Modification of the packaged atmosphere attempts to lower the oxygen level and increase the carbon dioxide level to slow bacterial growth and the respiration of fruits and vegetables. Carbon monoxide may also be introduced to keep the red color of fresh meats by binding to the hemoglobin. The atmosphere can be introduced to the package by flushing or by exposure through a permeable membrane (EMAP).
There is no direct risk to consumers based on the use of MAP or EMAP. In recent years, there has been debate regarding the use of carbon monoxide (CO) in the packaging of red meat. While no risk was found in the use of low levels of CO, the fact that CO maintains the color of the meat and can, in that way, hide visual evidence of spoilage was raised. The European Food Information Council (EFIC) released a report in 2004 reviewing the data. The report is available here.
The study in the Journal of Food Protection examined how the perceptions and observation of MAP packaged meat quality (primarily shelf life and color) are the prime influencer on purchasing. These also impact the price consumers are willing to pay for these qualities.
In this study, they attempted to determined the premiums that the test customers were willing to pay for the "cherry red" color and extended shelf life resulting from MAP with CO introduced. The full methods and results can be obtained here. In brief, researchers found customers who understood the technology preferred the longer shelf life and brighter red color. They were willing to pay a premium of $0.16 a pound for these features. Looking closer, when customers had further information on the MAP process and the use of CO the willingness to pay this premium was diminished, although it was still elevated. Researchers attributed this decrease to uncertainty and some distrust towards the science involved and its safety/reliability.
For meat packaging companies considering using MAP, this research lends additional support to the investment into the needed equipment and training.