Tofu preparation technology and tofu

Abstract

The present invention belongs to the technical field of food processing, and discloses a tofu preparation process and tofu. The tofu preparation process comprises the following steps: S1, preparing soy milk, using beans as raw materials to prepare soy milk; S2, preparing a modified liquid, adding curdlan, modified starch, white sugar and gluconolactone to water to obtain a modified liquid; S3, adding the modified liquid to the soy milk at a first temperature to obtain a process product; S4, heating the process product to a second temperature, keeping it warm for a first time, and cooling it to obtain soft tofu. Under the joint action of curdlan, modified starch, white sugar, gluconolactone and soy milk, the cross section of the frozen soft tofu after thawing has no holes, so that the soft tofu after thawing maintains its delicate and smooth taste before freezing, and the soy milk is made of beans as raw materials, and has a strong bean flavor, and the white sugar has the effect of alleviating the sour taste of the soft tofu after freezing, so that the bean flavor of the soft tofu after thawing is prominent.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, in particular to a tofu preparation process and tofu. Background Art

[0002] Tofu is the main raw material for vegetarian dishes in my country. Traditional tender tofu has a high water content and a short shelf life at room temperature. At low temperatures, it will form a sponge or layered structure due to protein denaturation, such as frozen tofu, thus destroying the tender and smooth taste of the tender tofu, and it is no longer the tender tofu we demand.

[0003] In the prior art, in order to improve the taste of frozen tofu, starch and transglutaminase are added to soy milk, and the antifreeze property of the tofu is improved to a certain extent, but the viscosity of soy milk is high and it is difficult to control the coagulation reaction. Furthermore, without changing the soy milk concentration, the solid content of the raw pulp is concentrated to 10-16%, which further improves the antifreeze property of tofu. However, since the process requirements for soy milk concentration are high and difficult to control, industrial production is difficult.

[0004] In the above existing scheme, not only is the process implementation complicated, but also only the physical properties of tofu are considered, that is, whether the tofu has freeze-resistance after freezing, and the taste and bean flavor of the tofu are not pursued. The taste and bean flavor of the tender tofu made by the above scheme after freezing are still significantly different from those of traditional tender tofu. Summary of the invention

[0005] The invention aims to provide a tofu preparation process and tofu. The soft tofu prepared by the tofu preparation process has a tender and smooth taste and a strong bean flavor after being thawed, and the influence of freezing on the taste and bean flavor of the soft tofu is reduced, and industrial production is convenient.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The tofu preparation process comprises the following steps:

[0008] S1, preparing soy milk, using beans as raw materials to prepare soy milk;

[0009] S2, preparing a modified liquid, adding curdlan, modified starch, white sugar and gluconolactone into water to obtain a modified liquid;

[0010] S3, adding the modified liquid to the soy milk at the first temperature to obtain a process product;

[0011] S4, heating the process product to a second temperature, keeping it warm for the first time, and obtaining soft tofu after cooling.

[0012] By adopting the above technical scheme, curdlan, modified starch, white sugar and gluconolactone are added to the soybean milk at the first temperature to form a qualified process product. If the soybean milk temperature is too low, the modified starch cannot be completely gelatinized, and the process product is prone to precipitation, resulting in tofu stratification. If the soybean milk temperature is too high, the modified starch gelatinizes too quickly, and the viscosity of the process product will increase rapidly, resulting in unevenness, precipitation and poor texture of the process product formed by heating. When the process product is heated at the second temperature, the curdlan in the process product forms an irreversible gel under the joint action of modified starch, white sugar and gluconolactone, and its properties are good. The soft tofu remains free of holes after freezing, thereby ensuring that the soft tofu has a delicate taste after thawing.

[0013] Optionally, based on weight parts, the soy milk is 100 parts, the curdlan used to prepare the modified liquid is 0.1-2 parts, the modified starch is 3-6 parts, the white sugar is 0.5-1 parts, the gluconolactone is 0.3-2 parts, and the water is 10-20 parts.

[0014] By adopting the above technical solution, the taste of the thawed soft tofu can be kept appropriate. The ratio of the modified liquid and its ratio to soybean milk will have a significant impact on the preparation of tofu. If the modified starch content in the modified liquid is too high, the process product is difficult to gelatinize. If the white sugar content is too high, it will affect the role of curdlan in the preparation of tofu. If the curdlan content is too high, the soft tofu caused by its gel effect will be strong and hardened in taste, which deviates from the essence of soft tofu. The tofu will not have a delicate taste after thawing.

[0015] Optionally, the modified starch is distarch phosphate.

[0016] By adopting the above technical solution, the thawed tofu can have an end face shape without pores, and the taste is no different from that of fresh tender tofu. At the same time, the thawed tofu has a strong bean flavor without bean smell.

[0017] Optionally, the first temperature is in the range of 60-80°C.

[0018] By adopting the above technical solution, the modified starch is well gelatinized and the process product has good uniformity, so that the prepared tofu has good uniformity.

[0019] Optionally, the second temperature is in the range of 80-100°C.

[0020] By adopting the above technical scheme, the curdlan forms an irreversible gel with good properties under the joint action of modified starch, white sugar and gluconolactone, which is convenient for forming tofu without holes and with a delicate taste.

[0021] Optionally, the first time is in the range of 10-30 minutes.

[0022] By adopting the above technical solution, the protein denaturation and coagulation requirements in the process product are met, and soft tofu that is coagulated into a shape is obtained.

[0023] Optionally, the method further includes the following steps: Step S5, freezing the cut soft tofu.

[0024] By adopting the above technical solution, the prepared soft tofu is cut and then preserved.

[0025] Optionally, the step S1 includes:

[0026] S101, soaking black beans or soybeans in water to obtain wet beans;

[0027] S102, grinding the wet beans with water and filtering out the residue to obtain a slurry of a first concentration;

[0028] S103, heating the slurry at the third temperature and maintaining it for the second time to obtain soy milk.

[0029] By adopting the above technical solution, black beans or soybeans are used as raw materials for soybean milk, and the beans are softened with water to obtain wet beans that are easy to grind. The wet beans are ground in a certain amount of water to keep the concentration of the slurry at a first concentration. Controlling the first concentration can control the soluble solid content in the soybean milk, which has an important influence on the preparation of tofu required later. The slurry is heated at a third temperature for a second time, so that the protein in the slurry is denatured to form flocs, which is convenient for the subsequent preparation of tofu.

[0030] Optionally, the first concentration is 8-12 degrees.

[0031] The concentration of soy milk is controlled by controlling the first concentration. Under this concentration, the gel-formed tofu has fewer pores and better taste after being frozen.

[0032] To achieve the above object, the present invention also adopts the following technical solutions:

[0033] Tofu is prepared by any of the above-mentioned tofu preparation processes.

[0034] Beneficial effects:

[0035] The tofu preparation process and tofu provided by the present invention control the process time and process temperature, and under the joint action of curdlan, modified starch, white sugar, gluconolactone and soybean milk, the cross section of the frozen tofu after thawing has no holes, so that the thawed tofu maintains its tender and smooth taste before freezing. In addition, the soybean milk is made from bean raw materials and has a strong bean flavor, and the white sugar has the effect of alleviating the sour taste of the frozen tofu, so that the bean flavor of the tofu after thawing is prominent. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the texture analysis curve of commercially available fresh tofu;

[0037] Figure 2 is the texture analysis curve of the soft tofu prepared in Example 1;

[0038] Figure 3 It is a comparison chart of thawing loss of tofu prepared in the prior art and tofu prepared in Example 1. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0040] This embodiment provides a tofu preparation process, which includes the following steps:

[0041] S1. Prepare soy milk, and use beans as raw materials to make soy milk; in this embodiment, the bean raw material is high-quality soybeans or peeled black beans, with a protein content greater than 44%. After washing, soak in normal temperature water for 4-14 hours, such as 6 hours, and the weight of the wet beans increases to 1.5-2.5 times, such as 2 times, of the dry beans. Use a grinder to grind and crush the soaked wet beans with 2-5 times (such as 3 times) of water, and separate them through a filter to obtain a first concentration of soy milk. The protein content measured by a saccharimeter is measured in degrees, and the first concentration is 8-12 degrees (such as 9 degrees). In this embodiment, the determination of the soy milk concentration is achieved by a soy milk concentration meter. The soy milk is heated to a third temperature (such as 95°C) by a heating device, and maintained for a second time (such as 5 minutes) to obtain soy milk.

[0042] S2, preparing a modified liquid, adding curdlan, modified starch, white sugar and gluconolactone to water to obtain a modified liquid; the modified starch includes oxidized starch, phosphate starch, etherified starch, cross-linked starch and physically modified starch, etc., and the modified starch is prepared from cassava starch, wheat flour starch, potato starch, corn starch, waxy corn starch, etc. Preferably, the modified starch is phosphate distarch.

[0043] Curdlan is a water-insoluble glucan composed of β-1,3-glycosidic bonds produced by microorganisms, which is easily dispersed in cold water. It can make the tofu taste smoother after thawing. In this embodiment, by weight (g), 100 parts of soy milk, 0.1-2 parts of curdlan, 3-6 parts of modified starch, 0.5-1 parts of white sugar, 0.3-2 parts of gluconolactone, and 10-20 parts of water.

[0044] S3, adding the modified liquid to the soybean milk at the first temperature to obtain a process product; the first temperature is in the range of 60-80°C. If the soybean milk temperature is lower than 60°C during mixing, the modified starch cannot be completely gelatinized, and precipitation is likely to occur, resulting in tofu stratification. If the temperature is higher than 80°C, the viscosity of the soybean milk will increase rapidly due to the excessive gelatinization of the modified starch, resulting in a poor texture of the formed tofu.

[0045] S4, heating the process product to the second temperature, keeping it warm for the first time, and cooling it to obtain soft tofu. The process product can be heated by steaming to condense it into soft tofu. Preferably, the second temperature is in the range of 80-100°C. Due to its unique properties, curdlan can form gels with completely different properties when heated to different temperatures: low-degree gel and high-degree gel. The water dispersion of curdlan is heated to about 55-65°C and then cooled to below 40°C to form a thermoreversible low-degree gel, which has low strength and is not suitable for the present invention. When the water dispersion of curdlan is heated to above 80°C, a thermoirreversible gel is formed, which has good properties and is suitable for application in the present invention. Optionally, the first time is in the range of 10-30min, which is selected according to the selection of the second temperature. In this embodiment, when the second temperature is 90°C, the first time is 20min. After keeping warm for the first time, the condensed soft tofu can be cooled naturally or placed in cold water to cool it down.

[0046] Step S5, freezing the cut soft tofu. After the cooled soft tofu is cut and packaged, it is directly placed in a -18°C freezer for frozen storage.

[0047] This embodiment also provides tofu prepared by the above tofu preparation process.

[0048] The tofu preparation process and tofu provided in this embodiment can keep a tender and smooth mouthfeel of the prepared soft tofu after freezing and thawing by adding curdlan during the preparation process, which is very close to soft tofu, and is resistant to boiling and not easy to break. White sugar is added during the preparation process of the tofu to make the bean flavor of the tofu more intense. Gluconolactone is used as a coagulant, and its coagulation speed is slower than that of calcium sulfate and magnesium chloride, and it starts to coagulate in about 5 minutes, which is suitable for industrial large-scale production.

[0049] Example 1

[0050] (1) 10 kg of high-quality peeled black beans were selected, washed twice, and soaked in 30 kg of water at 25°C for 6 hours. The peeled black beans after soaking were poured into a grinder and ground with 50 kg of water at 25°C. After filtering, soybean milk with a temperature of about 9 degrees was obtained. The soybean milk was poured into a sandwich pot, heated to 95°C, and maintained for 5 minutes to obtain about 50 kg of finished soybean milk.

[0051] (2) Prepare the modified liquid: pour distarch phosphate (2.5 kg), curdlan (0.25 kg), white sugar (0.3 kg) and gluconolactone (0.3 kg) into 5 kg water at 25°C, stir evenly and set aside.

[0052] (3) Cool the finished soy milk to 70°C, pour the modified liquid into the finished soy milk, stir evenly, move the process product, pour the process product into a steaming tray, 3 kg per tray, put the steaming tray into a steamer and steam at 90°C for 20 minutes.

[0053] (4) Soak the soft tofu obtained after steaming in clean cold water, cool it to room temperature, cut it into specified blocks using a mold, and store it in a -18°C freezer after packaging.

[0054] Example 2

[0055] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the soaked peeled black beans are ground together with 60 kg of water at 25° C. instead of being ground together with 50 kg of water at 25° C.

[0056] Example 3

[0057] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, distarch phosphate is replaced by starch acetate.

[0058] Example 4

[0059] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, the finished soy milk is cooled to 80° C. instead of 70° C.

[0060] Example 5

[0061] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, the process product is steamed at 100°C instead of 90°C.

[0062] Comparative Example 1

[0063] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, gluconolactone is replaced by calcium sulfate. By comparing the appearance of the tofu prepared in comparative embodiment 1 and embodiment 1, the tofu prepared in comparative embodiment 1 has a rough appearance and large pores, which reduces the tender and smooth characteristics of the tofu.

[0064] Comparative Example 2

[0065] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the curdlan is replaced by high acyl gellan gum. By comparing the appearance of the tofu prepared in comparative embodiment 2 and embodiment 1, the tofu prepared in comparative embodiment 2 has a rough appearance, large pores, and the tender and smooth characteristics of the tofu are reduced.

[0066] Comparative Example 3

[0067] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, no white sugar is added.

[0068] Comparative Example 4

[0069] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, distarch phosphate is replaced by corn starch.

[0070] (I) Tofu texture analysis

[0071] Commercially available fresh tofu and the soft tofu (not frozen) produced in Example 1 were heated in boiling water for 5 minutes, and then tested using a texture analyzer to obtain a full texture TPA curve, as shown in FIG. Figure 1 and Figure 2 As shown, from the respective texture graphs, it can be seen that the texture curve of the soft tofu produced in Example 1 is very close to that of the fresh, unfrozen ordinary tofu available on the market.

[0072] The texture analysis of the soft tofu prepared in this embodiment 1 was performed, and then the soft tofu was quick-frozen (condition -35 ° C), and then the frozen tofu was fully thawed, and then the texture analysis was performed again to obtain a texture analysis comparison table, as shown in Table 1. Among them, hardness refers to the force required to cause a certain deformation of the material, elasticity refers to the ratio of the deformed material to return to its original state after the force is removed, cohesion refers to the size of the internal binding force required to form the sample shape, and chewiness refers to the energy required to chew the solid food into a swallowable state. It can be concluded from the data in Table 1 that the fresh tofu and the tofu thawed after freezing have little difference in the above data, which reflects the characteristics of tofu when it can still maintain a fresh state after freezing and thawing, so that it maintains the taste and flavor of soft tofu. The soft tofu prepared by the tofu preparation process provided in this embodiment 1 has moderate hardness, moderate elasticity, good taste, high cohesion, is not easy to break, and has high chewiness.

[0073] Table 1 Texture analysis comparison table

[0074]

[0075] (II) Thawing loss analysis

[0076] The lactone tofu, brine tofu, tofu made by combining lactone and brine coagulants in the prior art, and the tofu made in Example 1 were subjected to freezing and thawing tests under the same conditions, and the weight loss after thawing was measured. The results are as follows: Figure 3The weight loss ratio of the tofu prepared in Example 1 after thawing to before freezing (ratio of weight after thawing to weight before thawing) is about 4%, while the weight loss ratio of lactone tofu is about 49%, the weight loss ratio of brine tofu is about 14%, and the weight loss ratio of tofu prepared by combining lactone and brine coagulants is about 20%. It can be seen that the tofu prepared by the process provided in this example has the smallest thawing loss, so that it is close to the quality before thawing.

[0077] (III) Tofu sensory evaluation test

[0078] The sensory evaluation items mainly include the following three items: organizational morphology, bean aroma and mouthfeel. For the same evaluation item of the same sample, 10 trained tasters are randomly selected to evaluate. There will be 10 evaluation results for one evaluation item of one sample. The average value of these 10 evaluation results is calculated and recorded in the following table. Each evaluation item of each sample is evaluated in this way until all evaluation items of all samples are evaluated.

[0079] The soft tofu prepared in Examples 1 to 5 and Comparative Examples 1 to 4 was frozen and then boiled in boiling water for 5 minutes to fully thaw, and then a sensory evaluation was performed. The specific evaluation criteria are shown in Table 2 and the evaluation results are shown in Table 3.

[0080] Table 2 Sensory evaluation standards

[0081]

[0082] Table 3 Sensory evaluation results

[0083] Example Organizational form Taste Taste the bean aroma Example 1 2.8 2.8 2.9 Example 2 2 2.3 2.5 Example 3 2.2 2.3 2.8 Example 4 1.8 2 2.2 Example 5 2 2.1 2.3 Comparative Example 1 2 1.8 2.1 Comparative Example 2 2.3 2.1 2.4 Comparative Example 3 2.2 1.7 1.4 Comparative Example 4 1.3 1.3 1.4

[0084] With a score of 2 as the passing score, it can be seen that Examples 1, 2, 3, 5 and Comparative Example 2 all performed as expected, among which Example 1 achieved the best values ​​in all evaluations and was the optimal example.

[0085] The texture, mouthfeel and bean flavor of the tofu in Comparative Example 2 are lower than those in Example 1, indicating that curdlan gum has a beneficial effect on the texture, mouthfeel and bean flavor of the tofu compared with high acyl gellan gum.

[0086] The bean flavor of the tofu in Comparative Example 3 is lower than that in Example 1, which shows that white sugar can effectively enhance the bean flavor and reduce the bean smell.

[0087] (IV) Soymilk coagulation time test

[0088] The coagulation reaction state of the soymilk in step (4) in Examples 1 to 5 and Comparative Examples 1 to 4 was evaluated by visual observation by a person skilled in the art, and the coagulation time of the soymilk was measured by a timer to obtain Table 4.

[0089] Table 4 Soymilk coagulation timetable

[0090]

[0091]

[0092] As can be seen from Table 4, the coagulation time of the soy milk in Comparative Example 1 is lower than that in Example 1, indicating that compared with calcium sulfate, the coagulation speed of gluconolactone on soy milk is slower, easier to control, and more suitable for industrial production. The coagulation time of the soy milk in Example 4 is lower than that in Example 1, and the lower temperature of the finished soy milk in step (3) can slow down the coagulation speed of the tofu made in step (4).

[0093] The soymilk coagulation time is less than 2 minutes, which is basically impossible to be industrialized on a large scale. The soymilk of Examples 1 to 5 and Comparative Examples 1 to 4 coagulates in more than 3 minutes, which can be industrialized, and among them, Examples 1, 3, 5 and Comparative Examples 3 and 4 coagulate in more than 6 minutes, so the soymilk coagulation time is long and the industrialization operability is stronger.

[0094] The invention uses the combination of curdlan, white sugar, gluconolactone modified starch and soybean milk to make the prepared tofu free of pores after thawing, with a delicate taste and a strong bean flavor. Meanwhile, the process is simple, the soybean milk solidification time is sufficient, and industrial production is convenient.

[0095] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A tofu preparation process, characterized in that: The following steps are involved: S1, preparing soy milk, using beans as raw materials to prepare soy milk; S2, preparing a modified liquid, adding curdlan, modified starch, white sugar and gluconolactone into water to obtain a modified liquid; S3, adding the modified liquid to the soy milk at the first temperature to obtain a process product; S4, heating the process product to a second temperature, keeping the temperature for the first time, and cooling to obtain soft tofu; The modified starch is distarch phosphate; Counting by weight, the soy milk is 100 parts, the curdlan used to prepare the modified liquid is 0.1-2 parts, the modified starch is 3-6 parts, the white sugar is 0.5-1 parts, the gluconolactone is 0.3-2 parts, and the water is 10-20 parts; The first temperature is in the range of 60-80°C; The second temperature is in the range of 80-100°C.

2. The tofu preparation process according to claim 1, characterized in that: The first time is in the range of 10-30 minutes.

3. The tofu preparation process according to claim 1, characterized in that: The following steps are also included: Step S5, freezing the cut soft tofu.

4. The tofu preparation process according to claim 1, characterized in that: The step S1 comprises: S101, soaking black beans or soybeans in water to obtain wet beans; S102, grinding the wet beans with water and filtering out the residue to obtain a slurry of a first concentration; S103, heating the slurry at the third temperature and maintaining it for the second time to obtain soy milk.

5. The tofu preparation process according to claim 4, characterized in that: The first concentration is 8-12 degrees.

6. Tofu, characterized in that The tofu is prepared by the tofu preparation process according to any one of claims 1 to 5.

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