Technical Field of the Invention

The present invention relates to a method for determining contamination of a production system for sterile liquid food products according to the preamble of claim 1. The invention further relates to a system for production of sterilised liquid food products according to the preamble of claim 7, and to a sampling device for aseptic sampling of a liquid food product flowing in a flow pipe according to the preamble of claim 12. Background Art

In a system for producing packages of a commercially sterilised liquid food product, such as UHT-milk, it is important to check the sterile properties of the product. This is presently often performed by taking out a large amount of packages (50-100 sample packages per day) of liquid food product and analysing the contents in order to determine whether or not contamination has occurred somewhere in the system. It is necessary to take out quite a large number of packages, since with low, but still unacceptable, contamination levels, a large volume of sampled liquid is required, in order to be able to detect contamination with good statistic reliability.

Another way of providing samples for testing is to take out samples from the liquid before it has been packaged, i.e. to connect some sort of device for taking out an amount of liquid from the system. A device for withdrawal of a medium from a container is described in WO 97/16715. Using this device a number of relatively small liquid samples can be taken out from a container. However, in the production of a commercially sterile liquid food product, such as UHT milk, on some occasions, there is a need for taking out quite large samples. Summary of the Invention

The subject of the present invention is to provide a method and a device for taking out liquid samples from a

system for producing a commercially sterile liquid food product, with which device it is possible to take out both small amounts and large amounts of liquid food product for testing. This subject is achieved by a method for determining contamination of a production system for commercially sterile liquid food products, said system having at least one flow pipe, through which the liquid food product flows, comprising the steps of arranging a sampling device in an opening in wall of the at least one flow pipe, said sampling device comprising a chamber and a tube which in its one end is connected to a needle-like nozzle and in its other end is connected to a collecting means, such as a bag, for collecting sampled liquid, the chamber having a elasti- cally deformable, penetrable wall which is sealingly arranged in the opening, inserting the nozzle into the flow pipe through the chamber and through the , elastically deformable, penetrable wall, passing liquid from the flow pipe to the collecting means through the needle-like nozzle and the tube, when the amount of sampled liquid in the collecting means has reached a predetermined value, performing an analysis of the contamination of the sampled liquid collected in the collecting means, based on the result of the analysis, determining whether food products produced during the time period that liquid was passed to the bag are contaminated or not.

A peristaltic pump can be used for passing the liquid through the tube. This makes it possible to adjust the flow rate of liquid through the tube in an easy and efficient manner. The production system can comprise a number of flow pipes and a number of sampling devices can be arranged in openings in walls of the flow pipes.

The production system further can comprise a number of packaging devices for packaging the liquid food product and the step of arranging the sampling devices in openings in walls of flow pipes can comprise arranging a respective sampling device upstream each packaging device.

This gives the advantage that a source of contamination can be easily located.

The method can further comprise the step of filling the chamber/s with a sterilising fluid, such as alcohol or hot steam, prior to the step of inserting the nozzle. This improves the sterile properties of the nozzle and protects against the effects of leakage from the conduit.

The tube can be flexible and the passing of liquid through the tube be stopped when the amount of liquid in the collecting means has reached a predetermined level, by pressing together the tube in a stop means between an abutment and a lever, on which lever the collecting means are arranged and which abuts the tube and presses it against the abutment when the amount of liquid in the collecting means has reached the predetermined level. This makes it possible to stop the sampling automatically.

Brief Description of the Drawings The present invention will now be described in more detail by way of an embodiment, reference being made to the accompanying drawing, in which

Fig. 1 is a schematic representation of a system for production of UHT-milk. Fig. 2 shows a sampling device according to the invention.

Fig. 3 is a detailed, partially sectional view of the sampling device connected to a conduit.

Fig. 4 shows a lever arrangement for a tube in the sampling system.

Detailed Description of Preferred Embodiments of the Invention

An exemplifying embodiment of a system for production of a liquid, commercially sterile, food product, for instance UHT treated liquid product, such as milk (UHT- milk) or fruit juice, is shown in Fig. 1. UHT stands for Ultra High Temperature and UHT treatment is a well known method for making a food product commercially sterile.

In the system 1, the liquid first goes through a UHT process (sterilisation), denoted 2. Thereafter it enters an aseptic tank 3 via a flow pipe or conduit 4a. From the tank 3 the liquid is passed to three packaging devices 5a-c, via the conduits 4b and 4c.

The packaging devices 5a and 5b are connected in a so-called series arrangement, which means that a valve arrangement (not shown) distributes an appropriate amount of liquid to the first packaging device 5a, which produces packages filled with the liquid at a certain rate and then passes the liquid which is not distributed to this device to the second packaging device 5b, which also produces packages at a certain rate.

A conduit 4d is arranged to recirculate the liquid, which has passed both the packaging devices 5a and 5b, without having been distributed to any of them, back to the aseptic tank. This arrangement is normally used when producing a UHT-treated fruit juice. It is especially useful when one of the packaging devices is not functioning properly and therefore is not able to handle as much liquid as it normally does. The packaging device 5c is instead connected to a "dead end", which means that the liquid which is not handled by the packaging device 5c is not recirculated. Instead it is discarded. This is normally the case when producing UHT-milk. Three sampling devices 6a, βb and 6c are connected to the conduits 4a-c in various positions for taking out samples of liquid for analysis of the microbial content.

The sampling device 4a is connected to the conduit 4a for taking samples of the liquid after it has gone through the UHT-treatment, but before it enters the aseptic bath. The sampling device 4b is connected to the conduit 4b to sample the liquid after it has left the aseptic tank 3, but before it has entered any of the packaging devices 5a-c.

Finally, the sampling device 4c is connected to the conduit 4c, at a location between the two series connected packaging devices 5a and 5b, for taking out samples of the liquid right before it enters the packaging device 5b.

The source of contamination can be easily located with this arrangement of sampling devices at different sampling points in the production system.

The fact that a sampling device is connected to the conduit right before each packaging device means that it is possible to determine if the liquid going into a packaging device is sterile or not. This means that the only source of contamination left is the packaging device itself. If the contamination occurs that close to the actual packaging, it will be present in such large concentration in the packages taken out that substan- tially fewer packages need to be taken out for testing.

A sampling device 6, which could be any of the sampling devices 6a-c, is shown in Figs 2-4. The sampling device β comprises a hose or flexible tube 7 which in one end is connected to a bag 8 for collecting sampled liquid and in the other end to a needle-like nozzle 9, which is shown in Fig. 3. The tube, the bag and the connections between the tube and the bag, and the tube and the nozzle, respectively, all are aseptic.

As can be seen in Fig. 3, the needle-like nozzle 9 is inserted from a chamber 10 into a flow pipe or conduit 4 through a membrane in the form of a elastically defor-

mable, penetrable wall 11. The wall 11 is sealingly arranged in an opening 12 in the conduit 4.

The sampling device may be retro fitted to an existing production system by exchanging part of a conduit for a conduit portion with a sampling device according to the invention where a wall 11 is sealingly arranged in an opening in a wall of the conduit portion.

The sampling device may also be arranged in an existing opening, wherein the wall 11 of course must be designed so that it fits accurately in the existing opening. Such an opening may for instance be a manometer opening, which when not in use is sealed by a blind plug.

The wall 11 is self-sealing, so that is closes the hole made by the nozzle 9, if the end portion 9a of the needle-like nozzle 9 is pulled out of the conduit 4 through the wall and into the chamber.

The chamber 10 can be filled with hot steam, which is supplied to the chamber from a steam generator (not shown) , or sterilizing gas, in order to minimise the risk that any living microorganisms are present in the chamber and can enter the conduit 4 together with the nozzle end 9a as it is passed from the chamber 10 through the wall 11 and into the conduit 4.

As an alternative, the chamber can be filled with another sterilising agent such as alcohol. The fact that the chamber 10 is filled with a sterilising agent also offers protection against the effects of a possible leakage from the conduit 4 or the nozzle 9.

Some of liquid flowing in the conduit 4 is passed through the needle-like nozzle 9 and via the tube 7 to the bag 8, either by itself as the flowing liquid in the conduit 4 forces liquid into the nozzle, or by a peristaltic pump 13. The peristaltic pump is used to adjust the volume flow rate of liquid through the tube to the bag from the conduit. As an alternative, a throttle valve (not shown) could be arranged on the tube to adjust the volume flow rate to the bag 8 from the conduit 4.

When the production system is started up, a large sample of several litres of liquid is needed for analysis, as is well known to the person skilled in the art. This is easily to obtained by adjusting the speed of the peristaltic pump or opening the throttle valve fully and thereby rapidly filling the bag.

When the system is past the start-up phase, the sampling device according to the invention is instead used to continuously take out a small amount of liquid from the system at each sampling point. This is accomplished by slowing down the peristaltic pump or restricting the flow through the throttle valve and only allowing a small volume flow rate through the tube.

The sampling device can then be arranged to con- tinuously take out a liquid sample during a whole day. Thereby it can be verified that no contamination has occurred in the system before a specific sample point that day. If all sampling points are clear during a whole day, the only contamination source left is the respective packaging device, the testing of which is described above.

As can be seen in Fig. 4, the hose or flexible tube 7 is according to a preferred embodiment arranged in a stop means 14 between an abutment 15 and a lever 16. In Fig. 4, the lever 16 held by a holding device 17 in a position to the left of a pivot 18. The holding device biases the lever in a direction away from the abutment 15, for instance by means of a spring.

The lever is balanced on the pivot 18, and the bag 7 rests on the lever 16 on the lever portion to the right of the pivot 18. When so much liquid has entered the bag that the force exerted by the weight of the bag 8 with contents has reached a certain magnitude, the holding device releases the lever, and the stop means then closes so that the flexible tube 7 is pressed together between the abutment 15 and the lever 16 and the flow of liquid through the tube 7 from the conduit 4 is stopped.

This lever and stop means arrangement could, as is apparent to a person skilled in the art, be accomplished in a number of different ways with the same result, i.e. that the liquid flow through the tube is stopped when the amount of liquid in the bag has reached a certain weight.

A testing equipment for performing a microbiological analysis of the content of a bag can be aseptically connected to one or more of the bags in the sampling devices. It can be arranged to take out samples of liquid from the bag in a continuous or intermittent manner.

Alternatively, a bag can be disconnected from the tube when it is filled with a desired amount of liquid and be taken away for testing by the testing equipment.

Finally, it should be noted that the liquid flowing through the conduit 4, and then into the nozzle 9, to be collected in the bag 8, can contain particles of different sizes, such as is the case for a fruit juice containing pulp.