Food or edible material: processes – compositions – and products – Packaged or wrapped product – Three or more layered diverse packaging materials having at...
Reexamination Certificate
1997-03-12
2002-09-10
Weinstein, Steve (Department: 1761)
Food or edible material: processes, compositions, and products
Packaged or wrapped product
Three or more layered diverse packaging materials having at...
C426S129000, C426S396000, C426S410000, C426S413000, C426S415000, C426S418000, C053S432000, C053S434000
Reexamination Certificate
active
06447826
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to the field of packaging. More specifically it deals with carbon dioxide releasing systems in conjunction with systems capable of absorbing oxygen. Bag and sachets incorporating such components are also discussed. Modified packages associated with the use of such systems are also discussed as are methods of use associated with the present invention.
BACKGROUND ART
The description of the present invention will be discussed predominantly in relation to meat products whose associated packaging problems are typical of those which the present invention considers. However it should be appreciated that the present invention can also be applied to other foodstuffs and articles to be packaged.
More specifically, and for simplicity of description, the problems associated with chilled and fresh meat will be discussed as the problems associated with these products are perhaps the most demanding. Consumer perception is that a red meat product is a fresh meat product and therefore preferable to discoloured products. Unfortunately, for fresh and chilled meats, storage under conditions where oxygen is present results in gradual browning of the meat. While in many cases (short term storage) the product is still acceptable, the consumer is deterred by the brownish appearance of the meat which they associate with a spoiled product.
Where there is longer term storage of meat products, the presence of oxygen can result in not only the browning of the meat but subsequent spoilage. Accordingly packages for long term storage of meat generally comprise an oxygen impermeable barrier film. Often the packages are evacuated or packed under a modified atmosphere.
Vacuum packaging is not generally considered appropriate for the retail display of chilled red meat, because of the meat's purple coloration. Low oxygen modified atmosphere systems are also not appropriate for the same reasons.
High oxygen/low carbon dioxide modified atmosphere systems are successfully used for retail cuts of red meat, but in this case, the storage life is low due to oxygen spoilage.
Recently a packaging system known as low oxygen/high carbon dioxide packaging has become very popular. The system has been directed mainly at non-retail ready markets, as the primal cuts used require further processing into consumer portions. Also the next requires re-exposure to oxygen to resume a red rather than purple colouration.
It has been found that chilled meat packaged under carbon dioxide is resistant to spoilage by aerobic bacteria. Anaerobic bacteria which may still survive under Carbon dioxide do not flourish below 2° C., which is above the storage temperature of most chilled meat products. Evidence suggests that a relatively high concentration of carbon dioxide will actively suppress the bacterial growth—the shelf life of Carbon dioxide packaged meat is thus much longer than for vacuum packed meat.
Like the vacuum packed product, meat stored under carbon dioxide will rebloom on exposure to oxygen, giving the red coloration which consumers associate with freshness. However, it is also believed that the display life, in the oxygenated state, of carbon dioxide packaged meat is longer than that of vacuum packed meat. This may be associated with the low oxygen concentration throughout the product lifetime, which is a key requirement of the carbon dioxide process.
The use of low oxygen/high carbon dioxide packaging is well known, as is the use of oxygen absorbing compositions with meat products. Combinations of the two systems are also known. However, many problems remain.
For instance systems which release carbon dioxide are well known. Of note is the work of Benedict, Strange, Palumbo and Swift (Journal of Agricultural and Food Chemistry, 23 (6) 1202-1208 1975). Gas permeable sachets consisting of citric acid and sodium bicarbonate were added to retail package of meat and the carbon dioxide released helped to extend shelf life. Codimer also patented a system where carbon dioxide and/or oxygen were generated in a package from the reaction of citric acid with sodium bicarbonate and/or sodium perborate (EP O 128 795 (1984)).
A number of other systems also appear in the prior art which both absorb oxygen and liberate carbon dioxide. These systems were designed to replace the oxygen absorbed from within the head space of the package with high levels of carbon dioxide. For example, Toppan claims highly specific compositions such as:
100 parts ferrous chloride
20-100 parts sodium bicarbonate
5-50 parts water supplying substance
0-10 parts absorbent
0-70 parts iron powder
No examples or disclosure is provided within this patent which produce large amounts of carbon dioxide and absorb small amounts of oxygen (U.S. Pat. No. 4,384,972 (1983)).
Mitsubishi described a system where the amount of carbon dioxide generated may be independent of the amount of oxygen absorbed. However the teaching of this specification limits the amount of carbon dioxide produced per mole of oxygen absorbed (U.S. Pat. No. 4,726,722 (1988)).
However the prior art fails to address the problems associated with the packaging of meat, and especially the packaging of meat in retail ready tray-based packages. The Mitsubishi system was intended to be used for sealing a package without evacuation or gas flushing and in its place greater than two moles of carbon dioxide per mole of oxygen absorbed was said to lead to pack deformation. At the time of this patent the prior art also considered that carbon dioxide gas flushing when packaging meat resulted in unwanted browning. Accordingly the art considered, and this is reflected in the limitations of the art, the excessive carbon dioxide, such as would also result through carbon dioxide gas flushing, was undesirable. However it has since been found that this browning is not due to carbon dioxide but rather to the incomplete removal of oxygen from within the package and may be a temporary condition, depending upon the levels of enzyme activity which relates to time post mortem.
Other prior art, such as EP O 527,228 (Toppan) describes oxygen absorbers/carbon dioxide generators such as mixtures of ascorbic acid and ferrous chloride. However the quantity of carbon dioxide released is dependent upon the amount of oxygen absorbed as well as on the pH of the composition. The pH may be determined by the addition of an alkali such as sodium bicarbonate, sodium carbonate of calcium hydroxide. However this disclosure is targeted at applications where a set amount of carbon dioxide and nitrogen is required within a container (e.g. container for growing bacteria samples). This, and the known prior art, fail to address the need of package meat for extended periods of time, and be able to regenerate or preserve a consumer acceptable red colouration at the retail level. In addition, there is a need, for retail ready packs, to prevent deformation of a pack due to variations in the internal atmosphere. These problems arise due to the fact that meat will absorb large quantities of carbon dioxide, generally within the first 48 hours of exposure. As this absorption process proceeds, the internal pressure of a package is reduced, unless there is a sufficient excess of carbon dioxide to completely saturate the meat, and there is a suitable mechanism by which the volume of the package may contract.
If meat is placed on a conventional sized tray, evacuated, gas flushed with carbon dioxide and the sealed under a barrier film, severe distortion will occur as the carbon dioxide is absorbed and the internal pressure of the system is reduced. This is because the volume of the tray cannot contract in a controlled manner like that of a bag, and because insufficient carbon dioxide is present to compensate for what is absorbed by the meat.
This problem becomes more noticeable as an attempt is made to keep a high product volume in relation to the volume of the package. High product to package volume systems are used conventionally (i.e. PVC overwrapped product on an expanded polystryene tray) for retail display of mea
Alston & Bird LLP
Sealed Air (NZ) Limited
Weinstein Steve
LandOfFree
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