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 O-2-MA, on micro-organisms associated with the spoilage of minimally-proce ssed vegetables was studied. Pure cultures of Pseudomonas fluorescens, Ente robacter agglomerans, Aureobacterium strain 27, Candida guilliermondii, C. sake, Salmonella typhimurium, Salm. enteritidis, Escherichia coli, Listeria monocytogenes, Leuconostoc mesenteroides var. mesenteroirdes, Lactobacillu s plantarum and Lactococcus lactis were cultured on an agar-surface model s ystem and incubated at 8 degrees C under an atmosphere composed of O-2 (80 Or 90%, balanced with N-2), CO2 (10 Or 20%, balanced with N-2), Or a combin ation of both gases. In general, exposure to high O-2 alone did not inhibit microbial growth strongly, while CO2 alone reduced growth to some extent i n 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 O-2 and 10-20% CO2 ma y provide adequate suppression of microbial growth, allowing a safe, prolon ged shelf-life.