JP2692411B2 - Method of thawing food by high frequency and heating food at low temperature - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of thawing frozen food or heating in vacuum low temperature cooking at high frequency.

[0002]

Conventionally, thawing of frozen food is natural extract, a method such as refrigerator-extracting or high-frequency thawing have been used. It is known that high frequency thawing can thawing in a short time. However, high-frequency thawing causes uneven thawing due to uneven distribution of high frequencies, and if a part of food is thawed first due to the shape of the food, the high frequency is concentrated in the thawed part due to the difference in dielectric loss between ice and water, and that part Was heated further and sometimes boiled. In order to solve this problem, for example, as shown in Japanese Patent Publication No. 2-122929, the high frequency output is divided into three stages according to the heating condition of the food, and the high frequency output is set for each category to select the type of food. The method of calculating the time for each segment and defrosting it according to the amount and amount has come to be used.

On the other hand, the vacuum low temperature cooking method is a recently developed method, in which food materials are vacuum-packed and fired (heated) in this state, and vegetables and fruit trees are at 85 to 95 ° C. and meats are at 58 to 95 ° C. It is a method of cooking at 68 ° C for a long time and eating, or storing at a low temperature after cooking and reheating when eating. This cooking method is rapidly spreading because it is cooked at a low temperature so that the flavor of the food material can be utilized and preserved. However, with this cooking method, it is difficult to control the heat retention during cooking or during reheating, and it has been said that high-frequency heating is not suitable because the temperature distribution becomes large. Therefore, heating in vacuum low-temperature cooking has been performed while controlling the temperature of hot water or a steam oven.

[0004]

However, the above-described method has the following problems.

That is, when thawing, most of the problems of simmering can be solved by irradiating the high frequency wave in three steps as described above, but even in this method, the high frequency output and the time can be set well depending on the type and weight of the food. There was a problem that it could not be done and the temperature distribution became large and it boiled. This is because the high frequency output currently used in the decompressor is as shown in FIG. That is, even if the output is divided into three stages of high, medium, and low, the irradiation intensity at the time of irradiation in each stage, that is, the irradiation output of the high frequency per unit time is the same. The only difference is the irradiation time or the interval between the irradiation time and the rest time. In FIG. 5, the irradiation intensity of the high frequency at the required time t ₀ of each stage is the same w ₀ , but the irradiation time and the irradiation stop time are different for each stage. Therefore, immediately after irradiation of a certain portion for a certain period of time, there is no difference in the amount of energy received at that portion between high, medium and low. Therefore, the irradiated part is heat conduction, convection,
Except for heat dissipation by radiation, the temperature rises in that part. Microscopically, it is considered that the temperature rise in that part is high and some of the constituents of the food change at this temperature.

Further, when the vacuum low temperature cooked food is heated in a hot water bath or a steam oven, it takes time to reach a predetermined temperature because the heating is performed from the outside. For this reason, high-frequency heating may be considered, but when cooking food consisting of various ingredients such as vacuum low-temperature cooking is subjected to high-frequency irradiation, the temperature rises differently because some foods absorb the high-frequency wells and those that do not. However, there was a problem that a large temperature distribution was generated in the cooked product and it was difficult to put it into practical use.

The present invention is intended to solve the above problems and provide a high frequency heating method in which a temperature distribution hardly occurs.

[0008]

In order to solve the above-mentioned problems, the present invention provides a method of heating food by repeating high frequency irradiation and stopping, and high frequency irradiation within a time range of 3 ± 0.75 seconds. Is a method of thawing and heating.

[0009]

In the present invention, the temperature distribution can be narrowed by the above method.

That is, when a food is irradiated with a high frequency, the irradiated part is heated and its temperature rises. After irradiation for 3 ± 0.75 seconds, the temperature of the portion rises, but at this irradiation time, the temperature of the portion does not change so much and the temperature difference is almost eliminated by thermal diffusion during the next irradiation stop time.
By repeating such a state, the food can be thawed or heated without making a large temperature difference.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

Example 1 Usually, when thawing a frozen food, there are three major stages as shown in FIG. That is, the first stage is a stage in which the temperature is -5 ° C or lower, the second stage is a stage in which the temperature is in the range of -5 to 0 ° C, and the third stage is a stage in which the temperature is 0 ° C or higher.

When the temperature in the first step is -5 ° C or lower, the frozen food has a small dielectric loss and is easily passed through a high frequency. That is, since the high frequency absorption is small and the high frequency half depth (the distance traveled in the object before the high frequency becomes half of the initial strength) is large, a temperature difference between the surface and the center of the object to be thawed does not occur so much. Therefore, at this stage, a high output is irradiated to speed up the thawing. The temperature range of the second stage is the maximum ice crystal formation zone, which is about 8 necessary for the phase transition from water to ice.
It requires 0 calories / gram and is the most energy-consuming stage during thawing. A temperature difference is likely to occur between the surface and the center of the thawed object, and when the surface melts, the surface temperature rises more and more due to the above reasons, the water generated by the melting of ice cannot stay in the food, and the umami component outside There is a risk of being washed away with. Therefore, in order to prevent a temperature difference, the output is reduced from the first stage and the thawing is performed for a long time. In the third stage, the thawing is almost completed and the temperature rises due to the specific heat of water, so that the dielectric loss is large and the high frequency absorption is large, so the output is further reduced compared to the second stage.

The thawing is performed in the above-mentioned three stages, but in the present invention, the radiating time of the high frequency is set to 3 seconds in each stage in the thawing. The output level depends on the length of the irradiation stop time. Reference time 3 seconds is the number values obtained experimentally, which when irradiated with high-frequency to be thawed, a time when the temperature rise of the irradiated does not cause such cooked by the reasons, the following irradiation It is considered that this is due to the time during which heat is diffused and the temperature tends to be uniform during the stop time. However, the reference time will vary slightly depending on the type, shape, and amount of food. This time is experimentally ± 20% of 3 seconds, that is, ± 0.75 seconds. When the time was longer than this, that is, when the time was longer than 3.75 seconds, the temperature distribution on the surface and the temperature difference from the inside became large. In addition, when the time is shorter than 2.15 seconds, the thawing time becomes long and the advantage of high frequency thawing decreases.

Examples will be shown below. Frozen food was inserted into a high-frequency heating device having an output of 500 W and having a high-frequency power supply port at the top and bottom and was thawed by high-frequency irradiation. FIG. 2 shows changes with time in the surface temperature and the central temperature at that time. The thawing method divided the high frequency output into three stages, first to third stages. The feature of the present invention is that the high frequency irradiation time of each stage is irradiated for 3 seconds at the rated output, then the irradiation is stopped for a fixed time, and then the irradiation is stopped for 3 seconds and then for a fixed time. It is a method of repeating the stop time and heating. That is, the irradiation time t at each stage shown in FIG.
_It means that _{1 is set} to 3 seconds. The output of each stage is the total irradiation time of that stage, that is, 3 times the number of times of irradiation divided by the time required for that stage. 1st stage, 2nd stage, 3rd stage
Since the irradiation stop time becomes longer in the order of stages, the output per unit time is decreased in the order. However, in FIG. 2, the irradiation time in the same step is constant in each step, but this does not necessarily have to be the same. Further, an irradiation stop time is provided between each step, but this is provided in order to reduce the difference between the surface temperature and the central temperature, and it is not necessarily provided depending on the amount and shape of the frozen food. The above conditions can be easily programmed by inputting an experimentally determined coefficient into the high-frequency heating device according to the type and amount of food.

Example 2 Vacuum low temperature cooking is generally stored in a chilled, heating up to about 60 ° C. when eating. In the case of high frequency heating, the surface and the inside of the food material are heated at the same time, so the amount of time required varies from a few tens of seconds to a few minutes depending on the amount. It can be reheated in 1/10 the time.

FIG. 3 shows a block diagram of the high-frequency heating device. Power supply ports 2 and 3 are provided above and below the heating chamber 1 into which the object to be heated is inserted.
Is provided and the high frequency generated by the high frequency generator 4 is applied from above and below the object to be heated. The operation unit 6 is composed of a keyboard for selecting cooking conditions such as thawing and low temperature cooking and heating conditions such as the amount of food. When these are set, the control unit 5 controls the output of the high frequency generator 4 according to these settings. .

FIG. 4 shows the irradiation method, the surface temperature, and the temperature of the central portion when the vacuum low-temperature cooked food is inserted into a high-frequency heating device with an output of 500 W having upper and lower high-frequency power supply ports and heating is performed by high-frequency irradiation. Show the relationship. The feature of the present invention is that the irradiation is stopped at a high output for a short irradiation stop time to raise the temperature of the food material, and then the irradiation stop time is taken to make the temperature of the surface and the inside uniform. This is because the food was irradiated with a long so-called low output to bring the food to a predetermined temperature, and the irradiation time t ₁ was set to 3 seconds as a reference.

This is because the temperature of the foodstuff is 0 ° C. or higher, so that the high frequency is well absorbed, and the high frequency half-depth is short, so that the temperature difference between the part irradiated with the high frequency and the non-irradiated part is likely to be large. This is because, if irradiated for a long period of time, the temperature of the part rises and the part softens and loses its shape, or the flavor of the food material deteriorates. The irradiation time of 3 seconds is a time in which the absorbed heat and the dissipated heat are in good equilibrium and the shape is not deformed or the temperature is partially raised too much. However, this time will vary slightly depending on the type, shape, and quantity of food. This time is experimentally ± 20% of 3 seconds, ie ± 0.75
Seconds. When the time was longer than this, that is, when the time was longer than 3.75 seconds, the temperature distribution on the surface and the temperature difference from the inside became large. Further, if the time is shorter than 2.15 seconds, the heating time becomes long and the advantage of high frequency heating becomes small.

Further, the reason why the irradiation stop time is provided between the high output and the low output is to reduce the temperature difference between the surface and the inside as described above, and it is not always necessary to provide it depending on the shape and amount of the food. Absent.

[0021]

As described above, according to the method of thawing foods and heating foods at a low temperature by the high frequency wave of the present invention, the following effects can be obtained.

(1) The irradiation time of one high frequency is 3 ± 0.
Since it is set to 75 seconds, the temperature difference between the surface and the central portion is small, and the amount of drip which is an umami component is small, so that thawing can be performed without partial boiling due to overheating.

(2) The irradiation time of one high frequency is 3 ± 0.
Since it is set to 75 seconds, the temperature difference between the surface and the central portion is small, and the heating can be performed without causing the shape loss due to overheating.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between heating time and temperature of frozen food.

FIG. 2 is a temperature change characteristic diagram during thawing by an example of the high frequency irradiation method of the present invention.

FIG. 3 is a block diagram of a high frequency heating device.

FIG. 4 is a temperature change characteristic diagram of food during heating according to an example of the high frequency irradiation method of the present invention.

FIG. 5 is a diagram showing an example of a conventional high-frequency irradiation method.

Claims (5)

(57) [Claims] 1. A method of thawing a food by high frequency, wherein irradiation of high frequency is repeated within a time range of 3 ± 0.75 seconds when the food is thawed by repeating high frequency irradiation and stopping. 2. A thawing method comprising a first step of -5 ° C. or lower, a second step in the range of -5 to 0 ° C., and three steps of 0 ° C. or higher, wherein the stop time at each step is different. -extracting method of food due to the high frequency. 3. A method of low temperature heating of food by high frequency, wherein high frequency irradiation is performed within a time range of 3 ± 0.75 seconds when heating food by repeating high frequency irradiation and stopping. 4. A vacuum-packaged food product is housed in a heating chamber, and the food product is irradiated with high-frequency energy to produce the food product at 100.degree.
In the method of heating a food to be heated to the following temperature, when the food is heated by repeating high-frequency energy irradiation and stopping, a low-frequency heating method of high-frequency food by high-frequency energy irradiation in a time range of 3 ± 0.75 seconds. 5. The method for heating food by repeating irradiation and stop of high-frequency energy to heat a food, wherein the stop time of high-frequency energy is different between the initial stage and the final stage of heating. Method of low temperature heating of food by high frequency.