Rapid oxygen absorption by using activators

Compositions – Reductive bleachant – deoxidant – reductant – or generative – Deoxidant or oxygen scavenging

Reexamination Certificate

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C252S191000, C426S124000

Reexamination Certificate

active

06616861

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a method for maximizing the rate of oxygen uptake of an iron-based oxygen absorber. More particularly, the invention relates to improved activators for iron-based oxygen scavenging packets.
BACKGROUND OF THE INVENTION
Perishable foods, such as meats, fruits, and vegetables, are typically placed into packaging systems after harvesting in order to preserve these foods for as long as possible. Maximizing the time in which the food remains preserved, especially the time between initial packaging at the plant and delivery at the retail grocery store, increases the profitability of all entities in the chain of distribution by minimizing the amount of spoilage.
The environment in which the food is preserved is a critical factor in the preservation process. Not only is maintaining an adequate temperature important, but the composition of the gases surrounding the food is important as well. By providing the appropriate gas composition to the environment surrounding the food, it can be better preserved when maintained at the proper temperature or even when it is exposed to variations in temperature. This gives the food producer some assurance that after the food leaves his or her control, the food will be in an acceptable condition when it reaches the retail grocery store and, ultimately, the consumer.
In particular, meat packaging systems which provide extremely low levels of oxygen are desirable because it is well known that the fresh quality of meat can be preserved longer under anaerobic conditions than under aerobic conditions. Maintaining low levels of oxygen minimizes the growth and multiplication of aerobic bacteria.
One way to insure a minimal level of oxygen in a meat package is to subject the package or rigid gas barrier materials to a vacuum in order to remove as much of the gas in the package as possible prior to sealing. The package can then be sealed and the meat maintained in a “zero” atmosphere environment (commonly referred to as vacuum packaging), provided that the packaging materials prevent oxygen migration). Under vacuum packaging conditions, red meat becomes purple. Since consumers prefer to see bright red meat, vacuum packaging has not been well accepted for consumer cuts of meat.
Another means for insuring a minimal level of oxygen in a meat package is to seal the meat in a refill-modified atmosphere packaging system. This kind of modified atmosphere packaging technology (MAP) is so successful that meat can be cut and packaged several weeks before purchase and still remain fresh. Such systems typically utilize multiple layers of packaging. The outside layer is generally a rigid container with good barrier properties. The inner layer is an oxygen permeable film. To provide a modified atmosphere environment, the air-evacuated package is typically filled with a mixture of gases consisting of about 30% carbon dioxide (CO
2
) and 70% nitrogen (N2). Refilling the air-evacuated package with such a mixture of gases is believed to suppress the growth of anaerobic bacteria. The outer layer is peeled off just prior to presenting the meat for sale at the supermarket. This allows oxygen to pass through the inner layer and contact the meat, causing it to rebloom to a bright red color. Such an evacuation and refill MAP process is described in U.S. Pat. No. 5,115,624 to Garwood. It is very expensive for three reasons. First, the rigid part of the package is expensive. Second, processing speeds are slow due to the vacuum and refill steps. And third, the equipment to perform these procedures is very complicated and expensive.
Another less expensive means for insuring a minimal level of oxygen in a meat package is to use a gas flush MAP process. The complicated steps of evacuating the package and refilling with the desired gas mixture are eliminated. The outer bag (a barrier layer) is simply flushed with the proper gas mixture as it is formed around the inner container. The flush process reduces the oxygen content of the package to about 2%. An oxygen scavenger is placed in the package to absorb additional oxygen just prior to, or simultaneously with, forming and flushing the outer bag. An example of such a gas-flush MAP system is described in U.S. Pat. No. 5,698,250.
A critical feature of a gas flush MAP packaging system is the ability to keep meat looking fresh and palatable. Oxidized meat turns an undesirable brown color. Thus, it is critically important to quickly remove the oxygen from the package in order to prevent the meat from turning brown. If oxygen is removed quickly, the packaged meat turns a purple red color, which quickly “blooms” to a bright red color upon removal of the outer layer of packaging.
Various types of oxygen scavengers are used in packaging systems in order to protect meat and other products from the detrimental effects of oxygen exposure.
Oxygen scavenging by polymer barrier films has been discussed in several patents. U.S. Pat. No. 5,350,622 discusses the incorporation of an oxygen scavenging layer into a barrier material with an adjustable capacity. Many polymer films, such as poly(ethylene-vinyl acetate), trans-poly(isoprene), poly(ethylene-vinyl acetate), etc., are discussed in this patent. Further modifications have been reported in U.S. Pat. Nos. 5,648,020, 5,498,364, 5,425,986 and 5,399,289.
Oxygen scavenging by using organic compounds, such as substituted and unsubstituted ethylenically unsaturated hydrocarbons and transition metal catalysts, have been reported in U.S. Pat. Nos. 5,700,554 and 4,769,175. Chelates and complexes of salicylic acid have also been proposed for speeding the oxygen absorption in U.S. Pat. No. 5,364,555. Polymer films having deoxidizers have been suggested in U.S. Pat. No. 4,299,719, which uses ferrous carbonate as the deoxidizer in the polymer film. Polyorganosiloxanes have been shown in U.S. Pat. No. 5,143,763 to have a good oxygen-absorbing capacity when present as a layer in the polymer. Several deoxidizers have been found to be suitable for oxygen scavenging and are reported in U.S. Pat. Nos. 5,085,878 and 4,996,068. In one example, salicylic acid chelate or its complex with metal ions has been suggested in U.S. Pat. No. 5,492,742. Several radiation induced oxygen absorbers have been reported in U.S. Pat. No. 5,211,875.
Other oxygen scavengers utilize the oxidation of particulate iron as a method to absorb oxygen. U.S. Pat. No. 4,127,503 discloses oxygen absorbers having a metal powder (iron) covered with a metal halide. A large number of absorbers with the absorbing speeds in the range of 0.05 to 6.8 mL oxygen/hour were prepared using different metal halides. The nature of the metal used in the absorber can affect performance, as disclosed in U.S. Pat. No. 5,207,943, where a highly reactive iron (electrolytically manufactured) drives the reaction efficiently even in a low moisture atmosphere. A sulfur-containing oxygen scavenger has been proposed in U.S. Pat. No. 4,166,807, which has the advantage of reducing the secondary hydrogen generation. U.S. Pat. Nos. 5,332,590 and 5,262,375 discuss the effect of electrolytically annealed iron on oxygen absorption. In one example, the rate of oxygen absorption at 38° F. (3.3° C.) is increased from 2.4 cc/hour using unannealed iron to 4 cc/hour with annealed iron. At a higher temperature (72° F., 22.2° C.), the rate of absorption increases to 16.6 cc/hour with the annealed iron. A similar iron-based oxygen absorber has been proposed for removing oxygen from any gaseous mixture in U.S. Pat. No. 4,588,561. A mixture of halogen-containing oxyacid salt, such as sodium perchlorate or sodium chlorate with iron, has been proposed in U.S. Pat. No. 4,711,741.
Water facilitates the oxidation of iron. A water attracting agent such as silica gel may be used to attract water and, at times, to supply water to the iron in the packet. A drawback to this technology, however, is the limited amount of water that can be supplied. Typically, a major portion of the water needed for the oxidation of particulate iron is provided by

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