Inhibition of Listeria monocytogenes on Normal Ultímate pH Beef (pH 5.3-5.5) at Abusive Storage Temperatures by Saturated Carbon Dioxide Controlled Atmosphere Packaging

Abstract

Beef striploin steaks (each weighing between 60 and 100 g) of normal ultimate pH (average 5.45) were inoculated with a mixture of two food isolates of Listeria monocytogenes, packaged under saturated carbon dioxide controlled atmosphere or vacuum, and stored at either 5 or 10°C. Saturated carbon dioxide packaging but not vacuum packaging inhibited growth of L. monocytogenes. During storage under vacuum at 5°C, numbers increased from 6.2-logl0 CFU per sample to 9.0-log10 CFU per sample in 23 days, and at 10°C numbers increased from 6.3-log10 CFU per sample to 9.5-log10 CFU per sample in 11 days. During storage under saturated carbon dioxide at 5°C, numbers decreased from 5.6-log10 CFU per sample to 5.0-log10 CFU per sample in 18 days, and at 10°C numbers decreased from 6.7-log10 CFU per sample to 5.2- logl0 CFU per sample in 44 days. The use of saturated carbon dioxide controlled atmosphere packaging to extend the storage life of fresh beef results in apparent destruction of L monocytogenes even at abuse temperatures.