A method for enhancing the gel strength of starch under restricted gelatinization conditions and uses thereof

Abstract

The application discloses a method for enhancing the gel strength of starch under restrictive gelatinization conditions and application thereof, and belongs to the field of food processing. Potato starch is prepared into a starch suspension, CGTase is added, and the starch is treated in an incomplete gelatinization mode. Through the conversion of cyclodextrin glucosyltransferase, starch gel with increased transparency and enhanced gel strength is obtained. The application solves the problem that the gel strength of starch after enzyme treatment is significantly reduced, and expands the use range of potato starch. Through the simple and green starch gelatinization degree control and enzymolysis method, the starch paste viscosity is reduced, and starch gel with enhanced gel strength is obtained in a short time. The obtained starch gel can be applied to 3D printing ink, has good printing precision, and is used for designing personalized products.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of food processing, and relates to a method for enhancing the gel strength of starch under limited gelatinization conditions by using enzyme and application thereof. BACKGROUND

[0002] Starch is the most abundant organic compound in nature after cellulose, which is a high molecular weight carbohydrate and usually exists in the storage organs of plants, such as seeds, roots, tubers and fruits. Starch is the main component of many foods and is the main source of energy in human diet. As a natural biological macromolecule, starch is widely available and low in price. However, due to the disadvantages of natural starch, such as easy retrogradation, poor water holding capacity, high viscosity during gelatinization and the like, the application of starch in production and life is very limited. For example, potato starch paste has high transparency and strong water holding capacity, but at a high concentration, its viscosity is high, which can cause uneven gelatinization of starch and easily cause resource waste and other problems.

[0003] The methods for reducing the viscosity of starch mainly include physical methods and chemical methods. The physical methods mainly improve the physicochemical properties of starch through mechanical action, including mechanical activation, heat treatment, irradiation treatment, microwave treatment and the like of starch. Although these methods can reduce the viscosity of starch, most of them require specific instruments and equipment. Chemical methods have been proven to be an economical and effective method for reducing the viscosity of starch, mainly including oxidation, esterification, grafting, acid treatment and the like of starch. Although oxidation, grafting, esterification and acid treatment can achieve certain effects, chemical modification has safety hazards.

[0004] Enzymatic treatment is a simple and green method for reducing the viscosity of starch. When using enzyme to reduce the viscosity of starch, the enzyme usually acts on the substrate dissolved in water, so the enzyme treatment is usually carried out after the starch is completely dissolved in water. After the enzyme acts on the starch dissolved in water, it can cut the starch to produce small molecules with low molecular weight, such as dextrin, starch syrup, malt oligosaccharide, maltose and glucose, thereby reducing the viscosity of starch. However, when using enzyme to treat starch, the starch molecules are cut into small molecules with low molecular weight. Although this method reduces the viscosity of starch, the thickening function and gel formation ability of starch are also poor or lost. The gel strength of starch reflects the structural properties and stability properties of starch gel to some extent. Starch gel with high strength has good rheological and sensory properties, and has a positive effect on the appearance, texture and taste of food. Therefore, how to reduce the viscosity of starch while obtaining a high-strength starch gel has become a research hotspot at present.

[0005] Compared with other starches, the gelatinized potato starch has the characteristic of high transparency of starch paste, which makes it have unique effect when it is applied in the production of food, cakes, modified starch and other products. However, the natural potato starch is easy to retrograde, and the transparency of the starch gel formed after the starch retrogradation is obviously reduced, and this process is irreversible. Therefore, it is necessary to maintain the high transparency of the potato starch paste or restore the high transparency by certain treatment (high pressure, high temperature, etc.).

[0006] With the continuous breakthrough of 3D printing materials and the continuous maturity of 3D printing technology, 3D printing has been successfully applied to many fields such as national defense, aviation, aerospace, automobile, industrial design and biomedical engineering in recent years. However, the application of 3D printing technology in the food industry is not satisfactory, which is mainly because of the particularity of food (edibility, hygiene, safety) and the characteristics of weak mechanical support, high viscosity, poor modeling and easy deterioration of food materials, which makes it difficult to develop food materials as 3D printing materials. The lack of food 3D printing materials has become a bottleneck restricting the rapid development of 3D printing technology in the food field.

[0007] Applying starch gel to 3D printing food is the current research hotspot, and the traditional starch gel is difficult to extrude when printing. The easy retrogradation and high viscosity make the original starch gel not suitable as 3D printing ink. In order to improve the 3D printing performance of starch-based gel, the most commonly used method is to add various hydrophilic colloids, thickeners, emulsifiers and other additives to starch. Although these methods can improve the printing accuracy, the processing steps are complex, the precision of the printed material is low, the modeling durability is poor, and the nutritional and quality loss is large during the processing. Therefore, the addition of colloids has potential risks. Therefore, how to have a fine appearance, uniform filaments and achieve high-precision printing has become a research hotspot in the food field when 3D printing starch-based food. SUMMARY

[0008] In view of the problems existing in the prior art, the present application aims to provide a method for enhancing the strength of starch gel under restrictive gelatinization conditions, that is, by adding cyclodextrin glucosyltransferase to the starch suspension and heating to gelatinize, and then storing to prepare starch gel, so as to prepare starch gel with low viscosity and high strength. This method not only can reduce the viscosity of gelatinized starch, but also can enhance the gel strength of starch gel and improve the hardness and modulus of starch gel. The starch gel prepared by the method of the present application has good printing performance and can be used for 3D printing of food.

[0009] In order to achieve the above purpose, the present application first provides a method for enhancing the strength of starch gel under restrictive gelatinization conditions, which comprises the following steps:

[0010] (1) mixing starch with water and dispersing them thoroughly to prepare a starch suspension;

[0011] (2) adding cyclodextrin glucosyltransferase into the starch suspension prepared in step (1);

[0012] (3) subjecting the mixture prepared in step (2) to gelatinization treatment and storing to form a starch gel.

[0013] In an embodiment of the present application, in step (1), the starch is potato starch.

[0014] In an embodiment of the present application, in step (1), the mixing is mixing and stirring at 20-40℃, the stirring speed is 150-200r / min, and the time is 10s-5min.

[0015] In the present application, the starch and water are mixed at 20-40℃ to ensure that the starch particles are not damaged under the condition of rapid dispersion.

[0016] In an embodiment of the present application, in step (1), the concentration of the starch suspension is 6-12%, preferably 8-10%, and further preferably 9%.

[0017] In an embodiment of the present application, in step (2), the enzyme activity of the cyclodextrin glucosyltransferase (CGTase) is 1-5KNU-CP / g, the CGTase is added in the form of diluted enzyme solution, the dilution multiple is 100, and the addition amount of the CGTase solution is 0.01-1.2g / g starch, preferably 0.01-0.5g / g starch.

[0018] In an embodiment of the present application, in step (2), the enzyme activity of the cyclodextrin glucosyltransferase (CGTase) is 3KNU-CP / g, the CGTase is added in the form of diluted enzyme solution, the dilution multiple is 100, and the addition amount of the CGTase solution is 0.02-0.48g / g starch.

[0019] In an embodiment of the present application, in step (3), the gelatinization treatment is carried out under the following conditions: the starch suspension mixed with the CGTase is incubated at 30-50℃ for 0-5min; the temperature is uniformly increased to 90-100℃ within 1-20min; the temperature is kept at 90-100℃ for 2-10min; and then the temperature is decreased to 30-50℃ within 1-20min.

[0020] The whole gelatinization process is carried out under stirring at a stirring speed of 150-200r / min.

[0021] In an embodiment of the present application, in step (3), the pasting treatment is performed by incubating the starch suspension mixed with CGTase at 30-50℃ for 0-2 min, then increasing the temperature to 90-100℃ at a constant rate within 2-10 min, keeping the temperature at 90-100℃ for 2-5 min, and then decreasing the temperature to 30-50℃ within 2-10 min.

[0022] In an embodiment of the present application, in step (3), the pasting treatment is performed by incubating the starch suspension mixed with CGTase at 50℃ for 1 min, then increasing the temperature to 95℃ at a constant rate within 3-8 min, keeping the temperature at 95℃ for 2-5 min, and then decreasing the temperature to 30-50℃ within 2-8 min.

[0023] In an embodiment of the present application, in step (3), the temperature of the pasted starch is kept at 30-50℃ for 1-10 min after the temperature is decreased to 30-50℃.

[0024] In an embodiment of the present application, in step (3), the storage temperature of the starch paste is 4-30℃.

[0025] In an embodiment of the present application, in step (3), the storage time of the starch paste is 12-48 h.

[0026] The present application also provides a starch gel prepared by the above method.

[0027] The present application also provides the use of the above starch gel in the preparation of 3D printed food.

[0028] In an embodiment of the present application, the use includes baked food, jelly or gel food, fruit puree, and cheese-like food.

[0029] The present application has the following advantages and beneficial effects:

[0030] 1. The present application uses a simple and green enzyme treatment method to solve the problem of uneven pasting of potato starch at a high concentration, which leads to resource waste, and achieves a significant viscosity reduction effect. At the same time, the present application solves the problem of weakened gel strength after enzyme treatment of starch. It is found that after treatment with CGTase, the gel strength of starch is not only not weakened, but also enhanced, which expands the application range in industrial production and daily life.

[0031] 2. The addition amount of CGTase has a relatively obvious influence on the gel strength and viscosity of potato starch, and it is found through research that when the addition amount of CGTase liquid reaches 1.2 g / g of starch, the addition of CGTase cannot increase the gel strength of potato starch, but can slightly weaken the gel strength, therefore, when the addition amount of CGTase is less than 1.2 g / g of starch, the addition of CGTase can increase the gel strength of potato starch. On the other hand, the treatment of CGTase can reduce the peak viscosity, valley viscosity, final viscosity and retrogradation value of starch, which indicates that the enzyme treatment has a good effect of reducing viscosity and inhibiting short-term retrogradation of starch.

[0032] 3. The concentration of the initially prepared starch suspension also has a significant influence on the performance of the starch gel, and when the concentration of the starch suspension is too low, the starch gel cannot be formed, and when the concentration of the starch reaches 6%, the effect of increasing the gel strength can be achieved.

[0033] 4. Through rheological analysis of the prepared potato starch gel, it is found that the G' of the potato starch gel increases with the increase of the addition amount of CGTase, and when the starch gel is heated from 25 DEG C to 90 DEG C, the potato starch gel shows obvious melting behavior, and during the heating process, the two moduli G' and G" continuously decrease, and the difference between them gradually decreases. The higher the enzyme addition amount of the starch gel, the stronger the temperature dependence.

[0034] 5. The transparency of the potato starch gel is significantly improved after heating, and the transparency is positively correlated with the CGTase concentration used in the enzyme treatment.

[0035] 6. The gel performance of potato is improved by enzyme treatment in the application, the feasibility of starch gel as 3D printing ink is determined, and more personalized products are designed. The transparency of the starch gel is improved after heating, and high-transparency products are expected to be designed. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a viscosity change comparison chart of the starch gel in Comparative Example 1 and Examples 1-3;

[0037] Figure 2 It is a viscosity change comparison chart of the starch gel in Comparative Example 1 and Examples 4-5;

[0038] Figure 3 It is a hardness comparison chart of the starch gel in Comparative Example 1 and Examples 1-5;

[0039] Figure 4 It is a viscosity comparison chart of the starch gel in Comparative Example 2 and Comparative Example 3;

[0040] Figure 5 It is a viscosity comparison chart of the starch gel in Comparative Example 4 and Example 6;

[0041] Figure 6 Hardness comparison plot for starch gels in Comparative Examples 2-4 and Example 6;

[0042] Figure 7 Viscosity comparison plot for starch gels in Comparative Examples 5-7;

[0043] Figure 8 Viscosity comparison plot for starch gels in Comparative Examples 8-9;

[0044] Figure 9 Hardness comparison plot for starch gels in Comparative Examples 5-9;

[0045] Figure 10 Viscosity comparison plot for starch gels in Example 5 and Comparative Example 10;

[0046] Figure 11 Viscosity comparison plot for starch gels in Example 6 and Comparative Example 11;

[0047] Figure 12 Hardness comparison plot for starch gels in Examples 5-6 and Comparative Examples 10-11;

[0048] Figure 13 Hardness comparison plot for starch gels in Examples 9-10 and Comparative Example 3;

[0049] Figure 14 Rheological properties (based on frequency sweep) of potato starch gels in Comparative Example 1 and Examples 1-3;

[0050] Figure 15 Rheological properties (based on temperature sweep) of potato starch gels in Comparative Example 1 and Examples 1-3;

[0051] Figure 16 Transparency of potato starch gels in Comparative Example 1 and Examples 1-3;

[0052] Figure 17 Photos of 3D printed objects created using potato starch gels in Comparative Example 1 and Examples 1-3 as edible ink. DETAILED DESCRIPTION

[0053] The present application will now be described in detail with reference to the accompanying drawings and examples.

[0054] The enzyme used in the examples and comparative examples of the present application is cyclodextrin glucosyltransferase (CGTase), which was purchased from Novozymes, Cyclomaltodextrin glycosyltransferase (CGTase, enzyme activity 3 KNU-CP / g, Toruzyme 3.0L). The CGTase was diluted 100 times before adding to the starch suspension.

[0055] Performance measurement methods in the following examples:

[0056] (1) Pasting profile of starch

[0057] The peak viscosity, trough viscosity, final viscosity, breakdown and setback of the starches of the examples and comparative examples were measured using RVA (Rapid Visco Analyzer) during the pasting process of starch, and the pasting profile was plotted.

[0058] (2) Gel firmness measurement

[0059] The properties of the starch gels prepared in the examples and comparative examples were measured using a texture analyzer equipped with a P50 probe, pre-test speed 1.0 mm / s, test speed 1.0 mm / s, post-test speed 1.0 mm / s, trigger force 5 g, and compression depth 50%.

[0060] (3) Rheological test

[0061] The rheological test was performed using a shear rheometer. The both sides of the plate were covered with methyl silicone oil to prevent water evaporation from the starch gel, and the rheological properties of the starch gel were measured.

[0062] Frequency sweep

[0063] The frequency test range was 0.1-100 rad / s, and the frequency sweep was performed at 1% strain, and the program temperature was 25°C, to determine the storage modulus (G') and loss modulus (G").

[0064] Temperature sweep

[0065] The temperature sweep was performed at a heating rate of 10°C / min from 25°C to 90°C at a frequency of 1 Hz to determine the storage modulus (G') and loss modulus (G").

[0066] (4) Transparency after heat treatment

[0067] The starch gels prepared in the examples and comparative examples were treated at 95°C for 8 min, and then cooled to room temperature. The transparency was measured at 620 nm using distilled water as a blank control, and the measurement was performed in triplicate.

[0068] Example 1

[0069] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the steps of:

[0070] (1) Mixing potato starch with water and preparing a starch suspension with a concentration of 9% (w / w), and stirring sufficiently to disperse uniformly.

[0071] (2) Adding CGTase solution diluted 100 times to the starch suspension obtained in step (1), and adding an amount of 0.05 g per 2.5 g of potato starch (enzyme activity of 6 x 10 -4 KNU-CP / g of starch).

[0072] (3) Gelatinizing the mixture obtained in step (2), and the gelatinization conditions are as follows: heating the mixture to 50°C, maintaining for 60 s and stirring, so that the CGTase is dispersed sufficiently in the starch suspension; after sufficient dispersion, uniformly increasing the temperature to 95°C in 3.7 min, maintaining for 2.5 min and stirring, so that the starch is partially gelatinized; then decreasing the temperature from 95°C to 50°C in 3.8 min, and maintaining at 50°C for 2 min, to prepare a modified starch paste; and storing the prepared modified starch paste in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is performed under stirring conditions, and the stirring speed is 160 r / min.

[0073] Example 2

[0074] Example 2 differs from Example 1 in that the amount of CGTase solution added is different.

[0075] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the steps of:

[0076] (1) Mixing potato starch with water and preparing a starch suspension with a concentration of 9% (w / w), and stirring sufficiently to disperse uniformly.

[0077] (2) Adding CGTase solution diluted 100 times to the starch suspension obtained in step (1), and adding an amount of 0.1 g per 2.5 g of potato starch (enzyme activity of 1.2 x 10 -3 KNU-CP / g of starch).

[0078] (3) The mixture obtained in step (2) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, and kept for 60 s and stirred, so that the CGTase is fully dispersed in the starch suspension; after full dispersion, the temperature is uniformly increased to 95°C within 3.7 min, and kept for 2.5 min and stirred, so that the starch is partially gelatinized; then the temperature is decreased from 95°C to 50°C within 3.8 min, and kept at 50°C for 2 min, to prepare a modified starch paste; the prepared modified starch paste is stored in a 4°C refrigerator for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0079] Example 3

[0080] Example 3 differs from Example 1 in that the amount of CGTase solution added is different.

[0081] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the following steps:

[0082] (1) Potato starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is configured, and fully stirred and dispersed uniformly.

[0083] (2) CGTase solution diluted by 100 times is added to the starch suspension obtained in step (1), and the amount added is 0.15 g / 2.5 g of potato starch (enzyme activity is 1.8 x 10 -3 KNU-CP / g of starch).

[0084] (3) The mixture obtained in step (2) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, and kept for 60 s and stirred, so that the CGTase is fully dispersed in the starch suspension; after full dispersion, the temperature is uniformly increased to 95°C within 3.7 min, and kept for 2.5 min and stirred, so that the starch is partially gelatinized; then the temperature is decreased from 95°C to 50°C within 3.8 min, and kept at 50°C for 2 min, to prepare a modified starch paste; the prepared modified starch paste is stored in a 4°C refrigerator for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0085] Example 4

[0086] Example 4 differs from Example 1 in that the amount of CGTase solution added is different.

[0087] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the following steps:

[0088] (1) Potato starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is configured, and fully stirred and dispersed uniformly.

[0089] (2) Add CGTase solution diluted 100 times to the starch suspension obtained in step (1) in an amount of 0.8 g / 2.5 g of potato starch (enzyme activity of 9.6 x 10 -3 KNU-CP / g of starch).

[0090] (3) Paste the mixture obtained in step (2) under the following conditions: heat the mixture to 50°C, maintain for 60 s and stir to allow the CGTase to be fully dispersed in the starch suspension; after sufficient dispersion, uniformly raise the temperature to 95°C in 3.7 min, maintain for 2.5 min and stir to partially paste the starch; then lower the temperature from 95°C to 50°C in 3.8 min and maintain at 50°C for 2 min to prepare a modified starch paste. Store the prepared modified starch paste in a refrigerator at 4°C for 48 h to form a gel. The entire pasting process is performed under stirring at a stirring speed of 160 r / min.

[0091] Example 5

[0092] Example 5 differs from Example 1 in that the amount of CGTase solution added is different.

[0093] A method for enhancing the gel strength of starch under restrictive pasting conditions, comprising the following steps:

[0094] (1) Mix potato starch with water and prepare a starch suspension having a concentration of 9% (w / w), and fully stir and disperse.

[0095] (2) Add CGTase solution diluted 100 times to the starch suspension obtained in step (1) in an amount of 1.2 g / 2.5 g of potato starch (enzyme activity of 1.44 x 10 -3 KNU-CP / g of starch).

[0096] (3) Paste the mixture obtained in step (2) under the following conditions: heat the mixture to 50°C, maintain for 60 s and stir to allow the CGTase to be fully dispersed in the starch suspension; after sufficient dispersion, uniformly raise the temperature to 95°C in 3.7 min, maintain for 2.5 min and stir to partially paste the starch; then lower the temperature from 95°C to 50°C in 3.8 min and maintain at 50°C for 2 min to prepare a modified starch paste. Store the prepared modified starch paste in a refrigerator at 4°C for 48 h to form a gel. The entire pasting process is performed under stirring at a stirring speed of 160 r / min.

[0097] Example 6

[0098] Example 6 differs from Example 3 in that the concentration of the starch suspension is different.

[0099] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the following steps:

[0100] (1) Mixing potato starch with water and preparing a starch suspension with a concentration of 6% (w / w), and stirring sufficiently to disperse uniformly.

[0101] (2) Adding CGTase solution diluted 100 times to the starch suspension obtained in step (1), and adding an amount of 0.15 g / 2.5 g of potato starch (enzyme activity of 1.8 x 10 -3 KNU-CP / g of starch).

[0102] (3) Gelatinizing the mixture obtained in step (2), and the gelatinization conditions are as follows: heating the mixture to 50°C, maintaining for 60 s and stirring, so that the CGTase is dispersed sufficiently in the starch suspension; after sufficient dispersion, uniformly increasing the temperature to 95°C in 3.7 min, maintaining for 2.5 min and stirring, so that the starch is partially gelatinized; then decreasing the temperature from 95°C to 50°C in 3.8 min, and maintaining at 50°C for 2 min, to prepare a modified starch paste; and storing the prepared modified starch paste in a 4°C refrigerator for 48 h to form a gel. The entire gelatinization process is carried out under stirring conditions, and the stirring speed is 160 r / min.

[0103] Example 7

[0104] The difference between Example 7 and Example 3 is the gelatinization time.

[0105] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the following steps:

[0106] (1) Mixing potato starch with water and preparing a starch suspension with a concentration of 9% (w / w), and stirring sufficiently to disperse uniformly.

[0107] (2) Adding CGTase solution diluted 100 times to the starch suspension obtained in step (1), and adding an amount of 0.15 g / 2.5 g of potato starch (enzyme activity of 1.8 x 10 -3 KNU-CP / g of starch).

[0108] (3) The mixture obtained in step (2) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, and kept for 60 s with stirring, so that the CGTase is fully dispersed in the starch suspension; after full dispersion, the temperature is uniformly increased to 95°C within 3.7 min, and kept for 4.5 min with stirring, so that the starch is partially gelatinized; then the temperature is decreased from 95°C to 50°C within 3.8 min, and kept at 50°C for 2 min, to prepare a modified starch paste. The prepared modified starch paste is stored in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0109] Example 8

[0110] Example 8 differs from Example 3 in that the gelatinization time is different.

[0111] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the following steps:

[0112] (1) Potato starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0113] (2) CGTase solution diluted 100 times is added to the starch suspension obtained in step (1), and the addition amount is 0.15 g / 2.5 g potato starch (enzyme activity is 1.8×10 -3 KNU-CP / g starch).

[0114] (3) The mixture obtained in step (2) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, and kept for 60 s with stirring, so that the CGTase is fully dispersed in the starch suspension; after full dispersion, the temperature is uniformly increased to 95°C within 7.7 min, and kept for 2.5 min with stirring, so that the starch is partially gelatinized; then the temperature is decreased from 95°C to 50°C within 7.8 min, and kept at 50°C for 2 min, to prepare a modified starch paste. The prepared modified starch paste is stored in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0115] Example 9

[0116] Example 9 differs from Example 3 in that the storage time of the modified starch paste is different.

[0117] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the following steps:

[0118] (1) Potato starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0119] (2) Adding CGTase solution diluted 100 times into the starch suspension obtained in step (1) in an amount of 0.15 g / 2.5 g of potato starch (enzyme activity of 1.8 x 10 -3 KNU-CP / g of starch).

[0120] (3) Subjecting the mixture obtained in step (2) to gelatinization under the following conditions: heating the mixture to 50°C, maintaining the temperature for 60 s while stirring, so that the CGTase is dispersed in the starch suspension; after the dispersion, uniformly increasing the temperature to 95°C over 3.7 min, maintaining the temperature for 2.5 min while stirring, so that the starch is partially gelatinized; then decreasing the temperature from 95°C to 50°C over 3.8 min, and maintaining the temperature at 50°C for 2 min, to prepare a modified starch paste. The modified starch paste prepared is stored in a refrigerator at 4°C for 12 h to form a gel. The entire gelatinization process is performed under stirring at a stirring speed of 160 r / min.

[0121] Example 10

[0122] Example 10 is different from Example 3 in that the storage time of the modified starch paste is different.

[0123] A method for enhancing the gel strength of starch under restrictive gelatinization conditions, comprising the following steps:

[0124] (1) Mixing potato starch with water, and preparing a starch suspension having a concentration of 9% (w / w), and stirring to disperse uniformly.

[0125] (2) Adding CGTase solution diluted 100 times into the starch suspension obtained in step (1) in an amount of 0.15 g / 2.5 g of potato starch (enzyme activity of 1.8 x 10 -3 KNU-CP / g of starch).

[0126] (3) Subjecting the mixture obtained in step (2) to gelatinization under the following conditions: heating the mixture to 50°C, maintaining the temperature for 60 s while stirring, so that the CGTase is dispersed in the starch suspension; after the dispersion, uniformly increasing the temperature to 95°C over 3.7 min, maintaining the temperature for 2.5 min while stirring, so that the starch is partially gelatinized; then decreasing the temperature from 95°C to 50°C over 3.8 min, and maintaining the temperature at 50°C for 2 min, to prepare a modified starch paste. The modified starch paste prepared is stored in a refrigerator at 4°C for 24 h to form a gel. The entire gelatinization process is performed under stirring at a stirring speed of 160 r / min.

[0127] Example 11

[0128] The prepared starch gel was loaded into the cylinder of a 3D printer (Shiyin Technologies Co. Ltd., Hangzhou, Zhejiang, China), and the printed model was a "transformer." The model of the printed product was 5.1 x 5.1 x 1.0 cm (length x width x height). The printing was performed at 25 °C, and the printing speed was 40 mm / s.

[0129] The preparation method of the starch gel used was the same as in Example 1.

[0130] Comparative Example 1

[0131] Comparative Example 1 differs from Example 1 in that no CGTase was added.

[0132] A method for preparing a starch gel, comprising the following steps:

[0133] (1) Mixing potato starch and water, and configuring a starch suspension with a concentration of 9% (w / w), and fully stirring and dispersing uniformly.

[0134] (2) The suspension obtained in step (1) was gelatinized, and the gelatinization conditions were as follows: the mixture was heated to 50 °C, maintained for 60 s and stirred; the temperature was uniformly increased to 95 °C in 3.7 min, maintained for 2.5 min and stirred, so that the starch was partially gelatinized; then the temperature was decreased from 95 °C to 50 °C in 3.8 min, and maintained at 50 °C for 2 min, to prepare a starch paste. The prepared starch paste was stored in a 4 °C refrigerator for 48 h to form a gel. The entire gelatinization process was performed under stirring conditions, and the stirring speed was 160 r / min.

[0135] Comparative Example 2

[0136] Comparative Example 2 differs from Example 1 in that no CGTase was added, and the concentration of the starch suspension was different.

[0137] A method for preparing a starch gel, comprising the following steps:

[0138] (1) Mixing potato starch and water, and configuring a starch suspension with a concentration of 3% (w / w), and fully stirring and dispersing uniformly.

[0139] (2) The suspension obtained in step (1) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, kept for 60 s and stirred; the temperature is uniformly raised to 95°C in 3.7 min, kept for 2.5 min and stirred, so that the starch is partially gelatinized; then the temperature is lowered from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a starch paste. The prepared starch paste is stored in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0140] Comparative Example 3

[0141] Comparative Example 3 differs from Example 3 in that the concentration of the starch suspension is different.

[0142] A method for preparing a starch gel, comprising the following steps:

[0143] (1) Potato starch is mixed with water to prepare a starch suspension with a concentration of 3% (w / w), and the mixture is fully stirred and dispersed.

[0144] (2) The starch suspension obtained in step (1) is added with CGTase liquid diluted 100 times, and the amount of addition is 0.15 g / 2.5 g of potato starch (enzyme activity is 1.8 x 10 -3 KNU-CP / g of starch).

[0145] (3) The mixture obtained in step (2) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, kept for 60 s and stirred, so that the CGTase is fully dispersed in the starch suspension; after full dispersion, the temperature is uniformly raised to 95°C in 3.7 min, kept for 2.5 min and stirred, so that the starch is partially gelatinized; then the temperature is lowered from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a modified starch paste. The prepared modified starch paste is stored in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0146] Comparative Example 4

[0147] Comparative Example 4 differs from Example 1 in that no CGTase is added, and the concentration of the starch suspension is different.

[0148] A method for preparing a starch gel, comprising the following steps:

[0149] (1) Potato starch is mixed with water to prepare a starch suspension with a concentration of 6% (w / w), and the mixture is fully stirred and dispersed.

[0150] (2) The suspension obtained in step (1) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, kept for 60 s and stirred; the temperature is uniformly increased to 95°C in 3.7 min, kept for 2.5 min and stirred, so that the starch is partially gelatinized; then the temperature is decreased from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a starch paste. The prepared starch paste is stored in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0151] Comparative Example 5

[0152] Comparative Example 5 differs from Example 1 in that no CGTase is added, and the starch type is different.

[0153] A method for preparing a starch gel, comprising the following steps:

[0154] (1) Corn starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0155] (2) The suspension obtained in step (1) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, kept for 60 s and stirred; the temperature is uniformly increased to 95°C in 3.7 min, kept for 2.5 min and stirred, so that the starch is partially gelatinized; then the temperature is decreased from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a starch paste. The prepared starch paste is stored in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0156] Comparative Example 6

[0157] Comparative Example 6 differs from Example 2 in that the starch type is different.

[0158] A method for preparing a starch gel, comprising the following steps:

[0159] (1) Corn starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0160] (2) CGTase solution diluted 100 times is added to the starch suspension obtained in step (1), and the addition amount is 0.1 g / 2.5 g potato starch (enzyme activity is 1.2 x 10 -3 KNU-CP / g starch).

[0161] (3) The mixture obtained in step (2) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, and kept for 60 s with stirring, so that the CGTase is fully dispersed in the starch suspension; after full dispersion, the temperature is uniformly increased to 95°C within 3.7 min, and kept for 2.5 min with stirring, so that the starch is partially gelatinized; then the temperature is decreased from 95°C to 50°C within 3.8 min, and kept at 50°C for 2 min, to prepare a modified starch paste; the prepared modified starch paste is stored in a 4°C refrigerator for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0162] Comparative Example 7

[0163] The difference between Comparative Example 7 and Example 3 is that the starch types are different.

[0164] A method for preparing a starch gel, comprising the following steps:

[0165] (1) Corn starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0166] (2) CGTase solution diluted 100 times is added to the starch suspension obtained in step (1), and the amount of addition is 0.15 g / 2.5 g of potato starch (enzyme activity is 1.8×10 -3 KNU-CP / g of starch).

[0167] (3) The mixture obtained in step (2) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, and kept for 60 s with stirring, so that the CGTase is fully dispersed in the starch suspension; after full dispersion, the temperature is uniformly increased to 95°C within 3.7 min, and kept for 2.5 min with stirring, so that the starch is partially gelatinized; then the temperature is decreased from 95°C to 50°C within 3.8 min, and kept at 50°C for 2 min, to prepare a modified starch paste; the prepared modified starch paste is stored in a 4°C refrigerator for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0168] Comparative Example 8

[0169] The difference between Comparative Example 8 and Example 1 is that no CGTase is added, and the starch types are different.

[0170] A method for preparing a starch gel, comprising the following steps:

[0171] (1) Rice starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0172] (2) The suspension obtained in step (1) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, kept for 60 s and stirred; the temperature is uniformly raised to 95°C in 3.7 min, kept for 2.5 min and stirred, so that the starch is partially gelatinized; then the temperature is lowered from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a starch paste. The prepared starch paste is stored in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0173] Comparative Example 9

[0174] The difference between Comparative Example 9 and Example 3 is that the starch types are different.

[0175] A method for preparing a starch gel, comprising the following steps:

[0176] (1) Rice starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0177] (2) CGTase liquid diluted 100 times is added to the starch suspension obtained in step (1), and the amount of addition is 0.15 g / 2.5 g of potato starch (enzyme activity is 1.8×10 -3 KNU-CP / g of starch).

[0178] (3) The mixture obtained in step (2) is gelatinized, and the gelatinization conditions are as follows: the mixture is heated to 50°C, kept for 60 s and stirred, so that the CGTase is fully dispersed in the starch suspension; after full dispersion, the temperature is uniformly raised to 95°C in 3.7 min, kept for 2.5 min and stirred, so that the starch is partially gelatinized; then the temperature is lowered from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a modified starch paste. The prepared modified starch paste is stored in a refrigerator at 4°C for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0179] Comparative Example 10

[0180] The difference between Comparative Example 10 and Example 1 is that no CGTase is added, and the gelatinization time is different.

[0181] A method for preparing a starch gel, comprising the following steps:

[0182] (1) Potato starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0183] (2) The suspension obtained in step (1) is gelatinized, and the gelatinization conditions are as follows: the mixed solution is heated to 50°C, kept for 60 s and stirred; it is uniformly heated to 95°C in 3.7 min, kept for 4.5 min and stirred, so that the starch is partially gelatinized; then it is cooled from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a starch paste; the prepared starch paste is stored in a 4°C refrigerator for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0184] Comparative Example 11

[0185] Comparative Example 11 differs from Example 1 in that no CGTase is added, and the gelatinization time is different.

[0186] A preparation method of a starch gel, comprising the following steps:

[0187] (1) Potato starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0188] (2) The suspension obtained in step (1) is gelatinized, and the gelatinization conditions are as follows: the mixed solution is heated to 50°C, kept for 60 s and stirred; it is uniformly heated to 95°C in 3.7 min, kept for 4.5 min and stirred, so that the starch is partially gelatinized; then it is cooled from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a starch paste; the prepared starch paste is stored in a 4°C refrigerator for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0189] Comparative Example 12

[0190] Comparative Example 12 differs from Example 4 in that the gelatinization method of the starch is different.

[0191] (1) Potato starch is mixed with water, and a starch suspension with a concentration of 9% (w / w) is prepared, and fully stirred and dispersed.

[0192] (2) The suspension obtained in step (1) is gelatinized, and the gelatinization conditions are as follows: the mixed solution is heated to 50°C, kept for 60 s and stirred; it is uniformly heated to 95°C in 3.7 min, kept for 4.5 min and stirred, so that the starch is partially gelatinized; then it is cooled from 95°C to 50°C in 3.8 min, and kept at 50°C for 2 min, to prepare a starch paste; the prepared starch paste is stored in a 4°C refrigerator for 48 h to form a gel. The entire gelatinization process is carried out under stirring, and the stirring speed is 160 r / min.

[0193] Results and analysis:

[0194] Examples 1-3 (low enzyme addition), Examples 4-5 (high enzyme addition) and Comparative Examples investigated the viscosity changes and gel hardness changes of potato starch with different enzyme addition amounts, and the results are shown in Figure 1 , Figure 2 , Figure 3 It can be seen from Figure 3 that, under low enzyme addition, the gel strength of potato starch is enhanced after the modified starch is treated by incomplete gelatinization; and under high enzyme addition, the gel strength of potato starch is weakened after the modified starch is treated by incomplete gelatinization, and the gel strength is slightly weakened when the enzyme addition amount is 1.2 g, but the change is not large, indicating that the addition of CGTase enzyme significantly affects the gelatinization characteristics of potato starch. It can be seen from Figure 1 and Figure 2 that the CGTase enzyme treatment can reduce the peak viscosity, trough viscosity, final viscosity and setback value of starch, indicating that the enzyme treatment has a good viscosity reduction effect. However, the enzyme treatment increases the breakdown value of starch, which is related to the degree of damage of starch after enzyme treatment. The decrease of starch setback value may be related to the decrease of total amylose content, the shortening of amylose chain length, and the formation of cyclodextrin in this process, which inhibits the short-term retrogradation of potato starch. Example 12 is to add CGTase to treat the completely gelatinized potato starch, and the viscosity of the starch paste is reduced and the gel with increased gel strength cannot be formed by retrogradation.

[0195] Comparative Examples 2-4 and Example 6 show the viscosity and hardness test results of the prepared starch gel when the potato concentration is 3% without enzyme and with CGTase 0.15 g, and when the potato concentration is 6% without enzyme and with enzyme. It can be seen from Figures 4-5 that, under the same starch suspension concentration, the addition of CGTase can significantly reduce the viscosity of starch. It can be seen from Figure 6 that, under a starch concentration of 3%, potato starch cannot form a starch gel even if the CGTase treatment is increased, and under a concentration of 6%, the gel strength is enhanced after the CGTase treatment.

[0196] Comparative Examples 5-7 show the viscosity and gel strength changes of corn starch after enzyme treatment. Figure 7 and Figure 9 The results show that after the CGTase treatment, the viscosity of corn starch is reduced, and the gel strength after retrogradation is weakened, which does not achieve the expected effect.

[0197] Comparative Example 8 and Comparative Example 9 also investigate the viscosity and gel strength changes of rice starch after enzyme treatment. Figure 8The results show that the hardness of the starch gel formed by 9% of the rice starch after 48h of retrogradation is 0.24kg, and after the treatment of 0.15g of enzyme, no gel is formed, which produces similar results to the corn starch. The reason can be that the surface of the corn starch and rice starch particles is rough, which is more prone to react with the enzyme, and the viscosity after gelatinization is lower, so the degradation of the branched chains and the straight chains of the corn starch and the rice starch is greater under the same amount of enzyme, and the molecular weight decreases more, so the gel strength is weakened.

[0198] Examples 7-8 and Comparative Examples 10-11 are to explore the effect of enzyme treatment on the viscosity and gel hardness of potato starch by changing the parameters in the gelatinization process. The results are shown in Figures 10-12 From the figure, it can be seen that within the gelatinization temperature and time of the present application, after adding CGTase, the viscosity is obviously reduced, but the hardness after retrogradation is obviously increased.

[0199] The starch gel treated with enzyme can form a gel after storage at 4℃ for more than 10h, and the hardness of the starch gel stored for 12h, 24h and 48h of the modified starch paste is shown in Figure 13 respectively corresponding to Example 9, Example 10 and Example 3. From Figure 13 It can be seen that the gel strength gradually increases during storage.

[0200] Since the enzyme treatment enhances the gel strength of the potato starch, Examples 1-3 and Comparative Example 1 are selected for specific analysis. First, rheological analysis:

[0201] Figure 14 The rheological properties of the potato starch gel of Comparative Example 1 and Examples 1-3 (based on frequency sweep); from Figure 14 It can be seen that the storage modulus (G') of the potato starch gel is greater than the loss modulus (G"), indicating that a weak gel system dominated by elasticity is formed, and the G' of the potato starch gel increases with the increase of the amount of CGTase, which also corresponds to the results of the texture.

[0202] Figure 15 The rheological properties of the potato starch gel of Comparative Example and Examples 1-3 based on temperature sweep; from Figure 15 It can be seen that the starch gel is heated from 25℃ to 90℃, and the potato starch gel shows obvious melting behavior, and the two moduli G' and G" continuously decrease during the heating process, and the difference between them gradually decreases, but the starch gel with higher enzyme amount has stronger temperature dependence, and the G' of Example 3 decreases more.

[0203] Figure 16The transparency of the heat-treated starch pastes of Comparative Example and Examples 1-3; the transparency of the potato starch gel increased significantly after heating, and the transparency was positively correlated with the CGTase concentration used for the enzyme treatment, with the highest transparency in Example 3.

[0204] Figure 17 Photos of 3D printed objects created using potato starch gels as edible ink for Comparative Example and Examples 1-3. The potato starch gel of Comparative Example 1 was difficult to extrude continuously and smoothly, and the printing accuracy was poor. The edible inks formed from the potato starch gels in Examples 2-3 exhibited better printing performance. The printed objects showed higher printing accuracy, smooth surfaces, and little signs of collapse. These results indicate that the enzyme-treated starches can be successfully used as edible inks.

Claims

1. A method for enhancing starch gel strength under restricted gelatinization conditions, characterized in that, The method includes the following steps: (1) Mix starch with water and disperse it thoroughly to prepare a starch suspension with a concentration of 6-12%; (2) Add cyclodextrin glucosyltransferase (CGT enzyme) to the starch suspension obtained in step (1). The enzyme activity of CGT enzyme is 1-5 KNU-CP / g. CGT enzyme is added in the form of diluted enzyme solution, with a dilution factor of 100 times. The amount of CGT enzyme solution added is 0.01-1.2g / g starch. (3) The mixture obtained in step (2) is gelatinized and stored to form a starch gel. The gelatinization conditions are as follows: the starch suspension containing CGT enzyme is kept at 30-50℃ for 1-5 min; the temperature is raised to 90-100℃ at a constant rate within 1-20 min; the temperature is maintained at this temperature for 1-10 min; and then the temperature is lowered to 30-50℃ within 1-20 min.

2. The method according to claim 1, characterized in that, In step (1), the starch is potato starch.

3. The method according to claim 1, characterized in that, In step (1), the mixing refers to mixing and stirring at 20-40℃ for 10s-5min.

4. The method according to claim 1, characterized in that, In step (1), the concentration of the starch suspension is 8-10%.

5. The method according to claim 1, characterized in that, In step (1), the concentration of the starch suspension is 9%.

6. The method according to claim 1, characterized in that, The CGT enzyme has an activity of 2-4 KNU-CP / g. The CGT enzyme is added in the form of a diluted enzyme solution, with a dilution factor of 100 times. The amount of CGT enzyme solution added is 0.01-0.5g / g starch.

7. The method according to claim 6, characterized in that, In step (2), the CGT enzyme has an enzyme activity of 3 KNU-CP / g. The CGT enzyme is added in the form of a diluted enzyme solution with a dilution factor of 100 times. The amount of CGT enzyme solution added is 0.02-0.48g / g starch.

8. The method according to claim 1, characterized in that, In step (3), the conditions for gelatinization are as follows: the starch suspension mixed with CGT enzyme is kept at 30-50℃ for 1-2 min; the temperature is raised to 90-100℃ at a constant rate within 2-10 min; the temperature is maintained at this temperature for 2-5 min; and then the temperature is lowered to 30-50℃ within 2-10 min.

9. The method according to claim 1, characterized in that, In step (3), the conditions for gelatinization are as follows: the starch suspension containing CGT enzyme is kept at 50°C for 1 min; the temperature is raised to 95°C at a constant rate within 3-8 min; the temperature is maintained at this temperature for 2-5 min; and then the temperature is lowered to 30-50°C within 2-8 min.

10. The method according to claim 1, characterized in that, In step (3), after the temperature of the gelatinized starch is reduced to 30~50℃, it is kept at this temperature for 1-10 minutes.

11. The method according to claim 1, characterized in that, In step (3), the storage temperature of the starch paste is 4-30℃.

12. The method according to claim 1, characterized in that, In step (3), the starch paste is stored for 12 to 48 hours.

13. Starch gel prepared by the method according to any one of claims 1 to 12.

14. The application of the starch gel according to claim 13 in the preparation of 3D printed food.

15. The application according to claim 14, characterized in that, The applications include baked goods, jellies or gels, fruit purees, and cheeses.

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