INVESTIGATIONS ON THE GROWTH OF LISTERIA-MONOCYTOGENES ON LAMB PACKAGED UNDER MODIFIED ATMOSPHERES

The growth of Listeria monocytogenes in air and modified atmosphere packaged lamb pieces and mince, stored at 5 or 0 degrees C was investigated at 42 days. The modified atmospheres included (i) vacuum pack; (ii) 80% O-2/20% CO2; (iii) 50% CO2/50% N-2; and (iv) 100% CO2. On lamb pieces at 5 degrees C, growth of L. monocytogenes occurred in air and all the modified atmospheres, except 100% CO2. L. monocytogenes growth on minced lamb at 5 degrees C was reduced compared with lamb pieces. Growth did not occur in vacuum packaged mince or in an atmosphere containing 100% CO2. At 0 degrees C, growth of the organism was completely inhibited on pieces and mince in all the modified atmospheres tested and in air. It was noted that pH did not increase or decrease in a regular manner throughout the storage period. Thus pH was eliminated as a factor controlling the growth of L. monocytogenes on modified atmosphere packaged lamb.