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Abstract

The successful control of food spoilage microorganisms require the use of indigenous antimicrobials in foods including certain botanical compounds that have been historically used for flavour enhancement as well as preservation. The present study was designed to evaluate the in vitro antimicrobial activity of ethanolic extracts of Syzygium aromaticum (clove) and Allium sativum (garlic) against Gram-positive and Gram-negative food associated bacteria (Bacillus subtilis, B. megaterium, B. polymyxa, B. sphaericus, Staphylococcus aureus and Escherichia coli) and molds (Penicillium oxalicum, Aspergillus flavus, A. luchuensis, Rhizopus stolonifer, Scopulariopsis sp. and Mucor sp.) assayed by agar well diffusion method and poisoned food technique, respectively. Clove extract showed better antimicrobial activity than the garlic extract. The zone of inhibition in clove ethanolic extract against all the food associated bacteria was in the range of 25mm to 32mm and in molds the percent mycelial growth inhibition ranged from 70% to 100%. The growth inhibition zone in garlic ethanolic extract against bacteria was in the range of 20mm to 31mm and in molds the percent mycelial growth inhibition ranged between 20% and 50%. The clove ethanolic extract exhibited the maximum zone of inhibition against E. coli whereas garlic ethanolic extract showed maximum activity against B. subtilis. Both the extracts exhibited maximum percent mycelial growth inhibition against R. stolonifer. However garlic extract was not effective against P. oxalicum. The MIC values of clove ethanolic extract for different bacterial isolates ranged from 5.0mg/ml to 20mg/ml and 10 mg/ml to 20mg/ml against molds. The MIC values of garlic ethanolic extract for different bacterial and fungal isolates ranged from 10 mg/ml to 20mg/ml. The value of MBC and MFC equaled the MIC. Based on this finding, it may be suggested that these extracts may be used as natural antimicrobial additives to reclaim the shelf-life of foods.

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