Ce Shi1, Xiaowei Zhang1, Na Guo2. 1. Department of Food Quality and Safety, College of Food Science and Engineering, Jilin University, 130062, Changchun, PR China. 2. Department of Food Quality and Safety, College of Food Science and Engineering, Jilin University, 130062, Changchun, PR China. Electronic address: jlnaguo@126.com.
Abstract
BACKGROUND: Foodborne diseases caused by foodborne pathogens have increasingly become a worldwide public health concern. Due to potential harmful effects of synthetic chemicals, there is a pressure for adoption of natural alternatives to obtain microbial safety of food. Tea tree oil (TTO) exhibited a wide range of pharmacological actions attribute to the broad spectrum activities. However, to the best of our knowledge, no systematic research on the mode of antibacterial actions of TTO against Listeria monocytogenes (L. monocytogenes) and Escherichia coli (E. coli) in vitro models have been conducted so far. RESULTS: The present investigation reported on the antimicrobial activities of TTO and examined its possible antimicrobial mode of action against L. monocytogenes and E. coli. Results showed that the susceptibility of L. monocytogenes were excellent with the lower minimal inhibitory concentration (MIC) values and larger inhibition zones. TTO changed the integrity of the membrane, as evidenced by the release of 260 nm absorbing intracellular materials and the alteration of membrane potential. The results of flow cytometry showed that TTO caused bacterial membrane permeabilization in a dose-dependent manner. The remarkable cellular morphological changes in bacteria caused by TTO were observed using the scanning electron microscope, indicating cell damage. In addition, antimicrobial preserving properties of TTO were evaluated by time-kill assay after its incorporation in cucumber juice, the results showed TTO successfully inhibited L. monocytogenes and E. coli development, at room temperature and in refrigerator (25 °C and 4 °C) respectively, demonstrating it had good preservative activities in food system. CONCLUSIONS: These findings suggested that TTO exhibited good antimicrobial effect against food-borne pathogens and could be potentially used in food industries as a food preservative.
BACKGROUND:Foodborne diseases caused by foodborne pathogens have increasingly become a worldwide public health concern. Due to potential harmful effects of synthetic chemicals, there is a pressure for adoption of natural alternatives to obtain microbial safety of food. Tea tree oil (TTO) exhibited a wide range of pharmacological actions attribute to the broad spectrum activities. However, to the best of our knowledge, no systematic research on the mode of antibacterial actions of TTO against Listeria monocytogenes (L. monocytogenes) and Escherichia coli (E. coli) in vitro models have been conducted so far. RESULTS: The present investigation reported on the antimicrobial activities of TTO and examined its possible antimicrobial mode of action against L. monocytogenes and E. coli. Results showed that the susceptibility of L. monocytogenes were excellent with the lower minimal inhibitory concentration (MIC) values and larger inhibition zones. TTO changed the integrity of the membrane, as evidenced by the release of 260 nm absorbing intracellular materials and the alteration of membrane potential. The results of flow cytometry showed that TTO caused bacterial membrane permeabilization in a dose-dependent manner. The remarkable cellular morphological changes in bacteria caused by TTO were observed using the scanning electron microscope, indicating cell damage. In addition, antimicrobial preserving properties of TTO were evaluated by time-kill assay after its incorporation in cucumber juice, the results showed TTO successfully inhibited L. monocytogenes and E. coli development, at room temperature and in refrigerator (25 °C and 4 °C) respectively, demonstrating it had good preservative activities in food system. CONCLUSIONS: These findings suggested that TTO exhibited good antimicrobial effect against food-borne pathogens and could be potentially used in food industries as a food preservative.