JP6544967B2 - How to freeze food - Google Patents

Description

  The present invention relates to a method of freezing food. More specifically, the present invention relates to a freezing method of a foodstuff which can suppress the growth of ice crystals inside the foodstuff even if it is a thick foodstuff or a foodstuff having a difference in composition inside the foodstuff.

  Frozen storage has been used as a method for long-term preservation while maintaining freshness of meat, fresh fish and other foods (hereinafter simply referred to as "foodstuffs"). Among these, it is generally well known to carry out rapid freezing by placing a food material from a normal temperature (external temperature) at once into a freezer at -30 ° C to -45 ° C.

  However, rapidly frozen food products have not been able to completely prevent the deterioration of quality and the deterioration of freshness such as color tone change, taste deterioration, occurrence of drip (runoff of liquid juice at the time of thawing). This is because the water contained in the food freezes and the ice crystals grow to destroy the cells.

  Enlargement of ice crystals occurs when the time of passing through the ice crystal formation temperature zone is slow during freezing. Therefore, as a method of freezing while suppressing the expansion of ice crystals, food material freezing technology utilizing supercooling is in the spotlight. This technique is intended to prevent ice crystal hypertrophy of water in cells by instantaneously freezing water from a supercooled state, and is considered to be able to suppress the destruction of cell membranes.

  In order to freeze water instantaneously from a supercooling state, generally a method of giving a temperature stimulus is known (patent document 1). Patent Document 1 discloses a technique for rapidly freezing an object to a freezing point of -40 degrees after cooling the object so as not to freeze to a temperature in the range of 0 ° C. to -5 ° C. based on the freezing point ing.

JP 2008-20116 A

  By the way, in order to freeze the water of the supercooling state in foodstuffs instantly, it is preferred that stimulus is added to the whole foodstuff. However, thick foods and foods (for example, red meat and fat, etc.) having a difference in composition within the food produce a difference in transmission of stimulation. As a result, the supercooled water near the surface layer of the food freezes instantly, but ice crystals may grow inside the food and cells may be destroyed.

  The present invention has been made in view of the above problems. That is, it is an object of the present invention to reliably transmit stimulation to the inside of the food even if it is a thick food or a food having a different composition inside the food, and suppress the enlargement of ice crystals generated inside the food. Freezing method.

  The present inventors examined a method of transmitting the stimulation to the inside of the food. And by simultaneously applying different stimuli, it is possible to reliably transmit the stimulus to the inside of the food even if it is a thick food or a food having a difference in composition inside the food, and shift to a frozen state It has been found that the present invention can be accomplished.

  In order to solve the above problems, the present invention is a freezing method of a foodstuff, wherein freezing of the foodstuff in which the supercooled water in the foodstuff is frozen by simultaneously giving at least two different stimuli to the foodstuff which has been supercooled Provide a way. Furthermore, in the freezing method of the present invention, it is preferable that the different stimuli are a thermal stimulus and a physical stimulus.

  According to this configuration, by simultaneously applying at least two different stimuli, it is possible to reliably transmit the stimulus to the inside of the food even if it is a thick food or a food whose composition is different inside the food. . As a result, ice crystals are enlarged inside the shrimp like slow freezing and the cells are not destroyed.

  According to the present invention, it is possible to suppress the deterioration of quality and the deterioration of freshness such as the color tone change of food, the deterioration of taste and the occurrence of drip (the outflow of liquid juice upon thawing) caused by the expansion of ice crystals.

  Hereinafter, a preferred embodiment for carrying out the present invention will be described by taking a shrimp freezing apparatus combining thermal stimulation and physical stimulation as an example. The embodiment described below shows an example of a representative embodiment of the present invention, and the scope of the present invention is not narrowly interpreted.

  The freezing apparatus according to the present invention comprises at least a subcooling freezer and a quick freezing machine. And, the supercooling freezer and the quick freezing machine are arranged to be continuous.

  In the freezing apparatus according to the present embodiment, the tip of the conveyer at the inlet side of the quick freezing machine is disposed below the outlet side conveyor of the subcooling freezer. At this time, the height difference of the conveyor conveyance surface contributes to the magnitude of the impact applied to the food. Although the height difference with the conveyor conveyance surface varies depending on the food, it is preferably 10 cm or more, more preferably 20 cm or more, and still more preferably 30 cm or more. If the difference in height is low, the impact applied to the food becomes weak, so the impact is not transmitted to the inside of the food, and the supercooled water inside the food can not be transferred to the frozen state.

<Supercooled freezer>
A subcooling freezer is a freezer for subcooling food. Here, the term "supercooling" refers to a state of being cooled so as not to freeze even at a temperature below the freezing point.
The supercooled freezer according to the present invention has a space provided with an inlet and an outlet. In the storage, an endless conveyor rotates between the inlet and the outlet. A portion of the inlet side conveyor extends out of the subcooling freezer. Also, a part of the conveyor on the outlet side extends into the quick freezer to guide the subcooled food into the quick freezer described later. Furthermore, a metal pad is placed on the conveyor.

  The inside of the supercooling freezer is preferably set so as to have a temperature condition of -3 to -7 ° C based on the freezing point of the food. If the temperature is higher than -3 ° C, the water in the center of the food will not be supercooled, and if the temperature is lower than -7 ° C, it may not be supercooled but may be frozen. In the case of the shrimp of the present embodiment, since the freezing point is around -3 to -5 ° C, it is preferable to set to -7 ° C.

  The time required to bring the food into the subcooling state varies depending on the food, but it is preferable to expose the material under the above temperature conditions for at least 30 minutes or more. If the time is less than 30 minutes, the water in the center of the food will not be supercooled. In the case of the shrimp of the present embodiment, it is preferable to expose for 40 minutes. In the present embodiment, the conveyor speed may be adjusted so as to be exposed for a predetermined time.

  Examples of the metal bat placed on the conveyor include, but are not limited to, metals having high thermal conductivity and which are not easily corroded, such as stainless steel, aluminum and titanium. In this embodiment, although the case where the metal bat is placed on the conveyor has been described as an example, a flexible metal plate may be used as the belt of the conveyor belt, or a metal plate may be used on the belt surface. May be provided.

<Fast freezing machine>
The quick freezer is a device for transferring the supercooled water in the food to a frozen state. In other words, it is an apparatus for freezing the subcooled food.
The quick freezing machine according to the invention also has a space with an inlet and an outlet. In the storage, an endless conveyor rotates between the inlet and the outlet. In addition, a part of the conveyor on the outlet side has a shape protruding for discharging the frozen food out of the quick freezer.

  The temperature in the rapid freezer is preferably set to a temperature condition lower than that of the supercooled freezer, so as to be a temperature condition of -15 to -40 ° C. based on the freezing point of the food, It is preferable that it is set. If the temperature is higher than or equal to the temperature in the subcooler, the supercooling state of the body is released and the food does not freeze. On the other hand, even if the temperature is lower than -40.degree. C., there is no difference in the effect, and the cost is increased. In the case of shrimp according to the present embodiment, it is preferable to set the setting temperature of the quick freezing machine between -20 ° C and -40 ° C.

  As a conveyor of a quick freezing machine, it is preferable that a metal plate is provided on a conveyor belt, or the belt itself is a flexible metal plate. Examples of the metal include metals having high thermal conductivity and which are not easily corroded, such as stainless steel, aluminum, titanium and the like. Also, a metal bat may be provided on the conveyor.

  Next, the usage method of the freezing apparatus of a present Example is demonstrated.

  First, the shrimps are arranged so that they do not overlap with the bats placed on the conveyor of the supercooled freezer. The vats lined with shrimps move into the supercooled freezer set at -7 ° C according to the movement of the conveyor to bring the shrimps into a subcooled state. At this time, it is preferable that cold air supplied into the supercooling freezer does not directly hit the shrimp. In addition, when moving in the supercooling freezer, it is preferable to move so as not to generate vibration. It is for preventing that only the surface layer of shrimp freezes by vibration.

  After the subcooling is completed, the shrimp is transferred onto a conveyor in a quick freezing machine set at -35 ° C. At this time, the shrimp is in a state of supercooling due to the shock when it falls from the conveyor of the supercooling freezer to the conveyor of the quick freezer and the temperature stimulation from the metal plate on the conveyor cooled to a lower temperature than in the supercooling freezer. It immediately shifts to the frozen state. That is, although only the surface layer has been frozen only by the conventional thermal stimulation, since the shock is also added in the present embodiment, the stimulation is transmitted to the inside. Thereby, the water of the subcooling state inside foodstuffs can be made to transfer to a frozen state promptly.

  Hereinafter, the present invention will be described in more detail based on examples. Moreover, each characteristic of this invention was evaluated by the following methods. The present invention is not limited to these examples.

Example 1
Three to five grams of spiny lobster shrimp were placed in a stainless steel vat and supercooled at -7 ° C for 30 minutes. Next, with respect to the stainless steel plate cooled to -22 degreeC, the pansy shrimp was dropped on the stainless steel plate by turning over the butt from distance of height 10 cm. Then, the number of frozen pansy shrimp was measured.

(Example 2)
Example 1 is the same as Example 1 except that the height is 30 cm.

(Example 3)
Example 1 is the same as Example 1 except that a stainless steel plate cooled to -37 ° C is used.

(Example 4)
Example 1 is the same as Example 1 except that it was dropped from a distance of 30 cm in height to a stainless steel plate cooled to -37 ° C.

(Comparative example 1)
Example 1 is the same as Example 1 except that a stainless steel plate cooled to -7 ° C., which is the same as the supercooling temperature, is used.

(Comparative example 2)
Example 1 is the same as Example 1 except that the stainless steel plate cooled to -7 ° C., which is the same as the supercooling temperature, is dropped from a distance of 30 cm in height.

(Comparative example 3)
Example 1 is the same as Example 1 except that a stainless steel plate cooled to -22 ° C is brought into contact with shrimp arranged in a vat.

(Comparative example 4)
Example 1 is the same as Example 1 except that a stainless steel plate cooled to -37 ° C is brought into contact with shrimp arranged in a vat.

(sensory evaluation)
The frozen sweet potato in each of Examples 1 to 4 and Comparative Examples 1 to 4 was boiled for 1 minute and then thawed. The thawed pan-fried shrimp was tasted by six panelists under blind conditions, and the texture and taste were evaluated in five steps. At this time, a control was obtained by quick-frozen peeled Banaei shrimp for 35 minutes at -30 ° C.

<Taste>
Evaluation 5: The taste of shrimp is stronger than the control 3: Equivalent to the control 1: The taste of shrimp is weaker than the control

<Texture>
Rating 5: meat quality is stronger than control 3: equivalent to control 1: meat quality is weaker than control (body is boso boso)

  The results are shown in Table 1.

  As is clear from the results in Table 1, in the examples in which the thermal stimulation and the impact were combined, the result was obtained that the number of freezes was large and the flavor and texture were good as compared with the comparative examples. Of the examples, Example 1 is less irritating at the temperature difference and / or height with the subcooling than the other examples. Therefore, unlike the other examples, in the freezing number, not all shrimps were frozen. However, it can still be seen that more shrimp are frozen than in the comparative example.

  On the other hand, when Example 1 and Comparative Example 1 are compared, the difference between the two is whether there is a temperature difference with the subcooling, that is, whether there is a temperature stimulus or not. As apparent from the results in Table 1, it was found that all the shrimps did not freeze and the flavor and texture were inferior only by the impact. Furthermore, when Example 1 and Comparative Example 3 are compared, the difference between the two is the difference as to whether or not there is an impact. As is clear from the results in Table 1, all the shrimps did not freeze in this case, and the result was that the flavor and texture were poor. From this, it was suggested that it is effective to give two stimuli at the same time because either stimulus alone is not enough. This can be confirmed also in comparison between Example 3 and Comparative Example 2 and Example 3 and Comparative Example 4.

  Next, when Comparative Example 1 and Comparative Example 2 and Comparative Example 3 and Comparative Example 4 are compared, it is found that the stimulation is weaker (Comparative Example 1 and Comparative example 1) than in the case where the stimulation is strong (Comparative Example 2 and Comparative Example 4). A slight but better result is obtained than Comparative Example 3). That is, it can be seen that when the type of stimulation is one, some improvement can be observed if the stimulation is made stronger. However, when Example 1 and Comparative Examples 1 to 4 are compared, Example 1 is a combination in which the effect was weak in the comparative example, but better results are obtained than any of the comparative examples. From this, it can be seen that combining the two stimuli can achieve an advantageous effect even if the temperature difference and height at which no single stimulus is effective.

  In addition, when it does not shift to a freezing state instantaneously from a supercooling state, ice crystals will be expanded inside a shrimp like slow freezing and a cell will be destroyed. As a result, after thawing, it can be considered that the taste and moisture of the shrimp flow out as drips, the taste is inferior, and the texture becomes boso boso.

  As described above, by combining and applying different stimuli simultaneously, the present invention reliably transmits the stimuli to the inside of the food even if it is a thick food or a food with a different composition inside the food Can go into a frozen state.

  In addition, although the case where the thermal stimulation and the impact were combined was demonstrated in the present Example, it is not restricted to this. For example, a metal plate such as stainless steel cooled to a temperature lower than the supercooling may be pressed from above onto a frozen object such as shrimp arranged on a conveyor or the like with respect to the subcooled food. In this case, thermal stimulation and pressure can be applied simultaneously. In addition, a wind having a temperature lower than the supercooling temperature may be blown to the shrimp or the like arranged in the vat. Even in such a case, different stimuli can be applied simultaneously.

Claims (1)

How to freeze food,
The supercooled water in the food is frozen by simultaneously giving a temperature stimulus with a difference of -30 ° C or more with respect to the temperature of supercooling and a physical impact due to a drop of 10 cm or more with a height difference to the supercooled food. How to freeze food.