Aseptic canning method

Abstract

An aseptic canning process for liquid products in which a small quantity of water is introduced into each can through its vent hole with external heat being applied to the cans at atmospheric pressure to convert the water in the cans into superheated steam for complete sterilization of the interior and exterior of the cans. The completely sterile cans are introduced into an inert gas cooling chamber with sterile inert gas being introduced into the chamber to continuously cool the chamber and the cans so that the hot sterile cans will be reduced in temperature. The cans are then filled with the product being inserted into the can through the vent hole causing most of the inert gas to leave the can but any head space or unfilled area in the can being occupied by inert gas. The can is then sealed and subsequently handled in any suitable manner. The can is maintained in an inert gas atmosphere during the cooling step, filling step and sealing step thereby maintaining aseptic conditions.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to the sterilization of containers and more particularly a system for aseptic canning of products employing vent hole cans and liquid products, in which the can is completely sterilized both interiorly and exteriorly and then cooled, filled and sealed under aseptic conditions.

2. Description of the Prior Art

The canning of various products is an accepted procedure in the distribution of various food products with a more stable shelf life of the food products without any loss in nutritional and flavor characteristics being the ultimate goal in all such systems. In many instances, the food products are sterilized by heating a full, sealed container which frequently produces overheating which is deleterious to both the nutritional and flavor characteristics of the food product.

Prior canning systems employing a container and a separate cover require that the containers and the covers be sterilized separately with the covers being united with the containers after the product has been introduced into the containers. The filling of open top cans in a sterile atmosphere results in considerable spillage and waste of sterile products and a large head space frequently occurs in the closed can. Also, present canning systems where the container, cover and product require the synchronized movement of three components results in the possibility of contamination during the interfaces and requires the use of elaborate and rather expensive control equipment. Also, the filling and closing operations of the open top can is accomplished at relatively high temperatures thus causing a vacuum in the closed can which may adversely affect the product during storage and subjects the can to a higher probability of contamination through seam leaks due to the reduced pressure within the can causing ingress of contaminated air. Moreover, maintaining all of the components at the high temperature requires the expenditure of a substantial quantity of heat energy thereby increasing the overall cost of the canning of the products.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an aseptic canning system employing a vent hole can and presterilized liquid product in which a small quantity of potable or filtered tap water is introduced into the vent hole can with the water then being converted into steam by the application of heat exteriorly of the can. The sterile can with superheated sterilizing steam therein moves into a cooling chamber through a gas valve to maintain sterile conditions where the hot can is subjected to a cooling operation by a sterile inert gas which reduces the pressure in the can thus assuring that the can will be filled with the sterile inert gas with the can being cooled to ambient or below ambient temperature. The can then passes to a filling chamber while maintaining it in a sterile inert gas atmosphere through a suitable gas valve mechanism where the can is filled through the vent hole with a sterile product at ambient or below ambient temperature so that the sterile inert gas will be displaced from the can by the sterile liquid product and any head space in the can will be occupied by the sterile inert gas all of which are at ambient or below ambient temperature. The filled can is then sealed by closing the vent hole by soldering or any other procedure under a sterile inert gas atmosphere so that the filled can will be substantially at ambient temperature or below ambient temperature thereby providing an aseptic canning system.

A further object of the invention is to provide an aseptic canning system which is efficient in operation, inexpensive to operate and maintain and does not require any elaborate control system.

Still another object of the invention is to provide an aseptic canning system in which the interfaces between the components of the system are reduced to two items, that is, an interface between the sterilized can and the sterile product rather than interfaces between three items as in conventional, open-top aseptic canning, that is, the can, the product and the can lid. Thus, this system reduces the possibility of contamination since the can is maintained sterile after its sterilization and the liquid product is presterilized thereby obtaining an interface between two sterile components in a sterile atmosphere provided by the sterile inert gas which may be nitrogen, nitrous oxide, or any other appropriate sterile inert gas.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawing forming a part hereof, wherein like numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a schematic view illustrating the aseptic canning system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A sanitary crimped vent hole can 10 of predetermined size is supplied to the canning system from any suitable source. This type of can is well known and the vent hole 12 is located in the center of the crimped lid. The can 10 may be positioned on a suitable conveyor structure such as a gravity conveyor or a powered conveyor of any suitable type and is conveyed in an upright manner, that is, with the vent hole 12 facing upwardly into a water spray or water injector station 14 where water spray jets inject a small quantity of filtered, potable water into the can through the vent hole and the exterior surface of the can is also wetted. The quantity of water injected into the can should approximate one ounce which can be determined in any suitable manner. The can with the small quantity of water therein then enters the can sterilizer station 16 where it is heated, under atmospheric pressure, until the can reaches a temperature of at least substantially above 212.degree.F and usually approximately 400.degree.F. Any desired conventional heat source may be used at the can sterilizing station such as electric heating elements, infrared lamps or other appropriate heat sources with the application of heat to the cans being from a position externally of the can. The water in the can is evaporated into superheated steam at approximately 400.degree.F at atmospheric pressure and completely sterilizes the interior of the can and the exterior of the can is also sterilized by the heat with the sterilization being accomplished in approximately one second or less depending on the temperature. The cans may be oriented vertically or may be rolled while in a horizontal attitude or otherwise oriented so that maximum exposure of the interior of the can to the superheated steam is accomplished. In the can sterilizing station, the can is completely sterilized with the superheated steam in the can being at a temperature of approximately 400.degree.F and at approximately atmospheric pressure.

The sterilized hot can then passes through a gas valve 18 of conventional construction so that the can will be introduced into a cooling chamber or sterile inert gas chamber 20 without coming into contact with ambient air. The gas valve is of conventional construction and is used to pass the can from one chamber to another without contact with ambient atmosphere.

In the inert gas chamber, jets of sterile inert gas such as nitrogen, nitrous oxide, or any other suitable inert gas are sprayed into the chamber from a suitable source of supply and under a suitable above atmosphere pressure with the gas expansion continuously cooling the chamber. The sterile inert gas chamber 20 is cooled sufficiently to lower the temperature of the hot, sterile can to at least a temperature below approximately 120.degree.F with the can being cooled to approximately room temperature, ambient temperature or below being preferable. While the can is being cooled, the superheated steam, which is relatively dry, inside the can will be cooled thus condensing any steam therein and creating a vacuum or reduced pressure interiorly of the can thus drawing the sterile inert gas into the can. Inasmuch as the inert gas is sterile, the condensed steam is sterile and the surfaces of the can are sterile, the can at this stage is completely sterile and substantially filled with sterile inert gas.

From the inert gas chamber 20, the cooled, completely sterile cans which are filled with inert gas pass through a gas valve 22 into a filling chamber 24 which includes a filling machine of conventional construction that is used for filling vent hole cans such as the well known Dickerson vent hole can filling machine. The filling chamber and the filling machine are maintained under a sterile inert gas atmosphere with the filling machine filling the can through the vent hole with a sterile liquid product. The liquid product expels most of the inert gas in the can and leaves a small head space which is occupied by the sterile inert gas. The filling operation takes place at ambient or near ambient or room temperature with a slight positive pressure being kept inside of this chamber to preclude ambient air contamination.

The filled can is then sealed by a conventional soldering technique such as silver soldering or by any other means of closing the vent hole can aseptically. The apparatus for closing the can is conventional and commercially available with the sealing operation being conducted at a soldering station 26 from where the can exits through a liquid seal 30 as shown with an appropriate liquid being used to maintain sterile conditions, clean the can and prevent escape of gas. The can which is filled and sealed and in sterile condition can be labelled and packaged in any suitable manner. The filling operation and the closing or soldering operation may be performed in a single enclosed casing or housing in which the interior atmosphere is free from contamination and filled with a sterile inert gas under a slight positive pressure. A plastic envelope or enclosure of "Lucite" or the like may completely surround the Dickerson filling and sealing assembly to maintain sterile conditions with the sterile inert gas being under a slight positive pressure to preclude any ambient air contamination. If desired, at appropriate locations in the casing 28 for the filling and soldering operation, surgical type gloves of plastic or the like can be provided in order to enable manual adjustments of cans or machinery if desired without the need of entering the casing and possibly contaminating it. The specific structural details of the filling machine as well as the soldering operation are not disclosed inasmuch as conventional and commercially available equipment is used.

This system can use gravity to move the cans through the various stations of the aseptic canning operation but it is pointed out that other conveyor systems can also be effectively used depending upon the particular installation requirements. The use of the aseptic canning system of this invention including the vent hole can enables elimination of a crimping operation in a sterile environment which is necessary when a separate cover and can must be joined after the can has been filled. As compared with this procedure, in the present invention, the can and cover which have been previously joined are sterilized in a single and efficient operation step. The sterilization of the can also facilitates the inclusion of sterile inert gas in the can in a simple and efficient manner with the filling and closing of the container also being in a sterile gas atmosphere resulting in exclusion of contaminating ambient air. Further, the total operation is conducted at or near atmospheric pressure with filling of the can being substantially at room temperature. This system also substantially reduces head space volume in the can as compared with conventional open top canning. Also, a slight positive pressure in the sterile can serves to reduce leakage and contamination during storage which can result from storing a container having a reduced pressure interiorly thereof. The small vent hole opening in the can substantially reduces the probability of contamination during the critical interfaces of introducing a sterile liquid into a sterile can. Further, the small vent hole opening and filler machine substantially reduce the spillage rate during the filling operation as compared to conventional open top canning systems which spillage occurs most frequently when moving a filled open topped can. The aseptic canning system of this invention eliminates the necessity of using saturated steam or air throughout the packaging system inasmuch as the present system sterilizes each can itself and not the entire atmosphere. This system uses conventional equipment and due to its simplicity and efficiency results in minimum initial cost, installation and operation and produces a canned product that has a desirable long shelf life during which the flavor and nutritional characteristics of the product are maintained.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims

What is claimed as new is as follows:

1. An aseptic canning method for filling and sealing vent hole cans with a sterile liquid product in which each can includes a can and lid which have been previously joined to form a closed can except for a small vent hole located centrally in the lid, said method consisting of the steps of supplying said vent hole cans, introducing a small quantity of water sufficient to generate superheated steam into the interior of each can through the small vent hole in the lid, applying heat externally of the can for converting the water to superheated steam thereby sterilizing the interior surface of the can, subjecting the hot can with superheated steam therein to cool sterile inert gas above atmospheric pressure whereby the gas cools the can with condensation of the steam and reduced pressure in the can causing the inert gas to substantially fill the can by being drawn in through the small vent hole in the lid, filling the can with sterile product through said vent hole while maintaining an inert gas atmosphere whereby the product entering the can expels the inert gas from the can with any head space between the can lid and the product being filled by inert gas, and closing the vent hole in the lid of the vent hole can while maintaining an atmosphere of inert gas.

2. The method as defined in claim 1 wherein said step of introducing water into the can includes subjecting the can to a water jet for placing approximately one ounce of water in each can, said application of heat being externally of the can for raising the temperature interiorly of the can to at least approximately 400.degree.F at substantially atmospheric pressure.

3. The method as defined in claim 2 wherein the cooling of the cans and filling thereof is carried out under substantially ambient temperature for discharging the filled cans at substantially ambient temperature.

4. The method as defined in claim 3 wherein the step of closing the vent hole in the can includes soldering the vent hole closed with final cooling of the closed container to ambient temperature leaving a residual positive pressure within the can to reduce the probability of contamination as compared with a can having a vacuum or reduced pressure internally thereof.