Patent Application
20100115893
The present invention relates to a method for producing a package and to a packaging machine.
Packaging machines, so-called tray closing machines are known in which products are packaged into pre-fabricated tray-shaped containers and closed with a film, for example from U.S. Pat. No. 7,290,380 B2. Furthermore, packaging machines that are able to form trays themselves from sheet material are known.
From a review article written by K. W. McMillin, ‘Where is MAP Going? A review and future potential of modified atmosphere packaging for meat’, published in Meat Science in the year of 2008, Vol. 80, pp. 43-65, several methods about modified atmosphere packaging (MAP), especially for meat products, have been known and discussed. Using the definition of the article, MAP is the removal and/or the replacement of the atmosphere surrounding the product before sealing in vapor-barrier materials. In general, a package protects products like meat against deteriorative effects including discoloration, off-flavor, off-odor development, nutrient loss, texture changes, pathogenicity, and other measurable factors. Usually, the consumer's decision whether to buy such a product depends on his optical impression of the product, preferably a bloomed red meat color as an important quality attribute.
On top of that, raw chilled meat during storage exhibits the chemical reactions of respiration, which is the active absorption of oxygen and release of carbon dioxide, but not as pronounced as for example for a muscle that is still alive. According to the article, it is generally supposed that the headspace must be approximately 1.5-2 times the meat volume and package collapse is to be prevented by headspace gas to meat volumes of 2 to 3. This is influenced by the absorption and the evolution of gas (e.g. oxygen, carbon dioxide, etc.).
In order to obtain the red meat color, commercially available packages typically contain a permeable film, usually leading to a very short shelf life. To prolong the shelf life, a so-called ‘motherbag’ is often used, which means a secondary packaging to have a low oxygen atmosphere during distribution. In the shops, the single packs are unpacked and the meat can start to bloom. Nevertheless, a difficulty with re-blooming of meat in such packages after low oxygen MAP storage has been inability to bloom and/or lack of color uniformity.
According to the pre-mentioned article, it is further known to use high-oxygen packages with a content of typically 60-80% oxygen, so that oxymyoglobin pigments can be maintained. Unfortunately, other oxidative reactions reducing the shelf life may be induced, too.
It is an object of this invention to provide a method for producing a package and a packaging machine in a manner which allows the reduction of the size of such a package.
The object is attained by a method for producing a package and a packaging machine according to embodiments of the invention as set forth below and specified in the claims.
The method for producing a package and the packaging machine according to invention have the advantage of reducing the headspace of the inner volume, where the product, especially the meat product, has been placed, too.
Thereby, a further advantage of the invention is the possibility of reducing the costs for such a package, because the necessary quantity of film or sheet material can be reduced in addition. Furthermore, in contrast to the usage of the described motherbag, the costs can additionally be reduced, because neither such a secondary package is needed any longer nor does the handling to pack it with the motherbag and unpack this motherbag again.
The reduction of the headspace is accompanied by the usage of a special gas mixture to surround the product. This gas mixture comprises carbon monoxide (CO), carbon dioxide (CO2) and nitrogen (N2).
A further advantage of the invention is the usage of carbon monoxide which helps preserving the bloomed red meat color and which is applied in small concentrations of less than 5% with respect to the volume. Advantageously, the carbon dioxide has antimicrobial effects.
The most preferable embodiment uses an anoxic gas mixture. The advantage of reducing the oxygen in the atmosphere as much as possible is to improve the shelf life.
The covering sheet material is a formable film, which can be for example a material that can be used to form trays, but also for example a shrinkable material, in principle any top web forming process to thermo-form such a film or sheet material. If the used sheet material from the top web is shrinkable, shrinking itself is usually done in a separate apparatus after having produced and separated the packages.
Furthermore, a packaging machine according to the invention can comprise a forming station to form trays where the product is put in or can be structured in a way that it is provided with formed trays, especially with trays where the product has already been put in.
Further features and advantages of the invention will arise from the description of embodiments with reference to the enclosed figures. The figures show:
As shown in
A piece of ground meat 7 is put into the pocket 5, here by a robot arm 6. A covering web 8 covers the tray 5 with the ground meat 7. In the station 10, the atmosphere is replaced by a gas mixture of 5% CO, 25% CO2, and 70% N2. Furthermore, the station 10 forms the covering web 8. Typically, shrinking the covering film 8 to fit to the tray 5 and the meat product 7 inside is done in a separate apparatus after having produced the separate packages. The gas itself is anoxic to reduce oxidative chemical processes reducing the shelf life. The covering web 8 and the web 3 with the trays 5 are sealed.
The packages are separated in the cutting station 11.
A further advantage is that an embodiment of the invention abandons the prejudice that the headspace must be 1.5-3 times larger than the volume taken by the meat product.
Especially formed states of myoglobin play an important role in the appearance of a packaged meat product. Deoxymyoglobin is the reduced form of myoglobin (bivalent iron cation, Fe2+) that gives purple color in the absence of oxygen when meat is first cut or has been vacuum packaged. Metmyoglobin is the oxidized pigment state of myoglobin, the dominant sarcoplasmic pigment in muscle, and the trivalent iron cation Fe3+ results in a brown or gray meat color. Oxymyoglobin is the reduced pigment form (bivalent iron cation Fe2+) in which oxygen occupies the ligand position and the perceived color is red (bloomed). Carboxymyoglobin is formed when deoxymyoglobin is exposed to CO.
CO in the package 100 makes the meat appear in bloomed red color.
