JPS6357028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a heat sterilization method in which an object to be sterilized in a retort is heat sterilized, then cooled and taken out.

Generally, after the material to be sterilized is introduced into the retort, it is heated to 100℃ using a heating sterilization medium such as hot water or steam.
A retort sterilization method is known in which the sterilized object is heated and sterilized under pressure at a high temperature exceeding 100 ml, and then the sterilized object is cooled and taken out.

Conventionally, as a cooling means in this heat sterilization method, as shown in FIG. Some devices spray a cooling medium such as water from a device 3 onto objects 2 to be sterilized stacked in multiple stages for cooling. In the figure, 4 is a supply pump connected to the shower device 3 via a supply pipe 5, and 6 is a discharge pipe for discharging the cooling medium accumulated in the lower part of the retort pot 1 after cooling the object to be sterilized. be.

However, in this sterilization method, the cooling medium is brought into direct contact with the object 2 to be sterilized, which has reached a high temperature of 120 degrees Celsius, to rapidly cool it down, so differences in cooling occur depending on the position of the object 2 to be sterilized in the retort. In addition, with molded containers, etc., if a container heated to a high temperature of over 100°C is directly exposed to water, etc., the internal pressure of the container will change rapidly, causing problems such as deformation of the container, and even with glass containers, etc. Containers that have been heated to temperatures as high as 120 degrees Celsius are likely to be damaged if they come into direct contact with water, and furthermore, so-called retort pouch foods made of flexible packaging materials may wrinkle where they are in direct contact with the cooling medium. The contents of this retort pouch food also had various problems, such as deformation when strongly hit by the cooling medium and separation of components due to rapid cooling.

In addition, in order to avoid the above problem, the object to be sterilized 2 heated to about 120°C is allowed to cool while being left in the retort without using means such as spraying a cooling medium to a temperature at which the above problem does not occur. However, the cooling time required to reach a temperature at which the above-mentioned problem does not occur is extremely long, which poses a problem in workability.

On the other hand, in order to prevent these problems, there is a method of spraying a cooling medium onto the object 2 to be sterilized while controlling the pressure inside the retort until the object 2 to be sterilized is cooled to a temperature at which the above-mentioned problems do not occur. This requires delicate pressure control, but this pressure control operation is difficult, and there is a limit to its effectiveness in preventing the problems mentioned above, such as being ineffective against damage caused by contact with cooling medium in glass containers, etc. It was hot.

The inventors have arrived at this invention as a result of repeated experimental research to solve this problem.
That is, this invention provides a heat sterilization method in which an object to be sterilized in a retort is heated and sterilized with a heat sterilization medium, and then the object to be sterilized is cooled and taken out. The atmosphere in the retort is cooled by the cooling medium without directly contacting the object to be sterilized until the object is sterilized.
This heat sterilization method is characterized in that the object to be sterilized is then brought into contact with the cooling medium using a conventional method.

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 schematically shows an embodiment of the present invention. In the figure, 11 is a retort pot, into which objects to be sterilized 12 stacked in multiple stages are introduced. An internal shower device 13 for dispersing a cooling medium for cooling the object 12 to be sterilized is provided in the upper part of the sterilization object 11, and these are similar in structure to the conventional example for normal cooling. A supply pipe 15 connected to the supply pump 14 is connected to the internal shower device 13 through a switching valve 17, and one end is connected to the internal shower device 13, and the other end is connected to the outside of the retort pot 11 provided above the outside for cooling the retort atmosphere. It is connected to the shower device 18. Reference numeral 16 denotes a discharge pipe for discharging the cooling medium accumulated in the lower part of the inside of the retort pot 11 and the lower part of the outside of the retort pot 11.

This embodiment is constructed as described above, and after retort sterilization of the object 12 in the retort pot 11 under pressurized conditions at a high temperature reaching 120° C., first, the switching valve 17 is connected to the external shower device 18 side. The retort pot 11 is cooled from the outside by spraying a cooling medium on the outer surface of the retort pot 11, and the atmosphere inside the retort is kept under pressure until the center temperature of the object 12 to be sterilized is cooled to at least 100°C. Cooling. In this case, the retort pot 11 is
After cooling the retort pot 11, the cooling medium sprinkled on the outer surface is collected below the retort pot 11 and discharged from the discharge pipe 16.

Next, the switching valve 17 is switched to the internal shower device 13 provided in the retort pot 11, and the internal shower device 13 performs normal cooling by directly spraying the cooling medium onto the object 12 to be sterilized. The object to be sterilized 12 is taken out from the retort pot 11.

For example, for molded containers, large cans, etc. that may be deformed due to sudden changes in the internal pressure of the container, the appropriate temperature for switching to normal cooling is when the center temperature of the contents is below 100°C. For items such as glass containers that are easily damaged by direct contact with the cooling medium, the temperature at the center of the contents is preferably cooled to 60 to 80°C. Further, in the case of the object to be sterilized 12 to be simply cooled slowly, it is appropriate that the temperature of the atmosphere inside the retort is about 70 to 80°C.

Figure 3 shows a shower device installed inside the retort pot.
Another example will be shown in which the atmosphere inside the retort is cooled by cooling the inner surface of the retort pot.

That is, two internal shower devices 13b facing each other are installed close to the inner wall of the upper part of the retort pot 11' so as to emit water toward the inner surface of the retort pot 11'.
The cooling medium is ejected from the internal shower device 13b toward the inner surface of the retort pot 11' so that the cooling medium does not come into direct contact with the object 12' to be sterilized, and at the same time, the cooling medium is discharged from the bottom so that it does not accumulate in the retort. By cooling the inner surface of this retort pot 11', the atmosphere inside the retort is cooled,
Thereafter, the object to be sterilized 12' is cooled by spraying a cooling medium from the internal shower device 13a in a conventional manner. The other configurations are the same as those of the previous embodiment, and corresponding parts are given the same numbers and dots, and their explanations will be omitted.

Furthermore, Fig. 4 shows a structure in which the internal shower device is arranged in two stages, upper and lower, on the object to be sterilized, and a baffle plate is provided between them. has been attached.

That is, a baffle plate 19 is provided in the upper part of the retort pot 11' between the upper internal shower device 13b and the lower internal shower device 13a, and has a width that completely covers the upper surface of the object to be sterilized 12'. The cooling medium sprayed from the internal shower device 13b cools the atmosphere inside the retort while dripping on the outside of the object 12' without directly contacting the object 12', and then cools the object 12' by a conventional method. The object to be sterilized 12' is taken out.

Next, FIG. 5 shows an example of a change in the temperature of the retort atmosphere in the above-described embodiment. A
B is a plot of the retort atmosphere temperature versus cooling time when the retort is left uncooled without cooling with a cooling medium, B is a plot of the retort atmosphere temperature when the outer surface of the retort pot 11 is cooled by the cooling medium spouted from the external shower device 18, and C is a plot of the retort atmosphere temperature when the retort is cooled by the cooling medium jetted from the external shower device 18. It shows the change in the retort atmosphere temperature when the inner surface of the retort pot 11' is cooled by the cooling medium jetted toward the inner surface of the retort pot from the device 13b, and D shows the change in the retort atmosphere temperature when the inner surface of the retort pot 11' is cooled by the cooling medium jetted toward the inner surface of the retort pot from the device 13b. This figure shows the change in the retort atmosphere temperature. As is clear from the changes in the retort atmosphere temperature with respect to these cooling times, for example, the retort atmosphere temperature
The cooling time for cooling from 120°C to 100°C is about 2 minutes for both retort pot outer surface cooling B and retort pot inner surface cooling C, and the cooling time is slightly longer than that for conventional method cooling D, but for left cooling A. This difference is extremely short compared to the above, and considering the above-mentioned effects, this difference can be considered to be almost negligible in terms of work efficiency.

In addition, in the case of cooling the outer surface of the retort pot, cooling the inner surface of the retort pot, and cooling with a baffle plate provided above the object to be sterilized, the above-mentioned cooling time can be changed by increasing or decreasing the flow rate of the cooling medium. .

Further, when cooling the atmosphere inside the retort, a fan is provided in the retort pot to stir the atmosphere inside the retort, thereby making the cooling of the object to be sterilized more uniform. That is, FIGS. 6 and 7 show an example of changes in retort atmosphere temperature and content temperature changes with respect to cooling time when no fan is provided in the retort pot. E is a plot of the temperature near the tray near the retort wall, and F is a plot of the temperature near the center of the tray. When the retort pot is directly water-cooled, the cooling rate of the retort atmosphere temperature is faster at location E near the retort wall; Sterilization is slow in places F away from walls, especially for items to be sterilized (pouches, cups, etc.)
It becomes slower near the center of trays (sterilization shelves) where cells are stacked side by side. FIGS. 8 and 9 show examples of changes in retort atmosphere temperature and contents temperature change with respect to cooling time when a fan is provided in the retort pot. In this case, by creating a flow between the trays using a fan, the cooling rate near the center of the tray F can be improved, the cooling rate of the retort atmosphere and the contents can be made uniform, and the temperature distribution can be made uniform.

As explained above, the heat sterilization method according to the present invention cools the object to be sterilized after retort sterilization by installing a fan inside the retort and cooling the object until the center temperature of the object is cooled to at least 100°C. Since the atmosphere inside the retort is cooled without bringing the medium into direct contact with the objects to be sterilized, there is no possibility of deformation of molded containers, etc., or damage of glass containers, etc., which are likely to occur when the medium is cooled from a high temperature of about 120°C to about 100°C. It also prevents the occurrence of wrinkles in retort pouches, etc., and prevents problems such as deformation of contents of retort pouches and separation of ingredients, etc., and prevents the occurrence of defective products in heat sterilization methods. In addition, by stirring the atmosphere inside the retort with a fan, the temperature distribution of the atmosphere inside the retort becomes uniform, and the cooling rate of the object to be sterilized can be improved.Furthermore, by directly cooling the atmosphere inside the retort, the cooling effect of the object to be sterilized can be improved. It has the effect of improving performance.

[Brief explanation of the drawing]

Fig. 1 is a structural explanatory diagram schematically showing cooling in a conventional heat sterilization method, Fig. 2 is a structural explanatory diagram schematically showing one embodiment of the heat sterilization method according to the present invention, and Fig. 3 is a structural explanatory diagram schematically showing cooling in a conventional heat sterilization method. Configuration explanatory diagram showing an example, No. 4
The figure is an explanatory diagram of the configuration of another embodiment. Figure 5 is a diagram showing changes in the temperature of the retort atmosphere depending on the cooling method. Figures 6 and 7 are the changes in the temperature of the retort atmosphere and contents when there is no fan. Figure 8 showing
9 and 9 are diagrams showing temperature changes in the retort atmosphere and contents when a fan is provided. 11, 11'... Retort pot, 12, 12'...
Object to be sterilized, 13, 13a, 13b... Internal shower device, 18... External shower device.

Claims (1)

[Claims] 1. A heat sterilization method in which an object to be sterilized in a retort is heated and sterilized with a heat sterilization medium, and then the object to be sterilized is cooled and taken out. The atmosphere inside the retort is stirred by the fan and the inner wall or outer wall of the retort or the atmosphere inside the retort is cooled with a cooling medium until the temperature is cooled to at least 100°C, and then the object to be sterilized is sterilized by a conventional method. A heat sterilization method characterized by bringing the cooling medium into contact with and cooling.