The present application claims the priority of the Italian patent applications no. IT102019000024093 and IT102020000021958, the content of which is incorporated in the present application by reference.

Field of the invention

[1] The present invention relates to a process, an apparatus and a computer program for defrosting deep- frozen or frozen foods.

[2] This process, apparatus or computer program is particularly suitable for defrosting foods both on an industrial scale, for example to supply wholesalers, supermarket and large-scale distribution chains in general, restaurants or hotels, and for family use or for single restaurants, inns or small grocery stores. Background

[3] The following processes are currently used to defrost deep-frozen or frozen foods:

P.l) defrosting in a static atmosphere cell;

P.2) defrosting in air or other gaseous substance with forced convection;

P.3) defrosting in water, with or without forced convection;

P.4) radio frequency defrosting.

[4] Defrosting in static air P.l) has logistical advantages and respective cost-effectiveness for large quantities of product.

[5] Defrosting in air with forced convection P.2) is faster than defrosting P.l) but it requires specific equipment, to be sized according to the environment and the arrangement of the product.

[6] Defrosting in water P.3) is suitable for more limited quantities of product, due to the requirements of managing the water bath; forced convection speeds up the process, but makes the management thereof more complex.

[7] Radio frequency defrosting P.4) is very fast but heats the food very unevenly.

[8] On the one hand, this entails strong risks of locally exceeding the food safety temperature prescribed by the food safety regulations or in any case by the competent authorities, on the other hand it makes the defrosted food very uneven, considerably deteriorating the organoleptic features thereof.

[9] In particular, radio frequency defrosting P.4) currently does not guarantee that the relevant safety temperatures will not be trespassed.

[10] An object of the present invention is to obviate the drawbacks mentioned above and in particular to provide a process and an apparatus for defrosting frozen or deep-frozen foods more evenly and/or quickly.

Summary of the invention

[11] Said object is achieved, according to a first aspect of the present invention, with a process having the features according to claim 1.

[12] In a second aspect of the invention, said object is achieved with an apparatus having the features according to claim 19.

[13] In a particular embodiment of the invention, the apparatus comprises a heating system configured to heat the treatment liquid contained in the treatment container.

[14] In a particular embodiment of the invention, the apparatus comprises a temperature control system configured to control the temperature of the treatment liquid contained in the treatment container.

[15] In a particular embodiment of the apparatus according to the invention, the temperature control system is configured to maintain the temperature of the treatment liquid within around a target temperature or to make it equal to said target temperature.

[16] In a particular embodiment of the apparatus according to the invention, the cooling system comprises a cold source configured to provide a flow of treatment liquid at a temperature substantially lower than the average temperature of the cooling liquid present in the treatment container.

[17] In a particular embodiment of the apparatus according to the invention, the cold source is arranged in a substantially high zone of the treatment container.

[18] In a third aspect of the invention, said object is achieved with a computer program having the features according to claim 28.

[19] Further features of the invention are the subject matter of the dependent claims. [20] The advantages attainable with the present invention shall become more readily apparent, to the person skilled in the art, by the following detailed description of particular, non-limiting embodiments, illustrated with reference to the following schematic figures.

List of Figures

Figure 1 shows a side view and a functional diagram of an apparatus for defrosting foods according to a first particular embodiment of the present invention;

Figure 2 shows a perspective view of an apparatus for defrosting foods according to a second particular embodiment of the present invention;

Figure 3 shows a first partially exploded perspective view of the apparatus of Figure 2;

Figure 4 shows a partially sectional view, according to the section plane IV-IV of the apparatus of Figure 2; Figure 5 shows a top view of the apparatus of Figure 2; Figure 6 shows a first perspective view of the cold source and of part of the remaining cooling system of the apparatus of Figure 2;

Figure 7 shows a side view of the cold source and of part of the remaining cooling system of Figure 6;

Figure 8 shows a perspective view of the portion of the treatment tank in which an ice probe and a temperature sensor of the apparatus of Figure 2 are arranged;

Figure 9 shows a detail of a partially sectional view, according to the section plane IX-IX of the apparatus of Figure 2; Figure 10 shows a detail of a partially sectional view, according to the section plane X-X, of the ice probe and of the temperature sensor of the apparatus of Figure 2; Figure 11 shows a perspective view of the recirculation system of the apparatus of Figure 2;

Figure 12 shows a first partially exploded perspective view of the apparatus of Figure 2;

Figure 12A shows a perspective view of a heating element of the compressor of the apparatus of Figure 2; Figure 13 shows a first perspective view of the cold source and part of the remaining cooling system of the apparatus of Figure 2.

Detailed description [21] Figure 1 relates to an apparatus for defrosting a frozen or deep-frozen food according to a first particular embodiment of the invention.

[22] Figures 2-11 instead relate to an apparatus for defrosting a frozen or deep-frozen food according to a second particular embodiment of the invention.

[23] This apparatus, indicated respectively with the overall reference 1, 1' comprises a treatment container 3 configured to contain a mass of treatment liquid 5 and one or more portions of a food to be treated 7. [24] In the treatment container 3 each portion of the food to be treated 7 can be at least partially immersed into the treatment liquid 5 or more preferably fully immersed into the treatment container 3.

[25] The process for defrosting a frozen or deep-frozen food 7 according to an aspect of the invention comprises the following steps:

5.1) providing a portion of a frozen or deep-frozen food 7 to be treated;

5.2) bringing the portion of food to be treated 7 into contact with the treatment liquid 5;

5.3) transmitting, through the treatment liquid 5, ultrasounds to the food to be treated 7;

[26] As already partly mentioned, in step S.2) the portion of the food to be treated 7 is brought into contact with the treatment liquid 5 by immersing it at least partially with this liquid 5, and more preferably by immersing it fully.

[27] Said treatment liquid 5 into which the food to be treated 7 is immersed at least partially can be substantially calm, that is, moved in its inside only by natural convective motions, or it can be current, that is, moved by forced convective motions or replaced more or less very quickly.

[28] Preferably in one or more of the steps S.l, S.2, S.3 the portion of the food to be treated 7 comprises a containment membrane 9 and a predetermined amount of the food to be treated 7 enclosed in the membrane 9.

[29] Advantageously, the containment membrane 9 separates at least chemically the predetermined quantity of food to be treated 7 from the treatment liquid 5, preventing the latter from wetting and/or impregnating the predetermined quantity of food to be treated 7. [30] Preferably the containment membrane 9 forms a bag containing the predetermined quantity of the food to be treated 7.

[31] This bag, and more generally the membrane, are preferably impermeable to gases and liquids.

[32] Preferably at least during one or more steps S.l, S.2 or S.3 a pneumatic depression with respect to the atmospheric pressure of the external environment is inside the bag 9, such as to cause - at least in some zones - the membrane containing the food to be treated 7 to adhere.

[33] This improves the transmission of the ultrasounds to the food to be treated 7, for example by spreading the ultrasounds more homogeneously onto the surface of the food 7 and increasing the quantity of energy transmitted thereby to the food.

[34] The absolute value of said pneumatic depression can be for example equal to or higher than 0.1-0,2 relative bar.

[35] More preferably at least during one or more steps S.l, S.2 or S.3 the bag 9 substantially forms a vacuum package.

[36] More generally, preferably at least during one or more steps S.l, S.2 or S.3 the containment membrane 9 and the predetermined quantity of the food to be treated 7 enclosed in the membrane 9 substantially form a vacuum package.

[37] The food to be treated 7 can be chosen from the following group: meat, fish, crustaceans, seafood, cheese, dairy products, vegetables, fruit, broth, soups, sweet or savoury pasta, possibly, sweet or savoury cream, sauce, preserves, tomato sauce, sweets, cakes.

[38] At least in step S.3 the ultrasounds have a frequency preferably comprised between 20 kHz and 1000 kHz

[39] In this regard, ultrasounds can have a frequency comprised for example between 20-40 kHz, 40-80 kHz, 80- 120 kHz, 120-160 kHz, 200-250 kHz, 250-300 kHz, 300-350 kHz, 350-400 kHz, 400-450 khz, 450-500 kHz.

Advantageously, the ultrasounds have a frequency comprised between 35—40 kHz or between 38—40 kHz.

[40] Said last two frequency ranges have proved to be particularly effective in giving the defrosted product good organoleptic properties.

[41] The treatment liquid 5 can be for example water or an aqueous solution of mineral salts.

[42] Advantageously at least during one or more of the steps S.2, S.3 and preferably in both of them the treatment liquid 5 has a temperature comprised between 0°-12°C and for example comprised between 0°-2°C, between 2°-4°C, 4°-5°C, 4°-6°C, between 6°-9°C, between 9°-12°C, between 12°-15°C, between 15°-18°C, between 18°- 21°C or between 21°-23°C.

[43] Advantageously at least during one or more of the steps S.2, S.3 and preferably in both the treatment liquid 5 has a temperature higher than 0° centigrade.

[44] For this purpose at least during one or more of the steps S.2, S.3 and preferably in both the treatment liquid can have a temperature equal to or higher than

0.5°C.

[45] Again for this purpose, said temperature is preferably equal to or lower than 21°C, and more preferably than 5°C.

[46] The aforementioned temperature as well as the target temperature described later can be measured and found respectively both inside the container 3, that is by directly measuring or considering respectively the temperature of the treatment liquid bath in which defrosting is carried out, and at a suitable point externally to the container 3 and/or to the treatment liquid bath, for example by measuring or considering it at the temperature sensor 22 or more generally at the outlet duct 27 of the recirculation system described below.

[47] The target temperature described later is preferably comprised within the preceding temperature ranges and/or preferably has the preceding temperature values.

[48] The temperature ranges of the treatment liquid 5 and/or of the target temperature comprised between 0.5- 5°C, 0.5-4°C have proved to be particularly effective for obtaining a defrosted product with excellent organoleptic features, especially if in combination with ultrasounds at a frequency comprised between 35- 40kHz or 38-40kHz.

[49] Preferably the containment membrane 9 is made of one or more of the following materials: polyethylene, polyvinyl chloride (PVC), ethylene vinyl acetate (EVA).

[50] The containment membrane 9 has an average thickness for example comprised between 50-400 micrometres or between 70-150 micrometres or between 90-130 micrometres.

[51] Advantageously at least during one or more steps S.2 or S.3 the temperature of the treatment liquid 5 is maintained in a predetermined tolerance range.

[52] Said predetermined tolerance range is preferably comprised between 0°-23°C and more preferably between 0°-21°C, between 0°-12°C or between 0°-5°C.

[53] More preferably, said tolerance range is comprised between 4 degrees more or less, and even more preferably between 2 degrees more or less, between one degree more or less or between 0.5 degrees more or less than a predetermined defrosting temperature which is preferably specific for each type of food to be treated 7.

[54] For this purpose, the previous teachings relating to the defrosting process described above can be advantageously carried out with a defrosting apparatus comprising, as in part already mentioned:

- a treatment container 3 that is capable of containing a mass of the treatment liquid 5;

- an ultrasound generator 15 configured to diffuse ultrasounds into the treatment liquid 5 contained in the treatment container 3.

[55] The treatment container 3 can comprise for example a tank open at the top (Figure 1), optionally of a more or less parallelepiped (Figure 1), cubic or cylindrical shape.

[56] The treatment container 3 is preferably metallic, for example made of stainless steel, so as to promote among other things the transmission and diffusion of the ultrasounds produced by the generators 15 in the liquid 5.

[57] Advantageously, the treatment container 3 is externally coated with a thermally insulating cover 6, which contributes both to maintaining the temperature of the treatment liquid bath low and more even from point to point, increasing the energy efficiency of the apparatus 1.

[58] Each ultrasonic generator 15 can be for example of the piezoelectric type or with magnetostrictive effect.

[59] Preferably during the normal operation of the apparatus 1, the ultrasound generator 15 is arranged externally to the container 3 and of the mass of treatment liquid 5 contained therein, and transmits the ultrasounds to the liquid 5 through the walls of the container 3 (Figure 1); in this way the ultrasound energy is distributed more evenly in the liquid and in the foods to be treated 7; in other embodiments not shown, however, the ultrasound generator 15 can also be arranged in the container 3 and in the mass of treatment liquid 5 contained therein, for example immersed into the liquid 5.

[60] The apparatus 1, 1' is preferably provided with a plurality of ultrasound generators 15, preferably arranged under the bottom of the container 3.

[61] Preferably the ultrasound generators 15 are fixed to the bottom or in any case to the wall of the container 3, with a density for example approximately comprised between 10-60 generators 17 per square metre of the bottom or more generally of the walls of the container 3; such density can for example be comprised between 20-50 generators 17/square metre, between 40-50 transducers/square metre or between 45-48 transducers/square metre.

[62] Alternatively or in combination, the apparatus 1,

1' can be provided with a total number of generators 17 comprised between 1-30, 2-20 or 15-18 or for example equal to 17 ultrasound generators 17.

[63] Preferably the ultrasonic generators 15 are or comprise piezoelectric actuators; they can clearly comprise actuators of different types, too.

[64] Advantageously, the apparatus 1 is provided with a temperature control system configured to control the temperature of the treatment liquid 5 contained in the treatment container.

[65] Advantageously, said temperature control system comprises a cooling system 11, 11' configured to cool the treatment liquid 5 contained in the treatment container 3.

[66] The cooling system 11, 11' can comprise for example a cold source 110, 110' configured to deliver a flow of treatment liquid 5 at a temperature substantially lower than the average temperature - or punctual and detected in a suitable point of the liquid treatment - of the coolant 5 present in the treatment container.

[67] The cold source 110, 110' can comprise for example a heat exchanger configured to be directly immersed in the treatment liquid 5 contained in the treatment container 3.

[68] The heat exchanger 110, 110' can comprise for example a coil within which a suitable refrigerant liquid flows, such as for example ammonia, carbon dioxide, water, propane, a Freon, liquid nitrogen or a suitable cooled refrigerant liquid, for example a refrigerating machine located externally to the treatment container 3 and comprising a compressor 4, a first heat exchanger working as an evaporator (not shown or coinciding for example with the heat exchanger 110), a second heat exchanger (not shown) working as a condenser and an expansion valve not shown.

[69] The cold source 110 can comprise as an alternative and for example the outlet of a fluidic circuit which introduces into the container 3 some treatment liquid 5 or other fluid - for example suitably blown-in liquid nitrogen - substantially colder than that already present in the container 3; such a fluidic circuit can comprise for example a refrigerating machine arranged out of the treatment container 3 and comprising a compressor, a first heat exchanger working as an evaporator, a second heat exchanger working as a condenser and an expansion valve not shown.

[70] Advantageously, the cooling system 11, 11' is configured to form and maintain a coating of ice on at least part, and more preferably, on the totality of the inner walls of the tank or other treatment container 3.

[71] Said layer of ice has an average thickness preferably equal to or higher than one centimetre, and more preferably equal to or higher than two, four, six centimetres and preferably lower than 10 centimetres.

[72] For this purpose, the treatment liquid 5 is substantially different from an eutectic mixture, and is, for example, made up of water alone or of a non eutectic aqueous mixture or solution, so as to facilitate the formation of the coating -i.e. the crust- of ice at not particularly low temperatures.

[73] In order to form and preserve a suitable layer of ice, the cooling system 11, 11' is preferably provided with one or more ice probes 19 (Figure 9).

[74] Each ice probe 19 can measure for example the thickness of the layer of ice that covers the inner wall of the container 3 by providing a continuous or discretised measurement - for example discretised in more than two states i.e. possible measured values, for example, three, five, ten, twenty, fifty or more states or possible measured values - for example in the form of an analogue or digital electrical signal.

[75] Alternatively, each ice probe 19 can simply provide an output signal with only two possible states, zero-one or on-off, which simply indicates whether the ice covering the inside of the tank at or around the probe 19 reached or not a certain predetermined thickness limit.

[76] In this case, the apparatus 1, 1' can be advantageously provided with a probe positioning system configured for adjusting the position of the probe 19 with respect to the internal walls of the treatment container 3, for example to move the sensitive part of the probe 19 away or closer thus regulating the thickness of the ice that is formed thereon.

[77] The probe positioning system can advantageously be operated by hand, for example by means of a knob, crank or lever.[78] The layer of ice allows to maintain the average temperature of the treatment liquid 5, detected in the defrosting bath or in other points of the fluidic circuit - or detected by the probe 21 and/or 22 within particularly narrow tolerances, for example within 4°C and/or to accurately maintain the temperature of the treatment liquid bath 5 in the range 0.5-5°C or 0.5-4°C.

[79] Again for this purpose, the cold source 110' can advantageously comprise, for example, a duct 1100 which can be traversed by a suitable refrigerant fluid and which extends along and preferably on the walls of the treatment container 3 so as to promote the formation of the ice crust (Figure 6, 7).

[80] Preferably the duct 110 extends around the treatment container 3 and outside it (Figure 6, 7); in embodiments not shown, however, it can extend along the inner walls of the container 3 or in any case close thereto and inside said inner walls; in that case the duct 1100 can be directly immersed into the bath of the treatment liquid 5.

[81] Preferably the duct 1100 forms a winding for example substantially helical and comprising one or more turns which preferably surround or in any case contain the container 3.

[82] The turns preferably and substantially have the same shape as the cross sections of the treatment container 3, for example rectangular (Figures 6, 7), square, rhomboid, polygonal, circular, oval, elliptical cross sections.

[83] The helical winding of the duct 1100 is particularly effective for covering the inner walls of the container 3 with a layer of ice.

[84] Preferably the helical winding of the duct 1100 extends approximately over at least 20 % of the surface of the sides of the treatment container 3 and around it or internally thereto, and more preferably it extends over at least about 30%, 50%, 70 % or 90% of the surface of the sides of the treatment container 3.

[85] Advantageously, the temperature cooling or control system 11, 11' comprises one or more temperature sensors 21, 22 to detect the temperature of the treatment liquid bath 5 present in the container 3 (Figure 8, 9, 11) or the temperature of other points of the apparatus 1, 1'.

[86] During normal operation of the apparatus 1, the first sensor 21 can be immersed in the treatment liquid bath 5 present in the container 3.

[87] The first sensor 21 can be for example the probe of a mechanical or electromechanical thermometer intended to simply provide a reading of the detected temperature or an electrical, electromechanical or electronic sensor capable of transmitting the temperature it detects to the logic unit 17 or other logic unit in the form of an electrical, electronic or optical signal.

[88] The second temperature sensor 22 can be arranged for example out of the container 3, for example along the outlet duct 27 of the recirculation system or more generally along a outlet duct that directs treatment liquid towards the container 3 and/or along an outflow duct which evacuates treatment liquid from the container 3.

[89] In an embodiment not shown, the second temperature sensor 22 is arranged within the container 3, preferably immersed in the bath of defrosting liquid 5.

[90] The apparatus 1 can also have only one of the two temperature sensors 21, 22 or both and possibly also further temperature sensors not shown.

[91] In order to make the temperature of the treatment liquid 5 in the container 3 more even, the apparatus 1 is preferably provided with a recirculation system 23 configured to withdraw the treatment liquid from the container 3 and feed it again, preferably continuously (Figure 3, 11). [92] The recirculation system 23 can comprise a inlet duct 25, an outlet duct 27 and a recirculation pump 29.

[93] The inlet duct 25 is fluidically connected to the container 3 through a inlet mouth 250.

[94] The outlet duct 27 opens into the container 3 through the outlet 270.

[95] The recirculation pump 29 is configured for sucking the treatment liquid from the container 3 through the duct 25 and feed it again through the duct

27.

[96] Preferably the inlet mouth 250 and the outlet 270 are arranged relatively far away one from another in the container 3, for example the inlet mouth 250 is preferably arranged on the bottom of the container 3 while the outlet 270 is preferably arranged in the upper part of the container 3.

[97] If the container 3 has a substantially rectangular or square plan, the withdrawal 250 and the delivery 270 mouths are preferably arranged at or close to corners at opposing ends of a diagonal of the plan itself.

[98] Advantageously, the temperature control system 11, 11 comprises a heating system configured to heat the treatment liquid 5 contained in the treatment container.

[99] The heating system can comprise for example a warm source 13 in turn comprising for example a Joule effect resistor, a heat exchanger in turn comprising a coil internally traversed by a warm fluid or another heating element configured to be directly immersed in the treatment liquid 5 contained in the treatment container

3.

[100] Said coil traversed by a warm fluid can for example be part of a refrigerating cycle machine such as for example a heat pump or the same refrigerating machine to which the compressor 4 belongs, suitably operated as a heat pump; in this case, said coil can comprise the duct 1100.

[101] The warm source 13 can comprise as an alternative and for example the outlet of a fluidic circuit which introduces into the container 3 some treatment liquid 5 which is substantially warmer than that already present in the container 3.

[102] Advantageously, the temperature control system is configured to maintain the temperature of the treatment liquid 5 contained in the treatment container above and/or below a predetermined threshold, advantageously while the ultrasound generator 15 is active and is diffusing ultrasounds into the food to be treated 7.

[103] For this purpose, the temperature control system 11, 11' can comprise a logic unit 17 -such as for example a microprocessor - which controls the operation of the possible cold 110, 110' and/or warm 13 sources for example on the basis of the detections of one or more of the temperature sensors 21, 22 and/or of the ice probe 19.

[104] For this purpose the logic unit 17 can be configured to control the operation of the possible cold 110, 110' and/or warm 13 sources in feedback or in open loop, in particular by controlling the operation of, for example, one or more of the following parts: the compressor 4, the refrigerating machine, the pump

29.

[105] In particular, the logic unit 17 is preferably configured to control the operation of the cooling 11, 11 and/or heating system so as to maintain the temperature of the treatment liquid present in the container 3 close to or coinciding with the preselected target temperature, and/or the temperature of the treatment liquid 5 measured at the preselected reference point close to or coinciding with the preselected target temperature.

[106] For this purpose the logic unit 17 may comprise for example one or more thermostats.

[107] The logic unit 17 or other logic unit (not shown) can control the operation of the one or more ultrasound generators 15 and possibly the operation of the apparatus 1 in general.

[108] In order to promote the formation of the ice coating, the logic unit 17 is advantageously configured to activate the compressor 4 or more generally the refrigerating machine or other cold source 110 when the layer of ice covering the inner walls of the container 3 has an insufficient thickness and/or extension, for example when the ice probe 19 detects and signals an ice thickness lower than or equal to a threshold thickness to the logic unit 17.

[109] Again in order to promote the formation of the ice coating, the logic unit 17 is advantageously configured to activate the recirculation system 23 only when the layer of ice covering the inner walls of the container 3 has reached a sufficient thickness and/or an extension, for example only when the ice probe 19 detects and signals an ice thickness equal to or higher than a threshold thickness to the logic unit 17.

[110] This threshold thickness is preferably equal to or higher than one centimetre, and more preferably equal to or higher than two, four, six centimetres.

[111] More generally, the logic unit 17 is advantageously configured to control the cooling system 11, 11' so as to produce and preserve the ice crust which covers the inner walls of the container 3.

[112] Advantageously, the cold source 110 is arranged in a substantially high zone of the treatment container, that is, located higher than half the maximum depth of the treatment container 3, so as to produce more intense and wider convective currents in the treatment liquid 5 contained in the container 3.

[113] Advantageously, the warm source 13 is arranged in a substantially low zone of the treatment container, that is, located lower than half the maximum depth of the treatment container 3, so as to produce more intense and wider convective currents in the treatment liquid 5 contained in the container 3.

[114] The container 3 has a capacity preferably comprises between 0.05-0.2 cubic metres or between 0.05-0.2 cubic metres. [115] Such relatively small dimensions render the apparatus 1, 1' particularly suitable for end users which can be considered as retailers or in any case medium-small ones such as for example single supermarket shops, fishmongers, restaurants or canteens.

[116] The container 3 can in any case have even smaller or greater capacities, for example equal to or higher than 0.4 cubic metres. [117] The apparatus 1, 1' can be substantially made as a cabinet having the overall shape of a parallelepiped (Figure 2, 3, 5), cube, prism or cylinder.

[118] The cabinet can possibly be sliding on wheels (Figure 2). [119] The container 3 is preferably mounted in the upper part of the cabinet.

[120] The compressor 4 or more generally the refrigerating machine -if any- which cools the treatment liquid 5 is preferably enclosed in the cabinet housed beneath the tank 3.

[121] The logic unit 17 and/or any other electric and/or electronic control units can be arranged in a box 170 (Figure 13) or other protective shell, made for example of a suitable plastic material. [122] Advantageously the compressor 4 is provided with a tray 40 configured to collect condensate water, if any, dripping from the body of the compressor 4, preventing it from spreading on the internal bottom of the cabinet which can form the apparatus 1, 1', risking to wet the box 170, the contents thereof, any other electrical devices or components and cause short circuits or other failures (Figure 12).

[123] An electric resistance, not shown, which is configured to heat and make evaporate any water that has accumulated in the tray 40 by Joule effect, can be advantageously arranged in the tray 40, a further resistance for the water is positioned, precisely adapted to make it evaporate.

[124] This electric resistance can operate continuously

- for example being always on - or preferably activated

- for example on and off or even adjusted - by a thermostat.

[125] Advantageously the compressor 4 is provided with one or more heating elements 42, each of which is configured to heat the compressor, preventing it from freezing if it works for too long at temperatures below zero or in any case at very low temperatures, and therefore preventing traces of the oil that lubricates the internal mechanisms thereof from contaminating the refrigerant fluid directed to the coil 1100 or other cooling duct 1100 or coming therefrom (Figure 12, 12A).

[126] Traces of oil or other lubricant in the refrigerant fluid compressed by the compressor 4 can in fact damage the expansion valve and other components of the refrigerating machine.

[127] Each of said heating elements 42 can be for example an electrical resistance heating the compressor 4 by Joule effect.

[128] This electrical resistance can for example have the form of a band surrounding or extending around the body of the compressor 4.

[129] Again in order to avoid or in any case reduce the contamination of the refrigerant fluid caused by the lubricant, the compressor 4 or in any case the respective refrigerating machine is advantageously provided with one or more filters 44 configured to filter the refrigerant liquid and retain any lubricant particles entrained by it.

[130] At least one of these filters 44 is preferably arranged in a point of the circuit where the refrigerant fluid is normally in the liquid state.

[131] Again to avoid or in any case reduce contamination of the refrigerant fluid caused by the lubricant, the compressor 4 or in any case the relative refrigerating machine is advantageously provided with one or more solenoid valves 46 configured to be closed and to close the duct that passes through it, for example when the refrigerant fluid reaches or trespasses a suitable temperature threshold and/or the compressor 4 switches off, avoiding backflow of refrigerant liquid into the compressor and damages to the lamination valve. [132] The cabinet can be provided with a lid 31 fixed to the upper part of the cabinet itself preferably by means of suitable hinges so as to be foldable, and so that it can be opened and closed for showing and covering the tank or other container 3, respectively (Figure 2, 3).

[133] Advantageously, the lid 31 forms or constitutes a cutting board on which, when it is lowered, the defrosted product can be cut.

[134] For this purpose, the lid 31 is preferably made of polyethylene or can be coated with a sufficiently thick and rigid polyethylene layer.

[135] When the possible lid 31 is closed or in any case lowered, the cabinet has one or more of the following external overall dimensions:

- an overall length LM preferably comprised between 0.6-4 metres, between 1-3 metres or between 1,2-2 metres or between 1,2-1.5 metres;

- an overall width WM preferably comprised between 0.3- 2 metres, between 0.4-1 metre or between 0.4-0.5 metres;

- an overall height HM preferably comprised between 0.3-1.5 metres, between 0.5-1 metre, between 0.6-0.9 metres or between 0.8-0.9 metres.

[136] These external overall dimensions also contribute to making the apparatus 1 particularly suitable for end users which can be considered as retailers or in any case medium-small ones.

[137] The apparatus 1, 1' can advantageously be provided with a grid 33 for defrosting for example fishes (Figure 3).

[138] The grid 33 can be arranged on the bottom of the treatment container 3 or in any case close to it so as to keep the various portions of food to be treated 7 resting on the grid 33 suitably spaced from the ultrasound generators 15, preventing the latter from being damaged.

[139] An example of operation and use of the defrosting apparatus 1,1' will be now described.

[140] An operator introduces into the treatment tank 3 a portion of food to be treated 7 preferably comprising the aforementioned bag or other containment membrane 9 and a predetermined quantity of food to be treated, for example a piece of frozen or deep-frozen meat or fish.

[141] The food portion 7 is preferably fully immersed into the liquid bath, preferably water or an aqueous solution, contained in the treatment container 3.

[142] Once the defrosting cycle of the apparatus 1 has been activated, the one or more ultrasound generators 15 start emitting ultrasounds which diffuse through the walls of the treatment container 3 and the mass of the treatment liquid 5 inside the food portion 7 defrosting it, both because the tissues or in any case the material of the food 7 vibrated by the ultrasounds heat up, and because the mechanical vibrations produced by the ultrasounds break up the macroscopic and microscopic ice crystals, possibly present in the food 7, increasing the exposed surface of the same crystals and thus accelerating the thawing thereof by heat diffusion.

[143] In the meantime, the temperature control system advantageously maintains the temperature of the water or other treatment liquid 5 within the predetermined limits, preventing the food 7 from overheating excessively and reaching, locally or worse still as a whole, temperatures considered as critical for the proliferation of microorganisms, in particular pathogens.

[144] In particular, the temperature control system 11, 11' can cool the treatment liquid 5 if it tends to heat up too much due to the effect of the ultrasounds or by simple heat exchange with the surrounding environment, and can heat the treatment liquid 5 up if it tends to cool down too much, for example if the temperature thereof tends to drop below zero degrees centigrade or a few degrees centigrade.

[145] Advantageously, the temperature control system 11, 11' generates and maintains a layer of ice which covers the inner surface of the container 3, stabilizing the temperature of the treatment liquid bath 5 and allowing, as it has been said, to control this temperature with narrower tolerances even using relatively cheap sensors, probes and in general electrical/electronic components.

[146] The treatment liquid 5 is thus substantially contained in a tank of ice.

[147] The bag or other waterproof and watertight containment membrane 9 prevents the liquid 5 from coming into direct - at least chemical - contact by wetting or in any case impregnating the food 7 and contaminating it, transmitting at the same time in a more effective and homogeneous way mechanical vibrations induced by cavitation and protecting the surface of the food from mechanical or thermal damage induced by the cavitation itself or from the risks of chemical, physical or microbiological contamination caused by a bath of the blank product in water.

[148] Once defrosted, the food package 7 can be removed from the treatment liquid bath 5 and used - for example cooked or consumed - or sent to the destinations of use such as a food establishment, a supermarket or other point of sale, a warehouse of a grocery wholesaler, a restaurant, canteen, fishmonger or butcher, a family or other private consumer.

[149] Starting from a state of inactivity, for example at the beginning of a work shift, the apparatus 1' can be started up by filling the container 3 with water - which acts as a treatment liquid 5 - and activating the compressor 4 and the relative refrigerating machine so that cold refrigerant liquid flows in the duct 1100 of the heat exchanger 110', such as for example refrigerant gas rapidly expanded by the lamination valve.

[150] The heat exchanger 110' thus begins to cool the treatment liquid 5 - that is water - contained in the container 3 until it covers itself and/or the inner walls of the container 3 with an ice crust.

[151] When the ice probe 19 detects that - for example in the surroundings thereof - the ice crust reaches the predetermined limit thickness, the logic unit 17 or other logic unit can detect this event and switch off the compressor 4 or in any case the refrigerating machine; preferably and at the same time the logic unitl7 or other logic unit activates the recirculation system 23, activating for example the possible pump 29 which sucks water or the treatment liquid from the container 3 in the inlet duct 25 and sends it to the outlet duct 27 from which the water or other treatment liquid is fed again into the container 3, mixing the water or other treatment liquid 5 in the container 3, making the temperature thereof more even and cooling the food to be treated 7 more effectively with more robust convective flows.

[152] Subsequently the logic unit 17 or other logic unit can reactivate the compressor 4 and/or the refrigerating machine and the possible warm source 13 for example if the thickness of the ice crust has been reduced again and/or to bring the temperature of water or other treatment liquid again sufficiently close to the preselected target temperature.

[153] Defrosting food 7 at temperatures only slightly above zero centigrade contributes considerably to preserving the organoleptic properties thereof.

[154] Thanks to the previous teachings it is possible to defrost frozen or deep-frozen foods much more quickly than with static atmosphere or forced convection cells, indicatively halving or reducing up to a third the defrosting times compared to the defrosting times in the current air-conditioned cells or in the current reverse blast chillers. [155] At the same time, the previous teachings allow the organoleptic features of the foods defrosted by ultrasound to be preserved very well, with better results than the known defrosting methods P.1-P.4 and allow the creation of very effective defrosting apparatuses using electronic or electromechanical components and sensors that are not excessively valuable and expensive.

[156] Compared to the known defrosting by radio frequency, the ultrasound defrosting processes and apparatuses described above produce less local overheating in the food and heat it more evenly, thus reducing local overheating, considerably prolonging the preservation thereof and reducing the risks of deterioration and bacterial contamination once they are defrosted and waiting to be sold, consumed or processed.

[157] It has been observed that the microbial flora possibly present in frozen foods is reduced and inactivated by the treatments with the apparatuses 1,

1

[158] The apparatus 1, 1' also allows a product be stored at the melting temperature of ice practically like in a cold storage room as required by Legislative Decree 853/04 of the European Union.

[159] The embodiments described above are susceptible to numerous modifications and variants, without departing from the scope of the present invention.

[160] For example, in an embodiment not shown, the portion of the food to be treated 7 can also lack the containment membrane 9 and for example consist of only the predetermined quantity of the food to be treated 7.

[161] The cold source 110, 110' can for example also comprise one or more eutectic plates fixed internally or externally to the walls of the container 3.

[162] The walls of the container 3 can be hollow and contain in their inside glycol or other cooling liquid which cools the treatment liquid bath 7 contained in the container 3 thereof.

[163] In other words, the container 3 could comprise two tanks, one of which contains the other, the defrosting liquid could be contained in the innermost tank and the glycol or other cooling liquid could be contained in the interspace between the inner and outer tank.

[164] Every reference in this description to “an embodiment”, “an embodiment example” means that a particular feature or structure described in relation to such embodiment is included in at least one embodiment of the invention and in particular in a specific variant of the invention as defined in a main claim.

[165] The matter that such expressions appear in various passages of the description does not imply that they are necessarily referred solely to the same embodiment.

[166] In addition, when a feature, element or structure is described in relation to a particular embodiment, it is observed that it is within the competence of the person skilled in the art to apply such feature, element or structure to other embodiments.

[167] Reference numerals differing only in different quotes, e.g. 21', 21", 21 ¹¹¹ unless otherwise specified indicate different variants of an element called in the same way.

[168] Furthermore, all of the details can be replaced by technically equivalent elements.

[169] In practice, the materials used, as well as the dimensions thereof, can be of any type according to the technical requirements.

[170] It must be understood that an expression of the type "A comprises B, C, D" or "A is formed by B, C, D" also comprises and describes the particular case in which "A consists of B, C, D".

[171] The expression "A comprises a B element" unless otherwise specified is to be understood as "A comprises one or more elements of B".

[172] References to a "first, second, third, ... n-th entity" have the sole purpose of distinguishing them from each other but the indication of the n-th entity does not necessarily imply the existence of the first, second ...(n-l)th entity.

[173] The examples and lists of possible variants of the present application are to be construed as non- exhaustive lists.