Note: Descriptions are shown in the official language in which they were submitted.
3~
BACKC:ROUND OF T~TE INVENTION
The present invention relates to a method of
freezing Eishery products wherein said fishery products
may comprise sea Eood, such as tuna, lobs`ter, oyster,
or whale meat,for example~ The fishery product is immersed
in brine.
As methods of freezing the fishery products,
conventionally there have been freezing by means of air
or brine (antifreeze solution) cooled by a cooling
medium, and by means of immersing them in liquid nitrogen
or liquid carbon dioxide.
Since the foregoing methods give rise to more or
less a great amount of drip after thawing, however, a loss
in weight or a worsening of the quality such as a
deterioration of the taste takes place.
A cause for the drip is believed to lie in a
breakage of muscular tissue of the meat of fishery products
by icy crystal due to the freezing thereofj which results
in an increase of salt concentration in the tissue, having
a relationship with a freezing rate. This produces a
drawback by increasing the production cost that the
liquid nitrogen is costly.
; On the other hand, the brine includes inorganic
brine such as calcium chloride and organic brine such as
ethylene glycol, propylene glycol, etc., furthermore-being
the solution prepared by mixing them and producing an
advantage of larger cooling effect for its comparatively
lower price.
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1 For this reason, an object of the present inven-
tion is to reduce the deterioration of the meat quality by
means of preventing or controlling an occurence of the
drip through an improvement of the brine requiring lower
S costs.
SUMMARY OF T~E lNVENTION
, .
As a result of the meticulous continued study by
the inventor, which has aimed at an increase of the
freezing rate being essential to the prevention of the
occurence of the drip, it has been discovered that if
rapeseed oil is added to the brine, the freezing rate and,
in addition, the thawing rate are considerably increased.
Accordingly, in one of its broad aspects, the
present invention resides in a method of freezing fishery
products, quickly finished by means of the brine, wherein
the brine is prepared by adding rapeseed oil to a solution
comprising propylene glycol, calcium chloride and water is
cooled and subesquently the fishery products are immersed
in said brine for freezing.
; 20 No matter how great or low the amount of added
rapeseed oil is, it properly meets the requirement, only
provided that it is within the range of making it possible
to control a rise in the liquid temperature, when
immersing the fishery products in the brine. The most
effective concentration is about 0.1 to 0.5% by weight.
As to the brine which comprises propylene glycol,
calcium chloride and water, -the proporation of the
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l propylene glycol is pre~erably in the range of about
30 to 45~ by weight. The proporation of the calcium chlo-
ride is preferably in the range of about 8 to 20~ by
weight, especially in the range of about lO to 15% by
weight. The remainder is water.
The temperature to which the brine is usually
cooled is in the range of about -30 to -50C, preferably
in the range of about -37 to -45C.
Cooling of the br;ne to which the rapeseed oil
has been added may cause fine icy crystal articles to
occur therein, resulting in uniform distribution of them.
- If the fishery products are immersed in the
brine under the foregoing conditions, the-freezing rate is
increased and the freezing time is considerably reduced
in comparison to the case of using brine to which no
rapeseed oil has been added. Even after putting the
fishery products into the brine, the temperature of the
liquid is not increased, being approximately constant~
- In the case of thawing the fishèry products which
have been frozen and stored by means of such a method, the
thawing time can be reduced to a larger extent.
The reason for such a marked increase in the
freezing rate, which has not been analyzed in detail, may
be that the icy crystals caused by an addition of the
rapeseed oil act as a source of supplying freezing latent
heat to the fishery products and a rise in temperature of
the liquid is prevented, therefore the fishery products
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1 being able to pass promptly through the zone of maximurn
icy crystal forma-tion (-0.5 C to -5 C~ As a result, it
is believed that there is probably a prevention or
reduction in the breakage of muscular tissue because of
the generation of large icy crystal as well as the deterio-
ration of the meat quality.
Furthermore, although the process of thawing the
fishery products are not fully understood, a prompt
thawing may enable a growth of the icy crystal to be pre-
vented, a breakage of the muscular tissue beingbelieved to be also prevented.
BRIEF DESCRIPTION` OF THE DRAWINGS
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The figure is a schematic illustration of the
freezing device which is used to put the present invention
into practice.
DETAILED DESCRIPTION OF THE INVENTION
AND PREFERRED EMBODIMENTS THEREOF
'
Referring first to the drawing, which illustrates
the freezing device for puttlng the present invention in
practice, in a typical manner, 1 is a tank, 2 is a
stirring a~is, 3 is a motor for rotating the stirring axis
2, ~ is a piping arranged in the tank 1, 5 i~ a compressor
and 6 is a basket for containing the meat pieces 7 of
fishery products. No matter what the processed form
of the meat pieces 7 may be, they are able to be used fox
this method. The meat pieces 7 may be taken as the form
of round, dress, fillet, steak, or example.
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1 The tank 1 is ~illed With the brine 8 and the
basket 6 is fully buried in the brine 8~ The brine 8
is cooled by a cooling medium which is circulated in the
piping 4, while repeating its compression, liquefaction,
and evaporation, by means of the compressor 5.
The method of freezing fishery products is to
immerse the basket 6 in which the meat pieces 7 have been
positioned in advance in the brine 8 for the predetermined
period and subsequently to pull up the same theref~rom.
The brine 8, which is cooled to between about
-30 C and -42C, has a slight amount of the rapeseed oil
added to the content of said brine including propylene
glycol (about 40% in weight), calcium chloride (about 10%
in weight), and water (about 50% in weight).
Table l shows the results obtained by experiments
performed, while the added amount of the rapeseed oil is
changed.
An experiment was performed under the condition
that the temperature of the brine 8 is -35 C, steak-like
whale meat about 20mm thick was used as the meat piece
7, and they were lined on the basket 6 at intervals of
about 10 mm.
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1 Table 1
. . __ : . _.. _.
Added amount ofFreezing Thawing Existence
rapeseed oil time time ~ of drip
(%) (min) (min)
O 20 20 larger
. ., . .. ,, .. .,_.. ... _ _ __
0.05 15 16 slight
_ _
0.1 10 _ __ nil
0.5 10 10 nil
_._ .
1.0 12 13 slight
As shown in Table 1, if the added amount of
rapeseed oil is within about 0.1 to 0.5% by weigh-t of the
brine, a favorable result is obtained. The
meat pieces 7 which are frozen by the brine 8 to which
the oil is added by the amount confined to such a
range holds as good a taste as a fresh piece.
On the other hand, an organoleptic test, performed
during the frozen state, shows that frozen meat pieces
7 for which no rapeseed oil was added, has numerous icy
crystals extending radially from its center to the surface
therèof. This phenomenon is believed to cause the drip.
In contrast with that, a frozen meat piece 7 for which
the rapeseed oil is added has one thick icy crystal
extending lineaxly or in a folded manner toward the surface
thereof, almost all of the structure of such meat piece
being normal.
Because the present invention uses no costly
liquid nitrogen, etc. but rather an economical brine and
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1 rapeseed oil, the costs in producing the frozen fishery
products are less.
Furthermore, since the brine to which the rape-
seed oil is added can reduce remarkably -the Ereezing and
thawing times, a deterioration of the meat ~uality of
fishery products in reduced. A reduction in the pro-
duction time for the frozen fishery products as a result
of the present invention leads to an advantage and an
advance in the production of frozen fishery products.
It will be understood by those skilled in
the art that although specific embodiments of the invention
have been disclosed, the invention encompasses functional
equivalents for placing the invention into practice.
