Whole-bean squeezed bean curd and preparation method thereof

Abstract

The invention discloses whole-bean squeezed bean curd and a preparation method thereof. According to the preparation method disclosed by the invention, the preparation process is optimized, and particularly various coagulators are compounded for use, so that the gel strength and water binding capacity of the whole-bean bean curd are improved, and the gel network structure and texture characteristics are enhanced, and therefore, the whole-bean squeezed bean curd which is full in bean flavor, compact in structure and fine and smooth in mouth feel is prepared. Compared with full-bean filled bean curd which is mainly researched and developed on the market, the full-bean squeezed bean curd disclosed by the invention provides a new product which is close to marinated bean curd in quality and mouth feel for a full-bean bean curd product, not only retains the mellow and elastic mouth feel texture of the hard bean curd, but also can retain the nutritional ingredients of the soybeans to the greatest extent; and the bean curd becomes another high-quality choice besides the traditional hard bean curd, lactone bean curd and whole-bean filled bean curd, and can meet the requirements of different consumer groups.

Description

Technical Field

[0001] The invention relates to whole bean squeezed tofu and a preparation method thereof, belonging to the technical field of food processing. Background Art

[0002] Tofu is a traditional Chinese food, which is made of soybean as the main raw material. It is rich in high-quality plant protein, minerals such as calcium, iron, magnesium, vitamin B and dietary fiber, and has a low fat content. It is a low-calorie, high-nutrition food. Traditional tofu processing generally consists of soaking, grinding, filtering, boiling, coagulation and pressing. Such processing technology will discharge many by-products, such as dregs and whey liquid. On the one hand, the nutrients such as water-insoluble protein and dietary fiber in soybeans are lost with the discharge of dregs, which reduces the nutrition of tofu. On the other hand, the fresh dregs have high water activity. If not handled in time, they are very easy to rot and deteriorate, causing pollution to the environment, and are not conducive to the clean production of enterprises. Therefore, if all the components of soybeans can be retained in tofu and made into whole soybean dregs-free tofu, it will not only improve the nutritional value of tofu, but also be conducive to the clean production of enterprises.

[0003] At present, the research and development of whole bean tofu in the food industry generally focuses on the production of filled whole bean tofu. This type of whole bean tofu is formed in one step after the slurry is filled into the mold, without the need for brain breaking and pressing processes. Its properties are similar to those of rennet tofu, with a higher water content, a softer texture, and a more delicate taste. However, the industry lacks research and development on whole bean pressed tofu, and the variety of whole bean tofu products is single, lacking products with quality and taste close to brine tofu. The tofu obtained after the pressing process has a tighter and more uniform tissue structure and a firmer texture, which not only improves the elasticity and toughness of tofu, but also makes it more suitable for a variety of cooking methods such as frying, stir-frying, and stewing, and its taste is closer to traditional old tofu. However, in the production of whole bean tofu, since it does not go through the filtering process, the presence of cellulose particles and dregs polysaccharides will interfere with the formation of an ordered network structure of the protein. The produced whole bean tofu has problems such as weak gel strength and loose structure, resulting in its low quality and poor taste.

[0004] At present, the production of filled whole bean tofu is by adding a high dose of glutamine transaminase to the original coagulant formula, and adopting a two-stage coagulation process. In the first stage of coagulation, the glutamine transaminase is first subjected to a long enzyme-linked reaction to strengthen the cross-linking effect between proteins and improve the gel network structure. However, pressed tofu requires the solidified tofu to be broken, the original network structure to be broken, and part of the water of the gel to be squeezed out by pressure, so that a new network structure is formed between the proteins to complete the secondary molding. The high concentration of glutamine transaminase and its long enzyme-linked reaction make the gel network too dense, and it is difficult to destroy the gel network structure and reshape it during the breaking and squeezing process, resulting in the finished product being only tofu blocks bonded together by pressure, lacking integrity, uniformity and being fragile. These problems put forward requirements for the development of whole bean pressed tofu technology and composite coagulants. Summary of the invention

[0005] In order to solve the shortcomings of the prior art, the present invention provides a preparation method of whole bean squeezed tofu. Aiming at the problems of weak gel strength and loose structure of whole bean squeezed tofu, the production process is optimized, especially the compound use of multiple coagulants is aimed at improving the water content, water retention, gel strength and other indicators of the whole bean squeezed tofu, enhancing the gel network structure and texture characteristics, so as to prepare whole bean squeezed tofu with full bean flavor, firm structure and delicate taste.

[0006] The present invention is achieved through the following technical solutions: The first object of the present invention is to provide a method for preparing whole soybean squeezed tofu, comprising the following steps: S1. Clean the dehulled soybeans, mix the cleaned dehulled soybeans with water and allow the soybeans to fully swell; S2, mixing the swollen soybeans with water and then coarsely grinding them using a pulper to obtain a coarsely ground slurry; S3, finely grinding the coarsely ground slurry using a colloid mill to obtain a finely ground slurry; S4, using a high-pressure homogenizer to perform high-pressure homogenization on the finely ground slurry to obtain a homogenized slurry; S5, putting the homogenized slurry into a slurry cooking system for slurry cooking; S6. Pour the boiled slurry into a container, cool it to 48-52°C in an ice water bath, add a coagulant and stir until the slurry is partially solidified; keep it at this temperature for 5-10 min, then raise the temperature to 83-87°C and keep it for 15-30 min; S7, breaking the solidified tofu pudding obtained in step S6 with a spoon, scooping it into a tofu mold and flattening it, applying pressure on the mold to squeeze it for a period of time, then cutting the squeezed tofu into pieces, packaging them in PET boxes, sealing them with a sealing machine, and sterilizing them to obtain the whole bean squeezed tofu; Wherein, based on the mass of the slurry, the components of the coagulant are: 0.75-1.25‰ of glutamine aminotransferase, 4.0-5.0‰ of plaster of Paris, and 0.25-0.75‰ of magnesium chloride.

[0007] In one embodiment of the present invention, in step S1, based on the dry weight of soybeans, the washed dehulled soybeans are mixed with water in a ratio of 1:2-5 and the soybeans are fully swollen.

[0008] In one embodiment of the present invention, in step S2, the swollen soybeans and water are coarsely ground in a ratio of 1:5-7 based on the dry weight of the soybeans.

[0009] In one embodiment of the present invention, in step S3, the particle size of the slurry after fine grinding reaches 42-59 μm.

[0010] In one embodiment of the present invention, in step S4, before high-pressure homogenization, a defoaming agent is added to the slurry for defoaming, and high-pressure homogenization is performed after there are no bubbles and scum to further refine the dregs in the soy milk.

[0011] In one embodiment of the present invention, in step S4, the pressure of high-pressure homogenization is 80-90 MPa, and homogenization is performed 1-4 times.

[0012] In one embodiment of the present invention, in step S5, the slurry cooking temperature is 90-100° C. and maintained for 3-8 minutes.

[0013] In one embodiment of the present invention, in step S7, the pressing pressure is 4-6 kg, and the pressing time is 15-25 min.

[0014] In one embodiment of the present invention, in step S7, the tofu is cut into sizes of 10×10×4 cm, and the size of the PET box used is 12×12×5 cm.

[0015] In one embodiment of the present invention, in step S7, pasteurization is adopted at a temperature of 94-96° C. for 15-25 min.

[0016] The second object of the present invention is to provide whole soybean squeezed tofu prepared by the preparation method.

[0017] Beneficial effects of the present invention: (1) The present invention provides a method for making whole soybean squeezed tofu. Compared with traditional tofu, the method does not require the dregs to be filtered, so that nutrients such as dietary fiber in soybeans can be well preserved. At the same time, the method avoids the pollution caused by fresh bean dregs during the production process, which is beneficial to the clean production of enterprises and the saving of pollution treatment costs.

[0018] (2) Compared with the existing whole bean stuffed tofu, the whole bean squeezed tofu of the present invention provides a new product for whole bean tofu products that is close to the quality and taste of brine-cured tofu. Moreover, by optimizing the production process, especially the compound use of multiple coagulants, the gel strength and water holding capacity of the whole bean tofu are improved, and the gel network structure and texture characteristics are enhanced, thereby preparing a whole bean squeezed tofu with a strong bean flavor, a firm structure and a delicate taste, which meets the needs of different consumer groups.

[0019] (3) The present invention provides a composite coagulant suitable for whole soybean squeezed tofu. Compared with common coagulants (magnesium chloride, calcium sulfate), the whole soybean squeezed tofu made by using the composite coagulant has a smooth surface, a compact texture, a neat cross section, is not easy to break, has a strong bean flavor, and is milky white in color. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is a picture of tofu prepared in Example 1; Figure 2 This is a picture of tofu prepared in Example 2; Figure 3 This is a picture of tofu prepared in Example 3; Figure 4 This is a picture of tofu prepared in Example 4; Figure 5 This is a picture of tofu prepared in Example 5; Figure 6 This is a picture of tofu prepared in Comparative Example 1; Figure 7 This is a picture of tofu prepared in Comparative Example 2; Figure 8 This is a picture of tofu prepared in Comparative Example 3; Fig. 9 This is a picture of tofu prepared in Comparative Example 4; Fig.10 This is a picture of tofu prepared in Comparative Example 5; Fig.11 This is a picture of tofu prepared in Comparative Example 6; Fig.12 This is a picture of tofu prepared in Comparative Example 7; Fig.13 This is a picture of the tofu prepared in Comparative Example 8. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific examples. These implementation cases are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the claims attached to the application.

[0023] Source of raw materials The soybeans used in the embodiments of the present invention are Northeast soybeans (produced in Heilongjiang) that have been subjected to a dehulling treatment.

[0024] The present invention is not limited to soybean species, and the method of the present invention can be applied to conventional commercially available soybeans.

[0025] The technical solution of the present invention is described in detail below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified, the reagents, materials and equipment used can be purchased from commercial sources, or prepared by conventional methods, or are commonly used in the industry.

[0026] Embodiment 1: A method for making whole soybean squeezed tofu comprises the following steps: Wash. Wash 1 kg of dehulled soybeans with clean water.

[0027] Soaking. Mix the washed dehulled soybeans with water until the weight reaches 3 kg and place in a refrigerator at 4°C for 12 h to ensure that the soybeans are fully swollen.

[0028] Coarse grinding. After the soybeans have been fully soaked, add water to a total weight of 7 kg and put them into a pulper for coarse grinding.

[0029] Fine grinding: The slurry is finely ground using a colloid mill so that the particle size of the finely ground slurry reaches 48 μm.

[0030] High-pressure homogenization. Add 1.5 g of defoamer to the slurry and stir. After there are no bubbles and scum, use a high-pressure homogenizer to further refine the dregs in the soy milk. The homogenization pressure is 85 MPa and homogenization is performed twice.

[0031] Boiling. The homogenized slurry is pumped into the boiling system for boiling at a temperature of about 95°C for 5 minutes.

[0032] Add the stewed slurry into a container, cool it to 50°C in an ice-water bath, add the coagulant and stir until the slurry is partially solidified; keep it at this temperature for 10 minutes, then raise the temperature to 85°C and keep it for 20 minutes. The coagulant formula is: 7 g food-grade transglutaminase, 31.5 g food-grade plaster of Paris, and 3.5 g food-grade magnesium chloride, dissolved in 100 ml water.

[0033] Break the solidified tofu pudding with a spoon, pour it into the tofu mold and flatten it, press a heavy object on the mold to press it, the pressing pressure is 5 kg, and the pressing time is 20 minutes.

[0034] Cut and pack. Use a cutting machine to cut the tofu into pieces. After cutting, put the tofu into a PET box, add water to cover the tofu, and seal it with a sealing machine.

[0035] Pasteurization: Use pasteurization at 95℃ for 20 min.

[0036] Storage. The sterilized tofu is placed in a cold storage to cool. Figure 1 As shown, the tofu has a smooth surface, a tight texture, a neat cut surface, and is not easy to break. In addition, the tofu has a strong bean fragrance and a milky white color.

[0037] Embodiment 2: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 5.25 g food-grade glutamine aminotransferase, 31.5 g food-grade plaster of Paris, and 3.5 g food-grade magnesium chloride. The other steps remain unchanged. Figure 2 As shown, the whole is similar to the tofu of Example 1.

[0038] Embodiment 3: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 7 g food-grade glutamine aminotransferase, 35 g food-grade plaster of Paris, and 3.5 g food-grade magnesium chloride. The other steps remain unchanged. The prepared tofu is as follows Figure 3 As shown, the whole is similar to the tofu of Example 1.

[0039] Embodiment 4: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 7 g food-grade glutamine aminotransferase, 31.5 g food-grade plaster of Paris, and 1.75 g food-grade magnesium chloride. The other steps remain unchanged. The prepared tofu is as follows Figure 4 As shown, the whole is similar to the tofu of Example 1.

[0040] Embodiment 5: After the coagulant was added, the temperature was set to 50 °C and maintained for 5 min before being raised to 85 °C and maintained for 20 min. The other steps remained unchanged. Figure 5 As shown, the whole is similar to the tofu of Example 1.

[0041] Comparative Example 1: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 35 g food-grade plaster of Paris. The other steps remain unchanged. Figure 6 As shown, the tofu has a smooth surface, a neat cross section, a strong bean flavor, and a milky white color. However, compared with Examples 1-4, it is softer in texture and less tough.

[0042] Comparative Example 2: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 31.5 g food-grade plaster of Paris, 3.5 g food-grade magnesium chloride. The other steps remain unchanged. Figure 7 As shown, the tofu had cracks on the surface and was brittle as a whole, with unsatisfactory texture and toughness. Comparative Example 3: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 7 g food-grade glutamine aminotransferase, 35 g food-grade plaster of Paris. The other steps remain unchanged. Figure 8 As shown, the tofu as a whole is similar to the tofu of Comparative Example 1, and its texture, toughness, and uniformity of cross section are better than those of Comparative Example 1, but it does not reach the quality of Examples 1-4.

[0043] Comparative Example 4: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 35 g food-grade magnesium chloride. The other steps remain unchanged. Fig. 9 As shown, the surface and cross section of the tofu are rough, and no stable gel network structure is formed.

[0044] Comparative Example 5: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 31.5 g food-grade magnesium chloride, 3.5 g food-grade plaster of Paris. The other steps remain unchanged. Fig.10 As shown, the tofu as a whole is similar to the tofu of Comparative Example 4.

[0045] Comparative Example 6: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 7 g food-grade glutamine aminotransferase, 35 g food-grade magnesium chloride. The other steps remain unchanged. Fig.11 As shown, the tofu as a whole is similar to the tofu of Comparative Example 4.

[0046] Comparative Example 7: Add the prepared coagulant to the slurry and stir continuously until the slurry is partially coagulated. The coagulant formula is: 7 g food-grade glutamine aminotransferase, 31.5 g food-grade magnesium chloride, and 3.5 g food-grade plaster of Paris. The other steps remain unchanged. Fig.12 As shown, the tofu as a whole is similar to the tofu of Comparative Example 4.

[0047] Comparative Example 8: After the coagulant was added, the temperature was set to 50 °C and maintained for 20 min, then raised to 85 °C and maintained for 20 min. The other steps remained unchanged. Fig.13 As shown, the tofu had cracks on the surface and was brittle as a whole, with unsatisfactory texture and toughness.

[0048] Result test example: Determination of water content: Tested by constant weight method at 105℃.

[0049] Determination of water holding capacity: Take a small piece of tofu sample and weigh it as W 1 Then put it in a centrifuge tube and centrifuge it at 20℃4000 rpm for 10 min. After filtering out the water separated by centrifugation, weigh it and record it as W 2 Then the tofu sample was placed at 105℃ and dried for 6 h, and the tofu sample was weighed again, recorded as W 3 The water holding capacity of tofu is calculated according to the following formula. The calculation formula is: Water holding capacity (%) = (W 2 -W 3 ) / (W 1 -W 3 )×100.

[0050] Determination of gel strength: Place the container of whole bean curd on the test platform, align the probe with the center of the sample, and measure the gel strength of the whole bean curd. The measurement conditions are: use a P / 0.5 probe, a measurement speed of 1 mm / s, and a maximum displacement of 15 mm. The definition of gel strength is: the stress (g) required for gel rupture.

[0051] Texture determination: Cut the tofu sample into a cube with a side length of 2 cm, then place it on the loading platform and align the probe with the center of the sample. The measurement conditions are: probe model P / 35, test rate 1 mm / s, trigger force 5 g, compression deformation rate 40%. The texture parameters obtained are hardness, elasticity, cohesion, stickiness and chewiness.

[0052] The test results are shown in Table 1.

[0053] Table 1

[0054] After testing, compared with comparative examples 1-8, the whole soybean squeezed tofu prepared according to Example 1 has the characteristics of high water content, high gel strength, qualified water holding capacity, excellent texture characteristics, and the best comprehensive index. Among them, comparative examples 2 / 4 / 5 / 6 / 7 / 8 are not provided because the tofu produced is unqualified and the index data measured are meaningless and cannot be compared with other examples.

[0055] The whole soybean tofu of Example 1 and tofu sold on the market were analyzed for nutritional components and dietary fiber content. The results are shown in Table 2.

[0056] Determination of dietary fiber content: refer to GB 5009.88-2023 for testing.

[0057] Table 2

[0058] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing whole soybean squeezed tofu, characterized in that: The steps include: S1. Clean the dehulled soybeans, mix the cleaned dehulled soybeans with water and allow the soybeans to fully swell; S2, mixing the swollen soybeans with water and then coarsely grinding them using a pulper to obtain a coarsely ground slurry; S3, finely grinding the coarsely ground slurry using a colloid mill to obtain a finely ground slurry; S4, using a high-pressure homogenizer to perform high-pressure homogenization on the finely ground slurry to obtain a homogenized slurry; S5, putting the homogenized slurry into a slurry cooking system for slurry cooking; S6. Pour the boiled slurry into a container, cool it to 48-52°C in an ice water bath, add a coagulant and stir until the slurry is partially solidified; keep it at this temperature for 5-10 min, then raise the temperature to 83-87°C and keep it for 15-30 min; S7, breaking the solidified tofu pudding obtained in step S6 with a spoon, scooping it into a tofu mold and flattening it, applying pressure on the mold to squeeze it for a period of time, then cutting the squeezed tofu into pieces, packaging them in PET boxes, sealing them with a sealing machine, and sterilizing them to obtain the whole bean squeezed tofu; Wherein, based on the mass of the slurry, the components of the coagulant are: 0.75-1.25‰ of glutamine aminotransferase, 4.0-5.0‰ of plaster of Paris, and 0.25-0.75‰ of magnesium chloride.

2. The preparation method according to claim 1, characterized in that: In step S1, based on the dry weight of soybeans, the washed dehulled soybeans are mixed with water in a ratio of 1:2-5 and the soybeans are fully swollen.

3. The preparation method according to claim 1, characterized in that: In step S2, the swollen soybeans and water are coarsely ground in a ratio of 1:5 to 7 based on the dry mass of the soybeans.

4. The preparation method according to claim 1, characterized in that In step S3, the particle size of the finely ground slurry reaches 42-59 μm.

5. The preparation method according to claim 1, characterized in that: In step S4, before high-pressure homogenization, a defoaming agent is added to the slurry for defoaming, and high-pressure homogenization is performed after there are no bubbles and scum to further refine the dregs in the soy milk.

6. The preparation method according to claim 1, characterized in that In step S4, the pressure of high pressure homogenization is 80-90 MPa, and homogenization is performed 1-4 times.

7. The preparation method according to claim 1, characterized in that In step S5, the slurry is boiled at a temperature of 90-100°C for 3-8 minutes.

8. The preparation method according to claim 1, characterized in that In step S7, the pressing pressure is 4-6 kg, and the pressing time is 15-25 min.

9. The preparation method according to claim 1, characterized in that In step S7, pasteurization is performed at a temperature of 94-96°C for 15-25 min.

10. Whole soybean squeezed tofu prepared by the preparation method according to any one of claims 1 to 9.

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