The present invention relates to a low scalping laminate material for packaging. More particularly, the present invention relates to a laminate material for packaging that includes a flavor loss barrier as well as an oxygen barrier.
Packages are in wide-spread use that are formed from laminated material for the storage of liquid foods. Typically, a laminated material is formed from a relatively rigid but foldable core layer onto which one or more liquid tight coatings of plastic are applied. A common core layer is paper or paperboard. This material provides good mechanical configurational stability and is relatively low-cost and typically recyclable. Liquid type plastic coatings are typically thermoplastic materials, such as polyethylene, which have good thermosealing characteristics and enhance the overall function of the package.
Laminated materials that are formed solely of paper or paperboard and a liquid-tight thermoplastic have one drawback in that they typically are highly oxygen permeable. This is particularly problematic for foods that have shelf life, flavor and/or nutrient contents that can dramatically deteriorate in contact with oxygen. Many fruit juices show a declining vitamin C content when they are exposed to oxygen.
As such, packaging materials have been developed in which a barrier layer of a gas impermeable material is provided on that side of the core layer that is on the inner surface of the package (toward the stored product). Experience has shown that superior oxygen impermeability is provided by material such as aluminum foil, EVOH (ethylene vinyl alcohol) and PVOH (polyvinyl alcohol).
While each of these gas impermeable layers provides benefits and advantages over previously known non-barrier containing packages, they each have their drawbacks, both individually and collectively. For example, although aluminum foil provides quite acceptable oxygen barrier characteristics, materials that include aluminum foil cannot be easily recycled and can have severe environmental impact. As such, many aluminum foil based materials have been dismissed for use in single-use food packaging.
EVOH and PVOH are highly sensitive to moisture and rapidly lose their barrier characteristics against oxygen gas when they are exposed to a damp environment. Thus, these material alone are unacceptable for food packaging use when, for example, the packages may be required to have an extended shelf life. To overcome the problems associated with moisture degradation, EVOH and PVOH barrier materials can be further coated or layered with an additional polymer, such as polyethylene.
Alternatively, EVOH and PVOH can be combined with one or more known food approved polymers performing a continuous, well-integrated layer that possesses superior gas barrier properties and that possess moisture resisting characteristics. These materials, however, result in a high-cost package both with respect to the materials of construction and the methods of production. In addition, the increased number of layers results in more complex manufacturing operations.
It has also been found that packaging materials can tend to xe2x80x9cscalpxe2x80x9d the flavor from the packaged product. For example, it has been observed that low-density polyethylene tends to scalp or draw flavors from the packaged product into the polyethylene layer. This is particularly true with fruit juices, such as orange juice and the like, and is particularly problematic for natural juices that are packaged that are not made from fruit juice concentrates. Typically, these not-from-concentrate juices do not have flavor additives or enhancers added to the juice to supplement the natural flavor. As a result, the scalping effect of the packaging material cannot be countered by the addition of such flavor enhancers.
To this end, while the scalping or loss of flavor may not be detectable to the average consumer, it is nevertheless readily apparent from a comparison of identical product stored in a high scalping material when compared to that product stored in a low or non-scalping material container.
It is believed that the scalping effect is a result of the interaction of polar molecules present in the juice and the polar molecules of the packaging material. It has also been observed that the greater the bulk (e.g. density or thickness) of the packaging material containing polar material, the greater the interaction between the juice product and the material. Again, this is problematic in that a sufficient quantity or bulk of polymeric material must be present on the inner surface of the carton in order to assure liquid tightness of the package, and to provide sufficient material for forming seals between the various carton panels in erecting or constructing the container.
Accordingly, there exists a need for a laminate packaging material that provides high oxygen barrier characteristics to prevent oxidizing the package product. Desirably, such a laminate material further provides structural or mechanical stability, even when subjected to humid environments, such as packages that may remain xe2x80x9con the shelfxe2x80x9d for prolonged periods of time. Most desirably, such a package further provides low-scalping characteristics to reduce loss of flavor from the packaged product.
A low scalping laminate material for food packaging is formed from a core layer of paper or paperboard, a polymeric coating applied to one side (i.e., the outside) of the core layer and a novel inner combination. The inner layer includes a first barrier layer disposed adjacent the opposing side of the core layer, a first tie layer adjacent the first barrier layer, a second barrier layer adjacent the first tie layer, a second tie layer adjacent the second barrier layer, and a polymeric coating adjacent the second tie layer. The inner polymeric coating is a food contacting surface.
The first and second barrier layers are formed from an admixture of an aromatic polyamide resin and polyamide 6, and the first and second tie layers are formed from one of a modified polyethylene and a polyolefin.
Preferably, the first barrier layer is an admixture of the aromatic polyamide resin in a concentration of about 60 percent to about 100 percent and the PA-6 is present in a concentration of about 0 percent to about 40 percent. Most preferably, the aromatic polyamide resin is present in a concentration of about 75 percent and the PA-6 is present in a concentration of about 25 percent.
In a preferred laminate, the first and second tie layers are formed from a low-density polyethylene having a maleic anhydride functional group.
The first and second barrier layers preferably have a thickness of about 4 grams per square meter to about 6 grams per square meter (gsm). The first tie layer preferably has a thickness of about 13 gsm to about 17 gsm, the second tie layer preferably has a thickness of about 3 gsm to about 5 gsm and the inner polymeric coating preferably has a thickness of about 6 gsm to about 8 gsm.
The inner and outer polymeric material is a non-polar polymeric material. A preferred material is low-density polyethylene. Also acceptable are linear low density polyethylene and modified linear low density polyethylene, and blends of these materials.
A carton for food storage includes upstanding side walls, a sealed bottom wall, and a sealed top wall. The carton has an interior region for contact with the food.
The carton is formed from a low scalping laminate material. The material includes a core layer of paper or paperboard, a first polymeric coating applied to a first side of the core layer, a first barrier layer adjacent a second side of the core layer, a first tie layer adjacent the first barrier layer, a second barrier layer adjacent the first tie layer; a second tie layer adjacent the second barrier layer, and a second polymeric coating adjacent the second tie layer.
The polymeric coating is configured for contact with food. The first and second barrier layers are formed from an admixture of an aromatic polyamide resin and polyamide 6, and wherein the first and second tie layers are formed from one of a modified polyethylene and a polyolefin.
These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims.