Patent Description:
Please note: <NUM> inch = <NUM>; <NUM> foot = <NUM> metre; <NUM> psig = <NUM> Bar.

Commercially-available packaged food items are often pasteurized or sterilized prior to being purchased by a consumer. Many of these items are also designed to be reheated by the consumer in an at-home microwave oven prior to consumption. However, because of the differences in conditions during the pasteurization or sterilization of the packaged foodstuff and its reheating, the foodstuff may develop "hot" and "cold" spots that are difficult or impossible to control simply with adjustments to the process and/or equipment. In some cases, for example, the hot and cold spots may occur because of spatial constraints (e.g., the orientation of the package within the heating chamber), or because of a physical property of the foodstuff (e.g., its dielectric constant).

Thus, a need exists for a package suitable for use in both commercial-scale pasteurization or sterilization and at-home consumer microwave ovens that facilitates uniform heating of packaged foodstuffs and other packaged items under a variety of conditions.

<CIT> discloses a microwave heating system configured to heat a plurality of articles. The microwave heating system includes a thermalization zone for adjusting the temperature of the articles disposed therein to be substantially uniform and a microwave heating zone for heating the thermalized articles. At least one of the thermalization zone and microwave heating zone are liquid-filled and may include a plurality of fluid agitators for discharging jets of liquid medium toward the articles at multiple locations within the chamber. <CIT> discloses a microwave heating package comprising a dimensionally stable first component for supporting a food item and a flexible second component dimensioned to receive the dimensionally stable first component. Each of the first component and the second component may include a microwave energy interactive element for altering the effect of microwave energy on a food item within the package. <CIT> discloses a microwaveable tray having different heating/shielding systems for the different food components of the microwavable meal. For example, the individual meal components can be placed in individual compartments that will be heated/shielded in their individually controlled cooking environments using a suitable microwave cooking technology. <CIT> discloses a food package for a microwave oven which has a grid in combination with a susceptor means. The combination of the grid and susceptor means provides a heater element which substantially maintains its reflectance, absorbance and transmittance during microwave heating. Substantial uniformity of heating is also achieved. The reflectance, transmittance and absorbance can be adjusted by changing certain design factors, including hole size, susceptor impedance, grid geometry, spacing between the grid and susceptor, and the spacing between adjacent holes.

The present invention comprises a process for heating a plurality of articles as defined in claim <NUM>. Embodiments that do not fall within the scope of the claims are to be interpreted as examples useful for understanding the invention. One embodiment of the present invention concerns a process for heating a plurality of articles in a microwave heating system, the process comprising: (a) loading a group of the articles into a carrier, wherein each of the articles includes a package at least partially filled with at least one foodstuff and each package includes at least one energy control element; (b) passing the loaded carrier through a microwave heating chamber in a direction of travel along a first convey line; (c) generating microwave energy, wherein the microwave energy is polarized and has a wavelength of no more than <NUM>; (d) during at least a portion of the passing, discharging at least a portion of the microwave energy into the microwave heating chamber; and (e) heating the articles using at least a portion of the microwave energy discharged into the microwave heating chamber to at least one of sterilize or pasteurize the foodstuff. During the heating, a portion of the foodstuff is heated to a substantially different temperature and/or at a substantially different heating rate than the portion of the foodstuff would have been heated to or at if the energy control element was not present.

We further disclose a process for heating a plurality of articles in a microwave heating system, the process comprising: (a) loading a carrier with a plurality of the articles, wherein each article comprises a package at least partially filled with at least one item to be heated; (b) passing the loaded carrier through a microwave heating chamber in a direction of travel along a convey line; (c) during at least a portion of said passing, directing microwave energy into the microwave heating chamber via one or more microwave launchers; and (d) during at least a portion of the directing, heating the articles with at least a portion of the microwave energy in order to increase the temperature of the coldest portion of each item to a target temperature. At least a portion of the packages include at least one microwave inhibiting element for inhibiting or preventing microwave energy from reaching at least a portion of the item during the heating.

We further disclose an article suitable for being pasteurized or sterilized in a microwave heating system, the article comprising at least one foodstuff; and a package comprising at least one compartment for holding the foodstuff. The package further comprises at least one energy control element for altering the interaction between at least a portion of the foodstuff and microwave energy when the package is exposed to microwave energy. The energy control element is configured to exhibit at least one of the following characteristics (i) and (ii) - (i) absorb polarized and non-polarized or randomly polarized microwave energy differently; and (ii) reflect polarized and non-polarized or randomly polarized microwave energy differently.

We further disclose a process for heating a packaged foodstuff using microwave energy, the process comprising: (a) at least partially filling a package with at least one foodstuff to form a packaged foodstuff, wherein the package includes at least one energy control element; (b) heating the packaged foodstuff using a first type of microwave energy to thereby sterilize or pasteurize the foodstuff, wherein the heating is performed in a commercial-scale microwave heating system and includes passing a carrier loaded with the packaged foodstuff along a convey line; and (c) reheating the article with a second type of microwave energy to thereby provide a ready-to-eat foodstuff. The first and second types of microwave energy have substantially different (i) polarizations, (ii) frequencies, and/or (iii) intensities and wherein the energy control element is substantially more effective at inhibiting or enhancing one of the first and second types of microwave energy than the other.

A further embodiment of the present invention concerns a process for designing a package for the sterilization and/or pasteurization of a foodstuff, wherein the process comprises: (a) filling an initial package with a test material to provide a test article; (b) heating the test article in a first microwave heating system using polarized microwave energy; (c) during at least a portion of the heating of step (b), measuring the temperature of the test material at one or more locations within the test article; (d) determining the location of at least one hot spot or cold spot based on the temperatures measured in step (c); (e) creating a modified package, wherein the creating includes one or more of the actions (i) through (iv) - (i) adding a microwave inhibiting element near a hot spot; (ii) adding a microwave enhancing element near a cold spot; (iii) removing a microwave inhibiting element from near a cold spot; and (iv) removing a microwave enhancing element from near a hot spot; (f) filling the modified package with the test material to provide a modified test article; and (g) heating the modified test article in the microwave heating system.

Various embodiments of the present invention are described in detail below with reference to the attached drawing Figures, wherein:.

The present invention relates to methods, systems, and packages for pasteurizing and sterilizing a foodstuff or other item in a larger-scale microwave heating system that may also be reheated in a consumer microwave oven to provide a satisfactory ready-to-eat foodstuff. Examples of microwave heating systems used for pasteurization or sterilization include any suitable liquid-filled, continuous microwave heating system including, for example, those similar to the microwave heating systems described in <CIT>. Additionally, although described herein generally with reference to a foodstuff, it should be understood that embodiments of the present invention also relate to the pasteurization or sterilization of other types of items such as medical and dental instruments or medical and pharmaceutical fluids, which may or may not need to be reheated by the consumer prior to use.

When a packaged food item is pasteurized or sterilized in a microwave heating system and is then subsequently reheated in a consumer microwave oven, the foodstuff may be exposed to different types and/or amounts of microwave energy. Additionally, in some cases, the package may include two or more different types of food items, at least one of which may need less exposure to microwave energy than one or more of the others. This requirement for less microwave exposure may exist because, for example, the foods have different dielectric properties and/or different heating requirements (e.g., target time and/or temperature) to achieve the desired level of pasteurization or sterilization.

When a food item having lower heating requirements such as, for example, requiring less microwave exposure, is also highly susceptible to heat degradation, packaging that item with another food item having higher heating requirements may not be possible with conventional packaging. This is because the lower heating requirement food item may experience too much degradation during the sterilization process or the higher heating requirement food item. In some cases, this discrepancy may be addressed by enhancing or reducing the microwave heating of certain areas of the foodstuff during the sterilization or pasteurization process. However, this same enhancement or reduction of microwave heating may or may not be desirable during microwave reheating by the consumer.

According to some embodiments of the present invention, packages that include at least one energy control element for adjusting how microwave energy interacts with at least a portion of a packaged item are provided. As used herein, the term "energy control element" refers to any element or device that interacts with microwave energy in order to alter the effect that microwave energy has on the item being heated. Energy control elements have not been used for adjusting microwave energy in a pasteurization or sterilization system, which typically utilizes a different type of microwave energy and field than the microwave energy utilized by an at-home microwave. Thus, conventional shielding panels and other devices used exclusively in at-home microwave ovens do not perform the same way in the microwave heating systems used for pasteurization or sterilization described herein.

Energy control elements may be used to enhance or reduce heating in problematic package areas. For example, in some cases, an energy control element may be located near an easily-sterilized food item to reduce heating and prevent overheating, while, in other cases, an energy control element may be used to enhance microwave heating near a packaged food having high heating requirements. Thus, strategically-located energy control elements are useful for reducing, or even eliminating, hot and/or cold spots in a single food package. Energy control elements may also be used in multi-food packages and, in particular, in multi-food packages that include two food items having different dielectric properties and/or for packages in which one or more food items require less heating than the another. Additionally, such energy control elements may be particularly useful when the food item requiring less heating is also more susceptible to thermal degradation.

In some cases, the energy control element may comprise a selective energy control element configured to enhance or reduce microwave heating in a certain way or to a certain degree in one heating environment (e.g., a microwave pasteurization or sterilization system) and may enhance and/or reduce microwave heating in a different way or to a different degree in another heating environment (e.g., reheating in at-home microwave oven). For example, in some cases, two different food items in a single package may need to receive similar amounts of microwave heating during pasteurization or sterilization to ensure adequate microbial lethality rates, but it may be desirable for one of the items to be reheated more than the other in a consumer microwave oven (e.g., apple sauce and lasagna). In other cases, two different items in a single package may need to receive different amounts of energy during pasteurization or sterilization to prevent degradation of the food requiring less heat for sterilization. However, during reheating, it may be desirable to provide both foods with the same level of heating to ensure proper end temperature (e.g., lasagna and green beans).

The selectivity of an energy control element may depend on one or more properties of the microwave energy used to heat the item. For example, the selectivity of the energy control element may depend on the frequency, polarity, or intensity of the microwave energy being used to heat the packaged item. Selective energy control elements may be substantially more effective at inhibiting or enhancing one type of microwave energy than another and, as a result, may perform differently when exposed to each type.

For example, a selective energy control element may be substantially more effective at inhibiting or enhancing a first type of microwave energy that has a different frequency than another type of microwave energy. For example, a selective energy control element may be substantially more effective at inhibiting or enhancing microwave energy having a frequency of not more than <NUM> than microwave energy having a frequency of at least <NUM>. Alternatively, a selective energy control element may be substantially more effective at inhibiting or enhancing microwave energy having a frequency of at least <NUM> than microwave energy having a frequency of not more than <NUM>. In some cases, a selective energy control element may be configured to inhibit or enhance at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent more of microwave energy of one frequency than another.

Examples of different frequencies of microwave energy include microwave energy having a frequency of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> and according to this invention not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> and microwave energy having a frequency of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>. Typically, microwave pasteurization and sterilization systems may employ microwave energy having a frequency of about <NUM> (e.g., not <NUM>), while at-home (consumer) microwave ovens usually utilize microwave energy having a frequency of about <NUM> (e.g., not <NUM>).

In some cases, a selective energy control element may be substantially more effective at inhibiting or enhancing a first type of microwave energy that has a different polarization than another type of microwave energy. For example, a selective energy control element may be substantially more effective at inhibiting or enhancing polarized microwave energy than non-polarized or randomly polarized microwave energy. Alternatively, a selective energy control element may be substantially more effective at inhibiting or enhancing non-polarized or randomly polarized microwave energy than polarized microwave energy. Typically, microwave pasteurization and sterilization systems employ polarized microwave energy, while at-home ovens utilize non-polarized or randomly polarized microwave energy. In some cases, a selective energy control element may be configured to inhibit or enhance at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent more of one of polarized and non-polarized or randomly polarized microwave energy than the other.

The selective energy control element may be substantially more effective at inhibiting or enhancing microwave energy with a substantially higher intensity, or it may be more effective at inhibiting or enhancing microwave energy at a lower intensity. Additionally, in some cases, the selective energy control element may inhibit or enhance one type of microwave energy while being substantially transparent to another. As used herein, the term "transparent" as it refers to microwave energy means that the material or element permits at least <NUM> percent of the incident microwave energy to pass therethrough without inhibiting or enhancing the interaction between the microwave energy and the foodstuff or other item. In some cases, a transparent material or element can permit at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent of the incident microwave energy to pass therethrough without inhibiting or enhancing the interaction between the microwave energy and the foodstuff or other item. When an energy control element is transparent to a type of microwave energy, it performs the same as if such an energy control element were absent.

It has been found that selective use of one or more energy control elements positioned near a foodstuff may be used to control the heating rate at which and/or temperature to which the foodstuff is being heated. As a result, the presence of hot and cold spots can be adjusted and easily-heated or easily-pasteurized or sterilized foodstuffs may be contained in a single package with foodstuffs that are not as easily reheated or pasteurized or sterilized. For example, in some cases, positioning an energy control element near a foodstuff or other item being heated, can cause the foodstuff or other item being heated to have a substantially different heating rate and/or a substantially different temperature than the foodstuff or other item would have been heated to or at if the energy control element was not present, under identical conditions. As used herein, the term "different" refers to values that are higher or lower than a given value. Thus, a "different" temperature may be higher or lower than a given temperature.

In some cases, the foodstuff or other item positioned near an energy control element may have heating rate that is at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM>/min different than the heating rate of the item if the energy control element was not present. Alternatively, or in addition, the foodstuff near the energy control element can have a heating rate that is not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>/min different than the heating rate if the energy control element was not present. In some cases, the heating rate of the foodstuff near the energy control element can be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent different (i.e., higher or lower) than the heating rate of the foodstuff if the energy control element was not present.

In some cases, the foodstuff or other item positioned near the energy control element may have a different temperature than if the energy control element was not present. For example, the difference in temperature may be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> and/or it can be not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>. In some cases, the temperature of the foodstuff near the energy control element can be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent different (i.e., higher or lower) than if the energy control element was not present.

Different types of energy control elements may be used, depending on whether the microwave heating is to be enhanced or reduced. When the energy control element is configured to enhance microwave heating, it is referred to as an "microwave enhancing element. " A susceptor is one type of microwave enhancing element. The microwave enhancing element may be configured to absorb at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent of the incident microwave energy that contacts it. As used herein, the term "incident microwave energy" refers to the microwave energy incident on the particular energy control element and is not necessarily equal to the total amount of microwave energy introduced into the heating chamber. Microwave enhancing elements absorb microwave energy and increase the temperature and/or heating rate of the materials positioned near the element.

In some cases, the microwave enhancing element may be configured to absorb at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM> percent of the total amount of incident microwave energy. Alternatively, or in addition, it may absorb not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> percent of the total amount of incident microwave energy.

The foodstuff or other item positioned near a microwave enhancing element may be heated to a higher temperature and/or at a faster heating rate than the foodstuff or other item would be heated to or at if the microwave enhancing element was not present. For example, the portion of the foodstuff positioned near the microwave enhancing element may achieve a temperature of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM>, at least about <NUM>, whereas the food may only have been heated to a temperature of not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> in the absence of the microwave enhancing element. When heated to a higher temperature, the foodstuff positioned near the microwave enhancing element may also be heated at a faster heating rate than if the susceptor were absent, or the heating rate may be slower or the same.

Additionally, or in the alternative, when a microwave enhancing element is used, the portion of the foodstuff or other article positioned near the microwave enhancing element may be heated at a faster heating rate than if the microwave enhancing element were absent. For example, when positioned near a microwave enhancing element, the foodstuff may have a heating rate of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM>/min, while the foodstuff may have a heating rate of not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>/min, if the microwave enhancing element were absent. When heated at a faster rate, the foodstuff positioned near the microwave enhancing element may achieve a temperature higher than, lower than, or similar to the foodstuff if the microwave enhancing element were absent.

When the energy control element is configured to inhibit microwave energy, it is referred to as an "microwave inhibiting element. " Some microwave inhibiting elements are reflectors. In some embodiments, a microwave inhibiting element may be configured to reflect at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent of the incident microwave energy that contacts it. Microwave inhibiting elements reduce or, in some cases, nearly eliminate, microwave energy contacting some portion of the foodstuff or other item. As a result, the foodstuff may be heated to a lower temperature and/or at a lower heating rate than if the microwave inhibiting element were absent. In some cases, the microwave inhibiting element may reflect at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM> percent of the total incident microwave energy. Alternatively, or in addition, it may reflect not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> percent of the total amount of incident microwave energy.

When a microwave inhibiting element is used, the foodstuff positioned near the microwave inhibiting element may receive less than the total amount of microwave energy directed toward it. As a result, it may be heated to a lower temperature and/or at a slower heating rate than if the microwave inhibiting element was not present. For example, the foodstuff positioned near the microwave inhibiting element may have a heating rate of not more than about <NUM>, not more than about <NUM>, not more than about <NUM> not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>/min, while the foodstuff may only have a heating rate of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM>/min, if the microwave inhibiting element was not present. When the portion of the foodstuff or other item positioned near the microwave inhibiting element is heated at a slower rate, it may achieve approximately the same temperature as, or a different temperature than, the foodstuff or other item would achieve if the microwave inhibiting element were not present.

Additionally, or in the alternative, the foodstuff positioned near the microwave inhibiting element may be heated to a lower temperature than it would be heated if the microwave inhibiting element were not present. For example, the foodstuff near the microwave inhibiting element may be heated to a temperature of not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>. If no microwave inhibiting element were present, the foodstuff may be heated, under identical conditions, to a temperature of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>. The foodstuff may be heated at the same or a different heating rate than if the microwave inhibiting element was not present.

In some embodiments, the energy control element, whether a microwave inhibiting element, a microwave enhancing element, or both, may be incorporated into the package. When the energy control element is part of the package, it may be incorporated into the package itself, or may be temporarily positioned on or around at least a portion, or all, of the package (e.g., as a sleeve or wrap). When the energy control element is an integral part of the package in which the foodstuff or other item being heated is held, it may be present on at least a portion, or all, of the top, bottom, and/or sides of the package. In some cases, one or more of these areas of the package may simply be formed of a material that acts as an energy control element, while the remaining portions of the package are formed from another, typically microwave transparent material including, but not limited to, plastics, cellulosics, and combinations thereof.

The package itself may be of any suitable form. For example, in some cases, the packages used may include pouches. The pouches may be individual, detached pouches that are not connected to any other pouches. The pouches can be flexible, semi-flexible, or rigid. Each pouch can include one internal compartment for holding a foodstuff or other item, or it may include two or more separate compartments. One example of a pouch is shown in <FIG>.

As shown in <FIG>, each pouch <NUM> has a top portion <NUM> and a base portion <NUM> that is wider than top portion <NUM>. The base portion <NUM> of the pouch <NUM> can be at least twice, at least three times, or at least four times wider than the top portion <NUM>. Alternatively, the base portion <NUM> and the top portion <NUM> have approximately the same width. The width of the top portion <NUM>, shown as Wi in <FIG>, can be at least about <NUM>, at least about <NUM>, or at least about <NUM> inches and/or not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> inches, or it can be in the range of from about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, or from about <NUM> to about <NUM> inches. Alternatively, the width of the top portion <NUM> may be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> inch, or it can be in the range of from about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, or about <NUM> to about <NUM> inches.

The width of the base portion <NUM>, shown as W<NUM> in <FIG>, can be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> inch, or it can be in the range of from about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, or about <NUM> to about <NUM> inches. The height of the pouch <NUM>, shown as H in <FIG>, can be at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> inches and/or not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> inches, or it can be in the range of from about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches. Pouches of other dimensions may also be suitable in various cases.

In other embodiments, the packages used may include trays. Trays generally have a top and a bottom and a general prism-like shape. Trays can have a square, rectangular, or elliptical cross-section, although other shapes may be suitable. One example of a tray <NUM> is illustrated in <FIG>. Each tray may have a single compartment for holding the foodstuff or other item to be heated, as shown in <FIG>, or it may include two or more compartments at least partially isolated from one another (not shown).

In some cases, tray <NUM> may have a top that is longer and wider than its bottom so that it has a generally trapezoidal shape, as generally shown in <FIG>. As used herein, the terms "length" and "width" refer to the longest and second longest, respectively, non-diagonal dimensions of a package. When the tray has a trapezoidal shape such that the top is longer and wider than the bottom, the length and width are measured at the largest cross-section (usually the top surface). The height is the shortest non-diagonal dimension measured perpendicular to the planes defined by the length and width. The length (L), width (W), and height (h) of tray <NUM> are shown in <FIG>.

The length (L) of each tray can be at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> inches and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> inches, or it can be in the range of from about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, or about <NUM> to about <NUM> inches. The width (W) of each tray may be at least about <NUM> inch, at least about <NUM> inches, at least about <NUM> inches, at least about <NUM> inches, or at least <NUM> inches and/or not more than about <NUM> inches, not more than about <NUM> inches, not more than about <NUM> inches, or not more than <NUM> inches, or it can be in the range of from about <NUM> inch to about <NUM> inches, about <NUM> inches to about <NUM> inches, about <NUM> inches to about <NUM> inches, about <NUM> inches to about <NUM> inches, or about <NUM> inches to about <NUM> inches. Each tray may have a height (h) of at least about <NUM> inches, at least about <NUM> inch, at least about <NUM> inches and/or not more than about <NUM> inches, not more than about <NUM> inches, or not more than about <NUM> inches, or it can be in the range of from about <NUM> to about <NUM> inches, about <NUM> to about <NUM> inches, or <NUM> to <NUM> inches. Trays of other dimensions may also be suitable, depending on the particular application.

When the energy control element is part of the package, whether a pouch, a tray, or other container, it may cover all or a portion of the total surface area of the package. For example, the energy control element may cover at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent of the total surface are of the package. In some cases, it may cover the entire surface area of the package.

Additionally, or in the alternative, the energy control element may cover not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> percent of the total surface area of the package.

Energy control elements can be in any suitable shape. In some cases, the energy control elements in the form of strips that are printed, labeled, laminated, or otherwise incorporated into all or a portion of the package. In some embodiments, these types of energy control elements may be microwave enhancing elements and can be formed from a metallic material. Such energy control elements may be incorporated into or onto all or a portion of the package surface by printing, by lamination, or by application of labels that include the strips. In some cases, lamination may be used with flexible packages, while labels and printing may be used for rigid packaging. When the package includes a tray and a lid, the energy control strips may be present on the lid, on the tray, or on both the tray and the lid. An example of a tray <NUM> including a plurality of energy control strips <NUM> is shown in <FIG> and <FIG>.

Although only covering one portion of the tray <NUM> in the embodiment shown in <FIG> and <FIG>, it should be understood that the energy control strips <NUM> may cover more or less of the surface area of the tray <NUM>, or may be positioned at different locations. Alternatively, or in addition, one or more of the energy control elements may be in a different shape, and/or the package may be a pouch or other type of container.

When the energy control elements are present as strips, the package may include at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, or at least <NUM> or more strips that are spaced apart from one another along at least one surface of the package. Each of the strips may have a width, or second longest dimension, of at least about <NUM>/<NUM>, at least about <NUM>/<NUM>, or at least about <NUM>/<NUM> of an inch and/or not more than about <NUM>/<NUM>, not more than about <NUM>/<NUM>, or not more than about <NUM>/<NUM> of an inch. The size of each strip may be the same as the others, or one or more may have a different width. The strips may be spaced such that there are at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, or at least <NUM> strips and/or not more than <NUM>, not more than <NUM>, not more than <NUM>, or not more than <NUM> strips per the predominant wavelength of microwave energy to which the package is exposed during at least one heating step. In some cases, the predominant wavelength of which microwave energy to which the package can be exposed during at least one heating step is at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> inches and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> inches.

In some cases, the spacing between adjacent strips may be as wide as, or wider than, the width of each strip. Further, the spacing between sets of adjacent strips may be the same or different. In some cases, the width of the open area between adjacent energy control strips can be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent wider than the average width of the two adjacent energy control strips. Alternatively, or in addition, the width of the open area between adjacent energy control strips can be not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> percent wider than the average width of the two adjacent energy control strips.

According to the invention, the packaged foodstuff is configured such that one or more foodstuffs in the package are positioned near the energy control element. For example, the energy control element may be positioned such that at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or up to <NUM> percent of at least one foodstuff is positioned near the energy control element.

Alternatively, part of the foodstuff (or another foodstuff) may not be positioned near the energy control element. For example, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent of the foodstuff in a package may not be positioned near the energy control element. This may occur when, for example, the package includes two or more different foodstuffs in a single or multi-compartment tray or pouch. Alternatively, the package may include two or more energy control elements (of the same or a different type) each positioned near different types of foodstuff. In this way, the temperature and heating profile of different foodstuffs within a single package can be effectively controlled to achieve more efficient and uniform heating of the foodstuff or other item within the package.

In some cases, the energy control element may be part of a carrier used to secure and transport the articles through a microwave heating system. Carriers may be used in larger-scale microwave heating systems configured for the pasteurization or sterilization of packaged foodstuffs and other items. Several views of an exemplary carrier are provided in <FIG>. As particularly shown in <FIG> and <FIG>, the carrier <NUM> includes an outer frame <NUM>, an upper support structure <NUM>, and a lower support structure (not shown). The outer frame <NUM> comprises two spaced-apart side members 18a,b and two spaced-apart end members 20a,b. The first and second end members 20a,b may be coupled to and extend between opposite ends of first and second side members 18a,b to form outer frame <NUM>. When each of side members 18a,b are longer than the end members 20a,b, the frame may have a generally rectangular shape, as shown <FIG> and <FIG>.

As shown in <FIG>, <FIG>, <FIG>, first and second side members 18a,b each include respective support projections 22a,b that are configured to engage respective first and second convey line support members, which are represented by dashed lines 24a and 24b in <FIG>. The first and second support projections 22a,b of carrier <NUM> present first and second lower support surfaces 42a,b for supporting carrier <NUM> on first and second convey line support members 24a,b. Convey line support members 24a,b may be a moving convey line element such as, for example, a pair of chains (not shown) located on each side of carrier <NUM> as it moves through the microwave heating zone in a direction represented by the arrow in <FIG>.

The first and second side members 18a,b and first and second end members 20a,b may be formed of any suitable material including, for example, a low loss material having a loss tangent of not more than about <NUM>-<NUM>, not more than about <NUM>-<NUM>, or not more than about <NUM>-<NUM>, measured at <NUM>. Each of the side members 18a,b and end members 20a,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 <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM>, at least about <NUM>, in order to withstand the elevated temperatures to which the carrier may be exposed during heating of the articles. Suitable low loss polymers can include, for example, 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.

As shown in <FIG> and <FIG>, the carrier <NUM> may include an upper support structure <NUM> and a lower support structure <NUM> for holding a group of articles within the carrier, while also permitting microwave energy pass through the carrier <NUM> to the articles. In the example shown in <FIG> and <FIG>, the upper and lower support structures <NUM>, <NUM> may each include a plurality of support members extending between the end members 20a,b in a direction substantially parallel to the side members 18a,b. The support members may extend in a direction substantially perpendicular to the end members 20a,b. As used herein, the terms "substantially parallel" and "substantially perpendicular" mean within <NUM>° of being parallel or perpendicular, respectively. In other instances (not shown), upper and lower support structures <NUM>, <NUM> could include a grid member or substantially rigid sheets of a microwave transparent or semi-transparent material extending between the side members 18a,b and end members 20a,b. Additional details regarding the number, dimensions, and configurations of support structures <NUM> and <NUM> are provided in <CIT>, the entirety of which is incorporated herein by reference.

When the upper and/or lower support structures <NUM>, <NUM> include individual support members as shown in <FIG> and <FIG>, one or more of the support members may be formed of a strong, electrically conductive material. Suitable electrically conductive materials can have a conductivity of at least about <NUM><NUM> Siemens per meter (S/m), at least about <NUM><NUM> S/m, at least about <NUM><NUM> S/m, at least about <NUM><NUM> S/m, or at least about <NUM><NUM> S/m at <NUM>, measured according to ASTM E1004 (<NUM>). Additionally, the electrically conductive material may have a tensile strength of at least about <NUM> MegaPascals (MPa), at least about <NUM> MPa, at least about <NUM> MPa, at least about <NUM> MPa, or at least about <NUM> MPa, measured according to ASTM E8/E8M-16a, and/or it may also have a yield strength of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> MPa at <NUM>, measured according to ASTM E8/E8M-16a. The Young's Modulus of the electrically conductive material can be at least about <NUM> GigaPascals (GPa), at least about <NUM> GPa, at least about <NUM> GPa, or at least about <NUM> GPa and/or not more than about <NUM> GPa, not more than about <NUM> GPa, not more than about <NUM> GPa, or not more than about <NUM> GPa, measured at <NUM>, measured according to ASTM E111-<NUM> (<NUM>). The electrically conductive material may be metallic and, in some cases, may be a metal alloy. The metal alloy may include any mixture of suitable metal elements including, but not limited to, iron, nickel, and/or chromium. The electrically conductive material may comprise stainless steel and may be food-grade stainless steel.

As particularly shown in <FIG>, carrier <NUM> defines a cargo volume <NUM> for receiving and holding a plurality of articles <NUM>. Cargo volume <NUM> is at least partially defined between the upper and lower support structures <NUM> and <NUM>, which are vertically spaced apart from one another, and the side 18a,b and end 20a,b members. The articles received in cargo volume <NUM> may be in contact with and/or held in position by at least a portion of the individual support members present in the upper and lower support structures <NUM> and <NUM>. Each of upper and lower support structures <NUM>, <NUM> may be coupled to outer frame <NUM> in a removable or hinged manner so that at least one of the upper and lower support structures <NUM>, <NUM> may be opened to load the articles <NUM> into carrier <NUM>, closed to hold the articles <NUM> during heating, and opened again to unload the articles <NUM> from the carrier. In some embodiments, as shown in <FIG>, the use of one or more longitudinal dividers <NUM> may create multiple compartments 36a-d within cargo volume <NUM> for receiving multiple rows of articles <NUM>.

Cargo volume <NUM> can be of any suitable size. In some cases, it can have a length measured between opposing internal surfaces of the first and second end members 20a,b, in the range of from about <NUM> to about <NUM> feet, about <NUM> to about <NUM> feet, or about <NUM> to about <NUM> feet. The cargo volume <NUM> may also have a width measured between opposing internal surfaces of the first and second side members 18a,b, in the range of from about <NUM> to about <NUM> feet, about <NUM> to about <NUM> feet, or from about <NUM> to about <NUM> feet. The height of the cargo volume, which can be measured between opposing internal surfaces of the upper and lower support structures <NUM>, <NUM>, can be in the range of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM> inches. Overall, the cargo volume can have a total volume in the range of from about <NUM> to about <NUM> cubic feet, about <NUM> to about <NUM> cubic feet, about <NUM> to about <NUM> cubic feet, or about <NUM> to about <NUM> cubic feet.

Additionally, in some embodiments, the carrier may further include at least one article spacing member <NUM> for adjusting the size and/or shape of the cargo volume <NUM>. Examples of article spacing members include dividers <NUM>, as shown in <FIG>, <FIG>, and <FIG>, for dividing the cargo volume <NUM> into two or more compartments and vertical spacers, such as 38a,b shown in <FIG>, for adjusting the vertical height between the upper and lower support structures <NUM>, <NUM>. When present, the article spacing member or members <NUM> may be permanently or removably coupled to the outer frame <NUM> or at least one of the upper and lower support structures <NUM>, <NUM>. When an article spacing member, such as a divider <NUM> or a vertical spacer <NUM>, is removably coupled to the outer frame <NUM> and/or to the upper and lower support members <NUM>, <NUM>, it may be selectively inserted into and removed from the carrier <NUM> in order to change the size and/or shape of the cargo volume <NUM> so that the carrier <NUM> may hold many types of articles having different sizes and/or shapes. Further details regarding such carriers are provided in the ' <NUM> Application.

When loaded into a carrier as described herein, the articles are placed within the cargo volume <NUM> defined between the upper and lower support structures of the carrier. As discussed above, the cargo volume may be a single volume, or it may be divided into two or more compartments, such as 36a-d shown in <FIG>, using one or more dividers <NUM>. When loaded into the cargo volume <NUM>, the articles may be placed in single rows along the length of the carrier. In some embodiments, the articles may be arranged in at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, or at least <NUM> single rows and/or not more than <NUM>, not more than <NUM>, not more than <NUM>, or not more than <NUM> single rows, or from <NUM> to <NUM> single rows, from <NUM> to <NUM> single rows, from <NUM> to <NUM> single rows, or from <NUM> to <NUM> single rows. Overall, each carrier may hold a total of at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM> articles and/or not more than <NUM>, not more than <NUM>, not more than <NUM>, not more than <NUM>, or not more than <NUM> articles, or it can hold from <NUM> to <NUM> articles, from <NUM> to <NUM> articles, from <NUM> to <NUM> articles, from <NUM> to <NUM> articles, or from <NUM> to <NUM> articles. Articles can be loaded into the carrier in any suitable manner, including manually or using an automated device.

When loaded into a carrier, each of the articles loaded into the cargo volume may be similar, or two or more articles may be different from one another. In some cases, the articles loaded into a carrier may include a first group of a first type of article and a second group of a second type of article, with the first type of article and second type of article having different packages and/or different types of contents within the packages. The articles may be spaced apart from one another within the carrier, or one or more articles may contact at least a portion of one or more other articles. It may be desirable, in some cases, to minimize spacing between the articles so that the average distance between consecutive edges of adjacent articles loaded in the carrier can be not more than about <NUM> inch, not more than about <NUM> inches, not more than about <NUM> inches, not more than about <NUM> inches, or not more than about <NUM> inch. There may be no gaps between the articles such that adjacent articles are in contact with one another when loaded into the carrier, or at least a portion of adjacent articles may overlap horizontally.

The particular arrangement of the articles within the cargo space may depend, at least in part, on the shape of the articles. For example, when the articles have a general trapezoidal-like shape, such that the articles are longer and wider on the top than on the bottom, the articles may be arranged in a nested configuration. <FIG> provides a side view of one row of articles 40a-f arranged in a nested configuration.

In the nested configuration, adjacent articles have opposite orientations. In the nested configuration, the articles 40a-f loaded into the carrier are sequentially oriented in the direction of travel, indicated by the arrow <NUM> in <FIG>, in a top down, top up, top down, top up configuration. As shown in <FIG>, the bottom of the second article 40b is oriented between the top of the first article 40a and the top of the third article 40c. Additionally, in the nested configuration, the tops of one set of alternating articles 40b, d, f and the bottoms of the other set of alternating articles 40a, c, e contact the upper support structure, while the bottoms and tops of each set of alternating articles contact the lower support structure when articles are loaded into the carri er.

Two top views of a plurality of articles arranged in different nested configurations in a carrier are provided in <FIG>. In each of <FIG>, the tops of articles are marked with a "T," the bottoms articles are marked with a "B," and the direction of travel of the carrier is shown by the arrow <NUM>. In the example shown in <FIG>, the articles are arranged in several spaced-apart rows that are each arranged in a nested configuration, and <FIG> shows a fully nested article pattern, wherein the individual rows of nested articles are not spaced from one another and the articles are arranged in a nested configuration in both the longitudinal and transverse directions.

According to the invention, articles as described herein may be heated in a microwave heating system used to pasteurize and/or sterilize the articles. In general, pasteurization involves the rapid heating of a material to a minimum temperature between <NUM> and <NUM>, while sterilization involves heating the material to a minimum temperature between about <NUM> and about <NUM>. The microwave systems described herein may be used for pasteurization or for sterilization. In some cases, pasteurization and sterilization may take place simultaneously, or nearly simultaneously, so that the articles being processed are both pasteurized and sterilized by the heating system.

Turning now to <FIG>, schematic diagrams of the main steps of a microwave heating process and the main elements of a microwave heating system suitable for pasteurizing and/or sterilizing articles according to embodiments of the present invention are provided. As used herein, the term "microwave energy" generally refers to electromagnetic energy having a frequency between <NUM> and <NUM>.

As shown in <FIG>, the articles loaded into one or more carriers can initially be introduced into a thermalization zone <NUM>, wherein the articles can be thermalized to a substantially uniform temperature. Once thermalized, the articles can optionally be passed through a pressure adjustment zone 114a before being introduced into a microwave heating zone <NUM>. In microwave heating zone <NUM>, the articles can be rapidly heated using microwave energy discharged into at least a portion of the heating zone by one or more microwave launchers, as generally shown as launchers <NUM> in <FIG>. The heated articles can then be passed through a holding zone <NUM>, wherein the coldest portion of each article can be maintained at a temperature at or above a predetermined target temperature (e.g., a pasteurization or sterilization target temperature) for a specified amount of time. The articles can also be passed to a quench zone <NUM>, wherein the temperature of the articles can be quickly reduced to a suitable handling temperature. Thereafter, the cooled articles can optionally be passed through a second pressure adjustment zone 114b before being removed from the system.

The above-described thermalization, microwave heating, holding, and/or quench zones of the microwave system depicted in <FIG> can be defined within a single vessel, or at least one of the above-described stages or zones can be defined within one or more separate vessels. Additionally, in some cases, at least one of the above-described steps can be carried out in a vessel that is at least partially filled with a liquid medium in which the articles being processed can be at least partially submerged. As used herein, the term "at least partially filled" denotes a configuration where at least <NUM> percent of the volume of the specified vessel is filled with a liquid medium. In certain embodiments, the volume of at least one of the vessels used in the thermalization zone, the microwave heating zone, the holding zone, and the quench zone can be at least about <NUM> percent, at least about <NUM> percent, at least about <NUM> percent, or <NUM> percent filled with a liquid medium.

The liquid medium used may be any suitable liquid medium. For example, the liquid medium may have a dielectric constant greater than the dielectric constant of air and, in one embodiment, can have a dielectric constant similar to the dielectric constant of the articles being processed. Water (or a liquid medium comprising water) may be particularly suitable for systems used to heat consumable articles. The liquid medium may also include one or more additives, such as, for example, oils, alcohols, glycols, and salts in order to alter or enhance its physical properties (e.g., boiling point) at the conditions of operation.

The microwave heating systems as described herein may include at least one conveyance system (not shown in <FIG>) for transporting the articles through one or more of the processing zones described above. Examples of suitable conveyance systems can include, but are not limited to, plastic or rubber belt conveyors, chain conveyors, roller conveyors, flexible or multi-flexing conveyors, wire mesh conveyors, bucket conveyors, pneumatic conveyors, screw conveyors, trough or vibrating conveyors, and combinations thereof. Any suitable number of individual convey lines can be used with the conveyance system, and the convey line or lines may be arranged in any suitable manner within the vessels.

In operation, the loaded carriers introduced into the microwave system depicted in <FIG> are initially introduced into a thermalization zone <NUM>, wherein the articles are thermalized to achieve a substantially uniform temperature. For example, at least about <NUM> percent, at least about <NUM> percent, at least about <NUM> percent, at least about <NUM> percent, or at least about <NUM> percent of all the articles withdrawn from the thermalization zone <NUM> have a temperature within about <NUM>, within about <NUM>, or within <NUM> of one another. As used herein, the terms "thermalize" and "thermalization" generally refer to a step of temperature equilibration or equalization.

When the thermalization zone <NUM> is at least partially filled with a liquid medium, the articles in the carrier passing through the thermalization zone <NUM> can be at least partially submerged in the liquid during the passing. The liquid medium in the thermalization zone <NUM> can be warmer or cooler than the temperature of the articles passing therethrough and, in some cases, can have an average bulk temperature of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>.

The thermalization step can be carried out under ambient pressure or it may be carried out in a pressurized vessel. When pressurized, thermalization may be performed at a pressure of at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> psig and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> psig. When the thermalization zone <NUM> is liquid filled and pressurized, the pressure may be in addition to any head pressure exerted by the liquid. Articles undergoing thermalization can have an average residence time in the thermalization zone <NUM> of at least about <NUM> seconds, at least about <NUM> minute, at least about <NUM> minutes, at least about <NUM> minutes and/or not more than about <NUM> minutes, not more than about <NUM> minutes, or not more than about <NUM> minutes. The articles withdrawn from the thermalization zone <NUM> can have an average temperature of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>.

When the thermalization zone <NUM> and microwave heating zone <NUM> may operate at substantially different pressures, the carrier withdrawn from the thermalization zone may be passed through a pressure adjustment zone 114a before entering the microwave heating zone. When used, the pressure adjustment zone 114a may be any zone or system configured to transition the carrier between an area of lower pressure and an area of higher pressure. The difference between the low and high pressure zones may vary depending on the system and can, for example, be at least about <NUM> psig, at least about <NUM> psig, at least about <NUM> psig, at least about <NUM> psig and/or not more than about <NUM> psig, not more than about <NUM> psig, not more than about <NUM> psig, or not more than about <NUM> psig. When the quench zone <NUM> shown in <FIG> is operated at a different pressure than the microwave heating zone <NUM>, another pressure adjustment zone 114b may be present to transition the carrier between the microwave heating zone <NUM> or hold zone <NUM> and quench zone <NUM>. In some cases, the first pressure adjustment zone 114a can transition the carrier from a lower pressure thermalization zone to a higher pressure microwave heating zone, while the second pressure adjustment zone 114b may transition the carrier from a higher pressure holding zone <NUM> (or a higher-pressure portion of the quench zone) to a lower pressure quench zone <NUM>, or portion thereof.

After thermalization, the loaded carrier may be introduced into the microwave heating zone <NUM>, wherein the articles may be heated using a portion of the microwave energy discharged into a microwave heating chamber via one or more microwave launchers. Various configurations of microwave heating systems of the present invention may employ microwave energy having a frequency within one or more of the above ranges, with a frequency of about <NUM> being preferred. Further, as discussed above, the microwave energy discharged into the microwave heating chamber may be polarized. In addition to microwave energy, the microwave heating zone may optionally utilize one or more other types of heat sources such as, for example, various conductive or convective heating methods of devices. However, it is generally preferred that at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> percent of the energy used to heat the articles can be microwave energy from a microwave source.

One example of a microwave heating zone <NUM> suitable for use in the inventive system is schematically illustrated in <FIG>. The microwave heating zone <NUM> shown in <FIG> generally includes a microwave heating chamber <NUM>, at least one microwave generator <NUM> for generating microwave energy, and a microwave distribution system <NUM> for directing at least a portion of the microwave energy from the generator or generators <NUM> to the microwave heating chamber <NUM>. The system further comprises one or more microwave launchers <NUM> for discharging microwave energy into the interior of the microwave heating chamber <NUM>. The microwave heating zone <NUM> may also include a convey system <NUM> having a convey line with a support for transport a plurality of carriers loaded with groups of articles through the microwave heating zone.

Each microwave launcher <NUM> may be configured to emit a particular amount of microwave energy into the microwave heating chamber <NUM>. For example, each microwave launcher <NUM> may be configured to emit at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM> kW and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> kW. When the system includes two or more microwave launchers, each launcher <NUM> 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 <NUM> can be at least about <NUM> kW, at least about <NUM> kW, at least about <NUM> kW, at least about <NUM> kW, at least about <NUM> kW, at least about <NUM> kW, at least about <NUM> kW, at least about <NUM> kW, at least about <NUM> kW, at least about <NUM> kW, or at least about <NUM> kW and/or not more than about <NUM> kW, not more than about <NUM> kW, not more than about <NUM> kW, not more than about <NUM> kW, not more than about <NUM> kW, not more than about <NUM> kW, not more than about <NUM> kW, or not more than about <NUM> kW.

When the system includes two or more microwave launchers <NUM>, at least some of the launchers, shown as groups 322a and 322b in <FIG>, may be positioned on the same side of the microwave heating chamber <NUM>. These same-side launchers 322a or 322b may be axially spaced from one another along the length of the microwave heating chamber, in a direction parallel to the direction of travel of the carrier <NUM> passing through the chamber. The microwave system may also include two or more same-side launchers that are laterally spaced from one another in a direction generally perpendicular to the direction of travel of the carriers through the chamber. Additionally, or in the alternative, the microwave heating system may also include at least two launchers positioned on opposite sides of the microwave chamber. These opposed or oppositely disposed launchers, such as those in groups 322a and 322b shown in <FIG>, may be oppositely facing, such that launch openings of the launchers are substantially aligned, or staggered such that the launch openings of opposed launchers are axially and/or laterally spaced from each other.

Each of the microwave launchers utilized in the microwave heating zone may be of any suitable configuration. Several exemplary microwave launchers are described with respect to <FIG>, and <FIG>. Turning first to <FIG>, one example of a microwave launcher <NUM> comprises a set of broader opposing sidewalls 832a,b and a set of narrower opposing end walls 834a,b, which collectively define a substantially rectangular launch opening <NUM>. The launch opening <NUM> can have a width (Wi) and a depth (Di) that are defined by the lower terminal edges of sidewalls 832a,b and 834a,b, respectively. The depth (Di) of launch opening <NUM> is less than its width (Wi) and is typically oriented in a direction perpendicular to the direction of travel of the carriers moving through the microwave heating chamber. In other words, launch opening <NUM> may be elongated in the direction of travel of the carriers (or the direction of extension of the microwave chamber), so that the width of the launcher defined by the longer terminal edges of the sidewalls 832a,b are oriented parallel to the direction of travel (or the direction of extension), while the depth of the launcher defined by the shorter terminal edges of the end walls 834a,b are aligned substantially perpendicular to the direction of travel (or extension).

Views of one of sidewalls <NUM> and several examples of suitable end walls <NUM> are shown in <FIG> and <FIG>, respectively. Optionally, at least one of the pair of sidewalls 832a,b and the pair of end walls 834a,b can be flared such that the inlet dimension (width W<NUM> or depth D<NUM>) is smaller than the outlet dimension (width Wi or depth Di), as respectively illustrated in <FIG> and <FIG>. If flared, the side and/or end walls define respective width and depth flare angles, θw and θd, as shown in <FIG> and <FIG>. The width and/or depth flare angles θw and/or θd can be at least about <NUM>°, at least about <NUM>°, at least about <NUM>°, or at least about <NUM>° and/or not more than about <NUM>°, not more than about <NUM>°, or not more than about <NUM>°. When present, the values for the width and depth flare angles θw and θd can be the same, or each of θw and θd may have a different value. In some cases, the end walls 838a,b of the microwave launcher <NUM> may have a depth flare angle θd that is smaller than the width flare angle θw. For example, the depth flare angle θd can be not more than about <NUM>°, such that the inlet depth D<NUM> and the outlet dimension Di of microwave launcher <NUM> are substantially the same, as shown in <FIG>, or the depth flare angle θd may be less than <NUM>°, such that Di is smaller than D<NUM>, as shown in <FIG>. Other examples of suitable microwave launchers are described in detail in the '<NUM> Application.

In some embodiments, the launch opening or openings defined by one or more microwave launchers used in the present invention may be at least partially covered by a substantially microwave-transparent window for fluidly isolating the microwave heating chamber from the microwave launcher. The microwave transparent windows, when present, may prevent fluid flow between microwave chamber and the microwave launchers, while still permitting a substantial portion of the microwave energy from the launchers to pass therethrough and into the microwave chamber. The windows may be formed of any suitable material, including, but not limited to, one or more thermoplastic or glass material such as glass-filled Teflon, polytetrafluoroethylene (PTFE), poly(methyl methacrylate (PMMA), polyetherimide (PEI), aluminum oxide, glass, and combinations thereof. The average thickness of each window may be at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>. Each window may be able to withstand a pressure difference of at least about <NUM> psig, at least about <NUM> psig, at least about <NUM> psi and/or not more than about <NUM> psig, not more than about <NUM> psig, or not more than about <NUM> psi without breaking, cracking, or otherwise failing.

Turning back to <FIG>, as the carrier <NUM> passes through the microwave heating zone <NUM>, the articles may be heated so that the coldest portion of the articles achieves a target temperature. When the microwave heating system is a sterilization or pasteurization system, the target temperature achieved by the articles can be a sterilization or pasteurization target temperature of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>. Unless otherwise indicated, the temperature of an article refers to the temperature measured at the coldest portion of that article.

The microwave heating chamber <NUM> may be at least partially liquid filled and at least a portion, or all, of the articles in the carrier may be submerged in the liquid medium during heating. The average bulk temperature of the liquid in the microwave heating chamber <NUM> 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 <NUM> can be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>.

As the carrier <NUM> passes through the microwave heating chamber <NUM>, the articles may be heated to the target temperature in a relatively short period of time, which can help minimize any damage or degradation of the articles. For example, the average residence time of each article passing through the microwave heating zone <NUM> can be at least about <NUM> seconds, at least about <NUM> seconds, at least about <NUM> seconds and/or not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, or not more than about <NUM> minute. The minimum temperature of the articles heated in the microwave heating zone <NUM> can increase by at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>.

In some embodiments, the microwave heating chamber <NUM> can be operated at approximately ambient pressure. Alternatively, it may be a pressurized microwave chamber <NUM> that operates at a pressure that is at least <NUM> psig, at least about <NUM> psig, at least about <NUM> psig, or at least about <NUM> psig and/or not more than about <NUM> psig, not more than about <NUM> psig, not more than about <NUM> psig, or not more than about <NUM> 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.

Referring again to <FIG>, upon exiting the microwave heating zone <NUM>, the loaded carrier may be passed to an optional holding zone <NUM>, wherein the temperature of the articles can be maintained at or above a certain target temperature for a predetermined period of time. For example, in the holding zone <NUM>, the temperature of the coldest part of the article can be held at a temperature at or above a predetermined minimum temperature of at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM>, at least about <NUM>, at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>, for a period of time (or "hold period") of at least about <NUM> minute, at least about <NUM> minutes, or at least about <NUM> minutes and/or not more than about <NUM> minutes, not more than about <NUM> minutes, or not more than about <NUM> minutes.

Thereafter, the heated articles, which may be sufficient pasteurized or sterilized, exit the holding zone <NUM>, may be introduced into a quench zone <NUM>, wherein the articles are cooled as rapidly as possible via submersion in a cooled fluid. The quench zone <NUM> may reduce the external surface temperature of the articles by at least about <NUM>, at least about <NUM>, at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, or not more than about <NUM> in a time period of at least about <NUM> minute, at least about <NUM> minutes, at least about <NUM> minutes and/or not more than about <NUM> minutes, not more than about <NUM> minutes, or not more than about <NUM> minutes. Any suitable fluid may be used in the quench zone <NUM> and, in some cases, the fluid may include a liquid similar to, or different than, the liquid used in the microwave heating zone <NUM> and/or the holding zone <NUM>. When removed from the quench zone <NUM>, the cooled articles can have a temperature of at least about <NUM>, at least about <NUM>, at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>. Once removed from quench zone <NUM>, the cooled, treated articles can then be removed from microwave heating zone <NUM> for subsequent storage or use.

Microwave heating systems of the present invention can be commercial-scale heating systems capable of processing a large volume of articles in a relatively short time. In contrast to conventional retorts and other small-scale systems that utilize microwave energy to heat a plurality of articles, microwave heating systems as described herein can be configured to achieve an overall production rate of at least about <NUM> packages per minute, at least about <NUM> packages per minute, at least about <NUM> packages per minute per convey line, at least about <NUM> packages per minute per convey line, at least about <NUM> packages per minute per convey line, or at least about <NUM> packages per minute per convey line, measured as described in the '<NUM> Application.

Articles processed in a microwave pasteurization or sterilization system as described above may subsequently be obtained by a consumer, who may reheat the articles prior to consumption. As discussed above, the reheating step may include heating one or more articles in a smaller-scale consumer-type microwave oven. Depending on the size of the oven, the total number of articles heated at once can be not more than <NUM>, not more than <NUM>, not more than <NUM>, or <NUM> or less. Typically, the microwave energy discharged by a consumer microwave oven is non-polarized or randomly polarized and has a frequency of about <NUM>. Additionally, articles re-heated in a consumer microwave oven are not secured in a carrier, as is done in a larger-scale pasteurization or sterilization system described previously.

The articles reheated in a consumer microwave oven may be heated for a period of at least about <NUM> seconds, at least about <NUM> seconds, at least about <NUM> seconds, at least about <NUM> seconds, at least about <NUM> seconds, at least about <NUM> minute, at least about <NUM> minutes, at least about <NUM> minutes, at least about <NUM> minutes, or at least about <NUM> minutes and/or not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, not more than about <NUM> minutes, or not more than about <NUM> minutes. Typically, consumer microwave ovens are operated at atmospheric pressure and do not include liquid-filled chambers.

The temperature achieved by the hottest portion of the foodstuff being reheated can be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>. The temperature achieved by the coldest portion of the foodstuff being reheated can be at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, at least about <NUM>, or at least about <NUM> and/or not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, not more than about <NUM>, or not more than about <NUM>.

According to the present invention, methods of designing a package for a particular foodstuff or other item to be heated in commercial microwave pasteurization/sterilization systems and at-home consumer microwave ovens as described herein are also provided. The major steps of one method <NUM> are shown in the flow chart provided in <FIG>.

As shown in <FIG>, the first step of method <NUM> for designing a package including one or more energy control elements is to fill an initial package with a test material to form a test article, as shown by block <NUM>. The initial package may be a commercially-available package, or it may be custom-made, and it may or may not already include one or more microwave energy control elements. In some cases, the initial package used in this method may be a modified package that resulted from a previous trial.

Any suitable test material may be used and can include, for example, a sample of the exact foodstuff or other item which will ultimately be used to fill the package, or a substitute material used to simulate the foodstuff or other item. One example of a suitable substitute test material is whey gel pudding, such as that commercially available from Ameriqual Group, LLC (Evansville, Indiana, USA). The initial package may be filled in any suitable manner. Generally, the initial package may be formed of conventional materials and may not include any type of energy control element, although situations where the initial package includes an energy control element are not excluded.

Once the initial package is filled, it may be heated in a microwave heating system using microwave energy, as shown by block 612a in <FIG>. The microwave heating system may be a large- or pilot-scale liquid-filled microwave heating system that utilizes polarized microwave energy, as described above with respect to <FIG>, or it may be a lab-scale system designed to simulate the behavior of a larger-scale system. Alternatively, the test article may be heated in a consumer-type microwave oven that utilizes non-polarized or randomly polarized microwave energy.

During at least a portion of the heating step, the temperature of the test material may be measured in one or more, preferably two or more, locations, as shown by block 612b in <FIG>. Such temperature measurement may be performed using any suitable instrument and, in some cases, may be performed using temperature probes positioned within the test material and sealed into the packages. In these cases, the temperature probe or probes would be placed into the packages along with the test material during the filling step, shown as block <NUM> in <FIG>. Alternatively, other types of temperature measurement devices may be used that may be positioned near or within the article after it has been filled.

After the article has been heated to a target temperature, it may be removed from the microwave heating zone and cooled. As shown by block <NUM> in <FIG>, from the temperature measurements taken during the heating step, the location of at least one hot or cold spot within the package may be determined. In some cases, such a determination may be performed using temperature data obtained during the heating, as well as commercially available modeling software. In some cases, the location of the hot or cold spot may depend on the position of the article within a carrier, while, in other cases, it may not. The article may exhibit at least one hot spot, at least one cold spot, or at least one hot spot and at least one cold spot.

As shown by block <NUM>, the method <NUM> of designing a modified package further includes the step of creating a modified package including at least one energy control element by taking one or more of the following actions: (i) adding a microwave inhibiting element near a hot spot; (ii) adding a microwave enhancing element near a cold spot; (iii) removing a microwave inhibiting element from near a cold spot; and (iv) removing a microwave enhancing element from a hot spot. In some cases, two or more, three or more, or even all four actions may be taken to form a modified package. As discussed previously, the microwave control element may be a selective microwave control element and may inhibit or enhance one type of microwave energy more than another.

Claim 1:
A process for heating a plurality of articles (<NUM>) in a microwave heating system, said process comprising:
(a) loading a group of said articles into a carrier (<NUM>), wherein each of said articles includes a package at least partially filled with at least one foodstuff and each package includes at least one energy control element;
(b) passing the loaded carrier through a microwave heating chamber (<NUM>) in a direction of travel along a first convey line;
(c) generating microwave energy, wherein the microwave energy is polarized and has a wavelength of no more than <NUM>;
(d) during at least a portion of said passing, discharging at least a portion of the microwave energy into said microwave heating chamber; and
(e) heating said articles using at least a portion of said microwave energy discharged into said microwave heating chamber to at least one of sterilize or pasteurize the foodstuff,
wherein, during said heating, a portion of the foodstuff is heated to a substantially different temperature and/or at a substantially different heating rate than said portion of said foodstuff would have been heated to or at if said energy control element was not present.