CN116462858B - Preparation method and application of amidated pectin gel - Google Patents

Abstract

The present disclosure relates to a preparation method of amidated pectin gel and its application. The preparation method includes the following steps: using citrus pectin as raw material, amino acid as modifier, in an aqueous solution without adding a catalyst, adjusting the pH value of the solution to a limited range value, obtaining amino acid amidated pectin through dialysis and alcohol precipitation, and Amino acid amidated pectin is dissolved in water to adjust the pH again, and calcium ions are added to prepare amidated pectin gel. This method prepares amidated pectin and its gel through two-step pH value control. The prepared amino acid amidated pectin has a high degree of amidation. At the same time, the amino acid amidated pectin can be produced without adding sucrose and with low calcium ion concentration. And strong gel can be formed in the pH range of 3 to 10. It can be used in yogurt, milkshakes, beverages, jelly, jam, baked goods and other foods, filling the application of amidated pectin gel in the field of food preparation in neutral and alkaline pH environments, and has broad application prospects.

Description

Preparation method and application of amidated pectin gel

Technical field

The present disclosure relates to the technical field of food processing, and in particular, to a preparation method of amidated pectin gel and its application.

Background technique

Preparing gels through pectin is a common method. The mechanism of pectin gel is divided into two types according to the degree of pectin esterification. High-ester pectin needs to form a gel under high sugar and high acid conditions, while low-ester pectin needs to form a gel under high sugar and high acid conditions. Glues usually require the addition of calcium ions to form an egg-box structure to gel. The conditions for high-ester pectin to form gels require high sugar, which is not good for human health. At the same time, the high-acid environment also limits the pH range of pectin gel. Therefore, people have conducted experiments on pectin in order to improve the gel properties of pectin. Many chemical modifications are made to improve the properties of pectin and thus expand its applications in food.

Amidated pectin refers to pectin containing CONH-R (R=H, OH, carbon free radical), which is a common pectin derivative. Compared with traditional high-ester pectin formed under high sugar and high acid gel conditions, amidated pectin has good gel properties under low sugar and low calcium ion concentration conditions, which is very conducive to gel formation and can be used as Gelling substances in the food industry. The traditional preparation method of amidated pectin is to hydrolyze the pectin methoxy group with ammonia water in an aminoalcohol system. Although this method is simple and widely used, the chemical reagents used are mostly harmful and its application in the food field is limited.

The amidation reaction of amino acids and pectin is a relatively mild reaction method. At present, the main method for synthesizing amino acid amidated pectin is to add papain under ultra-low temperature conditions, but ultra-low temperature conditions are usually not suitable for industrial production. In addition, carbodiimide catalysts have also been used to synthesize amino acid amidated pectin, but the safety of the catalyst has yet to be verified. Furthermore, the synthesis of amidated pectin in a catalyst-free aqueous solution is more suitable for the food industry. It has been reported that pectin can be synthesized with glycine, lysine, and arginine in a 40°C aqueous solution, and it has been proven that the pectin has no cytotoxic effect. However, the current preparation conditions for amino acid amidated pectin are limited, and its structural properties are single. At the same time, gel properties are an important basis for the application of amino acid amidated pectin. The current research on the gel conditions of amino acid amidated pectin is insufficient, resulting in The pH range required for gel is narrow, and a certain Ca ²⁺ concentration is required to form gel, which cannot meet the needs of diverse foods. Therefore, the present invention creatively invented a method for preparing amidated pectin and its gel through coordinated regulation of the two-step pH value, including preparing amino acid amidated pectin with specific structural properties by regulating pH, and further regulating the gel formation process. pH, the amidated pectin gel is obtained. The method is simple, low-cost and high-efficiency; the prepared amino acid amidated pectin can be formed under acidic, neutral and alkaline conditions as well as sugar-free and low calcium ion concentrations. Gel has a wide range of applications and great development potential.

Contents of the invention

The purpose of this disclosure is to provide a safe and efficient preparation method of amidated pectin gel and its application. The preparation method is simple and efficient, and the amidated pectin and its gel are prepared through two-step pH value control. Using citrus pectin as raw material and amino acid as modifier, in an aqueous solution without adding a catalyst, the pH value of the solution is adjusted to a limited range value, and then through dialysis and alcohol precipitation, amino acid amidated pectin is obtained, and the amino acid amidated pectin is obtained. The gel is dissolved in water and the pH is adjusted again, and calcium ions are added to prepare amidated pectin gel. The obtained amino acid amidated pectin has a high degree of amidation; the amino acid amidated pectin can form amidated pectin gel without adding sucrose and low calcium ion concentration, and within the pH range of 3-10, and can be used for In foods such as yogurt, milkshakes, beverages, jellies, jams and baked goods, it fills the application field of amidated pectin gel in the field of food preparation in neutral and alkaline pH environments.

In order to achieve the above objects, the first aspect of the present disclosure provides a method for preparing amidated pectin gel, which is characterized by comprising the following steps:

S1. Mix pectin and water and stir magnetically to obtain a first raw material liquid; add amino acids to the first raw material liquid, adjust to the first pH with an alkali solution, and then perform the first reaction to obtain a second raw material liquid;

S2. Dialyze the second raw material liquid to obtain the third raw material liquid;

S3. Use an acid solution to adjust the pH of the third raw material liquid to 3.5-4.5, then add ethanol to perform alcohol precipitation, and dry the resulting precipitate to obtain amino acid amidated pectin;

S4. Dissolve amino acid amidated pectin in deionized water to form a fourth raw material liquid, adjust the pH to a second pH, add calcium ions under heating and magnetic stirring conditions to obtain amidated pectin gel; the second pH It is 3~10.

Optionally, in step S1, the pectin is citrus pectin; the citrus pectin is one of commercial citrus pectin and pectin extracted from citrus peels; the amino acid is lysine; The ratio of pectin to water is 1g:20~60mL; the magnetic stirring time is 6~12h, the magnetic stirring speed is 100~300rpm, and the magnetic stirring temperature is 20~60°C; The weight ratio of lysine to pectin is 1:0.5-1.5.

Optionally, in step S1, the alkali solution is a sodium hydroxide solution of 0.01 to 1 mol/L; the first pH is 8 to 11; the reaction conditions of the first reaction include: a reaction temperature of 10°C to 50℃, reaction time is 6h~8h.

Optionally, in step S2, the dialysis treatment is performed using a dialysis membrane, the molecular weight of the dialysis membrane is 3500-10000 Da, the time of the dialysis treatment is 6-10 days, and the water change interval of the dialysis treatment is 3 ~5 hours. Optionally, in step S3, the acid solution is an aqueous solution of 0.01 to 1 mol/l hydrochloric acid.

Optionally, in step S3, the amount of ethanol used is 2 to 4 times the volume of the third raw material liquid; the concentration of ethanol is 90 to 100%; the alcohol precipitation time is 6 to 12 hours; The number of times of alcohol precipitation is 1 to 4 times.

Optionally, in step S3, the drying process is freeze-drying; the freeze-drying conditions include: a temperature of -60 to -50°C and a time of 36 to 72 hours.

Optionally, in step S4, the heating temperature is 50-90°C; the magnetic stirring time is 3-7 minutes, the magnetic stirring speed is 50-150 rpm; the calcium ion concentration is 0.05-1 mol. /L.

The second aspect of the disclosure provides an amidated pectin gel prepared using the preparation method described in the first aspect of the disclosure.

The third aspect of the disclosure provides a use of the amidated pectin gel described in the second aspect of the disclosure in food; the food includes yogurt, milkshakes, beverages, jelly and jam; the beverage is preferably a low-sugar beverage, The jelly is preferably a low-calorie jelly.

Through the above technical solution, the present disclosure provides a method for preparing amidated pectin gel through two-step pH value control. The prepared amidated pectin can be prepared to form gel under acidic, neutral and alkaline conditions, and the expansion It expands the application scope of pectin gel and can be used in foods such as yogurt, milkshakes, beverages, jelly, jam and baked goods, filling the application of amidated pectin gel in the field of food preparation in neutral and alkaline pH environments. have a broad vision of application. The method is simple to operate, the preparation method is efficient and safe, and it is easy to realize industrial production.

Other features and advantages of the present disclosure will be described in detail in the detailed description that follows.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. They are used to explain the present disclosure together with the following specific embodiments, but do not constitute a limitation of the present disclosure. In the attached picture:

Figure 1 is the infrared spectrum of amidated pectin and lysine prepared in Examples 1 to 3 and Comparative Example 1 of the present disclosure.

Figure 2 shows the hydrogen nuclear magnetic resonance spectrum ( ¹ H) of amidated pectin prepared in Examples 1 to 3 of the present disclosure, Comparative Example 1 and simply mixing cp and lysine (without amidation reaction).

Figure 3 is a diagram showing the appearance of gel formed by amidated pectin prepared in Examples 1 to 3 and Comparative Example 1 of the present disclosure under different cationic induction.

Figure 4 shows the gel strength of amidated pectin gels prepared in Examples 1, 4 to 10 of the present disclosure.

Figure 5 shows the rheological properties of amidated pectin gels prepared in Examples 1, 4 to 10 of the present disclosure.

Figure 6 is a diagram of the preparation process of amidated pectin gel of the present disclosure.

Detailed ways

Specific embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described here are only used to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

The present disclosure forms amidated pectin by regulating the pH value, and further regulates the pH value during the gel formation process of pectin to prepare amidated pectin gel. It provides a two-step method of collaboratively regulating the pH value to prepare amidated pectin gel. method. The prepared amidated pectin can form gel under acidic, neutral and alkaline conditions, filling the application field of amidated pectin gel in the field of food preparation in neutral and alkaline pH environments. The preparation method of the present disclosure It is simple to operate, easy to obtain raw materials, easy to realize industrial production, and has broad application prospects.

The first aspect of the present disclosure provides a method for preparing amidated pectin gel, which is characterized by comprising the following steps:

S1. Mix pectin and water and stir magnetically to obtain a first raw material liquid; add amino acids to the first raw material liquid, adjust to the first pH with an alkali solution, and then perform the first reaction to obtain a second raw material liquid;

S2. Dialyze the second raw material liquid to obtain the third raw material liquid;

S3. Use an acid solution to adjust the pH of the third raw material liquid to 3.5-4.5, then add ethanol to perform alcohol precipitation, and dry the resulting precipitate to obtain amino acid amidated pectin;

S4. Dissolve amino acid amidated pectin in deionized water to form a fourth raw material liquid, adjust the pH to the second pH, add calcium ions under heating and magnetic stirring conditions to obtain amidated pectin gel; the second pH is 3 ~10, preferably 6-8.

According to an embodiment of the present disclosure, in step S1, the pectin is citrus pectin; the citrus pectin is one of commercial citrus pectin and pectin extracted from citrus peels; the amino acid is lysine; The ratio of glue to water is 1g:20~60mL, preferably 1g:25~50mL; the magnetic stirring time is 6~12h, preferably 7~10h, and the magnetic stirring speed is 100~300rpm, preferably 150~250rpm. The temperature of magnetic stirring is 20-60°C, preferably 25-50°C; the weight ratio of amino acids to pectin is 1:0.5-1.5, preferably 1:1-1.5.

According to an embodiment of the present disclosure, in step S1, the alkali solution is a sodium hydroxide solution of 0.01 to 1 mol/L, preferably a sodium hydroxide solution of 0.05 to 0.7 mol/L; the first pH is 8 ~11; The reaction conditions of the first reaction include: the reaction temperature is 10°C-50°C, and the reaction time is 6h-8h.

According to an embodiment of the present disclosure, in step S2, the dialysis treatment is performed using a dialysis membrane; the molecular weight of the dialysis membrane is 3500-10000 Da, the dialysis time is 6-10 days, and the water change interval of the dialysis treatment is 3-5 hours. The purpose of dialysis is to remove excess lysine.

According to an embodiment of the present disclosure, in step S3, the acid solution is an aqueous solution of 0.01 to 1 mol/l hydrochloric acid.

According to an embodiment of the present disclosure, in step S3, the amount of ethanol used is 2 to 4 times the volume of the third raw material liquid; the concentration of ethanol is 90 to 100%, preferably 93% to 97%; the alcohol precipitation time is 6 to 12 hours, preferably 8 to 10 hours; the number of alcohol precipitations is 1 to 4 times, preferably 2 to 3 times.

According to an embodiment of the present disclosure, in step S3, the drying process is freeze-drying; the freeze-drying conditions include: a temperature of -60~-50°C and a time of 36~72 hours.

According to an embodiment of the present disclosure, in step S4, the heating temperature is 50-90°C, preferably 50-80°C; the magnetic stirring time is 3-7 minutes, and the magnetic stirring speed is 50-150 rpm; calcium ions The concentration is 0.05~1mol/L, preferably 0.1~0.5mol/L.

A second aspect of the disclosure provides an amidated pectin gel prepared by the preparation method of the first aspect of the disclosure.

The third aspect of the present disclosure provides a use of the amidated pectin gel described in the second aspect of the present disclosure in food; the food includes yogurt, milkshakes, beverages, jelly and jam; the beverage is preferably a low-sugar beverage, and the jelly is preferably Low calorie jelly.

The present disclosure is further described below through examples, but the present disclosure is not limited thereby.

The citrus pectin used in the following examples was purchased from Beijing Solebao Biotechnology Co., Ltd. Lysine was purchased from Shanghai Yuanye Biotechnology Co., Ltd. Freeze drying is performed in a freeze dryer.

Example 1

(1) Dissolve 2g of pectin in 50mL of deionized water, stir magnetically for 7 to 10 hours, then add 2g of lysine, stir and dissolve, adjust the pH of the solution to 10 with NaOH solution, and place the solution in a 40°C water bath for reaction 8 Hour.

(2) After the reaction, use a dialysis membrane with a molecular weight of 3500 Da to dialyze in deionized water, and change the water every 4 hours for 7 days.

(3) After dialysis, adjust the pH of the solution to 3.8, add ethanol to precipitate, and freeze-dry to obtain amino acid amidated pectin, recorded as Lys10.

(4) Dissolve 0.1g Lys10 in 5mL deionized water, and adjust the pH to 3 with 0.1mol/L HCl aqueous solution. Heat the above pectin solution to 80°C, and slowly add 0.5 mL CaCl ₂ solution (0.3 mol/L) under vigorous stirring. Leave it at room temperature for 12 hours to obtain amidated pectin gel.

Example 2

The preparation method of the amino acid amidated pectin in this example is the same as that in Example 1. The difference is that in step (1), the pH is adjusted to 8 with 0.1 mol/L HCl aqueous solution. The amino acid amide obtained in step (3) The pectin is recorded as Lys8; in step (4), dissolve 0.1g Lys8 in 3.5mL deionized water, adjust the pH to 4 with 0.1mol/L HCl aqueous solution, heat the above pectin solution to 80°C, and stir vigorously under Slowly add 1.5 mL of CaCl ₂ (0.1 mol/L) solution under stirring, and leave it at room temperature for 12 hours to obtain amidated pectin gel.

Example 3

The preparation method of the amino acid amidated pectin in this example is the same as that in Example 1. The difference is that in step (1), the pH is adjusted to 9 with 0.1 mol/L HCl aqueous solution. The amino acid amide obtained in step (3) The pectin is recorded as Lys9; in step (4), dissolve 0.1g Lys9 in 3.5mL deionized water, adjust the pH to 4 with 0.1mol/L HCl aqueous solution, heat the above pectin solution to 80°C, and stir vigorously Slowly add 1.5 mL of CaCl ₂ (0.1 mol/L) solution under stirring, and leave it at room temperature for 12 hours to obtain amidated pectin gel.

Example 4

The preparation method of the amino acid amidated pectin in this embodiment is the same as in Example 1, except that in step (4), the pH is adjusted to 4 with 0.1 mol/L NaOH aqueous solution.

Example 5

The preparation method of the amino acid amidated pectin in this embodiment is the same as in Example 1, except that in step (4), the pH is adjusted to 5 with 0.1 mol/L NaOH aqueous solution to obtain amidated pectin gel.

Example 6

The preparation method of the amino acid amidated pectin in this embodiment is the same as in Example 1, except that in step (4), the pH is adjusted to 6 with 0.1 mol/L NaOH aqueous solution to obtain amidated pectin gel.

Example 7

The preparation method of the amino acid amidated pectin in this embodiment is the same as that in Example 1, except that in step (4), the pH is adjusted to 7 with 0.1 mol/L NaOH aqueous solution to obtain amidated pectin gel.

Example 8

The preparation method of the amino acid amidated pectin in this embodiment is the same as that in Example 3. The difference is that in step (4), the pH is adjusted to 8 with 0.1 mol/L NaOH aqueous solution to obtain amidated pectin gel.

Example 9

The preparation method of the amino acid amidated pectin in this embodiment is the same as that in Example 3, except that in step (4), the pH is adjusted to 9 with 0.1 mol/L NaOH aqueous solution to obtain amidated pectin gel.

Example 10

The preparation method of the amino acid amidated pectin in this embodiment is the same as that in Example 3, except that in step (4), the pH is adjusted to 10 with 0.1 mol/L NaOH aqueous solution to obtain amidated pectin gel.

Comparative example 1

Dissolve 2 g of pectin in 50 mL of deionized water, stir magnetically for 7 to 10 hours, and place the solution in a 40°C water bath for 8 hours. After the reaction, dialyze in deionized water using a dialysis membrane with a molecular weight of 3500 Da, and change the water every 4 hours for 7 days. After dialysis, adjust the pH of the solution to 3.8, add ethanol to precipitate, and freeze-dry to obtain amino acid amidated pectin, which is recorded as cp.

Comparative example 2

Dissolve 0.1g Lys10 in 5mL deionized water, and adjust the pH to 2 with 0.01~0.1mol/L NaOH and HCl aqueous solution. Heat the above pectin solution to 80°C, and slowly add 0.5 mL CaCl ₂ solution (0.3 mol/L) under vigorous stirring. Leave at room temperature for 12 hours and observe gel formation.

Test example 1

The grafting rate, Fructose content (Fuc, mol%), rhamnose content (Rha, mol%), arabinose content (Ara, mol%), galactose content (Gal, mol%), glucose content (Glc, mol%), wood Sugar content (Xyl, mol%), galacturonic acid content (GalA, mol%), galacturonic acid-rhamnose content (HG, mol%), rhamnogalacturonic acid glycan content (RGI, mol %), as well as the degree of esterification (DE%), amidation degree (DA%), relative molecular mass (Mw), and molecular weight dispersion index (Mw/Mn).

Among them, the passing energy of element surface components is 100eV, the conventional scanning resolution is 1.0eV, and the detailed analysis is 50eV, and the resolution is 0.1eV. The degree of amidation (DA) of cp and Lys10 was determined using an elemental analysis instrument, which measured the carbon and nitrogen content of the sample (Elementar UNICUBE, Elementar, Germany). The sample was burned or cracked at high temperature, and the elements to be measured were converted into gas products. . The analyzed gases are separated by temperature programmed adsorption (TPD) and detected in TCD (or optional IR). Calculate the degree of pectin amidation according to the following equation:

In the formula: M _C and M _N are the carbon and nitrogen contents (%) measured by elemental analysis, K is the number of carbon atoms in the amino acid, and DM ₀ is the methoxylation degree of the original pectin (%). Additionally, n is the number of nitrogen atoms per amino acid.

Characterization of physical and chemical properties: Add 5 mL of trifluoroacetic acid to 10 mgcp, Lys8, Lys9 and Lys10 respectively and acidolyze at 120°C for 1 hour. Blow dry the trifluoroacetic acid with a nitrogen blower and adjust the volume to 10 mL. Use ion chromatography to determine the monosaccharide composition. 5 mg of citrus pectin was dissolved into a 1 mg/mL solution with 0.1 M NaCl, passed through a 0.22 μm microporous filter membrane, and the molecular weight was measured using SEC-MALLS with a flow rate of 0.5 mL/min.

The degree of esterification was determined using infrared spectroscopy. Infrared spectrum characterization: Potassium bromide tableting method was used to perform infrared scanning of cp, Lys, Lys8, Lys9 and Lys10. Weigh 1 mg of dry cp, Lys, Lys8, Lys9 and Lys10 respectively, grind and mix thoroughly with 100 mg of dry potassium bromide powder in an agate mortar, use a tablet press to make the mixed powder into transparent flakes, and use infrared The spectrometer scans from 4000 to 400 cm ^-1 .

Characterization by hydrogen nuclear magnetic resonance spectrum: Weigh 40 mg of cp, Lys8, Lys9, Lys10 and cp+Lys respectively, and dissolve them in 2 mL D ₂ O with constant stirring. The pectin solution was freeze-dried twice, redissolved in 2 mL D ₂ O, and then transferred into a 5 mL NMR tube. Proton nuclear magnetic resonance ( ^1H MNR) spectra were recorded at 600 MHz using an Avance III HD 600M spectrometer (Bruker, Germany). Chemical shifts are reported in ppm and compared to the residual solvent signal for _D2O at δH 4.70 ppm.

Test example 2

Gel experiment:

(1) Dissolve 0.1gcp, Lys8, Lys9 and Lys10 in 3.5mL deionized water, then add 1.5mL of 0.1mol/L, 0.5mol/L and 1mol/L _CaCl2 solutions and stir vigorously at 80°C for 5min. The gel was then allowed to equilibrate at room temperature for 12 h. The CaCl ₂ solution was replaced with 1mol/L NaCl, 0.5mol/L ZnCl ₂ and 0.5mol/L MgCl ₂ solutions to compare the effects of different cations inducing gelation. The test results are shown in Figure 3.

(2) The strength of the pectin gels obtained in Examples 1, 4 to 10 was analyzed using a TA-XT physical property detector. The analyzer parameters are as follows: probe mold, A-BE; front probe speed, 5.0mm/s; measurement speed 1.0mm/s; compression distance: 40%. The test results are shown in Figure 4.

(3) Rheology measurement was performed on the pectin gels obtained in Examples 1 and 4 to 10. First, a stress sweep test with a frequency of 1 Hz was performed to determine the linear viscoelastic region of the gel. An angular frequency scan of 0.1 to 10 Hz was used to monitor the changes in storage modulus (G') and loss modulus (G") of the cation-pectin mixture at 25°C with 0.1% deformation (less than the maximum value of the linear viscoelastic range). , the test results are shown in Figure 5.

Table 1

Table 1 shows the primary structure information and amidation degree of the amidated pectin prepared in Examples 1, 2, 3 and Comparative Example 1 of the present disclosure, in which the amidation degree (DA%) of the amidated pectin Lys10 prepared in Example 1 ) is the highest, reaching 26.98%. Compared with the prior art, the amidation degree of pectin is improved. Figure 1 infrared spectrum shows that pectin and lysine are amidated successfully. Figure 2 proton nuclear magnetic resonance spectrum further shows that lysine is incorporated into pectin molecules, proving the success of pectin amidation.

Table 2

pH 3 4 5 6 7 8 9 10 Gel hardness(g) 116.97 265.04 306.71 338.10 341.31 370.30 279.93 256.86

Figure 3 shows that the strength of the gel formed by the amidated pectin modified with lysine is higher than that of the pectin not modified with lysine.

It can be seen from Table 2 and Figure 4 that Lys10 can form gels without adding sugar and at low calcium ion concentrations, and can form strong gels in the range of pH 3-10, with the highest gel strength at pH 8; in addition, Lys8 and Lys9 can also form gels without adding sugar and at low calcium ion concentrations, and can form stronger gels in a wider range. As can be seen from Figure 5, the elastic modulus G' of all gel samples prepared by Lys10 at different pHs is greater than G", indicating that the gels of Lys10 at pH 3-10 have the properties of a viscoelastic solid and can form coagulation. Glue; the gel formed by Lys8 and Lys9 also has the properties of a viscoelastic solid and can form a gel. In Figure 6, when the pH is 2 in Comparative Example 1, pectin cannot form a gel, but it can form a gel at a pH of 3 to 10. The formation of gel expands the pH range in which pectin forms gel; therefore, the method provided in this application expands the application range of pectin gel and is of great significance to the development and utilization of pectin in the food industry.

In summary, amino acid amidated pectin is prepared through the method provided by the present invention. The pectin can form a gel without adding sucrose and low calcium ion concentration, and can be used in acidic, neutral and alkaline environments. It can form gel, filling the application field of amidated pectin gel in the field of low-calorie food preparation in neutral and alkaline pH environment.

The preferred embodiments of the present disclosure have been described in detail above. However, the present disclosure is not limited to the specific details in the above-mentioned embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure. These simple modifications All belong to the protection scope of this disclosure.

In addition, it should be noted that the specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner as long as there is no contradiction. In order to avoid unnecessary repetition, various possible combinations are not further described in this disclosure.

In addition, any combination of various embodiments of the present disclosure can also be carried out, and as long as they do not violate the idea of the present disclosure, they should also be regarded as the contents disclosed in the present disclosure.

Claims (10)

1. A method for preparing amidated pectin gel, comprising the steps of:

s1, mixing pectin and water, and magnetically stirring to obtain a first raw material liquid; adding amino acid into the first raw material liquid, regulating the pH to a first pH value by using an alkali solution, and then performing a first reaction to obtain a second raw material liquid; the amino acid is lysine;

s2, dialyzing the second raw material liquid to obtain a third raw material liquid;

s3, adjusting the pH value of the third raw material liquid to 3.5-4.5 by using an acid solution, adding ethanol for alcohol precipitation, and drying the obtained precipitate to obtain amino acid amidated pectin;

s4, dissolving the amino acid amidated pectin in deionized water to form a fourth raw material liquid, regulating the pH to a second pH, and adding calcium ions under the conditions of heating and magnetic stirring to obtain amidated pectin gel; the second pH is 3-10; the weight ratio of the amino acid to pectin is 1:0.5 to 1.5;

the first pH is 10; the reaction conditions of the first reaction include: the reaction temperature is 10-50 ℃ and the reaction time is 6-8 hours.

2. The method of claim 1, wherein in step S1, the pectin is citrus pectin; the ratio of pectin to water is 1g: 20-60 mL; the time of magnetic stirring is 6-12 h, the speed of the magnetic stirring is 100-300 rpm, and the temperature of the magnetic stirring is 20-60 ℃.

3. The method according to claim 1, wherein in step S1, the alkali solution is 0.01-1 mol/L sodium hydroxide solution.

4. The method according to claim 1, wherein in step S2, the dialysis treatment is performed using a dialysis membrane having a molecular weight of 3500-10000 Da, the dialysis treatment is performed for 6-10 days, and the water exchange interval of the dialysis treatment is 3-5 hours.

5. The method according to claim 1, wherein in the step S3, the acid solution is an aqueous solution of 0.01-1 mol/l hydrochloric acid.

6. The method according to claim 1, wherein in the step S3, the amount of the ethanol is 2-4 times the volume of the third raw material liquid; the concentration of the ethanol is 90-100%; the time of the alcohol precipitation is 6-12 hours; the times of alcohol precipitation are 1-4 times.

7. The method according to claim 1, wherein in step S3, the drying process is freeze drying; the conditions of the freeze-drying include: the temperature is between 60 ℃ below zero and 50 ℃ below zero, and the time is between 36 and 72 hours.

8. The method according to claim 1, wherein in step S4, the heating temperature is 50-90 ℃; the time of the magnetic stirring is 3-7 minutes, and the speed of the magnetic stirring is 50-150 rpm;

the concentration of the calcium ions is 0.05-1 mol/L.

9. Amidated pectin gel prepared by the method according to any one of claims 1 to 8.

10. Use of the amidated pectin gel of claim 9 in a food product; the food includes yogurt, milk shake, beverage, jelly, and jam.