Microfloral Comparison of Fresh and Thawed Frozen Fryers

Abstract

The microflora of fresh and thawed frozen fryers were compared to determine potential public health significance of pigmented colonies of gram positive cocci observed on plates from defrosted frozen chicken. Numbers of NaCl tolerant bacteria were determined. Frozen fryers purchased from local stores and laboratory frozen fryers were thawed 24 hr at 3.3 C, split into halves, and packaged in polyethylene after swabbing a 3 cm2 area of the skin surface. Fresh fryers used for comparison were treated in a similar manner. All fryers were stored at 3.3 C with bacterial samples taken on days 3 and 5, then daily until odor spoilage. Bacterial numbers were enumerated using serial dilutions and plating with Staphylococcus 110 media, nutrient, and MPH agars. Salmonella detection was by use of Selenite enrichment followed by streaking on MacConkey and S.S. agars. Shelf life was similar, 7.9 days for fresh and 8.1 days for thawed frozen fryers. Initial counts of aerobic bacteria were similar averaging 2.1 × 104/cm2. Numbers of salt tolerant bacteria were similar at day 1, averaging 1.1 × 103/cm2 and remaining constant at about this level on thawed frozen fryers until spoilage, but declining rapidly on fresh fryers. All salt tolerant bacteria were gram positive cocci of which 52% were pigmented. Of pigmented isolates, 42% were coagulase positive. Subsequent identification indicated that most NaCl tolerant isolates producing bright yellow pigment were Staphylococcus aureus. Three Salmonella species were isolated from both fresh and thawed frozen fryers. Aerobic bacteria averaged 6.1 × 107/cm2 at odor spoilage of which over 99% were Pseudomonads.