JPH03216164A - Production method of soy milk for hard tofu - Google Patents

Abstract

PURPOSE:To obtain the title soymilk having good taste and suitable for production of rigid aseptic soybean curd by preparing a soymilk so as to satisfy specific soluble sugar content in soymilk using a specific ultrafilter membrane of fractionated molecular weight. CONSTITUTION:Round soybean is immersed in water for 6-20hr and ground and preferably heated to 90-120 deg.C and filtered to give soymilk. The soymilk is prepared using an ultrafilter membrane (e.g. zirconia ceramic membrane) so as to satisfy the formula [X is concentration (%) of protein, provided that X is >= 3.61; Y is ratio of soluble sugar content to protein, provided that 0<=Y<0.35] to provide the aimed soymilk.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application Field The present invention relates to a method for producing soymilk for hard tofu, particularly soymilk suitable for producing hard aseptic tofu.

Prior Art and Problems> Reflecting the recent health-conscious eating habits, tofu is attracting a lot of attention both domestically and internationally. However, tofu has a distribution problem in terms of its shelf life due to microbial contamination.To solve this problem, for example, tofu can be manufactured on an automated line with sanitary properties, which is guaranteed for about one month at low temperatures.
Aseptically packed tofu, retort tofu, etc. that can be distributed at room temperature are being considered.

However, all of the tofu obtained by these methods are silken tofu, and it is difficult to produce tofu having a texture similar to that of firm tofu.

On the other hand, with the diversification of dietary habits, there is a demand for the supply of tofu that is harder than before, and as a countermeasure,
For example, a method of adding isolated soy protein to soy milk (Japanese Unexamined Patent Publication No. 5
No. 8-78559, Japanese Unexamined Patent Publication No. 62195262), etc. have been proposed.

However, adding isolated soy protein to soy milk has the problem of not only the difficulty of dispersing it in the process, but also the problem that the resulting tofu has a reddish tinge and the flavor deteriorates due to high-temperature heating for sterilization. In addition, methods for producing hard tofu include reducing the amount of water added to raw soybeans or concentrating soymilk in order to increase the protein content in soymilk.

However, the former method has a problem in terms of efficiency because the protein recovery rate decreases.

Regarding the latter, it is also known that soymilk is concentrated using a selective permeation membrane, but this method uses a reverse osmosis membrane or a membrane with a relatively small molecular weight cut-off of 5,000 to avoid changing the components as much as possible. The following ultrafiltration membrane is used, and it is not necessarily satisfactory for soy milk for hard tofu.

Under these circumstances, in order to produce hard tofu with good flavor, especially hard aseptic tofu, the present inventors used ultrafiltration membranes with various molecular weight cut-offs to improve filtration efficiency, protein loss, and soluble sugar content. After conducting tests and studies without taking into account the removal rate of However, it was found that the hardness of soymilk treated in this way increases in proportion to the removal rate of low-molecular-weight components using the soluble sugar content as an index.

The present invention was completed based on these findings, and the protein concentration of soymilk is reduced to X% (X≧3.61).
, the ratio of soluble sugar to protein is Y (however, 0≦Y
< 0.35), the soy milk is prepared using an ultrafiltration membrane with a molecular fraction i of 30,000 or more so as to satisfy the following formula Y≦0.093X − 0.336. This is a method for producing soymilk for hard tofu.

The present invention will be specifically explained below.

Means for Solving the Problems> The raw soymilk used in the present invention is no different from the production of soymilk in conventional tofu production.

For example, whole soybeans are soaked in water for 6 to 20 hours, the sufficiently swollen soybeans are ground, and the resulting soybeans are heated to about 90 to 120°C and then filtered, or the soybeans are heated after filtration. However, the former is preferable. It is also possible to directly subject raw soymilk to membrane treatment at low temperatures.

When removing soluble sugar by soaking, dehulled soybeans have been preferably used to increase removal efficiency, but whole soybeans may be used in the present invention. Of course, dehulled soybeans can also be used.

The protein concentration of soy milk is 1.5-5.0%, especially 20%.
~45% is preferred. The protein concentration was determined by multiplying the total nitrogen amount measured by the Keltal method by 571.

In addition, if soy milk is homogenized in advance, the efficiency of membrane treatment can be increased, and for the purpose of sterilization,
Microbial contamination during membrane treatment can be prevented by performing heat treatment for 50°0105 to 120 seconds.

Such raw soymilk is treated using an ultrafiltration membrane having a molecular weight cut off of 30,000 or more to remove soluble sugars.

Fractionated molecules! If a membrane with a molecular weight cut-off of 30,000 or less is used, the filtration efficiency will be poor, and an ultrafiltration membrane with a molecular weight cut-off that is too thick will also pass the protein in soymilk, resulting in a decrease in the raw material utilization rate. A film of about 000 to 150,000 is preferred.

The ultrafiltration membranes used are polysulfone, polyolefin,
The membrane may be made of a synthetic polymer material such as polyacrylonitrile, or a zirconia ceramic membrane, and may be of ordinary shape such as a flat membrane or hollow fiber. Soluble sugar can be removed to some extent by simply concentrating it with an ultrafiltration membrane, or in the case of soy milk with a high protein concentration, so-called "dialysis", which actively removes low-molecular components without adding water, may be effective. filtration is required. In addition, when performing retort processing, the ratio Y of soluble sugar content to protein is 0.
．． 17 or less (it is preferable to remove 3), this value corresponds to 45% or more of the soluble sugar content in the raw soybean.In addition, the soluble sugar content / protein of normal soy milk (soy milk without sugar removal) The amount is about 0.35%. If the removal of soluble sugar content is insufficient, tofu with sufficient hardness will not be obtained and the quality will deteriorate due to heating odor and browning during retort processing.

Soluble sugar refers to water-soluble sugar that is eluted by immersion in water, grinding, etc., and its total amount can be determined by the following method.

That is, raw soybeans are soaked in a certain amount of water, then ground together with the soaking water, and the resulting soy milk is adjusted to pH 4 with hydrochloric acid.
．． 5, the protein is precipitated, centrifuged, and the sugar concentration of the supernatant is determined as the amount of glucose using the phenol-sulfuric acid method.

The soymilk thus obtained can be suitably used as soymilk for hard tofu, especially hard aseptic tofu.

In the present invention, in order to quantitatively measure the hardness of tofu, a tensipresser (manufactured by Taketomo Denki) was used to cut the tofu into 17 mm square cubes, crush them by 12 mm with a circular plunger with a diameter of 40 mm, and crush them with a plunger. The amount of work from the time it came into contact with the tofu until it broke was measured, and the hardness was expressed as a reading on an integrated meter.

The numerical values measured in this manner were approximately 350 to 550 for the commercially available cotton type and 450 to 650 for the commercially available cotton type. For commercially available tofu like this, a hardness of 1,000 or more was required in order to clearly notice the difference in hardness.

Therefore, the present invention aimed for the measured value to exceed 1,000.

An experimental example is shown below.

Experimental Example 1 Whole soybeans were immersed in tap water for 16 hours to swell and then ground. The raw soybeans obtained were heated at 105°C for 30 seconds and filtered to obtain soymilk with a protein concentration of 5%. This was sterilized by heating at 125° C. for 10 seconds using a plate heater, and membrane treatment was performed while adding water to this raw soymilk 52 until the ratio of soluble sugar content to protein content became 0.16.

The filter used was Amicon's TS5E type (Guiaflor membrane 150 mmφ x 5 stages), and the ultrafiltration membrane was Amicon's YM (polysaccharide) and XM (vinyl/acrylic copolymer) series. and
Operating conditions are pressure 15kg/cm2・G, flow rate 50JIL.
/hr, soy milk temperature 5°C. The results are shown in Table 1.

Table 1 *1 Average permeation flow rate ITLi! / 0.1 rrr/hr Experimental Example 2 The same raw material soymilk 202 used in Experimental Example 1 was heated using Carbosep membrane (zirconia ceramic membrane) manufactured by Sumitomo Heavy Industries Envirotech Co., Ltd. at a pressure of 2.0 kg/cm2・G and a flow rate of Nk.
420 B/hr, while adding water under the operating conditions of soy milk temperature 45°C, the amount of soluble sugar/the amount of protein was 0.1
Processed until it reached 6.

The results are shown in Table 2.

Table 2 From the above experimental examples, the molecular weight cutoff is 30.000 to 150,00.
It can be seen that the ultrafiltration membrane of No. 0 can efficiently remove sugar.

Experimental Example 3 Raw material soymilk 209 obtained by a conventional method was heated using Carbosep membrane M-1 (zirconia ceramic membrane) manufactured by Sumitomo Heavy Industries Envirotech Co., Ltd. at a pressure of 240 kg/cm2 G, a flow rate of 420 Q/hr, and a soy milk temperature of 450 C. Under the operating conditions, water was not added until the protein concentration was 90% and the soluble sugar content/protein content was 0.11.

To this, water or the filtrate obtained during concentration is added as is, or the concentrated filtrate is added, and the protein concentration is 55 to 85%.
Make soy milk adjusted so that the soluble sugar content/protein content is 011 to 035, add G D L to each and boil at 120°C.
1. Retort tofu was obtained by pressure and heat sterilization for 50 minutes.

The hardness of these tofu was measured using a tensipresser and the results are shown in FIG.

From FIG. 1, it can be seen that as the value of soluble sugar content/protein content decreases, the hardness increases linearly.

In addition, for the hardness to exceed 1,000, the ratio of soluble sugar content to protein content varies depending on the protein concentration. The relationship between the minimum soluble sugar content and protein content ratio Y to the protein concentration of soymilk X% for hardness to exceed 1,000 is
Reading from the figure, it is as shown in Table 3.

Table 3 There is a linear relationship between X and Y in Table 3. Therefore, when calculating the regression equation from these values, Y = 0.093X - 0.336 (correlation coefficient r = 0.9855) becomes.

In other words, Y≦0.093X − 0.336 as X, Yl
)＜It will be a good thing if it is satisfied. Here, Y is a value smaller than 035 (soy milk without sugar removal) and larger than 0. Also, X is 361 or more (that is, 1
Even if 00% sugar is removed, the hardness will be 1 if the protein concentration is less than 3.61.
, 000).

Furthermore, when X is 7.38% or more, Y=0.35 or more, and it is possible to obtain tofu with a hardness of 1,000 or more even if the tofu is concentrated without removing sugar. However, if soy milk with a protein concentration of 738% or more is not sugar-removed, the viscosity will increase and there will be problems with operability.
, 5.5≦X≦85.

As described above, when the protein concentration is X and the ratio of soluble sugar M/protein amount is Y, XSY is Y≦0.093X
- If soy milk is prepared to satisfy the formula 0336 and tofu is produced by aseptic filling or retort processing, hard tofu with excellent flavor can be obtained.

Examples of the present invention are shown below.

Example 1 Whole soybeans were soaked in tap water for 16 hours, then 8 times the amount of water was added to the swollen soybeans, and then ground to make raw gourd, which was heated to 105°C.
1 After heating for 30 seconds, the mixture was filtered using a screw decanter to obtain soymilk. The protein concentration of this soymilk was 38%, and the soluble sugar content was 135%.

This soymilk was tested using a Carbosep 2SV7C test machine manufactured by Sumitomo Heavy Industries Envirotech at an operating pressure of 4 kg/C.
rI+2・G, operating temperature 50°C, flow rate 500Q/hr
After concentrating with water, remove low molecular components while adding water,
Soy milk with a soluble sugar content of 082% and a protein concentration of 70% was obtained.

The value of soluble sugar content/protein content of this soymilk is 0117, which satisfies Y≦0.32.

This soymilk was homogenized using a high-pressure homogenizer, then deaerated, heated at 120°C for 3 seconds using an indirect heating sterilizer, cooled immediately, and added 0% GDL as a coagulant.
After adding 35% and placing it in a gusset bag made of polypropylene laminated with aluminum and sealing it, I20
C. for 50 minutes to obtain retort tofu.

The hardness of this tofu is 1 according to the tensipresser measurement value.
, 670, and there was no browning and the flavor was excellent.

Example 2 Soybean milk was obtained using soybeans obtained by soaking dehulled soybeans in warm water at 50° C. for 2 hours. The protein concentration of this soy milk is 536%.
Soluble sugar content was 0.75%. After deaeration treatment, 1406C,
The mixture was sterilized for 3 seconds, cooled to 50°C, and homogenized using a high-pressure homogenizer under aseptic conditions. Then, it was introduced into a pre-sterilized CarboSep and concentrated, resulting in a protein concentration of 7.15.
%, Soluble sugar content 075% (Soluble sugar content/Protein content O
1O) of soymilk was obtained and stored in a sterile tank.

This soymilk satisfies Y≦0.33. GDL aqueous solution sterilized using a Menpuran filter was mixed aseptically at a ratio of 0.35% per volume of soymilk, filled and sealed in a container previously sterilized with hydrogen peroxide under an aseptic atmosphere, and heated to 90°C. The tofu was immersed in water for 60 minutes to solidify to obtain aseptic packaged tofu.

The hardness of the tofu thus obtained was measured using a tensipresser and a value of 1720 was obtained.

No changes were observed even after storage at room temperature for 6 months, and the hard tofu had a good flavor.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between soluble sugar content/protein content and hardness at each soymilk concentration. ? ●■● −〇１〇−△■△ × × Mouth soy milk concentration 85% 75% 6.5% 60% 55%

Claims (1)

[Claims] The protein concentration of soymilk is X% (however, X≧3.61), and the ratio of soluble sugar content to protein is Y (however, 0≦Y<0.
35), hard tofu characterized by preparing soymilk using an ultrafiltration membrane having a molecular weight cut off of 30,000 or more so as to satisfy the following formula Y≦0.093X−0.336 Method for producing soymilk.