Production method of broth

Abstract

To provide a production method of broth, capable of shortening an extraction time even in the case of extracting at a low-temperature, and producing broth in which flavor component is more extracted without increasing miscellaneous taste.SOLUTION: A production method of broth includes extracting flavor component by immersing a broth raw material in a liquid at 40°C or less. In the production method of broth, an immersion liquid obtained by immersing a broth raw material in a liquid is irradiated with microwaves for a fixed time so as to extract flavor component in a short time at a high efficiency compared to the case of no irradiation of microwaves.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing juice by irradiating a juice raw material with microwaves.

Background Art

[0002] Conventionally, methods for producing juice with suppressed off-flavors have been disclosed. For example, a method for producing juice excellent in aftertaste without an increase in astringency by concentrating an extract obtained by extracting a juice raw material with hot water at 60°C or higher to 1.1 times or more and rapidly cooling the concentrated extract to 20°C or lower has been disclosed (see Patent Document 1). Further, a method for extracting kelp stock with cold water by immersing kelp in a solvent at 0 to 20°C and extracting for 10 to 30 hours has been disclosed (see Patent Document 2). In addition, the applicant has disclosed a microwave aging method capable of improving the aging feeling of food and shortening the aging period by irradiating food with microwaves for aging (see Patent Document 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] When heating a juice raw material with hot water at 60°C or higher as in Patent Document 1, there is a problem that components other than flavor components such as off-flavors and bitterness are also eluted. Further, when extracting flavor components at a low temperature such as water as in Patent Document 2, there is a problem that the extraction takes a long time and the juice is damaged by microorganisms. Furthermore, there has been a growing demand for extraction methods that can more efficiently extract umami components from broth ingredients. In this situation, the inventor investigated a novel method for producing dashi (broth) by applying microwave aging technology as shown in Patent Document 3, and after diligent research, created the present invention.

[0005] The present invention aims to provide a method for producing dashi (Japanese soup stock) that allows for a shorter extraction time even when extracting umami components from dashi ingredients at low temperatures, and that produces dashi with more extracted umami components without increasing off-flavors. [Means for solving the problem]

[0006] The present invention is essentially a method for producing dashi (broth) as described in (1) to (9) below. (1) A method for producing dashi (Japanese soup stock) in which dashi ingredients are immersed in a liquid at 40°C or below to extract umami components, characterized in that microwaves are irradiated for a certain period of time into the immersion liquid in which the dashi ingredients are immersed, thereby extracting umami components in a shorter time and with higher efficiency compared to when microwaves are not irradiated. (2) The method for producing dashi according to (1) above, wherein the microwave is irradiated and the immersion liquid is cooled at the same time so that the external temperature of the immersion liquid is lower than the internal temperature of the immersion liquid. (3) The method for producing dashi according to (1) or (2) above, wherein the microwave is irradiated such that the internal temperature of the immersion liquid is in the range of 0°C and 25°C. (4) The method for producing dashi according to (1) or (2) above, wherein the microwave irradiation is performed such that the external temperature of the immersion liquid is in the range of -5°C or higher and lower than 20°C. (5) The method for producing dashi according to (2) above, wherein the microwave is irradiated and the immersion liquid is cooled at the same time, such that the difference between the internal temperature and external temperature of the immersion liquid is in the range of 5°C or higher and 20°C or lower. (6) The method for producing dashi according to (1) or (2) above, wherein the microwave irradiation is carried out for 30 minutes or more and 4 hours or less. (7) The method for producing dashi according to (1) or (2) above, wherein the dashi ingredients are a combination of kelp and dried bonito flakes or dried sardines. (8) The method for producing dashi according to (7) above, wherein the ratio of dried bonito flakes or dried sardines to kelp in the dashi ingredients (weight of dried bonito flakes or dried sardines / weight of kelp) is less than 2. (9) A method for producing dashi according to (1) or (2) above, wherein the dashi raw material, which has umami seasoning added to kelp, is immersed in the liquid and microwaves are irradiated for a certain period of time. [Effects of the Invention]

[0007] According to the present invention, by irradiating the immersion liquid in which the dashi ingredients are immersed with microwaves for a certain period of time, the extraction time can be shortened even when extracting umami components from the dashi ingredients at low temperatures, and a dashi in which more umami components are extracted can be produced without increasing off-flavors. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing the configuration of a microwave aging apparatus according to an embodiment. [Figure 2] This table shows the relationship between the broth extraction conditions in this example and the concentrations of inosinic acid and glutamic acid. [Figure 3] This graph shows the light absorption spectrum measured in Example 1. [Figure 4] This graph shows the light absorption spectrum measured in Example 2. [Figure 5] This graph shows the light absorption spectrum measured in Example 3. [Figure 6] This graph shows the light absorption spectrum measured in Example 4. [Figure 7] This graph shows the light absorption spectrum measured in Example 5. [Figure 8] This graph shows the light absorption spectra measured in Examples 7 and 9. [Figure 9]It is a graph showing the light absorption spectrum measured in Example 10.

Mode for Carrying Out the Invention

[0009] (Food to be aged) In the present invention, when extracting umami components from a juice extraction raw material by immersing the juice extraction raw material in a liquid such as water, by irradiating the immersion liquid in which the juice extraction raw material is immersed with microwaves for a certain period of time, it is possible to extract umami components from the juice extraction raw material more efficiently at a low temperature and in a short time. The juice extraction raw material is not particularly limited as long as it is a commonly used material, and examples include foods rich in glutamic acid such as kelp, foods rich in inosinic acid such as dried bonito flakes and dried small fish, or foods rich in guanylic acid such as shiitake mushrooms. As the juice extraction raw material, it is also possible to use kelp, or dried bonito flakes or dried small fish alone, but it is not limited to this configuration, and it is also possible to use a configuration in which kelp, and dried bonito flakes and / or dried small fish are used together. Similarly, for shiitake mushrooms, it is also possible to use a configuration in which they are used alone, but it is not limited to this configuration, and it is also possible to use a configuration in which shiitake mushrooms are used together with kelp, and / or dried bonito flakes and / or dried small fish.

[0010] (Method for producing juice) Conventionally, when extracting umami components from a juice extraction raw material to obtain juice, there are a method of boiling the juice extraction raw material in hot water to extract umami components, and a method of immersing the juice extraction raw material in relatively low-temperature water (room-temperature water or cold water lower than room temperature) for a long time to extract umami components. In the method of boiling the juice extraction raw material in hot water to extract umami components, there is a problem that in addition to umami components, off-flavors such as bitterness and astringency are also extracted. Also, in the method of immersing the juice extraction raw material in relatively low-temperature water to extract umami components, there are problems that it takes a long time to extract the juice, and the juice is easily damaged due to the growth of microorganisms.

[0011] This invention was completed based on the inventor's discovery that by irradiating a immersion liquid containing dashi ingredients with microwaves for a certain period of time, dashi can be efficiently extracted in a short time, even at a relatively low temperature. Furthermore, the inventor discovered that by irradiating the immersion liquid with microwaves to extract umami components, more umami components can be extracted without increasing off-flavors, compared to when umami components are extracted without microwave irradiation. The following describes embodiments of the dashi manufacturing method of this invention.

[0012] In the microwave irradiation according to this embodiment, using the microwave aging device 1 described later, microwave is irradiated to the immersion liquid placed in a container for a relatively long time (30 minutes or more) to extract umami components from the juice raw material and obtain juice. The wavelength of the irradiated microwave may be any wavelength that can dielectrically heat the water molecules in the immersion liquid. For example, it can be 2.4 to 2.5 GHz. Also, in this embodiment, in order to extract umami components from the juice raw material at a relatively low temperature, the internal temperature of the immersion liquid (the temperature of the liquid constituting the immersion liquid and the juice raw material) is higher than 0°C and lower than 25°C, more preferably within the range of 5°C or more and 20°C or less. Thus, the intensity of the microwave irradiation is controlled. Further, as described later, in the microwave aging device 1 according to this embodiment, the inside of the storage where the immersion liquid is statically placed can be cooled, and the external temperature (the temperature inside the storage) of the immersion liquid during microwave irradiation is lower than the internal temperature of the immersion liquid. Preferably, the external temperature of the immersion liquid is within the range of -5°C or more and lower than 20°C, more preferably within the range of 0°C or more and 10°C or less. Thus, the inside of the storage is cooled, and the extraction of umami components is performed in this environment. Particularly, in this embodiment, the heating of the immersion liquid by microwave irradiation and the cooling of the inside of the storage are performed so that the temperature difference between the internal temperature and the external temperature of the immersion liquid is higher than 5°C and lower than 20°C, more preferably 10°C or more and 15°C or less. Also, in this embodiment, the microwave irradiation is performed for a longer time than normal hot water extraction and for a shorter time than normal cold water extraction. Specifically, the microwave irradiation is performed for 30 minutes or more and 4 hours or less, more preferably 1 hour or more and 2 hours or less to extract umami components. The amount of the juice raw material used is not particularly limited, but it is desirable that the ratio of iriko to kelp (weight of iriko / weight of kelp) is less than 2, more preferably less than 1.7.

[0013] (Microwave aging device) Figure 1 is a diagram showing the configuration of the microwave aging apparatus 1 according to this embodiment. As shown in Figure 1, the microwave aging apparatus 1 according to this embodiment comprises a cooling unit 10, a microwave oscillation unit 20, a microwave aging unit 30, a control unit 50, and a UV lamp 60. The microwave aging apparatus 1 has the microwave aging unit 30 built inside the cooling unit 10. In the microwave aging apparatus 1 according to this embodiment, not only is it possible to produce dashi (Japanese soup stock), but also to age meats such as beef (including processed meat products such as ham), seafood, dairy products such as cheese, beans such as edamame (soybeans) and coffee beans, vegetables, fruits, noodles, bread, alcoholic beverages such as wine, and fermented foods (including fermented seasonings such as miso and soy sauce).

[0014] The cooling unit 10 is a device that cools the internal space of the cooling unit 10. As shown in Figure 1, the cooling unit 10 has a cooler 11, a first fan 12, a cooling chamber 13, and a cooling chamber door 14 (not shown). In this embodiment, the cooler 11 generates cold air by exchanging heat with the outside, and the first fan 12 blows the generated cold air into the cooling chamber 13 inside the cooling unit 10. This makes it possible to keep the temperature inside the cooling chamber 13 low. As will be described later, in this embodiment, the control unit 50 appropriately controls the operation of the microwave oscillation unit 20 and the temperature inside the cooling chamber 13 so that the external temperature (internal temperature) of the immersion liquid in which the broth ingredients are immersed is lower than the internal temperature of the immersion liquid. In addition, the user can put the immersion liquid in a container into and out of the microwave aging unit 30 installed inside the cooling chamber 13 by opening the cooling chamber door 14.

[0015] The microwave oscillator 20 emits microwaves to irradiate the immersion liquid in the container. While a magnetron oscillator can be used as the microwave oscillator 20, in this embodiment, a solid-state oscillator using semiconductor elements is used, which provides higher frequency and output stability compared to a magnetron. The microwave oscillator 20 emits microwaves by continuously varying the frequency between 2.4 and 2.5 GHz. The microwaves emitted by the microwave oscillator 20 are irradiated from the irradiation port 31 of the microwave aging unit 30 via the cable 21. By continuously varying the microwave frequency between 2.4 and 2.5 GHz, the distribution of the electromagnetic field in the microwave aging unit 30 is made uniform, so that microwaves are irradiated to the immersion liquid with a uniform distribution, and the extraction of umami components by uniform heating of the immersion liquid can be promoted.

[0016] As shown in Figure 1, the microwave aging unit 30 includes an irradiation port 31, a second fan 32, an aging chamber 33, and an aging chamber door 34 (not shown). The user can open the aging chamber door 34 to put the immersion liquid in a container into or out of the aging chamber 33.

[0017] The aging chamber 33 is a cavity with reflectors installed on all surfaces of its inner surface (inner wall) to reflect microwaves. An irradiation port 31 is installed on the inner surface of the aging chamber 33 to irradiate the aging chamber 33 with microwaves emitted by the microwave oscillation unit 20. In this embodiment, a small, high-gain patch antenna (planar antenna) is attached to the irradiation port 31, thereby irradiating the aging chamber 33 with microwaves emitted by the microwave oscillation unit 20. Shelves of any shape made of microwave-transparent materials such as Teflon® or polypropylene may be installed in the aging chamber 33. If metal materials such as stainless steel are used, a grid-like shelf with spacing of 20 mm or more, or a perforated metal shelf with an opening of 20 mm or more in diameter may be installed.

[0018] The second fan 32 blows cold air from the cooling chamber 13 into the aging chamber 33. In this embodiment, as shown in Figure 1, the second fan 32 is mounted on the outside of the aging chamber 33, and a first micro-aperture 35 is provided in the side wall of the aging chamber 33 to which the second fan 32 is mounted. The first micro-aperture 35 is opened to a size shorter than the wavelength of microwaves; for example, in this embodiment, the size of the first micro-aperture 35 is set to a diameter of 10 mm or less. The first micro-aperture 35 blocks microwaves irradiated into the aging chamber 33, allowing only the cold air blown by the second fan 32 to pass through. In addition, a second micro-aperture 36, with the same diameter as the first micro-aperture 35, is provided in the side wall of the aging chamber 33 facing the first micro-aperture 35. The second micro-aperture 36 blocks microwaves irradiated into the aging chamber 33, but the air inside the aging chamber 33, which has been heated by heat exchange with the immersion liquid, passes through the second micro-aperture 36 and is discharged into the cooling chamber 13. The first micro-opening 35 and the second micro-opening 36 may be provided over an area occupying most of one or more side walls to improve ventilation. Alternatively, the maturation chamber 33 can be constructed using perforated metal with the first micro-opening 35 and the second micro-opening 36 pre-formed, and a φ10 mm stainless steel plate can be used as such perforated metal.

[0019] The control unit 50 incorporates a program that controls the temperature so that the external and internal temperatures of the immersion liquid reach predetermined temperatures. Specifically, the control unit 50 controls the operation of the microwave oscillator 20, the cooler 11, the first fan 12, and the second fan 32 to control the microwave output from the microwave oscillator 20, the temperature of the cold air from the cooler 11, and the airflow of the first fan 12 and the second fan 32. For example, the control unit 50 can increase the internal temperature of the immersion liquid by increasing the microwave output of the microwave oscillator 20, and can decrease the external temperature of the immersion liquid by decreasing the temperature of the cold air from the cooler 11 or by increasing the airflow of the first fan 12 and the second fan 32.

[0020] Furthermore, the control unit 50 can control the oscillation of microwaves by the microwave oscillation unit 20. For example, in addition to fixed irradiation, which causes the microwave oscillation unit 20 to oscillate at a fixed output value and frequency, the control unit 50 can also cause intermittent irradiation, which causes the microwave oscillation unit 20 to repeatedly oscillate and stop at short periods (e.g., periods of a few milliseconds), sweep irradiation, which changes the frequency of the microwave oscillation unit 20 over time, and continuous irradiation, which changes the output value of the microwave oscillation unit 20 over time. Moreover, the control unit 50 does not need to continuously irradiate with microwaves while extracting umami components in the immersion liquid, and can be configured to irradiate with microwaves for at least 30 minutes or more. Furthermore, the control unit 50 can be configured to control the microwave oscillation unit 20 so as to switch the ON-OFF of microwave irradiation at regular intervals (e.g., several hours) (in the case of intermittent irradiation, to switch between periods of intermittent irradiation and periods without intermittent irradiation at regular intervals).

[0021] Furthermore, the control unit 50 can be connected to a temperature sensor that measures the internal and external temperature of the immersion liquid (for example, a fluorescent fiber optic thermometer (manufactured by Anritsu Keiki Co., Ltd.) that can measure temperature in a contact manner even in a microwave environment, or a radiation-type temperature sensor that measures the intensity of infrared or visible light without contact), and the control unit can be configured to perform temperature control as appropriate based on the measurement results of the temperature sensor.

[0022] Furthermore, the control unit 50 can be configured to control the microwave output of the microwave oscillator 20, the temperature of the cold air from the cooler 11, and the airflow of the first fan 12 and the second fan 32 according to the absorbance of the immersion liquid at a specific wavelength (for example, wavelengths of 250 nm or 260 nm corresponding to nucleic acids such as inosinic acid and guanylic acid, which are umami components) obtained from a non-contact spectrophotometer installed in the maturation chamber 33. Alternatively, the control unit 50 can be configured to automatically adjust the internal and external temperatures of the immersion liquid by allowing the user to input information about the dashi ingredients, such as the type (for example, kelp, dried bonito flakes, dried sardines, etc.) and size, using an input device such as an operation button or touch panel in the operation unit 40.

[0023] As described above, in the microwave aging apparatus 1 according to this embodiment, by simultaneously heating the immersion liquid with a heating mechanism (microwave oscillation unit 20 and microwave aging unit 30) and cooling the surface of the immersion liquid with a cooling mechanism (cooling unit 10 and second fan 32), it is possible to raise the internal temperature of the immersion liquid while keeping the external temperature of the immersion liquid low. Specifically, the internal temperature of the immersion liquid can be made higher than the external temperature of the immersion liquid. In particular, by dielectric heating of the immersion liquid by microwave irradiation, the immersion liquid can be heated uniformly to the inside, which can promote the extraction of umami components. Furthermore, by cooling the immersion liquid from the surface with the operation of the cooling unit 10 and the second fan 32, it is also possible to suppress the growth of bacteria on the surface of the immersion liquid.

[0024] Furthermore, the microwave aging apparatus 1 according to this embodiment is equipped with an operating unit 40 for user operation, and the user can operate the operating unit 40 to instruct a high-temperature extraction mode that extracts broth at a temperature higher than the broth extraction temperature described above. When the user instructs the high-temperature extraction mode, the control unit 50 can set the internal temperature of the immersion liquid to a temperature exceeding, for example, 25°C.

[0025] The UV lamp 60 is a device that generates ultraviolet light. In this embodiment, by irradiating the cold air circulating in the cooling chamber 13 and the maturation chamber 33 with ultraviolet light, bacteria floating in the cold air can be sterilized, and the growth of bacteria on the surface of the immersion liquid and in the cooling chamber 13 and the maturation chamber 33 can be further suppressed. Alternatively, the wall of the maturation chamber 33 can be configured to allow ultraviolet light to pass through a portion of it (at least a portion on the UV lamp 60 side), or the UV lamp can be directly installed in the maturation chamber 33. In this case, during the extraction of the broth, the ultraviolet light generated by the UV lamp 60 can be directly irradiated onto the surface of the immersion liquid placed in the maturation chamber 33. In this way, by irradiating the surface of the immersion liquid with ultraviolet light during the extraction of the broth, the growth of bacteria on the surface of the immersion liquid can be further suppressed. The control unit 50 can also control the operation of the UV lamp 60. For example, the control unit 50 can control the UV lamp 60 to irradiate with ultraviolet light for a certain period of time (for example, several hours) from the time when maturation is started or when the maturation chamber door 34 is closed (after being opened).

[0026] (Examples) Next, an example of the method for producing dashi according to the present invention will be described. In these examples (Examples 1-13), dried sardines (Ibuki-produced dried sardines (special) large size, heads and guts removed) and / or kelp (Hidaka kelp, Hokkaido-produced, Hirokon Foods Co., Ltd.) were used as broth ingredients. The broth ingredients were soaked in tap water, and the resulting soaking solution was irradiated with microwaves using the microwave aging apparatus 1 described above to extract the umami components. The immersion liquid (broth) from which the umami components were extracted was then stirred, filtered, and diluted. The concentrations of glutamic acid and inosinic acid, which are umami components, were measured in the diluted broth. The glutamic acid concentration was measured using the L-glutamic acid measurement kit "Yamasa" NEO (manufactured by Yamasa Soy Sauce Co., Ltd.), and the inosinic acid concentration was measured using an HPLC equipped with a UV detector. Furthermore, in this example, in order to estimate the concentration of inosinic acid, the absorbance at a wavelength of 250 nm, which inosinic acid absorbs, was measured using broth from an example in which umami components were extracted by microwave irradiation and broth from a comparative example in which umami components were extracted without microwave irradiation. Furthermore, in this example, the absorbance of the broth from the example and the broth from the comparative example was measured in the wavelength range of 220-320 nm. In this example, in order to create highly accurate optical absorption spectra, the absorbance of the broth from the example and the comparative example was measured in the wavelength range of 220-320 nm using broths diluted to predetermined dilution ratios, and optical absorption spectra for the example and the comparative example were created. The absorbance in the 220-320 nm range was measured in order to roughly determine the concentrations of various nucleic acids, amino acids, water-soluble polymers, etc., eluted from the broth raw materials.

[0027] Figure 2 shows the extraction conditions for the broth in these examples (Examples 1-13) and the concentrations of extracted glutamic acid and inosinic acid. In these examples, as the standard extraction conditions, a broth raw material consisting of 4g of dried sardines and 4g of kelp was immersed in 400ml of 400ml of tap water. The immersion solution was then irradiated with microwaves to maintain an internal temperature of 15°C and an external temperature of 5°C, while cooling was performed using the cooling unit 10 and the second fan 32, for 1 hour to extract the umami components. In the following examples, unless otherwise specified, the umami components were extracted under the standard extraction conditions. In Figure 2, conditions different from the standard extraction conditions are shown in gray.

[0028] (Example 1) In Example 1, 4g of kelp was immersed in 400ml of tap water as the raw material for dashi (broth). Microwaves were irradiated onto the immersion solution for 1 hour, and the solution was cooled by the cooling unit 10 and the second fan 32, so that the internal temperature of the immersion solution was 10°C and the external temperature of the immersion solution was 0°C. In Comparative Example 1, 4g of kelp was immersed in 400ml of tap water as the raw material for dashi, and the immersion solution was left to stand for 1 hour in an environment with an external temperature of 10°C without microwave irradiation (in this case, the internal temperature of the immersion solution was also 10°C).

[0029] Then, one hour after the start of extraction, the immersion solution was stirred, filtered, and then diluted eightfold. The concentration of glutamic acid, an umami component of kelp, was measured in the immersion solution (broth). Table 1 below shows the measurement results of glutamic acid concentration in Example 1 and Comparative Example 1. [Table 1] As shown in Table 1, in Example 1, where umami components were extracted by microwave irradiation, the amount of glutamic acid, an umami component, increased by 44% (1.44 times) compared to Comparative Example 1, where umami components were extracted without microwave irradiation.

[0030] Furthermore, the absorbance of the diluted broths of Example 1 and Comparative Example 1 was measured in the 220-320 nm range, and light absorption spectra were created. Figure 3 is a graph showing the light absorption spectra measured for Example 1 and Comparative Example 1. In addition, as a reference example (Reference Example 1), the light absorption spectrum of an aqueous solution of sodium glutamate, prepared by dissolving only sodium glutamate in tap water to a concentration of 125 ppm, is also shown. As shown in Figure 3, in Example 1, the absorbance in the 220-260 nm wavelength range is lower compared to Comparative Example 1, indicating that the elution of nucleic acids, amino acids, water-soluble polymers, etc. from the broth ingredients was suppressed. Note that, as shown in Reference Example 1, glutamic acid absorbs little light in the 220-320 nm wavelength range, and the amount of glutamic acid has almost no effect on the light absorption spectrum. Therefore, the light absorption spectrum in Figure 3 is thought to be due to components other than glutamic acid, including off-flavor components. Therefore, it was found that when kelp alone is used as the raw material for broth and irradiated with microwaves to extract umami components, the amount of glutamic acid extracted can be increased compared to when microwave irradiation is not performed, and the leaching of off-flavor components can be suppressed.

[0031] (Example 2) In Example 2, 4g of dried sardines were immersed in 400ml of tap water as the raw material for broth. Microwaves were irradiated onto the immersion solution for 1 hour, and the solution was cooled by the cooling unit 10 and the second fan 32, so that the internal temperature of the immersion solution was 15°C and the external temperature was 5°C. In Comparative Example 2, 4g of dried sardines were immersed in 400ml of tap water as the raw material for broth, and the solution was left to stand for 1 hour in an environment with an external temperature of 15°C without irradiating it with microwaves (in this case, the internal temperature of the immersion solution was also 15°C).

[0032] Then, one hour after the start of extraction, the immersion solution was stirred, filtered, and then diluted eightfold. The concentration of inosinic acid, the umami component of dried sardines, was measured in the immersion solution (broth). Table 2 below shows the measurement results of inosinic acid concentration in Example 2 and Comparative Example 2. [Table 2] As shown in Table 2, in Example 2, where umami components were extracted by microwave irradiation, it was found that inosinic acid, an umami component, increased by 31% compared to Comparative Example 2, where umami components were extracted without microwave irradiation. Furthermore, when the absorbance at 250 nm, the wavelength at which inosinic acid absorbs light, was measured for the diluted broths of Example 2 and Comparative Example 2, the results were 0.56 for Comparative Example 2 and 0.65 for Example 2. This confirmed that when the broth ingredients consist solely of dried sardines, the inosinic acid concentration increases when irradiated with microwaves.

[0033] Furthermore, the absorbance of the diluted broths of Example 2 and Comparative Example 2 was measured in the 220-320 nm range, and light absorption spectra were created. Figure 4 is a graph showing the light absorption spectra measured for the diluted Example 2 and Comparative Example 2. In addition, as a reference example (Reference Example 2), the light absorption spectrum of an aqueous solution of sodium inosinate, prepared by dissolving only sodium inosinate in tap water to a concentration of 100 ppm, is also shown. As shown in Figure 4, in Example 2, the absorbance in the 220-280 nm wavelength range was higher compared to Comparative Example 2, indicating that a large amount of nucleic acids, amino acids, and water-soluble polymers were eluted from the broth raw materials. However, as shown in Reference Example 2, inosinic acid is a type of nucleic acid and has the property of absorbing light around 250 nm, so it is thought that the amount of inosinic acid eluted from the dried sardines is reflected in the light absorption spectrum shown in Figure 4. In other words, the measurement results of the light absorption spectrum shown in Figure 4 correlated with the measurement results of the inosinic acid concentration in Table 2 above. It was found that in dried sardines, microwave irradiation has the effect of increasing the amount of inosinic acid extracted, but it was not possible to confirm that it had the effect of suppressing the elution of components such as off-flavors.

[0034] (Example 3) In Example 3, dashi was produced under standard extraction conditions. Specifically, 4g of dried sardines and 4g of kelp were immersed in 400ml of tap water as dashi ingredients, and the immersion solution was irradiated with microwaves for 1 hour, while the internal temperature of the immersion solution was 15°C and the external temperature was 5°C, and the solution was cooled by the cooling unit 10 and the second fan 32. In Comparative Example 3, 4g of dried sardines and 4g of kelp were immersed in 400ml of tap water as dashi ingredients, and the immersion solution was left to stand for 1 hour in an environment with an external temperature of 15°C (in this case, the internal temperature of the immersion solution was also 15°C).

[0035] Then, one hour after the start of extraction, the immersion solution was stirred, filtered, and the inosinic acid and glutamic acid concentrations were measured in the immersion solution (broth) diluted nine times. Table 3 below shows the measurement results of inosinic acid and glutamic acid concentrations in Example 3 and Comparative Example 3. [Table 3] As shown in Table 3, in Example 3, which was irradiated with microwaves, inosinic acid, an umami component abundant in dried sardines, increased by 19% compared to Comparative Example 3, which was not irradiated with microwaves, and glutamic acid, an umami component abundant in kelp, increased by 231% (3.31 times). In particular, compared to Example 1, in which broth was made using only kelp, Example 3, in which broth was made using a combination of kelp and dried sardines, showed a significant improvement in the extraction efficiency of glutamic acid (from 1.44 times to 3.31 times). Furthermore, when the absorbance of the diluted broths of Example 3 and Comparative Example 3 was measured at 250 nm, the point at which inosinic acid absorbs light, the results were 0.33 for Comparative Example 3 and 0.39 for Example 3. From the perspective of absorbance, it was confirmed that inosinic acid increases when microwave irradiation is applied to a combined broth of kelp and dried sardines.

[0036] Furthermore, the absorbance of the diluted broths from Example 3 and Comparative Example 3 was measured in the 220-320 nm range to create light absorption spectra. Figure 5 is a graph showing the light absorption spectra measured for Example 3 and Comparative Example 3. As shown in Figure 5, in Example 3, despite an increase in the amount of inosinic acid dissolved compared to Comparative Example 3, the absorbance in the wavelength range below 240 nm was lower, indicating that the elution of components other than umami components, such as off-flavors, from the broth ingredients was suppressed.

[0037] From the measurement results of glutamic acid concentrations and the light absorption spectrum results, it was found that when a dashi (broth) ingredient mixture of dried sardines and kelp is used, irradiation with microwaves promotes the extraction of inosinic acid and glutamic acid. In particular, the amount of glutamic acid extracted doubles, while the elution of components including off-flavors can be suppressed.

[0038] (Examples 4-6) In Example 3 described above, microwave irradiation was performed so that the internal temperature of the immersion liquid was 15°C and the external temperature was 5°C. In contrast, in Example 4, the dashi was produced under the same conditions as in Example 3, except that microwave irradiation was performed so that the internal temperature of the immersion liquid was 20°C and the external temperature was 5°C. Furthermore, in Example 5, the dashi was produced under the same conditions as in Example 3 (the difference between the internal and external temperatures of the immersion liquid was also 10°C, the same as in Example 3), except that microwave irradiation was performed so that the internal temperature of the immersion liquid was 20°C and the external temperature of the immersion liquid was 10°C. In addition, in Example 6, the dashi was produced under the same conditions as in Example 3 (the difference between the internal and external temperatures of the immersion liquid was also 10°C, the same as in Example 3), except that microwave irradiation was performed so that the internal temperature of the immersion liquid was 5°C and the external temperature of the immersion liquid was -5°C. For Comparative Examples 4 and 5, the immersion solution was left standing for 1 hour in an environment with an external temperature of 20°C without microwave irradiation (in this case, the internal temperature of the immersion solution was also 20°C). For Comparative Example 6, the immersion solution was left standing for 1 hour in an environment with an external temperature of 5°C without microwave irradiation (in this case, the internal temperature of the immersion solution was also 5°C).

[0039] Then, the immersion solutions of Examples 4-6 and Comparative Examples 4-6 were stirred one hour after the start of extraction, filtered, and then diluted nine-fold. The concentrations of glutamic acid and inosinic acid in these diluted immersion solutions (broth) were measured. Table 4 below shows the measurement results of glutamic acid and inosinic acid concentrations in Examples 4-6 and Comparative Examples 4-6. In addition, Table 4 below also includes the internal and external temperatures of the immersion solution during extraction as part of the extraction conditions. [Table 4] As shown in Table 4, in Examples 4-6, where umami components were extracted by microwave irradiation, glutamic acid increased by 70%, 285%, and 43%, respectively, compared to Comparative Examples 4-6, where umami components were extracted without microwave irradiation. Inosinic acid, another umami component, also increased by 13%, 13%, and 4%, respectively. Furthermore, when the absorbance at 250 nm was measured for the diluted broths of Example 4 and Comparative Example 4, the results were 0.32 for Comparative Example 4 and 0.37 for Example 4. Similarly, when the absorbance at 250 nm was measured for the diluted broths of Example 5 and Comparative Example 5, the results were 0.33 for Comparative Example 5 and 0.39 for Example 5. Thus, in Examples 4 and 5, it was confirmed from the absorbance that even when using a broth raw material combining dried sardines and kelp and irradiating with microwaves, the amount of inosinic acid extracted increased.

[0040] Furthermore, comparing Example 5 and Example 6, where the temperature difference between the external and internal temperatures of the immersion solution was the same at 10°C, Example 5, where the internal temperature of the immersion solution was higher at 20°C, showed a higher rate of increase in glutamic acid extracted by microwave irradiation. This indicates that even when the internal temperature of the immersion solution is raised to 20°C, the improvement in the efficiency of glutamic acid extraction by microwave irradiation is maintained. Although not shown in the figures, if the internal temperature of the immersion solution exceeds 25°C, many off-flavors will be extracted, so it is preferable to keep the internal temperature of the immersion solution below 20°C. Also, if the internal temperature of the immersion solution is below 0°C, it will take a long time to extract the umami components, so it is preferable to keep the internal temperature of the immersion solution above 0°C.

[0041] Furthermore, comparing Example 5 and Example 4, both of which had the same internal temperature of 20°C in the immersion solution, Example 5, where the temperature difference between the internal and external temperatures of the immersion solution was smaller at 10°C, showed a higher rate of increase in glutamic acid extracted by microwave irradiation. This indicates that if the temperature difference between the internal and external temperatures of the immersion solution is increased to over 15°C, the efficiency of glutamic acid extraction by microwave irradiation decreases. Although not shown in the figures, it was also found that the efficiency of glutamic acid extraction by microwave irradiation decreases when the temperature difference between the internal and external temperatures of the immersion solution is below 5°C. In addition, in Examples 4-6, where umami components were extracted by microwave irradiation, the temperature of the surface in contact with the outside air was lower compared to Comparative Examples 4-6, where umami components were extracted without microwave irradiation. This also helps to suppress spoilage of the broth by microorganisms.

[0042] Furthermore, the absorbance of the diluted broths from Examples 4 and 5 and Comparative Examples 4 and 5 was measured in the 220-320 nm range, and optical absorption spectra were created. Figure 6 is a graph showing the optical absorption spectra measured in Example 4 and Comparative Example 4, and Figure 7 is a graph showing the optical absorption spectra measured in Example 5 and Comparative Example 5. As shown in Figure 6, in Example 4, the absorbance in the 240-280 nm wavelength range was higher compared to Comparative Example 4, indicating that more nucleic acids, amino acids, and water-soluble polymers were eluted from the broth raw materials. Similarly, as shown in Figure 7, in Example 5, the absorbance in the 240-280 nm wavelength range was higher compared to Comparative Example 5, indicating that more nucleic acids, amino acids, and water-soluble polymers were eluted from the broth raw materials.

[0043] Furthermore, compared to Example 3, in which broth was extracted under standard extraction conditions, Example 5, with a higher internal temperature of 20°C, showed a high increase in glutamic acid concentration of 281%, similar to Example 3. In contrast, Example 4, with a larger temperature difference of 15°C between the internal and external temperatures, showed a lower increase in glutamic acid concentration of 70%. This indicates that glutamic acid extraction is further promoted by keeping the temperature difference between the internal and external temperatures below 10°C. Also, compared to Example 3, Example 5 had 5°C higher external and internal temperatures, resulting in increased glutamic acid extraction efficiency. However, the light absorption spectrum also showed higher absorbance below 240 nm, suggesting that the elution of off-flavor components was also promoted. These results indicate that the standard extraction conditions of Example 3 are more effective at extracting umami components without increasing off-flavors than the extraction conditions of Examples 4 and 5.

[0044] (Examples 7-9) In Examples 7-9, the dashi was produced under the same extraction conditions as in Example 3, except that the extraction time was varied during microwave irradiation. Specifically, in Examples 7-9, 4g of dried sardines and 4g of kelp were immersed in 400ml of tap water as dashi raw materials. Microwave irradiation was then applied to this immersion solution for 30 minutes (Example 7), 2 hours (Example 8), or 4 hours (Example 9) so that the internal temperature of the immersion solution was 15°C and the external temperature of the immersion solution was 5°C, while cooling was performed using the cooling unit 10 and the second fan 32. In Comparative Examples 7-9, 4g of dried sardines and 4g of kelp were immersed in 400ml of tap water as dashi raw materials, and this immersion solution was left to stand for 30 minutes (Comparative Example 7), 2 hours (Comparative Example 8), or 4 hours (Comparative Example 9) in an environment with an external temperature of 15°C without microwave irradiation. Furthermore, as a reference example 3, 4g of dried sardines and 4g of kelp were immersed in 400ml of tap water as dashi ingredients, and the immersion liquid was boiled and held for 5 minutes to extract the umami components (hereinafter also referred to as hot water extraction).

[0045] Then, 30 minutes, 2 hours, or 4 hours after the start of extraction, the immersion solution was stirred, filtered, and the concentrations of glutamic acid and inosinic acid were measured in the immersion solution (broth) diluted 9 times. Table 5 below shows the measurement results for Example 7 and Comparative Example 7 with an extraction time of 30 minutes, Example 8 and Comparative Example 8 with an extraction time of 2 hours, Example 9 and Comparative Example 9 with an extraction time of 4 hours, and Reference Example 3 which was extracted with hot water. Note that in Table 5 below, the extraction time is also listed as part of the extraction conditions. [Table 5] As shown in Table 5, in Example 7, where umami components were extracted for 30 minutes using microwave irradiation, the amount of glutamic acid, an umami component, extracted increased by 73% compared to Comparative Example 7, where umami components were extracted for 30 minutes without microwave irradiation. In Example 8, where umami components were extracted for 2 hours using microwave irradiation, the amount of glutamic acid, an umami component, extracted increased by 53% compared to Comparative Example 8, where umami components were extracted for 2 hours without microwave irradiation. Furthermore, in Example 9, where umami components were extracted for 4 hours using microwave irradiation, the amount of glutamic acid, an umami component, extracted increased by 258% compared to Comparative Example 9, where umami components were extracted for 4 hours without microwave irradiation. Furthermore, the absorbance at 250 nm, the wavelength at which inosinic acid absorbs light, was measured for the diluted broths of Example 7 and Comparative Example 7. The results were 0.26 for Comparative Example 7 and 0.25 for Example 7. Similarly, the absorbance at 250 nm, the wavelength at which inosinic acid absorbs light, was measured for the diluted broths of Example 9 and Comparative Example 9. The results were 0.48 for Comparative Example 9 and 0.52 for Example 9. These findings indicate that, in the extraction of glutamic acid by microwave irradiation, an improvement in extraction efficiency can be observed for at least up to 4 hours of extraction time. In Examples 7-9 and Comparative Examples 7-9, more inosinic acid was extracted with microwave irradiation than without, but the difference was small.

[0046] Furthermore, the absorbance in the 220-320 nm range was measured for the diluted broths of Examples 7 and 9, Comparative Examples 7 and 9, and Reference Example 3, and optical absorption spectra were created. Here, Figure 8(A) shows the optical absorption spectra of Example 7 and Comparative Example 7 with an extraction time of 30 minutes, Figure 8(B) shows the optical absorption spectra of Example 9 and Comparative Example 9 with an extraction time of 4 hours, and Figure 8(C) shows the optical absorption spectrum of Reference Example 3, which was extracted with hot water. As shown in Figure 8(A), when the extraction time was 30 minutes, the absorbance in the entire wavelength range of 220-320 nm was lower in Example 7, which was irradiated with microwaves, compared to Comparative Example 7, which was not irradiated with microwaves, indicating that the elution of nucleic acids, amino acids, water-soluble polymers, etc. from the broth raw materials was suppressed. On the other hand, as shown in Figure 8(B), when the extraction time was set to 4 hours, Example 9, which was irradiated with microwaves, showed higher absorbance across the entire wavelength range of 220-260 nm compared to Comparative Example 9, which was not irradiated with microwaves. This result indicated that more nucleic acids, amino acids, and water-soluble polymers were eluted from the broth raw materials.

[0047] Furthermore, comparing Example 7 and Example 9, Example 9, with an extraction time of 4 hours, showed higher absorbance in the 220-280 nm wavelength range compared to Example 7, with an extraction time of 30 minutes. From these findings, it was found that while increasing the extraction time increases the amount of glutamic acid and inosinic acid, which are umami components, it also increases the elution of non-umami components such as off-flavors. Moreover, comparing Example 9 with Reference Example 3, the light absorption spectra of Example 9, which underwent microwave irradiation for 4 hours, and Reference Example 3, which underwent hot water extraction, were similar in shape, suggesting that microwave irradiation for 4 hours almost completes the extraction of umami components from the broth raw materials.

[0048] (Example 10) In Example 10, the dashi was produced under the same extraction conditions as in Example 3, except that sodium inosinate, an umami seasoning, was added instead of dried sardines and microwave irradiation was performed. Specifically, in Example 10, 4 g of kelp was immersed in 400 ml of an aqueous solution prepared by adding 100 ppm of sodium inosinate to tap water, and this immersion solution was irradiated with microwaves for 1 hour so that the internal temperature of the immersion solution was 15°C and the external temperature of the immersion solution was 5°C, while cooling was performed by the cooling unit 10 and the second fan 32. As Comparative Example 10, 4 g of kelp was immersed in 400 ml of an aqueous solution prepared by adding 100 ppm of sodium inosinate to tap water, and the immersion solution was left to stand for 1 hour at an external temperature of 15°C.

[0049] Then, one hour after the start of extraction, the immersion solution was stirred, filtered, and the concentration of glutamic acid in the immersion solution (broth) diluted nine times was measured. Table 6 below shows the measurement results of glutamic acid concentration in Example 10 and Comparative Example 10. [Table 6] As shown in Table 6 above, in Example 10, where umami components were extracted by microwave irradiation, the amount of glutamic acid, an umami component, extracted increased by 28% compared to Comparative Example 10, where umami components were extracted without microwave irradiation. Thus, it was found that adding sodium inosinate instead of dried sardines can also increase the amount of glutamic acid extracted. Furthermore, when the absorbance at 250 nm was measured for the diluted broths of Example 10 and Comparative Example 10, both values ​​were 0.33, indicating that the inosinic acid concentration was approximately the same.

[0050] Furthermore, the absorbance of the diluted broths from Example 10 and Comparative Example 10 was measured at 220-320 nm to create optical absorption spectra. Figure 9 is a graph showing the optical absorption spectra measured for Example 10 and Comparative Example 10. As shown in Figure 9, in Example 10, where umami components were extracted by microwave irradiation, the absorbance in the wavelength range shorter than 225 nm was lower compared to Comparative Example 10, where umami components were extracted without microwave irradiation. Considering that the amount of inosinic acid dissolved remained almost unchanged, it was found that in Example 10, the elution of components other than umami components, such as off-flavors, from the broth raw materials was suppressed compared to Comparative Example 10.

[0051] Thus, based on the measurement results of glutamic acid concentration and the light absorption spectrum, it is considered that even when inosinic acid is added instead of dried sardines, microwave irradiation can promote the extraction of glutamic acid and suppress the elution of off-flavor components, similar to Example 3 in which dried sardines were added.

[0052] (Examples 11-13) In Examples 11 to 13, the dashi was produced under the same extraction conditions as in Example 3, except that the amount of dashi ingredients used was changed. Specifically, in Example 3 described above, 4g of dried sardines and 4g of kelp were immersed in 400ml of tap water to produce dashi. In contrast, in Example 11, 5g of dried sardines and 3g of kelp were immersed in 400ml of tap water, and the resulting immersion solution was irradiated with microwaves for 1 hour, while the immersion solution was cooled by the cooling unit 10 and the second fan 32, so that the internal temperature of the immersion solution was 15°C and the external temperature was 5°C. In Example 12, 3g of dried sardines and 5g of kelp were immersed in 400ml of tap water, and the resulting immersion solution was irradiated with microwaves for 1 hour, while the immersion solution was cooled by the cooling unit 10 and the second fan 32, so that the internal temperature of the immersion solution was 15°C and the external temperature was 5°C. Furthermore, in Example 13, 2g of dried sardines and 6g of kelp were immersed in 400ml of tap water as broth ingredients, and the resulting immersion solution was irradiated with microwaves for 1 hour, while simultaneously being cooled by the cooling unit 10 and the second fan 32, so that the internal temperature of the immersion solution was 15°C and the external temperature of the immersion solution was 5°C. For Comparative Example 11, 5g of dried sardines and 3g of kelp were immersed in 400ml of tap water, for Comparative Example 12, 3g of dried sardines and 5g of kelp were immersed in 400ml of tap water, and for Comparative Example 13, 2g of dried sardines and 6g of kelp were immersed in 400ml of tap water as broth ingredients. Each of these solutions was left to stand for 1 hour in an environment with an external temperature of 15°C (in this case, the internal temperature of the immersion solution was also 15°C).

[0053] Then, one hour after the start of extraction, the immersion solution was stirred, filtered, and the concentrations of glutamic acid and inosinic acid, diluted ninefold, were measured. Table 7 below shows the measurement results of glutamic acid and inosinic acid concentrations in Examples 11-13 and Comparative Examples 11-13. [Table 7] As shown in Table 7 above, in Examples 11-13, where umami components were extracted by microwave irradiation, the amount of glutamic acid extracted increased by 20%, 16%, and 41%, respectively, compared to Comparative Examples 11-13, where umami components were extracted without microwave irradiation. Similarly, the amount of inosinic acid extracted also increased by 8%, 0%, and 18%, respectively, in Examples 11-13, where umami components were extracted by microwave irradiation, compared to Comparative Examples 11-13, where umami components were extracted without microwave irradiation. Thus, it was found that when the ratio of dried sardines to kelp is less than 2 (weight of dried sardines / weight of kelp), microwave irradiation can increase the amount of glutamic acid and inosinic acid extracted.

[0054] As described above, in the method for producing dashi according to this embodiment, when extracting umami components by immersing dashi raw materials in a liquid, irradiating the immersion liquid in which the dashi raw materials are immersed with microwaves makes it possible to extract umami components with higher extraction efficiency in a short time of 30 minutes to 4 hours, even at relatively low temperatures. In particular, by making the external temperature of the immersion liquid lower than the internal temperature of the immersion liquid, more preferably by setting the internal temperature of the immersion liquid to be in the range of -5°C or higher and below 25°C, and the external temperature of the immersion liquid to be in the range of -5°C or higher and below 20°C, and by cooling the immersion liquid at the same time as irradiating with microwaves so that the difference between the internal and external temperatures of the immersion liquid is in the range of 5°C or higher and below 20°C, it becomes possible to extract umami components more efficiently. Furthermore, as shown in Examples 1 and 3 above, in the method for producing dashi according to this embodiment, when kelp is used as a dashi raw material, it is possible to increase the extraction efficiency of glutamic acid, which is an umami component, and to suppress the elution of off-flavor components contained in kelp. This is thought to be because, among the components contained in kelp, glutamic acid has a relatively high absorption efficiency of microwaves, while components such as off-flavors (e.g., polysaccharides) have a relatively low absorption efficiency of microwaves. Therefore, the elution of glutamic acid is promoted even at low temperatures, while the elution of components other than umami components, such as off-flavors, is suppressed because of the low temperature. In addition, in this embodiment, when dried bonito flakes or dried sardines were irradiated with microwaves, an improvement in the extraction efficiency of inosinic acid was also confirmed, although to a lesser extent than that of glutamic acid.

[0055] Furthermore, in this embodiment, by combining kelp and dried bonito flakes or sardines as broth ingredients, the extraction efficiency of glutamic acid was increased compared to when kelp alone was used to make broth. In particular, by setting the ratio of dried bonito flakes or sardines to kelp (weight of dried bonito flakes or sardines / weight of kelp) to less than 2, the extraction of umami components was made more efficient. From these findings, it is thought that inosinic acid has the effect of enhancing the extraction of glutamic acid by microwave irradiation, or the effect of suppressing the elution of components other than glutamic acid from kelp. It is thought that by combining broth ingredients rich in glutamic acid and broth ingredients rich in inosinic acid to make broth, the extraction efficiency of glutamic acid and the suppression of off-flavors can be synergistically increased. Furthermore, in the above-described embodiment, kelp and dried bonito flakes or sardines were used as broth ingredients. However, guanylic acid, which is the main umami component found in shiitake mushrooms, is the same nucleic acid as inosinic acid, which is abundant in dried bonito flakes or sardines. Since their microwave absorption efficiencies are similar, it is believed that, similar to inosinic acid, irradiating them with microwaves can improve the extraction efficiency of guanylic acid.

[0056] Although preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the embodiments described above. Various modifications and improvements can be made to the above embodiments, and such modified or improved forms are also included in the technical scope of the present invention. [Explanation of symbols]

[0057] 1…Microwave aging apparatus 10…Cooling section 11...Cooler 12…First fan 13…Cooling room 20...Microwave Oscillator 21… Cable 30... Microwave aging section 31…Irradiation port 32... Second fan 33…Aging Room 34…Aging chamber door 35...First minute aperture 36…Second minute aperture 37...Net plate 38…Chalk structure 39…Lighting Department 40...Operation unit 50…Control Unit 60... UV lamp

Claims

1. This method for producing soup stock comprises immersing soup stock ingredients in a liquid at 40°C or lower and irradiating the immersion liquid with microwaves for a certain period of time.

2. The method for producing soup stock according to claim 1 , wherein the immersion liquid is cooled simultaneously with the irradiation of microwaves so that the external temperature of the immersion liquid is lower than the internal temperature of the immersion liquid.

3. 3. The method for producing soup stock according to claim 1, wherein the microwave irradiation is performed so that the internal temperature of the soaking liquid is in the range of higher than 0°C and lower than 25°C.

4. 3. The method for producing soup stock according to claim 1, wherein the microwave irradiation is performed so that the external temperature of the soaking liquid is in the range of -5°C or higher and lower than 20°C.

5. 3. The method for producing soup stock according to claim 2, wherein the soaking liquid is cooled simultaneously with the microwave irradiation so that the difference between the internal temperature and the external temperature of the soaking liquid is in the range of more than 5° C. and less than 20° C.

6. The method for producing soup stock according to claim 1 or 2, wherein the microwave irradiation is carried out for 30 minutes or more and 4 hours or less.

7. 3. The method for producing soup stock according to claim 1 or 2, wherein the soup stock raw material is a soup stock raw material obtained by combining kelp, and dried fish or boiled dried fish.

8. The method for producing soup stock according to claim 7, wherein the ratio of the dried fish or boiled dried fish to kelp in the soup stock raw material (weight of the dried fish or boiled dried fish / weight of kelp) is less than 2.

9. 3. The method for producing soup stock according to claim 1 or 2, wherein the soup stock raw material, which is kelp and an umami seasoning, is immersed in the liquid, and the immersion liquid is irradiated with microwaves for a certain period of time.

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