A method for preparing cheese tofu and use of a raw material liquid containing casein

Abstract

This invention discloses a method for preparing cheese tofu and the application of a casein-containing raw material liquid, relating to the field of food manufacturing technology. The preparation method includes: mixing a raw material liquid containing 5%-25% casein with soybeans, then grinding the mixture at 80-95℃, followed by jet milling to obtain a residue-free liquid; sterilizing the residue-free liquid using VTIS direct steam injection, then flash evaporating the water to achieve a solid content ≥20% in the slurry, obtaining a sterile liquid; aseptically adding glucono-delta-lactone to the sterile liquid, and filling it into packaging boxes; heating the packaged material to 80-90℃, holding it at that temperature for 5-20 minutes, then rapidly cooling it to below 30℃, causing the sterile liquid to solidify and form cheese tofu within the packaging box. This cheese tofu combines the advantages of plant and animal proteins, significantly improving the product's nutritional value and shelf life stability.

Description

Technical Field

[0001] This invention relates to the field of food manufacturing technology, and more specifically, to a method for preparing cheese tofu and the application of a raw material liquid containing casein. Background Technology

[0002] Tofu has been a traditional food for thousands of years, and its production process is mainly based on the gelling properties of soybean protein. Traditional tofu production typically includes steps such as selecting soybeans, soaking, grinding, boiling, curdling, and shaping. In the grinding stage, conventional processes use room temperature or temperatures below 60°C for grinding. This method is insufficient to completely inactivate enzymes such as lipoxygenase in soybeans, resulting in a beany taste in the finished product.

[0003] In modern tofu production, filtration is commonly used to separate soybean pulp from soy milk. This process results in the loss of approximately 15%-20% of soluble protein and dietary fiber along with the soybean pulp. Regarding sterilization processes, conventional pasteurization (85℃ / 15 seconds) or ultra-high temperature (UHT) sterilization (135℃ / 4 seconds) cannot completely ensure the sterility of the liquid, affecting the product's shelf life. Currently, conventional tofu can only be stored for 10-20 days under refrigeration.

[0004] Therefore, the current nutritional value of tofu is insufficient to meet consumers' growing demands for both nutritional value and taste in food.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing cheese tofu and the application of a raw material liquid containing casein.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing cheese tofu, comprising: The raw material liquid containing casein is mixed with soybeans, and then ground at 80-95℃ to obtain the initial grinding liquid. The casein content in the raw material liquid containing casein is 5%-25% by mass. The initial grinding slurry is subjected to jet milling to obtain a residue-free slurry; The residue-free liquid was sterilized by direct steam injection using VTIS, followed by flash evaporation to remove water so that the solid content of the slurry was ≥20%, thus obtaining a sterile liquid. The gluconate-δ-lactone solution was aseptically added to the sterile feed solution, and then filled into a packaging box; The packaged material is heated to 80-90℃ and kept warm for 5-20 minutes, then rapidly cooled to a temperature below 30℃. The aseptic liquid solidifies and forms cheese tofu inside the packaging box.

[0008] In an optional embodiment, the casein-containing raw material liquid and the soybeans are mixed at a ratio of (0.6-3.6):1, where the casein content in the casein-containing raw material liquid is equal to the soybean protein content in the soybeans.

[0009] In an optional embodiment, the pressure of the jet mill is 15-80 MPa.

[0010] In an optional embodiment, the gluconate-δ-lactone solution comprises preparing an aqueous solution of gluconate-δ-lactone at a content of 25-30 wt%, and simultaneously adding 1-5 wt% calcium chloride or magnesium chloride, dissolving it completely, and then aseptically filtering it. Preferably, the amount of gluconate-δ-lactone solution added is calculated based on a mass-volume percentage of 0.2-0.8% for dry matter of lactone and a mass-volume percentage of 0.1-0.5‰ for dry matter of calcium chloride or magnesium chloride, where the total material volume is the combined volume of the sterile liquid and the gluconate-δ-lactone solution.

[0011] In an optional embodiment, the method for preparing cheese tofu further includes adding at least one ingredient before sterilization, wherein the amount of each ingredient added is 1%-10% of the mass of the residue-free liquid.

[0012] In an optional embodiment, the ingredients include at least one of sucrose, butter, and flavoring.

[0013] In an optional embodiment, before adding the ingredients, the residue-free liquid is subjected to enzyme inactivation treatment at a temperature of 95-110°C for 30-120 seconds.

[0014] In an optional embodiment, before aseptically adding the gluconate-δ-lactone to the aseptic solution, the aseptic solution is further subjected to aseptic homogenization at a pressure of 5-30 MPa.

[0015] Secondly, the present invention provides the application of a casein-containing raw material liquid in the preparation of cheese tofu, wherein the casein-containing raw material liquid has a casein content of 5%-25% by mass; Preferably, the casein content in the casein-containing raw liquid of the cheese tofu is (0.6-3.6):1 with the soy protein content in the soybeans.

[0016] The present invention has the following beneficial effects: The present invention provides a method for preparing cheese tofu by mixing a raw material liquid containing casein with soybeans. By adding casein to soybeans, this invention achieves amino acid complementarity, improves protein utilization, enhances digestion and absorption, prolongs nutrient supply, and may enhance antioxidant and slow-release functions. This combination combines the advantages of plant and animal proteins, significantly improving the nutritional value of the product, making it suitable for postoperative recovery, the elderly, and fitness enthusiasts. Furthermore, the invention employs a combination of high-temperature grinding and jet milling, which simultaneously destroys the soybean cell structure and inactivates endogenous enzymes, preventing them from reacting with oxygen to produce off-flavors. This effectively improves the beany taste caused by native endogenous enzymes in soybeans and achieves full bean utilization, avoiding nutrient waste. Subsequently, a combination of VTIS direct steam injection and flash evaporation is used to sterilize the residue-free liquid in a very short time, thereby maximizing the preservation of nutrients and natural flavor, significantly reducing protein denaturation and vitamin loss, and especially beneficial for preserving active proteins. Finally, glucono-delta-lactone is added using aseptic technology, and the mixture is directly heated and coagulated within the packaging box, significantly extending the shelf life and improving the stability of the cheese tofu. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram for IDDSI grading of food products; Figure 2 This is a schematic diagram of the cheese tofu provided in Embodiments 1-3 of the present invention when packaged in a packaging box; Figure 3 This is a schematic diagram of the cheese tofu provided in Embodiments 1-3 of the present invention being tested using a dinner fork. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] This invention provides a method for preparing cheese tofu, which includes the following steps: S1. Mix the raw material liquid containing casein with soybeans, and then grind it at 80-95℃ to obtain the initial grinding liquid; Casein is the most abundant protein in milk, accounting for about 80% of milk protein. It is a complete protein containing all the essential amino acids required by the human body, especially rich in lysine. Soybeans have a protein content as high as 40%, and their amino acid composition is close to human needs. In this invention, by adding casein to soybeans, amino acid complementarity can be achieved, protein utilization can be improved, digestion and absorption can be accelerated, nutrient delivery can be prolonged, and antioxidant and slow-release functions may be enhanced. This combination combines the advantages of plant and animal proteins, which can significantly improve the nutritional value of the product.

[0021] Casein digests slowly, releasing amino acids continuously after forming a curd; soy protein is absorbed quickly, providing a rapid nitrogen source. The combination creates a balanced amino acid release curve that meets immediate repair needs while maintaining a positive nitrogen balance at night or on an empty stomach, making it suitable for post-operative recovery, the elderly, and fitness enthusiasts.

[0022] In this invention, casein-containing raw liquid and soybeans are mixed at a ratio of (0.6-3.6):1, where the casein content in the raw liquid is equal to the soy protein content in the soybeans. By mixing according to the above ratio, the nutritional value of the product can be significantly improved while maintaining the product form of tofu.

[0023] In this invention, the casein-containing raw material solution contains 5%-25% by mass. Various types of casein-containing raw material solutions can be selected, and this invention does not limit their source. As long as the casein-containing raw material solution contains 5%-25% by mass, it can be used as the casein-containing raw material solution of this invention. The method for determining the casein-containing raw material solution by mass percentage can be any conventional method in the art, such as the Kjeldahl method, high-performance liquid chromatography, or the Folin-phenol method, as long as it allows for the measurement of its content.

[0024] Some typical but non-limiting sources include: concentrated high-purity β-casein liquid, casein liquid, residual casein liquid, MCC liquid / powder, casein micelle liquid / powder, etc. Casein liquid contains various types of casein, such as β-casein and αs1-casein. "Concentrated high-purity β-casein liquid" refers to a liquid product containing a high concentration of β-casein (usually with a purity >80%), obtained by separating, enriching, and concentrating from whey or casein raw materials through physical or biological techniques. "Casein liquid" is a liquid containing a large amount of casein, generally referring to skim milk or specially formulated solutions with casein as the main protein. "Residual casein liquid" is the casein liquid remaining after β-casein extraction, mainly composed of αs-casein, where the β-casein removal rate in residual casein liquid is between 10% and 80%.

[0025] It should be noted that there are no restrictions on the specific preparation methods of the above-mentioned sources. They can be prepared independently or industrial by-products can be selected as sources, as long as their casein content meets the above-mentioned range.

[0026] In this invention, a mixture of casein-containing raw material liquid and soybeans is ground at a high temperature (80-95℃). Traditionally, only soybeans are needed; the mixture is ground at room temperature to obtain soy milk, which is then boiled before proceeding with subsequent steps. This invention uses high-temperature grinding; the high temperature of 80-95℃ simultaneously destroys the soybean cell structure and inactivates endogenous enzymes, preventing them from reacting with oxygen to produce off-flavors. This effectively improves the beany taste caused by the native endogenous enzymes in soybeans.

[0027] S2. The initial grinding liquid is subjected to jet milling to obtain a residue-free liquid. This invention utilizes jet milling technology to pulverize soybean residue into micron-sized particles, achieving whole-bean utilization and avoiding nutrient waste, without the need for filtration. The pressure of the jet mill is 15-80 MPa.

[0028] Traditional tofu preparation involves filtration, which inevitably results in the loss of approximately 15%-20% of soluble protein and dietary fiber with the soybean residue. Soybean residue is typically soybean skin, rich in dietary fiber. The jet mill's purpose is to break down the soybean residue into colloidal microparticles, allowing for the use of the whole soybean without filtration, thus better preserving nutrients. Furthermore, this application includes a raw material liquid containing casein. Casein itself forms curds under high temperatures, and filtration would cause component separation, hindering the utilization of all nutrients. Therefore, the jet mill of this invention can significantly improve the nutritional value of the product.

[0029] S3. Sterilize the slurry without residue by direct steam injection using VTIS, and then flash evaporate the water to make the solid content of the slurry ≥20% to obtain a sterile slurry.

[0030] This invention employs VTIS direct steam injection for sterilization, unlike conventional pipeline sterilization methods. Because the slurry in this invention has a high solids content and contains amino acids, it is prone to clogging pipelines and undergoing Maillard reactions, leading to browning. VTIS direct steam injection, by directly spraying high-temperature steam into contact with the material, achieves sterilization in a very short time, thus maximizing the preservation of nutrients and natural flavor, significantly reducing protein denaturation and vitamin loss, and particularly beneficial for preserving active proteins. The subsequent flash evaporation removes the moisture introduced by the VTIS direct steam injection, maintaining the solids content of the slurry.

[0031] S4. Aseptically add gluconate-δ-lactone solution to the sterile feed solution, and then fill it into the packaging box.

[0032] In this invention, glucono-delta-lactone solution is added as a coagulant for sterile feed solutions. Compared to traditional brine (magnesium chloride) or gypsum (calcium sulfate), tofu made with glucono-delta-lactone has a smoother texture, better water retention, less protein loss, and no bitter taste. The glucono-delta-lactone solution comprises preparing an aqueous solution of glucono-delta-lactone at a content of 25-30 wt%, and simultaneously adding 1-5 wt% calcium chloride or magnesium chloride, dissolving it thoroughly, and then aseptically filtering. Preferably, the amount of glucono-delta-lactone solution added is calculated based on a mass-volume percentage of 0.2-0.8% for dry matter of glucono-delta-lactone and a mass-volume percentage of 0.1-0.5‰ for dry matter of calcium chloride or magnesium chloride, where the total material volume is the combined volume of the sterile liquid and the glucono-delta-lactone solution. In this invention, adding a small amount of calcium chloride or magnesium chloride can significantly improve the firmness of tofu products.

[0033] In this invention, after adding the gluconate-δ-lactone solution, there is no need to wait for it to solidify; it can be directly filled into packaging boxes, and then heated to solidify later. The size of the packaging boxes in this invention can be, for example, between 100mL and 1000mL, and the specific size can be determined according to actual needs.

[0034] S5. Heat the packaged material to 80-90℃ and keep it warm for 5-20 minutes. Then cool it rapidly to bring the temperature down to below 30℃. The aseptic liquid will solidify and form cheese tofu inside the packaging box.

[0035] This invention involves directly heating the packaged material using a hot air tunnel. Heating causes gluconate-δ-lactone to slowly hydrolyze in water to generate gluconic acid, gradually lowering the pH of the sterile solution and promoting acid-induced coagulation of soybean protein (especially β-conglycinin), forming a fine and uniform gel structure.

[0036] In addition, the method for preparing cheese tofu also includes adding at least one ingredient before sterilization, with each ingredient added at 1%-10% of the mass of the residue-free liquid. The ingredients include at least one of sucrose, butter, and flavoring.

[0037] The addition of the above ingredients can bring more cheese flavor to cheese tofu. However, it should be noted that after adding the above ingredients, the residue-free liquid needs to be subjected to enzyme inactivation treatment before adding the ingredients. The enzyme inactivation treatment temperature is 95-110℃ and the time is 30-120s.

[0038] Soy milk contains lipoxidase, which rapidly oxidizes fats. Furthermore, soy milk is high in protein and contains its own proteases. If these proteases are not pre-digested, the proteins will continue to break down, causing the soy milk to become thin, separate, settle, and develop a grainy texture. Adding butter or sucrose will further destabilize it, resulting in a poor appearance and taste. Soy milk also contains small amounts of starch and polysaccharides, as well as amylase. If the enzyme activity is not removed, it will slowly break down the sugars and starches, leading to unstable sweetness, a diluted flavor, and a tendency to turn sour and spoil.

[0039] Therefore, in this invention, by first inactivating the enzymes in the residue-free liquid before adding butter (fat), the fat is prevented from being rapidly oxidized, effectively preventing fat oxidation and avoiding the appearance of "bean-like or rancid" smells. It also effectively prevents protein decomposition, avoids layering, sedimentation, and thinning, and prevents starch / sugars from being decomposed, thus affecting sweetness and stability. Through the above method, the shelf life can be effectively extended and the stability of the shelf life can be improved.

[0040] In addition, before aseptically adding glucono-δ-lactone to the aseptic feed solution, the solution is aseptically homogenized at a pressure of 5-30 MPa. Aseptic homogenization improves the uniformity of the aseptic feed solution and prevents separation of butter and egg whites.

[0041] The cheese tofu prepared by the above method not only has a long shelf life, which can be stored at room temperature for 3-6 months, but also has high nutritional value and is suitable for the elderly.

[0042] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0043] Example 1 This embodiment provides a method for preparing cheese tofu, which includes the following steps: (1) 100 kg of casein liquid with a casein content of 10% was used as the casein-containing raw material liquid and mixed with 20 kg of dry soybeans (the soybean protein content was calculated as 35%, and the soybeans were soaked in water for 12 hours in advance). At this time, the casein content in the casein-containing raw material liquid and the soybean protein content in the soybeans were 10:7. After mixing, the mixture was ground at 85°C to obtain the initial grinding liquid. Then, the initial grinding liquid was treated by jet mill at 55 MPa to remove solid particles from the slurry, resulting in about 120 kg of residue-free liquid.

[0044] (2) The residue-free liquid was subjected to enzyme inactivation treatment at 105℃ for 30s.

[0045] (3) Add 6 kg of sucrose and 6 kg of butter to the enzyme-inactivated residue-free liquid at a ratio of 5% of the total mass of 120 kg residue-free liquid and stir thoroughly.

[0046] (4) The slag-free liquid after the ingredients are prepared is sterilized by VTIS steam direct injection at 135℃ for 0.09s. Then, the water is flash evaporated to make the solid content of the slurry ≥20% and then sterile homogenized at a pressure of 15MPa to obtain sterile liquid.

[0047] (5) Dissolve 440g of glucono-δ-lactone and 42g of anhydrous calcium chloride in 1460mL of RO water to prepare a glucono-δ-lactone solution containing approximately 30% glucono-δ-lactone and 2.8% anhydrous calcium chloride. Add the glucono-δ-lactone solution to the homogenized aseptic solution using aseptic addition technology (filtering with a 0.22-micron sterile membrane). Then, use an aseptic filling machine to fill the slurry into 250mL Tetra Pak cartons. Each package contains approximately 0.32% glucono-δ-lactone and approximately 0.3‰ anhydrous calcium chloride by mass.

[0048] (6) Heat the material after canning in step (5) to 80°C using a hot air tunnel and keep it warm for 15 minutes. Then use ice water to cool it down to 30°C. The slurry solidifies and forms cheese tofu in the packaging with a pH of 5.6.

[0049] Example 2 This embodiment is basically the same as Embodiment 1, except that in this embodiment, 3 kg of sucrose and 3 kg of butter are added to the enzyme-inactivated slurry at a ratio of 2.5% of the total mass of 120 kg of residue-free liquid and then thoroughly mixed.

[0050] Example 3 This embodiment is basically the same as Embodiment 1, except that in this embodiment, 100 kg of casein liquid with a casein content of 5% is used as the casein-containing raw material liquid and mixed with 20 kg of dry soybeans (the soybeans are calculated to have a soy protein content of 35%, and the soybeans are soaked in water for 12 hours in advance). At this time, the casein content in the casein-containing raw material liquid and the soy protein content in the soybeans are 5:7. After mixing, the mixture is ground at 85°C, and then the slurry is treated by jet mill at 55 MPa to remove solid particles from the slurry, resulting in about 120 kg of residue-free liquid.

[0051] Example 4 This embodiment provides a method for preparing cheese tofu, which includes the following steps: (1) 100 kg of casein liquid with a casein content of 25% was used as the casein-containing raw material liquid and mixed with 20 kg of dry soybeans (the soybean protein content was calculated as 35%, and the soybeans were soaked in water for 12 hours in advance). At this time, the casein content in the casein-containing raw material liquid and the soybean protein content in the soybeans were 25:7. After mixing, the mixture was ground at 80°C to obtain the initial grinding liquid. Then, the initial grinding liquid was treated by jet mill at 30 MPa to remove solid particles from the slurry, resulting in about 120 kg of residue-free liquid.

[0052] (2) The residue-free liquid was subjected to enzyme inactivation treatment at 95℃ for 120s.

[0053] (3) Add 4.8 kg of sucrose and 4.8 kg of butter to the enzyme-inactivated residue-free liquid at a ratio of 4% of the total mass of 120 kg residue-free liquid and stir thoroughly.

[0054] (4) The slag-free liquid after the ingredients are prepared is sterilized by VTIS steam direct injection at 135°C for 0.09s. Then, the water is flash-evaporated to make the solid content of the slurry ≥20% and then sterile homogenized at a pressure of 10MPa.

[0055] (5) Dissolve 60g of gluconate-δ-lactone (prepared at a mass volume percentage of 0.2% for dry matter of the whole material) in 300mL of RO water, and add it to the homogenized slurry using aseptic addition technology (filtered with a 0.22-micron sterile membrane). Then, use an aseptic filling machine to fill the slurry into 250mL Tetra Pak bricks.

[0056] (6) Heat the material after canning in step (5) to 80°C using a hot air tunnel and keep it warm for 20 minutes. Then use ice water to cool it down to 30°C. The slurry solidifies and forms cheese tofu inside the packaging.

[0057] Example 5 This embodiment provides a method for preparing cheese tofu, which includes the following steps: (1) 100 kg of casein liquid with a casein content of 15% was used as the casein-containing raw material liquid and mixed with 20 kg of dry soybeans (the soybeans were soaked in water for 12 hours in advance, with the casein content in the raw material liquid being 15:7. After mixing, the mixture was ground at 95°C to obtain the initial grinding liquid. Then, the initial grinding liquid was treated by jet mill at 60 MPa to remove solid particles from the slurry, resulting in about 120 kg of residue-free liquid.

[0058] (2) The residue-free liquid was subjected to enzyme inactivation treatment at 110℃ for 30s.

[0059] (3) Add 7.2 kg of sucrose and 7.2 kg of butter to the enzyme-inactivated residue-free liquid at a ratio of 6% of the total mass of 120 kg residue-free liquid and stir thoroughly.

[0060] (4) The slag-free liquid after the ingredients are prepared is sterilized by VTIS steam direct injection at 135°C for 0.09s. Then, the water is flash-evaporated to make the solid content of the slurry ≥20% and then sterile homogenized at a pressure of 20MPa.

[0061] (5) Dissolve 90g of gluconate-δ-lactone (prepared at a mass volume percentage of 0.3% for dry matter of the whole material) in 300mL of RO water, and add it to the homogenized slurry using aseptic addition technology (filtered with a 0.22-micron sterile membrane). Then, use an aseptic filling machine to fill the slurry into 250mL Tetra Pak bricks.

[0062] (6) Heat the material after canning in step (5) to 90°C using a hot air tunnel, keep it warm for 5 minutes, and then cool it quickly with ice water to make the temperature lower than 30°C. The slurry solidifies and forms cheese tofu inside the packaging.

[0063] Comparative Example 1 This comparative example provides a conventional method for preparing tofu, which includes: Soaking soybeans: Wash dried soybeans and soak them in cold water for 3-6 hours (10-12 hours in winter) until the soybeans are fully hydrated, expanded in volume, and have no hard core when squeezed. Change the water 1-2 times during this period to prevent odor. Making the soy milk: Add enough water to the soaked soybeans and grind them 2-3 times with a colloid mill until they are smooth and free of obvious particles; filter the soy milk into a pot with a filter cloth / screen, squeeze out the soy pulp, and you will get raw soy milk. Cooking the soy milk: Pour the soy milk into a clean, non-stick pan without water or oil, and cook over medium-low heat, stirring constantly to prevent it from sticking to the bottom. After bringing it to a boil over high heat, reduce the heat to low and maintain for 5-8 minutes, until the foam disappears, the soy milk thickens, and the aroma of soybeans is strong (avoid "false boiling" and ensure it is fully cooked). Cooling: Turn off the heat after cooking the soy milk and let it stand for 2-3 minutes to cool down to 80-85℃. Dissolve the glucono-delta-lactone: Take glucono-delta-lactone and dissolve it thoroughly in 10-20 ml of cooled boiled water / purified water, then pour it into the bottom of an insulated container / mold. Pour the cooled soy milk quickly into the glucono-delta-lactone solution from a height, and gently shake the container 2-3 times to mix well (do not stir vigorously to avoid damaging the gel structure); skim off the surface foam, cover the container, keep it warm and let it stand for 15-20 minutes until the soy milk is completely coagulated into a smooth tofu pudding. Pressing: Line the mold with a layer of damp gauze, gently scoop the solidified tofu into it, fold the gauze to wrap it; cover the mold with the lid, press it with a heavy object, and press for 20-30 minutes (the longer the pressing time, the firmer the tofu; 10-15 minutes is for a super tender texture, and more than 40 minutes is close to firm tofu). Demolding: Remove the heavy objects, peel off the gauze, invert the tofu to remove it, cut it into pieces and it is ready to eat.

[0064] Comparative Example 2 This comparative example is basically the same as Example 1, except that no raw material liquid containing casein was added in this comparative example; soybeans were used directly for preparation. The shelf life of this comparative example is basically the same as that of Example 1, but the nutritional value of Example 1 is higher, while the nutritional value of Comparative Example 2 is close to that of Comparative Example 1.

[0065] Comparative Example 3 This comparative example is basically the same as Example 1, except that the casein-containing raw material liquid is replaced with a whey protein-containing raw material liquid, wherein the whey protein content is 20%. It was found that the tofu could not be formed, and instead, large clumps of flocculent tofu floated in the liquid.

[0066] Comparative Example 4 This comparative example is essentially the same as Example 1, except that high-temperature grinding was not performed in this comparative example; instead, the mixture was ground at room temperature and then heated to 85°C. The results showed that a distinct beany odor was produced during the grinding process, and the final product, cheese tofu, also had a beany odor, failing to possess the characteristic of being odor-free.

[0067] Comparative Example 5 This comparative example is essentially the same as Example 1, except that jet milling was not used in this comparative example; instead, filtration was employed to remove the soybean residue from the initial grinding liquid. The results show that a large amount of soybean residue exists in the soy milk, requiring filtration, making it impossible to use whole soybeans for tofu production, thus significantly reducing its nutritional value.

[0068] Comparative Example 6 This comparative example is basically the same as Example 1, except that the enzyme inactivation treatment was omitted in this comparative example. The results show that during the mixing process, the soy milk undergoes browning and produces an oxidized taste under the action of oxygen and endogenous enzymes.

[0069] Experimental Example 1 The cheese tofu prepared in Examples 1-5 and Comparative Examples 1-2 and 5-6 were subjected to texture analysis. Due to significant defects in the finished product of Comparative Example 3-4, it was not further analyzed. The detection items, their limits of quantitation, limits of detection, and detection methods are shown in Table 1. Table 1. Statistical table of limits of quantitation, limits of detection, and detection methods for different detection items.

[0070] Please refer to Tables 2 and 3 for the test results: Table 2. Statistical table of detection results for different embodiments

[0071] Table 3. Statistical table of test results for different comparison ratios

[0072] Experimental Example 2 Color difference was measured on the products prepared in Example 1 and Comparative Example 2. In the color difference measurement data, L, a, and b are the values ​​published by the International Commission on Illumination (CIE) in 1976. a The core parameter of the b* (Lab) color space is the international standard color quantification system currently used in industrial color measurement, printing, textiles, coatings, food and other fields; ΔE is the total color difference value calculated based on the Lab value, used to quantify the overall visual difference between two colors.

[0073] Core definitions and numerical patterns of each parameter (1) L value (Lightness) Core meaning: It represents the lightness or darkness of a color, and is completely independent of the brightness dimension of color.

[0074] Numerical range: fixed at 0~100, L=0 represents pure black (no light reflection at all), L=100 represents ideal pure white (full light reflection).

[0075] Numerical pattern: The larger the L value, the brighter and lighter the color; the smaller the L value, the darker and deeper the color.

[0076] (2) a value (red-green axis, red-green color intensity) Core meaning: It represents the direction and saturation of color shift in the red-green hue, based on the visual characteristic that "red and green cannot be perceived simultaneously" of the human eye.

[0077] Numerical range: -128 to +127, with the origin a=0 being neutral gray (no red / green tones).

[0078] Numerical pattern: +a is red, the larger the value, the more intense the red; -a is green, the smaller the value (the larger the negative value), the more intense the green.

[0079] (3) b value (yellow-blue axis, yellow-blue tint) Core meaning: Represents the direction and saturation of color offset in the yellow-blue hue, and together with the a-axis, determines the hue and saturation of the color.

[0080] Numerical range: -128 to +127, with the origin b=0 being neutral gray (without yellow / blue tones).

[0081] Numerical pattern: +b is yellow, and the larger the value, the more prominent the yellow; -b is blue, and the smaller the value (the larger the negative value), the more prominent the blue.

[0082] (4) E (ΔE, total color difference) Core meaning: It measures the Euclidean distance between two colors in Lab 3D space, which is an overall color difference index that integrates three dimensions: lightness, red-green, and yellow-blue.

[0083] The basic general calculation formula (CIE 1976) is: ΔE=√[(ΔL)² + (Δa)² + (Δb)²], where ΔL, Δa, and Δb are the differences between the sample and the standard sample in the corresponding dimensions.

[0084] Numerical pattern: The larger the ΔE value, the more obvious the visual difference between the two colors; it can only reflect the overall size of the color difference, but cannot reflect the specific direction of color deviation.

[0085] For industry-standard ΔE human eye resolution references, please refer to Table 4: Table 4. Industry-standard ΔE human eye resolution reference standard

[0086] Please refer to Table 5 for the test results: Table 5. Comparison of color difference results between Example 1 and Comparative Example 2

[0087] As can be seen from Table 5, the product with added casein in Example 1 showed a significantly lower degree of color change during its shelf life compared to the sample without added casein in Comparative Example 2. The product without added casein showed a very obvious color change during its shelf life, turning noticeably yellow. This color change also resulted in a significantly shorter shelf life compared to the sample with added casein.

[0088] Experiment Example 3 The cheese tofu prepared in Examples 1-3 above was subjected to food grade classification tests and texture hardness tests.

[0089] (1) Food grade classification test Test tools: Syringe: 10 mL syringe, needle and plunger removed; the distance between the 10 mL mark and the 0 mL mark is approximately 61.5 mm. Standard stainless steel fork: fork width approximately 15 mm, fork gap spacing approximately 4 mm.

[0090] Test method: Remove and discard the plunger of the syringe. Hold the syringe nozzle with your finger and inject liquid into the syringe up to the 10mL limit. Release your finger from the nozzle and start timing simultaneously. After 10 seconds, hold the nozzle with your finger to stop the liquid flow. Perform the test in parallel three times and take the average value as the product's IDDSI rating.

[0091] The descriptions of the food grade classification status are shown in Table 6 and Figure 1 : Table 6. Statistical Table Describing the State at Different Levels

[0092] Note: Among them, the food suitable for the elderly and easy to eat (food for elderly care) is TSATA084-2025. (2) Texture hardness test The total texture (TPA) measurement process mimics the process of chewing food in the human mouth. By analyzing the force and time spectrum of the material during the movement of the probe, a series of texture parameters of the material can be obtained.

[0093] Test conditions: Probe: Model P / 35, 35mm disc probe. 2*2*2 cm cubic sample, test rate 100 mm / min, trigger force 5g, compression deformation rate 50%. See Table 7 for test results.

[0094] Table 7. Statistical table of test results for different examples

[0095] As can be seen from the table above, the IDDSI grades of Examples 1-3 of this application are all 7ec / 7, proving that they belong to the category of easily chewable, conventional food-grade tofu. The other examples and comparative examples, as long as the tofu product is prepared, all meet the 7ec / 7 grade. The cheese's hardness, within the above range, satisfies the requirements of a delicate texture, moderate firmness, and non-roughness. Example 1 has the highest overall hardness, which is beneficial for maintaining structural integrity during long-term storage and transportation and is suitable for Chinese cooking.

[0096] Experiment Example 4 The cheese tofu prepared in Examples 1-5 and Comparative Examples 1-2 and 5-6 were analyzed for amino acids according to GB5009.124-2016. The evaluation methods are shown in Table 8. Table 8. List of evaluation methods for amino acid analysis

[0097] The raw results of amino acid evaluation, PDCAAS score, and DIAAS chemical score are shown in Table 9. For the analysis of the score results calculated based on Table 9, please refer to Table 10.

[0098] Table 9. Statistical table of amino acid score data for different examples

[0099] Table 10. Statistical table of amino acid score analysis results for different examples

[0100] It should be noted that the protein digestibility of all amino acids is 1, therefore the digestible amino acid content = sample amino acid content; PDCAAS calculation formula: Individual score = Digestible amino acid content ÷ Reference value in the PDCAAS reference amino acid pattern (FAO1991_2-5), final PDCAAS (%) = 100 × minimum value of all individual scores. DIAAS calculation formula: Individual score = Digestible amino acid content ÷ DIAAS reference value * 100. For example, taking the final PDCAAS as an example, in Example 1, comparing all 9 PDCAAS scores, the minimum value is 1.039, corresponding to tryptophan Trp (a limiting amino acid); multiplying the minimum value by the digestibility (digestibility is 1), we get PDCAAS = 1.039. Since the PDCAAS result is greater than 1, according to the truncation rule, the PDCAAS of Example 1 is 1. Taking the final DIAAS as an example, in Example 1, comparing all 9 DIAAS chemical scores (DIAAS chemical score = digestible amino acid / reference value in the DIAAS reference amino acid pattern), the minimum value is 116.40, corresponding to the amino acid SAA (Met+Cys), resulting in DIAAS=116.40. Since the DIAAS result is greater than 100, according to the truncation, DIAAS=100.

[0101] In Comparative Example 1, comparing all 9 PDCAAS scores, the minimum value was 0.651, corresponding to the amino acid is isoleucine Ile (a limiting amino acid); therefore, PDCAAS = 0.651, which is less than the cutoff value, meaning PDCAAS remains at 0.651. Taking the final DIAAS as an example, in Comparative Example 1, comparing all 9 DIAAS chemical scores, the minimum value was 60.76, corresponding to the amino acid is isoleucine Ile; therefore, DIAAS = 60.76, which is less than the cutoff value, meaning PDCAAS remains at 60.76.

[0102] The calculation methods for PDCAAS and DIAAS in the remaining embodiments and Comparative Example 1 are the same as those described above, and will not be repeated here.

[0103] The term "truncate" means setting an upper limit for the calculated value. If the calculated value exceeds this limit, it is forcibly changed to the upper limit; otherwise, it remains unchanged. This is a unified standard stipulated by the FAO (Food and Nutrition Organization) to ensure fair comparison of protein scores from different foods and prevent scores from becoming infinitely high.

[0104] (1) PDCAAS is truncated to 1.00 Rule: PDCAAS can only be calculated up to 1.00. If the calculated result is ≥1.00, force it to be written as 1.00. If the calculated result is <1.00, the value remains unchanged. (2) DIAAS is truncated to 100 Rule: DIAAS (%) can only be reported up to 100%. If the calculated result is ≥100, force it to be written as 100. If the calculated result is less than 100, the value remains unchanged. From the table above, Figure 2 and Figure 3 It can be seen that Examples 1 and 2, according to T / CNSS 046-2026 "Specifications for Protein Quality Labeling in Prepackaged Foods", have PDCAAS≥0.9 and DIAAS≥100, indicating high-quality protein. Examples 3, 4, and 5, due to changes in the ratio of the two protein sources, have slightly lower amino acid nutritional values ​​compared to Examples 1 and 2, but are still higher than Comparative Examples 1 and 2.

[0105] Comparative Example 5, which did not employ whole bean processing, had the lowest nutritional value. Comparative Example 6, due to uninactivated enzymes causing browning and oxidation of amino acids, had a lower amino acid nutritional value compared to Example 1. Furthermore, because of browning and oxidation, although commercially sterile conditions were maintained, long-term storage was still not feasible.

[0106] In summary, the method for preparing cheese tofu provided by this invention involves mixing a raw material liquid containing casein with soybeans to prepare tofu. By adding casein to soybeans, this invention achieves amino acid complementarity, improves protein utilization, enhances digestion and absorption rhythm, prolongs nutrient supply, and may enhance antioxidant and slow-release functions. This combination combines the advantages of plant and animal proteins, significantly improving the nutritional value of the product, making it suitable for postoperative recovery, the elderly, and fitness enthusiasts. Furthermore, the combination of high-temperature grinding and jet milling in this invention simultaneously destroys the soybean cell structure and inactivates endogenous enzymes, preventing them from reacting with oxygen to produce off-flavors. This effectively improves the beany taste caused by native endogenous enzymes in soybeans and achieves full bean utilization, avoiding nutrient waste. Subsequently, the combination of VTIS direct steam injection and flash evaporation allows for sterilization of the residue-free liquid in a very short time, thereby maximizing the preservation of nutrients and natural flavor, significantly reducing protein denaturation and vitamin loss, and particularly benefiting the preservation of active proteins. By adding glucono-δ-lactone using aseptic technology, the product is directly heated and coagulated inside the packaging box, which significantly improves the shelf life and stability of the cheese tofu.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing cheese tofu, characterized in that, It includes: The raw material liquid containing casein is mixed with soybeans, and then ground at 80-95℃ to obtain the initial grinding liquid. The casein content in the raw material liquid containing casein is 5%-25% by mass. The initial grinding slurry is subjected to jet milling to obtain a residue-free slurry; The residue-free liquid was sterilized by direct steam injection using VTIS, followed by flash evaporation to remove water so that the solid content of the slurry was ≥20%, thus obtaining a sterile liquid. The gluconate-δ-lactone solution was aseptically added to the sterile feed solution, and then filled into a packaging box; The packaged material is heated to 80-90℃ and kept warm for 5-20 minutes, then rapidly cooled to a temperature below 30℃. The aseptic liquid solidifies and forms cheese tofu inside the packaging box.

2. The method for preparing cheese tofu according to claim 1, characterized in that, The casein-containing raw material solution and the soybeans are mixed at a ratio of (0.6-3.6):1, where the casein content in the casein-containing raw material solution is equal to the soybean protein content in the soybeans.

3. The method for preparing cheese tofu according to claim 1, characterized in that, The pressure of the jet mill is 15-80 MPa.

4. The method for preparing cheese tofu according to claim 1, characterized in that, The gluconate-δ-lactone solution comprises preparing an aqueous solution of gluconate-δ-lactone at a content of 25-30 wt%, and simultaneously adding 1-5 wt% calcium chloride or magnesium chloride, dissolving it completely, and then aseptically filtering it. The amount of gluconate-δ-lactone solution added is calculated based on the following: the dry matter of lactone accounts for 0.2-0.8% of the total material volume, and the dry matter of calcium chloride or magnesium chloride accounts for 0.1-0.5‰ of the total material volume. The total material volume is the combined volume of the sterile liquid and the gluconate-δ-lactone solution.

5. The method for preparing cheese tofu according to claim 1, characterized in that, The method for preparing cheese tofu further includes adding at least one ingredient before sterilization, wherein the amount of each ingredient added is 1%-10% of the mass of the residue-free liquid.

6. The method for preparing cheese tofu according to claim 5, characterized in that, The ingredients include at least one of sucrose, butter, and flavoring.

7. The method for preparing cheese tofu according to claim 5, characterized in that, Before adding the ingredients, the residue-free liquid is subjected to enzyme inactivation treatment at a temperature of 95-110°C for 30-120 seconds.

8. The method for preparing cheese tofu according to claim 5, characterized in that, Before aseptically adding the gluconate-δ-lactone to the aseptic solution, the process further includes aseptic homogenizing the aseptic solution at a pressure of 5-30 MPa.

9. The application of a casein-containing raw material liquid in the preparation of cheese and tofu, characterized in that, The casein content in the raw material solution containing casein is 5%-25% by mass; The casein content in the raw material liquid containing casein in the cheese tofu is (0.6-3.6):1 with the soy protein content in soybeans.

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