JPS6240274A - Freezing of fresh food - Google Patents

Abstract

PURPOSE:To enable the freezing of a food as a whole keeping the excellent state preventing the degradation of the core part, by proceeding the freezing of a food exclusively from the side contacting with a heat-transfer means while preventing the freezing of the food as a whole. CONSTITUTION:A surface of a het-transfer means such as vessel, tray, flat plate, etc., is made to contact with cooled brine 6 or low-boiling liquefied gas, and the other surface of the heat-transfer means 4 is made to contact with a fresh food 5 to be frozen, e.g., cattle meat, fish shellfish, vegetable, etc., to effect the progress of the freezing of the food exclusively from the side contacting with the het-transfer means 4. Consequently, the whole food can be frozen in good state without deteriorating the core part of the fresh food 5. The frozen food can keep the same fresh state by this process.

Description

[Detailed Description of the Invention] C. Industrial Application Field] This invention relates to a method for freezing fresh foods, specifically a method for freezing meat, seafood, vegetables, and other processed foods to preserve them in a fresh state for a long period of time. It is about the method.

[Conventional Technique 1] There is a liquid immersion method as a method of freezing food. This is brine (
This method freezes food by immersing it in antifreeze (antifreeze solution), but because the food is in close contact with the brine, the degree of freezing is large.

Freezing is intended to prevent the formation of drips and denaturation of proteins due to deterioration during frozen storage of food, and to make the tissue less susceptible to physical damage and component concentration caused by ice crystals. be. For this reason, the basic idea has been to freeze food so that the freezing rate is as high as possible, the final temperature is as low as possible, and the contact between the cooling medium and the food is as close as possible.

In this respect, the liquid immersion method is an excellent freezing method, and the inventors have been improving brine based on this theory.

[Problem that the invention seeks to solve]

However, with the liquid immersion method, ice crystals grow in the center of the food, and a single thick ice crystal extends from the center toward the surface, which destroys the structure of the food and deteriorates its quality. .

The mechanism of this phenomenon is unknown, but the condition is as if the tissue ruptures from the center to the surface, and the entire surface of the food freezes rapidly, causing distortion in the center due to freezing.
It is thought that this reached its limit and was destroyed.

As described above, the liquid immersion method has the disadvantage that the entire surface of the food is rapidly frozen, resulting in destruction of the center.

This drawback is even more serious in the liquefied gas method, which uses liquefied gas with an extremely low boiling point.

Therefore, an object of the present invention is to make it possible to freeze the entire food in good condition without deteriorating the quality of the center of the food.

[Means for solving problems]

The inventor believes that all conventional freezing methods attempt to increase the contact area with the food surface as much as possible in order to rapidly freeze the meat, but if the entire surface of the meat is frozen, ice crystals grow in the center and the tissue becomes damaged. In view of the disadvantage of destroying the food, the idea was to freeze the entire food by freezing it from one side of the food so that the end point of freezing would not be inside the food.

The method involves contacting one side of a heat transfer means such as a container, tray, or flat plate with cooled brine or low boiling point liquefied gas, and contacting the object to be frozen with the other side of the heat transfer means. Freezing progresses only from the surface.

[Effect]

In this invention, freezing proceeds only from one side of the food in contact with the heat transfer means without freezing the entire food, so ice crystals do not grow inside the food and destroy the tissue. Freezing progresses inward from the contact surface with the heat transfer means and ends when it reaches the food surface other than the contact surface. The quality is uniform throughout.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a schematic diagram of an apparatus embodying the method according to the present invention, in which (1) is a tank, and (2) is a tank (1).
Piping installed inside, (3) is the compressor, (4)
(5) is a container which is a heat transfer means, and (5) is an object to be frozen.

The tank (1) is filled with inorganic or organic brine (6).

The brine (6) is stirred by a stirring blade (not shown) in the tank (1), and is repeatedly compressed, liquefied, and evaporated by a compressor (3) to circulate ammonia, fluorocarbon, etc. in the pipe (2). Cooled by refrigerant.

The heat transfer means is not limited to a container as shown in FIG. 1, but may also be a tray or a flat plate that does not sink unless the object to be frozen (5) comes into direct contact with the brine (6).

Further, in this embodiment, the container (4) serving as a heat transfer means is floated on the brine (6), but the brine (6) is inside the container (4).
) may be removably fixed in the tank (1) as long as it does not fit inside the tank (1).

The material of the heat transfer means is metal, resin, glass, or a composite thereof.

In this embodiment, since the container (4) is floated, the convection of the brine (6) by the stirring blades is not impaired and the liquid temperature near the surface can be maintained at a low temperature.

The freezing method is from 1 to 1 after putting the object to be frozen (5) into the container (4).
The object to be frozen (5) is removed after floating in brine (6) for 2 hours and pulling up the container (4). One thing to be careful of when freezing is that frost and ice that adhere to the bottom of the container (4) will reduce the heat transfer efficiency, so be sure to close the container (4) when putting the object to be frozen (5) into the container (4). This is to remove frost and ice from the brine (6).

Although brine is used in this example, liquid nitrogen,
A low boiling point liquefied gas such as liquid carbon dioxide may also be used.

Next, experimental examples will be shown in which the freezing method according to the present invention was applied to various foods.

Experimental Example 1 A piece of pork having a wall thickness of approximately 7511 Iffl and a weight of 1.1 kg was placed on an aluminum tray and frozen using the above method, and the temperature at each part was measured. The pork is chilled beef refrigerated at O″C.

For brine, a container containing propylene glycol 40x, calcium chloride 10x, water 50K, and a small amount of rapeseed oil was used and maintained at -37°C.

As shown in Figure 2, temperature measurements were taken at a position 15 mm from the tray near the center of the meat mass (point A), and at a position 40 mm from the tray (point B).
The test was carried out at three points: point) and 75 mm position (point C).

Figure 3 shows the measurement results plotted as temperature vs. time, and shows that freezing progresses from the bottom to the top.After 3 hours of freezing, point A was -27°C and point B was -23°C. ，
The temperature was -8°C at point C, but reached its lowest temperature after 5 hours, at point A, -29°C, point B, -27°C, and point C, -21°C, and remained constant thereafter.

In this way, the product temperature is considerably lower than that of conventional methods.

We investigated the frozen state inside the mountain, but there was no difference between the surface and the center, and there was no growth of ice crystals throughout.

After thawing, a sensory test was conducted, and evaluation was made with chilled beef that had not been frozen as 100. The results are shown in Table 1. In addition, Table 1 also shows that meat that was directly immersed in brine and frozen was also evaluated in the same way.

(See the margins below) Table 1 As a result, the frozen meat obtained by the method of the present invention has the same quality as chilled beef that is not frozen, and has superior quality compared to directly soaked frozen meat whose center has been destroyed. had.

Experiment 2゜ Below, various foods were frozen.

Frozen tuna was thawed and frozen to a thickness of 75 mm. The freezing process was the same as in Experiment 1, and the meat quality after thawing was comparable to that of meat that had not been subjected to the freezing experiment.

When freezing a hamachi round with a body length of 400 mm, the upper surface reached 125°C in about 1 hour. The quality of the meat after thawing was the same as fresh meat.

It took about 20 minutes to freeze the oysters at 130"C. There was no big difference in the freezing time whether the oysters were left on or just the meat. Even after thawing, no drips were formed and the fleshy texture remained the same. there were.

When frozen shiitake mushrooms were thawed, they were as firm and fresh as fresh ones.

When tofu was frozen, the thawed product returned to its original state without becoming frozen tofu-like.

〔Effect of the invention〕

In this invention, freezing is performed from one side to the entire food without freezing the whole food, so that the whole food is frozen in a good condition without deteriorating the quality of the center part. Therefore, frozen food can remain in the same condition as fresh food.

Furthermore, the method of the present invention has the advantage that there is no need to package the food.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus embodying the method according to the invention. FIGS. 2 and 3 relate to Experimental Example 1. FIG. 2 is a cross-sectional view showing the measurement method, and FIG. 3 is a freezing curve of pork.

Claims (1)

[Claims] 1. Contact the cooled brine or low boiling point liquefied gas with one side of the heat transfer means such as a container, tray, flat plate, etc., and contact the object to be frozen with the other side of the heat transfer means, from the contact surface with the heat transfer means. A method for freezing fresh foods, which is characterized by proceeding with freezing only.