INHIBITION OF LISTERIA-MONOCYTOGENES ON NORMAL ULTIMATE PH BEEF (PH 5.3-5.5) AT ABUSIVE STORAGE TEMPERATURES BY SATURATED CARBON-DIOXIDE CONTROLLED-ATMOSPHERE PACKAGING

Beef striploin steaks (each weighing between 60 and 100 g) of normal u ltimate pH (average 5.45) were inoculated with a mixture of two food i solates of Listeria monocytogenes, packaged under saturated carbon dio xide controlled atmosphere or vacuum, and stored at either 5 or 10-deg rees-C. Saturated carbon dioxide packaging but not vacuum packaging in hibited growth of L. monocytogenes. During storage under vacuum at 5-d egrees-C, numbers increased from 6.2-log10 CFU per sample to 9.0-log10 CFU per sample in 23 days, and at 10-degrees-C numbers increased from 6.3-log10 CFU per sample to 9.5-log10 CFU per sample in 11 days. Duri ng storage under saturated carbon dioxide at 5-degrees-C, numbers decr eased from 5.6-log10 CFU per sample to 5.0-log10 CFU per sample in 18 days, and at 10-degrees-C numbers decreased from 6.7-log10 CFU per sam ple to 5.2-log10 CFU per sample in 44 days. The use of saturated carbo n dioxide controlled atmosphere packaging to extend the storage life o f fresh beef results in apparent destruction of L. monocytogenes even at abuse temperatures.