Patent Application
20180168199
The present invention relates to methods and systems for the microwave-assisted pasteurization and sterilization of liquid and semi-liquid materials in sealed containers.
In recent times, consumer preference has begun shifting toward more health-conscious beverages, such as teas, juices, and isotonics, many of which require hot filling in order to achieve desired shelf-life. However, the temperatures required for hot filling exceed the glass transition temperature of the polymers used to form the beverage containers. To prevent melting, the bottles and other containers used for hot-filled beverages are, on average, 20 to 35 percent thicker than those used for beverages that are not hot filled. Additionally, bottles used for hot filled beverages often include thermal expansion panels, which further increase the thickness of the bottle, while also limiting product design options and consumer appeal.
Thus, a need exists for methods and systems for processing isotonic beverages and other similar liquid and semi-liquid consumable items, that permits the use of thinner containers, while still providing the desired degree of pasteurization or sterilization needed to achieve a suitable shelf-life.
One embodiment of the present invention concerns a process for pasteurization or sterilization of a bottled liquid using a microwave heating system. The process comprises (a) providing a plurality of sealed bottles at least partially filled with a liquid, wherein the pressure within each of the sealed bottles is not more than 1.5 atm; (b) passing the at least partially filled bottles through a microwave heating chamber; and (c) during at least a portion of the passing, heating the bottles, wherein at least a portion of the heating is performed using microwave energy. Each of the bottles is formed from a polymeric material and the ratio of the dry empty weight of an individual bottle measured without a cap to the volume capacity for liquid in the individual bottle is not more than 0.040 g/mL.
Another embodiment of the present invention concerns a packaged liquid item. The packaged liquid item comprises a bottle presenting an opening and defining an internal volume, a cap sealing the opening, and a liquid at least partially filling the internal volume of the bottle. The liquid has a total sugar content of at least 1° Brix and the pressure within the sealed bottle is not more than 1.5 atm. The bottle is formed from a polymeric material, and the ratio of the dry empty weight of the bottle measured without the cap to the nominal liquid capacity of the bottle is not more than 0.040 g/mL.
Yet another embodiment of the present invention concerns a process for pasteurization or sterilization of a liquid or semi-liquid material. The process comprises (a) introducing a plurality of a bottles into a microwave heating chamber, wherein each of the bottles are at least partially filled with the liquid or semi-liquid material, wherein the ratio of the maximum length of each of the bottles to its maximum diameter is at least 2:1; (b) passing the bottles into a heating zone, wherein the heating zone is at least partially filled with a liquid medium; and (c) heating the bottles in the heating zone, wherein at least a portion of the heating is performed using microwave energy. The bottles are submerged in the liquid medium during the heating, and each of the bottles has a residence time within the heating zone that is within about 10 percent of the residence time of each of the other bottles heated in the heating zone.
Still another embodiment of the present invention concerns a process for the pasteurization or sterilization of bottled water using a microwave heating system. The process comprises (a) at least partially filling a plurality of bottles with water; (b) sealing the at least partially filled bottles of water with at least one sealing device; (c) passing the sealed bottles of water through a microwave heating chamber; (d) continuously directing microwave energy toward the bottles of water passing through the microwave heating chamber; and (e) heating the bottles of water to a target temperature sufficient to pasteurize or sterilize the water within the bottles using at least a portion of the microwave energy.
A further embodiment of the present invention concerns a process for pasteurization or sterilization of liquid or semi-liquid material. The process comprises (a) passing a plurality of containers at least partially filled with the liquid or semi-liquid material through a microwave heating chamber at least partially filled with a liquid medium, wherein the containers are at least partially formed from a polymeric material having a glass transition temperature; (b) discharging microwave energy into the microwave heating chamber via at least one microwave launcher; and (c) heating the containers using at least a portion of the microwave energy discharged into the microwave heating chamber. The containers are submerged in the liquid medium during the heating. The heating is sufficient to increase the minimum temperature of the coldest region of the liquid or semi-liquid medium to temperature at or above a target temperature for a predetermined amount of time, and the target temperature is greater than the glass transition temperature of the polymeric material. During at least a portion of the heating, the average temperature of the liquid medium at the wall of each of the containers is below the glass transition temperature of the polymeric material.
A still further embodiment of the present invention concerns a process for pasteurization or sterilization of liquid or semi-liquid material. The process comprises (a) at least partially filling a plurality of containers with the liquid or semi-liquid material, wherein the maximum temperature of the liquid or semi-liquid material during the filling is in the range of from 110° F. to a first target temperature; (b) passing the containers through a microwave heating zone on a convey line; (c) continuously directing microwave energy toward the containers passing through the microwave heating zone on the convey line; and (d) heating the containers to a second temperature that is greater than the first target temperature using at least a portion of the microwave energy in order to pasteurize or sterilize the liquid or semi-liquid material within each of the containers.
An even further embodiment of the present invention concerns a microwave heating system for heating a plurality of containers filled with a liquid or semi-liquid material. The system comprises at least one microwave generator for generating microwave energy, a microwave heating chamber for heating the containers, wherein the microwave heating chamber has an inlet and an outlet, and at least two spaced apart microwave launchers for emitting at least a portion of the microwave energy into the microwave heating chamber, wherein at least a portion of the microwave energy is used to heat the containers. The inlet to the microwave heating chamber is at a higher vertical elevation than the outlet of the microwave heating chamber.
Various embodiments of the present invention are described in detail below with reference to the attached drawing Figures, wherein:
The present invention generally relates to methods and systems capable of rapidly and uniformly pasteurizing, sterilizing, or pasteurizing and sterilizing a liquid or semi-liquid material in a bottle or other container without exposing the container or its contents to the harsh operating conditions that are common in traditional processes. The processes and system of the present invention may also reduce, or eliminate, the need for pretreatment steps such as hot filling and aseptic processing, while still providing liquid and semi-liquid products having the requisite degree of pasteurization or sterilization. At the same time, because the container and its contents are exposed to less severe operating conditions, the containers used to hold the liquid or semi-liquid may be between 10 and 50 percent thinner than conventional containers, which results in reduced operating and raw material costs. Furthermore, the liquid or semi-liquid being treated is not overheated or overcooked during processing, which permits a higher quality end product having desirable organoleptic properties, such as taste, texture, and color. Additionally, many of the liquids and semi-liquids processed as described herein may be shelf-stable, which may lead to a significant reduction in refrigeration requirements across the supply chain resulting in even more cost savings.
Embodiments of the present invention may be carried out in a variety of different microwave heating systems including, for example, those similar to the microwave heating systems described in U.S. Patent Application Publication No. US 2013/0240516 (“the '516 application”), which is incorporated herein by reference to the extent not inconsistent with the present disclosure. In addition, embodiments of the present invention can be carried out in the microwave heating system described in U.S. Pat. No. 7,119,313.
In general, pasteurization involves the rapid heating of a liquid or semi-liquid to a minimum temperature between 80° C. and 100° C., while sterilization involves heating the liquid or semi-liquid to a minimum temperature between about 100° C. and about 140° C. However, because pasteurization and sterilization may take place simultaneously, or nearly simultaneously, the processes and systems described herein may be configured for pasteurization, sterilization, or both pasteurization and sterilization. Processes and systems as described herein may be configured to pasteurize, sterilize, or pasteurize and sterilize a plurality of bottles or other types of containers, a liquid or semi-liquid material enclosed therein, or both.
Turning initially to
Subsequently, the bottles may then be passed to a quench zone 20, wherein the bottles may be cooled to a suitable handling temperature. In some cases, the quench zone 20 may be divided into a high-pressure cooling zone 24a and a low-pressure cooling zone 24b and can include another transfer zone 15b between the two cooling zones 24a,b. Alternatively, the quench zone 20 may include a single cooling zone with transfer zone 15b located upstream or downstream of the cooling zone (not shown). As used herein, the term “upstream” and “downstream” refer to the relative positions of various components or zones along the main flow path through the microwave heating system. A component or zone located prior to another can be said to be “upstream” of that component, while a component or zone located after another may be said to be “downstream” of that component.
In some cases, two or more of the thermalization zone 14, microwave heating zone 16, hold zone 18, and quench zone 20 may be defined within a single vessel, while, in other cases, at least one of these zones may be defined within one or more separate vessels. Additionally, in some cases, one or more of the vessels may be configured to be at least partially filled with a liquid medium in which the bottles being processed can be at least partially submerged during processing. As used herein, the term “at least partially filled” means at least 50 percent of the volume of the specified vessel is filled with a liquid medium. In some cases, the volume of at least one of the vessels used in the thermalization zone 14, microwave heating zone 16, hold zone 18, and quench zone 20 can be at least about 75 percent, at least about 90 percent, at least about 95 percent, or nearly 100 percent filled with a liquid medium.
When present, the liquid medium used may include any suitable type of liquid. In some cases, the liquid medium may have a dielectric constant greater than the dielectric constant of air and/or it may have a dielectric constant similar to the dielectric constant of the liquid or semi-liquid within the bottles being processed. Water (or a liquid medium comprising water) may be particularly suitable. The liquid medium may also include one or more additives, such as, for example, oils, alcohols, glycols, and salts, to alter or enhance its physical properties (e.g., boiling point) of the liquid medium at the conditions of operation of the system.
Additionally, the microwave heating system 10 may include a conveyance system (not shown in
Turning again to
Although processes and systems of the present invention are described herein with respect to processing “containers,” it should be understood that this term is not limited to a particular package shape or configuration, but instead broadly encompasses any item capable of holding some volume of liquid or semi-liquid material. Examples of suitable types of containers can include, but are not limited to, bottles, trays, jugs, cartons, bags, pouches, tubes, and tubs. Containers suitable for use in the present invention may range in size, and can have, for example, a nominal liquid capacity as low as 1 fluid ounce (fl. oz.) or as high as 150 fl. oz. or more. As used herein, the term “nominal liquid capacity” refers to the volume of liquid or semi-liquid material that the container is designed to hold, while the term “maximum liquid capacity” refers to the maximum possible volume of liquid that a given container is capable of holding.
Containers suitable for use with the present invention can have a nominal liquid capacity of at least about 1.5, at least about 2, at least about 4, at least about 6, at least about 8, at least about 10, at least about 12, at least about 15, at least about 18, at least about 20, at least about 22, at least about 24, at least about 28, at least about 30, at least about 32, at least about 34, at least about 36, at least about 38, at least about 40, at least about 42, at least about 48, at least about 52, or at least about 56 fl. oz., and/or not more than about 150, not more than about 140, not more than about 130, not more than about 128, not more than about 122, not more than about 120, not more than about 118, not more than about 112, not more than about 110, not more than about 106, not more than about 100, not more than about 96, not more than about 90, not more than about 86, not more than about 80, not more than about 76, not more than about 70, or not more than about 64 fl. oz. In some cases, containers used in the present invention can have a nominal liquid capacity in the range of from about 4 to about 40 fl. oz., about 6 to 38 fl. oz., or about 8 to 36 fl. oz.
The containers processable as described herein may have a variety of shapes including, but not limited to, cubic, cylindrical, prism, or polygonal. Each container can have a length (longest dimension) of at least about 2 inches, at least about 4 inches, at least about 6 inches and/or not more than about 18 inches, not more than about 12 inches, or not more than about 10 inches; a width (second longest dimension) of at least about 1 inch, at least about 2 inches, at least about 4 inches and/or not more than about 12 inches, not more than about 10 inches, or not more than about 8 inches; and/or a depth (shortest dimension) of at least about 0.5 inches, at least about 1 inch, at least about 2 inches and/or not more than about 8 inches, not more than about 6 inches, or not more than about 4 inches. In some applications, the containers can comprise individual items or packages having a generally rectangular or prism-like shape, while, in other applications, the containers may comprise elongated bottles having a ratio of the maximum length to maximum diameter of at least 2:1, at least about 2.5:1, or at least about 3:1. Other shapes are possible and should be considered to fall within the scope of the present invention.
Additionally, the containers may be formed of a wide variety of suitable materials. In some cases, the containers may be at least partially formed from a polymeric material having, for example, a glass transition temperature of at least about 50, at least about 55, at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, or at least about 85° C. Examples of suitable polymeric materials can include, but are not limited to, polyethylene terephthalate, polyethylene, polypropylene, polyamide, EVOH, polylactic acid, polyhydroxyalkanoates, polybutylene succinate, biopolymers, and combinations thereof. Containers formed from non-polymeric materials, such as glass or other at least partially microwave-transparent materials, may also be used in various embodiments in the present invention. In some cases, the containers may be formed of virgin materials, while, in others at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, at least about 50, at least about 55, at least about 60, at least about 65, at least about 70, or at least about 75 percent or more of the container may be formed from a recycled, recyclable, or compostable material.
It has been discovered that processes and systems as described herein may be particularly useful for the pasteurization or sterilization (or both) of microbiologically susceptible liquids and semi-liquids such as, for example, isotonic beverages, as well as teas, juices, and a variety of other food, beverage, pharmaceutical, medical, nutraceutical, and veterinary liquid and semi-liquid materials and for the purification of water. Microbiologically susceptible liquids and semi-liquids have various properties conducive to the growth of bacteria, mold, fungus, and other microbiological contaminants. For example, in some cases, microbiologically susceptible liquids and semi-liquids may have a non-acidic pH, may not be pressurized or carbonated, may have a high sugar content, and/or a low preservative content, although not all of these are required.
The properties of the liquid or semi-liquid material processed according to the present invention may vary widely. In general, the pH of the liquid or semi-liquid material can range from 0 to 13. In some cases, the pH can be at least about 3, at least about 3.5, at least about 4, at least about 4.5, at least about 5, at least about 5.5, at least about 6, or at least about 6.5, or higher, while, in other cases, the pH can be less than 3, not more than about 2.5, not more than about 2, not more than about 1.5, or not more than about 1. Additionally, the liquid or semi-liquid material could have a variety of viscosities and can be, for example, a liquid, or even a gel or paste.
The sugar content of the liquid or semi-liquid material, measured by the Brix scale, can be at least about 1, at least about 1.5, at least about 2, at least about 2.5, at least about 3, or at least about 3.5°, or it can be less than 2, less than 1.5, less than 1, or even 0° Brix. In some cases, the sugar content of the liquid or semi-liquid material can be at least about 2, at least about 2.5, at least about 3, at least about 3.5, at least about 4, at least about 4.5, or at least about 5 and/or not more than about 20, not more than about 18, not more than about 15, not more than about 12, not more than about 10, or not more than about 8 grams of sugar per milliliter of solution (g/mL).
In some applications, the liquid or semi-liquid material can have a preservative content of not more than about 3, not more than about 2.5, not more than about 2, not more than about 1.5, or not more than about 1 weight percent, or it may include higher concentrations of one or more preservatives. Examples of preservatives can include, but are not limited to, benzoic acid, sorbic acid, salts thereof, and combinations thereof. In some applications, the liquid or semi-liquid material may be nutritive or non-nutritive and can include pulp or particles having an average size of not more than 30, not more than about 25, not more than about 20, not more than about 15, not more than about 10, not more than about 5, not more than about 2, or not more than about 1 mm, or in the range of 1 to 30 mm, 2 to 27 mm, or 5 to 25 mm.
Optionally, the liquid or semi-liquid material may include one or more additives selected from the group consisting of natural or synthetic sweeteners such as sucrose, fructose, and high fructose corn syrup, acidification agents such as phosphoric and/or citric acid, colors, foaming agents, emulsifying agents, vitamins, electrolytes, and combinations thereof. The types and/or amounts of each additive may be varied depending on the particular application.
Specific examples of suitable liquid or semi-liquid materials can include, but are not limited to, beverages such as teas, juices, mineral drinks, electrolyte drinks, energy drinks, vitamin drinks, shakes, smoothies, dairy drinks, alcoholic drinks, and coffee drinks. Other suitable beverages can include shelf-stable dairy drinks, including, but not limited to milk and cream, as well as carbonated soft drinks. Examples of suitable liquid or semi-liquid material foods can include, but are not limited to, jams, jellies, soups, stews, sauces, salsas, creams such as whipped cream, condiments such as ketchup, mustard, mayonnaise, salsas, and syrups. In some applications, the food or beverage may be pressurized or carbonated, while, in other applications, the food or beverage may not be. Additionally, the liquid or semi-liquid material may also be a medical fluid such as, for example, sterile eye wash, and other sterile liquids or medicines. In some case, the liquid may be or comprise water.
Conventionally, many liquids and semi-liquids and, in particular, microbiologically susceptible liquid or semi-liquid material, are processed by hot filling or aseptically processing the material or its container before or during the fill step in order to achieve the requisite kill rate and/or desired shelf life for the final product. Examples of suitable kill rates can be in the range of 1 log to 8 log kill, in the range of 2 log to 7 log kill, or in the range of 3 log to 6 log kill. One drawback of these conventional processes is that the temperatures required for the hot filling and aseptic processing steps often exceed the glass transition temperature of the polymeric material from which the container is formed. As result, bottles and other containers used in hot filling and/or aseptic processes are often excessively thick and include design features, such as expansion panels, that are required to prevent deformation or damage to the container. For example, conventional bottles for isotonic beverages formed from polyethylene terephthalate (PET) typically have a ratio of the dry empty weight of an individual bottle measured without the cap to the nominal liquid capacity of the bottle greater than 0.050 g/mL.
However, it has been discovered that pasteurizing or sterilizing liquids and semi-liquids according to embodiments of the present invention may eliminate the need for hot filling, aseptic processing, and other such pretreatment steps. As a result, the thickness of the container being used may be reduced, thereby providing a substantial reduction of energy and raw material costs. Additionally, features such as expansion panels may be eliminated, increasing the appeal while also reducing the cost of the container. It has been found, for example, that polymeric bottles used for holding liquids having a sealed pressure of less than 1.5 atm can be not more than 0.040, not more than about 0.037, not more than about 0.035, not more than about 0.032, or not more than about 0.030 g/mL, which represents an overall reduction of 10 to 50 percent as compared to conventional hot-fill containers.
Turning back to
Typically, the target temperature may be lower than the conventional hot-fill temperature for a given liquid or semi-liquid material. In some applications when the containers being filled are formed from a polymeric material, the target filling temperature may be less than the glass transition temperature of the polymeric material and it can, in some cases, be at least about 2, at least about 5, at least about 8, at least about 10, or at least about 12° F. less than the glass transition temperature of the polymer material. This is in contrast to traditional hot-filling processes, which may introduce liquid or semi-liquid material into containers at or just above the glass transition temperature of a polymeric container.
In some cases, the liquid or semi-liquid material may be introduced into the containers at a relatively cool temperature of less than, for example, 80° F., and the filled bottles may then be preheated before or after being sealed. In other applications, the liquid or semi-liquid material may be introduced into the containers at a warm temperature between, for example, about 95, about 100, about 105, or about 110° F. and the target filling temperature. In such cases, the filled bottles may optionally be preheated in the filling zone before or after being sealed, and/or may be additionally heated to achieve a substantially uniform temperature in the thermalization zone 14, as shown in
As discussed previously, in some cases, the systems and processes of the present invention may reduce or eliminate the need for common pre-treatment steps such as, for example, hot filling, aseptic processing, reverse osmosis, and other similar processes. In some applications, the liquids and semi-liquids previously required to be hot-filled or aseptically processed may be directly introduced into containers in the present invention without these steps being performed. As a result, the containers and liquid or semi-liquid material are not pasteurized or sterilized prior to the filling step, and the liquid or semi-liquid may be introduced into the container at a lower temperature within one or more of the ranges described herein.
Before exiting the filling zone, the at least partially filled containers may be sealed with a sealing device to provide sealed containers suitable for introduction into the thermalization and/or microwave heating zones. The specific type of sealing device may depend on the particular type of container and can include, for example, caps or lids having a variety of different closures (e.g., snap-on, screw-on, etc.). The containers may require any number of sealing devices, and, in some cases, may not require any sealing device when, for example, the container is a single-use or tamper-evident container. The sealed containers may be pressurized or unpressurized, depending on the specific application. In some applications, the internal pressure of the sealed container can be greater than 3, at least about 3.25, at least about 3.5, or at least about 4 atm, while, in other applications, it may not more than about 3, not more than about 2.75, not more than about 2.5, not more than about 2.25, not more than about 2, not more than about 1.75, or not more than about 1.5 atm. When pressurized, the liquid or semi-liquid material may be pressurized with any suitable gas including, but not limited to, nitrogen, carbon dioxide, and combinations thereof. The containers can be filled and sealed using any suitable type of device or system including, but not limited to a rotary filler.
In other embodiments, the microwave system 10 may not include a filling zone and the filled bottles or other containers being pasteurized or sterilized may be introduced directly into the thermalization zone 14. In such embodiments, the bottles or other containers may be filled at another location by another party, and transported to the microwave heating system to be pasteurized or sterilized as described herein.
As shown in
In some applications, the thermalization zone 14 may include a chamber at least partially filled with a liquid medium, such that the containers are submerged in and pass through the liquid during the thermalization step. Optionally, the thermalization chamber may be operated under pressure, such that the containers are exposed to a pressure that is at least about 2, at least about 5, at least about 7, at least about 10, or at least about 15 psi greater than the pressure of the fluid surrounding the containers at ambient conditions. In some embodiments, at least a portion of the thermalization zone 14 may be operated within about 10, within about 8, within about 5, within about 2 or at ambient pressure. In other applications, the pressure in the thermalization chamber may only be due to the surrounding fluid pressure. In some cases, the system 10 may not include a thermalization zone such that the containers are directly introduced into the microwave heating zone 16 from the filling zone 12.
When pressurized, the thermalization step may be performed at a pressure of at least about 5, or at least about 10 psig and/or not more than about 80, not more than about 50, not more than about 40, or not more than about 25 psig. The containers passing through the thermalization zone 14 can have an average residence time of at least about 1 minute, at least about 5 minutes, at least about 10 minutes and/or not more than about 60 minutes, not more than about 20 minutes, or not more than about 10 minutes. The liquid or semi-liquid in the containers withdrawn from the thermalization zone 14 can have an average temperature of at least about 20° C., at least about 25° C., at least about 30° C., at least about 35° C. and/or not more than about 90° C., not more than about 75° C., not more than about 60° C., or not more than about 50° C.
In some embodiments, at least one transfer zone 15a may exist to transport the containers from the filling zone 12 to the thermalization zone 14, if present, and, if not present, to the microwave heating zone 16. When present, the transfer zone 15a may include one or more transfer devices for moving the plurality of containers from the filling zone 12 to the thermalization zone 14 or the microwave heating zone 16. Examples of transfer devices can include, but are not limited to, a revolving door, a screw drive, or gate valve. In other applications, the containers may be passed through a vertical column of water or other fluid having a height of at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, or at least about 30 feet in order to transition the containers from ambient pressure to the higher pressure of a liquid-filled thermalization zone 14 or microwave heating zone 16.
While being introduced into the thermalization zone 14 and, if no thermalization zone, into the microwave heating zone 16, the containers may be configured in any suitable arrangement to help facilitate their passage through the microwave heating system 10. In some cases, the containers passing through the thermalization zone 14 and/or the microwave zone 16 can be arranged in such a way as to control the total residence time of each container within each processing zone. For example, in some applications, each of the containers passed through one of the thermalization zone 14 and/or microwave heating zone 16 can have a residence time within that zone that is within about 25, within about 20, within about 15, within about 10, within about 5, or within about 2 percent of the residence times of each of the other containers passed through the same zone. Control of the residence time of the individual containers may help ensure overall product quality, consistency, and safety.
In some embodiments, the residence time of the containers may be controlled by securing the containers in one or more carriers, which are transported through the system via a conveyance system (not shown) including one or more convey lines. One example of a carrier suitable in the microwave heating system according to various embodiments of the present invention is described in U.S. Patent Application Publication No. 2017/0099706, which is incorporated herein by reference to the extent not inconsistent with the present disclosure. Several exemplary views of such a carrier are provided in
As shown in
Carriers suitable for use in the microwave heating system described herein may be formed of any suitable materials, including low loss materials, and, in some cases, even electrically conductive materials. For example, carriers suitable for use in microwave heating system 110 can comprise or be constructed of plastic, fiberglass, or any other dielectric material and may be made of one or more microwave-compatible and/or microwave-transparent materials and may be a lossy material. In some embodiments, the carrier can comprise substantially no metal.
In other embodiments, the carrier may include a plurality of support members, shown in
In some embodiments, the first and second side members 118a,b and first and second end members 120a,b may be formed of any suitable material including, for example, a low loss material having a loss tangent of not more than about 10−2, not more than about 10−3, or not more than about 10−2, measured at 20° C. Each of the side members 118a,b and end members 120a,b may be formed of the same material, at least one may be formed of a different material. Examples of suitable low loss tangent materials may include, but are not limited to, various polymers and ceramics. In some embodiments, the low loss tangent material may be a food-grade material.
When the low loss material is a polymeric material, it may have a glass transition temperature of at least about 80° C., at least about 100° C., at least about 120° C., or at least about 140° C., so that it may withstand the elevated temperatures to which the carrier may be exposed during heating of the containers. Examples of suitable low loss polymers can include, but are not limited to, polytetrafluoroethylene (PTFE), polysulfone, polynorbornene, polycarbonate (PC), acrylonitrile butadiene styrene (ABS), poly(methyl methacrylate) (PMMA), polyetherimide (PEI), polystyrene, polyvinyl alcohol (PVA), polyvinyl chloride (PVC), and combinations thereof. The polymer can be monolithic or it may be reinforced with glass fibers, such as, for example glass-filed PTFE (“TEFLON”). Ceramics, such as aluminosilicates, may also be used as the low loss material.
Another example of a carrier is illustrated in
Lower and upper securing surfaces 212a and 212b may be attached to one another by a securing device, shown as a fastener 219 in
In other applications, the containers may not be secured in a carrier. In such cases, the residence time may be controlled by passing the containers through one or more tunnels sized to permit no more than a single container from passing through at a time. For example, the ratio of the height of the tunnel, measured in a direction perpendicular to the direction of travel of the containers, to the dimension of the containers in the same direction, may be less than 1.5:1, not more than about 1.3:1, not more than about 1.25:1, or not more than about 1.1:1. In some cases, the containers passed through the tunnels may be bottles arranged in a single file line. The bottles may also be arranged in a generally side-by-side configuration, as shown in
As the bottles (or other containers) pass through the thermalization zone 14 and/or microwave heating zone 16 shown in
Referring again to
As the bottles pass through the microwave heating zone 16, the bottles may be heated so that the coldest portion of the contents of each bottle achieves a target temperature. When the microwave heating system is a sterilization or pasteurization system, the target temperature can be a sterilization or pasteurization target temperature of at least about 65° C., at least about 70° C., at least about 75° C., at least about 80° C., at least about 85° C., at least about 90° C., at least about 95° C., at least about 100° C., at least about 105° C., at least about 110° C., at least about 115° C., at least about 120° C., at least about 121° C., at least about 122° C. and/or not more than about 130° C., not more than about 128° C., or not more than about 126° C.
As the bottles or other containers pass through the microwave heating chamber, they may be heated to the target temperature in a relatively short time, which can help minimize any damage or degradation of the liquid or semi-liquid material being heated. For example, the average residence time of each bottle passing through the microwave heating zone can be at least about 5 seconds, at least about 20 seconds, at least about 60 seconds and/or not more than about 10 minutes, not more than about 8 minutes, not more than about 5 minutes, not more than about 3 minutes, not more than about 2 minutes, or not more than about 1 minute. The minimum temperature of the bottles heated in the microwave heating zone can increase by at least about 20° C., at least about 30° C., at least about 40° C., at least about 50° C., at least about 75° C. and/or not more than about 150° C., not more than about 125° C., or not more than about 100° C.
When the microwave heating chamber is liquid-filled, the average bulk temperature of the liquid in the microwave heating chamber may vary and, in some cases, can depend on the amount of microwave energy discharged into the microwave heating chamber. The average bulk temperature of the liquid in the microwave heating chamber can be at least about 70° C., at least about 75° C., at least about 80° C., at least about 85° C., at least about 90° C., at least about 95° C., at least about 100° C., at least about 105° C., at least about 110° C., at least about 115° C., or at least about 120° C. and/or not more than about 135°, not more than about 132° C., not more than about 130° C., not more than about 127° C., or not more than about 125° C. In some cases, this can be at least about 1, at least about 2, at least about 5, at least about 10, at least about 15° C. and/or not more than about 50, not more than about 45, not more than about 40, not more than about 35, not more than about 30, or not more than about 25° C. different (e.g., higher or lower) than the temperature of the contents of the bottle measured at its coldest point.
The microwave heating chamber can be operated at approximately ambient pressure. Alternatively, it may be a pressurized microwave chamber that operates at a pressure that is at least 5 psig, at least about 10 psig, at least about 15 psig, or at least about 17 psig and/or not more than about 80 psig, not more than about 60 psig, not more than about 50 psig, or not more than about 40 psig above ambient pressure. As used herein, the term “ambient” pressure refers to the pressure exerted by the fluid in the microwave heating chamber without the influence of external pressurization devices.
One example of a microwave heating zone 316 configured for use in the microwave heating system described herein is shown schematically in
The microwave generator 332 can be any suitable device for generating microwave energy of a desired wavelength (k). Examples of suitable types of microwave generators can include, but are not limited to, magnetrons, klystrons, traveling wave tubes, and gyrotrons. Although illustrated in
The microwave distribution system 334 comprises a plurality of waveguides for directing the microwave energy from the generator 332 to the microwave heating chamber 330. The waveguides can be constructed to propagate microwave energy in a specific predominant mode, which may be the same as or different than the mode of microwave energy generated by the generator. As used herein, the term “mode” refers to a generally fixed cross-sectional field pattern of microwave energy. Examples of suitable modes of microwave energy are TExy mode, wherein x and y are integers in the range of from 0 to 5 and TMab mode, wherein a and b are integers in the range of from 0 to 5.
The microwave heating zone 316 shown in
Additionally, or in the alternative, the microwave heating system may also include at least two launchers positioned on opposite sides of the microwave chamber as shown by upper and lower sets of microwave launchers 332a and 332b illustrated in
Any suitable type of microwave launcher may be used in the microwave heating zone. In some cases, one or more microwave launchers utilized in the microwave heating zone may be tilted at a launch tilt angle of at least 2, at least about 4, at least about 6° and/or not more than about 15, not more than about 10, not more than about 8, or not more than about 6°, as described in detail in the '516 application. Additionally, or in the alternatively, at least one launch opening may be at least partially covered with a microwave-transparent window, as also described in detail in the '516 application. Specific examples of suitable launcher configurations, including particular dimensions, shapes, and orientations, are also described in the '516 application.
As generally shown in
In still other embodiments, the microwave heating chamber 330 may be or comprise a spiral chamber or include at least one spiral section. For example, when microwave heating chamber 330 is a spiral chamber, it may include at least 1, at least 2, at least 3, at least 4, at least 5, or at least 6 bends or curves having an angle greater than 90°. Examples of such microwave heating chambers 330 are shown in
Referring again to
Upon introduction into the microwave heating zone 16, the containers may be passed through the microwave heating chamber while microwave energy is continuously discharged into the chamber. As discussed above, the heating chamber may be at least partially filled with a liquid medium so that the bottles or other containers are submerged in and move through the liquid medium as they are passed through the chamber. In some applications, the microwave chamber can be at least 50, at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, at least about 90, or at least about 95 percent filled with a liquid medium. The liquid medium can include or be water, and it may have a dielectric constant similar to the liquid or semi-liquid material being heated. At least a portion of the microwave energy discharged into the heating chamber may be used to heat the containers so that the coldest region of the liquid or semi-liquid material achieves a temperature at or above a target temperature for a predetermined period of time.
The period of time during which the coldest region of the liquid or semi-liquid material is maintained at or above the target temperature can be any time suitable to achieve the desired kill rate and/or cook time of the liquid or semi-liquid material. In some cases, this can be, for example, 30 seconds to 10 minutes, 45 seconds to 8 minutes, 1 minute to 6 minutes, with the specific time depending, at least in part, on the target temperature. The time may be at least about 30 seconds, at least about 45 seconds, at least about 1 minute, at least about 2 minutes, or at least about 5 minutes and/or not more than about 15 minutes, not more than about 10, not more than about 8, not more than about 6, or not more than about 4 minutes. The target temperature could be a minimum pasteurization temperature of, for example, at least about 70, at least about 75, or at least about 80° C., or it may be a minimum sterilization temperature of, for example, at least about 115, at least about 117, at least about 120, or at least about 121° C. The target temperature may also be within one or more of the ranges discussed previously. When the bottler or other container is at least partially formed from a polymeric material having a glass transition temperature, the target temperature to which the liquid or semi-liquid material is heated may be greater than or less than the glass transition temperature by, for example, at least about 2, at least about 5, at least about 8, at least about 10, at least about 12, or at least about 15° C.
As the bottles or other containers move through the microwave heating chamber 330, they pass by at least one launch opening defined by one or more microwave launchers. As the container passes near a launch opening, the temperature of at least a portion of the liquid or semi-liquid material in the container may increase rapidly to a temperature at or near the target temperature. When the container is at least partially formed from a polymeric material, the temperature of at least a portion of the liquid or semi-liquid material may increase to a temperature at or above the glass transition temperature of the polymer. At the same time, the average temperature of the liquid medium surrounding the container and, in particular, at the wall of the container may be at a temperature lower than the glass transition temperature of the polymer.
As the container moves away from the launch opening, the temperature of its contents may drop, and, in some cases, at least a portion of the liquid or semi-liquid material may drop to a temperature below the target temperature. When the container is formed from a polymer, the temperature of the liquid or semi-liquid material at the wall may drop below the glass transition temperature of the container. The container may be passed by any number of microwave launchers required to achieve a time/temperature combination sufficient for the coldest portion of the liquid or semi-liquid material to achieve a desired kill rate or cook time. However, because the container is only being exposed to elevated temperatures (e.g., near or above the glass transition temperature of the polymeric material) for relatively short periods of time, the container does not deform or rupture. As a result, it has been found that thinner polymeric containers may be used in some embodiments of the present invention while still achieving pasteurization or sterilization results equal to or better than conventional processes.
Turning now to
As shown in
As the container is heated, the liquid or semi-liquid material at the wall of the container may be kept at or above the glass transition temperature for a minimum amount of time, while still achieving a desired degree of pasteurization or sterilization. For example, as shown in
Additionally, the maximum temperature of the liquid or semi-liquid material at the wall of the container may be at or above the glass transition temperature of the polymeric material for a total period of time, referred to as t2 and represented in
In some cases, the values of t1 and t2 may be close, meaning that a significant portion of the total time during which the maximum temperature of the liquid or semi-liquid material at the wall of the vessel is above the glass transition temperature overlaps with the time during which the pasteurization or sterilization of the liquid or semi-liquid material takes place. In some cases, the ratio of t1 to t2 can be at least about 0.40, at least about 0.45, at least about 0.50, at least about 0.55, at least about 0.60, at least about 0.65, at least about 0.70, at least about 0.75, at least about 0.80, at least about 0.85, at least about 0.90, or at least about 0.95, with higher ratios generally indicating more efficient heating. In some embodiments, convective heat transfer from the warmer portion of the liquid or semi-liquid material in the container (typically located at or near the geometric center of the container) and the cooler liquid or semi-liquid near the container wall may help facilitate more even heating of the container contents in order to achieve the desired degree of pasteurization or sterilization.
In some cases, this convective heat transfer can be facilitated by inclusion of at least one agitation device within the microwave heating chamber. When used, the agitation device may be the same as, or different than, any agitation devices used in the thermalization zone 14. Suitable agitation devices can include, for example, dynamic agitation devices such as fluid jets or nozzles, ultrasonic pulses, sonic or acoustic pulses or devices, or static agitation devices such as rifling located along the inside wall of the heating chamber. Alternatively, or in addition, the microwave heating chamber can include at least one device to shake, spin, or otherwise disrupt the liquid or semi-liquid material inside the container. Use of agitation devices may help enhance the uniformity of heating of the container contents by, for example, increasing the heat transfer rate between the warmer liquid or semi-liquid material at or near the center of the container and the cooler liquid or semi-liquid near the container wall.
In some embodiments, the cooler temperature of the liquid or semi-liquid material at the wall of the container may be due, at least in part, to the lower temperature of the surrounding liquid (Tbath). For example, in some embodiments, the liquid medium surrounding the container during the heating step can have an average temperature, measured near the external wall of the container, that is at least about 2, at least about 5, at least about 10, at least about 15° C. and/or not more than about 30, not more than about 25, or not more than about 20° C. cooler than the temperature of the liquid or semi-liquid at the wall of the container. When the average temperature of the surrounding liquid is lower than the temperature of the liquid or semi-liquid material at the wall of the container, this temperature difference may help minimize the amount of time that the container wall is exposed to temperatures exceeding the glass transition temperature of the polymer used to form the container.
As a result, the temperature of the container wall be at its glass transition temperature for a minimal amount of time, or it may not even reach its glass transition temperature during the heating step. This helps prevents deformation or rupturing of the container during heating. In some embodiments, the temperature of the container wall may be at or above its glass transition temperature for less than 30 seconds, less than 20 seconds, less than 15 seconds, less than 10 seconds, less than 5 seconds, or less than 2 seconds total, or not at all, during the entire heating step. Alternatively, or in addition, the temperature of the container wall may be at least about 2, at least about 3, at least about 5, at least about 8, or at least about 10° C. lower than the glass transition temperature for at least about 50 percent, at least about 60 percent, at least about 70 percent, at least about 80 percent, or at least about 90 percent of the heating step.
Although generally shown in
When the system includes two or more microwave launchers, each launcher may emit the same amount of energy as one or more other launchers, or at least one launcher may emit a different (e.g., lower or higher) amount of energy, as compared to at least one of the other launchers. Overall, the total amount of energy discharged into the microwave heating chamber can be at least about 25 kW, at least about 30 kW, at least about 35 kW, at least about 40 kW, at least about 45 kW, at least about 50 kW, at least about 55 kW, at least about 60 kW, at least about 65 kW, at least about 70 kW, or at least about 75 kW and/or not more than about 100 kW, not more than about 95 kW, not more than about 90 kW, not more than about 85 kW, not more than about 80 kW, not more than about 75 kW, not more than about 70 kW, or not more than about 65 kW. Further, although shown as including three consecutive launchers, microwave heating systems employing two or fewer microwave launchers or four or more microwave launchers may also be used, and would be expected to exhibit similar temperature profiles.
In addition to reducing the thermal load to which the container is exposed, the use of microwave energy to efficiently heat a liquid or semi-liquid material as described herein may also improve the quality of the final product. For example, even when the container is not formed from a polymeric material (such as, for example, a glass container), heating the container as described above may reduce the thermal history of the liquid or semi-liquid material therein, thereby minimizing overcooking and heat degradation of the final product. This may help retain desirable organoleptic properties such as taste, texture, and color, as well as retain key functionalities when the liquid or semi-liquid material being processed is a medical, pharmaceutical, nutraceutical, or veterinary fluid. Overall, the systems and methods of the present invention reduce overall processing time, while providing products of equivalent or better quality and meeting or exceeding safety standards.
Referring again to
In the hold zone 18, the temperature of the coldest part of the contents of the bottles can be held at a temperature at or above a predetermined minimum temperature of at least about 70° C., at least about 75° C., at least about 80° C., at least about 85° C., at least about 90° C., at least about 95° C., at least about 100° C., at least about 105° C., at least about 110° C., at least about 115° C., or at least about 120° C., at least about 121° C., at least about 122° C. and/or not more than about 130° C., not more than about 128° C., or not more than about 126° C. When pressurized, the pressure within the hold zone 18 can be at least about 5, at least about 10, at least about 15, or at least about 20 psig and/or not more than about 60, not more than about 55, not more than about 50, not more than about 45, not more than about 40, not more than about 35, or not more than about 30 psig.
After exiting the hold zone, the containers may be passed to a cooling, or quench zone 20, wherein the bottles are cooled as rapidly as possible via submersion in a cooled fluid. In the quench zone 20, the temperature of the containers may be reduced by at least about 2, at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 40, or at least about 50° C. and/or not more than about 100° C., not more than about 75° C., or not more than about 50° C. to a temperature of not more than about 50, not more than about 45, not more than about 40, not more than about 35, not more than about 30, or not more than about 25° C.
Any suitable fluid may be used in the cooling zones and, in some cases, the fluid may include a liquid similar to or different than the liquid used in the microwave heating zone and/or the hold section. The temperature of the liquid in the cooling zones can be not more than about 50, not more than about 45, not more than about 40, not more than about 35, not more than about 30, or not more than about 27° C. The cooling zones may be pressurized, unpressurized (e.g., atmospheric), or it may include both pressurized and unpressurized sections. Similarly, if the microwave heating system includes a convey line, the convey line may or may not extend through the cooling zone. Additionally, the cooling zones may be at least partially liquid filled, or it may be under atmospheric conditions. In some applications, the cooling zone may include both a liquid-filled section and an atmospheric section.
As shown in
One particular application in which microwave heating systems of the present invention may be used is in the sterilization of bottled water. One example of such a system 510 is shown in
In some cases, the substantially untreated water may be subjected to sterilization and/or pasteurization in the microwave heating system 516 as described herein and the resulting bottles may have an overall contaminant level commensurate with bottled water that has undergone extensive processing prior to being bottled. Use of systems and methods of the present invention to prepare sterilized bottled water may help provide clean drinking water to areas of the world where potable water is scarce.
Microwave heating systems of the present invention can be commercial-scale heating systems capable of processing a large volume of containers in a relatively short time. In contrast to conventional retorts and other small-scale systems that utilize microwave energy to heat a plurality of containers, microwave heating systems as described herein can be configured to achieve an overall production rate of at least about 15 packages per minute per convey line, at least about 20 packages per minute per convey line, at least about 25 packages per minute per convey line, or at least about 30 packages per minute per convey line, measured as described in the '516 application.
When the containers include bottles, microwave heating systems of the present invention may have an overall production rate of at least 5, at least about 10, at least about 25, at least about 50, or at least about 100 bottles per minute and/or not more than about 1500, not more than about 1250, not more than about 1000, not more than about 900, not more than about 750, not more than about 500, not more than about 350, not more than about 200, not more than about 150, not more than about 100, or not more than about 75 bottles per minute. Lower production rates may be used for more delicate or specialty items, while higher rates may be used for processing commodity goods.
The preferred forms of the invention described above are to be used as illustration only, and should not be used in a limiting sense to interpret the scope of the present invention. Obvious modifications to the exemplary one embodiment, set forth above, could be readily made by those skilled in the art without departing from the spirit of the present invention.
The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.
This application claims priority to U.S. Provisional Patent Application No. 62/436,185, filed on Dec. 19, 2016, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62436185 | Dec 2016 | US |
