Preparation and properties of ginger essential oil nanocapsules

Ginger herb has remarkable antimicrobial and antioxidant activities. In the present study, the aim is to investigate the effect of chitosan as an encapsulation on the physicochemical characteristics of ginger essential oil. Encapsulation process with the ratios of chitosan to ginger essential oil (1:0, 1:0.4, 1:0.8 and 1:1.2 (w/w)) and sodium tripolyphosphate concentrations (0.5 and 1%  w/v) was performed by emulsion-gel method. Encapsulation efficiency, loading capacity, particle size distribution and zeta potential tests were carried out on samples. Also, Fourier-transform infrared spectroscopy, total phenolic compounds, free radical scavenging and minimum inhibitory concentration (MIC) tests were done on selected and control samples. According to the results of physical tests, the optimal sample was selected with the ratio of chitosan to essential oil (1:0.8 w/w) and salt concentration (0.5% w/v). This nanocapsule exhibited high encapsulation efficiency (23.1 %), suitable particle size (734 nm) and zeta potential (29.2 mV). Application of chitosan nanocapsule containing ginger essential oil indicated more MIC on Escherichia coli (0.97 μg/ml), Staphylococcus aureus (1.9 μg/ml), Salmonella typhimurium (3.90 μg/ml) and Pseudomonas aeruginosa (0.97 μg/ml) compared to other control samples. Also, the antioxidant activities (97%) and the amount of total phenolic compound (980 mg/g) of optimal chitosan nanocapsule were significantly improved. The application of chitosan nanocapsules has led to the improvement of the functional properties of the encapsulated ginger essential oil and is suggested as a natural alternative to chemical additives.