Hydrophilic polysaccharide colloid modified cold noodles and preparation method of fresh-keeping cold noodles

Abstract

The invention discloses hydrophilic polysaccharide colloid modified cold noodles and a preparation method of fresh-keeping cold noodles, and relates to the technical field of cold noodle processing. According to the method for preparing the hydrophilic polysaccharide colloid modified cold noodles, wheat flour is used as a raw material, hydrophilic colloids of different types and concentrations are added, the concentration of starch slurry is adjusted, and the cooking time of the wrappers is controlled, so that the wrappers are prepared. According to the preparation method of the fresh-keeping cold noodles, wheat flour is used as a raw material, D-sodium erythorbate with different addition amounts is added to prepare the wrappers, hydrophilic colloid is used for modifying the steamed wrappers, the hardness of the wrappers is reduced, the elasticity of the wrappers is improved, and the edible quality and the water binding capacity of the wrappers are greatly improved. D-sodium erythorbate is adopted to replace a traditional preservative (such as sodium dehydroacetate) to prepare the wrapper, and the growth of microorganisms is inhibited by using the double functions of oxidation resistance and bacteriostasis of D-sodium erythorbate. The method not only effectively prolongs the shelf life of the wrappers, but also meets the requirements of consumers on label cleaning food.

Description

Technical Field

[0001] The invention relates to the technical field of cold noodle processing, in particular to the improvement of the physical and chemical properties of cold noodle by using hydrophilic colloid and the preparation technology of fresh cold noodle. Background Art

[0002] Liangpi (or steamed noodle wrappers) is a traditional noodle-based food made primarily from wheat starch and flour. It's widely popular for its smooth texture and unique flavor. The traditional production process typically involves kneading, washing, and steaming the dough. While this method produces a pleasant texture, its high moisture content (60%-70%) and neutral pH make it susceptible to microbial growth (such as bacteria and mold) at room temperature, leading to spoilage. Consequently, its shelf life typically does not exceed 24 hours. Currently, commercially available Liangpi wrappers rely on chemical preservatives (such as sodium dehydroacetate) to extend their shelf life. However, according to the newly implemented "National Food Safety Standard for the Use of Food Additives" (GB 2760-2024), the use of dehydroacetic acid and its sodium salt (sodium dehydroacetate) will be strictly restricted starting February 8, 2025. This preservative is prohibited in starch products (such as Liangpi wrappers), bread, pastries, and baked goods fillings. At the same time, consumers are increasingly concerned about the health risks of synthetic additives, prompting the industry to urgently develop safer and more efficient natural cold noodle preservation technologies to meet market demand and comply with the new national standards.

[0003] Furthermore, traditional cold noodles are prone to aging, hardening, dehydration, and cracking during storage, seriously affecting their quality. Hydrophilic colloids are substances that can dissolve or disperse in water and, under certain conditions, react with water molecules to form a viscous solution or gel. In food processing, hydrophilic colloids have multiple functions, including thickening, viscosity enhancement, gel formation, and emulsification stabilization. Konjac gum, a natural hydrophilic colloid extracted from konjac tubers, is primarily composed of glucomannan and exhibits high viscosity, high stability, excellent water solubility, and gelation properties. It is widely used in the food industry as a stabilizer, thickener, and quality improver for products such as pasta and meat. Guar gum, a natural hydrophilic colloid extracted from guar beans, exhibits excellent thickening properties and emulsion stability and is commonly used in a variety of applications, including food and cosmetics. The incorporation of hydrophilic colloids such as konjac gum or guar gum into the production of cold noodles can effectively improve their texture, taste, and stability. Sodium dehydroacetate is a common food preservative with some effectiveness, but its safety remains a concern. In contrast, sodium D-erythorbate is a safer and more effective antioxidant and preservative alternative. Its use in food not only effectively extends shelf life but also preserves its nutritional content and taste. In research on cold noodle preservation technology, the use of sodium D-erythorbate instead of sodium dehydroacetate not only improves product safety but also better meets consumer demand for healthy foods.

[0004] At present, there are still significant deficiencies in the preservation technology of cold noodle. Traditional methods mainly rely on chemical preservatives such as sodium dehydroacetate to extend the shelf life, but this additive poses potential health risks and does not meet the demand of modern consumers for clean-label food. At the same time, although the single use of hydrophilic colloids in existing technologies can improve the textural properties of cold noodle, it is difficult to take into account the antibacterial and fresh-keeping functions, resulting in the product being prone to microbial spoilage and texture deterioration during storage. In addition, conventional processing technology lacks a systematic solution for water activity control and microbial inhibition, making it difficult for the shelf life of cold noodle to exceed the 24-hour limit. In response to the above technical bottlenecks, the present invention innovatively proposes to optimize the network structure of cold noodles by adding hydrophilic colloids such as konjac gum and guar gum, significantly improving its elasticity and water retention. At the same time, sodium D-isoascorbate, a safe and efficient antioxidant, is used to replace traditional preservatives. Its dual antioxidant and antibacterial functions inhibit the growth of microorganisms. Combined with vacuum packaging, a new preservation system with the synergistic effect of physical barrier and chemical preservation is constructed, thereby achieving the simultaneous improvement of the edible quality and shelf life of cold noodles while ensuring food safety, providing the industry with a green and efficient comprehensive solution. Summary of the Invention

[0005] In response to the problems of insufficient safety of preservatives, easy aging and regeneration, and short shelf life in existing cold noodle preservation technologies, the present invention provides a cold noodle preparation technology based on hydrophilic colloid modification and antioxidant preservation. Specifically, by adding konjac gum or guar gum to optimize the three-dimensional network structure of cold noodle, its elasticity and water holding capacity are significantly improved; at the same time, sodium D-isoascorbate is used to replace traditional preservatives, and its antioxidant and antibacterial synergistic effects are used to inhibit the growth of microorganisms; further combined with vacuum packaging technology, a physical barrier and chemical preservation synergistic system is constructed to ensure food safety while effectively extending the shelf life of the product and maintaining excellent edible quality. The present invention provides a green and efficient comprehensive solution for the cold noodle industry to address the shortcomings of the existing technology.

[0006] The first object of the present invention is to provide a method for preparing hydrophilic colloid-modified cold noodles (steamed noodles), which uses wheat flour as raw material, adds hydrophilic colloids of different types and concentrations, adjusts the starch slurry concentration, and controls the steaming time of the noodles to prepare the noodles, and is carried out according to the following steps:

[0007] (1) Mixing: Take an appropriate amount of flour, add 0.5-1 times the weight of water, mix well, knead into a smooth dough, and let it stand for about 30 minutes;

[0008] (2) Washing the dough: put the dough obtained in step (1) into clean water and knead and wash it, pouring the pulp water obtained from each washing into the slurry bucket until the pulp water becomes clear and removes the raw gluten blocks;

[0009] (3) Flour slurry precipitation: the flour slurry obtained in step (2) is allowed to stand for 6-8 hours to allow the starch to precipitate completely;

[0010] (4) draining the floating water: slowly draining the upper layer of clear water from step (3) to obtain water starch;

[0011] (5) adjusting the concentration: stirring the water starch precipitated in the lower layer in step (4) uniformly, and adjusting the starch slurry concentration to 14-18°Bé with the discharged slurry water or wheat starch;

[0012] (6) adding a hydrophilic colloid: adding guar gum or konjac gum to the starch slurry having a concentration adjusted in step (5) to disperse the guar gum or konjac gum in the starch slurry to a concentration of 0.2 to 1 wt %;

[0013] (7) Steaming: Pour 120g-150g of starch slurry into a dough sheet with a diameter of 24cm. After the starch slurry is evenly distributed, place it in a pot of boiling water and steam it with the lid on for about 2-4 minutes. When the dough sheet is bubbly and transparent, take it out and cool it to room temperature in cold water. Then peel off the dough sheet.

[0014] (8) Oiling: Apply a layer of soybean oil to the peeled dough and set aside;

[0015] (9) Cutting into strips, weighing and packaging: Cut the dough into appropriate sizes and weigh and package them.

[0016] In the step (1), 0.5 times of water is preferably added to knead the dough.

[0017] The preferred slurry water precipitation time in step (3) is 7 hours.

[0018] The preferred starch slurry concentration in step (5) is 15°Bé.

[0019] In the step (6), the concentration of guar gum is preferably 0.6 wt % and the concentration of konjac gum is preferably 0.4 wt %.

[0020] The weight of the starch slurry in step (7) is preferably 130 g.

[0021] The cooking time in step (7) is preferably 3 minutes.

[0022] The packaging method described in step (9) is preferably vacuum packaging.

[0023] A second object of the present invention is to provide a method for preparing fresh-keeping cold noodles (steamed noodles), which comprises using wheat flour as a raw material and adding different amounts of sodium D-isoascorbate to prepare the noodles, and performing the following steps:

[0024] (1) Mixing: Take an appropriate amount of flour, add 0.5 times the weight of water, mix well, knead into a smooth dough, and let it stand for about 30 minutes;

[0025] (2) Washing the dough: put the dough obtained in step (1) into clean water and knead and wash it, pouring the pulp water obtained from each washing into the slurry bucket until the pulp water becomes clear and removes the raw gluten blocks;

[0026] (3) Flour slurry precipitation: the flour slurry obtained in step (2) was allowed to stand for 7 hours to allow the starch to precipitate completely;

[0027] (4) draining the floating water: slowly draining the upper layer of clear water from step (3) to obtain water starch;

[0028] (5) Adjusting the concentration: Stir the water starch precipitated in the lower layer in step (4) evenly, and use the discharged slurry or wheat starch to adjust the starch slurry concentration to 15°Bé;

[0029] (6) adding konjac glucomannan and sodium D-erythorbate: adding konjac glucomannan and sodium D-erythorbate to the starch slurry with the concentration adjusted in step (5), respectively, wherein the konjac glucomannan is dispersed in the starch slurry to a concentration of 0.4 wt %, and the concentration of sodium D-erythorbate is 0.05 to 0.35 wt %;

[0030] (7) Steaming: Pour 130g of starch slurry into a dough sheet with a diameter of 24cm, distribute the starch slurry evenly, place in a pot of boiling water, cover and steam for about 3min. When the dough sheet is bubbly and transparent, remove and place in cold water to cool to room temperature, then peel off the dough sheet.

[0031] (8) Oiling: Apply a layer of soybean oil to the peeled dough and set aside;

[0032] (9) Cutting into strips, weighing and packaging: Cut the dough into appropriate sizes and weigh and package them.

[0033] In the step (6), the concentration of sodium D-isoascorbate is preferably 0.15 wt%.

[0034] The packaging method described in step (9) is preferably vacuum packaging.

[0035] The beneficial effects of the present invention are:

[0036] (1) The present invention utilizes hydrophilic colloid to modify the cold noodle, thereby reducing the hardness of the cold noodle, increasing the elasticity of the cold noodle, and greatly improving the edible quality and water holding capacity of the cold noodle. Specifically, when 0.4 wt % konjac gum is added, the hardness of the cold noodle is reduced from 1527.3 g to 1370.7 g, and the elasticity is increased from 86.8% to 89.6%.

[0037] (2) Based on the improvement of the quality of Liangpi by hydrophilic colloid, the present invention further optimizes the concentration of starch slurry and the cooking time of Liangpi, thereby further improving the edible quality of Liangpi.

[0038] (3) The present invention uses sodium D-isoascorbate to replace traditional preservatives (such as sodium dehydroacetate) to prepare Liangpi, utilizing its dual antioxidant and antibacterial functions to inhibit microbial growth. Experimental results show that the addition of 0.15 wt% sodium D-isoascorbate can extend the shelf life of Liangpi from 3 days to 5 days, and on the 5th day, the total number of colonies in Liangpi is 2.8×10 5 CFU·g -1 The total number of mold is 75 CFU g -1 , all in compliance with food safety standards. This method not only effectively extends the shelf life of cold noodles, but also meets consumers' demand for clean label food.

[0039] (4) The preparation method of the present invention is easy to operate, does not require complex equipment, is suitable for industrial production, and has high economic benefits and market application prospects. While improving the preservation performance, it also takes into account the color, flavor and texture of the cold noodles, thereby achieving a simultaneous improvement in the product's edible quality and storage stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The effects of different guar gum concentrations on the textural properties of the cool cortex in Example 1 are shown;

[0041] Figure 2 The different konjac glucomannan concentrations in Example 2 affect the textural properties of the cool cortex;

[0042] Figure 3 The effects of different starch slurry concentrations on the textural properties of Liangpi in Example 3;

[0043] Figure 4 The effects of different cooking times on the textural properties of the cold leather in Example 4 are shown;

[0044] Figure 5 This is the effect of adding hydrophilic colloid on the water distribution of Liangpi in Experimental Example 2;

[0045] Figure 6 This is the sensory evaluation of the cold noodles in Experimental Example 3;

[0046] Figure 7 This is the sensory analysis of the fresh-keeping cold noodles in Experimental Example 4. DETAILED DESCRIPTION

[0047] Unless otherwise specified, the terms used in the present invention are generally understood by those of ordinary skill in the art. The present invention will be further described in detail below with reference to specific examples and data. It is hereby noted that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention in any way.

[0048] Example 1: Optimization of the preparation of modified Liangpi using guar gum, carried out according to the following method:

[0049] (1) Mix the flour and add 0.5 times the weight of water. Mix well and knead into a smooth dough. Let it sit for about 30 minutes.

[0050] (2) washing the dough, kneading the dough obtained in step (1) in clean water, and pouring the pulp obtained from each washing into a slurry bucket until the pulp becomes clear, and removing the raw gluten blocks;

[0051] (3) Flour slurry precipitation: the flour slurry obtained in step (2) is allowed to stand for 7 hours to allow the starch to precipitate completely;

[0052] (4) draining the floating water and slowly draining the upper layer of clear water from step (3) to obtain water starch;

[0053] (5) adjusting the concentration, stirring the water starch precipitated in the lower layer in step (4) uniformly, and adjusting the starch slurry concentration to 15°Bé with the discharged slurry water or wheat starch;

[0054] (6) adding a hydrophilic colloid, adding guar gum to the starch slurry having a concentration adjusted in step (5), and dispersing the guar gum in the starch slurry to concentrations of 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, and 1 wt%, respectively;

[0055] (7) Steam until cooked, take 130g of starch slurry and pour it into a dough sheet with a diameter of 24cm. After the starch slurry is evenly distributed, put it into a boiling water pot and steam it with the cover for about 3min. When the dough sheet is bubbling and transparent, take it out and put it into cold water to cool to room temperature, then peel off the dough sheet.

[0056] (8) Oil the peeled dough and apply a layer of soybean oil on it, set aside;

[0057] Measurement Method: The texture characteristics of cold noodle products were measured using a texture analyzer. Specific parameters were as follows: Cold noodle samples of uniform thickness were selected and cut into 1cm x 1cm pieces with a thickness of 1mm. A P50 probe was used for the texture test, using a pressure test. Parameters were set as follows: TPA mode; pre-test speed: 1mm / s; post-test speed: 1mm / s; interval between compressions: 5.0 seconds; compressive deformation: 60%; trigger force: 5g.

[0058] The concentration of guar gum was optimized based on hardness and elasticity. The results are shown in Figure 1 As the concentration of guar gum increased, the hardness of the cold noodle first decreased and then increased, while the elasticity first increased and then decreased. Compared with the control group, when the guar gum concentration was 0.4%, the hardness of the cold noodle was the lowest, but the elasticity did not change significantly.

[0059] Example 2: Optimization of preparing modified Liangpi with konjac glucomannan, carried out according to the following method:

[0060] (1) Mix the flour and add 0.5 times the weight of water. Mix well and knead into a smooth dough. Let it sit for about 30 minutes.

[0061] (2) washing the dough, kneading the dough obtained in step (1) in clean water, and pouring the pulp obtained from each washing into a slurry bucket until the pulp becomes clear, and removing the raw gluten blocks;

[0062] (3) Flour slurry precipitation: the flour slurry obtained in step (2) is allowed to stand for 7 hours to allow the starch to precipitate completely;

[0063] (4) draining the floating water and slowly draining the upper layer of clear water from step (3) to obtain water starch;

[0064] (5) adjusting the concentration, stirring the water starch precipitated in the lower layer in step (4) uniformly, and adjusting the starch slurry concentration to 15°Bé with the discharged slurry water or wheat starch;

[0065] (6) adding a hydrophilic colloid, adding konjac glucomannan to the starch slurry having a concentration adjusted in step (5), and dispersing the konjac glucomannan in the starch slurry to have a concentration of 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, and 1 wt% respectively;

[0066] (7) Steam until cooked, take 130g of starch slurry and pour it into a dough sheet with a diameter of 24cm. After the starch slurry is evenly distributed, put it into a boiling water pot and steam it with the cover for about 3min. When the dough sheet is bubbling and transparent, take it out and put it into cold water to cool to room temperature, then peel off the dough sheet.

[0067] (8) Oil the peeled dough and apply a layer of soybean oil on it, set aside;

[0068] Determination method: Same as Example 1.

[0069] The concentration of konjac gum was optimized based on hardness and elasticity. The results are shown in Figure 2 As the concentration of konjac glucomannan increases, the hardness of the cold noodle decreases first and then increases, while the elasticity increases first and then decreases. Compared with the control group, when the concentration of konjac glucomannan is 0.4%, the hardness of the cold noodle decreases, but the elasticity increases significantly. Therefore, 0.4wt% of konjac glucomannan is selected to prepare the cold noodle.

[0070] Example 3: Optimization of the starch slurry concentration of Liangpi was carried out according to the following method:

[0071] (1) Mix the flour and add 0.5 times the weight of water. Mix well and knead into a smooth dough. Let it sit for about 30 minutes.

[0072] (2) washing the dough, kneading the dough obtained in step (1) in clean water, and pouring the pulp obtained from each washing into a slurry bucket until the pulp becomes clear, and removing the raw gluten blocks;

[0073] (3) Flour slurry precipitation: the flour slurry obtained in step (2) is allowed to stand for 7 hours to allow the starch to precipitate completely;

[0074] (4) draining the floating water and slowly draining the upper layer of clear water from step (3) to obtain water starch;

[0075] (5) adjusting the concentration, stirring the water starch precipitated in the lower layer in step (4) uniformly, and using the discharged slurry or wheat starch to adjust the starch slurry concentration to 14°Bé, 15°Bé, 16°Bé, 17°Bé, and 18°Bé respectively;

[0076] (6) adding a hydrophilic colloid, adding konjac glucomannan to the starch slurry having a concentration adjusted in step (5), and dispersing the konjac glucomannan in the starch slurry to a concentration of 0.4 wt%;

[0077] (7) Steam until cooked, take 130g of starch slurry and pour it into a dough sheet with a diameter of 24cm. After the starch slurry is evenly distributed, put it into a boiling water pot and steam it with the cover for about 3min. When the dough sheet is bubbling and transparent, take it out and put it into cold water to cool to room temperature, then peel off the dough sheet.

[0078] (8) Oil the peeled dough and apply a layer of soybean oil on it, set aside;

[0079] Determination method: Same as Example 1.

[0080] The concentration of starch slurry was optimized by hardness and elasticity. The results are shown in Figure 3 With the increase of starch slurry concentration, the hardness of the cold noodle first decreases and then increases, and then decreases again at 18°Bé. The elasticity first increases and then decreases, and there is no significant change after reaching 16°Bé, indicating that the edible quality of the cold noodle is better at 15°Bé, so 15°Bé is selected to prepare the cold noodle.

[0081] Example 4: Optimization of the cooking time of Liangpi was carried out according to the following method:

[0082] (1) Mix the flour and add 0.5 times the weight of water. Mix well and knead into a smooth dough. Let it sit for about 30 minutes.

[0083] (2) washing the dough, kneading the dough obtained in step (1) in clean water, and pouring the pulp obtained from each washing into a slurry bucket until the pulp becomes clear, and removing the raw gluten blocks;

[0084] (3) Flour slurry precipitation: the flour slurry obtained in step (2) is allowed to stand for 7 hours to allow the starch to precipitate completely;

[0085] (4) draining the floating water and slowly draining the upper layer of clear water from step (3) to obtain water starch;

[0086] (5) adjusting the concentration, stirring the water starch precipitated in the lower layer in step (4) uniformly, and adjusting the starch slurry concentration to 15°Bé with the discharged slurry water or wheat starch;

[0087] (6) adding a hydrophilic colloid, adding konjac glucomannan to the starch slurry having a concentration adjusted in step (5), and dispersing the konjac glucomannan in the starch slurry to a concentration of 0.4 wt%;

[0088] (7) Steam until cooked, divide the starch slurry into 5 portions, take 130g of starch slurry from each portion and pour it into a dough sheet with a diameter of 24cm. After the starch slurry is evenly distributed, put it into a boiling water pot and steam it for about 2min, 2.5min, 3min, 3.5min, and 4min respectively. Take it out and put it into cold water to cool to room temperature, and then peel off the dough sheet;

[0089] (8) Oil the peeled dough and apply a layer of soybean oil on it, set aside;

[0090] Determination method: Same as Example 1.

[0091] The steaming time of Liangpi was optimized based on its hardness and elasticity. Figure 4 The hardness of the cold skin first decreases and then increases with the steaming time, and its hardness is the lowest and has better elasticity when the steaming time is 3 minutes, indicating that the quality of the dough is better after steaming for 3 minutes, and the dough will not be too raw or overcooked to affect its edible quality. Therefore, the steaming time of 3 minutes is selected to prepare the cold skin.

[0092] Experimental Example 1: Effect of hydrophilic colloid addition on the color of cold noodles

[0093] Measurement Method: After calibrating a portable colorimeter with a calibration white plate, measure 4-5 points on each sample. Place a 4mm test aperture over the test area, ensuring no light leakage or shaking. Then, measure the sample's L*, a*, and b* values ​​using the colorimeter and take the average. Record the L*, a*, and b* values ​​separately. During colorimetric testing, the L* value represents the material's lightness or darkness, with + representing white and - representing black. The a* value represents the material's reddish-greenish hue, with + indicating a reddish, warm color and - indicating a greenish, cool color. The b* value represents a yellowish-blue color, with + indicating a yellowish color and - indicating a bluish color.

[0094] In colorimetric evaluation, L* represents lightness (larger values ​​indicate brighter colors), a* represents red-greenness (positive values ​​indicate red, negative values ​​indicate green, and larger absolute values ​​indicate more prominent colors), and b* represents yellow-blueness (positive values ​​indicate yellow, negative values ​​indicate blue, and larger absolute values ​​indicate more prominent colors). As shown in Table 1, different addition levels of guar gum significantly affect the colorimetric performance of cold noodles. In terms of lightness (L*), increasing guar gum addition showed an overall upward trend, brightening the noodles. The brightening effect was particularly pronounced at addition levels of 0.6% and 1.0%. Regarding red-greenness (a*), the green hue decreased with addition, shifting toward red, with varying addition levels exhibiting varying effects. In terms of yellow-blueness (b*), the blue hue continued to decrease with increasing addition level, shifting toward yellow, with significant differences observed between groups. This suggests that guar gum modulates colorimetric performance by altering the reflection and absorption of light in cold noodles, providing a valuable tool for optimizing their appearance and quality.

[0095] As can be seen from Table 2, L* slightly decreased at a 0.2% addition, and then gradually recovered, with 1.0% being significantly higher than some groups. This indicates that low additions (such as 0.2%) of konjac gum may cause changes in the structure of the cold noodle, resulting in a decrease in brightness, while high additions (≥0.6%) may make the cold noodle brighter by improving the network structure. The change in the absolute value of a* reflects the degree of green. After adding konjac gum, the overall absolute value first decreased and then fluctuated. The absolute values ​​of a* in the 0.6% and 1.0% groups are relatively large, indicating that at high additions, konjac gum may affect the distribution and content of pigments (or coloring substances such as carotenoids), making the green tone more obvious; low additions (0.2%, 0.4%) have relatively little effect on the degree of green. The b* value reflects the degree of blue, indicating that low addition of konjac gum may promote blue-related coloration. This effect is weakened at high addition (≥0.4%). It is speculated that konjac gum interacts with cold noodle ingredients (such as starch and protein), changing the system's absorption and reflection of light, thereby affecting the yellow-blue tone presentation.

[0096] Table 1 Effect of different addition amounts of guar gum on the color of cold noodles

[0097]

[0098] Table 2 Effect of different addition amounts of konjac gum on the color of cold noodles

[0099]

[0100] Experimental Example 2: Effect of adding hydrophilic colloid on the water distribution of cold noodles

[0101] Measurement Method: A 22MHz nuclear magnetic resonance imaging (NMR) analyzer was used to analyze the moisture distribution of cold noodle products. Steamed dough sheets were cut into 10mm x 10mm x 3mm cuboids, wrapped with plastic wrap, and placed in a 25mm diameter NMR test tube. Measurements were performed using a Q-CMPG pulse sequence. The measurement parameters were: sampling points (TD) = 2380056, sampling frequency (SW) = 200kHz, sampling interval (TW) = 1500.000ms, SF = 21MHz, half-echo time (TE) = 0.700ms, number of echoes (NECH) = 17000, and number of repeated scans (NS) = 4.

[0102] The transverse relaxation time (T2) is very sensitive to the change of water molecule migration and is usually regarded as an important indicator to characterize water migration. The transverse relaxation time (T2) is measured by low-field nuclear magnetic resonance to study the degree of binding between the sample and water. The water migration change of the cold noodle with konjac gum is shown in Figure 2. Figure 4 The relaxation time (horizontal axis) reflects the state of water. The short relaxation time (10 -1 -10 1 ) often corresponds to bound water (tightly bound to food ingredients, poor fluidity), long relaxation time (101 -10 4 ) corresponds to free water (relatively fluid and easily involved in material exchange, etc.). The cold noodle soup prepared with konjac gum (experimental group) may have limited the presence of free water by interacting with water and other cold noodle components (such as starch), resulting in a decrease in free water content or lowered fluidity. This is manifested as a decrease in free water content or fluidity in the experimental group, which may have an impact on the texture (such as hardness and elasticity) and shelf life (excessive free water is prone to microbial growth, etc.) of the cold noodle soup.

[0103] Experimental Example 3: Sensory Evaluation of Liangpi

[0104] Method: A ten-person evaluation panel, aged 18-50 years, with no history of food allergies and normal sense of smell and taste, was assembled. Five panelists were selected from food science majors (familiar with sensory terminology) and five from general consumers (representing general preferences). They were instructed to abstain from spicy foods, strong tea / coffee, or other foods that interfere with taste perception for 24 hours prior to testing. They received an hour-long pre-test training to help them understand the scoring criteria and familiarize themselves with the evaluation process. They were also instructed to practice rinsing their mouths with water to eliminate bad breath, chewing the sample five times to assess firmness (springiness) and mouthfeel (balance between firmness and firmness), and savoring the sample for 30 seconds after swallowing to record the purity and aftertaste of the flavor. The panel was placed in a booth close to the freshly prepared sample, illuminated by a white light source, and maintained at a room temperature of 25°C. Sample numbers (A, B, C, D, E) were labeled on disposable paper plates. Disposable chopsticks (for serving) and warm water (for rinsing) were provided, along with a scoring sheet (see Table 3, 6 criteria, 100 points). For the final results, the highest and lowest scores were removed, and the average score of the remaining eight people was calculated. The total score was then calculated based on the weights (total score = color × 10% + appearance × 10% + mouthfeel × 30% + toughness × 20% + viscosity × 20% + flavor × 10%). Finally, a radar chart was created to visualize the acceptability scores of the six sensory indicators of cold noodles.

[0105] Texture testing is to make an objective data evaluation of food by simulating the chewing process of the mouth through instruments, while sensory evaluation is the evaluation of food quality by sensory personnel through more intuitive subjective consciousness. Figure 6The sensory evaluation results showed that the total score of the freshly prepared cold noodles without the addition of hydrophilic colloids was in the lower middle level, at 78.24. This was mainly due to the fact that the color, taste, and toughness scores of the blank group were lower than those of the cold noodles prepared with the addition of colloids. This shows that the colloid significantly improved the physical, chemical, and structural properties of the cold noodles. This is consistent with the texture test results of the hardness and elasticity of the cold noodles. The addition of colloids changed the network structure of the cold noodles, thereby improving their edible quality. In addition, as can be seen in Table 4, the viscosity and taste scores of the cold noodles increased after the addition of colloids, indicating that guar gum and konjac gum made the cold noodles more viscous and tasted better, with moderate hardness and softness. Among them, the cold noodles with the addition of 0.4% konjac gum scored the highest, at 84.05. This is consistent with the effect of the addition of hydrophilic colloids on the textural properties and moisture distribution of the cold noodles.

[0106] Table 3 Sensory scoring criteria for Liangpi

[0107]

[0108] Table 4 Sensory scores of cold noodles with different hydrocolloids

[0109]

[0110] (Note: Sample 1 is a blank group. The addition amounts of guar gum in samples 2-6 are 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, and 1.0wt%, respectively. The addition amounts of konjac gum in samples 7-11 are 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, and 1.0wt%, respectively.)

[0111] Example 5: Preparation and optimization of fresh-keeping cold noodles with different addition amounts of sodium D-isoascorbate, according to the following method:

[0112] (1) Mix the flour and add 0.5 times the weight of water. Mix well and knead into a smooth dough. Let it sit for about 30 minutes.

[0113] (2) washing the dough, kneading the dough obtained in step (1) in clean water, and pouring the pulp obtained from each washing into a slurry bucket until the pulp becomes clear, and removing the raw gluten blocks;

[0114] (3) Flour slurry precipitation: the flour slurry obtained in step (2) is allowed to stand for 7 hours to allow the starch to precipitate completely;

[0115] (4) draining the floating water and slowly draining the upper layer of clear water from step (3) to obtain water starch;

[0116] (5) adjusting the concentration, stirring the water starch precipitated in the lower layer in step (4) uniformly, and adjusting the starch slurry concentration to 15°Bé with the discharged slurry water or wheat starch;

[0117] (6) adding konjac glucomannan and sodium D-isoascorbate, respectively adding konjac glucomannan and sodium D-isoascorbate to the starch slurry having the concentration adjusted in step (5), wherein konjac glucomannan is dispersed in the starch slurry at a concentration of 0.4wt%, and the concentrations of sodium D-isoascorbate are 0.05wt%, 0.10wt%, 0.15wt%, 0.20wt%, 0.25wt%, 0.30wt%, and 0.35wt%, respectively;

[0118] (7) Steam until cooked. Pour 130g of starch slurry into a 24cm diameter dough sheet. After the starch slurry is evenly distributed, place the sheet in a boiling water pot and steam for about 3 minutes. When the dough sheet is bubbly and transparent, remove the sheet and place it in cold water to cool to room temperature. Remove the sheet.

[0119] (8) Oil the peeled dough and apply a layer of soybean oil on it, set aside;

[0120] (9) Cut into strips, weigh and package. Cut the dough into appropriate sizes, weigh and vacuum pack.

[0121] Experimental Example 4: Sensory Analysis of Fresh Liangpi

[0122] Determination method: Before the experiment, wear an N95 mask and goggles to prevent inhalation of mold spores and eye contamination; wear a lab coat and nitrile gloves to avoid direct skin contact with deteriorated samples; the entire observation experiment needs to be carried out in a fume hood or biosafety cabinet to observe the appearance and morphology, and the observation data should be recorded every 48 hours.

[0123] Depend on Figure 7 It can be seen that the storage status of Liangpi with different concentrations of D-sodium isoascorbate added at room temperature is analyzed as follows:

[0124] (1) After 3 days of storage, the appearance of the seven samples with added sodium D-isoascorbate showed no significant change. Except for the sample without additives, which had a slight unpleasant odor after opening the bag (which basically dissipated in a short time), the other samples still emitted a fresh fragrance.

[0125] (2) After 5 days of storage, except for the samples with 0.5% to 0.15% sodium D-isoascorbate added, which showed good appearance, the samples without additives and with more than 0.2% sodium D-isoascorbate added showed serious mold and bacterial plaque.

[0126] (3) After 7 days of storage, all samples showed mildew to varying degrees.

[0127] Experimental Example 5: Microbial Detection of Fresh Liangpi

[0128] Determination method: The total bacterial count was determined according to GB 4789.2, and the total mold count was determined according to GB 4789.15. For microbial testing of the product, an initial sample was taken for testing. The initial microbial test was conducted at 0 hours, and then again after 1, 3, 5, and 7 days. GB 19295-2011 stipulates that the total bacterial count in raw noodle products should not exceed 3×10 6 cfu / g. The Shanghai cold noodle hygiene standard stipulates that the total colony count is ≤2×10 4 The hygienic standards for cakes and bread stipulate that the total colony count for cold processing is ≤1500 cfu / g and for hot processing is ≤1×10 4 cfu / g; Shaanxi Provincial Local Standard for Cold Noodles and Cold Noodles stipulates that the total number of colonies is ≤1×10 5 cfu / g; considering the total number of colonies ≤3×10 5 The standard for this study is 100 cfu / g. Hunan Province's local standards for wet rice noodles stipulate mold counts of ≤100 cfu / g (for factory use) and ≤150 cfu / g (for sale). The hygiene standards for pastries and breads stipulate mold counts of ≤100 cfu / g for cold processing and ≤150 cfu / g for hot processing. Shaanxi Province's local standards stipulate a total mold count of ≤150 cfu / g for cold noodles and cold pastries. As shelf life increases, mold may produce toxins, posing a food safety concern. Based on these indicators, a total mold count of ≤150 cfu / g was selected as the standard for this study.

[0129] Table 5 Total colony counts and mold counts of different Liangpi samples

[0130]

[0131] (Note: Samples 1-8 are blank, and samples with 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, and 0.35% of sodium D-isoascorbate added to the cold noodle)

[0132] As shown in Table 5, the total number of colonies in the cold noodles without preservatives can reach 2.4×10 3 cfu / g. Adding sodium D-isoascorbate can effectively reduce the total number of colonies in Liangpi to as low as 1.7×10 3 cfu / g. In subsequent measurements, the microbial count increased almost exponentially. By day 3, half of the samples had exceeded the standard for total colony counts. By day 5 of storage, all samples except sample 4 had exceeded the standard for total colony counts. Mold growth was slow, and some samples remained within the standard even after day 7.

[0133] When sodium D-isoascorbate is added to cold noodle soup, it inhibits bacterial growth at low concentrations, while its antibacterial effect deteriorates or even negatively affects it at higher concentrations. This is because at low concentrations, it can interfere with microbial metabolism by providing antioxidant protection and regulating the microenvironment. However, at high concentrations, its strong reducing properties can overly alter the redox balance of the system, triggering stress mechanisms that can proliferate microorganisms resistant to extreme environments, or disrupting the structure of cold noodle ingredients, facilitating microbial attachment and nutrient utilization. Furthermore, microorganisms can activate resistance mechanisms to adapt to high-concentration environments and even utilize its ingredients. Furthermore, excessive reactions with cold noodle ingredients can alter the matrix, disrupting the synergistic antibacterial balance, ultimately leading to a decrease in antibacterial efficacy and even negative effects.

Claims

1. A method for preparing hydrophilic colloid modified cold noodle, characterized in that Follow these steps: (1) Mixing: Take an appropriate amount of flour, add 0.5-1 times the weight of water, mix well, knead into a smooth dough, and let it stand for about 30 minutes; (2) Washing the dough: put the dough obtained in step (1) into clean water and knead and wash it, pouring the pulp water obtained from each washing into the slurry bucket until the pulp water becomes clear and removes the raw gluten blocks; (3) Flour slurry precipitation: the flour slurry obtained in step (2) is allowed to stand for 6-8 hours to allow the starch to precipitate completely; (4) draining the floating water: slowly draining the upper layer of clear water from step (3) to obtain water starch; (5) adjusting the concentration: stirring the water starch precipitated in the lower layer in step (4) uniformly, and adjusting the starch slurry concentration to 14-18°Bé with the discharged slurry water or wheat starch; (6) adding a hydrophilic colloid: adding guar gum or konjac gum to the starch slurry adjusted to a concentration in step (5) to disperse the guar gum or konjac gum in the starch slurry to a concentration of 0.2 to 1 wt%; (7) Steaming: Pour 120g-150g of starch slurry into a dough sheet with a diameter of 24cm. After the starch slurry is evenly distributed, place it in a pot of boiling water and steam it with the lid on for about 2-4 minutes. When the dough sheet is bubbly and transparent, take it out and cool it to room temperature in cold water. Then peel off the dough sheet. (8) Oiling: Apply a layer of soybean oil to the peeled dough and set aside; (9) Cutting into strips, weighing and packaging: Cut the dough into appropriate sizes and weigh and package them.

2. The method for preparing the hydrophilic colloid-modified cold noodle according to claim 1, characterized in that In the step (1), 0.5 times the mass of water is added to knead the dough.

3. The method for preparing the hydrophilic colloid-modified cold noodle according to claim 1, characterized in that The slurry water precipitation time in step (3) is 7 hours.

4. The method for preparing the hydrophilic colloid-modified cold noodle according to claim 1, characterized in that The starch slurry concentration in step (5) is 15°Bé.

5. The method for preparing the hydrophilic colloid-modified cold noodle according to claim 1, characterized in that In the step (6), the concentration of guar gum is 0.6 wt %, and the concentration of konjac gum is 0.4 wt %.

6. The method for preparing the hydrophilic colloid-modified cold noodle according to claim 1, characterized in that The weight of the starch slurry in step (7) is 130 g; The cooking time of step (7) is 3 minutes.

7. The method for preparing the hydrophilic colloid-modified cold noodle according to claim 1, characterized in that The packaging method described in step (9) is preferably vacuum packaging.

8. A method for preparing fresh-keeping cold noodles, characterized in that Follow these steps: (1) Mixing: Take an appropriate amount of flour, add 0.5 times the weight of water, mix well, knead into a smooth dough, and let it stand for about 30 minutes; (2) Washing the dough: put the dough obtained in step (1) into clean water and knead and wash it, pouring the pulp water obtained from each washing into the slurry bucket until the pulp water becomes clear and removes the raw gluten blocks; (3) Flour slurry precipitation: the flour slurry obtained in step (2) was allowed to stand for 7 hours to allow the starch to precipitate completely; (4) draining the floating water: slowly draining the upper layer of clear water from step (3) to obtain water starch; (5) Adjusting the concentration: Stir the water starch precipitated in the lower layer in step (4) evenly, and use the discharged slurry or wheat starch to adjust the starch slurry concentration to 15°Bé; (6) adding konjac glucomannan and sodium D-erythorbate: adding konjac glucomannan and sodium D-erythorbate to the starch slurry with the concentration adjusted in step (5), respectively, wherein the konjac glucomannan is dispersed in the starch slurry to a concentration of 0.4 wt %, and the concentration of sodium D-erythorbate is 0.05 to 0.35 wt %; (7) Steaming: Pour 130g of starch slurry into a dough sheet with a diameter of 24cm, distribute the starch slurry evenly, place in a pot of boiling water, cover and steam for about 3min. When the dough sheet is bubbly and transparent, remove and place in cold water to cool to room temperature, then peel off the dough sheet. (8) Oiling: Apply a layer of soybean oil to the peeled dough and set aside; (9) Cutting into strips, weighing and packaging: Cut the dough into appropriate sizes and weigh and package them.

9. The method for preparing fresh-keeping cold noodles according to claim 1, characterized in that In the step (6), the concentration of sodium D-isoascorbate is preferably 0.15 wt%.

10. The method for preparing fresh-keeping cold noodles according to claim 1, characterized in that The packaging method described in step (9) is preferably vacuum packaging.

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