The individual antibacterial activity of Thai red curry paste’s dry ingredients against Listeria monocytogenes using different ethanolic extraction

Abstract

Thai red curry paste is a main ingredient of Thai Red curry. The paste contains herbs which have the potential to be natural antibiotics. Six herbs contained in Thai red curry paste were tested for their individual antibacterial activity against Listeria monocytogenes 10403S. Six herbs tested were Chilli (Capsicum annuum), Kaffir lime (Citrus hystrixShallot (Allium ascalonicum L.), Garlic (Allium sativum), Lemongrass (Cymbopogon citratus), and Galangal (Alpinia galanga). The agar disk diffusion method was used for in-vitro screening antibacterial activity of each crude extract against L. monocytogenes 10403S on Beef Heart Infusion media (BHI) with five different ethanol concentrations; 0, 25, 50, 75, and 95%. The 95 % ethanol crude extracts gave the highest antibacterial activity against L. monocytogenes 10403S in all herbs. The dry galangal 95% crude ethanolic extract showed the highest antibacterial activity; 10.50 ± 1.16 mm. The minimum inhibitory concentrations (MICs), using a broth dilution method, were found to be between 4-128 µl/ml. The minimum bactericidal concentrations (MBCs), using a broth dilution method, were greater than 32-128 µl/ml. The results showed that the six dry herbs have significant antibacterial activity against the food-borne pathogen, L. monocytogenes 10403S.