JPS62228261A - Sterilization of food and equipment therefor - Google Patents

Abstract

PURPOSE:The food is rapidly heated up to the lower part of the sterilization temperature range and the temperature is kept for a prescribed time to effect sterilization, then the food is steeply cooled down to enable efficient sterilization, as the propagation of contaminant microorganisms in food is suppressed as much as possible. CONSTITUTION:A food such as pickle is rapidly heated up by means of the heater (a) to the lower part of the sterilization temperature range and transferred into the temperature uniform distributor (b) where the heat medium is kept at the temperature of the lower part and transferred to the thermostat sterilizer (c) to effect sterilization. In the sterilizer, the sterilization proceeds without additional energy consumption between the heat medium and the food. The food may be stacked up. The food sterilized is rapidly cooled down in the cooler (d) as fast as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method and apparatus for sterilizing food by heat.

[Conventional technology]

Traditionally, when commercializing food products such as pickles, food products were
Sterilization is performed by heating to about 80°C. This heating was carried out by placing a large amount of food into a large basket-like container and immersing the large container in hot water at the above temperature. As a large amount of food is piled up and immersed in hot water, there is a difference in the degree of heating between the areas near the outside and the area near the inside of the large container, and the food inside is not sufficiently heated. There is a risk that the food inside will not be sterilized because it will not be heated. Conventionally, in order to prevent such uneven heat sterilization, the above-mentioned 70
Measures were taken to increase the sterilization temperature and sterilization time, such as heating at a high temperature of ~80°C to sufficiently heat the inside.

[Problem that the invention seeks to solve]

However, in such conventional technology, 70
Since the food stack is placed in hot water of ~80°C and heated to this temperature, the heat is sequentially propagated from the outer periphery of the food to the inside until the food inside is heated to the specified level. It will take a long time. This long time required for internal heating not only reduces the efficiency of sterilization treatment, but also encourages the proliferation of bacteria.

In other words, most of the bacteria present in foods grow in the temperature range of approximately 25 to 45 degrees Celsius, and the fact that it takes a long time to reach a predetermined heating temperature as in the prior art described above As a result, in the conventional technology, bacteria are allowed to grow once and then are sterilized. Therefore, since the germs that have once multiplied are then sterilized, in addition to the heating time mentioned above, the time required for sterilization is also long and the heating temperature is also high, resulting in the problem that the sterilization efficiency is unsatisfactory. Ta.

Furthermore, according to the conventional technology, there is a need to kill the proliferated bacteria due to the fear that the sterilization of the food items closer to the outside and the items inside of the stacked large amount of food may vary. Because food is heated to a temperature of 70 to 80 degrees Celsius, if the food is not compatible with heating, such as pickles, this heating will cause the food to become boiled, resulting in loss of taste and flavor. There was also the problem that there was a significant decline in the

Therefore, this invention quickly passes through the temperature range of bacteria growth that occurs during heating, suppresses the growth of bacteria in food as much as possible, and minimizes the sterilization temperature range necessary for sterilization. By sterilizing food at low temperatures, the aim is to improve the efficiency of food sterilization and prevent the loss of food taste and flavor.

[Means for solving problems]

The method for sterilizing food according to the present invention involves rapidly heating the food to a low temperature range in the sterilization temperature range, and then uniformizing the temperature of the food while maintaining the food in the temperature range to achieve a uniform temperature distribution state. After sterilizing the food for a predetermined period of time, the food is rapidly cooled.

In addition, the sterilizer used directly to carry out the sterilization method is
(a) a rapid heating device that heats food to a low temperature range within the sterilization temperature range within a short time; (b) a tank in which a liquid heated to the low temperature range is stored; (c) a temperature equalizing device that makes the temperature of the food uniform in the low temperature range; It consists of a tank in which liquid is stored, a temperature maintenance device that maintains the temperature of the liquid in the tank, and a retention device that keeps the food supplied from the temperature equalization device in the tank for a predetermined period of time. It is equipped with a constant temperature sterilizer that sterilizes during retention, and (d) a cooling device that contains a cooling liquid in a tank and cools the food supplied from the constant temperature sterilizer.

[Effect]

Foods such as pickles are rapidly heated to a low temperature range within the sterilization temperature range by a rapid heating device. Since the heating state is rapid, the time that the food is in the breeding temperature range of bacteria is short during the temperature rise, so the growth of bacteria in the food is suppressed as much as possible. Depending on this heating, the temperature distribution within the food may be non-uniform. In order to rapidly heat the food, it is preferable to perform this heating step by separating the food into individual units, such as when packaging the food for retail sale.

Next, the heated food is passed through a temperature equalization device so that the temperature distribution within the food becomes uniform. This is because the liquid in the tank is maintained at a low temperature within the sterilization temperature range, and while the food is conveyed through this liquid by a conveyor, the heated thermal energy is uniformly applied to each part of the food. The excess or deficiency of heat on the food is corrected depending on the temperature of the liquid.
The temperature of the food becomes uniform at a predetermined temperature in each part. The heat lost to the liquid due to heat radiation, etc. is compensated for by the constant temperature heating device, and the liquid is always maintained within a predetermined temperature range. Here, since the temperature of the food becomes uniform, there is no risk of sterilization leakage due to uneven heating, so there is no need to heat the food to a temperature higher than necessary. It is preferable that this step of equalizing the temperature is also carried out by separating the food into individual units in the same manner as described above.

Next, the food is supplied to a constant temperature sterilizer, where the food is sterilized in a low temperature range of the sterilization temperature range. Since the temperature of the food is made uniform at a predetermined temperature in the temperature equalization device, sterilization proceeds here without consuming new thermal energy in the relationship between the liquid and the food.

Then, heat radiation from the tank itself is prevented and heat loss due to heat radiation is compensated for by a temperature holding device for maintaining the temperature of the liquid at a predetermined value using, for example, a heat insulating structure or a heating device. Here, since there is almost no exchange of thermal energy between the food and the liquid, the food may be in a stacked state.

The sterilized food is cooled as quickly as possible in a cooling device. The reason for speeding up the cooling is to shorten the time that food is in the temperature range where germs grow during cooling, thereby suppressing the growth of germs in the food as much as possible. The end of this cooling ends the food sterilization process.

〔Example〕

FIG. 1 shows an embodiment of this sterilizer. Foods to be sterilized include foods for which high temperature sterilization is not appropriate, such as pickled vegetables and fruits.

This device is a rapid heating device (a
), a temperature equalization device (b), a constant temperature sterilization device (c), and a cooling device (d) are arranged in series.

The rapid heating device (a) includes an endless conveyor 1 such as a net conveyor, and a rapid heating machine 3 that rapidly heats food 2 conveyed by the endless conveyor 1. Food 2 is a unit containing an appropriate amount of food using a bag made of plastic sheet, a net bag, etc., but it is also possible to use - pieces of food as one unit. In this embodiment, the rapid heating machine 3 consists of a high-frequency electromagnetic heating machine, and in relation to its output and the conveyance speed of the food 2 by the endless conveyor 1, the rapid heating machine 3 heats the food 2 to a temperature of 50°C, which is a low temperature range behind the sterilization temperature range. Although it is designed to rapidly heat up to about .degree. C., the rapid heating device 3 may be a heating device using other known heating means instead of a high frequency electromagnetic heating device. Further, the temperature equalization device (b) described below can also be used as the rapid heating device (a), but as explained below using FIG. 3, the temperature equalization device (bl) The most suitable results will be obtained if the and rapid heating device (a) are separated and a high frequency electromagnetic heating device is used as the rapid heating device 3 for the rapid heating device (al).

The food heated to the above temperature by the rapid heating device (al) is supplied to the temperature equalization device (b).Temperature equalization device (b)
is the constant temperature range of the above temperature range, that is, the sterilization temperature range 5
It includes a tank 5 containing a liquid 4 maintained at about 0° C. and a conveyor 6 carrying food 2 and passing through the tank 5. A cover 7 is arranged on the upper surface of the liquid 4 to keep the liquid 4 warm. Plate blades 6a are protruded from the conveyor 6 at predetermined intervals, so that the plurality of foods 2 are not stacked together on the conveyor 6 and are conveyed with a gap between the front and back. This is done by increasing the contact area of liquid 4. Reference numeral 8 denotes a constant temperature heating device, which maintains the liquid 4 at the temperature as described above. Reference numeral 9 denotes a drive device for the conveyor 6, and by adjusting the speed of this, the food products 2 on the top surface of the conveyor 6 are not stacked as described above and are kept in a predetermined manner, in balance with the speed of the endless conveyor 1 of the rapid heating device (a). It is set to have a spacing before and after. In this temperature equalization device (b), while the food 2 is being conveyed by the conveyor 6, heat is sufficiently propagated within the food 2, so that the entire temperature becomes uniform.

The food product 2 is then fed to a constant temperature sterilizer (c). The constant temperature sterilizer (c) includes a tank 11 containing a liquid 10 maintained at the temperature of about 50° C., a conveyor 12 that passes through the tank 11 with food products 2 stacked therein, and a conveyor 12 that keeps the liquid 10 warm. The conveyor 12 has plate blades 12a protruding from its upper surface to prevent the food 2 from moving back and forth in the traveling direction. 14 is a heating device for supplementing the heat dissipation of the liquid 10; therefore, the heat insulating cover 13 and the heating device 1
4 constitutes the temperature maintenance device of the present invention, and also constitutes a retention device in which the food 2 is kept in the tank 11 for a predetermined period of time by the conveyor 12. The means for stacking and supplying the food products 2 to the conveyor 12 is based on the speed and temperature uniformity of the conveyor 12.
determined in relation to the speed of the conveyor 6 of the converter H(b),
By making the speed of the conveyor 12 slower than that of the conveyor 6, the food products 2 are stacked on the conveyor 12, and the food products 2 are kept in the tank 11 for a predetermined period of time.

15 is a drive device for the conveyor 12.

Since the temperature of the food 2 has been made uniform at the above-mentioned temperature in the temperature equalization device (b), sterilization is proceeding here in the relationship between the liquid 10 and the food 2 without consuming new thermal energy. do. Here, since there is almost no exchange of thermal energy between the food 2 and the liquid 10, even if the food 2 is in a stacked state, it does not affect the progress of sterilization, and the predetermined period of time until sterilization is sufficiently achieved. liquid 10 over a period of
It is desirable that the food 2 be stacked in order to pass through the inside.

The food 2 sterilized in the constant temperature sterilizer (c) is supplied to a cooling device (dl) and cooled.The cooling device (d) is a conveyor 18 passing through a tank 17 containing cold water 16.
and a freezer 4ffl19 connected to the tank 17 to keep the cold water 16 at a predetermined low temperature. 20 is conveyor 1
8 drive device. A plate blade 18a is provided protruding from the conveyor 18. The food 2 supplied to the cooling device (d) is rapidly cooled by being passed through the cold water 16 by the conveyor 18, and the sterilization process ends when the cooling ends.

Next, the heating of food in this embodiment and the heating of food in the conventional example will be explained based on the graph shown in FIG.

In FIG. 3, a broken line Aa shows the temperature change on the outside of the food when heat sterilized according to the conventional example, and a broken line Ab shows the temperature change on the inside. In addition, the solid line Ba indicates the rapid heating device (
It shows the temperature change on the outside of the food when a high frequency electromagnetic heating machine is used as the rapid heating machine 3 in a), and the cotton Bb shown by the solid line is:
Shows the temperature change on the same inner side. Furthermore, a chain line Ca indicates the outside of the food when the temperature equalization device (b) also serves as the rapid heating device +8) without using the rapid heating device 3, which is a high-frequency electromagnetic heating device, in this example. The dashed line cb shows the temperature change on the same inner side.

In addition, range is a range of 25 to 40 degrees Celsius, which indicates the growth temperature range of bacteria, range E is a temperature range of around 50 degrees Celsius or higher, which is the sterilization temperature range for foods, and F is a temperature range for food sterilization in the range E. Indicates a high temperature range where the taste and flavor of food deteriorate.

As can be understood from this graph, line Aa.

In the case of the conventional example indicated by Ab, the temperature reaches the high temperature range F, and it takes time for the temperature to rise, and moreover, it remains in the germ growth temperature range Da indicated by diagonal lines for a long time. However, in this embodiment, especially in the case of the embodiment using a high-frequency electromagnetic heating machine, the time in the germ growth temperature range Db indicated by diagonal lines is short, and the temperature rises within a short time. High temperature range F
It doesn't reach that point. As described above, in this embodiment (i.e., this invention), not only is the sterilization time shortened because the heating is performed rapidly, but also the number of germs is small because the time taken to pass through the growth temperature range of germs is short. Also, from this point of view, the sterilization time can be shortened. Also, since the temperature does not rise to the high temperature range F, the taste and flavor of the food is improved.

Color, hardness, etc. are not impaired. According to the inventor's experiments,
The lower limit of the food sterilization temperature range E was 48°C. Therefore, when pickled vegetables and fruits are used as foods, the heating range according to the present invention can be said to be 48° C. or more and less than about 70° C. Therefore, the temperature of the food increases to 48
Sterilization begins when the temperature reaches ℃.
The rapid heating device (the part heated to 48°C by Al)
Sterilization has already started at this point, and sterilization of the entire food begins when the temperature of the entire food reaches 48° C. in the temperature equalization device (b). Thus, in the above temperature range, it is possible to kill or inactivate germs.

FIG. 2 shows a second embodiment of the device of this invention, in which the rapid heating device (a) and temperature equalization device (mounted) are the same as in the previous embodiment, but the constant temperature sterilization bag ff (as c1)
A case 21 in which foods 2 are stacked is placed in a tank 11 and left for a predetermined period of time to sterilize the food. Reference numeral 14 denotes a heating device, which has the same function as the heating device 14 of the previous embodiment. The food 2 sterilized here is supplied to the cooling device (d) with the case 21 by the hoist 22. Cold water 16 is supplied from a cold water supply pipe 23 into the tank 17 of the cooling device (DL), and the cold water 16 in the tank 17 is always maintained at a predetermined low temperature. Then, it is transported to the next process by the hoist 22 while being housed in the case 21.

〔Effect of the invention〕

As explained above, according to the present invention, since the heating is performed rapidly, the temperature range of bacteria growth that occurs during heating is quickly passed through, so that the growth of bacteria in the food during heating is suppressed as much as possible. . This has the effect of shortening the time required for sterilization because the heating speed is fast and the growth of germs is small, and sterilization can be performed in the lowest temperature range of the sterilization temperature range necessary for sterilization. Therefore, it is possible to maintain the taste, flavor, color, hardness, etc. of the food not much different from that before heating, which also has the effect of contributing to the improvement of quality.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the first embodiment of the device of this invention, and FIG.
The figure is an explanatory diagram showing the second embodiment, and FIG. 3 is a graph showing the heating states of the present invention and the conventional example.

Claims (3)

[Claims] (1) After rapidly heating the food to a low temperature range within the sterilization temperature range, the food is maintained at that temperature range while the temperature of the food is made uniform, and this uniform temperature distribution state is continued for a predetermined period of time for sterilization. A method for sterilizing food, which is characterized by rapidly cooling the food. (2) The step of rapidly heating the food to a low temperature range and the step of making the temperature of the food uniform are performed by separating the food into individual units, and the step of sterilizing the food by continuing the temperature distribution state is The method of sterilizing food according to claim 1, which is carried out in the form of a plurality of food units. (3) (a) A rapid heating device that heats food to a low temperature range within the sterilization temperature range within a short time. (b) Consisting of a tank in which the liquid heated to the low temperature range is stored, a conveyor that passes the food through the tank, and a constant temperature heating device that maintains the liquid in the tank in the low temperature range, the food A temperature equalization device that equalizes the temperature in the low temperature range. (c) A tank in which the liquid maintained in the low temperature range is stored, a temperature maintenance device that maintains the temperature of the liquid in the tank, and a retention device that retains the food supplied from the temperature equalization device in the tank for a predetermined period of time. A constant temperature sterilizer which sterilizes food during said retention period. (d) A cooling device that contains a cooling liquid in a tank and cools the food supplied from the constant temperature sterilization device. A food sterilization device comprising each of the devices (a) to (d) above.