Patent Publication Number: US-5896727-A

Title: Method and apparatus for removing and displacing package headspace sterilized air

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to process and apparatus for aseptically filling a package with a product under an atomosphere of sterile air containing oxygen and for removing and displacing the sterile air from the headspace of the filled package with nitrogen and for sealing the package so that the sealed, filled package headspace contains the nitrogen. 
     In the field of aseptic filling using certain types of machines, it is not possible to fill a package and seal it without leaving in it a small volume of gas, called headspace gas. As systems are normally used with sterile air, this headspace contains about 20% of oxygen. The presence of oxygen has a negative effect in the sense that, during preservation of the product contained in the package, it frequently happens that the product is sensitive to oxygen, which thus leads to degradation of its taste and/or of certain ingredients, such as vitamins and mineral salts. This phenomenon is unacceptable for the consumer, or for food legislation reasons. 
     One solution for reducing headspace air involves replacing the air with steam just before sealing. However, the drawback of this system is that the steam condenses on cold surfaces, the consequence being unacceptable risk of infection for neutral or slightly acidic products. A second solution consists in reducing the headspace by means of mechanical elements pressing the package, but it is not possible to remove the headspace air completely. German Patent Application Publication No. 31 08 817 also relates to a device enabling oxygen to be removed from the headspace of a package. In this device, the nozzle enabling the nitrogen to be injected is fastened to one of the sealing elements, thereby decreasing the efficiency of the nitrogen supplied since the nozzle moves and the stream of nitrogen changes direction. U.S. Pat. No. 4,934,127 and European Patent Application Publication No. 0 479 037 also relate to devices for removing the oxygen from the headspace of a package. The drawback of these devices is that the sealing of the package takes place downstream of the nitrogen injection station, this having the effect of allowing the quantity of nitrogen introduced beforehand to be distributed. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to develop a method which makes it possible to remove, in an efficient manner, the sterile air containing oxygen from the headspace of an aseptically filled package. &#34;Remove&#34; is meant to mean the fact of achieving a very low oxygen content in the headspace, namely about 2%, or even less. 
     According to the method of the invention, sterile nitrogen is ejected from a nozzle, which is fixed and placed between two movable package sealing elements which are moved together for sealing, and injected into the headspace for removing and displacing the sterile air with the nitrogen. 
     The method comprises aseptically filling a package having two movable sealing elements about a package opening with a product under an atmosphere of sterile air, wherein sterile air is present within a package headspace, and at room temperature and atmospheric pressure, injecting sterile nitrogen from a fixed nozzle, wherein the nozzle is positioned above the package opening between the movable sealing elements, into the package opening and headspace and moving the package sealing elements to seal the elements and the package. 
     The invention further provides apparatus for implementing the method wherein the apparatus comprises compartments wherein a package having two movable sealing elements us filled with a product wherein the sealing elements are sealed to seal the package and comprises a transporter device for conveying the package into and through the compartments and wherein the compartment in which the package is sealed includes a fixed nozzle positioned for injecting sterile nitrogen between the movable sealing elements into the package headspace. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the context of the present invention, the method is carried out and the apparatus provides for an aseptic filling mode wherein the air and nitrogen employed are pre-sterilized. In the apparatus of the invention, the transporter system is a stepped-advance system which provides for achieving a conventional filling rate, and the package used may be of any type provided that, when filled, its upper part is sealable. 
     The product which fills the package may be of any liquid type in the food field, for example a milk-based, fruit-juice-based or water-based product, and may furthermore contain a portion comprising separate pieces. Most particularly, oxygen-sensitive and slightly acidic products, such as dietetic products containing vitamins and mineral salts, are preferred. The object is to obtain products which have a long preservation time and in which there is no degradation of the taste and/or of certain ingredients during storage. 
     The method is implemented on a conventional industrial manufacturing line in which there are, especially, a filling compartment and a sealing compartment, and according to the invention, it is necessary to add a nitrogen injection step in the sealing compartment. 
     The filling and sealing compartments are subjected to a stream of sterile air so as to create turbulent conditions therein, and the rate of injection of the nitrogen is greater than the rate of injection of sterile air. In order to achieve a headspace having an oxygen content of less than 2%, it is necessary to work with a nitrogen flow rate per line of between 100 and 800 l/min at atmospheric pressure. 
     The duration of nitrogen injection per package is about one second. This rapid nitrogen injection makes it possible to be sparing with the quantity of nitrogen and limits the length of the production line. It is equally possible to operate with a continuous nitrogen supply as with a discontinuous nitrogen supply. 
     The efficacy of removal of the residual air from the headspace is improved by means of a specific arrangement of the supply of the nitrogen stream, that being wherein the nitrogen is supplied from the top at an angle of between 40 and 50° with respect to the vertical and with a flow counter to the direction of movement of the packages. 
     Further in the apparatus of the invention, placed in the nitrogen supply nozzle are a distributor and additional means, such as one or more metal plates, which enable uniform flows at the outlet of the nozzle to be obtained. 
     It is also necessary that the flow of nitrogen be supplied over a sufficient width in order to displace the residual air in the headspace properly, and provision is made for the nozzle to have a width greater than the width of the opening in the package. 
     The rest of the description is given with reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 illustrates apparatus according to the invention in the nitrogen-injection step. 
     FIG. 2 illustrates the same apparatus as FIG. 1 at a time when the sealing device seals a package. 
    
    
     DETAILED DESCRIPTION OF THE DRAWING FIGURES 
     As illustrated in FIG. 1, packages 1 are supplied by the transporter device 2 in the direction of the arrows 3 into the aseptic filling compartment 4 and then into the sealing compartment 5. Sterile air is injected into the two aforementioned compartments, respectively, via the pipes 6 and 7. The product 8 is supplied via the filling system 9 and is metered into the package 1 by means of the filling nozzle 10. The sealing compartment 5 comprises the fixed nitrogen injection nozzle 11, the nitrogen being supplied via the pipe 12, and comprises the two sealing elements 13, 14. 
     The aseptic filling compartment 4 and the sealing compartment 5 include openings 15, 16 and 17 through which the packages 1 on the transporter device 2 may pass. 
     In operation, package 1 is positioned by the transporter device, which has a stepped-advance system, under the filling nozzle 10, which then delivers the metered quantity of product 8. The compartment is permanently under an atmosphere of sterile air. Next, the transporter device positions the other packages under the nozzle 10, and the filled packages are supplied into the sealing compartment 5 and pass under the nitrogen injection nozzle 11 which, as illustrated, is positioned, with reference to a vertical perpendicular to the horizontal package transport on transporter 2, to direct the nitrogen gas into the package headspace at an angle to the vertical perpendicular and counter to the direction of package transport. The nitrogen flow rate is 300 l/min, and the sealing compartment is under an atmosphere of sterile air. The operation of sealing with the elements 13 and 14 is illustrated in FIG. 2 which, as compared with FIG. 1, shows the sealing elements after they have been moved together to seal the package, and after sealing, the transporter device 2 delivers the packages ready for use or for storage. 
     According to the invention, packages are obtained which may be stored for at least 6 months, without any degradation in the quality and taste of the product. Furthermore, vitamins and mineral salts are preserved, and in the example above, an oxygen content of 1% in the headspace is achieved.