The Survival of Salmonella typhimurium in Propylene Glycol/Water Mixtures

Abstract

The effect of propylene glycol, a coolant used in dairy processing plants, on the growth and survival of Salmonella typhimurium was studied. Cultures were inoculated into 0.1% reconstituted nonfat dry milk with glycol concentrations ranging from 0 to 50% (Aw 0.99-0.83) and were incubated at 37°C or −1°C. Serial dilutions were plated on tryptic soy agar (Difco), incubated at 37°C for 24 h and enumerated. At 37°C, 5% or more glycol inhibited the growth of S. typhimurium. At concentrations >20% glycol, Aw<0.96, no recovery was possible after 4 h at 37°C. At −1°C, a slow decline in population was seen regardless of glycol concentration. The higher the concentration, the faster the rate of decline in population. Aeration of the system resulted in a more rapid decrease in the number of S. typhimurium than the static system.