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Antimicrobial activity of PIT-fabricated cinnamon oil nanoemulsions: Effect of surfactant concentration on morphology of foodborne pathogens

Chuesiang, Piyanan, Siripatrawan, Ubonrat, Sanguandeekul, Romanee, McClements, David Julian, McLandsborough, Lynne
Food control 2019 v.98 pp. 405-411
Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus, Vibrio parahaemolyticus, antimicrobial properties, bacteria, cell walls, cinnamon oil, food pathogens, minimum inhibitory concentration, nanoemulsions, nonionic surfactants, scanning electron microscopy
The impact of surfactant concentration (10 to 20 wt%) on the antimicrobial activity of cinnamon oil nanoemulsions formed by the phase inversion temperature (PIT) method was studied against a number of foodborne pathogens: Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus and Vibrio parahaemolyticus. Minimum inhibitory concentration (MIC), dynamic time kill, and changes in bacteria morphology were determined. Increasing non-ionic surfactant (Tween®80) concentration from 10 to 20 wt% increased the MIC values of the nanoemulsions. However, dynamic time kill plots revealed that nanoemulsions with higher surfactant concentrations (15 and 20 wt%) led to faster or more prolonged inhibition of bacteria compared to those with lower concentration (10 wt%) or with bulk cinnamon oil. Morphological changes of the bacteria were more promoted for nanoemulsions containing higher surfactant concentrations as shown by field emission scanning electron microscopy (FE-SEM). The antimicrobial activity of the cinnamon oil nanoemulsions was attributed to their ability to disrupt bacterial cell wall structures and promote expulsion of internal cellular material.