Patent Application
20200178573
The present invention relates to a sterilization method and sterilization device for beverages other than water.
Conventionally, as a sterilization treatment using light, there is treatment which applies pulsed light from the ultraviolet to the visible range. In recent years, a sterilization treatment method using ultraviolet light is expected.
In particular, for food sterilization, disinfection using ultraviolet light (UV disinfection) is considered as a method in which the flavor is less likely to deteriorate than heat sterilization. From the viewpoint of luminous efficiency, there is known a method in which a mercury lamp (main emission wavelength is 254 nm) is used to sterilize an object by irradiating the object with ultraviolet light emitted from the lamp while suppressing deterioration of flavor (see Patent Documents 1 and 2 below).
Patent Document 3 below describes an apparatus that irradiates ultraviolet light as a sterilization treatment for fruit juice beverages, jellies, mousses and the like that are food and drink. Patent Document 3 further describes that sterilization treatment is performed by using ultraviolet light having a wavelength range of 200 to 300 nm, particularly 220 nm to 280 nm (UV-C).
Patent Document 1: JP-A-2004-201535
Patent Document 2: JP-B2-5924394
Patent Document 3: WO 2016/186068 A
It is an object of the present invention to provide a sterilization method and a sterilization device that further suppress deterioration of flavor while ensuring a sterilization effect in the sterilization method for a liquid material.
Conventionally, deterioration of flavor of foods including beverages has been analyzed by sensory inspection. On the other hand, with recent advances in chemical analysis technology, quantitative analysis using an analyzer has become possible. The present inventor conducted a quantitative analysis with this analyzer, and newly found a problem that, in a case of sterilizing a liquid material by irradiation with ultraviolet light, when light (wavelength: 254 nm) from a mercury lamp which was conventionally preferred was used, there was a problem that taste and smell (fragrance) changed due to generation of a new substance that did not exist before treatment or a large change in the amount of a specific substance.
In the sterilization method according to the present invention, a to-be-treated solution, which is a beverage other than water, is irradiated with ultraviolet light having an emission wavelength of 280 nm or more and 320 nm or less without being substantially irradiated with ultraviolet light having an emission wavelength of 260 nm or less.
It was confirmed that by irradiating the to-be-treated solution with light in the above-described wavelength band (UV-B), it was possible to suppress generation of substances that caused bitterness, unpleasant taste components, and malodorous components that occurred when light having a wavelength of 254 nm was irradiated and it was possible to sterilize the solution while preventing inhibition of flavor.
The sterilization device according to the present invention includes an ultraviolet light irradiation device which irradiates a to-be-treated solution, which is a beverage other than water, with ultraviolet light, having a main emission wavelength of 280 nm or more and 320 nm or less and substantially free of components having an emission wavelength of 260 nm or less, along a flow path through which the solution flows.
The present invention achieves a sterilization method and a sterilization device that further suppresses deterioration of flavor while ensuring a sterilization effect.
A treatment target in a sterilization device and a sterilization method of the present invention is a to-be-treated solution which is a beverage other than water. Examples of such a to-be-treated solution include alcoholic beverages such as wine, sake, and beer, coffee, juice, and liquid flavoring themselves.
This sterilization device includes a reactor 10. The reactor 10 includes a flow path 3 through which a to-be-treated solution 2 flows, and an ultraviolet light irradiation device 20 provided along the flow path 3. The ultraviolet light irradiation device 20 is configured to emit ultraviolet light having a main emission wavelength of 280 nm or more and 320 nm or less and substantially free of components having an emission wavelength of 260 nm or less.
In this specification, the light having a main emission wavelength of 280 nm or more and 320 nm or less refers to light whose wavelength band indicating a half value of an emission spectrum is in the range of 280 nm or more and 320 nm or less. The light substantially free of components having an emission wavelength of 260 nm or less refers to light not containing components at 260 nm or less in a wavelength band indicating the half value of the emission spectrum.
The reactor 10 has a cylindrical outer tube 11 and a cylindrical inner tube 12 that are arranged coaxially with each other. The flow path 3 for the to-be-treated solution 2 is constituted by a region sandwiched between an inner peripheral surface of the outer tube 11 and an outer peripheral surface of the inner tube 12.
Materials constituting the outer tube 11 in the reactor 10 are not particularly limited, and for example, a metal material such as stainless steel can be used. Materials constituting the inner tube 12 in the reactor 10 may be those through which the ultraviolet light from the ultraviolet light irradiation device 20 transmits, and for example, quartz glass and the like can be used.
The ultraviolet light irradiation device 20 is disposed along a central axis 5 of the reactor 10 inside the inner tube 12 in the reactor 10. As described above, the ultraviolet light irradiation device 20 includes a light source that emits ultraviolet light having a main emission wavelength of 280 nm or more and 320 nm or less and substantially free of components having an emission wavelength of 260 nm or less. When light containing a component having an emission wavelength of 260 nm or less (for example, light from a low-pressure mercury lamp (254 nm emission line)) is emitted to the to-be-treated solution 2, the flavor of the to-be-treated solution 2 is deteriorated. This point will be described later with reference to examples.
As the light source used as the ultraviolet light irradiation device 20, it is possible to use, for example, an XeBr excimer lamp (peak wavelength is 283 nm) in which a mixed gas of Xe and Br is sealed as a discharge gas, an excimer lamp (peak wavelength is 289 nm) in which Bra is sealed as a discharge gas, and an XeCl excimer lamp (peak wavelength is 308 nm) in which a mixed gas of Xe and Cl is sealed as a discharge gas.
Further, as the light source used as the ultraviolet light irradiation device 20, for example, an ultraviolet light emitting fluorescent lamp can be used. The ultraviolet light emitting fluorescent lamp irradiates a phosphor with light serving as exciting light and emitted from an excimer generated by dielectric barrier discharge, and emits ultraviolet light serving as radiated light and falling within a specific wavelength range obtained when the phosphor is excited. As the phosphor, for example, bismuth-activated yttrium aluminum borate that emits ultraviolet light having a peak wavelength of 290 nm by excitation can be used. Further, as the phosphor, cerium-activated lanthanum phosphate having an emission peak with a wide full width at half maximum at a peak wavelength near 320 nm by excitation may be used.
Furthermore, as the light source used as the ultraviolet light irradiation device 20, an LED element configured to have an emission wavelength of 280 nm or more and 320 nm or less and be substantially free of a component having an emission wavelength of 260 nm or less can also be used.
The amount of ultraviolet light applied to the solution 2, to be treated, by the ultraviolet light irradiation device 20 is preferably, for example, 170 mJ/cm2 or more, more preferably 170 to 500 mJ/cm2. When the ultraviolet light irradiation amount is 170 mJ/cm2 or more, sterilization treatment can be performed while suppressing changes in the taste and odor of the solution 2 itself.
The diameter of the flow path 3 in the reactor 10, that is, the distance between the inner peripheral surface of the outer tube 11 and the outer peripheral surface of the inner tube 12, is preferably 0.05 to 1 mm, for example. By adopting such a configuration, even if the to-be-treated solution 2 is formed of a material having a low transmittance of ultraviolet light from the ultraviolet light irradiation device 20 (for example, 99% of the light amount of the ultraviolet light applied to the solution 2 is opaque), the solution 2 can be sterilized uniformly.
The flow rate of the to-be-treated solution 2 circulated in the flow path 3 and the size of a region irradiated with ultraviolet light in the flow path 3 (that is, in the light source included in the ultraviolet light irradiation device 20, the length relating to the direction of the flow path 3) and other conditions can be appropriately set such that the ultraviolet light irradiation amount is within the above-described specific range.
In the sterilization device, the to-be-treated solution 2 is introduced into the flow path 3 and is radiated with ultraviolet light in the above-described wavelength band emitted from the ultraviolet light irradiation device 20 in the process of being circulated in the flow path 3, whereby the solution 2 is sterilized. Thereby, as shown in the results of examples described later, the sterilization effect can be shown while suppressing deterioration of the flavor of the to-be-processed solution 2 as a beverage.
Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes or modifications may be added to the embodiment. For example, the reactor 10 only needs to have a structure in which the ultraviolet light irradiation device 20 is provided along the flow path through which the to-be-treated solution 2 is circulated, and is not limited to the above structure.
The effects of the present invention will be described below with reference to examples.
The reactor 10 having the following specifications was manufactured according to the configuration shown in
The outer tube 11 is formed of stainless steel and has an inner diameter of φ27 mm. The inner tube 12 is formed of quartz glass and has an outer diameter of φ26.5 mm and a wall thickness of 1.0 mm. The length of the region irradiated with ultraviolet light from the ultraviolet light irradiation device 20 is 80 mm. The distance between the inner peripheral surface of the outer tube 11 and the outer peripheral surface of the inner tube 12, that is, a radial width of the flow path 3 is 0.5 mm.
As the light source included in the ultraviolet light irradiation device 20, an XeBr excimer lamp which emits ultraviolet light having a peak wavelength of 283 nm (half value was 280 nm to 286 nm) was used. The emission length of the XeBr excimer lamp is 80 mm.
As a light source included in the ultraviolet light irradiation device 20, an ultraviolet excimer fluorescent lamp (UV-XEFL320BB manufactured by USHIO INC.) that emits ultraviolet light having a peak wavelength of 320 nm (half value was 310 nm to 360 nm) was used. The emission length of the ultraviolet excimer fluorescent lamp is 80 mm.
As a light source included in the ultraviolet light irradiation device 20, an ultraviolet excimer fluorescent lamp (UV-XEFL290BB manufactured by USHIO INC.) that emits ultraviolet light having a peak wavelength of 290 nm (half value was 270 nm to 320 nm) was used. The emission length of the ultraviolet excimer fluorescent lamp is 80 mm.
As a light source included in the ultraviolet light irradiation device 20, a low-pressure mercury lamp which emits ultraviolet light having a peak wavelength of 254 nm (half value was 251 nm to 257 nm) was used. The emission length of the low-pressure mercury lamp is 80 mm.
As a light source included in the ultraviolet light irradiation device 20, a KrCl excimer lamp which emits ultraviolet light having a peak wavelength of 222 nm (half value was 215 nm to 229 nm) was used. The emission length of the KrCl excimer lamp is 80 mm.
Several types of materials were prepared as the to-be-treated solutions 2, and each of the to-be-treated solutions 2 was irradiated with the ultraviolet light of Example 1 and Comparative Example 1 to perform odor analysis. There are four types of materials prepared as the to-be-treated solutions 2: coffee beverage, apple juice, lemon juice, and wine.
The irradiation conditions of ultraviolet light are as follows.
Flow rate of test solution in flow path for to-be-treated solution: 0.72 mL/hour
Ultraviolet light intensity in flow path for to-be-treated solution: 3.6 mW/cm2
Treatment time: 139 seconds
Ultraviolet light irradiation amount: 500 mJ/cm2
Temperature of to-be-treated solution during treatment: 20° C.
An odor analysis test was conducted by the following method.
For each of the to-be-treated solution 2 after the ultraviolet light irradiation treatment, an odor component analysis test was conducted using a GC/MS/Olfactometry (Gas Chromatograph Mass Spectrometer QP-2010Plus manufactured by Shimadzu Corporation). More specifically, an analysis test was performed on each of the to-be-treated solution 2 after irradiation with ultraviolet light using the light source of Example 1 and the light source of Comparative Example 1. The results are shown in
From the analysis results of
From the analysis results of
According to the results of
From the analysis results of
A coffee beverage was prepared as the to-be-treated solution 2, and taste analysis was performed by irradiating the ultraviolet light of Example 1, Example 2 and Comparative Example 1. The irradiation conditions of ultraviolet light are the same as in verification 1.
A taste analysis test was conducted by the following method.
Each of the to-be-treated solutions 2 was subjected to the ultraviolet light irradiation treatment (sterilization treatment) using the reactor 10 described above. Then, for each of the to-be-treated solutions 2 after the ultraviolet light irradiation treatment, the taste analysis test was conducted using a taste sensor (taste recognition device “TS-5000Z” manufactured by Intelligent Sensor Technology, Inc.). The results are shown in
The chart shown in
(1) Acidic taste (initial taste): acidic taste exhibited by citric acid and tartaric acid
(2) Bitterness and coarse taste (initial taste): substance derived from bitterness, which corresponds to richness, hidden taste, or the like at low concentrations
(3) Astringency stimulation (initial taste): acrid taste due to astringent substances
(4) Umami (initial taste): deliciousness of amino acids, nucleic acids, etc.
(5) Saltiness (initial state): saltiness of inorganic salts such as salt
(6) Bitterness (aftertaste): bitterness of taste found in general foods
(7) Astringency (aftertaste): astringency of aftertaste derived from astringent substances
(8) Umami and richness (aftertaste): persistent rich taste of umami substances
According to
When the same verification was performed on the to-be-treated solutions 2 as apple juice, lemon juice, and wine, although Comparative Example 2 showed a change in taste compared to Examples 1 and 2, it was confirmed that the amount of change was remained within ±0.8.
From the above verification results, it was confirmed that when the coffee beverage was irradiated with ultraviolet light, not only the odor but also the taste changed when the light source of Comparative Example 1 was used.
Coffee flavor, grape flavor, and orange flavor were prepared as the to-be-treated solution 2, and the ultraviolet light of Examples 1 to 3 and Comparative Examples 1 to 2 was irradiated to perform sensory evaluation of the taste analysis. Specifically, three samples for each of Examples and Comparative Examples contained in a transparent flour container (70 g) of φ71 mm were prepared, and 10 people confirmed whether a change in flavor was confirmed before and after irradiation with ultraviolet light. The results of the sensory evaluation are shown in Table 1. In Table 1, Evaluation A indicates that the percentage of people who have confirmed the change in flavor is less than 3%, Evaluation B indicates that the percentage of people who have confirmed the change in flavor is 3% or more and less than 40%, and Evaluation C indicates that the percentage of people who have confirmed the change in flavor is 40% or more.
As for the coffee flavor, it was confirmed that after light irradiation from the light source of Comparative Example 1, the flavor was reduced as compared with before the light irradiation. Furthermore, it was confirmed that after light irradiation from the light source of Comparative Example 2, the flavor was reduced, and, at the same time, coarse taste increased as compared with before the light irradiation. On the other hand, after light irradiation from each of the light sources of Examples 1 to 3, deterioration of flavor was hardly confirmed as compared with before the light irradiation.
As for the grape flavor, it was confirmed that after light irradiation from the light source of Comparative Example 1, the flavor and aftertaste were reduced as compared with before the light irradiation. Furthermore, it was confirmed that after light irradiation from the light source of Comparative Example 2, the taste became light as compared with before the light irradiation. On the other hand, after light irradiation from each of the light sources of Examples 1 to 3, deterioration of flavor was hardly confirmed as compared with before the light irradiation.
As for the orange flavor, it was confirmed that after light irradiation from the light source of Comparative Example 1, the flavor was reduced as compared with before the light irradiation. Furthermore, it was confirmed that after light irradiation from the light source of Comparative Example 2, the taste became light as compared with before the light irradiation. On the other hand, after light irradiation from each of the light sources of Examples 1 to 3, deterioration of flavor was hardly confirmed as compared with before the light irradiation.
Bacillus cereus (JCM2152) in a spore state was used as a test bacterium, and a predetermined amount of the test bacteria was suspended in the to-be-treated solution 2 to prepare a test solution such that the number of bacteria initially generated was 105 CFU/mL. Here, a coffee jelly flavor was adopted as the to-be-treated solution 2.
A test solution before the ultraviolet light irradiation treatment (sterilization treatment) and a test solution after the ultraviolet light irradiation treatment (sterilization treatment) using the light source of Example 1 under the same conditions as in Verification 1 were applied onto an agar medium and cultured at 30° C. for 48 hours, and the number of colonies generated on the agar medium was then examined. The results are shown in
As an example, when the light source of Example 1 was used, the treatment time was 55 seconds or more and 84 seconds or less, and when the light source of Example 2 was used, the treatment time was 100 seconds or more and 300 seconds or less. The treatment time is sufficiently longer than the time (ms order) of sterilization treatment using a flash lamp in the food field such as meat and fish. Meat and fish contain a lot of oil, which is altered by absorbing light. Thus, in the food field, a method of irradiating light for an extremely short time to instantaneously increase the temperature and thus to perform sterilization treatment may be used.
According to the above verification results, it is considered that some components (e.g., compounds such as sugars, lipids, proteins, and carbohydrates) contained in beverages change due to the action of light and change the flavor. In particular, it can be seen that components contained in coffee beverages, fruit juice beverages including fruit juices such as apple juice and lemon juice, and alcoholic beverages such as wine include substances that change due to the action of light and change their flavor. In the field of beverages, the present invention newly discovers that a change in odor and taste occurs by irradiating ultraviolet light in a predetermined wavelength band in the field of beverages, and then ultraviolet light in a specific wavelength band excluding the predetermined wavelength band is irradiated, so that it is possible to suppress change/deterioration of odor and taste while ensuring the sterilization effect.
By the way, light has higher energy as the wavelength is shorter. According to the analysis described above, it is assumed that when the treatment is performed using the light source of Comparative Example 1 having a peak wavelength of 254 nm (half value is 251 to 257 nm), binding of a substance inherent in the to-be-treated solution 2 is broken, for example, so that new substances are generated or the amount of substances already contained has changed significantly. In view of this, it is considered that when light of a light source having a shorter wavelength than that of the light source of Comparative Example 1 is used, odor and taste further change. This point also appears in the results when each sample has been irradiated with light from the light source of Comparative Example 2 in Verification 3.
On the other hand, when the treatment was performed using the light source of Example 1, no significant changes in odor and taste were confirmed compared to the untreated case. In view of this, it is considered that when light of a light source having a longer wavelength than that of the light source of Example 1 is used, a degree of change in odor and taste is equal to or less than that of Example 1. This point also appears in the results when each sample was irradiated with light from the light sources of Examples 2 and 3 in Verification 3.
As shown in Verification 4, even when the light sources of Examples 2 and 3 were used, the sterilization effect was confirmed. Therefore, it can be seen that when ultraviolet light having an emission wavelength of 260 nm or less is not substantially irradiated and ultraviolet light having an emission wavelength of 280 nm or more and 320 nm or less is irradiated, the sterilization treatment can be performed while suppressing changes in taste and odor.
The ability of sterilization is improved by increasing an amount of irradiation light. That is, the ability of sterilization can be substantially ensured at a practical level by adjusting the output of the light source and the irradiation time. However, for light in the wavelength range longer than 320 nm, the sterilization effect cannot be sufficiently ensured unless the output of the light source is made extremely high and an extremely long irradiation time is ensured. In particular, as shown in
In view of the above points, it can be seen that when ultraviolet light having an emission wavelength of 260 nm or less is not substantially irradiated and ultraviolet light having an emission wavelength of 280 nm or more and 320 nm or less is irradiated, the sterilization treatment can be performed while suppressing changes in taste and odor under practical device design.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-104646 | May 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/019749 | 5/23/2018 | WO | 00 |
