ANTIBACTERIAL ACTIVITY OF GARLIC EXTRACT AND DEHYDRATED GARLIC POWDER AGAINST LISTERIA monocytogenes IN SYNTHETIC MEDIUM AND SOFT CHEESE

The antibacterial effect and minimal inhibitory concentration (MIC) of garlic extract and MIC of dehydrated garlic powder (DGP) against Listeria monocytogenes were studied.Its use as an additional barrier in the hurdle technology concept against cross contamination by such pathogen during soft cheese processing was investigated.The agar well diffusion method (Benkerroum and Sandine 1998) and the method of Hogg et al (1987) were used to determine the antilisterial activity and minimal inhibitory concentration (MIC) of garlic extract and its powder respectively.Garlic extract showed antilisterial effect on plates of tryptose soy agar as revealed by inhibition zones ranged from 10 to 19mm diameter, depending on the strain used.MIC for garlic extract was 2% while it was 3% for DGP 1 , DGP 2 , DGP 4 , DGP 5 and >5% for DGP 3 .The potency of garlic powder against the pathogen depends on the temperature used in its processing.Addition of 3% garlic extract to milk intended for soft cheese processing artificially contaminated with 10 4 cfu/ml of the pathogen resulted in producing safe soft cheese.The pathogen could not be detected in soft cheese after 24h from its addition to cheese milk.