Thermal Inactivation of Listeria innocua in Salmon (Oncorhynchus keta) Caviar Using Conventional Glass and Novel Aluminum Thermal-Death-Time Tubes

Abstract

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 65°C 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 5.7°C in the aluminum and 5.3°C 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.