Purpose: The purpose of this study is to develop an effective detection method for Salmonella from spices using cloves as a model.
Methods: Two clove varieties, Ceylon and Madagascar, were used in the study. Cloves were inoculated with Salmonella ser. Montevideo, Salmonella ser. Typhimurium, or Salmonella ser. Weltevreden at 1, 3 or 6 log CFU/g. Two sample sizes, 10 and 25 g, were compared. Trypticase soy broth (TSB) was used as preenrichment broth at a broth: clove ratio of 9:1. After adding TSB to cloves for preenrichment, three different preenrichment treatments were evaluated: cloves were left in the preenrichment TSB broth during preenrichment (PreE1); and the mixture was shaken vigorously for 30 (PreE2) or 60 sec (PreE3) and the decants were transferred to a new bag for preenrichment. The rest of the procedures were carried out according to the FDA BAM. Six trials with 4 replicates each were conducted.
Results: All samples from PreE2 and PreE3, at inoculation levels 6 log CFU/25g or 3 log CFU/25g, were positive for Salmonella. However, PreE1 only produced 38 positive from a total of 48 samples at inoculation level 6 log CFU/25g. It had 12 positive results among 48 samples at inoculation level 3 log CFU/25g. A similar trend was observed at inoculation level 1 log CFU/25g. Therefore, PreE3 with 25 g cloves/sample was validated by comparing with FDA BAM in 6 trials, with each trial consisting of 20 samples. The results showed the PreE3 detected Salmonella from 88 of 120 inoculated samples compared with 31 positive of 120 by BAM.
Significance: In conclusion, the newly designed method PreE3 was substantially superior to the current FDA BAM for the detection of Salmonella from cloves.