HK1131731B - Device for pasteurizing a mass of foodstuff - Google Patents

Description

Device for pasteurizing food substances

Technical Field

The present invention relates to pasteurising food substances. Such materials may include, for example, soy, fruit, potato, and/or meat. Such materials may also include other ingredients such as sugar, salt, spices, and the like.

Disclosure of Invention

The present invention provides an apparatus for pasteurizing food substances, such as substances containing soy ingredients, substances containing eggs, substances containing fruit (e.g. jams), substances containing potatoes, substances containing meat, etc., comprising:

a supply means through which the substance can be supplied to the device under pressure at a predetermined flow rate;

a first heating device comprising:

a first tube made of an electromagnetically inert material suitable for being in contact with food and connected to said feeding means;

two plate electrodes located on either side of the first tube and connected to an RF energy generator that energizes the electrodes at a frequency of about 10 to 50MHz such that the material within the first tube is dielectrically heated for a first residence time in the first tube;

a first sleeve filled with a heatable first liquid and extending around the first tube; and

a second heating device connected to the first pipe and in which a hot mass is maintained at a substantially constant temperature for a second residence time in the second pipe;

at the end of the second heating means, the hot mass is discharged for further processing, such as cooling, portioning and packaging.

Importantly, the first sleeve is filled with the first liquid. The first liquid already achieves a certain temperature increase of the passing substance for heating reasons, but more importantly, the liquid must be of such a type that the voltage between the electrodes is effectively prevented by this liquid via electrical breakdown of the food substance. Before proceeding with the following discussion, it has been noted that a very suitable liquid is demineralized water.

It is also possible to use more than one first tube, for example two, three or even four. The substance for pasteurization passes through each of these sub-tubes. Each sub-tube is provided with its own electrode, its own RF energy generator and (optionally) its own impedance matching circuit. By using multiple tubes and associated multiple generators, more material can be heated to a desired temperature per unit time. This type of energy generator is commercially available only up to a limited power, i.e. 70-90 kW. Using only one generator limits the process flow and the throughput of the device to the values corresponding thereto. The use of multiple generators makes it possible to increase the maximum achievable capacity to a value of two, three or four times, or even higher.

It has to be noted that the sub-pipes together forming the first pipe may in principle be connected to each other in series or in parallel as desired by the designer or user. The desired effect of increased capacity is achieved in all cases. In the case of parallel tubes, the substance is heated from the starting temperature to the desired end temperature in each sub-tube, while in the case of tubes connected to one another in series, the temperature increase is effected in a substantially stepwise manner, for example from about 10 ℃ to 40 ℃ in the first sub-tube and from about 40 ℃ to 70 ℃ in the second sub-tube, in the case of two tubes connected to one another in series.

The parallel tubes have a low flow resistance and therefore require the feed device to produce a low feed pressure. A drawback is that although the tubes occupy a relatively small space in the longitudinal direction, they necessarily have a larger dimension in the transverse direction.

The pasteurization treatment carried out by the device according to the invention can also be carried out by heating for a certain time to prepare the treatment substance. The mixture of meat ingredients, salt, spices and binding agent can thus be formed in a continuous process with the apparatus according to the invention into continuous sausages which are subsequently portioned under aseptic conditions, packaged and optionally further prepared and can then be shipped to the customer.

The majority of the first liquid of the present invention is water.

In a suggested embodiment, the first liquid is water, preferably demineralized water.

The second heating means can in principle be realized in any desired manner. It is obvious that the substance heated by these electrical means in the first tube must not dry out or otherwise deteriorate during its stay in the second heating means. Longer residence times in air often have undesirable consequences such as drying out and possibly even oxidation. In order to effectively eliminate these undesired phenomena, a variant of the invention may have the special feature that the second heating means comprise a second tube.

A suitable type of heating element must be added to the second tube.

Very suitable are embodiments comprising a second sleeve filled with a heatable second liquid and extending around the second tube.

For further processing of the pasteurized material in the apparatus, it is in many cases necessary to provide a cooling possibility before portioning and packaging. This cooling can be carried out after portioning and packaging, if desired.

It is often recommended that embodiments comprise a cooling device which is connected to the second heating device and in which the hot substance is provided for the possibility of cooling during its third residence time in the cooling devices, the cooled substance being discharged at the end of the cooling device for further processing.

As mentioned above, the second heating means preferably comprises a second tube. For the same reasons as described above, the above embodiment preferably has the feature that the cooling means comprises a third tube connected to said second tube.

The third tube may be coiled in a spiral shape to obtain a longer length in a relatively small space, whereby a rapid cooling may be obtained, optionally in combination with an external cooling medium, e.g. flowing through the air flow. In this cooling section, heat is removed from the pasteurized mass only by conduction, unlike dielectric heating in the first tube. Time is necessary for this purpose and is very long.

A portioning process can also be carried out in a manner known per se, optionally followed by a packaging process, in which the portions are guided through the cooling space by means of transport carriages. In this connection, a lift-tower (lift-tower) known per se is suitable.

It should be noted that the inner diameter of the tube need not be circular. Any desired and technically feasible shape may be chosen.

WO-A-88/02222 discloses an apparatus for cooking and preparing A meat-containing substance. In order to heat the substance delivered under pressure by the device, a field with a frequency of 10 to 41MHz, described as an electromagnetic field, is used, thereby effecting heating of the substance.

The medium is conveyed in the apparatus through a tube, leaves the apparatus in the hot state, and is cut into pieces or sheets in this state, if desired, immediately thereafter, for packaging.

WO-A-2004/039164 relates to A method and system for manufacturing sausage products without casing. According to this known technique, the mass is heated by a first heating element based on heat conduction, then heated to an elevated temperature by a second heating element, so as to obtain a sausage without casing, and then the product is finally cooled in a forced manner by the action of a cooler.

This specification mentions that microwave energy or high frequency or radio frequency energy may be used. The frequency range in question is not further defined in the present invention. Since microwaves have by definition a frequency of more than 300MHz, it is not possible to avoid hot and cold regions present in the substance to be heated, due to the relevant wavelengths. This is highly undesirable in the case of a sufficiently uniform heating, even if not allowed by food requirements. The temperature to be reached is finally selected for the pasteurization treatment, which requires a minimum temperature of 72 ℃ anywhere in the heated material, which must be maintained for a period of at least 2 minutes. In this respect, frequencies above 300MHz are of course unsuitable according to the invention. This is also why an RF frequency of about 10 to 50MHz is selected according to the invention.

In contrast to the two prior art techniques described above, it is believed necessary to use a fluid-filled cannula in accordance with the present invention to effectively prevent breakdown of the high RF voltage between the electrodes. According to the above-mentioned prior art, such drawbacks cannot be avoided and it has been found in practice that local burning or other deterioration of the substance is a consequence of such drawbacks. This is a very undesirable phenomenon which in most cases results in an under-control and deterioration which is totally undesirable for food products.

Each tube preferably has the same cross-sectional shape throughout.

The material that is completely transparent to said frequencies is a plastic, such as PTFE (polytetrafluoroethylene). Another advantage of this material is that it is very suitable for contacting food. This material is a smooth material to which food does not adhere or is difficult to adhere. Such a material can be given a finish very easily so that regular cleaning can be performed according to set requirements.

The electrodes may be of any suitable material. For example, an aluminum plate may be used.

The device has an in-line arrangement and is capable of performing continuous and very uniform heating, wherein it can be ensured that the temperature difference between the hottest and the coldest region in the heated substance is less than 5 ℃.

The system is capable of rapidly heating the core of material, for example, at a rate of about 1 deg.c/s.

The temperature of the supplied substance may be assumed to be about 0 to 10 ℃. The target temperature is reached at the electrode tip.

According to a certain aspect of the invention, the device has the special feature that the material of the second tube is stainless steel.

The device may also have the special feature that the material of the third tube is stainless steel.

It is very practical in an embodiment that the second tube and the third tube are joined together to form a unitary tube.

According to a subsequent aspect of the invention, the device has the special feature that the first residence time and the root mean square value (RMS) of the RF voltage on the electrodes can be adjusted such that the temperature of the substance at the end of the first tube is about 70 to 100 ℃.

The setting of said parameters for reaching said temperature depends inter alia on the salt content of the substance. Therefore, the parameter selection must be given in its literature.

According to a particular feature of the present invention, the device has an average effective inner diameter of the first tube of between about 20 mm and about 150 mm. Values of particular interest here are 50 to 115 mm.

Another aspect of the device sizing is that the electrode length is about 0.3 to 3 meters. The electrodes preferably have a length of about 0.5 to 1.5 meters.

In embodiments where each electrode has a shape that conforms to the outer shape of the tube, maximum efficiency of RF heating may be achieved.

In embodiments where the internal cross-sectional shapes of the interconnecting tubes are identical to each other and conform to the desired cross-sectional shape of the final product, a constant velocity for a given mass flow rate and generally without discontinuities can be achieved.

Various fluids are contemplated for filling the cannula. In a suggested embodiment, the second liquid is water (preferably demineralized water) or oil (preferably hot oil).

For the safety of operators and other persons present, in the proposed embodiment all RF voltage-carrying components are accommodated in an enclosure, in particular a faraday cage. The mesh of the faraday cage can be relatively large for relatively long wavelengths (relative to microwave radiation) associated with the frequencies used in accordance with the present invention.

In order to maximize the efficiency of heating the material for cooking and pasteurization, in the proposed embodiment the liquid in the first sleeve is maintained at a temperature of about 20 to 100 ℃.

The temperature at which the mass is pasteurized throughout the mass is not lower than a predetermined temperature, typically about 72 to 75 ℃, during a minimum of two minutes of residence time in the portion (e.g., second tube) where the mass is kept warm.

To this end, in a particular embodiment, the device may have the particular feature that the liquid in the second cannula is maintained at a temperature of about 70 to 100 ℃.

According to a preferred aspect of the invention, the electrodes are associated with an associated RF generator by means of an adjustable impedance matching circuit.

The device may for example feature a feeding device adapted to be connected to a pre-production device, such as a meat pump. For this purpose, the inlet side of the first pipe may be provided with a flange which is adapted to be sealingly connected to a correspondingly formed outer flange of a known meat pump.

The device may have the specific feature that the frequency is 12 to 29 MHz.

According to another aspect of the invention, the device is characterized in that the frequency value is 27 ± 2 MHz. For example, the frequency of 27.12MHz is a frequency that allows industrial applications (e.g., the device of the present invention).

According to another aspect of the invention, the device has the special feature that the frequency value is 13.5 ± 1 MHz. The frequency 13.56MHz is also a frequency that allows industrial applications, such as the device of the present invention.

It is noted that the third tube gradually cools the material subjected to cooking and pasteurization by internal conduction and external convection. Therefore, the third tube must generally have a relatively large length compared to the first and second tubes.

In certain embodiments, the device has the particular feature that the first and second sleeves are joined together to form a unitary sleeve. It is recommended in this case to fill the sleeve with heated demineralized water.

It is also generally noted that the sleeve through which the heating liquid flows has the function of the primary circuit of heat exchange, the relative tube of which forms the secondary circuit. Thus, heat exchange takes place between the heated liquid and the substance to be treated by transfer through the tube. As is generally known, such coaxial type heat exchangers have the highest efficiency in the case of return flow. For this purpose, the supply of the heating liquid is preferably situated on the downstream side of the transported substance, while the discharge of the heating liquid (already slightly cooled in the heat exchanger) is situated on the upstream side of the transported substance.

According to a final aspect of the invention, the device has the particular feature that a treatment section is located downstream of the second duct, in which treatment section the hot substance is subjected to a post-treatment, such as smoking, seasoning, grilling, etc.

Drawings

The present invention will now be described with reference to the accompanying drawings. In the drawings:

fig. 1 is a very simplified schematic diagram of an exemplary embodiment of a device according to the invention, shown partly in block diagram form and partly in cross-section; and

fig. 2 is a longitudinal section through the device in fig. 1.

Detailed Description

The figures show an apparatus 1 for cooking and pasteurizing a meat-containing substance 4, said substance 4 being supplied to the apparatus 1 by a meat pump 2 of a known type. The device comprises a feeding means 3 by which said food 4 is fed under pressure to said device at a predetermined flow rate; a first tube 5 made of an electromagnetically inert material suitable for contact with food products, in particular PTFE, and connected to said feeding means 3; two plate-like electrodes 6, 7 located on both sides of the first tube 5 and having a shape corresponding to the outer shape of the first tube 5, the electrodes being connected to an RF energy generator 8 which energizes the electrodes 6, 7 at a frequency of about 27.12MHz such that the substance 4 inside the first tube 5 is dielectrically heated during a first dwell time thereof in the first tube 5; a first sleeve 10, which extends around the first pipe 5 and is filled with demineralized water 9; a second pipe 11 connected to the first pipe 5 and maintaining the substance heated inside the first pipe 5 at a substantially constant temperature for a second residence time thereof in the second pipe of at least two minutes; a second sleeve 13 extending around the second tube 11 and filled with hot oil 12; and a relatively long third tube 14 which is connected to the second tube 11 and in which the hot mass is provided with the possibility of cooling during a third dwell time of the hot mass, the cooled mass being discharged at the end 15 of the third tube 14 for further processing, for example portioning and/or packaging.

The second tube 11 and the third tube 14 are joined together to form an integral, unitary stainless steel tube.

The first residence time and the rms value of the RF voltage on the electrode can be adjusted so that the temperature of the substance 4 is about 70-90 c at the end 16 of the first tube 5. In order to effect energy transfer with the greatest possible efficiency and thus heat the substance 4, the electrodes 6, 7 are connected to an RF generator 8 via an impedance matching circuit 17. The circuit 17 comprises a variable capacitor 8 connected in series to the electrodes 6, 7 and a second variable capacitor 19 connected in parallel to the electrodes 6, 7.

The RF generator 8 may be adapted to generate energy at a frequency of, for example, 27.12MHz or 13.56 MHz. Both of these frequencies are allowed frequencies that can be used for this type of industrial application.

The first liquid is maintained at a desired temperature, for example 40 c, by using a heating device 20 with a heat exchanger with a pump. In this embodiment, a softening device 22 is also included in the supply duct 21. In this case, water is used. Other liquids such as hot oil are also suitable.

The second liquid 12 may be brought to and maintained at the desired temperature in a similar manner.

The residence time of the hot substance in the second tube 11 must be a minimum of two minutes, as is required for pasteurization.

The RF voltage carrying components are all housed within a faraday cage 23. The faraday cage is grounded through a ground line 23. The electrode 6 is also connected to ground via a ground line 25 and the electrode is also connected to the RF generator via said ground line. Thus, the RF generator is also grounded. Faraday cage and said grounding are essential for the safety of the operator.

It is obvious that, also in accordance with the legal provisions, the device will also include safety technical measures which ensure, for example, that the RF voltage of the electrodes is immediately cut off, for example by immediately cutting off the RF energy generator, when the device is opened or the ground of the faraday cage is broken.

It is obvious that the invention is not limited to the described exemplary embodiments. As previously mentioned, the first tube may comprise a number of sections or combinations thereof connected in series or in parallel as desired, for example two parallel sub-tubes, each sub-tube comprising two sub-sections connected in series.

The use of tubes has the disadvantage of a higher flow resistance compared to open transport on, for example, a conveyor belt, wherein it must be noted that, for example, water or fat in the substance to be treated has a lubricating and sliding effect on the inner surface of the heating tube. In the case of cooling, for example, a high-humidity environment or a protective atmosphere (e.g. nitrogen) can be used, wherein the substance is transported in principle in a pressureless manner.

It is generally recommended that the pressure within the mass is not higher than about 4 bar.

Claims (40)

1. An apparatus for pasteurizing a food substance, the apparatus comprising:

a feeding means by which the food substance can be supplied to the apparatus under pressure at a predetermined flow rate;

a first heating device comprising:

a first tube made of an electromagnetically inert material suitable for being in contact with food and connected to said feeding means;

two plate-like electrodes located on either side of the first tube and connected to an RF energy generator which energizes the electrodes at a frequency of 10-50MHz such that the food substance within the first tube is dielectrically heated for a first residence time in the first tube;

a first sleeve filled with a heatable first liquid and extending around the first tube; and

a second heating means comprising a second tube, which is connected to the first tube and in which the hot food substance is kept at a constant temperature during its second residence time in the second tube;

the hot food substance is discharged at the end of the second heating means for further processing.

2. The apparatus of claim 1, wherein the food substance is a substance comprising a soy component.

3. The apparatus of claim 1, wherein the food substance is an egg-containing substance.

4. The apparatus of claim 1, wherein the food substance is a fruit-containing substance.

5. The apparatus of claim 4, wherein the fruit-containing food substance is jam.

6. The apparatus of claim 1, wherein the food substance is a potato-containing substance.

7. The apparatus of claim 1, wherein the food substance is a meat-containing substance.

8. The apparatus of claim 1, wherein a majority of the first liquid is water.

9. The apparatus of claim 1, wherein the first liquid is water.

10. The apparatus of claim 9, wherein the first liquid is demineralized water.

11. The apparatus of claim 1, comprising a second sleeve filled with a heatable second liquid and extending around the second tube.

12. An apparatus as claimed in claim 1, comprising cooling means which are connected to the second heating means and in which the hot food substance is provided for cooling during a third dwell time in the cooling means, the cooled food substance being discharged at the end of the cooling means for further processing.

13. The apparatus of claim 12, wherein the cooling device comprises a third tube connected to the second tube.

14. The apparatus of claim 1, wherein the material of the first tube is plastic.

15. The apparatus of claim 13, wherein the material of the first tube is PTFE.

16. The apparatus of claim 13, wherein the material of the second and/or third tube is stainless steel.

17. The apparatus of claim 13, wherein the second tube and the third tube are joined together to form a unitary tube.

18. The apparatus of claim 1, wherein the first residence time and the root mean square value of the RF voltage on the electrode can be adjusted such that the temperature of the food substance at the end of the first tube is from 70 ℃ to 100 ℃.

19. The apparatus of claim 1, wherein the first tube has an average effective inner diameter of 20 mm to 150 mm.

20. The apparatus of claim 1, wherein the electrode has a length of 0.3 meters to 3 meters.

21. The apparatus of claim 1, wherein each of the electrodes has a shape corresponding to an outer shape of the first tube.

22. The apparatus of any one of the preceding claims, wherein the internal cross-sectional shapes of the interconnected tubes are identical to each other and correspond to a desired cross-sectional shape of the final product.

23. The apparatus of claim 11, wherein the second liquid is water.

24. The apparatus of claim 23, wherein the water is demineralized.

25. The apparatus of claim 11, wherein the second liquid is oil.

26. The apparatus of claim 25, wherein the oil is hot oil.

27. The apparatus of claim 1, wherein all of the RF voltage-carrying components are contained within the housing.

28. The apparatus of claim 27, wherein the enclosure is a faraday cage.

29. The apparatus of claim 1, wherein the liquid within the first cannula is maintained at a temperature of 20 ℃ to 100 ℃.

30. The apparatus of claim 11, wherein the liquid in the second cannula is maintained at a temperature of 70 ℃ to 100 ℃.

31. The apparatus of claim 1, wherein the electrodes are connected to an associated RF energy generator via an adjustable impedance matching circuit.

32. The apparatus of claim 1, wherein the supply device is adapted to be connected to a pre-production device.

33. The apparatus of claim 32, wherein the pre-production device is a meat pump.

34. The apparatus of claim 1, wherein the frequency is 12MHz to 29 MHz.

35. The apparatus of claim 1, wherein the frequency is 27 ± 2 MHz.

36. The apparatus of claim 1, wherein the frequency is 13.5 ± 1 MHz.

37. The apparatus of claim 11, wherein the first and second sleeves are joined together to form a unitary sleeve.

38. The apparatus of claim 1, wherein a treatment section is arranged downstream of the second tube, in which treatment section the hot food substance is subjected to a post-treatment.

39. The apparatus of claim 1, wherein the first tube comprises at least two sub-tubes, each sub-tube adding two plate electrodes and an RF energy generator.

40. The apparatus of claim 39, wherein each sub-tube adds an impedance matching circuit.