Antimicrobial Activity of Myrtus communis L. and Rosmarinus officinalis L. Essential Oils against Listeria monocytogenes in Cheese

Abstract

Listeria monocytogenes has been referred to as a concern microorganism in cheese making due to its ability to survive and grow in a wide range of environmental conditions, such as refrigeration temperatures, low pH and high salt concentration at the end of the production process. Since cheese may be a potential hazard for consumers, especially high-risk consumers (e.g., pregnant, young children, the elderly, people with medical conditions), efforts of the dairy industry have been aimed at investigating new conservation techniques based on natural additives to meet consumers’ demands on less processed foods without compromising the food safety. Thus, the aim of this study was to evaluate the efficacy of Myrtus communis L. (myrtle) and Rosmarinus officinalis L. (rosemary) essential oils (EO) against Listeria monocytogenes ATCC 679 spiked in sheep cheese before ripening. After the cheesemaking process, the samples were stored at 8 °C for 2 h, 1 d, 3 d, 14 d and 28 d. The composition of EO was identified by gas chromatography-mass spectrometry (GC-MS) analysis. Constituents such as 1,8-cineole, limonene, methyl-eugenol, α-pinene, α-terpineol, α-terpinolene and β-pinene were present in both EO, accounting for 44.61% and 39.76% from the total of chemical compounds identified for myrtle and rosemary EO, respectively. According to the chemical classification, both EO were mainly composed of monoterpenes. Minimum inhibitory concentration (MIC) against L. monocytogenes was obtained at 31.25 μL/mL to myrtle EO and at 0.40 μL/mL to rosemary EO. Then, cheeses were inoculated with L. monocytogenes (Ca. 6 log CFU/mL) and EO was added at MIC value. The addition of rosemary and myrtle EO displayed lower counts of L. monocytogenes (p < 0.01) (about 1–2 log CFU/g) during the ripening period compared to control samples. Ripening only influences (p < 0.001) the growth of L. monocytogenes in control samples. Since rosemary and myrtle EO do not exert any negative impact on the growth of native microflora (p > 0.05), their use as natural antimicrobial additives in cheese demonstrated a potential for dairy processors to assure safety against L. monocytogenes.

Inhibitory Effect of Sodium Alginate Nanoemulsion Coating Containing Myrtle Essential Oil (Myrtus communis L.) on Listeria monocytogenes in Kasar Cheese

“…The growth of L. monocytogenes was suppressed in the coating samples (NE 1 ) containing 0.5% myrtle essential oil; however, no significant changes were observed in the bacterial counts during the storage ( p > 0.05). Similarly, previous studies have reported myrtle essential oil has a lower anti-listerial effect in the food matrix than in vitro analyses [ 12 , 13 ]. Saraiva et al [ 13 ] evaluated the efficacy of myrtle essential oil against L. monocytogenes in sheep milk cheese and reported that the addition of myrtle essential oil showed a lower L. monocytogenes (approximately 1–2 log cfu/g) count during the ripening period compared to the control samples.…”

“…Monoterpene hydrocarbons and oxygenated monoterpenes, such as 1,8-cineol, α-pinene, linalool, α-terpineol, and γ-terpinene in the myrtle essential oil, are responsible for the antibacterial activity against Gram-positive and Gram-negative bacteria, mainly Listeria spp. [ 12 , 13 , 21 , 22 ]. Similarly, in the present study, the antimicrobial activity of myrtle essential oil was associated with the high content of 1,8-cineol (38.64%), and α-pinene (30.19%).…”

“…The antibacterial properties of myrtle essential oils against pathogenic bacteria were reported in many studies and obtained results are promising. However, there are only a few reports on the application of myrtle essential oil as an antimicrobial in foods for the control of L. monocytogenes [ 12 , 13 ]. The antibacterial activity of myrtle essential oil was associated with α-pinene, 1,8-cineole, and linalool [ 14 , 15 , 16 ].…”

The Influence of Liquid Medium Choice in Determination of Minimum Inhibitory Concentration of Essential Oils against Pathogenic Bacteria

“…On the other hand, no strains were able to grow in MHB without lysed blood supplementation. Although the supplementation is in CLSI standards for antimicrobial susceptibility testing [ 14 ], many studies testing EOs against L. monocytogenes in MHB do not mention this M45 standard or any supplementation [ 15 , 16 , 17 , 18 , 19 , 20 ] and in another study only MHB for Streptococcus spp. was supplemented, although L. monocytogenes was included in the study [ 21 ].…”

Virucidal Activity of Essential Oils From Citrus x aurantium L. Against Influenza A Virus H1N1:Limonene as a Potential Household Disinfectant Against Virus

“…27 Recently, essential oils have been widely used as food preservatives or additives, replacing chemical additives, that is, nitrate and nitrite. [28][29][30][31][32][33] Essential oils could give effects at the cellular levels, that is, activating GABA and olfactory receptors, and transient receptor potential channels, and thus transferring signals to the olfactory bulb and the brain. 34 Since the outbreak of COVID-19 has spread worldwide, a few reports recently proposed that essential oils could be potential agents for the treatment of this deadly virus.…”