Calcium coagulant, its preparation method and application in preparing hard tofu

Abstract

The application relates to the technical field of food production, and discloses a calcium coagulant, a preparation method thereof and application of the calcium coagulant in preparation of hard bean curd. The calcium coagulant comprises the following raw materials in mass fractions: 30-40 parts of de-embittering gypsum, 22-28 parts of calcium lactate, 12-18 parts of calcium citrate, 10-16 parts of magnesium gluconate, 1-2 parts of sodium chloride, 0.5-0.8 parts of stearic acid, 2-3 parts of phospholipid, 2-3 parts of polyglucose and 0.5-1.5 parts of potassium citrate. The calcium coagulant is prepared by taking de-embittering gypsum, calcium lactate, calcium citrate and magnesium gluconate as cores, matching with functional auxiliary materials, and adopting the surface modification and the circulating fluidized bed granulation process, so that the problems of the existing hard bean curd coagulant, such as heavy astringency, difficult compatibility of hardness and flavor, uncontrollable coagulation rate, poor system stability, low water retention and easy caking during storage, are solved.

Description

Technical Field

[0001] This invention relates to the field of food production technology, and more specifically, to a calcium coagulant, its preparation method, and its application in the preparation of firm tofu. Background Technology

[0002] Tofu is a traditional Chinese plant-based protein product, rich in nutrients and widely consumed. Firm tofu, with its firm texture, high elasticity, resistance to steaming and boiling, and resistance to crumbling, is widely used in everyday cooking, frying, braising, and deep processing, making it a mainstream product in the soy product industry. In the industrial production of firm tofu, the coagulant is a key ingredient determining the tofu's hardness, texture, yield, taste, and batch stability. Existing coagulant systems specifically designed for firm tofu still have many inherent shortcomings, making it difficult to simultaneously meet the production demands for high-quality taste, high finished product hardness, high yield, and long-term storage stability, thus hindering the quality upgrade of the firm tofu industry.

[0003] Currently, the mainstream industrial production of firm tofu uses three systems: brine, ordinary gypsum, and magnesium chloride composite coagulant. Each technology has significant shortcomings. First, traditional brine coagulants rely on high concentrations of chloride salts to achieve rapid protein coagulation. While this improves the firmness of the tofu, the excessively high chloride ion content results in a noticeably bitter taste and severely degraded flavor. Furthermore, the high chloride salt-out process is intense and uncontrollable, leading to uneven cross-linking of soybean protein and problems such as hollowness, cracking, and loose texture in the finished product. Second, ordinary gypsum, as a traditional calcium-based coagulant, is low-cost and has a decent basic yield. However, virgin gypsum contains a large amount of free acidic impurities; using it directly without treatment will result in a strong astringent taste and a rough texture. Moreover, the rapid and concentrated coagulation rate of gypsum easily causes localized sudden coagulation and uneven overall coagulation, leading to substandard firmness and significant batch-to-batch variations in the finished tofu. Third, the industry generally adds magnesium chloride to improve the toughness and crack resistance of firm tofu, but magnesium chloride itself has a bitter taste and cannot fundamentally solve the flavor defects of the finished product. There is always a contradiction between hardness and flavor.

[0004] Furthermore, existing composite coagulant systems suffer from poor stability and low production tolerance. To improve the density of tofu, conventional processes add a small amount of sodium chloride to assist in salting out and modifying the protein structure. However, directly adding sodium chloride causes drastic fluctuations in the system's ion concentration, disrupting the acid-base and ion balance of the coagulation system. This results in an extremely narrow coagulation temperature window, placing very high demands on production temperature, stirring speed, and the addition ratio. The poor process tolerance hinders large-scale, standardized, and stable production. Simultaneously, existing coagulants lack effective pH buffering and system stabilization mechanisms, failing to counteract the ion shocks caused by salt addition. This easily leads to over- or under-coagulation, further reducing the quality stability of the finished firm tofu.

[0005] Furthermore, existing powder coagulants generally suffer from poor storage performance, dry texture of finished products, and limited yield, which are common pain points in the industry. Sodium chloride and gypsum are both highly hygroscopic raw materials. Traditional physical mixing processes can only achieve simple blending and cannot modify the surface of the raw materials. Powder products are prone to moisture absorption, clumping, and component segregation during long-term storage, resulting in decreased coagulation activity and inconsistent coagulation effects between batches, which seriously affects the product's shelf life and industrial applicability. At the same time, tofu formed by conventional coagulation systems has poor water retention, and subsequent pressing processes result in significant water loss. This not only greatly reduces the tofu yield but also leads to hard tofu that is too hard, dry, and loses its chewy and moist texture, failing to meet the core requirements of high firmness and excellent eating taste.

[0006] In summary, existing coagulation technologies for firm tofu generally suffer from the following pressing technical problems: 1. Traditional chloride salts, magnesium salts, and ordinary gypsum coagulants leave bitter and astringent residues, resulting in poor flavor in the finished product and failing to balance high firmness with excellent taste; 2. The coagulation rate is uncontrollable, and localized rapid coagulation easily leads to hollow, cracked, and loosely structured tofu, resulting in insufficient resistance to breakage and poor toughness; 3. Salt modification easily causes large fluctuations in system ions, unstable pH, a narrow coagulation temperature range, and low production error tolerance; 4. Conventional powder formulations are highly hygroscopic, lack modification and stabilization granulation processes, and are prone to clumping and failure during storage, resulting in poor batch stability; 5. Tofu has poor water retention, suffers severe water loss during pressing, has a low yield, and the finished product is prone to dryness and hardening. To address the above-mentioned technical deficiencies, this application proposes a novel calcium coagulant, its preparation method, and its application. Through a multi-element calcium-magnesium composite formulation combined with raw material modification and fluidized bed granulation technology, the above technical problems are specifically addressed, achieving a comprehensive improvement in the flavor, firmness, yield, and storage stability of firm tofu. Summary of the Invention

[0007] In view of this, the present invention proposes a calcium coagulant, its preparation method, and its application in the preparation of firm tofu. It aims to solve the problems of traditional coagulants in the current technology, which easily cause bitterness and astringency in firm tofu, make it difficult to balance hardness and edible flavor, make the coagulation rate uncontrollable and easily cause hollow, cracked, and uneven texture of tofu, make the coagulation system have large ion fluctuations, poor pH stability, narrow coagulation process window, low error tolerance in industrial production, poor water retention of tofu, serious water loss during pressing, low yield, dry taste of finished product, and strong hygroscopicity of coagulant powder, which easily clumps and separates during long-term storage and makes batch quality unstable.

[0008] This invention provides a calcium coagulant comprising the following raw materials in parts by weight: 30-40 parts of deacidifying gypsum, 22-28 parts of calcium lactate, 12-18 parts of calcium citrate, 10-16 parts of magnesium gluconate, 1-2 parts of sodium chloride, 0.5-0.8 parts of stearic acid, 2-3 parts of phospholipids, 2-3 parts of polydextrose, and 0.5-1.5 parts of potassium citrate.

[0009] Preferably, the method for preparing the deastringent gypsum is as follows: After crushing the gypsum, it is sieved, then citric acid solution is added for rinsing. After rinsing, it is filtered, rinsed with clean water, soaked in clean water, dried at low temperature, and ground into powder to obtain deacidified gypsum.

[0010] This invention also provides a method for preparing a calcium coagulant, comprising the following steps: Hydrophobic sodium chloride was obtained by ball milling a mixture of stearic acid and sodium chloride. The surface of the deabrasive gypsum was modified by mixing deabrasive gypsum with phospholipid, heating and ball milling. A mixed powder is obtained by mixing hydrophobic sodium chloride, hydrophobic deastringent gypsum, calcium lactate, calcium citrate, magnesium gluconate, sodium chloride, and potassium citrate. A binder is obtained by mixing polydextrose with water; A calcium coagulant is obtained by granulating the mixed powder and binder using a circulating fluidized bed.

[0011] Preferably, the parameters of the mixing ball mill are as follows: The ball-to-material ratio is 5~8:1, the rotation speed is 200~300 r / min, and the time is 2~5 h.

[0012] Preferably, the parameters of the heated ball mill are as follows: The ball-to-material ratio is 5~8:1, the rotation speed is 400~700 r / min, the time is 4~7 h, and the temperature is 70~80℃.

[0013] Preferably, the mass ratio of the polydextrose to water is 2~3:300~600.

[0014] Preferably, the parameters of the circulating fluidized bed in the spray granulation stage are as follows: Inlet air temperature: 40~60℃; Inlet air volume: 0.2~0.4m³ 3 The atomization pressure is 0.2~0.6MPa, and the spray rate of the binder is 0.5~0.8L / min.

[0015] This invention also provides an application of a calcium coagulant in the preparation of firm tofu, comprising the following steps: Heat the soy milk to a boil, then cool it down to 70-90℃. Add calcium coagulant and stir well. Let it stand to coagulate. After coagulating, stir and break up the soy milk and transfer it into a mold to press it into firm tofu.

[0016] Preferably, the amount of calcium coagulant added is 4% to 6% of the total protein in the soy milk.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention abandons the traditional high-bitterness magnesium chloride and high-chloride brine system, instead using deastringent gypsum, calcium lactate, calcium citrate, and magnesium gluconate to construct a bitter-free composite coagulation core. The deastringent gypsum is washed with citric acid to remove free acidic impurities, completely eliminating the astringency problem caused by traditional gypsum. Magnesium gluconate replaces traditional magnesium chloride, effectively strengthening the tofu's elasticity and improving its resistance to breakage, while leaving no residual bitterness from magnesium salts. Trace amounts of sodium chloride can moderately dissociate sodium and chloride ions, slightly salting out soybean protein and promoting the dense contraction of the protein network structure, effectively increasing the tofu's firmness. Unlike the strong salting-out effect of high-concentration brine, this method does not produce a bitter or astringent off-flavor, fundamentally solving the industry contradiction that "the higher the firmness of tofu, the worse the flavor."

[0018] Existing technologies involving salt modification easily lead to drastic fluctuations in system ion concentration and pH imbalance, resulting in a narrow coagulation temperature range and low production tolerance. This invention utilizes a compound of calcium citrate and potassium citrate to form a highly efficient buffer system, stabilizing the system's pH value, effectively counteracting the ion shocks caused by sodium chloride addition, buffering ion fluctuations, significantly widening the applicable coagulation temperature range, and reducing the stringent requirements on production temperature, feeding speed, and stirring processes. The process exhibits strong stability and high tolerance, making it highly suitable for large-scale, standardized, and continuous production of soy products. Simultaneously, calcium citrate can assist calcium ions in cross-linking proteins, further improving the density and molding stability of tofu.

[0019] Traditional coagulants-based firm tofu often suffers from poor water retention, significant water loss during pressing, and an overly hard and dry finished product. This invention addresses these issues by combining soybean lecithin and modified polydextrose for synergistic water retention. The lecithin adsorbs at the interface between soybean protein and water, locking in internal free water. The modified polydextrose exhibits excellent dispersibility and binding properties, forming a water-retaining protective film between protein network cells. This effectively inhibits water loss during pressing, preventing excessive hardening and a dry, tough texture in firm tofu while preserving its moist and chewy consistency. Furthermore, it significantly increases tofu yield, reduces raw material loss, and substantially improves production efficiency.

[0020] To address the shortcomings of traditional coagulant powders, such as high hygroscopicity, easy clumping during long-term storage, component segregation, and efficacy attenuation, this invention performs differentiated surface modification on the highly hygroscopic core raw materials: hydrophobic modification of sodium chloride is achieved through ball milling of stearic acid and sodium chloride, and hydrophobic modification of deastringent gypsum is achieved through heated ball milling of phospholipids, thus reducing the hygroscopicity of the powder from the raw material itself. Simultaneously, a polydextrose aqueous solution is used as a binder, combined with a circulating fluidized bed spray granulation process, to ensure uniform coating and molding of each component, preventing the powder from absorbing moisture and clumping during prolonged storage, and avoiding component segregation and ineffectiveness. This effectively extends the product's shelf life, ensures consistent coagulation effects across different batches, and significantly improves the product's storage, transportation, and industrial applicability.

[0021] This invention abandons the inorganic salt system with high chlorine, high bitterness, and high irritation, and adopts a compound of organic calcium and magnesium salts such as calcium lactate, calcium citrate, and magnesium gluconate. It can supplement the body with easily absorbed organic calcium and magnesium elements during the tofu forming process, achieving low phosphorus calcium supplementation. Compared with tofu prepared by traditional coagulants, it has higher nutritional value, which is in line with the current trend of healthy, green and nutritious food consumption, and the product has stronger market competitiveness. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0023] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] This invention provides a calcium coagulant comprising the following raw materials in parts by weight: The composition of the deabrasive gypsum is as follows: 30-40 parts, calcium lactate 22-28 parts, calcium citrate 12-18 parts, magnesium gluconate 10-16 parts, sodium chloride 1-2 parts, stearic acid 0.5-0.8 parts, phospholipids 2-3 parts, polydextrose 2-3 parts, and potassium citrate 0.5-1.5 parts; preferably, the composition of the deabrasive gypsum is as follows: 32-38 parts, calcium lactate 24-26 parts, calcium citrate 14-16 parts, magnesium gluconate 12-14 parts, sodium chloride 1.2-1.8 parts, stearic acid 0.6-0.7 parts, phospholipids 2.2-2.8 parts, polydextrose 2.2-2.8 parts, and potassium citrate 0.8-1.2 parts. The preferred composition of the first step is 34-36 parts of deacidifying gypsum, 24.5-25.5 parts of calcium lactate, 14.5-15.5 parts of calcium citrate, 12.5-13.5 parts of magnesium gluconate, 1.4-1.6 parts of sodium chloride, 0.62-0.68 parts of stearic acid, 2.4-2.6 parts of phospholipid, 2.4-2.6 parts of polydextrose, and 0.9-1.1 parts of potassium citrate. More preferably, the composition of the first step is 35 parts of deacidifying gypsum, 25 parts of calcium lactate, 15 parts of calcium citrate, 13 parts of magnesium gluconate, 1.5 parts of sodium chloride, 0.65 parts of stearic acid, 2.5 parts of phospholipid, 2.5 parts of polydextrose, and 1.0 part of potassium citrate.

[0028] In this invention, the preparation method of the deastringent gypsum is as follows: After crushing the gypsum, it is sieved, then citric acid solution is added for rinsing. After rinsing, it is filtered, rinsed with clean water, soaked in clean water, dried at low temperature, and ground into powder to obtain deacidified gypsum.

[0029] In this invention, the sieving is done through an 80-mesh sieve, the concentration of the citric acid solution is 0.5-1.5%, the soaking time for rinsing with water is 8-12 hours, and the low-temperature drying temperature is 60°C.

[0030] In this invention, the particle size of the deabrasive gypsum is 120 mesh.

[0031] This invention also provides a method for preparing a calcium coagulant, comprising the following steps: Hydrophobic sodium chloride was obtained by ball milling a mixture of stearic acid and sodium chloride. The surface of the deabrasive gypsum was modified by mixing deabrasive gypsum with phospholipid, heating and ball milling. A mixed powder is obtained by mixing hydrophobic sodium chloride, hydrophobic deacidifying gypsum, calcium lactate, calcium citrate, magnesium gluconate, sodium chloride, and potassium citrate. A binder is obtained by mixing polydextrose with water; A calcium coagulant is obtained by granulating the mixed powder and binder using a circulating fluidized bed.

[0032] In this invention, the parameters of the mixing ball mill are as follows: The ball-to-material ratio is 5~8:1, preferably 6~7:1, more preferably 6.3~6.8:1, and even more preferably 6.5:1; the rotation speed is 200~300 r / min, preferably 220~280 r / min, more preferably 240~260 r / min, and even more preferably 250 r / min; the time is 2~5 h, preferably 2.5~4 h, more preferably 3~3.5 h, and even more preferably 3.2 h.

[0033] In this invention, the parameters of the heated ball mill are as follows: The ball-to-material ratio is 5~8:1, preferably 6~7:1, more preferably 6~7:1, and even more preferably 6.5:1; the rotation speed is 400~700 r / min, preferably 6.5:1, more preferably 6.5:1, and even more preferably 550 r / min; the time is 4~7 h, preferably 5~6 h, more preferably 5.2~5.8 h, and even more preferably 5.5 h; the temperature is 70~80℃, preferably 72~78℃, more preferably 74~76℃, and even more preferably 75℃.

[0034] In this invention, the mass ratio of polydextrose to water is 2~3:300~600, preferably 2.2~2.8:350~550, more preferably 2.4~2.6:400~500, and even more preferably 2.5:450.

[0035] In this invention, the parameters of the circulating fluidized bed during the spray granulation stage are as follows: The inlet air temperature is 40~60℃, preferably 45~55℃, more preferably 48~52℃, and even more preferably 50℃; the inlet air volume is 0.2~0.4m³. 3 / min, preferably 0.25~0.35m 3 / min, further preferably 0.28~0.32m 3 / min, more preferably 0.30m 3 / min; the atomization pressure is 0.2~0.6MPa, preferably 0.3~0.5MPa, more preferably 0.35~0.45MPa, and more preferably 0.40MPa; the spray rate of the binder is 0.5~0.8L / min, preferably 0.55~0.75L / min, more preferably 0.60~0.70L / min, and more preferably 0.65L / min.

[0036] This invention also provides an application of a calcium coagulant in the preparation of firm tofu, comprising the following steps: Heat the soy milk to a boil, then cool it down to 70-90℃. Add calcium coagulant and stir well. Let it stand to coagulate. After coagulating, stir and break up the soy milk and transfer it into a mold to press it into firm tofu.

[0037] In this invention, the amount of calcium coagulant added is 4% to 6% of the total protein in the soy milk, preferably 4.5% to 5.5%, more preferably 4.8% to 5.2%, and even more preferably 5.0%.

[0038] Example 1 Weigh the raw materials according to the following mass ratio: 35 parts of deacidifying gypsum, 25 parts of calcium lactate, 15 parts of calcium citrate, 13 parts of magnesium gluconate, 1.5 parts of sodium chloride, 0.65 parts of stearic acid, 2.5 parts of phospholipid, 2.5 parts of polydextrose, and 1.0 part of potassium citrate.

[0039] The deabrasive gypsum is prepared by the following method: after crushing the gypsum, it is passed through an 80-mesh sieve. The gypsum powder is then rinsed with a 1% citric acid solution. After rinsing, it is filtered, rinsed with clean water, and then soaked in clean water for 12 hours. Subsequently, it is dried at a low temperature of 60℃ for 24 hours and then ground into powder to finally obtain deabrasive gypsum with a particle size of 120 mesh.

[0040] Prepare the calcium coagulant according to the following steps: (1) Preparation of hydrophobic sodium chloride: Stearic acid and sodium chloride were mixed in the formula amount and placed in a ball mill for mixing and ball milling modification. The ball-to-material ratio was controlled at 8:1, the rotation speed was 200 r / min, and the ball milling time was 3 h. After the ball milling was completed, hydrophobic sodium chloride was obtained.

[0041] (2) Preparation of hydrophobic deabrasive gypsum: The prepared deabrasive gypsum is mixed with the formula amount of phospholipid, and the surface is modified by heated ball milling. The ball-to-material ratio is controlled at 8:1, the rotation speed is 500 r / min, the temperature is 80℃, and the ball milling time is 5h to obtain hydrophobic deabrasive gypsum.

[0042] (3) Powder mixing: The obtained hydrophobic sodium chloride and hydrophobic deabrasive gypsum are thoroughly mixed with the formula amount of calcium lactate, calcium citrate, magnesium gluconate, sodium chloride and potassium citrate to obtain mixed powder.

[0043] (4) Preparation of adhesive: Mix polydextrose and water at a mass ratio of 2.5:450 and stir until completely dissolved to obtain adhesive.

[0044] (5) Fluidized bed granulation: The mixed powder is placed in a circulating fluidized bed and spray granulation is performed using a binder; the inlet air temperature of the fluidized bed is controlled at 50℃ and the inlet air volume is 0.3m³. 3 The atomization pressure was 0.4 MPa, the binder spray rate was 0.6 L / min, and the calcium coagulant product was obtained after granulation.

[0045] The prepared calcium coagulant was used to prepare firm tofu, as follows: After heating the soy milk to a boil, cool it down to 75°C. Add the calcium coagulant mentioned above at 4% of the total protein content of the soy milk, stir well, and let it stand to coagulate. After coagulation, break the tofu curd, transfer it into a mold, press it into shape, and make firm tofu.

[0046] Example 2 Weigh the raw materials according to the following mass ratio: 30 parts of deacidifying gypsum, 22 parts of calcium lactate, 12 parts of calcium citrate, 16 parts of magnesium gluconate, 2 parts of sodium chloride, 0.8 parts of stearic acid, 2 parts of phospholipid, 3 parts of polydextrose, and 1.5 parts of potassium citrate.

[0047] The deabrasive gypsum is prepared by the following method: after crushing the gypsum, it is passed through an 80-mesh sieve. The gypsum powder is then rinsed with a 0.5% citric acid solution. After rinsing, it is filtered, rinsed with clean water, and then soaked in clean water for 10 hours. Subsequently, it is dried at a low temperature of 60℃ for 24 hours and then ground into powder to finally obtain deabrasive gypsum with a particle size of 120 mesh.

[0048] Prepare the calcium coagulant according to the following steps: (1) Preparation of hydrophobic sodium chloride: Stearic acid and sodium chloride were mixed in the formula amount and placed in a ball mill for mixing and ball milling modification. The ball-to-material ratio was controlled at 5:1, the rotation speed was 300 r / min, and the ball milling time was 5 h. After the ball milling was completed, hydrophobic sodium chloride was obtained.

[0049] (2) Preparation of hydrophobic deabrasive gypsum: The prepared deabrasive gypsum is mixed with the formula amount of phospholipid, and the surface is modified by heated ball milling. The ball-to-material ratio is controlled at 5:1, the rotation speed is 700 r / min, the temperature is 70℃, and the ball milling time is 7h to obtain hydrophobic deabrasive gypsum.

[0050] (3) Powder mixing: The obtained hydrophobic sodium chloride and hydrophobic deabrasive gypsum are thoroughly mixed with the formula amount of calcium lactate, calcium citrate, magnesium gluconate, sodium chloride and potassium citrate to obtain mixed powder.

[0051] (4) Preparation of adhesive: Mix polydextrose and water at a mass ratio of 3:300 and stir until completely dissolved to obtain adhesive.

[0052] (5) Fluidized bed granulation: The mixed powder is placed in a circulating fluidized bed and sprayed with a binder for granulation; the inlet air temperature of the fluidized bed is controlled at 60℃ and the inlet air volume is 0.25m³. 3 The atomization pressure was 0.2 MPa, the binder spray rate was 0.5 L / min, and the calcium coagulant product was obtained after granulation.

[0053] The prepared calcium coagulant was used to prepare firm tofu, as follows: After heating the soy milk to a boil, cool it down to 80°C. Add the calcium coagulant mentioned above at 5% of the total protein content of the soy milk, stir well, and let it stand to coagulate. After coagulation, break the tofu curd, transfer it into a mold, press it into shape, and make firm tofu.

[0054] Example 3 Weigh the raw materials according to the following mass ratio: The composition of the plaster is as follows: 38 parts of deacidifying gypsum, 26 parts of calcium lactate, 16 parts of calcium citrate, 12 parts of magnesium gluconate, 1.2 parts of sodium chloride, 0.6 parts of stearic acid, 2.2 parts of phospholipid, 2.8 parts of polydextrose, and 1.2 parts of potassium citrate.

[0055] The deabrasive gypsum is prepared by the following method: after crushing the gypsum, it is passed through an 80-mesh sieve. The gypsum powder is then rinsed with a 0.5% citric acid solution. After rinsing, it is filtered, rinsed with clean water, and then soaked in clean water for 10 hours. Subsequently, it is dried at a low temperature of 60℃ for 24 hours and then ground into powder to finally obtain deabrasive gypsum with a particle size of 120 mesh.

[0056] Prepare the calcium coagulant according to the following steps: (1) Preparation of hydrophobic sodium chloride: Stearic acid and sodium chloride were mixed in the formula amount and placed in a ball mill for mixing and ball milling modification. The ball-to-material ratio was controlled at 7:1, the rotation speed was 220 r / min, and the ball milling time was 5 h. After the ball milling was completed, hydrophobic sodium chloride was obtained.

[0057] (2) Preparation of hydrophobic deabrasive gypsum: The prepared deabrasive gypsum is mixed with the formula amount of phospholipid, and the surface is modified by heated ball milling to obtain hydrophobic deabrasive gypsum.

[0058] (3) Powder mixing: The obtained hydrophobic sodium chloride and hydrophobic deabrasive gypsum are thoroughly mixed with the formula amount of calcium lactate, calcium citrate, magnesium gluconate, sodium chloride and potassium citrate to obtain mixed powder.

[0059] (4) Preparation of adhesive: Mix polydextrose and water at a mass ratio of 2.8:600 and stir until completely dissolved to obtain adhesive.

[0060] (5) Fluidized bed granulation: The mixed powder is placed in a circulating fluidized bed and sprayed with a binder for granulation; the inlet air temperature of the fluidized bed is controlled at 55℃ and the inlet air volume is 0.4m³. 3 The atomization pressure was 0.45 MPa, the binder spray rate was 0.7 L / min, and the calcium coagulant product was obtained after granulation.

[0061] The prepared calcium coagulant was used to prepare firm tofu, as follows: After heating the soy milk to a boil, cool it down to 90°C. Add the calcium coagulant mentioned above at 5.5% of the total protein content of the soy milk, stir well, and let it stand to coagulate. After coagulation, break up the tofu curd, transfer it into a mold, press it into shape, and make firm tofu.

[0062] Example 4 Weigh the raw materials according to the following mass ratio: 32 parts of deacidifying gypsum, 24 parts of calcium lactate, 16 parts of calcium citrate, 14 parts of magnesium gluconate, 1.8 parts of sodium chloride, 0.6 parts of stearic acid, 2.8 parts of phospholipid, 2.8 parts of polydextrose, and 0.8 parts of potassium citrate.

[0063] The deabrasive gypsum is prepared by the following method: after crushing the gypsum, it is passed through an 80-mesh sieve. The gypsum powder is then rinsed with a 0.5% citric acid solution. After rinsing, it is filtered, rinsed with clean water, and then soaked in clean water for 10 hours. Subsequently, it is dried at a low temperature of 60℃ for 24 hours and then ground into powder to finally obtain deabrasive gypsum with a particle size of 120 mesh.

[0064] Prepare the calcium coagulant according to the following steps: (1) Preparation of hydrophobic sodium chloride: Stearic acid and sodium chloride were mixed in the formula amount and placed in a ball mill for mixing and ball milling modification. The ball-to-material ratio was controlled at 6:1, the rotation speed was 280 r / min, and the ball milling time was 3 h. After the ball milling was completed, hydrophobic sodium chloride was obtained.

[0065] (2) Preparation of hydrophobic deabrasive gypsum: The prepared deabrasive gypsum was mixed with the formula amount of phospholipid, and the surface was modified by heated ball milling. The ball-to-material ratio was controlled at 6:1, the rotation speed was 600 r / min, the temperature was 78℃, and the ball milling time was 7h to obtain hydrophobic deabrasive gypsum.

[0066] (3) Powder mixing: The obtained hydrophobic sodium chloride and hydrophobic deabrasive gypsum are thoroughly mixed with the formula amount of calcium lactate, calcium citrate, magnesium gluconate, sodium chloride and potassium citrate to obtain mixed powder.

[0067] (4) Preparation of adhesive: Mix polydextrose and water at a mass ratio of 2.8:500 and stir until completely dissolved to obtain adhesive.

[0068] (5) Fluidized bed granulation: The mixed powder is placed in a circulating fluidized bed and sprayed with a binder for granulation; the inlet air temperature of the fluidized bed is controlled at 55℃ and the inlet air volume is 0.35m³. 3 The atomization pressure was 0.35 MPa, the binder spray rate was 0.8 L / min, and the calcium coagulant product was obtained after granulation.

[0069] The prepared calcium coagulant was used to prepare firm tofu, as follows: After heating the soy milk to a boil, cool it down to 85°C. Add the calcium coagulant mentioned above at 6% of the total protein content of the soy milk, stir well, and let it stand to coagulate. After coagulation, break the tofu curd, transfer it into a mold, press it into shape, and obtain firm tofu.

[0070] Comparative Example 1 Weigh the raw materials according to the following mass ratio: 35 parts gypsum, 25 parts calcium lactate, 15 parts calcium citrate, 13 parts magnesium gluconate, 1.5 parts sodium chloride, 0.65 parts stearic acid, 2.5 parts phospholipid, 2.5 parts polydextrose, and 1.0 part potassium citrate.

[0071] The above raw materials are directly mixed to obtain the finished calcium coagulant.

[0072] The prepared calcium coagulant was used to prepare firm tofu, as follows: After heating the soy milk to a boil, cool it down to 75°C. Add the calcium coagulant mentioned above at 4% of the total protein content of the soy milk, stir well, and let it stand to coagulate. After coagulation, break the tofu curd, transfer it into a mold, press it into shape, and make firm tofu.

[0073] Comparative Example 2 35 parts of deacidifying gypsum, 25 parts of calcium lactate, 15 parts of calcium citrate, 13 parts of magnesium gluconate, 1.5 parts of sodium chloride, 0.65 parts of stearic acid, 2.5 parts of phospholipid, 2.5 parts of polydextrose, and 1.0 part of potassium citrate.

[0074] The deabrasive gypsum is prepared by the following method: after crushing the gypsum, it is passed through an 80-mesh sieve. The gypsum powder is then rinsed with a 1% citric acid solution. After rinsing, it is filtered, rinsed with clean water, and then soaked in clean water for 12 hours. Subsequently, it is dried at a low temperature of 60℃ for 24 hours and then ground into powder to finally obtain deabrasive gypsum with a particle size of 120 mesh.

[0075] Prepare the calcium coagulant according to the following steps: (1) Preparation of hydrophobic sodium chloride: Stearic acid and sodium chloride were mixed in the formula amount and placed in a ball mill for mixing and ball milling modification. The ball-to-material ratio was controlled at 8:1, the rotation speed was 200 r / min, and the ball milling time was 3 h. After the ball milling was completed, hydrophobic sodium chloride was obtained.

[0076] (2) Preparation of hydrophobic deabrasive gypsum: The prepared deabrasive gypsum is mixed with the formula amount of phospholipid, and the surface is modified by heated ball milling. The ball-to-material ratio is controlled at 8:1, the rotation speed is 500 r / min, the temperature is 80℃, and the ball milling time is 5h to obtain hydrophobic deabrasive gypsum.

[0077] (3) Powder mixing: The obtained hydrophobic sodium chloride and hydrophobic deabrasive gypsum are thoroughly mixed with the formula amount of calcium lactate, calcium citrate, magnesium gluconate, sodium chloride and potassium citrate to obtain calcium coagulant.

[0078] The prepared calcium coagulant was used to prepare firm tofu, as follows: After heating the soy milk to a boil, cool it down to 75°C. Add the calcium coagulant mentioned above at 4% of the total protein content of the soy milk, stir well, and let it stand to coagulate. After coagulation, break the tofu curd, transfer it into a mold, press it into shape, and make firm tofu.

[0079] Comparative Example 3 After heating the soy milk to a boil, cool it down to 75°C. Add gypsum at 4% of the total protein content of the soy milk, stir well, and let it stand to coagulate. After coagulation, break up the tofu curd, transfer it into a mold, and press it into shape to make firm tofu.

[0080] The methods for preparing soy milk used in the above embodiments and comparative examples are as follows: High-quality soybeans were selected and soaked, with the water changed every 3 hours during the soaking process. After soaking, the moisture content of the soybeans was controlled to be 60%. The soaked soybeans were then continuously added to a grinding mill with 80℃ hot water at a mass ratio of 1:8 for initial grinding. The soybean residue and soy milk were ground again once, and the mixture was passed through a 120-mesh sieve to obtain soy milk. The protein content of the soy milk was tested to be 3.86%.

[0081] The various indicators of the firm tofu prepared in Examples 1-4 and Comparative Examples 1-3 were measured using the following methods: (1) Moisture content determination: Performed in accordance with GB5009.3-2016.

[0082] (2) Yield determination: The yield is calculated based on the weight of fresh firm tofu made from each liter of soy milk.

[0083] (3) Water retention test: Cut the sample into 5cm×5cm×5mm cubes, take 4 pieces (about 5g) into 50mL centrifuge tubes, centrifuge at 7104×g for 20min, wipe off the residual water on the surface with dry filter paper, weigh, dry at 102℃ to constant weight, and then... HC = (M1-M2) / (M0-M2) Calculate water retention capacity; W HC ——Water retention, %; M0—Original sample mass, g; M1 — Mass of the sample after centrifugation, in g; M2 — Mass of the sample after drying to constant weight, in g.

[0084] Table 1. Yield, moisture content, and water retention of firm tofu in Examples 1-4 and Comparative Examples 1-3

[0085] The calcium coagulants described in Examples 1-4 and Comparative Examples 1-3 were left at room temperature for 30 days and then used again to prepare firm tofu. The yield, moisture content, and water retention of the tofu were analyzed, and the results are as follows: Table 2. Yield, moisture content, and water retention of firm tofu prepared by calcium coagulant in Examples 1-4 and Comparative Examples 1-3 after being left at room temperature for 30 days.

[0086] The texture of the firm tofu in Examples 1-4 and Comparative Examples 1-3 was evaluated.

[0087] Sample processing Cut the tofu into 2cm×2cm×2cm cubes, 6 cubes of each sample; Remove surface brine / preservative water: Rinse gently once with distilled water, then blot dry with filter paper to remove any remaining surface liquid; Blank temperature control: room temperature 25℃, let stand for 30 minutes; Divided into two groups: original flavor group (eaten raw) and blanched group (boiled in boiling water for 1 minute, then cooled to room temperature). Tester preparation One hour before the test, participants should avoid spicy, sour, sweet, tobacco, alcohol, and salty foods. Before tasting each sample: Rinse your mouth with purified water 3 times, and wait at least 60 seconds before testing the next sample.

[0088] Scoring criteria: 0 points: No bitterness, only bean aroma and slight bean sweetness upon entry, no numbness, bitterness, astringency or astringency in the root of the tongue, tip of the tongue, or throat before or after swallowing; 1 point: Very slight bitterness, concentrated at the back of the tongue, disappears in an instant, does not affect the aroma of beans, can only be noticed by careful tasting; 2 points: Slightly bitter, noticeably astringent after a few seconds of tasting, causing a tightness on the tip of the tongue, and the bean flavor is slightly masked, but it is still edible. 3 points: Moderately bitter and astringent, immediately bitter and astringent upon entry, causing the oral mucosa to tighten and feel constricted, significantly overpowering the bean aroma; 4 points: Severe bitterness, with a bitter taste lingering in the mouth for a long time after swallowing (>3 minutes), and a feeling of dryness and numbness in the gums and throat; 5 points: Extremely bitter, difficult to swallow, stinging and bitter, makes you want to vomit immediately.

[0089] Table 3. Bitterness scores of firm tofu in Examples 1-4 and Comparative Examples 1-3

[0090] The data in Tables 1 to 3 show that the calcium coagulant prepared in this embodiment of the invention maintains a high yield, moisture content, and water retention of the resulting firm tofu after fresh use and 30 days at room temperature, with no obvious bitterness. In contrast, the tofu made from gypsum without de-astringency treatment or traditional gypsum in the comparative example has a noticeable bitterness, and its water retention and long-term storage stability are significantly reduced. Although the comparative examples using de-astringency gypsum and surface-modified but not granulated tofu have no bitterness, their yield and water retention decrease significantly after long-term storage. This indicates that the present invention, through the combination of de-astringency treatment, surface modification, and fluidized bed granulation, can effectively eliminate the bitterness of tofu and improve its water retention and storage stability.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A calcium coagulant, characterized in that, The raw materials include the following parts by weight: 30-40 parts of deacidifying gypsum, 22-28 parts of calcium lactate, 12-18 parts of calcium citrate, 10-16 parts of magnesium gluconate, 1-2 parts of sodium chloride, 0.5-0.8 parts of stearic acid, 2-3 parts of phospholipids, 2-3 parts of polydextrose, and 0.5-1.5 parts of potassium citrate.

2. The calcium coagulant according to claim 1, characterized in that, The preparation method of the deastringent gypsum is as follows: After crushing the gypsum, it is sieved, then citric acid solution is added for rinsing. After rinsing, it is filtered, rinsed with clean water, soaked in clean water, dried at low temperature, and ground into powder to obtain deacidified gypsum.

3. A method for preparing a calcium coagulant according to claim 1 or 2, characterized in that, Includes the following steps: Hydrophobic sodium chloride was obtained by ball milling a mixture of stearic acid and sodium chloride. The surface of the deabrasive gypsum was modified by mixing deabrasive gypsum with phospholipid, heating and ball milling. A mixed powder is obtained by mixing hydrophobic sodium chloride, hydrophobic deacidifying gypsum, calcium lactate, calcium citrate, magnesium gluconate, sodium chloride, and potassium citrate. A binder is obtained by mixing polydextrose with water; A calcium coagulant is obtained by granulating the mixed powder and binder using a circulating fluidized bed.

4. The method for preparing a calcium coagulant according to claim 3, characterized in that, The parameters of the mixing ball mill are as follows: The ball-to-material ratio is 5~8:1, the rotation speed is 200~300 r / min, and the time is 2~5 h.

5. The method for preparing a calcium coagulant according to claim 3, characterized in that, The parameters of the heated ball mill are as follows: The ball-to-material ratio is 5~8:1, the rotation speed is 400~700 r / min, the time is 4~7 h, and the temperature is 70~80℃.

6. The method for preparing a calcium coagulant according to claim 3, characterized in that, The mass ratio of the polydextrose to water is 2~3:300~600.

7. The method for preparing a calcium coagulant according to claim 3, characterized in that, The parameters of the circulating fluidized bed in the spray granulation stage are as follows: Inlet air temperature: 40~60℃; Inlet air volume: 0.2~0.4m³ 3 The atomization pressure is 0.2~0.6MPa, and the spray rate of the binder is 0.5~0.8L / min.

8. The application of the calcium coagulant according to claim 1 or 2 in the preparation of firm tofu, characterized in that, Includes the following steps: Heat the soy milk to a boil, then cool it down to 70-90℃. Add calcium coagulant and stir well. Let it stand to coagulate. After coagulating, stir and break up the soy milk and transfer it into a mold to press it into firm tofu.

9. The application of a calcium coagulant according to claim 8 in the preparation of firm tofu, characterized in that, The amount of calcium coagulant added is 4% to 6% of the total protein in the soy milk.

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