JPH0259709B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing soymilk for tofu, and more particularly, to a method for producing soymilk for tofu with high concentration and constant quality. [Prior Art] Conventionally, when tofu is produced in a factory, as shown in the flow sheet of Figure 5, soybeans are soaked in water and soaked, and then the soaked soybeans are ground with water and at the same time, an antifoaming agent is added. The common process was to heat this with live steam for a short time and then filter the okara to make soy milk. However, the quality of tofu varies due to the treatment of water used for soaking or washing soybeans, the unevenness of soybean milk, and the weakness of curds seen in stuffed tofu, etc.
There were many drawbacks such as short shelf life of tofu. In addition, in the production of drinking soy milk, saturated steam is injected onto the soybeans, the dehulled soybeans are cooled after being dried with hot air, and then hot water (80%
~100℃)
179045) or soaked soybeans that do not absorb water.
A method of grinding in hot water above ℃ but below the boiling point (JP-A-Sho)
53-66468), but these methods require grinding in high-temperature hot water, so the temperature of the extracted soymilk is high, and the air mixed in during grinding is also expelled, resulting in a natural The lipoxygenase in the soybean is deactivated and the grassy odor is removed, making it possible to obtain odorless soymilk suitable for drinking. It is known that thermal denaturation occurs at temperatures above 70℃.For example, New Food Industry Vol.23
No. 4 (1981) P. 27-41), the protein extraction rate decreases, and even if soy milk is heated in the next step, only weak curds are obtained, making it impossible to use soy milk for tofu production. There is. If the temperature conditions during hydro-milling are lowered and the soybean is milled in water below 70°C or in warm water to avoid thermal denaturation of the protein, the lipoxygenase and polyphenol oxidase in the soybean will not be deactivated. Because the temperature of the extracted soymilk is low, air (oxygen) remains in the soymilk, and the resulting soymilk becomes oxidized and brown over time, taking on a gray to dark red color, making it suitable for both drinking and tofu production. The problem remains that it is not suitable. [Problems to be Solved by the Invention] The present invention solves the problems of the prior art described above, and extracts soymilk suitable for producing tofu without heat denaturation without using the step of soaking soybeans. A method for producing soymilk for tofu that prevents discoloration of soymilk due to oxidation by degassing before and after the heat denaturation step of the next step, and produces tofu with a desired hardness without uneven sterilization (uneven denaturation). The goal is to provide the following. [Means for Solving the Problems] The present invention provides a means for solving the above-mentioned problems.
A process of hydrolyzing soybean protein without thermally denaturing the soybean protein at a temperature of 70°C or lower, and a process of directly separating the ground soybean curd into okara and soy milk using a centrifuge without boiling it. Next, the soybean milk is degassed and then directly heated with steam at a temperature of 100°C to 150°C to denature the soybean protein by heating, and the soybean protein is further degassed and cooled. The gist of this article is a method for producing soymilk. [Operation] The operation of the method of the present invention will be explained in order of steps. (Hydro-milling process) By hydro-milling raw soybeans at a temperature of 20°C to 70°C without denaturing soybean protein without using soaked soybeans, it is possible to produce tofu without heat denaturation. It is possible to obtain go, which is a suitable raw material for soymilk. At this stage, lipoxygenase remains, so a grassy smell remains, but since the purpose is not to obtain drinking soymilk, but to obtain soymilk for tofu production, there is no problem even if the grassy smell remains. If the temperature condition during hydro-grinding exceeds 70℃, the soybean protein will be thermally denatured, and if the temperature condition is below 20℃, the viscosity of the gou will increase, making it difficult to separate the okara from the soymilk, which is undesirable. . (Separation Step) Next, the ground soybeans, that is, go, are directly separated into okara and soy milk using a centrifuge without being boiled, and soy milk, which is a raw material for tofu, is extracted. Since this soymilk is separated from the soybean paste obtained by hydrolysis and grinding under the temperature conditions of 20°C or more and 70°C or less as described above, there is almost no thermal denaturation of the protein. In this case, the air (oxygen) mixed in during the grinding and separation processes remains in the soymilk without being removed, and the polyphenol oxidase that oxidizes the polyphenols contained in soybeans is not deactivated. Because the soybean remains, if left untreated, the soymilk will turn brown (redden) over time, making it impossible to obtain tofu with good color. (Deaeration and heat denaturation step) Therefore, it is necessary to quickly deaerate and eliminate oxygen to prevent the browning, so-called charring. This deaeration not only prevents discoloration of the soymilk due to oxidation, but also removes air bubbles in the soymilk, which allows the soymilk to be evenly denatured by heating without causing uneven sterilization (uneven denaturation) when directly heated with steam. can be given. In addition, it is generally known that when heating unheated soy milk, the firmness of tofu decreases due to air oxidation (for example, Japan Food Industry Association Journal VOL.25
No. 7 (1978) P. 21-25), degassing before heating can prevent a decrease in the firmness of tofu. If the heating temperature is below 100°C, sterilization may be insufficient, and if it is above 150°C, protein denaturation will be excessive, so adjust the heating time appropriately under the temperature conditions of 100 to 150°C. It is best to heat it directly. In addition, by adopting direct heating with steam, it is possible to heat soymilk with a high solids content (12% or more), which is difficult with indirect heating, without causing it to stick to the machine wall, and it is possible to uniformly heat denature the soymilk. can. (Degassing and Cooling Step) In the heating denaturation step, direct heating with steam is employed, so the heated steam enters the product soymilk and dilutes it. Therefore, the product soymilk is again cooled by degassing and evaporation under reduced pressure. Note that the cooling temperature may be appropriately selected depending on the type of tofu product (firm tofu, filled tofu, etc.). [Example] Hereinafter, an example of the present invention will be described in order of steps while comparing with a conventional example with reference to FIG. (Hydration grinding process) First, the soybeans are carefully selected and then processed without soaking.
Grind by using a grinder while adding warm water of 20 to 70°C with or without an antifoaming agent. As raw soybeans, whole soybeans, dehulled soybeans, or dehulled cob soybeans may be used, but considering the attached spore bacteria, soybean glycoside components, and the yield when separating the gou, It is preferable to use soybeans that have been dehulled and dehulled. It is preferable to add water at a low temperature to avoid heat denaturation of soybean protein, but water below 20°C will increase the viscosity after grinding, making it difficult to separate the okara and soy milk. It is best to keep the temperature at 70℃.
If the temperature is higher than that, the protein will be denatured by heating, making it unsuitable for use as soymilk for tofu, so it is necessary to select a temperature within the range of 20 to 70°C. FIG. 2 shows the relationship between grinding temperature and soymilk yield. According to this, the highest yield is shown when the grinding temperature is around 60°C, and it shows a tendency to decrease when the grinding temperature is below 40°C and above 70°C. The reason why the yield decreases below 40°C is because the viscosity of the obtained gou increases as the temperature conditions during grinding decrease, and the mechanical separation efficiency decreases, and is not due to chemical reasons. Therefore, yield can be increased by improving the performance of the centrifuge at 20°C.
It is practical to some extent. In addition, when the temperature exceeds 70℃, the yield similarly decreases, but this is because soybean protein adheres to the okara due to heat denaturation and is separated from the okara, which reduces the amount of protein in the soymilk and makes it difficult to use soymilk for tofu. becomes inappropriate. Therefore, the temperature conditions during hydrolysis grinding are 20 to 70℃, especially 60℃.
It can be said that the front and back are preferable. The grinding machine is not a conventional grinder, but a Hivis line mill (product name), for example.
It is preferable to use a multi-stage combination of a cutter like this and a mill grinder like Mycolloider (trade name), with the first stage for coarse crushing and the second stage for fine crushing. (Separation Step) Next, the soybean paste obtained in the grinding step is separated into okara and soy milk using a centrifuge without boiling.
It is preferable to use a decanter as the centrifuge. In the process of separating okara and soy milk, conventionally raw soybean paste is heated and boiled (at 95-105℃ for 1-8 minutes).
After that, it was separated using a squeezer (for example, Tofua), but in the present invention, boiling is not performed before this separation. Generally, one of the purposes of heating and boiling before separation is to maintain yield. However, according to the research conducted by the present inventor, boiling may cause uneven boiling of the soybean, and high-temperature heating may cause denaturation of soybean protein, which may cause protein to adhere to the soybean okara, reducing the protein extraction rate, or causing insolubilization. It was found that there are drawbacks such as deterioration of the quality of soymilk due to From this point of view, we can avoid deterioration in quality due to boiling, maintain the quality of soymilk through temperature conditions in the hydro-milling process, maintain yield by using a centrifugal separator instead of a squeezer, and improve quality. This satisfies both the yield and yield. (Deaeration, heat denaturation process) After the soymilk that comes out of the centrifuge is degassed, it is preheated (around 80℃), and live steam is blown into it.
The soybean protein is denatured by direct heating at temperatures between ℃ and 150℃. The reason for degassing before direct heating with steam has been mentioned above, but the main reason is to prevent browning of soymilk (so-called Go-yaki) and maintain a good color tone of tofu. To prevent uneven denaturation in a heat denaturation step and give uniform heat denaturation to soybean milk. To prevent the hardness of soymilk from becoming brittle. can be mentioned. Furthermore, since air bubbles are removed by this degassing, the use of an antifoaming agent in the grinding process can be omitted. Next, in the present invention, the soymilk that comes out of the centrifuge is degassed and preheated, and live steam is blown into it to produce a
Direct heating is performed at 150°C, which differs from conventional heating and boiling prior to separation in the following points. In other words, the effects of conventional boiling include thermal denaturation of proteins in soymilk, inactivation of trypsin inhibitors, and sterilization of bacteria in soymilk, but only by boiling below the boiling point. So, even though it is possible to kill general bacteria,
It is impossible to kill the spore-forming bacteria derived from the soybean raw material, and tens to hundreds of spore-forming bacteria survive in 1 ml of heat-treated liquid, causing a decline in the shelf life of the final product, tofu. . In contrast, in the present invention, since direct heating is performed above the boiling point, it is possible to achieve an almost sterile state by heating for a certain period of time (see Table 1).

[Table] In addition, in order to impart the desired thermal denaturation to soymilk, the heating temperature and heating time may be changed as appropriate. FIG. 3 shows the relationship between heating temperature and heating time and card tension. For example, if the heating temperature is 130°C or higher and the heating time is 6 seconds or more, tofu with poor elasticity will be produced, so heating for 6 seconds or less is appropriate. (Degassing and Cooling Step) Since direct heating with steam is employed in the heat denaturation step, the heated steam enters the product soymilk and dilutes it. Therefore, the product soymilk is again cooled by degassing and evaporation under reduced pressure. Note that the cooling temperature may be selected appropriately depending on the type of tofu product; for example, in the case of firm tofu, it is preferable to cool the soy milk to 70 to 80 °C, and in the case of filled tofu, it is preferable to cool the soy milk to 10 °C or less. . Next, another embodiment of the present invention will be described based on FIG. This embodiment has the following parts added to the first embodiment. Description of parts that overlap with the first embodiment will be omitted. In other words, the soybeans after grinding are passed through a separator and separated into okara and soy milk.Water is added to the separated okara, and then the soybeans are separated into okara and soy milk using a centrifugal separator such as a decanter. A circulation line is provided to separate the soymilk and use the resulting soymilk as water for adding water in the grinding process. Experimental example 1 300 kg of domestic soybeans (dehulling rate approximately 50%) were pulverized in approximately 1500 kg of warm water (60°C) using a Hibisline mill and a Mycolloider, and the resulting soybeans were made into soy milk and okara using a decanter. separated. Next, the obtained soymilk was degassed by passing through a dealerator, and then preheated to 80°C using a plate heat exchanger. Next, the mixture was directly heated at 130°C for 3 seconds using a steam injection, degassed using a deaerator, and cooled to 10°C using a plate heat exchanger to obtain soymilk for tofu. The solid content of the obtained soymilk was 12.5%, and the yield was
It was 63.3%. Using this soymilk and adding real bittern as a coagulant, filled tofu was produced by a known method. This tofu had good texture, flavor, and color, and had good storage stability without rotting even after one month of refrigeration. Table 2 shows the results of comparing the filled tofu obtained in the above experimental example with the filled tofu obtained by the conventional method.

[Table] (Note 1) Card tension measurement method: Hardness was determined using a rheometer (trade name) using adapter No. 1 at 10°C in the usual manner. Incidentally, tofu was judged based on the following criteria. Good for samples with card tension of 100g or more. Card tension Samples weighing less than 100g are too soft and have no commercial value. (Note 2) Measuring method of water separation rate; After cutting the sample into cubes of 5 mm on each side,
Centrifugation was performed for one minute, and the weight percent of the supernatant was defined as the water separation rate. The water separation rate indirectly indicates the degree of thermal denaturation of proteins. Example: Overheating; Card tension is weak and water separation rate is low. In case of insufficient heating; card tension is weak and water separation rate is high. The most ideal tofu is one with high card tension and low water separation rate. When investigating commercially available products, the water separation rate was approximately 11-21%.
Since the soy milk concentration (protein content) and type of coagulant are different, it is difficult to judge the superiority or inferiority in general. (Note 3) Bacterial count measurement method: To measure the viable bacterial count of tofu, use a ground product aseptically prepared in a homomixer as a sample, and calculate the viable bacterial count per 1 g of tofu after culturing at 37°C for 48 hours. I found the value. The medium for measuring the number of viable bacteria (standard agar medium) is
Sterile filtered 0.5% (w/w) TTC per 100ml
0.5 mL of the solution was added and used. Experimental example 2 300 kg of domestic soybeans (70% dehulling rate) were pulverized in approximately 1600 kg of warm water (40°C) using a Hibisline mill and a Mycolloider, and the resulting soybean was made into soy milk and okara using a decanter. separated. After adding warm water of approximately 40°C to the obtained okara and mixing it thoroughly, the soybean milk and okara were separated again, and the obtained soymilk with a low concentration was recycled for use in grinding soybeans. After degassing the soymilk thus obtained, it was preheated to 80℃ using a plate heat exchanger, heated at 120℃ for 10 seconds using steam injection, degassed using a deaerator, and heated to 80℃ using a plate heat exchanger. It was cooled to obtain soymilk for tofu. The solid content of the obtained soymilk was 13.0%, and the yield was
It was 73%. Using this soymilk, firm tofu and silken tofu were produced by a known method.
The obtained tofu had good texture, flavor, and color. [Effects] According to the method of this invention, there is a step of hydrolyzing the soybean protein without denaturing the soybean protein under a temperature condition of 20°C or higher and 70°C or lower without immersing the soybean, and boiling the soybean after the grinding. a step of separating okara and soymilk directly using a centrifuge without any process; and a step of heating the soybean milk directly with steam at a temperature of 100°C to 150°C after deaeration to heat-denature the soybean protein. The process of producing soymilk for tofu is simplified by further comprising the steps of deaeration and cooling, and it is possible to extract soymilk suitable for tofu production without heat denaturation without using the process of soaking soybeans. In addition, it is possible to provide a method for producing soymilk for tofu that prevents discoloration through deaeration and that can produce tofu with a desired hardness without uneven sterilization (uneven denaturation) in the next heat denaturation step. Problems such as the treatment of water used for soaking or washing, variations in the quality of tofu due to uneven boiling of soymilk, weak curd found in filled tofu, and short shelf life of tofu have been solved all at once, and high concentration It is possible to obtain soy milk for tofu of a certain quality, and to produce high quality tofu using 100% real bittern. Furthermore, since deaeration is performed before direct heating with steam, addition of an antifoaming agent can be omitted in the grinding process, and in other words, an additive-free product can be provided.

[Brief explanation of drawings]

FIG. 1 is a flowchart of the first embodiment. Figure 2 is a graph of the relationship between temperature and yield. Figure 3 is a graph showing the relationship between heating time and card tension. FIG. 4 is a flowchart of the second embodiment. Figure 5 is a flowchart of the conventional example.

Claims (1)

[Claims] 1. A process of hydrolyzing soybean protein without denaturing it by heating at a temperature of 20°C to 70°C without soaking the soybean, and directly processing the ground soybean without boiling it. A process of separating okara and soy milk using a centrifuge, and then degassing the soy milk and heating it to 100℃ using steam.
A method for producing soymilk for tofu, characterized by comprising a step of thermally denaturing soybean protein by direct heating at a temperature of 150°C or less, and a further step of degassing and cooling. 2. The method for producing soymilk for tofu according to claim 1, characterized in that the hydrolysis is carried out in multiple stages. 3. Claim 2, characterized in that the first stage of hydrolysis grinding is coarse grinding, and the second stage is fine grinding.
The method for producing soymilk for tofu as described in Section 1.