Preparation method of long-lasting, room-temperature-stored silken tofu

Abstract

This invention discloses a method for preparing long-lasting, room-temperature-stored silken tofu, comprising the following steps: S1. Soy milk refining; S2. Coagulant mixing; S3. Aseptic filling and sealing; S4. High-temperature sterilization; S5. Temperature-controlled coagulation and shaping; S6. Cooling and setting. Using temperature-responsive slow-release capsules as the coagulant, the capsule shell remains intact during the 95℃-105℃ high-temperature sterilization stage, effectively preventing premature release of glucono delta-lactone and avoiding abnormal coagulation of soy protein during sterilization. After sterilization, the temperature is lowered to 85℃±2℃, causing the capsule shell to rapidly swell and dissolve, stably releasing the coagulant. This allows glucono delta-lactone to react uniformly with soy protein, gently gelling to form a tofu with a delicate texture, smooth mouthfeel, and uniform internal structure. Combined with the high-barrier properties of Tetra Pak aseptic packaging and the gradient cooling and setting process, the product can be stored for up to 12 months at room temperature in the dark, effectively ensuring the stability of its flavor and quality.

Description

Technical Field

[0001] This invention belongs to the field of food production technology, and in particular relates to a method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu. Background Technology

[0002] Silken tofu is a gel-type soy product made primarily from high-quality soybeans and using glucono-delta-lactone as a protein coagulant. Compared to traditional brine tofu and gypsum tofu, silken tofu has a finer texture, smoother mouthfeel, higher water content, a delicate soy aroma, and is more easily absorbed. It contains plant protein, unsaturated fatty acids, soy lecithin, and various trace elements, meeting the health and light food consumption needs of modern people. It occupies an important market position in the catering, family consumption, and ready-to-eat food sectors and is widely favored by consumers at home and abroad.

[0003] Currently, conventional silken tofu on the market, although sterilized during the production process, still requires cold chain transportation and refrigerated storage throughout the process, and its shelf life is only 30-45 days. If high-temperature sterilization is directly used to extend its shelf life, it will cause glucono-δ-lactone to dissolve prematurely at high temperatures and trigger the coagulation of soy protein, resulting in a rough texture, clumping, honeycomb structure, severe water separation, and a hard texture, which seriously affects the product quality. Summary of the Invention

[0004] To address the problems in the prior art, the present invention proposes the following technical solution: A method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu includes the following steps: S1. Refined Soy Milk: High-quality non-GMO soybeans are selected and processed in sequence through washing, soaking, grinding, coarse filtration, fine filtration, deodorization, and concentration adjustment to obtain cooked soy milk with uniform concentration and no impurities. The cooked soy milk is then cooled to room temperature for later use. S2. Coagulant Mixing: Add the temperature-responsive sustained-release capsule coagulant to room-temperature cooked soy milk in a preset ratio, and use low-speed stirring to evenly disperse the capsule coagulant in the soy milk; S3. Aseptic filling and sealing: The well-mixed soy milk liquid is transported to the Tetra Pak aseptic filling production line, where Tetra Pak packaging is filled and sealed in an aseptic environment to form a closed aseptic packaging unit. S4. High-temperature sterilization treatment: After the Tetra Pak products are filled and sealed, they are sent into the sterilization equipment for rapid high-temperature constant-temperature sterilization. During the sterilization process, the capsule shell remains intact and the soy milk remains in a liquid and sterile state. S5. Temperature-controlled solidification and molding: After sterilization, the product is gradually cooled to 85℃±2℃ and kept warm for 30-40 minutes. The capsule shell quickly swells and dissolves to release gluconate-δ-lactone, triggering uniform coagulation of soy protein. S6. Cooling and Shaping: The solidified product is cooled to room temperature in stages using a gradient cooling process, and the tofu texture gradually stabilizes, resulting in Tetra Pak packaged silken tofu.

[0005] As a preferred embodiment of the above technical solution, the temperature-responsive sustained-release capsule coagulant includes a core and a heat-resistant edible capsule shell, wherein the core of the temperature-responsive sustained-release capsule coagulant is food-grade glucono-δ-lactone.

[0006] As a preferred embodiment of the above technical solution, the temperature-responsive sustained-release capsule has a particle size of 0.8-1.2 mm and a capsule shell wall thickness of 0.15-0.25 mm.

[0007] As a preferred embodiment of the above technical solution, the outer shell of the heat-resistant edible capsule is a modified edible film made of hydroxypropyl methylcellulose, sodium alginate, and chitosan, with the mass ratio of hydroxypropyl methylcellulose, sodium alginate, and chitosan being 65:20:15.

[0008] As a preferred embodiment of the above technical solution, the proportion of the capsule coagulant added is 0.3% of the weight of the soy milk.

[0009] As a preferred embodiment of the above technical solution, the low-speed stirring speed in step S2 is 30-50 r / min, and the stirring time is 3-5 min.

[0010] As a preferred embodiment of the above technical solution, the high-temperature constant temperature sterilization temperature in step S4 is 95℃-105℃, and the sterilization time is 10-25min.

[0011] As a preferred embodiment of the above technical solution, the segmented gradient cooling in S6 includes the following: first, cooling to 55-60℃ at a rate of 1.5℃ / min, and holding at a constant temperature for 15min; then slowly cooling to room temperature of 25-30℃ at a rate of 1℃ / min.

[0012] The beneficial effects of this invention are as follows: This product utilizes temperature-responsive, slow-release capsules encapsulating food-grade glucono-delta-lactone as a coagulant. The high-temperature resistant outer shell, composed of precisely proportioned hydroxypropyl methylcellulose, sodium alginate, and chitosan, maintains its integrity during the 95℃-105℃ high-temperature sterilization process. This effectively prevents premature release of glucono-delta-lactone, avoiding abnormal coagulation, clumping, honeycomb structure formation, and severe water separation of soy protein during sterilization, ensuring the soy milk remains in a liquid, sterile state throughout the sterilization process. After sterilization, the temperature is lowered to 85℃±2℃, causing the capsule shell to rapidly swell, dissolve, and stably release the coagulant. This allows glucono-delta-lactone to react evenly with the soy protein, gently gelling to form a tofu-like texture with a smooth mouthfeel and uniform internal structure. Combined with the high-barrier properties of Tetra Pak aseptic packaging and gradient cooling and shaping process, the product can be stored for up to 12 months at room temperature away from light, without the need for cold chain storage and transportation. It does not separate, shrink, age, or spoil during long-term storage, maintaining stable flavor and quality. No additional preservatives are added, making it safe and reliable for consumption. Attached Figure Description

[0013] Figure 1 The diagram shown is a process flow chart of an embodiment.

[0014] Figure 2 The diagram shown is a process flow chart of an embodiment. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings.

[0016] Figure 1 The preparation method of long-lasting, room-temperature-stored glucono-delta-lactone tofu includes the following steps: S1. Refined Soy Milk: Select high-quality non-GMO soybeans and soak them in clean water at room temperature for 8-12 hours, with the soaking water temperature controlled at 20-25℃, until the soybean water absorption rate is 110%-130% and the soybeans are plump and without a hard core. Then, after grinding, coarse filtration, fine filtration, deodorization, and concentration adjustment, a cooked soy milk with a solids concentration of 11%-13%, uniform concentration, and no impurities is obtained. Cool the cooked soy milk to room temperature of 25-30℃ for later use.

[0017] S2. Coagulant Mixing: Add the temperature-responsive sustained-release capsule coagulant to room-temperature cooked soy milk at a preset ratio. The addition ratio of the capsule coagulant is 0.3% of the weight of the soy milk. Use low-speed stirring to evenly disperse the capsule coagulant in the soy milk. The low-speed stirring speed is 30-50 r / min and the stirring time is 3-5 min. The temperature-responsive sustained-release capsule coagulant includes a core and a heat-resistant edible capsule shell, wherein the core of the temperature-responsive sustained-release capsule coagulant is food-grade glucono-δ-lactone.

[0018] The temperature-responsive sustained-release capsules have a particle size of 0.8-1.2 mm and a capsule shell wall thickness of 0.15-0.25 mm.

[0019] The outer shell of the heat-resistant edible capsule is a modified edible film made of hydroxypropyl methylcellulose, sodium alginate, and chitosan, with the mass ratio of hydroxypropyl methylcellulose, sodium alginate, and chitosan being 65:20:15.

[0020] S3. Aseptic filling and sealing: The well-mixed soy milk mixture is transported to the Tetra Pak aseptic filling production line, where Tetra Pak packaging is filled and sealed in an aseptic environment to form a closed aseptic packaging unit.

[0021] S4. High-temperature sterilization treatment: The Tetra Pak products, after being filled and sealed, are sent to a sterilization device for rapid high-temperature constant-temperature sterilization. The high-temperature constant-temperature sterilization temperature is 95℃-105℃, and the sterilization time is 10-25 minutes. During the sterilization process, the capsule shell remains intact, and the soy milk remains in a liquid and sterile state.

[0022] S5. Temperature-controlled solidification and molding: After sterilization, the product is gradually cooled to 85℃±2℃ and kept at that temperature for 30-40 minutes. The capsule shell rapidly swells and dissolves, releasing gluconate-δ-lactone, which triggers uniform coagulation of soy protein.

[0023] S6. Cooling and Shaping: The solidified product is cooled to room temperature in stages using a gradient cooling method. The staged gradient cooling includes the following steps: first, cooling to 55-60℃ at a rate of 1.5℃ / min and holding at a constant temperature for 15min; then, slowly cooling to room temperature (25-30℃) at a rate of 1℃ / min. The tofu texture gradually stabilizes, resulting in Tetra Pak packaged silken tofu.

[0024] This product utilizes temperature-responsive, slow-release capsules encapsulating food-grade glucono-delta-lactone as a coagulant. The high-temperature resistant outer shell, composed of precisely proportioned hydroxypropyl methylcellulose, sodium alginate, and chitosan, maintains its integrity during the 95℃-105℃ high-temperature sterilization process. This effectively prevents premature release of glucono-delta-lactone, avoiding abnormal coagulation, clumping, honeycomb structure formation, and severe water separation of soy protein during sterilization, ensuring the soy milk remains in a liquid, sterile state throughout the sterilization process. After sterilization, the temperature is lowered to 85℃±2℃, causing the capsule shell to rapidly swell, dissolve, and stably release the coagulant. This allows glucono-delta-lactone to react evenly with the soy protein, gently gelling to form a tofu-like texture with a smooth mouthfeel and uniform internal structure. Combined with the high-barrier properties of Tetra Pak aseptic packaging and gradient cooling and shaping process, the product can be stored for up to 12 months at room temperature away from light, without the need for cold chain storage and transportation. It does not separate, shrink, age, or spoil during long-term storage, maintaining stable flavor and quality. No additional preservatives are added, making it safe and reliable for consumption.

[0025] Example S1. Refined Soy Milk: Select non-GMO high-quality soybeans, wash them with clean water to remove impurities, soak them in water at 22℃ for 10 hours, the soybean water absorption rate reaches 120% and there is no hard core; after grinding, coarse filtration, 180-mesh fine filtration, vacuum deodorization, the solids concentration of cooked soy milk is adjusted to 12%, and cooled to 28℃ for use. S2. Coagulant Mixing: Add temperature-responsive sustained-release capsule coagulant at 0.3% of the weight of soy milk; the capsule core is glucono-δ-lactone, and the outer shell is made of hydroxypropyl methylcellulose, sodium alginate, and chitosan in a mass ratio of 65:20:15; the capsule particle size is 1.0 mm, and the outer shell wall thickness is 0.20 mm; stir at a low speed of 40 r / min for 4 min to ensure that the capsules are evenly dispersed and without breakage; S3. Aseptic filling and sealing: The liquid is fed into the Tetra Pak aseptic filling line, and filled and heat-sealed in an aseptic environment to form a closed and individual package; S4. High-temperature sterilization: Place the Tetra Pak into a spray sterilizer, set the sterilization temperature to 100℃, and sterilize at a constant temperature for 18 minutes. During the sterilization process, the capsule shell remains intact and does not break, and the soy milk remains liquid. S5. Temperature-controlled coagulation and molding: After sterilization, gradually cool down to 85℃, keep warm and stand for 35 minutes, the capsule shell swells and dissolves, releasing gluconate-δ-lactone, and the soybean protein gels and solidifies uniformly. S6. Cooling and setting: First, cool down to 58℃ at 1.5℃ / min and let stand at a constant temperature for 15min; then cool down to 28℃ at 1℃ / min and let stand to set, thus obtaining room temperature long-lasting silken tofu.

[0026] like Figure 2As shown, to verify the room temperature storage stability, edible quality, and safety performance of the product in this embodiment, multiple parallel tests were conducted on the prepared silken tofu. The tofu was tested after being fresh (0 months), stored at room temperature (25±5℃, relative humidity 40%-70%) for 6 months, and after 12 months. The tests covered storage stability, texture, water-holding capacity, acidity, flavor, and microbial safety. The testing methods were based on GB 2711-2014 "Non-Fermented Soy Products", GB 4789 series national standards for microbial testing, the TA-XT2i texture analyzer testing standard, and the centrifugal method for determining water-holding capacity. The average values ​​of each group were summarized as follows: Storage at room temperature and sensory indicators: Storage conditions: 25±5℃, relative humidity 40%~70%; Shelf life at room temperature: ≥12 months; no swelling, mold, or separation of water after 12 months of storage. Sensory characteristics: The texture is delicate with no honeycomb holes, the cut surface is smooth, and the aroma of soybeans is rich and fresh, without any sour, bitter or off-flavors.

[0027] Texture indicators: Fresh finished product: Hardness 200g, elastic recovery rate 87%; After 6 months of storage: hardness 208g, elastic recovery rate 86%; After 12 months of storage: hardness 215g, elastic recovery rate 84%; The hardness change rate during the entire storage process is ≤7.5%, with no obvious aging and hardening.

[0028] Water holding capacity index: Fresh finished product: moisture retention rate 93.2%; Storage for 6 months: water retention rate 90.5%; After 12 months of storage: water retention rate 88.6%; After 12 months of storage, the volume of free water inside the packaging is ≤3% of the total volume, with no obvious water separation.

[0029] Acidity index (as lactic acid): Fresh product: 0.09g / 100g; Storage for 6 months: 0.12g / 100g; Storage for 12 months: 0.14g / 100g; The acidity throughout the process is ≤0.15g / 100g, with no rancid taste.

[0030] Microbiological indicators: Fresh finished product: Total bacterial count ≤50 CFU / g, no coliform bacteria detected, no Salmonella, Staphylococcus aureus, or Shigella detected; After 12 months of storage: total bacterial count ≤80 CFU / g, coliform bacteria ≤10 CFU / 100g, and no pathogenic bacteria were detected; It fully complies with the national food safety standards for non-fermented soy products.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu, characterized in that, Includes the following steps: S1. Refined Soy Milk: High-quality non-GMO soybeans are selected and processed in sequence through washing, soaking, grinding, coarse filtration, fine filtration, deodorization, and concentration adjustment to obtain cooked soy milk with uniform concentration and no impurities. The cooked soy milk is then cooled to room temperature for later use. S2. Coagulant Mixing: Add the temperature-responsive sustained-release capsule coagulant to room-temperature cooked soy milk in a preset ratio, and use low-speed stirring to evenly disperse the capsule coagulant in the soy milk; S3. Aseptic filling and sealing: The well-mixed soy milk liquid is transported to the Tetra Pak aseptic filling production line, where Tetra Pak packaging is filled and sealed in an aseptic environment to form a closed aseptic packaging unit. S4. High-temperature sterilization treatment: After the Tetra Pak products are filled and sealed, they are sent into the sterilization equipment for rapid high-temperature constant-temperature sterilization. During the sterilization process, the capsule shell remains intact and the soy milk remains in a liquid and sterile state. S5. Temperature-controlled solidification and molding: After sterilization, the product is gradually cooled to 85℃±2℃ and kept warm for 30-40 minutes. The capsule shell quickly swells and dissolves to release gluconate-δ-lactone, triggering uniform coagulation of soy protein. S6. Cooling and Shaping: The solidified product is cooled to room temperature in stages using a gradient cooling process, and the tofu texture gradually stabilizes, resulting in Tetra Pak packaged silken tofu.

2. The method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu according to claim 1, characterized in that, The temperature-responsive sustained-release capsule coagulant includes a core and a heat-resistant edible capsule shell, wherein the core of the temperature-responsive sustained-release capsule coagulant is food-grade glucono-δ-lactone.

3. The method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu according to claim 2, characterized in that, The temperature-responsive sustained-release capsules have a particle size of 0.8-1.2 mm and a capsule shell wall thickness of 0.15-0.25 mm.

4. The method for preparing room-temperature stored long-lasting glucono-delta-lactone tofu according to claim 3, characterized in that, The outer shell of the heat-resistant edible capsule is a modified edible film made of hydroxypropyl methylcellulose, sodium alginate, and chitosan, with the mass ratio of hydroxypropyl methylcellulose, sodium alginate, and chitosan being 65:20:

15.

5. The method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu according to claim 4, characterized in that, The capsule coagulant is added at a ratio of 0.3% of the weight of the soy milk.

6. The method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu according to claim 1, characterized in that, In step S2, the low-speed stirring speed is 30-50 r / min, and the stirring time is 3-5 min.

7. The method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu according to claim 1, characterized in that, In step S4, the high-temperature constant temperature sterilization temperature is 95℃-105℃, and the sterilization time is 10-25 minutes.

8. The method for preparing long-lasting, room-temperature-stored glucono-delta-lactone tofu according to claim 1, characterized in that, The segmented gradient cooling in S6 includes the following: first, cooling to 55-60℃ at a rate of 1.5℃ / min, and holding at a constant temperature for 15min; then slowly cooling to room temperature of 25-30℃ at a rate of 1℃ / min.

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