Microstructural factors controlling the survival of food-borne pathogens in porous media

The survival of Salmonella typhimurium LT2. Escherichia coli K-12 and Pseud omonas putida in several model porous media poised at a water activity of 0 .94 is shown to depend critically on the microstructure of the particulate matrix and the microscopic water distribution. The porous media were made b y randomly dispersing a liquid inoculum containing ca. 10(7) cells/ml throu ghout the pores and interparticle spaces of packed beds of silica particles and Sephadex microspheres. The purely "microstructural stress" effects wer e isolated by comparison with a homogeneous liquid growth medium having the same water activity. The possibility of exploiting similar microstructural stress effects in food preservation is discussed. (C) 2001 Elsevier Scienc e B.V. All rights reserved.