engleski

Antilisterial activity of spices in vitro

Bacteria Listeria monocytogenes, with its ubiquity, and increased ability to grow and survive in adverse conditions, presents a significant challenge in food production. On the other hand, spices are known to have antimicrobial properties, in addition to their ability to improve sensory characteristics and digestibility of food. The aim of present study was to determine antibacterial activity of spices against L. monocytogenes. Fifteen spices (chilly, clove, cinnamon, coriander seed, cumin, curry, garlic, ginger, oregano, paprika, black and white pepper, rosemary, thyme and turmeric) were collected from retail from the same producer, and analyzed for presence of Listeria monocytogenes. For screening of antibacterial activity L. monocytogenes ATCC 7644 strain was used. The overnight culture of L. monocytogenes in BHI broth was subsequently diluted, to the level of 10 cfu/ml and all dilutions (1-7 log cfu/ml) were used for further screening of antibacterial activity. 5% suspension of spices and herbs was made in distillated water. 100 µL aliquot of suspension of each spice was put in wells of two micro-titer plates and incubated at 5 or 37 ºC for 30 min. Then 100 µL of serial dilution of L. monocytogenes were inoculated to each well with suspensions of spices, and plates were incubated at 5 ºC and 37 ºC. After incubation 100 µL of aliquot was spread onto Palcam agar and incubated 24 h at 37 ºC. L. monocytogenes were not detected in any spice samples. From 15 spices only cinnamon and clove showed strong antibacterial activity against L. monocytogenes at both temperatures, while at 37 °C strong antimicrobial activity was determined also for garlic, oregano, rosemary and thyme. Weaker antimicrobial activity (1-2 log reducing in number compared to control) was noticed for curry and rosemary at 5 °C and chilly, ginger and thyme (2-3 log decrease) at 37 °C. Spices which showed strong antibacterial activity, were not only preventing growth of L. monocytogenes, but killed all bacteria even in concentration of 7 log cfu/ml (there was no viable bacteria on the agar). Our results indicate potential that spices have as antimicrobial agents, and further research should be focused on determination on minimal inhibitory dose, and optimization of combination of spices.

spices; antibacterial activity; L. monocytogenes

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