Patent Publication Number: US-2021179335-A1

Title: Device to Force Moisture Removal Inside a Food Container

Description:
BACKGROUND 
     Crispy or crunchy food stored in a food container becomes soggy after a very short period of time. Because of this, delivered or take-out food rarely tastes as good as it is served in a restaurant, and lunches prepared at home in the morning are not as delicious as they should be. 
     This problem is caused by moisture trapped in the food container. Existing solutions, such as US Patent Publication No. 2010/00320210, passively vent the trapped moisture out of the container. These solutions are limited because relying on air circulation alone, the moisture is not removed fast enough, or at least in an amount of time that is meaningful to avoid condensation inside the container, and eventually the moisture comes back to the food. In addition, by introducing ambient air from outside the container (through an open vent), the temperature inside changes, making hot food colder or salads warmer. Furthermore, since the replacement air that enters the vented container contains moisture as well, adopting these solutions results in introducing more moisture into the food container and the food. 
     Other strategies, such as US Patent Publication No. 2013/0056369, use absorbent materials placed on the interior side of the lid with passive/natural convection to absorb moisture. Like the solutions previously stated, the absorbent materials do not work well when a relatively large amount of moisture comes up from sizzling food. 
     Because the problem affects not only people&#39;s enjoyment of their lunches but also customer satisfaction of businesses that serve take-out food, and food shelf life, food containers that quickly and effectively remove moisture in the containers are needed. 
     SUMMARY 
     The structure, overall operation and technical characteristics of the present invention will become apparent with the detailed description of preferred embodiments and the illustration of the related drawings as follows. 
     The invention is incorporated in a method, a food container, and a lid or a pad for a food container that actively removes moisture in the food container by introducing a localized cold spot (below the dew point temperature) inside the food container that forces condensation of the moisture at the cold spot. At a minimum, the temperature of the localized cold spot should be colder than the air inside the food container when the food is added. 
     The condensed moisture is then captured by an absorbent element placed adjacent to, or collocated with, the cold spot and between the cold spot and the stored food so that condensed moisture extracted from the air inside the food container is trapped within the adsorbing substrate and the food does not become soggy before consumption. 
     An exemplary food container may or may not be sealable, such as a covered salad bowl, a pizza box, or a Styrofoam® box. The localized cold spot may comprise any cold substance, such as ice or a gel packet, and optionally a holder for the cold substance. The optional cold substance holder may at least include a bottom portion exposed to, preferably inside, the interior of the food container. The bottom portion may be made of materials with at least some heat transfer capability (i.e. low thermal resistance or high thermal conductivity). An example of the cold substance holder is a small receptacle, such as a plastic sauce cup or a ramekin, attached to the lid on the interior side, after a cold substance, such as ice, is contained inside. 
     For an embodiment of the food container that does not include a cold substance holder, the cold substance, such as a frozen gel packet, or ice, may be coupled to the lid and exposed to the interior of the food container. The cold substance is preferably frozen before use so that the intended condensation formation may be sufficiently fast and sustained. With a proper cold substance, the temperature of the cold spot is substantially at or below the dew point temperature. Therefore, the moisture inside the food container is exposed to the cold spot and condensation of vapor inside the container is forced to happen at a controlled localized feature. 
     Additionally, because the condensation of the moisture is forced, the absorbent element need not, but may, be substantially made of a desiccant element with hygroscopic qualities. Any absorbent materials including some inexpensive options such as paper towels, napkins, sponges, air-laid fibers, and tissues may be adopted as the absorbent element. The absorbent element is placed between the cold spot and the food, preferably adjacent to and below the cold spot. In addition, the lid could further comprise a drip member, placed between the absorbent element and the food, and preferably coupled to the absorbent element, in order to prevent the absorbent element from releasing the captured condensate when reaching its saturation limit, which ideally would never happen. The drip member may be a tray or a film of materials that allows water vapor but not liquid water from moving in and out, such as a band aid. 
     Furthermore, in order to keep the temperature in the exemplary food container unaffected in a meaningful way, it is preferred that the cold spot comprises a frozen substance that is properly sized so that the heat released by the condensation phase change from vapor (to liquid) is offset by the heat absorbed by the phase change of the frozen substance to liquid. That is, the latent heat of vaporization must be balanced against the latent heat of fusion. As a general rule of thumb, for every 1 gram of ice as the frozen substance in a food container, ¼ gram of condensate can be formed without a temperature change within the food container. Alternatively, the heat released by the condensate formation may be absorbed by the frozen element without a phase change of the frozen substance to liquid. For example, ice made from an ordinary ice cube tray may be sufficient for condensing the vapor moisture inside a lunch box containing hot food, and when the ice cube melts, the food temperature is substantially unchanged. 
     Preferably, the amount of cold (preferably frozen) substance to be used would vary to coincide with the mass of the food inside the container and the moisture contained therein (by the food mass). Using well-known thermodynamic principles, those in the art can calculate custom versions of this invention for each meal, container, and specific application. In practice, it is preferred to create preset sizes (e.g., small, medium, large, etc,) depending on the approximate food mass and container size. 
     One embodiment of a condensation extracting insert for a food container with forced moisture removal comprises: a cold substance holder configured to contain a cold substance, such as ice or any non-toxic refrigerant gel/liquid, and a moisture absorbent element. The exemplary insert is configured, preferably with an adhesive attachment, to couple the insert to the interior wall of the food container&#39;s lid/cover, and its moisture absorbent element is located between the cold substance holder and food inside the food container. In addition, the exemplary insert may further comprise members stated above, such as a drip-proof member and an opening for accommodating the cold substance holder. 
     In another embodiment of the food container, the cold substance holder may be an independent inserted assembly that is self-supported and preferably removably coupled to the food container. The exemplary cold substance holder may comprise a receptacle for holding the cold substance, such as a small cup, a ramekin, or an adsorbing pad, and a stand for supporting the receptacle, such as a tripod. Alternatively, the cold substance holder may be merely a stand for supporting the cold substance, such as a pizza box tent for holding a frozen gel packet. See U.S. Pat. No. 4,498,586. Like the embodiments previously described, in this preferred embodiment, the absorbent element and the drip member are preferably placed near the cold spot, such as being attached to the bottom of the receptacle. 
     One embodiment of the method for actively removing moisture from a food container comprises the following steps:
         providing the following items:
           the food container having a lid, a base coupled to the lid, and an interior space formed between the lid and the base,   a cold substance holder having an interior bottom portion and an exterior bottom portion, and   a moisture absorbent element coupled to the exterior bottom portion of the cold substance holder;   
           placing a frozen element, such as an ice cube or a gel packet, onto the interior bottom portion of the cold substance holder;   placing the cold substance holder in the interior space of the food container and coupling the cold substance holder to the food container, either at the lid or the base, with the exterior bottom portion oriented toward the base of the food container;   placing food inside the food container; and   closing the food container.       

     Although the steps of the exemplary method are illustrated in a specific order, a person skilled in the art would know that the steps may be implemented in any alternate orders as long as forced condensation of moisture inside the food container is achieved and the condensed moisture is captured. In addition, the embodiment of the method may further comprise a step of providing a drip-proof member as illustrated above. Furthermore, the food container provided in this embodiment may have other members as stated above. 
     A third embodiment, which is presently preferred, employs adding a predetermined amount of liquid to an absorbent pad, pre-freezing it, and then sticking it to the inside of a food box. In this embodiment, the moisture-removing pad to be coupled to a food container comprises a cold-substance-holding, moisture absorbent layer (the “absorbent layer”) at the bottom side and an adhesive layer at its top side. The absorbent layer in this embodiment is configured to hold the cold substance either in its liquid or solid form. Once the cold substance is trapped inside the absorbent layer in its solid form, this embodiment may be placed inside a food container to force condensation as illustrated above and further absorb the condensate from the moisture inside the food container. As to the adhesive layer of this embodiment, it is configured to attach the embodiment to the upper interior wall of the food container, no matter what the ambient temperature is. In this embodiment, the adhesive layer may cover, entirely or partially, the top side of the embodiment as long as it provides sufficient adhesion. 
     Furthermore, the embodiment is preferably configured so that its absorbent layer is capable of absorbing, and not releasing, not only the condensate from the moisture but also the entire cold substance that turns into its liquid form after the heat exchange (i.e. melting). In an exemplary embodiment, the absorbent layer is made of air-laid fiber (or similar materials) with a 0.06″ thickness and comprises a footprint surface area of 3.5″×3.5.″ The adhesive layer could any adhesive known in the art and suitable for these conditions. 
     Water is the usual liquid, but any food safe substance that can be absorbed by the absorbent layer as a liquid, then frozen (or chilled) will suffice (because it will force condensation inside a food container). In practice, it has been found that adding 1 teaspoon of water (measured in liquid form) to an absorbent layer and then freezing it is generally sufficient to maintain the temperature of a food container with up to four (4) ounces of food. In general, for containers with more food than four (4) ounces of food, it is preferred to include an additional one (1) teaspoon of water in the absorbent layer for every additional three (3) ounces of food prior to freezing the pad. 
     Indeed, applicant&#39;s test results of an exemplary pad with 3.5″×3.5″×0.06″ air-laid absorbent fibers and 1 tablespoon of (20° F. frozen) water show a 35% reduction in relative humidity between treated and untreated food containers with no more than 12 ounces of 200° F. food. 
     However, when circumstances dictate, saltwater can be used in place of water as the liquid to be added to the absorbent layer. Saltwater can be advantageous because it has a lower freezing point than water. Introducing more latent heat exchange, more quickly (by the faster melting of the ice), will induce quicker condensation at the desired location. At present, saltwater having a salinity of 40-60 PPT (parts per thousand) is preferred, but other salinity level could work in a given situation. 
     The method of introducing the liquid (e.g. water) into the absorbent material is immaterial. Water can be added by spraying, misting, pouring, dipping, etc., provided the quantity introduced is appropriate for the given conditions. Following the introduction of the liquid, the entire pad is preferably frozen where it is stored waiting for use. When ready to use the frozen pad will be adhered to an inside surface of the food container, preferably the underside of the lid. 
     The presently preferred method for forcing moisture removal in a food container comprises the steps of:
         introducing a predetermined amount of cold substance into an absorbent layer;   freezing the pad with the cold substance in the absorbent layer; and   adhering the pad to an upper interior wall of the food container by an adhesive layer at a top side of the pad.       

     To use this exemplary embodiment inside a pizza box, the user may:
         spray, evenly pour, or drip 2 teaspoons of water on the absorbent layer; after the water is absorbed by the absorbent layer, put the embodiment in a freezer;   take the embodiment out of the freezer after the water inside the absorbent layer freezes (ideally at 20° F. or lower, depending on the operating limitations of the specific adhesive used in the adhesive layer); and   affix the embodiment inside the lid of the pizza box with the adhesive layer.       

     Now the pizza box is ready for a fresh pizza for delivery or to be enjoyed later. A person skilled in the art would know that a larger pizza may require two or more such embodiments. Indeed, Applicant&#39;s experiments show little or no discernible effect on the food quality by removing too much condensate using this method with more than enough such embodiments. 
     In addition, the embodiment may further comprise a backing layer configured to removably couple to the adhesive layer at the top side to prevent the adhesive layer from adhering to objects other than the intended lid of the food container before use. The embodiment may also have a moisture barrier layer between the adhesive layer and the absorbent layer so that the absorbed condensation or cold substance does not compromise the effectiveness of the adhesive layer. Moreover, the embodiment may further include another moisture barrier layer (i.e. a drip member as in other embodiments stated above) below the absorbent layer, configured to allow vapor, but not liquid, to pass through and thus prevent dripping. The moisture barrier layer between the adhesive layer and the absorbent layer and the moisture barrier layer below the absorbent layer in an embodiment may, or may not, be identical in materials or dimensions. 
     An alternate preferred embodiment with an absorbent layer, an adhesive layer, an upper moisture barrier layer between the absorbent layer and the adhesive layer, a lower moisture barrier layer at the bottom side of the absorbent layer, and a (removable) backing layer coupled to the adhesive layer may further include an opening at the top side through the backing layer, the adhesive layer, and the upper moisture barrier layer so that the cold substance may be introduced into the absorbent layer from the top side. The opening in this embodiment is preferably located in the middle of the pad and covering a 20-30% or less of the footprint surface area. This preferred embodiment is advantageous because the cold substance would be trapped at the back/upper side of the embodiment and dripping is further prevented when the cold substance turns into liquid after heat exchange with the moisture inside the food container. 
     Alternate embodiments of the pad may adopt different materials for the aforementioned elements and various shapes and dimensions based on the volume and dimension of the food container and amount of food. For instance, the absorbent layers in an embodiment may be made of any suitable materials, such as air-laid paper, cellulose sheets, trapped adsorbent powders, and so forth. The moisture barrier layer(s) in this embodiment may be any suitable commercially available moisture barriers, preferably with FDA approval and edible. Indeed, all the elements in any embodiment herein are preferably approved by FDA to be safely used inside a food container. 
     Additionally, the preferred shapes and dimensions of an exemplary absorbent layer depend on its absorbing capacity. For instance, a square embodiment to be used with an ordinary takeout box may have an absorbent layer that is made of standard air-laid fiber material with a standard density and preferably has a footprint surface area of at least 2″ by 2″ (i.e., 4 square inches) and a thickness of 0.06″. Generally speaking, for every additional 4 ounces of food, the air-laid absorbent layer of a similar embodiment is preferably 0.01″ thicker, but not to exceed 0.1″ total thickness, measured dry. Indeed, empirically, thicker pads show diminishing performance improvement and gradually cease to scale. 
     Furthermore, the backing layer of an exemplary embodiment may comprise two pieces of release paper (e.g. wax paper) overlapping in the middle of the embodiment or alternatively includes an additional tab or a folded edge so that the backing layer can be easily removed and discarded from the adhesive layer. In another embodiment, the adhesive layer may cover only about 90% of the total surface area with a gap in the middle, and/or along the perimeter/edges, so the backing layer, with two separate sheets meeting in the middle when the gap is in the middle, can be easily removed. Additionally, the opening on the top side of an embodiment of the pad, for introducing water to be frozen, preferably takes 20-30% (or less) of the footprint surface area of the absorbent layer; and the opening may be of various shapes and have a surface area preferably equal to a circle with a diameter ranging from 1 inch to 5 inches. 
     Finally, the preferred cold substance for an embodiment of the pad is water, but any suitable cold substance that can be absorbed by the absorbent layer as a liquid, freeze, and force condensation inside a food container by phase change (melting) can be adopted. When water is used as the cold substance in an embodiment of the pad, 1 teaspoon of water, measured in liquid form, in the absorbent layer, when frozen, is generally sufficient to maintain the temperature of a food container with up to 4 ounces of food. For a food container with more food, it is preferred to include an additional teaspoon of water in the absorbent layer for every additional 3 ounces of food. Indeed, Applicants&#39; test results of an exemplary pad with 3.5″×3.5″×0.08″ air-laid absorbent fibers and 0.6 teaspoon of water show a 35% reduction in relative humidity between treated and untreated food containers with no more than 12 oz of 200° F. food. 
     Furthermore, an alternate embodiment of the moisture-removing pad to be coupled to a food container comprises a moisture absorbent layer at the bottom side and an adhesive layer at its top side. In this embodiment, the moisture absorbent layer itself comprises a cold substance. For such an embodiment, external cold substance may or may not be used for moisture removal. For instance, an embodiment may comprise an air-laid (or similar) moisture absorbent layer that already absorbs sufficient moisture from the ambient air, so that no more cold substance need be added. 
     One object of this invention is to provide an effective and affordable solution for removing moisture inside a food container by forced moisture removal. 
     Another object of this invention is to provide an effective and affordable solution for removing moisture without affecting the temperature inside a food container in a meaningful way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, features and advantages of the present invention will be more readily appreciated upon reference to the following disclosure when considered in conjunction with the accompanying drawings, wherein reference numerals are used to identify the components in the various views. 
         FIG. 1  shows a cross sectional view of an embodiment. 
         FIG. 2  shows a cross sectional view of an alternate embodiment. 
         FIG. 3A  shows a top view of another embodiment, with the lid closed. 
         FIG. 3B  shows a top view of the embodiment in  FIG. 3A , with the lid open. 
         FIG. 3C  shows a cross sectional view of the embodiment in  FIG. 3A . 
         FIG. 4  shows a top view of another embodiment, with its lid open. 
         FIG. 5A  shows a top view of an embodiment of the pad to be attached inside a food container. 
         FIG. 5B  shows a perspective view of the embodiment in  FIG. 5A . 
         FIG. 6A  shows a perspective view of an embodiment of the pad and a pad-holding assembly. 
         FIG. 6B  shows a section view of the embodiment in  FIG. 6A . 
         FIG. 6C  shows a side view of the section view of  FIG. 6B . top view of an embodiment of the pad. 
         FIG. 6D  shows an embodiment of the pad. 
         FIG. 7A  shows a perspective exploded view of an embodiment of the pad/food container. 
         FIG. 7B  shows an exploded view of the pad shown in  FIG. 7A . 
         FIG. 7C  shows a perspective exploded view of an embodiment of the pad/food container. 
         FIG. 8  illustrates a presently preferred embodiment of the pad. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The preferred embodiments include a food container, a removable lid for a food container, and a method for removing moisture in the food container by forced condensation of the moisture and are illustrated in  FIGS. 1-5 . In  FIG. 1 , the embodiment is a food box  100  with a base  110  and a lid  120 . The base  110  may contain food, hot or cold. The lid  120  may comprise a frozen element  121 , a compartment  122  for containing the frozen element  121 , an absorbent material  123  placed below the frozen element  121  and the compartment  122 , and a drip tray  124 . The lid  120  and base  110  are coupled together to close the food box  100 . Preferably, the food box  110  may have a seal (not shown) between the lid  120  and the base  110  to achieve a better insulation and moisture control. 
     The frozen element  121  of the embodiment  100  in  FIG. 1  may be any proper cold substance such as an ice cube (frozen water) or a frozen gel packet that may induce condensation of vapor moisture. A suitable compartment for containing the frozen element may comprise a depressed area  122  on the lid  120  as shown in  FIG. 1 , with or without its own cover for closing the compartment. Alternatively, the compartment may be located above the rest of the lid. Either way, the bottom portion of the compartment may have at least some heat transfer capability for facilitating heat exchange between the frozen element and the vapor inside the food container. 
     In addition, the embodiment  100  in  FIG. 1  further comprises an absorbent material  123  placed inside the food container  100  and below, preferably very close to, the bottom portion of the compartment  122 . The absorbent material  123  may be made of any suitable materials for capturing and isolating the condensed moisture, such as paper towel as adopted in this embodiment. The absorbent material  123  in  FIG. 1  is supported by a drip tray  124 , but it may alternatively be coupled to the interior side of the lid by any suitable means, such as adhesives and tapes, without contacting the tray. The drip tray  124  may be replaced by any drip member placed between the absorbent material and the stored food, such as a plastic film or a band-aid. An alternate embodiment may not have a drip tray or anything alike. 
     An alternate embodiment  200  as shown in  FIG. 2  is substantially similar to the previous embodiment  100 . In this embodiment  200 , the cold substance holder  222  is an insert of the lid  220  configured to hold a cold substance  221  and made of a thermal-conductive material. Since the cold substance holder  223  is separate from the cover  225 , the cover  225  and the base  210  may be made of non-thermal-conductive materials so that the food inside is somewhat thermally insulated. In addition, the drip member  224 , a drip tray, of this embodiment  200  has a raised edge configured to stop the moisture absorbent element  223  and released condensate, if any, from moving out of the tray. 
       FIGS. 3A-3C  show another embodiment  300 . In this embodiment, the food container  300  is substantially made of Styrofoam®. A cold substance holder  322 , a plastic sauce cup (e.g. ramekin) in this embodiment, is placed in a hole cut from the lid  320  and affixed to the lid  320 . Right below the cold substance holder  322 , a piece of paper towel  323 , as an absorbent material, is coupled to a bottom of the cold substance holder  322  and the interior surface of the lid  320  by a band-aid-like, water resistant, and vapor permeable film  325 , working as a drip member of the embodiment, and coupled to the moisture absorbent material  323 . Like the embodiment  100 , this food box  300  preferably has a seal  326  between the lid  320  and the base  310  (attached to the lid  320  in this embodiment  300 ) to achieve a better insulation and moisture control. 
     In an alternate embodiment, the food container is identical to the embodiment  300  except that the paper towel  323  is coupled to the lid  320  by adhesive tape or backing on four sides without any drip member. In an experiment with this alternate embodiment, hot food, including a crispy toast, 2 eggs, and a small container with boiling water, was placed inside the embodiment and an ordinary Styrofoam® box as a control food container, respectively. After that, the lids were closed and an ice cube slightly larger than a standard ice cube  321  was placed in the sauce cup of the embodiment, which works as the cold substance holder. A short period later, the toast in the control food container became soggy while the toast in the embodiment was still crispy and hot. Therefore, the embodiment shows that the invention works as planned. 
     Another embodiment is shown in  FIG. 4 . In this embodiment  400 , the food container  400  comprises a base  410 , a lid  420  coupled to the base  410 , and a cold-substance holding assembly  430  removably coupled to the base  410 . The cold substance holding assembly  430  comprises a receptacle  431  configured to hold a cold substance  500 , a stand  432  coupled to and configured to elevate the receptacle  431 , a moisture absorbent element  433  coupled to a bottom of the receptacle  431 , and a drip member  434  coupled to and placed beneath the moisture absorbent element  433 . The receptacle  431  in this embodiment  400  may or may not have a cover. In another embodiment where the bottom of the receptacle has little heat transfer capability, the forced condensation may occur mostly above the receptacle, and therefore, the cold substance holding assembly may not include a moisture absorbent element or a drip member. 
       FIGS. 5A and 5B  show a preferred embodiment, which features an exemplary pad  500  to be attached inside a food container. This pad  500  comprises an absorbent layer  510 , an adhesive layer  520 , a backing layer  530 , an upper and lower moisture barrier layers  550  &amp;  560 , and an opening  540 . The absorbent layer  510  in this pad  500  is sandwiched between two moisture barrier layers  550  &amp;  560  that allow moisture in the air, but not liquid water (condensate), to go through. The adhesive layer  520  has a gap  521  in the middle so that the backing layer  530  with two halves can be easily removed. Additionally, the opening  540  cuts through the backing layer  530 , the adhesive layer  520 , and the upper moisture barrier layer  550  and is configured to allow cold substance (water) to be introduced to the absorbent layer  510  from the top. 
     The amount of cold substance to be used varies depending on how big the food container is and how much food is to be stored in the food container. For instance, if the food container is a common takeout box designed to store 10 oz of food, then 1 teaspoon of water should be sufficient, while 1 tablespoon of water is preferred. (As stated above, over-extraction of condensation does not appear to affect food quality.) Additionally, the cold substance (water) is preferably trapped in 20-30% of the footprint surface area (L×W) of the absorbent layer  510 . 
     A preferred method to use this pad  500  includes the steps of:
         1. Introducing a predetermined amount of a cold substance in liquid form (water) from the top into the opening  540 ;   2. allowing the absorbent layer  510  to absorb the water;   3. putting the pad  500  into a freezer and allowing the cold substance to turn into solid form (ice); and   4. retrieving the pad  500 , removing the backing layer  530 , and sticking the pad  500  to a food container by the adhesive layer  520 .       

     An alternate embodiment may have no moisture barrier like  560  at the bottom or any opening like  540  on the top. For such an embodiment, the cold substance can be introduced at the bottom, and the absorbent layer is preferably thicker so that no dripping will occur. Those in the art know how to size the pad for each particular circumstance so that no dripping occurs. 
     Another alternate embodiment of the moisture-removing pad to be coupled to a food container comprises a moisture absorbent layer at the bottom side and an adhesive layer at its top side. In this embodiment, no moisture is added to the absorbent element before freezing. The moisture absorbent layer absorbs sufficient moisture from the ambient air so that no additional water is needed. Otherwise, the same procedure is followed. That is, the moisture-removing pad is first frozen and then adhered to the food box. 
     Another embodiment is shown in  FIGS. 6A-6D . In this embodiment, the food container  600  comprises a base  610 , a lid  620  coupled to the base  610 , and a pad-holding assembly (or feature)  630  integrated within the lid  620 . The pad-holding assembly  630  is configured to expose a surface of a pad  640  to the interior of the food container  600  when a pad  640  is placed in the pad-holding assembly  630 . In this embodiment, no adhesive is needed to secure the pad  640  to the lid  620 . Gravity alone can be used to keep the pad  640  in the pad-holding assembly  630  and exposed to the interior of the container  600 . Alternatively, the size of the pad  640  can be configured to create a friction-fit with one or more surfaces of the pad-holding assembly  630 , which can help keep the pad  640  in place. 
     The pad-holding assembly  630  can be configured in a myriad of ways. One embodiment of the pad-holding assembly  630  is shown in  FIG. 6B . One or more cross-members  632  can be used to span the opening  634 . In addition, a lip  636  can be created (in part or in whole) around the perimeter of the opening  634 . The lip  636  can be used to support the outside edge  638  of the pad  640 . 
     In this embodiment, the pad  640  can be constructed in any of the ways previously described in this specification. It is preferred, however, that the pad  640  comprise an absorbent layer  650 , which will hold some cold substance, and a moisture barrier layer  652 . The absorbent layer  650  in this pad  640  is located above the moisture barrier layer  652  so that moisture in the air from inside the food container  600  can pass through the barrier layer  652 , but liquid water (condensate) in the pad  640  will not drip into the food container  600 . The moisture barrier layer  652  is optional if the absorbent layer is sized to avoid dripping condensation on the food as previously described. 
     As previously noted, the amount of cold substance to be used varies depending on how big the food container is and how much food is to be stored in the food container. For instance, if the food container is a common takeout box designed to store 10 oz of food, then 1 teaspoon of water should be sufficient, while 1 tablespoon of water is preferred. (As stated above, over-extraction of condensation does not appear to affect food quality.) Additionally, the cold substance (water) is preferably trapped in 20-30% of the footprint surface area (L×W) of the pad  640 . 
     A preferred method to use this pad  640  includes the steps of:
         1. Introducing a predetermined amount of a cold substance in liquid form (water) onto the pad  640 ;   2. allowing the absorbent layer  640  to absorb the water;   3. putting the pad  640  into a freezer and allowing the cold substance to turn into solid form (ice); and   4. retrieving the pad  640  and placing the pad  640  into the recessed holding assembly  630 .       

     An alternate embodiment may have no moisture barrier like  652  at the bottom. For such an embodiment, the pad should be configured so that no dripping will occur. Those in the art know how to size the pad for each particular circumstance so that no dripping occurs. 
     Another embodiment is shown in  FIGS. 7A-7C . In this embodiment, the food container  700  comprises a base  710 , a lid  720  coupled to the base  710 , and a pad  740 . The pad  740  is preferably comprises layers.  FIG. 7B  illustrates the preferred embodiment of a layered pad  740 . Absorbent layer  742  is the layer previously discussed throughout this specification that absorbs liquid. The absorbent layer  742  preferably comprises an air-laid fabric or textile. When pad  740  is placed into the food container  700 , absorbent layer  742  has a surface  750  that is exposed to the interior of food container  700 . 
     Continuing now with  FIG. 7B , adjacent to absorbent layer  742  is a double-sided adhesive layer  744 . Adjacent to double-sided layer  744  is a freezable element  746 . While it is preferred to freeze the entire pad  740 , the freezable element  746  is preferably a sealed packet containing water or saltwater. Adjacent to the freezable element  746  is a removable backing  748  which protects the adhesive when it is being stored. As previously described, the removable backing  748  allows the pad  740  to be frozen first, and then adhered to the lid  720  after removing the backing  748  at the desired time. 
     The adhesive used on the double-sided adhesive layers  744  can be any adhesive known in the art. In the alternative, rather than have separate adhesive layers, adhesive material can be applied to a surface of the container or pad layers as needed to create they layered-effect shown in  FIGS. 7A-7C . In operation, the pad  740 , would be frozen first and then applied to the container prior to adding food. 
     The presently preferred embodiment is shown in  FIG. 8 . This embodiment is similar to the embodiment shown in  FIGS. 5A and 5B , but preferably has no moisture barrier like  550  or  560  at the top or bottom, or any opening  520  through the adhesive layer  520 . This embodiment preferably has an adhesive layer  520 , but that is not required. The absorbent pad  510  can simply be placed in the food container or held in place by a sleeve or other device, or rest directly on top of the container contents. Still, it is preferred to use the adhesive pad  520  to sick the pad to an inside surface of the food container. 
     Optionally, this embodiment can be sold as a kit. When sold as a kit, it is preferred that the absorbent layer  510  already has fluid added to it. In other words, the preferred kit contains an absorbent layer  510  already containing an amount of fluid that has been absorbed by the absorbent layer  510 . In this way, a user can simply freeze the kit (or the contents of the kit) and it will be ready for use inside a food container anytime. 
     In the application where a kit is sold, such a kit could contain an absorbent layer  510 , comprised of woven or non-woven plant pulp, airlaid, synthetic sponge, natural sponge, etc. Additionally this kit could include a pre-measured quantity of water, in a packet or other container, to be added to the absorbent layer  510 . The pre-measured water quantity would be in accordance to ratios already outlined. Lastly, the kit may or may not include two sided tape for use as an adhesive layer  520 . 
     In typical operation, the end user would pour the pre-measured water quantity into the absorbent layer  510 , or provide his/her own water. The end user would then freeze the absorbent layer  510  with the water. The two-sided tape could be kept at room temperature and added to the frozen absorbent layer sub-assembly after freezing and just before adhering the absorbent layer  510  into a container for the purposes of controlling air moisture. Similarly, the two sided tape could be pre-installed to the absorbent layer and frozen along with the absorbent structure. Similarly, the two sided tape could be pre-installed into the container, after which adhering the frozen absorbent layer could be readily facilitated. 
     As previously noted, it is preferred that the fluid added to the absorbent layer  510  comprise water. When packaged as a kit, it is also preferred to add a preservative to the fluid to prevent mold from growing during shipping and storage. Those in the art can select any suitable agent known in the art with anti-mold or anti-microbial properties. The preferred agent is potassium sorbate, which is a synthetically produced tasteless salt. Other agents, such as calcium propanoate (aka calcium propionate), sodium benzoate, tricalcium phosphate, butylated hydroxyanisole, and hypochlorous acid could also work. Adding potassium sorbate at the ratio of 0.3% (⅓ of 1%) by mass (potassium sorbate (0.3%) to water (99.7%) ratio) has been found suitable. 
     When trying to keep hot food crispy (e.g., french fries), it is important not to cool down the contained food in the process. As previously noted, the best way to do this is to balance the heat released by the condensation phase change from vapor (to liquid) against the heat absorbed by the phase change of the frozen substance to liquid. Stated another way, the latent heat of vaporization (same as enthalpy of condensation, with positive/negative sign reversed) should be balanced against the latent heat of fusion (same as the enthalpy of melting, with positive/negative sign reversed). The enthalpy of condensation being attributed to the moisture removed from the air. While the enthalpy of melting is attributed to ice suspended in the absorbent substrate of invention. Thermodynamically, balancing the energy exchange is the preferred way to keep the temperature in the exemplary food container unaffected by adding the cold element. 
     Under thermodynamic theory, ice in the absorbent layer  510  will condense vapor in the food container without affecting temperature at a ratio of 7 to 1 by unit of mass. In other words, approximately 7 grams of ice melted in the absorbent layer  510  will balance (thermodynamically) against 1 gram of condensation removed from the air in the food container. 
     Empirically, we have found that the ratio is closer to 4 to 1. That is, for a single serving container (about 12 ounces of food) every 4 grams of frozen fluid in the absorbent layer  510 , will form 1 gram of condensate in the absorbent layer  510  without a temperature change within the food container. At present, we have found 2.7 tablespoons (or 40 ml) of frozen substance for 12 ounces of food to be optimal. However, as little as 1 teaspoon of frozen substance per 4 ounces of food has been found to help keep contained food from getting soggy. And, as much as 3 tablespoons of frozen fluid for every 4 ounces of food has also been found suitable to keep food from getting soggy without materially affecting enclosed food temperature. 
     It is also preferred that the absorbent layer  510  be less than fifty percent (50%) saturated with fluid. That way, there is ample absorbency left to keep moisture forced from the air in the absorbent layer and not drip onto the food. At most, the amount of condensation removed and captured by the absorbent layer  510  should be no more than 0.05 pounds per cubic foot of air (at normal ambient pressures) in the volume enclosed by the container. 
     Sometimes, it is desired to keep cold food from getting soggy. For example, salads can get soggy very quickly. For cold food, such as salad, it is not necessary to balance the cold content imbued unto the absorbent structure. It will be, in fact, desirable for the cold content to exceed the (exothermic) heat released during the formation of condensation. In other words, more ice can be added for the same amount of food in cold situations because it is acceptable for the food to get cooler. 
     While the invention has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those ordinarily skilled in the art without departing from the score and spirit disclosed herein.