JPH0369499B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing dried fried tofu using microwaves, and more particularly to a method for obtaining dried fried tofu that looks good, is uniformly dried, and has good restorability. Dried fried tofu has recently attracted attention as an ingredient for instant foods, and much work has been done to develop its manufacturing technology.
When using dried fried tofu as an ingredient in instant foods,
The biggest problem is its resiliency. Therefore,
Most of the traditional dry fried tofu manufacturing techniques have focused on improving its resiliency. For example, there is a known method in which dried fried tofu is immersed in a seasoning liquid or not, and then pressed with a roll or the like, and then dried by a method such as freeze drying, hot air drying, or high frequency heating drying. . Although the dry fried tofu obtained by this method has been improved to some extent in terms of restorability, it is still not satisfactory. Not only that, but the fried tofu was simply dried using the usual drying method, and no innovations were taken during the drying process. Therefore, the obtained dried fried tofu had an uneven shape and poor appearance, making it unsuitable for continuous filling and packaging using a machine. The present invention solves all of these conventional drawbacks, and has not only good restorability but also good appearance.
It attempts to provide a method for obtaining dry fried tofu that can be continuously filled by a machine.
The gist is that after storing the fried tofu in a microwave-permeable and gas-permeable container, it is covered with a gap that prevents the fried tofu from expanding in the thickness direction when drying, and then the microwave This is a method for producing dry fried tofu, which is characterized by drying. Hereinafter, the contents of the present invention will be explained in detail. Fried tofu obtained by a conventional method is immersed in a seasoning liquid or stored in a container as it is without being immersed, and then dried using microwaves. The container for storing the fried tofu needs to be microwave permeable and gas permeable. This 2
If a container is used that does not simultaneously satisfy these two conditions, the object of the present invention cannot be achieved. A specific example of a container that satisfies the above two conditions is made of a material that transmits microwaves, such as a synthetic resin such as Teflon (registered trademark, hereinafter the same).
Some containers have pores large enough to allow gas to pass through. Next, when storing fried tofu in a container that satisfies the above two conditions, the object of the present invention can be achieved by covering the container with a gap that is sufficient to prevent the fried tofu from expanding in the thickness direction when drying. It is extremely important to do so. When drying fried tofu, the fried tofu expands as water evaporates during the fried tofu. In this case, if the fried tofu is puffed completely freely, the puffiness of the fried tofu will also be non-uniform due to uneven and free evaporation of water during the fried tofu. In order to prevent such a phenomenon, it is effective to force the expansion direction of the fried tofu as described above, and in the case of the present invention, it is intended to suppress the expansion of the fried tofu in the thickness direction. Therefore, the gap between the top surface of the fried tofu and the lid must be such that it is necessary to achieve the above objective. The degree of the above-mentioned gap will naturally vary depending on the frying process, the thickness of the fried tofu, the number of pieces, etc. stored in the container, but it is desirable that the gap be such that it generally satisfies the following formula. That is, 0.4×XY≦Z
≦1.0×XY (where Z is the gap in mm, x is the thickness of one fried tofu in mm, and y is the number of fried tofu). Next, the fried tofu stored in the container is microwave-dried under the above-mentioned conditions. This microwave drying may be carried out under normal pressure or reduced pressure, but in order to effectively achieve the purpose of the present invention, it is preferable to dry the fried tofu under conditions that promote the expansion of the fried tofu. Drying is preferred. The higher the swelling ratio of the fried tofu during drying, the more the fried tofu will expand in a direction other than its thickness direction, that is, in the side direction of the fried tofu. As a result, the width of the fried tofu is expanded and the structure becomes sparse, which not only improves the drying efficiency but also improves the resilience after drying. Moreover, since the fried tofu is suppressed from expanding in the thickness direction, the fried tofu is pressed by the force that tends to expand in the thickness direction. As a result, the shape of the fried tofu becomes uniform and its surface becomes flat. This phenomenon eventually leads to uniform evaporation of moisture from the fried tofu, resulting in the effect of uniformly drying the fried tofu. By the method described above, it is possible to obtain dried fried tofu that satisfies the objectives of the present invention. Next, a case in which the method of the present invention described above is carried out using a reduced pressure microwave drying apparatus will be described with reference to the drawings. Deep-fried tofu 1 obtained by a conventional method is immersed in a seasoning liquid, or it is left with a large number of small holes 2 without being immersed.
Several sheets are stored in each frame 4 of a Teflon container 3 having a Then, a Teflon lid 6 having a large number of small holes 5 is placed. In this case, the gap a between the top surface of the fried tofu 1' on the top shelf and the bottom surface of the lid 6 is calculated using the formula 0.4×XY as described above.
It is preferable that ≦Z≦1.0×XY be satisfied. Next, after placing the container 3 in the reduced pressure microwave drying device 7, a vacuum pump 9 connected to the reduced pressure microwave drying device 7 via an exhaust pipe 8 is used to move the container 3 into the reduced pressure microwave drying device 7. to the desired degree of decompression. Then, the microwave oscillator 10 is activated to apply microwaves through the waveguide 11 into the vacuum microwave drying device 7 . The applied microwaves rapidly evaporate the moisture in the fried tofu 1 in the container 3, and due to this transpiration, the fried tofu 1 rapidly expands. In this case, the fried tofu 1 will expand in a direction other than its thickness direction, that is, in the direction of arrow A. The moisture evaporated from the fried tofu 1 is led to the cold trap 12 via the exhaust pipe 8, where it is condensed and discharged. After drying the fried tofu 1, it is taken out from the vacuum microwave drying device 7 to obtain dried fried tofu. Next, comparative experimental examples will be shown to clarify the effects of the present invention. Comparative Experimental Example - Method of the Invention Ten pieces of commercially available fried tofu (75 mm x 70 mm) were immersed in a seasoning liquid to obtain seasoned fried tofu. The weight of fried tofu before seasoning is 92g for 10 pieces, and after seasoning it is approx.
It was 260g. Thereafter, 10 sheets were stacked and pressed together using a flat plate to squeeze out the liquid until the weight reached 148 g. Then, the 10 sheets were stacked and stored in a Teflon container with many small holes, and a Teflon lid with many small holes was attached. In this case, the thickness of one piece of seasoned tofu was 2.7 mm, and the gap between the top surface of the topmost seasoned tofu and the bottom surface of the lid was 13 mm. Next, the seasoned fried tofu in the container was dried for 14 minutes under the conditions of a degree of vacuum of 2660 Pascals and a microwave output of 1 KW to obtain dried fried tofu with a moisture content of about 12%. ●Comparative Example 1 All the conditions were the same as in the method of the present invention, except that the container containing the fried tofu was subjected to vacuum microwave drying without putting a lid on it. ●Comparative Example 2 Seasoned fried tofu squeezed using the same method as the method of the present invention was placed on a tray one by one without overlapping, and then vacuum freeze-dried for 4 hours at a reduced pressure of 26.6 Pascal and a radiant shelf temperature of 80°C. did. Thereafter, it was left in a constant temperature and humidity chamber at 20°C and 90% relative humidity for 1 hour, and then left in an open room temperature for 5 hours to obtain dry fried tofu with a moisture content of about 12%. ●Comparative Example 3 Seasoned fried tofu squeezed using the same method as the method of the present invention was placed on a tray one by one without overlapping, and then kept at 60°C, relative humidity 40%, and wind speed 1.5 m/sec for 6 hours. Dry with hot air. After that, leave it at room temperature for 6 days.
After leaving it for a while, dry fried tofu with a moisture content of about 12% was obtained. For each dried fried tofu obtained by the above method, the size, shape, and restorability with hot water after drying were compared. The results are shown in Table 1.

【table】

[Table] As is clear from Table 1, according to the method of the present invention, the size of the dried fried tofu can be expanded, which improves the appearance, and the structure of the dried fried tofu becomes sparse. , it will be possible to shorten the restoration time. Moreover, each part of this dried fried tofu is dried uniformly, and its surface is flat and well-shaped. Therefore, during restoration, each part is restored uniformly, resulting in an even texture, and on the other hand, filling and packaging of this dried fried tofu can be carried out continuously by machine. The method for obtaining dried fried tofu with these characteristics is simply to satisfy the requirement of suppressing the expansion of fried tofu in the thickness direction during drying with microwaves, and thereby it is necessary to suppress the expansion of fried tofu in the thickness direction during drying by microwave. It is possible to solve all the problems that occur when drying is used, such as the need for a step to absorb moisture from dried fried tofu, difficulty in drying in a stacked state, and long drying time. Example 1 10 pieces of commercially available fried tofu (75 mm x 70 mm) were stacked and stored in a Teflon container with many small holes.
A Teflon lid with numerous small holes was applied. In this case, the thickness of one piece of fried tofu was 7 mm, and the gap between the top surface of the top fried tofu and the bottom surface of the lid was 30 mm. Next, the fried tofu in the container was dried for 10 minutes under the conditions of a degree of vacuum of 2660 Pascals and a microwave output of 1 KW. The dry fried tofu obtained is approximately 84mm x
It was enlarged to a size of 81 mm and looked very good, and the restoration time using hot water was 40 seconds. Example 2 Seasoned fried tofu was obtained by soaking 10 pieces of commercially available fried tofu (75 mm x 70 mm) in a seasoning liquid. Thereafter, 10 sheets were stacked and pressed with a flat plate to extract the liquid. then 10
The stacked sheets were stored in a Teflon container with many small holes, and a Teflon lid with many small holes was attached. In this case, the thickness of one piece of seasoned tofu was 2.7 mm, and the gap between the top surface of the topmost seasoned tofu and the bottom surface of the lid was 11 mm. Next, microwave the seasoned fried tofu in the above container under normal pressure with a microwave output of 1KW.
It was dried for 14 minutes under these conditions. The dry fried tofu thus obtained has been enlarged to approximately 85 mm x 82 mm in size and looks very good, and the reconstitution time with hot water is short.
It was hot in 50 seconds.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway view showing a specific example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a partially enlarged view of FIG. 1. In the figure, 1...Fried tofu, 2, 5...Small hole, 3...
Container, 4... Frame, 6... Lid, 7... Decompression microwave dryer, 8... Exhaust pipe, 9... Vacuum pump,
10...Microwave oscillator, 11...Waveguide.

Claims (1)

[Claims] 1. After storing the fried tofu in a microwave-permeable and gas-permeable container, cover the container with a gap to prevent the fried tofu from expanding in the thickness direction during drying, and then microwave drying. A method for producing dried fried tofu, which is characterized by: