MXPA97005181A - Control atmosphere package - Google Patents

Abstract

The present invention relates to a package for maintaining a modified atmosphere around the contents that are inside the package when stored in an environment, this modified atmosphere package comprising a tray having a base and side walls extending upwards from the base, these walls and base defining a cavity in which the content is arranged, one of said side walls including an indentation extending into said cavity, a membrane attached to an upper portion of the side walls, and enclosing an additional cavity, a structural member connected in a detachable manner to the upper portion of the side walls, this structural member disposed above the membrane to prevent this membrane from contacting an external structure, said structural member having at least one opening for directly expose the membrane to the mentioned environment, being the The contactor is free of contact with the structural member on the cavity so that the exposure to the environment is not impeded, and where the structural member has a first stacking ele- ment and the base of the tray has a second stacking element on the wall. base for allowing the stacking of a first modified atmosphere gasket with a second modified atmosphere gasket that is placed under the first modified atmosphere gasket, the indentation on the side wall of the first modified atmosphere gasket, exposing at least one gas the structural member of the second atmosphere modified packaging to the environment when the first and second modified atmosphere packaging is apil

Description

CONTROLLED ATMOSPHERE PACKAGE Field of the Invention The present invention relates generally to a package of controlled atmosphere for food. More particularly, the invention relates to a package of modified atmosphere and a package of ventilated environment, which inhibit the decomposition of the food contained therein. BACKGROUND OF THE INVENTION For a long time, containers have been used to store and transfer food before presenting the food in a market where it will be purchased by the consumer. After the meats, fruits, and vegetables are harvested, they are placed in containers to preserve these foods for as long as possible. The maximization of the time in which these foods remain conserved in the containers, increases the utilization of all the entities in the distribution chain, minimizing the amount of decomposition. The environment around which food is conserved is the most critical factor in the conservation process. Not only is it important to maintain an adequate temperature, but the molecular content of the gases surrounding these foods is also significant.

By providing an appropriate gas content to the environment surrounding the food, the food can be better preserved when maintained at the appropriate temperature, or even when exposed to variations in temperature. This gives the food producer some guarantee that, after the food leaves its control, the food will be in an acceptable condition when it reaches the consumer. Each type of food has an optimal gas concentration in which it is best preserved. For example, fish and crustaceans are much better preserved when exposed to high levels of carbon dioxide (C02), such as 60 percent to 80 percent. On the one hand, the beef is made coffee in the absence of oxygen (02), and the appropriate mixture is about 80 percent of 02 and 20 percent of C02. Alternatively, poultry are best preserved when exposed to nitrogen (N2) and carbon dioxide, the ideal concentration being approximately 75 percent N2 and 25 percent C02. With respect to fruits and vegetables, the process of decomposition is very different from that of meats, because 1 I fruits and vegetables remain alive after harvest. Fruits and vegetables undergo a process known as respiration, where they take oxygen and release energy from heat, carbon dioxide, water vapor, and occasionally ethylene. Each species has a different breathing rhythm.

The breathing rhythm is also affected by external factors, that is, carbon dioxide concentration, oxygen concentration, temperature, and ethylene concentration. In general, the tolerance of a species to decomposition at typical storage temperatures is improved by maintaining oxygen levels above 5 percent, while maintaining carbon dioxide levels below 20 percent. However, it is also desirable to prevent aerobic bacteria from growing and multiplying, which is done by maintaining a lower oxygen level. But anaerobic bacteria, such as Clostridium botulinim, will grow if there is no oxygen present. As such, the balance between these competing factors typically results in an oxygen concentration of less than 10 percent but greater than 5 percent for most fruits and vegetables. The rest of the gas is nitrogen until respiration occurs, which results in the addition of carbon dioxide, ethylene, and water vapor. To limit respiration and prevent rapid decomposition, it is desirable to continuously modify the gaseous environment surrounding the food, by filling in the oxygen supply that is consumed, and by eliminating the byproducts that occur during respiration. To help in the transmission of oxygen into the container, and in the removal of carbon dioxide, ethylene, and water vapor from the container, permeable polymeric films, or membranes, have been employed. 'In some situations, it is better to use a membrane with a high gas permeability, so that these gases can be easily transferred to and from the container. In other situations, it is better to maintain the initial environmental gas concentration, such as when meat is packed, which can be done by using a membrane with low permeability. In general, the velocity at which a specific gas is lost through a membrane is proportional to the difference between the concentrations of that specific gas on both sides of the permeable membrane. If there is 0 percent carbon dioxide on one side of the membrane, and a high concentration of carbon dioxide on the other, the per- ion would be high. On the other hand, if there is air with 20 percent oxygen on I both sides of the membrane, the permeation would be low. The rate of permeation from a container is proportional to the surface area of the permeable membrane. To ensure proper permeation is made, the surface area can not be obstructed. Otherwise, perméación from the surface will not be presented. As can be expected, this problem is encountered frequently during storage and shipping where numerous containers having these permeable film membranes are located adjacent to each other. When the containers are stacked, the problem is accentuated, since the possibility that a portion of the permeable membrane is vastly obstructed increases. Considering that heat is also a by-product of the breathing process, and that it is desirable to maintain lower temperatures, some fruits and vegetables, such as strawberries, require heat to dissipate. If not, then the higher temperature will cause more breathing, resulting in a "snowball" effect, and a product that decomposes quickly. In these situations, it is not convenient to use a contained environment enhanced by a permeable membrane, since this configuration would tend to contain the heat. Instead, no membrane is used in this type of package, and additional vents are provided to allow unhindered access of the cooling gas around the product. However, when these packages are stacked vertically to use less space in storage and transport, the air vents can be clogged due to the 'stacking' configuration. Attempts have been made to align the vents on the base of one vessel with the lid of another, to maintain a free flow of air between the adjacent vessels and to dissipate the heat. However, as the heat rises from the lower stacked container into the vertically adjacent container, the temperature in that container rises as well. As the hot air continues to rise from pack to pack, the heat is increased, such that the temperature of the air around the food in the top pack of the stack can become unacceptably high. Attempts have also been made to put vents on the side of the tray. But the addition of openings on the tray can compromise the structural integrity of the package. And since the vast majority of containers today are made of thinner, less expensive polymers, the issue of resistance is a big concern. In addition, the additional openings along the side of the package, make the enclosed food more susceptible to exposure to moisture, dirt, insects, and the like, during storage and transportation. As consumer tastes continue to transition from canned and frozen foods to fresh foods, the need for better containers is growing. This improved container must overcome the aforementioned drawbacks associated with the occlusion of the permeable membrane surface, and the maintenance of the appropriate environment during stacking.

SUMMARY OF THE INVENTION Briefly, the present invention relates to new and improved containers for transporting and storing food. More particularly, the invention relates to a package of modified atmosphere and a package of ventilated environment, which inhibit the decomposition of the food contained therein. The modified atmosphere package maintains an appropriate contained atmosphere around the content that is present therein, when stored in an environment. The modified atmosphere package includes a tray, a permeable membrane, and a lid. The tray has a base and side walls that extend upwards from the base. The side walls and the base define a cavity where the contents are arranged. A permeable membrane is attached to an upper portion of the side walls, and moves the cavity away. The cap is releasably connected to the upper portion of the side walls, and is disposed above the membrane to prevent the membrane from contacting an external structure that inhibits permeation through the membrane. The lid also has at least one opening to expose the membrane to the environment. A stacking element at the base of the tray and at the top of the tray allows multiple modified atmosphere packages to be easily stacked without clogging the membrane. The modified atmosphere package is useful when the husks of a 'fruit or vegetable have been broken and the content of high oxygen levels, which will cause rapid decomposition, needs to be protected'. Also shown is a ventilated environment package, which is very similar to the modified atmosphere package, with the exception that the permeable membrane is not, and the tray has at least one opening in its base. The opening of the lid is at least partially aligned with the opening of the base of the tray, and simultaneously exposed to the environment when two packages of ventilated environment are stacked. The air is allowed to flow through the opening in the base of the tray, through the food contained in the ventilated environment package, and out of the openings in the lid. The ventilated environment is useful for fruits and vegetables that have not been cut their external husks, and require a ventilated air environment. The lids used in the ventilated environment package and in the modified atmosphere package are interchangeable. Therefore, the producer of the items can use a lid and two trays to pack a wide variety of foods. The above summary of the presented invention is not intended to represent each embodiment, or each aspect of the present invention. This is the purpose of the figures and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages will become clearer upon reading the following detailed description, and upon reference to the drawings, in which: Figure 1 is an isometric view of a modified atmosphere package. Figure 2 is an isometric view separated into parts of the modified atmosphere package. Figure 3 is an isometric view of two stacked modified atmosphere packages. Figure 4 is a cross-sectional view of the two stacked packages of Figure 3, taken along line 4-4. Figure 5 is an enlarged cross-sectional view illustrating the communication of the lid opening of the stacked packages of Figure 4. Figure 6 is an isometric view separated into parts of a ventilated environment package. Figure 7 is an isometric view of two stacked ventilated environment packs. Figure 8 is an enlarged cross-sectional view illustrating communication of the opening of the lid with the opening of the base of the tray in Figure 7.

Although the invention is susceptible to different modifications and alternative forms, certain specific embodiments thereof have been shown by way of example in the drawings, and will be described in detail. However, it must be understood that the intention is not to limit the invention to the particular forms described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives that fall within the spirit and scope of the invention, as defined by the appended claims. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to Figure 1, a modified atmosphere package 2 is illustrated. The modified atmosphere package 2 includes a tray 4 having side walls 6 and a base 8 from which the side walls 6 extend towards above. The upper portions of the side walls 6 generally have an outwardly extending flange 10, which defines the periphery of the modified atmosphere package 2. A membrane 12 is attached along the upper portion of the side walls 6, which it completely encloses the cavity defined by the side walls 6 and the base 8. In general, the membrane 12 is attached to the modified atmosphere package 2 by a heat sealing process. The modified atmosphere pack 2 also has a lid 14 which is detachably connected to the upper portion of the side walls 6 in the flange 10. Accordingly, when initially packed, the lid 14 can make contact with the edges of the container. the membrane 12, which are attached to the modified atmosphere pack 2 when the lid 14 is connected to the flange 10. After the initial opening, the consumer can either discard the membrane 12 or stretch it again on the flange 10, and replace the lid 14. The tray 4, the membrane 12, and the lid 14 are more easily visualized in Figure 2, which is a separate view in parts of Figure 1. The lid 14 includes a plurality of openings 16, which allow, the membrane 12 is exposed to the environment. This is important because, when the food contained in the tray 14 undergoes respiration, the membrane 12 acts as a valve, which allows the resulting carbon dioxide, ethylene, and water vapor to be permeated from the respiration process. , through the membrane 12, while the oxygen is filled from the environment into the cavity through the membrane 12. If the lid 14 had no openings 16, this exchange of gases through the membrane 12 would be limited to the volume of gas under the lid 14. The permeation rate through the membrane 12 is proportional to the concentration of carbon dioxide, the concentration of oxygen, the. ethylene concentration, and the amount of food product contained. The material from which the membrane 12 is made also dictates the permeability rates. When a package is designed for a specific meat, vegetable, or fruit, the material that is most suitable for the needs of that particular food contained in the tray 4 is selected. However, if the effective surface area of the permeable membrane is reduced. 12 due to an adjacent package or object abutting the membrane 12, then efforts to design the package are wasted. When part of the surface area of the membrane 12 is covered, it can not exchange the gas in that region, and the desired gas concentrations are not maintained, which leads to more rapid decomposition. It should be noted that the side walls 6 and the base 8 can also be a path through which the gases permeate. However, compared to the thin membrane 12, these surfaces have a negligible permeation rate. But the modified atmosphere package 2 could be designed with multiple surfaces having permeable membranes. The lid 14 '-' ensures that no adjacent object or package obstructs the surface area of the membrane 12. To effect this result, the lid 14 is relatively rigid to withstand the force from an adjacent object, while the openings 16 allow free movement of ambient air around the membrane 12. The lid 14 also protects the thin membrane 12 from tearing, which can occur easily during storage and transport, if it comes in contact with a sharp object. In addition, the addition of lid 14 makes the product more tradable, as consumers tend to buy items packed in structurally strong packages, since these items are less likely to be damaged during the distribution process. Although the lid 14 with multiple openings 16 is shown, the same function could be performed with fewer openings 16, provided that ambient air can be freely moved within the region between the lid 14 and the membrane 12. Furthermore, the complexity of the lid 14, and could simply be a wire frame structure to prevent adjacent objects from contacting the membrane. The design type uses much less material than the fully encompassing lid 14 shown in Figures 1 and 2. Additionally, the modified atmosphere package 2 can have a curvilinear shape, as well as the polygonal shape shown in Figs. 1 and 2 Figure '3 illustrates a modified upper atmosphere package' 2a, which has been stacked vertically on a lower modified atmosphere package 2b. This provides a minimum storage volume, as well as a structurally strong element where multiple modified atmosphere packages 2a and 2b are transported. Accordingly, it is a requirement that the modified atmosphere packages 2 have a capacity to stack vertically, to be commercially practical. The details of the stacking characteristics are shown in Figure 4. The cover 14 includes a stacking recess 18 created by the vertical stacking walls 20. The base 8 of each of the trays 4 includes a stacking projection that extends downwards 22. The stacking projection 22 can be merely wall-mounted which extend downwards from the base 8. Alternatively, the shape of the base 8 itself may be sufficient as the stacking projection .. The stacking projection 22 on the tray 4 is. fits into the stacking recess 18 of the lid 14. This stacking function could be performed in different alternative methods. For example, the base 8 could be equipped with a recess projecting upwards, and the cover 14 could have a corresponding projection. Alternatively, multiple recesses and corresponding projections could be placed on these components. Figure 5 illustrates the interaction between openings 16 and environment AE. Regardless of which stacking methodology is employed, a primary concern is that the openings 16 are exposed to an environment AE when the upper modified atmosphere pack 2a is stacked on the lower modified atmosphere pack 2b as shown in Figures 3 to 5. The environment AE is allowed to circulate through the membrane 12 of the lower modified atmosphere package 2b. This allows the proper exchange of gases through the membrane 12, although the two packages 2a and 2b are stacked directly on top of each other. Several design features allow the exposure of the membrane 12 to the environment AE. The trays 4 include multiple ribs 24 that add structural stability to the trays 4. More importantly, each pair of ribs 24 on the upper modified atmosphere pack 2a provides an indentation 25 extending into the interior of the tray 4, which exposes the openings 16 of the lid 14 of the lower modified atmosphere package 2b to the environment AE. Accordingly, the stacking of multiple packs 2a and 2b is performed with the openings 16 of the lower modified atmosphere pack 2b aligned with the indentations 25 of the tray 4 of the upper modified atmosphere pack 2a. Although in the modality shown, the ribs 24 which provide these indentations 25 are structural, indentations may be employed that do not add to the structural integrity, but merely provide access to the openings 16. And the openings 16 could move from the walls 20 of the recess of stacking 18, to ensure that there are no obstructions in the stack. The reason that Figures 1 to 5 show the openings 16 on the inside of the walls 20, is that this lid 14 is interchangeable with a ventilated environment package, which will be described later with reference to Figures 6 to 8. Modified atmosphere package 2 is very useful for packing fruits or vegetables that have been pierced or open the shell during the packaging process. The shell is a natural protective membrane that exchanges gases during respiration. When the shell is cut to expose the inner portions, the modified atmosphere package 2 then acts as the shell to regulate respiration. The tray 4 of the modified atmosphere package 2 is typically made of a polymeric material such as polystyrene, polyester, or polypropylene, to name a few. In general, the thickness of the tray 4 is from about 0.127 millimeters to about 1016 millimeters, depending on the selected mat material and the size of the modified atmosphere pack 2. The lid 14 is typically made of a polymeric material such as polystyrene, polyester , or polypropylene, with numerous other alternatives available. Again, the thickness of the material of the lid 14 is from about 0.127 millimeters to about 1.016 millimeters. In general, the tray 4 and the lid 14 are thermoformed. If the membrane 12 is to be permeable, it can be made of a polymeric material such as polystyrene, polypropylene, polyethylene, or different polymers of the vinyl group. Alternatively, a more impermeable membrane 12 may be made of materials such as polyvinylidene chloride or ethylene vinyl alcohol in combination with polyethylene. The membrane 12 is generally 12.7 microns or less thick. As mentioned above, the protection provided by the lid 14 allows many types of lower strength materials for the membrane 12 to be used, which would normally not be possible if the lid 14 were not present. The modified atmosphere package 2 also it could be done by making the lid 14 connect to the tray 4 during the manufacturing process, in a joint. Accordingly, these two components of the modified atmosphere package 2 are produced in a simultaneous manner. After the food is placed inside the tray 4, then the membrane 12 is heat sealed to the tray 4. Finally, the lid 14 is rotated around the joint, and connected to the flange 10. In another Alternatively, the base 8 of the tray 4 could have a lower flange extending downward. This lower flange then engages the flange 10 of the upper portion of the side walls 6 of the modified atmosphere package 2, which is located in a stack just below it. Accordingly, the tray 4 has both required stacking characteristics. This lower flange has openings through which air could pass when the packages are stacked. Figure 6 illustrates a part-separated view of a ventilated environment package 38, including a ventilated environment tray 40 and the lid 14 as described with reference to Figures 1 to 5. The ventilated environment tray 40 and the cover 14 are connected in a separable manner with each other, to form the ventilated environment pack 38. The ventilated environment tray 40 includes the side walls 42 and a base 44. A flange 46 extends around the upper portion of the side walls, 42. The main difference between the ventilated medium tray 40 and the tray 4 of the Figures 1 to 5, is that the ventilated environment tray 40 includes base openings 48 along its base 44. The ventilated environment tray 40 is useful for storing fruits and vegetables that have not been opened by external husks during the packing process. The ventilated environment tray 40 uses approximately the same thicknesses and materials described with reference to the tray 4 of Figures 1 to 5. Although the ventilated environment package 38 uses the same lid 14 as in Figures 1 to 5, incorporates the permeable membrane 12. Without permeable membrane 12, gases from the environment flow freely from the openings of the base 48, through the ventilated environment pack 38 adjacent to the food, and out of the openings 16 of the lid 14. After a fruit or vegetable is harvested and packaged, the continuous breathing process produces heat, carbon dioxide, water vapor, and ethylene, which must be evacuated from the environment around the food. As the heat raises the temperature of the gases immediately adjacent to the food surface, these gases rise into the ventilated environment pack 38, due to the reduction in gas density associated with an increase in temperature. As the warmer gases are collected in the upper part of the ventilated environment pack 38 along the underside of the lid 14, the hot gases leak from the openings 16 in the lid 14. To maintain a balance pressure with the environment, then the gases are directed from the environment into the ventilated environment package 38 through the lower base openings 48. Because the gases in the environment are generally colder than the gases in the environment. hot gases escaping from the ventilated environment package 38, the products inside the ventilated environment package 38 constantly have fresh ambient air passing through them. This process of removing the heat by natural convection, provides an adequate cooling effect on the food, which in turn reduces the rate of breathing. Figures 7 and 8 accentuate a design advantage of the ventilated environment pack 38. Figure 7 illustrates a top vented environment pack 38a stacked on a bottom vented environment pack 38b. The stacking methodology is analogous to that described with reference to the modified atmosphere packs 2 of Figures 1 to 5. After all, the lid 14 is the same, and the ventilated room tray 40 is almost exactly the same that the modified atmosphere tray 4, except for the addition of the base openings 48. However, the ratio between the openings of base 48 of the upper ventilated environment pack 38a and the openings 16 of the cover 14 on the package of ventilated lower environment 38b, it is remarkable. This relationship is shown in detail in Figure 8. In the past, when numerous packages were piled with their 'lid and base holes aligned, the hot air 1' from the lowest package left that package through the cap, and entered the vertically adjacent package, whose additional heat was added to the hot gas that came out, and further went to the next vertically adjacent package, and so on. The result was that the combined heat produced from the lower packages was passed upward until it escaped from the upper package, while fresh air was directed into the stack from the lower package. This "chimney effect" caused the upper packets to be warmer than the lower packets, which results in higher breathing rates and faster decomposition in those higher packets. There was an additional problem if the openings were blocked, which stopped the natural flow of air. The ventilated environment package 38 solves this problem. As shown in Figure 8, the openings 16 along the lid 14 are larger than the base openings 48 on the base 44 of the ventilated environment tray 40. This is to allow the exit of the hot gas WG from the top <; 14 of the bottom ventilated environment pack 38b through the openings 16, while the cold GC gases enter through the same openings 16, pass through the base openings 48, and enter the environmental package ventilated upper 38a. It should be noted that some of the hot gas WG produced by the food in the lower ventilated environment pack 38b can also be mixed in the cold gas CG, and enter the upper vented environment pack 38a. In any case, the food contained in the ventilated environment packages 38 at the top of the pile will be colder. If the base openings 48 are blocked for any reason, then the extra exposure to the cold gas CG of the environment in the opening of the lid 16 is very beneficial. Several prior art designs incorporated vents along the sides of the packages. But, since the hottest gases rise to the top of the package, these packages are less susceptible to releasing all the heat. When the ventilated environment packages 38 are placed in piles, not only the temperature of all the ventilated environment packages 38 remains at an adequate level, but carbon dioxide, ethylene, and water vapor escape, while oxygen is replenished, which inhibits the growth of anaerobic bacteria. This process is extremely useful, since it increases the shelf life of the foods contained inside the ventilated environment package 38. In addition, the capacity of this lid 14 to enclose the contents in the modified atmosphere packages 2 and in the packages of ventilated environment 38, is beneficial. The fact that a producer can use a lid 14 for almost all varieties of fruits or vegetables, is extremely effective because of the cost. Although the present invention has been described with reference to one or more particular embodiments, those skilled in the art will recognize that many changes can be made thereto without departing from the spirit and scope of the present invention. It is contemplated that each of these modalities and obvious variations thereof fall within the spirit and scope of the claimed invention, which is stipulated in the following claims.

Claims (23)

1. NOVELTY OF THE INVENTION Having described the foregoing invention, it is considered as a novelty, and therefore, property is claimed as contained in the following: CLAIMS 1. A package to maintain a modified atmosphere around the content that is inside the package when stored in an environment, comprising this modified atmosphere package: a tray having a base and side walls extending upwardly from the base, these walls defining and this base a cavity in which the contents are arranged, - a membrane joined to an upper portion of the side walls, and enclosing said cavity; and a structural member connected in a detachable manner to the upper portion of the side walls, this structural member disposed above the membrane to prevent this membrane from contacting an external structure, said structural member having at least one opening for exposing the membrane to the mentioned environment. . ' 2. The modified atmosphere package according to claim 1, characterized in that the structural member includes a cover, the upper portion of the side walls defining a periphery, and this cover being detachably connected to a substantial portion of the container. said periphery. The modified atmosphere package according to claim 2, characterized in that a top segment of the lid has a first stacking element, and the base of the tray has a second stacking element, the first element being able to be coupled. of stacking with the second stacking element, providing the first and second stacking elements, the stacking of the modified atmosphere package with a second modified atmosphere package. 4. The modified atmosphere package according to claim 1, characterized in that the structural member has a first stacking element. and the base of the tray has a second stacking element, the first stacking element aon the second stacking element being able to be coupled, the first and second stacking elements providing the stacking of the modified atmosphere package with a second modified atmosphere package. . The modified atmosphere package according to claim 4, characterized in that the first stacking member includes a recess projecting downwardly, and the second stacking member includes a member projecting downwardly. 6. The modified atmosphere package according to claim 1, characterized in that the structural member and the tray are two separate components. The modified atmosphere package according to claim 1, characterized in that the tray is made of a material selected from the group consisting of polystyrene, polyester, and polypropylene. 8. The modified atmosphere package according to claim 1, characterized in that the structural member is made of a material selected from the group consisting of polystyrene, polyester, and polypropylene. 9. The modified atmosphere package according to claim 1, characterized in that the membrane is made of a material selected from the group consisting of polystyrene, polyethylene, and polypropylene. 10. The modified atmosphere package according to claim 1, characterized in that the side walls define a substantially polygonal periphery of the tray. 11. A configuration for maintaining a controlled environment around the packaged contents stored in an environment, comprising this configuration: lower and upper ventilated environment packages, including each of these packages of ventilated bottom and top environment: a tray that it has a base and side walls extending upwards from the base, the side walls and the base defining a cavity in which the contents are arranged, this base having a first opening and a first stacking element; and a lid connected in a detachable manner to an upper portion of the side walls, this lid having a second opening and a second stacking element; wherein the lower ventilated environment pack and the upper ventilated environment pack can be stacked when the first stacking element of the upper ventilated environment pack is coupled with the second stacking element of the lower ventilated environment pack, leaving the second opening of the lid of the lower ventilated environment pack at least partially aligned with the first opening of the base of the ventilated upper environment pack, and simultaneously exposing said environment when stacking the lower ventilated environment packets and higher. 12. Ventilated environment packs according to claim 11, characterized in that the first opening is smaller than the second opening. 13. The ventilated environment packs according to claim 11, characterized in that the first stacking member includes a member projecting downwardly, and the second stacking member includes a recess projecting downwardly. 14. The ventilated environment packs according to claim 11, characterized in that the first opening is adjacent to a edge, wherein one of the side walls meets said base. 15. The ventilated environment packages according to claim 14, characterized in that one of the sidewalls of the upper ventilated environment package includes an indentation extending inward toward the cavity adjacent to the first aperture. , exposing this indentation to the second opening on the lid of the ventilated environment package inferior to the environment when the upper and lower ventilated environment packages are stacked. 16. The ventilated environment packs according to claim 11, characterized in that the tray is made of a material selected from the group consisting of polystyrene, polyester, and polypropylene. 17. The ventilated environment packs according to claim 11, characterized in that the tapei is made of a material selected from the group consisting of polystyrene, polyester, and polypropylene. 18. The ventilated environment packs according to claim 11, characterized in that the side walls define a substantially polygonal periphery of said tray. 19. A game of storage and transport of food to pack, store, and transport a variety of foods, this game being able to maintain each of the variety of foods in a controlled environment, while exposed to an environment, comprising this set: at least one tray of modified atmosphere having a first base and first side walls extending upwardly from the first base, the first base having a first stacking element, the tray being enclosed by a membrane attached to a portion top of the first side walls; at least one ventilated environment tray having a second base and second side walls extending upwardly from the second base, the second base having a second stack member and an opening, and at least one cover having an opening of lid and a lid stacking element, the lid stacking element being able to be coupled with the first stacking element of the modified atmosphere tray and the second stacking element of the ventilated environment tray, the opening of the lid being sealed at least partially aligned with the opening of the second base of the ventilated environment package, and simultaneously being exposed to the environment when the second stack element engages the stack stacking element; this lid being connectable in a separable manner to the modified atmosphere tray in a first orientation wherein the lid is disposed above the membrane, to prevent the membrane from contacting an external structure, exposing the opening of the lid to this membrane to the environment; and the lid being connected in a detachable manner to the ventilated environment tray in a second orientation. 20. The set of claim 19, wherein the opening of the lid is larger than the opening of the second base of the ventilated room tray. 21. The set of claim 19, wherein the first and second stacking elements each include a projecting member downwardly, and the stacking member of the cover includes a recess extending downwardly. 22. The set of claim 19, wherein the modified atmosphere tray and the ventilated environment tray are substantially polygonal. 23. The set of claim 19, wherein the lid is made of a material selected from the group consisting of polystyrene, polyester, and polypropylene. SUMMARY OF THE INVENTION A package is described to maintain a modified atmosphere around the content that is inside the package when it is stored in an environment. The modified atmosphere package includes a tray, a membrane, and a structural member. The tray has a base and side walls extending upwardly from the base. The side walls and the base define a cavity where the contents are arranged. A membrane is attached to an upper portion of the side walls, and encloses the cavity. The structural member is detachably connected to the upper portion of the side walls, and is disposed above the membrane, to prevent the membrane from contacting an external structure that inhibits permeation through the membrane. The structural member also has at least one opening for exposing the membrane to the environment. The stacking elements at the base of the tray and on the upper part of the structural member allow the modified atmosphere packages to be easily stacked. It also shows a ventilated environment package which is very similar to the modified atmosphere package, with the exception that it has no permeable membrane, and the tray has at least one opening in its base. This opening of the lid is at least partially aligned with the opening of the base of the tray, and are simultaneously exposed to the environment when two packages of ventilated environment are stacked. The caps used in the ventilated environment package and the modified atmosphere package are interchangeable. The most representative figure of the invention is number 1