WATER AVAILABILITY AND THE SURVIVAL OF SALMONELLA-TYPHIMURIUM IN POROUS SYSTEMS

The survival of Salmonella Typhimurium LT2 in randomly packed beds of glass beads, microporous silica particles and Sephadex microspheres is examined. It is shown that the decrease in the percentage cell recove ry in these porous materials at reduced water content is not correlate d with the global water activity as determined by conventional vapour pressure measurements but rather with the osmotic shock induced by the sudden redistribution of water and air among the microscopic pores in the matrix surrounding the cells. For this reason the bacterial survi val and growth data correlates best with physical measurements, such a s NMR and electrical conductivity, which are sensitive to the microsco pic air-water distribution. The implications of this observation in fo od safety and preservation are discussed. (C) 1997 Elsevier Science B. V.