Fast-responding thermal-death-time tubes for the determination of thermal bacteria inactivation

The knowledge of thermal inactivation kinetics, usually expressed in terms of D- and z-values, is of crucial importance for the design of sanitation and sterilization processes. In this study, we designed a simple, fast-responding, and mechanically stable aluminum tube for inactivation measurements and compared these experiments with the successive-sampling method at different temperatures. Up to 65 degrees C, we determined a come-up time of approximately 15 s for the tubes, which is lower than the corresponding values of other devices, presumably because of lower wall thickness, material properties, and a higher surface to volume ratio. D-values of Escherichia coli calculated from tube inactivation experiments by first-order kinetics were 370 s (56 degrees C), 126 s (58 degrees C), 53.2 s (60 degrees C), 33.8 s (62 degrees C), and 3.22 s (65 degrees C), and the corresponding values determined with the successive-sampling flask method were insignificantly different (417, 138, 48.6, and 29.1?s for 56, 58, 60, and 62 degrees C, respectively). These data as well as those measured for Enterobacter cloacae, Pseudomonas putida, Serratia odorifera, and Yersinia rhodei were in close accordance with literature values.