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

Abstract

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 °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.