Water activity samples were collected immediately before inoculation and after 15 min mixing. The water activities of the peanut butter before and after inoculation were 0.200 ± 0.045 and 0.203 ± 0.052, respectively. It was concluded that addition of the inoculum did not have a significant effect (n ¼ 6; p > 0.05) on the water activity of the peanut butter.