FI71909C - Method of sterilizing packaging material. - Google Patents

Description

1 71909

Method for sterilizing packaging material

The invention relates to a method for sterilizing packaging materials, in particular containers of liquid filler preformed from preforms, with the features according to the preamble of claim 1.

Sterilization of various materials with superheated steam has long been known. However, efficient disinfection by superheated steam sterilization is possible in the packaging material, whether in the form of webs, e.g. due to sterilization times of the order of magnitude, only using temperatures in the range of about 125-150 ° C. This means that sterilization must be carried out at an elevated pressure of the order of 2.4 to 5 bar. But this increases the cost of sterilization significantly, because the sterilization device through which the packaging material must be passed must be sealed against the environment and must be designed for high pressure. In addition, high temperatures put undue strain on the material.

In order to be able to lower the temperatures necessary for sterilization in steam sterilization, a method such as that mentioned in the introduction, in which water vapor is acidified, has already been proposed (cf. GB 10 83 700). Also in this known method, the steam temperature required for sterilization cannot be reduced with an exposure time of about six seconds when using steam saturated below 118 ° C, so it must also be operated with an overpressure of water vapor of about two bars.

Furthermore, a method for sterilizing a packaging material (CH patent publication 361 636) is already known, according to which a two-step procedure is followed, namely 2 71909, in which a liquid bactericidal agent is first applied to the surface of the packaging material and then heated. However, according to this known method, on the other hand, special potent chemicals, such as hydrogen peroxide, formaldehyde or sodium hypochlorite, are used as bactericides, with the known disadvantage that all possible residues of these substances must be carefully removed from the packaging material. Moreover, in the framework of this known two-step method, the treatment can be performed in a few seconds only when the heating takes place by means of thermal radiation, whereby the temperature in the space between the web of material to be sterilized and the radiator is still 280 ° C. In contrast, within the framework of this known sterilization method, the idea arises of using steam as a heat carrier for heating, but still in a one-step procedure, in which case the steam also contains a bactericidal substance which is applied to the material web by means of steam.

Furthermore, it is already known to use an organic acid, e.g. formic acid and acetic acid, for sterilization in connection with preservation (cf. "Sterilization-Disinfection-Conservation-Chemotherapy" KH Wallhäusser, Georg Thieme-Verlag, Stuttgart 1967, pages 158). 180). The duration of the treatment in this known sterilization method is of the order of at least 15 minutes, so its application to the sterilization of the packaging material in a few seconds is not recommended.

Finally, it is known to perform sterilization of the packaging material with a gaseous bactericidal agent, e.g.

With a mixture of 30 hydrochloric acid in the vapor space, and water vapor at atmospheric pressure (U.S. Patent 3,139,323). However, even according to this known method, sufficient sterilization is achieved only if a waiting time of about 30 se-35 seconds follows after blowing the sterilant for about 20 seconds, so that a total sterilization time of about 50 seconds is required. However, this is too long a time for n 3 71909 mechanized sterilization, e.g. within the filling and packaging method. Although the exposure time can be reduced to about 10 seconds by preheating the packaging material to 60 ° C, preheating means additional equipment cost.

The object of the invention is therefore to provide a method as mentioned in the preamble of claim 1, by means of which the packaging material can be properly sterilized within a correspondingly short processing time, but the work can take place at atmospheric pressure.

According to the invention, this is achieved by a method according to the feature of claim 1.

The method according to the invention utilizes both the sterilizing effect obtained by using an organic acid as a sterilizing agent and the sterilizing effect obtained by subsequent steam heating. In this case, it has surprisingly been found that the pre-application of the acid weakens the resistance of the microorganisms to the subsequent heat treatment in which the steam and the acid act partly simultaneously, partly in succession, so much that it is possible to work with normal pressure saturated steam.

The acid is either sprayed or dusted in finely divided form on the surface of the packaging material to be treated, for example on the inner walls of the container, so as to form a thin film of liquid on this surface. But it is also possible for the acid to be dropped or poured on the surface to form an acid layer. It is also conceivable to use both measures together, for example when the vertical container is dusted at the same time so that the side walls are moistened at the same time, but acid is added dropwise so that an acid layer forms on the base and its corners and corners.

In order for the immediate superheated steam treatment to sterilize and remove the acid at the same time, it is expedient to use volatile acids in the water vapor which the water vapor poses with. It is particularly advantageous to work with acids which are contained in the fillers subsequently received by the packaging material or which are close relatives of these acids. This is the case, for example, when the filler is 5 milk or fruit juices, lactic acid and the corresponding nutrient acids. This avoids traces of the acid used for sterilization, which under certain conditions still remain in the packaging material and interfere with the filler as foreign substances.

The efficiency of the method can be further increased by either heating the acid before application to the surface to be sterilized, so that the heat contained in the steam causes a very rapid rise in temperature of both the acid and the surface to be treated, or by heating the surface itself with, for example, superheated steam.

According to another development of the method according to the invention, the treatment with the flowing hot air can be followed by the treatment with the flowing hot air.

The method according to the invention can be used naturally for the treatment of both continuously flowing web-like packaging material and also for already completed containers, for example folding containers made of cardboard blanks. For the latter, the already mentioned combined treatment is expedient, in which the acid is applied by spraying or dusting by means of nozzles into a thin film of acid on the walls, but at the same time a thin layer of acid is developed by dripping onto the bottom of the container.

30 Hot steam is then blown in, which vaporizes both the acid film and the acid layer at the bottom of the tank and causes heat treatment of the walls and bottom due to heat transfer.

But the method can also be carried out in such a way that only said acid layer is formed by dropping a layer on the bottom of the tank from which the volatile acid

II

The hot steam flowing in 5 71 90 9 enriches and still causes sufficient sterilization when sideways the side walls. In this procedure, it is expedient to ensure by means of a suitable device, for example a submersible pipe, that the hot steam is blown immediately into the acid layer at the bottom of the tank, so that the steam, when enriched and forced out of the tank, wipes out the side walls.

The spraying of the acid can take place with conventional spray nozzles which operate with compressed air or hot pressurized steam and which produce a fine mist and a consequent, uniform uniform wetting film on the surfaces to be sterilized. At the same time, when dusting with steam, the dusting material assumes part of the operation of the sterilization method. The acid is then partially vaporous. Preferred organic acids are formic acid, acetic acid, malic acid, citric acid, lactic acid and ascorbic acid.

The invention will be explained in the accompanying drawing by means of a fully schematic example-20 example.

The drawing schematically shows, for example, the transport distance of the milk packaging container inside the filling device. The filling device is not shown in more detail, as it may be of a known species, except for the order of the acid or superheated and hot steam supply devices described below. The same applies to a container-moving conveying device, such as a cell chain, and to the arrangement of its conveying distance within a sterilization air zone, as is usually the case in aseptic filling.

The containers 1, which are, for example, folded containers made of plastic-laminated cardboard, are moved in a step by means of a conveying device 2, for example a cell chain, from left to right so that they are successively positioned in the positions shown in the drawing. The clock time is, for example, 35 seconds. The volume of tank 1 is one liter.

At the preheating station I, hot air with a temperature of about 200 ° C is blown into the tank 1 therein. Thus, the inner surfaces of the tank are preheated to a temperature of about 50-70 ° C. At the next acid spray station II, an acid mist is generated inside the tank by means of a compressed air spray nozzle 3, which forms a fine, substantially continuous settling on the inner walls, including the bottom of the tank, so that the walls and bottom have an acid film. 90% lactic acid is used as the acid and the amount injected is 0.5 ml in the indicated volume of tank 1-10.

Thereafter, the next sterilization station III comprises, in the example, three synchronous stations in which atmospheric steam saturated with the respective steam lines 4, i.e. steam with a maximum temperature of 15,100 ° C, is blown into the tank. In this case, the acid film in the walls of the tank and the walls of the tank itself heat up to a suitable temperature. The microorganisms in them are killed partly by the action of the hot acid and partly by the subsequent steam treatment. By selecting a certain number of positions II and III 20 in the transport chain, which in this case can be changed, the effect of acid and steam can be changed.

Sterilization station III is followed by post-treatment station IV, where hot air at a temperature of 200 ° C is again blown in with suitable nozzles. The post-treatment lyase station IV comprises, for example, two synchronous locations, so that all the acid and water vapor residues leave the inside of the tank.

At the filling station V, the container 1 is filled with a filler, for example milk, and the upper end of the container is hermetically sealed at the sealing station VI.

The amount of steam passed through the sterilization station III is dimensioned so that the air contained in the tank protrudes approximately completely. Due to the holding time of the tank 1 at the sterilization station III, the exposure time of the steam 35 is about six seconds. Generally, an exposure time of 3 to 10 seconds is appropriate.

Il 7 71 909 At the after-treatment station IV, where hot air is blown into the tank, the wall surfaces of the tank must be free of all acid and steam condensers. However, since when the filler is milk, lactic acid is used, i.e. part of the filler's cognate acid, it does not cause damage if, after sterilization at station III, there may be minor traces of lactic acid inside the container. These traces are too small to cause coagulation or a change in the pH of the milk.

10 As mentioned, the lactic acid concentration is condensed to 90%. In general, the highest possible percentage of acid is used to make the pretreatment step at station II efficient.

Although not shown in the embodiment-15 mark, it is conceivable that by properly shaping the conveying device, the containers could be directed to stations II, III and VI with their open side facing downwards. In this case, any droplet-like acid deposits and condensates run down and drip down due to gravity. In this way, the non-volatile acids in the water vapor can also be removed after the treatment, since the steam condensate washes them down and out.

In order to demonstrate the effectiveness of the method according to the invention, the following table shows the result of a series of experiments, a series of experiments in which, with the arrangement according to the example described above, milk filling was performed aseptically under different conditions. Each individual test batch was performed in approximately 500 packs of one liter. The sterility study was performed by pH after 11 days of storage at room temperature.

In Experimental Lot A, which is a blank, the milk was placed in untreated packages with the result that 25% of the packages were non-sterile. When the packages were treated only with hot air (300 ° C, 8 s), such as test batch B 35, or only with steam (8 s), such as test batch C, the non-sterile fraction was 14 and 7%.

8 71909

In Experimental Lot D, packages were treated with 0.3 mL of acid and hot air (300 ° C, 8 s). In this case, a small effect was observed when formic acid was used, but not when acetic and lactic acid were used.

In test batch E, which corresponds to the method according to the invention, the packages were treated with acid and steam (0.3 or 1 ml of acid + 8 s steam effect), whereby 0.3 ml of acid was injected (E 2, E 2, E ^) or 1 ml of acid was added dropwise (E2, E ^, Eg). This gave a clear sterilization-10 effect, in four cases out of six a very good sterility fraction was achieved. The advantage of the method according to the invention is clear.

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Claims (9)

71 909 A method for sterilizing packaging material 5, especially preformed liquid filler containers 5, which comprises applying hot water vapor and an organic acid to a surface to be sterilized for several seconds on a surface to be sterilized, characterized in that the packaging material is first acidified then heated with flowing steam at atmospheric pressure. Method according to Claim 1, characterized in that the acid is sprayed or dusted onto the surface. Method according to Claim 1 or 2, characterized in that the acid is added or poured onto the surface. Process according to one of Claims 1 to 3, characterized in that the acid used is water-volatile acid. Process according to one of Claims 1 to 4, characterized in that the acid used is the acid contained in the filler or an acid closely related thereto. Process according to one of Claims 1 to 5, characterized in that an acid selected from the group consisting of formic acid, acetic acid, malic acid, citric acid, lactic acid and ascorbic acid is used. Method according to one of Claims 1 to 6, characterized in that the surface is heated before the application of the acid. Method according to one of Claims 1 to 7, characterized in that the acid is heated before application to the surface. Method according to one of Claims 1 to 8, characterized in that the surface is treated with flowing hot air after heating with flowing steam. li 71 909