JPH07289173A - Method for concentrating, cooking and sterilizing food - Google Patents

Abstract

PURPOSE:To thermally concentrate and sterilize a food, while preventing the thermal deterioration of the food. CONSTITUTION:The method for concentrating, cooking and sterilizing a food vacuum chamber 1, and subsequently irradiating the food raw material 10 with microwaves through a wave guide 4 in a vacuumapplied state to immediately and uniformly heat the interior of the food raw material and immediately produce and keep a boiling state at 40-80 deg.C for the concentration and sterilization of the food raw material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for concentrated cooking and sterilization of foods in which food materials are heated under reduced pressure for concentrated cooking and sterilization.

[0002]

2. Description of the Related Art Conventionally, as a concentrated cooking method for foods, there are a heating evaporation method, a vacuum evaporation method, a freeze-drying method, a method using a reverse osmosis membrane, etc. Examples of concentrated foods include jam, concentrated juice and paste. Etc. are known. A conventional method for producing a concentrated food product will be described below by taking a jam as an example.

To make jam, first of all, fruit, sugar,
Put food ingredients such as pectin in a container, heat the container from the outside with a gas, heat medium, plate heater, etc. to mix the food ingredients in the container while heating, and then continue heating under normal pressure to concentrate. After that, the process of filling the finished product in a container such as a bottle or a can, sealing with a cap, sterilizing with hot water, and then cooling. However, in such a conventional method, during heating and concentration, the food material is heated and maintained at a boiling temperature near 100 ° C, and thus the obtained jam has a darker color tone than the original fruit, Further, there is a problem that the flavor is reduced and the loss of vitamin C and the like due to heat is large.

Therefore, in order to improve such problems,
A method of heating and concentrating a food material under reduced pressure is known. In this method, by heating the food material under reduced pressure, boiling is caused at a temperature lower than 100 ° C., and the deterioration of fruits due to the heat as described above can be reduced.

[0005]

However, the conventional method has the following problems because it uses the external heating such as gas or plate heater to heat the food material in the container. That is, heat is transferred to the food material from the wall surface of the container containing the food material due to external heating, but as the food material is heated and concentrated, the viscosity gradually increases and convection becomes less likely to occur, resulting in heat transfer. Becomes worse. Therefore, in order to perform heating rapidly, it is necessary to raise the temperature of the wall surface of the container considerably higher than the boiling temperature of the food material, but in that case, the viscosity of the food material is high and it is difficult to flow, so even in the boiling state There was a problem in that the difference in temperature caused by the temperature was considerably increased, and some parts were overheated to cause charring of the inner wall of the container or deterioration of food. In order to avoid this, if the heat input is lowered to lower the wall surface temperature of the container, the time for heat transfer becomes longer, and the deterioration of flavor, freshness, etc. is not improved,
Further, since a low temperature part is generated in the food material, there is a problem that sterilization is insufficient in the low temperature part.

The present invention has been made in view of the above-mentioned conventional problems, and it is necessary to prevent the deterioration of flavor, freshness, etc. due to heat by shortening the heating and concentrating time and reducing the temperature distribution. An object of the present invention is to provide a concentrated cooking and sterilization method of foods that can be sterilized easily.

[0007]

Means for Solving the Problems As a result of studies to solve these problems, the inventors of the present invention have found that the boiling point under reduced pressure is 40 ° C at which the effect of sterilization begins to appear, and the freshness is not easily lost at 80 ° C.
If it can be carried out promptly at a temperature within the range up to, it is possible to carry out sterilization while minimizing food deterioration, and if internal heating by microwave is used as a means to achieve this, it will be rapid and uniform. The present invention has been completed by finding out that various heating is possible. That is, the present invention is
The food raw material is placed under a reduced pressure such that the boiling temperature of the food raw material is in the range of 40 to 80 ° C., and in that state, microwave irradiation is performed on the food raw material to internally heat the food raw material, and
A summary is a method for concentrated cooking and sterilization of foods, which comprises rapidly producing and maintaining a boiling state at a temperature in the range of 0 to 80 ° C. for concentration and sterilization.

Examples of foods produced by the method of the present invention include jam, concentrated juice, paste and the like.

The microwave frequency used in the present invention is 91.
Although 5 MHz, 2450 MHz and the like are conceivable, it is common to use 2450 MHz in Japan, and it is convenient to use this.

[0010]

In the above-mentioned method of the present invention, the moisture in the food material is internally heated by the microwave so that a uniform and rapid heat input to the food material is possible. A boiling state is rapidly generated and maintained at a temperature within the range of C and a small temperature distribution. For this reason, concentrated cooking can be performed in a short time, and almost no part exceeding 80 ° C is generated in the raw material of the food, so that deterioration of the food hardly occurs and a food excellent in color tone, flavor, freshness, etc. is obtained. be able to. In addition, 40 in food ingredients
Almost no part lower than ° C is generated, so that sterilization failure does not occur.

As described above, the method of the present invention is to bring the food material into a boiling state at a temperature within the range of 40 to 80 ° C. by subjecting the food material to a reduced pressure, and to condense and sterilize the food material at the boiling temperature. However, it is usually preferable to adopt the following two methods for the specific implementation. A method in which the processing temperature (boiling temperature) of food ingredients is kept constant during the processing period. A method of changing the processing temperature (boiling temperature) of food ingredients during the processing period with an appropriate time schedule. Here, these treatment temperatures (boiling temperature) are determined by the pressure applied to the food material, so when carrying out the method of the present invention, the pressure applied to the food material (reduced pressure) is set so as to obtain the desired treatment temperature. And it will be controlled.

Hereinafter, the setting of the processing temperature (boiling temperature) and the pressure setting of the food material will be described. Generally, it is preferable to concentrate the food material at a low temperature in terms of color tone, flavor and the like. From this point, it is preferable to set the pressure at which the processing temperature (boiling temperature) becomes low. However, certain characteristics of food quality may be desirable at higher temperatures. For example, in the case of producing strawberry jam, the one treated with a pressure of 55 Torr and treated at a treatment temperature of 40 ° C, which is the boiling point of the strawberry jam, is close to the original fruit and has a fresh color and aroma. Can be produced, but the odor of strawberries remains. On the other hand, a product treated with a pressure of 355 Torr and treated at a treatment temperature of 80 ° C, which is the boiling point of the food, has a blue odor but disappears in color and aroma. The feature appears. Further, for sterilization, a higher temperature is preferable, and from this point, it is preferable to set a pressure at which the treatment temperature (boiling temperature) becomes high. As described above, the treatment temperature (boiling temperature) has a great influence on the food quality and the sterilization effect, and therefore, the treatment temperature should be set in consideration of these factors.

For example, in the case where the food material is treated at a constant treatment temperature (boiling temperature) during the treatment period, it should be within the range of 40 to 80 ° C in consideration of the characteristics required for the intended food. One processing temperature is set and the pressure applied to the food material is set accordingly. Then, while operating this set pressure on the food material and maintaining it at the set pressure, by internally heating the food material by microwave irradiation, a boiling state is rapidly caused and maintained,
The food material is brought to a boiling state at a predetermined processing temperature, and concentrated and sterilized. In this way the processing temperature (boiling temperature)
In the case of treating with constant, it is sufficient to keep the pressure applied to the food material constant during the treatment period, so that it is easy to carry out, and since the treatment temperature is always constant, there is an advantage that the quality is stable. can get.

Even when the processing temperature (boiling temperature) of the food material is changed according to an appropriate time schedule, the processing temperature is determined in consideration of the characteristics required for the intended food. The treatment temperature and the period are set in consideration of the treatment purpose at the treatment temperature (for example, mainly for the purpose of concentration or for the purpose of sterilization). For example,
The processing period of the food material can be divided into a period of mainly performing a concentration process and a period of mainly performing a sterilization process, and a preferable processing temperature and period can be set for each. In this case, the boiling temperature of the food material is maintained at a first temperature in the range of 40 to 80 ° C to perform the desired concentration, and then the boiling temperature of the food material is higher than the first temperature. It is preferable to use a two-stage schedule in which the temperature is changed to the second temperature and desired sterilization is performed in a short time. If such a two-stage schedule is adopted, even if a long time of about 30 minutes is required for the concentration process, by setting the first temperature at which the concentration process is performed to a relatively low temperature, the flavor, freshness, etc. of food can be reduced. It is possible to prevent the deterioration of food, and it is possible to carry out sufficient sterilization even in a short time by setting the second temperature for carrying out the sterilization treatment to a high temperature. Absent. Therefore, it is possible to perform necessary concentration and good sterilization while preventing deterioration of food. Specific examples of the two-stage schedule include a two-stage schedule of 40 ° C. × 30 minutes + 80 ° C. × 2 minutes. In this case, the necessary concentration is almost completed in the first 30 minutes without impairing the freshness such as flavor, and the sufficient sterilization can be performed in the second 2 minutes. Since microwaves can perform uniform heating throughout the interior, the temperature can be rapidly raised to 80 ° C, which is advantageous for sterilization, and 80 ° C even in a short time of 2 minutes.
The effect of C sterilization can be obtained. Needless to say, it is also possible to further divide the period during which the concentration process is mainly performed and perform the concentration process at different process temperatures.

The method of the present invention may also be used in combination with conventional heat-concentration cooking means. For example, vacuum concentration cooking by external heating is performed at a low treatment temperature (for example, around 40 ° C.), and after a certain degree of concentration, the food material is subjected to a high treatment temperature (for example, 80 ° C.) under reduced pressure by the method of the present invention. By performing microwave heating (near C) for a short time to perform final concentration and sterilization, a high sterilization level can be obtained without causing much deterioration of food.

In carrying out the method of the present invention, it is necessary to uniformly heat and raise the temperature of the food raw material. For that purpose, a certain technique of microwave engineering is adopted to make the food raw material even under reduced pressure. The microwave may be applied. The depth of the food material is such that microwaves are absorbed almost evenly. A container such as a spherical flask-shaped container may be used in consideration of bumping as a container for the food material. Since microwaves are also used as the material of the container, it is preferable to use a material with as little dielectric loss as possible, for example, glass, polyolefins such as polyethylene and polypropylene, fluororesins, and silicone resins.

[0017]

【Example】

Example 1 The apparatus shown in FIG. 1 was prepared as an apparatus for carrying out the method of the present invention. That is, in FIG.
Is a decompression chamber, and is configured to be sucked in a decompressed state by the vacuum pump 2 and to be internally radiated with microwaves generated by the microwave oscillator 3 through the waveguide 4. Further, in order to maintain the inside of the decompression chamber 1 at a desired decompression state, a pressure sensor 5 for detecting the pressure inside the decompression chamber 1, a ventilation pipe 7 provided with a solenoid valve 6, and an electromagnetic wave in response to a signal from the pressure sensor 5 are used. A control device (not shown) for opening and closing the valve 6 is provided. Furthermore, since sterilization is performed at the same time as cooking in the decompression chamber 1, it is necessary to sterilize the decompression chamber, and in the process of returning to normal pressure from the time of depressurization, a vent pipe is provided so as not to take in various bacteria in the atmosphere. A filter 8 for removing bacteria is attached to 7. In addition, 9 is a flat-bottomed flask-shaped container set in the decompression chamber 1, and 10 is a food material to be cooked contained therein.

As a food material 10, 150 g of a mixed material of strawberry 500: sugar 250: pectin 1: citric acid 1 was placed in a flask-shaped container 9 having a capacity of 1 liter and set in the decompression chamber 1. Then, with the vacuum pump 2, the pressure in the decompression chamber 1 was reduced to 55 Torr, which is the pressure at which the raw material boils at 40 ° C., and was maintained at a microwave output of 300 W for 30 minutes to perform microwave irradiation. 10 was boiled under reduced pressure at about 40 ° C. and concentrated and cooked to obtain 107 g of strawberry jam.

Comparative Example 1 150 g of the same raw material as in Example 1 was used, a plate heater was placed on the bottom surface of the flask-like container 9 for heating, and the plate heater output was 300 W under the same reduced pressure conditions as in Example 1. The mixture was heated and heating time was 30 minutes to obtain 133 g of strawberry jam. The strawberry jam obtained in each of Example 1 and Comparative Example 1 was sensory-evaluated by a panel of 20 people. The results are shown in Table 1.

[0020]

[Table 1]

As is apparent from Table 1, in Comparative Example 1, the concentrated cooking was insufficient and the flavor was deteriorated, but in Example 1, these were remarkably improved.

[Embodiment 2] Using the same apparatus and the same raw material as in Embodiment 1, the pressure in the decompression chamber 1 was 55 Torr (reduced pressure boiling temperature 40 ° C.) 92.5 Torr (reduced pressure boiling temperature 50 ° C.) 150 Torr (Depressurized boiling temperature 60 ° C) was set, and a jam was produced at a microwave heating output of 300 W and a microwave irradiation time of 30 minutes. The treated jam was aseptically taken out, brought into a sterile room, the amount of evaporated water was corrected, and 1 g of each was dispensed into a sterilized petri dish. 10 cc of sterilized culture agar was poured into the medium to make a medium, and the medium was cultured at 30 ° C. for 48 hours in an incubator to count the number of bacteria. The results are shown in Table 2.

[Comparative Example 2] The same number of jams were manufactured under the conditions corresponding to those of Example 2 using the plate heater in the same manner. The obtained jam was cultivated by aseptic operation in the same manner as in Example 2, and the number of bacteria was counted. At the same time, in contrast, the raw material before the heat treatment was cultured and the number of bacteria was counted. The results are shown in Table 2.

As is clear from Table 2, the sterilization state of the jam obtained in Example 2 was found to be improved as compared with the corresponding Comparative Example 2 at each temperature. This is probably because the temperature distribution in Example 2 was smaller than that in Comparative Example 2 and no abnormally low temperature portion was generated.

[0025]

[Table 2]

Example 3 Using the same equipment and the same raw material as in Example 1, microwave irradiation was carried out at the reduced pressure boiling temperature shown in Table 3 and for the time shown in Table 3 to perform concentrated cooking. In addition, the total weight (weight including the flask-shaped container 9) before and after the treatment was measured to measure the weight loss (water evaporation amount). The results are shown in Table 3.

[Comparative Example 3] Similarly, a plate heater was used to perform concentrated cooking under the conditions shown in Table 3, and the total weight before and after the treatment was measured to determine the weight loss. The results are also shown in Table 3. The temperature of the bottom wall surface of the flask-shaped container 9 at this time was measured, and the results are also shown.

When the raw materials in the flask-shaped container after the concentrated cooking in each of Example 3 were observed, no abnormality was found under any of the conditions. On the other hand, in the case of Comparative Example 3, in all cases, some sticking was observed at the bottom of the container. This is probably because the bottom of the container is at a high temperature as shown in Table 3. Incidentally, in Example 3, the phenomenon that the temperature of the container wall became higher than the processing temperature was not observed. Further, as is clear from Table 3, it was confirmed that in Example 3, compared with Comparative Example 3, even at the same temperature, the concentration rate was faster and the sticking hardly occurred.

[0029]

[Table 3]

[0030]

EFFECTS OF THE INVENTION As is clear from the above description, according to the present invention, by irradiating a food material with microwaves, the food material is internally heated and a substantially uniform rapid heat input is possible. By decompressing so that it boils at a temperature in the range of 40 to 80 ° C, it is possible to maintain the boiling state in the range of 40 to 80 ° C with a small temperature distribution. In addition, there is little discoloration of food, deterioration of flavor, freshness, and the like, and it has an effect that concentrated cooking and sterilization can be performed in a short time.

Here, the boiling temperature of the food material is set to 40-80.
When the temperature is kept constant within the range of ° C, it is sufficient to keep the pressure applied to the food material constant, so that it is easy to carry out and the food quality can be kept uniform. can get. The boiling temperature is 40 to 80 ° C.
The desired concentration is maintained at a first temperature within the range of, and then changed to a second temperature higher than the first temperature, and if a method of performing desired sterilization in a short time is adopted, The effect that the bactericidal effect can be greatly improved can be obtained without causing much discoloration, flavor, freshness, etc. of the food.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus used for carrying out the method of the present invention.

[Explanation of symbols] 1 decompression chamber 2 vacuum pump 3 microwave oscillator 4 waveguide 5 pressure sensor 6 solenoid valve 7 ventilation pipe 8 filter 9 flask-shaped container 10 food material

Claims (3)

[Claims] 1. A food material having a boiling temperature of 4
It is placed under a reduced pressure in the range of 0 to 80 ° C, and in that state, the food material is subjected to microwave irradiation to internally heat the food material, and boiling at a temperature in the range of 40 to 80 ° C. A method for concentrated cooking and sterilization of foods, which comprises rapidly producing and maintaining a state for concentration and sterilization. 2. The boiling temperature of the food material is 40 to 80.
2. The method of concentrated cooking and sterilization of food according to claim 1, wherein the concentration and sterilization are carried out while maintaining a constant temperature within a range of ° C. 3. The boiling temperature of the food material is 40-80.
Maintain the first temperature in the range of ° C to achieve the desired concentration,
After that, the boiling temperature of the food material is changed to a second temperature higher than the first temperature, and desired sterilization is performed in a short time, concentrated cooking and sterilization of the food according to claim 1. Method.