DE8118819U1 - Frozen food container with device for automatic triggering of crystallization and pressure equalization - Google Patents

Description

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Gefriergutbehäl tar with device for automatic triggering of crystallization and pressure equalization .

The utility model application relates to the design of frozen food containers for deep freezing one in one Protective solution suspended frozen goods, in particular one biological material, in suitable freezers.

Field of use:

Biological material (living cells) can be kept almost indefinitely ^{at temperatures below -12O 0 C.} In this so-called cryopreservation, the cells are frozen in a protective solution and stored in liquid nitrogen at -196 ° C. If the freezing process is carried out correctly, the cells continue to live without damage after a suitable thawing process.

The frozen goods containers containing the suspended frozen goods are introduced into a cooling vessel containing cooling medium. The cooling medium temperature in the vicinity of this The container is lowered to the desired temperature below the crystallization temperature of the protective solution, where the phase transition of the protective solution used from the liquid to the solid state of aggregation (crystallization) is particularly critical. Due to the heat of crystallization released This is because inadmissible heating of the frozen food can occur, which leads to a considerable reduction cell survival rates.

State of the art :

The deep freezing of biological material is either in Chamber freezing systems or so-called open systems carried out. With the chamber freezers, the frozen food placed together with a protective solution in suitable containers in a freezing chamber, which is controlled by injecting can be tempered by liquid nitrogen and heating in such a way that there is a desired temperature for the chamber (e.g. constant) cooling rate (temperature change per time)

results.

With the open systems, the cooling principle consists in the temperature profile over liquid nitrogen in a thermally insulated, To use an open fireplace at the top by inserting the frozen food into this fireplace.

Without additional measures to influence the crystallization In principle, a cooling process results in a temperature profile (T) in the biological material according to FIG. 3, if the cooling medium temperature is lowered with a constant gradient. It becomes clear that there is severe hypothermia (super cooling) of the protective solution containing the biological cells occurs up to a temperature (T), which is significantly below the temperature (T) at which crystallization could start if crystallization nuclei occur would be available in the protective solution. The heat released by the spontaneous onset of crystallization leads to a temperature rise depending on the type of protective solution. To keep this harmful temperature rise small, Various methods are used, namely short-term strong lowering of the cooling medium temperature in order to achieve the To compensate or "seed" the heat of crystallization Protective solution at or just below the temperature (T) (seeding-oDoint) with an ice crystal or brief contact the container "at the seeding point" with tweezers immersed in liquid nitrogen (contact release).

The main disadvantage of all the methods mentioned is that they have to be carried out manually and therefore depend to a large extent on the skill of the experimenter.

The contact initiation of the crystallization can be automated , however, leads to poorly reproducible results because in some cases there are not enough crystal nuclei in other cases the crystallization starts too violently.

So far, plastic tubes have mainly been used as frozen food containers used, which are mechanically tightly closed on both sides.

sen are. During the thawing process, an increase in pressure occurs inside the container, which often leads to the freezer container bursting and thus to the loss of the biological material.
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Task and solution

The invention is based on the object of the frozen goods container to be designed so that the triggering of the crystallization in the containers automatically without manual intervention takes place, and that the overpressure generated during thawing is controlled.

This object is achieved by the features specified in the characteristics of claims 1 and 2, which both by means of a chamber freezer as well as an open system are applicable.

The invention is based on the idea that, due to the device, only the temperature of the cooling medium in the environment of the frozen food container is adjustable that with optimal freezing, however, the course of the frozen food temperature is decisive for whether the frozen food is damaged will. The deviations between frozen food temperature and ambient temperature are mainly due to the relative sluggish heat transfer on the container wall and depending on the type due to the release of the heat of crystallization released.

If a frozen food container is now used, which is a main part and one open to the main part at one end and one at the other End has closed or closable tube, and becomes the main part inside with the frozen food containing protective solution is filled while the tube is only filled with protective solution, so the sensitive frozen food is spatially separated from the tube contents, in which it is safe spontaneous crystallization can also take place. Furthermore, when the cooling medium temperature is lowered, at least in the vicinity of the crystallization temperature, i.e. in the critical temperature range due to crystallization for the frozen food, a lower temperature is set in the vicinity of the tube than in the vicinity of the main

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sometimes, a more or less violent crystallization sets in when the temperature in the tube drops, however Only then does the crystallization - starting from the mouth of the stirrer - affect the interior of the main part and the frozen food over when the protective solution inside the main part reaches the crystallization temperature or slightly has fallen below. This ensures that the crystallization the protective solution is triggered at the earliest possible point in time, so that the harmful temperature rise becomes minimal.

In an apparatus for performing this method therefore contains the cooling vessel a zone into which the frozen goods container with the tube arranged on its main part protrudes and which can be cooled to the temperature below the ambient temperature of the main part.

The cooling medium temperature is advantageously set automatically. The actual frozen food temperature is used for this measured inside the frozen food container and a suitable one Control device supplied.

The problem of the pressure increase in the frozen food containers during the defrosting process is achieved in that an opening in the main part of the frozen food container with a movable elastic stopper is closed. This plug is not attached directly to the end of the main part, but in such a way that a shift towards the end of the main part is possible. Through this increase in volume the main part is the overpressure created during the thawing process degraded to the extent that destruction of the frozen food container is avoided.

Advantageous versions of the frozen goods container are based on an embodiment and 3 figures explained in more detail.

Embodiments :
Show it:

Fig. 1 and 2 frozen food containers, as they are preferred for deep freezing of biological material with automatic input

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conduction of crystallization can be used; 3 shows the temperature profile of the frozen food with constant cooling of the surrounding cooling medium without additional measures would take to trigger the crystallization, as he already did was explained at the beginning.

There are tubes on the main parts (1,11) of the frozen food containers (6,12) arranged, which protrude into a colder zone of the cooling vessel. The tubes are filled with protective solution (without frozen food to be protected) is filled. Crystallization begins in them before the protective solution enters the main parts reach the crystallization temperature (T). If the main part temperature is now lowered below the crystallization temperature, the protective solution crystals grow out of the tubes into the interior of the main parts (1,11) and trigger a gentle, controllable crystallization there the protective solution containing the frozen food. It is used to visually check the crystallization process also advantageous if the interior of the frozen food container can be seen from at least one side.

In Fig. 1 and 2 are advantageous designs of the frozen food container and the temperature sensor. The frozen food container is a spare part that can be produced easily and cheaply in large numbers. It consists of one Main part (1) with an opening (2) for filling in the frozen food and, if necessary, to accommodate the temperature sensor (3) and one arranged on the main part, at one end (4) open to the main part inner, at the other end (5) sealed tube (6). The main part (1) can be a transparent, easily sterilizable cylinder, for example made of plastic. In the embodiment according to FIG. 1, the tube (6) with its angled upper End (4) through one end of the cylinder (1) closable stopper (8), for example made of silicone, ge ■ leads and melted shut at the other end. The plug (8) is advantageously to the extent that it can be pushed into the cylinder (1) so that it can withstand temperature-related pressure and volume changes is axially movable. This creates a lockable

Reservoir with pressure compensation.

The end (2) of the cylinder (1) is either fixed or

via a conical lock, which is also made of plastic |

can be executed, or a ceramic cut, ab- £ closed. Through this conical closure (9) protrudes

Measuring part (3) of the sensor into the interior of the vessel. At the lock,

(9) is a plug (10) for the measurement output of the temperature £

attached to the sensor. \

For biological material, the one in the |

j 10 Frozen food immersible metallic measuring part of the temperature \

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made of a biologically compatible metal!

! and / or with a sterilizable jacket, e.g. ceramic ₉ '

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\ surrounded.

j For use in an open system, the one in Fig. 1

j 15 frozen goods container shown with its main part transversely to the temperature gradient in the open chimney at a f Holding device attached. The end of the tube (5) protrudes deeper | into the interior of the cooling vessel and is thus one

; exposed to a lower temperature than the main part. Consequential;

The protective solution continues to crystallize in the tube on when the main part of the frozen food is still exposed to temperatures above the crystallization temperature lie. Crystallization nuclei therefore grow from the tube (6) as the frozen food container is lowered further into the interior of the main part, so that the crystallization takes place automatically in the main part without any further manipulation is triggered as soon as the frozen food temperature in the main part reaches the crystallization temperature or slightly falls below.

The main part does not have to be cylindrical (more generally: elongated) e.g. a bowl shape is also possible, as shown in Fig. 2 on a Petri bowl (11) made of PVC, which with a silicone rubber hood (13) is shown is. In this version, the pressure is equalized via the elastic silicon rubber cover (13).

For use with a closed chamber, the Any shape of the main part. Also for the tubular

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no specific form is required, e.g. also hose-like with bends and changeable Be executed diameter.

If the holding device holds several frozen food containers, then so it can happen that the frozen food temperature in the different containers differs slightly from one another. The crystallization can then start at slightly different times and at slightly different speeds expire.

In these cases it is of particular advantage that the frozen food can be viewed. It is therefore possible to change the points in time for start and end of crystallization in all containers to be observed optically in order to cool down quickly to optimally adapt to the respective conditions. In particular can then the duration in which during the crystallization only a low cooling rate is specified, should be selected as short as possible.

Claims (3)

illtll i> · · ι · ·>. , ■ It «it tr ·· claims 1. frozen stock with a device for the automatic Off · {solution crystallization and pressure compensation for the Deep-freezing of a frozen product suspended in a protective solution, in particular a biological material, characterized in that it consists of a main part (1) which is provided with an opening (2) for filling the frozen product and, if necessary, for receiving a temperature sensor (3), and a on the main part (1) arranged, at its one end (4) to the main part inner open, at the other end (5) closed or closable tube (6) consists (Fig. 1). 2. Frozen goods container according to claim 1 characterized in that a second opening (7) of the main part (1) is closed with a movable stopper (8) (Fig. 1), 3. Frozen food container according to claim 1 and 2 characterized in that the main part is elongated or shell-shaped and the tube is arranged transversely on the main part (Fig. 1, Fig. 2).