Discussion of the Z-value to use in calculating the F0-value for high-temperature sterilization processes.
The appropriate z-value to use in integrating heat process time-temperature data in the temperature range of 120.0-140.0 degrees C (248.0-284.0 degrees F) is discussed. We conclude that for control of Clostridium botulinum there is little risk in extrapolating a public health F0-value for C. botulinum to temperatures in the 132.0-138.0 degrees C (270.0-280.0 degrees F) range using a z-value of 10.0 degrees C (18.0 degrees F). It would seem prudent, at this time, when extrapolating data to conditions in the 132.0-138.0 degrees C (270.0-280.0 degrees F) range, that as a starting point an F0-value of 3.0 minutes be used as the minimum public health process. A design z-value of 10.0 degrees C (18.0 degrees F) is appropriate for Clostridium sporogenes to temperatures of 140.0 degrees C (284.0 degrees F). To control thermophilic microorganisms such as Bacillus stearothermophilus and Bacillus coagulans with processes at temperatures from 120.0-140.0 degrees C (248.0-284.0 degrees F), the effective z-value will be in the range of 7.0-8.0 degrees C (12.6-14.4 degrees F) instead of 10.0 degrees C (18.0 degrees F). This means that when we design and calculate processes at temperatures from 120.0-140.0 degrees C (248.0-284.0 degrees F), using a z-value of 10.0 degrees C (18.0 degrees F), the lethal effect against these organisms will be much larger than indicated by the F0-value of the process.
Pflug
I J
IJ
University of Minnesota, Department of Food Science and Nutrition, Minneapolis 55455, USA.
D003014:Clostridium botulinum; D006358:Hot Temperature; D013242:Sterilization / Q000592:standards*; D013696:Temperature; D013997:Time Factors