Heat sterilization method for aseptic filling facility

Abstract

Provided is a heat sterilization method for use in an aseptic filling facility and capable of minimizing excessive sterilization time and energy consumption while ensuring an appropriate sterilization effect merely by measuring sterilization time. This heat sterilization method for an aseptic filling facility is characterized in that a plurality of sterilization temperatures are set in a sterilization target section, sterilization completion times at which a target F value is attained are set for each of the set sterilization temperatures, timers corresponding to each set sterilization temperature are respectively started at the point in time when the temperature of the sterilization target section reaches each set sterilization temperature, the sterilization times are each measured, and sterilization is completed when one of the measured times from the timers first reaches said sterilization completion time.

Description

Heat sterilization method for aseptic filling equipment

[0001] The present invention relates to a heat sterilization method for aseptic filling equipment, and more particularly, to a heat sterilization method for aseptic filling equipment that can reduce the time and energy required for sterilization without impairing the sterilization effect.

[0002] When aseptically filling a beverage into a container, it is important that the filling equipment is sterilized and in an aseptic state together with the sterilization of the beverage and the container. Before starting to fill the contents, each equipment is sterilized to make it aseptic. The sterilization process (SIP) of the filling equipment is carried out by holding at a predetermined temperature for a certain period of time. As one criterion for sterilization, the F value is defined. The F value, which is an index of the sterilization state, is defined by the product of temperature and time. Therefore, if the minimum temperature is exceeded during sterilization, it is possible to shorten the sterilization time. However, since the management and control of sterilization conditions are complicated, even when the minimum temperature required for sterilization is exceeded, sterilization is carried out for the specified time. As a result, sterilization is carried out for an unnecessarily long time, and excessive energy is consumed.

[0003] In order to solve such problems, for example, in Patent Document 1 below, in a sterilization method for a beverage filling device including a beverage supply system pipe that sends a beverage into a filling machine through a heat sterilization unit, hot water or heated steam is sent to the beverage supply system pipe, and the F value is calculated while detecting the temperatures at multiple locations of the beverage supply system pipe at predetermined time intervals. When the minimum F value among them reaches the target value, the sterilization process is terminated. A sterilization method for a beverage filling device is described.

[0004] Japanese Patent No. 6217652

[0005] In the sterilization method described in Patent Document 1 above, by calculating the F value at predetermined time intervals and managing it, it is possible to shorten the sterilization time and reduce the energy required for sterilization. However, it is necessary to measure the temperature at multiple locations in the device at predetermined time intervals and calculate the F value from the obtained data. Since there are many processes required for management, it is complicated, and it is desired to shorten the sterilization time and reduce energy consumption more efficiently by a simpler method.

[0006] Therefore, the object of the present invention is to provide a heat sterilization method that can suppress excessive sterilization time and energy consumption while ensuring an appropriate sterilization effect simply by measuring the sterilization time.

[0007] According to the present invention, a heat sterilization method for aseptic filling equipment is provided, characterized in that multiple sterilization temperatures are set for the part to be sterilized, a sterilization completion time is set for each set sterilization temperature which is the target F value, a timer corresponding to each set sterilization temperature is started when the temperature of the part to be sterilized reaches each set sterilization temperature and the sterilization time is measured, and sterilization is terminated when one of the timers first reaches the sterilization completion time.

[0008] In the heat sterilization method of the present invention, it is preferable that: (1) when the temperature of the part to be sterilized rises above each set sterilization temperature and falls below each set sterilization temperature, the measurement by each timer is stopped and the measurement time is reset to zero, and when the temperature of the part to be sterilized rises above each set sterilization temperature again, each timer is started and the sterilization time is measured; (2) when the temperature of the part to be sterilized rises above each set sterilization temperature and falls below each set sterilization temperature, the measurement by each timer is temporarily stopped, and when the temperature of the part to be sterilized rises above each set sterilization temperature again, each timer is restarted and the measurement of the sterilization time is resumed; (3) when the stopped time of each timer has elapsed for a predetermined time, the measurement time of each timer is reset to zero, and the measurement is restarted from the time when the temperature of the part to be sterilized rises above each set sterilization temperature again; and (4) the F value corresponds to 232.8 minutes.

[0009] According to the heat sterilization method of the present invention, by pre-setting the sterilization completion time for each set sterilization temperature that corresponds to the target F value, measuring the sterilization time at each set sterilization temperature, and completing sterilization when the sterilization completion time is first reached, it is possible to perform sterilization with the optimal sterilization time according to the sterilization temperature without being affected by fluctuations in the sterilization temperature, thereby suppressing excessive sterilization and easily achieving a reduction in sterilization time and energy consumption. Furthermore, because the sterilization time can be shortened, equipment can be efficiently sterilized when changing production, resulting in superior productivity. Moreover, since it is only necessary to measure the sterilization time by pre-setting the sterilization completion time for each set sterilization temperature, no special equipment for calculation processing is required, and existing equipment can be used as is, making it economically superior. Furthermore, even if the temperature falls below the set sterilization temperature during sterilization, it is possible to measure an effective sterilization time, thus ensuring reliable sterilization.

[0010] This is a flowchart showing an example of an aseptic filling system. This is a diagram illustrating an example of a method for measuring sterilization time in the heat sterilization method of the present invention. This is a diagram illustrating another example of a method for measuring sterilization time in the heat sterilization method of the present invention. This is a diagram illustrating another example of a method for measuring sterilization time in the heat sterilization method of the present invention.

[0011] In the heat sterilization method for aseptic filling equipment of the present invention, prior to sterilization, multiple sterilization temperatures are set for the part to be sterilized in the aseptic filling equipment, and the sterilization completion time is set for each set sterilization temperature that will result in a target F value. The sterilization temperature is determined by the type of contents to be filled. For example, in the case of neutral beverages such as tea beverages, a lower limit of 130°C is set, and the sterilization completion time is set to satisfy the F value, which is an indicator of sterilization. The F value has been empirically established to ensure reliable sterilization even for contents other than those for which sterilization conditions are defined by the Food Sanitation Law. In the case of the above-mentioned neutral beverages, an F value of 232.8 obtained by sterilizing at 130°C for 30 minutes is a general indicator of sterilization. In addition, for mineral waters, an F value equivalent to 85°C for 30 minutes is a general indicator of sterilization, and for acidic beverages with a pH of less than 4, an F value equivalent to 65°C for 10 minutes is a general indicator of sterilization. In this invention, a plurality of temperatures above the lower limit of the sterilization temperature (minimum sterilization temperature) are set. For example, in the case of the neutral beverage described above, the minimum sterilization temperature is set to 130°C, and six temperatures are set: 130°C, 131°C, 132°C, 133°C, 134°C, and 135°C. For each of the six set sterilization temperatures, the sterilization completion time (30 minutes, 24 minutes, 19 minutes, 15 minutes, 12 minutes, and 9.5 minutes) that result in a target F value of 232.8 are set.

[0012] The parts to be sterilized cannot be defined in general terms, as they depend on the type of contents and containers to be filled, or the size of the filling machine. However, in the example of an aseptic filling system for beverages into PET bottles shown in the flow diagram in Figure 1, the parts to be sterilized are the supply pipe for the sterilized contents (beverage) to the filling machine, the conveying device for the sterilized containers (PET bottles), the conveying device for the sterilized caps, and the filling and sealing device (filling machine and capping machine), all installed within the aseptic chamber. Multiple thermometers and timers corresponding to different set sterilization temperatures are installed in each part of the parts to be sterilized, allowing the sterilization status of each device to be checked. Sterilization devices may be set according to each device, or, depending on the scale, a sterilization device capable of sterilizing the entire aseptic chamber may be installed.

[0013] The sterilization of the target area is started with multiple set sterilization temperatures and corresponding sterilization completion times set for each temperature. The sterilization method is not limited as long as it can heat the target area to a minimum sterilization temperature or higher, but heating with heated steam is preferred. In addition to sterilizing by directly spraying heated steam onto the target area, the target area can also be sterilized by flowing heated steam through piping or by filling a sterile chamber with heated steam and maintaining a high temperature throughout the chamber.

[0014] The sterilization target unit, equipped with a number of thermometers and timers corresponding to multiple set sterilization temperatures, is heated. When each set sterilization temperature is reached, the timer corresponding to that temperature starts to measure the sterilization time. Sterilization ends when any of the timers first reach the set sterilization completion time. In other words, if heating sterilization is continued, the sterilization target unit will be heated to a temperature higher than the minimum sterilization temperature. However, since a sterilization completion time is set for that temperature, sterilization will be completed in a shorter time than the sterilization time at the minimum sterilization temperature.

[0015] The sterilization device has a temperature controller set to maintain a temperature above the minimum sterilization temperature, and heating is controlled to prevent excessive temperature increases once the temperature exceeds the minimum sterilization temperature. Therefore, once the minimum sterilization temperature is exceeded, heating is controlled, which may cause the temperature to temporarily fall below the set sterilization temperature. If the sterilization process ends with a completion time that includes sterilization time at a temperature below the set sterilization temperature, sterilization may be insufficient. However, in this invention, by employing the following two methods, it is possible to prevent insufficient sterilization while suppressing excessive sterilization.

[0016] Specifically, Figures 2 to 4 show the relationship between the temperature of the part to be sterilized and the measurement time while heat sterilization is in progress. The curve (i) represents the temperature of the part to be sterilized, and the broken line (ii) represents the measurement time (sterilization time) measured by the timer. In the first method, while heat sterilization is in progress, as shown in Figure 2, when the temperature of the part to be sterilized exceeds the set sterilization temperature, the timer measures the time shown at t1 in Figure 2. Subsequently, when the temperature falls below the set sterilization temperature, the timer measurement is stopped, and the measured time up to that point is reset to zero. When the temperature of the part to be sterilized reaches the set sterilization temperature again, the timer restarts and the sterilization time is measured again from the beginning, and the sterilization time shown at t2 in Figure 2 is measured. This is repeated, and sterilization ends when one of the timers installed for each set sterilization temperature reaches the set sterilization completion time. According to this first method, since sterilization is performed continuously at a temperature above the set sterilization temperature for a period longer than the sterilization completion time, reliable sterilization under the intended sterilization conditions can be ensured even if the temperature temporarily drops.

[0017] In the second method, as shown in Figure 3, when the temperature of the part to be sterilized exceeds the set sterilization temperature, the time indicated by t1 in Figure 3 is measured by a timer. Then, when the temperature falls below the set sterilization temperature, the timer measurement is temporarily stopped. When the temperature of the part to be sterilized reaches the set sterilization temperature again, the timer is restarted and the sterilization time indicated by (t1 + t2) in Figure 3 is measured. This is repeated, accumulating the measured time (t1 + t2 + ...), and sterilization is completed when any of the timers set for each set sterilization temperature reach the set sterilization completion time. In this second method, heating at a temperature above the set sterilization temperature is performed for a total time (cumulative time) that exceeds the sterilization completion time, and since sterilization can be performed with the minimum necessary sterilization time, it is highly economical. Generally, since the temperature drop of the part to be sterilized is small and short-lived, there is no problem in measuring the sterilization time as a cumulative time. However, by pre-determining an upper limit on the time below the set sterilization temperature (timer stop time), and resetting the timer to zero if the set sterilization temperature is not reached after a certain period of time, as shown in Figure 4, insufficient sterilization can be prevented.

[0018] Furthermore, in both the first and second methods, if the temperature falls below the minimum sterilization temperature during the continuation of heat sterilization, it may be determined that there is a malfunction in the sterilization device, and sterilization may be stopped at that point.

[0019] In the heat sterilization method for the aseptic filling apparatus of the present invention, the multiple sterilization temperatures set in the sterilization target section are determined based on a minimum sterilization temperature set from a target F value. In the example described above, the F value was 232.8 and the minimum sterilization temperature was 130°C, with six set sterilization temperatures and sterilization completion times set in 1°C increments from 130°C to 135°C. However, the method is not limited to this, and it is preferable to set 5 to 20 settings in increments of 0.5°C to 1°C within a range of +5°C to +10°C from the minimum sterilization temperature. A thermometer and timer are set in the sterilization target section according to this number of settings. The target F value for sterilization is preferably equivalent to 232.8 minutes for neutral beverages, but the method is not limited to this, and can be appropriately changed depending on the equipment status, sterilization frequency, and type of beverage. As described above, heat sterilization is preferable using heated steam because it can reliably sterilize even the smallest details of the equipment, but the method is not limited to this, and can also be done using hot water or the like, as long as it can be heated to the minimum sterilization temperature.

[0020] The heat sterilization method for sterile filling equipment of the present invention is particularly suitable for use in beverage filling equipment, but it can also be used in filling equipment for foods other than beverages, or as a sterilization heating method within a sterile chamber (clean room).

Claims

1. A heat sterilization method for aseptic filling equipment, characterized in that multiple sterilization temperatures are set for the part to be sterilized, a sterilization completion time is set for each set sterilization temperature that corresponds to a target F value, a timer corresponding to each set sterilization temperature is started when the temperature of the part to be sterilized reaches each set sterilization temperature to measure the sterilization time, and sterilization is terminated when one of the timers first reaches the sterilization completion time.

2. The heat sterilization method according to claim 1, wherein when the temperature of the part to be sterilized rises above each set sterilization temperature and falls below each set sterilization temperature, the measurement by each timer is stopped and the measurement time is reset to zero, and when the temperature of the part to be sterilized rises again to each set sterilization temperature, each timer is started and the sterilization time is measured.

3. The heat sterilization method according to claim 1, wherein when the temperature of the part to be sterilized rises above each set sterilization temperature and then falls below each set sterilization temperature, the measurement by each timer is temporarily suspended, and when the temperature of the part to be sterilized rises again to each set sterilization temperature, the timer is restarted and the measurement of the sterilization time is resumed.

4. The heat sterilization method according to claim 3, wherein when the stop time of each timer has elapsed for a predetermined period of time, the measurement time of each timer is reset to zero, and the measurement is restarted when the temperature of the part to be sterilized reaches the set sterilization temperature again.

5. The heat sterilization method according to claim 1, wherein the F value corresponds to 232.8 minutes.

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