JP2002345446A - Heat sterilizer for gas-containing vessel for carrying out preheating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deformation of a gas-containing vessel and breaking of a bag caused by temperature difference between respective gas-containing vessels in a heat sterilizer for heat sterilizing the gas-containing vessels by a batch type operation. SOLUTION: In the heat sterilizer for sterilizing a food, and the like, in the gas-containing vessel 6 by carrying out a sterilization treatment comprising a heat-up process for raising the temperature of the gas-containing vessel 6 to the sterilization temperature after housing the gas-containing vessel 6 in which the food, and the like, are sealed with a gas in a treatment tank 7, a sterilization process for maintaining the gas-containing vessels at the sterilization temperature for a predetermined time and a cooling process for cooling them after sterilization, when carrying out the sterilization treatment, at first, a preheating for heating the gas-containing vessels to a temperature equal to or higher than the filling temperature of the gas-containing vessels and lower than 80 deg.C is carried out to bring the temperatures of respective vessels to be uniform and, after finishing the pre-heating, each process of the sterilization treatment is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating and sterilizing apparatus for pre-heating a gas-containing container.

[0002]

2. Description of the Related Art A hermetically packed food is stored in a processing tank,
2. Description of the Related Art Retort foods that sterilize foods by heating the inside of a treatment tank and enable storage at room temperature are widely used. When packing the food, the gas may be filled together with the food, and the air-filled cup container may be sterilized. The manufacturing process of the aerated retort food includes a cooking process of cooking the food, a filling process of packing the cooked food with gas, a loading process of storing the aerated container in the processing tank, and heating the processing tank to the sterilization temperature. , A heating step of raising the temperature of the aerated container to the sterilization temperature, a sterilization step of maintaining the set temperature at the sterilization temperature, a cooling step of cooling the sterilized aerated container, and taking out the treated aerated container from the processing tank. Process.

When sterilizing an air-containing container, the gas pressure in the air-containing container changes depending on the temperature. When the pressure in the aerated container becomes higher than the pressure in the processing tank, the container expands, and when the pressure in the aerated container becomes lower than the pressure in the processing tank, the container shrinks, causing deformation or bag breakage in the container. May be done. Therefore, when heat-sterilizing the gas-containing container, it is necessary to adjust the pressure in the processing tank so that the pressure in the gas-containing container is equal to the surrounding pressure. Pressure P in the aerated container
Can be obtained by the following equation. P = {(273 + t2) / (273 + t1)} × (10
1.3-Pw1) + Pw2 P: Internal pressure of the aerated container (kPa) t1: Filling temperature (° C.) t2: Temperature of the aerated container during processing (° C.) Pw1: Saturated vapor pressure for t1 (kPa) Pw2: For t2 Saturated Vapor Pressure (kPa) By controlling the pressure in the treatment tank to be substantially equal to the internal pressure of the aerated container determined by the above equation, deformation of the container and bag breakage can be prevented.

[0004] However, the heat sterilizer is processed in a batch system.
Temperature, the temperature of the gas-containing container at the time of starting the temperature rise varies. If the temperature raising step is performed in this state, the internal pressure of each air-containing container varies due to the variation in the temperature inside each air-containing container. The internal pressure of the gas container is largely different from the internal pressure of the processing tank, and when a low-strength container is used, the container may be deformed. This is because the temperature of the gas-containing container during the filling process is constant, but the time from the filling process to the start of the sterilization treatment differs for each gas-containing container, and the amount of temperature decrease from the filling temperature is different. Of the group that sterilizes at once, the initial filling that was done at an early stage
At the start of the sterilization process, the temperature has dropped significantly,
The final filling, which was filled immediately before the start of the sterilization treatment, was still at the filling temperature even at the start of the sterilization treatment, so that a temperature difference occurred.

[0005] Fig. 4 shows a state of a temperature change when there is a difference in the temperature of the air-containing vessel at the start of the temperature raising step in a heat sterilization apparatus that performs sterilization in a batch system. 4 shows a change in the pressure inside the air-containing container in the case of No. 4. Here, it is assumed that the temperature at the time of filling is 50 ° C., and at time T0 at the start of the temperature raising step, the final filling amount is 50 ° C., but the aerated container for the initial filling has dropped to 20 ° C. The temperature and the pressure at each time point from the time T0 to the time T6 are shown by a black circle for the initial filling, a white triangle for the last filling, and an atmosphere temperature in the processing tank by a two-dot chain line in FIG. I have.

At time T0 at the start of the temperature raising step, the temperature of the initial filling is 20 ° C. and the temperature of the final filling is 50 ° C.
It is. In the temperature raising step, the ambient temperature in the processing tank is increased to a sterilization temperature of 120 ° C., and the temperature of the aerated container housed in the processing tank is increased. At this time, the temperature difference between the initial filling amount and the final filling amount decreases with the passage of time, but the temperature difference does not disappear immediately because both rise. Here, the temperature from time T0 to time T6 is 20 ° C. → 40 ° C. → 65 ° C. → 90 ° C. → 1 for the initial filling.
It changes in the order of 05 ° C → 115 ° C → 120 ° C, and 50 ° C → 65 ° C → 85 ° C → 105 ° C → 115 ° C for the final filling
It is assumed that the temperature changes in the order of → 120 ° C. → 120 ° C.

When the internal pressure of the air-containing container at each of the above-mentioned temperatures is determined by the above-described equation for calculating the internal pressure of the air-containing container, the result is as shown in FIG. In this case, the difference between the pressure inside the gas-filled container for the initial filling and the pressure inside the gas-filled container for the final filling from time T0 to time T6 is 18 kPa → 24 kPa → 38 kPa → 55 kPa → 51
kPa → 31 kPa → 0 kPa. Although the temperature difference is larger at the beginning of the temperature raising step, the pressure difference in the aerated container increases until time T3 and thereafter decreases, and if the pressure difference in each of the aerated containers causes deformation, It can be predicted that this will occur in the middle stage of the heating process, where the pressure difference peaks.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a heat sterilization apparatus for heat sterilization of an air-containing container in a batch system. The purpose is to prevent bag breakage.

[0009]

According to a first aspect of the present invention, there is provided a temperature increasing method in which an aerated container in which food or the like is sealed together with a gas is accommodated in a treatment tank, and the aerated container is heated to a sterilization temperature. Process, a sterilization process of maintaining a predetermined time at the sterilization temperature, by performing a sterilization process consisting of a cooling process of cooling the aerated container after the completion of the sterilization, in a heat sterilization device for sterilizing food and the like in the aerated container, sterilization process First, in order to equalize the temperature of each aerated container, the temperature must be higher than the filling temperature of the aerated container.
Preheating is performed by heating at a temperature lower than 0 ° C., and after the preheating, each step of the sterilization treatment is performed. By performing preheating, the temperature of each aerated container can be made uniform,
If the temperature raising step is performed in a state where the temperatures of the air-containing containers are uniform, no pressure difference is generated between the individual air-containing containers, so that deformation and breakage of the air-containing containers can be prevented.

According to a second aspect of the present invention, in the heat sterilization apparatus for an aerated container for performing the preheating, the temperature of the preheating is set equal to the filling temperature of the aerated container. If the temperature of the preheating is increased, the pressure difference between the aerated containers increases during the preheating, which may cause deformation of the aerated container. For example, the pressure difference between the aerated containers does not increase during the preheating, and the deformation of the aerated container can be reliably prevented.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart of a heat sterilization apparatus for carrying out the present invention, FIG. 2 is an explanatory diagram of the temperature in an aerated container in one embodiment, and FIG. 3 is an explanatory diagram of the internal pressure of an aerated container in FIG.
The heat disinfection apparatus accommodates a large number of aerated containers 6 in a cylindrical processing tank 7 and sterilizes the food in the aerated container 6 by heating and pressurizing the processing tank 7. Circulating water is taken out of the processing tank 7 from the bottom of the processing tank 7, and then the aerated container 6
A circulating pipe for injecting circulating water into A circulation pump 9 for flowing the circulating water and a heat exchanger 8 for heating the circulating water are provided in the middle of the circulation pipe, and a heating control valve 2 for controlling the supply of steam to the heat exchanger 8 is provided.

At the top of the processing tank 7, a compressor 10
A pressurized pipe for sending pressurized air from the tank to the processing tank 7 is provided, and a pressurizing valve 5 for controlling the supply of pressurized air to the processing tank 7 is provided in the middle of the pressurized pipe. A pressure reducing pipe for discharging air from inside the processing tank 7 is provided above the processing tank 7, and a pressure reducing valve 4 for controlling exhaust from the processing tank 7 is provided in the middle of the pressure reducing pipe. Processing tank 7
A pressure measuring device 3 for detecting the internal pressure is provided, and an operation control device 1 connected to the pressure measuring device 3 is provided. The operation control device 1 includes a pressure reducing valve 4, a pressurizing valve 5, a circulation pump 9, and a heating control valve. Also connect 2. The operation control device 1 controls operations of the pressure reducing valve 4, the pressurizing valve 5, the circulation pump 9, and the heating control valve 2.

The manufacturing process of the retort food includes a cooking process of cooking the food, a filling process of packing the cooked food in a container with a gas such as air, a carrying-in process of storing the aerated container in the treatment tank, and a temperature of the aerated container. Preheating step to homogenize, heating step to heat the aerated container to the sterilization temperature, sterilization step to maintain the set temperature at the sterilization temperature, cooling step to cool the aerated container after the sterilization step, and air from the treatment tank It consists of an unloading process for taking out the container.

In the case of the filling step, the filling step is carried out one by one, and the sterilization treatment is performed in a large amount of aerated containers at a time. Therefore, the waiting time from the filling step to the sterilization treatment is different, and the temperature which decreases during the waiting time is also different. Each will be different. When sterilizing the air-containing container, the operation control device 1 performs preheating before starting the temperature raising step. The operation control device 1 controls the operation of the circulation pump 9 and the opening of the heating control valve 2 in a state in which a large number of aerated containers are accommodated in the processing tank 7. Steam is supplied to the heat exchanger 8, and hot water having absorbed heat in the heat exchanger 8 is injected into the processing tank 7 to heat the processing tank 7. In the case of preheating, the heating control valve 2 is operated so that the atmospheric temperature in the processing tank 7 is maintained at a predetermined temperature lower than the sterilization temperature of the gas-containing container, and the temperature difference between the gas-containing containers 6 is eliminated.

FIG. 2 shows a case where the filling temperature is 50 ° C. and the initial filling amount has dropped to 20 ° C. at the time T0 at the start of the sterilization treatment. The temperature at each time point from the time T0 to the time T1 is represented by a black circle for the initial filling, a white triangle for the final filling, and a two-dot chain line for the atmosphere temperature in the treatment tank. In the case of preheating, the operation control device 1
The heating control valve 2 is operated so as to maintain the atmosphere temperature in the processing tank 7 at 50 ° C. which is equal to the filling temperature, and the temperature of the aerated container for the initial filling is raised to 50 ° C. Since the temperature of the final filling was not different from the filling temperature, and the temperature of the initial filling was significantly lower than the filling temperature, there was a temperature difference between the final filling and the initial filling at time T0. If the internal atmosphere temperature is heated to and maintained at 50 ° C., which is the filling temperature, the temperature of the final filling does not change and the temperature of the initial filling rises, so that the temperature difference between the aerated containers 6 disappears. By performing the preheating, the pressure difference between the initial charge and the final charge as shown in FIG. 3 is eliminated.

When the time set for the preheating is reached at the time T2, the operation control device 1 ends the preheating and starts the temperature raising step. In the temperature increasing step, the opening and closing of the heating control valve 2 is controlled so that the atmosphere temperature in the processing tank 7 becomes the sterilization temperature of 120 ° C., and the aerated container 6 is heated to the sterilization temperature. Further, the operation control device 1 controls the pressurizing valve 5 and the pressure reducing valve 4 so that the pressure in the processing tank 7 changes at a value close to the pressure in the aerated container 6. In this case, since the temperature difference between the aerated containers is eliminated by preheating, all the aerated containers rise at substantially the same temperature, and the pressure difference between the aerated containers becomes small. Therefore, the internal pressure of the processing tank can be controlled to a pressure substantially equal to the internal pressure of the entire aerated container, and there is no aerated container having a pressure outside the internal pressure of the processing tank.

Thereafter, at time T7, when the temperature of the aerated container 6 reaches the sterilization temperature of 120 ° C., the operation control device 1 shifts from the temperature raising step to the sterilization step, and maintains the aerated container 6 at the sterilization temperature for a predetermined time. To sterilize. When the sterilization is completed, a cooling step for cooling the inside of the processing tank 7 is performed, and the sterilization processing step is completed by removing the aerated container 6 from the inside of the processing tank 7.

When the temperature raising step was performed in a state where there was a temperature difference in the gas-containing container without performing the preheating, the pressure difference increased in the middle stage of the temperature raising step as shown in FIG. By eliminating the temperature difference before increasing the temperature of the container, a pressure difference due to the temperature difference of each aerated container does not occur at the time of the temperature raising step, and it is possible to prevent the deformation and breakage of the aerated container. .

In this embodiment, the preheating temperature is set equal to the filling temperature, but another value may be adopted. When the preheating temperature is set equal to the filling temperature, the pressure difference in each aerated container does not become larger than that at the time T0, so that deformation of the container can be reliably prevented.
Another value can be adopted as long as the container does not deform even if the pressure difference becomes slightly larger than the time point of zero. However, when the temperature is higher than the filling temperature, if the temperature is too high, the deformation of the aerated container may occur while the temperature of the aerated container is raised to the preheating temperature. Needs to be lower than the pressure difference increases, and the preheating temperature is lower than 80 ° C. Further, when the temperature is lower than the filling temperature, during the preheating, the final filling which has been higher than the preheating temperature is wasted to be cooled to the preheating temperature. Should be avoided.

[0020]

According to the present invention, in a heat sterilization apparatus for heat-sterilizing an air-containing container in a batch system, deformation and breakage of the air-containing container caused by a temperature difference between the air-containing containers can be prevented. Can be.

[Brief description of the drawings]

FIG. 1 is a flow chart of a heat sterilization apparatus for implementing the present invention.

FIG. 2 is an explanatory diagram of a temperature change in one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a pressure change in FIG. 2;

FIG. 4 is an explanatory diagram of a temperature change in a conventional example.

FIG. 5 is an explanatory diagram of a pressure change in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 operation control device 2 heating control valve 3 pressure measuring device 4 pressure reducing valve 5 pressurizing valve 6 aerated container 7 treatment tank 8 heat exchanger 9 circulation pump 10 compressor

Claims (2)

[Claims] 1. An air-containing container in which foods and the like are sealed together with a gas are accommodated in a treatment tank, and a heating step of raising the temperature of the air-containing container to a sterilization temperature; a sterilization step of maintaining the sterilization temperature at a sterilization temperature for a predetermined time; By performing a sterilization process consisting of a cooling step of cooling the air-containing container after completion, when performing a sterilization process in a heat sterilization device that sterilizes foods and the like in the air-containing container, first, equalize the temperature of each air-containing container. In order to perform the preheating, the preheating is performed by heating at a temperature equal to or higher than the filling temperature of the aerated container and lower than 80 ° C., and the sterilization process is performed after the completion of the preheating. For heat sterilization equipment. 2. The preheated air-sterilized container according to claim 1, wherein the preheating temperature is equal to the filling temperature of the air-containing container. For heat sterilization equipment.