In general, there are two main kinds of headspace-altering packaging techniques: The first is modified atmosphere packaging (MAP), and the second is controlled atmosphere packaging (CAP). MAP is generally achieved by altering the initial headspace gas concentration in the pack. After vacuuming the pack, high oxygen (aerobic) or low oxygen (anaerobic) gas formulations are often used in this category. On the other hand, CAP may not only alter the headspace initially but also actively maintain it throughout the storage period of the packed product.
Among both headspace preservation approaches, MAP is the most widespread in meat and poultry, and it is where the use of carbon monoxide (CO) gas has been developed most. In fact, CO is generally used in trace amounts along with MAP’s three main gases: carbon dioxide (CO2), to inhibit bacteria and moulds; nitrogen (N2), to avoid oxidation of fats and pack collapse; and oxygen (O2), to prevent anaerobic growth.
In addition to the headspace preservation techniques above, CO can also be used to help the product shelf-life performance when irradiation preservation is used.
Preservation role of carbon monoxide (CO) gas
In small concentrations (0.3 percent to 0.5 percent) in MAP gaseous mixtures, CO gas has been found to maintain the color of the meat. Specifically in poultry, CO gas helps maintain its initial pale beige color by avoiding the formation of carboxymyoglobin which turns the chicken meat darker in color. At these low concentrations CO has no major effect on avoiding bacterial growth.
CO has been approved by FDA (2002) for use as a component of a gas mixture in a MAP system as Generally Recognized as Safe (GRAS) up to 0.4%. Conversely, CO extends the lag phase and slows growth rate of E. coli, Achromobacter and P. fluorescence at concentrations as high as 25 percent to 30 percent, while P. aeruginosa is unaffected even at these high concentrations.
In meat products, the latest packaging technology is anaerobic (low/essentially no oxygen) MAP with low levels (0.4 percent) of CO, 20 percent-to-30 percent CO2, and the remainder nitrogen (CO-MAP). This packaging method has been shown to offer several advantages over aerobic packaging with PVC or high-oxygen MAP, including better flavor acceptability, no bone darkening, no premature browning during cooking, increased tenderness (due to less protein oxidation in an anaerobic environment), among others.
The main perceived disadvantage is the consumer controversy over potential exposure to the low levels (less than 0.5 percent) of CO. This perception has partially subsided, so retail sales of meat in these packages continue on a limited scale in the U.S. On the other hand, the use of CO gas in fresh meat packaging makes meat look fresher than it is and masks spoilage, deceiving consumers and jeopardizing their health. In 2008, a statement was added to product labels that reminds consumers, "Color is not an accurate indicator of freshness. Refer to use- or freeze-by date."
Current use of CO gas
The use of CO gas could be optimized by addressing its main perceived disadvantages and by reaching out and properly educating the consumer of poultry meat products. A key approach would be drawing a parallel and adapting from the experience of the red meat industry, which over the recent years had to deal with these issues (in many occasions even reaching public national debate).
The USDA-FSIS directive 7120.1, revision 3 (7/6/10) (“safe and suitable ingredients used in the production of meat, poultry, and egg products”) has stated that for case-ready fresh cuts of poultry as well as ground poultry, CO gas can be used as part of Precept’s (Precept Foods LLC, joint venture between Cargill and Hormel) MAP systems, as follows: CO. 0.3 percent (with a process tolerance of 20 percent, allowing for a carbon monoxide concentration up to 0.36 percent); in combination with N2 (0 to 80 percent) and CO2 (20 percent to 100 percent). Labeling requirements for this case are none under the accepted conditions of use (GRAS). Products packaged in this MAP system must be coded with a “Use or Freeze by” date not to exceed 28 days after packaging for ground poultry and 35 days for whole muscle.
By Katrina G. Marino, assistant professor, Dept. of Food Science and Technology, University of Georgia
Source: Meatingplace
