JP7207953B2 - Method for producing dried fried tofu - Google Patents

Description

The present invention relates to a method for producing dried fried tofu.

Conventionally, dry dried fried tofu is known as an ingredient for instant foods and the like (see, for example, Patent Documents 1 to 3), and dried fried tofu is produced by roughly two methods. The first method is to make fried tofu using soymilk traditionally obtained from whole soybeans and then dry it. It is a method of making and drying.

Of these, when making dried fried tofu by the traditional method of making fried tofu using soymilk obtained from whole soybeans and drying it, normal hot air drying has poor resilience, so microwave and hot air drying are used. A drying technique used and a technique for impregnating soymilk with gas are disclosed (see Patent Documents 1 and 2).

However, when dry fried tofu is prepared using these methods and reconstituted with hot water, it has generally good resilience and texture, but it is difficult to make the tissue after fried to a homogeneous foam state, and it depends on the flavor. It was difficult to suppress the occurrence of "stains" in fried tofu after drying due to uneven seasoning and uneven expansion due to microwaves. Deep-fried tofu with "stains" has an uneven texture, uneven taste, and depending on the degree, the seasoning does not dry out, causing spoilage, so it had to be discarded. In addition, if there are large cavities inside the deep-fried tofu after frying, the structure weakens when the fried tofu is puffed and dried by microwaves. As a result, there were problems such as the bulging part cracking and the texture becoming hard.

Japanese Patent No. 3007769 Japanese Patent No. 3457015 Japanese Patent No. 4558691

An object of the present invention is to produce dried fried tofu that suppresses the occurrence of "stains" and "blisters" in fried tofu after drying due to uneven seasoning due to seasoning and uneven swelling due to microwave drying.

The inventors attempted to produce dried fried tofu with a homogeneous spongy texture. However, within the range of the conventional air mixture amount, it was not possible to sufficiently suppress the occurrence of "stains" and "swelling" of fried tofu after drying due to uneven seasoning due to seasoning and swelling due to microwaves. Therefore, as a result of intensive research, by mixing soymilk with an amount of air that far exceeds the amount of air mixed in the past, by deliberately suppressing the spread of fried tofu during frying, uneven seasoning due to seasoning and microwaves The inventors have found that it is possible to produce dried fried tofu in which the occurrence of "stains" and "blisters" due to uneven swelling can be sufficiently suppressed, leading to the present invention.

That is, a soymilk producing step of producing soymilk from whole soybeans, an air mixing step of mixing air into the soymilk produced in the soymilk producing step, and a coagulant for the soymilk mixed with air in the air mixing step A coagulation step of producing a soymilk coagulum by adding and reacting, and a tofu dough production step of dehydrating and molding the soymilk coagulum produced in the coagulation step to produce a tofu dough for fried tofu, By frying the tofu dough for fried tofu produced in the tofu dough production process, a frying process for producing fried tofu, a seasoning process for seasoning the fried tofu produced in the frying process, and the seasoning in the seasoning process A method for producing dried fried tofu, comprising a drying step of drying the fried tofu with a microwave and then drying with hot air, wherein 20 to 35 ml of air is mixed into 1 L of soymilk in the air mixing step. It is characterized by a method for producing dried fried tofu.

Moreover, in the frying process according to the present invention, it is preferable to fry so that the moisture content of the fried tofu after frying is 35 to 45% by weight.

According to the present invention, it is possible to produce dried fried tofu that suppresses the occurrence of "stains" and "swells" in fried tofu after drying due to uneven seasoning due to seasoning and uneven swelling due to microwave drying.

It is a photograph showing an example of dried fried tofu with "spots". It is a photograph showing an example of dried fried tofu (right side) with "blister" and an example of normal fried tofu (left side). 1 is a photograph of a cross-section of a sample of dried fried tofu of Comparative Example 1 cut in the short side direction near the center. 2 is a cross-sectional photograph of a sample of dried fried tofu of Example 2 cut in the short side direction near the center. 10 is a cross-sectional photograph of a sample of dried fried tofu of Comparative Example 3 cut in the short side direction near the center. 4 is an electron micrograph (x10) taken near the center of a cross section cut in the short side direction near the center of the dried fried tofu sample of Comparative Example 1. FIG. 10 is an electron micrograph (x10) taken near the center of a cross section cut in the direction of the short side near the center of the dried fried tofu sample of Example 2. FIG. 10 is an electron micrograph (x10) taken near the center of a cross section cut in the short side direction near the center of the dried fried tofu sample of Comparative Example 3. FIG.

The present invention will be described in detail below. However, the present invention is not limited to the following description.

1. Soymilk Production Process First, soymilk is produced from raw soybeans. As a method for producing soymilk, whole soybeans are soaked in water, swollen so that the weight of whole soybeans after soaking is 2.0 to 2.3 times the weight before soaking, and then grinded. The soybean curd refuse and soybean milk are separated by boiling and heating the prepared go, adding reconstituted water and filtering. At this time, it is preferable to adjust the Brix of soymilk to 4-7. If the Brix is too low, the amount of protein coagulated in the coagulation step, which will be described later, is reduced, so large cavities are likely to occur in the frying step, which will be described later. Conversely, if the Brix is high, the number of tofu layers increases in the tofu dough preparation process described below, so that the tofu dough is difficult to dehydrate, and the dough is difficult to stretch in the frying process described later. The produced soymilk may be stored in a heated tank or the like, but if stored for a long time, protein denaturation will proceed due to heating, so it is preferable to use it as soon as possible in order to stabilize the production of fried tofu.

2. Air mixing process The prepared soymilk is mixed with air before being reacted with a coagulant in the coagulation process described below. In the present invention, it is necessary to entrain the soymilk with a considerably larger amount of air than usual, so it is preferable to forcibly entrain the air in the piping for sending the soymilk to the coagulation step, which will be described later. Further, by passing the forcibly mixed soymilk containing air through a liquid feeding pump, the air can be mixed finely and homogeneously. The amount of air mixed is 20 to 35 mL per 1 L of soymilk. By mixing more air than usual, the elongation of the tofu dough deteriorates in the frying process described later, but the fried tofu after frying has a fine and homogeneously puffed structure. As a result, the seasoning process, which will be described later, becomes uniform with less uneven flavoring, and in the drying process, which will be described later, when the fried tofu is dried with microwaves, the swelling of the fried tofu becomes uniform and the drying is smooth. If the amount of air mixed in is less than 20 mL, the swelling of the fried tofu will be uneven and will result in a structure containing large cavities. , the texture is also firm. More preferably, 25 to 30 mL is mixed per 1 L of soymilk.

3. Coagulation step By adding a coagulant to the prepared soymilk, proteins in the soymilk are coagulated. Coagulants include magnesium chloride, calcium chloride, calcium sulfate, gluconodeltalactone. Reaction conditions such as the concentration and amount of coagulant added, coagulation temperature, and time vary depending on the type of beans used, the Brix of soymilk, and the coagulant, and are therefore preferably adjusted as appropriate. For example, about 3% by weight of bittern containing magnesium chloride is mixed with soy milk equivalent to 1 kg of soybeans, and reacted at 65 to 75° C. for 5 to 12 minutes.

In the present invention, it is preferable to mix the heat-moisture treated starch with the aerated soymilk before adding the coagulant. By mixing the heat-moisture treated starch, it is possible not only to suppress the elution of the seasoning liquid of the fried tofu into the soup during cooking, but also to increase the strength of the dried fried tofu itself. The mixed amount of the heat-moisture treated starch is preferably 0.8 to 1.4 g per 1 L of soymilk. If it is less than 0.8 g, it is difficult to obtain the effect. The mixing method is not particularly limited, but it is preferable to suspend the heat-moisture-treated starch in water in advance, form a slurry, and homogeneously mix with soymilk mixed with air in a pipe or a coagulation tank.

4. Tofu Dough Making Step Next, tofu particles (moromi) obtained by solidifying soymilk are crushed and broken, and a tofu dough for deep-fried tofu is made while being compressed and dehydrated in a molding machine. Since the size and thickness of the tofu dough vary depending on the desired size and thickness of fried tofu, it is preferable to adjust them appropriately. It is preferable to dehydrate the dough so that the water content of the dough is in the range of 70 to 80% by weight. If it is less than 70% by weight, the tofu dough will be too hard and difficult to expand, and if it is more than 80% by weight, the tofu dough will be soft and fragile.

When the tofu dough is large, it is preferable to pierce the tofu dough with a needle or the like at regular intervals. By making a hole, the fried tofu does not partially swell excessively in the frying process described later, and it becomes easy to swell uniformly. The method of making holes is not particularly limited, but it is preferable to uniformly make holes at intervals of 5 mm to 15 mm with a needle having a diameter of about 0.5 to 1.5 mm. The drilled holes are filled in the frying process, which will be described later, leaving almost no traces.

5. Frying process The prepared tofu dough is placed in a mold and fried in edible oil to prepare fried tofu. The type of edible oil is not particularly limited, but since dried fried tofu may be stored for a long period of time before being eaten, it is preferable that it is resistant to oxidation, dissolves during storage, and does not ooze out oil. It is preferred to use oils that are semi-solid to solid at ambient temperature. Specific oils include refined palm oil and palm olein oil.

Fry at about 80-200°C. It is preferable that the first half of frying is performed at a relatively low temperature, and after the tofu dough is stretched out, the frying temperature is rapidly raised in the latter half of frying to firmly fix the shape of the surface and reduce the water content. Specifically, in the first half of frying, the temperature is raised from 85-95°C to 125-135°C to stretch the tofu dough, and in the second half of frying, the surface of the tofu dough is solidified with oil at a high temperature of 155-190°C. It is preferable to reduce the water content. The frying time should be about 15 to 25 minutes in total for the first half and the second half.

At this time, by reducing the water content to a certain extent in the frying process, swelling due to microwaves tends to occur smoothly in the drying process described later, and "stains" due to uneven drying are less likely to occur. A preferable water content is 35 to 45% by weight. If the content is less than 35% by weight, the fried tofu becomes hard and is crushed by the squeezing rollers in the flavoring step, which will be described later, making it difficult for the flavoring liquid to spread evenly. On the other hand, if it is higher than 45% by weight, it takes a long time to swell the fried tofu with microwaves in the drying process described later, and the seasoning liquid accumulates near the center of the fried tofu, which tends to cause "stains". In addition, in the present invention, the soymilk contains more air than usual, so that the fried tofu spreads poorly, but the porous structure is fine and homogeneous. Glue is good and unevenness of seasoning is reduced.

Moreover, it is preferable to pierce the prepared deep-fried tofu using a needle or the like. By making a hole, it is possible to prevent the deep-fried tofu from swelling greatly in the drying process using microwaves, which will be described later. The method of making holes is not particularly limited, but it is preferable to uniformly make holes at intervals of 5 mm to 15 mm with a needle having a diameter of about 0.5 to 1.5 mm.

6. Seasoning process The fried tofu prepared in the frying process is seasoned by immersing it in a seasoning liquid. Raw materials for seasoning liquids include sugar, salt, soy sauce, mirin, seafood stock such as kombu dashi and bonito, as well as common seasoning liquid ingredients such as pigments, as well as to prevent cracking of dried fried tofu due to overdrying during storage. Therefore, it is preferable to add moisturizing ingredients such as liquid sugar and isomerized sugar. The less water the flavoring liquid has, the easier it is to dry in the drying process described later. It is preferable to adjust the flavoring liquid so that the Brix of the flavoring liquid is in the range of 50-60. In addition, since fried tofu has a porous structure, it is difficult to adjust the amount of seasoning by immersion alone. It is preferable to adjust the adhesion amount.

7. Drying Step Next, the seasoned fried tofu is dried. Examples of the drying method include hot air drying, microwave drying, and vacuum freeze drying. In the present invention, drying is performed with microwaves and then with hot air drying. In the case of vacuum freeze-drying, if the flavoring liquid is thick, the flavoring liquid will be concentrated by freezing, resulting in a non-freezing state and non-uniform foaming, so it is necessary to make the flavoring liquid thinner. Also, when drying only by hot air drying, the seasoned fried tofu is compressed by the squeezing roll, so it takes a long time to dry if it is left as it is. Burning is more likely to occur. In addition, when drying only by microwave drying, the compressed fried tofu expands again due to the rise in internal temperature and becomes a porous structure, which improves the restorability. Therefore, after puffing, it is necessary to dry intermittently while controlling the internal temperature so as not to burn. In the present invention, after swelling the seasoned fried tofu by microwave drying, it is dried with hot air at a temperature that does not burn, so that the fried tofu after drying has a porous structure, and the restorability is improved. Instead, hot air drying can efficiently dry the moisture inside.

Drying by microwave is preferably carried out until the seasoned fried tofu has a moisture content of 15 to 25% by weight. If the water content is less than 15% by weight, there is a high possibility that scorching will occur. Conversely, if the water content is more than 25% by weight, not only will the swelling not be sufficient, but the hot air drying time, which will be described later, will be prolonged.

Hot air drying is preferably performed at a temperature of 40 to 75° C. until the water content reaches 7 to 16% by weight. If it is less than 40°C, drying will take a long time, and if it is 75°C or more, it will have a burnt flavor. Also, if the moisture content is higher than 16% by weight, it may rot, and if it is lower than 7% by weight, it will be overdried and easily cracked. Since the fried tofu produced by the method according to the present invention has a very fine porous structure, there is no unevenness in the flavoring liquid, there is no overfoaming due to microwaves, and there is no swelling unevenness such as non-swelling, and it is homogeneous. Since it expands and foams, the occurrence of "blemishes" due to uneven taste is suppressed.

The dried fried tofu produced by the method according to the present invention may be used as it is as an ingredient for instant foods, but it may also be packaged and sold as dried fried tofu, or cut into pieces and dried into small pieces for instant food. It may be used as an ingredient or packaged and sold.

EXAMPLES The present embodiment will be described in more detail below with reference to Examples.

(Example 1)
60 kg of soybeans were placed in a tank containing 360 kg of water at a water temperature of 20° C. and soaked for 12 hours to swell the soybeans. 23 kg of swollen soybeans are ground with a grinder while 57 kg of water is added, and the prepared soybean paste is boiled with steam for 3 minutes and 30 seconds to a final temperature of 100°C. The bean curd refuse was separated with a 120-mesh screen to obtain a soymilk with a Brix of 5.5.

Compressed air was forced into the pipe for sending the obtained soymilk from the soymilk tank to the coagulation tank so that 20 ml of air per liter of soymilk was mixed.

The air-mixed soymilk was passed through a liquid-sending pump so that the air was finely and uniformly mixed in the soymilk, and then 43 L of the soymilk was sent to the coagulation tank.

Next, 600 ml of a starch solution suspended in water so that the content of the heat-moisture-treated starch becomes 9% by weight was mixed with the soymilk sent to the liquid-sending tank, and stirred. 1000 ml of a coagulating liquid containing 3.5% by weight of calcium, 3.5% by weight of caramel color, and 1% by weight of calcium carbonate was added, stirred, and allowed to stand for 7 minutes to solidify. Next, the coagulated soymilk was broken by stirring to prepare moromi, which was then transferred to a molding machine.

The moromi transferred to the molding machine was placed on a net, dehydrated naturally for 5 minutes, then pressed to make a tofu sheet with a thickness of 8 mm, and cut into 65 mm long sides and 50 mm short sides to make tofu dough ( 70 wt% moisture). The cut tofu dough was uniformly pierced with a needle of φ1 mm so that 20 holes per sheet.

Next, the tofu dough is placed in a frying retainer of 75 mm x 105 mm x height 30 mm and φ6 mm small holes are evenly spaced at 3.2 mm intervals in a zigzag pattern. Fried tofu was prepared by frying in a fryer having The frying conditions are as follows: fry for 10 minutes in a low-temperature bath with a stepwise increase in temperature from 90 to 130°C, then fry for 10 minutes in a high-temperature bath with a stepwise increase in temperature from 170 to 185°C (water content: 40% by weight). made. The prepared deep-fried tofu was uniformly pierced with 120 holes per sheet with a needle of φ2 mm so that the seasoning could easily permeate inside.

Next, 48% by weight of liquid sugar, 20% by weight of soy sauce, 10% by weight of reduced starch syrup, 4% by weight of dextrin, 2.5% by weight of salt, 1.5% by weight of glutamine soda, and 14% by weight of water. The deep-fried tofu is immersed in a flavoring tank containing a liquid (Brix 54) and crushed with a roll. It was adjusted.

The fried tofu that had undergone the seasoning process was dried with a microwave so that the water content was 20% by weight (drying conditions: 1.35 kw, 2 minutes and 30 seconds).

Then, it was dried with hot air at 60° C. until the water content reached 12% by weight (45 minutes), and cooled by blowing air to prepare a dried fried tofu sample.

(Example 2)
A dried fried tofu sample was prepared according to the method of Example 1, except that the amount of air mixed in was 25 ml per liter of soymilk.

(Example 3)
A dried fried tofu sample was prepared according to the method of Example 1, except that the amount of air mixed in was 30 ml per liter of soymilk.

(Example 4)
A dried fried tofu sample was prepared according to the method of Example 1, except that the amount of air mixed in was 35 ml per liter of soymilk.

(Example 5)
Dried fried tofu samples were prepared according to the method of Example 2, except that they were fried in a hot bath (12 minutes) so that the moisture content after frying was 35% by weight.

(Example 6)
Dried fried tofu samples were prepared according to the method of Example 2, except that they were fried in a hot bath (8 minutes and 45 seconds) so that the moisture content after frying was 45% by weight.

(Comparative example 1)
A dried fried tofu sample was prepared according to the method of Example 1, except that the amount of air mixed in was 10 ml per liter of soymilk.

(Comparative example 2)
A dried fried tofu sample was prepared according to the method of Example 1, except that the amount of air mixed in was 15 ml per liter of soymilk.

(Comparative Example 3)
A dried fried tofu sample was prepared according to the method of Example 1, except that the amount of air mixed in was 40 ml per liter of soymilk.

The produced samples were evaluated for spots, swelling, and size. As for the stains, as shown in FIG. 1, the deep-fried tofu has a dent and the seasoning liquid has accumulated. The occurrence of 3% or more and less than 5% was rated as Δ, the occurrence of 1% or more and less than 3% was rated as ◯, and the occurrence of less than 1% was rated as ⊚.

As for blistering, as shown in FIG. 2, the thickness is clearly thick, and the standard size of the thickness is 11 mm, and those with a thickness of 15 mm or more are judged as NG, and the samples prepared in each test section are sorted by camera, and 5% or more occur. Those with 3% or more and less than 5% were rated as Δ, those with 1% or more and less than 3% were rated as ◯, and those with less than 1% were rated as ⊚.

Regarding the size of fried tofu, the standard size is 96 mm on the long side and 72 mm on the short side. , 5% or more was rated as x, 3% or more and less than 5% was rated as Δ, 1% or more and less than 3% was rated as ◯, and less than 1% was rated as ⊚.

In addition, the evaluation of the texture when eating each sample was described in the comment column. Each sample was placed in a container, poured with 500 ml of hot water, allowed to stand for 5 minutes, and then eaten.

Table 1 shows the evaluation results.

As shown in the evaluation results of Examples 1 to 4 and Comparative Examples 1 to 3 in Table 1, the more the amount of air mixed in, the more the occurrence of spots and blisters can be suppressed. However, as the amount of mixed air increased, the size of fried tofu decreased. From the above results, the amount of air mixed is preferably 20 to 35 ml, more preferably 25 to 30 ml, per liter of soymilk.

In addition, from the results of Examples 2, 5, and 6 in Table 1, it can be seen that when the moisture content after frying increases, the swelling tends to become uneven during swelling drying with microwaves, and stains and swelling tend to occur. . Conversely, when the moisture content after frying is low, stains and swelling are less likely to occur, but the texture becomes firmer. Therefore, the preferred moisture content after frying is 35 to 45% by weight.

In addition, samples of Examples 1 to 4 and Comparative Examples 1 to 3 were cut to analyze the cross-sectional porous structure. The analysis method was to cut the central part of a sample free of stains or blisters in the direction of the short side, degrease it with ether, and photograph it with an electron microscope (JSM-6380LA, 10 magnifications) manufactured by JEOL Ltd. , the captured digital images were analyzed by Image-Pro Premier 9.1 manufactured by Media Cybernetics. Measurement is performed by measuring the number of pores, the cross-sectional area of the sample to be observed, and the total area of the pores, and calculating the porosity (total pore area/cross-sectional area) and average pore porosity (porosity/number of pores). bottom. The number of samples was N=5, and the average value was taken as the sample value. The analytical results are listed in Table 2 below.

As shown in Table 2, the porosity decreases as the amount of air mixed into the soymilk increases. In particular, the porosity between Comparative Example 2 and Example 1 (between 15 ml/L and 20 ml/L) and between Example 4 and Comparative Example 3 (between 35 ml/L and 40 ml/L) This is a large drop, which is considered to be consistent with the evaluation of the size of fried tofu. In addition, it can be seen that the average pore porosity tends to decrease as the amount of air mixed into the soymilk increases, resulting in a fine and homogeneous porous structure. It is considered that the expansion during the frying process and microwave drying becomes uniform due to the presence of many fine air bubbles. As a result, the flavoring liquid spreads evenly, the drying time becomes uniform, and the occurrence of stains and blisters can be suppressed. However, at the same time, too much air entrainment is believed to result in less puffing and consequently smaller fried tofu size. Therefore, a preferable porous structure of fried tofu has a porosity of 35 to 40% and an average pore porosity of 0.15 to 0.26%.

Claims (2)

A soymilk production process for producing soymilk of Brix 4 to 7 from whole soybeans,
An air mixing step of forcibly mixing 20 to 35 ml of air into the soymilk in a pipe for sending soymilk to 1 L of soymilk produced in the soymilk producing step;
A coagulation step of adding a coagulant to the soymilk that has been aerated in the air mixing step and reacting it to produce a coagulate of soymilk;
A tofu dough preparation step of dehydrating and molding the soymilk coagulum prepared in the coagulation step so that the moisture content of the tofu dough is 70 to 80% by weight to prepare a tofu dough for fried tofu;
A frying step of producing fried tofu by frying the tofu dough for fried tofu prepared in the tofu dough preparation step at 80 to 200 ° C. so that the moisture content of the fried tofu after frying is 35 to 45% by weight ;
A seasoning step in which the fried tofu prepared in the frying step is immersed in a seasoning liquid with a Brix of 50 to 60 and seasoned by adjusting the amount of the seasoning liquid attached with a squeeze roller ;
After drying the fried tofu seasoned in the seasoning step with a microwave until the moisture content reaches 15 to 25% by weight, the dried tofu is dried with hot air in the range of 40 to 75°C until the moisture content reaches 7 to 16% by weight. and a method for producing dried fried tofu. 2. The method for producing dried fried tofu according to claim 1, wherein 25 to 35 mL of air is mixed with 1 L of soymilk in the air mixing step.

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