Growth and survival of Salmonella in ground black pepper (Piper nigrum)

A four serovar cocktail of Salmonella was inoculated into ground black pepper (Piper nigrum) at different water activity (a(w)) levels at a starting level of 4-5 log cfu/g and incubated at 25 and at 35 degrees C. At 35 degrees C and a(w) of +/- 0.9886 0.0006, the generation time in ground black pepper was 31 3 mm with a lag time of 4 +/- 1 h. Growth at 25 degrees C had a longer lag, but generation time was not statistically different from growth at 35 degrees C. The a(w) threshold for growth was determined to be 0.9793 +/- 0.0027 at 35 degrees C. To determine survival during storage conditions, ground black pepper was inoculated at approximately 8 log cfu/g and stored at 25 and 35 degrees C at high (97% RH) and ambient (<= 40% RH) humidity. At high relative humidity, a(w) increased to approximately 0.8-0.9 after approximately 20 days at both temperatures and no Salmonella was detected after 100 and 45 days at 25 and 35 degrees C, respectively. Under ambient humidity, populations showed an initial decrease of 3-4 log cfu/g, then remained stable for over 8 months at 25 and 35 degrees C. Results of this study indicate Salmonella can readily grow at permissive a(w) in ground black pepper and may persist for an extended period of time under typical storage conditions. Published by Elsevier Ltd.