JPH02211855A - Sterilization of liquid by microwave and equipment therefor - Google Patents

Abstract

PURPOSE:To enable sterilization of liquid foods without damage to peculiar tastes and flavors, etc., of the foods by alternately repeating rapid heating using the microwave irradiation method and rapid cooling after heating and sterilizing the liquid in a short time while maintaining the liquid in a low temperature state. CONSTITUTION:Food (S) such as refined Japanese rice wine is introduced into a teflon tube 3 by a quantitative pump 5, then rapidly heated by irradiation of microwave generated from a microwave generator 1 and subsequently introduced into a cooler 4 for rapid cooling using cooling water. By further alternately repeating rapid heating and cooling for sterilization of the food liquid (S) in a short time while keeping the liquid in a low-temperature state, circumstances of microorganisms in the food are remarkably changed and the objective sterilization of the food can be carried out without damage to the original flavors, etc., of the food.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and an apparatus for sterilizing liquid foods without impairing the unique taste, aroma, flavor, etc. of the foods.

[Prior Art] Conventionally, heat exchange sterilizers such as batch type and plate type are generally used to sterilize liquid foods, but there are also methods such as forced injection of heated steam.

[9! Problem M that Akira is trying to solve] However, in conventional heat sterilization methods, the heating time is long, ranging from several minutes to several tens of minutes, so the ingredients such as the original taste, aroma, flavor, etc. of the food are degraded. The problem is that it tends to get lost.

The present invention has been made in view of the above-mentioned problems, and its purpose is to improve the original taste, aroma, and taste of foods.
To provide a method and device for sterilizing liquid food, which can sterilize while retaining flavor and the like.

[Means for Solving the Problems] In order to achieve the above object, the present invention alternately repeats rapid heating by microwave irradiation and rapid cooling after heating to sterilize the liquid in a short time while keeping it in a low temperature state. It is characterized by Also, a microwave oscillator that generates microwaves, a waveguide attached to the microwave oscillator,
It has a sterilizer that has a tube that has a small dielectric loss and is not easily heated in a microwave electric field and is equipped with a cooler that penetrates the waveguide and cools the tube that exits the waveguide. Irradiating the flowing liquid with microwaves via a waveguide,
After that, rapid heating and cooling are repeated using a cooler.

[Function] By the method and apparatus for sterilizing liquid food configured as described above, the temperature of the liquid food is rapidly raised from the inside and then rapidly cooled. By repeating this heating and cooling process, the environment of microorganisms within the food can be significantly changed, making it possible to sterilize the food in a short period of time.

[Example] Hereinafter, a basic test for sterilizing sake (burn rs) using microwaves, which is an example of the liquid sterilization method using microwaves according to the present invention, will be described.

Hi-Ochibacterium is a type of lactic acid bacteria that proliferates even at alcohol concentrations of 15 to 20%, and is a harmful bacterium that causes cloudiness, growth, and strange flavors in sake.

Introduction: As shown in Figure 7, ordinary sake is heated and sterilized twice (65-70℃, 3 minutes), called ``hiire'', before bottling to completely sterilize the hiochi bacteria and store it at room temperature. It is being distributed.

However, "pasting" for a long time also causes the aroma and flavor of the squeezed product to be lost.

On the other hand, Namazake has recently become a popular choice for gourmets.
The product is bottled and shipped without ``pastoring,'' preserving its freshly squeezed aroma and flavor, and then distributed at a lower temperature, which incurs considerable costs. For this reason, there is a desire among sake manufacturers to preserve the aroma and flavor by sterilizing sake at low temperatures and to distribute it in that state at room temperature.

Therefore, we conducted a basic test to explore the possibility of applying the liquid sterilization method using microwaves to sake. As a result, the heating stage rM (temperature = 63-65℃ 9
time: 1.0 to 3.8 seconds), it was confirmed that Hiochi bacteria could be completely sterilized.

Microwave (ultra short wave) heating is a method of converting microwave energy into molecular motion of food components (mainly water) to instantly raise the temperature of each part of the inner and outer layers of the food. Method (1) Test apparatus Figure 4 shows the test apparatus.

a. Rapid heating and cooling type microwave sterilization test device The test device shown in Fig.
W) At the tip of the waveguide 2 of 1, a Teflon tube 3 (inner diameter 4φ) is placed perpendicular to the axial direction of the waveguide 2.

Five pieces (thickness: 1 mm, length: 55 ma+) are penetrated.

A cooler 4 in which cooling water is circulated is attached to each outlet of the Teflon tube 3. Then, the sample (sake) S is transferred to a Teflon tube 3 by a metering pump 5.
sent to.

The sample S passing through the Teflon tube 3 in the waveguide 2 is rapidly heated by the microwave irradiation generated by the microwave oscillator l. Immediately after leaving the waveguide 2, the heated sample S passes through a cooler 4 and is rapidly cooled by cooling water.

Then, the sample S is sent out after repeating rapid heating and cooling five times.

This device aims to sterilize Hiochi bacteria by rapidly changing the environmental temperature.

A thermoelectric seal C is attached to the Teflon tube 3 before and after passing through the cooler 4, and a recorder R connected to the thermoelectric seal C records temperature changes.

b. Spiral type microwave sterilization test device Figure 4 (b)
The test device shown in FIG. It was placed in This device aims to sterilize the sample S by irradiating the sample S with microwaves for a relatively long time and increasing the temperature.

(2) Sterilization test Table 1 shows an overview of the sterilization test.

a. Sample preparation Sample S was made by adding pure water to unprocessed sake (alcohol temperature 20%) to give the same alcohol concentration (16%) as commercially available sake, and adding hiochi bacteria to obtain 103 missing drops. It was adjusted to about /- and used for the test.

b. Test operation The rapid heating and cooling type microwave sterilization test device keeps the microwave output constant (1.5 kW) and adjusts the sterilization temperature (maximum temperature reached) by changing the flow rate of the sample S with the constant I pump 5. did.

On the other hand, the spiral type microwave sterilization test device
The sterilization temperature was adjusted by keeping the flow rate constant (300 mf/min) and changing the microwave output.

C1 temperature setting The temperature increase status of the sample S was measured with thermocouples TC attached to various parts of the test equipment, and when the temperature reached a steady state for each condition, the sample S was collected and the number of missing bacteria was measured. . Furthermore, the highest temperature reached at that time was defined as the sterilization temperature.

d. Bacterial count measurement Colonies were counted after culturing at 30° C. for 7 to 10 days using the agar plate culture method using Hiochi Bacteria Detection Medium (31 Medium) from Japan Brewing Association.

11. Test results (1) The temperature change over time of sample S when passing through two types of microwave sterilization test devices was as shown in FIG.

In the case of the rapid heating/quenching type test device shown in FIG. Although the pattern of increasing the temperature each time the temperature increased, the width of the temperature increase gradually decreased.

In the case of the spiral test device shown in Figure 5(b),
It passes through the waveguide 2 in 3.8 seconds and reaches its maximum temperature at the exit of the waveguide 2. After passing through the waveguide 2, it is rapidly cooled in the cooler 4.

(2) Heating efficiency As shown in Table 2, the heating efficiency when microwave sterilization was applied to sake was about 50%.

Compared to the rapid heating and cooling type testing equipment, the spiral type testing equipment, which requires a relatively long microwave irradiation time, had slightly better heating efficiency.

(3) Sterilization efficiency Table 6r2 and Table 3 show the relationship between microwave sterilization temperature and hiochi bacteria survival rate.

a.Rapid heating and cooling type microwave! In No. 111, no bactericidal effect was observed up to the maximum temperature of 50°C, and sterilization started around 56°C, and jJ2 bacteria were completely killed at 63°C.

In this case, the time it takes for the sample 8 to pass through the waveguide 2 is about 1.0 seconds.

b. In spiral type microwave sterilization, the sterilization effect was observed from the maximum temperature reached at 55°C, and complete sterilization was achieved at 65°C. In this case, the time the sample S passes through the waveguide is 3.8 seconds.

■, Discussion From the results of the basic test above, Micro ifI! j! 2rl
i has the following effects.

(1) Sterilization effect a, thermal effect By irradiating the sample 3 with microwaves, both the liquid and the body are internally heated to a uniform temperature.

b. Metamorphism effect The polar groups, ions, etc. of the biopolymers that make up the bacteria are violently vibrated by the action of an electric field, and the proteins and nucleic acids of the body are denatured.

In this test, the heating temperature of sake hiochi bacteria was 63 to 6.
It is sterilized at 5℃, and the conventional sterilization method "Pasteurization J temperature (6℃)"
5 to 70°C), no significant temperature difference was observed. However, complete sterilization can be achieved in an extremely short time compared to conventional methods, from several tens of minutes to several tens of minutes, demonstrating the effectiveness of liquid sterilization using microwaves for sake. was confirmed.

(2) Quality evaluation Although we did not conduct quality evaluations such as sensory tests this time, the heating time is extremely short due to microwave heating, which can instantly raise the temperature of each part of the inner and outer layers of the food. It is thought that no quality deterioration has occurred.

<3> The heating effect of liquid BrIJ using microwaves is about 50%, which is not as high as that of ordinary oil boilers, etc., and the "burning" step of conventional sterilization methods is completely replaced with liquid sterilization using microwaves. In this case, the equipment itself becomes large and the economic advantage is not considered to be significant.

However, since liquid sterilization using microwaves is easy to control temperature and there is little quality deterioration due to heating, we believe that it is particularly effective for application to high-quality sake, etc., where the aroma and flavor of freshly squeezed sake is important. It will be done.

Next, a first example of a liquid sterilization device using microwaves will be described.
It is shown in Figs.

The sterilizer IO shown in FIG. 1 includes a plurality of pipes 12 passed through a waveguide 11, a processing liquid cooling coil 13 connected to the container pipe 12, and a cooler 14 containing the processing liquid cooling coil 13. It is equipped with

The tube 12 is suitably one that has low dielectric loss and is not easily heated in a microwave electric field; for example, a Teflon tube is used. The container tubes 12 are connected by a processing liquid cooling coil 13 formed in a spiral shape.
It forms a continuous passage. Both ends of this passage are defined as an untreated liquid outlet 15 and a treated liquid outlet 16.

A sterilizer lO, which shows a liquid sterilization system using microwaves in FIGS. 2 and 3, is attached to the tip of a waveguide 11 connected to a microwave oscillator 17 via a microwave tuner 18. The microwave oscillator 17 is connected to a power supply AC via a slider 19. Then, the untreated liquid population 15 and the treated liquid outlet 16 of the sterilizer 10
are an untreated liquid tank 20 and a treated liquid tank 21, respectively.
It is connected to the. Further, the untreated liquid tank 20 is provided with a metering pump 22 that sends the untreated liquid to the sterilizer 10.

Cooling water taken in from the cooling water outlet 14a and sent out from the cooling water outlet 14b circulates inside the cooler 14, and cools the disposed processing liquid cooling coil 13.

The untreated liquid (for example, sake) sent to the sterilizer 10 and passing through the pipe 12 in the waveguide 11 is passed through the microwave oscillator 17.
The temperature is raised instantaneously by irradiation with microwaves oscillated from the inside. Immediately after leaving the waveguide 11, the heated untreated liquid is sent to the treated liquid cooling coil 13, where it is rapidly cooled by the cooling water in the cooler 14. Then, the treated liquid is repeatedly rapidly heated and cooled while being sent from the untreated liquid population 15 to the treated liquid outlet 16.

The repetition of rapid heating and cooling is performed using a tube 12 that is passed through the waveguide 11
It is also possible to make it into one line and let it flow again.

Alternatively, it is possible to separate the central portion of the waveguide 11 into, for example, a Y-shape to form two microwave passages in parallel, and the tube 12 to pass through both passages continuously. In this case, the number of microwave passages is not limited to two, and the same applies if the microwave passages are passed through a plurality of sterilizers in succession.

Note that the microwave output is adjusted by the slider 19 to raise the temperature to the target temperature, and at the same time, the microwave tuner 18 adjusts the reflected waves to be minimized.

[Effects] As explained above, the microwave sterilization method of the present invention alternately repeats rapid heating by microwave irradiation and rapid cooling after heating to sterilize the liquid in a short period of time while keeping it in a low temperature state. It is characterized by this. In addition, a microwave oscillator that generates microwaves, a waveguide attached to the microwave oscillator, and a tube that has a small dielectric loss and is not easily heated in the microwave electric field are passed through the waveguide, and the It has a sterilizer equipped with a cooler that cools the tube that exits the wave tube, and the liquid flowing inside the tube is irradiated with microwaves through the waveguide, and then is rapidly heated and cooled by the cooler. It is characterized by repetition. As a result, it becomes possible to sterilize liquid foods while retaining the original taste, aroma, flavor, etc. of the foods.

(Left below) Table 4, Ii! Brief explanation of J side Figures 1 to 3 show a liquid sterilizer using microwaves according to the present invention. Figure 1 is an explanatory diagram showing the liquid sterilizer, and Figure 2 is a front view of the entire system. , FIG. 3 is a plan view of the entire system.

Figures 4 to 7 show sake produced by microwaves according to the present invention (
This shows the basic sterilization test for Hi-Ochibacterium. Figure 4 shows the test equipment, (a) is an explanatory diagram showing the rapid heating and cooling type, (
b) is an explanatory diagram showing the spiral type, Figure 5 is an explanatory diagram showing the change in sample temperature over time, (a) is an explanatory diagram for the rapid heating and rapid cooling type, (b) is an explanatory diagram for the spiral type, and Figure 6 is an explanatory diagram for the spiral type. Explanatory diagram showing the relationship between microwave sterilization temperature and hiochi bacteria survival rate, No. 7 rj! I is an explanatory diagram showing the types of sake related to pasteurization.

10... Sterilizer 11... Waveguide 12.
...Tube 14...Cooler 17...Microwave oscillator (blank below) Figure 14b 14a Figure (a) (b) Darkness (a) Figure

Claims (2)

[Claims] (1) A method for sterilizing liquid using microwaves, which is characterized in that rapid heating by microwave irradiation and rapid cooling after heating are repeated alternately to sterilize the liquid in a short period of time while keeping it in a low temperature state. (2) A microwave oscillator that generates microwaves, a waveguide attached to the microwave oscillator, and a tube that is in the microwave electric field and has small dielectric loss and is not easily heated, passing through the waveguide. Along with letting
a sterilizer equipped with a cooler that cools the tube exiting the waveguide, the liquid flowing in the tube is irradiated with the microwave through the waveguide, and then the liquid flowing in the tube is irradiated with the microwave, and then A liquid sterilizer using microwaves that is characterized by repeated rapid heating and cooling.