Purpose: Better understanding of the antimicrobial efficiency in terms of minimum lethal concentrations was examined to determine the applicability of essential oils against common food spoilage microorganisms.
Methods: Three genera of lactic acid bacteria, including Leuconostoc citrovorum, Lactobacillus buchneri, and Pediococcus acidilactici, were evaluated for survival up to 72h in de Man, Rogosa, Sharpe broth containing one of four essential oil components: carvacrol, cinnamaldehyde, eugenol, or thymol.
Results: Thymol was bactericidal (> 4-log reduction) against L. citrovorum at 1000 ppm and resulted in a 2-log CFU/ml reduction of P. acidilactici and > 2-log reduction of L. buchneri. Cinnamaldehyde caused a > 2-log reduction against all three species after 48h at concentrations ranging from 2000 to 2500 ppm. A > 3-log reduction was demonstrated for all three species after exposure to 2000 ppm carvacrol for 6 h. Eugenol at 2000 and 2500 ppm was required for > 3-log CFU/ml reduction after 6 h. P. acidilactici and L. buchneri recovered to initial inoculum concentrations after exposure to 2000 ppm eugenol by 48-72h. Eugenol at 3000 ppm caused a > 3-log reduction of P. acidilactici for the entirety of the 72h study period, but L. buchneri recovered to initial populations at the same concentration.
Significance: Essential oils at 1000-3000 ppm can inactivate common spoilage lactic acid bacteria, but regrowth over time may be a concern and may require multiple antimicrobial hurdles to achieve a desired shelf life in foods.