High-elasticity composite hydrogel based on deacetylated konjac glucomannan and preparation method thereof

Abstract

The invention discloses a deacetylated konjac glucomannan composite hydrogel and a preparation method thereof, the raw materials comprise deacetylated konjac glucomannan, agar, guar gum and water, the water and polysaccharide powder are mixed according to a certain proportion, magnetically stirred for 15 minutes, then placed in a water bath kettle at 90 DEG C for water bath for 30 minutes, taken out and cooled to room temperature, and the deacetylated konjac glucomannan composite hydrogel is obtained. And refrigerating in a refrigerator at 4 DEG C for 24 hours. The high-elasticity deacetylated konjac glucomannan composite hydrogel is obtained by controlling the adding amount of raw material powder, the deacetylation degree, the stirring time, the water bath temperature and the water bath time, improving the problems of poor gel strength, overlarge viscosity and poor thermal stability of konjac glucomannan single gel and remarkably improving the elasticity and the water-holding capacity of the gel.

Description

Technical Field

[0001] The present invention belongs to the field of food industry, and particularly relates to a highly elastic composite hydrogel based on deacetylated konjac glucomannan and a preparation method thereof. Background Art

[0002] Konjac glucomannan (KGM) is a natural polysaccharide composed of D-glucose and D-mannose linked by β-1,4 glycosidic bonds. It is a high-quality dietary fiber. Existing research has shown that KGM can enhance satiety and reduce the rise of postprandial blood glucose, and has broad application prospects in weight loss and diabetes treatment. When preparing gels alone, KGM has defects such as low cohesiveness, weak mechanical properties, and instability, and is often improved through compounding and modification.

[0003] Deacetylation is an important way to modify KGM. Deacetylation forms deacetylated konjac glucomannan (DKGM), and its structure and properties have significant changes. Specifically: Molecular structure change: During the deacetylation process, the acetyl groups of KGM are removed, resulting in enhanced intermolecular and intramolecular hydrogen bond interactions and improved steric effects, thereby increasing the solubility and crystallinity of KGM. In addition, deacetylation converts KGM from a semi-flexible linear molecule into an elastic microsphere structure, increasing the asymmetry of the configuration.

[0004] Physicochemical property change: After deacetylation, the water absorption rate, swelling property, and gel strength of KGM are significantly improved. This is because the presence of acetyl groups inhibits the formation of intermolecular and intramolecular hydrogen bonds, and these hydrogen bonds are enhanced after deacetylation, thereby improving the water retention capacity and gel properties of KGM.

[0005] Enhanced functional characteristics: Deacetylated KGM has a wider application in the food industry. For example, the addition amount of deacetylated KGM in flour products can be increased because its water absorption rate decreases and the gel strength increases, making the texture characteristics of the dough better. In addition, the adsorption effect of deacetylated KGM on saturated fatty acids and unsaturated fatty acids is significantly improved, which is beneficial to the preservation and health function of food.

[0006] Microscopic structure change: It is found by scanning electron microscopy that the surface of KGM after deacetylation treatment changes from a loose lamellar structure to a tight groove structure and still exists in an amorphous α structure. This structural change further enhances the gel properties and functional characteristics of KGM.

[0007] In summary, the acetyl group is an important group in KGM related to solubility, gelation, and thermal stability. After deacetylation, the gelation ability of KGM is enhanced, and the formed gel has thermal irreversibility. It also significantly improves its physical and chemical properties and functional characteristics, making its application in the food industry more extensive and effective.

[0008] Single KGM has the disadvantages of weak mechanical properties and thermal instability. Even though the mechanical properties of single KGM after deacetylation are improved, there are still disadvantages such as insufficient elasticity and weak chewiness. Summary of the Invention

[0009] The purpose of the present invention is to provide a preparation method of a highly elastic composite hydrogel based on deacetylated konjac glucomannan, which improves the disadvantages of insufficient elasticity and weak chewiness existing in the existing konjac gel.

[0010] The purpose of the present invention is achieved through the following technical solutions: A preparation method of a highly elastic composite hydrogel based on deacetylated konjac glucomannan, comprising the following steps: Step 1: Mix three raw material powders and add distilled water to obtain a feed liquid; the mass ratio of deacetylated konjac glucomannan, guar gum (GG), and agar (AG) to the volume of water is (0.4 - 2.0):(0.4 - 2.0):(0.4 - 2.0):100. Step 2: Magnetically stir the feed liquid to obtain a sol after sufficient swelling. Step 3: Heat the sol in a water bath, cool it to room temperature, then refrigerate it at 0 - 4°C for more than 10 hours, and then take it out and place it at room temperature for more than 1 hour to obtain a highly elastic composite hydrogel.

[0011] As a more preferred technical solution of the present invention: the mass ratio of deacetylated konjac glucomannan, guar gum, and agar is 1.7:0.8:1.7.

[0012] As a more preferred technical solution of the present invention: magnetically stir at a speed of 700 - 900 rpm / min for 5 - 25 min.

[0013] As a more preferred technical solution of the present invention: magnetically stir at a speed of 800 rpm / min for 15 min.

[0014] As a more preferred technical solution of the present invention: the water bath temperature is 75 - 95°C, and the water bath time is 20 - 60 min.

[0015] As a more preferred technical solution of the present invention: the water bath temperature is 90°C, and the water bath time is 30 min.

[0016] Another object of the present invention is to provide a highly elastic composite hydrogel obtained by the above preparation method.

[0017] Compared with the konjac gel products on the existing market, a highly elastic deacetylated konjac glucomannan composite hydrogel and its preparation method of the present invention have the following beneficial effects: For the prepared highly elastic deacetylated konjac glucomannan composite hydrogel, on the basis of the deacetylated konjac glucomannan gel improving the problems of poor gel strength, thermal instability, and easy water separation of ordinary konjac gum, the gel texture characteristics and thermal stability are further improved. In particular, the problem of poor elasticity of a single deacetylated konjac gel is significantly improved.

[0018] Using moderately deacetylated deacetylated konjac glucomannan, which includes both soluble dietary fiber (undedeacetylated part) and insoluble dietary fiber (deacetylated part), can more effectively regulate the intestinal digestion and metabolism function.

[0019] The raw materials are deacetylated konjac glucomannan, guar gum, agar, and water, without including other components, and have low calories. The three components act synergistically to reduce the high viscosity characteristic of konjac glucomannan, reduce the application difficulty, and expand the application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The specification drawings forming a part of the present invention are used to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, and do not constitute an improper limitation to the present invention.

[0021] Figure 1 is a finished product diagram of the composite gel of the present invention; Figure 2 is a graph showing the elastic change trend of the composite gel formed under the condition of changing the addition amount of deacetylated konjac glucomannan; Figure 3 is a graph showing the elastic change trend of the composite gel formed under the condition of changing the addition amount of agar; Figure 4 is a graph showing the elastic change trend of the composite gel formed under the condition of changing the addition amount of guar gum; Figure 5 is a graph showing the elastic change trend of the composite gel formed under the condition of changing the degree of deacetylation; Figure 6 is a graph showing the elastic change trend of the composite gel formed under the condition of changing the stirring time; Figure 7 is a graph showing the elastic change trend of the composite gel formed under the condition of changing the water bath time; Figure 8 is a graph showing the elastic change trend of the composite gel formed under the condition of changing the water bath temperature. Detailed implementation manners

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the following examples are used to illustrate the present invention, but not to limit the scope of the present invention.

[0023] The embodiments of the present invention are described in detail below. The following described embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention. For those without specific technical or conditions noted in the embodiments, the techniques or conditions described in the literature in the field or in accordance with the product instructions are followed. For the reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchase.

[0024] Example 1 Weigh deacetylated konjac glucomannan with a deacetylation degree of 40% and an addition amount of 1.7%, 0.8% of agar, and 1.7% of guar gum, and add 100 mL of distilled water at 50 °C thereto.

[0025] The feed liquid is magnetically stirred at a speed of 800 rpm / min for 15 min to fully swell the raw materials.

[0026] The fully swollen sol is water-bathed in a water bath at 90 °C for 30 min, and then taken out and cooled to room temperature.

[0027] The cooled gel is refrigerated at 4 °C for 24 h.

[0028] After taking it out and placing it at room temperature for 2 h, the finished product of deacetylated konjac glucomannan composite gel is obtained.

[0029] Comparative Example 1 Weigh deacetylated konjac glucomannan with a deacetylation degree of 39.10% and an addition amount of 1.6%, 1.2% of agar, and 1.2% of guar gum, and add 100 mL of distilled water at 50 °C thereto.

[0030] The feed liquid is magnetically stirred at a speed of 800 rpm / min for 15 min to fully swell the raw materials.

[0031] The fully swollen sol is water-bathed in a water bath at 85 °C for 40 min, and then taken out and cooled to room temperature.

[0032] The cooled gel is refrigerated at 4 °C for 24 h.

[0033] After taking it out and placing it at room temperature for 2 h, the finished product of deacetylated konjac glucomannan composite gel is obtained.

[0034] Comparative Example 2 Weigh deacetylated konjac glucomannan with a deacetylation degree of 25.81% and an addition amount of 1.2%, 0.8% agar, and 1.6% guar gum, and add 100 mL of distilled water at 50 °C to it.

[0035] Magnetically stir the material liquid at a speed of 800 rpm / min for 15 min to fully swell the raw materials.

[0036] Water-bath the fully swollen sol in a water-bath pot at 85 °C for 40 min, and then take it out and cool it to room temperature.

[0037] Refrigerate the cooled gel at 4 °C for 24 h.

[0038] Take it out and place it at room temperature for 2 h to obtain the finished product of deacetylated konjac glucomannan composite gel.

[0039] Comparative Example 3 Weigh deacetylated konjac glucomannan with a deacetylation degree of 39.10% and an addition amount of 1.6%, 0.4% agar, and 1.2% guar gum, and add 100 mL of distilled water at 50 °C to it.

[0040] Magnetically stir the material liquid at a speed of 800 rpm / min for 15 min to fully swell the raw materials.

[0041] Water-bath the fully swollen sol in a water-bath pot at 85 °C for 40 min, and then take it out and cool it to room temperature.

[0042] Refrigerate the cooled gel at 4 °C for 24 h.

[0043] Take it out and place it at room temperature for 2 h to obtain the finished product of deacetylated konjac glucomannan composite gel.

[0044] Comparative Example 4 Weigh deacetylated konjac glucomannan with a deacetylation degree of 39.10% and an addition amount of 1.2%, 1.2% agar, and 1.6% guar gum, and add 100 mL of distilled water at 50 °C to it.

[0045] Magnetically stir the material liquid at a speed of 800 rpm / min for 15 min to fully swell the raw materials.

[0046] Water-bath the fully swollen sol in a water-bath pot at 85 °C for 40 min, and then take it out and cool it to room temperature.

[0047] Refrigerate the cooled gel at 4 °C for 24 h.

[0048] Take it out and place it at room temperature for 2 h to obtain the finished product of deacetylated konjac glucomannan composite gel.

[0049] Comparative Example 5 Weigh 2% of deacetylated konjac glucomannan with a deacetylation degree of 39.10%, 0.8% of agar, and 1.2% of guar gum, and add 100 mL of distilled water at 50 °C to it.

[0050] Magnetically stir the feed liquid at a speed of 800 rpm / min for 15 min to fully swell the raw materials.

[0051] Water bath the fully swollen sol in a water bath at 90 °C for 40 min, and then take it out and cool it to room temperature.

[0052] Refrigerate the cooled gel at 4 °C for 24 h.

[0053] Take it out and place it at room temperature for 2 h to obtain the finished product of deacetylated konjac glucomannan composite gel.

[0054] Comparative Example 6 Weigh 1.2% of deacetylated konjac glucomannan with a deacetylation degree of 39.10%, 0.8% of agar, and 1.2% of guar gum, and add 100 mL of distilled water at 50 °C to it.

[0055] Magnetically stir the feed liquid at a speed of 800 rpm / min for 15 min to fully swell the raw materials.

[0056] Water bath the fully swollen sol in a water bath at 85 °C for 40 min, and then take it out and cool it to room temperature.

[0057] Refrigerate the cooled gel at 4 °C for 24 h.

[0058] Take it out and place it at room temperature for 2 h to obtain the finished product of deacetylated konjac glucomannan composite gel.

[0059] Texture tests of different composite gels Use a texture analyzer (Brookfield CT3, USA) to measure the texture properties of the composite gel after refrigeration and standing at room temperature.

[0060] Table 1 Texture test results of deacetylated konjac glucomannan composite gels in Example 1 and Comparative Examples 1 - 6 According to the results in Table 1, it shows that the texture properties of the deacetylated konjac glucomannan composite gel obtained using 1.7% of deacetylated konjac glucomannan with a deacetylation degree of 40%, 0.8% of agar, and 1.7% of guar gum are optimally improved. Among them, the elasticity, chewiness, and cohesiveness are all greatly enhanced. The elasticity reaches 11.22 mm, the chewiness (in the low base value range) is increased by more than 3 mJ, which may significantly improve the taste, and the difference in cohesiveness is more than 10%.

[0061] This proves that the preparation method of this gel effectively improves the gel properties and obtains a highly elastic deacetylated konjac glucomannan composite gel.

[0062] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A preparation method of a highly elastic composite hydrogel based on deacetylated konjac glucomannan, characterized in that, It includes the following steps: Step 1: Add distilled water to the mixture of three raw material powders to obtain a liquid material; the mass ratio of deacetylated konjac glucomannan, guar gum and agar to the volume of water is (0.4 - 2.0):(0.4 - 2.0):(0.4 - 2.0):100; Step 2: Magnetically stir the liquid material to obtain a sol after sufficient swelling; Step 3: Water-bath heat the sol in a water-bath pot, cool it to room temperature, then refrigerate it at 0 - 4 °C for more than 10 hours, and then take it out and place it at room temperature for more than 1 hour to obtain a highly elastic composite hydrogel.

2. The preparation method of the highly elastic composite hydrogel based on deacetylated konjac glucomannan according to claim 1, characterized in that, The mass ratio of the deacetylated konjac glucomannan, guar gum and agar is 1.7:0.8:1.

7.

3. The preparation method of the highly elastic composite hydrogel based on deacetylated konjac glucomannan according to claim 1, characterized in that, Magnetic stirring is carried out at a speed of 700 - 900 rpm / min for 5 - 25 min.

4. The preparation method of the highly elastic composite hydrogel based on deacetylated konjac glucomannan according to claim 1, characterized in that, Magnetic stirring is carried out at a speed of 800 rpm / min for 15 min.

5. The preparation method of the highly elastic composite hydrogel based on deacetylated konjac glucomannan according to claim 1, characterized in that The water-bath temperature is 75 - 95 °C, and the water-bath time is 20 - 60 min.

6. The preparation method of the highly elastic composite hydrogel based on deacetylated konjac glucomannan according to claim 1, characterized in that, The water-bath temperature is 90 °C, and the water-bath time is 30 min.

7. A highly elastic composite hydrogel, characterized in that, It is obtained by adopting the preparation method of the highly elastic composite hydrogel based on deacetylated konjac glucomannan in claim 1.

Images