Effects of modified atmosphere storage on colour and microbiological shelf life of normal and pale, soft and exudative pork

Pale, soft and exudative (PSE) and normal pork loins (n = 9 of each) were deboned, divided and packaged in modified atmospheres (MA) of 100% carbon dioxide containing 0, 0.5 and 1.0% residual oxygen (O(2)). The meat was stored at 3 °C, first in MA for 21 days, followed by 5 additional days under retail display conditions with access to air. Before packaging, PSE loins were more light and less red than those of normal meat. The drip loss after MA storage was twice as high from PSE meat as from normal meat. PSE meat was not more discoloured after MA storage than normal meat. The level of residual O(2) in the MA had a significant impact on the colour of the two types of meat. Discoloration was observed on both PSE and normal meat with 0.5% O(2) and even more clearly with 1.0% O(2), as demonstrated by instrumental and visual colour analyses. After MA storage, the microbiological shelf life and flora were not affected by the type of meat, or level of residual O(2).