GB2269307A - Food product - Google Patents

Abstract

Dehydrated vegetable pieces, e.g., potatoes, are provided together with a method of preparing the pieces which includes controlled blanching and dehydration followed by freezing, steaming, further dehydration and deep fat or oil frying.

Description

BACKGROUhtD OF THE INVENTION FIELD OF INVENTION The invention relates to a method for producing fried or sauteed dehydrated vegetables capable of rapid reconstitution. More particularly, the invention is directed to a sequence of dehydrating, freezing, steaming and further dehydration steps prior to deep fat frying carried out under controlled conditions so as to produce a product having a porous interior and exterior surface.

DESCRIPTION OF THE PRIOR ART Dehydration is one of the oldest methods for preserving food. Many procedures have been developed in an attempt to produce dehydrated products which upon reconstitution resemble fresh food in taste, texture, and appearance.

Recently, there has been a general concern for quick rehydrating products. Most of these efforts have not been completely satisfactory. A problem common to prior dehydration methods is a phenomenon referred to as casehaardening or the formation of a horny, vitreous material primarily on the surface of the food. It has been postulated that this may result from the collapse of the cellular structure of the vegetable which dehydrates into a dense mass of material of low rehydration characteristics. In the case of potatoes, too high a degree of starch gelatinization contributes to the nonporous surface.

It is well known in the prior art that potatoes may be dehydrated, but extensive problems have resulted in producing a final product that has high consumer perceptible qualities. Flavor loss from the processing steps has caused lower quality than is desired.

Additionally, storage of the dehydrated product may necessitate specific conditions such as refrigeration, including freezing. Upon rehydration, non-uniform wateer absorption in the product may result which also lowers product quality.

U.S. Patent 3,634,095 deals with crisp fried snack foods.

U.S. Patent 3,881,028 deals with French fried potatoes that are storage stable.

U.S. Patent 4,889,734 deals with rehydratable vegetables.

SUMMARY OF THE INVENTION The present invention relates generally to the production of dehydrated fried/sauteed food materials and preferably vegetables. More particularly, the invention is directed to a process for dehydrating potatoes which are capable of quick rehydration in water to more closely resemble the taste, texture, and appearance of freshly cooked potatoes.

The product of this invention exhibits reconstitution properties and characteristics which are not exhibited by dehydrated vegetables currently available in the market.

The dehydrated product of the present invention is porous throughout its interior as well as on its exterior surface.

It does not exhibit the shrunken appearance typical of conventionally dried vegetables. Moreover, the quick rehydrating vegetable products of the present invention are preferably produced in larger sizes than in the past. Upon rehydration, the product reconstitutes rapidly to a uniform degree. The resultant product does not exhibit objectionable firm, chewy, interiors and mushy exterior surfaces which tend to slough during reconstitution as is typically the case with conventionally dried products. The products of the present invention have been found to be particularly useful as they can be essentially completely rehydrated in preparation for consumption in less than about 10 to 15 minutes.

Preliminary to initial partial dehydration the foodstuff is subjected to treatments with aqueous media at temperatures about 1200F to preferably as high as about 2120F for up to 75 minutes to blanch the foodstuff and preferably at 1900F for between 3 to 75 minutes to cook the foodstuff. When pressurized steam is used, the product is subjected to temperature higher than 2120F.

The initial partial dehydration of the foodstuff takes place by subjecting the foodstuff to a forced air stream with a dry bulb temperature of about 1600F to 2000F for a time sufficient to remove about 20% to 35% by weight of the moisture.

After the first partial dehydration, the material is frozen. Freezing the food material prior to further processing contributes significantly to producing dehydrated products with the desired characteristics and can be accomplished preferably by exposing foodstuff to an atmosphere having a temperature between about -200C to +200F for up to about 60 minutes or until the product is frozen throughout.

It is believed that the advantages of the present invention are achieved by subjecting, e.g., raw potatoes to a dehydration step to about 55% moisture, this is followed by freezing, steaming and further dehydration in a gaseous medium at a temperature lower than the gelatinization point of potato starch preferably below a dry bulb temperature of 1600F and dehydrating the foodstuff to an intermediate moisture content of about 12 to 20% by total weight then after the moisture has equilibrated deep fat frying.

By utilizing thicker potato pieces (in their smallest dimension 3/16 inch) than are conventionally forced air or gas dried, the initial step of drying causes controlled starch gelatinization. This controlled gelatinization results from the moisture-heat interaction on the starch granules. The heat and moisture are critical to the final rehydrated texture. Freezing midway through drying allows for some starch retrogradation which also contributes to the desired final texture. The further dehydration step down to about 13 to 20% preferably 15 to 17% moisture coupled with moisture equilibration, then frying in oil at or above about 3500F to about 4000F, results in controlled cell expansion. This also produces a final moisture of less than about 6 to 10%, preferably 7% and a fat content of less than about 8 to 15%, preferably 13%.

This controlled expansion allows for rapid rehydration without total collapse. The desired sauteed texture is achieved by simmering in water for less than about 10 to 15 minutes.

It has been found that the second partial dehydration should be terminated when the moisture content of the foodstuff, for example, potatoes is about 13% to 20% and preferably 15 to 17% by weight. These dehydrated materials are then allowed to equilibrate to a more or less uniform moisture content.

The combination of moisture content and equilibration of this moisture coupled with frying in oil at a temperature of about 3500 to 4000F for a time of 15 to 20 seconds appears to be critical.

If the moisture is too low, there will be little to no expansion of the dehydrated foodstuff. If the moisture is too high, the foodstuff will be subject to uncontrolled puffing and fracture. This will also result in a higher amount of fat being absorbed by the foodstuff.

The appropriate conditions of the invention ensure desirable expansion which will allow oil adsorption into the pieces of foodstuff so that they are dry to the touch.

These pieces of foodstuff contain low moisture of less than about 7 to 10% preferably about 7% and about 10% to 15% fat, preferably 13t. In addition, the conditions control the physical characteristics of the foodstuff surface properties, cell size and the like, so that it may be rapidly rehydrated in hot water in less than about 10 to 15 minutes.

Foodstuff which is particularly suitable for purposes of the present invention include vegetable and fruit materials containing at least about 15% starch such as potatoes, sweet potatoes, parsnips, plantain, bananas and the like.

Particularly good results are achieved with potatoes, processed in accordance with the present invention.

Among the many advantages realized by the practice of the present invention include the production of foodstuff, such as dehydrated vegetables, which rapidly rehydrate to replace at least 85 and preferably 90-958 of the previously removed moisture in less than about 10 to 15 minutes.

An object of the present invention is to produce a dehydrated food product which, when reconstituted, closely resembles the taste, texture and appearance of its freshly cooked food counterpart.

Another object of the present invention is to produce dehydrated food products essentially free of a casehardened exterior.

Still another object of the present invention is to provide a dehydrated food product which is substantially completely reconstituted by a process comprising rehydrating the dehydrated foodstuff in an aqueous medium to replace at least about 85% and preferably at least 90-95% of the moisture previously removed by the dehydration process.

DESCRIPTION OF THE PREFERRED EMBODIMENT Preliminary to carrying out the process of the present invention the foodstuff, which is preferably vegetable material, e.g., potatoes is normally cleaned of dirt and debris, peeled, and trimmed if necessary, prior to dividing into pieces if so desired.

Potatoes may be cut into large pieces having a size of about 3/16" or slightly thicker slices. The potatoes may also be cut into pieces having other shapes and sizes such as 3/16" or slightly larger such as 1/3" dice in addition to slices and strips. The potato pieces are then subjected to treatments comprising at least blanching and at least initially partially dehydrating foodstuff by subjecting the same to a dry bulb temperature in the range of about 1600F to 2000F for a time sufficient to effect the removel of between about 20 to 35% by weight moisture from the foodstuff. The foodstuff, thus, dehydrated if potatoes will contain about 45 to 60% moisture.

Freezing the food material after initial partial dehydration contributes significantly to producing dehydrated products with the desired characteristics and can be accomplished preferably by exposing foodstuff to an atmosphere having a temperature between about -200F to +200F for up to about 60 minutes or until the product is frozen throughout. Particularly good results are achieved when potato pieces as well as other vegetables are subjected to a freezing operation after significant dehydration takes place. Although freezing may be carried out in a number of ways, immersion freezing in a refrigerated liquid or brine is least preferred.While tunnel or blast freezing at temperatures between about -200F to +200F may be used, it is preferred to subject potatoes to cold air having a temperature of -200F to 00F in a freezing chamber such as a spiral freezer, for at least about 45, and preferably 60 to 120 minutes such that surface moisture is removed by the cold air flow. Although freezing preliminary to steaming and the final partial drying is important to the process of the present invention, the particular manner by which the foodstuff is frozen is not critical. It has been found that any expedient for freezing can be used with minimal affect on the characteristics of the final product if the frozen foodstuff is subsequently subjected to dehydration in an atmosphere having dry bulb temperatures as herein described.

After freezing, the foodstuff is subjected to treatments with aqueous media at temperatures above about 1200F to preferably as high as about 2120F for up to 75 minutes to thaw and/or precook, and for between 3 to 5 minutes for atmospheric steam is preferred. When pressurized steam is used, the product is subjected to temperature higher than 2120F.

The steamed material is then again dehydrated to a moisture content of 13 to 20% and preferably about 15% by total weight in an atmosphere having a dry bulb temperature preferably of less than about 1600F, and more preferably between 1100 and 1600F. Dehydrating foodstuff in accordance with the present invention to a moisture content of about 15% by total weight is typically effected in less than about 6 hours total drying time, and preferably between about 3 to 5 1/2 hours, but depends on the type of drier employed.

This steamed dehydrated material is then allowed to equilibrate for from 2 to 24 hours, preferably 4 to 20 hours at room temperature, to ensure good distribution of the moisture.

The equilibrated material is then fried in fat or oil at a temperature of about 3500F to 4000F for about 15 to 30 seconds.

For potatoes, superior results are achieved with this sequence of steps. Among the advantages resulting from such procedures are the inactivation of enzymes, gelatinization of starch and strengthening of the cellular tissue to withstand subsequent processing.

Prior to preparation, the raw potatoes are washed, peeled, trimmed, and cut into appropriate sizes in a conventional manner. It is particularly advantageous if they are cut with one thin dimension of about three-sixteenth inch. For example, the potatoes are cut into round slices -with thickness of i" x i" x 3/16", " " x 3/16" or, if desired, %" x %" x 3/16". The potatoes may be of any variety, although a high solid content variety such as the Idaho Russet Burbank is normally used for processing and is ideally suited for preparing this product.The diced potatoes may be washed to remove surface starch, blanched in steam or water to a negative peroxidase value, treated with wataer sprays to remove surface starch to avoid sticking during dehydration, treated with well-known preservatives such as sodium bisulfite or calcium chloride, and then partially dehydrated or dried to between about 50% and about 60% water by weight, typically in a throughcirculation conveyer drier.

If desired, pieces to be converted into snacks can be blanched somewhat longer than those prepaared for normal purposes.

The initial dehydration is controlled so that the product is removed from the drier within the moisture range of about 50% to 60% by weight (wet basis). The partially dried potato pieces are then frozen. The potatoes are then thawed at room temperature for 2 hours and steamed for 4 minutes. The steamed potatoes are further dried down to about 15% moisture. These potatoes are then held at room temperature to equilibrate for from 2 to 24 hours to distribute the moisture substantially evenly through the pieces. The equilibration step is necessary because during the dehydration of diced potatoes, water is removed more rapidly from the surface of the pieces than it can be replaced by diffusion from within the interior of the individual piece. Consequently, the product is considerably "case-hardened" at the point of removal within this moisture range.In other words, there is a large moisture gradient within each piece from the wetter interior to the surface. The redistribution of the proper amount of moisture within each potato piece, results in a uniform texture in the final fried product.

In previous attempts to produce a fried product from such partially dehydrated pieces, variations in the moisture content of the partially dehydrated pieces resulted in some products being overfried, others underfried. To attempt to overcome this problem, the 15% moisture pieces are equilibrated for a sufficient period of time prior to frying. Without equilibration, expansion is uncontrolled.

In addition, about 15% to 17% moisture is necessary prior to frying to achieve appropriate expansion and a surface which allows adsorption of the oil.

Potatoes and other vegetable material may also be treated with solutions containing agents to reduce discoloration and minimize stickiness of the product prior to the partial dehydration step without adversely affecting the quality of the finished product. Although minimizing stickiness may be accomplished by surface drying the foodstuff, care must be taken to avoid removing significant amounts of natural moisture from the product prior to partial drying in accordance with the present invention. Otherwise, casehardening is likely to occur and the quality of the product reconstituted from the finished dried state is adversely affected.

The moisture content of potato pieces are typically within the range of about 73 to87% by total weight prior to the removal of any moisture therefrom. For example, a Russet Burbank dice has a moisture content of about 81% by total weight before any dehydration occurs. Other vegetables include sweet potatoes, about 83%; Red Pontiac potatoes, about 858; White Rose potatoes, about 85%. As is generally known, however, the natural moisture contents of all vegetables vary within ranges. "The Composition of Foods Raw, Processed and Prepared," Agricultural Handbook No. 8, Agricultural Research Service, U.S.D.A., U.S. Government Printing Office, Washington, D.C. 20402 sets forth the moisture content ranges for a variety of food materials including those which can be processed in accordance with the present invention.Although porosity is an essential characteristic in the resultant product, excessive puffing or expansion of the product during dehydration is to be avoided because attendant cell rupture releases soluble solids such as starches and sugars contained within the cell. Upon subsequent reconstitution those solids are readily solubilized into and are leached from the food material being rehydrated. The nutritional value of the product is thus substantially reduced. Such products also tend to be brittle and break or slough during reconstitution. It has been found that such objectionable features are avoided by subjecting foodstuff to the sequence of dehydration then freezing followed by partial dehydration in accordance with the present invention, which is believed to be responsible for the desired attributes of the products of the present invention.

The dehydrated fried/sauteed potato pieces having a storage stable moisture content were packaged in a conventional manner for handling and storage purposes. To prepare the dehydrated foodstuff of the invention for consumption, the product is merely placed in hot water and permitted to stand until essentially reconstituted and heated.

Particularly good results are achieved when water having a temperature within the range of about 1700F to 2120F is added to the dehydrated foodstuff or the product is added to water which is brought to a boil and simmered for up to 10 to 15 minutes. The potatoes and other vegetables prepared in this manner are essentially completely reconstituted and have a taste, texture, appearance, and other organoleptic characteristics more closely resembling vegetable prepared directly from the fresh state than heretofore has been commercially available. The reconstituted vegetables make excellent ingredients for soups, stews, sauces, casseroles and side dishes with potatoes also being particularly suitable for use in side dishes.

In addition to the high quality of the food products made in accordance with the present invention, they are also quick rehydrating. For purposes of the present invention, quick rehydrating means reconstitution of the dehydrated product in less than about 15 minutes to a moisture content closely approaching the moisture content of the raw material from which it was made. Replacement of at least 85% and preferably greater than 90 to 95% of the water is required in order for the product to resemble its fresh food counterpart.

In this following example, all parts, proportions and percentages are by weight unless specified otherwise.

EXAMPLE 1 3/16" thick slices of potatoes are preliminarily blanched dehydrated and frozen according to the invention. The moisture contest is 51.4%. These potatoes are thawed for about 1 hour thinly spread out on a steam belt and then steamed with atmospheric steam for 4 minutes. Steamed potatoes are placed in a forced air Aeroglide (Trademark) tray dryer at 1200F dry bulb and 1000F wet bulb for about 1/2 hour. The potatoes are then agitated to approximate commercial conditions dried for 30 minutes and again agitated after 1 hour. Moistures are taken and the results for three samples after the first hour are as follows: 1.

2. 48.4% 3. 45.3% 4. 41.7% After 90 minutes, the dry bulb temperature is reduced to 1100F. The trays are agitated every half hour and moistures are taken hourly.

2nd Hr 3rd Hr 4th Hr ~ 4 i Hr Sample Moisture 1 37% 17.2% 13.5% 2 38.7% 26.8t 14.8% 3 34.5% ~ 24.4% 14.7% 4 20.4% 15.3% When the moisture reaches about 15%, individual sample trays are removed.

The moisture in each of the samples is allowed to equilibrate overnight at room temperature. The samples are fried in oil at two temperatures; 3650F for 20 seconds and 390OF for 17 seconds. After frying and further equilibration, the moistures are as follows:

II I d Sample Moisture~ )) 1 809 Average I) 2 6,46 6.9% 3 7.18 4 5.81 Visual observation of fried samples for color are correlated to moisture content as follows: : Light - 11% moisture Medium - 8.12% moisture Dark - 5.15% moisture It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in the light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims.

Claims (21)

1. A method for producing a quick-reconstituting foodstuff comprising: removing moisture from a foodstuff after blanching in a first dehydrating step by subjecting said foodstuff to a forced stream of gaseous medium having a first dry bulb temperature in the range of about 1600F to 2000F; freezing said dehydrated foodstuff; steaming said frozen dehydrated foodstuff with atmospheric stem to thaw said foodstuff and to at least partially gelatinize starch contained in said foodstuff; removing further moisture from said foodstuff in a second dehydrating step by subjecting said foodstuff to a forced stream of gaseous medium having a second dry bulb temperature of about 1100F to 1600F to reduce the moisture to about 13 to 20%; allowing the moisture in said steamed foodstuff to equilibrate for about 2 to 24 hours; frying/sauteeing said equilibrated foodstuff in fat or oil at a temperature of about 3500F to 4000F for about 10 to 30 seconds.

2. The method in accordance with claim 1 wherein said foodstuff comprises vegetable material.

3. The method for in accordance with claim 2 wherein said vegetable material is potatoes.

4. The method in accordance with claim 1 wherein said first dry bulb temperature is about 1800F.

5. The method in accordance with claim 1 wherein said subjecting said first dehydrating step removes an amount of moisture of about 20 to 35% by weight from said foodstuff.

6. The method in accordance with claim 5 wherein the amount of moisture removed is about 30% by weight.

7. The method in accordance with claim 6 wherein said first dehydrating step results in the foodstuff having a moisture content of about 55%.

8. The method in accordance with claim 1 wherein said freezing takes place at a temperature of about -200F to +200F.

9. The method in accordance with claim 1 further comprising steaming said foodstuff for about 4 minutes.

10. The method in accordance with claim 9 wherein said foodstuff is selected from the group consisting of potatoes, sweet potatoes, parsnips, bananas and plantains.

11. The method in accordance with claim 10 further comprising subdividing said foodstuff into pieces prior to said subjecting.

12. The method in accordance with claim 11 wherein said pieces have a minimum dimension of about 3/16" to 3/4".

13. The method in accordance with claim 1 wherein said second dry bulb temperature is less than about 1400F.

14. The method in accordance with claim 1 wherein said second dehydrating step reduces the amount of moisture in said foodstuff to about 13 to 17% by weight of moisture.

15. The method in accordance with claim 14 wherein the amount of moisture removed is about 50% by weight moisture to a final moisture of about 15%.

16. The method in accordance with claim 1 wherein said frying temperature is in the range of about 3600 to 3800.

17. The method in accordance with claim 16 wherein frying takes place at a temperature of 3750F.

18. The method in accordance with claim 16 wherein said foodstuff is cooked at said frying temperature for 10 to 20 seconds.

19. The method of claim 1 wherein said frying step results in a foodstuff having a moisture content of about 6% to 10%.

20. The method of claim 1 wherein said equilibrating step takes place for about 4 to 16 hours.

21. Potato pieces prepared by the process of claim 1.