Method for improving tofu quality and moisture content distribution using soaking and water for pulping

Abstract

The application discloses a method for improving the quality and moisture content distribution of bean curd by soaking and using water for pulp grinding, and comprises the following steps: (1) pretreatment: accurately weighing CaCl2, MgCl2, KCl and cellulase according to different proportions, dissolving in deionized water, and preparing for use; (2) adjusting pH value: taking sodium bicarbonate, dissolving in the prepared deionized water, and adjusting the pH value; (3) raw material preparation: weighing 500g of yellow beans, pouring into the prepared deionized water in step (2), and soaking for about 8-10h; (4) bean curd preparation: preparing the bean curd product rich in various ions according to the process flow by using the soaked yellow beans. The application has the advantages of simple process, low production cost and suitability for industrial production, and solves the problem that the quality of bean products is different due to different water qualities in different regions for yellow bean processing enterprises.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and specifically relates to a method for improving the quality and moisture content distribution of tofu by using water for soaking and grinding. Background Technology

[0002] Tofu, a traditional Chinese soy product, is popular throughout China. It's a gelatinous product made from soybeans, processed through grinding, boiling, and coagulation. Northern-style tofu typically has a water content of around 85%, making water usage crucial in its production. Studies show that the content of metal ions in water affects tofu quality; therefore, the quality of tofu varies depending on the water quality in different regions.

[0003] This invention primarily studies the adjustment of different metal ion content in water by adding K to deionized water. ＋ Ca 2＋ Mg 2＋ The content and proportion of the enzyme are adjusted and applied to the tofu preparation process. Cellulase is then added to the water used to make the tofu to degrade the cellulose in the soy milk, thereby changing the structure and shape of the tofu, making it more delicate and smooth. This also gives the tofu better water and oil absorption, which helps to improve the taste and flavor of the tofu and improve its quality. The product with the best quality is obtained through texture analysis, gel strength testing, moisture distribution measurement, and sensory evaluation. Summary of the Invention

[0004] Due to varying water quality across different regions, the quality of tofu produced varies, resulting in differences in taste and flavor. This invention addresses this issue by adding Ca to deionized water as a base. 2＋ Mg 2＋ K ＋ In addition to cellulase, a special deionized water for soaking and grinding in the tofu preparation process was prepared, and its content was adjusted according to the preparation process. This water was then added to the tofu production process. Through experimental testing and sensory evaluation, the highest quality tofu was determined, and the Ca content in the prepared deionized water was identified. 2＋ Mg 2＋ K ＋ The above technology solves the problem of inconsistent local water quality and tofu quality. By using specially formulated deionized water, tofu of higher quality than that commonly sold in the market can be produced. Without affecting the nutritional value, the taste and flavor are also improved, making it easier to meet consumer demand.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A method for improving tofu yield and texture by using water during soaking and grinding includes the following steps:

[0007] (1) Pretreatment: Weigh out 50-130mg CaCl2, 60-65mg KCl, 35-200mg MgCl2 and 0.5g cellulase respectively, dissolve them in 1L of deionized water, and prepare for use.

[0008] (2) Adjust pH value: Weigh an appropriate amount of baking soda (NaHCO3), dissolve it in the prepared deionized water, and adjust the pH value accordingly.

[0009] (3) Raw material preparation and soaking: Select plump soybeans without insect holes, weigh 200-500g, pour them into the deionized water prepared in step (2), soak at 35-40℃, and soak for about 8-10 hours.

[0010] (4) Tofu preparation: Soaked soybeans are prepared according to the process flow to obtain tofu products rich in various ions.

[0011] As a preferred technical solution of this application, in step (1), the specific proportion of deionized water includes:

[0012] 1) Add 50.91 mg of CaCl2, 63.64 mg of KCl, and 200 mg of MgCl2, then add 0.5 g of cellulase and mix and dissolve in 1 L of deionized water.

[0013] 2) Add 90.91 mg of CaCl2, 63.64 mg of KCl, and 200 mg of MgCl2, then add 0.5 g of cellulase and mix and dissolve in 1 L of deionized water;

[0014] 3) The concentrations of CaCl2 (127.27 mg), KCl (63.64 mg), and MgCl2 (36.36 mg) are mixed with 0.5 g of cellulase and dissolved in 1 L of deionized water.

[0015] As a preferred technical solution of this application, in step (2), the optimal amount of sodium bicarbonate added is 18 mg / L.

[0016] As a preferred technical solution of this application, in step (4), during the tofu preparation process, the water used in the soaking and grinding steps is the deionized water prepared in (2), and the ground soy milk is filtered with a 200-mesh filter cloth before being boiled.

[0017] As can be seen from the above technical solution, the method for improving tofu quality and moisture content distribution by utilizing soaking and grinding water provided by the present invention has the following beneficial effects:

[0018] (1) By adding Ca to deionized water 2＋ Mg 2＋ K ＋It effectively improves the quality of soy products and also solves the problem of different water quality in different regions leading to different quality of soy products.

[0019] (2) Adding cellulase during the tofu preparation process can enzymatically decompose the cellulose in soybeans, which helps to improve the fluidity, taste and overall quality of soy milk, improve the coagulation ability of soy milk, and also change the structure and shape of tofu, giving it good water absorption, making it more delicate, and improving the eating experience of tofu.

[0020] (3) Adding a certain amount of cellulase is beneficial to the swelling rate of soybeans and the yield of tofu when soaking soybeans. Through the action of cellulase, the soaking speed of water is accelerated, that is, the soaking time is shortened, the mechanical strength and grinding time of grinding are reduced, and the soybean fiber is destroyed. At the same time, due to the action of a small amount of pectinase contained in cellulase, it plays a good role in improving the flavor of tofu and in peeling and degumming soybeans.

[0021] (4) Add a small amount of baking soda to adjust the pH value of deionized water to make the prepared soy products more tender and smooth.

[0022] Tofu prepared using specially formulated deionized water has a denser structure, reduces whey precipitation, and increases yield. Attached Figure Description

[0023] Figure 1 The effects of water used in tofu preparation on gel strength in Examples 1, 2, and 3 and Comparative Examples 1 and 2;

[0024] Figure 2 The relaxation curves of moisture content distribution in the samples of Examples 1, 2, and 3 and Comparative Examples 1 and 2 are shown.

[0025] Figure 3 Imaging of the moisture content distribution of samples from Examples 1, 2, and 3 and Comparative Examples 1 and 2;

[0026] Figure 4 Images of the finished tofu products from Examples 1, 2, and 3, and Comparative Examples 1 and 2. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0028] The present invention will be further described in detail below with reference to the embodiments. Reagents or instruments used without a specified manufacturer are considered to be conventional products that can be purchased on the market.

[0029] Example 1 (Tofu Preparation)

[0030] (1) Prepare deionized water: accurately weigh 50.91 mg CaCl2, 63.64 mg KCl and 200 mg MgCl2, then add 0.5 g cellulase and mix and dissolve in 1 L of deionized water. Prepare and set aside.

[0031] (2) Adjust pH value: Weigh 18mg of sodium bicarbonate (NaHCO3), dissolve it in the prepared deionized water, and adjust the pH value to a suitable level.

[0032] (3) Soaking: Select 500g of plump soybeans without insect holes, pour them into the deionized water prepared in steps (1) and (2), soak at 35-40℃, and soak for about 8-10 hours.

[0033] (4) Grinding: The soaked soybeans in step (3) are ground into soy milk with 3L of prepared deionized water.

[0034] (5) Filtering: The ground soy milk is filtered a second time using a 200-mesh fine gauze to prevent the soy residue remaining at the bottom of the pot from sticking to the bottom and causing the pot to burn during the boiling process. After filtering, the soy milk is boiled.

[0035] (6) Boiling the soy milk: Pour the filtered soy milk into a pot and boil it. Maintain a heat of 800W during the process and stir constantly with a silicone spatula to prevent burning and affecting the flavor of the tofu. After boiling (95℃), reduce the heat to 300W and boil for another 5 minutes to prevent false boiling.

[0036] (7) Curdling: Let the cooked soy milk stand at 80-85℃, pour in the brine (anhydrous magnesium chloride), stir briefly, and let stand for 20 minutes. The brine recipe is 10g of anhydrous magnesium chloride dissolved in 200mL of prepared deionized water, and 500g of dried soybeans soaked and mashed into a paste, then add 160ml of brine.

[0037] (8) Pressing tofu: The soy milk after coagulation is in the shape of tofu curds. Pour it all into a tofu mold and press it down. After 20 minutes, you will get a tofu product rich in various ions.

[0038] Example 2

[0039] The rest is the same as in Example 1, except that in step (1), 90.91 mg CaCl2, 63.64 mg KCl and 200 mg MgCl2 are accurately weighed, and then 0.5 g cellulase is added and mixed and dissolved in 1 L of deionized water, and prepared for later use.

[0040] Example 3

[0041] The rest is the same as in Example 1, except that in step (1), 127.27 mg CaCl2, 63.64 mg KCl, and 36.36 mg MgCl2 are accurately weighed, and 0.5 g of cellulase is added and mixed and dissolved in 1 L of deionized water for later use.

[0042] Comparative Example 1

[0043] Except that the tofu was prepared using deionized water with only cellulase added instead of pre-mixed deionized water, the process was the same as in Example 1.

[0044] Comparative Example 2

[0045] Except for the fact that tap water was used instead of pre-mixed deionized water in the tofu preparation process, everything else was the same as in Example 1.

[0046] Performance testing

[0047] Test Method

[0048] (a) The yield test method for tofu is as follows:

[0049] The application weighs the pressed tofu, and the ratio of the tofu's mass to the mass of the soybeans before soaking is the product yield.

[0050] (ii) The sensory evaluation criteria for the products are shown in Table 1.

[0051] Table 1 Sensory evaluation indexes for products from Examples 1, 2, and 3 and Comparative Examples 1 and 2 (unit: points)

[0052]

[0053] (III) The color difference detection method for tofu is as follows:

[0054] Color difference was measured using a colorimeter. Tofu prepared with deionized water of different formulations was taken and measured three times for each sample at room temperature. The average value was calculated.

[0055] (iv) The methods for detecting the textural properties of tofu are as follows:

[0056] The prepared samples were shaped into 2cm x 2cm x 2cm cubes. A texture analyzer was used for testing under the following conditions: TA36 probe, TA-MTP fixture; pre-test speed 5.00 mm / s, test speed 1.00 mm / s, post-test speed 5.00 mm / s; trigger point load 5g; target depth 10.0mm; test time 5s; number of cycles 2; 8 tests per sample group; average value taken. The hardness, elasticity, cohesiveness, and chewiness of the samples were measured.

[0057] (v) The method for testing the gel strength of tofu is as follows:

[0058] The gel strength of the samples was determined using a texture analyzer with a P / 5 probe, and the maximum force used for puncture was recorded as the gel strength. The probe speed was maintained at a constant 5.0 mm / s before, during, and after the test, with a trigger force of 5 g, penetrating the sample to the maximum target depth of 5 mm. The maximum force was recorded, and all samples were tested in triplicate.

[0059] (vi) The method for detecting the moisture composition distribution of tofu is as follows:

[0060] Low-field NMR relaxation measurements were performed using a benchtop low-field NMR imaging and analysis system. Sixg of tofu sample was accurately weighed and placed vertically at the center of the magnetic field, with a measurement temperature of 32℃. First, the center frequency and pulse width of the tofu sample were obtained using an FID sequence. Then, a CPMG sequence was set to scan the sample. The sequence parameters were set as follows: main frequency SF1 = 21MHz, offset frequency O1 = 147.60225kHz, pulse time at 90 degrees P1 = 11.52μs, pulse time at 180 degrees P2 = 20.56μs, number of sampling points TD = 250024, sampling frequencies SW = 100 and 250kHz, sampling interval TW = 1000ms, echo time TE = 0.200ms, number of echoes NECH = 5000, and number of accumulations NS = 4. Each type of sample was analyzed three times consecutively, and the average value was taken.

[0061] Experimental Results

[0062] 1. A comparison was made between the water ratio and tofu yield in tofu preparation without using deionized water and in Examples 1, 2, and 3. The results are as follows:

[0063] Table 2. Comparison of water formulation parameters and tofu yield of Examples 1, 2, and 3 with Comparative Example 1

[0064]

[0065] 2. Sensory comparison was conducted between the tofu prepared without using deionized water and the tofu prepared in Examples 1, 2, and 3. The results are as follows:

[0066] Table 3. Sensory comparison results of tofu prepared in Examples 1, 2, and 3 and Comparative Examples 1 and 2.

[0067] Note: Examples 1, 2, and 3 are samples prepared with deionized water; Comparative Example 1 is a sample prepared with deionized water without the addition of cellulase; and Comparative Example 2 is a sample prepared with tap water.

[0068] After sensory evaluation of Examples 1, 2, and 3 and Comparative Examples 1 and 2, the total scores of the samples prepared with deionized water were calculated. The total score of Example 1 was 83.67, the total score of Example 2 was 82.34, the total score of Example 3 was 84.07, the total score of Comparative Example 1 was 79.31, and the total score of Comparative Example 2 was 76.42. After sensory evaluation of the five groups of samples, it can be seen from the results that the tofu prepared with deionized water in Examples 1, 2, and 3 had higher sensory scores than that in Comparative Example 1. The main reason is that the coordinated action of metal ions in the deionized water, along with the improvement of the soaking and grinding techniques and cellulase, greatly improved the coagulation ability, thus enhancing the taste and flavor of the product. Furthermore, adjusting the pH value of the deionized water improved the texture and structure of the product.

[0069] 3. Color difference measurement results of tofu prepared with different soaking and grinding water.

[0070] Table 4 Results of Color Difference Measurement for Tofu

[0071] Note: All experiments were repeated three times, and results are expressed as mean ± standard deviation. One-way ANOVA was performed using SPSS 26 software to analyze the data for statistical significance. Different lowercase letters (ac) indicate significant differences for the same indicator (P < 0.05).

[0072] As shown in Table 4, the color of the sample prepared from deionized water is slightly different from that of the sample prepared from tap water. The differences in brightness and red-green gradient are small. In the yellow-blue gradient, Example 1 shows a larger yellow color. Overall, the color difference of the five groups of samples is not significant.

[0073] 4. Results of texture determination of samples from Examples 1, 2, and 3 of this invention and Comparative Example 1

[0074] Table 5. Texture determination results

[0075] Note: All experiments were repeated three times, and results are expressed as mean ± standard deviation. One-way ANOVA was performed using SPSS 26 software to determine statistical significance. Different lowercase letters (ad) indicate significant differences for the same indicator (P < 0.05).

[0076] As shown in Table 5, there were no significant differences in viscosity, elasticity, cohesiveness, and resilience among the five groups of tofu samples, but there were certain differences in hardness and chewiness. This indicates that the synergistic effect of potassium, calcium, and magnesium ions in the deionized water, as well as the degradation effect of cellulase, enhanced the structure and morphology of proteins in tofu, improving the taste of tofu itself. Sensory evaluation also showed that the taste and texture of the tofu were better than those of the samples prepared with tap water.

[0077] 5. Results of gel strength measurement of samples from Examples 1, 2, and 3 and Comparative Examples 1 and 2 of the present invention

[0078] Table 6 Results of gel strength test

[0079] Note: All experiments were repeated three times, and results are expressed as mean ± standard deviation. One-way ANOVA was performed using SPSS 26 software to analyze the data for statistical significance. Different lowercase letters (ac) indicate significant differences for the same indicator (P < 0.05).

[0080] Gel strength is an important factor in evaluating the gel properties of food. As shown in Table 6, since most of the water is removed during the pressing process of tofu, Example 1 has the highest gel strength (1052.48±47.86 g×mm), followed by Example 2 (931.96±98.44 g×mm), and Comparative Example 2 has the lowest (438.07±42.50 g×mm). Due to the addition of calcium, potassium, magnesium ions and cellulase to the water used to make the tofu, a synergistic effect occurs between the ions, and the cellulase degrades the cellulose in the soy milk, resulting in a more uniform and compact gel network structure during the coagulation process. Therefore, the gel strengths of Examples 1, 2, and 3 are all higher than those of Comparative Examples 1 and 2.

[0081] 6. Results of moisture composition distribution determination in samples from Examples 1, 2, and 3 and Comparative Examples 1 and 2 of this invention

[0082] Table 7. Distribution of moisture components in tofu

[0083] Note: All experiments were repeated three times, and results are expressed as mean ± standard deviation. One-way ANOVA was performed using SPSS 26 software to analyze the significance of differences, where T0... 22 A represents the relaxation time of 10~100ms. 22 T is the peak area during its relaxation time; 23 A represents the relaxation time of 100~1000ms. 23 Let be the peak area during its relaxation time.

[0084] LF-NMR is mainly used to analyze the water distribution in gels. It can assess water molecules immobilized by the gel network structure by analyzing T2 relaxation time and corresponding peak areas, and visually represent this information using a pseudo-color imaging system. The shortest relaxation time (T2) (0–10 ms) is identified as strongly bound water, tightly bound to non-aqueous components such as macromolecules in food and unaffected by the tissue structure. In the range of 10–100 ms (T2…),… 22 Water within the relaxation time is considered to be weakly bound water existing in the tissue structure, and the longest relaxation time is 100~1000ms (T).23 The water within the tissue is free water distributed in the interstitial spaces. According to previous research, T cells, which are tightly bound to proteins... 21 The components (0~10ms) have little impact on the water retention and textural properties of food, and their content is less than 5%, so they will not be discussed in detail.

[0085] After removing T21 data, the T of tofu 22、 T 23 The relaxation time and peak area data are compiled in Table 6. According to the data in Table 6, the relaxation time of Example 1 is as follows: 22 The relaxation time was approximately 38 ms. In Example 2, the T22 relaxation time was approximately 34 ms, in Example 3, it was approximately 36 ms, in Comparative Example 1, it was approximately 35 ms, and in Comparative Example 2, it was approximately 30 ms. The peak area of ​​the T22 component in Examples 1, 2, and 3 was larger than that in Comparative Examples 1 and 2, at 17837.89, 17227.63, and 16541.54 respectively, and 16021.43 and 14681.42 respectively, indicating that the tofu prepared using deionized water had a high moisture content. During the transformation from soy milk to hot soy milk, the moisture composition did not change, with the vast majority existing as free water. When the liquid form of soy milk transformed into a solid form with a protein network structure (gel and tofu), some of the free water in the soy milk transferred to the protein network structure of the gel and tofu. Due to interionic influence, more bound water influenced by proteins was generated. After extrusion, the tofu network structure formed was more compact, making water less mobile and thus reducing its activity.

[0086] like Figure 2 As shown, Example 1 has the largest peak area, indicating the highest moisture content. Comparative Example 1 has peak areas smaller than Examples 1, 2, and 3, indicating the lowest moisture content. Combined with... Figure 3 As shown, Example 1 has a compact structure and uniform moisture distribution, which is why it has good gel strength. Next are Examples 2, 3 and Comparative Example 1. Comparative Example 2 has the most dispersed moisture distribution and the lowest bound water content.

[0087] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the quality and moisture content distribution of tofu using water used for soaking and grinding, characterized in that, Specifically, the following steps are included: (1) Pretreatment: Weigh out 50-130mg CaCl2, 60-65mg KCl, 35-200mg MgCl2 and 0.5g cellulase respectively, dissolve them in 1L of deionized water, and prepare for use; (2) Adjust pH value: Weigh 15-20mg of baking soda, dissolve it in the prepared deionized water, and adjust the pH value; (3) Raw material preparation and soaking: Select plump soybeans without insect holes, weigh 200-500g, pour them into the deionized water prepared in step (2), soak at 35-40℃, and soak for 8-10 hours; (4) Tofu preparation: Soaked soybeans are prepared according to the process flow to obtain tofu products rich in various ions.

2. The method for improving tofu quality and moisture content distribution using soaking and grinding water according to claim 1, characterized in that... The following deionized water is prepared from the following raw materials: The concentrations of CaCl2 (50.91 mg), KCl (63.64 mg), and MgCl2 (200 mg) were mixed with 0.5 g of cellulase and dissolved in 1 L of deionized water.

3. The method for improving tofu quality and moisture content distribution using soaking and grinding water according to claim 1, characterized in that... The following deionized water is prepared from the following raw materials: The concentrations of CaCl2 (90.91 mg), KCl (63.64 mg), and MgCl2 (200 mg) were mixed with 0.5 g of cellulase and then dissolved in 1 L of deionized water.

4. The method for improving tofu quality and moisture content distribution using soaking and grinding water according to claim 1, characterized in that... The following deionized water is prepared from the following raw materials: The concentrations of CaCl2 (127.27 mg), KCl (63.64 mg), and MgCl2 (36.36 mg) were mixed with 0.5 g of cellulase and dissolved in 1 L of deionized water.

5. A method for improving tofu quality and moisture content distribution using soaking and grinding water according to any one of claims 2-4, characterized in that: The added cellulase has an enzyme activity of 10000 U / g.

6. A method for improving tofu quality and moisture content distribution using soaking and grinding water according to any one of claims 2-4, characterized in that: In step (2), the optimal amount of baking soda to be added is 18 mg / L.

7. A method for improving tofu quality and moisture content distribution using soaking and grinding water according to any one of claims 2-4, characterized in that: In step (4), during the tofu preparation process, the water used in the soaking and grinding stages is the deionized water prepared in step (2). The ground soy milk is filtered through a 200-mesh filter cloth before being boiled.

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