JP2013031438A - Frozen dry tofu and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frozen dry Tofu (bean curd) having smooth and soft texture.SOLUTION: The frozen dry Tofu is obtained by freeze drying Tofu, and the frozen dry Tofu has a protein content of 32.5 to 37.5 wt.%. The method of producing frozen dry Tofu includes the steps of obtaining Tofu by coagulating a soybean mixture containing soybean milk with a coagulant, and freeze-drying the obtained Tofu. The soybean milk is obtained by filtering and separating raw soybean paste obtained by grinding soybeans having a content of protein of 30 to 35 wt.% and having been soaked in water, and the soybean milk has a solid content of 8 to 12 Brix.

Description

  The present invention relates to freeze-dried tofu and a method for producing the same, and particularly relates to freeze-dried tofu and a method for producing the same that can obtain the original texture of tofu by reconstitution with hot water.

  Freeze-dried tofu obtained by freeze-drying tofu is widely used as an ingredient for instant miso soup. However, if the tofu is simply lyophilized, protein denaturation is likely to occur, and it becomes spongy and becomes so-called “frozen tofu” (also known as “Takano Tofu” or “frozen tofu”). There is a problem that it is difficult to obtain a feeling.

  Thus, studies have been made to improve the texture when lyophilized tofu is restored. For example, Patent Document 1 proposes producing freeze-dried tofu with improved texture by using soymilk to which oligosaccharides or polysaccharides are added. Patent Document 2 proposes producing freeze-dried tofu with improved texture by using soy milk to which enzymes, thickeners and starch are added. Patent Document 3 proposes producing freeze-dried tofu with improved texture by using soy milk to which starch paste is added.

  However, although the freeze-dried tofu proposed by the said patent documents 1-3 improved the texture to some extent, the further improvement is requested | required.

JP-A-10-271972 JP-A-11-313630 JP 2002-34488 A

  The present invention provides a freeze-dried tofu having a smooth and soft texture and a method for producing the same in order to solve the above-described conventional problems.

  The present invention is freeze-dried tofu obtained by freeze-drying tofu, wherein the protein content in the freeze-dried tofu is 32.5 to 37.5% by weight.

  Further, the present invention is a method for producing the above freeze-dried tofu, comprising a step of adding a coagulant to a soymilk mixed solution containing soymilk to coagulate to obtain tofu, and a step of freeze-drying the obtained tofu The soymilk is obtained by immersing soybeans having a protein content of 30 to 35% by weight in water and filtering and separating the koji juice obtained by grinding. The density is Brix8 to Brix12.

  The present invention can provide freeze-dried tofu having a smooth and soft texture by setting the protein content in freeze-dried tofu to 32.5 to 37.5% by weight. Moreover, according to the manufacturing method of this invention, protein content is 32. by adjusting the density | concentration of the solid content of soybean milk to Brix8-Brix12 using the soybean whose protein content is 30-35 weight%. Freeze-dried tofu that is 5 to 37.5% by weight can be easily obtained.

FIG. 1 is a scanning electron microscope (SEM) photograph of the surface of freeze-dried tofu obtained in an example of the present invention. FIG. 2 is a scanning electron microscope (SEM) photograph of the surface of freeze-dried tofu obtained in one comparative example of the present invention.

  In the lyophilized tofu, the protein content is 32.5 to 37.5% by weight, preferably 34 to 36% by weight, and more preferably 35 to 36% by weight. When the protein content in the freeze-dried tofu is 32.5 to 37.5% by weight, a soft and smooth texture can be obtained when restored. Further, when the protein content is 33.5 to 36.5% by weight, it has a soft and smooth texture and has few cracks and is excellent in appearance. When making freeze-dried tofu having a large size of 10 mm, 10 mm, and 8 mm in length, width, and height, respectively, if the protein content is 33 to 36% by weight, there are few cracks and excellent appearance. In the present invention, “protein content” refers to that measured by the Kjeldahl method.

  The freeze-dried tofu preferably has a restored hardness in the range of 0.05 to 0.14 kg, more preferably 0.07 to 0.13 kg, and 0.08 to 0.12 kg. More preferably. In the present invention, the “hardness after restoration” means that after restoring freeze-dried tofu with hot water at 95 ° C., using a texturometer GTX-2 (manufactured by Zenken Co., Ltd.), a jig 9 mmφ chromium, clearance 1.2 mm, Hardness measured under measurement conditions of voltage 10V and mastication speed 6 times / minute.

The freeze-dried tofu, it is preferable that the size of the ice crystals trace is 15000Myuemu ² or less, more preferably 2100～7500Myuemu ^2, more preferably from 2100～7000Myuemu ^2, a 2100～6500Myuemu ² Is particularly preferred. In the present invention, the “size of ice crystal trace” means that a scanning electron micrograph of the surface of freeze-dried tofu is converted into an image in TIFF format, and an image in TIFF format is converted to RGB0 (white) with dots less than RGB140. This means that after binarizing so that dots of RGB140 or more are displayed as RGB255 (black) and binarizing, an area composed of continuous black dots is used as an ice crystal trace, and the area is calculated by image analysis software. . A region having an area of 2000 μm ² or less (corresponding to a circle having a diameter of 50 μm) is removed as noise. When the ice crystal trace is 15000 μm ² or less, the texture is excellent and the shape retention is good.

  Although the said freeze-dried tofu is not specifically limited, For example, it can obtain by freeze-drying the tofu obtained by adding a coagulant | solidification agent to the soymilk mixed liquid containing soymilk, and coagulating.

  First, a soymilk mixed solution is prepared. The soy milk is not particularly limited, and various soy milks prepared by a known method can be used. For example, it can be obtained by immersing soybeans in water and filtering soup obtained by grinding to separate soy milk. In the above, the soy milk after separation is preferably boiled at 93-100 ° C, more preferably 97-100 ° C. In boiling, it is preferable to add an antifoaming agent to the soy milk. As said antifoamer, a silicone resin, glycerol fatty acid ester, etc. can be used, for example.

  Although it does not specifically limit as said soybean, From a viewpoint of making content of protein in freeze-dried tofu into 32.5-37.5 weight%, soybean with a content of (crude) protein of 30-35 weight% It is preferable to use it. Further, from the viewpoint that the protein content of freeze-dried tofu is easily 32.5 to 37.5% by weight, the concentration of the solid content of the soymilk is preferably Brix8 or more, more preferably Brix9 to Brix12. Yes, more preferably Brix10 to Brix11.

  The soymilk mixed solution preferably contains starch. Starch can prevent freezing and denaturation of soy protein, and when restored, the original smooth texture of tofu tends to be obtained. The starch is not particularly limited as long as it is a edible starch. For example, raw starch obtained from cereals and potatoes, or processed starch obtained by processing these can be used. Specific examples include potato starch, wheat starch, corn starch, and tapioca starch. From the viewpoint of not reducing the texture and flavor after restoration of freeze-dried tofu, the starch content in the soymilk mixture is 5.5 to 8.3 parts by weight with respect to 100 parts by weight of the solid content of soymilk. It is preferably 5.5 to 7.4 parts by weight, more preferably 6.1 to 6.7 parts by weight.

  The soymilk mixture preferably further contains an oligosaccharide. Oligosaccharide can prevent soy protein from being frozen and denatured, and when it is reconstituted with water, the original smooth texture of tofu is easily obtained. Although it does not specifically limit as said oligosaccharide, For example, maltose, tefinose, stachyose etc. can be used. From the viewpoint of not lowering the texture and flavor after restoration of freeze-dried tofu, the content of oligosaccharides in the soymilk mixture is 12.0 parts by weight or less with respect to 100 parts by weight of the solid content of soymilk. Preferably, the amount is 7.5 to 11.2 parts by weight, and more preferably 8.2 to 9.0 parts by weight.

  Moreover, the said soymilk liquid mixture may contain the quality modifier which is effective in the quality improvement of freeze-dried tofu other than starch and oligosaccharide as needed. For example, guar gum, locust bean gum, carrageenan, xanthan gum, gellan gum, curdlan, glucomannan, gelatin, sodium alginate, pectin used to improve texture, prevent water separation, improve shape retention, and prevent cracking during restoration A thickener such as agar may also be included.

  Next, a coagulant is added to the soymilk mixture to obtain a soymilk coagulant. The coagulant is not particularly limited as long as it is a coagulant for tofu. For example, divalent metal salts such as calcium chloride, magnesium chloride and calcium sulfate, acids such as glucono delta lactone, lactic acid, malic acid and citric acid can be used. The amount of the coagulant added may be the same amount as in the case of normal tofu production. For example, when calcium sulfate is used as a coagulant, it is preferably 5.4 to 7.2 parts by weight, preferably 5.9 to 6.5 parts by weight, based on 100 parts by weight of the solid content of soy milk. More preferred.

  Next, the soymilk coagulation liquid is coagulated to obtain tofu. The heating temperature for coagulation may be higher than the temperature at which the coagulant acts. For example, it is preferable to hold | maintain for 15 to 30 minutes at the product temperature of 75-90 degreeC, and it is more preferable to hold | maintain for 15 to 30 minutes at the product temperature of 80-85 degreeC. The coagulation is preferably performed by filling the soymilk coagulation liquid into a desired container such as a filled tofu container, a coagulation can or a filling tray.

The tofu obtained by heat coagulation as described above is subjected to a cooling treatment at 0 to 10 ° C. and then freeze-dried. Usually, before being lyophilized, the raw tofu is cut to an appropriate size, eg length x width x height 15mm x 12mm x 8mm, 12mm x 12mm x 12mm, 12mm x 12mm x 6mm, etc. To be frozen. Freezing can be performed by various methods such as air freezing, air blast freezing, contact freezing, immersion freezing, liquefied gas spray freezing, and vacuum freezing. The temperature for freezing is not particularly limited, but is generally in the range of -10 ° C to -100 ° C, preferably -20 ° C to -70 ° C. If the freezing is performed by rapid freezing, freezing and denaturation of tofu is prevented, and an excellent quality freeze-dried tofu can be obtained. Further, the freezing, when vacuum freeze, the smaller the size of the ice crystals traces, for example, in 15000Myuemu ² or less, preferably becomes 2100～7500Myuemu ^2, more preferably becomes 2100～7000Myuemu ^2, more preferably 2100 It becomes ˜6500 μm ² and the texture when restored is more excellent. When freezing is performed by vacuum freezing, the freezing condition under vacuum may be set to a vacuum pressure such as 4 Torr (533.2 Pa) or less so that the temperature becomes equal to or lower than the eutectic point of tofu. After freezing, freeze-dry with a conventional vacuum freeze dryer. The shelf heating temperature during freeze-drying is preferably 40 to 90 ° C, more preferably 40 to 60 ° C.

  The freeze-dried tofu can be easily restored with hot water, and can be used as an ingredient for instant food or liquid food. Instant food includes instant noodles and instant soup. Examples of liquid foods include ramen, soup, miso soup, and pots. From the viewpoint of excellent resilience, it is preferable to restore with hot water at 80 ° C. or higher, more preferably with hot water at 90 ° C. or higher.

  The present invention will be specifically described below with reference to examples. In addition, this invention is not limited to the following Example.

Example 1
Soy beans having a protein content of 33% by weight were immersed in water and ground to obtain soymilk. After adding a silicone resin formulation (“KM-72F” manufactured by Shin-Etsu Chemical Co., Ltd.) having a silicone resin content of 30% by weight as an antifoaming agent to the separated soymilk to 0.0133% by weight, Boiled at 97 ° C for 7 minutes. Then, after adjusting so that the density | concentration of the solid content of soymilk might be Brix8, it cooled to 70 degreeC. To soy milk after cooling, starch, water candy (“Hymaltose syrup” manufactured by Nippon Food Processing Co., Ltd.), and water are 0.665% by weight, 1.200% by weight, 2.933% by weight, respectively. To obtain a soymilk mixture. Calcium sulfate as a coagulant and water were added to the obtained soymilk mixture so as to be 0.622% by weight and 4.156% by weight, respectively, to obtain a soymilk coagulant. The soymilk coagulation liquid thus obtained was poured into a filling tray, heated to 80 ° C. with steam, and then held for 15 minutes to coagulate the soymilk coagulation liquid to obtain tofu. After cooling the tofu to a product temperature of about 5 ° C, it was cut so that the length x width x height was 15 mm x 12 mm x 8 mm, placed in a vacuum freeze dryer and frozen under a vacuum pressure of 100 Pa or less. . Then, it dried with the vacuum freeze dryer until the water content became 3% or less, and freeze-dried tofu was obtained.

(Example 2)
Lyophilized tofu was obtained in the same manner as in Example 1, except that the solid content of soymilk was adjusted to Brix9.

(Example 3)
Lyophilized tofu was obtained in the same manner as in Example 1 except that the solid content of soymilk was adjusted to Brix10.

Example 4
Lyophilized tofu was obtained in the same manner as in Example 1, except that the solid content of soymilk was adjusted to Brix11.

(Example 5)
Lyophilized tofu was obtained in the same manner as in Example 1 except that the concentration of soy milk solids was adjusted to Brix 12.

(Comparative Example 1)
Lyophilized tofu was obtained in the same manner as in Example 1 except that the concentration of soy milk solids was adjusted to Brix13.

(Comparative Example 2)
Freeze-dried tofu was obtained in the same manner as in Comparative Example 1 except that freezing was not performed under vacuum and air blast freezing was performed for 120 minutes in an atmosphere of −30 ° C.

(Comparative Example 3)
The soymilk was adjusted so that the solid content was Brix7, and freeze-dried tofu was produced in the same manner as in Example 1. However, it was not possible to obtain freeze-dried tofu with shape retention.

(Comparative Example 4)
A freeze-dried tofu was obtained in the same manner as in Example 1 except that soybean having a protein content of about 40% by weight was used and the soymilk solid content was adjusted to Brix11.

(Comparative Example 5)
Soy milk was prepared in the same manner as in Example 1 except that soybean having a protein content of about 40% by weight was used and the soymilk solid content was adjusted to Brix13. The obtained soymilk was cooled to 70 ° C. To soy milk after cooling, starch, syrup (“Hymaltose syrup” manufactured by Nippon Food Processing Co., Ltd.), and water are 0.998 wt%, 1.800 wt%, and 2.000 wt%, respectively. To obtain a soymilk mixture. Lyophilized tofu was obtained in the same manner as in Example 1 except that the obtained soymilk mixed solution was used.

  The protein content of freeze-dried tofu obtained in Examples and Comparative Examples, the size of ice crystal traces, and the hardness after reconstitution of freeze-dried tofu with hot water were measured as follows, and the results are shown in the table below. It was shown in 1. In addition, the texture and appearance of the freeze-dried tofu obtained in Examples and Comparative Examples were subjected to sensory evaluation as follows, and the results are shown in Table 1 below. 1 and 2 show SEM photographs of the surfaces of the freeze-dried tofu obtained in Example 3 and Comparative Example 2, respectively.

(Protein content)
The protein content was measured by the Kjeldahl method. To the freeze-dried tofu, a decomposition accelerator and concentrated sulfuric acid were added, decomposed by heating, allowed to cool, and 30% sodium hydroxide solution was added. Thereafter, the mixture was distilled by heating, collected in a 4% boric acid solution, and titrated and calculated with a 0.05 mol / L sulfuric acid standard solution.

(Size of ice crystal trace)
The surface of the freeze-dried tofu was photographed with a scanning electron microscope (SEM) and converted into an image in TIFF format. The TIFF format image was binarized so that dots less than RGB140 were displayed as RGB0 (white) and dots higher than RGB140 were displayed as RGB255 (black). After binarization, an area composed of continuous black dots was used as an ice crystal trace, and the area was calculated using image analysis software to obtain the size of the ice crystal trace. A region having an area of 2000 μm ² or less (corresponding to a circle having a diameter of 50 μm) was removed as noise.

(Hardness)
Using a texturometer GTX-2 (manufactured by Zenken Co., Ltd.), the hardness of the freeze-dried tofu that had been reconstituted with hot water at 95 ° C. for 30 seconds was measured. The calculation method of hardness was measured as the maximum value of the peak of the waveform, and the hardness (kg) = the height of the first peak / the input voltage was calculated. As measurement conditions, the jig was 9 mmφ chrome, the clearance was 1.2 mm, the voltage was 10 V, and the mastication speed was 6 times / minute.

(Sensory evaluation of texture 1)
95 ° C. hot water was poured into the freeze-dried tofu, and the subject was allowed to eat the freeze-dried tofu restored after 30 seconds, and the softness was evaluated in the following three stages. There were 14 subjects, and the average values are shown in Table 1 below.
3 Very soft (similar to normal silken tofu)
2 Soft (just like normal cotton tofu)
1 Hard (Normal to Koya Tofu)

(Sensory evaluation of texture 2)
95 ° C. hot water was poured into the freeze-dried tofu, and the subject was allowed to eat the freeze-dried tofu restored after 30 seconds, and the smoothness was evaluated in the following three stages. There were 14 subjects, and the average values are shown in Table 1 below.
3 Very smooth (ordinary to silken tofu)
2 Smooth (normal cotton tofu)
1 There is a rough surface (normal Koya tofu)

(Sensory evaluation of appearance)
The appearance of freeze-dried tofu that was restored after 30 seconds was poured into freeze-dried tofu and evaluated in three stages as follows. There were 14 subjects, and the average values are shown in Table 1 below.
3 Few cracks 2 Slightly cracked 1 Many cracks

From the results shown in Table 1 above, it was found that the freeze-dried tofu of Examples having a protein content of 32.5 to 37.5% by weight has a smooth and soft texture after restoration. Moreover, it turned out that there are few cracks after a restoration | restoration as content of protein is 33.5-36.5 weight%, and it is excellent in an external appearance. Moreover, it turned out that it has a smoother texture after restoration | restoration as content of protein is 33 to 36 weight%. It was found that when the protein content was 34 to 36% by weight, it had a soft and smooth texture after restoration, had few cracks and was excellent in appearance. In freeze-dried tofu, having the above-mentioned appearance and texture indicates high quality and is close to silk-strained tofu. On the other hand, the freeze-dried tofu of Comparative Example 1 and Comparative Example 2 having a protein content of 38% by weight was hard and poor in texture after restoration. In particular, as can be seen from FIG. 2, the freeze-dried tofu of Comparative Example 2 that was not frozen under vacuum had an ice crystal trace size exceeding 20000 μm ² , and the hardness increased 0.14 kg after restoration. It was over and the texture was bad. Moreover, the freeze-dried tofu of Comparative Example 4 and Comparative Example 5 in which the protein content exceeds 37.5% by weight also had a poor texture after restoration. In particular, the starch and the freeze-dried tofu of Comparative Example 5 in which the amount of starch candy is 1.5 times the amount of Example 1 also exceeds 37.5% by weight of the protein content. It was hard and had a bad texture.

Claims (5)

A freeze-dried tofu obtained by freeze-drying tofu,
The freeze-dried tofu in which the protein content in the freeze-dried tofu is 32.5 to 37.5% by weight.   The freeze-dried tofu according to claim 1, wherein the freeze-dried tofu has a restored hardness of 0.07 to 0.14 kg. The freeze-dried tofu according to claim 1 or 2, wherein the freeze-dried tofu has an ice crystal trace size of 15000 µm ² or less. A method for producing the freeze-dried tofu according to any one of claims 1 to 3,
Adding a coagulant to the soymilk mixture containing soymilk and coagulating to obtain tofu;
Including freeze-drying the obtained tofu,
The soy milk is obtained by immersing soybeans having a protein content of 30 to 35% by weight in water and filtering and separating the koji juice obtained by grinding. The soy milk has a solid content concentration of A method for producing freeze-dried tofu, which is Brix8 to Brix12.   The method for producing freeze-dried tofu according to claim 4, comprising a step of vacuum-freezing tofu before freeze-drying, wherein the degree of vacuum at the time of vacuum freezing is 100 Pa or less.