CN116462858B

CN116462858B - Preparation method and application of amidated pectin gel

Info

Publication number: CN116462858B
Application number: CN202310213210.8A
Authority: CN
Inventors: 郑金铠; 王继荣; 赵成英; 芦星淼; 杜以政
Original assignee: Institute of Food Science and Technology of CAAS
Current assignee: Institute of Food Science and Technology of CAAS
Priority date: 2023-03-06
Filing date: 2023-03-06
Publication date: 2024-03-01
Anticipated expiration: 2043-03-06
Also published as: CN116462858A

Abstract

The present disclosure relates to a method for preparing amidated pectin gel and its application. The preparation method comprises the following steps: the preparation method comprises the steps of taking citrus pectin as a raw material, taking amino acid as a modifier, adjusting the pH value of the solution to a limited range value in an aqueous solution without a catalyst, obtaining amino acid amidated pectin through dialysis and alcohol precipitation, dissolving the amino acid amidated pectin in water, adjusting the pH value again, and adding calcium ions to prepare the amidated pectin gel. According to the method, amidated pectin and gel thereof are prepared through double-link pH value regulation, the amidated pectin of the prepared amino acid is high in amidation degree, and meanwhile, the amidated pectin of the amino acid can form stronger gel under the condition of not adding sucrose and low calcium ion concentration and in the pH range of 3-10. The amidated pectin gel can be used in food such as yoghurt, milk shake, beverage, jelly, jam, baked food and the like, fills up the application of the amidated pectin gel in the field of food preparation in neutral and alkaline pH environments, and has wide application prospect.

Description

Preparation method and application of amidated pectin gel

Technical Field

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

Background

The preparation of gels from pectins is a common method, and the pectin gel mechanism is divided into two types according to the degree of esterification of the pectin, high-ester pectins need to be formed into gels under high sugar and high acid, and low-ester pectins generally need to be added with calcium ions to form egg-box structures for gelling. The high sugar required by the gel-forming conditions of high ester pectin is not beneficial to human health, and the pH range of the pectin gel is limited by the high acid environment, so that many chemical modifications are carried out on the pectin to improve the gel properties of the pectin, so that the pectin properties are improved, and the application of the pectin in foods is enlarged.

Amidated pectin refers to pectin containing CONH-R (r=h, OH, carbon radicals), which is a common pectin derivative. Compared with the traditional high-ester pectin formed under the high-sugar high-acid gel condition, the amidated pectin has good gel performance under the conditions of low sugar and low calcium ion concentration, is very favorable for forming gel, and can be used as a gel substance in the food industry. The traditional amidated pectin is prepared by hydrolyzing pectin methoxy groups with ammonia water in an ammonia alcohol system. Although this method is simple and widely used, the chemical agents used are mostly harmful, and its use in the food field is limited.

Amidation of amino acids with pectin is a milder reaction scheme. At present, the main method for synthesizing amino acid amidated pectin is to add papain under ultralow temperature conditions, but the ultralow temperature conditions are not suitable for industrial production generally. In addition, carbodiimide catalysts have also been used to synthesize amino acid amidated pectins, but the safety of the catalysts has yet to be verified. In addition, the synthesis of amidated pectin in an aqueous solution without catalyst is more suitable for the food industry. Pectin is reported to be synthesized with glycine, lysine and arginine in 40 ℃ aqueous solution, and has proved that the pectin has no cytotoxicity. However, the current preparation conditions of amino acid amidated pectin are limited, and the structural property is single; meanwhile, the gel property is an important basis for the application of the amino acid amidated pectin, the condition research of the existing amino acid amidated pectin gel is insufficient, the pH range required for forming the gel is narrow, and a certain Ca is needed ²⁺ The concentration can form gel, and the requirement of diversified foods cannot be met. Therefore, the invention creatively discloses a method for preparing amidated pectin and gel thereof by the pH value cooperative regulation of double-ring nodes, which comprises the steps of preparing the amino acid amidated pectin with specific structural properties by regulating the pH value, and further regulating the pH value in the gel forming process to obtainThe method is simple, low in cost and high in efficiency until amidated pectin gel is obtained; the prepared amino acid amidated pectin can form gel under acidic, neutral and alkaline conditions and under sugar-free and low-calcium ion concentration, and has wide application range and great development potential.

Disclosure of Invention

The purpose of the present disclosure is to provide a safe and efficient preparation method of amidated pectin gel and application thereof, wherein the preparation method is simple and efficient, and amidated pectin and gel thereof are prepared through two-link pH value regulation. The preparation method comprises the steps of taking citrus pectin as a raw material, taking amino acid as a modifier, adjusting the pH value of the solution to a limited range value in an aqueous solution without a catalyst, dialyzing and precipitating with alcohol to obtain amino acid amidated pectin, dissolving the amino acid amidated pectin in water, adjusting the pH value again, and adding calcium ions to prepare the amidated pectin gel. The obtained amino acid amidated pectin has high amidation degree; the amino acid amidated pectin can form amidated pectin gel in pH3-10 without adding cane sugar and low calcium ion concentration, and may be used in sour milk, milk shake, beverage, jelly, jam, baked food, etc. and has filled in the application of amidated pectin gel in preparing food in neutral and alkaline pH environment.

To achieve the above object, a first aspect of the present disclosure provides a method for preparing an 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;

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, adjusting 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.

Optionally, in step S1, the pectin is citrus pectin; the citrus pectin is one of commercial citrus pectin and pectin extracted from citrus peel; the amino acid is lysine; the ratio of pectin to water is 1g: 20-60 mL; the time of the 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 ℃; the weight ratio of the lysine to the pectin is 1:0.5-1.5.

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

Optionally, in step S2, the dialysis treatment is performed by 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 exchange interval of the dialysis treatment is 3-5 hours. Optionally, in step S3, the acid solution is an aqueous solution of 0.01-1 mol/l hydrochloric acid.

Optionally, in 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 h; the times of alcohol precipitation are 1-4 times.

Optionally, in step S3, the drying treatment is freeze drying; the conditions of the freeze-drying include: the temperature is between 60 ℃ below zero and 50 ℃ below zero for 36 to 72 hours.

Optionally, 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.

The second aspect of the present disclosure provides an amidated pectin gel prepared by the method of the first aspect of the present disclosure.

A third aspect of the present disclosure provides a use of an amidated pectin gel according to the second aspect of the present disclosure in a food product; the food comprises yoghurt, milk shake, beverage, jelly and jam; the beverage is preferably a low sugar beverage and the jelly is preferably a low calorie jelly.

Through the technical scheme, the method for preparing the amidated pectin gel through the two-link pH value regulation and control can prepare the amidated pectin gel under acidic, neutral and alkaline conditions, so that the application range of the pectin gel is enlarged, the method can be used in foods such as yoghurt, milk shake, beverage, jelly, jam and baked foods, and the application of the amidated pectin gel in the field of neutral and alkaline pH environment food preparation is filled, and the method has a wide application prospect. The method is simple to operate, efficient and safe in preparation method and easy to realize industrial production.

Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:

FIG. 1 is an infrared spectrum of amidated pectin and lysine prepared in examples 1-3, comparative example 1 of the present disclosure.

FIG. 2 shows the hydrogen nuclear magnetic resonance spectra of amidated pectin prepared by mixing cp and lysine alone (without amidation reaction) in examples 1-3, comparative example 1 of the present disclosure ¹ H)。

Fig. 3 is a graph showing the appearance of gels formed under different cation induction of amidated pectins prepared in examples 1 to 3 and comparative example 1 of the present disclosure.

Fig. 4 is a graph showing gel strength of amidated pectin gels prepared in examples 1, 4-10 of the present disclosure.

Fig. 5 is a graph showing the rheological properties of amidated pectin gels prepared in examples 1, 4-10 of the present disclosure.

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

Detailed Description

Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.

The method for preparing the amidated pectin gel by regulating the pH value in the process of forming the amidated pectin gel by regulating the pH value is provided. The prepared amidated pectin can form gel under acidic, neutral and alkaline conditions, fills the application of the amidated pectin gel in the field of food preparation in neutral and alkaline pH environments, is simple and convenient to operate, has easily obtained raw materials, is easy to realize industrial production, and has wide application prospect.

The first aspect of the present disclosure provides a method for preparing an amidated pectin gel, comprising the steps of:

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 to 10, preferably 6 to 8.

According to one 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 peel; the amino acid is lysine; the ratio of pectin to water was 1g:20 to 60mL, preferably 1g: 25-50 mL; the magnetic stirring time is 6-12 h, preferably 7-10 h, the magnetic stirring speed is 100-300 rpm, preferably 150-250 rpm, the magnetic stirring temperature is 20-60 ℃, preferably 25-50 ℃; the weight ratio of amino acid to pectin is 1:0.5-1.5, preferably 1:1-1.5.

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

According to one 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 changing interval of dialysis treatment is 3-5 hours. The purpose of dialysis is to remove excess lysine.

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

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

According to one embodiment of the present disclosure, in step S3, the drying process is freeze drying; the conditions for lyophilization included: the temperature is between 60 ℃ below zero and 50 ℃ below zero for 36 to 72 hours.

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

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

A third aspect of the present disclosure provides a use of an amidated pectin gel according to the second aspect of the present disclosure in a food product; food products include yogurt, milkshake, beverages, jellies, and jams; the beverage is preferably a low sugar beverage and the jelly is preferably a low calorie jelly.

The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereby.

The citrus pectin used in the examples below was purchased from Beijing Soy Biotechnology Co. Lysine was purchased from Shanghai Seiyaka Biotechnology Co. The freeze-drying is performed in a freeze-dryer.

Example 1

(1) 2g of pectin is dissolved in 50mL of deionized water, stirred magnetically for 7-10 h, 2g of lysine is added, the pH of the solution is adjusted to 10 by NaOH solution after stirring and dissolution, and the solution is placed in a water bath at 40 ℃ for reaction for 8h.

(2) After the reaction was completed, the reaction was dialyzed against deionized water using a dialysis membrane having a molecular weight of 3500Da, and water was changed every 4 hours for 7 days.

(3) After the dialysis is completed, the pH of the solution is adjusted to 3.8, ethanol is added for ethanol precipitation, and the amino acid amidated pectin, which is marked as Lys10, is obtained by freeze drying.

(4) 0.1g of Lys10 was dissolved in 5mL of deionized water and the pH was adjusted to 3 with 0.1mol/L aqueous HCl. Heating the pectin solution to 80deg.C, and slowly adding 0.5ml NaCl under vigorous stirring ₂ Solution (0.3 mol/L). The resulting amidated pectin gel was allowed to stand at room temperature for 12 hours.

Example 2

The preparation method of the amino acid amidated pectin of this example is the same as in example 1, except that: in the step (1), the pH value is regulated to 8 by using 0.1mol/L HCl aqueous solution, and the amino acid amidated pectin obtained in the step (3) is marked as Lys8; in step (4), 0.1g Lys8 was dissolved in 3.5mL deionized water, the pH was adjusted to 4 with 0.1mol/L HCl aqueous solution, the pectin solution was heated to 80℃and 1.5mL CaCl was slowly added with vigorous stirring ₂ (0.1 mol/L) solution, and standing at room temperature for 12 hours to obtain amidated pectin gel.

Example 3

The preparation method of the amino acid amidated pectin of this example is the same as in example 1, except that: in the step (1), the pH value is regulated to 9 by 0.1mol/L HCl aqueous solution, and the amino acid amidated pectin obtained in the step (3) is marked as Lys9; in step (4), 0.1g Lys9 was dissolved in 3.5mL deionized water and dissolved in 0.1mol/L HClThe pH of the solution was adjusted to 4, the pectin solution was heated to 80℃and 1.5mL CaCl was slowly added with vigorous stirring ₂ (0.1 mol/L) solution, and standing at room temperature for 12 hours to obtain amidated pectin gel.

Example 4

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

Example 5

The preparation method of the amino acid amidated pectin of this example is the same as in example 1, except that: in the step (4), the pH is adjusted to 5 by using 0.1mol/L NaOH aqueous solution, and amidated pectin gel is obtained.

Example 6

The preparation method of the amino acid amidated pectin of this example is the same as in example 1, except that: in the step (4), the pH is adjusted to 6 by using 0.1mol/L NaOH aqueous solution, and amidated pectin gel is obtained.

Example 7

The preparation method of the amino acid amidated pectin of this example is the same as in example 1, except that: in the step (4), pH is adjusted to 7 by using 0.1mol/L NaOH aqueous solution, and amidated pectin gel is obtained.

Example 8

The preparation method of the amino acid amidated pectin of this example is the same as in example 3, except that: in the step (4), the pH is adjusted to 8 by using 0.1mol/L NaOH aqueous solution, and amidated pectin gel is obtained.

Example 9

The preparation method of the amino acid amidated pectin of this example is the same as in example 3, except that: in the step (4), the pH is adjusted to 9 by using 0.1mol/L NaOH aqueous solution, and amidated pectin gel is obtained.

Example 10

The preparation method of the amino acid amidated pectin of this example is the same as in example 3, except that: in the step (4), the pH is adjusted to 10 by using 0.1mol/L NaOH aqueous solution, and amidated pectin gel is obtained.

Comparative example 1

2g of pectin is dissolved in 50mL of deionized water, magnetically stirred for 7-10 hours, and the solution is placed in a water bath at 40 ℃ for 8 hours. After the reaction was completed, the reaction was dialyzed against deionized water using a dialysis membrane having a molecular weight of 3500Da, and water was changed every 4 hours for 7 days. After the dialysis is finished, the pH of the solution is regulated to 3.8, ethanol is added for ethanol precipitation, and freeze drying is carried out, so that amino acid amidated pectin which is marked as cp is obtained.

Comparative example 2

0.1g of Lys10 is dissolved in 5mL of deionized water, and the pH is adjusted to 2 with 0.01-0.1 mol/L NaOH and HCl aqueous solution. Heating the above solution on the fruit gel to 80deg.C, and slowly adding 0.5ml NaCl under vigorous stirring ₂ Solution (0.3 mol/L). The gel was allowed to stand at room temperature for 12 hours, and the gel formation was observed.

Test example 1

The amino acid amidated pectin Lys10 obtained in step (3) in examples 1 to 3 and the amino acid amidated pectin cp prepared in comparative example 1 were measured for grafting ratio, fructose content (Fuc, mol%), rhamnose content (Rha, mol%), arabinose content (Ara, mol%), galactose content (Gal, mol%), glucose content (Glc, mol%), xylose content (Xyl, mol%), galacturonic acid content (GalA, mol%), galacturonic acid-rhamnose content (HG, mol%), rhamnogalacturonan content (RGI, mol%), and degree of esterification (DE%), degree of amidation (DA%), relative molecular mass (Mw), molecular weight dispersion index (Mw/Mn) by an elemental analyzer, ion chromatography, infrared spectroscopy, SEC-MALLS.

Wherein, the passing energy of the element surface component is 100eV, the conventional scanning resolution is 1.0eV, 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 measures the carbon and nitrogen content of the sample (Elementar UNICUBE, elementar, germany), which burns or cracks at high temperatures, the element to be measured being converted into a gaseous product. The analyte gas was separated by temperature programmed adsorption (TPD) and detected in TCD (or optionally IR). Pectin amidation was calculated according to the following equation:

wherein: m is M _C 、M _N Carbon and nitrogen contents (%), K is the number of carbon atoms in the amino acid, DM, measured by elemental analysis ₀ The degree of methoxylation (%) of the original pectin. In addition, n is the number of nitrogen atoms per amino acid.

Physical and chemical property characterization: 5mL of trifluoroacetic acid is added into 10mgcp, lys8, lys9 and Lys10 respectively for acidolysis for 1h at 120 ℃, the trifluoroacetic acid is blown dry by a nitrogen blowing instrument, the volume is fixed to 10mL, and the monosaccharide composition is determined by ion chromatography. 5mg of citrus pectin was dissolved in 0.1M NaCl to a solution of 1mg/mL, passed through a 0.22 μm microporous filter membrane, and the molecular weight was determined by SEC-MALLS at a flow rate of 0.5mL/min.

The degree of esterification was determined by infrared spectroscopy. Characterization by infrared spectrum: infrared scans of cp, lys, lys, lys9 and Lys10 were performed using potassium bromide tabletting. Weighing 1mg of dry cp, lys, lys, lys9 and Lys10 respectively, fully grinding and mixing with 100mg of dry potassium bromide powder in an agate mortar, making the mixed powder into transparent slices by a tablet press, and measuring 4000 to 400cm by an infrared spectrometer ^-1 Scanning is performed in a range.

Nuclear magnetic resonance hydrogen spectrum characterization: weighing cp, lys8, lys9, lys10 and cp+Lys 40mg respectively, dissolving in 2mL D ₂ The O is continuously stirred and dissolved. The pectin solution was lyophilized twice repeatedly and then dissolved in 2mL D ₂ O and then transferred to a 5mL NMR tube. Recording proton nuclear magnetic resonance @ 600MHz using an Avance III HD 600M spectrometer (Bruker, germany) ¹ Hmnr) spectra. Chemical shifts are reported in ppm and are reported in relation to D ₂ The residual solvent signal at δH24.70 ppm was compared with O.

Test example 2

Gel experiment:

(1) 0.1gcp, lys8, lys9 and Lys10 were dissolved in 3.5mL deionized water, then 1.5mL of 0.1mol/L, 0.5mol/L and 1mol/L CaCl were added ₂ The solution was stirred vigorously at 80℃for 5min. The gel was then allowed to equilibrate for 12h at room temperature. CaCl is added with ₂ The solution is replaced by 1mol/L NaCl and 0.5mol/L ZnCl ₂ And 0.5mol/L MgCl ₂ Solutions, comparing the effect of different cations on the induced gel. TestingThe results are shown in FIG. 3.

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

(3) Rheological measurements were performed on the pectin gels obtained in examples 1, 4 to 10. Stress sweep testing was first performed at a frequency of 1Hz to determine the linear viscoelastic region of the gel. The change in storage modulus (G ') and loss modulus (G') of the cation-pectin mixture at 25℃was monitored at 0.1% deformation (less than the maximum value of the linear viscoelastic range) using an angular frequency sweep of 0.1-10 Hz, and the test results are shown in FIG. 5.

TABLE 1

Table 1 shows the primary structure information and the amidation degree of the amidated pectin prepared in examples 1, 2 and 3 and comparative example 1, wherein the amidation degree (DA%) of the amidated pectin Lys10 prepared in example 1 is highest, and reaches 26.98%, which is improved compared with the amidation degree of pectin in the prior art. The infrared spectrum of fig. 1 shows that the pectin was successfully amidated with lysine, and the hydrogen nuclear magnetic resonance spectrum of fig. 2 further shows that lysine is incorporated into the pectin molecule, demonstrating 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

FIG. 3 shows that amidated pectin obtained after modification with lysine forms a gel with a higher strength than pectin without lysine modification.

As can be seen from table 2 and fig. 4, lys10 forms a gel without sugar and at low calcium ion concentration, and forms a stronger gel in the pH range 3-10, with the highest gel strength at pH 8; in addition, lys8 and Lys9 can form gels without sugar and at low calcium ion concentrations, and can form stronger gels over a wider range. As can be seen from FIG. 5, all gel samples prepared from Lys10 at different pH values have elastic modulus G' greater than G ", which indicates that the gel of Lys10 at pH3-10 has the property of viscoelastic solid and can form gel; the gels formed by Lys8 and Lys9 also have the properties of viscoelastic solids, both of which can form gels. In FIG. 6, pectin does not form a gel when the pH is 2 in comparative example 1, and can form a gel when the pH is 3-10, so that the pH range of the pectin for forming the gel is enlarged; therefore, the method provided by the application expands the application range of the pectin gel and has important significance for development and utilization of pectin in the food industry.

In conclusion, the amino acid amidated pectin prepared by the method provided by the invention can form gel under the condition of not adding sucrose and low calcium ion concentration, and can form gel in acidic, neutral and alkaline environments, so that the application of the amidated pectin gel in the field of low-calorie food preparation in neutral and alkaline pH environments is filled.

The preferred embodiments of the present disclosure have been described in detail above, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.

In addition, the specific features described in the above embodiments may be combined in any suitable manner without contradiction. The various possible combinations are not described further in this disclosure in order to avoid unnecessary repetition.

Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.

Claims

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;

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.