Viability of Airborne Salmonella newbrunswick Under Various Conditions

Abstract

Death rates of Salmonella newbrunswick aerosolized from distilled water or skimmilk into a closed chamber were determined at 10 and 21 C and 30, 50, 70, 90% relative humidity (RH,). Initial death rates (natural logarithms of slopes of survivor curves without negative sign) for the first 20 min at 10 C ranged from 0.0112 to 0.0346 at 90 and 30% RH, and at 21 C from 0.0141 to 0.056. The D values corresponding to these death rates, ranged from 41 min at 21 C and 30% RH to 206 min at 10 C and 90% RH. The secondary death rates for the 20 to 90 min aerosol age ranged from 0.0057 to 0.0099 at 10 C and 90 or 30% RH, and from 0.0141 to 0.0182 at 21 C and the same relative humidities. The protection of skimmilk solids was shown by decreases in death rates. The corresponding D values for S. newbrunswick aerosolized in skimmilk at 10 C ranged from 245 min to 404 min at 90 and 30% RH and at 21 C from 164 to 470 min. Activation energies for the initial period of death ranged from 3,520 to 7,357 cal per mole at 90 and 30% RH. These values increased to 13,360 and 8,649 cal per mole for the secondary period of death. The negative entropies for the airborne death of S. newbrunswick may indicate concentration of solutes in the bacteria. Concentration of solutes or aggregation of macromolecules may result in physicochemical changes which ultimately cause death. © 1972, American Dairy Science Association. All rights reserved.