Fresh wet noodles adopting fermented soybean milk as preservative and processing method of fresh wet noodles

Abstract

The invention discloses fresh wet noodles adopting fermented soybean milk as a preservative and a processing method of the fresh wet noodles. According to the fresh wet noodles, fermented soybean milk prepared from streptococcus thermophilus 937 serves as a preservative, firstly, 100 parts of plain flour, 30 parts of fermented soybean milk, 8.25 parts of water and 1.5 parts of salt are mixed to form dough, and then the dough is fermented, pressed, cut into strips, sealed and refrigerated. According to the invention, the fermented soybean milk is used as a preservative, and the addition of the fermented soybean milk improves the strength of the noodles, enhances the viscoelasticity of the noodles, improves the sensory quality and taste of the fresh wet noodles, makes up for the deficiency of lysine in wheat, and can effectively inhibit the activity of polyphenol oxidase in the fresh wet noodles, slow down the browning rate and prolong the shelf life of the fresh wet noodles.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and particularly relates to a fresh wet noodle using fermented soy milk as a preservative and a processing method thereof. Background Art

[0002] Noodles are one of the most popular staple foods in Asia. Fresh wet noodles are deeply loved by consumers because of their high moisture content, chewy, smooth and elastic texture after cooking, and strong wheat fragrance. However, due to the high moisture content and rich nutrition of fresh wet noodles, quality deterioration problems such as browning and mildew are likely to occur during storage, resulting in a short shelf life and restricting the industrial production and market promotion of fresh wet noodles. In order to prevent the quality deterioration of fresh wet noodles and extend the shelf life, existing methods usually add preservatives such as alcohol, preservatives or water activity reducing agents to fresh wet noodles, or use the method of adding alkali for preservation. However, these preservation methods are likely to cover up the original wheat fragrance of fresh wet noodles, produce alcohol smell or alkali taste, and at the same time, the additives will also cause consumers' resistance and rejection psychology.

[0003] Currently, most of the preservation and quality improvement of fresh wet noodles adopt chemical preservation. Chinese Patent Application CN201810583925.1 discloses a fresh wet noodle using yogurt as a preservative and a processing method thereof, which uses the addition of 80% yogurt to improve the quality of fresh wet noodles, slow down the browning rate of fresh wet noodles, and extend the shelf life. However, the cost of yogurt in this method is relatively high, and it is not suitable for vegetarians and lactose intolerant people. Chinese Patent Application No. N202110341052.5 discloses a fermented fresh wet noodle, the raw materials of which are calculated by mass percentage, consisting of 100% flour, 15-33% starch, 0.22-0.65% salt, 0.05-0.1% edible alkali, 0.05-0.3% sodium alginate, 0.25-0.46% Saccharomyces cerevisiae, 0.05-0.12% Lactobacillus plantarum and 31-40% water. Through multi-stage and multi-step fermentation of Saccharomyces cerevisiae and Lactobacillus plantarum, the starch composition, protein content and gluten strength of the noodles are improved by using the metabolic characteristics of different microorganisms. Combined with physical treatments such as high-temperature sterilization, ultraviolet irradiation sterilization and quick freezing, the shelf life of the fermented fresh wet noodle is extended. However, this fresh wet noodle undergoes 3 long-term fermentations, superimposed with multiple processing links such as high-temperature sterilization, ultraviolet irradiation sterilization, quick freezing and hot air thawing. Among them, high-temperature sterilization will cause the noodles to turn from raw to cooked, and ultraviolet radiation and freeze-thaw treatment will further damage their microstructure, resulting in a decline in the quality of fresh wet noodles and poor sensory experience for consumers.

[0004] Fermented soy milk is fermented milk obtained by inoculating lactic acid bacteria after grinding soybeans. A large number of studies at home and abroad have shown that probiotic fermentation treatment, as one of the effective means to reduce anti-nutritional factors in soy milk at present, using lactic acid bacteria to ferment soy dairy products can not only retain its original nutrients such as amino acids and vitamins to a great extent, but also the lactic acid bacteria and their metabolites have multiple probiotic functions, and can eliminate the beany smell and produce unique flavor substances, reduce the generation of harmful microbial flora and toxins, and improve the storage stability and safety of products. However, there is no report on the use of fermented soy milk as a preservative for fresh wet noodles. Summary of the Invention

[0005] The purpose of the present invention is to provide a fresh wet noodle using fermented soy milk as a preservative and its processing method.

[0006] The technical solution to achieve the purpose of the present invention is as follows:

[0007] The fresh wet noodle using fermented soy milk as a preservative is made from the following raw materials by weight: 100 parts of medium gluten flour, 30 parts of fermented soy milk, 8.25 parts of water, and 1.5 parts of salt; the fermented soy milk is prepared by the following method: mix soy milk and skim milk powder in a mass ratio of 7:3, add 6% of the total mass of soy milk and skim milk powder of granulated sugar, mix evenly, sterilize under high pressure, cool, inoculate Streptococcus thermophilus 937, and ferment at a constant temperature until the pH is 4.5 to obtain fermented soy milk.

[0008] Furthermore, the specific preparation method of fermented soy milk is: according to the mass ratio of soybeans to water of 1:2, wash the soybeans and soak them in water at 4°C for 12h, then according to the mass ratio of wet soybeans to boiling water of 1:4, grind the soybeans with boiling water for 8min and then pass through a 120-mesh sieve to remove impurities to obtain soy milk; after passing the skim milk powder through a 120-mesh sieve, mix the soy milk and skim milk powder in a mass ratio of 7:3, add 6% of the total mass of soy milk and skim milk powder of granulated sugar, mix evenly, homogenize twice at 20MPa, sterilize at 105°C under high pressure for 15min, cool, inoculate Streptococcus thermophilus 937 at an inoculation amount of 3%, ferment in a constant temperature incubator at 37°C until the pH is 4.5, and refrigerate in a 4°C refrigerator for 24h.

[0009] The processing method of the above fresh wet noodle includes the following steps:

[0010] (1) Kneading: Weigh medium gluten flour, fermented soy milk, water and salt according to the ratio, and stir in a kneading machine to form a uniform dough;

[0011] (2) Fermentation: Then put it into an incubator at 32°C and a relative humidity of 75% for fermentation;

[0012] (3) Pressing: Press the fermented dough into noodle sheets through a noodle machine;

[0013] (4) Slicing the strips: Slicing the dough sheets into strips;

[0014] (5) Sealing with a self-sealing bag: Packing the sliced noodles into a self-sealing bag and sealing it;

[0015] (6) Refrigerating: Placing the self-sealing bag in a refrigerator at 4°C for refrigeration.

[0016] Furthermore, in step (1), the stirring time is 10 min.

[0017] Furthermore, in step (2), the fermentation time is 30 min.

[0018] Furthermore, in step (3), the specific steps of pressing are as follows: First, adjust the distance between the rollers to 2.00 mm, repeat pressing 5 - 7 times until the surface of the dough sheet is smooth, then adjust the distance to 1.00 mm, and press 8 - 10 times to make the dough sheet more delicate.

[0019] Furthermore, in step (4), the specific steps of slicing the strips are as follows: Slice the dough sheet into strips at a rolling distance of 1 mm. The final thickness of the noodles is 1 mm, the width is 2 mm, and the length is 20 cm.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention uses the addition of fermented soy milk to achieve the preservation effect. Among them, soy milk can make up for the lysine deficiency of wheat protein and strengthen the nutrition of fresh wet noodles.

[0022] (2) The fermentation of lactic acid bacteria can not only relieve the beany flavor and degrade the anti-nutritional factors in soy milk, but also the metabolic substances such as organic acids, exopolysaccharides, and enzymes produced by fermentation have a positive effect on improving the dough properties and enhancing the product flavor.

[0023] (3) The addition of fermented soy milk can effectively inhibit the activity of polyphenol oxidase in fresh wet noodles, and at the same time, the organic acids produced by fermented soy milk can inhibit the growth of molds in fresh wet noodles.

[0024] (4) The preservation method designed in the present invention avoids the traditional preservation method of adding chemical preservatives, and solves the consumers' concern about the impact of adding chemical preservatives on human health.

[0025] (5) The fresh wet noodles of the present invention can be stored for 16 days under the refrigeration condition of 4°C, and the preservation effect is better than the conventional preservation means of fresh wet noodles. Description of the Drawings

[0026] Figure 1 Total number of mold colonies of fresh wet noodles made from different lactic acid bacteria-fermented soy milk during storage at 4°C;

[0027] Figure 2Effect of the addition amount of fermented soy milk on the sensory quality of fresh wet noodles;

[0028] Figure 3 Appearance diagrams of fresh wet noodles made with different addition amounts of fermented soy milk;

[0029] Figure 4 Effect of the addition amounts of 0% and 30% fermented soy milk on polyphenol oxidase (A), a* value (B), b* value (C) and L* value (D) during the storage of fresh wet noodles. Specific embodiments

[0030] The present invention will be further described in detail below in conjunction with specific embodiments and the accompanying drawings.

[0031] The following test methods are adopted in the following embodiments:

[0032] (1) Determination method of cooking loss rate: Put the accurately weighed raw noodles into 500 g of boiling distilled water, quickly fish them out after cooking to the optimal cooking time, cook the remaining noodle soup to an appropriate amount, then pour it into a pre-weighed glass dish, put it into an oven at 105 °C, dry it to a constant weight, and then calculate the loss rate of the cooked noodles according to the following formula.

[0033]

[0034] M——Dry matter mass in the noodle soup (g),

[0035] G——Mass of the noodles before cooking (g),

[0036] W——Moisture content of the raw noodles before cooking (%).

[0037] (2) Determination method of sensory score: A 20-person expert group composed of food research scholars and students from the School of Food Science evaluated the cooked noodle samples. They used the 9-point hedonic method to evaluate the sensory attributes (hardness, overall flavor, chewiness, resilience, color and surface roughness) of the noodles. The higher the score, the stronger the preference, and 9 points is the best.

[0038] (3) Determination methods of noodle hardness, chewiness, elasticity and breaking force: Fish out the fresh wet noodles after cooking to the optimal cooking time, drain them after rinsing with cold water, dry the surface moisture with filter paper, align and cover them on double-layer plastic wrap. Complete the test of the same batch of samples on the texture analyzer within 15 minutes. Place three noodles without physical damage and uniform thickness at a fixed position on the texture analyzer platform, and measure their texture characteristics. Each sample is measured 6 times, and the average value is taken after removing the maximum and minimum values. The parameter settings are as follows: P / 50 probe, test rate is 1.00 mm / s, dwell time is 1 s, strain is 75%, and trigger force is 5 g.

[0039] (4) Determination methods of chromaticity and polyphenol oxidase: Cut a 5 cm × 5 cm thin slice from the rolled dough sheet, measure the color change with a colorimeter, measure 8 points on each dough sheet, and record the L*, a*, and b* values. Mix the freeze-dried and ground noodle sample (1.5 g) thoroughly with 10 mL of phosphate buffer solution (PBS, 0.2 mol / L, pH 6.00), and then add 2 mL of catechol solution. The reaction is carried out in a water bath oscillator at 37 °C and 180 r / min for 15 min. Place the extracted sample in ice water for 3 min to terminate the reaction. The sample is centrifuged at 4 °C and 8000 × g for 10 min, and the absorbance of the supernatant is measured at a wavelength of 420 nm. The polyphenol oxidase activity is expressed as a percentage of the polyphenol oxidase activity of the blank control.

[0040] (5) Determination method of free amino acids: Liquid chromatography conditions ACQUITY BEH C18 chromatographic column (2.1 × 100 mm, 1.7 μm, Waters, USA), injection volume 5 μL, column temperature 40 °C, mobile phase A - 50% methanol aqueous solution (containing 0.1% formic acid), B - 10% methanol aqueous solution (containing 0.1% formic acid). The gradient elution conditions are: 0 - 6.5 min, 90% - 70% B; 6.5 - 7 min, 70% - 0% B; 7 - 14 min, 0% B; 14 - 14.5 min, 0% - 90% B; 14.5 - 17.5 min, 90% B; flow rate 0 - 8.0 min, 0.3 mL / min; 8.0 - 17.5 min, 0.4 mL / min. Mass spectrometry conditions: Electrospray ionization source, positive ion mode. The ion source temperature is 500 °C, the ion source voltage is 5500 V, the collision gas is 6 psi, the curtain gas is 30 psi, and the nebulizing gas and auxiliary gas are both 50 psi.

[0041] The Streptococcus thermophilus 937 described in the present invention has a preservation number of CGMCC NO.25410, is provided by the Jiangsu Key Laboratory of Dairy Biotechnology and Safety Control, can be commercially purchased, and has been fully disclosed in the literature [Di Lijun, Nutrition and Food Hygiene. Optimization of Freeze-Drying Protectants for Streptococcus thermophilus 937 and Study on the Protection Mechanism of Salts [D]. Yangzhou University [2025-04-23].].

[0042] In the following examples, the Lactobacillus fermentum grx08, with a preservation number of CGMCC No: 7695, has been fully disclosed in Chinese Patent 201310309222.7 and can be commercially purchased.

[0043] Example 1

[0044] 1. Preparation of fermented soy milk: Clean soybeans according to the mass ratio of soybeans to water of 1:2, soak them in water at 4°C for 12 h, then according to the mass ratio of wet soybeans to water = 1:4, grind them with boiling water for 8 min, and then pass through a 120-mesh sieve to remove impurities to obtain soy milk. At the same time, pass skim milk powder through a 120-mesh sieve for later use. Mix soy milk and skim milk in a mass ratio of 7:3, add 6% white granulated sugar based on the total mass of soy milk and skim milk, mix evenly, homogenize twice at 20 MPa, sterilize at 105°C for 15 min, and after cooling, inoculate Streptococcus thermophilus 937 and Lactobacillus fermentum grx08 respectively at an inoculation amount of 3%, put them in a constant temperature incubator at 37°C and ferment until the pH is 4.5, and then refrigerate in a 4°C refrigerator for 24 h to obtain fermented soy milk fermented by Streptococcus thermophilus 937 and fermented soy milk fermented by Lactobacillus fermentum grx08 respectively.

[0045] 2. Preparation of fresh wet noodles using fermented soy milk as a preservative:

[0046] The fresh wet noodles are made from the following raw materials by weight: 100 parts of medium-gluten flour, 30 parts of fermented soy milk, 8.25 parts of water, and 1.5 parts of salt; and are processed through the following steps:

[0047] (1) Kneading: Weigh medium-gluten flour, fermented soy milk, water, and salt according to the ratio, and stir in a kneading machine for 10 min to form a uniform dough.

[0048] (2) Fermentation: Put the dough into an incubator at 32°C and a relative humidity of 75% and ferment for 30 min.

[0049] (3) Pressing: Press the fermented dough through a noodle machine. First, adjust the roller spacing to 2.00 mm and repeat pressing 5 - 7 times until the surface of the dough sheet is smooth, then adjust the spacing to 1.00 mm and press 8 - 10 times to make the dough sheet more delicate.

[0050] (4) Cutting: Cut the dough sheet into strips. Cut the dough sheet into strips at a rolling distance of 1 mm. The final thickness of the noodles is 1 mm, the width is 2 mm, and the length is 20 cm.

[0051] (5) Sealing with a self-sealing bag: Put the cut noodles into a self-sealing bag and seal it.

[0052] (6) Refrigeration: Put the self-sealing bag into the refrigerator for refrigeration, and the refrigeration temperature is 4°C.

[0053] According to the above method, use the fermented soy milk fermented by Streptococcus thermophilus 937 and the fermented soy milk fermented by Lactobacillus fermentum grx08 as preservatives to prepare fresh wet noodles respectively, and name them St-937-N and Grx-08-N respectively. At the same time, set the fresh wet noodles without adding fermented soy milk as the control group (Control). The effects of different lactic acid bacteria-fermented soy milk on the quality of fresh wet noodles are shown in Table 1 and Figure 1 .

[0054] Table 1 Comparison of cooking and texture quality of fresh wet noodles fermented by different lactic acid bacteria

[0055]

[0056] As shown in Table 1, the optimal cooking time, cooking loss rate, and broken noodle rate of the fresh wet noodles in the St-937-N group were significantly lower than those of the other two groups (p < 0.05). The hardness, stickiness, and elasticity of the fresh wet noodles in the St-937-N group were significantly higher than those in the Grx-08-N group. This may be because Streptococcus thermophilus 937 is a strain with high extracellular polysaccharide production. The extracellular polysaccharide can bind to gluten proteins through hydrogen bonds or hydrophobic interactions to form a dense composite network structure, thus resisting thermal stress at high temperatures during cooking, reducing the breakage of the gluten network and the dissolution of soluble solids, resulting in a decrease in the cooking loss and broken noodle rate of the fresh wet noodles in the St-937-N group. At the same time, the extracellular polysaccharide can form a composite gel structure with gelatinized starch through intermolecular forces, improving the water-holding capacity of the noodles, and thus enhancing the viscoelasticity and hardness of the fresh wet noodles in the St-937-N group.

[0057] As Figure 1 shown, the fresh wet noodles made from soy milk fermented by the two strains can effectively inhibit the growth of mold colonies and extend the shelf life compared with the control group. This is attributed to the organic acids and bacteriocins produced by Streptococcus thermophilus 937 and Lactobacillus fermentum grx08 during metabolism, which have a good antibacterial effect by reducing the pH and destroying the cell membrane integrity. Based on the above results, the present invention selects fermented soy milk fermented by Streptococcus thermophilus 937 as a preservative to make fresh wet noodles.

[0058] Example 2

[0059] Using the fermented soy milk fermented by Streptococcus thermophilus 937 in Example 1 as a raw material to make fresh wet noodles, by weight, it is made from the following raw materials: 100 parts of medium-gluten flour, 10 parts of fermented soy milk fermented by Streptococcus thermophilus 937, 24.75 parts of water, and 1.5 parts of salt; it is processed through the following steps:

[0060] (1) Kneading: Weigh medium-gluten flour, fermented soy milk, water, and salt according to the ratio, and stir in a kneading machine for 10 min to form a uniform dough.

[0061] (2) Fermentation: Put the dough into an incubator at 32 °C and relative humidity of 75% and ferment for 30 min.

[0062] (3) Pressing: Press the fermented dough through a noodle machine. First, adjust the roller spacing to 2.00 mm and repeat pressing 5 - 7 times until the surface of the noodle sheet is smooth. Then adjust the spacing to 1.00 mm and press 8 - 10 times to make the noodle sheet more delicate.

[0063] (4) Slicing the strips: Slice the dough sheets into strips at a rolling gap of 1 mm. The final thickness of the noodles is 1 mm, the width is 2 mm, and the length is 20 cm.

[0064] (5) Sealing with a self-sealing bag: Put the sliced noodles into a self-sealing bag and seal it.

[0065] (6) Refrigeration: Put the self-sealing bag into the refrigerator for refrigeration at a temperature of 4°C.

[0066] Example 3

[0067] This example is generally the same as Example 2, except that the fresh wet noodles are made from the following raw materials by weight: 100 parts of medium-gluten flour, 20 parts of fermented soy milk, 16.5 parts of water, and 1.5 parts of salt.

[0068] Example 4

[0069] This example is generally the same as Example 2, except that the fresh wet noodles are made from the following raw materials by weight: 100 parts of medium-gluten flour, 40 parts of fermented soy milk, 0 parts of water, and 1.5 parts of salt.

[0070] Table 2 Cooking characteristics of fresh wet noodles with different addition amounts of fermented soy milk

[0071]

[0072] The cooking characteristics of fresh wet noodles made with different addition amounts of fermented soy milk are shown in Table 2. Compared with the control group, the cooking time of fresh wet noodles with added fermented soy milk is significantly shortened (p < 0.05), and the cooking loss rate and broken noodle rate are also significantly reduced (p < 0.05). Among them, the fresh wet noodles with 30% addition amount of fermented soy milk have the lowest cooking loss rate and broken noodle rate, and the shortest optimal cooking time. This may be because the exopolysaccharide produced by the metabolism of Streptococcus thermophilus 937 binds to gluten proteins through hydrogen bonds to form a stable three-dimensional network structure, inhibiting the exudation of soluble substances, thereby reducing the cooking loss rate. However, when the addition amount of fermented soy milk is 40%, the dilution effect of dietary fiber in soy milk on gluten proteins will damage the gluten network structure, resulting in an increase in the cooking loss rate and broken noodle rate. In summary, adding an appropriate amount of fermented soy milk can improve the noodle yield and reduce the cost.

[0073] With the upgrading of consumption, consumers' attention to the sensory attributes (aroma, appearance, texture, flavor) and nutritional value of food has been significantly improved. As a direct evaluation method for measuring the quality of noodles, sensory evaluation can comprehensively measure noodles through multi-dimensional indicators. The sensory quality results of fresh wet noodles after cooking are as Figure 2As shown in the figure, a professional sensory evaluation panel scored the hardness, elasticity, viscosity, chewiness, surface roughness and overall flavor of cooked noodles with 0%, 10%, 20%, 30% and 40% fermented soy milk addition. There were significant differences in the hardness, chewiness, elasticity, etc. of the noodles added with fermented soy milk (p<0.05). Among them, the noodles with 30% fermented soy milk addition showed the best performance in terms of hardness, elasticity, chewiness and overall flavor, and were significantly higher than the control group (p<0.05).

[0074] Table 3 Effects of Fermented Soy Milk with Different Addition Amounts on the Texture Characteristics of Fresh Wet Noodles

[0075]

[0076] The texture analyzer was used to measure the eating characteristics of cooked fresh wet noodles made with different amounts of fermented soy milk addition, including hardness, chewiness, elasticity and adhesiveness. The results are shown in Table 3. One-way ANOVA showed that there was no significant difference in the cohesiveness of cooked fresh wet noodles among groups (p>0.05), but there were significant differences in hardness, adhesiveness, elasticity and chewiness (p<0.05). The chewiness of fresh wet noodles added with 40% fermented soy milk was significantly higher than that of the control group (p<0.05). In addition, the hardness and elasticity of fresh wet noodles showed a trend of first increasing and then decreasing with the increase of the addition amount of fermented soy milk, and reached the highest at 30% addition amount, which were 6.81 and 0.14 respectively (p<0.05), indicating that the noodles prepared with 30% fermented soy milk addition were more chewy and elastic. This may be because the hydrogen bond interaction between the exopolysaccharide produced by Streptococcus thermophilus 937 and proteins increased the strength of the gluten network structure, making its hardness and elasticity reach the optimum. However, when the addition amount was higher than 30%, the hardness and elasticity decreased (p>0.05). On the one hand, the dietary fiber content in fermented soy milk reduced the relative content of gluten proteins in the noodles; on the other hand, the low pH environment formed by fermentation stimulated the activity of amylase and changed the properties of starch, thus destroying the cross-linking degree between starch and proteins, and decreasing the strength of the starch and protein network structure, ultimately leading to the decrease of hardness and elasticity.

[0077] Table 4 Effects of Fermented Soy Milk with Different Addition Amounts on the Color of Fresh Wet Noodles

[0078]

[0079] Color is one of the core indicators of noodle quality. It affects consumers' acceptance of noodles and can also reflect the deterioration degree of noodle quality. As Figure 3As shown in the figure, with the increase in the addition amount of fermented soy milk, the main color of the fresh wet noodles changes from dark white to bright white. When the addition amount of fermented soy milk is 40%, the surface roughness of the fresh wet noodles increases. This may be because the water-soluble dietary fiber in the fermented soy milk exudes and adheres to the noodle surface, forming an uneven structure and reducing its smoothness. As can be seen from Table 4, the addition amount of fermented soy milk has a significant impact on the L*, a*, and b* values of the noodles. Generally speaking, compared with the noodles in the control group, the addition of fermented soy milk increases the L* value of the noodles and increases the a* value. With the increase in the addition amount of fermented soy milk, the a* value of the noodles gradually increases, indicating that the color of the fresh wet noodles tends to be red. When the addition amount of fermented soy milk increases within the range of 10% - 30%, the b* value of red and green degree has no significant change (p > 0.05). When the addition amount is 40%, the b* value reaches 16.59, and the yellow tone significantly deepens (p < 0.05). In summary, appropriate addition (≤30%) can improve the brightness of the fresh wet noodles and optimize the appearance quality of the fresh wet noodles.

[0080] Table 5 Free amino acid content of fresh wet noodles made with different addition amounts of fermented soy milk

[0081]

[0082] As shown in Table 5, a relatively high concentration of free amino acids (FAA) was observed in the fresh wet noodles with 30% fermented soy milk added. Among them, the increases in lysine (Lys), phenylalanine (Phe), tyrosine (Tyr), and leucine (Leu) were the most significant. Specifically, the Lys content increased from 2.46 mg ± 0.21 / 100 g to 3.44 mg ± 0.00 / 100 g (p < 0.05), effectively making up for the inherent defect of lysine in wheat flour and making the amino acid composition of the fresh wet noodles more balanced.

[0083] The color deterioration of fresh wet noodles is mainly due to the synergistic effect of enzymatic browning and non-enzymatic browning. Among them, polyphenol oxidase (PPO) catalyzes the oxidation of monophenols and polyphenols to form o-quinone compounds, and o-quinone spontaneously polymerizes or reacts with amino acids to form brown pigments, eventually forming brown polymers. Due to the relatively high water content of fresh wet noodles and the water activity (Aw) being at a relatively high level, it significantly accelerates the enzymatic reaction and non-enzymatic browning processes such as the Maillard reaction, resulting in the product being prone to color deepening. Under the storage condition of 4°C, the changes in L*, a*, and b* values are as Figure 4As shown. With the extension of storage time, the L* values of both groups of noodles showed a downward trend, the a* values had a slightly downward trend, and the b* values changed little. The browning trend of the 30% fermented soy milk addition group slowed down. This may be because lactic acid bacteria fermentation produced organic acids, and the decrease in pH inhibited the activity of polyphenol oxidase, resulting in a slower decrease in the L* value in the later stage of storage. However, the L* value still showed a downward trend as a whole. With the extension of storage time, compared with the control group, the inhibitory effect of the 30% fermented soy milk addition group on PPO was more significant, and PPO showed a further downward trend. The possible reason is that the decrease in the content of polyphenol, the substrate that can be contacted, limited the enzymatic browning process. When stored for 12 days, the L* value of the 30% fermented soy milk addition group was the highest, with the highest lightness.

[0084] In summary, compared with other fresh wet noodles, by adding fermented soy milk as a fresh wet noodle preservative, the present invention improves the nutrition and flavor of fresh wet noodles. Through the metabolism of lactic acid bacteria, biological fortification of limiting amino acids such as lysine is achieved, and at the same time, a unique fermented flavor is imparted to fresh wet noodles. Further, the addition of fermented soy milk makes the noodles more chewy and elastic. Moreover, fermented soy milk can effectively inhibit the activity of polyphenol oxidase and the growth of molds in fresh wet noodles, thus significantly slowing down the browning rate and quality deterioration of fresh wet noodles and extending the shelf life of fresh wet noodles.

Claims

1. Fresh wet noodles using fermented soy milk as a preservative, characterized in that, By weight parts, it is made from the following raw materials: 100 parts of medium-gluten flour, 30 parts of fermented soy milk, 8.25 parts of water, and 1.5 parts of salt; the fermented soy milk is prepared by the following method: mix soy milk and skim milk in a mass ratio of 7:3, add 6% of granulated sugar based on the total mass of soy milk and skim milk, mix evenly, sterilize under high pressure, and after cooling, inoculate Streptococcus thermophilus ( Streptococcus thermophilus ), ferment at a constant temperature until the pH is 4.5 to obtain fermented soy milk.

2. The fresh wet noodles according to claim 1, characterized in that, The specific preparation method of fermented soy milk is as follows: Clean soybeans according to the mass ratio of soybeans to water of 1:2, soak them in water at 4°C for 12 h, then according to the mass ratio of wet soybeans to boiling water of 1:4, grind them with boiling water for 8 min, and then pass through a 120-mesh sieve to remove impurities to obtain soy milk; after skim milk powder passes through a 120-mesh sieve, mix the soy milk and skim milk powder according to the mass ratio of 7:3, add granulated sugar with a mass of 6% of the total mass of soy milk and skim milk, mix evenly, homogenize twice at 20 MPa, sterilize at 105 °C under high pressure for 15 min, cool, and inoculate Streptococcus thermophilus 937 at an inoculation amount of 3%, ferment in a constant temperature incubator at 37°C until the pH reaches 4.5, and refrigerate in a 4°C refrigerator for 24 h.

3. The processing method of the fresh wet noodles according to claim 1 or 2, characterized in that, It includes the following steps: (1) Kneading: Weigh medium-gluten flour, fermented soy milk, water and salt according to the ratio, and stir in a kneading machine to form a uniform dough; (2) Fermentation: Then put it into an incubator at 32°C and a relative humidity of 75% for fermentation; (3) Pressing: Press the fermented dough into a sheet through a noodle machine; (4) Slicing: Cut the sheet into strips; (5) Sealing with a self-sealing bag: Put the cut noodles into a self-sealing bag and seal; (6) Refrigeration: Place the self-sealing bag in a 4°C refrigerator for refrigeration.

4. The processing method according to claim 3, characterized in that, In step (1), the stirring time is 10 min.

5. The processing method according to claim 3, characterized in that, In step (2), the fermentation time is 30 min.

6. The processing method according to claim 3, characterized in that, In step (3), the specific pressing steps are as follows: First, adjust the roller spacing to 2.00 mm, repeat pressing 5 - 7 times until the surface of the sheet is smooth, then adjust the spacing to 1.00 mm, and press 8 - 10 times to make the sheet more delicate.

7. The processing method according to claim 3, characterized in that, In step (4), the specific slicing steps are as follows: Cut the sheet into strips at a rolling distance of 1 mm, and the final thickness of the noodles is 1 mm, the width is 2 mm, and the length is 20 cm.

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