modified by acyl chloride is significantly reduced. This is because after the esterification reaction of the polysaccharide, the ester group replaces the free hydroxyl group, which destroys the hydrogen bonding between molecules, making the molecules loose and unable to aggregate, resulting in a decrease in the gel strength of the above polysaccharides. Low-strength polysaccharides have softer gel properties, can give products stable tissue morphology and soft elastic characteristics, and have good application prospects in food processing fields such as dairy products, beverages, meat products, as well as fine chemicals and biomedicine.

[0168] In addition, the transparency is also significantly improved due to the introduction of hydrophilic groups, which increases the dispersion of polysaccharide molecules in water and enhances the permeability of light to them.

[0169] In addition, the solidification temperature and dissolution temperature both decreased, which was due to the introduction of ester groups that weakened the binding force between polysaccharide molecules.

[0170] Determination of gel strength of anhydride modified agar after alkali treatment (except adding alkali to the modified agar solution or immersing the modified agar gel in alkali, the other methods are the same as the above method for determining gel strength)

[0171] A 1.5 wt% solution of anhydride modified agar prepared in the example was prepared and heated in a boiling water bath until it was completely dissolved. The alkali solution described in Examples 1-2 was added to the dissolved modified agar solution, and the gel solution was poured into a plate until it was just full, cooled at room temperature, solidified, or, after solidification, the gel was immersed in the alkali solution described in Examples 3-5 and Comparative Example 3 and allowed to stand overnight. The plate was placed on the left tray of a tray balance, and a cross-sectional area of ​​1 cm 2 The plunger is fixed after just touching the gel, a beaker is placed on the tray on the right side of the balance, and distilled water is poured evenly and slowly. When the surface of the gel breaks, stop pouring water immediately, and record the weight of the beaker and distilled water at this time. The value is the gel strength of the agar modified by acid anhydride and treated with alkali. Agar modified by 4% succinic anhydride ethanol solution is used as a control.

[0172] Comparative Example 1 (4% succinic anhydride ethanol solution modified agar), Example 1 and Example 2 - Adding alkali to modified agar solution

[0173] Table 4

[0174]

[0175]

[0176] The results of modified agar gel soaked in alkali solution after natron comparison example 1, comparison example 3 (0.01M, 1M, 5M sodium carbonate solution), and example 3-modified agar gel soaked in alkali solution of different concentrations are shown in Table 5

[0177] Table 5

[0178]

[0179] Example 4, Example 5, Comparative Example 3 (0.01M, 1M, 5M sodium hydroxide solution) - Results are shown in Table 6

[0180] Table 6

[0181]

[0182]

[0183] The results show that the gel strength of the gel can be improved to varying degrees by adding alkali solution to the modified agar solution to form a gel, or by soaking the modified agar gel in alkali solution. When 12 ml of 0.2 M sodium carbonate was added to the modified agar solution, and the modified agar gel was soaked in 0.4 M sodium carbonate solution and 0.1 M sodium hydroxide solution, the gel strength of the modified agar was improved most significantly. This is because the alkali treatment is a deesterification process, and the hydroxyl groups in the alkali solution can hydrolyze the ester groups on the modified polysaccharide, and the ester groups are converted into hydroxyl groups, so that the loose molecular structure after modification is reordered to form an ordered gel network structure, thereby improving the gel strength of the modified agar. Different concentrations and different types of alkali solutions have different abilities to hydrolyze ester groups, and the gel strength will also change to varying degrees, making the gel strength of the modified agar adjustable after different alkali treatments. When the modified agar gel is soaked in a high concentration alkali solution (1M, 5M), the polysaccharide chain of the modified agar is broken, and part of the modified agar is degraded, and a tight network structure cannot be formed, resulting in a sudden drop in the gel strength of the modified agar. When the concentration of the alkali solution is very low, such as 0.01M, it has almost no effect on the gel strength of the agar gel. Therefore, a low concentration of alkali solution (0.05-0.4M) can be used to treat the modified agar solution or gel to improve its gel strength.

[0184] Example 6 - Infrared spectroscopy and analysis - Figure 1 (Abstract with photos)

[0185] Determination method: After the agarose sample and potassium bromide powder are dried, they are placed in an agate mortar in a certain proportion, mixed and ground thoroughly, and then transferred to a grinder for tableting. The sample is measured using a Fourier transform infrared spectrometer.

[0186] Analysis: 0.2 M sodium carbonate was added to the succinic anhydride modified agar prepared in Comparative Example 2, 0.2 M sodium carbonate was added to the modified agar solution prepared in Example 2, 0.2 M sodium carbonate was soaked in the modified agar gel prepared in Example 3, and 0.2 M sodium hydroxide was soaked in the modified agar gel prepared in Example 4 for infrared spectral analysis. The analysis results are shown in the figure. Figure 1 The results showed that the esterification reaction was at 1720 cm -1 and 1570cm-1 New absorption peaks were generated at 1720 cm -1 The stretching vibration absorption peak of C=O is 1570cm -1 The position is the antisymmetric stretching vibration of the free -COO-. This indicates that after the agar was modified with succinic anhydride, an esterification reaction occurred. From the infrared spectrum, we can see that when alkali is added to the modified agar solution or the modified agar gel is treated with alkali, the hydroxyl group can hydrolyze the ester group contained in the modified agar to varying degrees. -1 and 1570cm -1 The absorption peaks of C=O and -COO- at 1720 cm-1 weaken or disappear after alkali treatment. In the infrared spectrum, the amount of 0.2 M sodium carbonate added to the modified agar solution is 3 ml, which is a small amount. -1 The absorption peak of C=O at 1720cm was significantly weakened, but not completely disappeared, that is, under this condition, the ester group in the modified agar was hydrolyzed, but not completely hydrolyzed; when the modified agar was immersed in 0.2M sodium carbonate solution or 0.2M sodium hydroxide solution, the absorption peak of 1720cm -1 The absorption peaks of C=O at the positions disappeared, that is, the ester group could be completely hydrolyzed, and the network structure of the modified agar gel changed from loose and disordered to dense and orderly. Correspondingly, the gel strength was significantly improved.

[0187] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for regulating the strength of a colloidal gel, characterized in that: The steps include: S1. Mix agar or carrageenan or sodium alginate with an ethanol-water solution, and then add an esterifying agent to modify it under alkaline conditions; S2. The modified agar or carrageenan or sodium alginate is filtered, then washed with an ethanol-water solution, dried and crushed to obtain a solid powder; S3. Add the obtained solid powder to distilled water and heat it to completely dissolve it to obtain a colloidal solution; if it is a carrageenan solution, potassium chloride needs to be added; if it is a sodium alginate solution, calcium chloride needs to be added; S4. adding an alkaline solution to the colloidal solution and allowing it to cool to form a gel; or, After the colloidal solution is cooled to form a gel, the gel is added into an alkaline solution for soaking.

2. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In steps S1 and S2, the volume concentration of ethanol in the ethanol-water solution can be independently 75-90 v / v%, preferably 80 v / v%.

3. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In step S1, the esterifying agent is at least one of an organic acid, an acid anhydride, and an acid chloride; the esterifying agent is prepared into an organic solution and added dropwise or directly in batches; Preferably, the organic acid is valeric acid; the acid anhydride is any one of succinic anhydride, glutaric anhydride and maleic anhydride; the acyl chloride is acetyl chloride; The alkaline condition has a pH value of 8.0-8.

5.

4. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In step S1, the mass volume ratio of the agar or carrageenan or sodium alginate to the esterifying agent is: 3g:1mL.

5. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In step S1, the concentration of the esterification agent is 2 w / w%-4 w / w%.

6. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In step S3, add 0.2 g potassium chloride or calcium chloride to 100 mL of the system.

7. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In step S4, the base is one of sodium hydroxide, potassium hydroxide, sodium carbonate or a complex thereof.

8. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In step S4, the concentration of the alkaline solution is 0.05M-0.4M.

9. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In step S4, the amount of the alkaline solution added is (3ml-12ml) alkaline solution: 1.5g modified agar or carrageenan or sodium alginate.

10. The method for regulating the strength of a colloidal gel according to claim 1, characterized in that: In step S4, the soaking time is 18h-24h.

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