Antimicrobial Activity of White Mustard Essential Oil on Salmonella spp. in Vitro and in Ground Chicken

Introduction:  Salmonella remains the leading cause of foodborne illness by a bacterial pathogen in the U.S. Preventive measures are needed in order to make food safer by inhibiting the growth of this pathogen. Natural antimicrobials have shown potential against microorganisms while meeting current consumer needs of less artificial preservatives and products.

Purpose:  In this study, the antimicrobial activity of WMEO and carvacrol were evaluated against Salmonella spp. in tryptic soy broth and in ground chicken.

Methods:  Five serovars of Salmonella (Enteritidis, Typhimurium, Heidelberg, Senftenberg, Hartford, and Orion) individually and in a cocktail were exposed to WMEO concentrations of 0.84%, 0.42% and 0.21% at 22°C for 24h in tryptic soy broth (TSB) using the macrodilution method. In addition a five strain cocktail of nalidixic acid resistant Salmonella serovars (Enteritidis, Typhimurium, Heidelberg, Montevideo and Kentucky) were inoculated to achieve a total population of 10⁵ CFU/g in triplicate 100 g ground chicken samples with 7 treatments (positive control, un-inoculated control, 0.75% WMEO, 0.5% WMEO, 0.75% WMEO with 0.1% carvacrol, 0.5% WMEO with 0.1% carvacrol, and 0.1% carvacrol alone). Samples were plated every 2 days on TSA with 100ppm nalidixic acid over a storage period of 12 days at 4°C and 10°C.

Results:  Treatment with 0.84% WMEO decreased populations of Salmonella spp. in TSB by 2-4 log CFU/mL, while 0.42% WMEO had a bacteriostatic effect and 0.21% slowed the growth rate. There was no difference (P > 0.05) in sensitivity between serovars. In chicken, WMEO alone and in combination with carvacrol decreased Salmonella counts by approx. 1 log, while carvacrol alone had no effect.

Significance:  Results indicate the potential use of WMEO in the control of Salmonella spp. due to its consistent antimicrobial effect between serovars. It provides a possible preventive measure for the food industry to control Salmonella spp. in food.