JP2004305001A - Method for retort sterilization of beverage packed in resealable container and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for retort sterilization by which the same retort sterilizing effects on a resealable container as those of a method for hot-water sterilization can be realized with inexpensive equipment without a boiler tank. <P>SOLUTION: Water is introduced into the bottom of a retort vessel 2 within the range so as not to bring a material to be sterilized into direct contact therewith. Steam is then blown into the water to heat the water. The resultant heated water is circulated and sprinkled in a shower form from the upper part on the material to be sterilized. A pressurized gas is simultaneously introduced to heat the material to be sterilized in a prescribed pressurized state to a sterilizing temperature. After completing the sterilization, cooling water is gradually introduced into the heated water in the bottom of the retort vessel while sending the heated water in the bottom of the retort vessel used in the sterilizing step in the shower form from the upper part. The amount corresponding to the amount introduced is discharged from the bottom of the retort vessel to the outside. The temperature of the cooling water circulated through the interior of the retort is gradually lowered to carry out slow cooling while controlling the temperature lowering rate in the retort. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for sterilizing a retort, and particularly to a method and an apparatus for sterilizing a retort of a resealable packaged beverage.
[0002]
[Prior art]
As a method for heat sterilization of canned food, bottled food, or bagged food such as pouches (hereinafter collectively simply referred to as "heated objects") in a retort, in the case of a batch system, a steam sterilization method, heat There are a water sterilization method and a hot water shower sterilization method (see Patent Literatures 1 to 3), and according to the pressure state in the kettle, a pressureless sterilization method, a constant pressure sterilization method, an equal pressure sterilization method, and a cooling method after heating. Other methods include a non-pressurized cooling method, a constant-pressure cooling method, and an equal-pressure cooling method, and the optimum combination is performed depending on the type of container and contents. In recent years, with the development of heat-resistant materials, resealable sealed containers such as PET bottles or screw-cap type bottle-shaped metal cans have been filled with contents requiring retort sterilization. There is a demand for retort sterilization. In the case of a resealable sealed container, the sealing property is inferior to that of a normal canned container that is double-wrapped and sealed, and if the internal pressure of the container increases and the differential pressure with the inside of the kettle increases, sealing may be impaired, The retort sterilization must be performed by a pressure sterilization / pressure cooling method. This tendency is remarkable when the container or its lid is thinned due to a gauge down or the like. In addition, in order to increase the retort processing amount per one time and to speed up the sterilization process, generally in the case of canning or bottles, sterilization is carried out without leaving a gap in a basket. Since the contact condition with the heating medium is not uniform depending on the position of the object to be heated, the temperature (product temperature) of the object to be heated varies widely depending on the position in the basket. Sterilization is said to be desirable.
[0003]
On the other hand, most of the general cans use steam as a heating medium and perform non-pressurized sterilization and pressurized cooling, and this method is the mainstream of retort sterilization. The reason is that if hot water is used as a heating medium, a boiler tank for boiling hot water is required in addition to the sterilizing pot, which increases the equipment cost of the retort device. Therefore, even if it has a normal steam sterilizer, it cannot be used for both hot water sterilization and steam sterilization in the same apparatus, so beverages that require retort sterilization such as low acid beverages that have been put into practical use in recent years are required. In order to start the production of resealable container-packed products, significant modifications such as adding a boiler tank to the conventional steam heating retort device or installing a separate hot water sterilization retort device would be necessary, Requires equipment costs.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 61-260863 [Patent Document 2]
Japanese Patent Application Laid-Open No. H11-221062 [Patent Document 3]
Japanese Patent Publication No. 7-95935
[Problems to be solved by the invention]
In order to retort sterilize the resealable hermetically sealed packaged beverage, pressure sterilization is necessary in order to prevent the occurrence of breakage, deformation or leakage of the container due to an increase in the internal pressure of the container as described above. However, when air is introduced by steam sterilization and sterilization is performed in a pressurized state by air (a so-called steam-air mixing method), air to be heated near the center of the basket becomes air-insulated with air mixed with steam, and sterilization is performed. Insufficient heating results in insufficient heating. In the case of heated objects that are packed in a densely packed basket, rotating the fan is the same as rotating the fan toward the wall because there is no space between the heated objects between the heated objects. There is no effect of the fan in the state, and it is impossible to eliminate the variation in the sterilization temperature. For this reason, if the sterilization temperature is increased to completely sterilize the heated object near the center, the difference between the temperature of the heated object outside the basket becomes even greater, and the sterilization value greatly varies, and the quality of the product also increases. Influences. For this reason, in order to completely sterilize resealable containers such as PET bottles and metal bottle cans, or containers with low strength, a hot water retort device with a high equipment cost of sterilizing by dipping in hot water is required. There is a problem that you have to rely on it.
[0006]
The present invention has been devised in view of the above circumstances, and does not require significant remodeling of an existing retort apparatus having no boiler tank, and even in a state where objects to be heated are densely packed. It is another object of the present invention to provide a retort sterilizing method and apparatus capable of realizing the same retort sterilizing effect as that of the hot water sterilization method for resealable packaged beverages with inexpensive equipment.
[0007]
[Means for Solving the Problems]
The retort sterilization method of the present invention for solving the above-mentioned problems is a retort sterilization method for resealable packaged beverages, in which water is introduced within a range in which an object to be sterilized does not directly contact the bottom of the retort pot, and steam is introduced into the water. Blow and heat, circulate the heated water, shower it from above and apply it to the object to be sterilized, and pressurized gas such as pressurized air or nitrogen gas or other inert gas in the retort pot And heating to a sterilization temperature under a predetermined pressurized state.
In general, heating during sterilization increases the internal pressure of the container to be heated, but according to this method, since the inside of the retort pot is pressurized by pressurized gas, the pressure difference between the inside and the outside of the container is reduced, and the thin resealing is performed. Even in the case of an airtight container, deformation of the container during heating is small, and good sealing performance is maintained. In addition, since hot water is brought into contact with the object to be heated, heat exchange is fast, and the hot water is constantly circulated from the upper part in a shower shape, so that the temperature and pressure are easily uniformized regardless of the location in the retort pot.
[0008]
In the above retort sterilization method, after sterilization, the cooling water is gradually introduced into the heating water at the bottom of the retort pot while the heating water at the bottom of the retort pot is showered from the top, and discharged to the outside from the bottom of the retort pot by that amount. It is desirable to have a cooling step of gradually lowering the temperature of the cooling water circulating in the retort and removing the cooling while controlling the temperature decreasing speed in the retort. Thereby, abrupt container deformation during the cooling process is prevented, and good sealing performance is maintained. In the cooling step, it is desirable to pressurize the inside of the retort kettle until the temperature of the object to be sterilized becomes 40 ° C. or less. If the cooling end temperature is higher than 40 ° C., heat-resistant bacteria that have not been killed by retort sterilization may grow during cooling, and the cooling end temperature in the pot is preferably 40 ° C. or lower. If the inside is pressurized, the cooling water can be drained in a pressurized state, so the drainage time is desirably reduced.
The retort sterilization method of the present invention is suitable for sterilization at a sterilization temperature of 100 ° C. to 130 ° C. or heat sterilization of a synthetic resin bottled beverage or a bottled metal canned beverage having a screw cap in a container at a reduced pressure at room temperature. It is. Further, it is suitable for sterilization of resealable packaged beverages in which the inside of the container is in a positive pressure state at room temperature by using a nitrogen gas or a mixed gas of a nitrogen gas and an inert gas. This is because, in order to make these packaged beverages into packaged beverages that can be distributed at room temperature, retort sterilization at a high temperature is usually required in many cases.
Further, in the retort sterilization method, the resealable container-packed beverage is densely arranged in a single-stage state so that the body portions of adjacent containers are in contact with each other on the partition plate, and the container group is vertically aligned. It is preferable to arrange a plurality of stages and sterilize them in a retort kettle because a large number of objects to be sterilized can be processed at once and the working efficiency increases. As a method of arranging a plurality of stages, an upper partition plate may be directly placed on the lower container and stacked, or an interval may be provided between the lower container and the upper partition plate. The former has the advantage of efficient use of space, while the latter has the advantage that the upper stage is not loaded on the container.
[0009]
The retort sterilizing apparatus for resealable packaged beverages of the present invention for carrying out the above-mentioned retort sterilizing method is provided with a shower pan or a shower nozzle at an upper inside thereof, and a basket support for supporting a retort basket for storing an object to be sterilized below the shower pan or shower nozzle. A water retrieving unit having a retort pot equipped with a table, a water introducing means for introducing water in a range in which an object to be sterilized does not directly contact the bottom of the retort pot, steam for blowing steam into the water introduced to the bottom of the retort pot and heating Blowing means, heated water circulating means for circulating the heated water at the bottom of the retort and supplying it to the upper shower pan or shower nozzle to apply a shower to the object to be sterilized, and introducing gas into the retort kettle to pre-determine the inside of the kettle Pressurizing means for pressurizing, temperature decreasing rate of cooling water circulating in the retort by gradually introducing cooling water into the heated water at the bottom of the retort pot And it is characterized in that a cooling water temperature lowering speed control means for controlling the. The pressurizing means introduces gas into the retort pot during the circulation of hot water, performs equal pressure control to pressurize the inside of the retort pot in accordance with an increase in the internal pressure of the object to be sterilized, and performs sterilization during cooling. It is desirable to perform equal pressure control for increasing the pressure in the retort pot in accordance with the decrease in the internal pressure in the retort pot until the product temperature of the product drops to a predetermined temperature.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in FIGS.
The retort sterilization apparatus used in the retort sterilization method according to the embodiment of the present invention is capable of performing a pressurized shower sterilization / cooling method, and its outline is shown in FIG. The retort sterilization apparatus 1 includes a shower pan 3 above the inside of a retort pot 2, a basket support table 4 below which supports a retort basket 5, and a position where a heated object accommodated in the basket 5 is not directly immersed. Until then, water can be introduced into the kettle. Note that a shower nozzle may be used instead of a shower pan, and heating water / cooling water may be applied to the object to be sterilized in a shower. A water inlet pipe 6 for introducing water is connected to the upper part of the retort pot 2, and a plurality of outlets 7 arranged in the pot at the tip of the water inlet pipe transfer water along the inner wall of the pot of the retort pot. The cooling water is arranged toward the inner wall of the kettle so that it flows down to the bottom. Water circulation pipes 9 and 10 for supplying water collected in the lower part of the retort pot to the shower pan 3 are connected to the lower and upper parts of the retort pot via a circulation pump 11. In addition, a cooling water source and a steam supply source are switchably connected to a lower portion of the retort pot, and a cooling water / steam introduction pipe 13 for supplying cooling water and steam to the retort pot and a drain pipe 14 are connected thereto. I have. Further, an air introduction pipe 8 for introducing pressurized air connected to a pressurized air source is connected to an upper portion of the retort pot. The air introduction pipe 8 is provided with a pressure control valve 16 so as to control the pressure inside the retort pot by controlling the amount of air introduced. In the figure, reference numeral 12 denotes a flow control valve.
[0011]
In the apparatus of the above embodiment, the water introduction pipe 6 constitutes water introduction means, the cooling water / steam introduction pipe 13 constitutes steam blowing means, and the water circulation pipes 9, 10 and the circulation pump 11 constitute heating water circulation means. A pressurized air supply source (not shown), an air introduction pipe 8 and a pressure control valve 16 constitute a pressurizing means, and control a cooling water supply pump, a cooling water / steam introduction pipe 13, a drain pipe, and a flow rate of these pipes. The flow control valve described above constitutes cooling water descending speed control means, but these means are not necessarily limited thereto.
[0012]
The retort sterilization process of the resealable container according to the present invention in the retort apparatus configured as described above will be described with reference to FIG.
The retort basket 5 containing the object to be heated is set on the basket support 4 and stored in the retort pot 2 to complete the preparation for the start of sterilization (FIG. 2 (1)). When the sterilization is started, first, water serving as a heating medium is supplied from the water introduction pipe 6 and the cooling water / steam introduction pipe 13 to the bottom of the pot. At this time, the water from the water inlet pipe 6 is supplied to the upper part of the retort pot, but flows down to the bottom along the inner wall of the pot as shown by an arrow, so that the water reaches the bottom without water being applied to the basket (FIG. 2). (2)). When water is supplied to the bottom to a predetermined water level, steam is blown into the water through a cooling water / steam introduction pipe 13 to heat the water to a desired sterilization temperature to produce hot water. The steam may be blown directly into the water in the kettle, or may be introduced into a circulation pipe. Next, hot water is applied as a shower to the object to be heated from above the retort via the shower pan 3 by the circulation pump 11. This is continued by circulating hot water until the contents of the container reach the predetermined sterilization temperature and sterilization time (FIG. 2, (3)). At this time, air pressurized by an air compressor (not shown) is introduced into the retort pot through the air introduction pipe 8, the inside of the retort pot is controlled to a predetermined pressure, and the internal pressure of the container that rises due to heating and an external pressure increase. Balance the pressure to protect the container. In the pressure control, an equal pressure control of pressurizing the inside of the retort pot with air was performed in accordance with an increase in the internal pressure during sterilization.
[0013]
In the above example, the heating by the hot water shower was performed from the beginning of the heating. However, in some cases, the primary heating step (the initial heating step from room temperature to 100 ° C.) is performed by heating only with steam, and the secondary heating step is performed. The (heating step from 100 ° C. to the sterilization temperature) and subsequent steps may be performed by hot water shower heating under a pressurized state using a pressurized gas. By doing so, the pressurized gas can be saved, and it is effective when nitrogen gas or other inert gas is used as the pressurized gas.
[0014]
When the sterilization is completed, the process proceeds to the cooling step (4), in which the cooling water is introduced into the hot water circulated by the pump 11 by the cooling water / steam introduction pipe 13, and the introduced amount is discharged from the drain pipe 14. The object to be heated is cooled while controlling the temperature of the cooling water circulating in the retort pot by lowering it in a shower while collecting and recovering it. At that time, the inside of the retort pot is pressurized until the temperature of the material to be sterilized becomes 40 ° C. or lower. This protects the container against differential pressure. When cooled to a predetermined temperature, the pressurization is stopped and the cooling water accumulated at the bottom of the retort kettle 2 is drained through the drain pipe 14 and exhausted from the exhaust pipe 15, and the inside of the retort kettle is initialized. It is returned to the state, the seal is released, and the retort basket is carried out to finish the retort sterilization (FIG. 2 (5)). In order to promote drainage, pressurized drainage may be performed by continuing pressurization until drainage.
In the above example, the cooling is performed by the shower-like cooling water. However, depending on the case, the cooling may be performed by the full-water cooling instead of the shower-like cooling water.
[0015]
As described above, by retort sterilizing an object to be heated consisting of a synthetic resin bottled beverage or a bottle-shaped metal canned beverage having a screw cap, hot water circulated by a hot water shower forms a water curtain on the container surface. The contact state is always maintained, and the same action as in the case of hot water sterilization can be performed to efficiently heat and sterilize. And even if it is housed in a retort basket in a dense state without gaps, since it is hot water shower under pressure, it is possible to heat even the heated object located in the center of the basket uniformly, Sterilization with little variation. Moreover, even if the container has a small differential pressure between the container internal pressure and the external pressure, and is thin and weak in strength and sealability, it can be sterilized and cooled well without leakage or damage. Therefore, in the present invention, with an inexpensive retort apparatus without a boiler tank, a synthetic resin bottled beverage or a bottle-shaped metal canned beverage having a screw cap is subjected to hot water pressure sterilization and the same effect as pressure cooling. In addition, heat sterilization and pressure cooling can be performed.
When the resealable container is a metal can, it is desirable that the entire outer surface of the can be coated with an organic resin. By doing so, it is possible to prevent the occurrence of external rust at the time of air pressure sterilization. Also, the use of nitrogen gas or an inert gas as the pressurized gas can suppress the generation of rust.
[0016]
【Example】
In the retort apparatus shown in FIG. 1, a bottle-shaped metal canned beverage made of steel and having a cylindrical inner and outer surface and having a 200-ml screw cap was placed on a stripping plate by the above-described method. Were placed in a densely packed single-stage so that they were in contact with each other, placed in a retort basket in six-tier stacks, sterilized by a hot water shower at 123 ° C. for 20 minutes, and then pressurized and cooled for 13 minutes. At this time, the temperature change of the object to be heated located in the center of the second stage from the bottom, the center of the middle stage, and the center of the second stage from the top, and the ambient temperature in the retort pot Was measured. The result is shown in FIG.
[0017]
In the graph of FIG. 3 and the graphs of FIGS. 4 and 5 described later, the a diagram shows the change in the ambient temperature in the pot, and the b diagram shows the change in the product temperature of the object to be heated located at the center of the second stage from the bottom. , C diagram shows the change in the temperature of the object to be heated located in the center of the middle stage, and d diagram shows the change in the temperature of the object to be heated located in the center of the upper stage. As a result, as is clear from FIG. 3, the temperature change of each object to be sterilized in each stage until the primary heating temperature (100 ° C.) is reached, and the retort until the secondary heating temperature (sterilization temperature) is reached. There was almost no variation depending on the position in the basket. Therefore, even in a multi-stage dense state, regardless of the position of the object to be heated, heating can be performed at substantially the same sterilization temperature for the same time, and excellent sterilization can be performed.
In addition, the fact that there is no variation in the temperature rise depending on the position of the basket means that the pressurizing condition at the time of sterilization can be set to the optimum condition for all the objects to be sterilized. As a result, even if the damaged state, deformed state, and sealed state of the container are inspected for each heated object after sterilization, no damaged or deformed container is observed, and the sealed state is maintained well. I was
[0018]
Further, as Comparative Example 1, the same objects to be sterilized were similarly stacked in multiple stages in a retort basket, and sterilized without pressure and cooled with 100% steam. Then, the change in the product temperature of the sterilization target located at the same position as the example in the retort basket was measured. The result is shown in FIG. In addition, FIG. 5 shows the results of Comparative Example 2 in the case where the pasteurization and cooling were performed with 85% steam. As a result, in the case of these comparative examples, before reaching the primary heating temperature, the temperature change (shown by b) of the second stage from the earliest heating time among the three measurement positions, As can be seen from the temperature change (indicated by d) in the second stage of heating, there was a shift of about 3 to 4 minutes, and it was observed that the variation in the temperature rise was large. This means that the pressurizing condition in the retort pot cannot be optimally controlled for all the objects to be heated in response to the increase in the internal pressure. In addition, in the case of Comparative Example 2, there was considerable variation even before reaching the sterilization temperature.
Similarly, the cooling time also varies widely, and it is understood that it is impossible to optimally control all the objects to be heated in accordance with the internal pressure change due to the cooling. As a result, deformation was observed in some containers, and it was confirmed that retort heat sterilization of resealable packaged beverages could not be applied to practical use by the conventional method using a steam retort device.
In the present invention, the object to be sterilized is limited to resealable packaged beverages. However, the sterilization method and apparatus of the present invention can be applied to ordinary metal cans having no resealability, and in particular, a gauge-down thin lid. Alternatively, the method is preferably applied to retort sterilization of a metal can having a can body.
[0019]
【The invention's effect】
As described above, according to the method and apparatus for retorting sterilized resealable packaged beverages of the present invention, the resealable container can be sterilized and leaked similarly to the hot water sterilization method using an existing inexpensive retort apparatus having no boiler tank. In addition, there is little variation in the heating / cooling temperature depending on the position of the object to be sterilized in the retort basket, and there is no deformation or breakage of the container and no leakage of the contents.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a retort sterilizer for resealable packaged beverages according to an embodiment of the present invention.
FIG. 2 is a schematic view showing the steps of an embodiment of the retort sterilization method according to the present invention.
FIG. 3 is a graph showing a heating time-temperature change of an object to be heated due to a difference in a position in a retort basket according to the embodiment of the present invention.
FIG. 4 is a graph showing a heating time-temperature change of an object to be heated due to a difference in a position in a retort basket in Comparative Example 1.
FIG. 5 is a graph showing a heating time-temperature change of an object to be heated due to a difference in a position in a retort basket in Comparative Example 2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Retort apparatus 2 Retort pot 3 Shower pan 4 Basket support stand 5 Retort basket 6 Water introduction pipe 8 Air introduction pipe 9, 10 Water circulation pipe 11 Circulation pump 13 Cooling water / steam introduction pipe 14 Drain pipe 15 Exhaust pipe 16 Pressure control valve

Claims (10)

A retort sterilization method for a resealable packaged beverage, in which water is introduced in a range in which an object to be sterilized does not directly contact the bottom of the retort pot, steam is blown into the water, and the heated water is circulated. A retort sterilization method, comprising: applying a pressurized gas into the retort kettle and heating it to a sterilization temperature under a predetermined pressurized state while applying a shower gas to the object to be sterilized. After completion of the sterilization, the cooling water was gradually introduced into the heating water at the bottom of the retort pot while the heating water at the bottom of the retort pot used in the sterilization step was showered from the top, and the amount corresponding to the introduced amount was adjusted to the retort pot. The retort sterilizing method according to claim 1, further comprising a cooling step of discharging the cooling water from the bottom to the outside, gradually lowering the temperature of the cooling water circulating in the retort, and removing the cooling water while controlling the temperature decreasing speed in the retort. The retort sterilization method according to claim 1, wherein in the cooling step, the inside of the retort pot is pressurized until the temperature of the object to be sterilized becomes 40 ° C. or less. The retort sterilization method according to any one of claims 1 to 3, wherein the sterilization temperature is such that the temperature of the object to be sterilized is in a range of 100C to 130C. The retort sterilization method according to any one of claims 1 to 4, wherein the resealable packaged beverage is a bottled metal canned beverage having a screw cap. The retort sterilization method according to any one of claims 1 to 4, wherein the resealable packaged beverage is a bottled beverage made of a synthetic resin in a reduced pressure state at room temperature. The retort sterilization method according to any one of claims 1 to 4, wherein the resealable packaged beverage is in a positive pressure state at room temperature with nitrogen gas or a nitrogen mixed gas. The resealable container-packed beverage is placed in a retort kettle with a plurality of vertically arranged shelves and containers in a state where the body parts of the containers adjacent to each other are in contact with each other on the shelves so that the trunks of the containers are in contact with each other. The retort sterilization method according to any one of claims 1 to 7, wherein the method is sterilization. A retort pot equipped with a shower pan or a shower nozzle above the inside and a basket supporter for supporting a retort basket for storing the object to be sterilized is provided below the object, and the object to be sterilized does not directly contact the bottom of the retort pot. Water introducing means for introducing water in the range, steam blowing means for blowing and heating steam introduced into the bottom of the retort pot, circulating heated water at the bottom of the retort and supplying it to the upper shower pan or shower nozzle. Means for circulating heated water to be applied to the material to be sterilized in the form of a shower, means for introducing gas into the retort pot to pressurize the inside of the pot to a predetermined pressurized state, and gradually introducing cooling water into the heated water at the bottom of the retort pot. Cooling water temperature lowering speed control means for controlling the temperature lowering speed of the cooling water circulating in the retort. Retort sterilization apparatus of Le of the packaged beverage. The pressurizing means introduces gas into the retort pot during the circulation of hot water, performs equal pressure control to pressurize the inside of the retort pot in accordance with an increase in the internal pressure of the material to be sterilized, and performs sterilization during cooling. 10. The retort sterilizing apparatus for resealable container-packed beverages according to claim 9, wherein equal pressure control is performed to pressurize the inside of the retort pot in accordance with the decrease in the internal pressure in the retort pot until the product temperature drops to a predetermined temperature.

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