US 3291563 A
Description (OCR text may contain errors)
Dec. 13, 1966 W McK MARTIN APPARATUS FOR STERILE PACKAGING Original Filed Sept. 22, 1960 United States Patent Office 3,29l,563 Patented Dec. 13, 1966 3,291,563 APPARATUS FOR STERILE PACKAGIN William McK. Martin, 457 Virginia Ave., San Mateo, Calif.
Original application Sept. 22, 1960, Ser. No. 59,143, now Patent No. 3,180,740, dated Apr. 27, 1965. Divided and this application Oct. 7, 1964, Ser. No. 409,042
3 Claims. (Cl. 21-94) This application is a division of application Serial No. 59,143 liled September 22, 1960, now Patent Number 3,180,740, which is a continuation-in-part of my copending application Serial No. 556,141, iiled December 29, 1955, which in turn is a continuation-in-part of my application Serial No. 478,996, iiled December 31, 1954, and now abandoned.
This invention relates to process and apparatus for sterile or aseptic canning of foods -and the like.
By the terrns sterile canning and aseptic canning is meant the packaging of food products in sealed glass, metal or other containers under conditions wherein the containers and their covers or closures, are presterilized, the food product is also presterilized, the sterile food product is placed in the sterile containers, the sterile covers are then applied to the lilled containers, and the filling and closing operations are carried out in a sterile atmosphere. If these precautions and conditions are observed, then it is unnecessary to post-sterilize the canned food as by heating in a retort. The process and apparatus -of the invention, therefore, relate to prerather than poststerilization of food products.
The process and apparatus of the present invention are,
of course, applicable to the sterile canning or packaging of products other than food-s, eg., the sterile packaging or biological preparations. The invention is also applicable to the sterilization of equipment used forsterile canning.
- Several methods of sterile canning have been proposed heretofore, some of which are at present or have in the past been in commercial use, and all of wihich employ heat to sterilize the containers and covers. One suc'h method is described in Dunkley U.S. Patent No. 1,270,- 798 hereinafter referred to as Dunkley method. The Dunkley method employs steam as a heating medium to sterilize containers and covers and to maintain sterile conditions during the filling .and closing operations. High pressure steam is injected into the containers as they pass through a chest in which the container sterilizing, lling and closing operations are carried out. The chest isV open to the atmosphere at Iboth ends. Hence the injected steam expands to atmospheric pressure. If the steam employed is high pressure, dry saturated steam, it is feasible t-o achieve steam temperatures in the chest which are considerably above 212 F.; e.g., temperatures of about 280 F. have been measured at the outlet nozzles. Even so, it has been amply demonstrated that the Dunkley method is not operable unless excessively long exposure times are employed. The reason for this is that, at such temperatures resistant food spoilage organisms ysuch as B. stearolhermophz'lus (NCA No. 1518), B. polymzxa and other resistant bacterial spores are not killed unless exposed for excessively long periods of time.
A second .and later method is the Ball method of Ball U.S.- Patent No. 2,029,303. The Ball method employs steam as the heating and sterilizing medium but it employs high pressure, hence high temperature steam. As a consequence of high pressure Ball must employ sealing and valving means to permit the introduction of empty -containers and of covers and the efllux of lled, sealed containers without loss of pressure and temperature from the system. The Ball method is operable and can be made to accomplish sterilization in much shorter time than the Dunkley method. However, the valving and sealing means employed are expensive and cumbbersome. For this and other reasons the Ball method is not a desirable method of carrying out aseptic or sterile canning.
A third method which is at present in large scale commercial use is that of Martin Patent No. 2,549,216, hereinafter referred to :as the Dole aseptic canning system or the Dole method. This method employs steam as in the case of Dunkley and Ball, but it combines the high temperature (hence short sterilization time) o-f Ball with the desirable atmospheric pressure feature of Dunkley. This is accomplished by imparting external sensible heat to the steam at atmospheric pressure by means of a heat exchanger, to yield dry steam at a high temperature (eg, 400 F. or higher) and at atmospheric pressure.
Yet another method is that of my copending application Serial No. 478,996, above referred to, wherein flame and/or hot combustion gases generated in situ Within the sterilizing apparatus are employed. Such method is referred to hereinafter as the Martin flame method.
While the latter methods (i.e., the Dole and the Martin flame methods) provide practical processes for sterile canning wherein atmospheric pressures can be employed and sterilization times are relatively short, they have, nevertheless, certain shortcomings and disadvantages, as follows: Both these methods employ sterilizing temperatures of about 350 to 500 F. That is, the containers Iand covers are heated and maintained at such temperatures for a suiiicient time to accomplish sterilization. With ordinary tin cans employing double end seams and soldered side seams, failure may occur, particularly at the soldered side seams and the double end seams, by reason of softening of the `solder or sealing compound. In the case of glass containers excessive `breakage has occurred because of thermal shock, as when Ihot glass containers lfrom the sterilizer are filled with relatively cool product. Also, such high temperatures have a deleterious effect upon the sealing compound and gasket material of covers for metal and glass containers.
It is an object of the present invention to provide a means for sterile canning which is capable of employing substantially lower temperatures than presently used, yet Which will effect sterilization in a short time comparable to that of the Dole method and the Martin dame method.
It is a particular object of the present invention to provide a method of aseptic canning whereby the temperature can be lowered substantially from that employed lby present `day .commercial methods without, however, suffering a proportionate increase in time required, preferably, with no increase in time required.
It is a further object of the present invention to provide improvements upon the Dunkley method of sterile canning which will -obviate the time diticulty inherent in that method..
A further object is to provide means whereby atmospheric steam can be employed as in the Dunkley process, without the necessity of long contact periods (as in the Dunkley method) and without the necessity of adding superbe-at to the steam.
Yet another object is to provide improvements upon high temperature sterilization methods whereby lower temperatures may be employed without a serious sacriice of speed and with consequent advantage with respect to container failure.
These and other objects of the invention will be apparent from the ensuing description and the appended claims.
One embodiment of the invention is illustrated diagrammatically and by way of example in the figure which will be described hereinafter. y
In accordance with my present invention I preheat containers to precondition and predispose the microorganisms which contaminate them to the action of heat. By this I mean that the containers, prior to the time they are subjected to heat sterilization, are subjected to a suitable conditioning treatment to render the bacteria and other michoorganisms which it is desired to kill, more susceptible to the lethal effect of heat. Stated another way, I pretreat containers in such manner as to render heat sterilization more efficient. I then subject the pretreated containers to sterilizing heat but under milder condi- 'tions (i.e.,l at a lower temperature and/or a shorter exposure time) than in present commercial methods.
Such pretreatment is preferably given to the covers also, although this is optional. That is, my present invention may be applied to containers with or without application to covers. In the latter case (no application to covers), the covers will be sterilized by prior or conventional methods.
Pretreatment may take any of several forms, some of which are preferred and some of which are better suited for certain conditions than others.
Preferably the containers are pretreated with an added agent which is effective to accelerate or facilitate the lethal effect of heat on bacteria and other microorganisms. Such pretreatment may take any of several forms such as the following:
(l) Application of a film yof water to the surfaces `of containers, etc.; i.e., wetting or moistening the containers, -covers or the like. Such film of water acts as a heat conductor, hence renders thermal methods of sterilization more efficient and consequently permits the use of ya lower temperature during the thermal sterilization step. This procedure wets `bacterial spores, causes penetration of water into the spores, predisposes the spores to the lethal action of heat and acts as an efficient heat conductor.
(2) Pretreatment of such surfaces with a bactericidal agent such as an acid (e.g., acetic acid), an alkali, chlorine, formaldehyde, ethyl alcohol, methyl alcohol or propyl alcohol, preferably in admixture with or dissolved in water or alcohol, such toxic agent being effective to kill the contaminating microorganisms or to reduce their resistance to heat and therefore render them more susceptible to being killed' by heat during the high temperature sterilization stage. of the process. Alcohol is preferred as a bactericidal agent because of its low cost, its toxicity tc bacteria and its lack of toxicity to human beings..
Pretreatment of such surfaces to adjust their pH to a range wherein the microorganisms thereon are more susceptible to being killed by heat.
It will be understood that these techniques may be applied, not only to containers but also to covers, to processing equipment and the like. F or convenience container surfaces will be referred to frequently herein but it will be Iunderstood that other surfaces are also contemplated.
Preferably the third method is employed, i.e., surface treatment to modify pH. The modifying agent may be an aqueous acid solution of suitable pH, c g., to 4, preferably l to 3, or it may be an aqueous alkali solution of suitable pH, e.g., to 14. Suitable acids include hydrochloric, sulfuric and acetic acids, and suitable alkalis include sodium and potassium hydroxides, 5% llye solutions such as customarily used in washing glass con-tainers in canneries, and trisodium phosphate.
Preferably the containers are treated with a surfactant solution prior to the pH modification, although surfactan-ts compati-ble with the pI-I modifier may be used in conjunction with the pH modification, i.e., may be incorporated in the acid or alkali solution. The advantage of using a surfactant is that it penetrates and wets contaminating material including bacterial spores and renders them more accessible to the acid alkali. Examples of I also have a bactericidal effect.
suitable surfactants are alkyl benzene sulfonates (such as the Nacconals and Oronite Detergent) and such nonionic surfactants as Antaron L-520 (a tall oil-ethylene oxide polymer).
The containers are preferably sprayed with surfactant solution, then with acid or alkaline solution; they are preferably held in inverted position to allow drainage of excess moisture; and the sprayed containers are then held for a suffi-cient time to cause the sprayed surfaces and adhering particles and microorganisms to be thoroughly wetted and permeated. The containers, with their surfaces stll wet with acid or alkaline solution, are then subjected to heat sterilization 'by any suitable means, such as steam at 212 to 270 F. land atmospheric pressure as in the Dunkley method, steam at superatmospheric pressure as in the Ball method, superheated steam at atmospheric pressure as in the Dole method or llame and combustion gases as in the Martin flame method.
The time and temperature of exposure to sterilizing heat will, of course, be regulated to achieve sterilization, but it will be found that substantially less rigorous conditions (eg, lower temperatures in the Ball, Dole and Martin methods and shorter contact times in the Dunkley method) are required because of and by reason of pretreatment of the containers in accordance with the present invention.
It will be apparent to those skilled in the art that pretreatment in accordance with the present invention may be carried out in a variety of Ways and by a variety of techniques. One such technique, which is preferred, is illustrated diagrammatically in ligure to which reference is made now.
Referring to the figure, glass or metal containers are conveyed at 10 to a twister 11 in which they are inverted so that they are upsideV down and have their open ends at the bottom. The inverted containers are then conveyed at 12 to a preheater 13 wherein they are preheated to, say, F. This preheating step is particularly advantageous with glass containers because it insures amore gradual heating of the gass, thereby reducing thermal shock and breakage caused by thermal shock when the glass containers are heated to sterilizing temperature at a later stage in the process. The preheating step may, however, be omitted. The containers are next conveyed at 14 to a Washing unit 15 in which a hot cleaning solution is sprayed onto the exterior and interior surfaces of the containers to wash them and remove gross impurities such as large dust particles, grease, etc. The cleaning solution may be of any suitable type, eg., an aqueous soap, lye, synthetic detergent or trisodium phosphate solution. Such solutions, besides cleaning in a sanitary sense, Moreover, this washingV with solution of detergent or surfactant facilitates subsequent wetting and penetration by the acid, alkali or bac- Itericidal agent used in the chemical pretreatment step described hereinafter.
The Washed containers are next conducted at 16 to a steaming unit 17 in which they are sprayed with steam to remove excess cleaning solution by mechanical action of the steam and by condensation of steam upon the container surfaces and resulting flow of condensed steam downwardly over the container surfaces. The containers are next conveyed at 1S to rinsing unit 19 wherein hot water, preferably at 20() to 210 F., is sprayed onto the interior and exterior surfaces to rinse the containers thoroughly. The containers are then conveyed at 20 to a steaming unit 25 in which steam jets are played onto the interior and exterior surfaces of the containers to remove adhering films or droplets of water; i.e., to remove excess moisture.
At this stage the containers will have been thoroughly cleansed and will, in fact, have been pretreated in accordance with one embodiment of :the invention. That is, bacterial spores, etc. will have been thoroughly wetted and penetrated by moisture, lhence are more susceptible to the lethal effect of heat, particularly dry heat such as used in the Dole, Dunkley and Martin methods. The containers can, therefore, be conducted directly to the high temperature sterilization unit. However, it is preferred to continue the pretreatment by adjusting the pH of the surfaces of the containers by spraying them with acid or alkaline solution of appropriate pH, or with a bactericidal agent such as alcohol. This is accomplished by conducting the containers at 30 to a chemical pretreating unit 31 wherein a suitable liquid is sprayed onto the interior and exterior surfaces of the containers. Such liquid may be, for example, an aqueous solution of acid such as acetic, hydrochloric or sulfuric acid, an aqueous solution of chlorine, an aqueous solution of an alkali such as sodium or potassium hydroxide, alcohol or formaldehyde and, in general, any chemical which is bactericidal and/ or which predisposes bacteria tothe lethal effects of heat. Aqueous acid or alkaline solutions are preferred, the most advantageous being hydrochloric acid and acetic acid solutions of a pH about 0 to 3, and a sodium hydroxide solution of pH about to 14. The chemically pretreated containers are then conveyed at 32 to a container sterilizer 33. The latter may be of the Dunkley, all, Dole or Martin type referred to hereinabove, wherein heat is employed as the sterilizing medium. That is, the heating medium may be atmospheric steam at 212 F.-270 F., superheated high pressure steam, superheated atmospheric stream, flame or combustion gases. It will be found that substantially lower temperatures, e.g., as much as 200 F. lower, suffice in the container sterilizer 33 than are required in the prior high temperature methods wherein containers are sterilized by dry heat but without pretreatment as described hereinabove. Thus, sterilizing temperatures of 200 to 300 F may lbe employed instead of 400 to 500 F., without corresponding increase of exposure time. Alternatively, higher temperatures (400-500 F.) but shorter exposure times may be employed. Where container failure and breakage are the chief difllculty, the tempera- .ture will be lowered, but in the case of containers and covers where high temperature is not a disadvantage, the exposure time may be shortened to speed up the process.
Temperatures of about 270 F. are obtainable in the Dunkley process provided dry, saturated, high pressure steam is expanded into the containers. Steams at about 100 p.s.i. gauge, such as commonly used Vin canneries, is adequate for the purpose. As noted above, in the Dunkley process temperatures of this order require excessive contact times. It is a particularly impotrant advantage of the process of this invention that the Dunkley process is made operable with short contact times. The Dunkley process, thus modified is the preferred embodiment of the present invention and it avoids the necessity of adding superheat by external means, and the high temperatures and container failure which characterize the Dole method.
The sterile containers are then conveyed at 34 to a rinsing unit 35 similar to the rinsing unit 19 wherein sterile water (c g., stream condensate) is sprayed onto the exterior and interior surfaces of the containers to wash the chemical fluid from the containers. This rinsing 0peration may be omitted if a volatile chemical agent such as acetic acid, hydrochloric acid, formaldehyde or alcohol is used.
The sterile containers are next conveyed at 40 to a steaming unit 41 similar to the steam unit 25 and are then conveyed at 42 to a twister 43 wherein they are turned to upright position and are then conveyed at 44 to a filler 45. Sterile product enters at 46 and the containers are filled. The filled sterile containers are then conveyed at 47 to a sealer 48. The sealer 48 is supplied with sterile covers at 49 which are applied in the sealer to the filled con- Itainers. The sealed, sterile filled containers are removed from the system at 50.
It will be understood, of course, that certain parts of the system will be enclosed, although not necessarily air tight. Thus, the container sterilizer 33, the lines or conduits shown at 34, 40, 42, 44 and 47, the rising unit 35, the steaming unit 41, the twister 43, the filler 45, and the sealer 48 will be enclosed, not necessarily to prevent communication with the atmosphere but to provide a jacket or chest which can be kept fllled with sterile medium. Thus steam, hot combustion gases, or other suitable sterile gas may be introduced into the enclosures of the aforesaid ducts and conveyors and units to maintain a sterile atmosphere and to `prevent ingress of nonsterile air from outside. It will also be understood that the covers supplied at 49 will be sterilized by the same or some other suitable method, and that the various washing and chemical pretreatment steps described hereinabove may be applied to the covers.
It will also be understood that the entire system, cornmencing with container sterilizer 33, and including conveyor equipment, the interior surfaces of enclosures, etc. will be presterilized before sterile canning is commenced. In presterilizing the equipment, any suitable means may be employed, e.g., superheated steam or hot combustion gases, and the time required for presterilization may be reduced by rst pretreating the equipment, `as by wetting it with water or aqueous acid solution. A preferred method of presterilization is illustrated in the figure.
Before describing this method of presterilization, it is desired to comment as follows lon a modification of the present invention which is particularly well adapted to glass containers. Referring -again to the figure, if the. wash liquid used in the washing unit 15 is bactericidal, e.g., a 5% lye solution such as commonly used to wash glass containers, it sufllces to h-old the washed containers sufllciently long to insure sterility, -then drain them and give them a sterile rinse, then conduct the filling and closing operations under sterile conditions. This procedure, which eliminates the chemical pretreatment and heat sterilization carried out at 31 and 33, is better adapted to glass containers than to metal containers.
Referring again to the figure, a presterilization technique is there shown which will now be described. A volatile chemical sterilizing or bactericidal medium, e.g., an aqueous solution of acetic or hydrochloric acid of pH about 0 to 3, or an aqueous solution of formaldehyde, or ethyl alcohol is maintained at 55 in a tank 56 and is pumped at a metered rate by a pump 57 through a line 58 into the inner chamber 59 of a vaporizer 60. The vaporizer 60 has a jacket 61 providing an annular space `62 into which high pressure steam is introduced at 63, steam and condensate being removed through a line 64 and steam trap 65. The temperature of the steam jacket and the rate of flow of chemical fluid into the chamber 59 are such that the chemical fluid is completely vaporized and passes through lines 66 to the elements 33, 35, 41, 43, 45 and 48 of the system, also, of course, into the ducts and conveyors connecting these elements.
The vapors of chemical fluid will condense upon the cold surfaces of these .elements thereby forming a film of liquid of substantially the same composition and pH as that in the tank 56. As vapors continue to enter these elements they will heat the exposed surfaces and will sterilize them. This presterilization Aof the system is accomplished at relatively low temperatures of the order of 200 to 250 F. This is advantageous because higher temperatures of the order of 400 to 500 F. cause distortion of mechanical parts and cause lubrication difficulties.
It may be desirable, after presterilization has been accomplished, to pass steam through the elements 33, 35, 41, 43, 45 and 48 to vaporize and drive off the chemical medium, e.g., acetic acid, hydrochloric acid, etc.
It will, therefore, be apparent that a method and apparatus have been provided which, among other things, achieves sterilization of containers, covers processing equipment and the like at lower temperatures than employed in present commercial methods, such as the Dole method; which renders the Dunkley method operable; and which is effective to achieve sterile or aseptic canning at high speeds and With fewer difficulties, such as container failure, resulting from the use of high temperatures.
I claim: 1. Canning apparatus comprising la preheater for preheating containers, means for washing and Water-wetting the preheated containers, a container sterilizer unit employing dry heat as the sterilizing medium connected to said means for washing and Water-wetting for treating the containers While they are still Wet, means to move said containers sequentially through the preheater, the means for washing and Water-wetting and through the said sterilizer unit, means for feeding the containers from the sterilizing unit sequentially to a ller unit and to a closing element, means for supplying sterilized covers to the closing element, and means for maintaining sterile conditions in the ller and closing element.
2. The apparatus of claim 1 having pre-sterilizing means for the apparatus, including means for volatilizing a volatile bactericidal chemical liquid and means for `distributing said Volatilized liquid in said apparatus in association With steam in order to sterilize said apparatus, said apparatus initially being cold, so that said volatilized liquid and steam at iirst condense on the cold surfaces of said apparatus, to enable sterilization at relatively low temperatures in the order of 200 to 250 F.
3. The apparatus of claim 2 having means for sending steam alone through the apparatus after presterilization is accomplished to vaporize and drive off said bactericidal liquid.
References Cited by the Examiner UNITED STATES PATENTS 1,270,798v 7/1918 Dunkley 99-182 2,014,750 9/1935 Stegemann 21-80 2,549,216 471951 Martin 99-182 2,761,603 4/1956 Fairchild 99;-182 X 2,771,645 11/1956 Martin 99-182 2,862,821 12/1958 Wilbur et al. 99-182- 20 MORRIS O. WOLK, Primary Examiner.
F. W. BROWN, Assistant Examiner.