Food preparation comprises all acts of preparing food for consumption. The many different types of preparations include cooking of food (ingredients), but also other types such as the use of chemical, biological, mechanical means or techniques. For preparing food by the use of heat also the terms heat treatment, boiling or cooking, are used.

Known methods of cooking food are grilling, baking, cooking (in hot or boiling water), frying or roasting, smoking.

In the preparation of solid food by heating, as relevant in the present application, two processes, separately or together, play an important role, namely tissue disruption and cell disruption, wherein the term disruption means as much as distortion, separation, rupture, splitting , crushing etc.

- Tissue disruption : tissue consists of cells attached to each other and can be made digestible by separating the cells from each other.

- Cell disruption: cells contain substances which become more easily accessible to humans (and animals) when the cells are opened up. Below, regarding the treatment of solid foods, in particular attention is given to cooking (possibly pre-cooking) thereof, wherein cell disruption and/or tissue disruption may play a role, although possibly in different ratios for different kinds of food (meat, fish, vegetables, potatoes). Furthermore, apart from cooking, as treatment could be mentioned the drying of food (for instance meat, fruits), where in particular the cell disruption appears to be of importance, or the pleating (peeling off) of food (like tomatoes, eel), for what kind of preparation disruption of tissue is particularly important.

It is generally known to prepare solid food, particularly by cooking, and make it (better) suitable for human or animal consumption, by baking and/or grilling the solid food, for example meat, fish, potatoes, vegetables, generally by heating to such extend that the (cell or tissue) structure of the food is degraded and/or broken - referred to as (cell) disruption - in order to make the food sufficiently soft and digestible, by which the (macro) nutrients are released through the opened up cell walls by heating and subsequently, also by using heat, converted into states, absorbable by the body.

Besides that heating of the food has the effect of disruption of the cells of the food product itself and thereby making the food product more digestible, moreover the heating may be needed in order to denature (or change to an such an extent) specific proteins and/or other substances in cells of microorganisms, such as bacteria, germs etc. that they lose their capacity of cell-division and cannot exercise a pathogenic effect on consumers.

Though since time immemorial the treatment of both the cells of foods as well the cells of harmful organisms are achieved by means of conventional heating (cooking, baking, etc.), there are some disadvantages. Disruption by heating costs a lot of energy, while the food usually must be heated a long period of time ("boiling", "frying"). Besides the longer time required to maintain the temperature, it also costs much energy to bring the food onto this temperature. Besides a lot of energy, the well-known processes of cooking and baking/frying therefore cost also much time. Moreover, particularly during boiling in water, the taste and quality decreases by thermal degradation of these nutrients, among others because some nutrients (proteins, carbohydrates, fats, micronutrients, bio-active substances, vitamins, minerals, etc.) end up in the (to pour out) boiling water. Particularly where large groups of people (or animals) are served, where larger quantities of food should be prepared and where the food safety is very important, food is often overcooked resulting in seriously affecting the taste, structure ("bite") and beneficial nutrients. An additional consequence is that where the taste of these foods is low, such as "junk food", consumers have a tendency to compensate for the small taste enjoyment ("taste sensation") thereof, by taking in more of such food, with the result, as is often the case today, of numerous cases of obesity, etc. When there is too much structure lost, there is truly the tendency to eat less of such food and leading to a chance on under-nourishment.

The object of the present invention is to provide an improved method of treatment - by using heat, also called cooking - of a substantially solid food product. According to the invention a method is provided for treating a substantially solid food product comprising a step wherein cell and/or tissue disruption occurs of the food, in particular (but not exclusively, see below) corresponding to the result of a cooking treatment of food, which method preferably comprises the steps:

a. placing the food product in a treatment room which is arranged for generating a pulsed electric field (for brevity hereinafter referred to as PEF);

b. subjecting the food to a pulsed electric field with an electric field strength within a predetermined range, with a number of pulses within a predetermined range and with a pulse width within a predetermined range;

such that the cell and/or tissue structure of the food is degraded and/or broken corresponding to the result of a cooking treatment, that is thermal heating, in order make the food product, or part thereof, soft, processable and/or digestible.

Preferably, the used term "treatment" comprises the preparation, cooking or pre- cooking of the food product, like a meat, fish product or potatoes, vegetables, and/or drying thereof. It also appeared that the method is also suitable for loosening of, for example, the skin of fish (eel) and the outer skins of tomatoes ("pleating") and fruit (plum) so that the term "treating" is also considered to include these applications. In general, "treating" is here defined as converting and/or preparing the food product such, that:

a. it better meets the needs and desires with respect to consumption and/or (for example industrial) processing thereof and

b. the human (or animal) food components (proteins, starches, fibres) become (better) available for and can be utilized by the body through the digestive tract of human (or animal),

c. the cell and/or tissue structure of the food product is degraded and/or broken corresponding with the result of a cooking treatment, that is thermal heating, in order to make the food product, or part thereof, soft, processable and/or digestible. It should be noted that it is known per se to subject food products, both liquid and (semi-) solid, to a pulsed electric field (PEF) :

- US5549041 discloses a device for subjecting solid and semi-solid food products to a pulsed electric field, formed by means of a series of high voltage pulses applied to two electrodes provided on either side of the food product concerned in a treatment chamber. The (pulse shaped or pulsed) fields, generated by the high voltage pulses, have field strengths in the range from 20-100 kV/cm. The proposed device aims at providing a "food processor" to effectively preventing the growth of microorganisms. The use of PEF for treating food as defined above, is not mentioned.

- US6083544 discloses a method for improving a "meals-ready-to-eat (MRE), rotational retort process" in which a PEF process (also) is used to inactivate microorganisms, through which the food is sterilized. Also from this publication the use of PEF for treating foods or foodstuffs, such as in particular, the (pre-) cooking, is not known. On the contrary, this publication states that "the resultant product of the PEF process is not ready to eat". The field strength range indicated in this publication is 20-45 kV / cm.

- W09949561 discloses a system for generating high voltage bipolar pulses to induce "stress and mortality in biological cells." This system is also intended for pasteurization and/or sterilization, in other words for deactivation of microorganisms, not for treatment (such as pre-cooking or cooking etc.) of food. Applicant, to his own great surprise and of the PEF and food experts, has found that subjecting food to a series of PEF pulses, especially of relatively low field strength, results in being or getting cooked of the particular food as if it was cooked or prepared by using only heat. Moreover is the treatment time, resulting in a good "ready-to-eat" product, exceptionally short and are the taste and nutritional value well preserved. Although tests are still ongoing, it appears that the here proposed "PEF cooking process", in other words the cooking of food by means of PEF, without having to bring the food on a high (cooking) temperature - which process is introduced under the name "e-Cooking"®, which name hereafter will also be used to indicate the method or the device according to the present invention - is par excellence suitable for, for example, the cooking of fish and meat. However, e-Cooking ® is also very suitable for cooking potatoes and vegetables, again without the need to bring them to the high cooking temperature of 100 °C. Besides that, it appears that by means of PEF pulses for instance tomatoes can be easily peeled, which is important for consecutive industrial processing of tomatoes.

Benefits of the proposed, combined, - namely electric field pulses for breaking the cell walls (1) and for (ohms) generating (just enough) heat for the conversion of the contents of broken cells (2) necessary for the intake into the body - method are:

- e-Cooking® (PEF-) method according to the invention heats volumetrically: the core temperature and the temperature at the edge of the product are almost identical; - e-Cooking® (PEF-) method is very quick: the food product doesn't need to be conventionally heated to high temperatures (100 °C water and baking/roasting 170- 200 °C);

- e-Cooking® (PEF-) method is energy efficient: just precise supply of power only to the food product and the directly surrounding fluid. Besides the food does not need

(during a long period) to be brought on or above the cooking/bake/roast temperature and then be cooled to the desired serving/consumption temperature;

- e-Cooking® (PEF-) method interacts exclusively and very precise and controllable with the cell structures and some nutrients such as proteins, starches, enzymes;

- in the e-Cooking® (PEF-) method the desired nutritional value, taste and texture, remain much better preserved than with a conventional cooking treatment such as cooking/grilling/baking.

Preferably, the food product is heated by the pulsed electric field with a rise in temperature within a predetermined range, or heated to a final end-temperature within a predetermined range, so the food is suitable for the intended consumption and/or processing thereof. In particular, the temperature rise is within a predetermined range of 10 - 100 °C or the final temperature is within a predetermined range of 35 - 100 °C.

The food product is subjected to a PEF treatment such long that the temperature of the food product has increased with a predetermined value or that the temperature has reached a predetermined end-temperature.

The invention also relates to the use of a pulsed electric field for the treatment of food products and a system for treating a food product according to a method of the invention.

Hereinafter the invention will be further discussed by means of a simple embodiment of an installation for treating a food product using an e-Cooking® (PEF) system arranged therefore. The system shown has, moreover, many similarities with the system in shown in US5549041; but it is used there for the deactivation of microorganisms at very high electric field strengths compared to the here proposed e- Cooking® method, while here - by using significantly lower field strengths - it is used for cooking of food.

Figure 1 schematically shows an embodiment of an installation for treating a food product by means of e-Cooking® System based on the use of PEF; Table A shows an overview of a number of food treatments using an e-Cooking® device. In Figure 1 is shown an embodiment of the system for treating a food product wherein cell disruption occurs, comprising a treatment space 1, surrounded by an externally accessible and closable outer housing 2, which is arranged for placing and - after the treatment thereof - again removing of the food product 3. Within the outer housing 2, a second, electrically isolated, process chamber 4 can be closed by means of a cover 5. A ground electrode 6 is located at the bottom of the process chamber 4; on top of the process chamber 4 against the cover 5, there is a voltage electrode 7. Preferably, the space in the process chamber 4 not occupied by food product 3, is supplemented by an amount of the surrounding fluid or broth to prevent air inclusion and unwanted electrical breakdown through air.

The process chamber may be actively vented beforehand if necessary by applying an under-pressure. In addition, during the process, an over-pressure may be applied in the chamber. By applying both under-pressure as well over-pressure among others exchange of substances may be facilitated.

How exactly the cover 5 and the right electrode 7 can be moved up and down and how the electrode 7 is mechanically and electrically connected with a (hereafter to discuss) PEF generator 8, is of less importance and is not shown in detail. In the meanwhile developed further preferred embodiments are the subject of another patent application by the applicant of the present patent application.

The means for generating one or more pulsed electric fields is formed by the PEF generator 8, which is contained in a housing 9. In the shown embodiment of the PEF generator is derived from www.fao.org/ag/ags/AGSI/Nonthermal/Nonthermal Figurel l.gif, where with DC a voltage source is indicated and with S a switching device; the diagram further shows a number of capacitors, inductors and resistors, with which the desired pulse shape can be achieved. Also, one of the circuits shown in W09949561 can be used, albeit for a different purpose and - with different values for the generated voltages and field strengths - than is therein specified. It is however possible, as is indicated in W09949561, to generate bipolar pulses with the PEF generator 8 instead of unipolar pulses. PEF generator 8 is connected to a control module 10 (located within or outside the housing 9), which is arranged for controlling and/or setting such pulsed electric fields. The control module 10 may be computer controlled and adjusted by a common integrated or remote terminal, PC or touch screen interface. Means for the creation of such controllable pulsed electric fields in the process chamber 4 formed by 3 food product placed plate-shaped electrodes 6 and 7 through wires 11 (earth) and 12 (high voltage) with the PEF generator 8 is connected.

The various components are arranged for subjecting the food product 3 to a pulsed electric field of sufficient electric field strength and with a sufficient number of pulses for the occurrence of such a disruption of the cells and building up of a necessary temperature increase of the food product, that the food product is then converted and therefore suitable for the intended human or animal consumption and efficient digestion, allowing the body to take in optimally the nutrients from the cells.

As previously explained the treatment of food is based on such specific high-frequent administering of voltage pulses, that the structure of animal and plant cells changes. Cells can be detached from each other (for instance "flaky" cod), and cell walls can be opened allowing for the cell contents to become accessible. But also a relatively low temperature (54-80 °C) can accurately be built up (by resistive heating), wherein substances change in structure (proteins, starches, pectin's, fibres) and therefore become (better) digestible. Similarly, other substances such as vitamins, bioactive substances and other micro-nutrients, are degraded as little as possible at this temperature and time.

The power supply is used only for the food product itself and for its direct surrounding fluid (against electrical breakdown through air ). As a result a huge energy saving is possible. It is estimated that it is possible to use one third to one sixth of the energy compared to conventional electric cooking. This does not include exhaustion of hot, humid air, which is created to a much lesser extent with e-Cooking® than with conventional cooking etc.

Since cooking "on demand" (only on request starting with meal preparation and only what is needed) becomes possible, less food wastage can be achieved.

e-Cooking®, as this new method is called, is a safe method of food preparation just because the food is hot and not the environment (the pan). For a short period of time, the food is subjected to one or more pulses with an electric field strength suitable for this purpose. This field strength is considerably lower than the field strengths used (see the discussion of the prior art) for the decontamination of food products by inactivation of undesirable micro-organisms, for what field strengths of 20 kV/cm and higher are used. The here proposed method uses a combination of distortion (disruption) of food cells (cell walls) and/or tissue by the applied field strength (<20 kV/cm) and preferably, inducing of resistive heating, by which very homogeneous cooking of food products can be achieved. In practice, this method of food preparation can be successfully applied by using pulses with field strengths from about 200 V/cm.

To achieve the desired degree of cooking for the products the following parameters must be set up correctly:

a. the field strength;

b. the pulse width;

c. the pulse shape (preferably with steep sides;

possibly also the pulse frequency;

d. the net processing time, in other words: the pulse width multiplied by the number of pulses;

e. optional time interval between pulses in view of the load of the device, which must deliver the pulses to or in view of the in the mean time relaxation (mortification) of the food;

f. the conductivity of the surrounding liquid/broth;

g. starting temperature of product and liquid.

The amount of energy supplied to the product is related to the available power of the developed system. This power is squared influenced by the applied voltage. This voltage is furthermore also determined by the height of the product. Example 1

A braising steak should normally simmer 4 to 5 hours in a pot to become cooked, in other words, to make thus edible and digestible in the body. Treatment in an e- Cooking® device shown in Figure 1, with 1000 pulses of 10 ps with a pause time of 0.1 seconds between pulses, lasted 100 seconds or 1.7 minutes. The core temperature is 75 °C and the surrounding fluid reaches only 56 ° C. This result is astonishing, even for professionals in the meat industry who were confronted herewith. Example 2

With "poaching" of cod, it is very important, according to professional cooks, that the temperature does not exceed 54 °C. With the e-Cooking® device this can be achieved uniquely and precisely. The result is a beautiful "flaky" product.

Example 3

This example concerns the treatment "cooking" of a potato slice. The treatment in the e-Cooking® device with 1700 pulses of 10 MS and a pause time of 0. 1 seconds between pulses lasted about 170 seconds or 2.8 minutes. The core temperature was 87 °C and the surrounding fluid became only 79.5 °C.

Example 4

The treatment of vegetables with the e-Cooking ® device provides also a good result. There was a somewhat higher chamber used (4 cm), as a result of which (on a constant voltage across the electrodes) the field strength was lower. Thus more pulses were needed and the cooking took some more time, namely about 5 minutes. The core temperature of the broccoli and the Brussels sprouts in this example was 88 °C.

Table A gives an overview of the above-mentioned examples of food preparation with the in this patent application proposed "e-Cooking®" method according to the invention; in practice performed in a laboratory specimen of an "e-Cooking®" device. In addition to the above very specific conditions also similar effects occurred with other conditions (4 to 60 milliseconds pulses at 2 kV/cm).

Field Pulse Number Pause- Product Broth Degree Colour,

Food Amount

strength width of time temperatemperaof Structure smell, Product (g)

(kV/cm) (MS) pulses (s) ture (°C) ture (°C) cooking taste

Braising

90 1.75 10 1,000 0,1 75 56 Good Good Good meat

Perfectly Very

Cod 49 0.88 10,000 40 1,0 52 45 Good

"flaky" Good

Potato 80 1.75 10 1,700 0,1 87 79 Good Good Good

Vegetables

31 0.88 10 3,000 0,1 88 88 Good Good Good (Broccoli,

Sprouts 45 0.88 10 4,000 0,1 88 82 Good Good Good

Table A