Composite plant protein enhanced konjac cup noodles

Abstract

The present application relates to the technical field of instant food processing, in particular to a composite plant protein enhanced konjac cup noodle, which comprises the following steps: activating pea, rice and egg white protein by cysteine, and then pre-crosslinking the activated pea, rice and egg white protein with konjac-chitosan compound under the action of transglutaminase to form active seeds; mixing the active seeds with the remaining konjac flour, starch, edible glue and the like, and then adding water to the mixture to mature the mixture through gradient temperature; and finally extruding the mixture through a multi-zone double screw, and then performing gradient steam shaping and segmented drying to obtain noodle cakes. The present application builds a uniform gel structure with interpenetrating konjac glucmannan network and plant protein network in the noodle cakes through pre-crosslinking and gradient process, and forms a skin-core secondary structure with dense outer layer and porous inner core. The obtained product has a dry basis protein content of more than 25%, can be completely rehydrated in boiling water within 60-90 seconds, has good chewiness and processing stability, and solves the problems of poor taste, low protein content and slow rehydration of traditional konjac noodles.

Description

Technical Field

[0001] This invention relates to the field of convenience food processing technology, and more specifically, to a compound plant protein-enhanced konjac cup noodle. Background Technology

[0002] With the popularization of healthy eating concepts, low-calorie, high-fiber products made primarily from konjac are gaining popularity. Konjac glucomannan, a natural water-soluble dietary fiber, is widely used in the development of meal replacements and low-carbohydrate noodle products due to its low-calorie, high-viscosity, and good film-forming properties. Konjac glucomannan can form an irreversible gel under alkaline conditions, giving the products a unique chewy and crisp texture. However, pure konjac products have extremely low protein content and limited nutritional diversity, making it difficult to meet the nutritional needs of meal replacement foods.

[0003] In existing technologies, the protein content is typically increased by physically mixing plant protein powder with konjac powder. However, this method has a fundamental flaw: the introduction of a large amount of hydrophobic plant protein severely interferes with the formation of a uniform, continuous three-dimensional gel network by hydrophilic konjac glucomannan molecules, leading to phase separation. This results in a product with a rough texture, brittleness, and a powdery, sticky mouthfeel after rehydration. Konjac is primarily composed of dietary fiber, with extremely low protein content (typically <2%), failing to meet modern consumers' health needs for high-protein, balanced nutrition. Furthermore, konjac gel is sensitive to temperature, pH, and shear; its network structure is prone to collapse during high-temperature extrusion and drying, leading to prolonged rehydration time and uneven texture. Therefore, how to integrate a high proportion of plant protein into a high-konjac-content matrix and form a uniform, stable composite gel structure with both excellent taste and rapid rehydration has become a long-standing and unresolved technical challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a composite plant protein-enhanced konjac cup noodle to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, in one aspect, the present invention provides a composite plant protein-enhanced konjac cup noodle, comprising the following raw materials in parts by weight:

[0006] The ingredients are: 15-25 parts konjac flour, 30-45 parts compound plant protein, 10-20 parts starch, 2-5 parts edible gum, 0.5-1.5 parts alkali, 3-8 parts moisture regulator, 0.3-1.0 parts pH regulator, 0.05-0.15 parts transglutaminase (based on total protein), 0.15-0.45 parts cysteine ​​hydrochloride (based on compound protein), and 1.5-3.0 parts chitosan quaternary ammonium salt (relative to konjac flour).

[0007] The konjac flour serves as the gel matrix, and its main component, glucomannan, forms a basic gel network framework under alkaline conditions, providing the product with a basic chewy and crisp texture, high water retention, and dietary fiber.

[0008] The composite plant protein is composed of pea protein isolate, rice protein, and egg white protein in a weight ratio of (6-7):(2-3):(1-2). Pea protein provides the main protein nutrition and good gelling properties; rice protein is rich in cysteine, and its sulfhydryl groups provide key active sites for subsequent cross-linking reactions; egg white protein, as a heat-sensitive gelling protein, contributes to network strength during the heating stage. This compound not only provides comprehensive amino acid nutrition but also serves as a diverse set of cross-linking nodes in the composite network.

[0009] The starch is preferably potato acetate starch, which is used to improve the viscosity and plasticity of the material during processing.

[0010] The edible gum is one or more of gellan gum, guar gum, or xanthan gum, used to assist in thickening and stabilizing the structure, and to synergistically enhance the water-holding capacity and textural stability of the system with the main gel network.

[0011] The alkaline agent is sodium bicarbonate, which is used to provide the alkaline environment (pH>9) necessary for the formation of stable, thermally irreversible gels from konjac glucomannan.

[0012] The moisture regulator is trehalose, which can effectively protect the spatial structure of proteins during processing and storage, reduce the damage to the protein network caused by high-temperature drying, and maintain the integrity of the gel network.

[0013] The pH adjuster is gluconate-δ-lactone, which acts as a delayed acidifying agent. It hydrolyzes and slowly releases hydrogen ions in the later stages of processing, and is used to finely control the pH gradient during the gelation process.

[0014] The transglutaminase is the core biocatalyst, which can specifically catalyze the formation of ε-(γ-glutamyl) lysine covalent bonds between protein molecules and between proteins and compounds containing primary amino groups, thereby achieving molecular cross-linking.

[0015] The cysteine ​​hydrochloride, as a protein structure modifier, partially reduces the disulfide bonds of protein molecules under mild conditions, breaking them to generate active thiol groups, thereby increasing the flexibility and reactive sites of protein molecules and creating conditions for deep cross-linking.

[0016] The chitosan quaternary ammonium salt is a cationic polysaccharide interface modifier. It electrostatically recombines with negatively charged konjac glucomannan to form a positively charged konjac-chitosan complex. This complex not only alters the interfacial properties between the two phases, but its abundant amino and hydroxyl groups on its molecular chains also provide additional cross-linking sites, becoming a molecular bridge connecting the protein network and the konjac network.

[0017] On the other hand, the present invention provides a method for preparing the above-mentioned composite plant protein enhanced konjac cup noodles, comprising the following steps:

[0018] S1. Preparation of Active Protein Preforms (Molecular Activation Stage): The complex plant protein is mixed with a 0.5%-1.0% cysteine ​​hydrochloride solution and stirred at 35-45℃ for 10-20 minutes. Under these conditions, cysteine ​​acts as a reducing agent, controllably breaking some disulfide bonds within and between protein molecules, transforming them into active thiol groups. This process significantly enhances the flexibility and surface reactivity of the protein molecules and exposes more hydrophobic regions, laying the molecular foundation for subsequent deep interactions with polysaccharide components.

[0019] S2. Preparation of the konjac-chitosan complex (interface modification stage): A portion of konjac flour was mixed with chitosan quaternary ammonium salt in a weakly acidic aqueous solution. Under acidic conditions, the cationicity of the chitosan quaternary ammonium salt was enhanced, and it formed a stable complex with a fundamentally altered surface charge through strong electrostatic attraction and hydrogen bonding with negatively charged konjac glucomannan. This process cationically modifies konjac polysaccharide, greatly improving its thermodynamic compatibility with the enhanced hydrophobicity of activated proteins.

[0020] S3. Formation of pre-crosslinked seeds (molecular-level interpenetrating network construction stage): Under mild conditions of pH 5.5-6.5 and temperature 40-50℃, the active protein preform obtained in S1 is mixed with the konjac-chitosan complex solution obtained in S2, and transglutaminase is added. The mixture is incubated for 15-25 minutes. Transglutaminase catalyzes two key reactions in a non-gelling pH environment: first, it activates the formation of covalent isopeptide bonds between glutamine residues and lysine residues between protein molecules; second, it crosslinks the glutamine residues on the protein with the primary amino groups on the konjac-chitosan complex molecular chain. Before macroscopic gelation, pre-crosslinked seeds linked by covalent bonds are pre-constructed at the microscopic scale.

[0021] S4. Gradient Mixing and Maturation (Macro-Network Assembly Guidance Stage): The pre-crosslinked seed slurry obtained in S3 is mixed with the remaining konjac flour, starch, edible gum, moisture regulator, alkali agent, and glucono-δ-lactone microcapsules. A gradient temperature water addition method is used: first, water at 55-65℃ is added and stirred at high speed; then, water at 25-35℃ is added and stirred at low speed; finally, ice water at 0-10℃ is added and stirred at low speed until homogeneous. The mixture is then allowed to stand and mature for 15-30 minutes. This gradient temperature water addition strategy utilizes the difference in kinetic energy of water molecules at different temperatures to achieve precise control over the hydration process. Hot water promotes the pregelatinization of konjac and starch, room temperature water ensures uniform dispersion, and ice water inhibits premature reaction and utilizes the temperature difference to form an internal swelling gradient. During the standing process, in the alkaline environment of the slowly released alkali agent, konjac glucomannan begins to hydrate and orient itself, and initially assembles around the existing pre-crosslinked seeds, forming a structure-oriented heterogeneous precursor.

[0022] S5. Gradient Temperature Extrusion Molding (Network Gradient Curing Stage): The cured composite material is fed into a twin-screw extruder with three temperature control zones: Zone 1 35-45℃, Zone 2 60-70℃, and Zone 3 85-95℃. The material is extruded through the die. During this process, gluconate-δ-lactone microcapsules melt and release in the high-temperature zone, generating a pH gradient from the surface to the interior at the moment of noodle extrusion through the die (the pH is lower at the surface and gradually increases towards the interior). This pH gradient regulates the kinetics of gel formation: the slightly acidic environment at the surface preferentially promotes the hydrophobic aggregation of the protein network and its electrostatic binding with cationic konjac, forming a relatively dense initial network; while in the continuously released alkaline environment of the core, konjac glucomannan can fully unfold and form a highly cross-linked three-dimensional gel network. The gradient connection of the network structure is achieved through the pH transition zone, thereby spontaneously forming a stable gradient gel structure.

[0023] S6. Steam Gradient Shaping and Pulsed Drying (Structural Functionalization Shaping Stage): The extruded noodles are first treated with supersaturated steam at 105-110℃ for 20-40 seconds, then with saturated steam at 98-100℃ for 1-2 minutes, followed by microwave-hot air pulsed drying: first, microwave treatment at 3-5W / g for 20-40 seconds, then hot air drying at 50-60℃ until the moisture content is 12-18%, and finally intermittent microwave pulse drying until the final moisture content is ≤10%. The supersaturated steam impact causes the surface of the noodles to instantly and drastically lose water and shrink, forming a dense and smooth skin. The saturated steam fully matures the core network, and the microwave drying rapidly vaporizes the internal moisture. The generated steam pressure expands the core of the gradient gel network, forming a large number of micropores. The hot air and pulsed microwaves ensure uniform drying, ultimately forming a skin-core two-dimensional structure with a dense outer layer and a porous inner core. This structure is the physical basis for achieving rapid rehydration in boiling water for 60-90 seconds, while also giving the product a layered texture of a soft outer layer and a chewy inner core.

[0024] S7. Packaging: Place the dried and shaped dough cake and seasoning packet into a cup, seal it, and you will get the composite plant protein konjac cup noodles.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] In this composite plant protein-enhanced konjac cup noodles, pre-crosslinked seed technology and gradient process are used to make the plant protein network and konjac polysaccharide network interpenetrate and intertwine at the molecular level to form a uniform and stable single-phase composite gel structure. Even with a dry basis protein content as high as 25%-30%, the product still maintains excellent texture, and its tensile strength and elongation at break are significantly improved compared with pure konjac noodles.

[0027] Secondly, the unique gel network and porous skin-core structure create highly efficient water absorption and conduction channels, enabling rapid and complete rehydration in boiling water within 60-90 seconds, making it more convenient to eat. The dense skin layer locks in the flavor and provides a chewy texture, while the porous core layer continuously releases flavor and contributes a bouncy texture during chewing, resulting in a rich and lasting flavor experience.

[0028] Meanwhile, the pre-crosslinked seed slurry improves the mixing uniformity and cohesiveness of high-protein, high-fiber materials, solving the problems of dust and uneven dispersion in production, and improving production efficiency and product consistency. The carefully selected compound plant protein formula provides comprehensive amino acid nutrition and works synergistically with konjac dietary fiber to meet the needs of healthy meal replacements. Attached Figure Description

[0029] Figure 1 This is an overall flowchart of Embodiment 1 of the present invention. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: This example provides a method for preparing compound plant protein-enhanced konjac cup noodles, based on... Figure 1 As shown, it includes the following steps:

[0032] S1. Preparation of active protein preform: Weigh 18 parts of pea protein isolate, 9 parts of rice protein, and 3 parts of egg white protein (total 30 parts) and place them in a mixer. Separately prepare a 0.8% cysteine ​​hydrochloride solution (based on the total amount of complex protein, the amount of cysteine ​​hydrochloride added is 0.24 parts), heat to 40℃, and add it to the protein powder while stirring. Continue stirring for 15 minutes to obtain the active protein preform slurry.

[0033] S2. Preparation of konjac-chitosan complex: Weigh 20 parts of konjac flour, take 6 parts of it, and add them together with 1.8 parts of chitosan quaternary ammonium salt into an acetic acid aqueous solution with pH 5.0. Stir and react at 60℃ for 45 minutes to obtain konjac-chitosan complex solution.

[0034] S3. Formation of pre-crosslinked seeds: The active protein preform slurry obtained in S1 is mixed with the konjac-chitosan complex solution obtained in S2. The pH of the system is adjusted to 6.0, and the temperature is maintained at 45℃. 0.08 parts (based on total protein) of transglutaminase are added, and the mixture is stirred slowly for 20 minutes to obtain a mixed slurry containing pre-crosslinked seeds.

[0035] S4. Gradient Mixing and Maturation: The slurry obtained in S3 is dry-mixed with the remaining 14 parts konjac flour, 15 parts potato acetate starch, 3 parts gellan gum, 5 parts trehalose, 1.2 parts sodium bicarbonate, and 0.6 parts glucono-δ-lactone microcapsules (wall material is hydrogenated vegetable oil, melting point 50℃). Then, a gradient water addition method is used for mixing: first, 65℃ hot water (50% of the total water volume) is added and stirred at high speed for 2 minutes; then, 30℃ room temperature water (30% of the total water volume) is added and stirred at medium speed for 3 minutes; finally, 5℃ ice water (20% of the total water volume) is added and stirred at low speed until uniform. The mixture is then allowed to stand at room temperature for 20 minutes to mature.

[0036] S5. Gradient Temperature Extrusion Molding: The cooked material is fed into a twin-screw extruder, with the temperature set at 40℃ in zone one, 65℃ in zone two, and 90℃ in zone three. The material is extruded through a circular die to obtain noodles with a diameter of approximately 1.2mm.

[0037] S6. Steam gradient shaping and pulse drying: The extruded noodles are first subjected to 108°C supersaturated steam impact for 30 seconds, then treated with 100°C saturated steam for 90 seconds, and then dried: first treated with microwave at a power density of 4W / g for 30 seconds, then dried with hot air at 55°C to a moisture content of about 15%, and finally pulse dried in an intermittent mode (microwave treatment for 10 seconds, stop for 20 seconds) to a final moisture content of 9.5%.

[0038] S7. Packaging: Place the dough (about 55g) and the seasoning packet into a cup or bowl, seal, and you will get the finished product.

[0039] Example 2: This example provides a method for preparing composite plant protein konjac cup noodles, including the following steps:

[0040] S1. Preparation of active protein preforms: Weigh 21 parts of pea protein isolate, 12 parts of rice protein, and 4 parts of egg white protein (total 37 parts), prepare a 1.0% cysteine ​​hydrochloride solution (addition amount 0.37 parts), and treat the protein powder at 45℃ for 12 minutes.

[0041] S2. Preparation of konjac-chitosan complex: Weigh 22 parts of konjac flour, take 8 parts of it, and combine it with 2.2 parts of chitosan quaternary ammonium salt in an acetic acid aqueous solution at pH 5.2 for 50 minutes.

[0042] S3, Formation of pre-crosslinked seeds: Mix the products of S1 and S2, adjust the pH to 5.8, and maintain the temperature at 50°C. Add 0.055 parts of transglutaminase and react for 18 minutes.

[0043] S4. Gradient Mixing and Maturation: Dry mix the S3 slurry with the remaining 14 parts konjac flour, 18 parts potato acetate starch, 2 parts guar gum, 2 parts xanthan gum, 7 parts trehalose, 0.8 parts sodium bicarbonate, and 0.8 parts glucono-δ-lactone microcapsules. The water addition sequence is: 60℃ hot water (40%) → 35℃ room temperature water (40%) → 10℃ ice water (20%), and let it stand for 25 minutes to mature.

[0044] S5, Gradient Temperature Extrusion Molding: The extruder parameters are set to Zone 1 45℃, Zone 2 70℃, and Zone 3 95℃.

[0045] S6. Steam gradient shaping and pulse drying: The noodles are treated with 105℃ supersaturated steam for 35 seconds, then with 98℃ saturated steam for 2 minutes. The drying process is as follows: microwave treatment at 3.5W / g for 35 seconds, hot air drying at 60℃ to 16% moisture content, and pulse drying to 9.0% final moisture content.

[0046] Example 3: This example provides a method for preparing composite plant protein konjac cup noodles, including the following steps:

[0047] S1. Preparation of active protein preforms: Weigh 24 parts of pea protein isolate, 15 parts of rice protein, and 6 parts of egg white protein (total 45 parts), prepare a 0.6% cysteine ​​hydrochloride solution (addition amount 0.27 parts), and treat the protein powder at 38℃ for 18 minutes.

[0048] S2. Preparation of konjac-chitosan complex: Weigh 25 parts of konjac flour, take 10 parts of it, and combine it with 3.0 parts of chitosan quaternary ammonium salt in an acetic acid aqueous solution at pH 5.5 for 40 minutes.

[0049] S3. Formation of pre-crosslinked seeds: Mix the products of S1 and S2, adjust the pH to 6.2, and maintain the temperature at 42℃. Add 0.068 parts of transglutaminase and react for 22 minutes.

[0050] S4. Gradient Mixing and Maturation: Dry mix the S3 slurry with the remaining 15 parts konjac flour, 12 parts corn starch, 4 parts xanthan gum, 3 parts trehalose, 1.5 parts sodium bicarbonate, and 1.0 part glucono-δ-lactone microcapsules. The water addition sequence is: 55℃ hot water (45%) → 25℃ room temperature water (35%) → 0℃ ice water (20%), and let it stand for 15 minutes to mature.

[0051] S5, Gradient Temperature Extrusion Molding: The extruder parameters are set to Zone 1 35℃, Zone 2 60℃, and Zone 3 85℃.

[0052] S6. Steam gradient shaping and pulse drying: The noodles are treated with 110℃ supersaturated steam for 25 seconds, then with 100℃ saturated steam for 1.5 minutes. The drying process is as follows: microwave treatment with 5W / g for 25 seconds, hot air drying at 50℃ to 14% moisture content, and pulse drying to 10.0% final moisture content.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 1 is that chitosan quaternary ammonium salt is not added, and step S2 is omitted. In step S3, the active protein preform from step S1 is directly mixed with all 20 parts of the konjac flour solution, and other steps and parameters are the same as in Example 1. This comparative example is used to investigate the effect of the absence of an interface modifier on the product structure and performance.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that the S3 pre-crosslinking step is omitted. The products of S1 and S2 are simply mixed and then directly proceed to step S4. No transglutaminase pretreatment reaction is added or performed. Other steps and parameters are the same as in Example 1. This comparative example is used to investigate the effect of the absence of the pre-crosslinking seed formation step on product uniformity and texture.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 is that the extrusion process in S5 is changed to constant temperature extrusion, with the temperature of all three zones set to 90°C. Other steps and parameters are the same as in Example 1. This comparative example is used to investigate the impact of missing gradient temperature extrusion on the formation of the internal network gradient structure of the product.

[0059] Comparative Example 4 (Traditional Process vs. Traditional Process)

[0060] Following conventional konjac noodle production methods: 20 parts konjac flour, 30 parts of the same compound plant protein powder as in Example 1, 15 parts starch, 1.2 parts alkali agent, and all other dry powder ingredients are mixed evenly in one go. Then, room temperature water is added and stirred directly into a dough. This dough is then extruded using a single-screw extruder (90℃ constant temperature), shaped, boiled in water to set its form, and finally dried with ordinary hot air (80℃) until the moisture content is ≤10%. This comparative example represents the conventional method of direct processing after physical mixing in existing technologies.

[0061] Test Example 1: The following performance tests were conducted on the pancake products prepared in Examples 1-3 and Comparative Examples 1-4 above, and the results are summarized in Table 1.

[0062] Test method:

[0063] Sensory evaluation: Ten trained sensory evaluators were invited to score the rehydrated noodles (out of 10). Evaluation criteria included: appearance (uniform color, smooth surface), elasticity / chewiness, stickiness, and overall acceptability.

[0064] Rehydration time: Place the dough in 400ml of boiling water, gently separate it with chopsticks, and record the time required for the center of the noodles to be free of hard core and the texture to reach its optimal.

[0065] Texture analysis (TPA): Using a texture analyzer and a P / 36R probe, two compression tests were performed on fully rehydrated noodles (compression ratio 50%, test speed 1 mm / s). Hardness, elasticity, and chewiness were measured. Each sample was tested in parallel six times, and the average value was taken.

[0066] Cooking loss rate: Accurately weigh 10g of dried noodle cake (W1), cook it in boiling water for the optimal rehydration time, remove it, blot the surface moisture with filter paper, and weigh it (W2). Collect the cooking water, evaporate it, and weigh it (W3). Cooking loss rate = W3 / W1 × 100%. This value reflects the integrity of the network structure.

[0067] Protein content (dry basis): determined according to Method I of GB 5009.5-2016 "National Food Safety Standard - Determination of Protein in Food".

[0068] Microstructure observation: A cross-section of the rehydrated strip was taken, freeze-dried, and then sputter-coated with gold. The internal pores and network structure were observed using a scanning electron microscope (SEM).

[0069] Table 1: Performance Test Results of Examples and Comparative Examples

[0070] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Sensory rating (out of 10) 8.7 8.5 8.9 6.2 5.8 7.1 4.5 Rehydration time (seconds) 70 75 65 120 110 95 >180 (Hard lump still exists in the core) Texture-hardness (g) 3250±120 3480±135 3020±110 2850±150 4100±180 (Crispy) 3600±130 2650±200 (loose) Texture-elasticity 0.88±0.02 0.86±0.03 0.89±0.02 0.76±0.04 0.72±0.05 0.81±0.03 0.68±0.06 Texture - Chewability (g) 1850±95 1950±105 1780±90 1350±110 1750±120 (slow-paced) 1680±100 1050±130 Cooking loss rate (%) 5.2 5.8 4.9 8.5 12.3 7.0 15.6 Protein content (dry basis, %) 28.5 31.8 33.6 28.5 28.5 28.5 28.5

[0071] Note: Comparative Example 4 still had obvious hard lumps in the core after 180 seconds and could not be fully rehydrated, so it was recorded as >180.

[0072] As shown in Table 1, Examples 1-3 performed excellently in all test indicators, with high sensory scores (>8.5), short rehydration time (65-75 seconds), balanced and ideal textural parameters (hardness, elasticity, chewiness), and low cooking loss rate (<6%), indicating the formation of a stable and uniform composite gel network.

[0073] In Comparative Example 1, after interfacial modification with chitosan quaternary ammonium salt deficiency, the product's sensory score, elasticity, and chewiness significantly decreased, while the cooking loss rate increased. SEM observation revealed a clear two-phase separation structure, with distinct gaps between the protein aggregates and the konjac gel network. This confirms the crucial role of interfacial modification in achieving two-phase compatibility.

[0074] In Comparative Example 2, the product lacking the pre-crosslinking step exhibited abnormally high hardness but decreased elasticity, with a noticeable grainy and powdery texture during chewing, and a sharp increase in cooking loss (12.3%). This indicates that the absence of molecular-level pre-crosslinking prevented the proteins from effectively integrating with the konjac network during subsequent processing, resulting in a fragile network and easy loss of components.

[0075] Comparative Example 3, after being subjected to isothermal extrusion, showed a prolonged rehydration time and a slight decrease in textural elasticity. SEM revealed an uneven distribution of internal pores, lacking the gradient transition structure from the surface to the interior seen in the previous examples. This demonstrates that gradient temperature extrusion is crucial for forming an ideal skin-core porous structure and rapid rehydration channels.

[0076] Traditional processing methods resulted in the worst performance, with rehydration being extremely difficult, resulting in a powdery, brittle, and sticky texture, and a very high cooking loss rate (15.6%). This clearly demonstrates that without the specific interface modification and gradient process treatments of this invention, the high-protein konjac system cannot achieve acceptable practical performance.

[0077] Test Example 2: This test example is used to verify the potential impact of the new process of the present invention on safety. The following safety indicators were tested on the products of Examples 1, 2, and 3 and Comparative Example 4, which served as a control of the traditional process, in accordance with relevant national standards. The results are summarized in Table 2.

[0078] Test samples: Finished dough sheets from Examples 1, 2, and 3, and finished dough sheet from Comparative Example 4.

[0079] Test items and methods:

[0080] Microbiological indicators: Refer to GB 4789 series standards.

[0081] Total bacterial count: GB 4789.2-2022;

[0082] Coliform bacteria: GB 4789.3-2016;

[0083] Mold and yeast count: GB 4789.15-2016;

[0084] Pathogenic bacteria (Salmonella, Staphylococcus aureus): GB 4789.4-2016, GB 4789.10-2016.

[0085] Heavy metals and pollutants:

[0086] Lead (Pb): GB 5009.12-2017;

[0087] Arsenic (As): GB 5009.11-2014;

[0088] Cadmium (Cd): GB 5009.15-2014;

[0089] Aluminum (Al) residue: GB 5009.182-2017 (considering possible contact during processing).

[0090] Additive and processing aid residues:

[0091] Sulfur dioxide residue: GB 5009.34-2022 (considering the possibility of its introduction in some raw materials);

[0092] Propylene glycol (potential as a solvent for some edible gums): GB 5009.251-2016;

[0093] Alkali residue: The total alkalinity of the water immersion solution was determined by titration, expressed as sodium carbonate.

[0094] Allergen labeling compliance: Check whether the product label clearly indicates the allergens contained therein (e.g., soy protein, egg products).

[0095] Table 2: Test Results of Food Safety Indicators

[0096] Testing items National standard limits (or requirements) Example 1 Example 2 Example 3 Comparative Example 4 Total bacterial count (CFU / g) ≤10000 120 85 200 850 Coliform bacteria (CFU / g) ≤10 ＜10 ＜10 ＜10 ＜10 Mold (CFU / g) ≤150 Not detected Not detected Not detected 20 salmonella 0 / 25g Not detected Not detected Not detected Not detected Staphylococcus aureus ≤100CFU / g Not detected Not detected Not detected Not detected Lead (Pb), mg / kg ≤0.5 0.02 0.03 0.02 0.04 Arsenic (As), mg / kg ≤0.5 0.08 0.07 0.09 0.10 Cadmium (Cd), mg / kg ≤0.1 0.01 0.01 0.01 0.01 Aluminum (Al) residue, mg / kg ≤100 (dry sample) 5.2 6.0 4.8 8.5 Sulfur dioxide residue, g / kg ≤0.05 Not detected Not detected Not detected 0.012 Propylene glycol, g / kg ≤3.0 Not detected Not detected Not detected Not detected <![CDATA[Residual alkali agent (calculated as Na2CO3), %]]> - 0.12 0.10 0.14 0.25

[0097] As shown in Table 2, the total bacterial count, coliform bacteria, mold, and pathogenic bacteria levels of all the products in the examples were far superior to the national standard limits, and significantly better than those of Comparative Example 4 using the traditional process. In particular, the total bacterial count of the products in the examples (≤200 CFU / g) was an order of magnitude lower than that of Comparative Example 4 (850 CFU / g). This is mainly due to the pulsed drying process of the present invention (combination of microwave and hot air). The rapid sterilization effect of microwaves effectively reduced the initial microbial load of the products, improving their hygienic quality.

[0098] The heavy metal (lead, arsenic, cadmium) content of all products was far below the national standard limits, and there was no significant difference between the examples and the comparative examples, indicating good control over the safety of raw materials. Regarding aluminum residue, the products in the examples (4.8-6.0 mg / kg) were significantly lower than those in comparative example 4 (8.5 mg / kg). This is because traditional processes using ordinary aluminum equipment introduce more aluminum through friction when processing viscous materials, while the process of this invention results in better material formability and less wear on equipment. Trace amounts of sulfur dioxide residue were detected in comparative example 4, possibly related to the ordinary starch used, while no sulfur dioxide was detected in the examples due to the optimized raw materials and composite process.

[0099] Alkali residue is a key safety indicator for konjac products. The alkali residue in the product of the example (0.10%-0.14%) was significantly lower than that in Comparative Example 4 (0.25%). This is because the present invention uses gluconate-δ-lactone microcapsules as a pH adjuster, which releases acid in the later stage of extrusion, neutralizing some of the residual alkali. This achieves more precise control over the pH and alkali residue of the final product, reducing the alkaline taste and potential irritation during consumption.

[0100] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite vegetable protein-enhanced konjac cup noodle, characterized in that, Includes the following steps: S1. The compound plant protein and cysteine ​​hydrochloride solution are stirred at 35-45℃ for 10-20 minutes to obtain an active protein preform slurry; the compound plant protein is composed of pea protein isolate, rice protein and egg white protein in a weight ratio of 6-7:2-3:1-2. S2. A portion of konjac flour and chitosan quaternary ammonium salt are mixed in a weakly acidic aqueous solution to form a konjac-chitosan complex solution; the amount of chitosan quaternary ammonium salt added is 1.5-3.0% of the total weight of the konjac flour. S3. Mix the active protein preform slurry obtained in S1 with the konjac-chitosan complex solution obtained in S2, adjust the pH to 5.5-6.5, maintain the temperature at 40-50℃, add transglutaminase and react for 15-25 minutes to obtain a mixed slurry containing pre-crosslinked seeds; the amount of transglutaminase added is 0.05-0.15 parts based on the total protein content; S4. Mix the slurry obtained in S3 with the remaining konjac flour, starch, edible gum, moisture regulator, alkali agent and glucono-δ-lactone microcapsules. Mix using a gradient temperature water addition method and let stand for 15-30 minutes to mature. S5. The matured compound material is fed into a twin-screw extruder and subjected to gradient temperature extrusion in the first zone of 35-45℃, the second zone of 60-70℃, and the third zone of 85-95℃, and then extruded into shape through a die. S6. The extruded noodles are first treated with supersaturated steam at 105-110℃ for 20-40 seconds, then treated with saturated steam at 98-100℃ for 1-2 minutes, and then microwaved, hot air dried and intermittent pulsed microwave dried in sequence until the final moisture content is ≤10%, to obtain a noodle cake with a skin-core two-dimensional structure. S7. Pack the dried and shaped dough and seasoning into a cup and seal it; In step S4, the gradient temperature water addition method is as follows: first, add hot water at 55-65℃ and stir at high speed; then, add room temperature water at 25-35℃ and stir at high speed; finally, add ice water at 0-10℃ and stir at low speed until uniform.

2. The preparation method of the composite plant protein-enhanced konjac cup noodles according to claim 1, characterized in that, In step S1, the amount of cysteine ​​hydrochloride added is 0.15-0.45 parts based on the total amount of the compound plant protein.

3. The preparation method of the composite plant protein-enhanced konjac cup noodles according to claim 1, characterized in that, In step S4, the mixed raw materials, by weight, comprise: Konjac flour 15-25 parts, compound plant protein 30-45 parts, starch 10-20 parts, edible gum 2-5 parts, alkali agent 0.5-1.5 parts, moisture regulator 3-8 parts, pH regulator 0.3-1.0 parts.

4. The preparation method of the composite plant protein-enhanced konjac cup noodles according to claim 1, characterized in that, The starch is potato acetate starch; the edible gum is one or more of gellan gum, guar gum, or xanthan gum; the alkali agent is sodium bicarbonate; the moisture regulator is trehalose; and the pH regulator is glucono-δ-lactone.

5. The preparation method of the composite plant protein-enhanced konjac cup noodles according to claim 1, characterized in that, In step S6, the power density of the microwave treatment is 3-5 W / g, and the treatment time is 20-40 seconds; the temperature of the hot air drying is 50-60℃, and the moisture content is dried to 12-18%.

6. The preparation method of the composite plant protein-enhanced konjac cup noodles according to claim 1, characterized in that, In step S6, the intermittent pulse microwave drying is performed in a cycle of 10 seconds of microwave treatment followed by a 20-second pause.

7. A composite plant protein-enhanced konjac cup noodle prepared by the preparation method according to any one of claims 1-6.

8. The composite plant protein-enhanced konjac cup noodles according to claim 7, characterized in that, The interior of the dough has a uniform gel structure in which the konjac glucomannan network formed by cross-linking through transglutaminase interpenetrates with the plant protein network, and the dough has a skin-core secondary structure with a dense outer layer and a porous inner core.

9. The composite plant protein-enhanced konjac cup noodles according to claim 8, characterized in that, The dough can be completely rehydrated in boiling water within 60-90 seconds, and the dry-basis protein content is 25%-33.6%.

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