JPH09276376A - Continuous heat sterilizing method and continuous heat sterilizing unit for liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to perform mass-sterilization and to improve sterilization efficiency, by irradiating ultrasonic waves to liquid while the liquid is retained at a sterilizing temperature for a prescribed time to be sterilized passing through a sterilizer. SOLUTION: Liquid before sterilization stored in a storage tank is passed through heat exchanging parts 110 and 130, heating parts 120 and 140, and cooling parts 150 and 160 by liquid delivering pumps 102 and 103. The liquid is heated by the heat exchanging parts 110 and 130 and the heating parts 120 and 140. A passage 145 constitutes a retaining means to retain the liquid at a sterilizing temperature until the liquid reaches the cooling means 150. The retaining time is adjusted according to the length of the passage 145. Further, an ultrasonic irradiation means 170 is mounted on the passage 145 to irradiate ultrasonic waves to the liquid in the passage 145 for a tim, for instance, not longer than 5sec. Though known means is used as the ultrasonic irradiation means 17, it is preferable to select materials for parts to be in contact with the liquid taking heat resistance, cleanability, and hygiene in consideration. Thus, masssterilization can be achieved by employing both heating and ultrasonic waves.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a continuous heat sterilization method for liquid and a continuous heat sterilizer. More specifically, the present invention relates to a continuous heat sterilization method and apparatus suitable for mass-scale sterilization treatment of liquids on an industrial scale, and the killing rate and sterilization of bacteria in the liquid even under the same sterilization conditions as conventional ones. The present invention relates to a highly efficient continuous heat sterilization method and continuous heat sterilization apparatus.

In the present invention, a liquid is a food in a liquid state,
Feed or medicine.

[0003]

2. Description of the Related Art Conventionally, various sterilization methods have been adopted in the fields of foods, feeds and pharmaceuticals, but heat sterilization methods are often used especially for liquids. The heat sterilization method is a method of killing various bacteria by heating a liquid, and in particular, the continuous heat sterilization method is most suitable in the food, feed and pharmaceutical industries because it can be mass-produced on an industrial scale. It is popular.

The continuous heat sterilization method is a method in which a liquid is heated to a predetermined sterilization temperature by a heat exchanger or the like, kept at that temperature for a predetermined time for sterilization, and then cooled by a heat exchanger or the like. All the operations can be carried out while continuously passing the liquid.

On the other hand, generally, in the heat sterilization method, there has been proposed a method of irradiating an object to be sterilized with ultrasonic waves to increase the sterilization effect. For example, the following prior arts (a) and (b) have been proposed. It has been known.

(A) When the suspension of fungal spores is irradiated with ultrasonic waves and then subjected to heat treatment, the sterilization efficiency is improved as compared with the case where only heat treatment is carried out (antibacterial and antifungal, No. 14). roll,
No. 6, pp. 35-47, 1986).

(B) When a liquid or paste-like low water activity substance is combined with ultrasonic irradiation and heat treatment, the lower the water activity of the substance, the higher the sterilization efficiency (JP-A-1-137960). Issue).

Further, the above (a) is an invention of a heat sterilization method for a liquid or paste-like low water activity substance, which is a method of heat sterilization at the same time as or after ultrasonic treatment. It is disclosed that, as the ultrasonic processing conditions, a frequency of 20 KHz, an output of 400 W, and a processing time of 1 minute or more,
A mode in which it is preferably 10 minutes or more is disclosed [See JP-A-1-137960, page (2), right column, upper column, line 15 to left column, lower column, line 9, hereinafter referred to as prior art. ].

[0009]

However, the prior arts (a) and (b) mentioned above mention the effect of combining ultrasonic irradiation and heat sterilization.
The specific embodiments thereof only disclose a small amount of processing on a laboratory scale, and there is nothing about whether or not the prior art of (a) above can be applied to actual industrial scale production. Not mentioned. That is, conventionally, the technique of using ultrasonic waves in combination with the heat sterilization method has been studied on a laboratory scale, but has not yet been established as a mass treatment technique on an actual industrial scale.

The reason for this is that the following problems exist. That is, when a large amount of liquid is sterilized, it is necessary to use a continuous heat sterilization method to perform heating, holding, and cooling while passing the liquid. If ultrasonic waves are used together with such a continuous heat sterilization method, ultrasonic waves will be applied to the liquid that is continuously passed through, and eventually, instantaneous ultrasonic irradiation will stop. . For example, according to the conventional technique of (a) above, ultrasonic waves need to be irradiated for 1 minute or longer, preferably 10 minutes or longer, but in a general continuous heat sterilization method, the liquid flow rate is 0.2.
The liquid is passed at about 2 m / sec, and in order to irradiate ultrasonic waves for 1 minute, it is necessary to arrange a plurality of ultrasonic wave irradiating means over a length of 12 to 120 m if simply calculated. Therefore, it has been impossible to use ultrasonic waves together with the continuous heat sterilization method unless the treatment capacity of the sterilizer is significantly reduced.

Therefore, in order to use ultrasonic waves in combination with heat sterilization, it is common technical knowledge to irradiate ultrasonic waves for a long time.
Due to such technical common sense, it has not been conventionally adopted in the continuous heat sterilization method.

As a result of intensive studies on the effect of ultrasonic waves in such a continuous heat sterilization method, the present inventors have found that if the ultrasonic waves are irradiated under specific conditions, the irradiation time is instantaneous. The inventors have found that a significantly higher effect can be obtained than the methods described in the above-mentioned (a) and (a), and have completed the present invention.

An object of the present invention is to provide a continuous heat sterilization method for liquids, which enables large-scale sterilization of liquids in spite of the combined use of ultrasonic waves and has higher sterilization efficiency than ever before. is there.

Another object of the present invention is to provide a liquid continuous heating sterilizer capable of mass sterilizing a liquid in spite of the combined use of ultrasonic waves and having a higher sterilization efficiency than ever before. That is.

[0015]

The present invention devised to solve the above problems will be described below. The elements of the present invention will be described in order to facilitate correspondence with the elements of the embodiments described later. The code of the elements of the example is enclosed in parentheses. The reason why the present invention is described in association with the reference numerals of the embodiments described below is to facilitate understanding of the present invention and not to limit the technical scope of the present invention to the embodiments.

FIG. 1 is a view showing an embodiment of the apparatus of the present invention,
FIG. 3 is a diagram showing another embodiment of the device of the present invention.

A first aspect of the present invention for solving the above-mentioned problems is to pass a liquid through a sterilizer to heat it to a predetermined sterilization temperature, and sterilize it by holding it at the sterilization temperature for a predetermined time. A continuous heat sterilization method for a liquid, which is cooled and discharged, characterized by irradiating ultrasonic waves while holding and sterilizing for a predetermined period of time.

In the first aspect of the present invention, it is preferable that the liquid is irradiated with ultrasonic waves for 5 seconds or less.

A second invention of the present invention for solving the above-mentioned problems is a storage tank (not shown) for storing a liquid, and a liquid passing pump (102, 1 for passing the liquid from the storage tank).
04, 202, 204, 233), heating means (110, 120, 130, 140, 210, 220, for heating the liquid passed through the liquid passing pump to a predetermined sterilization temperature.
207), holding means (145, 208) for holding and sterilizing the liquid heated to the sterilization temperature for a predetermined time, and cooling means (130, 110, 15) for cooling the sterilized liquid.
0, 160, 230, 210), and a liquid continuous heat sterilizer provided with the holding means (145, 20).
8) A continuous heating and sterilizing apparatus (100, 200) for a liquid, which is provided with an ultrasonic wave irradiating means (170, 270) arranged to irradiate the liquid with an ultrasonic wave.

Also, in the second aspect of the present invention, the flow paths (145, 20) for transferring the liquid heated by the holding means to the predetermined sterilization temperature to the cooling means (130, 230).
8) is also a desirable mode.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail. First, a continuous heat sterilization method for liquid, which is the first invention of the present invention, will be described.

The method of the present invention comprises heating and holding a liquid,
And a cooling step, but as described in detail below, all of these steps can be performed by a conventionally known method.

First, the liquid is passed through a sterilizer and heated to a predetermined sterilization temperature. As the heating means, known means such as a heat exchanger can be used, and in the case of a heat exchanger, a plate type, other double tube type, multiple tube type, scraping type, etc. can be exemplified, and a liquid can be used. Any material may be used as long as it can be continuously heated. Alternatively, a direct heating method such as an injection method in which vapor is blown into a liquid or an infusion method in which liquid is blown into vapor can be used.

The liquid that has reached the predetermined sterilization temperature is held for a predetermined time. As a means for holding the liquid in this way, it is desirable to provide a flow path for transferring the liquid that has reached the sterilization temperature, and to set the holding time to the time until the liquid finishes passing through the flow path.

Further, in the method of the present invention, ultrasonic waves are applied while the liquid is kept at the sterilization temperature in this way. For example, when the means for holding the liquid is the flow path, a mode in which the flow path is provided with means for irradiating ultrasonic waves can be exemplified. When the liquid passes through the place where the means for radiating the ultrasonic wave is provided, the ultrasonic wave is radiated.

By irradiating the liquid having reached the sterilization temperature with ultrasonic waves, the sterilization efficiency is remarkably improved. Moreover, as described in the later-described test example, the degree to which the sterilization efficiency is improved is significantly superior to the methods disclosed in the prior arts (a) and (a).

The reason for this is as follows. That is, first, in the present invention, the ultrasonic waves are applied while the liquid is heated to the sterilization temperature, so that the ultrasonic waves can be efficiently applied to the bacteria in the liquid. That is, in the prior arts of (a) and (a), as is clear from the specific examples described, a mode of irradiating ultrasonic waves before heating the liquid and a mode of irradiating ultrasonic waves after cooling the liquid. Aspect [See Japanese Patent Application Laid-Open No. 1-137960, page (2), right column, lower line, line 1 to page (3), left column, lower column, line 8 and the like. ] Is disclosed, and none of the specific examples irradiates ultrasonic waves in a state where the liquid is heated. The present invention
Since the liquid is heated to the sterilization temperature and irradiated with ultrasonic waves at the same time, the sterilization efficiency is remarkably improved as compared with the prior arts of the above (A) and (A).

The second reason is that ultrasonic waves are directly penetrated into the liquid. For example, the above-mentioned prior art (a) suggests a method of heating a liquid and irradiating ultrasonic waves at the same time as in the present invention. However, as is clear from a specific example, a mode in which the liquid is first irradiated with ultrasonic waves, and then the liquid is heated by filling the container with a hermetically sealed container and then immersing the container in a heating medium. 1
See, for example, on page (3), left column, lower column, line 9 to right column, lower column, fourth line, etc. of JP-A-137960. ] Is only disclosed. That is, the above-mentioned prior art (a) suggests a method of irradiating ultrasonic waves at the same time as heating a liquid, but the specific example thereof is not disclosed. Therefore,
According to this specific example, first, a liquid is filled in a container and hermetically sealed, and the container is immersed in a heating medium and heated, and at the same time, the heating medium is irradiated with ultrasonic waves. Therefore, in the above-mentioned prior art (a), the ultrasonic wave only indirectly reaches the liquid via the heating medium and the container.

On the other hand, in the present invention, since the liquid is directly irradiated with ultrasonic waves, the sterilization efficiency is remarkably improved even though the actual irradiation time is a moment.

Therefore, in the method of the present invention, irradiation of ultrasonic waves does not require a long time as in the prior art, and is instantaneous, more specifically, 0.1 seconds or more and 5 seconds or less for a liquid. Is enough.

Further, since the sterilization efficiency is increased by using the method of the present invention, it becomes possible to sterilize at a temperature lower than the conventional sterilization temperature. The reduction of the sterilization temperature can reduce the heat denaturation of the liquid, and can reduce the adhesion of kogation to the heat transfer surface when the heating means is a heat exchanger.

Next, the liquid that has been sterilized is cooled. As a cooling means, a heat exchanger can be used as in the case of heating. When a direct heating method such as the injection method or the infusion method is adopted,
A means for removing vapor contained in the liquid, for example, an expansion vessel is used. In this case, a phenomenon occurs in which the temperature of the liquid drops when the vapor is removed from the liquid, which can be understood as a cooling step.

The above heating and cooling steps do not have to be performed in one step, and may be a mode in which the temperature is raised or lowered stepwise in a plurality of steps.

Next, the liquid continuous heat sterilizer (100, 200) according to the second aspect of the present invention will be described.

The apparatus (100, 200) of the present invention comprises a storage tank (not shown), a liquid passing pump (102, 104, 2).
02, 204, 233), heating means (110, 120,
130, 140, 210, 220, 207), holding means (145, 208), and cooling means (130, 110,
150, 160, 230, 210), but known devices can be used for these. The storage tank is a tank for storing the liquid before sterilization, from which the liquid is passed by the liquid passing pumps (102, 104, 202, 204, 233). Such a liquid feed pump (102,
As 104, 202, 204, 233), in addition to a centrifugal pump, a metering pump such as a positive displacement pump can be exemplified.

Heating means (110, 120, 130, 14
0, 210, 220, 207), plate type,
Double tube type, multiple tube type, scraping type heat exchanger (11
0, 120, 130, 140, 210, 220) or a direct heating method (207) such as an injection method or an infusion method. In short, any material can be used as long as it can heat the liquid to the sterilization temperature.

The holding means (145, 208) is a flow path (145, 20) for transferring the liquid heated to a predetermined sterilization temperature.
8) is desirable, in which case the liquid having reached the sterilization temperature is discharged from the heating means (140, 207),
Until the cooling means (130, 230) is reached, the sterilization temperature is maintained. It should be noted that such channels (145, 208) can be adjusted for holding time depending on the length of the channels.

In the apparatus (100, 200) of the present invention, the holding means (145, 208) has an ultrasonic wave irradiation means (17).
0, 270) are arranged. Ultrasonic wave irradiation means (17
Although a known ultrasonic wave generator can be used for (0, 270), it is desirable that the portion that comes into contact with the liquid is a material in consideration of heat resistance, washability, and hygiene.

The number of ultrasonic wave irradiation means (170, 270) may be one or plural, and the ultrasonic wave irradiation means (170, 270) can be installed in an arbitrary manner depending on the conditions such as the flow rate of the liquid and the width of the conduit. However, it is desirable that the liquid transferred through the flow paths (145, 208) can be reliably irradiated with ultrasonic waves.

Such ultrasonic wave irradiation means (170, 27)
An example of 0) is illustrated in Example 2 below. FIG. 2 is a partial sectional view showing an example of the ultrasonic wave irradiation means. In the case where the holding means is the flow path (145), the flow path (145) is provided with an ultrasonic wave irradiation chamber (171a) through which the liquid flows in and out, and the ultrasonic wave irradiation chamber (171a) is provided with an ultrasonic wave. Part of the sound wave transducers (172, 175) (17
2) is installed and an ultrasonic wave generation source (176) is connected to the ultrasonic vibrators (172, 175). With such a configuration, since the ultrasonic wave is irradiated to the liquid inside the ultrasonic wave irradiation chamber (171a), the ultrasonic wave can be surely irradiated.

Cooling means (130, 110, 150, 16
A known heat exchanger can be used for 0, 230, 210), but in the case of an injection system or an infusion system, an expansion vessel or the like (230).
Is used. The heating means (110, 120, 13
0, 140, 210, 220, 207) and cooling means (130, 110, 150, 160, 230, 210)
May be heated or cooled stepwise by a plurality of devices, and another device such as a homogenizer (103, 105,
205) can be added.

As described above, in the method and apparatus of the present invention, the plate type heat exchanger, which has good cleaning property and is suitable for large-scale processing, is the most preferable as the heating or cooling means. If the liquid has a low viscosity,
It is suitable when flowing through a plate heat exchanger, and those having a water activity close to 1, particularly those having a water activity of 0.94 or more are suitable.

Although the sterilization conditions in the present invention are not particularly limited, it is preferable that the sterilization temperature is high, and it is preferable that the sterilization temperature is 85 ° C. to 150 ° C. and the holding time is 2 seconds to 30 seconds.

Next, the present invention will be described in detail by showing test examples.

Test Example 1 This test was conducted to examine the sterilization efficiency of the continuous heat sterilization method of the present invention and the conventional continuous heat sterilization method.

1) Preparation of sample Bacillus brevis (ATCC 824)
Bacterial spore suspension of 6) (bacteria concentration 74 × 10 ⁷ / ml)
Was prepared by a conventional method. 0.1 l of this suspension is added to 100
It was evenly dispersed in 1 l of milk to prepare a sample solution having a bacterial concentration of 74 × 10 ⁴ / ml.

2) Test Method Test Sample Milk plate sterilizer (10) described in Example 1 below.
0) small test equipment (processing capacity 100 l / h)
The sample solution is heat-sterilized under the conditions of a sterilization temperature of 140 ° C. and a holding time of 6 seconds, during which ultrasonic waves are applied for 0.4 seconds, 15 kHz, 1
Irradiation was performed at 200W. For the sample solution after sterilization, the number of surviving bacteria is determined by the conventional method (edited by the Pharmaceutical Society of Japan, “Hygiene Test Method, Note 199
0 ", page 181," Standard plate count ", Kinbara Publishing,
(1990).

Control sample Under the same sterilization condition, heat sterilization was performed without irradiating ultrasonic waves, and the sterilized sample solution was measured for the number of surviving bacteria by the same method as described above.

3) Test results The results are shown in Table 1. The test sample has a survival cell count of about 1/500 compared to the control sample, and it is clear that the test sample has a greater bactericidal effect than the control sample. From these results, it was confirmed that the method of the present invention has improved sterilization efficiency as compared with the conventional continuous heat sterilization method.

The above test was repeated and other samples, devices and conditions were also tested, but almost the same results were obtained.

[0051]

[Table 1] Test Example 2 This test was conducted to examine the degree of improvement in sterilization efficiency with respect to the known methods described in the above-mentioned (a) and (a) related art.

1) Preparation of Sample A sample solution was prepared by the same method as in Test Example 1 above.

2) Test method Control A A sample liquid was used as a glass thin tube (US, DRAMOND, 1
(Capacity: 00 μl), immersed in an oil bath heated to 140 ° C. for 2 seconds, the tube was then opened, and the number of surviving cells was measured by the same method as in Test Example 1.

Control B: The tip of the ultrasonic horn of an ultrasonic treatment device (manufactured by Seiko Instruments & Electronics Co., SH 7040) was dipped in the sample solution and irradiated with ultrasonic waves at 20 kHz and 40 W for 1 minute, and then the control. Like A, it was sealed in a glass thin tube, treated under the same heating conditions as Control A, opened, and the number of surviving bacteria was measured in the same manner.

3) Test results The results are shown in Table 2. As is clear from Table 2, the number of surviving bacteria in Control B is reduced to only about 1/10 as compared with Control A, and the difference between Control A and Control B is the same as in Test 1 above. It was observed that the difference was very small when compared to the difference between the sample and the control sample. From this result, it was found that the method of the present invention markedly improves the sterilization efficiency as compared with the known heat sterilization method using ultrasonic waves together.

The above test was repeated and other samples and conditions were also tested, but almost the same results were obtained.

[0057]

[Table 2]

[0058]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 An example of the apparatus of the present invention is shown in FIG. FIG. 1 is a view showing an embodiment of the apparatus of the present invention, and is a schematic view of a plate type sterilizer for milk (a sterilizer for heating and sterilizing milk by a plate type heat exchanger).

The plate sterilizer 100 for milk shown in FIG.
The first heat exchanging unit 110 and the second heat exchanging unit 130, the first heating unit 120 and the second heating unit 140, the first cooling unit 150, and the second cooling unit 160 are provided, each of which is a plate type. It is composed of a heat exchanger and has a holding tank 103 and a homogenizer 105. A pipe line from the second heating unit 140 to the second heat exchange unit 130 is a holding pipe 145, and the holding pipe 145 is provided with an ultrasonic irradiation device 170 (manufactured by Ultrasonic Industrial Co., USH-1200Z20S). Has been.

An ultrasonic irradiation box 171 is arranged in the holding tube 145, and a part of the ultrasonic transducer 175 projects into the inside of the ultrasonic irradiation box 171 as an ultrasonic horn (not shown). The ultrasonic irradiation box 171 is provided so as to come into contact with the milk. An ultrasonic transmitter 176 is connected to the ultrasonic vibrator 175.

Next, the operation of the apparatus shown in FIG. 1 will be described. FIG.
In FIG. 1, unsterilized milk is stored in a storage tank (not shown) and is introduced into the milk plate sterilizer 100 from the direction of arrow M. The unsterilized milk is first stored in the buffer tank 101 and then the first by the pushing pump 102.
Liquid is passed through the heat exchange section 110. This first heat exchange section 110
After heat exchange with milk after sterilization in the first heating section 1
The liquid is passed through 20 and heated by hot water HW1. Then
The pushing pump 1 is stored in the holding tank 103 for a predetermined time.
The liquid is passed through the homogenizer 105 by 04. The unsterilized milk is discharged from the homogenizer 105 at a constant flow rate and passed through the second heat exchange section 130. Then, the second heat exchange unit 130
In (2), the milk after sterilization is again heat-exchanged and heated, and then heated by the hot water HW2 in the second heating section 140 to reach the sterilization temperature.

The milk that has reached the sterilization temperature is transferred through the holding tube 145. During this time, the milk is maintained at the sterilization temperature, and when passing through the ultrasonic irradiation device 170,
Ultrasonic waves are emitted instantaneously. That is, when milk passes through the ultrasonic irradiation box 171, it comes into contact with an ultrasonic horn (not shown) projecting inside the ultrasonic irradiation box 171. Ultrasonic transducer 17
5 is ultrasonically vibrated by the ultrasonic wave transmitter 176, and the milk passing through the inside of the ultrasonic wave irradiation box 171 is irradiated with ultrasonic waves.

The time for irradiating the milk with ultrasonic waves is during the time that the milk passes through the ultrasonic irradiation box 171 and is only for a moment, but a large amount of damage is given to the bacteria in the milk, and the sterilization efficiency is high. Is significantly improved.

The milk is heat-exchanged with unsterilized milk by the second heat exchange section 130 and the first heat exchange section 110 to be cooled,
Water W in the first cooling unit 150 and second cooling unit 16
At 0, it is cooled by chilled water CW.

Thus, the plate sterilizer 100 for milk of FIG. 1 is a device having a higher sterilization efficiency than the conventional sterilizer of the same kind by the action of the ultrasonic irradiation device 170.

Embodiment 2 FIG. 2 is a partial cross-sectional view showing an example of ultrasonic wave irradiation means installed in the plate sterilizer 100 for milk of FIG.

In FIG. 2, a section below the line XX ′ in the drawing shows a cross section, and in FIG. 2, the elements common to FIG. 1 are designated by the same reference numerals as those in FIG. Description is omitted.

The holding tube 145 is provided with an ultrasonic irradiation box 171. Of the holding tube 145, the ultrasonic irradiation box 17
The inlet side to 1 is the inlet pipe 146, and also the ultrasonic irradiation box 17
The outlet side of 1 is the outlet pipe 147. Ultrasonic irradiation box 171
Is provided with an ultrasonic wave irradiation chamber 171a. For this ultrasonic wave irradiation chamber 171a, an inflow passage 146a formed by an inlet pipe 146 and an outflow passage 147a formed by an outlet pipe 147.
Are in communication with each other.

An ultrasonic horn 172 is inserted in the ultrasonic wave irradiation chamber 171a.
The O-rings 173 and 174 are used for the ultrasonic irradiation box 17
It is fixed at 1.

The ultrasonic horn 172 is connected to an ultrasonic vibrator 175, and a transistor type ultrasonic transmitter (not shown) is connected to the ultrasonic vibrator 175.

Next, the operation of the apparatus shown in FIG. 2 will be described.

Milk is fed from the direction of arrow Y to the ultrasonic wave irradiation chamber 1
71a and flows out in the direction of arrow Z. When the transistor type ultrasonic transmitter vibrates the ultrasonic vibrator 175, the vibration is transmitted to the ultrasonic horn 172 to generate ultrasonic waves. Then, the milk flowing into the ultrasonic wave irradiation chamber 171a through the inflow passage 146a is irradiated with ultrasonic waves. The milk after being irradiated with ultrasonic waves flows out from the outflow passage 147a.

In the second embodiment, the positional relationship between the inflow passage 146a and the ultrasonic irradiation chamber 171a is devised so that milk flows in from the axial direction of the ultrasonic horn 172 (that is, the direction of arrow Y). Therefore, the inflowing milk can be reliably irradiated with ultrasonic waves.

Embodiment 3 FIG. 3 is a view showing another embodiment of the apparatus of the present invention, which is a schematic diagram of a direct heat sterilizer for milk (an injection type sterilizer for heat sterilization by blowing steam into milk). Is. In FIG. 3, the direct heat sterilizer 200 for milk is
First heat exchange section 21 constituted by a plate heat exchanger
0 and the 1st heating part 220, the injection nozzle 207 which injects steam into milk, the decompression evaporation chamber 230, and the aseptic homogenizer 205 are provided. Further, the flow path from the injection nozzle 207 to the reduced pressure evaporation chamber 230 has a holding pipe 208.
The holding tube 208 is provided with an ultrasonic wave irradiation device 270.

Next, the operation of the apparatus shown in FIG. 3 will be described. FIG.
In the above, unsterilized milk is stored in a storage tank (not shown), and the direct heat sterilizer 2 for milk from the direction of the arrow M
00 is introduced. The unsterilized milk is temporarily stored in the buffer tank 201 and then passed through the first heat exchange unit 210 by the push pump 202. After heat exchange with the sterilized milk in the first heat exchange section 210, the first heating section 22
0 and is preheated by the steam from the steam source 206.

The preheated milk flows to the injection nozzle 207, where the steam from the steam source 206 is blown. Milk that has been blown with steam rises in temperature and reaches the sterilization temperature. The milk that has reached the sterilization temperature flows through the holding tube 208, and during this time, the milk is maintained at the sterilization temperature, and furthermore, when passing through the ultrasonic irradiation device 270, ultrasonic waves are instantaneously irradiated. Although ultrasonic waves are irradiated for only a moment, bacteria in milk are given a large amount of damage and the sterilization efficiency is remarkably improved.

The sterilized milk flows into the vacuum evaporation chamber 230. The depressurized evaporation chamber 230 is depressurized by being sucked by the vacuum pump 232 via the condenser 231.
The milk, after flowing into the vacuum evaporation chamber 230, is instantaneously boiled and cooled, and the steam generated by the boiling is condensed by a condenser.
It is condensed by 231 and discharged from the vacuum pump 232.

The cooled milk is sent to the aseptic homogenizer 205 by the pushing pump 233, is heat-exchanged with the unsterilized milk in the first heat exchange section 210, and is discharged. After discharging, it is cooled by another cooling means (not shown).

In each of the above heating, sterilization and cooling steps, the flow rate of milk, the amount of steam blown from the injection nozzle, the sterilization temperature, the liquid level in the reduced pressure evaporation chamber 230, etc.
It is automatically controlled by a control device (not shown).

Thus, the direct heat sterilizer 2 for milk of FIG.
The device 00 has a higher sterilization efficiency than the conventional sterilizer of the same kind due to the action of the ultrasonic irradiation device 270.

Example 4 Next, the implementation of the method of the present invention using the apparatus of Example 1 will be described.

Milk having a milk solids content of 12.1% (weight; the same applies hereinafter), milk fat of 3.5% and a temperature of 4 ° C. was passed through the plate sterilizer 100 for milk of FIG. First heating unit 12
The outlet temperature of 0 was adjusted to 75 ° C., and the holding tank 103 was held for 1 minute. Homogenizer 105 flow rate 200
It operates at 1 / h and the uniform pressure is 150 kg / c in the first stage.
m ² and the second stage are set to 20 kg / cm ² , and the outlet temperature (sterilization temperature) of the second heating section 140 is set to 120 lower than usual.
Set to ° C.

The second heat exchange section 13 is passed through the holding tube 145.
The time to reach 0 is 1.5 seconds, and the ultrasonic wave irradiating device 170 is operated so that milk passing therethrough has a frequency of 20 kHz, 12
Ultrasonic waves were applied at 00W. The irradiation time for milk is
From the volume of the ultrasonic irradiation chamber 171a and the flow rate of milk,
It was 27 seconds.

Next, the milk is cooled to 45 ° C. through the second heat exchanging section 130 and the first heat exchanging section 110, and the temperature of the water is kept at 15 ° C. in the first cooling section 150, and the temperature in the second cooling section 160. The second cooling unit 16 is cooled with chilled water at 1 ° C., respectively.
0 outlet was set to 5 ° C.

Under the above conditions, the device was operated for 5 hours, and about 1
Tons of pasteurized milk was obtained. Comparative Example The sterilization temperature was changed to 130 ° C. which is a normal temperature, and the ultrasonic irradiation device 170 was stopped to perform sterilization. That is, sterilization was performed under the same conditions as in Example 3 except that the sterilization temperature was changed and the milk was not irradiated with ultrasonic waves.

Next, the sterilized milk obtained in Example 4 and Comparative Example was filled in a 200 ml brick pack in the usual way, and a storage test was conducted. That is, 300 brick packs of each of Example 4 and Comparative Example were stored at 10 ° C. for 7 days, and a flavor test and a microbial test were performed. However, none of the brick packs had an abnormal taste, Escherichia coli-positive one, or general bacteria of 50,000 / ml or more.

From these results, it was confirmed that according to the method of the present invention, a sufficient sterilization effect can be obtained even at a sterilization temperature lower than usual.

[0089]

The present invention relates to a sterilization method and apparatus combining a continuous heating sterilization method and ultrasonic irradiation, which have been considered to be impossible at all in the past, and the effects achieved by the present invention are as follows. It is as follows.

(1) According to the method and apparatus of the present invention, the heat sterilization method by the combined use of heating and ultrasonic waves, which has been conventionally conducted only on a small scale, is used as a large-scale liquid mass sterilization technique. Can be utilized.

(2) According to the method and apparatus of the present invention, the liquid can be directly irradiated with ultrasonic waves. Therefore, compared with the conventional method in which ultrasonic irradiation and heat sterilization are simply combined, Greatly improved sterilization efficiency.

(3) The method and apparatus of the present invention have extremely high sterilization efficiency as compared with the conventional continuous heat sterilization method and apparatus, and can be operated at a sterilization temperature lower than usual, so that the liquid heat It is possible to reduce denaturation and save energy.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the device of the present invention.

FIG. 2 is a partial cross-sectional view showing an example of ultrasonic wave irradiation means installed in the plate sterilizer for milk 100 of FIG.

FIG. 3 is a diagram showing another embodiment of the apparatus of the present invention.

[Explanation of symbols]

 100 Plate type sterilizer for milk 105 Homogenizer 110 First heat exchange section 120 First heating section 130 Second heat exchange section 140 Second heating section 145 Holding tube 146 Inlet tube 147 Outlet tube 150 First cooling section 160 Number 2 Cooling unit 170 Ultrasonic irradiation device 171 Ultrasonic irradiation box 172 Ultrasonic horn 173 O-ring 174 O-ring 175 Ultrasonic transducer 200 Direct heating sterilizer for milk 205 Aseptic homogenizer 207 Injection nozzle 208 Holding pipe 210 First Heat exchange section 220 First heating section 230 Decompression evaporation chamber 270 Ultrasonic irradiation device

Claims (4)

[Claims] 1. A continuous heat sterilization method for a liquid, which comprises passing a liquid through a sterilizer, heating it to a predetermined sterilization temperature, holding it at the sterilization temperature for a predetermined time to sterilize, cooling and discharging the liquid. A continuous heat sterilization method for a liquid, which comprises irradiating ultrasonic waves while holding for a time and sterilizing. 2. The continuous heat sterilization method for a liquid according to claim 1, wherein the irradiation of ultrasonic waves is 5 seconds or less. 3. A storage tank for storing a liquid, a liquid passage pump for passing the liquid from the storage tank to a sterilizer, a heating means for heating the liquid passed by the liquid passage pump to a predetermined sterilization temperature, and the sterilization. Holding means for holding the liquid heated to a temperature for a predetermined period of time to sterilize it, and a cooling means for cooling the sterilized liquid in a continuous heating and sterilizing apparatus for liquids, ultrasonic waves are placed on the liquid arranged in the holding means. An apparatus for continuously heating and sterilizing a liquid, which is provided with an ultrasonic wave irradiation means for irradiation. 4. The liquid continuous heat sterilizer according to claim 3, wherein the holding means is a flow path for transferring the liquid heated to the predetermined sterilization temperature to the cooling means.