Challenges of freezing methods

The conventional freezing method is the air blast method (air freezing).
This type is found in general household freezers.

However, one problem with conventional freezing is that the taste deteriorates when thawed, and the problem of taste deterioration has become common knowledge in freezing.

[Frozen = taste deteriorates! ? ]

Why does food lose its flavor when thawed using traditional freezing methods?
There are several reasons for this:

Cell destruction by freezing

The water inside food cells freezes and turns into ice crystals.

With the traditional slow freezing method (slow freezing), the water expands significantly and the resulting ice crystals become large.
These larger ice crystals then pierce the food cells from the inside, creating holes.
(Cells are 20 to 30 microns, whereas in traditional slow freezing, ice crystals are about 100 microns.)

These punctured holes in the cells cause the taste to deteriorate.

When frozen food is thawed, the umami drips out from these holes, and along with the water, taste components and nutrients are also lost.

As a result, the texture of the food itself becomes worse.

The temperature range where the water in food crystallizes is called the "maximum ice crystal formation temperature range", and when food passes slowly through this temperature range, the water expands and the ice crystals become larger.
In order to achieve good freezing, the biggest challenge was ``how to get through this temperature range quickly.''

It is no exaggeration to say that current rapid freezing technology has evolved to solve this problem.

*By passing through this temperature range in a short period of time, the expansion of water is suppressed, and ice crystals settle within the cells and do not break through the cells.

Freezer burn/oxidation

If frozen food is stored for a long time, the water will evaporate from the surface and it will become dry.
This is a condition called "freezer burn."
This is caused by the phenomenon that air on the food surface evaporates and becomes frost, and that frost evaporates and recrystallizes.

Additionally, during frozen storage, the lipids in food become oxidized due to the influence of oxygen in the air.
This is a condition called "oil burn."

Slow freezing creates holes in cell membranes and allows oxygen to enter to replace the water that has been taken away, promoting oxidation.
In addition, protein deterioration also damages food.

Note that some lipids in foods are easily oxidized and others are difficult to oxidize, and in the case of the former, more care must be taken when storing them.
For example, green fish such as mackerel are prone to oxidation.

The advent of rapid freezing

These problems are the cause of ``freezing = taste loss'' and have become common knowledge.

On the other hand, if food is properly frozen and stored properly, it will be possible to reproduce the taste and texture of the food as much as possible before freezing.

This is where rapid freezing technology came into play.

By solving the above problems, rapid freezing technology has become a means to solve the problems of conventional freezing methods, such as not only the problem of taste deterioration but also the problems of distribution management, storage cost, and storage period.