Patent Application
20110318460
1. Field of the Disclosure
The present disclosure provides a method of assembling a food package that prevents collapse of the headspace in a food package and reduces the amount of gases inserted into the package headspace during assembly and modifies the atmosphere therein.
2. Description of the Related Art
Modified Atmosphere Packaging (MAP) is a technique that modifies the atmospheric gases in a retail food package to preserve food freshness, extend shelf life, and enhance food appearance. MAP generally involves altering the ratio of natural atmospheric gases within the food package (O2, N2, and CO2), water vapor, and, in the case of fresh produce, controlling levels of a fourth gas, ethylene. Altering O2/CO2 ratios by MAP can be used to inhibit microbial respiration. Removal of O2 slows the growth of aerobic microorganisms, lipid oxidation, and pigment oxidation. Elevation of CO2 levels can retard microbial growth and some enzymatic activity, and reduce moisture loss from the food.
In recent years, MAP has been increasingly used. When MAP is used, the packager generally has one opportunity to modify the atmosphere in the package (for instance, by injecting CO2 into the package headspace), before the package is sealed. After this initial injection of MAP gas into the headspace of the food package, the volume of the MAP gas inside of a sealed food package gradually depletes over time.
Anticipating these losses, conventional MAP techniques generally require the operator to inject large volumes of MAP gases in the headspace of the food package prior to sealing, and, thus, food packages are required to be much larger than the food product enclosed. This results in the need for a large headspace. Thus, wasted space results to store, ship, and display the food product.
In addition, loss of gas volume inside of a food package can cause the food package to collapse inward, providing a food package that is visually unappealing to consumers. If enough internal gas pressure is lost, the lid film can begin to adhere to the surface of the food product, reducing consumer appeal and making the food product more susceptible to “freezer burn.”
Also, conventional MAP techniques are made worse when the food package uses a “biofriendly” lid film, which are generally not as elastic or stretchable as conventional lid film. Thus, the MAP gases are required to be injected at high pressures to keep a “bubble” pressure against the lid film.
Further, conventional MAP techniques may have a higher failure rate for “biofriendly” food trays, such as those made of PET (polyethylene), since glues that adhere the lid film to the food tray tend not to stick as well to the biofriendly food trays as to conventional food trays.
Thus, conventional MAP techniques have two general technical problems—the gradual loss of the original injected MAP gases after the food package is sealed with no mechanism to replenish the loss of gas and also the need for a large initial volume. As noted above, both of these technical problems can be exacerbated when using a “biofriendly” lid film and/or food tray.
The present disclosure provides a method for assembling a food package having a lid film and an absorbent pad having an active agent that can supply and replenish levels of Modified Atmosphere Packaging (MAP) gas inside the food package after sealing.
The present method provides overall dimensions of the food package (i.e., the food tray and lid film) and headspace that can be reduced as much as about 20% as compared to conventional MAP methods.
Referring to the drawings and, in particular,
Referring to
Referring to
Method 10 includes step 16 of removing and/or replacing a portion (or all) of the ambient air enclosed in headspace area 38. Removal of ambient air in headspace 38 can be by reduced pressure (vacuum) and/or by replacement by gas flushing with one or more atmosphere-modifying (MAP) gases. Removing a portion or all ambient air from headspace area 38 temporarily reduces the volume of air in the headspace area. An initial amount of one or more atmosphere-modifying (MAP) gases is injected into headspace area 38, so that the resulting gases (and/or their ratios) in the headspace area are different than for ambient air. Injection of the MAP gas can be at a greater pressure in headspace 38 than for ambient air, creating an internal gas pressure that pushes upward on lid film 34 to form a “bubble” (also called “dome” interchangeably herein) that deflects lid film 34 upward. An embodiment of a “bubble” created by method 10 is a deflection of lid film 34 that is nine (9) mm to twenty (20) mm above the horizontal plane across the top of food tray 32. Headspace 38 is a reservoir of MAP gas, which preserve food product 36, prolong shelf life, and/or enhance the attributes of food product 36 (including color, aroma, and/or overall appearance).
Method 10 includes step 18 of adhering lid film 34 to an exterior side of food tray 32 (such as by heat-sealing) that forms an airtight seal that completely encloses food product 36 and absorbent pad 40 in food package 30.
Conventional MAP techniques require extra volumes of MAP gas during the initial injection to compensate for gas losses due to adsorption/absorption of MAP gases inside the food package over time. Such gas losses are caused by absorption/adsorption of gas on the surface of food product 36, dissolving gases in the liquid purge from food product 36, and/or leakage of MAP gases through lid film 34 or food tray 32 to escape food package 30. Method 10 requires a smaller initial headspace area 38 in food package 30 than is required with conventional MAP techniques. Method 10 also reduces “concave” packages (where the lid film deflects inward toward the food product) that can be the result from gas losses over time.
After sealing lid film 34 to food tray 32 with an airtight seal, method 10 includes step 20 of generating one or more atmosphere-modifying gases by activation of the active agents 47 in absorbent pad 40. The atmosphere-modifying gas(es) thus generated by absorbent pad 40 are released into headspace area 38 to replenish and replace MAP gases lost therein. The replenishment step maintains sufficient gas volume and pressure in headspace 38 to prevent weakening or collapse of food package 30, and to reduce or prevent any contact of lid film 34 with food product 36. In a preferred embodiment, lid film 34 does not contact food product 36.
As shown in
Steps 12, 14, 16, and 18 of method 10 can be performed by a human operator or by a machine, or a combination of both. For example, gas flushing of headspace 38 (removing ambient air from the headspace and injecting MAP gases to replace it therein) can be performed by a human operator or by machine. An example of method 10 has a human operator who sets up a production line of machines that place absorbent pad 40 and food product 36 on food tray 32, place lid film 34 around food tray 32 to enclose food product 36 and absorbent pad 40, perform a gas flush of headspace area 38 to replace ambient air with MAP gases, and adhere lid film 34 to food tray 32 with an airtight seal to form food package 30.
As used herein, “lid film” is a barrier film or semi-barrier film having a low gas transmission rate that is used to enclose and seal a food package using MAP techniques.
Referring to
A “pocket,” as used herein, means an area between two layers that can hold an active agent in position prior to use. For example, in another exemplary embodiment of absorbent pad 40, a pocket for active agents 47 can be formed between top layer 42 and bottom layer 44. In yet another exemplary embodiment, an absorbent pad having first layer 46 adjacent to top layer 42 can have a pocket formed between any of: top layer 42 and first layer 46, bottom layer 44 and first layer 46, and/or between top layer 42 and bottom layer 44. In these exemplary embodiments, each layer 46 can be formed of one or more individual or layers of a material, preferably tissue, placed on each other to form layer 46. The active agent(s) can be positioned in any pocket, and may be present in more than one pocket.
The pad architecture of absorbent pad 40 affects the performance of the active agent in food package 30. This performance depends not only on the active agents used, but also where the active agents are placed in absorbent pad 40 in relation to absorbent layers 46 and top and bottom layers 42, 44. Varying the pad architecture can regulate the length of time before active agent 47 is activated to generate the atmosphere-modifying gas, the rate at which that generated gas is released into headspace area 38. Also, the pad architecture can physically separate the individual chemical components of a system for delayed activation that can provide an “extended release” effect of an atmosphere-modifying gas into headspace area 38.
Top layer 42 of absorbent pad 40 is a film that is polyethylene, polypropylene, polyester, or any combinations thereof. Alternatively, top layer 42 can be a nonwoven material or coffee filter tissue (CFT), or other wet-strength paper. A preferred embodiment of top layer 42 is polyethylene film. Top layer 42 may be solid or perforated, and is preferably perforated to facilitate purge from food product 36 to get to absorbent layers 46.
Bottom layer 44 of absorbent pad 40 is a material that permits fluid uptake therethrough. Examples of bottom layer 44 include, but are not limited to, polyethylene film (which can be perforated to facilitate fluid strikethrough to absorbent layers 46), coffee filter tissue (which is about 99.5% or more of a cellulosic material, plus a small amount (about 0.5%) of water-strengthening resin to provide strength to the material when wet), and a nonwoven material treated with a surfactant (i.e., wetting agent). Bottom layer 44 can be made of any material that is porous to liquids and gases, while retaining any solid contents inside absorbent pad 40.
In all preferred embodiments, absorbent layer 46 is made of tissue. In a further exemplary embodiment of absorbent pad 40, active agent 47 is a carbon dioxide (CO2)-generation system. An example of a CO2 generation system that can be used with the present method is a mixture of an acid and a base, such as citric acid and sodium bicarbonate, respectively, that react to form CO2. The acid may be an organic acid or an inorganic acid (including, but not limited to, boric acid) that is food-safe. In the exemplary embodiment in
An example of active agent 47 is a CO2 generation system that is a mixture of citric acid and sodium bicarbonate, which are mixed with cellulose to form one or more laminate layers that are placed in the pocket formed between absorbent layers 46. Incorporating the chemical components of the CO2 generation system in one or more laminate layers permits a large amount of the CO2 generation system to be used in absorbent pad 40 without compromising its function by having large amounts of loose chemicals collecting on one side or the other if the pad were picked up by an edge.
Scaling, i.e., selecting the proper amounts of active agent 47 to place in absorbent pad 40, starts with the amount of absorbent material, the type of food product 36 being packaged, and the amount of liquid purge exuded from the food. For example, if too much absorbent material is used relative to the amount of liquid purge, then there may be insufficient liquid to dissolve the active agent(s) so they can react to form the atmosphere-modifying gas. On the other hand, too little absorbent material can allow the liquid purge to “drown” or dilute the active agent(s) and thereby impair their effectiveness. For ground meat products, scaling is critical because ground meats produce very little liquid purge to activate the components of the CO2-generating system.
In an exemplary embodiment, a total of about 3.8 grams of a CO2-generation system is incorporated in one or more plies of a laminate layer placed in the pocket between tissue layers 46 in absorbent pad 40. For these embodiments, absorbent pad 40 has a nominal absorbency (i.e., the weight of liquid purge that can be absorbed) of about 35 grams to about 75 grams, and preferably about 50 grams to about 65 grams. In another exemplary embodiment, about 2.0 grams of a CO2-generation system are incorporated in one or more plies of a laminate in absorbent pad 40, which is about 4 wt % based on a nominal absorbency of 50 grams, and about 3.1 wt % based on a nominal absorbency of 65 grams. The amount of CO2 generated by this embodiment is sufficient to permit a reduction in headspace area 38 corresponding to a reduction in depth of food tray 32 from about two-and-a-half (2.5″) to about two inches (2″), which is a reduction of approximately 20%.
As noted above, the disadvantages of conventional MAP techniques are exacerbated when certain “biofriendly” materials are used for lid film 34 and/or food tray 32. “Biofriendly” lid film tends to be less elastic than a conventional lid film. Therefore for the overwrap, and so a greater internal pressure of MAP gas is needed to “bubble” up against the overwrap. Using a larger total amount of a CO2 generation system, such as 5 grams, can generate almost 750 cc of CO2 gas that can exert a greater internal “bubble” pressure than the 570 cc of CO2 gas that can be generated by 3.8 grams of CO2 generation system (using the approximation that each 1 gram of CO2-generating chemicals is able to generate about 150 cc of CO2 gas). These large amounts of the CO2-generating system can be effectively placed in absorbent pad 40 in two plies of a laminate material. Likewise, food trays 32 made of “biofriendly” materials such as PET (polyethylene) tend to adhere poorer to lid film 34, causing a greater loss of the initial injected MAP gas using conventional MAP technique. For such instances, using a larger amount of active agent 47 can replenish some or all of the loss of gas because of an imperfect seal about the periphery of food package 30.
Another embodiment of active agent 47 is an antimicrobial agent. An example of an antimicrobial agent in absorbent pad 40 is citric acid, sorbic acid, or a mixture thereof. However, any food-safe antimicrobial can be used, including other organic acids, quaternary ammonium compounds, inorganic acids (such as boric acid) or combinations of antimicrobials.
The atmosphere-modifying gases used in Modified Atmosphere Packaging (MAP) include nitrogen, oxygen, carbon dioxide, carbon monoxide, water vapor, or any combinations thereof.
Examples of food products 36 for which the present method can be used include, but are not limited to, turkey, chicken, pork, and beef. Any food product 38 may be a single piece (such as a turkey breast), several smaller pieces, or ground (such as ground turkey or ground sirloin). Ground food products have a very large surface area, and readily absorb/adsorb MAP gases and water vapor in the headspace, leading to loss of gas volume in the food package. In addition, certain food products, such as poultry, have a natural porosity that enhances their absorption of MAP gases such as CO2. In such instances, a larger amount of active agent 47 may be required to replenish the loss of the original injection of MAP gases in the food package.
Absorbent food pads having active agents, such as those disclosed in U.S. patent application Ser. No. 11/335,373, published as US 2006/0172048, are suitable for use in the present method, and the disclosure of such absorbent food pads is hereby incorporated by reference in the present application. Likewise, the absorbent pads with active agents and specific pad architectures disclosed in PCT/US2009/036442, published as WO 2009/111768, are suitable for use in the present method, and the disclosure of such absorbent food pads and architectures is hereby incorporated by reference.
Another exemplary embodiment of absorbent pad 40 has top layer 42 that is a perforated polyethylene film that is 0.65 mil, bottom layer 44 that is a nonwoven material that is 25 GSM (grams per square meter), three absorbent (3) tissue layers 46 that are adjacent to top layer 42, two absorbent (2) tissue layers 46 that are adjacent to bottom layer 44, and two (2) laminate layers containing a total of 3.8 grams of a co2-generation system and a cellulosic material placed between tissue layers 46.
Yet another exemplary embodiment of absorbent pad 40 has top layer 42 that is a perforated polyethylene film that is 0.65 mil, bottom layer 44 that is a nonwoven material that is 25 GSM, two (2) absorbent tissue layers 46 that are adjacent to top layer 42, two (2) absorbent tissue layers 46 that are adjacent to bottom layer 44, and two (2) laminate layers containing a total of 5.0 grams of a CO2-generation system and a cellulosic material placed between tissue layers 46.
Still another exemplary embodiment of absorbent pad 40 has top layer 42 that is a polyethylene film that is 0.65 mil but not perforated, bottom layer 44 that is a nonwoven material that is 20 GSM, two (2) absorbent tissue layers 46 that are adjacent to top layer 42, two (2) absorbent tissue layers 46 that are adjacent to bottom layer 44, and one laminate layer containing the CO2-generation system between tissue layers 46.
The present method considerably reduces gas injected into the food package as compared with conventional MAP techniques. Since the operator does not have to “overfill” the present food package with MAP gas using the present method, the food package itself does not require the headspace to be as large, permitting the overall dimensions of the food package to be reduced to more closely match the actual size of the food product. The present method thereby reduces costs of materials (tray, lid film, and/or pressurized gases), reduces freight costs, yet also allows smaller food packages that look better for consumer display and permit more packages to be displayed for sale, without any loss of effectiveness in food preservation. The method may also represent operational savings by reducing cycle times and increasing line speeds.
After sealing the food package, the volume of the injected MAP gas inevitably decreases over time, even if the seal is tight, due to adsorption or absorption of gas (such as CO2) by the food product, to dissolution of MAP gases in the liquid purge, and/or leakage of MAP gases through the food tray or lid film 34 to the outside of the food package. The active agent(s), when activated, gradually release gases that occupy the headspace and partially or completely replace the loss of volume of the initial injected MAP gas. The replacement of gas volume in the headspace can reduce or even prevent collapse of the lid film that can make the food package feel “flimsy” when lifted by a consumer, and can also prevent the lid film 34 from contacting or adhering to the food product, which is unappealing to the consumer and can increase susceptibility of the food product to freezer burn.
The capability of the active agents to generate MAP gases also reduces the requirement for large headspaces for conventional MAP techniques that must compensate for gas losses over time. The amount of the active agent(s), their placement within the pad architecture, and their mechanism of activation can be selected to control the release rate of volume of MAP gases from the absorbent pad into the headspace. Thus, the present method provides the benefit that a food product can be packaged in a food package having a small headspace, having small overall dimensions, and a small injection gas volume, because the active agent(s) generates MAP gases in the headspace area to compensate for volume losses and chemical effects of the initial injected MAP gas.
The word “about” as used herein for dimensions, weights, weight-percentages, or measures of absorbency, means a range that is ±10% of the stated value, more preferably ±5% of the stated value, and most preferably ±1% of the stated value, including all subranges therebetween.
As used herein, all references to the plural can also mean the singular and to the singular can also mean the plural, unless otherwise indicated.
It should be understood that the foregoing description is only illustrative of the present disclosure. Various alternatives and modifications can be devised by those skilled in the art without departing from the disclosure. Accordingly, the present disclosure is intended to embrace all such alternatives, modifications, and variances that fall within the scope of the disclosure.
