Fresh bean curd and preparation method thereof

Abstract

The invention relates to the field of food processing, in particular to fresh bean curd and a preparation method thereof. The preparation method comprises the following steps: (1) preparing soybean milk: soaking, grinding and filtering soybeans to obtain soybean milk, and heating the soybean milk to obtain the soybean milk; (2) preparing modified arabinoxylan: adding arabinoxylan into water to obtain a mixed solution; adjusting the pH value of the mixed solution, then adding n-octylene succinic anhydride, carrying out a stirring reaction to obtain a reaction solution, adjusting the pH value of the reaction solution to be neutral, and carrying out centrifugation and drying to obtain the product, and (3) preparing fresh bean curd: uniformly mixing the soybean milk obtained in the step (1), the modified araboxylan obtained in the step (2), gluconic acid-delta-lactone, magnesium chloride and okra polysaccharide, cooking, cooling, solidifying and forming, thereby obtaining the fresh bean curd. The fresh bean curd prepared by the method has excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the field of food processing, and particularly to a fresh tofu and a preparation method thereof. Background Art

[0002] Tofu is an important ingredient in China. It has strong compatibility and a rich variety of cooking methods, and is deeply loved by the masses. Moreover, tofu is a non-fermented ingredient, which is simple to make, rich in nutrition, high in protein content, and has a wide range of audiences.

[0003] Currently, the mainstream tofu products on the market can be roughly divided into gypsum tofu, brine tofu, and inner ester tofu. Gypsum tofu is relatively hard and not easily broken as a whole. This advantage enables it to maintain a good shape during the cooking process and is not easily scattered. However, the taste of gypsum tofu is slightly bitter, and its hard texture makes the granular feeling more obvious when eaten, affecting the eating experience of some consumers. During the production process of brine tofu, the coagulation effect is too fast. Although this characteristic improves the production efficiency, it also brings difficulties in production control. Due to the too fast coagulation speed, brine tofu is prone to large lumps of aggregation and surface pits, affecting the appearance and texture of the product. Inner ester tofu is deeply loved by the public for its smooth, white surface and odorless characteristics. Its taste is delicate and melts in the mouth, and it is very suitable for mild cooking methods such as cold dressing and steaming. However, the mechanical properties of existing fresh tofu are low and it is extremely fragile. This shortcoming limits its application in various food processing methods. Especially in more intense cooking processes such as cutting and stir-frying, the fragility of fresh tofu has become a pain point for consumers when making dishes.

[0004] Based on the above background, there is an urgent need to provide a new fresh tofu with excellent mechanical properties. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the first object of the present invention is to provide a preparation method of fresh tofu, which is simple to operate and easy for large-scale production.

[0006] The second object of the present invention is to provide a fresh tofu with excellent mechanical properties.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A preparation method of fresh tofu, comprising the following steps:

[0009] (1) Prepare soymilk: The soybeans are soaked, ground, and filtered to obtain a slurry, and the slurry is heat-treated to obtain soymilk;

[0010] (2) Preparation of modified arabinoxylan: Add arabinoxylan to water to obtain a mixed solution; adjust the pH of the mixed solution, then add octenyl succinic anhydride and stir to react to obtain a reaction solution, adjust the pH of the reaction solution to neutral, and then centrifuge and dry to obtain it;

[0011] (3) Preparation of fresh tofu: Mix the soymilk in step (1), the modified arabinoxylan in step (2), glucono-δ-lactone, magnesium chloride, and okra polysaccharide evenly, and then steam, cool and solidify into shape to obtain it.

[0012] Further, in step (2), the mass ratio of the arabinoxylan to the octenyl succinic anhydride is 50:(1 - 3); the concentration of arabinoxylan in the mixed solution is 15 - 20 wt%.

[0013] Further, the arabinoxylan is water-soluble arabinoxylan.

[0014] Further, in step (2), the temperature of the stirring reaction is 40 - 60 °C, and the time of the stirring reaction is 6 - 8 h; adjust the pH of the mixed solution to 8 - 9.5.

[0015] Further, based on the dry weight of soybeans, in step (3), the mass of the modified arabinoxylan is 0.3 - 0.5% of the dry weight of soybeans, the mass of glucono-δ-lactone is 0.3 - 1% of the dry weight of soybeans, the mass of magnesium chloride is 0.1 - 0.3% of the dry weight of soybeans, and the mass of okra polysaccharide is 0.1 - 0.5% of the dry weight of soybeans.

[0016] Further, in step (3), the temperature of the steaming is 90 - 100 °C, and the time of the steaming is 25 - 30 min.

[0017] Further, in step (1), the temperature of the heat treatment is 80 - 100 °C, and the time of the heat treatment is 10 - 15 min.

[0018] Further, in step (1), the soaking is carried out by soaking soybeans in water for 6 - 8 h according to the mass ratio of soybeans to water of 1:(1.5 - 2.5).

[0019] Further, in step (1), the number of times of grinding the soybeans is 3 times, and the amount of water added during the grinding process is 6 - 8 times the dry weight of soybeans.

[0020] A kind of fresh tofu is prepared by the above preparation method.

[0021] The beneficial effects of the present invention:

[0022] 1. The present invention provides a method for preparing fresh tofu. During the tofu forming process, in addition to adding a coagulant, modified arabinoxylan and okra polysaccharide are also added. Experimental results prove that the synergistic effect of the two can improve the mechanical properties of fresh tofu. Among them, the modified arabinoxylan is prepared by the esterification reaction of octenyl succinic anhydride and water-soluble arabinoxylan. The carboxyl group in the modified arabinoxylan can interact with the amino group in the tofu, thereby enhancing the mechanical properties of the tofu. The okra polysaccharide itself has high viscosity and can also make the protein network more compact by promoting protein aggregation, thereby enhancing the mechanical properties of the tofu.

[0023] 2. The present invention also provides a fresh tofu, which has excellent mechanical properties. Detailed implementation mode

[0024] The present invention will be further described in detail below with reference to the embodiments, but the implementation modes of the present invention are not limited thereto. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field. The test methods without specific experimental conditions in the following embodiments are usually carried out according to conventional experimental conditions or according to the experimental conditions recommended by the manufacturer. Unless otherwise specified, the reagents and raw materials used in the present invention can be obtained commercially.

[0025] Example 1

[0026] Example 1 provides a method for preparing fresh tofu, which is as follows:

[0027] (1) Preparation of soymilk

[0028] According to the mass ratio of soybean to water of 1:2, the soybean is soaked in water at room temperature for 7h; then the soaked soybean is ground, and the number of grinding times is 3 times. The water addition amount during the grinding process is 7 times the dry weight of the soybean; after grinding, the slurry is obtained through filtration. The slurry is heated at 90°C for 12min and then cooled to room temperature to obtain soymilk.

[0029] (2) Preparation of modified arabinoxylan

[0030] According to the mass ratio of water-soluble arabinoxylan to octenyl succinic anhydride of 50:2, the water-soluble arabinoxylan (CAS: 9040-27-1) is added to water to obtain a mixed solution. The concentration of water-soluble arabinoxylan in the mixed solution is 18wt%; the pH of the mixed solution is adjusted to 9, heated to 50°C, and octenyl succinic anhydride is added and stirred for reaction for 7h. After the reaction, the reaction solution is obtained. After cooling to room temperature, the pH of the reaction solution is adjusted to neutral, and then centrifuged and dried at 60°C for 4h to obtain modified arabinoxylan.

[0031] (3) Preparation of fresh tofu

[0032] Weigh 0.4% of modified arabinoxylan based on the dry weight of soybeans, 0.6% of glucono-δ-lactone based on the dry weight of soybeans, 0.2% of magnesium chloride based on the dry weight of soybeans, and 0.4% of okra polysaccharide based on the dry weight of soybeans; according to the mass ratio, mix the soy milk in step (1), the modified arabinoxylan, glucono-δ-lactone, magnesium chloride, and okra polysaccharide in step (2) evenly, cook at 95°C for 28 minutes, and then cool and solidify to obtain fresh tofu.

[0033] Example 1 also provides a kind of fresh tofu, which is prepared by the above preparation method.

[0034] Example 2

[0035] Example 2 provides a preparation method of fresh tofu, which is as follows:

[0036] (1) Prepare soy milk

[0037] Soak soybeans in water according to the mass ratio of soybeans to water of 1:1.5 at room temperature for 6 hours; then grind the soaked soybeans, and the number of grinding times is 3 times. The water addition amount during the grinding process is 6 times the dry weight of soybeans; after grinding, filter to obtain slurry, heat the slurry at 80°C for 15 minutes, and then cool to room temperature to obtain soy milk.

[0038] (2) Prepare modified arabinoxylan

[0039] Add water-soluble arabinoxylan to water according to the mass ratio of water-soluble arabinoxylan to octenyl succinic anhydride of 50:1 to obtain a mixed solution. The concentration of water-soluble arabinoxylan in the mixed solution is 15 wt%; adjust the pH of the mixed solution to 8, heat it to 40°C, add octenyl succinic anhydride and stir for reaction for 8 hours. After the reaction, obtain a reaction solution. After cooling to room temperature, adjust the pH of the reaction solution to neutral, centrifuge, and dry at 60°C for 4 hours to obtain modified arabinoxylan.

[0040] (3) Prepare fresh tofu

[0041] Weigh each raw material based on the dry weight of soybeans, including 0.3% of modified arabinoxylan based on the dry weight of soybeans, 0.3% of glucono-δ-lactone based on the dry weight of soybeans, 0.1% of magnesium chloride based on the dry weight of soybeans, and 0.1% of okra polysaccharide based on the dry weight of soybeans; according to the mass ratio, mix the soy milk in step (1), the modified arabinoxylan, glucono-δ-lactone, magnesium chloride, and okra polysaccharide in step (2) evenly, cook at 90°C for 30 minutes, and then cool and solidify to obtain fresh tofu.

[0042] Example 2 also provides a kind of fresh tofu, which is prepared by the above preparation method.

[0043] Example 3

[0044] Example 3 provides a method for preparing fresh tofu, which is as follows:

[0045] (1) Preparation of soymilk

[0046] Soybeans are soaked in water at a mass ratio of soybeans to water of 1:2.5 for 8 h at room temperature; then grinding is carried out, and the number of grinding times is 3 times. The addition amount of water during the grinding process is 8 times the mass of soybeans; after grinding, the slurry is obtained through filtration. After the slurry is heated at 100 °C for 10 min, it is cooled to room temperature to obtain soymilk.

[0047] (2) Preparation of modified arabinoxylan

[0048] Water-soluble arabinoxylan is added to water at a mass ratio of water-soluble arabinoxylan to octenyl succinic anhydride of 50:3 to obtain a mixed solution, and the concentration of water-soluble arabinoxylan in the mixed solution is 20 wt%; the pH of the mixed solution is adjusted to 9.5, the temperature is raised to 60 °C, octenyl succinic anhydride is added and stirred for reaction for 6 h. After the reaction is completed, the reaction solution is obtained. After cooling to room temperature, the pH of the reaction solution is adjusted to neutral, and after centrifugation and drying at 60 °C for 4 h, modified arabinoxylan is obtained.

[0049] (3) Preparation of fresh tofu

[0050] Calculated based on the dry weight of soybeans, each raw material is weighed, including 0.5% of modified arabinoxylan based on the dry weight of soybeans, 1% of glucono-δ-lactone based on the dry weight of soybeans, 0.3% of magnesium chloride based on the dry weight of soybeans, and 0.5% of okra polysaccharide based on the dry weight of soybeans; according to the mass ratio, the soymilk in step (1), the modified arabinoxylan in step (2), glucono-δ-lactone, magnesium chloride, and okra polysaccharide are mixed evenly, steamed at 100 °C for 25 min, and then cooled and solidified into shape to obtain fresh tofu.

[0051] Example 3 also provides a fresh tofu prepared by the above preparation method.

[0052] Comparative Example 1

[0053] The difference between Comparative Example 1 and Example 1 is that water-soluble arabinoxylan is used instead of modified arabinoxylan, and the rest is the same as in Example 1.

[0054] Comparative Example 2

[0055] The difference between Comparative Example 2 and Example 1 is that okra polysaccharide is omitted, and the rest is the same as in Example 1.

[0056] Comparative Example 3

[0057] The difference between Comparative Example 3 and Example 1 is that okra polysaccharide is omitted and the mass of modified arabinoxylan is increased to 0.7%, and the rest is the same as in Example 1.

[0058] Comparative Example 4

[0059] The difference between Comparative Example 4 and Example 1 is that the modified arabinoxylan is omitted, and the mass of okra polysaccharide is increased to 0.7%, and the rest is the same as in Example 1.

[0060] Effect verification

[0061] The texture indexes (hardness, elasticity, chewiness, adhesiveness) of the tofu obtained in Examples 1-3 and Comparative Examples 1-4 were detected, and the results are shown in Table 1.

[0062] Among them, the measuring methods of hardness, elasticity, chewiness, and adhesiveness are as follows:

[0063] The tofu refrigerated at 4°C for 12 h was cut into cubes of 0.1 cm × 0.1 cm × 0.1 cm, and three compression experiments were carried out using a Brookfield texture analyzer CT-3. The test probe was an acrylic probe with a flat surface. The target value was 40% of the original height, the trigger point load was 5 g, the test speed was 0.5 mm / s, the return speed was 0.5 mm / s, and the cycle was repeated twice. The TexturePro CT V1.8 software was used to record the curve of the compression process and calculate the hardness, elasticity, chewiness, and adhesiveness.

[0064] Table 1

[0065] Grouping Hardness / g Elasticity / mm Chewiness / mJ Viscosity / g Example 1 116.41 2.97 2.17 27.75 Example 2 116.12 2.96 2.15 27.41 Example 3 115.77 2.94 2.14 26.83 Comparative Example 1 107.36 2.62 1.97 23.60 Comparative Example 2 100.28 1.83 1.80 16.18 Comparative Example 3 103.50 2.05 1.85 17.39 Comparative Example 4 94.63 1.50 1.66 13.56

[0066] It can be seen from observing Table 1 that the tofu obtained in Examples 1-3 has excellent mechanical properties.

[0067] Compared with Examples 1-3, in Comparative Example 1, water-soluble arabinoxylan was used instead of modified arabinoxylan; in Comparative Example 2, okra polysaccharide was omitted; in Comparative Example 3, okra polysaccharide was omitted and the amount of modified arabinoxylan was increased; in Comparative Example 4, modified arabinoxylan was omitted and the amount of okra polysaccharide was increased, and the mechanical properties of the obtained tofu were reduced. The above results show that the modified arabinoxylan and okra polysaccharide act synergistically to improve the mechanical properties of fresh tofu. Specifically, the modified arabinoxylan is prepared by an esterification reaction of octenyl succinic anhydride and arabinoxylan. The carboxyl group in the modified arabinoxylan interacts with the amino group in the tofu, thereby enhancing the mechanical properties of the tofu. Okra polysaccharide itself has high viscosity and can also promote protein aggregation, making the protein network more compact, thereby enhancing the mechanical properties of the tofu. In addition, the hydrophobicity of the modified arabinoxylan is also improved. After the modified arabinoxylan enters the stomach with the tofu, it is hydrolyzed into soluble cellulose in a strong acid environment, so as to achieve the intake of dietary fiber and promote gastrointestinal motility.

[0068] The above embodiments are only the preferred embodiments of the present invention, and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for preparing fresh tofu, characterized in that: The following steps are involved: (1) preparing soybean milk: soaking, grinding and filtering soybeans to obtain slurry, and heating the slurry to obtain soybean milk; (2) Preparing modified arabinoxylan: adding arabinoxylan to water to obtain a mixed solution; adjusting the pH of the mixed solution, then adding n-octenyl succinic anhydride to carry out stirring reaction to obtain a reaction solution, adjusting the pH of the reaction solution to neutral, centrifuging and drying to obtain; (3) Preparing fresh tofu: the soy milk of step (1), the modified arabinoxylan of step (2), glucono-δ-lactone, magnesium chloride and okra polysaccharide are uniformly mixed, and the mixture is steamed, cooled and solidified to obtain fresh tofu.

2. The method for preparing fresh bean curd according to claim 1, characterized in that: The mass ratio of arabinoxylan to n-octenylsuccinic anhydride in step (2) is 50:(1-3); the concentration of arabinoxylan in the mixed solution is 15-20wt%.

3. The method for preparing fresh bean curd according to claim 2, characterized in that: The arabinoxylan is water-soluble arabinoxylan.

4. The method for preparing fresh bean curd according to claim 1, characterized in that: In step (2), the stirring reaction temperature is 40-60° C., and the stirring reaction time is 6-8 hours; and the pH of the mixed solution is adjusted to 8-9.

5.

5. The method for preparing fresh bean curd according to claim 1, characterized in that: Based on the dry weight of soybeans, the mass of the modified arabinoxylan in step (3) is 0.3-0.5% of the dry weight of soybeans, the mass of glucono-δ-lactone is 0.3-1% of the dry weight of soybeans, the mass of magnesium chloride is 0.1-0.3% of the dry weight of soybeans, and the mass of okra polysaccharide is 0.1-0.5% of the dry weight of soybeans.

6. The method for preparing fresh bean curd according to claim 1, characterized in that: The cooking temperature in step (3) is 90-100° C., and the cooking time is 25-30 minutes.

7. The method for preparing fresh bean curd according to claim 1, characterized in that: The temperature of the heating treatment in step (1) is 80-100° C., and the time of the heating treatment is 10-15 min.

8. The method for preparing fresh bean curd according to claim 1, characterized in that: The soaking in step (1) is performed by soaking the soybeans in water for 6-8 hours at a mass ratio of soybeans to water of 1:(1.5-2.5).

9. The method for preparing fresh bean curd according to claim 1, characterized in that: The number of refining in step (1) is 3 times, and the amount of water added during the refining process is 6-8 times the dry weight of the soybeans.

10. A fresh tofu, characterized in that: The preparation method is described in any one of claims 1 to 9.