Microbial Changes of Precooked Beef Slices as Affected by Packaging Procedure

Precooked beef slices from top round roasts were used in replicate trials to determine the effects of packaging treatment upon microbial growth during retail storage. Roasts were dry roasted to an internal temperature of 60°C, cooled for 1 h, then sliced (3 to 4 mm) and packaged in vacuum or an atmosphere containing 15% CO₂/40% O₂/45% N₂. Slices were stored either at 2, 6 or 10°C for up to 21 d. Enumeration of psychrotrophs, mesophiles, thermophiles and molds was determined after 0, 7, 14 and 21 d of storage. At 6 and 10°C storage, psychrotrophic organisms did not increase (P<0.05) on vacuum packaged beef slices during the 21-d storage period, but did increase (P<0.05) on slices stored in the gas mixture. Conversely, at 2°C storage, psychrotrophs increased (P<0.05) in vacuum at day 21 but not under gas atmosphere storage. Mesophiles did not increase significantly at 2 or 6°C storage within either packaging treatment during 21 d of storage. Mold growth did not occur on slices stored at 2°C.