Inhibitory activity of Syzygium aromaticum and Cymbopogon citratus (DC.) Stapf. essential oils against Listeria monocytogenes inoculated in bovine ground meat

Abstract

This research evaluated the antimicrobial effect of the clove (Syzygium aromaticum) and lemongrass (Cymbopogon citratus (DC.) Stapf.) essential oils (EOs) against Listeria monocytogenes ATCC 19117 growth added to bovine ground meat stored under refrigeration (5 ± 2 °C) for three days. The EOs, extracted by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC- MS), were tested in vitro using an agar well diffusion methodology for determination of Minimum Inhibitory Concentration (MIC). The MIC concentrations for both essential oils on culture tested of L. monocytogenes were 1.56%. The EOs concentrations applied in contaminated ground beef were 1.56, 3.125 and 6.25% (w/v) based on MIC levels and possible activity reductions by food constitu- ents. The bacteria populations were significantly reduced (p £ 0.05) after one day of storage in ground meat samples treated with clove and lemongrass EOs at concentrations of 1.56%. There were no sig- nificant counts of L. monocytogenes in samples at the other concentrations of the two oils applied af- ter the second day of storage. The sensory acceptability evaluation of the bovine ground meat samples treated with EOs showed that the addition at concentrations higher than 1.56% promote un- desirable alterations of taste, odor and characteristic color. The application of EOs at low concentra- tions in food products can be used in combination with other preservation methods, such as refrigeration, to control pathogens and spoilage bacteria during shelf-life; which goes according to current market trends, where consumers are requesting natural products.