JP2596866B2 - Retort sterilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retort sterilization method, and more particularly, to a retort sterilization method in which an article filled in a soft packaging bag is pressurized and heated while rotating to cool to room temperature.

[0002]

2. Description of the Related Art As a method for subjecting a so-called aerated soft packaging bag, which contains a gas and hermetically sealed, to a heat and pressure sterilization treatment, Japanese Patent Laid-Open Publication No.
No. 1-63271 discloses a method in which heat sterilization and cooling are carried out while maintaining a constant pressurized state to prevent breakage of a filled soft packaging bag.

[0003] In the pressurized heat sterilization method disclosed in Japanese Patent Application Laid-Open No. 61-13771, when the filled soft packaging bag is pressurized and heated, the filling is not performed in consideration of the linear pressure increase. A technique for changing the pressure in a pressurized heat sterilization tank according to the internal pressure of a soft packaging bag is disclosed.

[0004]

In the pressurized heat sterilization treatment, the pressure inside the pressurized heat sterilization tank is greatly reduced at the start of cooling after heating, and the pressure inside the filled soft packaging bag and the pressure inside the pressurized heat sterilization tank are reduced. A large pressure difference is generated between them, and the filled soft packaging bag breaks, and the filled soft packaging bag expands and is likely to be damaged by contact with the member supporting the soft packaging bag. However, the above-mentioned prior art does not deal with such a problem at all.

[0005] The present invention has been made in view of such problems of the prior art, and in the pressurized heat sterilization treatment, the pressure between the internal pressure of the filled soft packaging bag and the internal pressure of the pressurized heat sterilization tank during cooling. To prevent a large pressure difference from occurring
An object of the present invention is to provide a rotary retort sterilization method that does not cause breakage of a filled soft packaging bag or damage caused by contact of a soft packaging bag with a member supporting the expanded flexible packaging bag.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a retort sterilization method for pressurizing and heating sterilized articles filled in a soft packaging bag, wherein the sterilization tank is cooled after the sterilization is almost completed. A retort sterilization method characterized in that the pressure in the sterilization tank is made higher than the pressure in the sterilization processing before.

[0007]

According to the present invention, in the pressurized heat sterilization treatment, the pressure in the sterilization treatment tank is reduced during the sterilization treatment after the sterilization treatment is almost completed and before the inside of the sterilization treatment tank is cooled. Since the pressure is higher than the pressure, a large pressure difference does not occur between the internal pressure of the filled flexible packaging bag and the internal pressure of the pressurized heat sterilization tank during cooling, and the filled flexible packaging bag breaks or the filled flexible packaging bag expands. This has the effect that damage due to contact with the member supporting the lever does not occur.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotary retort sterilizer according to an embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a sealed soft packaging bag filled with contents, that is, a so-called rotary retort sterilizer 1 for sterilizing while rotating the filled flexible packaging bag, has a horizontal cylindrical shape for performing pressurized heat sterilization. The pressurized heat sterilization tank 2, a hot water tank 3 provided above the pressurized heat sterilization tank 2, and temporarily stores hot water, a storage unit 4 for storing control information of the rotary retort sterilizer 1, a storage unit The control unit 5 controls the operation and the like of the pressurized and heated sterilization tank 2 based on the stored information of 4, and these are connected by a communication pipe or a connection line.

As shown in FIG. 2, the pressurized heat sterilization tank 2 is supported by a horizontal cylindrical sterilization drum 201 and a plurality of bearings 202, and rotates around the axis of the sterilization drum 201. And a frame 203. Near the bottom of the rotating frame 203, two rails 2
04 is arranged. The rail 204 is provided with a cart 20 on which a plurality of trays 206 containing the filled flexible packaging bags are placed.
8 is provided so as to be able to slide in parallel with the axis of the rotating frame 203.

The sterilizing drum 201 has an upper water supply / drain port 210 and a water supply / exhaust port 211 on the upper surface, and a lower water supply / drain port 212 on the lower surface. Sterilization drum 20
1 is provided with a holding mechanism 214 for fixing the trays 206 to the sterilization processing drum 201 so that the accommodated tray 206 does not come off the carriage 208 and the carriage 208 does not come off the rail 204. ing.

As shown in FIG. 1, the sterilizing drum 201 is provided with an opening / closing door 224 for taking in and out the tray 206 and the carriage 208 on one side, and the other side is closed. The above-mentioned closed side of the sterilization processing drum 201 has a rotary drive shaft 2 penetrating therethrough.
26 are provided. The rotary drive shaft 226 is for transmitting a driving force from a rotary power source (not shown) arranged outside the sterilizing drum 201 to the rotary frame 203.

As shown in FIG. 3, the tray 206 is formed of a plate material having a plurality of circular holes formed in an aluminum plate. The bottom surface 230 of the tray 206 has a so-called double-bottom structure in which aluminum plates are arranged at intervals of, for example, 1 cm or more, preferably 2 cm or more, and a surrounding plate 232 is provided on the entire outer periphery. Above the surrounding plate 232 at the four corners of the tray 206, there are provided anti-skids 234 for preventing the upper and lower ones from skidding each other when the trays 206 are stacked. Shroud 23
2, a handle 233 is provided at an appropriate position.

The width of the tray 206 at its central portion, which is parallel to the rotation axis when housed in the sterilizing drum 201, is as wide as, for example, 10% or more, preferably 15 to 40%, of the width of the tray 206 in the same direction. A central heating medium passage 235 having the same height as the surrounding plate 232 is provided. Accordingly, when the tray 206 is rotated around the rotation axis in a state where many trays 206 are stacked, a sufficient amount of hot water (heating medium) is supplied through the heating medium flow passage 235 to an area for accommodating a filling and packaging bag described later. 240. The tray 206 is further provided with a tray
A plurality of radial heating medium passages 236 having a relatively narrow width and a height lower than the shroud plate 232 are provided parallel to each other at intervals in a direction perpendicular to the rotation axis when housed in the housing 1. .

In tray 206, shroud 232, central heating medium passage 235 and radial heating medium passage 236
The rectangular portion formed by the above is the accommodation region 240 of the filled flexible packaging bag, and accommodates the filled flexible packaging bag in a lying state. When a vertically long packaging bag such as a standing voucher is used as the filled soft packaging bag, the contained filled flexible packaging bag is pressurized while being rotated with its longitudinal direction substantially orthogonal to the rotation axis. Heat sterilization means that the generation of heat sterilization rams can be more effectively prevented, and a sufficient sterilization effect can be achieved in a shorter time. Also, when using the standing bouch, it is possible to effectively prevent the occurrence of scratches and bag breakage due to movement in the tray if the standing bouch is stored in a state where the bottom portion faces outward. Is desirable. The tray 206 is stacked on a cart 208 as shown in FIG.

As shown in FIG. 1, the hot water tank 3 has an intake / exhaust port 250 on the upper surface, a first water supply / drain port 252 and a second water supply / drain port 254 on the lower surface, and a steam supply port at the lower part in the hot water tank 3. A pipe 256 is arranged. The control unit 5 controls the valves 326 and 330 based on the output signal of the storage unit 4 and the outputs of a pressure sensor (not shown) and a temperature sensor (not shown) provided in the pressurized heat sterilization tank 2. Control opening and closing.

The storage unit 4 stores pressure / temperature control information for sterilizing the filled flexible packaging bag carried into the pressurized and heated sterilizing tank 2 while maintaining the air content of more than 2%. doing. As shown in FIG. 4, the pressure / temperature control information becomes a temperature graph A and a pressure region graph B when the horizontal axis indicates the progress and the vertical axis indicates the pressure and the temperature. The pressure shown in FIG.
In order to control the temperature, the pressurized heat sterilization tank 2 is operated as follows. That is, during the period from the start of sterilization L to M, hot water is heated to a predetermined temperature to perform pressurized heat sterilization. In the period MN, the pressure in the pressurized heat sterilization tank 2 is set to a high pressure, the hot water in the pressurized heat sterilization tank 2 is returned to the hot water tank 3, and then the cooling water is supplied to the pressurized heat sterilization tank 2. .
The period NO is immediately after the pressure in the pressurized heat sterilization tank 2 is increased by a predetermined value, and the cooling water is supplied to the pressurized heat sterilization tank 2.
The primary cooling of the filled flexible packaging bag is performed by flowing in the inside. Period O
P is a preparation period for further cooling to a lower temperature, and in order to replace the cooling water with a lower temperature, the high-temperature cooling water in the pressurized heat sterilization tank 2 is discharged, and a new low-temperature cooling is performed. Supply water. In the period PQ, secondary cooling is performed by circulating cooling water. In the period QR, the cooling water is discharged, and one cycle of pressurized heat sterilization and cooling ends.

Next, a pressurized heat sterilization tank 2 and a hot water tank 3,
The connection of the devices related thereto will be described. The lower water supply / drainage port 212 of the pressurized heat sterilization tank 2 is connected to the valve 30.
2. Circulation pump 304, steam mixing unit 306, valve 30
8 is connected to the second water supply / drain port 254. The hot water in the pressurized heat sterilization tank 2 can be returned to the hot water tank 3 by this connection path.

The lower water supply / drain opening 212 is also provided with the valve 30.
2. Water supply source 3 via valve 310 and water supply pump 312
13. The cooling water can be supplied to the pressurized and heated sterilization tank 2 through this connection path. The lower water supply / drain port 212 is further connected to the outside via a valve 314. The hot water and the cooling water in the pressurized heat sterilization tank 2 can be discharged to the outside by this connection path.

The upper water supply / drain port 210 is connected to the lower water supply / drain port 212 via a valve 316, a steam mixing section 306, a circulation pump 304, and a valve 302. The steam mixing section 306 is arranged at the steam supply source 320 via the valve 318. With these connecting paths, hot water in the pressurized heat sterilization tank 2 can be taken out, reheated by mixing steam in the steam mixing section 306, and returned to the pressurized heat sterilization tank 2 again.

The supply / exhaust port 211 of the pressurized heat sterilization tank 2
Is connected to an air vent 328 via a valve 326 and to a pressurized air source 332 via a valve 330. The first water supply / drain port 252 of the hot water tank 3 is connected to a water supply source 313 via a valve 334, a valve 310, and a water supply pump 312. The hot water tank 3 can be supplied with water through this connection path. The first water supply / drain port 252 is also connected to the outside via a valve 336.

The steam supply pipe 256 of the hot water tank 3 is connected to a steam supply source 320 via a valve 340. With this connection path, the hot water in the hot water tank 3 can be heated by mixing steam. The intake / exhaust port 250 of the hot water tank 3 is connected to an air vent 352 via a valve 350 and to a pressurized air source 356 via a valve 354.

The soft packaging bag to be sterilized by the rotary retort sterilizer 1 is, for example, a standing pouch, and has a specific gravity of 1 kg or more, preferably 2.5 kg to 5 kg. The material of the soft packaging bag is, for example, a laminate of first layer (outer layer) polyethylene terephthalate / second layer nylon / third layer aluminum / fourth layer unstretched polypropylene.

What is sterilized is a liquid material such as soup, stew, curry or the like filled in a vertically long soft packaging bag. The filling is performed by a volume ratio of a head space (space) to the total volume of the soft packaging bag after sealing, that is, an air content of 2 to 20.
%. The head space is generally air, but may be nitrogen gas or argon gas. More specifically, the air content is, for example, 3 to 20%, and preferably 3 to 10%.

When the air content is 2% or less, the ratio of the head space to the volume of the filling is small, and sufficient stirring is not performed on the entire filling during sterilization. On the other hand, if the air content is 2
In the case of 0% or more, the stirring efficiency of the filling at the time of sterilization does not increase in proportion to the rise of the air content, and the filling soft packaging bag becomes bulky with respect to the filling, and the transport and storage of the filling soft packaging bag are performed. Disadvantageous. Furthermore, if the headspace is filled with air, the possibility of the filler oxidizing during disinfection and discoloring or deteriorating the quality is increased, and if the headspace is filled with an inert gas, It is uneconomical.

In order to simultaneously and uniformly pressurize and heat sterilize a plurality of filled flexible packaging bags by a single pressurized heating and sterilization process, a variation in the air content is set for the plurality of filled flexible packaging bags. The porosity should be within -3 to + 50%, preferably within -3 to + 10%. Next, the sterilizing operation of the rotary retort sterilizer 1 having the above configuration will be described. [Hot water preparation step] The valve 310 and the valve 334 are opened, the water supply pump 312 is operated, and the water supply source 313 is opened.
Supplies a predetermined amount of water to the hot water tank 3. After the water supply ends, the valve 310 and the valve 334 are closed and the valve 340 is opened, and steam is injected from the steam supply source 320 into the water in the hot water tank 3 via the steam supply pipe 256. Adjust the opening and closing of the valves 350 and 354, and
Is set to be 5 to 10 ° C. higher than the scheduled sterilization temperature. In this case, it is desirable to prevent the bumping in the hot water tank 3 by adjusting the pressure in the hot water tank 3 by adjusting the opening and closing of the valves 350 and 354. [Step of Carrying the Filled Flexible Packaging Bag into the Pressurized and Heated Sterilization Tank] The filled flexible packaging bag is stored in a rectangular storage area 240 formed in the tray 206 in a lying state. When the filling pouch is a self-supporting standing pouch, if the thick bottom of the standing pouch is made to be radially outward, the filling pouch occurs due to movement in the tray 206. Damage and breakage of the bag can be effectively prevented, and the filler can be effectively agitated in the filled soft packaging bag. The thickness of the filled flexible packaging bag is equal to or slightly greater than the height of the shroud 232 from the inner bottom surface 230.

Subsequently, the tray 206 is stacked on the carriage 208 at a predetermined level. Thus, the filled flexible packaging bag accommodated in the accommodation area 240 of the tray 206 is pressed by the bottom surface of the tray 206 on the upper stage. Next, the door 224 of the sterilization processing drum 201 is opened, and the plurality of carts 208 prepared are sequentially carried into the sterilization processing drum 201. Thereafter, the stacked trays 206 and carts 20
8 is fixed to the rotating frame 203 by the pressing mechanism 214,
The door 224 is closed. [Pressurized heat sterilization step] Valve 334, Valve 3
16 is opened, and the circulation pump 304 is operated to supply the hot water in the hot water tank 3 to the sterilization drum 201 from the upper water supply / drain port 210. The amount of hot water supplied is determined so that the rotated tray 206 is always in the hot water.
As a result, the temperature of the pressurized heat sterilization tank 2 is gradually increased to reach the sterilization set temperature.

The rotation frame 203 starts rotating when the supply of hot water to the hot water tank 3 is completed. The rotation speed of the rotating frame 203 is
It varies depending on the kind of the filling material, the filling amount, the viscosity, the air content of the filled soft packaging bag, and the like, but is 10 to 50 rpm, preferably 20 to 50 rpm.
30 rpm. Next, the valve 334 and the valve 308
Is closed and the valve 302 is opened, the circulation pump 304 is operated, and hot water flows from the upper part to the lower part in the sterilization processing drum 201.

At the same time, the opening and closing of the valve 318 is controlled so that the hot water discharged from the
Mix steam from 20. In this way, the temperature inside the sterilization processing drum 201 is controlled so as to be a time-temperature curve A shown in FIG. As a method of controlling the temperature in the pressurized heat sterilization tank 2, for example, there is PID control or the like. After the hot water is introduced into the pressurized heat sterilization tank 2 and until the cooling process is almost completed (point P in FIG. 4), the pressure sensor (not shown) is used to control the inside of the pressurized heat sterilization tank 2. To detect the pressure.

The temperature in the pressurized heat sterilization tank 2 is set to 10
When sterilization is performed at 0 ° C. or more, the valve 326 is set so that the pressure falls within the time pressure region B in FIG. 4 in which the air content of the filled flexible packaging bag exceeds 2%. , And controls the opening and closing of the valve 330. As a result, a sufficient head space is secured in the filled soft packaging bag until the pressurized heat sterilization treatment is completed, and the filled soft packaging bag is rotated by rotating the filled flexible packaging bag. Is sufficiently stirred, sterilization can be performed with high heat efficiency in a short time, and generation of heat sterilization unevenness can be effectively prevented. [Cooling Step] The rotation of the sterilization processing drum 201 is stopped at the time when the pressurized heat sterilization is almost completed (at the time point M in FIG. 4). Thereafter, the pressure in the pressurized heat sterilization tank 2 is increased by 0.1 to 0.8 kg / sq.
m, preferably 0.2 to 0.4 kg / cm 2 (time pressure range C in FIG. 4). Next, by closing the valve 310 and opening the valve 308, the hot water in the pressurized heat sterilization tank 2 is supplied through the lower water supply / drain port 212, the valve 302, the circulation pump 304, and the valve 308. To return to the hot water tank 3.

Thereafter, the valve 308 is closed, the valve 310 is opened, and the water supply pump 312 is operated, and a predetermined amount of cooling water is pressurized from the lower water supply / drain port 212 through the valve 310 and the valve 302. Water is supplied into the heat sterilization tank 2. After that, the valve 310 is closed and the valve 316 is opened, and then the circulation pump 3 is closed.
Activate 04. Thus, the cooling water is caused to flow in the sterilization processing drum 201 to start the cooling processing. Thereafter, if desired, as shown in FIG. 4, cooling may be performed again with fresh low-temperature cooling water.

Due to these coolings, the pressure in the pressurized heat sterilization tank 2 rapidly decreases. The reason is that the gas in the pressurized heat sterilization tank 2 is rapidly cooled by the circulation of the cooling water supplied to the pressurized heat sterilization tank 2 to reduce its volume, and in addition to the pump of the circulation pump 310 It is presumed to be due to the negative pressure generated by the action. This sudden decrease in pressure in the pressurized heat sterilization tank 2 is detected by the pressure sensor (not shown). If such a sudden pressure drop occurs, the filled flexible packaging bag should break.

However, in the rotary retort sterilizer 1, as described above, the pressure in the pressurized heat sterilization tank 2 is set to be 0.1 to less than the pressure in the pressurized heat sterilization treatment prior to the supply of the cooling water. Since the pressure in the heat sterilization tank 2 is increased by 0.8 kg / square cm, even if the pressure in the heat sterilization tank 2 suddenly decreases, the pressure in the pressure heat sterilization tank 2 is increased by the filled soft packaging bag. It can be maintained at a height that does not cause the bag to expand and break.

Further, the above cooling is started (the circulation of the cooling water is started).
At the same time, the rotating frame 203 is rotated again. In this case, the rotation speed is 10 to 50 rpm, preferably 2
Desirably, it is 0 to 30 rpm. From the start of the cooling, that is, the circulation of the cooling water, to the time when the temperature of the filling material in the filling flexible packaging bag falls to the temperature at the time of filling, the pressure of the pressurized heat sterilization tank 2 is changed to the time pressure shown in FIG. Control is performed so that the air content of the filled flexible packaging bag exceeds 2% while being within the region D. As a result, the filled flexible packaging bag can secure a sufficient head space therein, and the filling material is sufficiently stirred in the filled flexible packaging bag with the rotation of the rotating frame 203. Cooling is efficient and uniform.

In a modification of the present embodiment, in the pressurized heat sterilization treatment tank 2, a predetermined pressure heat sterilization treatment tank 2 is used in order to make the air content of the filled soft packaging bag exceed 2% during the pressure heat sterilization treatment. Means for storing the internal pressure change curve of the filled flexible packaging bag corresponding to the time-temperature curve, and the pressure and filling in the pressurized heat sterilization tank 2 detected by the means for detecting the pressure in the pressurized heat sterilization tank 2. A circuit for calculating a pressure difference between the pressure change curve of the flexible packaging bag and
When the temperature in the pressurized heat sterilization tank 2 is 100 ° C. or more, the pressure difference is controlled by controlling the pressurized air supply unit and the exhaust unit so that the air content of the filled soft packaging bag exceeds 2%. There is a rotary retort sterilizer that includes a control means for obtaining.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a rotary retort sterilizer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the sterilization processing drum of the embodiment.

FIG. 3 is a perspective view of the tray of the embodiment.

FIG. 4 is a graph showing a method for controlling the pressure and temperature in the pressurized heat sterilization tank of the above embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary retort sterilizer 2 Pressurization heat sterilization processing tank 3 Hot water tank 4 Storage part 5 Control part 201 Sterilization processing drum 202 Bearing 203 Rotating frame 204 Rail 206 Tray 208 Dolly 210 Upper supply / drainage port 212 Lower supply / drain port 224 Opening / closing door 226 Rotating drive shaft 234 Central heating medium passage 235 Radial heating medium passage 240 Storage area 250 Inlet / exhaust port 252 First water supply / drainage port 254 Second water supply / drainage port 313 Water supply source 320 Steam supply source

Claims (3)

(57) [Claims] In a retort sterilization method for pressurizing and heating sterilizing an article filled in a flexible packaging bag, after the sterilization treatment is almost completed and before the inside of the sterilization treatment tank is cooled, the inside of the sterilization treatment tank is cooled. A retort sterilization method, wherein the pressure is higher than the pressure at the time of the sterilization treatment. 2. The retort sterilization method according to claim 1, wherein the sterilization tank is a rotary retort sterilizer. 3. The pressure before the inside of the sterilization treatment tank is cooled is 0.1 to 0.8 kg / sq.
The retort sterilization method according to claim 1, wherein the height is higher by cm.