JP2006067943A - Method for heating fluid food having upper limit critical temperature - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for heating fluid food capable of heating accurately at a heating temperature to nearly denaturation temperature and desired temperature which does not reach the denaturation temperature without making a device complicated and high price, and causing no temperature unevenness in the case that it is necessary to heat fluid food denaturing by heating to fixed temperature or above at nearly denaturation temperature aiming at for instance sterilization. <P>SOLUTION: This method for heating the fluid food 1 comprises a first heating process of heating the fluid food 1 through pouring into a liquid passage 4 irradiated with high-frequency wave and constituted by insulating partitions, and a second heating process of heating the fluid food heated in the first heating process to nearly upper limit critical temperature (denaturation temperature or the like), and having a heat reserving tank 6 keeping the temperature for a prescribed time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention can be used when a liquid food that is denatured when heated to a certain temperature or higher, such as a liquid food containing soy protein such as soy milk or animal protein such as milk, is sterilized by heating. The present invention relates to a heating method in which the temperature can be raised and heated to a set temperature that is close to the temperature to be reduced and lower than the denaturation temperature without any variation, and therefore, solidification or the like is not caused and the cleaning operation is easy.

In a fluid food that denatures when heated above a certain temperature, for example, a protein-based food having a freezing point near 80 ° C. such as soy milk, when the temperature is raised to the sterilization temperature of the target bacteria during heat sterilization Since it must not be accompanied by protein denaturation, strict temperature rise and temperature maintenance are required.
Conventionally, when a protein food is sterilized by heating, a plate heat exchanger or a tube heat exchanger is used for heat sterilization. A plate heat exchanger is provided with pipes through which heated steam that passes in the stacking direction passes through a number of stacked heat exchange plates, and heats and sterilizes fluid protein-containing foods that pass between the heat exchange plates with steam. In addition, the tube heat exchanger heats and sterilizes a fluid protein-containing food while flowing in the tube.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 9-150896) discloses a method and apparatus for producing a container-packed beverage with high deaeration efficiency by sterilizing a container-packed beverage such as a tea beverage at a high temperature in a short time. In the manufacturing process, a plate heat exchanger is used in a preheating process for deaeration, a heat sterilization process, and a subsequent cooling process.

JP-A-9-150896

Proteins have the property of condensing and solidifying around 64 ° C, while the temperature required for sterilization needs to be maintained for a certain period of time around 60 ° C, so it is accurately controlled at a temperature around 60 ° C that does not cause coagulation. There is a need. However, when a conventional plate heat exchanger or the like is used for heat sterilization, it is difficult to accurately maintain the heating temperature at a predetermined temperature because steam or the like is used as a heating medium. Since there is a large temperature difference with the part, there is a problem that temperature unevenness occurs in the heated part, and this causes local coagulation of the protein.
When local solidification occurs, the solidified material accumulates on the heat transfer surface of the heat exchanger and clogs the flow path of the fluid food, so the work of disassembling and cleaning the device each time occurs, which is extremely complicated. It was.

  In view of the problems of the prior art, the present invention is complicated and expensive when the liquid food that is denatured when heated to a certain temperature or higher needs to be heated to a temperature near the denaturation temperature for, for example, sterilization. Therefore, an object of the present invention is to provide a heating method in which the heating temperature is close to the denaturation temperature and can be accurately heated to a desired temperature that does not reach the denaturation temperature, and temperature unevenness does not occur.

  The method of the present invention achieves such an object, and in the method of uniformly heating a liquid food having an upper critical temperature to a temperature near the critical temperature without variation, the liquid food is irradiated with a high frequency and is constituted by an insulating partition. A primary heating step of heating by flowing inside the liquid flow path, and a secondary heating for heating the fluid food heated in the primary heating step to a temperature near the upper critical temperature and maintaining the temperature for a predetermined time And a process.

In the method of the present invention, in the primary heating step, the liquid food flowing through the liquid flow path is irradiated with high frequency electromagnetic waves and heated. That is, because high frequency is used, it is easy to heat the liquid food to an accurate set temperature by adjusting its output and frequency, and by adjusting the diameter, length, etc. of the insulating cylindrical body. Become.
In the case of heating with microwaves, it is difficult to accurately heat to the set temperature, and it is difficult to heat the whole liquid food without unevenness. On the other hand, in the present invention, by using a high frequency, it takes a little longer to heat than microwaves, but it becomes easy to heat the fluid food to an accurate set temperature.

After the primary heating step, a secondary heating step of heating the fluid food heated in the primary heating step to a temperature near the critical temperature and maintaining the temperature for a predetermined time is performed. By passing through at least these two heating steps, the temperature can be accurately raised to a temperature near the upper critical temperature of the food and not exceeding the upper critical temperature.
In the present invention, preferably, a high frequency of 4 to 20 MHz is irradiated from the pair of electrodes. The reason for this is that if it is below 4 MHz, the temperature rise required for sterilization, that is, it does not reach around 60 ° C., and if it exceeds 20 MHz, the temperature rise is too fast and the temperature rises accurately without exceeding the upper critical temperature. This is because, in the case of fluid food containing protein, local coagulation is caused.

In the case of liquid food containing protein, since the freezing point of protein is around 64 ° C, it is preferably heated to a temperature of 45 to 55 ° C in the primary heating step and a temperature of 64 ° C or less in the secondary heating step. And maintain at that temperature.
Further, in the present invention, it is necessary to configure the partition wall of the liquid flow channel for flowing the liquid food with an insulating partition wall, and a general insulating resin can be used as the material applied to the insulating partition wall. When the target food is a protein-containing food, in order to completely sterilize the protein-containing food, it is necessary to hold at a temperature around 60 ° C. for a certain period of time. The liquid food is put into a heat retaining tank maintained at a temperature near the critical temperature for a predetermined time.

In the present invention, it is preferable that the liquid flow path is composed of a plurality of parallel flow paths installed between the upstream header and the downstream header.
Further, preferably, on the upstream side of the primary heating step, the fluid food before heating is preheated by exchanging heat with the fluid food after being heated in the secondary heating step.

  As described above, according to the present invention, the heated food is heated in the primary heating step, in which the liquid food is heated by flowing through the liquid flow path constituted by the insulating partition walls and irradiated with the high frequency, and the primary heating step. In order to employ high-frequency heating by heating the liquid food to a temperature near the upper critical temperature and maintaining the temperature for a predetermined time, the heated body itself generates heat from the inside, and therefore heat There is an advantage that the energy efficiency is high because it does not take time for transmission and energy is given only to the object to be heated, and heating of the heat medium and preheating of the apparatus are unnecessary. Further, unlike microwave heating, there is an advantage that temperature unevenness due to local energy concentration (current concentrates where it easily flows) does not occur.

  Further, by passing through at least these two heating steps of the primary heating step and the secondary heating step, the temperature can be accurately raised to a temperature near the upper critical temperature of the food and not exceeding the upper critical temperature. Therefore, not only protein-containing foods, but also fluid foods having an upper critical temperature such as a denaturation point need to be heated to near the upper critical temperature for sterilization etc., the desired temperature without exceeding the upper critical temperature. In addition, the temperature can be raised with high accuracy and without unevenness, and the temperature raising temperature can be set accurately without requiring a complicated operation with a simple apparatus. Therefore, a desired sterilizing effect can be obtained.

Further, preferably, by irradiating the liquid flow path with a high frequency of 4 to 20 MHz, it is possible to raise the temperature of the liquid food to a desired temperature more accurately and without unevenness and efficiently. In particular, in the case of foods containing proteins, the temperature can be raised to a temperature at which sterilization can be accurately performed around 60 ° C. without reaching the freezing point of around 64 ° C.
Therefore, in the case of protein-containing foods, there is an advantage that washing operations are facilitated because they are not accidentally solidified.

In addition, unlike conventional plate heat exchangers, temperature unevenness does not occur depending on the location, so that sterilization can be easily performed without locally coagulating proteins.
In addition, because the object to be heated itself generates heat by high-frequency irradiation, it does not take time for heat transfer, and energy is given only to the object to be heated, so heating of the heat medium, preheating of the apparatus, etc. are unnecessary. There is an advantage of high energy efficiency. Further, unlike microwave heating, there is an advantage that temperature unevenness due to local energy concentration (current concentrates where it easily flows) does not occur.

In addition, preferably, in the secondary heating step, the fluid food is put into a heat retaining tank maintained at a temperature near the critical temperature, so that the heat retaining at a temperature near the critical temperature can be more reliably performed.
Preferably, the liquid flow path is composed of a plurality of parallel flow paths mounted between the upstream header and the downstream header, so that the high frequency electromagnetic wave is uniform with respect to the flowing food flowing through the liquid flow path. The temperature rise of the fluid food can be made more uniform.

  Also preferably, on the upstream side of the primary heating step, the fluid food before heating is preheated by exchanging heat with the fluid food after being heated in the secondary heating step, thereby improving the overall thermal efficiency. In addition, there is a margin in the temperature raising process, so that the temperature can be raised to the set temperature more accurately.

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.
FIG. 1 is a system diagram of a temperature sterilization apparatus using high frequency irradiation according to a first embodiment of the present invention, and FIG. 2 is an enlarged elevation view of an insulating liquid flow path 4 in the first embodiment.

1 and 2, 1 is a liquid food containing protein that is held near normal temperature and stored in a storage tank 2, and the liquid food 1 has a partition wall made of an insulating resin by a pressure pump 5 for sterilization, For example, the liquid flow is made inside the liquid flow path 4 made of a Teflon pipe. (* Teflon is a registered trademark name)
The liquid flow path 4 is installed between a pair of plate-like electrodes 3a and 3b, and the electrodes 3a and 3b are connected to a high frequency power source (not shown) to irradiate the liquid flow path 4 with the high frequency k. A gap g of a certain distance or more is required between the pair of plate-like electrodes 3a and 3b and the liquid flow path 4.

The liquid flow path 4 has a length sufficient to raise the temperature of the liquid food 1 within the liquid flow path 4 to a temperature close to 60 ° C. necessary for sterilization and below the protein coagulation temperature. For example, it sets so that it may pass through the liquid flow path 4 over time for 1 minute or more. FIG. 2 shows an enlarged elevation view of the liquid flow path 4.
In FIG. 2, 41 is an inlet pipe into which liquid food flows, 42 is an upstream header connected to the inlet pipe 41, 43 is a plurality of parallel flow paths mounted on the upstream header 42 and the downstream header 44, and 45 is a downstream header. 44 is an outlet pipe connected to 44.
Referring again to FIG. 1, the liquid food 1 heated to the temperature required for sterilization in the liquid flow path 4 is heated to exit the liquid flow path 4 and then sterilized in the heat retaining tank 6 via the pump 5. Is held for a certain period of time.

  According to the first embodiment, by irradiating a high frequency of 4 to 20 MHz from a pair of electrodes, the structure is simple as shown in FIG. The temperature can be increased to a sterilizable temperature around ℃, and temperature unevenness does not occur depending on the location unlike conventional plate heat exchangers, so the sterilization process can be easily performed without coagulating proteins. Can do.

In addition, because the object to be heated itself generates heat by high-frequency irradiation, it does not take time for heat transfer, and energy is given only to the object to be heated, so heating of the heat medium, preheating of the apparatus, etc. are unnecessary. There is an advantage of high energy efficiency.
Further, after the liquid food 1 is passed through the insulating liquid flow path 4, sterilization can be performed more reliably by pumping the liquid food 1 to the heat retaining tank 6 that is stored for a certain time for sterilization by the pump 5.

In addition, since the liquid food 1 flows in parallel through a plurality of parallel flow paths 43 mounted between the upstream header 42 and the downstream header 44, the high-frequency k is uniformly irradiated to the liquid food 1. 1 is heated uniformly without temperature variation.
The liquid flow path 4 can be easily cleaned if the upstream header 42 and the downstream header 44 are removed.

Next, a second embodiment of the present invention will be described. FIG. 3 is a system diagram of a temperature sterilization apparatus using high frequency irradiation according to the second embodiment, and FIG. 4 is an enlarged elevation view of the liquid flow path 4 in the second embodiment.
3 to 4, the insulating liquid flow path 14 forms a flow path between the high-frequency electrodes 13 a and 13 b, as shown in FIG. 4, from the inlet pipe 141 through the meandering flow path 142 to the outlet pipe 143. . Reference numeral 17 denotes a preheater that preheats the liquid food 11 before being heated at high frequency by exchanging heat with the liquid food that has been heated and sterilized. The preheated liquid food 11 flows into the liquid flow path 14. To do.

19 is a temperature control device that detects the temperature of the fluidized food 11 after irradiation between the high-frequency electrodes 13a and 13b and raises the temperature, changes the output of the high-frequency power source based on the detected value, and controls it to the set temperature. is there.
Reference numeral 20 denotes a jacket portion surrounding the flow path of the fluid food 11 provided in the heat retaining tank 16, and hot water 21 is supplied to the jacket portion 20.

In the second embodiment, the liquid food 11 having a temperature of 10 ° C. is sent to the preheater 17 by a pump (not shown) installed on the upstream side, and exchanges heat with the sterilized liquid food by the preheater 17. The temperature is raised to 40 ° C. Thereafter, while flowing through the meandering flow path 142 of the liquid flow path 14, the high frequency electrodes 13 a and 13 b are irradiated with high frequency, and the temperature is raised to 60 ° C. Then, the liquid flows from the outlet pipe 143 to the heat retaining tank 16. be introduced.
In the heat retaining tank 16, 62 ° C. hot water 21 is supplied to the jacket portion 20 to keep the liquid food 11 at a temperature of 60 ° C. The fluid food 11 exiting the heat retaining tank 16 exchanges heat with the fluid food 11 before the temperature rise by the preheater 17 and is cooled to 30 ° C.

According to the second embodiment, the liquid food 11 is heated and heated in advance by exchanging heat with the sterilized liquid food in the preheater 7 in advance. Improve dramatically.
Moreover, since the temperature of the fluidized food 11 is accurately controlled by the temperature control device 19 and then the hot water 21 having a predetermined temperature is supplied to the jacket portion 20 surrounding the fluidized food 11 in the heat retaining tank 16, the optimum temperature necessary for sterilization is obtained. Can be kept at temperature.
Further, since the liquid flow path 14 is constituted by the meandering flow path 142, the fluid food 11 can be heated and heated uniformly by high frequency, and the long flow of the meandering flow path 142 flows. A sufficient heating temperature raising effect can be achieved with the ability.

  FIG. 5 shows another embodiment of the liquid flow paths 4 and 14, and this embodiment is composed of a plurality of parallel flow paths 24 each having a different inlet and outlet, as shown in FIG. In this case, the flow rate of each flow path can be adjusted, and thereby the temperature of the fluidized food can be controlled more precisely.

  According to the present invention, for example, when a liquid food having an upper critical temperature is heated to near the upper critical temperature, by using a high frequency, the temperature can be raised to a set temperature accurately and uniformly with a simple structure. Even when heated for sterilization or the like, since it can be sterilized without causing coagulation or the like, a heating method that facilitates cleaning can be provided.

1 is a system diagram of a temperature sterilization apparatus according to a first embodiment of the present invention. It is an enlarged elevation view of the liquid flow path 4 in the first embodiment. It is a systematic diagram of the temperature rising sterilizer which concerns on 2nd Example of this invention. It is an expanded elevation view of the liquid flow path 14 in 2nd Example. It is an enlarged elevation view showing a third embodiment of the liquid flow path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Liquid food 2 Storage tank 3a, 3b, 13a, 13b High frequency electrode 4, 14 Insulating liquid flow path 5 Pumping pump 6, 16 Heat retention tank 17 Preheater 19 Temperature control device 20 Jacket part 21 Hot water 41, 141 Inlet pipe 42 Upstream header 24, 43 Parallel flow path 44 Downstream header 45, 143 Outlet pipe 142 Meandering flow path k High frequency

Claims (7)

  In a method for uniformly heating a liquid food having an upper critical temperature up to a temperature near the critical temperature, the liquid food is heated by flowing the liquid food into a liquid channel composed of an insulating partition, irradiated with a high frequency. An upper critical temperature comprising: a secondary heating step; and a secondary heating step of heating the fluid food heated in the primary heating step to a temperature near the critical temperature and maintaining the temperature for a predetermined time. A method for heating a fluid food.   The method for heating a liquid food product having an upper critical temperature according to claim 1, wherein the liquid channel is irradiated with a high frequency of 4 to 20 MHz.   2. The method for heating a liquid food having an upper critical temperature according to claim 1, wherein the partition walls of the liquid flow path are made of an insulating resin.   2. The method for heating a liquid food having an upper critical temperature according to claim 1, wherein in the secondary heating step, the liquid food is put into a heat retaining tank maintained at a temperature near the critical temperature.   In the case where the fluid food is a food containing protein such as soybean protein or animal protein, the fluid food is heated to a temperature of 45 to 55 ° C in the primary heating step, and is 64 ° C or less in the secondary heating step. The method for heating a fluid food having an upper critical temperature according to claim 1, wherein the temperature is maintained at that temperature.   The method for heating a liquid food product having an upper critical temperature according to claim 1, wherein the liquid channel is composed of a plurality of parallel channels installed between an upstream header and a downstream header. .   2. The upper critical temperature according to claim 1, wherein the preheated fluid food is preheated by exchanging heat with the fluid food heated in the secondary heating step on the upstream side of the primary heating step. A method for heating a fluid food.

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