Aseptic processing system

Abstract: An aseptic storage tank (1) includes a draught tube (6) into which food product enters in use. By increasing and decreasing relative pressure in the head space of the tube the contents in the tube (6) are forced into and out of the tank (1) to keep the food product therein in motion.

Description: This invention relates to aseptic processing systems and particularly to storage vessels. In aseptic food processing it is necessary for viscous food products and in particular food products containing particulate matter to be maintained in homogeneous suspension especially before filling and packaging, and also before the food product is sterilized. The food product, before filling, is conveniently stored in a vessel such as an aseptic tank. The food product is usually maintained in homogeneous suspension within an aseptic tank by mechanical agitation. This has the disadvantage that the mechanical agitation can damage the particulate matter which may thereby lose its integrity. Mechanical agitators are also inconvenient to clean. It is desirable to provide a relatively simple system and method of maintaining the food product in a storage vessel in homogeneous suspension, without damaging the food product. It has been proposed in US-A-3 450 389 to achieve mixing of rocket propellant compositions in a vessel having an internal draught tube which extends from the top of the vessel towards the base of the vessel to form two separate chambers in the vessel. The top of the draught tube is sealed to the lid of the vessel and the base of the vessel is formed with an inverted conical bottom which extends into the foot of the draught tube to form an annular gap between the foot of the draught tube and the wall of the conical bottom of the vessel. Pressure is applied alternately to each chamber to cause the contents of the vessel and draught tube to flow first from the vessel into the draught tube and then in the reverse direction. This causes intense mixing of the contents in the base of the vessel and draught tube due to a shearing action. We have now devised a form of storage vessel and auxiliary enclosure which can be used for the processing of food products, notably one containing particulate material. According to the present invention there is provided a storage vessel (1) in combination with an auxiliary enclosure in the form of a draught tube (6) in fluid flow communication with the storage vessel (1) so that in use contents in the storage vessel (1) enter the bottom of the draught tube (6), and means (11) and (13) for increasing and decreasing the pressure in the storage vessel (1) relative to the pressure in the auxiliary enclosure (6) and vice versa so as to move the contents within the auxiliary enclosure (6) away from or towards the storage vessel (1) respectively and thereby cause at least most of the contents of the storage vessel (1) to be in motion, characterised in that the base of the storage vessel (1) is provided with a cup shaped bottom (2, 3 and 4) of radius smaller than that of the storage vessel (1) and in that the open end of the auxiliary enclosure (6) extends downwardly into the space formed by the cup shaped bottom (2, 3 and 4) of the storage vessel (1). The auxiliary enclosure may be disposed within the vessel, the auxiliary enclosure having a bottom opening located close to the bottom of the vessel for communication with the contents of the vessel. The auxiliary enclosure provides a "draught tube" which is preferably sealed at one end to the top of the storage vessel with its other, open end located close to the base of the storage vessel. The draught tube is preferably located centrally within a cylindrically shaped storage vessel. The base of the storage vessel has a cup-shaped bottom of radius smaller than that of the storage vessel, with the draught tube extending into the space provided by the cup-shaped bottom. Food product is preferably introduced into and extracted from the storage vessel through apertures at the bottom of the storage vessel. The relative pressure in the head space of the storage vessel may be altered by introducing or extracting sterilized gas into the storage vessel through apertures within the head space in the form of spray balls. According to a second aspect of the present invention there is provided an aseptic processing system comprising the combination of a storage vessel and an auxiliary enclosure according to the invention. A storage vessel according to the invention will now be described, by way of example, with reference to the accompanying drawing which shows a schematic form of the storage vessel. Referring to the drawing, the storage vessel comprises a cylindrically-shaped aseptic tank 1 having a base 2 which slopes downwards towards the central axis of the tank 1 until it reaches a vertical step 3 and then it continues on the same slope as before to the central axis, so that a cup-shaped bottom 4 is formed within the tank 1. An auxiliary enclosure in the form of a draught tube 6, which is sealed to the top of the tank 1, has an open end close to the base of the tank 1 which extends into the cup-shaped bottom 4. Food product 7 containing particulate matter is introduced into the tank 1 via valve 8 in a pipe 9 connected to the base 2 of the tank 1. Spray ball 11 within the head space 12 of the draught tube 6 and spray balls 13 within the headspace 14 of the main tank 1, allow gas to be introduced into and extracted from the tank 1 and tube 6. As food product 7 is introduced into the tank 1, valve 16 is opened and valve 17 is energised to connect the common port 18 to the top tee connections 19 and the air within the container is exhausted through pressure relief valve 21. The level of the food product 7 within the tank is sensed using level transmitter 22. The pressure within the headspaces 12 and 14 are maintained at this stage at approximately four times atmospheric pressure. When the tank is filled to approximately two thirds of its capacity, valve 19 is released and valve 23 is opened so that the pressure in the headspace 12 of the draught tube 6 reduces to typically three times atmospheric pressure. This causes the food product 7 to move up within the draught tube 6 to balance the pressures within the head spaces 12 and 14 of the tank 1. The level of the food product 7 within the draught tube 6 is sensed using level transmitter 24 and when the food product reaches its highest level, just below the spray ball 11, the valve 23 is closed. At this point valve 26 is opened causing air pressurized at five times atmospheric pressure to pass through a sterilizing filter 27 into the headspace 12. As the pressure within the headspace 12 rises the food product 7 is forced downwards within the draught tube 6, and into the outer compartment of the tank 1. The level of the food product 7 within the draught tube 6 is again sensed and when it reaches its lowest level, valve 26 is closed and valve 23 is opened, and the cycle is repeated. By increasing and decreasing the pressure within the headspace 12 of the draught tube the food product 7 is kept in motion so that it tends to be maintained in homogeneous suspension. The food product 7 is extracted from the tank 1 again via valve 8, and when it reaches a certain lower level the pressure within the tank 1 is stabilized. The cup-shaped bottom 4 of the tank 1 causes the particulate matter within the food product 7 to mix thoroughly throughout the food product 7 by forcing it up into the bulk of the food product 7 when the pressure in the headspace 12 is increased. In order to clean the tank 1 cleaning fluid 28 is introduced into the system above valve 19 and forced through the spray balls 11 and 13 to clean the inner walls of the tank 1 and the walls of the draught tube 6. The mixing rate of the food product 7 can be adjusted by varying the setting of pressure relief valves 21 and 23 to either increase the rate of rise and fall of the food product 7 or to decrease its rate. By means of the described embodiment a storage vessel is provided which is particularly useful in aseptic processing systems. There is no drive shaft to a mechanical agitator which must be kept sterile, and furthermore no shadows caused by blades on a mechanical agitator exist which complicate the cleaning of such storage vessels. In particular, the particulate matter within a food product is not damaged while being maintained in homogeneous suspension. It will be appreciated that the draught tube or auxiliary enclosure is not limited to being located within the storage vessel since it may be mounted outside the storage vessel and be of any suitable shape and configuration.

Claims: A storage vessel (1) in combination with an auxiliary enclosure in the form of a draught tube (6) in fluid flow communication with the storage vessel (1) so that in use contents in the storage vessel (1) enter the bottom of the draught tube (6), and means (11) and (13) for increasing and decreasing the pressure in the storage vessel (1) relative to the pressure in the auxiliary enclosure (6) and vice versa so as to move the contents within the auxiliary enclosure (6) away from or towards the storage vessel (1) respectively and thereby cause at least most of the contents of the storage vessel (1) to be in motion, characterised in that the base of the storage vessel (1) is provided with a cup shaped bottom (2, 3 and 4) of radius smaller than that of the storage vessel (1) and in that the open end of the auxiliary enclosure (6) extends downwardly into the space formed by the cup shaped bottom (2, 3 and 4) of the storage vessel (1). A combination of a storage vessel (1) and an auxiliary enclosure (6) as claimed in claim 1, characterised in that the draught tube (6) is disposed within the storage vessel (1) and has a bottom opening located close to the base of the storage vessel (1). A combination of a storage vessel (1) and an auxiliary enclosure (6) as claimed in claim 2, characterised in that the draught tube (6) is sealed at one end to the top of the storage vessel (1). A combination of a storage vessel (1) and an auxiliary enclosure (6) as claimed in any one of the preceding claims, characterised in that the draught tube (6) is located centrally within the cylindrically shaped storage vessel (1). A combination of a storage vessel (1) and an auxiliary enclosure (6) as claimed in any one of the preceding claims, characterised in that the base of the storage vessel (1) slopes downwardly towards the central axis of the storage vessel (1) until it reaches a vertical step (3) and then continues on the same slope (4) as before to the central axis so as to form the cup shaped bottom (2, 3 and 4) in the base of the storage vessel (1). A combination of a storage vessel (1) and an auxiliary enclosure (6) as claimed in any one of the preceding claims, characterised in that apertures (9) are provided at the bottom of the storage vessel (1) for introducing food product into and extracting food product from the storage vessel (1). A combination of a storage vessel (1) and an auxiliary enclosure (6) as claimed in any one of the preceding claims, characterised in that spray balls (13, 11) are mounted in a head space (14) of the storage vessel (1) and in a head space (12) above the contents of the auxiliary enclosure (6) whereby sterilized gas may be introduced into or extracted from the storage vessel (1) and/or the draught tube (6) so as to alter the pressure within the headspace (14) within the storage vessel (1) relative to the pressure in the headspace (12) above the contents in the auxiliary enclosure (6). An aseptic system for processing food products, characterised in that it includes a combination of a storage vessel (1) and an auxiliary enclosure (6) as claimed in any one of the preceding claims. The use of an aseptic system as claimed in claim 8 for aseptically processing food products, characterised in that the food products are maintained in homogeneous suspension within the combination of a storage vessel (1) and the auxiliary enclosure (6). The use of an aseptic system as claimed in claim 9, characterised in that the food products contain particulate solids.

Inventors: SILLETT CHRISTOPHER, SILLETT, CHRISTOPHER
Applicants: APV UK, APV UK LIMITED
Application year: 1989
Main classification: B01F11
IPC codes: B01F11