Inactivation Kinetics of Probiotic Bacteria during the Drying of Single Milk Droplets

Abstract

The changes in the droplet temperature, the droplet water content, and the survival of two probiotic bacterial strains with time during the drying of single milk droplets were measured experimentally and modelled mathematically. A new model of the inactivation kinetics, which is dependent on the rate of change in the droplet water content during the drying process, was established. The model parameters were obtained using the genetic algorithm parameter optimization scheme devised in MATLAB for drying at different air temperatures, and this procedure yielded the kinetics model that best fitted with the experimental results, after examining a number of possible formulations.

Keywords:

• Bacterial inactivation
• Drying
• Kinetic parameters
• Milk droplet
• Modeling
• Probiotics

Acknowledgments

The authors thank M. J. Stevenson and I. J. Woo for the laboratory work and technical assistance. Dr. J. Harnett from the Fonterra Research Centre is also acknowledged for his support in the experimental stage of this study.