Preparation method of smooth and chewy fresh wet noodles

Abstract

The invention belongs to the field of food processing, and relates to a preparation method of smooth and chewy fresh wet noodles. The preparation method comprises the following steps: firstly, modifying konjac polysaccharide with the substitution degree of 0.01-1 to obtain acetylated konjac glucomannan; and then mixing the modified polysaccharide with 0.1-5% of medium gluten wheat flour, adding 1% of sodium chloride and 32% of water, and performing dough kneading, curing, roller pressing, slitting and other processes to prepare the fresh wet noodles. According to the present invention, the product has excellent texture characteristics, the hardness reaches 2874.46 gf when the substitution degree is 0.3, the elasticity reaches 0.83, the chewiness reaches 1593.51 gf, the viscosity is 1921.88 gf, and various indexes are superior to the indexes of the non-modified control group. Meanwhile, the product has good antibacterial property, and the total number of bacterial colonies is obviously lower than that of a control group after the product is stored for 10 days. The acetylated konjac polysaccharide can effectively inhibit the growth of microorganisms and prolong the shelf life of the product. The technical problems that traditional fresh wet noodles are short in shelf life, poor in taste and not chewy are solved, and the method is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of fresh wet noodles preparation, specifically to a method for preparing smooth and chewy fresh wet noodles. Background Technology

[0002] Fresh wet noodles, as a traditional noodle dish, are widely popular among consumers for their rich wheat aroma, high nutritional value, and chewy texture.

[0003] However, traditional fresh noodles currently face the following technical challenges: 1. Short shelf life hinders industrialization. Traditional fresh noodles have a high moisture content, typically >30%, providing ideal conditions for the growth and reproduction of microorganisms such as bacteria and mold, making the product extremely prone to spoilage. This results in a very short shelf life, heavy reliance on cold chain transportation and sales, and significantly restricts large-scale production, cross-regional distribution, and market promotion. 2. Traditional recipe products have texture and nutritional defects. Traditional fresh wet noodles made from ordinary wheat flour have inherent defects. After steaming or boiling, they are prone to problems such as soft texture, insufficient elasticity, and poor chewiness. During the steaming or boiling process, water-soluble vitamins, minerals and other nutrients are easily dissolved and lost, reducing their nutritional value. 3. Direct application of konjac glucomannan leads to textural degradation. Although konjac glucomannan is a potential improver for flour products, its practical application suffers from the following fundamental technical drawbacks: ① Strong hydrophilicity leads to negative effects. Due to its extremely strong hydrophilicity and water-holding capacity, it will competitively bind water in the system with gluten protein. ② It damages the gluten network structure. Excessive water absorption and swelling will hinder the full hydration and normal cross-linking of gluten proteins, thereby weakening or even destroying the formation and stability of the gluten network. ③ Lacking antioxidant properties, it is prone to producing poor texture, which ultimately leads to deterioration of the noodle texture, manifested as an overly soft, sticky, and non-chewy texture, or hardening, unevenness, and other undesirable phenomena, thus reducing the quality of the product.

[0004] In summary, current technologies have not yet provided an effective method that can leverage the advantages of konjac glucomannan, such as improving preservation and enhancing water retention, to address the aforementioned technical problems while simultaneously overcoming its own shortcomings. In other words, current technologies cannot significantly improve the texture and storability of fresh wet noodles while maintaining their freshness, moisture, and nutritional value. Summary of the Invention

[0005] To solve the above-mentioned technical problems, this invention modifies konjac glucomannan into acetylated konjac glucomannan, and uses the modified acetylated konjac glucomannan as a modifier to prepare fresh wet noodles through a series of processes such as ingredient mixing, maturation, pressing and cutting into strips and packaging.

[0006] Through the aforementioned improvements, combined with the process of this invention, the textural properties of the noodles are significantly improved. This results in konjac polysaccharide fresh wet noodles that not only possess a chewy and smooth texture and a crystal-clear appearance, but also exhibit excellent antioxidant properties and free radical scavenging capabilities, thereby fundamentally extending their shelf life. Furthermore, the process of this invention is simple, cost-controllable, and suitable for the stable production of high-quality, shelf-stable fresh wet noodle products.

[0007] Specifically, the method for preparing smooth and chewy fresh wet noodles provided by the present invention is as follows: (1) Preparation of acetylated konjac glucomannan: ① Add konjac polysaccharide to a 50% ethanol aqueous solution, heat in a 65℃ water bath for 2 hours, filter, discard the filtrate, and obtain pretreated konjac polysaccharide; ② Add acetic acid, acetic anhydride and concentrated sulfuric acid to the pretreated konjac polysaccharide, heat in a water bath, then wash with an ethanol aqueous solution until neutral, and dry to obtain acetylated konjac glucomannan; (2) Ingredient preparation and dough preparation: Take the acetylated konjac glucomannan from (1) and mix it with wheat flour, add water, and then add 1% sodium chloride by mass. Place it in a dough mixer to prepare dough flakes. (3) Maturation: Cover the dough flakes in (2) with plastic wrap and let them mature at room temperature; (4) Pressing and cutting the dough: Press the cooked dough flakes from step (3) into sheets, then place them in a noodle machine for six roller pressings and cutting into strips to obtain acetylated konjac polysaccharide fresh wet noodles.

[0008] The above preparation method also includes (5) packaging: sealing the noodles in (4) into bags.

[0009] Preferably, in (1), the degree of substitution of the acetylated konjac glucomannan is 0.01~1.

[0010] Preferably, in (1), acetylated konjac glucomannan is prepared: ① Add konjac polysaccharide to an ethanol-water solution, heat and stir at 65°C for 2 hours to uniformly disperse the konjac polysaccharide in the ethanol-water solution, then quickly filter and discard the filtrate to obtain pretreated konjac polysaccharide; the mass concentration of the konjac polysaccharide is 0.1 g / mL, and the volume fraction of ethanol in the ethanol-water solution is 50%; ② Add acetic acid, acetic anhydride, and concentrated sulfuric acid to the pretreated konjac polysaccharide and heat in a water bath at 30-60℃ for 1-3 h. Acetic acid is added in two parts. The volume ratio of acetic acid to acetic anhydride is 1:1 to 2:1 in the first addition and 200-800:1 in the second addition. After the reaction is completed, the product is precipitated with ethanol and then washed sequentially with 100%, 80%, 70%, and 60% ethanol aqueous solutions until neutral. After drying, acetylated konjac glucomannan is obtained.

[0011] Preferably, in (2), the amount of acetylated konjac glucomannan added is 0.1% to 5% of the mass of wheat flour, and the wheat flour is medium gluten wheat flour.

[0012] Preferably, the settling and ripening time is 8 to 15 minutes.

[0013] Further preferred, the settling and ripening time is 10 minutes.

[0014] This application also includes the application of acetylated konjac glucomannan in the processing of fresh and wet foods, wherein the acetylated konjac glucomannan is prepared by step (1).

[0015] This application also includes the application of acetylated konjac glucomannan in the preparation of fresh konjac noodles, wherein the acetylated konjac glucomannan is prepared by step (1).

[0016] In this invention, acetylated konjac glucomannan is added to medium-gluten flour as a base. Its moderate hydrophilicity enhances the gluten network structure, while the resulting polysaccharide gel imparts a chewy texture to the noodles. Therefore, the noodles obtained through this method not only retain their freshness and moisture but also possess a chewy texture. Furthermore, the introduction of acetyl groups further enhances the noodles' antioxidant and antibacterial properties, effectively extending the storage time of fresh, moist noodles and solving the technical problem of short shelf life.

[0017] In summary, the beneficial effects of the present invention are as follows: (1) Fresh konjac noodles have excellent texture and good taste. By modifying konjac glucomannan with acetyl groups, its water absorption and hydrophobicity are balanced, allowing more water molecules to be used for starch hydration, forming a stronger gluten network structure and giving fresh wet noodles a more chewy and smooth texture. At the same time, acetylated konjac glucomannan forms a tighter complex with starch through hydrophobic interaction, resisting the damage caused by high-temperature shearing.

[0018] (2) Noodles have excellent antioxidant and antibacterial properties. Introducing acetyl groups enhances the antioxidant and antibacterial properties of noodles, extending the shelf life of fresh wet noodles. This is primarily because the addition of acetylated konjac glucomannan reduces the free water content in the dough, thereby lowering its water activity and inhibiting the growth of microorganisms such as mold and bacteria. Simultaneously, the polyphenol oxidase (PPO) in fresh wet noodles... 2+ / Cu 2+ Catalysis can trigger enzymatic browning. Acetyl groups can chelate metal ions (such as Cu) at the active site of PPO. 2+ This inhibits enzyme activity. Detailed data analysis is available in the Examples section. Attached Figure Description

[0019] Figure 1 This represents the total bacterial count during the storage period of fresh wet noodles. Detailed Implementation

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following further description of this application is provided.

[0021] Unless otherwise specified, the test methods or experimental methods described in the following examples are all conventional methods; unless otherwise specified, the raw materials and additives are obtained from conventional commercial sources or prepared by conventional methods.

[0022] Example 1 (1) Prepare acetylated konjac glucomannan with a degree of substitution of 0.1 and mix it with medium-gluten wheat flour (mass fraction of 1.5%) to obtain mixed powder.

[0023] (2) Ingredient preparation and dough preparation: Take a certain amount of mixed powder, add 1% sodium chloride and 32% water (based on the mass of wheat flour), place it in a dough mixer, stir at low speed for 1 min and then at high speed for 9 min to obtain dough flakes.

[0024] (3) Maturation: Cover with plastic wrap and let it mature at room temperature for 10 minutes.

[0025] (4) Pressing and cutting the dough: Press the cooked dough flakes from step (3) into sheets, then put them into a noodle machine for six roller pressings and cutting into strips to form noodles.

[0026] (5) Packaging: The noodles from step (4) are sealed in bags to obtain fresh konjac noodles.

[0027] The steps for preparing acetylated konjac glucomannan are as follows: ① Add konjac polysaccharide to an ethanol-water solution, heat and stir at 65°C for 2 hours to uniformly disperse the konjac polysaccharide in the ethanol-water solution, then quickly filter and discard the filtrate to obtain pretreated konjac polysaccharide; the mass concentration of the konjac polysaccharide is 0.1 g / mL, and the volume fraction of ethanol in the ethanol-water solution is 50%; ② Add acetic acid, acetic anhydride and concentrated sulfuric acid to the pretreated konjac polysaccharide and heat in a water bath at 30°C for 2 h. Acetic acid is added in two parts. The volume ratio of acetic acid to acetic anhydride is 1:1 in the first addition and 400:1 in the second addition. After the reaction is complete, the product is precipitated with ethanol and then washed sequentially with 100%, 80%, 70% and 60% ethanol aqueous solutions until neutral. After drying, acetylated konjac glucomannan is obtained.

[0028] Example 2 (1) Prepare acetylated konjac glucomannan with a degree of substitution of 0.3 and mix it with medium-gluten wheat flour (mass fraction of 1.5%) to obtain mixed powder.

[0029] The preparation method is the same as in Example 1, except that in step ②, acetic acid, acetic anhydride and concentrated sulfuric acid are added to the pretreated konjac polysaccharide and then heated in a water bath at 50°C for 2 hours.

[0030] (2) Ingredient preparation and dough preparation: Take a certain amount of mixed powder, add 1% sodium chloride and 32% water (based on the mass of wheat flour), place it in a dough mixer, stir at low speed for 1 min and then at high speed for 9 min to obtain dough flakes.

[0031] (3) Maturation: Cover with plastic wrap and let it mature at room temperature for 10 minutes.

[0032] (4) Pressing and cutting the dough: Press the cooked dough flakes from step (3) into sheets, then put them into a noodle machine for six roller pressings and cutting into strips to form noodles.

[0033] (5) Packaging: The noodles from step (4) are sealed in bags to obtain fresh konjac noodles.

[0034] Example 3 (1) Prepare acetylated konjac glucomannan with a degree of substitution of 0.5 and mix it with medium-gluten wheat flour (mass fraction of 1.5%) to obtain mixed powder. The preparation method is the same as in Example 1, except that in step ②, acetic acid, acetic anhydride and concentrated sulfuric acid are added to the pretreated konjac polysaccharide and then heated in a water bath at 55°C for 2 h.

[0035] (2) Ingredient preparation and dough preparation: Take a certain amount of mixed powder, add 1% sodium chloride and 32% water (based on the mass of wheat flour), place it in a dough mixer, stir at low speed for 1 min and then at high speed for 9 min to obtain dough flakes.

[0036] (3) Maturation: Cover with plastic wrap and let it mature at room temperature for 10 minutes.

[0037] (4) Pressing and cutting the dough: Press the cooked dough flakes from step (3) into sheets, then put them into a noodle machine for six roller pressings and cutting into strips to form noodles.

[0038] (5) Packaging: The noodles from step (4) are sealed in bags to obtain fresh konjac noodles.

[0039] Example 4 (1) Prepare acetylated konjac glucomannan with a degree of substitution of 0.7, and mix it with medium-gluten wheat flour (mass fraction of 1.5%) to obtain mixed powder. The preparation method is the same as in Example 1, except that in step ②, acetic acid, acetic anhydride and concentrated sulfuric acid are added to the pretreated konjac polysaccharide and the mixture is heated in a water bath at 60°C for 2 h.

[0040] (2) Ingredient preparation and dough preparation: Take a certain amount of mixed powder, add 1% sodium chloride and 32% water (based on the mass of wheat flour), place it in a dough mixer, stir at low speed for 1 min and then at high speed for 9 min to obtain dough flakes.

[0041] (3) Maturation: Cover with plastic wrap and let it mature at room temperature for 10 minutes.

[0042] (4) Pressing and cutting the dough: Press the cooked dough flakes from step (3) into sheets, then put them into a noodle machine for six roller pressings and cutting into strips to form noodles.

[0043] (5) Packaging: The noodles from step (4) are sealed in bags to obtain fresh konjac noodles.

[0044] Example 5 (1) Prepare acetylated konjac glucomannan with a degree of substitution of 1, and mix it with medium-gluten wheat flour (mass fraction of 1.5%) to obtain mixed powder. The preparation method is the same as in Example 1, except that ② acetic acid, acetic anhydride and concentrated sulfuric acid are added to the pretreated konjac polysaccharide and heated in a water bath at 60°C for 2 h; wherein the volume ratio of acetic acid to acetic anhydride is 1:1.5.

[0045] (2) Ingredient preparation and dough preparation: Take a certain amount of mixed powder, add 1% sodium chloride and 32% water (based on the mass of wheat flour), place it in a dough mixer, stir at low speed for 1 min and then at high speed for 9 min to obtain dough flakes.

[0046] (3) Maturation: Cover with plastic wrap and let it mature at room temperature for 10 minutes.

[0047] (4) Pressing and cutting the dough: Press the cooked dough flakes from step (3) into sheets, then put them into a noodle machine for six roller pressings and cutting into strips to form noodles.

[0048] (5) Packaging: The noodles from step (4) are sealed in bags to obtain fresh konjac noodles.

[0049] Comparative Example 1 (1) Ingredient preparation and dough preparation: Take all-purpose flour, add 1% sodium chloride and 32% water (based on the mass of wheat flour), place it in a dough mixer, mix at low speed for 1 min and then at high speed for 9 min to obtain dough flakes.

[0050] (2) Maturation: Cover with plastic wrap and let it mature at room temperature for 10 minutes.

[0051] (3) Pressing and cutting the dough: Press the cooked dough flakes from step (2) into sheets, then put them into a noodle machine for six roller pressings and cutting into strips to form noodles.

[0052] (4) Packaging: The noodles from step (3) are sealed in bags to obtain fresh wet noodles.

[0053] Comparative Example 2 (1) Mix unmodified konjac glucomannan with medium-gluten wheat flour to obtain mixed powder.

[0054] (2) Ingredient preparation and dough preparation: Take the mixed powder, add 1% sodium chloride and 32% water (based on the mass of wheat flour), place it in a dough mixer, stir at low speed for 1 min and then at high speed for 9 min to obtain dough flakes.

[0055] (3) Maturation: Cover with plastic wrap and let it mature at room temperature for 10 minutes.

[0056] (4) Pressing and cutting the dough: Press the cooked dough flakes from step (3) into sheets, then put them into a noodle machine for six roller pressings and cutting into strips to form noodles.

[0057] (5) Packaging: The noodles from step (4) are sealed in bags to obtain fresh konjac noodles.

[0058] The texture properties of fresh konjac noodles (Examples 1-3) were improved compared to the blank control (Comparative Example 1) and the sample with added unmodified konjac glucomannan (Comparative Example 2) after the optimal steaming time of 5 min.

[0059] Table 1. Texture properties of fresh wet noodles prepared in the examples and comparative examples after steaming for 5 minutes.

[0060] Table 1 shows that the textural determination method for fresh wet noodles utilizes cutting-edge experimental techniques. The reference is "The effects of chitosan oligosaccharides on the structure and shelf-life of whole-millet cakes," published in the journal Food Chemistry in 2025, DOI:10.1016 / j.foodchem.2024.142267.

[0061] As can be seen from Table 1, the hardness, elasticity, chewiness, and adhesiveness of Example 2 are all improved compared to Comparative Examples 1 and 2. The decrease in elasticity of Comparative Example 2 with added konjac glucomannan indicates that its excessive water absorption competes with gluten for water, weakening the gluten network. However, the excessively substituted acetylated konjac glucomannan leads to the destruction of the fresh wet noodle network structure due to its strong hydrophobic interaction. In summary, the addition of our prepared modifier enhances the water retention of the gluten network and the stability of starch gel, comprehensively optimizing the edible texture of the noodles, solving the problems of traditional fresh wet noodles being easy to become soft and lacking toughness, and making the texture of the product closer to the chewy characteristics of handmade noodles.

[0062] from Figure 1 The results show that, with a moderate degree of substitution (DS=0.2~0.4), fresh wet noodles prepared with acetylated konjac glucomannan (AKGM) exhibited a significant antibacterial effect during storage, with a significantly lower total bacterial count than the sample without the modifier. By day 10, the total bacterial count in the control group without AKGM reached 5.48 log CFU / g, indicating a significant decline in its microbial quality and reduced food safety. With a moderate degree of substitution (DS=0.3), fresh wet noodles prepared with acetylated konjac glucomannan (AKGM) also showed a significant antibacterial effect during storage, with a significantly lower total bacterial count than the sample without the modifier (day 10: AKGM: 4.54 log CFU / g, KGM: 4.69 log CFU / g, KB: 5.49 log CFU / g; the national standard stipulates that a count above 5.48 log CFU / g indicates the sample has spoiled and is inedible). This demonstrates that the introduction of AKGM can effectively inhibit microbial growth.

[0063] Comprehensive experimental data show that AKGM with an appropriate degree of substitution can effectively enhance the water-holding capacity of the gluten network and the stability of the starch gel, thereby improving the hardness, elasticity, chewiness, and adhesiveness of the noodles, alleviating the problem of soggy texture caused by high moisture content, and making its taste closer to traditional handmade noodles. However, excessive substitution or unmodified raw materials can damage the gluten network structure due to excessive hydrophobicity or excessive water absorption and swelling, thus affecting the overall texture. Therefore, this modifier not only helps improve the eating quality of fresh konjac noodles but also extends their shelf life.

[0064] Table 2. Color changes of fresh wet noodles made with acetylated konjac glucomannan during storage. Color difference Days KB KGM AKGM L* 0 <![CDATA[88.31±0.54 b ]]> <![CDATA[90.52±0.13 a ]]> <![CDATA[91.02±0.10 a ]]> 3 <![CDATA[82.32±0.43 b ]]> <![CDATA[82.84±0.43 a ]]> <![CDATA[84.24±0.19 a ]]> 5 <![CDATA[78.12±0.55 c ]]> <![CDATA[81.20±0.35 b ]]> <![CDATA[82.71±0.36 a ]]> 7 <![CDATA[76.32±0.85 b ]]> <![CDATA[80.46±0.80 a ]]> <![CDATA[81.54±0.21 a ]]> 10 <![CDATA[74.06±1.22 b ]]> <![CDATA[78.97±0.63 a ]]> <![CDATA[80.57±0.82 a ]]> a* 0 <![CDATA[0.54±0.26 a ]]> <![CDATA[0.51±0.03 a ]]> <![CDATA[0.36±0.02 a ]]> 3 <![CDATA[0.44±0.01 a ]]> <![CDATA[0.29±0.05 b ]]> <![CDATA[0.40±0.06 a ]]> 5 <![CDATA[0.56±0.04 a ]]> <![CDATA[0.21±0.02 c ]]> <![CDATA[0.40±0.02 b ]]> 7 <![CDATA[0.75±0.15 a ]]> <![CDATA[0.18±0.05 b ]]> <![CDATA[0.66±0.05 a ]]> 10 <![CDATA[1.10±0.15 a ]]> <![CDATA[0.33±0.04 b ]]> <![CDATA[0.49±0.06 b ]]> b* 0 <![CDATA[16.63±0.16 a ]]> <![CDATA[14.05±0.02 b ]]> <![CDATA[14.79±0.78 b ]]> 3 <![CDATA[22.61±0.24 a ]]> <![CDATA[18.56±0.20 c ]]> <![CDATA[20.33±0.60 b ]]> 5 <![CDATA[22.49±0.09 a ]]> <![CDATA[18.87±0.15 c ]]> <![CDATA[21.31±0.28 b ]]> 7 <![CDATA[23.49±0.3 a ]]> <![CDATA[20.16±0.5 c ]]> <![CDATA[21.95±0.18 b ]]> 10 <![CDATA[24.62±0.17 a ]]> <![CDATA[20.76±0.61 c ]]> <![CDATA[21.70±0.16 b ]]>

[0065] During storage, the brightness (L value) of the noodles gradually decreased, while the redness (a value) and yellowness (b value) gradually increased, indicating that oxidative browning had occurred. Among them, the L value of the noodles in Example 2 decreased the slowest, and the a and b values ​​increased less, which shows that AKGM can effectively inhibit the oxidative discoloration of noodles and demonstrates a direct antioxidant effect.

Claims

1. A method for preparing a fresh and wet noodle with smooth and tough texture, characterized in that: (1) preparing acetylated konjac glucomannan: ①adding konjac polysaccharide into 50% ethanol aqueous solution, heating in a water bath at 65℃ for 2h, then performing suction filtration, discarding the filtrate, and obtaining pretreated konjac polysaccharide; ②adding acetic acid, acetic anhydride and concentrated sulfuric acid into the pretreated konjac polysaccharide, heating in a water bath, then washing with ethanol aqueous solution until neutral, drying, and obtaining acetylated konjac glucomannan; (2) mixing and kneading: mixing the acetylated konjac glucomannan in (1) with wheat flour, adding water, and adding 1% sodium chloride by mass percentage, and then placing in a kneader to prepare dough; (3) maturing: covering the dough in (2) with plastic wrap, and maturing at room temperature; (4) pressing and cutting: pressing the matured dough in step (3) into noodle sheets, and then placing in a noodle machine to perform 6 times of roller pressing and cutting, and obtaining acetylated konjac polysaccharide fresh and wet noodles; (5) packaging: packaging the noodles in (4) in bags. In (1), the degree of substitution of the obtained acetylated konjac glucomannan is 0.01-1. In (1), the acetylated konjac glucomannan is prepared by: ①adding konjac polysaccharide into ethanol aqueous solution, heating and stirring at 30-60℃ for 1-3h to uniformly disperse the konjac polysaccharide in the ethanol aqueous solution, then performing rapid suction filtration, discarding the filtrate, and obtaining pretreated konjac polysaccharide; the mass concentration of the konjac polysaccharide is 0.1g / mL, and the volume fraction of ethanol in the ethanol aqueous solution is 50%; ②adding acetic acid, acetic anhydride and concentrated sulfuric acid into the pretreated konjac polysaccharide in sequence, heating in a water bath at 30-60℃ for 1-3h; wherein, the acetic acid is added in two times, the volume ratio of the acetic acid to the acetic anhydride in the first time is 1:1-2:1, and the volume ratio of the acetic acid to the concentrated sulfuric acid in the second time is 200-800:1; after the reaction, the product is precipitated with ethanol, and then washed with ethanol aqueous solution with volume fractions of 100%, 80%, 70% and 60% in sequence until neutral, and dried to obtain acetylated konjac glucomannan. In (1), the acetylated konjac glucomannan is prepared by: ①adding konjac polysaccharide into ethanol aqueous solution, heating and stirring at 50-80℃ for 1-3h to uniformly disperse the konjac polysaccharide in the ethanol aqueous solution, then performing rapid suction filtration, discarding the filtrate, and obtaining pretreated konjac polysaccharide; the mass concentration of the konjac polysaccharide is 0.1g / mL, and the volume fraction of ethanol in the ethanol aqueous solution is 50%; ②adding acetic acid, acetic anhydride and concentrated sulfuric acid into the pretreated konjac polysaccharide in sequence, heating in a water bath at 30-60℃ for 1-3h; wherein, the acetic acid is added in two times, the volume ratio of the acetic acid to the acetic anhydride in the first time is 1:1, and the volume ratio of the acetic acid to the concentrated sulfuric acid in the second time is 400:1; after the reaction, the product is precipitated with ethanol, and then washed with ethanol aqueous solution with volume fractions of 100%, 80%, 70% and 60% in sequence until neutral, and dried to obtain acetylated konjac glucomannan. ​ ​ ​ 2. A process for preparing a fresh and wet surface with smoothness and firmness according to claim 1, characterized in that: ​ 3. A method of preparing a fresh, wet, and smooth surface of a road according to claim 1, characterized in that: ​ 4. A method of preparing a fresh, wet, and smooth surface of a road according to claim 1, characterized in that: ​ ​ ​ 5. A method of preparing a fresh, wet, and smooth surface of a road according to claim 1, characterized in that: ​ ​ ​ 6. A method of preparing a fresh, wet, and smooth surface of a road according to claim 1, characterized in that: In the (2), the acetylated konjac glucomannan is added in an amount of 0.1% to 5% of the mass of the wheat flour, and the wheat flour is medium gluten wheat flour.

7. A method of preparing a fresh, wet, and smooth surface of a road according to claim 1, characterized in that, The standing and curing time is 8 to 15 minutes.

8. A method of preparing a fresh, wet, and smooth surface of a road according to claim 7, characterized in that, The standing and curing time is 10 minutes.

9. Use of acetylated konjac glucomannan in the processing of fresh and wet food products, characterized in that, The acetylated konjac glucomannan is prepared by the steps of (1) in claim 1.

10. Use of acetylated konjac glucomannan in the preparation of konjac fresh and wet noodles, characterized in that, The acetylated konjac glucomannan is prepared by the steps of (1) in claim 1.

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