JPH0324180B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a snack food that has a fresh flavor, is appropriately puffed, and has a light texture. Many snack foods have been developed in the past, and a wide variety of research and development efforts have been conducted on drying techniques. Typical examples include hot air drying, microwave drying, freeze drying, deep-frying, and reduced pressure drying.In addition, drying methods include heating and dehydrating the material by exposing it to a stream of superheated steam for a short period of time. There is a puffing drying method in which a puffed product is obtained by rapidly releasing it into the atmosphere. However, snack foods obtained by such conventional drying methods have a runner-up problem in that the heat during drying generates a heated odor, or the flavor of the food evaporates or changes in quality. This runner-up ranking has been a major problem for snack foods, such as fruit snacks, where fresh flavor is important. The present invention aims to provide a novel drying method developed to obtain a snack food that overcomes this problem. The gist is (a) vegetables, (b) fruits, (c) grains, (d) beans, (e) solids such as dough products mainly made from grains, or (f) processed and cooked these solids. At least one type of food selected from the group consisting of solid matter and solid matter is subjected to rapid depressurization at a rate sufficient to cause the food to swell and to such an extent that the water in the food freezes; After the water inside freezes,
This is a method for producing snack food, which is characterized by heating and drying and then returning the pressure to normal pressure. The method of the present invention will be described in detail below. Foods that can be dried by the method of the present invention include vegetables, fruits, grains,
Solid dough products made mainly of beans and grains, or solid products prepared by processing and cooking these solids,
To effectively achieve the objectives of the present invention, the water content is approximately
It is desirable to have a solid content of 50% or more. In the present invention, the food is first placed under reduced pressure, but at least the following two conditions must be satisfied in placing the food under reduced pressure. The first condition is to subject the food product to a certain reduced pressure quickly enough for puffing to occur. When food is placed under reduced pressure, the boiling point of water naturally decreases, which causes transpiration of water, especially free water, in the food. In other words, by placing the food under reduced pressure for a short period of time, the food is expanded. Therefore, the speed sufficient to cause the food to puff up as used in the present invention refers to the speed sufficient to cause the moisture in the food to evaporate rapidly in a short period of time. The swelling phenomenon caused by water evaporation of food differs depending on the type of food.
Therefore, the speed sufficient for expansion to occur varies depending on the type of food, but is preferably within 1 second. Next, the second condition is that the specific degree of reduced pressure mentioned in the first condition is set to a degree of reduced pressure sufficient to cause the moisture in the food to freeze. The relationship between freezing of water and the degree of decompression is that depressurization lowers the boiling point of water, which causes transpiration of water, but this evaporation of water removes the heat of vaporization, and as a result, The relationship is that the temperature of the water decreases and eventually it freezes. The degree of vacuum at which water freezes under reduced pressure due to this phenomenon is approximately 609 Pascals (4.58 torr). Therefore, the degree of vacuum sufficient to freeze the water in the food according to the present invention is about 609 Pascal or less. Preferably it is about 106 Pascals (0.8 torr) or less. After satisfying the above two conditions and placing the food under reduced pressure, the food is held until the moisture in the food freezes, preferably until the food temperature no longer decreases. By this treatment, the shape of the puffed food is maintained and the snack food finally obtained is puffed, making it possible to give it a crispy and light texture. After freezing the moisture in the food, the food is dried by heating using a conventional heating method such as infrared heating or microwave heating. In this heating drying process, if the frozen water in the food is completely melted and then evaporated, it tends to cause the food in a puffed state to shrivel, whereas if the frozen water is evaporated by sublimation, the final The texture of the snack food obtained tends to be different from the texture targeted by the present invention. Therefore, in heating drying, it is preferable to evaporate the frozen water in the food without completely melting it and in a non-sublimated state, that is, in a semi-frozen state, in order to prevent the above drawbacks. As the controlling means, radiation heating using infrared rays or the like is most preferable. Next, the snack food obtained by heating and drying is returned to normal pressure and then transferred to the next process such as a packaging process. Next, the method of the present invention will be explained using an apple as an example. First, the apple is cut into pieces and then immersed in an appropriate seasoning liquid. Next, the obtained apple pieces are subjected to vacuum swelling treatment, but the vacuum swelling treatment conditions in this case are (1) the degree of vacuum is approximately 600 pascals (4.5 torr);
It should preferably be about 106 Pascals (0.8 torr) or less. (2) The rate of pressure reduction is to be carried out from normal pressure to the desired degree of pressure reduction within 1 second. By subjecting the apple pieces to vacuum swelling treatment according to these conditions, the water in the apple pieces is rapidly evaporated, thereby freezing the remaining water in the apple pieces and maintaining the puffed state of the apple pieces. Figure 1 shows an outline of the change in temperature of apples over time during vacuum swelling treatment. The vertical axis represents temperature (°C), the horizontal axis represents decompression treatment time (minutes), and the curve represents changes in product temperature. When apple pieces are treated under the above two reduced pressure treatment conditions, the temperature of the apple pieces rapidly decreases and becomes supercooled, as shown in A. This phenomenon occurs because the water in the apple pieces evaporates rapidly and takes away the heat of vaporization, and the rapid evaporation of water at this time causes the apple pieces to swell. Thereafter, as shown in B, the temperature of the apple pieces rose slightly. This phenomenon occurs because the temperature of the apple pieces increases due to the thermal energy released when the water in the supercooled apple pieces freezes. The temperature of the apple pieces gradually decreases as shown in c, but this is thought to be because the frozen water in the apple pieces is gradually sublimating. After the phenomenon of C occurs, the temperature of the apple pieces becomes constant as shown in D, so it is preferable to heat-dry the apple pieces at this point. There is no problem in achieving the purpose of The heating and drying means uses radiation heating, conduction heating, or microwave heating to dry the apple pieces until the temperature of the apple pieces reaches room temperature. After drying, the apple pieces obtained are returned to normal pressure and then taken out. The curve showing the change in product temperature shown in Figure 1 shows almost the same tendency not only for apple pieces but also for other foods, but as the moisture content of the food decreases, the change in product temperature increases. The trend becomes less noticeable. The same applies to cases where the water content is extremely high. Next, in order to clarify the effects of the method of the present invention, a comparative experimental example will be described using an apple as an example. Before that, a specific apparatus used in the comparative experimental example will be explained based on FIG. 2. However, the apparatus shown in FIG. 2 is an example of a specific apparatus that can be used in carrying out the method of the present invention, and the apparatus is not limited thereto. Reference numeral 1 indicates a drying chamber, and lids 2 and 3 are provided at the upper and lower portions of the drying chamber 1, and a shelf 4 on which food A is placed is provided inside. The shelf 4 can be turned over by means of a handle 5.
An infrared lamp 6 is installed inside the lid 2 of the drying chamber 1. A vacuum chamber 7 is connected to the side wall of the drying chamber 1 by a pipe 8.
A Kotoku 9 is installed to open and close it. A cold trap 10 and a vacuum pump 11 are connected to the vacuum chamber 7 through a pipe 12 in order to reduce the internal pressure, and the vacuum chamber 7 is also provided with a vacuum gauge 13. A vacuum gauge 14 for measuring the degree of reduced pressure inside the drying chamber 1 is provided on one side wall of the drying chamber 1, and an air supply pipe 15 is connected separately from this.
A cock 16 is provided on the air supply pipe 15 to open and close the air supply pipe 15. The following comparative experiment was conducted using the above apparatus. Comparative Example Γ Method of the Invention Fresh apples were peeled and cored using a conventional method, and then sliced with a slice cutter to a thickness of 4 mm, a short radius of 10 mm, and a long radius of 25 mm.
Shred and shape into fan-shaped chips with a width of 20 mm and a width of 20 mm to obtain 1 kg of apple pieces. Next, 1 kg of the apple pieces were mixed with 0.8 kg of sucrose, 0.01 kg of L-ascorbic acid, and 3.18 kg of water.
4 kg of syrup solution at room temperature and normal pressure. The lid 2 of the drying chamber 1 is opened, and 100 g of the apple pieces thus obtained are supplied onto the shelf 4 in the drying chamber 1, and then the lid 2 is closed. Separately, the vacuum pump 11 is operated with the pot 9 closed to reduce the pressure inside the vacuum chamber 7 to about 66.5 Pascals (0.5 torr). When the above operation is completed, the air inside the drying chamber 1 is transferred to the vacuum chamber 7 through the pipe 8 when the chamber 9 is opened with the chamber 16 closed.
The inside and the inside of the vacuum chamber 7 reach the same degree of reduced pressure in a very short time (within 1 second). The degree of decompression at this time is approximately
It is 332.5 pascals (about 2.5 torr). Immediately thereafter, the inside of the drying chamber 1 is lowered to about 66.5 Pascal (0.5 Torr) by the vacuum pump 11, and 66.5 Pascal is maintained until the drying is completed. During this time, the temperature of the apple pieces in the drying chamber 1 changes as shown in FIG. After putting the apple under vacuum, maintain it for 3 minutes (time point X in Figure 1)
Then, the apple pieces are dried using an infrared lamp (100V, 185W, irradiation distance 10cm) until the quality of the apple pieces reaches about 30℃. After that, close the pot 9, stop the vacuum pump 11, and gradually open the pot 16 to return the inside of the drying chamber 1 to normal pressure, then open the lid 3, turn the handle 5, and invert the shelf 4. , take out the dried apple pieces. Γ Conventional freeze-drying method Approximately 100 g of apple pieces obtained by the same method as the present invention are freeze-dried for 4 hours at an ultimate vacuum of approximately 13.3 Pascal (0.1 torr) and a product temperature rise of 30°C or less. Dried apple pieces with a moisture content of 5% by weight were obtained. ΓConventional reduced-pressure microwave drying method Approximately 100 g of apple pieces immersed in a syrup solution in the same manner as the method of the present invention are dried under conditions of a reduced pressure of approximately 1330-3990 Pascals (10-30 torr) and a theoretical temperature rise of 30°C or less. Microwave irradiation with an output of 4.5 kilowatts was applied for 3 minutes to reduce the moisture content to 20% by weight, but significant scorching occurred and subsequent drying had to be discontinued. Table 1 shows the results of the sensory test for each of the above dried apple pieces. However, in the table, the method of the invention, the conventional freeze-drying method, and the conventional vacuum microwave drying method are shown.

【table】

[Table] As is clear from the comparative experiment examples described above, the dried apple pieces obtained by the method satisfying the various conditions of the present invention are the best as a snack fruit, and this is true not only for apples but also for other foods. The same applies when using . As described above, the snack food obtained by the method of the present invention is moderately puffed while retaining its original shape, and therefore has a light and crispy texture, making it highly desirable as a snack food. It is. Furthermore, since the method of the present invention expands and dries under reduced pressure, the heating temperature is relatively low, and as a result, quality deterioration such as volatilization of flavor and deterioration due to heating can be minimized. Therefore, the snack food obtained effectively retains the flavor before drying. Example 1 (Example using fruit) Bananas were expanded and dried under reduced pressure using the apparatus shown in FIG. That is, bananas were sliced into approximately 5 mm thick slices. Thereafter, the lid 2 of the drying chamber 1 is opened, and the banana pieces are supplied in a single layer onto the shelf 4 in the drying chamber 1.
Close. Separately, the vacuum pump 11 is operated with the pot 9 closed, and the vacuum chamber 7 is closed.
Reduce the pressure inside to about 30 pascals (about 0.22 torr). After the above operations are completed, open the dryer 9 with the dryer 16 closed, and within 1 second, dry the inside of the drying chamber 1 approximately 160 times.
Pascal (1.2torr). Immediately thereafter, the inside of the drying chamber 1 is brought to 30 Pascals using the vacuum pump 11, and the temperature is maintained at 30 Pascals until the drying is completed. The banana pieces are kept under reduced pressure for 30 minutes, and then dried using an infrared lamp (100V, 185W, irradiation distance 10cm) until the temperature of the banana pieces reaches about 30°C.
Thereafter, the pot 9 is closed, the vacuum pump 11 is stopped, the pot 16 is gradually opened to return the inside of the drying chamber 1 to normal pressure, the lid 3 is opened, the handle 5 is rotated, the shelf 4 is reversed, Remove the dried banana pieces. Example 2 (Example using dough) 1 kg of mochi with a water content of about 45% by weight was obtained using an electric mochi making machine. To this, 500 g of boiled adzuki beans with a water content of about 70% by weight, which had a mixture of red beans and grains, was gradually added and kneaded until the mixture was almost uniform. Approximately 10 g of the thus obtained dough having a moisture content of approximately 60% by weight was broken into disks having a thickness of approximately 5 mm and a diameter of approximately 5 cm, and the disks were arranged in a single layer on a tray. Thereafter, the tray was placed on the shelf 4 in the drying chamber 1, and the lid 2 was closed. Thereafter, it was treated in the same manner as in Example 1 to obtain kakimochi-style snack chips. The obtained product had no heating odor. Example 3 (Example using processed and cooked solid material) The edible part of a banana was ground in a juicer mixer to obtain 1 kg of banana juice with a water content of about 75% by weight. After heating and concentrating this to a water content of approximately 50% by weight, a mixture of 50 g of granulated sugar, 5 g of low methoxyl pectin, and 0.8 g of calcium lactate was gradually added while heating, and mixed until the mixture became almost homogeneous. After cooling the mixture to room temperature and making it jam-like,
Each 10 g of this was filled into a small tray measuring 3 cm x 5 cm x 0.5 cm. Thereafter, after arranging the 10 trays on a large tray, the large tray was placed on the shelf 4 in the drying chamber 1 shown in the figure, and the lid 2 was closed. Thereafter, the process was carried out in the same manner as in Example 1 to obtain banana-flavored snack chips.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing the change in temperature of apple pieces over time during vacuum swelling treatment. FIG. 2 is a schematic diagram showing an example of a specific apparatus that can be used in carrying out the method of the present invention. 1... Drying room, 2, 3... Lid, 4... Shelf, 5...
...Handle, 6...Infrared lamp, 7...Vacuum chamber, 8...Pipe, 9...Kotuku, 10...
...Cold trap, 11...Vacuum pump, 12
...Pipe, 13,14...Vacuum gauge, 15...Air supply pipe, 16...Kotuku, A...Food.

Claims (1)

[Claims] 1. (a) Vegetables, (b) Fruits, (c) Grains, (d) Beans, (e) Solids such as dough products based on grains, or (f) Solids prepared by processing these solids. At least one food selected from the group consisting of A method for producing a snack food, which comprises freezing, heating and drying, and then returning to normal pressure.