Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE: Vertical Flow French Fryer
Technical Field of the Invention
[0001] This invention concerns a method and apparatus for frying potato strips
commonly called "French fried potatoes" and particularly relates to a
continuous process for
frying potato strips in large volumes from very deep packs of strips generally
vertically
arranged in the cooking oil.
Background of the Invention
[0002] Most French fried potatoes produced within the process food industry
have been
prepared in a sequence of steps including the cutting of whole potato into a
multiplicity of
potato strips which are then blanched in hot water. A water removal or drying
step follows
which employs circulating air to remove surface water from the strips as well
as a
predetermined, partial removal of internal water prior to depositing the
strips into a vat of hot
cooking oil for a time period sufficient to reduce the moisture content of the
potato strips to
fall within a predetermined internal moisture range. Following removal from
the cooking oil
the strips are transferred to a quick freezer and then packaged for later
finish frying before
serving to customers. Some French fries are not frozen but chilled to be
consumed within a
short period after processing, usually not more than a few days. Other fries
may not be
processed by blanching and drying.
[0003] The prior art may embrace cooking of potato products as thin slices
which float
while frying, resulting in potato chips, a thin, dry brittle product. This is
contrasted to cooking
potato strips which sink while frying, resulting in the characteristic French
fried potatoes
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R a
which have body. In either field the frying step may occur in deep-frying
apparatus having a
vat to contain a volume of cooking oil with means serving for oil inputs and
discharge
including provisions for cooking oil re-heating and re-circulation with
appropriate controls for
cooking oil temperatures and product dwell time. The potato products were
deposited in and
removed from the vat of cooking oil via conveyors of various types or impelled
along a
process path by mechanical stirrers. In the case of potato strips the process
time in the
cooking oil was relatively short, as the finished moisture content of French
fries falls in the
range of 62% to 68%. This contrasts with potato slices which require
substantially longer
times in the cooking oil, the finishing moisture content of the resulting
potato chips falls in
the range of 1 1/2% to 2%.
[0004] The Benson et al. U.S. Patent 5,580,598, granted Dec. 3, 1996,
disclosed
flexibility in changeover from one processing method and product to another
and taught
mechanical means for stirring the products in the cooking oil as well as for
urging the
products along the processing path. The products and cooking oil moved
concurrently
through the cooker, being that cooking oil was introduced at the product feed
end of the vat
and removed at the product discharge end.
[0005] The Benson et al. U.S. Patent 5,167,979, granted Dec. 1, 1992,
disclosed control
of the time-temperature curves in cooking oil to achieve various styles of
potato chips from
potato slices. These were moved along the processing path and agitated by
mechanical
means. Cooking oil inlets and outlets were shown arranged in the cooker bottom
but it was
not taught that the oil flow would determine the orientation of the potato
slices during the
cooking cycle, the mechanical agitating means determining that function.
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[0006] The Haraldsson et al. U.S. Patent 5,865,102, granted Feb. 2, 1999,
disclosed
deep frying potato slices in a pan having a plurality of cooking oil inlets
and a plurality of
cooking outlets, all located in the bottom of the pan. Lateral oil inlets were
positioned in the
sides of the pan to create turbulence in the cooking oil transversely of the
longitudinal
direction of the pan. The concept was to use turbulence to encourage
separation of the
potato slices while cooking in oil. Orientation of the slices in the cooking
oil was not taught
nor was control of steam generated from the cooking potato slices.
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Summary and Objects of the Invention.
[0007] In summary, the invention resides in the method of continuous
preparation of
French fried potatoes from potato strips comprising the steps of providing a
vat of cooking oil
equipped with a product carrying conveyor capable of passing a current of
cooking oil there
through from an oil inlet disposed there below. Loading a volume of uncooked
potato slices
into the vat for carriage on the conveyor so as to build a pack of strips and
to create a "boil"
of steam from the strips, supplying cooking oil through the oil inlet at a
volume and velocity
to create an upward force vector acting with the "boil" to orient the strips
in generally vertical
positions thereby permitting steam to pass freely from the slice pack and then
removing the
slices from the vat while recirculating and reheating the cooking oil.
[0008] Another aspect of the invention resides in apparatus useful in the
continuous
cooking of French fried potato in a deep pack of uncooked strips. A fryer pan
is configured
with multiple cooking oil inlets in the bottom portion thereof through which
oil is pumped into
the pan in upwardly moving streams. A potato strip carrying conveyor having a
belt through
which oil moves readily extends the length of the pan and is inclined upwardly
at a discharge
end of the pan. Means are provided for removal of cooking oil at locations
including at the
product discharge end and along the sides of the conveyor.
[0009] A general object of this invention is to provide in the continuous
preparation of
French fried potatoes a process which enables the rapid escape of steam from a
pack of
potato strips during the deep frying step thereby promoting more uniform
cooking of the
potato strips and recognizing that without a vertical orientation of the
strips the pack of strips
inhibits the flow of oil through the pack because of generated steam creating
steam pockets
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in the center of the pack which limits the operational depth of the pack.
[0010] Another object of this invention is to provide apparatus for continuous
deep
frying of potato strips in a vat of cooking oil that causes the strips to
assume a generally
vertical orientation during passage through the cooking oil.
[0011] Still another object of this invention is to provide in apparatus of
the foregoing
object means serving to create and maintain a force vector in the cooking oil
directing the
potato strips toward a non-supine orientation.
[0012] Yet another object of this invention is to provide a process and
apparatus that
enables the continuous cooking of potato strips in a pack thereof which is
substantially
double, or more, in depth from that of the prior art.
[0013] A further object of this invention is to provide a process and
apparatus that
greatly increases product output while promoting better product uniformity by
affording
dissipation of steam from the pack of potato strips while cooking.
[0014] Still another object of this invention is to provide a frying system
containing
substantially less cooking oil resulting in better oil quality due to faster
turnover of oil as the
carry out of the oil on the product is replaced with fresh cooking oil.
[0015] These and other objects of the present invention will be apparent from
the
following description of the preferred embodiments taken in association with
the following
drawings.
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Brief Description of the Drawings.
[0016] Fig. 1 is an elevation view, partially schematic, of the vertical flow
French fryer
apparatus configured to perform the processes of the present invention;
[0017] Fig. 2 is an enlarged sectional view taken in the direction of the
arrows along
the lines 2-2 of Fig. 1;
[0018] Fig. 3 is an enlarged plan view, partially broken away, taken in the
direction of
the arrows along the lines 3-3 of Fig. 1;
[0019] Figs. 4 -7 are each detail views of the slat type product conveyor
useful in the
practice of the present inventions;
[0020] Fig. 8 is a plan view in full scale of a portion of a mesh belt product
conveyor
use in the practice of the present inventions;
[0021] Fig. 9 is fragmentary, conceptual view showing from within the pack of
cooking
potato strips showing the generally vertically orientated potato slices and
the steam bubbles
emanating upwardly during the cooking process; and
[0022] Fig. 10 is a fragmentary, conceptual view of the prior art methodology
showing
from within the pack of cooking potato strips the generally supinely
orientated potato strips
and the steam bubbles trapped within the pack inhibiting oil movement there
through.
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Description of. the Preferred Embodiments.
[0023] A vertical flow fryer 10 for cooking French fried potatoes from potato
strips,
made in accordance with and embodying the principles of the present
inventions, is shown in
Fig.1. The vertical flow fryer 10 includes a fryer pan 11, a conveyor belt 12,
and arrays of
cooking oil inlets 13 arranged along the bottom wall of the pan 11. The pan
11, at a product
discharge end 14, is inclined upwardly and the conveyor belt 12 traverses this
incline so as to
facilitate discharge of cooked slices unto a product discharge conveyor 16. An
oil outlet sump
17 is disposed at the inclined discharge end 14 of the pan for receiving oil
to be reheated in
the heat exchanger 18, filtered 19 and returned via the oil pump 21 to the
fryer pan 11
through the inlet manifolds 13. A product in feed conveyor 22 is mounted over
the inlet end
of the fryer pan 11, as shown in Fig. 1 for delivery of uncooked potato strips
from potato
cutting apparatus (not shown) into the hot cooking oil 23 contained in the pan
11 thereby
creating a "boil" in the cooking oil as water is driven off the strips as
steam. The energy
released in the "boil" is utilized in the practice of the present inventions.
[0024] Referring now to Figs. 1 and 2, the product carrying conveyor 12 is
arranged in
the fryer pan 11 inwardly of the pan sidewall so as to afford on each side of
the conveyor 12
an oil flow channel 24 defined by the upstanding inner pan walls 26 spaced
from the pan
longitudinally extending side walls. The inner pan walls 26 at a lower portion
thereof are
integral with the conveyor frame as indicated in Fig. 2. At portions above the
conveyor 12 belt
and above the projected product load height the pan walls 26 are provided with
flow-over
edge flanges 27 so that cooking oil may well up trough the conveyor belt,
through the
product slice pack 28 and into the channels 24 from over the edge flanges 27
for return for
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filtering and reheating. The oil flow channels 24 serve as a conduit for the
cooking oil to flow
towards the oil outlet 17 at the discharge end of the pan.
[0025] It will be understood that contact of the pack of potato strips 28 with
the
cooking oil 23 occurs in the fryer 10 in the zone between the pan inner walls
26, as indicated
in Fig. 2, and from the drop off point from the in feed conveyor 22 to the
product emergent
point on the inclined discharge portion 14 of the conveyor and pan, as
indicated in Fig. 1.
Referring specifically to Fig. 3, there is indicated by cross-hatching 29 the
zone above the oil
inlet manifolds 13 and above the conveyor belt 14 wherein vertical flow occurs
through the
strip pack 28. This flow has been found to tilt the strips into a generally
vertical orientation
engendered, it is believed, by the force vector of the input oil and the
"boil" within the
cooking oil. As indicated in Fig. 9, steam escaping from the "boil" flows more
freely through a
pack of vertically disposed slices than through a pack of supine slices, as in
the prior art, Fig.
10. There, it has been long observed, the resulting slices displayed a non-
uniformity of
cooking. By contrast, the present vertical flow fryer system 10 results in
very uniform
cooking. Moreover, the depth of the slice pack 28 processed in the fryer 10
may be generally
twice the depth of slice packs of prior art fryers.
[0026] The belt of the conveyor 12, as indicated in Figs. 4 -7, is preferably
constructed
as a steel slat 31 having, in lateral cross section, a channel shape
comprising a broad web 32
with depending flanges 33. To facilitate the ready passage of cooking oil
there through a
multiplicity of slots or oil passageways 34 are formed in the web 32 of the
conveyor slat 31.
At each end the individual slats 31 are joined to a continuous roller chain
34, as indicated in
Figs. 5 and 7, by fasteners 38 thus constituting the conveyor belt which is
driven by
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conventional mechanisms (not shown). A wire mesh belt 37 is shown in Fig. 8
which can
serve as a satisfactory conveying belt for the fryer 10 although it is not as
stiff as the slat belt
of Figs. 4 - 7. The mesh belt 37 is shown in full scale in Fig. 8 and affords
ready passage of
cooking oil there through and good support for the slice pack 28.
[0027] A number of arrows are displayed in the drawings indicating various
movement
of product flow or cooking oil flow. In Fig. 1 the French fry slice product
flow is indicated by
the arrow 15. Upward oil flow through the slice pack 28 is indicated as in
Figs. 1 and 2 by the
arrows 20. The flow of cooking oil from the cooking oil outlet sump 17 through
the filtering
and re heating cycle as in Fig. 1 is indicated by the arrows 25.
[0028] It will be readily apparent that various modifications may be made to
the
structures and processes of these inventions and still be within the scope of
the present
invention. Accordingly, the scope of these inventions shall only be limited
within terms and
spirit of the following claims.
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