Manufacturing method of coagulant for soybean curd

Abstract

To provide a manufacturing method of a coagulant for soybean curds of water-in-oil emulsification type capable of suppressing generation of temporal precipitates from bittern water, even if the bittern water in which a concentration of magnesium chloride hexahydrate is increased to the vicinity of solubility is used, and the defect of the production line caused by the precipitate can be suppressed.SOLUTION: A method of manufacturing a coagulant for soybean curds for obtaining a water-in-oil type emulsion composition with bittern water containing 65 to 80 mass% of magnesium chloride hexahydrate as an aqueous phase, in which when each concentrations of sodium ion and potassium ion in the bittern water is confirmed, and when a total value of each concentration is lower than a reference value, the bittern water and oil are mixed to emulsify and disperse, and when a total value of each concentration exceeds the reference value, the precipitates are removed by holding the bittern water under a temperature where a sodium salt and / or a potassium salt is specifically precipitated, and after lowering the total value of each concentration of a sodium ion and a potassium ion in the bittern water to the reference value of the total value, the bittern water and oil are mixed to emulsify and disperse.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a tofu coagulant. [Background technology]

[0002] Tofu is produced by adding a coagulant to soy milk to crosslink proteins and gel them. The network structure formed by crosslinking proteins holds many water molecules, which gives tofu its characteristic elasticity and freshness. Nigari water, made by dissolving bittern, whose main component is magnesium chloride hexahydrate, in water, has long been used as the coagulant. Magnesium chloride imparts a moderate sweetness to tofu, so the use of nigari water makes it possible to produce tofu with a good flavor. On the other hand, the coagulation action of magnesium chloride is fast-acting, and the coagulation reaction progresses quickly before it can be uniformly dispersed in the soy milk. Therefore, skilled techniques are required to obtain high-quality tofu with a highly uniform gel structure using nigari water as a coagulant.

[0003] It is known that by mixing nigari water with oils and an emulsifier to form a water-in-oil emulsion and dispersion, and using this as a coagulant, the coagulation reaction of soy milk caused by magnesium chloride is delayed, and silk-like tofu with a smooth and dense texture can be obtained (for example, Patent Documents 1 and 2). In such water-in-oil tofu coagulants, if the magnesium chloride concentration in the aqueous phase is low, it becomes necessary to add more coagulant to induce sufficient coagulation of the soy milk. As a result, the obtained tofu has an unpleasant taste due to the oil and emulsifier contained in the coagulant. On the other hand, water-in-oil tofu coagulants with a higher magnesium chloride concentration are also known. For example, Patent Document 3 describes a water-in-oil tofu coagulant that contains a certain amount of magnesium chloride in the range of 24 to 28 mass % and a certain amount of potassium in the range of 0.4 mass % or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-304923 [Patent Document 2] Japanese Patent Application Publication No. 10-57002 [Patent Document 3] JP 2014-117160 A Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoints of the flavor of the tofu obtained and the economics of tofu production, it is desirable to reduce the amount of water-in-oil type tofu coagulant used in tofu production as much as possible. For this reason, water-in-oil type tofu coagulants have come to be produced using high-concentration bittern water in which the concentration of magnesium chloride hexahydrate has been increased to near its solubility. However, it has become clear that when high-concentration bittern water is used in a tofu coagulant production line, precipitation occurs under certain conditions and produces sediments over time. These sediments accumulate in the storage tanks of the tofu coagulant production line and clog the transport pumps, hindering the stable operation of the production line.

[0006] The present invention relates to a method for producing a water-in-oil type tofu coagulant, which can suppress the generation of precipitates due to precipitation over time from bittern water even when bittern water in which the concentration of magnesium chloride hexahydrate is increased to near its solubility is used, and can suppress the occurrence of malfunctions in the production line due to the precipitates. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to provide a method for producing the above-mentioned tofu coagulant. As a result, they have found that the precipitates that form over time from high-concentration bittern water are not magnesium salts derived from magnesium chloride hexahydrate, which is the main component, but are mainly sodium salts and potassium salts that are present in small amounts in the bittern water. That is, even in the case of the above-mentioned high-concentration bittern water, if the concentration of magnesium chloride hexahydrate is below the solubility limit, magnesium salts are unlikely to precipitate, but if sodium ions or potassium ions are present in a certain concentration or more, sodium salts or potassium salts will specifically precipitate over time, which has become evident as an impediment to the stable production of a coagulant. Furthermore, as a result of further investigations, the inventors have found that by checking the concentrations of sodium ions and potassium ions in high concentration bittern water in advance, and when the sum of these ion concentrations exceeds a certain value (reference value), it is possible to specifically precipitate and remove sodium salts or potassium salts while leaving the magnesium chloride concentration substantially unchanged, and as a result, it is possible to stably produce a water-in-oil type tofu coagulant using high concentration bittern water from which the salts have been removed. The present invention has been completed through further investigation based on these findings.

[0008] The present invention relates to a method for producing a tofu coagulant, comprising obtaining a water-in-oil type emulsion composition in which bittern water contains 65 to 80 mass % of magnesium chloride hexahydrate as an aqueous phase, In preparing the water-in-oil emulsion composition, the concentrations of sodium ions and potassium ions in the bittern water are confirmed, When the total value of each concentration is equal to or less than the reference value, the bittern water and the oil are mixed and emulsified and dispersed, When the total value of each of the concentrations exceeds a reference value, the bittern water is maintained at a temperature at which sodium salt and / or potassium salt specifically precipitates to remove the precipitate, and the total value of the concentrations of sodium ions and potassium ions in the bittern water is reduced to the reference value or less, and then the bittern water is mixed with oils and fats to emulsify and disperse. The present invention relates to a method for producing a tofu coagulant.

[0009] The present invention also provides a tofu coagulant comprising a water-in-oil emulsion composition having bittern water as an aqueous phase, The concentration of magnesium chloride hexahydrate in the bittern water is 65 to 80% by mass, and the total concentration of sodium ions and potassium ions is 0.24% by mass or less. This relates to a tofu coagulant. Effect of the Invention

[0010] According to the method for producing a tofu coagulant of the present invention, even though bittern water in which the concentration of magnesium chloride hexahydrate is increased to near its solubility is used, it is possible to suppress precipitation from the bittern water during the production process of the coagulant, thereby suppressing the generation of precipitates over time, and it is possible to stably produce a water-in-oil type tofu coagulant while suppressing malfunctions on the production line caused by the precipitates. Furthermore, the tofu coagulant of the present invention can be produced stably without causing any trouble on the production line because the precipitation from the bittern water constituting the aqueous phase component during production is suppressed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A preferred embodiment of the method for producing a tofu coagulant of the present invention (hereinafter simply referred to as the "production method of the present invention") will be described. The manufacturing method of the present invention is a method that enables stable mass production on a manufacturing line of a tofu coagulant consisting of a water-in-oil emulsion composition in which an oil phase mainly composed of oils and fats is the continuous phase, and bittern water (aqueous phase) containing magnesium chloride hexahydrate at a high concentration near its solubility ("near the solubility" means "at or near the solubility") is the dispersed phase. In the present invention, "solubility" means the solubility in water (the concentration of magnesium chloride hexahydrate in a saturated aqueous solution of magnesium chloride hexahydrate), and is expressed in units of "mass %" (100 x amount of solute [g] / {amount of solute [g] + amount of water [g]}). Tofu coagulants (water-in-oil tofu coagulants) made of a water-in-oil type emulsion composition are known per se, and in the present invention, an oil phase component and an aqueous phase component are mixed and emulsified and dispersed by a normal method to obtain a water-in-oil type emulsion composition. Usually, an oil composition made by mixing an oil and a lipophilic emulsifier is mixed with bittern water, and emulsified and dispersed to obtain a water-in-oil type emulsion composition. In addition, by using a specific oil and fat component as described in JP-A-2015-192613 and JP-A-2017-12090, a water-in-oil type emulsion composition can be obtained without using an emulsifier. The present invention can be applied regardless of the presence or absence of an emulsifier. From the viewpoint of the stability of the water-in-oil type emulsion, it is preferable to use an emulsifier. In addition, the ratio of the oil phase to the aqueous phase may be appropriately set according to the purpose. For the production of such a water-in-oil type tofu coagulant, for example, the above-mentioned patent documents can be referred to as necessary. A preferred embodiment of the present invention will be described below, focusing on configurations characteristic of the present invention.

[0012] In the manufacturing method of the present invention, bittern water containing magnesium chloride hexahydrate at a concentration of 65 to 80 mass%, preferably 69 to 80 mass%, is used as an aqueous phase component. In the bittern water, magnesium chloride hexahydrate is in a dissolved state in water. That is, in the present invention, the concentration of magnesium chloride hexahydrate in the bittern water is equal to or lower than the solubility of magnesium chloride hexahydrate in water.

[0013] The concentration of magnesium chloride hexahydrate in the bittern water is preferably within the following range from the viewpoint of preventing the formation of precipitates. [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 5% by mass] (referred to as the "L concentration") or more, and [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed] (referred to as the "U concentration") or less. The "L concentration" (mass %) is preferably [the solubility (mass %) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 4 mass %], and more preferably [the solubility (mass %) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 3 mass %]. The "U concentration" (mass %) is preferably [the solubility (mass %) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 0.5 mass %].

[0014] In the present invention, the "minimum temperature to which the bittern water is exposed" refers to the minimum temperature to which the bittern water is exposed in the production of the coagulant. Specifically, it is the lowest temperature to which the bittern water is exposed during transportation, storage, when or after being introduced into a tank in a production line, or while flowing in a liquid delivery pipe. This minimum temperature can be set according to the capacity of the equipment for temperature control of transportation, storage, production lines, etc., but the lower limit is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, from the viewpoint of being able to make the concentration of magnesium chloride hexahydrate as high as possible while preventing troubles such as the generation of precipitates. The upper limit of this minimum temperature is preferably 40°C or less, more preferably 30°C or less, and even more preferably 25°C or less, from the viewpoint of preventing crystallization in the aqueous phase of the coagulant when the completed coagulant is placed at room temperature.

[0015] The solubility curve of magnesium chloride hexahydrate (temperature-dependent saturated solution concentration of magnesium chloride hexahydrate) is publicly known, and can be found in, for example, the Chemical Handbook, Basic Edition, 5th Revised Edition.

[0016] The bittern water may contain, in addition to magnesium chloride hexahydrate, other components such as potassium and sodium to the extent that the effects of the present invention are not hindered. For example, it may contain one or more selected from sodium salts such as sodium chloride, sodium glutamate, and sodium citrate, potassium salts such as potassium chloride, monopotassium phosphate, dipotassium phosphate, monopotassium citrate, and tripotassium citrate, and calcium salts such as calcium sulfate and calcium chloride.

[0017] The bittern water used in the present invention is usually prepared by dissolving bittern, which is a food additive, in water, but it is also possible to use commercially available magnesium chloride hexahydrate reagent (high purity product) dissolved in water as bittern water. It is also possible to obtain bittern water in which the concentration of magnesium chloride hexahydrate is in the high concentration range specified in the present invention by dissolving bittern or magnesium chloride hexahydrate reagent in commercially available bittern water. Here, the concentration of magnesium chloride hexahydrate is calculated from the blending amount in principle, but if this is difficult or impossible, it can be confirmed by the same method as the method for confirming the concentration of magnesium ions shown below. In addition, it is preferable that the obtained or prepared bittern water does not usually have any precipitation and does not contain any precipitate at the stage of obtaining or preparing it. If it contains any precipitate, the precipitate is removed by a normally expected operation such as filtration before applying it to the production line. According to the production method of the present invention, when such bittern water is applied to the production line, future precipitation or precipitate occurrence can be predicted and the occurrence of malfunctions in the production line due to precipitate can be suppressed. Therefore, when the concentrations of sodium ions and potassium ions in the bittern water are confirmed in the production method of the present invention, the application of the production method of the present invention is particularly suitable when the bittern water does not have any precipitation and does not contain any precipitate. Here, "no precipitation" and "no precipitate" mean that the bittern water does not substantially contain any precipitate or precipitate. Specifically, it means that no precipitation occurs by visual observation or the like and no precipitate can be confirmed. After obtaining or preparing the bittern water used in the present invention, it is usually stored at room temperature, but from the viewpoint of suppressing salt precipitation, it is preferable to store it in a temperature-controllable place, and the storage temperature can be appropriately adjusted. The storage temperature is usually a temperature equal to or higher than the temperature at which the concentration of magnesium chloride in the bittern water reaches the saturated solubility.

[0018] In addition to magnesium chloride, bittern water also contains salt and minerals. In the manufacturing method of the present invention, the concentrations of sodium ions and potassium ions are confirmed before the bittern water is mixed with oil and fat and emulsified and dispersed. Here, in the present invention, the term "confirmation" is used to mean confirmation by measuring the concentration of each ion as shown in the following examples, and confirmation of the concentration described in documents such as a delivery note or quality standard certificate attached when the product is obtained. The concentration of each ion can be measured by various methods according to conventional methods, but in the present invention, it is measured by atomic absorption spectrometry. The specific measurement conditions in atomic absorption spectrometry are as described in the column of examples. In addition, normal nigari water contains more sodium ions than potassium ions.

[0019] When the total value (mass%) of the confirmed sodium ion concentration and potassium ion concentration of the bittern water is equal to or lower than the reference value, the bittern water can be used as it is as an aqueous phase component and mixed with fats and oils to emulsify and disperse, thereby producing a water-in-oil type tofu coagulant. Such bittern water does not produce precipitates over time under specific temperature control, and does not cause malfunctions in the production line. Therefore, stable mass production of tofu coagulants is possible in the production line. The reference value is appropriately set depending on the concentration of magnesium chloride hexahydrate in the bittern water and the temperature conditions to which the bittern water is exposed. For example, when the standard value is set to 0.24% by mass, if the total value of the sodium ion concentration and the potassium ion concentration is equal to or less than the standard value, as shown in the examples described below, in bittern water with a magnesium chloride hexahydrate concentration of about 73 to 74% by mass, the generation of precipitate due to precipitation over time is suppressed even at a temperature of about 10° C., in bittern water with a concentration of about 65 to 70% by mass, the generation of precipitate due to precipitation over time is suppressed even at a temperature of about 0° C., and in bittern water with a concentration of about 78% by mass, the generation of precipitate due to precipitation over time is suppressed at a temperature of about 40° C. Therefore, from the viewpoint of further suppressing precipitation over time at a temperature where temperature control is relatively easy, the above standard value is preferably 0.24% by mass, and more preferably 0.23% by mass.

[0020] When the total value of sodium ions and potassium ions confirmed for the above-mentioned bittern water exceeds the standard value, the bittern water shall not be used as an aqueous phase component while the total value of these ions remains above the standard value. However, by holding this bittern water for a certain period of time at a temperature at which sodium salts and / or potassium salts specifically precipitate, and then removing the precipitate, it becomes possible to use the bittern water as an aqueous phase component. By removing the precipitate, the total concentration of sodium ions and potassium ions in the bittern water becomes equal to or lower than the above-mentioned reference value. Here, the "temperature at which sodium salts and / or potassium salts specifically precipitate" is a temperature at which magnesium salts do not precipitate (i.e., a temperature at which the concentration of magnesium chloride hexahydrate in the bittern water is equal to or lower than the solubility (saturated solution concentration) of magnesium chloride hexahydrate at that temperature).

[0021] The present inventors have found that the precipitation or precipitate that occurs over time in bittern water containing magnesium chloride hexahydrate at a high concentration near its solubility (high-concentration bittern water) is not magnesium salt derived from magnesium chloride hexahydrate, but sodium salt or potassium salt. In other words, even in high-concentration bittern water, if the concentrations of sodium ions and potassium ions are low (if the total value of the concentrations of sodium ions and potassium ions is below a reference value), the high-concentration bittern water can stably maintain a solution state, and on the other hand, if the concentrations of sodium ions and potassium ions are high in the high-concentration bittern water (if the total value of the concentrations of sodium ions and potassium ions exceeds a reference value), sodium salt and potassium salt can be specifically precipitated without precipitating magnesium salt derived from magnesium chloride hexahydrate (while maintaining the content of magnesium chloride hexahydrate in the bittern water), by controlling the temperature, and by removing the sodium salt and potassium salt in this way, the solution state of high-concentration bittern water can be stably maintained, which led to the completion of the present invention.

[0022] The temperature at which the sodium salt and / or potassium salt specifically precipitates can be appropriately set depending on the concentration of magnesium chloride hexahydrate in the bittern water used. For example, when the concentration of magnesium chloride hexahydrate in the bittern water is 65% by mass or more and less than 74% by mass, the temperature at which the sodium salt and / or potassium salt specifically precipitates is preferably 0° C. or more and 20° C. or less, more preferably 0° C. or more and 15° C. or less, and even more preferably 0° C. or more and 10° C. or less. When the concentration of magnesium chloride hexahydrate in the bittern water is 69% by mass or more and less than 74% by mass, the temperature at which the sodium salt and / or potassium salt specifically precipitates is preferably 0° C. or more and 20° C. or less, more preferably 0° C. or more and 15° C. or less, and even more preferably 0° C. or more and 10° C. or less. In addition, when the concentration of magnesium chloride hexahydrate in the bittern water is 74% by mass or more and 80% by mass or less, specifically, when the concentration of magnesium chloride hexahydrate is X% by mass and the temperature when the solubility of magnesium chloride hexahydrate is X% by mass is Y°C, the temperature at which the sodium salt and / or potassium salt is specifically precipitated is preferably Y°C or more and [Y+20]°C or less, more preferably [Y+3]°C or more and [Y+15]°C or less, and even more preferably [Y+5]°C or more and [Y+10]°C or less. In such a temperature range according to the concentration of magnesium chloride hexahydrate, when the total value of the concentrations of sodium ions and potassium ions exceeds a reference value, sodium salts and / or potassium salts can be precipitated without precipitating magnesium salts. Note that the temperature to be specifically applied within the above temperature range is the temperature at which the concentration of magnesium chloride hexahydrate in the bittern water is less than the solubility of magnesium chloride hexahydrate at that temperature.

[0023] The time for which the bittern water is held at a temperature at which sodium salts and / or potassium salts specifically precipitate is preferably 12 hours or more, more preferably 14 hours or more, and even more preferably 16 hours or more, from the viewpoints of production efficiency and ensuring that the total value of sodium ions and potassium ions is equal to or less than the reference value. From the same viewpoint, the time is preferably 48 hours or less, more preferably 40 hours or less, and even more preferably 32 hours or less.

[0024] In relation to the above-mentioned embodiment, the present invention discloses the following method for producing a tofu coagulant in the form of a water-in-oil emulsion.

[0025] <1> A method for producing a tofu coagulant, comprising obtaining a water-in-oil type emulsion composition having bittern water as an aqueous phase by using bittern water containing 65 to 80 mass % of magnesium chloride hexahydrate, In preparing the water-in-oil emulsion composition, the concentrations of sodium ions and potassium ions in the bittern water are confirmed, When the total value of each concentration is equal to or less than the reference value, the bittern water and the oil are mixed and emulsified and dispersed, When the total value of each of the concentrations exceeds a reference value, the bittern water is maintained at a temperature at which sodium salt and / or potassium salt specifically precipitates to remove the precipitate, and the total value of the concentrations of sodium ions and potassium ions in the bittern water is reduced to the reference value or less, and then the bittern water is mixed with oils and fats to emulsify and disperse. A method for producing a tofu coagulant.

[0026] <2> The concentration of magnesium chloride hexahydrate in the bittern water is preferably 69 to 80% by mass. <1> A method for producing the tofu coagulant described in claim 1. <3> The concentration of magnesium chloride hexahydrate in the bittern water is preferably equal to or more than [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 5% by mass], more preferably equal to or more than [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 4% by mass], and even more preferably equal to or more than [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 3% by mass]. <1> or <2> A method for producing the tofu coagulant described in claim 1. <4> The concentration of magnesium chloride hexahydrate in the bittern water is preferably equal to or less than the solubility (mass%) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed, and more preferably equal to or less than the solubility (mass%) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 0.5% by mass. <1> ~ <3> 1. The method for producing the tofu coagulant according to claim 1 . <5> The concentration of magnesium chloride hexahydrate in the bittern water is preferably from [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 5% by mass] to [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed], more preferably from [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 4% by mass] to [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed], and even more preferably from [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 3% by mass] to [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 0.5% by mass]. <1> ~ <4> 1. The method for producing the tofu coagulant according to claim 1 . <6> The lower limit of the "minimum temperature to which the bittern water is exposed" is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher. <3> ~ <5> 1. The method for producing the tofu coagulant according to claim 1 . <7> The upper limit of the "minimum temperature to which the bittern water is exposed" is preferably 40° C. or less, more preferably 30° C. or less, and even more preferably 25° C. or less. <3> ~ <6> 1. The method for producing the tofu coagulant according to claim 1 . <8> The "minimum temperature to which the bittern water is exposed" is preferably 0°C or higher and 40°C or lower, more preferably 10°C or higher and 30°C or lower, and even more preferably 15°C or higher and 25°C or lower. <3> ~ <7> 1. The method for producing the tofu coagulant according to claim 1 .

[0027] <9> The reference value is preferably 0.24% by mass, more preferably 0.23% by mass. <1> ~ <8> 1. The method for producing the tofu coagulant according to claim 1 . <10> When the total value of the concentrations of sodium ions and potassium ions exceeds a reference value, When the concentration of magnesium chloride hexahydrate in the bittern water is 65% by mass or more and less than 74% by mass, the temperature at which the sodium salt and / or potassium salt is specifically precipitated is preferably 0° C. or more; When the concentration of magnesium chloride hexahydrate in the bittern water is 74% by mass or more and 80% by mass or less, the concentration of magnesium chloride hexahydrate is X% by mass, and the temperature when the solubility of magnesium chloride hexahydrate is X% by mass is Y°C, the temperature at which the sodium salt and / or potassium salt specifically precipitates is preferably Y°C or more, more preferably [Y+3]°C or more, and even more preferably [Y+5]°C or more. The above <1> ~ <9> 1. The method for producing the tofu coagulant according to claim 1 . <11> When the total value of the concentrations of sodium ions and potassium ions exceeds a reference value, When the concentration of magnesium chloride hexahydrate in the bittern water is 65% by mass or more and less than 74% by mass, the temperature at which the sodium salt and / or potassium salt is specifically precipitated is preferably 20° C. or less, more preferably 15° C. or less, and even more preferably 10° C. or less. When the concentration of magnesium chloride hexahydrate in the bittern water is 74% by mass or more and 80% by mass or less, the concentration of magnesium chloride hexahydrate is X% by mass, and the temperature when the solubility of magnesium chloride hexahydrate is X% by mass is Y°C, the temperature at which the sodium salt and / or potassium salt specifically precipitates is preferably [Y+20]°C or less, more preferably [Y+15]°C or less, and even more preferably [Y+10]°C or less. The above <1> ~ <10> 1. The method for producing the tofu coagulant according to claim 1 . <12> When the total value of the concentrations of sodium ions and potassium ions exceeds a reference value, When the concentration of magnesium chloride hexahydrate in the bittern water is 65% by mass or more and less than 74% by mass, the temperature at which the sodium salt and / or potassium salt is specifically precipitated is preferably 0° C. or more and 20° C. or less, more preferably 0° C. or more and 15° C. or less, and even more preferably 0° C. or more and 10° C. or less. When the concentration of magnesium chloride hexahydrate in the bittern water is 74% by mass or more and 80% by mass or less, the concentration of magnesium chloride hexahydrate is X% by mass, and the temperature when the solubility of magnesium chloride hexahydrate is X% by mass is Y°C, the temperature at which the sodium salt and / or potassium salt specifically precipitates is preferably Y°C or more and [Y+20]°C or less, more preferably [Y+3]°C or more and [Y+15]°C or less, and even more preferably [Y+5]°C or more and [Y+10]°C or less. The above <1> ~ <11> 1. The method for producing the tofu coagulant according to claim 1 . <13> The time for which the bittern water is kept at a temperature at which sodium salts and / or potassium salts specifically precipitate is preferably 12 hours or more, more preferably 14 hours or more, and even more preferably 16 hours or more. <1> ~ <12> 1. The method for producing the tofu coagulant according to claim 1 . <14> The time for which the bittern water is kept at a temperature at which sodium salts and / or potassium salts specifically precipitate is preferably 48 hours or less, more preferably 40 hours or less, and even more preferably 32 hours or less. <1> ~ <13> 1. The method for producing the tofu coagulant according to claim 1 . <15> The time for which the bittern water is kept at a temperature at which sodium salts and / or potassium salts specifically precipitate is preferably 12 hours or more and 48 hours or less, more preferably 14 hours or more and 40 hours or less, and even more preferably 16 hours or more and 32 hours or less. <1> ~ <14> 1. The method for producing the tofu coagulant according to claim 1 .

[0028] <16> No precipitation occurs in the bittern water at the stage of obtaining or preparing the bittern water. <1> ~ <15> 1. The method for producing the tofu coagulant according to claim 1 . <17> At the time of confirming the concentrations of sodium ions and potassium ions in the bittern water, no precipitation is formed in the bittern water. <1> ~ <16> 1. The method for producing the tofu coagulant according to claim 1 . <18> The confirmation of the concentrations of the sodium ions and the potassium ions is performed by measuring the concentrations of the sodium ions and the potassium ions. <17> A method for producing the tofu coagulant described in claim 1. <19> The emulsification and dispersion is carried out in the presence of an emulsifier. <1> ~ <18> 1. The method for producing the tofu coagulant according to claim 1 .

[0029] <20> A method for producing a tofu coagulant, comprising mixing bittern water and oil and dispersing the mixture into an emulsion, The concentration of magnesium chloride hexahydrate in the bittern water is from 65% by mass to 80% by mass, and the total concentration of sodium ions and potassium ions is 0.24% by mass or less. <21> The concentration of magnesium chloride hexahydrate in the bittern water is preferably 69 to 80% by mass. <20> A method for producing the tofu coagulant described in claim 1. <22> The concentration of magnesium chloride hexahydrate in the bittern water is preferably equal to or more than [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 5% by mass], more preferably equal to or more than [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 4% by mass], and even more preferably equal to or more than [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 3% by mass]. <20> or <21> A method for producing the tofu coagulant described in claim 1. <23> The concentration of magnesium chloride hexahydrate in the bittern water is preferably equal to or less than the solubility (mass%) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed, and more preferably equal to or less than the solubility (mass%) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 0.5% by mass. <20> ~ <22> 1. The method for producing the tofu coagulant according to claim 1 . <24> The concentration of magnesium chloride hexahydrate in the bittern water is preferably from [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 5% by mass] to [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed], more preferably from [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 4% by mass] to [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed], and even more preferably from [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 3% by mass] to [the solubility (% by mass) of magnesium chloride hexahydrate at the lowest temperature to which the bittern water is exposed - 0.5% by mass]. <20> ~ <23> 1. The method for producing the tofu coagulant according to claim 1 . <25> The lower limit of the "minimum temperature to which the bittern water is exposed" is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher. <22> ~ <24> 1. The method for producing the tofu coagulant according to claim 1 . <26> The upper limit of the "minimum temperature to which the bittern water is exposed" is preferably 40° C. or less, more preferably 30° C. or less, and even more preferably 25° C. or less. <22> ~ <25> 1. The method for producing the tofu coagulant according to claim 1 . <27> The "minimum temperature to which the bittern water is exposed" is preferably 0°C or higher and 40°C or lower, more preferably 10°C or higher and 30°C or lower, and even more preferably 15°C or higher and 25°C or lower. <22> ~ <26> 1. The method for producing the tofu coagulant according to claim 1 . <28> No precipitation occurs in the bittern water at the stage of obtaining or preparing the bittern water. <20> ~ <27> 1. The method for producing the tofu coagulant according to claim 1 .

[0030] <29> The above <1> ~ <28> 1. A method for producing tofu, comprising mixing the tofu coagulant obtained by the method for producing a tofu coagulant according to any one of claims 1 to 9 with soy milk.

[0031] <30> A tofu coagulant comprising a water-in-oil emulsion composition having bittern water as an aqueous phase, The concentration of magnesium chloride hexahydrate in the bittern water is 65 to 80% by mass, and the total concentration of sodium ions and potassium ions is 0.24% by mass or less. Tofu coagulant. <31> The concentration of magnesium chloride hexahydrate in the bittern water is preferably 69 to 80% by mass. <30> The tofu coagulant according to claim 1. <32> The total concentration of the sodium ions and potassium ions is 0.23 mass% or less. <30> or <31> The tofu coagulant according to claim 1.

[0032] <33> The above <30> ~ <32> 10. A method for producing tofu, comprising mixing the tofu coagulant according to claim 1 with soy milk. EXAMPLES

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0034] 100 g of each of bittern water (magnesium chloride aqueous solution; Experimental Examples 1 to 22) was obtained so as to have the composition (unit: mass%) shown in Tables 2 to 4 below. As the magnesium chloride hexahydrate (MgCl2·6H2O) shown in Tables 2 to 4, a magnesium chloride hexahydrate reagent (special reagent grade, purity 98.0 mass% or more, Fujifilm Wako Pure Chemical Industries, Ltd.) was used. As the potassium chloride (KCl) shown in Tables 2 to 4, a potassium chloride reagent (special reagent grade, Fujifilm Wako Pure Chemical Industries, Ltd.) was used. As the sodium chloride (NaCl) shown in Tables 2 to 4, a sodium chloride reagent (special reagent grade, Fujifilm Wako Pure Chemical Industries, Ltd.) was used.

[0035] In the case of the bittern water having a magnesium chloride hexahydrate concentration of 73.5 mass % (Experimental Examples 1 to 7) and 70.0 mass % (Experimental Examples 16 to 22), magnesium chloride hexahydrate, potassium chloride, and sodium chloride were completely dissolved in water at room temperature. Furthermore, when preparing bittern water having a magnesium chloride hexahydrate concentration of 78.0 mass % (Experimental Examples 8 to 15), the water was heated to 60° C. in advance to completely dissolve magnesium chloride hexahydrate, potassium chloride, and sodium chloride. After dissolving the bittern water, it was visually confirmed that no precipitate was formed, and then the concentration of each ion was measured and the presence or absence of precipitation was evaluated after leaving the bittern water to stand.

[0036] <Measurement of sodium ion and potassium ion concentrations in bittern water> As a sample for the calibration curve, sodium standard solution (Na1000, Fujifilm Wako Pure Chemical, product number 199-10831) was adjusted to 20±2°C, and then 100μl, 400μl, 600μl, and 1000μl were precisely placed in a 100ml glass measuring flask using a micropipette. After adding about 80% ultrapure water, 1ml of 2N hydrochloric acid was added, and the flask was filled up to 100ml with ultrapure water, mixed inverted, and used as the analytical standard solution. Similarly, potassium standard solution (K1000, Fujifilm Wako Pure Chemical, product number 165-17471) was adjusted to 20±2°C, and then 100μl, 200μl, 300μl, and 400μl were precisely placed in a 100ml glass measuring flask using a micropipette. After adding about 80% ultrapure water, 1ml of 2N hydrochloric acid was added, and the flask was filled up to 100ml with ultrapure water, mixed by inversion, and used as the analytical standard solution. Similarly, magnesium standard solution (Mg1000, Fujifilm Wako Pure Chemical, product number 165-17471) was adjusted to 20±2°C, and then 50μl, 100μl, 150μl, and 200μl were precisely placed into a 100ml glass measuring flask using a micropipette. After adding about 80% ultrapure water, 1ml of 2N hydrochloric acid was added, and the flask was filled up to 100ml with ultrapure water, mixed by inversion, and used as the analytical standard solution. To prepare the analytical sample, approximately 0.2 g of bittern water was weighed out (precisely weighed to the nearest 0.1 mg) into a 100 ml glass measuring flask, and after adding approximately 80% ultrapure water, 1 ml of 2N hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added. The flask was then filled up to 100 ml with ultrapure water, and the flask was inverted and mixed to prepare the analytical sample. The prepared analytical standard solutions and analytical samples were quantified using a polarized Zeeman atomic absorption spectrometer (Z2000 manufactured by Hitachi High-Technologies Corporation). The analytical conditions are shown in Table 1 below, and the analytical results (concentrations (mass%)) are shown in Tables 2 to 4 below, respectively. [Table 1]

[0037] Test example: Evaluation of precipitation of bittern water after standing Bitter water having a magnesium chloride hexahydrate concentration of 73.5% by mass (Experimental Examples 1 to 7) was allowed to stand at 10° C. for 24 hours, and the state of the bittern water after standing was visually evaluated based on the following evaluation criteria. Furthermore, bittern water with a magnesium chloride hexahydrate concentration of 78.0 mass % (Experimental Examples 8 to 15) was allowed to stand at 40° C. for 24 hours, and the state of the bittern water after standing was visually evaluated based on the following evaluation criteria. Furthermore, bittern water with a magnesium chloride hexahydrate concentration of 70.0 mass % (Experimental Examples 16 to 22) was allowed to stand at 0° C. for 24 hours, and the state of the bittern water after standing was visually evaluated based on the following evaluation criteria. <Evaluation criteria> Y: The solution is transparent and there is no precipitate due to crystalline precipitation. N: Precipitation due to crystal precipitation is observed.

[0038] [Table 2]

[0039] [Table 3]

[0040] [Table 4]

[0041] In the case of the bittern water (Experimental Examples 1 to 4, 8 to 11, and 16 to 18) in which the total value (mass %) of the sodium ion concentration and the potassium ion concentration was 0.24 mass % or less, no formation of precipitate was confirmed even when the bittern water was left to stand for 24 hours at the above-mentioned temperatures corresponding to the respective magnesium chloride hexahydrate concentrations.

[0042] In the above bittern waters with magnesium chloride hexahydrate concentrations of 73.5 mass%, 78.0 mass%, and 70.0 mass%, in which the total value (mass%) of sodium ion concentration and potassium ion concentration exceeded 0.24 mass% (Experimental Examples 5-7, 12-15, and 19-22), the precipitates formed after standing were composed of sodium salts and potassium salts. When the magnesium ion concentration of the bittern water from which the precipitate had been removed was measured under the same conditions as above, no reduction in magnesium ions was confirmed.

[0043] In addition, when the sodium ion concentration and potassium ion concentration of the above-mentioned bittern water from which the precipitate had been removed (Experimental Examples 5 to 7, 12 to 15, and 19 to 22) were measured again by the above-mentioned measurement method, the total value of these concentrations was 0.24 mass% or less. Furthermore, even when the bittern water from which the precipitate had been removed was stored for 24 hours at the respective temperatures at which it was left to stand, no new precipitate was observed.

[0044] In the above experimental examples, when a tofu coagulant was produced using bittern water (Experimental Examples 1-4, 8-11, and 16-18) whose total value of sodium ion concentration and potassium ion concentration was below the standard value, a good coagulant was obtained. In addition, in the above experimental examples, when a tofu coagulant was produced using bittern water (Experimental Examples 5-7, 12-15, and 19-22) whose total value of sodium ion concentration and potassium ion concentration was above the standard value, the bittern water was held for a certain period of time at a temperature at which sodium salts and / or potassium salts specifically precipitate, and the precipitate was removed. The bittern water was then used as an aqueous phase component, and a good coagulant was obtained.

Claims

1. A tofu coagulant comprising a water-in-oil type emulsion composition having bittern water as an aqueous phase, the total concentration of sodium ions and potassium ions being 0.24 mass% or less, The concentration of magnesium chloride hexahydrate in the bittern water is 69% by mass or more and less than 74% by mass, and the bittern water does not produce precipitation when left to stand for 24 hours at least at any temperature between 0° C. and 10° C. Tofu coagulant.

2. The tofu coagulant according to claim 1, wherein the total concentration of sodium ions and potassium ions in the nigari water is 0.23 mass% or less.

3. The tofu coagulant according to claim 1 or 2, wherein the concentration of magnesium chloride hexahydrate in the nigari water is 70.0 mass% or more and 73.5 mass% or less.

4. A method for producing a tofu coagulant, comprising the steps of: The present invention includes obtaining a water-in-oil emulsion composition having a water phase including bittern water (A) having a total concentration of sodium ions and potassium ions exceeding 0.24% by mass, the total concentration of said sodium ions and potassium ions being reduced to 0.24% by mass or less, and bittern water (B) having a total concentration of sodium ions and potassium ions of 0.24% by mass or less, The method for producing a tofu coagulant, wherein the concentration of magnesium chloride hexahydrate in the bittern water (B) is 69% by mass or more and less than 74% by mass, and the bittern water (B) does not produce precipitation when left to stand for 24 hours at least at any temperature between 0°C and 10°C.