Preparation method for improving quality and yield of dried tofu

Abstract

The invention discloses a preparation method for improving quality and yield of dried tofu, which comprises the following steps: S1, grinding fully soaked bean materials to obtain raw pulp and bean dregs, and heating the raw pulp to obtain cooked pulp; s2, crushing bean dregs into fine bean dregs with the particle size of 5-20 microns, and mixing the fine bean dregs with the cooked pulp to obtain mixed cooked pulp; s3, curdling the mixed cooked pulp with a composite coagulator to obtain tofu pudding, and sequentially squeezing the tofu pudding to remove water, marinating, frying and seasoning to obtain the tofu pudding, and the composite coagulator is any one or a mixture of two of magnesium chloride, calcium sulfate and beta-glucolactone. According to the leisure dried bean curd and the preparation method thereof, the elasticity of the leisure dried bean curd is increased, the water retention capacity of the leisure dried bean curd is enhanced, the final yield is improved, the texture of the leisure dried bean curd is improved, the water binding capacity, the elasticity, the softness and the baking characteristic of the leisure dried bean curd are improved, and the quality of the dried bean curd is improved.

Description

Technical Field

[0001] The present invention discloses a preparation method for improving the quality and yield of dried tofu, belonging to the field of food processing technology. Background Art

[0002] Snack dried tofu, also known as instant dried tofu, is a unique non-fermented soy product in China. There are two main categories of snack dried tofu. One is made from soybeans through processes such as grinding, boiling, curdling, pressing, marinating, mixing, packaging, and sterilization. The other is made from soy protein as the raw material, adding auxiliary materials such as starch and transglutaminase, and then through flavoring, marinating, baking, mixing, packaging, and sterilization. Snack dried tofu not only has a unique flavor but also has nutritional value and dietary therapy value, and is deeply loved by the public. In recent years, the production and consumption of snack dried tofu have been steadily increasing, becoming an important part of China's snack food industry. However, snack dried tofu made from soybeans may have the problem of low yield during the production process. The main component of snack dried tofu is the protein in soybean seeds. In addition to protein, there are other nutritional components such as fiber and fat in soybean seeds. Among them, the soybean seed coat accounts for 8% of the total weight of the soybean seeds. The main component of the soybean seed coat is dietary fiber, and among this part of the fiber, the proportion of insoluble dietary fiber is relatively large, which is generally not used as the raw material for making the embryo of dried tofu during the production process. And when soybeans are directly ground without peeling after soaking, during the grinding process, when the insoluble dietary fiber is filtered out in the form of bean dregs, it may carry away a part of the protein by binding to the protein, reducing the utilization rate of the protein and resulting in a low yield of snack dried tofu. The reduction of the yield of dried tofu will cause waste of raw materials, increase costs, and reduce the profits of enterprises.

[0003] In recent years, with the continuous expansion of the snack dried tofu processing industry, improving the yield of snack dried tofu, reducing costs, and reducing waste are urgent problems for enterprises and factories. Improving the yield of dried tofu mainly starts from two ways. One is to improve the protein extraction rate during the grinding process, and the other is to expand the utilization rate of bean dregs.

[0004] The Chinese invention patent with the publication number CN 107980917 A discloses a production process of snack dried tofu. In this method, the soaked soybeans are ground, the ground paste is centrifuged to remove bean dregs, and the cooked soy milk is obtained after eight-connected tank heating and ripening treatment. Then, it is filtered through a 120-mesh sieve to remove bean dregs for the second time, and subsequent operations such as curdling are carried out. The dried tofu obtained by this method is relatively delicate, but the amount of bean dregs is large, and the protein content attached to the bean dregs is relatively large, resulting in a decrease in the production rate and soybean yield. Moreover, using magnesium chloride for curdling has poor water retention. Summary of the Invention

[0005] The present invention provides a preparation method for improving the quality and yield of dried tofu in order to overcome the deficiencies of the above prior art. This method can improve the processing yield of dried tofu while improving the texture of dried tofu, and improve the water retention, elasticity, softness, and baking characteristics of dried tofu, thereby enhancing the quality of dried tofu.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A preparation method for improving the quality and yield of dried tofu, comprising the following steps:

[0008] S1. Grind the fully soaked bean materials to obtain raw pulp and bean dregs, and heat the raw pulp to obtain cooked pulp;

[0009] S2. Crush the bean dregs into fine bean dregs with a particle size of 5-20 μm, and mix them with the cooked pulp to obtain a mixed cooked pulp;

[0010] S3. Use a composite coagulant to coagulate the mixed cooked pulp to obtain bean curd. Press the water out of the bean curd, marinate it, fry it, and season it in sequence to obtain the product. The composite coagulant is any one or a mixture of two of magnesium chloride, calcium sulfate, and β-gluconolactone.

[0011] Further, the soaking in step S1 is to soak and soften the soybeans with water. Preferably, the soaking is to mix the soybeans and water, and the mass ratio of soybeans to water is 1:2-1:4, and the soaking time is 4-8 hours.

[0012] Further, the pressing in step S3 is carried out using a press; preferably, the specific method is to pour the bean curd into a pressing box, lower the pressing plate, squeeze the bean curd, squeeze out the water in the bean curd, and cut it into blocks after forming a semi-finished dried tofu product.

[0013] Further, the marinating is carried out by boiling soup with spices and auxiliary materials.

[0014] Further, when the bean dregs are mixed with the cooked pulp, the temperature of the cooked pulp is controlled at 90-95 °C, and the mixing time is 15-25 min.

[0015] Further, the frying temperature is 115-120 °C, and the frying time is 2-6 min.

[0016] Further, before coagulating the mixed cooked pulp with the composite coagulant in step S3, curdlan needs to be added to the mixed cooked pulp.

[0017] Further, the fine bean dregs in step S2 are obtained by freeze-drying the bean dregs and grinding them with a high-energy nano impact mill for more than 2 hours.

[0018] Further, the composite coagulant described in step S3 is magnesium chloride, calcium sulfate, and β-gluconolactone, and their addition amounts are 1% - 1.5%, 1% - 2%, and 0.1% - 0.2% of the cooked pulp by mass percentage, respectively.

[0019] Further, the addition amount of the soybean dregs described in step S2 is 1% - 2% of the cooked pulp.

[0020] Further, the addition amount of the curdlan is 1% - 4% of the cooked pulp.

[0021] Curdlan can be used to improve the elasticity of food and enhance the water retention capacity of food. The present invention utilizes the gel properties of curdlan to increase the elasticity and water retention of the leisure dried tofu, improve the problems of poor taste and poor water retention of traditional leisure dried tofu, and it will not change the taste and flavor of the product, protecting the commercial value of the leisure dried tofu to a large extent.

[0022] Further, the specific steps of step S2 are as follows:

[0023] Step S21: Mix the fully soaked beans with the grinding slurry, conduct the first grinding, and separate to obtain soybean dregs 1 and raw pulp water 1; mix soybean dregs 1 with the grinding slurry, conduct the second grinding to obtain soybean dregs 2 and raw pulp water 2; mix soybean dregs 2 with the grinding slurry and conduct the third grinding, and the grinding slurry is edible water.

[0024] Step S22: Repeat step S21, where the grinding slurry in the first grinding is the raw pulp water 3 of step S21, and the grinding slurry in the second grinding is a mixture of the raw pulp water 3 of step S21 and edible water, and accordingly obtain soybean dregs 1, soybean dregs 2, and soybean dregs 3, as well as raw pulp water 1, raw pulp water 2, and raw pulp water 3.

[0025] Step S23: Repeat step S22 several times, where the grinding slurry in the first grinding is any one or several of the raw pulp water 3 of the steps, and the grinding slurry in the second grinding is a mixture of any one or several of the raw pulp water 3 of the steps and edible water.

[0026] Step S24: Combine the soybean dregs 3 of the above steps to obtain soybean dregs; combine the raw pulp water 1 and raw pulp water 2 of the above steps as the raw pulp.

[0027] Among them, in step S22 and step S23, the grinding slurry in the second grinding is a mixture of raw pulp water 3 and edible water with a mass ratio of 1:3 - 1:5.

[0028] Preferably, in the first grinding, the mass ratio of the fully soaked beans to the grinding slurry is 1:6 to 1:8, and the grinding is carried out for 30 to 120 s; preferably, in the second grinding, the mass ratio of the bean dregs 1 to the grinding slurry is 1:3 to 1:5, and the grinding time is 20 to 60 s; preferably, in the third grinding, the mass ratio of the bean dregs 2 to the grinding slurry is 1:1 to 1:2, and the grinding time is 10 to 60 s.

[0029] Preferably, the time of the cyclic pulp grinding is 4 to 8 hours.

[0030] By using the method of multiple grindings, the protein in soybeans can be fully extracted, the protein adhesion in the bean dregs can be reduced, and the yield can be increased.

[0031] Furthermore, heating the raw pulp to obtain the cooked pulp in step S1 is as follows: the raw pulp water is heated by gradient to obtain the cooked pulp water, and the heating temperatures of the gradient heating are sequentially set as: 40 - 50 °C, 50 - 60 °C, 60 - 70 °C, 70 - 80 °C, 80 - 90 °C, 90 - 100 °C, 100 - 110 °C, 115 - 121 °C; preferably, the gradient heating is carried out by an eight - tank full - automatic pulp burner.

[0032] Furthermore, the bean material in step S1 is soybeans, mung beans or chickpeas.

[0033] Furthermore, step S3 also needs to include packaging and sterilization; preferably, the sterilization is heat treatment sterilization, the heat treatment sterilization temperature is 125 - 135 °C, and the treatment time is 20 - 30 min.

[0034] Furthermore, the water content of the dried bean curd is 55% - 65%, and the size of the blocks cut from the semi - finished dried bean curd is 2 - 4 mm thick, 4 - 6 cm long, and 3 - 5 cm wide.

[0035] The present invention has the following technical effects:

[0036] (1) In the present invention, the brain curdling is carried out by mixing the bean dregs with an average particle size of 5 - 20 μm and the cooked pulp. While increasing the yield of the dried bean curd, the influence of the addition of the bean dregs on the taste is reduced. The introduction of an appropriate amount of bean dregs can fill the network structure of the protein, increase the tenderness and elasticity of the dried bean curd, and make it not easy to break.

[0037] (2) The present invention uses a composite coagulant of magnesium chloride, calcium sulfate and β - gluconolactone with a specific composition and ratio for brain curdling. The obtained bean embryo can have a better taste and water - holding capacity, overcoming the bitterness of the product caused by using a single coagulant calcium sulfate, the lack of soy aroma; the poor water - holding property caused by using a single coagulant magnesium chloride as the coagulant; and the slightly sour taste and the disadvantage of being not suitable for subsequent processing caused by using a single coagulant β - gluconolactone as the coagulant.

[0038] (3) Before making the tofu, the curdlan is further mixed with the mixed cooked slurry in the present invention, which further improves the water holding capacity and texture of the dried tofu and enhances the quality of the dried tofu.

[0039] (4) This method is simple, with high yields, water holding capacities, and texture properties of the dried tofu, good taste, and is suitable for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It shows the particle size changes of the soybean dregs ground for different times.

[0041] Figure 2 It is a comparison chart of the water holding capacities of Examples 2, 3, and 4 and Comparative Examples 1, 2, and 3 of the present invention.

[0042] Figure 3 It is the experimental effect diagram of Example 1 of the present invention relative to different treatment groups. DETAILED DESCRIPTION OF THE INVENTION

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Example 1

[0045] I. Experimental Method

[0046] 1. Preparation of Dried Tofu

[0047] (1) The soybeans are soaked and softened with 3 times (by mass) of water to obtain softened soybeans, and then ground to obtain raw slurry and soybean dregs: after the soybean dregs are freeze-dried, they are ground with a high-energy nano impact mill for different times (0 h, 1 h, 2 h, 3 h, 4 h), and the particle size of the ground soybean dregs is detected; the raw slurry is heated to obtain cooked slurry;

[0048] Among them, the grinding method is as follows: the grinding is first carried out for the first time and then for cyclic grinding.

[0049] The first grinding is as follows:

[0050] The softened soybeans are mixed with water at a mass ratio of 1:7 and ground for the first time for 120 s to separate soybean dregs 1 and raw slurry water 1; soybean dregs 1 are mixed with water at a mass ratio of 1:4 and ground for the second time for 50 s to obtain soybean dregs 2 and raw slurry water 2; soybean dregs 2 are mixed with water at a mass ratio of 1:2 and ground for the third time for 30 s to separate soybean dregs and raw slurry water 3;

[0051] The cyclic grinding is as follows:

[0052] Another portion of softened soybeans is mixed with raw pulp water 3 at a mass ratio of 1:8, and undergoes the first grinding for 120 s to obtain bean dregs 1 and raw pulp water 1; bean dregs 1, water, and raw pulp water 3 are mixed at a mass ratio of 1:4:1, and undergo the second grinding for 60 s to obtain bean dregs 2 and raw pulp water 2; bean dregs 2 and water are mixed at a mass ratio of 1:2, and undergo the third grinding for 30 s to obtain bean dregs and raw pulp water 3. Continuously input new softened soybean materials, and repeat the cyclic grinding steps for a cumulative grinding time of 4 hours, where the raw pulp water 3 can be the raw pulp water 3 obtained from any one or several previous steps; combine all the bean dregs obtained from the first grinding and the cyclic grinding, freeze-dry them, and then grind them with a high-energy nano impact mill; combine all the raw pulp water 1 and raw pulp water 2 obtained from the first grinding and the cyclic grinding as the raw pulp.

[0053] The raw pulp is heated in a gradient manner using an eight-tank full-automatic pulp cooker to obtain cooked pulp water. The heating temperatures of the eight-tank full-automatic pulp cooker are sequentially set as: 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 115 °C.

[0054] (2) Mix the bean dregs after grinding with the high-energy nano impact mill with the cooked pulp to obtain a mixed cooked pulp. Control the temperature of the cooked pulp at 90 °C, the mixing time is 20 minutes, and the addition amount of the bean dregs is 1% of the cooked pulp;

[0055] (3) Use magnesium chloride (accounting for 3.9% of the mass of the cooked pulp) as a coagulant to coagulate the mixed cooked pulp to obtain bean curd. The bean curd is pressed to remove water using a press (pressed until the water content is 60%), and then successively undergoes: cutting (3 mm thick, 4 cm long, 4 cm wide), stewing and marinating with spices and auxiliary materials, frying (115 °C, 5 min), and seasoning to obtain dried bean curd.

[0056] (4) After successively packaging and sterilizing (125 °C, 20 min), the finished product of dried bean curd is obtained. The sterilization temperature is 125 °C, and the treatment time is 20 min; obtain the leisure soy dried bean curd.

[0057] The soybeans are soaked and softened with 3 times the amount of water, ground into pulp according to the method in step (1), and the obtained raw pulp is made into cooked pulp. The obtained cooked pulp is coagulated to obtain coagulated bean curd, which is pressed to remove water, stewed, fried, and seasoned to obtain leisure dried bean curd as a control.

[0058] 2. Detection of dried bean curd

[0059] Perform quality determination and yield determination on the dried bean curd prepared from the bean dregs obtained by grinding with the high-energy nano impact mill for different times.

[0060] Among them, the calculation method of the yield is: the percentage of the weight of the obtained dried bean curd sample in the soybean raw material;

[0061] The method for measuring the water holding capacity (WHC) is as follows: Weigh the dried bean curd sample and record it as m1. Then place it in a 50 mL centrifuge tube with cotton wool at the bottom and centrifuge at a speed of 10,000 rpm for 10 min at 4°C. After thoroughly removing the liquid, weigh the remaining sample and record it as m2. Water holding capacity = (m2 / m1) × 100%.

[0062] II. Experimental test results

[0063] The influence of different grinding times of the high-energy nano impact mill on the particle size of soybean dregs is shown in Figure 1 , it can be seen that when the grinding time is 2 hours, the particle size is less than 20 μm;

[0064] As can be seen from Table 1, when the grinding time is more than 2 hours, the yield increases significantly, and the water holding capacity remains basically unchanged. When the particle size of soybean dregs is too large, both the yield and the particle size decrease.

[0065] Table 1 Influence of different grinding times on the yield and water holding capacity

[0066] Property Control 0h 1h 2h 3h 4h Yield 178.77 143.87 156.93 199.28 210.37 223.22 Water holding capacity 47.88 39.26 45.31 46.47 47.23 47.42

[0067] Example 2

[0068] This example provides a preparation method for improving the quality and yield of dried soybean curd, and the specific steps are as follows:

[0069] (1) The only difference from step (1) of Example 1 is that the grinding time of the high-energy nano impact mill is 2 h.

[0070] (2) Mix the soybean dregs ground by the high-energy nano impact mill with the cooked slurry to obtain a mixed cooked slurry; when mixing, control the temperature of the cooked slurry at 90°C, the mixing time is 15 min, and the addition amount of soybean dregs is 1% of the mass of the cooked slurry; then add 2% of the mass of the cooked slurry of curdlan gum.

[0071] (3) Use a composite coagulant containing magnesium chloride, calcium sulfate, and β-gluconolactone to coagulate the soybean milk into bean curd. The mass ratios of magnesium chloride, calcium sulfate, and β-gluconolactone in the composite coagulant to the cooked slurry are 1.3%, 1%, and 0.1% respectively. Press the water out of the bean curd using a press (press until the moisture content is 60%), then cut it successively (3 mm thick, 4 cm long, 4 cm wide), braise it with spices and auxiliary materials, fry it (115°C, 5 min), and season it to obtain the leisure dried bean curd.

[0072] (4) The method is the same as step (4) of Example 1; obtain the leisure dried soybean curd.

[0073] Example 3

[0074] This example provides a preparation method for improving the quality and yield of dried mung bean curd, and the specific steps are as follows:

[0075] (1) The soybeans and mung beans are soaked and softened by adding water. The ratio of soybeans, mung beans to water is 3:2:15. The softened soybeans and mung beans are obtained, and then ground into raw pulp and bean dregs. After the bean dregs are freeze-dried, they are ground by a high-energy nano impact mill for 2 hours; the raw pulp is heated to obtain cooked pulp;

[0076] Among them, the method of grinding is: the grinding is first carried out for the first grinding, and then the circulating grinding is carried out,

[0077] The method of grinding is: the grinding is first carried out for the first grinding, and then the circulating grinding is carried out,

[0078] The first grinding is: the mixed material of softened soybeans and mung beans is mixed with water according to the mass ratio of 1:7, and the first grinding is carried out for 120 s, and the bean dregs 1 and the raw pulp water 1 are separated; the bean dregs 1 are mixed with water according to the mass ratio of 1:4, and the second grinding is carried out for 50 s to obtain the bean dregs 2 and the raw pulp water 2; the bean dregs 2 are mixed with water according to the mass ratio of 1:2, and the third grinding is carried out for 30 s to separate the bean dregs and the raw pulp water 3.

[0079] The circulating grinding is: take another portion of the mixed material of softened soybeans and mung beans and mix it with the raw pulp water 3 according to the mass ratio of 1:7, and carry out the first grinding for 120 s to separate the bean dregs 1 and the raw pulp water 1; the bean dregs 1, water and the raw pulp water 3 are mixed according to the mass ratio of 1:4:1, and the second grinding is carried out for 60 s to obtain the bean dregs 2 and the raw pulp water 2; the bean dregs 2 are mixed with water according to the mass ratio of 1:2, and the third grinding is carried out for 30 s to separate the bean dregs and the raw pulp water 3. Continuously add new softened soybean and mung bean mixed materials and repeat the circulating grinding step, with a cumulative grinding time of 4 hours. Among them, the raw pulp water 3 can be the raw pulp water 3 obtained from any one or several previous steps; all the bean dregs obtained from the first grinding and the circulating grinding are combined, freeze-dried, and then ground by a high-energy nano impact mill; all the raw pulp water 1 and raw pulp water 2 obtained from the first grinding and the circulating grinding are combined as the raw pulp. The raw pulp is heated by gradient to obtain the cooked pulp water, and the method is the same as the heating method in step (1) of Example 1.

[0080] (2) The bean dregs after being ground by the high-energy nano impact mill are mixed with the cooked pulp to obtain a mixed cooked pulp; when mixing, the temperature of the cooked pulp is controlled at 90 °C, the mixing time is 15 min, and the addition amount of the bean dregs is 1% of the mass of the cooked pulp; then 1.5% of curdlan based on the mass of the cooked pulp is added.

[0081] (3) Use a composite coagulant containing magnesium chloride, calcium sulfate, and β-gluconolactone to coagulate the soymilk into beancurd. The mass ratios of the composite coagulant magnesium chloride, calcium sulfate, and β-gluconolactone to the cooked soymilk are 1.3%, 1%, and 0.1% respectively. The beancurd is pressed to remove water using a press (pressed until the water content is 60%), and then successively cut (3 mm thick, 4 cm long, 4 cm wide), stewed with spices and auxiliary materials in a soup, fried (115 °C, 5 min), and seasoned to obtain the leisure dried beancurd.

[0082] (4) The method is the same as step (4) of Example 1; obtain the leisure mung bean dried beancurd.

[0083] Example 4

[0084] This example provides a preparation method for improving the quality and yield of chickpea dried beancurd, and the specific steps are as follows:

[0085] (1) Soak and soften the chickpeas with 2.5 times (by mass) of water, then grind to obtain raw soymilk and bean dregs. After freeze-drying the bean dregs, grind them with a high-energy nano-impact mill for 2 h, and detect the particle size of the ground bean dregs. Heat the raw soymilk to obtain cooked soymilk;

[0086] Among them, the grinding method is: the grinding is first carried out for the first grinding, and then for the cyclic grinding.

[0087] The grinding method is: the grinding is first carried out for the first grinding, and then for the cyclic grinding.

[0088] The first grinding is: mix the softened chickpea material with water at a mass ratio of 1:8, carry out the first grinding for 120 s, and separate to obtain bean dregs 1 and raw soymilk water 1; mix bean dregs 1 with water at a mass ratio of 1:4, carry out the second grinding for 60 s to obtain bean dregs 2 and raw soymilk water 2; mix bean dregs 2 with water at a mass ratio of 1:2, carry out the third grinding for 30 s, and separate to obtain bean dregs and raw soymilk water 3.

[0089] Circular grinding: Take another portion of softened chickpea material and mix it with raw pulp water 3 in a mass ratio of 1:8, and conduct the first grinding for 120 s to separate the bean dregs 1 and raw pulp water 1; Mix bean dregs 1, water and raw pulp water 3 in a mass ratio of 1:3:1, conduct the second grinding for 60 s to obtain bean dregs 2 and raw pulp water 2; Mix bean dregs 2 and water in a mass ratio of 1:2, conduct the third grinding for 30 s to separate the bean dregs and raw pulp water 3. Continuously input new softened soybean and mung bean mixed materials, repeat the circular grinding steps, and accumulate the grinding for 4 hours. Among them, the raw pulp water 3 can be the raw pulp water 3 obtained from any one or several previous steps; Combine all the bean dregs obtained from the first grinding and circular grinding, freeze-dry them, and then conduct high-energy nano impact mill grinding; Combine all the raw pulp water 1 and raw pulp water 2 obtained from the first grinding and circular grinding as the raw pulp. The raw pulp is heated in a gradient manner to obtain cooked pulp water, and the method is the same as the heating method in step (1) of Example 1.

[0090] (2) Mix the bean dregs after high-energy nano impact mill grinding with the cooked pulp to obtain a mixed cooked pulp; When mixing, control the temperature of the cooked pulp at 90 °C, the mixing time is 12 min, and the addition amount of the bean dregs is 1.2% of the mass of the cooked pulp; Then add curdlan gum accounting for 1.8% of the mass of the cooked pulp.

[0091] (3) Use a composite coagulant containing magnesium chloride, calcium sulfate, and β-gluconolactone to coagulate the soybean milk into bean curd. The mass ratios of the composite coagulants magnesium chloride, calcium sulfate, and β-gluconolactone in the cooked pulp are 1.3%, 1%, and 0.1% respectively. The bean curd is pressed using a press to remove water (pressed to a moisture content of 60%), and then successively cut (3 mm thick, 4 cm long, 4 cm wide), stewed with spices and auxiliary materials in a soup, fried (115 °C, 5 min), and seasoned to obtain the snack dried bean curd.

[0092] (4) The method is the same as step (4) of Example 1 to obtain the snack dried chickpea curd.

[0093] Comparative Example 1

[0094] The preparation method refers to Example 2, the difference is that in step (2), no bean dregs and curdlan gum are added, and in step (3), only magnesium chloride (accounting for 3.9% of the mass of the cooked pulp, and this concentration of magnesium chloride is required as a single coagulant to make the bean embryo required for the dried bean curd) is used as the coagulant, and the other steps are the same. The obtained dried bean curd.

[0095] Comparative Example 2

[0096] The preparation method refers to Example 3, the difference is that in step (2), no bean dregs and curdlan gum are added, and in step (3), only magnesium chloride (accounting for 3.9% of the mass of the cooked pulp) is used as the coagulant, and the other steps are the same. The obtained dried bean curd.

[0097] Comparative Example 3

[0098] The preparation method refers to Example 4, with the difference that in step (2), okara and curdlan are not added, and in step (3), only magnesium chloride (with a mass ratio of 3.9% to the cooked soy milk) is used as the coagulant, and the other steps are the same. The dried tofu thus prepared.

[0099] Comparative Example 4

[0100] The preparation method refers to Example 2, with the difference that in step (2), only okara is added, curdlan is not added, and in step (3), only magnesium chloride (with a mass ratio of 3.9% to the cooked soy milk) is used as the coagulant, and the other steps are the same. The dried tofu thus prepared.

[0101] Comparative Example 5

[0102] The preparation method refers to Example 2, with the difference that in step (2), only curdlan is added, okara is not added, and in step (3), only magnesium chloride is used as the coagulant (with a mass ratio of 3.9% to the cooked soy milk), and the other steps are the same. The dried tofu thus prepared.

[0103] Comparative Example 6

[0104] The preparation method refers to Example 2, with the difference that in step (2), okara and curdlan are not added, and only in step (3), the same mass of composite coagulant is used to coagulate the soy milk, and the other steps are the same. The dried tofu thus prepared.

[0105] Comparative Example 7

[0106] The preparation method refers to Example 2, with the difference that in step (3), the composite coagulant is the same amount of magnesium chloride and calcium sulfate as in Example 1, and β-gluconolactone is not added.

[0107] Comparative Example 8

[0108] The preparation method refers to Example 2, with the difference that in step (3), the composite coagulant is the same amount of magnesium chloride + β-gluconolactone as in Example 1, and calcium sulfate is not added.

[0109] Test Example 1

[0110] I. Test Method

[0111] For the leisure dried tofu prepared in Examples 2-4 and Comparative Examples 1-3, it was cut into cylinders with a height of about 1.5 cm and a bottom diameter of 1 cm as samples to detect their texture properties and water holding capacity to evaluate their quality.

[0112] For the determination of texture properties, a texture analyzer was used to detect the texture properties of the samples.

[0113] Determination of water holding capacity (WHC): Weigh the dried tofu sample and record it as m1. Then place it in a 50 mL centrifuge tube with cotton wool at the bottom and centrifuge at 10,000 rpm for 10 min at 4°C. After completely removing the liquid, weigh the remaining sample and record it as m2. Water holding capacity = (m2 / m1) × 100%.

[0114] II. Test Results

[0115] The texture test results of Examples 2-4 and Comparative Examples 1-3 are shown in Table 2, and the water holding capacity test results are as Figure 2 shown

[0116] The results show that compared with Comparative Examples 1 to 3, when preparing dried tofu in Examples 2 to 4, the elasticity increases, and the chewiness is improved; the gel strength is enhanced, indicating that the tofu gel is not damaged; the hardness is enhanced, which can further improve its chewiness. The use of soybean dregs, curdlan, and composite coagulant significantly increases the water holding capacity of dried tofu.

[0117] Table 2 Texture property test results of Examples 2-4 and Comparative Examples 1-3

[0118] Texture properties Comparative example 1 Comparative example 2 Comparative example 3 Example 2 Example 3 Example 4 Gel strength (g*cm) 34.61 20.99 17.96 37.11 26.95 29.37 Hardness (gf) 72.405 48.815 56.105 74.216 54.986 57.59 Brittleness (gf) 82.405 48.815 56.105 74.216 54.986 57.59 Adhesiveness (gf*sec) -14.33 -15.25 -12.46 -2.16 -2.9 -2.84 Elasticity 0.6981 0.6114 0.6858 0.8016 0.8032 0.7423 Chewiness (gf) 28.212 19.355 24.401 39.423 31.513 25.068 Gumminess (gf) 40.412 31.659 35.581 49.183 39.232 33.771 Cohesiveness 0.4904 0.6485 0.6342 0.6627 0.7135 0.5864 Resilience 0.1792 0.2931 0.264 0.3295 0.3658 0.2486

[0119] Test Example 2

[0120] I. Test Method

[0121] Referring to the method of Test Example 2, test the yield and texture properties of the casual dried tofu of each group in Example 2, Comparative Example 1, and Comparative Examples 4-8. The yield test method is the same as that in Example 1, and the data of Comparative Example 1 refer to Table 2; use a texture analyzer to detect the texture properties of the samples.

[0122] II. Test Results

[0123] The results are as Figure 3 and Table 3 show. The results indicate that adding back soybean dregs (Comparative Example 4 compared with Comparative Example 1) can increase its yield. However, due to the water content in soybeans, the proportion of soybean dregs after freeze-drying is relatively low. Although its utilization rate is high, its effect on increasing the yield is relatively small; adding curdlan (Comparative Example 1 compared with Comparative Example 5) can increase the water holding capacity of casual dried tofu, resulting in an increase in the water content in the final dried tofu. When using a composite coagulant (Comparative Example 1 compared with Comparative Example 6), it has a beneficial effect on improving the extraction rate of protein. Moreover, when using a mixture of magnesium chloride and calcium sulfate as the coagulant and a mixture of a single coagulant and β-gluconolactone, their texture properties are lower than those of the composite coagulant (Comparative Examples 7-8 compared with Example 2).

[0124] Table 3 Texture property test of each group

[0125]

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the solutions. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can modify or equivalently replace the technical solutions of the present invention on the basis of understanding the solutions, without departing from the purpose and scope of the technical solutions of the present invention, and all of them should be covered by the scope of the claims of the present invention.

Claims

1. A preparation method for improving the quality and yield of dried tofu, characterized in that, It includes the following steps: S1. Grind the fully soaked bean materials to obtain raw pulp and bean dregs, and heat the raw pulp to obtain cooked pulp; S2. Crush the bean dregs into fine bean dregs with a particle size of 5 - 20 μm, and mix them with the cooked pulp to obtain a mixed cooked pulp; S3. Use a composite coagulant to coagulate the mixed cooked pulp to obtain bean curd. Then, press and dewater, marinate, fry, and season the bean curd in sequence to obtain the product. The composite coagulant is any one or a mixture of two of magnesium chloride, calcium sulfate, and β - gluconolactone.

2. The method according to claim 1, wherein Before coagulating the mixed cooked pulp with the composite coagulant in step S3, curdlan gum needs to be added to the mixed cooked pulp.

3. The method according to claim 1, characterized in that The crushing of the bean dregs in step S2 is obtained by freeze - drying the bean dregs and then grinding them with a high - energy nano - impact mill for more than 2 hours.

4. The method according to claim 1, characterized in that The composite coagulant in step S3 is magnesium chloride, calcium sulfate, and β - gluconolactone, and their addition amounts are 1% - 1.5%, 1% - 2%, and 0.1% - 0.2% of the cooked pulp by mass percentage respectively.

5. The method according to claim 1, characterized in that, The addition amount of the fine bean dregs in step S2 is 1% - 2% of the cooked pulp.

6. The method according to claim 2, wherein The addition amount of the curdlan gum is 1% - 4% of the cooked pulp.

7. The method according to claim 1, characterized in that, The specific steps of step S2 are: Step S21: Mix the fully soaked beans with the grinding slurry, conduct the first grinding, and separate to obtain bean dregs 1 and raw pulp water 1; Mix bean dregs 1 with the grinding slurry, conduct the second grinding, to obtain bean dregs 2 and raw pulp water 2; Mix bean dregs 2 with the grinding slurry and conduct the third grinding to obtain bean dregs 3 and raw pulp water. The grinding slurry is edible water; Step S22: Repeat step S21, where the grinding slurry in the first grinding is the raw pulp water 3 in step S21, and the grinding slurry in the second grinding is a mixture of the raw pulp water 3 in step S21 and edible water, and correspondingly obtain bean dregs 1, bean dregs 2, and bean dregs 3, as well as raw pulp water 1, raw pulp water 2, and raw pulp water 3; Step S23: Repeat step S22 several times, where the grinding slurry in the first grinding is the raw pulp water 3 of any one or several steps, and the grinding slurry in the second grinding is a mixture of the raw pulp water 3 of any one or several steps and edible water; Step S24: Combine the bean dregs 3 from the above steps to obtain bean dregs; Combine the raw pulp water 1 and raw pulp water 2 from the above steps as the raw pulp; Among them, in step S22 and step S23, the grinding slurry in the second grinding is a mixture of raw pulp water 3 and edible water with a mass ratio of 1:3 - 1:

5. Preferably, in the first grinding, the mass ratio of the fully soaked beans to the grinding slurry is 1:6 - 1:8, and the grinding time is 30 - 120 s; Preferably, in the second grinding, the mass ratio of bean dregs 1 to the grinding slurry is 1:3 - 1:5, and the grinding time is 20 - 60 s; Preferably, in the third grinding, the mass ratio of bean dregs 2 to the grinding slurry is 1:1 - 1:2, and the grinding time is 10 - 60 s.

8. The method according to claim 1, characterized in that, The step of heating the raw pulp to obtain the cooked pulp in step S1 is as follows: the raw pulp water is heated by gradient heating to obtain the cooked pulp water, and the heating temperatures of the gradient heating are sequentially set as: 40-50 °C, 50-60 °C, 60-70 °C, 70-80 °C, 80-90 °C, 90-100 °C, 100-110 °C, 115-121 °C; preferably, the gradient heating is carried out by an eight-tank full-automatic pulp burner.

9. The method according to claim 1, wherein The bean material described in step S1 is soybean, mung bean or chickpea.

10. The method according to claim 1, characterized in that, Step S3 also needs to include packaging and sterilization steps; preferably, the sterilization is heat treatment sterilization, the heat treatment sterilization temperature is 125-135 °C, and the treatment time is 20-30 min.

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