Modelling the inactivation of Lactobacillus plantarum during a drying process

Abstract

Drying is an important step in many bioseparation processes. In the present work the inactivation of Lactobacillus plantarum in a fluidized-bed drying process is modelled. The inactivation is described with two different mechanisms: thermal inactivation and dehydration inactivation. These inactivation mechanisms are described as two processes, occurring simultaneously during the drying process. The thermal inactivation process has been quantitatively described before. The dehydration inactivaton is quantified by fitting an arbitrary set of equations to the measured inactivation data obtained at a drying temperature of 30°C. At this temperature the thermal inactivation can be neglected. Both inactivation models are coupled to the drying kinetics described earlier. The overall model predicts the measured inactivation of L. plantarum during a fluidized-bed drying process, up to a drying temperature of 55°C. From experiments it is concluded that the influence of the drying rate on the residual activity of L. plantarum can be neglected and that the moisture concentration rather than the water activity is the esential parameter in dehydraton inactivation.