Optimization of Salmonella detection in garlic, onion, cinnamon, red chili pepper powders and green tea

Abstract

Salmonella is the causative agent of many outbreaks related to spice consumption. However, because of the antimicrobial properties of various spices which hinders recovery and detection, Salmonella detection in spices remains a challenge. The objective of this study was to optimize an enrichment broth for Salmonella growth in different spices and tea, in order to maintain an adequate pH and decrease the antimicrobial effects of spices during Salmonella enrichment and subsequent detection. Salmonella contaminated spice and tea dried samples were prepared and the detection of Salmonella was assessed using the developed broth and automated DNA extraction and RT-PCR. Double strength Buffered Peptone Water (BPW) was used to maintain pH, and L-cysteine and DL-serine were added to the broth to reduce the effects of antimicrobial compounds in spices. The modified enrichment broth allowed the growth of Salmonella from each spice sample. Sample to broth ratios varied from 1:9 (garlic powder, chili peppers and tea), to 1:20 (cinnamon). The pH value of each enrichment varied but remained above 4.8. The addition of L-cysteine (30 mmol/L) allowed Salmonella recovery and growth in garlic and onion samples and the addition of DL-serine (11.23 mmol/L) allowed the recovery and growth in cinnamon. The results indicated that Salmonella detection was achieved in <24 h in the modified (BPW + L-cysteine and DL-serine) enrichment broth followed by detection by RT-PCR. This protocol could allow for a more rapid, robust, and sensitive enrichment method for Salmonella in spices.