Introduction: In 2010, a large outbreak of salmonellosis was attributed to the consumption of contaminated black pepper. Black pepper and white pepper have previously been linked to foodborne disease outbreaks. The survival and growth of Salmonella in black pepper are not well understood. A better understanding of Salmonella in dry products will enhance risk assessments for these products.
Purpose: To determine if Salmonella can grow and establish stable populations on ground black pepper and to determine the minimum water activity for such growth to occur.
Methods: Unsterilized and sterilized commercial ground black pepper at different water activity levels was inoculated with a three serovar cocktail of Salmonella at a starting level of approximately 4-5 log CFU/g and then incubated at 25 and 37°C. Immediately after inoculation and at appropriate intervals over a 48-hour period, triplicate samples were plated on both trypticase soy agar with yeast extract (TSAYE) and xylose lysine deoxycholate agar (XLD) for microbial enumeration.
Results: At a water activity of 0.9916-0.9884, the generation time at 37 and 25oC for Salmonella was 0.54 and 1.22 h, respectively, with lag times of 4 to 6 h. Reducing the water activity to 0.9756-0.9739 increased the generation time to 3.96 and 4.93 h at 37 and 25oC, with lag times of 18-24 h. Growth was not observed at water activities below 0.97. The presence of background microflora appeared to enhance growth and survival of Salmonella.
Significance: Salmonella can grow on black pepper at an alarmingly fast rate when the water activity is permissive. Black pepper having permissive water activity may not appear noticeably wet. Native background microflora on black pepper may enhance Salmonella survival.