U.S. patent number 3,658,559 [Application Number 04/878,418] was granted by the patent office on 1972-04-25 for process of preserving potatoes in closed packages.
This patent grant is currently assigned to Plasco Limited Company. Invention is credited to Franz Mohwinkel.
United States Patent |
3,658,559 |
Mohwinkel |
April 25, 1972 |
PROCESS OF PRESERVING POTATOES IN CLOSED PACKAGES
Abstract
A process for preserving foodstuffs such as potatoes in closed
packages of foil packing material wherein the peeled, raw and if
required sliced or diced potatoes are vacuum-packed without any
included liquid and cooked or steamed and then cooled at a external
pressure exceeding the internal pressure in the packing and
controlled independently of the temperature, and wherein during the
vacuum-packing process each potato or piece of potato is brought
into direct contact with the inside of the packing material through
at least a part of its surface area, preferably a third.
Inventors: |
Mohwinkel; Franz (Ahlften uber
Soltau, DT) |
Assignee: |
Plasco Limited Company (Vaduz,
FL)
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Family
ID: |
5738291 |
Appl.
No.: |
04/878,418 |
Filed: |
November 20, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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804694 |
Mar 5, 1969 |
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Foreign Application Priority Data
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Jun 28, 1969 [DT] |
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P 19 32 900.1 |
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Current U.S.
Class: |
426/412 |
Current CPC
Class: |
B65D
81/2023 (20130101); B65B 25/02 (20130101); A23B
7/0056 (20130101); B65B 25/041 (20130101) |
Current International
Class: |
A23B
7/005 (20060101); B65B 25/02 (20060101); B65D
81/20 (20060101); B65B 25/04 (20060101); B65b
031/02 (); 203L 001/12 () |
Field of
Search: |
;99/100,17,150,154,168,171,185,207,221,186,211,214,215,216 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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579,098 |
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Jul 1959 |
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CA |
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816,313 |
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Jul 1959 |
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GB |
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Other References
AVI Publication, Potato Processing Dec. 5, 1968 p. 588 .
National Potato U. Conference, May 1962 p. 32..
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Primary Examiner: Yudkoff; Norman
Assistant Examiner: Mullen; Martin G.
Parent Case Text
This is a continuation-in-part of my co-pending application, Ser.
No. 804,694, filed Mar. 5, 1969.
Claims
Having now described this invention, what is claimed is:
1. A process for cooking and preserving potatoes in a closed and
sealed package of plastic material comprising: vacuum-packing
peeled, raw and sliced or diced potatoes in said package without
adding any liquid so that there is no water or other liquid in the
closed and sealed package other than the natural juices within the
potatoes therein, cooking and then cooling said packaged potatoes
at an external pressure exceeding the internal pressure in the
package, and wherein during the vacuum-packing step each piece of
potato in said package is brought into direct contact with the
plastic material enveloping the pieces of potatoes to be cooked and
preserved.
2. The process of claim 1, wherein during the vacuum-packing
process each piece of potato is brought into direct contact with
the inside of the packing material through at least a third of its
surface area.
3. The process of claim 1, wherein cooking by steaming is performed
with a cooking temperature of about 121.degree. C. at an internal
pressure in the packings of about 3 atms. absolute pressure for a
cooking period of about 25 minutes.
4. The process of claim 1, wherein cooking by steaming is performed
with a cooking temperature of about 100.degree. C. at an internal
pressure in the packages of about 3 atms. absolute pressure for a
cooking period of about 2 hours.
5. The process defined in claim 1 wherein the package is
substantially transparent.
6. The process defined in claim 1 and further wherein the said
packaged potatoes, after said cooking and cooling, are stored at
room temperature without being refrigerated.
Description
The present invention relates to the art of preserving and
sterilizing foods and, more particularly, to a novel process for
preserving foodstuffs such as potatoes in closed packages using
pressure cookers (autoclaves) or cooking receptacles, and to the
packaged goods thus preserved.
In the known processes of preserving potatoes by canning or
bottling them in water a product is obtained which can be preserved
for a relatively long period but which, as a result of being stored
in a preserving liquid, deteriorates in flavor and loses valuable
nutrient substances which are leached out by the liquid. Moreover,
canning and, in particular, bottling are expensive and inconvenient
and, when buying, the customer cannot see the product in the can,
which is a possible disadvantage.
The object of this invention is to remove the present disadvantages
and to provide an improved process of producing preserved potatoes
which hardly differ in taste from fresh boiled potatoes and which,
even in the wrapped state, afford an attractive appearance.
A further object of this invention is to provide a process of
producing well preserved potatoes which are readily usable without
further cooking, but only warming up.
Yet another object of this invention is to provide a process of
producing a product which keeps for a relatively long period of
time and which is neither leached out nor deteriorated in
appearance and particularly color and taste compared to the natural
product.
A further object of this invention is to produce a potato-product
which is available to the user in packages, the quality of which he
or she can judge by eye.
Further and other objects and advantages of the invention will be
apparent from the following detailed description thereof.
In my process for cooking or steaming potatoes in closed packages
with the aid of cooking autoclaves or cooking receptacles, peeled
raw potatoes are vacuum-packed in plastics containers with the
treating temperature of about + 100.degree. C. or somewhat higher,
while the absolute pressure in the cooking autoclaves or cooking
receptacles is kept considerably higher than the absolute internal
pressure of the container by supplying the latter, during the
preserving treatment with steam, with so much compressed air that,
at a temperature of about + 100.degree. C., the total pressure in
the steam space considerably exceeds the corresponding partial
pressure of the steam of 1 atms., or the total pressure in the
cooking receptacle considerably exceeds the steam pressure
corresponding to this temperature. With this process, the potatoes
are vacuum-packed in plastic-foil containers without any addition
of liquid and are cooked and cooled under an external pressure
exceeding the internal pressure of the closed containers and
controlled independently of the temperature.
It is an essential feature of this process that at least one part
of the surface of each potato or each piece of potato is brought
into direct contact with the inside of the packing foild during the
vacuum-packing process step.
If potatoes vacuum-packed in packages of foil material without any
liquid undergo the cooking process in autoclaves or cooking
receptacles, the danger arises that if the cooking temperature is
relatively high, about + 120.degree. C., or if during the cooking
process, for one reason or another, it unintentionally increases
and the packaged potatoes are exposed for a longer time to a
temperature of this value, incrustation and discoloration of the
surface of the potatoes or pieces of potato occurs. This leads to a
considerable reduction in the quality of the product.
On the other hand, for practical reasons, it is desired to use
temperatures of this level for cooking the potatoes since these
temperatures are usually used in the common canning and bottling
preserving methods wherein the potatoes are treated with liquid,
and furthermore, the internationally accepted standard for the
sterilisation effect is based on a cooking temperature of
121.degree. C.
I have found that with the new process in which the potatoes are
treated without liquid, these high temperatures can be used
provided that the form of the packing bears a certain relation to
the form of the articles of produce to be packed, namely so that
during the filling and vacuum-sealing processes, one point of the
surface of each individual article of produce comes into direct
contact with the packing material and is fixed in this position for
the subsequent stages of treatment. In this manner, with the
process according to the invention, cooking can be undertaken at
any of the usual cooking temperatures. As with the known processes,
for each individual case the optimum conditions during the cooking
stage are practically determined from the relation: cooking
temperature .times. cooking time. In the temperature region in
question, from about 100.degree.-125.degree. C. and in the
respective range of the cooking period of from about 20 minutes up
to 2 hours, the height of temperature level and the length of
period of time are in reciprocal relationship, i.e., under
generally uniform conditions, practically uniform results are
obtained if cooking is undertaken for about 2 hours at 100.degree.
C. or about 25 minutes at 121.degree. C.
With the method according to the invention, the external pressure
surrounding the filled packages is controlled and thus adjusted
independently of the temperature during the cooking process and the
subsequent cooling, so that it considerably exceeds the internal
pressure in the package containers. By way of example, with a
cooking temperature of 121.degree. C., at which the internal
pressure in the packages corresponds approximately to the steam
pressure of the water present in the packed potatoes, thus at about
1 atmospheric excess pressure, the external pressure is set at one
atmosphere higher, namely at about 3 atms. absolute pressure.
The arrangement according to the invention, of bringing each
individual piece of the produce to be treated into direct contact
with the wall of the packing material, seems surprising at first,
for usually a direct contact is allowed only when it is consciously
desired to brown the external surface of the pieces of potatoes,
e.g., during the preparation of roast potatoes. However according
to the invention, this step has the reverse effect of avoiding
browning or other chemical change at any points of the surface of
the pieces of produce to be treated.
Having carried out thorough investigations, I am able to
theoretically explain the surprising effect which is reached with
the previously described technical steps of the process according
to the invention, as follows:
When cooking or sterilising vacuum-packed potatoes or pieces of
potatoes which are packed in foil material without any liquid,
completely different conditions are valid for the conduction of
heat and heat transfer compared to the preserving of potatoes with
liquid in cans or bottles. With the known method of preserving, the
cans and bottles filled with the potatoes and liquid and then
closed are heated from the outside and the heat transfer within the
containers takes place through the transition of heat via the wall
of the container heated by the external heating medium and the
liquid, generally water, to the produce enclosed in the can or
bottle which is to be heated. Since the liquid material, such as
water, is a good conductor of heat, after a relatively short period
of heating, the heat is equally and thoroughly distributed in the
inner space of the packing container. It is known that this
transfer of heat can be speeded up by moving or tumbling the cans
during heating.
If on the other hand, potatoes are vacuum-packed in packaging
containers without any liquid, such a type of heat transfer cannot
take place. Though even then the wall of the packing material is
brought to the desired temperature owing to its direct contact with
the external heating medium, however, since transmitting medium is
missing from the inner space of the vacuum-packing, the heat can
only be transferred from the wall of the packing material directly
on to individual pieces of produce at those parts where the packing
material is in direct contact with the packed produce. Heating of
the entire inner space of the package or distribution of the heat
supplied from the outside is in this case only possible by way of
the packed potatoes and only at those parts where the pieces of
produce are in contact. This and the fact that potato itself is a
poor conductor of heat compared to water impedes the uniform heat
conduction and can lead to localization of heating. It must be
added here that the potatoes, particularly the uncut or
comparatively large pieces, are extremely sensitive and in the case
of a high or particularly lengthy heating caramelization or burning
occurs, as a result of such a localisation of heat. It is therefore
practically impossible without this reduction in quality to
maintain heating until the heat from the layers of the packed
produce in direct contact with the packing foil has passed to the
produce located furthest from the packing material towards the
center of the packing and the balance of heat has been adjusted.
The outermost potatoes would burn or, if this were prevented, the
innermost potatoes would be insufficiently sterilized.
These problems could be removed with the measures according to the
invention. It is thus unnecessary to transfer heat from one potato
or piece of potato to another; each individual piece of the produce
is immediately supplied with heat from the outer heating medium
through the direct contact between the piece and the packaging
material.
The invention will now be explained with reference to the
accompanying drawings which illustrate an embodiment of the
packaging according to the invention and, for comparison, a known
type of packaging.
In the drawing:
FIG. 1 is a side view of a package corresponding to the process
according to the invention;
FIG. 2 is a cross-sectional view of the package according to FIG.
1;
FIG. 3 is a plan view of FIG. 2;
FIG. 4 is a plan view of FIG. 1;
FIG. 5 is a cross-sectional view of a modified embodiment of the
type of package used with the process according to the
invention;
FIG. 6 is a plan view of the embodiment of FIG. 5;
FIG. 7 is a cross-sectional view of an embodiment used for
comparison;
FIG. 8 is a plan view of the embodiment according to FIG. 7;
FIG. 9 is a side view of another form of comparison;
FIG. 10 is a cross-sectional view of the embodiment according to
FIG. 9; and
FIG. 11 is a cross-sectional view of the form of a large package in
the case of the process according to the invention.
In all drawings, comparable parts are provided with the same
reference numerals.
FIGS. 1 to 4 illustrate the most favourable form of package
according to the invention. Each potato 1a or piece of potato 1b is
in direct contact with the packing material 2 which is surrounded
by the external heating medium 3, consisting of steam or water. As
is clearly seen in FIG. 2, the majority of the individual potatoes
or pieces, if they are diced, have two side faces directly on the
packing material so that in cross-section about a third of the
surface of the packed produce 1a and 1b is able to absorb the heat
supplied by way of the heating medium 3 and the packing foil 2. As
illustrated by the arrows in FIGS. 2, 3 and 4, this heat only needs
to cover a relatively short path in order to reach the parts
furthest away from the outer edge of the package, namely the core 4
of the packed produce, which enables a uniformly favourable heating
to occur in a reasonable time, whilst also taking into account the
relatively poor conduction of heat of the potatoes.
A sufficiently uniform supply of heat which can be reached in a
reasonable time is, as has been found, also possible with the
embodiments illustrated in FIGS. 5 and 6. In the arrangement
indicated, each potato 1a or piece of potato 1b is not heated from
two sides but from one side, since the side faces of each piece 1a
and 1b (in diced form) is in contact with the packing foil 2 which
is surrounded by the heating medium 3. The path which must be
covered by the heat supplied from the heating medium 3 via the
packing foil 2 in order to reach the core 5 which is here located
between the individual pieces of produce adjoining the packing foil
on each side is about twice as long as with the embodiment in FIGS.
1 to 4, but as has been found, can still be achieved in suitable
times so that at least with ordinary types of potatoes, this
embodiment of the process according to the invention illustrated in
FIGS. 5 and 6 leads to very favorable results.
FIGS. 7 and 8 illustrate containers which have such a poor
conduction of heat that a suitable sterilization of the inner
potatoes 1c or pieces of potatoes 1d is not possible without a
severe decrease in quality. As indicated by the arrows, the heat
transferred from the heating medium 3 to the packing foil 2, and
from there to the potatoes 1a or pieces of potato 1b in dirct
contact with the packing, must flow not only through one individual
piece of potato 1a or 1b, but must also pass from there to an inner
potato 1c or piece of potato 1d, which is not in direct contact
with the packing material and likewise diffuse through this
portion. The time required for this is so long, or the supply of
heat so high that the quality of the potatoes necessary for the
present purpose can no longer be maintained. Even more unfavorable
are the proportions in a large packing, with a capacity of about 3
kg, as is seen in FIGS. 9 and 10. The external heating medium 3 can
only directly heat surfaces of the packing material 2 which are
small in comparison with the entire surface of the packed potatoes
and pieces of potato 1a + 1b + 1c + 1d and the heat is only
directly transferred from the packing material 2 to the few
potatoes 1a or pieces of potatoes 1b lying on the outer edge of the
large package. The path of heat inwardly from the outside outlined
by the arrow in FIG. 10 clearly shows that a sufficient
sterilisation of the inner core zone is not possible without the
outer lying potatoes 1a or pieces of potato 1b being severely
burnt.
The difference between this known type of large package according
to FIGS. 9 and 10 and the type which must constitute a large
package when treated in accordance with the process according to
the invention, can be seen at a glance by comparing FIG. 10 with
FIG. 11. FIG. 11, like FIG. 2, illustrates the short path which the
heat takes during the cooking process for the fully uniform heating
of the packed produce for potatoes packed according to the
invention.
Products preserved according to the process of my invention are
able to be stored over periods as long as 6 months or more at room
temperature without being in any manner perished. In fact tests
have been made wherein packages of potatoes made according to this
invention have been subjected to controlled temperatures and
humidity conditions approximating those at the equator and for
periods of as long as six months with virtually no impairment of
the wholesomeness of the potatoes.
An example of materials that may be used for the plastic container
2 is a thermoplastic synthetic organic polymer such as the product
commercially marketed by Messrs. Wolff Walsrode AG, Federal
Republic of Germany, under the commercial designation COMBITHEN S
PA 3/10 K 3060 "SIEGEL-RANDBEUTEL."
It will be appreciated that various modifications and variations in
addition to those suggested above may be made in the process of the
invention, and accordingly it will be understood that the invention
is to be limited only within the scope of the appended claims.
* * * * *