Microbial inactivation during superheated steam drying of fish meal

Microbial inactivation during superheated steam drying (SSD) of fish meal was investigated in a pilot scale fluidized bed dryer. The exposure times required for 90% reduction in population (D-values) of the surrogate organisms Clostridium sporogenes (spores) and Escherichia coli at 300 degrees C were 0.33 and <0.10 min, respectively. Corresponding D-values obtained during hot air drying at the same temperature were 54 and 1.12min. D-value for spores of the thermophile Geobacillus stearothermophilus during SSD was 3.54min, compared to 228min in boiling water. The results achieved with surrogate organisms indicate that the target pathogens will be efficiently inactivated by short time SSD.