(approx. 0.4–0.70 log) than that in MAP of low O2 alone and MAP
of moderate O2 with CO2 (Fig. 10A). Baby spinach exposed to low
O2 alone showed slightly higher microbial counts consistent with
the anticipated antimicrobial effect of CO2. Low O2 resulted in
lower microbial counts when compared with moderate O2. MAP
of moderate O2 with CO2 was shown to be the gas composition that most allowed psychrophilic growth because it was close
to the optimum O2 for the growth of aerobic bacteria. The CO2
level reduced the bacteria growth on baby spinach. Pseudomonas
populations showed similar behaviour to those observed for psychrophilic bacteria. Modified atmosphere packaging of low O2 with
CO2 reduced Pseudomonas significantly compared with moderate
O2 with CO2 (Fig. 10B). However, populations of coliforms and Listeria spp. were not greatly affected by the type of atmosphere. After
12 d, these groups of microorganisms increased similarly regardless
of the atmosphere composition (Fig. 10C and D).