FOOD COOKING METHOD

Abstract

A method for cooking a food including free water, uses a cooking vessel having at least one cooking surface, the cooking surface being such that a drop of distilled water can form a contact angle with the cooking surface that is greater than or equal to 150 at ambient temperature, and the food being such that its water activity a.sub.w is greater than or equal to 0.5. The method includes heating the cooking surface to a minimum temperature of 125 C.; placing the food on the cooking surface; and cooking the food on the cooking surface.

Claims

1. A method for cooking a food containing free water by means of a cooking vessel having at least one cooking surface, the cooking surface being such that a drop of distilled water is able to present a contact angle with the cooking surface greater than or equal to 150 at ambient temperature, the food being such that its water activity a.sub.w is greater than or equal to 0.5, the method comprising: heating the cooking surface to a minimum temperature of 125 C.; placing the food on the cooking surface; and cooking the food on the cooking surface.

2. The cooking method according to claim 1, wherein the water activity a.sub.w of the food is between 0.8 and 1.

3. The cooking method according to claim 1, wherein the food is placed on the cooking surface after the heating of the cooking surface.

4. The cooking method according to claim 1, wherein the food is placed on the cooking surface before the heating of the cooking surface.

5. The cooking method according to claim 1, wherein the food is placed on the cooking surface during the heating of the cooking surface.

6. The cooking method according to claim 1, wherein, while the food is being cooked, the temperature of the food is less than or equal to the boiling point of water.

7. The cooking method according to claim 1, wherein the cooking surface is kept at a constant temperature while the food is being cooked.

8. The cooking method according to claim 1, wherein the temperature of the cooking surface is increased while the food is being cooked.

9. The cooking method according to claim 1, wherein the temperature of the cooking surface is decreased while the food is being cooked.

10. The cooking method according to claim 1, wherein the cooking surface is such that a drop of distilled water is able to present a contact angle with said cooking surface greater than or equal to 170 at ambient temperature.

11. The cooking method according to claim 1, wherein the cooking surface is heated to a temperature of between 125 C. and 250 C.

12. The cooking method according to claim 11, wherein the cooking surface is heated to a temperature of between 125 C. and 230 C.

13. The cooking method according to claim 1, wherein water is added while the food is being cooked.

14. The cooking method according to claim 1, wherein the cooking vessel is selected from the group consisting of saucepans and frying pans, woks and skillets, Dutch ovens and kettles, crepe pans, gridirons, grates and barbecue grills.

Description

[0043] FIG. 1 illustrates the principle of measurement of a contact angle between a drop of distilled water and a cooking surface.

[0044] Advantageously, the cooking surface may be such that a drop of distilled water is able to present a contact angle with said cooking surface greater than or equal to 155 at ambient temperature, and preferably a contact angle with said cooking surface greater than or equal to 170 at ambient temperature. The use of the method according to the invention with superhydrophobic surfaces permits putting the food in a Leidenfrost state at a lower temperature than with hydrophobic surfaces, which permits having less water loss and better preservation of the food and its organoleptic properties.

[0045] The Leidenfrost temperature of water on a hot surface is evaluated by measuring, for different temperatures, the tilt angle of the surface permitting the mobility of a drop of water (tilt angle also being known as angle of inclination and directly related to the adhesive strength). When the tilt angle is equal to 0 and the drop is mobile, the adhesion is equal to 0 and thus the drop is in a Leidenfrost state. The Leidenfrost temperature is known with a precision of +/10 C.

[0046] The cooking surface of the cooking vessel may be produced using different techniques which are described extensively in the literature and therefore known to the person skilled in the art (chemical attack, structuring by nano-embossing, laser, electroplating of polymers, partial decomposition, lithography, etc.) In one embodiment of this invention, water may be added while the food is being cooked. This increases the life span of the Leidenfrost phenomenon by offsetting the phenomena of water escaping to the environment in the form of steam. Water may be added, for example, by deglazing the cooking surface.

[0047] The cooking vessel used in the method of this invention may be chosen from the group comprising saucepans and frying pans, woks and skillets, Dutch ovens and kettles, crepe pans, gridirons, grates and barbecue grills.

[0048] According to one embodiment of this invention, the cooking method may be used to cook a fried egg. Cooking a raw egg on a bed of steam, that is, with the cooking surface in a Leidenfrost state, makes the egg white more uniform in appearance and taste by avoiding hot spots. In addition, cooking the raw egg in a Leidenfrost state on a superhydrophobic surface is done at a temperature between 125 C. and 180 C., which is perfectly suitable for obtaining the desired texture and color which are produced after denaturation of proteins (this denaturation takes place at temperatures of between 60 and 100 C., 60 C. for ovotransferrin and between 84.4 and 92.5 C. for ovalbumin). Cooking eggs at too high a temperature results in significant drying, which yields an unsatisfactory result (dry, rubbery).

EXAMPLES

[0049] Tests

[0050] Measurement of Contact Angles

[0051] The hydrophobic nature of the surfaces used in the examples is evaluated by measuring the contact angle of a drop of water on the coating using a Krss brand DSA100 goniometer.

[0052] FIG. 1 illustrates the principle of measurement of a contact angle between a cooking surface 10 of a cooking vessel 12 and a drop of distilled water 14 placed on the surface 10. The reference 16 designates the liquid/gas interface between the drop 14 and the ambient air. FIG. 1 is a cross section according to a plane perpendicular to the surface 10. In the section plane, the contact angle corresponds to the angle, measured from the inside of the water drop 14, between the surface 10 and the tangent T to the interface 16 at the point of intersection between the solid 10 and the interface 16.

[0053] To measure the contact angle, the vessel 12 is placed in a room at the temperature of 20 C. and a relative humidity of 50%. A drop of distilled water 14 having a volume of 2.5 L is placed on the surface 10 of the vessel 12. The angle is measured by using an optical process, for example, by using a drop shape analysis device, such as the DSA100 device marketed by the company Kruss. The measurements are repeated five times and the value of the contact angle measured between the water drop and the cooking surface is equal to the average of these five measurements.

[0054] Measurement of Leidenfrost Temperatures

[0055] The Leidenfrost temperature of water on a hot surface is evaluated by measuring, for different temperatures, the tilt angle of the surface permitting the mobility of a drop of water (tilt angle also being known as angle of inclination and directly related to the adhesive strength). When the tilt angle is equal to 0 and the drop is mobile, the adhesion is equal to 0 and thus the drop is in a Leidenfrost state. The Leidenfrost temperature is known with a precision of +/10 C.

[0056] Measurement of Water Activity

[0057] The water activity is measured using an electric hygrometer type of a.sub.w-meter, which operates by measuring the resistance of a hygroscopic salt or by changing the capacitance of a capacitor comprising a hygroscopic polymer.

[0058] The water activity is determined by the following formula:

a.sub.w=p/po=ERH(%)/100

[0059] where [0060] p=Pressure of the water vapor in the food [0061] po=Pressure of the pure water vapor [0062] ERH=Mean relative humidity

[0063] Production of Tested Surfaces and Physicochemical Properties

[0064] The tests are performed in articles of identical shapes having a stainless steel substrate. [0065] For certain tests, the article's cooking surface is left bare (surface 1), as is the case for a hydrophilic surface with a contact angle with the cooking surface equal to 70 [0066] For other tests, a surface of the article is coated with a PTFE-based coating of a total thickness of 35 microns (surface 2), as is the case for a hydrophobic surface with a contact angle with the cooking surface equal to 110: [0067] For yet other tests, a surface of the article is coated with a glaco layer, that is, a layer based on hydrophobic silica colloid dispersed in an isopropyl alcohol, applied by means of spraying and provided by the company Soft 99; the glaco layer has a total thickness of 100 nanometers (surface 3) (the case for a superhydrophobic surface with a contact angle with the cooking surface equal to 175);

[0068] The physicochemical properties of the prepared surfaces are summarized in the table below:

TABLE-US-00001 Leidenfrost Contact temperature of a Surface angle with drop of distilled number Substrate Coating water () water ( C.) 1 stainless steel 70 250 10 2 stainless steel PTFE 110 240 10 3 stainless steel glaco 175 130 10

[0069] Egg White Cooking Tests

[0070] For each test, 20 grams of raw egg whites are used. Cooking is done without fat. The water activity of this egg white is 0.99 for a pH of 7.8.

[0071] Cooking is stopped when the top of the egg white is smooth and coagulated and the culinary results are evaluated for each test. The adhesion and mobility of the egg are visually characterized by tilting the article at a slight tilt angle of less than 10.

[0072] The culinary results are summarized in the table below:

TABLE-US-00002 Cooking Non-stick Surface temperature Mobility of property after number ( C.) the egg white cooking Appearance of the white 1 260 no The white has stuck The white is cooked to the surface nonhomogeneously, large burst bubbles are observed which give its upper surface a very rough appearance. The edges of the white are thin and dried. The bottom of the white is very browned. 2 250 no The white has stuck The white is cooked to the surface nonhomogeneously, large burst bubbles are observed which give its upper surface a very rough appearance. The edges of the white are thin and dried. The bottom of the white is very browned. 3 140 C. The egg slides No adhesion to the The white is cooked very spontaneously surface uniformly; it is still very supple. from one edge The edges are still high around of the article to the entire periphery. the other The lower surface is white. 3 180 C. The egg slides No adhesion to the The white is cooked very spontaneously surface uniformly; it is still very supple. from one edge The edges are still high around of the article to the entire periphery. the other The lower surface is lightly colored.

[0073] The egg whites were cooked according to the method of the invention with surface number 3. The Leidenfrost state was established for this cooking with this surface number 3 and the results are satisfactory as indicated in the table above.

[0074] Whitefish Cooking Test (Cod)

[0075] For each test, 20 grams of cod are used. Cooking is done without fat. The water activity of this cod is 0.99.

[0076] The cooking is stopped when the top of the cod has turned completely opaque, and no longer translucent. The culinary results are evaluated for each test. The adhesion and mobility of the cod are visually characterized by tilting the article at a slight tilt angle of less than 10.

TABLE-US-00003 Cooking Non-stick Surface temperature Mobility in property after Appearance of the food and number ( C.) cooking cooking condition of cooking surface 2 180 no Cod sticks slightly Food is not colored. Residue in the frying pan 2 250 no Cod sticks slightly Food has a light crust. Residue in the frying pan 3 180 yes No adhesion to the Food is not colored. No residue in surface the frying pan 3 230 yes No adhesion to the Food is not colored. No residue in surface the frying pan

[0077] The cod was cooked according to the method of the invention with surface number 3. The Leidenfrost state was established for this cooking with this surface number 3 and the results are satisfactory as indicated in the table above.

[0078] Scallops Cooking Test

[0079] For each test, 20 grams of scallops are used. Cooking is done without fat. The water activity of these scallops is 0.99.

[0080] The cooking is stopped when the top of the scallop has turned completely opaque, and no longer translucent. The culinary results are evaluated for each test. The adhesion and mobility of the scallop are visually characterized by tilting the article at a slight tilt angle of less than 10.

TABLE-US-00004 Cooking Non-stick Surface temperature Mobility in property after Appearance of the food and number ( C.) cooking cooking condition of cooking surface 2 200 no adhesion of the Food is colored scallop Residue in the frying pan 2 250 no adhesion of the Food is colored scallop Residue in the frying pan 3 200 yes No adhesion to the Food is lightly colored surface No residue in the frying pan 3 230 yes No adhesion to the Food is lightly colored surface No residue in the frying pan

[0081] The scallops were cooked according to the method of the invention with surface number 3. The Leidenfrost state was established for this cooking with this surface number 3 and the results are satisfactory as indicated in the table above.