WO1982001118A1

WO1982001118A1 - Method and apparatus for removing fats from fried foods and resulting product

Info

Publication number: WO1982001118A1
Application number: PCT/US1981/001327
Authority: WO
Inventors: D Little Inc Arthur
Original assignee: Caragay A; Krukonis V
Priority date: 1980-10-02
Filing date: 1981-10-02
Publication date: 1982-04-15
Also published as: JPS57501660A; BR8108827A; EP0060884A4; EP0060884A1

Abstract

Method for reducing the fat content of fried foods and the resulting low-fat food materials. Fried food products such as potato chips and sticks, French fried potatoes, corn curls, onion-flavored rings, doughnuts and the like are treated with a fat extractant, preferably fluidic state carbon dioxide, to dissolve out a major portion of the fat introduced during frying. Such snack items as potato chips and the like retain their crispiness and flavor characteristics, while at the same time their nutritive value is increased and their caloric content is decreased.

Description

METHOD AND APPARATUS FOR REMOVING FATS FROM FRIED FOODS

AND RESULTING PRODUCT

This invention relates to the production of fried foods and more particularly to the removal of a portion of the residual oils and fats remaining in fried foods after frying and to the resulting food product.

Many snack food items such as potato chips, potato sticks, corn curls, onion rings, doughnuts and the like are prepared by frying or cooking either vegetable materials, e.g., potatoes, onions, etc., or doughs, e.g., masa doughs, breadlike doughs etc., in hot fats. In the process of deep- fat frying or cooking, the food products thus prepared pick up and retain relatively large amounts of the fats and oils. Thus, for example, a typical potato chip may contain about 40 weight percent residual oil and fat, which can be a mixture of glycerides, fatty acids, aldehydes and ketones. The typical potato chip also contains 5 to 6% protein, about 50% carbohydrates and about 2 to 4% moisture.

Recent dietary research has led to the branding of such fried snack foods as "competitive" foods and the labeling of them as "less nutritious" foods providing "empty calories." If, however, it were possible to remove an effective amount of the residual oils and fats and thus to increase the ratio of protein and complex carbohydrates to fat in these foods, their nutritive value could be measurably increased.

Fats and oils are glycerides (fatty acid esters of glycerol) of animal and vegetable origin which contains varying amounts and types of fatty acids. During storage of the fats and oils and during the cooking and frying operations, the glycerides undergo further breakdown leading to the formation of free fatty acids, aldehydes and ketones. These various chemical species can exhibit positive and negative effects on the flavor characteristics of the fried food product.

One such negative effect is the onset of rancidity. Foods prepared by deep-fat frying, therefore, present serious problems of stability due to the fact that the residual oils and fats undergo oxidation changes leading to rancidity. By removing at least a portion of the residual fats, and particularly some of the free fatty acids, it is possible to decrease the rate at which such oxidative changes take place and hence to increase the stability and storage time for such foods.

With the removal of oils and fats from fried foods the ratio of protein and complex carbohydrates to fat is increased; and since proteins provide fewer calories than fats, it is possible to provide such foods which have fewer calories per unit weight than those presently available.

It is therefore a primary object of this invention to provide a method for removing at least a portion of the residual oils and fats added to foods in their preparation by deep-fat frying. It is another object of this invention to provide a method of the character described which results in increasing the nutritive value, decreasing the caloric content and increasing the storage stability of deep-fat fried food products. An additional object is to provide such a method which permits the recovery and reuse of at least a portion of the oils and fats removed.

It is a further primary object of this invention to provide apparatus for removing a portion of the residual oils and fats from fried foods which can be integrated into the apparatus for performing the frying and which provide for the recovery and reuse of at least a portion of the oils and fats removed.

It is another primary object of this invention to provide deep-fat fried foods which retain their textural mouth feel characteristics, e.g., crispiness, but which have a lower fat content and hence a higher protein-to-fat ratio along with a lower caloric content than such foods in their present form. It is a further object to provide foods of the character desired which exhibit a desirable flavor profile.

Other objects of the invention will in part be obvious and will in part be apparent hereinafter. The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, the apparatus embodying features of construction, combinations and arrangements of parts which are adapted to effect such steps, and the article possessing the feature, properties and the relation of elements, which are exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which

Fig. 1 is a plot of solubility as a function of the pressure of supercritical carbon dioxide at 55°C of a commercially available highly refined vegetable oil, the supercritical carbon dioxide serving as an example of one form of fluidic solvent state extractant for the practice of this invention;

Fig. 2 is a diagrammatic representation of the test apparatus used in treating various fried foods in accordance with the method of this invention; and

Fig. 3 illustrates diagrammatically exemplary apparatus for the practice of this invention integrated with apparatus for deep-fat frying.

According to one aspect of this invention there is provided a method of removing from a fried food product at least a portion of the fats introduced therein during frying, comprising the steps of contacting a fried food product containing fats absorbed therein during frying with an extractant which is normally a gas but is in a fluidic solvent state for the fats and which is nontoxic and inert with respect to the fats, thereby to dissolve at least a portion of the fats in the extractant; and separating the resulting treated food product from the extractant containing the fats dissolved therein, thereby to provide a defatted fried food product which retains the textural mouth feel of the fried food product and which has a lower caloric content and a higher nutrient value than the fried food product.

According to another aspect of this invention there is provided a modified fried food product characterized in that at least a portion of the fats introduced therein and absorbed thereby during frying has been removed by contacting the fried food containing the fats with an extractant which is normally a gas but is in its fluidic solvent state for the fats and which is nontoxic and inert with respect to the fats, thereby to dissolve at least 10% by weight of the fats in the extractant, and subsequently separating the resulting treated food product from the extractant containing the fats dissolved therein; whereby the modified fried food product has a higher nutritive value and lower caloric content on an equal weight basis than the unmodified product.

According to yet another aspect of this invention there is provided an apparatus for preparing a low-fat fried food product, comprising in combination frying means containing frying oil at a predetermined temperature; means for introducing a raw food product to be fried into the frying means and means for withdrawing the resulting fried food product from the frying means; pressure vessel means; means to convey the fried food product containing fats absorbed from the oil from the frying means to the pressure vessel means; means to circulate an extractant, which is normally a gas under temperature and pressure conditions rendering the gas a fluidic state solvent for the absorbed fats, through the pressure vessel in contact with the fried food product contained therein to transfer at least a portion of the fats from said fried food product to the extractant and to produce a low-fat fried food product; means to withdraw the low-fat food product from the pressure vessel means; means to withdraw the extractant containing dissolved fats from the pressure vessel means; means to subject the extractant containing the dissolved fats to a physical treatment which renders the extractant essentially a nonsolvent for the fats to form two separable phases comprising a solvent extractant and recovered oil; means to recycle the recovered oil to the frying means; and means to convert the nonsolvent extractant to a fluidic state solvent for circulation through the pressure vessel means.

In the detailed description of this invention which follows and in the claims, the glycerides, fatty acids, aldehydes and ketones which comprise the cooking oils used and which are absorbed during cooking and hence removed by the treatment of this invention will generally be referred to as "fat" or "fats", the term being used in its broadest sense to include both these fatty acids and glycerides.

In the deep-fat frying process these fats are absorbed by the food product being processed while some, or most, of the contained moisture is removed. In such snack items as potato chips or sticks, corn curls, onion-flavored rings, etc., there is achieved as the result of frying a balance in the fats, other constituents, moisture and flavoring which gives the taste and texture that consumers have come to associate with and require in these food products. It is totally unexpected that a major change in the ratio of fats to other constituents; e.g., potatoes, dough, etc., can be effected while at the same time retaining essentially the same desired taste and texture in the products.

The extractant used in the practice of this invention to remove a portion of the cooking fats is a relatively low molecular weight material, e.g., not over about 150, which is in a gaseous state at normal pressure and temperature and which can be converted to a fluidic state, e.g., a liquid or supercritical fluid, by subjecting it to a combination of pressure and temperature which changes its physical state.

Carbon dioxide in its fluidic solvent state within the temperature and pressure ranges stated is the preferred extractant in treating fried foods in accordance with the practice of this invention. The characteristics of carbon dioxide in its fluidic solvent state which make it desirable for this invention are that it is inert to the food products, is a solvent for the fats to be removed, is nontoxic, is readily and completely removable, and does not detract from the flavor or texture of the resulting treated food products. Any extractant used in accordance with this invention should have these characteristics. Carbon dioxide is, moreover, relatively inexpensive and easily handled without contributing any problems for safety or environmental pollution.

The ability of carbon dioxide as a liquid in its near critical state and as a fluid in its supercritical state to serve as an extracting solvent has been known for a number of years. (See for example Francis, A.W., J. Phys. Chem.58, 1099 (1954) and Ind. Eng. chem. 47, 230 (1955).) Near critical and supercritical fluids, including carbon dioxide, have been suggested as solvents for a wide range of materials including various oils (U.S. Patents 1,805,751, 2,130,147, 2,281,865); flavor components (U.S. Patent 3,477,856); caffein in coffee (U.S. Patent 3,843,832); cocoa butter from a cocoa mass (U.S. Patent 3,923,847); fats from grains and the like (U.S. Patent 3,939,281); residual hexane from de-fatted grain (U.S. Patent 3,966,981); and a variety of materials such as paraffins, glycerol, oils and fats from a variety of compositions (U.S. Patent 3,969, 196). A very detailed review of the general field of extraction with supercritical gases is to be found in Angewandte Chemie-International Edition in English, 17 : 10, pp 701-784 (October 1978).

As exemplary of the solvent capability of carbon dioxide, the solubility in fluidic carbon dioxide at 55°C of a typical, commercially available, highly refined vegetable oil similar to those used in deep fat frying is plotted in Fig. 1 as a function of pressure. It will be seen from Fig. 1 that when carbon dioxide is maintained at a temperature of about 55°C and a pressure of about 135 atmospheres or greater, an appreciable amount of oil can be extracted. However, the conditions used in plot Fig. 1 are only illustrative; and, as previously noted, a relatively wide range of temperature and pressure may be used so long as the extractant is maintained during solvation in a fluidic solvent state, i.e., in the fluid state where it exhibits a dissolving power for the oil (fats in the fried food product).

A number of commercially available fried foods were treated in accordance with this invention by contacting them with supercritical carbon dioxide at 55°C and 4000 psi (272 atmospheres). The apparatus used in these experimental tests is shown diagrammatically in Fig. 2. Accurately weighed quantities of the various fried foods to be treated were introduced at ambient temperature and pressure into a chamber 10 defined within a pressure vessel 11 as layers, e.g., layers 12-17, stacked therein. The pressure vessel used comprised a Schedule 160 stainless steel pipe six inches long and two inches in outside diameter. It was closed on both ends with pressure- sealed caps 18 and 19. A valve-controlled high-pressure fluid inlet line 20 and a valve-controlled high-pressure fluid discharge line 21 were in fluid communication with chamber 10. Carbon dioxide gas under about 1000 psi from a supply cylinder 22 was compressed by compressor 23 to the required 272 atmospheres and the temperature of the compressed carbon dioxide adjusted in heat exchanger 24.

In the runs made, the fluidic state carbon contacted the food product of stack 12 first, then that of stack 13 and so on. Subsequent to its contacting the topmost stack, the extractant fluid was discharged through line 21, expanded through valve 26, passed into vessel 25 and discharged to the atmosphere, the solvate constituting the fats, along with a minor amount of moisture which had been removed in treating the food products was collected in vessel 25. No attempt was made to convert the carbon dioxide to its fluidic solvent state and recirculate it. In commercially-scaled apparatus this can, of course, be done by altering either the pressure and/or the temperature of the extractant fluid to make it a nonsolvent for the fats and hence to form two phases which can readily be separated. An overall apparatus system including means for recovering and recycling the fats to the cooking oil is described below in conjunction with the description of Fig. 3. Subsequent to the gradual depressurizaticn of chamber 10 after the supply of fluidic state carbon dioxide was closed off, the various food samples were reweighed and the loss in weight determined. Five such runs were made using varying amounts of fluidic state carbon dioxide at 55°C and 272 atmospheres. In the first two runs, the stacks comprised different types of fried foods, whereas in the remaining three runs the same or related foods were used. The results are summarized below in Tables 1-5, the arrows indicating the direction of fluidic state carbon dioxide flow through the pressure vessel 11.

A comparison of the weight loss experienced by these food products during a run and the weight of the fats recovered from the carbon dioxide effluent showed an agreement of about 90 to 95% which was within the expected experimental errors associated with the technique used. Thus the figures for weight loss can be considered to be satisfactory estimators for fats removed since the moisture content of such snack items as potato chips and sticks and corn chips typically ranges between about 2% and 4% by weight and since the fats are more readily soluble in fluidic state carbon dioxide than water.

It will be seen from a comparison of Tables, 1 and 2 that the various food products react differently and characteristically to the treatment, and that their position with respect to the order in which they are contacted generally reflects only the ability of the fluidic state carbon dioxide to dissolve additional fat when it makes contact. The potato chip formed directly from raw potatoes showed greater weight losses under the particular conditions chosen than those formed from a reconstituted potato dough; and more fats are removed from the potato chips than from the onion-flavored rings or french fries. This may be attributed to either lower fat and/or moisture content of these last-named materials. Potato chips formed directly from potatoes and purchased from a supermarket were arranged in five separate sections in the test apparatus. The flow of fluidic state carbon dioxide in this run was stopped when about 40% of the theoretical amount of the solvent required to remove all of the fats had been circulated through the pressure vessel. The results are tabulated in Table 3.

Likewise, commercially purchased potato sticks were arranged in seven separate sections in the pressure vessel and again the flow of fluidic state carbon dioxide was stopped after about 40% of the theoretically required solvent had been circu lated through the layers of potato sticks. The results are summarized in Table 4.

From Tables 1-4 it will be seen that it is possible to reduce the weight of the fried potato products formed directly from potatoes by about 25%. Since potato chips, for example, are typically about 40? fat by weight, this means that about 63? of the total fats are removed, leaving potato chips which are then approximately 85% complex carbohydrates, protein and other constituents and 15% fat. On an equal weight basis, this means that the caloric content of a gram of treated potato chips is reduced to 4.8 calories from 6 .2 calories , or a reduction of about 23% . Thus , the nutritive value (percent protein and complex carbohydrates) has been increased and the caloric content decreased.

The potato chips and potato sticks thus treated were tasted by five trained flavor analysts who found the treated products to be crispy and to have a well defined potato flavor. Moreover, the treated products appeared to become crispier with increasing fat removal. It was determined by the flavor panelists that these treated products essentially maintained the necessary delicate balance between fat and potato taste to make them acceptable to consumers. The method of this invention is also applicable to fried foods formed from breadlike dough, e.g., doughnuts or similar products. This will be apparent from the data in Table 5 which were obtained using the apparatus of Fig. 2. The layers in the pressure vessel were alternately a doughnut and a doughnut dough product formed when the hole is cut in the doughnut, i.e., a doughnut hole shape.

Inasmuch as doughnuts typically have a moisture content of about 25%, it is to be expected that some of the weight loss experienced in the treatment with fluidic state carbon dioxide was due to moisture loss as well as loss of fats contents. However, visual observation of the effluent collected in vessel 25 (Fig. 2) indicated that there was more fat removed than water. The treated doughnut products had a somewhat dry texture.

Apparatus for preparing a low-fat fried food product in accordance with this invention is illustrated diagrammat ically in Fig. 3. The raw food to be processed 30 (e.g., sliced raw potatoes, masa dough cut into designed shapes, etc) is carried by a conveyor 31 from a product supply 32 to a frying means 33 containing frying oil 34 at a predetermined temperature. The fried food product 35 is taken out of the oil by suitable conveyor means 36 and carried by further conveyor means 37 to the pressure vessel 38 through which the fluidic extractant is circulated to contact the fried food product 35. The treated, low-fat food product 39 is withdrawn from pressure vessel 38 through a chute 40 having a pressure valve 41 and taken, subsequent to the addition of salt and any other desired flavoring, by conveyor 42 to a packager 43.

The fluidic extractant is provided to vessel 38 through a conduit 44, the fluid flow through which is controlled by valve 45; and it is withdrawn from vessel 38 by means of valve- controlled conduit 46. Valve 47 in conduit 46 is of the type which effects expansion and pressure reduction of the extractant. As a result of this expansion the dissolving power of the extractant is decreased with resultant formation of two phases, namely a nonsolvent fluid and the fats extracted from the food product in vessel 38. It may be desirable to raise the temperature of the nonsolvent fluid at least to that point where the fats remain an easily pourable liquid. This may be accomplished in an out-of-contact heat exchanger 48 with the use of an externally supplied heat transfer liquid supplied through line 49.

In separator 50 the nonsolvent fluid 51 is separated from the liquid fat 52, the former being withdrawn through line 53 having valve 54 and the latter through a line 55 having valve 56. The gas which is to be converted to its fluidic solvent state is originally provided from a cylinder 57 through line 58 and valve 59 to main line 60 with which the recovered non-solvent fluid line 53 is connected. The fluid in line 60 is then taken into pump/compressor 61 for compression to the pressure desired for the fluidic solvent state. If it is necessary to adjust the temperature of the extractant fluid, this may be done in heat exchanger 62 by circulating a heat exchange liquid through line 63 in out-of-contact heat exchange with the fluid prior to its entering line 44. It is, of course, within the scope of this invention to combine heat exchangers 48 and 62, using the circulating fluids as all or part of the heat exchange liquids in the system.

The fats recovered in separator 50 can be returned through line 55 to a frying oil supply 65 from which the quantity of oil in frying means 33 is replenished. Makeup oil from supply means 66 may also be added. Under some circumstances it may be desirable to add certain components, e.g., fatty acids, to the recycled fats from separator 50 to balance the various constituents in the frying oil. This may be done in mixing means 67 which is an optional apparatus component.

In a typical batch operation as illustrated in Fig. 3 it would be desirable to have several treating units 70 (enclosed in the dot/dash line) associated with each frying unit so that the frying operation could proceed continuously. In the operation of a typical treating unit 70, using carbon dioxide as the extractant and potato chips as the fried food product, the treating is begun by filling pressure vessel 38 with fresh fried chips and the closing valve 47 in chute 40 as well as valves 47, 54 and 56. In starting up, carbon dioxide is supplied from cylinder 57 through line 58, valve 59 and line 60 to pump/compressor 61. Once the system has been provided with sufficient carbon dioxide, it will usually not be necessary to draw any more carbon dioxide from cylinder 57 than that required to make up any losses. After the treatment of the chips in vessel 38 has been completed, valve 45 is closed, valves 47 and 54 are opened and when sufficient fat 52 has accummulated in separator 50, valve 56 is opened. If pressure or gravity feed of fat 52 from separator 50 is not feasible then line 55 may have a liquid pump associated with it. Valve 41 in chute 40 is opened to allow the chips to be discharged for delivery to packager 43. With the completion of the discharge of the chips from vessel 38, the cycle is begun again.

It will be appreciated that the apparatus of Fig. 3 may be designed to provide continuous, rather than batch, treatment of the fried food product.

It will be seen from the data presented that it is possible through treatment with an extractant of the type defined to remove a portion of the fats absorbed in deep fat frying of food products such as potato chips, potato sticks, corn curls and the like without effecting any appreciable change in the textural mouth feel characteristics of these food products. The amount of such fats removed may range from about 10% to as much as 75% by weight. The removal of such fats results in raising the nutrient value and lowering the caloric content for an equal weight of treated and untreated food products. The final product produced is therefore a low-fat fried food product.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the described product without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

Claims

WE CLAIM :

1. A method of removing from a fried food product at least a portion of the fats introduced therein during frying, comprising the steps of

(a) contacting a fried food product containing fats absorbed therein during frying with an extractant which is normally a gas but is in a fluidic solvent state for said fats and which is nontoxic and inert with respect to said fats, thereby to dissolve at least a portion of said fats in said extractant; and

(b) separating the resulting treated food product from said extractant containing said fats dissolved therein, thereby to provide a defatted fried food product which retains the textural mouth feel of said fried food product and which has a lower caloric content and a higher nutrient value than said fried food product.

2. A method in accordance with claim 2 wherein said extractant is carbon dioxide ranging in temperature between about 0°C and about 185°C and in pressure between about 30 and 275 atmospheres.

3. A method in accordance with claim 2 wherein said fried food product is formed from potatoes, corn, a dough or mixture thereof.

4. A method in accordance with claim 3 wherein said fried food product comprises potato chips formed directly from raw potatoes or from a reconstituted potato dough.

5. A method in accordance with claim 3 wherein said fried food product comprises corn chips.

6. A method in accordance with claim 3 wherein said fried food product comprises a crisp flavored product formed from a dough.

7. A fried food product characterized in that at least 10% by weight of the fats introduced therein and absorbed thereby during frying has been removed, whereby said fried food product has a higher nutritive value and lower caloric content on an equal weight basis than it had prior to the removal of said fats and retains the textural mouth feel of said product prior to removal of said fats.

8. A fried food product in accordance with claim 7 formed from potatoes, corn, a dough or mixtures thereof.

9. A fried food product in accordance with claim 8 comprising potato chips formed directly from raw potatoes or from a reconstituted potato dough.

10. A fried food product in accordance with claim 8 comprising corn chips.

11. A fried food product, in accordance with claim 8 comprising a crisp flavored product formed from a dough.

12. A modified fried food product characterized in that at least a portion of the fats introduced therein and absorbed thereby during frying has been removed by contacting said fried food containing said fats with an extractant which is normally a gas but is in its fluidic solvent state for said fats and which is nontoxic and inert with respect to said fats, thereby to dissolve at least 10% by weight of said fats in said extractant, and subsequently separating the resulting treated food product from said extractant containing said fats dissolved therein; whereby said modified fried food product has a higher nutritive value and lower caloric content on an equal weight basis than the unmodified product.

13. A fried food product in accordance with claim 12 wherein said extractant is carbon dioxide ranging in temperature between about 0°C and about 185°C and in pressure between about 30 and 275 atmospheres.

14. A fried food product in accordance with claim 12 formed from potatoes, corn, dough or mixture thereof.

15. A fried food product in accordance with claim 14 comprising potato chips formed directly from raw potatoes or from reconstituted potato dough.

16. A fried food product in accordance with claim 14 comprising corn chips.

17. A fried food product in accordance with claim 14 comprising a crisp flavored product formed from a dough.

18. An apparatus for preparing a low-fat fried food product, comprising in combination

(a) drying means containing frying oil at a predetermined temperature;

(b) means for introducing a raw food product to be fried into said frying means and means for withdrawing the resulting fried food product from said frying means;

(c) pressure vessel means;

(d) means to convey said fried food product containing fats absorbed from said oil from said frying means to said pressure vessel means;

(e) means to circulate an extractant, which is normally a gas under temperature and pressure conditions rendering said gas a fluidic state solvent for said absorbed fats, through said pressure vessel in contact with said fried food product contained therein to transfer at least a portion of said fats from said fried food product to said extractant and to produce a low-fat fried food product;

(f) means to withdraw said low-fat fried food product from said pressure vessel means;

(g) means to withdraw said extractant containing dissolved fats from said pressure vessel means;

(h) means to subject said extractant containing said dissolved fats to a physical treatment which renders said extractant essentially a nonsolvent for said fats to form two separable phases comprising a solvent extractant and recovered oil;

(i) means to recycle said recovered oil to said frying means; and

(j) means to convert said nonsolvent extractant to a fluidic state solvent for circulation through said pressure vessel means.

19. An apparatus in accordance with claim 18 wherein said means to subject said extractant containing said dissolved fats to a physical treatment comprises means to reduce the pressure of said extractant.

20. An apparatus in accordance with claim 19 including means to adjust the temperature of said nonsolvent extractant resulting from said physical treatment.