Essential Oils from Thymus capitatus and Thymus algeriensis as Antimicrobial Agents to Control Pathogenic and Spoilage Bacteria in Ground Meat

Abstract

The antibacterial effects of essential oils (EOs) extracted from Thymus capitatus and Thymus algeriensis were assessed and evaluated against four pathogenic bacteria (Escherichia coli (ATCC 25922), Listeria monocytogenes (ATCC 19118), Staphylococcus aureus (ATCC 25923), and Salmonella typhimurium (ATCC 1402)) and one spoilage bacterium (Pseudomonas aeruginosa (ATCC 27853)). Both investigated EOs presented significant antimicrobial activities against all tested bacteria with a greater antibacterial effect of T. capitatus EO. In fact, the results indicated that the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of T. capitatus EO are in the range of 0.006–0.012% and 0.012–0.025%, respectively, while those of T. algeriensis EO ranged between 0.012 and 0.025% and 0.05%, respectively. Furthermore, the inhibitory effects of both EOs were appraised against the spoilage bacterium P. aeruginosa, inoculated in minced beef meat, at two different loads (105 and 108 CFU) mixed with different concentrations of EOs (0.01, 0.05, 1, and 3%) and stored at 4°C for 15 days. The obtained data demonstrated that the antibacterial effect of tested EOs varies significantly in regard to the levels of meat contamination and the concentrations of EOs. In fact, in the presence of 0.01 and 0.05% of oils, a decrease in bacterial growth p < 0.01 was observed; but, such an effect was more pronounced in the presence of higher concentrations of EOs (1 and 3%), regardless the level of meat contamination. Besides, at the low contamination level, both EOs exerted a rapid and a more pronounced antibacterial effect, as compared to the high contamination level. The results illustrated the efficacy of both EOs as preservatives in food against well-known pathogens of food-borne diseases and food spoilage, particularly in P. aeruginosa in beef meat. As regards sensory evaluation, the presence of T. capitatus EO proved to improve the sensory quality of minced beef meat.

Antibacterial Effect of Eight Essential Oils against Bacteria Implicated in Bovine Mastitis and Characterization of Primary Action Mode of Thymus capitatus Essential Oil

“…In addition, the evaluated EO caused a decrease in the growth of E. coli within the first ten minutes. Our data corroborate a previous study about the rapid antibacterial effect of T. capitatus EO against E. coli –BLSE producers [ 17 , 29 ], probably because it contained a high concentration of carvacrol and thymol. Xu et al [ 39 ] showed that carvacrol is able to embrittle and depolarize the cytoplasmic membrane.…”

“…However, weak activity was observed when the EOs containing ketone or esters such as β-myrcene, α-thujone or gerenyl acetate [27,28]. Thus, previous findings showed that the T. capitaus EO has very significant antibacterial activity compared to the other tested EOs, which might be due to its major constituents: thymol and carvacrol [17,[29][30][31]. In previous studies, we demonstrated that thymol (81.49%), α-cubebene (3.44%), α-terpinene (3.83%) and β-ocimene (3.16%) were identified as the major components of T. capitatus [30].…”

Unraveling the Phytochemistry, Traditional Uses, and Biological and Pharmacological Activities of Thymus algeriensis Boiss. & Reut

“…and S. aureus CFSA2. Similarly, it was found that Bacillus cereus (ATCC10876), Micrococcus luteus (NRLL B-4375), and Proteus mirabilis (ATCC35659) were inhibited at 2.34, 7.03, and 4.68 mg/mL, respectively, of the EO extracted from the aerial parts of T. algeriensis growing in the north of Tunisia [ 68 ]. In addition, Zaïri et al revealed that the best antibacterial activity was obtained using the EO from T. algeriensis leaves (MIC = 0.5 mg/mL) which also inhibited the fungus Aspergillus flavus by up to 42.86% [ 69 ].…”

Nanoencapsulation of Thyme Essential Oils: Formulation, Characterization, Storage Stability, and Biological Activity

“…Consequently, generally high concentrations of EO are required for effective antimicrobial action to ensure the desired product shelf-life. Because of the intense aroma of EOs, this could lead to alteration of the product's sensory attributes, further limiting their application in food [9][10][11].…”

“…In fact, in meats, the use of EOs contributed to pathogen control, hence reducing the risk of foodborne outbreaks and ensuring safe meat products for the consumers [11,12]. However, the hydrophobic nature of EOs and their high reactivity with product matrix represent a huge challenge for their direct incorporation into food products [13].…”