The poultry industry utilizes high-oxygen (HiOx)–modified atmospheric packaging (MAP) (70% to 80% O₂ and remaining carbon dioxide [CO₂]) to promote appearance. However, greater O₂ concentration accelerates lipid oxidation and premature browning in cooked meat. Premature browning is defined as the premature denaturation of proteins and changes in color before the product reaches a safe internal cooking temperature. This can cause a health concern for consumers as they will potentially consume product that has not reached the lethality temperature for most microorganisms.

In this study, three types of packaging were used: traditional polyvinyl chloride (PVC) film, a high-oxygen (HiOx)–modified atmospheric packaging (MAP; 80% oxygen + 20% carbon dioxide [CO₂]), and a carbon monoxide (CO)-MAP (0.4% CO + 19.6% CO₂ + 80% nitrogen) on ground chicken. Sixty 100g patties of a finely ground chicken product were formed manually, 20 for each packaging type. 

Instrumental color measurements (Lightness, redness, yellowness, reflectance, and Chroma or color intensity) were taken on the surface of the product on days 0, 1, 2, and 4 of retail display. Additionally, a trained panel conducted visual color evaluations on days 0, 2, and 4. The panelists repeatedly evaluated each ground chicken patty to assess muscle color and discoloration. Lipid oxidation (rancidity levels), pH, and microbial growth were determined on the first and last day of display. Fatty acid profiles were determined on day 0 to characterize saturated and unsaturated fatty acids. The pH was normal for poultry ranging from 5.97 to 6.06. 

Ground chicken in traditional PVC overwrap packaging had a greater pH than the modified atmosphere packaging types. The lower pH of the two modified atmosphere packaging types could be explained by the breakdown of the included carbon dioxide into the water fraction of meat, increasing carbonic acid. Fatty acid analysis indicated that ground chicken has 72.8% unsaturated fatty acids and 27.2% saturated fatty acids. With this higher proportion on unsaturated fatty acids than beef or pork, chicken is more susceptible to lipid oxidation, off-flavor development. In addition, the release of pro-oxidants during grinding can further accelerate oxidative changes. 

Instrumental color analysis indicated both HiOx-MAP and CO-MAP had greater redness than traditional PVC on day 4 of storage. Visual panelists noted less surface discoloration in CO-MAP than PVC and HiOx-MAP on day 4 of storage. Limited discoloration allows for consumers to be more willing to purchase the product for an extended amount of time. Furthermore, changes in lean color scores were more noticed during 4 days of storage in PVC than CO-MAP and HiOx-MAP. Lipid oxidation was greater in PVC and HiOx-MAP than CO-MAP. HiOx-MAP had the highest levels of lipid oxidation as previously found leading to premature browning. Ground chicken in 0.4% CO along with 19.6% O₂ and 80% N₂ maintained a bright light-pink color preferred by consumers without inducing lipid oxidation. 

The current research suggests that packaging in CO-MAP provides an opportunity for the industry to extend the shelf life of ground chicken. The consequence of extended shelf life in these packaging technologies can lead to a more sustainable food supply and in return provide protein sources for an ever-growing population. 

For more information, please see the authors' work published in Meat and Muscle Biology: Kathryn Hearn, Morgan Denzer, Rachel Mitacek, Naveena B. Maheswarappa, Conner McDaniel, Ravi Jadeja, Gretchen Mafi, Ali Beker, Adel Pezeshki, Ranjith Ramanathan, “Effects of Modified Atmospheric Packaging on Ground Chicken Color and Lipid Oxidation” Meat and Muscle Biology 5(1). p.36, 1-9. doi: https://doi.org/10.22175/mmb.12599."