Foods, for example meat and meat products, are normally packed in finished consumer packages, in which instance the packaging operation of the food takes place either centrally for outward distribution of the consumer packages to supermarkets and other retail outlets, or locally on site at a point of sale.
Irrespective of whether the food is packed centrally in the chain of distribution or locally at the point of sale, it is of critical importance that the package and its subsequent handling and storage of the packed food take place under such conditions and employing such methods that the packed food is given the very best possibility of reaching the consumer in pristine condition and freshness.
The rational distribution of foods on a large scale requires that the packaging operation and subsequent package handling be both simple and convenient, and obviously cost-effective as well, so as not to burden unnecessarily distribution economy. These taco requirements are contradictory inasmuch as pristine condition and freshness (so-called extended shelf life) generally require product-specific consumer packages and packaging environments, with inevitably higher costs per produced consumer package as a result, while simplicity and convenience in distribution generally presuppose standardized consumer packages from easily produced and readily available packaging materials which, while keeping distribution costs down, largely result in a deterioration in product protection properties in the produced consumer package.
For example, the packing of particularly oxygen gas sensitive and perishable foods, such as fresh meat takes place in that cut or sliced pieces of the meat are placed in suitable portions in correspondingly dimensioned plastic trays which, after filling at normal ambient atmospheric conditions, are closed by means of a thin plastic film which is applied over the filled plastic tray and is wrapped around the bottom edges of the tray and secured against the bottom of the tray for enveloping the tray and its contents. This conventional packing technique employing plastic trays is circumstantial in that it requires separate equipment for handling the pre-formed plastic trays and the thin plastic film, respectively. A further factor that renders this particular technique less convenient and attractive is that different types of foods generally require pre-formed plastic trays of different dimensions and geometric outer configurations. A further drawback in this context relates to the enveloping plastic film which must be adapted such that, at least for a certain guaranteed shelf life for the food in question, it ensures that the enveloped packaging atmosphere is not injuriously affected in respect of the packed food as a result of the migration or transport of gas through the plastic film. Consequently, plastic films of polyethylene and similar readily available polymer materials are not employed, since these generally lack the requisite gas barrier properties to afford the desired product protection for the packed food.
It is also known in the art to pack cut or sliced meat and similar foods under vacuum in flexible plastic packages. In order to give the finished package the desired combination of mechanical and physical protective properties, the material in these prior art plastic packages is constructed from a plurality of mutually bonded layers of the same or different materials (so-called multilayer materials) which, together in union, give the package the desired combination of protective properties. A packaging material of the multilayer type for vacuum packing of foods must possess particularly good gas barrier properties in order to maintain the vacuum inside the finished package during the guaranteed shelf life of the packed food, and thus requires that at least some of the material layers included in the packaging material consist of such a specifically gas-tight polymer, which is often extremely expensive. A multilayer material of the type under consideration here often requires interjacent material layers of chemical binder or adhesive in order to bond together the individual material layers with superior and lasting bonding strength, to form a well-integrated packaging material.
According to yet a further known packaging technique, fresh meat is packed in a modified atmosphere in a package consisting of a multilayer barrier film. This so-called MAP technique (modified atmosphere packaging) is very similar to the above-described vacuum packaging technique, but differs from it principally in that the packaging atmosphere, instead of a vacuum, consists of a mixture of gases specifically composed to suit the product which is to be packed, such as O.sub.2, N.sub.2, CO.sub.2. The packaging atmosphere is composed such that the packed product (fresh meat) is given the desired shelf life, at the same time as the product (in particular when the packed meat is beef) must retain its consumer-attractive pristine, fresh appearance throughout its entire shelf life. In order to achieve and maintain the best possible MAP conditions within the package, this packaging technique requires the employment of at least one material layer of a barrier film (for example polyamide/polyethylene) in the multilayer structure of the packaging material. As has already been mentioned in connection with the vacuum packaging technique above, a packaging material of the multilayer type is complicated and, in addition expensive, in particular when it involves a material layer of a barrier film. The MAP packaging technique further suffers from the drawback that the packaging atmosphere, or gas mixture, which is required to achieve the desired shelf life and quality targets for the product necessitates careful product-adapted regulation and monitoring throughout the entire packaging process.