Preparation method of fermented probiotic reinforced dried bean curd

Abstract

The invention relates to the technical field of bean product processing, in particular to a preparation method of fermented probiotic fortified dried bean curds.The preparation method comprises the steps that soybeans and black beans serve as raw materials, mixed soybean milk is prepared through soaking, cleaning and pulping, lactic acid bacteria and bifidobacterium leavening agents are inoculated, the pH and the temperature are adjusted for primary fermentation, then fermented soybean milk is obtained through heat treatment and filtration, and the fermented soybean milk is obtained; the preparation method comprises the following steps: preparing microcapsules containing active bifidobacteria from sodium alginate-chitosan, heating fermented soybean milk, curdling with brine, pressing into bean curd blanks, soaking with functional components, smearing with a probiotic microcapsule suspension, carrying out vacuum drying, soaking with seasoning liquid, carrying out hot air drying, carrying out surface smearing with liquid for air drying, and carrying out vacuum packaging and sterilization to obtain a finished product. According to the process, fermentation and probiotic microcapsule technologies are combined, functional characteristics are given to the product, the digestibility and bioavailability of soybean protein are improved through lactobacillus fermentation, various functional peptides with physiological activity are generated, and the nutritional value of the product is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of soybean product processing technology, and in particular to a dried soybean product with probiotic function prepared using bio-fermentation technology and microcapsule protection technology, and its preparation method. Background Technology

[0002] Dried tofu is a traditional Chinese soy product, popular among consumers for its high protein content, pleasant taste, and long shelf life. With the development of modern food science and increased consumer health awareness, the development of functional soy products has become a research hotspot in the industry.

[0003] Currently, the market for dried bean curd products primarily focuses on improving sensory characteristics, with less emphasis on functionality. Chinese patent CN 107980917 B discloses a manufacturing process for a type of casual dried bean curd. This process involves multi-stage heating, sodium carbonate soaking, and two-stage seasoning to produce a product with a soft, firm, and elastic texture, a pure and rich soybean aroma, and good flavor absorption. However, this technology mainly focuses on sensory characteristics, failing to fully utilize the health benefits of soybeans, and the high-temperature processing during preparation may lead to the loss of some nutrients.

[0004] In addition, Chinese patent CN 103416783 B discloses a formula and production process for ready-to-eat fish and bean curd. This technology combines fish and bean products, enriching the nutritional components and flavor of the product. However, it adds a lot of modified starch and konjac gum, making it difficult for the seasoning to penetrate into the product and affecting the flavor of the product.

[0005] Currently, the technology of introducing probiotics into soy products mainly faces the following challenges: (1) High-temperature processing during the processing of dried bean curd can cause probiotics to become inactive; (2) Traditional processes cannot guarantee the stable survival of probiotics in the final product; (3) The addition of probiotics may affect the sensory characteristics of the product; (4) There is a lack of scientific and reasonable compound functional formula design.

[0006] Therefore, developing an innovative soy product that retains the good sensory characteristics of traditional dried tofu while also having probiotic functions is of great significance for improving the nutritional value and health benefits of soy products. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing fermented probiotic-enhanced dried bean curd. By using bio-fermentation technology and microcapsule protection technology, this invention solves the technical problems of probiotics being difficult to survive and functional components being easily lost during the traditional dried bean curd preparation process, and prepares an innovative dried bean curd product that has both good taste and probiotic function.

[0008] To achieve the above objectives, the present invention provides a method for preparing fermented probiotic-fortified dried bean curd, comprising the following steps:

[0009] S1, Raw material processing: Take soybeans and black beans, soak and wash them;

[0010] S2, Preparation of starter culture: Select lactic acid bacteria and bifidobacteria, and mix them to prepare the starter culture;

[0011] S3, Soybean preparation: Mix the processed soybeans with black beans, add water and grind into a paste to make mixed soy milk;

[0012] S4, Primary Fermentation: Adjust the pH and temperature of the mixed soy milk, inoculate with a starter culture, and ferment at a constant temperature until the specified pH value is reached.

[0013] S5, Soy milk processing: The fermented soy milk is heat-treated, filtered to remove residue, and fermented soy milk is obtained.

[0014] S6, Preparation of probiotic microcapsules: Sodium alginate-chitosan microcapsules containing food-grade certified active Bifidobacteria are prepared using food-grade materials;

[0015] S7, Coagulation: Heat the fermented soybean milk, add brine to coagulate, and let it stand to form tofu blocks;

[0016] S8, pressing and shaping: cut the tofu blocks into pieces and press them to obtain tofu blanks;

[0017] S9, Functional soaking: Prepare a soaking solution containing functional ingredients and soak the tofu blocks;

[0018] S10, Probiotic Fortification: Cool the tofu blocks and coat them with a probiotic microcapsule suspension;

[0019] S11, Low-temperature drying: Vacuum drying of tofu blocks to reduce moisture content;

[0020] S12, Seasoning treatment: Prepare seasoning liquid and soak dried tofu;

[0021] S13, Secondary drying: The seasoned dried tofu is dried with hot air;

[0022] S14, Surface treatment: Prepare a coating solution, apply it to the surface of the dried bean curd, and air dry;

[0023] S15, Packaging and Sterilization: Vacuum pack the dried bean curd, sterilize it, and cool it to obtain the finished product.

[0024] Preferably, in step S1, the weight ratio of soybeans to black beans is 100:10-15, and the soaking time is adjusted according to the ambient temperature, with soybeans soaked for 10-15 hours and black beans soaked for 6-10 hours.

[0025] Further, in step S2, the lactic acid bacteria include Streptococcus thermophilus and Lactobacillus bulgaricus, and the ratio of Streptococcus thermophilus, Lactobacillus bulgaricus, and Bifidobacterium is 1:1:1, and the bacterial content in the fermentation agent is 10. 9 -10 10 CFU / g.

[0026] In one embodiment of the present invention, in step S4, the pH of the mixed soy milk is adjusted to 6.8-7.0, the temperature is adjusted to 37-40°C, the amount of starter culture is 2-3% of the weight of the soy milk, the fermentation time is 4-6 hours, and the final pH of the fermentation is 5.2-5.5.

[0027] Preferably, in step S6, the method for preparing probiotic microcapsules is as follows: take 0.8-1.2 parts of food-grade chitosan and dissolve it in 1% food-grade lactic acid solution; take 1.5-2.0 parts of food-grade sodium alginate and dissolve it in deionized water; take 2-3 parts of food-grade certified active Bifidobacterium powder and disperse it in food-grade triglycerides to form a bacterial suspension; mix the bacterial suspension with the sodium alginate solution and drip it into a chitosan solution containing 0.2M food-grade calcium chloride through a 1.5mm nozzle; stir for 30 minutes to form microcapsules, filter, wash, and store at 4°C.

[0028] In addition, in step S9, the formula for the functional soaking solution is as follows: 0.5-0.8 kg of green tea extract, 0.2-0.3 kg of curcumin, 0.5-0.8 kg of soybean peptide, and 1.0-1.5 kg of salt are added per 100 kg of water; the temperature of the soaking solution is 85-90℃, and the soaking time is 10-15 minutes.

[0029] Meanwhile, in step S10, the tofu curd is cooled to 45-50℃, and the concentration of the probiotic microcapsule suspension is 10. 10 The dosage is 3-5% of the weight of the tofu curd, and the probiotic is a Bifidobacterium strain that has obtained food-grade safety certification.

[0030] More preferably, in step S11, the vacuum drying conditions are a temperature of 55-60℃, a pressure of 50-100Pa, and a drying time of 4-6 hours, resulting in a dried bean curd with a moisture content of 45-50%.

[0031] In another embodiment of the present invention, in step S12, the seasoning liquid is formulated as follows: per 100kg of water, add: 10-12kg of light soy sauce; 3-5kg of dark soy sauce; 5-7kg of white sugar; 2-3kg of salt; 1.0-1.5kg of five-spice powder; 0.3-0.5kg of Sichuan peppercorns; 0.3-0.5kg of star anise; 0.2-0.3kg of cinnamon; and 0.2-0.3kg of fennel. The seasoning liquid is first boiled and then simmered for 30 minutes. After filtration, it is cooled to 80-85℃ before use. The soaking time is 8-12 hours, and the temperature is maintained at 50-60℃ during the soaking process.

[0032] Finally, in step S14, the components of the coating solution, by weight, include: 3-5 parts edible gelatin; 2-3 parts fructooligosaccharides; 1-2 parts maltodextrin; 0.5-1 parts plant polyphenols; 0.2-0.3 parts food-grade pectin or sodium alginate; and 15-20 parts water. The coating solution is heated to 60°C before use, and after application, it is air-dried at 40-45°C for 30-40 minutes. In step S15, the sterilization temperature after vacuum packaging is 95-98°C, and the sterilization time is 15-20 minutes.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) This invention improves the digestibility and bioavailability of soybean protein through lactic acid bacteria fermentation, producing a variety of physiologically active functional peptides and significantly improving the nutritional value of the product. Compared with traditional dried bean curd, the protein digestibility of the product of this invention is increased by 15-25%, and the bioavailability is increased by 20-30%.

[0035] (2) This invention uses sodium alginate-chitosan microcapsule technology to protect probiotics, enabling them to maintain high activity during processing and survive for a long time in the product. Tests have shown that the probiotic content in the finished product reaches 10^7-10^8 CFU / g, and after 90 days of storage, it can still maintain a viable count of more than 10^5 CFU / g, which is much higher than that of traditional addition methods.

[0036] (3) This invention improves the antioxidant activity of the product and extends its shelf life by adding natural antioxidants such as green tea extract and curcumin. Experiments show that the DPPH free radical scavenging rate of the product of this invention is 46.3 percentage points higher than that of traditional dried bean curd, and the shelf life is extended by 30-50%.

[0037] (4) This invention uses low-temperature vacuum drying technology to retain more nutrients and flavor substances, reducing the nutrient loss caused by traditional high-temperature processing. Tests have shown that the product retains 25-40% more B vitamins and isoflavones than with traditional processes.

[0038] (5) This invention combines the special flavor compounds produced by the biological fermentation process with traditional technology, so that the product has a richer flavor profile and a better taste. The consumer acceptance test score is 6-10 points higher than that of traditional dried bean curd (out of 100 points).

[0039] (6) The addition of black beans in this invention increases the anthocyanin content of the product, enhances the product’s antioxidant capacity and visual appeal, and at the same time gives the product a unique flavor profile. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0041] Example 1

[0042] A method for preparing fermented probiotic-fortified dried tofu, comprising the following steps:

[0043] (1) Raw material processing: Take 100kg of high-quality soybeans, soak them at 15℃ for 12 hours, and clean them; take 10kg of black beans, soak them for 8 hours, and clean them.

[0044] (2) Preparation of starter culture: Streptococcus thermophilus ATCC 19258, Lactobacillus bulgaricus ATCC 11842, and Bifidobacterium longum ATCC 15707 were selected and mixed in a 1:1:1 ratio to prepare the starter culture, with a bacterial count of 1×10⁻⁶. 10 CFU / g.

[0045] (3) Soybean preparation: Mix the processed soybeans with black beans, add 4 times the weight of water (i.e. 440 kg of water), grind with a colloid mill to obtain mixed soy milk.

[0046] (4) Primary fermentation: Adjust the pH of the mixed soy milk to 6.8 and the temperature to 38℃. Inoculate with a starter culture at a rate of 2% of the weight of the soy milk (i.e., 11 kg). Ferment at a constant temperature for 4 hours until the pH of the soy milk drops to 5.4. In this step, lactic acid bacteria fermentation not only reduces the content of anti-nutritional factors in the soy milk but also produces special flavor substances, providing a unique flavor base for the final product.

[0047] (5) Soy milk treatment: The fermented soy milk is heat-treated at 85℃ for 5 minutes to inhibit the fermentation process, and then filtered through a 150-mesh sieve to remove residue, thus obtaining fermented soy milk. Heat treatment can partially kill the fermentation bacteria, avoid over-fermentation leading to excessive acidity in the soy milk, and at the same time retain the beneficial substances produced during fermentation.

[0048] (6) Preparation of probiotic microcapsules: Dissolve 0.8 kg of food-grade chitosan in 1% food-grade lactic acid solution; dissolve 1.5 kg of food-grade sodium alginate in deionized water; and take food-grade certified active Bifidobacterium lactis... Chr. Hansen (company name) powder (2 kg) was dispersed in food-grade triglycerides to form a bacterial suspension. This suspension was then mixed with sodium alginate solution and dripped through a 1.5 mm nozzle into a chitosan solution containing 0.2 M food-grade calcium chloride. The mixture was stirred for 30 minutes to form microcapsules, which were then filtered, washed, and stored at 4°C. Microencapsulation technology provides a physical barrier for probiotics, protecting them from damage by acid, heat, and mechanical stress, significantly improving their survival rate during processing and storage.

[0049] (7) Coagulation: Heat the fermented soybean milk to 90°C, add brine (magnesium chloride solution, concentration 25g / L), stir to coagulate, and let stand for 15 minutes to form tofu blocks. During the coagulation process, the soybean milk protein coagulates to form a network structure, while also encapsulating some of the functional substances produced during fermentation.

[0050] (8) Pressing and shaping: Cut the tofu blocks into 4cm×4cm×2cm pieces, place them in a mold and press them at a pressure of 0.05MPa for 40 minutes to obtain tofu blanks with a water content of 65%. The pressing process not only makes the product more regular in shape, but also removes excess water and makes the structure more compact.

[0051] (9) Functional soaking: Prepare the soaking solution by adding 0.5 kg of green tea extract (EGCG content ≥45%), 0.2 kg of curcumin (purity ≥95%), 0.5 kg of soybean peptides (molecular weight <1000Da), and 1.0 kg of salt per 100 kg of water; heat the soaking solution to 85°C and soak the tofu blocks for 10 minutes. In this step, the green tea extract and curcumin can penetrate into the surface of the tofu, providing antioxidant protection, while the soybean peptides enhance the functionality and flavor of the product.

[0052] (10) Probiotic fortification: Cool the tofu blank to 45°C and evenly coat it with a probiotic microcapsule suspension. The suspension concentration is 1×10^10 CFU / mL, and the amount used is 3% of the weight of the tofu blank (i.e., about 9.9 kg). The coating process should be gentle to avoid mechanical damage to the microcapsules and to ensure that the probiotic activity is preserved to the maximum extent.

[0053] (11) Low-temperature drying: The tofu blanks are placed in a vacuum drying oven and dried for 4 hours at a temperature of 55°C and a pressure of 50Pa to reduce the moisture content to 50%. Low-temperature vacuum drying can retain the nutrients and flavor substances in the product to the maximum extent, while ensuring the survival rate of probiotics in the microcapsules.

[0054] (12) Seasoning process: Prepare the seasoning liquid by adding 10kg light soy sauce, 3kg dark soy sauce, 5kg white sugar, 2kg salt, 1.0kg five-spice powder, 0.3kg Sichuan peppercorns, 0.3kg star anise, 0.2kg cinnamon, and 0.2kg fennel seeds to every 100kg of water. Bring the seasoning liquid to a boil, then simmer for 30 minutes. Filter and cool to 80℃. Immerse the tofu in the seasoning liquid for 8 hours, maintaining the temperature at 50℃ during the immersion process. The synergistic effect of the various spices and seasonings in the seasoning liquid penetrates the tofu, giving the product a rich flavor profile.

[0055] (13) Secondary drying: Take out the seasoned dried bean curd and dry it with hot air at 60°C for 2 hours to reduce the moisture content to 35%. Secondary drying not only adjusts the moisture content of the product, but also promotes the combination of seasonings and product and enhances the flavor.

[0056] (14) Surface treatment: Prepare a coating solution containing 3 parts edible gelatin, 2 parts fructooligosaccharides, 1 part maltodextrin, 0.5 parts plant polyphenols, 0.2 parts food-grade pectin, and 15 parts water; heat the coating solution to 60°C, apply it evenly to the surface of the dried bean curd, and air dry at 40°C for 30 minutes. The surface coating forms a protective film, which can maintain the moisture balance of the product and further protect the probiotics and functional ingredients inside.

[0057] (15) Packaging and sterilization: Vacuum-pack the dried bean curd and sterilize it at 95°C for 15 minutes. Then cool it to room temperature to obtain the fermented probiotic-fortified dried bean curd product. The sterilization conditions are carefully designed to ensure the microbial safety of the product and to maximize the preservation of the activity of the probiotics in the microcapsules.

[0058] Example 2

[0059] A method for preparing fermented probiotic-fortified dried tofu, comprising the following steps:

[0060] (1) Raw material processing: Take 100kg of high-quality soybeans, soak them at 28℃ for 6 hours, and clean them; take 15kg of black beans, soak them for 6 hours, and clean them.

[0061] (2) Preparation of starter culture: Streptococcus thermophilus ATCC 19258, Lactobacillus bulgaricus ATCC 11842, and Bifidobacterium longum ATCC 15707 were selected and mixed in a 1:1:1 ratio to prepare the starter culture, with a bacterial count of 9 × 10⁻⁶. 9 CFU / g.

[0062] (3) Soybean preparation: Mix the processed soybeans with black beans, add 5 times the weight of water (i.e., 575 kg of water), grind with a colloid mill to obtain mixed soy milk.

[0063] (4) Primary fermentation: Adjust the pH of the mixed soy milk to 7.0 and the temperature to 40℃. Inoculate with a starter culture at a rate of 3% of the soy milk weight (i.e., 34.5 kg). Ferment at a constant temperature for 6 hours until the pH of the soy milk drops to 5.2. Under these optimized fermentation conditions, lactic acid bacteria can more effectively break down oligosaccharides in soybeans, reducing the potential for bloating caused by the product.

[0064] (5) Soy milk treatment: The fermented soy milk is heat-treated at 85℃ for 5 minutes, and then filtered through a 150-mesh sieve to remove residue, thus obtaining fermented soy milk.

[0065] (6) Preparation of probiotic microcapsules: 1.2 kg of food-grade chitosan was dissolved in 1% food-grade lactic acid solution; 2.0 kg of food-grade sodium alginate was dissolved in deionized water; 3 kg of food-grade certified active Bifidobacterium lactis (Bifidobacterium lactis HN019, Danisco) powder was dispersed in food-grade triglycerides to form a bacterial suspension; the bacterial suspension was mixed with the sodium alginate solution and dripped into a chitosan solution containing 0.2 M food-grade calcium chloride through a 1.5 mm nozzle; the mixture was stirred for 30 minutes to form microcapsules, which were then filtered, washed, and stored at 4°C. The HN019 strain exhibited high tolerance to gastric acid and bile salts, enhancing the functional expression of the product in the digestive tract.

[0066] (7) Coagulation: Heat the fermented soybean milk to 95°C, add brine (magnesium chloride solution, concentration 30g / L), stir to coagulate, and let stand for 20 minutes to form tofu blocks.

[0067] (8) Pressing and molding: Cut the tofu blocks into 5cm×5cm×2cm pieces, place them in a mold and press them for 30 minutes at a pressure of 0.06MPa to obtain tofu blanks with a water content of 70%.

[0068] (9) Functional soaking: Prepare the soaking solution by adding 0.8 kg of green tea extract, 0.3 kg of curcumin, 0.8 kg of soybean peptide, and 1.5 kg of salt per 100 kg of water; heat the soaking solution to 90°C and soak the tofu blocks for 15 minutes. The increase in green tea extract content significantly improved the antioxidant activity of the product.

[0069] (10) Probiotic fortification: Cool the tofu to 50°C and evenly coat it with a probiotic microcapsule suspension. The suspension concentration is 1×10⁻⁶. 10 The dosage is CFU / mL, which is 5% of the weight of the tofu (approximately 42.8 kg). A higher dosage of microcapsules ensures a sufficient amount of probiotics in the final product.

[0070] (11) Low temperature drying: Place the tofu blanks in a vacuum drying oven and dry them for 6 hours at a temperature of 60℃ and a pressure of 100Pa to reduce the moisture content to 45%.

[0071] (12) Seasoning treatment: Prepare the seasoning liquid by adding 12kg of light soy sauce, 5kg of dark soy sauce, 7kg of white sugar, 3kg of salt, 1.5kg of five-spice powder, 0.5kg of Sichuan pepper, 0.5kg of star anise, 0.3kg of cinnamon and 0.3kg of fennel to every 100kg of water; bring the seasoning liquid to a boil and then simmer for 30 minutes, filter and cool to 85℃; immerse the dried tofu in the seasoning liquid for 12 hours, maintaining the temperature at 60℃ during the soaking process.

[0072] (13) Secondary drying: Take out the seasoned dried bean curd and dry it with hot air at 65°C for 3 hours to reduce the moisture content to 30%.

[0073] (14) Surface treatment: Prepare a coating solution containing 5 parts edible gelatin, 3 parts fructooligosaccharide, 2 parts maltodextrin, 1 part plant polyphenols, 0.3 parts food-grade sodium alginate, and 20 parts water; heat the coating solution to 60°C, coat it evenly on the surface of the dried bean curd, and air dry it at 45°C for 40 minutes.

[0074] (15) Packaging and sterilization: Vacuum pack the dried bean curd, sterilize it at 98°C for 20 minutes, and cool it to room temperature to obtain the fermented probiotic-fortified dried bean curd product.

[0075] Example 3

[0076] A method for preparing fermented probiotic-fortified dried tofu, comprising the following steps:

[0077] (1) Raw material processing: Take 100kg of high-quality soybeans, soak them at 10℃ for 15 hours, and clean them; take 12kg of black beans, soak them for 10 hours, and clean them.

[0078] (2) Preparation of starter culture: Streptococcus thermophilus, Lactobacillus bulgaricus, and Bifidobacterium were selected and mixed in a 1:1:1 ratio to prepare the starter culture, with a bacterial count of 5 × 10⁻⁶. 9 CFU / g.

[0079] (3) Soybean preparation: Mix the processed soybeans with black beans, add 4.5 times the weight of water, grind with a colloid mill to obtain mixed soy milk.

[0080] (4) Primary fermentation: Adjust the pH of the mixed soy milk to 6.9 and the temperature to 39°C. Inoculate with a fermenting agent at a rate of 2.5% of the weight of the soy milk. Ferment for 5 hours under constant temperature conditions until the pH of the soy milk drops to 5.3.

[0081] Steps (5) to (15) are carried out according to Example 1, but the formula of the soaking solution used in step (9) is to add 0.7 kg of green tea extract, 0.25 kg of curcumin, 0.6 kg of soybean peptide and 1.2 kg of salt per 100 kg of water; the formula of the coating solution in step (14) is 4 parts of edible gelatin, 2.5 parts of fructooligosaccharide, 1.5 parts of maltodextrin, 0.8 parts of plant polyphenols, 0.25 parts of food-grade pectin and 18 parts of water.

[0082] In this embodiment, by adjusting the formulations of the soaking solution and the coating solution, the product can maintain the activity of probiotics while having a more balanced functional and sensory property.

[0083] Example 4

[0084] A method for preparing fermented probiotic-fortified dried bean curd is basically carried out according to Example 2, but the probiotic used in step (6) is food-grade certified active Bifidobacterium animalis subsp. lactis Bi-07 (DuPont). In step (11), the vacuum drying conditions are a temperature of 58°C, a pressure of 75Pa, and a drying time of 5 hours, so that the moisture content is reduced to 48%.

[0085] This adjustment allows the product to maintain high probiotic activity while having better storage stability and texture.

[0086] Comparative Example 1 - No Fermentation Treatment

[0087] A method for preparing dried bean curd is carried out according to the steps of Example 1, but step (4) primary fermentation and step (10) probiotic fortification are omitted. The ground soy milk is directly heated to 90°C and then coagulated.

[0088] Comparative Example 2 - No Microcapsule Protection

[0089] A method for preparing probiotic tofu is carried out according to the steps of Example 1, but microcapsules are not prepared in step (6). Instead, in step (10), active Bifidobacterium powder is directly dispersed in water and coated on the surface of tofu.

[0090] Comparative Example 3 - No functional ingredients added

[0091] A method for preparing probiotic dried bean curd is carried out according to the steps of Example 1, but the soaking solution in step (9) contains only 1.0 kg salt / 100 kg water and does not contain green tea extract, curcumin and soybean peptides.

[0092] Comparative Example 4 - High-Temperature Sterilization Treatment

[0093] A method for preparing fermented probiotic dried bean curd is carried out according to the steps of Example 1, but the sterilization conditions in step (15) are 121°C for 20 minutes.

[0094] The experimental results and evaluations are as follows:

[0095] To evaluate the performance of the fermented probiotic-fortified dried tofu prepared by the method of the present invention, systematic tests were conducted on the products of Examples 1-4 and Comparative Examples 1-4, and the results are as follows:

[0096] Table 1. Results of probiotic activity test in the product (CFU / g)

[0097] sample After preparation Store for 30 days (25℃). Store for 60 days (25℃). Store for 90 days (25℃). Example 1 <![CDATA[3.6×10 8 ]]> <![CDATA[2.8×10 7 ]]> <![CDATA[5.4×10 6 ]]> <![CDATA[8.3×10 5 ]]> Example 2 <![CDATA[5.2×10 8 ]]> <![CDATA[4.1×10 7 ]]> <![CDATA[8.6×10 6 ]]> <![CDATA[1.2×10 6 <!-- 6 -->]]> Example 3 <![CDATA[4.1×10 8 ]]> <![CDATA[3.3×10 7 ]]> <![CDATA[6.8×10 6 ]]> 9.5×10^5 Example 4 <![CDATA[4.8×10 8 ]]> <![CDATA[3.9×10 7 ]]> <![CDATA[7.2×10 6 ]]> <![CDATA[1.0×110 6 ]]> Comparative Example 1 <![CDATA[<10 3 ]]> <![CDATA[<10 2 ]]> <![CDATA[<10 2 ]]> <![CDATA[<10 2 ]]> Comparative Example 2 <![CDATA[2.1×10 6 ]]> <![CDATA[1.5×10 4 ]]> <![CDATA[<10 3 ]]> <![CDATA[<110 2 ]]> Comparative Example 3 <![CDATA[3.2×10 8 ]]> <![CDATA[1.9×10 7 ]]> <![CDATA[3.1×10 6 ]]> <![CDATA[4.2×10 5 ]]> Comparative Example 4 <![CDATA[8.5×10 4 ]]> <![CDATA[<10 3 ]]> <![CDATA[<10 2 ]]> <![CDATA[<10 2 ]]>

[0098] As shown in Table 1, the probiotic activity in the products of this invention is significantly higher than that in the comparative products, and they also exhibit excellent storage stability. Comparative Example 1, lacking fermentation and probiotic fortification, contained almost no live probiotics; Comparative Example 2, without microencapsulation protection, saw a rapid decline in probiotic activity during processing and storage; Comparative Example 3, while containing probiotics, exhibited poor storage stability; and Comparative Example 4 suffered from inactivation of most probiotics due to high-temperature sterilization. This demonstrates that the microencapsulation protection technology and optimized processing technology of this invention work synergistically to effectively protect probiotic activity.

[0099] Table 2 Product Functionality and Sensory Evaluation

[0100] sample DPPH free radical scavenging rate (%) ACE inhibitory activity (IC50, mg / mL) Protein digestibility (%) Sensory rating (out of 100) Example 1 74.6 0.32 85.3 89 Example 2 82.1 0.28 87.2 92 Example 3 78.5 0.3 86.1 90 Example 4 80.3 0.29 86.8 91 Comparative Example 1 28.3 1.85 70.2 83 Comparative Example 2 71.2 0.35 84.6 87 Comparative Example 3 35.6 0.38 83.9 86 Comparative Example 4 69.8 0.36 82.5 84

[0101] Table 2 shows that the products of the embodiments of the present invention have significantly improved antioxidant activity (DPPH free radical scavenging rate), ACE inhibitory activity, and protein digestibility, while maintaining good sensory characteristics. Among them, Example 2 has the best overall performance due to the increased amount of black beans added and the optimized content of functional components. Comparative Example 1 has significantly reduced functionality due to the lack of fermentation treatment; Comparative Example 3 has significantly reduced antioxidant activity due to the lack of added functional components; Comparative Example 4 has a lower sensory score due to the loss of some functional components caused by high-temperature sterilization.

[0102] The above results demonstrate that the present invention, through the innovative combination of fermentation process and microencapsulation protection technology, successfully solves the technical problem of probiotics' difficulty in surviving in traditional tofu preparation. Furthermore, through the scientific formulation of functional ingredients, it significantly enhances the physiological activity and sensory quality of the product, achieving a perfect unity of functionality and sensory quality.

[0103] Based on the above experimental results, the process parameter combination of Example 2 was determined to be the optimal implementation scheme of the present invention. This scheme fully leverages the advantages of lactic acid bacteria fermentation and microencapsulation technology, ensuring the excellent sensory quality of the product while achieving the long-term stable presence of highly active probiotics. In particular, by optimizing the proportion of black beans added, the formula of the functional soaking solution, and the dosage of probiotic microcapsules, the product's antioxidant activity, ACE inhibitory activity, and protein digestibility all reached optimal levels, with a sensory score as high as 92 points, far exceeding traditional dried bean curd products.

[0104] The uniqueness of this invention lies in its first successful integration of soy product processing technology with modern bio-fermentation technology, microencapsulation protection technology, and functional factor enhancement technology, resulting in an innovative dried bean curd product that combines traditional flavor with modern functionality. This method not only solves the technical bottlenecks faced in the development of traditional functional soy products but also provides new ideas and methods for the development of other functional foods.

[0105] This invention utilizes conventional food processing equipment and processes, uses readily available raw materials, and is simple to operate, making it suitable for industrial production. While fermentation and microencapsulation technologies have certain technical barriers, these technologies are relatively mature in the food industry and can be implemented using existing equipment. The product of this invention not only possesses excellent functional and sensory characteristics but also has a long shelf life and high market value, demonstrating broad industrialization prospects and application potential.

[0106] 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 principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing fermented probiotic-fortified dried bean curd, characterized in that, Includes the following steps: S1, Raw material processing: Take soybeans and black beans, soak and wash them; S2, Preparation of starter culture: Select lactic acid bacteria and bifidobacteria, and mix them to prepare the starter culture; S3, Soybean preparation: Mix the processed soybeans with black beans, add water and grind into a paste to make mixed soy milk; S4, Primary Fermentation: Adjust the pH and temperature of the mixed soy milk, inoculate with a starter culture, and ferment at a constant temperature until the specified pH value is reached. S5, Soy milk processing: The fermented soy milk is heat-treated, filtered to remove residue, and fermented soy milk is obtained. S6, Preparation of probiotic microcapsules: Sodium alginate-chitosan microcapsules containing food-grade certified active Bifidobacteria are prepared using food-grade materials; S7, Coagulation: Heat the fermented soybean milk, add brine to coagulate, and let it stand to form tofu blocks; S8, pressing and shaping: cut the tofu blocks into pieces and press them to obtain tofu blanks; S9, Functional soaking: Prepare a soaking solution containing functional ingredients and soak the tofu blocks; S10, Probiotic Fortification: Cool the tofu blocks and coat them with a probiotic microcapsule suspension; S11, Low-temperature drying: Vacuum drying of tofu blocks to reduce moisture content; S12, Seasoning treatment: Prepare seasoning liquid and soak dried tofu; S13, Secondary drying: The seasoned dried tofu is dried with hot air; S14, Surface treatment: Prepare a coating solution, apply it to the surface of the dried bean curd, and air dry; S15, Packaging and Sterilization: Vacuum pack the dried bean curd, sterilize it, and cool it to obtain the finished product.

2. The method for preparing fermented probiotic-fortified dried bean curd according to claim 1, characterized in that, In step S1, the weight ratio of soybeans to black beans is 100:10-15. The soaking time is adjusted according to the ambient temperature, with soybeans soaked for 10-15 hours and black beans soaked for 6-10 hours.

3. The method for preparing fermented probiotic-fortified dried tofu according to claim 1, characterized in that, In step S2, the lactic acid bacteria include Streptococcus thermophilus and Lactobacillus bulgaricus, and the ratio of Streptococcus thermophilus, Lactobacillus bulgaricus and Bifidobacterium is 1:1:1, and the bacterial content in the fermentation agent is 10. 9 -10 10 CFU / g.

4. The method for preparing fermented probiotic-fortified dried bean curd according to claim 1, characterized in that, In step S4, the pH of the mixed soy milk is adjusted to 6.8-7.0, the temperature is adjusted to 37-40℃, the amount of starter culture is 2-3% of the weight of the soy milk, the fermentation time is 4-6 hours, and the final pH of the fermentation is 5.2-5.

5.

5. The method for preparing fermented probiotic-fortified dried bean curd according to claim 1, characterized in that, In step S6, the method for preparing probiotic microcapsules is as follows: Take 0.8-1.2 parts of food-grade chitosan and dissolve it in 1% food-grade lactic acid solution; Dissolve 1.5-2.0 parts of food-grade sodium alginate in deionized water; Take 2-3 portions of food-grade certified active Bifidobacterium powder and disperse it in food-grade triglycerides to form a bacterial suspension. The bacterial suspension was mixed with sodium alginate solution and then dripped into a chitosan solution containing 0.2M food-grade calcium chloride through a 1.5mm nozzle. Stir for 30 minutes to form microcapsules, filter, wash and store at 4°C.

6. The method for preparing fermented probiotic-fortified dried bean curd according to claim 1, characterized in that, In step S9, the formula for the functional soaking solution is to add the following per 100 kg of water: Green tea extract 0.5-0.8 kg; Curcumin 0.2-0.3 kg; Soybean peptides 0.5-0.8 kg; Salt 1.0-1.5 kg; The temperature of the soaking solution is 85-90℃, and the soaking time is 10-15 minutes.

7. The method for preparing fermented probiotic-fortified dried bean curd according to claim 1, characterized in that, In step S10, the tofu curd is cooled to 45-50℃, and the concentration of the probiotic microcapsule suspension is 10. 10 The dosage is 3-5% of the weight of the tofu curd, and the probiotic is a Bifidobacterium strain that has obtained food-grade safety certification.

8. The method for preparing fermented probiotic-fortified dried bean curd according to claim 1, characterized in that, In step S11, the vacuum drying conditions are a temperature of 55-60℃, a pressure of 50-100Pa, and a drying time of 4-6 hours. After drying, the moisture content of the dried bean curd is 45-50%.

9. The method for preparing fermented probiotic-fortified dried bean curd according to claim 1, characterized in that, In step S12, the seasoning liquid is formulated as follows: Add the following to every 100 kg of water: 10-12kg of light soy sauce; 3-5kg of dark soy sauce; 5-7 kg of white granulated sugar; 2-3 kg of salt; Five-spice powder 1.0-1.5kg; Sichuan peppercorns: 0.3-0.5 kg; Star anise 0.3-0.5kg; Cinnamon 0.2-0.3 kg; 0.2-0.3 kg of fennel; The seasoning liquid is first boiled and then simmered for 30 minutes. After filtration, it is cooled to 80-85℃ before use. The soaking time is 8-12 hours, and the temperature is maintained at 50-60℃ during the soaking process.

10. The method for preparing fermented probiotic-fortified dried bean curd according to claim 1, characterized in that, In step S14, the components of the application liquid, by weight, include: 3-5 parts edible gelatin; 2-3 parts of fructooligosaccharides; 1-2 parts maltodextrin; 0.5-1 part of plant polyphenols; 0.2-0.3 parts of food-grade pectin or sodium alginate; 15-20 parts water; The coating solution is heated to 60°C before use, and then air-dried at 40-45°C for 30-40 minutes after application; in step S15, the sterilization temperature after vacuum packaging is 95-98°C, and the sterilization time is 15-20 minutes.