The influence of oxygen and carbon dioxide on the growth of prevalent Enterobacteriaceae and Pseudomonas species isolated from fresh and controlled-atmosphere-stored vegetables

To obtain more insight into the specific impact of modified gas conditions on the composition of microflora of minimally processed vegetables, the prevalent bacteria on mungbean sprouts and cut chicory endive were determined during storage under controlled atmospheric (CA) conditions at 8 degrees C. Enumeration of the total mesophilic counts, Enterobacteriaceae, Pseudomonas species, and lactic acid bacteria indicated that Enterobacteriaceae and Pseudomonas species constituted the major populations found on these products before and after CA storage. identification of the predominant species within these populations revealed that on fresh and CA-stored mungbean sprouts, Enterobacter cloacae, Pantoea agglomerans, Pseudomonas fluorescens, Ps, viridilivida and Ps. corrugate were the prevalent species. On chicory endive, Rahnella aquatilis and several Pseudomonas species were found on the fresh product, while after CA storage, Escherichia vulneris and Ps, fluorescens were the main species. Growth of the predominant epiphytes was subsequently quantified in pure culture, using an agar model system at 8 degrees C under 1.5 or 21% O-2 with 0, 5, 20, or 50% CO2. In general, these CA conditions did not strongly influence maximum population densities and lag rimes were not detected. For each of the strains, however, maximum specific growth rates were reduced at increased CO, concentrations, independent of the 0, concentration applied. This effect was more pronounced for Pseudomonas species than for Enterobacteriaceae. Notably, the agar model study showed that individual species of Enterobacteriaceae or Pseudomonas responded similarly to the specific CA conditions applied. This did not correlate with the shift in predominant species observed on chicory endive. Our data underline the complexity of the ecological conditions to which micro-organisms on vegetables are subjected during storage under modified gas conditions. (C) 1998 Academic Press.