Composite cereal high-nutrition bean curd and preparation process thereof

Abstract

The present application relates to a kind of composite cereal high-nutrition bean curd and its preparation process, belong to food processing technical field.The present application provides a kind of preparation process to the problems of insufficient nutrient release, many anti-nutritional factors remain, rough taste and other problems of existing cereal bean curd, including the following steps: first, soybean is soaked, grinds pulp, three-stage cooking pulp and obtains uniform soybean milk;Then, composite cereal is crushed at low temperature, three-step composite enzymolysis and plant lactobacillus and saccharomyces cerevisiae double bacteria synergistic fermentation, concentrate and obtain fermented cereal liquid;The fermented cereal liquid is mixed with uniform soybean milk, and composite coagulating agent and stabilizer are added, and finally, the composite cereal high-nutrition bean curd with good taste, rich in various nutrients and long shelf life is prepared by water bath coagulation, demolding and cooling.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology and relates to a compound grain high-nutrition tofu and its preparation process. Background Technology

[0002] Tofu, a traditional soy product, is rich in high-quality plant protein, soy isoflavones, and various minerals, making it a popular choice among consumers. However, traditional tofu has a relatively simple nutritional profile, with lower levels of dietary fiber, B vitamins, and specific minerals, making it difficult to meet the modern consumer's demand for balanced and functional nutrition.

[0003] To enhance the nutritional value of tofu, some studies have attempted to combine grains and soybeans to prepare compound grain tofu. Grains are rich in dietary fiber, B vitamins, polyphenols, and various trace elements, and they are complementary to soybean protein in terms of amino acid composition. Theoretically, this can significantly improve the overall nutritional quality of the product.

[0004] However, existing compound grain tofu technology has the following drawbacks: Grain cell walls are composed of dense cellulose, hemicellulose, and lignin. Simple crushing or gelatinization cannot fully disrupt the cell wall structure, resulting in the encapsulation of starch, protein, dietary fiber, and polyphenols, making them difficult for human digestive enzymes to access, thus leading to low actual nutrient utilization. Secondly, grains generally contain anti-nutritional factors such as phytic acid and trypsin inhibitors. Phytic acid forms insoluble complexes with minerals such as calcium, iron, and zinc, reducing their bioavailability; trypsin inhibitors inhibit protein digestion and absorption. Furthermore, directly adding grain powder results in a coarse, grainy tofu texture, and the raw, unpleasant odor of grains masks the natural aroma of soybeans, affecting consumer acceptance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a compound grain high-nutrition tofu and its preparation process.

[0006] The objective of this invention can be achieved through the following technical solutions: A process for preparing compound grain high-nutrition tofu, the process comprising the following steps: S1-1: Soak soybeans in water for 8-12 hours with a soybean-to-water ratio of 1:(3-5). After draining, add 4-6 times the amount of water to grind the soybeans into a paste. Filter the paste through an 80-100 mesh sieve and then boil the paste to obtain a homogeneous soy milk. S1-2: The compound grain raw materials are pulverized at low temperature to 100-200 mesh, and then subjected to compound enzymatic hydrolysis after adding 3-5 times the amount of water. S1-3: After sterilizing the enzymatically hydrolyzed grain slurry, cool it and adjust the pH to 6.0~6.5. At the same time, inoculate it with Lactobacillus plantarum and Saccharomyces cerevisiae, ferment it at 37℃ until the pH drops to 4.0~4.5, and concentrate it to 1 / 2~2 / 3 of the original volume to obtain fermented grain liquid. S1-4: After heating and sterilizing the fermented grain liquid, mix it with the homogenized soy milk, add the compound coagulant and stabilizer to obtain the mixed slurry, pour the mixed slurry into the mold, coagulate in a water bath at 70~85℃ for 20~40 minutes, demold, let stand and cool to obtain the compound grain high nutrition tofu.

[0007] As a preferred technical solution of the present invention, the boiling step in S1-1 is to first heat the mixture to 70~80℃ and keep it at that temperature for 10 minutes, then heat it to 90~95℃ and keep it at that temperature for 5 minutes, and then let it cool to 40℃.

[0008] As a preferred embodiment of the present invention, the composite grain raw materials in S1-2 are oats, buckwheat, millet and highland barley mixed in a mass ratio of (2~4):(1~3):(0.5~1.5):(3~5). As a preferred embodiment of the present invention, the composite grain raw materials are oats, buckwheat, millet and highland barley mixed in a mass ratio of 3:2:1:4.

[0009] As a preferred embodiment of the present invention, the complex enzymatic hydrolysis treatment in S1-2 involves first adding cellulase and hydrolyzing at 50-55°C and pH 4.5-5.5 for 60-90 minutes, then adding neutral protease and hydrolyzing at 45-50°C and pH 6.5-7.0 for 40-60 minutes, and finally adding phytase and hydrolyzing at 55°C and pH 5.0-5.5 for 30-40 minutes.

[0010] In a preferred embodiment of the present invention, the inoculum quantity of *Lactobacillus plantarum* in S1-3 is 10. 6 ~10 8 CFU / mL.

[0011] In a preferred embodiment of the present invention, the inoculation amount of brewing yeast in S1-3 is 10. 5 ~10 7 CFU / mL.

[0012] As a preferred technical solution of the present invention, the composite coagulant in S1-4 is composed of gypsum, glucono-delta-lactone and transglutaminase in a mass ratio of (2~4):(4~6):(1~3), and the amount of composite coagulant added is 1.5%~3.0% of the total mass of fermented grain liquid and homogenized soy milk.

[0013] As a preferred embodiment of the present invention, the stabilizer in S1-4 is one or more of sodium carboxymethyl cellulose, sodium alginate or konjac glucomannan, and the amount added is 0.1% to 0.5% of the total mass of fermented grain liquid and homogenized soy milk.

[0014] As a preferred embodiment of the present invention, the mass ratio of fermented grain liquid to homogenized soybean milk in S1-4 is (5~20):100.

[0015] The boiling process adopts a segmented process: first, the temperature is raised to 70-80℃ and kept at that temperature for 10 minutes, and then the temperature is raised to 90-95℃ and kept at that temperature for 5 minutes. This process can remove the beany and bitter tastes, while avoiding excessive denaturation of proteins and retaining heat-sensitive active ingredients such as soy isoflavones, providing a high-quality protein base for subsequent blending with grain slurry.

[0016] Based on the complementary nature of nutrients in various grains, the compound grain formula uses a scientific ratio of oats, buckwheat, millet, and highland barley. Oats provide β-glucan and high-quality protein, buckwheat is rich in rutin and flavonoids, millet provides B vitamins and γ-aminobutyric acid (GABA), and highland barley provides high levels of β-glucan and resistant starch. This combination achieves a synergistic effect in dietary fiber and enrichment of antioxidants. The compound grains are pulverized at low temperature to 100-200 mesh to maximize the retention of heat-sensitive nutrients and increase the contact area for enzymatic hydrolysis. Subsequently, cellulase, neutral protease, and phytase are added sequentially for a three-step enzymatic hydrolysis. Cellulase first hydrolyzes cell wall cellulose, releasing embedded starch, protein, and polyphenols. Then, neutral protease hydrolyzes grain protein into small peptides and free amino acids, improving protein digestibility. Phytase further degrades anti-nutritional factors such as phytic acid, releasing chelated minerals such as calcium, iron, and zinc. The three-step enzymatic hydrolysis works synergistically to significantly improve the bioavailability of cereal nutrients, while providing usable sugars and amino acid precursors for subsequent fermentation.

[0017] The product is inoculated with Lactobacillus plantarum and Saccharomyces cerevisiae. Lactobacillus plantarum produces a large amount of lactic acid, which lowers the pH and synthesizes natural antibacterial substances such as lactobacillusin, while degrading residual anti-nutritional factors. Saccharomyces cerevisiae produces ester aroma substances, giving the product a unique fermented malt aroma. The synergistic fermentation of the two not only further improves the solubility of proteins and polyphenols, but also extends the product's refrigerated shelf life through the organic acids and antibacterial substances produced by metabolism.

[0018] Fermented grain liquid and homogenized soy milk are mixed in a certain proportion to ensure that the active ingredients of grains are evenly dispersed in the soy protein matrix. A composite coagulant and stabilizer consisting of gypsum, glucono-delta-lactone and transglutaminase are added. Gypsum provides calcium ions to promote protein gelation, glucono-delta-lactone slowly releases acid to ensure uniform coagulation, transglutaminase catalyzes the formation of covalent cross-links between soy protein and grain protein, and the stabilizer enhances the water-holding capacity and dehydration resistance of the system.

[0019] The beneficial effects of this invention are: The process of this invention first uses soaking, grinding, and segmented boiling to effectively remove the beany smell while retaining the active ingredients of soybeans, obtaining a high-quality soy milk base. Low-temperature pulverization and a three-step enzymatic hydrolysis are then employed to fully break down grain cell walls, hydrolyze proteins, and degrade phytic acid, significantly improving the bioavailability of grain nutrients. Next, synergistic fermentation with *Lactobacillus plantarum* and *Saccharomyces cerevisiae* generates lactic acid, ester aroma compounds, and natural antibacterial substances, further enhancing nutrient solubility and flavor, and extending the product's shelf life. Finally, the fermented grain liquid is combined with soy milk, and a compound coagulant and stabilizer are added to ultimately produce a high-nutrition, compound grain tofu with a good taste, rich in various nutrients, and with a long shelf life. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0021] It should be noted that, unless otherwise specified, the present invention does not specifically limit the source of the raw materials used in the following embodiments. Commercially available products or products prepared by conventional preparation methods that are well known to those skilled in the art can be used. Experimental methods that do not specify specific conditions are all conventional methods and conventional conditions well known in the art.

[0022] Lactobacillus plantarum ATCC 8014: purchased from Wuhan Gray Algae Biotechnology Co., Ltd., product number HZB113265; Saccharomyces cerevisiae: purchased from Wuhan Gray Algae Biotechnology Co., Ltd., product number HZB227182.

[0023] Example 1

[0024] A process for preparing compound grain high-nutrition tofu, the process comprising the following steps: S1-1: Soak soybeans in water for 10 hours with a soybean-to-water ratio of 1:4. After draining, add 5 times the amount of water to grind the soybeans into a paste. Filter the paste through a 100-mesh sieve. To cook the paste, first heat the paste to 75°C and keep it warm for 10 minutes, then heat it to 92°C and keep it warm for 5 minutes. Cool the paste to 40°C to obtain a uniform soy milk. S1-2: The compound grains are oats, buckwheat, millet, and highland barley mixed in a mass ratio of 3:2:1:4. The compound grains are pulverized at low temperature to 150 mesh, and 4 times the amount of water is added to obtain a mixture. Enzymatic hydrolysis is performed sequentially: 0.2% (by mass) of cellulase is added to the mixture, and enzymatic hydrolysis is carried out at 52℃ and pH 5.0 for 75 min; 0.1% (by mass) of neutral protease is added to the mixture, and enzymatic hydrolysis is carried out at 48℃ and pH 6.8 for 50 min; 0.05% (by mass) of phytase is added to the mixture, and enzymatic hydrolysis is carried out at 55℃ and pH 5.2 for 35 min. After enzymatic hydrolysis, the enzymes are inactivated at 90℃ for 5 min. S1-3: Cool the enzymatic hydrolysate to 37℃, adjust the pH to 6.2, and inoculate with *Lactobacillus plantarum* (1×10⁻⁶). 7 CFU / mL) and Saccharomyces cerevisiae (1×10) 6 (CFU / mL), fermented at 37℃ until the pH drops to 4.2, then concentrated under vacuum to 3 / 5 of the original volume to obtain fermented grain liquid; S1-4: After the fermented grain liquid is heated and sterilized, it is mixed with soy milk at a mass ratio of 10:100. A compound coagulant and a stabilizer are added. The compound coagulant is a mixture of gypsum, glucono-delta-lactone and transglutaminase at a mass ratio of 3:5:2, and the amount added is 2.0% of the total mass of the fermented grain liquid and soy milk. The stabilizer is sodium carboxymethyl cellulose, and the amount added is 0.3% of the total mass of the fermented grain liquid and soy milk. The mixture is poured into a mold, coagulated in a 78°C water bath for 30 minutes, demolded, and allowed to cool to obtain the compound grain high-nutrition tofu.

[0025] Example 2

[0026] The only difference between this embodiment and Embodiment 1 is that the compound grain raw materials are oats, buckwheat, millet and highland barley mixed in a mass ratio of 2:1:0.5:3, while the rest are the same as in Embodiment 1.

[0027] Example 3

[0028] The only difference between this embodiment and Embodiment 1 is that the compound grain raw materials are oats, buckwheat, millet and highland barley mixed in a mass ratio of 4:3:1.5:5, while the rest are the same as in Embodiment 1.

[0029] Example 4

[0030] The only difference between this embodiment and Embodiment 1 is that the composite coagulant is composed of gypsum, gluconolactone, and transglutaminase in a mass ratio of 2:4:1, and the amount of composite coagulant added is 1.5% of the total mass of the mixed slurry. All other aspects are the same as in Embodiment 1.

[0031] Example 5

[0032] The only difference between this embodiment and Embodiment 1 is that the composite coagulant is composed of gypsum, gluconolactone, and transglutaminase in a mass ratio of 4:6:3, and the amount of composite coagulant added is 3.0% of the total mass of the mixed slurry. All other aspects are the same as in Embodiment 1.

[0033] Example 6

[0034] The only difference between this embodiment and Embodiment 1 is that the mass ratio of fermented grain liquid to homogenized soy milk is 5:100; all other aspects are the same as in Embodiment 1.

[0035] Example 7

[0036] The only difference between this embodiment and Embodiment 1 is that the mass ratio of fermented grain liquid to homogenized soy milk is 20:100; all other aspects are the same as in Embodiment 1.

[0037] Comparative Example 1 The only difference between this comparative example and Example 1 is that no enzymatic hydrolysis was performed; all other aspects are the same as in Example 1.

[0038] Comparative Example 2 The only difference between this comparative example and Example 1 is that no fermentation process is performed; the mixture is directly concentrated and then mixed with soy milk. All other aspects are the same as in Example 1.

[0039] Comparative Example 3 The only difference between this comparative example and Example 1 is that phytase is not added; otherwise, they are the same as in Example 1.

[0040] Comparative Example 4 The only difference between this comparative example and Example 1 is that Lactobacillus plantarum is not added; otherwise, they are the same as in Example 1.

[0041] Comparative Example 5 The only difference between this comparative example and Example 1 is that brewing yeast is not added; otherwise, they are the same as Example 1.

[0042] Comparative Example 6 The only difference between this comparative example and Example 1 is that the compound grains are oats, buckwheat, millet, and highland barley mixed in a mass ratio of 1:1:1:1, while the rest are the same as in Example 1.

[0043] Comparative Example 7 The only difference between this comparative example and Example 1 is that no compound grains are added; otherwise, they are the same as Example 1.

[0044] Nutritional component determination: The fat content of tofu was determined according to GB 5009.6-2016 standard; the protein content was determined according to GB 5009.5-2016 standard; and the total dietary fiber content was determined according to GB 5009.88-2014 standard. Shelf life test: The samples were refrigerated at 4℃, and the total bacterial count was determined according to GB 4789.2-2022. The pH value was also measured, and sensory changes were observed. Shelf life was defined as: total bacterial count ≤ 1×10⁻⁶. 5 The longest storage period with CFU / g and acceptable sensory characteristics (no abnormal odor, no signs of spoilage) is summarized in Table 1.

[0045] Table 1

[0046] Sensory evaluation: A sensory panel consisting of 10 trained food professionals conducted blind tests on the following indicators using a 9-point scale (1 point = very poor, 9 points = very good): color, bean aroma, grain flavor, texture, and overall acceptability. The final sensory score was the average of the scores for the above 5 items. The specific results are summarized in Table 2.

[0047] Table 2

[0048] The data above show that the protein content of Examples 1-7 is 9.0-9.8 g / 100g, and the fat content is 6.2-7.2 g / 100g, slightly lower than that of traditional tofu, but the total dietary fiber is significantly increased, demonstrating the nutritional fortification effect of the grain compound. Comparative Example 1, which did not undergo enzymatic hydrolysis, has a high dietary fiber content, but the texture is rough because the fiber was not modified by enzymatic hydrolysis. The shelf life of Examples 1-7 is 14-16 days, significantly longer than that of Comparative Examples 1-7, with Comparative Example 1 only lasting 9 days and Comparative Example 2 only 11 days. This indicates that the lactobacillus produced by the synergistic effect of enzymatic hydrolysis and fermentation, as well as the low pH environment, can effectively inhibit microbial growth and extend shelf life. Although Comparative Example 6 has a shelf life of 15 days, its total sensory score is lower than that of Example 1. The total sensory scores of Examples 1-7 are between 8.06 and 8.42, significantly better than the comparative examples. Example 1 has a total sensory score of 8.34, demonstrating excellent grain flavor and a delicate texture. Comparative Example 1, lacking enzymatic hydrolysis, had a coarse texture and poor grain flavor. Overall, the enzymatic hydrolysis combined with dual-strain fermentation and optimized grain ratio of this invention not only preserves the bean aroma but also imparts a pleasant fermented wheat aroma to the product, significantly improving the texture of the tofu and extending its shelf life.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are still within the scope of the present invention.

Claims

1. A preparation process for a compound grain high-nutrition tofu, characterized in that, The preparation process includes the following steps: S1-1: Soak soybeans in water for 8-12 hours with a soybean-to-water ratio of 1:(3-5). After draining, add 4-6 times the amount of water to grind the soybeans into a paste. Filter the paste through an 80-100 mesh sieve and then boil the paste to obtain a homogeneous soy milk. S1-2: The compound grain raw materials are pulverized at low temperature to 100-200 mesh, and then subjected to compound enzymatic hydrolysis after adding 3-5 times the amount of water. S1-3: After sterilizing the enzymatically hydrolyzed grain slurry, cool it and adjust the pH to 6.0~6.

5. At the same time, inoculate it with Lactobacillus plantarum and Saccharomyces cerevisiae, ferment it at 37℃ until the pH drops to 4.0~4.5, and concentrate it to 1 / 2~2 / 3 of the original volume to obtain fermented grain liquid. S1-4: After heating and sterilizing the fermented grain liquid, mix it with the homogenized soy milk, add the compound coagulant and stabilizer to obtain the mixed slurry, pour the mixed slurry into the mold, coagulate in a water bath at 70~85℃ for 20~40 minutes, demold, let stand and cool to obtain the compound grain high nutrition tofu.

2. The preparation process of a compound grain high-nutrition tofu according to claim 1, characterized in that, The boiling step in S1-1 involves first heating the mixture to 70-80°C and holding it for 10 minutes, then heating it to 90-95°C and holding it for 5 minutes, and finally cooling it to 40°C.

3. The preparation process of a compound grain high-nutrition tofu according to claim 1, characterized in that, The composite grain raw materials in S1-2 are oats, buckwheat, millet and highland barley mixed in a mass ratio of (2~4):(1~3):(0.5~1.5):(3~5).

4. The preparation process of a compound grain high-nutrition tofu according to claim 3, characterized in that, The compound grain raw materials are oats, buckwheat, millet and highland barley mixed in a mass ratio of 3:2:1:

4.

5. The preparation process of a compound grain high-nutrition tofu according to claim 1, characterized in that, The S1-2 compound enzymatic hydrolysis treatment involves first adding cellulase and hydrolyzing at 50-55℃ and pH 4.5-5.5 for 60-90 minutes, then adding neutral protease and hydrolyzing at 45-50℃ and pH 6.5-7.0 for 40-60 minutes, and finally adding phytase and hydrolyzing at 55℃ and pH 5.0-5.5 for 30-40 minutes.

6. The preparation process of a compound grain high-nutrition tofu according to claim 1, characterized in that, The inoculum size of *Lactobacillus plantarum* in S1-3 is 10. 6 ~10 8 CFU / mL.

7. The preparation process of a compound grain high-nutrition tofu according to claim 1, characterized in that, The inoculation amount of brewer's yeast in S1-3 is 10. 5 ~10 7 CFU / mL.

8. The preparation process of a compound grain high-nutrition tofu according to claim 1, characterized in that, The composite coagulant in S1-4 is composed of gypsum, glucono-delta-lactone and transglutaminase in a mass ratio of (2~4):(4~6):(1~3), and the amount of composite coagulant added is 1.5%~3.0% of the total mass of fermented grain liquid and homogenized soybean milk.

9. The preparation process of a compound grain high-nutrition tofu according to claim 1, characterized in that, The stabilizer in S1-4 is one or more of sodium carboxymethyl cellulose, sodium alginate, or konjac glucomannan, and the amount added is 0.1% to 0.5% of the total mass of fermented grain liquid and homogenized soy milk.

10. The preparation process of a compound grain high-nutrition tofu according to claim 1, characterized in that, The mass ratio of fermented grain liquid to homogenized soybean milk in S1-4 is (5~20):100.

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