WO1995023637A1

WO1995023637A1 - Plant for treatment of food products which may be pumped

Info

Publication number: WO1995023637A1
Application number: PCT/SE1995/000164
Authority: WO
Inventors: Lennart EDSÖ
Original assignee: Tetra Laval Holdings & Finance S.A.
Priority date: 1994-03-01
Filing date: 1995-02-17
Publication date: 1995-09-08
Also published as: MA23463A1; SE9400705D0; SE9400705L

Abstract

A plant for high pressure treatment/sterilization of food products which may be pumped to inactivate/reduce microorganisms and enzymes comprises a space (10) with flexible wall (9). The product is subjected in this space (10) for such a high pressure that inactivation/reduction takes place. Means (5) are arranged to convey the product to and from the said space (10). Cut off valves (7, 8) are arranged at the inlet to and the outlet from the said space. According to the invention the plant comprises a number of elongate tubes (2, 3) each connected to a distribution and a collection chamber, which tubes all contain a treatment space (10) within the tube (2, 3). In the treatment space (10) the product is separated from a second space (14) in the tube (2) by a flexible wall (9). The second space (14) is connected with means (11, 12) arranged to pressurize this second space (14) firstly when said means (5) for conveying the product has delivered product to the space (10) and the cut off valves (7, 8) are closed. The space (10) and at that also the product is pressurized to a predetermined pressure during a predetermined time. Said means (11, 12) are then arranged to reduce the pressure to normal pressure. The means (5) for conveying product are arranged to press treated product out from the treatment space (10) by means of not yet treated product.

Description

Plant for treatment of food products which may be pumped

The present invention relates to a plant for high pres¬ sure treatment/sterilization of food products which may be pumped in order to inactivate/reduce microorganisms and enzymes. The plant comprises a space with a flexible wall in which the product is subjected to such a high pressure that inactivation/reduction takes place and means to convey the product to and from the said space. At the inlet to and at the outlet from said space there are arranged cut off valves.

A plant of this kind is described in DE 42 42 311. This publication gives a detailed description of the relatively new technique for sterilization by applying high pressure. In the introduction to the said patent application there are examples of earlier arrangements to treat a liquid material with a high pressure. Here it is shown (fig. 5 A) an arrangement where a piston is pressed against a product in a chamber. As may be seen in the description there are problems both with the hygiene and saftety when using such an arrangement, where the piston is in direct contact with the product.

A further arrangement is shown in fig 5 B. In this a movable piston is actuated by medium with a high pressure on one of its sides, which pressure is transmitted to a treatment chamber where the product which is to be treated is situated. Neither here hygienic problems may be avoided since the piston and its gasket are not separated from the food product which is to be treated.

A further arrangement for sterilization is shown in fig 5 C in the German patent application mentioned above. This arrangement comprises a chamber in which there is a receptacle of flexible material. The product which is to be treated is pumped to the receptacle. Pressure medium is fed to a space between the walls of the chamber and the flexible receptacle in order to affect the product in the flexible receptacle. The product is then pressed out from the receptacle by means of sterile gas. In this arrangement there are no sliding pistons which may contaminate the product which is to be treated. On the other hand there is a risk that product will remain in the bottom of the flexible receptacle.

According to DE 42 42 311 there is suggested an arrangement which shall avoid the problems described above. This arrangement comprises a cylindrical pressure vessel with open upper and lower ends. The vessel has upper and lower delimiting parts provided with channels for delivery of product, pressure media and sterile gas. Within the pressure vessel there is clamped a cylindrical tube of flexible material which divides the inner of the pressure vessel into a treatment chamber and a pressure chamber. Product is delivered to the treatment chamber by way of a delivery channel in the bottom of the chamber. Treated product is forced out from the chamber through a channel in the bottom part by means of sterile gas. Cleaning of the arrangement may take place by spraying cleaning liquid into the chamber or by disassembly of the arrangement.

According to the invention there is now proposed a plant for treatment of food products which may be pumped, which shows some similarities to the arrangements which are described in DE 42 42 311 but which offers possibility for a higher capacity and probably also lower production costs than the described arrangements. In the description of DE 42 42 311 one has only incidentally commented on the problems which prevail during the time when the arrangement is pressurized. During this time the high pressure not only affects the product in the flexible space but also the upper and lower detachable parts which form the bottom and cap in the treatment chamber. In the description to DE 42 42 311 it is said that the parts are kept in place by pressure bodies or other clamping means.

The present invention is mainly characterized in that the plant comprises a number of elongate tubes, each connected in one of its ends to a distribution chamber and in its other end to a collection chamber. All tubes contain a treatment space within the tube. The product is separated from a second space in the tube by a flex¬ ible wall. This second space in the tube is connected to means arranged to pressurize this space firstly when said means for conveying product has delivered product in such an amount that the treatment chamber is filled with product and the passages to and from this space has been closed by means of the cut off valves, after which the second space and consequently also the product is pressurized to a predetermined pressure during a predetermined time. After this time the pressure is relieved to normal pressure. The said means for conveying the product are arranged to force treated product out from the treatment chamber by means of not yet treated product.

The plant according to the invention is with advantage arranged in such a way that the treatment space is arranged to be surrounded by a flexible wall while the second space consists of an annular channel between the flexible wall and the inner wall of the tube. Alternatively the treatment chamber may be arranged in one half of the tube while the second space is arranged in the other half of the tube. The flexible wall then separates the both halves of the tube from each other.

The choice between these two embodiments of the plant according to the invention depends on the possibility to select material for the tube and the flexible wall.

Depending on the desired pressure conditions and the qualities of the product which is to be treated stain¬ less steel, polymers approved for food or some extruded polymer material may be of interest. If the tube is designed with two halves separated by a flexible wall an extruded polymer may be used. The pressure is in such a case absorbed by a surrounding outer tube of pressure steel.

The plant according to the invention is suitably designed such that the means for conveying product to the tubes is arranged to convey product to a certain number of tubes, at which the treated product simultaneously is pressed out from the tubes. At the same time another number of tubes are arranged to be connected to the means which pressurize the second space in the tubes. Depending on the desired treatment time two or more cycles of treatment steps may proceed simultaneously. With such an arrangement there is obtained with a suitable choice of cycles a continuos flow of treated product delivered from the plant in spite of the fact that the high pressure treatment is carried through as a batch process.

The plant is with advantage arranged such that the means which pressurizes the second space in each tube consists of a high pressure pump and/or a store of medium with a high pressure. The high pressure medium which during a certain time has actuated the product in a certain number of tubes is after finished treatment conveyed to another number of tubes in order to pressurize the second space and at that also the product in these tubes. With such an arrangement the supplied pressure energy is used maximally. After a certain period it may be suitable to collect the high pressure media in order to adjust the temperature of the same. Depending on the product this may mean a cooling or a heating. This collection may take place directly after every pressu- rization or after a certain number of pressurizations.

The plant according to the invention is with advantage built up of steel tubes with an inner diameter of 25-80 mm and with a length of 4-12 m.

The flexible wall in the tubes consists suitably of a material which is approved for food such as a polymer or of a thin flexible steel membrane.

In order to obtain the desired inactivation of micro¬ organisms and enzymes the product is pressurized by means of water with a pressure of at least 4000 bar during the time needed for the product. Depending on the type of product the treatment time may vary from some seconds up to some or severals minutes.

The plant according to the invention is described further with reference to the attached drawing, fig. 1 of which shows a schematical representation of an embo¬ diment of the plant. In order to make the figure more clear there are only shown two tubes in the drawing. In practice a number of tubes may be used to increase the capacity of the plant.

In fig. 2 there is shown an inlet part of a tube in fig 1.

A plant 1 comprising two tubes 2,3 is supplied with the product 4 which is to be treated in the plant. The product is fed by way of a feeding pump 5 and a tube 6 to the tube 2, the cut off valve 7 of which is opened and untreated product presses treated product through the cut off valve 8 in the other end of the tube. In the tube 2 there is a hose 9 of a flexible material which delimits a space 10. When the product has filled the space in the hose the valve 7 is closed and a high pressure pump 11 feeds high pressure medium to an annular space 14 outside the flexible hose 9 by way of the three way valve 12 and the pipe 13. When the desired pressure during a predetermined time has been obtained the valve 12 is switched over. While the product is pressure treated in the tube 2 the hose 16 in the tube 3 has been filled with product by the feeding pump 5. When the product in the tube 2 has been exposed for the desired pressure during a predetermined time the valve 15 is opened and high pressure medium is allowed to flow into the space 17 in the tube 3. Through the valve 12 there is delivered the needed amount of additional medium with a high pressure from the pump 11. The valve 8 in the outlet end of the tube 2 is opened when the pressure in the space 14 has been reduced. At the same time the valve 7 is opened and not yet treated product presses the treated product to a connection conduit 18. In order to ensure that not treated product is not allowed to pass the tube untreated the valve 8 is closed already before the mixing zone of treated and not treated product has reached the outlet out of the tube 9. The amount of product which is pumped to the tubes is controlled by means of a flow meter 19.

In fig 2 there is shown the inlet part to the tube 2 or 3. The product is pumped into the tube through the opening 20 by way of a valve which is built into a valve plate 21. The valve shall close the connection between the tube and may consist of a high pressure valve. In the tube 2 which for example may consist of a steel tube wi-ch an outer diameter of 250 mm and an inner of 80 there is a hose 9 of rubber (uretan or silicone). The inlet 22 for high pressure medium leads to the space 14 between the hose 9 and the tube 2.

Claims

1. Plant for high pressure treatment/sterilization of food products which may be pumped to inactivate/reduce microorganisms and enzymes comprising a space with a flexible wall (9), in which the product is subjected to such a high pressure that inactivation/reduction takes place and means (5) to convey the product to and from the said space, at which cut off valves (7,8) are arranged at the inlet to and the outlet from the said space, c h a r a c t e r i z e d i n a number of elongate tubes (2,3) each connected to a distribution and a collection chamber, which tubes all contain a treatment space (10) within the tube, in which treatment space the product is separated from a second space (14) in the tube by means of a flexible wall (9 ) , which said second space (14) is connected to means (11,12) arranged to pressurize this second space firstly when said means ( 5) for conveying the product has delivered product to the treatment space (10) and the cut off valves (7,8) has been closed, after which the space (10) and at that also the product is pressurized to a predetermined pressure during a predetermined time and that the said means (11,12) then are arranged to reduce the pressure to normal pressure and in that said means (5) for conveying the product are arranged to press treated product out from the treatment space by means of not yeat treated product.

2. Plant according to claim 1, c h a r a c t e ¬ r i z e i n that the treatment space (10) is arranged to be surrounded by a flexible wall (9 ) while the second space (14) consists of an annular channel between the flexible wall (9 ) and the inner wall of the tube.

3. Plant according to claim 1, c h a r a c t e ¬ r i z e d i n that the treatment space is arranged in one half of the tube while the other space is arranged in the second half of the tube, at which the flexible wall separates the two halves of the tube from each other.

4. Plant according to claim 1, c h a r a c t e ¬ r i z e d i n that the said means ( 5) for conveying product to the tubes (2,3) is arranged to convey product to a certain number of tubes, at which at the same time treated product is pressed out from the tubes, while another number of tubes are arranged to be connected to the means which pressurize the second space in the tubes, which makes it possible to obtain a continuous flow of treated product out from the plant in spite of the fact that the high pressure treatment is carried out as a batch process.

5. Plant according to claim 1, c h a r a c t e r i ¬ z e d i n that the means which pressurize the second space in each tube consists of a high pressure pump (11) and/or a store of medium with high pressure, at which conduits are arranged to convey high pressure media which during a certain time has actuated the product in a certain number of tubes to another number of tubes in order to pressurize the second space and at that the product in these tubes, at which a part of the pressure energy is recovered.

6. Plant according to claim 5, c h a r a c t e r i z e d i n that the high pressure medium after a certain time is collected in a collection vessel for adjustment to a desired temperature.

7. Plant according to claim 1, c h a r a c t e r i ¬ z e d i n that the tubes consist of steel tubes (2,3) with an inner diameter of 25-80 mm and with a length of 4-12 m.

8. Plant according to claim 1, c h a r a c t e r i ¬ z e d i n that the flexible wall (9) which separates the treatment chamber in the tubes consists of a material approved for food as a polymer or of a thin flexible steel membrane.

9. Plant according to claim 5, c h a r a c t e r i ¬ z e d i n that the media has a pressure of at least 4000 bar and the product is subjected to the high pressure during the time which is needed for the product.