JPS63230033A - Production of dried vegetable - Google Patents

Abstract

PURPOSE:To dry vegetables without damage in quality and nutritive values by allowing them to move as they are irradiated with far infrared rays from a special unit in a certain range of temperature. CONSTITUTION:The vegetable drier is composed of the vegetable conveyer in the housing 10 whose inner atmosphere is to be heated at 40-150 deg.C and of the far infrared beam irradiators P1-P8 along the conveying path. The far infrared beam irradiators P1-P8 has the structure where the far infrared beam-irradiating substance 2 made of a ceramic such as zirconia is set on the outer surface of the flat box 1 and a heat transfer medium heated at 120-250 deg.C is passed through the inside of the box 1.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a method for producing so-called dried vegetables by drying various vegetables, and particularly relates to a method for producing dried vegetables using far infrared rays. .

BACKGROUND OF THE INVENTION In recent years, the amount of dried vegetables used as a type of processed food has increased. In other words, dried vegetables have become widely used as ingredients for cooked foods due to their convenience, and their use in the restaurant industry has also increased, and they are also being used as raw materials for snacks containing vegetables. There is. In producing such dried vegetables, it is desirable that the loss of nutrients due to drying is small, the flavor (aroma) and color do not change, and of course high productivity (efficiency) is also required. Ru.

As a conventional method for producing dried vegetables, the mainstream is a hot air drying method in which vegetables are dried with hot air, and in some cases, a freeze-drying method is also applied as a method for producing high-quality dried vegetables. Recently, a method of drying vegetables by irradiating them with far-infrared rays generated using an electric heater has also been used in some cases.

Problems to be Solved by the Invention In the hot air drying method, which is the mainstream method for producing dried vegetables in the past, productivity is low because drying takes an extremely long time, and the vegetables discolor and eventually lose their flavor. There is a problem in that there is a large loss of nutrients such as vitamins.

On the other hand, although the freeze-drying method can produce dried vegetables of much higher quality than the hot-air drying method, it still suffers from the problem of loss of flavor and is costly, with equipment costs and operating costs significantly increasing. The disadvantage is great.

Recently, a method of drying by irradiating far infrared rays has attracted attention, and in some cases it has been put into practical use.

The method using far-infrared irradiation not only provides relatively high-quality dried vegetables, but also has the cost advantage of significantly lower equipment and operating costs compared to freeze-drying, and hot air drying. It has the advantage of efficiency in that it can be dried in a shorter time than the method,
Furthermore, irradiation with far-infrared rays can also be expected to have a sterilizing effect, which is advantageous in terms of food hygiene. However, the conventional far-infrared irradiation method uses an electric heater as a heating source for generating far-infrared rays, and therefore has the following problems.

In other words, far-infrared generating devices generally generate far-infrared rays by heating a far-infrared emitting material such as a ceramic with a heating source, and conventional devices generally use an electric heater such as a nichrome wire as the heating source. It was getting worse. However, in this case, the temperature of the far-infrared emitting material is not uniform and varies by several tens of degrees Celsius depending on the location, resulting in variations in the amount of far-infrared radiant energy and the problem of burning the surface of the vegetables to be dried. there were.

It is also known that the wavelength of the far infrared rays emitted from ordinary far infrared emitting materials becomes shorter as the temperature increases; on the other hand, the penetration of far infrared rays into the interior of the material irradiated with far infrared rays decreases as the wavelength increases. However, with conventional far-infrared generators using electric heaters,
As mentioned above, there are variations in the temperature of far-infrared emitting substances, so in order to reliably give a certain amount of energy to the vegetables to be dried, the average heating temperature (target heating temperature) should be as high as 300 to 350 degrees Celsius. As a result, the average wavelength of the far infrared rays generated becomes shorter, and the penetration of far infrared rays into the inside of the object (vegetables) decreases. It rises and dries, but the drying of the inside is delayed, and it takes a long time to dry the whole thing.Also, if the inside is sufficiently dried, the surface may become burnt, or even if it is not burnt, the surface may become dry. This resulted in a loss of flavor and discoloration of the surface.

This invention was made against the background of the above-mentioned circumstances, and it is possible to dry vegetables efficiently and at low cost without impairing the quality of the dried vegetables by irradiating them with far infrared rays. The purpose is to provide a manufacturing method.

Means for Solving the Problems In order to solve the above-mentioned problems, the method of the present invention uses a far infrared ray generator of a type different from conventional ones, and appropriately controls its temperature and the atmosphere temperature. I did it like that.

That is, in the method of the present invention, while transporting fresh vegetables to be dried through a predetermined transport path, the vegetables are irradiated with far infrared rays to dry them. A far-infrared ray emitting material layer is formed on the outer surface of one oblique surface of a flat box-shaped casing through which a heat medium flows, and far infrared rays are generated by heating the far-infrared rays emitting material layer with the heat medium. We decided to use the same equipment. Then, the far-infrared ray generator is arranged so that the far-infrared ray emitting material layer faces the transport path of vegetables to be dried, and the temperature of the heat medium flowing through the far-infrared ray generator is set in a range of 120 to 250'C. It is characterized by controlling the ambient temperature within the range of 40 to 150°C to generate far infrared rays, and controlling the ambient temperature of the vegetable transport path within the range of 40 to 150°C.

Function: In the method of the present invention, basically, while the Pegi vegetables to be dried are transported along a predetermined transport path, far-infrared rays from a far-infrared generator placed opposite to the transport path are used to irradiate the vegetables. The vegetables are dried by irradiation to obtain dried vegetables. The far-infrared ray generator used here does not directly heat the far-infrared emitting material with an electric heater (N-thermal heater) as in the past, but with a separately heated heat medium (silicon oil, petroleum-based A device configured to emit far infrared rays from the far infrared ray emitting material layer by heating the far infrared ray emitting material layer with oil, etc.) is used. In other words, a far-infrared emitting material layer is formed on one flat surface of a flat box-shaped casing through which a heat medium flows.
A heating medium flowing inside the flat housing heats the far-infrared emitting material layer to emit far-infrared rays.

In such a far-infrared ray generator, the far-infrared ray emitting material layer is uniformly heated over the entire surface from the back side (casing side), so there is almost no variation in the temperature of the far-infrared ray emitting material layer, and the temperature of the heat medium is By appropriately controlling the temperature, the temperature of the far-infrared emitting material layer can be easily and accurately controlled to an appropriate temperature. Therefore, the far-infrared radiation energy from the far-infrared ray emitting material layer does not vary depending on the location, and the wavelength of the emitted far-infrared rays does not vary, and these can be controlled uniformly and accurately.

As mentioned above, it is possible to uniformly and accurately control the amount of far-infrared radiant energy without causing variations.
There is no need to set the heating temperature (target heating temperature) of the far-infrared emitting material layer to a relatively low temperature, taking into account variations as in the case of using a conventional electric heater. Can be done. In other words, in the case of a conventional far-infrared generator using an electric heater, the temperature of the far-infrared emitting material layer varies depending on the location, and the amount of radiant energy also varies depending on the location, which makes it difficult to set the target temperature (average temperature). If the heating temperature is set to a low temperature, the amount of far-infrared energy received by the vegetables may be significantly reduced depending on the position of the vegetables in the vegetable transport system, and the vegetables may not be dried sufficiently, so it is necessary to set the target heating temperature high. However, the far-infrared ray generator used in the present invention does not have this problem, and therefore the target temperature can be set low. Therefore, in the method of this invention, instead of the high temperature of 300 to 350'C as in the conventional far infrared generator using an electric heater,
In order to heat the far-infrared emitting material layer to a low temperature of 50°C, the temperature of the heat medium flowing inside the housing is controlled at 120 to 250°C. By controlling the temperature to below 250°C, it is possible to not only prevent the surface of vegetables from burning, but also to lengthen the wavelength of the far infrared rays that are generated, which improves the penetration of far infrared rays into the interior of the vegetables. becomes.

Good penetration of far-infrared rays into the inside of vegetables means that they can be efficiently dried to the inside of vegetables, which increases energy usage efficiency and shortens the time required for drying. Since energy is prevented from being concentrated only on the surface of the vegetable, it is possible to effectively prevent the surface from burning, the flavor of the surface being lost, and the surface from discoloring.

If the heating temperature for the far-infrared emitting material layer, that is, the temperature of the heat medium exceeds 250° C., the above-mentioned effects cannot be obtained, and only the surface of the vegetables may become burnt. On the other hand, if the temperature is lower than 120°C, it will generally be difficult to generate far-infrared rays with sufficient energy, although this will vary depending on the type of far-infrared emitting substance, and therefore it will be difficult to sufficiently dry vegetables. For these reasons, the temperature of the heat medium was controlled within the range of 120 to 250°C. The most preferable temperature of the heat medium is 1
50-200'C.

Roughly speaking, the method of this invention not only directly irradiates far-infrared rays onto the vegetables on the transfer line as in (e) above, but also controls the ambient temperature of the transfer line within the range of 40 to 150°C. By keeping the ambient temperature higher than room temperature (outside air temperature) in this way, the heat given to vegetables by far infrared rays is prevented from being taken away from the surface of the vegetables by the outside air, increasing efficiency. It can be dried well. If the ambient temperature is less than 40'C, the effect of (a) above cannot be obtained, while if it exceeds 150°C, the surface of the vegetables may change color (browning) or lose their flavor. The ambient temperature was controlled within the range of 40 to 150'C. The most preferable ambient temperature is
Stay within the range of 50-100°C.

Embodiment FIGS. 1 and 2 show an example of a far-infrared ray generator used in the method for producing dried vegetables of the present invention.

In FIGS. 1 and 2, the far-infrared ray generator P includes a housing 1 having an overall flat airtight box shape, and two parts of the housing 1.
One oblique plane 1A among the two wide planes (ViA plane)
A far-infrared ray emitting material layer 2 is formed on the outer surface of the device with a predetermined thickness. Of the outer walls of the casing 1, at least the wall surface constituting the flat surface 1A is made of a material with good thermal conductivity, such as a metal plate such as copper, copper alloy, aluminum alloy, steel, stainless steel, etc. There is. The inside of the casing 1 is partitioned by a plurality of partition plates 1B so that a meandering long flow path 5 is formed between the heat medium inlet 3 and the heat medium outlet 4. As the material used for the far-infrared emitting material layer 2, any material M that can efficiently generate far-infrared rays can be used, such as zirconia (ZrO2) ceramic, titania (TiO2) ceramic, Or silicon nitride (Si3N4) ceramic, silicon carbide (Si
C) type ceramics, composite ceramics thereof, etc. can be used for the grain, and from the point of view of ease of cleaning, etc., it is desirable to use dense and substantially non-porous crystallized glass. Although the far-infrared emitting material layer 2 may be formed by any method, it can be suitably formed by a thermal spraying method (for example, a plasma spraying method) or a coating and baking method.

In the far-infrared ray generation station P as described above, the heat medium 6 previously heated to 120 to 250° C. at another location is caused to flow into the housing 1 from the heat medium inlet 3. While the heat medium 6 flows through the flow path 5, the far-infrared emitting material layer 2 is heated to 120 to 250° C. via the flat surface 1A, and far-infrared rays are emitted from the far-infrared emitting material layer 2. Here, either liquid or gas can be used as the heat medium,
For example, silicon oil, petroleum oil, paraffin, glycerin, and inorganic heating medium can be used as liquids, and inert gases such as Ar gas, nitrogen gas, carbon dioxide gas, etc. can be used as gases. However, from the viewpoint of heat transport, it is desirable to use a liquid. In particular, silicone oil does not pose a hygiene or safety problem to food even if it leaks.
It is most suitable as a heat medium.

FIG. 3 shows an example of the overall configuration of an apparatus (vegetable drying apparatus) for carrying out the method of the present invention. In FIG. 3, a long rectangular device exterior body 10 that is elongated from side to side is
The other end serves as a vegetable loading port 11, and the left end serves as a dried vegetable discharge port 12.

A conveyor 14 that forms a vegetable transport path 13 along the longitudinal direction is disposed within the device exterior body 10. This conveyor 14 uses a mesh belt as an endless annular belt for conveying vegetables, and is driven by a drive mechanism 16 consisting of a motor etc.
The conveyor surface 17 is configured to move from the side of the vegetable loading port 11 toward the side of the dried vegetable discharge port 12.

In the upper part of the device exterior body 10, there are shown the above-mentioned FIG.
A plurality of far-infrared generators P1 with the configuration shown in FIG.
P4 is the vegetable loading inlet 11 along the longitudinal direction of the device exterior body 10.
They are arranged in parallel from the side toward the dried vegetable outlet 12 side. These far-infrared ray generators P1 to P4 are
The far-infrared radiation surface, that is, the surface of the far-infrared radiation material layer 2 in FIGS. 1 and 2, is arranged substantially horizontally so as to face the transfer surface 17 of the conveyor 14.

Further, on the lower surface side of the transfer surface 17 of the conveyor 14, a plurality of far infrared ray generators P5 to P8 are arranged in parallel. These far-infrared ray generators P5 to P8 are also arranged so that their far-infrared ray emitting surfaces face the transfer surface 17 of the conveyor 14 from below. Roughly speaking, a near-infrared heater Q is disposed in the upper part of the apparatus exterior body 10, particularly at a position closer to the vegetable loading port 11 than the far-infrared generators P1 to P4.

Further, a hot air outlet 18 is provided on the upper surface of the apparatus exterior body 10 at a position close to the vegetable loading inlet 11, and this hot air outlet 18 is equipped with a blower 19 and a heat exchanger 20 for generating hot air. They are connected via a duct 21. In addition, a hot air outlet 2 is also provided on the lower surface side of the transfer surface 17 of the conveyor 14.
2 is provided, and the hot air generated by the blower 19 and the heat exchanger 20 is also guided to this hot air outlet 22. Roughly, an exhaust port 23 whose opening/closing degree can be adjusted is provided at a suitable location on the upper surface of the device exterior body.

FIG. 4 schematically shows an example of the main piping system connected to the drying apparatus shown in FIG. 3.

In FIG. 4, a fuel 30 made of gaseous fuel such as propane gas or liquid fuel such as kerosene is sent to a heating medium heating boiler 31 and used to heat a heating medium 6 such as silicone oil. The light is sent to an infrared heater Q and used to generate near-infrared light. The heat medium 6 heated to 120 to 250°C by the heat medium heating boiler 31 is sent to far infrared ray generators P1 to P4 and P5 to P8 via a pressure pump 33, and the heated heat medium 6 is A portion is sent to a heat exchanger 20 for generating hot air. The heat medium 6 sent to the far-infrared generators P1 to P4 and P5 to P8 passes through the flow path 5 in the housing 1, as already explained for the far-infrared generator P shown in FIGS. 1 and 2. 120~2.5
It is heated to 0℃ and emits far infrared rays. -5 heat exchanger 2
The heated heat medium 6 sent to 0 heats the air from the blower 19 and turns it into hot air 34. This hot air 34 is supplied to the exterior body 1 of the drying device from the hot air outlet 18.22 shown in FIG.
blown into 0. Note that the temperature of this hot air 34 is determined by the ambient temperature inside the device exterior body 10, especially the transfer surface of the conveyor 14]
The ambient temperature near No. 7 is adjusted to 40 to 150°C, preferably 50 to ioo°C. The heat medium 6 discharged from the far-infrared generators P1 to P4, Ps to P8 and the heat exchanger 20 returns to the heat medium heating boiler 31, is heated again, and is circulated and reused. In FIG. 4, 35 is an expansion tank, and 36 is an exhaust pipe of the boiler 31 for heating the heat medium.

When producing dried vegetables using the apparatus shown in FIG. 3 and FIG. The vegetables are sequentially placed on the transfer surface 17 of the conveyor 14 from the vegetable loading port 11 provided in the container. The vegetables 37 placed on the transfer surface 17 are continuously or intermittently transferred to the left in the figure as the conveyor 14 is driven. During this transfer, the vegetables 37 first pass under the near-infrared heater Q and are irradiated with near-infrared rays by the near-infrared heater Q, thereby first removing moisture from the surface layer of the vegetables. Next, the vegetables 37 sequentially pass between the far infrared ray generators P1 to P4 on the upper surface side and the far infrared ray generators P5 to P8 on the lower surface side. At this point, as already mentioned, in each of the far infrared ray generators P1 to P4 and P5 to P8, the radiation material layer is heated to 120 to 250° C., preferably 150° C., by the heating medium.
The vegetables 37 are heated to ~200°C, and relatively long wavelength far infrared rays are emitted, and the relatively long wavelength far infrared rays are irradiated onto the vegetables 37 from above and below. Also hot air outlet 18.2
Heat ff134 is blown out from 2, and the ambient temperature around the vegetables on the transfer surface 17 is controlled to 40 to 150'C1, preferably 50 to 100C. At such an ambient temperature, as described above, far infrared rays with relatively long wavelengths are irradiated onto the vegetables from above and below, thereby promoting drying of the vegetables, and finally, sufficiently dried vegetables are discharged from the dried vegetable outlet 12. It is carried outside.

Here, in the examples shown in FIGS. 3 and 4, the vegetables are irradiated with near-infrared rays before the vegetables are irradiated with far-infrared rays. Although near-infrared rays have low penetration into materials, they are effective in removing moisture adhering to the surface and moisture in the surface layer. -5 Far infrared rays have good penetration into the interior of a substance, but if moisture is present near the surface, it is absorbed by the moisture and becomes difficult to penetrate into the interior. However, as mentioned above, by irradiating near-infrared rays in advance, the moisture adhering to the surface of vegetables and the moisture in the surface layer can be quickly removed, which allows the far-infrared rays irradiated in the next step to reach the inside of the vegetables sufficiently. can be infiltrated. Therefore, in the case of the examples shown in Figures 3 and 4, the far infrared rays penetrate into the inside of the vegetables more fully than when simply irradiating them with far infrared rays, thereby preventing discoloration of the surface and deterioration of flavor. Whole vegetables can be dried in a shorter time without drying. As already mentioned, the heating temperature of the far-infrared emitting material layer in the far-infrared generator is 120 to 250°C, preferably 150°C.
Controlling the temperature to a relatively low temperature of ~200℃ and irradiating with relatively long-wavelength far infrared rays also prevents burnt surfaces, discoloration, flavor deterioration, and loss of vitamins, while increasing efficiency. Of course, it also contributes to drying in a short time.

It goes without saying that the method of the present invention can be applied to a wide variety of vegetables, including root vegetables, fruit vegetables, leafy vegetables, and potatoes. The present inventors have already conducted drying experiments on carrots, pumpkins, daikon radish, green onions, potatoes, sweet potatoes, and burdock root, but in all cases, problems such as burning on the surface, discoloration, and deterioration of flavor (aroma) occur. It has been confirmed that drying can be carried out efficiently and in a short time of less than one hour without any drying. In addition, it is thought that it can be applied to onions, cabbage, etc.

Effects of the Invention As is clear from the above explanation, the method for producing dried vegetables of the present invention can dry vegetables in a much shorter time and more efficiently than in the hot air drying method, which is the mainstream of conventional methods for producing dried vegetables. Vegetables can be obtained as well as discoloration and flavor (aroma)
It does not cause deterioration of vegetable quality such as deterioration of vegetables or loss of nutrients, and it is also advantageous in terms of cost because it can be produced with significantly lower equipment and operating costs than the freeze-drying method. ZaraniThe far-infrared generator used in the method of this invention has less variation in the temperature of the far-infrared emitting material compared to conventional far-infrared generators using electric heaters, and can be controlled accurately. In the method of the invention, the heating temperature of the far-infrared emitting material is controlled to a low temperature of 120 to 250 degrees Celsius, and as a result, vegetables are irradiated with far-infrared rays of a relatively long wavelength, which makes it difficult to use conventional far-infrared ray generators using electric heaters. Compared to drying methods using drying methods, it effectively prevents quality deterioration such as burning and discoloration of the vegetable surface, deterioration of flavor, and loss of nutrients such as vitamins, resulting in more efficient and high-quality drying. You can get vegetables. Furthermore, the far infrared rays used in the method of this invention also have a sterilizing effect, so it is possible to obtain dried vegetables containing a small amount of germs, so they can be used for sanitary purposes, such as food for infants or hospital food. It is ideal for producing dried vegetables for food products with strict requirements.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an example of a far-infrared ray generator used in the method of the present invention, FIG. 2 is a cross-sectional plan view taken along the line ■-■ in FIG. 1, and FIG. FIG. 4 is a longitudinal cross-sectional view showing an example of the overall structure of the drying device for implementation, and FIG. 4 is a line diagram showing the main piping system of the device shown in FIG. 3. p, pt~P4, Ps~P8... far infrared ray generator, 1... housing, 2... far infrared emitting material layer, 6
...Heating medium, 13...Transfer system path, 14...Conveyor, 17...Transfer surface. Applicant Hirokami Hoshino Shihoro Town Agricultural Cooperative Association

Claims (1)

[Scope of Claims] A method for producing dried vegetables by irradiating the fresh vegetables with far infrared rays while transporting the fresh vegetables along a required transport path, wherein a heat medium is circulated inside the far infrared ray generator. A far-infrared ray emitting material layer is formed on the outer surface of one of the flat surfaces of a flat box-shaped casing, and the far-infrared rays are generated by heating the far-infrared rays emitting material layer with the heat medium. , the far-infrared ray generating device is arranged such that the far-infrared ray emitting material layer faces the transport path, and 120 to
The vegetables on the transfer system are irradiated with the far infrared rays generated by passing a heating medium controlled within the range of 250°C through the casing of the far-infrared generator, and the ambient temperature in the transfer system is set at 40 to 150°C. A method for producing dried vegetables characterized by controlling within a range of.