JP7456704B2 - Method for producing dried vegetables and dried vegetables - Google Patents

Description

The present invention relates to a method for producing dried vegetables and dried vegetables.

Dried vegetables have traditionally been recognized as highly shelf-stable foods with little contamination by microorganisms, but contaminated dried vegetables can promote the growth of microorganisms if the conditions are favorable for microbial growth. Therefore, it is necessary to sterilize before drying to increase safety.

Common methods for sterilizing foodstuffs such as green onions and onions include methods using disinfectants and bacteriostatic agents such as sodium hypochlorite, and heating methods such as blanching. However, it is known that these methods have a large impact on quality, such as loss of texture and flavor, broken shape, and deterioration of color tone.

In particular, when sterilizing with sodium hypochlorite, it must be washed with a large amount of water to remove the unique odor that adheres, and a residence time of several minutes to several tens of minutes is required. Furthermore, it has the disadvantage that the concentration for continuous sterilization is extremely variable. In addition, due to the unique hypochlorite odor, it is difficult to perceive the flavor of vegetables, and the flavor of vegetables is washed away after multiple washings.

Regarding blanching, in order to obtain a sufficient sterilization effect, blanching at 80 to 100°C for several tens of seconds to several tens of minutes may cause the quality to deteriorate due to flavor leakage and moisture absorption. Specifically, there is a drawback that quality deterioration such as texture due to the destruction of shape and softening of the structure occurs.

As a technique related to blanching treatment, Patent Document 1 describes dried vegetables characterized by cutting raw vegetables into required sizes, blanching them, immersing the blanched vegetables in an emulsified oil and fat solution, and then freeze-drying the vegetables. A manufacturing method is disclosed. Patent Document 1 describes that freeze-dried vegetables obtained by incorporating emulsified oils and fats into vegetables, especially freeze-dried products of leafy and soft vegetables, do not have an adverse effect on flavor or appearance, and are free from brittleness, which is a drawback of freeze-dried products. It is stated that resistance to breakage due to properties can be imparted.

JP2001-178358

Patent Document 1 describes that a dried product is obtained that is less likely to break than a product freeze-dried without any further processing after blanching. However, Cited Document 1 is only a technology related to blanching, and as mentioned above, it cannot be denied that blanching can cause loss of shape and deterioration of quality due to softening of the tissue, so there is a demand for further improvements in shape and quality.

In addition, the natural sweetness of vegetables may be preferred, and it may be necessary to preserve the sweetness of such dried vegetables while performing appropriate sterilization treatment. As a result of the inventors' investigations, it was found that, as shown in Comparative Examples 2-1 and 2-2 described below, conventional sterilization treatments using sodium hypochlorite or blanching result in the loss of sweetness in vegetables after treatment.

As described above, there is a need for dried vegetables selected from dried green onions and dried onions that are sufficiently sterilized, hygienic, and have excellent texture, flavor, shape, and color. Furthermore, dried vegetables that can be sufficiently sweetened are desired.
An object of the present invention is to provide dried vegetables selected from dried green onions and dried onions, which are sufficiently sterilized, hygienic, and have excellent texture, flavor, shape, and color. Another object of the present invention is to provide dried vegetables that can be sufficiently sweetened.

As a result of intensive research to solve the above problems, the present inventors have found that (a) the above problems can be solved by producing dried vegetables through a process of treating cut green onions or onions with superheated steam containing fine water droplets. The present invention was completed based on the discovery that the problem can be solved.

Specific embodiments of the present invention are as follows. In this specification, when a numerical range is expressed using "A to B", the range includes A and B, which are the numerical values at both ends.
[1] A method for producing dried vegetables selected from dried green onions and dried onions, comprising: (a) treating cut green onions or onions with superheated steam containing fine water droplets; and (b) the above-mentioned steps. The method described above, comprising the step of drying the green onions or onions after the treatment in step (a).
[2] The method according to [1], wherein the treatment in step (a) is performed at a temperature of 90°C or higher and 140°C or lower.
[3] The method according to [1] or [2], wherein the treatment in step (a) is performed for 1 second or more and 5 minutes or less.
[4] The method according to any one of [1] to [3], including the step of (i) treating the cut green onions or onions with a pH adjusting solution before the step (a).
[5] Between the step (a) and the step (b), (ii) including a step of treating the green onions or onions after the treatment in the step (a) with a pH adjusting solution or water; [ The method described in any one of [1] to [4].
[6] The method according to [4] or [5], wherein the pH of the pH adjusting solution in step (i) or (ii) is 5.0 or more and 7.5 or less.
[7] The method according to any one of [4] to [6], wherein the treatment in step (i) or (ii) is performed for 5 seconds or more and 20 minutes or less.
[8] The method according to any one of [4] to [7], wherein the treatment in step (i) or (ii) is immersion or spraying.
[9] The method according to any one of [1] to [8], wherein the dried vegetable contains 40.0% by mass or more of sugar and 0.075% by mass or less of pyruvic acid.
[10] The dried vegetable having a sugar content of 40.0% by mass or more and a pyruvic acid content of 0.075% by mass or less, the dried vegetable being selected from dried green onions and dried onions.

According to the production method of the present invention, dried vegetables selected from dried green onions and dried onions can be obtained, which are sufficiently sterilized, hygienic, and have excellent texture, flavor, shape, and color. Moreover, according to the production method of the present invention, dried vegetables with a sufficient sweetness can be obtained.

FIG. 1 is a schematic diagram showing an apparatus for generating superheated steam containing fine water droplets. It is a graph showing the evaluation results of texture, flavor, shape, and color tone of Examples 1-7 to 1-12 and Comparative Examples 1-4 to 1-6. 2 is a graph showing the results of sugar content and pyruvic acid content in Example 2-1 and Comparative Examples 2-1 to 2-4. It is a graph showing the evaluation results of sweetness and spiciness of Example 2-2 and Comparative Examples 2-5 to 2-8.

Hereinafter, the method for producing dried vegetables and the dried vegetables of the present invention will be explained in detail. However, the present invention is not limited to the following description.

(Method for producing dried vegetables)
The method for producing dried vegetables of the present invention includes (a) a step of treating cut green onions or onions with superheated steam containing fine water droplets, and (b) green onions or onions after the treatment in step (a). including the step of drying.

The type of cut green onions or onions to be treated in step (a) is not particularly limited, but green onions are particularly preferred. Examples of green onions include white onions, green onions, Kujo green onions, Shimonita green onions, leeks, and red onions, and examples of onions include yellow onions, red onions, Pekorosu, and the like. The cut green onions or onions may be fresh or frozen. For frozen products, green onions or onions that have been heat-treated while thawing may be used, or green onions or onions that have been seasoned may be used. The method of cutting green onions or onions is not particularly limited, but thin slicing and diagonal slicing are preferred.

The superheated steam containing fine water droplets in step (a) is a gas-liquid two-phase heating medium in which high-temperature fine water droplets are dispersed in superheated steam.

The method of generating superheated steam containing fine water droplets is not particularly limited and can be generated using a known device, but a device that injects hot water such as the device disclosed in JP-A No. 2007-228870 and the like can be used. It can be generated by a device having a heating chamber equipped with a device for injecting superheated steam. As an apparatus for generating superheated steam containing such fine water droplets, it is desirable that the inside of the heating chamber can be further heated by conduction heating, radiation heating, high frequency heating, or the like. As a device for generating superheated steam containing fine water droplets, an Aqua Cooker (registered trademark) manufactured by Taiyo Seisakusho Co., Ltd. can be used.

An example of an apparatus for generating superheated steam containing fine water droplets is shown in FIG. In FIG. 1, an apparatus for generating superheated steam containing fine water droplets is composed of a chamber 10, a superheated steam generator 20, and a fine water droplet (hot water) generator 30. Vegetables 40 to be processed are placed on a table inside the chamber 10, and the inside of the chamber 10 can be heated by the internal heater 50. The superheated steam generator 20 includes a heater 61 and a channel 71, and can heat the steam (V) passing through the channel 71 with the heater 61 to turn it into superheated steam. The superheated steam generated by the superheated steam generator 20 is injected into the chamber 10 from the nozzle 81. The fine water droplet (hot water) generator 30 includes a heater 62 and a flow path 72, and can heat water (W) passing through the flow path 72 with the heater 62 to turn it into hot water. The hot water generated by the fine water droplet (hot water) generator 30 is injected into the chamber 10 from the nozzle 82, and the hot water is dispersed in the superheated steam filling the chamber 10 as fine water droplets.

The temperature of the superheated steam containing fine water droplets in step (a) is preferably 90°C or more and 140°C or less, more preferably 100°C or more and 140°C or less.

The heat treatment time using superheated steam containing fine water droplets in step (a) varies depending on the cutting method and size, the type of leeks or onions, and the temperature conditions, but is preferably from 1 second to 5 minutes, more preferably from 1 second to 150 seconds, even more preferably from 5 seconds to 80 seconds, and most preferably from 10 seconds to 30 seconds. However, if the heat treatment time is too long, there is a possibility of quality deterioration due to deformation or softening of the tissue, and if the heat treatment time is too short, microbial control will not be possible, so it should be set appropriately.

The amount of water in the superheated steam containing fine water droplets may be sufficient to cover the surface of the green onions or onions, and the amount of water in the superheated steam containing fine water droplets may be sufficient to cover the surface of the green onions or onions. can be brought into contact with superheated steam containing fine water droplets.
The amount of water in the heating chamber in step (a) (the total amount of superheated steam and hot water introduced into the chamber per 100 seconds) (ml/100 seconds) is preferably 1200 ml or more and 3000 ml or less, and 1500 ml or more and 2700 ml or less. is more preferable, and most preferably 1800 ml or more and 2400 ml or less.

In an apparatus that generates superheated steam containing fine water droplets, it is preferable to place the green onions or onions to be treated evenly so that they do not overlap to some extent, but there is no problem even if they are in a thick layer.

The method of drying in step (b) is not particularly limited, but includes hot air drying, freeze drying, etc. Among these, freeze drying is preferred. The pressure during freeze-drying is not particularly limited, but can be 200 Pa or less. Further, in step (b), for example, the product can be pre-frozen for about 2 to 24 hours in a freezer with an internal temperature of -20 to -35°C, and then freeze-dried in a vacuum freeze dryer.
Before step (b), the green onions or onions treated in step (a) may be soaked in sugar or seasoned, or the surface of the green onions or onions may be soaked in oil or fat or an emulsifier. It may be processed.

The method for producing dried vegetables of the present invention can include, before step (a), the step of (i) treating cut green onions or onions with a pH adjusting solution. Moreover, the method for producing dried vegetables of the present invention includes, between step (a) and step (b), a step (ii) of treating the vegetables after the treatment in step (a) with a pH adjusting solution or water. be able to. By performing either or both of the above step (i) and step (ii), the pH of the vegetables after the treatment in step (a) can be adjusted to preferably 4.0 or more and 8.0 or less, more preferably 4. It can be adjusted to .5 or more and 7.8 or less, most preferably 5.0 or more and 7.5 or less. By adjusting the pH of green onions or onions, it is possible to prevent the green onions or onions from turning brown (browning) after drying. The reason why browning of green onions or onions after drying can be prevented by adjusting the pH of green onions or onions in this way is not clear, but it is presumed as follows.
It is thought that the pH of condensed water of superheated steam containing fine water droplets becomes as high as about 9.0 to 10.0 because carbon dioxide dissolved in water evaporates and basic ions become predominant. When green onions or onions that have been treated with superheated steam containing fine water droplets are heated in a drying process, browning occurs due to the amino acids and reducing sugars contained in the green onions or onions. It is thought that a Maillard reaction may occur. The reaction rate of the Maillard reaction varies depending on the conditions, and it is known that the reaction is accelerated under high pH (basic) conditions. Therefore, it is considered that after treatment with high pH water, the Maillard reaction progresses during freeze-drying, resulting in browning of green onions or onions. In the present invention, it is considered that browning due to the Maillard reaction can be suppressed by neutralizing by treating with a pH adjusting liquid or water before and/or after the treatment with superheated steam containing fine water droplets.

The pH adjusting liquid is not particularly limited, but is preferably an acid liquid. The acid used in the acid solution is preferably an organic acid, and acids that can be used in foods, such as acetic acid, lactic acid, citric acid, malic acid, and gluconic acid, can be appropriately selected and used.
The pH of the pH adjusting liquid can be adjusted to preferably 4.0 or more and 8.0 or less, more preferably 4.5 or more and 7.8 or less, and most preferably 5.0 or more and 7.5 or less.
The treatment time in step (i) or (ii) can be set as appropriate, but is preferably 5 seconds or more and 30 minutes or less, preferably 5 seconds or more and 20 minutes or less, and most preferably 10 seconds or more and 20 minutes or less.
The type of treatment in step (i) or (ii) is not particularly limited, but immersion or spraying is preferred, and immersion is more preferred.

Although the sugar content of the dried vegetables obtained by the production method of the present invention is not particularly limited, it is preferably 40.0% by mass or more, more preferably 45.0% by mass or more, and 48.0% by mass or more based on the whole dried vegetables. Most preferably it is % by mass or more. The upper limit of the sugar content of the dried vegetables is not particularly limited, but the upper limit of the sugar content is preferably 70.0% by mass, and most preferably 75.0% by mass. By controlling the sugar content of the dried vegetables within the above numerical range, dried vegetables with excellent sweetness can be obtained.
In the present invention, sugar content (mass%) refers to the sum of fructose content (mass%), glucose content (mass%), and sucrose content (mass%). means. The content (mass%) of each of fructose, glucose, and sucrose can be measured according to the method described in the Examples below.

The content of pyruvic acid in the dried vegetables obtained by the production method of the present invention is not particularly limited, but is preferably 0.075% by mass or less, more preferably 0.070% by mass or less, and 0.075% by mass or less, more preferably 0.070% by mass or less, based on the whole dried vegetables. The most preferable amount is 0.065% by mass or less. The lower limit of the content of pyruvic acid in the dried vegetables is not particularly limited, and the lower the ratio is, the more preferable it is, but the lower limit of the content of pyruvic acid is preferably 0.03% by mass, more preferably 0.04% by mass. Preferably, 0.05% by weight is most preferred. By controlling the sugar content of the dried vegetables within the above numerical range, dried vegetables with excellent sweetness can be obtained. The content of pyruvic acid (mass%) can be measured according to the method described in the Examples below.

The dried vegetables produced in this manner have a strong sweetness that is superior to existing methods in terms of a texture similar to that of fresh vegetables, good flavor, shape, color tone, etc. when reconstituted with hot water.

(dried vegetables)
The dried vegetables of the present invention have a sugar content of 40.0% by mass or more, a pyruvic acid content of 0.075% by mass or less, and are selected from dried green onions and dried onions. As the sugar content and the pyruvic acid content, those within the numerical ranges shown in the above-mentioned (method for producing dried vegetables) can be used.
The types of green onions or onions used for the dried green onions or dried onions of the present invention are not particularly limited, and the types shown in the above (method for producing dried vegetables) can be used.
The production method for the dried vegetables of the present invention is not particularly limited, but it is preferable to produce them using the production method shown in (Method for producing dried vegetables) above.

This embodiment will be specifically described below using examples.

(Example 1) Confirmation of superiority of superheated steam treated product containing fine water droplets

(Example 1-1)
Nebuka green onions (white onions) from Hokkaido were washed and then cut diagonally at intervals of 8 mm, and only the white parts of the leaf sheaths of the cut white onions were taken out. Then, 200 g of the white part of the leaf sheath that was taken out was placed in a heating cooking device (Aqua Cooker (registered trademark) manufactured by Taiyo Seisakusho Co., Ltd.) that uses superheated steam containing fine water droplets, and the temperature was set at 120°C. The treatment was performed for 10 seconds under the condition that the amount of water in the heating chamber was 2000 ml/100 seconds. After pre-freezing the white onions after processing with a heating cooking device in a freezer with an internal temperature of -35°C, vacuum freeze-drying was performed for 18 hours at a pressure of 100 Pa and a shelf heating temperature of 50 to 70°C to obtain dried white onions. .

(Example 1-2)
Dried white onions were obtained in the same manner as in Example 1-1, except that the processing time using the cooking device was changed to 20 seconds instead of 10 seconds.

(Examples 1 to 3)
Dried white leek was obtained in the same manner as in Example 1-2, except that after the treatment with the heating cooking appliance and before the vacuum freeze-drying treatment, a container filled with water was prepared, and the white leek was completely immersed in the water in the container and left to stand for 10 minutes.

(Examples 1 to 4)
Dried white onions were obtained in the same manner as in Example 1-3, except that instead of treatment with water using a container filled with water, a 0.008% aqueous citric acid solution (pH = 5) was used and the white onions were immersed in the citric acid solution and left to stand for 10 minutes.

(Example 1-5)
Dried white onions were obtained in the same manner as in Example 1-1, except that the processing time using the heating cooking device was changed to 40 seconds instead of 10 seconds.

(Examples 1 to 6)
Dried white leek was obtained in the same manner as in Example 1-1, except that the treatment time in the heating cooking appliance was changed from 10 seconds to 120 seconds.

(Comparative example 1-1)
Nebuka green onions (white onions) from Hokkaido were washed and then cut diagonally at intervals of 8 mm, and only the white parts of the leaf sheaths of the cut white onions were taken out. Then, prepare a container containing a sodium hypochlorite aqueous solution with a concentration of 200 ppm, completely immerse 200 g of the white part of the leaf sheath that was taken out in the sodium hypochlorite aqueous solution in the container, and leave it for 10 minutes. The white onions were taken out of the container and thoroughly washed with water. The washed white onions were pre-frozen in a freezer with an internal temperature of -35°C, and then vacuum freeze-dried at a pressure of 100 Pa and a shelf heating temperature of 50 to 70°C for 18 hours to obtain dried white onions.

(Comparative example 1-2)
Nebuka green onions (white onions) from Hokkaido were washed and then cut diagonally at intervals of 8 mm, and only the white parts of the leaf sheaths of the cut white onions were taken out. Then, prepare a container filled with boiling water, completely immerse 200 g of the white part of the leaf sheath in the container, and blanch it for 150 seconds at a temperature of 98°C. The white onions were taken out and thoroughly cooled with cold water. The cooled white onions were pre-frozen in a freezer with an internal temperature of -35°C, and then vacuum freeze-dried at a pressure of 100 Pa and a shelf heating temperature of 50 to 70°C for 18 hours to obtain dried white onions.

(Comparative example 1-3)
Dried white onions were obtained in the same manner as in Example 1-1, except that 200 g of the white part of the leaf sheath, which was taken out without being treated with a heating cooking device, was freeze-dried as it was.

The dried white leek samples of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3 were evaluated as follows. The evaluation results are shown in Table 6 below.

(Evaluation based on general viable bacteria count)
The general viable bacterial count was measured for each of the dried white leek samples of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3 as described below. The test was performed in accordance with the "2015 Food Sanitation Inspection Guideline - Microorganisms" supervised by the Ministry of Health, Labor and Welfare, and the culture was performed at 35°C for 48 hours.
If the general viable cell count is 5.0 x ¹⁰³ or less, the number of microorganisms is small and it can be said that there are no hygiene problems as a food.

(Sensory evaluation: texture)
Dried white onions from Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3 were placed in a container made of foamed styrene sheet (diameter 145 mm, depth 75 mm, bowl-shaped), and the container was placed at a depth of 70 mm. Pour boiling water at 95°C into the container and let it stand for 2 minutes and 30 seconds to reconstitute the water. After reconstitution, the white onions of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3 soaked in hot water were evaluated for texture by five panelists. For the evaluation of the texture of each white onion, the white onion of Comparative Example 1-3, which was dried without being treated with a heating cooking device, was taken as a standard product, and those that were equivalent to the standard product were given a rating of 3. Each panelist evaluated the evaluation using the following three-level criteria, and the average value of the five panelists was calculated. When the average value had a decimal part, the score was calculated by rounding to the first decimal place.

(Sensory evaluation: flavor)
Regarding the white onions of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3, which were soaked in boiling water after being rehydrated using the same procedure as above (sensory evaluation: texture). The flavor was evaluated by five panelists. To evaluate the flavor of each white onion, the white onion of Comparative Example 1-3, which was dried without being treated with a heating cooking device, was taken as a standard product, and those that were equivalent to the standard product were given a 3, and each The evaluation was performed by panelists using the following three-level criteria, and the average value of the five panelists was calculated. When the average value had a decimal part, the score was calculated by rounding to the first decimal place.

(Evaluation of shape)
The shapes of the dried white onions of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3 were observed. The shape of each dried white onion was evaluated using the following three-level scoring criteria.

(Evaluation of color tone)
The color tone of each of the dried white onions of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3 was observed. The color tone of each dried white onion was evaluated using the following three-level scoring criteria.

(comprehensive evaluation)
Regarding the dried white onions of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3, the overall number of viable bacteria and the evaluation of texture, flavor, shape, and color were evaluated according to the following criteria. We conducted an evaluation.

As can be seen from the results in Table 6 above, Examples 1-1 to 1-4, which were treated with superheated steam containing fine water droplets, had a small number of viable bacteria and were sufficiently sterilized. Good results were obtained in terms of flavor, shape, and color tone, and the product had sufficient quality. In particular, Example 1-3, in which the process of immersion in water was further performed, and Example 1-4, in which the process of immersion in a citric acid aqueous solution was further performed, were different from Examples 1-1 and 1, in which these treatments were not performed. -2, the color tone was better.

On the other hand, Comparative Example 1-1, which was treated with an aqueous sodium hypochlorite solution, had a small number of viable bacteria and an excellent texture evaluation, but the flavor was particularly poor compared to Examples 1-1 to 1-6. It was inferior, had a whitish discoloration, and had some core loss. Comparative Example 1-2, which was subjected to blanching treatment, had a small number of viable bacteria, but was particularly inferior in texture, flavor, and shape compared to Examples 1-1 to 1-6. Comparative Example 1-3, which was not treated with superheated steam containing fine water droplets, had good texture, flavor, and color, but the general viable bacteria count was lower than in Examples 1-1 to 1-6. In addition, core omission occurred, and the shape evaluation was inferior to Examples 1-1 to 1-6.

From the results of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3, it is clear that dry whites with good texture, flavor, shape, and color can be obtained by treatment with superheated steam containing fine water droplets. It turns out that green onions are obtained. Furthermore, it has been found that in addition to the treatment with superheated steam containing fine water droplets, dry white onions with a more stable color tone can be obtained by further performing a treatment of immersion in water or an aqueous citric acid solution. Furthermore, microbial control is possible even with a short-time treatment using superheated steam containing fine water droplets, and the texture is closer to that of raw food when rehydrated than existing methods such as treatment with an aqueous sodium hypochlorite solution or blanching treatment. It was found that dried white onions with excellent characteristics in terms of flavor, color, etc. can be obtained.

(Examples 1-7 to 1-12 and Comparative Examples 1-4 to 1-6)
Regarding the above-mentioned evaluation of texture, flavor, shape, and color tone, the number of panelists was increased to 25 and evaluation was performed. The evaluation results are shown in Table 7 and FIG. 2 below.
The dried white onions of Examples 1-7 to 1-12 and Comparative Examples 1-4 to 1-6 were prepared in the same manner as in Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3, respectively. That's what I got.

(Sensory evaluation: texture)
For the evaluation of the texture of each white onion, the white onion of Comparative Example 1-6, which was dried without being treated with a heating cooking device, was used as a standard product. From the perspective of whether or not it retains a crunchy texture similar to that of raw white onions, ``0'' indicates that it is equivalent to the standard product, and ``1'' indicates that it is better than the standard product. The score was "2" if it was even better than the standard product, "-1" if it was inferior to the standard product, and "-2" if it was even worse than the standard product. Then, the average value of the evaluations of the 25 panelists was calculated.

(Sensory evaluation: flavor)
For flavor evaluation of each white onion, the white onion of Comparative Example 1-6, which was dried without being treated with a heating cooking device, was used as a standard product. From the perspective of whether the flavor is close to the state of raw white onions and is good, ``0'' indicates that it is equivalent to the standard product, ``1'' indicates that it is better than the standard product, and ``1'' indicates that it is even better than the standard product. A score of "2" indicates that the quality is good, a score of "-1" indicates that the product is inferior to the standard product, and a "-2" indicates that the product is even worse than the standard product. Then, the average value of the evaluations of the 25 panelists was calculated.

(Evaluation of shape)
For evaluation of the shape of each dried white onion, the dried white onion of Comparative Example 1-6 was used as a standard product. From the perspective of whether the shape is good (no core loss or crushing), ``0'' indicates that it is equivalent to the standard product, ``1'' indicates that it is superior to the standard product, A score of "2" indicates that the product is even better than the standard product, a score of "-1" indicates that the product is inferior to the standard product, and a score of "-2" indicates that the product is even worse than the standard product. Then, the average value of the evaluations of the 25 panelists was calculated.
Note that core removal here refers to a phenomenon in which the core of the green onion and the layered leaves surrounding it separate.

(Evaluation of color tone)
For evaluation of the color tone of each dried white onion, the dried white onion of Comparative Example 1-6 was used as a standard product. From the perspective of whether the color tone is close to that of raw white onions, "0" indicates that it is equivalent to the standard product, "1" indicates that it is better than the standard product, and "1" indicates that it is even better than the standard product. "2" indicates that the product is inferior to the standard product, "-1" indicates that the product is inferior to the standard product, and "-2" indicates that the product is even worse than the standard product. Then, the average value of the evaluations of the 25 panelists was calculated.

As can be seen from the results in Table 7 and Figure 2 above, Examples 1-7 to 1-10, which were treated with superheated steam containing fine water droplets, also had good results in terms of texture, flavor, shape, and color, and were of sufficient quality. In particular, Example 1-9, which was further treated by immersing in water, and Example 1-10, which was further treated by immersing in an aqueous citric acid solution, had better color than Examples 1-7 and 1-8, which were not treated in this way.

On the other hand, Comparative Example 1-4 treated with an aqueous sodium hypochlorite solution was particularly inferior in flavor and shape compared to Examples 1-7 to 1-12. Comparative Example 1-5, which was subjected to blanching treatment, was particularly inferior in texture, flavor, and shape compared to Examples 1-7 to 1-12.

From the results of Examples 1-7 to 1-12 and Comparative Examples 1-4 to 1-6, dry whites with good texture, flavor, shape, and color can be obtained by treatment with superheated steam containing fine water droplets. It turns out that green onions are obtained. Furthermore, it has been found that in addition to the treatment with superheated steam containing fine water droplets, dry white onions with a more stable color tone can be obtained by further performing a treatment of immersion in water or an aqueous citric acid solution. Furthermore, the treatment with superheated steam containing fine water droplets is superior to existing methods such as treatment with an aqueous sodium hypochlorite solution or blanching treatment in terms of texture, flavor, and color that are closer to those of raw food when reconstituted with hot water. It was found that dried white onions with excellent properties were obtained.

The results of Examples 1-7 to 1-12 and Comparative Examples 1-4 to 1-6 are highly consistent with the results of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-3. As shown in Figure 2, the results of Examples 1-7 to 1-12 and Comparative Examples 1-4 and 1-5 include many results that show significant differences (*p<0.05, **p<0.01) when compared to Comparative Example 1-6, and can be said to be highly reliable results.

(Example 2) Sensory test and sugar and pyruvic acid analysis for each heat treatment Regarding the perception of sweetness of green onions by treatment method, an analysis was performed on the relationship between sensory test and the content of sugar and pyruvic acid. Cystine sulfoxides, which are sulfur-containing components that are precursors of irritating substances such as the hotness and smell of green onions, are decomposed by the action of the enzyme alliinase present in cells due to cell damage or destruction, and irritating substances such as thiosulfinates are generated, and pyruvic acid is generated simultaneously in this process. Taking advantage of this characteristic, pyruvic acid was measured instead of measuring volatile substances that are highly volatile and difficult to quantify, and was used as an index of the amount of irritating substances generated that cause hotness.

(Example 2-1)
Dried white onions were obtained in the same manner as in Example 1-2.

(Comparative example 2-1)
Dried white onions were obtained in the same manner as in Comparative Example 1-1.

(Comparative example 2-2)
Dried white onions were obtained in the same manner as in Comparative Example 1-2.

(Comparative example 2-3)
Nebuka green onions (white onions) from Hokkaido were washed and then cut diagonally at intervals of 8 mm, and only the white parts of the leaf sheaths of the cut white onions were taken out. Then, 200 g of the white part of the removed leaf sheath was placed in a cooking device that uses saturated steam and processed for 20 seconds at a set temperature of 98°C and a saturated steam amount of 120 kg/h. . After pre-freezing the white onions after processing with a heating cooking device in a freezer with an internal temperature of -35°C, vacuum freeze-drying was performed for 18 hours at a pressure of 100 Pa and a shelf heating temperature of 50 to 70°C to obtain dried white onions. .

(Comparative example 2-4)
Dried white onions were obtained in the same manner as in Comparative Example 1-3.

The dried white onions of Example 2-1 and Comparative Examples 2-1 to 2-4 were evaluated as follows. The evaluation results are shown in Table 10 below.

(Sensory evaluation: sweetness)
The white onions of Example 2-1 and Comparative Examples 2-1 to 2-4 were soaked in boiling water after being rehydrated using the same procedure as in Example 1 (sensory evaluation: texture). The sweetness was evaluated by five panelists. In evaluating the sweetness of each white onion, the white onion of Comparative Example 2-4, which was dried without being processed using a heating cooking device, was used as a standard product, and those that were equivalent to the standard product were given a 3, and each The evaluation was performed by a panelist using the following 5-level criteria, and the average value of the 5 panelists was calculated. When the average value had a decimal part, the score was calculated by rounding to the first decimal place.

(Sensory evaluation: spiciness)
The white onions of Example 2-1 and Comparative Examples 2-1 to 2-4 were soaked in boiling water after being rehydrated using the same procedure as in Example 1 (sensory evaluation: texture). The spiciness was evaluated by five panelists. The spiciness of each white onion was evaluated using the white onion of Comparative Example 2-4, which was dried without being treated with a heating cooking device, as a standard product, and those that were equivalent to the standard product were given a score of 4. The evaluation was performed by a panelist using the following 5-level criteria, and the average value of the 5 panelists was calculated. When the average value had a decimal part, the score was calculated by rounding to the first decimal place.

(Measurement of sugar content)
For the dried white onions of Example 2-1 and Comparative Examples 2-1 to 2-4, the content (mass%) of fructose, glucose, and sucrose was analyzed according to the following procedure, and the total sum was determined. The sugar content (mass%) was determined. Sugar was measured by high performance liquid chromatography (HPLC). The dried white onions of Example 2-1 and Comparative Examples 2-1 to 2-4 were ground using a coffee mill. Approximately 40 mL of pure water was added to 1 g of the ground dry white onions, stirred, and heated in an ultrasonic water tank. After extraction for 10 minutes, the extracted aqueous solution was transferred to a 50 mL volumetric flask, and pure water was added to make the volume 50 mL. The resulting aqueous solution was filtered with filter paper and then passed through a 0.45 μm filter to obtain an HPLC sample. Using 1% solutions of fructose, glucose, and sucrose as standard solutions, the obtained HPLC samples were quantified by HPLC.
HPLC conditions are as follows.
Column: ULTRON PS-80N 300×8.0mmI.D.×2+PS-80N.G 50×8.0mmI.D. (Shinwa Manufacturing), Mobile phase: Water, Flow rate 0.8mL/min, Temperature: 60℃, Detection Instrument: Differential refractometer.

(Measurement of pyruvic acid production amount)
The dried white onions of Example 2-1 and Comparative Examples 2-1 to 2-4 were ground using a coffee mill. Approximately 40 mL of pure water was added to 1 g of the ground dry white onions, stirred, and heated in an ultrasonic water tank. After extraction for 10 minutes, the extracted aqueous solution was transferred to a 50 mL volumetric flask, and pure water was added to make the volume 50 mL. The resulting aqueous solution was filtered through a filter paper, passed through a 0.45 μm filter, and the filtrate was taken out. 2 ml of 6% trichloroacetic acid was added to 0.5 ml of the filtrate, stirred, and left at room temperature for 1 hour. To the resulting mixture, 1 ml of 0.0125% dinitrophenylhydrazine (dissolved in 2 mol·L ⁻¹ HCL) was added, stirred, and then held at 37° C. for 10 minutes. To the obtained mixture, 5 ml of 0.8 mol·L ⁻¹ NaOH was added and stirred for 5 minutes, and the absorbance of the obtained mixture at 420 nm was measured using a colorimeter. A calibration curve was created using a pyruvic acid standard solution, and the content (% by mass) of pyruvic acid in dried white onions was calculated from the absorbance obtained based on the calibration curve.

The relationship between the sugar content (mass %) and the pyruvic acid content (mass %) in Table 10 is shown in FIG. 3 as a graph.

As can be seen from the results in Table 10 and FIG. 3, Example 2-1 treated with superheated steam containing fine water droplets had a strong sweet taste, while no pungency was felt at all.

On the other hand, it was found that Comparative Example 2-1 treated with an aqueous sodium hypochlorite solution had both a higher sugar content and a higher pyruvic acid content than Example 2-1. Furthermore, it was found that Comparative Example 2-1 had a weaker sweetness and a stronger spiciness than Example 2-1, despite having a higher sugar content. In Comparative Example 2-1, unlike Example 2-1, hypochlorous acid odor remained.

Comparative Example 2-2, which was subjected to blanching treatment, was found to have a lower sugar content and a higher pyruvic acid content than Example 2-1. Furthermore, it was found that Comparative Example 2-2 had a weaker sweetness and a stronger spiciness than Example 2-1.

Comparative Example 2-3, which was processed using a cooking device that uses saturated steam, had a similar sugar content to Example 2-1, but was found to have a higher pyruvic acid content. Also, Comparative Example 2-3 was found to have a weaker sweetness and a stronger spiciness than Example 2-1, despite having a similar sugar content.

Comparative Example 2-4, which was not subjected to treatment with superheated steam containing fine water droplets, was found to have higher sugar content and pyruvic acid content than Example 2-1. Furthermore, it was found that Comparative Example 2-4 had a weaker sweetness and a stronger spiciness than Example 2-1, despite having a higher sugar content.

From the above, it is inferred that sweetness varies not only by the sugar content but also by the amount of irritating substances that can be determined based on the pyruvic acid content. It is presumed that by treating with superheated steam containing fine water droplets, the content of irritating substances is reduced, thereby increasing the sweetness and weakening the spiciness.

In Example 2-1, the pyruvate ratio is the lowest and the sugar ratio is maintained to a certain extent, so it can be said that the sweetness is felt most strongly, and this state is confirmed by the results of sensory evaluation. is also supported. As shown in Example 2, it was found that by treating with superheated steam containing fine water droplets, it was possible to produce dried vegetables with a stronger sweetness than in the conventional method.

(Example 2-2 and Comparative Examples 2-5 to 2-8)
Regarding the above-mentioned sweetness and spiciness evaluations, the number of panelists was increased to 25 and the evaluations were conducted. The evaluation results are shown in Table 11 and FIG. 4 below.
The dried white onions of Example 2-2 and Comparative Examples 2-5 to 2-8 were obtained in the same manner as in Example 2-1 and Comparative Examples 2-1 to 2-4, respectively.

(Sensory evaluation: sweetness)
For evaluating the sweetness of each white onion, the white onion of Comparative Example 2-8, which was dried without being treated with a heating cooking device, was used as a standard product. ``0'' if it is equivalent to the standard product, ``1'' if it is better than the standard product, ``2'' if it is even better than the standard product, and ``-'' if it is inferior to the standard product. 1", and if it was even worse than the standard product, it was rated "-2". Then, the average value of the evaluations of the 25 panelists was calculated.

(Sensory evaluation: spiciness)
For the evaluation of the spiciness of each white onion, the white onion of Comparative Example 2-8, which was dried without being treated with a heating cooking device, was used as a standard product. ``0'' if it is equivalent to the standard product, ``1'' if it is better than the standard product, ``2'' if it is even better than the standard product, and ``-'' if it is inferior to the standard product. 1", and if it was even worse than the standard product, it was rated "-2". Then, the average value of the evaluations of the 25 panelists was calculated.

As can be seen from the results in Table 11 and Figure 4 above, Example 2-2, which was treated with superheated steam containing fine water droplets, was more effective than Comparative Example 2-8, which was not treated with superheated steam containing fine water droplets. , it had an extremely strong sweet taste, while its spiciness was very weak.

On the other hand, it was found that Comparative Example 2-5, which was treated with an aqueous sodium hypochlorite solution, had a weaker sweetness and a very strong spiciness compared to Example 2-2.

Comparative Example 2-6, which was subjected to blanching treatment, and Comparative Example 2-7, which was treated with a heating cooking device using saturated steam, were found to have weaker sweetness and stronger spiciness than Example 2-2. Ta.

From the results of Example 2-2 and Comparative Examples 2-5 to 2-8, it was found that it is possible to produce dried vegetables with a stronger sweetness than the conventional method by treating with superheated steam containing fine water droplets. Ta.

The results of Example 2-2 and Comparative Examples 2-5 to 2-8 are in extremely good agreement with the results of Example 2-1 and Comparative Examples 2-1 to 2-4. As shown in FIG. 4, the results of Example 2-2 and Comparative Examples 2-5 to 2-7 are all significantly different from Comparative Example 2-8: **p<0 .01, which can be said to be an extremely reliable result.

(Reference example) Sensory evaluation using sugar and pyruvic acid From the results of Example 2, we believe that the sugar content is not simply an indicator of sweetness, and that the content of pyruvic acid is also related to the indicator of sweetness. It will be done. In order to prove this, an aqueous solution having the same sugar content and pyruvic acid content as in the dried white onions of Example 2 was prepared, and its sweet taste was verified.

(Reference example 1)
By adding predetermined amounts of fructose, glucose, and sucrose to purified water and dissolving them by heating, and adding a predetermined amount of pyruvic acid to the resulting aqueous solution, 21.3% by mass of fructose, 24.2% by mass of glucose, An aqueous solution containing 3.1% by mass of sucrose and 0.062% by mass of pyruvic acid was prepared. Reference Example 1 corresponds to Example 2-1.

(Reference example 2)
By adding predetermined amounts of fructose, glucose, and sucrose to purified water and dissolving them by heating, and adding a predetermined amount of pyruvic acid to the resulting aqueous solution, 22.6% by mass of fructose, 23.0% by mass of glucose, An aqueous solution containing 3.7% by mass of sucrose and 0.062% by mass of pyruvic acid was prepared.

(Reference example 3)
By adding predetermined amounts of fructose, glucose, and sucrose to purified water and dissolving them by heating, and adding a predetermined amount of pyruvic acid to the resulting aqueous solution, 22.6% by mass of fructose, 23.0% by mass of glucose, An aqueous solution containing 3.7% by mass of sucrose and 0.091% by mass of pyruvic acid was prepared. Reference Example 3 corresponds to Comparative Example 2-3.

(Reference example 4)
By adding predetermined amounts of fructose, glucose, and sucrose to purified water and dissolving them by heating, and adding a predetermined amount of pyruvic acid to the resulting aqueous solution, 24.2% by mass of fructose, 26.0% by mass of glucose, An aqueous solution containing 2.5% by mass of sucrose and 0.212% by mass of pyruvic acid was prepared. Reference Example 4 corresponds to Comparative Example 2-4.

(Reference example 5)
By adding predetermined amounts of fructose, glucose, and sucrose to purified water and dissolving them by heating, and adding a predetermined amount of pyruvic acid to the resulting aqueous solution, 24.2% by mass of fructose, 26.0% by mass of glucose, An aqueous solution containing 2.5% by mass of sucrose and 0.091% by mass of pyruvic acid was prepared.

The aqueous solutions of Reference Examples 1 to 5 were evaluated as follows. The evaluation results are shown in Table 14 below.

(Sensory evaluation: sweetness)
The aqueous solutions of Reference Examples 1 to 5 were evaluated for sweetness by five panelists. The sweetness of each aqueous solution was evaluated by each panelist using the following five-level criteria, and the average value of the five panelists was calculated. For each of Reference Examples 1 to 5, prepare standard products that have the same sugar content and do not contain pyruvic acid, and compare them with the standard products of Reference Examples 1 to 5 to find 5 products that are the same or sweeter than the standard products. The evaluation was given as 4 if the taste was less sweet than the standard product, 3 if the taste was sweet but also sour, 2 if the taste was more sour, and 1 if there was no sweetness at all. When the average value had a decimal part, the score was calculated by rounding to the first decimal place.

(Sensory evaluation: Sourness)
The aqueous solutions of Reference Examples 1 to 5 were evaluated for acidity by five panelists. The sourness of each aqueous solution was evaluated by each panelist using the following five-level criteria, and the average value of the five panelists was calculated. For each of Reference Examples 1 to 5, a standard product with the same sugar content and no pyruvic acid was prepared. A rating of 4 was given for those that felt less sour than the standard product, 3 for those that felt sour but also sweet, 2 for those that felt a stronger sweetness, and 1 for those that did not feel sour at all. When the average value had a decimal part, the score was calculated by rounding to the first decimal place.

As can be seen from the results in Table 14 above, Reference Example 1 prepared in accordance with Example 2-1 treated with superheated steam containing fine water droplets had a strong sweet taste, while no sour taste was felt at all. .

Reference Example 2 is a sample in which the sugar content is the same as Reference Example 3 and the pyruvic acid content is the same as Reference Example 1. Reference Example 2, like Reference Example 1, exhibits a strong sweetness, but does not have any sourness.

On the other hand, in Reference Example 3 prepared in accordance with Comparative Example 2-3, which was processed using a cooking device using saturated steam, the sugar content was about the same as in Reference Example 1, and the pyruvic acid This sample has a high content of . In Reference Example 3, the sourness of pyruvic acid remained as an aftertaste and the sweetness was difficult to perceive. It was found that Reference Example 3 had a weaker sweetness and a stronger sourness than Reference Example 2, even though the sugar content was about the same.

Reference Example 4, which was prepared in accordance with Comparative Example 2-4 without treatment using superheated steam containing fine water droplets, was found to have a weak sweetness and a strong sourness compared to Reference Example 1, despite having a high sugar content. When the pH of the aqueous solution of Reference Example 4 was measured, it was found to be a fairly low value of 1.7, and the sourness was stronger than the sweetness, resulting in a bitter taste.

Reference Example 5 is a sample in which the sugar content is similar to that of Reference Example 4 and the pyruvic acid content is similar to that of Reference Example 3. It was found that Reference Example 5 had a weaker sweetness and a stronger sourness than Reference Example 1, despite having a higher sugar content.
The results of Reference Examples 4 and 5 show that the strong sourness and bitterness caused by pyruvic acid can be somewhat offset by adding sugar, but the perception of sweetness depends largely on the content of pyruvic acid.

From the results of Reference Examples 1 to 5, it was found that the sweetness decreased even when a small amount of pyruvic acid was added, and further decreased as the amount of pyruvic acid added increased. Therefore, it was found that sugar content and pyruvic acid content can be used as indicators of sweetness in conjunction with sensory evaluation. If the content of pyruvic acid is low and the content of sugar is maintained to some extent, it can be said that the food is in a state where it is easy to perceive sweetness.
In reality, ingredients other than sugar and pyruvic acid are included, and multiple factors such as differences in texture interact to form the taste, but from the results of Example 2 and Reference Examples, it is clear that pyruvic acid is present even in green onions. It is thought that the content affects how sweetness is perceived.

10...Chamber 20...Superheated steam generator 30...Fine water droplet (hot water) generator 40...Vegetables 50...Internal heaters 61, 62...Heaters 71, 72...Flow paths 81, 82...Nozzle V...Steam W...Water

Claims (10)

A method for producing dried vegetables with a sweet taste selected from dried green onions and dried onions, comprising: (a) treating cut green onions or onions with superheated steam containing fine water droplets; and (b) ) The method described above, comprising the step of drying the green onions or onions after the treatment in step (a). The method according to claim 1, wherein the treatment in step (a) is performed under a temperature condition of 90°C or higher and 140°C or lower. The method according to claim 1 or 2, wherein the treatment in step (a) is performed for 1 second or more and 5 minutes or less. The method according to any one of claims 1 to 3, comprising the step of (i) treating the cut green onions or onions with a pH adjusting solution before the step (a). Between the step (a) and the step (b), the method includes a step of (ii) treating the green onions or onions after the treatment in the step (a) with a pH adjusting solution or water. 4. The method according to any one of 4. The method according to claim 4 or 5, wherein the pH of the pH adjustment liquid in the step (i) or (ii) is 5.0 or more and 7.5 or less. The method according to any one of claims 4 to 6, wherein the treatment in step (i) or (ii) is carried out for 5 seconds or more and 20 minutes or less. The method according to any one of claims 4 to 7, wherein the treatment in step (i) or (ii) is immersion or spraying. The method according to any one of claims 1 to 8, wherein the dried vegetable contains 40.0% by weight or more of sugar and 0.075% by weight or less of pyruvic acid. Dried vegetables with a sweet taste , which have a sugar content of 40.0% by mass or more and a pyruvic acid content of 0.075% by mass or less, and are selected from dried green onions and dried onions. vegetables.

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