Thermal inactivation of Listeria innocua in salmon (Oncorhynchus keta) caviar using conventional glass and novel aluminum thermal-death-time tubes

Differences in the come-up times and thermal inactivation parameters of Listeria innocua in salmon (Oncorhynchus keta) caviar containing 2.5% salt using conventional thermal-death-time (TDT) glass tubes and a novel aluminum tube were tested and compared. Generally, the come-up times and decimal reduction times (D-values) were shorter and the change in temperature required to change the D-value (z-value) was longer in the aluminum than in the glass tubes. The D-values at 60, 63, and 65degreesC for the aluminum TDT tubes were 2.97, 0.77, and 0.40 min, respectively, and for the glass TDT tubes, these values were 3.55, 0.84. and 0.41 min. The z-values were 5.7degreesC in the aluminum and 5.3degreesC in the glass. Because of the shorter come-up time, the aluminum TDT tubes may provide a more precise measurement of microbial thermal inactivation than the glass TDT tubes, particularly for viscous materials, solid foods, and foods containing particulate matter.