Note: Descriptions are shown in the official language in which they were submitted.
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METHODS AND APPARATUS FOR PASTEURIZING LIOUID EGG
The in~tant invention relato~ to method~ and
apparatus for pasteurizing liguid egg which has been
Realed in a container and which doe~ not require a~eptic
packaging technique~ and equipment.
There are a number of techniques known in the
prior art for pasteurizing and proce~sing liquid egg.
The more popular approaches involve the use of
conventional plate heat exchangers, steam infusion
6ystems or combinations of both. Electroheating systems
have recently been introduced which provide, among other
things, a superior faster more uniform and complete
pasteurization.
There are also a number of packaging
techniques known in the prior art which have been used
in connection with pasteurization techniques for
providing an extended refrigerated shelf life for the
packaged pasteurized liquid egg. Generally, these
techniques have involved use of aseptic packaging
techniques and equipment to package the pasteurized
liquid egg and prevent the introduction of micro-
organisms to the pasteurized liquid egg. These
techniques require that all holding tanks, tubing,
packaging materials, filling and sealing machines be
aseptic and that no opportunity exists for the
introduction of micro-organisms. The techniques for
attaining and maintaining the aseptic characteristics is
expensive and time consuming.
The concept of pasteurization of food products
in sealed containers has been used in other areas of the
food processing industry. These include, for example,
dog food in U.S. Patent No. 3,738,847, issued June 12,
1973 to Bechtel; a sediment-free, chocolate-flavored
beverage in U.S. Patent No. 3,615,659, issued
October 26, 1971; chee~e in U. S. Patent 4,627,984,
issued December 9, 1986; an egg product resembling a
hard boiled egg half in U.S. Patent No. 3,843,825,
is~ued October 22, 1972: beer in U.S. Patent
3 9 1
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No. 4,490,401, issued December 25, 1984; and fruit and
vegetable ~uices in U.S. Patent No. 4,946,041, issued
August 7, 1990.
In each of the above described patents, the
food product which has been treated has been other than
whole liquid egg. None of these prior patents recognize
the unique characteristics and unigue problems of whole
liquid egg which make the described processes
inappropriate for pasteurizing whole liquid egg. Liquid
egg is unique, and when considering its preparation,
processing and/or storage, a number of often competing
criteria must be considered, including, without
limitation: storage stability, content of potentially
pathogenic bacteria, foaming ability, emulsion
properties, viscosity, detrimental coagulation, and
pourability. Those persons familiar with the qualities
of liquid egg and the myriad problems that are caused
when liquid egg is improperly processed on apparatu~
other than conventional plate heat exchanger6 and known
packaging equipment, would not be expected to go to
other available non-egg pasteurization processes or
devices to pasteurize liquid egg.
The technigues normally applied to whole
liquid egg are batch pasteurization or continuous
pasteurization, followed by packaging which may include
aseptic packaging. When aseptic packaging is employed,
great care must be observed to insure that no micro-
organisms are introduced into the pasteurized whole
liquid egg after pasteurization and prior to the sealing
of the container holding the whole liquid egg.
One known prior art pasteurization technique
applied to whole liquid egg is that shown in U. S.
Patent No. 5,048,404, i~sued September 17, 1991, which
employs pul6ed high voltage systems to pasteurize the
liquid egg product. The liquid foodstuff is heated to
about 122-F to 158-F and the cooled to 41-F to 50-F and
packaged.
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Similarly, in copending U.S. Patent
Application No. 08/007,553, ~iled January 22, 1993
entitled ~Nethods and Apparatus for Electroheating Food
Employing Concentri¢ Electrodes~ by Thaddeus Polny and
assigned to the as6ignee of the instant invention, there
i8 described an apparatus ~or the pasteurization o~
liguid egg by electroheating. Again, after the
pasteurization is completed, the liquid egg i6 cooled
and packaged.
Techniques for the post pasteurization of
citrus and other ~uices and drinks after same have been
placed in cartons without observing the usual aseptic
techniques and packaging materials, in which the cartons
are sealed and then subjected to post pasteurization
techniques, are described in an article entitled ~Gable
Top Challenges The Brick~ in the January 1992 issue of
PACXAGTNG DIGEST. A first technique used by FBI Brands
describes the use of a hot-water pasteurizer which
raises the temperature of the materials in the sealed
containers to 167-F, holds them at such temperatures
for 7 to lO minutes and then cools them, but does not
- describe how this cooling takes place. Such a technique
applied to liquid egg would cause the egg to be at least
partially cooked, and would cause caking and undesirable
coagulation. There is no mention made of agitating the
filled cartons or hot water bath to assure uniform
heating of the contents, nor any mention made of
instantly submerging the pasteurized cartons in an ice
bath to terminate any further effects of the heating
step.
The same article also mentions the use of a
pasteurizing tunnel into which 20 filled cartons are
~oved at one time. The pa~teurization tunnel is stated
to include preheat, heat and cooling. Again, FBI states
'Our pasteurization goal is 167-F which we hold for 5
to lO minute~.~ Such pasteurization temperatures and
the time of holding at ~uch temperatures would render
liquid egg unu~able. The article fails to mention how
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heating i8 carried out in the tunnel or where and how
cooling takes place. No mention is made of rapid
cooling after the pastQurization is complete to prevent
overheating of the contents of the cartons. Thi~
technique would also result in an unusable liquid egg.
In accordance with the present invention,
there is now provided a method of pasteurizing liquid
egg sealed in its container or re-pasteurizing
pasteurized liquid egg packaged in a container which was
not aseptically handled. The liquid egg contained in a
sealed container is pasteurized by heating the container
to a selected pasteurizing temperature and holding same
for a period of time sufficient to achieve
pasteurization. The pasteurized liquid egg is then
cooled after which it can be stored in a conventional
manner. Liquid egg which has previously been
pasteurized but which is not aseptically packaged can be
re-pasteurized in its sealed container to eliminate any
micro-organisms which could be introduced because of
non-aseptic packaging.
It is also an object of the present invention
to provide a technigue for pasteurizing liquid egg
sealed in a container.
In accordance with this aspect of the present
invention, there is provided a hot fluid bath into which
the sealed container of unpasteurized liquid egg (or the
sealed container of pasteurized egg not aseptically
packaged) may be totally immersed for a prescribed
length of time in such hot fluid raised to an
appropriate pasteurized temperature, with the bath or
container, or both, agitated to provide for uniform heat
transfer. Thereafter, the sealed container is removed
from the hot fluid bath and plunged into an ice bath to
quickly reduce the temperature of the liquid egg in the
container. The liquid egg can now be stored in a
conventional manner.
Additional equipment and techniques for post-
paokaging pasteurization of liquid egg ln sealed
containers according to the concepts of the invention
are also disclosed and described herein. These include
the use of a tunnel with hot water spray in one portion
to conduct the pasteurization, and cold water spray in a
5further portion to quickly cool the packaged liquid egg.
A specially constructQd container with foil layers
therein can be heated by contact with external
electrodQs, or contents of a sealed container can be
heated by infra-red lamp, radiant heaters, or in a
10tunnel subjected to steam or hot gases, or by being
placed in an autoclave. After the pac~aged liquid egg
is raised to the pasteurization temperature and held
there for the prescribed time, the packaged liquid egg
is quickly cooled by an ice bath, water spray or the
15like.
Other objects and features of the invention
will be pointed out in the following description and
claims and illustrated in the accompanying drawings,
which disclose, by way of example, the principles of the
20invention, and the best mode which has been presently
contemplated for carrying them out.
In the drawings in which similar element~ are
given similar reference characters:
FIG. 1 is a schematic representation of one
25configuration of a sealed container pasteurizing system
according to the concepts of the instant invention.
FIG. 2 is a schematic representation of
another configuration of a sealed container pasteurizing
~ystem in accordance with the concepts of the invention.
30FIG. 3 is a fragmentary side elevation, in
sections, of a first form of container used with the
pa~te~rizing system according to the concepts of the
invention.
FIG. 4 is a fragmentary side elevation, in
35section~, of a further form of container used with the
- pasteurizing system according to the concepts of the
invention.
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FIG. 5 is a 6chematic representation of 6till
another form of heating device for pasteurizing the
contents of a sealed container according to the concepts
of the invention.
FIG. 6 i8 yet another form of heating device
for pasteurizing the contents Or a ~ealed container.
FIGS. 7 to 10 are further forms of heating
devices for pasteurizing the contents of a sealed
container according to the concepts of the invention.
The term liquid egg in accordance with the
present invention is meant to include not only liquid
egg white and liquid egg yolk, but also combinations of
each in any predetermined or desirable ratio. The term
liquid egg also includes liquid egg white, liquid egg
yolk, or combinations thereof (referred to as ~liquid
whole egg~) with additives such as salt, sugar, milk,
stabilizers, dextrins, cyclodextrins, peroxides, acids
and food stuffs including solid or particulate
foodstuffs. Liguid egg from which cholesterol has been
removed is also included.
As used herein, the terms ~pasteurization~,
~pasteurize~ and ~pasteurized~ refer to the killing of
sufficient pathogenic micro-organisms contained within
food and in particular liquid egg 80 as to render the
liquid egg edible without threat of, for example,
Salmonella infection. ~Pasteurization~ may also be
thought of as a treatment which is designed to
eliminate, for all practical purposes, pathogenic micro-
organisms and, -in particular, Salmonella, and
secondarily, to reduce the number of spoilage micro-
organisms present to improve the keeping quality of the
food product. At U.S.D.A. minimum time and temperature
parameters, pasteurization will generally produce liquid
whole egg which will have a refrigerated shelf life of
between about 7 and 14 days. For liquid whole egg, a
minimum temperature of 140-F and minimum holding time
of 3.5 minutes i~ required. The definition of
pastourization, in terms of attained tomperature and
21193~1
holding times, for other foods is generally provided by
government regulations and/or industry standard~. They
are therefore readily available.
~Extended refrigerated 3helf life~ means that
the liquid egg is safe to consume for a period of at
lea~t 3 weeks after treatment in accordance with the
present invention. This, of course, assumes proper
refrigerated storage. Preferably, the term ~extended
refrigerated shelf life~ means that the liquid egg is
safe to consume for a period of at least 4 weeks after
treatment in accordance with the present invention and
more often 10 to 12 weeks after treatment, or longer.
An extended refrigerated shelf life can also be imparted
to other perishable foods by the practice of the present
invention.
The term ~retained baking functionality~ means
that despite the application of heat in accordance with
the present invention, the liquid egg is useful for most
commercial and home, if not all, baking applications.
Baking functionality relates primarily to the
emulsification properties of the liquid egg. This
function directly relates to the stability of water/oil,
water/air, oil/air, or water/oil/air phases.
Emulsifications influences the viscosity of the-batter,
volume of the baked goods and stability thereof. The
stability of a two or three phase system also greatly
affects the texture of the resulting baked product. In
a cake, a desirable soft uniform crumb can be achieved
only with the proper emulsification system. In fact,
the quality of certain baked goods, such as, for
example, sponge cake, is considered wholly dependent
upon~the quality of the egg used. Good egg product,
that i~ one having high baking functionality, yields
high volume and soft texture.
The term ~egg functionality~ means all of the
characteristics which affect liquid egg preparation,
proce~ing and/or storage and includes, but i8 not
liDited to, ~torage stability, content of potentially
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pathogenic bacteria, foaming ability, emulsion
properties, vi6cosity, detrimental coagulation,
pourability and retained baking functionality.
The term pasteurization ie to be di~tingui~hed
from sterilization wherein all of the pathogenic micro-
organism~ and the spoilage micro-organisms are
destroyed. When liguid egg is sterilized, the resulting
liquid eggs have no taste and only limited use such as
for scrambling. The liquid eggs produced as a result of
sealed carton pasteurization retain all of their
desirable properties and characteristics.
Turning now to ~IG. 1, there is shown a
schematic representation of a sealed container liquid
egg pastsurizing system 20 according to the instant
invention. Liquid egg i8 conducted through supply
line 22 to a container 24 to be filled. Supply line 22
may provide unpasteurized liquid egg or -it may provide
pasteurized liquid egg from a batch or continuous liquid
egg pasteurizing system, one form of which is described
and claimed in the above identified application Serial
No. 07/862,198 filed April 2, 1992. The liquid egg is
placed in an erected container blank 24 at a filing
station. The container blank 24 is the type widely used
in the food industry and may be of the type available
from International Paper Company and others, and when
completed forms the so-called gable-top container. When
erected container blank 24 is filled as determined by
column measurement, photoelectric cells or total
container weight, the container 24 with ~iquid egg
therein is advanced to a heat sealing station 26 wherein
the open end of container blank 24 is sealed.
The container blank 24 as is shown in FIG. 3
is of a multi-layer construction and may include an
inner foil layer 28 to protect the flavor of the
contents, one or more cardboard or fiber layers 30 and
an outer polyethylene layer 32 which can be auitably
printed with labels, directions, etc.
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The filled and sealed container 24' is next
placed in a vat 34 and filled with a fluld ~uch as
water 36. A heater 38 will heat the water 36 to the
de~ired temperature rangs for pasteurization. ~he
S technique shown i8 a batch process and as many
containers 24' as desired can be placed in the selected
vat size. The temperaturQ selected can be in the range
of 140-F to about 155-F. Temperature controller 40 will
sense the temperature of the water 36 in vat 34 and turn
the heater 38 on or off until the desired temperature is
reached, and maintain the temperature of the water 36
uniformly for the pasteurization period as set by the
timer 42. The amount of heat added by heater 38 will
depend upon the number of filled containers 24' placed
in the vat, the make-up of the containers and their
contents. The pasteurization period for unpasteurized
liquid eggs at l40-F is approximately 30 minutes and the
pasteurization period for previously pasteurized liquid
eggs is about three to four minutes at lS5-F.
The water 36 in the vat 34 is agitated by
agitator 44 to maintain a uniform temperature in vat 34
80 that heat is uniformly transferred to the liquid egg
in container 24'. Alternatively, the container 24' can
be gently agitated by an agitator similar to agitator 50
in the cooling vat 46. Such agitation helps the
contQnts of the container 24' to move around and assure
a more even temperature distribution within
container 24'. Also, the contents of vat 34 may be
pressurized from a source of pressure 52 to prevent the
deformation of the container~ 24' due to the heating of
its contents.
Cooling vat 46 is filled with an ice and water
combination 48 to provide a rapid cool down of the
heated contents of container 24' from the pasteurizing
temperatures of 140-F to 155-F to below 40-F. Also
cooling could be provided by chilled or refrigerated
water, expanding liquified gases, etc.
2 il9391
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once the contents of container 24' have been
properly cooled, the liquid egg may be stored and used
in any conventional manner.
It has been found from testing the results of
the above procedures that with raw, unpasteurized eggs
having psychotrophs of 2000 and a total plate count
of 1600, the psychotrophs were reduced to 100 and the
total plate count was reduced to below 100. In
previously pasteurized liquid eggs having psychrotrophs
10of 700 and a total plate count of 100, the psychotrophs
were reduced to 100 and the total plate count reduced
below 100. These values correspond favorably with
similar readings taken of pasteurized liquid eggs placed
in aseptic packaging.
15Turning now to FIG. 2, there is shown a
further technique and apparatus 60 for pasteurizing and
cooling liquid egg in a sealed, filled container 24'.
The containers 24' are advanced on a conveyor belt 62
through a tunnel 64. A fluid such as hot water, from a
source (not shown) is fed to a manifold 68 which
contains a series of spray heads 70 which apply
controlled streams of hot water or other fluid to the
containers 24'. The containers 24' can be retained in a
heating portion 66 of the tunnel 64 or the heating
portion 66 may be made long enough that the moving
container~ 24' are heated to and maintained at the
pa6teurizing temperature for the desired period. After
pasteurization, container~ 24' are moved to cooling
portion 72 and sub~ected to a cold water spray from the ~ p
spray heads 76 connected to cold water manifold 74
supplied from a source of cold water (not shown). Of
cour~e, another typ-e of cooling fluid could be employed
instead of cold water. The containers 24' will remain
in the cooling portion 72 of tunnel 64 for sufficient
time to reduce the temperature of the contents of
containers 24' below 40-F. This may be done by stopping
the conveyor belt 62 in tunnel 64 or having the cooling
portion long enough for the cool down to take place. A
.
. ~ ,qt, . ~, .-".~ : r - ~
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sample container with heat and cooling sensor~ inserted
therein may be used to provide to an operator or
automatic controls accurate readings of the temperatures
within container 24'.
Turning to FIGS. 4 and 5, a ~urther form o~
container i8 shown along with the apparatus employed to
heat the container 24' contents. Referring to FIG. 4 a
unique container 80 construction i8 shown. A foil
layer 82 on the inside of the container 80 is similar to
foil layer 28 of FIG. 3. It serves to prevent contact
of the conta~ner 80 contents with the container
materials to prevent any reaction that might effect the
liquid egg contained within. A foil layer 84 is
positioned on the outer surface of container 80 and i8
connected by lands 86 to foil layer 82. The lands 86
permit,current applied to foil layer 84 to be conducted
to foil layer 82. An insulating layer of
polyethylene 88 and a layer of cardboard or fiber 90 is
placed between the foil layers 82 and 84. The filled
and sealed container 80~ is positioned between two
electrodes 92. The electrodes 92 are in direct contact
with foil layer 84. Current i6 passed from a source
(not shown) to an electrode 92, and by lands 86 to foil
layer 82 and then through the liquid egg in contact with
foil layer 82 on all sides and then to the second
electrode 92. Heating takes place in the container by
means of electroheating. Once the temperature has risen
to the pasteurizing temperature and has been maintained
there for the prescribed period, the containers 80' are
quickly immersed in an ice and water bath to chill the
content6 of containers 80' below 40F. After which the
pa~teurized liquid egg may be used in a conventional
manner.
FIG. 6 shows how the contents of a filled,
sealed container 24' may be heated by a set of infra-red
- lamp~ 94. A radiant heater as shown by coils 96 in
FIG. 7 can be used to heat the contents of
container 24'. FIG. 8 show6 how container 24' may be
211~39~
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placed in a tunnel 98 and sub~ected to steam or other
hot gases lO0 to carry out the pasteurlzation o~ the
contents of container 24'.
FIG. 9 shows how containers 24' can be heated
in an autoclave 102 under controlled temperature and
pressure. FIG. lO show~ a conventional oven 104 which
may be gas fired or electric or otherwise which may be
used to heat the contents of containers 24'. The heated
content6 of containers 24' may then be cooled,
regardless of which technique is used to heat the
container 24' contents by immersion in an ice-water
bath, by a ~pray of cold water, by refrigeration or the
like.
While there have been shown and described and
lS pointed out the fundamental novel feat~res of the
invention applied to the preferred embodiments, it will
be understood that various omissions and substitutions
and changes in the details of the devices illustrated
and in their operation may be made by those skilled in
~ 20 the art, without departing from the spirit of the
;~ invention.
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