A tensile-resistant potato starch hydrogel and its preparation method

Abstract

The present invention discloses a tensile-resistant potato starch hydrogel and a preparation method thereof, which relates to the technical field of starch hydrogels. The method includes the following steps: S1, preparation of gel sheets; S2, aging of gel sheets; S3, rehydration of gel sheets; S4, testing of tensile properties and texture properties: the A / TG method is used to test the tensile properties and texture properties of the rehydrated potato starch gel; S5, determination of the optimal aging time, rehydration temperature and rehydration time of the potato starch hydrogel. By using the above-mentioned tensile-resistant potato starch hydrogel and the preparation method thereof, a starch hydrogel PSH<subgt;‑18< / subgt;‑100‑20S with excellent tensile strength is obtained, and the tensile strength is 750% to 800%. Moreover, its preparation parameters are determined, providing a theoretical basis for the application of starch hydrogels in foods.

Description

Technical Field

[0001] The present invention relates to the technical field of starch hydrogels, and in particular to a tensile-resistant potato starch hydrogel and a preparation method thereof. Background Art

[0002] Natural starch is polymerized from dextran, mainly amylose and amylopectin (S. Zhang et al., 2023). Compared with other natural starches, potato starch has phosphate groups inside the molecule, and the negative charges between the groups repel each other, forming unique physical and chemical properties, with a lower gelatinization temperature, easy to gelatinize and expand, and higher viscosity and transparency of the starch after gelatinization (Ma et al., 2023). In the industrial production of starch-based foods, the gelatinization and retrogradation processes will cause changes in the microstructure and mechanical properties of starch gels, directly affecting the quality of products; therefore, how to regulate the gelatinization and degradation of starch hydrogels and improve product quality still needs to be continuously explored (Chang, Zheng, Zhang, & Zeng, 2021). Starch retrogradation is a process in which starch granules absorb a large amount of water under heating conditions, expand and rupture, the intermolecular forces between starch granules are destroyed, and the starch structure becomes disordered; gelatinized starch spontaneously re-aggregates into an ordered structure during cooling at low temperature or room temperature; starch retrogradation is also divided into long-term retrogradation and short-term retrogradation. Short-term retrogradation occurs in the initial stage of cooling of gelatinized starch. Amylose winds around each other through hydrogen bonds, and the molecular chains re-arrange and polymerize to form a starch gel with a certain hardness and elasticity; long-term aging is mainly caused by the recrystallization of the outer chains of linear starch, which is a process with a relatively long duration and leads to the problem of the decline in the quality of starch-based foods (Jiang Jikai et al., 2021).

[0003] Factors such as aging temperature, aging time, and starch composition (amylose and amylopectin) have an impact on the aging process. The temperature factor is the main factor affecting starch retrogradation. It has been found that when the gelatinized starch cools, starch begins to retrograde; freezing can regulate its mechanical properties by improving the microstructure of starch (Chen, Singh, Midgley, & Archer, 2020). During the aging process, different temperatures will affect the nucleation type of starch molecules, thereby affecting the aging rate of starch. It has been reported at home and abroad that the network structure and mechanical properties of starch gels can be controlled by aging at room temperature (25°C), low temperature (4°C), and room temperature / low temperature cycling (Satmalee & Charoenrein, 2009). The results show that low-temperature aging is more likely to make starch molecules form an ordered crystal structure than room-temperature aging, thereby accelerating the aging rate of starch gels and forming higher gel strength and toughness. Han et al. studied the effects of high-temperature (50°C) and low-temperature aging on the quality of rice noodles and found that the cooking loss of rice noodles treated by low-temperature aging was significantly reduced and the texture properties were improved (Han, Seo, Lim, & Park, 2011). Gong et al. found that the quick-freezing temperature would affect the quality of oat roll products; quick-freezing at -40°C and -80°C could inhibit the enthalpy and orderliness of starch gels, delay the growth of ice crystals, protect the internal structure of starch gels, and improve product quality. (Gong et al., 2020). Jia et al. also found that the potato starch gel treated by quick-freezing maintained the shape of starch granules and improved the quality of surimi (Jia et al., 2018); therefore, there are significant differences in the mechanical properties, rehydration, and microstructure of starch gels aged at different temperatures (J; Jiang et al., 2020); currently, many researchers have found that starch gel products with a porous network structure can be manufactured by adding enzymes and using various drying methods such as vacuum freezing to enhance the mechanical properties of the gels and reduce the time required for rehydration (J. Zhang et al., 2022); the porous structure can increase the specific surface area and promote the migration of water molecules, so it is generally believed that larger pore sizes are helpful for the rehydration of dry noodles (J. Zhang et al., 2024).

[0004] Therefore, starting from potato starch, this application studies the effects of the differences in the microscopic network structures formed by aging treatments at different temperatures (25°C, 4°C, -18°C, -30°C) on the rehydration and mechanical properties of potato starch hydrogels. The water distribution of starch gels is measured by low-field nuclear magnetic resonance relaxation time, the microscopic pore size of gels is measured by scanning electron microscopy, and the short-range order of gels is measured by Fourier transform infrared spectroscopy to jointly analyze the mechanical properties of rehydrated starch gels at different temperatures. Summary of the Invention

[0005] The purpose of the present invention is to provide a stretch-resistant potato starch hydrogel and a preparation method thereof, and to obtain a starch hydrogel PSH- 18 -100-20S, the tensile strength is 750% to 800%, and its preparation parameters are determined, providing a theoretical basis for the application of starch hydrogel in food.

[0006] To achieve the above object, the present invention provides a method for preparing a stretch-resistant potato starch hydrogel, which is characterized by comprising the following steps:

[0007] S1. Preparation of gel sheet: potato starch and deionized water were mixed in appropriate proportions and stirred to form a slurry. 4 ml of the slurry was poured into a silicone mold at a time. The mold containing the slurry sample was placed in a steamer and steamed in boiling water for 3-4 minutes to obtain a potato starch gel sheet. The potato gel sheet was sealed and cooled at room temperature.

[0008] S2. Aging of gel sheet: Aging the cooled potato starch gel sheet for 12 hours to obtain PSH 25 、PSH4、PSH -18 and PSH -30 ;

[0009] S3. Rehydration of gel sheet: PSH 25 、PSH4、PSH -18 and PSH -30 Rehydration was performed to obtain potato starch hydrogel PSH x -YZ, where X is the aging temperature of potato starch gel, Y is the rehydration temperature, and Z is the rehydration time;

[0010] S4. Tensile and texture properties testing: The tensile and texture properties of the rehydrated potato starch gel were tested using the A / TG method.

[0011] S5. Determine the optimal aging time, rehydration temperature and rehydration time of potato starch hydrogel.

[0012] Furthermore, in step S1, the w / v ratio of potato starch to deionized water is 2:(2-3.5), and the thickness of the obtained potato starch gel sheet is 1.5-3.0 mm.

[0013] Furthermore, the aging temperatures of the potato starch gel sheet in step S2 are 25°C, 4°C, -18°C, and -30°C.

[0014] Furthermore, in step S3, the rehydration temperature is 70° C., 85° C., and 100° C., and the rehydration time is 10 s, 20 s, 30 s, 40 s, and 50 s.

[0015] Further, the specific operation of the tensile property test in step S4 is as follows: dry the surface moisture of the rehydrated potato starch hydrogel, select a potato starch gel with uniform thickness for measurement, and obtain a stress-strain curve; the parameter settings are: automatic displacement trigger mode, the speed before the test is 3 mm / s, the speed during the test is 1 mm / s, the speed after the test is 3 mm / s, the sample width is 2 mm, the length is 18 mm, and the strain height is 10 mm.

[0016] Further, the specific operation of the texture property test in step S4 is as follows: dry the surface of the rehydrated potato starch hydrogel, select a potato starch gel with uniform thickness for measurement; the parameter settings are: the speed is 0.5 mm / s, the morphology is 50%, the speed before and after the test is 3 mm / s, the trigger force is 5 g, and a force-time curve is obtained by performing a full texture analysis to obtain full texture parameters, including hardness, viscosity, elasticity, adhesiveness, and chewiness.

[0017] Further, in step S5, the optimal aging time of the potato starch hydrogel is -18 °C, the optimal rehydration temperature is 100 °C, and the optimal rehydration time is 20 s.

[0018] Further, under the conditions of the optimal aging time, the optimal rehydration temperature, and the optimal rehydration time, the tensile strength of the potato starch hydrogel is 750% - 800%.

[0019] The present invention also provides a potato starch hydrogel prepared by the above preparation method.

[0020] The advantages and positive effects of the anti-tensile potato starch hydrogel and its preparation method of the present invention are as follows:

[0021] 1. This application studied the changes in the rehydration performance and mechanical properties of potato starch hydrogels under different microstructures, indicating that at an appropriate cooking temperature, it is effective in improving the rehydration and mechanical properties of potato starch hydrogels.

[0022] 2. This application obtained a starch hydrogel PSH- 18 -100-20S with excellent tensile strength, and its tensile strength is 750% - 800%, and its preparation parameters were determined, providing a theoretical basis for the application of starch hydrogels in food.

[0023] Next, through the drawings and examples, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0024] Figure 1 It is the tensile result of the rehydrated PSH specimen in the embodiment of the present invention;

[0025] Figure 2Spin relaxation times of potato starch gels in the embodiments of the present invention at different aging temperatures and rehydration temperatures;

[0026] Figure 3 MRI images of potato starch gels in the embodiments of the present invention;

[0027] Figure 4 Gel microstructures of potato starch gels regenerated at different temperatures and rehydrated at different temperatures in the embodiments of the present invention, where the aging temperature of A is 25°C, the aging temperature of B is 4°C, the aging temperature of C is -18°C, and the aging temperature of D is -30°C;

[0028] Figure 5 Infrared spectra of potato starch gels under different regeneration temperatures and different rehydration conditions in the embodiments of the present invention;

[0029] Figure 6 Artificial stretching conditions of PSH25, PSH4, PSH - 18, and PSH - 30 after rehydration at different times in the embodiments of the present invention;

[0030] Figure 7 Water contents of PSH at different aging temperatures, different rehydration temperatures and times during the cooking process in the embodiments of the present invention due to short rehydration time. Detailed implementation manners

[0031] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0032] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs.

[0033] Experimental materials such as potato starch in this application are all commercially available as usual.

[0034] Embodiment

[0035] 1. Sample preparation:

[0036] 1.1 Preparation of potato starch hydrogel:

[0037] Mix potato starch and deionized water in a ratio of 2:3 (w / v), stir evenly to form a slurry. Pour 4 ml of the slurry into a silicone mold each time. Place the mold containing the slurry sample in a steamer and cook with boiling water for 4 minutes to obtain a potato starch gel sheet with a thickness of about 2 mm.

[0038] 1.2 Aging of potato starch hydrogel:

[0039] Seal the potato gel slices and cool them at room temperature. The cooled potato gel is aged for 12 h at different temperatures (25 °C, 4 °C, -18 °C, -30 °C) to obtain PSH 25 、PSH4、PSH -18 and PSH -30

[0040] 1.3 Rehydration of potato starch hydrogel:

[0041] The aged potato starch gel is rehydrated at different temperatures for different times to obtain PSH x -Y-Z, where X is the aging temperature of the potato starch gel, Y is the rehydration temperature, and Z is the rehydration time, for subsequent experiments. The rehydration temperatures are 70 °C, 85 °C, and 100 °C, and the rehydration times are 10 s, 20 s, 30 s, 40 s, and 50 s.

[0042] 1.4 Tensile properties of potato starch hydrogel PSH:

[0043] The tensile properties of the rehydrated potato starch gel were tested by the A / TG method (TA). The surface moisture of the rehydrated PSH was dried, and potato starch gels with uniform thickness were selected for measurement. Each sample was measured at least 5 times to obtain the stress-strain curve. The parameter settings were in the automatic displacement trigger mode, with a pre-test speed of 3 mm / s, a mid-test speed of 1 mm / s, a post-test speed of 3 mm / s, a sample width of 2 mm, a length of 18 mm, and a strain height of 10 mm.

[0044] 1.5 Texture properties of potato starch hydrogel:

[0045] The texture properties of the rehydrated potato starch gel were tested by A / TG. The surface of the PSH was dried, and potato starch gels with uniform thickness were selected for measurement. Each sample was measured at least 5 times. The speed was 0.5 mm / s, the morphology was 50%, with pre-test and post-test speeds of 3 mm / s and a trigger force of 5 g. Using the force-time curve of the total texture analysis, the total texture parameters were obtained, including hardness, viscosity, elasticity, adhesion, and chewiness.

[0046] 1.6 Moisture distribution of potato starch hydrogel during the water replenishment process:

[0047] The moisture distribution of potato starch hydrogel samples was analyzed using a low-field nuclear magnetic resonance (NMR) analyzer. The potato starch hydrogel with uniform thickness was wrapped with a film to prevent water loss, placed in an NMR tube with a diameter of 40 mm, and subjected to CPMG sequence measurement at the center of the radiofrequency coil in the center of the permanent magnetic field. Each sample was measured three times, and the data was reversed after the experiment. The relaxation time and area ratio characteristics of the following populations were determined: T21, T22, and T23; and A21, A22, A23. The data was analyzed using MultiExp InvAnalysis software. Each sample was examined five times, and then the average value was determined.

[0048] Magnetic resonance imaging (MRI) described the water migration process inside the PSH during the rehydration process. Standard SPIN-ECHO (SE) imaging sequences were used to acquire magnetic resonance images. The instrument parameters were TR = 500 ms, TE = 20 ms, and RG = 20 db. The MRI image processing software was used for imaging pseudo-coloring.

[0049] 1.7 Scanning electron microscopy of potato starch hydrogel during water replenishment:

[0050] The potato starch gels aged at different temperatures and the hydrogels rehydrated under different conditions were freeze-dried and placed on an aluminum carrier stage bonded with conductive tape and sputter-coated with gold. The network structure of the freeze-dried gels was observed by scanning electron microscopy.

[0051] 1.8 Fourier transform infrared (FTIR):

[0052] Tests were carried out using a Nicolet 6700 FTIR spectrometer. Infrared characterization was performed by Fourier transform infrared spectroscopy (FTIR), with slight modifications to the previous method, specifically: the aged and freeze-dried potato starch gels were ground into a uniform fine powder foam and sieved through a 100-mesh sieve; and the parameters were: air as the background, scanning range 400 - 4000 cm -1 , and the number of scans was 64 times. After the scanning was completed, the spectrum was subjected to baseline correction and curve smoothing using OMNIC 8.0, deconvolution was performed, and the data was exported to calculate 1047 cm -1 / 1022 cm -1 , and finally the infrared spectrum of the potato starch gel was obtained.

[0053] 1.9 Statistical analysis:

[0054] All experiments were repeated at least 3 times. The results were subjected to analysis of variance and Duncan's test using SPSS software version 25.0 to compare the mean differences at a 0.05 confidence level. When p < 0.05, we considered the differences to be statistically significant. All images were created using Origin 8.5 software.

[0055] 2. Results:

[0056] 2.1 Tensile properties of rehydrated potato starch gels:

[0057] Figure 1 Figure shows the tensile results of rehydrated PSH specimens. PSH showed significant differences during the aging temperature change process from room temperature of 25 °C to low temperature of 4 °C. P -18 SH-100 had much better mechanical properties than the potato starch hydrogels aged at other four temperatures. PSH -18 -100-20S sample had a strain between 7,50% and 800% after rehydration, and its tensile strength was higher than that of other samples such as PSH4-100-20S (620% - 680%). This indicates that when the starch gel was aged at -18 °C, the frozen water in the starch gel could form a large number of small and dense ice crystals, causing less damage to the starch gel structure. Therefore, when the starch gel was aged at -18 °C, its stress was lower than that of other PSHs, while its tensile strength was higher. This observation can be attributed to the existence of microstructural changes during the freezing process. It has been reported that freezing can shorten the rehydration time by accelerating the water absorption of noodles. In addition, the microporous structure also reduces the amount of water required for rehydration. Rehydration experiments on potato starch gels under the same degradation conditions showed that as the rehydration process continued, the tensile strain value first increased and then decreased. This may be due to the fact that the overlong rehydration time of the potato starch gel caused the starch gel to absorb water and swell, breaking the hydrogen bonds between starch molecules, resulting in a decrease in the tensile strain of PSH. High temperature conditions accelerated the migration of water molecules in the starch, promoting the interaction between water molecules and the starch gel. Therefore, under ideal rehydration temperature and rehydration time, the tensile strain value of PSH was the largest. In addition, Figure 6 shows the artificial tensile conditions of PSH 25 , PSH4, PSH [[ID=...]] (The content seems to be incomplete here, but I continue based on the provided text) -18 and PSH -30 after rehydration at different times, which also proves that rehydration at high temperature for a short time is more conducive to improving the tensile properties of PSH.

[0058] 2.2 Texture properties of potato starch hydrogels:

[0059] Tables 1, 2, 3 and 4 show the effects of rehydration temperature and aging temperature on the texture properties of PSH.

[0060] Table 1

[0061]

[0062] Table 2

[0063]

[0064] Table 3

[0065]

[0066] Table 4

[0067]

[0068] There was no significant difference in the elasticity of PSH at different freezing temperatures (P>0.05). The aging of amylose led to an increase in hardness. When the starch gel was at -30 °C and -18 °C, its hardness and chewiness were lower than those at 4 °C. We speculated that the increase in hardness under quick freezing was lower than that at 4 °C. PSH became hard due to the degradation of starch, but when aging under freezing conditions, the water molecules in the starch gel quickly froze to form a stable and dense ice crystal structure. The formation of ice crystals caused the ordered structure of the starch gel to break, thus inhibiting the aging of the potato starch gel. Therefore, the hardness of potatoes under freezing conditions was less than that during aging at 4 °C. When the aging temperature decreased from 4 °C to -30 °C, the hardness of the gel decreased significantly from 3080.16±154.76 (PSH4-100-30s) to 2222.36±26.40 g (PSH -30 -100-30S). The tiny ice crystals produced by the rapid freezing of the hydrogel had little effect on elasticity because they retained the internal structure by causing less damage to the microstructure. As the rehydration temperature increased, the hardness of the potato starch gel decreased steadily during rehydration because the starch absorbed water and swelled, exerting pressure on the gel and increasing its strength. Research showed that the cooking temperature significantly affected the digestibility of starch, and the digestibility of starch in turn had a significant impact on the texture of starch products. Specifically, the chewing force and hardness levels of all PSH samples decreased with the increase in the rehydration temperature. As shown in Table 4, for the PSH -18 -100-20S sample, as the water temperature increased from 70 °C to 100 °C, the hardness decreased from 4790.13 to 2344.30. The chewiness and resilience of PSH -18 -100-20 after rehydration also decreased to 1738.99 and 0.33 respectively. At the same time. The rehydration time may also affect the texture properties of the potato starch gel. Long-term rehydration will damage the structural integrity of the gel, causing the contents to overflow and disturbing the orientation of the gel. Previous research results showed that appropriate aging conditions, combined with the rehydration temperature and time, could enhance the texture characteristics of the rehydrated starch gel during aging.

[0069] 2.3 Moisture migration:

[0070] Figure 2Spin relaxation times of potato starch hydrogels at different aging temperatures and rehydration temperatures. Three peaks were observed in the samples, denoted as T21, T22, and T23, respectively. The peak area ratios of the three peaks represent different types of water contents, denoted as A21, A22, and A23, respectively, indicating the existence of multi-component water in the aging and rehydration processes of potato starch hydrogels. The distribution range of T23 is 30 - 1000 ms, mainly related to the free water in the starch hydrogel network. The distribution range of T22 is 1 - 10 ms, corresponding to the less mobile water body. The bound or rigid water distribution (T21) ranges from 0.1 to 1 ms and is considered to be the water with the lowest mobility. Compared with T21 and T22, the area ratio of T23 is the highest, indicating that the rehydration of PSH is mainly affected by the increase in free water, which reflects the weak interaction between water and starch. Compared with the gel relaxation time at 4 °C, the T23 values of the frozen gel samples after 12 h of regeneration are larger, and the T22 values are smaller, indicating that gel freezing and ice crystal melting lead to an increase in the pore size inside the gel. Under gel freezing conditions, the starch gel is basically not regenerated, the water flow inside the gel increases, and A23 increases. The interaction between water and starch gel is weak, and the migration of water after freezing may be due to the growth of ice crystals. Under the same aging conditions, with the increase of rehydration temperature, the areas of A23 and A22 gradually increase, indicating that at these three rehydration temperatures, the higher the rehydration temperature, the faster the migration speed of gel water molecules, and the water molecules are mainly located in the flowing water outside the starch granules; the interaction with the starch gel is weak, and the ability of PSH to bind water increases with the increase of rehydration temperature and time.

[0071] Figure 3 MRI image of potato starch hydrogel. With the increase of rehydration temperature and time, water moves and diffuses from the outside to the inside of PSH; the peripheral pseudo-color of PSH changes from green to yellowish-green and then to red; the green area in the center gradually shrinks until it disappears. When the rehydration time increases, water gradually penetrates into the inside of PSH and spends most of the time outside in the first stage. Compared with 85 °C and 100 °C, the water absorption after rehydration at 70 °C is weaker, and it can be seen from the MRI image that a larger area shows yellowish-green. For PSH -18For the samples, as the rehydration time increased from 10 s to 20 s, the higher the proton density, the higher the moisture content. Therefore, during the rehydration process, the water absorption of the starch gel is regulated by the rehydration temperature and time. The higher the rehydration temperature, the faster the water absorption rate of the starch gel. The water permeability is affected by the aging temperature. When the aging temperature is -18 °C, water molecules will be frozen into small ice crystals. When freeze - aging potato starch gel, at lower temperatures (-18 °C, -30 °C), the water in the starch gel quickly freezes into small ice crystals. The increase in ice crystals may squeeze the potato starch gel, which to a certain extent destroys the structure of the potato starch gel, and the pore size of the internal gel becomes larger due to the freezing and melting of ice crystals. Finally, T23 turns to the right and the area of A23 increases. These larger pores are conducive to the rapid migration of water. It can be concluded that the larger pores in the loose structure may help absorb more water. Figure 7 For the moisture content of PSH during the cooking process due to short rehydration time at different aging temperatures and different rehydration temperatures and times. For all samples, the moisture content of PSH increased slowly, and compared with other aging temperatures, the moisture content of PSH - 18 was higher than that of other samples.

[0072] 2.4 SEM of PSH:

[0073] Figure 4 For the gel microstructure of regenerated potato starch gel at different temperatures and rehydrated at different temperatures. As can be seen from Figure 4 it, the gelatinized gel showed a network structure after rehydration at different temperatures and freeze - drying. Different temperature conditions led to different degrees of regeneration, so the uniformity of the gel network structure size was also different. As the aging temperature decreased, the micro - pore structures of all gel samples changed greatly. The pore structure gradually changed from a fine and dense pore structure to a larger and uneven void structure, and the network walls gradually became thicker from thinner. The pore structure of the gel after freeze - aging at -18 °C was denser than that at 4 °C and room temperature. The reason is that the starch gel freezes rapidly at -18 °C, and the nuclei around it do not form large ice crystals but smaller ice crystals during the refrigeration process, thus forming a stable and dense structure, improving the strength of the starch gel and inhibiting the aging of the starch gel, resulting in a relatively dense void of the gel after freeze - drying. As the rehydration temperature increased, the micro - pore structures of all PSH gel samples changed greatly, and the pore structure gradually changed to a larger pore structure.

[0074] 2.5 FTIR spectra:

[0075] Figure 5Infrared spectra of potato starch gels under different regeneration temperatures and different rehydration conditions. The degradation of starch forms a double helix structure, which constitutes the short-range ordered structure of potato starch. The peak shapes of the infrared spectra of potato starch gels under different regeneration temperatures and different rehydration conditions are basically similar, indicating that during the gel regeneration process, only the number of ordered structures changes, and no other functional groups are generated or changed. Therefore, the starch gel mainly forms a network structure by hydrogen bond interaction. The peak at 3000 - 3500 cm -1 is the intermolecular -OH stretching vibration of the typical absorption band, and the absorption peaks at 1022 and 1047 cm -1 correspond to the amorphous region and the crystalline region in the starch granules respectively. The ratio of 1047 / 1022 cm -1 represents the short-range order degree of starch molecules. The short-range ordered structure specifically refers to the single helix and double helix structures formed by amylose and amylopectin molecules. The retrogradation of starch will form a double helix structure, which also constitutes the short-range ordered structure of potato starch. As can be seen from Figure 5 , all the peaks of the infrared spectra of potato starch gels produced at different aging temperatures are basically similar in type, indicating that during the gel aging process, only the change in the ordered structure is the change, and no other functional groups are generated or changed. Therefore, R1047 / 1022 is used to reflect the short-range order of starch crystals. Under the same conditions, the PSH 25 , PSH4, PSH -18 , PSH -30 sample R1047 / 1022 cm -1 are 0.35, 0.53, 0.46, 0.41 respectively; this shows that the starch ages rapidly at 4°C, and more short-range order is formed, and the crystallinity is more. Freezing reduces the short-range ordered structure. With the increase of the rehydration temperature and time, it also increases the absorbance ratio of 1047 / 1022 cm -1 , which indicates that high temperature promotes the growth of short-range ordered starch molecules.

[0076] The above results show that freezing and aging (-18°C, -30°C) quickly freezes the starch gel, and large ice crystals will not form around the nucleus. On the contrary, small ice crystals will form during the cooling process, resulting in the formation of a stable and dense structure, thereby enhancing the strength of the starch gel. Compared with the aging temperatures of 4°C and 25°C, the potato gels under freezing and aging conditions show superior mechanical properties. Under the condition of -18°C, PSH -18The tensile strength of -100-20S is 750% to 800%. In addition, low-field nuclear magnetic resonance results show that there are significant differences in the water content of potato starch gels aged at different temperatures. Under freezing conditions, due to the freezing and melting of ice crystals, the increase in internal pore size accelerates the migration of water molecules, resulting in a right shift of T23. The MRI results also show that as the rehydration temperature and time increase, water diffuses from the outer region to the inner region of the potato starch gel, and the water absorption rate is very fast. The porous structure formed by freeze-aging increases the specific surface area, which is conducive to the migration of water molecules and shortens the rehydration time. In summary, the research shows that the microstructure formed by freeze-aging is an effective strategy to enhance the mechanical properties and rehydration properties of starch gels, providing a theoretical basis for the application of starch gels in food.

[0077] Therefore, the present invention adopts the above-mentioned anti-tensile potato starch hydrogel and its preparation method to obtain a starch hydrogel PSH with excellent tensile strength. -18 -100-20S, with a tensile strength of 750% to 800%, and its preparation parameters are determined, providing a theoretical basis for the application of starch hydrogels in food.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a tensile-resistant potato starch hydrogel, characterized in that, It includes the following steps: S1. Preparation of the gel sheet: Mix potato starch and deionized water at a ratio of w / v = 2:3, stir evenly to form a slurry. Each time, pour 4 ml of the slurry into a silicone mold, place the mold containing the slurry sample in a steamer, and steam it with boiling water for 3 - 4 minutes to obtain a potato starch gel sheet with a thickness of 1.5 - 3.0 mm. Seal the potato gel sheet and cool it at room temperature; S2. Aging of the gel sheet: Aging the cooled potato starch gel sheet at -18°C for 12 h to obtain PSH -18 ; S3. Rehydration of the gel sheet: Rehydrate the PSH -18 to obtain a potato starch hydrogel; Among them, the rehydration temperature is 100 °C and the rehydration time is 20 s; The tensile strength of the obtained potato starch hydrogel is 750% - 800%.

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