Microstructural effects on microbial survival: phase-separating dextran solutions

Evolving microstructure in a model dextran solution is shown to exert a maj or influence on the survival of Escherichia coli K-12 frag 1 and Salmonella typhimurium LT2. The microstructure results from microscopic phase separat ion, which develops over several hours resulting in hardening of the soluti on into a glassy state. The microstructure is characterized by an array of physical methods including image analysis, electron spin resonance and bulk rheology, and it is shown that bacterial survival depends on the formation of microscopic, water-rich domains and not primarily on bulk water activit y or hardness. (C) 2001 Elsevier Science B.V. All rights reserved.