Summary: Thermograms obtained by differential scanning calorimetry of a range of bacteria of different heat resistances were compared. Equations were derived to calculate the rate at which the numbers of viable organisms in a calorimeter decline as the temperature is raised at a constant rate. Vegetative bacteria scanned at 10°C min showed multi-peaked thermograms with four major peaks (denoted and ) occurring in the regions 68–73, 77–84, 89–99 and 105–110°C respectively. Exceptions were that peak (the largest peak) occurred at 79–82°C in and an additional peak, , was detected in at 119°C. At temperatures below the main peak there were major differences in thermograms between species. There was a direct relationship between the onset of thermal denaturation and the thermoresistance of different organisms. Heat-sensitive organisms displayed thermogram features which were absent in the more heat-resistant types. When samples were cooled to 5°C and re-heated, a small endothermic peak, , was observed at the same temperature as . Peaks and were identified as the melting endotherms of DNA. In all vegetative organisms examined, maximum death rates, computed from published and values, occurred at temperatures above the onset of thermal denaturation, i.e. cell death and irreversible denaturation of cell components occurred within the same temperature range.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error