Growth and activity of Shewanella putrefaciens isolated from spoiling fish.

A total of 101 cultures of H2S-producing organisms isolated from spoiling cod was studied. All cultures were identified as Shewanella putrefaciens. Two groups were distinguished on the basis of pattern of trimethylamine oxide reduction determined by conductance measurement, generation time at 25 degrees C and salt tolerance. The S. putrefaciens cultures were further characterized in a number of model experiments in order to examine the spoilage activity under various conditions. A good correlation between bacterial counts, detection time in conductance measurements and production of trimethylamine and off-odour was found. There were no differences in spoilage potential between strains of S. putrefaciens, and neither initial level of inoculum nor batch of cod used as substrate influenced the levels of bacterial count corresponding to a certain production of trimethylamine and off-odour.