FIELD OF THE INVENTION The present invention relates to a process for producing a french fried potato product which upon reheating in a conventional or convection oven or under a heat lamp-type food warmer closely resembles the size, shape, appearance, color, texture, taste, aroma, and total eating experience of french fried potato products which have been deep fat fried immediately prior to eating.

BACKGROUND OF THE INVENTION

This is a continuation-in-part application of U.S. Application Ser. No. 374,325, filed June 30, 1989.

The market for french fried potato strips, commonly referred to as french fries, is currently estimated at approximately 6.5 - 7 billion dollars annually. The bulk of this market is the fast-food restaurant business, wherein parfried and frozen potato strips are commonly purchased in bulk from commercial suppliers and stored at freezer temperatures until shortly before serving. At that point, the parfried and frozen potato strips are prepared for eating by deep fat frying in fat or oil.

McDonald's™ french fries, long considered the state-of the art in the fast-food industry, apparently

are processed according to the process described in U.S. Patent No. 3,397,993 (Strong). Therein, raw potato strips are blanched by steam or hot water until generally translucent throughout, dehydrated in hot air to cause a weight loss of at least 20 percent, parfried for 30-60 seconds at 375°F and then frozen to about 0°F. The frozen potato strips are shipped and/or stored until final fry is desired. They are finish fried by immersing in a deep fat or oil bath, usually containing a medium consisting mainly of beef tallow, at a temperature of about 300-375°F for 1.5 - 3.5 minutes.

Another method for preparing french fries for fast food restaurants is taught in U.S. Patent No. 3,649,305 (Wilder) , wherein potato strips are dehydrated to reduce their moisture content by 10-30 percent, blanched, parfried for 30-90 seconds at about 300-400°F and then frozen. The frozen strips are then fried in oil for 1.5 - 3 minutes at 325-375°F.

Many attempts have been made to duplicate the flavor, aroma, color, texture and total eating experience of deep fat fried french fries prepared according to the above or similar methods. These efforts have met with varied results. These processes use pan-frying the potato strips in oil, oven baking, or microwaving the potato strips. Such prior art methods may produce limp, soggy, greasy, or dehydrated products which do not approximate the total eating experience of fast-food french fried potatoes. Examples of prior art methods include those described in U.S. Patent No. 3,597,227, Reissue No. 27,531 (Murray et al.), U.S. Patent No. 3,865,964 (Kellermeier et al.) U.S. Patent No. 3,751,268 (Van Patten et al.), U.S. Patent No. 4,317,842 (El-Hag et al.), U.S. Patent No. 4,551,340 (El-Hag et al.), U.S Patent No. 4,109,020 (Gorfien et al.), U.S. Patent Nos. 4,456,624 and 4,559,232 (both to Glantz et al.), U.S. Patent No. 4,632,838 (Doenges) , U.S. Patent No. 4,590,080 (Pinegar) , U.S. Patent No.

4,219,575 (Saunders et al.) and U.S. Patent No. 4,272,553 (Bengtsson et al.).

U.S. Patent No. 4,317,842 (El-Hag et al.), for instance, discloses a process for producing french fried potatoes which upon oven baking is intended to simulate deep fat fried potato strips. Raw potatoes are washed, peeled, cut, blanched and otherwise processed in a conventional manner. The potato strips are then coated with a 4 percent potato starch solution and soaked in an oil bath at a temperature of from 120°-210°F for 2-6 minutes. If the potato strips are conventional frozen potato strips as received by fast food restaurants, they are parfried and frozen prior to coating in the starch solution and oil soaking. The oil-soaked potato strips are then parfried frozen. They are reconstituted by oven baking, preferably using a special conductive heat transferring apparatus.

Another reference, U.S. Patent No. 3,865,964 (Kellermeier) discloses a process for producing an oven baked french fried product by spraying edible oil or fat onto frozen potato strips, freezing the potato strips, and then baking the potato strips in an oven.

It is an object of the present invention to provide a french fried product which upon reheating to a suitable temperature for consumption closely resembles the flavor, aroma, texture, mouthfeel and total eating experience of a deep-fat fried fast food french fry.

It is yet another object of the present invention to provide a french fried product which when reheated to a suitable serving temperature by conventional or convection oven, or a conventional food warming device such as a heat lamp, closely resembles the flavor, aroma texture, mouthfeel and total experience of a deep-fat fried fast food french fry.

It is a further object of the present invention to provide a french fried product which may be kept warm for an extended period of time after reheating in a

conventional or convection oven without becoming soggy, limp, or suffering structural damage.

It is yet another object of the present invention to provide a french fried potato product which can be reheated in bulk or in the consumer's home in a very short period of time, and which is virtually indistinguishable from deep-fat fried french fried potatoes which may be purchased in fast-food restaurants.

It is a further object of the present invention to provide a french fried product which upon reheating to a suitable temperature for consumption closely resembles the flavor, aroma, texture, mouthfeel and total eating experience of a deep-fat fried fast food french fry.

SUMMARY OF THE INVEN'-ION

In accordance with the above-mentioned objectives, one aspect of the present invention relates to a process for preparing french fried potatoes suitable for subsequent reheating in a conventional or convection oven or under a heat lamp-type warmer to obtain a product having a crisp exterior and a tender interior, comprising blanching potato strips, applying a dust- coating of potato granules to the blanched potato strips to provide a thin coating of potato granules which adheres on the surface of the potato strips, and finish frying the dust-coated potato strips to a fully cooked, ready-to-eat condition. In a preferred embodiment, a coating of toasted potato granules is applied on the finish fried potato strips to provide a thin coating of toasted potato granules which adheres on the surface of the potato strips. The potato strips preferably are then frozen. Optionally, the blanched potato strips are parfried prior to dust-coating with potato granules.

Another aspect of the present invention relates to a process for preparing french fried potatoes suitable for subsequent reheating to obtain a product having a

crisp exterior and a tender interior, comprising coating parfried potato strips with toasted potato granules to provide a thin coating which adheres on the surface of the potato strips. The coated potato strips may then be frozen for subsequent reconstitution. In preferred embodiments, the potato strips are finish fried to a fully cooked, ready-to-eat condition prior to the application of the toasted potato granules.

Another aspect of the present invention relates to a process for preparing improved french fried potatoes suitable for subsequent reheating in a conventional or convection oven to obtain a product having a crisp exterior and a tender interior, comprising parfrying potato strips, cooling the parfried potato strips, finish frying the potato strips to a fully cooked, ready-to-eat condition, applying a coating of toasted potato granules on the finish fried potato strips, and gently freezing the finish fried potato strips without substantial desiccation to minimize structural damage. In one embodiment, the parfried potato strips are frozen.

Preferably, the finish fried potato strips are frozen in a tunnel cooled by a gentle flow of a freezing agent in the vapor state such as liquid nitrogen in a manner which substantially avoids desiccation and structural damage.

Another aspect of the present invention relates to a process for preparing fully cooked potato strips suitable for subsequent reheating to obtain a product having a crisp exterior and tender interior, comprising finish frying potato strips in a continuous fryer having three cooking zones. The temperature of the frying medium in each zone may be individually adjusted to optimize the product.

Another aspect of the present invention relates to a process for preparing frozen parfried potato strips for finish frying and further freezing to obtain a

product having a crisp exterior and tender interior upon subsequent reheating which comprises tempering frozen parfried potato strips by placing them in a controlled environment and gently agitating or tumbling them in the controlled environment to enhance exposure of all of the surfaces of the potato strips to the ambient air to maximize temperature equilibration. At the end of the tampering process, the potato strips preferably have an average internal temperature from about 27°F to about 35°F.

Another aspect of the present invention relates to a finish fried potato strip* suitable for subsequent reheating substantially without cooking to obtain a product having a crisp exterior and a tender interior having a thin layer of toasted potato granules which adheres on the surface of potato strip.

Another aspect of the present invention relates to a finish fried potato strip adapted to substantially withstand moisture migration to the surface of the potato strip and structural damage while frozen, comprising an exterior portion having a first layer comprising potato granules which have been applied to the surface of the potato strip and thereafter deep-fat fried such that the potato granules are substantially integral with the potato strip, and a second layer comprising a coating of toasted potato granules which adhere to the surface of the first layer. The potato strips are suitable for subsequent reheating substantially without cooking to obtain a product having a crisp exterior and tender interior.

The frozen finish fried potato strips may be reheated to a suitable eating temperature by warming for a short period of time in a conventional or convection oven, or by warming via a conventional food warming device such as a heat lamp. Also, the potato strips may be reheated in a conventional or convection oven and then may be kept at eating temperatures via the use of a

food warming device for an extended period of time.

DETAILED DESCRIPTION

The process of the present invention is practiced upon conventional potato strips first by the initial preparation of whole potatoes into strips which may be treated as discussed below. Basically, whole potatoes are washed, peeled and then cut into strips having the desired size and shape. Thereafter, the potato strips are blanched. Blanching has a leaching effect on sugars present in the potato strips and serves to even out the sugar levels throughout the potato strips, which in turn reduces the occurrence of dark or unevenly colored finished fries. This is caused mainly by the action of enzymes, which are inactivated in the blanching step. Commercial procedures for washing, peeling, cutting and blanching in the production of french fried potatoes are discussed in "Potato Processing" by William F. Talburt and Ora Smith, Third Edition, 1975, published by the AVI Publishing Company Inc. , Westport, Connecticut at pages 415-423. In particular, blanching is usually carried out by exposing the raw cut strips to either water or steam for a suitable time and temperature well known in the prior art.

The potato strips which are used in the present invention may be of varying size and shape. However, it is preferred in one embodiment that the relatively thin and elongated potato strips known in the art as "shoestrings" be used. Shoestring potato strips, as the term is used herein, is defined as potato strips which are from about 3/16 to about 5/16 inch square in cross- section and from about 2 to about 5 inches in length. Preferred is a shoestring potato strip from about 1/4 to about 5/16 inch (per side) square in cross-section and from about 2 to about 4.5 inches in length.

In another embodiment of the present invention, it is preferred to use irregularly cut potato strips known

in the art as "crinkle-cut" strips. Such strips usually average from about 5/16 to about 7/16 inch square in cross-section and from about 2 to about 3 inches in length. Preferred is a crinkle cut potato strip which is about 5/16 inch square in cross-section.

Also, straight cut thick fries of about 1/2 inch square in cross-section and from about 2.5 to about 2.5 inches in length may be used.

It is preferred that the potato strips that are to be dust-coated are previously parfried, or parfried and frozen. Such potato strips are widely available in the food industry from various sources, and are made commercially available to fast food restaurants, distributors, etc.

An example of a preferred manner in which the potato strips may be processed prior to dust-coating is taught in U.S. Patent No. 3,397,993 (Strong), assigned to McDonald's System Inc., and hereby incorporated by reference. Strong teaches that after the strips are washed free of starch by barrel washing, fluming, etc., they are then blanched preferably by steam for about 2- 10 minutes until all portions of the strips receive enough heat to turn them into a generally translucent condition throughout. Alternatively, a hot water blanch may be used for about 3-8 minutes at a temperature of about 160-200°F. The strips are then dehydrated by subjecting them to heated air currents for about 5-20 minutes at a temperature of about 150-350"F to reduce their moisture content. Thereafter, the strips are parfried in a deep fat fryer for a short period of time, preferably from about 15 to about 60 seconds at a temperature from about 300° to about 375°F. The parfrying has the effect of further reducing the moisture content and partially frying the raw potato strips.

Although the Strong disclosure is discussed above as an example of the manner in which the potato strips

may be treated prior to dust-coating, it is not meant to be exclusive. Many other procedures well-known in the art are also suitable, such as that which is disclosed in U.S. Patent No. 3,649,305 (Wilder), hereby incorporated by reference.

The term "parfrying" refers to the partial frying of a potato strip to a degree less than that of a fully cooked or "finish fried" potato strip.

In most instances, the oil used to accomplish the parfrying of the potato strips comprises refined beef tallow, oleo stock or a blend of beef tallow and a lesser amount of one or more vegetable oils, i.e. usually 10-15 percent.

Finally, the potato strips are frozen, for instance by placing them directly into a freezer, by first cooling the strips and then freezing them to about 0°F, or blast freezing them at a temperature of from about -25° F to about -30°F by the use of freon, etc. The frozen strips are then packaged as desired, stored and/or shipped for further processing.

It is also important to note that other fats and oils in addition to or in the place of beef tallow may be used to parfry the potato strips. For instance, partially hydrogenated cottonseed oil, soybean, palm, sunflower, safflower, coconut, canola, peanut oils and the like, or combinations thereof can also be used. Additionally, it is envisioned that reduced-calorie or calorie-less fats, or fat-substitutes such as Olestra™ from the Procter and Gamble Co., would also be useful in parfrying and/or finish frying.

The potato strips may be further pretreated prior to freezing according to conventional methods known in the art. For instance, the potato strips may be treated with sodium acid pyrophosphate (SAPP) , a chelating agent used to prevent discoloration of the strips. Dextrose (corn sugar) may be used in order to provide a golden

color upon frying. Sulfur dioxide may be used to inhibit browning. Other pretreatments known in the art may also be used.

The parfried and frozen potato strips generally have a moisture content of about 60-70 percent, a fat content of from about 4 to about 7 percent by weight, and a potato solids content of from about 23 to about 36 percent by weight of the potato strip.

In another embodiment of the present invention, raw unpeeled white potatoes are obtained for processing. Usually, raw white potatoes have a moisture content of about 75-85 percent by weight. Although any variety of potato would be useful to practice the present invention, Russet Burbank or Katahdin potatoes are examples of preferred potatoes. The potatoes are washed, peeled, trimmed, sorted, cut, blanched, and optionally pretreated in any conventional manner or as detailed in the above-mentioned Potato Processing reference. Thereafter, the potato strips are preferably dust-coated. In another embodiment of the present invention, the tempered potato strips are finish fried without the application of the above-mentioned dust- coating.

By a further teaching of the present invention, potato strips are prepared as disclosed in pending applications U.S. Serial Nos. 017,140, filed February 20, 1987 and continuation-in-part application U.S. Serial No. 108,722, filed October 14, 1987, and then dust-coated and otherwise treated in accordance with the present invention to render a superior engineered or simulated french fried potato product.

If the potato strips have been parfried and frozen, it is preferred that they are thawed to an internal temperature from about 27"F to about 30°F prior to further treatment. The potato strips may be thawed according to any process known in the art which substantially avoids desiccation and/or structural

da age of the potato strips. However, it is especially preferred that the frozen parfried potato strips be tempered according to the process of the present invention.

More particularly, it has been found that the frozen parfried potato strips can be quickly warmed from their frozen internal temperature from about 0°F to about -15°F to a temperature range suitable for dust- coating by placing the frozen parfried potato strips in a controlled environment kept at a temperature from about 35°F to about 45°F, more preferably from about 36°F to about 39°F, and a relative humidity from about 75 to about 100 percent until the potato strips attain an internal temperature from about 27°F to about 35°F, and more preferably from 27°F to about 30°F. Clean air is preferably circulated through the controlled environment, with the air velocity being kept to a minimal level. Preferably, the air velocity within the controlled environment is from about 0 to about 200 feet/minute, and most preferably less than about 100 feet/minute.

It has been found that the time period necessary to temper the frozen parfried potato strips can be greatly decreased by gently agitating or tumbling the frozen parfried potato strips in the controlled environment to enhance exposure of all of the surfaces of the potato strips to the ambient air within the controlled environment. The agitation may be accomplished by any means known in the art.

In a preferred embodiment, the frozen parfried potato strips are gently tumbled by placing them on a plurality of conveyors which are adapted to tumble the potato strips from conveyor to conveyor. Tumbling the potato strips in this manner enhances exposure of all of the surfaces of the potato strips to the ambient air within the controlled environment, thereby more evenly and more quickly equilibrating the temperature of all of

the potato strips to the desired level.

Desirably, the tempering process described above is adapted to produce tempered potato strips ready for further processing in about 1-2 hours or less in a manner such that the tempered potato strips are substantially structurally intact and have not been subjected to any substantial amount of desiccation.

Most preferably, the controlled environment is a substantially enclosed room in which the potato strips are tempered at a temperature of about 38°F, a relative humidity of about 85 to about 100 percent, and an air velocity of less than 100 feet/minute. The potato strips are preferably conveyed directly from a freezer or cold room at a temperature of about -10°F and carried via a bucket conveyor to the uppermost conveyor in a plurality of vertically stacked conveyors. The potato strips are moved in a horizontal direction from one end of the uppermost conveyor belt to an opposite end. The layer of potato strips on the conveyor belts is preferably about five inches thick or less. When the potato strips reach the opposite end of the uppermost conveyor belt, they tumble onto a second conveyor belt oriented below the first conveyor. The second conveyor belt conveys the potato strips in an opposite horizontal direction relative to the uppermost conveyor belt. When the potato strips reach an opposite end of the second conveyor belt, they tumble downward onto a third conveyor belt which conveys the potato strips in an opposite horizontal direction relative to the second conveyor belt, and so on. The process continues until the potato strips reach the desired temperature, preferably from about 29°F to about 35°F, and most preferably from about 29°F to about 30°F.

In the case of a stop-product situation, the conveyors may be stopped at any point during the process. It is also possible, if the stop-product situation continues for any extended period of time, to

decrease the temperature of the air within the controlled environment to substantially stop continued warming of the potato strips. The number and length of the vertically stacked conveyors, the size of the controlled environment, the speed at which the conveyors move the potato strips, etc., determine the amount of potato strips processed within a given period of time.

The tempered potato strips are then transported from the tempering room, e.g. via a conveyor belt, to be finish fried.

In one embodiment, the tempered potato strips are dust-coated with potato granules prior to finish frying to provide a thin coating of the potato granules which adheres on the surface of the potato strips. The term "potato granules" is defined for purposes of the present invention as comprising any granular product which has been derived from potato products, such as finely ground potatoes, potato flour, dehydrated potato, potato flakes, potato starch, etc., or a mixture of any of the above. All of the above-mentioned granular products are available commercially from any number of sources.

The dust-coating of the parfried potato strips can be carried out in any conventionally known manner. For instance, the potato strips are placed onto a screened or perforated conveyor belt with vibration action and potato granules are sprinkled onto the potato strips from above. Thereafter the excess potato granules are removed via the vibratory action. A thin, even coating of potato granules is thereby accomplished.

It is preferred that when shoestring parfried potato strips are used, at least 50 percent of the potato granules are derived from finely ground potatoes, and in the most preferred embodiments, the dust-coating is comprised only of potato granules derived from finely ground potatoes.

On the other hand, it is preferred that the dust- coating for crinkle-cut potato strips comprise at least

50 percent potato flour, and in the most preferred embodiments, the dust-coating is comprised only of potato flour.

The dust-coating should produce a coating indistinguishable from the surface appearance of a conventional french fried potato. The term "conventional french fried potato" is defined herein as a deep fat fried potato strip having a crisp, golden exterior and a tender interior, such as the McDonald's™ french fry. Due to the use of fine granules, it is possible to obtain a dust-coated product which is both smooth and which provides a uniform appearance. In this regard, a dusting powder having 90-95% of its granules through U.S. 40 mesh and which includes no more than 8 percent moisture is preferred, such as that which is available from Basic American Foods Company. A cross- sectional view (perpendicular to the long axis of shoestring potato strip) , shows that the dust-coating blends imperceptively into the potato strip as part of a crisp layer formed during finish frying.

Any number of processes are known in the art for the preparation of potato granules which may be used satisfactorily in the present invention. One such process is the "add-back" process, in which cooked potatoes are partially dried by "adding back" enough previously dried granules to give a "moist mix" which can be granulated into a fine powder after holding, as described in more detail in "Potato Processing" by Talburt and Smith.

The dust-coated parfried potato strips according to the present invention will have a layer of potato granules sufficient to cover the potato strips and provide a coherent coating. The dust-coating preferably comprises from about 0.3 to about 1.5 percent or as much as 5 percent by weight of the potato strip. In more preferred embodiments, the dust-coating comprises from about 0.2 to about 0.5 percent by weight of the potato

strip, and it is most preferred that the dust-coating comprise about 0.3 percent by weight of the potato strip.

The dust-coated crinkle-cut potato strips according to the present invention preferably have a layer of potato flour sufficient to cover the potato strips and provide a coherent coating.

The potato flour used for dust-coating is preferably fine flour having a fine particle size which produces a coating indistinguishable from the surface appearance of a conventional french fried potato. An especially preferred potato flour for use in the present invention is a pure, fine potato flour packed by Lamb- Weston. The potato flour may be made by any method known in the art, such as those processes discussed in the above-mentioned publication on "Potato Processing" by Talburt and Smith.

Preferably, crinkle-cut parfried potato strips will have a coating which comprises from about 0.3 to about 5 percent by weight of the potato strip. In preferred embodiments, the dust-coating comprises from about 2 to about 3 percent by weight of the potato strip, and most preferred is a dust-coating of about 2.5 percent.

Although the potato strips may be dust-coated and thereafter placed in a frying medium while still frozen, it is preferable to temper the potato strips before frying.

The parfried potato strips are then finish fried after tempering with or without an intermediate dust- coating step. The frying medium is preferably a vegetable shortening or fat, although beef tallow, a blend of beef tallow and one or more vegetable oils, etc. can also be used. In preferred embodiments of the present invention, however, the frying medium is a vegetable shortening which mimics the physical properties, and mouth-feel of beef tallow. A partially hydrogenated vegetable oil with melting and mouthfeel

characteristics which approximate those of beef tallow, and has a Wiley melting point from about 95° to about 99°F, a solid fat index at 50°F of from about 34 to about 43 and a solid fat index at 92°F from about 3 to about 8 is most preferred. An example of a commercially available product having such characteristics is Van den Bergh's Code #321.

The temperature of the frying medium before the parfried potato strips are added is approximately 370- 375°F. This temperature is depressed (to approximately 340°F) when the potato strips are added and then rises to about 360°F during the course of frying. The potato strips are fried in this medium from about 3 to about 5 minutes. Preferably, shoestring potato strips are fried for about 3 to about 4 minutes, while crinkle-cut potato strips are fried for about 4.5 to about 5 minutes. In a continuous process, the temperature profile of the frying medium is preferably from about 380° to about 300°F.

The frying temperature and time are inversely proportional and are adjusted to cook the potato strips in a short period of time (2-5 minutes) to provide a product having a crisp exterior and a tender interior. It is preferred that the finish frying step occur promptly after dust-coating.

In a preferred embodiment for commercial production, the continuous fryer comprises a plurality of zones in which the frying medium circulates. The temperature of the frying medium in each zone may be individually adjusted by the operator as desired to optimize the product. Preferably, the continuous fryer comprises three cooking zones. The potato strips are introduced via a conveyor belt into a first zone of the fryer in which the frying medium is heated to a temperature from about 360"F to about 380"F, then into a second zone in which the frying medium is heated to a temperature from ^' about 320°F to about 360°F, and finally

pass through a third zone in which the frying medium is heated to a temperature from about 300°F to about 360°F. In a most preferred embodiment, the frying medium in zone 1 is preferably heated to about 365°F; the frying medium in zone 2 is preferably heated to about 340°F, and the frying medium in zone 3 is preferably heated to about 320°F. The potato strips preferably pass through each zone in about one minute. The finish-fried potato strips which exit from the opposite end of the continuous fryer preferably have an internal temperature from about 190°F to about 220°F.

Preferably, the frying medium is transferred from a storage area and introduced into a plurality of heat exchangers where it is heated to the desired temperature and filtered to remove impurities. The heated frying medium circulates into the desired zone of the continuous fryer. The used oil may then be recirculated.

In contrast to traditional continuous fryers, the continuous fryer of the present invention does not use baffles to segregate one zone from another; rather the frying medium is free-flowing, and the inlet and outlet ports are distributed such that a temperature differential between the zones can be maintained. The temperature differentials may be measured, e.g., via thermocouples. The oil in each zone is ciruclated via independent pumps into independent heat exchangers which creates zone heating across the fryer.

The time necessary to finish fry the potato strips in the continuous fryer may be manipulated, for example, by manipulating the temperature of the frying medium, the dwell time, the pounds of potato strips per cubic foot introduced into the continuous fryer, etc.

The finish fried potato strips which leave the opposite end of the continuous fryer are then preferably transported on a perforated inclined belt or the like (e.g., at a 45° upward angle) such that excess frying

medium is allowed to drain from the surface of the potato strips via gravity.

When the potato strips are shoestring potatoes, it is preferred that they are finished fried to a moisture content from about 20 to about 46 percent, a fat content from about 14 to about 20 percent and from about 35 to about 63 percent potato solids. It is more preferred that the finish fried shoestring potato strips have a moisture content from about 36 to about 44 percent and most preferably from about 38 to about 40 percent, and a fat content from about 14 to about 18 percent. The density of the finish fried potato strip is preferably from about 0.4 to about 0.65 g/ml.

The potato strips are then preferably coated with toasted potato granules. The term "toasted potato granules" includes toasted finely ground potato, toasted potato flakes, and toasted dehydrated potato. The potato granules may be toasted by any means known in the art. The toasted potato granules used in the present invention have a moisture content from about 0.1 to about 4.0 percent. In one embodiment, this moisture content may be achieved by toasting potato granules in a convection oven kept at a temperature of about 300°F for about 45 minutes.

Preferably, the coating of toasted potato granules which adheres to the potato strips is from about 0.2 to about 0.5 percent by weight of the potato strip, and most preferably about 0.3 percent by weight of the potato strip.

When the potato strips are coated with toasted potato granules after frying, the intermediate step of dust-coating with potato granules (prior to finish frying) is optional.

In a further preferred embodiment, the finish fried potato strips are further coated with a layer of fat- encapsulated salt. The coating of fat-encapsulated salt is preferably from about 0.8 to about 1.2 percent by

weight of the potato strip, and most preferably about 1.0 percent for a product having 50 percent salt content. Preferably, the fat-encapsulated salt has a salt content from about 35 to about 65 percent by weight and the fat has a melting point from about 140°F to about 160°F. An example of a suitable fat encapsulated salt is Van den Bergh's Durkote sodium chloride 150-65 VS, which would preferably be applied as a 0.8 percent coating. The fat-encapsulated salt is preferably applied concurrently with the dust-coating of toasted potato granules. Optionally, finely ground salt in an amount from about 0.2 to about 0.6 percent , and more preferably 0.4 percent, may be applied in substitution of the fat-encapsulated salt.

Then the potato strips are preferably promptly frozen. By "promptly frozen", it is meant that the finish fried potato strips are drained of excess oil and allowed to cool to a temperature of from about 100"F to about 150°F, and most preferably to about 160°F before freezing. In most circumstances, the cooling period will be from about 1 to about 5 minutes in order to reach the aforementioned temperatures.

In contrast to the conventional freezing methods which are utilized in the prior art whereby cold air from freon coils, etc. is blown directly onto the potato strips by a fan resulting in significant (e.g. 10%) surface desiccation and dehydration, in the present invention the potato strips preferably are frozen in a manner which substantially avoids desiccation and thus structural damage. For example, the potato strips may be carefully frozen at a temperature of about -20°F to about -70°F for about 10 to about 20 minutes, until the internal temperature of the potato strips is about - 10°F. Prompt freezing in this manner preserves the flavor and aroma present in the finish fried potato strips, and also preserves the structural integrity of the same. Slow freezing appears to cause a

significantly greater percentage of the potato strips to have a collapsed structure upon reheating.

In a preferred embodiment, the potato strips are frozen in a tunnel cooled by liquid nitrogen without direct exposure to high fan velocities. More particularly, the liquid nitrogen comes out of a tank and into a freezing tunnel and is circulated in the vapor form. The potato strips pass through the freezing tunnel on a multi-conveyor belt system and are frozen by the liquid nitrogen vapor, which is gently circulated via one or more fans located above the conveyor belt. It is important to note that a freezing blast is preferably not directly applied to the potato strips; rather, there is a gentle flow over the potato strips so as not to cause unnecessary dehydration and also so as not to damage the surface.

It is especially preferred that the freezing tunnel includes a plurality of zones which expose the potato strips to liquid nitrogen vapor at a temperature from about -30°F to about -70"F, the temperature of the liquid nitrogen vapor gradually increasing from a first end where the finish-fried potato strips enter to an opposite end where the frozen potato strips exit. The temperature within each zone may be individually adjusted by the operator as desired to optimize the product.

Most preferably, the freezing tunnel includes three zones, a first zone corresponding to the first end of the freezing tunnel in which the potato strips are exposed to liquid nitrogen vapor at a temperature from about -55°F to about -65°F, a second zone corresponding to the center of the freezing tunnel in which the potato strips are exposed to liquid nitrogen vapor at a temperature from about -40°F to about -50°F; and an third zone corresponding to the opposite end of the tunnel in which the potato strips are exposed to liquid nitrogen vapor at a temperature from about -25°F to

about -35°F. The potato strips which exit the opposite end of the freezing tunnel preferably have an internal temperature from about -20°F to about -30°F and most preferably about -25°F. The freezing process is conducted, for example, for about 5-10 minutes. The potato strips are preferably conveyed through each zone in about 3 minutes.

The freezing of the potato strips in this manner produces a frozen product without any substantial desiccation and without freezer burn. The internal ice crystals which are formed during the freezing process are as small as possible so as to cause minimal structural damage.

Alternatively, any other manner known in the art to accomplish a continuous, gradual freezing of the potato strips to the above-mentioned temperatures without the formation of large ice crystals and without significant structural damage to the potato strips may be used. The frozen potato strips are then packed into tightly sealed packages and stored at normal freezer temperatures of approximately 0°F to about -20°F. The containers may contain a large amount of the potato strips, i.e. a few pounds, or may be designed to hold a suitable serving size, e.g., about 64 grams (2.25 ounces) . Preferably, the potato strips are conveyed from the freezing tunnel to a packaging area via a conveyor belt in a controlled environment kept at a temperature from about -20°F to about 0°F, and the package is purged with a blast of liquid nitrogen vapor prior to filling with the frozen potato strips.

It is especially preferred that the potato strips are not exposed to a temperature above about 0°F after being frozen in the freezing tunnel and being packaged. The frozen packaged product may be removed from a freezer and reheated in a short period of time such that the potato strips attain a suitable consumption temperature. The potato strips of the present invention

may be reheated in a conventional or convection oven, by heating under a heat lamp-type food warmer, or in the apparatus disclosed in International Patent Application

PCT No. , (Shanbhag, Bonne and Milani) filed concurrently on February 22, 1990. In addition, the potato strips of the present invention may be reheated in a microwave oven.

Since the potato strips have preferably been fully cooked during the finish frying step, the reheating step is adapted to substantially only reheat the strip to a suitable consumption temperature without any substantial change in the composition of the potato strips. A suitable consumption temperature is preferably from about 130°F to about 170°F.

For example, the frozen potato strips may be removed from the freezer, distributed on any suitable restaurant-style metal sheet pan, and reheated in a conventional or convection oven until the product attains an internal temperature of at least about 140°F. The metal sheet pan is preferably perforated. The reheating time of course is dependent upon the type of oven used, the temperature setting, and the amount and depth of potato strips to be reheated. For example, a 770 gram sample (about 12 servings) of the frozen potato strips may be reheated in a convection oven set at 350°F in about 3-5 minutes, while the same quantity of frozen finish fried potato strips may be reheated in a conventional electric oven set at 450°F in about 7-10 minutes.

In contrast to prior art oven-prepared french fries, it is not necessary to spread the potato strips of the present invention on the pan in a monolayer. The potato strips of the present invention may be spread on the pan to a depth from about one to about one and one- half inches.

Since the potato strips preferably have been fully cooked during the finish frying, the reheating time is

adjusted to reconstitute the strip (substantially only heating as opposed to cooking) to its condition immediately after finish frying.

The reheated potato strips may be eaten immediately. On the other hand, the reheated potato strips may be allowed to cool for about 30-60 seconds. The product is then on the average from about 160°F to about 17Q- - F and ready to serve. .The potato- strips- are- crisp on the outside, tender on the inside, golden in color, and closely resemble the flavor, aroma, texture and total eating experience of McDonald's™ french fries.

The ready-to-eat potato strips may be kept at an acceptable temperature for consumption (i.e. 140-155°F) via the use of a food warming device such as a commercially available heat lamp. The potato strips can be maintained at such temperatures for an extended period of time without becoming soggy, limp or suffering structural damage.

The composition of the reheated, ready-to-serve shoestring french fried potato products of the present invention preferably includes from about 20 to about 46 percent moisture, from about 14 to about 25 percent fat, and from about 35 to about 63 percent potato solids.

If the potato strips are crinkle-cut or steak fries, the percentage moisture and fat content is preferably adjusted upwardly. Depending upon the dimensions of the potato strip, a finish fried crinkle- cut product may include, for example, from about 30 to about 50 percent moisture and from about 13 to about 22 percent fat. The density of the finish fried crinkle- cut potato strip is from about 0.4 to about 0.6 g/ml.

In an alternative embodiment of the present invention, the final freezing step (after finish frying) may be omitted if shipping and/or storage is not necessary. In this embodiment, the potato strips are allowed to cool at room temperature or are refrigerated after finish frying and thereafter a serving portion is

simply reheated as detailed above when desired. After reheating, the product has characteristics which were described above.

Various aspects of the process of the present invention, including the tempering, coating, continuous frying, and freezing process may be used alone or in combination in the preparation of potato strips for reconstitution by heating. Reconstitution may be accomplished in a conventional or convection, a heat lamp-type food warmer, or a microwave oven.

DETAILED DESCRIPTION OF THE PARTICULAR EMBODIMENTS The following examples illustrate various aspects of the present invention. They are not intended to limit the claims.

EXAMPLES l and 2 Conventional frozen parfried shoestring potato strips made available to fast food restaurants are obtained for subsequent processing. One skilled in the art will appreciate that such conventional frozen potato strips are derived from whole potatoes which have been peeled, cut, possibly treated with one or more of the chemicals discussed previously, and either water or steam blanched. These potato strips are thereafter parfried for approximately 30-60 seconds at about 375°F and frozen.

One portion of the above-mentioned potato strips representing Example 1 is then further processed. First, the frozen potato strips are allowed to temper at 34°F in a temperature controlled chamber for 4 hours with physical mixing of the potato strips to maximize even heat transfer and minimize processing time. The tempered strips are then dust-coated with potato granules (U.S. 40 mesh/ground potato) . The dust-coating of the potato granules comprises about one percent by weight of the potato strip. The dust-coated potato strips are promptly placed into a deep-fat fryer. The frying medium used is Van den Bergh's Code #321. The temperature of the frying medium before the potato strips are added is approximately 355°F to 365°F. This temperature is depressed when the potato strips are added, and increases during the frying time. The temperature range of the frying medium during frying is from about 340°F to about 370°F. The potato strips are fried for about 3 minutes. Thereafter, the potato strips are removed from the fryer and the oil is allowed to drain from their surface. The potato strips are

allowed to cool for about one minute to a temperature of about 170°F and then are promptly frozen by placing them on a belt which passes through a freezing tunnel which is cooled by an indirect flow of liquid nitrogen vapor. The potato strips are exposed to an initial temperature in the freezing tunnel of about -55"F. The temperature of the freezing tunnel was gradually increased as the potato strips passed through the tunnel until the temperature at the opposite end of the tunnel is about -10°F. The freezing process was conducted for about 13 minutes. The internal temperature of the potato strips after freezing is about -15°F. Example 2 is prepared in an identical manner except that the dust-coating step is omitted.

The frozen potato strips of Example 1 and 2 were separately packed in polyethylene bags of a type commonly used to store frozen foods and stored at freezer temperatures (approximately 0°F to -10°F) . The composition of potato strips prepared according to Example 2 prior to reheating were subjected to compositional analysis. Compositional analysis was also performed on certain commercially available products designed for conventional oven reconstitution. In comparative Example A, McCain shoestring french fries were analyzed prior to final oven cooking. In comparative Example B, Ore-Ida shoestring french fries were analyzed prior to final oven cooking. The results are provided in Table 1.

A 770 gram sample (equivalent to approximately 12

servings) of each Example was removed from the freezer after 24 hours, placed on restaurant-style metal sheet pans (18" L x 13" W x 1" H) to a depth of between one and one-and-one-half inches, and separately reheated in a convection oven set at 350°F for 3.5 minutes until the french fries reached a temperature of about 200°F. The heated portions were then allowed to cool for about one minute, at which time they were ready to serve. The french fried potato product of Example 1 had a crisp, golden exterior and a fluffy, light interior, and had an aroma, flavor, mouthfeel and total eating experience closely resembling that attained by the conventional state of the art commercially available deep fat fried fast-food product, i.e. McDonald's™ french fries. Example 2 was virtually identical in all of the aforementioned properties.

After the potato strips of Examples 1 and 2 had been stored for 7 days at freezer temperatures, another 770 gram portion of each was removed from the freezer and separately reheated in a convection oven as detailed above. The french fried potato product of both Example 1 and 2 were virtually identical to that which was prepared after 24 hours of freezing.

The potato strips prepared according to Example 2 were subjected to compositional analysis after convection oven reheating. Comparative Examples A and B were then analyzed after final cooking in the same manner. The results are provided in Table 2.

TABLE 2

COMPOSITION AFTER REHEATING IN CONVECTION OVEN

EXAMPLE 3-4

Example 3 was prepared in an identical manner as Example 1 and Example 4 was prepared in an identical manner as Example 2, except that Examples 3 and 4 were removed from frozen storage and reheated using a conventional oven rather than a convection oven.

In this instance 770 gram samples (equivalent to approximately 12 servings) of Examples 3 and 4 were reheated from the frozen state separately by placing them on restaurant-style metal sheet pans (as described previously) in a conventional electric oven set at 450°F for 8 minutes, until the french fries reached a temperature of about 200°F.

The heated portions were then allowed to cool for approximately one minute, at which time they were ready to serve. The french fried potato product of Example 3 had a crisp, golden exterior and a fluffy, light interior. The french fried potato product also had an aroma, flavor, mouthfeel and total eating experience closely resembling that attained by the conventional state of the art commercially available deep fat fried fast-food product, i.e. McDonald's™ french fries. Example 4 was virtually identical in all of the aforementioned properties.

After the potato strips of Examples 3 and 4 had been stored for 7 days at freezer temperatures, another 770 gram portion of each was removed from the freezer and separately reheated in a conventional oven as detailed above. The french fried potato product of both Examples 3 and 4 were virtually identical to that which was prepared after 24 hours of freezing.

Compositional analysis was performed on potato strips reheated according to Example 4 after conventional oven reheating. Comparative Examples C and D were analyzed after final cooking in a conventional oven in the same manner. The results are provided in

Table 3

TABLE 3

COMPOSITION AFTER REHEATING IN CONVENTIONAL OVEN

Example %H ₂ 0

4 33.7

C (McCain shoestring) 43.9

D (Ore-Ida shoestring) 54.7

Examples 5-6

In Example 5, potato strips prepared and reheated in a convection oven according to the process described in Example 2 were then held under a heat lamp-type warmer (Merco Model EZ-FW-24 Food Warmer) with a 680 watt infra-red heating tube for 60 minutes. The french fries were then subjected to compositional analysis. Comparative Examples E and F were analyzed after final preparation and warming under the heat lamp in the same manner. The results are provided in Table 4.

In Example 6, french fries prepared and reheated in a conventional oven as described in Example 4 were held under a heat lamp for 60 minutes and thereafter subjected to compositional analysis. Comparative Examples G and H were analyzed after final oven cooking in the same manner. The results are provided in Table 5.

TABLE 5

COMPOSITION AFTER CONVENTIONAL OVEN HEATING FOLLOWED BY

HOLDING UNDER HEAT LAMP

Example ₂ o %Fat Density (g/ml)

10 31.4 18.0 0.36

G (McCain shoestring) 46.4 8.4 0.56 H (Ore-Ida shoestring) 56.0 8.1 0.74

EXAMPLE 7 Conventional frozen potato strips similar to those obtained in Example 1 are distributed onto a conveyor belt which transfers the potato strips into a tempering room having a temperature of about 38°F, a room relative humidity of about 85 to about 100 percent, and a room air velocity of less than about 100 feet/minute. The potato strips are transferred to the top of a series of vertically stacked conveyors which move the potato strips in a horizontal direction from one end of a conveyor to an opposite end, where the potato strips tumble onto a second conveyor belt disposed below the uppermost conveyor. The process continues until the potato strips are tumbled onto the last (bottom) conveyor, which in turn transfers the potato strips for further processing. The tempering process takes about 1.25 hours. The potato strips have an internal temperature at the time they leave the tempering room of about 29°F to about 30°F.

The tempered potato strips are then transferred to a tumble drum, where they are dust-coated with potato granules (U.S. 40 mesh/ground potato). The dust-coating of the potato granules comprises about 0.3 percent by weight of the potato strip.

The dust-coated potato strips are then promptly conveyed into a continuous fryer having three temperature zones. The frying medium used is Van den Bergh's Code #321. The oil level within the fryer without product is preferably about 8-9 inches. When product is added,the oil level within the continuous fryer preferably rises to about 9-10 inches. The temperature of the frying medium in the first three zones to which the dust-coated potato strips are exposed is approximately 365°F. The temperature of the frying medium in the next zone is about 340°F. The temperature of the frying medium in the last zone is about 320°F. The potato strips are conveyed through the continuous fryer such that the potato strips are cooked within each zone for about one minute. The internal temperature of the potato strips leaving the continuous fryer is about 190-220°F.

Thereafter, the potato strips are removed from the continuous fryer and conveyed at an upward angle of about 45° so that excess oil is allowed to drain from their surface.

The potato strips, which now have an internal temperature of about 160°F, are then promptly conveyed into a freezing tunnel. The potato strips are initially exposed to liquid nitrogen vapor at a temperature of about -60°F in a first end of the freezing tunnel. The potato strips are subsequently conveyed through a second (central) zone in which the potato strips are exposed to liquid nitrogen vapor at a temperature of about -45°F, and a finally through third zone at the opposite end of the tunnel where the potato strips are exposed to liquid nitrogen vapor at a temperature of about -30°F. The potato strips are exposed to each zone for about 3 minutes. The potato strips which exit the freezing tunnel have an internal temperature of about - 25°F.

The potato strips are then promptly conveyed in a

rontrolled environment kept at about -15°F to about -20"F and packaged, and are stored at freezer temperatures.

A 770 gram sample (equivalent to approximately 12 servings) of the frozen finish fried potato strips is removed from the freezer after 24 hours, placed on restaurant-style metal sheet pans (18" L x 13" W x l" H) to a depth of between one and one-and-one half inches, and reheated in a convection oven set at 350°F for 3.5 minutes until the french fries reached a temperature of about 200°F. The heated portion is then allowed to cool for about one minute, at which time it is ready to serve.

A second 770 gram sample of Example 7 is reheated after freezing for 24 hours by placing the potato strips on restaurant-style metal sheet pans (as described previously) in a conventional electric oven set at 450°F for 8 minutes, until the french fries reach a temperature of about 200°F.

The heated portions are then allowed to cool for approximately one minute, at which time they are ready to serve.

A third and fourth 770 gram sample of Example 7 are reheated after freezing for 24 hours by convection and conventional ovens respectively as detailed above and then held under a heat lamp-type warmer (Merco Model EZ-FW-24 Food Warmer) with a 680 watt infra-red heating tube for 60 minutes.

A fifth sample of Example 7 is reheated using the aforementioned food warmer as the sole source of heat. In this case, the food warmer is enclosed with a metal foil sheath to improve heating efficiency and the enclosure is allowed to pre-heat to a temperature of about 195°F. A onolayer of the frozen potato strips (approximately 385 grams or 6 servings) spread out on a metal 18" L x 13" W x 1 1/2" H sheet pan is then introduced into the enclosure and allowed to heat for

10-12 minutes to a temperature of 145-160°F.

The reheated french fried potato product of Example 7 reheated in each of the manners outlined above has a crisp, golden exterior and a fluffy, light interior, and an aroma, flavor, mouthfeel and total eating experience closely resembling that attained by the conventional state of the art commercially available deep fat fried fast-food product, i.e. McDonald's™ french fries.

After the potato strips of Example 7 have been stored for 7-28 days at freezer temperatures, further 770 gram portion are reheated as detailed above. The french fried products after freezing for 7-28 days are virtually identical to those obtained after freezing for 24 hours.

EXAMPLE 8 Example 2 is prepared in identical fashion as Example 7 with the exception that after the potato strips exit the continuous fryer, they are conveyed to a second tumble drum before freezing. At the second tumble drum, the potato strips are coated with 0.3 percent toasted potato granules (U.S. 40 mesh/ground potato; moisture content about 2-3 percent by weight of the potato granules), by weight of the potato strips. Thereafter, the potato strips (which now have an internal temperature of about 160°F) are conveyed to the freezing tunnel and treated as per Example 7.

After storing at freezer temperatures for 24 hours, 770 gram portions of Example 2 are removed from the freezer and separately reheated in a convection oven set at 350°F for about 3.5 minutes; in a conventional electric oven at 450°F for about 8 minutes; and by holding under the heat lamp-type food warmer for 60 minutes. The reheated portions are then allowed to cool for approximately 30 seconds, at which time they are ready to serve.

The reheated product of Example 8 is virtually

identical to the reheated product of Example 7.

After the potato steps of Example 8 are stored for 7-28 days at freezer temperatures, additional 770 gram portions of each are removed from the freezer and separately reheated as detailed above. The reheated potato strips of Example 8 are noticeably crisper as compared to the potato strips of Examples 1-7.

EXAMPLES 9 AND 10 Example 9 is prepared in identical fashion as Example 8 with the exception that after finish frying, the potato strips are coated in the second tumble drum with 0.3 percent by weight toasted potato granules and about 0.8 percent by weight fat-encapsulated salt granules (Van den Bergh's Durkote sodium chloride 150-65 VS) . The reheated potato strips have a noticeable salt flavoring and have substantially the same texture as the potato strips of Example 8.

Example 10 is prepared in identical fashion as Example 9, except that the intermediate step of dust- coating with potato granules before finish frying is omitted. The reheated potato strips of Example 10 are slightly less crisp than those of Example 9, but are highly palatable and represent an improvement over the prior art.

EXAMPLES 11-13

In Examples 11-13, whole raw potatoes are washed, peeled, cut into shoestring potato strips, and blanched in water for 15 minutes, and air dryed.

The potato strips of Example 11 are then parfried in Van den Bergh's Durtex™ Code #321 for one minute at 375"F. Thereafter, the parfried potato strips are dust-coated and otherwise treated as set forth in Example 9, omitting the intermediate freezing and tempering steps.

In Example 12, the potato strips are treated in

accordance with Example 9 except that the dust-coating step after the tempering step is omitted. The tempered potato strips are instead conveyed directly to the continuous fryer.

In Example 13, the potato strips are treated similarly to the potato strips of Example 9, except that the parfrying step is omitted. Instead, the dust-coated potato strips are fried in the continuous fryer for- a comparatively longer period of time, such that the potato strips leaving the continuous fryer are in a fully cooked, ready-to-eat condition.

The reheated potato strips of Example 11 and 12 are substantially similar to those of Example 9. The reheated potato strips of Example 13, while not as good as the reheated portions of Example 9, are still highly palatable and represent an improvement over the prior art.

The examples provided above are not meant to be exclusive. Many other variations of the present invention would be obvious to those skilled in the art, and are contemplated to be within the scope of the appended claims.