Modified atmosphere packaging decreased Pseudomonas fragi cell metabolism and extracellular proteolytic activities on meat.

Modified atmosphere packaging (MAP) is considered an effective method for extending the shelf life of meat. The use of optimal mixture of gases (CO2 and N2) in food packaging containers has been proved to effectively inhibit the growth of microorganisms in poultry meat. In general, a minimum CO2 concentration range of 20%-30% is required for the inhibitory effect. The aim of this study was to investigate the mechanism by which MAP (CO2/N2 30%/70%) inhibits Pseudomonas fragi, a dominant spoilage microorganism in aerobically stored chilled meat. The cell physiological changes were determined by measuring membrane integrity, membrane potential, ATP level, and extracellular proteolytic activity. The results showed that samples stored under MA retained cell membrane integrity, but lost significant membrane potential and ATP synthesis activity. Furthermore, the peptides issued from 2 structural proteins (myosin and actin) were mainly identified in air samples, indicating that these fragments result from bacterial proteolytic activity while MAP inhibited this activity. Overall, the study found that cell metabolism and extracellular protease activity decreased under MAP conditions. This study showed that MAP is an effective food preservation strategy and revealed mechanisms by which MAP inhibits spoilage.