JP2013051906A - Method for producing tofu, and tofu produced by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing Tofu that is rich in desired minerals, and to provide Tofu produced by the same.SOLUTION: The method for producing Tofu includes a step for mixing soy milk with water solution containing only inorganic salt or organic salt of one metal selected from iron(II), iron(III), nickel(II), manganese(II), zinc(II), or copper(II). There is provided Tofu produced by the method.

Description

  The present invention relates to a method for producing tofu using an aqueous solution containing only a specific metal salt in place of a conventional coagulant such as bittern, and tofu obtained thereby.

  In recent national nutrition surveys, the lack of minerals has been a problem, and is now supplemented in tablet form. However, for elderly people who are worried about mineral shortages, taking with a tablet is highly resistant, and intake from a food form is desired.

  Soybean is extremely important as an ancient Japanese food resource, and has recently been regarded internationally as a food resource for the 21st century in relation to population growth. Tofu is usually produced by preparing soy milk from soybeans, adding a coagulant thereto, and coagulating and molding the protein contained in the soybeans. At present, magnesium chloride, gypsum, glucono delta lactone (GDL), and the like are used as coagulants, including the traditional Shiota bittern.

  In recent years, several attempts have been made to ingest minerals from tofu containing abundant minerals. For example, Japanese Patent Laid-Open No. 2000-14351 (Patent Document 1) discloses a method for producing tofu that coagulates soy milk to which a mineral raw material microorganism has been added. Further, for example, in Japanese Patent Application Laid-Open No. 2001-224326 (Patent Document 2), deep sea water taken from a deep sea 200 m or deep below the sea surface is concentrated by a reverse osmosis membrane method, an electrodialysis method, or a heating evaporation method. A method for producing tofu using deep-sea water-derived bitter juice, characterized in that sodium chloride is separated from the liquid to produce bitter juice, and the bitter juice is mixed in soy milk and solidified.

  However, a method for producing tofu by coagulating soymilk using an aqueous solution containing only one metal salt other than calcium chloride and magnesium chloride has not been known so far.

JP 2000-14351 A JP 2001-224326 A

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing tofu rich in a desired mineral, and tofu obtained thereby. .

  The method for producing tofu according to the present invention includes any one metal selected from iron (II), iron (III), nickel (II), manganese (II), zinc (II) and copper (II) as a metal salt. And a step of mixing an aqueous solution containing only an inorganic salt or an organic salt with soy milk.

  In the method for producing tofu according to the present invention, when the aqueous solution contains only an inorganic salt of iron (II) as a metal salt, the concentration of the metal salt is preferably 6 mM or more.

  In the method for producing tofu according to the present invention, when the aqueous solution contains only an iron (III) inorganic salt as a metal salt, the concentration of the metal salt is preferably 4 mM or more.

  In the method for producing tofu according to the present invention, when the aqueous solution contains only an inorganic salt of iron (II) as a metal salt, or contains only an inorganic salt of iron (III), the aqueous solution is a reducing agent that is harmless to the human body. It is preferable that it is further included. In this case, the reducing agent is preferably alcorbic acid.

  Moreover, in the manufacturing method of the tofu of this invention, when the said aqueous solution contains only the inorganic salt of nickel (II) as a metal salt, it is preferable that the density | concentration of the said metal salt is 7 mM or more.

  Moreover, in the manufacturing method of the tofu of this invention, when the said aqueous solution contains only the inorganic salt of manganese (II) as a metal salt, it is preferable that the density | concentration of the said metal salt is 6 mM or more.

  Moreover, in the manufacturing method of the tofu of this invention, when the said aqueous solution contains only the inorganic salt of zinc (II) as a metal salt, it is preferable that the density | concentration of the said metal salt is 5 mM or more.

  Moreover, in the manufacturing method of the tofu of this invention, when the said aqueous solution contains only the inorganic salt of copper (II) as a metal salt, it is preferable that the density | concentration of the said metal salt is 6 mM or more.

  The present invention also provides tofu produced by the above-described method of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the tofu which contains a desired mineral abundantly can be manufactured simply, and a mineral can be ingested with a food form instead of a tablet.

In Experimental Example 1, the results of adding solutions A, B, C, D, E, F, G, H, I, J, K, L, M, N, O and water (control group) to soy milk are shown. It is a photograph. In Experimental example 1, it is a graph which shows the precipitation rate computed about solution A, H, D, F, B, J, N, and L containing the chloride of each metal. It is a graph which shows the relationship between the density | concentration of a metal ion and the precipitation rate in Experimental example 2, Fig.3 (a) is a calcium chloride dihydrate aqueous solution, FIG.3 (b) is a copper chloride (II) dihydrate aqueous solution. 3 (c) shows the results for a magnesium chloride hexahydrate aqueous solution, and FIG. 3 (d) shows the results for a manganese (II) chloride tetrahydrate aqueous solution. It is a graph which shows the relationship between the density | concentration of a metal ion and the precipitation rate in Experimental example 2, Fig.4 (a) is nickel chloride (II) hexahydrate aqueous solution, FIG.4 (b) is zinc chloride (II) dilute hydrochloric acid solution. 4 (c) shows the results for an aqueous solution of iron (II) chloride tetrahydrate, and FIG. 4 (d) shows the results for an aqueous solution of iron (III) chloride hexahydrate. In Experimental example 2, it is a figure which shows the fitting analysis result about a magnesium chloride hexahydrate aqueous solution, FIG. 5 (a) has shown before fitting analysis, FIG.5 (b) has each shown after fitting analysis. Concentration and precipitation of metal ions for iron (II) chloride tetrahydrate aqueous solution (FIG. 4 (c)) and iron (III) hexahydrate aqueous solution (FIG. 4 (d)) conducted in Experimental Example 2. It is the graph which piled up the graph which shows the relationship with a rate. Except that 2% ascorbic acid was added, the relationship between the concentration of metal ions and the precipitation rate in the aqueous iron (II) chloride tetrahydrate solution was the same as in Example 2 except that ascorbic acid was added. It is a graph compared with the case where there was no. In Experimental example 4, it is a graph which shows the relationship between the density | concentration of a metal ion at the time of using each of 2 types of soymilk, and a precipitation rate. It is a graph which shows the precipitation rate computed about solution a, b, c, d containing the lactate of each metal.

  The method for producing tofu according to the present invention includes any one metal selected from iron (II), iron (III), nickel (II), manganese (II), zinc (II) and copper (II) as a metal salt. And a step of mixing an aqueous solution containing only the salt and soy milk. As proved in the experimental examples described later, the present inventor can coagulate soy milk and produce tofu even when using the above-mentioned metal salt that has not been used so much in the production of tofu. I found out that I can do it.

  The soy milk used as a raw material for tofu in the present invention is not particularly limited, and commercially available soy milk can be suitably used. Tofu is produced by coagulating the protein contained in soymilk with a coagulant, but the soymilk used in the present invention preferably contains 4.7 g / 100 mL or more of protein, and contains 5 g / 100 mL or more. More preferably.

  The aqueous solution used in the present invention is an inorganic salt of any one metal selected from iron (II), iron (III), nickel (II), manganese (II), zinc (II) and copper (II). Or an organic salt is included. Examples of inorganic salts include chlorides, sulfates, borides, carbides, fluorides, iodides, nitrates, and the like. Among them, calcium chloride, calcium sulfate, and the like are included in coagulants used in conventional manufacturing methods. It is preferable to use a chloride or a sulfate because it is in the form of an inorganic salt similar to that of Organic salts include acetates, gluconates, lactates, acrylates, citrates, oxalates, etc. Among them, they can be used as food additives and are expected to increase the absorption rate. In view of the above, it is preferable to use acetate, gluconate, citrate and lactate.

  In the method for producing tofu according to the present invention, when the aqueous solution contains only an inorganic salt of iron (II) as a metal salt, the concentration of the metal salt is preferably 6 mM or more. As will be demonstrated in the experimental examples described later, the tofu produced in the range where the concentration of the metal salt in the aqueous solution is relatively low is in a state like silken tofu, and in the range where the concentration of the metal salt in the aqueous solution is relatively high. The tofu produced is in the state of cotton tofu. When the aqueous solution contains only an inorganic salt of iron (II) as a metal salt, the concentration of the metal salt is within the range of 6 to 7 mM as described above if the tofu is in a state like silken tofu. It is preferable that if the tofu is in a state like cotton tofu, the concentration of the metal salt is preferably 10 mM or more among the above.

  Moreover, in the manufacturing method of the tofu of this invention, when the said aqueous solution contains only the inorganic salt of iron (III) as a metal salt, it is preferable that the density | concentration of the said metal salt is 4 mM or more. When the aqueous solution contains only an inorganic salt of iron (III) as a metal salt, the concentration of the metal salt is within the range of 4 to 5 mM, as described above, if a tofu in a state like silken tofu is produced. It is preferable that if the tofu is in a state like cotton tofu, the concentration of the metal salt is preferably 6 mM or more among the above.

  In the method for producing tofu according to the present invention, when the aqueous solution contains only an inorganic salt of iron (II) or iron (III) as a metal salt, the aqueous solution further contains a reducing agent that is harmless to the human body. Is preferred. Iron is more easily consumed by the human body in the form of iron (II) than in the form of iron (III), so that the tofu produced by the method of the present invention is iron (II) than in the form of iron (III). It is preferable to include in the form. However, even if it contains the form of iron (II), it is assumed that it will oxidize in the air and naturally form iron (III). For this reason, by containing a reducing agent that is harmless to the human body in the aqueous solution, iron can be present in the form of iron (II) rather than iron (III) in the produced tofu, and more ingested by the human body. It becomes possible to include iron in tofu in a form that is easily processed.

  The reducing agent used is not particularly limited as long as it is harmless to the human body, and examples thereof include ascorbic acid and gallic acid. Among these, ascorbic acid is particularly preferably used as a reducing agent that is harmless to the human body because it is known to increase the absorption of iron (II) in the human body.

  Moreover, in the manufacturing method of the tofu of this invention, when the said aqueous solution contains only the inorganic salt of nickel (II) as a metal salt, it is preferable that the density | concentration of the said metal salt is 7 mM or more. If the aqueous solution contains only the inorganic salt of nickel (II) as the metal salt, the concentration of the metal salt is within the range of 7 to 8 mM, as described above, if the tofu is in a state like silken tofu. It is preferable that if the tofu is in a state like cotton tofu, the concentration of the metal salt is preferably 11 mM or more among the above.

  Moreover, in the manufacturing method of the tofu of this invention, when the said aqueous solution contains only the inorganic salt of manganese (II) as a metal salt, it is preferable that the density | concentration of the said metal salt is 6 mM or more. When the aqueous solution contains only an inorganic salt of manganese (II) as the metal salt, the concentration of the metal salt is within the range of 6 to 7 mM as described above if the tofu is in a state like silken tofu. It is preferable that if the tofu is in a state like cotton tofu, the concentration of the metal salt is preferably 11 mM or more among the above.

  In the method for producing tofu according to the present invention, when the aqueous solution contains only an inorganic salt of zinc (II) as a metal salt, the concentration of the metal salt is preferably 5 mM or more. When the aqueous solution contains only the inorganic salt of zinc (II) as the metal salt, the concentration of the metal salt is within the range of 5 to 7 mM as described above if the tofu in a state like silken tofu is produced. It is preferable that if the tofu is in a state like cotton tofu, the concentration of the metal salt is preferably 9 mM or more among the above.

  In the method for producing tofu according to the present invention, when the aqueous solution contains only an inorganic salt of copper (II) as a metal salt, the concentration of the metal salt is preferably 6 mM or more. When the aqueous solution contains only an inorganic salt of copper (II) as a metal salt, the concentration of the metal salt is preferably 6 mM or more among the above-mentioned if the tofu in a state like silken tofu is produced. Moreover, if the tofu of a state like a cotton tofu is manufactured, it is preferable that the density | concentration of the said metal salt is 9 mM or more among the above-mentioned.

  The water used as the solvent in the aqueous solution containing the metal salt used in the present invention is not particularly limited as long as it is tap water, purified water, ultrapurified water, or the like. However, the zinc (II) chloride must be prepared as a dilute hydrochloric acid solution.

  In the method for producing tofu according to the present invention, as long as soy milk and an aqueous solution containing a metal salt are mixed, there is no particular limitation on the addition form, and an aqueous solution containing a metal salt may be added to soy milk. Alternatively, soy milk may be added to the aqueous solution containing the metal salt.

  In the method for producing tofu of the present invention, the steps other than the step of mixing soy milk and an aqueous solution containing a metal salt are not particularly limited, and may be performed through the same steps as those of a conventionally known method for producing tofu.

  The present invention also provides tofu produced by the above-described method of the present invention. That is, the tofu of the present invention contains any one metal selected from the above-mentioned iron (II), iron (III), nickel (II), manganese (II), zinc (II) and copper (II). It is a waste. Thus, according to the mineral to ingest, the desired mineral can be ingested with the form of food by eating the tofu containing an appropriate metal.

  Here, the tofu may be washed with water several times before being eaten, but, of course, the metal concentration decreases with each washing. The tofu of the present invention is preferably eaten in a state where it is freshly made and not washed with water.

  Mineral deficiency is a problem for health, but excessive intake of minerals can also cause problems. For this reason, in the case of functional nutritional foods, the amount of nutritional components included in the intake standard amount is determined, but even when eating the tofu of the present invention and ingesting minerals, intake the amount according to this Is preferred. For example, the amount of nutrients contained in the intake standard amount is in the range of 2.25 to 10 mg for iron, and 2.10 to 15 mg for zinc.

  Hereinafter, although an example of an experiment is given and the present invention is explained in detail, the present invention is not limited to these.

<Experimental example 1>
900 μL of commercially available soy milk with no ingredients (organic soy milk (trade name), Sujata Meiraku Group: protein content: about 5 g / 100 mL) was put in a 1.5 mL microtube and kept at 80 ° C. for 15 minutes. At this time, the weight (w ₀ ) of the soymilk was measured.

Next, the following solutions were prepared.
Solution A: 200 mM calcium chloride dihydrate (Nacalai Tesque) aqueous solution Solution B: 200 mM magnesium chloride hexahydrate (Wako Pure Chemical) aqueous solution Solution C: 200 mM magnesium sulfate heptahydrate (Wako Pure Chemical) aqueous solution Solution D: 200 mM iron (II) chloride tetrahydrate (Wako Pure Chemical) aqueous solution Solution E: 200 mM iron (II) sulfate heptahydrate (Wako Pure Chemical) aqueous solution Solution F: 200 mM iron (III) chloride Hexahydrate (Wako Pure Chemical) aqueous solution-Solution G: 100 mM iron (III) sulfate n hydrate (Wako Pure Chemical) aqueous solution-Solution H: 200 mM Copper (II) chloride dihydrate (Wako Pure Chemical) aqueous solution Solution I: 200 mM copper sulfate (Nacalai Tesque) aqueous solution Solution J: 200 mM manganese (II) chloride tetrahydrate (Wako Pure Chemicals) aqueous solution Solution K: 200 mM manganese (II) sulfate Japanese solution (Wako Pure Chemicals) aqueous solution ・ Solution L: 200 mM nickel chloride (II) hexahydrate (Wako Pure Chemicals) aqueous solution ・ Solution M: 200 mM nickel sulfate (II) hexahydrate (Wako Pure Chemicals) aqueous solution ・ Solution N: 200 mM zinc chloride (II) (Wako Pure Chemical Industries) dilute hydrochloric acid solution ・ Solution O: 200 mM zinc sulfate (II) (Wako Pure Chemical Industries) aqueous solution 200 mM zinc chloride (II) diluted hydrochloric acid solution (solution N) has a small amount. Prepared by adding hydrochloric acid (10 mL of concentrated hydrochloric acid to 100 mL of preparation). As for calcium sulfate, a solution having a target concentration became cloudy, and a uniform solution could not be prepared.

  To the soymilk, 100 μL of each solution was added so that each metal ion had a final concentration of 20 mM. In addition, what added water instead of the solution containing a metal salt was made into the control group. Mix quickly after addition of the solution. FIG. 1 is a photograph showing the results of adding each solution to soy milk. As shown in FIG. 1, tofu-like precipitation was observed in all the mixed solutions containing chlorides or sulfates of each metal.

Each mixture was heated at 80 ° C. for 1 hour, cooled on ice for 15 minutes, and then centrifuged at 8,000 rpm at 4 ° C. for 15 minutes. After fully removing the supernatant, the weight (w ₁ ) of the precipitate was measured. As shown in the following formula, the percentage of the value obtained by dividing the weight of the precipitate (w ₁ ) by the weight of the soy milk (w ₀ ) before adding the solution was calculated as the precipitation rate.

Precipitation rate (%) = (w ₁ / w ₀ ) × 100
The above experiment was carried out 5 times independently, and the average value and standard deviation of the respective precipitation rates were calculated. FIG. 2 is a graph showing precipitation rates calculated for solutions A, H, D, F, B, J, N, and L containing chlorides of the respective metals. From FIG. 3, the precipitation rate of copper (II), iron (II), iron (III), manganese (II), zinc (II), and nickel (II) chloride is the same as that of conventional calcium and magnesium. It was found that precipitation occurred. Similar results were obtained for sulfate (not shown).

  From the above results, a solution containing any one metal salt selected from iron (II), iron (III), nickel (II), manganese (II), zinc (II) and copper (II) as a metal salt; It was confirmed that a tofu-like precipitate can be formed by mixing with soy milk.

Further, after measuring the weight (w ₁ ), the precipitate was heated at 105 ° C. for 120 minutes. The dry weight was measured, and the weight difference before and after drying was taken as the water content (w ₂ ) in tofu. By dividing w ₂ weight w ₁ of the soy milk was calculated percentage.

Water content (%) = (w ₂ / w ₁ ) × 100
<Experimental example 2>
Calcium chloride dihydrate aqueous solution, copper chloride (II) dihydrate aqueous solution, magnesium chloride hexahydrate aqueous solution, manganese (II) tetrahydrate aqueous solution, nickel chloride (II) hexahydrate aqueous solution, chloride For zinc (II) dilute hydrochloric acid solution, iron chloride (II) tetrahydrate aqueous solution, and iron chloride (III) hexahydrate aqueous solution, solutions with different metal ion concentrations in the range of 0 to 20 mM were prepared. did. The precipitation rate was calculated in the same manner as in Experimental Example 1 except that the solutions prepared in this way were used, and the concentration of metal ions necessary for the formation of tofu-like precipitates was examined.

  3 and 4 are graphs showing the relationship between metal ion concentration and precipitation rate, FIG. 3 (a) is a calcium chloride dihydrate aqueous solution, and FIG. 3 (b) is copper (II) chloride dihydrate. FIG. 3 (c) shows the results for the aqueous solution of hydrate, FIG. 3 (c) shows the results for the aqueous solution of magnesium chloride hexahydrate, FIG. 3 (d) shows the results for the aqueous solution of manganese (II) chloride tetrahydrate, and FIG. Nickel (II) hexahydrate aqueous solution, FIG. 4 (b) is zinc chloride (II) dilute hydrochloric acid solution, FIG. 4 (c) is iron (II) chloride tetrahydrate aqueous solution, FIG. 4 (d) is iron chloride ( III) The results for the hexahydrate aqueous solution are shown respectively. From the results shown in FIG. 3 and FIG. 4, it was found that for any metal salt, the precipitation rate once increased to about 60% when the addition concentration was increased and decreased to about 50% when the concentration was further increased.

  Hereinafter, the first rise as shown in the graphs shown in FIGS. 3 and 4 is referred to as “first stage”, and the subsequent decline is referred to as “second stage”. The state of the precipitate in the first stage was like silken tofu, and the state of the precipitate in the second paragraph was like cotton tofu. This indicates that the precipitate formation takes place in two stages, meaning that the formation of a fine particle precipitate occurs in the first stage and the formation of a coarse precipitate in the second stage.

  Moreover, it turned out that the state like silken tofu and the state like cotton tofu are mixed in at the concentration at the end of the first stage (concentration immediately before the precipitation rate starts to drop). The reason why the precipitation rate decreased by about 10% during the transition from the first stage to the second stage was thought to be due to the reduced water content of the tofu-like precipitate. In fact, when the water content in the first and second stage tofu-like precipitates was measured, the water content of the second stage tofu-like precipitates was found to be about 10% less. The low water content in precipitates like cotton tofu is consistent with general tofu. Table 1 shows the metal ion concentration required for each step, as read from FIGS. 3 and 4. In addition, it has been empirically known that the texture of tofu produced using it varies depending on the concentration of metal ions contained in the coagulant. Not.

Based on the first stage plots in FIGS. 3 and 4, fitting analysis was performed with a Kaleida graph using the following formula, and the concentration of metal ions at the midpoint of precipitation formation was calculated. In the following formula, P is the precipitation rate, κ ₁ , κ ₂ , κ ₃ are constants, M is the metal ion concentration, and M _1/2 is the metal ion concentration when the precipitation rate is half of the first stage. doing.

  As an example, a fitting analysis for a magnesium chloride hexahydrate aqueous solution is shown in FIG. FIG. 5A shows before fitting analysis, and FIG. 5B shows after fitting analysis.

The R value was 0.999 or more for all fittings to the plots of each metal ion. Table 2 shows the R value and M _1/2 determined at that time. It is shown that a tofu-like precipitate is reliably formed by adding twice the concentration of these.

<Experimental example 3>
It is considered that iron is more easily taken into the human body in the form of Fe (II) than in the form of Fe (III). Therefore, when iron content is contained in the tofu of the present invention, it is preferable to use the Fe (II) form rather than the Fe (III) form. However, even if iron is contained in tofu in the form of Fe (II), it is oxidized in the air, and when this is eaten, the iron contained in the tofu is in the form of Fe (III). It is also possible that Then, this inventor tried to make tofu contain the metal salt of Fe (II) and the reducing agent harmless to a human body.

Concentration and precipitation of metal ions for iron (II) chloride tetrahydrate aqueous solution (FIG. 4 (c)) and iron (III) hexahydrate aqueous solution (FIG. 4 (d)) conducted in Experimental Example 2. FIG. 6 shows a graph obtained by superimposing graphs showing the relationship with the rate. In FIG. 6, the plot for Fe ²⁺ is indicated by a black circle, and the plot for Fe ³⁺ is indicated by a white circle. As it can be seen from FIG. 6, the formation of tofu-like precipitate in the Fe ²⁺ and Fe ^3+, high increase rate of sedimentation rates with less concentration towards the Fe ³⁺ in the first stage, even Fe ³⁺ in the second stage It can be seen that the behavior is generally different, such as high precipitation rate.

  Except that 2% ascorbic acid was added, the relationship between the concentration of metal ions and the precipitation rate in the aqueous iron (II) chloride tetrahydrate solution was the same as in Example 2 except that ascorbic acid was added. The graph compared with the case where there was no is shown in FIG. In FIG. 7, the plot for the case where ascorbic acid is added (+ ASA) is shown by a black circle, and the plot for the case where no ascorbic acid is added (-ASA) is shown by a white circle. FIG. 7 shows that even when ascorbic acid is added, the behavior is almost the same as when ascorbic acid is not added, and it can be seen that the addition of ascorbic acid does not adversely affect the formation of tofu-like precipitates.

<Experimental example 4>
Ingredients-free soymilk used in Experimental Example 1 (Organic soymilk (trade name), Sujata Meiraku Group: Protein content: about 5 g / 100 mL), as well as ingredient-free soymilk (organic soymilk (trade name), Marsan Eye : Protein content: about 4.7 g / 100 mL) as soy milk, and in the same manner as in Experimental Example 2, magnesium chloride hexahydrate aqueous solution and iron (II) chloride tetrahydrate aqueous solution are in the range of 0 to 20 mM. Solutions with varying concentrations of metal ions by 1 mM were prepared. FIG. 8 is a graph showing the relationship between the concentration of metal ions and the precipitation rate when each of the two types of soymilk is used. In FIG. 8, the plot for the magnesium chloride hexahydrate aqueous solution when using Marsan-ai soy milk is black circle, and the plot for the magnesium chloride hexahydrate aqueous solution when using Sujata Meiraku Group soy milk is the white circle , Plots of ferric chloride (II) tetrahydrate aqueous solution when using Marsan-ai soy milk, black triangle, ferric chloride (II) tetrahydrate aqueous solution when using Sujata Meiraku Group soymilk Are plotted with white circle triangles. FIG. 8 shows that a tofu-like precipitate is formed with almost the same behavior even when the type of soy milk is changed.

<Experimental example 5>
The precipitation rate was calculated in the same manner as in Experimental Example 1 except that the following organic salt solution was used.

-Solution a: 200 mM magnesium lactate aqueous solution-Solution b: 200 mM DL-calcium lactate aqueous solution-Solution c: 200 mM iron lactate aqueous solution-Solution d: 400 mM sodium lactate aqueous solution Solutions a, b, and c are added to soy milk It was cloudy in the state before doing. FIG. 9 is a graph showing precipitation rates calculated for solutions a, b, c, and d containing lactate of each metal. From FIG. 9, it was confirmed that a tofu-like precipitate was formed even in the organic salt solution.

  The embodiments and experimental examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (10)

  Contains only inorganic or organic salts of any one metal selected from iron (II), iron (III), nickel (II), manganese (II), zinc (II) and copper (II) as metal salts A method for producing tofu, comprising a step of mixing an aqueous solution and soy milk.   The method for producing tofu according to claim 1, wherein the aqueous solution contains only 6 mM or more of an inorganic salt of iron (II) as a metal salt.   The method for producing tofu according to claim 1, wherein the aqueous solution contains only 4 mM or more of an inorganic salt of iron (III) as a metal salt.   The method for producing tofu according to claim 2 or 3, wherein the aqueous solution further contains a reducing agent that is harmless to a human body.   The method for producing tofu according to claim 4, wherein the reducing agent is ascorbic acid.   The method for producing tofu according to claim 1, wherein the aqueous solution contains only 7 mM or more of an inorganic salt of nickel (II) as a metal salt.   The method for producing tofu according to claim 1, wherein the aqueous solution contains only 6 mM or more inorganic salt of manganese (II) as a metal salt.   The method for producing tofu according to claim 1, wherein the aqueous solution contains only 5 mM or more of an inorganic salt of zinc (II) as a metal salt.   The method for producing tofu according to claim 1, wherein the aqueous solution contains only 6 mM or more of an inorganic salt of copper (II) as a metal salt.   A tofu produced by the method according to claim 1.