METHOD AND APPARATUS FOR PREPARING A POTATO BASED FOOD PRODUCT

Abstract: Potato chips having a flavor, texture and appearance similar to batch cooked chips and decreased oil content are prepared on a continuous basis by depositing freshly sliced potato slices (14) enveloped in natural starches released during the slicing process in a precooking sluice (16) where they are conveyed in a continuous stream of heated precooking oil (22) which caramelizes the natural starch envelope prior to the precooked slices being deposited in a second continuous stream of cooking oil (44) heated to a higher temperature where the final cooking of the potato chips takes place.

Description: Potato chips were originally prepared on a batch basis with the hand cut potato slices immersed in a kettle of hot cooking oil and cooked until they achieved a desired appearance, at which time the chips were removed from the cooking oil and allowed to drain. With the increased popularity of potato chips and the commensurate increase in demand for this product, processes and equipment were developed to prepare potato chips on a continuous basis and thereby increase production volumes. Demand for potato chips continues to increase and is met for the most part by chips prepared on a continuous basis. However, there has also, more recently, been an increased demand for so-called "kettle cooked" chips which have the appearance and flavor of chips cooked by the old-fashioned batch process. Obviously, the same problem exists today with respect to batch-prepared potato chips that existed with the original introduction of potato chips, i.e., batch production is slow, which results in both an increased price for the batch-prepared product and insufficient volume to meet demand. It should be noted that in the production of potato chips on a continuous basis using more or less conventional equipment and processes, raw potatoes are first peeled and then sliced and the resulting slices washed, usually with water, to remove the starch which is released during the cutting process and coats the potato slices, and the washed slices are then dropped in a fryer containing a continuous stream of heated cooking oil at a temperature of 162 to 191°C (325° to 375°F) In the ensuing cooking process moisture is released from the slices and replaced to some extent by the cooking oil, so that the final product will have an oil content of 35% to 45% by weight and a moisture content of 1.5% to 2.2% by weight. U.S. patent No. 4,503,127 discloses a method of preparing potato chips which eliminates the step of washing the starch-coated potato slices, and instead conveys the unwashed slices into a bath of oil or water having a temperature below the gelatinization temperature of the starch on the slices, e.g., between 50° to 60°C (122° to 140°F), then cooling the thus treated potato slices to at least 40°C (104°F) and preferably 32°C (90°F), and thereafter frying the cooled slices in vegetable oil at a temperature of 85°C (365°F). The product prepared in this manner is said to be uniform in texture and appearance, less oily and contain more food solids than similar products prepared by traditional methods. The Background of the Invention section of patent No. 4,503,127 also discusses several prior art patents, namely U.S. patents No. 2,091,675; 2,179,035; 2,611,705; 3,223,024; 3,402,059; 3,997,678; 4,068,572; 4,251,895; 4,272,554; 4,277,510; 4,283,425; 4,283,437; 4,392,420; and Re. 27,531, the disclosures of which are incorporated herein by reference. However, none of the above-noted patents are concerned with the preparation of kettle cooked chips, let alone preparation of chips of this type on a continuous basis. Furthermore, US-A-3484252 discloses a method of producing potato puffs having a configuration of a ball or a banana. The potatoes are sliced and immersed in a bath of hot oil or fat at 135°C (275°F) for approximately six minutes. They are then plunged into another bath at 218°C (425°F) for approximately five seconds. FR-A-2 285 816 discloses a method of producing deep-fried sliced potatoes, so-called potato chips or crisps, by conveying the potato slices through a fat bath having zones provided with separate adjustment of the fat temperature. The temperature of the zones is maintained constant at about 135° to 150°C or increases from zone to zone in the direction of advance of the potato slices from the above temperature to a maximum temperature of 175°C The potato slices are then treated with superheated steam at a minimum temperature of 110°C. It is an object of the present invention to provide a method and an apparatus for producing on a continuous, high volume basis potato chips having an appearance, texture and flavor heretofore found in chips prepared on a batch basis. According to one aspect of the present invention, there is provided a method of preparing a potato-based food product comprising the steps of: slicing raw potatoes into thin slices enveloped in a natural starch coating released from crushed potato cells during slicing; precooking the starch-enveloped slices in a liquid at a temperature of 93° to 149°C (200° to 300°F) for a first time period of ten to twenty seconds; immediately cooking the resulting precooked slices in a liquid at a temperature of 149° to 205°C (300° to 400°F) for a second period of five to ten minutes. In this context, the term "immediately" is intended to mean "without an intermediate stage or step", as defined in Webster's Third New International Dictionary (unabridged edition) at pages 1129 and 1180. The method, in accordance with the present invention, is achieved by introducing unwashed potato slices which are enveloped in a natural starch coating released during the slicing process into a sluice containing a continuous stream of cooking oil heated to a temperature of 93° to 149°C (200° to 300°F), and preferably in a range of 126° to 144°C (260° to 290°F) for ten to twenty seconds, and preferably from twelve to eighteen seconds, and thereafter frying the precooked slices in a fryer containing a continuous stream of cooking oil at a temperature of 149° to 205°C (300° to 400°F), and preferably in the range of 151° to 156°C (305° to 312°F) for five to ten minutes, and preferably from five to seven minutes. In this manner the layer of natural starch enveloping in the freshly sliced potatoes is caramelized in the precooking sluice to form a barrier which resists the penetration of cooking oil in the subsequent frying step to provide a potato chip having a lower oil content, 28% to 35% by weight, than chips cooked in a conventional manner, e.g. 35% to 45% by weight. Additionally, the caramelized starch coating on the slices tend to retard the rate at which moisture leaves the slice, so that as the moisture escapes it tends to puff the potato slices, resulting in an uneven, more textured appearance with small air pockets under the surface of the chip, which imparts a lightness and crisper, crunchier quality to the chip. Despite the fact that the caramelized starch coating appears to retard the rate at which moisture escapes from the potato slices, the final moisture content is substantially the same as potato chips cooked in a conventional manner i.e. 1.5% to 2.2% by weight. According to another aspect of the present invention there is provided an apparatus for preparing the potato-based food product of the invention, said apparatus comprising:- means for slicing potatoes into thin slices suitable for potato chips; and an elongated sluice having an upstream end for receiving natural starch enveloped potato slices from said slicing means and carrying said slices in a continuous stream of heated precooking oil to a downstream end of said sluice; and being characterized by:- an elongated fryer having an upstream end communicating with said downstream end of said sluice for receiving precooked slices from said sluice and conveying said slices in a continuous stream of heated cooking oil to a downstream end of said fryer, said fryer being of substantially greater capacity than said sluice; first conduit means in communication with said downstream end of said fryer and said upstream end of said sluice; means for pumping liquid through said first conduit means from said downstream end of said fryer to said upstream end of said sluice; second conduit means communicating with said downstream end of said fryer and a heat exchanger; third conduit means communicating with said heat exchanger and said upstream end of said fryer; means in said sluice for regulating the flow of potato slices along with sluice; and means positioned in said sluice at said upstream end thereof to prevent sticking of potato slices to surfaces of said sluice at said upstream end thereof. The apparatus for practicing the process of the present invention can be provided at relatively modest cost through the modification of an existing fryer used in a conventional manner for the continuous production of conventional potato chips. Thus, where a conventional potato slicer and a conventional fryer are already in use, this equipment can be adapted to the process of the present invention by installing at the upstream end of the fryer a sluice to contain the continuous stream of precooking oil, with the sluice being fed directly from the slicer with freshly cut potato slices enveloped in their own natural starches, and the water shower or other washing equipment simply eliminated. In many instances the conventional fryer will be associated with a heat exchanger which receives oil from the downstream end of the fryer, reheats it to a desired temperature and recirculates the heated oil back to the upstream end of the fryer. This conventional fryer can also be adapted to the process of the present invention, with only a portion of the oil from the downstream end of the fryer being conveyed to the heat exchanger, while the remaining portion is diverted to the upstream end of the sluice with appropriate control to ensure that the oil introduced into the sluice is in the desired range of temperature for caramelizing the starch envelope on the raw potato slices. Additionally, it has been found desirable to provide at the upstream end of the sluice a pad of a synthetic fluorine resinous material, such as that sold under the trademark TEFLON, to eliminate sticking of the starch-coated slices to the bottom of the sluice at this point. Also, the oil level in the sluice, and the degree of precooking in the sluice may be controlled through the use of a variable speed paddle wheel located within the sluice. In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which: Fig. 1 is a somewhat schematic view showing the equipment utilized in practicing the process of the present invention; Fig. 2 is a block diagram showing the steps of the process of the present invention; Fig. 3 is a perspective view of the precooking sluice; and Fig. 4 is a plan view thereof. As seen in Fig. 1, raw, peeled potatoes 10 are fed to a slicer 12, which cuts the potatoes into thin slices 14. The thickness of the slices can be varied somewhat depending upon the characteristics of the final chip desired. For example, conventional potato chips will usually have a thickness of 0.228 to 0.244mm (.0058 inch to .0062 inch), while thicker chips may range up to 0.473mm (.012 inch) in thickness. Regardless of this the slices 14 are dropped into a sluice 16 adjacent an upstream end 18 thereof. It is possible that the slices may be fed directly from the slicer 12 into the sluice 16, although in most instances it will be desirable to use an open mesh conveyor 20 to allow small pieces of potato and excess liquid to drop off before the slices are fed to the sluice. The sluice contains a moving stream of precooking oil 22, which is fed into the upstream end of the sluice as seen in Fig. 3 of the drawings by means of a manifold 24 having a series of outlets 26. It will also be noted from Fig. 3 of the drawings that a pad 28 of a non-sticking type material, such as that sold under the trademark TEFLON, is positioned at the upstream end of the sluice to prevent sticking of the raw, starch-coated potato slices to the bottom of a sluice. A flow control paddle wheel 30 is mounted intermediate the ends of the sluice and is rotated by a separate power source 32 in the direction of oil flow to control the depth of the oil upstream of the control paddle wheel and the degree of precooking of the chips in the sluice. At its downstream end 34 the sluice is provided with a discharge chute 36 which conveys the precooked chips into the fryer 38 and a baffle 40 is positioned above the discharge chute to deflect and direct the precooked chips into the upstream end 42 of the fryer. The fryer 38 contains a continuous stream of cooking oil 44 and one or more flow control paddles 46, and at its downstream end 48 a conveyor 50 lifts the cooked chips from the fryer and conveys them to subsequent stations for post-cooking operations. In order to maintain the precooking and cooking oils at their desired temperatures, a heat exchanger of conventional design may be utilized adapted to the apparatus and process of the present invention. Thus, a heat exchanger 52 is shown which receives cooking oil 44 from a conduit 54 at the discharge side of a pump 56. The pump 56, in turn, receives oil from the fryer via a conduit 58. After heating in the heat exchanger 52 the heated oil is conveyed by means of a conduit 60 back to the upstream end 42 of the fryer 38 where it mixes with the relatively cooler oil from the sluice 16. It will also be seen from Fig. 1 of the drawings that the discharge side of the pump 56 is also in communication with a conduit 62 which feeds oil from the downstream end of the fryer 38 to the upstream end 18 of the sluice 16. By appropriate control of the flow through the above described conduits and heat exchanger, the temperature in the sluice and in the fryer can be maintained within desired ranges. It will also be apparent that the representation in Fig. 1 is somewhat schematic, and, for example, in practice both the sluice 16 and the fryer 38 will be covered and insulated to reduce heat loss and losses due to evaporation. Regardless of this, it will be seen with reference to Figs. 1 and 2 of the drawings that the process in accordance with the present invention consists of feeding potato slices directly from the slicer and without an intermediate washing step into the upstream end of the sluice 16 where a continuous stream of oil is maintained at a temperature of from 90° to 149°C (200° to 300°F), and preferably in a range of 126° to 144°C (260° to 290°F) for a period of from ten to twenty seconds, and preferably for twelve to eighteen seconds, where the potato slices are precooked, causing a caramelization of the natural starch which envelopes each of the potato slices and to provide a caramelized envelope which acts as a barrier to oil penetration and retards the rate of moisture escape. The thus enveloped potato slices are then conveyed to the fryer 38 where they are immersed in a cooking oil having a temperature in the range of 149° to 205°C (300° to 400°F), and preferably in a range of 151° to 156°C (305° to 312°F) for a period of from five to ten minutes, and preferably for a period of from five to seven minutes. The resulting chips will ordinarily have an oil content of 28% to 35% by weight and a moisture content of 1.5% to 2.2% by weight and will exhibit a textured appearance with small air pockets under the surface which impart a lightness, and a crisper crunchier quality to the chip.

Claims: A method of preparing a potato-based food product comprising the steps of: slicing raw potatoes (10) into thin slices (14) enveloped in a natural starch coating released from crushed potato cells during said slicing; precooking said starch-enveloped slices in a liquid (22) at a temperature of 93° to 149°C (200° to 300°F) for a first time period of ten to twenty seconds; and immediately cooking the resulting precooked slices in a liquid (44) at a temperature of 149° to 205°C (300° to 400°F) for a second time period of five to ten minutes. A method as claimed in claim 1, wherein said precooking takes place at a temperature of 126° to 144°C (260° to 290°F). A method as claimed in claim 1 or 2, wherein said cooking takes place at a temperature of 151° to 156° (305° to 312°F). A method as claimed in claim 1, 2 or 3, wherein said first time period is twelve to eighteen seconds. A method as claimed in claim 1, 2, 3 or 4, wherein said second time period is five to seven minutes. A method as claimed in any preceding claim, wherein said liquid is a vegetable oil, and a portion of said vegetable oil used in said cooking step is recirculated to said precooking step. A method as claimed in any preceding claim, wherein the potatoes (10) are sliced into slices (14) 0.197 to 0.244mm (.005 inch to .012 inch) in thickness. A method as claimed in any preceding claim, wherein said precooking takes place in a first moving stream of oil (22) and said cooking takes place in a second moving stream of oil (44). A method as claimed in claim 8, and comprising recirculating a first portion of said oil from a downstream end (48) of said second stream to an upstream end (18) of said first stream. A method as claimed in claim 9, and comprising: recirculating a second portion of said oil from said downward end (48) of said second stream to a heat exchanger (52); raising the temperature of said second portion of said oil in said heat exchanger; and recirculating said second portion of said oil from said heat exchanger to an upstream end (42) of said second stream. A method of preparing a potato-based food product as claimed in claim 1, comprising the steps of:- slicing the potatoes (10) into slices (14) 0.197 to 0.244 mm (.005 inch - .012 inch) in thickness to provide thin slices of potato with surfaces of said slices enveloped in a natural starch coating released from potato cells crushed during said slicing; immersing said thin, starched-coated potato slices into a first moving stream of oil (22) having a temperature of 126° to 144°C (260° to 290°F); maintaining said slices in said first stream as it moves from an upstream end (18) to a downstream end (34) thereof for a period of twelve to eighteen seconds to caramelize said starch coating and provide a natural, caramelized starch envelope for each of said slices; transferring said caramelized starch enveloped slices from said first stream to a second moving stream (44) of oil having a temperature of 151° to 156C° (305° to 312°F); maintaining said slices in said second stream as it moves from an upstream end (42) to a downstream end (48) thereof for a period of five to seven minutes to cook said slices into potato chips having a moisture content of 1.5% to 2.2% and an oil content of 28% to 35% by weight; recirculating a first portion of said oil from said downstream end of said second stream to said upstream end of said first stream; recirculating a second portion of said oil from said downstream end of said second stream to a heat exchanger (52); raising the temperature of said second portion of said oil in said heat exchanger; and recirculating said second portion of said oil from said heat exchanger to said upstream end of said second stream. Apparatus for preparing a potato-based food product according to claim 1, said apparatus comprising:- means (12) for slicing potatoes (10) into thin slices (14) suitable for potato chips; and an elongated sluice (16) having an upstream end (17) for receiving natural starch enveloped potato slices from said slicing means and carrying said slices in a continuous stream of heated precooking oil (22) to a downstream (34) end of said sluice; and being characterized by:- an elongated fryer (38) having an upstream (42) end communicating with said downstream end (34) of said sluice for receiving precooked slices from said sluice and conveying said slices in a continuous stream of heated cooking oil (44) to a downstream end (48) of said fryer, said fryer being of substantially greater capacity than said sluice; first conduit means (62) in communication with said downstream end (48) of said fryer and said upstream end (18) of said sluice (16); means (56) for pumping liquid through said first conduit means (62) from said downstream end of said fryer to said upstream end of said sluice; second conduit means communicating with said downstream end (48) of said fryer and a heat exchanger (52); third conduit means (60) communicating with said heat exchanger (52) and said upstream end (42) of said fryer (38); means (30) in said sluice for regulating the flow of potato slices along with sluice; and means (28) positioned in said sluice at said upstream end thereof to prevent sticking of potato slices to surfaces of said sluice at said upstream end thereof.

Inventors: JOHNSON, NORMAN B.
Applicants: MIKE-SELL'S POTATO CHIP CO.
Application year: 1987
Main classification: A23L1
IPC codes: A23L1, A47J37