SummaryA relationship between temperature and sterilizing efficiency of heat treatment at constant time is described and checked experimentally using spores of Bacillus coagulans 604 in a pilot ultra-high-temperature plant. The relation is:whereN0andNare initial and final concentrations of spores,Tthe temperature (°C),zthe temperature coefficient (°C,z=10/logQ10) andAa dimensionless constant. A special effect of the injection of spores into live steam is observed. The sterilizing efficiency curve can be used in determining the heating temperature for a desired sterilizing efficiency and in predicting the influence of temperature fluctuation on sterilizing efficiency.