Method for directly preparing konjac bean curd from fresh konjac

Abstract

This invention discloses a method for directly preparing konjac tofu from fresh konjac, belonging to the field of konjac food processing technology. This invention achieves integrated production from raw material to ready-to-eat product directly using fresh konjac as raw material through a complete processing flow: raw material pretreatment – ​​antioxidant impregnation – grading and crushing – precision molding – dealkalization and detoxification – seasoning and packaging – aseptic sterilization. This invention utilizes optical color sorting for impurity removal, colloidal impregnation to prevent browning, grading and crushing for homogenization, combined with precision molding and multiple dealkalization processes. The finished product retains the natural flavor of fresh konjac, possessing both a tender and chewy texture and ready-to-eat safety. The process parameters are controllable and highly adaptable.

Description

Technical Field

[0001] This invention belongs to the field of konjac food processing technology, and more specifically, relates to a method for directly preparing konjac tofu from fresh konjac. Background Technology

[0002] Konjac, a crop used for both food and medicine, has a long history of cultivation and processing in the Sichuan, Chongqing, Yunnan, and Guizhou regions. In the 1970s and 1980s, people in the region used traditional stone mill techniques to grind fresh konjac into a paste at a ratio of 3-5 times the amount of material to water, and then coagulate it to make konjac tofu. The product had a delicate and chewy texture and retained its natural flavor.

[0003] However, traditional processes have many inherent drawbacks: fresh konjac processing relies solely on manual washing and impurity removal, which is incomplete and affects the purity of konjac tofu; fresh konjac contains polyphenol oxidase, which easily causes browning during processing, resulting in a dark color for konjac tofu; the single crushing method leads to poor uniformity of the slurry, affecting the quality and taste of konjac tofu; after molding, the alkali residue is not fully neutralized, and there is a lack of standardized shaping procedures, resulting in unstable quality of konjac tofu; traditional products are mostly semi-finished products, requiring secondary cooking, and there is a numbness problem caused by alkali residue, which limits their promotion.

[0004] Current konjac tofu processing techniques mostly use dried konjac powder as raw material. While this improves efficiency, it sacrifices the natural flavor and delicate texture of fresh konjac. Some fresh konjac processing techniques lack precise shaping control, antioxidant measures, and grading processes, resulting in either uneven texture or significant issues like browning and alkali residue. Furthermore, they lack a complete process covering fresh konjac pretreatment, shaping, and ready-to-eat processing, failing to meet modern consumers' demands for convenient, high-quality konjac tofu. Therefore, there is an urgent need for a method that directly prepares konjac tofu from fresh konjac using a complete process, controllable parameters, no need for powder production, and a method that balances traditional flavor with modern quality. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, the technical problem to be solved by this invention is to provide a method for directly preparing konjac tofu from fresh konjac. Through a complete processing flow of raw material pretreatment, antioxidant impregnation, grading and crushing, precise molding, dealkalization and detoxification, seasoning and packaging, and aseptic sterilization, the method directly uses fresh konjac as raw material to achieve integrated production from raw material to ready-to-eat finished product.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for directly preparing konjac tofu from fresh konjac includes the following steps:

[0008] 1) Select fresh or thawed konjac, remove the sprouts and rinse with clean water, remove impurities with an optical color sorter, and process into konjac cubes or konjac strips;

[0009] 2) Prepare a colloidal aqueous solution and inject it into the water tank. Then, send the konjac cubes or konjac strips treated in step 1) into the tank for soaking. After soaking, drain the surface water.

[0010] 3) Put the konjac cubes or konjac strips after soaking in step 2) into a high-speed pulverizer and grind them to a particle size of 2.5~4.5mm. Then, send them to a colloid mill for secondary grinding to obtain konjac slurry with a particle size of 75~92μm.

[0011] 4) Pour the konjac slurry obtained in step 3) into a mixing tank and mix evenly. After standing, a uniform konjac slurry is obtained.

[0012] 5) Add alkali solution to the konjac pulp obtained in step 4), stir and refine at 15~55℃ for 20~120s, adjust the pH of the system to 11.8~12.5; pour into a mold, heat-form at 75~85℃ for 7~10min to obtain konjac tofu embryo; cut the embryo into the set shape, place it at 90~95℃ for 4~6min, adjust the pH of the embryo to 8~9, and complete the shaping.

[0013] 6) Soak and wash the konjac tofu embryo obtained in step 5) with clean water, and stir to help remove alkali until the pH value of the embryo is 7~7.5;

[0014] 7) After quick-freezing the konjac tofu embryos after dealkalization in step 6), place them in a refrigerator and gradually thaw them from -10℃ to 4℃ for 6~8 hours. After thawing, put them into boiling water and cook them. After removing them, press them to dehydrate them, season them, and then vacuum seal them.

[0015] 8) After the konjac tofu embryos packaged in step 7) are floated in clean water, sterilized at high temperature, cooled to room temperature and dried, and after passing the foreign matter detection, they are packaged to obtain the ready-to-eat konjac tofu product.

[0016] Preferably, in step 1), the freezing temperature of the frozen fresh konjac is -28~-18℃, the freezing storage time is no more than 12 months, and the thawing method is to thaw it in the refrigerator to room temperature.

[0017] Preferably, in step 2), the colloidal aqueous solution is selected from any one or more of gum arabic aqueous solution, sodium carboxymethyl cellulose aqueous solution, and chitosan aqueous solution.

[0018] Preferably, in step 2), the colloidal aqueous solution is a mixed colloidal aqueous solution containing 0.015 wt% gum arabic, 0.01 wt% sodium carboxymethyl cellulose, and 0.008 wt% chitosan.

[0019] Preferably, in step 3), the initial crushing temperature is 20~35℃, and the secondary crushing temperature is 28~45℃.

[0020] Preferably, in step 5), the alkaline solution is a calcium hydroxide solution or a sodium carbonate solution, and the mass of the alkaline solution is 1.4 to 2% of the mass of the original pulp.

[0021] Preferably, in step 7), the quick-freezing temperature is -28℃ to -15℃ and the quick-freezing time is 2 to 4 hours.

[0022] Preferably, in step 7), the water is pressed and dehydrated to a moisture content of 60-85 wt%.

[0023] Preferably, in step 8), the high-temperature sterilization process is as follows: the food is placed in a high-temperature steam sterilizer at 100~121℃ for 15~35 minutes.

[0024] Preferably, in step 8), the product is dried at 54-59°C until the moisture content is 57-60 wt%.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0026] 1) This invention uses a colloidal impregnation process formed by gum arabic, sodium carboxymethyl cellulose, and chitosan, alone or in combination, to significantly inhibit the activity of polyphenol oxidase in fresh konjac, control the browning degree of the finished product to within 3.5, solve the problem of dark color of konjac tofu in traditional processes, and produce a white and uniform finished product, thus improving the appearance quality.

[0027] 2) This invention employs a graded pulverization process, which involves primary pulverization using a high-speed pulverizer and secondary pulverization using a colloid mill. This process precisely controls the pulverization temperature and particle size, and, combined with stirring and dissolving steps, significantly improves the uniformity of the konjac slurry. Furthermore, through precise thermoforming and shaping heat treatment, a stable gel structure is formed, which not only preserves the natural tender flavor of fresh konjac but also possesses an excellent chewy texture. This overcomes the shortcomings of traditional stone mill processes, such as uneven slurry distribution, a hard texture, and loss of natural flavor in dry powder raw material processing.

[0028] 3) This invention uses a triple dealkalization and detoxification process involving multiple soaking and washing, boiling in water, and gradient freeze-thaw to fully remove alkaloids and residual alkali from konjac, so that the pH value of the finished product is stable in the neutral range and the numbing sensation score is ≤1.6, reaching the level of no numbing sensation or very slight numbing sensation that can be ignored, and it can be eaten directly without secondary cooking.

[0029] 4) This invention effectively kills microorganisms through a combination of vacuum sealing packaging and high-temperature steam sterilization, along with flotation to remove damaged packaging and foreign object detection; the moisture content is controlled by drying to further improve storage stability and extend the product's shelf life. Attached Figure Description

[0030] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described below with reference to specific embodiments. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0032] The optical color sorter used in the following examples is set with a red light sensitivity of 80% and a green light sensitivity of 75%.

[0033] like Figure 1 As shown, this application provides a method for directly preparing konjac tofu from fresh konjac. This method uses fresh konjac or konjac that has been frozen at -18℃ for no more than 6 months and thawed to room temperature as raw material. The entire process eliminates the need for flour production, achieving integrated processing from raw material to ready-to-eat product. The specific process is as follows: First, the fresh konjac undergoes debudding, multiple rinses with clean water, and precise impurity removal via optical color sorting. It is then processed into konjac cubes or strips of a set size. Subsequently, it undergoes colloid impregnation to inhibit browning, followed by a grading process involving high-speed pulverization and secondary pulverization using a colloid mill. This slurry is then stirred and allowed to settle to form a uniform raw slurry. Next, a specific proportion of alkali solution is added for precise shaping and heat treatment to set the shape. After repeated soaking and washing, thorough dealkalization is achieved. Following this, the product undergoes gradient freeze-thaw cycles, boiling, pressing and dehydration, seasoning, and vacuum sealing. Finally, it undergoes high-temperature sterilization, drying, and foreign matter detection to obtain a ready-to-eat konjac tofu product with uniform color, chewy texture, no numbness, and that meets food safety standards.

[0034] Example 1

[0035] A method for directly preparing konjac tofu from fresh konjac, the specific steps of which are as follows:

[0036] 1) Select 5kg of fresh konjac, remove the sprouts and rinse 3 times with clean water, put it into an optical color sorter to remove impurities, the impurity removal rate is 99.2%; process it into 20mm×20mm konjac cubes using a dicing machine;

[0037] 2) Prepare 20L of 0.015wt% gum arabic aqueous solution, pour it into the water tank, and put the konjac cubes into the tank for immersion for 8 minutes, during which the water flow rate is maintained at 0.5m / s. After immersion, drain the surface water with a filter screen.

[0038] 3) Place the konjac cubes after impregnation into a high-speed grinder and initially grind them to a particle size of 3mm at 25℃; then send them to a colloid mill for secondary grinding twice, controlling the grinding temperature at 30℃, and finally obtain konjac slurry with a particle size of 85μm.

[0039] 4) Pour the slurry obtained in step 3) into a mixing tank, stir for 10 minutes to mix evenly, and let stand for 3 hours to allow the slurry to fully dissolve, thus obtaining a uniform konjac slurry;

[0040] 5) Add 75g of 10wt% calcium hydroxide solution (1.5% of the original slurry mass) to the konjac slurry, stir and refine at 45℃ for 60s, and adjust the pH to 12; then pour into a mold, heat-form at 80℃ for 8min to obtain konjac tofu embryo; cut the embryo into flower shapes, place it at 90℃ for 5min, adjust the pH of the embryo to 8.5, and complete the shaping.

[0041] 6) Add water at a ratio of 2:1 (by weight of water to konjac tofu embryo), soak and wash twice for 20 minutes each time, stirring to help remove alkali. The pH of the embryo is measured to be 7.2, indicating that it has reached neutrality.

[0042] 7) Place the konjac tofu embryos into a quick-freezing warehouse and quick-freeze at -18℃ for 3 hours; then place them in a refrigerator and gradually thaw them from -10℃ to 4℃ for 7 hours; after thawing, boil them in boiling water for 20 minutes, then remove them and press them at 0.3MPa to dehydrate them to a moisture content of 70wt%; add 50g of salt to season them, preserving the original flavor of fresh konjac; pack the seasoned konjac tofu embryos into aluminum foil vacuum packaging bags and vacuum seal them at -0.09MPa.

[0043] 8) Place the inner packaged konjac tofu embryo into a flotation tank for water flotation to remove damaged packaging, and then put it into a 121℃ high-temperature steam sterilizer for 18 minutes for sterilization. After sterilization, rinse the surface moisture with water, cool to room temperature, and dry at 55℃ until the moisture content is 58wt%. After passing the foreign matter test, package it into outer packaging to obtain the ready-to-eat konjac tofu product.

[0044] Example 2

[0045] A method for directly preparing konjac tofu from fresh konjac, the specific steps of which are as follows:

[0046] 1) Select 5 kg of fresh konjac that has been frozen at -18℃ for 4 months, thaw it in the refrigerator to room temperature, remove the sprouts and rinse it twice with clean water, remove impurities with an optical color sorter, and the impurity removal rate is 99.1%; process it into konjac strips of 10mm×100mm using a strip cutting machine.

[0047] 2) Prepare 20L of aqueous solution of 0.01wt% sodium carboxymethyl cellulose and 0.008wt% chitosan composite colloid, pour it into the water tank, and send the konjac strips into the tank to soak for 10min, during which the water flow rate is maintained at 0.5m / s. After soaking, use a filter screen to drain the surface water.

[0048] 3) Place the soaked konjac strips into a high-speed grinder and initially grind them to a particle size of 4mm at 30℃; then send them to a colloid mill for secondary grinding three times, controlling the grinding temperature at 40℃, and finally obtain konjac slurry with a particle size of 92μm.

[0049] 4) Pour the slurry obtained in step 3) into a mixing tank, stir for 15 minutes to mix evenly, and let stand for 4 hours to allow the slurry to fully dissolve, thus obtaining a uniform konjac slurry;

[0050] 5) Add 100g of 8wt% sodium carbonate solution (2% of the original slurry mass) to the konjac slurry, stir and refine at 50℃ for 120s, and adjust the pH of the system to 12.5; then pour into a mold, heat-form at 75℃ for 10min to obtain konjac tofu embryo; cut the embryo into flower shapes, place it at 95℃ for 4min, adjust the pH of the embryo to 9, and complete the shaping;

[0051] 6) Add water at a ratio of 2:1 (water to konjac tofu embryo by weight), soak and wash 3 times for 15 minutes each time, stirring to help remove alkali, and check the pH value of the embryo to 7, which means it has reached neutrality;

[0052] 7) Place the konjac tofu embryos into a quick-freezing warehouse and quick-freeze at -25℃ for 2.5 hours; then place them in a refrigerator and gradually thaw them from -10℃ to 4℃ for 6.5 hours; after thawing, boil them in boiling water for 18 minutes, then remove them and press them with 0.35MPa to dehydrate them to a moisture content of 65wt%; add 45g of salt to season them, preserving the original flavor of fresh konjac; pack the seasoned konjac tofu embryos into aluminum foil vacuum packaging bags and vacuum seal them at -0.095MPa.

[0053] 8) Place the inner packaged konjac tofu embryo into a flotation tank for water flotation to remove damaged packaging; then send it to a 121℃ high-temperature steam sterilizer for sterilization for 16 minutes. After sterilization, rinse the surface with water to remove moisture, cool to room temperature, and dry at 58℃ until the moisture content is 57wt%. After passing the foreign matter test, package it into outer packaging to obtain the ready-to-eat konjac tofu product.

[0054] Example 3

[0055] A method for directly preparing konjac tofu from fresh konjac, the specific steps of which are as follows:

[0056] 1) Select 5kg of fresh konjac, remove the sprouts and rinse with clean water 3 times, remove impurities with an optical color sorter with an impurity removal rate of 99.3%, and process into konjac strips of 8mm×80mm by a strip cutting machine;

[0057] 2) Prepare 20L of a composite colloid aqueous solution containing 0.015wt% gum arabic, 0.01wt% sodium carboxymethyl cellulose and 0.008wt% chitosan, pour it into a water tank, and feed the konjac strips into the tank for immersion for 12 minutes, maintaining a water flow rate of 0.4m / s during this period. After immersion, drain the surface moisture with a filter screen.

[0058] 3) Place the soaked konjac strips into a high-speed grinder and initially grind them to a particle size of 2.5 mm at 20°C; then send them to a colloid mill for secondary grinding twice, controlling the grinding temperature at 28°C, and finally obtain konjac slurry with a particle size of 80 μm.

[0059] 4) Pour the slurry obtained in step 3) into a mixing tank, stir for 8 minutes to mix evenly, and let stand for 2.5 hours to allow the slurry to fully dissolve, thus obtaining a uniform konjac slurry;

[0060] 5) Add 70g of 10wt% calcium hydroxide solution (1.4% of the original slurry mass) to the konjac slurry, stir and refine at 42℃ for 80s, and adjust the pH of the system to 11.8; then pour into a mold, heat-form at 78℃ for 9min to obtain konjac tofu embryo; cut the embryo into flower shapes, place it at 92℃ for 5min, adjust the pH of the embryo to 8.2, and complete the shaping;

[0061] 6) Add water at a ratio of 2:1 (water to konjac tofu embryo by weight), soak and wash twice for 20 minutes each time, stirring to help remove alkali. The pH value of the embryo is 7.1, indicating that it has reached neutrality.

[0062] 7) Place the konjac tofu embryos into a quick-freezing chamber and quick-freeze at -22℃ for 3.5 hours; then place them in a refrigerator and gradually thaw them from -10℃ to 4℃ for 7.5 hours; after thawing, boil them in boiling water for 19 minutes, then remove them and press them at 0.32MPa to dehydrate them to a moisture content of 62wt%; add 45g of salt and 5g of MSG to season them, preserving the original flavor of fresh konjac; pack the seasoned konjac tofu embryos into aluminum foil vacuum packaging bags and vacuum seal them at -0.092MPa.

[0063] 8) Place the inner packaged konjac tofu embryo into a flotation tank for water flotation to remove damaged packaging; then send it to a 121℃ high-temperature steam sterilizer for sterilization for 17 minutes. After sterilization, rinse the surface with water to remove moisture, cool to room temperature, and dry at 54℃ until the moisture content is 60wt%. After passing the foreign matter test, package it into outer packaging to obtain the ready-to-eat konjac tofu product.

[0064] Example 4

[0065] A method for directly preparing konjac tofu from fresh konjac, the specific steps of which are as follows:

[0066] 1) Select 5kg of fresh konjac, remove the sprouts and rinse twice with clean water, remove impurities with an optical color sorter, and the impurity removal rate is 99.2%; process into 15mm×15mm konjac cubes using a dicing machine;

[0067] 2) Prepare 20L of 0.015wt% gum arabic aqueous solution, pour it into the water tank, and put the konjac strips into the tank for immersion for 9 minutes, during which the water flow rate is maintained at 0.5m / s. After immersion, drain the surface water with a filter screen.

[0068] 3) Place the konjac cubes after impregnation into a high-speed grinder and initially grind them to a particle size of 4.5 mm at 35°C; then send them to a colloid mill for secondary grinding 4 times, controlling the grinding temperature at 45°C, and finally obtain konjac slurry with a particle size of 75 μm.

[0069] 4) Pour the slurry obtained in step 3) into a mixing tank, stir for 12 minutes to mix evenly, and let stand for 5 hours to allow the slurry to fully dissolve, thus obtaining a uniform konjac slurry;

[0070] 5) Add 90g of 8wt% sodium carbonate solution (1.8% of the original konjac slurry) to the konjac slurry, stir and refine at 55℃ for 100s, and adjust the pH of the system to 12.2; then pour into a mold and heat-form at 85℃ for 7min to obtain konjac tofu embryo; cut the embryo into flower shapes, place it at 93℃ for 6min, adjust the pH of the embryo to 8.8, and complete the shaping;

[0071] 6) Add water at a ratio of 2:1 (by weight of water to konjac tofu embryo), soak and wash 3 times for 16 minutes each time, stirring to help remove alkali. The pH value of the embryo is 7.3, which indicates that it has reached neutrality.

[0072] 7) Place the konjac tofu embryos into a quick-freezing warehouse and quick-freeze at -15℃ for 4 hours; then place them in a refrigerator and gradually thaw them from -10℃ to 4℃ for 8 hours; after thawing, boil them in boiling water for 22 minutes, then remove them and press them at 0.38MPa to dehydrate them to a moisture content of 68wt%; add 50g of salt to season them, preserving the original flavor of fresh konjac; pack the seasoned konjac tofu embryos into aluminum foil vacuum packaging bags and vacuum seal them at -0.095MPa.

[0073] 8) Place the inner packaged konjac tofu embryo into a flotation tank for water flotation to remove damaged packaging; then send it to a 121℃ high-temperature steam sterilizer for sterilization for 19 minutes. After sterilization, rinse the surface with water to remove moisture, cool to room temperature, and dry at 58℃ until the moisture content is 59wt%. After passing the foreign matter test, package it into outer packaging to obtain the ready-to-eat konjac tofu product.

[0074] Example 5

[0075] A method for directly preparing konjac tofu from fresh konjac, the specific steps of which are as follows:

[0076] 1) Select 5 kg of fresh konjac that has been frozen at -18℃ for 6 months, thaw it in the refrigerator to room temperature, remove the sprouts and rinse it with clean water 3 times, remove impurities with an optical color sorter, and the impurity removal rate is 99%; process it into konjac strips of 12mm×120mm using a strip cutting machine;

[0077] 2) Prepare 20L of 0.01wt% sodium carboxymethyl cellulose aqueous solution, pour it into the water tank, and put the konjac strips into the tank for immersion for 11 minutes, maintaining a water flow rate of 0.5m / s during this period. After immersion, drain the surface water with a filter screen.

[0078] 3) Place the soaked konjac strips into a high-speed grinder and initially grind them to a particle size of 3.5 mm at 28°C; then send them to a colloid mill for secondary grinding three times, controlling the grinding temperature at 38°C, and finally obtain konjac slurry with a particle size of 90 μm.

[0079] 4) Pour the slurry obtained in step 3) into a mixing tank, stir for 14 minutes to mix evenly, and let stand for 4.5 hours to allow the slurry to fully dissolve, thus obtaining a uniform konjac slurry;

[0080] 5) Add 80g of 10wt% calcium hydroxide solution (1.6% of the original konjac slurry) to the konjac slurry, stir and refine at 48℃ for 70s, and adjust the pH of the system to 12.1; then pour into a mold, heat-form at 82℃ for 8.5min to obtain konjac tofu embryo; cut the embryo into flower shapes, place it at 91℃ for 5min, adjust the pH of the embryo to 8.6, and complete the shaping;

[0081] 6) Add water at a ratio of 2:1 (water to konjac tofu embryo by weight), soak and wash twice for 20 minutes each time, stirring to help remove alkali. The pH value of the embryo is 7.5, indicating that it has reached neutrality.

[0082] 7) Place the konjac tofu embryos into a quick-freezing warehouse and quick-freeze at -28℃ for 2 hours; then place them in a refrigerator and gradually thaw them from -10℃ to 4℃ for 6 hours; after thawing, boil them in boiling water for 17 minutes, then remove them and press them at 0.34MPa to dehydrate them to a moisture content of 63wt%; add 48g of salt for seasoning to retain the original flavor of fresh konjac; pack the seasoned konjac tofu embryos into aluminum foil vacuum packaging bags and vacuum seal them at -0.095MPa.

[0083] 8) Place the inner packaged konjac tofu embryo into a flotation tank for water flotation to remove damaged packaging; then send it to a 121℃ high-temperature steam sterilizer for sterilization for 16 minutes. After sterilization, rinse the surface moisture with water, cool to room temperature, and dry at 59℃ until the moisture content is 58wt%. After passing the foreign matter test, package it into outer packaging to obtain the ready-to-eat konjac tofu product.

[0084] Comparative Example 1

[0085] The traditional stone mill process is used, and the specific preparation process is as follows: 5 kg of fresh konjac is selected as raw material. After manually removing the buds, it is rinsed twice with clean water without optical color sorting to remove impurities. It is then manually cut into irregular blocks. The blocks of fresh konjac are placed in a traditional stone mill, and clean water is added at a material-to-water ratio of 1:4. The stone mill is manually pushed to grind the konjac into a paste. After grinding, the paste is filtered through 80-mesh gauze to remove coarse residue, resulting in konjac slurry. An appropriate amount of quicklime powder is added to the konjac slurry to adjust it to a viscous consistency. The paste is then left to stand naturally at room temperature for 2 hours to complete the curdling process, resulting in konjac tofu embryos. After curdling, the paste is rinsed once with clean water and allowed to drain naturally to obtain traditional konjac tofu semi-finished products. These products require secondary cooking before consumption.

[0086] Example 6

[0087] The konjac tofu products obtained in Examples 1-5 and Comparative Example 1 were subjected to finished product testing. The degree of browning (ΔE value) was determined according to GB / T 15682-2008. For the tingling sensation rating, a professional sensory evaluation team of 10 people was formed. All members had received training in konjac product taste evaluation and abstained from spicy and irritating foods for 1 hour before the evaluation. The finished products were cut into 2cm×2cm×1cm pieces, numbered, and randomly provided to the evaluators. The scoring criteria were: 1 point (no tingling sensation), 2-3 points (very slight tingling, negligible), 4-6 points (moderate tingling, affecting taste), and 7-10 points (severe tingling, inedible). Scores were collected, the highest and lowest scores were discarded, and the average of the remaining 8 scores was taken. The elongation at break (toughness) was determined according to GB / T 23587-2009 "Vermicelli" tensile property test method and GB 4789.2-2020. The results are shown in Table 1.

[0088] Table 1. Finished product test results of konjac tofu products obtained in Examples 1-5 and Comparative Example 1

[0089] browning degree Numbness rating Elongation at break % Total bacterial count (CFU / g) Example 1 3.2 1.3 85.6 <![CDATA[2.3×10 2 ]]> Example 2 3.5 1.5 82.4 <![CDATA[1.9×10 2 ]]> Example 3 2.9 1.2 88.7 <![CDATA[1.7×10 2 ]]> Example 4 3.1 1.4 86.3 <![CDATA[2.1×10 2 ]]> Example 5 3.3 1.6 83.5 <![CDATA[2.0×10 2 ]]> Comparative Example 1 12.8 7.5 42.3 <![CDATA[1.8×10 5 ]]>

[0090] As shown in Table 1, this invention constructs a complete process of raw material pretreatment - antioxidant impregnation - grading and crushing - precision molding - dealkalization and detoxification - seasoning and packaging - aseptic sterilization, covering all aspects of fresh konjac processing. Compared with the semi-finished product production mode of traditional processes and the defects of some existing fresh konjac processes that lack precise control and complete processes, this invention achieves the goals of no need for flour making, controllable parameters, stable quality, and ready-to-eat safety. It not only retains the tender and chewy flavor of traditional fresh konjac tofu, but also meets the multiple demands of modern food industry for efficiency, quality, safety, and convenience, and has significant promotion and application value.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for directly preparing konjac tofu from fresh konjac, characterized by, Includes the following steps: 1) Select fresh or thawed konjac, remove the sprouts and rinse with clean water, remove impurities with an optical color sorter, and process into konjac cubes or konjac strips; 2) Prepare a colloidal aqueous solution and inject it into the water tank. Then, send the konjac cubes or konjac strips treated in step 1) into the tank for soaking. After soaking, drain the surface water. 3) Put the konjac cubes or konjac strips after soaking in step 2) into a high-speed pulverizer and grind them to a particle size of 2.5~4.5mm. Then, send them to a colloid mill for secondary grinding to obtain konjac slurry with a particle size of 75~92μm. 4) Pour the konjac slurry obtained in step 3) into a mixing tank and mix evenly. After standing, a uniform konjac slurry is obtained. 5) Add alkali solution to the konjac pulp obtained in step 4), stir and refine at 15~55℃ for 20~120s, adjust the pH of the system to 11.8~12.5; pour into a mold, heat-form at 75~85℃ for 7~10min to obtain konjac tofu embryo; cut the embryo into the set shape, place it at 90~95℃ for 4~6min, adjust the pH of the embryo to 8~9, and complete the shaping. 6) Soak and wash the konjac tofu embryo obtained in step 5) with clean water, and stir to help remove alkali until the pH value of the embryo is 7~7.5; 7) After quick-freezing the konjac tofu embryos after dealkalization in step 6), place them in a refrigerator and gradually thaw them from -10℃ to 4℃ for 6~8 hours. After thawing, put them into boiling water and cook them. After removing them, press them to dehydrate them, season them, and then vacuum seal them. 8) After the konjac tofu embryos packaged in step 7) are floated in clean water, sterilized at high temperature, cooled to room temperature and dried, and after passing the foreign matter detection, they are packaged to obtain the ready-to-eat konjac tofu product.

2. The method for directly preparing konjac tofu from fresh konjac according to claim 1, characterized in that, In step 1), the freezing temperature of the frozen fresh konjac is -28~-18℃, the freezing storage time is no more than 12 months, and the thawing method is to thaw it in the refrigerator to room temperature.

3. The method for directly preparing konjac tofu from fresh konjac according to claim 1, characterized in that, In step 2), the colloidal aqueous solution is selected from any one or more of gum arabic aqueous solution, sodium carboxymethyl cellulose aqueous solution, and chitosan aqueous solution.

4. The method for directly preparing konjac tofu from fresh konjac according to claim 3, characterized in that, In step 2), the colloidal aqueous solution is a mixed colloidal aqueous solution containing 0.015 wt% gum arabic, 0.01 wt% sodium carboxymethyl cellulose, and 0.008 wt% chitosan.

5. The method for directly preparing konjac tofu from fresh konjac according to claim 1, characterized in that, In step 3), the initial crushing temperature is 20~35℃, and the secondary crushing temperature is 28~45℃.

6. The method for directly preparing konjac tofu from fresh konjac according to claim 1, characterized in that, In step 5), the alkaline solution is a calcium hydroxide solution or a sodium carbonate solution, and the mass of the alkaline solution is 1.4 to 2% of the mass of the original pulp.

7. The method for directly preparing konjac tofu from fresh konjac according to claim 1, characterized in that, In step 7), the quick-freezing temperature is -28℃ to -15℃, and the quick-freezing time is 2 to 4 hours.

8. The method for directly preparing konjac tofu from fresh konjac according to claim 1, characterized in that, In step 7), the water is pressed and dehydrated to a moisture content of 60-85 wt%.

9. The method for directly preparing konjac tofu from fresh konjac according to claim 1, characterized in that, In step 8), the high-temperature sterilization process is as follows: the food is placed in a high-temperature steam sterilizer at 100~121℃ for 15~35 minutes.

10. The method for directly preparing konjac tofu from fresh konjac according to claim 1, characterized in that, In step 8), the product is dried at 54-59°C until the moisture content is 57-60 wt%.

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