Antibacterial properties and stability of emulsions containing Cuminum cyminum and Oliveria decumbens Vent. essential oils prepared by ultrasound

Physical and antibacterial properties of ultrasound assisted emulsions from two essential oils (Cuminum cyminum and Oliveria decumbens) at concentrations of 1, 3, 5, 10 and 15% were studied. The results showed that all emulsions were stable after centrifugation. Although the samples were stable after heat-cool cycles, they became unstable at the freeze-thaw cycles. Emulsion samples with concentrations of 10 and 15%, were stored at 45 ºC for 35-days were unstable and became two-phase. Measuring the turbidity of emulsion samples with a spectrophotometer showed that with increasing concentrations of dispersed phase, the emulsion turbidity increased. Both emulsions showed antibacterial activity. But the  C. cyminum emulsions showed higher inhibition zones against Escherichia coli, while O. decumbens emulsions represented higher inhibition zone against Staphylococcus aureus. Generally, the inhibition zone diameters of both emulsions increased dose dependently.