WO2018165732A1

WO2018165732A1 - Method of making dehydrated fried potato products

Info

Publication number: WO2018165732A1
Application number: PCT/CA2017/050327
Authority: WO
Inventors: Timothy D. Durance; Guopeng Zhang; Shafique Ahmad
Original assignee: Enwave Corporation
Priority date: 2017-03-13
Filing date: 2017-03-13
Publication date: 2018-09-20

Abstract

A process for making a shelf-stable, dehydrated, crunchy, fried potato product, not requiring preservatives or refrigeration and in a form that is convenient for use as a snack food. In one embodiment, a potato is cut into slices, fried in oil to lower its moisture content, and the fried potato slices are dehydrated in a microwave-vacuum dehydrator to produce a dehydrated French fry having the aroma, appearance and flavor of fresh French fries. The process also makes dehydrated, crunchy, fried potato snack products in the form of patties and the like.

Description

METHOD OF MAKING DEHYDRATED FRIED POTATO PRODUCTS

Field of the Invention

The invention pertains to methods of making dehydrated potato products, in particular dehydrated French fries, patties and similar products.

Background of the Invention

It is known in the food processing art to make dehydrated food products by means of microwave vacuum-dehydration. Examples in the patent literature include WO

2014/085897 (Durance et al.), and US 6,313,745 (Durance et al.). Microwave-vacuum treatment of potatoes is known, but is used principally in the reduction of the fat content of fries. US 8,613,969 (Barber) discloses a method for producing low-oil dried food products. Potato slices are fried in a fryer to a moisture content above 2 wt.% and processed inside a centrifuge under vacuum pressure to reduce the oil and moisture content. The interior of the vacuum centrifuge may be heated. US 2006/0051471 (Barry) discloses a method for cooking potato slices to reduce the acrylamide content. A high-temperature first heating step is followed by a lower- temperature second heating step. The first heating step comprises par-frying raw potato slices in cooking oil until the raw potato slices have a moisture level from 3% to 10%. The second heating step comprises vacuum frying the par-fried potato slices at less than 1 0°C until the par-fried potato slices have a low moisture content. The first heating step can comprise atmospheric frying, vacuum frying, microwave-assisting frying, or baking, and the second heating step can comprise vacuum frying, low temperature oven drying, or vacuum oven drying. Xiaojian Quan et al., "Low oil French fries produced by combined pre-frying and pulsed- spouted microwave vacuum drying method," Food and Byproducts Processing, 99 (2016): 109-115, discloses a combined method of pre-frying and pulsed-spouted microwave vacuum drying to produce lower oil French fries. Potato slices are first pre- fried using a vacuum fryer for 15 minutes so that the moisture content of the potato slices is about 18.5%. The pre-fried potato slices are then subjected to pulsed-spouted microwave vacuum drying to obtain a product with low oil and moisture content.

Despite these prior art drying processes, there is a need in the food-processing industry for a process that can produce a dehydrated, fried potato snack product, including a French fry snack product that has the aroma, appearance and flavor of fresh French fries, while being preserved by the dehydration to be shelf-stable and require no refrigeration. The present invention is directed to methods for making such food products.

Summary of the Invention

The invention provides a method of making a shelf-stable dehydrated potato product, not requiring preservatives or refrigeration and in a form that is suitable as a snack food.

According to one aspect of the invention, there is provided a method of making a crunchy, dehydrated potato product, comprising frying potato slices in oil to reduce the moisture content therein, and exposing the fried potato slices to microwave radiation in a microwave-vacuum dehydrator at a pressure less than atmospheric to produce the crunchy, dehydrated potato product, such as dehydrated French fries or potato wedges.

According to another aspect of the invention, there is provided a method of making a crunchy, dehydrated potato product, comprising the steps of forming a shaped potato mass, such as a patty, comprising cut-up potato; frying the shaped potato mass in oil and thereby reducing the moisture content therein; and exposing the fried, shaped potato mass to microwave radiation in a microwave-vacuum dehydrator at a pressure that is less than atmospheric to produce the crunchy, dehydrated potato product.

Another aspect of the invention provides crunchy, dehydrated fried potato snack products made by the methods of the invention.

Unlike potato chips, which because of their thinness can be fried in oil until they are thoroughly dehydrated, French fries, potato patties and similar potato products, being substantially thicker than potato chips, would be oxidized and darkened due to Maillard browning reactions to the point of blackness if fried in oil until dehydrated. In the invention, after a preliminary step of frying, Maillard browning reactions and oxidation of the French fries, patties, etc. during the drying process are minimized by microwave- vacuum drying them under suitable conditions. Further aspects of the invention and features of specific embodiments of the invention are described below.

Detailed Description Dehydrated French Fries

In a first embodiment of the invention, the preparation method begins with a raw potato, and produces from it a dried, crunchy French fry potato product, intended as a snack food. The raw potato is first cut into conventional French fry-shaped slices, having a thickness of at least 5 mm, or in the range of 5 to 15 mm. Alternatively, the potato may be cut into conventional potato wedge-shaped slices. Typically raw potato moisture content is 80 wt.%, or within the range of 75 to 85 wt.%.

The raw potato slices are then fried in cooking oil until their moisture content is reduced to 55 wt.% or less. The moisture needs to be reduced by frying to this level to get adequate cooking for cooked flavor and texture. The moisture level may be reduced to a level in the range of 30 to 55 wt.%. The frying method may be deep-frying.

Optionally, the raw or blanched potato slices can be frozen and the frying is then done on the frozen slices. Prior to freezing, raw potato products may be blanched by a brief exposure to heat, to inactivate potato enzymes which can discolor the potato. Blanching can be accomplished by brief exposure to hot steam, hot water, or hot oil.

Following frying, the potato slices are subjected to drying by means of microwave radiation and reduced pressure in a microwave-vacuum dehydrator. The pressure in the vacuum chamber is maintained during the drying process in the range of 20 to 40 Torr, alternatively 5 to 80 Torr. Lower pressures give better puffing and less browning, especially of French fries and wedges, because lower pressure equates to lower drying temperatures. The step of microwave-vacuum drying may be conducted in two or more stages having different conditions in order to optimize the drying conditions and quality of the product. For example, in a first stage, the microwave power level may be higher than in a second stage; or the pressure, drying time or speed of rotation of the drying basket (where a rotating basket is employed) may be different. Likewise, three or more drying stages may be employed. In the first stage, higher power is used to create maximum puffing and faster drying. Lower power is used in later stages to avoid over- drying and excessive temperatures in dry portions of the load that may lead to dark or burned portions.

Once sufficient drying of the fried potato slices has occurred, for example to a moisture level less than 5 wt.%, alternatively less than 2 wt.%, the radiation is stopped, the pressure in the vacuum chamber is equalized with the atmosphere, and the crunchy, dehydrated French fry product is removed from the microwave-vacuum dehydrator. It will be understood that "drying" means that the moisture level is reduced to a desired level, not necessarily to zero. Initial oil content of raw potatoes may be in the range of 8 to 15 wt.%. After microwave- vacuum drying oil content may be in the range of 15 to 30 wt.%. The final oil content depends on the initial oil content and the amount of mass removed as water. The microwave-vacuum process of the invention does not substantially remove fat or oil from the potato pieces.

The crunchy, dehydrated French fry product is packaged in a form suitable for storage, distribution and marketing. An example is packaging in oxygen-barrier bags, which are flushed with an inert gas, such as nitrogen, to remove most of the oxygen gas, and then sealed.

An example of a microwave-vacuum dehydrator that is suitable for drying the fried potato slices is a resonant cavity-type microwave apparatus, as shown in WO

2009/049409 (Durance et al.), commercially available from EnWave Corporation of Vancouver, Canada, under the trademark nutraREV. Using this apparatus, the fried potato slices are placed for drying in a cylindrical basket that is transparent to microwave radiation and has openings to permit the escape of moisture. The loaded basket is placed in the vacuum chamber with its longitudinal axis oriented generally horizontally. The pressure in the chamber is reduced and the microwave generator is actuated to radiate microwaves in the vacuum chamber. The basket is rotated within the vacuum chamber, about a generally horizontal axis, so as to slowly and gently tumble the French fries. The rotation of the basket may be effected, for example, by means of rollers on which the basket is supported, or by means of a rotatable cage in which the basket is placed. Another example of a microwave-vacuum dehydrator suitable for carrying out the step of drying is a travelling-wave microwave apparatus, as shown in WO 2011/085467 (Durance et al.), commercially available from EnWave Corporation under the trademark quantaREV. Using this type of apparatus, the fried potato slices are fed into the vacuum chamber and conveyed across a microwave-transparent window on a conveyor belt while being subjected to drying by means of low pressure and microwave radiation. With this apparatus, the fried potato pieces are dried while resting on a tray or conveyor belt, and are not subjected to tumbling.

Dehydrated Potato Patties and Similar Products

The second embodiment of the invention pertains to the production of dehydrated potato products in the form of shaped potato masses, such as patties and tater tots, made from cut-up potatoes. After forming the raw shaped masses, the production process is essentially the same as that described above for the dehydrated French fry products.

The raw shaped potato mass is made according to conventional food processing practices. For simplicity of description, reference is made herein to potato patties, but it will be understood that the process is the same for other shaped potato masses. Raw potato is cut up into small pieces, e.g., grated, riced, diced, julienned, etc., to form small potato pieces suitable for shaping into patties. Other ingredients may be included in the patties, such as cooking oil, dextrose, sugar, salt, sodium phosphate and natural flavors. The patties have a thickness in the range of 8 to 15 mm.

The raw patties are then fried in cooking oil until their moisture content is reduced to a level in the range of 40 to 60 wt.%. Optionally, the raw patties can be frozen and the frying is then done on the frozen patties. Optionally, the raw patties may be blanched prior to freezing.

Following frying, the patties are subjected to drying by means of microwave radiation and reduced pressure in a microwave-vacuum dehydrator. The method of conducting the microwave-vacuum drying, and the types of equipment suitable for this, are the same as described above for the French fry product.

The dehydrated potato patties are then packaged in the manner described above for dehydrated French fries.

Example 1

A 745 gram sample of freshly fried commercial French fries having a moisture content of about 40 wt.% was placed in a perforated polypropylene drying basket. The basket was loaded into a nutraREV microwave-vacuum dehydrator manufactured by EnWave Corporation. The dehydrator has a pair of spaced horizontal rollers for rotation of the basket. The basket was rotated about its longitudinal, horizontal axis at 8 rpm during the drying process. The microwave-vacuum drying was done at in two stages, namely, a first stage of 900 seconds at 1500 W of power, and a second stage of 180 seconds at 1000 W of power, all at an absolute pressure in the range of 23 to 27 Torr. The maximum product temperature in the vacuum chamber was 88°C. The final product weighed 465 g, was very crunchy, had a moisture content below 5 wt.%, and a water activity below 0.40. Example 2

Frozen crinkle-cut potato fries were fried (from frozen) for 4 minutes at 180 °C (350°F) with vegetable oil, and then were well drained. A 865 gram sample of the fries, having a moisture content of about 53 wt.%, was placed in a perforated polypropylene drying basket. The basket was loaded into a nutraREV microwave-vacuum dehydrator of the type described in Example 1. The basket was rotated about its longitudinal, horizontal axis at 6 rpm during the drying process. The microwave-vacuum drying was done at in three stages, namely, a first stage of 750 seconds at 2000 W of power, and a second stage of 750 seconds at 1000 W, and a third stage of 240 seconds at 800 W., all at an absolute pressure in the range of 23 to 27 Torr. The maximum product temperature in the vacuum chamber was in the range of 96°C. The final product weighed 420 g, was crunchy, and had a moisture content below 5 wt.%.

Example 3

A 785.9 g sample of fresh commercial French fries having a moisture content of 40 wt.% was placed in three trays, with the fries piled on top of each other two or three fries deep. The trays were then loaded into the vacuum chamber of a quantaREV microwave-vacuum dehydrator manufactured by EnWave Corporation. The chamber was evacuated to 25 Torr absolute pressure, plus or minus 1 Torr The trays were moved across the microwave window, at a speed of 4 inches per minute. A speed greater than 2 inches per minute is preferred. The microwave-vacuum drying was done for 3600 seconds at 2400 W (using four magnetrons of 600 W each), at an absolute pressure in the range of 24 to 26 Torr. The maximum product temperature in the vacuum chamber was 97°C. The final product weighed 485.2 g, was very crunchy, had a final moisture content of 2 wt.% and water activity Aw of 0.12 at 25°C.

The dried fries were packaged in oxygen-barrier film bags formed from plastic laminated with aluminum foil, laminated pouches. The pouches were filled with dry fries, flushed with nitrogen gas to remove all but 2 vol.% gaseous oxygen, then sealed and stored at room temperature (about 20°C). The result was a delicious crunchy snack product that can be eaten cold, and stored and distributed over a period of several months without significant flavor or texture changes. In effect, the product was a French fry that can be marketed like potato chips.

Example 4

McCain (trademark) frozen potato wedges (pre-fried by the manufacturer) weighing 1 ,305 g, having a moisture content of 72 wt.%, a thickness of 15-1 mm and a calculated initial fat content of 8.2 wt.% were placed in a perforated polypropylene drying basket. The basket was loaded into the vacuum chamber of a nutraREV microwave-vacuum dehydrator. The microwave-vacuum drying was done without tumbling in three stages, namely, a first stage of 3600 seconds at 2000 W of power, a second stage of 757 seconds at 1750 W, and a third stage of 1720 seconds at 1000 W., all at an absolute pressure in the range of 24 to 26 Torr. The maximum product temperature in the vacuum chamber was 75°C. The final product weighed 440 g, was crunchy, had a moisture content of 5.7 wt.%, a water activity Aw of 0.20, and a calculated final fat content of 24 wt.%.

Example 5

McCain (trademark) frozen hash brown patties (pre-fried by the manufacturer) weighing 1 ,170 g, having a moisture content of 61 wt.%, a thickness of 10-12 mm and a calculated initial fat content of 12 wt.% were placed in a perforated polypropylene drying basket. The basket was loaded into the vacuum chamber of a nutraREV microwave- vacuum dehydrator. The microwave-vacuum drying was done without tumbling in three stages, namely, a first stage of 3600 seconds at 2000 W of power, a second stage of 757 seconds at 1750 W, and a third stage of 1720 seconds at 1000 W., all at an absolute pressure in the range of 24 to 26 Torr. The maximum product temperature in the vacuum chamber was 79°C. The final product weighed 435 g, was crunchy, had a moisture content of 4.8 wt.%, a water activity Aw of 0.21 , and a calculated final fat content of 32 wt.%. Example 6

Taco Bell (trademark) fresh tater tots weighing 1 ,125 g, having a moisture content of 48 wt.%, a thickness of 20-22 mm and a calculated initial fat content of 9.5 wt.% were placed in the vacuum chamber of a nutraREV microwave-vacuum dehydrator. The microwave-vacuum drying was done without tumbling in three stages, namely, a first stage of 3600 seconds at 2000 W of power, a second stage of 757 seconds at 1750 W, and a third stage of 1720 seconds at 1000 W., all at an absolute pressure in the range of 24 to 26 Torr. The maximum product temperature in the vacuum chamber was 91 °C. The final product weighed 595 g, was crunchy, had a moisture content of 3.0 wt.%, a water activity Aw of 0.21 , and a calculated final fat content of 18 wt.%.

Example 7

Raw potatoes were peeled and cut into 5 mm x 5 mm cross-section dimension French fry shapes, about 60 mm long, then deep fried in cooking oil at 188°C for 5 to 6 minutes, to a golden brown color. The moisture content of the potato after frying was 50 wt.%. A mass of 760 g of fried potato pieces was placed in a nutraREV basket and rotated at 8 rpm. Vacuum was applied to an absolute pressure of 24-26 Torr. Microwave power was applied in stage one at 1500 W for 1000 seconds, then in stage two at 750 W for 800 seconds. The maximum product temperature was 90°C and final weight was 380 g. The final moisture content of the finished product was 1.0 wt.%.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof. The scope of the invention is to be construed in accordance with the following claims.

Claims

1. A method of making a crunchy, dehydrated potato product, comprising:

(a) frying potato slices in cooking oil and thereby reducing the moisture content therein; and

(b) exposing the fried potato slices produced in step (a) to microwave radiation in a microwave-vacuum dehydrator at a pressure that is less than atmospheric to produce the crunchy, dehydrated potato product.

2. A method according to claim 1 , wherein the potato slices prior to step (a) have a thickness greater than 5 mm.

3. A method according to claim 1 , wherein the potato slices prior to step (a) have a thickness in the range of 5 to 15 mm.

4. A method according to any preceding claim, wherein the potato slices are in the shape of French fries.

5. A method according to any one of claims 1-3, wherein the potato slices are in the shape of wedges.

6. A method according to any preceding claim, wherein an absolute pressure in the dehydrator during step (b) is in the range of 5 to 80 Torr.

7. A method according to any one of claims 1-5, wherein an absolute pressure in the dehydrator during step (b) is in the range of 20 to 40 Torr.

8. A method according to any preceding claim, wherein step (b) is done in at least two stages and a microwave power level of the microwave-vacuum dehydrator is higher in the first stage than in the second stage.

9. A method according to any preceding claim, wherein step (b) is done in at least three stages and a microwave power level of the microwave-vacuum dehydrator is higher in the first stage than in the second stage, and higher in the second stage than in the third stage.

10. A method according to any preceding claim, wherein the dehydrator is a resonant cavity microwave dehydrator.

11. A method according to any one of claims 1-9, wherein the dehydrator is a travelling wave microwave dehydrator.

12. A method according to any preceding claim, wherein the fried potato slices produced in step (a) have a moisture content in the range of 30 to 55 wt.%.

13. A method according to any one of claims 1-11 , wherein the fried potato slices produced in step (a) have a moisture content of 55 wt.% or less. 4. A method according to any preceding claim, wherein step (b) dries the potato slices to a moisture content less than 5 wt.%.

15. A method according to any preceding claim, wherein step (b) dries the potato slices to a moisture content less then 2 wt.%.

16. A method according to any preceding claim, further comprising, before step (a), freezing the potato slices, and step (a) is done using the frozen potato slices.

17. A method according to any preceding claim, further comprising, after step (a), draining any excess oil from the fried potato slice.

18. A method according to any preceding claim, further comprising, during step (b), tumbling the potato slices.

19. A method according to any preceding claim, further comprising, before step (a), cutting a raw potato to make the potato slices.

20. A method according to any preceding claim, further comprising sealing the dried, crunchy potato product in an oxygen-barrier package and flushing the package with an inert gas.

21. A method according to claim 20, wherein the inert gas comprises nitrogen.

22. A crunchy, dehydrated French fry potato product made by the method of any preceding claim.

23. A method of making a crunchy, dehydrated potato product, comprising:

(a) forming a shaped potato mass comprising cut-up potato;

(b) frying the shaped potato mass in cooking oil and thereby reducing the moisture content therein; and

(c) exposing the fried, shaped potato mass produced in step (b) to microwave radiation in a microwave-vacuum dehydrator at a pressure that is less than atmospheric to produce the crunchy, dehydrated potato product.

24. A method according to claim 23, wherein the shaped potato mass is in the shape of a potato patty.

25. A method according to claim 23, wherein the shaped potato mass is in the shape of a tater tot.

26. A method according to any one of claims 23-25, wherein the shaped potato mass prior to step (b) has a thickness in the range of 8 to 15 mm.

27. A method according to any one claims 23-25, wherein the shaped potato mass prior to step (b) has a thickness of 8 mm or greater.

28. A method according to anyone of claims 23-27, wherein an absolute pressure in the dehydrator during step (c) is in the range of 5 to 80 Torr.

29. A method according to any one of claims 23-27, wherein an absolute pressure in the dehydrator during step (c) is in the range of 20 to 40 Torr.

30. A method according to any one of claims 23-29, wherein step (c) is done in at least two stages and a microwave power level of the microwave- vacuum dehydrator is higher in the first stage than in the second stage.

31. A method according to any one of claims 23-30, wherein step (c) is done in at least three stages and a microwave power level of the microwave-vacuum dehydrator is higher in the first stage than in the second stage, and higher in the second stage than in the third stage.

32. A method according to any one of claims 23-31 , wherein the dehydrator is a resonant cavity microwave dehydrator.

33. A method according to any one of claims 23-31 , wherein the dehydrator is a travelling wave microwave dehydrator.

34. A method according to any one of claims 23-33, wherein the fried, shaped potato mass produced in step (b) has a moisture content in the range of 40 to 60 wt.%.

35. A method according to any one of claims 23-34, wherein step (c) dries the fried, shaped potato mass to a moisture content less than 1 wt.%.

36. A method according to any one of claims 23-24, wherein step (c) dries the fried, shaped potato mass to a moisture content less then 5 wt.%.

37. A method according to any one of claims 23-36, further comprising, before step (c), freezing the shaped potato mass, and step (b) is done using the frozen shaped potato mass.

38. A method according to any one of claims 23-37, further comprising, during step (c), tumbling the fried, shaped potato mass.

39. A method according to any one of claims 23-38, further comprising, before step (a), cutting a raw potato to make the cut-up potato.

40. A method according to any one of claims 23-39, further comprising sealing the dried, crunchy potato product in an oxygen-barrier package and flushing the package with an inert gas, particularly nitrogen.

41. A crunchy, dehydrated potato product made by the method of any one of claims 23-40.