Comparative Growth Rates of Listeria monocytogenes and Pseudomonas fragi on Cooked Chicken Loaf Stored Under Air and...

Chicken loaves (25g) were prepared from manually deboned broiler leg quarters, sterilized, and cooled. The loaves were inoculated with approximately log CFU/g 3.0 each of Listeria monocytogenes and Pseudomonas fragi , and stored under air and two modified atmospheres (MA) at 3, 7, and 11°C. The MA gas mixes contained 50% CO₂ and 10% O₂ (MA1) and 80% CO₂ and no O₂ (MA2), balance proprietary. L. monocytogenes and P. fragi grew under air at all three temperatures, with growth of P. fragi being more rapid. The MA1 reduced growth of both species at all three temperatures. However, L. monocytogenes growth was less severely affected and exceeded growth of P. fragi at 7 and 11°C. The MA2 inhibited growth of both species with P. fragi growth being inhibited more than growth of L. monocytogenes at 3, 7, and 11°C. L. monocytogenes grew somewhat faster under MA1 than under MA2. Neither MA1 nor MA2 appeared to be effective at inhibiting growth of L. monocytogenes on cooked poultry loaf.