SALMONELLA SURVIVAL DURING INOCULATION AND STORAGE OF DRIED SPICES CONTAINING ANTIMICROBIAL COMPONENTS

Abstract

To provide an adequate initial microbial level for spices containing antimicrobial compounds for use in stability testing of foodborne pathogens, a dry-transfer inoculation was designed and compared with a traditional aqueous inoculation protocol. A five serovar cocktail of Salmonella spp. was prepared at different concentrations (~11 log CFU/mL, ~8 log CFU/mL and ~4 log CFU/mL). It was inoculated onto 1g silica beads and four types of dried ground spices (clove, oregano, ginger, and black pepper). Both spices and beads were dried for 24h at ambient conditions (~22°C). Silica beads were then used as a carrier to inoculate the same four types of spices. The results suggest that dry-transfer of Salmonella via inoculated silica beads provided a greater starting inoculum than aqueous transfer alone and are a viable alternative to aqueous inoculation when spices contain antimicrobial components. This dry-transfer inoculated ground clove with 8.4 log CFU/g and 3.9 log CFU/g initial populations was then used to determine the survival of Salmonella on spices containing antimicrobial components. Salmonella spp. survival on silica beads with 9.2 log CFU/g and 5.9 log CFU/g initial populations and subsequent transfer to ground clove was also examined. Samples were enumerated at selected time point up to 210 d. Results of this study indicate that Salmonella transfer and recovery from beads and in ground clove was not affect by storage and that Salmonella may persist for an extended period of time. The calculation of recovery was, however, affected by detection limits in clove. To improve detection limits an oil extraction was used and compared to the BAM method (detection limit 3.7 log CFU/g). After oil extraction the clove samples were soaked for 1 h (or 24 h for low inoculum concentration) in TSB at 37ᵒC and subsequently enumerated on tryptic soy agar with 0.6% yeast extract and xylose lysine deoxycholate agars. The result demonstrates that the oil extraction detection method holds promise as an alternative method to detect Salmonella in dry spices containing antimicrobial components and can provide a lower detection limit (1.7 log CFU/g).M.S. in Food Process Engineering, May 201