Preparation method and application of starch gel of bamboo leaf extract

Abstract

The present application relates to the technical field of food additive, and particularly relates to a preparation method and application of a starch gel containing bamboo leaf extract, wherein sodium alginate, konjac glucomannan and chitosan are dissolved in water to obtain a first mixed solution, calcium carbonate is added into a bamboo leaf extract solution to obtain a second mixed solution, the second mixed solution is added drop by drop into the first mixed solution, and then the gel microspheres containing the bamboo leaf extract are obtained by standing, filtering and freeze-drying; the gel microspheres are added into an acetic acid-sodium acetate buffer solution, and then an ethanol solution is added for surface treatment; the starch gel is dissolved in water, and then the gel microspheres after surface treatment are put into the starch gel to obtain the bamboo leaf extract-starch gel. The bamboo leaf extract-starch gel can be used as a food additive to prepare rice cakes, so as to prolong the water-locking performance and shelf life of the rice cakes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food additives, in particular to a preparation method and application of a starch gel containing indocalamus leaf extract. BACKGROUND

[0002] Indocalamus leaf generally refers to the leaf of the plant Indocalamus latifolius, which can be used as food packaging material, such as for wrapping rice dumplings. Indocalamus leaf itself has high medicinal value, and its extract contains various elements, polyphenols and polysaccharides, and has the effects of inhibiting bacteria and retaining water.

[0003] Rice cake is a traditional food, but the raw material of rice cake is indica rice, which contains a large amount of amylose. Amylose is prone to aging, which causes the rice cake to become hard. Rice cake cannot be stored for a long time. Even if it is not spoiled during storage, the taste of the rice cake will decrease sharply due to aging, water loss and other reasons, making it difficult to swallow.

[0004] Therefore, it is a feasible method to add indocalamus leaf extract to rice cake and other foods to extend the shelf life without adding additional food additives. However, experiments have found that directly adding indocalamus leaf extract during the preparation of rice cake does not have obvious effects. SUMMARY

[0005] The present application aims to solve the problem of the combination of indocalamus leaf extract and rice cake as described in the background art. A preparation method and application of indocalamus leaf extract-starch gel are proposed. The indocalamus leaf extract-starch gel obtained by the preparation method can effectively extend the shelf life of rice cake and maintain the elasticity of rice cake for a long time.

[0006] The technical solution adopted by the present application to solve the technical problem is a preparation method of indocalamus leaf extract-starch gel, which comprises the following steps:

[0007] 1) Dissolve sodium alginate, konjac glucomannan and chitosan in water to obtain a first mixture, wherein the mass ratio of sodium alginate, konjac glucomannan and chitosan is (2-3):(1-2):(1-2), and the mass fraction of chitosan in the first mixture is 1-2%;

[0008] 2) Add calcium carbonate to the indocalamus leaf extract solution to obtain a second mixture, wherein the mass fraction of calcium carbonate in the second mixture is 1-5%;

[0009] 3) Drop the second mixture into the first mixture drop by drop, stand, filter and freeze-dry to obtain gel microspheres containing indocalamus leaf extract;

[0010] 4) adding the gel microspheres into acetic acid-sodium acetate buffer solution, controlling pH to be 6-7, then adding ethanol solution, stirring for 5-30 min to obtain the surface-treated gel microspheres.

[0011] 5) adding modified starch into water to prepare modified starch milk, adding crosslinking agent into the modified starch milk, heating to 65-85℃ for 1-3 h, washing, freeze-drying to obtain starch gel, the mass fraction of starch in the modified starch milk being 30-50%;

[0012] 6) dissolving the starch gel in water, placing into the surface-treated gel microspheres, using ultrasonic oscillation for 0.5-1 h, standing, filtering, freeze-drying to obtain the reed leaf extract / starch gel.

[0013] In the above technical solution, the sodium alginate, konjac glucomannan and chitosan are complexed with calcium ions to form gel microspheres, so that the reed leaf extract is wrapped in the gel microspheres, the inside of the gel microspheres is a dense three-dimensional network structure, the surface of the gel microspheres is treated in step 4) to produce holes, so that the reed leaf extract is controlled to be slowly released, finally, the gel microspheres are wrapped with starch gel, so that the starch permeates the holes of the gel microspheres, fills into the network structure and forms a layer of outer shell on the surface of the gel microspheres, so that the reed leaf extract is not easily released and invalid during the making of rice cakes, but after the making is completed, the outer starch gel shell is partially destroyed, the reed leaf extract can be slowly released into the rice cakes, locks the water in the rice cakes and inhibits the growth of microorganisms, so as to prolong the shelf life of the rice cakes.

[0014] As a preferred, the preparation method of the reed leaf extract is:

[0015] The reed leaf is cut and mixed with 65% volume fraction of ethanol solution, a reed leaf extract solution is obtained by using carbon dioxide supercritical fluid technology, and the reed leaf extract is obtained by freeze-drying, wherein the mass ratio of the reed leaf to the ethanol solution is 1:12-14, and the parameters of the carbon dioxide supercritical fluid are: extraction pressure 18-20 MPa, extraction temperature 45-50℃, carbon dioxide flow rate 20-25 L / h, separation pressure 4-6 MPa, and separation temperature 30-33℃.

[0016] As a preferred, the mass fraction of calcium chloride in the second mixed solution is 1-3%.

[0017] As a preferred, in step 4), the mass ratio of the gel microspheres to the ethanol solution is 1:20-50, the volume fraction of the ethanol solution is 25%, and further, the mass ratio of the gel microspheres to the ethanol solution is 1:30.

[0018] As preferred, the preparation method of the modified starch is: dispersing starch in water, adding sodium hydroxide and chloroacetic acid, incubating at 30-40℃ for 2-4h, filtering, washing, drying to obtain carboxymethyl starch, adding the carboxymethyl starch into an enzyme solution for enzymolysis to obtain the modified starch, the molar ratio of the starch to chloroacetic acid is 1:3-5, the molar ratio of the chloroacetic acid to sodium hydroxide is 1:2-4, and the enzyme is added in an amount of 50-120 U / g, further, the molar ratio of the starch to chloroacetic acid is 1:4, the molar ratio of the chloroacetic acid to sodium hydroxide is 1:3, and the enzyme is added in an amount of 100 U / g.

[0019] As preferred, the specific conditions of the enzymolysis are: enzymolysis at a temperature of 20-40℃ and a pH of 6-8 for 12-36h, filtering, and washing until no enzyme residue is left.

[0020] As preferred, the enzyme is α-amylase.

[0021] As preferred, the crosslinking agent is sodium trimetaphosphate, and the crosslinking agent is added in an amount of 0.02-0.06g / ml, further, the crosslinking agent is added in an amount of 0.03g / ml.

[0022] As preferred, the preparation method of the reed leaf extract / starch gel is the following steps:

[0023] 1) dissolving sodium alginate, konjac glucomannan and chitosan in water to obtain a first mixed solution, the mass ratio of the sodium alginate, konjac glucomannan and chitosan is 3:1:1, and the mass fraction of chitosan in the first mixed solution is 1%;

[0024] 2) adding calcium carbonate into a reed leaf extract solution to obtain a second mixed solution, and the mass fraction of calcium carbonate in the second mixed solution is 1.5%;

[0025] 3) adding the second mixed solution drop by drop into the first mixed solution, standing, filtering, and freeze-drying to obtain gel microspheres containing reed leaf extract;

[0026] 4) adding the gel microspheres into an acetic acid-sodium acetate buffer solution, controlling the pH to be 6, and then adding an ethanol solution, stirring for 10min to obtain surface-treated gel microspheres.

[0027] 5) adding modified starch into water to prepare a modified starch milk, adding a crosslinking agent into the modified starch milk, heating to 70℃ and incubating for 2h, washing, and freeze-drying to obtain a starch gel;

[0028] 6) dissolving the starch gel in water, placing into the surface-treated gel microspheres, ultrasonic oscillation for 0.5h, standing, filtering, and freeze-drying to obtain reed leaf extract / starch gel.

[0029] A reed extract / starch gel prepared by the preparation method.

[0030] Application of the reed extract-starch gel in the food field, the reed extract / starch gel is used for preparing rice cakes, specifically, the raw materials required for preparing rice cakes are mixed with the reed extract-starch gel, fermented, steamed, and cooled to obtain rice cakes, and the prepared rice cakes have excellent water locking and bacteriostatic properties, thereby obtaining a longer shelf life.

[0031] The beneficial effects of the present application are:

[0032] 1、The present application uses sodium alginate, konjac glucomannan and chitosan to form gel microspheres by complexation reaction with calcium ions, so that the reed extract can be wrapped in the gel microspheres, compared with only using sodium alginate, the addition of konjac glucomannan makes the release rate of reed extract uniform, and the addition of chitosan makes the gel microspheres can coat more reed extract.

[0033] 2、The present application is treated by ethanol, so that the surface of the gel microspheres appears holes, which is convenient for the subsequent release of reed extract, and the starch fills the internal voids of the gel microspheres and forms a coating on the surface of the gel microspheres, protecting the activity of the reed extract during the processing of rice cakes;

[0034] 3、The present application uses modified starch, which is first carboxymethylated and then enzymatically hydrolyzed, so that the starch gel prepared from the modified starch has better water locking performance;

[0035] 4、The reed extract of the present application is extracted by carbon dioxide supercritical fluid technology, so that the effective components in the reed are ensured to have higher activity. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed description is illustrative only and is intended to provide further description of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0037] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, they refer to the presence of a feature, step, operation, device, component and / or combinations thereof.

[0038] The application will be further described in conjunction with specific examples. The following examples are only for the purpose of explaining the application, but do not constitute a limitation of the application. The test samples and test procedures used in the following examples include the following (if the specific conditions of the experiments are not specified in the examples, the general conditions or the conditions recommended by the reagent company are usually used; the reagents, consumables, etc. used in the following examples can be obtained from commercial channels if not otherwise specified).

[0039] Preparation of reed leaf extract

[0040] The reed leaf is cut and mixed with a 65% volume fraction of ethanol solution to obtain a reed leaf extract solution by using carbon dioxide supercritical fluid technology, and the reed leaf extract is obtained by freeze-drying. The mass ratio of the reed leaf to the ethanol solution is 1:13, and the parameters of the carbon dioxide supercritical fluid are as follows: extraction pressure 20 MPa, extraction temperature 48℃, carbon dioxide flow rate 22 L / h, separation pressure 5 MPa, and separation temperature 32℃.

[0041] Preparation of modified starch

[0042] 1) The starch is dispersed in water, sodium hydroxide and chloroacetic acid are added, and the reaction is carried out at 30-40℃ for 2-4h, then filtered, washed and dried to obtain carboxymethyl starch. The molar ratio of starch to chloroacetic acid is 1:4, and the molar ratio of chloroacetic acid to sodium hydroxide is 1:3.

[0043] 2) The carboxymethyl starch is added to an enzyme solution, and the enzymolysis is carried out at 30℃ for 24h, then filtered, washed until no enzyme residue is left to obtain modified starch. The amount of enzyme added is 100 U / g, and the enzyme is α-amylase.

[0044] Example 1

[0045] A preparation method of a reed leaf extract / starch gel, which comprises the following steps:

[0046] 1) 3 parts of sodium alginate, 1 part of konjac glucomannan, 1 part of chitosan and 100 parts of water are mixed to obtain a first mixed solution;

[0047] 2) 1.5 parts of calcium carbonate is added to 100 parts of reed leaf extract solution to obtain a second mixed solution;

[0048] 3) The second mixed solution is added dropwise into the first mixed solution, and then left to stand, filtered and freeze-dried to obtain gel microspheres containing reed leaf extract;

[0049] 4) The gel microspheres are added to an acetic acid-sodium acetate buffer solution, the pH is controlled at 6, and then a 25% ethanol solution is added, and stirring is performed for 10 min to obtain surface-treated gel microspheres, wherein the mass ratio of the gel microspheres to the ethanol solution is 1:30;

[0050] 5) 3 parts of modified starch are added to 10 parts of water to prepare a modified starch milk, sodium trimetaphosphate is added to the modified starch milk, heating is performed to 70°C for 2 h, washing is performed, and freeze-drying is performed to obtain a starch gel, wherein the amount of sodium trimetaphosphate added is 0.03 g / ml of the modified starch milk;

[0051] 6) The starch gel is dissolved in water, and is placed into the surface-treated gel microspheres, ultrasonic oscillation is performed for 1 h, standing is performed, filtration is performed, and freeze-drying is performed to obtain the reed leaf extract / starch gel.

[0052] Comparative Example 1

[0053] A preparation method of a reed leaf extract / starch gel, the preparation method comprising the following steps:

[0054] 1) 3 parts of sodium alginate and 100 parts of water are mixed to obtain a first mixed solution;

[0055] 2) 1.5 parts of calcium carbonate are added to 100 parts of a reed leaf extract solution to obtain a second mixed solution;

[0056] 3) The second mixed solution is added dropwise into the first mixed solution, standing is performed, filtration is performed, and freeze-drying is performed to obtain gel microspheres containing the reed leaf extract;

[0057] 4) The gel microspheres are added to an acetic acid-sodium acetate buffer solution, the pH is controlled at 6, and then a 25% ethanol solution is added, and stirring is performed for 10 min to obtain surface-treated gel microspheres, wherein the mass ratio of the gel microspheres to the ethanol solution is 1:30;

[0058] 5) 3 parts of modified starch are added to 10 parts of water to prepare a modified starch milk, sodium trimetaphosphate is added to the modified starch milk, heating is performed to 70°C for 2 h, washing is performed, and freeze-drying is performed to obtain a starch gel, wherein the amount of sodium trimetaphosphate added is 0.03 g / ml of the modified starch milk;

[0059] 6) The starch gel is dissolved in water, and is placed into the surface-treated gel microspheres, ultrasonic oscillation is performed for 1 h, standing is performed, filtration is performed, and freeze-drying is performed to obtain the reed leaf extract / starch gel.

[0060] Example 2

[0061] A preparation method of a reed leaf extract / starch gel, the preparation method comprising the following steps:

[0062] 1) 3 parts of sodium alginate, 1 part of konjac glucomannan, 1 part of chitosan and 100 parts of water are mixed to obtain a first mixed solution;

[0063] 2) 1.5 parts of calcium carbonate are added to 100 parts of the extract solution of the reed canary grass to obtain a second mixed solution;

[0064] 3) The second mixed solution is added dropwise into the first mixed solution, and then left to stand, filtered, and freeze-dried to obtain gel microspheres containing the extract of the reed canary grass;

[0065] 4) The gel microspheres are added to an acetic acid-sodium acetate buffer solution, and the pH is controlled to be 6, and then 25% ethanol solution is added, and stirred for 10 min to obtain the gel microspheres after surface treatment, wherein the mass ratio of the gel microspheres to the ethanol solution is 1:20;

[0066] 5) 3 parts of modified starch are added to 10 parts of water to prepare a modified starch milk, sodium trimetaphosphate is added to the modified starch milk, heated to 70°C and kept for 2 h, washed, and freeze-dried to obtain starch gel, wherein the amount of sodium trimetaphosphate added is 0.03 g / ml of the modified starch milk;

[0067] 6) The starch gel is dissolved in water, and then placed into the gel microspheres after surface treatment, and ultrasonic oscillation is performed for 1 h, left to stand, filtered, and freeze-dried to obtain the extract of the reed canary grass / starch gel.

[0068] Example 3

[0069] A preparation method of an extract of reed canary grass / starch gel, the preparation method comprising the following steps:

[0070] 1) 3 parts of sodium alginate, 1 part of konjac glucomannan, 1 part of chitosan and 100 parts of water are mixed to obtain a first mixed solution;

[0071] 2) 1.5 parts of calcium carbonate are added to 100 parts of the extract solution of the reed canary grass to obtain a second mixed solution;

[0072] 3) The second mixed solution is added dropwise into the first mixed solution, and then left to stand, filtered, and freeze-dried to obtain gel microspheres containing the extract of the reed canary grass;

[0073] 4) The gel microspheres are added to an acetic acid-sodium acetate buffer solution, and the pH is controlled to be 6, and then 25% ethanol solution is added, and stirred for 10 min to obtain the gel microspheres after surface treatment, wherein the mass ratio of the gel microspheres to the ethanol solution is 1:40;

[0074] 5) 3 parts of modified starch are added to 10 parts of water to prepare a modified starch milk, sodium trimetaphosphate is added to the modified starch milk, heated to 70°C for 2h, washed, and freeze-dried to obtain a starch gel, wherein the amount of sodium trimetaphosphate added is 0.03g / ml of modified starch milk;

[0075] 6) The starch gel is dissolved in water, placed into the surface-treated gel microspheres, ultrasonically oscillated for 1h, left to stand, filtered, and freeze-dried to obtain the reed leaf extract / starch gel.

[0076] Example 4

[0077] A preparation method of a reed leaf extract / starch gel, comprising the following steps:

[0078] 1) 3 parts of sodium alginate, 1 part of konjac glucomannan, 1 part of chitosan, and 100 parts of water are mixed to obtain a first mixed solution;

[0079] 2) 1.5 parts of calcium carbonate are added to 100 parts of a reed leaf extract solution to obtain a second mixed solution;

[0080] 3) The second mixed solution is added dropwise into the first mixed solution, left to stand, filtered, and freeze-dried to obtain gel microspheres containing reed leaf extract;

[0081] 4) The gel microspheres are added to an acetic acid-sodium acetate buffer solution, the pH is controlled to be 6, and then 25% ethanol solution is added, stirred for 10 min to obtain surface-treated gel microspheres, wherein the mass ratio of the gel microspheres to the ethanol solution is 1:50;

[0082] 5) 3 parts of modified starch are added to 10 parts of water to prepare a modified starch milk, sodium trimetaphosphate is added to the modified starch milk, heated to 70°C for 2h, washed, and freeze-dried to obtain a starch gel, wherein the amount of sodium trimetaphosphate added is 0.03g / ml of modified starch milk;

[0083] 6) The starch gel is dissolved in water, placed into the surface-treated gel microspheres, ultrasonically oscillated for 1h, left to stand, filtered, and freeze-dried to obtain the reed leaf extract / starch gel.

[0084] Comparative Example 2

[0085] A preparation method of a reed leaf extract / starch gel, comprising the following steps:

[0086] 1) 3 parts of sodium alginate, 1 part of konjac glucomannan, 1 part of chitosan, and 100 parts of water are mixed to obtain a first mixed solution;

[0087] 2) 1.5 parts of calcium carbonate is added to 100 parts of the extract solution of the reed canary grass to obtain a second mixture;

[0088] 3) The second mixture is added dropwise into the first mixture, and then left to stand, filtered, and freeze-dried to obtain the gel microspheres containing the extract of the reed canary grass;

[0089] 4) 3 parts of modified starch is added to 10 parts of water to prepare a modified starch milk, and sodium trimetaphosphate is added to the modified starch milk, heated to 70°C for 2 hours, washed, and freeze-dried to obtain the starch gel, wherein the amount of sodium trimetaphosphate added is 0.03 g / ml of the modified starch milk;

[0090] 5) The starch gel is dissolved in water and placed into the gel microspheres, and then ultrasonic oscillation is applied for 1 hour, left to stand, filtered, and freeze-dried to obtain the extract of the reed canary grass / starch gel.

[0091] Comparative Example 3

[0092] A preparation method of the extract of the reed canary grass / starch gel, which comprises the following steps:

[0093] 1) 3 parts of sodium alginate, 1 part of konjac glucomannan, 1 part of chitosan, and 100 parts of water are mixed to obtain a first mixture;

[0094] 2) 1.5 parts of calcium carbonate is added to 100 parts of the extract solution of the reed canary grass to obtain a second mixture;

[0095] 3) The second mixture is added dropwise into the first mixture, and then left to stand, filtered, and freeze-dried to obtain the gel microspheres containing the extract of the reed canary grass;

[0096] 4) The gel microspheres are added to an acetic acid-sodium acetate buffer solution, and the pH is controlled to be 6, and then a 25% ethanol solution is added, and stirred for 10 minutes to obtain the surface-treated gel microspheres, wherein the mass ratio of the gel microspheres to the ethanol solution is 1:30;

[0097] 5) 3 parts of starch is added to 10 parts of water to prepare a starch milk, and sodium trimetaphosphate is added to the starch milk, heated to 70°C for 2 hours, washed, and freeze-dried to obtain the starch gel, wherein the amount of sodium trimetaphosphate added is 0.03 g / ml of the starch milk;

[0098] 6) The starch gel is dissolved in water and placed into the surface-treated gel microspheres, and then ultrasonic oscillation is applied for 1 hour, left to stand, filtered, and freeze-dried to obtain the extract of the reed canary grass / starch gel.

[0099] Application Examples 1-7

[0100] The rice cakes were prepared using the bamboo leaf extract / starch gel prepared in Examples 1-4 and Comparative Examples 1-3 as one of the raw materials, and the rice cakes prepared in Examples 1-4 are denoted as Application Examples 1-4, and the rice cakes prepared in Comparative Examples 1-3 are denoted as Application Examples 5-7, wherein the specific preparation method of the rice cakes is as follows:

[0101] 100 parts by mass of indica rice powder, 14 parts by mass of yeast, 20 parts by mass of white granulated sugar, 4 parts by mass of edible lard, and 10 parts by mass of the bamboo leaf extract / starch gel were mixed, and fermented at 30°C for 4 h, and then steamed and cooled to obtain the rice cakes.

[0102] Application Example 8

[0103] The rice cakes were prepared according to the same method as in Application Examples 1-7, except that the bamboo leaf extract / starch gel was not added to the raw materials of the rice cakes.

[0104] Application Example 9

[0105] The rice cakes were prepared according to the same method as in Application Examples 1-7, except that the bamboo leaf extract / starch gel was not added to the raw materials of the rice cakes.

[0106] The rice cakes prepared in Application Examples 1-8 were sealed in sterilized transparent packaging bags, and placed in a food cabinet at room temperature for 24, 48, and 72 h to simulate the daily selling environment. The hardness change of the rice cakes was evaluated by pressing the surface of the rice cakes with a finger, and the evaluation standard was from hard, relatively hard, relatively soft, to soft. The specific evaluation results are shown in Table 1.

[0107] Table 1: Hardness change table of the rice cakes prepared in Application Examples 1-8

[0108] 0h 24h 48h 72h Application Example 1 Soft Soft Soft Soft Application Example 2 Soft Soft Soft Rather Soft Application Example 3 Soft Soft Soft Rather Soft Application Example 4 Soft Soft Rather Soft Rather Hard Application Example 5 Soft Soft Rather Hard Rather Hard Application Example 6 Soft Rather Soft Rather Hard Hard Application Example 7 Soft Rather Soft Rather Soft Rather Hard Application Example 8 Soft Rather Hard Hard Hard Application Example 9 Soft Rather Hard Rather Hard Hard

[0109] It can be seen that the shelf life of the rice cakes prepared without adding the bamboo leaf extract / starch gel is shorter, and the water content is easily lost, resulting in the hardening of the rice cakes. It can be seen from Application Examples 1-4 and Application Example 6 that surface treatment of the gel microspheres can delay the loss of water in the rice cakes. It can be seen from the comparison between Application Example 1 and Application Example 7 that the bamboo leaf extract / starch gel prepared using modified starch has better water locking performance to extend the shelf life of the rice cakes. It can be seen from Application Examples 1-4 that with the increase of the amount of ethanol, the water locking performance of the rice cakes first increases and then decreases, which may be because with the increase of the amount of ethanol, the opening of the gel microspheres becomes larger or even the structure is destroyed, resulting in the loss of the bamboo leaf extract during the steaming process of the rice cakes. It can be seen from Application Example 9 that the direct addition of the bamboo leaf extract has a certain effect on extending the shelf life, but the effect is not obvious, which may be because the activity of the bamboo leaf extract is lost or lost during the fermentation and steaming process of the rice cakes.

[0110] The various embodiments are described in the specification in a progressive manner, each embodiment focusing on the differences from other embodiments, and the same or similar parts among the various embodiments can be mutually referred to. For the device disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the relevant parts can be referred to the method part.

[0111] The above has carried on the detailed introduction to the preparation method and application of the bamboo leaf extract starch gel provided by the present application. The principle and implementation mode of the present application are described by applying specific examples in this paper. The above embodiment description is only used to help understand the method and core idea of the present application. It should be pointed out that for ordinary skilled persons in the technical field, some improvements and modifications can be made to the present application without departing from the principle of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method of preparing a bamboo leaf extract / starch gel, characterized by: The preparation method comprises the following steps: 1) dissolving sodium alginate, konjac glucomannan and chitosan in water to obtain a first mixed solution, the mass ratio of the sodium alginate, konjac glucomannan and chitosan being (2-3):(1-2):(1-2), and the mass fraction of chitosan in the first mixed solution being 1-2%; 2) adding calcium carbonate into an extract solution of reed canary grass leaves to obtain a second mixed solution, the mass fraction of calcium carbonate in the second mixed solution being 1-5%; 3) adding the second mixed solution drop by drop into the first mixed solution, standing, filtering, and freeze-drying to obtain gel microspheres containing the extract of reed canary grass leaves; 4) adding the gel microspheres into an acetic acid-sodium acetate buffer solution, controlling the pH to be 6-7, and then adding an ethanol solution, stirring for 5-30 min to obtain the gel microspheres after surface treatment; the mass ratio of the gel microspheres to the ethanol solution is 1:20-50, and the volume fraction of the ethanol solution is 25%; 5) preparing a modified starch milk by adding water to modified starch, adding a crosslinking agent into the modified starch milk, heating to 65-85°C and keeping for 1-3 h, washing, and freeze-drying to obtain starch gel; the mass fraction of starch in the modified starch milk is 30-50%; the crosslinking agent is sodium trimetaphosphate, and the addition amount of the crosslinking agent is 0.02-0.06 g / ml; 6) dissolving the starch gel in water, placing into the gel microspheres after surface treatment, and using ultrasonic oscillation for 0.5-1 h, standing, filtering, and freeze-drying to obtain the extract of reed canary grass leaves / starch gel; The preparation method of the extract of reed canary grass leaves is as follows: cutting reed canary grass leaves, mixing with an ethanol solution with a volume fraction of 65%, and using carbon dioxide supercritical fluid technology to extract to obtain an extract solution of reed canary grass leaves, and freeze-drying to obtain the extract of reed canary grass leaves; the mass ratio of the reed canary grass leaves to the ethanol solution is 1:12-14, and the parameters of the carbon dioxide supercritical fluid are as follows: extraction pressure 18-20 MPa, extraction temperature 45-50°C, carbon dioxide flow rate 20-25 L / h, separation pressure 4-6 MPa, and separation temperature 30-33°C; The preparation method of the modified starch is as follows: dispersing starch in water, adding sodium hydroxide and chloroacetic acid, keeping at 30-40°C for 2-4 h, filtering, washing, and drying to obtain carboxymethyl starch, and adding the carboxymethyl starch into an enzyme solution to obtain the modified starch by enzymolysis; the molar ratio of the starch to chloroacetic acid is 1:3-5, the molar ratio of the chloroacetic acid to sodium hydroxide is 1:2-4, and the addition amount of the enzyme is 50-120 U / g; the enzyme is α-amylase.

2. The method of claim 1, wherein: The mass fraction of calcium chloride in the second mixed solution is 1-3%.

3. The method of claim 1, wherein: The specific conditions of the enzymolysis are as follows: enzymolysis at a temperature of 20-40°C and a pH of 6-8 for 12-36 h, filtering, and washing until no enzyme residue is left.

4. The extract of reed canary grass leaves / starch gel prepared by the preparation method in any one of claims 1-3.

5. Use of the extract of the leaves of Musa textilis / starch gel as claimed in claim 4 in the field of food products, characterized in that: The extract of reed canary grass leaves / starch gel is used for preparing rice cakes, specifically by mixing raw materials required for preparing rice cakes with the extract of reed canary grass leaves / starch gel, fermenting, steaming, and cooling to obtain rice cakes.