Acid resistance of Salmonella Typhimurium ATCC 14028 after desiccation stress during peanut storage

Abstract

Salmonella is a relevant pathogen, which causes foodborne outbreaks associated with both high and low moisture foods (LMF). This study evaluated the effect of previous desiccation stress on the acid resistance of S. Typhimurium ATCC 14028 using blanched peanut kernels as an LMF model. Salmonella was recovered from the peanut samples throughout 180 days of blanched peanut kernels storage at 28 ºC. During this period two death rates were verified, 0.04 log cfu/g/day in the first 30 days and 0.007 log cfu/g/day between 30 and180 days.Regarding acid resistance, there was no difference (P > 0.05) in the Salmonella growth/death kinetics between the undesiccated sample (TSB)and the cells recovered from peanut samples over 180 days of storage after 4 h at pHs 3.0, 3.5, 4.5 and 7.2. The average growth rate observed for pH 7.2 was 0.44 log cfu/ml/h. At pH 4.5, the Salmonella counts did not change significantly over 4 h. In contrast, Salmonella populations declined by 0.14 to 0.29 log cfu/ml/h at pH 3.5. At pH 3.0 declines were estimated to be 0.65 log cfu/ml/h for the undesiccated sample and 2.07 log cfu/ml/h for Salmonella recovered from peanuts stored for 120 days. Therefore, our data indicated that desiccation stress caused during the peanut storagedid not influence the Salmonella acid resistance.