PROCESS FOR PRODUCING TOFU COAGULANT

Abstract

A method for producing tofu coagulant includes preparing a water phase of a mineral salt coagulant solution for tofu and an oil phase of a food fat derived from plant materials, and stirring and mixing, while cooling to 50 C. or lower, at least one of the water phase and the oil phase, or cooling to 50 C. or lower immediately after emulsification of the composition stirred and mixed. The tofu coagulant with a W/O type composition is formed.

Claims

1. A method for producing tofu coagulant, comprising: preparing a water phase of a mineral salt coagulant solution for tofu and an oil phase of a liquid food fat, and stirring and mixing at least one of the water phase and the oil phase while cooling to 50 C. or lower, or stirring and mixing at least one of the water phase and the oil phase which were cooled to 50 C. or lower, or cooling to 50 C. or lower immediately after emulsification of the composition stirred and mixed, so that the tofu coagulant with a W/O type composition is formed, wherein the W/O type composition does not contain an emulsifier for food including one composition selected from the group consisting of polyglycerol esters of fatty acids, phospholipids, and monoacylglycerol as an additive, the mineral salt coagulant solution contains at least one selected from the group consisting of magnesium chloride, calcium chloride, magnesium sulfate, and crude seawater magnesium chloride, a concentration of the mineral salt coagulant solution is 2-6.1M, and the food fat contains 1.0-20% of diacylglycerol relative to a total weight of the food fat.

2. A method for producing tofu coagulant according to claim 1, wherein the water phase of the mineral salt coagulant solution is added to the oil phase of the food fat is added between 1:0.25 and 1:3.

3. A method for producing tofu coagulant according to claim 1, wherein the food fat is a plant-derived ingredient and comprises 0.1% of less of phospholipid, 1% or less of monoacylglycerol, and 98% or less of triacylglycerol.

4. A method for producing tofu coagulant according to claim 1, wherein an acid value of the food fat is 0.1 or higher, or free fatty acids of the food fat is 0.05% or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 is a schematic view illustrating a tofu curding system with one-way continuous path according to the present invention.

[0041] FIG. 2 is a schematic view illustrating a tofu curding system with one-way continuous path and heat exchanger attached according to the present invention.

[0042] FIG. 3 is a schematic view illustrating a tofu curding system with circular path according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] Next, the description will be made concerning concrete embodiments according to the present invention by referring to the drawings.

Machine Explanation

[0044] According to the invention, FIG. 1 shows a tofu curding system Z1 with one-way continuous path, and FIG. 2 shows a tofu curding system Z2 with one-way continuous path and cooling means R1 and R2 attached, and FIG. 3 shows a tofu curding machine Z3 with circular path H3. The tofu curding system Z1 and Z2 are continuous type, and the tofu curding system Z3 is batch type. Continuous type tofu curding system Z1 (Z2) is consist coagulant preparation part and soymilk coagulation part. Coagulant preparation part is, pre-mixture a food fat and a mineral salt solution as Nigari separately, and sending each material to an emulsifying dispersion machine M1 by pumps P1, P2 and make a emulsified tofu coagulant, see in FIG. 1. Soymilk coagulation part is mixture the tofu coagulant and high-temperature soymilk from tank T3, and sending mixture materials to a coagulation dispersion machine M2 by pump P3, and sending pre-product to curding machine, continuously as see in FIG. 1. Tofu curding system Z2 comprises cooling means (heat exchangers) R1, R2. Cooling means R1 is attached pipe H1 that output of pump Pl. Cooling means R2 is attached pipe H2 that output of pump P2. Either cooling means R1 or R1 is able to work. Tofu curding system Z2 comprises fat circular path H4a, mineral salt solution circular path H4b and soymilk circular path H5, is shown in FIG. 2.

[0045] Also, batch type tofu curding system Z3 is consist coagulant preparation part and soymilk coagulation part. Coagulant preparation part is, pre-mixture a food fat and a mineral salt solution as Nigari at tank T4 together in, and sending mixtures material to an emulsifying dispersion machine M1 by a pump P4 and make a tofu coagulant, see in FIG. 3. Stirring and mixture equipment is attached to tank T4. Switching valve KB is attached output of the emulsifying dispersion machine M1 and can be return overflow of the tofu coagulant to the tank T4. Soymilk coagulation part is mixture the tofu coagulant and high-temperature soymilk from tank T3, and sending mixture material to a coagulation dispersion machine M2 by pump P3, and sending pre-product to curding machine, as see in FIG. 3. Tofu curding system Z3 can be set cooling means (heat exchangers) on pipe H3 and tank T4, and can be set cooling means (heat exchangers) on pipe H4.

[0046] Emulsifying dispersion machine M1 has the strong performance of the emulsified dispersion, and preferably high-pressure homogenizer stator and rotor-type high-rotation type mixing, static mixers even better. The disperser coagulated dispersion machine M2, is weaken rather than machine M1 is no problem. For example, static mixer such a made by Noritake, and static mixer TS manufactured by Takai Tofu & Soymilk Equipment Co., is used to machine M2.

[0047] According to the invention of the tofu coagulant comprises a mineral salt solution as water phase and a food fat as oil phase. The tofu coagulant is not included synthetic emulsifiers and stabilizers that both food additives are necessary to uses current emulsification. According to the tofu coagulant, wherein the mineral salt solution comprising at least any one of a magnesium chloride, calcium chloride, sodium chloride, potassium chloride, magnesium sulfate, magnesium chloride seawater crude, in particular the magnesium chloride as Nigari. The invention, Nigari is acceptable including less than the solubility of calcium sulfate, calcium sulfate and particulate matter, and organic acids such as citric acid and gluconic acid.

[0048] The present invention of tofu coagulant has food fat that comprises DAG between 1% or more. The invention uses the food fat as liquid condition that can be use translucent or milky-white either. Just, it is necessary to use liquid food fat. That is to say, at least before the emulsifying dispersion, keep the food fat temperature higher than it maximum melting point. The DAG is natural ingredient of the food fat. The present invention of tofu coagulant can use the commercial food fat. For example, Rice oil, Corn oil, Soybean oil, Rapeseed oil, Sesame oil, Palm oil, Olive oil, Virgin-olive oil, Pure-olive oil), Grape-seed oil, Hazelnut oil, Palm oil, Cottonseed oil, Peanut oil, Macadamia-nut oil, Almond oil, Avocado oil, Linseed oil, Pumpkinseed oil, Walnut oil, Sesame oil, comprises DAG between 1 and 10%, see table 4.

[0049] DAG content is depended on oil material, oil expression and purification. For example, virgin olive oil and pure olive oil comprises DAG, but content of DAG are deference. The invention, mixture virgin olive oil and pure olive oil, is no problem and it can be control emulsification stability and slow-acting characteristic by deferent DAG contents mixture. The food fat comprises Monoacylglycerol (MAG) 1% or less and the food fat is not contains lecithin (phospholipid) such as emulsification, preferably. Lecithin and MAG are cause of weak slow-acting. Salad oil is acceptable that rejected depositions by wintering, but DAG content should be keep 1% or more.

[0050] Table 4 shows emulsion easiness that how easy to W/O emulsion after emulsifying dispersion, emulsion stability that how keep W/O emulsion warms 45 degC. Emulsion stability test procedure is, put the emulsion on glass plate and put cover glass on it and immediately view and photo by digital microscope (manufactured by Keyence Corporation named VHX-500F), after that input it chamber 45 degC and 1 hour, after that put out it and view and photo again, and compare both emulsions different. Measure particle diameters in photos and calculate particle size distribution.

[0051] Emulsifying dispersion temperature is depends on melting point of fat. In case of the fat temperature is 45 degC, most of food fat is liquid. Emulsifying dispersion condition is adjustable such 35 degC and 2 hours or more, 25 degC and 4 hours or more, 15 degC and 8 hours or more, 5 degC and 16 hours or more. The invention of tofu coagulant, water phase size average is between 0.1 and 20 micro meter, average between 1 and 10 micrometer is preferably, average between 1 and 5 micrometer is more preferably.

[0052] According to the present invention, when the fat is solidified, pre-warmed over the melting point and liquid fat is stirred and mixed. And when the fat is solidified by cooling after emulsified, pre-warmed over the melting point and liquid the emulsified tofu coagulant is used before addition to soymilk. When use a fat easy to solidify, attaches a keeping heat means on pipes, tanks, and valves, preferably.

Example 1

[0053] Magnesium chloride solution as Nigari that is made by AKO KASEI CO., LTD., that named Soft-Wafer. Food fat is pure olive oil made by J-OIL MILLS, Inc. Temperature of the magnesium chloride solution is 19.1 degC, and temperature of the olive oil is 10.3 degC or 4.1 degC. The food fat is not including silicone. Magnesium chloride and water ratio is 2:1, and make a magnesium chloride solution that concentration is 66.7% w/w as density 1.34 and 4.3 M. Pre-mixture the magnesium chloride solution 500 g and olive oil 500 g separately, and sending each material to an emulsifying dispersion machine M1 and make a emulsified tofu coagulant. Emulsifying dispersion machine M1 is manufactured by Pacific Machinery & Engineering Co., Ltd., named Milder for laboratory. Machine M1 rotor speed is 10000 rpm and squeezing out put valve and continuously emulsifying and dispersion, and make the tofu coagulant. Coagulation dispersion machine M2 is manufactured by PRIMIX Corporation, named Homo-mixer Mark 2-40 type. Curding machine is batch type and manufactured by Takai Tofu & Soymilk Equipment Co., named Mini-Curdy. The coagulation dispersion machine M2 is attached on the curding machine. The tofu curding system Z1 is same as FIG. 1, but cooling mean is addition to tank and cooling water temperature is 10 degC.

[0054] For tofu curding action, prepare soymilk for silken tofu 13% brix, temperature 80 degC, 12 liter input flat box. The tofu coagulant amount, concentration of magnesium chloride solution that converted to magnesium chloride (hexahydrate) weight 2.8 g for soymilk 1 liter. The emulsified tofu coagulant within 60 minutes after emulsifying and dispersion, is input the soymilk and stirred and dispersed about 20 seconds by coagulation dispersion machine M2 that rotation speed 2000 rpm, and make a tofu. To aged, wait 30 minutes after made the tofu, and evaluate the tofu checking by visual, touching and eating. See table 1. As the result, example 1-1, example 1-3 are produced a smooth pudding-like silken tofu. In case of example 1-2 is shorten emulsifying time 0.5 minutes, thus emulsion temperature increase near 30 degC by stir heat as friction heat. Therefore, the emulsion was unstable and slightly rough surface of the tofu and emergent. Example 1-1 is used cooling means and suppressed the emulsion temperature after emulsification. Example 1-3 is pre-cooled the fat and suppressed the emulsion temperature after emulsification. The comparative examples, that only Nigari input the soymilk 80 degC and stirred and dispersed, is a rough surface weak tofu, so it is not show in table 1.

TABLE-US-00001 TABLE 1 Fat Nigari Emulsifying Coagulant Cooling temperature Temperature time Temperature Tofu means (degC.) (degC.) (sec.) (degC.) Evaluation Example 1-1 yes 10.3 19.1 120 22.3 good Example 1-2 no 10.3 19.1 050 29.0 not so good Example 1-3 yes 04.1 03.6 230 19.0 very good

Example 2

[0055] Magnesium chloride solution as Nigari that is made by Naikai Salt Industries CO., LTD., that named White-Nigari. Food fat is pure olive oil made by J-OIL MILLS, Inc. Magnesium chloride solution is into freezer, and olive oil is into refrigerator. Temperature of the magnesium chloride solution is 7 degC, and temperature of the olive oil is 4.1 degC. The food fat is not including silicone. Magnesium chloride and water ratio is 2:1, and make a magnesium chloride solution that concentration is 66.7% w/w as density 1.34 and 4.3 M. Pre-mixture the magnesium chloride solution 500 g and olive oil 500 g separately, and sending each material to an emulsifying dispersion machine M1 and make a tofu coagulant. Emulsifying dispersion machine M1 is manufactured by Pacific Machinery & Engineering Co., Ltd., named Milder for laboratory. Machine M1 rotor speed is 10000 rpm and squeezing out put valve and continuously emulsifying and dispersion, and make the tofu coagulant. Coagulation dispersion machine M2 is connected two mixers which one is manufactured by Noritake Co., Ltd., and other is manufactured by Takai Tofu & Soymilk Equipment Co., The coagulation dispersion machine M2 is attached on the curding machine. The tofu curding system Z1 is same as FIG. 1.

[0056] For tofu curding action, prepare soymilk for silken tofu 13% brix, temperature 80 degC and continuously flow, and addition the tofu coagulant after made within 5 or 60 minutes. The tofu coagulant amount, concentration of magnesium chloride solution that converted to magnesium chloride hexahydrate weight 2.5 g for soymilk 1 liter. The soymilk flow 200, 300 and 400 liter/hour, and receive it to a box as 3 liters, and check the product slow-acting time by visual. Slow-acting time is between into the box and beginning to curd. To aged, wait 30 minutes after made the tofu, and cut out to cylindrical tofu that diameter 20 mm and height 20 mm, and set it on Rheometer, and evaluate the tofu hardness. Rheometer is manufactured by Fudo Engineering Co., Ltd., named NRM-2002J and plunger diameter 20 mm, sample table rising speed 60 mm/ minute. And evaluate the tofu checking by visual, touching and eating. See table 2. As the result, example 2-2 is produced a smooth pudding-like silken tofu. Example 2-2 as soymilk flow 300 liter/hour is made a most hard tofu. Example 2-1 as soymilk flow 200 liter/hour is made a little soft tofu. Example 2-3 as soymilk flow 420 liter/hour is made a little rough surface tofu.

TABLE-US-00002 TABLE 2 Fat Nigari Slow-acting Tofu Tofu flow temperature Temperature time hardness Tofu (Liter/hour) (degC.) (degC.) (sec.) (10.sup.2 N/m.sup.2) Evaluation Example 2-1 200 4.1 7 30.0 81.2 good Example 2-2 300 4.1 7 12.3 89.2 very good Example 2-3 420 4.1 7 05.4 83.7 good

Example 3

[0057] Magnesium chloride solution as Nigari that is made by Naikai Salt Industries CO., LTD., that named White-Nigari. Food fat is selected one of the, corn oil (made by Boso oil and fat CO., LTD.) and palm oil (made by Fuji oil CO., LTD.) mixtures ratio 1:1, soybean oil (made by J-OIL MILLS), rice oil (made by J-OIL MILLS), corn oil (made by Boso oil and fat CO., LTD.), rapeseed oil (made by J-OIL MILLS). Temperature of Nigari is 13 degC, and each temperature of the oil is 13 degC. The food fat is not including silicone. Magnesium chloride and water ratio is 2:1, and make a magnesium chloride solution that concentration is 66.7% w/w as density 1.34 and 4.3 M. Pre-mixture the magnesium chloride solution 500 g and olive oil 500 g separately, and sending each material to an emulsifying dispersion machine M1 and make a tofu coagulant. Emulsifying dispersion machine M1 is manufactured by Pacific Machinery & Engineering Co., Ltd., named Milder for laboratory. Machine M1 rotor speed is 10000 rpm and squeezing out put valve and continuously emulsifying and dispersion, and make the tofu coagulant. Coagulation dispersion machine M2 is connected two mixers which one is manufactured by Noritake Co., Ltd., and other is manufactured by Takai Tofu & Soymilk Equipment Co., The coagulation dispersion machine M2 is attached on the curding machine. The tofu curding system Z1 is same as FIG. 1. Curding machine is batch type and manufactured by Takai Tofu & Soymilk Equipment Co., named Mini-Curdy, and rotation speed is 2000 rpm.

[0058] For tofu curding action, prepare soymilk for silken tofu 13% brix, temperature 80 degC and continuously flow, and addition the tofu coagulant after made within 5 or 60 minutes. The tofu coagulant amount, concentration of magnesium chloride solution that converted to magnesium chloride hexahydrate weight 2.8 g for soymilk 1 liter. The soymilk flow 200, 300 and 400 liter/hour, and receive it to a box as 3 liters, and check the product slow-acting time by visual. Slow-acting time is between into the box and beginning to curd. To aged, wait 30 minutes after made the tofu, and cut out to cylindrical tofu that diameter 20 mm and height 20 mm, and set it on Rheometer, and evaluate the tofu hardness. Rheometer is manufactured by Fudo Engineering Co., Ltd., named NRM-2002J and plunger diameter 23 mm, sample table rising speed 60 mm/ minute. And evaluate the tofu checking by visual, touching and eating. See table 3.

[0059] As the result, example 3-2 uses as soybean oil is acceptable, made a smooth and hard tofu, but slow-acting time is shorten and little weak. Because, content of soybean oil DAG is rather smaller than the corn oil DAG and palm oil DAG Example 3-3, example 3-4 and example 3-5 are produced a smooth and hard tofu, and corn oil, rice oil, rapeseed oil each is able to prepare the emulsified tofu coagulant. As the result, example 3-1 uses as mixtures corn oil and palm oil, slow acting time is enough, and made a smooth tofu, but hardness is not enough a little. Corn oil and palm oil comprise DAG relatively high and low cost. Palm oil has slow-acting character and high melting point. Thus, palm oil and corn oil mixtures ratio is between 1:1 and 1:10, is obtained liquid food fat, and easy to handling, made a smooth and hard tofu.

TABLE-US-00003 TABLE 3 Fat and Nigari Slow-acting Tofu Fat temperature time hardness Tofu (oil type) (degC.) (sec.) (10.sup.2 N/m.sup.2) Evaluation Example 3-1 Cone and Palm 13 40 47.1 very good Example 3-2 Soybean 13 15 53.0 good Example 3-3 Rapeseed 13 30 45.1 good Example 3-4 Cone 13 25 48.0 good Example 3-5 Rice 13 30 58.8 good

Example 4

[0060] Table 4 (table 4-1, table 4-2 and table 4-3) shows emulsion easiness that how easy to W/O emulsion after emulsifying dispersion, emulsion stability that how keep W/O emulsion during warms 45 degC. Emulsifying dispersion test is used such a tofu curding system Z3 is batch type. Coagulation dispersion machine M2 is manufactured by Yamato Scientific Co., Ltd, named Ultra-disperser LK-22 with generator shaft: S-25N-10 G, and it rotation speed is 20,000 rpm. Stir the fat 50 g and added 4M magnesium chloride 50 g and emulsifying 3 minutes.

[0061] As shown in table 4, correlation between DAG content and emulsion easiness is high, and correlation between DAG content and emulsion stability is high. But, correlation between MAG content and emulsion easiness is low, and correlation between MAG content and emulsion stability is low. DAG content is depended on oil material, oil expression and purification. Thus, same material but DAG content is different. In the table 4, plant oil comprises DAG between 1 and 10%. The invention, the food fat is a plant-derived ingredient and comprising phospholipid is 0.1% or less, monoacylglycerol is 1% or less, triacylglycerol is 98% or less. According to palm oil, corn oil and pure olive oil, warms 45 degC and 120 minutes and confirms emulsion stability. Virgin olive oil, soybean oil and palm oil are rather unstable. Macadamia-nut oil, Safflower oil, Perrila Oil can't confirms emulsion stability. If use tofu curding system Z2 with one-way continuous path and cooling means R1 and R2 attached, those Macadamia-nut oil, Safflower oil, Perrila Oil will be reach more stable emulsion. Only DAG is a good correlation with emulsion easiness or emulsion stability, as shown in table 4. Those phospholipid, MAG and free fatty acid are almost rejected de-gumming and de-acidification wintering at purified process. TAG is a main content of fat in generally, is not important to this invention. Thus, TAG is between 0 and 98%. DAG is a fat which is same as conventional TAG As Japanese Agricultural Standards, acid value most of the food fat is 0.2 or less. Sesame oil acid value is 4 or less, and Olive oil acid value is 2 or less. The invention, food fat means food plant oil or food processing oil specified Japanese Agricultural Standards or same Standards. Table 4 shows a part of food fats applicable to the invention. Therefore, the food fat is not limited and it can be use meet the conditions of the invention.

[0062] Table 4 (table 4-1, table 4-2 and table 4-3) shows characteristics of plant oils. Emulsion easiness (*a) is how easy to W/O emulsion after emulsifying dispersion on batch test, and scale with 10 points. Emulsion stability (*b) is how keep W/O emulsion during warms 45 degC on batch test, and scale with 10 points. Free fatty acid value (*c) is calculated that is ((acid value/56)(average molecular weight38)/3/1000)100. Saturated fatty acid (*d) and Double bond (*d) are calculated fatty acid composition. MAG (*1), DAG (*1) and TAG (*1) are analyzing result of Japan institute of oil & fats, other foods inspection foundation. DAG literature (*2) is cited R. P. D'alonzo, W. J. Kozarek and R. L. Wade.: J. Am. Oil Chem. Soc., 59, 292, Year 1982, Journal of the American Oil Chemists' Society. Acid value (*3) is measured by Takai Tofu & Soymilk Equipment Co., Viscosity (*4) is measured by Takai Tofu & Soymilk Equipment Co., and used B type viscosity meter with BL adapter.

TABLE-US-00004 TABLE 4-1 Pure Virgin Palm Cone olive olive oil oil oil oil Emulsion easiness (*a) 7 5 5 3 Emulsion stability (*b) min. 120 120 120 60 MAG (*1) % 0.2 0.8 1.0 0.4 DAG measured (*1) % 7.5 5.2 5.4 3.6 DAG literature (*2) % 5.8 2.8 5.5 5.5 TAG (*1) % 92.7 94.4 94.4 94.9 Acid value (*3) 0.11 0.13 0.18 0.76 Fatty acid value (*c) % 0.05 0.05 0.09 0.38 Saturated fatty acid (*d) % 50.7 14.3 14.2 14.2 Double bond (*d) % 1.8 4.0 2.8 2.8 Viscosity at room (*4) mPa .Math. s 70 52 62 Viscosity at 10 degC. mPa .Math. s 108 133 133 (*4) Slow-acting character very very very good good good good

TABLE-US-00005 TABLE 4-2 Cotton Rice seed Peanut Soybean oil oil oil oil Emulsion easiness (*a) 7 7 2 2 Emulsion stability (*b) min. 120 20 90 20 MAG (*1) % 0.4 0.3 0.5 0.4 DAG measured (*1) % 9.9 7.8 3.6 3.2 DAG literature (*2) % 3.1 2.2 1.0 TAG (*1) % 89.7 91.3 95.7 97.2 Acid value (*3) 0.16 0.12 0.20 0.10 Fatty acid value (*c) % 0.08 0.06 0.10 0.05 Saturated fatty acid % 21.6 26.2 13.4 14.7 (*d) Double bond (*d) % 3.6 3.9 3.6 4.6 Viscosity at room (*4) mPa .Math. s 73 55 72 49 Viscosity at 10 degC. mPa .Math. s 133 114 122 100 (*4) Slow-acting character good good not so not so good good

TABLE-US-00006 TABLE 4-3 Coconut Rapeseed Macadamia Safflower oil oil nut oil oil Emulsion easiness (*a) 2 2 0 0 Emulsion stability (*b) min. 20 60 0 0 MAG (*1) % 0.5 0.4 0.3 0.4 DAG measured (*1) % 2.5 3.2 2.2 2.4 DAG literature (*2) % 2.2 2.1 TAG (*1) % 97.2 96.1 97.5 96.6 Acid value (*3) 0.11 0.12 0.06 0.08 Fatty acid value (*c) % 0.04 0.06 0.03 0.04 Saturated fatty acid (*d) % 30.4 26.2 10.3 11.3 Double bond (*d) % 0.3 3.9 2.6 4.9 Viscosity at room (*4) mPa .Math. s 52 55 73 55 Viscosity at 10 degC. (*4) mPa .Math. s 117 135 129 Slow-acting character not so not so bad Bad good good

[0063] To study relation between mineral salt concentration and tofu quality included coagulant cost, is as shown in table 5 (table 5-1 and table 5-2). Use the tofu curding system Z1 with one-way continuous path as shown in FIG. 1. Particularly, use the tofu curding system Z2 with one-way continuous path and cooling means R1 and R2 attached as shown in FIG. 2. It is effective suppressed stirring heat up and keeping emulsion stable. Invention example is used olive oil that consist DAG 5.4% w/w. Comparative example is used safflower oil that consist DAG 2.4% w/w. Mineral salt solution is used 1M magnesium chloride, 2M magnesium chloride, 4M magnesium chloride, 4M calcium chloride. 4M magnesium chloride and 4M calcium chloride are saturated aqueous solution at room temperature. Mineral salt solution (water phase) and the food fat (oil phase) ratio is between 1:0.2 and 1:3, preferably the ratio is between 1:0.4 and 1:1.5. Emulsion is cooled 50 degC or less on the emulsifying or after the emulsifying for keeping emulsion stable. In case of corn oil, melting point is between 15 and 10 degC. Thus, corn oil cooling temperature is between 10 and 25 degC when just emulsified at 30 degC. In case of palm oil, melting point is between 27 and 50 degC in literature, but actual melting point is 60 degC and after that it is not milky near 30 degC by warm test. Thus, palm oil cooling temperature is between 30 and 50 degC when just emulsified at 60 degC or near. Emulsion viscosity is higher and stable when the oil phase is smaller, tendency. Commercial emulsifier tofu coagulant viscosity is between 1 and 2 Pa.s at room temperature which is concerned handling put out bottle. As above describe, in the invention doesn't need bottle and when uses the system Z1, Z2, Z3, invention tofu coagulant viscosity 2 to 10 Pa.s is acceptable to use, also invention tofu coagulant viscosity 10 to 100 Pa.s is possible to use when select high power pump.

[0064] Table 5 (table 5-1 and table 5-2) shows relation between mineral salt concentration and tofu quality included coagulant cost. Coagulant basis is commercial emulsifier tofu coagulant that is made by Kao Corporation named Magness-fine TG.

TABLE-US-00007 TABLE 5-1 Comparative Example Example Comparative 5-1 5-1 5-2 5-2 Mineral salt 1M 2M 4M 4M solution MgCl.sub.2 MgCl.sub.2 MgCl.sub.2 MgCl.sub.2 Food fat Olive oil Olive oil Olive oil Safflower oil Water phase:Oil 1:1 1:1 1:1 1:1 phase ratio Emulsion very good very good good NG stability at separated 45 degC few minutes Slow-acting very good very good very good NG character Tofu condition soft a little soft hard weak, emergent Cost of too high a little half cost half cost coagulant NG high OK OK OK

TABLE-US-00008 TABLE 5-2 Example Example Comparative 5-3 5-4 5-3 Mineral salt solution 4M 2M 4M CaCl.sub.2 MgCl.sub.2 MgCl.sub.2 Food fat Olive oil Olive oil Olive oil Water phase:Oil 1:1 1:0.2 1:3.5 phase ratio Emulsion stability good good very good at 45 degC. separated 1 hour Slow-acting character very good good very good Tofu condition hard hard a little soft oily smell Cost of coagulant half cost half cost too high OK OK NG

[0065] Actually, the water phase and the oil phase ratio is between 1:0.5 and 1:1.5 that is economical cost range. In case of the oil phase is smaller, emulsion is unstable and slow-acting character is low. In case of the oil phase is bigger, addition amount to tofu is increased and cost is getting high.

[0066] The invention of tofu coagulant, the concentration of magnesium chloride is 2 M or more. The dense magnesium chloride concentration between 3 and 5 M, is preferably, and upper limit is 6.1 M or under. Saturated aqueous solution of magnesium chloride is 4.8 M at 10 degC, 5 M at 40 degC, 5.6 M at 80 degC, 6.1 M at 100 degC, for example. Magnesium chloride 6.1 M is maximum, cause 100 degC is upper limit. Saturated aqueous solution of magnesium sulfate is 3.8 M maximum, and calcium chloride is 8.8 M maximum. It can be use the tofu coagulant which water phase is even if cloudy or part of solidify. Also, it can be use the tofu coagulant which oil phase is slurry such a calcium sulfate particles included. But it is not useful, because the emulsified tofu coagulant unstable and pump and pipe are affected deposition of the oil phase.

[0067] Practically, it is necessary to increase oil phase (continuous phase) as water phase (disperse phase) amount. Thus, decreasing water phase and suppressing the oil phase volume that is advantageously to cost reduction. Moreover, increasing the concentration of magnesium chloride in the water phase, fewer usages to the coagulant and possibly reaches more cost reduction. Study to W/O type emulsion characteristic that is used 0.5M magnesium chloride solution and processing oil and does not use additives as emulsifiers, is disclosed in prior art document 2. Refer FIG. 1 of prior art document 2, dense magnesium chloride and dense calcium chloride is unstable, estimation, but, emulsion is stable cause of emulsion viscosity increasing. Dense mineral salt solution is specially damaged heat up by stirring heat and dissociation effect. Therefore, in the invention, uses one-way continuous path and cooling means at system Z2. Most of commercial magnesium chloride seawater crude is 2 M or more. Concentration 2M is sum of magnesium chloride mol, magnesium sulfate mol, calcium chloride mol and calcium sulfate mol in solution 1 liter.

[0068] The present invention of a method for producing tofu coagulant, wherein interfacial tension of the food fat against distilled water is 34 mN/m or less at room temperature. The water phase as magnesium chloride and the oil phase such olive oil and rice bran oil are stirred and mixed to W/O type emulsion. DAG interfacial tension is low, and the content of DAG effect to total food fat interfacial tension to decrease, and emulsion is stabilized by the action of surface-active phase. TAG and DAG interfacial tension is cited prior art document 3. However, relation between DAG content and food fat interfacial tension is not disclosed. Moreover, about W/O type emulsion, relation between mineral salt solution as Nigari and DAG content of food fat is not disclosed.

Example 6

[0069] For about typically food fat, measure the interfacial tension at room temperature. Test equipment is manufactured Kyowa Interface Science Co., ltd. named DropMaster DM301. Perrila oil and macadamia-nut oil are sample that is difficult emulsifying. Table 6 shows characteristics of plant oils. Processing oil* is commercial processing oil include DAG highly. Emulsion easiness (*a) is how easy to W/O emulsion after emulsifying dispersion on batch test, and scale with 10 points. Emulsion stability (*b) is how keep W/O emulsion during warms 45 degC on batch test, and scale with 10 points.

TABLE-US-00009 TABLE 6 Comparative Comparative Example Example Comparative 6-1 6-2 6-1 6-2 6-3 Food fat Perrila Macadamia- Soybean Cone oil Processing oil nut oil oil oil* Interfacial 34.2 29.2 32.5 26.1 12.5 tension (mN/m) Emulsion 0 0 2 5 10 easiness (*a) Emulsion 0 0 2 10 10 stability (*b) DAG (%) 3.6 2.2 3.2 5.2 87.1

[0070] As shown in table 6, when the interfacial tension at room temperature over the 34 mN/N, difficult to emulsion and unstable. In the invention, the interfacial tension at room temperature is 34 mN/m or less, particularly the interfacial tension 30 mN/m or less, which is easy obtained W/O type emulsion and stable condition. See table 6. As comparative 6-1, Perrila oil interfacial tension is 34.2 mN/m that why Perrila oil couldn't to be emulsion. As example 6-1, Soybean oil interfacial tension is 32.5 mN/m that why Soybean oil could be emulsion. Perrila oil DAG content is 3.6%, and Soybean oil DAG content is 3.2%. Therefore, according emulsification, the interfacial tension is more effective than DAG content. On the other hand, Macadamia-nut oil DAG is 2.2%, and Soybean oil DAG content is 3.2%. In case of it, as comparative 6-2, Macadamia-nut oil DAG is 2.2% that why Macadamia-nut oil couldn't to be emulsion. If a surface-active agent into the emulsifier, the interfacial tension is below 10 mN/m. Therefore, according to the invention, wherein interfacial tension of the food fat against distilled water is between 10 and 34 mN/m at room temperature, and particularly the interfacial tension is between 10 and 30 mN/m. The food fat as oil phase including DAG is 1 wt % or more, and particularly DAG is 3 wt % or more, and/or, the interfacial tension is between 10 and 34 mN/m, and particularly the interfacial tension is between 10 and 30 mN/m. Refer to such Corn oil DAG 5.2% and interfacial tension 26.1, or Soybean oil DAG 3.2% and interfacial tension 32.5, or Processing oil DAG 87.1% and interfacial tension 12.5. See table 6. The food fat interfacial tension is decreased when temperature is increased. In case of it, advantageous to emulsify, but emulsion viscosity is decreased and doing to re-aggregate and unstable emulsified phase. In case of the interfacial tension of the food fat is between 10 and 34 mN/m and DAG is less than 1 wt % that is difficult to emulsify and unstable.

[0071] The invention of tofu coagulant, water phase size (diameter) average is between 0.01 and 20 micro meter. The present invention enables to maintain the W/O emulsified state and fully delays coagulation reaction of soymilk. The average water phase diameter is between 0.01 and 20 micrometer and preferably between 0.1 and 10 micrometer. According to the present invention, when the water phase size average is bigger than criteria, emulsification is unstable. In opposition, when the water phase size average is smaller than criteria, emulsification viscosity is increased and difficult to measure and difficult to disperse in soymilk and cause of coagulating irregular. To measure on flow meter the water phase diameter, put the emulsion on glass plate and put cover glass on it and immediately view and photo by digital microscope (manufactured by Keyence Corporation named VHX-500F, and high-resolution lens VH-Z500W) by transmission shooting, after that measure particle diameters in photos 100 micrometer square area, and measure particle diameter by compass and calculate average diameter, median diameter and standard deviation. The water phase size is able to control by food fat, temperature and machine conditions. When the water phase size is smaller, coagulation slow-acting effect is up. In opposition, when the water phase size is bigger, coagulation slow-acting effect is down. As above embodiments, the soymilk temperature is between 0 and 99 degC, the temperature between 60 and 95 degC is preferably, and the temperature between 75 and 85 degC is practical and more preferably.

[0072] As above, embodiments describe producing method for silken tofu. The scope of the invention, as well as silken tofu, kinugoshi-tofu, momen-tofu, namaage-tofu, atuage-tofu, can utilize a variety of tofu products.