Microbial populations of fresh-cut spinach leaves affected by controlled atmospheres

The effect of controlled atmospheres (CA) containing low oxygen and high carbon dioxide at low temperatures on micro-organisms on fresh-cut spinach leaves was studied. Control samples in air were compared with those kept in 0.8% O-2-N-2 or 0.8% O-2-10% CO2-N-2 at one of two temperatures, 5 and 10 degrees C, for 9 or 7 days, respectively. The populations of various microorganisms on the leaf surfaces were assessed, but coliforms and lactic acid bacteria were not detected and yeast remained uniformly low. At 5 degrees C, CA decreased micro-organisms growth by between 10- and 100-fold, except for lactic acid bacteria and yeasts. At a temperature of 10 degrees C, populations increased regardless of the atmospheric composition to 10-100 times those at the lower temperature. Thus, low oxygen atmospheres could be used to control spoilage micro-organisms on cut spinach leaves for at least 7 days, so long as the storage does not exceed 5 degrees C.