Antimicrobial Efficacy of Natural Phenolic Compounds against Gram Positive Foodborne Pathogens

Protection of food from pathogens and spoilage organisms has been achieved by a variety of methods. Due to consumer preference, health and economic concerns in recent years, there is considerable interest to employ natural antimicrobials as an alternative to control the growth of microorganisms. This study evaluates the antimicrobial efficacy of natural plant derived phenolic compounds (PDPC) including chlorogenic acid, coumarin, curcumin, ellagic acid, (-) epicatechin, eugenol, rosmarinic acid, rutin, tannic acid, thymol, thymoquinone, and xanthohumol) as preservatives in food products. Several strains of Bacillus, Listeria and Clostridium species were treated with 12 natural PDPCs. Concentrations of 5, 10, 15, and 20 ppm of each compound were evaluated by broth micro-dilution method and the MICs were determined by using optical density after 24 and 60 hours of incubation. Thymoquinone, xanthohumol and ellagic acid demonstrated the highest antimicrobial efficacy (MIC <20 ppm). Structural alterations in treated bacteria were observed via scanning electron microscopy. The results demonstrated that the PDPCs have varying antimicrobial activities against both aerobic and anaerobic Gram-positive foodborne pathogens following 24 hour and 60 hour incubation periods, respectively. Natural sources of phenolic compounds contain major antimicrobial components and have great potential to control the growth of pathogens and be used as natural antimicrobials and food preservatives for extended storage.This study highlighted the antimicrobial efficacy of some PDPCs which may replace the artificial antimicrobials and preservatives in food industry to partially or completely control or inhibit the growth of harmful bacteria.