Antimicrobial activity of Star Anise, Aniseed and Cinnamon against foodborne bacteria.

Salmonella spp, Escherichia coli and Staphylococcus aureus frequently contaminate chicken meat and result in outbreaks of food poisoning. Chemical preservatives were commonly used to reduce bacterial contamination.The objectives of this study wereto determine the antimicrobial activity of the crude extracts and essential oil of aniseed, cinnamon and star anise against foodborne bacteria and to evaluate the decontamination potential of the essential oil of the spices on chicken meat. Crude extract of star anise, aniseed and cinnamon were extracted using water, ethanol and methanol. Essential oils were extracted using Sohxlet apparatus. Antimicrobial activity was determine by testing the crude extracts and essential oils against Salmonella spp, E. coli and S. aureus using agar well diffusion assay. Minimal inhibitory concentration (MIC) of essential oil was determined by microtitre broth dilution method. Decontamination activity of the essential oil was determined using total plate count (TPC) of chicken meat before and after treatment with the 0.1%, 0.5% and 1.0% essential oils. Aqueous extract of star anise had the highest mean of inhibition zone against S. aureus (12.33 mm) compared to ethanol and methanol extract. Ethanol and methanol extracts of cinnamon gave the same mean of inhibition zone (15.67 mm) against S. aureus. Essential oil of cinnamon inhibited the growth of E. coli at all the tested concentration and essential oil of star anise inhibited E. coli at the concentration of 80% (mean diameter of zone of inhibition= 9.33 mm) and 100% (mean diameter of inhibition zone = 11.67 mm). Aniseed oil did not inhibited growth S. Enteritidis at all concentration but cinnamon oil inhibited the growth of S. Enteritidis at all concentration tested while star anise oil inhibited S. Enteritidis at the concentration of 80% and 100% respectively. MIC of aniseed against S. aureus and S. aureus ATCC 6538 was 0.6 µ g/µ l. The lowest MIC of essential oil of star anise was 0.08 µ g/µ l against S. aureus and the highest was 0.8 µ g/µ l against E. coli, S. Typhimurium and E. coli ATCC 25922. Cinnamon oil had the lowest MIC which is 0.02 µ g/µ l against S. aureus and S. aureus ATCC 6538 where its highest value was against S. Enteritidis which is 0.1 µ g/µ l. After being treated with 1.0% essential oil for 24h the TPC of the chicken meat reduced from 6.14 log CFU/mL to 5.28 log CFU/mL for aniseed, to 5.16 log CFU/mL for star anise and to 5.04 log CFU/mL for cinnamon. In conclusion, this study showed that the essential oils of the spices had better antimicrobial activity compared to the crude extracts.