Preparation process and application of long shelf life hot dry noodles

Abstract

This invention relates to the field of food processing technology, specifically to a preparation process and application of long-shelf-life hot dry noodles, comprising: S1, inoculating a wheat flour substrate with *Lactobacillus rhamnosus* and *Lactobacillus paracasei* for fermentation to obtain a starter culture; S2, mixing wheat flour, starter culture, water, edible salt, and edible alkali to form a dough; S3, after the dough has matured, rolling it into sheets and cutting it into strips to make raw noodles; S4, shaping and steaming: shaping the dough into noodles, steaming until semi-cooked, removing and cooling to room temperature; S5, subjecting the cooled noodles to a stepped microwave treatment using low power followed by high power; S6, mixing the microwave-treated noodles with edible oil, vacuum packaging, and refrigerating. This invention utilizes a novel process that combines the synergistic fermentation of *Lactobacillus rhamnosus* and *Lactobacillus paracasei* with the synergistic effect of microwave treatment. By optimizing fermentation time, the proportion of fermentation liquid added, and microwave treatment parameters, it effectively solves the problem of short shelf life of hot dry noodles while maintaining their excellent edible quality.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a preparation process and application of long-shelf-life hot dry noodles. Background Technology

[0002] Hot dry noodles, a typical representative of traditional Chinese noodles, are beloved by consumers for their unique sesame paste flavor and chewy texture. However, as a high-moisture noodle product, with a moisture content typically ranging from 30% to 35%, hot dry noodles are highly susceptible to microbial contamination during storage and distribution, leading to spoilage, short shelf life, and quality degradation. This severely restricts its industrial production and cross-regional sales. Statistics show that even under refrigeration at 4℃, hot dry noodles prepared using traditional methods generally have a shelf life of no more than 3 days.

[0003] Currently, the main technologies for extending the shelf life of high-moisture flour products fall into the following categories:

[0004] Adding chemical preservatives, such as calcium propionate and potassium sorbate, can inhibit microorganisms to some extent, but may pose potential food safety risks and may affect the natural flavor of noodles, which does not meet the current market's pursuit of clean labels and natural healthy foods.

[0005] Heat sterilization treatment, such as pasteurization or ultra-high temperature (UHT) sterilization, can effectively kill microorganisms. However, high heat treatment can easily cause noodles to become over-gelatinized, making them soft and mushy, losing their proper chewiness and elasticity, and seriously damaging their edible quality.

[0006] Reducing water activity: This involves adding humectants such as polyols or using a drying process to reduce water activity, thereby inhibiting microbial growth. However, this method often alters the composition and texture of the noodles, leading to a decline in key sensory qualities such as elasticity and smoothness.

[0007] Oxygen-barrier packaging technologies, such as vacuum packaging or modified atmosphere packaging, create a low-oxygen environment to slow down microbial growth and oxidative spoilage. However, this technology has limited effectiveness in controlling molds and anaerobic bacteria, and it is also more expensive and requires more stringent production equipment.

[0008] This reveals a common contradiction in existing technologies: while effectively extending shelf life, it is difficult to maintain the original excellent texture and flavor of hot dry noodles. A single technological approach often addresses one aspect while neglecting others, failing to systematically solve the synergistic challenge of safety, shelf life, and quality maintenance.

[0009] In recent years, biological preservation technology and physical non-thermal sterilization technology have received widespread attention due to their safety and environmental friendliness. Among them, microbial fermentation, represented by specific lactic acid bacteria (such as *Lactobacillus rhamnosus* and *Lactobacillus paracasei*), can produce various natural antibacterial substances such as organic acids and bacteriocins during metabolism, providing a biological solution for food preservation. Microwave treatment, as a highly efficient physical method, can rapidly inactivate microorganisms through the synergistic effect of thermal and non-thermal effects, with relatively little impact on food texture. However, simply combining these two technologies or applying them individually still has significant shortcomings: First, the antibacterial spectrum and effect of single-strain fermentation are limited, and the stability and standardized application of fermentation products face challenges; second, improper control of microwave treatment parameters can easily lead to uneven heating of food or poor killing effect on certain heat-resistant spores; most importantly, existing technical solutions fail to systematically optimize the compounding ratio of specific functional strains, the preparation form of fermentation metabolites, and the synergistic mechanism between them and subsequent stepped microwave treatment parameters from a system synergy perspective, resulting in suboptimal overall preservation and quality maintenance effects.

[0010] Therefore, there is an urgent need in this field for an innovative, comprehensive technology that can synergistically resolve the contradiction between the shelf life and edible quality of hot dry noodles. Summary of the Invention

[0011] To address the problems of short shelf life of hot dry noodles due to microbial growth in existing technologies, and the impact of using chemical preservatives or high-temperature sterilization on taste and safety, this invention aims to provide a preparation process and application for long-shelf-life hot dry noodles. Through the synergistic fermentation of *Lactobacillus rhamnosus* and *Lactobacillus paracasei*, combined with microwave treatment with optimized parameters, a composite preservation technology system is created. This technology fully utilizes the antibacterial effect of microbial metabolites and the physical sterilization effect of microwaves, achieving a synergistic preservation effect. Without relying on chemical preservatives, it significantly inhibits microbial growth, effectively extends the product's shelf life, and at the same time, maintains the unique chewy texture and excellent quality of hot dry noodles.

[0012] This invention is achieved through the following technical solution:

[0013] A process for preparing long-shelf-life hot dry noodles is provided, comprising the following steps:

[0014] S1. Preparation of starter culture: Lactobacillus rhamnosus and Lactobacillus paracasei are inoculated into wheat flour substrate and fermented to obtain starter culture;

[0015] S2. Kneading the dough: Mix wheat flour, leavening agent, water, salt and baking soda to form a dough;

[0016] S3. Rolling and cutting: After the dough has matured, roll it into sheets and cut it into strips to make raw noodles;

[0017] S4. Shaping and steaming: Shape the risen dough into noodles, steam until half-cooked, remove and cool to room temperature; steam in boiling water for 30 seconds, remove and quickly rinse with cold water for 10 seconds to cool to room temperature.

[0018] S5. Microwave treatment: The cooled noodles are subjected to a stepped microwave treatment, first at low power and then at high power.

[0019] S6. Mixing with oil and packaging: The microwaved noodles are mixed with cooking oil, vacuum-packed, and refrigerated. Mixing with cooking oil effectively prevents the noodles from sticking together, and the vacuum level is controlled at -0.09Mpa to -0.1Mpa.

[0020] Furthermore, in step S1, the inoculation ratio of Lactobacillus rhamnosus and Lactobacillus paracasei is one of 1:2, 1:1, or 2:1.

[0021] Through the synergistic fermentation of Lactobacillus rhamnosus and Lactobacillus paracasei, a stable symbiotic relationship is established, and the metabolism produces the most abundant antibacterial substances.

[0022] Furthermore, in step S1, the fermentation temperature is 30~37℃, the fermentation time is 24~72h, the pH is adjusted to 4.0~5.0 during the fermentation process, and the amount of lactic acid bacteria inoculated is 1%~3% of the wheat flour mass.

[0023] Fermentation temperature is controlled in a gradient of 30-37℃: 0-24 hours at 32℃, the aim is to allow *Lactobacillus rhamnosus* and *Lactobacillus paracasei* to grow and multiply rapidly, quickly becoming the dominant bacteria and establishing a strong "microbial power" advantage. At 32℃, a relatively fast growth rate is ensured while avoiding premature activation of certain metabolic pathways due to excessively rapid temperature increases. 24-48 hours at 35℃, the temperature rises to 35℃, and the lactic acid bacteria produce organic acids (such as lactic acid and acetic acid) and flavor compounds. The bacterial community begins to shift from a rapid growth mode to a vigorous primary metabolic mode, producing large amounts of acid, thereby rapidly lowering the pH of the system and creating a strong antibacterial environment. 48-72 hours at 37℃, the synthesis of secondary metabolites such as bacteriocins is promoted. 37℃ is conducive to the peak activity of related synthetic enzyme systems. The pH is stabilized within the optimal antibacterial range of 4.0-4.5. This acidic environment is also within the range where many metabolic enzymes of lactic acid bacteria (such as lactate dehydrogenase) have high activity, ensuring metabolic efficiency. Guided by a gradient temperature, the fermentation broth simultaneously accumulates high levels of antibacterial substances such as organic acids and bacteriocins, exhibiting a synergistic and multi-faceted inhibitory effect against putrefactive bacteria. This results in a broader and more potent antibacterial spectrum compared to products from single-temperature fermentation. The phased metabolism may also produce more complex and coordinated flavor precursors, laying the foundation for the final flavor of hot dry noodles.

[0024] Furthermore, in step S1, the obtained fermenting agent is a fermentation liquid and / or a fermentation powder made by spray drying of the fermentation liquid, wherein: the spray drying conditions are an inlet air temperature of 180°C and an outlet air temperature of 80°C, and the amount of fermentation powder added accounts for 2% to 10% of the mass of wheat flour.

[0025] A solid-state fermentation-spray drying process for preparing starter culture was established, which improved the stability and ease of use of the fermentation products.

[0026] Furthermore, in step S2, the mass ratio of wheat flour, starter culture, water, edible salt and edible alkali is 100:100:(30~40):(0.4~1):(0.3~1), and the stirring time is 10~15 min.

[0027] Furthermore, in step S3, the dough maturation temperature is 25~30℃, and the maturation time is 20~30min.

[0028] Furthermore, in step S5, the process involves first processing with 440W power for 30 seconds, then with 600W power for 30 seconds, for a total processing time of 60 seconds. The microwave frequency is 2450MHz, and the temperature is controlled at 40~50℃.

[0029] A stepped microwave treatment method is used. First, the noodles are preheated and homogenized at 440W for 30 seconds. The microwave energy gently penetrates the noodles, allowing the internal and external moisture to absorb energy and heat up evenly and synchronously, avoiding violent vaporization, surface hardening, or localized burns caused by instantaneous surface overheating. Then, the noodles are treated at 600W for another 30 seconds. The higher energy allows for more effective penetration into the core of the material, ensuring that the core temperature also reaches the sterilization threshold. Simultaneously, the pre-heated bacteria are thoroughly sterilized. The total treatment time is 60 seconds. Under these conditions, microorganisms are effectively killed without causing significant changes in the noodle texture. Measurements show that the thermal effect at these parameters can raise the core temperature of the material to 45-50℃, while the non-thermal effect disrupts the microbial cell membrane structure, minimizing excessive gelatinization of starch and severe denaturation of proteins in the noodles. This is crucial for maintaining the noodles' elasticity and firmness. The organic acids and bacteriocins produced during fermentation have greatly inhibited microbial activity and altered the integrity of their cell membranes. This makes the microorganisms more sensitive to heat and electromagnetic fields during subsequent microwave treatment, allowing for the use of milder microwave parameters (relatively low temperature and short time) to achieve sterilization requirements, resulting in a synergistic preservation effect of 1 (biological inhibition) + 1 (physical sterilization) > 2.

[0030] A type of hot dry noodles produced using a long-shelf-life hot dry noodle preparation process has a total bacterial count of less than 10 after 10 days of storage. 5 CFU / g, hardness of 1800~1900g, elasticity of 0.82~0.85, and cooking loss rate of less than 2%.

[0031] Furthermore, the moisture content is 30%~35%, the protein content is 10%~12%, and the fat content is less than 1%.

[0032] Application of a long-shelf-life hot dry noodles preparation process in extending the shelf life of noodle products.

[0033] The beneficial effects of this invention are:

[0034] I. Synergistic effects of biological and physical methods significantly extend shelf life while perfectly maintaining product quality, systematically resolving the core contradictions in the industry.

[0035] This invention creatively combines the compound fermentation of specific lactic acid bacteria with programmed step microwave treatment to construct a multi-layered preservation system of biological antibacterial, physical sterilization, and physical texture protection.

[0036] This synergistic effect is reflected in:

[0037] Fermentation enhances microwave processing: The organic acids, ethanol, and antimicrobial peptides produced by lactic acid bacteria fermentation work together to preserve freshness. Ethanol and organic acids effectively lower the pH of the dough, creating an acidic environment unfavorable to microbial growth. Antimicrobial peptides directly act on spoilage bacteria and pathogenic bacteria, inhibiting their growth and reproduction. They can pre-inhibit and weaken microorganisms, reduce their heat resistance, and optimize the gluten network, enabling subsequent microwave processing to achieve highly efficient sterilization at lower temperatures and in shorter times, avoiding damage to texture caused by high temperatures.

[0038] Benefits of microwave treatment for solidification and amplification of fermentation: Stepped microwave treatment, while gently sterilizing (center temperature 45~50℃), further fixes the optimized gluten structure formed during fermentation and promotes the even distribution and activity retention of natural antibacterial substances produced during fermentation, thus achieving a synergistic preservation effect of 1+1>2. Ultimately, the product's shelf life is extended to more than 10 days under refrigeration at 4℃, and it still maintains excellent edible quality after storage.

[0039] In this invention, the two stages of initial steaming and final microwave cooking work together. Steaming in boiling water for 30 seconds can quickly gelatinize the starch on the surface of the noodles, set the shape, and kill some surface microorganisms. Microwave cooking, at a lower core temperature, deeply and uniformly sterilizes the semi-cooked noodles through thermal and non-thermal effects (damage to cell membranes) and achieves final cooking. This process effectively sterilizes while protecting the protein network and starch structure of the noodles to the greatest extent, thus preserving the unique chewy and smooth texture of hot dry noodles.

[0040] II. Achieves clean labeling, high safety, and no chemical additives.

[0041] This invention completely eliminates chemical preservatives (such as calcium propionate and potassium sorbate), using only the inherent raw materials of hot dry noodles (wheat flour and water) and food-grade lactic acid bacteria for fermentation. The fermentation product itself is a functional ingredient. The microwave processing temperature is strictly controlled below 50°C, effectively avoiding the generation of harmful heat processing substances such as acrylamide. The entire process is natural and safe, and the product meets current market demands for clean labels and healthy foods.

[0042] Third, the effect of extending shelf life is clear and has a reliable microbiological basis.

[0043] The synergistic effect of compound lactic acid bacteria fermentation and microwave treatment achieves multiple strikes against microorganisms:

[0044] Biochemical inhibition: The organic acids (lactic acid, acetic acid) produced by fermentation lower the pH of the system, creating an acidic environment; substances such as ethanol and bacteriocins can destroy the cell membranes of microorganisms.

[0045] Physical sterilization: The thermal effect of stepped microwaves denatures microbial proteins, while its non-thermal effect (electromagnetic field) further disrupts cell membrane integrity. Highly efficient sterilization is achieved through a dual mechanism of thermal and non-thermal effects. The thermal effect denatures and inactivates microbial cell proteins, while the non-thermal effect disrupts cell membrane structure through the electromagnetic field. This alternating power strategy effectively avoids localized overheating, ensuring uniform sterilization while minimizing damage to the noodle texture. A significant synergistic effect exists between lactic acid bacteria fermentation and microwave treatment. Fermentation products enhance the sterilization effect of microwaves, while microwave treatment, in turn, promotes the uniform distribution and activity retention of fermentation products in the dough. This synergistic effect allows the total bacterial count to remain above 10 even after 10 days of storage. 5 Food safety standards below CFU / g have clear and reliable effects on shelf life.

[0046] IV. Excellent eating quality and textural characteristics

[0047] This process, while extending shelf life, unexpectedly and significantly improves and maintains the core edible quality of hot dry noodles:

[0048] Excellent texture: The fermentation process optimizes the gluten network, and the stepped microwave treatment precisely controls the starch gelatinization degree, so that the hardness of the finished noodles is maintained in the ideal range of 1800~1900g, with an elasticity of up to 0.82~0.85, and a chewy and smooth texture.

[0049] Excellent cooking performance: The steaming and boiling loss rate is as low as 0.9%~1.1%, which is significantly reduced compared to traditional processes. The noodles are resistant to overcooking and do not cloud the soup. The water absorption rate is increased to about 185%, resulting in a fuller taste.

[0050] V. It has strong process adaptability, making it easy for industrial production and promotion.

[0051] The core steps of this invention are highly compatible with existing industrial production lines:

[0052] Fermentation unit: Standard fermenters can be used, which makes it easy to achieve large-scale and controllable production.

[0053] Microwave processing section: It can be modularly embedded into existing continuous noodle production lines to replace or improve traditional steaming or drying stations without requiring large-scale modifications to the entire line.

[0054] This design greatly reduces the equipment investment costs and transformation difficulties for enterprises to upgrade their technology, which is conducive to the rapid promotion and application of this technology. Attached Figure Description

[0055] Figure 1 This is a table showing the changes in the total bacterial count of hot dry noodles in Examples 1-3 and Comparative Examples 1-8 of this invention.

[0056] Figure 2 This is a table showing the textural properties of hot dry noodles from Examples 1-3 and Comparative Examples 1-8 after 10 days.

[0057] Figure 3 This table shows the cooking loss rate of hot dry noodles after 10 days in Examples 1-3 and Comparative Examples 1-8 of this invention.

[0058] Figure 4 This is a comparison table of the overall benefits of the present invention and traditional processes. Detailed Implementation

[0059] To enable those skilled in the art to better understand the present invention, the invention will now be further described in conjunction with specific embodiments. In the following examples and comparative examples, *Lactobacillus rhamnosus* and *Lactobacillus paracasei* were used as production strains, commercially available medium-high gluten flour was used, and all other raw materials were food-grade.

[0060] Example 1:

[0061] A preparation process for long-shelf-life hot dry noodles includes the following steps:

[0062] S1. Preparation of baking powder: Take 500g of wheat flour, inoculate Lactobacillus rhamnosus and Lactobacillus paracasei into the wheat flour matrix at a ratio of 1:2, and carry out solid-state fermentation at 30~37℃ for 48~72h. The fermentation product is spray-dried to obtain baking powder. The spray-drying conditions are: inlet air temperature 180℃ and outlet air temperature 80℃.

[0063] S2. Kneading the dough: Take 500g of wheat flour, 500g of baking powder, 350g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0064] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0065] S4. Pre-cooking: Shape the risen dough into noodles, put them into boiling water and steam for 30 seconds, then remove and cool to room temperature.

[0066] S5. Microwave Treatment: Spread the semi-cooked dough evenly on the microwave conveyor belt, treat it first at 440W for 30 seconds, then at 600W for 30 seconds. The microwave frequency is 2450MHz, and the dough temperature is controlled at 45±2℃ during the treatment.

[0067] S6. Packaging and Storage: After microwave treatment, immediately package using a vacuum packaging machine with a vacuum degree of -0.095MPa, and then store in a 4℃ constant temperature oven.

[0068] Example 2:

[0069] A preparation process for long-shelf-life hot dry noodles includes the following steps:

[0070] S1. Preparation of baking powder: Take 500g of wheat flour, inoculate Lactobacillus rhamnosus and Lactobacillus paracasei into the wheat flour matrix at a ratio of 1:1, and carry out solid-state fermentation at 30~37℃ for 48~72h. The fermentation product is spray-dried to obtain baking powder. The spray-drying conditions are: inlet air temperature 180℃ and outlet air temperature 80℃.

[0071] S2. Kneading the dough: Take 500g of wheat flour, 500g of baking powder, 350g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0072] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0073] S4. Pre-cooking: Shape the risen dough into noodles, put them into boiling water and steam for 30 seconds, then remove and cool to room temperature.

[0074] S5. Microwave treatment: Spread the semi-cooked dough evenly on the microwave equipment conveyor belt, treat it first at 440W for 30s, then at 600W for 30s, with a microwave frequency of 2450MHz, and control the dough temperature at 45±2℃ during the treatment.

[0075] S6. Packaging and Storage: After microwave treatment, immediately package using a vacuum packaging machine with a vacuum degree of -0.095MPa, and then store in a 4℃ constant temperature oven.

[0076] Example 3:

[0077] A preparation process for long-shelf-life hot dry noodles includes the following steps:

[0078] S1. Preparation of baking powder: Take 500g of wheat flour, inoculate Lactobacillus rhamnosus and Lactobacillus paracasei into the wheat flour matrix at a ratio of 2:1, and carry out solid-state fermentation at 30~37℃ for 48~72h. The fermentation product is spray-dried to obtain baking powder. The spray-drying conditions are: inlet air temperature 180℃ and outlet air temperature 80℃.

[0079] S2. Kneading the dough: Take 500g of wheat flour, 500g of baking powder, 350g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0080] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0081] S4. Pre-cooking: Shape the risen dough into noodles, put them into boiling water and steam for 30 seconds, then remove and cool to room temperature.

[0082] S5. Microwave Treatment: Spread the semi-cooked dough evenly on the microwave conveyor belt, treat it first at 440W for 30 seconds, then at 600W for 30 seconds. The microwave frequency is 2450MHz, and the dough temperature is controlled at 45±2℃ during the treatment.

[0083] S6. Packaging and Storage: After microwave treatment, immediately package using a vacuum packaging machine with a vacuum degree of -0.095MPa, and then store in a 4℃ constant temperature chamber.

[0084] Comparative Example 1:

[0085] This comparative example shows the traditional method for making hot dry noodles, as follows:

[0086] S1. Kneading the dough: Take 1000g of wheat flour, 350g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0087] S2. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into a 2mm thick sheet by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0088] S3. Packaging and Storage: Immediately after the noodles are made, they are packaged using a vacuum packaging machine with a vacuum degree of -0.095MPa, and then stored in a constant temperature chamber at 4℃.

[0089] Comparative Example 2:

[0090] This comparative example is a traditional method for making hot dry noodles. The difference between this example and Example 1 is that no fermented wheat flour is added in the subsequent steps. Instead, microwave treatment is added to the method described in Comparative Example 1, as follows:

[0091] S1. Mixing the dough: 1000g wheat flour, 350g water, 10g salt, 3g baking soda, and 2g calcium propionate (0.2% of the wheat flour mass) are added to a dough mixer and mixed at 80 rpm for 12 minutes to form a uniform dough.

[0092] S2. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into a 2mm thick sheet by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0093] S3. Microwave Treatment: Spread the raw dough evenly on the microwave conveyor belt, treat it first at 440W for 30 seconds, then at 600W for 30 seconds. The microwave frequency is 2450MHz, and the dough temperature is controlled at 45±2℃ during the treatment.

[0094] S4. Packaging and Storage: After microwave treatment, immediately package using a vacuum packaging machine with a vacuum degree of -0.095MPa, and then store in a constant temperature chamber at 4℃.

[0095] Comparative Example 3:

[0096] This comparative example uses the traditional method for making hot dry noodles. Based on Comparative Example 1, it adds a 1:1 ratio of Lactobacillus rhamnosus and Lactobacillus paracasei yeast for fermentation, without microwave treatment. Details are as follows:

[0097] S1. Preparation of baking powder: Take 500g of wheat flour, inoculate Lactobacillus rhamnosus and Lactobacillus paracasei into the wheat flour matrix at a ratio of 1:1, and carry out solid-state fermentation at 30~37℃ for 48~72h. The fermentation product is spray-dried to obtain baking powder. The spray-drying conditions are: inlet air temperature 180℃ and outlet air temperature 80℃.

[0098] S2. Kneading the dough: Take 500g of wheat flour, 500g of baking powder, 350g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0099] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0100] S4. Packaging and Storage: Immediately after the noodles are made, they are vacuum-packed with a vacuum degree of -0.095MPa and then stored in a constant temperature chamber at 4℃.

[0101] Comparative Example 4:

[0102] This comparative example uses the traditional method for making hot dry noodles. Based on Comparative Example 1, it adds Lactobacillus rhamnosus and Lactobacillus paracasei yeast in a 1:2 ratio for fermentation, without microwave treatment. Details are as follows:

[0103] S1. Preparation of baking powder: Take 500g of wheat flour, inoculate Lactobacillus rhamnosus and Lactobacillus paracasei into the wheat flour matrix at a ratio of 1:2, and carry out solid-state fermentation at 30~37℃ for 48~72h. The fermentation product is spray-dried to obtain baking powder. The spray-drying conditions are: inlet air temperature 180℃ and outlet air temperature 80℃.

[0104] S2. Kneading the dough: Take 500g of wheat flour, 500g of baking powder, 350g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0105] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0106] S4. Packaging and Storage: Immediately after the noodles are made, they are vacuum-packed with a vacuum degree of -0.095MPa and then stored in a constant temperature chamber at 4℃.

[0107] Comparative Example 5:

[0108] This comparative example uses the traditional method for making hot dry noodles. Based on Comparative Example 1, it adds a 2:1 ratio of Lactobacillus rhamnosus and Lactobacillus paracasei yeast for fermentation, without microwave treatment. Details are as follows:

[0109] S1. Preparation of baking powder: Take 500g of wheat flour, inoculate Lactobacillus rhamnosus and Lactobacillus paracasei into the wheat flour matrix at a ratio of 2:1, and carry out solid-state fermentation at 30~37℃ for 48~72h. The fermentation product is spray-dried to obtain baking powder. The spray-drying conditions are: inlet air temperature 180℃ and outlet air temperature 80℃.

[0110] S2. Kneading the dough: Take 500g of wheat flour, 500g of baking powder, 350g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0111] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0112] S4. Packaging and Storage: Immediately after the noodles are made, they are vacuum-packed with a vacuum degree of -0.095MPa and then stored in a constant temperature chamber at 4℃.

[0113] Comparative Example 6:

[0114] This comparative example is based on the traditional method for making hot dry noodles. It involves adding a 1:1 fermentation broth of *Lactobacillus rhamnosus* and *Lactobacillus paracasei* to the base of Comparative Example 1, followed by microwave treatment, as detailed below:

[0115] S1. Preparation of fermentation broth: The preserved strains were inoculated into MRS medium and activated at 30°C for 24 hours. The activated strains Lactobacillus rhamnosus and Lactobacillus paracasei were mixed in a 1:1 ratio, with an inoculation amount of 3%, and cultured at 32°C for 18 hours. The seed liquid was then inoculated into sterilized wheat flour at a material-to-water ratio of 1:0.6, and fermented for 60 hours according to the above temperature program to prepare the fermentation broth.

[0116] S2. Kneading the dough: Take 1000g of wheat flour, 50g of fermentation liquid, 300g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0117] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0118] S4. Microwave Treatment: Spread the raw dough evenly on the microwave conveyor belt, treat it first at 440W for 30 seconds, then at 600W for 30 seconds. The microwave frequency is 2450MHz, and the dough temperature is controlled at 45±2℃ during the treatment.

[0119] S5. Packaging and Storage: After microwave treatment, immediately package using a vacuum packaging machine with a vacuum degree of -0.095MPa, and then store in a constant temperature chamber at 4℃.

[0120] Comparative Example 7:

[0121] This comparative example is based on the traditional method of making hot dry noodles. It involves adding a 1:2 ratio of *Lactobacillus rhamnosus* and *Lactobacillus paracasei* to the fermentation liquid of Comparative Example 1, followed by microwave treatment, as detailed below:

[0122] S1. Preparation of fermentation broth: The preserved bacterial strains were inoculated into MRS medium and activated at 30℃ for 24h. The activated bacterial strains Lactobacillus rhamnosus and Lactobacillus paracasei were mixed in a 1:2 ratio, with an inoculation amount of 3%, and cultured at 32℃ for 18h. The seed liquid was then inoculated into sterilized wheat flour at a material-to-water ratio of 1:0.6, and fermented for 60h according to the above temperature program to prepare the fermentation broth.

[0123] S2. Kneading the dough: Take 1000g of wheat flour, 50g of fermentation liquid, 300g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0124] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0125] S4. Microwave Treatment: Spread the raw dough evenly on the microwave conveyor belt, treat it first at 440W for 30 seconds, then at 600W for 30 seconds. The microwave frequency is 2450MHz, and the dough temperature is controlled at 45±2℃ during the treatment.

[0126] S5. Packaging and Storage: After microwave treatment, immediately package using a vacuum packaging machine with a vacuum degree of -0.095MPa, and then store in a constant temperature chamber at 4℃.

[0127] Comparative Example 8:

[0128] This comparative example is based on the traditional method of making hot dry noodles. It involves adding a 2:1 ratio of *Lactobacillus rhamnosus* and *Lactobacillus paracasei* to the fermentation liquid of Comparative Example 1, followed by microwave treatment, as detailed below:

[0129] S1. Preparation of fermentation broth: The preserved strains were inoculated into MRS medium and activated at 30°C for 24 hours. The activated strains Lactobacillus rhamnosus and Lactobacillus paracasei were mixed in a 2:1 ratio, with an inoculation amount of 3%, and cultured at 32°C for 18 hours. The seed liquid was then inoculated into sterilized wheat flour at a material-to-water ratio of 1:0.6, and fermented for 60 hours according to the above temperature program to prepare the fermentation broth.

[0130] S2. Kneading the dough: Take 1000g of wheat flour, 50g of fermentation liquid, 300g of water, 10g of salt, and 3g of baking soda, put them into a dough mixer, and mix at 80rpm for 12 minutes to form a uniform dough.

[0131] S3. Rolling and cutting: The dough is cooked at 28℃ for 25 minutes, then rolled into 2mm thick sheets by a rolling mill, and then cut into strips with a width of 1.8mm to make hot dry noodles.

[0132] S4. Microwave Treatment: Spread the raw dough evenly on the microwave conveyor belt, treat it first at 440W for 30 seconds, then at 600W for 30 seconds. The microwave frequency is 2450MHz, and the dough temperature is controlled at 45±2℃ during the treatment.

[0133] S5. Packaging and Storage: After microwave treatment, immediately package using a vacuum packaging machine with a vacuum degree of -0.095MPa, and then store in a constant temperature chamber at 4℃.

[0134] Hot dry noodles from each embodiment and each comparative example were taken as samples for comparative analysis:

[0135] (a) Determination of total bacterial count

[0136] Following the method outlined in GB 4789.2-2016 "National Food Safety Standard - Microbiological Examination of Food: Determination of Total Colony Count", the total bacterial count (CFU / g) of hot dry noodles was determined at 0, 5, 10, and 15 days. Each sample was tested in triplicate, and the average value was taken. Results are as follows: Figure 1 As shown.

[0137] from Figure 1 It can be seen that the total bacterial count in Examples 1-3 was below 10 after 10 days of storage. 5 The CFU / g level met food safety standards. However, Comparative Example 1 (blank control) exceeded 10 CFU / g after 5 days. 5 The CFU / g indicates that the synergistic effect of fermentation and microwave treatment significantly extended the shelf life. Comparative Example 2 (microwave only) showed some effect, but not as good as the examples; Comparative Examples 6, 7, and 8 showed poorer effects, indicating that using baking powder for preservation is superior.

[0138] (ii) Texture analysis

[0139] The hardness (g) and elasticity of hot-dry noodles after 10 days of storage were determined using a physical property analyzer (model: TA.XT Plus). Test conditions: TPA mode, probe P / 36R, initial compression speed 2.0 mm / s, test speed 1.0 mm / s, post-test speed 4.0 mm / s, compression ratio 40%, repeated compression twice with a 15-s interval. Each sample was measured five times, and the average value was taken. Results are as follows: Figure 2 As shown.

[0140] from Figure 2 It can be seen that the noodles in Examples 1-3 have lower hardness and higher elasticity, indicating that they have a soft and chewy texture. The poor texture of Comparative Example 1 shows that fermentation and microwave treatment can effectively maintain the quality.

[0141] (III) Determination of cooking loss

[0142] A sample of hot dry noodles (accurately weighed 100g) was boiled in 500mL of boiling water for 5 minutes. After draining, the weight of the noodles after boiling was measured. The cooking loss rate was calculated using the formula: Cooking loss rate (%) = (Weight of noodles before boiling - Weight of noodles after boiling) / Weight of noodles before boiling × 100%. Each sample was measured in triplicate, and the average value was taken. The results are as follows. Figure 3 As shown. From Figure 3 It can be seen that the steaming loss rate of Examples 1 to 3 is the lowest, the breakage rate when cooked is low, and the water absorption rate is high. Example 1 shows that the noodles have an intact structure and good resistance to cooking.

[0143] The technical solution of this invention, through the synergistic effect of *Lactobacillus rhamnosus* and *Lactobacillus paracasei* fermentation and multi-stage microwave treatment, demonstrates significant advantages in extending the shelf life of hot dry noodles, maintaining edible quality, and optimizing the production process. Specifically, these advantages are reflected in four aspects: shelf life, total bacterial count (15 days), texture hardness, and cooking loss rate. A comparison of its comprehensive benefits with traditional processes can be found in [link to relevant documentation]. Figure 4 As shown.

[0144] The finished noodles have a firmness controlled within the ideal range of 1800-1900g, an elasticity maintained at a high level of 0.82-0.85, and a cooking loss rate of less than 1%. These indicators are significantly better than those of traditional processing methods. The entire technology system, through the organic combination of biological and physical methods, perfectly preserves the unique eating quality and taste characteristics of hot dry noodles while extending shelf life.

[0145] Of course, the above description is not limited to the examples above. Technical features not described in this invention can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solutions of this invention and are not intended to limit this invention. This invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention do not depart from the spirit of this invention and should also fall within the scope of protection of the claims of this invention.

Claims

1. A preparation process for long-shelf-life hot dry noodles, characterized in that: Includes the following steps: S1. Preparation of starter culture: Lactobacillus rhamnosus and Lactobacillus paracasei are inoculated into wheat flour substrate and fermented to obtain starter culture; S2. Kneading the dough: Mix wheat flour, leavening agent, water, salt and baking soda to form a dough; S3. Rolling and cutting: After the dough has matured, roll it into sheets and cut it into strips to make raw noodles; S4. Pre-cooking: Shape the risen dough into noodles, put them into boiling water and steam for 30 seconds, then remove and cool to room temperature. S5. Microwave treatment: The cooled noodles are subjected to a stepped microwave treatment, first at low power and then at high power. S6. Mixing with oil and packaging: Mix the microwaved noodles with cooking oil, vacuum pack and refrigerate.

2. The preparation process of long-shelf-life hot dry noodles according to claim 1, characterized in that: In step S1, the inoculation ratio of Lactobacillus rhamnosus and Lactobacillus paracasei is one of 1:2, 1:1 or 2:

1.

3. The preparation process of long-shelf-life hot dry noodles according to claim 1, characterized in that: In step S1, the fermentation temperature is 30~37℃, the fermentation time is 24~72h, the pH is adjusted to 4.0~5.0 during the fermentation process, and the amount of lactic acid bacteria inoculated is 1%~3% of the wheat flour mass.

4. The preparation process of long-shelf-life hot dry noodles according to claim 1, characterized in that: In step S1, the obtained starter is a fermentation liquid and / or a starter powder made by spray drying the fermentation liquid, wherein: the spray drying conditions are an inlet air temperature of 180°C and an outlet air temperature of 80°C, and the amount of starter powder added accounts for 2% to 10% of the mass of wheat flour.

5. The preparation process of long-shelf-life hot dry noodles according to claim 1, characterized in that: In step S2, the mass ratio of wheat flour, starter culture, water, edible salt and edible alkali is 100:100:(30~40):(0.4~1):(0.3~1), and the stirring time is 10~15 min.

6. The preparation process of long-shelf-life hot dry noodles according to claim 1, characterized in that: In step S3, the dough maturation temperature is 25~30℃ and the maturation time is 20~30min.

7. The preparation process of long-shelf-life hot dry noodles according to claim 1, characterized in that: In step S5, the process involves first processing with 440W power for 30 seconds, then with 600W power for 30 seconds, for a total processing time of 60 seconds. The microwave frequency is 2450MHz, and the temperature is controlled at 40~50℃.

8. A type of hot dry noodles prepared by the process described in any one of claims 1 to 7, characterized in that, After 10 days of storage, the total bacterial count is below 10. 5 CFU / g, hardness of 1800~1900g, elasticity of 0.82~0.85, and cooking loss rate of less than 2%.

9. The hot dry noodles according to claim 8, characterized in that: The moisture content is 30%~35%, the protein content is 10%~12%, and the fat content is less than 1%.

10. The application of the preparation process according to claim 1 in extending the shelf life of flour products.

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