Bacterial populations associated with bulk packaged beef supplemented withdietary vitamin E

Five Simmentaler type calves were fed diets supplemented with 500 mg vitami n E per day and five fed control diets. Pump steaks from each carcass were PVC-overwrapped and bulk packaged in 100% CO2 or 20% CO2:80% O-2. Bulk pack s were stored up to 42 days at 4 degrees C and PVC-overwrapped samples subs equently displayed up to 7 days at 4 degrees C. After display the Aerobic P late Count (APC) of steaks was determined and four colonies were randomly s elected from the highest dilution APC plates showing growth. A total of 627 colonies were obtained. Gram-reaction, catalase, oxidase, morphology and m otility of the isolates were determined. The gram-negative and gram-positiv e isolates were then identified using a dichotomous identification key. Ent erobacteriaceae, Pseudomonas spp. and Acinetobacter spp. predominated on ru mp steaks from both feeding treatments and in packaging treatments. After 4 2 days bulk storage Enterobacteriaceae, Pseudomonas spp., lactic acid bacte ria and Acinetobacter spp. predominated in 20% CO2:80% O-2 and 100% CO2 bul k packaging. Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp. pr edominated on rump steaks, from both feeding and packaging treatments, duri ng the aerobic display period of 7 days. (C) 2000 Elsevier Science B.V. All rights reserved.