A PROCESS FOR ASEPTIC PACKAGING

Field of invention:

The present invention relates to food packaging, more particularly to the process of aseptic packaging.

Background of the invention:

Currently known methods of packaging involve filling a package with food products such as edible liquids. In the traditional canning process, the food products are heated in the container for about 20 to 50 minutes.

The process of aseptic packaging is a major advance over traditional canning techniques. Aseptic packaging involves filling a sterilized package with a sterile food in a confined hygienic environment. Aseptic packaging methods such as flash heating and cooling substantially reduce the energy use and nutrient loss associated with conventional sterilization. As a result, aseptically packaged products can retain more nutritional value and exhibit more natural texture, colour and taste, all the while using less energy. The aseptic package of the prior art is typically a, multi-layer lamination that combines the best attributes of paper, plastic and aluminum to form a singular, high-performance beverage container. The combination of quality aseptic processing, shelf stability and source reduction also makes the aseptic package ideal for a variety of food products.

The liquid food or beverage is sterilized outside the package using an Ultra- High Temperature (UHT) process that rapidly heats, and then cools the product before filling. The processing equipment allows the time (generally

3 to 15 seconds) and temperature (195° to 285°F) to be tailored to place the least amount of thermal stress on the product while ensuring safety.

Aseptic packaging of liquids has many benefits:

• Convenience -- because aseptic packages are portable, lightweight, and shatterproof.

• Food Safety -- the aseptic packaging process and carton together ensure that the liquid food or beverage inside is free from . harmful bacteria and contaminants.

• No refrigeration -- beverages and liquid foods can be stored in cabinets instead of a refrigerator thereby saving energy.

• More nutrition — because the aseptic process places less heat stress on foods and beverages than traditional canning processes, products can retain more nutrients as well as natural taste, color and texture.

Flexible packages for aseptic packaging are made from three materials:

1. Paper - provides stiffness, strength and the brick shape.

2. Polyethylene plastic (polymeric materials in aseptic packaging) — provides leak proofing and keeps the exterior dry.

3. Aluminium - provides light and oxygen barrier thereby eliminating the need for refrigeration.

The sterilization of packaging material in the prior art is carried out by the following methods:

1. Subjecting the packaging material to ultrasonic vibrations through a liquid medium and then subjecting the packaging material to ultraviolet radiation like gamma rays.

2. The aseptic packaging material is immersed in a bath Of H ₂ O _2, which is generally heated between 60 ⁰ C and 80 ⁰ C. The coat of H ₂ O ₂ maintains the sterilized condition. Sodium chlorate can also be used.

To increase the coating adaptability of the packaging material, there is necessity to increase its surface energy level. The surface energy of a packaging film, often referred to as the "dyne" level (dynes/cm) is a critical film property when printing, coating or laminating packaging films. The main objective of any surface treatment method is to increase the surface energy of the film surface to improve wet-out and adhesion of coatings, inks and adhesives used in converting the film into packaging.

Typical polymers used for packaging films without surface treatment will naturally have a surface energy of 29 to 45 dynes/cm. A typical rule of thumb to ensure good wet-out and adhesion to a substrate is that the surface energy of the substrate should be 7-10 dynes/cm higher than the surface tension of the coating being applied. As an example, water has a surface tension of 72 dynes/cm compared to the surface tension of methanol which is 22.6 dynes/cm. The surface energy of a polyester film is approximately 42 dynes/cm thus allowing the methanol to easily wet-out the surface of the polyester, however the water (-72 dynes/cm) which is 50 dynes higher than the methanol, will form droplets without wetting the polyester film.

There are several different ways of treating a film to increase its surface energy that can be effective if used correctly, such as corona discharge,

flame treatment, priming and chemical etching and can be used individually or in combination, to increase the surface energy of a packaging film.

Priming

Priming of a film is done in conjunction with corona treatment to increase the surface energy and improve adhesion of a coating, ink or adhesive. _The film is corona treated to increase the surface . energy, enough to provide good adhesion for the primer coating to the film. A primer is selected that will provide a high surface energy for good adhesion and possibly improve the surface texture of the film. This method however, greatly increases the cost of the film.

Chemical Treatment

Chemical treatment of a film typically involves cleaning, etching and rinsing the film. Cleaning removes surface contaminants. Etching involves the use of an acid, base or oxidizing agents such as nitric acid (NHO ₃ ) or potassium chromate (K ₂ Cr ₂ O ₇ ) in order to chemically alter the polymer surface. Finally, the film is rinsed and cleaned of the etching chemicals and dried. This process is usually done following film manufacturing, which significantly adds to the final cost of the film. This treatment method is often slow and creates waste disposal issues.

Flame Treatment

Flame treatment involves the use of a burner unit that generates a flame with a specific plasma value (PV) ratio or fuel to oxygen ratio. The film is made to pass directly through flame tips, which have formed oxygen rich plasma there by treating the surface of the film with the flame. This treatment method is known to produce high surface energy levels and long

lasting treatment levels. In the past this method was considered dangerous due to the presence of long open flame. However, improvements in equipment design and controls have greatly reduced the hazards.

Corona Treatment

Corona discharge equipment consists of a high-frequency power generator, a high-voltage transformer, a stationary electrode, and a treater ground roll. Standard utility electrical power is converted into higher frequency power which is then supplied to the treater station. The treater station applies this power through ceramic or metal electrodes over an air gap onto the material's surface. The effects of corona treatment diminish over time. Therefore, many surfaces will require a second "bump" treatment at the time they are converted to ensure bonding with printing inks, coatings, and adhesives. This treatment method is user friendly and can be run at high line speeds (in excess of 1000 feet per minute). The line speed controls the final treatment level. Corona Treating Equipment is widely used throughout a diverse range of industries including medical, electronics, automotive component, cable, ophthalmic, pipe, printing, packaging, domestic appliance, cosmetics packaging, food and beverage packaging.

Various patents that form the background art for this invention are as follows:

United States Patent no. 4888223 discloses a method for preparation of food packaging material. The film laminate in the form of seamless tube is made up of a base layer formed from polyamide resin, an intermediate adhesive

layer and a layer formed from ethylene-vinyl alcohol copolymer and an innermost, food-contacting layer formed from polyolefin resin. The innermost, food-containing surfacing of polyolefin resin layer is subjected to corona discharge applied from one pair of positions outside the seamless tube.

United States Patent no. 6858106 discloses a method of manufacturing of a laminating packaging material which does not have the delaminating between the layers. The deoxidant of vitamin E, ascorbic acid or its derivative is adhered/attached, to the inside of a barrier layer web, the barrier layer is temporarily rolled round by the reel shape, kept, and laminated by the extrusion lamination by the molten polyolefin. In this method, on further laminating a corona treatment is also suggested to the surface of laminating material, such as the aluminum foil, and additional processing such as ozonization can be carried out if needed.

European Patent no. 1177891 discloses a method for manufacturing a laminate for packaging containing an aluminum foil. This method involves a step of covering the surface of the laminate with an adhesive layer, rolling round the web shape laminate obtained by the lamination of aluminum foil to a reel shape and a step of processing the aluminum foil surface by corona discharge after unwinding the laminate from the reel and laminating the fibrous carrier layer. This disclosure provides a sterilizing process for multilayer laminate and only the inner most layers is subjected to corona treatment, which does not sterilize the entire packaging laminate.

United States Patent no. 6183691 discloses a method and apparatus for sterilizing packages. The method provide packaging to be sterilized at the

sterilization station, the packaging is a partially formed carton having an interior, an exposed exterior and a fitment. The method includes subjecting the packaging to a predetermined quantity of vapor phase hydrogen peroxide thereby creating a packaging coated with a thin layer of hydrogen peroxide. The next step is irradiating the coated packaging with ultraviolet radiation and last step is drying the irradiated packaging with heated air.

European Patent no. 0484730 discloses a method of sterilizing a packaging material by means of a sterilizing agent in liquid form. In this method the packaging material is first discharged in order to eliminate electrostatic surface charges occurring on the strip. The sterilizing agent is then applied to the packaging material in a finely distributed, electro statically charged form to create a coherent, homogeneous film. The packaging material is finally heated to drive away the sterilizing agent from the ready sterilized packaging material.

All these processes disclosed hereon above do not ensure the complete removal of the hydrogen peroxide, which is important as it causes health harazards. The object of the present invention is to obviate said drawbacks by providing a triple stage sterilizing process.

Object of the invention

An object of the present invention is to provide a method for aseptic packaging of a sterile product.

Another object of the present invention is to provide a method for aseptic packaging film.

Yet another object of the present invention is to provide a method which cleans the film thoroughly to remove the impurities.

One more object of the present invention is to provide a method which reduces the microbiological load.

Still another object of the present invention is to provide a method wherein the sterilizing agent is uniformly spread.

Yet another object of the present invention is to provide a method to double sterilize the film to completely remove the undesirable sterilizing agent.

Yet another object of the present invention is to provide a method which sterilizes the packaging without causing any health hazards.

Summary of the invention

In accordance with this invention there is provided a process for aseptic packaging, comprising the following steps

a) conditioning the operative inner surface of the packaging film for uniformly receiving the sterilizing agent thereon; b) applying sterilizing agent on said conditioned surface and soaking in said sterilizing agent bath; and c) uniformly spreading said sterilizing agent on said conditioned surface and then forming, filling and sealing said film bearing said conditioned inner surface by treating during forming, filling and sealing an enclosure formed of said film with hot air

with temperature ranging from 100-150 degree Celsius and pressure ranging from 0.5 Bar to 2.0 Bar to sterilize the film and to vaporize said sterilizing agent off the conditioned inner surface while simultaneously Filling the formed enclosure with a product to be packed inside packaging.

Preferably, the conditioning is performed by at least one process selected from a group of processes consisting of corona discharge, plasma arc and flame treatment.

Typically, the conditioning is performed to provide a surface energy between 30 to 45 dynes/cm.

Preferably, the sterilizing agent used is from a group consisting of Hydrogen Peroxide, Oxonia and peracetic acid.

Typically, the sterilizing agent is applied by one of the methods of spraying, dipping in a bath squeezing rollers and vapor deposition.

The step of treating during forming, filling and sealing is performed by introducing hot air and a sterile product to be filled via a coaxial tube, the product being discharged through the inner annulus and the hot air being discharged through the outer annulus and providing a laminar flow of hot sterile air on the inside of the film in the opposite direction of film pulling thereby creating the scrubbing arid vaporizing effect to ensure evacuation of sterilization liquid adhered to the inner surface of said film before

introducing of the sterile product inside formed package, wherein the flow rate of the hot air is from 500 to 2000 lit/min.

Description of the invention

The present invention will now be described with reference to accompanying drawings, which do not limit the scope of the invention in any way but merely illustrates the same. In the accompanying drawings;

FIG 1: shows the representative flowchart to demonstrate the process in accordance with the present invention;

FIG 2: is the side view of the schematic diagram of the method in accordance with this invention.

FIG 3: is the front view of the schematic diagram of the method in accordance with this invention; and

Detailed description of the invention

Accordingly, the present invention provides a method for sterilizing a composite packaging laminate or a film. The first stage of this method is to increase the surface energy of the film by conditioning the film . Second stage is impinging the said film with high speed jets of hydrogen peroxide and then applying the hydrogen peroxide on the inside surface of the film. The third stage is sterilizing of the film which includes forming, filling and sealing of the packaging laminate.

The laminate first undergoes conditioning to increasing the surface energy of the operative inner surface of the film to 30 to 45 dynes/cm. The method of conditioning may include corona discharge, plasma arc and flame treatment. Condition permits receiving of the sterilizing agent uniformly on the film surface and improves the wetting and adhesion of the sterilizing agent on the film surface. It has been found that if the conditioning provides a surface energy below 30 dynes/cm, then the application of sterilizing agent will be sporadic and not uniform, which leads to insufficient scrubbing and vaporizing.

According to one of the embodiment of the present invention, the entire sterile product filling path surfaces are cleaned to remove impurities and to reduce microbiological load and sterilize the filling path. This involves an initial cleaning process of cleaning-in-place (CIP) and sterilization-in-place (SIP). An in built CIP and SIP unit is provided with this method, in accordance with this invention which is ¹ designed to control the process parameters. Both the CIP and SIP are monitored through a PLC. The cleaning in place involves circulation of different cleaning solutions like hot water, caustic soda brine, nitric acid, in the product filling path for specific parameters like concentration of the cleaning solution and residence time of the solution. After the CIP, the complete sterile product filling path is steam sterilized to make the system free of any microorganisms. The steam at a temperature of 115 to 140 degree C is contacted with the inner surfaces of the product tank for 20 to 60 min. The conditioned film roll is pulled over the filling Pipe for the film sterilizing process. Cleaning-in-place is carried out after every machine stoppage or once in a day. The machine is sterilized using culinary steam before next production. If there is any interruption

during CIP and SIP, the cycle is made to restart from the beginning and any drop in temperature during the cycle is interrupted by a audio - visual alarm.

The conditioned film is rolled on to a film roller (10). The film is then moved to a film unwinding machine (12) to unwind the film roll and further rolled to a hydrogen peroxide bath (16) for sterilization. The film is sterilized in two stages by a sterilizing agent. Preferably, hydrogen peroxide is used as a sterilizing agent.

First stage sterilization:

The inner surface of the film which has been conditioned having a surface energy between 35 to 40 dynes/cm is subjected to a high speed jets (14), where 35 % to 50 % concentration of hydrogen peroxide is impinged tangentially on the film at a pressure of around 2 - 5 bar. The film is passed vertically over two guide rollers (18) while it is impinged. The high speed jets cause mechanical dislodgement of bacteria from the inner surface of the film and also remove dust.

Second stage Sterilization:

The film from the first stage sterilization is then soaked in the hydrogen peroxide bath (16) by passing in the soaking tank containing hydrogen peroxide (16) of 35% to 50 % concentration at a temperature of 30 to 35 degree C. The minimum residual time of the film in the bath is around 5 - 10 sec. The time varies as per the speed of the roller and the film length. The film leaving the hydrogen peroxide tank (16) is then wiped off using a wiper (15) to remove excess hydrogen peroxide adhering to the film surface. The sterilized film is further passed over metallic rollers (18) for uniform

dispersion of hydrogen peroxide on the inner surface of the film by a calendaring effect of the rollers. Optionally, the microbiological load on the film is further reduced with the exposure to UV light for 1 to 3 sec.

The third and final stage sterilization is done by hot sterile air, synchronizing with forming and filling of the packaging, wherein train of sterilized pouches is formed. The forming and filling equipment (8) for hot air sterilization consists of a folding roller (22) with a coaxial filling tube fitted at the center (24), wherein the sterile air is introduced through the outer tube of the coaxial tube and the product through the inner tube, a horizontal seal (28) for horizontal sealing and a vertical seal (26) for vertical sealing. The sealing is achieved with an impulse or constant sealing element or jaw. The current range during a typical impulsive sealing is maintained between 30 - 60 amps and heat expose time between 300 to 600 milliseconds depending upon film thickness and film properties. Curing/cooling of the typical impulse sealers is achieved by circulating chilled water through the sealing jaws when they are in closed condition. The curing time varies from 100 to 300 milliseconds. The air for sterilization is supplied from the air blower, which is heated by an air heater, to a temperature of 100 - 150 degree C and at a pressure of 0.5 to 2 bar. The hot sterile air from the air heater also provides purging on top of the product in the product tank (36), wherein air is introduced to the tank. The hot sterile air also maintains the modified atmosphere during filling process thus avoiding contamination from outside air.

The film from the second stage sterilization is rolled on to the folding collar (22) where the film is folded to form a tube. One of the edges of the film is

vertically sealed by the vertical sealer (26). Further the tube is sealed horizontally by a horizontal seal (28) at the operative bottom end with the other end open. The hot sterile air is introduced into the coaxial tube (24) at a flow rate of 500 lit/min - 2000 lit/min. The inner surface of the film tube is scrubbed by hot air to remove/scrub off hydrogen peroxide from the sterilized film. This vapor simultaneously liberates nascent oxygen which further reduces the microbial load and also acts as a disinfectant. The scrubbed film on the folding collar (22) is pulled continuously by pulling rollers (34) at a speed ranging from 1000 - 2500 rpm. Simultaneously a typical sterile product like sterile liquid at a flow rate of 6 lit/min to 60 lit/min is introduced from a product tank (36) in to the film tube. After the filling, the operative upper end of the film tube is sealed by the horizontal seal (28) to form a pouch. The flow of the product is controlled by a constant flow valve (40) fitted to the product tank (36). The sealed pouches are discharged from the pouch discharge unit (38).

In the final stage, in situ sterilization of packaging material is carried out where the film tubes are hot air sterilized and parallely filled with the product; this method minimizes the contamination of the sterilized pouches and helps in achieving a cent percent sterilization. Hot air removes excess hydrogen peroxide as well and the quantity of hydrogen peroxide is about 0.1 - 5 ppm in the final packaging. Before the introduction of next batch of sterile product into the product tank, the filling system undergoes a CIP and SIP process. The method of forming, filling and sealing process is carried as described in the above method after the CIP process. These aseptic pouches can be used for packaging of milk, vegetable purees, fruit juices and the like.

Test procedure and Results for aseptic packaging in accordance with this invention are as shown in Table 1, 2 and 3.

Log count reduction (LCR):

Validation of the pre-sterilization of an aseptic packaging machine and validation of the machine's sterilization of the packages require many evaluations, including a microbial count reduction. The uniformity of the log count reduction (LCR) must be demonstrated for the standard sterilization technique to be applied to the machine and to the packages.

(The test Procedures are designed by the working group formed for standardizing the test procedures and worked out originally at Fraunhofer Institute of Food Technology & Packaging, Munich)

Count Reduction Test Procedure

In the count reduction test the packaging materials were infected with the test microorganism and passed through the aseptic plant, in doing so the number of viable spores was determined before and after passage of the sterilization device and from the difference in microorganism counts, the killing rate was determined.

• strain used was Spores of Bacillus Subtilis (SA22), imported from Germany

• these strains were applied to the film on the roll a specific locations

• 25 pouches were formed without any product but with film sterilization

• 20 pouches were selected, partially filled with sterile buffer which also contained the wetting agent. The buffer was violently shaken for 3 min.

• the contents were then plated using plate count agar and incubated at 30 degree C for 5 days.

• the count reduction achieved was calculated

• required minimum mean Logarithmic count reduction (MLCR) is 4. MLCR = log (initial count) - log (final count)

End Point Test Procedure

In the end point test the packaging was artificially inoculated with test micro organisms as in the count reduction test. The infected packaging was filled with a sterile culture medium and after incubation phases the number of unsterile packaging units was determined. The end point provides the effectiveness of the package and as well as information about the entire process from supplying the product and filling through the recontamination free closure of the packs.

^β packing material was artificially contaminated in various gradations with test spores (B. Subtilis)

• packages were filled with sterile product on the aseptic filling machine

• packages were incubated at 30 degree C for 2 weeks

• the contents of the packages were then tested by plating them & incubating the petri dishes at 30 degree C for 5 days

• pack is un-sterile if more than three colonies are found on the petri dish.

• minimum Mean Logarithmic Count Reduction (MLRC) to be achieved is 4.

MLCR = log (initial count per pack) - (log ln(number of packs tested/number of sterile packs))

Firstly, the pouches were subjected to web sterilization. Three trials as shown in Table 1 were carried out as per the count reduction test procedure as follows:

Spores of B. Subtillis (SA22) were planted on the film, with an initial count of 108/ml. The film was then passed through 35% H2O2 solution at room temperature & swabs were taken at the other end, difference between initial load & load after web sterilization are as shown in table 1 (where D=one decimal reduction).

Table 1: Results of Web sterilization system

The required minimum Mean Logarithmic Count Reduction (MLCR) is 4. The results in table 1 show a MLCR greater than 4, which has superior aseptic properties than the packages in the prior art.

Secondly, the sterility of these pouches was tested by microbial analysis as per the end point test procedure and the results are as shown in Table 2.

Table 2: Performance of Aseptic packaging formed.

*MLCR = log (initial count per pack) - (log ln,(number of packs tested/number of sterile packs))

Minimum MLCR required is 4. MLCR achieved is greater than 4.

A MLCR of greater than 4 was achieved. The no. of un-sterile pouches was found to be zero in two trials, with a MLCR of infinity, where in total sterility was achieved.

Further, trails were carried out at 3 different sterile air temperatures in accordance with this invention as per example 1 , 2 and 3 and the results are summarized in Table 3.

Table 3: Summary of Results of Test conducted in accordance with this invention

The average load on the film was measured before the experiment and found to be 'A'. The load at the outlet of the hydrogen peroxide bath was calculated and found to be 'B'. Further the film was air sterilized after it was treated in a hydrogen peroxide bath. The experiment was carried out at 3 different air temperature and the results were tabulated as shown in Table 3. The load reduction increases as the sterile air temperature is increased.

The invention will now be described with respect to the following examples which do not limit the invention in any way and only exemplify the invention.

Example 1

A corona treated laminate of 38 dynes/cm surface energy and thickness of 90 micron was sterilized by impinging the laminate surface with high speed jets of hydrogen peroxide of 40 % concentration at temperature of 30 degree C. The sterilized film was passed into a hydrogen peroxide bath for second sterilization, wherein the film was contacted with the bath for 6 sec. The hydrogen peroxide sterilized film was wiped by passing through a wiping/squeezing roller. Then the wet film was passed over the folding collar with coaxial filling tube at the center. A tube was formed by the vertical sealing of the film and then into a pouch by a horizontal sealing of the tube on the folding collar. The film was then air sterilized by passing hot air through the outer tube of the coaxial filling tube, at a temperature 85 degree C and a pressure of 1.5 bar. The flow rate of the hot air was maintained at 1500 lit/min. Thereafter a sterile Product from the product tank at a flow rate of 45 lit/min was introduced through the inner tube and was sealed at the lower end.

Example 2

A corona treated laminate of 38 dynes/cm surface energy and thickness of 90 microns was sterilized by impinging the laminate surface with high speed jets of hydrogen peroxide of 40 % concentration at temperature of 30 degree C. The sterilized film was passed into a hydrogen peroxide bath for second

sterilization, wherein the film was contacted with the bath for 6 sec. The hydrogen peroxide sterilized film was wiped by passing through a wiping/squeezing roller. Then the wet film was passed over the folding collar with coaxial filling tube at the center. A tube was formed by the vertical sealing of the film and then into a pouch by a horizontal sealing of the tube on the folding collar. The film was then air sterilized by passing hot air through the outer tube of the coaxial filling tube, at a temperature 90 degree C and a pressure of 1.5 bar. The flow rate of the hot air was maintained at 1500 lit/min. Thereafter Product from the product tank at a flow rate of 45 lit/min was introduced through the inner tube and was sealed at the lower end.

Example 3

A corona treated laminate of 38 dynes/cm surface energy and thickness of 90 micron was sterilized by impinging the laminate surface with high speed jets of hydrogen peroxide of 40 % concentration at temperature of 30 degree C. The sterilized film was passed into a hydrogen peroxide bath for second sterilization, wherein the film was contacted with the bath for 6 sec. The hydrogen peroxide sterilized film was wiped by passing through a wiping/squeezing roller. Then the wet film was passed over the folding collar with coaxial filling tube at the center. A tube was formed by the vertical sealing of the film and then into a pouch by a horizontal sealing of the tube on the folding collar. The film was then air sterilized by passing hot air through the outer tube of the coaxial filling tube, at a temperature 95 degree C and a pressure of 1.5 bar. The flow rate of the hot air was maintained at 1500 lit/min. Thereafter Product from the product tank at a

flow rate of 45 lit/min was introduced through the inner tube and was sealed at the lower end.

Example 4

This experiment was carried out as per example 1 , wherein a surface energy below 30 dynes/cm level was provided. A drop of microbial load reduction by more than 1 log was observed.

Example 5

This experiment was carried out as per example 1 , wherein a surface energy higher than 45 dynes/cm was provided. The application of the sterilizing agent was observed as a thick layer and not finer globules as desired leading to insufficient scrubbing and vaporizing effect and dropping of microbial load reduction by more than 1 log.

Example 6

This experiment was carried out as per example 1, wherein the residence time in hydrogen bath was reduced below 5 seconds. The log reduction of microbial load was dropped by more than 1 log.

Example 7

This experiment was carried out as per example 1, wherein the residence time in hydrogen bath was increased above 15 seconds, no further increase in log reduction of bacterial load was observed.

Example 8

This experiment was carried out as per example 1, wherein air temperature was dropped below 100 degree C. In this example, the vaporizing effect was insufficient and the desired log reduction in microbial load was dropped.

Example 9

This experiment was carried out as per example 1 , wherein air temperature was increased above 150 degree C. At this high air temperature the film melted and got stuck to the jacketed Filling pipe leading to stoppage in the process.

Example 10

This experiment was carried out as per example 1, wherein the pressure of hot air was maintained at less than 0.5 bar. An insufficient scrubbing action was observed at this low pressure.

Example 11

This experiment was carried out as per example 1 , wherein the pressure of hot air was maintained above 2 bar. At this high pressure the film tube bulged leading to stoppage of the film movement.

Example 12

This experiment was carried out as per example 1, wherein the hot air flow rate was maintained below 500 lit/min. This resulted in insufficient air volumes and reduced the speed available for scrubbing and vaporizing the sterilizing agent.

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Example 13

This experiment was carried out as per example 1 , wherein air flow rate was maintained above 2000 lit/min. This reduced the scrubbing and vaporizing effect.

While considerable emphasis has been placed herein on the particular features of the preferred embodiment and the improvisation with regards to it, it will be appreciated the various modifications can be made in the preferred embodiments without departing from the principles of the invention. These and the other modifications in the nature of the invention will be apparent to those skilled in art from disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to interpreted merely as illustrative of the invention and not as a limitation.