Preparation method of solidified sour soybean milk without beany flavor

Abstract

The invention provides a preparation method of solidified sour soybean milk without beany flavor, and belongs to the technical field of soybean protein processing. The method integrates four core technologies of regulation and control of gel through lactobacillus fermentation, secondary solidification, ultrahigh-pressure cold sterilization and surface spraying biological preservation, soybeans are used as raw materials, lactobacillus plantarum is selected as a single fermentation strain, beany flavor precursor substances are degraded through strain specific metabolism, a stable gel system is constructed in combination with a two-time solidification process, and the soybean flavor is obtained. The ultrahigh-pressure cold sterilization technology keeps the integrity of the product to the greatest extent while killing harmful microorganisms, and avoids gel collapse and nutrient substance denaturation caused by high-temperature sterilization; homologous fermentation supernate is sprayed on the surface, so that the shelf life is prolonged on the premise of not damaging the gel. The sour soybean milk prepared through the method solves the problems that traditional sour soybean milk is heavy in beany flavor, gel is prone to bleeding, chemical preservatives are added and the like, the obtained product has nutritive value and tender and smooth taste, the technology is simple, and the sour soybean milk is suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of soybean protein processing technology, specifically relating to a method for preparing a coagulated soy milk without a beany smell. Background Technology

[0002] Set-type fermented soy milk is a gel-like plant-based food made from soybeans through lactic acid bacteria fermentation. It is rich in high-quality plant protein, dietary fiber, and probiotics, aligning with the trend towards healthy eating and plant-based foods. However, the inherent beany taste of soybeans (mainly derived from volatile aldehydes and ketones produced by lipoxygenase) has always been a major issue affecting consumer acceptance. While existing fermented soy milk production processes have some deodorizing effect, they also have several drawbacks: soy milk produced using the raw soy milk method has a stronger beany and bitter taste due to the action of endogenous enzymes in soybeans; the gel network formed by a single coagulant is fragile, causing the fermented soy milk to easily separate and have a coarse texture; while high-temperature enzyme inactivation can deactivate lipoxygenase, it also destroys some nutrients and produces a burnt taste. Among existing technologies for removing the beany smell from soy milk, ohmic heating combined with supercritical carbon dioxide deodorization is effective but expensive and cannot solve the gel texture problem of fermented soy milk. While fermentation with kombucha can increase aroma and vitamin content, the fermentation cycle is long and acidity is difficult to control. Regarding extending shelf life, some processes rely on chemical preservatives such as sodium benzoate, which contradicts current green and healthy consumption concepts. Therefore, there is an urgent need for a synergistic technology integrating biological deodorization, intelligent processing, and green preservation, aiming to remove the beany smell while improving the nutrition and texture of fermented soy milk, thereby meeting the market demand for high-quality fermented soy milk. Summary of the Invention

[0003] This invention aims to provide a method for preparing a coagulated fermented soy milk without beany odor. By integrating multiple technologies, it achieves efficient removal of beany odor, optimized texture stability, and long-lasting freshness, thereby improving the quality of fermented soy milk products and the feasibility of industrial production.

[0004] The technical problem to be solved by this invention is achieved through the following technical solutions: 1. Raw material pretreatment: Soaking at a specific temperature and adding compound salt disrupts the soybean cell structure, laying the foundation for subsequent removal of beany odor and gel formation; high-temperature grinding and multi-stage homogenization improve the smoothness of the soy milk while initially inactivating some lipoxygenases. 2. Lactic acid bacteria fermentation to regulate gel: *Lactobacillus plantarum* is selected as the fermentation strain. This strain can degrade beany odor precursors such as linolenic acid and linoleic acid in soybeans. Simultaneously, the lactic acid produced by metabolism lowers the pH of the system, inducing cross-linking of soybean protein molecules to form a uniform primary gel. Furthermore, the flavor substances produced during fermentation can further optimize the taste of the soy milk and mask any residual slight off-odors. A fractional fermentation strategy is adopted. The activated bacterial solution is inoculated into the base soy milk at a 4% inoculation rate. Besides producing the finished product, a portion of the base soy milk inoculated with the bacterial solution is used to prepare a highly active fermentation supernatant (containing *Lactobacillus plantarum* antimicrobial peptides) to provide raw materials for subsequent surface antibacterial treatment, achieving the recycling of metabolites from homologous strains. The process employs a pre-filling followed by fermentation process, avoiding the secondary contamination risks associated with traditional pre-fermentation followed by filling and ensuring the product's microbial safety. III. Low-Temperature Secondary Coagulation: A low-temperature secondary coagulation process is performed on the pre-gel formed during fermentation. This low-temperature secondary coagulation under refrigeration requires no external coagulant. It relies on the slow rearrangement of gel molecules and hydrophobic interactions to build a dense and stable three-dimensional gel network, significantly improving the gel's water retention and elasticity. Simultaneously, the gel matrix can adsorb and encapsulate trace amounts of undegraded odor substances from the fermentation process, further purifying the product's flavor. IV. Cold Sterilization Treatment: Ultra-high pressure cold sterilization technology is used to kill harmful microorganisms while preserving the gel structure to the greatest extent possible, avoiding gel collapse caused by high-temperature sterilization. V. Biological Preservation: A sterile spraying device is used to evenly spray the homologous fermentation supernatant onto the surface of the fermented soy milk. The packaging is immediately sealed after spraying.

[0005] The beneficial effects of this invention are as follows: This method achieves efficient removal of the beany odor through single-strain fermentation with *Lactobacillus plantarum*, while simultaneously imparting a pure taste to the product. The secondary coagulation and surface spraying preservation process ensures excellent gel water retention and stable texture, eliminating water separation issues during storage. The ultra-high pressure cold sterilization process extends the shelf life of the food without damaging its texture. The overall process route is simplified, eliminating the need for multi-strain compounding, making it suitable for continuous industrial production, and effectively balancing product quality, health benefits, and production efficiency. Attached Figure Description

[0006] Figure 1 This is a roadmap of the method of the present invention.

[0007] Figure 2 Sensory evaluation standards for yogurt

[0008] Figure 3 These are the sensory evaluation results of the fermented soy milk in each embodiment.

[0009] Figure 4 This is a statistical analysis of the sensory evaluation results of the fermented soy milk in each embodiment.

[0010] Figure 5 Radar charts showing sensory evaluations of yogurt in various embodiments. Detailed Implementation

[0011] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0012] Example 1 I. Raw material pretreatment: Take 10 kg of soybeans, wash and remove impurities, add 58℃ warm water at a material-to-liquid ratio of 1:11 and soak for 5.5 h. Add 8 g of compound salt (sodium chloride: potassium citrate: disodium hydrogen phosphate = 1:1:1) to the soaking solution. After draining, add 92℃ hot water to grind into a paste, pass through a 180-mesh sieve, homogenize at 28 MPa, sterilize at 110℃ for 11 min, and rapidly cool to 36℃ to obtain the base soybean milk. II. Regulation of Lactic Acid Bacterial Fermentation and Primary Coagulation: Strain Activation: *Lactobacillus plantarum* was inoculated into MRS medium and cultured at 36℃ for 13 h, followed by two subcultures. Fermentation by Substrate: The activated bacterial solution was inoculated into the base soybean milk at a rate of 4%, stirred thoroughly, and then dispensed into 200 mL sterile plastic cups under a Class 100 cleanroom environment. Fermentation was carried out at 36℃ for 7 h until the system pH reached 4.2, forming a primary gel. A separate portion of the inoculated soybean milk was subjected to high-density fermentation at 36℃ for 16 hours to obtain a highly active fermentation broth. The broth was centrifuged at 4000 r / min for 15 min and filtered through a 0.22 μm membrane for sterilization and then stored for later use. 3. Low-temperature secondary coagulation: Place the fermented soy milk in a 3℃ cold storage for 14 hours to complete the secondary coagulation. IV. Ultra-high pressure cold sterilization is adopted, with a pressure of 350 MPa, a temperature of 25℃, and a pressure holding time of 8 min; V. Biological preservation and finished product: Under sterile conditions, 0.8 mL of the above-mentioned sterilized fermentation supernatant is sprayed onto the surface of each cup of fermented soy milk using a sterile spraying device. After spraying, the cup mouth is sealed immediately to obtain the finished product, a coagulated fermented soy milk without beany smell.

[0013] Example 2 I. Raw material pretreatment: Take 10 kg of soybeans, wash and remove impurities, add 58℃ hot water at a material-to-liquid ratio of 1:15 and soak for 5.5 hours. Add 8 g of compound salt (sodium chloride: potassium citrate: disodium hydrogen phosphate = 1:1:1) to the soaking solution. After draining, add 92℃ hot water to grind into a paste, pass through a 180-mesh sieve, homogenize at 28 MPa, sterilize at 110℃ for 11 minutes, and quickly cool to 36℃ to obtain the base soybean milk. II. Regulation of Lactic Acid Bacterial Fermentation and Primary Coagulation: Strain Activation: *Lactobacillus plantarum* was inoculated into MRS medium and cultured at 36℃ for 13 h, followed by two subcultures. Substrate Fermentation: The activated bacterial solution was inoculated into the base soybean milk at a 4% inoculation rate. After thorough mixing, the mixture was dispensed into 200 mL sterile plastic cups under a Class 100 clean environment and fermented at 36℃ for 10 h until the pH reached 3.9, forming a primary gel. A separate portion of the inoculated soybean milk was subjected to high-density fermentation at 36℃ for 16 hours to obtain a highly active fermentation broth. This broth was centrifuged at 4000 r / min for 15 min and filtered through a 0.22 μm membrane for sterilization and then stored for later use. 3. Low-temperature secondary coagulation: Place the fermented soy milk in a 3℃ cold storage for 14 hours to complete the secondary coagulation. IV. Ultra-high pressure cold sterilization treatment: set pressure 350 MPa, temperature 25℃, and hold pressure for 8 min; after depressurization, the gel structure was not significantly damaged. V. Biological preservation and finished product: Under sterile conditions, 0.8 mL of the above-mentioned sterilized fermentation supernatant is sprayed onto the surface of each cup of fermented soy milk using a sterile spraying device. After spraying, the cup mouth is sealed immediately to obtain the finished product, a coagulated fermented soy milk without beany smell.

[0014] Example 3 I. Raw material pretreatment: Take 10 kg of soybeans, wash and remove impurities, add 58℃ hot water at a material-to-liquid ratio of 1:8 and soak for 5.5 h. Add 8 g of compound salt (sodium chloride: potassium citrate: disodium hydrogen phosphate = 1:1:1) to the soaking solution. After draining, add 92℃ hot water to grind into a paste, pass through a 180-mesh sieve, homogenize at 28 MPa, sterilize at 110℃ for 11 min, and rapidly cool to 36℃ to obtain a thick base soybean milk. II. Regulation of Lactic Acid Bacterial Fermentation and Primary Coagulation: Strain Activation: *Lactobacillus plantarum* was inoculated into MRS medium and cultured at 36℃ for 13 h, followed by two subcultures. Substrate Fermentation: The activated bacterial solution was inoculated into the base soybean milk at a 4% inoculation rate. After thorough mixing, the mixture was dispensed into 200 mL sterile plastic cups under a Class 100 cleanroom environment and fermented at 36℃ for 5 h until the system pH reached 4.5, forming a primary gel. A separate portion of the inoculated soybean milk was subjected to high-density fermentation at 36℃ for 16 hours to obtain a highly active fermentation broth. This broth was centrifuged at 4000 r / min for 15 min and filtered through a 0.22 μm membrane for sterilization and then stored for later use. 3. Low-temperature secondary coagulation: Place the fermented soy milk in a 3℃ cold storage for 14 hours to complete the secondary coagulation. IV. Ultra-high pressure cold sterilization treatment: set pressure 350 MPa, temperature 25℃, and hold pressure for 8 min; after depressurization, the gel structure is dense and there is no water separation. V. Biological preservation and finished product: Under sterile conditions, 0.8 mL of the above-mentioned sterilized fermentation supernatant is sprayed onto the surface of each cup of fermented soy milk using sterile spraying equipment. After spraying, the cup mouth is sealed immediately to obtain the finished product of coagulated fermented soy milk without beany smell.

[0015] Example 4 I. Raw material pretreatment: Take 10 kg of soybeans, wash and remove impurities, add 58℃ hot water at a material-to-liquid ratio of 1:11 and soak for 5.5 h. Add 8 g of compound salt (sodium chloride: potassium citrate: disodium hydrogen phosphate = 1:1:1) to the soaking solution. After draining, add 92℃ hot water to grind into a paste, pass through a 180-mesh sieve, homogenize at 28 MPa, sterilize at 110℃ for 11 min, and rapidly cool to 36℃ to obtain the base soybean milk. II. Regulation of Lactic Acid Bacterial Fermentation and Primary Coagulation: Strain Activation: *Lactobacillus plantarum* was inoculated into MRS medium and cultured at 36℃ for 13 h, followed by two subcultures. Substrate Fermentation: The activated bacterial solution was inoculated into the base soybean milk at a 4% inoculation rate. After thorough mixing, the mixture was dispensed into 200 mL sterile plastic cups under a Class 100 cleanroom environment and fermented at 36℃ for 7 h until the pH reached 4.2, forming a primary gel. A separate portion of the inoculated soybean milk was subjected to high-density fermentation at 36℃ for 16 hours to obtain a highly active fermentation broth. This broth was centrifuged at 4000 r / min for 15 min and filtered through a 0.22 μm membrane for sterilization and then stored for later use. 3. Low-temperature secondary coagulation: Place the fermented soy milk in a 3℃ cold storage for 24 hours to complete the secondary coagulation. IV. Ultra-high pressure cold sterilization treatment: set pressure 350 MPa, temperature 25℃, and hold pressure for 8 min; after depressurization, the gel water retention was significantly improved. V. Biological preservation and finished product: Under sterile conditions, 0.8 mL of the above-mentioned sterilized fermentation supernatant is sprayed onto the surface of each cup of fermented soy milk using a sterile spraying device. After spraying, the cup mouth is sealed immediately to obtain the finished product, a coagulated fermented soy milk without beany smell.

Claims

1. A method for preparing a coagulated soy milk without a beany odor, characterized in that, Includes the following steps: (1) Raw material processing: Soak soybeans in a compound brine at 55-60℃, the compound brine containing sodium chloride, potassium citrate and disodium hydrogen phosphate; after soaking, grind the soybeans at 90-95℃ and homogenize them under high pressure to obtain base soybean milk; (2) Inoculation and fermentation: Lactobacillus plantarum is inoculated into the soybean milk base obtained in step (1) for fermentation, and at the same time, it is filled into bottles. The fermentation continues until the pH of the system is 3.9-4.5 and a primary gel is formed, thus completing the first coagulation. (3) Low-temperature solidification: The product after the first solidification is left to stand at 2-4℃ for 12-24 hours to complete the second solidification; (4) Ultra-high pressure treatment: The coagulated soy milk after secondary coagulation is sterilized under ultra-high pressure under certain conditions; (5) Surface spraying and packaging: Spray the supernatant of Lactobacillus plantarum fermentation onto the surface of the fermented soy milk after ultra-high pressure treatment. The spraying amount is 0.5-1.0 mL per 100 g of fermented soy milk, and then seal and package it.

2. The preparation method according to claim 1, characterized in that, In the compound saline solution described in step (1), the mass ratio of sodium chloride, potassium citrate, and disodium hydrogen phosphate is 1:1:

1.

3. The preparation method according to claim 1, characterized in that, The inoculation amount of Lactobacillus plantarum in step (2) is 3%-5% of the mass of the base soybean milk, and the fermentation is a single strain fermentation of Lactobacillus plantarum.

4. The preparation method according to claim 1, characterized in that, The ultra-high pressure treatment in step (4) is performed at a pressure of 300-400 MPa, a temperature of 20-30℃, and a holding time of 5-10 minutes.

5. The preparation method according to claim 1, characterized in that, The fermentation supernatant mentioned in step (5) is obtained by centrifuging Lactobacillus plantarum at 36°C for 16 hours, centrifuging at 4000 r / min for 15 min, and filtering with a 0.22 μm filter membrane to remove bacteria. It contains Lactobacillus plantarum antimicrobial peptides.

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