JPS584904B2 - Freezing preservation method of raw nori leaves - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for freezing and preserving fresh nori thallus (hereinafter referred to as raw algae) picked from seawater.

Conventionally, it has been difficult to freeze and preserve raw algae alive (that is, with cells still alive) for a long period of time, and this has not been put to practical use.

In addition, there are few research reports on the cryopreservation of proto-algae, and a relatively recent one is a report on Migita's ``living cryopreservation of a laver laver thallus'' (Nagasaki University Faculty of Fisheries Research Report, No. 2).
No. 1 (1966), pages 131 to 138).

According to Migita's report, several individual leaflets have a water content of 20 to 4.
When cryopreserved at -20°C in a semi-dry state of 0%, the cell survival rate is high for two months even under a wide range of cooling rates, but as the water content of the original algae increases, the above survival rate decreases significantly. It is recognized that

However, it is possible to uniformly and quickly remove water from a large amount of raw algae.
Drying to 0 to 40% is extremely difficult to implement industrially, and it must be said that even if it were possible to maintain cell survival of the original algae for a period of about two months, it would be impractical.

The present inventors investigated the frozen preservation of raw algae with a water content of approximately 80%, which can be obtained through centrifugal dehydration treatment that allows mass processing of raw algae, and found that the cooling rate and storage temperature can be controlled. The present invention was based on the knowledge that raw algae can be cryopreserved for a long period of time while maintaining an extremely high cell survival rate.

Therefore, the purpose of the present invention is to develop an industrially practical cryopreservation method for raw algae that can be frozen for a long period of 6 months or more with a high cell survival rate of 90% or more even with a water content of about 80%. It is about providing.

The present invention will be explained in detail below.

A feature of the present invention is that raw algae with a water content of about 80%, such as obtained by centrifugal dehydration of raw algae, are cooled to about -5°C at an average cooling rate of 3°C or less per minute, and then Minute average 10
The method is to freeze the product at a cooling rate of about -25° C. to about 35° C. and then store it frozen at the freezing temperature.

The reason why the present invention targets raw algae with a water content of approximately 80% is that centrifugal treatment is usually appropriate for dehydrating a large amount of raw algae, and dehydration below the above water content cannot be obtained with this treatment. Depends.

In the present invention, first and foremost, raw algae containing about 80% moisture are cooled to about -5°C at a slow cooling rate of 3°C/mm or less on average.

According to the data measured by magnetic resonance (N.M.R.) and differential scanning calorimetry (D.S.C.) on the cooling process of the proto-algae, extracellular freezing begins at -6' to -8°C. As a result, most of the free water within the cell is dehydrated to the outside of the cell due to the water vapor pressure difference between the inside and outside of the cell and the semipermeable membrane function of the cell membrane, and it is observed that this water comes into contact with ice chips outside the cell and freezes.

Therefore, it is important that the semipermeable membrane function is not lost when cooling the raw algae, and if this semipermeable membrane function is lost, the active substances inside the cells will come out of the cells and die.

In order to prevent the loss of the semipermeable membrane function mentioned above, it is necessary to slowly cool the raw algae, and according to the experimental results of the present inventors, the temperature drops to around -5°C at an average cooling rate of 3°C/mm or less. Cooling preserves the semipermeable membrane function and imparts freeze resistance to the proto-algae, thereby avoiding subsequent cell death before the freezing point.

Note that if the cooling rate is set to an average of 2° C./mm or less, cell death can be more effectively avoided.

Next, in the present invention, the raw algae cooled as described above are subsequently frozen to about -25° to about -35°C, and this freezing is carried out while maintaining a cooling rate of 10°C/mm or less on average. This is very important.

N. M. R. According to the measurement data of The free water within the cell freezes all at once without being dehydrated to the outside of the cell, leading to the death of the cell.

According to the present invention, when the above-mentioned chilled proto-algae is frozen at an average cooling rate of 10°C/mm or less, dehydration of free water and freezing thereof outside the cells can be smoothly carried out at a temperature of -6° to -10°C. If the water is subsequently frozen to around -25° to -35°C at the above-mentioned cooling rate, substantially all of the free water will be frozen.

When preserving raw algae by freezing, it is important to dehydrate the free water inside the cells to the outside of the cells and freeze them completely.
It is necessary to freeze it to around 5° to -35°C.

Incidentally, when the cooling rate is set to an average of 1° C./mm or less, the above effect becomes even more remarkable.

Note that the temperature at which free water remains in the cells, for example -20°C
When raw algae are stored at freezing temperatures around or above freezing temperatures, intracellular metabolism occurs and the cells deteriorate during storage.

However, when cryopreserving raw algae, it is necessary to keep the bound water within the cells from freezing to maintain the survival of the cells, and therefore freezing at temperatures lower than -40°C should be avoided.

In the present invention, when the physiological activity of the raw algae to be frozen and preserved as described above is weak, for example, when using raw algae that has been harvested for some time, it is necessary to activate the raw algae in advance.

This activation treatment is performed by aeration culturing the raw algae in seawater to which nutritional substances such as inorganic salts have been added.

Through the above treatment, the cells of the original algae become healthy and have strong physiological activity, and as a result, they exhibit a so-called cold shock protective effect.

As described above, the present invention dehydrates and freezes the intracellular free water of the proto-algae to the outside of the cells, and at the same time adopts freezing conditions that maintain the intracellular bound water in an unfrozen state. Even raw algae containing a certain amount of water can maintain an extremely high cell survival rate and be frozen and preserved, so it can be said that it will make a great contribution to the nori industry.

EXAMPLES The present invention and its effects will be specifically explained below with reference to Examples.

Example 1 Fresh raw algae immediately after being harvested were immediately dehydrated using a centrifugal dehydrator until the water content was approximately 80%, and then placed in a polyethylene bag (0.03 mm thick) with a thickness of approximately 0.75 to 1 mm. ．．
Pack it so that it is 0cm thick and store it in the refrigerator to a thickness of 0.2~
It was cooled to -5°C at a cooling rate of 0.5°C/mm.

In this case, the dehydrated raw algae is added to frozen bread for about 1. Oc
A material packed to a thickness of m may be cooled as described above.

Next, the raw algae in the refrigerator were lowered to -30°C at a cooling rate of around 0.5°C/mm, and stored at that temperature.

However, when frozen bread was used, it was placed in a polyethylene bag and sealed after freezing.

After 6 months had passed, the raw algae were taken out of the refrigerator and the cell viability was determined using a conventional method. As a result, the cell survival rate was over 95%.

In addition, when the preserved raw algae was made into paper using a conventional method, no difference was observed compared to the product made from paper immediately after harvesting.
A comparable product was obtained.

Example 2 Raw algae 6 hours after harvesting were used as a nitrogen source and phosphorus source, and NaNO3 was added at 100 m, p/Z, and Na2 HP 0.442.
The cells were activated by aeration culture for 5 hours in seawater to which 20 mg/l of H20 was added.

The raw algae activated as described above were stored frozen in the same manner as described in Example 1.

After 6 months, the original algae showed a cell survival rate of 95% or more.

A product obtained by paper-making this preserved raw algae, similar to that in Example 1, was obtained which was in no way inferior to the product immediately after being harvested.

In addition, when raw algae that was not subjected to activation treatment were frozen in the same manner, the cell survival rate after 6 months was lower than 90%, and the product was cloudy.

Claims (1)

[Claims] 1. After reducing the water content of raw nori leaves or raw nori leaves that have been subjected to bioactivity activation treatment to about 80%,
Cool to about -5°C at a slow cooling rate of 3°C/mm or less on average, and then cool to about -5°C at an average cooling rate of 10°C/mm or less.
1. A biological cryopreservation method for nori leaves, characterized by freezing them at 25° to about 35° C. and preserving them in a viable state by freezing them within this temperature range.