Physical and Sensory Characteristics of Beef Packaged in Modified Gas Atmospheres

One hundred and ninety-six boneless beef roasts (longissimus muscles) were vacuum packaged. Twenty-eight roasts remained vacuum packaged to serve as controls while the remaining packages were injected with one of six gas mixtures: (a) 100% O₂, (b) 20% CO₂ + 80% N₂, (c) 50% CO₂ + 50%O₂, (d) 20% CO₂ + 80% O₂, (e) 25% CO₂ + 25% O₂ +50% N₂ or(f) 51% CO₂ + 30% O₂ + 18% N₂ + 1% CO. Five cuts from each packaging treatment were stored in a 1-3-C cooler for 7, 14, 21, 28 or 35 days and subsequently evaluated for relative percentages of various gases in the intact packages, off-odor, surface discoloration. overall appearance, metmyoglobin percentages and palatability. Packages initially injected with modified gas atmospheres containing O₂ increased in relative percentages of CO₂ with advancing storage times. Roasts stored in modified atmospheres initially containing high levels of O₂ exhibited a greater incidence of off-odor, more surface discoloration, lower overall appearance ratings, shorter retail caselife and lower overall palatability ratings than vacuum-packaged roasts or roasts stored in an atmosphere initially containing 20% CO₂ + 80% N₂.