A wrapped bean curd and a method for preparing the same

Abstract

The application provides a wrapped bean curd, which comprises the following raw materials in percentage by mass: 6-12% of soybean protein isolate powder, 1-6% of starch, 1.5-6.5% of egg white powder, 1-6.5% of plant protein powder, 2-6.5% of defatted soybean powder, 0.1-0.5% of glutamine transaminase, 0.1-3% of a compound containing metal elements, 60-75% of water and 5-12% of edible oil. The application uses soybean protein isolate as the raw material, starch, plant protein powder, defatted soybean powder, glutamine transaminase, metal ions and egg white powder as the auxiliary materials, adopts the biological enzyme coupling and the composite gel network technology to make the protein molecules form a relatively stable cross-linking system, and the water, the protein and the fat exist in the form of bound water. Under the condition of long-term freezing and repeated freezing, the product still has a smooth and fresh taste. The metal ion treatment technology is used to give the product the characteristics of crisp outside and tender inside. The integration of the three technologies can ensure the product taste, has the characteristics of simple operation and high automation degree, and effectively improves the industrial production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of food technology, specifically relating to a type of tofu with a coating and its preparation method. Background Technology

[0002] Traditional tofu products primarily use soybeans as raw material, with added auxiliary materials such as glucono-β-lactone, compound coagulant magnesium chloride, mono- and diglyceride fatty acid esters, calcium sulfate, magnesium chloride, and calcium hydroxide. These materials cause protein aggregation and denaturation, resulting in different textures. Traditional "bao jiang" tofu, on the other hand, is a semi-finished product made through processes such as grinding, boiling, curdling, setting, pouring, and pressing. It is then treated with metal ion soaking to give it a crispy exterior and tender interior, resulting in a smooth texture. However, traditional "bao jiang" tofu has several drawbacks: complex processing, high labor costs, and low automation and production efficiency. Furthermore, it is stored using either refrigeration or freezing. Refrigerated tofu is prone to developing a sour or rancid odor during transportation or storage, leading to an unpleasant consumer experience. While frozen tofu has a longer shelf life and slightly better flavor, prolonged freezing alters the form of water, causing it to solidify and expand, disrupting the original structure and gradually diminishing the crispy exterior and tender interior texture. Therefore, there is an urgent need to provide a type of tofu with a good product structure and taste that can be frozen for a long time or repeatedly frozen and thawed. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a tofu with a coating and a method for preparing the same. The tofu with a coating provided by the present invention still has a good product structure and taste after being frozen for a long time or repeatedly frozen and thawed.

[0004] This invention provides a type of tofu with a coating, comprising the following raw materials in weight percentages:

[0005] The ingredients include 6-12% soy protein isolate, 1-6% starch, 1.5-6.5% egg white powder, 1-6.5% plant protein powder, 2-6.5% soy flour, 0.1-0.5% transglutaminase, 0.1-3% compounds containing metal elements, 60-75% water, and 5-12% edible oil.

[0006] Preferably, the raw materials also include: 0.5-1.0% compound seasoning and 0.25-0.5% characteristic flavoring.

[0007] Preferably, the starch includes one or more combinations of corn starch, acetate starch, acetylated distarch phosphate, and potato starch.

[0008] Preferably, the plant protein powder includes one or more combinations of rice protein powder, mung bean protein powder, pea protein powder, and wheat protein powder.

[0009] Preferably, the metal-containing compound includes one or more combinations of calcium hydroxide, magnesium chloride, sodium carbonate, and sodium bicarbonate.

[0010] Preferably, the edible oil includes one or more of corn oil, soybean oil, flaxseed oil, sunflower oil, and peanut oil.

[0011] Preferably, the compound seasoning is one or more of salt, white sugar, and monosodium glutamate.

[0012] Preferably, the characteristic flavoring includes one or more combinations of soy milk flavoring, fresh soy milk powder, and soy milk powder flavoring.

[0013] This invention also provides a method for preparing frozen tofu semi-finished product, comprising the following steps:

[0014] A) Mix soy protein isolate, egg white powder, vegetable protein powder, and defatted soy flour to obtain a base mixture;

[0015] Starch, transglutaminase, and a compound containing a metal element are mixed to obtain a structural mixture;

[0016] The compound seasoning and characteristic flavoring are mixed to obtain a compound flavor mixture;

[0017] B) Mix the base mixture with water to obtain a tofu protein paste;

[0018] C) Mix and emulsify the edible oil with the coated tofu protein slurry to obtain a coated tofu emulsion slurry;

[0019] D) Mix the structural mixture, the compound flavor mixture, and the coated tofu emulsion to obtain the coated tofu slurry;

[0020] E) After the tofu slurry is fermented, the enzymes are inactivated to obtain shaped tofu with a coating.

[0021] F) After cutting the formed tofu into pieces, refrigerate to obtain frozen tofu semi-finished product.

[0022] The present invention also provides a method for preparing coated tofu, which is obtained by frying or baking the above-mentioned frozen coated tofu semi-finished product.

[0023] Compared with existing technologies, this invention provides a type of tofu with a crispy coating, comprising the following raw materials by weight percentage: 6-12% soy protein isolate, 1-6% starch, 1.5-6.5% egg white powder, 1-6.5% vegetable protein powder, 2-6.5% defatted soy flour, 0.1-0.5% transglutaminase, 0.1-3% metal-containing compounds, 60-75% water, and 5-12% edible oil. This invention uses soy protein isolate as the raw material, and starch, vegetable protein powder, defatted soy flour, transglutaminase, metal ions, and egg white powder as auxiliary materials. It employs bio-enzyme coupling and composite gel network technology to form a relatively stable cross-linked system between and within protein molecules. Water, protein, and fat exist in the form of bound water. Under long-term freezing and repeated freezing conditions, the product retains a smooth and tender texture. The metal ion treatment technology imparts a crispy exterior and tender interior. The integration of these three technologies ensures the product's taste while offering simple operation and a high degree of automation, effectively improving industrial production efficiency. Attached Figure Description

[0024] Figure 1 This is a photo of the semi-finished tofu with a coating after freezing for 24 hours.

[0025] Figure 2 Photos of frozen tofu (with a coating of tofu) before and after frying;

[0026] Figure 3 A photo of semi-finished tofu with a coating that has been frozen for 8 months;

[0027] Figure 4 This is a photo of a semi-finished tofu product, frozen for 8 months, after being deep-fried. Detailed Implementation

[0028] This invention provides a type of tofu with a coating, comprising the following raw materials in weight percentages:

[0029] The ingredients include 6-12% soy protein isolate, 2-6% starch, 1.5-6.5% egg white powder, 1-6.5% plant protein powder, 2-6.5% defatted soy flour, 0.1-0.5% transglutaminase, 2-6% compounds containing metal elements, 60-75% water, and 7-12% edible oil.

[0030] The raw materials for preparing the tofu with a coating provided by the present invention include 6-12% soy protein isolate powder, which can be any value between 6%, 7%, 8%, 9%, 10%, 11%, 12%, or 6-12%.

[0031] The raw materials for preparing the coated tofu provided by this invention also include 2-6% starch, which can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or any value between 2 and 6%. The starch includes one or more combinations of corn starch, acetate starch, hydroxypropyl distarch phosphate, acetylated distarch phosphate, and potato starch.

[0032] The raw materials for preparing the tofu with a coating provided by the present invention also include 1.5% to 6.5% egg white powder, which can be 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or any value between 1.5% and 6.5%.

[0033] The raw materials for preparing the tofu with a coating provided by this invention also include 1-6.5% plant protein powder, which can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or any value between 1% and 6.5%. The plant protein powder includes one or more combinations of rice protein powder, mung bean protein powder, pea protein powder, and wheat protein powder.

[0034] The raw materials for preparing the tofu with a coating provided by this invention also include 2-6.5% soybean flour, which can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or any value between 2 and 6.5%. The soybean flour is selected from defatted soybean flour or soy milk powder.

[0035] The raw materials for preparing the tofu with a coating provided by the present invention also include 0.1-0.5% of transglutaminase, which can be any value between 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.1-0.5%.

[0036] The raw materials for preparing the tofu with a crisp coating provided by this invention also include 2-6% of a compound containing a metal element, which can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or any value between 2-6%. In this invention, the compound containing the metal element is a compound capable of providing metal ions for the preparation of the tofu with a crisp coating. Preferably, the compound containing the metal element includes one or more combinations of calcium hydroxide, magnesium chloride, sodium carbonate, and sodium bicarbonate.

[0037] The raw materials for preparing the tofu with a coating provided by the present invention also include 60-75% water, which can be any value between 60%, 65%, 70%, 75%, or 60-75%.

[0038] The raw materials for preparing the tofu with a coating provided by this invention also include 7-12% edible oil, which can be any value between 7%, 8%, 9%, 10%, 11%, 12%, or 7-12%. The edible oil includes one or more combinations of corn oil, soybean oil, flaxseed oil, sunflower oil, and peanut oil.

[0039] In some specific embodiments of the present invention, in order to improve the flavor of the tofu with a coating, the raw materials for preparing the tofu with a coating also include 0.5-1.0% of compound seasoning and 0.25-0.5% of characteristic flavoring.

[0040] Specifically, the raw materials for preparing the tofu with a crispy skin provided by the present invention further include 0.5% to 1.0% of a compound seasoning, which can be any value between 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or 0.5% to 1.0%. Preferably, the compound seasoning is one or more combinations of salt, white sugar, and monosodium glutamate.

[0041] The raw materials for preparing the tofu with a coating provided by this invention further include 0.25% to 0.5% of a characteristic flavoring, which can be any value between 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or 0.25% to 0.5%. The characteristic flavoring includes one or more combinations of soy milk flavor enhancer, fresh soy milk powder, and soy milk powder flavoring.

[0042] This invention also provides a method for preparing frozen tofu semi-finished product, comprising the following steps:

[0043] A) Mix soy protein isolate, egg white powder, vegetable protein powder, and defatted soy flour to obtain a base mixture;

[0044] Starch, transglutaminase, and a compound containing a metal element are mixed to obtain a structural mixture;

[0045] The compound seasoning and characteristic flavoring are mixed to obtain a compound flavor mixture;

[0046] B) Mix the base mixture with water to obtain a tofu protein paste;

[0047] C) Mix and emulsify the edible oil with the coated tofu protein slurry to obtain a coated tofu emulsion slurry;

[0048] D) Mix the structural mixture, the compound flavor mixture, and the coated tofu emulsion to obtain the coated tofu slurry;

[0049] E) After the tofu slurry is fermented, the enzymes are inactivated to obtain shaped tofu with a coating.

[0050] F) After cutting the formed tofu into pieces, refrigerate to obtain frozen tofu semi-finished product.

[0051] Specifically, the present invention first prepares a base mixture, a structural mixture, and a complex flavor mixture. The mixing method is not particularly limited; any mixing method known to those skilled in the art is acceptable.

[0052] Then, the base mixture is mixed with water to obtain a tofu protein slurry. Preferably, the mixing is carried out in the following manner:

[0053] Place the base mixture and water in a chopper, mix the water and powder at 300-500 rpm for 30-40 seconds until uniform, then increase the speed to 1500-2000 rpm and chop for 3 minutes 30-5 minutes until the slurry is smooth and free of particles, thus obtaining the tofu protein slurry.

[0054] Next, the tofu protein slurry is mixed and emulsified with edible oil to obtain a tofu emulsion slurry. Specifically, edible oil is weighed as needed and added to the tofu protein slurry, and the mixture is chopped at a speed of 1500-2000 r / min for 2-3 minutes to obtain the tofu emulsion slurry.

[0055] Furthermore, the structural mixture, the complex flavor mixture, and the coated tofu emulsion are mixed to obtain the coated tofu slurry.

[0056] Specifically, the structural mixture and the compound flavor mixture are added to the emulsified tofu slurry in sequence. First, mix at 300-500 r / min for 30-40 seconds until uniform, then increase the speed to 1500-2000 r / min and chop for 1 minute and 30 seconds to obtain the tofu slurry.

[0057] The tofu slurry is fermented and then enzymes are inactivated to obtain shaped tofu. Specifically, the tofu slurry is spread onto a forming mold for fermentation. The fermentation temperature is 50–55℃ (any value between 50, 51, 52, 53, 54, and 55℃) and the fermentation time is 40–60 minutes (any value between 40, 50, and 60 minutes). After fermentation, enzymes are inactivated. The enzyme inactivation temperature is 85–88℃ (any value between 85, 86, 87, and 88℃) and the fermentation time is 30–40 minutes (any value between 30, 35, and 40 minutes).

[0058] The proofing process is the process by which the tofu skin is formed.

[0059] Then, the formed tofu is cut and refrigerated to obtain frozen tofu semi-finished product. It is cut into rectangular blocks (2.5cm long x 2.5cm wide x 1cm high) using a cutting machine and stored at -18℃ or below to obtain frozen tofu semi-finished product. The storage time can be up to 9 months.

[0060] The present invention also provides a method for preparing coated tofu, wherein the above-mentioned frozen coated tofu semi-finished product is obtained by frying or baking.

[0061] The frying temperature is 165–180℃, and the time is 1 min 45–2 min 30 s. The baking temperature is 160–180℃, and the time is 3–5 min.

[0062] This invention also provides a method for preparing tofu with a coating, comprising the following steps:

[0063] A) Mix soy protein isolate, egg white powder, vegetable protein powder, and defatted soy flour to obtain a base mixture;

[0064] Starch, transglutaminase, and a compound containing a metal element are mixed to obtain a structural mixture;

[0065] The compound seasoning and characteristic flavoring are mixed to obtain a compound flavor mixture;

[0066] B) Mix the base mixture with water to obtain a tofu protein paste;

[0067] C) Mix and emulsify the edible oil with the coated tofu protein slurry to obtain a coated tofu emulsion slurry;

[0068] D) Mix the structural mixture, the compound flavor mixture, and the coated tofu emulsion to obtain the coated tofu slurry;

[0069] E) After the tofu slurry is fermented, the enzymes are inactivated to obtain shaped tofu with a coating.

[0070] F) After the formed tofu is cut into pieces, it is fried or baked to obtain tofu with a coating.

[0071] This method involves directly frying or baking the prepared tofu with a coating, without freezing or storing it, thus directly producing tofu with a coating.

[0072] This invention uses soy protein isolate as raw material and starch, plant protein powder, defatted soy flour, transglutaminase, metal ions, egg white powder, etc. as auxiliary materials. It adopts bio-enzyme coupling and composite gel network technology to form a relatively stable cross-linking system between and within protein molecules. Water, protein, and fat exist in the form of bound water. Under long-term freezing and repeated freezing conditions, the product still has a smooth and tender taste. The metal ion treatment technology gives the product a crispy outside and tender inside. The integration of the three technologies can ensure the taste of the product while being simple to operate and highly automated, effectively improving the efficiency of industrial production.

[0073] To further understand the present invention, the following description, in conjunction with embodiments, illustrates a type of tofu with a coating and its preparation method. The scope of protection of the present invention is not limited by the following embodiments.

[0074] Example 1

[0075] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0076] Soy protein isolate 10.28%, wheat protein 1.96%, egg white powder 1.96%, defatted soy flour 2.02%, edible oil 10.12%, wheat protein 2.23%, metal-containing compounds 0.48%, transglutaminase 0.37%, compound seasonings 0.82%, characteristic flavorings 0.26%, ice water balance.

[0077] The edible oils, by mass fraction, comprise 6.75% soybean oil and 3.37% olive oil.

[0078] The starch comprises, by mass fraction, 1.12% acetylated distarch phosphate and 1.11% hydroxypropyl distarch phosphate.

[0079] The metal-containing compound comprises, by mass fraction, 0.24% calcium hydroxide and 0.24% sodium bicarbonate.

[0080] The compound seasoning, by mass fraction, comprises 0.41% sugar, 0.21% monosodium glutamate, and 0.20% salt.

[0081] The characteristic flavorings, by mass fraction, include 0.18% soy milk powder flavoring and 0.08% soy milk flavor enhancer.

[0082] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0083] (1) Preparation of base mixture: Weigh out soy protein isolate powder, wheat protein powder, egg white powder and defatted soy flour as needed, mix the powders evenly to obtain base mixture;

[0084] (2) Preparation of structural mixture: Weigh acetylated distarch phosphate, potato starch, transglutaminase, calcium hydroxide, and sodium bicarbonate as needed, mix the powders evenly to obtain structural mixture;

[0085] (3) Preparation of compound flavor mixture: Weigh out salt, sugar, monosodium glutamate, soy milk flavor enhancer and soy milk powder flavor as needed, mix the above powders evenly to obtain compound flavor mixture;

[0086] (4) Hydration stage: Place the base mixture from step (1) and ice water in a chopper. First, mix the water and powder at 300 r / min for 30 seconds until they are uniform. Then, increase the speed to 1500 r / min and chop for 3 minutes and 30 seconds until the slurry is smooth and free of particles, and obtain the tofu protein slurry.

[0087] (5) Emulsification stage: Weigh soybean oil and olive oil as needed, slowly add them to step (4), control the speed to 1500 r / min and chop for 2 min to obtain the tofu emulsion slurry;

[0088] (6) Structure building stage: Add the structure mixture from step (2) and the compound flavor mixture from step (3) to step (5) in sequence. First, mix at 300r / min for 30s until uniform, then increase the speed to 1500r / min and chop for 1min30s to obtain the tofu slurry.

[0089] (7) Shaping stage: Spread the tofu paste from step (6) onto the shaping mold, place it in a steamer, let it rise at 55°C for 40 minutes, inactivate the enzyme at 85°C for 30 minutes, and cool it to room temperature to obtain the shaped tofu.

[0090] (8) Semi-finished product stage: The formed tofu from step (7) is cut into a cuboid with a length of 2.5cm × width of 2.5cm × height of 1cm using a cutting machine, packaged using vacuum packaging equipment, and stored in an environment below -18℃ for 24 hours to obtain semi-finished tofu.

[0091] (9) Finished product stage: Place the semi-finished tofu from step (8) in a deep fryer at 165℃ and fry for 1 minute and 45 seconds. When the product skin turns golden yellow, the finished tofu is obtained.

[0092] See Figure 1 , Figure 1 The first image shows the tofu semi-finished product frozen for 24 hours. The second image shows the tofu semi-finished product after being frozen for 24 hours and then fried in a 165℃ deep fryer for 1 minute and 45 seconds. Figure 2 , Figure 2 These are photos of tofu before and after frying, showing the tofu's outer layer of skin.

[0093] Even after being frozen for an extended period (8 months), tofu with a crispy outer layer, a creamy interior, and a smooth texture retains its characteristic crispness and tenderness when deep-fried and tasted. Figure 3 and Figure 4 As shown, the combination of chopping and mixing technology with bio-enzyme coupling technology, composite gel network technology and compound technology containing metal elements can effectively change the state of water inside tofu, preventing the product from shrinking and its structure from being damaged during long-term freezing. This ensures that the product retains its good taste even after long-term freezing.

[0094] Example 2

[0095] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0096] Soy protein isolate 10.28%, wheat protein powder 1.96%, egg white powder 1.96%, defatted soy flour 2.02%, soybean oil 10.12%, corn starch 2.23%, metal-containing compounds 0.48%, transglutaminase 0.37%, compound seasonings 0.82%, characteristic flavorings 0.26%, ice water balance.

[0097] The metal-containing compound comprises, by mass fraction, 0.12% magnesium chloride and 0.36% sodium bicarbonate.

[0098] The compound seasoning, by mass fraction, comprises 0.23% sugar, 0.15% monosodium glutamate, and 0.12% salt.

[0099] The characteristic flavorings, by mass fraction, include 0.17% soy milk powder flavoring and 0.08% soy milk flavor enhancer.

[0100] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0101] (1) The steps are the same as in Example 1;

[0102] (2) Preparation of structural mixture: Weigh corn starch, transglutaminase, magnesium chloride and sodium bicarbonate as needed, mix the powders evenly to obtain structural mixture;

[0103] Steps (3) to (9) are the same as in Example 1.

[0104] Example 3

[0105] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0106] Soy protein isolate 9.02%, pea protein 4.96%, egg white powder 5.45%, defatted soy flour 6.23%, soybean oil 10.12%, starch 2.50%, sodium carbonate 0.20%, transglutaminase 0.33%, compound seasoning 0.82%, characteristic flavoring 0.37%, room temperature water balance.

[0107] The starch comprises, by mass fraction, 1.28% acetylated distarch phosphate and 1.22% acetate starch.

[0108] The compound seasoning, by mass fraction, comprises 0.31% sugar, 0.31% monosodium glutamate, and 0.20% salt.

[0109] The characteristic flavorings, by mass fraction, include 0.20% soy milk powder flavoring and 0.17% soy milk flavor enhancer.

[0110] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0111] (1) Preparation of base mixture: Weigh out soy protein isolate powder, pea protein powder, egg white powder and defatted soy flour as needed, mix the powders evenly to obtain base mixture;

[0112] (2) Preparation of structural mixture: Weigh acetylated distarch phosphate, starch acetate, transglutaminase and sodium carbonate as needed, mix the powders evenly to obtain structural mixture;

[0113] Steps (3) to (9) are the same as in Example 1.

[0114] Example 4

[0115] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0116] Soy protein isolate 6.29%, rice protein powder 6.50%, egg white powder 6.41%, defatted soy flour 4.02%, edible oil 7.11%, acetylated distarch phosphate 2.21%, metal-containing compounds 0.45%, transglutaminase 0.50%, compound seasonings 1.00%, characteristic flavorings 0.45%, ice water balance.

[0117] The edible oils, by mass fraction, comprise 4.13% soybean oil and 2.98% corn oil.

[0118] The compound containing the metal element comprises, by mass fraction, 0.30% calcium hydroxide and 0.15% sodium bicarbonate.

[0119] The compound seasoning, by mass fraction, includes 0.40% sugar, 0.34% monosodium glutamate, and 0.26% salt.

[0120] The characteristic flavorings, by mass fraction, include 0.28% soy milk powder flavoring and 0.17% soy milk flavor enhancer.

[0121] (1) Preparation of base mixture: Weigh out soy protein isolate powder, rice protein powder, egg white powder and defatted soy flour as needed, mix the powders evenly to obtain base mixture;

[0122] (2) Preparation of structural mixture: Weigh acetylated distarch phosphate, transglutaminase, calcium hydroxide and sodium bicarbonate as needed, mix the powders evenly to obtain structural mixture;

[0123] Steps (3) to (9) are the same as in Example 1.

[0124] Example 5

[0125] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0126] Soy protein isolate 8.56%, wheat protein 3.82%, egg white powder 2.93%, defatted soy flour 2.65%, soybean oil 11.50%, potato starch 2.21%, metal-containing compounds 0.39%, transglutaminase 0.45%, compound seasonings 0.66%, characteristic flavorings 0.50%, ice water balance.

[0127] The compound containing the metal element comprises, by mass fraction, 0.20% calcium hydroxide and 0.19% sodium bicarbonate.

[0128] The compound seasoning, by mass fraction, comprises 0.30% sugar, 0.19% monosodium glutamate, and 0.17% salt.

[0129] The characteristic flavorings, by mass fraction, include 0.25% soy milk powder flavoring and 0.25% soy milk flavor enhancer.

[0130] (1) Preparation of base mixture: Weigh out soy protein isolate powder, wheat protein powder, egg white powder and defatted soy flour as needed, mix the powders evenly to obtain base mixture;

[0131] (2) Preparation of structural mixture: Weigh potato starch, transglutaminase, calcium hydroxide and sodium bicarbonate as needed, mix the powders evenly to obtain structural mixture;

[0132] Steps (3) to (9) are the same as in Example 1.

[0133] Comparative Example 1

[0134] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0135] Soy protein isolate 10.28%, wheat protein 1.96%, defatted soy flour 2.02%, edible oil 10.12%, starch 2.23%, metal-containing compounds 0.48%, transglutaminase 0.37%, compound seasonings 0.82%, characteristic flavorings 0.26%, ice water balance.

[0136] The edible oils, by mass fraction, comprise 6.75% soybean oil and 3.37% olive oil.

[0137] The starch comprises, by mass fraction, 1.12% acetylated distarch phosphate and 1.11% potato starch.

[0138] The metal-containing compound comprises, by mass fraction, 0.24% calcium hydroxide and 0.24% sodium bicarbonate.

[0139] The compound seasoning, by mass fraction, comprises 0.41% sugar, 0.21% monosodium glutamate, and 0.20% salt.

[0140] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0141] (1) Preparation of base material mixture: Weigh out soybean protein isolate, wheat protein powder and defatted soybean flour as needed, mix the powders evenly to obtain base material mixture;

[0142] Steps (2) to (9) are the same as in Example 1.

[0143] Comparative Example 2

[0144] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0145] Soy protein isolate 10.28%, wheat protein 1.96%, egg white powder 1.96%, defatted soy flour 2.02%, edible oil 10.12%, starch 2.23%, metal-containing compounds 0.48%, compound seasonings 0.82%, characteristic flavorings 0.26%, ice water balance.

[0146] The edible oils, by mass fraction, comprise 6.75% soybean oil and 3.37% olive oil.

[0147] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0148] The starch comprises, by mass fraction, 1.12% acetylated distarch phosphate and 1.11% potato starch.

[0149] The metal-containing compound comprises, by mass fraction, 0.24% calcium hydroxide and 0.24% sodium bicarbonate.

[0150] The compound seasoning, by mass fraction, comprises 0.41% sugar, 0.21% monosodium glutamate, and 0.20% salt.

[0151] The characteristic flavorings, by mass fraction, include 0.18% soy milk powder flavoring and 0.08% soy milk flavor enhancer.

[0152] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0153] (1) The steps are the same as in Example 1;

[0154] (2) Preparation of structural mixture: Weigh acetylated distarch phosphate, potato starch, calcium hydroxide and sodium bicarbonate as needed, mix the powders evenly to obtain structural mixture;

[0155] Steps (3) to (9) are the same as in Example 1.

[0156] Comparative Example 3

[0157] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0158] Soy protein isolate 10.28%, wheat protein 1.96%, egg white powder 1.96%, defatted soy flour 2.02%, edible oil 10.12%, starch 2.23%, transglutaminase 0.37%, compound seasoning 0.82%, characteristic flavoring 0.26%, ice water balance.

[0159] The edible oils, by mass fraction, comprise 6.75% soybean oil and 3.37% olive oil.

[0160] The starch comprises, by mass fraction, 1.12% acetylated distarch phosphate and 1.11% potato starch.

[0161] The compound seasoning, by mass fraction, comprises 0.41% sugar, 0.21% monosodium glutamate, and 0.20% salt.

[0162] The characteristic flavorings, by mass fraction, include 0.18% soy milk powder flavoring and 0.08% soy milk flavor enhancer.

[0163] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0164] (1) The steps are the same as in Example 1;

[0165] (2) Preparation of structural mixture: Weigh acetylated distarch phosphate, potato starch and transglutaminase as needed, mix the powders evenly to obtain structural mixture;

[0166] Steps (3) to (9) are the same as in Example 1.

[0167] Comparative Example 4

[0168] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0169] Soy protein isolate 11.28%, wheat protein 1.96%, egg white powder 1.96%, defatted soy flour 2.02%, edible oil 10.12%, metal-containing compounds 0.48%, transglutaminase 0.37%, compound seasonings 0.82%, characteristic flavorings 0.26%, ice water balance.

[0170] The edible oils, by mass fraction, comprise 6.75% soybean oil and 3.37% olive oil.

[0171] The metal-containing compound comprises, by mass fraction, 0.24% calcium hydroxide and 0.24% sodium bicarbonate.

[0172] The compound seasoning, by mass fraction, comprises 0.41% sugar, 0.21% monosodium glutamate, and 0.20% salt.

[0173] The characteristic flavorings, by mass fraction, include 0.18% soy milk powder flavoring and 0.08% soy milk flavor enhancer.

[0174] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0175] (1) Preparation of base mixture: Weigh out soy protein isolate powder, wheat protein powder, egg white powder and defatted soy flour as needed, mix the powders evenly to obtain base mixture;

[0176] (2) Preparation of structural mixture: Weigh glutamine transaminase, calcium hydroxide and sodium bicarbonate as needed, mix the powders evenly to obtain structural mixture;

[0177] Steps (3) to (9) are the same as in Example 1.

[0178] Comparative Example 5

[0179] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0180] Soy protein isolate 10.28%, wheat protein 1.96%, whey powder 1.96%, defatted soy flour 2.02%, edible oil 10.12%, starch 2.23%, metal-containing compounds 0.48%, transglutaminase 0.37%, compound seasonings 0.82%, characteristic flavorings 0.26%, ice water balance.

[0181] The edible oils, by mass fraction, comprise 6.75% soybean oil and 3.37% olive oil.

[0182] The starch comprises, by mass fraction, 1.12% acetylated distarch phosphate and 1.11% potato starch.

[0183] The metal-containing compound comprises, by mass fraction, 0.24% calcium hydroxide and 0.24% sodium bicarbonate.

[0184] The compound seasoning, by mass fraction, comprises 0.41% sugar, 0.21% monosodium glutamate, and 0.20% salt.

[0185] The characteristic flavorings, by mass fraction, include 0.18% soy milk powder flavoring and 0.08% soy milk flavor enhancer.

[0186] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0187] (1) Preparation of base mixture: Weigh out soy protein isolate powder, wheat protein powder, whey powder and defatted soy flour as needed, mix the powders evenly to obtain base mixture;

[0188] Steps (2) to (9) are the same as in Example 1.

[0189] Comparative Example 6

[0190] This embodiment provides a novel tofu with a coating and its preparation method using a chopping and mixing process. The raw materials include the following components by mass fraction:

[0191] Pea protein powder 5.14%, rice protein powder 5.14%, wheat protein powder 1.96%, egg white powder 1.96%, defatted soy flour 2.02%, edible oil 10.12%, starch 2.23%, compounds containing metal elements 0.48%, transglutaminase 0.37%, compound seasonings 0.82%, characteristic flavorings 0.26%, ice water balance.

[0192] The edible oils, by mass fraction, comprise 6.75% soybean oil and 3.37% olive oil.

[0193] The starch comprises, by mass fraction, 1.12% acetylated distarch phosphate and 1.11% potato starch.

[0194] The metal-containing compound comprises, by mass fraction, 0.24% calcium hydroxide and 0.24% sodium bicarbonate.

[0195] The compound seasoning, by mass fraction, comprises 0.41% sugar, 0.21% monosodium glutamate, and 0.20% salt.

[0196] The characteristic flavorings, by mass fraction, include 0.18% soy milk powder flavoring and 0.08% soy milk flavor enhancer.

[0197] A novel type of coated tofu and its preparation method using a chopping and mixing process, the preparation process specifically includes the following steps:

[0198] (1) Preparation of base mixture: Weigh pea protein powder, rice protein powder, wheat protein powder, egg white powder and defatted soybean powder as needed, mix the above powders evenly to obtain base mixture;

[0199] Steps (2) to (9) are the same as in Example 1.

[0200] (I) Sensory evaluation of the new type of tofu with a coating

[0201] Twenty sensory evaluators conducted descriptive sensory evaluations on the tofu products of Examples 1-5 and Comparative Examples 1-6 in seven aspects: product color, bean aroma, firmness, delicacy, crispness of the outer skin, coating, and smoothness. The sensory evaluation criteria are shown in Table 1, and the sensory evaluation results are shown in Table 2.

[0202] Table 1 Sensory Evaluation Criteria for Novel Type of Tofu with Creamy Skin

[0203]

[0204] Table 2 Sensory evaluation results of the new type of coated tofu

[0205]

[0206]

[0207] As shown in Table 2, the novel tofu with a creamy coating in Examples 1-5 generally achieved high sensory scores, exhibiting good soybean aroma, firm structure, and delicate texture. After frying, the products were golden yellow with a noticeably crispy outer layer and a well-distributed, evenly coated interior, resulting in a smooth and tender texture. In all five examples, using potato starch, corn starch, or a combination of both improved the crispiness of the outer layer. Compared to Example 1, Comparative Examples 1 and 2, lacking egg white powder or TG enzyme, significantly affected the firmness and delicate texture of the novel tofu with a creamy coating, and also reduced the creamy and tender texture after frying. This is likely because egg white powder and soy protein isolate, under the action of TG enzyme, synergistically formed a gel network structure in the food system with better elasticity and toughness. Comparative Example 3, lacking a compound containing metal elements, affected the creamy and tender texture of the product. This is likely because the interaction between protein molecular chains is disrupted under the action of compounds containing metal elements, thus providing the product with a fluffy, delicate texture, smooth mouthfeel, and creamy coating. The state of the product was as follows: In Comparative Example 4, no starch was added, and the crispness of the product surface was significantly reduced. This may be because starch in the product structure system can, on the one hand, increase the hardness of the product and make the texture supportive, and on the other hand, starch gelatinizes under certain temperature conditions, which can interact with soy protein and egg white protein to provide the crispness of the product surface during frying. The sensory evaluation results of Comparative Example 4 and Comparative Example 6 show that only by using soy protein isolate as raw material and through bio-enzyme coupling technology, composite gel network technology and compound treatment technology containing metal elements can the new type of coated tofu be given a firm and delicate structure, as well as a crispy outer skin, a coated interior and a tender and smooth feel after frying. This provides soy product companies with the advantages of simple operation, high degree of automation and long shelf life, thus replacing traditional coated tofu.

[0208] Long-term freezing experiment

[0209] The semi-finished tofu products from Examples 1 and 2 were frozen at -18°C for 3 months, 6 months, and 9 months, respectively. Then, the frozen semi-finished tofu products were fried in a deep fryer at 165°C for 1 minute and 45 seconds to obtain the tofu with a creamy coating.

[0210] The tofu with a coating was evaluated using a descriptive sensory approach, considering seven aspects: product color, bean aroma, firmness, delicacy, crispness of the outer skin, coating texture, and smoothness. The sensory evaluation criteria are shown in Table 1, and the sensory evaluation results are shown in Table 3.

[0211] Table 3 Sensory evaluation results of the novel coated tofu in Examples 1-5

[0212]

[0213] As shown in Table 3, during the frozen storage process of Examples 1 and 2, the flavor, texture, and taste of the products will change to some extent over time. This is mainly reflected in the product's delicacy, crispness of the outer skin, coating, and smoothness. Under frozen conditions, the optimal shelf life of the new type of coated tofu should not exceed 9 months. Compared with Example 1, the changes in texture and taste of Example 2 are more obvious. The difference between the two is mainly reflected in the different types of starch. Example 1 uses modified starch hydroxypropyl distarch phosphate, while Example 2 uses unmodified starch. Because starch is treated by physical, chemical, or enzymatic methods, new functional groups are introduced into the starch molecules, changing the properties of the starch molecules, thereby changing the natural characteristics of the starch (modified starch). After combining with proteins and water, it has better melt stability, can better maintain the original structural characteristics of the product, and extend the shelf life of the product.

[0214] Repeated freeze-thaw experiment

[0215] Repeated freeze-thaw experiments were conducted on the semi-finished tofu product from Example 1. The specific method is as follows:

[0216] Using the color, flavor, and texture of the novel coated tofu as evaluation indicators, the product of Example 1 was stored at -18℃. Samples were taken out every 2 hours, thawed naturally at room temperature, and then a portion was deep-fried at 165℃ for 1 minute and 45 seconds for sensory evaluation. The remaining portion was returned to -18℃ for continued storage, repeating this freeze-thaw cycle 6 times. Next, the frozen-thawed tofu semi-finished product was placed in a deep fryer at 165℃ and deep-fried for 1 minute and 45 seconds to obtain coated tofu. Then, a descriptive sensory evaluation was performed on the coated tofu in seven aspects: product color, bean aroma, firmness, delicacy, crispness of the outer skin, coating texture, and smoothness. The sensory evaluation criteria are shown in Table 1, and the sensory evaluation results are shown in Table 4.

[0217] Table 4 Sensory evaluation results of the novel coated tofu in Example 1.

[0218] Color 46.7 45.9 46.0 44.6 43.5 42.8 41.6 Bean flavor 45.9 46.0 44.8 45.3 44.7 44.9 43.6 Firmness 47.4 45.5 44.8 43.6 42.5 40.6 37.5 Delicate 46.7 45.8 45.4 44.6 42.8 40.2 38.9 Crispy outer layer 47.5 46.5 45.8 44.6 45.2 44.8 45.2 Patina 47.6 47.0 46.0 45.4 45.6 41.7 38.5 smooth 46.5 46.7 45.8 44.9 46.3 41.8 36.8

[0219] As shown in Table 4, with the extension of repeated freeze-thaw cycles, the overall color, soybean aroma, and crispness of the new type of tofu did not change significantly, while the firmness and delicacy of the product changed more noticeably. Within 10 hours of repeated freezing, the taste and texture of the new type of tofu could meet consumer demand. This indicates that using soy protein isolate as raw material, through bio-enzyme coupling technology, composite gel network technology, and metal-containing compound treatment technology, not only endows the new type of tofu with better taste, texture, and flavor, but also maintains good quality and taste even under repeated freezing for 10 hours, thus extending the product's shelf life.

[0220] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a frozen tofu semi-finished product, characterized in that, Includes the following steps: A) Mix soy protein isolate, egg white powder, vegetable protein powder, and defatted soy flour to obtain a base mixture; Starch, transglutaminase, and a compound containing a metal element are mixed to obtain a structural mixture; The compound seasoning and characteristic flavoring are mixed to obtain a compound flavor mixture; B) Mix the base mixture with water to obtain a tofu protein paste; C) Mix and emulsify the edible oil with the coated tofu protein slurry to obtain a coated tofu emulsion slurry; D) Mix the structural mixture, the compound flavor mixture, and the coated tofu emulsion to obtain the coated tofu slurry; E) After the tofu slurry is proofed, the enzymes are inactivated to obtain shaped tofu. The proofing temperature is 50~55℃ and the enzyme inactivation temperature is 85~88℃. F) After cutting the formed tofu with a coating, refrigerate it to obtain a frozen tofu semi-finished product; The coated tofu is prepared from the following raw materials in the indicated weight percentages: The ingredients include: 6-12% soy protein isolate, 1-6% starch, 1.5-6.5% egg white powder, 1-6.5% vegetable protein powder, 2-6.5% defatted soy flour, 0.1-0.5% transglutaminase, 0.1-3% metal-containing compounds, 60-75% water, 5-12% edible oil, 0.5-1.0% compound seasonings, and 0.25-0.5% characteristic flavorings. The starch includes one or more combinations of corn starch, acetate starch, hydroxypropyl distarch phosphate, acetylated distarch phosphate, and potato starch. The metal-containing compound includes one or more combinations of magnesium chloride, sodium carbonate, and sodium bicarbonate. The plant protein powder includes one or more of rice protein powder, mung bean protein powder, pea protein powder, and wheat protein powder.

2. The preparation method according to claim 1, characterized in that, The edible oils include one or more combinations of corn oil, soybean oil, flaxseed oil, sunflower oil, and peanut oil.

3. The preparation method according to claim 1, characterized in that, The compound seasoning includes salt, white sugar, and monosodium glutamate.

4. The preparation method according to claim 1, characterized in that, The characteristic flavorings include one or more combinations of soy milk flavorings, fresh soy milk powder, and soy milk powder flavorings.

5. A method for preparing tofu with a coating, characterized in that, The frozen tofu semi-finished product prepared by the preparation method according to any one of claims 1 to 4 is obtained by frying or baking.

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