Effect of elevated oxygen and carbon dioxide on the surface growth of vegetable-associated micro-organisms

The impact of a novel type of Modified Atmosphere (MA), referred to as high O2-MA, on micro-organisms associated with the spoilage of minimally-processed vegetables was studied. Pure cultures of Pseudomonas fluorescens, Enterobacter agglomerans, Aureobacterium strain 27, Candida guilliermondii, C. sake, Salmonella typhimurium, Salm. enteritidis, Escherichia coli, Listeria monocytogenes, Leuconostoc mesenteroides var. mesenteroides, Lactobacillus plantarum and Lactococcus lactis were cultured on an agar-surface model system and incubated at 8 degrees C under an atmosphere composed of O2 (80 or 90%, balanced with N2), CO2 (10 or 20%, balanced with N2), or a combination of both gases. In general, exposure to high O2 alone did not inhibit microbial growth strongly, while CO2 alone reduced growth to some extent in most cases. Consistently strong inhibition was observed only when the two gases were used in combination. With minimally-processed vegetables, where CO2 levels of around 20% or above cannot be used because of physiological damage to the produce, the combined treatment of high O2 and 10-20% CO2 may provide adequate suppression of microbial growth, allowing a safe, prolonged shelf-life.