CZ343898A3 - French fries baked in an oven with the taste and texture of French fries fried in hot oil - Google Patents

Abstract

The present invention relates to French fried potatoes produced from an oven that approximate the attributes and characteristics of French fries that have been finished by deep fat frying. The oven-finished French fries of the present invention can be differentiated from commercial and prior-art oven fries in that they possess a combination of attributes, in particular, bulk moisture, total fat, internal moisture, surface water activity and a Texture Value, that renders them virtually indistinguishable from deep fried French fries. The oven-finished French fries comprise from about 32 % to about 50 % bulk moisture, from about 8 % to about 25 % total fat, from about 55 % to about 80 % internal moisture content, a surface water activity of less than or equal to about 0.55, and a Texture Value (maximum force [grams] or area under the force deformation curve [gram sec] within the first one-third of a specific compression test) of at least about 200.

Description

OVEN-BAKED FRIES WITH THE FLAVOR AND TEXTURE OF FRIES FRIED IN HOT OIL

Current status

The present patent relates to oven-baked potato chips. In particular, it relates to oven-baked potato chips, which in their properties and characteristics are similar to potato chips fried by immersion in hot oil.

French fries are among the most popular everyday foods, whether prepared at home or purchased at fast food restaurants. French fries fried by immersion in hot oil are particularly popular because of their excellent textural dichotomy. This textural dichotomy results in a product that has the right crispy exterior and the right soft and moist interior. The immersion frying method has been shown to be exceptionally well suited to creating this desirable textural dichotomy in French fries.

Recently, attention has been focused on the use of ovens for the preparation of potato chips from a partially fried (here pre-fried) frozen state. Products baked in the oven according to the former method are not at all equivalent to potato chips fried by immersion in hot oil. This is because during baking in the oven, moisture penetrates from the inner core to the crust area. This results in potato chips baked in the oven being soft, i.e. their surface is not brittle.

Attempts to improve texture by using longer heating times, higher oven temperatures, rapid heating (e.g., in a microwave oven), etc., have generally failed to achieve the desired balance of a moist interior and a dry, brittle crust. The finished French fries are generally leathery, dry, and tough. Examples of some methods for treating pre-fried French fries or methods for preparing fully cooked French fries, which after baking or reheating in the oven generally have poor textural properties (i.e., a dry interior and a tough or soggy outer crust), can be found in previous methods, see e.g., U.S. Patent 5,000,970 (Shanbhag et al.), U.S. Patent 5,302,410 (Calder et al.), U.S. Patent 3,865,964 (Kellermeier et al.), and U.S. Patent 5,242,699 (Bednař et al.). Poor textural properties affect the palatability of oven-baked products. There is currently a strong demand for oven-baked potato chips that have the texture, mouthfeel and taste of deep-fried potato chips in the serving state.

The oven-baked potato chips of the present invention have one or more advantages in terms of organoleptic properties, particularly the crispiness of the crust and the moistness of the inner core. The oven-baked potato chips have essentially the same textural dichotomy as deep-fried potato chips. The outer surface (i.e., the crust) is moderately crispy and not excessively oily, and the inner part (i.e., the core) is well-cooked, tender, and moist, yet not soggy.

The oven-baked potato chips of the present invention can be distinguished from commercial, prior art potato chips by exhibiting a combination of characteristics, particularly bulk moisture, total fat content, internal moisture, surface water activity (Aw) and texture value, that render them virtually indistinguishable from deep-fried potato chips. The oven-baked potato chips of the present invention can also be distinguished from commercial oven-baked potato chips based on subjective evaluations (i.e., evaluations by trained sensory evaluators).

The aim of the present invention is therefore to obtain oven-baked potato chips which are far superior to commercial chips and chips baked in the oven according to previous methods in terms of taste and consumer properties and their taste comparability to potato chips fried by immersion in hot oil.

It is also an object of the present invention to provide oven-baked potato chips that are essentially indistinguishable from deep-fried potato chips available in fast food restaurants.

It is a further object of the present invention to provide oven-baked potato chips that have a moist interior surrounded by a crisp yet tender exterior.

These and other objects of the present invention will be elucidated hereinafter.

All percentages are by weight unless otherwise stated.

The essence of the invention

The present invention relates to oven-baked potato chips with the following parameters:

a) volumetric humidity of 32 to 50% by weight;

b) 8 to 25% by weight of total fats;

c) 55 to 80% by weight of internal humidity;

d) surface water activity (Aw) less than or equal to 0.55; and

e) Texture value of at least 200; where the Texture Value is the maximum force (g) or area under the force vs. deformation curve (g.s) within the first third of the compression test.

Oven-baked potato chips have a texture that is essentially indistinguishable from commercial potato chips prepared by immersion in hot oil, such as McDonald's™ potato chips.

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Detailed description of the invention

The present invention relates primarily to features of oven-baked potato chips. The present invention further relates to oven-baked potato chips that are suitable for immediate consumption and are substantially indistinguishable from potato chips prepared by immersion in hot oil.

Definition

As used herein, the term deep-fried potato chips refers to potato chips that have been prepared into a consumable form by dipping them in hot oil.

As used herein, the term pre-fried refers to potato chips that have been subjected to at least one frying process (e.g., deep-frying) but which have not been fully fried.

As used herein, the term oven-baking refers to the conversion of a product into a consumable form by heat treatment in a toaster, toaster oven, forced air convection oven, rapid air convection oven, hot air blast oven, infrared oven, combination convection/infrared oven, microwave oven, combination microwave/convection oven, or conventional domestic oven. Heat treatment typically involves reducing the moisture content of the food.

As used herein, the term fat or oil refers to an edible fatty substance in the general sense including natural or synthetic fats and oils that contain primarily triglycerides, such as soybean oil, corn oil, cottonseed oil, canola oil, sunflower oil, palm oil, coconut oil, fish oil, lard and tallow, which may have been partially or completely hydrogenated or otherwise modified, and non-toxic fatty substances with properties similar to triglycerides, which are referred to herein as fatty substances, and which materials may be partially or completely indigestible. The terms fat and oil are used interchangeably.

As used herein, the term baked means a product that has been subjected to heat treatment and thereby converted into a consumable form.

As used herein, the term conditioned oil refers to oil that has been previously used for frying for such a period of time that a frying flavor has developed in it.

As used herein, the term oven-baked means a product that has been subjected to an oven baking process to convert it into a consumable form.

As used herein, the term oven baking refers to baking in an oven such as a forced air convection oven, a hot air draft oven, an infrared oven, a combination infrared radiation and convection oven, a toaster, a toasting oven, a microwave oven, a combination microwave and forced air convection oven, or a conventional domestic oven.

As used herein ^: the term Texture Value means the maximum force (g) or area under the Force vs. Deformation (gs) curve recorded within the first third of the compression test (see the Analytical Test Methods section for details).

Oven-baked potato fries

The most important features of the present invention are the Texture Value, Bulk Moisture, Internal Moisture Content, Surface Water Activity and the Amount of Fat Present in the Oven-Baked Product. Importantly, it is the combination of these features, and not a single feature, that distinguishes the present invention from commercial potato chips and oven-baked chips of prior art and makes them essentially indistinguishable from deep-fried potato chips.

The distinguishing features of the present invention lie, in part, in the recognition of the most important physical characteristics of pre-fried French fries and their thermal properties, which relationship can be used to ensure that oven-baked French fries have a moist, crispy interior and a crispy crust for various oven-baking processes. Specifically, the present invention finds that a certain range of surface water activity A _w and texture values are required for optimal consumption properties of oven-baked French fries.

One embodiment of the present invention is pre-fried potato chips, which can be prepared by manufacturing processes known in the art. Pre-fried potato chips can be prepared from various types of raw potatoes known to be suitable for the preparation of potato chips. Preferably, the pre-fried potato chips are prepared from Russet Burbank, Shepody or Katahdin potatoes. The pre-fried potato chips can have a variety of shapes and sizes. However, preference is given to the use of relatively thin and elongated potato strips known in the art as shoestrings. Shoestring potato chips as used herein refer to potato strips that have a square cross-section of 0.5 to 0.8 cm and are 6 to 12 cm long. Thicker potato strips, e.g., curly strips, straight cut thick potato strips (also known as regular cut) and steak cuts, can also be used.

The potato strips are blanched according to conventional procedures known in the art. After blanching, the potato strips may undergo further processing known in the art. For example, the potato strips may be treated with sodium acid pyrophosphate (SAPP), a chelating agent used to prevent discoloration of the strips. Dextrose (corn syrup) may also be used to treat the surface of the strips to achieve the desired level of browning during subsequent processing. In addition, the potato strips may be partially dried to reduce their moisture content. The potato strips are then subjected to one or more frying stages at an oil temperature of 132 to 196°C. The frying process may • · · 9 9. 9, ,· 99 . » · · ·.· .» .

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In a preferred embodiment, the blanched potato strips are reduced in moisture to not less than 60% by weight. The potato strips are then fried at an oil temperature of 132 to 166°C for a time sufficient to form pre-fried potato chips containing 30 to 58% by weight moisture. After frying, the pre-fried potato chips may be immediately cooled or frozen. Cooling or freezing of the pre-fried potato chips may be accomplished by methods known in the art. Repeated steps of frying, cooling, or freezing may be employed during the processing of the pre-fried potato chips. The pre-fried potato chips may also be treated with various surface treatments (e.g., oil coating; application of a hydrocolloid coating; application of water, aqueous solutions, or dispersions, etc.) either before or after cooling or freezing. Pre-fried potato chips can be stored frozen at temperatures of -57 to -6.7 ^° C.

The moisture, fat content and thermal properties of pre-fried potato chips are _important in the production of oven-baked potato chips according to the present invention. Of particular importance is the distribution of water in the pre-fried potato chips and the control of water migration from the inner core to the crust of the pre-fried potato chips during storage and oven-baking. By controlling the transfer of moisture from the inner core to the crust during frozen storage and oven-baking, it is possible to produce oven-baked potato chips suitable for consumption that are characterized by a delicious moist interior surrounded by a crispy crust with a low moisture content. The textural dichotomy that results from the oven-baking process is very similar to the properties of potato chips that have been finished by immersion frying in hot oil.

Moisture migration from the inner core to the crust region during frozen storage can be controlled in part by frying the potato strips to bulk moisture contents that are preferably equal to or greater than 40 wt. %, more preferably equal to or greater than 42 wt. %, and most preferably equal to or greater than 44 wt. %. Moisture migration can also be minimized during frozen storage by wetting the crust prior to frozen storage to increase A _w and thereby reduce or eliminate the difference in A _w between the inner core and the crust that is the driving force for moisture transfer. Wetting the crust can be accomplished by applying water, a water mist, an aqueous solution, or an aqueous dispersion to the surface of the pre-fried potato chips. Preferably, a spray process is used to wet the crust of the pre-fried potato chips.

Moisture migration from the inner core to the crust region during oven baking can be minimized by using oven baking conditions that rapidly or preferentially dry the surface of the potato chips. This can be achieved by selecting oven conditions (temperature, • .4 ·· -4. .-4 ·>, Λ • 4 Φ ·’·'··' 4 ·. .

• · · · ··4 ··· « 4 4 · ' ··.«»··· 4· . . 6 yzdúctíu), which provide a relatively large surface heat transfer coefficient, at oven temperature. Higher surface heat transfer coefficients are desirable because they lead to faster cooking times and the formation of a more pronounced low-moisture brittle crust area; Preferred surface heat transfer coefficients at oven temperature are 50 to 400 W/rri ^2o C. Preferential drying of the surface of the pre-fried potato chips can also be achieved by coating the pre-fried potato chips with edible fat or oil, which will increase the transfer of heat from the ambient air to the surface of the potato chips, during the finishing in the oven. Desirable thermal conductivities at oven temperatures in the crust of the pre-fried potato chips are 0.1 to 0.3 W/m°C. Desirable thermal conductivities for the high moisture inner core are 0.4 to 0.7 W/m°C. Coating the pre-fried potato chips with fat or oil serves to provide an additional barrier against moisture loss from the inner core as the coating oil is partially absorbed into the outer crust area during baking. The surface of the pre-fried potato chips can also be modified to improve the absorption of radiant heat from the oven. A typical method of doing this is to change the color, porosity, or reflectivity of the surface of the pre-fried potato chips.

Thermal conductivities and surface heat transfer coefficients can be calculated using the following procedure:

Surface heat transfer coefficient

The general equation for heat transfer across a phase interface is well known:

Q, = UA (T ₂ - T _t ) - AH _W + Q, , where '

Q _t = amount of heat transferred across the interface (W or equivalent energy units).

U = surface heat transfer coefficient (W/m ² °C or equivalent)

A = surface area of the interface ( ^m2 or equivalent)

T ₂ “ temperature on the hot side of the interface (°C or equivalent)

T, - temperature on the colder side of the interface (°C or equivalent)

AH _W - heat loss due to evaporation of water from the surface

Q _r = radiant heat transfer = AFo (Ti ⁴ - Tr), where F is the shape factor and σ is the Štefan-Bólzman constant.

Careful measurement of the temperature on both sides of the interface as a function of time, as well as the moisture content on both sides of the interface as a function of time and the temperature of any infrared heat source to which the surface is directly exposed, will allow the calculation of the surface heat transfer coefficient, (U).

Thermal conductivity

The thermal conductivity for a food material with a crust can be calculated if we know U, T ₂ and Ti.

k= UL (T ₂ - TJ / (U -T), where k = thermal conductivity (W/m°C or equivalent)

L - crust thickness (m or equivalent)

T - reference temperature.

Without wishing to be bound by theory, it is believed that potato chips prepared according to prior art methods lack the desirable textural dichotomy associated with high quality potato chips because the properties of the pre-fried potato chips (moisture, fat content, surface fat, thermal properties) and the oven-baking conditions are not optimized to produce final oven-baked potato chips characterized by a moist interior and a crispy, low-moisture crust. For example, many commercial or prior art pre-fried potato chips have such a high moisture content that when baked in the oven as recommended, the oven-baked potato chips do not have a sufficiently low bulk moisture content or their crust has not been sufficiently dried to provide a crispy surface texture. By using more severe oven conditions, it is possible to remove water from the surface of the potato chips, thereby improving the crispiness of the crust. At the same time, excessive internal moisture often transfers from the inner core to the surface, resulting in oven-baked potato chips exhibiting one or more of the following textural deficiencies: a tough surface texture; an interior that is perceived as excessively dry; or an excessively crispy overall texture (i.e., oven-baked potato chips do not have the desirable textural dichotomy associated with deep-fried potato chips).

Other methods for controlling water migration and water distribution of pre-fried potato chips are also possible. However, a preferred method, as described herein, involves controlling the bulk moisture content and thermal properties (i.e., the thermal conductivity of the high moisture inner core, the thermal conductivity of the crust, and the surface heat transfer coefficient) of the pre-fried potato chips. The bulk moisture content of the pre-fried potato chips can be controlled by the operating conditions used in the production of the pre-fried potato chips; e.g., the conditions used to dry the potato strips prior to frying; the pre-frying conditions; and the extent of surface wetting of the pre-fried potato chips, if used. The thermal properties of the pre-fried potato chips can be similarly modified and can additionally be adjusted by applying various ingredients to the surface of the pre-fried potato chips (e.g., oil coating; hydrocolloid coating, etc.).

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The pre-fried potato chips of the present invention have a moisture content by weight greater than 30%. Typically, the moisture content by weight is 38 to 58%, preferably 40 to 56%, more preferably 42 to 54%, and even more preferably 44 to 50% by weight moisture by weight.

The bulk moisture and thermal properties of pre-fried potato chips provide a method for controlling moisture loss from pre-fried potato strips during oven-baking such that the resulting potato chips have essentially the same textural dichotomy as deep-fried potato chips. In addition, the bulk moisture and thermal properties of pre-fried potato chips demonstrate how pre-fried potato chip processing conditions and oven-baking conditions can be modified to provide optimal textural characteristics of oven-baked potato chips.

Another embodiment of the present invention is oven-baked potato chips. Oven-baked potato chips of the present invention can be baked in various types of ovens, including convection ovens, forced air ovens, hot air blast ovens, infrared ovens, combination convection/infrared radiant ovens, toaster ovens, toaster ovens, microwave ovens, combination microwave/convection ovens with forced air circulation, or conventional domestic ovens. The baking time is less than or equal to 15 min, preferably less than or equal to 10 min, more preferably less than or equal to 5 min, and most preferably less than or equal to 3 min. After removal from the oven, the baked potato chips can optionally be coated with oil to enhance palatability and mouthfeel. Preferably, the oil used to coat the fried potato chips is a flavored or conditioned oil. The oil can be applied to the surface of the fried potato chips by methods known in the art; by spraying hot oil onto the surface or by rapidly dipping the potato chips into a tank of hot oil. Oven-baked potato chips of the present invention can be distinguished from commercial or prior art potato chips by exhibiting a combination of characteristics, particularly a certain texture value, bulk moisture, internal moisture, surface activity of water A _v; and total fat content, which make them essentially indistinguishable from potato chips finished by immersion in hot oil. In addition, oven-baked potato chips of the present invention can be distinguished from commercial or prior art potato chips by subjective evaluation (i.e., expert sensory evaluators).

Texture value

A critical feature of the present invention is the Texture Value of oven-baked potato chips. This value depends on a combination of factors such as moisture content, crust crispness, degree of crust dehydration, and other physical properties of the potato chips. The Texture Value is determined using a Texture Analyzer equipped with a rectangular flfl'· ' .· ♦'·'·· ?·,-·'·'·*· . · * fl fl'·.'·· fl · fl.fl · · • ·*» » · ·-.··· flflfl flflfl··* · ·

- 9* ··· ·'·' ·· · *·-· ·· *·· with a blunt steel plate sensor. A compressibility test is performed in which the plate compresses the potato chips while the resistance force is sensed (see the analytical test section, methods for details). A deformation force curve is obtained from the force (g) versus time ($) plot. Two textural parameters obtained from the deformation force curves are used to characterize the texture of the potato chips, the average maximum force (g) and the average area (g.s) in the first third of the compressibility test. We found that both of these parameters correlate with the crispness of the potato chips and either of them can be designated as a Texture Value. The high-quality potato chips of the present invention exhibit a distinct textural dichotomy and are characterized by a Texture Value (i.e., maximum thickness or area) of at least 200. Preferably, the Texture Value is from 210 to 1000, more preferably from 220 to 600, and even more preferably from 240 to 500. In addition, the oven-baked potato chips of the present invention have a ratio of average area to average maximum thickness of at least 1.0, preferably 1.04 or greater, more preferably 1.08 or greater, even more preferably 1.12 or greater, and most preferably 1.16 or greater. Commercial oven-baked . Potato chips prepared according to the oven manufacturer's instructions lack the textural dichotomy characteristics evident in the potato chips of the present invention. Typical values of average maximum force (g) and average area (g.s) for commercial potato chips, and potato chips baked in the oven according to the previous procedures are less than 200 and the ratio of average area to average maximum force is about 1.0 or less.

Commercial oven-baked potato chips may exhibit an average maximum thickness or area of at least 200 or greater. However, oven-baked potato chips of the present invention can be distinguished from commercial oven-baked potato chips based on bulk or internal moisture content and the fact that the ratio of average area to average maximum thickness of commercial oven-baked potato chips generally remains at or below 1.0.

Volumetric humidity

Another critical feature of the present invention is the volumetric moisture content of the oven-baked potato chips. The volumetric moisture is the total amount of water in the potato chips of the present invention. The oven-baked potato chips of the present invention have a volumetric moisture of 32 to 50% by weight. The oven-baked shoestring potato chips of the present invention have a volumetric moisture of 32 to 46% by weight. Preferably, the volumetric moisture of the oven-baked shoestring potato strips should be 33 to 44% by weight, and more preferably, the volumetric moisture should be 34 to 40% by weight. The oven-baked potato chips of the thicker strip shape of the present invention (i.e., regular cuts, curly cuts, and steak fries) typically have a volumetric moisture of from 35 to 50% by weight. Preferably, the oven-baked shoestring potato chips of the present invention have a volumetric moisture of from 35 to 50% by weight.

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··· ·· ·· λ**’ ··· ·* ·· thicker strips have a bulk moisture content of 38 to 48 wt. % and more preferably from 40 to 46 wt. %. The bulk moisture content of these products can be measured using well-known techniques and commercially available instruments. Oven-baked potato chips with a bulk moisture content of much greater than 50 wt. % will not achieve sufficient crust structure to exhibit the desired textural dichotomy (i.e., the potato chips will lack crispiness). At bulk moisture contents of much less than 32 wt. %, the oven-baked potato chips may be too dry. Maintaining the bulk moisture content of oven-baked potato chips of the present invention between 32 and 50 wt. % enables the production of oven-baked potato chips that have both a crispy crust with low moisture content and an inner core with high moisture content.

Indoor humidity

The internal moisture content is also an important characteristic of the products of the present invention. The internal moisture content of oven-baked potato chips is the moisture content of the internal starch matrix. As mentioned above, the internal part (i.e., the core) is well cooked, soft, floury, and moist, yet not gooey. The oven-baked potato chips of the present invention have an internal moisture content of from 55 to 80 wt.%, preferably 60 to 77 wt.%, more preferably 63 to 75 wt.%.

Surface Aw of the crust

The distinguishing characteristic of the oven-baked potato chips of the present invention is the outer crust. The outer crust is composed of a lubricating starch and an oil or fat. Preferably, the outer crust has substantially the same composition as the crust of deep-fried potato chips made from raw potatoes. However, it may contain ingredients typically used on the surface of potato strips, such as starch, hydrocolloids, vegetable gums, flavorings, and the like.

It is important that the outer crust is crispy and has a relatively low water activity (A _w ). The texture of fried and baked food products is known to depend in part on the A _w of the product. Crispy textures are generally associated with A* values less than or equal to 0.55. Surface A _w is a measure of the water activity in the crust of oven-baked potato chips (see the Analytical Test Methods section for details on measuring A _w ). Surface A _w is equal to the water vapor pressure in the outer crust divided by the vapor pressure of pure water at the same temperature.

The oven-baked potato chips of the present invention preferably have a surface A _w of less than or equal to 0.55, preferably 0.10 to 0.52, more preferably 0.15 to 0.5, and even more preferably 0.2 to 0.45.

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Total fat content

Edible oil, natural or synthetic, is generally present on the surface and inside the crust of oven-baked potato chips of the types disclosed in the present invention. Edible oils contribute to the flavor, lubricity, and texture of the oven-baked potato chips. Edible oils and fats present on the surface and inside the crust of oven-baked potato chips are well known to those skilled in the art and include, but are not limited to, beef tallow, lard, cottonseed oil, canola oil, soybean oil, corn oil, palm oil, fish oil, safflower oil, sunflower oil, coconut oil, peanut oil, medium chain triglycerides, structured triglycerides containing a combination of short or medium chain fatty acids and long chain fatty acids (e.g., caprepinic acid), and the like, or combinations thereof. Oils may be conditioned or flavored, see Flavored Vegetable Oils as Beef Tallow Substitutes in Deep Frying Applications, Food

Technologies, Str. 90-94 (1989) and US Pat. No. 5,104,678 (Yang et al.).

The oils may be partially or fully hydrogenated or otherwise modified. In addition, non-toxic fatty materials with properties similar to triglycerides, such as sucrose polyesters and Olean™ from Procter and Gamble and low-energy fats, polyesters, polyols and fatty acids and various polyesters of esterified polyols or combinations of normal fats and fat substitutes, may also be present on the surface or within the crust of oven-baked potato chips.

Some preferred oils are soybean oil and corn oil. The total amount of oil or fat present in or on the oven-baked potato chips of the present invention is 8 to 25% by weight. Shoestring potato chips of the present invention typically have a fat content of 12 to 25% by weight, preferably 13 to 23% by weight, more preferably 14 to 20% by weight of total fat. Thicker cut oven-baked potato chips (e.g., regular cut, curly cut, and steak cut) typically have a total fat content of 8 to 22% by weight. Preferably, thicker cut oven-baked potato chips have a total fat content of 10 to 20% by weight, and more preferably 12 to 18% by weight.

Preferably, the edible fat or oil present on the surface or within the crust of oven-baked potato chips of the present invention has a free fatty acid content of 0.8% or less.

Other components

Flavorings such as salt, pepper, butter, onion, or garlic may be added to the oil for pre-frying the potato chips or to the oven-baked potato chips to enhance the palatability or adjust the palatability to any desired taste. One skilled in the art will appreciate that the foregoing list of flavorings is by no means exhaustive, but is tot · t · ·· toto··,.

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Other ingredients known in the art that may also be added to edible fats and oils used to fry or coat pre-fried potato strips include antioxidants such as TBHQ, chelating agents such as citric acid, and antifoaming agents such as monomethylpolysiloxane.

The oven-baked potato chips of the present invention can also be distinguished from commercial and prior art oven-baked potato chips based on sensory evaluation and NMR analysis. Sensory evaluation shows that the oven-baked potato chips of the present invention exhibit the desirable textural dichotomy (i.e., a crispy surface surrounding a moist interior) typically associated with deep-fried potato chips. Commercial and prior art oven-baked potato chips typically do not exhibit this desirable textural dichotomy. NMR analysis provides a cross-sectional image indicating the distribution of moisture and fat within the potato chips. The high quality oven-baked potato chips of the present invention are characterized by NMR patterns that appear qualitatively similar to those of deep-fried potato chips, i.e., both products are characterized by patterns that show a high moisture inner core and a low moisture crust that contains fat. In contrast, the NMR patterns of typical commercial oven-baked potato chips appear qualitatively different, i.e., the dichotomous nature of the low moisture crust surrounding the high moisture inner core is not readily apparent.

The embodiments described are therefore to be considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims.

ANALYTICAL TEST METHODS

A number of parameters are used to characterize the elements of the pre-fried potato strips and the baked potato chips of the present invention. They are quantified by specific, experimental analytical procedures. Each of these procedures is described in detail below.

Total moisture content test

The moisture content of pre-fried potato chips and finished potato chips is determined by the following method in a forced air oven:

1. Uniformly grind a representative sample of potato strips or potato chips in a blender or conventional food processor.

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2; Weigh accurately about 5 g of crushed sample (weight A) into a pre-weighed metal dish or plate.

3. Place the metal dish containing the sample in a forced air convection oven at 105°C for 2 hours.

4. After 2 hours, remove the metal dish containing the dried sample and allow it to cool to room temperature in a desiccator on a desiccant such as anhydrous calcium sulfate.

5. Reweigh the metal pan containing the dried sample and calculate the mass of the dried sample (mass B) by subtracting the tare mass of the pan.

6. Calculate the percentage moisture content of the sample using the formula:

% moisture = [ (A -B)/Á]x 100

Potato Chips Texture Values Test

The texture value of the finished French fries, which correlates with the crispiness of the fries, is measured using a TA-XT2 Texture Analyzer (version 05.16 equipped with a 25-1 filling chamber, Texture Technologies Corp., Scarsdale, NY). The Texture Analyzer is connected to a standard personal computer (e.g., IBM 433DX) that records the data using a software program called XT.RA Dimension (version 3.7H, Texture Technologies Corp., Scarsdale, NY).

The texture analyzer is equipped with a rectangular sensor with a blunt steel plate (thickness 2.5 - 3.0 mm, width .70 mm, length 90 mrh) which is vertically attached to the main arm. The compression test is taken on one potato chip and the result is a graph of force (g) against time (s) from which the texture value is obtained.

Texture Analyzer assembly and calibration procedure:

1: Build the Texture Analyzer by following these steps:

Mode: Compression force measurement Choice: Back to the start Units of force: grams Time units: seconds Distance format: Deformation Speed before test: 2.0 mm/s Speed during test: . 1.0 mm/s Speed after test: 10 mm/s .Deformation; 85.0% Trigger type; Car 10

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• Force threshold:··*□ »'t>. ?··-' 2Ó/g '<>c ^r . ··» File type:· ·»·*''. m·.' · ^'Lětus .'Ť-2^3·'·'' ^,J · ” Monitor á output: M3 . Points in the graph * Collection speed'cfát.- xych 200 pps - * · force units:

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'3'.Calibrate the force by placing a 5 kg load on the calibration plate, and press the '.'calibration button on the • Texture Analyzer keyboard. -v íitoyeki i.;? »yr·. * .

4. Calibrate the distance of the sensor plate from the base plate using a starting distance ^{of 1} “ sensor from the plate of 10 mm for shoestring potato chips (increase the starting distance

......sensor distance to 15 mm for thick cuts or steak fries).

. Ensure that the bottom surface of the sensing plate is parallel to the surface of the base plate.

Sample Measurement Procedure ό ΐ 1: Immediately after removing the finished potato chips from the fryer (immersion <» in hot oil) or oven (baking in the oven), place a batch of potato chips under the heating lamp for one minute before beginning the texture analysis. The air temperature under the heating lamp is between 54.3 and 82.2°C. After the one-minute delay, place one...potato chip flat on ^the Texture Analyzer base plate (oriented perpendicular to the width of the Sensor). Begin

Compression test (1.0 mm/s test speed), while manually holding the ends of the potato <^1; fries flat against the base plate.

3. The resulting force (g) vs. time (s) data is stored for later analysis. Analyze nine more potato chips from the same batch using the same procedure. Ten potato chip samples from each batch are randomly selected. The texture analysis of the ten potato chip samples must be completed within 3 - 4 minutes {3 - 4 min after step 1).

•fc 14, Steps No. 1 - No. 2 are repeated for each new batch of potato chips. Generally, 5 to 10 batches of each type of potato chips are evaluated in this manner.

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Data analysis

1. 2 force vs. time graph for each individual potato chip the following parameters are evaluated:

- Maximum force (g) in the first third of the test.

- Area (g.s) under the curve in the first third of the test. {e.g. if a compression test requires 6 seconds to complete, the maximum force and area are obtained from the time interval 0 - 2 s).

2. After analyzing the force vs. time data for all 10 potato chip samples ^selected from a given batch, the 10 maximum force values are averaged and the 10 area values are averaged. A computer program written in Excel automates the task of analyzing the force vs. time data for each potato chip sample and calculating the averages of the maximum force and area values for each potato chip batch.

3. The remaining batches of the specific potato chip types are analyzed in a similar manner (5-10 batches are tested; 1.0 chips are analyzed in each batch). The average of the maximum force (g) and area (g.s) for the specific potato chip type is then calculated.

4. For the purposes of this invention, either the overall average maximum force or the flat force may be referred to as the Texture Value. Both texture measurements correlate with the crispiness of the finished potato chips.

Determination of internal moisture content of potato chips

The internal moisture of the finished potato chips, i.e. the moisture content of the internal starch matrix, is determined as follows:

1. Immediately after removing the finished potato chips from the fryer (immersion in hot oil) or oven (baking in the oven), immerse the potato chips in liquid nitrogen for 20 seconds to completely freeze the product and stabilize the internal moisture distribution.

2. Store frozen potato chips at -80°C until analysis.

3. Remove a few potato chips from the freezer and place them on a stainless steel tray. Let the potato chips warm slightly for a few minutes at room temperature to make them easier to peel.

4. Carefully cut the crust off one side of each frozen French fries with a razor blade. Turn the fries over and repeat until the crust is removed from all four sides.

5. Collect the frozen inner starch matrix (white solidified material) and immediately place in a sealed glass vial. Be careful to collect only the inner starch matrix; do not include any solid crust remnants.

6. Repeat steps 3 to 5 until approximately 5g of frozen inner starch matrix has been collected. This may require about 15 to 20 potato chips.

7. Accurately weigh approximately 5 g of the internal starch matrix (weight A) into a pre-weighed metal dish or plate.

• 4 • ·' ·. · ''··,»/' ·” : v. · '· ·····», »«·': /.i . '.*** ·*· -'·.··.···· · ···.-.· .> ·.· , ² 8: Place the metal dish containing the inner starch matrix in a convection oven at 105°C, for 2 hours ' 9. After 2 hours, remove the metal dish containing the dried sample and allow it to cool . to room temperature in a desiccator on a desiccant such as anhydrous calcium sulfate.

10. Reweigh the metal pan containing the dried sample and calculate the mass of the dried sample (mass B) by subtracting the tare mass of the pan.

11. Calculate the percentage moisture content of the sample using the formula:

%-moisture =.[.(A - B)/A] x 100

Determination of surface water activity (Aw) of potato chips

The surface area A _w of the finished potato chips is determined as follows:

1. Immediately after removing the finished potato chips from the fryer (immersion in hot oil) or oven (baking in the oven), immerse the potato chips in liquid nitrogen for 20 seconds to completely freeze the product and stabilize the internal moisture distribution.

2. Store frozen potato chips at -80 ^° C until analysis.

3. Transfer a bag of potato chips (0.25 - 0.5 kg) from the -80°C freezer to a cooler containing dry ice; ensure that the bag is completely packed in dry ice so that the potato chips are kept frozen at a low temperature.

4. Remove only one potato chip from the bag at a time and quickly cut the surface of the chip using a single-edged razor blade. Collect the surface scrapings in a stainless steel bowl and immediately transfer the scrapings to a covered glass vial.

Be careful to only collect scraps from the outer crust of the potato chips, do not cut the chip so that you cut through the crust area and expose the inner starch matrix.

5. Repeat step 4 until approximately 0.3 - 0.7 g of surface clippings have been collected. This may require cutting approximately 10 to 20 potato chips.

6. Determine the water activity (A _w ) of the surface sections using a Rotronic Hygroscope Model DT relative humidity meter (Rotronic Instrument Corp, Huntington, NY) as follows:

a. Transfer the surface clippings to a plastic dish for A^ determination (Rotronic Instrument Corp.)

b. Immediately place the plastic dish for determining A _w into one of the humidity chambers of the Rotronic Hygroscope Model ĎT relative humidity meter and close the chamber cover tightly.

c. Allow the meter reading to stabilize (wait 1 hour or more) before recording the reading and temperature.

d. Convert the stabilized meter reading to %RH using the previously prepared calibration graph (meter reading vs. %RFH) established using the following RH standards:

* . · ·.#·*'· ··> .»· * ····· ». ··· ··· . · · · · ·. · ··.·.··17 ·*· ·* ··..···....·· .

11%RH Standard lithium chloride solution (see Greenspan L., 1977, J.Res.Natl.Bur.

Stand., Section A, 81A:89).

35%RH Standard solution from Rotronic Instrument Corp.

50%RH Standard solution from Rotronic Instrument Pump.

65%RH Standard solution from Rotronic Instrument Corp.

e. Convert the %RH of the surface cuttings to surface A _w using the following formula: Surface A _w = (%RH /100)

Total fat content test

The total fat content of pre-fried potato strips and finished potato chips is determined by the solvent extraction method as follows:

Apparatus:

1. Soxtec HT6 extraction system; the unit includes a heating block and a condenser.

2. Recirculating water bath for condenser cooler

3. Recirculating oil bath for the heater block.

4. Extraction beakers.

5. Extraction cartridges, 26 mm (Fischer TC1522-0018).

6. Nitrogen as a purge gas.

7. Vacuum drying room.

8. Analytical balances (4-barrel).

9. Dispensing pipette (50 ml).

Materials:

1. Methylene chloride (Baker 9315-33)

2. Cooking stones (Chemware PTFE Fischer 09-191-20)

3. Silicone oil (Fischer TC 1000.-2779)

4. Glass wool (Fischer 11-390)'

Procedure:

1. Evenly mash a representative sample of potato strips in a blender or conventional food processor.

2. Weigh accurately (to 4 decimal places) a piece of glass wool (large enough to hold the sample piece in the cartridge) and the extraction cartridge; record the weight of the cartridge + glass wool (weight A).

3. Fill the crushed sample into the cartridge and cover the filled cartridge with a pre-weighed piece of glass wool.

• 0 · · · · 0 ··.··· 0 0 ···..·· ·0 0«· 00 0 0

4. Weigh accurately (to 4 decimal places) the crushed sample, cartridge + glass wool (weight B).

5. Place two or more boiling stones in the extraction beaker and weigh (to 4 decimal places); record the weight of the extraction beaker + boiling stones (weight C).

6. Place the filled cartridges into the extraction unit and lift the cartridges into the washing position.

7. Pipette 50 mL of methylene chloride into each pre-weighed extraction beaker with boiling stones.

8. Set the heating bath to 110°C and the cooling water bath to 28.3°C and allow the temperatures to stabilize.

9. Lower the filled cartridges into the extraction beakers containing the solvent and boil in the solvent for 60 min, leaving the vent cock open.

10. Lift the cartridges to the wash position and wash for 60 min.

11. Turn the condenser vent valve to the closed position and allow the solvent to evaporate for 60 minutes. Open the nitrogen purge to accelerate evaporation.

12. Transfer the beaker to a vacuum oven preheated to 120°C for 30 min at full vacuum (about 30 torr or less).

13. Allow the beaker to cool to room temperature and weigh (to 4 decimal places); record the weight of the beaker + boiling stones + extracted fat (weight D’j;

14. Calculate the total fat percentage using the following formula:

Fat % = [ (D - C) / (B - A) ] x 100

EXAMPLES

Example 1.

Two oven-baked potato chips and one deep-fried potato chip product are prepared using the following procedure:

A. Oven-baked potato chips according to the present invention:

Frozen pre-fried shoestring potato strips are a suitable starting product (e.g., Simplot Parfries; J.R. Simplot Co., Caldwell, ID). A typical processing procedure may include: selected and graded Russet Burbank potatoes are peeled, washed, trimmed, and cut axially into shoestring-shaped strips (approximately 6 mm square cross-section). The potato strips are blanched in hot water and steam and partially dried with hot air to reduce the weight of the potato strips by 15%. The partially dried strips are then pre-fried in partially hydrogenated soybean oil (Iodine number 67) for 60 s at an oil temperature of 190.5°C. The pre-fried potato strips are then cooled φφ ·

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44 · , ΦΦ , ΦΦ and frozen in a blast freezer at -34.4°C and packaged. The pre-fried potato strips have a moisture content of 64% by weight and a fat content of 6% by weight.

0.5 kg of frozen pre-fried potato strips are further processed by deep frying in hot oil in a 22 kg capacity kitchen fryer containing Primex 108 vegetable oil (a blend of partially hydrogenated soybean oil and corn oil supplied by Procter and Gamble Co.) for 3 min at 143.3°C. The resulting pre-fried potato chips are immediately frozen by immersion in liquid nitrogen for 20 s. The moisture content of the resulting pre-fried potato chips is about 47 wt. % and the fat content is about 15 wt. %. Immediately after freezing, the pre-fried potato chips are coated with oil by immersion in liquid vegetable oil (containing Primex 108) at 168°C for 1 to 3 seconds. The obtained oil-coated pre-fried potato chips are again frozen by immersion in liquid nitrogen. The frozen pre-fried potato chips are packed in sealed laminated foil bags and stored at a normal freezer temperature of about -18°C to -29°C. The oil-coated pre-fried potato chips contain about 9% by weight of surface fat per weight of the potato chips. The total fat content is about 22% by weight and the volumetric moisture content is about 43% by weight.

128 g of frozen oil-coated pre-fried potato chips prepared according to the above procedure are placed on an open mesh oven tray in a single layer and then baked at 204°C in a forced air convection oven (Wells Manufacturing Co., Model No. M42003S) for 1 minute. The potato chips are then transferred to a solid stainless steel baking tray in a single layer and baked for an additional 1.5 minutes. There is a turbulent flow of hot air inside the baking chamber. The air velocity in the center of the baking chamber (directly above the loaded chips) is 274 m/min. After removal from the oven, the potato chips are immediately evaluated for various technical parameters or are salted and evaluated for palatability and texture by a sensory panel.

B. Commercial Oven-Baked Potato Chips: Frozen retail Ore-lda® Shoestring potato chips (Ore-lda Foods Inc., Boise, ID) are purchased from a local grocery store. The potato chips contain 63% moisture and 6% fat by weight. The potato chips are baked in a conventional household oven (General Electric) as follows: 0.22 kg of frozen potato chips are evenly distributed in a single layer on a 22 x 32 cm solid baking sheet and baked for 10 min at 232°C. After removal from the oven, the potato chips are immediately evaluated for various technical parameters, or salted and evaluated for palatability and texture by a sensory panel.

9 9 99 C. Deep-fried French fries (McDonald's™ French fries; gold standard):

The frozen pre-fried shoestring potato strips used as the starting pre-fried French fries of Product A in this example (Simplot Par-fries; J.R. Simplot Co., Caldwell, ID) are further processed by deep frying in hot oil. The pre-fried potato strips have a moisture content of about 64% by weight and a fat content of about 6% by weight.

0 _; 75 kg of frozen pre-fried potato strips are allowed to thaw for 1 hour at room temperature (21°C) and then deep-fried in a 22 kg oil capacity kitchen fryer containing conditioned Primex 108 vegetable oil (a blend of partially hydrogenated soybean oil and corn oil supplied by Procter and Gamble Co.) for 3 min at 168°C. After removal from the fryer, the deep-fried potato chips are immediately evaluated for various technical parameters or are salted and evaluated for palatability and texture by a sensory panel.

For potato chips prepared by the above procedures (A, B and C), the volumetric moisture, total fat content, internal moisture content, surface A _w and texture value are determined. The results are shown in the following table:

Product Volumetric humidity Total fat Indoor humidity . Surface. A _w Max. strength Area Ratio of strength/max. area A Oven-baked computer of this invention 38% by weight 18% by weight 67% (wt.) 0.3. 205g 243 gs .1.19 B Oven-baked commercial 48% . wt. . 9% by weight. 72% by weight 0.6 Í33g 113 gs 0.85 e Fried in oil Gold .standard 37% by weight ' 17% wt. 74% by weight 0.4 243g 294 gs 1.21

The data in the table show that the oven-baked potato chips of the present invention (A) have technical characteristics that are very similar to the gold-standard deep-fried potato chips (C). Commercial oven-baked potato chips (B) have parameters outside the desired ranges for surface activity A _w and texture parameters (maximum thickness, area and area to maximum thickness ratio).

The above-mentioned potato chips are also evaluated for palatability and texture by a sensory panel. A panel of approximately 40 trained assessors assess the products for various sensory attributes on a scale of 1 to 9. Two sensory tests are conducted, each evaluating the oven-baked product directly against the deep-fried potato chips. The results of the sensory test are presented below; each numerical value represents the average for that attribute.

• · ♦ «« * ·« * ·'·'···.··· » ♦ · · . ’ ·’ - 9 ' ·· φ.··., ;-«»

Product Sensory test #1 Sensory test no.2 A B C. D in the oven baked according to this invention deep fried in hot oil Gold Standard baked in a commercial oven fried, by dipping in hot oil ' Gold Standard Base size 40 40 33 33 Potato flavor 5.2 .5.5 ^5.1A 6.3 ^B ' - The taste of fried food 5.6 5.3 ^4.3A Flavor 1.5 1.5 3.7 ^and '. .1.4" Surface crispiness '5.5 5.7 ^{2.7A 5.8B} Indoor humidity 5.5 . 5.2 5.7 . .5,6. Overall acceptability . 6.0 6.6 ^3.3A

Note: For each sensory test, values with a superscript letter are significantly different at the 95% confidence level.

The results of the sensory tests showed that the oven-baked potato chips of the present invention (A) had palatability and textural characteristics very similar to the potato chips fried by immersion in hot oil (C). The oven-baked potato chips of the present invention particularly exhibited the desirable textural dichotomy, i.e., a moist interior and a crispy crust, which is typically associated with potato chips fried by immersion in hot oil. In contrast, the commercial oven-baked potato chips (B) did not exhibit the desirable textural dichotomy, as shown by a significantly lower surface crispness value.

Example 2.

Two oven-baked potato chips and one deep-fried potato chip are prepared using the following procedure:

D. Oven-baked potato chips according to the present invention:

The frozen pre-fried shoestring potato strips used as the starting pre-fried potato chips in Example 1A are an acceptable starting product for this example (Simplot Pre-Fried Potato Chips, J.R. Simplot Co., Caldwell, ID). The pre-fried potato strips have a moisture content of 64% by weight and a fat content of 6% by weight.

0.5 kg of frozen pre-fried potato strips are further processed by immersion frying in hot oil in a 20 kg capacity kitchen fryer containing Primex 108 vegetable oil (a blend of partially hydrogenated soybean oil and corn oil supplied by Procter and Gamble Co.) for 3 minutes at a temperature of 143.3°C. The resulting pre-fried potato strips are immediately frozen by immersion in liquid nitrogen for 20 seconds. The moisture content of the resulting pre-fried potato chips is 48 wt. % and the fat content is 14 wt. %. The frozen pre-fried potato chips are packaged in laminated foil bags and stored at -18 ^° C.

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Frozen pre-fried potato chips are baked in a dual-impact hot air oven (WOÍverine Corporation, Merrimac, MA; model 2.0 x 051 pilot-scale Jetzone oven) equipped with a continuous conveyor. The pre-fried chips are arranged in a single layer on open wire mesh trays located on the oven conveyor belt. Hot air impinging on the product from both the top and bottom is supplied from two rows of tubes located above and below the conveyor belt. The air velocity measured at the product level is 1676 m/min. The air temperature inside the oven chamber is 232°C and the belt speed is set so that the residence time in the oven is 1.25 min. Immediately after exiting the oven, the chips are lightly sprayed with hot (65°C) conditioned vegetable oil Primex 108; 3% oil by weight of the potato chips is sprayed onto the surface. The potato chips, baked in the oven, are then immediately evaluated for various technical parameters or salted and their taste and texture are sensory evaluated.

E. Commercial oven-baked potato chips

Frozen Ore-lda Vend Fry samples for use in the Ore-lda French Fry Vendor (shoestring strips; Ore-lda Foods, Inc. Boise, ID) are purchased from a local distributor and stored at -18°C or below. Frozen Ore-lda Vend French fries are placed in the freezer of an Ore-lda Model 890 French Fry Vendor vending machine (Ore-lda National VendorS, Division of Dynamics Corp., Bridgeton, MO). Vend French fries are baked in the French Fry Vendor according to the manufacturer's recommendations: 100 g of frozen Vend French fries are placed in a rotating basket and then baked for 40 s with forced air at 240°C flowing through the basket. After the baking cycle is complete, the oven-baked potato chips are automatically turned out and immediately evaluated for various technical parameters or they are salted and their taste and texture are sensory evaluated.

F. Deep-fried potato chips (McDonald's potato chips; gold standard): .

Frozen pre-fried shoestring potato strips are used as the starting pre-fried potato chips for the preparation of Product D in this example (Simplot Parfries; J.R. Simplot Co., Caldwell, ID) and are further processed by deep frying in hot oil. The pre-fried potato strips have a moisture content of 64% by weight and a fat content of 6% by weight.

0.7 kg of frozen pre-fried potato strips are allowed to thaw for 1 hour at room temperature (21.1°C) and then fried by immersion in hot oil in a 20 kg capacity kitchen fryer containing Primex 108 vegetable oil (a blend of partially hydrogenated soybean oil and corn oil) supplied by ·· ♦ ♦ · ·· > · · ·♦ * · · ·' . ! ··*··. ·· ··· ··· ·· ···'. ·* »·

Procter and Gamble Co.) for 3 minutes at a temperature of 168°C. After removal from the fryer, the deep-fried potato chips are immediately evaluated for various technical parameters or salted and their taste and texture are sensory evaluated.

The above potato chips (D, E and F) are evaluated for volumetric moisture, total fat content, internal moisture content, surface area, A^ activity and texture value. The results are summarized in the following table:

Product Volumetric humidity Total fat content Indoor humidity Surface AiV Max. force Area Area/max force ratio D pre-toasted according to this invention 42% by weight 15% by weight . 73% by weight 0.3 276g 324 Q.s 1.17 E. pre-toasted commercial 50% by weight 11% by weight: 72% by weight 0.6 191g 185 9-S 0;97 F' Fried by dipping in hoikéhóolgeGold Standard 39% by weight 16% by weight 76% by weight 0.4 266 ,g 335 9-S 1.26

The results show that the oven-baked potato chips of the present invention (D) have characteristics that are very similar to the hot oil-fried potato chips (F), which are considered the gold standard. Commercial oven-baked potato chips (E) fall outside the desired range for surface activity A _w and texture parameters (maximum thickness, area, ratio of area to maximum thickness).

The potato chips are also evaluated sensory- ly for taste and texture. The oven-baked potato chips of the present invention (D) have a taste and texture similar to the gold standard deep-fried potato chips (F). The oven-baked potato chips of the present invention in particular exhibit the desired textural dichotomy, i.e., a moist interior and a crispy crust, which are typically associated with deep-fried potato chips. In contrast, the commercial oven-baked potato chips (E) lack sufficient crispness and do not exhibit the desired textural dichotomy.

Example 3

The non-digestible, fat preparation was used to prepare the pre-fried potato strips in the following example. The non-digestible fat preparation is Olean™ from the Procter and Gamble Company, which contains a mixture of liquid and solid sucrose polyesters. Selected and graded Russet Burbank potatoes are peeled, washed, trimmed, and cut along the axis into shoestring strips (6 mm square cross- _section ). The potato strips are blanched in hot water or steam and partially dried with hot air so that the weight of the potato strips is .

• . · · '· .; » and ' that ' that - that

Óyl . · ····· ·»♦··<··· ··· ·· '··.'···' · · ·· strips reduced by 15% by weight. The partially dried potato strips are then pre-fried in Olean for 60 seconds at an oil temperature of 190.5°C. The pre-fried potato strips are then cooled, frozen in a blast freezer (-34.4-C) and packaged. The pre-fried potato chips have a moisture content of 64% by weight and a fat content of 8% by weight.

0.5 kg of packaged frozen pre-fried potato strips are further processed by frying in a 20 kg kitchen fryer with oil containing Olean for 3 minutes at 149°C. The resulting pre-fried potato strips are immediately frozen by immersion in liquid nitrogen for 20 seconds, packed in laminated foil bags and stored at a normal freezer temperature of -17.8°C. The pre-fried potato chips have a moisture content of 46% by weight and a fat content of 20% by weight.

128 g of frozen pre-fried potato chips are placed on an open wire mesh baking sheet in a single layer and baked at 204°C in a forced air convection oven (Wells Manufacturing Co., Model No. M42003S) for 2.5 min. The baking chamber is provided with turbulent airflow with an air velocity at the center of the baking chamber directly above the product layer of 274 m/min. The potato chips are then transferred to a wire mesh basket in a single layer and the basket is placed in the operating zone of a high velocity hot air impingement oven (manufactured by Industrial Combustion Services Inc., Tyrone, GA). Hot air at 190°C is directed onto the surface of the potato chips at a velocity of 1,524 m/min. The potato chips are left in the oven with a blast of hot air for 15 seconds.

The resulting low-energy oven-baked potato chips have a texture and palatability very similar to the gold standard deep-fried potato chips. The finished potato chips have a bulk moisture content of 35% by weight, a total fat content of 15% by weight, an internal moisture content of 72% by weight, a surface A _w of 0.4 and a Texture Value of 250.

Example 4

The frozen pre-fried shoestring potato strips used as the starting pre-fried potato chips in Example 1A are a suitable starting product in this example (Simplot Par-fries; J.R. Simplot Co., Caldwell, ID). The pre-fried potato strips have a moisture content of 64% by weight and a fat content of 6% by weight.

0.5 kg of frozen pre-fried potato strips are further processed by frying in a 20 kg oil capacity kitchen fryer containing Primex 108 vegetable oil (a blend of partially hydrogenated soybean oil and corn oil supplied by Procter and Gamble Co.) for 3 minutes at 168.3°C. The resulting pre-fried potato strips are immediately frozen by immersion in liquid nitrogen for 20 seconds and allowed to age at -17.8°C. The pre-fried potato chips have a moisture content of 38% ·* « 9 9 9· « v V 1 • , · · · ·· ·<-'·· '< Ί • 9·· * · φ .99« 991 •9 ·,·♦.· 9 ,·.·.,;··.. -I

999 9 9 - 9«. 9 9 9 ' 99 ..>9, wt. and fat content of 17 wt. %. The surface of the frozen potato chips is then moistened by spraying a fine water mist at 21.1°C onto the surface of the pre-fried potato chips. During the moistening process, the frozen pre-fried potato chips are tossed to achieve uniform wetting of the surface of the pre-fried potato chips. The spraying of the water mist continues until 7% (by weight of the pre-fried potato chips) of water is sprayed onto the surface of the pre-fried potato chips. The frozen moistened pre-fried potato chips are then stored at a temperature of -17.8 to -,6.7°C. The moistened pre-fried potato chips contain 43 wt. % total moisture and 15 wt. % total fat. Wetting the surface of pre-fried potato chips will increase the A _w value of the crust region and thereby reduce or eliminate the A _w difference between the inner core and the crust region, which is the driving force for moisture migration during frozen storage.

128 g of frozen moistened pre-fried potato chips are prepared for consumption by baking in a forced air convection oven (Wells Manufacturing Co., Model No. M42003S). The moistened pre-fried potato chips are arranged in a single layer on an open wire mesh baking sheet and baked for 1.5 min at an air temperature of 218.3 ^Ů C. There is turbulent hot air flow in the baking chamber. The air velocity in the center of the baking chamber (immediately above the product layer) is 274 m/min.). In the oven, the baked potato chips exhibit a desirable textural dichotomy, i.e., a crispy surface texture and a moist interior. The finished potato chips have a Volumetric Moisture Content of 39 wt.%, a Total Fat Content of 16 wt.%, an Internal Moisture Content of 72 wt.%, a Surface A _w of 0.4 and a Texture Value of 290 (Maximum Strength = 237 g; Area = 289 gs; Area to Maximum Strength Ratio = 1.22).

Claims (9)

PATENT CLAIMS 1. Oven-baked potato chips with the following parameters: a) 32 to 50 wt. bulk moisture; b) 8 to 25 wt. total fat; and c) A texture value of at least 200; said texture value is the maximum force (g) or area (g.s) · below the force strain curve during the first third of the compression test. The product according to claim 1, wherein said oven-baked French fries have a bulk moisture content of 33 to 44% by weight, a total fat content of 13 to 23% by weight. and Texture value 210 to 1000. An article according to claims 1 and 2, wherein said oven-baked potato chips have a surface water activity of less than or equal to 0.55 and an internal humidity of 55 to 80% by weight. The product of claim 3, wherein said oven-baked potato fries are potato strips shoestring. Product according to claims 1, 2, 3 or 4 having a surface heat transfer coefficient at an oven temperature of 50 to 400 W / m ² ° C. Product according to claims 1, 2, 3 or 4 having a thermal conductivity of the crust region at a baking temperature of 0.1 to 0.3 W / m ° C, An article according to claim 1, 2, 3 or 4 having a thermal conductivity of the inner core at an oven temperature of 0.4 to 0.7 W / m ° C. The article of claim 7, wherein the ratio of the average area to the average maximum force is at least AND/ 1.0 when measuring texture value. The article of claim 8, wherein the surface A _w is less than or equal to 0.55.