Note: Descriptions are shown in the official language in which they were submitted.
~ h~L~5~
Background_of the Invention
Field of the Invention: This invention relates to and
has among its objects the provision of novel potato products and
novel processes for making them. It is a particular object of the
invention to provide a precooked, non-par-fried potato piece,
such as a French-fried potato, shoestring potato, and the like,
which subsequently can be finish-cooked prior to consumption.
It is another object of the invention to prepare a precooked
boiling potato which can be finish cooked by boiling in water.
Further objects of the invention will be evident from
, ~
the following description wherein parts and percentages are by
weight unless otherwise specified. Texture here relates to the
surface layer of the strip and also includes the center. Good
quality fried potato strips are rigid with a crisp surface layer and
a firm b~t mealy inner core. Rigidity ccncerns the ability of the
'''
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finished product to resist bending and is thus distinguished
from texture. A thick, leathery surface can impart rigidity to
a fry. It should be obvious that a crisp, rigid, rather than a
leathery, rigid, finished fry is preferred. The terms "fat" and
- "oil" are used synonymously herein as designating an edible glyc-
` eride whether normally solid or liquid.
Description of the Prior Art: Most restaurants, includ-
ing the large franchise chains, prefer to prepare their French-fried
potatoes from the frozen or chilled par-fried product rather than
to go through the cumbersome procedure of preparing French frie
from raw potatoes. Although these par-fried products offer
convenience and savings in labor costs, one problem which has
beset the industry is that when the products are prepared for
the table (either by oven heating or by deep-fat frying), they
are unstable as to texture. Immediately after removal from the
oven or deep-fat fryer, the potato strips have a desirable crisp
texture, but as they cool they become limp and soggy. rhis
problem is particularly acute in large restaurant operations.
Guests who receive the first portions of each batch enjoy French
fries of desirable crisp texture, whereas others who receive
subsequent portions of the batches can only contemplate with
dismay the soggy, limp strips on their plates.
Standard commercial French-fried potato products are par-
fried prior to distribution. To prepare them for the table the
product is given a finish-fry. The double frying increases the fat
content of the French-fried product. Although some fat is necessary
for the characteristic flavor of the French-fries, excessive fat is
to be avoided for dietary and other reasons.
~- French-fried potatoes for home consumption are usually
prepared by cutting raw potatoes into stripsS blanching the
potatoes in hot water, par-frying the potato strips in oil~ and
then preserving the strips by chilling or freezing them. To prepare them
for consumption the French-fried potatoes are either baked in ovens or
finish-fried in oil.
Potatoes, especially high solids tubers, tend to fall apart or
--~ slough when they are retorted in cans or pouches or when they are prepared
for consumption by boiling. Thus, the types of potatoes that can be used
for soups, stews, salads, whole-boiling potatoes, or the like, are limited
to low-solids varieties.
A procedure for preparing precooked baking potatoes has previously
been described. In this known process, potatoes are cooked to their centers
without damage to their surface tissue. An important feature oE the cooking
is that the temperature thereof for a part of the time, be above the
temperature at which sloughing of the potato surface would occur if the
potatoes were cooked to their centers at that temperature. Following the
cooking procedure the potatoes are heated in air and then frozen or chilled
to preserve them. The above-described method cannot be used to prepare
French-fried potatoes.
In U.S. Patent No. 4,194,016 of March 1980, Weaver, et al., there
isdisclosed a process for making precooked fruits and vegetables.
Potatoes, for example, are cooked to their centers at a temperature below
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the temperature at which sloughing of the surface tissue would
occur if the potatoes were cooked to their centers at that
: ,~
temperature. Then, the so-treated potatoes are heated in air
~: and then frozen or chilled to preserve them. It is noted also
in this application that the method described therein cannot
be used to prepare French-fried potatoes.
Finally, a process for preparing French-fried potatoes
is described by Strong in Canadian Patent No. 806,128, issued
. February ll, 1969. In the patented process potato strips are
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- 10 blanched until all portions receive enough heat to turn them
to a generally translucent condition throughout. The blanching
may be conducted using steam for 2 to lO minutes or hot water
at 71-93C. for 3 to 8 minutes. The blanched strips are
dehydrated in hot air at 65-177C. for 5 to 20 minutes to a
moisture reduction of 20 to 30% of their initial weight. Then,
the strips are par-fried at 149-191C. for 15 to 60 seconds
and then frozen to preserve them.
The process of Strong has certain disadvantages, however.
From an economic standpoint, the Strong process requires con-
siderable expenditure of energy and money in the heating and
par-frying steps. In addition, the texture of the final
product is unpredictable: in many instances the product is
puffed and blistered. Furthermore, if the potatoes employed
in the Strong process are high in reducing sugars, a lengthy
preconditioning step is necessary to obtain an acceptable
product.
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Summary of the Invention
~ le invention described herein provides a means for preparing
precooked potato products, such as non-par-fried, French-fried potato
pieces, and the like, of excellent texture, color and flavor. In addition,
precooked boiling potatoes from both high and low solids potatoes can be
prepared by the method of the invention.
The process of the invention may be generally described as
comprising the following steps:
(1) washing, peeling, and cutting raw potatoes;
(2) cooking the potatoes at a temperature below the temperature
at which sloughing of the potato surface would occur if the whole potato
were cooked to its center at that temperature for a period of 5 to 45
minutes, said temperature being below 83C;
(3) heating the so-cooked potatoes in air at a temperature of
from about 66C to about 93 C for a period of from about 5 to about 30
minutes; and
(4) then, cooking the potatoes at a temperature of about 50 to
100C.
` One important advantage of the invention is that the finish-fried
potato product possesses a uniform texture and freshly-fried flavor
equivalent to that of a freshly cut and fried potato piece. Known commercial
methods are unable to yield a non par-fried product exhibiting these
qualities.
Another advantage of the process of the invention is that it
yields a product of uniform color and texture. Freshly-cut and fried
potato pieces generally do not posses uniform color and texture throughout
the year because raw tubers vary in sugar
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- content and solids content at different times after harvest. The finish-
fried products prepared in accordance with the invention exhibit an excel-
lent uniform golden brown color. They have a crisp exterior, a firm, but
-- mealy interior~ and maintain their rigidity for long periods of time after
they are finish-fried.
- A further advantage of the invention is the elimination of the
..;
` par-frying step prior to freezing or chilling. As explained above, commer-
cial products are par-fried at the processing plant. The method of the in-
; ~ vention avoids a par-frying step of this nature. This reduces the capital
r~ 10 investment and removes the expenses associated with frying in oil heretofor
encountered by the processing industry. Furthermore, the finish-fried pot-
ato product contains less oil because of the surface produced during the
process of the invention and because only one frying step is applied to the
potato piece. The storage life of the product is increased as a result of
the absence of a par-frying step. Finally~ the surface of the finish-fried
; product is crisp, does not appear to be soaked with oil, and is not shirv-
., .
; eled.
,
Description of the Preferred Embodiments
The process of the invention will next be described in detail with
emphasis on preparing a precooked, non-par-fried, French-fried potato piece.
It should be noted that a precooked boiling potato can be prepared according
to the same process. However, potatoes may be cut into pieces or left whole
depending on the type of product desired.
In the process of the invention raw potatoes are peeled and then
~ cut into pieces of about 0.6 to 1.3 centimeters square and about 10 centi-
- meters long. The potato pieces are then subjected to a cooking step, the
.:
temperature and length of this cooking step being dependent upon the size
of the potato pieces to be treated. In this step the potato pieces are
cooked with either water or steam, or a combination of both, at a tempera-
- 30 ture below the temperature at which sloughing of the surface tissue would
`o $~
occur if the whole potatoes were cooked to their centers at that tempera-
ture. Generally, for potatoes this temperature is about 81-83C. The
pieces are heated until they are cooked to the center, and often longer;
i.e.~ for a period of about 5 to 45 minutes. The usual mode of cooking
potatoes in water involves immersing the potatoes therein at the proper
temperature. Alternatively, steam can be applied to the potatoes at the
desired temperature, and at atmospheric or superatmospheric pressure.
It must be emphasized that the duration of the cooking step is
dependent upon the size of the potato pieces, maturity, and composition of
potato used. Exact conditions for a particular lot of potatoes can be de-
termined using pilot trials in accordance with the process and rationale of
the invention.
The so-cooked potatoes are next heated (dried) in air, preferably
at a temperature of about 66 to 93C. for about 5 to 30 minutes. During
this period the moisture content of the potatoes is generally reduced about
10 to 60%, depending upon the temperature, the time, the air flow, and the
size, type, and composition of the potato piece. The heating step is usual-
ly carried out immediately after the cooking step. However, the cooked po-
tatoes may stand for several minutes to several hours before being heated
with no deleterious effects on the quality of th0 product.
It should be noted that the heating step is critical to the method
. ~
; of the invention. By application of heat the retrogradation of starch is
~ promoted. Further, the texture and flavor of the final product is enhanced.
, ~..
However, although it appears that the reduction of moisture content is re-
sponsible for the improved texture, it may be that the important feature is
solely the application of heat regardless of the extent of moisture removal.
In any event, the heating step must be employed to obtain a good quality
potato product.
Next, the cooked and heated potato pieces are again subjected to
a cooking period. The temperature employed during this coo]cing step is
"' X
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, dependent on the preservation technique employed on the product to maintain
it until it is finish-cooked, but is generally within the range of about
,- 50-100C. If the product is to be frozen or retorted to preserve it, the
temperature of the second cooking must be below 81-83C., i.e., the temper-
~ ature at which sloughing of surface tissue would occur if the whole potato
- ~ were cooked to its center at that temperature. On the other hand, if the
product is chilled until it is finish-cooked, the temperature of the second
~ cooking can be from about 50 to 100C. It should be noted, however, that
; the exterior and interior texture of the potato piece changes with change in
- 10 temperature in the second cook. The second cooking step is otherwise simi-
lar to the above-mentioned first cooking step; either water or steam or both
can be employed as the cooking medium. The second cooking period is from
: ::
about 5 to 45 minutes, preferably 5 to 30 minutes. The period is dependent
on the texture and flavor desired in the finish-cooked product, the temper-
:,
ature, the characteristics of the raw material, such as sugar content, and
~ the nature of the heating-in-air step. Again, pilot trials can be used to
~ ascertain the proper conditions. It should be noted that the second cooking
:
~ procedure is a necessary one. If the step is omitted, the resulting product
:.
will be inferior in flavor and texture and will puff and blister if fried.
~ It is necessary to equilibrate the product if the second cooking
~,
step is conducted above 81-83C. Usually, the product, after the second
cooking step, is held at a temperature of about 1 to 25C. for a period of
about 2 to 24 hours. Longer equilibration times will not add to or subtract
from the quality of the product. The equilibration time depends on the type
of product being made, the solids content of the potatoes, and the tempera-
ture employed.
Following the second cooking step the potatoes are treated to pre-
serve them. Usually, the so-prepared products are frozen and then packaged
for retail sale or institutional use. The potatoes can be frozen in any
conventional manner including refrigeration rooms, blast freezing, and the
.~
-- 6 --
5~
like. It may be desirable to remove surface water by blowing, shaking, or
the like, prior to freezing the product. The prepared product can also be
- chilled at about 0.5 to 8.0C. to preserve it for future use. Finally, the
so-prepared potatoes may be placed in cans or plastic pouches and then re^
torted as a preservation means.
It may be necessary in conjunction with the process of the inven-
tion to treat the so-cooked and so-heated potatoes to prevent after-cooking
darkening. Any conventional technique may be used to this end. For ex-
ample, the potatoes can be dipped, after the first or second cook, or both,
in dilute aqueous solution of citric acid, sodium acid pyrophosphate, sodium
bisulfite, and the like.
: To prepare them for consumption the products of the invention are
fried in hot oil to the desired level of crispness and color. In general,
the potato pieces are contacted with the oil at a temperature of about 177
; to 191C. for a period of about 2 to 4 minutes. The so-prepared potatoes
,:,
- exhibit the appearance, flavor, and texture of a freshly-cut and fried po-
tato piece.
A par-frying step is not necessary in the process of the inven-
tion. However, it may be desirable to par-fry the products of the invention
~; 20 in hot oil prior to preserving them. For example, in the event that the
; product of the invention is to be finish-cooked by baking in an oven, the
product necessarily would have to be par-fried prior to freezing or chilling
`` for the purpose of preservation. Otherwise, the final product would not
have the characteristic of a fried potato piece.
Excellent fried potato pieces of the nature of French-fried po-
; tatoes can be prepared by the process of the invention. It should be empha-
sized, however, that thin-sliced or shredded potatoes of the nature of hash-
brown potatoes cannot be prepared according to the aforementioned procedure
unless the product treated in accordance with the invention is equilibrated
for a period of about 12-48 hours at a temperature of about 1 to 25C.
.
Further, fried potatoes prepared by the process of the invention can be
baked to finish-cook them provided they are first par-fried in hot oil.
It is within the compass of the invention to finish-cook potatoes
prepared in accordance with its teaching by boiling in water. Thus, the so-
prepared potatoes can be employed in salads and in soups and stews, which
require long cooking periods. It is noteworthy that the potatoes of the in-
vention do not slough or disintegrate when subjected to boiling for extended
periods. Generally, the potatoes are boiled in water for 15 to 30 minutes
at a temperature of about 90-100C. in order to finish-cook them. The fin-
ish-cooking time will vary with the size and type of potato piece and with
..
the manner in which they are preserved. The final product has the appear-
ance, flavor, and texture of a freshly boiled product.
EXAMPLES
The invention is further demonstrated by the following illustra-
, tive examples. Some of the experiments are not in accordance with the in-
,'!: vention but are provided for purposes of comparison.
Example l
Raw potatoes (Russet Burbank variety) were washed, peeled, and cut
into pieces 0.95 cm. square and 10 cm. in length. The potato pieces were
then subjected to a cooking step using either water or steam, or a combina-
tion of both. Water cooking was conducted by immersing the potato pieces in
water. Steam cooking was accomplished by exposing the pieces to steam at
the desired temperature. Next, the potato pieces were heated in air by plac-
ing them in a forced-air oven. Then, the so-heated pieces were again cooked
in either water or steam or a combination of both as described above. The
above procedure was repeated at varying times and temperatures.
Potato pieces from each treatment were divided into two lots, one
of which was frozen, the other chilled. The so-prepared products were fin-
ish-cooked by frying in oil at a temperature of 185C. for 2.5 minutes.
The experiments and results are summarized in the following table.
h O o o o o o o o
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- 10 -
. .
'
Example 2
The procedure of Example l was followed. After the second cook-
ing step, but prior to either freezing or chilling, the products were par
fried in oil at 185 C. To prepare them for consumption the potato pieces
were either finish-fried in oil at about 185C. for Z.5 minutes, or baked
in an oven at 218C. for 12 minutes. The results are tabulari~ed in the
; following table.
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~ - 12 -
Example 3
The procedure outlined in Example 1 was followed. In some runs
; after the second cooking step potato pieces were placed in plastic pouches,
which were then sealed. The pouches containing the potato strips were re-
torted at 121C. for 15 minutes at a pressure of 15 psig.
In other runs potato strips were frozen immediately after the sec-
~ ond cook or were held at about 5C. for 16 hours.
: The products in all runs were prepared for consumption by frying
for 3 minutes in oil at about 186C.
-:,.
The results are summarized in the following table.
- 13 -
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- 14 -
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Example 4
~' Potato pieces were treated according to the general procedure
outlined in Example 1. One half of the potato pieces was frozen immediate-
ly after the second cook, the other half was held at 0.5C. for 12 hours
.. , 5 after the second cook. To finish-cook them the pieces were fried for 3
minutes in oil at 186C. The results are summarized in the following
table.
. - 15 -
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- 16 -
~ Example 5
- Whole potatoes and potato pieces were treated as in Example 1.
After the second cook whole potatoes were placed in cans (#303) or in plas-
tic pouches, sealed, and retorted at 121C. for 15 minutes ~pouches) and
30 minutes ~cans) at a pressure of 15 psig. In other runs the potatoes
were frozen immediately after the second cook or were held at about 5C.
for 16 hours. All products w~re prepared for consumption by boiling in
water for 30 minutes. The results are tabularized below.
. .
- 17 -
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- 18 -
